Polyfunctional group catalyst for high-boiling cracking conversion of polycrystalline silicon and organic silicon

Abstract

The invention relates to a polyfunctional catalyst for high-boiling cracking conversion of polycrystalline silicon and organic silicon. The molecular formula of the polyfunctional catalyst is # imgabs0. The catalyst has poison resistance and high-efficiency catalytic performance with double active centers.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental protection, and in particular relates to a multifunctional catalyst for high-boiling cracking and conversion of polysilicon and organosilicon. Background Art

[0002] Polysilicon is an important semiconductor material, widely used in the electronics and photovoltaic industries. The application of polysilicon in the photovoltaic field helps promote the transformation of the energy structure, promote the large-scale application of renewable energy, and support the global sustainable development goals. The polysilicon production process produces high-boiling materials polysilane, which can undergo bond breaking reaction with hydrogen chloride under the action of catalysts, usually using gas-liquid reactors. The catalysts used are organic amines, such as methylamine, tri-n-butylamine, phenylamine and other substances. Existing catalysts use the lone pair of electrons on the N atom in organic amines as activation centers.

[0003] In the prior art, Chinese patent application CN114573629A discloses that: introducing high-boiling chlorosilane and chlorinating agent reacts under the action of a catalyst to produce an organosilicon monomer. The catalyst is one or a combination of formamide, tributylamine, copper chloride, and cyclohexane. The use of high-boiling chlorosilane to prepare the organosilicon monomer can not only reduce the production cost of the organosilicon monomer, but also realize the recycling of high-boiling chlorosilane, and can also improve the quality of the produced polysilicon.

[0004] Chinese patent application CN117985723A discloses: a method for cracking high-boiling polysilicon, which uses a composite organic catalyst, which includes 22wt% to 31wt% of tri-n-butylamine, 68wt% to 75wt% of tri-n-octylamine and 1wt% to 3wt% of N,N-dimethylaniline; the cracking product includes at least 35mol% of trichlorosilane. The use of the composite organic catalyst to crack high-boiling polysilicon can effectively improve the high-boiling product per-pass conversion efficiency without increasing the raw material input and operating costs, so that the proportion of trichlorosilane in the cracking product is higher.

[0005] Existing catalysts use the lone pair of electrons on the N atom in organic amines as activation centers, which have the disadvantages of low activity, short life, poor toxicity resistance, etc. Therefore, it is necessary to provide a high-performance catalyst with toxicity resistance and dual active centers. Summary of the invention

[0006] The technical problem to be solved by the present invention is that the existing catalyst uses the lone pair of electrons on the N atom in the organic amine as the activation center, which shows low activity, short life and poor anti-toxicity in actual use.

[0007] The technical solution adopted by the present invention to solve the technical problem is: a multifunctional catalyst for high-boiling cracking and conversion of polysilicon and organosilicon, the molecular formula of the multifunctional catalyst is:

[0008]

[0009] Among them, R1 and R2 can be the same or different, and R1 and R2 can be selected from the following groups or combinations thereof, and these groups include but are not limited to: H, alkyl, aryl, phenyl, pyridyl, pyrimidyl, thienyl, furyl, silane, hydroxyl, amino, carboxyl, ester and halogenated and silylated groups of the above groups.

[0010] Specifically, the catalyst is CH3-NH-P=O.

[0011] Specifically, CH3-NH-P=O is generated by the reaction of methylamine and phosphorous acid.

[0012] Specifically, the method further includes: preparing a methylamine aqueous solution whose mass percentage accounts for 33% of the total solution and a phosphorous acid whose mass percentage accounts for 85% of the total solution; slowly adding 85% of the phosphorous acid into a three-necked flask under stirring, ensuring that the temperature is kept at room temperature; pouring 50 mL of the 33% methylamine aqueous solution into a dropping funnel; slowly dropping the methylamine aqueous solution into the phosphorous acid under stirring, maintaining the dropping speed so that the reaction temperature does not exceed 30° C.; reacting for 2-3 hours; after the reaction is completed, transferring the reaction mixture to a vacuum distillation apparatus; vacuum distillation conditions: temperature 80-100° C., pressure 10-20 mmHg, under reduced pressure conditions; distilling to remove water and unreacted methylamine; collecting the residue after distillation and purifying it.

[0013] A high boiling point cracking method using the catalyst comprises: raw material pretreatment, catalyst addition, product separation and catalyst recovery.

[0014] Specifically, the raw material pretreatment includes: high boiling point pretreatment: preliminary purification of high boiling points generated in the polysilicon production process to remove large particle impurities and moisture.

[0015] Specifically, product separation includes: after the reaction is completed, the reaction product is quickly cooled to prevent unnecessary side reactions; the gas product is separated from the liquid product by a gas-liquid separator; and the target components in the liquid product are further separated by a distillation or rectification tower to obtain a pure target product.

[0016] The present invention has the following beneficial effects:

[0017] 1) The molecular structure of the catalyst contains a nitrogen-phosphorus double center (NP=O), in which the nitrogen atom (N) and the phosphorus-oxygen double bond (P=O) serve as active sites. In the cracking reaction of polysilicon high-boiling materials, the catalyst with the NR-P=O structure can form a coordination bond with the silicon atom in polysilane, reducing the activation energy of the cracking reaction. At the same time, the P=O bond can accept electrons from silane, promote the cracking reaction, and generate silane gas.

[0018] 2) Some catalyst molecules contain fluorinated phenyl groups, which improve the acid resistance and stability of the catalyst. In some catalyst molecules, trimethylsilyl (-SiMe3) is used to protect the lone pair of electrons on the nitrogen atom to increase chemical stability and catalytic activity.

[0019] 3) Use appropriate proportions to mix the preferred catalyst components to obtain a composite catalyst. In the mixing ratio of catalysts A and B (molecular formula see below) of 75:25, catalyst A occupies a dominant position. The fluorine atoms in catalyst A have an electron-withdrawing effect, which helps to activate the CH bond in n-dodecane. It has stronger active sites or more suitable electronic properties, thus playing a greater role in the catalytic process. Catalyst B has the effect of enhancing the effect of catalyst A. Catalyst B helps catalyst A improve the reaction efficiency by providing additional alkaline sites or changing the reaction environment, helps catalyst A stabilize the transition state, and / or promotes the regeneration of catalyst A, thereby improving the overall catalytic efficiency. If the proportion of catalyst B is too high (, it will lead to competition between the two catalysts, thereby reducing the overall catalytic efficiency. Catalyst B also helps to inhibit certain side reactions, so that more reactants are converted into target products.

[0020] 4) The method of adding catalysts A and B separately can also provide more precise control, improve reaction efficiency and selectivity, simplify the process flow, and facilitate the recovery and reuse of catalysts, thereby achieving better economic and technical benefits in industrial applications. The addition of catalyst B with HCl can provide a local acidic environment, improve the selectivity of the reaction path, reduce unnecessary side reactions, and increase the yield of the target product. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to clearly illustrate the technical solution of the present invention, the drawings of specific implementation methods are briefly introduced below.

[0022] Figure 1 The present invention is a flow chart of a high boiling point cracking method using the catalyst provided by the present invention. DETAILED DESCRIPTION

[0023] The present invention will be described in more detail below with reference to the accompanying drawings, in which preferred embodiments of the present invention are shown, and it should be understood that those skilled in the art can modify the present invention described herein and still achieve the beneficial effects of the present invention. Therefore, the following description should be understood as being widely known to those skilled in the art, and not as a limitation of the present invention.

[0024] For the sake of clarity, not all features of the actual embodiments are described. In the following description, well-known functions and structures are not described in detail because they would obscure the present invention with unnecessary details. It should be recognized that in the development of any actual embodiment, a large number of implementation details must be made to achieve the specific goals of the developer.

[0025] In order to make the purpose and features of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are further described below in conjunction with the accompanying drawings. It should be noted that the accompanying drawings are all in a very simplified form and use non-precise ratios, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0026] Example - Multifunctional Catalyst

[0027] The present invention first provides a multifunctional catalyst for high-boiling cracking and conversion of polysilicon and organosilicon, the molecular formula of the multifunctional catalyst is:

[0028]

[0029] Among them, R1 and R2 can be the same or different, and R1 and R2 can be selected from the following groups or combinations thereof, and these groups include but are not limited to: H, alkyl, aryl, phenyl, pyridyl, pyrimidyl, thienyl, furyl, silane, hydroxyl, amino, carboxyl, ester and halogenated and silylated groups of the above groups.

[0030] The molecular structure of the catalyst contains a nitrogen-phosphorus double center (NP=O), in which the nitrogen atom (N) and the phosphorus-oxygen double bond (P=O) serve as active sites. In the cracking reaction of polysilicon high-boiling materials, the catalyst with the NR-P=O structure can form a coordination bond with the silicon atom in polysilane, reducing the activation energy of the cracking reaction. At the same time, the P=O bond can accept electrons from silane, promote the cracking reaction, and generate silane gas.

[0031] As a necessary explanation, the preparation method of the CH3-NH-P=O structure catalyst is introduced below by taking a specific compound as an example.

[0032] Example 1

[0033] Methylamine reacts with phosphorous acid to form CH3NHP=O

[0034] CH3NH2+H3PO3→CH3NHP=O+2H2O

[0035] Prepare an aqueous solution of methylamine (33% by mass of the total solution) and phosphorous acid (H3PO3, 85% by mass of the total solution).

[0036] Place a 250mL three-necked flask in an ice bath to cool; add phosphorous acid: slowly add 50mL (about 65g) of 85% phosphorous acid to the three-necked flask while stirring. Make sure the temperature remains at room temperature (about 20-25°C). Add methylamine: pour 50mL (about 33g methylamine) of 33% aqueous methylamine solution into the dropping funnel. Under stirring, slowly drop the methylamine aqueous solution into the phosphorous acid, keeping the drop rate so that the reaction temperature does not exceed 30°C. This step takes about 30 minutes. Use a thermometer to monitor the reaction temperature to ensure that the temperature does not exceed 30°C. After the addition is complete, continue to stir and keep the reaction temperature at 30-40°C for 2-3 hours until the reaction is complete. After the reaction is complete, transfer the reaction mixture to a vacuum distillation apparatus. Vacuum distillation conditions: temperature 80-100°C, pressure 10-20mmHg. Under reduced pressure conditions (about 10-20mmHg), distill to remove water and unreacted methylamine. The temperature is controlled at 80-100°C. The residue after distillation, namely methylaminophosphorous acid (CH3NHP=O), is collected and purified.

[0037] It is particularly preferred that the molecular formula of the multifunctional catalyst for high-boiling cracking conversion of polysilicon and organosilicon is:

[0038]

[0039] Example 2, for The synthesis method is as follows:

[0040] 1. Synthesis of fluoroaniline

[0041] C6H5F+NH3→F-C6H4-NH2+H2

[0042] Solvent: anhydrous ethanol, temperature: 78°C, time: 12 hours, catalyst: palladium carbon (Pd / C), pressure: normal pressure

[0043] Fluorobenzene (1.2 moles, representing the minimum unit of reaction, is used here to reflect the ratio of reactants. The actual reaction can be increased proportionally. All reaction processes below have the same meaning and will not be repeated here) and palladium on carbon (0.1 mole %) are added to a round-bottom flask equipped with a reflux condenser. Anhydrous ethanol (about 200 mL) is used as a solvent. Under nitrogen protection, ammonia (excessive) is slowly introduced. Reflux reaction for 12 hours. After the reaction is completed, cool to room temperature and filter to remove palladium on carbon. The solvent is removed by reduced pressure distillation to obtain a crude product, fluoroaniline. The product is purified by recrystallization or column chromatography.

[0044] 2. Introduction of silane groups

[0045] F-C6H4-NH2+(CH3)3SiCl→F-C6H4-NH-Si(CH3)3+HCl

[0046] Solvent: anhydrous dichloromethane (CH2Cl2), temperature: 0℃ to room temperature, time: 4 hours, pressure: normal pressure

[0047] Add fluoroaniline (1.7 mol) to a flask equipped with a stirring rod, add anhydrous dichloromethane (about 200 mL) as a solvent, and cool to 0°C in an ice bath; slowly add trimethylsilyl chloride ((CH3)3SiCl, 1.1 mol) dropwise while stirring. After the addition is complete, remove the ice bath and allow the reaction mixture to gradually warm to room temperature. Continue stirring at room temperature for 4 hours. After the reaction is completed, remove the solvent by vacuum distillation. Wash the product with a saturated sodium bicarbonate solution to remove the generated HCl. Dry with anhydrous sodium sulfate and filter to obtain silane-protected fluoroaniline. Purify the product by column chromatography.

[0048] 3. Synthesis of phosphoramide

[0049]

[0050] Add silyl-protected fluoroaniline (1 mol) to a flask equipped with a stirring bar. Add anhydrous dichloromethane (about 200 mL) as a solvent. Cool to 0°C in an ice bath. Slowly add phosphorus oxychloride (POCl3, 1.1 mol) while stirring. After the addition is complete, remove the ice bath and allow the reaction mixture to gradually warm to room temperature. Continue stirring at room temperature for 6 hours. After the reaction is completed, remove the solvent by vacuum distillation. Wash the product with saturated sodium bicarbonate solution to remove excess acid. Dry with anhydrous sodium sulfate and filter to obtain the target catalyst molecule. Purify the product by column chromatography to obtain a pure target catalyst. Confirm the presence of the P=O bond by infrared spectroscopy (IR).

[0051] The catalyst prepared in Example 2 above contains fluorophenyl groups, which improves the acid resistance and stability of the catalyst. The trimethylsilyl group (-SiMe3) protects the lone pair of electrons on the nitrogen atom, further improving the performance of the catalyst.

[0052] Example 3: For The synthesis method is as follows:

[0053] 1. Synthesis of pyridinamine

[0054] C5H5N+NH3→C5H4N-NH2+H2

[0055] Pyridine (1 mole) and palladium on carbon (0.1 mole %) were added to a round-bottom flask equipped with a reflux condenser. Anhydrous ethanol (about 200 mL) was added as a solvent. Ammonia (excess) was slowly introduced under nitrogen protection. The reaction was refluxed for 8 hours. After the reaction was completed, it was cooled to room temperature and the palladium on carbon was filtered out. The solvent was removed by distillation under reduced pressure to obtain a crude product, pyridinamine. The product was purified by column chromatography.

[0056] 2. Introduction of silane groups

[0057] C5H4N-NH2+(CH3)3SiCl→C5H4N-NH-(Si(CH3)3)+HCl

[0058] Add pyridinamine (1 mol) to two flasks equipped with stirring bars. Add anhydrous dichloromethane (about 200 mL) as solvent. Cool to 0°C in an ice bath. Slowly add trimethylsilyl chloride ((CH3)3SiCl, 1.3 mol) dropwise while stirring. After the addition is complete, remove the ice bath and allow the reaction mixture to gradually warm to room temperature. Dry with anhydrous sodium sulfate and filter to obtain silane-protected pyridinamine. Purify the product.

[0059]

[0060] Add alkyl-protected pyridinamine (1 mol) to a flask equipped with a stirring bar. Add anhydrous dichloromethane (about 200 mL) as a solvent. Cool to 0°C in an ice bath. Slowly add phosphorus oxychloride (POCl3, 1.1 mol) dropwise while stirring. After the addition is complete, remove the ice bath and allow the reaction mixture to gradually warm to room temperature. Continue stirring at room temperature for 4 hours. After the reaction is completed, remove the solvent by vacuum distillation. Wash the product with saturated sodium bicarbonate solution to remove excess acid. Dry with anhydrous sodium sulfate and filter to obtain the target catalyst molecule. Purify the product by column chromatography to obtain a pure target catalyst. Confirm the presence of the P=O bond by infrared spectroscopy (IR) detection.

[0061] The catalyst in Example 3 above contains a pyridine ring to increase chemical stability and catalytic activity, and a trimethylsilyl group (-SiMe3) to protect the lone pair of electrons on the nitrogen atom. It is combined with multiple different amine groups to form a complex catalyst molecule.

[0062] The catalysts in the above-mentioned Examples 2 and 3 can be used alone, which is sufficient to improve the anti-toxicity and catalytic efficiency of the catalyst.

[0063] More preferably, the catalysts of Examples 2 and 3 are used in combination to increase the catalyst activity during the reaction of high boiling points with HCl.

[0064] Example 4: A multifunctional catalyst for high-boiling cracking conversion of polycrystalline silicon and organosilicon used in combination.

[0065] The catalyst prepared in Example 2 is defined as catalyst A, and the catalyst prepared in Example 3 is defined as catalyst B. The coordinated use of the two catalysts has a better effect.

[0066] Use an electronic balance to accurately weigh the sample of n-dodecane (e.g., 500 g) used as the reagent for the evaluation experiment. Weigh catalysts A and B according to the set ratio (see Table 1), and keep the total mass consistent (e.g., total weight 1 g). Place the mixture of n-dodecane and catalysts A and B into a reactor and add an appropriate amount of solvent (anhydrous dichloromethane). Close the reactor and introduce protective gas to exclude air. Turn on the agitator and heat the reactor to a predetermined temperature (e.g., 25°C). After 4 hours, stop the reaction and stop heating. Open the reactor and transfer the reaction mixture to a separatory funnel. Wash the catalyst with a solvent and then separate the liquid product. Remove the solvent using a rotary evaporator to obtain a pure cracking product.

[0067] Use GC or GC-MS to analyze the composition of the cracking products, and calculate the relative content of each product by peak area. Taking the short-chain alkanes produced by the cracking of n-dodecane as the target product, the data obtained are as follows:

[0068] Table 1

[0069]

[0070] At a ratio of 75:25, catalyst A occupies a dominant position. The fluorine atoms in catalyst A have an electron-withdrawing effect, which can activate the CH bonds in n-dodecane, have stronger active sites or more suitable electronic properties, and play a greater role in the catalytic process. Catalyst B only accounts for 25%. By providing additional alkaline sites or changing the reaction environment, catalyst B provides a stable transition state environment for catalyst A, and / or promotes the regeneration of catalyst A, thereby improving the overall catalytic efficiency. If the proportion of catalyst B is too high (for example, 50:50 or higher), it will lead to competition between the two catalysts, thereby reducing the overall catalytic efficiency. Catalyst B also helps to inhibit certain side reactions, allowing more reactants to be converted into target products.

[0071] Example 5: A method for cracking high boiling points using the above catalyst. The above catalyst can be the single component catalyst prepared in Examples 1-3, or the composite catalyst in Example 4.

[0072] The method includes:

[0073] 1. Raw material pretreatment

[0074] High boiling point pretreatment: The high boiling points generated during the polysilicon production process are initially purified to remove large particle impurities and moisture.

[0075] Preparation of Catalyst A: Catalyst A (Example 2) was prepared into a solution at a ratio of 75% of the total catalyst amount.

[0076] Preparation of HCl and catalyst B: Catalyst B (Example 3) was dissolved in HCl solution at a ratio of 25% of the total catalyst amount so as to be added into the reaction system together with HCl.

[0077] 2. Add catalyst

[0078] Select a continuous stirred tank reactor and uniformly add the catalyst A solution to the high boiling point through a metering pump or injection system. Introduce the HCl solution containing catalyst B into the reactor through another independent feed port. At 300-400°C and normal pressure, maintain a constant stirring speed to ensure good mixing and mass transfer, and react for 6 hours.

[0079] 3. Product separation

[0080] After the reaction is completed, the reaction product is quickly cooled to prevent unnecessary side reactions. The gas product is separated from the liquid product by a gas-liquid separator.

[0081] The target components in the liquid product are further separated by a distillation or rectification tower to obtain a pure target product.

[0082] 4. Catalyst recovery

[0083] Precipitation / Filtration: For solid catalysts, they can be recovered by precipitation or filtration.

[0084] Comparative test:

[0085]

[0086]

[0087] Through the above comparative tests, we can know that:

[0088] The method of adding catalysts A and B separately can provide more precise control, improve reaction efficiency and selectivity, simplify the process flow, and facilitate the recovery and reuse of catalysts, achieving better economic and technical benefits in industrial applications. Adding catalyst B with HCl can create a local acidic environment, improve the selectivity of the reaction path, reduce unnecessary side reactions, and increase the yield of the target product.

[0089] In summary, the present invention has the following beneficial effects:

[0090] 1) The molecular structure of the catalyst contains a nitrogen-phosphorus double center (NP=O), in which the nitrogen atom (N) and the phosphorus-oxygen double bond (P=O) serve as active sites. In the cracking reaction of polysilicon high-boiling materials, the catalyst with the NR-P=O structure can form a coordination bond with the silicon atom in polysilane, reducing the activation energy of the cracking reaction. At the same time, the P=O bond can accept electrons from silane, promote the cracking reaction, and generate silane gas.

[0091] 2) Some catalyst molecules contain fluorinated phenyl groups, which improve the acid resistance and stability of the catalyst. In some catalyst molecules, trimethylsilyl (-SiMe3) is used to protect the lone pair of electrons on the nitrogen atom to increase chemical stability and catalytic activity.

[0092] 3) Use appropriate proportions to mix the preferred catalyst components to obtain a composite catalyst. In the mixing ratio of catalysts A and B (molecular formula see below) of 75:25, catalyst A occupies a dominant position. The fluorine atoms in catalyst A have an electron-withdrawing effect, which helps to activate the CH bond in n-dodecane. It has stronger active sites or more suitable electronic properties, thus playing a greater role in the catalytic process. Catalyst B has the effect of enhancing the effect of catalyst A. Catalyst B helps catalyst A improve the reaction efficiency by providing additional alkaline sites or changing the reaction environment, helps catalyst A stabilize the transition state, and / or promotes the regeneration of catalyst A, thereby improving the overall catalytic efficiency. If the proportion of catalyst B is too high (, it will lead to competition between the two catalysts, thereby reducing the overall catalytic efficiency. Catalyst B also helps to inhibit certain side reactions, so that more reactants are converted into target products.

[0093] 4) The method of adding catalysts A and B separately can also provide more precise control, improve reaction efficiency and selectivity, simplify the process flow, and facilitate the recovery and reuse of catalysts, thereby achieving better economic and technical benefits in industrial applications. The addition of catalyst B with HCl can provide a local acidic environment, improve the selectivity of the reaction path, reduce unnecessary side reactions, and increase the yield of the target product.

[0094] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A multifunctional catalyst for high-boiling cracking and conversion of polysilicon and organosilicon, characterized in that: The molecular formula of the multifunctional catalyst is: Among them, R1 and R2 can be the same or different, and R1 and R2 can be selected from the following groups or combinations thereof, and these groups include but are not limited to: H, alkyl, aryl, phenyl, pyridyl, pyrimidyl, thienyl, furyl, silane, hydroxyl, amino, carboxyl, ester and halogenated and silylated groups of the above groups.

2. The catalyst according to claim 1, characterized in that: The catalyst is CH3-NH-P=O.

3. A method for preparing the catalyst according to claim 2, characterized in that: CH3-NH-P=O is generated by the reaction of methylamine and phosphorous acid.

4. The preparation method according to claim 3, characterized in that: The method further comprises: preparing a methylamine aqueous solution whose mass percentage accounts for 33% of the total solution and a phosphorous acid whose mass percentage accounts for 85% of the total solution; slowly adding 85% of the phosphorous acid into a three-necked flask under stirring, ensuring that the temperature is kept at room temperature; pouring 50 mL of the 33% methylamine aqueous solution into a dropping funnel; slowly dropping the methylamine aqueous solution into the phosphorous acid under stirring, maintaining the dropping speed so that the reaction temperature does not exceed 30° C.; reacting for 2-3 hours; after the reaction is completed, transferring the reaction mixture to a vacuum distillation device; vacuum distillation conditions: temperature 80-100° C., pressure 10-20 mmHg, under reduced pressure; distilling to remove water and unreacted methylamine; collecting the residue after distillation, and purifying it.

5. A high boiling point cracking method using the catalyst according to any one of claims 1 to 2, comprising: Raw material pretreatment, catalyst addition, product separation, and catalyst recovery.

6. The high boiling point cracking method according to claim 5, characterized in that: Raw material pretreatment includes: High boiling point pretreatment: Preliminary purification of high boiling points generated during the polysilicon production process to remove large particle impurities and moisture.

7. The high boiling point cracking method according to claim 6, wherein the product separation comprises: After the reaction is completed, the reaction product is quickly cooled to prevent unnecessary side reactions. The gas product is separated from the liquid product by a gas-liquid separator; The target components in the liquid product are further separated by a distillation or rectification tower to obtain a pure target product.

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