CN114130416A

CN114130416A - Preparation method of carbon-supported multi-metal catalyst and application of carbon-supported multi-metal catalyst in N-alkylation reaction

Info

Publication number: CN114130416A
Application number: CN202111544565.2A
Authority: CN
Inventors: 陈华; 黄鹏; 杨立强; 鞠景喜; 谢智平; 魏青; 马银标; 潘剑明
Original assignee: Zhejiang Weitong Catalytic New Materials Co ltd
Current assignee: Zhejiang Weitong Catalytic New Materials Co ltd
Priority date: 2021-12-16
Filing date: 2021-12-16
Publication date: 2022-03-04

Abstract

The application discloses a preparation method of a carbon-supported multi-metal catalyst and application of the carbon-supported multi-metal catalyst in N-alkylation reaction, wherein the preparation method of the carbon-supported multi-metal catalyst comprises the steps of providing a multi-metal solution and a carbon and nitrogen material precursor solution, wherein the multi-metal solution at least comprises two transition metal ions; mixing the multi-metal solution with the precursor solution of the carbon and nitrogen material to coordinate to obtain a coordination solution; mixing the coordination solution with the carbon carrier slurry to carry out loading to obtain a loaded precursor; and roasting the loaded precursor in an inert gas atmosphere to obtain the carbon-loaded multi-metal catalyst. Through the mode, the metal particle size of the obtained catalyst can be reduced, the metal dispersity is improved, and the catalytic capacity is further improved.

Description

Preparation method of carbon-supported multi-metal catalyst and application of carbon-supported multi-metal catalyst in N-alkylation reaction

Technical Field

The application relates to the technical field of metal catalysis, in particular to a preparation method of a carbon-supported multi-metal catalyst and application of the carbon-supported multi-metal catalyst in an N-alkylation reaction.

Background

Supported catalysts are those in which a composition is formed on the surface of a support, the composition typically containing one or more transition metals bound to the support. Among them, carbide and nitride materials have been considered as carriers for supporting various types of catalysts, which exhibit properties similar to metals, such as high melting point, hardness, strength, and the like. Carbide and nitride materials have been reported to exhibit catalytic properties similar to those of noble metals and are suitable for use in various types of catalytic reactions.

In the long-term research and development process, the inventor of the application finds that the preparation methods of the supported catalyst comprise a liquid phase reduction method, a gas phase reduction method, a colloid method, a microemulsion method, an immersion method and the like, but all have certain problems, such as complicated preparation process, serious pollution and the like, and industrial preparation and batch production are difficult to realize. How to break through the difficult problem of synthesis and promote the application of the supported catalyst is a great challenge in the current research.

Disclosure of Invention

The technical problem mainly solved by the application is to provide a preparation method of a carbon-supported multi-metal catalyst and application of the carbon-supported multi-metal catalyst in an N-alkylation reaction, so that the metal particle size of the obtained catalyst can be reduced, the metal dispersity is improved, and the catalytic capability is further improved.

In order to solve the technical problem, the application adopts a technical scheme that: providing a preparation method of a carbon-supported multi-metal catalyst, wherein the method comprises the steps of providing a multi-metal solution and a carbon and nitrogen material precursor solution, wherein the multi-metal solution at least comprises two transition metal ions; mixing the multi-metal solution with the precursor solution of the carbon and nitrogen material to coordinate to obtain a coordination solution; mixing the coordination solution with the carbon carrier slurry to carry out loading to obtain a loaded precursor; and roasting the loaded precursor in an inert gas atmosphere to obtain the carbon-loaded multi-metal catalyst.

Wherein the multi-metal solution is a bimetallic solution of metal palladium and metal ruthenium.

Wherein providing the multi-metal solution comprises: providing a palladium precursor and a ruthenium precursor; mixing a palladium precursor, a ruthenium precursor and a solvent, and dissolving at the normal temperature of 80 ℃ to obtain the bimetallic solution.

Wherein, the palladium precursor comprises palladium dichloride, the palladium precursor and ruthenium precursor are mixed with a solvent, and the dissolving under the condition of normal temperature to 80 ℃ also comprises: and adding concentrated hydrochloric acid with the same mass as the palladium dichloride into the mixed solution to promote the dissolution of the palladium dichloride.

Wherein the mass ratio of the palladium element to the ruthenium element is 0.5: 1-0.1: 1.

Wherein the palladium precursor comprises one or more of palladium dichloride, sodium chloropalladate, potassium chloropalladate and palladium acetate.

Wherein the ruthenium precursor comprises one or more of ruthenium trichloride, ammonium chlororuthenate and potassium chlororuthenate.

Wherein the solvent comprises one or more of water, ethanol and acetone.

Wherein providing a carbon and nitrogen material precursor solution comprises providing a carbon and nitrogen material precursor; mixing a carbon and nitrogen material precursor with a solvent, and dissolving at the normal temperature of 80 ℃ to obtain a carbon and nitrogen material precursor solution; wherein the precursor of the carbon and nitrogen material comprises one or more of melamine, urea, dicyanodiamine, 1, 10-phenanthroline and 2, 2' -bipyridyl; the solvent is one or more of water, ethanol and acetone.

Wherein, mixing the multi-metal solution with the precursor solution of the carbon and nitrogen material comprises: mixing the bimetallic solution and the precursor solution of the carbon and nitrogen material; stirring for 0.5-6 h at the temperature of 40-70 ℃ to coordinate to obtain a coordination solution; wherein, the solvent used by the bimetallic solution and the precursor solution of the carbon and nitrogen material is the same.

Wherein the ratio of the molar amount of the carbon-nitrogen material precursor to the total molar amount of the palladium element and the ruthenium element is 1: 1-4: 1.

Wherein, the mass fraction of the ruthenium element in the coordination solution is 0.5-10%.

Wherein the method further comprises providing a carbon carrier, the carbon carrier comprising activated carbon; mixing and pulping the activated carbon and the deionized water to obtain activated carbon slurry.

Wherein the mass ratio of the deionized water to the dry-based activated carbon is 5: 1-20: 1.

Wherein mixing the coordination solution with the carbon carrier slurry to carry out loading comprises: mixing the coordination solution with the activated carbon slurry; keeping the temperature of the mixed solution at 20-70 ℃, and regulating the pH of the mixed solution to 2.0-5.0; stirring the mixed solution at the temperature of 20-70 ℃ and the pH of 2.0-5.0 for 1-8 h at the stirring speed of 200-1000 r/min.

Wherein the mass ratio of the ruthenium element to the dry activated carbon is 0.5: 99.5-10: 90.

Wherein, the pH value of the mixed solution can be regulated to 2.0-5.0 by using an acid solution or an alkali solution; the mass fraction of acid in the acid solution is 1-20%; the mass fraction of alkali in the alkali solution is 1-20%; the acid in the acid solution is one or more of glacial acetic acid and concentrated hydrochloric acid; the alkali in the alkali solution is one or more of sodium carbonate, sodium bicarbonate, potassium carbonate and sodium acetate.

Wherein, the method also comprises: carrying out suction filtration on the stirred mixed solution, and washing with deionized water until the pH value of the filtrate is 6.0-8.0; and drying the obtained filter cake at the drying temperature of 60-90 ℃ until the water content of the filter cake is 5-20% to obtain a loaded precursor.

Wherein the roasting of the loaded pre-form in an inert gas atmosphere comprises: the inert atmosphere is nitrogen, the roasting temperature is 400-800 ℃, the heating rate is 5-20 ℃/min, and the roasting time is 4-12 h.

Wherein, the method also comprises: and carrying out dry reduction or wet reduction on the carbon-supported multi-metal catalyst.

Wherein the reduction of the carbon-supported multi-metal catalyst comprises: cooling the carbon-supported multi-metal catalyst obtained by roasting to 200-500 ℃, and introducing a mixed gas of nitrogen and hydrogen to reduce the carbon-supported multi-metal catalyst; carrying out suction filtration and washing on the reduced mixture until the pH value of the filtrate is 6.0-8.0; the reduction time is 1-4 h, and the flow ratio of the nitrogen and hydrogen mixed gas is 95: 5-80: 20.

Wherein the reduction of the carbon-supported multi-metal catalyst comprises: cooling the carbon-supported multi-metal catalyst obtained by roasting to normal temperature to 80 ℃, adding deionized water for pulping, wherein the pulping temperature is 40-60 ℃, the pulping time is 1-3 h, and the weight ratio of the carbon-supported multi-metal catalyst to the deionized water is 1: 5-1: 20; adding a reducing agent solution into the carbon-supported multi-metal catalyst slurry, and stirring and reducing for 1-3 h; after the reduction is finished, stopping stirring, and aging for 0-18 h; and carrying out suction filtration and washing on the aged mixture until the pH value of the filtrate is 6.0-8.0.

The reducing agent is sodium borohydride, and the ratio of the molar weight of the sodium borohydride to the total molar weight of the palladium element and the ruthenium element in the reducing agent is 3: 1-20: 1.

If the obtained carbon-supported multi-metal catalyst slurry is acidic, adjusting the pH of the carbon-supported multi-metal catalyst slurry to 7.0-9.0 by using an alkali liquor, and maintaining the preset pH value for 30-120 min after the preset pH value is reached; the time for adjusting the pH of the slurry is 10-60 min; the alkali is one or more of sodium acetate, sodium carbonate, sodium hydroxide, potassium carbonate and potassium hydroxide; the mass concentration of the alkali liquor is 1-20%.

In order to solve the above technical problem, another technical solution adopted by the present application is: the carbon-supported multi-metal catalyst is prepared by using any one of the preparation methods of the carbon-supported multi-metal catalyst.

Wherein the N-alkylation reaction is the N-alkylation reaction of aniline and alcohol.

The beneficial effect of this application is: different from the situation of the prior art, the carbon-nitrogen material is introduced into the carbon-supported catalyst, so that the metal particle size of the obtained catalyst can be reduced, the metal dispersity is improved, the catalytic capability is further improved, and meanwhile, the method is simple in step.

Drawings

FIG. 1 is a schematic flow diagram of a method for preparing a carbon-supported multimetallic catalyst according to an embodiment of the present application;

FIG. 2 is a Transmission Electron Microscopy (TEM) picture of the product obtained after melamine calcination in a nitrogen atmosphere;

FIG. 3 is a Transmission Electron Microscopy (TEM) picture of the Pd-Ru-N/C @ AC catalyst obtained by doping melamine and then calcining.

Detailed Description

In order to make the purpose, technical solution and effect of the present application clearer and clearer, the present application is further described in detail below with reference to the accompanying drawings and examples.

The application provides a preparation method of a carbon-supported multi-metal catalyst, in the method, a carbon and nitrogen material is introduced, the metal particle size of the catalyst can be reduced, the metal dispersity is improved, the catalytic capability is further improved, and meanwhile, the method is simple in steps and is green and environment-friendly.

Referring to fig. 1, fig. 1 is a schematic flow chart of a method for preparing a carbon-supported multi-metal catalyst according to an embodiment of the present disclosure. In this embodiment, the method for preparing the carbon-supported multi-metal catalyst comprises:

s110: providing a multi-metal solution and a carbon and nitrogen material precursor solution.

The multi-metal solution includes at least two transition metal ions, more specifically, a group VIII metal, such as ruthenium, palladium, platinum, iron, cobalt, rhodium, rhenium, iridium, nickel, and the like.

The precursor of the carbon-nitrogen material is a compound capable of preparing and forming the carbon-nitrogen material (N/C material for short), and is generally a nitrogen-containing ligand such as amines, pyridines and the like. For example, one or more of melamine, urea, dicyanodiamine, 1, 10-phenanthroline and 2, 2' -bipyridine can be mixed.

The N/C material has surface properties important for catalysis, such as alkaline surface function, electron-rich property, hydrogen bond motif and the like, and in addition, the high thermal stability and hydrothermal stability (such as insolubility in acidic, neutral or alkaline solvents) of the N/C material enable the material to be used in liquid or gas environments, at elevated temperature and the like, thereby enhancing the wide application of the N/C material in heterogeneous catalysis.

S130: and mixing the multi-metal solution with the precursor solution of the carbon and nitrogen material to coordinate to obtain a coordination solution.

S150: and mixing the coordination solution with the carbon carrier slurry to carry out loading to obtain a loaded precursor.

S170: and roasting the loaded precursor in an inert gas atmosphere to obtain the carbon-loaded multi-metal catalyst.

In the embodiment, the carbon-nitrogen material is introduced into the carbon-supported catalyst, so that the metal particle size of the obtained catalyst can be reduced, the metal dispersity is improved, the catalytic capability is further improved, and meanwhile, the method is simple in step.

The preparation of the multi-metal solution can be respectively preparing each metal solution, and then mixing each metal solution to obtain the multi-metal solution; the metal precursors may be mixed and then dissolved together to obtain a multi-metal solution.

In one embodiment, the multi-metal solution may be a bimetallic solution, for example, a bimetallic solution containing metallic palladium (Pd) and metallic ruthenium (Ru). The scheme of the present application will be described in detail below by taking the preparation of a Pd-Ru bimetallic solution as an example, but is not limited thereto and should not be taken as limiting the scope of the claims of the present application.

Wherein, the palladium metal solution and the ruthenium metal solution can be respectively prepared as follows:

providing a palladium precursor, wherein the palladium precursor can be one or a mixture of palladium dichloride, sodium chloropalladate, potassium chloropalladate and palladium acetate.

And dissolving the palladium precursor by using a solvent to obtain a palladium metal solution. The solvent may be one or more of water, ethanol and acetone.

Specifically, the palladium precursor is added into the solvent, and stirred at normal temperature to 80 ℃ until the palladium precursor is completely dissolved, wherein hydrochloric acid can be properly added to promote the dissolution of the palladium precursor. For example, when the palladium precursor is palladium dichloride, a mass of concentrated hydrochloric acid equal to the mass of palladium dichloride may be added to the solution to facilitate dissolution of the palladium dichloride.

Similarly, a ruthenium precursor is provided, and the ruthenium precursor can be one or a mixture of more of ruthenium trichloride, ammonium chlororuthenate and potassium chlororuthenate.

And dissolving the ruthenium precursor by using a solvent to obtain a ruthenium metal solution. Likewise, the solvent may be one or more of water, ethanol, and acetone, but the solvents selected for the palladium metal solution and the ruthenium metal solution should be the same. Specifically, the ruthenium precursor is added into a solvent, and stirred at the temperature of between normal temperature and 80 ℃ until the ruthenium precursor is completely dissolved.

And mixing the palladium metal solution and the ruthenium metal solution to obtain the Pd-Ru bimetallic solution. Wherein the mass ratio of the palladium element to the ruthenium element in the Pd-Ru bimetallic solution is 0.5: 1-0.1: 1, for example, the mass ratio can be 0.5:1, 0.46:1, 0.43:1, 0.39:1, 0.34:1, 0.28:1, 0.25:1, 0.17:1, 0.14:1, and the like.

In another embodiment, the palladium precursor and the ruthenium precursor may be mixed first, the mixture may be added to the solvent, and the mixture may be stirred at room temperature to 80 ℃ until the mixture is completely dissolved. The mass ratio of the palladium element to the ruthenium element in the mixture is 0.5:1 to 0.1:1, and for example, the mass ratio may be 0.5:1, 0.46:1, 0.43:1, 0.39:1, 0.34:1, 0.28:1, 0.25:1, 0.17:1, 0.14:1, or the like.

In one embodiment, the step of providing the precursor solution of carbon and nitrogen material is as follows:

providing a carbon and nitrogen material precursor, wherein the carbon and nitrogen material precursor can be one or a mixture of melamine, urea, dicyanodiamine, 1, 10-phenanthroline and 2, 2' -bipyridyl.

And dissolving the precursor of the carbon and nitrogen material by using a solvent to obtain a precursor solution of the carbon and nitrogen material. Likewise, the solvent may be one or more of water, ethanol and acetone, but the solvent used for the carbon-nitrogen material precursor solution should be the same as the solvent used for the bimetallic solution.

In one embodiment, when the ruthenium precursor is one of ruthenium trichloride, ammonium chlororuthenate or potassium chlororuthenate, water is selected as the solvent. When the metal uses water as a solvent, the precursor of the carbon and nitrogen material is selected from one of urea or dicyanodiamine. When the palladium precursor is palladium acetate, the ruthenium precursor is one of ruthenium trichloride, ammonium chlororuthenate and potassium chlororuthenate, the solvent for dissolving Pd-Ru bimetal is one of ethanol and acetone, the carbon-nitrogen material precursor is one of melamine, urea, 1, 10-phenanthroline or 2, 2' -bipyridine, and the solvent used by the bimetal solution is the same as the solvent of the carbon-nitrogen material precursor.

And mixing the prepared carbon-nitrogen material precursor solution with the bimetal solution to coordinate to obtain a coordination solution.

The ratio of the molar amount of the carbon-nitrogen material precursor to the total molar amount of the palladium element and the ruthenium element in the bimetallic solution is 1: 1-4: 1, and for example, the molar ratio may be 1:1, 1.39:1, 1.88:1, 2.03:1, 2.34:1, 2.67:1, 3.12:1, 3.45:1, 3.73:1, 4:1, and the like. And the mass fraction of the ruthenium element in the coordination solution is 0.5-10 percent; for example, the mass fraction may be 0.5%, 0.8%, 1.2%, 1.8%, 2.5%, 3.3%, 4.0%, 4.6%, 5.2%, 5.9%, 6.6%, 7.3%, 8.1%, 8.8%, 9.3%, 10.0%, etc.

Specifically, the Pd-Ru bimetallic solution and the carbon-nitrogen material precursor solution are mixed and stirred for 0.5-6 h at the temperature of 40-70 ℃ to complete coordination, so that a coordination solution is obtained. For example, the temperature may be 40 ℃, 44 ℃, 49 ℃, 53 ℃, 58 ℃, 61 ℃, 66 ℃ or the like, and the stirring time may be 0.8h, 1.1h, 1.5h, 2.2h, 2.8h, 3.5h, 4.0h, 4.7h, 5.3h, 5.6h or the like. Specifically, the reaction can be comprehensively set according to conditions such as the amount of the reaction, the kind of the reaction raw material, and the reaction temperature.

In one embodiment, the carbon support may be one or a mixture of more of activated carbon, carbon black, (oxidized) graphene, carbon fibers, carbon nanotubes. The embodiments of the present invention will be described in detail below by taking the example that the carbon carrier is activated carbon, but the invention is not limited thereto, and should not be construed as limiting the scope of the claims of the present invention.

And mixing the carbon carrier with deionized water to obtain carbon carrier slurry. Specifically, adding activated carbon into deionized water for pulping, and stirring for 1-3 h to obtain uniform carbon pulp. The mass ratio of the deionized water to the activated carbon (dry basis) is 5: 1-20: 1, and can be, for example, 5:1, 7:1, 9:1, 13:1, 15:1, 18:1, 20:1, and the like. The specific surface area of the activated carbon can be 800m²/g～1600m²G, pore volume 0.2cm³/g～0.6cm³(ii) of/g.

And adding the coordination solution into the carbon slurry for impregnation loading. The mass ratio of the ruthenium element to the activated carbon (dry basis) is 0.5:99.5 to 10:90, and may be, for example, 1:99, 1.3:98.7, 2.5:97.5, 3.7:96.3, 4.2:95.8, 5.5:94.5, 6.8:93.2, 7.1:92.9, 8.5:91.5, 9.4:90.6, or the like.

Specifically, the temperature of the mixed solution is kept at 20-70 ℃, and the pH of the mixed solution is regulated to 2.0-5.0. The pH of the mixed solution can be adjusted to 2.0-5.0 by using an acid aqueous solution or an alkali aqueous solution according to the current pH of the mixed solution. Wherein the acid can be one or more of glacial acetic acid and concentrated hydrochloric acid; the alkali can be one or more of sodium carbonate, sodium bicarbonate, potassium carbonate, and sodium acetate. The mass fraction of acid/alkali in the aqueous solution is 1-20%.

And rapidly stirring the mixed solution at the temperature of 20-70 ℃ and the pH of 2.0-5.0 to finish the loading. The stirring time is 1-8 h, and the stirring speed is 200-1000 r/min.

And after loading, carrying out suction filtration, washing with deionized water until the pH value of the filtrate is 6.0-8.0, drying the obtained filter cake at the drying temperature of 60-90 ℃ until the water content of the filter cake is 5-20%, and thus obtaining the loaded precursor. The filter cake may have a water content of 5.2%, 5.9%, 6.6%, 7.3%, 8.1%, 8.8%, 9.3%, 10.0%, 11.5%, 12.8%, 13.2%, 14.8%, 15.5%, 16.3%, 17.0%, 19%, etc.

And placing the dried loaded precursor in an inert gas atmosphere for roasting to obtain the carbon-loaded Pd-Ru-N/C catalyst.

Wherein, the inert atmosphere can be one or a mixture of helium, argon and nitrogen; the roasting temperature is 400-800 ℃, the heating rate is 5-20 ℃/min, and the roasting time is 4-12 h.

In the above embodiment, the N/C material is introduced into the catalyst, so that the size of metal particles can be significantly reduced, the obtained catalyst is a superfine nano-scale catalyst, the metal dispersity is improved, and the solvent used in the preparation method is low in toxicity and is more environment-friendly. Furthermore, by adjusting the pH of the mixed solution during loading, the metal palladium and the metal ruthenium are completely adsorbed on the surface of the carrier in an ionic state, and the catalytic activity of the catalyst is further improved.

The carbon-supported superfine nano Pd-Ru-N/C catalyst obtained by the embodiment can be used as a catalyst for catalytic reaction, such as catalysis of formic acid fuel cells, Suzuki coupling reaction, alcohol oxidation reaction, hydrogenation reaction and the like.

In other embodiments, the resulting carbon-supported Pd-Ru-N/C catalyst can be further processed to obtain a plurality of catalysts of different catalytic properties. For example, the carbon-supported Pd-Ru-N/C catalyst can be further reduced to obtain the carbon-supported Pd-Ru-N/C @ AC catalyst.

Wherein, dry reduction or wet reduction can be selected to further reduce the carbon-supported Pd-Ru-N/C catalyst.

In one embodiment, the carbon-supported Pd-Ru-N/C catalyst can be reduced at high temperature by using a mixed gas of hydrogen and nitrogen.

Specifically, the loaded pre-body obtained in the embodiment is roasted to obtain the carbon-loaded Pd-Ru-N/C catalyst, then the temperature is reduced to 200-500 ℃, and mixed gas of nitrogen and hydrogen is introduced to reduce the carbon-loaded Pd-Ru-N/C catalyst for 1-4 h. The flow ratio of the nitrogen gas to the hydrogen gas mixture is 95: 5-80: 20. And after the reduction is finished, performing suction filtration and washing until the pH of the filtrate is 6.0-8.0 to obtain the carbon-supported Pd-Ru-N/C @ AC catalyst.

In another embodiment, the carbon-supported Pd-Ru-N/C catalyst obtained after calcination can be reslurried and a reducing agent solution is slowly added to carry out wet reduction on the carbon-supported Pd-Ru-N/C catalyst.

Specifically, the loaded pre-body obtained in the embodiment is roasted to obtain the carbon-loaded Pd-Ru-N/C catalyst, then the carbon-loaded Pd-Ru-N/C catalyst is cooled to the normal temperature to 80 ℃, and the carbon-loaded Pd-N/C catalyst is re-pulped by deionized water, wherein the pulping temperature is 40 ℃ to 60 ℃, and the pulping time is 1h to 3 h. The weight ratio of the carbon-supported Pd-Ru-N/C catalyst to the deionized water is 1: 5-1: 20.

And if the obtained slurry is acidic, adjusting the pH of the slurry to 7.0-9.0 by using alkali liquor, and maintaining the preset pH value for 30-120 min after the preset pH value is reached. The time for adjusting the pH of the slurry is 10-60 min. The alkali can be one or more of sodium acetate, sodium carbonate, sodium hydroxide, potassium carbonate, and potassium hydroxide. The mass concentration of the alkali liquor is 1-20%. If the pH of the resulting slurry is alkaline, no adjustment of the slurry pH is necessary.

Adding a reducing agent solution into the carbon-supported Pd-Ru-N/C catalyst slurry. The adding speed of the reducing agent is slow, and the reducing agent is stirred and reduced for 1 to 3 hours after being added. And after the reduction is finished, stopping stirring, aging for 0-18 h, performing suction filtration and washing until the pH of the filtrate is 6.0-8.0, and thus obtaining the carbon-supported Pd-Ru-N/C @ AC catalyst.

Wherein, sodium borohydride can be selected as the reducing agent. The ratio of the molar amount of sodium borohydride to the total molar amount of palladium element and ruthenium element in the reducing agent is 3: 1-20: 1.

The preparation method of the reducing agent solution comprises the following steps: adding a NaOH aqueous solution into deionized water, adjusting the pH value of the water to 8-11, and slowly adding sodium borohydride solid into the water under the stirring condition to obtain a reducing agent aqueous solution.

In one embodiment, the reduced Pd-Ru-N/C @ AC on carbon catalyst can be used to catalyze N-alkylation reactions. For example, it can be used to catalyze the N-alkylation of aniline with alcohol.

Among them, secondary and tertiary amines are important intermediates in medicine, polymers, dyes and agriculture. The substitution reaction of amine and halogenated hydrocarbon can be used for synthesizing secondary amine and tertiary amine, but the selectivity is difficult to control (products comprise secondary amine, tertiary amine and quaternary ammonium salt), and the generated halogen salt is not easy to separate as a byproduct. For this purpose, alcohols can be used instead of halides to react with amines to give amines. The alcohol is selected as the raw material, so that the method has the advantages of low toxicity, easy storage, low price and the like, only water is generated as a byproduct in the reaction, and the selectivity is easy to control. However, the use of alcohols as alkylating agents has the disadvantage that the hydroxyl group is a relatively difficult leaving group, and hydrogen-borrowing strategies are generally employed in which alcohols are dehydrogenated to give aldehydes, which are then subjected to reductive amination with amines. The reaction of amines with alcohols is therefore very advantageous, with the by-product being only water which is not polluting for the environment and without the need to add any reducing agent. Most of the catalysts used in the alkylation reaction using alcohol as a raw material at present are homogeneous catalysts, and although the homogeneous catalysts have high activity, the homogeneous catalysts cannot be recycled, are air-sensitive and expensive, so that the industrial popularization of the homogeneous catalysts is greatly limited. Therefore, the trend was to prepare highly active recyclable heterogeneous catalysts.

In this regard, the present application provides a Pd-Ru-N/C @ AC on carbon catalyst useful for catalyzing N-alkylation reactions.

The N-alkylation reaction is as follows:

the carbon-supported Pd-Ru-N/C @ AC catalyst is used for catalyzing N-alkylation reaction as follows:

the template reaction is carried out as follows:

using Schlenk techniques, the entire course of the reaction was carried out under an inert gas argon atmosphere. Reaction raw materials: aniline (1mmol), benzyl alcohol (1.3mmol), and 1 mol% Ru Pd-Ru-N/C @ AC (Ru 0.01mmol), Cs₂CO₃(1mmol), n-butyl ether (2mL) was stirred at 140 ℃ for 12 h. After the reaction is finished, cooling to normal temperature, adding 100 mu L of n-hexadecane as an internal standard for gas chromatography, taking 3X 15mL of diethyl ether as an extracting agent, combining organic phases, filtering, separating the catalyst, filtering the filtrate by using a 0.45 mu m filter membrane, and performing gas chromatography, wherein the conversion rate, the yield and the selectivity of the reaction are determined byAnd (5) calibrating by a gas chromatography internal standard method.

In the embodiment, the N/C material and the metal palladium are used for improving the catalytic activity of the ruthenium-based catalyst in the N-alkylation reaction of the aniline, and specifically, the metal palladium is introduced into an active center of the ruthenium-based catalyst, so that the generation ratio of byproducts can be reduced, and the selectivity of a target product is improved. Meanwhile, due to the introduction of metal palladium as a cocatalyst, the reduction temperature of metal Ru is reduced and the energy consumption is reduced by utilizing the capability of palladium in dissociating hydrogen. Meanwhile, the metal particle size of the obtained catalyst can be reduced by introducing the N/C material, the metal dispersion degree is improved, and the catalytic capability is further improved. And after the reaction, the catalyst can be recycled.

The present invention will be described in detail with reference to several specific examples, but the present invention is not limited thereto, and should not be construed as limiting the scope of the claims of the present invention.

Example 1:

1.24g of PdCl are weighed out₂Adding into 10mL deionized water, heating to 50 deg.C, adding 1.25mL concentrated hydrochloric acid, and adding 10g RuCl after completely dissolving₃·xH₂And O, continuously stirring until the solution is completely dissolved to obtain a bimetallic solution, and marking as a solution A.

And weighing 5g of urea, adding the urea into 20g of 50 ℃ water, and stirring to dissolve completely to obtain a precursor solution of the carbon and nitrogen material, wherein the solution is marked as solution B.

And slowly adding the solution A into the solution B, heating to 60 ℃, stirring for 4 hours, and stopping stirring to obtain a coordination solution, which is marked as solution C.

Weighing 120g of dry weight of activated carbon, pulping in 1000mL of deionized water, stirring for 1h, adding the solution C, raising the temperature to 43 ℃, stirring at the speed of 400r/min, adjusting the pH of the system to 3.0 by using a 2% sodium carbonate aqueous solution, stirring for 2h, performing suction filtration, washing by using deionized water until the pH of the filtrate is 6.0-7.0, and drying the filter cake at the temperature of 70 ℃ to ensure that the filter cake contains 11.2% of water.

In the nitrogen atmosphere, the heating rate is set to be 5 ℃/min, the roasting temperature is set to be 600 ℃, after roasting for 4h, the temperature is reduced to 350 ℃, the gas atmosphere is changed into 85% nitrogen and 15% hydrogen, the total gas flow is 200mL/min, and the reduction time is 4 h. And after the reduction is finished, performing suction filtration and washing until the pH of the filtrate is 7.2 to obtain the carbon-supported Pd-Ru-N/C @ AC catalyst which is recorded as Cat.

Comparative example 1:

weighing 10g RuCl₃·xH₂O was added to 11.24g of water and 1.25mL of concentrated HCl was added, warmed to 50 deg.C and stirred to dissolve completely to give a ruthenium metal solution, denoted as solution A.

In the nitrogen atmosphere, the heating rate is set to be 5 ℃/min, the roasting temperature is set to be 600 ℃, after roasting for 4h, the temperature is reduced to 350 ℃, the gas atmosphere is changed into 85% nitrogen and 15% hydrogen, the total gas flow is 200mL/min, and the reduction time is 4 h. After the reduction is finished, carrying out suction filtration and washing until the pH value of the filtrate is 7.2 to obtain a catalyst Cat-1^a。

Comparative example 2:

1.24g of PdCl are weighed out₂Adding into 10mL water, heating to 50 deg.C, adding 1.25mL concentrated hydrochloric acid, and adding 10g RuCl after completely dissolving₃·xH₂And O, continuously stirring until the solution is completely dissolved, and continuously adding 20g of water to obtain a mixed solution marked as solution A.

Weighing 120g of dry weight of activated carbon, pulping in 1000mL of deionized water, stirring for 1h, adding the solution A, raising the temperature to 43 ℃, stirring at the speed of 400r/min, adjusting the pH of the system to 3.0 by using a 2% sodium carbonate aqueous solution, stirring for 2h, performing suction filtration, washing by using deionized water until the pH of the filtrate is 6.0-7.0, and drying the filter cake at the temperature of 70 ℃ to ensure that the filter cake contains 11.2% of water.

In the nitrogen atmosphere, the heating rate is set to be 5 ℃/min, the roasting temperature is set to be 600 ℃, after roasting for 4h, the temperature is reduced to 350 ℃, the gas atmosphere is changed into 85% nitrogen and 15% hydrogen, the total gas flow is 200mL/min, and the reduction time is 4 h. After the reduction is finished, carrying out suction filtration and washing until the pH value of the filtrate is 7.2 to obtain a catalyst Cat-1^b。

Comparative example 3: metal palladium + N/C material

And (3) adjusting the pH value of the solution C to 3.0 by using a 2% sodium carbonate aqueous solution, stirring for 2h, performing suction filtration, washing by using deionized water until the pH value of the filtrate is 6.0-7.0, and drying the filter cake at 70 ℃ to ensure that the filter cake contains 11.2% of water.

In the nitrogen atmosphere, the heating rate is set to be 5 ℃/min, the roasting temperature is set to be 600 ℃, after roasting for 4h, the temperature is reduced to 350 ℃, the gas atmosphere is changed into 85% nitrogen and 15% hydrogen, the total gas flow is 200mL/min, and the reduction time is 4 h. After the reduction is finished, carrying out suction filtration and washing until the pH value of the filtrate is 7.2 to obtain a catalyst Cat-1^c。

The N-alkylation reaction of aniline is catalyzed by using the catalysts, and the reaction process is as follows:

using Schlenk techniques, the entire course of the reaction was carried out under an inert gas argon atmosphere. Reaction raw materials: aniline (1mmol) and benzyl alcohol (1.3mmol) while adding 1 mol% of catalyst, Cs₂CO₃(1mmol), n-butyl ether (2mL) was stirred at 140 ℃ for 12 h. After the reaction was completed, 100. mu.L of the mixture was added thereto after it was cooled to room temperatureThe reaction is carried out by taking the n-hexadecane as an internal standard for gas chromatography, taking 3X 15mL of diethyl ether as an extracting agent, combining organic phases, filtering, separating the catalyst, filtering the filtrate by using a 0.45 mu m filter membrane, and carrying out gas chromatography, wherein the conversion rate, the yield and the selectivity of the reaction are calibrated by a gas chromatography internal standard method. The results are detailed in Table 1.

Table 1: aniline N-alkylation reaction parameters

The data in the table show that the carbon-supported Pd-Ru-N/C @ AC catalyst prepared by the method introduces metal palladium into the active center of the ruthenium catalyst, can reduce the generation proportion of byproducts in the N-alkylation reaction of aniline, and improves the selectivity of a target product. Meanwhile, the carbon-supported Pd-Ru-N/C @ AC catalyst is ultrafine nano-scale particles, so that the dispersity is high, the catalytic performance is high, and the reaction yield is high.

Example 2:

weighing 2g of PdCl₂Adding into 10mL deionized water, heating to 50 deg.C, adding 2mL concentrated hydrochloric acid, and adding 5g RuCl after completely dissolving₃·xH₂And O, continuously stirring until the solution is completely dissolved to obtain a bimetallic solution, and marking as a solution A.

And weighing 2.5g of urea, adding the urea into 15g of 50 ℃ water, and stirring to dissolve completely to obtain a precursor solution of the carbon and nitrogen material, which is marked as solution B.

Weighing 181g of dry weight of activated carbon, pulping in 1500mL of deionized water, stirring for 1h, adding the solution C, raising the temperature to 47 ℃, stirring at 400r/min, adjusting the pH of the system to 3.0 by using a 2% sodium carbonate aqueous solution, stirring for 2h, performing suction filtration, washing by using deionized water until the pH of the filtrate is 6.7, and drying the filter cake at 90 ℃ to ensure that the filter cake contains 15.1% of water.

In the nitrogen atmosphere, the heating rate is set to be 5 ℃/min, the roasting temperature is set to be 600 ℃, after roasting for 4h, the temperature is reduced to 350 ℃, the gas atmosphere is changed into 85% nitrogen and 15% hydrogen, the total gas flow is 200mL/min, and the reduction time is 4 h. And after the reduction is finished, performing suction filtration and washing until the pH of the filtrate is 7.9 to obtain the carbon-supported Pd-Ru-N/C @ AC catalyst which is recorded as Cat.

Comparative example 4:

In the nitrogen atmosphere, the heating rate is set to be 5 ℃/min, the roasting temperature is set to be 600 ℃, after roasting for 4h, the temperature is reduced to 200 ℃, the gas atmosphere is changed into 85% nitrogen and 15% hydrogen, the total gas flow is 200mL/min, and the reduction time is 4 h. After the reduction is finished, performing suction filtration and washing until the pH of the filtrate is 7.9 to obtain the carbon-supported Pd-Ru-N/C @ AC catalyst which is recorded as Cat-2^a。

Comparative example 5:

In the nitrogen atmosphere, the heating rate is set to be 5 ℃/min, the roasting temperature is set to be 600 ℃, after roasting for 4h, the temperature is reduced to 300 ℃, the gas atmosphere is changed into 85% nitrogen and 15% hydrogen, the total gas flow is 200mL/min, and the reduction time is 4 h. After the reduction is finished, performing suction filtration and washing until the pH of the filtrate is 7.9 to obtain the carbon-supported Pd-Ru-N/C @ AC catalyst which is recorded as Cat-2^b。

Comparative example 6:

Setting the heating rate at 5 ℃/min and the roasting temperature at 600 ℃ in the nitrogen atmosphere, roasting for 4h, cooling to 400 ℃, changing the gas atmosphere into 85% nitrogen and 15% hydrogen,the total gas flow is 200mL/min, and the reduction time is 4 h. After the reduction is finished, performing suction filtration and washing until the pH of the filtrate is 7.9 to obtain the carbon-supported Pd-Ru-N/C @ AC catalyst which is recorded as Cat-2^c。

using Schlenk techniques, the entire course of the reaction was carried out under an inert gas argon atmosphere. Reaction raw materials: aniline (1mmol) and benzyl alcohol (1.3mmol) while adding 1 mol% of catalyst, Cs₂CO₃(1mmol), n-butyl ether (2mL) was stirred at 140 ℃ for 12 h. After the reaction is finished, cooling to normal temperature, adding 100 mu L of n-hexadecane as an internal standard for gas chromatography, taking 3X 15mL of diethyl ether as an extracting agent, combining organic phases, filtering, separating the catalyst, filtering the filtrate by using a 0.45 mu m filter membrane, performing gas chromatography, and calibrating the conversion rate, yield and selectivity of the reaction by a gas chromatography internal standard method. The results are detailed in Table 2.

Table 2: aniline N-alkylation reaction parameters

The data in the table show that the carbon-supported Pd-Ru-N/C @ AC catalyst prepared by the method has the advantages that metal palladium is introduced into the ruthenium catalyst as a cocatalyst, the reduction temperature of the metal Ru is reduced by utilizing the capability of palladium in dissociating hydrogen, an effective catalyst can be prepared at a lower temperature, and the energy consumption is reduced; while maintaining high selectivity of the aniline N-alkylation reaction.

Example 3:

weighing 2.34g Pd (OAc)₂With 10g of RuCl₃·xH₂O, added together to 20mL of acetone and stirred until completely dissolved, to give a bimetallic solution, denoted as solution A.

Weighing 8.5g of 1, 10-phenanthroline, adding into 20mL of acetone, stirring and completely dissolving to obtain a precursor solution of the carbon and nitrogen material, and marking as solution B.

And slowly adding the solution A into the solution B, stirring at normal temperature for 2 hours, and stopping stirring to obtain a coordination solution which is marked as a solution C.

Weighing 70g of dry weight of activated carbon, pulping in 1000mL of deionized water, stirring for 1h, adding the solution C, stirring at normal temperature at the stirring speed of 300r/min, adjusting the pH of the system to 3.0 by using a 1% acetic acid aqueous solution, stirring for 2h, performing suction filtration, washing by using deionized water until the pH of the filtrate is 6.5, and drying the filter cake at 80 ℃ to ensure that the filter cake contains 14.8% of water.

In the nitrogen atmosphere, the heating rate is set to be 6 ℃/min, the roasting temperature is set to be 700 ℃, after roasting for 2h, the temperature is reduced to 350 ℃, the gas atmosphere is changed into 85% nitrogen and 15% hydrogen, the total gas flow is 200mL/min, and the reduction time is 4 h. And after the reduction is finished, cooling to normal temperature, adding deionized water, pulping, filtering and washing until the pH of the filtrate is 7.7 to obtain the carbon-supported Pd-Ru-N/C @ AC catalyst which is recorded as Cat.

Comparative example 7:

And weighing 4g of melamine, adding the melamine into 20mL of acetone, stirring and completely dissolving to obtain a precursor solution of the carbon and nitrogen material, and marking as a solution B.

In the nitrogen atmosphere, the heating rate is set to be 6 ℃/min, the roasting temperature is set to be 700 ℃, after roasting for 2h, the temperature is reduced to 350 ℃, the gas atmosphere is changed into 85% nitrogen and 15% hydrogen, the total gas flow is 200mL/min, and the reduction time is 4 h. After the reduction is finished, cooling to normal temperature, adding deionized water to form slurry, performing suction filtration and washing until the pH of the filtrate is 7.7 to obtainTo carbon-supported Pd-Ru-N/C @ AC catalyst, which is recorded as catalyst Cat-3^a。

using Schlenk techniques, the entire course of the reaction was carried out under an inert gas argon atmosphere. Reaction raw materials: aniline (1mmol) and benzyl alcohol (1.3mmol) while adding 1 mol% of catalyst, Cs₂CO₃(1mmol), n-butyl ether (2mL) was stirred at 140 ℃ for 12 h. After the reaction is finished, cooling to normal temperature, adding 100 mu L of n-hexadecane as an internal standard for gas chromatography, taking 3X 15mL of diethyl ether as an extracting agent, combining organic phases, filtering, separating the catalyst, filtering the filtrate by using a 0.45 mu m filter membrane, performing gas chromatography, and calibrating the conversion rate, yield and selectivity of the reaction by a gas chromatography internal standard method. The results are detailed in Table 3.

Table 3: aniline N-alkylation reaction parameters

The data in the table show that the carbon-supported Pd-Ru-N/C @ AC catalyst prepared by the method can reduce the size of metal particles of the obtained catalyst due to the introduction of the N/C material, the obtained catalyst is ultrafine nano-scale particles, the metal dispersion degree is improved, the catalytic capacity is further improved, and the aniline N-alkylation reaction has higher yield and product selectivity. Referring to FIGS. 2 and 3, FIG. 2 is a Transmission Electron Microscope (TEM) image of the product obtained by calcining melamine under nitrogen, and FIG. 3 is a Transmission Electron Microscope (TEM) image of the Pd-Ru-N/C @ AC catalyst obtained by calcining the doped melamine. FIG. 2 shows that the baked N/C material has a graphite layered structure, and in FIG. 3, the nano size of the metal is about 1-2 nm, and the uniformity is good.

Example 4:

weighing 1.17g Pd (OAc)₂With 10g of RuCl₃·xH₂And O, adding the components into 20mL of ethanol together, and stirring until the components are completely dissolved to obtain a bimetallic solution which is marked as a solution A.

Weighing 15.7g of 2, 2' -bipyridine, dissolving in 50mL of ethanol, and stirring to dissolve completely to obtain a precursor solution of the carbon-nitrogen material, which is marked as solution B.

Weighing 180g of dry weight of activated carbon, pulping in 1500mL of deionized water, stirring for 1h, adding the solution C, stirring at normal temperature at the stirring speed of 300r/min, adjusting the pH of the system to 3.0 by using a 1% acetic acid aqueous solution, stirring for 3h, performing suction filtration, washing by using deionized water until the pH of the filtrate is 6.3, and drying the filter cake at 70 ℃ to ensure that the filter cake contains 11.3% of water.

In the nitrogen atmosphere, the heating rate is set to be 5 ℃/min, the roasting temperature is set to be 600 ℃, after roasting for 3h, the temperature is reduced to 350 ℃, the gas atmosphere is changed into 85% nitrogen and 15% hydrogen, the total gas flow is 200mL/min, and the reduction time is 4 h. And after reduction, cooling to normal temperature, adding water to form slurry, performing suction filtration and washing until the pH value of the filtrate is 6.9, and obtaining the catalyst Cat.

Comparative example 7:

Weighing 180g of dry weight of activated carbon, pulping in 1500mL of deionized water, stirring for 1h, adding the solution C, stirring at normal temperature at the stirring speed of 300r/min, adjusting the pH of the system to 2.0 by using a 2% sodium carbonate aqueous solution, stirring for 3h, performing suction filtration, washing by using deionized water until the pH of the filtrate is 6.3, and drying the filter cake at 70 ℃ to ensure that the filter cake contains 11.3% of water.

Setting the heating rate at 5 ℃/min and the roasting temperature at 600 ℃ in the nitrogen atmosphere, roasting for 3h, cooling to 350 ℃,the gas atmosphere is changed into 85 percent of nitrogen and 15 percent of hydrogen, the total gas flow is 200mL/min, and the reduction time is 4 h. Reducing the temperature to normal temperature after reduction, adding water to form slurry, performing suction filtration and washing until the pH of the filtrate is 6.9 to obtain a catalyst Cat-4^a。

Comparative example 8:

Weighing 180g of dry weight of activated carbon, pulping in 1500mL of deionized water, stirring for 1h, adding the solution C, stirring at normal temperature at the stirring speed of 300r/min, adjusting the pH of the system to 4.0 by using a 2% sodium carbonate aqueous solution, stirring for 3h, performing suction filtration, washing by using deionized water until the pH of the filtrate is 6.3, and drying the filter cake at 70 ℃ to ensure that the filter cake contains 11.3% of water.

In the nitrogen atmosphere, the heating rate is set to be 5 ℃/min, the roasting temperature is set to be 600 ℃, after roasting for 3h, the temperature is reduced to 350 ℃, the gas atmosphere is changed into 85% nitrogen and 15% hydrogen, the total gas flow is 200mL/min, and the reduction time is 4 h. Reducing the temperature to normal temperature after reduction, adding water to form slurry, performing suction filtration and washing until the pH of the filtrate is 6.9 to obtain a catalyst Cat-4^b。

Comparative example 9:

Weighing 180g of dry weight of activated carbon, pulping in 1500mL of deionized water, stirring for 1h, adding the solution C, stirring at normal temperature at the stirring speed of 300r/min, adjusting the pH of the system to 5.0 by using a 2% sodium carbonate aqueous solution, stirring for 3h, performing suction filtration, washing by using deionized water until the pH of the filtrate is 6.3, and drying the filter cake at 70 ℃ to ensure that the filter cake contains 11.3% of water.

In the nitrogen atmosphere, the heating rate is set to be 5 ℃/min, the roasting temperature is set to be 600 ℃, after roasting for 3h, the temperature is reduced to 350 ℃, the gas atmosphere is changed into 85% nitrogen and 15% hydrogen, the total gas flow is 200mL/min, and the reduction time is 4 h. Reducing the temperature to normal temperature after reduction, adding water to form slurry, performing suction filtration and washing until the pH of the filtrate is 6.9 to obtain a catalyst Cat-4^c。

using Schlenk techniques, the entire course of the reaction was carried out under an inert gas argon atmosphere. Reaction raw materials: aniline (1mmol) and benzyl alcohol (1.3mmol) while adding 1 mol% of catalyst, Cs₂CO₃(1mmol), n-butyl ether (2mL) was stirred at 140 ℃ for 12 h. After the reaction is finished, cooling to normal temperature, adding 100 mu L of n-hexadecane as an internal standard for gas chromatography, taking 3X 15mL of diethyl ether as an extracting agent, combining organic phases, filtering, separating the catalyst, filtering the filtrate by using a 0.45 mu m filter membrane, performing gas chromatography, and calibrating the conversion rate, yield and selectivity of the reaction by a gas chromatography internal standard method. The results are detailed in Table 4.

Table 4: aniline N-alkylation reaction parameters

Further, after the impregnation in example 4, comparative example 7, comparative example 8 and comparative example 9 were respectively extracted, the metal content of the primary filtrate was measured, and the results are shown in table 5.

Table 5: content of metals in different mixed liquids

The data in the table show that the carbon-supported Pd-Ru-N/C @ AC catalyst prepared by the method can enable metal palladium and metal ruthenium to be completely adsorbed on the surface of the carrier in an ionic state by adjusting the pH value of the mixed liquid during loading, so that the catalytic activity of the catalyst and the selectivity of a target product are improved.

Example 5:

weighing 2g of Na₂PdCl₄Adding into 20mL water, heating to 60 deg.C, adding 14.35g K after completely dissolving₂RuCl₆Stirring was continued until complete dissolution to give a bimetallic solution, denoted as solution a.

3.66g of dicyanodiamine is weighed and added into 40g of water with the temperature of 60 ℃, and after the dicyanodiamine is completely stirred and dissolved, a precursor solution of the carbon and nitrogen material is obtained and marked as solution B.

And slowly adding the solution A into the solution B, stirring for 4 hours, and stopping stirring to obtain a coordination solution which is marked as a solution C.

Weighing 180g of dry weight of activated carbon, pulping in 1800mL of deionized water, stirring for 1h, adding the solution C, raising the temperature to 55 ℃, stirring at 500r/min, adjusting the pH of the system to 3.0 by using a 1% acetic acid aqueous solution, stirring for 4h, performing suction filtration, washing by using deionized water until the pH of the filtrate is 6.4, and drying the filter cake at 75 ℃ to ensure that the filter cake contains 17.0% of water.

In the nitrogen atmosphere, the heating rate is set to be 5 ℃/min, the roasting temperature is set to be 500 ℃, after roasting for 4h, the temperature is reduced to 350 ℃, the gas atmosphere is changed into 85% nitrogen and 15% hydrogen, the total gas flow is 200mL/min, and the reduction time is 4 h. And after the reduction is finished, performing suction filtration and washing until the pH value of the filtrate is 7.7 to obtain a catalyst Cat-5.

Example 6:

In a nitrogen atmosphere, setting the heating rate to be 5 ℃/min, setting the roasting temperature to be 400 ℃, roasting for 4h, cooling to 63 ℃, adding 2000mL of water, making the pre-catalyst into a slurry state again, heating to 52 ℃, stirring for 2h, and adjusting the pH value to be 7.7.

Preparing a reducing agent solution: 16.5g NaBH was weighed₄Slowly added to aqueous NaOH (pH 9.7) and stirred to dissolve completely.

And slowly adding a reducing agent solution into the slurry, continuing stirring for 1h after the addition is finished, aging for 6h, and performing suction filtration and washing until the pH value of the filtrate is 7.8. Obtaining the catalyst Cat-6.

Example 7:

weighing 2.22g K₂PdCl₄Adding into 20mL water, heating to 60 deg.C, adding 14.35g K after completely dissolving₂RuCl₆Stirring was continued until complete dissolution to give a bimetallic solution, denoted as solution a.

5.4 g of urea is weighed and added into 40g of water with the temperature of 60 ℃, and after the urea is completely stirred and dissolved, a precursor solution of the carbon and nitrogen material is obtained and marked as solution B.

Weighing 180g of dry weight of activated carbon, pulping in 1400mL of deionized water, stirring for 2h, adding the solution C, raising the temperature to 61 ℃, stirring at the speed of 400r/min, adjusting the pH of the system to 3.0 by using a 1% acetic acid aqueous solution, stirring for 4h, performing suction filtration, washing by using deionized water until the pH of the filtrate is 6.6, and drying the filter cake at 70 ℃ to ensure that the filter cake contains 15.0% of water.

Setting the heating rate at 15 ℃/min and the roasting temperature at 500 ℃ in a nitrogen atmosphere, roasting for 3h, cooling to 62 ℃, adding 2000mL of water, making the pre-catalyst into a slurry state again, heating to 49 ℃, stirring for 2h, and adjusting the pH to 7.32.

Preparing a reducing agent solution: 16.5g NaBH was weighed₄Slowly added to the aqueous NaOH solution (pH 10.3) and stirred to dissolve completely.

And slowly adding a reducing agent solution into the slurry, continuing stirring for 3h after the addition is finished, aging for 4h, and performing suction filtration and washing until the pH value of the filtrate is 7.4. Obtaining the catalyst Cat-7.

Comparative example 7:

In the nitrogen atmosphere, the heating rate is set to be 15 ℃/min, the roasting temperature is set to be 500 ℃, after roasting for 3h, the temperature is reduced to 350 ℃, the gas atmosphere is changed into 85% nitrogen and 15% hydrogen, the total gas flow is 200mL/min, and the reduction time is 3 h. After completion of the reduction, the reaction mixture was washed with suction until the pH of the filtrate became 7.4. Obtaining the catalyst Cat 7^a。

using Schlenk techniques, the entire course of the reaction was carried out under an inert gas argon atmosphere. Reaction raw materials: aniline (1mmol) and benzyl alcohol (1.3mmol) while adding 1 mol% of catalyst, Cs₂CO₃(1mmol), n-butyl ether (2mL) was stirred at 140 ℃ for 12 h. After the reaction is finished, cooling to normal temperature, adding 100 mu L of n-hexadecane as an internal standard for gas chromatography, taking 3X 15mL of diethyl ether as an extracting agent, combining organic phases, filtering, separating the catalyst, filtering the filtrate by using a 0.45 mu m filter membrane, performing gas chromatography, and calibrating the conversion rate, yield and selectivity of the reaction by a gas chromatography internal standard method. The results are detailed in Table 6.

Table 6: aniline N-alkylation reaction parameters

In summary, the catalyst provided by the application obviously reduces the size of metal particles and improves the metal dispersion degree by introducing the N/C material. By adjusting the pH of the mixed solution during the impregnation and loading, the metal palladium and the metal ruthenium are completely adsorbed on the surface of the carrier in an ionic state. Because the metal palladium is introduced as the cocatalyst, the reduction temperature of the metal Ru is reduced and the energy consumption is reduced by utilizing the capability of palladium in dissociating hydrogen. And the catalyst is used for catalyzing aniline N-alkylation reaction, and metal palladium is introduced into an active center, so that the generation ratio of byproducts can be reduced, and the selectivity of a target product is improved.

The above description is only for the purpose of illustrating embodiments of the present application and is not intended to limit the scope of the present application, and all modifications of equivalent structures and equivalent processes, which are made by the contents of the specification and the drawings of the present application or are directly or indirectly applied to other related technical fields, are also included in the scope of the present application.

Claims

1. A preparation method of a carbon-supported multi-metal catalyst is characterized by comprising the following steps:

providing a multi-metal solution and a carbon and nitrogen material precursor solution, wherein the multi-metal solution at least comprises two transition metal ions;

mixing the multi-metal solution with the precursor solution of the carbon and nitrogen material to coordinate to obtain a coordination solution;

mixing the coordination solution with the carbon carrier slurry to carry out loading to obtain a loaded precursor;

and roasting the supported pre-body in an inert gas atmosphere to obtain the carbon-supported multi-metal catalyst.

2. The method for preparing a carbon-supported multimetallic catalyst as defined in claim 1,

the multi-metal solution is a bimetallic solution of metal palladium and metal ruthenium;

preferably, the mass ratio of the palladium element to the ruthenium element in the bimetallic solution of metal palladium and metal ruthenium is 0.5: 1-0.1: 1.

3. The method for preparing a carbon-supported multimetallic catalyst as defined in claim 2,

the palladium precursor comprises one or more of palladium dichloride, sodium chloropalladate, potassium chloropalladate and palladium acetate; and/or

The ruthenium precursor comprises one or more of ruthenium trichloride, ammonium chlororuthenate and potassium chlororuthenate; and/or

The solvent comprises one or more of water, ethanol and acetone.

4. The method of preparing a carbon-supported multimetallic catalyst as claimed in claim 1, wherein said providing a carbon and nitrogen material precursor solution comprises:

providing a precursor of a carbon and nitrogen material;

mixing the carbon and nitrogen material precursor with a solvent, and dissolving at the normal temperature of 80 ℃ to obtain a carbon and nitrogen material precursor solution;

the carbon and nitrogen material precursor comprises one or more of melamine, urea, dicyanodiamine, 1, 10-phenanthroline and 2, 2' -bipyridyl in a mixed mode; the solvent is one or more of water, ethanol and acetone.

5. The method of preparing the carbon-supported multimetallic catalyst as defined in claim 2, wherein the mixing the multimetallic solution with the carbon and nitrogen material precursor solution comprises:

mixing a bimetallic solution of metal palladium and metal ruthenium with the precursor solution of the carbon-nitrogen material;

stirring for 0.5-6 h at the temperature of 40-70 ℃ to coordinate to obtain a coordination solution;

the bimetallic solution of metal palladium and metal ruthenium is the same as the solvent used by the precursor solution of the carbon-nitrogen material;

preferably, the ratio of the molar weight of the carbon-nitrogen material precursor to the total molar weight of palladium and ruthenium in the bimetallic solution of metal palladium and metal ruthenium is 1: 1-4: 1;

preferably, the mass fraction of the ruthenium element in the coordination solution is 0.5-10%.

6. The method for preparing the carbon-supported multimetallic catalyst according to claim 5, wherein the mixing the complexing solution with the carbon support slurry to perform the supporting comprises:

mixing the coordination solution with the activated carbon slurry;

keeping the temperature of the mixed solution at 20-70 ℃, and regulating the pH of the mixed solution to 2.0-5.0 by using inorganic acid or inorganic base;

stirring the mixed solution at the temperature of 20-70 ℃ and the pH of 2.0-5.0 for 1-8 h at the stirring speed of 200-1000 r/min;

preferably, the mass ratio of the ruthenium element to the dry activated carbon is 0.5: 99.5-10: 90.

7. The method for preparing a carbon-supported multimetallic catalyst as defined in claim 6, wherein the method comprises:

carrying out suction filtration on the stirred mixed solution, and washing with deionized water until the pH value of the filtrate is 6.0-8.0;

and drying the obtained filter cake at the drying temperature of 60-90 ℃ until the water content of the filter cake is 5-20% to obtain the load precursor.

8. The method for preparing a carbon-supported multimetallic catalyst as claimed in claim 1, wherein the calcining the supported precursor under an inert gas atmosphere comprises:

the inert atmosphere is nitrogen, the roasting temperature is 400-800 ℃, the heating rate is 5-20 ℃/min, and the roasting time is 4-12 h.

9. The method for preparing the carbon-supported multimetallic catalyst according to any one of claims 2 to 8, further comprising performing dry reduction on the carbon-supported multimetallic catalyst;

preferably, the dry reduction of the carbon-supported multi-metal catalyst comprises:

cooling the carbon-supported multi-metal catalyst obtained by roasting to 200-500 ℃, and introducing a mixed gas of nitrogen and hydrogen to reduce the carbon-supported multi-metal catalyst;

carrying out suction filtration and washing on the reduced mixture until the pH value of the filtrate is 6.0-8.0;

wherein the reduction time is 1-4 h, and the flow ratio of the nitrogen and hydrogen mixed gas is 95: 5-80: 20.

10. The method for preparing the carbon-supported multimetallic catalyst according to any one of claims 2 to 8, further comprising wet reducing the carbon-supported multimetallic catalyst;

preferably, the wet reduction of the carbon-supported multi-metal catalyst comprises:

cooling the carbon-supported multi-metal catalyst obtained by roasting to normal temperature to 80 ℃, adding deionized water for pulping, wherein the pulping temperature is 40-60 ℃, the pulping time is 1-3 h, and the weight ratio of the carbon-supported multi-metal catalyst to the deionized water is 1: 5-1: 20;

adding a reducing agent solution into the carbon-supported multi-metal catalyst slurry, and stirring and reducing for 1-3 h;

after the reduction is finished, stopping stirring, and aging for 0-18 h;

performing suction filtration and washing on the aged mixture until the pH value of the filtrate is 6.0-8.0;

preferably, the reducing agent is sodium borohydride, and the ratio of the molar amount of the sodium borohydride in the reducing agent to the total molar amount of the palladium element and the ruthenium element is 3: 1-20: 1.

11. The method of preparing a carbon-supported multimetallic catalyst as defined in claim 10, wherein the reducing the carbon-supported multimetallic catalyst comprises:

if the obtained carbon-supported multi-metal catalyst slurry is acidic, adjusting the pH of the carbon-supported multi-metal catalyst slurry to 7.0-9.0 by using an alkali liquor, and maintaining the preset pH value for 30-120 min after the preset pH value is reached;

wherein the time for adjusting the pH of the slurry is 10-60 min; the alkali is one or more of sodium acetate, sodium carbonate, sodium hydroxide, potassium carbonate and potassium hydroxide; the mass concentration of the alkali liquor is 1-20%.

12. Use of a carbon-supported multimetallic catalyst in an N-alkylation reaction, wherein the carbon-supported multimetallic catalyst is prepared by a method of preparing a carbon-supported multimetallic catalyst according to any one of claims 1 to 11;

preferably, the N-alkylation reaction is an N-alkylation reaction of aniline with an alcohol.