Composite catalyst for improving synthesis of methyl chlorosilane and preparation method thereof

Abstract

The invention relates to a composite catalyst for improving synthesis of methylchlorosilane and a preparation method of the composite catalyst, and belongs to the technical field of composite catalysts. The catalyst comprises a main catalyst (a compound of cuprous chloride and metal zinc, the molar ratio of Cu to Zn being 1: (0.1-0.5)), a co-catalyst (alumina or stannic chloride, the mass of which is 5%-20%) and a carrier (porous silica gel or nitrogen-doped activated carbon, the loading capacity of which is 3-8 times). Through optimization of catalyst composition, carrier functionalization (such as sulfydryl modification) and a preparation process, the selectivity (greater than or equal to 85%) of dimethyldichlorosilane is remarkably improved, and the stability and activity of the catalyst are enhanced. The preparation method comprises the steps of ball milling and heat treatment of the main catalyst, addition of the cocatalyst, acid pickling and modification of the carrier, loading and drying of the catalyst and the like. The method has the advantages of high selectivity, good stability, simple process and the like, and is suitable for efficient synthesis of methyl chlorosilane.

Description

Technical Field

[0001] The present invention relates to the technical field of composite catalysts, and particularly to a composite catalyst for improving the synthesis of methylchlorosilane and a preparation method thereof. Background Art

[0002] Methylchlorosilane is a class of important organosilicon compounds, which are widely used in the fields of organosilicon materials, medicine, pesticides, etc. Among them, dimethyldichlorosilane, (CH3)2SiCl2, is one of the most important monomers, and its synthesis efficiency and selectivity directly affect the production cost and product quality of the organosilicon industry. At present, methylchlorosilane is mainly prepared by the direct synthesis method (Rochow Process) in industry. In this method, silicon powder and chloromethane are used as raw materials and react under the action of a catalyst. The performance of the catalyst has a decisive influence on the selectivity and yield of the reaction.

[0003] Existing composite catalysts can improve the synthesis efficiency of methylchlorosilane to a certain extent, but still have the following disadvantages:

[0004] 1. Insufficient catalyst selectivity: In the synthesis reaction of methylchlorosilane, the selectivity of dimethyldichlorosilane of existing catalysts is usually lower than 85%, resulting in an increase in by-products, a decrease in the yield of the target product, and an increase in the difficulty of subsequent separation and purification.

[0005] 2. Poor catalyst stability: Existing catalysts are prone to deactivation under high-temperature reaction conditions, resulting in a decrease in catalytic efficiency. During the reaction process, the catalyst needs to be frequently replaced or regenerated, increasing the production cost.

[0006] 3. Poor carrier performance: The pore size distribution of traditional carriers such as ordinary porous silica gel or activated carbon is uneven, and the specific surface area is limited, resulting in uneven dispersion of the active components of the catalyst and affecting the catalytic effect. In addition, the surface of the carrier lacks functional modification, making it difficult to form a strong interaction with the active components of the catalyst, reducing the overall performance of the catalyst.

[0007] 4. Limited co-catalyst effect: The addition amount and type selection of existing co-catalysts (such as alumina, stannous chloride) are relatively single, and the synergistic catalytic effect cannot be fully exerted, resulting in limited improvement in the overall activity of the catalyst.

[0008] 5. Complex preparation process: The preparation process of existing catalysts usually involves multiple complex treatment processes, such as high-temperature treatment, pickling, surface modification, etc. The steps are cumbersome and time-consuming, increasing the production cost and process difficulty.

[0009] 6. Insufficient application of nano - metallic zinc: In existing catalysts, the morphology and particle size of metallic zinc are not well - controlled, and the high specific surface area and activity of nano - zinc powder are not fully utilized, resulting in limited reaction activity of the catalyst.

[0010] 7. Insufficient functionalization of the support: Existing supports lack functional modifications (such as mercapto functional group modification), making it difficult to form strong interactions with the active components of the catalyst, which affects the stability and activity of the catalyst.

[0011] 8. Insufficient application of nitrogen - doped activated carbon: In existing catalysts, the modification degree of activated carbon is limited, and the high specific surface area and surface activity of nitrogen - doped activated carbon are not fully utilized, resulting in limited improvement in the overall performance of the catalyst.

[0012] In summary, the existing composite catalysts have many deficiencies in terms of selectivity, stability, support performance, cocatalyst effect, preparation process, etc. There is an urgent need to develop a new type of composite catalyst and its preparation method to improve the selectivity and efficiency of methyl chlorosilane synthesis, reduce production costs, and meet the requirements of industrial applications. Summary of the Invention

[0013] The technical problems to be solved by the present invention are: insufficient selectivity of the catalyst, poor stability of the catalyst, poor support performance, limited cocatalyst effect, complex preparation process, insufficient application of nano - metallic zinc, insufficient functionalization of the support, and insufficient application of nitrogen - doped activated carbon.

[0014] The technical solution adopted by the present invention is: A composite catalyst for improving the synthesis of methyl chlorosilane, comprising the following components:

[0015] a. Main catalyst: A composite of cuprous chloride (CuCl) and metallic zinc (Zn), where the molar ratio of Cu to Zn is 1:0.1 - 0.5;

[0016] b. Cocatalyst: Selected from at least one of alumina (Al2O3) and stannous chloride (SnCl2), and its mass is 5% - 20% of the total mass of the main catalyst;

[0017] c. Support: Porous silica gel or modified activated carbon, and its loading amount is 3 - 8 times the total mass of the main catalyst and the cocatalyst;

[0018] Among them, in the direct synthesis reaction of methyl chlorosilane, the selectivity of dimethyldichlorosilane of the composite catalyst is ≥85%.

[0019] As a further scheme of the present invention: The metallic zinc exists in the form of nano - zinc powder or zinc foil fragments, with a particle size of 20 - 200 nm and a specific surface area ≥50 m 2 / g.

[0020] As a further solution of the present invention: the porous silica carrier is pretreated by pickling, with a pore size distribution of 5-50 nm, and the surface is modified with a mercapto (-SH) functional group.

[0021] As a further solution of the present invention: the modified activated carbon is nitrogen-doped activated carbon, with a nitrogen element content of 2-8 wt%, and is prepared by high-temperature carbonization of a biomass precursor.

[0022] A preparation method of a composite catalyst for improving the synthesis of methylchlorosilane, comprising the following steps:

[0023] S1. Preparation of the main catalyst

[0024] S1.1: Weigh cuprous chloride (CuCl) and metallic zinc (Zn), and mix them in a molar ratio of Cu to Zn of 1:0.1-0.5;

[0025] S1.2: Put the mixed CuCl and Zn into a ball mill and carry out mechanical ball milling to fully mix the two and form a composite;

[0026] S1.3: Heat-treat the ball-milled composite under an inert atmosphere (such as nitrogen or argon), with a temperature of 200-300 °C and a time of 2-4 hours to enhance the stability of the composite;

[0027] S2. Addition of the co-catalyst

[0028] S2.1: Select alumina (Al2O3) or tin chloride (SnCl2) as the co-catalyst, and its mass is 5%-20% of the total mass of the main catalyst;

[0029] S2.2: Mix the co-catalyst with the main catalyst composite and make it uniformly dispersed by mechanical stirring or ultrasonic treatment;

[0030] S3. Pretreatment of the carrier

[0031] S3.1: Select porous silica or modified activated carbon as the carrier;

[0032] S3.2: If porous silica is used, pickling pretreatment is required;

[0033] S3.3: If modified activated carbon is used, ensure that it is nitrogen-doped activated carbon, with a nitrogen element content of 2-8 wt%, and is prepared by high-temperature carbonization of a biomass precursor;

[0034] S4. Loading of the catalyst

[0035] S4.1: Mix the mixture of the main catalyst and the co-catalyst with the carrier in a ratio of 3-8 times the loading amount of the total mass of the main catalyst and the co-catalyst;

[0036] S4.2: Uniformly disperse the mixture in an appropriate amount of solvent (such as ethanol or water) under stirring conditions to form a slurry;

[0037] S4.3: Load the slurry onto the carrier by impregnation or spraying method, and then dry it at 60 - 80 °C;

[0038] S4.4: Heat-treat the dried catalyst in an inert atmosphere at a temperature of 300 - 400 °C for 2 - 4 hours to enhance the stability of the catalyst;

[0039] S5. Catalyst Characterization and Application

[0040] S5.1: Characterize the prepared composite catalyst, including specific surface area, pore size distribution, and elemental analysis;

[0041] S5.2: Apply the catalyst to the direct synthesis reaction of methylchlorosilane to ensure that the selectivity of dimethyldichlorosilane is ≥ 85%.

[0042] As a further scheme of the present invention: The pickling pretreatment step is as follows:

[0043] Soak the porous silica gel in 1 - 2 M hydrochloric acid or sulfuric acid solution for 2 - 4 hours;

[0044] Rinse with deionized water until neutral, and then dry at 100 - 120 °C;

[0045] Modify the dried porous silica gel with mercapto (-SH) functional groups, and the method is as follows:

[0046] Soak the porous silica gel in an ethanol solution containing a mercapto silane coupling agent (such as 3-mercaptopropyltrimethoxysilane) for 12 - 24 hours;

[0047] Rinse with ethanol to remove the unreacted coupling agent, and then dry at 60 - 80 °C.

[0048] Advantages of the present invention:

[0049] 1. Improve catalyst selectivity: By optimizing the composition and ratio of the main catalyst (the complex of cuprous chloride and metallic zinc) (the molar ratio of Cu to Zn is 1:0.1 - 0.5) and combining with the synergistic effect of the cocatalyst (aluminum oxide or stannous chloride), the selectivity of dimethyldichlorosilane is significantly improved, reaching ≥ 85% in the direct synthesis reaction of methylchlorosilane, effectively reducing the generation of by-products and lowering the cost of subsequent separation and purification.

[0050] 2. Enhance catalyst stability: Through heat treatment under an inert atmosphere (200 - 300 °C, 2 - 4 hours) and surface modification of the support (such as thiol functional group modification), the present invention significantly improves the stability of the catalyst, making it less likely to deactivate under high-temperature reaction conditions, extending the service life of the catalyst, reducing the frequency of catalyst replacement or regeneration, and lowering production costs.

[0051] 3. Optimize support performance: The present invention uses porous silica gel or nitrogen-doped activated carbon as the support, and through pickling pretreatment and surface modification (such as thiol functional group modification), the support has a uniform pore size distribution (5 - 50 nm) and a high specific surface area (≥50 m 2 / g), ensuring that the active components of the catalyst can be evenly dispersed, and significantly enhancing the catalytic effect.

[0052] 4. Improve the effect of the cocatalyst: By optimizing the addition amount of the cocatalyst (aluminum oxide or tin chloride) (5% - 20% of the total mass of the main catalyst) and combining with the synergistic effect of the main catalyst, the present invention gives full play to the catalytic effect of the cocatalyst and significantly improves the overall activity of the catalyst.

[0053] 5. Simplify the preparation process: The preparation method of the present invention realizes the efficient preparation of the catalyst through simple and feasible process steps such as mechanical ball milling, impregnation method or spraying method, avoiding the complex multi-step treatment process in the traditional process, and reducing production costs and process difficulties.

[0054] 6. Make full use of the high activity of nano metal zinc: The present invention uses nano zinc powder or zinc foil fragments (particle size 20 - 200 nm, specific surface area ≥50 m 2 / g) as the source of metal zinc, making full use of the high specific surface area and activity of the nano material, and significantly improving the reaction activity of the catalyst.

[0055] 7. Enhance support functionalization: By pickling pretreatment and thiol functional group modification of the porous silica gel support, the present invention enhances the interaction between the support and the active components of the catalyst, and improves the stability and activity of the catalyst.

[0056] 8. Make full use of the advantages of nitrogen-doped activated carbon: The present invention uses nitrogen-doped activated carbon as the support (nitrogen element content 2 - 8 wt%), which is prepared by high-temperature carbonization of biomass precursors, making full use of the high specific surface area and surface activity of nitrogen-doped activated carbon, and significantly improving the overall performance of the catalyst. Detailed implementation manners

[0057] The following details the specific implementation manners of the present invention through multiple examples, and conducts a comparative analysis of the effects of each example.

[0058] Example 1

[0059] S1. Preparation of the main catalyst

[0060] S1.1: Weigh cuprous chloride (CuCl) and nano zinc powder (Zn), and mix them in a ratio of 1:0.1 in terms of the molar ratio of Cu to Zn.

[0061] S1.2: Put the mixture into a ball mill and mechanically ball mill for 2 hours to fully mix the two and form a complex.

[0062] S1.3: Heat-treat the ball-milled complex under a nitrogen atmosphere at a temperature of 200 °C for 2 hours.

[0063] S2. Addition of the co-catalyst

[0064] S2.1: Select alumina (Al2O3) as the co-catalyst, and its mass is 5% of the total mass of the main catalyst.

[0065] S2.2: Mix the co-catalyst with the main catalyst complex and make it uniformly dispersed by mechanical stirring.

[0066] S3. Pretreatment of the carrier

[0067] S3.1: Select porous silica gel as the carrier and conduct pickling pretreatment:

[0068] S3.1.1: Immerse the porous silica gel in a 1M hydrochloric acid solution for 2 hours.

[0069] S3.1.2: Rinse with deionized water until neutral, and then dry at 100 °C.

[0070] S3.1.3: Conduct mercapto (-SH) functional group modification on the dried porous silica gel:

[0071] S3.2: Immerse the porous silica gel in an ethanol solution containing 3-mercaptopropyltrimethoxysilane for 12 hours.

[0072] S3.3: Rinse with ethanol to remove the unreacted coupling agent, and then dry at 60 °C.

[0073] S4. Loading of the catalyst

[0074] S4.1: Mix the mixture of the main catalyst and the co-catalyst with the carrier in a ratio of 3 times the total mass for loading.

[0075] S4.2: Uniformly disperse the mixture in ethanol under stirring conditions to form a slurry.

[0076] S4.3: Load the slurry onto the carrier by the impregnation method, and then dry at 60 °C.

[0077] S4.4: Heat-treat the dried catalyst under a nitrogen atmosphere at a temperature of 300 °C for 2 hours.

[0078] S5. Application and Characterization of the Catalyst

[0079] S5.1: Characterize the catalyst, and the results show that the specific surface area is 60 m 2 / g and the pore size distribution is 5 - 20 nm.

[0080] S5.2: Apply the catalyst to the direct synthesis reaction of methylchlorosilane, and the selectivity of dimethyldichlorosilane is 86%.

[0081] Example 2

[0082] S1. Preparation of the Main Catalyst

[0083] S1.1: Weigh cuprous chloride (CuCl) and nano zinc powder (Zn), and mix them in a molar ratio of Cu to Zn of 1:0.3.

[0084] S1.2: Put the mixture into a ball mill and mechanically ball mill for 3 hours.

[0085] S1.3: Heat-treat the ball-milled composite under an argon atmosphere at a temperature of 250 °C for 3 hours.

[0086] S2. Addition of the Promoter

[0087] S2.1: Select stannous chloride (SnCl2) as the promoter, and its mass is 10% of the total mass of the main catalyst.

[0088] S2.2: Mix the promoter with the main catalyst composite and make it uniformly dispersed by ultrasonic treatment.

[0089] S3. Pretreatment of the Support

[0090] S3.1: Select nitrogen-doped activated carbon as the support, and the nitrogen element content is 5 wt%.

[0091] S3.2: The support is prepared by high-temperature carbonization of biomass precursors.

[0092] S4. Loading of the Catalyst

[0093] S4.1: Mix the mixture of the main catalyst and the promoter with the support in a ratio of 5 times the loading amount of the total mass.

[0094] S4.2: Uniformly disperse the mixture in water under stirring conditions to form a slurry.

[0095] S4.3: Load the slurry onto the support by spraying method, and then dry it at 70 °C.

[0096] S4.4: Heat-treat the dried catalyst under an argon atmosphere at a temperature of 350 °C for 3 hours.

[0097] S5. Application and Characterization of the Catalyst

[0098] S5.1: Characterize the catalyst, and the results show that the specific surface area is 80 m 2 / g and the pore size distribution is 10 - 30 nm.

[0099] S5.2: Apply the catalyst to the direct synthesis reaction of methylchlorosilane, and the selectivity of dimethyldichlorosilane is 88%.

[0100] Example 3

[0101] S1. Preparation of the Main Catalyst

[0102] S1.1: Weigh cuprous chloride (CuCl) and zinc foil fragments (Zn), and mix them in a molar ratio of Cu to Zn of 1:0.5.

[0103] S1.2: Put the mixture into a ball mill and mechanically ball mill for 4 hours.

[0104] S1.3: Heat-treat the ball-milled composite under a nitrogen atmosphere at a temperature of 300 °C for 4 hours.

[0105] S2. Addition of the Promoter

[0106] S2.1: Select alumina (Al2O3) and tin chloride (SnCl2) as the promoters, and their masses are 10% and 5% of the total mass of the main catalyst, respectively.

[0107] S2.2: Mix the promoter with the main catalyst composite and make it uniformly dispersed by mechanical stirring and ultrasonic treatment.

[0108] S3. Pretreatment of the Support

[0109] S3.1: Select porous silica gel as the support and conduct pickling pretreatment:

[0110] S3.1.1: Immerse the porous silica gel in a 2M sulfuric acid solution for 4 hours.

[0111] S3.1.2: Rinse with deionized water until neutral, and then dry at 120 °C.

[0112] S3.1.3: Modify the dried porous silica gel with a mercapto (-SH) functional group:

[0113] S3.2: Immerse the porous silica gel in an ethanol solution containing 3-mercaptopropyltrimethoxysilane for 24 hours.

[0114] S3.3: Rinse with ethanol to remove the unreacted coupling agent, and then dry at 80 °C.

[0115] S4. Loading of the catalyst

[0116] S4.1: Mix the mixture of the main catalyst and the promoter with the carrier at a ratio of 8 times the total mass of the loading amount.

[0117] S4.2: Uniformly disperse the mixture in ethanol under stirring conditions to form a slurry.

[0118] S4.3: Load the slurry onto the carrier by the impregnation method, and then dry at 80 °C.

[0119] S4.4: Heat-treat the dried catalyst in a nitrogen atmosphere at a temperature of 400 °C for 4 hours.

[0120] S5. Application and characterization of the catalyst

[0121] S5.1: Characterize the catalyst, and the results show that the specific surface area is 100 m 2 / g, and the pore size distribution is 20 - 50 nm.

[0122] Comparative analysis

[0123]

[0124]

[0125] Analysis results:

[0126] 1. Influence of the Cu / Zn molar ratio: As the Cu / Zn molar ratio increases (from 1:0.1 to 1:0.5), the activity of the catalyst gradually increases, and the selectivity of dimethyldichlorosilane increases from 86% to 90%.

[0127] 2. Influence of the promoter: The effect of the composite promoter (Al2O3 + SnCl2) is better than that of the single promoter, and the selectivity increases from 88% to 90%.

[0128] 3. Influence of the carrier: After pickling and mercapto modification of the porous silica gel, the specific surface area and pore size distribution are better, and the catalytic effect is significantly improved.

[0129] 4. Influence of the loading amount: As the loading amount increases (from 3 times to 8 times), the activity of the catalyst gradually increases, and the selectivity increases from 86% to 90%.

[0130] In summary, Example 3 is optimal in terms of catalyst composition, support treatment, and loading amount, with the highest selectivity for dimethyldichlorosilane (90%), and has the best industrial application prospects.

[0131] The above examples are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing examples, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing examples, or perform equivalent replacements for some of the technical features. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A composite catalyst for improving the synthesis of methylchlorosilane, characterized in that: It comprises the following components: a. Main catalyst: a complex of cuprous chloride and metallic zinc, where the molar ratio of Cu to Zn is 1:0.1 - 0.5; b. Promoter: at least one selected from alumina and stannous chloride, and its mass is 5% - 20% of the total mass of the main catalyst; c. Carrier: porous silica gel or modified activated carbon, and its loading amount is 3 - 8 times the total mass of the main catalyst and the promoter; Among them, in the direct synthesis reaction of methylchlorosilane, the selectivity of dimethyldichlorosilane of the composite catalyst is ≥85%.

2. The composite catalyst for improving the synthesis of methylchlorosilane according to claim 1, characterized in that: The metallic zinc exists in the form of nano zinc powder or zinc foil fragments, with a particle size of 20 to 200 nm and a specific surface area ≥ 50 m 2 / g.

3. The composite catalyst for improving the synthesis of methylchlorosilane according to claim 2, wherein: The porous silica gel carrier is pretreated by pickling, with a pore size distribution of 5 - 50 nm and a mercapto functional group modified on the surface.

4. The composite catalyst for improving the synthesis of methylchlorosilane according to claim 3, characterized in that: The modified activated carbon is nitrogen-doped activated carbon, with a nitrogen element content of 2 - 8 wt%, and is prepared by high-temperature carbonization of biomass precursors.

5. The preparation method of a composite catalyst for improving the synthesis of methylchlorosilane according to claim 4, characterized in that: It comprises the following steps: S1. Preparation of the main catalyst S1.1: Weigh cuprous chloride and metallic zinc, and mix them according to the molar ratio of Cu to Zn of 1:0.1 - 0.5; S1.2: Put the mixed CuCl and Zn into a ball mill for mechanical ball milling to fully mix the two and form a complex; S1.3: Heat-treat the ball-milled complex in an inert atmosphere at a temperature of 200 - 300 °C for 2 - 4 hours to enhance the stability of the complex; S2. Addition of the promoter S2.1: Select alumina or stannous chloride as the promoter, and its mass is 5% - 20% of the total mass of the main catalyst; S2.2: Mix the promoter with the main catalyst complex and make it evenly dispersed by mechanical stirring or ultrasonic treatment; S3. Pretreatment of the carrier S3.1: Select porous silica gel or modified activated carbon as the carrier; S3.2: If using porous silica gel, pickling pretreatment is required; S3.3: If using modified activated carbon, ensure that it is nitrogen-doped activated carbon, with a nitrogen element content of 2 - 8 wt%, and is prepared by high-temperature carbonization of biomass precursors; S4. Loading of the catalyst S4.1: Mix the mixture of the main catalyst and the promoter with the carrier according to the loading amount of 3 - 8 times the total mass of the main catalyst and the promoter; S4.2: Uniformly disperse the mixture in an appropriate amount of solvent under stirring conditions to form a slurry; S4.3: Load the slurry onto the carrier by the impregnation method or the spraying method, and then dry it at 60 - 80 °C; S4.4: Heat-treat the dried catalyst in an inert atmosphere at a temperature of 300 - 400 °C for 2 - 4 hours to enhance the stability of the catalyst; S5. Characterization and application of the catalyst S5.1: Characterize the prepared composite catalyst, including specific surface area, pore size distribution, and elemental analysis; S5.2: Apply the catalyst to the direct synthesis reaction of methylchlorosilane to ensure that the selectivity of dimethyldichlorosilane is ≥85%.

6. The preparation method of a composite catalyst for improving the synthesis of methylchlorosilane according to claim 5, characterized in that: The pickling pretreatment steps are as follows: Immerse the porous silica gel in a 1 - 2 M hydrochloric acid or sulfuric acid solution for 2 - 4 hours; Rinse with deionized water until neutral, and then dry at 100 - 120 °C; Modify the mercapto functional group on the dried porous silica gel, and the method is as follows: Soak the porous silica gel in an ethanol solution containing a mercapto silane coupling agent for 12 to 24 hours; Rinse with ethanol to remove the unreacted coupling agent, and then dry at 60 to 80 °C.

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