Laboratory work in organic chemistry: Textbook. Installation for purification by distillation of organochlorine products and methods of purification by distillation of carbon tetrachloride, chloroform, trichlorethylene, methylene chloride and perchlorethylene Methods

Distill substances at a temperature significantly lower than their boiling point. The essence of steam distillation is that high-boiling, immiscible or slightly miscible, i.e. Substances that are slightly soluble in water volatilize when water vapor is passed into them; then they condense together with the steam in the refrigerator. In order to determine whether a substance is volatile with water vapor, a small amount of it must be heated in a test tube with 2 ml of water. The bottom of a second test tube containing ice is held above this test tube. If the drops condensing on the cold bottom of the second test tube are cloudy, then the substance is volatile with water vapor. Table 6 Data on some substances distilled with steam Substance Boiling point, 0C Content of pure substance of a mixture of substance with substance in steam distillate, % Aniline 184.4 98.5 23 Bromobenzene 156.2 95.5 61 Naphthalene 218.2 99 .3 14 Phenol 182.0 98.6 21 Nitrobenzene 210.9 99.3 15 o-Cresol 190.1 98.8 19 The sequence of work is as follows. It is recommended to first heat the flask with liquid and water until almost boiling. This preheating is intended to prevent the volume of the mixture in the flask from increasing too much due to the condensation of water vapor during distillation. In the future, the distillation flask need not be heated. When a strong stream of steam comes out of the steam generator, close the rubber tube placed on the tee with a clamp and begin distillation with steam. A fairly strong stream of steam should pass through the liquid in the flask. A sign of the end of distillation is the appearance of a transparent distillate (pure water). If the substance being distilled has appreciable solubility in water (for example, aniline), a small amount of clear distillate should be collected. At the end of the distillation, open the clamp and only then extinguish the burners (thereby eliminating the danger of drawing liquid from the distillation flask into the steam generator). In the receiver, after distillation, two layers are obtained: water and organic matter. The latter is separated from the water in a separating funnel, dried in the usual way and distilled for final purification. Sometimes salting out and extraction are used to reduce the loss of a substance due to its partial solubility in water. High-boiling substances that are difficult to distill with steam having a temperature of 100°C can be distilled with superheated steam, unless there is a danger of decomposition of the substance at a higher temperature. To generate superheated steam, steam superheaters of various devices are used. Typically, steam from the steam generator enters a metal coil that has a pipe for measuring temperature and is heated by the flame of a strong burner. It is necessary to maintain a certain temperature of the superheated steam in order to control the rate of distillation and avoid decomposition of the substance. The distillation flask should be immersed in an oil or metal bath heated to the required temperature, and the neck of the flask should be tightly wrapped with asbestos cord. If distillation is carried out at temperatures above 120-130°C, it is necessary to connect first an air and then a water refrigerator to the distillation flask in series. The use of superheated steam makes it possible to increase the rate of distillation of poorly volatile substances many times over (Fig. 39). In contrast to ordinary, simple distillation, during which steam and condensate pass through the apparatus once in a direction, in countercurrent distillation, or rectification, part of the condensate constantly flows towards the steam. This principle is implemented in distillation distillation columns. Rectification is a method of separating or purifying liquids with fairly close boiling points by distillation using special columns in which rising vapors interact with liquid flowing towards them (reflux), which is formed as a result of partial condensation of vapors. As a result of repeated repetition of the processes of evaporation and condensation, the vapors are enriched in the low-boiling component, and the reflux, enriched in the high-boiling component, flows into the distillation flask. Efficient columns used in industry or scientific research can separate liquids that differ in boiling point by less than 1°C. Conventional laboratory columns allow the separation of liquids with a boiling point difference of at least 10°C. The distillation column must be thermally insulated so that the processes occurring in it occur under conditions as close as possible to adiabatic. If there is significant external cooling or overheating of the column walls, its correct operation is impossible. To ensure close contact of vapors with liquid, distillation columns are filled with a packing. Glass beads, glass or porcelain rings, short pieces of glass tubes or stainless steel wire, and glass spirals are used as nozzles. Distillation columns are also used with a star-type Christmas tree pin. The efficiency of the column depends on the amount of reflux supplied to the irrigation. To obtain a sufficient amount of reflux, the distillation column must be connected to a condenser. The role of a condenser with partial condensation of vapors can be performed by a conventional reflux condenser. A simple setup for separating a mixture of liquids is shown in Fig. 38. 52 Condensers are widely used, in which complete condensation of all vapors passing through the column occurs. Such condensers are equipped with a tap for distillate selection. Rectification can be carried out both at atmospheric pressure and in vacuum. As a rule, rectification in vacuum is carried out for high-boiling or thermally unstable mixtures. Questions for control: 1. Explain the types and methods of distillation. 2. In what cases is distillation used at atmospheric pressure, at reduced pressure (in vacuum) and with water steam. Why? 3. Explain the operating principle and design of a distillation device at atmospheric pressure. 4. Explain the operating principle and design of a steam distillation device. Practical part 4.1.4.1. Distillation at atmospheric pressure Reagents: substance to be purified. Equipment: device for simple distillation. Assemble the device for simple distillation at atmospheric pressure as shown in Fig. 38. Fig. 38. Device for simple distillation: 1 - Wurtz flask; 2 - thermometer; 3 - downward Liebig refrigerator; 4 - allonge; 5 - receiving flask. Using a funnel, distillation flask 1 is filled no more than two-thirds with the liquid being distilled. Before filling the device, measure the volume or weight of the liquid. The distillation apparatus is assembled from dry, clean parts and mounted on stands. Turn on the cooling water. A bath (water, oil) or a heating mantle is used as a heater. By controlling the temperature of the bath using a second thermometer 2 mounted on a tripod, the heating is set to such a level that ensures uniform, slow boiling of the contents of the flask. No more than two drops of clean and transparent distillate per second should fall into the receiver. Only under such conditions does the thermometer in the flask indicate the temperature corresponding to the equilibrium point between vapor and liquid; If distilled too quickly, the vapors easily overheat. The distillation temperature is recorded in a log. The distillation cannot be continued dry! It is completed at the moment when the boiling temperature is 2-3 degrees higher than the one at which the main fraction passed. At the end of the distillation, determine the volume or weight of the distillate, as well as the residue in the distillation flask. Exercise. Purify one of the proposed solvents as directed by the teacher. In organic synthesis, the “purity” of the solvents used is very important. Often even small impurities interfere with the reaction, so purification of solvents is an urgent task for a synthetic chemist. Chloroform 0 20 Bp.=61.2 C; nd =1.4455; d415=1.4985 An azeotropic mixture (chloroform-water-ethanol) contains 3.5% water and 4% alcohol, it boils at 55.5°C. Commercial chloroform contains alcohol as a stabilizer that binds phosgene formed during decomposition. Cleaning. Shake with concentrated sulfuric acid, wash with water, dry over calcium chloride and distill. Attention! Due to the risk of explosion, chloroform should not be brought into contact with sodium. Carbon tetrachloride 0 20 Bp = 76.8 C; nd =1.4603 An azeotropic mixture with water boils at 66°C and contains 95.9% carbon tetrachloride. A ternary azeotrope with water (4.3%) and ethanol (9.7%) boils at 61.8°C. Cleaning and drying. Distillation is usually sufficient. The water is removed in the form of an azeotropic mixture (the first parts of the distillate are discarded). If high demands are placed on drying and purification, then carbon tetrachloride is refluxed for 18 hours with phosphorus (V) oxide and distilled with a reflux condenser. Carbon tetrachloride must not be dried with sodium (risk of explosion!). Ethanol 0 Bp = 78.33 C; nd20=1.3616;d415=0.789 Ethanol is miscible with water, ether, chloroform, benzene in any ratio. The azeotropic mixture with water boils at 78.17°C and contains 96% ethanol. A ternary azeotrope mixture with water (7.4%) and benzene (74.1%) boils at 64.85°C. 54 Impurities. Synthetic alcohol is contaminated with acetaldehyde and acetone, ethyl alcohol obtained during fermentation is contaminated with higher alcohols (fusel oils). Pyridine, methanol and gasoline are added for denaturation. Drying. Dissolve 7 g of sodium in 1 liter of commercial “absolute” alcohol, add 27.5 g of phthalic acid diethyl ether and boil for 1 hour under reflux. Then it is distilled with a small column. Distilling alcohol contains less than 0.05 water. Traces of water can be removed from commercial “absolute” alcohol in another way: 5 g of magnesium is boiled for 2-3 hours with 50 ml of “absolute” alcohol, to which 1 ml of carbon tetrachloride is added, then 950 ml of “absolute” alcohol are added, and another 5 are boiled. h with reflux condenser. In conclusion, they distill. Water detection. Alcohol containing more than 0.05% water precipitates a voluminous white precipitate from the benzene solution of aluminum triethylate. 4.1.4.2. Steam distillation Reagents: substance to be purified. Equipment: device for simple distillation. Assemble the steam distillation apparatus as shown in Fig. 39. Fig. 39. Device for distillation with water steam: 1- steam generator; 2 - tee with clamp; 3 - distillation flask; 4 - refrigerator; 5 - allonge; 6 - receiving flask; 7 - safety tube; 8 – supply tube; 9 – tube that removes steam Steam is formed in steam generator 1 (a flask is also suitable instead). The safety tube 7 is used to equalize the pressure, the connecting link is used to release condensate. Steam through the supply tube 8 enters the distillation flask 3, which contains the mixture to be separated. Typically this flask is also heated. The distillate enters refrigerator 4, condenses and flows through allonge 5 into receiver 6. Small amounts of the substance can be distilled without using a steamer, but by adding a certain amount of water directly into the distillation flask. Task 1. Conduct steam distillation of natural raw materials (rose petals, spruce needles) to obtain an aqueous extract of essential oil. To do this, natural raw materials are loaded into the flask, filled with water and distilled with steam. Task 2. Obtain anhydrous oxalic acid from its mixture with water by azeotropic distillation of water. Distillation of a mixture of two liquids that are insoluble in each other is also used to dry organic substances by the so-called azeotropic distillation of water. For this purpose, the substance to be dried is mixed with an organic solvent, for example, benzene or carbon tetrachloride, and the mixture is heated in a distillation apparatus. In this case, water is distilled off with vapor of the organic substance (at a temperature lower than the boiling point of the lowest boiling component of the mixture, for example, benzene or CCl4). With a sufficiently large amount of organic solvent, complete dehydration of the substance being dried can be achieved. 4.1.4.3. Rectification Reagents: substance to be purified. Equipment: Device for fractional distillation. Rectification at atmospheric pressure Assemble the device for distillation of the mixture as shown in Fig. 40. Fig. 40. Device for fractional distillation: 1 - distillation flask; 2 - reflux condenser; 3 - thermometer; 4 - refrigerator; 5 - allonge; 6 - receiving flask Task. Separate a mixture of ethanol and butanol into its components by rectification at atmospheric pressure. Collect the following fractions: a) up to 82°C (“pure ethanol”); b) from 83 to 110°C (intermediate fraction); c) remainder. Measure the volume of the fraction and residue. 4.1.4.4. Distillation in vacuum Reagents: substance to be purified. Equipment: Device for distillation under reduced pressure. 56 Fig. 41. Device for distillation under reduced pressure: 1 - Claisen flask or round-bottomed flask with a Claisen nozzle; 2 - capillary connected to a rubber hose with a clamp; 3 - thermometer; 4 - refrigerator; 5 - allonge; 6 - receiving flask; 7 - safety bottle; 8 - pressure gauge Task. Distill quinoline under reduced pressure. T kip. quinoline at atmospheric pressure -237.7°C, and at 17 mm Hg. Art. -114°C. Questions for the colloquium: 1. Why is a reflux condenser used in fractional distillation? 2. What are azeotropic mixtures? What methods are there for separating them? 3. At what temperature (above or below 100°C) will water boil in the mountains? Explain your answer. 4. Where do impurities remain when organic compounds are purified by distillation? 4.1.5. Thin layer chromatography (TLC) Chromatography refers to a whole group of physicochemical separation methods based on the work of Tsvet (1903) and Kuhn (1931). There are chromatography in columns, thin layer, on paper, and gas. The separation of substances in these cases occurs either as a result of distribution between two liquid phases (partition chromatography), or due to different adsorbability of the substance by some adsorbent (adsorption chromatography). Thin layer chromatography involves using, for example, aluminum oxide as a sorbent. In this case, both distribution and adsorption play a role in separation. The mobile phase, in the flow of which the mixture to be separated moves, is called the eluent, and the solution leaving the stationary phase layer and containing the dissolved components of the mixture is called the eluate. Depending on the direction in which the eluent moves across the plate, there are:  ascending thin layer chromatography 57  descending thin layer chromatography  horizontal thin layer chromatography  radial thin layer chromatography. Ascending thin layer chromatography This type of chromatography is the most common and is based on the fact that the front of the chromatographic system rises along the plate under the action of capillary forces, i.e. the front of the chromatographic system moves from bottom to top. For this method, the simplest equipment is used, since any container with a flat bottom and a tight-fitting lid that can freely fit a chromatographic plate can be used as a chromatographic chamber. The ascending thin layer chromatography method has a number of disadvantages. For example, the rate at which the front rises along the plate occurs unevenly, i.e. in the lower part it is highest, and as the front rises it decreases. This is due to the fact that in the upper part of the chamber the saturation of solvent vapors is less, so the solvent from the chromatographic plate evaporates more intensely, therefore, its concentration decreases and the speed of movement slows down. To eliminate this drawback, strips of filter paper are attached to the walls of the chromatographic chamber, along which the rising chromatographic system saturates the chamber with vapor throughout its entire volume. Some chromatography chambers are divided into two trays at the bottom. This improvement allows not only to reduce the consumption of the chromatograph system (a smaller volume is required to obtain the required height of the chromatograph system) but also to use an additional cuvette for a solvent that increases the saturated vapor pressure in the chamber. Another disadvantage is the need to monitor the solvent front, since the solvent front line may “run away” to the upper edge. In this case, it is no longer possible to determine the actual value of Rf. Descending thin layer chromatography This chromatography method is based on the fact that the front of the chromatographic system descends along the plate mainly under the influence of gravity, i.e. the front of the mobile phase moves from top to bottom. For this method, a cuvette with a chromatographic system is attached to the upper part of the chromatographic chamber, from which a solvent is supplied to the chromatographic plate using a wick, which flows down and the test sample is chromatographed. The disadvantages of this method include the complexity of the equipment. This method is mainly used in paper chromatography. 58 Horizontal thin layer chromatography This method is the most complex in terms of equipment but the most convenient. Thus, in the chromatographic chamber the plate is placed horizontally and the system is fed to one edge of the plate using a wick. The solvent front moves in the opposite direction. There is one more trick that allows you to simplify the camera extremely. To do this, a chromatographic plate on an aluminum base is slightly bent and placed in the chamber. In this case, the system will receive input from both sides simultaneously. Only plates with an aluminum backing are suitable for this purpose, since the plastic and glass base is “unbending”, i.e. does not retain its shape. The advantages of this method include the fact that in a horizontal cuvette, the system is saturated with vapors much faster, the speed of the front is constant. And when chromatography is performed on both sides, the front does not “run away”. Radial thin-layer chromatography Radial thin-layer chromatography involves applying the test substance to the center of the plate and adding an eluent that moves from the center to the edge of the plate. The distribution of the components of the mixture occurs between the water absorbed by the carrier1 and the solvent moving through this stationary phase (mobile phase). In this case, Nernst's law applies. The component of the mixture that is more easily soluble in water moves more slowly than the one that is more soluble in the mobile phase. Adsorption consists in the fact that adsorption equilibria are established between the carrier and the components of the mixture - each component has its own, resulting in different speeds of movement of the components. A quantitative measure of the rate of transfer of a substance when using a particular adsorbent and solvent is the Rf value (retardation factor or mobility coefficient). The value of Rf is determined as the quotient of the distance from the spot to the starting line divided by the distance of the solvent (front line) from the starting line: Distance from the spot to the starting line Rf = Distance from the solvent front to the start The value of Rf is always less than one, it does not depend on the length chromatograms, but depends on the nature of the chosen solvent and adsorbent, temperature, concentration of the substance, and the presence of impurities. Thus, at low temperatures, substances move more slowly than at higher temperatures. Contaminants contained in the mixture of solvents used, inhomogeneity of the adsorbent, and foreign ions in the analyzed solution can change the Rf value. 1 An adsorbent carrier, such as alumina, starch, cellulose, and water form a stationary phase. 59 Sometimes the factor Rs is used: Distance traveled by a substance from the line to the start Rs= Distance traveled by a substance, taken as a standard, from the line to the start In contrast to Rf, the value of Rs can be greater or less than 1. The value of Rf is determined by three main factors. FIRST FACTOR - the degree of affinity of the organic compound being chromatographed to the sorbent, which increases in the following series: alkanes< алкены < простые эфиры < нитросоединения < альдегиды < нитрилы < амиды < спирты < тиофенолы < карбоновые кислоты По мере увеличения числа функциональных групп энергия адсорбции возрастает (Rf уменьшается). Наличие внутримолекулярных взаимодействий, например водородных связей, наоборот уменьшает ее способность к адсорбции (Rf увеличивается). Так, о-нитрофенолы и о-нитроанилины имеют большее значение Rf , чем м- и п-изомеры. Плоские молекулы адсорбируются лучше, чем неплоские. ВТОРОЙ ФАКТОР - свойства самого сорбента, которые определяются не только химической природой вещества, но и микроструктурой его активной поверхности. В качестве сорбентов чаще всего используются оксид алюминия, силикагель, гипс с размером гранул 5-50 мкм. Оксид алюминия обладает удельной поверхностью 100- 200 м2/г, имеет несколько адсорбционных центров. Одни из них избирательно сорбируют кислоты, другие - основания. При этом для кислот c рКа <5 и оснований c рКа >9 is characterized by chemisorption. Aluminum oxide is also effective for separating acyclic hydrocarbons with different numbers of double and triple bonds. Silica gel (SiO2×H2O) has a significantly greater sorption capacity than aluminum oxide. In TLC, large-porous grades of silica gel with a pore size of 10-20 nm and a specific surface of 50-500 m2/g are used. Silica gel is chemically inert to most active organic compounds, however, due to its acidic properties (pH 3-5), it quite strongly sorbs bases with pKa>9. Gypsum is a sorbent with a small sorption capacity and low activity. Used for chromatography of polar compounds, as well as compounds containing a large number of different functional groups. THIRD FACTOR - the nature of the eluent, which displaces the molecules of the substances under study adsorbed on the active centers. In order of increasing eluent ability, eluents can be arranged in the following row: 60

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The invention relates to the production of organochlorine products, in particular to the field of their purification by distillation. The installation for purification by distillation of organochlorine solvents contains a cube connected to the source of the initial solvent, a packed distillation column of periodic action installed on the latter and communicated with it, the top of which is connected to a reflux condenser, and the latter, from the outlet side, is connected to the top of the distillation column and to collection tanks distillation product, while the installation is additionally equipped with at least two tanks for the selection of products of reactive qualifications and a separator for the selection of an aqueous intermediate fraction installed at the outlet of the reflux condenser and connected to the distillation column and a tank for collecting pregon through the separator; the distillation column is composed of three glass frames of the same height, hermetically connected to each other, and the diameter of the packed distillation column is from 0.06 to 0.07 of the height of the distillation column with the height of the latter from 2800 to 3200 mm, the cube is made of enameled cast iron, and the reflux condenser and containers for collecting the distillation product - from glass. The invention makes it possible to increase the efficiency of the installation for purification by distillation of organochlorine products and to carry out deep cleaning by distillation of carbon tetrachloride, chloroform, trichlorethylene, methylene chloride and perchlorethylene. 6 n.p. f-ly, 1 ill.

Drawings for RF patent 2241513

The invention relates to the production of organochlorine products, in particular to the field of their purification by distillation.

There is a known installation for the distillation of small industrial batches of solvents, containing a water evaporation chamber with electric heaters, a steam pipe, and a water cooling system (see RF patent 2068729, class B 01 D 3/32, 11/10/1996.

This installation is quite simple. However, it does not make it possible to obtain particularly pure chemicals, which narrows the scope of use of this installation.

A known installation for the purification of organochlorine solvents, in particular methyl chlorides, contains a distillation column and a system of refrigerator-condensers installed at the outlet from the top of the column (see application WO 98/37044, class C 07 C 17/38, 08/27/1998).

This installation allows you to remove impurities from methyl chlorides. However, it also does not allow achieving high purity of the resulting product, which is associated with limited capabilities for separating the product after it leaves the top of the distillation column.

The closest to the invention in terms of technical essence and the achieved result in terms of the device, as the object of the invention, is an installation for purification by distillation of organochlorine solvents, containing a cube connected to the source of the initial solvent, installed on the latter and connected with it, a packed distillation column of periodic action, the top of which is connected to the reflux condenser, and the latter, from the outlet side, is connected to the top of the distillation column and to containers for collecting the distillation product (see Japanese patent JP 2001072623, class C 07 C 17/383, 03/21/2001).

This installation allows for the purification of organochlorine products. However, the efficiency of this installation is not fully used, which is due to the fact that it does not allow obtaining several distillation products of varying degrees of purity.

There is a known method for purifying methane chlorohydrocarbons, in particular chloroform and methyl chloride, as well as isolating methylene chloride in the form of a distillation column distillate. In this case, chloroform is purified with sulfuric acid (see RF patent 2127245, class C 07 C 17/16, 03/10/1999).

However, this method does not allow obtaining reactive grade products. In particular, methylene chloride is obtained with a purity of only 99.7%.

There is a known method for purifying chloroform in a rectification mode using antimony pentachloride as an oxidizing agent (see RF patent No. 2096400, class C 07 C 17/383, 11/20/1997).

However, the use of a solvent can create problems when disposing of production waste, which also narrows the scope of use of this method for purifying organochlorine solvents.

There is a known method for purifying organochlorine products from tar and soot, in particular methylene chloride, chloroform, carbon tetrachloride and trichlorethylene. The purification method consists in introducing fuel with a boiling point from 150 to 500°C into organochlorine products before evaporation or rectification (see RF patent 2051887, class C 07 C 17/42, 01/10/1996).

This method makes it possible to achieve the purification of organochlorine products from resin and soot, but does not make it possible to achieve the purity of distillation products of reactive qualifications, for example, “pure for analysis.”

The closest to the invention in terms of the method, as the object of the invention, is a method for purifying organochlorine solvents, which consists in loading the original solvent into a cube, heating it in the cube to boiling point and sending the vapors to a distillation column, from the last pair they enter a reflux condenser, where they are condensed, and from the reflux condenser, the condensate is fed through a separator into the upper part of the distillation column in the form of reflux, which, in contact with solvent vapor, condenses its highly volatile components, and the solvent in the form of a liquid phase, enriched with highly volatile components, is sent back to the cube to form cube is thus left, and the solvent vapors, enriched with highly volatile non-condensed components, are sent to a reflux condenser, in which they are cooled and condensed, and then, after stabilizing the operation of the distillation column, part of the condensate is sent in the form of reflux to the distillation column, and the other part of the condensate as a distillation product - in a container for collecting the distillation product (see. the above Japanese patent JP 2001072623).

However, this known method for the purification of organochlorine products does not take into account the features of purification by distillation of such products as carbon tetrachloride, chloroform, trichlorethylene, methylene chloride and perchlorethylene, which does not allow full use of the capabilities of the distillation unit and obtain products of the required high degree of purity, in particular qualification products “chemically pure” or “special purity”.

The problem to be solved by the present invention is to increase the efficiency of the installation for purification by distillation of organochlorine products and to carry out deep purification by distillation of carbon tetrachloride, chloroform, trichlorethylene, methylene chloride and perchlorethylene.

The specified problem in terms of the device, as an object of the invention, is solved due to the fact that the installation for purification by distillation of organochlorine solvents contains a cube connected to the source of the initial solvent, installed on the latter and connected with it, a packed distillation column of periodic action, the top of which is connected to a reflux condenser, and the latter, from the exit side, is connected to the top of the distillation column and to tanks for collecting the distillation product, while the installation is additionally equipped with at least two tanks for selecting products of reactive qualifications and a separator installed at the outlet of the reflux condenser and connected to the distillation column and containers for collecting the aqueous intermediate fraction and pre-run through the separator, the distillation column is made up of three glass frames of the same height, hermetically connected to each other, and the diameter of the packed distillation column is from 0.06 to 0.07 of the height of the distillation column with the height of the latter from 2800 to 3200 mm, the cube is made of enameled cast iron, and the reflux condenser and containers for collecting distillation products are made of glass.

In part of the method, as an object of the invention, this problem is solved due to the fact that the method of purification by distillation of carbon tetrachloride consists in loading technical carbon tetrachloride (CTC) into a cube, heating it in the cube to the boiling point and sending the vapors to a distillation column and then to the reflux condenser, where they are condensed; from the reflux condenser, the condensate is fed through the separator to the upper part of the distillation column in the form of reflux, which, in contact with the vapors of the ChCU, condenses its highly volatile components; the ChCC in the form of a liquid phase, enriched with the nonvolatile components, is sent back to the cube with thus forming a residue in the cube, and the CCA vapors, enriched with highly volatile non-condensed components, are sent to a reflux condenser, in which they are cooled and condensed, and then, after stabilizing the operation of the distillation column, part of the condensate is sent in the form of reflux to the distillation column, and the other part of the condensate as a product distillation in a container for collecting the distillation product, while maintaining the reflux ratio equal to 4, loading the technical CCU into the cube is carried out at room temperature of the CCU, while the pressure in the cube is maintained equal to atmospheric pressure, the CCC is heated to a temperature of 75-77 ° C and for 30 -40 min, all condensate from the reflux condenser is sent back to the distillation column in the form of reflux and the reflux flow is maintained from 180 to 200 dm 3 /h, and the condensate from the reflux condenser is fed into the distillation column through a separator, through which the aqueous intermediate fraction and pregon are taken from the condensate, and after that, after the reflux condenser, part of the condensate is selected - products of reactive qualifications into separate containers in the following sequence: “clean”, “clean for analysis”, “chemically pure”, and the selection of the specified condensate is carried out in the following quantities: aqueous intermediate fraction from 2.0 up to 2.5% vol, pregon from 2 to 6% vol, “pure” - from 28 to 30% vol, “pure for analysis” - from 25 to 28% vol and “chemically pure” - from 28 to 30% vol , all of the amount of CHO loaded into the still, after which the distillation process is stopped, the still residue is disposed of, and the distillation products are sent to their destination.

Another method, as the object of the invention, is a method of purification by distillation of chloroform, which consists in loading technical chloroform into a cube, heating it in the cube to boiling point and sending the vapors to a distillation column and then to a reflux condenser, where they are condensed, condensate from the reflux condenser through the separator it is fed to the upper part of the distillation column in the form of reflux, which, in contact with chloroform vapor, condenses its highly volatile components; chloroform in the form of a liquid phase, enriched with highly volatile components, is sent back to the cube, thus forming a residue in the cube, and chloroform vapor, enriched with highly volatile non-condensed components, are sent to a reflux condenser, in which they are cooled and condensed, and then, after stabilizing the operation of the distillation column, part of the condensate is sent in the form of reflux to the distillation column, and the other part of the condensate as a distillation product is sent to a container for collecting distillation products, at in this case, the reflux ratio is maintained equal to 4, the loading of technical chloroform into the cube is carried out at room temperature of chloroform, while the pressure in the cube is maintained equal to atmospheric pressure, the chloroform is heated to a temperature of 60-65 ° C and within 30-40 minutes all the condensate from the reflux condenser is sent back to the distillation column in the form of reflux and the reflux flow is maintained from 110 to 130 dm 3 /h, and the condensate from the reflux condenser is fed into the distillation column through a separator, through which the aqueous intermediate fraction and pregon are taken from the condensate, and then a part is taken after the reflux condenser condensate - products of reactive qualifications into separate containers in the following sequence: “pure”, “pure for analysis”, “chemically pure”, and the selection of the specified condensate is carried out in the following quantities: aqueous intermediate fraction from 2.0 to 3.0% vol. pregon from 10 to 12% vol, “clean” - from 20 to 25% vol, “clean for analysis” - from 28 to 30% vol and “chemically pure” - from 12 to 15% vol, all based on the amount loaded into the cube chloroform, after which the distillation process is stopped, the bottom residue is disposed of, and the distillation products are sent to their destination.

Another method, as the object of the invention, is a method of purification by distillation of trichlorethylene, which consists in loading technical trichlorethylene into a cube, heating it in the cube to boiling point and sending the vapors to a distillation column and then to a reflux condenser, where they are condensed, and from reflux condensate through a separator is fed into the upper part of the distillation column in the form of reflux, which, in contact with trichlorethylene vapor, condenses its highly volatile components; trichlorethylene in the form of a liquid phase, enriched with highly volatile components, is sent back to the cube, thus forming a residue in the cube, and the vapor trichlorethylene, enriched with highly volatile non-condensed components, is sent to a reflux condenser, in which they are cooled and condensed, and then, after stabilizing the operation of the distillation column, part of the condensate is sent in the form of reflux to the distillation column, and the other part of the condensate as a distillation product is sent to a container for collecting the distillation product , while maintaining a reflux ratio of 4, loading technical trichlorethylene into the cube is carried out at room temperature of trichlorethylene, while the pressure in the cube is maintained equal to atmospheric pressure, trichlorethylene is heated to a temperature of 89-95 ° C and within 30-40 minutes all condensate from the reflux condenser is sent back to the distillation column in the form of reflux, the reflux flow is maintained from 100 to 120 dm 3 /h, and the condensate from the reflux condenser is fed into the distillation column through a separator, through which the aqueous intermediate fraction and pregon are taken from the condensate, and then taken after reflux condensate part of the condensate - products of reactive qualifications in separate containers in the following sequence: “pure”, “chemically pure”, “special purity”, and the selection of the said condensate is carried out in the following quantities: aqueous intermediate fraction from 1.0 to 2.0% vol. , pregon from 15 to 17% vol., “pure” - from 18 to 20% vol., “chemically pure” - from 28 to 30% vol. and “special purity” - from 10 to 12% vol., all from the amount loaded into the cube trichlorethylene, after which the distillation process is stopped, the bottom residue is disposed of, and the distillation products are sent to their destination.

Another method, as the object of the invention, is a method of purification by distillation of methylene chloride, which consists in loading technical methylene chloride into a cube, heating it in the cube to boiling point and sending the vapors to a distillation column and then to a reflux condenser, where they are condensed, and from the reflux condenser, the condensate is fed through a separator to the upper part of the distillation column in the form of reflux, which, in contact with methylene chloride vapor, condenses its highly volatile components; methylene chloride in the form of a liquid phase, enriched with highly volatile components, is sent back to the cube, thus forming a residue in the cube , and methylene chloride vapors, enriched with highly volatile non-condensed components, are sent to a reflux condenser, in which they are cooled and condensed, and then, after stabilizing the operation of the distillation column, part of the condensate is sent in the form of reflux to the distillation column, and the other part of the condensate as a distillation product is sent to containers to collect the distillation product, while maintaining a reflux ratio of 4, loading technical methylene chloride into the cube is carried out at room temperature of methylene chloride, while the pressure in the cube is maintained equal to atmospheric pressure, the original solvent is heated to a temperature of 40-44 ° C and for For 30-40 minutes, all condensate from the reflux condenser is sent back to the distillation column in the form of reflux and the reflux flow is maintained from 200 to 240 dm 3 /h, and the condensate from the reflux condenser is fed into the distillation column through a separator, through which the aqueous intermediate fraction is taken from the condensate and the pregon , and after that, after the reflux condenser, part of the condensate is selected - products of reactive qualifications into separate containers in the following sequence: “pure” and “chemically pure”, and the selection of the said condensate is carried out in the following quantities: aqueous intermediate fraction from 1 to 3% vol., pregon from 13 to 15% vol, “pure” - from 20 to 23.5% vol and “chemically pure” - from 45 to 50% vol, all based on the amount of methylene chloride loaded into the cube, after which the distillation process is stopped, the bottom residue is disposed of, and the distillation products are sent to their destination.

And another method of purification by distillation of perchlorethylene consists in loading technical perchlorethylene into a cube, heating it in the cube to boiling point and sending the vapors to a rectification column and then to a reflux condenser, where they are condensed, and from the reflux condenser the condensate is fed through a separator to the upper part distillation column in the form of phlegm, which, in contact with perchlorethylene vapor, condenses its highly volatile components, perchlorethylene in the form of a liquid phase, enriched with highly volatile components, is sent back to the cube, thus forming a residue in the cube, and perchlorethylene vapor, enriched with highly volatile non-condensed components, is sent into a reflux condenser, in which they are cooled and condensed, and then, after stabilizing the operation of the distillation column, part of the condensate is sent in the form of reflux to the distillation column, and the other part of the condensate as a distillation product is sent to a container for collecting the distillation product, while maintaining a reflux ratio equal to 4, technical perchlorethylene is loaded into the cube at room temperature perchlorethylene, while the pressure in the cube is maintained equal to atmospheric pressure, the perchlorethylene is heated to a temperature of 125-130 ° C and within 30-40 minutes all condensate from the reflux condenser is sent back to the distillation column in in the form of reflux, maintain a reflux flow from 120 to 150 dm 3 /h, and the condensate from the reflux condenser is fed into the rectification column through a separator, through which the aqueous intermediate fraction and pregon are taken from the condensate, and after that part of the condensate is taken after the reflux condenser - products of reactive qualifications in separate containers in the following sequence: “clean”, “chemically pure”, and the selection of the specified condensate is carried out in the following quantities: aqueous intermediate fraction from 2.0 to 5.0% vol., pregon from 7 to 9% vol., “clean” - from 40 to 43% by volume and “chemically pure” - from 38 to 40% by volume, all from the amount of perchlorethylene loaded into the cube, after which the distillation process is stopped, the bottom residue is disposed of, and the distillation products are sent to their destination.

In the course of the analysis, it was revealed that the implementation of the distillation column, reflux condenser and containers for collecting the distillation product from glass, for example from Simax glass, assembled from three drawers of the same height, hermetically connected to each other with a diameter ranging from 0.06 to 0.07 from height of the distillation column with a total height of the distillation column from 2800 to 3200 mm, allows you to obtain during rectification products of the qualification “chemically pure” and “pure for analysis” with a total yield of pure product up to 75% of its original quantity, which is quite economically justified. In addition, during the installation of the installation, materials were used, the use of which during rectification purification makes it possible to obtain products of reactive qualifications, namely a cast iron cube with an enamel coating and fluorine rubber gaskets at the joints of the installation structural elements.

In the course of the study, optimal conditions were obtained for purification by distillation of carbon tetrachloride, chloroform, trichlorethylene, methylene chloride and perchlorethylene. For carbon tetrachloride, the following parameters were set: reflux ratio equal to 4, loading the initial solvent into the cube at room temperature and heating the initial product to a temperature of 75-77°C. Heating to a lower temperature does not allow organizing the distillation process, and heating above the specified range does not allow achieving stable operation of the column. The operation of the distillation column “on its own” for 30-40 minutes, when all the condensate from the reflux condenser is sent back to the distillation column as reflux and the reflux flow is maintained from 180 to 200 l/h, allows you to achieve a stable operating mode, in which you can achieve the required degree of purification of carbon tetrachloride. The supply of condensate from the reflux condenser to the distillation column through a separator makes it possible to select the aqueous intermediate fraction and preheat from the condensate. All of the above allows you to begin the selection of reactive grade products after the reflux condenser into separate containers in the following sequence: “clean”, “clean for analysis”, “chemically pure”.

Considering the stable nature of the operation of the distillation column, it is possible to determine the amount of purified distillation product selected from each of the purity qualifications, namely selection in the following quantities: aqueous intermediate fraction from 2.0 to 2.5% vol., pre-distillation from 2 to 6% vol., “pure” ” - from 28 to 30% vol., “analytically pure” - from 25 to 28% vol. and “chemically pure” - from 28 to 30% vol., all based on the amount of the original solvent loaded.

In a similar way, the above operating modes were experimentally obtained for the purification by distillation of chloroform, trichlorethylene, methylene chloride and perchlorethylene. As a result, it was possible to solve the problem posed by the invention - to increase the efficiency of the installation for purification by distillation of organochlorine products and to carry out high-quality purification by distillation of carbon tetrachloride, chloroform, trichlorethylene, methylene chloride and perchlorethylene.

The drawing shows a schematic diagram of an installation for purification by distillation of organochlorine solvents.

The installation for purification by distillation of organochlorine solvents contains a cube 1 connected to the source of the original product, a periodic packed distillation column 2 installed on the latter and communicated with it, the top of which is connected to the reflux condenser 3, and the latter, from the exit side of it, is connected to the top of the distillation column 2, and to containers 4, 5, 6 for collecting the distillation product of reactive grade. The installation is additionally equipped with a separator 8 installed at the outlet of the reflux condenser 3 and connected to the distillation column 2 and containers 7, 9, respectively, for collecting the pre-run and selecting the aqueous intermediate fraction. Distillation column 2 is made of three glass frames of the same height, hermetically connected to each other using fluorine rubber gaskets. The diameter "D" of the packed distillation column is from 0.06 to 0.07 of the height "H" of the distillation column 2, with the height of the latter from 2800 to 3200 mm. Cube 1 is made of enameled cast iron, and containers 4, 5, 6 for collecting the distillation product are made of glass.

The purification method by distillation of carbon tetrachloride is carried out as follows. Carbon tetrachloride is loaded into cube 1, heated in cube 1 to the boiling point and the vapors are sent to the distillation column 2 and then the vapors are sent to the reflux condenser 3, where the vapors are condensed by cooling. Next, reflux is fed into the distillation column 2 from its top, which, in contact with carbon tetrachloride vapor, condenses the highly volatile components of carbon tetrachloride, thus forming a residue, the latter is sent back to the cube, and the carbon tetrachloride vapor with highly volatile non-condensed components is sent to the reflux condenser 3, in in which the volatile component is cooled and condensed. After this, part of the condensate is sent in the form of reflux to the distillation column 2, and the other part as a distillation product is sent to containers 4, 5, 6 for collecting the distillation product. During distillation, the reflux ratio is maintained at 4. Carbon tetrachloride is loaded into cube 1 at room temperature of carbon tetrachloride, while pressure in cube 1 is maintained at atmospheric pressure. Then carbon tetrachloride is heated to a temperature of 75-77°C and within 30-40 minutes all condensate from the reflux condenser 3 is sent back to the distillation column 2 in the form of reflux and the reflux flow is maintained from 180 to 200 dm 3 /h, and the condensate from the reflux condenser fed into the rectification column 2 through the separator 8, through which the aqueous intermediate fraction is taken from the condensate into a special container 9, and after that the selection is carried out after the preheat separator into the container 7 and then from the reflux condenser, the condensate - the product of reactive qualifications - is taken into separate containers in the following sequence : “clean” into container 4, “clean for analysis” into container 5 and “chemically pure” into container 6, and the selection of the said condensate is carried out in the following quantities: aqueous intermediate fraction from 2.0 to 2.5% vol., pregon from 2 to 6% vol, “pure” - from 28 to 30% vol, “pure for analysis” - from 25 to 28% vol and “chemically pure” - from 28 to 30% vol, all from the amount of 1 tetrachloride loaded into the cube carbon. After this, the distillation process is stopped, the bottom residue is disposed of, and the distillation products are sent to their destination.

In a similar way, but taking into account the above-mentioned operating parameters and parameters for selecting rectification products, chloroform, trichlorethylene, methylene chloride and perchlorethylene are purified.

The initial raw material is technical carbon tetrachloride GOST 4-84 “Higher” and “First grade”, a collection container is loaded from barrels under vacuum (P = 0.5 at).

Cube 1 is heated by steam (P=0.7-1.2 at).

Carbon tetrachloride vapor rises through the packed part of distillation column 2, and then passes through a steam line, the temperature of the vapor in which is measured by a thermometer (t=75-77°C). After passing through the steam line, the vapors condense in dephlegmator 3, cooled with cold water.

Condensed vapors enter separator 8 and return back to distillation column 2. Reflux return 180-200 dm 3 /hour. Distillation column 2 operates in self-propelled mode for 30-40 minutes.

During the operation of distillation column 2, the aqueous intermediate fraction accumulating in the upper layer of separator 8 is selected, for which the valve is opened and the aqueous fraction is poured into collection 9. As water is withdrawn, the product in separator 8 gradually becomes clearer. Distillation column 2 works “on its own” until carbon tetrachloride is completely clarified.

The number of selections depends on the quality of the feedstock, namely the presence of water in it, and ranges in volume from 8 to 10 dm 3.

After the distillation column 2 operates “on its own”, the selection of preheat in a volume of 8-24 dm 3 begins. The valve is opened and the pregon enters the collection (tank) 7. After the pregon is taken, the temperature in the upper part of the distillation column changes. When the temperature in the two subsequent pre-run selections changes within 1-0.5°C and a positive laboratory analysis is obtained, you can proceed to the selection of the finished product.

First, a “pure” product is selected in an amount of 112-120 dm 3 into container (collector) 4, for which the valves at its inlet are opened, then a “pure for analysis” product is selected in an amount of 100-112 dm 3, for this the valve is closed on container 4 and open the valve on container 5. Having filled container 5, close the valve on this container and open the valve on container 6 to select a “chemically pure” product in an amount of 112-120 dm 3. Having finished selecting the finished product, close the valves at the outlet of the reflux condenser.

To complete the operation of the column, stop the supply of steam to the jacket of cube 1. Cool the top of the distillation column 2 to room temperature, then turn off the water on the reflux condenser 3. The cube is cooled to 30°C. The pre-run, product and bottom residue are subjected to physical and chemical methods of quality analysis. The bottom residue is poured into waste barrels. Distillation column 2 begins to be prepared for the next start-up, as described above.

The feedstock (chloroform GOST 20015-88, highest and first grade or technical) is loaded from collection barrels under vacuum (P = 0.5 at). Of the latter, the feedstock is poured into the cube in an amount of 400 dm 3.

Chloroform vapor rises through the packed part of distillation column 2, passes through a steam line, the temperature of the vapor in which is measured by a thermometer (t=60-65°C). After passing through the steam line, the vapors condense in dephlegmator 3, cooled with cold water.

The condensed vapors enter separator 8 and return back to distillation column 2. Column 2 operates in “self-propelled” mode for 30-40 minutes.

During the operation of the column “on its own”, the aqueous intermediate fraction accumulating in the upper layer of the separator 8 is selected, for which the valve at the entrance to the container (collector) 9 is opened. The number of selections depends on the quality of the feedstock, namely on the presence of water in it. The total amount of selection is 8-12 dm 3.

After the column works “on itself”, the selection of pre-run begins in a volume of 40-48 dm 3. The pre-gap enters container 7. After the pre-gap is collected (the average temperature in the cube is 62°C, and in the upper part of the distillation column is 61.2°C), the selection of the commercial product begins.

First, a “pure” product is selected in an amount of 80-100 dm 3 into container 4, for which we open the valves at its inlet, then a “pure for analysis” product is selected in an amount of 112-120 dm 3, for this we close the valve on container 4 and open the valve on container 5. Having filled container 5, close the valve on this container 5 and open the valve on container 6 to select a “chemically pure” product in a volume of 48-60 dm 3 . Having finished selecting the finished product, close the valves.

To complete the operation of distillation column 2, the supply of steam to the jacket of cube 1 is stopped. Cube 1 is cooled with water through the jacket. Cool the top of the distillation column 2 to room temperature, then turn off the cooling water at the reflux condenser 3. The cube is cooled to 30°C. Preliminarily, the product and bottom residue are subjected to physical and chemical methods of quality analysis; 21 dm 3 of chloroform is used for washing. The bottom residue is poured into waste barrels. Predrain is poured into waste barrels. The product from containers 4, 5, 6 is sent for packaging, having previously been stabilized with ethyl alcohol (1% by weight of the finished product), the column begins to be prepared for the next start-up, as described above.

The feedstock (technical trichlorethylene) is loaded from collection barrels under vacuum (P=0.5 at). Of the latter, the feedstock is poured into the cube in an amount of 400 dm 3.

Before starting work, the columns open the air line. Cube 1 is heated with steam (P=0.5 at). Why open the corresponding valve on the steam supply line from the steam generator and the valve for extracting steam condensate.

Trichlorethylene vapor rises through the packed part of distillation column 2, passes through a steam line, the temperature of the vapor in which is measured by a thermometer (t=89-95°C). After passing through the steam line, the vapors condense in dephlegmator 3, cooled with cold water.

The condensed vapors enter separator 8 and return back to distillation column 2. Column 2 operates in “self-propelled” mode for 30-40 minutes. Reflux consumption is 100-120 dm 3 /h.

After the column works “on itself”, the selection of preheat in a volume of 60-68 dm 3 begins. The pre-heat enters container 7. After selecting the pre-run, the selection of the commercial product begins.

First, a “pure” product is selected in an amount of 72-80 dm 3 into container 4, for which the valves at its inlet are opened, then a “chemically pure” product is selected in an amount of 112-120 dm 3, for this the valve on container 4 is closed and open the valve on container 5. Having filled container 5, close the valve on this container 5 and open the valve on container 6 to select a product of the “special pure” qualification in a volume of 40-48 dm 3 . Having finished selecting the finished product, close the valves.

To complete the operation of distillation column 2, the supply of steam to the jacket of cube 1 is stopped. Cube 1 is cooled with water through the jacket. Cool the top of the distillation column 2 to room temperature, then turn off the cooling water at the reflux condenser 3. The cube is cooled to 30°C. Preliminarily, the product and bottom residue are subjected to physical and chemical methods of quality analysis. The bottom residue is poured into waste barrels. Predrain is poured into waste barrels. The product from containers 4, 5, 6 is sent for packaging, and the column begins to be prepared for the next start-up, as described above.

The feedstock (technical methylene chloride) is loaded from collection barrels under vacuum (P=0.5 at). Of the latter, the feedstock is poured into the cube in an amount of 400 dm 3.

Methylene chloride vapor rises through the packed part of distillation column 2, passes through a steam line, the temperature of the vapor in which is measured by a thermometer (t=40-44°C). After passing through the steam line, the vapors condense in dephlegmator 3, cooled with cold water.

The condensed vapors enter separator 8 and return back to distillation column 2. Column 2 operates in “self-propelled” mode for 30-40 minutes. Reflux consumption is 200-240 dm 3 /h.

During the operation of the column, the aqueous intermediate fraction accumulating in the upper layer of the separator 8 is selected, for which the valve at the entrance to the container (collector) 9 is opened. The number of selections depends on the quality of the feedstock, namely the presence of water in it. The total amount of selection is 4-12 dm 3.

After the column works “on its own”, the selection of preheat in a volume of 52-60 dm 3 begins. The pre-heat enters container 7. After selecting the pre-run, the selection of the commercial product begins.

First, a “pure” product is selected in an amount of 80-94 dm 3 into container 4, for which the valves at its inlet are opened, then a “chemically pure” product is selected in an amount of 180-200 dm 3, for this the valve on container 4 is closed and open the valve on container 5. Having finished selecting the finished product, close the valves.

The feedstock (technical perchlorethylene) is loaded from collection barrels under vacuum (P=0.5 at). Of the latter, the feedstock is poured into the cube in an amount of 400 dm 3.

Perchlorethylene vapor rises through the packed part of distillation column 2, passes through a steam line, the temperature of the vapor in which is measured by a thermometer (t=125-130°C). After passing through the steam line, the vapors condense in dephlegmator 3, cooled with cold water.

The condensed vapors enter separator 8 and return back to distillation column 2. Column 2 operates in “self-propelled” mode for 30-40 minutes. The reflux consumption is 120-150 dm 3 /h.

After the column works “on its own”, the selection of preheat in a volume of 28-36 dm 3 begins. The pre-heat enters container 7. After selecting the pre-run, the selection of the commercial product begins.

First, a “pure” product is selected in an amount of 160-172 dm 3 into container 4, for which the valves at its inlet are opened, then a “chemically pure” product is selected in an amount of 152-160 dm 3, for this the valve on container 4 is closed and open the valve on container 5. Having finished selecting the finished product, close the valves.

To complete the operation of distillation column 2, the supply of steam to the jacket of cube 1 is stopped. Cube 1 is cooled with water through the jacket. Cool the top of the distillation column 2 to room temperature, then turn off the cooling water at the reflux condenser 3. The cube is cooled to 30°C. Preliminarily, the product and bottom residue are subjected to physical and chemical methods of quality analysis. The bottom residue is poured into waste barrels. Predrain is poured into waste barrels. The product from containers 4, 5 is sent for packaging, the column begins to be prepared for the next start-up, as described above.

The present invention can be used in the chemical and perfume industries.

CLAIM

1. An installation for purification by distillation of organochlorine solvents, containing a cube connected to the source of the initial solvent, a packed periodic distillation column installed on the latter and communicated with it, the top of which is connected to a reflux condenser, and the latter, from the outlet side of it, is connected to the top of the distillation column and to tanks for collecting the distillation product, characterized in that the installation is additionally equipped with at least two tanks for selecting products of reactive qualifications and a separator installed at the outlet of the reflux condenser and connected to the distillation column and tanks for collecting the aqueous intermediate fraction and pre-run through the separator, the distillation column is made up of three glass frames of the same height, hermetically connected to each other, and the diameter of the packed distillation column is from 0.06 to 0.07 of the height of the distillation column with the height of the latter from 2800 to 3200 mm, the cube is made of enameled cast iron, and the reflux condenser and containers for collecting distillation products are made of glass.

2. A method of purification by distillation of carbon tetrachloride, which consists in loading technical carbon tetrachloride (CTC) into a cube, heating it in the cube to boiling point and sending the vapors to a distillation column and then to a reflux condenser, where they are condensed, and condensate from the reflux condenser through a separator is supplied to the upper part of the distillation column in the form of reflux, which, in contact with the vapors of the ChCU, condenses its highly volatile components; the ChCC in the form of a liquid phase, enriched with the highly volatile components, is sent back to the cube, thus forming a residue in the cube, and the vapors of the ChCC, enriched with the highly volatile non-condensed components are sent to a reflux condenser, in which they are cooled and condensed, and then, after stabilizing the operation of the distillation column, part of the condensate is sent in the form of reflux to the distillation column, and the other part of the condensate as a distillation product is sent to a container for collecting the distillation product, characterized in that that the reflux number is maintained equal to 4, the loading of technical CCU into the cube is carried out at room temperature of the CCU, while the pressure in the cube is maintained equal to atmospheric pressure, the CCC is heated to a temperature of 75-77°C and within 30-40 minutes all condensate from the reflux condenser is sent back into the distillation column in the form of reflux and maintain the reflux flow from 180 to 200 dm 3 /h, and the condensate from the reflux condenser is fed into the distillation column through a separator, through which the aqueous intermediate fraction and pre-head are taken from the condensate, and then part of the condensate is taken after the reflux condenser - products of reactive qualifications into separate containers in the following sequence: “pure”, “pure for analysis”, “chemically pure”, and the selection of the specified condensate is carried out in the following quantities: aqueous intermediate fraction from 2.0 to 2.5 vol.%, pre-run from 2 to 6 vol.%, “pure” - from 28 to 30 vol.%, “pure for analysis” - from 25 to 28 vol.% and “chemically pure” - from 28 to 30 vol.%, all depending on the quantity CHU loaded into the still, after which the distillation process is stopped, the still residue is disposed of, and the distillation products are sent to their destination.

3. A method of purification by distillation of chloroform, which consists in loading technical chloroform into a cube, heating it in the cube to boiling point and sending the vapors to a rectification column and then to a reflux condenser, where they are condensed; from the reflux condenser, the condensate is fed through a separator to the upper part of the rectification columns in the form of reflux, which, in contact with chloroform vapor, condenses its highly volatile components, chloroform in the form of a liquid phase, enriched with highly volatile components, is sent back to the cube, thus forming a residue in the cube, and chloroform vapor, enriched with highly volatile non-condensed components, is sent to a reflux condenser in which they are cooled and condensed, and then, after stabilizing the operation of the distillation column, part of the condensate is sent in the form of reflux to the distillation column, and the other part of the condensate as a distillation product is sent to a container for collecting the distillation product, characterized in that the reflux number is maintained equal 4, the loading of technical chloroform into the cube is carried out at room temperature of chloroform, while the pressure in the cube is maintained equal to atmospheric pressure, the chloroform is heated to a temperature of 60-65 ° C and within 30-40 minutes all condensate from the reflux condenser is sent back to the distillation column in the form reflux and maintain a reflux flow from 110 to 130 dm 3 /h, and the condensate from the reflux condenser is fed into the rectification column through a separator, through which the aqueous intermediate fraction and pregon are taken from the condensate, and after that part of the condensate is taken after the reflux condenser - products of reactive qualifications into separate containers in the following sequence: “clean”, “clean for analysis”, “chemically pure”, and the selection of the specified condensate is carried out in the following quantities: aqueous intermediate fraction from 2.0 to 3.0 vol.%, preheat from 10 to 12 vol. .%, “pure” - from 20 to 25 vol.%, “pure for analysis” - from 28 to 30 vol.% and “chemically pure” - from 12 to 15 vol.%, all based on the amount of chloroform loaded into the cube, after this, the distillation process is stopped, the bottom residue is disposed of, and the distillation products are sent to their destination.

4. A method for purifying the distillation of trichlorethylene, which consists in loading technical trichlorethylene into a cube, heating it in the cube to boiling point and sending the vapors to a distillation column and then to a reflux condenser, where they are condensed, and from the reflux condenser the condensate is fed through a separator to the upper part distillation column in the form of reflux, which, in contact with trichlorethylene vapor, condenses its highly volatile components, trichlorethylene in the form of a liquid phase, enriched with highly volatile components, is sent back to the cube, thus forming a residue in the cube, and trichlorethylene vapor, enriched with highly volatile non-condensed components, is sent to a reflux condenser in which they are cooled and condensed, and then, after stabilizing the operation of the distillation column, part of the condensate is sent in the form of reflux to the distillation column, and the other part of the condensate as a distillation product is sent to a container for collecting the distillation product, characterized in that the reflux number is maintained equal 4, technical trichlorethylene is loaded into the cube at room temperature of trichlorethylene, while the pressure in the cube is maintained equal to atmospheric pressure, trichlorethylene is heated to a temperature of 89-95 ° C and within 30-40 minutes all condensate from the reflux condenser is sent back to the distillation column in the form reflux and maintain a reflux flow from 100 to 120 dm 3 /h, and the condensate from the reflux condenser is fed into the distillation column through a separator, through which the aqueous intermediate fraction and pre-head are taken from the condensate, and after that part of the condensate is taken after the reflux condenser - products of reactive qualifications into separate containers in the following sequence: “pure”, “chemically pure”, “special purity”, and the selection of the specified condensate is carried out in the following quantities: aqueous intermediate fraction from 1.0 to 2.0 vol.%, preheat from 15 to 17 vol. %, “pure” - from 18 to 20 vol.%, “chemically pure” - from 28 to 30 vol.% and “special purity” - from 10 to 12 vol.%, all from the amount of trichlorethylene loaded into the cube, after that the distillation process is stopped, the bottom residue is disposed of, and the distillation products are sent to their destination.

5. A method of purification by distillation of methylene chloride, which consists in loading technical methylene chloride into a cube, heating it in the cube to boiling point and sending the vapors to a distillation column and then to a reflux condenser, where they are condensed, and from the reflux condenser the condensate is fed through a separator to the upper part of the distillation column in the form of reflux, which, in contact with methylene chloride vapor, condenses its highly volatile components, methylene chloride in the form of a liquid phase, enriched with highly volatile components, is sent back to the cube, thus forming a residue in the cube, and methylene chloride vapor, enriched highly volatile non-condensed components are sent to a reflux condenser, in which they are cooled and condensed, and then, after stabilizing the operation of the distillation column, part of the condensate is sent in the form of reflux to the distillation column, and the other part of the condensate as a distillation product is sent to a container for collecting the distillation product, characterized in that that maintain the reflux ratio equal to 4, the loading of technical methylene chloride into the cube is carried out at room temperature of methylene chloride, while the pressure in the cube is maintained equal to atmospheric pressure, the initial solvent is heated to a temperature of 40-44 ° C and within 30-40 minutes the entire condensate from the reflux condenser is sent back to the distillation column in the form of reflux and the reflux flow is maintained from 200 to 240 dm 3 /h, and the condensate from the reflux condenser is fed into the distillation column through a separator, through which the aqueous intermediate fraction and pregon are taken from the condensate, and then taken after dephlegmator, part of the condensate - products of reactive qualifications in separate containers in the following sequence: “pure” and “chemically pure”, and the selection of the said condensate is carried out in the following quantities: aqueous intermediate fraction from 1 to 3 vol.%, preheat from 13 to 15 vol. %, “pure” - from 20 to 23.5 vol.% and “chemically pure” - from 45 to 50 vol.%, all from the amount of methylene chloride loaded into the cube, after which the distillation process is stopped, the bottom residue is disposed of, and the products distillations are directed to their destination.

6. A method of purification by distillation of perchlorethylene, which consists in loading technical perchlorethylene into a cube, heating it in the cube to boiling point and sending the vapors to a distillation column and then to a reflux condenser, where they are condensed, and from the reflux condenser the condensate is fed through a separator to the upper part distillation column in the form of phlegm, which, in contact with perchlorethylene vapor, condenses its highly volatile components, perchlorethylene in the form of a liquid phase, enriched with highly volatile components, is sent back to the cube, thus forming a residue in the cube, and perchlorethylene vapor, enriched with highly volatile non-condensed components, is sent into a reflux condenser, in which they are cooled and condensed, and then, after stabilizing the operation of the distillation column, part of the condensate is sent in the form of reflux to the distillation column, and the other part of the condensate as a distillation product is sent to a container for collecting the distillation product, characterized in that the reflux ratio is maintained equal to 4, the loading of technical perchlorethylene into the cube is carried out at room temperature perchlorethylene, while the pressure in the cube is maintained equal to atmospheric pressure, the perchlorethylene is heated to a temperature of 125-130 ° C and within 30-40 minutes all condensate from the reflux condenser is sent back to the distillation column in in the form of reflux and maintain a reflux flow from 120 to 150 dm 3 /h, and the condensate from the reflux condenser is fed into the distillation column through a separator, through which the aqueous intermediate fraction and pregon are taken from the condensate, and after that part of the condensate is taken after the reflux condenser - products of reactive qualifications in separate containers in the following sequence: “clean”, “chemically pure”, and the selection of the specified condensate is carried out in the following quantities: aqueous intermediate fraction from 2.0 to 5.0 vol.%, pregon from 7 to 9 vol.%, “clean ” - from 40 to 43 vol.% and “chemically pure” - from 38 to 40 vol.%, all from the amount of perchlorethylene loaded into the cube, after which the distillation process is stopped, the bottom residue is disposed of, and the distillation products are sent to their destination.

Methods for purifying organic solvents depend on the nature and purpose of the solvent. In most cases, organic solvents are individual compounds and can be characterized by their physicochemical properties. The most basic solvent purification operation is simple or fractional distillation. However, distillation often fails to get rid of a number of impurities, including small amounts of water.

Traditional purification methods can produce a solvent that is approximately 100% pure. With the help of adsorbents, in particular molecular sieves (zeolites), this problem is solved more efficiently and with less time. In laboratory conditions, ion exchangers are most often used for this purpose - zeolites of the NaA or KA brands.

When preparing pure anhydrous solvents, precautions should be taken especially strictly, since most organic solvents are flammable substances, the vapors of which form explosive mixtures with air, and in some of them (ethers) explosive peroxide compounds are formed during long-term storage. Many organic solvents are highly toxic, both when their vapors are inhaled and when they come into contact with the skin.

All operations with flammable and combustible organic solvents must be carried out in a fume hood with ventilation running, gas burners and electric heating devices turned off. Liquids should be heated and distilled in a fume hood in preheated baths filled with an appropriate coolant. When distilling organic liquids, it is necessary to constantly monitor the operation of the refrigerator.

If flammable solvents (gasoline, diethyl ether, carbon disulfide, etc.) are accidentally spilled, it is necessary to immediately extinguish all open flame sources and turn off electrical heating devices (de-energize the work area during the day). The area where the liquid has been spilled should be covered with sand, the contaminated sand should be collected with a wooden scoop and poured into a garbage container placed outdoors.

When drying solvents, active drying agents should not be used until preliminary rough drying has been carried out using conventional drying agents. Thus, it is forbidden to dry crude diethyl ether with sodium metal without first drying it with calcined CaCl2.

When working with ethers and other substances (diethyl ether, dioxane, tetrahydrofuran), during storage of which peroxide compounds can form, peroxides are first removed from them, and then distilled and dried. Anhydrous organic solvents must be distilled carefully. All elements of the distillation installation (distillation flask, reflux condenser, refrigerator, still, distillate receiver) are pre-dried in an oven. The distillation is carried out without access to air, and the distillation is provided with a calcium chloride tube filled with ascarite and fused CaCl2 to absorb CO2 and H2O. It is advisable to discard the first portion of distillate, which serves to wash all equipment.

Methods for purification and dehydration of the most commonly used solvents are discussed below.

Acetone

Acetone CH3COCH3 is a colorless liquid; d25-4 = 0.7899; tboil = 56.24 °C; n20-D = 1.3591. Highly flammable. Vapors form explosive mixtures with air. Technical acetone usually contains water, with which it is mixed in any proportion. Sometimes acetone is contaminated with methyl alcohol, acetic acid and reducing agents.

A test for the presence of reducing substances in acetone is carried out as follows. To 10 ml of acetone add 1 drop of 0.1% aqueous solution of KMnO4; After 15 minutes at room temperature, the solution should not become discolored.

To purify, acetone is heated for several hours with anhydrous K2CO3 (5% (wt.)) in a flask with reflux, then the liquid is poured into another flask with a reflux condenser 25-30 cm high and distilled over anhydrous K2CO3 (about 2% (wt.)) ) and crystalline KMnO4, which is added to acetone until a stable purple color appears in a water bath. The resulting acetone no longer contains methyl alcohol, but contains a small amount of water.

To completely remove water, acetone is redistilled over anhydrous CaCl2. To do this, pour 1 liter of acetone into a 2-liter round-bottomed flask equipped with an effective reflux condenser closed with a calcium chloride tube containing CaCl2, add 120 g of CaCl2 and boil in a water bath with closed electric heating for 5-6 hours. Then the reaction flask is cooled and acetone is poured in into another similar flask with a fresh portion of CaCl2 and boil again for 5-6 hours. After this, the reflux condenser is replaced with a downward condenser, to which, using a longge connected to a calcium chloride tube filled with CaCl2, a receiver bottle cooled with ice is attached, and acetone is distilled over CaCl2.

Instead of such a lengthy and labor-intensive operation, which often leads to condensation of acetone, it is better to use NaA zeolite. By keeping acetone over this zeolite for a long time (5% (mass)), acetone is absolutized.

In small quantities, very pure acetone can be obtained from the adduct (addition product) of acetone and NaI, which decomposes even with low heating, releasing acetone. To do this, when heating in a water bath, dissolve 100 g of NaI in 440 ml of dry, freshly distilled acetone. The resulting solution is quickly cooled to -3°C by immersing the vessel in a mixture of ice and NaCl. The separated solid NaI-C3H6O adduct is separated on a Buchner funnel, transferred to a distillation flask and heated in a water bath. When heated slightly, the adduct decomposes and the released acetone is distilled off. The distillate is dried with anhydrous CaCl2 and re-distilled with a reflux condenser over CaCl2. The regenerated NaI can be reused for the same reaction.

An express method for purifying acetone from methyl alcohol and reducing substances is as follows: add a solution of 3 g of AgNO3 to 700 ml of acetone in a 1-liter flask. in 20 ml of distilled water and 20 ml of 1 N. NaOH solution. The mixture is shaken for 10 minutes, after which the precipitate is filtered off on a funnel with a glass filter, and the filtrate is dried with CaSO4 and distilled with a reflux condenser over CaCl2.

Acetonitrile

Acetonitrile CH3CN is a colorless liquid with a characteristic ethereal odor; d20-4 = 0.7828; tboil = 81.6°C; n20-D = 1.3442. It is miscible with water in all respects and forms an azeotropic mixture (16% (wt.) H2O) with boiling point = 76°C. A good solvent for a number of organic substances, in particular amine hydrochlorides. It is also used as a medium for carrying out certain reactions, which it accelerates catalytically.

Acetonitrile is a strong inhalation poison and can be absorbed through the skin.

For absolutization, acetonitrile is distilled twice over P4O10, followed by distillation over anhydrous K2CO3 to remove traces of P4O10.

You can pre-dry acetonitrile over Na2SO4 or MgSO4, then mix it with CaH2 until the evolution of gas (hydrogen) stops and distill it over P4O10 (4-5 g/l). The distillate is refluxed over CaH2 (5 g/l) for at least 1 hour, then slowly distilled, discarding the first 5 and last 10% of the distillate.

Benzene

Benzene C6H6 is a colorless liquid; d20-4 = 0.8790; tmelt = 5.54 °C; tboil = 80 10°С; n20-D = 1.5011. Benzene and its homologues - toluene and xylenes - are widely used as solvents and media for azeotropic drying. Benzene should be handled with caution due to its flammability and toxicity, as well as the formation of explosive mixtures with air.

Benzene vapors with repeated exposure disrupt the normal function of the hematopoietic organs; in its liquid state, benzene is strongly absorbed through the skin and irritates it.

Technical benzene contains up to 0.02% (wt.) water, a little thiophene and some other impurities.

Benzene forms an azeotropic mixture with water (8.83% (mass) H2O) with boiling point = 69.25°C. Therefore, when distilling wet benzene, the water is almost completely distilled off with the first portions of the distillate (turbid liquid), which are discarded. As soon as the clear distillate begins to distill, the drying process can be considered complete. Additional drying of distilled benzene is usually carried out with calcined CaCl2 (for 2-3 days) and sodium wire.

In the cold season, care must be taken to ensure that the distilled benzene does not crystallize in the refrigerator tube, washed with cold water (4-5°C).

Benzene and other hydrocarbons dried with sodium metal are hygroscopic, meaning they can absorb moisture.

Commercial technical benzene contains up to 0.05% (mass) of thiophene C4H4S (tbp = 84.12°C; tm = 38.3°C), which cannot be separated from benzene either by fractional distillation or crystallization (freezing). Thiophene in benzene is detected as follows: a solution of 10 mg of isatin in 10 ml of conc. H2SO4 is shaken with 3 ml of benzene. In the presence of thiophene, the sulfuric acid layer turns blue-green.

Benzene is purified from thiophene by repeated shaking with conc. H2SO4 at room temperature. Under these conditions, thiophene is preferentially sulfonated rather than benzene. For 1 liter of benzene take 80 ml of acid. The first portion of H2SO4 turns blue-green. The bottom layer is separated, and benzene is shaken with a new portion of acid. Purification is carried out until a faint yellow color of the acid is achieved. After separating the acid layer, the benzene is washed with water, then with a 10% Na2CO3 solution and again with water, after which the benzene is distilled.

A more effective and simpler method for purifying benzene from thiophene is to boil 1 liter of benzene with 100 g of Raney nickel in a flask under reflux for 15-30 minutes.

Another way to purify benzene from thiophene is to fractionally crystallize it from ethyl alcohol. A saturated solution of benzene in alcohol is cooled to approximately -15°C, solid benzene is quickly filtered off and distilled.

Dimethyl sulfoxide

Dimethyl sulfoxide (CH3)2SO is a colorless, syrupy liquid without a distinct odor; d25-4 = 1.1014; tboil = 189°С (with decomposition); tmelt = 18.45 °C; n25-D = 1.4770. Miscible with water, alcohols, acetone, ethyl acetone, dioxane, pyridine and aromatic hydrocarbons, but immiscible with aliphatic hydrocarbons. A universal solvent for organic compounds: ethylene oxide, heterocyclic compounds, camphor, resins, sugars, fats, etc. It also dissolves many inorganic compounds, for example, at 60°C it dissolves 10.6% (wt.) KNO3 and 21.8% CaCl2. Dimethyl sulfoxide is practically non-toxic.

For purification, dimethyl sulfoxide is kept for 24 hours over active Al2O3, after which it is distilled twice at a pressure of 267-400 Pa (2-3 mmHg) over fused KOH (or BaO) and stored over NaA zeolite.

Under the influence of reducing agents, dimethyl sulfoxide is converted into (CH3)2S sulfide, and under the influence of oxidizing agents - into (CH3)2SO2 sulfone; it is incompatible with acid chlorides of inorganic and organic acids.

N,N-Dimethylformamide

N,N-Dimethylformamide HCON(CH3)2 is a colorless, highly mobile liquid with a weak specific odor; d25-4 = 0.9445; tboil = 153°C; n24-D = 1.4269. Miscible in any ratio with water, alcohol, acetone, ether, chloroform, carbon disulfide, halogen-containing and aromatic compounds; dissolves aliphatic hydrocarbons only when heated.

Dimethylformamide is distilled at atmospheric pressure without decomposition; decomposes under the influence of ultraviolet rays to form dimethylamine and formaldehyde. The dimethylformamide reagent, in addition to methylamine and formaldehyde, may contain methylformamide, ammonia and water as impurities.

Dimethylformamide is purified as follows: 10 g of benzene and 4 ml of water are added to 85 g of dimethylformamide and the mixture is distilled. First, benzene is distilled off with water and other impurities, and then the pure product.

Diethyl ether

Diethyl ether (C2H5)2O is a colorless, highly mobile, volatile liquid with a peculiar odor; d20-4 = 0.7135; tboil = 35.6°C; n20-D = 1.3526. Extremely flammable; vapors form explosive mixtures with air. Vapors are approximately 2.6 times heavier than air and can spread across the surface of the desktop. Therefore, it is necessary to ensure that all gas burners nearby (up to 2-3 m) from the place of work with ether are extinguished, and electric stoves with an open spiral are disconnected from the network.

When diethyl ether is stored under the influence of light and atmospheric oxygen, explosive peroxide compounds and acetaldehyde are formed in it. Peroxide compounds cause extremely violent explosions, especially when trying to distill ether to dryness. Therefore, when determining the boiling point and non-volatile residue, the ether should first be checked for the content of peroxides. In the presence of peroxides, these determinations cannot be made.

Many reactions have been proposed for the detection of peroxide in diethyl ether.

1. Reaction with potassium iodide KI. A few milliliters of ether are shaken with an equal volume of a 2% aqueous solution of KI, acidified with 1-2 drops of HCl. The appearance of a brown color indicates the presence of peroxides.

2. Reaction with titanyl sulfate TiOSO4. The reagent is prepared by dissolving 0.05 g of TiOSO4 in 100 ml of water, acidified with 5 ml of diluted H2SO4 (1:5). When shaking 2-3 ml of this reagent with 5 ml of the test ether containing peroxide compounds, a yellow color appears.

3. Reaction with sodium bichromate Na2Cr2O7. To 3 ml of ether add 2-3 ml of a 0.01% aqueous solution of Na2Cr2O7 and one drop of diluted H2SO4 (1:5). The mixture is shaken vigorously. The blue color of the ether layer indicates the presence of peroxides.

4. Reaction with ferrothiocyanate Fe(SCN)2. A colorless solution of Fe(SCN)2, when exposed to a drop of liquid containing peroxide, turns red due to the formation of ferrithiocyanate (Fe2+ > Fe3+). This reaction allows the detection of peroxides at concentrations up to 0.001% (wt). The reagent is prepared as follows: 9 g of FeSO4-7H2O is dissolved in 50 ml of 18% HCl. Add granulated zinc and 5 g of sodium thiocyanate NaSCN to the solution in an open vessel; after the red color disappears, add another 12 g of NaSCN, shake gently and the solution is separated by decantation.

To remove peroxides, iron (II) sulfate is used. When shaking 1 liter of ether, usually take 20 ml of a solution prepared from 30 g of FeSO4-7H2O, 55 ml of H2O and 2 ml of conc. H2SO4. After washing, the ether is shaken with a 0.5% KMnO4 solution to oxidize acetaldehyde into acetic acid. Then the ether is washed with a 5% NaOH solution and water, dried for 24 hours over CaCl2 (150-200 g CaCl2 per 1 liter of ether). After this, CaCl2 is filtered on a large folded paper filter and the ether is collected in a dark glass bottle. The bottle is tightly closed with a cork stopper with a calcium chloride tube bent at an acute angle inserted into it, filled with CaCl2 and glass wool swabs. Then, opening the bottle, quickly add sodium wire into the ether at the rate of 5 g per 1 liter of ether.

After 24 hours, when hydrogen bubbles stop evolving, add another 3 g of sodium wire per 1 liter of ether and after 12 hours the ether is poured into a distillation flask and distilled over the sodium wire. The receiver must be protected by a calcium chloride tube containing CaCl2. The distillate is collected in a dark glass flask, which, after adding 1 g of sodium wire per 1 liter of ether, is closed with a cork stopper with a calcium chloride tube and stored in a cool and dark place.

If the surface of the wire has changed significantly and when adding wire, hydrogen bubbles are released again, then the ether should be filtered into another bottle and another portion of sodium wire should be added.

A convenient and very effective way to purify diethyl ether from peroxides and at the same time from moisture is to pass the ether through a column with active Al2O3. A column 60-80 cm high and 2-4 cm in diameter, filled with 82 g of Al2O3, is sufficient to purify 700 ml of ether containing a significant amount of peroxide compounds. Spent Al2O3 can be easily regenerated if a 50% acidified aqueous solution of FeSO4-7H2O is passed through a column, washed with water, dried and thermally activated at 400-450 °C.

Absolute ether is a very hygroscopic liquid. The degree of moisture absorption by ether during its storage can be judged by the bluing of anhydrous white CuSO4 powder when it is added to ether (a colored hydrate CuSO4-5H2O is formed).

Dioxane

Dioxane (CH2)4O is a colorless flammable liquid with a slight odor; d20-4 = 1.03375; tboil = 101.32 °C; tmelt = 11.80° C; n20-D = 1.4224. Miscible with water, alcohol and ether in any ratio. Forms azeotropic mixtures with water and alcohol.

Technical dioxane contains ethylene glycol acetal, water, acetaldehyde and peroxides as impurities. The method for purifying dioxane should be chosen depending on the degree of its contamination, which is determined by adding sodium metal to the dioxane. If a brown precipitate is formed, then the dioxane is highly contaminated; if the surface of the sodium changes slightly, then dioxane contains few impurities and is purified by distilling over a sodium wire.

Heavily contaminated dioxane is purified as follows: 0.5 l dioxane, 6 ml conc. HCl and 50 ml of H2O are heated in a silicone (oil) bath in a stream of nitrogen in a flask with reflux at 115-120 °C for 12 hours.

Once cooled, the liquid is shaken with small portions of fused KOH to remove water and acid. Dioxane forms the top layer, it is separated and dried with a fresh portion of KOH. The dioxane is then transferred to a clean distillation flask and refluxed over 3-4 g of sodium wire for 12 hours. The purification is complete if the surface of the sodium remains unchanged. If all the sodium has reacted, then you need to add a fresh portion and continue drying. Dioxane, which does not contain peroxide compounds, is distilled on a column or with an effective reflux condenser at normal pressure. The purification of dioxane from peroxides is carried out in the same way as the purification of diethyl ether.

Methyl alcohol (methanol)

Methyl alcohol (methanol) CH3OH is a colorless, highly mobile flammable liquid with an odor similar to that of ethyl alcohol; d20-4 = 0.7928; tboil = 64.51 °C; n20-D = 1.3288. Miscible in all respects with water, alcohols, acetone and other organic solvents; does not mix with aliphatic hydrocarbons. Forms azeotropic mixtures with acetone (tbp = 55.7 °C), benzene (tbp = 57.5 °C), carbon disulfide (tbp = 37.65 °C), as well as with many other compounds. Methyl alcohol does not form azeotropic mixtures with water, so most of the water can be removed by distilling the alcohol.

Methyl alcohol is a strong poison that primarily affects the nervous system and blood vessels. It can enter the human body through the respiratory tract and skin. Particularly dangerous when taken orally. The use of methyl alcohol in laboratory practice is allowed only in cases where it cannot be replaced by other, less toxic substances.

Synthetic absolute methyl alcohol, produced by industry, contains only traces of acetone and up to 0.1% (wt.) water. In laboratory conditions, it can be prepared from technical CH3OH, in which the content of these impurities can reach 0.6 and even 1.0%. In a 1.5 liter flask with a reflux condenser protected by a calcium chloride tube with CaCl2, place 5 g of magnesium shavings, fill them with 60-70 ml of methyl alcohol containing no more than 1% water, add an initiator - 0.5 g of iodine (or the corresponding amount of methyl iodide, ethyl bromide) and heat until the latter dissolves. When all the magnesium has converted to methylate (a white precipitate forms at the bottom of the flask), 800-900 ml of technical CH3OH is added to the resulting solution, boiled in a flask with reflux for 30 minutes, after which the alcohol is distilled off from the flask with a reflux condenser 50 cm high, collecting fraction with a boiling point of 64.5-64.7 ° C (at normal pressure). The receiver is equipped with a calcium chloride tube containing CaCl2. The water content in the alcohol obtained in this way does not exceed 0.05% (wt.). Absolute methyl alcohol is stored in a vessel protected from air moisture.

Additional drying of methyl alcohol containing 0.5-1% water can be accomplished with magnesium metal without initiating the reaction. To do this, add 10 g of magnesium shavings to 1 liter of CH3OH and the mixture is left in a flask with a reflux condenser, protected by a calcium chloride tube with CaCl2. The reaction begins spontaneously, and soon the alcohol boils. When all the magnesium has dissolved, the boil is maintained by heating in a water bath for some more time, after which the alcohol is distilled, discarding the first portion of the distillate.

Anhydrous methyl alcohol is also obtained by keeping it over NaA or CA zeolite or passing it through a column filled with these molecular sieves. To do this, you can use a laboratory-type column.

The presence of acetone in methyl alcohol is determined by testing with sodium nitroprusside. The alcohol is diluted with water, made alkaline and a few drops of a freshly prepared saturated aqueous solution of sodium nitroprusside are added. In the presence of acetone, a red color appears, which intensifies upon acidification with acetic acid.

To remove acetone, the following method has been proposed: 500 ml of CH3OH is boiled for several hours with 25 ml of furfural and 60 ml of 10% NaOH solution in a flask with reflux, and then the alcohol is distilled off on an efficient column. A resin remains in the flask - a product of the interaction of furfural with acetone.

Petroleum ether, gasoline and naphtha

When distilling light gasoline, a number of low-boiling hydrocarbon fractions are obtained, which are used as solvents. The vapors of these hydrocarbons have a narcotic effect.

The industry produces the following reagents:

The high volatility of petroleum ether, gasoline and naphtha, their easy flammability and the formation of explosive mixtures with air require special care when working with them.

Petroleum ether, gasoline and naphtha should not contain impurities of unsaturated and aromatic hydrocarbons.

The presence of unsaturated hydrocarbons is usually determined using two reagents: a 2% solution of Br2 in CCl4 and a 2% aqueous solution of KMnO4 in acetone. To do this, add a reagent solution drop by drop to 0.2 ml of hydrocarbon in 2 ml of CCl4 and observe the color change. The test is considered negative if no more than 2-3 drops of bromine solution or KMnO4 solution are discolored.

Unsaturated hydrocarbons can be removed by repeatedly shaking a portion of hydrocarbons with 10% (vol.) conc. on a mechanical shaker for 30 minutes. H2SO4. After shaking with each portion of acid, the mixture is allowed to settle, then the bottom layer is separated. When the acid layer is no longer colored, the hydrocarbon layer is shaken vigorously with several portions of a 2% KMnO4 solution in a 10% H2SO4 solution until the color of the KMnO4 solution ceases to change. In this case, unsaturated hydrocarbons are almost completely removed and aromatic ones are partially removed. To completely remove aromatic hydrocarbons, you need to shake hydrocarbons (petroleum ether, etc.) with oleum containing 8-10% (wt.) SO3. A bottle with a ground-in stopper, in which shaking is done, is wrapped in a towel. After separating the acid layer, the hydrocarbon fraction is washed with water, a 10% Na2CO3 solution, again with water, dried over anhydrous CaCl2 and distilled over a sodium wire. It is recommended to store petroleum ether over CaSO4 and distill it before use.

The traditional chemical method for purifying saturated hydrocarbons from unsaturated ones is very labor-intensive and can be replaced by adsorption. Impurities of many unsaturated compounds are removed by passing the solvent through a glass column with active Al2O3 and especially on zeolites, such as NaA.

Tetrahydrofuran

Tetrahydrofuran (CH2)4O is a colorless mobile liquid with an ethereal odor; d20-4 = 0.8892; tboil = 66°C; n20-D = 1.4050. Soluble in water and most organic solvents. Forms an azeotropic mixture with water (6% (wt.) H2O), boiling point = 64°C. Tetrahydrofuran is prone to the formation of peroxide compounds, so you must check for the presence of peroxides in it (see Diethyl ether). Peroxides can be removed by boiling with a 0.5% Cu2Cl2 suspension for 30 minutes, after which the solvent is distilled and shaken with fused KOH. The upper layer of tetrahydrofuran is separated, 16% (mass) KOH is added again and the mixture is boiled for 1 hour in a flask under reflux. Then tetrahydrofuran is distilled over CaH2 or LiAlH4, 10-15% of the head fraction is discarded and about 10% of the residue is left in the cube. The head fraction and bottoms are added to the technical products intended for purification, and the collected middle fraction is dried over a sodium wire. The purified product is stored without access to air and moisture.

Chloroform

Chloroform CHCl3 is a colorless mobile liquid with a characteristic sweetish odor; d20-4 = 1.4880; tboil = 61.15°C; n20-D = 1.4455. Soluble in most organic solvents; practically insoluble in water. Forms an azeotropic mixture with water (2.2% (wt.) H2O), boiling point = 56.1 °C. It is non-flammable and does not form explosive mixtures with air, but is toxic - it affects internal organs, especially the liver.

Chloroform almost always contains up to 1% (wt.) ethyl alcohol, which is added to it as a stabilizer. Another impurity of chloroform may be phosgene, which is formed during the oxidation of chloroform in light.

The test for the presence of phosgene is performed as follows: 1 ml of a 1% solution of n-dimethylaminobenzaldehyde and diphenylamine in acetone is shaken with chloroform. In the presence of phosgene (up to 0.005%), an intense yellow color appears after 15 minutes. Chloroform is purified by shaking three times with separate portions of conc. H2SO4. For 100 ml of chloroform, take 5 ml of acid each time. Chloroform is separated, washed 3-4 times with water, dried on CaCl2 and distilled.

Purification of chloroform is also achieved by slowly passing the drug through a column filled with active Al2O3 in an amount of 50 g per 1 liter of chloroform.

Chloroform should be stored in dark glass bottles.

Carbon tetrachloride

Carbon tetrachloride CCl4 is a colorless, non-flammable liquid with a sweetish odor; d20-4 = 1.5950; tboil = 76.7°C; n25-D = 1.4631. Practically insoluble in water. With water it forms an azeotropic mixture (4.1% (mass) H2O), boiling point = 66°C. Dissolves a variety of organic compounds. It has a less narcotic effect than chloroform, but is superior in toxicity, causing severe liver damage.

Carbon tetrachloride is sometimes contaminated with carbon disulfide, which is removed by stirring CCl4 at 60°C in a reflux flask with a 10% (v/v) concentrated alcohol solution of KOH. This procedure is repeated 2-3 times, after which the solvent is washed with water, stirred at room temperature with small portions of conc. H2SO4 until it stops coloring. Then the solvent is washed again with water, dried over CaCl2 and distilled over P4O10.

Drying of CCl4 is achieved by azeotropic distillation. Water is removed with the first cloudy portions of the distillate. As soon as the clear liquid begins to distill, it can be considered anhydrous.

Ethyl acetate

Ethyl acetate CH3COOC2H5 is a colorless liquid with a pleasant fruity odor; d20-4 = 0.901; tboil = 77.15°C; n20-D = 1.3728. Forms an azeotropic mixture with water (8.2% (wt.) H2O), boiling point = 70.4 °C.

Technical ethyl acetate contains water, acetic acid and ethyl alcohol. Many methods have been proposed for purifying ethyl acetate. In one of them, ethyl acetate is shaken with an equal volume of a 5% NaHCO3 solution and then with a saturated CaCl2 solution. After this, ethyl acetate is dried with K2CO3 and distilled in a water bath. For final drying, 5% P4O10 is added to the distillate and shaken vigorously, then filtered and distilled over a sodium wire.

Ethanol

Ethyl alcohol C2H5OH is a colorless liquid with a characteristic odor; d20-4 = 0.7893; tboil = 78.39 °C; n20-D = 1.3611. Forms an azeotropic mixture with water (4.4% (wt.) H2O). It has a high dissolving ability for a wide variety of compounds and is indefinitely miscible with water and all common organic solvents. Industrial alcohol contains impurities, the qualitative and quantitative composition of which depends on the conditions of its production.

The produced absolute alcohol, which is obtained by azeotropic distillation of 95% technical alcohol with benzene, may contain small amounts of water and benzene (up to 0.5% (wt.)).

Dehydration of 95% alcohol can be done by prolonged boiling with calcined CaO. For 1 liter of alcohol take 250 g of CaO. The mixture is boiled in a 2-liter flask with a reflux condenser, closed with a tube containing CaO, for 6-10 hours. After cooling, the flask is connected to a distillation unit at atmospheric pressure and the alcohol is distilled off. Yield 99-99.5% alcohol 65-70%.

Barium oxide BaO has higher dehydrating properties. In addition, BaO is able to dissolve somewhat in almost absolute alcohol, turning it yellow. This sign is used to determine when the process of absolutization is completed.

Further dehydration of 99-99.5% alcohol can be carried out using several methods: using magnesium (ethyl alcohol with a water content of no more than 0.05%), sodium and diethyl oxalic acid.

Pour 1 liter into a 1.5 liter round-bottomed flask with a reflux condenser and a calcium chloride tube containing CaCl2. 99% ethyl alcohol, after which 7 g of sodium wire is added in small portions. After the sodium has dissolved, 25 g of oxalic acid diethyl ether is added to the mixture, boiled for 2 hours and the alcohol is distilled off.

Absolute alcohol is prepared in the same way using orthophthalic acid diethyl ester. In a flask equipped with a reflux condenser and a calcium chloride tube with CaCl2, place 1 liter of 95% alcohol and dissolve 7 g of sodium wire in it, then add 27.5 g of phthalic acid diethyl ether, boil the mixture for about 1 hour and distill off the alcohol. If a small amount of sediment forms in the flask, this proves that the original alcohol was of fairly good quality. Conversely, if a large amount of sediment falls out and boiling is accompanied by tremors, then the original alcohol was not dried enough.

Drying of ethyl alcohol is currently carried out in column-type devices with NaA zeolite as a packing. Ethyl alcohol containing 4.43% water is fed for drying into a column with a diameter of 18 mm with a packing layer height of 650 mm at a speed of 175 ml/h. Under these conditions, in one cycle it is possible to obtain 300 ml of alcohol with a water content of no more than 0.1-0.12%. Zeolite is regenerated in a column in a nitrogen stream at 320 °C for 2 hours. When distilling ethyl alcohol, it is recommended to use thin-section devices; In this case, the polished sections are thoroughly cleaned and not lubricated. It is advisable to discard the first part of the distillate and complete the distillation when a little alcohol remains in the distillation flask.

Since carbon tetrachloride (CTC) is a prohibited ozone depleting substance under the Montreal Protocol, but is inevitably formed as a by-product in the production of chloromethanes, choosing the most effective method for processing CTC is an urgent task.
Various transformations of CCA have been especially intensively studied recently; there is a large amount of experimental data. Below we will evaluate various options for converting CCC based on our own research and data from other authors.
The works examine the problem of processing CCM into environmentally friendly products, but they do not fully cover possible processing options, and also, in our opinion, the advantages and disadvantages of individual methods of recycling CCM are not sufficiently objectively reflected.
It is possible to note some contradictions in the articles . Thus, the topic of the articles is the processing of CHCs into environmentally friendly products; in the text and conclusions, the conversion of CCCs into chloromethane is recommended as promising methods, and in the introduction, chloromethanes are called the main chemical pollutants of the environment. In fact, chloromethanes are not included in the Stockholm Convention on Persistent Organic Pollutants, and in terms of toxicity and release volume, chloromethanes are not the main pollutants even among other organochlorine compounds.
The articles talk about the high persistence of chloromethanes. At the same time, it is known that all chloromethanes, except methyl chloride, are unstable products and require stabilization to maintain their properties. The decomposition of chloromethanes occurs in the boilers of rectification columns, in the evaporator for supplying chemical chemicals to the reactor. According to the encyclopedia, chloroform without a stabilizer is unlikely to last without changing its properties for 24 hours if it is in contact with the atmosphere.
CHC processing processes can be classified according to the degree of usefulness of the resulting processed products. This does not mean that the usefulness of the recycling processes themselves will be in the same sequence, since much will depend on the cost of processing and subsequent separation of the resulting products.
The choice of method is also influenced by the presence of a large number of other products in the processed waste in addition to ChC (for example, in distillation stills for the production of chloromethane), when the separation of ChC from this waste can require significant costs. The same situation arises when neutralizing chemical chemicals contained in small quantities in gas emissions. In this case, non-selective complete combustion to produce CO2 and HCl with practically zero utility due to the low profitability of their extraction may be the most acceptable solution. Therefore, in each specific case, the choice can be made only after a technical and economic comparison.

CHC combustion
When burning CHC using air as an oxidizer, a simultaneous supply of hydrocarbon fuel is required to supply heat and bind chlorine into hydrogen chloride. Alternatively, if there is a small amount of hydrogen chloride, it can be converted to sodium chloride by injecting a sodium hydroxide solution into the combustion gases. Otherwise, hydrogen chloride is separated from combustion gases in the form of hydrochloric acid.
Disposal of hydrochloric acid itself can be a problem due to supply exceeding demand. The separation of hydrogen chloride from hydrochloric acid by stripping makes it more expensive than chlorine. In addition, hydrogen chloride has limited use in oxychlorination and hydrochlorination processes. Converting hydrogen chloride to chlorine using hydrochloric acid electrolysis or oxygen oxidation (Deacon process) is a rather expensive and technologically complex operation.
The authors of the works give preference to catalytic oxidation as a method of complete oxidation of CCC compared to conventional thermal combustion. According to comparison with combustion, catalytic oxidation processes are characterized by a greater depth of destruction of organochlorine waste and are not accompanied by the formation of dioxins.
These statements are not true and may lead to misconceptions about the effectiveness of the methods being compared. The article does not provide any data to support higher conversion rates in catalytic oxidation. In the references cited in support of this statement, for example, the degree of conversion is really high 98-99%, but this is not the level that is achieved during thermal combustion. Even if the conversion rate is stated as 100% or 100.0%, this only means that the accuracy of this data is 0.1%.
The US Resource Conservation and Recovery Act requires destructive removal efficiency of at least 99.9999% for major organic hazardous contaminants. In Europe, it is also recommended to adhere to this minimum value for the degree of decomposition of unusable pesticides and polychlorinated biphenyls in combustion plants.
A set of requirements for the combustion process has been developed, called BAT - Best Available Technique (best acceptable method). One of the requirements, along with a temperature of  1200°C and a residence time of  2 s, is the turbulence of the reaction flow, which allows, basically, to eliminate the problem of breakthrough of the burnt substance in the near-wall layer and ensure ideal displacement mode. Apparently, in a tubular reactor filled with a catalyst, it is more difficult to eliminate the leakage of the burned substance in the near-wall layer. In addition, there are difficulties in uniformly distributing the reaction flow throughout the tubes. At the same time, further progress in eliminating the “near-wall effect” made it possible to achieve a conversion degree of 99.999999% during combustion in a liquid rocket engine.
Another controversial statement by the authors is the absence of PCDD and PCDF in the catalytic oxidation products. No numbers are provided to support this. The work provides only two references confirming the absence of dioxins during catalytic oxidation. However, one of the links, apparently due to some error, has nothing to do with catalytic oxidation, since it is devoted to the biotransformation of organic acids. Another paper looks at catalytic oxidation, but does not report any evidence of the absence of dioxins. On the contrary, data are provided on the formation of another persistent organic pollutant - polychlorinated biphenyl during the catalytic oxidation of dichlorobenzene, which may indirectly indicate the possibility of the formation of dioxins.
The work rightly notes that the temperature range of catalytic processes of oxidation of organochlorine wastes is favorable for the formation of PCDD and PCDF, however, the absence of PCDD and PCDF may be due to the catalytic destruction of the sources of their formation. At the same time, it is known that processes for the synthesis of high-molecular compounds even from C1 compounds are successfully carried out using catalysts.
European countries have environmental requirements for waste incineration, according to which the maximum emission limit for dioxins into the atmosphere is 0.1 ng TEQ/Nm3.
The environmental indicators presented above for the process of thermo-oxidative (fire) neutralization of liquid organochlorine waste are available in. Finally, it should be noted that in the Inventory of Existing PCB Destruction Facilities, the most widely used and proven method for PCB destruction is high-temperature incineration. Catalytic oxidation is not used for this purpose.
In our opinion, catalytic oxidation, despite the use of precious metals on a carrier as a catalyst, has an advantage in destroying residual amounts of toxic substances in gas emissions, since, due to the low temperature of the process, significantly less fuel consumption is required for heating the reaction gas than with thermal combustion . The same situation arises when optimal combustion conditions are difficult to create, for example, in catalytic afterburners in automobile engines. In addition, the catalytic oxidation of organochlorine waste under pressure (the "catoxide process") has been used by Goodrich to directly feed combustion gases containing hydrogen chloride into an ethylene oxidative chlorination reactor to produce dichloroethane.
The combination of thermal and catalytic oxidation of waste gases has been reported to achieve higher efficiencies than pure catalytic oxidation. Qualified processing of organochlorine waste is also discussed in. In our opinion, it is more expedient to use conventional thermal combustion to burn CHC in the form of a concentrated product.
In conclusion of this section, it is advisable to consider one more aspect of the oxidation of CCA. According to CHC, it is a non-flammable substance, so its combustion can only be carried out in the presence of additional fuel. This is true when using air as an oxidizing agent. In oxygen, CHC is capable of burning with an insignificant thermal effect, the calorific value is 242 kcal/kg. According to another reference book, the heat of combustion of liquid is 156.2 kJ/mol (37.3 kcal/mol), and the heat of combustion of steam is 365.5 kJ/mol (87.3 kcal/mol).
Oxidation with oxygen can be one of the methods for processing CCC, in which the carbon component is lost, but the chlorine spent on producing CCC is regenerated. This process has an advantage over conventional combustion due to the production of concentrated products.
CCl4 + O2 → CO2 + 2Cl2
The process of oxidative dechlorination of CCA also produces carbon dioxide and, if necessary, phosgene.
2CCl4 + O2 → 2COCl2 + 2Cl2

Hydrolysis of CHC

Another interesting, in our opinion, process of processing CHC into carbon dioxide and hydrogen chloride is hydrolysis.
CCl4 + 2H2O → CO2 + 4HCl
There are few publications in this area. The interaction of OH-groups with chloromethanes in the gas phase is discussed in the article. The catalytic hydrolysis of ChCA to HCl and CO2 on magnesium oxide at temperatures above 400°C was studied in. The rate constants for homogeneous hydrolysis of CHC in the liquid phase were obtained in the work.
The process works well, according to our data, at relatively low temperatures of 150-200°C, uses the most accessible reagent and should not be accompanied by the formation of dioxins and furans. All you need is a reactor that is resistant to hydrochloric acid, for example, coated inside with fluoroplastic. Perhaps such a cheap and environmentally friendly recycling method can be used to destroy other waste.

Interaction of CCA with methanol
Close to hydrolysis and actually proceeding through this stage is the process of vapor-phase interaction of ChCU with methanol to produce methyl chloride in the presence of a catalyst - zinc chloride on activated carbon. Relatively recently, this process was first patented by Shin-Etsu Chemical (Japan). The process proceeds with high conversions of CHC and methanol close to 100%.
CCl4 + 4CH3OH → 4CH3Cl + CO2 + 2H2O
The authors believe that the interaction of CCN with methanol occurs in 2 stages: first, CCC is hydrolyzed to carbon dioxide and hydrogen chloride (see above), and then hydrogen chloride reacts with methanol to form methyl chloride and water.
CH3OH + HCl → CH3Cl + H2O
In this case, to initiate the reaction, a small amount of water present in the atmosphere is sufficient. It is believed that the first stage limits the speed of the overall process.
With a close to stoichiometric ratio of CTC to methanol (1:3.64), the reaction proceeded stably during the experiment, which lasted 100 hours, with a conversion of CTC of 97.0% and methanol of 99.2%. The selectivity for the formation of methyl chloride was close to 100%, since only traces of dimethyl ether were detected. The temperature in the catalyst layer was 200 o C.
Then it was proposed to divide the process into two reaction zones: in the first, the hydrolysis of CCA occurs, and in the second, the interaction of hydrogen chloride with methanol introduced into this zone occurs. Finally, the same company patented a method for producing chloromethanes without the formation of ChC, which includes the following stages:
. production of chloromethanes by chlorination of methane;
. interaction of hydrogen chloride released in the first stage with methanol to form methyl chloride and dilute hydrochloric acid;
. hydrolysis of ChCA with dilute hydrochloric acid in the presence of a catalyst - metal chlorides or oxides on a carrier.
The disadvantage of the heterogeneous catalytic process of interaction of CCC with methanol is the relatively short service life of the catalyst due to its carbonization. At the same time, high-temperature regeneration to burn out carbon deposits is undesirable due to the volatilization of zinc chloride, and when using activated carbon as a carrier, it is generally impossible.
In conclusion of this section, it can be mentioned that we have made attempts to move away from solid catalysts in the process of processing CCC with methanol. In the absence of a catalyst at a molar ratio of methanol:BCC = 4:1 and with an increase in temperature from 130 to 190°C, the conversion of PCQ increased from 15 to 65%. The manufacture of the reactor requires materials that are stable under these conditions.
Carrying out a catalytic liquid-phase process at relatively low temperatures of 100-130°C and a methanol:CPC molar ratio of 4:1 without pressure made it possible to achieve a PCI conversion of only 8%, while it is possible to obtain almost 100% conversion of methanol and 100% selectivity for methyl chloride. To increase the conversion of CCA, an increase in temperature and pressure is required, which could not be achieved in laboratory conditions.
A method of alcoholysis of ChCU has been patented, including the simultaneous supply of ChCC and ³ 1 alcohol ROH (R = alkyl C 1 - C 10) into the catalytic system, which is an aqueous solution of metal halides, especially chlorides I B, I I B, V I B and V I I I groups In the liquid-phase interaction of methanol and ChC (in a ratio of 4:1) in a laboratory reactor with a magnetic stirrer in the presence of a catalytic solution of zinc chloride at a temperature of 180°C and a pressure of 3.8 bar, the conversion of ChC and methanol was 77%.

Chlorination using ChC
CCA is a safe chlorinating agent, for example, in the preparation of metal chlorides from their oxides. During this reaction, CHC is converted into carbon dioxide.
2Ме2О3 + 3CCl4 → 4МеCl3 + 3СО2
Work was carried out on the production of iron chlorides using ChCA as a chlorinating agent; the process takes place at a temperature of about 700°C. By chlorination using ChC in industry, their chlorides are obtained from the oxides of elements of groups 3-5 of the Periodic Table.

Interaction of CHC with methane

The simplest solution to the problem of processing CCS would be the interaction of CCS with methane in a methane chlorination reactor to produce less chlorinated chloromethanes, since in this case it would practically only require the organization of recycling of unreacted CCS, and the subsequent isolation and separation of reaction products can be carried out on the main system production.
Previously, when studying the process of oxidative chlorination of methane, both in the laboratory and in a pilot plant, it was noticed that when the reaction gas from the process of direct chlorination of methane containing all chloromethanes, including ChC, is fed into the reactor, the amount of the latter after the oxychlorination reactor decreases, although it should was with increasing amounts of all other chloromethanes to increase.
In this regard, it was of particular interest to conduct a thermodynamic analysis of the reactions of methane with ChC and other chloromethanes. It turned out that the most thermodynamically probable is the interaction of CHC with methane. At the same time, the equilibrium degree of conversion of CHC under conditions of excess methane, which is realized in an industrial chlorinator, is close to 100% even at the highest temperature (the lowest equilibrium constant).
However, the actual occurrence of a thermodynamically probable process depends on kinetic factors. In addition, other reactions can occur in the CCA system with methane: for example, pyrolysis of CCA to hexachloroethane and perchlorethylene, the formation of other C2 chlorine derivatives due to the recombination of radicals.
An experimental study of the interaction reaction between CCA and methane was carried out in a flow reactor at temperatures of 450-525 ° C and atmospheric pressure, with an interaction time of 4.9 s. Processing of experimental data gave the following equation for the rate of exchange reaction of methane with CHC:
r = 1014.94 exp(-49150/RT).[СCl 4 ]0.5.[CH 4 ], mol/cm 3 .s.
The data obtained made it possible to evaluate the contribution of the exchange interaction of CCC with methane in the process of methane chlorination and to calculate the necessary recycle of CCC for its complete conversion. Table 1 shows the conversion of ChC depending on the reaction temperature and concentration of ChC at approximately the same concentration of methane, which is realized in an industrial chlorinator.
The conversion of CCC naturally decreases with decreasing process temperature. Acceptable CHC conversion is observed only at temperatures of 500-525 o C, which is close to the temperature of bulk methane chlorination at existing chloromethane production plants of 480-520 o C.
The total conversions of CHC and methane can be characterized by the following summary equation and material balance:
CCl 4 + CH 4 → CH 3 Cl + CH 2 Cl 2 + CHCl 3 + 1,1-C 2 H 2 Cl 2 + C2Cl 4 + HCl
100.0 95.6 78.3 14.9 15.2 7.7 35.9 87.2 mol
The second line gives the amounts of reacted methane and the resulting products in moles per 100 moles of reacted CCA. The selectivity of the conversion of CHC into chloromethanes is 71.3%.
Since the separation of commercial CCS from distillation stills of chloromethane production was a certain problem, and difficulties periodically arose with the sale of distillation stills, the processing of CCS in a methane chlorination reactor aroused interest even before the ban on the production of CCS due to its ozone-depleting ability.
Pilot tests of CHC processing in a methane chlorination reactor were carried out at the Cheboksary settlement. "Khimprom". The results obtained basically confirmed the laboratory data. The selectivity of the conversion of CCA to chloromethanes was higher than in laboratory conditions.
The fact that the selectivity of the reaction process of CCA in an industrial reactor turned out to be higher than in a laboratory reactor can be explained by the fact that when methane is chlorinated in a laboratory reactor, the outer walls, heated by a casing with an electric coil, overheat. Thus, at a temperature in the reaction zone of 500°C, the temperature of the walls of the laboratory chlorinator was 550°C.
In an industrial reactor, heat is accumulated by the central brick column and lining, and the outer walls of the chlorinator, on the contrary, are cooled.
Pilot tests of the return of chemical chemicals to the methane chlorination reactor were previously carried out at the Volgograd settlement. "Khimprom". ChC was fed into an industrial chlorinator without separation as part of the distillation still, along with all the impurities of C2 chlorinated hydrocarbons. As a result, about 100 m3 of distillation stills were processed within a month. However, processing the data obtained caused difficulties due to the large number of components in low concentrations and the insufficient accuracy of the analyzes.
To suppress the formation of side chlorohydrocarbons of the ethylene series during the interaction of ChC with methane, it is proposed to introduce chlorine into the reaction mixture at a ratio of chlorine to ChC  0.5.
The production of chloromethanes and other products by the interaction of CCA with methane at temperatures of 400-650 o C in a hollow reactor is described in the patent. An example is given where the conversion of CCA was in mol %: to chloroform - 10.75, methylene chloride - 2.04, methyl chloride - 9.25, vinylidene chloride - 8.3 and trichlorethylene - 1.28.
Then the same company "Stauffer" patented a method for producing chloroform by reacting ChCU with C2-C3 hydrocarbons and C1-C3 chlorohydrocarbons. According to the examples given, only chloroform is obtained from CCA and methylene chloride at a temperature of 450°C in a hollow reactor, and at a temperature of 580°C - chloroform and perchlorethylene. From ChC and methyl chloride at a temperature of 490°C, only methylene chloride and chloroform were formed in equal quantities, and at a temperature of 575°C, trichlorethylene also appeared.
A process was also proposed for the production of methyl chloride and methylene chloride by the interaction of methane with chlorine and ChC in a fluidized contact bed at a temperature of 350-450 o C. The process of chlorination of methane to chloroform in a fluidized contact bed with the introduction of CCA into the reaction zone to ensure heat removal is described. In this case, the reaction of CHC with methane occurs simultaneously.
The exchange reaction between CCA and paraffin leads to the formation of chloroform and chlorinated paraffin.
When developing the process of oxidative chlorination of methane, it was found that the oxidative dechlorination of ChC in the presence of methane is more efficient than the interaction of methane and ChC in the absence of oxygen and a catalyst.
The data obtained indicate that the process of oxidative dechlorination of ChCC in the presence of methane and a catalyst based on copper chlorides occurs at a lower temperature than the interaction of ChCC with methane in the absence of oxygen, producing only chloromethanes without the formation of by-product chlorinated hydrocarbons. Thus, the conversion of CCC at temperatures of 400, 425 and 450°C averaged 25, 34 and 51%, respectively.
An additional advantage of oxidative processing of CCC is the absence of carbonization of the catalyst. However, the need for a catalyst and oxygen reduces the advantages of this method.
A method for producing chloromethanes by oxidative chlorination of methane without obtaining chemical chemicals in the final products due to its complete recycling into the reaction zone has been patented. One of the claims of this application states that it is possible to obtain chloroform alone as the final product by returning methane and all chloromethanes except chloroform to the reaction zone.

Processing of chemical chemicals with hydrogen
Hydrodechlorination of ChCC with hydrogen (as well as methane), in contrast to oxidative transformations with oxygen, allows for the beneficial use of the carbon component of ChCC. Catalysts, kinetics, mechanism and other aspects of hydrodechlorination reactions are discussed in reviews.
One of the main problems of the CCA hydrodechlorination process is selectivity; often the reaction proceeds before the formation of methane, and the yield of chloroform, as the most desirable product, is not high enough. Another problem is the fairly rapid deactivation of the catalyst, mainly due to carbonization during the decomposition of CCS and reaction products. At the same time, selective production of chloroform can be achieved more easily than catalyst stability. Recently, quite a lot of works have appeared where high selectivity for chloroform is achieved; there is much less data on the stability of the catalyst.
In the patent, Ru, Rh, Pd, Os, Ir, Pt, Cu, Ag or Au are proposed as catalysts for the hydrogenolysis of PCI and chloroform. On a catalyst containing 0.5% platinum on alumina, at temperatures of 70-180 o C, 97.7-84.8% chloroform and 2.3-15.2% methane were obtained from ChC; At higher temperatures, methylene chloride is also formed.
In the works, the hydrodechlorination of CCA was carried out on platinum catalysts. The choice of MgO as a support was made on the basis of higher selectivity for chloroform and duration of catalyst operation compared to other supports: Al2O3, TiO2, ZrO2, SiO2, aluminosilicate and NaY zeolite. It has been shown that for stable operation of the Pt/MgO catalyst with a PTC conversion of more than 90%, it is necessary to maintain a reaction temperature of 140°C, an H2/PCC ratio of more than 9, and a space velocity of 9000 l/kg.h. The influence of the nature of the initial platinum compounds on the activity of the resulting catalyst - 1% Pt/Al2O3 - was discovered. On catalysts prepared from Pt(NH 3) 4 Cl 2, Pt(NH3)2(NO3)2 and Pt(NH3)4(NO3)2, the CCA conversion is close to 100%, and the selectivity to chloroform is 80%.
Modification of the catalyst - 0.25% Pt/Al2O3 with lanthanum oxide made it possible to obtain a chloroform yield of 88% with a selectivity of 92% at 120°C, a space velocity of 3000 h-1 and a molar ratio of H2:CCl4 = 10.
According to the data, calcination of the support - aluminum oxide at temperatures of 800 - 900 ° C reduces Lewis acidity, thereby increasing the stability and selectivity of the catalyst. On aluminum oxide with a specific surface area of 80 m2/g, containing 0.5% Pt, the conversion of PTC is 92.7% with a selectivity for chloroform of 83% and is retained for 118 hours.
In contrast to the data in the patent, when producing methylene chloride and chloroform by hydrodechlorination, ChCU recommends treating the carrier with hydrochloric acid or hydrochloric acid and chlorine, and promoting platinum with small amounts of metals, for example, tin. This reduces the formation of byproducts and increases the stability of the catalyst.
When hydrodechlorination of CCC on catalysts containing 0.5-5% Pd on sibunit (coal) or TiO2 at a temperature of 150-200°C, the conversion of CCC was 100%. Non-chlorinated C2-C5 hydrocarbons were formed as by-products. The catalysts worked stably for more than 4 hours, after which regeneration was carried out by blowing with argon while heating.
It is reported that when using a bimetallic composition of platinum and iridium promoted with small amounts of third metals, such as tin, titanium, germanium, rhenium, etc., the formation of by-products is reduced and the duration of the catalyst is increased.
When studying the non-catalytic interaction of CCA with hydrogen using the pulse compression method in a free-piston installation at a characteristic process time of 10-3 s, two areas of the reaction were found. At a temperature of 1150K (degree of conversion up to 20%), the process proceeds relatively slowly. By adjusting the composition of the initial mixture and the process temperature, it is possible to obtain a 16% yield of chloroform with a selectivity close to 100%. In a certain temperature range, under conditions of self-ignition of the mixture, the reaction can be directed to the predominant formation of perchlorethylene.
Great advances in the development of an active, stable and selective catalyst for the gas-phase hydrodechlorination of CCC with hydrogen were achieved by Sud Chemie MT. The catalyst is noble metals of the V group deposited on microspherical aluminum oxide (the composition of the catalyst is not disclosed by the company). The process is carried out in a fluidized bed of catalyst at temperatures of 100-150°C, pressure of 2-4 ata, contact time of 0.5-2 seconds and a hydrogen:BC ratio in the reaction zone of 6-8:1 (mol.).
The conversion of CCA under these conditions reaches 90%, selectivity for chloroform is 80-85%. The main by-product is methane, with methyl chloride and methylene chloride formed in minor quantities.
The works investigated the hydrodechlorination of CCC on palladium catalysts in the liquid phase. At temperatures of 20-80°C on palladium acetate with the addition of acetic acid and using C7-C12 paraffins, methyl ethyl ketone, dimethylformamide, dioxane and benzyl alcohol as solvents, the only reaction product was methane. Carrying out the reaction in isopropyl and tert-butyl alcohols as solvents made it possible to obtain chloroform and methyl chloride as the main products; methane formation ranged from trace amounts to 5%.
It is noted that the side reaction of hydrochlorination of alcohols used as solvents occurs with a conversion of 7-12% of the supplied amount and the formation of isomers of chlorine derivatives, which creates a problem of their disposal and complicates the isolation of marketable products. Therefore, there are no plans to implement this method yet.
Apparently, in order to exclude by-products, the patent proposes to carry out the reaction of hydrodechlorination of CCA to chloroform in a halogenated aliphatic solvent, in particular in chloroform. The catalyst is a suspension of platinum on a carrier. The conversion of ChC is 98.1% with a selectivity of chloroform formation of 99.3%.
The same process for producing chloroform in the presence of Pt and Pd catalysts on a carrier using  1 solvent (pentane, hexane, heptane, benzene, etc.) is described in the patent. The process is said to be carried out continuously or batchwise on an industrial scale.
The most commonly used catalysts for the hydrodechlorination of CCA to chloroform and other chloromethanes are supported palladium, platinum, rhodium and ruthenium. Such a catalyst is sprayed and suspended in liquid ChCU and treated with hydrogen at a pressure of 8000 kPa and a temperature below 250°C. The method is reported to be suitable for producing chloroform on an industrial scale.
When studying the hydrochlorination of CCA in a liquid-phase bubbling reactor, it was shown that the most active and selective catalyst is palladium supported on activated carbon. The advantage of activated carbon as a carrier is due to a more uniform distribution of the metal on its surface compared to such inorganic carriers as aluminum oxide and silica gel. According to the activity of metals, catalysts can be arranged in the series Pd/C  Pt/C  Rh/C  Ru/C  Ni/C. The main by-product is hexachloroethane.
It was later discovered that the rate of the process is limited by the chemical reaction on the surface.

Transformation of CHC into PCE

Under harsh temperature conditions, perchlorethylene is formed from CHC. The process of producing perchlorethylene from CCS involves the absorption of heat and the release of chlorine, which is fundamentally different from the production of perchlorocarbons (perchlorethylene and CCS) from methane or waste from the production of epichlorohydrin, where the processes occur with the supply of chlorine and the release of heat.
At 600°C H = 45.2 kcal/mol, and the equilibrium degree of conversion at atmospheric pressure is 11.7% 5. It should be noted that the data of various authors on the magnitude of the thermal effect of the reaction differ significantly, which raised doubts about the possibility of complete processing of CCC into perchlorethylene in the production of perchlorocarbons due to the lack of heat for this reaction. However, complete recycling of CHC has currently been carried out in the production of perchlorocarbons at the Sterlitamak JSC "Kaustik".
The thermal transformation of CCA increases significantly in the presence of chlorine acceptors. It is obvious that the acceptor, by binding chlorine, shifts the equilibrium of the reaction:
2CCl 4 → C 2 Cl 4 + 2Cl 2
towards the formation of perchlorethylene.
The transformation of CCA into perchlorethylene in the presence of a chlorine acceptor performs another very important function - it turns an endothermic process into an exothermic one and eliminates the almost impossible supply of heat through the wall at such temperatures in the presence of chlorine.
The introduction of organic chlorine acceptors (methane, ethylene, 1,2-dichloroethane) during the thermal dechlorination of CCA made it possible to increase the yield of PCE to 50 wt%. , however, at the same time, the amount of by-products (hexachloroethane, hexachlorobutadiene, resins) also increased simultaneously. Therefore, in work 53, to implement the process in industry, it is recommended to add an acceptor (methane or ethylene) in an amount of 0.3 of the stoichiometry.
Patent 54 proposes to carry out the process of non-catalytic thermal transformation of CHC into perchlorethylene at a temperature of 500-700 o C using hydrogen chlorine as an acceptor, due to which few by-product chlorohydrocarbons are formed.
The conversion of CCS into PCE, if there is a sale of the latter, has very important advantages over other methods of processing CCS from the production of chloromethanes:
. for processing, it is not necessary to separate CCS from distillation stills;
. C2 chlorohydrocarbons contained in stills are also converted into PCE.
The process of converting CCA into perchlorethylene in the presence of CH4 is accompanied by the formation of a large number of by-products, some of which (hexachloroethane, hexachlorobutadiene) are processed during the process, others (hexachlorobenzene) are sent for disposal. At the same time, methane, by binding chlorine, turns into ChC, which also needs to be processed, i.e. CHC processing capacity is increasing.
When hydrogen is used as a chlorine acceptor, the amount of by-products decreases, only the yield of hydrogen chloride increases. The process is carried out in a fluidized bed of silica gel. Process temperature 550-600 o C, ratio ChC:H2 = 1:0.8-1.3 (mol.), contact time 10-20 s. CHC conversion reaches 50% 55. The disadvantage of this process is the need to create a separate large technological scheme, as well as the presence of difficult-to-dispose waste - hexachlorobenzene.
The formation of heavy by-products can also be minimized when producing perchlorethylene by chlorinating hydrocarbons and their chlorine derivatives in the presence of ChC and hydrogen.

Other methods for processing CCC
Some methods for restoring CCS are proposed in. For example, chloroform can be obtained by slow reduction of CCl4 with iron with hydrochloric acid, zinc dust with a 50% NH4Cl solution at 50-60 o C, ethanol at 200 o C.
The electrochemical reduction of CCA produces mainly chloroform and methylene chloride. In the presence of aluminum chloride, CCA alkylates aromatic compounds. In free radical reactions and telomerization reactions, CCA serves as a halogen carrier.

conclusions

1. Since CHC is inevitably formed during the chlorination of methane and chloromethanes, the development of methods for its effective processing is an urgent task.
2. When destroying chemical chemicals by high-temperature combustion, existing environmental requirements for a destructive removal efficiency of 99.9999% and a dioxin content in emissions of no more than 0.1 ng TEQ/nm3 are achieved. Similar indicators were not revealed during the catalytic oxidation of ChC.
During the catalytic oxidation of CCA with oxygen, it is possible to obtain chlorine and/or phosgene.
3. An interesting method for processing CCC from the point of view of a cheap reagent and low process temperature is hydrolysis to carbon dioxide and hydrogen chloride.
4. The combination of hydrolysis of ChC and the interaction of the resulting HCl with methanol also gives a rather interesting process of processing ChC with methanol to produce methyl chloride and CO 2.
5. Hydrodechlorination with hydrogen makes it possible to utilize CCA to obtain the desired less chlorinated chloromethanes. The main disadvantage of this process, as well as the interaction with methanol, is the gradual decrease in catalyst activity due to carbonization.
6. The simplest solution to the problem of processing CCS is the interaction of CCS with methane when it is returned to the methane chlorination reactor. However, in addition to chloromethanes, impurities of C2 chlorohydrocarbons are formed. The formation of impurities can be avoided by reacting CCA with methane in the presence of a catalyst and oxygen at a lower temperature, but this will require the creation of a separate stage and the presence of oxygen.
7. Pyrolysis of CHC in the presence of methane, hydrogen or other chlorine acceptors allows one to obtain perchlorethylene. The process is complicated by the formation of high-molecular-weight by-products.
8. CCA is a safe chlorinating agent, for example, when producing metal chlorides from their oxides.
9. There are a number of other methods for processing CCC, for example, electrochemical reduction or using reducing reagents. CCA can also be used as an alkylating agent.

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Table 1. Interaction of CHC with methane

	T-ra,	Concentrations, % mol.		CHC conversion, %
p/p	o C	SS l 4	CH 4	for chlorine	by carbon
1	525	22,5	53,4	27,4	25,4
2	525	9,7	53,0	29,4	31,9
3	500	24,9	48,8	12,0	11,9
4	475	23,4	47,8	6,4	5,7
5	450	29,5	51,1	2,9	1,9

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