JP2808695B2 - Preparation of thiophosgene - Google Patents

Description

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> As a conventional production method, perchloromethyl mercaptan (hereinafter abbreviated as PCMM) is supplied in the presence of iodide in an organic solvent-water mixed solvent, and sulfur dioxide or hydrogen sulfide is supplied and reduced in gaseous form. A method for producing thiophosgene is known (JP-A-62-176910).

<Problems of the Prior Art> In the method described in Japanese Patent Application Laid-Open No. 62-176910, since sulfur dioxide and / or hydrogen sulfide are supplied in gaseous form, excess gas not dissolved in the reaction solution is reacted. Spills out of the vessel. Therefore, accompanying the outflow of the gas,
Thiophosgene, which is the target substance, is released outside the reactor, resulting in a decrease in yield. When run on a large scale, the effluent of thiophosgene from the reactor is very dangerous.

<Means for Solving the Problems> The present inventors have conducted intensive studies on an industrial and safe production method of thiophosgene.
By adopting a method of supplying and reacting MM, thiophosgene production can be carried out without adjusting the aqueous solution of the sulfurous acid in the reactor after transferring the aqueous solution, and the heat generation is small, and furthermore, the reaction is carried out outside the reactor. And found that it could be produced safely without thiophosgene spills. However, this method can safely produce thiophosgene, but the thiophosgene yield is lower than the conventionally known method of supplying and reacting sulfur dioxide in an organic solvent-water mixed solvent of PCMM. Had disadvantages. The present inventors have further conducted a diligent study on a method of supplying PCMM to a sulfurous acid aqueous solution to cause a reaction, and as a result, one or a mixture of two or more kinds of catalysts selected from sulfur monochloride, sulfur dichloride or iodine was added to PCMM. The inventors have found that thiophosgene can be produced in a high yield irrespective of the supply rate of PCMM by supplying the dissolved PCMM to a mixed solvent of a sulfurous acid aqueous solution and an organic solvent and causing the reaction, and thus completed the present invention.

That is, in the present invention, a mixed solution of a sulfurous acid aqueous solution and an organic solvent is dissolved with one or a mixture of two or more kinds of catalysts selected from sulfur monochloride, sulfur dichloride and iodine.
The present invention provides a process for producing thiophosgene, which comprises supplying and reacting PCMM. <Function> Hereinafter, the present invention will be described in detail.

In the method of the present invention, water is charged into a reactor in advance, and gaseous sulfur dioxide is supplied by bubbling and dissolved therein to prepare an aqueous sulfurous acid solution. Next, while stirring the obtained aqueous sulfurous acid solution, PCMM in which the catalyst is dissolved is supplied to the aqueous sulfurous acid solution and reacted. The addition of the organic solvent to the reaction system may be performed before or after the sulfur dioxide is dissolved. The PCMM in which the catalyst is dissolved may be supplied and reacted without a solvent, or may be supplied and reacted as an organic solvent solution.

As the organic solvent used in the present invention, any one can be used as long as it is inert to PCMM, sulfur dioxide, sulfurous acid and a catalyst.Generally, dichloromethane, chloroform, carbon tetrachloride, Halogenated hydrocarbon solvents such as dichloroethane, benzene, toluene,
Aromatic hydrocarbon solvents such as xylene, ethylbenzene and mesitylene are fried.

The amount of the organic solvent can be used in any ratio with respect to PCMM.
９9 weight ratio.

The catalyst used in the present invention is sulfur monochloride, sulfur dichloride and iodine, each of which may be used alone or as a mixture of two or more.

The catalyst can be added in any amount with respect to the PCMM to be used for the reaction.However, if the amount is too small, the reaction rate is small and not industrial, and if a large amount is used, there is no significant improvement in the reaction rate. Not economical. Therefore, the amount is preferably 0.5 to 3.0 mol%. Furthermore, as the concentration, for PCMM to be supplied or the total amount of the supplied solution,
It is desirable that the content be 4.0 wt% or less.

The concentration of the aqueous sulfurous acid solution used for the reaction can be any concentration as long as it is below the saturation solubility in water.However, if the concentration in the aqueous solution is 4 wt% or less, the solution volume becomes large and it is not economical. In some cases, sulfurous acid gas is generated by sulfuric acid and hydrochloric acid by-produced by the reaction. Preferably, the concentration in the aqueous solution is 4% or more and 90% by weight or less of the saturated dissolution amount.

In addition, the amount of sulfurous acid charged is equimolar to PCMM.
The molar ratio may be in the range of 5.0 times, but excessive use is not preferred because the generated thiophosgene may be decomposed in some cases.If the amount is less than equimolar, the conversion is less than the amount required for the reaction of PCMM. Lower. Therefore, the molar ratio is preferably in the range of 1.1 to 3 times the molar amount.

The reaction temperature can be in the range of 0 to 60 ° C,
At 0 ° C., condensation of water may occur. At 20 ° C. or higher, the solubility of sulfurous acid in water becomes low, so a large amount of water is required, and the size of the reactor is undesirably large. Therefore, the reaction temperature is preferably in the range of 5 to 20C.

The supply rate of PCMM or its organic solvent solution can be any rate, and the supply time can be set in consideration of the size of the reactor used and the heat removal capacity.

After supplying PCMM, the target thiophosgene is obtained by aging for about 0.5 to 8 hours.

<Effect> The present invention provides a safe and high-yield production method of thiophosgenesgene.

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

Example 1 54.7 kg of water was charged into a 100 glass-lined reactor equipped with a cooling jacket equipped with a stirrer, and 4.76 kg of sulfur dioxide was supplied and dissolved while bubbling in a gaseous state from a cylinder while stirring. Then, after attaching a thiophosgene trap charged with 2.0 kg of aniline and 3.0 kg of carbon tetrachloride to the vent line, 14.0 kg of carbon tetrachloride was charged into the obtained sulfurous acid aqueous solution, and then iodine 45 was added to 12.0 kg of PCMM.
A mixture of PCMM and iodine in which 8.8 g had been dissolved was supplied over 3 hours by a metering pump, and aging was performed for 5 hours. PCMM
The temperature during feeding was 18-20 ° C, and aging was performed at 20 ° C. After completion of the reaction, the mixture was settled and separated, and then a thiophosgene-containing solution 21.3 was added.
kg gained.

The obtained solution was quantified by gas chromatography.As a result, the yield of thiophosgene was 7.28 kg and the yield was 98.1.
% And the PCMM conversion was 99.9%.

Further, diphenylthiourea generated by scattering of thiophosgene was not detected in the aniline trap installed in the vent line.

Examples 2 to 5 Using the same reaction apparatus as in Example 1, the reaction was carried out under the conditions shown in Table 1. The results are shown in Table 1.

Comparative Example 1 Using the same reactor as in Example 1, iodine, sulfur dichloride, sulfur dioxide, water and toluene were charged under the conditions shown in Table 1, and then PCMM was supplied to carry out the reaction.

 The results are shown in Table 1.

Comparative Example 2 Using the same reaction apparatus as in Example 1, water, a catalyst, a solvent, and PCMM were charged, and then a reaction was carried out by supplying sulfur dioxide gas.

 The results are shown in Table 1.

Note that 140 g of thiophosgene had flowed out to the vent line.

Claims (1)

(57) [Claims] 1. A perchlormethyl mercaptan in which one or a mixture of two or more kinds of catalysts selected from sulfur monochloride, sulfur dichloride and iodine is dissolved is supplied to a mixed solution of an aqueous solution of sulfurous acid and an organic solvent to cause a reaction. A process for producing thiophosgene, comprising: