Copper-based catalyst, preparation method thereof and application of copper-based catalyst in direct synthesis of trimethoxysilane

Abstract

The invention discloses a copper-based catalyst, a preparation method thereof and application of the copper-based catalyst in direct synthesis of trimethoxysilane, and the novel copper-based catalyst with a highly dispersed mixed valence active center is successfully constructed through a three-step sequential strategy of nitrogen doping, sulfydryl modification and copper ion loading. The catalyst shows excellent catalytic performance in direct synthesis reaction of trimethoxysilane, not only significantly improves the reaction efficiency and product selectivity, but also has good cycle stability and easy separation characteristics, effectively solves the technical problems of low activity and poor stability of a traditional catalytic system, and is suitable for industrial production. Important technical support is provided for green and efficient preparation of the organic silicon monomer, and the method has remarkable industrial application value and popularization prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalysts, in particular to a copper-based catalyst, a preparation method thereof and application thereof in direct synthesis of trimethoxysilane. BACKGROUND

[0002] Trimethoxysilane, as an important organosilicon monomer, is widely used in the fields of silicone rubber, silicone resin, coupling agent and sealing material, etc., and is an indispensable key raw material in modern chemical and material industries. With the rapid development of new energy, electronic information and high-end equipment manufacturing industries, the demand for high-purity trimethoxysilane continues to grow, and the development of efficient and green synthesis process has important economic value and strategic significance.

[0003] At present, the industrial preparation of trimethoxysilane mainly adopts direct synthesis method, that is, under the existence of catalyst, silicon powder and methanol are directly reacted at high temperature to generate the target product. This method has the advantages of wide raw material sources and relatively simple process, but the existing technology still faces many challenges. Traditional copper-based catalysts are mostly prepared by impregnation method or coprecipitation method, which has problems such as low dispersion of metal active components, uneven particle size distribution, easy agglomeration and deactivation, etc., resulting in low catalytic activity. The reaction temperature usually needs to be maintained at 280-350℃, which consumes a lot of energy. At the same time, the selectivity of the catalyst is poor, and there are many side reactions, which affect the yield and purity of the target product. More importantly, the stability and recycling performance of the existing catalysts are limited, and sintering, poisoning and loss of active components may occur during the reaction, which requires frequent replacement, increasing the production cost and environmental burden.

[0004] For the selection of the carrier, although activated carbon is widely used due to its developed pore structure and good chemical stability, the types of surface functional groups of ordinary activated carbon are limited, and the interaction with metal ions is weak, making it difficult to achieve uniform dispersion and firm anchoring of active components. Some studies attempt to modify activated carbon by acid-base treatment or high-temperature treatment, but the effect is limited, and the pore structure of the carrier may be damaged.

[0005] In terms of catalyst preparation technology, traditional methods can only achieve the loading of single valence state metal, and it is difficult to fully exert the synergistic catalytic effect of different valence copper species. In addition, the existing surface modification techniques mostly use physical adsorption or weak chemical action, and the binding strength between the metal and the carrier is insufficient, which may lead to migration and aggregation of active components under reaction conditions.

[0006] Therefore, it is urgent to develop a new type of copper-based catalyst preparation technology, which can realize the comprehensive improvement of catalyst activity, selectivity and stability through functional modification of the carrier and precise regulation of the metal active component, and provide technical support for the green and efficient preparation of trimethoxysilane. SUMMARY

[0007] In order to solve the problems in the prior art, the present application provides a copper-based catalyst, a preparation method thereof and application of the catalyst in direct synthesis of trimethoxysilane.

[0008] In order to achieve the above-mentioned purposes, the present application adopts the following technical solutions:

[0009] The preparation method of the copper-based catalyst comprises the following steps:

[0010] (1) dispersing activated carbon into anhydrous ethanol, slowly adding acrylonitrile under stirring, continuously stirring, rotary evaporation and drying of the product, calcining under nitrogen atmosphere, and obtaining nitrogen-doped activated carbon after cooling;

[0011] The nitrogen-doped activated carbon is prepared as follows: in an anhydrous ethanol solvent, acrylonitrile molecules are uniformly dispersed and penetrated into the surface and microporous structure of the activated carbon by solvation. During high-temperature nitrogen calcination, the cyan group in acrylonitrile is broken to release active nitrogen atoms. These nitrogen atoms are chemically combined with the defect sites and edge carbon atoms on the surface of the activated carbon to form various nitrogen-containing functional groups such as pyridine nitrogen, pyrrole nitrogen and graphite nitrogen. At the same time, the organic carbon skeleton of acrylonitrile is carbonized at high temperature, further enriching the pore structure of the carrier. This process realizes the uniform doping of nitrogen atoms in the activated carbon matrix, providing additional electron donor sites and surface active centers for the carrier.

[0012] Preferably, in step (1), the amount ratio of activated carbon, anhydrous ethanol and acrylonitrile is 10g: 150-250mL: 20-40g.

[0013] Preferably, in step (1), the continuous stirring condition is continuous stirring at room temperature for 2-6h, and the calcination condition is heating at a rate of 5-10℃ / min to 400-600℃, and constant temperature calcination for 1-3h.

[0014] (2) dispersing the nitrogen-doped activated carbon into anhydrous toluene, ultrasonic treatment, adding mercaptopropyltrimethoxysilane under nitrogen atmosphere, heating reaction, cooling, centrifuging, washing and drying the product to obtain a modified carrier;

[0015] Mercapto-functional modification: mercaptopropyltrimethoxysilane occurs a hydrolysis reaction with trace amounts of water molecules or hydroxyl groups adsorbed on the surface of the carrier to generate active silicon hydroxyl groups in the initial stage of the reaction, and the silicon hydroxyl groups ​Subsequently, these silicon hydroxyl groups undergo dehydration condensation reaction with the hydroxyl groups on the support surface, forming stable covalent bonds, firmly grafting the thiol-containing organic segments to the support surface. This modification process introduces a large number of thiol groups on the support surface, which serve as soft basic ligands, providing ideal binding sites for the subsequent anchoring of metal ions.

[0016] Preferably, in step (2), the amount of nitrogen-doped activated carbon, anhydrous toluene, and mercaptopropyltrimethoxysilane is 10 g: 100-200 mL: 3-6 mL.

[0017] Preferably, in step (2), the ultrasonic treatment is for 20-40 min, and the heating reaction conditions are refluxing at 100-112°C for 12-24 h.

[0018] (3) Disperse the modified support into deionized water, ultrasonic treatment, and add copper ammine complex ion solution under nitrogen atmosphere, stirring reaction, centrifugation, washing, and drying the product to obtain the copper-based catalyst.

[0019] Copper-based catalyst loading: cuprous chloride and cuprous oxide are dissolved in ammonia water to form cuprous ammine complex ions mainly , but during the dissolution process, part of is oxidized to , forming complex ions, and the final solution contains and mixed complex ions. When this copper ammine complex solution contacts the thiol-modified support, a ligand exchange reaction occurs. According to the soft and hard acid-base theory, and ions, as soft acids, have strong affinity with the thiol groups (soft bases) on the support surface, and their coordination ability far exceeds that of ammonia molecules. Therefore, the ammonia ligands in both copper ammine complex ions are gradually replaced by thiol groups, and ions are firmly anchored on the support surface by forming and coordination bonds, respectively, while releasing ammonia molecules. The bonds formed have covalent properties, ensuring the high dispersion and stable loading of copper active components. After washing to remove residual ammonia and chloride ions, the final copper-based catalyst containing and mixed valence active sites is obtained, in which copper ions are uniformly distributed on the support surface in the form of atoms or small clusters, providing diverse active centers for catalytic reactions.

[0020] Preferably, in step (3), the ratio of the modified carrier, deionized water and cuprammonium complex solution is 10g: 80-160mL: 40-80mL; the cuprammonium complex solution is obtained by dissolving cuprous chloride powder and cuprous oxide powder in 25-28wt% ammonia water, and 0.5-2g of cuprous chloride powder and 0.5-2g of cuprous oxide powder are contained in 40-80mL of the cuprammonium complex solution.

[0021] Preferably, in step (3), the ultrasonic treatment is performed for 20-40min; and the stirring reaction is performed at 20-35℃ for 6-12h.

[0022] Preferably, the average particle size of the cuprous chloride powder is 2-4μm; and the average particle size of the cuprous oxide powder is 300-500nm.

[0023] The application also claims a copper-based catalyst prepared by the preparation method.

[0024] The application also claims the use of the copper-based catalyst in the direct synthesis of trimethoxysilane, comprising the following steps:

[0025] The copper-based catalyst is pre-activated at 350-450℃ for 6-12h in a methyl chloride atmosphere to obtain an activated catalyst; the activated catalyst, silicon powder and a promoter are put into a gas-liquid-solid three-phase reactor in a mass ratio of 10-5: 5-2: 1-2: 0.1-0.3, and then activated again at 200-250℃ for 30-60min; after the activation, methanol is introduced at a flow rate of 0.1-5mL / min to prepare trimethoxysilane.

[0026] Preferably, the promoter is selected from one or more of sodium chloride, calcium chloride, calcium phosphate, sodium acetate, potassium phosphate and potassium chloride.

[0027] Compared with the prior art, the application has the following beneficial effects:

[0028] 1. The copper-based catalyst of this invention exhibits significant technical advantages in the direct synthesis of trimethoxysilanes. Through pretreatment activation in a chloromethane atmosphere and secondary activation in a heat transfer oil medium, the copper active sites on the catalyst surface are fully activated, effectively reducing the reaction temperature for the direct synthesis of trimethoxysilanes from methanol and silicon powder, significantly improving the mildness of the reaction conditions compared to traditional processes. The catalyst's high dispersion characteristics and mixed valence state active centers greatly enhance the conversion efficiency of silicon powder. Simultaneously, the synergistic effect of the promoter further enhances the catalytic activity, making the entire synthesis process promising for industrial application and providing a new technical route for the efficient and green preparation of trimethoxysilanes. The prepared solid catalyst is easy to separate from the reaction system, can be recycled multiple times while maintaining stable catalytic performance, significantly reducing industrial production costs and environmental burden.

[0029] 2. This invention provides a copper-based catalyst with unique structural advantages and catalytic performance. The first step, nitrogen doping, introduces nitrogen-containing functional groups such as pyridine nitrogen, pyrrole nitrogen, and graphitic nitrogen, which not only enhance the electron-donating ability and surface activity of the support but also provide abundant anchoring sites for subsequent metal loading. This effectively suppresses the collapse and rearrangement of the support structure, ensuring the structural integrity and long-term stability of the material during the reaction process. Simultaneously, the strong electron-donating effect of nitrogen atoms significantly enhances the electron density and intrinsic catalytic activity of the supported copper species. The second step, thiol functionalization, introduces a large number of thiol groups onto the support surface through a silane coupling reaction. This surface modification strategy significantly increases the number of active functional groups that interact softly with copper ions, constructing a robust metal anchoring network and effectively preventing the aggregation and loss of active metal components. The third step involves the formation of... Covalent coordination ensures and Ions are highly dispersed on the support surface in atomic or small cluster form. This strong chemical bonding mode not only achieves stable fixation of high-valence copper species, but also significantly improves the mechanical strength and recyclability of the catalyst. The mixed-valence active centers not only maximize metal utilization efficiency, but also provide diverse active sites for catalytic reactions, thereby achieving a synergistic improvement in catalytic activity, selectivity and stability. Even after multiple reaction cycles, it can still maintain excellent catalytic conversion ability, providing an efficient catalytic solution for direct synthesis reactions. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some schematic diagrams of certain embodiments of the present invention, and therefore should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 The image shows a SEM image of the copper-based catalyst prepared in Example 1.

[0032] Figure 2 The image shows the gas chromatogram of the trimethoxysilane prepared in Example 1. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Of course, the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0034] Unless otherwise specified, all chemical reagents and materials in this invention are purchased from the market or synthesized from raw materials purchased from the market.

[0035] Cuprous chloride powder was prepared by the following steps: 16.5g of copper sulfate pentahydrate, 5.8g of sodium chloride, and 1.1g of polyvinylpyrrolidone were weighed and placed in a flask, and 120mL of deionized water was added and stirred to prepare solution 1; 6.8g of sodium bisulfite and 0.85g of sodium carbonate were weighed and added to 250mL of deionized water to prepare solution 2; solution 2 was added dropwise to solution 1 at a constant flow rate using a constant flow pump, and after the reaction was complete, the cuprous chloride precipitate was filtered; the precipitate was washed three times with anhydrous ethanol and dried in a vacuum drying oven at 50℃ for 6h to obtain cuprous chloride powder.

[0036] Cuprous oxide powder was prepared by the following steps: 3.0 g of cuprous chloride and 105 g of sodium chloride were added to 300 mL of deionized water to prepare a complex solution; 5.9 g of sodium phosphate was weighed and added to 60 mL of deionized water to prepare a sodium phosphate solution; 50 mL of deionized water was added to a beaker, and the complex solution and sodium phosphate solution were simultaneously added dropwise to the beaker over a period of 20–35 min; after the addition was complete, the mixture was reacted in a constant temperature water bath at 45–65 °C; the resulting orange precipitate was collected by centrifugation, washed with deionized water and anhydrous ethanol, and then dried in a vacuum oven at 50 °C for 6 h to obtain cuprous oxide powder.

[0037] A method for preparing a copper-based catalyst includes the following steps:

[0038] (1) Disperse 10g of activated carbon into 150-250mL of anhydrous ethanol, slowly add 20-40g of acrylonitrile while stirring, continue stirring at room temperature for 2-6h, rotary evaporate and dry the product, then heat it to 400-600℃ at a rate of 5-10℃ / min under nitrogen atmosphere, calcine at constant temperature for 1-3h, and obtain nitrogen-doped activated carbon after cooling.

[0039] (2) Disperse 10g of nitrogen-doped activated carbon into 100-200mL of anhydrous toluene, sonicate for 20-40min, add 3-6mL of mercaptopropyltrimethoxysilane under a nitrogen atmosphere, reflux at 100-112℃ for 12-24h, cool, centrifuge, wash and dry the product to obtain the modified support.

[0040] (3) Disperse 10g of modified support into 80-160mL of deionized water, sonicate for 20-40min, and add 40-80mL of copper-ammonia complex ion solution containing 0.5-2g of cuprous chloride powder with an average particle size of 2-4μm and 0.5-2g of cuprous oxide powder with an average particle size of 300-500nm under a nitrogen atmosphere. The copper-ammonia complex ion solution is obtained by dissolving cuprous chloride powder and cuprous oxide powder in 25-28wt% ammonia water. Stir the reaction at 20-35℃ for 6-12h, centrifuge, wash and dry the product to obtain the copper-based catalyst.

[0041] A method for the direct synthesis of trimethoxysilanes includes the following steps:

[0042] The copper-based catalyst was pretreated and activated at 350-450℃ for 6-12 h in a chloromethane atmosphere to obtain an activated catalyst. The heat transfer oil, activated catalyst, silicon powder, and accelerator were added to a gas-liquid-solid three-phase reactor at a mass ratio of 10-5:5-2:1-2:0.1-0.3 and reactivated at 200-250℃ for 30-60 min. After activation, methanol was introduced at a flow rate of 0.1-5 mL / min to prepare trimethoxysilane.

[0043] The accelerator is selected from one or more of sodium chloride, calcium chloride, calcium phosphate, sodium acetate, potassium phosphate, and potassium chloride.

[0044] The present invention will be further described below through specific embodiments.

[0045] Example 1

[0046] A method for preparing a copper-based catalyst includes the following steps:

[0047] (1) Disperse 10g of activated carbon into 200mL of anhydrous ethanol, slowly add 40g of acrylonitrile while stirring, continue stirring at room temperature for 6h, evaporate and dry the product by rotary evaporation, then heat to 600℃ at a rate of 10℃ / min under nitrogen atmosphere, calcine at constant temperature for 1h, and obtain nitrogen-doped activated carbon after cooling.

[0048] (2) Disperse 10g of nitrogen-doped activated carbon into 150mL of anhydrous toluene, sonicate for 30min, add 6mL of mercaptopropyltrimethoxysilane under a nitrogen atmosphere, reflux at 112℃ for 12h, cool, centrifuge, wash and dry the product to obtain the modified support.

[0049] (3) Disperse 10g of modified support into 120mL of deionized water, sonicate for 30min, and add 60mL of copper ammonia complex ion solution containing 2g of cuprous chloride powder with an average particle size of 3μm and 0.5g of cuprous oxide powder with an average particle size of 400nm under a nitrogen atmosphere. The copper ammonia complex ion solution is obtained by dissolving cuprous chloride powder and cuprous oxide powder in 26wt% ammonia water. Stir the reaction at 35℃ for 6h, centrifuge, wash and dry the product to obtain the copper-based catalyst.

[0050] Figure 1 The image shows the SEM image of the prepared copper-based catalyst.

[0051] A method for the direct synthesis of trimethoxysilanes includes the following steps:

[0052] The copper-based catalyst was pretreated and activated at 400℃ for 9 hours in a chloromethane atmosphere to obtain the activated catalyst. The heat transfer oil, activated catalyst, silicon powder, and accelerator sodium chloride were added to a gas-liquid-solid three-phase reactor in a mass ratio of 8:3:1.5:0.2 and activated again at 220℃ for 45 minutes. After activation, methanol was introduced at a flow rate of 2.5 mL / min to prepare trimethoxysilane.

[0053] The distillate contained 92.3% trimethoxysilane and had a methanol conversion rate of 98.13%.

[0054] Figure 2 The gas chromatogram of the prepared trimethoxysilane is shown.

[0055] Example 2

[0056] A method for preparing a copper-based catalyst includes the following steps:

[0057] (1) Disperse 10g of activated carbon into 200mL of anhydrous ethanol, slowly add 35g of acrylonitrile while stirring, continue stirring at room temperature for 5h, evaporate and dry the product by rotary evaporation, then heat to 550℃ at a rate of 8℃ / min under nitrogen atmosphere, calcine at constant temperature for 2h, and obtain nitrogen-doped activated carbon after cooling.

[0058] (2) Disperse 10g of nitrogen-doped activated carbon into 150mL of anhydrous toluene, sonicate for 30min, add 5mL of mercaptopropyltrimethoxysilane under a nitrogen atmosphere, reflux at 108℃ for 16h, cool, centrifuge, wash and dry the product to obtain the modified support.

[0059] (3) Disperse 10g of modified support into 120mL of deionized water and sonicate for 30min. Add 60mL of copper ammonia complex ion solution containing 1.5g of cuprous chloride powder with an average particle size of 3μm and 1g of cuprous oxide powder with an average particle size of 400nm under a nitrogen atmosphere. The copper ammonia complex ion solution is obtained by dissolving cuprous chloride powder and cuprous oxide powder in 26wt% ammonia water. Stir the reaction at 30℃ for 8h. Centrifuge, wash and dry the product to obtain the copper-based catalyst.

[0060] A method for the direct synthesis of trimethoxysilanes includes the following steps:

[0061] The copper-based catalyst was pretreated and activated at 400℃ for 9 hours in a chloromethane atmosphere to obtain the activated catalyst. The heat transfer oil, activated catalyst, silicon powder, and accelerator sodium chloride were added to a gas-liquid-solid three-phase reactor in a mass ratio of 8:3:1.5:0.2 and activated again at 220℃ for 45 minutes. After activation, methanol was introduced at a flow rate of 2.5 mL / min to prepare trimethoxysilane.

[0062] The distillate contained 91.7% trimethoxysilane and had a methanol conversion rate of 96.7%.

[0063] Example 3

[0064] A method for preparing a copper-based catalyst includes the following steps:

[0065] (1) Disperse 10g of activated carbon into 200mL of anhydrous ethanol, slowly add 25g of acrylonitrile while stirring, continue stirring at room temperature for 3h, evaporate and dry the product by rotary evaporation, then heat to 450℃ at a rate of 6℃ / min under nitrogen atmosphere, calcine at constant temperature for 2h, and obtain nitrogen-doped activated carbon after cooling.

[0066] (2) Disperse 10g of nitrogen-doped activated carbon into 150mL of anhydrous toluene, sonicate for 30min, add 4mL of mercaptopropyltrimethoxysilane under a nitrogen atmosphere, reflux at 104℃ for 20h, cool, centrifuge, wash and dry the product to obtain the modified support.

[0067] (3) Disperse 10g of modified support into 120mL of deionized water and sonicate for 30min. Add 60mL of copper ammonia complex ion solution containing 1g of cuprous chloride powder with an average particle size of 3μm and 1.5g of cuprous oxide powder with an average particle size of 400nm under a nitrogen atmosphere. The copper ammonia complex ion solution is obtained by dissolving cuprous chloride powder and cuprous oxide powder in 26wt% ammonia water. Stir the reaction at 25℃ for 10h. Centrifuge, wash and dry the product to obtain the copper-based catalyst.

[0068] A method for the direct synthesis of trimethoxysilanes includes the following steps:

[0069] The copper-based catalyst was pretreated and activated at 400℃ for 9 hours in a chloromethane atmosphere to obtain the activated catalyst. The heat transfer oil, activated catalyst, silicon powder, and accelerator sodium chloride were added to a gas-liquid-solid three-phase reactor in a mass ratio of 8:3:1.5:0.2 and activated again at 220℃ for 45 minutes. After activation, methanol was introduced at a flow rate of 2.5 mL / min to prepare trimethoxysilane.

[0070] The distillate contained 91.3% trimethoxysilane and had a methanol conversion rate of 96.2%.

[0071] Example 4

[0072] A method for preparing a copper-based catalyst includes the following steps:

[0073] (1) Disperse 10g of activated carbon into 200mL of anhydrous ethanol, slowly add 25g of acrylonitrile under stirring, continue stirring at room temperature for 2h, evaporate and dry the product by rotary evaporation, then heat to 400℃ at a rate of 5℃ / min under nitrogen atmosphere, calcine at constant temperature for 3h, and obtain nitrogen-doped activated carbon after cooling.

[0074] (2) Disperse 10g of nitrogen-doped activated carbon into 150mL of anhydrous toluene, sonicate for 30min, add 3mL of mercaptopropyltrimethoxysilane under a nitrogen atmosphere, reflux at 100℃ for 24h, cool, centrifuge, wash and dry the product to obtain the modified support.

[0075] (3) Disperse 10g of modified support into 120mL of deionized water, sonicate for 30min, and add 60mL of copper ammonia complex ion solution containing 0.5g of cuprous chloride powder with an average particle size of 3μm and 2g of cuprous oxide powder with an average particle size of 400nm under a nitrogen atmosphere. The copper ammonia complex ion solution is obtained by dissolving cuprous chloride powder and cuprous oxide powder in 26wt% ammonia water. Stir the reaction at 20℃ for 12h, centrifuge, wash and dry the product to obtain the copper-based catalyst.

[0076] A method for the direct synthesis of trimethoxysilanes includes the following steps:

[0077] The copper-based catalyst was pretreated and activated at 400℃ for 9 hours in a chloromethane atmosphere to obtain the activated catalyst. The heat transfer oil, activated catalyst, silicon powder, and accelerator sodium chloride were added to a gas-liquid-solid three-phase reactor in a mass ratio of 8:3:1.5:0.2 and activated again at 220℃ for 45 minutes. After activation, methanol was introduced at a flow rate of 2.5 mL / min to prepare trimethoxysilane.

[0078] The distillate contained 90.8% trimethoxysilane and had a methanol conversion rate of 95.4%.

[0079] Comparative Example 1

[0080] A method for preparing a copper-based catalyst includes the following steps:

[0081] (1) Disperse 10g of activated carbon into 200mL of anhydrous ethanol, slowly add 40g of acrylonitrile while stirring, continue stirring at room temperature for 6h, evaporate and dry the product by rotary evaporation, then heat to 600℃ at a rate of 10℃ / min under nitrogen atmosphere, calcine at constant temperature for 1h, and obtain nitrogen-doped activated carbon after cooling.

[0082] (2) Disperse 10g of nitrogen-doped activated carbon into 150mL of anhydrous toluene, sonicate for 30min, add 6mL of mercaptopropyltrimethoxysilane under a nitrogen atmosphere, reflux at 112℃ for 12h, cool, centrifuge, wash and dry the product to obtain the modified support.

[0083] (3) Disperse 10g of modified support into 120mL of deionized water, sonicate for 30min, add 60mL of copper ammonia complex ion solution containing 2.5g of cuprous chloride powder with an average particle size of 3μm under nitrogen atmosphere. The copper ammonia complex ion solution is obtained by dissolving cuprous chloride powder in 26wt% ammonia water. Stir the reaction at 35℃ for 6h, centrifuge, wash and dry the product to obtain the copper-based catalyst.

[0084] A method for the direct synthesis of trimethoxysilanes includes the following steps:

[0085] The copper-based catalyst was pretreated and activated at 400℃ for 9 hours in a chloromethane atmosphere to obtain the activated catalyst. The heat transfer oil, activated catalyst, silicon powder, and accelerator sodium chloride were added to a gas-liquid-solid three-phase reactor in a mass ratio of 8:3:1.5:0.2 and activated again at 220℃ for 45 minutes. After activation, methanol was introduced at a flow rate of 2.5 mL / min to prepare trimethoxysilane.

[0086] The distillate contained 87.9% trimethoxysilane and had a methanol conversion rate of 86.3%.

[0087] Comparative Example 2

[0088] A method for preparing a copper-based catalyst includes the following steps:

[0089] (1) Disperse 10g of activated carbon into 200mL of anhydrous ethanol, slowly add 40g of acrylonitrile while stirring, continue stirring at room temperature for 6h, evaporate and dry the product by rotary evaporation, then heat to 600℃ at a rate of 10℃ / min under nitrogen atmosphere, calcine at constant temperature for 1h, and obtain nitrogen-doped activated carbon after cooling.

[0090] (2) Disperse 10g of nitrogen-doped activated carbon into 150mL of anhydrous toluene, sonicate for 30min, add 6mL of mercaptopropyltrimethoxysilane under a nitrogen atmosphere, reflux at 112℃ for 12h, cool, centrifuge, wash and dry the product to obtain the modified support.

[0091] (3) Disperse 10g of modified support into 120mL of deionized water, sonicate for 30min, add 60mL of copper ammonia complex ion solution containing 2.5g of cuprous oxide powder with an average particle size of 400nm under nitrogen atmosphere. The copper ammonia complex ion solution is obtained by dissolving cuprous oxide powder in 26wt% ammonia water. Stir the reaction at 35℃ for 6h, centrifuge, wash and dry the product to obtain the copper-based catalyst.

[0092] A method for the direct synthesis of trimethoxysilanes includes the following steps:

[0093] The copper-based catalyst was pretreated and activated at 400℃ for 9 hours in a chloromethane atmosphere to obtain the activated catalyst. The heat transfer oil, activated catalyst, silicon powder, and accelerator sodium chloride were added to a gas-liquid-solid three-phase reactor in a mass ratio of 8:3:1.5:0.2 and activated again at 220℃ for 45 minutes. After activation, methanol was introduced at a flow rate of 2.5 mL / min to prepare trimethoxysilane.

[0094] The distillate contained 88.6% trimethoxysilane and had a methanol conversion rate of 86.9%.

[0095] Comparative Example 3

[0096] A method for preparing a copper-based catalyst includes the following steps:

[0097] (1) Disperse 10g of activated carbon into 200mL of anhydrous ethanol, slowly add 40g of acrylonitrile while stirring, continue stirring at room temperature for 6h, evaporate and dry the product by rotary evaporation, then heat to 600℃ at a rate of 10℃ / min under nitrogen atmosphere, calcine at constant temperature for 1h, and obtain nitrogen-doped activated carbon after cooling.

[0098] (2) Disperse 10g of nitrogen-doped activated carbon into 120mL of deionized water and sonicate for 30min. Add 60mL of a copper-ammonia complex solution containing 2g of cuprous chloride powder with an average particle size of 3μm and 0.5g of cuprous oxide powder with an average particle size of 400nm under a nitrogen atmosphere. The copper-ammonia complex solution is obtained by dissolving cuprous chloride powder and cuprous oxide powder in 26wt% ammonia water. Stir the reaction at 35℃ for 6h. Centrifuge, wash and dry the product to obtain the copper-based catalyst.

[0099] A method for the direct synthesis of trimethoxysilanes includes the following steps:

[0100] The copper-based catalyst was pretreated and activated at 400℃ for 9 hours in a chloromethane atmosphere to obtain the activated catalyst. The heat transfer oil, activated catalyst, silicon powder, and accelerator sodium chloride were added to a gas-liquid-solid three-phase reactor in a mass ratio of 8:3:1.5:0.2 and activated again at 220℃ for 45 minutes. After activation, methanol was introduced at a flow rate of 2.5 mL / min to prepare trimethoxysilane.

[0101] The distillate contained 46.8% trimethoxysilane and had a methanol conversion rate of 71.3%.

[0102] Comparative Example 4

[0103] A method for preparing a copper-based catalyst includes the following steps:

[0104] (1) Disperse 10g of activated carbon into 150mL of anhydrous toluene, sonicate for 30min, add 6mL of mercaptopropyltrimethoxysilane under nitrogen atmosphere, reflux at 112℃ for 12h, cool, centrifuge, wash and dry the product to obtain the modified support.

[0105] (2) Disperse 10g of modified support into 120mL of deionized water and sonicate for 30min. Add 60mL of copper ammonia complex ion solution containing 2g of cuprous chloride powder with an average particle size of 3μm and 0.5g of cuprous oxide powder with an average particle size of 400nm under a nitrogen atmosphere. The copper ammonia complex ion solution is obtained by dissolving cuprous chloride powder and cuprous oxide powder in 26wt% ammonia water. Stir the reaction at 35℃ for 6h. Centrifuge, wash and dry the product to obtain the copper-based catalyst.

[0106] A method for the direct synthesis of trimethoxysilanes includes the following steps:

[0107] The copper-based catalyst was pretreated and activated at 400℃ for 9 hours in a chloromethane atmosphere to obtain the activated catalyst. The heat transfer oil, activated catalyst, silicon powder, and accelerator sodium chloride were added to a gas-liquid-solid three-phase reactor in a mass ratio of 8:3:1.5:0.2 and activated again at 220℃ for 45 minutes. After activation, methanol was introduced at a flow rate of 2.5 mL / min to prepare trimethoxysilane.

[0108] The distillate contained 65.4% trimethoxysilane and had a methanol conversion rate of 78.1%.

[0109] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a copper-based catalyst, characterized in that, Includes the following steps: (1) Disperse activated carbon in anhydrous ethanol, slowly add acrylonitrile while stirring, continue stirring, evaporate and dry the product by rotary evaporation, then calcine under nitrogen atmosphere, and obtain nitrogen-doped activated carbon after cooling; (2) Nitrogen-doped activated carbon was dispersed in anhydrous toluene, ultrasonically treated, mercaptopropyltrimethoxysilane was added under a nitrogen atmosphere, heated to react, and the product was cooled, centrifuged, washed and dried to obtain the modified support. (3) The modified support is dispersed in deionized water, ultrasonically treated, and copper ammonia complex ion solution is added under nitrogen atmosphere. The reaction is stirred, and the product is centrifuged, washed, and dried to obtain the copper-based catalyst.

2. The preparation method according to claim 1, characterized in that, In step (1), the ratio of activated carbon, anhydrous ethanol, and acrylonitrile is 10g: 150~250mL: 20~40g.

3. The preparation method according to claim 1, characterized in that, In step (1), the continuous stirring condition is to stir continuously at room temperature for 2 to 6 hours; the calcination condition is to heat up to 400 to 600°C at a rate of 5 to 10°C / min and calcinate at a constant temperature for 1 to 3 hours.

4. The preparation method according to claim 1, characterized in that, In step (2), the ratio of nitrogen-doped activated carbon, anhydrous toluene, and mercaptopropyltrimethoxysilane is 10g: 100~200mL: 3~6mL.

5. The preparation method according to claim 1, characterized in that, In step (2), the ultrasonic treatment lasts for 20 to 40 minutes; the heating reaction conditions are reflux reaction at 100 to 112°C for 12 to 24 hours.

6. The preparation method according to claim 1, characterized in that, In step (3), the ratio of modified carrier, deionized water, and copper ammonia complex solution is 10g: 80~160mL: 40~80mL; the copper ammonia complex solution is obtained by dissolving cuprous chloride powder and cuprous oxide powder in 25~28wt% ammonia water, and each 40~80mL of copper ammonia complex solution contains 0.5~2g of cuprous chloride powder and 0.5~2g of cuprous oxide powder.

7. The preparation method according to claim 1, characterized in that, In step (3), the ultrasonic treatment lasts for 20 to 40 minutes; the stirring reaction conditions are 20 to 35°C for 6 to 12 hours.

8. The preparation method according to claim 6, characterized in that, The average particle size of the cuprous chloride powder is 2~4μm; the average particle size of the cuprous oxide powder is 300~500nm.

9. A copper-based catalyst prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the copper-based catalyst as described in claim 9 in the direct synthesis of trimethoxysilanes, characterized in that, Includes the following steps: The copper-based catalyst was pretreated and activated at 350-450℃ for 6-12 h in a chloromethane atmosphere to obtain an activated catalyst. The heat transfer oil, activated catalyst, silicon powder, and accelerator were added to a gas-liquid-solid three-phase reactor at a mass ratio of 10-5:5-2:1-2:0.1-0.3 and reactivated at 200-250℃ for 30-60 min. After activation, methanol was introduced at a flow rate of 0.1-5 mL / min to prepare trimethoxysilane.

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