JPS58159456A - Preparation of methyl mercaptan - Google Patents

Abstract

PURPOSE:To prepare the titled compound useful as a synthetic raw material of methionine, in high yield and selectivity, by reacting methanol with H2S essentially in the first reactor and reacting the by-products with H2S essentially in the second reactor, wherein each reaction is carried out in the presence of a catalyst suitable for the respective reaction system. CONSTITUTION:Methyl mercaptan is prepared by the vapor-phase reaction of methanol and hydrogen sulfide. In the above process, the reaction is carried out at 300-430 deg.C in the first reactor containing an active alumina catalyst (e.g. a mixture of active alumina and potassium tungstate) which catalyzes essentially the reaction of methanol with hydrogen sulfide, and methyl mercaptan is separated from the reaction product. The unreacted methanol and H2S are mixed with fresh methanol and unreacted H2S, and reacted at 300-400 deg.C in the second reactor containing an active alumina catalyst (e.g. a mixture of active alumina and phosphotungstic acid) which catalyzes essentially the reaction of H2S with dimethyl sulfide, and methyl mercaptan is separated as a reaction product.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing methyl mercaptan from methanol and hydrogen sulfide.
This article relates to an industrially advantageous production method that can obtain methyl mercaptan in a high yield from methionine. It is a useful compound as a raw material.

゛) 4-methylbutane is carbon disulfide, -carbon oxide'
This is a method in which methanol and hydrogen sulfide are catalytically reacted in the gas phase in the presence of a catalyst using a substance such as or methane as a raw material.

This method was reported in 1910 by Sabatier et al.
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82B, 1217.1569 (1910)), various improvements have been made to the catalysts used in the reaction. In order to improve catalysts, there are methods that focus on improving the conversion rate and selectivity of raw methanol, and also on improving catalyst life. For example, if the reaction is carried out using activated alumina as a catalyst at a hydrogen sulfide/methanol molar ratio of 3, the methanol conversion rate will be 100% and the methyl mercaptan selectivity will be 30%. Regarding the use of this catalyst, even if the molar ratio of hydrogen sulfide to methanol was 2, a catalyst that would yield a methanol conversion of 90% and a methyl mercaptan of 98% was repeatedly investigated.

Namely, activated alumina-potassium tungstate (2-20% mixture of activated alumina), activated alumina-cadmium sulfide (10-50% mixture of activated alumina), activated alumina-tungstic acid (2% mixture of activated alumina), and activated aluminum. Narin Tungsten II # (mixture of 1 to 4 tungstate of counteractive cetoalumina) As a result of considering the catalyst activity +4 of other alkali metal sulfides, phosphoric acid, etc., active alumina-potassium tungstate was the best in terms of selectivity. We obtained the following knowledge. However, when the reaction is carried out in one reactor using an activated alumina-potassium tungstate catalyst, the molar ratio of hydrogen sulfide and methanol is 3, and the conversion rate of methanol is the highest, and the selectivity is 95%, which is higher than that of Sowa. Attempting to increase the conversion rate results in a decrease in selectivity. Therefore, in practice, the amount is 492 to 95 mm, which is always smaller and less valuable than 5 to 8 percent dimethitane, so in the conventional method, it is recycled into the same reactor and converted to methyl mercaptan. In this case, the recycling method using a high selectivity catalyst such as activated alumina-potassium tungstate, the recycling amount is 2 to 3 times that of methanol, and the vapor waste is reduced. This method has disadvantages such as increased utility costs, loss of industrial advantage compared to the case of using activated alumina catalyst alone, and lower productivity per reactor volume.

In order to reduce the amount recycled, the inventors of the present invention continued to conduct intensive studies on catalysts that are advantageous for the reaction between dimethyl sulfide containing or not containing methanol and hydrogen sulfide. The present invention was achieved by discovering that hydrogen sulfide and hydrogen sulfide were substantially reacted in the second reactor; and that each reactor had an effective catalyst.

That is, the gist of the present invention is that when producing methyl mercaptan by a gas phase reaction of methanol and hydrogen sulfide, the presence of an activated alumina-based catalyst that substantially causes the methanol and hydrogen sulfide to react in the first reactor. After the reaction is carried out at a temperature of 300°C to 430°C and methyl mercaptan is separated and obtained, unreacted methanol and hydrogen sulfide are collected in the first stage along with fresh methanol and hydrogen sulfide.
The by-product dimethyl sulfide is recycled to the reactor together with fresh and unreacted hydrogen sulfide in a second reactor.
This is a method for producing methyl mercaptan, which is characterized in that hydrogen sulfide and dimethyl sulfide are reacted in the presence of an activated alumina-based catalyst at a temperature of 300°C to 450°C to separate and obtain methyl mercaptan.

The activated alumina catalyst used in the present invention is a mixture of activated alumina and potassium tungstate in the first reactor and activated alumina and potassium tungstate in the second reactor.
Good results are obtained when using phosphotungstic acid or activated alumina-tungstic acid or activated alumina-cadmium sulfide catalysts. The mixing ratio of the catalyst may be 0.01 to 0.2 parts by weight per 1 part by weight of activated alumina, or the activated alumina may support other catalyst components. If the amount of other catalyst components mixed or supported on activated alumina is less than 0.01 part by weight, the catalytic effect will not be exhibited, and if it is added in excess of 0.2 parts by weight, no particular effect will be obtained. be.

The reaction temperature in each reactor should be in the range of 300°C to 450°C, but the first reactor is often 14". The molar ratio of methanol to hydrogen sulfide is 5 mol or less per 1 mol of methanol, usually The molar ratio of dimethyl sulfide and hydrogen sulfide is often 5 moles or less, usually 1 to 3 times, per mole of dimethyl sulfide.

The reaction pressure is usually atmospheric pressure or 8 kg/-, but it is determined in relation to the reaction temperature and is not necessarily limited to this range.

Generally, the higher the reaction pressure, the lower the appropriate reaction temperature.

In the present invention, methanol and hydrogen sulfide are reacted in the presence of a catalyst suitable for this type of reaction, and the reactants are separated to obtain methyl mercaptan and dimethyl sulfide. Methyl mercaptan can be obtained in high yield by reacting with hydrogen sulfide in a second reactor filled with a catalyst to be reacted.

Next, the present invention will be explained by examples.

Reference example Hydrogen sulfide 8 Nidimethyl sulfide 2: Methanol 10
The molar ratio of the raw material gas is 390°C and the space velocity is 1000 hr.
-1, 9-pass reaction was carried out on each catalyst shown in Table-1, and the results shown in Table-1 were obtained. The methanol conversion rate was 100% in all cases. The methyl mercaptan production rate is expressed in moles relative to methanol, with the case of activated alumina catalyst being 100.

10- Example 1 Reaction tube 1 with a tube diameter of 251111 was filled with activated alumina 1,000 Od of all 11 diameters mixed with 10 T of potassium tungstate as a catalyst (catalyst layer length approximately 100@a), and the temperature was set at 390°C. was held at .

A mixed gas of hydrogen sulfide/methanol preheated to 370°C and adjusted to a molar ratio of 2 was added to this at a space velocity of 70 Q hr-
I got through with l. Analysis of the reaction mixture by gas chromatography revealed that the yield of methyl mercaptan was 92%.

The by-product dimethyl sulfide was 7qI) based on the methanol used, and about 1% of inert gas was generated.
The methanol conversion rate was 100%.

On the other hand, a reaction tube 2 having a tube diameter of 25III11 and a length of 500 fl was filled with 4 Q ml of an 8 u diameter active asmina catalyst mixed with 2% (P2O5-24WOa). temperature to 40
A mixed gas of hydrogen sulfide/dimethyl sulfide with a molar ratio of 3, which was maintained at 0°C and preheated to 370°C, was heated at a space velocity of 700.
The reaction mixture was analyzed by gas chromatography, and the yield of methyl mercaptan was 40%.
Met.

From the above values, it can be seen that the amount of circulating gas required to produce 1 mole of methyl mercaptan is 1.28 mole of hydrogen sulfide, 0.10 mole of dimethyl sulfide, and a total of 1.38 mole. To explain the flow sheet in this example with reference to FIG. 1, fresh methanol 3 and fresh hydrogen sulfide 4 are supplied to a reaction tube 1 and reacted, and the reaction product is separated into methyl mercaptan 6 in a condensation separator 5, and then separately obtained. Inert gas 7 and water 8 are separated, and unreacted hydrogen sulfide 9 and methanol 10 are circulated and returned to the fresh hydrogen sulfide and fresh methanol 9 supply path, respectively.

Yu.

The by-product dimethyl sulfide 11 is circulated and supplied to the reaction tube 2, where it is reacted with fresh hydrogen sulfide and unreacted hydrogen sulfide.

Example 2 2-chi (P2) which is the catalyst component of reaction tube 2 in Example 1
As a result of the same operation as in Example 1 except that 10% carbon dioxide was used instead of O5-24WO3), the amount of circulating gas required to produce 1 mole of methyl mercaptan was 1.3 hydrogen sulfide.
0 mol, dimethyl sulfide 0.12 mol, total 1.
It was 42 moles.

Example 3 2% (P2
The procedure was carried out in the same manner as in Example 1 except that 5% tungstic acid was used instead of O5-24WO8). As a result, the amount of circulating gas required to produce 1 mole of methyl mercaptan was 1.29 moles of hydrogen sulfide and 0 moles of dimethyl sulfide. .11 mol, total 1.40 mol.

Comparative Example 1 A reaction tube with an inner diameter of 25 m was filled with activated alumina 40d,
The amount of methyl mercaptan produced was determined by changing the mixing ratio of methanol, hydrogen sulfide, and dimethyl sulfide and passing them through the reaction tube. As a result, the temperature was 890℃
, at a space velocity of 1000 hr-1, the molar ratio of hydrogen sulfide/dimethyl sulfide/methanol is 8.3/2.
．． It was found that when the ratio was 5/1, the production ratio of methyl mercaptan to methanol was 13 parts to 100 parts. That is, at this time, it is found that the circulating dimethyl sulfide maintains a steady state at a molar ratio of 2.5 mol, and the amount of circulating hydrogen sulfide is 2.3 mol. Compared to Example 2, this means that the circulating amount is 1.02 mol more for hydrogen sulfide and 2.20 mol more for dimethyl sulfide, which is a total of 3.22 mol more. The flow chart of this comparative example will be explained with reference to FIG. 2. Fresh methanol 2 and fresh hydrogen sulfide 3 are supplied to the reaction tube 1, and the reaction products from the reaction tube 1 are separated by the condensation separator 4. separated into components. Methyl mercapkun 5 has been certified as a product and is an inert gas 6.
and water 7 are removed, and unreacted hydrogen sulfide 8 and unreacted methanol 9 are circulated to the supply paths of fresh hydrogen sulfide 3 and fresh methanol 2, respectively. Dimethyl sulfide 10 produced as a by-product is also circulated and returned to the reaction tube 1.

Comparative Example 2 The same procedure as Comparative Example 1 was carried out except that the activated alumina catalyst in Comparative Example 1 was replaced with an activated alumina 14-2-2 (P2O524WO3) catalyst, and the molar ratio of hydrogen sulfide/dimethyl sulfide/methanol was 2. It was found that when .8/1.5/'1, the methyl mercaptan/methanol production ratio was 10 (1%). Therefore, in this case, the circulating amount was 1.3 mol of hydrogen sulfide per 1 mol of methyl mercaptan. 1.5 moles of dimethyl sulfide, totaling 28 moles of H,
This is 1.42 moles more than the total amount in Example 2.

Comparative Example 3 Same as Example 2 except that reaction tube 1 was filled with activated alumina catalyst and reaction tube 2 was filled with 2% potassium tank state catalyst.
The reaction was carried out under the same conditions.

The yield of methyl mercaptan in reaction tube 1 was 48 cm, and 51 cm of dimethyl sulfide was produced as a by-product. In reaction tube 2, the conversion rate of dimethyl sulfide to methyl mercaptan was 22%. In Comparative Example 3, 4.10 moles of unreacted hydrogen sulfide and 0.90 moles of unreacted dimethyl sulfide were recycled to obtain 1 mole of methylmerf and 1 mole of butane, for a total circulating amount of 5,00 moles.

Therefore, compared to Example 2, the total circulating amount is increased by 362 moles.

Comparative Example 4 Activated alumina-2% (P2O
The reaction was carried out in the same manner as in Comparative Example 3 except that 5-24WO3) was used. The conversion rate of dimethyl sulfide to methyl mercaptan in reaction tube 2 was 40%.

In this reaction, to produce 1 mole of methyl mercaptan, 359 moles of unreacted hydrogen sulfide and 6 moles of unreacted dimethyl sulfide were produced, for a total circulating amount of 4.35 moles.

Therefore, compared to the case of Example 2, the total circulating amount is 2.97 mol more.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet showing the methyl mercaptan manufacturing process of the present invention, and FIG. 2 is a flow sheet showing the conventional manufacturing process.

Claims (7)

[Claims] (1) When producing methyl mercaptan by causing a gas phase reaction between methanol and hydrogen sulfide, in the first reactor, the reaction temperature is 300°C to 430°C in the presence of an activated alumina catalyst that causes the methanol and hydrogen sulfide to substantially react. Reaction at temperature of °C? After separating and obtaining methyl mercaptan, unreacted methanol and hydrogen sulfide are circulated to the first reactor together with fresh methanol and hydrogen sulfide, and by-product dimethyl sulfide is recycled together with fresh and unreacted mercaptan and hydrogen sulfide. In the second reactor, substantially 45
A method for producing methyl mercaptan, which comprises performing a reaction at a temperature of 0° C. to separate and obtain methyl mercaptan. (2) The method according to claim (1), wherein the catalyst in the first reactor is a mixture of activated alumina and potassium tungstate, and the catalyst in the second reactor is a mixture of activated alumina and phosphotungstic acid. (3) The method according to claim (2), wherein activated alumina and potassium tungstate or phosphotungstic acid are mixed at a ratio of 0.01 to 0.2 parts by weight per 1 part by weight of activated alumina. (4) The method according to claim (1), wherein the catalyst in the first reactor is a mixture of activated alumina and potassium tungstate, and the catalyst in the second reactor is a mixture of activated alumina and tungstic acid. (5) The method according to claim (4), in which activated alumina and potassium tungstate are mixed. (6) The catalyst in the first reactor is a mixture of activated alumina and potassium tungstate, and the catalyst in the second reactor is activated ('
The method according to claim (1), which is a mixture of alumina and cadmium sulfide. (7) The method according to claim (6), wherein activated alumina and potassium tungstate or cadmium sulfide are mixed at a ratio of 0.01 to 0.2 parts by weight per 1 part by weight of activated alumina.