Preparation method of supported porous carbon for catalyzing hydrosilylation reaction

Abstract

The invention relates to a preparation method of supported porous carbon for catalyzing hydrosilylation reaction, which comprises the following steps: (S1) mixing thermoplastic phenolic resin, polyindole boric acid and a stabilizer, and heating to react to obtain modified phenolic resin; the mass ratio of the thermoplastic phenolic resin to the polyindole boric acid is 100: (15-25); (S2) dissolving the modified phenolic resin, a pore-foaming agent and a curing agent in a solvent, removing the solvent, and crushing to obtain solid particles; (S3) carrying out thermocuring, pre-oxidation, carbonization, activation and oxidation treatment on the solid particles in sequence to obtain oxidized porous carbon; (S4) modifying the oxidized porous carbon with vinyl siloxane to obtain vinyl siloxane modified porous carbon; and (S5) dipping the vinyl siloxane modified porous carbon in an alcoholic solution of platinum salt to obtain the supported porous carbon. The supported porous carbon prepared by the invention has excellent catalytic efficiency and good stability when being used for catalyzing hydrosilylation reaction, and can be recycled.

Description

Technical Field

[0001] The present invention belongs to the technical field of porous carbon, and in particular relates to a method for preparing supported porous carbon for catalyzing hydrosilylation reaction. Background Art

[0002] The hydrosilylation reaction is a type of reaction in which compounds containing Si-H bonds react with unsaturated organic compounds containing carbon-carbon double bonds in the presence of a catalyst to produce organosilicon compounds. The hydrosilylation reaction is the most widely studied and applied reaction in organosilicon chemistry and one of the most important methods for synthesizing organosilicon products containing C-Si bonds. Catalysts play a crucial role in the hydrosilylation reaction. Classic homogeneous platinum catalysts, such as Speier's catalyst and Karstedt's catalyst, are commonly used in industrial production. While these catalysts exhibit higher catalytic activity and selectivity than existing heterogeneous catalysts, they suffer from difficulties in catalyst separation, the easy loss of active components, and the inability to recycle them.

[0003] Porous carbon is one of the common supports for loaded catalysts due to its rich pore structure and large specific surface area. However, the structural stability of the catalyst-loaded porous carbon in the prior art needs to be improved, and the structural stability of porous carbon directly affects the catalytic efficiency. In addition, there are few reports in the prior art specifically on loaded porous carbon for hydrosilylation reactions, and the loaded catalyst is easily lost, resulting in poor recycling performance. For example, CN116851021A discloses a method for preparing a loaded platinum catalyst for hydrosilylation. The method uses a urea-modified phenolic resin as a carbon precursor to prepare a silica-carbon sphere substrate, which is then etched with hydrofluoric acid to obtain a disordered "hollow porous spherical structure" and a carbon substrate with a large number of exposed active sites. The substrate is then nitrogen-doped in an ammonia atmosphere to obtain nitrogen-doped porous carbon spheres. Finally, the nitrogen-doped porous carbon spheres are placed in a solution of H2PtCl6 and ultrasonically treated to obtain nitrogen-doped porous carbon spheres@Pt catalyst. Although the platinum-loaded porous carbon spheres have a high catalytic efficiency when first used, they can only be recycled three times.

[0004] Therefore, it is necessary to develop a suitable porous carbon that can form a loaded porous carbon with stable structure, high catalytic efficiency and recyclability after loading the catalyst, specifically for hydrosilylation reaction. Summary of the Invention

[0005] In order to develop a supported porous carbon that has a stable structure, is recyclable, and has high catalytic efficiency for catalyzing hydrosilylation reactions, the present invention adopts the following technical solutions:

[0006] A method for preparing supported porous carbon for catalyzing hydrosilylation reaction comprises the following steps:

[0007] (S1) mixing thermoplastic phenolic resin, polyindole boronic acid, and a stabilizer uniformly, heating and reacting to obtain a modified phenolic resin; the mass ratio of the thermoplastic phenolic resin to the polyindole boronic acid is 100:(15-25);

[0008] (S2) dissolving the modified phenolic resin, the porogen, and the curing agent in a polar solvent to form a polymer solution, removing the solvent, and crushing the solution to obtain solid particles;

[0009] (S3) the solid particles are sequentially subjected to thermal curing, pre-oxidation, carbonization, and activation pore expansion to obtain porous carbon; the porous carbon is further subjected to oxidation treatment to obtain oxidized porous carbon;

[0010] (S4) modifying the oxidized porous carbon with vinylsiloxane to obtain vinylsiloxane-modified porous carbon;

[0011] (S5) Immersing the porous carbon modified with vinylsiloxane in an alcohol solution of a platinum salt, adding an acid binding agent, and heating and ultrasonically treating the porous carbon to obtain a supported porous carbon that catalyzes a hydrosilylation reaction.

[0012] Preferably, in step (S1), the mass ratio of the thermoplastic phenolic resin to the polyindole boronic acid is 100:(20-25).

[0013] The present invention uses polyindole boronic acid to modify the phenolic resin. The boric acid group of the polyindole boronic acid reacts with the hydroxyl group in the phenolic resin to form a borate ester, thereby forming a network structure in the side chain portion of the phenolic resin, thereby improving its thermal stability. At the same time, the polyindole boronic acid contains a polyindole group with a bicyclic structure. The polyindole has a relatively good thermal stability and can still maintain structural stability at high temperatures, thereby further improving the thermal stability of the modified phenolic resin. In addition, the subsequent thermal curing and pre-oxidation further improve the thermal stability of the phenolic resin. The porogen (polyvinyl pyrrolidone or polymethyl methacrylate) has a low decomposition temperature and first decomposes at a low temperature stage of carbonization. The gas generated by the decomposition escapes from the system, thereby leaving pores. Through the modification of the polyindole boronic acid, thermal curing, and pre-oxidation, the phenolic resin has excellent thermal stability, so it decomposes at a high temperature stage to form a carbon skeleton with a stable structure. This stable structure allows the phenolic resin to have higher stability when used to catalyze a hydrosilylation reaction after loading a platinum catalyst. The inventors also unexpectedly discovered that the supported porous carbon prepared by the present invention not only improves structural stability but also enhances catalytic activity when catalyzing the hydrosilylation reaction. This is likely due to the introduction of boron into the porous carbon through polyindole boronic acid modification. Boron doping modifies the electronic environment of the porous carbon, enhancing its interaction with platinum, and regulating the valence state of platinum, maintaining more active sites. However, the introduction of boron requires controlling the appropriate ratio. If the amount is too low, the catalytic activity is not significantly improved, while if the amount is too high, the structural stability is reduced.

[0014] In addition, the present invention adopts the method of modifying vinylsiloxane on porous carbon, and then utilizing the coordination effect of the vinyl group in vinylsiloxane on platinum to "anchor" the platinum catalyst in the porous carbon, which is more stable and firm than simple physical adsorption.

[0015] Furthermore, the polyindole boronic acid in step (S1) is at least one of poly(4-indole boronic acid), poly(5-indole boronic acid), and poly(6-indole boronic acid), and has a number average molecular weight of 3000 to 5000.

[0016] Furthermore, the polyindole boronic acid in step (S1) is prepared by a method comprising the following steps: dissolving an indole boronic acid monomer in alcohol to obtain a solution A, dissolving an oxidant in water to obtain a solution B, adding the solution B to the solution A and stirring the mixture at 20 to 30° C. for 5 to 8 hours, filtering and separating the precipitate, washing, and drying to obtain the polyindole boronic acid.

[0017] Preferably, the molar ratio of the indole boronic acid monomer to the oxidant is 1:(1.5-2.5); the indole boronic acid monomer is at least one of 4-indole boronic acid, 5-indole boronic acid, and 6-indole boronic acid; the oxidant is at least one of potassium persulfate and ammonium persulfate; and the alcohol is a C2-C4 alcohol, such as ethanol, propanol, isopropanol, or n-butanol.

[0018] Preferably, the washing is water washing 2 to 3 times, and the drying is vacuum drying at 50 to 60° C. for 12 to 24 hours.

[0019] Furthermore, in step (S1), the number average molecular weight of the thermoplastic phenolic resin is 800-1500, and the hydroxyl content is 2wt%-5wt%; the stabilizer is trimethyl phosphate, and its amount is 0.1-0.3wt% of the thermoplastic phenolic resin; the heating reaction is: adding the thermoplastic phenolic resin and polyindole boric acid into a twin-screw mixer, mixing at 50-70°C for 15-30 minutes; then adding the stabilizer thereto, heating to 180-200°C and mixing for 40-60 minutes.

[0020] Furthermore, in step (S2), the mass ratio of the modified phenolic formaldehyde, the porogen, and the curing agent is 100:(15-30):(5-8), preferably 100:(20-25):(5-8).

[0021] Furthermore, in step (S2), the porogen is at least one of polyvinyl pyrrolidone and polymethyl methacrylate, and its number average molecular weight is 6000-15000. The porogen has a low decomposition temperature and a low residual carbon rate. In the subsequent carbonization stage, it decomposes before the phenolic resin, and the gas generated by the decomposition escapes from the system, thereby leaving pores; the curing agent is at least one of hexamethylenetetramine, trimethylhexamethylenediamine, and diethylaminopropylamine. Under the action of the curing agent, a self-crosslinking reaction occurs when the phenolic resin is thermally cured in the subsequent step (S3); the polar solvent is at least one of N,N-dimethylformamide (DMF), N,N-dimethylformamide (DMAC), and N-methylpyrrolidone (NMP); the solvent removal is to rotary evaporation of the polymer solution; and the crushing is to crush the polymer into 100-400 meshes.

[0022] Furthermore, in step (S3), the thermal curing conditions are: 160-180°C for 3-5 hours; the pre-oxidation conditions are: 250-300°C for 2-4 hours in an air atmosphere; and the carbonization conditions are: 700-900°C for 3-6 hours in an inert atmosphere of nitrogen and / or argon. During the thermal curing stage, the phenolic resin undergoes a self-crosslinking reaction to form a network structure; the pre-oxidation stage converts the molecular chains of the phenolic resin into heat-resistant ring or trapezoidal structures, improving the thermal stability of the material; during the carbonization stage, the porogen first decomposes at low temperature, and the cross-linked modified phenolic resin then decomposes at high temperature, thereby forming a carbon skeleton with rich pores and a stable structure.

[0023] Furthermore, in step (S3), the activation and pore expansion agent is at least one of carbon dioxide, water vapor, and ammonia; and the activation conditions are: temperature 800°C to 1000°C, and time 5 hours to 8 hours. The activation and pore expansion expand the pore structure.

[0024] The oxidation treatment in step (S3) is a conventional oxidation process, which is a technique well known to those skilled in the art and is not particularly limited. Its function is to introduce oxygen-containing groups into the porous carbon, thereby facilitating the reaction with the silanol groups in the hydrolyzed vinyl siloxane in step (S4), thereby firmly modifying the vinyl siloxane on the porous carbon in the form of a chemical bond; and the vinyl groups in the vinyl siloxane modified on the porous carbon can be coordinated with the platinum salt in step (S5). For example, the oxidant can be selected from at least one of potassium permanganate, potassium nitrate, ferric oxide, sulfuric acid, nitric acid, oxygen, and ozone. Depending on the selected oxidant, the oxidation method is different. When potassium permanganate, potassium nitrate or ferric oxide is selected as the oxidant, a solid phase oxidation method is adopted, such as mixing porous carbon and potassium permanganate in a mass ratio of 1:(0.2-0.4) and then heating to 250-350°C and keeping warm for 5-8 hours; when sulfuric acid or nitric acid is selected as the oxidant, a liquid phase oxidation method is adopted, such as immersing porous carbon in 3-5 mol / L nitric acid or sulfuric acid at 40-65°C for 3-6 hours; when oxygen or ozone is selected as the oxidant, a gas phase oxidation method is adopted, that is, a heating and ventilation method is adopted, such as heating to 200-300°C and keeping warm for 2-5 hours.

[0025] Furthermore, in step (S4), the mass ratio of the oxidized porous carbon to the vinyl siloxane is 100:(4-7); and the vinyl siloxane is at least one of vinyl triethoxy silane and vinyl trimethoxy silane.

[0026] Furthermore, in step (S4), the modification method is as follows: oxidized porous carbon is dispersed in an alcohol-water solution to obtain a dispersion; vinyl siloxane is added to water, the pH is adjusted to 4-6, and a hydrolysis reaction is carried out at 20-30°C for 20-40 minutes to obtain a hydrolysis solution; the hydrolysis solution is added to the dispersion, and the reaction is stirred at 55-65°C for 4-8 hours to obtain vinyl siloxane-modified oxidized porous carbon. After the reaction is completed, it is necessary to filter, wash with pure water, and dry at 80-90°C. The vinyl siloxane modified in the porous carbon is coordinated with the platinum salt in step (S5), thereby "anchoring" the platinum catalyst in the porous carbon, which is more stable and firm than simple physical adsorption.

[0027] Preferably, the alcohol content in the alcohol aqueous solution is 30-60 wt %, and the alcohol is selected from at least one of methanol and ethanol.

[0028] Furthermore, in step (S5), the mass ratio of the porous carbon, platinum salt and acid binding agent is 10:(0.3-0.5):(0.6-1.5).

[0029] Furthermore, in step (S5), the platinum salt is at least one of H2PtCl6 and PtCl4; the concentration of the alcohol solution of the platinum salt is 5-10 mg / mL, and the alcohol is a C2-C4 alcohol, such as ethanol, propanol, isopropanol or n-butanol; and the acid binding agent is at least one of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, magnesium carbonate, and calcium carbonate.

[0030] Furthermore, in step (S5), the conditions for the heating and ultrasonic treatment are: temperature 60-80°C, frequency 20-30 kHz, and time 30-60 min. After the heating and ultrasonic treatment, the product is filtered, washed with pure water, and dried at 90-110°C.

[0031] In step (S5), the platinum loading in the supported porous carbon is 1.0-1.5 wt%.

[0032] The present invention also provides the use of supported porous carbon in a hydrosilylation reaction, wherein the amount of supported porous carbon used is 10 to 30 ppm based on the Pt content of the reaction system. A hydrosilylation reaction is a reaction in which a compound containing a Si-H bond reacts with an unsaturated organic compound with a carbon-carbon double bond in the presence of a catalyst to form an organosilicon compound. The reaction system herein is the sum of the compound containing a Si-H bond and the unsaturated organic compound with a carbon-carbon double bond.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. The present invention modifies the phenolic resin with polyindole boronic acid, thermally cures it, and pre-oxidizes it, so that the phenolic resin has excellent stability. Combined with the use of a porogen, porous carbon with abundant pores and a stable structure is formed after carbonization and activation. This abundant pores and stable structure enable the porous carbon loaded with a platinum catalyst to have excellent catalytic efficiency and good stability when catalyzing the hydrosilylation reaction, and can be recycled.

[0035] 2. The supported platinum catalyst of the present invention adopts a coordination method. Compared with pure physical adsorption platinum catalyst, platinum is not easily lost, thereby improving the catalytic stability of the supported porous carbon. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a SEM image of the oxidized porous carbon obtained by implementing step 1 (S3). DETAILED DESCRIPTION

[0037] To make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be described in detail below. The following examples are convenient for better understanding of the present invention, but are not intended to limit the present invention. The experimental methods in the following examples are all conventional methods unless otherwise specified.

[0038] Thermoplastic phenolic resin was selected from Hebei Zetian Chemical Co., Ltd., with a number average molecular weight of about 1000 and a hydroxyl content of 3.4 wt%.

[0039] The polymethyl methacrylate was selected from Wanhua Chemical Group, and its number average molecular weight was about 12,000.

[0040] The hydrogen-containing silicone oil was selected from Jiangxi Bluestar Xinghuo Silicone Co., Ltd., with a hydrogen content of 0.1 wt%.

[0041] Preparation Example 1

[0042] 16.1 g (0.1 mol) of 5-indoleboric acid was dissolved in 500 mL of propanol to obtain solution A; 45.6 g (0.2 mol) of ammonium persulfate was dissolved in 150 mL of pure water to obtain solution B; solution B was added dropwise to solution A over 30 min, and the mixture was stirred at 20° C. for 6 h to allow a precipitate to precipitate; after the reaction, the precipitate was separated by filtration, washed twice with pure water, and dried at 55° C. for 12 h to obtain poly(5-indoleboric acid).

[0043] The number average molecular weight of poly(5-indoleboronic acid) was determined to be about 3500 by gel permeation chromatography.

[0044] Preparation Example 2

[0045] 16.1 g (0.1 mol) of 6-indoleboric acid was dissolved in 500 mL of propanol to obtain solution A; 45.6 g (0.2 mol) of ammonium persulfate was dissolved in 150 mL of pure water to obtain solution B; solution B was added dropwise to solution A over 30 min, and the mixture was stirred at 25° C. for 7 h to allow a precipitate to precipitate; after the reaction, the precipitate was separated by filtration, washed twice with pure water, and dried at 55° C. for 12 h to obtain poly(6-indoleboric acid).

[0046] The number average molecular weight of poly(6-indoleboronic acid) was determined to be about 3900 by gel permeation chromatography.

[0047] Comparative Preparation Example 1

[0048] 17.5 g (0.1 mol) of 1H-indole-6-acetic acid was dissolved in 500 mL of propanol to obtain solution A; 45.6 g (0.2 mol) of ammonium persulfate was dissolved in 150 mL of pure water to obtain solution B; solution B was added dropwise to solution A over 30 min, and after the addition was completed, the mixture was stirred at 25° C. for 7 h to allow a precipitate to precipitate; after the reaction was completed, the precipitate was separated by filtration, washed twice with pure water, and dried at 55° C. for 12 h to obtain polyindoleacetic acid.

[0049] The number average molecular weight of the polyindoleacetic acid was determined to be about 4100 by gel permeation chromatography.

[0050] Example 1

[0051] (S1) adding 100 g of thermoplastic phenolic resin, 15 g of poly(5-indoleboric acid) obtained in Preparation Example 1, and 0.2 g of trimethyl phosphate as a stabilizer to a horizontal twin-screw mixer, heating to 55° C. and mixing at 100 rpm for 20 min, then heating to 190° C. and mixing at 200 rpm for 50 min to react, extruding, cooling, and pelletizing to obtain a modified phenolic resin;

[0052] (S2) dissolving 100 g of modified phenolic resin, 15 g of polymethyl methacrylate, and 7 g of hexamethylenetetramine in 1000 mL of DMF to form a polymer solution; the polymer solution was subjected to rotary evaporation and crushed to 200 mesh to obtain solid particles;

[0053] (S3) The solid particles were placed in a tube furnace and heated to 160 ° C for thermal curing for 4 hours; then the temperature was raised to 260 ° C at 3 ° C / min in an air atmosphere (flow rate 40 mL / min) and kept warm for 3 hours for pre-oxidation; then the temperature was raised to 800 ° C at 8 ° C / min in a nitrogen atmosphere (flow rate 80 mL / min) for carbonization for 4.5 hours; finally, the nitrogen was turned off, and water vapor was introduced (flow rate 100 mL / min), and the temperature was kept at 900 ° C for 6 hours for activation and pore expansion to obtain porous carbon; the water vapor was turned off and switched to nitrogen atmosphere, and the temperature was lowered to 300 ° C, and then the nitrogen was turned off and switched to air atmosphere (flow rate 50 mL / min) for oxidation treatment to obtain oxidized porous carbon (its SEM is as shown in FIG). Figure 1 shown);

[0054] (S4) dispersing 50 g of oxidized porous carbon in 800 mL of a propanol aqueous solution (propanol content 40 wt%) to obtain a dispersion; adding 3.0 g of vinyltriethoxysilane to 50 mL of pure water, adjusting the pH to 5.0, and hydrolyzing the mixture at 25° C. for 30 min to obtain a hydrolyzed solution; then adding the hydrolyzed solution to the dispersion, stirring the mixture at 60° C. for 4 h, then filtering and washing with pure water until the filtrate is colorless, and drying the mixture in an oven at 80° C. for 12 h to obtain vinylsiloxane-modified porous carbon;

[0055] (S5) 10 g of vinylsiloxane-modified porous carbon was added to 600 mL of isopropanol and ultrasonicated at room temperature for 5 min to fully disperse the vinylsiloxane-modified porous carbon. Then, 45 mL of an 8 mg / mL PtCl4 isopropanol solution was added, and 1.0 g of an acid-binding agent, sodium carbonate, was added. The mixture was heated to 70°C and ultrasonicated at 25 kHz for 50 min. The mixture was then filtered, washed twice with pure water, and dried at 95°C for 24 h to obtain a supported porous carbon for hydrosilylation reaction.

[0056] The platinum content in the prepared supported porous carbon was tested by ICP-MS, and the platinum content was determined to be 1.2 wt %.

[0057] The prepared supported porous carbon was applied to a hydrosilylation reaction. The specific steps were as follows: 150 g of hydrogenated silicone oil with a hydrogen content of 0.1%, 17.5 g of allyl glycidyl ether, and 0.28 g of the supported porous carbon prepared in Example 1 (i.e., 20 ppm in terms of Pt) were mixed, and then the temperature was raised to 75°C for a hydrosilylation reaction for 5 h. After the temperature was maintained to remove low-boiling substances, an organosilicon product was obtained; and the supported porous carbon was centrifuged, washed, and dried to obtain a supported porous carbon, which was recycled and put into the hydrosilylation reaction again for use in a repeatability experiment to investigate the cyclic stability of the supported porous carbon.

[0058] Example 2

[0059] The rest is the same as Example 1, except that in step (S1), the poly(6-indoleboronic acid) prepared in Preparation Example 2 is used instead of the poly(5-indoleboronic acid) prepared in Preparation Example 1.

[0060] The platinum content in the prepared supported porous carbon was tested by ICP-MS, and the platinum content was determined to be 1.1 wt %.

[0061] The prepared supported porous carbon was applied to a hydrosilylation reaction. The specific steps were as follows: 150 g of hydrogenated silicone oil with a hydrogen content of 0.1%, 17.5 g of allyl glycidyl ether, and 0.30 g of the supported porous carbon prepared in Example 2 (i.e., 20 ppm in terms of Pt) were mixed, and then the temperature was raised to 75°C for a hydrosilylation reaction for 5 h. After the temperature was maintained to remove low-boiling substances, an organosilicon product was obtained; and the supported porous carbon was centrifuged and dried to obtain a supported porous carbon, which was recycled and put into the hydrosilylation reaction again for use in a repeatability experiment to investigate the cyclic stability of the supported porous carbon.

[0062] Example 3

[0063] The rest is the same as Example 1, except that the amount of poly(5-indoleboric acid) used in step (S1) is 20 g, and the amount of polymethyl methacrylate used in step (S2) is 20 g.

[0064] The platinum content in the prepared supported porous carbon was tested by ICP-MS, and the platinum content was determined to be 1.3 wt %.

[0065] The prepared supported porous carbon was applied to a hydrosilylation reaction. The specific steps were as follows: 150 g of hydrogenated silicone oil with a hydrogen content of 0.1%, 17.5 g of allyl glycidyl ether, and 0.26 g of the supported porous carbon prepared in Example 3 (i.e., 20 ppm in terms of Pt) were mixed, and then the temperature was raised to 75°C for a hydrosilylation reaction for 5 h. After the temperature was maintained to remove low-boiling substances, an organosilicon product was obtained; and the supported porous carbon was centrifuged and dried to obtain a supported porous carbon, which was recycled and put into the hydrosilylation reaction again for use in a repeatability experiment to investigate the cyclic stability of the supported porous carbon.

[0066] Example 4

[0067] The rest is the same as Example 1, except that the amount of poly(5-indoleboric acid) used in step (S1) is 25 g, and the amount of polymethyl methacrylate used in step (S2) is 25 g.

[0068] The platinum content in the prepared supported porous carbon was tested by ICP-MS, and the platinum content was determined to be 1.5 wt %.

[0069] The prepared supported porous carbon was applied to a hydrosilylation reaction. The specific steps were as follows: 150 g of hydrogenated silicone oil with a hydrogen content of 0.1%, 17.5 g of allyl glycidyl ether, and 0.22 g of the supported porous carbon prepared in Example 4 (i.e., 20 ppm in terms of Pt) were mixed, and then the temperature was raised to 75°C for a hydrosilylation reaction for 5 h. After the temperature was maintained to remove low-boiling substances, an organosilicon product was obtained; and the supported porous carbon was centrifuged and dried to obtain a supported porous carbon, which was recycled and put into the hydrosilylation reaction again for use in a repeatability experiment to investigate the cyclic stability of the supported porous carbon.

[0070] Example 5

[0071] The rest is the same as Example 1, except that the amount of polymethyl methacrylate used in step (S2) is 30 g.

[0072] The platinum content in the prepared supported porous carbon was tested by ICP-MS, and the platinum content was determined to be 1.4 wt %.

[0073] The prepared supported porous carbon was applied to a hydrosilylation reaction. The specific steps were as follows: 150 g of hydrogenated silicone oil with a hydrogen content of 0.1%, 17.5 g of allyl glycidyl ether, and 0.24 g of the supported porous carbon prepared in Example 5 (i.e., 20 ppm in terms of Pt) were mixed, and then the temperature was raised to 75°C for a hydrosilylation reaction for 5 h. After the temperature was maintained to remove low-boiling substances, an organosilicon product was obtained; and the supported porous carbon was centrifuged and dried to obtain a supported porous carbon, which was recycled and put into the hydrosilylation reaction again for use in a repeatability experiment to investigate the cyclic stability of the supported porous carbon.

[0074] Example 6

[0075] The rest is the same as Example 1, except that: in step (S4), vinyltrimethoxysilane is used instead of vinyltriethoxysilane, and the amount used is 2 g.

[0076] The platinum content in the prepared supported porous carbon was tested by ICP-MS, and the platinum content was determined to be 1.2 wt %.

[0077] The prepared supported porous carbon was applied to a hydrosilylation reaction. The specific steps were as follows: 150 g of hydrogenated silicone oil with a hydrogen content of 0.1%, 17.5 g of allyl glycidyl ether, and 0.28 g of the supported porous carbon prepared in Example 6 (i.e., 20 ppm in terms of Pt) were mixed, and then the temperature was raised to 75°C for a hydrosilylation reaction for 5 h. After the temperature was maintained to remove low-boiling substances, an organosilicon product was obtained; and the supported porous carbon was centrifuged and dried to obtain a supported porous carbon, which was recycled and put into the hydrosilylation reaction again for use in a repeatability experiment to investigate the cyclic stability of the supported porous carbon.

[0078] Comparative Example 1

[0079] The rest is the same as Example 1, except that in step (S1), the polyindoleacetic acid prepared in Comparative Preparation 1 is used instead of the poly (5-indoleboronic acid) prepared in Preparation Example 1.

[0080] The platinum content in the prepared supported porous carbon was tested by ICP-MS, and the platinum content was determined to be 1.6 wt %.

[0081] The prepared supported porous carbon was applied to the hydrosilylation reaction. The specific steps were as follows: 150g of hydrogenated silicone oil with a hydrogen content of 0.1%, 17.5g of allyl glycidyl ether, and 0.21g of the supported porous carbon prepared in Comparative Example 1 (i.e., 20ppm in terms of Pt) were mixed, and then the temperature was raised to 75°C for the hydrosilylation reaction for 5h. After the temperature was maintained to remove the low-boiling substances, the organosilicon product was obtained; and the supported porous carbon was centrifuged and dried to obtain the supported porous carbon, which was recycled and put into the hydrosilylation reaction again for use in a repeatability experiment to investigate the cyclic stability of the supported porous carbon.

[0082] Comparative Example 2

[0083] The rest is the same as Example 1, except that step (S1) is omitted, and in step (S2), thermoplastic novolac resin is used instead of modified phenolic resin, that is, the phenolic resin is not modified by polyindole boronic acid.

[0084] The platinum content in the prepared supported porous carbon was tested by ICP-MS, and the platinum content was determined to be 0.8 wt %.

[0085] The prepared supported porous carbon was applied to the hydrosilylation reaction. The specific steps were as follows: 150g of hydrogenated silicone oil with a hydrogen content of 0.1%, 17.5g of allyl glycidyl ether, and 0.42g of the supported porous carbon prepared in Comparative Example 2 (i.e., 20ppm in terms of Pt) were mixed, and then the temperature was raised to 75°C for the hydrosilylation reaction for 5h. After the temperature was maintained to remove the low-boiling substances, the organosilicon product was obtained; and the supported porous carbon was centrifuged and dried to obtain the supported porous carbon, which was recycled and put into the hydrosilylation reaction again for use in a repeatability experiment to investigate the cyclic stability of the supported porous carbon.

[0086] Comparative Example 3

[0087] The rest is the same as Example 1, except that the pre-oxidation is omitted in step (S3), specifically:

[0088] (S1) Same as Example 1;

[0089] (S2) Same as Example 1;

[0090] (S3) placing the solid particles in a tube furnace and heating them to 160°C for thermal curing for 4 hours; then heating them to 800°C at a rate of 8°C / min under a nitrogen atmosphere (flow rate of 80 mL / min) for carbonization for 4.5 hours; finally, turning off the nitrogen, introducing water vapor (flow rate of 100 mL / min), and keeping them at 900°C for 6 hours for activation and pore expansion to obtain porous carbon; turning off the water vapor, switching to a nitrogen atmosphere, cooling it to 300°C, then turning off the nitrogen, switching to an air atmosphere (flow rate of 50 mL / min) and keeping them at this temperature for 3 hours for oxidation treatment to obtain oxidized porous carbon;

[0091] (S4) Same as Example 1;

[0092] (S5) Same as Example 1.

[0093] The platinum content in the prepared supported porous carbon was tested by ICP-MS, and the platinum content was determined to be 1.0 wt %.

[0094] The prepared supported porous carbon was applied to a hydrosilylation reaction. The specific steps were as follows: 150 g of hydrogenated silicone oil with a hydrogen content of 0.1%, 17.5 g of allyl glycidyl ether, and 0.34 g of the supported porous carbon prepared in Comparative Example 3 (i.e., 20 ppm in terms of Pt) were mixed, and then the temperature was raised to 75°C for a hydrosilylation reaction for 5 hours. After the temperature was maintained to remove low-boiling substances, an organosilicon product was obtained; and the supported porous carbon was centrifuged and dried to obtain the supported porous carbon, which was recycled and put into the hydrosilylation reaction again for use in a repeatability experiment to investigate the cyclic stability of the supported porous carbon.

[0095] Comparative Example 4

[0096] The rest is the same as Example 1, except that step (S4) is omitted, and in step (S5), oxidized porous carbon is used instead of porous carbon modified with vinylsiloxane, that is, pure physical adsorption platinum catalyst.

[0097] The platinum content in the prepared supported porous carbon was tested by ICP-MS, and the platinum content was determined to be 1.1 wt %.

[0098] The prepared supported porous carbon was applied to the hydrosilylation reaction. The specific steps were as follows: 150g of hydrogenated silicone oil with a hydrogen content of 0.1%, 17.5g of allyl glycidyl ether, and 0.30g of the supported porous carbon prepared in Comparative Example 4 (i.e., 20ppm in terms of Pt) were mixed, and then the temperature was raised to 75°C for the hydrosilylation reaction for 5h. After the temperature was maintained to remove the low-boiling substances, the organosilicon product was obtained; and the supported porous carbon was centrifuged and dried to obtain the supported porous carbon, which was recycled and put into the hydrosilylation reaction again for use in a repeatability experiment to investigate the cyclic stability of the supported porous carbon.

[0099] Analysis and Results

[0100] Determination of Residual Hydrogen Content After the Hydrosilylation Reaction: The organosilicon products prepared in the Examples and Comparative Examples were tested for residual hydrogen content using the gas volume method described in Appendix A of HG / T 4804-2015, Methyl High-Hydrogen Silicone Oils. Lower residual hydrogen content indicates higher catalytic efficiency. The test results are shown in Table 1.

[0101] Table 1 Residual hydrogen content

[0102]

[0103]

[0104] As can be seen from Table 1, the residual hydrogen content in the organosilicon product prepared by the supported porous carbon catalyzed hydrosilylation reaction prepared in the embodiment of the present invention is significantly lower than that in the comparative example, and is lower than 25 ppm upon first use. The product can be recycled, and the residual hydrogen content in the organosilicon product prepared after the tenth use does not exceed 30 ppm. This indicates that the supported porous carbon catalyzed hydrosilylation reaction of the present invention has very excellent catalytic efficiency and can be recycled.

[0105] At the same time, as can be seen from Table 1, although the cyclic reusability and stability of the supported porous carbon obtained by using polybenzyl acetic acid to modify the phenolic resin in Comparative Example 1 are acceptable, the residual hydrogen content is on the high side, indicating that the catalytic efficiency of the supported porous carbon obtained in Comparative Example 1 when catalyzing the hydrosilylation reaction is not as good as that of the embodiment. Comparative Example 2 is not modified with polybenzyl boric acid, and the residual hydrogen content of the supported porous carbon obtained in Comparative Example 2 is both on the high side when used for the first time and after being used for 10 times, indicating that the catalytic efficiency and stability of the supported porous carbon obtained in Comparative Example 2 when catalyzing the hydrosilylation reaction are not as good as those of the embodiment. The modified phenolic resin in Comparative Example 3 is not pre-oxidized, and although the catalytic efficiency of the supported porous carbon obtained in the first use is high, the cyclic reusability is poor, i.e., the stability is poor. The oxidized porous carbon in Comparative Example 4 is not modified with vinylsiloxane, i.e., it is a pure physically adsorbed platinum catalyst. Although the catalytic efficiency of the supported porous carbon obtained in the first use is high, the cyclic reusability is poor, i.e., the stability is poor.

[0106] The above specific embodiments are merely illustrative of the present invention and do not limit the present invention. It will be appreciated by those skilled in the art that the specific structures of the present invention may have other variations.

Claims

1. A method for preparing supported porous carbon for catalyzing hydrosilylation reaction, characterized in that: The following steps are involved: (S1) mixing thermoplastic phenolic resin, polyindole boronic acid, and a stabilizer uniformly, heating and reacting to obtain a modified phenolic resin; the mass ratio of the thermoplastic phenolic resin to the polyindole boronic acid is 100:(15-25); (S2) dissolving the modified phenolic resin, the porogen, and the curing agent in a polar solvent to form a polymer solution, removing the solvent, and crushing the solution to obtain solid particles; (S3) the solid particles are sequentially subjected to thermal curing, pre-oxidation, carbonization, and activation pore expansion to obtain porous carbon; the porous carbon is further subjected to oxidation treatment to obtain oxidized porous carbon; (S4) modifying the oxidized porous carbon with vinylsiloxane to obtain vinylsiloxane-modified porous carbon; (S5) Immersing the porous carbon modified with vinylsiloxane in an alcohol solution of a platinum salt, adding an acid binding agent, and heating and ultrasonically treating the porous carbon to obtain a supported porous carbon that catalyzes a hydrosilylation reaction.

2. The preparation method according to claim 1, characterized in that The mass ratio of the thermoplastic phenolic resin to the polyindole boronic acid in step (S1) is 100:(20-25).

3. The preparation method according to claim 1, characterized in that In step (S1), the polyindole boronic acid is at least one of poly(4-indole boronic acid), poly(5-indole boronic acid), and poly(6-indole boronic acid), and has a number average molecular weight of 3000 to 5000. The polyindole boronic acid is prepared by a method comprising the following steps: dissolving an indole boronic acid monomer in alcohol to obtain a solution A, dissolving an oxidant in water to obtain a solution B, adding the solution B to the solution A, stirring and reacting at 20 to 30° C. for 5 to 8 hours, filtering and separating the precipitate, washing, and drying to obtain the polyindole boronic acid. Preferably, the molar ratio of the indole boronic acid monomer to the oxidant is 1:(1.5-2.5); the indole boronic acid monomer is at least one of 4-indole boronic acid, 5-indole boronic acid, and 6-indole boronic acid; the oxidant is at least one of potassium persulfate and ammonium persulfate; and the alcohol is a C2-C4 alcohol.

4. The preparation method according to claim 1, characterized in that In step (S1), the number average molecular weight of the thermoplastic phenolic resin is 800-1500, and the hydroxyl content is 2wt%-5wt%; the stabilizer is trimethyl phosphate, and its usage is 0.1-0.3wt% of the thermoplastic phenolic resin; the heating reaction comprises: adding the thermoplastic phenolic resin and polyindole boric acid into a twin-screw mixer, mixing at 50-70°C for 15-30 minutes; then adding the stabilizer thereto, raising the temperature to 180-200°C and mixing for 40-60 minutes.

5. The preparation method according to claim 1, characterized in that In step (S2), the mass ratio of the modified phenolic formaldehyde, the porogen, and the curing agent is 100:(15-30):(5-8), preferably 100:(20-25):(5-8); and / or The porogen is at least one of polyvinyl pyrrolidone and polymethyl methacrylate, and its number average molecular weight is 6000-15000; the curing agent is at least one of hexamethylenetetramine, trimethylhexamethylenediamine, and diethylaminopropylamine; the polar solvent is at least one of N,N-dimethylformamide (DMF), N,N-dimethylformamide (DMAC), and N-methylpyrrolidone (NMP); the solvent removal is to rotary evaporation of the polymer solution; and the crushing is to crush the polymer into 100-400 meshes.

6. The preparation method according to claim 1, characterized in that In step (S3), the heat curing conditions are: keeping warm at 160-180°C for 3-5 hours; the pre-oxidation conditions are: keeping warm at 250-300°C in an air atmosphere for 2-4 hours; the carbonization conditions are: keeping warm at 700-900°C in an inert atmosphere for 3-6 hours, and the inert atmosphere is nitrogen and / or argon; and / or The activation and pore-expanding reagent is at least one of carbon dioxide, water vapor, and ammonia, and the activation conditions are: temperature 800° C. to 1000° C., and time 5 h to 8 h.

7. The preparation method according to claim 1, characterized in that In step (S4), the mass ratio of the oxidized porous carbon to the vinyl siloxane is 100:(4-7); and the vinyl siloxane is at least one of vinyl triethoxysilane and vinyl trimethoxysilane.

8. The preparation method according to claim 1, characterized in that In step (S4), the modification method is as follows: oxidized porous carbon is dispersed in an alcohol aqueous solution to obtain a dispersion; vinyl siloxane is added to water, the pH is adjusted to 4 to 6, and a hydrolysis reaction is carried out at 20 to 30° C. for 20 to 40 minutes to obtain a hydrolyzed solution; Add the hydrolyzed solution to the dispersion and stir at 55-65°C for 4-8 hours to obtain vinylsiloxane-modified oxidized porous carbon. After the reaction, filter, wash with pure water, and dry at 80-90°C. Preferably, the alcohol content in the alcohol aqueous solution is 30-60 wt %, and the alcohol is selected from at least one of methanol and ethanol.

9. The preparation method according to claim 1, characterized in that In step (S5), the mass ratio of the porous carbon, the platinum salt, and the acid binding agent is 10:(0.3-0.5):(0.6-1.5); and / or The platinum salt is at least one of H2PtCl6 and PtCl4; the concentration of the alcohol solution of the platinum salt is 5 to 10 mg / mL, and the alcohol is a C2-C4 alcohol, such as ethanol, propanol, isopropanol or n-butanol; the acid binding agent is at least one of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, magnesium carbonate, and calcium carbonate; The conditions of the heating ultrasonic treatment are: temperature 60-80° C., frequency 20-30 KHz, and time 30-60 min.

10. Use of the supported porous carbon prepared by the preparation method according to any one of claims 1 to 9 in a hydrosilylation reaction, characterized in that: The amount used is 10 to 30 ppm based on the Pt content in the reaction system.

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