Process for the catalytic cleavage of polychlorosiloxanes to produce chlorosilanes

Abstract

The application provides a method for preparing chlorosilane by catalytic cracking of polychlorosiloxane, which comprises the following steps: adding high-boiling material, a chlorine source, a catalyst and a reducing agent into a reactor to generate silicon tetrachloride through a catalytic cracking reaction; the high-boiling material comprises at least one of polychlorosilane and polychlorosiloxane; the catalyst is a supported catalyst, the carrier material of the catalyst is a porous material, and the active component of the catalyst comprises at least one of copper, nickel, zinc and rare earth elements. The method can effectively open Si-Si bonds and Si-O bonds, and realize the cracking of high-boiling materials such as polychlorosilane and polychlorosiloxane generated in the production process of polysilicon, especially the cracking of oxygen-containing polychlorosilane. Under the joint action of the reducing agent, the catalyst and the silicon-based additive, the conversion rate of polychlorosiloxane is higher, and the energy consumption of the reaction can be effectively reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalytic cracking of polychlorosiloxane, and particularly relates to a method for preparing chlorosilane by catalytic cracking of polychlorosiloxane. BACKGROUND

[0002] Trichlorosilane (TCS) is an important raw material for preparing polysilicon, which is generally synthesized by a synthesis reaction of silicon and hydrogen chloride, or prepared by a cold hydrogenation reaction of silicon powder, hydrogen and silicon tetrachloride. However, whether it is a synthesis reaction or a cold hydrogenation reaction, in addition to the target products such as trichlorosilane and silicon tetrachloride, a certain amount of polychlorosilane and / or polychlorosiloxane by-products will also be generated, such as tetrachlorodisiloxane (H2Si2OCl4), pentachlorodisiloxane (HSi2OCl5), pentachlorodisilane (HSi2Cl5), hexachlorodisiloxane (Si2OCl6) and hexachlorodisilane (Si2Cl6). Compared with trichlorosilane and silicon tetrachloride, polychlorosilane and polychlorosiloxane have a higher boiling point, which is generally referred to as silicon-containing high-boiling substances.

[0003] The silicon-containing high-boiling substances have a high boiling point and a large viscosity, and are easy to be enriched in the system. If the high-boiling substances are not removed in time, it will cause the efficiency of the heating equipment to decrease and the pipeline to be blocked, which is not conducive to the safe and stable operation of the equipment. For the treatment of silicon-containing high-boiling substances, the industry initially adopted the following method: first, trichlorosilane and silicon tetrachloride were heated and volatilized to enrich the silicon-containing high-boiling substances, and then the silicon-containing high-boiling substances were hydrolyzed together with the deactivated silicon powder and metal chlorides as slurry for slagging treatment. However, this method has the following problems: (1) After hydrolysis, the silicon dioxide and silicate are treated as waste, and the effective use of silicon atoms and chlorine atoms in the silicon-containing high-boiling substances cannot be realized, resulting in a great waste of silicon and chlorine elements; (2) A large amount of hydrogen chloride is generated during the hydrolysis process, which needs to be neutralized by a large amount of alkali, resulting in a high alkali consumption; (3) It causes unnecessary waste of silicon powder and metal chlorides. Research results show that the reaction of silicon and chlorine is an exothermic reaction with a reaction heat of 660 kJ / mol, which is a good heat supplement agent and can significantly reduce the energy consumption required for the reaction. However, the deactivated silicon powder and single crystal silicon cutting powder have low activity, which limits their effective use.

[0004] CN 102232080 A proposes a method for catalytic cracking of polychlorosilane and polychlorosiloxane to prepare chlorosilane, the catalyst used is titanium chloride, tin tetrachloride, tin dichloride, iron chloride, aluminum trichloride, and platinum group metal catalyst, which makes the cracking reaction of polychlorosilane and / or polychlorosiloxane form monomer chlorosilane (HSiCl3 and SiCl4) and higher-order polychlorosilane and polychlorosiloxane; however, the catalyst in this patent is easy to lose, the utilization rate is not high, the cocatalyst (platinum group) is expensive, and when the polymerization degree of polychlorosiloxane reaches 4 or more, a solid is formed, which cannot be further cracked, affecting the catalytic conversion efficiency. US5922893A reports a method for preparing organosilicon monomers by reacting organosilicon high-boiling substances with hydrogen chloride using organic amine as catalyst. This method has poor cracking effect on oxygen-containing high-boiling substances, and the chlorosilane raw material containing polychlorosilane and polychlorosiloxane has high metal ions, which is easy to form complex with organic amine functional groups, causing catalyst poisoning and affecting catalytic conversion efficiency. CN 108658082A discloses a high-boiling substance cracking process in polysilicon production. This method needs to separate the high-boiling substance from the metal chloride before the cracking reaction occurs, and the process route is complex, with high one-time investment. In addition, compared with Si-Si bond, Si-O bond has higher bond energy, and oxygen-containing high-boiling substance is more difficult to crack than non-oxygen-containing high-boiling substance, so the above technical solutions have poor cracking effect on oxygen-containing high-boiling substance. SUMMARY

[0005] Therefore, the present application provides a method for catalytic cracking of polychlorosiloxane to prepare chlorosilane, which can effectively crack the high-boiling substance generated in the production of polysilicon and organosilicon, especially oxygen-containing high-boiling substance.

[0006] To solve the above technical problems, the present application adopts the following technical solutions:

[0007] The present application provides a method for catalytic cracking of polychlorosiloxane to prepare chlorosilane, which comprises adding high-boiling substance raw material, chlorine source, catalyst and reducing agent into a reactor to generate silicon tetrachloride through catalytic cracking reaction; and the high-boiling substance raw material comprises at least one of polychlorosilane and polychlorosiloxane.

[0008] The catalyst is a supported catalyst, the carrier raw material of the catalyst is a porous material, and the active component of the catalyst comprises at least one of copper, nickel, zinc and rare earth elements.

[0009] Further, the method further adds a silicon-based additive into the reactor; the silicon-based additive comprises at least one of metal silicon powder, deactivated silicon powder and monocrystalline silicon cutting powder; and / or

[0010] The high-boiling material includes at least one of tetrachlorodisiloxane, pentachlorodisiloxane, hexachlorodisiloxane, pentachlorodisilane and hexachlorodisilane.

[0011] Further, the reducing agent includes a solid reducing agent and a gaseous reducing agent, wherein the solid reducing agent includes at least one of activated carbon, graphite, coal powder, coal gangue and petroleum coke, and the gaseous reducing agent includes at least one of hydrogen, carbon monoxide and a carbon-containing silicon-based high-boiling material.

[0012] Further, the catalyst is a gradient multi-element catalyst, which includes an inner core catalyst and an outer shell catalyst, the outer shell catalyst is coated on the outer surface of the inner core catalyst, and the content of active components in the inner core catalyst is higher than that in the outer shell catalyst.

[0013] Further, the pore size of the carrier raw material of the inner core catalyst is ≤1.5 nm, and the pore volume is 0.02-0.1 cm 3 / g; the pore size of the carrier raw material of the outer shell catalyst is ≥2.5 nm, and the pore volume is ≥0.1 cm 3 / g.

[0014] Further, the carrier raw material of the inner core catalyst and the outer shell catalyst includes at least one of activated carbon, silica-alumina gel, molecular sieve, diatomite, activated alumina, silica gel and activated clay.

[0015] The active components of the inner core catalyst and the outer shell catalyst include at least one of copper nitrate, cuprous chloride, copper chloride, nickel nitrate, nickel chloride, zinc nitrate, zinc chloride, cerium nitrate, lanthanum nitrate and yttrium chloride.

[0016] Further, the preparation method of the catalyst includes the following steps: preparing an inner core carrier, uniformly mixing the carrier raw material of the inner core catalyst with a binder, balling, drying, screening and reserving; preparing a catalyst carrier, uniformly mixing the carrier raw material of the outer shell catalyst, a binder and a deoxidizing agent, adding the inner core carrier, continuously balling, drying, roasting and reserving; loading active components, dissolving the active components in a solvent to prepare an impregnation solution, immersing the catalyst carrier in the impregnation solution, taking out and drying to obtain the catalyst.

[0017] Further, the chlorine source is a chlorine-containing gas, which includes at least one of chlorine, hydrogen chloride and chloromethane.

[0018] Further, in the method, the high-boiling material and the chlorine source are mixed and heated to be vaporized, and then are introduced into the reactor; and / or

[0019] The volume flow ratio of the high-boiling material gas to the chlorine source gas is (1:10)-(10:1).

[0020] Further, the temperature for heating and vaporizing the high-boiling material and the chlorine source is 50-200 DEG C; and / or the reaction gas velocity into the reactor is 0.01-10 m / s.

[0021] The beneficial effects of the above technical solution of the present application are as follows:

[0022] The present application provides a method for preparing chlorosilane by catalytic cracking of polychlorosiloxane, which comprises adding high-boiling material, chlorine source, catalyst and reducing agent into a reactor to generate silicon tetrachloride through catalytic cracking reaction; the high-boiling material comprises at least one of polychlorosilane and polychlorosiloxane; the catalyst is a supported catalyst, the carrier material of the catalyst is a porous material, and the active component of the catalyst comprises at least one of copper, nickel, zinc and rare earth elements.

[0023] The method provided in the present application has at least the following advantages:

[0024] (1) In the presence of catalyst and reducing agent, high-boiling material and chlorine source are introduced into the reactor to generate reduction, chlorination and chlorination cracking reaction. In the reaction process, Si-Si bond and Si-O bond are opened to realize the cracking of high-boiling material such as polychlorosilane and polychlorosiloxane generated in the production process of polysilicon, especially the cracking of oxygen-containing polychlorosilane;

[0025] (2) The reaction heat generated by the silicon chlorination reaction can provide a heat supplement for the cracking reaction of polychlorosiloxane, reduce the energy consumption required by the reaction, increase the added value of silicon-containing industrial waste such as deactivated silicon powder and silicon mud, and enrich the source of silicon tetrachloride; the combined action of silicon-based additives and catalysts promotes the reduction and cracking reactions, and improves the conversion efficiency;

[0026] (3) The catalyst in the present application is a gradient multi-component catalyst. Compared with the shell catalyst, the active component content in the core catalyst is higher, which can effectively solve the problem of reduced catalytic performance caused by smaller particle size of the catalyst due to wear and reaction;

[0027] (4) The high-boiling material generated in the production process of polysilicon is used as the raw material to produce silicon tetrachloride, which reduces the silicon consumption; realizes the green recycling of high-boiling material, deactivated silicon powder and other silicon-containing industrial waste in the production process of polysilicon, reduces the amount of waste emissions, reduces environmental pollution, and reduces the consumption of chlorine and alkali. DETAILED DESCRIPTION

[0028] In order to further understand the present application, the preferred embodiments of the present application are described below in conjunction with examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present application, but not for limiting the present application.

[0029] The application provides a method for preparing chlorosilane by catalytic cracking of polychlorosiloxane, which comprises the following steps: adding high-boiling raw material, chlorine source, catalyst and reducing agent into a reactor to generate silicon tetrachloride through catalytic cracking reaction; the high-boiling raw material comprises at least one of polychlorosilane and polychlorosiloxane; wherein the catalyst is a supported catalyst, the carrier raw material of the catalyst is a porous material, and the active component of the catalyst comprises at least one of copper, nickel, zinc and rare earth elements.

[0030] The application provides a method for preparing chlorosilane by catalytic cracking of polychlorosiloxane, which is a gas-solid phase reaction. In the presence of a catalyst and a reducing agent, high-boiling raw material and chlorine source are introduced into a reactor to generate silicon tetrachloride through reduction, chlorination and chlorination cracking reaction. In the reaction process, Si-Si bond and Si-O bond are opened to realize the cracking of high-boiling substances such as polychlorosilane and polychlorosiloxane generated in the production process of polysilicon, especially the cracking of oxygen-containing polychlorosilane. According to some embodiments of the application, the method can also add a silicon-based additive to the reactor; the silicon-based additive comprises at least one of metal silicon powder, deactivated silicon powder and single crystal silicon cutting powder. The high-boiling raw material can comprise at least one of tetrachlorodisiloxane, pentachlorodisiloxane, hexachlorodisiloxane, pentachlorodisilane and hexachlorodisilane.

[0031] According to some embodiments of the application, the mass fraction of metal silicon powder in the silicon-based additive is 0-30%; and the particle size of the silicon-based additive is 0.1-1.5 mm.

[0032] In the application, a silicon-based additive can also be added to the reactor as raw material for reaction. The benefits of adding a silicon-based additive mainly include: (1) using the reaction heat generated by the silicon chlorination reaction to provide a heat supplement for the cracking reaction of polychlorosiloxane, thereby reducing the energy consumption required by the reaction; (2) using the combined action of the silicon-based additive and the catalyst to promote the reduction and cracking reactions, thereby improving the conversion efficiency; and (3) increasing the added value of deactivated silicon powder, silicon mud and other silicon-containing industrial waste, thereby enriching the source of silicon tetrachloride raw material.

[0033] According to some embodiments of the application, the reducing agent comprises a solid reducing agent and a gas reducing agent, wherein the solid reducing agent comprises at least one of activated carbon, graphite, coal powder, coal gangue and petroleum coke, and the gas reducing agent comprises at least one of hydrogen, carbon monoxide and carbon-containing silicon-based high-boiling substances. In the application, the particle size of the solid reducing agent is 0.01-5 mm. The molar ratio of the reducing agent to the high-boiling raw material is (0.1:1)-(10:1).

[0034] According to some embodiments of the present invention, the high-boiling-point raw material can be polychlorosiloxane, a mixture of polychlorosilane, and silicon tetrachloride; wherein the polychlorosiloxane is a mixture of tetrachlorodisiloxane, pentachlorodisiloxane, and hexachlorodisiloxane, and the polychlorosilane is a mixture of pentachlorodisilane and hexachlorodisiloxane. Specifically, the mass fraction of the polychlorosiloxane is 5-90%, the mass fraction of the polychlorosilane is 5-65%, and the balance is silicon tetrachloride. In the present invention, silicon tetrachloride is produced using high-boiling points generated during the polysilicon production process as raw materials, providing a new method and material source for the preparation of silicon tetrachloride. At the same time, it achieves the green recycling of high-boiling points during the polysilicon production process and reduces waste emissions.

[0035] According to some embodiments of the present invention, the reactor is a fixed bed reactor, a fluidized bed reactor, a tubular reactor, a bubble reactor, a tank reactor, an S-type reactor, a ceramic reactor, etc.

[0036] According to some embodiments of the present invention, the catalyst is a gradient multi-component catalyst, which includes a core catalyst and a shell catalyst. The shell catalyst is coated on the outer surface of the core catalyst, and the content of active components in the core catalyst is higher than that in the shell catalyst.

[0037] According to some embodiments of the present invention, the pore size of the carrier material of the core catalyst is ≤1.5nm, and the pore volume is 0.02-0.1cm 3 / g; the pore size of the carrier material of the shell catalyst is ≥2.5nm, and the pore volume is ≥0.1cm 3 / g.

[0038] According to some embodiments of the present invention, the mass ratio of the catalyst to the high-boiling material is (1-10):100.

[0039] According to some embodiments of the present invention, the carrier raw materials of the core catalyst and the shell catalyst include at least one of activated carbon, silica-alumina gel, molecular sieve, diatomaceous earth, activated alumina, silica gel, and activated clay; the active components of the core catalyst and the shell catalyst include at least one of copper nitrate, cuprous chloride, cupric chloride, nickel nitrate, nickel chloride, zinc nitrate, zinc chloride, cerium nitrate, lanthanum nitrate, and yttrium chloride.

[0040] According to some embodiments of the present invention, the method for preparing the catalyst comprises the following steps:

[0041] (1) Preparation of core carrier: uniformly mix the carrier raw material of the core catalyst with the binder, granulate with a rolling ball, dry, sieve, and set aside;

[0042] (2) Preparation of catalyst carrier: the carrier raw material, binder and deoxidizer of the shell catalyst are mixed uniformly, then the core carrier is added, and the balling is continued, and then the catalyst carrier is dried and calcined for standby;

[0043] (3) Active component loading: the active component is dissolved in a solvent to prepare an impregnation solution, the catalyst carrier is impregnated in the impregnation solution, and the catalyst is obtained by taking out and drying.

[0044] According to some embodiments of the present application, in the preparation of the catalyst, the binder used is one or a mixture of two of polyvinyl alcohol, stearic acid and stearate, and the mass fraction of the binder is 0.1-5%.

[0045] According to some embodiments of the present application, the deoxidizer in step (2) comprises at least one of graphite and activated carbon.

[0046] According to some embodiments of the present application, the solvent of the impregnation solution in step (3) is an aqueous solution of hydrochloric acid or an aqueous solution of ammonium chloride, and the concentration is 0.25-2.5 mol / L.

[0047] According to some embodiments of the present application, the surfactant in step (3) is a mixture of polyethylene glycol and an ethylene oxide-propylene oxide copolymer, and the molecular weight is greater than 1000; the viscosity regulator is one or a mixture of two or more of methyl cellulose, carboxymethyl cellulose and polyacrylamide, and the molecular weight is greater than 500; and the mass fraction of the surfactant and the viscosity regulator is 0.1-1.2%.

[0048] According to some embodiments of the present application, the calcination atmosphere in step (2) is nitrogen, the calcination temperature is 300-650℃, and the calcination time is 4-16h.

[0049] According to some embodiments of the present application, in step (3), the concentration of the active component is 3-10 mol / L; and / or the impregnation time is 2-24h.

[0050] According to some embodiments of the present application, the particle size of the catalyst is 0.5-3mm.

[0051] The present invention provides a catalyst with a double gradient structure, which includes a core catalyst and a shell catalyst, wherein the shell catalyst is coated on the outer surface of the core catalyst. In the present invention, by providing the carrier raw material of the core catalyst with a smaller pore size and pore volume, it can be ensured that the loss of active components of the catalyst during the drying process is less, so that the active components in the core catalyst are higher. At the same time, in the present invention, when preparing the catalyst, the viscosity, fluidity, surface tension and capillary force of the solution in the catalyst can be adjusted through the combined action of a surfactant and a viscosity modifier, making it more difficult for the active components that have penetrated into the interior of the carrier to move, thereby suppressing the loss of the catalyst during the drying process and making the active components in the core catalyst higher. This can effectively solve the problem of catalyst particle size reduction due to wear and reaction, which ultimately causes reduced catalytic performance.

[0052] According to some embodiments of the present invention, the pore size of the carrier material of the core catalyst is ≤1.5nm, and the pore volume is 0.02-0.1cm 3 / g; the pore size of the carrier material of the shell catalyst is ≥2.5nm, and the pore volume is ≥0.1cm 3 / g.

[0053] According to some embodiments of the present invention, the chlorine source is a chlorine-containing gas, including at least one of chlorine, hydrogen chloride, and methyl chloride.

[0054] According to some embodiments of the present invention, in the method: the high boiling point raw material and the chlorine source are mixed, heated and vaporized, and then introduced into the reactor; and / or the volume flow ratio of the high boiling point raw material gas and the chlorine source gas is (1:10) to (10:1).

[0055] According to some embodiments of the present invention, the temperature at which the high-boiling material and the chlorine source are heated and vaporized is 50-200° C.; and / or the reaction gas velocity introduced into the reactor is 0.01-10 m / s.

[0056] According to some embodiments of the present invention, the method for preparing chlorosilanes by catalytic cracking of polychlorosiloxanes comprises the following steps:

[0057] (1) Mixing the catalyst, reducing agent, and silicon-based additive and adding them to the reactor;

[0058] (2) The high-boiling material is heated and vaporized, mixed with the chlorine source gas in proportion, and introduced into the reactor; the temperature of the reactor is adjusted to carry out the reaction.

[0059] According to some embodiments of the present invention, the mass ratio of the catalyst to the reducing agent is (1:5) to (5:1), preferably, the mass ratio of the catalyst to the reducing agent is (1:2) to (2:1), and more preferably, the mass ratio of the catalyst to the reducing agent is 1:1. The mass ratio of the catalyst to the silicon-based additive is (1:10) to (10:1), preferably, the mass ratio of the catalyst to the silicon-based additive is (4:1) to (1:1), and more preferably, the mass ratio of the catalyst to the reducing agent is 2:1.

[0060] According to some embodiments of the present invention, the reaction temperature for the catalytic cracking of polychlorosiloxane is 200-1200°C.

[0061] The present invention will be further described below through some specific examples.

[0062] The components of the high-boiling material raw materials described in the following examples are shown in Table 1; the high-boiling material raw materials include: tetrachlorodisiloxane, pentachlorodisiloxane, hexachlorodisiloxane, pentachlorodisiloxane and hexachlorodisiloxane; the polychlorosiloxane includes: tetrachlorodisiloxane, pentachlorodisiloxane and hexachlorodisiloxane.

[0063] Table 1

[0064]

[0065] Example 1

[0066] Preparation of catalyst: The carrier used for the catalyst in this embodiment is silica-alumina gel, and the loaded active component is a mixture of zinc chloride and nickel chloride.

[0067] The steps for preparing the catalyst are:

[0068] (1) Preparation of core carrier beads: Select pore size of 0.55-0.91 nm and pore volume of 0.063 cm 3 / g of silica-alumina gel was used as the core carrier; polyvinyl alcohol and stearic acid were mixed in a mass ratio of 1:1 as the adhesive;

[0069] The core carrier raw materials and the adhesive are mixed evenly, granulated by rolling, dried, and sieved to prepare core carrier pellets with a particle size of 0.1 to 0.3 mm, which are ready for use. The mass fraction of the adhesive is 0.95%, and the drying temperature is 100 to 110°C.

[0070] (2) Preparation of catalyst carrier: Select pore size of 2.5-4.5 nm and pore volume of 0.18 cm 3 / g of silica-alumina gel was used as the shell carrier; polyvinyl alcohol and stearic acid were mixed in a mass ratio of 1:1 as the adhesive; activated carbon was selected as the deoxidizer;

[0071] The shell carrier raw material, adhesive, and deoxidizer are uniformly mixed, wherein the mass fraction of the adhesive is 1% and the mass fraction of the deoxidizer is 0.5%; the core carrier beads prepared in step (1) are added, and the pelletizing is continued. When the particle size reaches 1 to 2 mm, the pellets are dried and calcined at a temperature of 420 to 650° C. to obtain a catalyst carrier;

[0072] (3) Active ingredient loading:

[0073] Preparation of the impregnation solution: The selected impregnation solution solvent is a hydrochloric acid aqueous solution with a concentration of 1.2 mol / L. The active components, zinc chloride and nickel chloride, are dissolved in the hydrochloric acid aqueous solution, and a surfactant viscosity modifier is added thereto; wherein the concentration of zinc chloride is 3 mol / L, and the concentration of nickel chloride is 3 mol / L. The selected surfactant is a mixture of polyethylene glycol and ethylene oxide-propylene oxide copolymer with a molecular weight greater than 1000, and the selected viscosity modifier is methyl cellulose with a molecular weight greater than 500. The mass fraction of the surfactant and viscosity modifier is 0.69% each.

[0074] The catalyst support prepared in step (2) was immersed in the impregnation solution for 12 hours, and then dried at 105-110° C. in a nitrogen atmosphere for 6 hours for standby use;

[0075] (4) Calcination: The catalyst dried in step (4) was calcined in a nitrogen atmosphere at a temperature of 430-450° C. for 12 h to obtain catalyst A.

[0076] Catalytic cracking of polychlorosiloxanes:

[0077] The reducing agent in this embodiment is a mixture of coal gangue and petroleum coke, with a particle size range of 0.1 to 0.3 mm, wherein the mass ratio of coal gangue to petroleum coke is 1:1; the silicon-based additive is a mixture of metallic silicon powder and deactivated silicon powder, wherein the mass fraction of metallic silicon powder is 25%; and the chlorine source is chlorine gas.

[0078] (1) Catalyst A, reducing agent, and silicon-based additive were mixed in a mass ratio of 2:2:0.5, added to a fluidized bed reactor, and nitrogen was introduced to fluidize the reactor;

[0079] (2) The high-boiling material (components shown in Table 1) was heated to 155-160°C and vaporized, mixed with chlorine in a certain ratio (the volume flow ratio of the high-boiling material to chlorine was 1.2:1), and introduced into the fluidized bed reactor at a gas velocity of 0.55 m / s; wherein the mass ratio of catalyst A to the high-boiling material was 1:10;

[0080] (3) Adjust the frequency of the fluidized bed to increase the temperature of the fluidized bed. When the frequency of the induction heating is 325 kw, the system begins to crack and generate products, and the product contains silicon tetrachloride raw material. At this time, the temperature of the fluidized bed is 285°C, and the induction heating power of the fluidized bed is reduced. The reaction continues. In this embodiment, when the frequency of the induction heating of the fluidized bed is reduced to 120 kw or less, the reaction of the fluidized bed stops. Therefore, the frequency of the induction heating of the fluidized bed is kept at 125 kw to continue the reaction. After the reaction continues for 30 min, the reaction is stopped, and the product is sampled and analyzed. According to the calculation, the conversion rate of the high-boiling substance is about 87%, the conversion rate of the polychlorosiloxane is about 83%, and the conversion rate of the deactivated silicon powder is about 65%.

[0081] Example 2

[0082] Preparation of catalyst B: The preparation method of the catalyst is the same as that of Example 1, except that in this embodiment, the active alumina with a pore size of 0.67-0.84 nm and a pore volume of 0.073 cm 3 / g is selected as the inner core carrier, and the active alumina with a pore size of 2.8-4.3 nm and a pore volume of 0.21 cm 3 / g is selected as the outer shell carrier. At the same time, the active component is a mixture of zinc chloride, nickel chloride, and lanthanum nitrate, wherein the concentration of zinc chloride is 2 mol / L, the concentration of nickel chloride is 2 mol / L, and the concentration of lanthanum nitrate is 2 mol / L.

[0083] Catalytic cracking of polychlorosiloxane:

[0084] The reducing agent in this embodiment is a mixture of coal gangue and coal powder with a particle size range of 0.1-0.3 mm, and the mass ratio of coal powder to coal gangue is 1:1; the silicon-based additive is a mixture of metal silicon powder and single crystal silicon cutting powder, wherein the mass fraction of metal silicon powder is 15%; and the chlorine source is chlorine gas.

[0085] (1) Mix catalyst B, reducing agent, and silicon-based additive in a mass ratio of 2:2:0.6, and add them to the fluidized bed reactor. Nitrogen is introduced to make it in a fluidized state;

[0086] (2) Heat the high-boiling substance raw material (components are the same as in Example 1) to 165-170°C to vaporize, mix it with chlorine gas in a certain proportion (the volume flow ratio of high-boiling substance raw material to chlorine gas is 1.3:1), and introduce it into the fluidized bed reactor at a gas velocity of 0.53 m / s; wherein the mass ratio of catalyst B to high-boiling substance raw material is 1:10;

[0087] (3) Adjust the frequency of the fluidized bed to increase the temperature of the fluidized bed. When the frequency of the induction heating is 325 kw, the system begins to crack and generate products, and the silicon tetrachloride raw material is extracted from the products. At this time, the temperature of the fluidized bed is 285°C. The induction heating power of the fluidized bed is reduced, and the reaction continues. In this embodiment, when the frequency of the induction heating of the fluidized bed is reduced to below 80 kw, the reaction of the fluidized bed stops. Therefore, the frequency of the induction heating of the fluidized bed is kept at 90 kw to continue the reaction. After the reaction continues for 30 min, the reaction is stopped, and the products are sampled and analyzed. According to the calculation, the conversion rate of the high-boiling substance is about 86.5%, the conversion rate of the polychlorosiloxane is about 84.6%, and the conversion rate of the single-crystal silicon cutting powder is about 86.7%.

[0088] Example 3

[0089] Preparation of catalyst C: The preparation method of the catalyst is the same as that in Example 1, except that in this embodiment, the catalyst carrier selected is activated carbon, in which activated carbon with a pore size of 0.77-0.92 nm and a pore volume of 0.081 cm 3 / g is selected as the inner core carrier, and activated carbon with a pore size of 2.9-5.6 nm and a pore volume of 0.23 cm 3 / g is selected as the outer shell carrier. At the same time, the active component is a mixture of zinc chloride, nickel chloride, copper chloride, lanthanum nitrate, and cerium nitrate, in which the concentration of zinc chloride is 2 mol / L, the concentration of nickel chloride is 2 mol / L, the concentration of copper chloride is 2 mol / L, and the concentration of lanthanum nitrate is 2 mol / L.

[0090] Catalytic cracking of polychlorosiloxane:

[0091] In this embodiment, the reducing agent is a mixture of activated carbon and petroleum coke with a particle size range of 0.15-0.34 mm, and the mass ratio of activated carbon to petroleum coke is 2:1; the silicon-based additive is a mixture of metal silicon powder, deactivated silicon powder, and single-crystal silicon cutting powder, in which the mass ratio of metal silicon powder, deactivated silicon powder, and single-crystal silicon cutting powder is 4:4:2; and the chlorine source is chlorine gas.

[0092] (1) Mix the catalyst C, the reducing agent, and the silicon-based additive in a mass ratio of 2:2:1, and add them to the fluidized bed reactor. Then, introduce nitrogen gas to make them in a fluidized state;

[0093] (2) Heat the high-boiling substance raw material (components are the same as in Example 1) to 165-170°C to vaporize, mix it with chlorine gas in a certain proportion (the volume flow ratio of the high-boiling substance raw material to chlorine gas is 1.3:1), and introduce it into the fluidized bed reactor at a gas speed of 0.53 m / s; wherein the mass ratio of the catalyst C to the high-boiling substance raw material is 1:10;

[0094] (3) Adjust the induction heating frequency of the fluidized bed to increase the temperature of the fluidized bed. When the induction heating frequency is 325 kw, the system begins to generate cracking reaction and products, and the silicon tetrachloride raw material is extracted from the products. At this time, the temperature of the fluidized bed is 285°C. The induction heating power of the fluidized bed is reduced to 0 kw. The reaction continues to proceed. After the reaction continues for 30 min, the reaction is stopped. The product is sampled and analyzed. According to the calculation, the one-time conversion rate of the high-boiling substance is about 88.9%. The one-time conversion rate of the polysiloxane is greater than about 92.4%. The conversion rate of the deactivated silicon powder is about 82%. The conversion rate of the single crystal silicon cutting powder is about 95%.

[0095] Example 4

[0096] The catalyst in this example is the same as the catalyst in Example 3, which is catalyst C.

[0097] Polychlorosiloxane catalytic cracking:

[0098] The reducing agent in this example is a reducing gas, which is a carbon-containing high-boiling substance containing a silicon group generated in the production process of a silicone monomer. The silicon-based additive is a mixture of metal silicon powder, deactivated silicon powder, and single crystal silicon cutting powder, wherein the mass ratio of the metal silicon powder, the deactivated silicon powder, and the single crystal silicon cutting powder is 4:4:2. The chlorine source is chlorine gas.

[0099] (1) Mix the catalyst C and the silicon-based additive according to a mass ratio of 2:1, and add them to the fluidized bed reactor. Nitrogen is introduced to make it in a fluidized state.

[0100] (2) Heat the high-boiling substance raw material (components are the same as in Example 1) to 165-170°C to vaporize, mix it with the reducing gas and the chlorine gas according to a certain proportion (the volume flow ratio of the high-boiling substance raw material: reducing gas: chlorine gas is 1.3:1.3:1), and introduce it into the fluidized bed reactor at a gas velocity of 0.53 m / s. The mass ratio of the catalyst C to the high-boiling substance raw material is 1:10.

[0101] (3) Adjust the induction heating frequency of the fluidized bed to increase the temperature of the fluidized bed. When the induction heating frequency is 325 kw, the system begins to generate cracking reaction and products, and the silicon tetrachloride raw material is extracted from the products. At this time, the temperature of the fluidized bed is 285°C. The induction heating power of the fluidized bed is reduced to 0 kw. The reaction continues to proceed. After the reaction continues for 30 min, the reaction is stopped. The product is sampled and analyzed. According to the calculation, the one-time conversion rate of the high-boiling substance is about 88.9%. The one-time conversion rate of the polysiloxane is greater than about 92.4%. The conversion rate of the deactivated silicon powder is about 82%. The conversion rate of the single crystal silicon cutting powder is about 95%.

[0102] Example 5

[0103] The catalyst in this example is the same as that in Example 1, which is catalyst A.

[0104] Catalytic cracking of polychlorosiloxane:

[0105] The reducing agent in this example is a mixture of coal gangue and petroleum coke, with a particle size range of 0.2-0.6 mm, and a mass ratio of coal gangue to petroleum coke of 2:1; the chlorine source is chlorine gas.

[0106] (1) Catalyst A and the reducing agent were mixed in a mass ratio of 1:1, and then uniformly mixed and packed into a fixed bed reactor;

[0107] (2) The high-boiling material (components same as in Example 1) was heated to 165-170°C to vaporize, and mixed with chlorine gas in a certain ratio (volume flow ratio of high-boiling material: reducing gas: chlorine gas was 1.5:1), wherein the mass ratio of catalyst A to high-boiling material was 1:10; the mixed gas was introduced into the fixed bed reactor for cracking reaction, with a reaction temperature of 420-430°C, a fixed bed layer height of 5.5 m, and a gas velocity of 0.6 m / s. After the reaction was completed, the products were sampled and analyzed, and it was calculated that the total primary conversion rate of the high-boiling material was about 82%, and the primary conversion rate of polychlorosiloxane was about 80%.

[0108] Example 6

[0109] The catalyst in this example is the same as that in Example 2, which is catalyst B.

[0110] Catalytic cracking of polychlorosiloxane:

[0111] The reducing agent in this example is a mixture of coal gangue and coal powder, with a particle size range of 0.1-0.2 mm, and a mass ratio of coal gangue to coal powder of 1:1; the chlorine source is chlorine gas.

[0112] (1) Catalyst B and the reducing agent were mixed in a mass ratio of 1:1, and then uniformly mixed and packed into a fixed bed reactor;

[0113] (2) The high-boiling material (components same as in Example 1) was heated to 165-170°C to vaporize, and mixed with chlorine gas in a certain ratio (volume flow ratio of high-boiling material: reducing gas: chlorine gas was 1.2:1), wherein the mass ratio of catalyst B to high-boiling material was 1:10; the mixed gas was introduced into the fixed bed reactor for cracking reaction, with a reaction temperature of 420-430°C, a fixed bed layer height of 5.5 m, and a gas velocity of 0.2 m / s. After the reaction was completed, the products were sampled and analyzed, and it was calculated that the total primary conversion rate of the high-boiling material was about 86%, and the primary conversion rate of polychlorosiloxane was about 81%.

[0114] Example 7 ​

[0115] The catalyst in this example is the same as that in Example 3, which is catalyst C.

[0116] Catalytic cracking of polychlorosiloxane:

[0117] The reducing agent in this example is a mixture of coal gangue and coal powder, with a particle size range of 0.2-0.6 mm, and the mass ratio of coal gangue to coal powder is 1:1; the chlorine source is chlorine gas.

[0118] (1) Mix catalyst C and reducing agent in a mass ratio of 1:1, uniformly mix, and then load into a fixed bed reactor;

[0119] (2) Heat the high-boiling material (components same as in Example 1) to 165-170°C to vaporize, mix with chlorine gas in a certain proportion (volume flow ratio of high-boiling material: reducing gas: chlorine gas is 1.2:1), and pass the mixed gas into the fixed bed reactor for cracking reaction, with a reaction temperature of 420-430°C, a fixed bed layer height of 5.5 m, and a gas velocity of 0.2 m / s. After the reaction is completed, the product is sampled and analyzed, and it is calculated that the total conversion rate of high-boiling material is about 90%, and the conversion rate of polychlorosiloxane is about 85%.

[0120] Comparative Example 1

[0121] The catalyst in this example is the same as that in Example 3, which is catalyst C.

[0122] Catalytic cracking of polychlorosiloxane:

[0123] The reducing agent in this example is a mixture of activated carbon and petroleum coke, with a particle size range of 0.15-0.34 mm, and the mass ratio of activated carbon to petroleum coke is 2:1;

[0124] (1) Mix catalyst C and reducing agent in a mass ratio of 1:1, add to a fluidized bed reactor, and pass in nitrogen to make it in a fluidized state;

[0125] (2) Heat the high-boiling material (components same as in Example 1) to 165-170°C to vaporize, mix with chlorine gas in a certain proportion (volume flow ratio of high-boiling material: chlorine gas is 1.3:1), and pass into the fluidized bed reactor, with a gas velocity of 0.53 m / s; wherein the mass ratio of catalyst C to high-boiling material is 1:10;

[0126] (3) Adjust the frequency of the fluidized bed induction heating and increase the furnace temperature. When the induction heating frequency is 625 kW, the system begins to undergo cracking reaction and generate products. Silicon tetrachloride raw material is extracted from the products. At this time, the fluidized bed temperature is 475 ° C. The fluidized bed induction heating power is started to be reduced. It is found that when the medium frequency induction heating power of the fluidized bed is reduced to below 420 kW, the reaction stops.

[0127] Comparative Example 2

[0128] Catalytic cracking of polychlorosiloxanes:

[0129] The reducing agent in this comparative example is a mixture of activated carbon and petroleum coke, with a particle size range of 0.15 to 0.34 mm, and a mass ratio of activated carbon to petroleum coke of 2:1; the silicon-based additive is a mixture of metallic silicon powder, deactivated silicon powder and single crystal silicon cutting powder, wherein the mass ratio of metallic silicon powder, deactivated silicon powder and single crystal silicon cutting powder is 4:4:2; and the chlorine source is chlorine gas.

[0130] (1) A reducing agent and a silicon-based additive are mixed in a mass ratio of 2:1, added to a fluidized bed reactor, and nitrogen is introduced to fluidize the reactor;

[0131] (2) The high-boiling material (composition is the same as in Example 1) is heated to 165-170° C. and vaporized, mixed with chlorine in a certain ratio (the volume flow ratio of the high-boiling material to the chlorine is 1.3:1), and introduced into the fluidized bed reactor at a gas velocity of 0.53 m / s; wherein the mass ratio of the reducing agent to the high-boiling material is 1:10;

[0132] (3) Adjust the medium frequency induction heating frequency of the fluidized bed and increase the furnace temperature. When the induction heating frequency reaches 325 kW, the system begins to undergo cracking reaction and generate products. Silicon tetrachloride raw material is extracted from the products. At this time, the fluidized bed temperature is 285°C. The fluidized bed induction heating power is reduced to 65 kW, and the fluidized bed reaction stops. The medium frequency induction heating frequency of the fluidized bed is maintained at 75 kW, and the reaction continues. After the reaction lasts for 30 minutes, the reaction is stopped and the products are sampled and analyzed. After calculation, the high boiling point conversion rate is about 35%, the polychlorosiloxane conversion rate is about 29%, the deactivated silicon powder conversion rate is about 67%, and the single crystal silicon cutting powder conversion rate is about 79%.

[0133] Comparative Example 3

[0134] The catalyst in this comparative example is the same as the catalyst in Example 3, namely Catalyst C.

[0135] Catalytic cracking of polychlorosiloxanes:

[0136] The silicon-based additive in this comparative example is a mixture of metallic silicon powder, deactivated silicon powder and single crystal silicon cutting dust, wherein the mass ratio of metallic silicon powder, deactivated silicon powder and single crystal silicon cutting dust is 4:4:2; and the chlorine source is chlorine gas.

[0137] (1) Catalyst C and silicon-based additives were mixed in a mass ratio of 2:1, and nitrogen was introduced to fluidize the mixture;

[0138] (2) The high-boiling material (composition is the same as in Example 1) is heated to 165-170° C. and vaporized, mixed with chlorine in a certain ratio (the volume flow ratio of the high-boiling material to the chlorine is 1.3:1), and introduced into the fluidized bed reactor at a gas velocity of 0.53 m / s; wherein the mass ratio of catalyst C to the high-boiling material is 1:10;

[0139] (3) Adjust the medium frequency induction heating frequency of the fluidized bed and increase the furnace temperature. When the induction heating frequency reaches 325 kW, the system begins to undergo cracking reaction and generate products. Silicon tetrachloride raw material is extracted from the products. At this time, the fluidized bed temperature is 285°C. The fluidized bed induction heating power is reduced to 45 kW, and the fluidized bed reaction stops. Maintain the medium frequency induction heating frequency of the fluidized bed at 50 W, and the reaction continues. After the reaction lasts for 30 minutes, the reaction is stopped and the products are sampled and analyzed. After calculation, the high boiling point conversion rate is about 58%, the polychlorosiloxane conversion rate is less than 10%, the deactivated silicon powder conversion rate is less than 5%, and the single crystal silicon cutting powder conversion rate is about 65%.

[0140] In summary, the above embodiments and comparative examples show that when the reaction raw materials are composed of high-boiling-point raw materials, chlorine source gas, catalyst, reducing agent and silicon-based additive, under the condition of the presence of catalyst, polychlorosiloxane and deactivated silicon powder are reduced, chlorinated and chlorinated cracking reactions are carried out in the reactor to generate silicon tetrachloride. The combined effect of reducing agent, catalyst and silicon-based additive can make the conversion rate of polychlorosiloxane higher, and can effectively reduce reaction energy consumption. The present invention can reduce the fluidized bed induction heating power by adding silicon-based additive in the reaction process, and reduces energy consumption by utilizing the heat generated by silicon-chlorine reaction. It can be seen from the comparison of Example 3 and Comparative Examples 2 and 3 that, by adding catalyst and reducing agent of the present invention, the primary conversion rate of high-boiling-point raw materials and polychlorosiloxane can be significantly improved.

[0141] Unless otherwise defined, the technical or scientific terms used in the present invention shall have the ordinary meaning understood by persons having ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Words such as "connect" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship also changes accordingly.

[0142] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing chlorosilanes by catalytic cracking of polychlorosiloxanes, characterized in that: The method is: A high-boiling material raw material, a chlorine source, a catalyst and a reducing agent are added to a reactor to generate silicon tetrachloride by catalytic cracking reaction; the high-boiling material raw material includes polychlorosilane and polychlorosiloxane; Wherein, the catalyst is a supported catalyst, the carrier raw material of the catalyst is a porous material, and the active component of the catalyst includes at least one of copper, nickel, zinc and rare earth elements; The catalyst is a gradient multi-component catalyst, comprising a core catalyst and a shell catalyst, wherein the shell catalyst is coated on the outer surface of the core catalyst, and the content of active components in the core catalyst is higher than that in the shell catalyst.

2. The method according to claim 1, wherein A silicon-based additive is further added to the reactor, wherein the silicon-based additive comprises at least one of metallic silicon powder, deactivated silicon powder, and single crystal silicon cutting powder; and / or The high-boiling material comprises at least one of tetrachlorodisiloxane, pentachlorodisiloxane, hexachlorodisiloxane, pentachlorodisilane and hexachlorodisiloxane.

3. The method according to claim 1, wherein The reducing agent includes a solid reducing agent and a gas reducing agent, wherein the solid reducing agent includes at least one of activated carbon, graphite, coal powder, coal gangue, and petroleum coke, and the gas reducing agent includes at least one of hydrogen, carbon monoxide, and carbon-containing silicon-based high boiling substances.

4. The method according to claim 1, wherein The pore size of the carrier material of the core catalyst is ≤1.5nm, and the pore volume is 0.02~0.1cm 3 / g; The pore size of the carrier material of the shell catalyst is ≥2.5nm, and the pore volume is ≥0.1cm 3 / g.

5. The method according to claim 4, characterized in that The carrier material of the core catalyst and the shell catalyst includes at least one of activated carbon, silica alumina, molecular sieve, diatomaceous earth, activated alumina, silica gel, and activated clay; The active components of the core catalyst and the shell catalyst include at least one of copper nitrate, cuprous chloride, cupric chloride, nickel nitrate, nickel chloride, zinc nitrate, zinc chloride, cerium nitrate, lanthanum nitrate, and yttrium chloride.

6. The method according to claim 4, characterized in that The preparation method of the catalyst is: Preparation of core carrier: uniformly mixing the carrier raw material of the core catalyst and the adhesive, granulating by rolling, drying, sieving and setting aside; Preparation of catalyst carrier: after uniformly mixing the carrier raw materials, adhesive and deoxidizer of the shell catalyst, adding the core carrier, continuing ball granulation, drying, roasting and setting aside; Active component loading: the active component is dissolved in a solvent to prepare an impregnation solution, the catalyst carrier is immersed in the impregnation solution, and then taken out and dried to obtain the catalyst.

7. The method according to claim 1, wherein The chlorine source is a chlorine-containing gas, including at least one of chlorine, hydrogen chloride, and methyl chloride.

8. The method according to any one of claims 1 to 7, characterized in that The high boiling point material and the chlorine source are mixed, heated and vaporized, and then introduced into the reactor; The volume flow ratio of the high-boiling material raw material gas to the chlorine source gas is (1:10) to (10:1).

9. The method according to claim 8, characterized in that The temperature at which the high-boiling material and the chlorine source are heated and vaporized is 50-200° C.; and / or The reaction gas velocity introduced into the reactor is 0.01-10 m / s.

Images