JPH0337110A - Production of thiophosgene - Google Patents

Abstract

PURPOSE:To improve yield and conversion ratio by reacting a solution of perchloromethylmercaptan in an organic solvent with an aqueous solution of sulfurous acid in the presence of a catalyst. CONSTITUTION:A reactor is charged with perchloromethylmercaptan, a catalyst and an organic solvent. An aqueous solution of sulfurous acid is fed to the reactor and the reaction is carried out. Dichloromethane, carbon tetrachloride, etc., are used as the organic solvent. The concentration of perchloromethylmercaptan in the organic solvent is preferably 10-70wt.%. Sulfur monochloride, sulfur dichloride, alkali metal iodide, iodine or a mixture thereof is used as the catalyst. Consequently, thiophosgene is safely produced with slight heat generation by the reaction without outflow of excessive sulfur dioxide.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for producing thiophosgene. Thiophosgene is very useful as a synthetic intermediate for pharmaceuticals and agricultural chemicals.

<Prior art> The conventional manufacturing method is to reduce perchloromethyl mercaptan (hereinafter abbreviated as PCMM) by supplying sulfur dioxide or hydrogen sulfide in gaseous form in an organic solvent-water mixed solvent in the presence of iodide. A method for producing thiophosgene is known (Japanese Unexamined Patent Publication No. 176910/1982).

<Problems with the prior art> In the method described in JP-A-62-176910, sulfur dioxide and/or hydrogen sulfide are supplied in gaseous form, so excess gas that is not dissolved in the reaction liquid is reacted. Spills out of the container. Therefore, the target thiophosgene is released out of the reactor along with the outflow of the gas, resulting in a decrease in yield. Furthermore, when the process is carried out on a large scale, thiophosgene flowing out from the reactor is very dangerous.

Means for Solving the Problems> The present inventors conducted intensive studies on an industrial and safe production method for thiophosgene, and found that by dissolving sulfur dioxide in water, supplying it as an aqueous sulfite solution, and causing the reaction, The present inventors have discovered that thiophosgene can be produced safely in a high yield with little heat generated by the reaction and no gaseous outflow of excess sulfur dioxide, leading to the completion of the present invention.

That is, the present invention provides a method for producing thiophosgene, which is characterized by supplying and reacting an aqueous subacid solution to a solution of perchloromethyl mercaptan in an organic solvent in the presence of a catalyst, and the catalyst used in the present invention is , sulfur monochloride, sulfur dichloride, alkali metal iodide, or iodine, or a mixture of two or more thereof.

Effect〉 The present invention will be explained in detail below.

In the method of the present invention, PCMM, a catalyst, and an organic solvent are charged in advance into a reactor, and an aqueous sulfite solution is supplied to the reactor for reaction. Among the catalysts, alkali metal iodides having low solubility in organic solvents may be charged in solid form, or may be dissolved in a small amount of water without any problem.

The organic solvent used in the present invention is PCMM.

Any material can be used as long as it is inert to sulfur dioxide and sulfur dioxide, but - in the membrane, halogenated hydrocarbon solvents such as dichloromethane, chloroform, carbon tetrachloride, dichloroethane, benzene, toluene, Aromatic hydrocarbon solvents such as xylene, ethylbenzene, and mesitylene are used.

The concentration of PCMM in the organic solvent can be carried out at any concentration, but for reasons such as economical efficiency and ease of reaction control,
Preferably, the concentration ranges from 10 to 70 wt%.

The catalysts used in the present invention include sulfur monochloride, sulfur dichloride, alkali metal iodides, and iodine, each of which may be used alone or as a mixture of two or more. Any alkali metal iodide can be used, but potassium iodide and sodium iodide are preferred.

The amount of catalyst added can be at any concentration relative to the PCMM used in the reaction, but if it is too small, the reaction rate is too low to be industrially practical, and if it is used in a large amount, no significant improvement in the reaction rate will be seen. Because of this, it is not economical.
The amount of catalyst added is P as one kind or a mixture of two or more kinds.
0.3-5 for CMM. The Qmo range is preferably 1%.

The concentration of the sulfite aqueous solution used in the reaction can be any concentration as long as it is below the saturated solubility in water, but if the concentration in the aqueous solution is below 4 wt%, the amount of liquid will be large and it is not economical, and the saturated dissolution amount is Sulfur dioxide gas may be generated due to sulfuric acid and hydrochloric acid produced as by-products of the reaction.
Preferably, the concentration in the aqueous solution is 4 wt% or more and the saturated dissolved amount is 90 wt% or less.

In addition, the amount of sulfite supplied is 1°0 to 5% relative to PCMM.
．． It is fine as long as it is in the range of 0 times the molar amount, but using too much excess may cause decomposition of the generated thiophosgene, which is undesirable. If it is less than equimolar, the conversion rate will be lower because it is less than the amount necessary for the reaction of PCMM. It gets lower. Therefore, it is preferably in a range of 1.1 to 3 times the molar amount.

The reaction temperature can range from 0 to 60°C, but
At 0°C, water may condense, and at 20°C or higher, the solubility of sulfurous acid in water decreases, requiring a large amount of water and increasing the size of the reactor, which is not preferable. Therefore, the reaction temperature is preferably in the range of 5 to 20°C.

By increasing the supply rate of the sulfurous acid aqueous solution, it is possible to complete the reaction in a short time, but the amount of heat generated per unit time is large, so the reaction cannot be carried out at a specified temperature. It is preferable to set the feed rate to .

After feeding the sulfurous acid aqueous solution, the target thiophosgene is produced in high yield by aging for about 0.5 to 8 hours.
Obtained with high conversion rate.

Effects> The present invention provides a high-yield and safe method for producing thiophosgene.

<Examples> The present invention will be specifically described below with reference to Examples, but the present invention is not limited to these Examples.

[Reference Example 1] Constant temperature method for gasifying thiophosgene A 52 round bottom flask equipped with a blowing tube was charged with 3 carbon tetrachloride, 0 kg and 2.0 kg of aniline, and 400 g of thiophosgene was heated and gasified therein for 8 hours. The reaction was continued for 1 i. Immediately after the supply of thiophosgene was completed, 500 ml of water was added 12 to separate the layers, and the organic layer was analyzed by reverse phase liquid chromatography to quantify the produced diphenylthiourea.

As a result of quantitative analysis, the amount of diphenylthiourea produced was 768.5g.
It was confirmed that the method had a thiophosgene collection rate of 97.0% and was sufficiently applicable to the collection and quantitative determination of gasified thiophosgene.

[Example 1] 62.0 g of water was charged into a TOOG glass-lined reactor equipped with a stirrer and a cooling jacket, and while stirring, 6.19 g of sulfur dioxide was supplied from a cylinder while bubbling in gaseous form and dissolved. The obtained sulfite aqueous solution was extracted and transferred to a supply tank.

Next, after washing the reactor with water, a thiophosgene trap containing 2.0 kg of aniline and 3 kg of carbon tetrachloride was installed in the vent line, and then a PCMM12
．． 449.9 g of solid potassium iodide and 18.0 kg of carbon tetrachloride were charged, and the mixture was cooled with stirring to bring the temperature to 15°C. The sulfur dioxide aqueous solution prepared above was supplied to the solution over a period of 3 hours using a metering pump, and the solution was further aged for 3 hours. During the supply of the sulfurous acid aqueous solution, an increase in the amount of liquid in the reactor caused a gas outflow of approximately 63 D from the vent line, but after the supply was completed and the aging stage began, the reactor became under negative pressure.

After the reaction was completed, the mixture was stabilized and separated to obtain 25.3 kg of the desired carbon tetrachloride solution of thiophosgene.

As a result of analysis by gas chromatography, 7.27 kg of thiophosgene (yield 97.9%) and unreacted PCMM were found.
It contained 24 g (conversion rate 99.8%).

Further, when diphenylthiourea was quantified using the liquid chromatography described above in the aniline trasobu connected to the vent line, no detection was found.

[Examples 2 to 4] Using the same apparatus as in Example 1, reactions were carried out under predetermined conditions using the sulfite aqueous solution, raw materials, and catalyst charging composition shown in Table 1. The results are shown in Table 1.

In addition, diphenylthiourea was not detected in the aniline trap in all Examples.

[Comparative Examples 1 and 2] In the same apparatus as in Example 1, PCM was prepared using the reaction composition shown in Table 1.
M, a catalyst, a solvent, and water were charged and stirred. Next, sulfur dioxide was supplied without bubbling, and the reaction was carried out under the conditions shown in Table 1.

The results are shown in Table 1.

During the supply of sulfur dioxide, approximately 5001 ON of gas components were generated in Comparative Example 1 and approximately 90 ON in Comparative Example 2. In addition, the heat generation was large and the equipment used in this test had insufficient heat removal, so it was impossible to carry out the test at the initial set temperature.

Claims (2)

[Claims] (1) A method for producing thiophosgene, which comprises supplying an aqueous sulfite solution to a solution of perchloromethyl mercaptan in an organic solvent in the presence of a catalyst and allowing the reaction to occur. (2) The production method according to claim (1), wherein the catalyst is one or a mixture of two or more of sulfur monochloride, sulfur dichloride, alkali metal iodide, and iodine.