Preparation method of bimetallic mesoporous confinement molecular sieve catalyst
By preparing bimetallic mesoporous domain limited molecular sieve catalysts, the problems of low reaction activity, large oxidant dosage and poor selectivity in the benzene oxidation reaction in the prior art are solved, and the effect of synchronous acquisition of phenol and benzenequinone under low oxidant dosage and short reaction time is achieved.
Patent Information
- Application Number
- CN202510224190.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-27
- Publication Date
- 2025-05-06
AI Technical Summary
The prior art has problems in the benzene oxidation reaction that the catalyst reactivity is low, the amount of oxidant is large, the selectivity is poor, and it is difficult to obtain phenol and benzenequinone products at the same time.
The preparation method of bimetallic mesoporous domain molecular sieve catalyst is adopted. By adding dodecamine, cobalt salt and copper salt to the ethanol solution, and then adding tetraethyl orthosilicate, the bimetallic mesoporous domain molecular sieve catalyst with good catalytic activity and large specific surface area is prepared by stirring, standing, centrifugal washing, drying and calcining.
With low oxidant dosage and short reaction time, this catalyst can achieve relay catalysis, synchronously obtain phenol and benzenequinone products, which have good selectivity and stability, and can be recycled multiple times.
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Figure CN119926475A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a method for preparing a bimetallic mesoporous confined molecular sieve catalyst. Background Art
[0002] The oxidation of benzene to produce phenol, benzoquinone and other related products is of great significance. As an indispensable key chemical raw material, phenol has shown extensive and key applications in many fields, such as synthetic resins, plastics, pharmaceutical intermediates, etc., and its market demand has also been showing a trend of sustained and stable growth. Benzoquinone also plays an important role in the pharmaceutical field and is an important cornerstone for the synthesis of many drugs. It also occupies a unique position in the dye industry, providing the possibility for the presentation of various colors.
[0003] At present, more than 90% of the industrial production of phenol adopts the isopropylbenzene method, and the rest include the chlorobenzene hydrolysis method, the cyclohexanone-cyclohexanol method, etc. However, these production methods have the disadvantages of long process flow, serious equipment corrosion, serious three-waste pollution, low atomic utilization rate and high cost. Nowadays, with the rise of the concept of green and sustainable development, it is necessary to find a production route for efficient benzene hydroxylation to phenol. And in this reaction process, on the one hand, it is the choice of hydroxylating agent, and on the other hand, it is the choice of catalyst. Among several hydroxyl oxidants, H2O2 has the advantages of short reaction route, high atomic utilization rate, no pollution to the environment, and good catalytic effect. In the reaction system of benzene oxidation with hydrogen peroxide as the oxidant, the catalysts selected in the prior art mainly include molecular sieves (such as TS-1 molecular sieve), heteropoly acids, supported metals and single atom catalysts. These catalysts have many defects. For example, some supported metal catalysts have low reaction activity and low benzene conversion rate under the same reaction conditions. In order to obtain a higher benzene conversion rate, various catalysts generally have the problem of large amount of oxidant used. For example, the H2O2 utilization rate of single-atom catalysts is usually less than 10%. A large amount of H2O2 undergoes side reactions to generate oxygen, and the utilization rate is low. Under low oxidant dosage and short reaction time, the catalyst selectivity is poor, and most of them can only obtain the product phenol, and phenol and benzoquinone products cannot be obtained at the same time. In addition, the generated phenol is easily oxidized, resulting in reduced selectivity. Summary of the invention
[0004] Purpose of the invention: The purpose of the present invention is to provide a method for preparing a bimetallic mesoporous confined molecular sieve catalyst. The catalyst prepared by this method is used in a reaction system for oxidizing benzene using hydrogen peroxide as an oxidant. It has good reaction activity and a large specific surface area, can greatly reduce the amount of oxidant used, and can achieve relay catalysis under low oxidant dosage and short reaction time to simultaneously obtain phenol and benzoquinone products.
[0005] Technical solution: The method for preparing the bimetallic mesoporous confined molecular sieve catalyst of the present invention comprises the following steps:
[0006] (1) adding dodecylamine (dodecylamine is used as a surfactant, i.e., micelles, and its amino group is used to connect metal ions), cobalt salt, and copper salt to an ethanol solution to obtain a mixed solution, and vigorously stirring the mixed solution at a high temperature;
[0007] (2) After stirring, add all the required amount of tetraethyl orthosilicate, stir vigorously at a constant temperature, and then let it stand; the two steps of vigorous stirring are to ensure that the components in the entire reaction system are fully contacted, which is conducive to the smooth progress of subsequent reactions, and to facilitate the hydrolysis and polycondensation of tetraethyl orthosilicate, so as to form a uniform polymer network in the system; standing still can make the polymer network further grow uniformly and arrange in an orderly manner, forming a mesoporous material with a specific pore size and pore structure;
[0008] (3) The solution of step (2) is centrifugally washed and then dried at a constant temperature, ground into powder after drying, and then calcined in a nitrogen atmosphere to obtain a bimetallic mesoporous confined molecular sieve catalyst.
[0009] Wherein, in step (1), the molar ratio of the cobalt salt to the copper salt is 1-3:0.25-1.
[0010] Wherein, in step (1), the temperature during the vigorous stirring is 40 to 50° C.; and the time of the vigorous stirring is 10 to 30 minutes.
[0011] Wherein, in step (2), the added mass volume ratio of surfactant to tetraethyl orthosilicate is 1.5-2g:10-15mL.
[0012] Wherein, in step (2), the water bath temperature is 40-50° C., and the vigorous stirring time is 4-6 h.
[0013] Wherein, in step (2), the standing temperature is 40 to 50° C., and the standing time is 16 to 24 hours.
[0014] Wherein, in step (1) and step (2), the rotation speed corresponding to the vigorous stirring is not less than 1000 r / min.
[0015] In step (3), the heating rate is 2-2.5°C / min, the calcination time is 2-5h, and the calcination temperature is 500-700°C.
[0016] In step (3), the bimetallic mesoporous confined molecular sieve catalyst uses Si mesoporous spheres as carriers, and CoCu bimetallic active sites are in situ grown in the pores of the carriers.
[0017] The bimetallic mesoporous confined molecular sieve catalyst of the present invention has a good benzene oxidation effect. In a reaction system with H2O2 as an oxidant, under the reaction conditions of 0.3mL benzene, 1.5mL H2O2, 2.5mL CH3COOH, a catalyst dosage of 10mg, and 70°C, the conversion rate of benzene within 10h can reach 83.6%, the yield of phenol can reach 659.7μmol, and the yield of benzoquinone can reach 1253.7μmol; and the catalyst always maintains a high conversion rate within 10h, has good selectivity and stability, and can be recycled for many times. The bimetallic mesoporous confined molecular sieve catalyst of the present invention can realize catalytic oxidation of benzene to generate phenol, and then relay catalytic oxidation of phenol to generate benzoquinone.
[0018] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: the bimetallic mesoporous confined molecular sieve catalyst prepared by the method of the present invention is used in a reaction system in which benzene is oxidized using hydrogen peroxide as an oxidant, has a large specific surface area, is conducive to sufficient contact with the reaction substrate and the oxidant, and also has good catalytic activity. It can effectively reduce the amount of oxidant added and shorten the reaction time at a low catalyst dosage, realize relay catalysis at a low oxidant dosage and a short reaction time, and simultaneously obtain phenol and benzoquinone products. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figure 1 TEM images of CoCu / SCN-6 prepared in Example 2 and CoCu / SCNO-6 prepared in Comparative Example 1; wherein, (a) is a TEM image of CoCu / SCNO-6; (b) is a TEM image of CoCu / SCN-6; (c) is a HAADF-STEM image and an elemental mapping image of CoCu / SCN-6;
[0020] Figure 2 N2 adsorption-desorption isotherms (a) and pore size distribution curves (b) of CoCu / SCN-5, CoCu / SCN-6, CoCu / SCN-7 and CoCu / SCNO-6 prepared in Examples 1 to 3 and Comparative Example 1;
[0021] Figure 3The conversion rate, selectivity and yield of CoCu / SCN-5, CoCu / SCN-6, CoCu / SCN-7 and CoCu / SCNO-6 prepared in Examples 1 to 3 and Comparative Example 1 are curves of change over time under the reaction conditions of 0.3 mL benzene, 1.5 mL H2O2 (30%), 10 mg catalyst, 2.5 mL CH3COOH and 70°C; wherein (a, b) correspond to the data of CoCu / SCN-5; (c, d) correspond to the data of CoCu / SCN-6; (e, f) correspond to the data of CoCu / SCN-7; (g, h) correspond to the data of CoCu / SCNO-6;
[0022] Figure 4 The conversion rate, selectivity and yield of Co / SCN-6, Cu / SCN-6, Co / SCN-6-1 and Cu / SCN-6-1 prepared in Comparative Examples 2 to 4 are curves of change over time under the reaction conditions of 0.3 mL benzene, 1.5 mL H2O2 (30%), 10 mg catalyst, 2.5 mL CH3COOH and 70°C; wherein (a, b) correspond to the data of Co / SCN-6; (c, d) correspond to the data of Cu / SCN-6; (e, f) correspond to the data of Co / SCN-6-1; (g, h) correspond to the data of Cu / SCN-6-1;
[0023] Figure 5 This is a graph showing the conversion rate, selectivity and yield of CoCu / SCN-6 prepared in Example 2 under the reaction conditions of 0.3 mL benzene, 1.5 mL H2O2 (30%), 10 mg catalyst, 2.5 mL CH3COOH, and 10 h as a function of temperature. DETAILED DESCRIPTION
[0024] Example 1
[0025] The method for preparing the bimetallic mesoporous confined molecular sieve catalyst of the present invention comprises the following steps:
[0026] (1) 1.5 g of dodecylamine, 2 mmol of cobalt nitrate and 1 mmol of copper nitrate were added to 60 mL of 30% ethanol solution in sequence to obtain a mixed solution, and the mixed solution was vigorously stirred at 45° C. and 1000 r / min for 15 min until the metal salt was completely dissolved;
[0027] (2) adding 9 mL of tetraethyl orthosilicate to the solution obtained in step (1) at once, stirring vigorously at a speed of 1000 r / min for 4 h in a 45° C. water bath, and then standing at 45° C. for 20 h;
[0028] (3) The solution of step (2) was centrifuged and washed five times with deionized water and ethanol, and then dried in an oven. After drying, the powder was ground into powder, and then calcined in a nitrogen atmosphere at 500° C. for 3 h at a heating rate of 2° C. / min to obtain a bimetallic mesoporous confined molecular sieve catalyst, denoted as CoCu / SCN-5.
[0029] Example 2
[0030] The method for preparing the bimetallic mesoporous confined molecular sieve catalyst of the present invention comprises the following steps:
[0031] (1) 1.75 g of dodecylamine, 2 mmol of cobalt nitrate and 0.75 mmol of copper nitrate were added to 60 mL of 30% ethanol solution in sequence to obtain a mixed solution, and the mixed solution was vigorously stirred at 45° C. and 1000 r / min for 10 min until the metal salt was completely dissolved;
[0032] (2) adding 10 mL of tetraethyl orthosilicate to the solution obtained in step (1) at once, stirring vigorously at a speed of 1000 r / min for 4 h in a 45° C. water bath, and then standing at 45° C. for 20 h;
[0033] (3) The solution of step (2) was centrifuged and washed five times with deionized water and ethanol, and then dried in an oven. After drying, the powder was ground into powder, and then calcined in a nitrogen atmosphere at 600° C. for 3 h at a heating rate of 2° C. / min to obtain a bimetallic mesoporous confined molecular sieve catalyst, denoted as CoCu / SCN-6.
[0034] Figure 1 TEM images of the sample (b-c) and elemental mapping images of cobalt, copper, silicon, carbon, nitrogen and oxygen (d).
[0035] Example 3
[0036] The method for preparing the bimetallic mesoporous confined molecular sieve catalyst of the present invention comprises the following steps:
[0037] (1) 1.75 g of dodecylamine, 2 mmol of cobalt nitrate and 0.75 mmol of copper nitrate were added to 60 mL of 30% ethanol solution in sequence to obtain a mixed solution, and the mixed solution was vigorously stirred at 45° C. and 1000 r / min for 10 min until the metal salt was completely dissolved;
[0038] (2) adding 11 mL of tetraethyl orthosilicate to the solution obtained in step (1) at once, stirring vigorously at a speed of 1000 r / min for 4 h in a 45° C. water bath, and then standing at 45° C. for 20 h;
[0039] (3) The solution of step (2) was centrifuged and washed five times with deionized water and ethanol, and then dried in an oven. After drying, the powder was ground into powder, and then calcined under a nitrogen atmosphere at 700° C. for 3 h at a heating rate of 2° C. / min to obtain a bimetallic mesoporous confined molecular sieve catalyst, denoted as CoCu / SCN-7.
[0040] Comparative Example 1
[0041] A method for preparing a bimetallic mesoporous confined molecular sieve catalyst comprises the following steps:
[0042] (1) 1.75 g of dodecylamine, 2 mmol of cobalt nitrate and 0.75 mmol of copper nitrate were added to 60 mL of 30% ethanol solution in sequence to obtain a mixed solution, and the mixed solution was vigorously stirred at 45° C. and 1000 r / min for 10 min until the metal salt was completely dissolved;
[0043] (2) adding 10 mL of ethyl orthosilicate to the solution obtained in step (1) at once, stirring vigorously at a speed of 1000 r / min for 4 h in a 45° C. water bath, and then standing at 45° C. for 18 h;
[0044] (3) The solution of step (2) was centrifuged and washed five times with deionized water and ethanol, and then dried in an oven. After drying, the powder was ground into powder, and then calcined in an air atmosphere at 600° C. for 3 h at a heating rate of 2° C. / min to obtain a bimetallic mesoporous confined molecular sieve catalyst, denoted as CoCu / SCNO-6.
[0045] Comparative Example 2
[0046] A method for preparing a molecular sieve catalyst comprises the following steps:
[0047] (1) 1.75 g of dodecylamine and 2 mmol of cobalt nitrate were added to 60 mL of 30% ethanol solution in sequence to obtain a mixed solution, and the mixed solution was vigorously stirred at 45° C. and 1000 r / min for 10 min until the metal salt was completely dissolved;
[0048] (2) adding 10 mL of ethyl orthosilicate to the solution obtained in step (1) at once, stirring vigorously at a speed of 1000 r / min for 4 h in a 45° C. water bath, and then standing at 45° C. for 20 h;
[0049] (3) The solution of step (2) was centrifuged and washed 5 times with deionized water and ethanol, and then placed in an oven for drying. After drying, it was ground into powder, and then calcined under a nitrogen atmosphere at 600° C. for 3 h at a heating rate of 2° C. / min to obtain a molecular sieve catalyst, which was recorded as Co / SCN-6.
[0050] Comparative Example 3
[0051] A method for preparing a molecular sieve catalyst comprises the following steps:
[0052] (1) 1.75 g of dodecylamine and 0.75 mmol of copper nitrate were added to 60 mL of 30% ethanol solution in sequence to obtain a mixed solution, and the mixed solution was vigorously stirred at 45° C. and 1000 r / min for 10 min until the metal salt was completely dissolved;
[0053] (2) adding 10 mL of ethyl orthosilicate to the solution obtained in step (1) at once, stirring vigorously at a speed of 1000 r / min for 4 h in a 45° C. water bath, and then standing at 45° C. for 20 h;
[0054] (3) The solution of step (2) was centrifuged and washed five times with deionized water and ethanol, and then dried in an oven. After drying, the powder was ground into powder, and then calcined in a nitrogen atmosphere at 600° C. for 3 h at a heating rate of 2° C. / min to obtain a bimetallic mesoporous confined molecular sieve catalyst, denoted as Cu / SCN-6.
[0055] Comparative Example 4
[0056] A method for preparing a molecular sieve catalyst comprises the following steps:
[0057] (1) 1.75 g of dodecylamine and 2.75 mmol of cobalt nitrate were added to 60 mL of 30% ethanol solution in sequence to obtain a mixed solution, and the mixed solution was vigorously stirred at 45° C. and 1000 r / min for 15 min until the metal salt was completely dissolved;
[0058] (2) adding 10 mL of ethyl orthosilicate to the solution obtained in step (1) at once, stirring vigorously at a speed of 1000 r / min for 4 h in a 45° C. water bath, and then standing at 45° C. for 20 h;
[0059] (3) The solution of step (2) was centrifuged and washed 5 times with deionized water and ethanol, and then placed in an oven for drying. After drying, it was ground into powder and then calcined under a nitrogen atmosphere at 600° C. for 3 h at a heating rate of 2° C. / min to obtain a molecular sieve catalyst, which was recorded as Co / SCN-6-1.
[0060] Comparative Example 5
[0061] A method for preparing a molecular sieve catalyst comprises the following steps:
[0062] (1) 1.75 g of dodecylamine and 2.75 mmol of copper nitrate were added to 60 mL of 30% ethanol solution in sequence to obtain a mixed solution, and the mixed solution was vigorously stirred at 45° C. and 1000 r / min for 10 min until the metal salt was completely dissolved;
[0063] (2) adding 10 mL of tetraethyl orthosilicate to the solution obtained in step (1) at once, stirring vigorously at a speed of 1000 r / min for 4 h in a 45° C. water bath, and then standing at 45° C. for 20 h;
[0064] (3) The solution of step (2) was centrifuged and washed five times with deionized water and ethanol, and then dried in an oven. After drying, the powder was ground into powder, and then calcined in a nitrogen atmosphere at 600°C for 3 h at a heating rate of 2°C / min to obtain a bimetallic mesoporous confined molecular sieve catalyst, which was recorded as Cu / SCN-6-1.
[0065] Figure 2 The N2 adsorption-desorption isotherms and pore size distribution curves of the prepared CoCu / SCN-5, CoCu / SCN-6, CoCu / SCN-7 and CoCu / SCNO-6 can be analyzed to obtain the specific surface area, pore volume and pore size distribution of different catalysts. The shape and data of the curve in the figure can be used to judge the influence of different preparation conditions on the mesoporous structure of the catalyst. The catalyst calcined under a nitrogen atmosphere has a mesoporous structure that is more conducive to the reaction, and compared with Comparative Example 1 (CoCu / SCNO-6) calcined under an air atmosphere, it has a larger specific surface area and a more suitable pore size, which is conducive to the full contact of the reaction substrate and the oxidant with the catalyst, thereby affecting the catalytic activity and selectivity.
[0066] Figure 3The conversion rate of benzene, product selectivity and yield of different catalysts prepared in Examples 1 to 3 and Comparative Example 1 are changed over time under the reaction conditions of 0.3 mL benzene, 1.5 mL H2O2 (30%), 10 mg catalyst, 2.5 mL CH3COOH, and 70°C. The conversion rates of benzene in Examples 1 to 3 and Comparative Example 1 are 82.4%, 83.6%, 72.9% and 83.2% respectively; the yields of phenol are 626.3 μmol, 659.7 μmol, 560.7 μmol and 543.3 μmol respectively; the yields of benzoquinone are 1179.8 μmol, 1253.7 μmol, 933.3 μmol and 1206.1 μmol respectively. It can be seen that the catalysts prepared by the present invention (such as CoCu / SCN-5, CoCu / SCN-6, CoCu / SCN-7) have a higher conversion rate of benzene than that of Comparative Example 1 (CoCu / SCNO-6) within the same reaction time, and phenol and benzoquinone products can be obtained simultaneously, and a high conversion rate is always maintained within 10 hours, indicating that the catalysts of the present invention have good catalytic activity, selectivity and stability.
[0067] Figure 4 The molecular sieves prepared in comparative examples 2 to 5 are used as catalysts in a reaction system for oxidizing benzene using hydrogen peroxide as an oxidant, specifically: 0.3 mL benzene, 1.5 mL H2O2, 2.5 mL CH3COOH, 10 mg catalyst dosage, 70°C reaction conditions, after 10 hours of reaction, the conversion rate of benzene, product selectivity and yield change over time. The conversion rates of benzene in comparative examples 2 to 5 are 40.9%, 46.6%, 32.9% and 59.6% respectively; the yields of phenol are 247.732 μmol, 16.322 μmol, 235.513 μmol and 368.304 μmol respectively; the yields of benzoquinone are 0 μmol, 823.935 μmol, 0 μmol and 1172.861 μmol respectively.
[0068] Figure 5 The curve of conversion rate, selectivity and output changing with temperature for CoCu / SCN-6 prepared in Example 2 under reaction conditions of 0.3mL benzene, 1.5mL H2O2 (30%), 10mg catalyst, 2.5mLCH3COOH, 10h reflects the influence of temperature on the catalyst performance. It can be concluded from the figure that within a certain temperature range, as the temperature rises, the conversion rate of benzene, the output of phenol and benzoquinone and the selectivity may change. This helps to determine the optimum reaction temperature of the catalyst, and also shows that temperature is an important factor affecting the catalytic reaction.
Claims
1. A method for preparing a bimetallic mesoporous confined molecular sieve catalyst, characterized in that: The steps include: (1) adding a surfactant, a cobalt salt and a copper salt to an ethanol solution to obtain a mixed solution, and vigorously stirring the mixed solution at a high temperature until the metal salt is completely dissolved; (2) after stirring, add all the required amount of tetraethyl orthosilicate, stir vigorously at constant temperature and then let stand; (3) The solution of step (2) is centrifugally washed and then dried at a constant temperature, ground into powder after drying, and then calcined in a nitrogen atmosphere to obtain a bimetallic mesoporous confined molecular sieve catalyst.
2. The preparation method according to claim 1, characterized in that: In step (1), the surfactant is dodecylamine.
3. The preparation method according to claim 1, characterized in that: In step (1), the molar ratio of the cobalt salt to the copper salt is 1-3:0.25-1.
4. The preparation method according to claim 1, characterized in that: In step (1), the temperature during the vigorous stirring is 40 to 50° C.; and the vigorous stirring time is 10 to 30 min.
5. The preparation method according to claim 1, characterized in that: In step (2), the added mass volume ratio of the surfactant to tetraethyl orthosilicate is 1.5-2 g:10-15 mL.
6. The preparation method according to claim 1, characterized in that: In step (2), the water bath temperature is 40-50° C. and the vigorous stirring time is 4-6 h.
7. The preparation method according to claim 1, characterized in that: In step (2), the standing temperature is 40 to 50° C. and the standing time is 16 to 24 hours.
8. The preparation method according to claim 4 or 6, characterized in that: In step (1) and step (2), the rotation speed corresponding to the vigorous stirring is not less than 1000 r / min.
9. The preparation method according to claim 1, characterized in that: In step (3), the heating rate is 2-2.5°C / min, the calcination time is 2-5h, and the calcination temperature is 500-700°C.
10. The preparation method according to claim 1, characterized in that: In step (3), the bimetallic mesoporous confined molecular sieve catalyst uses Si mesoporous spheres as carriers, and CoCu bimetallic active sites are in situ grown in the pores of the carriers.