JP2808696B2 - Method for producing thiophosgene - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for producing thiophosgene of the present invention. 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 JP-A-62-176910, since the gas is supplied in the form of sulfur dioxide and / or hydrogen sulfide, excess gas not dissolved in the reaction solution is reacted. Spills out of the vessel. For this reason, thiophosgene, which is the target substance, is discharged out of the reactor accompanying the outflow of the gas, and the yield is reduced. When run on a large scale, the effluent of thiophosgene from the reactor is very dangerous.

<Means to be Solved by the Invention> 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. It was found that thiophosgene could be produced safely without spillage. 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 studied the method of supplying PCMM to an aqueous sulfurous acid solution and reacting the same. As a result, by supplying a specific amount of PCMM to sulfur dioxide and reacting it with sulfur dioxide per unit time (Hr), a high yield was obtained. It has been found that thiophosgene can be produced at a high rate, and the present invention has been completed.

That is, the present invention is characterized in that PCMM is supplied to a mixed solution of a sulfurous acid aqueous solution in which a catalyst is dissolved and an organic solvent in a supply amount of 0.45 times by weight or more per unit time (Hr) with respect to 1 part by weight of sulfur dioxide. The present invention provides a method for producing thiophosgene, and further comprises, as a catalyst, one or a mixture of two or more of sulfur monoxide, sulfur dioxide, alkali metal iodide and iodine. It provides a manufacturing method.

 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 is supplied thereto and reacted. The addition of the catalyst and the organic solvent to the reaction system may be performed before or after the sulfur dioxide is dissolved.

As the organic solvent used in the present invention, any solvent can be used as long as it is inert to PCMM, sulfur dioxide and sulfurous acid.Generally, halogens such as dichloromethane, chloroform, carbon tetrachloride, and dichloroethane can be used. And aromatic hydrocarbon solvents such as benzene, toluene, xylene, ethylbenzene and mesitylene.

The amount of the organic solvent to be used can be any ratio with respect to PCMM, but is preferably 0.4 to 9 times by weight with respect to PCMM for reasons such as economy and ease of reaction control.

The catalyst used in the present invention is sulfur monochloride, sulfur dichloride, alkali metal iodide or iodine,
Each may be used alone or as a mixture of two or more. As the alkali metal iodide, any substance can be used, but potassium iodide and sodium iodide are preferred.

The catalyst can be added in any concentration with respect to the PCMM used in the reaction.However, if the amount is too small, the reaction rate is small and not industrial, and if a large amount is used, the reaction rate is not greatly improved. It is not economical, therefore, the amount of catalyst added is one or more of PCMM
Is preferably in the range of 0.3 to 5.0 mol%.

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.

The amount of sulfurous acid charged is equimolar to 5.
The molar amount may be in the range of 0-fold molar amount, but excessive use is not preferred because the generated thiophosgene may be decomposed in some cases, and if it is less than equimolar, the conversion is less than the amount required for the reaction of PCMM. Lower. For this reason, preferably
It is 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, which is not preferable because the reactor size becomes large. Therefore, the reaction temperature is preferably in the range of 5 to 20C.

PCMM enables the reaction to be completed in a short time by increasing the supply amount per unit time of sulfur dioxide, but [(PCMM weight: kg) / (weight of sulfur dioxide: kg) / (Unit time: Hr)] is 3.0 (kg / kg / H
Above r), not only no remarkable effect is observed, but also the control of the reaction may be difficult due to the large amount of heat generated per unit time. On the other hand, when the ratio is 0.45 or less, a decrease in yield is not preferable. Therefore, preferably, [(PCMM weight: kg) / (sulfur dioxide weight: kg) / (unit time: Hr)] is 0.45 to 3.0.
(Kg / kg / Hr).

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 46.3 water was charged into a 100 glass-lined reactor equipped with a cooling jacket equipped with a stirrer, and 6.63 kg of sulfur dioxide was supplied and dissolved while bubbling in a gaseous state from a cylinder with stirring. Next, a thiophosgene trap charged with 2.0 kg of aniline and 3.0 kg of carbon tetrachloride was attached to the vent line, and iodine was added to the obtained aqueous sulfurous acid solution.
68.4 g and 41.0 kg of chloroform were charged and cooled while stirring, and the temperature in the reactor was adjusted to 10 ° C. After cooling, PCMM1
2.3 kg was supplied by a metering pump in 2 hours, and after aging at 12 ° C. for 4 hours, the solution was settled and separated to obtain 48.4 kg of a thiophosgene-containing solution. During the supply of PCMM, the temperature of the contents became 12 ° C. due to heat generation.

The obtained solution was quantified by gas chromatography, and as a result, the amount of thiophosgene produced was 7.43 kg, and the yield was 97.7%.
%, And the conversion rate of PCMM was 99.7%.

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 Examples 1 and 2 Using the same reactor as in Example 1, the reaction was carried out by supplying PCMM over 3 hours or more under the conditions shown in Table 1. The results are shown in Table 1.

Comparative Example 3 Using the same reactor as in Example 1, water, a catalyst, a solvent, and PCMM were charged, and sulfur dioxide was supplied as a gas to carry out a reaction.

 The results are shown in Table 1.

In addition, 165 g of thiophosgene was flowing out to the vent line.

Claims (2)

(57) [Claims] 1. A method in which perchloromethyl mercaptan is supplied to a mixed solution of a sulfurous acid aqueous solution in which a catalyst is dissolved and an organic solvent at a rate of 0.45 times by weight or more per unit time (Hr) per 1 part by weight of sulfur dioxide to cause a reaction. Characteristic method for producing thiophosgene. 2. The process according to claim 1, wherein one or a mixture of two or more of sulfur monochloride, sulfur dichloride, alkali metal iodide and iodine is used as the catalyst.