Highly selective platinum catalyst and method for synthesis of vinyl bis caps

Abstract

The application relates to the technical field of organic silicon synthesis, and particularly discloses a high-selectivity platinum catalyst and a vinyl double-seal head synthesis method. The high-selectivity platinum catalyst comprises a carrier and a platinum active component loaded on the carrier, the platinum active component is obtained by reducing and activating a platinum precursor and a ligand under a hydrogen atmosphere at 250-350 DEG C after coordination modification, and the molar ratio of the ligand to the platinum element in the platinum precursor is 2-3:1. In the application, the platinum active component is obtained by reducing and activating the platinum precursor and the ligand after coordination modification, and the ligand and the platinum element form a specific coordination structure of the platinum active center, guide the direct silicon-hydrogen addition reaction of acetylene and a hydrogen-containing double-seal head, thus the dimethyl chlorosilane intermediate is not needed, the process flow is simplified, and the effects of improving the reaction yield, environmental protection and process economy are achieved.

Description

Technical Field

[0001] This application relates to the field of organosilicon synthesis technology, and more specifically, to a highly selective platinum catalyst and a method for synthesizing vinyl dual-headed compounds. Background Technology

[0002] Vinyl dimethylsiloxane, chemically known as 1,3-divinyl-1,1,3,3-tetramethyldisiloxane, is an important crosslinking agent and end-capping agent for high-value-added silicone products such as addition-type liquid silicone rubber, silicone pressure-sensitive adhesives, and silicone encapsulation materials. With the rapid development of emerging industries such as new energy vehicles, 5G communications, and flexible electronics, the market demand for high-performance silicone materials is increasing, placing higher requirements on the purity, yield, and greenness of the production process of vinyl dimethylsiloxane.

[0003] Currently, the industrial synthesis of vinyl dimethylsilane-terminated products mostly uses dimethylchlorosilane as a starting material. First, it undergoes a hydrosilylation reaction with acetylene under a platinum catalyst to generate a vinyl dimethylchlorosilane intermediate. Then, the vinyl dimethylchlorosilane is hydrolyzed and condensed under alkaline conditions to obtain the vinyl dimethylsilane product. However, dimethylchlorosilane is highly corrosive, requiring high-quality materials for the reaction equipment, increasing equipment investment and maintenance costs. Furthermore, the hydrolysis step generates a large amount of chlorinated wastewater, placing a heavy burden on environmental treatment and resulting in poor overall economic efficiency. Summary of the Invention

[0004] To address the problems of existing methods for synthesizing vinyl double-headed compounds, which require high-quality reaction equipment, increasing equipment investment and maintenance costs, and generating large amounts of chlorinated acid wastewater during the hydrolysis step, resulting in a heavy environmental treatment burden and poor overall process economics, this application provides a highly selective platinum catalyst and a method for synthesizing vinyl double-headed compounds.

[0005] This application provides a highly selective platinum catalyst and a method for synthesizing vinyl dual-headed products, employing the following technical solution: In a first aspect, this application provides a highly selective platinum catalyst, employing the following technical solution: A highly selective platinum catalyst includes a support and a platinum active component supported on the support. The platinum active component is obtained by coordination modification of a platinum precursor and a ligand, followed by reduction activation at 250-350°C under a hydrogen atmosphere. The molar ratio of platinum in the ligand to the platinum precursor is 2-3:1. The mass of the platinum active component is 0.1%-0.5% of the total mass of the highly selective platinum catalyst.

[0006] By adopting the above technical solution, since the platinum active component is obtained by coordination modification and reduction activation of platinum precursor and ligand, and the ligand and platinum element form a specific coordination structure for the platinum active center, this coordination structure can break through the limitations of the traditional electrophilic and nucleophilic reaction mechanism and guide the direct hydrosilylation reaction between acetylene and hydrogen-containing double-ended heads. Therefore, there is no need to use dimethylchlorosilane intermediate, avoiding equipment corrosion and the generation of chlorinated acid wastewater. At the same time, the process flow is simplified, thereby achieving the effects of improved reaction yield, improved environmental protection, and enhanced process economy. This solves the problems of existing methods for synthesizing vinyl double-ended heads, which have high requirements for the material of reaction equipment, increase equipment investment and maintenance costs, and generate a large amount of chlorinated acid wastewater in the hydrolysis step, resulting in a heavy environmental treatment burden and poor overall process economy.

[0007] Preferably, the support is selected from activated alumina, silica, or activated carbon, the specific surface area of ​​the support is 400-800 m² / g, the average pore size is 5-8 nm, and the ligand is triphenylphosphine.

[0008] By adopting the above technical solution, the platinum active component is uniformly dispersed on the support surface by selecting a support with a specific specific surface area and pore size range and combining it with triphenylphosphine ligand. At the same time, the steric hindrance effect provided by triphenylphosphine can further suppress non-selective reaction pathways, thereby achieving the effect of uniform distribution of catalyst active centers and stable reaction selectivity.

[0009] Preferably, the reaction temperature for coordination modification is 50-70°C, the reaction time is 1.5-3 hours, the heating rate for reduction activation is 2-5°C / min, and the isothermal reduction activation time is 2-5 hours.

[0010] By adopting the above technical solution, the process parameters of coordination modification and reduction activation work together to enable the platinum precursor and ligand to fully react and form a stable complex structure. At the same time, the heating rate and isothermal time during the reduction activation process can precisely control the particle size distribution of platinum nanoparticles, thereby achieving the effect of uniform active center structure and stable catalytic performance.

[0011] Secondly, this application provides a method for synthesizing vinyl double-ended structures, employing the following technical solution: A method for synthesizing vinyl dual-head catalysts, using the aforementioned highly selective platinum catalyst, includes the following steps: The highly selective platinum catalyst is packed into the catalyst layer of a fixed-bed reactor. The fixed-bed reactor is provided with an adsorbent layer, an inert isolation layer and the catalyst layer in sequence from top to bottom. The adsorbent layer is filled with a composite adsorbent for removing moisture and dissolved oxygen from the reactants. The reaction temperature of the catalyst layer is 85-95°C. Hydrogen-containing double-ended heads and acetylene are continuously fed into the fixed-bed reactor, flowing sequentially from top to bottom through the adsorbent layer, the inert isolation layer, and the catalyst layer. A hydrosilylation reaction occurs in the catalyst layer to generate vinyl double-ended heads.

[0012] By adopting the above technical solution, since the adsorbent layer, inert isolation layer and catalyst layer are arranged sequentially from top to bottom in the fixed bed reactor, the reactants flow through the adsorbent layer to remove moisture and dissolved oxygen before contacting the catalyst. This avoids the cumulative poisoning of trace impurities on the surface of the catalyst active center. At the same time, the inert isolation layer prevents the adsorbent and catalyst from mixing. This results in improved long-term catalyst stability and sustained reaction selectivity, solving the problem of activity decay caused by trace impurity poisoning of high-selectivity platinum catalysts in continuous production.

[0013] Preferably, the composite adsorbent comprises a hydrophobically modified molecular sieve and a nano-zero-valent iron-supported deoxidizer.

[0014] By adopting the above technical solution, since the composite adsorbent contains both hydrophobically modified molecular sieve and nano-zero-valent iron supported deoxidizer, moisture is captured by the physical adsorption of molecular sieve, and dissolved oxygen is removed by the chemical oxidation reaction of nano-zero-valent iron. The two adsorbents work synergistically to purify moisture and dissolved oxygen in the reactants at the same time, thereby achieving the effects of improved impurity removal efficiency and enhanced catalyst protection.

[0015] Preferably, the mass ratio of the hydrophobically modified molecular sieve to the nano-zero-valent iron supported deoxidizer is 1.5-2.5:1.

[0016] By adopting the above technical solution, the mass ratio of the hydrophobically modified molecular sieve to the nano-zero-valent iron supported deoxidizer is matched to achieve a balance between the water adsorption capacity and dissolved oxygen removal capacity. This avoids the incomplete removal of corresponding impurities due to the low proportion of a certain component, thereby achieving the best overall impurity removal effect and the most sufficient catalyst protection.

[0017] Preferably, the hydrophobically modified molecular sieve is obtained by modifying a type A molecular sieve with a pore size of 0.5-0.8 nm with γ-aminopropyltriethoxysilane, and the nano-zero-valent iron supported deoxidizer is obtained by supporting nano-zero-valent iron on mesoporous carbon.

[0018] By adopting the above technical solution, the A-type molecular sieve, after being modified to be hydrophobic, maintains its selective adsorption capacity for water molecules while reducing its non-specific adsorption of reactants. The nano-zero-valent iron loaded on mesoporous carbon obtains high specific surface area and good dispersibility. The intrinsic characteristics of the two adsorbents are combined with their functionalized modified structures, thereby achieving the effect of strong selective adsorption capacity for impurities and low loss of effective components.

[0019] Preferably, the filling height of the adsorbent layer is 25%-35% of the total height of the fixed bed reactor, the filling height of the inert isolation layer is 5%-10% of the total height of the fixed bed reactor, and the filling height of the catalyst layer is 50%-60% of the total height of the fixed bed reactor.

[0020] By adopting the above technical solution, the proportion of the loading height of the adsorbent layer, the inert isolation layer and the catalyst layer is matched so that the reactants have sufficient residence time in the adsorbent layer to complete the removal of impurities. At the same time, the catalyst layer has sufficient reaction space to ensure reaction efficiency, thereby achieving a synergistic optimization of purification effect and reaction efficiency.

[0021] Preferably, the feed inlet and discharge outlet of the fixed bed reactor are monitored for moisture removal rate or dissolved oxygen removal rate, respectively. When the moisture removal rate or dissolved oxygen removal rate drops to 70%-75%, the material is switched to the standby reactor.

[0022] By adopting the above technical solution, the removal rates of moisture and dissolved oxygen in the adsorbent layer are monitored online, and the system automatically switches to a standby reactor when the removal rate drops to a set threshold. This avoids irreversible damage to the catalyst caused by impurities penetrating after the adsorbent becomes saturated, thereby achieving the effects of extended catalyst life and continuous and stable production process.

[0023] Preferably, the feed molar ratio of the hydrogen-containing double-ended head to acetylene is 1.1-1.5:1, the total residence time in the fixed-bed reactor is 40-60 minutes, and the partial pressure of acetylene in the fixed-bed reactor is 0.3-0.8 MPa.

[0024] By adopting the above technical solution, the synergistic effect of the feed molar ratio of acetylene to hydrogen-containing dual-head catalyst, the reaction residence time, and the partial pressure of acetylene ensures that the reactants maintain appropriate contact time and reactant concentration in the catalyst bed. This avoids over-addition due to excess acetylene or incomplete conversion due to insufficient residence time, thereby achieving a synergistic improvement in reaction conversion rate and selectivity. In summary, this application has the following beneficial effects: 1. Since the platinum active component used in this application is obtained by coordination modification and reduction activation of platinum precursor and ligand, and the ligand and platinum element form a specific coordination structure of platinum active center, this coordination structure can break through the limitations of traditional electrophilic and nucleophilic reaction mechanism and guide acetylene to undergo direct hydrosilylation reaction with hydrogen-containing double head. Therefore, there is no need to use dimethylchlorosilane intermediate, avoiding equipment corrosion and the generation of chlorinated acid wastewater. At the same time, the process flow is simplified, thereby achieving the effects of improved reaction yield, improved environmental protection, and enhanced process economy. This solves the problem that the existing method of synthesizing vinyl double head has high requirements for the material of reaction equipment, increases equipment investment and maintenance costs, and the hydrolysis step generates a large amount of chlorinated acid wastewater, resulting in a heavy environmental treatment burden and poor overall process economy.

[0025] 2. In this application, by sequentially setting an adsorbent layer, an inert isolation layer, and a catalyst layer from top to bottom in a fixed-bed reactor, the reactants flow through the adsorbent layer to remove moisture and dissolved oxygen before contacting the catalyst, thus avoiding the cumulative poisoning of trace impurities on the surface of the catalyst's active centers. At the same time, the inert isolation layer prevents the adsorbent from mixing with the catalyst, thereby improving the long-term stability of the catalyst and maintaining the reaction selectivity.

[0026] 3. This application combines hydrophobically modified molecular sieves with nano-zero-valent iron supported deoxidizers. By modifying the pore size and modification method of the hydrophobically modified molecular sieves and the loading structure of the nano-zero-valent iron supported deoxidizers, moisture is captured by the physical adsorption of the molecular sieves, and dissolved oxygen is removed by the chemical oxidation reaction of the nano-zero-valent iron. The two adsorbents work synergistically to purify both moisture and dissolved oxygen in the reactants. At the same time, the hydrophobic modification reduces the non-specific adsorption of reactants by the molecular sieves, and the mesoporous carbon support ensures the good dispersibility of the nano-zero-valent iron. Thus, the technical effects of strong selective adsorption capacity for impurities, low loss of effective components, and sufficient catalyst protection are achieved. Attached Figure Description

[0027] Figure 1 This is a flowchart of a method for synthesizing vinyl double-ended structures provided in this application. Detailed Implementation

[0028] The present application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0029] Technical Concept: Existing methods for synthesizing vinyl dual-ends mostly use dimethylchlorosilane as a starting material, which is obtained through a two-step reaction of hydrosilylation and hydrolysis condensation. However, dimethylchlorosilane is highly corrosive, requiring high-quality materials for the reaction equipment, which increases equipment investment and maintenance costs. At the same time, the hydrolysis step generates a large amount of chlorinated acidic wastewater, resulting in a heavy environmental treatment burden and poor overall economic efficiency. To solve the above problems, some studies have attempted to use a direct hydrosilylation method with acetylene and hydrogen-containing dual-ends to bypass the dimethylchlorosilane intermediate. However, in continuous production, trace amounts of moisture, dissolved oxygen, and polar byproducts generated in the reaction system gradually accumulate on the surface of the catalyst active sites, leading to catalyst activity decay and decreased reaction selectivity, which restricts the long-term stability of the process.

[0030] Based on this discovery, this application prepares a highly selective platinum catalyst by coordination modification and reduction activation of platinum precursors and ligands. This allows the platinum active centers to form specific coordination structures, overcoming the limitations of traditional electrophilic and nucleophilic reaction mechanisms and achieving highly selective direct addition of acetylene to hydrogen-containing dual-heading catalysts. Furthermore, by sequentially arranging an adsorbent layer, an inert isolation layer, and a catalyst layer from top to bottom within a fixed-bed reactor, and by loading a composite adsorbent composed of hydrophobically modified molecular sieves and nano-zero-valent iron-supported deoxidizers into the adsorbent layer, the reactants flow through the adsorbent layer before contacting the catalyst, enabling simultaneous removal of reactants. The trace amounts of moisture and dissolved oxygen in the feed prevent the cumulative poisoning of the catalyst's active sites by impurities. At the same time, by monitoring the impurity removal rate of the adsorbent layer online and automatically switching to a standby reactor when the removal rate drops to a set threshold, the reactants are ensured to always flow through an adsorbent layer with sufficient purification capacity. This effectively maintains the long-term high selectivity and stability of the catalyst. This solves the problems of existing methods for synthesizing vinyl compounds with dual end caps, which have high requirements for the materials of the reaction equipment, increase equipment investment and maintenance costs, and generate a large amount of chlorinated acid wastewater in the hydrolysis step, resulting in a heavy environmental treatment burden and poor overall process economy.

[0031] Unless otherwise specified, all experimental methods used below are conventional methods. All materials, reagents, methods, and instruments used, unless otherwise specified, are conventional materials, reagents, methods, and instruments in this field, which can be obtained commercially or prepared according to literature methods by those skilled in the art.

[0032] Preparation Example 1: Preparation of Highly Selective Platinum Catalysts Weigh 10g of activated alumina support and place it in a 1.0mol / L hydrochloric acid solution. Reflux at 70°C for 4 hours. Wash the treated support with deionized water until the pH of the washing solution reaches 7.0, and then dry it in an oven at 110°C for 12 hours to obtain the pretreated support. Under nitrogen protection, 0.5 g of chloroplatinic acid and 0.8 g of triphenylphosphine were dissolved in 50 mL of anhydrous ethanol, with a molar ratio of chloroplatinic acid to triphenylphosphine of 1:2.5. The mixture was stirred at 60°C for 2 hours to obtain a modified platinum complex solution. The pretreated activated alumina support was immersed in the above-mentioned modified platinum complex solution for 8 hours at a temperature of 25°C. After immersion, it was vacuum dried at 70°C for 8 hours to remove the solvent. The dried supported material was placed in a tube furnace, and a hydrogen-nitrogen mixture with a hydrogen gas fraction of 10% was used as the reducing atmosphere at a gas flow rate of 100 mL / min. The mixture was heated to 300°C at a heating rate of 3.5°C / min and isothermal reduction activation was performed for 3.5 hours to obtain a highly selective platinum catalyst.

[0033] Preparation Example 2: Preparation of Hydrophobically Modified Molecular Sieves 10 g of type A molecular sieve with a pore size of 0.65 nm was weighed and placed in an ethanol solution of 2% γ-aminopropyltriethoxysilane (0.2 g of γ-aminopropyltriethoxysilane and 9.8 g of ethanol). The solution was impregnated at 60°C for 4 hours, then removed and dried at 80°C for 6 hours to obtain a hydrophobically modified molecular sieve.

[0034] Preparation Example 3: Preparation of Nano-Zero-Valence Iron Supported Deoxidizer Weigh 2g of mesoporous carbon and impregnate it in 50mL of 0.1mol / L ferrous sulfate solution. Disperse the mixture ultrasonically for 30 minutes. Under nitrogen protection, add 50mL of 0.2mol / L sodium borohydride solution to the system and stir to reduce for 45 minutes to generate nano-zero valent iron loaded in the pores of the mesoporous carbon. Wash the product four times with deionized water and vacuum dry it at 60°C for 10 hours to obtain nano-zero valent iron supported deoxidizer.

[0035] Preparation Example 4: Preparation of Composite Adsorbent The hydrophobically modified molecular sieve obtained in Preparation Example 2 was mixed with the nano-zero-valent iron supported deoxidizer obtained in Preparation Example 3 at a mass ratio of 2:1 to obtain a composite adsorbent.

[0036] To better understand the above technical solutions, the technical solutions of the present invention will be clearly and completely described below in conjunction with embodiments.

[0037] The following is a further description with reference to the embodiments: Example 1: Please refer to the appendix Figure 1A highly selective platinum catalyst includes a support and a platinum active component supported on the support. The platinum active component is obtained by coordination modification of a platinum precursor and a ligand, followed by reduction activation at 300°C under a hydrogen atmosphere. The molar ratio of platinum in the ligand and the platinum precursor is 2.5:1. The mass of the platinum active component is 0.3% of the total mass of the highly selective platinum catalyst.

[0038] The support is selected from activated alumina, silica, or activated carbon, with a specific surface area of ​​600 m² / g and an average pore size of 6.5 nm. The ligand is triphenylphosphine. The coordination modification reaction temperature is 60°C, the reaction time is 2.25 hours, the reduction activation heating rate is 3.5°C / min, and the isothermal reduction activation time is 3.5 hours.

[0039] A method for synthesizing vinyl dual-head catalysts, using the aforementioned highly selective platinum catalyst, includes the following steps: A highly selective platinum catalyst is packed into the catalyst layer of a fixed-bed reactor. The fixed-bed reactor is arranged from top to bottom as an adsorbent layer, an inert isolation layer, and a catalyst layer. The adsorbent layer is filled with a composite adsorbent for removing moisture and dissolved oxygen from the reactants. The reaction temperature of the catalyst layer is 90°C. The composite adsorbent comprises a hydrophobically modified molecular sieve and a nano-sized zero-valent iron-supported deoxidizer. The mass ratio of the hydrophobically modified molecular sieve to the nano-sized zero-valent iron-supported deoxidizer is 2:1. The hydrophobically modified molecular sieve is obtained by modifying a type A molecular sieve with a pore size of 0.65 nm with γ-aminopropyltriethoxysilane, and the nano-sized zero-valent iron-supported deoxidizer is obtained by supporting nano-sized zero-valent iron on mesoporous carbon. The packing height of the adsorbent layer is 30% of the total height of the fixed-bed reactor, the packing height of the inert isolation layer is 7.5% of the total height of the fixed-bed reactor, and the packing height of the catalyst layer is 55% of the total height of the fixed-bed reactor.

[0040] Hydrogen-containing double-ended heads and acetylene are continuously fed into a fixed-bed reactor, flowing from top to bottom through an adsorbent layer, an inert isolation layer, and a catalyst layer. In the catalyst layer, a hydrosilylation reaction occurs to generate vinyl double-ended heads.

[0041] In this reactor, the moisture removal rate and dissolved oxygen removal rate are monitored at the feed inlet and outlet. When the moisture removal rate or dissolved oxygen removal rate drops to 72.5%, the material is switched to a standby reactor. The feed molar ratio of hydrogen-containing double-headed head to acetylene is 1.3:1, and the total residence time in the fixed-bed reactor is 50 minutes. The partial pressure of acetylene in the fixed-bed reactor is 0.55 MPa.

[0042] Example 2: This example differs from Example 1 above in that: A highly selective platinum catalyst includes a support and a platinum active component supported on the support. The platinum active component is obtained by coordination modification of a platinum precursor and a ligand, followed by reduction activation at 350°C under a hydrogen atmosphere. The molar ratio of platinum in the ligand to the platinum precursor is 3:1, and the mass of the platinum active component is 0.5% of the total mass of the highly selective platinum catalyst.

[0043] The support is selected from activated alumina, silica, or activated carbon, with a specific surface area of ​​800 m² / g and an average pore size of 8 nm. The ligand is triphenylphosphine. The coordination modification reaction temperature is 70°C, the reaction time is 3 hours, the reduction activation heating rate is 5°C / min, and the isothermal reduction activation time is 5 hours.

[0044] A method for synthesizing vinyl dual-head catalysts, using the aforementioned highly selective platinum catalyst, includes the following steps: A highly selective platinum catalyst is packed into the catalyst layer of a fixed-bed reactor. The fixed-bed reactor is arranged from top to bottom as an adsorbent layer, an inert isolation layer, and a catalyst layer. The adsorbent layer is filled with a composite adsorbent for removing moisture and dissolved oxygen from the reactants. The reaction temperature of the catalyst layer is 95°C. The composite adsorbent comprises a hydrophobically modified molecular sieve and a nano-sized zero-valent iron-supported deoxidizer. The mass ratio of the hydrophobically modified molecular sieve to the nano-sized zero-valent iron-supported deoxidizer is 2.5:1. The hydrophobically modified molecular sieve is obtained by modifying type A molecular sieves with a pore size of 0.8 nm with γ-aminopropyltriethoxysilane, and the nano-sized zero-valent iron-supported deoxidizer is obtained by supporting nano-sized zero-valent iron on mesoporous carbon. The packing height of the adsorbent layer is 35% of the total height of the fixed-bed reactor, the packing height of the inert isolation layer is 10% of the total height of the fixed-bed reactor, and the packing height of the catalyst layer is 60% of the total height of the fixed-bed reactor.

[0045] Hydrogen-containing double-ended heads and acetylene are continuously fed into a fixed-bed reactor, flowing from top to bottom through an adsorbent layer, an inert isolation layer, and a catalyst layer. In the catalyst layer, a hydrosilylation reaction occurs to generate vinyl double-ended heads.

[0046] In this reactor, the moisture removal rate and dissolved oxygen removal rate are monitored at the feed inlet and outlet, respectively. When the moisture removal rate or dissolved oxygen removal rate drops to 75%, the material is switched to a standby reactor. The feed molar ratio of hydrogen-containing double-headed head to acetylene is 1.5:1, and the total residence time in the fixed-bed reactor is 60 minutes. The partial pressure of acetylene in the fixed-bed reactor is 0.8 MPa.

[0047] Example 3: This example differs from Example 1 above in that: A highly selective platinum catalyst includes a support and a platinum active component supported on the support. The platinum active component is obtained by coordination modification of a platinum precursor and a ligand, followed by reduction activation at 250°C under a hydrogen atmosphere. The molar ratio of platinum in the ligand and the platinum precursor is 2:1. The mass of the platinum active component is 0.1% of the total mass of the highly selective platinum catalyst.

[0048] The support is selected from activated alumina, silica, or activated carbon, with a specific surface area of ​​400 m² / g and an average pore size of 5 nm. The ligand is triphenylphosphine. The coordination modification reaction temperature is 50°C, the reaction time is 1.5 hours, the reduction activation heating rate is 2°C / min, and the isothermal reduction activation time is 2 hours.

[0049] A method for synthesizing vinyl dual-head catalysts, using the aforementioned highly selective platinum catalyst, includes the following steps: A highly selective platinum catalyst is packed into the catalyst layer of a fixed-bed reactor. The fixed-bed reactor is arranged from top to bottom as an adsorbent layer, an inert isolation layer, and a catalyst layer. The adsorbent layer is filled with a composite adsorbent for removing moisture and dissolved oxygen from the reactants. The reaction temperature of the catalyst layer is 85°C. The composite adsorbent comprises a hydrophobically modified molecular sieve and a nano-sized zero-valent iron-supported deoxidizer. The mass ratio of the hydrophobically modified molecular sieve to the nano-sized zero-valent iron-supported deoxidizer is 1.5:1. The hydrophobically modified molecular sieve is obtained by modifying a type A molecular sieve with a pore size of 0.5 nm with γ-aminopropyltriethoxysilane, and the nano-sized zero-valent iron-supported deoxidizer is obtained by supporting nano-sized zero-valent iron on mesoporous carbon. The packing height of the adsorbent layer is 25% of the total height of the fixed-bed reactor, the packing height of the inert isolation layer is 5% of the total height of the fixed-bed reactor, and the packing height of the catalyst layer is 50% of the total height of the fixed-bed reactor.

[0050] Hydrogen-containing double-ended heads and acetylene are continuously fed into a fixed-bed reactor, flowing from top to bottom through an adsorbent layer, an inert isolation layer, and a catalyst layer. In the catalyst layer, a hydrosilylation reaction occurs to generate vinyl double-ended heads.

[0051] In this reactor, the moisture removal rate and dissolved oxygen removal rate are monitored at the feed inlet and outlet, respectively. When the moisture removal rate or dissolved oxygen removal rate drops to 70%, the material is switched to a standby reactor. The feed molar ratio of hydrogen-containing double-headed head to acetylene is 1.1:1, and the total residence time in the fixed-bed reactor is 40 minutes. The partial pressure of acetylene in the fixed-bed reactor is 0.3 MPa.

[0052] Comparative Example 1: A method for synthesizing vinyl double-ended structures, comprising the following steps: Dimethylchlorosilane and acetylene were reacted at 80°C for 4 hours in the presence of chloroplatinic acid catalyst to produce vinyldimethylchlorosilane; The obtained vinyldimethylchlorosilane was subjected to a hydrolysis-condensation reaction in an aqueous sodium hydroxide solution at a reaction temperature of 50°C for 2 hours. After the reaction was completed, the mixture was allowed to stand and separate into layers. The organic phase was then dried with anhydrous sodium sulfate and distilled under reduced pressure at 120°C and -0.09 MPa. The fraction was collected to obtain the vinyl double-ended product.

[0053] Comparative Example 2: This comparative example differs from Example 1 above in that: The fixed-bed reactor does not have an adsorbent layer or an inert isolation layer; it is only filled with a catalyst layer, the height of which is 90% of the total height of the fixed-bed reactor. Hydrogen-containing double-headed tubes and acetylene are directly introduced into the reactor to react with the catalyst.

[0054] Comparative Example 3: This comparative example differs from Example 1 above in that: The composite adsorbent layer does not contain nano-zero-valent iron supported deoxidizers, but only hydrophobically modified molecular sieves.

[0055] Performance testing: Hydrogen-containing dual-head conversion rate: The content of hydrogen-containing dual-head before and after the reaction was determined by gas chromatography, and the conversion rate was calculated according to the following formula: Conversion rate (%) = (Initial mass of hydrogen-containing dual-head - Mass of hydrogen-containing dual-head after reaction) / Initial mass of hydrogen-containing dual-head × 100%; Chromatographic conditions: The chromatographic column was an HP-5 capillary column (30m × 0.32mm × 0.25μm), the carrier gas was helium, the flow rate was 1.5mL / min, the injection port temperature was 260°C, the detector temperature was 290°C, and the column oven temperature program was: initial temperature 50°C held for 2 minutes, then increased to 280°C at 15°C / min and held for 5 minutes; Vinyl dicapeptide selectivity: The content of vinyl dicapeptides in the reaction product was determined by gas chromatography, and the selectivity was calculated using the following formula: Selectivity (%) = mass of vinyl dicapeptides / (conversion mass of hydrogen-containing dicapeptides × theoretical conversion coefficient) × 100%; chromatographic conditions were the same as above; Catalyst activity retention rate: After 500 hours of continuous operation, the catalyst in the reactor was taken and reacted under the same reaction conditions. The conversion rate of hydrogen-containing dual-head reactor was measured, and the activity retention rate was calculated according to the following formula: Activity retention rate (%) = Conversion rate after 500 hours / Initial conversion rate × 100%; Product purity: The purity of the finally collected vinyl double-headed product was determined by gas chromatography under the same chromatographic conditions as above; The test results are shown in Table 1. Table 1

[0056] As can be seen from Examples 1 to 3 and Comparative Examples 1 to 3, and Table 1, this application achieves the direct addition reaction of acetylene with hydrogen-containing dual-headed compounds using a highly selective platinum catalyst, avoiding side reaction pathways in the intermediate conversion process, significantly improving the conversion efficiency of the reactants, while effectively ensuring the selectivity of the target product and correspondingly improving the purity of the product.

[0057] Based on Examples 1 to 3 and Comparative Example 2, and in conjunction with Table 1, it can be seen that the pre-adsorbent layer in the reactor can continuously remove trace impurities from the reactants, prevent impurities from accumulating on the surface of the catalyst active centers, and enable the catalyst to maintain stable catalytic activity during long-term operation. In contrast, the catalyst activity of the reaction system lacking this layer significantly decreases after continuous operation.

[0058] As can be seen from Examples 1 to 3 and Comparative Example 3, and Table 1, the synergistic effect of the dehydration component and the deoxygenation component in the composite adsorbent is the key to maintaining the long-term activity of the catalyst. Both moisture and dissolved oxygen can poison the active center of the catalyst. Only by removing both types of impurities at the same time can the catalyst be protected in all aspects.

[0059] Based on Examples 1 to 3 and Table 1, it can be seen that the catalysts prepared in this application can maintain stable conversion rates, selectivity, and catalyst activity retention rates, which can meet the stable operation requirements of continuous production. Under the preferred combination of process parameters, each performance index can reach the optimal balance state, indicating that there is a synergistic adaptation relationship between the catalyst preparation conditions and the reaction process conditions, which jointly affect the final reaction effect.

[0060] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A highly selective platinum catalyst, characterized in that, The catalyst includes a support and a platinum active component supported on the support. The platinum active component is obtained by coordination modification of a platinum precursor and a ligand, followed by reduction activation at 250-350°C under a hydrogen atmosphere. The molar ratio of the ligand to the platinum element in the platinum precursor is 2-3:

1. The mass of the platinum active component is 0.1%-0.5% of the total mass of the highly selective platinum catalyst.

2. The highly selective platinum catalyst according to claim 1, characterized in that: The carrier is selected from one of activated alumina, silica, or activated carbon, the specific surface area of ​​the carrier is 400-800 m² / g, the average pore size is 5-8 nm, and the ligand is triphenylphosphine.

3. The highly selective platinum catalyst according to claim 1, characterized in that: The coordination modification reaction temperature is 50-70°C, the reaction time is 1.5-3 hours, the reduction activation heating rate is 2-5°C / min, and the isothermal reduction activation time is 2-5 hours.

4. A method for synthesizing vinyl double-ended structures, characterized in that: The method of using a highly selective platinum catalyst according to any one of claims 1-3 includes the following steps: The highly selective platinum catalyst is packed into the catalyst layer of a fixed-bed reactor. The fixed-bed reactor is provided with an adsorbent layer, an inert isolation layer and the catalyst layer in sequence from top to bottom. The adsorbent layer is filled with a composite adsorbent for removing moisture and dissolved oxygen from the reactants. The reaction temperature of the catalyst layer is 85-95°C. Hydrogen-containing double-ended heads and acetylene are continuously fed into the fixed-bed reactor, flowing sequentially from top to bottom through the adsorbent layer, the inert isolation layer, and the catalyst layer. A hydrosilylation reaction occurs in the catalyst layer to generate vinyl double-ended heads.

5. The method for synthesizing vinyl double-ended structures according to claim 4, characterized in that: The composite adsorbent comprises a hydrophobically modified molecular sieve and a nano-zero-valent iron-supported deoxidizer.

6. The method for synthesizing vinyl double-ended structures according to claim 5, characterized in that: The mass ratio of the hydrophobically modified molecular sieve to the nano-zero-valent iron supported deoxidizer is 1.5-2.5:

1.

7. The method for synthesizing vinyl double-ended structures according to claim 5, characterized in that: The hydrophobically modified molecular sieve is obtained by modifying a type A molecular sieve with a pore size of 0.5-0.8 nm with γ-aminopropyltriethoxysilane, and the nano-zero-valent iron supported deoxidizer is obtained by supporting nano-zero-valent iron on mesoporous carbon.

8. The method for synthesizing vinyl double-ended structures according to claim 4, characterized in that: The adsorbent layer is filled to a height of 25%-35% of the total height of the fixed-bed reactor, the inert isolation layer is filled to a height of 5%-10% of the total height of the fixed-bed reactor, and the catalyst layer is filled to a height of 50%-60% of the total height of the fixed-bed reactor.

9. The method for synthesizing vinyl double-ended structures according to claim 4, characterized in that: The feed inlet and outlet of the fixed-bed reactor are monitored for moisture removal rate or dissolved oxygen removal rate, respectively. When the moisture removal rate or dissolved oxygen removal rate drops to 70%-75%, the material is switched to the standby reactor.

10. A method for synthesizing vinyl double-ended structures according to claim 4, characterized in that: The feed molar ratio of the hydrogen-containing double-ended head to acetylene is 1.1-1.5:1, and the total residence time in the fixed-bed reactor is 40-60 minutes, with an acetylene partial pressure of 0.3-0.8 MPa in the fixed-bed reactor.

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