Catalyst as well as preparation method and application thereof

Abstract

The invention discloses a catalyst preparation method, which comprises: (1) dissolving a copper salt, adding a silicon source, and uniformly stirring to obtain a solution A; (2) dissolving a precipitator to obtain a solution B; (3) heating deionized water to a first temperature, maintaining the temperature, starting stirring, dropwise adding the solution A and the solution B into the deionized water at the same time to form a turbid liquid, and aging the turbid liquid after dropwise adding is completed; (4) filtering the aged turbid liquid while the turbid liquid is hot to obtain a blue precipitate, and washing and drying the blue precipitate to obtain a catalyst intermediate; and (5) grinding the catalyst intermediate into fine powder, and roasting to obtain a catalyst product. The invention also discloses the catalyst prepared by the method and application thereof. Compared with the prior art, the catalyst prepared by the invention is high in active component dispersity, large in specific surface area, high in activity and simple in preparation process, and the catalyst is applied to a silicon tetrachloride cold hydrogenation reaction, so that the reaction can maintain a relatively high conversion rate.

Description

Technical Field

[0001] The invention belongs to the technical field of polysilicon production, and in particular relates to a catalyst for cold hydrogenation reaction of silicon tetrachloride and a preparation method and application thereof. Background Art

[0002] Polysilicon is the basic material of the global electronics industry and photovoltaic industry. It is widely used in artificial intelligence, automatic control, information processing and photovoltaic power generation, and is considered to be the "cornerstone of the microelectronics building". In the production process of polysilicon, a large amount of silicon tetrachloride by-product is produced. It is very active and easily hydrolyzed in humid air to produce toxic and corrosive fumes, which are harmful to the human body and the environment.

[0003] In the modified Siemens process, the hydrogenation reaction technology of silicon tetrachloride is one of the core technologies of the process, which realizes the recycling and reuse of silicon tetrachloride and reduces the production cost of polysilicon. The cold hydrogenation reaction of silicon tetrachloride is carried out in a fluidized bed reactor or a fixed bed reactor. Silicon tetrachloride and hydrogen are passed through a bed layer with silicon powder to generate trichlorosilane. The overall reaction equation is: Compared with thermal hydrogenation reaction, cold hydrogenation reaction has lower temperature and less energy consumption. Adding catalyst can also increase the reaction rate. Under the same reaction residence time, it can increase the conversion rate of silicon tetrachloride and the yield of trichlorosilane.

[0004] At present, cold hydrogenation reactions mainly use heterogeneous catalysts, and mainly transition metal (Cu, Ni, Fe and Co, etc.) catalysts. These catalysts have some problems, such as:

[0005] Chinese patent CN103055861B discloses a catalyst, which is obtained by heating copper and silicon to melt, cooling and solidifying the melt, and extracting the solidified alloy with an acid or alkaline solution. The synthesis of the catalyst requires a high temperature of more than 1000°C and has low activity.

[0006] Chinese patent CN108283925A discloses a catalyst for hydrogenation of silicon tetrachloride, wherein a silicon source is acidified and a soluble salt of Ni or Co is added.

[0007] Pseudo-boehmite was added with urea as a curing agent, and a catalyst with microsphere shape and relatively concentrated particle size distribution was obtained by spray drying. The specific surface area of ​​the catalyst was only 30m 2 / g, with low activity.

[0008] Chinese patent CN105536789A discloses a method of melting cuprous chloride at high temperature and directly impregnating amorphous silicon aluminum with molten metal salt. This method avoids the problem of too low single metal loading during aqueous solution impregnation, but its active component dispersion is low.

[0009] In addition, these catalysts have poor stability and their catalytic activity decreases significantly after a period of use. Summary of the invention

[0010] The technical problem to be solved by the present invention is to provide a catalyst and a preparation method and application thereof in view of the above-mentioned deficiencies in the prior art. The catalyst prepared by the method has high active component dispersion, large specific surface area, high activity and simple preparation process. The catalyst is applied to the cold hydrogenation reaction of silicon tetrachloride, and the reaction can maintain a high conversion rate.

[0011] The technical solution of the present invention to solve the above technical problems is:

[0012] According to one aspect of the present invention, there is provided a method for preparing a catalyst, comprising:

[0013] (1) After the copper salt is dissolved, a silicon source is added and stirred evenly to obtain a solution A;

[0014] (2) dissolving the precipitant to obtain solution B;

[0015] (3) heating the deionized water to a first temperature and maintaining the temperature, starting stirring, and then simultaneously dropping the solution A and the solution B into the deionized water to form a suspension, and after the dropping is completed, performing an aging treatment on the suspension;

[0016] (4) filtering the aged suspension while hot to obtain a blue precipitate, which is then washed and dried to obtain a catalyst intermediate;

[0017] (5) Grinding the catalyst intermediate into fine powder and then calcining it to obtain a catalyst product.

[0018] Optionally, the copper salt is one or more of copper nitrate, copper chloride, copper sulfate and copper acetate.

[0019] Optionally, the silicon source is one or more of ethyl orthosilicate, methyl orthosilicate and tetrapropoxysilane.

[0020] Optionally, the precipitant is (NH4)2CO3.

[0021] Optionally, the first temperature is 78-82°C, the pH of the suspension is controlled to be 7-7.5, the aging treatment time is 12 hours or more, and the aging treatment temperature is 78-82°C.

[0022] Optionally, the total addition time of the solution A and the solution B does not exceed 2 hours.

[0023] Optionally, the calcination includes: placing the catalyst intermediate fine powder in an air atmosphere and heating it to a second temperature at a rate of 10°C / min, and maintaining it for a period of time, and then performing a first calcination to remove chemically bound water and NH4 + 、CO3 2- 、NO3 - 、CH3COO - Etc., increase the void structure and specific surface area of ​​the catalyst, and increase the interaction between the active components and the carrier, and finally obtain the catalyst.

[0024] Optionally, the second temperature is 500-700° C. and maintained for 3-6 hours.

[0025] Optionally, the calcination also includes: placing the catalyst obtained after the first calcination in ethanol, adding a carbon source, and stirring until the solvent is completely evaporated, so that the carbon source is evenly loaded on the catalyst surface; placing the catalyst after adsorbing the carbon source in a nitrogen atmosphere and heating it to a third temperature at a rate of 10°C / min, and maintaining it for a period of time, and then calcining it for a second time to carbonize the carbon source loaded on the catalyst surface to form a carbon protective layer.

[0026] Optionally, the carbon source is a phenolic substance.

[0027] Optionally, the phenolic substance is one of phenol, o-cresol, m-cresol and p-cresol.

[0028] Optionally, the third temperature is 500-700° C. and maintained for 3-6 hours.

[0029] According to a second aspect of the present invention, there is provided a catalyst, which is prepared using the above-mentioned preparation method.

[0030] Optionally, the catalyst includes an active component and a carrier, wherein: the active components are Cu and Cu2O, which are uniformly dispersed in the carrier; the carrier is porous amorphous SiO2; and the mass ratio of the active component to the carrier is 1:9 to 4:6.

[0031] Optionally, the catalyst further includes a carbon protective layer, and the carbon protective layer is coated on the outside of the carrier.

[0032] Optionally, the mass of the carbon coating layer is 1%-5% of the total mass of the catalyst.

[0033] According to a third aspect of the present invention, there is provided an application of the above-mentioned catalyst, wherein the catalyst is applied to cold hydrogenation reaction of silicon tetrachloride.

[0034] Beneficial effects:

[0035] The catalyst prepared by the present invention has the advantages of high active component dispersion, many active sites, large specific surface area, high activity, uniform particle size, simple preparation process, etc. In addition, by forming a carbon protective layer for coating and modification, a physical barrier can be formed, copper sintering can be reduced, and the agglomeration of active component particles can be reduced, so that the catalyst activity is more stable and the service life is longer, that is, the stability of the catalyst can be increased, and the catalyst also has the advantage of good stability. The catalyst of the present invention is applied to the cold hydrogenation reaction of silicon tetrachloride, and the reaction can maintain a high conversion rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of a process for preparing a catalyst according to an embodiment of the present invention;

[0037] Figure 2 This is a TEM image of the catalyst prepared in Example 9 of the present invention after reduction;

[0038] Figure 3 The XRD images of the catalysts prepared in Examples 6 and 9 of the present invention after reduction;

[0039] Figure 4 The XRD images of the catalysts prepared in Examples 6 and 9 of the present invention after 100 hours of reaction. DETAILED DESCRIPTION

[0040] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings in the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0041] In view of the problems that the catalyst for the cold hydrogenation reaction of silicon tetrachloride in the prior art has low dispersibility of active components, small specific surface area, low activity, etc., the present invention discloses a method for preparing the catalyst, comprising:

[0042] (1) After the copper salt is dissolved, a silicon source is added and stirred evenly to obtain a solution A;

[0043] (2) dissolving the precipitant to obtain solution B;

[0044] (3) heating the deionized water to a first temperature and maintaining the temperature, starting stirring, and then simultaneously dropping the solution A and the solution B into the deionized water to form a suspension, and after the dropping is completed, performing an aging treatment on the suspension;

[0045] (4) filtering the aged suspension while hot to obtain a blue precipitate, which is then washed and dried to obtain a catalyst intermediate;

[0046] (5) Grinding the catalyst intermediate into fine powder and then calcining it to obtain a catalyst product.

[0047] Correspondingly, the present invention also provides a catalyst prepared by the above preparation method and its application.

[0048] Example 1

[0049] like Figure 1 As shown, this embodiment discloses a method for preparing a catalyst, comprising:

[0050] (1) After the copper salt is dissolved, a silicon source is added and stirred evenly to obtain a solution A;

[0051] (2) dissolving the precipitant to obtain solution B;

[0052] (3) The deionized water is heated to a first temperature and maintained, stirring is started, and then solution A and solution B are simultaneously added dropwise to the constant temperature deionized water to hydrolyze the silicon source and Cu 2+ On the one hand, it forms a complex with the precipitant to form a copper-ammonia complex ion, and on the other hand, it forms a blue copper hydroxide precipitate. The formed precipitate is uniformly mixed with the hydrolyzate of the silicon source and presents a suspension state at the same time, that is, a suspension is obtained. After the copper salt silicon solution (i.e., solution A) is added dropwise, the precipitant (i.e., solution B) is stopped, and stirring is continued to age the suspension.

[0053] (4) filtering the aged suspension while hot to obtain a blue precipitate, which is then washed and dried to obtain a catalyst intermediate;

[0054] (5) The catalyst intermediate is ground into fine powder and then roasted to obtain a catalyst product. The catalyst prepared by this method includes an active component and a carrier, wherein the active components are Cu and Cu2O, which are uniformly dispersed in the carrier; the carrier is porous amorphous SiO2; by weight, the ratio of Cu active component to carrier SiO2 is 1:9 to 4:6, with a loading amount adjustable within a wide range.

[0055] Compared with the prior art, the present method can generate active components in situ while the silicon source is hydrolyzed to form a carrier, that is, the active components of the catalyst and the carrier are formed synchronously, so that the strong interaction between the metal and the carrier can be utilized to promote the active components Cu and Cu2O to be highly dispersed in the carrier. The catalyst prepared by the present method has the advantages of high dispersion of active components, many active sites, large specific surface area, high activity, uniform particle size, simple preparation process, etc.

[0056] In some embodiments, the copper salt in step (1) is one or more of copper nitrate, copper chloride, copper sulfate and copper acetate, but is not limited thereto.

[0057] In this embodiment, copper salt is added into deionized water and dissolved by sufficient stirring at room temperature to obtain a transparent light blue solution.

[0058] In some embodiments, the silicon source in step (1) is one or more of tetraethyl orthosilicate (TEOS), methyl orthosilicate (TMOS) and tetrapropoxysilane (TPOS), but is not limited thereto.

[0059] In this embodiment, the light blue solution obtained by dissolving the silicon source and the copper salt is mixed and stirred at a speed of 200 rpm for 5-10 min to obtain a uniform light blue solution without stratification, which is recorded as solution A.

[0060] In some embodiments, the precipitant in step (2) is (NH4)2CO3.

[0061] In this embodiment, the precipitant is added to water (preferably deionized water) and dissolved by sufficient stirring at room temperature, wherein the stirring speed is 200 rpm and the stirring time is 5-10 min, and a clear solvent without precipitates is obtained, which is recorded as solution B.

[0062] In some embodiments, the first temperature in step (3) is 78-82° C. In this embodiment, the first temperature is 80° C.

[0063] In some embodiments, the suspension in step (3) is controlled to be neutral or alkaline. In this embodiment, the pH of the suspension is controlled to be 7 to 7.5 to ensure that the Cu 2+ On the one hand, it can complex with the precipitant to generate copper ammonia complex ions, and on the other hand, it can generate blue copper hydroxide precipitate, and then the generated precipitate is evenly mixed with the hydrolyzate of the silicon source to obtain the suspension.

[0064] In some embodiments, the aging treatment time is 12 hours or more, and the aging treatment temperature is 78-82°C.

[0065] In this embodiment, the aging treatment time is 12 hours and the aging treatment temperature is 80°C.

[0066] In some embodiments, the dripping speed of solution A and solution B in step (3) is 2-6 seconds / drop, and the dripping time of solution A and solution B does not exceed 2 hours as a whole.

[0067] In this embodiment, the dropping speed of solution A and solution B is close to 3 seconds / drop.

[0068] In some embodiments, the washing in step (4) is specifically washing with deionized water for 3 to 5 times. In this embodiment, the number of washing times is 4 times.

[0069] In some embodiments, the drying in step (4) is specifically to place the filtered blue precipitate in an oven for drying at a temperature of 60 to 120° C. for a drying time of 8 to 16 hours. In this embodiment, the drying temperature is 100° C. for a drying time of 12 hours.

[0070] In some embodiments, the calcination in step (5) comprises:

[0071] (5-1) The catalyst intermediate fine powder is placed in an air atmosphere and heated from room temperature to a second temperature at a certain speed (e.g., 10°C / min) and maintained for a period of time to perform the first calcination to remove chemically bound water and NH4 + 、CO3 2- 、NO3 - 、CH3COO - Etc., increase the void structure and specific surface area of ​​the catalyst, and increase the interaction between the active components and the carrier. After calcination is completed and cooled to room temperature, a catalyst with highly dispersed active components can be obtained.

[0072] In some embodiments, the second temperature is 500-700° C. and maintained for 3-6 hours.

[0073] In this embodiment, the second temperature is 550° C., and the second temperature is maintained for 4 hours.

[0074] In some embodiments, the calcination in step (5) further comprises:

[0075] (5-2) Carbon layer coating: The catalyst with highly dispersed active components obtained after the first calcination is placed in an easily evaporable solvent such as ethanol, and a certain amount of carbon source is added. The mixture is stirred overnight at room temperature until the solvent is completely evaporated or dried, so that the carbon source is evenly loaded on the catalyst surface.

[0076] (5-3) Inert gas calcination: The catalyst with carbon source adsorbed on the surface is placed in a nitrogen or inert gas atmosphere and heated from room temperature to a third temperature at a certain speed (e.g., 10°C / min) and maintained for a period of time, and then calcined for the second time to carbonize the carbon source loaded on the catalyst surface to form a carbon protective layer. After the calcination is completed, the temperature is cooled to room temperature to obtain a catalyst with highly dispersed active components having a carbon protective layer.

[0077] By forming a carbon protective layer on the surface of the catalyst, a physical barrier can be formed, which can reduce the sintering of copper and the agglomeration of active component particles, making the activity of the catalyst more stable and its service life longer.

[0078] In some embodiments, the carbon source is a phenolic substance, but is not limited thereto. Compared with other carbon sources, the use of phenolic substances as carbon sources can achieve better adsorption effects by using silanol groups to form hydrogen bonds with phenolic hydroxyl groups in phenolic substances, and can be pyrolyzed to form a uniform carbon protective layer during the subsequent calcination process. The amount of carbon source used is 1%-5% of the mass of the carbon protective layer to the total mass of the catalyst.

[0079] In this embodiment, the phenolic substance is one or more of phenol, o-cresol, m-cresol and p-cresol, but is not limited thereto.

[0080] In some embodiments, the third temperature is 500-700° C., and the maintenance time is 3-6 hours.

[0081] In this embodiment, the third temperature is 550° C. and the maintenance time is 4 hours.

[0082] The catalyst prepared by the preparation method of the catalyst of the present embodiment has the advantages of high dispersion of active components, many active sites, large specific surface area, high activity, uniform particle size, simple preparation process, etc. In addition, by forming a carbon protective layer for coating and modification, a physical barrier can be formed, the sintering of copper can be reduced, the agglomeration of active component particles can be reduced, the catalyst activity can be more stable, the service life can be longer, and the stability of the catalyst can be increased. The catalyst prepared by the method of the present embodiment is applied to the cold hydrogenation reaction of silicon tetrachloride, and the reaction can maintain a high reaction conversion rate.

[0083] Example 2

[0084] This embodiment discloses a catalyst, which is prepared by using the catalyst preparation method described above.

[0085] Specifically, the catalyst includes an active component and a carrier, wherein: the active components are Cu and Cu2O, which are uniformly dispersed in the carrier; the carrier is porous amorphous SiO2; by weight, the ratio of the Cu active component to the carrier SiO2 is 1:9 to 4:6, which can be adjusted according to actual needs.

[0086] In some embodiments, the catalyst further includes a carbon protective layer, which is coated on the outside of the carrier, and the mass of the carbon protective layer is 1%-5% of the total mass of the catalyst.

[0087] The catalyst of the present embodiment has high active component dispersion, many active sites, large specific surface area, high activity, uniform particle size, and simple preparation process. In addition, by forming a carbon protective layer, the catalyst activity can be made more stable and the service life can be longer, that is, the stability of the catalyst can be increased, and the catalyst also has the advantage of good stability. The catalyst of the present embodiment is applied to the cold hydrogenation reaction of silicon tetrachloride, and the reaction can maintain a high reaction conversion rate.

[0088] Example 3

[0089] This embodiment discloses an application of the above catalyst, wherein the catalyst is applied to the cold hydrogenation reaction of silicon tetrachloride, and the specific steps include:

[0090] A certain amount of the above catalyst powder and silicon powder were evenly mixed and filled into a fixed bed reactor. The reaction conditions were controlled as follows: after nitrogen purging, the temperature was raised to 550°C at a rate of 10°C / min in a nitrogen / hydrogen mixed gas atmosphere for reduction. The reduction pressure was 3MPa and the reduction time was 3h. Subsequently, silicon tetrachloride gas was introduced for cold hydrogenation reaction to generate trichlorosilane product, and the product was collected for analysis.

[0091] Example 4

[0092] This embodiment discloses a method for preparing a catalyst, which is used to prepare a Cu / SiO2 catalyst 1 with an active component of 10% by mass. The method is similar to the method for preparing the catalyst described in Example 1, and the steps are as follows:

[0093] (1) Weigh 1.04×10 -2 mol copper salt (calculated on the basis of the amount of copper, such as copper nitrate) is dissolved in 60 ml of deionized water to obtain a copper salt solution, and then 0.1 mol of silicon source (calculated on the basis of the amount of silicon, such as tetraethyl orthosilicate) is weighed and added to the copper salt solution, and stirred at room temperature at a speed of 200 rpm for 1 h to obtain solution A.

[0094] (2) Weigh 12.01 g (NH4)2CO3 and dissolve it in water. After it is fully dissolved, prepare a 0.25 mol / L solution to obtain solution B.

[0095] (3) Take a three-necked flask, add 100 ml of deionized water and fix it in a water bath to a constant temperature of 80°C. Place solution A and solution B at both ends of the three-necked flask respectively, and add them to the three-necked flask at a rate of 3 seconds / drop. Turn on stirring and keep stirring to mix evenly. After the addition is completed, maintain aging at 80°C for 12 hours;

[0096] (4) After aging, filter while hot to obtain a blue precipitate, wash the blue precipitate with 500 ml of deionized water for 3-5 times, and then dry it in an oven at 100° C. for 12 hours to obtain a catalyst intermediate;

[0097] (5-1) After drying, the catalyst intermediate was ground into fine powder, and then calcined in air at a rate of 10°C / min to 600°C for 4 hours, and then cooled to room temperature to obtain Catalyst 1.

[0098] Example 5

[0099] This embodiment discloses a method for preparing a catalyst, which is used to prepare a Cu / SiO2 catalyst 2 with an active component of 20% by mass. The steps are the same as those of embodiment 4, except that:

[0100] In step (1), solution A is 2.34×10 -2 mol copper salt was dissolved in 60 ml deionized water, and then 0.1 mol silicon source was added and stirred at 200 rpm for 1 h at room temperature.

[0101] Example 6

[0102] This embodiment discloses a method for preparing a catalyst, which is used to prepare a Cu / SiO2 catalyst 3 with an active component of 30% by mass. The steps are the same as those of embodiment 4, except that:

[0103] In step (1), solution A is 4.02×10 -2 mol copper salt was dissolved in 60 ml of deionized water, and then 0.1 mol silicon source was added and stirred at 200 rpm for 1 h at room temperature;

[0104] In step (1), solution B is 24.02 g (NH4)2CO3 dissolved in water, which is fully dissolved to form a 0.5 mol / L solution.

[0105] Example 7

[0106] This embodiment discloses a method for preparing a catalyst, which is used to prepare a Cu / SiO2 catalyst 4 with an active component of 40% by mass. The steps are the same as those of embodiment 4, except that:

[0107] In step (1), solution A is 6.25×10 -2 mol copper salt was dissolved in 60 ml deionized water, and then 0.1 mol silicon source was added and stirred at 200 rpm for 1 h at room temperature.

[0108] Example 8

[0109] This embodiment discloses a method for preparing a catalyst, which is used to prepare a Cu / SiO2@1C catalyst 5 with an active component of 30% by mass. The steps are the same as those of embodiment 6, except that it further comprises:

[0110] (5-2) 5 g of the solid catalyst 3 was added to a beaker, and 40 ml of ethanol and 0.065 g of phenol were added. The mixture was stirred at 400 rpm overnight at room temperature until the solvent was completely evaporated.

[0111] (5-3) The solid was taken out and ground, and then calcined under a nitrogen atmosphere. The temperature was raised to 600 °C at a rate of 10 °C / min and maintained for 4 h. The temperature was then cooled to room temperature to obtain Catalyst 5.

[0112] Example 9

[0113] This embodiment discloses a method for preparing a catalyst, which is used to prepare a Cu / SiO2@3C catalyst 6 with an active component of 30% by mass. The steps are the same as those of Example 6, except that it further includes:

[0114] (5-2) 5 g of the solid catalyst 3 was added to a beaker, and 40 ml of ethanol and 0.196 g of phenol were added. The mixture was stirred at 400 rpm overnight at room temperature until the solvent was completely evaporated.

[0115] (5-3) The solid was taken out and ground, and then calcined under a nitrogen atmosphere. The temperature was raised to 600 °C at a rate of 10 °C / min and maintained for 4 h. The temperature was then cooled to room temperature to obtain Catalyst 6.

[0116] Example 10

[0117] This embodiment discloses a method for preparing a catalyst, which is used to prepare a Cu / SiO2@5C catalyst 7 with an active component of 30% by mass. The steps are the same as those of embodiment 6, except that it further comprises:

[0118] (5-2) 5 g of the solid catalyst 3 was added to a beaker, and 40 ml of ethanol and 0.327 g of phenol were added. The mixture was stirred at 400 rpm overnight at room temperature until the solvent was completely evaporated.

[0119] (5-3) The solid was taken out and ground, and then calcined under a nitrogen atmosphere. The temperature was raised to 600 °C at a rate of 10 °C / min and maintained for 4 h. The temperature was then cooled to room temperature to obtain catalyst 7.

[0120] Comparative Example 1

[0121] This comparative example provides a commercially available CuCl catalyst, which is designated as catalyst 8.

[0122] Taking the application in the cold hydrogenation reaction of silicon tetrachloride as an example, the performance of the catalyst prepared in Examples 4-10 is evaluated as follows:

[0123] Weigh 1g of the catalyst prepared in Examples 4-10 and the catalyst 8 provided in the comparative example, respectively, mix them with 9g of silicon powder, and then fill them into the constant temperature section of the fixed bed reactor. Heat to the reaction temperature of 540°C under a nitrogen atmosphere, purge for 1h, and then introduce hydrogen to carry out reduction for 3h. The bubbler temperature is adjusted according to the experimental pressure and the H2 / silicon tetrachloride feed ratio. After the temperature of the silicon tetrachloride liquid is constant, the silicon tetrachloride vapor is brought into the reactor with H2. The molar ratio of hydrogen to silicon tetrachloride is controlled to be 10:1, and the reaction temperature is controlled to be 540°C. The experimental results are shown in Table 1 and Figure 2-4 shown.

[0124] Table 1

[0125] catalyst Conversion rate (540℃10h) Conversion rate (540℃100h) 1 20.3％ 19.1％ 2 26.7％ 25.4％ 3 31.3％ 29.1％ 4 29.1％ 27.6％ 5 30.3％ 29.4％ 6 29.9％ 29.6％ 7 27.3％ 27.1％ 8 19.5％ 16.1％

[0126] It can be seen from Table 1 that when catalysts 1-7 are used, the conversion rate of the cold hydrogenation reaction of silicon tetrachloride reaches more than 20% after 10 hours of reaction. It can be seen that the catalysts prepared by this method have high activity; and, compared with the existing catalyst 8, the catalysts with a carbon protective layer prepared by this method (i.e., catalysts 5-7) have little difference in conversion rate after 10 hours of reaction and after 100 hours of reaction. It can be seen that the catalysts with a carbon protective layer prepared by this method have better stability and can maintain a high conversion rate for a long time in the cold hydrogenation reaction of silicon tetrachloride.

[0127] Figure 2 This is a TEM image of the catalyst prepared in Example 9 after reduction. Figure 2 It can be seen that the Cu nanoparticles are highly dispersed and evenly distributed, which depends on the strong interaction between the metal and the support and the restriction of the migration of metal particles by the carbon protective layer.

[0128] Figure 3 and Figure 4 The XRD images of the catalysts prepared in Example 6 and Example 9 after reduction and after 100 hours of reaction, respectively, are shown. The diffraction peak at 2Theta of 43.3° is the diffraction peak of the (111) crystal plane of Cu. Among them, the diffraction peak of catalyst 3 in Example 6 is sharper than that of catalyst 6 in Example 9, indicating that the modification of the carbon protective layer is beneficial to slowing down the sintering of the active metal components in the catalyst. The Scherrer formula shows that the growth of the unmodified catalyst particles is more obvious, which shows that after the carbon protective layer is covered, the sintering of the active components of the catalyst is weakened.

[0129] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, but the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method for preparing a catalyst, It is characterized in that include: (1) After the copper salt is dissolved, a silicon source is added and stirred evenly to obtain a solution A; (2) dissolving the precipitant to obtain solution B; (3) heating the deionized water to a first temperature and maintaining the temperature, starting stirring, and then simultaneously dropping the solution A and the solution B into the deionized water to form a suspension, and after the dropping is completed, performing an aging treatment on the suspension; (4) filtering the aged suspension while hot to obtain a blue precipitate, which is then washed and dried to obtain a catalyst intermediate; (5) Grinding the catalyst intermediate into fine powder and then calcining it to obtain a catalyst product.

2. The method for preparing the catalyst according to claim 1, It is characterized in that The copper salt is one or more of copper nitrate, copper chloride, copper sulfate and copper acetate.

3. The method for preparing the catalyst according to claim 1, It is characterized in that The silicon source is one or more of ethyl orthosilicate, methyl orthosilicate and tetrapropoxysilane.

4. The method for preparing the catalyst according to claim 1, It is characterized in that The precipitant is (NH 4 ) 2 CO 3 .

5. The method for preparing the catalyst according to claim 1, It is characterized in that The first temperature is 78-82°C, the pH of the suspension is controlled to be 7-7.5, the aging treatment time is 12 hours or more, and the aging treatment temperature is 78-82°C.

6. The method for preparing the catalyst according to claim 1, It is characterized in that The total addition time of the solution A and the solution B does not exceed 2 hours.

7. The method for preparing the catalyst according to claim 1, It is characterized in that The roasting comprises: The catalyst intermediate fine powder is placed in an air atmosphere and heated to a second temperature at a rate of 10°C / min and maintained for a period of time, and then calcined for the first time to obtain a catalyst.

8. The method for preparing the catalyst according to claim 7, It is characterized in that The second temperature is 500-700° C. and maintained for 3-6 hours.

9. The method for preparing the catalyst according to claim 7, It is characterized in that The roasting also includes: The catalyst obtained after the first calcination is placed in ethanol, and a carbon source is added, and stirred until the solvent is completely evaporated so that the carbon source is evenly loaded on the catalyst surface; The catalyst after adsorbing the carbon source is placed in a nitrogen atmosphere and heated to the third temperature at a rate of 10°C / min and maintained for a period of time, and then calcined for the second time to carbonize the carbon source loaded on the catalyst surface to form a carbon protective layer.

10. The method for preparing the catalyst according to claim 9, It is characterized in that The carbon source is phenolic substances.

11. The method for preparing the catalyst according to claim 10, It is characterized in that The phenolic substance is one of phenol, o-cresol, m-cresol and p-cresol.

12. The method for preparing the catalyst according to claim 9, It is characterized in that The third temperature is 500-700° C. and maintained for 3-6 hours.

13. A catalyst, It is characterized in that The catalyst is prepared by the method for preparing the catalyst according to any one of claims 1 to 12.

14. The catalyst according to claim 13, It is characterized in that The catalyst comprises an active component and a carrier, The active components are Cu and Cu 2 O, which is uniformly dispersed in the carrier; The carrier is porous amorphous SiO 2 ; The mass ratio of the active component to the carrier is 1:9 to 4:

6.

15. The catalyst according to claim 13, It is characterized in that The invention also comprises a carbon protection layer, wherein the carbon protection layer is coated on the outside of the carrier.

16. The catalyst according to claim 15, It is characterized in that The mass of the carbon coating layer is 1%-5% of the total mass of the catalyst.

17. Use of the catalyst according to any one of claims 13 to 16, It is characterized in that The catalyst is applied to the cold hydrogenation reaction of silicon tetrachloride.

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