Carbon-based metal monatomic catalyst for preparing p-benzene diol from benzene and application thereof

Abstract

The application discloses a carbon-based metal monatomic catalyst for preparing p-benzopinacol from benzene and an application thereof, and the catalyst is prepared by loading active components copper and first and second additives calcium on a carbon carrier; wherein the first additive is any one or more of iron, vanadium, titanium and manganese, the carbon carrier is mainly composed of carbon elements and simultaneously contains at least one of nitrogen and oxygen elements; and metal elements in the catalyst exist in the form of isolated monatomic atoms, so that the atomic utilization rate can be improved. The catalyst can change the path of benzene oxidation reaction, and realizes efficient conversion of benzene to p-benzopinacol. Under the condition that the molar ratio of benzene to hydrogen peroxide is 1:5, the conversion rate of benzene can reach more than 97%, and the selectivity of p-benzopinacol can reach more than 86%; under the condition that the molar ratio of benzene to hydrogen peroxide is 1:3, the conversion rate of benzene can still reach more than 80%, and the selectivity of p-benzopinacol can reach more than 84%, excellent performance is realized, the utilization rate of hydrogen peroxide is high, the catalyst preparation method is simple, the cost is low, the catalyst can be recycled, and the catalyst is suitable for mass production.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of catalysis technology, and particularly relates to a carbon-based metal monatomic catalyst for preparing hydroquinone from benzene. BACKGROUND

[0002] Hydroquinone is an important fine chemical, which is widely used in the polyester industry, rubber industry, dye industry, pesticide, medicine, food additive and other fields. In industry, hydroquinone is produced by first preparing phenol from benzene and propylene through a three-step cumene process, and then preparing hydroquinone from phenol and hydrogen peroxide through a phenol hydroxylation process. The key phenol hydroxylation process involves catalysts and production processes which are monopolized by the Belgian Solvay Group (perchloric acid, Rhone Poulenc process), Japan Ube Industries Co., Ltd. (strong acid, UBE process), and Italy Enichem Company (titanium-silicon molecular sieve, Enichem process). At the same time, the reaction process from benzene to phenol involves three steps and liquid acidic catalysts, the whole production process is long, the pollution is serious, and the yield is not high.

[0003] The oxidation of benzene with hydrogen peroxide is an ideal alternative route to obtain phenol, which has been widely studied in the past decade. It has a series of advantages such as short reaction route, no pollution, high efficiency, etc. However, the conventional catalysts not only have low activity in the reaction, but also have complex products, which are difficult to separate, resulting in high separation cost (Molecular Catalysis, 2021, 515, 111873). In recent years, researchers have found that single-atom catalysts not only have high catalytic activity in the oxidation of benzene, but also exhibit high selectivity for phenol, solving the problems of long reaction route and serious pollution in the conversion of benzene to phenol. For example, Zhao Zhongkui's team (Nature communications, 2022, 6996, 13) reported a copper-based single-atom catalyst, which can achieve 83.7% conversion and 98.1% selectivity for phenol in the oxidation of benzene. Chen Chen's team (Nature communications, 2019, 4290, 10) reported an iron-based single-atom catalyst, which can achieve 78.4% conversion and 100% selectivity for phenol in the oxidation of benzene. Li Yuliang's team (National Science Review, 2022, 9, 9) reported a copper-based single-atom catalyst, which can achieve 86% conversion and 96% selectivity for phenol in the oxidation of benzene. Song Weiguo's team (ACS Catalysis, 2023, 13(2), 1316) reported a copper-based single-atom catalyst, which can achieve 86% conversion and 96% selectivity for phenol in the oxidation of benzene. As can be seen, the single-atom catalysts reported in the literature can usually only obtain low-value-added phenol (about 8000 yuan / ton) in the oxidation of benzene, which has poor technical and economic properties and is difficult to be applied in industrial application.

[0004] The patent CN118324609A discloses a method for directly preparing p-dihydroxybenzene by phenoxylization, which provides a green and environmentally friendly way with high added value for directly obtaining p-dihydroxybenzene (about 50000 yuan / ton) by phenoxylization. The method is to mix one or more of water-soluble metal salts of manganese, iron, cobalt, copper, vanadium, titanium and zinc in deionized water, then add one or more of oxygen-containing organic compounds such as formaldehyde, methanol, ethanol, dimethyl ether and benzyl alcohol, etc., mix completely, then add one or more of nitrogen-containing organic compounds such as dicyandiamide, triethylamine, melamine, urea and aniline, etc., remove water by heating and stirring to form a catalyst precursor gel, then dry and pyrolyze at 500-800℃ for 0.1-3h to obtain a catalyst. Then the catalyst is placed in a reaction kettle, organic solvent, benzene and hydrogen peroxide are added, and the reaction is carried out at 40-100℃. The conversion rate of benzene can be more than 80%, and the selectivity of p-dihydroxybenzene can be more than 80%. Among them, the catalyst obtained by pyrolyzing iron nitrate, formaldehyde and dicyandiamide at a mass ratio of 1:1:3 at 600℃ for 2h, under the conditions of acetonitrile as the organic solvent, benzene and hydrogen peroxide at a molar ratio of 1:10, and the reaction at 60℃ for 6h, the conversion rate of benzene is 95.63%, and the selectivity of p-dihydroxybenzene is 86.21%. However, when the molar ratio of benzene to hydrogen peroxide is reduced to 1:5, the conversion rate of benzene is only 29.82%, and the selectivity of p-dihydroxybenzene is only 17.21%, and the utilization rate of hydrogen peroxide is low. In this method, by changing the types, mass ratios, etc. of the soluble metal salt, oxygen-containing organic compound and nitrogen-containing organic compound, the activity of the catalyst is significantly reduced, and the conversion rate of benzene and the selectivity of p-dihydroxybenzene are both very low, indicating that the applicability of the catalyst is poor. SUMMARY

[0005] The purpose of the present application is to provide a carbon-based metal monatomic catalyst for preparing p-dihydroxybenzene from benzene, which has high activity, high p-dihydroxybenzene selectivity, high stability and high utilization rate of hydrogen peroxide in the catalyst system.

[0006] The carbon-based metal monatomic catalyst provided by the present application is prepared by loading active components and first and second additives on a carbon carrier; the active component is copper, the first additive is any one or more of iron, vanadium, titanium and manganese, and the second additive is calcium; the carbon carrier mainly consists of carbon elements and contains at least one of nitrogen and oxygen elements; the active component accounts for 15-30% of the total mass of the catalyst, the first additive accounts for 1-5% of the total mass of the catalyst, and the second additive accounts for 1-5% of the total mass of the catalyst; the active component and the first and second additives exist in the form of isolated metal monatomic atoms.

[0007] The preparation method of the catalyst of the present application comprises the following steps:

[0008] Step 1: pyrolyzing the carbon carrier precursor in an inert gas.

[0009] Step 2: dissolving the water-soluble salt of copper and the precursors of the first assistant, calcium salt in deionized water, adding the carbon carrier pyrolyzed in step 1 to the solution, removing water by heating and stirring or immersing for 20-24 hours, then centrifuging and washing to remove water, and drying to form a catalyst precursor powder.

[0010] Step 3: carbonizing the catalyst precursor powder at high temperature in an inert atmosphere or vacuum to obtain a carbon-based metal monatomic catalyst.

[0011] In step 1, the carbon carrier precursor is preferably pyrolyzed at 500-650°C for 1-4 hours.

[0012] In step 1, the carbon carrier precursor is preferably selected from any one or more of melamine, dicyandiamide, guanine, and urea.

[0013] In step 2, the water-soluble salt of copper is preferably any one of copper nitrate, copper chloride, and copper sulfate.

[0014] In step 2, the precursor of the first assistant iron is preferably any one of iron nitrate, iron chloride, and iron sulfate; the precursor of the first assistant titanium is preferably any one of titanium chloride, titanium nitride, titanium silicalite, and titanium dioxide; the precursor of the first assistant manganese is preferably any one of manganese chloride and manganese acetylacetonate; and the precursor of the first assistant vanadium is preferably any one of vanadium chloride, vanadyl sulfate, and vanadium acetylacetonate.

[0015] In step 2, the calcium salt is preferably any one of calcium nitrate, calcium chloride, calcium carbonate, and calcium sulfate.

[0016] In step 3, the catalyst precursor powder is preferably carbonized at 500-800°C for 1-4 hours in an inert atmosphere or vacuum.

[0017] The application also provides the use of the above-mentioned carbon-based metal monatomic catalyst in the preparation of hydroquinone by the oxidation of benzene, specifically by dissolving benzene in acetonitrile, adding the carbon-based metal monatomic catalyst, adding dropwise a 20-30% mass concentration hydrogen peroxide aqueous solution, stirring uniformly, and stirring at 40-80°C under normal pressure for 5-8 hours; wherein the molar ratio of benzene to hydrogen peroxide is 1:2-5.

[0018] Compared with the prior art, the application has the following advantages:

[0019] The catalyst of the present invention uses copper as the active component, with one or more of iron, vanadium, titanium, and manganese added as a first auxiliary agent, and calcium added as a second auxiliary agent. A carbon material containing nitrogen and / or oxygen is used as a carrier, and the metal elements are present as isolated metal single atomic sites, thereby improving atomic utilization. The catalyst can alter the pathway of the benzene oxidation reaction and enhance its reactivity, achieving efficient conversion of benzene to hydroquinone. At a benzene to hydrogen peroxide molar ratio of 1:5, the benzene conversion rate can reach over 97%, with a hydroquinone selectivity of 86%. At a benzene to hydrogen peroxide molar ratio of 1:3, the catalyst still achieves excellent performance, achieving a benzene conversion rate of over 80% and a hydroquinone selectivity of 84%, while also achieving high hydrogen peroxide utilization. The catalyst preparation method of the present invention is simple, cost-effective, suitable for large-scale production, and highly stable for recycling. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is the XRD pattern of the catalyst in Example 1.

[0021] Figure 2 These are the TEM and mapping results of the catalyst in Example 1. DETAILED DESCRIPTION

[0022] The present invention will be further described in detail below with reference to the accompanying drawings and examples, but the protection scope of the present invention is not limited to these examples.

[0023] Example 1

[0024] The carbon-based metal single-atom catalyst of this embodiment uses copper as the active component, iron as the first auxiliary agent, calcium as the second auxiliary agent, and carbon nitride as the carrier. Copper accounts for 20% of the total mass of the catalyst, iron accounts for 2% of the total mass of the catalyst, and calcium accounts for 5% of the total mass of the catalyst. The preparation method is as follows:

[0025] Step 1: Take 1g of melamine and pyrolyze it at 600℃ in a nitrogen atmosphere for 2h to obtain carbon nitride.

[0026] Step 2: Dissolve 760 mg of copper nitrate and 86 mg of ferric nitrate in 50 mL of deionized water, then add 205 mg of calcium nitrate. After stirring and dissolving completely, add the carbon nitride obtained in step 1 to the solution. Stir continuously at 60°C for 12 hours to remove moisture, and dry in an oven at 60°C and grind to obtain a catalyst precursor powder.

[0027] Step 3: Place the catalyst precursor powder in a tube furnace and carbonize it at 600°C for 2 hours under a nitrogen atmosphere to obtain a carbon-based metal single atom catalyst.

[0028] Depend on Figure 1 It can be seen that the sample does not show any metal diffraction peaks. Figure 2No obvious particles of the sample were seen in the TEM dark field image, indicating that copper, iron and calcium in the obtained catalyst existed in the form of single atoms.

[0029] 0.4 mL (4.5 mmol) of benzene was dissolved in 10 mL of acetonitrile in a round-bottom flask. 25 mg of the carbon-based metal single-atom catalyst was added and stirred thoroughly. Afterward, 2.4 mL (22.5 mmol) of a 27% aqueous hydrogen peroxide solution was added dropwise. The mixture was stirred at 60°C under atmospheric pressure for 6 hours. After completion of the reaction, the conversion and selectivity were measured by gas chromatography. The results are shown in Table 1.

[0030] Example 2

[0031] In this example, 503 mg of copper sulfate was used to replace the copper nitrate in Example 1, and the rest was the same as in Example 1.

[0032] Example 3

[0033] In this embodiment, 423 mg of copper chloride was used to replace the copper nitrate in Example 1, and the other aspects were the same as those in Example 1.

[0034] Example 4

[0035] The carbon-based metal single-atom catalyst of this embodiment uses copper as the active component, manganese and vanadium as the first promoter, calcium as the second promoter, and carbon nitride as the carrier. Copper accounts for 20% of the total mass of the catalyst, manganese accounts for 2% of the total mass of the catalyst, vanadium accounts for 1% of the total mass of the catalyst, and calcium accounts for 3% of the total mass of the catalyst. The preparation method is as follows:

[0036] Step 1: Take 1g of melamine and pyrolyze it at 600℃ in a nitrogen atmosphere for 2h to obtain carbon nitride.

[0037] Step 2: Dissolve 760 mg of copper nitrate, 46 mg of manganese chloride, and 32 mg of vanadyl sulfate in 50 mL of deionized water, then add 123 mg of calcium nitrate. After stirring and dissolving completely, add the carbon nitride obtained in step 1 to the solution. Stir continuously at 60°C for 12 hours to remove moisture, dry in an oven at 60°C, and grind to obtain a catalyst precursor powder.

[0038] Step 3: Place the catalyst precursor powder in a tube furnace and carbonize it at 600°C for 2 hours under a nitrogen atmosphere to obtain a carbon-based metal single atom catalyst.

[0039] 0.4 mL (4.5 mmol) of benzene was dissolved in 10 mL of acetonitrile in a round-bottom flask. 25 mg of the carbon-based metal single-atom catalyst was added and stirred thoroughly. Afterward, 2.4 mL (22.5 mmol) of a 27% aqueous hydrogen peroxide solution was added dropwise. The mixture was stirred at 60°C under atmospheric pressure for 6 hours. After completion of the reaction, the conversion and selectivity were measured by gas chromatography. The results are shown in Table 1.

[0040] Example 5

[0041] The carbon-based metal monatomic catalyst of this example is copper as the active component, vanadium as the first additive, calcium as the second additive, and oxygen-containing carbon nitride as the carrier. The copper accounts for 15% of the total mass of the catalyst, the vanadium accounts for 2% of the total mass of the catalyst, and the calcium accounts for 2% of the total mass of the catalyst. The preparation method is as follows:

[0042] Step 1: 0.5 g of urea and 0.5 g of cyanuric acid were mixed and pyrolyzed at 600°C for 2 h under a nitrogen atmosphere to obtain oxygen-containing carbon nitride.

[0043] Step 2: 570 mg of copper nitrate and 92 mg of vanadyl sulfate were dissolved in 50 mL of deionized water, and then 82 mg of calcium nitrate was added. After stirring until complete dissolution, the oxygen-containing carbon nitride obtained in Step 1 was added to the solution. The solution was continuously stirred at 60°C for 12 h to remove water, and then dried in an oven at 60°C. After grinding, a catalyst precursor powder was obtained.

[0044] Step 3: The catalyst precursor powder was placed in a tube furnace and carbonized at 600°C for 2 h under a nitrogen atmosphere to obtain a carbon-based metal monatomic catalyst.

[0045] 0.4 mL (4.5 mmol) of benzene was dissolved in a round-bottom flask containing 10 mL of acetonitrile, and 25 mg of the carbon-based metal monatomic catalyst was added. After stirring uniformly, 1.4 mL (13.7 mmol) of a 27% mass concentration hydrogen peroxide aqueous solution was added dropwise. The reaction was stirred at 60°C under normal pressure for 6 h. After the reaction was completed, the conversion rate and selectivity were detected by gas chromatography, and the results are shown in Table 1.

[0046] Example 6

[0047] In the carbon-based metal monatomic catalyst of this example, titanium is the first additive. 79 mg of titanium chloride replaces the copper nitrate in Example 1, and the other conditions are the same as in Example 1.

[0048] Example 7

[0049] In the carbon-based metal monatomic catalyst of this example, vanadium is the first additive. 137 mg of vanadyl acetylacetonate replaces the copper nitrate in Example 1, and the other conditions are the same as in Example 1.

[0050] Example 8

[0051] In this example, 58 mg of iron chloride replaces the iron nitrate in Example 1, and the other conditions are the same as in Example 1.

[0052] Example 9

[0053] In this example, 125 mg of calcium carbonate replaces the calcium nitrate in Example 1, and the other conditions are the same as in Example 1.

[0054] Example 10

[0055] In this example, 170 mg of calcium sulfate is used to replace the calcium nitrate in Example 1, and the other conditions are the same as in Example 1.

[0056] Example 11

[0057] In this example, 139 mg of calcium chloride is used to replace the calcium nitrate in Example 1, and the other conditions are the same as in Example 1.

[0058] Example 12

[0059] In this example, 1 g of guanine is used to replace the melamine in Example 1, and the other conditions are the same as in Example 1.

[0060] Example 13

[0061] In this example, 1 g of dicyandiamide is used to replace the melamine in Example 1, and the other conditions are the same as in Example 1.

[0062] Table 1 catalytic performance of different catalysts in the reaction

[0063]

[0064]

[0065] From the experimental results in Table 1 above, it can be seen that the carbon-based metal monatomic catalyst of the present application used for catalyzing the reaction of benzene and hydrogen peroxide has high conversion rate of phenol, and the selectivity of hydroquinone in the reaction product is obviously higher than the selectivity of phenol, which can be used for catalyzing the oxidation of benzene to prepare high-value-added product hydroquinone.

[0066] The carbon-based metal monatomic catalyst in Example 1 above is used to catalyze the oxidation of benzene to prepare hydroquinone according to the conditions in Example 1, and its performance of being used for 6 cycles is tested, and the results are shown in Table 2. As can be seen from Table 2, the catalyst has good cycle reaction ability and high stability.

[0067] Table 2 6-cycle reaction results of the catalyst in Example 1

[0068] Number of cycles Conversion rate (%) Phenol selectivity (%) Hydroquinone selectivity (%) 1 85 9 84 2 80 11 79 3 79 13 72 4 80 16 65 5 74 12 60

Claims

1. A carbon-based metal single-atom catalyst for preparing hydroquinone from benzene, characterized in that: The catalyst is prepared by loading an active component and a first auxiliary agent and a second auxiliary agent on a carbon support; wherein the active component is copper, the first auxiliary agent is any one or more of iron, vanadium, titanium, and manganese, the second auxiliary agent is calcium, the carbon support comprises carbon, and the carbon support also contains at least one of nitrogen and oxygen; the active component accounts for 15% to 30% of the total mass of the catalyst, the first auxiliary agent accounts for 1% to 5% of the total mass of the catalyst, and the second auxiliary agent accounts for 1% to 5% of the total mass of the catalyst; the active component and the first auxiliary agent and the second auxiliary agent all exist in the form of isolated metal single atoms; The preparation method of the catalyst comprises the following steps: Step 1: Pyrolyzing the carbon support precursor in an inert gas; Step 2: Dissolve the water-soluble copper salt, the precursor of the first auxiliary agent, and the calcium salt in deionized water, add the carbon support pyrolyzed in step 1 to the solution, heat and stir to remove water or soak for 20 to 24 hours and then centrifuge to remove water, and dry to form a catalyst precursor powder; Step 3: Carbonize the catalyst precursor powder at high temperature in an inert atmosphere or vacuum to obtain a carbon-based metal single atom catalyst.

2. The carbon-based metal single-atom catalyst for preparing hydroquinone from benzene according to claim 1, characterized in that: In step 1, the carbon support precursor is pyrolyzed at 500-650° C. for 1-4 hours.

3. The carbon-based metal single-atom catalyst for preparing hydroquinone from benzene according to claim 1, wherein: In step 1, the carbon support precursor is selected from any one or more of melamine, dicyandiamide, guanine, and urea.

4. The carbon-based metal single-atom catalyst for preparing hydroquinone from benzene according to claim 1, wherein: In step 2, the water-soluble salt of copper is any one of copper nitrate, copper chloride, and copper sulfate.

5. The carbon-based metal single-atom catalyst for preparing hydroquinone from benzene according to claim 1, wherein: In step 2, the precursor of the first auxiliary agent iron is any one of ferric nitrate, ferric chloride, and ferric sulfate; the precursor of the first auxiliary agent titanium is titanium chloride; the precursor of the first auxiliary agent manganese is any one of manganese chloride and manganese acetylacetonate; the precursor of the first auxiliary agent vanadium is any one of vanadium chloride, vanadyl sulfate, and vanadium acetylacetonate.

6. The carbon-based metal single-atom catalyst for preparing hydroquinone from benzene according to claim 1, characterized in that: In step 2, the calcium salt is selected from any one of calcium nitrate, calcium chloride, calcium carbonate, and calcium sulfate.

7. The carbon-based metal single-atom catalyst for preparing hydroquinone from benzene according to claim 1, wherein: In step 3, the catalyst precursor powder is carbonized at 500-800° C. for 1-4 hours in an inert atmosphere or vacuum.

8. Use of the carbon-based metal single-atom catalyst according to any one of claims 1 to 7 in catalyzing the oxidation of benzene to produce hydroquinone.

9. Use of the carbon-based metal single-atom catalyst according to claim 8 in catalyzing the oxidation of benzene to produce hydroquinone, characterized in that: Benzene is dissolved in acetonitrile, a carbon-based metal single-atom catalyst is added, and after stirring evenly, a 20% to 30% mass concentration of hydrogen peroxide aqueous solution is added dropwise, and the mixture is stirred at 40 to 80° C. under normal pressure for 5 to 8 hours; wherein the molar ratio of benzene to hydrogen peroxide is 1:2 to 5.

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