Rice straw oxidized carbon-supported bimetallic complex catalyst, preparation method and use

Abstract

The present invention relates to the technical field of agricultural waste resource utilization and catalyst preparation, and specifically discloses a rice straw oxidized carbon immobilized bimetallic complex catalyst, a preparation method and uses. Based on the preparation of existing immobilized single platinum catalysts, the present invention improves the metal introduction method and adopts a specific step-by-step complexation method to anchor two metal components on the surface of vinyl-modified rice straw oxidized carbon, successfully constructing a stable, platinum-nickel mass ratio and a special platinum-nickel bimetallic vinyl complex structure as a catalytic active center on the surface of rice straw oxidized carbon. Compared with immobilized single platinum, this bimetallic catalyst is used for olefin hydrosilylation reaction, not only effectively reducing the amount of precious metal platinum while maintaining the original catalytic effect, but also showing higher activity and selectivity for the addition of long-chain terminal olefins to tertiary silanes under mild conditions (normal pressure, solvent-free, low temperature), which can reduce the catalytic cost and expand the application range of the catalytic reaction.

Description

Technical Field

[0001] The present invention belongs to the technical field of resource utilization of agricultural waste and catalyst preparation, and specifically relates to a rice straw oxidized carbon immobilized platinum-nickel bimetallic complex catalyst, a preparation method and uses. Technical Background

[0002] Organosilicon compounds are a new class of chemical products with excellent performance, a wide variety, and a broad range of applications. Various alkylsilanes, siloxane intermediates, and polymers derived from them (such as silicone resins, silicone rubber, and silicone oils) have found widespread application in industries such as construction, automotive, electronics, textiles, cosmetics, light industry, food, and healthcare. Hydrosilanes are important precursors for the preparation of numerous organosilicon compounds. Under the action of catalysts, they activate silicon-hydrogen bonds, reacting with unsaturated carbon bonds to form highly stable silicon-carbon bonds. These reactions, due to their relatively mild reaction conditions and ease of operation, are an important means for the large-scale synthesis of organosilicon monomers and polymers in industry.

[0003] Homogeneous noble metal platinum complexes such as Speier (J. Am. Chem. Soc., 1957, 79(4): 574) and Karstedt (USA, 3775452[P], 1973) have been considered to be the most effective hydrosilylation catalysts and are applicable to various types of hydrosilylation reactions. Non-noble metal catalysts such as complexes of transition metals cobalt, iron and nickel as catalytic active components have also been studied in depth. However, classic platinum complex catalysts are homogeneous and difficult to recover from the reaction medium. The metal components are easily lost and have a great impact on product quality and the environment. Existing transition metal catalysts are only suitable for the hydrosilylation of unsaturated hydrocarbons with primary and secondary silanes (such as RSiH3 and R2SiH2) with small steric hindrance. Since tertiary silanes (R3SiH) with large steric hindrance are difficult to react with unsaturated hydrocarbons, the catalyst for this reaction needs to have high catalytic activity and regioselectivity. Therefore, transition metal catalysts have low catalytic activity and selectivity for such reactions or even no catalytic activity. In addition, in order to reduce the probability of side reactions, the hydrosilylation reaction of tertiary silanes and unsaturated hydrocarbons is still a homogeneous or heterogeneous catalyst with precious metal platinum as the active center.

[0004] The inventor has been granted a patent (ZL 202210694641.6) for a rice straw oxidized carbon supported divalent platinum vinyl complex catalyst, preparation method, and application. The synthesis process is low-toxic, highly safe, simple to operate, and requires low equipment. It has excellent catalytic performance for the hydrosilylation reaction of representative tertiary silanes (triethoxysilane, (EtO)3SiH) with different olefins under solvent-free, atmospheric pressure conditions. The catalyst is easy to separate and the active components are not easily lost. It can be reused multiple times and helps to improve the resource utilization rate of rice straw waste, showing good application prospects. However, as the research progressed, the inventors found that the catalyst preparation process consumed precious metal platinum, resulting in a high production cost. The catalyst exhibited excellent catalytic activity and selectivity for the hydrosilylation reaction of short-chain terminal olefins with a representative tertiary silane (triethoxysilane) at relatively low temperatures, but the catalytic activity and selectivity for the hydrosilylation reaction of long-chain olefins, such as 1-octadecene, with triethoxysilane, which are more difficult to react, were less than ideal. Summary of the Invention

[0005] To solve the above problems, the present invention makes the following improvements to the authorized patent (ZL 202210694641.6): by screening cheap nickel metal as an auxiliary agent, rationally optimizing the introduction method and amount of the nickel auxiliary agent, and providing a rice straw carbon oxide immobilized bimetallic complex catalyst and its preparation method and application, and then introducing an appropriate amount of nickel component as an auxiliary agent to modify and change the original single platinum coordination structure, effectively reducing the amount of precious metal platinum in the catalyst while maintaining or even improving the performance of the single platinum immobilized catalyst, thereby achieving the goal of reducing catalytic costs and making the resulting catalyst more industrially applicable. The specific technical solution is as follows:

[0006] A rice straw oxidized carbon immobilized bimetallic complex catalyst is prepared by using rice straw oxidized carbon obtained by carbonization, activation and oxidation of waste rice straw as a carrier. The hydroxyl groups on the surface of the oxidized carbon react with the ligand compound to introduce vinyl ligand groups on the carrier for anchoring the bimetallic active components, thereby finally making the Pt in the precursor chloroplatinic acid aqueous solution 4+ Ni in nickel chloride aqueous solution 2+ The electrons are successively obtained to form a solid-supported bimetallic catalyst (with the following structure) with a special platinum and nickel vinyl complex as the catalytic active center, and its specific surface area is 120 to 160 m 2 / g, an average pore diameter of 6.0-6.4 nm, a platinum loading amount based on the obtained catalyst of 0.6-0.8 wt%, and a nickel loading amount based on the obtained catalyst of 0.4-0.5 wt%.

[0007]

[0008] The preparation method of the rice straw oxidized carbon immobilized bimetallic complex catalyst comprises the following steps:

[0009] (1) Preparation of hydroxyl-rich rice straw oxidized carbon (ROC);

[0010] (2) Preparation of rice straw oxidized carbon (VTES-ROC) containing sufficient vinyl ligands;

[0011] (3) Preparation of rice straw oxidized carbon-supported bimetallic complex catalyst (Pt x Ni y -VTES-ROC, x:y is the mass ratio of platinum and nickel metals loaded on the catalyst): using the precipitation method, tetravalent platinum ions and divalent nickel ions were introduced into the surface of VTES-ROC with appropriate concentrations and amounts of chloroplatinic acid aqueous solution and nickel chloride aqueous solution as precursors, respectively. The two metal ions were anchored by the chelation coordination of vinyl groups, and finally a rice straw oxidized carbon immobilized bimetallic complex catalyst (Pt x Ni y -VTES-ROC).

[0012] The preparation process of step (1) and step (2) of the present invention is the same as that of the inventor's authorized patent (ZL 202210694641.6). The details are as follows:

[0013] Step (1): The dried rice straw after pretreatment is first subjected to appropriate carbonization treatment in a high-temperature tube furnace to obtain rice straw charcoal (RC), and then KOH is used as an activator to further activate RC to obtain rice straw activated carbon (RAC) that is conducive to subsequent oxidation treatment; finally, RAC is oxidized with a nitric acid solution of appropriate concentration to obtain rice straw oxidized carbon (ROC) rich in hydroxyl groups on the surface. Specifically, after removing the stem head, leaves and excess roots from the rice straw, the rice straw is washed with water and cut into 2-4 cm, first dried at 50-60°C for 12 hours to constant weight, and then placed in a high-temperature tube furnace, and heated at a rate of 10-15°C / min to 500-600°C for 2 hours under the protection of 10mL / min nitrogen, and then cooled to room temperature, so that the rice straw can be properly carbonized to obtain a specific surface area of ​​100-130m 2 / g, average pore size 9.7-10.2nm, mesoporous rice straw char (RC); RC was lightly activated, the activator was KOH, the mass ratio of activator to rice straw char (RC) was 1:4-8, and the material-liquid ratio of RC to distilled water was 1:1 (g / mL), 1 part by mass of KOH was dissolved in 4-8 volumes of distilled water, and then 4-8 parts by mass of RC were immersed in the above-mentioned alkali solution, placed in a high-temperature tube furnace under the protection of 10mL / min nitrogen and raised to 500-800℃ at a rate of 10-15℃ / min for 0.5-2h, and then cooled to room temperature. The obtained material was washed with 0.5M hydrochloric acid solution, filtered to neutrality, and finally vacuum dried at 60℃ to constant weight. This activation condition can effectively remove nitrogen-containing impurities in the carbon, and at the same time can lightly activate and etch the carbon, resulting in a slightly increased specific surface area (130-150m 2 / g), the average pore size is reduced (7.3-7.6nm), and the porous rice straw activated carbon (RAC) is still mainly mesopores. This activation condition can appropriately increase the specific surface area of ​​RAC, and the mesopores are mainly present on the surface of the material, which is convenient for subsequent modification to introduce metal active components and catalytic reactants and products into and out of the pores; RAC is oxidized, and the oxidant is a nitric acid solution of appropriate concentration to obtain rice straw oxidized carbon (ROC) rich in hydroxyl groups on the surface, that is, according to the material-liquid ratio of 1:8-12 (g / mL), 5 parts of rice straw activated carbon (RAC) are added to 40-60 volumes of 10M nitric acid solution for oxidation treatment, and the reaction is stirred in an oil bath at 85-95℃ for 5-7h. After the reaction, it is cooled, filtered, washed with deionized water to neutrality, and vacuum dried at 60℃ to constant weight to obtain a slightly increased specific surface area (150-170m 2 / g), rice straw oxidized carbon (ROC) with a slightly reduced average pore size (6.2-6.5 nm) and rich in hydroxyl groups (5-6 mmol / g of new oxygen-containing groups).

[0014] In step (2), a vinyl ligand is introduced into the rice straw oxidized carbon (ROC) prepared in step (1) using an appropriate amount of vinyl triethoxysilane (VTES) as a ligand compound to obtain rice straw oxidized carbon (VTES-ROC) containing a sufficient amount of vinyl ligand. Specifically, according to the material-liquid ratio of 1:20-30 (g / mL), 2 parts by mass of rice straw oxidized carbon (ROC) obtained in step (1) are added to 40-60 volumes of N-methylpyrrolidone (NMP), and ultrasonicated at room temperature for 10 minutes to allow the carbon material to be fully dispersed in the solvent. 0.5-1.5 mL of 1 M nitric acid solution and 5-7 mL of vinyl triethoxysilane (VTES) are sequentially added dropwise at a rate of 1 drop / second to the above system while maintaining the ultrasonic state to prevent VTES from self-polymerization due to too rapid addition and reducing the amount of VTES introduced into ROC. The ultrasonication is continued for 10 minutes at room temperature. After the ultrasonication, the above system is transferred to an oil bath for stirring and slowly heated to 85-95°C for reaction for 20-26 hours. After the reaction, the system is cooled, washed with water and ethanol, and filtered, and vacuum-dried at 60°C to constant weight. Based on the above modification conditions, rice straw oxidized carbon (VTES-ROC) with introduced vinyl ligand groups is obtained, and its specific surface area is 180-200 m 2 / g, an average pore size of 5.8 to 6.0 nm, an introduction amount of VTES based on the oxidized carbon carrier of 3 to 5 wt%, a vinyl content of 0.15 to 0.26 mmol / g, and the introduction of sufficient coordination groups facilitates subsequent modification to form a metal complex with a special structure as a catalytic active center; all steps of ultrasound and the reaction process are performed in a dark environment to prevent the solvent NMP from being decomposed by light for a long time.

[0015] Furthermore, step (3) is specifically as follows: according to the material-liquid ratio of 1:60-80 (g / mL), 0.5 parts by weight of the rice straw oxidized carbon (VTES-ROC) introduced with vinyl ligand groups obtained in step (2) is added to 30-40 mL of anhydrous ethanol, and ultrasonicated at room temperature for 5 minutes to allow the carbon material to be fully dispersed in the solvent. While maintaining the ultrasonic state, 1.1-1.3 mL of Pt is first added dropwise at a rate of 1 drop / second in the above system. 4+ The Pt in the precursor is controlled by adding 3.766 g / L chloroplatinic acid aqueous solution. 4+ It can be evenly dispersed on VTES-ROC, and then 0.015-0.035g NaHCO3 crystals are added and ultrasonicated for 5 minutes. Then the above system is transferred to an oil bath at a temperature of 35-45℃ and stirred for 10-14 hours, which is beneficial to the Pt 4+ The alkaline precipitation fully chelates with the vinyl group, and then 0.85-1.05 mL Ni is added dropwise at a rate of 1 drop / second. 2+The nickel chloride aqueous solution with a concentration of 2.469 g / L was reacted for 10 to 14 hours to fully chelate the nickel ions with the vinyl groups. The mixture was then filtered, washed with anhydrous ethanol until neutral, and vacuum dried at 60°C to a constant weight. Based on the above preparation conditions, the rice straw oxidized carbon-supported bimetallic complex catalyst (Pt 1.5 Ni1-VTES-ROC), with a specific surface area of ​​120 to 160 m 2 / g, an average pore diameter of 6.0-6.4 nm, a platinum loading amount based on the obtained catalyst of 0.6-0.8 wt%, and a nickel loading amount based on the obtained catalyst of 0.4-0.5 wt%.

[0016] The present invention also provides the above-mentioned special platinum and nickel bimetallic vinyl complex as the catalytic active center immobilized catalyst (Pt x Ni y -VTES-ROC) shows that compared with the single platinum complex supported catalyst provided by the authorized patent (ZL 202210694641.6), the catalyst obtained by the present invention not only shows better catalytic activity and selectivity for the hydrosilylation reaction of short-chain terminal olefins with representative tertiary silanes (triethoxysilane) under mild conditions (normal pressure, solvent-free, low temperature), but also shows better catalytic activity and selectivity for the hydrosilylation reaction of long-chain olefins with large steric hindrance and difficult reaction, such as 1-octadecene, with triethoxysilane. It can maintain good catalytic stability after repeated use, and the active components are not easily lost, indicating that the catalyst with the special structure of the present invention is better than that of the authorized patent (ZL 202210694641.6) provides a single platinum complex supported catalyst, which can not only ensure the same catalytic effect on the original reaction system while reducing the amount of precious metal platinum on the catalyst, but also shows a better catalytic effect on the hydrosilylation reaction of long-chain terminal olefins and tertiary silanes, with better catalytic performance, greatly enhancing the industrial application potential of the catalyst.

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

[0018] (1) The present invention provides a rice straw oxidized carbon immobilized bimetallic complex catalyst, a preparation method, and an application thereof. By introducing an appropriate amount of inexpensive nickel metal as a catalytic promoter under specific preparation steps and parameters, the binding ability of platinum coordination is promoted, ultimately forming a rice straw oxidized carbon immobilized bimetallic complex catalyst having a special platinum and nickel vinyl complex structure as the catalytic active center. The platinum loading amount based on the obtained catalyst is 0.6-0.8wt%, and the nickel loading amount based on the obtained catalyst is 0.4-0.5wt%. The mass ratio of platinum to nickel in the catalyst is 1.5:1, and the molar ratio is approximately 1:2.

[0019] (2) The order and ratio of the introduction of the two metal components are very important. Pt with weaker chelating ability in the metal precursor is given priority. 4+ It forms a divalent platinum vinyl coordination compound with some vinyl groups on the surface of the catalyst support, and then introduces an appropriate amount of Ni 2+ To the support surface, using Ni 2+ The strong chelating coordination ability between vinyl and vinyl interacts with the existing divalent platinum vinyl coordination compound to form Figure 4 Ni 2+ With Pt 2+ The structure of the co-coordinated vinyl group is relatively stable compared to the single Pt 2+ The coordinated vinyl structure is more stable, and the mass ratio of platinum to nickel should be controlled at 1.5:1. Changing the introduction order or introducing too much or too little nickel will destroy the formation of this special structure and affect catalytic activity.

[0020] (3) The catalytic active center of this special structure has excellent catalytic activity and selectivity for the target reaction under relatively mild conditions (normal pressure, solvent-free, low temperature), and can effectively reduce the amount of precious metal platinum on the basis of maintaining the catalytic performance of a single platinum-supported catalyst. Compared with the authorized patent, the platinum loading is reduced by 20-45%, and the cost is significantly reduced. In addition, compared with a single platinum-supported catalyst, the provided bimetallic catalyst forms a special bimetallic coordination compound structure under the action of an appropriate amount of nickel additive, Ni 2+ Will be with Pt 2+ Competitive coordination of vinyl groups results in electronic shift on the vinyl group, which makes the platinum coordination center Pt 2+ This increased binding energy further enhances the catalyst's activity and regioselectivity, demonstrating enhanced catalytic performance in the addition reaction of long-chain olefins with tertiary silanes under mild conditions, broadening the catalyst's application range. Furthermore, the two metal components form a stable chelate coordination structure with the vinyl groups on the support, maintaining good catalytic stability and facilitating separation of the target product from the catalyst, further enhancing the catalyst's potential for industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 For Example 1 of the present invention (Pt 1.5 The X-ray photoelectron spectroscopy (XPS) of the catalyst (Pt-VTES-ROC) prepared in Example 1 and the comparative example 1 was 4f Spectral comparison and peak separation results.

[0022] Figure 2 The catalyst (Pt 1.5 The X-ray photoelectron spectroscopy (XPS) of the catalyst (Ni-VTES-ROC) prepared in Ni1-VTES-ROC) and Comparative Example 3 was as follows:2p Spectral comparison and peak separation results.

[0023] Figure 3 For Example 1 of the present invention (Pt 1.5 Ni1-VTES-ROC) and comparative examples 4 and 5 to prepare catalysts (Pt 1.6 Ni1-ROC and Pt 1.6 Comparison of the stability of Ni1-RAC) in 1-octene hydrosilylation system.

[0024] Figure 4 Schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0025] The present invention is further described below with reference to specific examples, but the present invention is not limited to the following examples. The methods described are conventional methods unless otherwise specified. The raw materials described can be obtained from public commercial channels unless otherwise specified.

[0026] Example 1:

[0027] Synthesis of rice straw oxidized carbon supported bimetallic complex catalyst (Pt 1.5 Ni1-VTES-ROC):

[0028] (1) Preparation of rice straw oxidized carbon (ROC): After removing the stem, leaves and excess roots from the rice straw, the rice straw was washed with water and cut into 2-4 cm pieces. It was dried at 50-60 °C for 12 h to constant weight, placed in a high-temperature tube furnace and heated to 500-600 °C at a rate of 10-15 °C / min for 2 h under the protection of 10 mL / min nitrogen, and then cooled to room temperature to obtain a specific surface area of ​​100-130 m 2 / g, average pore size 9.7-10.2nm rice straw charcoal (RC);

[0029] According to the mass ratio of activator KOH to RC of 1:4-8 and the material-liquid ratio of RC to distilled water of 1:1 (g / mL), 1 part of KOH was dissolved in 4-8 volumes of distilled water, and then 4-8 parts of RC were immersed in the above-mentioned alkali solution. The mixture was placed in a high-temperature tube furnace and heated to 500-800°C at a rate of 10-15°C / min under the protection of 10mL / min nitrogen for 0.5-2h, and then cooled to room temperature. The obtained product was washed with 0.5M hydrochloric acid solution, filtered to neutrality, and finally vacuum dried at 60°C to constant weight to obtain a specific surface area of ​​130-150m 2 / g, rice straw activated carbon (RAC) with an average pore size of 7.3-7.6nm.

[0030] According to the material-liquid ratio of 1:8-12 (g / mL), 5 parts of rice straw activated carbon (RAC) were added to 40-60 volumes of 10M nitric acid solution for oxidation treatment, and stirred in an oil bath at 85-95 ° C for 5-7 hours. After the reaction, it was cooled, filtered, washed with deionized water to neutrality, and vacuum dried at 60 ° C to constant weight to obtain a specific surface area of ​​150-170 m 2 / g, rice straw oxidized carbon (ROC) with an average pore size of 6.2-6.5 nm.

[0031] (2) Preparation of rice straw oxidized carbon containing vinyl ligand (VTES-ROC): 2 parts by mass of ROC obtained in step (1) were added to 40-60 volumes of N-methylpyrrolidone (NMP) at a material-liquid ratio of 1:20-30 (g / mL). Ultrasonic treatment was performed at room temperature for 10 min to allow the carbon material to be fully dispersed in the solvent. 0.5-1.5 mL of 1 M nitric acid solution and 5-7 mL of vinyltriethoxysilane (VTES) were added dropwise to the above system at a rate of 1 drop / s while maintaining the ultrasonic state. Ultrasonic treatment was continued at room temperature for 10 min. The above system was then transferred to an oil bath for stirring and slowly heated to 85-95°C for reaction for 20-26 h. After the reaction was completed, the system was cooled, washed with water and ethanol, and filtered. It was then vacuum dried at 60°C to constant weight. Based on the above modification conditions, rice straw oxidized carbon (VTES-ROC) with the introduction of vinyl ligand was obtained, and its specific surface area was 180-200 m 2 / g, an average pore diameter of 5.8-6.0 nm, an introduction amount of VTES based on the oxidized carbon carrier of 3-5 wt%, and a vinyl content of 0.15-0.26 mmol / g.

[0032] (3) Rice straw oxidized carbon immobilized bimetallic complex catalyst (Pt x Ni y Preparation of VTES-ROC: 0.5 parts by weight of the rice straw oxidized carbon (VTES-ROC) with vinyl ligand groups introduced in step (2) was added to 30-40 mL of anhydrous ethanol at a material-liquid ratio of 1:60-80 (g / mL). Ultrasonication was performed at room temperature for 5 min. 1.0-1.3 mL of PTFE was added dropwise at a rate of 1 drop / s in the above system while maintaining the ultrasonic state. 4+ The mixture was diluted with 3.766 g / L chloroplatinic acid aqueous solution, and then 0.015-0.035 g NaHCO3 crystals were added and ultrasonicated for 5 min. The above system was transferred to an oil bath at a temperature of 35-45 ° C and stirred for 10-14 h. Then 0.85-1.05 mL Ni was added dropwise at a rate of 1 drop / second. 2+The nickel chloride aqueous solution with a concentration of 2.469 g / L was reacted for 10 to 14 hours, filtered, washed with anhydrous ethanol until neutral, and vacuum dried at 60 ° C to constant weight. Based on the above preparation conditions, the rice straw oxidized carbon immobilized bimetallic complex catalyst (Pt x Ni y -VTES-ROC).

[0033] ICP analysis showed that when the metal components were introduced into the surface of the modified support according to the method provided in step (3), the different amounts of the two precursors (chloroplatinic acid aqueous solution and nickel chloride aqueous solution) would result in different amounts of the two metal components introduced. Therefore, the obtained immobilized bimetallic catalyst was recorded as Pt x Ni y -VTES-ROC, where x:y represents the mass ratio of platinum and nickel elements loaded on the catalyst surface. Based on the dosage range shown in step (3) and the ICP analysis results, this example prepared a solid-supported bimetallic catalyst containing three different mass ratios of platinum and nickel, namely: Pt 1.5 Ni1-VTES-ROC,Pt 3.1 Ni1-VTES-ROC and Pt 0.9 The catalytic performance comparison results of Ni1-VTES-ROC are shown in Table 1. It can be seen that the introduction of too much or too little nickel component will affect the catalytic performance. When the mass ratio of platinum to nickel metal in the catalyst is 1.5:1 (molar ratio is about 1:2), it is appropriate. At this time, the specific surface area is 120-160m 2 / g, an average pore diameter of 6.0-6.4 nm, a platinum loading amount based on the obtained catalyst of 0.6-0.8 wt%, and a nickel loading amount based on the obtained catalyst of 0.4-0.5 wt%.

[0034] Comparative Example 1:

[0035] Authorized patent (ZL 202210694641.6) Preparation of Rice Straw Oxidized Carbon Supported Single Platinum Vinyl Complex Catalyst (Pt-VTES-ROC):

[0036] At a material-liquid ratio of 1:50-60 (g / mL), 0.5 parts of the vinyl ligand rice straw oxidized carbon (VTES-ROC) prepared in Example 1 was added to 25-30 mL of anhydrous ethanol, and ultrasonicated at room temperature for 5 min. 1.5 mL of Pt was added dropwise at a rate of 1 drop / s in the above system while maintaining the ultrasonic state. 4+A 3.766 g / L aqueous solution of chloroplatinic acid was added, to which 0.015-0.025 g of NaHCO3 crystals were added. Ultrasonication was continued for 5 minutes, and the system was then placed in an oil bath at 35-45°C and stirred for 24 hours. The mixture was filtered, washed with anhydrous ethanol until neutral, and vacuum-dried at 60°C to constant weight. ICP analysis showed a platinum loading of 1.01 wt%.

[0037] Figure 1 XPS spectra showed that Pt 1.5 Most of the platinum in Ni1-VTES-ROC and Pt-VTES-ROC is in the form of Pt 2+ Form of existence (Pt 2+ 4f7 / 2 The peak is around 72.4eV), which is because the Pt 4+ Chelating coordination occurs with the vinyl group introduced on the surface of the carrier, and the electron valence is reduced to form a Pt 2+ The vinyl coordination structure is centered. 1.5 Ni1-VTES-ROC Pt 2+ 4f7 / 2 The peak is 72.6eV, which is higher than 72.4eV of Pt-VTES-ROC, indicating that the introduced Ni 2+ Make Pt 2+ 4f7 / 2 The peak shifts to a higher binding energy, which is attributed to the introduction of Ni 2+ After that, Pt 2+ with Ni 2+ The stable platinum-nickel bimetallic vinyl complex with the center is characterized by the formation of Ni 2+ With Pt 2+ The structure of the co-coordinated vinyl group (such as Figure 4 As shown), in Pt 4+ Gaining electrons to become Pt 2+ After that, Ni 2+ Then with Pt 2+ Competitive coordination of vinyl groups results in electronic shift on the vinyl groups, which makes the platinum coordination center Pt 2+ The binding energy is increased, thereby achieving the purpose of improving catalytic performance.

[0038] Comparative Example 2:

[0039] Preparation of rice straw oxidized carbon supported on a small amount of single platinum vinyl complex catalyst (L-Pt-VTES-ROC):

[0040] At a material-liquid ratio of 1:60-80 (g / mL), 0.5 parts by weight of rice straw oxidized carbon (VTES-ROC) prepared in Example 1 was added to 30-40 mL of anhydrous ethanol, and ultrasonicated at room temperature for 5 min. 1.0-1.3 mL of Pt 4+ The catalyst was prepared by adding 0.015-0.035 g of NaHCO3 crystals to a 3.766 g / L aqueous solution of chloroplatinic acid. Ultrasonication was continued for 5 minutes, and the system was then placed in an oil bath at 35-45°C and stirred for 24 hours. The mixture was filtered, washed with anhydrous ethanol until neutral, and dried under vacuum at 60°C to constant weight. ICP analysis showed that the platinum loading on the catalyst was low, only 0.7-0.8 wt%. This catalyst was designated L-Pt-VTES-ROC.

[0041] Comparative Example 3:

[0042] Preparation of rice straw oxidized carbon supported single nickel vinyl complex catalyst (Ni-VTES-ROC):

[0043] At a material-liquid ratio of 1:60-80 (g / mL), 0.5 parts of rice straw oxidized carbon (VTES-ROC) prepared in Example 1 with the introduction of vinyl ligand groups was added to 30-40 mL of anhydrous ethanol, and ultrasonicated at room temperature for 5 min. 0.85-1.05 mL of Ni was added dropwise at a rate of 1 drop / s in the above system while maintaining the ultrasonic state. 2+ A 2.469 g / L nickel chloride aqueous solution was added, to which 0.015-0.035 g of NaHCO3 crystals were added. Ultrasonication was continued for 5 minutes, and the system was then transferred to an oil bath at 35-45°C and stirred for 24 hours. The mixture was filtered, washed with anhydrous ethanol until neutral, and dried under vacuum at 60°C to constant weight. ICP analysis showed that the single nickel loading in the catalyst was 0.4-0.5 wt%.

[0044] Figure 2 XPS spectra showed that Ni-VTES-ROC and Pt 1.5 Ni in Ni1-VTES-ROC 2p3 / 2 The binding energies of the characteristic peaks are 855.4 and 855.2 eV, respectively, which are lower than those of Ni in aqueous solution. 2+ 2p3 / 2 The binding energy of Ni in the precursor is (855.6eV). 2+ It can interact with the vinyl groups introduced on the catalyst surface, gaining electrons and reducing the binding energy. 2+ The mass and volume are small, so only a small number of electrons are needed from the vinyl group to form a stable Ni 2+ The vinyl complex at the center, and then the Ni 2+Fixed on the catalyst surface. 1.5 Ni in Ni1-VTES-ROC 2+ 2p3 / 2 The binding energy is further reduced compared to Ni-VTES-ROC because Ni 2+ Pt 4+ It is easier to interact with vinyl, so in the bimetallic system Ni 2+ It will compete with the formed divalent platinum vinyl complex for the coordination of vinyl, causing the electrons on the vinyl to shift toward Ni 2+ , so that Pt 1.5 Ni in Ni1-VTES-ROC 2+ 2p3 / 2 The binding energy is further reduced.

[0045] Comparative Example 4:

[0046] Direct loading of platinum and nickel bimetallic catalysts on rice straw oxidized carbon (Pt 1.6 Preparation of Ni1-ROC:

[0047] According to the material-liquid ratio of 1:60-80 (g / mL), 0.5 g of rice straw oxidized carbon (ROC) prepared in Example 1 was mixed with 30-40 mL of anhydrous ethanol, and ultrasonicated for 5 min at room temperature to fully disperse the carbon material into the solvent. While maintaining the ultrasonic state, 1.1-1.3 mL of Pt 4+ The mixture was diluted with 3.766 g / L chloroplatinic acid aqueous solution, and then 0.015-0.035 g NaHCO3 crystals were added and ultrasonicated for 5 min. The above system was transferred to an oil bath at a temperature of 35-45 ° C and stirred for 10-14 h. Then 0.85-1.05 mL Ni was added dropwise at a rate of 1 drop / second. 2+ The nickel chloride aqueous solution with a concentration of 2.469 g / L was reacted for 10 to 14 hours, filtered, washed with anhydrous ethanol until neutral, and vacuum dried at 60°C to constant weight. Finally, a rice straw oxidized carbon directly loaded with platinum and nickel bimetallic catalyst was obtained. ICP analysis showed that when a specific amount of precursor was added, the platinum loading in the catalyst was 0.7 to 0.8 wt% and the nickel loading was 0.4 to 0.5 wt%, recorded as Pt 1.6 Ni1-ROC.

[0048] Comparative Example 5:

[0049] Direct loading of platinum and nickel bimetallic catalysts on rice straw activated carbon 1.6 Preparation of Ni1-RAC:

[0050] According to the material-liquid ratio of 1:60-80 (g / mL), 0.5 g of rice straw activated carbon (RAC) prepared in Example 1 was mixed with 30-40 mL of anhydrous ethanol, and ultrasonicated for 5 min at room temperature to fully disperse the carbon material into the solvent. While maintaining the ultrasonic state, 1.1-1.3 mL of Pt 4+ The mixture was diluted with 3.766 g / L chloroplatinic acid aqueous solution, and then 0.015-0.035 g NaHCO3 crystals were added and ultrasonicated for 5 min. The above system was transferred to an oil bath at a temperature of 35-45 ° C and stirred for 10-14 h. Then 0.85-1.05 mL Ni was added dropwise at a rate of 1 drop / second. 2+ The nickel chloride aqueous solution with a concentration of 2.469 g / L was reacted for 10 to 14 hours, filtered, washed with anhydrous ethanol until neutral, and vacuum dried at 60°C to constant weight. Finally, a rice straw activated carbon directly loaded with platinum and nickel bimetallic catalyst was obtained. ICP analysis showed that when a specific amount of precursor was added, the platinum loading in the catalyst was 0.7 to 0.8 wt% and the nickel loading was 0.4 to 0.5 wt%, recorded as Pt 1.6 Ni1-RAC.

[0051] Example 1 and Figure 1 、 2 The XPS analysis results in the present invention prove that according to the preparation steps and parameters provided by the present invention, sufficient vinyl ligands can be successfully introduced into the rice straw oxidized carbon, which can then react with the Pt in the precursor. 4+ and Ni 2+ Formation of stable Pt 2+ and Ni 2+ It has a special vinyl chelate coordination structure as the center.

[0052] Example 2:

[0053] The catalytic performance of the catalysts obtained in Example 1 and Comparative Examples 1-5 in the addition reaction of different olefins with triethoxysilane was investigated.

[0054] (1) 1-Octene System: 5 mmol of 1-octene, 5 mmol of triethoxysilane, and the same amount of catalyst were added to a 10 mL reaction flask. The amount of catalyst used in each reaction was 0.0195 g. The molar ratio of the active component Pt to each reactant in the reaction system was calculated based on the platinum loading in the different catalysts obtained by ICP analysis. The reaction was heated to 50-60°C for 2-3 hours. After the reaction was completed, the supernatant was collected and analyzed by gas chromatography to determine catalytic activity and selectivity. The catalyst obtained after centrifugation was used in a repeatability experiment to determine the stability of the catalyst.

[0055] (2) 1-octadecene system: replace 1-octene in (1) with 1-octadecene, and keep other conditions unchanged.

[0056] The conversion and selectivity of hydrosilylation reaction of different olefins catalyzed by different catalysts are shown in Table 1. The stability test of the reaction system of 1-octene and triethoxysilane addition was carried out. The stability comparison is shown in Figure 3 .

[0057] From the data in Table 1, it can be seen that compared with the other two directly loaded bimetallic catalysts (Comparative Examples 4 and 5), Pt 1.5 Ni1-VTES-ROC has better catalytic performance and selectivity in catalyzing the hydrosilylation reaction of different olefins. Figure 3 It can be seen that Pt 1.5 After six reuses, the Ni1-VTES-ROC catalyst maintained a conversion rate of 89.9%, demonstrating excellent reproducibility. This suggests that introducing sufficient vinyl ligands onto the support surface can, on the one hand, enhance the activity and selectivity of the catalyst by forming specific metal chelate active centers through chelation coordination, and, on the other hand, anchor the metal active components to the catalyst surface through stable chelation coordination, thereby improving the catalyst's stability.

[0058] Compared with the catalyst loaded with single platinum metal (Pt-VTES-ROC), although Pt 1.5 Ni1-VTES-ROC has a low content of precious metal platinum, but it can still show better selectivity when catalyzing the hydrosilylation reaction of different olefins while ensuring that the conversion rate does not decrease. In addition, simply reducing the amount of platinum in the catalyst (L-Pt-VTES-ROC), using a single nickel-coordinated solid catalyst (Ni-VTES-RSOC), and using a bimetallic catalyst with too high or too low Ni content (Pt 3.1 Ni1-VTES-ROC and Pt 0.9 Ni1-VTES-ROC) does not have good catalytic performance when catalyzing the above reactions. Figure 1 and Figure 2 Analysis shows that the reason is that according to the bimetallic catalyst preparation method provided by the present invention, a proper amount of platinum ions is first introduced to form a divalent platinum vinyl complex with the vinyl group on the carrier surface, and then a proper amount of nickel ions is introduced to compete with the formed divalent platinum vinyl complex for coordination, thereby forming a special bimetallic chelate coordination structure in which platinum and nickel share the vinyl group. The formation of this structure not only makes Pt 4+ The electrons on the vinyl group form the active center of the divalent platinum vinyl complex, and the Ni 2+ The formation of a shared vinyl coordination structure with the formed divalent platinum complex leads to the electronic shift on the vinyl and the divalent platinum complex center Pt 2+The binding energy of Pt is slightly improved, which can not only maintain the good catalytic activity of single platinum solid catalyst but also further improve the catalytic selectivity. Under mild conditions (normal pressure, solvent-free, low temperature), it shows higher activity and selectivity for the addition of long-chain terminal olefins to tertiary silanes. At the same time, it can significantly reduce the amount of precious metal platinum in the catalytic reaction and reduce the catalytic cost. In addition, due to the strong chelation effect, Pt 2+ with Ni 2+ The active components are not easily lost, which increases the life of the catalyst and greatly enhances the industrial application potential of the catalyst.

[0059] Table 1 Conversion and selectivity of hydrosilylation reaction of different olefin systems catalyzed by different catalysts

[0060]

[0061]

[0062] While the specific embodiments of the present invention have been described in detail above, these are merely exemplary and the present invention is not limited thereto. It will be apparent to those skilled in the art that any equivalent modifications and substitutions to the present invention fall within the scope of the present invention. Therefore, any equivalent changes and modifications made without departing from the spirit and scope of the present invention are encompassed within the scope of the present invention.

Claims

1. A method for preparing a bimetallic complex catalyst supported on rice straw oxidized carbon, characterized by: The steps include: (1) Preparation of hydroxyl-rich rice straw oxidized carbon (ROC); (2) Preparation of rice straw oxidized carbon (VTES-ROC) containing sufficient vinyl ligands: (3) Preparation of rice straw oxidized carbon-supported bimetallic complex catalyst Pt 1.5 Ni1-VTES-ROC: Using appropriate concentrations and amounts of chloroplatinic acid aqueous solution and nickel chloride aqueous solution as precursors, tetravalent platinum ions and divalent nickel ions were introduced onto the surface of VTES-ROC. The two metal ions were anchored by the chelation coordination of vinyl groups to form a rice straw oxidized carbon-supported bimetallic complex catalyst Pt with a special platinum and nickel vinyl complex structure as the catalytic active center. 1.5 Ni1-VTES-ROC,Pt 1.5 Ni1 indicates that the mass ratio of platinum to nickel elements is 1.5:

1.

2. The method for preparing a rice straw oxidized carbon-supported bimetallic complex catalyst according to claim 1, characterized in that: Step (3) is specifically as follows: 0.5 parts by weight of the rice straw oxidized carbon VTES-ROC with the vinyl ligand group introduced obtained in step (2) is added to 30-40 mL of anhydrous ethanol at a material-liquid ratio of 1:60-80 g / mL, and ultrasonicated at room temperature for 5 minutes to allow the carbon material to be fully dispersed in the solvent. 1.1-1.3 mL of Pt 4+ The Pt in the precursor is controlled by adding 3.766 g / L chloroplatinic acid aqueous solution. 4+ It can be evenly dispersed on VTES-ROC, and then 0.015-0.035g NaHCO3 crystals are added and ultrasonicated for 5 minutes. Then the above system is transferred to an oil bath at a temperature of 35-45℃ and stirred for 10-14 hours, which is beneficial to the Pt 4+ The alkaline precipitation fully chelates with the vinyl group, and then 0.85-1.05 mL Ni is added dropwise at a rate of 1 drop / second. 2+ The nickel chloride aqueous solution with a concentration of 2.469 g / L was continued to react for 10 to 14 hours to fully chelate the nickel ions with the vinyl groups. Finally, the mixture was filtered, washed with anhydrous ethanol until neutral, and vacuum dried at 60 ° C to constant weight to obtain the rice straw oxidized carbon immobilized bimetallic complex catalyst Pt 1.5 Ni1-VTES-ROC.

3. The rice straw oxidized carbon-supported bimetallic complex catalyst prepared by the method according to any one of claims 1-2, characterized in that: Its specific surface area is 120~160m 2 / g, an average pore diameter of 6.0-6.4 nm, a platinum loading of 0.6-0.8 wt% based on the obtained catalyst, and a nickel loading of 0.4-0.5 wt% based on the obtained catalyst; the catalyst structure is as follows:

4. Use of the rice straw oxidized carbon-supported bimetallic complex catalyst prepared by the preparation method according to any one of claims 1-2, characterized in that: It is used to catalyze the hydrosilylation of long-chain terminal olefins with triethoxysilane under normal pressure, solvent-free and low-temperature conditions.

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