[BMIM] Cl (at) MCM-41 catalyst and method for synthesizing methyl trichlorosilane by using [BMIM] Cl (at) MCM-41 catalyst

Abstract

The invention relates to a [BMIM] Cl (at) MCM-41 catalyst and a method for synthesizing methyl trichlorosilane, the preparation method of the catalyst comprises the following steps: a) preparing an MCM-41 mesoporous molecular sieve by adopting a hydrothermal synthesis method, the specific method for preparing the MCM-41 mesoporous molecular sieve is as follows: taking cetyltrimethylammonium bromide (CTAB) as a template agent, taking tetraethyl orthosilicate (TEOS) as a silicon source, and adopting a hydrothermal synthesis method for preparing the MCM-41 mesoporous molecular sieve; the preparation method comprises the following steps of: mixing and stirring the MCM-41 molecular sieve serving as a raw material and tetramethylammonium hydroxide (TMAOH) serving as an alkali solution to form gel, dealcoholizing, crystallizing, washing, drying and calcining to obtain the MCM-41 mesoporous molecular sieve. The [BMIM] Cl (at) MCM-41 is used as the catalyst for synthesizing methyl trichlorosilane by a Grignard reagent method, the mesoporous structure of the MCM-41 improves the diffusion efficiency of reactants, and the structure is matched with the molecular size of the ionic liquid to form a uniformly dispersed active center and shorten the contact path of the reactants.

Description

Technical Field

[0001] The invention belongs to the technical field of organosilicon compound synthesis and relates to a [BMIM]Cl@MCM-41 catalyst and a method for synthesizing methyltrichlorosilane therefrom. Background Art

[0002] The rapid development of the organosilicon industry is inseparable from the synthesis of organosilicon monomers and the widespread application of their products. Over a thousand organosilicon products are widely used in various sectors of the national economy and have become one of the fastest-growing varieties of new chemical materials. The most important and complex part of organosilicon production is monomer synthesis. Traditional methods for synthesizing methyltrichlorosilane include the direct method, the disproportionation method, and the Grignard reagent method. However, the direct method has a low silicon powder conversion rate (65%) and produces a high amount of dimethyldichlorosilane as a byproduct (accounting for >18%). The disproportionation method requires high temperature and pressure and is energy-intensive. The traditional Grignard reagent method requires a relatively low temperature (-30°C). During industrialization, MeMgX reacts rapidly with SiCl4, resulting in local overheating and explosion risks. The traditional catalyst CuCl has poor selectivity and cannot inhibit excessive substitution of methyl groups.

[0003] To this end, [BMIM]Cl@MCM-41 catalyst and its method for synthesizing methyltrichlorosilane were designed to overcome the above problems. Summary of the Invention

[0004] The present invention aims to overcome the shortcomings of the prior art by providing a [BMIM]Cl@MCM-41 catalyst with a rational design, improved reaction selectivity, reduced reaction energy consumption, and lower production costs, and a method for synthesizing methyltrichlorosilane. The present invention utilizes an ionic liquid-modified mesoporous molecular sieve ([BMIM]Cl@MCM-41) as a catalyst to efficiently prepare methyltrichlorosilane (CH3SiCl3) through the reaction of silicon tetrachloride (SiCl4) with a methyl Grignard reagent (CH3MgX). The catalyst production process is environmentally friendly and exhibits excellent recyclability.

[0005] The present invention is achieved through the following technical solution: a [BMIM]Cl@MCM-41 catalyst, wherein the preparation method of the catalyst comprises the following steps:

[0006] a) preparing MCM-41 mesoporous molecular sieve, wherein the preparation adopts a hydrothermal synthesis method, specifically comprising: using hexadecyltrimethylammonium bromide (CTAB) as a template, tetraethyl orthosilicate (TEOS) as a silicon source, and tetramethylammonium hydroxide (TMAOH) as an alkali solution, mixing and stirring them into a gel, and then dealcoholizing them, followed by crystallization, water washing, drying, and calcination to obtain the MCM-41 mesoporous molecular sieve.

[0007] b) 1-Butyl-3-methylimidazole chloride ([BMIM]Cl) was dissolved in anhydrous ethanol, and calcined MCM-41 was added. The mixture was ultrasonically treated and vacuum dried to obtain the [BMIM]Cl@MCM-41 catalyst.

[0008] Preferably, in step a), the molar ratio of CTAB to TEOS is 0.1-0.5:1, and the alkaline solution TMAOH is added to control the pH to 9-11 to form a micellar structure.

[0009] Preferably, the crystallization conditions in step a) are 100-120° C. for 48-72 h; and the calcination conditions are 500-800° C. for 4-8 h.

[0010] Preferably, in step b), the mass ratio of [BMIM]Cl to MCM-41 is 1:5; and the ratio of anhydrous ethanol to [BMIM]Cl is 25 mL / 1 g.

[0011] A method for synthesizing methyltrichlorosilane comprises the following steps: adding SiCl4 and the catalyst according to claim 1 into a dry reactor, dropwise adding CH3MgCl to the reaction system, stirring and reacting for several hours, adding hydrochloric acid to quench, separating the liquids, and distilling to obtain the product CH3SiCl3.

[0012] Preferably, the mass ratio of SiCl4 to catalyst is 50-100:1.

[0013] Preferably, the molar ratio of the added CH3MgCl to the added SiCl4 is 1.5-2.0:1.

[0014] Preferably, after adding SiCl4 and the catalyst into the reactor, the reactor needs to be replaced with nitrogen for at least 3 times.

[0015] As a preference, the stirring reaction condition in the reactor is stirring at room temperature for 2 hours.

[0016] As a preference, the quenching concentration of the added dilute hydrochloric acid is 10%.

[0017] The beneficial effects of the present invention are as follows:

[0018] Compared with the prior art, the present invention uses [BMIM]Cl@MCM-41 as a catalyst for the Grignard reagent method to synthesize methyltrichlorosilane. The mesoporous structure of MCM-41 improves the diffusion efficiency of the reactants, and the structure matches the molecular size of the ionic liquid to form a uniformly dispersed active center, shortening the contact path of the reactants and reducing side reactions (such as the formation of (CH3)2SiCl2). The selectivity is increased to 99.7%. -As a weak Lewis acid site, it polarizes the Si-Cl bond through electrostatic interaction, promoting the nucleophilic substitution reaction of SiCl4. At the same time, the imidazolium cation stabilizes the reaction intermediate (such as SiCl3-) through hydrogen bonding, reducing the reaction energy barrier. This synergistic effect enables the reaction to proceed efficiently at room temperature (25°C); the chemical bonding between the hydroxyl groups on the surface of MCM-41 and [BMIM]Cl effectively inhibits the loss of ionic liquid during the reaction, achieving a catalyst activity of >98% after recycling ≥10 times; the production process of this catalyst system is green and environmentally friendly, and the catalyst can be recovered by simple magnetic separation after the reaction, reducing production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a comparison chart of the catalyst stability of the present invention. DETAILED DESCRIPTION

[0020] In order to enable those skilled in the art to more clearly understand the objectives, technical solutions and advantages of the present invention, the present invention is further described below with reference to the accompanying drawings and embodiments.

[0021] In the description of the present invention, it should be understood that the orientations or positional relationships indicated by terms such as “upper”, “lower”, “left”, “right”, “inside”, “outside”, “horizontal” and “vertical” are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, rather than indicating or implying that the device or component referred to must have a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0022] The present invention will be described in detail below with reference to the accompanying drawings: Figure 1 As shown, a [BMIM]Cl@MCM-41 catalyst, the preparation method of the catalyst comprises the following steps:

[0023] a) preparing MCM-41 mesoporous molecular sieve, wherein the preparation adopts a hydrothermal synthesis method, specifically comprising: using hexadecyltrimethylammonium bromide (CTAB) as a template, tetraethyl orthosilicate (TEOS) as a silicon source, and tetramethylammonium hydroxide (TMAOH) as an alkali solution, mixing and stirring them into a gel, and then dealcoholizing them, followed by crystallization, water washing, drying, and calcination to obtain the MCM-41 mesoporous molecular sieve.

[0024] b) 1-Butyl-3-methylimidazole chloride ([BMIM]Cl) was dissolved in anhydrous ethanol, and calcined MCM-41 was added. The mixture was ultrasonically treated and vacuum dried to obtain the [BMIM]Cl@MCM-41 catalyst.

[0025] In the step a), the molar ratio of CTAB to TEOS is 0.1-0.5:1, and the alkaline solution TMAOH is added to control the pH to 9-11 to form a micellar structure.

[0026] In step a), the crystallization conditions are 100-120° C. for 48-72 hours; and the calcination conditions are 500-800° C. for 4-8 hours.

[0027] In step b), the mass ratio of [BMIM]Cl to MCM-41 is 1:5; the ratio of anhydrous ethanol to [BMIM]Cl is 25 mL / 1 g. A method for synthesizing methyltrichlorosilane comprises: adding SiCl4 and the catalyst of claim 1 to a dry reactor, dropwise adding CH3MgCl to the reaction system, stirring the reaction for several hours, quenching with hydrochloric acid, separating the liquids, and distilling to obtain the product CH3SiCl3.

[0028] The mass ratio of SiCl4 to catalyst is 50-100:1.

[0029] The molar ratio of the dropwise added CH3MgCl to the added SiCl4 is 1.5-2.0:1.

[0030] After adding SiCl4 and catalyst into the reactor, the gas must be replaced with nitrogen for at least 3 times.

[0031] The stirring reaction condition in the reactor is stirring at room temperature for 2 hours.

[0032] The concentration of the added dilute hydrochloric acid for quenching is 10%.

[0033] 1) Synthesis of catalyst ([BMIM]Cl@MCM-41)

[0034] MCM-41 mesoporous molecular sieve was prepared by hydrothermal synthesis, with hexadecyltrimethylammonium bromide (CTAB) as template, tetraethyl orthosilicate (TEOS) as silicon source, and tetramethylammonium hydroxide (TMAOH) as alkali source. The mixture was stirred into a gel and dealcoholized. The gel was then crystallized at 110°C for 48h, washed with water, dried in vacuum at 60°C for 12h, and calcined at 550°C for 5h to obtain MCM-41 mesoporous molecular sieve.

[0035] (1-Butyl-3-methylimidazole) chloride ([BMIM]Cl) was dissolved in anhydrous ethanol, added with calcined MCM-41, and ultrasonically treated for 2 h. The [BMIM]Cl@MCM-41 catalyst was obtained by vacuum drying.

[0036] 2) Synthesis of methyltrichlorosilane

[0037] In a dry reactor, SiCl4 and [BMIM]Cl@MCM-41 catalyst were added, and CH3MgCl was added dropwise to the reaction system. The reaction was stirred for several hours, and then hydrochloric acid was added to quench the reaction. After separation, the product CH3SiCl3 was obtained by distillation. The molar ratio of deionized water to TEOS was 40-250:1.

[0038] Example

[0039] Dissolve 14.5784g of CTAB in 100mL of deionized water and stir until completely dissolved, forming a transparent micellar solution. Add TMAOH as an alkaline modifier to adjust the solution's pH to 9-12. Slowly add 21g of tetraethylorthosilicate (TEOS) dropwise with vigorous stirring. A white flocculent precipitate gradually forms. Continue stirring for 3 hours to complete the hydrolysis and condensation reaction. Transfer the mixture to a polytetrafluoroethylene-lined autoclave and crystallize at 110°C for 48 hours, controlling the heating rate at 10°C / min. After the reaction, cool to room temperature, filter, and repeatedly wash with deionized water and ethanol until the filtrate is neutral. Remove any residual template and dry at 80°C for 12 hours. Then, calcine 10g of MCM-41 in a muffle furnace at 550°C for 5 hours in air at a rate of 2°C / min to completely remove the template, yielding a white MCM-41 powder.

[0040] 2 g of [BMIM]Cl was dissolved in 50 mL of anhydrous ethanol, and the calcined MCM-41 was added, followed by ultrasonic treatment for 2 h and vacuum drying at 60 °C for 12 h to obtain the [BMIM]Cl@MCM-41 catalyst.

[0041] 1) Synthesis of methyltrichlorosilane

[0042] In a dry reactor, 100g of SiCl4 and 1.5g of catalyst were added and the atmosphere was replaced with nitrogen three times. CH3MgCl3 (1.05 mol) was added dropwise to the reaction system and stirred at 25°C for 2 hours. The reaction was quenched by adding 10% dilute hydrochloric acid. The liquid was separated and the 62-70°C fraction was collected by distillation to obtain the product CH3SiCl3. The product was analyzed by gas chromatography (GC), and the results are shown in the table below.

[0043] Table 1 GC test results of methyltrichlorosilane

[0044] project index Mass fraction of monomethyltrichlorosilane / %≥ 99.5 Mass fraction of trimethyl monochlorosilane / %≤ 0.03 Mass fraction of silicon tetrachloride / %≤ 0.02 Mass fraction of trichlorosilane / %≤ 0.01 Mass fraction of dimethyldichlorosilane / %≤ 0.3

[0045] The experimental data is shown below, comparing the performance of [BMIM]Cl@MCM-41 with conventional catalysts (CuCl and ZnCl / ZSM-5). As shown in the chart below, the [BMIM]Cl@MCM-41 catalyst improves reaction selectivity, reduces reaction energy consumption, and lowers production costs. Furthermore, the catalyst production process is environmentally friendly and exhibits excellent recyclability.

[0046] Table 2 Comparison of traditional processes

[0047]

[0048]

[0049] The specific embodiments described herein are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical concepts disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A [BMIM]Cl@MCM-41 catalyst, characterized in that: The preparation method of the catalyst comprises the following steps: a) preparing MCM-41 mesoporous molecular sieve, wherein the preparation of MCM-41 mesoporous molecular sieve adopts a hydrothermal synthesis method, specifically comprising: using hexadecyltrimethylammonium bromide as a template, tetraethyl orthosilicate as a silicon source, and tetramethylammonium hydroxide as an alkali solution, mixing and stirring them into a gel, and then dealcoholizing them, followed by crystallization, washing, drying, and calcining to obtain the MCM-41 mesoporous molecular sieve; b) [BMIM]Cl was dissolved in anhydrous ethanol, and calcined MCM-41 was added. The mixture was ultrasonically treated and vacuum dried to obtain the [BMIM]Cl@MCM-41 catalyst.

2. The [BMIM]Cl@MCM-41 catalyst according to claim 1, characterized in that: In the step a), the molar ratio of CTAB to TEOS is 0.1-0.5:1, and the alkaline solution TMAOH is added to control the pH to 9-11 to form a micelle structure.

3. The [BMIM]Cl@MCM-41 catalyst according to claim 1, characterized in that: In step a), the crystallization conditions are 100-120° C. for 48-72 hours; and the calcination conditions are 500-800° C. for 4-8 hours.

4. The [BMIM]Cl@MCM-41 catalyst according to claim 1, characterized in that: In step b), the mass ratio of [BMIM]Cl to MCM-41 is 1:5; and the ratio of anhydrous ethanol to [BMIM]Cl is 25 mL / 1 g.

5. A method for synthesizing methyltrichlorosilane, characterized in that: The method comprises the following steps: adding SiCl4 and the catalyst according to claim 1 into a dry reaction kettle, dropwise adding CH3MgCl into the reaction system, stirring and reacting for several hours, adding hydrochloric acid to quench, separating the liquids and distilling to obtain the product CH3SiCl3.

6. The method for synthesizing methyltrichlorosilane according to claim 5, wherein: The mass ratio of SiCl4 to catalyst is 50-100:

1.

7. The method for synthesizing methyltrichlorosilane according to claim 5, wherein: The molar ratio of the dropwise added CH3MgCl to the added SiCl4 is 1.5-2.0:

1.

8. The method for synthesizing methyltrichlorosilane according to claim 5, wherein: After adding SiCl4 and catalyst into the reactor, the gas must be replaced with nitrogen for at least 3 times.

9. The method for synthesizing methyltrichlorosilane according to claim 5, wherein: The stirring reaction condition in the reactor is stirring at room temperature for 2 hours.

10. The method for synthesizing methyltrichlorosilane according to claim 5, wherein: The concentration of the added dilute hydrochloric acid for quenching is 10%.

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