CN114054035A - Catalyst for catalyzing silicon tetrachloride conversion and preparation method thereof - Google Patents

Catalyst for catalyzing silicon tetrachloride conversion and preparation method thereof Download PDF

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CN114054035A
CN114054035A CN202111445310.0A CN202111445310A CN114054035A CN 114054035 A CN114054035 A CN 114054035A CN 202111445310 A CN202111445310 A CN 202111445310A CN 114054035 A CN114054035 A CN 114054035A
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silicon
catalyst
copper
powder
nano
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CN114054035B (en
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吕学谦
闵中龙
王文
顾宗珍
范协诚
银波
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Xinte Energy Co Ltd
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Xinte Energy Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/83—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with rare earths or actinides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
    • B01J27/24—Nitrogen compounds
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/08—Compounds containing halogen
    • C01B33/107—Halogenated silanes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/50—Improvements relating to the production of bulk chemicals
    • Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts

Abstract

The invention provides a catalyst for catalyzing silicon tetrachloride conversion and a preparation method thereof, wherein the catalyst has a core-shell structure, the core comprises a catalyst carrier, and the shell comprises an active component; the active component comprises silicon-copper multi-element alloy, simple substance copper and nano ceramic, wherein the silicon-copper multi-element alloy comprises silicon, copper, transition metal elements and/or rare earth elements. The catalyst is applied to the cold hydrogenation reaction process, and the silicon tetrachloride directly reacts with active components, namely a silicon-copper phase and elemental copper in the catalyst, so that the catalytic reaction time is greatly shortened, and the catalytic reaction rate and the conversion rate can be effectively improved; the catalyst prepared by the mechanical alloying preparation method has the advantages of rich aperture, fine crystal grains and high defect density.

Description

Catalyst for catalyzing silicon tetrachloride conversion and preparation method thereof
Technical Field
The invention relates to the technical field of polycrystalline silicon production, and particularly relates to a catalyst for catalyzing silicon tetrachloride conversion and a preparation method thereof.
Background
A large amount of silicon tetrachloride and hydrogen chloride byproducts are generated in the production process of polycrystalline silicon, wherein the silicon tetrachloride has high pollution and cannot be directly discharged, the method for recycling the silicon tetrachloride in the industry at present is to prepare the trichlorosilane through hydrochlorination, namely, the silicon tetrachloride is catalytically converted into the trichlorosilane through a hydrochlorination reaction, and then the trichlorosilane is rectified and purified, and the catalyst is the most critical factor for determining the hydrochlorination conversion rate.
At present, a Silicon Tetrachloride (STC) cold hydrogenation process adopted by domestic polysilicon manufacturers is carried out in a fluidized bed reactor, and among a plurality of catalysts, a copper catalyst is a catalyst with high efficiency and low cost. Monovalent cuprous chloride (CuCl) is used as the catalyst because the reaction conditions of monovalent copper with silicon and/or hydrogen are milder than divalent copper and the reaction temperature is lower. In the hydrochlorination process, CuCl in the fluidized bed collides with silicon powder to react, and a silicon-copper phase catalytic active body is generated in situ; the silicon copper phase active body adsorbs silicon tetrachloride to form a dichlorosilance intermediate, the dichlorosilance intermediate reacts with hydrogen and hydrogen chloride to form trichlorosilane, desorption is carried out, and then the adsorption-reaction-desorption cyclic process is carried out, namely the catalytic reaction process is an adsorption-catalysis process. The active intermediate is preferentially formed at defect centers such as a silicon-copper interface, a crystal boundary, other types of interfaces and the like, and the density of the defect centers is a key factor for determining the activity of the catalyst.
However, in a fluidized bed reactor, the catalytic conversion of silicon tetrachloride has the following problems: (1) in the fluidized bed reactor, the particle size of cuprous chloride is gradually reduced and limited by a fluidized bed filtering system, the cuprous chloride with small size cannot be completely utilized and flows into a back-end system, and the cuprous chloride and unreacted silicon powder are abandoned together in a slurry process as wastes which are difficult to separate from other components in residual liquid, so that great waste is caused; (2) in the catalytic reaction process, cuprous chloride and silicon powder are in collision contact instead of direct contact, the contact time is short, cuprous chloride is diffused and reacts insufficiently, and the amount of a silicon-copper phase generated by in-situ reaction is small, so that the catalytic efficiency is low; (3) the catalytic active component is formed by in-situ reaction in the cold hydrogenation reaction process, the grain sizes and grain sizes of cuprous chloride and metal silicon powder are larger, the grain boundary area is small, the defect centers are fewer, the reaction activity between the metal silicon powder and the cuprous chloride is lower, the amount of the formed silicon-copper phase is smaller, and the densities of the silicon-copper interface and other defect centers are lower; (4) in the catalytic reaction process, electron transfer exists, and the adsorption and dissociation efficiency of the silicon tetrachloride on the catalyst needs to be further improved; (5) the silicon tetrachloride catalytic conversion temperature is high (500-550 ℃), crystal grains are easy to grow, and active centers are reduced; (6) in a fluidized bed, silicon tetrachloride is catalytically hydrogenated to generate trichlorosilane and hydrogen chloride, the hydrogen chloride reacts with silicon powder to generate trichlorosilane, and in the production process of metal silicon powder, the solidification rate of metal silicon melt is low, so that the grain size of the metal silicon melt is large, and the silicon powder has low reaction activity, so that the silicon powder has insufficient reaction.
In recent years, a supported catalyst prepared by using a molecular sieve, silicon dioxide, aluminum oxide and the like as carriers and supporting monovalent copper ions is developed in the industry, and compared with a pure cuprous chloride catalyst, the unit consumption of cuprous chloride is obviously reduced, but the problems cannot be effectively solved.
Disclosure of Invention
In view of the above, the invention provides a catalyst for catalyzing the conversion of silicon tetrachloride and a preparation method thereof, the catalyst has a core-shell structure, the active components have rich pore diameters and high defect density, and the catalytic conversion rate of silicon tetrachloride can be effectively improved in the cold hydrogenation reaction process.
In order to solve the technical problems, the invention adopts the following technical scheme:
in a first aspect, the invention provides a catalyst for catalyzing the conversion of silicon tetrachloride, the catalyst has a core-shell structure, the core comprises a catalyst carrier, and the shell comprises an active component;
the active component comprises silicon-copper multi-element alloy, simple substance copper and nano ceramic, wherein the silicon-copper multi-element alloy comprises silicon, copper, transition metal elements and/or rare earth elements.
Further, the transition metal element comprises at least one of chromium, nickel and titanium, and the rare earth element comprises at least one of cerium, lanthanum and yttrium.
Further, the nano ceramic comprises at least one of nano aluminum oxide, nano zirconium oxide, nano yttrium oxide, nano silicon carbide, nano silicon oxide, nano silicon nitride and nano titanium carbide.
Further, the catalyst carrier comprises a carrier raw material and a binder, wherein the carrier raw material comprises at least one of quartz powder, corundum powder, fly ash, coal gangue, clay minerals and kaolin.
Further, the mass ratio of the catalyst carrier to the active component is (20-50): (40-80).
Further, the mass ratio of the silicon-copper multi-element alloy, the elemental copper and the nano ceramic is (70-95): (2.5-15): (0.5-5).
Further, the mass fraction of copper in the silicon-copper multi-element alloy is 70-89.5%, the mass fraction of silicon is 10-25%, and the mass fraction of transition metal elements and/or rare earth elements is 0.5-15%.
In a second aspect, the present invention provides a method for preparing the catalyst as described above, the method comprising:
mixing copper powder, cuprous chloride powder, silicon powder, a modifier and an auxiliary agent, and preparing the active component powder by adopting a mechanical alloying method; mixing a carrier raw material with a binder, and granulating to prepare the catalyst carrier; mixing the active component powder with the catalyst carrier, and granulating to obtain the catalyst;
wherein the modifier is nano ceramic powder and comprises at least one of nano aluminum oxide, nano zirconium oxide, nano yttrium oxide, nano silicon carbide, nano silicon oxide, nano silicon nitride and nano titanium carbide;
the auxiliary agent is at least one of transition metal oxide, transition metal chloride, rare earth oxide and rare earth chloride.
Further, the mechanical alloying method is a mechanical ball milling method, copper powder, cuprous chloride powder, silicon powder, a modifier and an auxiliary agent are mixed, the obtained mixture is subjected to ball milling in an inert gas atmosphere, the rotating speed of the ball milling is 200-300 r/min, and the ball milling time is 10-24 hours.
In a third aspect, the present invention provides a method for catalyzing the conversion of silicon tetrachloride, wherein the method comprises:
mixing modified silicon powder, silicon powder and the catalyst in the embodiment, and introducing silicon tetrachloride at 500-550 ℃ to perform hydrochlorination;
wherein, the modified silicon powder is as follows: and carrying out ball milling on the silicon powder in an inert gas atmosphere to prepare modified silicon powder, wherein the rotating speed of the ball milling is 200-300 r/min, and the ball milling time is 10-36 h.
The technical scheme of the invention has the following beneficial effects:
the invention provides a catalyst for catalyzing silicon tetrachloride conversion, which has a core-shell structure, wherein the core comprises a catalyst carrier, and the shell comprises an active component; the active component comprises silicon-copper multi-element alloy, simple substance copper and nano ceramic, wherein the silicon-copper multi-element alloy comprises silicon, copper, transition metal elements and/or rare earth elements.
The invention has at least the following beneficial effects:
(1) the particle size of the catalyst can be regulated and controlled by controlling the size of the catalyst carrier, so that unnecessary waste caused by the over-small particle size of the conventional catalyst is reduced; the cost of the catalyst carrier is low;
(2) the catalyst is applied to the cold hydrogenation reaction process, and the silicon tetrachloride directly reacts with active components, namely a silicon-copper phase and elemental copper in the catalyst, so that the catalytic reaction time is greatly shortened, and the catalytic reaction rate and the conversion rate can be effectively improved;
(3) the active components of the catalyst comprise silicon-copper multi-component alloy, simple substance copper and nano ceramic, wherein the silicon-copper multi-component alloy comprises silicon, copper, transition metal elements and/or rare earth elements. The active components are prepared by a mechanical alloying method, and have the advantages of rich pore diameter, fine crystal grains and high defect density;
(4) a small amount of transition metal elements and/or rare earth elements are added in the silicon-copper multi-element alloy, so that the growth of crystal grains can be inhibited, and the interface defects can be increased, thereby improving the activity of active components and improving the conversion and catalytic conversion efficiency of silicon tetrachloride;
(5) the addition of transition metal elements and/or rare earth elements in the silicon-copper multi-element alloy is beneficial to promoting the migration of electrons, the dissociation of silicon tetrachloride and the formation of dichlorosilylene intermediate, and the catalytic efficiency is improved;
(6) the nano ceramic in the catalyst is uniformly distributed in the active component during overlong preparation, so that the interface defect can be increased, the growth of crystal grains in the preparation (roasting) and use processes of the catalyst can be inhibited, and the structural thermal stability of the catalyst is improved;
(7) the catalyst has a developed pore structure, can strengthen the adsorption of silicon tetrachloride and intermediate dichlorosilylene, and improves the catalytic conversion efficiency of the silicon tetrachloride.
Detailed Description
For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention in conjunction with the following examples, but it will be understood that the description is intended to illustrate the features and advantages of the invention further, and not to limit the invention.
In a first aspect, the invention provides a catalyst for catalyzing the conversion of silicon tetrachloride, the catalyst has a core-shell structure, the core comprises a catalyst carrier, and the shell comprises an active component; the active component comprises silicon-copper multi-element alloy, simple substance copper and nano ceramic, wherein the silicon-copper multi-element alloy comprises silicon, copper, transition metal elements and/or rare earth elements.
According to some embodiments of the invention, the transition metal element comprises at least one of chromium, nickel, titanium, and the rare earth element comprises at least one of cerium, lanthanum, yttrium.
According to some embodiments of the invention, the nanoceramic comprises at least one of nano-alumina, nano-zirconia, nano-yttria, nano-silicon carbide, nano-silica, nano-silicon nitride, nano-titanium carbide.
The catalyst for catalyzing the conversion of the silicon tetrachloride has a core-shell structure, wherein the core is mainly a catalyst carrier, and the shell is mainly an active component. The particle size of the catalyst can be regulated and controlled by controlling the size of the catalyst carrier, so that unnecessary waste caused by the undersize particle size of the conventional catalyst is reduced. The active components comprise silicon-copper multi-element alloy, simple substance copper and nano ceramic, wherein the silicon-copper multi-element alloy comprises silicon, copper, transition metal elements and/or rare earth elements. The catalyst is applied to the cold hydrogenation reaction process, and the silicon tetrachloride directly reacts with the active components, namely the silicon-copper phase and the elemental copper in the catalyst, so that the catalytic reaction time is greatly shortened, and the catalytic reaction rate and the conversion rate can be effectively improved. The active component is prepared by a mechanical alloying method, and has the advantages of rich aperture, fine crystal grains and high defect density. Meanwhile, a small amount of transition metal elements and/or rare earth elements are added in the silicon-copper multi-element alloy, so that on one hand, the growth of crystal grains can be inhibited and the interface defects can be increased by adding the small amount of transition metal elements and/or rare earth elements, thereby improving the activity of active components and improving the conversion catalytic conversion efficiency of silicon tetrachloride. On the other hand, the addition of the transition metal element and/or the rare earth element is beneficial to promoting the migration of electrons, the dissociation of silicon tetrachloride and the formation of a dichlorosilylene intermediate, and the catalytic efficiency is improved. In addition, the nano ceramic in the catalyst is uniformly distributed in the active component during overlong preparation, so that the interface defect can be increased, the growth of crystal grains in the preparation (roasting) and use processes of the catalyst can be inhibited, and the structural thermal stability of the catalyst is improved.
According to some embodiments of the present invention, the catalyst support comprises a support raw material and a binder, wherein the support raw material comprises at least one of quartz powder, corundum powder, fly ash, coal gangue, clay mineral and kaolin. The raw materials of the carrier are easy to obtain and low in price.
According to some embodiments of the invention, the binder comprises at least one of polyvinyl alcohol, stearic acid, a stearate salt.
According to some embodiments of the invention, the mass ratio of the catalyst carrier to the active component is (20-50): (40-80).
According to some embodiments of the invention, the mass ratio of the silicon-copper multicomponent alloy, the elemental copper and the nanoceramic is (70-95): (2.5-15): (0.5-5).
According to some embodiments of the invention, the silicon-copper multi-element alloy comprises 70% to 89.5% by mass of copper, 10% to 25% by mass of silicon, and 0.5% to 15% by mass of transition metal elements and/or rare earth elements.
In a second aspect, the present invention provides a method for preparing the catalyst as described above, the method comprising:
mixing copper powder, cuprous chloride powder, silicon powder, a modifier and an auxiliary agent, and preparing the active component powder by adopting a mechanical alloying method; mixing a carrier raw material with a binder, and granulating to prepare the catalyst carrier; mixing the active component powder with the catalyst carrier, and granulating to obtain the catalyst;
wherein the modifier is nano ceramic powder and comprises at least one of nano aluminum oxide, nano zirconium oxide, nano yttrium oxide, nano silicon carbide, nano silicon oxide, nano silicon nitride and nano titanium carbide;
the auxiliary agent is at least one of transition metal oxide, transition metal chloride, rare earth oxide and rare earth chloride.
According to some embodiments of the invention, the mechanical alloying method is a mechanical ball milling method, copper powder, cuprous chloride powder, silicon powder, a modifier and an auxiliary agent are mixed, and the obtained mixture is subjected to ball milling in an inert gas atmosphere, wherein the rotation speed of the ball milling is 200-300 r/min, and the ball milling time is 10-24 h. In the invention, the inert gas can be nitrogen, the ball-to-material ratio of ball milling is 5:1, the grinding balls are silicon nitride ceramic grinding balls, the grinding balls are grinding balls with the diameters of 14-16mm, 7-8.5mm and 2.5-3.5mm, the mixing is carried out according to the mass ratio of 1:1:1 in sequence, the rotating speed of ball milling is 200-300 r/min, and the ball milling time is 10-24 h.
According to the invention, the active component powder is prepared by adopting a mechanical alloying method, and on one hand, the active components of the catalyst can be fully and uniformly mixed by a high-energy ball milling method to form a supersaturated solid solution, increase a silicon-copper interface and increase defect centers and active sites; on the other hand, the catalyst can also play a role in refining grains, and increases defect centers and catalytic active centers. Meanwhile, cuprous chloride powder is converted into elemental copper in the preparation process, the catalytic activity of the elemental copper is high, and the catalytic efficiency of the catalyst can be further improved.
In a third aspect, the present invention provides a method for catalyzing the conversion of silicon tetrachloride, wherein the method comprises:
mixing modified silicon powder, silicon powder and the catalyst in the embodiment, and introducing silicon tetrachloride at 500-550 ℃ to perform hydrochlorination; wherein, the modified silicon powder is as follows: and carrying out ball milling on the silicon powder in an inert gas atmosphere to prepare modified silicon powder, wherein the rotating speed of the ball milling is 200-300 r/min, and the ball milling time is 10-36 h.
According to the invention, the high-energy ball milling is carried out on the silicon powder, so that the distortion energy of the silicon powder can be increased, the crystal grains can be refined, the defect centers such as crystal boundaries and the like can be increased, and the reaction activity of the silicon powder can be increased.
The invention is further illustrated by the following specific examples.
Example 1
In the catalyst in this example: according to the mass fraction, the mass fraction of the catalyst carrier is 20%, the mass fraction of the active component is 77%, and the catalyst also comprises a binder with the mass fraction of 2% (the binder is a mixture of vinyl alcohol and stearic acid, the mass ratio of the binder to the stearic acid is 1: 1), and a pore-forming agent with the mass fraction of 1% (the pore-forming agent is a mixture of ammonium bicarbonate and ammonium chloride, and the mass ratio of the pore-forming agent to the ammonium bicarbonate is 1: 1).
The catalyst carrier comprises 97.5% by mass of carrier raw materials (the carrier raw materials are a mixture of clay minerals, kaolin and fly ash, the mass ratio of the clay minerals to the kaolin to the fly ash is 1:2:2), and 2.5% by mass of binder (the binder is a mixture of vinyl alcohol and stearic acid, and the mass ratio of the vinyl alcohol to the stearic acid is 1: 1);
the active component comprises 80% by mass of silicon-copper multi-element alloy (the silicon-copper multi-element alloy is silicon-copper-nickel-cerium multi-element alloy, wherein the copper is 80% by mass, the silicon is 15% by mass, the nickel oxide is 2.5% by mass, and the cerium oxide is 2.5% by mass), 15% by mass of simple substance copper (the simple substance copper is from cuprous chloride powder, and the cuprous chloride reacts with the silicon powder to generate active simple substance copper), and 5% by mass of nano ceramic (the nano ceramic is a mixture of nano aluminum oxide and nano zirconium oxide, and the mass ratio of the two is 1: 1).
Preparing a catalyst:
(1) preparing active component powder by adopting mechanical alloying: uniformly mixing copper powder, cuprous chloride powder, metal silicon powder, a modifier (a mixture of nano aluminum oxide and nano zirconium oxide) and an auxiliary agent (a mixture of nickel oxide and cerium oxide) according to a ratio, carrying out high-energy ball milling in a nitrogen atmosphere, wherein the ball-material ratio is 5:1, the used grinding balls are silicon nitride ceramic grinding balls, the grinding balls are grinding balls with the diameters of 14-16mm, 7-8.5mm and 2.5-3.5mm, the compatibility is carried out in sequence according to the mass ratio of 1:1:1, the rotating speed of the ball mill is 240r/min, the ball milling time is 18h, and after the ball milling is finished, carrying out vacuum packaging for later use;
(2) preparing a catalyst carrier: crushing a carrier raw material, mixing with a binder, rolling ball granulation, drying and screening to prepare small balls with the diameter of 0.65-0.8 mm, and roasting for later use; the roasting temperature is 500 ℃, and the roasting time is 2 hours;
(3) catalyst forming preparation: uniformly mixing the active component powder prepared in the step (1), a binder and a pore-forming agent according to a ratio, adding the catalyst carrier prepared in the step (2), continuing rolling ball granulation, and drying and roasting when the particle size reaches a target for later use; the roasting temperature is 500 ℃, and the roasting time is 2 hours.
The catalyst prepared by the method has the particle size range of 1.0-1.8 mm, the median diameter of 1.45mm and the specific surface area of 75m2(ii) in terms of/g. The catalyst prepared by the method is used for carrying out hydrochlorination, the mass ratio of the silicon powder objezoensis to the catalyst is 200:1, and when the hydrochlorination temperature is 500-550 ℃, the catalytic conversion efficiency of the silicon tetrachloride is 30.8%.
Example 2
In the catalyst in this example: according to the mass fraction, the mass fraction of the catalyst carrier is 50%, the mass fraction of the active component is 46%, and the catalyst also comprises a binder (the binder is a mixture of vinyl alcohol and stearic acid, the mass ratio of the vinyl alcohol to the stearic acid is 1: 1) with the mass fraction of 2% and a pore-forming agent (the pore-forming agent is a mixture of ammonium bicarbonate and ammonium chloride, the mass ratio of the ammonium bicarbonate to the ammonium chloride is 1: 1).
The catalyst carrier comprises 97.5% by mass of carrier raw materials (the carrier raw materials are a mixture of clay minerals, kaolin and fly ash, the mass ratio of the clay minerals to the kaolin to the fly ash is 1:2:2), and 2.5% by mass of binder (the binder is a mixture of vinyl alcohol and stearic acid, and the mass ratio of the vinyl alcohol to the stearic acid is 1: 1);
the active component comprises 85% of silicon-copper multi-element alloy (the silicon-copper multi-element alloy is silicon-copper-nickel-cerium-yttrium multi-element alloy, wherein the mass fraction of copper is 77.5%, the mass fraction of silicon is 15%, the mass fraction of nickel oxide is 2.5%, the mass fraction of cerium oxide is 2.5%, the mass fraction of yttrium oxide is 2.5%), 12% of simple substance copper (the simple substance copper is derived from cuprous chloride powder), and 3% of nano ceramic (the nano ceramic is a mixture of nano silicon oxide and nano silicon nitride, and the mass ratio of the two is 1: 1).
Preparing a catalyst:
(1) preparing active component powder by adopting mechanical alloying: uniformly mixing copper powder, cuprous chloride powder, metal silicon powder, a modifier (a mixture of nano silicon oxide and nano silicon nitride) and an auxiliary agent (a mixture of nickel oxide, cerium oxide and yttrium oxide) according to a ratio, carrying out high-energy ball milling in a nitrogen atmosphere, wherein the ball-material ratio is 5:1, the used grinding balls are silicon nitride ceramic grinding balls, the grinding balls are grinding balls with the diameters of 14-16mm, 7-8.5mm and 2.5-3.5mm, the grinding balls are sequentially matched according to the mass ratio of 1:1:1, the rotating speed of a ball mill is 250r/min, the ball milling time is 25h, and after the ball milling is finished, carrying out vacuum packaging for later use;
(2) preparing a catalyst carrier: crushing a carrier raw material, mixing with a binder, rolling ball granulation, drying and screening to prepare small balls with the diameter of 0.30-0.40 mm, and roasting for later use; the roasting temperature is 500 ℃, and the roasting time is 2 hours;
(3) catalyst forming preparation: uniformly mixing 46 wt.% of active component powder, 2 wt.% of binder and 2 wt.% of pore-forming agent, which are prepared in the step (1), adding 50 wt.% of the catalyst carrier prepared in the step (2), continuing ball rolling and granulating, and drying and roasting when the particle size reaches a target value for later use; the roasting temperature is 500 ℃, and the roasting time is 2 hours.
The catalyst prepared by the method has the particle size range of 0.5-0.85 mm, the median diameter of 0.68mm and the specific surface area of 98m2(ii) in terms of/g. The catalyst prepared by the method is used for carrying out hydrochlorination, the mass ratio of the silicon powder objezoensis to the catalyst is 200:1, and when the hydrochlorination temperature is 500-550 ℃, the catalytic conversion efficiency of the silicon tetrachloride is 30.6%.
Example 3
In the catalyst in this example: according to the mass fraction, the mass fraction of the catalyst carrier is 30%, the mass fraction of the active component is 67%, and the catalyst also comprises a binder (the binder is a mixture of vinyl alcohol and stearic acid, the mass ratio of the vinyl alcohol to the stearic acid is 1: 1) with the mass fraction of 2% and a pore-forming agent (the pore-forming agent is a mixture of ammonium bicarbonate and ammonium chloride, the mass ratio of the ammonium bicarbonate to the ammonium chloride is 1: 1) with the mass fraction of 1%.
The catalyst carrier comprises 97.5% by mass of carrier raw materials (the carrier raw materials are a mixture of clay minerals, kaolin and fly ash, the mass ratio of the clay minerals to the kaolin to the fly ash is 1:2:2), and 2.5% by mass of binder (the binder is a mixture of vinyl alcohol and stearic acid, and the mass ratio of the vinyl alcohol to the stearic acid is 1: 1);
the active component comprises 85% of silicon-copper multi-element alloy (the silicon-copper multi-element alloy is silicon-copper-nickel-cerium-yttrium multi-element alloy, wherein the mass fraction of copper is 80%, the mass fraction of silicon is 14%, the mass fraction of nickel oxide is 2%, the mass fraction of cerium oxide is 2%, the mass fraction of yttrium oxide is 2%), 12.5% of simple substance copper (the simple substance copper is derived from cuprous chloride powder), and 2.5% of nano ceramic (the nano ceramic is a mixture of nano silicon oxide and nano silicon nitride, and the mass ratio of the two is 1: 1).
Preparing a catalyst:
(1) preparing active component powder by adopting mechanical alloying: uniformly mixing copper powder, cuprous chloride powder, metal silicon powder, a modifier (a mixture of nano silicon oxide and nano silicon nitride) and an auxiliary agent (a mixture of nickel oxide, cerium oxide and yttrium oxide) according to a ratio, carrying out high-energy ball milling in a nitrogen atmosphere, wherein the ball-material ratio is 5:1, the used grinding balls are silicon nitride ceramic grinding balls, the grinding balls are grinding balls with the diameters of 14-16mm, 7-8.5mm and 2.5-3.5mm, the grinding balls are sequentially matched according to the mass ratio of 1:1:1, the rotating speed of a ball mill is 250r/min, the ball milling time is 25h, and after the ball milling is finished, carrying out vacuum packaging for later use;
(2) preparing a catalyst carrier: crushing a carrier raw material, mixing with a binder, rolling ball granulation, drying and screening to prepare small balls with the diameter of 0.35-0.50 mm, and roasting for later use; the roasting temperature is 500 ℃, and the roasting time is 2 hours;
(3) catalyst forming preparation: mixing 67 wt.% of active component powder, 2 wt.% of binder and 1 wt.% of pore-forming agent obtained in the step (1) uniformly, adding 30 wt.% of catalyst carrier obtained in the step (2), continuing rolling ball granulation, and drying and roasting when the particle size reaches a target value for later use; the roasting temperature is 500 ℃, and the roasting time is 2 hours.
The catalyst prepared by the method has the particle size range of 0.65-1.2 mm, the median diameter of 0.90mm and the specific surface area of 88m2(ii) in terms of/g. The catalyst prepared by the method is used for carrying out hydrochlorination, the mass ratio of the silicon powder objezoensis to the catalyst is 200:1, and when the hydrochlorination temperature is 500-550 ℃, the catalytic conversion efficiency of the silicon tetrachloride is 31.2%.
Example 4
Preparing modified silicon powder: the modified silicon powder is prepared by high-energy ball milling (mechanical alloying). The preparation process comprises the steps of carrying out high-energy ball milling on the metal silicon powder in a nitrogen atmosphere, and packaging for later use after the ball milling is finished. The ball-material ratio is 5:1, specifically, the adopted grinding balls are zirconia ceramic grinding balls, the grinding balls are grinding balls with the diameters of 14-16mm, 7-8.5mm and 2.5-3.5mm, the grinding balls are combined according to the mass ratio of 1:1:1 in sequence, the rotating speed of the ball mill is 240r/min, and the ball milling time is 12 hours. The modified silicon powder is in a round cake shape, the powder is crushed and cold welded in the high-energy ball milling process, the particle size of the powder is not obviously reduced, and meanwhile, the grain refinement is carried out.
The prepared modified silicon powder, the Eschka silicon powder and the catalyst prepared in example 3 are mixed, wherein the mass fraction of the modified silicon powder is 5%, the mass fraction of the Eschka silicon powder is 94.5%, and the mass fraction of the catalyst prepared in example 3 is 0.5%. And (3) putting the mixture into a cold hydrogenation reaction system for cold hydrogenation reaction, wherein when the hydrogenation temperature of chlorine is 500-550 ℃, the catalytic conversion efficiency of the silicon tetrachloride is 32.4%. Meanwhile, the amount of slag discharged in the silicon tetrachloride system (mainly deactivated silicon powder and unreacted catalyst) is reduced by 7.1%.
Comparative example
The orosilicon powder and cuprous chloride are mixed according to the proportion (the mixing proportion is the same as that in example 3), and the reaction is carried out according to the cold hydrogenation reaction condition in example 3, so that the catalytic conversion efficiency of the silicon tetrachloride is 24.6 percent.
Unless defined otherwise, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs. The use of "first," "second," and similar terms in the present application do not denote any order, quantity, or importance, but rather the terms are used to distinguish one element from another. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships are changed accordingly.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (10)

1. The catalyst for catalyzing the conversion of silicon tetrachloride is characterized by having a core-shell structure, wherein the core comprises a catalyst carrier, and the shell comprises an active component;
the active component comprises silicon-copper multi-element alloy, simple substance copper and nano ceramic, wherein the silicon-copper multi-element alloy comprises silicon, copper, transition metal elements and/or rare earth elements.
2. The catalyst of claim 1, wherein the transition metal element comprises at least one of chromium, nickel, and titanium, and the rare earth element comprises at least one of cerium, lanthanum, and yttrium.
3. The catalyst of claim 1, wherein the nanoceramic comprises at least one of nano-alumina, nano-zirconia, nano-yttria, nano-silicon carbide, nano-silica, nano-silicon nitride, and nano-titanium carbide.
4. The catalyst of claim 1, wherein the catalyst support comprises a support material and a binder, and the support material comprises at least one of quartz powder, corundum powder, fly ash, coal gangue, clay minerals, and kaolin.
5. The catalyst according to claim 1, wherein the mass ratio of the catalyst carrier to the active component is (20-50): (40-80).
6. The catalyst according to claim 1, wherein the mass ratio of the silicon-copper multicomponent alloy, the elemental copper and the nanoceramic is (70-95): (2.5-15): (0.5-5).
7. The catalyst according to claim 1, wherein the mass fraction of copper in the silicon-copper multi-element alloy is 70 to 89.5%, the mass fraction of silicon is 10 to 25%, and the mass fraction of the transition metal element and/or the rare earth element is 0.5 to 15%.
8. A method for preparing the catalyst according to any one of claims 1 to 7, wherein the method comprises:
mixing copper powder, cuprous chloride powder, silicon powder, a modifier and an auxiliary agent, and preparing the active component powder by adopting a mechanical alloying method; mixing a carrier raw material with a binder, and granulating to prepare the catalyst carrier; mixing the active component powder with the catalyst carrier, and granulating to obtain the catalyst;
wherein the modifier is nano ceramic powder and comprises at least one of nano aluminum oxide, nano zirconium oxide, nano yttrium oxide, nano silicon carbide, nano silicon oxide, nano silicon nitride and nano titanium carbide;
the auxiliary agent is at least one of transition metal oxide, transition metal chloride, rare earth oxide and rare earth chloride.
9. The preparation method according to claim 8, wherein the mechanical alloying method is a mechanical ball milling method, the copper powder, the cuprous chloride powder, the silicon powder, the modifier and the auxiliary agent are mixed, the obtained mixture is subjected to ball milling in an inert gas atmosphere, the rotation speed of the ball milling is 200-300 r/min, and the ball milling time is 10-24 h.
10. A method for catalyzing the conversion of silicon tetrachloride is characterized by comprising the following steps:
mixing modified silicon powder, silicon powder and the catalyst of any one of claims 1 to 7, and introducing silicon tetrachloride at 500 to 550 ℃ to perform hydrochlorination;
wherein, the modified silicon powder is as follows: and carrying out ball milling on the silicon powder in an inert gas atmosphere to prepare modified silicon powder, wherein the rotating speed of the ball milling is 200-300 r/min, and the ball milling time is 10-36 h.
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