Monatomic catalyst for preparing SiH4 by disproportionating SiHCl3 and preparation method of monatomic catalyst

Abstract

The invention discloses a monatomic catalyst for preparing SiH4 by disproportionating SiHCl3 and a preparation method of the monatomic catalyst. According to the catalyst, transition metal serves as an active center, single atoms are dispersed on a high-temperature-resistant carrier, and high loading capacity (0.5-5 wt%) and stable dispersion of the metal are achieved through a coordination anchoring method or a high-temperature pyrolysis method. The catalyst has monatomic active sites, strong interaction between metal and a carrier is achieved, and reaction activity and SiH4 selectivity are improved. According to the preparation method, a large-scale technology is adopted, and uniform distribution and stability of monatomic are ensured by optimizing the proportion of a precursor and heat treatment conditions. The catalyst can realize high SiHCl3 conversion rate and high SiH4 selectivity at a low temperature (150-300 DEG C), has a long service life, is suitable for industrial continuous production, and has the advantages of high efficiency, low energy consumption and long-period operation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalysts, in particular to a single-atom catalyst for disproportionating SiHCl3 to prepare SiH4 and a preparation method thereof. BACKGROUND

[0002] Silane (SiH4) is widely used in the fields of semiconductor microelectronic ICs, photovoltaic solar cells PV, liquid crystal displays LCD, polycrystalline silicon preparation, etc. At present, the main preparation methods of SiH4 include metal hydride method, silicon-magnesium alloy method and trichlorosilane (SiHCl3) disproportionation method, etc. The SiHCl3 disproportionation method has the advantages of high production efficiency, low power consumption and low cost. The initial fixed equipment investment of the related process is large, but the raw material and production processing cost is low and the byproduct discharge amount is extremely small. The commercial production of SiH4 usually uses the SiHCl3 disproportionation method.

[0003] The existing new silane method is a method for producing high-purity SiH4 by using a catalyst to catalyze the chlorosilane disproportionation reaction. The chlorosilane disproportionation reaction is as follows:

[0004] The above steps (2) and (3) are so-called chlorosilane disproportionation reactions. Both have the same principle and can be reacted under the same conditions (such as temperature and pressure, etc.) using the same catalyst. At present, the active carbon supported transition metal catalyst (such as active carbon supported Pt, Pd, Rh, Co, Cu, La, etc.) is a commonly used catalyst for this reaction.

[0005] The traditional catalysts (such as supported metal particle catalysts) for the chlorosilane disproportionation reaction have the problems of low activity, poor selectivity, high reaction temperature (usually > 400℃), etc., and are easy to be deactivated due to metal agglomeration. The single-atom catalyst can significantly improve the atom utilization rate and reaction efficiency due to its atomic-level dispersed active sites, but its application in the SiHCl3 disproportionation reaction has not been reported. In addition, the existing single-atom catalysts have low loading and poor stability, which is difficult to meet the industrialization demand. Therefore, it is of important industrial value to develop a single-atom catalyst with high loading and high stability to realize low-temperature and high-efficiency catalysis of the SiHCl3 disproportionation reaction. SUMMARY

[0006] In view of the deficiencies of the prior art, the present application aims to provide a single-atom catalyst for disproportionating SiHCl3 to prepare SiH4 and a preparation method thereof, so as to solve the problems raised in the background art.

[0007] According to an aspect of the present application, a single-atom catalyst for disproportionating SiHCl3 to prepare SiH4 comprises: Carrier: high-temperature-resistant material doped with SiC or Al2O3 prepared by atomic layer deposition (ALD) technology, having a high specific surface area and a uniform pore structure, a specific surface area ≥ 200 m² / g, and a pore size of 2-50 nm; Active center: transition metal dispersed in the form of a single atom on the carrier, selected from at least one of Pt, Pd, Rh, Co, Cu, and La; The metal loading is 0.5-5 wt%, and the transition metal single atom is dispersed on the surface of the carrier by coordination anchoring or high-temperature pyrolysis and interacts strongly with the functional groups on the surface of the carrier to inhibit the agglomeration of metal atoms.

[0008] Preferably, the transition metal is Pt, Pd, or Rh, and the loading is 0.8-1.5 wt%.

[0009] Preferably, the carrier is a SiC-doped material, and the SiC carrier is treated with an oxygen plasma to introduce hydroxyl (-OH) functional groups to improve the anchoring ability of the metal precursor. The carrier is a mesoporous Al2O3 material, and the Al2O3 carrier is synthesized by a sol-gel method, dried, and calcined to obtain a carrier with a mesoporous structure and -OH functional groups on the surface.

[0010] A preparation method of the single-atom catalyst includes the following steps: (1) A SiC- or Al2O3-doped carrier is prepared by atomic layer deposition (ALD) technology or a sol-gel method; (2) A transition metal precursor is loaded on the carrier by coordination anchoring or high-temperature pyrolysis, and the transition metal precursor is a metal organic complex or a metal salt, wherein: Coordination anchoring: the carrier and the metal organic complex are mixed in a solvent, dried, and then heat-treated at 300-800°C in an inert atmosphere or a reducing atmosphere for 1-6 h to obtain a single-atom catalyst; High-temperature pyrolysis: the metal salt and the carrier are mixed and pyrolyzed at 600-800°C in an inert atmosphere for 2-6 h to decompose the metal salt to release single atoms and disperse them on the surface of the carrier.

[0011] Preferably, the metal organic complex is Pt(acac)2, Pd(NO3)2, or RhCl3; the solvent is ethanol, methanol, or water; and the heat treatment atmosphere is H2, N2, H2 / N2 mixed gas, or Ar / H2 mixed gas.

[0012] Preferably, in step (2), the drying temperature of the coordination anchoring method is 60-80°C, and the heat treatment temperature is 450-600°C; and the pyrolysis temperature of the high-temperature pyrolysis method is 700°C.

[0013] Preferably, the carrier in step (1) is treated by oxygen plasma to introduce hydroxyl groups, or modified by amino groups; and after the impregnation in step (2), freeze-drying or vacuum drying is used.

[0014] An application of the monatomic catalyst in the preparation of SiH4 by the disproportionation of SiHCl3, wherein the monatomic catalyst is loaded in a fixed bed reactor, SiHCl3 and H2 mixed gas is introduced at 150-300 ℃, and continuous reaction is carried out under normal pressure, and the volume ratio of SiHCl3 to H2 is 1:3.

[0015] Preferably, the catalyst life is ≥500h, the conversion rate of SiHCl3 is ≥90%, and the selectivity of SiH4 is ≥92%.

[0016] Compared with the prior art, the present application has the following advantages: 1. High activity and selectivity: the strong interaction between the monatomic sites and the carrier inhibits side reactions, and the selectivity of SiH4 is ≥92%.

[0017] 2. Low temperature and high efficiency: the reaction temperature is as low as 150-300 ℃, and the energy consumption is reduced by more than 30%.

[0018] 3. Excellent stability: the high-temperature resistance of the carrier and the strong bond between the metal and the carrier prevent the aggregation of atomic groups, and the life is ≥500h.

[0019] 4. Industrialization potential: the atomic layer deposition (ALD) technology and controllable preparation method are suitable for large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a flowchart of a preparation method of a monatomic catalyst for the preparation of SiH4 by the disproportionation of SiHCl3 according to an embodiment of the present application. DETAILED DESCRIPTION

[0021] In order to make the content of the present application more easily understood, the technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the drawings in the embodiments of the present application.

[0022] The monatomic catalyst for preparing SiH4 by disproportionating SiHCl3 comprises a carrier and an active center, the carrier is a high-temperature-resistant material doped with SiC or Al2O3 prepared by atomic layer deposition (ALD) technology, the carrier has a high specific surface area and a uniform pore structure, the specific surface area is greater than or equal to 200 m² / g, and the pore size is 2-50 nm; the active center is a transition metal monatomic atom, which is dispersed on the carrier in the form of a monatomic atom and is selected from at least one of Pt, Pd, Rh, Co, Cu and La; the metal loading is 0.5-5 wt%, the transition metal monatomic atom is dispersed on the surface of the carrier by a coordination anchoring method or a high-temperature pyrolysis method, and a strong interaction is generated between the transition metal monatomic atom and the functional groups on the surface of the carrier to inhibit the agglomeration of the metal atoms; wherein the SiC carrier is treated by oxygen plasma to introduce hydroxyl (-OH) functional groups to improve the anchoring ability of the metal precursor; and the Al2O3 carrier is synthesized by a sol-gel method, dried and calcined to obtain a carrier with a mesoporous structure and containing -OH functional groups on the surface.

[0023] As shown in Figure 1 A preparation method of a monatomic catalyst for preparing SiH4 by disproportionating SiHCl3, comprising the following steps: (1) preparing a doped SiC or Al2O3 carrier by atomic layer deposition (ALD) technology or a sol-gel method; (2) loading a transition metal precursor on the carrier by a coordination anchoring method or a high-temperature pyrolysis method, wherein the transition metal precursor is a metal organic complex or a metal salt, and the coordination anchoring method comprises the following steps: the coordination anchoring method: mixing the carrier and a metal organic complex (such as Pt(acac)2, Pd(acac)2, Rh(acac)3, Co(acac)2, Cu(OAc)2, La(NO3)3, etc.) in a suitable solvent (such as ethanol or methanol), anchoring the metal precursor on the carrier by coordination of the -OH functional groups on the surface of the carrier, drying, and then performing heat treatment at 300-800°C in an inert gas or a reducing atmosphere to obtain the monatomic catalyst; the high-temperature pyrolysis method: mixing a metal salt (such as RuCl3, Co(acac)2, Cu(OAc)2, etc.) and the carrier at a set ratio, and directly calcining at 600-800°C in N2 or an inert atmosphere to decompose the metal salt to release monatomic atoms and disperse the monatomic atoms on the surface of the carrier.

[0024] optimizing the ratio of the precursors and the heat treatment conditions to stably disperse the metal in the form of monatomic atoms, controlling the loading to be 0.5-5 wt%, and the heat treatment conditions comprising calcining at 300-800°C in an inert atmosphere or a reducing atmosphere for 1-6 h.

[0025] The application relates to a method for preparing SiH4 by using a prepared monatomic catalyst to disperse SiHCl3, wherein the monatomic catalyst is filled in a fixed bed reactor, a mixed gas of SiHCl3 and H2 with a volume ratio of 1:3 is introduced into the reactor at 150-300 DEG C, and continuous reaction is carried out under normal pressure; in the reaction, the catalyst life is greater than or equal to 500 h, the conversion rate of SiHCl3 is greater than or equal to 90%, and the selectivity of SiH4 is greater than or equal to 92%. Example 1

[0026] 1. Catalyst preparation: a SiC carrier is prepared by using an atomic layer deposition (ALD) technology, and hydroxyl groups are introduced on the surface of the carrier by oxygen plasma treatment. Pt(acac)2 is dissolved in ethanol, and the carrier is immersed in the solution, dried at 80 DEG C, and calcined in a H2 / N2 mixed gas at 500 DEG C for 4 h to obtain a 1.2wt% Pt monatomic catalyst, which is marked as a Pt / SiC catalyst.

[0027] 2. Preparation of SiH4: the Pt / SiC catalyst is filled in a fixed bed reactor, and a SiHCl3 / H2 mixed gas (with a volume ratio of 1:3) is introduced into the reactor at 180 DEG C. The reaction results show that the conversion rate of SiHCl3 is 98%, the selectivity of SiH4 is 97%, and the catalyst life is 600 h. Example 2

[0028] 1. Catalyst preparation: a mesoporous Al2O3 carrier is synthesized by a sol-gel method, Pd(NO3)2 solution is immersed in the carrier, and freeze-drying is carried out, and a 0.8wt% Pd monatomic catalyst is obtained by reducing the carrier in a H2 atmosphere at 450 DEG C for 3 h, which is marked as a Pd / Al2O3 catalyst.

[0029] 2. Preparation of SiH4: under the reaction condition of 200 DEG C, the Pd / Al2O3 catalyst catalyzes the dismutation of SiHCl3, the conversion rate of SiHCl3 is 93%, and the selectivity of SiH4 is 96%. The catalyst maintains stable catalytic performance within 550 h, and there is no carbon deposition or metal agglomeration. Example 3

[0030] 1. Catalyst preparation: RhCl3 and an amino-modified SiC carrier are refluxed in methanol for 12 h, vacuum drying is carried out at 60 DEG C, and a 1.5wt% Rh monatomic catalyst is obtained by heat treatment of the carrier in an Ar / H2 atmosphere at 600 DEG C for 2 h, which is marked as a Rh / SiC catalyst.

[0031] 2. Preparation of SiH4: under the reaction condition of 220 DEG C, the Rh / SiC catalyst shows a SiHCl3 conversion rate of 96% and a SiH4 selectivity of 95%. The proportion of SiCl4 generated in the side reaction is less than 2%, and the catalyst life is 580 h. Example 4

[0032] 1. Catalyst preparation: Co(acac)2 was mixed with Al2O3 support by ball milling and calcined at 700℃ for 5h under N2 atmosphere to prepare 2wt% Co single-atom catalyst, labeled as Co / Al2O3 catalyst.

[0033] 2. SiH4 preparation: The SiHCl3 conversion of Co / Al2O3 catalyst was 90% and the SiH4 selectivity was 94% at 250℃. The catalyst remained stable in catalytic performance for 500h without carbon deposition or metal agglomeration. Example 5

[0034] 1. Catalyst preparation: Cu(OAc)2 was used as precursor to deposit Cu single-atom on SiC support by gas-phase migration method. After H2 reduction, the loading amount was 0.5wt%, labeled as Cu / SiC catalyst.

[0035] 2. SiH4 preparation: The Cu / SiC catalyst achieved 95% SiHCl3 conversion and 93% SiH4 selectivity at low temperature of 150℃. The reaction energy consumption was reduced by 40% compared with traditional catalysts, and the catalyst lifetime was 500h. Example 6

[0036] 1. Catalyst preparation: La(NO3)3 was co-precipitated with Al2O3 support, calcined at 500℃, and then 3wt% La single-atom catalyst was prepared by citric acid complexation-pyrolysis method, labeled as La / Al2O3 catalyst.

[0037] 2. SiH4 preparation: The La / Al2O3 catalyst catalyzed the SiHCl3 disproportionation reaction with a conversion rate of 91% and a SiH4 selectivity of 92% at 300℃. The catalyst had strong resistance to chlorine poisoning, and the catalyst lifetime was 530h.

[0038] Comparative Example 1 Different from Example 1: The catalyst was the most commonly used Pt / C catalyst, which was prepared by impregnation method. High specific surface area activated carbon was selected and treated with H2O2 to increase the surface oxygen-containing functional groups, and then washed to neutral and dried at 120℃. The pretreated activated carbon was immersed in chloroplatinic acid (H2PtCl6) solution (concentration of 1-10wt%), and stirred uniformly. Deionized water was used for washing, and vacuum drying was used to prepare Pt / C catalyst. The reaction results showed that the SiHCl3 conversion was 90% and the SiH4 selectivity was 85%, and the catalyst lifetime was 450h.

[0039] Table 1 Performance comparison of catalysts

[0040] It should be pointed out that the catalyst can be integrated into the existing silane production device, significantly improving the efficiency and product purity, reducing energy consumption, and being suitable for large-scale preparation of photovoltaic and electronic-grade high-purity silane.

[0041] The above is the preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A single-atom catalyst for the preparation of SiH4 from disproportionated SiHCl3, characterized in that, include: Support: High-temperature resistant materials doped with SiC or Al2O3 prepared by atomic layer deposition (ALD) technology, with a specific surface area ≥200m² / g and a pore size of 2-50nm; Active center: a transition metal dispersed on the support in the form of a single atom, selected from at least one of Pt, Pd, Rh, Co, Cu, and La; The metal loading is 0.5-5 wt%, and the transition metal single atoms are dispersed on the surface of the support by coordination anchoring or high-temperature pyrolysis, and interact strongly with the functional groups on the surface of the support.

2. The single-atom catalyst according to claim 1, characterized in that, The transition metal is Pt, Pd, or Rh, with a loading of 0.8-1.5 wt%.

3. The single-atom catalyst according to claim 1, characterized in that, The surface of the carrier is treated with oxygen plasma or modified with amino groups to form functional groups for anchoring metals.

4. A method for preparing a single-atom catalyst according to any one of claims 1-3, characterized in that, Includes the following steps: (1) Prepare doped SiC or Al2O3 supports using atomic layer deposition (ALD) or sol-gel method; (2) The transition metal precursor is loaded onto the carrier by coordination anchoring or high-temperature pyrolysis, wherein the transition metal precursor is a metal-organic complex or a metal salt, wherein: Coordination anchoring method: The support and the organometallic complex are mixed in a solvent, dried, and then heat-treated at 300-800℃ for 1-6 hours in an inert or reducing atmosphere to obtain a single-atom catalyst. High-temperature pyrolysis method: The metal salt is mixed with the support and pyrolyzed at 600-800℃ in an inert atmosphere for 2-6 hours, so that the metal salt decomposes and releases single atoms and disperses on the surface of the support.

5. The method for preparing the single-atom catalyst according to claim 4, characterized in that: The organometallic complex is Pt(acac)2, Pd(NO3)2 or RhCl3; The solvent is ethanol or methanol; The heat treatment atmosphere is H2, N2, a mixture of H2 and N2, or a mixture of Ar and H2.

6. The method for preparing the single-atom catalyst according to claim 4, characterized in that, In step (2): The drying temperature for the coordination anchoring method is 60-80℃, and the heat treatment temperature is 450-600℃. The pyrolysis temperature of the high-temperature pyrolysis method is 700℃.

7. The method for preparing the single-atom catalyst according to claim 4, characterized in that: In step (1), the carrier is treated with oxygen plasma to introduce hydroxyl groups, or modified with amino groups; After impregnation in step (2), freeze drying or vacuum drying is performed.

8. The application of the single-atom catalyst according to any one of claims 1-3 in the disproportionation of SiHCl3 to prepare SiH4, characterized in that, The single-atom catalyst was packed into a fixed-bed reactor, and a mixture of SiHCl3 and H2 gas was introduced at 150-300°C. The reaction was carried out continuously under normal pressure, with a volume ratio of SiHCl3 to H2 of 1:

3.

9. The application according to claim 8, characterized in that, Single-atom catalyst lifetime ≥ 500 h, SiHCl3 conversion ≥ 90%, SiH4 selectivity ≥ 92%.

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