Catalyst for preparing tetramethoxysilane from silicon powder and methanol, and preparation method and activation method thereof

Abstract

The invention discloses a catalyst for preparing tetramethoxysilane from silicon powder and methanol as well as a preparation method and an activation method of the catalyst, and belongs to the technical field of catalysts. The preparation method provided by the invention adopts a coprecipitation process, has the advantages of simple flow and wide original source, does not introduce chlorine and other impurity elements in the preparation, and has good economic advantages and large-scale production applicability. The prepared catalyst has the advantages of high specific surface area, high copper species dispersity, excellent strength, no crushing after long-term use, no loss of active components, high reaction activity and long service life. The invention also provides an activation method of the catalyst, specific reduction and oxidation mechanisms are combined, so that the activated catalyst has extremely high reaction activity, the high silicon powder conversion rate can be realized in application without pre-mixing silicon powder and the catalyst, the difficulty of preparing tetramethoxysilane from the silicon powder and methanol is reduced, and continuous production is favorably realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalysts, in particular to a catalyst for preparing tetramethoxysilane from silicon powder and methanol, and a preparation method and an activation method thereof. BACKGROUND

[0002] Tetramethyl silicate (TMOS) is a colorless liquid and an important chemical raw material, which has a wide range of applications in industry. The core of its application lies in its easy hydrolysis, and the hydrolysis reaction can be well controlled. By controlling the hydrolysis reaction, silanol, silicic acid, sol, gel material, etc. can be generated, and then applied in the fields of electronics, optics, materials, chemical industry, etc. In the future, with the growth of new material demand, the application potential of TMOS in the fields of high-performance materials and green energy will be further expanded.

[0003] At present, there are two methods for preparing TMOS in industry: method one is to react SiCl4, a by-product of the silicone industry, with methanol; method two is to directly react silicon powder with methanol under the action of a copper catalyst and a high-boiling organic medium. Method one has the defects of high toxicity and strong corrosion of raw material SiCl4, and it also produces a large amount of strong corrosive HCl gas in the reaction process, and has problems such as large equipment investment, low yield, high energy consumption, etc. The main production process of TMOS at present is method two. For example, the Chinese invention patent with publication number CN118440106A mixes silicon powder and cuprous chloride uniformly, pretreats them, then mixes them with a solvent and potassium chloride, and reacts by adding methanol dropwise under heating. However, the main purpose of the reaction in method two is to obtain trimethoxysilane, and TMOS is obtained as a by-product, so there are still technical problems such as weak reaction selectivity and low yield.

[0004] There are also many reports on laboratory attempts to prepare TMOS. For example, the Chinese invention patent with publication number CN117384200A discloses a preparation method of tetramethoxysilane and its application. The catalytic system for the reaction of silicon powder and methanol is improved. After the impurities are removed, the suspension agent, silicon powder and pretreated catalyst are mixed and then directly reacted with methanol. By using the impurity-removed suspension agent, the silicon powder, the pretreated catalyst and the methanol are uniformly dispersed in the suspension agent and react, so that the reaction is more complete, and a TMOS with high purity is obtained. The Chinese invention patent with publication number CN107216348A provides a method for preparing tetramethoxysilane by a direct method. Silicon powder and catalyst Cu2O are used as raw materials to prepare TMOS by gas-solid reaction in a fixed bed reactor. The Chinese invention patent with publication number CN115672363A proposes a catalyst for synthesizing tetramethoxysilane, a preparation method and application thereof. Copper salt, copper oxide, alkali metal compound and alkaline earth metal compound are used as catalysts. The catalyst and silicon powder are mixed and pressed into tablets, and then reacted in a fixed bed reactor.

[0005] However, the existing technology has the problem that the main active component of the existing copper-based catalyst is Cu2O or CuCl, which has poor dispersibility and low activity. Therefore, the catalyst must be mixed with silicon powder in advance to have good catalytic effect, so that the catalyst cannot be reused and continuous production is difficult to achieve.

[0006] In view of the above defects of the prior art, in a first aspect of the present application, a catalyst for preparing tetramethoxysilane from silicon powder and methanol is provided, which has high reaction activity and long service life. The catalyst is composed of the following stable oxides in mass percentage: CuO 30%~75%, ZnO 15%~40%, Al2O35%~30%, and SiO20.5%~5%. SUMMARY

[0007] In view of the above defects of the prior art, in a first aspect of the present application, a catalyst for preparing tetramethoxysilane from silicon powder and methanol is provided, which has high reaction activity and long service life. The catalyst is composed of the following stable oxides in mass percentage: CuO 30%~75%, ZnO 15%~40%, Al2O35%~30%, and SiO20.5%~5%.

[0008] In a second aspect of the present application, a preparation method of the catalyst for preparing tetramethoxysilane from silicon powder and methanol according to the first aspect of the present application is provided, which is convenient in process, has a wide source of raw materials and low cost. The method comprises the following steps: (1) Prepare raw materials according to the composition. Dissolve a soluble copper salt and a soluble zinc salt in water to obtain a mixed solution I; (2) Add a precipitating agent to water, and then add tetramethoxysilane or tetraethoxysilane to obtain a mixed solution II; (3) adding the mixed solution I into the mixed solution II to carry out a co-precipitation reaction, and then adding an aluminum hydroxide oxide to mix, and filtering, washing and drying to obtain a catalyst precursor; (4) calcining the obtained catalyst precursor to obtain a finished product oxidized catalyst, i.e. a catalyst for preparing tetramethoxysilane by using silicon powder and methanol.

[0009] The above process mainly uses a co-precipitation method to prepare the catalyst, does not need to use other complex preparation processes, is easy to mass produce in an industrialized manner, and has a low preparation cost.

[0010] Preferably, in the step (1), the soluble copper salt is copper nitrate trihydrate or copper sulfate pentahydrate; and the soluble zinc salt is zinc nitrate hexahydrate or zinc sulfate heptahydrate.

[0011] The soluble copper salt and the soluble zinc salt in the preparation raw material of the catalyst have a wide source, and facilitate the preparation of the catalyst.

[0012] Preferably, in the step (1), the total concentration of the metal ions in the mixed solution I is 0.2-2.5 mol / L.

[0013] Controlling the total concentration of the metal ions in the mixed solution I within the above range not only improves the preparation efficiency of the catalyst, avoids the generation of a large amount of wastewater, but also prevents the product of the co-precipitation reaction from being wrapped with a large amount of metal ions, and facilitates the filtering and washing of the product of the co-precipitation reaction.

[0014] Preferably, in the step (2), the precipitant is one of sodium carbonate, ammonium carbonate and potassium carbonate.

[0015] The above types of precipitants have a wide source and a low price.

[0016] Preferably, in the step (2), the molar amount of the precipitant is 1.2 times the total molar amount of the metal ions in the mixed solution I; and the concentration of the precipitant in the mixed solution II is 0.1-2 mol / L.

[0017] Preferably, in the step (3), the adding time is 10-180 min; the temperature of the co-precipitation reaction is 25-80℃; the drying temperature is 80-150℃, and the time is 2-24 h.

[0018] Preferably, in the step (3), the aluminum hydroxide oxide is one of boehmite, bayerite, gibbsite, pseudoboehmite and aluminum hydroxide.

[0019] The above types of aluminum hydroxide oxides are commonly used aluminum hydroxide oxides in the industry, and can all generate active alumina after calcination, and have a low price.

[0020] Preferably, the temperature of the roasting in step (4) is 320-500 ℃, and the time is 1-10 h.

[0021] In a third aspect of the present application, a method for activating a catalyst for preparing tetramethoxysilane from silicon powder and methanol according to the first aspect of the present application or prepared by the method according to the second aspect of the present application is provided, comprising the following steps: S1, adding the catalyst for preparing tetramethoxysilane from silicon powder and methanol into a reactor, and passing N2 to heat; The space velocity of the N2 is 100-3000 h-1 by volume at standard conditions. -1 The pressure is normal pressure-1.0 MPa. S2, heating to 100-140 ℃ and keeping the temperature for 1-6 h to remove air and physically adsorbed water in the catalyst; S3, continuously heating to 170-280 ℃, and reducing by adding H2, wherein the content of H2 is 0.1 vol.%-20 vol.%, and the reduction is continued for 2-100 h; after the reduction is completed, the H2 is stopped, and the N2 is continued to be passed; S4, oxidizing the reduced catalyst using N2O or water vapor to activate the catalyst; The conditions for activating using N2O are as follows: after the treatment in S3 is completed, the N2 is continued to be passed, N2O is passed at 25-80 ℃, the amount of the N2O is 0.1 vol.%-10 vol.% of the N2, and the oxidation time is 1-24 h. The conditions for activating using water vapor are as follows: after the treatment in S3 is completed, the N2 is continued to be passed, water vapor is passed at 120-220 ℃, the amount of the water vapor is 5 vol.%-30 vol.% of the N2, and the oxidation time is 1-24 h.

[0022] Based on the above technical solution, the design concept and principle of the present application are as follows: The catalyst is prepared by the coprecipitation method, the preparation process of the catalyst is simplified, TMOS is added in the reaction process, the prepared catalyst has good oil resistance, and the strength of the catalyst can be increased, so that the catalyst does not break and the active component does not lose during long-term use. The catalyst and the preparation process thereof do not introduce chlorine element, and when the catalyst is used for preparing tetramethoxysilane from silicon powder and methanol, the product TMOS is easy to purify and can be used for high-end quartz material production.

[0023] In addition, the catalyst for preparing tetramethoxysilane from silicon powder and methanol has a large specific surface area, and copper species is in a highly dispersed state. After being activated by the activation method provided by the application, the catalyst has extremely high reactivity. As presented in one or more embodiments of the application, the catalyst can be applied without pre-mixing silicon powder and the catalyst, facilitating continuous production and enabling the silicon powder conversion rate to be more than 95%. The activation mechanism of the application is that N2O and water vapor used have low oxidizability, and under the provided activation conditions, the surface of copper microcrystals generated by H2 reduction is designed to be converted into Cu2O. The principle of forming Cu2O species under the conditions has been reported in many documents (for example, International Journal of Hydrogen Energy, 2014, volume 39: P317-324.). The application is designed based on the mechanism to activate the catalyst.

[0024] The catalyst prepared by the application and the catalyst activation method can obtain high catalytic activity of silicon powder and methanol. It needs to be particularly pointed out that if the activation conditions are changed, the catalyst activity will decrease. The reason is that lower oxidation temperature will cause incomplete oxidation of the catalyst surface, and higher reaction temperature will cause excessive oxidation.

[0025] Compared with the prior art, the application has the following advantages and beneficial effects: The application provides a catalyst for preparing tetramethoxysilane from silicon powder and methanol, which has high specific surface area and copper species dispersity, and excellent strength, and has the advantages of high reactivity and long service life.

[0026] The application provides a preparation method of a catalyst for preparing tetramethoxysilane from silicon powder and methanol, which adopts a co-precipitation process, has a simple process, a wide original source, does not introduce chlorine and other impurity elements in preparation, and has good economic advantages and scalability for production.

[0027] The application provides an activation method of a catalyst for preparing tetramethoxysilane from silicon powder and methanol, which combines specific reduction and oxidation mechanisms, so that the activated catalyst has extremely high reactivity, can achieve high silicon powder conversion rate (≥95%) without pre-mixing silicon powder and the catalyst in application, reduces the difficulty of preparing tetramethoxysilane from silicon powder and methanol, and facilitates continuous production. DETAILED DESCRIPTION

[0028] The application will be further described by way of examples below, but the application is not limited in the scope of the examples. In the following examples, the experimental methods not specified in the specific conditions are selected according to the conventional methods and conditions or the product instructions.

[0029] Example 1 The catalyst for preparing tetramethoxysilane from silicon powder and methanol in the present example, calculated as oxides, consists of the following mass percentages of components: CuO 52%, ZnO 15%, Al2O3 30%, SiO2 3%.

[0030] The preparation method of the above catalyst is as follows: (1) Dissolve 395.1 g Cu(NO3)2·3H2O and 137.1 g Zn(NO3)2·6H2O in 10.5 L deionized water to obtain a mixed solution I; (2) Dissolve 241 g (NH4)2CO3 in 25.0 L deionized water, then add 19.0 g tetramethoxysilane to obtain a mixed solution II; (3) Add the mixed solution I obtained in step (1) to the mixed solution II obtained in step (2) at a constant speed to carry out a co-precipitation reaction, then add 98.7 g boehmite and stir for 30 min, then filter, and the obtained filter residue is sequentially washed and dried to obtain a catalyst precursor; wherein the addition time is 10 min; the co-precipitation reaction temperature is 25 ℃; the drying temperature is 80 ℃, and the time is 24 h; (4) Calcine the catalyst precursor obtained in step (3) to obtain an oxidized catalyst, i.e. a catalyst for preparing tetramethoxysilane from silicon powder and methanol; wherein the calcination temperature is 320 ℃, and the time is 10 h.

[0031] The prepared catalyst is activated, and the activation method is as follows: S1, add 50 g of the oxidized catalyst to a reactor and introduce N2 for heating; the space velocity of N2 introduced is 500 h -1 at standard conditions; the pressure is normal pressure; S2, heat to 100 ℃ and keep constant for 6 h to remove air and physically adsorbed water in the catalyst; S3, continue to heat to 170 ℃, and reduce by introducing H2, wherein the content of H2 is 0.1 vol.%, and the reduction is continued for 100 h; after reduction is completed, stop introducing H2 and continue to introduce N2; S4, activate the reduced catalyst using N2O; the specific conditions are as follows: keep N2 introduced and cool to 25 ℃, then introduce N2O, the amount of N2O introduced is 10 vol.% of N2, and the gas introduction time is 1 h; after treatment is completed, a catalyst with catalytic activity is obtained.

[0032] Example 2 The catalyst for preparing tetramethoxysilane using silicon powder and methanol in this embodiment is composed of the following components by mass percentage, based on stable oxides: CuO 50%, ZnO 40%, Al2O 35%, SiO 25%.

[0033] The preparation method of the above catalyst is as follows: (1) Dissolve 379.9 g Cu(NO3)2·3H2O and 365.5 g Zn(NO3)2·6H2O in 10.5 L of deionized water to obtain mixed solution I; (2) Dissolve 323 g (NH4)2CO3 in 25.0 L of deionized water, and then add 32.0 g tetramethoxysilane to obtain mixed solution II; (3) The mixed solution I obtained in step (1) is added at a constant rate to the mixed solution II obtained in step (2) to carry out a coprecipitation reaction. Then, 19.1 g of Bayerite is added and stirred for 30 min. After filtration, the filter residue is washed and dried to obtain the catalyst precursor. The addition time is 30 min; the coprecipitation reaction temperature is 40 ℃; the drying temperature is 100 ℃ and the time is 18 h. (4) The catalyst precursor obtained in step (3) is calcined to obtain an oxidized catalyst, namely a catalyst for preparing tetramethoxysilane using silicon powder and methanol; wherein the calcination temperature is 350 °C and the time is 5 h.

[0034] The prepared catalyst was activated using the following method: S1. Add 50 g of oxidized catalyst to the reactor and introduce N2 to raise the temperature; the space velocity of N2 introduced is 100 h⁻¹ based on standard volume. -1 The pressure is 0.3 MPa; S2. Heat to 140 ℃ and hold at that temperature for 6 h to purge air and remove physically adsorbed water from the catalyst; S3. Continue heating to 200 °C, add H2 for reduction, where the H2 content is 20 vol.%, and continue reduction for 60 h. After reduction is completed, stop the introduction of H2, and continue to introduce N2. S4. Activate the reduced catalyst with N2O. The specific conditions are as follows: keep N2 flowing in while cooling to 60 °C, then introduce N2O at a rate of 5 vol.% of N2 for 24 h. After the treatment, a catalyst with catalytic activity is obtained.

[0035] Example 3 The catalyst for preparing tetramethoxysilane from silicon powder and methanol in the embodiment, calculated as oxides, consists of the following components by mass percentage: CuO 75%, ZnO 15%, Al2O3 9.5%, SiO2 0.5%.

[0036] The preparation method of the catalyst is as follows: (1) Dissolve 569.8 g of Cu(NO3)2·3H2O and 137.1 g of Zn(NO3)2·6H2O in 1.1 L of deionized water to obtain a mixed solution I; (2) Dissolve 325 g of (NH4)2CO3 in 1.68 L of deionized water, then add 12.0 g of tetramethoxysilane to obtain a mixed solution II; (3) Uniformly add the mixed solution I obtained in step (1) into the mixed solution II obtained in step (2) to perform a co-precipitation reaction, then add 36.3 g of gibbsite and stir for 30 min, then perform filtration to obtain a filter residue, which is sequentially washed and dried to obtain a catalyst precursor; wherein the addition time is 30 min; the co-precipitation reaction temperature is 80 ℃; the drying temperature is 150 ℃, and the time is 2 h; (4) Perform calcination on the catalyst precursor obtained in step (3) to obtain an oxidized catalyst, i.e., a catalyst for preparing tetramethoxysilane from silicon powder and methanol; wherein the calcination temperature is 500 ℃, and the time is 1 h.

[0037] Perform activation on the prepared catalyst, and the activation method is as follows: S1, add 50 g of the oxidized catalyst into a reactor, and pass N2 to heat; in terms of volume at standard conditions, the space velocity of N2 is 3000 h -1 , and the pressure is 1.0 MPa; S2, heat to 120 ℃ and keep constant for 3 h to remove air and physically adsorbed water in the catalyst; S3, continue to heat to 280 ℃, and reduce by adding H2, wherein the content of H2 is 8 vol.%, and the reduction is continued for 2 h; after reduction is completed, stop adding H2, and continue to pass N2; S4, activate the reduced catalyst using N2O; the specific conditions are as follows: keep passing N2 to cool to 80 ℃, then pass N2O, the amount of N2O is 8 vol.% of N2, and the passing time is 2 h; after treatment is completed, a catalyst with catalytic activity is obtained.

[0038] Example 4 The catalyst for preparing tetramethoxysilane from silicon powder and methanol in the embodiment consists of the following components in mass percentage: CuO 30%, ZnO 40%, Al2O3 27%, and SiO2 3%.

[0039] The preparation method of the catalyst is as follows: (1) 235.8 g of CuSO4·5H2O and 353.3 g of ZnSO4·7H2O were dissolved in 3.0 L of deionized water to obtain a mixed solution I; (2) 358 g of K2CO3 was dissolved in 3.0 L of deionized water, and then 26.0 g of tetraethoxysilane was added to obtain a mixed solution II; (3) The mixed solution I obtained in step (1) was uniformly added to the mixed solution II obtained in step (2) to perform a co-precipitation reaction, and then 103.2 g of aluminum hydroxide was added and stirred for 30 min, followed by filtration to obtain a filter residue, which was sequentially washed and dried to obtain a catalyst precursor; wherein the addition time was 180 min, the co-precipitation reaction temperature was 60 ℃, and the drying temperature was 120 ℃, and the time was 12 h; (4) The catalyst precursor obtained in step (3) was calcined to obtain an oxidized catalyst, i.e., a catalyst for preparing tetramethoxysilane from silicon powder and methanol; wherein the calcination temperature was 450 ℃, and the time was 2 h.

[0040] The prepared catalyst was activated, and the activation method was as follows: S1, 50 g of the oxidized catalyst was added to a reactor, and N2 was introduced for temperature rising; the space velocity of N2 was 2000 h -1 at standard conditions, and the pressure was 0.8 MPa; S2, the temperature was raised to 120 ℃, and the temperature was kept constant for 1 h to remove air and physically adsorbed water in the catalyst; S3, the temperature was continuously raised to 250 ℃, and H2 was introduced for reduction, wherein the content of H2 was 5 vol.%, and the reduction was continued for 10 h; after the reduction was completed, the introduction of H2 was stopped, and the introduction of N2 was continued; S4, the reduced catalyst was activated using H2O, and the specific conditions were as follows: the temperature was lowered to 180 ℃ while keeping N2 introduced, then H2O was introduced, the amount of H2O was 5 vol.% of N2, and the gas introduction time was 12 h; after the treatment was completed, a catalyst with catalytic activity was obtained.

[0041] Example 5 The catalyst for preparing tetramethoxysilane from silicon powder and methanol in the embodiment consists of the following components in mass percentage: CuO 60%, ZnO 25%, Al2O3 13%, and SiO2 2%.

[0042] The preparation method of the catalyst is as follows: (1) 455.8 g of Cu(NO3)2·3H2O and 228.4 g of Zn(NO3)2·6H2O were dissolved in 8.0 L of deionized water to obtain a mixed solution I; (2) 338 g of Na2CO3 was dissolved in 6.0 L of deionized water, and then 3.0 g of tetramethoxysilane was added to obtain a mixed solution II; (3) The mixed solution I obtained in step (1) was uniformly added to the mixed solution II obtained in step (2) to perform a co-precipitation reaction, and then 41.1 g of pseudoboehmite was added and stirred for 30 min, followed by filtration to obtain filter residue, which was sequentially washed and dried to obtain a catalyst precursor; wherein the addition time was 60 min, the co-precipitation reaction temperature was 60 ℃, and the drying temperature was 100 ℃, and the time was 12 h; (4) The catalyst precursor obtained in step (3) was calcined to obtain an oxidized catalyst, i.e., a catalyst for preparing tetramethoxysilane from silicon powder and methanol; wherein the calcination temperature was 380 ℃, and the time was 5 h.

[0043] The prepared catalyst was activated, and the activation method was as follows: S1, 50 g of the oxidized catalyst was added to a reactor, and N2 was introduced for temperature rising; the space velocity of N2 was 1500 h-1 by volume at standard conditions, and the pressure was 0.5 MPa; -1 S2, the temperature was raised to 120 ℃, and kept constant for 1 h to remove air and physically adsorbed water in the catalyst; S3, the temperature was continuously raised to 220 ℃, and H2 was introduced for reduction, wherein the content of H2 was 5 vol.%, and the reduction was continued for 10 h; after the reduction was completed, the introduction of H2 was stopped, and the introduction of N2 was continued; S4, the reduced catalyst was activated using H2O, and the specific conditions were as follows: the temperature was reduced to 220 ℃ while keeping N2 introduced, and then H2O was introduced, the amount of which was 10 vol.% of N2, and the gas introduction time was 1 h; after the treatment was completed, a catalyst with catalytic activity was obtained.

[0044] Example 6 ​The catalyst for preparing tetramethoxysilane from silicon powder and methanol in the embodiment consists of the following components in mass percentage: CuO 55%, ZnO 25%, Al2O3 18%, and SiO2 2%.

[0045] The preparation method of the catalyst is as follows: (1) 417.9 g of Cu(NO3)2·3H2O and 228.4 g of Zn(NO3)2·6H2O were dissolved in 8.0 L of deionized water to obtain a mixed solution I; (2) 318 g of Na2CO3 was dissolved in 6.0 L of deionized water, and then 13.0 g of tetramethoxysilane was added to obtain a mixed solution II; (3) The mixed solution I obtained in step (1) was added to the mixed solution II obtained in step (2) at a constant speed to perform a co-precipitation reaction, and then 59.2 g of pseudoboehmite was added and stirred for 30 min, followed by filtration. The obtained filter residue was sequentially washed and dried to obtain a catalyst precursor; wherein the addition time was 60 min; the co-precipitation reaction temperature was 60 ℃; the drying temperature was 100 ℃, and the time was 12 h; (4) The catalyst precursor obtained in step (3) was calcined to obtain an oxidized catalyst, i.e., a catalyst for preparing tetramethoxysilane from silicon powder and methanol; wherein the calcination temperature was 380 ℃, and the time was 5 h.

[0046] The prepared catalyst was activated, and the activation method was as follows: S1, 50 g of the oxidized catalyst was added to a reactor, and N2 was introduced for temperature rising; the space velocity of N2 was 1500 h -1 at standard conditions, and the pressure was 0.5 MPa; S2, the temperature was raised to 120 ℃, and the temperature was kept constant for 1 h to remove air and physically adsorbed water in the catalyst; S3, the temperature was continuously raised to 220 ℃, and H2 was introduced for reduction, wherein the content of H2 was 10 vol.%, and the reduction was continued for 5 h. After the reduction was completed, the introduction of H2 was stopped, and the introduction of N2 was continued; S4, the reduced catalyst was activated using H2O, and the specific conditions were as follows: the temperature was lowered to 220 ℃ while N2 was introduced, then H2O was introduced, the amount of H2O was 30 vol.% of N2, and the gas introduction time was 24 h; after the treatment was completed, a catalyst with catalytic activity was obtained.

[0047] Comparative Example 1 The catalyst in the present comparative example was prepared by the method of Example 5. The obtained catalyst was not subjected to activation treatment.

[0048] The catalyst consists of the following mass percentages of components, calculated as stable oxides: CuO 60%, ZnO 25%, AI2O3 13%, SiO2 2%.

[0049] The catalyst in this comparative example was prepared as follows: (1) 455.8 g Cu(NO3)2-3H2O, 228.4 g Zn(NO3)2-6H2O were dissolved in 8.0 L deionized water to obtain mixed solution I; (2) 338 g Na2CO3was dissolved in 6.0 L deionized water, then 3.0 g tetramethoxysilane was added to obtain mixed solution II; (3) The mixed solution I obtained in step (1) was added to the mixed solution II obtained in step (2) at a uniform speed to carry out a co-precipitation reaction, then 41.1 g pseudoboehmite was added and stirred for mixing for 30 min, then filtration was carried out, the obtained filter residue was sequentially washed and dried to obtain a catalyst precursor; wherein, the time of addition was 60 min; the temperature of the co-precipitation reaction was 60 °C; the temperature of drying was 100 °C, and the time was 12 h; (4) The catalyst precursor obtained in step (3) was calcined to obtain an oxidized catalyst, which was a catalyst for preparing tetramethoxysilane using silicon powder and methanol; wherein, the temperature of calcination was 380 °C, and the time was 5 h.

[0050] Comparative Example 2 The catalyst in this comparative example was prepared using the method of Example 5. The activation process of the obtained catalyst only carried out reduction treatment, and did not carry out oxidation treatment.

[0051] The catalyst in this comparative example was prepared as follows: (1) 455.8 g Cu(NO3)2-3H2O, 228.4 g Zn(NO3)2-6H2O were dissolved in 8.0 L deionized water to obtain mixed solution I; (2) 338 g Na2CO3was dissolved in 6.0 L deionized water, then 3.0 g tetramethoxysilane was added to obtain mixed solution II; (3) The mixed solution I obtained in step (1) was added to the mixed solution II obtained in step (2) at a uniform speed to carry out a co-precipitation reaction, then 41.1 g pseudoboehmite was added and stirred for mixing for 30 min, then filtration was carried out, the obtained filter residue was sequentially washed and dried to obtain a catalyst precursor; wherein, the time of addition was 60 min; the temperature of the co-precipitation reaction was 60 °C; the temperature of drying was 100 °C, and the time was 12 h; (4) The catalyst precursor obtained in step (3) is calcined to obtain an oxidation state catalyst, i.e., a catalyst for preparing tetramethoxysilane by using silicon powder and methanol; wherein the calcination temperature is 380 ℃, and the time is 5 h.

[0052] The prepared catalyst is activated, and the activation method is as follows: S1, 50 g of the oxidation state catalyst is added into a reactor, and N2 is introduced for temperature rising; the space velocity of N2 is 1500 h -1 , and the pressure is 0.5 MPa; S2, the temperature is raised to 120 ℃, and kept for 1 h to remove air and physically adsorbed water in the catalyst; S3, the temperature is continuously raised to 220 ℃, and H2 is introduced for reduction, wherein the content of H2 is 10 vol.%, and the reduction is continuously performed for 5 h.

[0053] Test Example 1 The activity of the catalysts activated in Examples 1-6, the catalyst not activated in Comparative Example 1, and the catalyst partially activated in Comparative Example 2 is tested to study the effect in the application of preparing tetramethoxysilane by using silicon powder and methanol, and the specific method is as follows: 1 L of dodecylbenzene is added into a reactor, 10 g of the activated catalyst is added, 50 g of silicon powder is added, stirring is started, N2 is introduced, and heating is performed to 260 ℃; heating is continuously performed, methanol is introduced by bubbling with N2, the amount of methanol introduced is 4 g / min, 25 g of silicon powder is added every 2 h, a total of 5 batches of silicon powder is added, the total amount of silicon powder is 175 g, after the last batch of silicon powder is added, the reaction is continuously performed for 2 h after the introduction of methanol is stopped; the reactor outlet gas is cooled to -10 ℃, the reaction distillate is obtained, the product is collected, weighed, analyzed by gas chromatography to calculate the content of TMOS and the total amount of TMOS, and the total amount of Methyltrimethoxysilane (MTMS) byproduct is also calculated. The test results are shown in Table 1.

[0054] Table 1: Activity detection results of catalysts in Examples 1-6 and Comparative Examples 1 and 2

[0055] As can be seen from Table 1, the catalysts prepared in Examples 1-6 of the present application can make the silicon powder conversion rate reach more than 95% after activation treatment without pre-mixing with silicon powder, and continuous production is realized by continuously adding silicon powder. The specific surface area of the catalysts of the present application is tested, and the results show that the specific surface area of the above examples is 84-126 m 2 / g, which also helps to promote the improvement of catalytic activity. In addition, the active sites of the catalyst are located on the surface, and if the stability is poor, the activity will quickly decrease. To explore the stability of the catalyst, in addition to the above tests, taking the sample of Example 5 as an example, after taking the same experimental method to continuously carry out 6 times after subsequent cooling and restarting the reaction, it is observed that the catalyst activity does not decrease obviously, and the conversion rate of the silicon powder still remains at 95.4%, and the selectivity of TMOS is 85%.

[0056] The above results show that the catalyst of the present application has excellent catalytic activity and stability. In contrast, the catalytic activity of Comparative Example 1 is greatly reduced because it is not subjected to activation treatment. The activity of Comparative Example 2 is also low because it is only subjected to reduction without oxidation, and thus the catalytically active unit is not formed.

[0057] In summary, the catalyst and the activation method provided by the present application have very high catalytic activity for the reaction of silicon powder and methanol, and can realize the continuous generation of TMOS, and the product is free of chlorine and easy to purify. The by-product is MTMS, which has a higher value than TMOS, and has a good industrial application prospect.

[0058] The above describes the preferred embodiments of the present application in detail. It should be understood that those skilled in the art can make many modifications and changes to the present application without creative labor according to the concept of the present application. Therefore, any technical solution obtained by logical analysis, reasoning or limited experiment on the basis of the prior art according to the concept of the present application shall be within the protection scope defined by the claims.

Claims

1. A catalyst for preparing tetramethoxysilane using silicon powder and methanol, characterized by, Consists of the following stable oxide components in percentage by mass: CuO 30%~75%, ZnO 15%~40%, Al2O3 5%~30%, SiO2 0.5%~5%.

2. The method for preparing a catalyst for preparing tetramethoxysilane from silicon powder and methanol according to claim 1, characterized by, Comprise the following steps: (1) Prepare raw materials according to the component composition; dissolve the soluble copper salt and the soluble zinc salt in water to obtain a mixed solution I; (2) Add a precipitant to water, and then add tetramethoxysilane or tetraethoxysilane to obtain a mixed solution II; (3) Add the mixed solution I to the mixed solution II to perform a co-precipitation reaction, and then add aluminum hydrated oxide to mix, and then perform filtering, washing, and drying to obtain a catalyst precursor; (4) Perform calcination on the obtained catalyst precursor to obtain a finished product oxide catalyst, i.e., a catalyst for preparing tetramethoxysilane by using silicon powder and methanol.

3. The method of claim 2, wherein: In the step (1), the soluble copper salt is copper nitrate trihydrate or copper sulfate pentahydrate; and the soluble zinc salt is zinc nitrate hexahydrate or zinc sulfate heptahydrate.

4. The method of claim 2, wherein: In the step (1), the total concentration of metal ions in the mixed solution I is 0.2~2.5 mol / L.

5. The method of claim 2, wherein: In the step (2), the precipitant is one of sodium carbonate, ammonium carbonate, and potassium carbonate.

6. The method of claim 2, wherein: In the step (2), the molar amount of the precipitant is 1.2 times the total molar amount of metal ions in the mixed solution I; and the concentration of the precipitant in the mixed solution II is 0.1~2 mol / L.

7. The method of claim 2, wherein: In the step (3), the time for adding is 10~180 min; the temperature for the co-precipitation reaction is 25~80 ℃; and the temperature for drying is 80~150 ℃, and the time is 2~24 h.

8. The method of claim 2, wherein: In the step (3), the aluminum hydrated oxide is one of boehmite, bayerite, gibbsite, pseudoboehmite, and aluminum hydroxide.

9. The method of claim 2, wherein: In the step (4), the temperature for calcination is 320~500 ℃, and the time is 1~10 h.

10. A method for activating a catalyst for producing tetramethoxysilane from silicon powder and methanol according to claim 1 or a catalyst for producing tetramethoxysilane from silicon powder and methanol produced by the production method according to any one of claims 2 to 9, characterized by, Comprise the following steps: S1, add the catalyst for preparing tetramethoxysilane by using silicon powder and methanol into a reactor, and then introduce N2 to heat; The space velocity of N2 is 100-3000 h -1 at a normal pressure to 1.0 MPa; S2, heat to 100~140 ℃, and keep the temperature constant for 1~6 h to empty air and remove physically adsorbed water in the catalyst; S3, continue to heat to 170~280 ℃, and introduce H2 for reduction, wherein the content of H2 is 0.1 vol.%~20 vol.%, and the reduction lasts for 2~100 h; after the reduction is completed, stop introducing H2, and continue to introduce N2; S4, use N2O or water vapor to oxidize the reduced catalyst to activate the catalyst; In the case of using N2O for activation, after the treatment in S3 is completed, continue to introduce N2, and introduce N2O at 25~80 ℃, wherein the amount of N2O introduced is 0.1 vol.%~10 vol.% of N2, and the oxidation time is 1~24 h; In the case of using water vapor for activation, after the treatment in S3 is completed, continue to introduce N2, and introduce water vapor at 120~220 ℃, wherein the amount of water vapor introduced is 5 vol.%~30 vol.% of N2, and the oxidation time is 1~24 h.

Images