RU2185365C1 - Method of synthesis of hexachloroethane - Google Patents

Abstract

FIELD: chloroorganic compounds, chemical technology. SUBSTANCE: invention relates to a field of chloroorganic synthesis, in part, a method of synthesis of hexachloroethane that is used in processes of aluminium articles molding. Method is performed by decomposition of carbon tetrachloride by effect of two-component system: manganese complex [MnCl₂, Mn(OAc)₂, Mn(acac)₃] -ketone (acetone, cyclopentanone, cyclohexanone, adamantane-2) at 200 C for 1-3 h in the mole ratio [Mn]:[ketone]:[CCl₄] = 1:(2-4):(1000-2000), respectively, using alcohol solvents. EFFECT: increased yield of end product. 1 tbl, 15 ex

Description

 The invention relates to the field of organochlorine synthesis, in particular, to a method for producing hexachloroethane. Hexachloroethane is an important organochlorine product and is used in the casting processes of aluminum parts.

In industry, hexachloroethane is produced by chlorination of 1,2-dichloroethane over activated carbon, which serves as a catalyst. (Industrial organochlorine products. Edited by L. Oshin, A. M., Chemistry. 1978. P. 195 [1]). The process is carried out according to the following procedure: 1,2-dichloroethane enters the evaporator, turning into gas, is mixed with chlorine, then the resulting mixture is sent to a tubular reactor, heated to 270-290 ^o C and filled with activated carbon AG-3. Chlorine is usually supplied in a 30% excess with respect to 1,2-dichloroethane. The reaction produces a complex mixture of chlorine-containing compounds: Hcl, trichloroethane, tetrachlorethylene, tetrachloroethane, hexachlorobutadiene and hexachloroethane. The yield of hexachloroethane is 17%.

Недостатками данного метода синтеза гексахлорэтана являются:
1) низкий выход гексахлорэтана - 17%;
2) использование газообразного хлора, что требует применения дорогостоящего коррозионностойкого оборудования. Кроме того, необходим специальный технологический узел (резервуары, трубопроводы, контрольно-измерительная аппаратура, насосы, защитная зона) для хранения, дозировки, а также для утилизации хлора и хлорсодержащих отходов;
3) высокая температура реакции (270-290^oС) и связанные с этим большие энергозатраты;
4) низкая селективность реакции, образование побочных трудноразделяемых продуктов.

The disadvantages of this method of synthesis of hexachloroethane are:
1) low yield of hexachloroethane - 17%;
2) the use of gaseous chlorine, which requires the use of expensive corrosion-resistant equipment. In addition, a special technological unit (tanks, pipelines, instrumentation, pumps, protective zone) is needed for storage, dosage, and also for the disposal of chlorine and chlorine-containing waste;
3) a high reaction temperature (270-290 ^o C) and the associated large energy costs;
4) low selectivity of the reaction, the formation of side hardly separated products.

A known method of producing hexachloroethane by chlorination of tetrachlorethylene in the presence of anhydrous ferric chloride (Industrial organochlorine products. Edited by L. Oshin, M. Chemistry. 1978, 196. [2]). According to this method, under optimal conditions (100-110 ^o C, 4 h, molar ratio [C ₂ Cl ₄ ]: [FeCl ₃ ] = 100: 1) the yield of hexachloroethane is 40-45%.

Метод имеет следующие недостатки:
1) низкий выход гексахлорэтана (40-45%);
2) использование в качестве реагента высокотоксичного и экологически опасного хлора;
3) сложность аппаратурного оформления процесса, т.к. для хранения, дозировки и утилизации отходов хлора требуется специальное технологическое оборудование из коррозионностойких материалов.

The method has the following disadvantages:
1) low yield of hexachloroethane (40-45%);
2) the use of highly toxic and environmentally hazardous chlorine as a reagent;
3) the complexity of the hardware design process, because For the storage, dosage and disposal of chlorine waste, special technological equipment from corrosion-resistant materials is required.

In fairness, it should be noted that hexachloroethane was first obtained from carbon tetrachloride by passing its vapor through a glass tube heated to 500 ^o C (W. Kolbe // Lieb. Ann. 1851, B. 54, S. 14 [3]). The decomposition of CCl ₄ proceeds non-selectively and leads to the production (along with hexachloroethane) of chlorine, dichloroacetylene and unidentified products.

The laws of thermal decomposition of CCl ₄ were investigated in later works (A. E. Shilov, R. D. Sabirova // DAN USSR. Ser. Phys. Chem., 1957, T. 114, 5, S. 1058 [4]; A.E. Shilov, R.D. Sabirova // ZhFH, 1960, T. 34, S. 860 [5]; A.E. Shilov, R.D.Sabirova // ZhFH, 1959, T. 33, C . 1365 [6]). The authors of these studies found that the high-temperature decomposition of CCl ₄ in the range from 227 to 874K is accompanied by the formation of chlorine, tetrachlorethylene, and hexachloroethane, the yield of which does not exceed 1.7%.

На состав продуктов термического разложения ССl₄ существенное влияние оказывает материал реактора. Так, Коршак В.В. с сотрудниками исследовали разложение CCl₄ в фарфоровой трубке, нагретой до 400-700^oС, и установили, что основным продуктом реакции является тетрахлорэтилен, а гексахлорэтан образуется в количестве ~10%, а максимальная конверсия ССl₄ не превышает 52% (В.В.Коршак, Ю.А.Степихеев, Л.Ф.Вертолатова // ЖОХ, 1947, 17, С. 1626 [7]).

The composition of the products of thermal decomposition of CCl _{4 is} significantly affected by the material of the reactor. So, Korshak V.V. The researchers investigated the decomposition of CCl ₄ in a porcelain tube heated to 400-700 ^° C, and found that the main reaction product is tetrachlorethylene and hexachloroethane is produced in an amount of ~ 10%, and the maximum CCl ₄ conversion does not exceed 52% (B.V Korshak, Yu.A. Stepikheev, L.F. Vertolatova // Zhokh, 1947, 17, S. 1626 [7]).

The method of producing hexachloroethane by thermal decomposition of CCl ₄ has the following disadvantages:
1) decomposition of CCl ₄ with a noticeable speed occurs at elevated temperatures (400-700 ^o C), therefore, it requires large energy costs;
2) the process of decomposition of CCl ₄ is non-selective and leads to the formation of a mixture of difficult to separate products;
3) low yield of the target product.

 By the similarity of the three features (feedstock, final product, catalysis), we took this method as a prototype.

 The authors propose a method for the synthesis of hexachloroethane from carbon tetrachloride, free of these disadvantages.

The essence of the method is to obtain hexachloroethane from CCl ₄ under the action of a two-component catalytic system: manganese complex - ketone. The most active catalysts were obtained using manganese compounds such as Mn (acac), Mn (OAc) ₂ , MnCl ₂ in combination with ketones (acetone, cyclohexanone, cyclopentanone, adamantanon-2), taken in the ratio [Mn]: [ketone ] = 1: 2-4.

спирт = CH₃OH, С₂Н₅ОН, С₃Н₇OН, С₄Н₉ОН
[кетон]:ацетон, циклопентанон, циклогексанон, адамантанон-2
Катализатор способствует разложению ССl₄ на свободный хлор и, вероятно, радикал ССl₃, который димеризуется с образованием гексахлорэтана (2).

alcohol = CH ₃ OH, C ₂ H ₅ OH, C ₃ H ₇ OH, C ₄ H ₉ OH
[ketone]: acetone, cyclopentanone, cyclohexanone, adamantanone-2
The catalyst facilitates the decomposition of CCl ₄ into free chlorine and, probably, the radical CCl ₃ , which dimerizes to form hexachloroethane (2).

In the absence of ketones, the conversion of CCl ₄ does not exceed 5%. The structure of the ketone slightly affects the direction of the reaction, however, the presence of any of these ketones increases the conversion of carbon tetrachloride and the reaction rate. To obtain hexachloroethane (2) with a quantitative yield, it is necessary to use solvents, the most preferred of which are primary alcohols (methanol, ethanol, propanol-1 and butanol-1). When carrying out the reaction without a solvent (i.e., when CCl ₄ serves as both a reagent and a solvent), the yield of hexachloroethane is 70%.

It was found that the optimum temperature is 200 ^o С, at t <200 ^o С the reaction rate is significantly slowed, which leads to a decrease in the conversion of CCl ₄ . An increase in temperature> 210 ^o With leads to the formation of by-products: hexachlorobutadiene and polychloromethanes.

 The proposed method has the following advantages over the prototype.

 1. High (quantitative) yield of the target product.

 2. The availability and low cost of catalyst components.

 3. Low consumption of manganese catalyst.

 4. Simplification of the procedure for the isolation of the target products after removal of the solvent - hexachloroethane is isolated under reduced pressure.

 5. The formation of a small amount of waste.

 6. Unreacted carbon tetrachloride can be reacted without further purification.

 7. Cost reduction and simplification of the technology as a whole by reducing energy and labor costs, environmental safety of the process.

 The proposed method is illustrated by examples.

EXAMPLE 1. 0.01 mmol Mn (acac) ₃ , 0.02-0.04 mmol of acetone and 20 mmol of carbon tetrachloride were placed in a stainless steel stainless steel autoclave (V = 17 ml), the autoclave was sealed and the reaction mixture was heated at 200 ^o C for 3 hours. After the reaction, the autoclave was cooled to room temperature, opened, the reaction mass was filtered through a layer of Al ₂ O ₃ . Unreacted CCl _{4 was} distilled off, the residue was isolated by distillation. Received a white crystalline product with 70% yield, T. subl. 186.5 ^o C. (lit. data: 184 ^o C [2]).

IR (v, cm ^-1 ): 760
¹³ C NMR spectrum (δ, ppm): 105.20.

EXAMPLE 2. In a steel micro autoclave (V = 17 ml) or in a glass ampoule (V = 20 ml) (the results of parallel experiments are practically the same), 0.01 mmol Mn (acac) ₃ , 0.02-0.04 mmol of adamantanol was placed -2.20 mmol CCl of ₄ and 5 ml of alcohol (ethanol, methanol, etc.), the autoclave was closed (the ampoule was sealed), and the reaction mixture was heated at 200 ^° C for 1 h. After appropriate treatment, hexachloroethane was obtained in quantitative yield (~ 99%).

Claims (1)

A method of producing hexachloroethane by decomposition of carbon tetrachloride, characterized in that the reaction is carried out in the presence of a two-component manganese catalyst system [MnCl ₂ , Mn (OAc) ₂ , Mn (acac) ₃ ] - ketone (acetone, cyclopentanone, cyclohexanone, adamantane-2), at a temperature of 200 ^o C, for 1-3 hours at a molar ratio of [Mn]: [ketone]: [CCl ₄ ] = 1: 2-4: 1000-2000 in alcoholic solvents.

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