JPH03197310A - Industrial production of thiophosgene - Google Patents

Abstract

PURPOSE:To improve yield by reacting a solution of perchloromethylmeroaptan in aliphatic hydrocarbon solvent with aqueous solution of sulfurous acid in the presence of catalyst, separating the reaction solution and washing with water. CONSTITUTION:A container containing 5-15C straight chain, branched-chain or cyclic aliphatic hydrocarbon solvent such as pentane is charged with perchloromethylmercaptan (PCMM for short) in an amount to give 10-70wt.% concentration and further one or more catalysts of SCl, SCl2, an alkali metal iodide such as KI and I2 in an amount to give 0.3-5.0mol% based on PCMM. Then the solution is made to react with >= equimolar amount based on PCMM, preferably 1.1-3.0 mol of 4-90wt.% aqueous solution of sulfurous acid at 5-20 deg.C for 2-24 hours. After the reaction is over, a thiophoegene-containing mixed solution is allowed to stand, separated, formed thiophosgene is washed with an equal or more amount of water to give high purity thiophosgene.

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to an industrial method for producing thiophosgene.

Thiophosgene is very useful as a synthetic intermediate for pharmaceuticals and agricultural chemicals.

<Prior art> The conventional manufacturing method involves perchloromethyl mercaptan (
There is a known method for producing thiophosgene by supplying and reducing sulfur dioxide or hydrogen sulfide in gaseous form in an organic solvent-water mixed solvent in the presence of an iodine compound (hereinafter referred to as PCMM) (Japanese Unexamined Patent Publication No. 176910/1982). Public bulletin).

<Problems with the Prior Art> In the method described in JP-A No. 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 product, thiophosgene, is released out of the reactor along with the outflow of the gas, resulting in a decrease in yield. Also, when carried out on a large scale,
Escape of thiophosgene from the reactor is very dangerous.

Furthermore, the organic solvents described in the patent include carbon tetrachloride,
These include halogenated hydrocarbon solvents such as dichloromethane, chloroform, and dichloroethane, and aromatic hydrocarbon solvents such as benzene. In recent years, toxicity problems have been pointed out for halogenated hydrocarbon solvents, and handling standards have become stricter under laws and regulations related to environmental pollution. It has become to.

On the other hand, when aromatic hydrocarbon solvents such as benzene are used as reaction solvents, there is a risk of producing highly toxic chlorinated aromatic hydrocarbons as by-products since PCMM, which is a reaction raw material, is a perchlorinated product.

Means for Solving the Problems> As a result of intensive study on an industrial and safe production method for thiophosgene, the present inventors discovered that by supplying an aqueous sulfite solution to an aliphatic hydrocarbon solvent of PCMM in the presence of a catalyst and causing the reaction. , compared to the case where sulfur dioxide and/or hydrogen sulfide are supplied in gaseous form and reacted, the heat generated by the reaction is small, and excess sulfur dioxide does not flow out of the system.
It has been discovered that typhosgene can be produced safely with high yield.

Furthermore, the aliphatic hydrocarbon solvent used as a reaction solvent is
It has been found that it is less toxic and stable than halogenated hydrocarbon solvents, and does not have the same adverse effect on reactions.

In addition, impurities mixed into the thiophosgene obtained by the reaction have low solubility in aliphatic hydrocarbons and dissolve in or decompose in water, but thiophosgene is relatively stable in water and does not dissolve in water. They discovered that it hardly dissolves and completed the present invention.

That is, the present invention provides: (1) A sulfurous acid aqueous solution is supplied to a solution of perchloromethyl mercaptan in an aliphatic hydrocarbon solvent in the presence of a catalyst, and the resulting reaction solution is separated, and then 1 An industrial method for producing thiophosgene, characterized by washing with water in an amount equal to or more than twice its weight.

(2) The 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.

(3) the aliphatic hydrocarbon solvent has 5 to 15 carbon atoms;
The present invention provides a method according to claim (1), characterized in that the compound is a linear, branched or cyclic compound.

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

In the method of the present invention, PCMM and aliphatic hydrocarbon are charged in advance into a reactor, and an aqueous sulfurous acid solution is supplied thereto for reaction. The catalyst is usually added to the reactor in advance before the reaction starts, but the alkali metal iodide, which has low solubility in the aliphatic hydrocarbon solvent of PCMM, may be added to the reactor as a solid, or it can be fed. Even if it is dissolved in an aqueous sulfite solution and used in this reaction, there is no problem.

As the aliphatic hydrocarbon solvent used in the present invention, any linear, branched or cyclic compound having 5 to 15 carbon atoms can be used, including industrially available pentane, hexane, heptane, octane, nonane,
Straight chain aliphatic hydrocarbons such as decane, undecane, dodecane, tridecane, dimethylbutane, methylpentane, dimethylpentane, methylhexane, trimethylpentane,
Branched aliphatic hydrocarbons such as dimethylhexane, methylhebutane, cyclopentane, cyclohexane, cyclohebutane, cyclooctane, methylcyclopentane, methylcyclohexane, methylcyclohebutane, methylcyclooctane, dimethylcyclopentane, dimethylcyclohexane, dimethylcyclo Cycloaliphatic hydrocarbons such as hebutane, dimethylcyclooctane, ethylcyclopentane, ethylcyclohexane, ethylcyclohebutane, and ethylcyclooctane, and mixtures such as petroleum ether, petroleum benzine, and ligroin, are preferably used industrially. Easily available pentane, hexane,
heptane, octane, cyclohexane, petroleum ether,
Petroleum benzine and ligroin.

Although any concentration of PCMM in the aliphatic hydrocarbon solvent can be used, it is preferably in the range of 10 to 70 wt % for reasons such as economic efficiency and ease of reaction control.

Catalysts used in the present invention include sulfur monochloride, sulfur dichloride, alkali metal iodides, and iodine.
Each 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 any concentration relative to the PCMM used for 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, there will be no noticeable effect on the reaction rate. It's not economical. For this reason, the amount of catalyst added is determined by adding one type or a mixture of two or more types.
The range of 0.3 to 5.0 m01% based on MM is preferable.

The concentration of the sulfite aqueous solution used in the reaction is 5, relative to water,
Any concentration is possible as long as it is below the saturation solubility of sulfur dioxide, but if the concentration in the aqueous solution is below 4 wt%, the amount of liquid to be supplied will be large, making it uneconomical.
Sulfur dioxide gas is generated by the sulfuric acid and hydrochloric acid produced as by-products of the reaction, and flows out of the reactor. This may cause the target product thiophosgene to flow out. Therefore, it is preferable to reduce the concentration in the aqueous solution. It is 4 wt% or more and 90 wt% or less of the saturated dissolution amount.

Further, the amount of sulfite to be supplied may be equal to or more than equimolar to PCMM, but using too much excess may cause decomposition of the generated thiophosgene, which is not preferable.
If the amount is less than 1 times the molar amount, the raw material PCMM may remain. For this reason, preferably 1.1 times or more molar amount to 3
．． The range is 0 times the molar amount.

The reaction temperature can be -10 to 40'C and below the boiling point of the aliphatic hydrocarbon solvent used, but at 0°C water may condense, and at 20°C or higher the reaction will not proceed. The saturated solubility of sulfur dioxide in the aqueous sulfite solution provided decreases, and the amount of the aqueous sulfite solution required for reaction with PcMM becomes large, which is not preferable. Therefore, the reaction temperature is preferably 5°C or higher and 20°C or lower.

The reaction can be completed in a short time by increasing the supply rate of the sulfite aqueous solution, but
Since the amount of heat generated per unit time is large, it is preferable to set the feed rate to such a rate that the reaction can be carried out at a predetermined temperature.

After the aqueous sulfite solution is supplied, the reaction is usually further aged for 2 to 24 hours to complete the reaction.

After the reaction is completed, the mixed solution containing thiophosgene is allowed to settle, and after separation, the mixture is further washed with water in an amount equal to or more than 1 times the weight of the produced thiophosgene.

The amount of washing water can be adjusted to any ratio, but if the amount is less than 1 times the amount by weight, the liquid separation operation will be difficult, and if the amount is more than 10 times the amount by weight, no special benefits will be brought about. The number of times of cleaning may be one time, or it may be divided into several times without any problem.

Effects> The present invention provides a high-yield and safe industrial 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.

In this example, the impurity sulfur chloride was analyzed by gas chromatography, and the iodine ion was analyzed by ion chromatography.

[Example 1] A 100p glass-lined reactor with a cooling jacket equipped with a stirrer was charged with 51% of water. CN! While stirring, 5.6 kg of sulfur dioxide was supplied and dissolved in gaseous form from a cylinder while stirring, and the resulting aqueous sulfurous acid solution was extracted and transferred to a supply tank.

Next, after washing the reactor with water, 2.0 kg of aniline and 3.0 kg of carbon tetrachloride were added to the vent line. Install a thiophosgene trap loaded with 0 kg, then
, 8 kg, potassium iodide solid 77°1 g and 21.6 kg of cyclohexane were charged, and cooled while stirring.
The temperature was 10°C. After supplying the sulfurous acid aqueous solution prepared above over a period of 3 hours, the reaction was further carried out at 12° C. for 6 hours.

After the reaction solution was stabilized and separated, 7 g of water was added, stirred again, and washed.

After washing, the thiophosgene solution was separated and analyzed by gas coulomadography, and the yield of thiophosgene was 6. 5k
g, yield 97.3%, PCMM conversion rate 100%, and the iodine ion concentration in the thiophosgene solution was 32 ppm.

Furthermore, as a result of analyzing the vent trap, no thiophosgene was found to be scattered.

[Examples 2 to 5] Reactions were carried out using the same apparatus as in Example 1 under the conditions shown in Table 1.

The results are shown in Table 1.

[Comparative Examples 1 to 3] Reactions were carried out using the same apparatus as in Example 1 under the conditions shown in Table 1.

The results are shown in Table 1.

Claims (3)

[Claims] (1) In the presence of a catalyst, an aqueous sulfurous acid solution is supplied to a solution of perchloromethyl mercaptan in an aliphatic hydrocarbon solvent, and the resulting reaction solution is separated. An industrial method for producing thiophosgene, which is characterized by washing with. (2) The 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. (3) the aliphatic hydrocarbon solvent has 5 to 15 carbon atoms;
The method according to claim (1), wherein the compound is a linear, branched or cyclic compound.