CS241092B2 - Process for the preparation of perchloromethylmercaptan - Google Patents

Abstract

The invention relates to a method for producing perchloromethylmercaptan by chlorination of carbon disulfide in an aqueous medium. In this method, the starting materials and gaseous chlorine are introduced at ambient pressure or at elevated pressure, at a temperature above the boiling point of carbon disulfide, into an aqueous catalyst medium containing sulfuric acid and hydrochloric acid and maintained in constant circulation, the reactants are adsorbed in the aqueous medium with increased stirring intensity or by using elevated pressure, after the reaction has taken place, the organic phase is separated from the resulting reaction mixture and fractionated, expediently by steam distillation, and the aqueous medium is introduced back into the reaction process as a catalyst.

Description

241092

The present invention relates to an improved process for the preparation of perchloromethylmercaptan.

Perchloromethylmercaptan or trichloromethylsulphonyl chloride is an important intermediate used in the manufacture of fungicidal, bactericidal and germicidal compositions, lubricating oil additives, soil disinfectants, and pharmaceuticals.

According to a widely used process, carbon disulphide is chlorinated in an aqueous medium, and sulfuric acid and hydrochloric acid are formed as intermediate products due to oxidation and hydrolytic decomposition, which can be used as by-products. The reaction proceeds according to the following equation: CS2 + 5 Clz + 4 H2O - CIS - CCl3 + + H2SO4 + 6 HC1

The by-products can be easily separated from the desired product. In fact, two phases are formed, the acidic aqueous phase and the organic phase containing, in addition to the perchloromethylmercaptan obtained, also the starting carbon disulphide and carbon tetrachloride formed as a result of the chlorinating. Carbon disulfide and carbon tetrachloride can be separated from perchloromethylmercaptan on the basis of the large difference in boiling point.

A process for the preparation of perchloromethylmercaptaine in an aqueous medium is also described in U.S. Pat. No. 1,437,908. In this process, the importance and importance of hydrochloric acid in the choking of carbon disulphide in an aqueous medium is emphasized. The chlorination rate and yield depend on the initial hydrochloric acid concentration. The optimum acid concentration is 15 to 20%. The reaction rate is enhanced by multivalent metals (e.g., cobalt, lead, nickel) and emulsifiers. Yield 88%, product purity 95%. U.S. Pat. No. 3,993,693 describes a continuous process. In this process, the starting sulfuric acid concentration is 40%, and the residence time in the reactor is 3.5 hours. A yield of 78.4% is achieved. The aqueous phase is separated by distillation into sulfuric acid and hydrochloric acid.

According to German Patent Publication No. 2,156,329, water, carbon disulfide and chlorine are continuously introduced in a continuous 3 m tubular reactor. The yield was 89.5%, the yield with respect to space and time was 28.8 kg / 100 l / h. In the known processes, the relationship between the reaction temperature increase and the yield is found to be higher than 30 ° C, the reaction rate is slower than 30 ° C and virtually no perchloromethyl mercaptan is formed above 40 ° C. For this reason, the chlorination is carried out at a lower temperature. U-realization of the reaction is therefore complicated, since during the reaction the released heat exceeds the normal value (670 J / mol). The large amount of heat generated must be removed at a lower temperature, requiring the cooling system to build up and operate, and to increase the built-in cooling surface. conductivity; therefore, larger equipment must be used. Another difficulty is the fact that they have to process and handle large volumes of highly flammable and hazardous materials.

In addition to the main reaction, chlorination occurs. The amount of carbon tetrachloride thus formed is proportional to the conversion step. In order to prevent chlorination, the chlorination is carried out only to the lower chlorination stage. The carbon disulphide is reintroduced into the reaction. The unreacted carbon disulfide is recovered by distillation. In the distillation or vacuum distillation process, the presence of a low-temperature autoignition temperature (98 [deg.] C.) is a fire hazard. SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved process for the preparation of perchloromethyl mercaptan and to eliminate the aforementioned disadvantages.

The invention is based on the finding that the rate of chlorination of carbon disulphide in the aqueous medium under certain conditions increases proportionally with the increase in temperature. The rate is influenced by physical and chemical means. The physical route is the solubility of chlorine gas in aqueous and organic phases. Chemical is the reaction to be carried out. At a temperature above 30 ° C, the solubility of the gaseous chlorine in the aqueous medium is lower, resulting in a reduction in the reaction rate. It has been found that when the reaction temperature rises, the reaction rate is reduced because chlorine is no longer more soluble in the aqueous medium. If the solubility of the chlorine is maintained, the reaction rate will be higher when the temperature increases. In view of the fact that the contact of the three different phases or the reaction in the three different phases of the existing reactants is important for the reaction, the special mixing of the reactants to achieve their better contact must be used. This is possible with the aid of mechanical agitators, turbine agitators, centrifugal pumps, vibratory agitators, turbulent flow in pipes, ultrasonic generators or similar devices, optionally in combination with each other.

It is preferable to carry out the process continuously, whereby the starting materials are continuously pushed forward in a suitable machine, with intensive and effective mixing. Instead of intensive mixing, pressurization may also be used, or a combination of mixing and overpressure may be used.

The invention therefore relates to a process for the preparation of perchloromethyl mercaptan by choking carbon disulphide in an aqueous medium, which comprises introducing a starting material and a chlorine gas at ambient temperature or at elevated pressure at a temperature above the carbon disulphide. circulation, to an aqueous catalyser medium containing sulfuric acid and hydrochloric acid; reactants with an increase in agitation or using an elevated pressure adsorbing aqueous medium; after the reaction from the reaction mixture, the organic phase is separated off and the fractionation is expediently carried out by distillation with water vapor and the aqueous medium is fed back as a catalyst.

In view of the fact that in the process according to the invention with respect to the methods known from the prior art it is used at elevated temperature, the reaction rate is higher and the reactor time is shorter. Therefore, the continuous process can be carried out in smaller installations. With smaller reactors, there is also less material in the plant. Since the reaction is carried out at a higher temperature, process water can be used to cool it and it is unnecessary to incorporate special cooling equipment into the process. As a result of the greater reaction velocity, the smaller amount of flammable substances is used at once, so that the problems with the danger of fire and health problems are reduced. The increased reaction rate has the advantage that the residence time of the reactants in the system is short, thereby minimizing the risk of precipitation.

The invention is further illustrated by the following non-limiting examples. Example 1 (Comparative Example)

A 1.5 liter flask equipped with an intensive suction stirrer was weighed with 76 g of carbon disulfide, 570 ml of water, and 500 ml of acidic solution containing 12% sulfuric acid and 26.7% hydrochloric acid. The flask is equipped with a gas introduction tube extending below the surface of the liquid in the flask. The vent tube of a very carefully sealed flask is installed with water-filled bubbler to show that the non-reactive gases are leaving the flask. By the action of a high velocity suction agitator, the gas space of the bulb is introduced into the liquid by the gas stream and thereby intensively contacts the gaseous and liquid phases. g) chloroacetic gas gaseous, such that no significant leakage of chlorine gas occurs. The temperature of the reaction mixture is maintained at 30 ° C by cooling. The required amount of chlorine can be introduced in about three hours. On the reaction and after stirring, the reaction mixture is separated into two phases. The lower phase yielded 165 g of organic layer (perchloromethylmercaptan content 91.2%), yield 81%, containing 3.1% of unreacted carbon disulphide, 5.3% of carbon tetrachloride as a result of chlorination. 0.4% of other impurities Example 2

76 grams of carbon disulfide, 325 grams of water and 750 ml of acidic solution containing 12% sulfuric acid and 2: 8.7% of hydrochloric acid are weighed into the apparatus of Example 1. During cooling, 200 grams of chlorine gas is introduced during 30 minutes. After phase separation, 127 g (73.92%) of perchloromethylmercaptan, 24.9-3% of syrup and 0.76 g of carbon tetrachloride are obtained. The yield, based on chlorine, is 89.55%. The partial chlorination yield may be improved, the amount of carbon tetrachloride resulting from the conversion may be reduced and the rate of formation of the methylmercaptan perchlorate increased to about 2.2 times. The chlorinated crude mixture is worked up by steam distillation. In the steam distillation, 33 g of the carbon black (85% carbon disulphide) and 86 g of perchloromethylmercaptan distillate are obtained. The content of chloromethylmercaptan in the main distillate is 98.2%. Example 3

A valve opening at 50 kPa is incorporated into the gas discharge conduit of the apparatus of Example 1. 76 grams of carbon disulfide, 325 ml of water and 750 roles of 12% acid sulfuric acid and 26.7% hydrochloric acid were weighed into the apparatus. chlorine. The reaction product obtained contained 125 g of perchloromethyl mercaptan (73.1%), 25.8% of carbon disulfide and 0.78% of carbon tetrachloride. The yield was 87.2% (with respect to introduced chlorine). The reaction rate can be increased by making the chlorination pressure. The reaction mixture can be processed periodically from above by water-steam distillation. Example 4

Continuous chlorination is carried out in a reactor equipped with a stirrer and divided into several chambers (length 2 m, diameter 200 m). 13.0 kg / hs carbon, 42.5 kg / h chlorine, 69 kg / h water and are introduced into the bottom of the reactor as a catalyst of 400 kg / h of acidic aqueous solution containing 12% sulfuric acid and 28.7% hydrochloric acid. The reactant leaving the acid water / organic phase mixture is separated in a separator. The major acid portion is recycled as the catalyst after heating. The organic phase reactor (24.95 kg / h) contained 83.2% perchloromethylmercaptan, 15% carbonate, 1.15% carbon tetrachloride and 0.65% other impurities. The chlorinated reaction mixture is introduced in the middle of the rectification

Claims (1)

241092 of 94% methyl percaptan. The carbon disulphide obtained by distillation returns to the process as a batch. columns. Carbon disulfide is removed from the product using water vapor introduced into the bottom of the column and the reflux of the column column produced. 19.95 kg / h of perchloric acid are obtained. The catalysts are introduced into the aqueous catalyst medium containing sulfuric acid and hydrochloric acid and maintained in a continuous circulation. the aqueous medium is returned to the reaction as a catalyst. Severografia, n. P., Závod 7, Most Price 2,40 Kcs