CN106362739A - Nano-gold catalyst supported on mesoporous carbon-silicon dioxide composite body and preparation method thereof - Google Patents

Abstract

The invention relates to a mesoporous carbon-silica composite loaded nano-gold catalyst and a preparation method thereof. The catalyst has an ordered two-dimensional hexagonal mesoscopic structure, a specific surface area of ^400-900m2 /g, and a pore diameter of 3.0-7.0nm. The percentage content of gold nanoparticles is 1-5wt%, and the particle size is 2-10nm; during preparation, the surfactant is dissolved in an organic solvent to obtain solution A; the silicon source is added to the acid solution, and pre-hydrolyzed , to prepare solution B; mix solution A and solution B, stir evenly, then add carbon source, volatilize the organic solvent to obtain a solid intermediate, and then perform a low-temperature thermosetting reaction. After the reaction, reflux extraction with an acidic solution to remove The surfactant is used to prepare the carrier precursor; the carrier precursor is mixed with gold source, calcined at high temperature, carbonized and reduced. Compared with the prior art, the invention has simple operation and low cost, can be used to catalyze the selective hydrogenation reduction reaction of nitrophenol compounds, and has considerable application prospects in industrial catalysis.

Description

Mesoporous carbon-silica composite supported nano-gold catalyst and preparation method thereof

technical field

The invention belongs to the technical field of mesoporous material preparation, and relates to a mesoporous carbon-silicon dioxide composite loaded nano-gold catalyst and a preparation method thereof.

Background technique

As a new generation of catalytic materials, gold nanocatalysts are widely used in organic synthesis and fine chemical production. The catalytic activity of gold catalysts has been shown to be closely related to their size. Gold catalysts with small size (<5nm) usually have better catalytic activity, but are generally difficult to prepare. Ordered mesoporous materials have high specific surface area, large pore volume, and uniform pore size, and can be widely used in adsorption, catalysis, and separation. Using ordered mesoporous materials as carriers to stabilize gold nanoparticles, small-sized gold nanoparticles can be obtained, and its development has attracted widespread attention.

At present, the common preparation methods for mesoporous carbon-supported gold catalysts include deposition-precipitation method, sol-gel method and so on. Due to the weak interaction between the carrier and gold, the introduced active metal has poor dispersion, and the gold nanoparticles are easy to agglomerate and grow during the high-temperature calcination process of the catalyst, and the gold is easy to be lost and poisoned and deactivated during the reaction process. Therefore, there is a need to develop a method for synthesizing gold catalysts with simple operation, low cost, stable gold nanoparticles, and difficult loss.

Contents of the invention

The purpose of the present invention is to provide a highly ordered, uniform size distribution of gold nanoparticles and stable performance of mesoporous carbon-silicon dioxide composite loaded nano-gold catalyst in order to overcome the defects of the above-mentioned prior art.

Another object of the present invention is to provide a method for preparing a mesoporous carbon-silicon dioxide composite-loaded nano-gold catalyst with simple steps, good controllability, low cost and easy realization of large-scale production.

The purpose of the present invention can be achieved through the following technical solutions:

Mesoporous carbon-silica composite loaded nano-gold catalyst, the catalyst has an ordered two-dimensional hexagonal mesoscopic structure, the specific surface area is 400-900m ² /g, the pore diameter is 3.0-7.0nm, and the percentage of gold nanoparticles The content is 1-5wt%, and the particle size of the gold nanoparticles is 2-10nm.

A preparation method for a mesoporous carbon-silicon dioxide composite loaded nano-gold catalyst, the method specifically includes the following steps:

(1) The surfactant is dissolved in an organic solvent to prepare solution A;

(2) adding the silicon source into the acid solution and performing pre-hydrolysis to obtain solution B;

(3) Mix solution A and solution B, stir evenly, control the reaction temperature to 20-40°C, and the reaction time to 0.5-2 hours, then add a soluble carbon source, and react at 15-45°C for 1-4 hours, The organic solvent is volatilized to obtain a solid intermediate;

(4) The solid intermediate is subjected to a low-temperature thermosetting reaction, the reaction temperature is 80-120 ° C, and the reaction time is 12-36 hours. After the reaction is completed, it is extracted with an acidic solution to remove the surfactant and obtain the carrier. Precursor;

(5) The carrier precursor is mixed with the gold source, calcined at high temperature under an inert gas atmosphere, and then carbonized and reduced to prepare a mesoporous carbon-silica composite supported nano-gold catalyst.

The surfactant described in step (1) is a nonionic surfactant, and the mass percentage of the nonionic surfactant in solution A is 0.5-35%, preferably 5-20%.

The organic solvent includes one or more of C ₁ -C ₄ alcohols, benzene, toluene, tetrahydrofuran, chloroform, dichloromethane or ether.

Preferably, the C ₁ -C ₄ alcohols include methanol, ethanol, n-propanol or n-butanol.

The organic solvent is preferably tetrahydrofuran, ethanol or ether.

Described nonionic surfactant is selected from polyethylene oxide-polypropylene oxide, polyethylene oxide-polybutylene oxide, alkane-polyoxyethylene diblock or alkane-polyoxyethylene One or more of alkane tri-block copolymers can be represented by these general formulas: C _a H _2a+1 EO _b , EO _c PO _d EO _c , EO _c BO _d EO _c , EO _c BO _d , EO _c PO _d etc., wherein, the value range of a is 10-18, the value range of b is 5-25, the value range of c is 5-135, and the value range of d is 25-135.

Preferably, the nonionic surfactant is an alkane-polyethylene oxide diblock or alkane-polyethylene oxide triblock copolymer, such as: C _a H _2a+1 EO _b , EO _c PO _d EO _c etc., wherein the value range of a is 12-18, the value range of b is 5-25, the value range of c is 20-135, and the value range of d is 50-135.

More preferably, the nonionic surfactant is selected from Brij56 (C ₁₆ H ₃₃ EO ₁₀ ), Brij76 (C ₁₈ H ₃₇ EO ₁₀ ), Brij78 (C ₁₆ H ₃₃ EO ₂₀ ), P123 (EO ₂₀ PO ₇₀ EO ₂₀ ), F127 (EO ₁₀₆ PO ₇₀ EO ₁₀₆ ) or F108 (EO ₁₃₂ PO ₅₀ EO ₁₃₂ ). The above surfactants are available from BASF or Sigma-Aldrich.

Most preferably, the nonionic surfactant is P123 (EO ₂₀ PO ₇₀ EO ₂₀ ) or F127 (EO ₁₀₆ PO ₇₀ EO ₁₀₆ ).

The molar ratio of silicon in the silicon source in step (2) to water in the acid solution is 1:2-10, and the molar ratio of the soluble carbon source in step (3) to silicon source is 0.01-0.5:1.

The silicon source is formed by mixing an inorganic silicon source and an organic silicon source at a molar ratio of 0-5:1, and the organic silicon source is a sulfur-containing organic silicon source, and the sulfur-containing organic silicon source and the surface The molar ratio of active agent is 12-50:1.

The inorganic silicon source includes one or more of ethyl orthosilicate, methyl orthosilicate, silicon tetrachloride or propyl orthosilicate, and the sulfur-containing organic silicon source includes 3-mercapto One of propyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, bis(triethoxypropylsilane) tetrasulfide or bis(triethoxypropylsilane) disulfide or Various.

The soluble carbon source is a phenolic resin with a relative molecular mass of 200-5000.

Preferably, the phenolic resin is a resole phenolic resin.

The acid solution is a hydrochloric acid solution with a molar concentration of 0.1-0.5 mol/L.

The condition of the acidic solution reflux extraction described in step (4) is: the sulfuric acid solution that adopts mass percentage composition to be 40-60% or the nitric acid solution reflux extraction that mass percentage composition is 30-60%, remove surfactant, control The extraction temperature is 80-100° C., and the extraction time is 12-48 hours.

The gold source in step (5) is chloroauric acid, and the conditions for the high-temperature calcination are: control the heating rate to 1-5°C/min, raise the temperature to 200-900°C, and calcine at a constant temperature for 2-5 hours.

The inert gas is nitrogen or argon.

The present invention adopts non-ionic surfactant as structure-directing agent, utilizes organosilicon source and inorganic silicon source and soluble resin (that is, carbon source) and non-ionic surfactant to self-assemble and synthesize precursor, and then undergoes reflux extraction to obtain mercapto A functionalized ordered mesoporous polymer material; finally adding chloroauric acid solution, impregnating loaded gold, calcining and reducing to obtain an ordered mesoporous carbon-silica composite loaded nano-gold catalyst. For example, the present invention first uses phenolic resin as a carbon source, 3-mercaptopropyltrimethoxysilane as a source of organic functional groups, tetraethyl orthosilicate as an inorganic silicon source, and a triblock copolymer as a template, through the method of multiple co-assembly A mercapto-functionalized ordered mesoporous polymer-silica composite material was prepared, and gold was loaded onto the mesoporous polymer by further utilizing the coordination between mercapto and gold, and the gold nanoparticles were reduced in situ by high-temperature calcination to obtain mesoporous Carbon-Silica Composite Supported Gold Catalyst.

Compared with the prior art, the present invention has the following characteristics:

1) The synthesized mercapto-functionalized hybrid mesoporous material of the present invention can introduce a large amount of mercapto groups on the pore surface and the pore space, and use the strong binding effect between the mercapto groups and gold to disperse and stabilize the gold during the high-temperature carbonization process of the catalyst. Species, to obtain gold catalysts with highly dispersed gold nanoparticles, small size and high stability;

2) The present invention utilizes mercapto groups to coordinate with gold to load gold nanoparticles, and the synthesized mesoporous carbon-silica composite loaded nano-gold catalyst has a highly ordered two-dimensional hexagonal mesoscopic structure with a specific surface area of 400-900m ² /g, the pore size is 3.0-7.0nm, the gold content is 1-5wt%, the gold nanoparticles have a uniform particle size distribution, and the size is 2-10nm;

3) The present invention is simple in operation and low in cost. The catalyst can be used to catalyze the selective hydrogenation reduction reaction of nitrophenol compounds. The conversion rate of p-nitrophenol can reach 98%, and the selectivity of p-nitrophenol is 95%. has considerable application prospects.

Description of drawings

Fig. 1 is the small-angle X-ray diffraction spectrum of embodiment 2 mesoporous carbon-silicon dioxide composite loaded nano-gold catalyst material;

Fig. 2 is the small-angle X-ray diffraction spectrum of embodiment 3 mesoporous carbon-silicon dioxide composite loaded nano-gold catalyst material;

Fig. 3 is the small-angle X-ray diffraction spectrum of embodiment 4 mesoporous carbon-silicon dioxide composite loaded nano-gold catalyst material;

Fig. 4 is the wide-angle X-ray diffraction spectrum of embodiment 4 mesoporous carbon-silicon dioxide composite loaded nano-gold catalyst material;

Fig. 5 is the small-angle X-ray diffraction spectrum of embodiment 5 mesoporous carbon-silicon dioxide composite loaded nano-gold catalyst material;

Fig. 6 is the wide-angle X-ray diffraction spectrum of the nano-gold catalyst material supported by the mesoporous carbon-silicon dioxide composite in Example 5.

detailed description

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is carried out on the premise of the technical solution of the present invention, and detailed implementation and specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments.

For example, the source of inorganic silicon is ethyl orthosilicate, which can also be replaced by methyl orthosilicate, silicon tetrachloride or propyl orthosilicate; the organic silicon source used in the embodiment is 3-mercaptopropyltrimethoxy Silane, one or more of 3-mercaptopropyltriethoxysilane, bis(triethoxypropylsilane) tetrasulfide or bis(triethoxypropylsilane) disulfide can also be used Mixture replacement. The molecular weight of the resole phenolic resin is 200<Mw<5000.

As the organic solvent other than ethanol, methanol, ethanol, n-propanol, n-butanol, benzene, toluene, diethyl ether, tetrahydrofuran, chloroform or dichloromethane can also be used.

Surfactant is P123 (EO ₂₀ PO ₇₀ EO ₂₀ ), Brij76 (C ₁₈ H ₃₇ EO ₁₀ ) Brij56 (C ₁₆ H ₃₃ EO ₁₀ ), F127 (EO ₁₀₆ PO ₇₀ EO ₁₀₆ ) or F108 (EO ₁₃₂ PO ₅₀ EO ₁₃₂ ) instead. The above surfactants are available from BASF or Sigma-Aldrich.

Example 1

Preparation of phenolic resin precursor solution. Put 4.0g of phenol in a three-necked flask, heat it in a water bath at 62°C to make it a transparent liquid; prepare 3.70g of 20% sodium hydroxide solution by weight (weigh 0.34g NaOH, add 1.36g deionized water), Slowly drip into the liquid. After 10 minutes, 15.1 g of formaldehyde solution with a mass percentage of 20-37% was added, refluxed at 70° C. for 3 hours, cooled to room temperature, and adjusted to neutral pH with 4 mol/L hydrochloric acid. Distill under reduced pressure at 75-90° C. to obtain the residue as the target product phenolic resin. After being cooled to room temperature, ethanol or ether solutions of phenolic resin prepolymers with a mass percent concentration of 5-20 wt % are prepared respectively for use.

Example 2

At 40°C, dissolve 1.60g of F127 (0.13mmol) in 10.00g of absolute ethanol and stir for 1 hour to obtain solution A; 0.41g of organosilicon source 3-mercaptopropyltriethoxysilane (1.7mmol) and 0.85 g inorganic silicon source TEOS (4.2mmol) was hydrolyzed under the condition of 5.0g (0.2mol/L) hydrochloric acid for 30 minutes to obtain solution B; mix the two solutions, add 2.0g soluble resole phenolic resin (5.0mmol), at 60°C Stir for 2 hours. Then spread the mixed solution evenly in a petri dish, and place it at room temperature for 7 hours to volatilize the organic solvent; then transfer it to an oven at 100°C, and after 24 hours, reflux the product in a solution of 48wt% sulfuric acid for 48 hours to remove surface activity. agent to obtain a brown solid. Take 0.4g of the above-mentioned brown solid, add 1.0mL of chloroauric acid solution (0.048mmol), stir well, filter, obtain the solid and reduce it by high-temperature calcination, and obtain the nano-gold catalyst material supported by the mesoporous carbon-silica composite. The material has a highly ordered two-dimensional hexagonal mesoscopic structure, a pore size of 3.6nm, a specific surface of 679m ² /g, a gold content of 1wt%, and a uniform size distribution of gold nanoparticles with a size of 3nm. Its characteristic XRD spectrum is shown in Fig. 1 .

Add 100mL sodium borohydride aqueous solution (176mmol.L ^-1 ), 3.5mL p-nitrophenol solution (0.019mmol.L ^-1 ), 0.02g catalyst into a 250mL flask, stir at 30°C, react for a certain period of time and then cool down. The catalyst was separated by centrifugation. Analyzed by UV-Vis chromatography. The yield of p-nitrophenol was 95%.

Example 3

At 40°C, dissolve 0.80g F127 (0.065mmol) in 10.00g absolute ethanol and stir for 1 hour to obtain solution A; 1.0g organic silicon source 3-mercaptopropyltriethoxysilane (4.25mmol) and 0.85 g of inorganic silicon source TEOS (4.2mmol) was hydrolyzed under the condition of 1.0g (0.2mol/L) hydrochloric acid for 30 minutes to obtain solution B; mix the two solutions, add 1.0g soluble resole phenolic resin (2.5mmol), at 60°C Stir for 4 hours. Then spread the mixed solution evenly in a petri dish, and place it at room temperature for 9 hours to volatilize the organic solvent; then transfer it to an oven at 100°C, and after 24 hours, reflux the product in a solution of 48wt% sulfuric acid for 24 hours to remove surface activity. agent to obtain a brown solid. Take 0.4g of the above-mentioned brown solid, add 2.0mL of chloroauric acid solution (0.048mmol), stir well, filter, obtain the solid and reduce it by high-temperature calcination, and obtain the nano-gold catalyst material supported by the mesoporous carbon-silica composite. The material has a highly ordered two-dimensional hexagonal mesoscopic structure, a pore size of 4.6nm, a specific surface of 479m ² /g, a gold content of 2wt%, and a uniform particle size distribution of gold nanoparticles with a size of 5nm. Its characteristic XRD spectrum is shown in Fig. 2 .

Add 100mL sodium borohydride aqueous solution (176mmol.L ^-1 ), 3.5mL p-nitrophenol solution (0.019mmol.L ^-1 ), 0.02g catalyst into a 250mL flask, stir at 30°C, react for a certain period of time and then cool down. The catalyst was separated by centrifugation. Analyzed by UV-Vis chromatography. A 92% yield of p-nitrophenol was obtained.

Example 4

At 40°C, dissolve 0.80g F127 (0.065mmol) in 10.00g absolute ethanol and stir for 1 hour to obtain solution A; 1.0g organic silicon source 3-mercaptopropyltriethoxysilane (4.25mmol) and 1.6 g inorganic silicon source TEOS (8.0mmol) was hydrolyzed under the condition of 1.0g (0.2mol/L) hydrochloric acid for 30 minutes to obtain solution B; mix the two solutions, add 1.0g soluble resole phenolic resin (2.5mmol), at 60°C Stir for 4 hours. Then spread the mixed solution evenly in a petri dish, and place it at room temperature for 9 hours to volatilize the organic solvent; then transfer it to an oven at 100°C, and after 24 hours, reflux the product in a solution of 48wt% sulfuric acid for 24 hours to remove surface activity. agent to obtain a brown solid. Take 0.4g of the above-mentioned brown solid, add 3.0mL of chloroauric acid solution (0.048mmol), fully stir, filter, obtain the solid and reduce it by high-temperature calcination, and obtain the nano-gold catalyst material supported by the mesoporous carbon-silica composite. The material has a highly ordered two-dimensional hexagonal mesoscopic structure, a pore size of 5.6nm, a specific surface of 779m ² /g, a gold content of 3wt%, and a uniform particle size distribution of gold nanoparticles with a size of 8nm. Its characteristic small-angle XRD spectrum is shown in Figure 3, and its characteristic wide-angle XRD spectrum is shown in Figure 4.

Add 100mL sodium borohydride aqueous solution (176mmol.L ^-1 ), 3.5mL p-nitrophenol solution (0.019mmol.L ^-1 ), 0.02g catalyst into a 250mL flask, stir at 30°C, react for a certain period of time and then cool down. The catalyst was separated by centrifugation. Analyzed by UV-Vis chromatography. The yield of p-nitrophenol was 91%.

Example 5

At 40°C, dissolve 0.80g F127 (0.065mmol) in 10.00g absolute ethanol and stir for 1 hour to obtain solution A; 1.0g organic silicon source 3-mercaptopropyltriethoxysilane (4.25mmol) and 1.6 g inorganic silicon source TEOS (8.0mmol) was hydrolyzed under the condition of 1.0g (0.2mol/L) hydrochloric acid for 30 minutes to obtain solution B; mix the two solutions, add 1.0g soluble resole phenolic resin (2.5mmol), at 60°C Stir for 4 hours. Then spread the mixed solution evenly in a petri dish, and place it at room temperature for 9 hours to volatilize the organic solvent; then transfer it to an oven at 100°C, and after 24 hours, reflux the product in a solution of 48wt% sulfuric acid for 24 hours to remove surface activity. agent to obtain a brown solid. Take 0.4g of the above-mentioned brown solid, add 5.0mL of chloroauric acid solution (0.048mmol), stir well, filter, and obtain the solid through high-temperature calcination and reduction to obtain a mesoporous carbon-silica composite supported nano-gold catalyst material. The material has a highly ordered two-dimensional hexagonal mesoscopic structure, a pore diameter of 5.6nm, a specific surface of 379m ² /g, a gold content of 5wt%, and a uniform particle size distribution of gold nanoparticles with a size of 10nm. Its characteristic small-angle XRD spectrum is shown in Figure 5, and its characteristic wide-angle XRD spectrum is shown in Figure 6.

Add 100mL sodium borohydride aqueous solution (176mmol.L ^-1 ), 3.5mL p-nitrophenol solution (0.019mmol.L ^-1 ), 0.02g catalyst into a 250mL flask, stir at 30°C, react for a certain period of time and then cool down. The catalyst was separated by centrifugation. Analyzed by UV-Vis chromatography. A 90% yield of p-nitrophenol was obtained.

Example 6

The preparation method of the mesoporous carbon-silica composite loaded nano-gold catalyst in this embodiment specifically includes the following steps:

(1) The surfactant is dissolved in an organic solvent to prepare solution A;

(2) adding the silicon source into the acid solution and performing pre-hydrolysis to obtain solution B;

(3) Mix solution A and solution B, stir evenly, control the reaction temperature to 20°C, and the reaction time is 2 hours, then add a soluble carbon source, react at 15°C for 4 hours, and volatilize the organic solvent to obtain a solid intermediate thing;

(4) The solid intermediate is subjected to a low-temperature thermosetting reaction, the reaction temperature is 80 ° C, and the reaction time is 36 hours. After the reaction is completed, it is extracted with an acidic solution under reflux to remove the surfactant and obtain a carrier precursor;

(5) The carrier precursor is mixed with the gold source, calcined at high temperature under an inert gas atmosphere, and then carbonized and reduced to prepare a mesoporous carbon-silica composite supported nano-gold catalyst.

In step (1), the surfactant is a nonionic surfactant, the mass percentage of the nonionic surfactant in solution A is 0.5%, and the nonionic surfactant is Brij56 (C ₁₆ H ₃₃ EO ₁₀ ) .

Organic solvents include n-propanol, tetrahydrofuran, ethanol, and ether.

In step (2), the molar ratio of silicon in the silicon source to water in the acid solution is 1:2, and in step (3) the molar ratio of soluble carbon source to silicon source is 0.01:1.

Wherein, the silicon source is formed by mixing the inorganic silicon source and the organosilicon source in a molar ratio of 0.4:1, and the organosilicon source is a sulfur-containing organosilicon source, and the molar ratio of the sulfur-containing organosilicon source to the surfactant is 12:1.

The source of inorganic silicon is mixed with ethyl orthosilicate, silicon tetrachloride and propyl orthosilicate in a mass ratio of 2:1:1, and the organic silicon source containing sulfur is 3-mercaptopropyltriethoxysilane .

The soluble carbon source is phenolic resin with a relative molecular mass of 200.

In step (4), the conditions for reflux extraction of the acidic solution are: use 40-60% by mass sulfuric acid solution for reflux extraction, remove the surfactant, control the extraction temperature to 80° C., and the extraction time to 48 hours.

In step (5), the gold source is chloroauric acid, and the conditions for high-temperature calcination are: control the heating rate to 1° C./min, raise the temperature to 200° C., and perform constant-temperature calcination.

Example 7

The preparation method of the mesoporous carbon-silica composite loaded nano-gold catalyst in this embodiment specifically includes the following steps:

(1) The surfactant is dissolved in an organic solvent to prepare solution A;

(2) adding the silicon source into the acid solution and performing pre-hydrolysis to obtain solution B;

(3) Mix solution A and solution B, stir evenly, control the reaction temperature to 40°C, and the reaction time is 0.5 hours, then add a soluble carbon source, react at 45°C for 1 hour, and volatilize the organic solvent to obtain a solid intermediate thing;

(4) The solid intermediate is subjected to a low-temperature thermosetting reaction, the reaction temperature is 120° C., and the reaction time is 12 hours. After the reaction is completed, reflux extraction with an acidic solution is used to remove the surfactant to obtain a carrier precursor;

(5) The carrier precursor is mixed with the gold source, calcined at high temperature under an inert gas atmosphere, and then carbonized and reduced to prepare a mesoporous carbon-silica composite supported nano-gold catalyst.

In step (1), the surfactant is a nonionic surfactant, the mass percentage of the nonionic surfactant in solution A is 35%, and the nonionic surfactant is F108 (EO ₁₃₂ PO ₅₀ EO ₁₃₂ ) .

Organic solvents include chloroform, dichloromethane, tetrahydrofuran, ethanol, and ether.

In step (2), the molar ratio of silicon in the silicon source to water in the acid solution is 1:10, and in step (3) the molar ratio of soluble carbon source to silicon source is 0.5:1.

Wherein, the silicon source is formed by mixing the inorganic silicon source and the organosilicon source in a molar ratio of 5:1, and the organosilicon source is a sulfur-containing organosilicon source, and the molar ratio of the sulfur-containing organosilicon source to the surfactant is 50:1.

The source of inorganic silicon is mixed with ethyl orthosilicate, methyl orthosilicate and propyl orthosilicate in a mass ratio of 1:1:1, and the source of sulfur-containing organic silicon is 3-mercaptopropyltrimethoxysilane It is mixed with bis(triethoxypropylsilane) disulfide at a molar ratio of 1:1, and the soluble carbon source is phenolic resin with a relative molecular mass of 5000.

In step (4), the conditions for reflux extraction of the acidic solution are: use 30-60% by mass nitric acid solution for reflux extraction, remove the surfactant, control the extraction temperature to 100° C., and the extraction time to 12 hours.

In step (5), the gold source is chloroauric acid, and the conditions for high-temperature calcination are: control the heating rate to 5° C./min, raise the temperature to 900° C., and perform constant-temperature calcination.

Example 8

The preparation method of the mesoporous carbon-silica composite loaded nano-gold catalyst in this embodiment specifically includes the following steps:

(1) The surfactant is dissolved in an organic solvent to prepare solution A;

(2) adding the silicon source into the acid solution and performing pre-hydrolysis to obtain solution B;

(3) Mix solution A and solution B, stir evenly, control the reaction temperature to 30°C, and the reaction time is 1 hour, then add a soluble carbon source, react at 30°C for 2 hours, and volatilize the organic solvent to obtain a solid intermediate thing;

(4) The solid intermediate is subjected to a low-temperature thermosetting reaction, the reaction temperature is 100° C., and the reaction time is 24 hours. After the reaction is completed, it is extracted with an acidic solution to remove the surfactant to obtain a carrier precursor;

(5) The carrier precursor is mixed with the gold source, calcined at high temperature under an inert gas atmosphere, and then carbonized and reduced to prepare a mesoporous carbon-silica composite supported nano-gold catalyst.

In step (1), the surfactant is a nonionic surfactant, the mass percentage of the nonionic surfactant in solution A is 26%, and the nonionic surfactant is F127 (EO ₁₀₆ PO ₇₀ EO ₁₀₆ ) .

Organic solvents include n-butanol, methanol, toluene, tetrahydrofuran, ethanol, and ether.

In step (2), the molar ratio of silicon in the silicon source to water in the acid solution is 1:5, and in step (3) the molar ratio of soluble carbon source to silicon source is 0.1:1.

Wherein, the silicon source is formed by mixing the inorganic silicon source and the organosilicon source in a molar ratio of 2:1, and the organosilicon source is a sulfur-containing organosilicon source, and the molar ratio of the sulfur-containing organosilicon source to the surfactant is 20:1.

The inorganic silicon source is ethyl orthosilicate, and the sulfur-containing organosilicon source is composed of 3-mercaptopropyltrimethoxysilane and bis(triethoxypropylsilane) tetrasulfide, bis(triethoxypropylsilane) ) disulfides are mixed at a molar ratio of 2:1:1, and the soluble carbon source is phenolic resin with a relative molecular mass of 500.

In step (4), the conditions for the reflux extraction of the acidic solution are: reflux extraction with a nitric acid solution with a mass percentage of 30-60%, removing the surfactant, controlling the extraction temperature to 85° C., and the extraction time to 24 hours.

In step (5), the gold source is chloroauric acid, and the conditions for high-temperature calcination are: control the heating rate to 3°C/min, raise the temperature to 720°C, and perform constant-temperature calcination.

Claims (10)

1. Mesoporous carbon-silica composite supported nano-gold catalyst, characterized in that the catalyst has an ordered two-dimensional hexagonal mesoscopic structure, a specific surface area of 400-900m ² /g, and a pore diameter of 3.0-7.0nm. The percentage content of the gold nanoparticles is 1-5wt%, and the particle size of the gold nanoparticles is 2-10nm. 2. the preparation method of mesoporous carbon-silica composite loaded nano-gold catalyst as claimed in claim 1, is characterized in that, the method specifically comprises the following steps: (1) The surfactant is dissolved in an organic solvent to prepare solution A; (2) adding the silicon source into the acid solution and performing pre-hydrolysis to obtain solution B; (3) Mix solution A and solution B, stir evenly, control the reaction temperature to 20-40°C, and the reaction time to 0.5-2 hours, then add a soluble carbon source, and react at 15-45°C for 1-4 hours, The organic solvent is volatilized to obtain a solid intermediate; (4) The solid intermediate is subjected to a low-temperature thermosetting reaction, the reaction temperature is 80-120 ° C, and the reaction time is 12-36 hours. After the reaction is completed, it is extracted with an acidic solution to remove the surfactant and obtain the carrier. Precursor; (5) The carrier precursor is mixed with the gold source, calcined at high temperature under an inert gas atmosphere, and then carbonized and reduced to prepare a mesoporous carbon-silica composite supported nano-gold catalyst. 3. the preparation method of mesoporous carbon-silicon dioxide composite loaded nano-gold catalyst according to claim 2, is characterized in that, the tensio-active agent described in step (1) is nonionic surfactant, and this nonionic The mass percentage of surfactant in solution A is 0.5-35%, and the organic solvent includes one of C ₁ -C ₄ alcohols, benzene, toluene, tetrahydrofuran, chloroform, dichloromethane or ether or more. 4. the preparation method of mesoporous carbon-silica composite loaded nano-gold catalyst according to claim 3, is characterized in that, described nonionic surfactant is selected from polyethylene oxide-polypropylene oxide , one or more of polyethylene oxide-polybutylene oxide, alkane-polyethylene oxide diblock or alkane-polyethylene oxide triblock copolymer. 5. the preparation method of mesoporous carbon-silicon dioxide composite loaded nano-gold catalyst according to claim 2, is characterized in that, the mol ratio of silicon and water in the acid solution in the silicon source described in step (2) is 1:2-10, the molar ratio of the soluble carbon source and silicon source in step (3) is 0.01-0.5:1. 6. the preparation method of mesoporous carbon-silicon dioxide composite loaded nano-gold catalyst according to claim 5, is characterized in that, described silicon source is 0-5 by molar ratio of inorganic silicon source and organosilicon source :1 mixed, and the organosilicon source is a sulfur-containing organosilicon source, and the molar ratio of the sulfur-containing organosilicon source to the surfactant is 12-50:1. 7. the preparation method of mesoporous carbon-silicon dioxide composite supported nano-gold catalyst according to claim 6, is characterized in that, described inorganic silicon source comprises tetraethyl orthosilicate, tetramethyl orthosilicate, One or more of silicon chloride or propyl orthosilicate, and the sulfur-containing organosilicon source includes 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, bis( One or more of triethoxypropylsilane) tetrasulfide or bis(triethoxypropylsilane) disulfide. 8 . The method for preparing a mesoporous carbon-silica composite supported nano-gold catalyst according to claim 5 , wherein the soluble carbon source is a phenolic resin with a relative molecular mass of 200-5000. 9. the preparation method of mesoporous carbon-silica composite loaded nano-gold catalyst according to claim 2, is characterized in that, the condition of the acidic solution reflux extraction described in step (4) is: adopt mass percentage composition 40-60% sulfuric acid solution or 30-60% nitric acid solution by mass percentage is reflux extraction, surfactant is removed, extraction temperature is controlled at 80-100°C, and extraction time is 12-48 hours. 10. the preparation method of mesoporous carbon-silicon dioxide composite supported nano-gold catalyst according to claim 2, is characterized in that, the gold source described in step (5) is chloroauric acid, and the described high-temperature calcined The conditions are: control the heating rate to 1-5° C./min, raise the temperature to 200-900° C., and calcine at a constant temperature for 2-5 hours.