Carbon-based metal monatomic catalyst for preparing hydroquinone from benzene and application of carbon-based metal monatomic catalyst

Abstract

The invention discloses a carbon-based metal monatomic catalyst for preparing hydroquinone from benzene and application of the carbon-based metal monatomic catalyst. The catalyst is prepared by loading an active component copper, a first auxiliary agent and a second auxiliary agent calcium on a carbon carrier, wherein the first auxiliary agent is any one or more of iron, vanadium, titanium and manganese, and the carbon carrier is mainly composed of a carbon element and contains at least one of nitrogen and oxygen elements; metal elements in the catalyst exist in the form of isolated monatomic, so that the atom utilization rate can be increased. The catalyst provided by the invention can change a benzene oxidation reaction path, and realizes efficient conversion from benzene to hydroquinone. Under the condition that the molar ratio of benzene to hydrogen peroxide is 1: 5, the conversion rate of benzene can reach 97% or above, and the selectivity of hydroquinone can reach 86% or above; under the condition that the molar ratio of benzene to hydrogen peroxide is 1: 3, the excellent performance that the conversion rate of benzene is 80% or above and the selectivity of hydroquinone is 84% or above can still be achieved, the utilization rate of hydrogen peroxide is high, and the catalyst is simple in preparation method, low in cost, capable of being recycled and suitable for mass production.

Description

Technical Field

[0001] The invention belongs to the technical field of catalysis, and in particular relates to a carbon-based metal single-atom catalyst for preparing hydroquinone from benzene. Background Art

[0002] Hydroquinone is an important fine chemical widely used in the fields of polyester industry, rubber industry, dye industry, pesticide, medicine, food additives, etc. In industry, the production of hydroquinone first uses benzene and propylene as raw materials to obtain phenol through a three-step isopropylbenzene method, and then uses phenol and hydrogen peroxide as raw materials to produce hydroquinone through a phenol hydroxylation method. Among them, the catalyst and production process involved in the key phenol hydroxylation method are monopolized by the Belgian Solvay Group (perchloric acid, Rhone Poulenc process), Japan Ube Industries (strong acid, UBE process), and Italy Enichem (titanium silicon molecular sieve, Enichem process). At the same time, since the reaction process from benzene to phenol involves three-step reactions and liquid acid catalysts, the entire production process is long, the pollution is serious, and the yield is not high.

[0003] The oxidation reaction of benzene with hydrogen peroxide is an ideal alternative route to obtain phenol. It has been widely studied in the past decade and has a series of advantages such as short reaction route, no pollution, and high efficiency. However, conventional catalysts are not only less active in this reaction, but also the products are complex and difficult to separate, resulting in high separation costs (Molecular Catalysis, 2021, 515, 111873). In recent years, researchers have found that single-atom catalysts not only have high catalytic activity in the benzene oxidation reaction, but also show high selectivity for phenol, solving the problem 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 that can achieve 83.7% conversion rate and 98.1% phenol selectivity in the benzene oxidation reaction. Chen Chen's team (Nature communications, 2019, 4290, 10) reported an iron-based single-atom catalyst that can achieve a conversion rate of 78.4% and a phenol selectivity of 100% in the benzene oxidation reaction. Li Yuliang's team (National Science Review, 2022, 9, 9) reported a copper-based single-atom catalyst that can achieve a conversion rate of 86% and a phenol selectivity of 96% in the benzene oxidation reaction. Song Weiguo's team (ACS Catalysis, 2023, 13 (2), 1316) reported a copper-based single-atom catalyst that can achieve a conversion rate of 86% and a phenol selectivity of 96% in the benzene oxidation reaction. It can be seen that the single-atom catalysts reported in the literature can usually only obtain low-value-added phenol (about 8,000 yuan / ton) in the benzene oxidation reaction, with poor technical and economic performance, and it is difficult to put into industrial application.

[0004] Patent CN118324609A discloses for the first time a method for directly preparing hydroquinone by benzene oxidation, which provides a green and environmentally friendly, high value-added way for directly obtaining high value-added hydroquinone (about 50,000 yuan / ton) by benzene oxidation. The method is to mix and dissolve one or more water-soluble metal salts of manganese, iron, cobalt, copper, vanadium, titanium and zinc elements in deionized water, then add one or more oxygen-containing organic compounds, such as formaldehyde, methanol, ethanol, dimethyl ether and benzyl alcohol, etc., and after complete dissolution, add one or more nitrogen-containing organic compounds, such as dicyandiamide, triethylamine, melamine, urea and aniline, etc., heat and stir to remove moisture, form a catalyst precursor gel, dry and then pyrolyze at 500-800°C for 0.1-3h to obtain a catalyst; then put the catalyst into a reactor, add an organic solvent, benzene and hydrogen peroxide, and react at 40-100°C, the conversion rate of benzene can reach more than 80%, and the selectivity of hydroquinone can reach more than 80%. Among them, the catalyst obtained by pyrolysis at 600℃ for 2h with a mass ratio of ferric nitrate, formaldehyde and dicyandiamide of 1:1:3, reacted at 60℃ for 6h under the conditions of acetonitrile as organic solvent and a molar ratio of benzene to hydrogen peroxide of 1:10, the conversion rate of benzene was 95.63%, and the selectivity of hydroquinone was 86.21%. However, when the molar ratio of benzene to hydrogen peroxide was reduced to 1:5, the conversion rate of benzene was only 29.82%, and the selectivity of hydroquinone was only 17.21%, and the utilization rate of hydrogen peroxide was low. In this method, the activity of the catalyst was significantly reduced by changing the types and mass ratios of soluble metal salts, oxygen-containing organic compounds and nitrogen-containing organic compounds, and the conversion rate of benzene and the selectivity of hydroquinone were both very low, indicating that the applicability of the catalyst was poor. Summary of the invention

[0005] The purpose of the present invention is to provide a carbon-based metal single-atom catalyst for preparing hydroquinone from benzene. The catalyst is used to prepare hydroquinone using benzene and hydrogen peroxide as raw materials, and has the advantages of high activity, high hydroquinone selectivity, high stability, etc., and the utilization rate of hydrogen peroxide in the catalytic system is high.

[0006] The carbon-based metal single atom catalyst provided by the present invention is prepared by loading an active component and a first auxiliary agent and a second auxiliary agent on a carbon carrier; 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, and the carbon carrier is mainly composed of carbon elements and contains at least one of nitrogen and oxygen elements; 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.

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

[0008] Step 1: Pyrolyze the carbon support precursor in an inert gas.

[0009] Step 2: Dissolve the water-soluble salt of copper, 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 moisture or soak for 20 to 24 hours and then centrifuge and wash to remove moisture, and form a catalyst precursor powder after drying.

[0010] 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.

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

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

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

[0014] In the above step 2, it is preferred that 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 any one of titanium chloride, titanium nitride, titanium silicon molecular sieve, and titanium dioxide; 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, vanadium sulfate, and vanadium acetylacetonate.

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

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

[0017] The present invention also provides the use of the above-mentioned carbon-based metal single-atom catalyst in catalyzing the oxidation of benzene to prepare hydroquinone. The specific method is: dissolving benzene in acetonitrile, adding the carbon-based metal single-atom catalyst, stirring evenly, and then dripping a hydrogen peroxide aqueous solution with a mass concentration of 20% to 30%, stirring and reacting 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.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The catalyst of the present invention uses copper as an active component, and simultaneously adds any one or more of iron, vanadium, titanium, and manganese as a first auxiliary agent, adds calcium as a second auxiliary agent, and uses a carbon material containing nitrogen or / and oxygen elements as a carrier, wherein the metal elements are all present in the form of isolated metal single atom sites, which can improve the atomic utilization rate. The catalyst can change the path of the benzene oxidation reaction, and can improve its reaction performance, and realize the efficient conversion of benzene to hydroquinone. 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 hydroquinone can reach 86%; under the condition that the molar ratio of benzene to hydrogen peroxide is 1:3, the excellent performance of the conversion rate of benzene of more than 80%, the selectivity of hydroquinone of 84% can still be achieved, and the utilization rate of hydrogen peroxide is high. The preparation method of the catalyst of the present invention is simple, low-cost, suitable for mass production, and has high recycling stability. 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 is further described in detail below in conjunction with the accompanying drawings and embodiments, but the protection scope of the present invention is not limited to these embodiments.

[0023] Example 1

[0024] The carbon-based metal single-atom catalyst of this embodiment uses copper as an active component, iron as a first auxiliary agent, calcium as a second auxiliary agent, and carbon nitride as a 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 1 g of melamine and pyrolyze it at 600°C for 2 h in a nitrogen atmosphere to obtain carbon nitride.

[0026] Step 2: Take 760 mg of copper nitrate and 86 mg of ferric nitrate and dissolve them in 50 mL of deionized water, then add 205 mg of calcium nitrate, stir and dissolve completely, add the carbon nitride obtained in step 1 to the solution, continue stirring 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 tubular 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 2The TEM dark field image also did not show any obvious particles of the sample, indicating that copper, iron and calcium in the obtained catalyst existed in single atomic form.

[0029] 0.4 mL (4.5 mmol) of benzene was dissolved in a round-bottom flask containing 10 mL of acetonitrile, 25 mg of carbon-based metal single-atom catalyst was added, and after stirring evenly, 2.4 mL (22.5 mmol) of 27% aqueous hydrogen peroxide solution was added dropwise, and the mixture was stirred at 60° C. for 6 h at normal pressure. After the reaction, the conversion rate and selectivity were detected by gas chromatography, and 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 is used to replace the copper nitrate in Example 1, and the rest is the same as Example 1.

[0034] Example 4

[0035] The carbon-based metal single-atom catalyst of this embodiment uses copper as an active component, manganese and vanadium as a first auxiliary agent, calcium as a second auxiliary agent, and carbon nitride as a 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 1 g of melamine and pyrolyze it at 600°C for 2 h in a nitrogen atmosphere to obtain carbon nitride.

[0037] Step 2: Take 760 mg of copper nitrate, 46 mg of manganese chloride and 32 mg of vanadyl sulfate and dissolve them in 50 mL of deionized water, then add 123 mg of calcium nitrate, stir and dissolve completely, add the carbon nitride obtained in step 1 to the solution, continue stirring 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.

[0038] Step 3: Place the catalyst precursor powder in a tubular 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 a round-bottom flask containing 10 mL of acetonitrile, 25 mg of carbon-based metal single-atom catalyst was added, and after stirring evenly, 2.4 mL (22.5 mmol) of 27% aqueous hydrogen peroxide solution was added dropwise, and the mixture was stirred at 60° C. for 6 h at normal pressure. After the reaction, the conversion rate and selectivity were detected by gas chromatography, and the results are shown in Table 1.

[0040] Example 5

[0041] The carbon-based metal single-atom catalyst of this embodiment uses copper as an active component, vanadium as a first auxiliary agent, calcium as a second auxiliary agent, and oxygen-containing carbon nitride as a carrier. Copper accounts for 15% of the total mass of the catalyst, vanadium accounts for 2% of the total mass of the catalyst, and calcium accounts for 2% of the total mass of the catalyst. The preparation method is as follows:

[0042] Step 1: Mix 0.5 g of urea and 0.5 g of cyanuric acid, and pyrolyze them at 600 °C for 2 h in a nitrogen atmosphere to obtain oxygen-containing carbon nitride.

[0043] Step 2: Take 570 mg of copper nitrate and 92 mg of vanadyl sulfate and dissolve them in 50 mL of deionized water, then add 82 mg of calcium nitrate, stir and dissolve completely, add the oxygen-containing carbon nitride obtained in step 1 to the solution, continue stirring 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.

[0044] Step 3: Place the catalyst precursor powder in a tubular furnace and carbonize it at 600°C for 2 hours under a nitrogen atmosphere to obtain a carbon-based metal single atom catalyst.

[0045] 0.4 mL (4.5 mmol) of benzene was dissolved in a round-bottom flask containing 10 mL of acetonitrile, 25 mg of carbon-based metal single-atom catalyst was added, and after stirring evenly, 1.4 mL (13.7 mmol) of 27% aqueous hydrogen peroxide solution was added dropwise, and the mixture was stirred at 60° C. for 6 h at normal pressure. After the reaction, 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 single-atom catalyst of this embodiment, titanium is the first auxiliary agent, and 79 mg of titanium chloride is used to replace the copper nitrate in Example 1. The rest is the same as Example 1.

[0048] Example 7

[0049] In the carbon-based metal single-atom catalyst of this embodiment, vanadium is used as the first auxiliary agent, and 137 mg of vanadium acetylacetonate is used to replace the copper nitrate in Example 1. The rest is the same as Example 1.

[0050] Example 8

[0051] In this example, 58 mg of ferric chloride was used to replace the ferric nitrate in Example 1, and the rest was the same as in Example 1.

[0052] Example 9

[0053] In this embodiment, 125 mg of calcium carbonate was used to replace the calcium nitrate in Example 1, and the rest was the same as in Example 1.

[0054] Example 10

[0055] In this embodiment, 170 mg of calcium sulfate was used to replace the calcium nitrate in Example 1, and the rest was the same as in Example 1.

[0056] Embodiment 11

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

[0058] Example 12

[0059] In this example, 1 g of guanine was used to replace the melamine in Example 1, and the rest was the same as in Example 1.

[0060] Embodiment 13

[0061] In this embodiment, 1 g of dicyandiamide is used to replace the melamine in Example 1, and the rest is the same as Example 1.

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

[0063]

[0064]

[0065] It can be seen from the experimental results in Table 1 above that the carbon-based metal single-atom catalyst of the present invention is used to catalyze the reaction of benzene and hydrogen peroxide, the conversion rate of phenol is high, and the selectivity of hydroquinone in the reaction product is significantly higher than the selectivity of phenol, and can be used to catalyze the oxidation of benzene to prepare high value-added product hydroquinone.

[0066] The carbon-based metal single atom catalyst in Example 1 was used to catalyze the oxidation of benzene to prepare hydroquinone under the conditions of Example 1, and its performance after 6 cycles was tested. The results are shown in Table 2. Table 2 shows that the catalyst has good cyclic reaction ability and high catalyst stability.

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

[0068] Cycle times 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 carrier; 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, and the carbon carrier is mainly composed of carbon elements and contains at least one of nitrogen and oxygen elements; 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 salt of copper, 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 moisture or soak for 20 to 24 hours and then centrifuge to remove moisture, 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, characterized in that: In step 1, the carbon carrier 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, characterized in that: 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, characterized in that: 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 any one of titanium chloride, titanium nitride, titanium silicon molecular sieve, and titanium dioxide; 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, vanadium 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, characterized in that: 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 prepare hydroquinone.

9. Use of the carbon-based metal single-atom catalyst according to claim 8 in catalyzing the oxidation of benzene to prepare 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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