Preparation method of dimethyl disulfide

Abstract

The invention discloses a dimethyl disulfide preparation method, which comprises: (1) introducing methyl mercaptan into a fixed bed filled with a catalyst, and carrying out a decomposition reaction; (2) after the reaction is finished, carrying out gas-liquid separation on the mixture to obtain a liquid product and a gas mixture; and (3) carrying out pressurized refining on the obtained gas mixture, and separating out methyl mercaptan for cyclic utilization. The dimethyl disulfide compound can be obtained through a one-step method, sulfur does not need to be added in the process, hydrogen sulfide is not generated after the reaction is finished, and the method is easy to operate, environmentally friendly and good in market prospect.

Description

Technical Field

[0001] The invention belongs to the field of chemical synthesis and separation and purification, and specifically relates to a method for preparing dimethyl disulfide. Background Art

[0002] Dimethyl disulfide (hereinafter referred to as DMDS) is a light yellow transparent liquid with a foul odor. It is insoluble in water and miscible with ethanol, ether and acetic acid. The relative density is 1.0625, the boiling point is 109.7℃, the melting point is -85℃, the flash point is 24℃, and the explosion limit is 1.1-16%. It cannot coexist with strong alkalis, strong oxidants and strong reducing agents. Dimethyl disulfide is often used as a solvent and can also be used as the main raw material for the production of methylsulfonyl chloride and methylsulfonic acid. It is also used as a vulcanizing agent for gasoline hydrogenation catalysis, a coking inhibitor for oil refining equipment and a soil fumigant. It can also be used to synthesize the intermediates of organophosphorus insecticides fenthion and fenamiphos, p-methylthiophenol, an intermediate of thiopropylphos and methylthion. In addition, GB2760-1996 regulations allow the use of dimethyl disulfide as a food flavoring. It can be seen that dimethyl disulfide is a high value-added product.

[0003] There are three main methods for synthesizing disulfide compounds: first, the dimethyl sulfate method, which is prepared by the reaction of sodium sulfide and dimethyl sulfate. This route has the problem that the raw materials are highly toxic and extremely difficult to obtain; second, the methyl mercaptan oxidation method, which is prepared by the reaction of methyl mercaptan with an oxidant. Common oxidants include hydrogen peroxide, sodium perchlorate, potassium permanganate, etc. This route has a violent reaction, a large amount of heat release, and extremely high safety risks during the production process; third, the methanol sulfidation method, which is prepared by the reaction of methanol, hydrogen sulfide and sulfur or directly by the methyl mercaptan sulfidation method with sulfur. This route uses methyl mercaptan with an extremely low threshold value and will produce the highly toxic compound hydrogen sulfide. The odor is difficult to control during the production process, and environmental and safety issues are more prominent.

[0004] Therefore, developing a green and environmentally friendly dimethyl disulfide synthesis technology has excellent commercial application value. Summary of the invention

[0005] The invention provides a method for preparing dimethyl disulfide. During the process, sulfur does not need to be added, and hydrogen sulfide is not generated after the reaction is completed. The method is simple to operate, green and environmentally friendly, and has good market prospects.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] A method for preparing dimethyl disulfide comprises the following steps:

[0008] (1) introducing methyl mercaptan into a fixed bed loaded with a catalyst to cause a decomposition reaction;

[0009] (2) After the reaction is completed, the mixture is separated into gas and liquid to obtain a liquid product and a gas mixture;

[0010] (3) The obtained gas mixture is pressurized and refined to separate methyl mercaptan for recycling.

[0011] The chemical reaction equation is as follows:

[0012]

[0013] Preferably, the fixed bed in step (1) is loaded with a catalyst and the entire fixed bed is impregnated with dimethyl disulfide.

[0014] The catalyst in step (1) is a mixture of alkaline earth metal oxide and aluminum oxide, wherein the alkaline earth metal is one or more of magnesium oxide, calcium oxide, strontium oxide and barium oxide, preferably magnesium oxide; the mass ratio of the alkaline earth metal to aluminum oxide is (0.01-0.5):1, preferably (0.05-0.1):1; the function of the catalyst is mainly to improve the selectivity of the product dimethyl disulfide.

[0015] The preparation method of the catalyst comprises the following steps:

[0016] Weigh aluminum oxide and place it in a container, add an alkaline earth metal chloride aqueous solution thereto, stir and filter to obtain a solid, and then calcine to obtain a composite catalyst.

[0017] Preferably, the stirring time is 1-48 hours; the calcination temperature is 400-800° C., and the calcination time is 10-48 hours.

[0018] Preferably, the decomposition reaction temperature is 60-100°C, preferably 70-85°C.

[0019] Preferably, the decomposition reaction pressure is 0-10.0 MPaG, preferably 0.1-1.0 MPaG.

[0020] Preferably, the volume space velocity of the decomposition reaction is 0.1-2h -1 , preferably 0.2-0.5h -1 .

[0021] The gas-liquid separation temperature in step (2) is 0-20°C, preferably 5-10°C, and the pressure is consistent with the pressure of the fixed bed reactor.

[0022] The gas mixture obtained in step (3) is a mixture of hydrogen and methyl mercaptan, which are separated by pressure refining. The refining temperature is 30-100°C, preferably 40-80°C; the refining pressure is 0.5-10.0 MPaG, preferably 1-5.0 MPaG.

[0023] The beneficial effects of the present invention are:

[0024] First, no sulfur needs to be added during the process, which reduces the cost of raw materials, and there is no sulfur residue in the product, which is of high quality;

[0025] Second, the reaction does not produce the highly toxic hydrogen sulfide.

[0026] Third, the process is simple to operate, green and environmentally friendly, and has good market prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The process flow chart of the preparation method described in Example 1;

[0028] Among them, 1-fixed bed reactor, 2-gas-liquid separator, 3-refining tower, 4-raw material storage tank. DETAILED DESCRIPTION

[0029] Common chemical reagents such as methyl mercaptan, calcium oxide, magnesium oxide and aluminum oxide used in the present invention were purchased from Shanghai Titan Technology Co., Ltd.

[0030] In the embodiments of the present invention, the content and purity of each component are tested and calculated by the external standard method of high performance liquid chromatograph (Shimadzu LC-20AD), and the conversion rate is calculated based on the content of the product; the liquid chromatography conditions are as follows: chromatographic column: WAters XSelect HSS T3, 4.6 μm×250 mm; injection volume: 2 to 10 μL, fine-tuned according to the sample conditions; column temperature: 40° C.; flow rate: 1 mL / min; detector: ultraviolet detector (UV), detection wavelength of 254 to 400 nm; mobile phase: acetonitrile / 0.1% phosphoric acid aqueous solution; when measuring the sample, first establish a liquid phase external standard curve with a pure product, and calculate the mass fraction (content) of each test substance based on the linear relationship between concentration and liquid phase peak area.

[0031] The fixed bed reactor of the present invention has a height-to-diameter ratio of 10, a diameter of 50 mm, and a catalyst particle size of 2 mm, so as to ensure that the pressure drop of the fixed bed layer is within a normal range and eliminate the radial wall effect of the bed layer.

[0032] The preparation method of the catalyst with different alkaline earth metal contents in the present invention is as follows: weigh 100g of aluminum oxide and place it in a 500mL three-necked flask, add a certain mass and concentration of alkaline earth metal chloride aqueous solution thereto, stir for 24 hours and filter to obtain a solid, and calcine in a muffle furnace at 500°C for 24 hours to obtain an aluminum oxide catalyst with different alkaline earth metals. The aluminum oxide catalyst with different alkaline earth metals can be prepared according to the type and amount of alkaline earth metals added, including but not limited to the mixed catalysts shown in the following table:

[0033]

[0034]

[0035] Embodiment 1:

[0036] Under nitrogen atmosphere, 100 g / h of methyl mercaptan is passed through a fixed bed 1 filled with a catalyst, wherein the catalyst is MgO and Al. 2 O 3 A mixture of MgO and Al 2 O 3 The mass ratio of is 0.05:1. The reactor temperature is controlled at 70°C, the reaction pressure is 0.1MPaG, and the volume space velocity of the reactor is 0.2h -1 , so that methyl mercaptan reacts under the action of the catalyst to generate dimethyl disulfide and hydrogen. When the reaction system is stable, the conversion rate of the raw material is 99%, the selectivity of the product dimethyl disulfide is 80.5%, and the selectivity of methyl hydrogen disulfide is 19.5%. The obtained gas mixture is passed into the gas-liquid separator 2, and the mixture is cooled. The system temperature is controlled to 5°C and the pressure is 0.1MPaG, which is consistent with the pressure at the reaction end. . A mixture of methyl hydrogen disulfide and dimethyl disulfide is separated and sent to the refining tower 3. Hydrogenation refining is carried out at a pressure of 1.0MPaG and a temperature of 40°C. Among them, methyl hydrogen disulfide with a purity of 99.5% and 0.5% methyl mercaptan are obtained at the top of the tower, and this part of the product can be sent to the upstream raw material methyl mercaptan storage tank 4 for recycling. The product dimethyl disulfide is obtained in the tower bottom, and the tower bottom product is collected and analyzed. Its specific composition is as follows (the composition is all mass percentage, %):

[0037] DMDS, % DMTS, % CH3SH, % CH3SSH, % CH4, % 99.8 0.1 0.03 0.05 0.02

[0038] As can be seen from the above table, the present invention can obtain dimethyl disulfide with a purity of >99% without producing highly toxic hydrogen sulfide. The process is green and environmentally friendly and has good commercial application prospects.

[0039] Example 2

[0040] Under nitrogen atmosphere, 100 g / h of methyl mercaptan is passed through a fixed bed 1 filled with a catalyst, wherein the catalyst is MgO and Al. 2 O 3 A mixture of MgO and Al 2 O 3 The mass ratio of is 0.1:1. The reactor temperature is controlled at 60°C, the reaction pressure is 1.0 MPaG, and the volume space velocity of the reactor is 2h -1, so that methyl mercaptan reacts under the action of the catalyst to generate dimethyl disulfide and hydrogen. When the reaction system is stable, the conversion rate of the raw material is 98.0%, the selectivity of the product dimethyl disulfide is 81.5%, and the selectivity of methyl hydrogen disulfide is 18.5%. The resulting gas mixture is passed into the gas-liquid separator 2, and the mixture is cooled. The system temperature is controlled to 0°C and the pressure is 1MPaG, which is consistent with the pressure at the reaction end. A mixture of methyl hydrogen disulfide and dimethyl disulfide is separated and sent to the refining tower 3. Hydrofining is carried out at a pressure of 1.0MPaG and a temperature of 50°C. Among them, methyl hydrogen disulfide with a purity of 99.5% and 0.5% methyl mercaptan are obtained at the top of the tower, and this part of the product can be sent to the upstream raw material methyl mercaptan storage tank 4 for recycling. The product dimethyl disulfide is obtained in the tower bottom, and the tower bottom product is collected and analyzed. Its specific composition is as follows (the composition is all mass percentage, %):

[0041] DMDS, % DMTS, % CH3SH, % CH3SSH, % CH4, % 99.5 0.4 0.04 0.05 0.01

[0042] Example 3

[0043] Under nitrogen atmosphere, 100 g / h of methyl mercaptan is passed through a fixed bed 1 filled with a catalyst, wherein the catalyst is CaO and Al. 2 O 3 A mixture of CaO and Al 2 O 3 The mass ratio of is 0.08:1. The reactor temperature is controlled at 80°C, the reaction pressure is 3.0MPaG, and the volume space velocity of the reactor is 1.6h -1 , so that methyl mercaptan reacts under the action of the catalyst to generate dimethyl disulfide and hydrogen. When the reaction system is stable, the conversion rate of the raw material is 98.5%, the selectivity of the product dimethyl disulfide is 83.5%, and the selectivity of methyl hydrogen disulfide is 16.5%. The resulting gas mixture is passed into the gas-liquid separator 2, and the mixture is cooled. The system temperature is controlled to 10°C and the pressure is 3MPaG, which is consistent with the pressure at the reaction end. A mixture of methyl hydrogen disulfide and dimethyl disulfide is separated and sent to the refining tower 3. Hydrofining is carried out at a pressure of 5.0MPaG and a temperature of 80°C. Among them, methyl hydrogen disulfide with a purity of 99.3% and 0.7% methyl mercaptan are obtained at the top of the tower, and this part of the product can be sent to the upstream raw material methyl mercaptan storage tank 4 for recycling. The product dimethyl disulfide is obtained in the tower bottom, and the tower bottom product is collected and analyzed. Its specific composition is as follows (the composition is all mass percentage, %):

[0044] DMDS, % DMTS, % CH3SH, % CH3SSH, % CH4, % 99.6 0.3 0.02 0.06 0.02

[0045] Example 4

[0046] Under nitrogen atmosphere, 100 g / h of methyl mercaptan is passed through a fixed bed 1 filled with a catalyst, wherein the catalyst is SrO and Al. 2 O 3 A mixture of SrO and Al 2 O 3 The mass ratio of is 0.05:1. The reactor temperature is controlled at 90°C, the reaction pressure is 5.0MPaG, and the volume space velocity of the reactor is 1.0h -1 , so that methyl mercaptan reacts under the action of the catalyst to generate dimethyl disulfide and hydrogen. When the reaction system is stable, the conversion rate of the raw material is 98.9% after sampling and analysis, the selectivity of the product dimethyl disulfide is 80.3%, and the selectivity of methyl hydrogen disulfide is 19.7%. The resulting gas mixture is passed into the gas-liquid separator 2, and the mixture is cooled. The system temperature is controlled to 15°C and the pressure is 5MPaG, which is consistent with the pressure at the reaction end. A mixture of methyl hydrogen disulfide and dimethyl disulfide is separated and sent to the refining tower 3. Hydrofining is carried out at a pressure of 7.0MPaG and a temperature of 90°C. Among them, methyl hydrogen disulfide with a purity of 99.0% and 1.0% methyl mercaptan are obtained at the top of the tower, and this part of the product can be sent to the upstream raw material methyl mercaptan storage tank 4 for recycling. The product dimethyl disulfide is obtained in the tower bottom, and the tower bottom product is collected and analyzed. Its specific composition is as follows (the composition is all mass percentage, %):

[0047] DMDS, % DMTS, % CH3SH, % CH3SSH, % CH4, % 99.4 0.5 0.02 0.04 0.04

[0048] Example 5

[0049] Under nitrogen atmosphere, 100 g / h of methyl mercaptan is passed through a fixed bed 1 filled with a catalyst, wherein the catalyst is BaO and Al. 2 O 3 A mixture of BaO and Al 2 O 3 The mass ratio of is 0.05:1. The reactor temperature is controlled at 100°C, the reaction pressure is 10.0 MPaG, and the volume space velocity of the reactor is 0.5 h -1, so that methyl mercaptan reacts under the action of the catalyst to generate dimethyl disulfide and hydrogen. When the reaction system is stable, the conversion rate of the raw material is 98.3%, the selectivity of the product dimethyl disulfide is 79.8%, and the selectivity of methyl hydrogen disulfide is 20.2%. The resulting gas mixture is passed into the gas-liquid separator 2, and the mixture is cooled. The system temperature is controlled to 20°C and the pressure is 10MPaG, which is consistent with the pressure at the reaction end. A mixture of methyl hydrogen disulfide and dimethyl disulfide is separated and sent to the refining tower 3. Hydrofining is carried out at a pressure of 10MPaG and a temperature of 100°C. Among them, methyl hydrogen disulfide with a purity of 98.5% and 1.5% methyl mercaptan are obtained at the top of the tower, and this part of the product can be sent to the upstream raw material methyl mercaptan storage tank 4 for recycling. The product dimethyl disulfide is obtained in the tower bottom, and the tower bottom product is collected and analyzed. Its specific composition is as follows (the composition is all in mass percentage, %):

[0050] DMDS, % DMTS, % CH3SH, % CH3SSH, % CH4, % 99.5 0.3 0.05 0.09 0.06

Claims

1. A method for preparing dimethyl disulfide, comprising the following steps: (1) introducing methyl mercaptan into a fixed bed loaded with a catalyst to cause a decomposition reaction; (2) After the reaction is completed, the mixture is separated into gas and liquid to obtain a liquid product and a gas mixture; (3) The obtained gas mixture is pressurized and refined to separate methyl mercaptan for recycling.

2. The preparation method according to claim 1, characterized in that The fixed bed of step (1) is filled with a catalyst and the entire fixed bed is impregnated with dimethyl disulfide; the catalyst is a mixture of alkaline earth metal oxide and aluminum oxide, preferably, the alkaline earth metal is one or more of magnesium oxide, calcium oxide, strontium oxide and barium oxide, more preferably magnesium oxide; the mass ratio of the alkaline earth metal to aluminum oxide is (0.01-0.5):1, preferably (0.05-0.1):

1.

3. The preparation method according to claim 1 or 2, characterized in that: Weigh aluminum oxide and place it in a container, add an alkaline earth metal chloride aqueous solution thereto, stir and filter to obtain a solid, and then calcine to obtain a composite catalyst.

4. The preparation method according to claim 3, characterized in that: The stirring time is 1-48 hours; the calcination temperature is 400-800° C., and the calcination time is 10-48 hours.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The decomposition reaction temperature is 60-100°C, preferably 70-85°C; and / or, the decomposition reaction pressure is 0-10.0 MPaG, preferably 0.1-1.0 MPaG; and / or, the decomposition reaction volume space velocity is 0.1-2h -1 , preferably 0.2-0.5h -1 .

6. The preparation method according to any one of claims 1 to 5, characterized in that: The gas-liquid separation temperature in step (2) is 0-20°C, preferably 5-10°C.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The gas mixture obtained in step (3) is a mixture of hydrogen and methyl mercaptan, which are separated by pressure refining. Preferably, the refining temperature is 30-100°C, preferably 40-80°C; the refining pressure is 0.5-10.0 MPaG, preferably 1-5.0 MPaG.

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