Process for preparing mercaptans and apparatus therefor

Abstract

The application belongs to the field of non-metallic compounds, and particularly relates to a preparation method and a preparation device of mercaptan. The preparation method is prepared by reacting a sulfuric acid monoester salt RO SO2OM1 with a sulfhydryl M2SH in a solvent, wherein the sulfuric acid monoester salt is a monomethyl sulfate CH3OSO2OM1 or a monoethyl sulfate C2H5OSO2OM1, M1 and M2 are independently Na or K, and the solvent is one or a mixture of multiple of methanol, ethanol, n-propanol, isopropanol, hexafluoroisopropanol, N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone and dimethyl sulfoxide. The application has the technical features of (1) high economic benefit, (2) high conversion rate and good selectivity, (3) simple process and mild conditions, (4) environmental friendliness and resource recycling, and (5) safety improvement.

Description

Technical Field

[0001] This invention belongs to the field of non-metallic compounds, and specifically relates to a method and apparatus for preparing thiols. Background Technology

[0002] In the fluorochemical industry (e.g., the production of hydrofluoroethers and hydrofluoroolefins), dimethyl sulfate or diethyl sulfate is used extensively as a raw material. After reaction, dimethyl sulfate or diethyl sulfate produces corresponding sodium / potassium / cesium monomethyl sulfate or sodium / potassium / cesium monoethyl sulfate salts.

[0003] Currently, the treatment of these sulfate monoesters is a challenge in the industry. The main disposal methods include: (1) outsourcing the treatment as hazardous solid waste: This method requires high treatment costs, increases production costs, and causes serious waste of resources. (2) calcining with sodium hydroxide or potassium hydroxide to produce methanol or ethanol, while obtaining sodium sulfate or potassium sulfate as byproducts: This method can recover the alkyl groups in the sulfate monoester in the form of methanol or ethanol. However, methanol and ethanol are bulk basic chemicals with market prices usually in the thousands of yuan / ton, which is low value. The economic benefits of this conversion path are very limited and cannot compensate for the environmental protection costs of fluorochemical enterprises.

[0004] Methanethiol and ethanethiol are important intermediates in organic synthesis. Methanethiol is mainly used in the synthesis of pesticides such as methionine and phoxim, as well as pharmaceutical products. It has a large market demand and high economic value, with market prices reaching tens of thousands of yuan per ton, significantly higher than methanol. Ethyl mercaptan is also an important intermediate used in the synthesis of insecticides and polymer regulators. Its price is also significantly higher than ethanol. Producing methanethiol or ethanethiol offers better economic benefits than producing methanol and ethanol.

[0005] Currently, the mainstream industrial method for producing methanethiol uses methanol and hydrogen sulfide as raw materials, reacting them at high temperatures under the action of a catalyst. Examples include Chinese Patent CN119869562A (publication date 2025-04-25) which discloses the preparation of a cobalt sulfide catalyst and its application in the hydrogenation of hydrogen sulfide and carbon dioxide to produce methanethiol; Chinese Patent CN119702010A (publication date 2025-03-28) which discloses a method for preparing a cobalt-molybdenum catalyst and its application in the hydrogenation of CO2 / H2S to produce methanethiol; and Chinese Patent CN119733533A (publication date 2025-04-01) which discloses a CuKMoS2 / SiO2 catalyst for the synergistic preparation of methanethiol from carbon dioxide and hydrogen sulfide. This process has the following problems: strong corrosiveness to equipment, the need for high reaction temperatures (>300℃), the use of specialized catalysts with potential deactivation issues, and the cost of raw materials methanol and hydrogen sulfide. Another method suitable for industrial production is the sodium sulfide-dimethyl sulfate process. This method uses sodium hydrosulfide to react with dimethyl sulfate. The process is simple and easy to operate, but it generates a large amount of waste liquid and requires the use of highly toxic dimethyl sulfate, and has been gradually phased out. The mainstream industrial method for producing ethanethiol uses ethanol and hydrogen sulfide as raw materials, reacting them at high temperatures under the action of a catalyst. Examples include Chinese patent CN120286058A (publication date 2025-07-11) which discloses a method for preparing and applying a single-atom catalyst for the catalytic degradation of ethanethiol, and Chinese patent CN120054553A (publication date 2025-05-30) which discloses a method for preparing and applying a catalyst for the selective production of ethanethiol. This process also suffers from high equipment corrosivity, the need for high reaction temperatures (>300℃), the use of specialized catalysts with deactivation issues, and the cost of raw materials ethanol and hydrogen sulfide. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method and apparatus for preparing thiols.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing a thiol involves reacting a sulfate monoester salt ROSO2OM1 with a hydride M2SH in a solvent to obtain the sulfate monoester salt, which is either a methyl sulfate salt CH3OSO2OM1 or an ethyl sulfate salt C2H5OSO2OM1, wherein M1 and M2 are independently Na or K. The solvent is one or a mixture of methanol, ethanol, n-propanol, isopropanol, hexafluoroisopropanol, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide.

[0009] The sulfate monoester salt ROSO2OM1 is a byproduct of fluorochemicals; the mass content of ROSO2OM1 is >80%.

[0010] Specifically, the steps include: adding the sulfate monoester salt ROSO2OM1 and the hydrosulfide M2SH to a solvent, mixing and heating to obtain the product thiol.

[0011] The molar ratio of ROSO2OM1 to M2SH is (0.5~1):(0.7~1).

[0012] The reaction temperature is 30℃~120℃; preferably 60~120℃; the reaction time is 1~12h.

[0013] The present invention also includes a thiol preparation apparatus for the preparation of the thiol, comprising a reactor, a cold trap connected in sequence with the reactor, and an alcohol absorption device; a temperature monitoring device is provided inside the reactor.

[0014] Compared with the prior art, the beneficial effects of the present invention are:

[0015] (1) High economic benefits: It transforms hazardous solid waste that requires payment for treatment into high-value-added mercaptan products with low raw material costs and high economic value.

[0016] (2) High conversion rate and good selectivity: By controlling the reaction stoichiometric ratio, the target thiol is directly generated, avoiding the generation of by-products such as thioethers, and the conversion rate of the target product is high.

[0017] (3) Simple process and mild conditions: The reaction is carried out at normal pressure and low temperature, without the need for expensive catalysts and high temperature and high pressure equipment. The operation is simple and the investment cost is low.

[0018] (4) Environmentally friendly and resource-recycling: It realizes the reduction and resource utilization of solid waste from fluorochemicals. The main product, mercaptan, has high value, and the by-product, sulfate, can also be sold, resulting in less waste.

[0019] (5) Improved safety: It avoids the high temperature and high pressure process of traditional methanol and ethanol processes, and does not use highly toxic dimethyl sulfate and diethyl sulfate, significantly reducing the danger of the production process. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the apparatus for preparing thiols. Detailed Implementation

[0021] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and preferred embodiments.

[0022] Figure 1An apparatus for preparing thiols is shown, comprising a reactor 1, a cold trap 2 connected sequentially to the reactor, and an alcohol absorption device 3; a temperature monitoring device is provided inside the reactor.

[0023] A method for preparing thiols involves reacting a sulfate monoester salt ROSO2OM1 with a hydride M2SH in a solvent. The sulfate monoester salt is either a monomethyl sulfate salt CH3OSO2OM1 or a monoethyl sulfate salt C2H5OSO2OM1, wherein M1 and M2 are independently Na or K.

[0024] The sulfate monoester salt ROSO2OM1 is a byproduct of fluorochemicals; the mass content of ROSO2OM1 is >80%.

[0025] The specific steps include: adding the sulfate monoester salt ROSO2OM1 and the hydrosulfide M2SH to a solvent, mixing and heating to obtain the product thiol. The molar ratio of ROSO2OM1 to M2SH is 0.5:1 to 3:1, which can be 0.5:1, 1:1, 2:1, or 3:1; preferably 1:1 to 1.5:1, more preferably (0.5 to 1):(0.7 to 1). The reaction temperature is 30℃ to 120℃; preferably 60 to 120℃, and the reaction time is 1 to 12 hours. For this reaction, higher temperatures, such as 60℃, 75℃, 90℃, and 120℃, can accelerate the reaction, while at lower temperatures, such as 10℃, 20℃, and 30℃, the equilibrium principle can be utilized to remove the product and promote the reaction.

[0026] The solvent is one or a mixture of water, methanol, ethanol, n-propanol, isopropanol, hexafluoroisopropanol, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide.

[0027] The preparation method is illustrated below with specific examples.

[0028] Example 1: The preparation method of thiols includes the following steps: In reactor 1, a 500 mL three-necked flask equipped with a stirrer, thermometer, and gas outlet tube (for connection to cold trap 2 and alcohol absorption device 3), 200 mL of water is added as a solvent. Sodium hydrosulfide hydrate (80.0 g, 1.0 mol, based on 70% NaSH content) is added. While stirring, potassium monomethyl sulfate (166.7 g, 1.0 mol, based on 90% purity), a byproduct of fluorochemicals, is slowly added, controlling the reaction temperature at 85°C. After the addition is complete, the reaction continues at this temperature for 6 hours. The methanethiol gas produced in the reaction is collected by condensation. Crude methanethiol is obtained, with a yield of 80% based on potassium monomethyl sulfate.

[0029] Example 2: In the same apparatus, 150 mL of ethanol was added as a solvent. Sodium hydrosulfide hydrate (56.0 g, 0.7 mol, based on 70% NaSH content) was added. While stirring, potassium monoethyl sulfate (91.1 g, 0.5 mol, based on 90% purity), a byproduct of fluorochemicals, was slowly added, with the reaction temperature controlled at 78°C (ethanol reflux temperature). After reacting for 12 hours, the reaction mixture was subjected to atmospheric distillation to obtain ethanethiol product in 88% yield based on potassium monoethyl sulfate.

[0030] Example 3: In the same apparatus, 200 mL of N,N-dimethylformamide (DMF) was added as a solvent. Potassium hydrosulfide (79.2 g, 1.1 mol) was added. While stirring, potassium monoethyl sulfate (182.2 g, 1.0 mol, 90% purity), a byproduct of fluorochemicals, was slowly added, with the reaction temperature controlled at 120 °C. The reaction was allowed to proceed for 6 hours. After the reaction was complete, the reaction mixture was subjected to atmospheric distillation, and the fraction collected at 35-37 °C yielded ethanethiol, with a yield of 85% based on potassium monoethyl sulfate.

[0031] Example 4: In the same apparatus, 200 mL of water was added as a solvent. Sodium hydrosulfide hydrate (80.0 g, 1.0 mol, based on 70% NaSH content) was added. While stirring, potassium monomethyl sulfate (166.7 g, 1.0 mol, based on 90% purity), a byproduct of fluorochemicals, was added. The reaction temperature was controlled at 30°C. After cooling, a vacuum pump was used to promptly remove the reaction product to promote the reaction. The reaction was continued at this temperature for 12 hours. The methanethiol gas produced was collected by condensation. Crude methanethiol was obtained, with a yield of 30% based on potassium monomethyl sulfate.

[0032] Comparative Example 1: In this comparative example, the solvent ethanol was replaced with methanol, and the reaction temperature was changed from 78°C (ethanol reflux temperature) to 65°C (methanol reflux temperature). All other aspects were the same as in Example 2. Ethanol was obtained in a yield of 74% based on potassium monoethyl sulfate.

[0033] Comparative Example 2: In this comparative example, the solvent ethanol was replaced with n-propanol, and everything else was the same as in Example 2. Ethyl mercaptan was obtained, with a yield of 83% based on potassium monoethyl sulfate.

[0034] Comparative Example 3: In this comparative example, the solvent ethanol was replaced with isopropanol, and everything else was the same as in Example 2. Ethanol was obtained in a yield of 76% based on potassium monoethyl sulfate.

[0035] Comparative Example 4: In this comparative example, the solvent ethanol was replaced with hexafluoroisopropanol, and the reaction temperature was changed from 78°C (ethanol reflux temperature) to 59°C (hexafluoroisopropanol reflux temperature). All other aspects were the same as in Example 2. Ethanol was obtained in a yield of 78% based on potassium monoethyl sulfate.

[0036] Comparative Example 5: In this comparative example, the solvent N,N-dimethylformamide was replaced with N,N-dimethylacetamide, and everything else was the same as in Example 3. Ethanol was obtained in a yield of 84% based on potassium monoethyl sulfate.

[0037] Comparative Example 6: In this comparative example, the solvent N,N-dimethylformamide was replaced with N-methylpyrrolidone, otherwise the process was the same as in Example 3. Ethanol was obtained in a yield of 80% based on potassium monoethyl sulfate.

[0038] Comparative Example 7: In this comparative example, the solvent N,N-dimethylformamide was replaced with dimethyl sulfoxide, and everything else was the same as in Example 3. Ethanol was obtained in a yield of 65% based on potassium monoethyl sulfate.

[0039] It should be noted that the comparative examples in this application are only for illustrative purposes and are themselves part of the embodiments.

[0040] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing thiols, characterized in that, The product is prepared by reacting a sulfate monoester salt ROSO2OM1 with a hydride M2SH in a solvent. The sulfate monoester salt is either a monomethyl sulfate salt CH3OSO2OM1 or a monoethyl sulfate salt C2H5OSO2OM1, wherein M1 and M2 are independently Na or K. The solvent is one or a mixture of methanol, ethanol, n-propanol, isopropanol, hexafluoroisopropanol, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide.

2. The method for preparing thiols according to claim 1, characterized in that, Specifically, the steps include: adding the sulfate monoester salt ROSO2OM1 and the hydrosulfide M2SH to a solvent and mixing them to react to obtain the product thiol; the molar ratio of ROSO2OM1 to M2SH is (0.5~1):(0.7~1).

3. The method for preparing thiols according to claim 2, characterized in that, The reaction temperature is 30℃~120℃.

4. An apparatus for preparing thiols, characterized in that, Used for the preparation of thiols according to any one of claims 1-3.

5. The apparatus for preparing thiols according to claim 4, characterized in that, It includes a reactor, a cold trap connected sequentially to the reactor, and an alcohol absorption device; the reactor is equipped with a temperature monitoring device.

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