A method for preparing dimethylhydrochlorosilane

Abstract

The present invention provides a method for preparing dimethylhydrochlorosilane. The method comprises: performing a cracking and disproportionation reaction on dimethyldichlorosilane in the presence of a catalyst to prepare dimethylhydrochlorosilane; the catalyst is a noble metal@ZSM-5 bifunctional catalyst formed by encapsulating noble metal M nanoparticles in a ZSM-5 molecular sieve; the method is simple to operate, has mild reaction conditions, and has excellent single-pass conversion rate and dimethylhydrochlorosilane selectivity.

Description

Technical Field

[0001] The present invention relates to the technical field of organosilicon monomer production, and in particular to a method for preparing dimethylhydrochlorosilane. Background Art

[0002] Methylchlorosilane is a very important platform raw material for the synthesis of organosilicon materials. Dimethylhydrochlorosilane, or (CH3)2-SiH-Cl, has a boiling point of 34-36°C. Because it carries active hydrogen Si-H at its terminal positions, it easily reacts with C=C in organic compounds to prepare various carbon-functional silanes or long-chain alkylsilanes and reactive silicone oils. The Si-C bond can connect with Si-O chains to form a bridging agent that binds polysiloxanes to organic polymers. Currently, market demand for methylhydrochlorosilane monomers continues to increase. The 3-5% methylhydrochlorosilane produced by the "direct process" to produce dimethyldichlorosilane is far from meeting market demand.

[0003] Therefore, it is urgent to develop a method for preparing methylhydrochlorosilane monomer.

[0004] US4966986A discloses a method for preparing methylhydrochlorosilane monomers by a fluidized bed reaction. In the fluidized bed reaction, silicon powder and copper powder are mixed, first treated with HCl under heating conditions, and then CH3Cl-H2 is introduced for reaction. The resulting product contains approximately 39% monomethylhydrodichlorosilane [CH3-SiH-Cl2] and approximately 14-22% dimethylhydromonochlorosilane [(CH3)2-SiH-Cl]. However, the yield of the main product dimethyldichlorosilane [(CH3)2-Si-Cl2] in this process is low.

[0005] US6077967A discloses a method for preparing dimethylhydrochlorosilane monomer using trimethylchlorosilane and methylhydrodichlorosilane as raw materials, wherein the catalyst used in the method is anhydrous aluminum chloride. CN16803971A also discloses a method for preparing dimethylhydrochlorosilane using methylhydrodichlorosilane and trimethylchlorosilane as raw materials, reacting at 250-400°C in a two-stage fixed-bed reactor in the presence of an AlCl3 catalyst. However, the AlCl3 catalyst used is prone to sublimation during the reaction, resulting in the loss of its active centers, rapid catalyst deactivation, and poor cyclic stability.

[0006] US5646326A discloses that Pt / C or Ru / Al2O3 is used as a catalyst and dimethyldichlorosilane is used as a raw material, with conversion rates of 3.9% and 14.8% respectively. For the two catalysts, the products of (CH3)2-SiH-Cl and CH3-SiH-Cl2 account for 40.8% and 52.0%, 27.2% and 49.5% respectively.

[0007] CN1091136A discloses a method for reacting dimethyldichlorosilane with methylhydrogendichlorosilane or methylsilane in the presence of a catalyst. The disadvantage of this method is that the catalyst having such a silicic acid structure is difficult to prepare and is expensive.

[0008] CN106632447A discloses a two-stage fixed-bed process for preparing dimethyldichlorosilane using dimethyldichlorosilane as a raw material, hydrogen as a cracking gas, Pt, Pd, and Ni bimetallic active components, and activated carbon as a carrier. The reaction temperature is 200-500°C. The process is complex, the catalyst uses a high loading of the metal active component of approximately 5-15%, and the single-pass conversion rate of dimethyldichlorosilane is low.

[0009] US4115426A and US5329038A disclose the preparation of dimethylhydrochlorosilane [(CH3)2-SiH-Cl] using an organic amine and Mg as catalysts, dimethyldichlorosilane as a raw material, and HCl as a cracking gas, with a yield as high as 71%. However, due to the high reactivity of metal hydrides, the reaction system must be carried out in an organic solvent, and separation of the organic solvent from the target product, dimethylhydrochlorosilane, is difficult after the reaction.

[0010] Based on the above analysis, it can be seen that the preparation of dimethylhydrochlorosilane is technically difficult, the catalyst cost is high, and the operation process is complicated.

[0011] Therefore, there is an urgent need to develop a method for preparing dimethylhydrochlorosilane to solve the above technical difficulties and further improve the conversion rate and selectivity. Summary of the Invention

[0012] In view of the problems existing in the prior art, the present invention provides a method for preparing dimethylhydrochlorosilane. The method solves the problems of poor catalyst cycle stability, low conversion rate and low dimethylhydrochlorosilane selectivity in the existing process by using a noble metal@ZSM-5 (M@ZSM-5) bifunctional catalyst formed by encapsulating noble metal M nanoparticles in ZSM-5 molecular sieve to carry out a catalytic cracking and disproportionation reaction.

[0013] To achieve this object, the present invention adopts the following technical solutions:

[0014] In a first aspect, the present invention provides a method for preparing dimethylhydrochlorosilane, the method comprising: performing a cracking and disproportionation reaction on dimethyldichlorosilane in the presence of a catalyst to prepare dimethylhydrochlorosilane;

[0015] The catalyst is a noble metal@ZSM-5 bifunctional catalyst formed by encapsulating noble metal M nanoparticles in ZSM-5 molecular sieve.

[0016] The method for preparing dimethylhydrochlorosilane provided by the present invention uses noble metal M nanoparticles as catalytically active substances, can achieve rearrangement of four groups connected to silicon atoms in dimethyldichlorosilane, has few by-products, and has high reaction selectivity. A ZSM-5 molecular sieve catalyst with acidic sites is selected, which has higher catalytic activity. In addition, the encapsulation technology significantly improves the uniformity of the distribution of the noble metal M nanoparticles, reduces the aggregation of the noble metal M nanoparticles and the reduction of their activity during the catalytic process, and improves the catalytic activity of the catalyst.

[0017] The following technical features are further preferred technical features of the present invention, but do not limit the technical solutions of the present invention.

[0018] Preferably, the temperature of the pyrolysis and disproportionation reaction is 150°C to 300°C, for example, 150°C, 167°C, 184°C, 200°C, 217°C, 234°C, 250°C, 267°C, 284°C, or 300°C, but is not limited to the values ​​listed above, and other values ​​not listed within this range are also applicable. A reaction temperature of 150°C to 300°C is preferred because it has the advantages of achieving low conversion and selectivity at the same time.

[0019] Preferably, the hydrogen pressure of the cracking and disproportionation reaction is 3.0 to 6.0 MPa, for example, 3.0 MPa, 3.4 MPa, 3.7 MPa, 4 MPa, 4.4 MPa, 4.7 MPa, 5 MPa, 5.4 MPa, 5.7 MPa or 6.0 MPa, but is not limited to the listed values, and other values ​​not listed within this range are also applicable.

[0020] Preferably, the residence time of dimethyldichlorosilane in the cracking and disproportionation reaction is 0.5 to 4 hours, for example, 0.5 hours, 1 hour, 1.5 hours, 2 hours, 3 hours or 4 hours, etc., but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0021] Preferably, the reaction is carried out under stirring conditions.

[0022] Preferably, the stirring speed is 300-600 r / min, for example, it can be 300 r / min, 334 r / min, 367 r / min, 400 r / min, 434 r / min, 467 r / min, 500 r / min, 534 r / min, 567 r / min or 600 r / min, but is not limited to the listed values. Other values ​​not listed in this range are also applicable.

[0023] Preferably, the single-pass dosage of the catalyst is 0.1 to 10 wt% of dimethyldichlorosilane, for example, it can be 0.1 wt%, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt% or 10 wt%, etc., but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0024] Preferably, the noble metal M nanoparticles include any one or a combination of at least two of Pt, Pd, Ru, Au or Ag, wherein typical but non-limiting combinations are a combination of Pt and Pd, a combination of Ru and Pd, a combination of Pt and Ru, a combination of Ag and Pd, a combination of Ag and Au, and the like.

[0025] Preferably, the particle size of the precious metal M nanoparticles is 0.5 to 3 nm, for example, it can be 0.5 nm, 0.8 nm, 1.1 nm, 1.4 nm, 1.7 nm, 1.9 nm, 2.2 nm, 2.5 nm, 2.8 nm or 3 nm, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0026] Preferably, the content of the precious metal M in the catalyst is 0.1 to 1.0 wt%, for example, it can be 0.1 wt%, 0.3 wt%, 0.5 wt%, 0.6 wt%, 0.8 wt% or 1.0 wt%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0027] In the present invention, the content of the precious metal is preferably 0.1 to 1.0 wt %. Although the precious metal content is low, it still has an excellent catalytic effect and has both cost advantages and high yield advantages.

[0028] Preferably, the silicon-aluminum ratio SiO2 / Al2O3 in the catalyst is 100:1 to 500:1, for example, it can be 100:1, 140:1, 180:1, 230:1, 270:1, 320:1, 360:1, 410:1, 450:1 or 500:1, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0029] Preferably, the catalyst is obtained by in-situ synthesis.

[0030] Preferably, the in-situ synthesis method comprises: adding a noble metal precursor during the in-situ synthesis process of the ZSM-5 molecular sieve, so as to achieve uniform encapsulation of the noble metal M nanoparticles in the ZSM-5 molecular sieve.

[0031] The present invention preferably uses a catalyst prepared by the above encapsulation method, in which the noble metal M nanoparticles are more evenly distributed and have better catalytic performance.

[0032] Preferably, the ZSM-5 molecular sieve is a sodium-free aluminosilicate molecular sieve.

[0033] Preferably, no sodium element is added in the in-situ synthesis method.

[0034] Preferably, the relative crystallinity of the ZSM-5 molecular sieve catalyst encapsulating the precious metal M nanoparticles is 80 to 120%, for example, it can be 80%, 85%, 86%, 88%, 90%, 92%, 95%, 98%, 100%, 105%, 110% or 120%, etc., but is not limited to the listed values, and other values ​​not listed within this range are also applicable.

[0035] The relative crystallinity in the present invention refers to the degree of crystallinity compared with the crystallinity of the pure ZSM-5 molecular sieve before the addition of the noble metal precursor.

[0036] Preferably, the preparation method of the catalyst comprises: mixing a silicon source, an aluminum source, a noble metal precursor, a structure directing agent and water, and sequentially subjecting the mixture to hydrothermal crystallization, cooling, solid-liquid separation, calcination and reduction to obtain the catalyst.

[0037] In the present invention, the aluminum source is selected from any one of aluminum hydroxide, pseudo-boehmite, SB powder, dry glue powder, aluminum sol, aluminum isopropoxide or silica alumina, or a combination of at least two of them. Typical but non-limiting combinations include a combination of aluminum hydroxide and pseudo-boehmite, a combination of SB powder and pseudo-boehmite, a combination of dry glue powder and pseudo-boehmite, a combination of aluminum hydroxide and aluminum sol, and the like. Preferably, it is a combination of any one of SB powder, aluminum sol or silica alumina, or a combination of at least two of them.

[0038] In the present invention, the silicon source is selected from any one of solid silica gel, white carbon black, silica sol, silica alumina or tetraethyl orthosilicate, or a combination of at least two thereof, wherein typical but non-limiting combinations are a combination of solid silica gel and white carbon black, a combination of solid silica gel and silica alumina, a combination of silica sol and white carbon black, and a combination of solid silica gel and tetraethyl orthosilicate, preferably at least one of white carbon black, silica sol or silica alumina.

[0039] The silica-alumina gel can be used as both a silicon source and an aluminum source, and is selected from a sodium-free silica-alumina gel with a ratio of SiO2:Al2O3=100:1 to 500:1; preferably, the sodium-free silica-alumina gel has a ratio of SiO2:Al2O3=100 to 500:1.

[0040] The structure directing agent (SDA) is selected from any one or a combination of at least two of triethylamine, tributylamine, diisopropylamine, diisobutylamine, isobutylamine, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetramethylethyldiamine, dimethyldiethylammonium hydroxide, monomethyltriethylammonium hydroxide, monomethyltripropylammonium hydroxide, dimethyldipropylammonium hydroxide, diethyldipropylammonium hydroxide or monoethyltripropylammonium hydroxide, wherein a typical but non-limiting combination is a combination of triethylamine and tributylamine, a combination of diisopropylamine and tributylamine, a combination of diisobutylamine and tributylamine, a combination of isobutylamine and diisobutylamine, a combination of tetrapropylammonium hydroxide and isobutylamine, and a combination of tetraethylammonium hydroxide and dimethyldiethylammonium hydroxide; preferably, it is any one or a combination of at least two of triethylamine, hexamethyleneimine, tetraethylammonium hydroxide, tetrapropylammonium hydroxide or dimethyldiethylammonium hydroxide.

[0041] Preferably, the catalyst is prepared by the method of CN109731608B, except that the non-noble metal is replaced by a noble metal.

[0042] Preferably, the noble metal precursor comprises any one or a combination of at least two of nitrate, chloride, sulfate or noble metal complex, wherein typical but non-limiting combinations are a combination of nitrate and chloride, a combination of chloride and noble metal complex, a combination of noble metal complex and sulfate, and a combination of nitrate and sulfate.

[0043] As a preferred technical solution of the present invention, the method includes the following steps: mixing dimethyldichlorosilane and a catalyst, wherein the single-pass amount of the catalyst accounts for 2 to 10 wt% of the dimethyldichlorosilane, and performing a cracking and disproportionation reaction under a hydrogen pressure of 3.0 to 6.0 MPa, 150 to 300° C. and stirring conditions, and the reaction time is 0.5 to 4 hours to prepare dimethylhydrochlorosilane.

[0044] The catalyst is a noble metal @ ZSM-5 (M@ZSM-5) bifunctional catalyst formed by encapsulating noble metal M nanoparticles in ZSM-5 molecular sieve, wherein the particle size of the noble metal M nanoparticles is 0.5 to 3 nm; the content of noble metal M in the catalyst is 0.1 to 1.0 wt%; and the silicon-aluminum ratio SiO2 / Al2O3 in the catalyst is 100:1 to 500:1.

[0045] Compared with the prior art, the present invention has at least the following beneficial effects:

[0046] (1) The method for preparing dimethylhydrochlorosilane provided by the present invention uses a ZSM-5 molecular sieve catalyst encapsulated with precious metals, which has the advantages of high selectivity and high conversion rate, wherein the single-pass conversion rate of dimethyldichlorosilane is above 50%, the selectivity of (CH3)2-SiH-Cl is above 70%, and the yield of (CH3)2-SiH-Cl is above 40%;

[0047] (2) The method for preparing dimethylhydrochlorosilane provided by the present invention is simple to operate and the process is controllable;

[0048] (3) Compared with other existing precious metal catalysts, the method for preparing dimethylhydrochlorosilane provided by the present invention has a low precious metal content and a greater cost advantage. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 This is a TEM analysis diagram of the Pt@ZSM-5 dual-function encapsulated catalyst in Example 1 of the present invention. DETAILED DESCRIPTION

[0050] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation methods.

[0051] The present invention is further described in detail below. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0052] Example 1

[0053] This embodiment provides a method for preparing dimethylhydrochlorosilane, comprising: mixing 50.5 g of dimethyldichlorosilane and 4.0 g of a Pt@ZSM-5 dual-function encapsulated catalyst; performing a cracking and disproportionation reaction under conditions of a hydrogen pressure of 6.0 MPa, 240° C., and 500 rpm for 1 hour to prepare dimethylhydrochlorosilane; after the reaction, cooling the reaction material to room temperature, releasing the pressure and removing the reaction material, and separating the catalyst from the liquid product to obtain a product containing dimethylhydrochlorosilane; the specific results are shown in column A1 of Table 1.

[0054] The particle size of the Pt nanoparticles is 0.6-0.8 nm; the content of precious metals in the catalyst is 0.34 wt%; the silicon-aluminum ratio SiO2 / Al2O3 in the catalyst is 100:1; the Pt@ZSM-5 dual-function encapsulated catalyst is prepared according to the method of Example 1 in CN109731608B, with the parameters adjusted accordingly, replacing the non-precious metal with a precious metal precursor, which is a complex solution of platinum nitrate and ethylenediamine. TEM analysis of the Pt@ZSM-5 catalyst is shown in Figure 1. Figure 1 As shown, from Figure 1It can be seen that the Pt particle size distribution in the Pt@ZSM-5 catalyst is uniform and the particle size is very small, and it is evenly encapsulated in the ZSM-5 molecular sieve crystals.

[0055] Example 2

[0056] This embodiment provides a method for preparing dimethylhydrochlorosilane, which includes: mixing 50.5 g of dimethyldichlorosilane and 5.0 g of Ru@ZSM-5 dual-function encapsulated catalyst, performing a cracking and disproportionation reaction for 2 hours under conditions of 6.0 MPa hydrogen pressure, 260° C., and 600 r / min to prepare dimethylhydrochlorosilane; after the reaction, cooling the reaction material to room temperature, releasing the pressure and removing it, and separating the catalyst from the liquid product to obtain a product containing dimethylhydrochlorosilane; the specific results are shown in column A2 of Table 1.

[0057] The particle size of the Ru nanoparticles is 0.7 to 0.9 nm; the content of precious metals in the catalyst is 0.81 wt%; the silicon-aluminum ratio SiO2 / Al2O3 in the catalyst is 160:1; the Ru@ZSM-5 dual-function encapsulated catalyst is prepared according to the method of Example 3 in CN109731608B, with the parameters adjusted accordingly, and the non-precious metal is replaced by a precious metal precursor, and the precious metal precursor is a complex of ruthenium nitrate and ethylenediamine.

[0058] Example 3

[0059] This embodiment provides a method for preparing dimethylhydrochlorosilane, which includes: mixing 51 g of dimethyldichlorosilane and 2.0 g of Au@ZSM-5 bifunctional encapsulated catalyst, performing a cracking and disproportionation reaction for 2 hours under conditions of 5.0 MPa hydrogen pressure, 220° C., and 400 rpm to prepare dimethylhydrochlorosilane; after the reaction, cooling the reaction material to room temperature, releasing the pressure and removing it, and separating the catalyst from the liquid product to obtain a product containing dimethylhydrochlorosilane; the specific results are shown in column A3 of Table 1.

[0060] The particle size of the Au nanoparticles is 0.6-0.8 nm; the content of precious metal in the catalyst is 0.56 wt%; the silicon-aluminum ratio SiO2 / Al2O3 in the catalyst is 250:1; the Au@ZSM-5 dual-function encapsulated catalyst is prepared according to the method of Example 4 in CN109731608B, with the parameters adjusted accordingly, and the non-precious metal is replaced by a precious metal precursor, and the precious metal precursor is gold chloride.

[0061] Example 4

[0062] This embodiment provides a method for preparing dimethylhydrochlorosilane, comprising: mixing 51 g of dimethyldichlorosilane and 3.5 g of an Ag@ZSM-5 dual-function encapsulated catalyst, performing a cracking and disproportionation reaction at a hydrogen pressure of 3.0 MPa and 160° C. for 4 hours to prepare dimethylhydrochlorosilane; after the reaction, cooling the reaction material to room temperature, releasing the pressure and removing the reaction material, and separating the catalyst from the liquid product to obtain a product containing dimethylhydrochlorosilane; the specific results are shown in column A4 of Table 1.

[0063] The particle size of the Ag nanoparticles is 1.1 to 1.5 nm; the content of precious metal in the catalyst is 0.95 wt%; the silicon-aluminum ratio SiO2 / Al2O3 in the catalyst is 450:1; the Ag@ZSM-5 bifunctional encapsulated catalyst is prepared according to the method of Example 5 in CN109731608B, with the parameters adjusted accordingly, and the non-precious metal is replaced by a precious metal precursor, and the precious metal precursor is a complex of silver nitrate and ethylenediamine.

[0064] Comparative Example 1

[0065] This comparative example provides a method for preparing dimethylhydrochlorosilane, which is the same as Example 1 except that the Pt@ZSM-5 molecular sieve catalyst encapsulated with Pt nanoparticles is replaced with a Pt / ZSM-5 catalyst prepared by an impregnation method (the Pt content is 0.34wt%, Si2O3 / Al2O3=100:1, and the specific impregnation method is carried out according to the method of Comparative Example 1 in CN109731608B), and nickel nitrate is replaced with platinum nitrate. The specific results are shown in column D1 of Table 1.

[0066] Comparative Example 2

[0067] This comparative example provides a method for preparing dimethylhydrochlorosilane. The method is the same as Example 2, except that the Ru@ZSM-5 molecular sieve catalyst encapsulated with Ru nanoparticles is replaced with a Ru / ZSM-5 catalyst prepared by an impregnation method (Ru content is 0.81wt%, Si2O3 / Al2O3=160:1, the specific impregnation method is carried out according to the method of Comparative Example 1 in CN109731608B, and nickel nitrate is replaced with ruthenium nitrate, and the molar ratio of mixture B is: SiO2 / Al2O3=160:1). The specific results are shown in column D2 of Table 1.

[0068] Comparative Example 3

[0069] This comparative example provides a method for preparing dimethylhydrochlorosilane. The method is identical to Example 2, except that the Ru@ZSM-5 molecular sieve catalyst encapsulated with Ru nanoparticles is replaced with a Ru / Al2O3 catalyst prepared by an impregnation method (the Ru content is 0.81 wt %, Al2O3 is directly used instead of the ZSM-5 molecular sieve, and the specific impregnation steps are the same as those in Comparative Example 2). The specific results are shown in column D3 of Table 1.

[0070] Comparative Example 4

[0071] This comparative example provides a method for preparing dimethylhydrochlorosilane. The method is identical to Example 2, except that the Ru@ZSM-5 molecular sieve catalyst encapsulated with Ru nanoparticles is replaced with a Ru@H-Beta molecular sieve catalyst encapsulated with Ru nanoparticles (prepared according to the method of Example 7 in CN109731608B, with a Ru content of 0.55 wt %, and SiO / AlO = 60:1). The specific results are shown in column D4 of Table 1.

[0072] Comparative Example 5

[0073] This comparative example provides a method for preparing dimethylhydrochlorosilane, which is carried out using the method of Example 4 in CN106632447A. The results show that the single-pass conversion rate of dimethyldichlorosilane is only 25.3%, the selectivity of dimethylhydrochlorosilane is 92.8%, and the calculated yield of dimethylhydrochlorosilane is only 23.49%.

[0074] Comparative Example 6

[0075] This comparative example provides a method for preparing dimethylhydrochlorosilane. Catalyst C1a is prepared using the method for preparing catalyst C1a described in CN106632447A. Catalyst C1a is substituted for the Pt@ZSM-5 molecular sieve catalyst encapsulated with Pt nanoparticles in Example 1. All other conditions are the same as those in Example 1. The specific results are shown in column D6 of Table 1.

[0076] The products obtained in the above examples and comparative examples were analyzed by GC-MS. The selectivity of each component in the product and the single-pass conversion rate of high boiling points are shown in Table 1, where A1 to A4 represent Examples 1 to 4, respectively, and D1 to D6 represent Comparative Examples 1 to 6, respectively.

[0077] Table 1

[0078]

[0079]

[0080] As can be seen from Table 1, the method for preparing dimethylhydrochlorosilane provided by the present invention can convert dimethyldichlorosilane into dimethylhydrochlorosilane with high selectivity and conversion rate, and the single-pass conversion rate of dimethyldichlorosilane is above 50%, and the selectivity of (CH3)2-SiH-Cl is above 80%, which are much higher than the conversion rate and selectivity of using other catalysts.

[0081] By comparing the data of Example 1 and Comparative Example 1, and Example 2 and Comparative Example 2, it can be seen that the noble metal@ZSM-5 dual-function encapsulated catalyst prepared by the in situ synthesis method in Examples 1 and 2 significantly improves the conversion rate of dimethyldichlorosilane and the selectivity of dimethylhydrochlorosilane compared to the catalyst prepared by the impregnation method. Under the same conditions, the conversion rate of dimethyldichlorosilane is increased from less than 41% to more than 60%, and the selectivity of dimethylhydrochlorosilane is increased from less than 66.1% to more than 90%.

[0082] By comparing Example 2 and Comparative Example 4, it can be seen that in Example 2, ZSM-5 molecular sieve is selected as the carrier. Under the same in situ synthesis method, compared with Comparative Example 4 using Beta molecular sieve as the carrier, in Example 2, the selectivity of (CH3)2-SiH-Cl is 96.1%, and the single-pass conversion rate of dimethyldichlorosilane is 72.3%, while in Comparative Example 4, the selectivity of (CH3)2-SiH-Cl is only 78.1%, and the single-pass conversion rate of dimethyldichlorosilane is only 45.1%. This shows that the present invention significantly improves the reaction conversion rate and the selectivity of (CH3)2-SiH-Cl compared to other supported catalysts by selecting the noble metal @ ZSM-5 dual-function encapsulated catalyst.

[0083] By comparing Example 1 with Comparative Examples 5 to 6, it can be seen that the Pt@ZSM-5 bifunctional encapsulated catalyst prepared by the in situ synthesis method in Example 1 is compared with the catalysts in Comparative Examples 5 to 6. Although Comparative Example 5 adopts a fixed bed reactor method, the single-pass conversion rate of dimethyldichlorosilane is only 25.3%, the selectivity of dimethylhydrochlorosilane is 92.8%, and the calculated yield of dimethylhydrochlorosilane is only 23.49%. Comparative Example 6 uses the same reaction method as Example 1, and its selectivity and yield of dimethylhydrochlorosilane are significantly lower than those in Example 1, indicating that the catalyst selected in the present invention is significantly improved over the catalyst in the prior art.

[0084] In summary, the method for preparing dimethyldichlorosilane provided by the present invention is simple to operate, has mild reaction conditions, has excellent single-pass conversion rate and selectivity for dimethylhydrochlorosilane, and is suitable for industrial production.

[0085] The applicant declares that the present invention is intended to illustrate the detailed structural features of the present invention through the above-described embodiments, but the present invention is not limited to the above-described detailed structural features. This does not mean that the present invention must rely on the above-described detailed structural features in order to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent replacements for selected components, additions of auxiliary components, and selection of specific embodiments, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for preparing dimethylhydrochlorosilane, characterized in that: The method comprises: performing a cracking and disproportionation reaction on dimethyldichlorosilane under the action of a catalyst to prepare dimethylhydrochlorosilane; The catalyst is a noble metal@ZSM-5 bifunctional catalyst formed by encapsulating noble metal M nanoparticles in ZSM-5 molecular sieve; The temperature of the cracking and disproportionation reaction is 150-300°C; The noble metal M nanoparticles are any one of Pt, Pd, Ru, Au or Ag, or a combination of at least two thereof; The content of the noble metal M in the catalyst is 0.1-1.0 wt %; The silicon-aluminum ratio in the catalyst is SiO2 / Al2O3=100:1~500:1; The catalyst is obtained by an in-situ synthesis method; The ZSM-5 molecular sieve is a sodium-free aluminosilicate molecular sieve.

2. The method according to claim 1, characterized in that The hydrogen pressure of the cracking and disproportionation reaction is 3.0-6.0 MPa.

3. The method according to claim 1, characterized in that The single-pass usage of the catalyst accounts for 0.1-10 wt % of dimethyldichlorosilane.

4. The method according to claim 1, wherein The particle size of the noble metal M nanoparticles is 0.5-3 nm.

5. The method according to claim 1, characterized in that The in-situ synthesis method comprises: adding a noble metal precursor during the in-situ synthesis process of the ZSM-5 molecular sieve, so as to achieve uniform encapsulation of noble metal M nanoparticles in the ZSM-5 molecular sieve.

6. The method according to claim 5, characterized in that The preparation method of the catalyst comprises: mixing a silicon source, an aluminum source, a noble metal precursor, a structure directing agent and water, and sequentially performing hydrothermal crystallization, cooling, solid-liquid separation, roasting and reduction to obtain the catalyst.

7. The method according to claim 1, characterized in that The method comprises the following steps: mixing dimethyldichlorosilane and a catalyst, wherein the single-pass amount of the catalyst accounts for 2-10 wt% of the dimethyldichlorosilane, and performing a cracking and disproportionation reaction under a hydrogen pressure of 3.0-6.0 MPa, 150-300° C., and stirring conditions for a reaction time of 0.5-4 hours to prepare dimethylhydrochlorosilane; The catalyst is a noble metal@ZSM-5 bifunctional catalyst formed by encapsulating noble metal M nanoparticles in ZSM-5 molecular sieve, wherein the particle size of the noble metal M nanoparticles is 0.5-3 nm; the content of noble metal M in the catalyst is 0.1-1.0 wt %; and the silicon-aluminum ratio SiO2 / Al2O3 in the catalyst is 100:1-500:1.

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