A supported carbon-wrapped bimetallic catalyst and its application

Abstract

The present invention discloses a method for preparing a supported carbon-wrapped bimetallic catalyst, the preparation method comprising: (1) weighing the supported bimetallic catalyst, mixing it with water, adding an aqueous solution of a soluble sugar carbon source compound and an aqueous solution of hydroxyethyl cellulose, soaking at room temperature for 0.5 to 10 hours, and vacuum drying until the water is dried to obtain a dry product; (2) then calcining the dried product at 400 to 1000° C. for 2 to 20 hours in an inert atmosphere, a hydrogen atmosphere or a vacuum state to obtain a calcined product; (3) then reducing the temperature to 100 to 180° C., treating the calcined product in an air atmosphere for 4 to 10 hours to obtain a supported carbon-wrapped bimetallic catalyst. The catalyst prepared by the present invention has a complete carbon layer with a suitable structure and thickness to wrap the metal active component, is used for hydrogenation and rearrangement of nitrobenzene compounds to prepare alkoxy-substituted or phenolic hydroxyl-substituted aniline compounds, and has high stability and high selectivity for target products.

Description

(I) Technical field

[0001] The invention relates to a supported carbon-wrapped bimetallic catalyst and application thereof. (II) Background technology

[0002] In the actual production process of high-end fine chemicals such as pharmaceuticals and electronic chemicals, catalytic hydrogenation reactions are often required in strongly acidic solvents, and the active metal components of the catalyst are prone to dissolution and loss in an acidic environment. For example, supported precious metal catalysts have excellent hydrogenation performance and are widely used, but precious metals also lose in a strongly acidic reaction environment. There are two major problems with the loss of precious metals: irreversible deactivation of the catalyst and the residual precious metals in the product.

[0003] The irreversible deactivation of the catalyst caused by the loss of precious metals makes it difficult to reuse the catalyst and increases the cost. Therefore, supported precious metal catalysts are difficult to use in catalytic hydrogenation reactions in strong acidic systems. In addition, the loss of precious metals during the reaction leads to residues in the product, which also has an important impact on the quality of high-end fine chemicals such as pharmaceuticals and electronic chemicals. Pharmaceuticals, electronic chemicals, etc. have strict requirements on the residual metal ions (especially heavy metal ions), and the loss of precious metals during the reaction is one of the main reasons for the excessive residual heavy metal ions in high-end fine chemicals. Therefore, expensive and complex post-processing processes such as resin adsorption separation are required to remove the residual metal ions in the product.

[0004] Inventing a supported precious metal catalyst with good catalytic hydrogenation activity and stability in a strong acidic environment is of great significance. Using an acid-insoluble inert substance to wrap precious metal particles is one of the effective methods to avoid the loss of precious metals. However, how to exert the catalytic hydrogenation performance of the wrapped precious metals, especially the regulation of the selective hydrogenation performance, is a difficult point in the preparation of such catalysts, which is also the reason why the wrapped precious metal catalysts have not yet been used in acidic environments.

[0005] Para-aminophenol is an important chemical raw material and organic intermediate, widely used in medicine, dyes, antioxidants, photosensitive materials and pesticides. In the pharmaceutical industry, para-aminophenol can be used to synthesize drugs such as acetaminophenol (paracetamol), acetaminophen, antoconazole, vitamin B, and complex amides. At present, the largest use of para-aminophenol is to synthesize paracetamol, an antipyretic and analgesic drug. In the rubber industry, para-aminophenol can be used to synthesize paraphenylenediamine antioxidants such as 4010, 4010NA, 4020, and 4030. These antioxidants are highly efficient, non-toxic, and pollution-free, and are supporting antioxidants for radial tire products. In the dye industry, para-aminophenol can be used as an intermediate for a variety of dyes, mostly used in the synthesis of dispersed materials, sulfur dyes, acid dyes, azo dyes, and fur dyes. For example, it is used to synthesize 5-aminosalicylic acid as an intermediate for azo dyes and sulfur dyes. Para-aminophenol can also be used in the production of photographic developers (Metol), as well as antioxidants, petroleum product additives, acrylonitrile dimerization catalysts, urea addition reaction inhibitors, and synthetic herbicides and pesticides.

[0006] The traditional production route of p-aminophenol is the chlorobenzene route, where chlorobenzene is nitrated to p-nitrochlorobenzene, hydrolyzed to p-nitrophenol, and then reduced (iron powder, alkali sulfide or hydrogen) to obtain p-aminophenol through three chemical reactions and a series of separation processes. Although this method is mature, it has large three waste emissions and low product purity.

[0007] The catalytic hydrogenation of nitrobenzene to produce hydroxyaniline, and then the Bamberger rearrangement reaction occurs in an acidic medium to produce p-aminophenol in one step. This is a green and efficient synthesis process, but its disadvantages are low selectivity for the target product p-aminophenol, and the precious metal of the hydrogenation catalyst (the main active component is Pt) is easily lost in a strongly acidic reaction environment, resulting in catalyst deactivation.

[0008] Therefore, it is very meaningful to explore a catalyst suitable for hydrogenation reactions under acidic conditions, especially a stable and efficient catalyst for the selective hydrogenation of nitrobenzene to prepare p-aminophenol. (III) Summary of the invention

[0009] The primary purpose of the present invention is to provide a method for preparing a supported carbon-encapsulated bimetallic catalyst.

[0010] The second object of the present invention is to provide the use of a supported carbon-wrapped platinum catalyst in the preparation of alkoxy-substituted or phenolic hydroxyl-substituted aniline compounds from nitrobenzene compounds.

[0011] To solve the above-mentioned invention object, the present invention adopts the following technical solution:

[0012] In a first aspect, the present invention provides a method for preparing a supported carbon-encapsulated bimetallic catalyst, wherein the method comprises:

[0013] (1) weighing a supported bimetallic catalyst, mixing it with water, adding an aqueous solution of a soluble sugar carbon source compound and an aqueous solution of hydroxyethyl cellulose, immersing at room temperature for 0.5 to 10 hours, and vacuum drying until the water is dried to obtain a dry product;

[0014] (2) then calcining the dried product at 400 to 1000° C. for 2 to 20 hours in an inert atmosphere, a hydrogen atmosphere or a vacuum state to obtain a calcined product;

[0015] (3) then lowering the temperature to 100-180° C. and treating the calcined product in an air atmosphere for 4-10 hours to obtain a supported carbon-encapsulated bimetallic catalyst;

[0016] The supported bimetallic catalyst comprises a carrier and a metal active component supported on the carrier, wherein the metal active component is composed of a main active component and a metal auxiliary agent, wherein the main active component is Pt, and the metal auxiliary agent is one of Ru, Au, and Ag;

[0017] The soluble sugar carbon source compound is at least one of glucose, sucrose, fructose, maltose, lactose and xylose;

[0018] The mass ratio of the hydroxyethyl cellulose, the soluble sugar carbon source compound and the supported bimetallic catalyst is 0.05-0.1:0.1-0.5:1.

[0019] Preferably, the carrier of the supported bimetallic catalyst is activated carbon, TiO2 or diatomaceous earth.

[0020] Preferably, in the supported bimetallic catalyst, the loading amount of Pt (relative to the carrier) is 0.5-5wt%, and the mass ratio of the metal additive to Pt is 0.1-2:1.

[0021] The supported bimetallic catalyst of the present invention can be prepared by using commercially available products or by methods reported in literature.

[0022] Preferably, in step (1), the mass ratio of the supported bimetallic catalyst to water is 1:1-5.

[0023] Preferably, the concentration of the aqueous solution of the soluble sugar carbon source compound is 10 to 50 wt%.

[0024] Preferably, the concentration of the aqueous solution of hydroxyethyl cellulose is 10-20 wt %.

[0025] Preferably, in step (1), the vacuum drying temperature is 60 to 100° C., and the drying time is 4 to 15 hours.

[0026] Preferably, the inert atmosphere is one or more of nitrogen, argon and helium.

[0027] The supported carbon-wrapped bimetallic catalyst of the present invention has a carbon layer of appropriate thickness and structure that wraps metal platinum, which can protect the metal active components and prevent them from being easily lost in an acidic environment, and maintain the catalytic performance of the bimetallic through the quantum tunneling effect, and has good selective catalytic hydrogenation performance in an acidic solution.

[0028] In a second aspect, the present invention provides an application of the supported carbon-coated bimetallic catalyst in the preparation of alkoxy-substituted or phenolic hydroxyl-substituted aniline compounds of formula (II), (III) or (IV) from nitrobenzene compounds of formula (I), wherein the application is as follows: hydrogen is introduced into a reaction container containing nitrobenzene compounds of formula (I), solvent R6OH and a strong acid to carry out hydrogenation and Bamberger rearrangement reaction to obtain alkoxy-substituted or phenolic hydroxyl-substituted aniline compounds of formula (II), (III) or (IV); the strong acid is sulfuric acid with a concentration of more than 98%, hydrochloric acid with a concentration of more than 35%, or phosphoric acid with a concentration of more than 75%;

[0029]

[0030] In formula (I) or formula (II), (III) or (IV), one or more of -R1, -R2, -R3, -R4 and -R5 are independently selected from one of the following groups: -H, -CH3, -CH2CH3, -OH, -NH2, -OCH3, -COOCH3, -NHCH2CH3, -N(CH3)2, -F, -Cl or -Br, and at least one of -R1, -R3 and -R5 is -H; -R6 is selected from one of the following groups: -H, -CH3 or -CH2CH3.

[0031] Generally speaking, when the para position R3 of the nitro group is H, product II is obtained; when the para position of the nitro group is not H, product III or IV is obtained.

[0032] Preferably, the mass ratio of the solvent R6OH, the strong acid, the nitrobenzene compound, and the supported carbon-encapsulated bimetallic catalyst is 300-550:50-100:60-200:1.

[0033] As a further preference, the solvent R6OH is water, and a surfactant is also added to the reaction system, wherein the surfactant is one of dodecyltrimethylammonium bromide, dodecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, and hexadecyltrimethylammonium chloride, and the mass ratio of the added mass of the surfactant to the mass of the nitrobenzene compound shown in formula (I) is 0.005 to 0.04:1.

[0034] Preferably, the reaction temperature is 50-120° C. and the hydrogen pressure is 0.3-3.0 MPa.

[0035] The supported carbon-encapsulated bimetallic catalyst of the present invention is particularly suitable for the selective hydrogenation of nitrobenzene to prepare p-aminophenol. The application method of the supported carbon-encapsulated bimetallic catalyst in the hydrogenation of nitrobenzene to prepare p-aminophenol is as follows: distilled water, 98wt% concentrated sulfuric acid, nitrobenzene, a surfactant, and a supported carbon-encapsulated platinum catalyst are added to an acid-resistant high-pressure reactor, and the mass ratios thereof are 300-550:50-100:60-200:0.4-1:1, respectively, and the target product p-aminophenol is obtained through a hydrogenation rearrangement reaction.

[0036] Preferably, the surfactant is hexadecyltrimethylammonium chloride.

[0037] Preferably, the reaction temperature is 60-90° C.; the reaction pressure is 0.6-2.0 MPa.

[0038] The present invention provides a method for preparing a supported carbon-coated bimetallic catalyst and its application in preparing alkoxy-substituted or phenolic hydroxyl-substituted aniline compounds by hydrogenation and Bamberger rearrangement reaction of nitrobenzene compounds in a solvent R6OH and a strong acid. In the actual production process of high-end fine chemicals such as medicines and electronic chemicals, it is often necessary to carry out catalytic hydrogenation reactions in strong acidic solvents, and the active metal components of the catalyst are prone to dissolution and loss, resulting in catalyst deactivation. The present invention uses an acid-insoluble protective layer, a carbon layer, to wrap the active metal, thereby achieving the effect of protecting the active metal under acidic reaction conditions.

[0039] However, a simple carbon layer does not have catalytic hydrogenation activity, and the catalytic performance of the active metal must be transmitted through the outermost carbon of the middle carbon layer. In order to transmit the catalytic hydrogenation performance of the active metal to the outermost layer, it is necessary to create defects or incorporate heteroatoms in the carbon layer. In addition, the adsorption capacity of the complete carbon layer to hydrogen and nitrobenzene is relatively weak. If electron-rich oxygen-containing functional groups are grafted on the outermost carbon layer, the adsorption activation capacity to hydrogen can be significantly enhanced. At the same time, the acidic oxygen-containing functional groups can help the reaction intermediate phenylhydroxylamine to further undergo Bamberger rearrangement reaction, thereby increasing the reaction rate and selectivity of the target product. Therefore, controlling the thickness, compactness, electron transmission capacity, incorporation of heteroatoms, and the types and quantities of functional groups on the outer carbon of the carbon layer is the key to determining the performance of the catalyst. The present invention obtains a suitable carbon layer thickness and carbon layer structure, which is convenient for exerting the quantum tunneling effect and obtaining a catalyst with excellent performance under acidic conditions. For selective hydrogenation reactions, it is necessary to simultaneously regulate the metal active component and the carbon layer to obtain good selectivity of the target product.

[0040] Compared with the prior art, the present invention has the following advantages:

[0041] 1) In the preparation of the catalyst of the present invention, hydroxyethyl cellulose is used to allow the carbon source and the metal to contact and fuse better, so that the carbon layer on the carbon-coated catalyst is more evenly wrapped on the metal; by treating it in an air atmosphere at an appropriate temperature, oxygen atoms can be introduced into and on the surface of the carbon layer to form acidic oxygen-containing functional groups, which helps to improve the catalytic activity and selectivity of the target product.

[0042] 2) In the present invention, since the active metal in the catalyst is covered by the carbon layer, the metal component will not be lost when it is in an acidic hydrogenation environment. Therefore, the catalyst of the present invention has good stability in the hydrogenation reaction in an acidic environment, and the catalyst is used 10 times continuously without obvious deactivation. In addition, the carbon layer has a suitable structure and thickness, and the catalytic performance of the bimetallic is maintained through the quantum tunneling effect.

[0043] 3) The supported carbon-coated bimetallic catalyst used in the present invention is used for catalytic hydrogenation rearrangement of nitrobenzene compounds to prepare alkoxy-substituted or phenolic hydroxyl-substituted aniline compounds, which has better stability and higher selectivity for the target product than the bimetallic catalyst not coated with carbon. (IV) Specific implementation methods

[0044] The technical solution of the present invention is described below with specific embodiments, but the protection scope of the present invention is not limited thereto:

[0045] The commercially available catalysts used in the embodiments of the present invention, 3% Pt-1% Ru / C, 5% Pt-0.5% Au / TiO2, 0.5% Pt-1% Ag / diatomaceous earth, 2% Pt-1% Ru / C, 4% Pt-4% Au / C, and 1% Pt-0.5% Ag / C, were all purchased from Deqing County Degong Chemical Co., Ltd.

[0046] Embodiment 1

[0047] Weigh 10g of commercially available 3% Pt-1% Ru / C, add it into 15ml of water and mix evenly, then add 20g of 20wt% lactose aqueous solution and 5g of 10wt% hydroxyethyl cellulose aqueous solution in sequence, soak at room temperature for 2h, vacuum dry at 40°C for 20h to remove moisture, and then calcine it at 400°C under nitrogen for 20h; then, reduce the temperature to 100°C and treat it in air atmosphere for another 10h to obtain a supported carbon-encapsulated platinum-ruthenium catalyst.

[0048] Embodiment 2

[0049] Weigh 10g of commercially available 5% Pt-0.5% Au / TiO2, add it into 15ml of water and mix evenly, add 20g of 20wt% glucose aqueous solution and 5g of 20wt% hydroxyethyl cellulose aqueous solution, soak at room temperature for 2h, vacuum dry at 60℃ for 10h to remove moisture, and then calcine it at 900℃ under hydrogen for 2h; then, reduce the temperature to 180℃ and treat it in air atmosphere for another 4h to obtain a supported carbon-encapsulated platinum-gold catalyst.

[0050] Embodiment 3

[0051] Weigh 10g of commercially available 0.5% Pt-1% Ag / diatomaceous earth, add it into 15ml of water and mix evenly, add 5g of 20wt% sucrose aqueous solution and 5g of 15wt% hydroxyethyl cellulose aqueous solution, soak at room temperature for 2h, vacuum dry at 20℃ for 40h to remove moisture, and then calcine it at 600℃ under vacuum for 4h; then, reduce the temperature to 150℃ and treat it in air atmosphere for another 6h to obtain a supported carbon-encapsulated platinum-silver catalyst.

[0052] Embodiment 4

[0053] Weigh 10g of commercially available 2% Pt-1% Ru / C, add it into 15ml of water and mix evenly, add 10g of 30wt% fructose aqueous solution and 3g of 20wt% hydroxyethyl cellulose aqueous solution, soak at room temperature for 2h, freeze-dry at -20℃ for 20h to remove moisture, and then calcine it at 500℃ under helium for 10h; then, reduce the temperature to 120℃ and treat it in air atmosphere for another 8h to obtain a supported carbon-encapsulated platinum-ruthenium catalyst.

[0054] Embodiment 5

[0055] Weigh 10g of commercially available 4% Pt-4% Au / C, add it into 15ml of water and mix evenly, add 50g of 20wt% maltose aqueous solution and 8g of 10wt% hydroxyethyl cellulose aqueous solution, soak at room temperature for 2h, dry it at 100℃ for 3h to remove moisture, and then calcine it at 800℃ under argon for 5h; then, reduce the temperature to 160℃ and treat it in air atmosphere for another 6h to obtain a supported carbon-encapsulated platinum catalyst.

[0056] Embodiment 6

[0057] Weigh 10g of commercially available 1% Pt-0.5% Ag / C, add it into 15ml of water and mix evenly, add 10g of 20wt% xylose aqueous solution and 5g of 10wt% hydroxyethyl cellulose aqueous solution, soak at room temperature for 2h, vacuum dry at 50℃ for 8h to remove moisture, and then calcine it at 700℃ under nitrogen for 6h; then, reduce the temperature to 130℃ and treat it in air atmosphere for another 9h to obtain a supported carbon-encapsulated platinum-silver catalyst.

[0058] Embodiment 7

[0059] 300 g of distilled water, 60 g of 98 wt % concentrated sulfuric acid, 100 g of nitrobenzene, 0.5 g of hexadecyltrimethylammonium chloride, and 1 g of the supported carbon-encapsulated platinum-ruthenium catalyst prepared in Example 1 were added to an acid-resistant high-pressure reactor, the reactor was closed, and the air in the reactor was replaced with nitrogen three times and then with hydrogen three times; the temperature was raised to 60° C. and the hydrogen pressure was 1 MPa, stirring was started, the stirring rate was 900 r / min, and the reaction was carried out for 3 h; the reaction was stopped, and after the temperature dropped to room temperature, the reaction solution was taken out, the catalyst was filtered out, and the filtrate was analyzed by liquid chromatography, the nitrobenzene conversion rate was 100 wt %, and the p-aminophenol selectivity was 86.4 wt %.

[0060] Embodiment 8

[0061] 500 g of distilled water, 100 g of 98 wt % concentrated sulfuric acid, 200 g of nitrobenzene, 1 g of hexadecyltrimethylammonium chloride, and 1 g of the supported carbon-encapsulated platinum-gold catalyst prepared in Example 2 were added to an acid-resistant high-pressure reactor, the reactor was closed, and the air in the reactor was replaced with nitrogen three times, and then replaced with hydrogen three times; the temperature was raised to 90° C. and the hydrogen pressure was 2 MPa, stirring was started, the stirring rate was 900 r / min, and the reaction was carried out for 3 h; the reaction was stopped, and after the temperature dropped to room temperature, the reaction solution was taken out, the catalyst was filtered out, and the filtrate was analyzed by liquid chromatography, the nitrobenzene conversion rate was 100 wt %, and the p-aminophenol selectivity was 85.8 wt %.

[0062] Embodiment 9

[0063] 400 g of distilled water, 50 g of 98 wt % concentrated sulfuric acid, 70 g of nitrobenzene, 0.6 g of hexadecyltrimethylammonium chloride and 1 g of the supported carbon-wrapped platinum-silver catalyst prepared in Example 3 were added to an acid-resistant high-pressure reactor, the reactor was closed, the air in the reactor was replaced with nitrogen three times, and then replaced with hydrogen three times; the temperature was raised to 80° C. and the hydrogen pressure was 0.6 MPa, stirring was started, the stirring rate was 900 r / min, and the reaction was carried out for 3 h; the reaction was stopped, and after the temperature was reduced to room temperature, the reaction solution was taken out, the catalyst was filtered out, and the filtrate was analyzed by liquid chromatography, the nitrobenzene conversion rate was 100 wt %, and the p-aminophenol selectivity was 85.9 wt %.

[0064] Embodiment 10

[0065] In an acid-resistant high-pressure reactor, 450 g of distilled water, 65 g of 98 wt% concentrated sulfuric acid, 170 g of nitrobenzene, 0.7 g of hexadecyltrimethylammonium chloride, and 1 g of the supported carbon-encapsulated platinum-ruthenium catalyst prepared in Example 4 were added, the reactor was closed, and the air in the reactor was replaced with nitrogen three times, and then replaced with hydrogen three times; the temperature was raised to 80° C. and the hydrogen pressure was 1.6 MPa, stirring was started, the stirring rate was 900 r / min, and the reaction was carried out for 3 h; the reaction was stopped, and after the temperature dropped to room temperature, the reaction solution was taken out, the catalyst was filtered out, and the filtrate was analyzed by liquid chromatography, the nitrobenzene conversion rate was 100 wt%, and the p-aminophenol selectivity was 86.3 wt%.

[0066] Embodiment 11

[0067] 550 g of distilled water, 75 g of 98 wt % concentrated sulfuric acid, 110 g of nitrobenzene, 0.75 g of hexadecyltrimethylammonium chloride, and 1 g of the supported carbon-wrapped platinum-gold catalyst prepared in Example 5 were added to an acid-resistant high-pressure reactor, the reactor was closed, and the air in the reactor was replaced with nitrogen three times, and then replaced with hydrogen three times; the temperature was raised to 75° C. and the hydrogen pressure was 1.2 MPa, stirring was started, the stirring rate was 900 r / min, and the reaction was carried out for 3 h; the reaction was stopped, and after the temperature dropped to room temperature, the reaction solution was taken out, the catalyst was filtered out, and the filtrate was analyzed by liquid chromatography, the nitrobenzene conversion rate was 100 wt %, and the p-aminophenol selectivity was 86.5 wt %.

[0068] Embodiment 12

[0069] 500 g of distilled water, 90 g of 98 wt % concentrated sulfuric acid, 100 g of nitrobenzene, 0.5 g of hexadecyltrimethylammonium chloride and 1 g of the supported carbon-wrapped platinum-silver catalyst prepared in Example VI were added to an acid-resistant high-pressure reactor, the reactor was closed, the air in the reactor was replaced with nitrogen three times, and then replaced with hydrogen three times; the temperature was raised to 75° C. and the hydrogen pressure was 1.5 MPa, stirring was started, the stirring rate was 900 r / min, and the reaction was carried out for 3 h; the reaction was stopped, and after the temperature dropped to room temperature, the reaction solution was taken out, the catalyst was filtered out, and the filtrate was analyzed by liquid chromatography, the nitrobenzene conversion rate was 100 wt %, and the p-aminophenol selectivity was 85.6 wt %.

[0070] Embodiments 13 to 17

[0071] Solvent, acid, nitrobenzene compound, and 1 g of the supported carbon-encapsulated platinum-ruthenium catalyst prepared in Example 1 were added to an acid-resistant high-pressure reactor, the reactor was closed, and the air in the reactor was replaced with nitrogen three times, and then replaced with hydrogen three times; the temperature was raised to the reaction temperature, the hydrogen pressure was the reaction pressure, stirring was started, the stirring rate was 900 r / min, and the reaction was carried out for 3 hours; the reaction was stopped, and after the temperature dropped to room temperature, the reaction liquid was taken out, the catalyst was filtered out, and the filtrate was analyzed by liquid chromatography. The results are shown in Table 1.

[0072] Table 1 Catalytic hydrogenation rearrangement reaction of different raw materials

[0073]

[0074]

[0075] Embodiment 18

[0076] 300g of distilled water, 60g of 98wt% concentrated sulfuric acid, 100g of nitrobenzene, 0.5g of hexadecyltrimethylammonium chloride, and 1g of the supported carbon-wrapped platinum-ruthenium catalyst prepared in Example 1 were added to an acid-resistant high-pressure reactor, the reactor was closed, and the air in the reactor was replaced with nitrogen three times, and then replaced with hydrogen three times; the temperature was raised to 60°C, the hydrogen pressure was 1MPa, stirring was started, the stirring rate was 900r / min, and the reaction was carried out for 3h; the reaction was stopped, and after the temperature dropped to room temperature, the reaction solution was taken out, the catalyst was filtered to remove, and the filtrate was analyzed by liquid chromatography. The recovered catalyst continued to be used in the experiment, the reaction conditions were the same as above, and the results are shown in Table 2.

[0077] Table 2 Application results of Example 1 for preparing catalyst

[0078] Number of applications Catalyst addition amount / g Nitrobenzene conversion rate / % Selectivity for aminophenol / % 1 1.0 100 86.4 2 0 100 86.6 3 0 100 86.0 4 0.05 100 86.2 5 0 100 86.8 6 0 100 85.9 7 0.05 100 86.2 8 0 100 86.3 9 0 100 85.8 10 0.05 100 86.9

[0079] Comparative Example 1

[0080] Comparative Example 1 investigated the performance of supported carbon-encapsulated bimetallic catalysts prepared from different carbon sources. Compared with the catalyst in Example 1, replacing the carbon source with starch significantly reduced the selectivity for aminophenol.

[0081] Weigh 10g of commercially available 3% Pt-1% Ru / C, add it into 15ml of water and mix evenly, add 20g of 20wt% starch aqueous solution and 5g of 10wt% hydroxyethyl cellulose aqueous solution, soak at room temperature for 2h, vacuum dry at 40℃ for 20h to remove moisture, and then calcine it at 400℃ under nitrogen for 20h; then, reduce the temperature to 100℃ and treat it in air atmosphere for another 10h to obtain a supported carbon-encapsulated platinum-ruthenium catalyst.

[0082] In an acid-resistant high-pressure reactor, 300 g of distilled water, 60 g of 98 wt% concentrated sulfuric acid, 100 g of nitrobenzene, 0.5 g of hexadecyltrimethylammonium chloride, and 1 g of the supported carbon-encapsulated bimetallic catalyst prepared above were added, the reactor was closed, and the air in the reactor was replaced with nitrogen three times, and then replaced with hydrogen three times; the temperature was raised to 60° C. and the hydrogen pressure was 1 MPa, and stirring was started at a stirring rate of 900 r / min and the reaction was carried out for 3 h; the reaction was stopped, and after the temperature dropped to room temperature, the reaction solution was taken out, the catalyst was filtered out, and the filtrate was analyzed by liquid chromatography, the nitrobenzene conversion rate was 100 wt%, and the p-aminophenol selectivity was 57.1 wt%.

[0083] Comparative Example 2

[0084] Comparative Example 2 investigated the performance of the supported carbon-encapsulated bimetallic catalyst prepared at a lower carbonization temperature. Compared with the catalyst in Example 1, lowering the carbonization temperature significantly reduced the selectivity for aminophenol.

[0085] Weigh 10g of commercially available 3% Pt-1% Ru / C, add it into 15ml of water and mix evenly, add 20g of 20wt% lactose aqueous solution and 5g of 10wt% hydroxyethyl cellulose aqueous solution, soak at room temperature for 2h, vacuum dry at 40℃ for 20h to remove moisture, and then calcine it at 300℃ under nitrogen for 20h; then, reduce the temperature to 100℃ and treat it in air atmosphere for another 10h to obtain a supported carbon-encapsulated platinum-ruthenium catalyst.

[0086] In an acid-resistant high-pressure reactor, 300 g of distilled water, 60 g of 98 wt% concentrated sulfuric acid, 100 g of nitrobenzene, 0.5 g of hexadecyltrimethylammonium chloride, and 1 g of the supported carbon-encapsulated bimetallic catalyst prepared above were added, the reactor was closed, and the air in the reactor was replaced with nitrogen three times, and then replaced with hydrogen three times; the temperature was raised to 60° C. and the hydrogen pressure was 1 MPa, stirring was started, the stirring rate was 900 r / min, and the reaction was carried out for 3 h; the reaction was stopped, and after the temperature dropped to room temperature, the reaction solution was taken out, the catalyst was filtered out, and the filtrate was analyzed by liquid chromatography, the nitrobenzene conversion rate was 100 wt%, and the p-aminophenol selectivity was 62.5 wt%.

[0087] Comparative Example 3

[0088] Comparative Example 3 investigated the performance of the supported carbon-encapsulated bimetallic catalyst prepared at a higher carbonization temperature. Compared with the catalyst in Example 1, increasing the carbonization temperature significantly reduced the nitrobenzene conversion rate and the selectivity for p-aminophenol.

[0089] Weigh 10g of commercially available 3% Pt-1% Ru / C, add it into 15ml of water and mix evenly, add 20g of 20wt% lactose aqueous solution and 5g of 10wt% hydroxyethyl cellulose aqueous solution, soak at room temperature for 2h, vacuum dry at 40℃ for 20h to remove moisture, and then calcine it at 1200℃ under nitrogen for 20h; then, reduce the temperature to 100℃ and treat it in air atmosphere for another 10h to obtain a supported carbon-encapsulated platinum-ruthenium catalyst.

[0090] In an acid-resistant high-pressure reactor, 300 g of distilled water, 60 g of 98 wt% concentrated sulfuric acid, 100 g of nitrobenzene, 0.5 g of hexadecyltrimethylammonium chloride, and 1 g of the supported carbon-encapsulated bimetallic catalyst prepared above were added, the reactor was closed, and the air in the reactor was replaced with nitrogen three times, and then replaced with hydrogen three times; the temperature was raised to 60° C. and the hydrogen pressure was 1 MPa, and stirring was started at a stirring rate of 900 r / min and the reaction was carried out for 3 h; the reaction was stopped, and after the temperature dropped to room temperature, the reaction solution was taken out, the catalyst was filtered out, and the filtrate was analyzed by liquid chromatography, the nitrobenzene conversion rate was 72.9 wt%, and the p-aminophenol selectivity was 65.3 wt%.

[0091] Comparative Example 4

[0092] Comparative Example 4 investigates the performance of a supported carbon-encapsulated bimetallic catalyst prepared with less carbon source.

[0093] Weigh 10g of commercially available 3% Pt-1% Ru / C, add it into 15ml of water and mix evenly, add 2g of 20wt% lactose aqueous solution and 2g of 10wt% hydroxyethyl cellulose aqueous solution, soak at room temperature for 2h, vacuum dry at 40°C for 20h to remove moisture, and then calcine it at 400°C under nitrogen for 20h; then, reduce the temperature to 100°C and treat it in air atmosphere for another 10h to obtain a supported carbon-encapsulated platinum-ruthenium catalyst.

[0094] In an acid-resistant high-pressure reactor, 300 g of distilled water, 60 g of 98 wt% concentrated sulfuric acid, 100 g of nitrobenzene, 0.5 g of hexadecyltrimethylammonium chloride, and 1 g of the supported carbon-encapsulated bimetallic catalyst prepared above were added, the reactor was closed, and the air in the reactor was replaced with nitrogen three times, and then replaced with hydrogen three times; the temperature was raised to 60° C. and the hydrogen pressure was 1 MPa, and stirring was started at a stirring rate of 900 r / min and the reaction was carried out for 3 h; the reaction was stopped, and after the temperature dropped to room temperature, the reaction solution was taken out, the catalyst was filtered out, and the filtrate was analyzed by liquid chromatography, the nitrobenzene conversion rate was 100 wt%, and the p-aminophenol selectivity was 59.6 wt%.

[0095] Comparative Example 5

[0096] Comparative Example 5 investigates the performance of a supported carbon-encapsulated bimetallic catalyst prepared from a relatively large amount of carbon source.

[0097] Weigh 10g of commercially available 3% Pt-1% Ru / C, add it into 15ml of water and mix evenly, add 30g of 20wt% lactose aqueous solution and 5g of 10wt% hydroxyethyl cellulose aqueous solution, soak at room temperature for 2h, vacuum dry at 40℃ for 20h to remove moisture, and then calcine it at 400℃ under nitrogen for 20h; then, reduce the temperature to 100℃ and treat it in air atmosphere for another 10h to obtain a supported carbon-encapsulated platinum-ruthenium catalyst.

[0098] In an acid-resistant high-pressure reactor, 300 g of distilled water, 60 g of 98 wt% concentrated sulfuric acid, 100 g of nitrobenzene, 0.5 g of hexadecyltrimethylammonium chloride, and 1 g of the supported carbon-encapsulated bimetallic catalyst prepared above were added, the reactor was closed, and the air in the reactor was replaced with nitrogen three times, and then replaced with hydrogen three times; the temperature was raised to 60° C. and the hydrogen pressure was 1 MPa, and stirring was started at a stirring rate of 900 r / min and the reaction was carried out for 3 h; the reaction was stopped, and after the temperature dropped to room temperature, the reaction solution was taken out, the catalyst was filtered out, and the filtrate was analyzed by liquid chromatography, the nitrobenzene conversion rate was 75.3 wt%, and the p-aminophenol selectivity was 62.1 wt%.

[0099] Comparative Example 6

[0100] Comparative Example 6 investigated the performance of a supported carbon-encapsulated bimetallic catalyst prepared after high-temperature carbonization without air atmosphere treatment.

[0101] Weigh 10g of commercially available 3% Pt-1% Ru / C, add it into 15ml of water and mix evenly, add 20g of 20wt% lactose aqueous solution and 5g of 10wt% hydroxyethyl cellulose aqueous solution, soak at room temperature for 2h, vacuum dry at 40℃ for 20h to remove moisture, and then calcine it at 400℃ under nitrogen for 20h to obtain a supported carbon-encapsulated platinum-ruthenium catalyst.

[0102] In an acid-resistant high-pressure reactor, 300 g of distilled water, 60 g of 98 wt% concentrated sulfuric acid, 100 g of nitrobenzene, 0.5 g of hexadecyltrimethylammonium chloride, and 1 g of the supported carbon-encapsulated bimetallic catalyst prepared above were added, the reactor was closed, and the air in the reactor was replaced with nitrogen three times, and then replaced with hydrogen three times; the temperature was raised to 60° C. and the hydrogen pressure was 1 MPa, stirring was started, the stirring rate was 900 r / min, and the reaction was carried out for 3 h; the reaction was stopped, and after the temperature dropped to room temperature, the reaction solution was taken out, the catalyst was filtered out, and the filtrate was analyzed by liquid chromatography, the nitrobenzene conversion rate was 91.4 wt%, and the p-aminophenol selectivity was 72.1 wt%.

[0103] Comparative Example 7

[0104] Comparative Example 7 investigated the performance of the supported carbon-encapsulated platinum-copper bimetallic catalyst.

[0105] Weigh 10g of commercially available 3% Pt-1% Cu / C, add it into 15ml of water and mix evenly, add 20g of 20wt% lactose aqueous solution and 5g of 10wt% hydroxyethyl cellulose aqueous solution, soak at room temperature for 2h, vacuum dry at 40°C for 20h to remove moisture, and then calcine it at 400°C under nitrogen for 20h; then, reduce the temperature to 100°C and treat it in air atmosphere for another 10h to obtain a supported carbon-encapsulated platinum-copper catalyst.

[0106] 300 g of distilled water, 60 g of 98 wt % concentrated sulfuric acid, 100 g of nitrobenzene, 0.5 g of hexadecyltrimethylammonium chloride and 1 g of the supported carbon-coated platinum-copper catalyst prepared above were added to an acid-resistant high-pressure reactor, the reactor was closed, and the air in the reactor was replaced with nitrogen three times and then with hydrogen three times; the temperature was raised to 60° C. and the hydrogen pressure was 1 MPa, stirring was started, the stirring rate was 900 r / min, and the reaction was carried out for 3 h; the reaction was stopped, and after the temperature dropped to room temperature, the reaction solution was taken out, the catalyst was filtered out, and the filtrate was analyzed by liquid chromatography, the nitrobenzene conversion rate was 91.4 wt %, and the p-aminophenol selectivity was 68.3 wt %.

[0107] Comparative Example 8

[0108] Comparative Example 8 investigated the performance of the supported carbon-encapsulated platinum-ruthenium bimetallic catalyst prepared without the addition of hydroxyethyl cellulose.

[0109] Weigh 10g of commercially available 3% Pt-1% Ru / C, add it into 15ml of water and mix evenly, add 20g of 20wt% lactose aqueous solution, soak at room temperature for 2h, vacuum dry it at 40℃ for 20h to remove moisture, and then calcine it at 400℃ under nitrogen for 20h; then, reduce the temperature to 100℃ and treat it in air atmosphere for another 10h to obtain a supported carbon-encapsulated platinum-ruthenium catalyst.

[0110] In an acid-resistant high-pressure reactor, 300 g of distilled water, 60 g of 98 wt% concentrated sulfuric acid, 100 g of nitrobenzene, 0.5 g of hexadecyltrimethylammonium chloride, and 1 g of the supported carbon-encapsulated platinum-ruthenium catalyst prepared above were added, the reactor was closed, and the air in the reactor was replaced with nitrogen three times, and then replaced with hydrogen three times; the temperature was raised to 60° C. and the hydrogen pressure was 1 MPa, and stirring was started at a stirring rate of 900 r / min and the reaction was carried out for 3 h; the reaction was stopped, and after the temperature dropped to room temperature, the reaction solution was taken out, the catalyst was filtered out, and the filtrate was analyzed by liquid chromatography, the nitrobenzene conversion rate was 100 wt%, and the p-aminophenol selectivity was 77.6 wt%.

[0111] Comparative Example 9

[0112] Comparative Example 9 investigated the performance of the supported carbon-coated platinum-ruthenium bimetallic catalyst prepared without adding sugar compounds.

[0113] Weigh 10g of commercially available 3% Pt-1% Ru / C, add it into 15ml of water and mix evenly, add 5g of 20wt% hydroxyethyl cellulose aqueous solution, soak at room temperature for 2h, vacuum dry at 40℃ for 20h to remove moisture, and then calcine it at 400℃ under nitrogen for 20h; then, reduce the temperature to 100℃ and treat it in air atmosphere for another 10h to obtain a supported carbon-encapsulated platinum-ruthenium catalyst.

[0114] In an acid-resistant high-pressure reactor, 300 g of distilled water, 60 g of 98 wt% concentrated sulfuric acid, 100 g of nitrobenzene, 0.5 g of hexadecyltrimethylammonium chloride, and 1 g of the supported carbon-encapsulated platinum-ruthenium catalyst prepared above were added, the reactor was closed, and the air in the reactor was replaced with nitrogen three times, and then replaced with hydrogen three times; the temperature was raised to 60° C. and the hydrogen pressure was 1 MPa, stirring was started, the stirring rate was 900 r / min, and the reaction was carried out for 3 h; the reaction was stopped, and after the temperature dropped to room temperature, the reaction solution was taken out, the catalyst was filtered out, and the filtrate was analyzed by liquid chromatography, the nitrobenzene conversion rate was 100 wt%, and the p-aminophenol selectivity was 62.7 wt%.

[0115] Comparative Example 10

[0116] Comparative Example 5 investigates the performance of the supported platinum-ruthenium catalyst without carbon coating.

[0117] 300g of distilled water, 60g of 98wt% concentrated sulfuric acid, 100g of nitrobenzene, 0.5g of hexadecyltrimethylammonium chloride, and 1g of a commercially available 3% Pt-1% Ru / C catalyst were added to an acid-resistant autoclave, the autoclave was closed, the air in the autoclave was replaced with nitrogen three times, and then replaced with hydrogen three times; the temperature was raised to 60°C, the hydrogen pressure was 1MPa, stirring was started, the stirring rate was 900r / min, and the reaction was carried out for 3h; the reaction was stopped, and after the temperature dropped to room temperature, the reaction liquid was taken out, the catalyst was filtered to remove, and the filtrate was analyzed by liquid chromatography. The recovered catalyst was further used in the experiment, and the reaction conditions were the same as above. The results are shown in Table 3.

[0118] Table 3 Application results of commercial Pt / C catalysts

[0119] Number of applications Catalyst addition amount / g Nitrobenzene conversion rate / % Selectivity for aminophenol / % 1 1.0 100 51.3 2 0 94.7 50.2 3 0 89.1 49.8 4 0.05 85.5 50.6 5 0 77.3 49.0

Claims

1. A method for preparing a supported carbon-encapsulated bimetallic catalyst, the preparation method comprising: (1) weighing a supported bimetallic catalyst, mixing it with water, adding an aqueous solution of a soluble sugar carbon source compound and an aqueous solution of hydroxyethyl cellulose, immersing at room temperature for 0.5 to 10 hours, and vacuum drying until the water is dried to obtain a dry product; (2) then calcining the dried product at 400 to 1000° C. for 2 to 20 hours in an inert atmosphere, a hydrogen atmosphere or a vacuum state to obtain a calcined product; (3) then lowering the temperature to 100-180° C. and treating the calcined product in an air atmosphere for 4-10 hours to obtain a supported carbon-encapsulated bimetallic catalyst; The supported bimetallic catalyst comprises a carrier and a metal active component supported on the carrier, wherein the metal active component is composed of a main active component and a metal auxiliary agent, wherein the main active component is Pt, and the metal auxiliary agent is one of Ru, Au, and Ag; The soluble sugar carbon source compound is at least one of glucose, sucrose, fructose, maltose, lactose and xylose; The mass ratio of the hydroxyethyl cellulose, the soluble sugar carbon source compound and the supported bimetallic catalyst is 0.05-0.1:0.1-0.5:

1.

2. The preparation method according to claim 1, Features: The carrier of the supported bimetallic catalyst is activated carbon, TiO 2 Or diatomaceous earth.

3. The preparation method according to claim 1, Features: In the supported bimetallic catalyst, the loading amount of Pt is 0.5-5wt%, and the mass ratio of the metal auxiliary agent to Pt is 0.1-2:

1.

4. The preparation method according to claim 1, Features: In step (1), the mass ratio of the supported bimetallic catalyst to water is 1:1-5.

5. The preparation method according to claim 1, Features: The concentration of the aqueous solution of the soluble sugar carbon source compound is 10-50 wt %, and the concentration of the aqueous solution of hydroxyethyl cellulose is 10-20 wt %.

6. The preparation method according to claim 1, Features: In step (1), the vacuum drying temperature is 60 to 100° C., and the drying time is 4 to 15 hours.

7. Use of the supported carbon-coated bimetallic catalyst prepared by the preparation method according to claim 1 in preparing alkoxy-substituted or phenolic hydroxyl-substituted aniline compounds of formula (II), (III) or (IV) from nitrobenzene compounds of formula (I), the application comprising: 6 Into a reaction container containing OH and a strong acid, hydrogen is introduced to carry out hydrogenation and Bamberger rearrangement reaction to obtain an alkoxy-substituted or phenolic hydroxyl-substituted aniline compound represented by formula (II), (III) or (IV); the strong acid is sulfuric acid with a concentration of more than 98%, hydrochloric acid with a concentration of more than 35%, or phosphoric acid with a concentration of more than 75%; In formula (I) or formula (II), (III) or (IV), -R 1 , -R 2 , -R 3 , -R 4 , -R 5 One or more of them are independently selected from the following groups: -H, -CH 3 、-CH 2 CH 3 , -OH, -NH 2 、-OCH 3 、-COOCH 3 、-NHCH 2 CH 3 、-N(CH 3 ) 2 , -F, -Cl, -Br, and -R 1 , -R 3 , -R 5 At least one of them is -H; -R 6 Select one of the following groups: -H, -CH 3 、-CH 2 CH 3 .

8. The use according to claim 7, Features: The solvent R 6 The mass ratio of OH, strong acid, nitrobenzene compound and supported carbon-wrapped bimetallic catalyst is 300-550:50-100:60-200:

1.

9. The use according to claim 8, Features: The solvent R 6 OH is water, and a surfactant is added to the reaction system. The surfactant is one of dodecyltrimethylammonium bromide, dodecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide and hexadecyltrimethylammonium chloride. The mass ratio of the added surfactant to the mass ratio of the nitrobenzene compound shown in formula (I) is 0.005-0.04:

1.

10. The use according to any one of claims 7 to 9, Features: The reaction temperature is 50-120° C.; the hydrogen pressure is 0.3-3.0 MPa.

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