A method for synthesizing ethyl mercaptan from hydrogen sulfide using vacancy-rich and modified molecular sieves

Abstract

The invention discloses a method for synthesizing ethyl mercaptan from hydrogen sulfide by catalyzing vacancy-rich and modified molecular sieves. The method uses ethylene and hydrogen sulfide as raw materials and the vacancy-rich and modified molecular sieves as catalysts to prepare ethyl mercaptan. The vacancy-rich and modified molecular sieves are prepared by replacing an aluminum source with a gallium source during a traditional mesoporous molecular sieve preparation process, then treating the prepared molecular sieve in concentrated nitric acid to separate the gallium element from the skeleton, thereby generating defects, and finally loading Mo and La on the molecular sieve. The catalyst has the characteristics of high selectivity and high conversion rate in synthesizing ethyl mercaptan, and has a long service life, and is suitable for industrial production and market promotion and application. The invention provides a new approach for the efficient production of ethyl mercaptan.

Description

Technical Field

[0001] The invention relates to a method for synthesizing ethyl mercaptan from hydrogen sulfide by catalyzing vacancy-rich and modified molecular sieves, and belongs to the field of ethyl mercaptan preparation. Background Art

[0002] Ethyl mercaptan is well known for its strong, pungent odor, detectable at concentrations of 1 part per 500 million in the air. It is also listed in the Guinness Book of World Records as the stinkiest substance. However, due to its malodorous properties, it is used as a warning agent for petroleum and natural gas, as an odorant for various reagents, and, in the pesticide industry, as an intermediate in the production of various pesticides and antimicrobial agents. Furthermore, ethyl mercaptan has a relatively good chain transfer constant, making it an ideal chain transfer agent in industry.

[0003] Currently, there are three main process routes for the synthesis of ethanethiol. The first one uses anhydrous ethanol, fuming sulfuric acid and sodium hydrosulfide as raw materials. Some domestic companies also adopt this route, but the route is long and the yield is low. The second one uses ethyl chloride and sodium hydrosulfide as raw materials, but it has high requirements for raw materials. The third one is to use ethylene and hydrogen sulfide for gas-phase catalysis. This process route has a higher yield and the raw materials are easy to obtain. It is also a path for hydrogen sulfide resource utilization, so it has higher application and development potential.

[0004] The synthesis of ethyl mercaptan using ethylene and hydrogen sulfide as raw materials is a catalytic reaction that requires the participation of a catalyst. The life and activity of the catalyst are crucial. However, a large number of research conclusions have shown that the deactivation of the catalyst is due to sulfur or carbon deposition on the catalyst. Therefore, the development of a highly active catalyst that is resistant to sulfur and carbon is the key to the efficient industrial synthesis of ethyl mercaptan. Summary of the Invention

[0005] The present invention provides a method for synthesizing ethyl mercaptan from hydrogen sulfide using vacancy-rich and modified molecular sieves as catalysts. The method uses ethylene and hydrogen sulfide as raw materials and vacancy-rich and modified molecular sieves as catalysts to prepare ethyl mercaptan.

[0006] The specific steps of the above method are as follows:

[0007] 1. Place the gallium salt in an aqueous solution containing hexadecyltrimethylammonium bromide, add ethanol and ammonia water after mixing, adjust the pH of the mixture to 9-10, then dropwise add tetraethyl orthosilicate, stir for 2-3 hours, heat at 60-80°C for reaction, filter, dry the solid at 25-35°C overnight, and finally calcine at 500-700°C to obtain Ga-MCM-41;

[0008] The concentration of cetyltrimethylammonium bromide in the aqueous solution containing cetyltrimethylammonium bromide is 0.2-0.3 mol / L; the molar ratio of tetraethyl orthosilicate to cetyltrimethylammonium bromide is 1:0.3-0.4; and the molar ratio of tetraethyl orthosilicate to gallium salt is 30-50:1;

[0009] 2. Place Ga-MCM-41 in nitric acid, stir at 90-100°C for 12-15h, filter, wash the solid to neutral dryness, use the equal volume impregnation method, place the dried solid in a solution containing lanthanum salt and ammonium molybdate, ultrasonically impregnate, dry, treat in an oxygen atmosphere at 300-400°C for 2-3h, and then treat in a H2 atmosphere at 600-700°C for 2-3h to obtain vacancy-rich and modified molecular sieves;

[0010] The loading amount of lanthanum is 3-5wt%, and the loading amount of molybdenum is 3-5wt%;

[0011] 3. Place the vacancy-rich and modified molecular sieves in a tubular furnace reactor, introduce a mixture of ethylene and hydrogen sulfide, and heat at 240-260°C, 1.5-1.8 MPa, and a gas hourly space velocity of 250-300 h -1 Ethyl mercaptan synthesis was carried out under the following conditions.

[0012] The present invention replaces the aluminum source with a gallium source in the traditional mesoporous molecular sieve preparation process, then treats the prepared molecular sieve in concentrated nitric acid to separate the gallium element from the framework, thereby generating defects, and finally loads Mo and La on the molecular sieve to prepare a vacancy-rich and modified molecular sieve. The catalyst has the characteristics of high selectivity and high conversion rate in synthesizing ethyl mercaptan, and has a long service life, making it suitable for industrial production and market promotion and application. The present invention provides a new approach for the efficient production of ethyl mercaptan. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 N2 adsorption-desorption isotherms of Ga-MCM-41 and deGa-MCM-41 catalysts in Example 1-2;

[0014] Figure 2 is the infrared spectrum of each catalyst in Example 1-2. DETAILED DESCRIPTION

[0015] The present invention is further described in detail below through examples, but the protection scope of the present invention is not limited to the contents described above. Example 1

[0016] 1. Gallium nitrate was placed in an aqueous solution containing 0.2 mol / L hexadecyltrimethylammonium bromide. After mixing, ethanol and ammonia solution (25%) were added. The pH of the mixture was adjusted to 9. After stirring for 10 minutes, tetraethyl orthosilicate was added dropwise. The molar ratio of tetraethyl orthosilicate to hexadecyltrimethylammonium bromide was 1:0.3, and the molar ratio of ethyl orthosilicate to gallium salt was 30:1. After stirring for 2 hours, the mixture was heated at 65°C for reaction, filtered, and the solid was dried at 25°C overnight. Finally, it was calcined at 550°C for 24 hours to obtain Ga-MCM-41.

[0017] 2. Ga-MCM-41 was placed in a 13 mol / L nitric acid solution, stirred at 100°C for 12 hours, filtered, and the solid was washed with water until the washing solution was neutral, and dried at 100°C (deGa-MCM-41). The dried solid was placed in a solution containing lanthanum nitrate and ammonium molybdate using an equal volume impregnation method and ultrasonically impregnated for 15 minutes (the lanthanum loading was 5 wt% and the molybdenum loading was 5 wt%), dried at 60°C, and 0.4 g of the dried solid was placed in a tubular furnace reactor and treated at 350°C in an oxygen atmosphere for 2 hours, and then at 700°C in a H2 atmosphere for 2 hours to obtain vacancy-rich and modified molecular sieve LaMo / deGa-MCM-41;

[0018] The N2 adsorption and desorption isotherms of the intermediates Ga-MCM-41 and deGa-MCM-41 are shown in Figure 1 As can be seen from the figure, after the gallium removal treatment in strong acid, the typical IV type isotherm of MCM-41 mesoporous material is still obtained, indicating that the basic skeleton of the molecular sieve has not changed, providing a carrier with a certain supporting strength for the subsequent metal loading; the infrared spectra of each catalyst are shown in Figure 2 The shaded area in the figure can be attributed to Si-(OH) x Species, as shown in the figure, after acid treatment Si-(OH) x The increase indicates that the successful removal of gallium has resulted in defects on the surface, which has caused Si-(OH) x Increase, after loading metal Si-(OH) x The peak intensity of the metal was reduced, indicating that the metal successfully combined with Si-(OH) x The interaction between the two species revealed the reasons for the improved catalytic performance of the catalyst.

[0019] 3. Place the vacancy-rich and modified molecular sieves in a tubular furnace reactor and introduce a mixture of ethylene and hydrogen sulfide (volume ratio 1:3) at a flow rate of 12 mL / min at 1.8 MPa and a gas hourly space velocity of 300 h -1 2. Ethyl mercaptan synthesis was carried out at 240°C. After 2 hours of reaction, the ethylene conversion rate was 91% and the ethyl mercaptan selectivity was 82%. After continuous operation for 500 hours, the conversion rate was 87% and the selectivity was 80%.

[0020] At the same time, Ga-MCM-41 prepared in step 1 and deGa-MCM-41 prepared in step 2 were used as control catalysts for ethanethiol synthesis under the same conditions as above. The results showed that under the action of Ga-MCM-41, the ethylene conversion rate was 59% and the ethanethiol selectivity was 53%. After continuous operation for 30 hours, the ethylene conversion rate was 37% and the ethanethiol selectivity was 49%.

[0021] Under the action of deGa-MCM-41, the ethylene conversion rate was 33% and the ethanethiol selectivity was 60%. After continuous operation for 30 hours, the ethylene conversion rate was 19% and the ethanethiol selectivity was 57%. Example 2

[0022] 1. Gallium nitrate was placed in an aqueous solution containing 0.3 mol / L hexadecyltrimethylammonium bromide. After mixing, ethanol and ammonia solution (25%) were added. The pH of the mixture was adjusted to 10. After stirring for 10 minutes, tetraethyl orthosilicate was added dropwise. The molar ratio of tetraethyl orthosilicate to hexadecyltrimethylammonium bromide was 1:0.4, and the molar ratio of ethyl orthosilicate to gallium salt was 50:1. After stirring for 2 hours, the mixture was heated at 75°C for reaction, filtered, and the solid was dried at 30°C overnight. Finally, it was calcined at 600°C for 24 hours to obtain Ga-MCM-41.

[0023] 2. Ga-MCM-41 was placed in a 13 mol / L nitric acid solution, stirred at 110 ° C for 12 hours, filtered, and the solid was washed with water until the washing solution was neutral, and dried at 110 ° C (deGa-MCM-41). The dried solid was placed in a solution containing lanthanum nitrate and ammonium molybdate by an equal volume impregnation method and ultrasonically impregnated for 15 minutes (the lanthanum loading was 3wt%, and the molybdenum loading was 3wt%), dried at 60 ° C, and 0.4 g of the dried solid was placed in a tubular furnace reactor and treated at 300 ° C for 2 hours in an oxygen atmosphere, and then treated at 650 ° C for 2 hours to obtain a vacancy-rich and modified molecular sieve (LaMo / deGa-MCM-41);

[0024] 3. Place the vacancy-rich and modified molecular sieves in a tubular furnace reactor and introduce a mixture of ethylene and hydrogen sulfide (volume ratio 1:3) at a flow rate of 10 mL / min at 1.6 MPa and a gas hourly space velocity of 250 h -1 2. Ethyl mercaptan synthesis was carried out at 250 ° C. After 2 hours of reaction, the ethylene conversion rate was 96% and the ethyl mercaptan selectivity was 76%. After continuous operation for 300 hours, the conversion rate decreased by only 5% and the selectivity decreased by 1%.

[0025] At the same time, Ga-MCM-41 prepared in step 1 and deGa-MCM-41 prepared in step 2 were used as control catalysts for ethanethiol synthesis under the same conditions as above. The results showed that under the action of Ga-MCM-41, the ethylene conversion rate was 62% and the ethanethiol selectivity was 51%. After continuous operation for 30 hours, the ethylene conversion rate decreased by 23% and the ethanethiol selectivity decreased by 3%.

[0026] Under the action of deGa-MCM-41, the ethylene conversion rate was 32% and the ethanethiol selectivity was 65%. After continuous operation for 30 hours, the ethylene conversion rate decreased by 13% and the ethanethiol selectivity decreased by 6%.

Claims

1. A method for synthesizing ethyl mercaptan from hydrogen sulfide using vacancy-rich and modified molecular sieves, characterized in that: Ethylene and hydrogen sulfide are used as raw materials and vacancy-rich and modified molecular sieves are used as catalysts to prepare ethyl mercaptan; The vacancy-rich and modified molecular sieve is prepared by placing a gallium salt in an aqueous solution containing hexadecyltrimethylammonium bromide, adding ethanol and ammonia solution after mixing, adjusting the pH of the mixture to 9-10, then adding tetraethyl orthosilicate dropwise, stirring for 2-3 hours, heating at 60-80°C for reaction, filtering, drying the solid at 25-35°C overnight, and finally calcining at 500-700°C to obtain Ga-MCM-41; placing the Ga-MCM-41 in nitric acid, stirring at 90-100°C for 12-15 hours, filtering, washing the solid to neutral dryness, and using an equal volume impregnation method, ultrasonically impregnating the dried solid in a solution containing lanthanum salt and ammonium molybdate, drying, treating at 300-400°C in an oxygen atmosphere for 2-3 hours, and then treating at 600-700°C in a H2 atmosphere for 2-3 hours to obtain the obtained product; The loading amount of lanthanum is 3-5wt%, the loading amount of molybdenum is 3-5wt%; and the molar ratio of tetraethyl orthosilicate to gallium salt is 30-50:

1.

2. The method according to claim 1, wherein: The concentration of cetyltrimethylammonium bromide in the aqueous solution containing cetyltrimethylammonium bromide is 0.2-0.3 mol / L.

3. The method according to claim 1, wherein: The molar ratio of tetraethyl orthosilicate to hexadecyltrimethylammonium bromide is 1:0.3-0.

4.

4. The method according to claim 1, wherein: At 240-260℃, 1.5-1.8MPa, gas hourly space velocity 250-300 h -1 Ethyl mercaptan synthesis was carried out under the following conditions.

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