Supported metal-based catalyst as well as preparation method and application thereof

Abstract

The invention relates to the technical field of catalysis, and discloses a supported metal-based catalyst as well as a preparation method and application thereof. The supported metal-based catalyst comprises a carrier and active components, the carrier comprises nitrogen-doped carbon black, and the active components comprise Pd nanoparticles and bismuthyl carbonate; the supported metal-based catalyst contains oxygen vacancies. According to the supported metal-based catalyst, the catalytic activity of the Pd center is enhanced through the synergistic effect of Pd and bismuthyl carbonate, the catalytic efficiency is guaranteed in the alcohol oxidation esterification reaction, meanwhile, the dosage of the catalyst is reduced, and the cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of catalysis technology, specifically to a supported metal-based catalyst, its preparation method, and its application. Background Technology

[0002] Methyl benzoate, also known as methyl benzoate, is an important ester compound. Besides its use as an intermediate in organic synthesis and as a solvent for cellulose esters, cellulose ethers, resins, and rubber, it also has significant applications in the fragrance, coating, and food industries. The main industrial synthesis of methyl benzoate uses benzoic acid and methanol as raw materials and concentrated sulfuric acid as a catalyst, proceeding through an esterification reaction. While this method offers advantages such as high reactivity and low cost, it also suffers from problems including numerous byproducts, high corrosiveness to equipment, complex product separation processes, and environmental pollution.

[0003] With the continuous development of green synthetic chemistry, there is a desire to develop more direct catalytic methods with higher atom economy, namely the direct oxidative esterification of alcohols. Compared with reactions such as the reaction of alcohols with acids to form esters, the esterification of alcohols with acyl chlorides or acid anhydrides, and the reaction of aldehydes with alcohols to form esters, the direct oxidative esterification of alcohols has higher atom economy. It uses inexpensive and readily available alcohols as starting materials, and aldehydes, ketones, or carboxylic acids are generated in situ in the reaction system to participate in the reaction, ultimately forming esters. The most critical technical challenge in the direct oxidative esterification of alcohols to prepare methyl benzoate lies in the efficient catalyst and catalytic system. Although noble metal-based homogeneous catalysts such as acetonitrile and palladium chloride have high activity during use, they suffer from drawbacks such as high cost and difficulty in catalyst recovery; while non-noble metal catalysts such as zinc bromide have lower activity, and the reaction process requires the additional consumption of large amounts of trifluoroacetic acid, hydrogen peroxide, and other reagents, making the reaction process environmentally unfriendly. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of high cost and low activity of homogeneous catalysts in the direct oxidative esterification of alcohols to prepare methyl benzoate in the prior art. This invention provides a supported metal-based catalyst, its preparation method, and its application. The support of this supported metal-based catalyst includes nitrogen-doped carbon black, and the active components include Pd nanoparticles and bismuth oxycarbonate. Furthermore, the catalyst contains oxygen vacancies, and the catalytic activity of the Pd centers is enhanced through the synergistic effect of Pd and bismuth oxycarbonate. In the alcohol oxidative esterification reaction, the amount of catalyst used is reduced while ensuring catalytic efficiency, thus lowering costs.

[0005] To achieve the above objectives, a first aspect of the present invention provides a supported metal-based catalyst, the supported metal-based catalyst comprising a support active component, the support comprising nitrogen-doped carbon black, the active component comprising Pd nanoparticles and bismuth oxycarbonate; the supported metal-based catalyst contains oxygen vacancies.

[0006] Preferably, based on the total amount of the supported metal-based catalyst, the content of Pd nanoparticles is 0.1-10 wt%, the content of bismuth oxycarbonate (based on bismuth element) is 1-20 wt%, and the content of the support is 70-98.9 wt%.

[0007] Preferably, the oxygen vacancy concentration of the supported metal-based catalyst is 5 × 10⁻⁶. 12 -5×10 13 spins / g.

[0008] A second aspect of the present invention provides a method for preparing a supported metal-based catalyst, the method comprising:

[0009] (1) In the presence of an aqueous solvent, nitrogen-doped carbon black and bismuth salt are mixed, and the resulting mixture is reacted with carbonate source and borohydride aqueous solution;

[0010] (2) The reaction product obtained in step (1) is mixed with an aqueous solution of palladium salt, and then an aqueous solution of borohydride is added to react and Pd@Bi2O2CO3 / NCB supported metal-based catalyst is obtained.

[0011] The third aspect of the present invention provides the application of the supported metal-based catalyst described in the first aspect above or the supported metal-based catalyst prepared by the method described in the second aspect above in the alcohol oxidation esterification reaction.

[0012] Through the above technical solution, the present invention has the following beneficial effects:

[0013] (1) The supported metal-based catalyst provided by the present invention includes nitrogen-doped carbon black as the support and Pd nanoparticles and bismuth oxycarbonate as the active components. Through the synergistic effect of Pd and bismuth oxycarbonate, the surface charge of Pd center is regulated, which enhances the catalytic activity of Pd center and helps to reduce the amount of Pd precious metal used. Moreover, the supported metal-based catalyst contains oxygen vacancies, which further increases the catalytic activity. In the alcohol oxidation esterification reaction, the amount of catalyst used is reduced while ensuring catalytic efficiency. The nitrogen doped in the nitrogen-doped carbon black regulates the surface charge of carbon black, enhances the interaction between the support and the active components and promotes the dispersion of the active components, thereby improving the stability of the supported metal-based catalyst.

[0014] (2) The supported metal-based catalyst provided by the present invention adopts a heterogeneous catalytic system, the catalyst is easy to separate, can be reused, and has low cost; and the supported metal-based catalyst does not use any organic solvent in the preparation process, but only water as a solvent, which is safe, environmentally friendly and simple to prepare. Attached Figure Description

[0015] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof.

[0016] Figure 1 These are TEM images, dark-field images, and mapping elemental distribution diagrams of the Pd@Bi2O2CO3 / NCB supported metal-based catalyst prepared in Example 2.

[0017] Figure 2 These are the XRD patterns of the Pd@Bi2O2CO3 / NCB supported metal-based catalysts prepared in Examples 1-5;

[0018] Figure 3 This is a graph showing the cycle performance of the Pd@Bi2O2CO3 / NCB supported metal-based catalyst prepared in Example 2 when catalyzing the oxidative esterification of benzyl alcohol and methanol to produce methyl benzoate. Detailed Implementation

[0019] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0020] The first aspect of the present invention provides a supported metal-based catalyst, the supported metal-based catalyst comprising a support active component, the support comprising nitrogen-doped carbon black, the active component comprising Pd nanoparticles and bismuth oxycarbonate; the supported metal-based catalyst contains oxygen vacancies.

[0021] In this invention, the supported metal-based catalyst achieves regulation of the surface charge of the Pd center through the synergistic effect of Pd and bismuth oxycarbonate, thereby enhancing the catalytic activity of the Pd center and reducing the amount of Pd precious metal used. The supported metal-based catalyst contains oxygen vacancies, which further increases the catalytic activity, and reduces the amount of catalyst used while ensuring catalytic efficiency in the alcohol oxidation esterification reaction. The nitrogen doped in the nitrogen-doped carbon black regulates the surface charge of the carbon black, enhances the interaction between the support and the active component, promotes the dispersion of the active component, and improves the stability of the supported metal-based catalyst.

[0022] In this invention, the surface of the supported metal-based catalyst contains oxygen vacancies. In some embodiments of this invention, preferably, the oxygen vacancy concentration of the supported metal-based catalyst is 5 × 10⁻⁶. 12 -5×10 13 spins / g, for example, can be 5 × 1012 spins / g, 1×10 13 spins / g, 2×10 13 spins / g, 3×10 13 spins / g, 4×10 13 spins / g, 5×10 13 spins / g, and any value within the range of any two values, preferably 1×10 13 -2×10 13 spins / g.

[0023] In this invention, unless otherwise specified, the oxygen vacancy concentration of the supported metal-based catalyst is tested by electron paramagnetic resonance (EPR) method.

[0024] In this invention, controlling the oxygen vacancy concentration of the supported metal-based catalyst within the aforementioned range helps to further ensure that the supported metal-based catalyst has high activity and selectivity. Within the preferred range, it exhibits even better catalytic performance.

[0025] In some embodiments of the present invention, preferably, based on the total amount of the supported metal-based catalyst, the content of the Pd nanoparticles is 0.1-10 wt%, the content of bismuth oxycarbonate (based on bismuth element) is 1-20 wt%, and the content of the support is 70-98.9 wt%. In this invention, based on the total amount of the supported metal-based catalyst, the content of the Pd nanoparticles can be 0.1 wt%, 0.8 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, or any value within any range of two such values, preferably 0.8-5 wt%; the content of bismuth oxycarbonate (calculated as bismuth) can be 1 wt%, 3 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 12 wt%, 14 wt%, 16 wt%, 18 wt%, 20 wt%, or any value within any range of two such values, preferably 5-10 wt%; the content of the support is preferably 82-95.5 wt%.

[0026] In this invention, unless otherwise specified, the contents of Pd nanoparticles and bismuth oxycarbonate in the supported metal-based catalyst are determined by inductively coupled plasma mass spectrometry (ICP-MS).

[0027] In this invention, the contents of Pd nanoparticles and bismuth oxycarbonate (calculated as bismuth) are controlled within the above-mentioned range. Through the synergistic effect of appropriate amounts of Pb nanoparticles and bismuth oxycarbonate, the catalytic activity and stability of the Pd center are improved. With a low content of Pd nanoparticles, the supported metal-based catalyst has high catalytic activity and low cost.

[0028] In some embodiments of the present invention, preferably, the mass ratio of the Pd nanoparticles to bismuth oxycarbonate (calculated as bismuth element) is 1:0.1-200. For example, it can be 0.1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 50, 100, 150, 200, or any value within the range of any two values, preferably 1:1-10.

[0029] In this invention, controlling the mass ratio of Pd nanoparticles to bismuth oxycarbonate (calculated as bismuth element) within the above-mentioned range is more conducive to leveraging the synergistic effect of Pd and bismuth oxycarbonate, resulting in higher catalytic activity and stability of the supported metal-based catalyst, preventing the aggregation of active Pd nanoparticles, further reducing the amount of Pd used, and controlling the catalyst cost.

[0030] In this invention, the particle size of the Pd nanoparticles has a wide range of selection, as long as the content of Pd nanoparticles in the supported metal-based catalyst meets the above-mentioned range. Preferably, the particle size of the Pd nanoparticles is 3-10 nm.

[0031] In this invention, the Pd nanoparticles are uniformly dispersed on the surface of bismuth oxycarbonate. The lower the Pd loading, the smaller the particle size of the Pd nanoparticles. Under the same Pd loading, the smaller the particle size of the Pd nanoparticles, the higher the catalytic activity of the Pd center, which is beneficial to the catalytic reaction.

[0032] In this invention, unless otherwise specified, the particle size of the Pd nanoparticles is obtained by transmission electron microscopy (TEM).

[0033] In this invention, the nitrogen doping amount in the nitrogen-doped carbon black has a wide selection range. Preferably, the nitrogen doping amount in the nitrogen-doped carbon black is 0.1-5 At.%, for example, it can be 0.1 At.%, 0.2 At.%, 0.5 At.%, 1 At.%, 1.5 At.%, 2 At.%, 2.5 At.%, 3 At.%, 3.5 At.%, 4 At.%, 4.5 At.%, 5 At.%, and any value within the range of any two values, preferably 1.5-3.5 At.%.

[0034] In this invention, unless otherwise specified, the nitrogen doping amount in the nitrogen-doped carbon black is obtained by X-ray photoelectron spectroscopy (XPS). The nitrogen doping amount in this invention is an atomic percentage.

[0035] In this invention, controlling the nitrogen doping amount in nitrogen-doped carbon black within the above-mentioned range is beneficial for regulating the surface charge of carbon black, thereby enhancing the interaction between the support and the active component and promoting the dispersion of the active component, which is more conducive to improving the stability of the supported metal-based catalyst.

[0036] A second aspect of the present invention provides a method for preparing a supported metal-based catalyst, the method comprising:

[0037] (1) In the presence of an aqueous solvent, nitrogen-doped carbon black and bismuth salt are mixed, and the resulting mixture is reacted with carbonate source and borohydride aqueous solution;

[0038] (2) The reaction product obtained in step (1) is mixed with an aqueous solution of palladium salt, and then an aqueous solution of borohydride is added to react and Pd@Bi2O2CO3 / NCB supported metal-based catalyst is obtained.

[0039] In this invention, the method for preparing supported metal-based catalysts is advantageous in reducing the loading of precious metals while ensuring catalytic activity, thereby reducing the cost of the catalyst. Furthermore, no organic solvents are used in the preparation process; only water is used as the solvent, making it safe, environmentally friendly, and simple to prepare.

[0040] In some embodiments of the present invention, preferably, the mass ratio of the nitrogen-doped carbon black to the bismuth salt (calculated as bismuth element) is 1:0.01-0.3, for example, it can be 0.01, 0.02, 0.05, 0.06, 0.08, 0.1, 0.12, 0.14, 0.16, 0.18, 0.2, 0.22, 0.25, 0.28, 0.3, or any value within the range of any two values, preferably 1:0.05-0.25.

[0041] In this invention, controlling the mass ratio of nitrogen-doped carbon black and bismuth salt within the above-mentioned range is beneficial to optimizing the distribution of active components on the support surface, thereby enabling the supported metal-based catalyst to have higher activity and selectivity in catalytic reactions, as well as excellent stability.

[0042] In this invention, the type of bismuth salt is not particularly limited; various bismuth salts conventionally used in the art can be used in this invention, as long as a bismuth source can be provided. Preferably, the bismuth salt is selected from at least one of bismuth nitrate, bismuth chloride, and bismuth acetate, with bismuth nitrate being the most preferred.

[0043] In this invention, the method of mixing nitrogen-doped carbon black and bismuth salt in step (1) is not particularly limited. It can be mixing nitrogen-doped carbon black and bismuth salt with an aqueous solvent, or mixing an aqueous solution of nitrogen-doped carbon black and an aqueous solution of bismuth salt. Preferably, the method in step (1) includes mixing an aqueous solution of nitrogen-doped carbon black and an aqueous solution of bismuth salt.

[0044] In this invention, the mixing conditions of nitrogen-doped carbon black and bismuth salt in step (1) are not particularly limited, as long as the nitrogen-doped carbon black and bismuth salt are mixed evenly. Preferably, the mixing conditions in step (1) include: a temperature of 20-30°C and a time of 5-15 minutes.

[0045] In this invention, the concentration of the nitrogen-doped carbon black aqueous solution is not particularly limited, as long as it can sufficiently disperse the nitrogen-doped carbon black. Preferably, the concentration of the nitrogen-doped carbon black is 0.002-0.02 g / mL.

[0046] In this invention, the concentration of the bismuth salt aqueous solution is not particularly limited, as long as it is sufficient to dissolve the bismuth salt. Preferably, the concentration of the bismuth salt aqueous solution is 0.1-5 g / L.

[0047] In this invention, preferably, in step (1), the obtained mixture is reacted with a carbonate source and an aqueous solution of borohydride to obtain Bi2O2CO3 / NCB. In this invention, the borohydride acts as a reducing agent, promoting the formation of Bi2O2CO3 containing oxygen vacancies and precipitating it on the surface of nitrogen-doped carbon black, which is beneficial to enhancing the catalytic activity of the catalyst.

[0048] In some embodiments of the present invention, preferably, in step (1), the mass ratio of nitrogen-doped carbon black to borohydride is 1:0.01-5, for example, it can be 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, and any value in any range of any two values, preferably 1:0.1-2.

[0049] In this invention, the type of borohydride is not particularly limited. Preferably, the borohydride is selected from at least one of sodium borohydride, potassium borohydride, and manganese borohydride.

[0050] In some embodiments of the present invention, preferably, the method in step (1) includes: adding an aqueous solution of borohydride and a carbonate source simultaneously to the obtained mixture. In the present invention, the simultaneous addition of an aqueous solution of sodium borohydride and a carbonate source to the obtained mixture is beneficial in giving the obtained Bi₂O₂CO₃ more oxygen vacancies, which can better achieve electronic modulation, enhance the redox performance of the catalyst, promote mass transport, accelerate the reaction kinetics, and thus improve the catalytic activity of the catalyst.

[0051] In some embodiments of the present invention, preferably, the carbonate source is selected from at least one of carbon dioxide, alkali metal carbonates, and alkali metal bicarbonates, with carbon dioxide being more preferred. The type of alkali metal carbonate used in the present invention is not particularly limited; for example, the alkali metal carbonate may be selected from sodium carbonate and / or potassium carbonate. The type of alkali metal bicarbonate used in the present invention is not particularly limited; for example, the alkali metal bicarbonate may be selected from sodium bicarbonate and / or potassium bicarbonate.

[0052] In some embodiments of the present invention, preferably, the carbon dioxide is introduced at a rate of 1-600 mL / min relative to 0.1 g of nitrogen-doped carbon black, more preferably 30-300 mL / min.

[0053] In this invention, preferably, the amount of the alkali metal carbonate is 1-1000 mmol relative to 1g of nitrogen-doped carbon black, more preferably 30-600 mmol.

[0054] In this invention, the reaction conditions in step (1) are not particularly limited. Preferably, the reaction conditions in step (1) include: a temperature of 20-30°C and a time of 60-180 min. In this invention, controlling the reaction conditions within the above range is beneficial for a more complete reaction.

[0055] In some embodiments of the present invention, preferably, the mass ratio of the nitrogen-doped carbon black to the palladium salt (calculated as palladium element) is 1:0.001-0.2, for example, it can be 0.001, 0.002, 0.005, 0.01, 0.03, 0.05, 0.07, 0.09, 0.1, 0.12, 0.14, 0.16, 0.18, 0.2, and any value within the range of any two values, preferably 1:0.01-0.16.

[0056] In this invention, controlling the mass ratio of nitrogen-doped carbon black to palladium salt (based on palladium element) within the above-mentioned range is beneficial for forming uniformly distributed palladium nanoparticles and bismuth oxycarbonate on the surface of nitrogen-doped carbon black, thereby increasing the number of active sites of the supported metal-based catalyst and making the supported metal-based catalyst have higher activity and selectivity in the catalytic reaction.

[0057] In this invention, the type of palladium salt is not particularly limited; various bismuth salts conventionally used in the art can be used in this invention, as long as a palladium source can be provided. Preferably, the palladium salt is selected from at least one of potassium tetrachloropalladium, palladium nitrate, and palladium chloride, with potassium tetrachloropalladium being the most preferred.

[0058] In this invention, the concentration of the palladium salt aqueous solution is not particularly limited, as long as it is sufficient to dissolve the palladium salt. Preferably, the concentration of the palladium salt aqueous solution is 0.1-5 g / L.

[0059] In this invention, the conditions for mixing the reaction product with the palladium salt aqueous solution in step (2) are not particularly limited, as long as the reaction product and palladium salt are mixed evenly. Preferably, the mixing conditions in step (2) include: a temperature of 20-30°C and a time of 5-20 minutes.

[0060] In this invention, in step (2), the borohydride is used as a reducing agent to reduce Pd ions to Pd nanoparticles, which are then fixed on the Bi2O2CO3 / NCB composite structure to obtain a Pd@Bi2O2CO3 / NCB supported metal-based catalyst.

[0061] In some embodiments of the present invention, preferably, in step (2), the mass ratio of nitrogen-doped carbon black to borohydride is 1:0.01-5, for example, it can be 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, and any value in any range of any two values, preferably 1:0.1-2.

[0062] In this invention, controlling the mass ratio of nitrogen-doped carbon black and borohydride within the above-mentioned range is beneficial for obtaining Pd nanoparticles by fully reducing Pd ions while controlling the amount of borohydride.

[0063] In this invention, the type of borohydride described in step (2) is not particularly limited; it may be the same as or different from the borohydride described in step (1). Preferably, the type of borohydride described in step (2) is the same as the type of borohydride described in step (1). Preferably, the borohydride is selected from at least one of sodium borohydride, potassium borohydride, and manganese borohydride.

[0064] In this invention, the reaction conditions in step (2) are not particularly limited. Preferably, the reaction conditions in step (2) include: a temperature of 20-30°C and a time of 60-180 min. In this invention, controlling the reaction conditions within the above range is beneficial for a more complete reaction.

[0065] In this invention, preferably, the method in step (2) further includes: filtering, washing, and drying the reaction product obtained from the reaction to obtain a Pd@Bi2O2CO3 / NCB supported metal-based catalyst. In this invention, the washing method and conditions are not particularly limited; conventional washing methods and conditions used in the art can be employed, as long as water-soluble residues, including boron compounds, can be removed. Preferably, the washing agent is selected from at least one of water, methanol, ethanol, isopropanol, and acetone. In this invention, the drying method and conditions are not particularly limited; conventional drying methods and conditions used in the art can be employed. For example, the drying temperature can be 40-80°C, and the drying time can be 2-24 hours.

[0066] In some embodiments of the present invention, preferably, the method for preparing the nitrogen-doped carbon black includes: acidifying carbon black powder, mixing the resulting acidified carbon black with an aqueous nitrogen source solution to obtain nitrogen-doped carbon black. In the present invention, the carbon black is preferably Vulcan XC-72 carbon black, purchased from Guangzhou Jingyi New Materials Co., Ltd.

[0067] In this invention, the acidification conditions are not particularly limited. Preferably, the acidification conditions include: a temperature of 90-120°C and a time of 8-16 hours.

[0068] In this invention, preferably, the acidification method includes: mixing carbon black powder with an acid solution, reacting under reflux conditions, and separating the resulting reaction product to obtain a solid, which is the acidified carbon black. Preferably, the acidification method further includes: dialyzing the separated solid to neutral, and drying the resulting solid, which is the acidified carbon black. The mixing method and conditions described in this invention are not particularly limited, but the mixing method is preferably ultrasonic and / or stirring. The separation described in this invention is a solid-liquid separation, and the separation method is not particularly limited, but sedimentation separation is preferred. The dialysis and drying methods and conditions described in this invention are not particularly limited, and conventional dialysis and drying methods and conditions used in the art can be employed.

[0069] In some embodiments of the present invention, preferably, the mixing conditions include: a temperature of 90-120°C and a time of 16-32 hours.

[0070] In this invention, preferably, the mixing method includes: mixing acidified carbon black with an aqueous nitrogen source solution, reacting under reflux conditions, and separating the resulting reaction product to obtain a solid, which is nitrogen-doped carbon black. Preferably, the mixing method further includes: washing the separated solid until neutral, and drying it to obtain a solid, which is nitrogen-doped carbon black. The separation described in this invention is a solid-liquid separation, and the separation method is not particularly limited, but centrifugal separation is preferred. The washing and drying methods and conditions described in this invention are not particularly limited, and conventional washing and drying methods and conditions used in the art can be adopted.

[0071] In this invention, the type of nitrogen source is not particularly limited, and various nitrogen sources conventionally used in the art can be used in this invention. Preferably, the nitrogen source is selected from at least one of urea, ammonia, and hydrazine hydrate, with urea being the most preferred.

[0072] In this invention, the concentration of the nitrogen source aqueous solution has a wide selection range. Preferably, the concentration of the nitrogen source aqueous solution is 0.3-0.7 g / mL.

[0073] In a preferred embodiment of the present invention, the method for preparing the supported metal-based catalyst includes:

[0074] (1) Mix nitrogen-doped carbon black aqueous solution (calculated as nitrogen-doped carbon black) and bismuth salt aqueous solution (calculated as bismuth element) at a mass ratio of 1:0.01-0.3. Add borohydride aqueous solution to the resulting mixture and simultaneously introduce carbon dioxide to carry out the reaction. The mass ratio of nitrogen-doped carbon black to borohydride is 1:0.01-5.

[0075] (2) The reaction product obtained in step (1) is mixed with an aqueous solution of palladium salt (calculated as palladium element) at a mass ratio of 1:0.001-0.2, and then an aqueous solution of borohydride is added to carry out the reaction. The mass ratio of nitrogen-doped carbon black to borohydride is 1:0.01-5 to obtain a Pd@Bi2O2CO3 / NCB supported metal-based catalyst.

[0076] The third aspect of the present invention provides the application of the supported metal-based catalyst described in the first aspect above or the supported metal-based catalyst prepared by the method described in the second aspect above in the alcohol oxidation esterification reaction.

[0077] In some embodiments of the present invention, preferably, the method of alcohol oxidative esterification reaction includes: mixing benzyl alcohol, fatty alcohol and the supported metal-based catalyst to carry out oxidative esterification reaction.

[0078] In some embodiments of the present invention, preferably, the ratio of the supported metal-based catalyst to benzyl alcohol is 3-10 mg / mmol, for example, it can be 3 mg / mmol, 4 mg / mmol, 5 mg / mmol, 6 mg / mmol, 7 mg / mmol, 8 mg / mmol, 9 mg / mmol, 10 mg / mmol, or any value within the range of the two values ​​above. In the present invention, the supported metal-based catalyst, through the synergistic effect of Pd and Bi2O2CO3, regulates the surface charge of the Pd center, enhancing the catalytic activity of the Pd center, thereby helping to reduce the amount of catalyst used while ensuring catalytic efficiency and effectively reducing costs.

[0079] In this invention, the alcohol oxidative esterification reaction uses benzyl alcohol as the reactant and a fatty alcohol as both the reactant and solvent. The amounts of benzyl alcohol and fatty alcohol can be selected within a wide range. Preferably, the ratio of fatty alcohol to benzyl alcohol is 0.5-5 mL / mmol, for example, it can be 0.5 mL / mmol, 1 mL / mmol, 1.5 mL / mmol, 2 mL / mmol, 2.5 mL / mmol, 3 mL / mmol, 3.5 mL / mmol, 4 mL / mmol, 4.5 mL / mmol, 5 mL / mmol, or any value within the range of any two of the above values.

[0080] In some embodiments of the present invention, preferably, the raw materials for the alcohol oxidative esterification reaction further include carbonates. Specifically, this includes mixing benzyl alcohol, fatty alcohol, carbonates, and the supported metal-based catalyst to carry out the oxidative esterification reaction.

[0081] In some embodiments of the present invention, preferably, the reaction conditions include: a reaction temperature of 50-80°C, a reaction pressure of atmospheric pressure, and a reaction time of 2-10 h in an air or oxygen atmosphere. In the present invention, the supported metal-based catalyst allows the alcohol oxidative esterification reaction to proceed under relatively mild conditions.

[0082] In this invention, the amount of carbonate used has a wide range of options. Preferably, the molar ratio of benzyl alcohol to carbonate is 32-1:1, more preferably 16-2:1. In this invention, controlling the molar ratio of benzyl alcohol to carbonate within the above range is beneficial for providing an alkaline environment and promoting the oxidative esterification reaction of alcohol.

[0083] In this invention, the type of carbonate is not particularly limited, and various carbonates conventionally used in the art can be used in this invention. Preferably, the carbonate is selected from at least one of Na2CO3, K2CO3, and Cs2CO3.

[0084] In some embodiments of the present invention, preferably, the benzyl alcohol is benzyl alcohol.

[0085] In some embodiments of the present invention, preferably, the fatty alcohol is methanol.

[0086] The present invention will be described in detail below through embodiments.

[0087] Benzyl alcohol conversion rate = [Initial moles of benzyl alcohol - Remaining moles of benzyl alcohol in the filtrate] × 100% / Initial moles of benzyl alcohol;

[0088] Methyl benzoate yield = number of moles of methyl benzoate produced in the filtrate × 100% / initial number of moles of benzyl alcohol;

[0089] methyl benzoate selectivity = number of moles of methyl benzoate produced in the filtrate × 100% / [(initial number of moles of benzyl alcohol - number of moles of benzyl alcohol remaining in the filtrate)].

[0090] Preparation Example 1

[0091] 400 mL of concentrated nitric acid aqueous solution with a solute mass fraction of 65% was added to a 1000 mL round-bottom flask, and then 60 g of Vulcan XC-72 carbon black (purchased from Guangzhou Jingyi New Materials Co., Ltd.) was added. The mixture in the round-bottom flask was then stirred by sonication for 30 min. The round-bottom flask was then placed in an oil bath at 100 °C, and the mixture in the round-bottom flask was refluxed under stirring for 12 hours. After the reaction was completed, 600 mL of water was added to the round-bottom flask for sedimentation. After sufficient sedimentation, the supernatant was separated, and the remaining sediment was dialyzed in a dialysis bag until neutral and then dried to obtain acidified carbon black (CB).

[0092] 240 mL of a urea aqueous solution with a solute concentration of 0.5 g / mL was added to a blank 1000 mL round-bottom flask. Then, 6 g of the acidified carbon black obtained above was added. The mixture in the round-bottom flask was stirred ultrasonically for 30 min. The flask was then placed in an oil bath at 100 °C, and the mixture was refluxed under stirring for 24 hours. After the reaction was completed, the mixture was centrifuged and filtered. The resulting filter cake was washed until neutral and then dried to obtain nitrogen-doped carbon black (NCB). XPS analysis showed that the nitrogen doping content in NCB was 1.93 At.%.

[0093] Example 1

[0094] (1) Weigh 100 mg of NCB powder (prepared in Preparation Example 1) and ultrasonically disperse it in 30 mL of water to obtain an NCB dispersion. Dissolve 11.7 mg of Bi(NO3)3·5H2O in 10 mL of water and then add it dropwise to the NCB dispersion. After the addition is complete, stir at 25 °C for 5 min and keep the resulting reaction solution warm.

[0095] (2) Weigh 50 mg of NaBH4 and dissolve it in 10 mL of water. Then add it dropwise to the reaction solution described in step (1). While adding the solution, pass CO2 gas (100 mL / min) through the solution. After the addition is complete, continue to pass CO2 gas (100 mL / min). Stir the solution at 25 °C for 2 h to obtain the reaction product containing Bi2O2CO3 / NCB. Keep the solution warm.

[0096] (3) Weigh 3.1 mg of K2PdCl4 and dissolve it in 10 mL of water. Then add it dropwise to the reaction product obtained in step (2). After the addition is complete, stir at 25°C for 10 min and keep the reaction solution warm.

[0097] (4) Weigh 50 mg of NaBH4 and dissolve it in 10 mL of water. Then add it dropwise to the reaction solution obtained in step (3). After the addition is complete, stir at 25 °C for 3 h and filter. After washing and drying, the filter cake obtained is Pd@Bi2O2CO3(1 / 5) / NCB supported metal catalyst. The supported metal catalyst is tested to contain oxygen vacancies.

[0098] The XRD pattern of the supported metal-based catalyst prepared in this embodiment is shown below. Figure 2 As shown, by Figure 2 It can be seen that the reduction of Bi(NO3)3·5H2O by NaBH4 under a CO2 atmosphere does not yield metallic Bi, but instead produces Bi2O2CO3; the reduction of K2PdCl4 by NaBH4 yields nano-metallic Pd. Therefore, this supported metal-based catalyst is a composite catalyst with NCB as the support and Pd@Bi2O2CO3 as the active component.

[0099] ICP-MS analysis showed that the actual Pd loading in the Pd@Bi2O2CO3(1 / 5) / NCB supported metal-based catalyst was 0.99 wt%, and the actual Bi loading was 5.2 wt%.

[0100] Example 2

[0101] (1) Weigh 100 mg of NCB powder (prepared in Preparation Example 1) and ultrasonically disperse it in 30 mL of water to obtain an NCB dispersion. Dissolve 11.7 mg of Bi(NO3)3·5H2O in 10 mL of water and then add it dropwise to the NCB dispersion. After the addition is complete, stir at 25 °C for 5 min and keep the resulting reaction solution warm.

[0102] (2) Weigh 50 mg of NaBH4 and dissolve it in 10 mL of water. Then add it dropwise to the reaction solution described in step (1). While adding the solution, pass CO2 gas (100 mL / min) through the solution. After the addition is complete, continue to pass CO2 gas (100 mL / min). Stir the solution at 25 °C for 2 h to obtain the reaction product containing Bi2O2CO3 / NCB. Keep the solution warm.

[0103] (3) Weigh 6.1 mg of K2PdCl4 and dissolve it in 10 mL of water. Then add it dropwise to the reaction product obtained in step (2). After the addition is complete, stir at 25°C for 10 min and keep the reaction solution warm.

[0104] (4) Weigh 50 mg of NaBH4 and dissolve it in 10 mL of water. Then add it dropwise to the reaction solution obtained in step (3). After the addition is complete, stir at 25 °C for 3 h and filter. The filter cake is washed and dried to obtain Pd@Bi2O2CO3(2 / 5) / NCB supported metal catalyst.

[0105] The XRD pattern of the supported metal-based catalyst prepared in this embodiment is shown below. Figure 2 As shown, by Figure 2 It can be seen that the supported metal-based catalyst contains diffraction peaks of Bi2O2CO and metal Pd, proving that the supported metal-based catalyst is a composite catalyst with NCB as support and Pd@Bi2O2CO3 as active component.

[0106] The TEM image, dark-field image, and mapping elemental distribution map of the Pd@Bi2O2CO3(2 / 5) / NCB supported metal-based catalyst prepared in this embodiment are shown below. Figure 1 As shown, by Figure 1 It can be seen that Bi₂O₂CO₃ is supported on the NCB surface in an amorphous form, while Pd is supported on the Bi₂O₂CO₃ surface of the catalyst in the form of nanoparticles, which are uniformly dispersed and have a particle size of 3-10 nm. ICP-MS analysis shows that the actual Pd loading in this Pd@Bi₂O₂CO₃(2 / 5) / NCB supported metal-based catalyst is 2 wt%, and the actual Bi loading is 5.4 wt%.

[0107] Testing revealed that the supported metal-based catalyst surface contains oxygen vacancies, with an oxygen vacancy concentration of 1.799 × 10⁻⁶. 13 spins / g.

[0108] Example 3

[0109] (1) Weigh 100 mg of NCB powder (prepared in Preparation Example 1) and ultrasonically disperse it in 30 mL of water to obtain an NCB dispersion. Dissolve 11.7 mg of Bi(NO3)3·5H2O in 10 mL of water and then add it dropwise to the NCB dispersion. After the addition is complete, stir at 25 °C for 5 min and keep the resulting reaction solution warm.

[0110] (2) Weigh 50 mg of NaBH4 and dissolve it in 10 mL of water. Then add it dropwise to the reaction solution described in step (2). While adding the solution, pass CO2 gas (100 mL / min) through the solution. After the addition is complete, continue to pass CO2 gas (100 mL / min). Stir the solution at 25 °C for 2 h to obtain the reaction product containing Bi2O2CO3 / NCB. Keep the solution warm.

[0111] (3) Weigh 15.3 mg of K2PdCl4 and dissolve it in 10 mL of water. Then add it dropwise to the reaction product obtained in step (2). After the addition is complete, stir at 25 °C for 10 min and keep the reaction solution warm.

[0112] (4) Weigh 50 mg of NaBH4 and dissolve it in 10 mL of water. Then add it dropwise to the reaction solution obtained in step (3). After the addition is complete, stir at 25 °C for 3 h and filter. After washing and drying, the filter cake obtained is Pd@Bi2O2CO3(5 / 5) / NCB supported metal catalyst. The supported metal catalyst is tested to contain oxygen vacancies.

[0113] The XRD pattern of the supported metal-based catalyst prepared in this embodiment is shown below. Figure 2 As shown, by Figure 2 It can be seen that the supported metal-based catalyst contains diffraction peaks of Bi2O2CO and metal Pd, proving that the supported metal-based catalyst is a composite catalyst with NCB as support and Pd@Bi2O2CO3 as active component.

[0114] ICP-MS analysis showed that the actual Pd loading in the Pd@Bi2O2CO3(5 / 5) / NCB supported metal-based catalyst was 3.9 wt%, and the actual Bi loading was 4.3 wt%.

[0115] Example 4

[0116] The method described in Example 1 is different except that in step (1), the amount of Bi(NO3)3·5H2O is increased from 11.7 mg to 23.3 mg; a Pd@Bi2O2CO3(1 / 10) / NCB supported metal-based catalyst is obtained, and the supported metal-based catalyst is found to contain oxygen vacancies.

[0117] The XRD pattern of the supported metal-based catalyst prepared in this embodiment is shown below. Figure 2 As shown, by Figure 2 It can be seen that the supported metal-based catalyst contains diffraction peaks of Bi2O2CO and metal Pd, proving that the supported metal-based catalyst is a composite catalyst with NCB as support and Pd@Bi2O2CO3 as active component.

[0118] ICP-MS analysis showed that the actual Pd loading in the Pd@Bi2O2CO3(1 / 10) / NCB supported metal-based catalyst was 1.4 wt%, and the actual Bi loading was 8 wt%.

[0119] Example 5

[0120] The method described in Example 1 is different in that, in step (1), the amount of Bi(NO3)3·5H2O is increased from 11.7 mg to 23.3 mg; in step (3), the amount of K2PdCl4 is increased from 3.1 mg to 6.1 mg; and a Pd@Bi2O2CO3(2 / 10) / NCB supported metal-based catalyst is obtained. The supported metal-based catalyst is found to contain oxygen vacancies.

[0121] The XRD pattern of the supported metal-based catalyst prepared in this embodiment is shown below. Figure 2 As shown, by Figure 2 It can be seen that the supported metal-based catalyst contains diffraction peaks of Bi2O2CO and metal Pd, proving that the supported metal-based catalyst is a composite catalyst with NCB as support and Pd@Bi2O2CO3 as active component.

[0122] ICP-MS analysis showed that the actual Pd loading in the Pd@Bi2O2CO3(2 / 10) / NCB supported metal-based catalyst was 2 wt%, and the actual Bi loading was 10 wt%.

[0123] Example 6

[0124] The method described in Example 1 is different in that, in step (1), the amount of Bi(NO3)3·5H2O is increased from 11.7 mg to 23.3 mg; in step (3), the amount of K2PdCl4 is increased from 3.1 mg to 15.3 mg; and a Pd@Bi2O2CO3(5 / 10) / NCB supported metal-based catalyst is obtained. The supported metal-based catalyst is found to contain oxygen vacancies.

[0125] ICP-MS analysis showed that the actual Pd loading in the Pd@Bi2O2CO3(5 / 10) / NCB supported metal-based catalyst was 4.9 wt%, and the actual Bi loading was 12.7 wt%.

[0126] Example 7

[0127] The method described in Example 1 is different except that in step (3), the amount of K2PdCl4 added is 1.5 mg; a Pd@Bi2O2CO3(0.5 / 5) / NCB supported metal-based catalyst is obtained, and the supported metal-based catalyst is found to contain oxygen vacancies.

[0128] ICP-MS analysis showed that the actual Pd loading in the Pd@Bi2O2CO3(0.5 / 5) / NCB supported metal-based catalyst was 0.43 wt%, and the actual Bi loading was 5.0 wt%.

[0129] Example 8

[0130] The method described in Example 1 is different except that in step (1), the amount of Bi(NO3)3·5H2O added is 4.7 mg; a Pd@Bi2O2CO3(1 / 2) / NCB supported metal-based catalyst is obtained, and the supported metal-based catalyst is found to contain oxygen vacancies.

[0131] ICP-MS analysis showed that the actual Pd loading in the Pd@Bi2O2CO3(1 / 2) / NCB supported metal-based catalyst was 0.98 wt%, and the actual Bi loading was 1.9 wt%.

[0132] Example 9

[0133] (1) Weigh 100 mg of NCB powder (prepared in Preparation Example 1) and ultrasonically disperse it in 30 mL of water to obtain an NCB dispersion. Dissolve 11.7 mg of Bi(NO3)3·5H2O in 10 mL of water and add it dropwise to the NCB dispersion. After the addition is complete, stir at 25 °C for 5 min. Then, while stirring, pass CO2 gas (100 mL / min) and stir at 25 °C for 2 h to obtain a reaction solution.

[0134] (2) Weigh 50 mg of NaBH4 and dissolve it in 10 mL of water. Then add it dropwise to the reaction solution described in step (1). Stir at 25°C for 2 hours. After stirring at 25°C for 2 hours, keep the reaction product containing Bi2O2CO3 / NCB warm.

[0135] (3) Weigh 6.1 mg of K2PdCl4 and dissolve it in 10 mL of water. Then add it dropwise to the reaction product obtained in step (2). After the addition is complete, stir at 25°C for 10 min and keep the reaction solution warm.

[0136] (4) Weigh 50 mg of NaBH4 and dissolve it in 10 mL of water. Then add it dropwise to the reaction solution obtained in step (3). After the addition is complete, stir at 25 °C for 3 h and filter. The filter cake obtained is washed and dried to obtain Pd@Bi2O2CO3(2 / 5)-1 / NCB supported metal-based catalyst.

[0137] Testing revealed that the supported metal-based catalyst surface contains oxygen vacancies, with an oxygen vacancy concentration of 1.551 × 10⁻⁶. 13 spins / g.

[0138] ICP-MS analysis showed that the actual Pd loading in the Pd@Bi2O2CO3(5 / 10) / NCB supported metal-based catalyst was 1.9 wt%, and the actual Bi loading was 5.1 wt%.

[0139] Comparative Example 1

[0140] (1) Weigh 100 mg of NCB powder (prepared in Preparation Example 1) and ultrasonically disperse it in 30 mL of water to obtain an NCB dispersion. Dissolve 6.1 mg of K2PdCl4 in 10 mL of water and then add it dropwise to the NCB dispersion. After the addition is complete, stir at 25 °C for 10 min and keep the resulting reaction solution warm.

[0141] (2) Weigh 50 mg of NaBH4 and dissolve it in 10 mL of water. Then add it dropwise to the reaction solution. After the addition is complete, stir at 25 °C for 3 h and filter. The filter cake is washed and dried to obtain Pd(2) / NCB supported metal-based catalyst.

[0142] ICP-MS analysis showed that the actual Pd loading in this Pd(2) / NCB supported metal-based catalyst was 0.99 wt%.

[0143] Comparative Example 2

[0144] (1) Weigh 100 mg of NCB powder (prepared in Preparation Example 1) and ultrasonically disperse it in 30 mL of water to obtain an NCB dispersion. Dissolve 15.3 mg of K2PdCl4 in 10 mL of water and then add it dropwise to the NCB dispersion. After the addition is complete, stir at 25 °C for 10 min and keep the resulting reaction solution warm.

[0145] (2) Weigh 50 mg of NaBH4 and dissolve it in 10 mL of water. Then add it dropwise to the reaction solution. After the addition is complete, stir at 25 °C for 3 h and filter. The filter cake is washed and dried to obtain Pd(5) / NCB supported metal-based catalyst.

[0146] ICP-MS analysis showed that the actual Pd loading in this Pd(5) / NCB supported metal-based catalyst was 4.6 wt%.

[0147] Comparative Example 3

[0148] (1) Weigh 100 mg of NCB powder (prepared in Preparation Example 1) and ultrasonically disperse it in 30 mL of water to obtain an NCB dispersion. Dissolve 30.7 mg of K2PdCl4 in 10 mL of water and then add it dropwise to the NCB dispersion. After the addition is complete, stir at 25 °C for 10 min and keep the resulting reaction solution warm.

[0149] (2) Weigh 50 mg of NaBH4 and dissolve it in 10 mL of water. Then add it dropwise to the reaction solution. After the addition is complete, stir at 25 °C for 3 h and filter. The filter cake is washed and dried to obtain Pd(10) / NCB supported metal-based catalyst.

[0150] ICP-MS analysis showed that the actual Pd loading in this Pd(10) / NCB supported metal-based catalyst was 9.4 wt%.

[0151] Comparative Example 4

[0152] (1) Weigh 100 mg of NCB powder (prepared in Preparation Example 1) and ultrasonically disperse it in 30 mL of water to obtain an NCB dispersion. Dissolve 11.7 mg of Bi(NO3)3·5H2O in 10 mL of water and then add it dropwise to the NCB dispersion. After the addition is complete, stir at 25 °C for 5 min and keep the resulting reaction solution warm.

[0153] (2) Weigh 50 mg of NaBH4 and dissolve it in 10 mL of water. Then add it dropwise to the reaction solution described in step (2). While adding the solution, pass CO2 gas (100 mL / min) through the solution. After the addition is complete, continue to pass CO2 gas (100 mL / min). Stir the solution at 25 °C for 2 h and then filter it. After washing and drying the filter cake, you will get Bi2O2CO3(5) / NCB supported metal-based catalyst.

[0154] According to ICP-MS testing, the actual Bi loading in this Bi2O2CO3(5) / NCB supported metal-based catalyst is 4.2 wt%.

[0155] Comparative Example 5

[0156] (1) Weigh 100 mg of NCB powder (prepared in Preparation Example 1) and ultrasonically disperse it in 30 mL of water to obtain an NCB dispersion. Dissolve 23.3 mg of Bi(NO3)3·5H2O in 10 mL of water and then add it dropwise to the NCB dispersion. After the addition is complete, stir at 25 °C for 5 min and keep the resulting reaction solution warm.

[0157] (2) Weigh 50 mg of NaBH4 and dissolve it in 10 mL of water. Then add it dropwise to the reaction solution described in step (2). While adding the solution, pass CO2 gas (100 mL / min) through the solution. After the addition is complete, continue to pass CO2 gas (100 mL / min). Stir the solution at 25 °C for 2 h and then filter it. After washing and drying the filter cake, you will get Bi2O2CO3(10) / NCB supported metal-based catalyst.

[0158] According to ICP-MS testing, the actual Bi loading in this Bi2O2CO3(10) / NCB supported metal-based catalyst is 8.8 wt%.

[0159] Test Example 1

[0160] The catalytic performance of the supported metal-based catalysts prepared in the examples and comparative examples was tested. The test method included: mixing 10 mg of the supported metal-based catalyst (or NCB prepared in Preparation Example 1), 4 mL of methanol (used as both reactant and solvent), 0.25 mmol of potassium carbonate, and 2 mmol of benzyl alcohol, and ultrasonically dispersing them thoroughly. A magnetic stirrer was then placed in the mixture, and the reaction was carried out under an oxygen atmosphere at atmospheric pressure (1 atm) with magnetic stirring. The reaction temperature was 60 °C, and the reaction time was 8 h. After the reaction was completed, the mixture was allowed to cool naturally to room temperature (25 °C), and stirring was stopped. The supported catalyst (or NCB prepared in Preparation Example 1) and K2CO3 were filtered out, and the filtrate was analyzed by HPLC to obtain the benzyl alcohol conversion rate, methyl benzoate yield, and methyl benzoate selectivity. The results are shown in Table 1.

[0161] Table 1

[0162] Number Pd / wt% Bi / wt% Conversion / % Yield / % Selectivity / % Preparation 1 / / 0 0 0 Example 1 0.99 5.2 ＞99.9 94.8 94.8 Example 2 2 5.4 >99.9 95.3 95.3 Example 3 3.9 4.3 >99.9 95.7 95.7 Example 4 1.4 8 >99.9 95.6 95.6 Example 5 2 10 >99.9 99 99 Example 6 4.9 12.7 >99.9 97.9 97.9 Example 7 0.43 5 85 71.8 84.5 Example 8 0.98 1.9 90.1 79.5 88.2 Example 9 1.9 5.1 100 93 93 Comparative Example 1 1.8 / 92.9 67 72.1 Comparative Example 2 4.6 / 98 82.7 84.1 Comparative Example 3 9.4 / 99 88.6 89.5 Comparative Example 4 / 4.2 0 0 0 Comparative Example 5 / 8.8 0 0 0

[0163] As shown in Table 1, the Pd@Bi2O2CO3 / NCB supported metal-based catalyst prepared by the method provided in this invention contains oxygen vacancies and exhibits excellent catalytic activity for oxidative esterification reactions with relatively low amounts of Pd noble metal, resulting in high methyl benzoate yield and selectivity. Combining Example 1, Comparative Examples 1-5, and Table 1, it can be seen that compared with Example 1, the supported metal-based catalysts in Comparative Examples 1-3 do not contain Bi2O2CO3, leading to poor catalytic activity; the supported metal-based catalysts in Comparative Examples 4 and 5 do not contain Pd, resulting in no catalytic activity.

[0164] Test Example 2

[0165] The supported metal-based catalyst prepared in Example 2 was subjected to cycle performance testing, and the above steps were repeated for the supported metal-based catalyst. The cycle performance of the supported metal-based catalyst is as follows: Figure 3 As shown, by Figure 3 It can be seen that after 5 cycles, the conversion rate, yield and selectivity did not change significantly, indicating that the supported metal-based catalyst has excellent cycle stability.

[0166] Test Example 3

[0167] The supported metal-based catalyst prepared in Example 2 was used as the catalyst for the alcohol oxidative esterification reaction. Benzyl alcohol was used as the raw material, and fatty alcohol was used as the raw material and solvent for the alcohol oxidative esterification reaction. Specific reaction conditions included: mixing 2 mmol of benzyl alcohol or its derivative, 4 mL of fatty alcohol, 0.25 mmol of potassium carbonate, and 10 mg of the supported metal-based catalyst, and then ultrasonically dispersing them thoroughly. A magnetic stirrer was placed in the mixture, and the reaction was carried out under an oxygen atmosphere at atmospheric pressure (1 atm). The reaction temperature was 60°C, and the reaction time was 8 h. After the reaction was completed, the mixture was allowed to cool naturally to room temperature (25°C), and then stirring was stopped. The supported metal-based catalyst was recovered by filtration, and the filtrate was separated by column chromatography to obtain the product. The results are shown in Table 2.

[0168] Table 2 Results of alcohol oxidation-esterification reaction catalyzed by Pd@Bi2O2CO3 / NCB supported metal-based catalyst

[0169]

[0170]

[0171] As can be seen from the results in Table 2, the Pd@Bi2O2CO3 / NCB supported metal-based catalyst prepared by the method provided in this invention has excellent substrate versatility and can be used for catalytic reactions of oxidation esterification of various benzyl alcohols and fatty alcohols to generate corresponding ester compounds.

[0172] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A supported metal-based catalyst, characterized in that, The supported metal-based catalyst includes a support and an active component. The support includes nitrogen-doped carbon black, and the active component includes Pd nanoparticles and bismuth oxycarbonate. The supported metal-based catalyst contains oxygen vacancies.

2. The supported metal-based catalyst according to claim 1, wherein, Based on the total amount of the supported metal-based catalyst, the content of Pd nanoparticles is 0.1-10 wt%, the content of bismuth oxycarbonate (calculated as bismuth) is 1-20 wt%, and the content of the support is 70-98.9 wt%. Preferably, based on the total amount of the supported metal-based catalyst, the content of Pd nanoparticles is 0.8-5 wt%, the content of bismuth oxycarbonate (calculated as bismuth) is 4-13 wt%, and the content of the support is 82-95.2 wt%. Preferably, the oxygen vacancy concentration of the supported metal-based catalyst is 5 × 10⁻⁶. 12 -5×10 13 spins / g. Preferably 1×10⁻⁶ 13 -2×10 13 spins / g.

3. The supported metal-based catalyst according to claim 1 or 2, wherein, The mass ratio of the Pd nanoparticles to bismuth oxycarbonate (calculated as bismuth element) is 1:0.1-200, preferably 1:1-10.

4. The supported metal-based catalyst according to any one of claims 1-3, wherein, The nitrogen doping content in the nitrogen-doped carbon black is 0.1-5 At.%, preferably 1.5-3.5 At.%.

5. A method for preparing a supported metal-based catalyst, characterized in that, The method includes: (1) In the presence of an aqueous solvent, nitrogen-doped carbon black and bismuth salt are mixed, and the resulting mixture is reacted with carbonate source and borohydride aqueous solution; (2) The reaction product obtained in step (1) is mixed with an aqueous solution of palladium salt, and then an aqueous solution of borohydride is added to react and Pd@Bi2O2CO3 / NCB supported metal-based catalyst is obtained.

6. The method according to claim 5, wherein, The method in step (1) includes: adding a borohydride aqueous solution to the obtained mixture while simultaneously adding a carbonate source; Preferably, the carbonate source is selected from at least one of carbon dioxide, alkali metal carbonates and alkali metal bicarbonates, and is preferably carbon dioxide; Preferably, the carbon dioxide introduction rate is 1-600 mL / min relative to 0.1 g nitrogen-doped carbon black, and more preferably 30-300 mL / min; Preferably, the mass ratio of the nitrogen-doped carbon black to the bismuth salt (calculated as bismuth element) is 1:0.01-0.3, more preferably 1:0.05-0.25; Preferably, the bismuth salt is selected from at least one of bismuth nitrate, bismuth chloride, and bismuth acetate, and is preferably bismuth nitrate; Preferably, in step (1), the mass ratio of nitrogen-doped carbon black to borohydride is 1:0.01-5, more preferably 1:0.1-2; Preferably, the method in step (1) includes: mixing an aqueous solution of nitrogen-doped carbon black and an aqueous solution of bismuth salt; Preferably, the concentration of the bismuth salt aqueous solution is 0.1-5 g / L; Preferably, the reaction conditions in step (1) include: a temperature of 20-30°C and a time of 60-180 min.

7. The method according to claim 5 or 6, wherein, The mass ratio of nitrogen-doped carbon black to palladium salt (based on elemental palladium) is 1:0.001-0.2, preferably 1:0.01-0.16; Preferably, the palladium salt is selected from at least one of potassium tetrachloropalladium, palladium nitrate, and palladium chloride, and is preferably potassium tetrachloropalladium; Preferably, the concentration of the palladium salt aqueous solution is 0.1-5 g / L; Preferably, in step (2), the mass ratio of nitrogen-doped carbon black to borohydride is 1:0.01-5, more preferably 1:0.1-2; Preferably, the reaction conditions in step (2) include: a temperature of 20-30°C and a time of 60-180 min.

8. The method according to any one of claims 5-7, wherein, The method for preparing nitrogen-doped carbon black includes: acidifying carbon black powder, mixing the acidified carbon black with an aqueous nitrogen source solution to obtain nitrogen-doped carbon black; Preferably, the acidification conditions include: a temperature of 90-120°C and a time of 8-16 hours; Preferably, the mixing conditions include: a temperature of 90-120°C and a time of 16-32 hours; Preferably, the nitrogen source is selected from at least one of urea, ammonia and hydrazine hydrate, and is preferably urea; Preferably, the concentration of the nitrogen source aqueous solution is 0.3-0.7 g / mL.

9. The application of a supported metal-based catalyst according to any one of claims 1-4 or a supported metal-based catalyst prepared by the method according to any one of claims 5-8 in an alcohol oxidative esterification reaction.

10. The application according to claim 9, wherein, The method for the alcohol oxidative esterification reaction includes: mixing benzyl alcohol, fatty alcohol and the supported metal-based catalyst to carry out the oxidative esterification reaction; Preferably, the ratio of the supported metal-based catalyst to benzyl alcohol is 3-10 mg / mmol; Preferably, the ratio of fatty alcohol to benzyl alcohol is 0.5-5 mL / mmol; Preferably, the raw materials for the alcohol oxidative esterification reaction further include carbonates; Preferably, the reaction conditions include: under an air or oxygen atmosphere, a reaction temperature of 50-80°C, a reaction pressure of atmospheric pressure, and a reaction time of 2-10 hours; Preferably, the molar ratio of benzyl alcohol to carbonate is 32-1:1, more preferably 16-2:1; preferably, the carbonate is selected from at least one of Na2CO3, K2CO3 and Cs2CO3; Preferably, the benzyl alcohol is benzyl alcohol; Preferably, the fatty alcohol is methanol.

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