SU1735266A1 - Method for producing chloral - Google Patents

Abstract

The essence of the invention: product: trichloroacetic aldehyde BF C2H130, bp. 97.8 ° C. Reagent 1: an organic phase containing ethanol. Reagent 2: chlorine. Reaction conditions: the subsequent hydrolysis of chlorination products with water in the presence of catalytic amounts of hydrochloric acid, ethanol, separated in the hydrolysis step, is treated with an equimolar amount of austaldehyde to produce a mixture that is added to the same amount of ethanol, pre-mixed with an equal amount of 25- 29% hydrochloric acid, the obtained product is maintained at 10-60 ° C. defend and separate into aqueous and organic phases, the latter is directed to chlorination. 1 tab.

Description

The invention relates to aldehydes, in particular, to an improved method for the production of chloral, an intermediate product in the production of chloroform, the herbicide sodium trichloroacetate (THAN) and the insecticide 1,1-di (4-methoxy-phenyl, 2,2-trichloroethane (mesoxa).

A known method of producing chloral by chlorination of ethyl alcohol in a continuous countercurrent scheme in a cascade of reactors with the separation of the target product in the form of chloral hydrate from the reaction mass by rectification of the latter in a stream of heated to 90 ° C off-gases (chlorine and hydrogen chloride) and returning the distillation residue a complex mixture of high-boiling components in the chlorinator.

This method is characterized by a high specific consumption of chlorine and the formation of a significant amount of by-products — hydrogen chloride, ethyl chloride, and ethyl esters of chloroacetic acids, which is due to the presence of a chlorinated ethanol stage.

The closest in technical essence to the present invention is a method for producing chloral, in which ethyl alcohol is chlorinated by any known method, and the resulting mixture of chlorination products is subjected to hydrolysis with water taken in excess from stoichiometry. In this case, the hydrolysis step is combined with distillation of the azeotrope of ethyl alcohol, and benzene is added to the resulting aqueous solution of chloral and the chlorine is separated by azeotrol distillation of water with benzene. The resulting azeotrope of ethyl alcohol is sent to the chlorination system, where it is added to fresh alcohol. When chloral is released, the water fraction and benzene are also obtained, which are returned to the process.

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This method does not affect the improvement of the chlorination stage, therefore it has all the disadvantages that are characteristic of chlorinating ethyl alcohol. Thus, 4.5 mol of chlorine is consumed to produce 1 mol of chloral from ethyl alcohol, and 5.8 mol of abgas hydrogen chloride is liberated. As a result, byproducts such products as ethyl chloride (7.7 wt.%) And ethyl chloride are formed. chloroacetic acid esters (2 wt.%), for the isolation and utilization or disposal of which requires the creation of specialized plants. Thus, the disadvantages of this method are the high specific consumption of chlorine and the formation of a significant amount of these by-products.

The purpose of the invention is to reduce the specific consumption of chlorine, to reduce the yield of abgas hydrogen chloride and to avoid the formation of by-products ethyl chloride and ethyl esters of chloroacetic acid.

The goal is achieved in that according to the method of producing chloral by stepwise chlorination of an organic phase containing ethanol, chlorine gas, followed by hydrolysis of chlorination products with water in the presence of catalytic amounts of hydrochloric acid and separation of the desired product and excess water, with the return of water on hydrolysis and ethanol to the chlorination stage, ethanol, isolated at the hydrolysis stage, is treated with an equimolar amount of acetaldehyde to form a mixture, to The latter is added to the same amount of ethanol, pre-mixed with an equal amount of 25-29% hydrochloric acid, the resulting product is kept at 10-60 ° C, settled and separated into aqueous and organic phases, the latter is directed to chlorination.

Example. 1-stage. 48.4 g of 95% ethanol (1 mol) are taken, and 44 g (1 mol) of acetaldehyde are added with stirring and cooling. By mixing 48.4 g of 95% ethanol with the same mass of 27% hydrochloric acid, a second mixture is prepared, to which the first mixture is added with stirring and cooling. The resulting mass is incubated for 4 hours at a temperature of 10-60 ° C. The mass is then settled and divided into two layers: aqueous (74.7 g) and organic (112.6 g). The composition of the organic phase, wt.%: Diethylacetal 80.1; ethanol 14.4; acetaldehyde 5.2; HCI 0.3. The concentration of HC in the aqueous phase is 16.87%.

For the purpose of purification, the organic and aqueous phases are separately distilled in a packed distillation column (10 tons). The maximum temperature in the bottom of the column is maintained at 102 ° C during the distillation of the organic phase and 79 ° C during the distillation of the aqueous phase. The reflux number in the course of the distillation of the phases is increased from 8 to 30, the distillate is collected in one

0 receiver. As a result of the distillation, 89.1 g of a purified organic phase with a boiling point of 102 ° C are obtained; 63.5 g of purified aqueous phase (HC1 concentration 18.58%); 32.2 g of the light fraction of the following composition, wt%: ethanol 62.42; acetaldehyde 30.74; water and HCI 6.84. The yield of the organic phase for chlorination per cycle is 75.5%. The yield can be increased by returning to the light fraction process. The aqueous phase formed during the preparation of the organic phase for chlorination, after being stabilized with abgas hydrogen chloride to a concentration of 25-29%, can be used industrially as an abgas hydrochloric acid.

The results of experiments that differ in the conditions of the present stage, the values of the temperature of exposure and the concentration of hydrochloric acid are presented in the table.

It can be seen from the table that it is advisable to limit the process to the limits of a temperature of 10-60 ° C and a concentration of cobalt acid of 25-29%.

The indicated limits of the concentration of HCI allow the use of chlorine produced in the process of unpurified standard hydrochloric acid.

2-stage. In a vessel protected from light, chlorine gas is treated with 59 g of the organic phase obtained in the first stage. Chlorine control

5 and refrigerant for cooling the vessel, the temperature in the vessel is maintained: at the beginning of chlorination 20–40 ° C, in the middle of the process 40–60 ° C and at the end of the process 60–90 ° C. A total of 112 g of chlorine (1.58 mol) are consumed.

0 The exhaust gases are bubbled through a 5% solution of caustic soda and collected in a gasholder. 109.8 g of the reaction mass containing 99.5% trichloroacetaldehyde diethylacetal and 0.5% dichloroacetaldehyde diethyl acetal are obtained. In the composition of the reaction mass, ethyl esters of chloroacetic acids were not detected. The presence of ethyl chloride in it has not been established by the method of chromatographic analysis of the gas phase of the gas-holder. The specific chlorine consumption for obtaining trichloroacetaldehyde diethyl acetal is 3.2 mol / mol, the yield of abgas hydrogen chloride calculated from the residual content of sodium hydroxide and the concentration of sodium hypochlorite in solution, 3.2 mol / mol.

3 stage. In the cube nozzle distillation column (10 tons, tons). heated and agitated, 100 g (0.45 mol) of trichloroacetaldehyde diethyl acetate obtained in the second stage are placed, and 81 g of water acidified with 1 ml of 10% hydrochloric acid is added. While stirring the contents, the temperature in the cube is raised to 78 ° C, and ethyl alcohol released in the form of a 95% solution is distilled off from the reaction mass. In the process of distillation, the reflux number is increased from 8 to 30. At the end of the hydrolysis and distillation in the receiver, 49.2 g of the alcoholic fraction with an admixture of chloral are obtained, in the bottom of the column 132.8 g of an aqueous solution of chloral concentration 48.3 wt.%. The yield of chloral is 96.67%.

The specific consumption of chlorine, calculated from the yield of chloral, is 3.31 mol / mol. The same yield of abgas hydrogen chloride.

The yield of chloral over acetaldehyde, taking into account the three stages of the process, is 92.76%. The expense ratio for acetaldehyde is 1.078 mol / mol.

The proposed method in comparison with the known allows to obtain 1 mol

Chloral reduce the specific consumption of chlorine by more than 1 mol (3.31 mol instead of 4.5), and reduce the yield of abgas hydrogen chloride by 2.5 mol (3.31 mol instead of 5.8 mol), exclude conditions for the occurrence of side processes with the formation of ethyl chloride and ethyl esters of chloroacetic acids — both are absent in the reaction products.

Claims (1)

Claims The method of producing chloral by stepwise chlorination of an organic phase containing ethanol with chlorine gas, followed by hydrolysis of chlorination products with water in the presence of catalytic amounts of hydrochloric acid and separation of the resulting product by hydrolysis of ethanol, the desired product and excess water, returning water to hydrolysis and ethanol stage of chlorination, characterized in that, in order to reduce the specific consumption of chlorine, reduce abgas hydrogen chloride and eliminate the formation of side p of the products, the ethanol separated in the hydrolysis stage is treated with an equimolar amount of acetaldehyde to obtain a mixture which is added to the same amount of ethanol previously mixed with an equal amount of 25-29% hydrochloric acid, the resulting product is maintained at 10-60 ° C; they are settled and separated into aqueous and organic phases, the latter is directed to chlorination. Table continuation Note. When using hydrochloric acid concentrations of less than 25%, it is difficult to divide the reaction mixture into organic and aqueous phases.