A method for preparing dimethyl disulfide by methyl mercaptan sulfidation

Abstract

The present invention discloses a method for preparing dimethyl disulfide by methyl mercaptan sulfidation, which includes: (1) loading a yttrium-modified alumina catalyst in a shell-and-tube fixed-bed reactor, and then filling a solution of dimethyl disulfide and / or dimethyl polysulfide into the shell-and-tube fixed-bed reactor; (2) mixing liquid methyl mercaptan and liquid sulfur evenly through a pipeline mixer and continuously introducing them into the bottom of the shell-and-tube fixed-bed reactor to carry out a sulfidation reaction to generate a crude sulfide including dimethyl disulfide, dimethyl polysulfide, and hydrogen sulfide gas; (3) successively passing the crude sulfide through a first-stage, a second-stage, and a third-stage distillation column to remove hydrogen sulfide, methyl mercaptan, and dimethyl polysulfide respectively, so as to obtain high-quality dimethyl disulfide. The present invention uses a yttrium-modified activated alumina catalyst, which can greatly improve the activity of the catalyst and its selectivity for dimethyl disulfide, and make the single-pass conversion rate of dimethyl disulfide reach more than 90%.

Description

Technical Field

[0001] The present invention relates to the technical field of fine chemical engineering, and specifically relates to a method for preparing dimethyl disulfide by methyl mercaptan sulfidation method. Background Art

[0002] Dimethyl disulfide is an important chemical product, which can be used as a pesticide intermediate, a presulfiding agent for the oil refining industry, a lubricating oil additive, and so on. At present, the domestic production capacity of dimethyl disulfide far cannot meet the market demand, and its market gap basically depends on foreign imports. The synthesis methods of dimethyl disulfide are mainly divided into two types currently: dimethyl sulfate method and methyl mercaptan method.

[0003] The process of synthesizing dimethyl disulfide by the dimethyl sulfate method is relatively mature and the investment cost is relatively low. However, this process cannot be continuously produced, and has high energy consumption, large pollution, and low product yield. The methyl mercaptan method can achieve continuous production and has good product quality, but this process is relatively complex, the equipment investment is large, and the investment amount is about 4-5 times that of the dimethyl sulfate method. The methyl mercaptan method can be further divided into methyl mercaptan oxidation method and methyl mercaptan sulfidation method. The reaction raw material of the methyl mercaptan oxidation method uses air, which is relatively dangerous. The problems existing in the existing methyl mercaptan sulfidation method are: the reaction efficiency between methyl mercaptan and sulfur is relatively low, and the activity of the catalyst is relatively low, resulting in low single-pass conversion rate of dimethyl disulfide.

[0004] Chinese Patent CN 115108952 A discloses a method for preparing dimethyl disulfide by methyl mercaptan sulfidation method, which adopts a two-stage reaction mode to ensure a relatively high single-pass conversion rate of dimethyl disulfide. However, this method has the disadvantages of long process flow and high energy consumption, and this patent uses an organic amine catalyst, and the degradation of the organic amine introduces impurities, increasing the purification difficulty and reducing the product purity. Summary of the Invention

[0005] In order to solve the technical problems of long process flow, high energy consumption, using an organic amine catalyst in the existing patent technology CN 115108952 A, the degradation of the organic amine introducing impurities, increasing the purification difficulty and reducing the product purity, the present invention provides a method for preparing dimethyl disulfide by methyl mercaptan sulfidation method.

[0006] The technical solution adopted by the present invention is:

[0007] A method for preparing dimethyl disulfide by methyl mercaptan sulfidation method, comprising the following steps:

[0008] (1) Load a yttrium-modified alumina catalyst into a shell-and-tube fixed-bed reactor, and then fill a dimethyl disulfide and / or dimethyl polysulfide solution into the shell-and-tube fixed-bed reactor to submerge the alumina catalyst in the solution;

[0009] (2) Continuously introduce liquid methyl mercaptan and liquid sulfur into the bottom of a shell-and-tube fixed-bed reactor after mixing them evenly through a pipeline mixer. Under the action of a catalyst, methyl mercaptan and liquid sulfur complete the sulfidation reaction to produce a crude sulfide including dimethyl disulfide, dimethyl polysulfide, and hydrogen sulfide gas;

[0010] (3) Let the crude sulfide pass through a primary distillation column to remove hydrogen sulfide, a secondary distillation column to remove methyl mercaptan, and a tertiary distillation column to remove dimethyl polysulfide in sequence to obtain high-quality dimethyl disulfide.

[0011] In the present invention, by combining a yttrium-modified alumina catalyst and a shell-and-tube fixed-bed reactor, the single-pass conversion rate of dimethyl polysulfide (DMDS) can reach more than 90%, and the mass content of dimethyl polysulfide (DMPS) in the crude product is less than 0.5%; moreover, through the pipeline mixer, liquid sulfur is evenly dispersed and dissolved in liquid methyl mercaptan, which can reduce the reaction temperature of the reactor from the existing above 130 °C to below 80 °C, reducing energy consumption.

[0012] Preferably, the methyl mercaptan removed in the secondary distillation column continuously enters the pipeline mixer to be mixed with the raw materials and then enters the shell-and-tube fixed-bed reactor for recycling.

[0013] Preferably, the dimethyl polysulfide removed in the tertiary distillation column continuously enters the pipeline mixer to be mixed with the raw materials and then enters the shell-and-tube fixed-bed reactor for recycling.

[0014] By recycling methyl mercaptan and dimethyl polysulfide, the utilization rate of raw materials can be improved, and the yield of dimethyl disulfide can be increased.

[0015] Preferably, in step (2), the reaction pressure is 0.8 - 1.0 MPa, the reaction temperature is 50 - 80 °C, the molar ratio of methyl mercaptan to sulfur in the feed is (1.5 - 2.5):1, and the volume space velocity is 0.2 - 0.6 h -1 .

[0016] Preferably, the tube diameter of the shell-and-tube fixed-bed reactor is 30 - 50 mm, and the length-diameter ratio is 50 - 100.

[0017] The shell-and-tube reactor of the present invention greatly increases the length-diameter ratio. For a single tube, it has the advantages of small volume, large specific surface area, less backmixing, and easy control.

[0018] Preferably, the alumina catalyst is an alumina sphere with a particle size of 3 - 5 mm. It can also prevent the pressure drop from increasing too much while ensuring a relatively large specific surface area per unit volume of the catalyst.

[0019] Preferably, the modification method of the alumina catalyst is:

[0020] (7.1) Add alumina balls with a particle size of 3 - 5 mm to a 25% aqueous solution of yttrium nitrate, heat and stir evenly, then impregnate for a period of time, wash with distilled water, filter and dry;

[0021] (7.2) After high-temperature calcination of the dried alumina balls for a period of time, yttrium-modified activated alumina is obtained.

[0022] The introduction of yttrium element can effectively improve the activity and selectivity of the alumina catalyst, making the single-pass conversion rate of dimethyl disulfide reach more than 90%, and the sulfur conversion rate reach 100%.

[0023] Preferably, the proportion of yttrium oxide in the activated alumina is 0.02 - 0.05%. When the yttrium content is less than 0.02%, the modification effect cannot be achieved. When the yttrium content is higher than 0.05%, the activity of the catalyst does not increase significantly, and the manufacturing cost increases.

[0024] Preferably, in step (7.1), the heating temperature is 45 - 55 °C, and the impregnation time is 12 - 24 h. By controlling the length of the impregnation time, the proportion of the finally formed Y2O3 in the catalyst can be regulated.

[0025] Preferably, in step (7.2), the calcination temperature is 480 - 500 °C, and the calcination time is 6 - 8 h.

[0026] The beneficial effects of the present invention:

[0027] 1. The process flow of the present invention is short, the energy consumption is low, and the single-pass conversion rate of dimethyl disulfide reaches more than 90%; moreover, the present invention uses a yttrium-modified alumina catalyst to replace the organic amine catalyst, which can avoid the impurity problems caused by the degradation of organic amines.

[0028] 2. The catalytic activity of traditional alumina catalysts is generally low, the selectivity is poor, and the single-pass conversion rate is low, resulting in a large amount of recycle feed, which inevitably leads to an increase in side reactions. The yttrium-modified alumina catalyst can greatly improve the catalyst activity and its selectivity for dimethyl disulfide, reduce the recycle feed amount of dimethyl polysulfide, effectively reduce the occurrence of side reactions, and further increase the service life of the alumina catalyst by 1.5 - 2 times. Description of the Drawings

[0029] Figure 1 It is the process flow chart of the method for preparing dimethyl disulfide by the methyl mercaptan sulfidation method of the present invention. Detailed Embodiments

[0030] The following further illustrates the present invention with specific examples for the convenience of understanding the present invention, but does not limit the present invention accordingly.

[0031] The raw materials used in the following examples are all commercially available.

[0032] The tube length-to-diameter ratio of the tubes in the shell-and-tube fixed-bed reactor used in the following examples is 100, the diameter is 40 mm, and five tubes are connected in parallel in a single reactor.

[0033] Example 1

[0034] Catalyst preparation:

[0035] Weigh 100g of commercially available activated alumina (3-5mm particle size) and add 100mL of a 25% aqueous yttrium nitrate solution. Stir thoroughly with a magnetic stirrer at 45°C. After soaking for 24 hours, wash three times with distilled water and filter. Oven dry at 120°C and calcine in a muffle furnace at 480°C for 8 hours to obtain yttrium-modified activated alumina catalyst A, in which Y2O3 accounts for 0.05%.

[0036] Method for preparing dimethyl disulfide:

[0037] (1) 4.5 L of activated alumina A (per tube) was loaded into the tube-in-tube fixed bed reactor 2, and then a dimethyl disulfide solution was filled into the tubes of the tube-in-tube fixed bed reactor 2 and the alumina catalyst A was immersed in the solution;

[0038] (2) Liquid methyl mercaptan and liquid sulfur are uniformly mixed in a pipeline mixer 1 and continuously introduced into the bottom of a tubular fixed bed reactor 2. Methyl mercaptan and liquid sulfur undergo a sulfurization reaction in the tubular fixed bed reactor 2 at a reaction temperature of 80° C. and a reaction pressure of 0.8 MPa. The feed ratio of methyl mercaptan to liquid sulfur is 2. The volumetric space velocity of the reactor is controlled to be 0.2 h / min. -1 ;

[0039] (3) The crude sulfide generated by the sulfidation reaction is sequentially passed through a primary distillation tower 3 to remove hydrogen sulfide, a secondary distillation tower 4 to remove methyl mercaptan, and a tertiary distillation tower 5 to remove dimethyl polysulfide to obtain fine dimethyl disulfide;

[0040] The composition of the sulfide obtained in step (2) and dimethyl disulfide A obtained in step (3) was determined by gas chromatography and is shown in Table 1.

[0041] Example 2

[0042] Catalyst preparation:

[0043] Weigh 100g of commercially available activated alumina (3-5mm particle size) and add 100mL of a 25% aqueous yttrium nitrate solution. Stir thoroughly with a magnetic stirrer at 50°C. After immersion for 18 hours, wash three times with distilled water and filter. Oven dry at 120°C and calcine at 500°C for 6 hours to obtain yttrium-modified activated alumina catalyst B, in which the Y2O3 content is 0.02%.

[0044] Method for preparing dimethyl disulfide:

[0045] (1) Charge 4.5 L of activated alumina B (per tube) into the shell-and-tube fixed-bed reactor 2, and then fill the tubes of the shell-and-tube fixed-bed reactor 2 with a dimethyl disulfide solution to submerge the alumina catalyst B in the solution;

[0046] (2) Continuously introduce liquid methanethiol and liquid sulfur into the bottom of the shell-and-tube fixed-bed reactor 2 after mixing them evenly through a pipeline mixer 1. The methanethiol and liquid sulfur undergo a sulfidation reaction in the shell-and-tube fixed-bed reactor 2 at a reaction temperature of 70 °C and a reaction pressure of 0.9 MPa; the feed ratio of methanethiol to liquid sulfur is 1.5; the space velocity is 0.6 h -1 ;

[0047] (3) The crude sulfide produced by the sulfidation reaction is successively passed through a first-stage distillation column 3 to remove hydrogen sulfide, a second-stage distillation column 4 to remove methanethiol, and a third-stage distillation column 5 to remove dimethyl polysulfide, obtaining high-quality dimethyl disulfide;

[0048] The components of the sulfide obtained in step (2) and the dimethyl disulfide B obtained in step (3) are detected by gas chromatography, and the results are shown in Table 1.

[0049] Example 3

[0050] Catalyst preparation:

[0051] Weigh 100 g of commercially available activated alumina with a particle size of 3 - 5 mm, add 100 mL of 25% aqueous yttrium nitrate solution, stir evenly with a magnetic stirrer at a temperature of 55 °C, impregnate for 12 h, wash 3 times with distilled water, and filter. Dry in an oven at 120 °C and calcine in a muffle furnace at 490 °C for 6.5 h to obtain a yttrium-modified activated alumina catalyst C, in which the proportion of Y2O3 is 0.04%.

[0052] Method for preparing dimethyl disulfide:

[0053] (1) Charge 4.5 L of activated alumina C (per tube) into the shell-and-tube fixed-bed reactor 2, and then fill the tubes of the shell-and-tube fixed-bed reactor 2 with a dimethyl disulfide solution to submerge the alumina catalyst C in the solution;

[0054] (2) Continuously introduce liquid methanethiol and liquid sulfur into the bottom of the shell-and-tube fixed-bed reactor 2 after mixing them evenly through a pipeline mixer 1. The methanethiol and liquid sulfur undergo a sulfidation reaction in the shell-and-tube fixed-bed reactor 2 at a reaction temperature of 50 °C and a reaction pressure of 1.0 MPa; the feed ratio of methanethiol to liquid sulfur is 2.5; the space velocity is 0.4 h -1 ;

[0055] (3) The crude sulfide produced by the sulfidation reaction is successively passed through a first-stage rectification column 3 to remove hydrogen sulfide, a second-stage rectification column 4 to remove methyl mercaptan, and a third-stage rectification column 5 to remove dimethyl polysulfide, obtaining high-quality dimethyl disulfide;

[0056] The components of the sulfide obtained in step (2) and dimethyl disulfide C obtained in step (3) are detected by gas chromatography, and the results are shown in Table 1.

[0057] Comparative Example 1

[0058] Method for preparing dimethyl disulfide:

[0059] (1) Charge 4.5 L (per tube) of commercially available activated alumina into the tubular fixed-bed reactor 2, with the catalyst particle size of 3 - 5 mm, and then fill the dimethyl disulfide solution into the tubes of the tubular fixed-bed reactor 2 to submerge the alumina catalyst C in the solution;

[0060] (2) Mix liquid methyl mercaptan and liquid sulfur evenly through a pipe mixer 1 and continuously feed them into the bottom of the tubular fixed-bed reactor 2. The methyl mercaptan and liquid sulfur undergo a sulfidation reaction in the tubular fixed-bed reactor 2 at a reaction temperature of 80 °C and a reaction pressure of 1.0 MPa; the feed ratio of methyl mercaptan to liquid sulfur is 2.5; the volume space velocity is 0.5 h -1 ;

[0061] (3) The crude sulfide produced by the sulfidation reaction is successively passed through a first-stage rectification column 3 to remove hydrogen sulfide, a second-stage rectification column 4 to remove methyl mercaptan, and a third-stage rectification column 5 to remove dimethyl polysulfide, obtaining high-quality dimethyl disulfide;

[0062] The composition of the sulfide obtained in the examples and comparative examples is detected by gas chromatography, and the sulfur conversion rate is calculated. The results are shown in Table 1.

[0063] Table 1 Detection results of examples and comparative examples

[0064]

[0065] As can be seen from the above table, by using the yttrium-modified activated alumina catalyst of the present invention, the catalyst activity and its selectivity for dimethyl disulfide can be greatly improved.

[0066] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can still be made, and these improvements and modifications are also within the protection scope of the present invention.

Claims

1. A method for preparing dimethyl disulfide by the sulfurization of methanethiol, characterized in that, It includes the following steps: (1) Load a yttrium-modified alumina catalyst into a shell-and-tube fixed-bed reactor, and then fill the shell-and-tube fixed-bed reactor with a solution of dimethyl disulfide and / or dimethyl polysulfide to submerge the alumina catalyst in the solution; (2) Continuously introduce liquid methanethiol and liquid sulfur into the bottom of the shell-and-tube fixed-bed reactor after mixing them evenly through a pipeline mixer. Under the action of the catalyst, methanethiol and liquid sulfur complete the sulfidation reaction to produce a crude sulfide including dimethyl disulfide, dimethyl polysulfide, and hydrogen sulfide gas; (3) Pass the crude sulfide through a primary distillation column to remove hydrogen sulfide, a secondary distillation column to remove methanethiol, and a tertiary distillation column to remove dimethyl polysulfide to obtain high-quality dimethyl disulfide; The modification method of the alumina catalyst is as follows: (7.1) Add alumina balls with a particle size of 3 - 5 mm to an aqueous solution of yttrium nitrate, heat and stir evenly, then impregnate for a period of time, wash with distilled water, filter, and dry; (7.2) After high-temperature calcination of the dried alumina balls for a period of time, yttrium-modified activated alumina is obtained; The proportion of yttrium sesquioxide in the activated alumina is 0.02 - 0.05%.

2. The method for preparing dimethyl disulfide by methanethiol sulfidation according to claim 1, characterized in that, The methanethiol removed in the secondary distillation column continuously enters the pipeline mixer to be mixed with the raw materials and then enters the shell-and-tube fixed-bed reactor for recycling.

3. A method for preparing dimethyl disulfide by methanethiol sulfidation according to claim 1, characterized in that, The dimethyl polysulfide removed in the tertiary distillation column continuously enters the pipeline mixer to be mixed with the raw materials and then enters the shell-and-tube fixed-bed reactor for recycling.

4. The method for preparing dimethyl disulfide by methanethiol sulfidation according to claim 1, characterized in that, In step (2), the reaction pressure is 0.8 to 1.0 MPa, the reaction temperature is 50 to 80 °C, the molar ratio of methanethiol to sulfur in the feed is (1.5 to 2.5):1, and the volume space velocity is 0.2 to 0.6 h -1 .

5. A method for preparing dimethyl disulfide by methanethiol sulfidation according to claim 1, characterized in that, The tube diameter of the shell-and-tube fixed-bed reactor is 30 - 50 mm, and the length-diameter ratio is 50 - 100.

6. The method for preparing dimethyl disulfide by methanethiol sulfidation according to claim 1, wherein, In step (7.1), the heating temperature is 45 - 55 °C, and the impregnation time is 12 - 24 h.

7. A method for preparing dimethyl disulfide by methyl mercaptan sulfidation according to claim 1, characterized in that, In step (7.2), the calcination temperature is 480 - 500 °C, and the calcination time is 6 - 8 h.

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