Bimetal carbon-nitrogen solid catalyst, preparation method and application of bimetallic carbon-nitrogen solid catalyst in catalytic preparation of 2, 3, 5-trimethyl-1, 4-benzoquinone

Abstract

The invention discloses a bimetallic carbon-nitrogen solid catalyst, a preparation method and application of the bimetallic carbon-nitrogen solid catalyst in catalytic preparation of 2, 3, 5-trimethyl-1, 4-benzoquinone, and the preparation method of the catalyst comprises the following steps: dissolving a metal M1 salt, a metal M2 salt, a carbon source and a nitrogen source in water, adding magnetic nano Fe3O4, uniformly stirring, then freeze-drying to sublimate water, roasting for 4-8 hours at 400-600 DEG C in an inert gas atmosphere, washing and drying to obtain the bimetallic carbon-nitrogen solid catalyst. The metal M1 is one of Co and Ni, and the metal M2 is one of Fe and Cu; or the metal M1 and the metal M2 are respectively Co and Ni. By utilizing the synergistic effect of bimetal, the active sites of the bimetal can effectively activate oxygen molecules and promote the oxygen molecules to participate in the reaction, so that the reaction rate and the product yield are improved; in addition, the catalyst is low in preparation cost, simple to recycle and capable of being repeatedly utilized, and has operability on actual industrial production.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalytic chemistry, and particularly relates to a magnetic bimetallic carbonitride solid catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] Vitamin E, also known as tocopherol, is a commonly used drug and health product, and also has many uses in the fields of food, feed industry, and cosmetics. 2,3,5-Trimethyl-1,4-benzoquinone (TMBQ) is a key intermediate for the synthesis of vitamin E. Through a reduction reaction with it as the raw material, 2,3,5-trimethyl-1,4-hydroquinone (TMHQ) can be obtained, and then vitamin E can be prepared by condensation with isophytol. At present, there are various processes for preparing TMBQ, such as the mesitylene method, 2,3,6-trimethylphenol method (TMP), pseudocumene method (TMB), and isophorone method. Among them, using 2,3,6-trimethylphenol (TMP) as the raw material and preparing TMBQ by thermal oxidant is the mainstream process. According to the classification of oxidants, there are the hydrogen peroxide method (CN107488110A and CN102633614B) and the oxygen method (CN101665422A, CN102108047A).

[0003] Compared with the hydrogen peroxide method, the oxygen method is relatively safe and has advantages such as cheap raw materials. At present, the catalysts used in the oxygen thermal oxidation method are mainly salt catalysts such as CuCl2, etc. (CN106699537B, CN1986513A, CN101113131A, and CN107185571A), but there are problems such as large dosage, strong corrosiveness, difficult separation, easy generation of a large amount of wastewater, and excessive metal ions in the product. Using solid catalysts can avoid the above problems. Recently, Catal. Sci. Technol., 2023, 13, 6126 and patent CN111153785A respectively reported that Co-N-C and Cu catalysts were used for the catalytic oxidation of TMP by oxygen to prepare 2,3,5-trimethyl-1,4-benzoquinone. Although the yield can reach more than 80%, there are problems such as insufficient stability of the active sites, many side reaction dimers, poor recyclability of the catalyst, and inability to be reused multiple times. Therefore, it is of great significance to further study solid catalysts with high selectivity and efficient recyclability.

[0004] The present invention synthesizes a magnetic bimetallic carbonitride solid catalyst. By utilizing the synergistic effect of the bimetals, the bimetallic active sites can effectively activate oxygen molecules and promote their participation in the reaction, thereby increasing the reaction rate and product yield. In addition, the catalyst is cheap to prepare, simple to recycle, and can be reused multiple times, which is operable for actual industrial production. Summary of the Invention

[0005] Aiming at the above technical problems existing in the prior art, the purpose of the present invention is to provide a magnetic bimetallic carbonitride solid catalyst, a preparation method thereof and an application thereof.

[0006] In order to achieve the above object of the present invention, the following technical solutions are specifically adopted:

[0007] A preparation method of a magnetic bimetallic carbonitride solid catalyst, comprising the following steps:

[0008] Step 1: Add magnetic nano-Fe3O4 to a solution of metal M1 salt, metal M2 salt, carbon source and nitrogen source dissolved in water, stir evenly, then add molten salt, mix and freeze-dry, and sublimate water under vacuum;

[0009] Wherein, metal M1 is one of Co and Ni, and metal M2 is one of Fe and Cu; or the metal M1 and metal M2 are Co and Ni respectively;

[0010] Step 2: Then dry at 110-150 °C, calcine in an inert gas atmosphere at 400-600 °C for 4-8 h to obtain a magnetic bimetallic carbonitride material, wash to remove the remaining metal M1-M2 salts and molten salt in the material, dry, and then calcine again under the same conditions to obtain a catalyst product.

[0011] Further, the molar ratio of the metal M1 salt to the metal M2 salt is 0.5-2:1, preferably 0.75-1.1:1; both the metal M1 salt and the metal M2 salt are metal chlorides.

[0012] Further, the carbon source is one or more of glucose, sucrose, lactose, cellulose, starch, and the mass ratio of the total amount of metal M1-M2 salts to the carbon source is 1-3 mmol: 1 g.

[0013] Further, the nitrogen source is one or more of urea, dicyandiamide, and melamine, and the mass ratio of the nitrogen source to the carbon source is 0.2-0.4:1.

[0014] Further, the mass ratio of magnetic nano-Fe3O4 to the carbon source is 0.05-0.1:1, the average particle size of magnetic nano-Fe3O4 is 5-50 nm, preferably 10-50 nm, and the molten salt is one or more of LiCl, NaCl, KCl, ZnCl2.

[0015] Further, the above-mentioned inert gas is nitrogen, argon or helium.

[0016] Further, the stirring temperature in Step 1 is 20-60 °C, the stirring time is 1-5 h; the temperature of freeze-drying is -50 to -20 °C, and the vacuum pressure in the sublimation stage is 10-100 Pa.

[0017] Further, in step 2 of the washing, it is washed successively with a dilute acid solution having a concentration of 0.001 to 0.01 mol·L -1 and deionized water, and the acid is one or more of nitric acid, hydrochloric acid, sulfuric acid, and phosphoric acid.

[0018] The present invention also discloses the application of the magnetic bimetallic carbon nitride solid catalyst in the reaction for catalytic preparation of 2,3,5-trimethyl-1,4-benzoquinone, which is characterized in that in a solvent, the raw material 2,3,6-trimethylphenol and the catalyst are added, and then oxygen is introduced, and the reaction is heated under atmospheric pressure to obtain the product 2,3,5-trimethyl-1,4-benzoquinone; after the reaction is completed, it is cooled to room temperature, and the catalyst is sucked out by a magnet, and the catalyst can be reused after being washed and dried with an alcohol solvent.

[0019] Further, the solvent is one of water, methanol, acetonitrile, DMF or ethanol, the dosage of the catalyst is 5% to 10% of the mass of the raw material 2,3,6-trimethylphenol, and the feeding rate of the oxygen is 5 to 20 mL·min -1 , the stirring reaction temperature is 20 - 80 °C, and the reaction time is 4 - 15 h.

[0020] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: The bimetallic carbon nitride solid catalyst provided by the present invention utilizes the synergistic effect of the bimetals, and the bimetallic active sites can effectively activate oxygen molecules and promote their participation in the reaction, thereby improving the reaction rate and product yield; at the same time, the bimetallic carbon nitride solid catalyst exhibits high stability and enhanced adsorption and conversion capabilities of the catalyst for reaction intermediates, effectively avoiding the generation of side reactions; in addition, the catalyst is cheap to prepare, simple to recycle and can be reused multiple times, which has operability for actual industrial production. This catalyst has high activity and high selectivity for oxidizing 2,3,6-trimethylphenol to prepare 2,3,5-trimethyl-1,4-benzoquinone, is easy to recycle and reuse, and the reaction has the advantages of environmental friendliness, and is very suitable for industrial production. Description of the Drawings

[0021] Figure 1 XRD pattern of the catalyst in Example 1.

[0022] Figure 2 Infrared spectrum of the catalyst in Example 1.

[0023] Figure 3 N2 adsorption-desorption isotherm pattern of the catalyst in Example 1.

[0024] Figure 4 Figure of sucking out the catalyst by a magnet.

[0025] Figure 5Bar chart of the number of catalyst recycling times, raw material conversion rate, and product selectivity. Detailed implementation mode

[0026] The method described in the present invention will be described in detail below with reference to specific examples.

[0027] Example 1:

[0028] Dissolve 282.6 mg of CoCl2·6H2O (1.19 mmol) and 187.8 mg of CuCl2·2H2O (1.10 mmol) in 30 mL of water. Then add 1273.1 mg of glucose and 424.4 mg of urea and stir at 30 °C for 6 h. Continue to add 100 mg of magnetic nano-Fe3O4 with an average diameter of 10 nm and stir at 30 °C for 2 h. Then add 1000 mg of NaCl molten salt and mix. Freeze-dry at -30 °C and sublime under a vacuum pressure of 60 Pa. After drying at 120 °C, calcine at 400 °C for 4 h in an inert gas nitrogen atmosphere to obtain a magnetic bimetallic carbon nitride material; wash three times with 0.001 mol·L -1 hydrochloric acid solution and deionized water to wash away the remaining metal particles and NaCl. Then calcine the obtained catalyst C1 again under the same conditions. The XRD pattern of the catalyst sample is shown in Figure 1 , and it can be seen that Co and Cu are dispersed on the carrier; the infrared spectrum is shown in Figure 2 ; the N2 adsorption-desorption isotherm pattern is shown in Figure 3 , and the specific surface area is: 106 m 2 ·g -1 , the average pore diameter is: 21.01 nm, and the pore volume is: 0.41 cm 3 ·g -1 .

[0029] In 10 mL of methanol, add 3 mmol of 2,3,6-trimethylphenol (TMP) and catalyst C1 (the mass of catalyst C1 is 6% of the mass of TMP). Then pass oxygen at a rate of 10 mL·min -1 , and stir and heat up to 60 °C. After reacting for 8 h, stop heating and cool to room temperature. The conversion rate of 2,3,6-trimethylphenol is detected to be 99.8%, and the selectivity of 2,3,5-trimethyl-1,4-benzoquinone is 99.7%. Finally, use a magnet to suck out the catalyst (see Figure 4 ), and the catalyst can be reused after washing and drying with ethanol.

[0030] The recycled catalyst is applied to the next batch of catalytic experiments according to the above catalytic reaction process. In this way, the results of raw material conversion rate and product selectivity under different catalyst recycling times are shown in Figure 5 .

[0031] Example 2:

[0032] Dissolve 282.6 mg of CoCl₂·6H₂O (1.19 mmol) and 375.6 mg of CuCl₂·2H₂O (2.20 mmol) in 30 mL of water. Then add 1273.1 mg of glucose and 424.4 mg of urea and stir at 20 °C for 5 h. Continue to add 100 mg of magnetic nano-Fe₃O₄ with an average diameter of 20 nm and stir at 20 °C for 2 h. Then add 1000 mg of LiCl molten salt and mix. Freeze-dry at -40 °C and sublime under a vacuum pressure of 80 Pa. After drying at 110 °C, calcine in an inert gas nitrogen atmosphere at 400 °C for 5 h to obtain a magnetic bimetallic carbon nitride material; wash three times with 0.001 mol·L -1 sulfuric acid solution and deionized water to wash away the remaining metal particles and LiCl, and then calcine the obtained catalyst C₂ again under the same conditions.

[0033] In 10 mL of acetonitrile, add 3 mmol of 2,3,6-trimethylphenol (TMP) and catalyst C₂ (the mass of catalyst C₂ is 5% of the mass of TMP), and then pass oxygen at a rate of 15 mL·min -1 . Stir and heat up to 40 °C. After reacting for 12 h, stop heating and cool to room temperature. The conversion rate of 2,3,6-trimethylphenol is detected to be 97.0%, and the selectivity of 2,3,5-trimethyl-1,4-benzoquinone is 97.0%. Finally, suck out the catalyst with a magnet. After washing and drying the catalyst with ethanol, it can be reused.

[0034] Example 3:

[0035] First, dissolve 282.6 mg of CoCl₂·6H₂O (1.19 mmol) and 93.9 mg of CuCl₂·2H₂O (0.55 mmol) in 30 mL of water. Then add 1273.1 mg of glucose and 424.4 mg of urea and stir at 40 °C for 4 h. Continue to add 100 mg of magnetic nano-Fe₃O₄ with an average diameter of 30 nm and stir at 40 °C for 2 h. Then add 1000 mg of KCl molten salt and mix. Freeze-dry at -20 °C and sublime under a vacuum pressure of 40 Pa. After drying at 130 °C, calcine in an inert gas nitrogen atmosphere at 500 °C for 5 h to obtain a magnetic bimetallic carbon nitride material; wash three times with 0.001 mol·L -1 nitric acid solution and deionized water to wash away the remaining metal particles and KCl, and then calcine the obtained catalyst C₃ again under the same conditions.

[0036] In 10 mL of DMF, 3 mmol of 2,3,6-trimethylphenol (TMP) and catalyst C3 (the mass of catalyst C3 is 10% of the mass of TMP) were added, and then oxygen was introduced at a rate of 20 mL·min -1 , and the mixture was stirred and heated to 50 °C. After reacting for 15 h, heating was stopped and the mixture was cooled to room temperature. The conversion rate of 2,3,6-trimethylphenol was detected to be 99.0%, and the selectivity of 2,3,5-trimethyl-1,4-benzoquinone was 98.2%. Finally, the catalyst was magnetically separated, washed with ethanol, dried, and then could be reused.

[0037] Example 4:

[0038] First, 282.6 mg of CoCl2·6H2O (1.19 mmol) and 187.8 mg of CuCl2·2H2O (1.10 mmol) were dissolved in 30 mL of water. Then, 1273.1 mg of starch and 424.4 mg of urea were added and stirred at 50 °C for 8 h. Subsequently, 100 mg of magnetic nano-Fe3O4 with an average diameter of 40 nm was added and stirred at 50 °C for 2 h. Then, 1000 mg of ZnCl2 molten salt was added and mixed. The mixture was freeze-dried at -50 °C and sublimated under a vacuum pressure of 20 Pa, dried at 140 °C, and then calcined at 500 °C for 6 h in an inert gas argon atmosphere to obtain a magnetic bimetallic carbon nitride material; it was washed three times with 0.001 mol·L -1 phosphoric acid solution and deionized water to wash away the remaining metal particles and ZnCl2, and then the obtained catalyst C4 was calcined again under the same conditions.

[0039] In 10 mL of water, 3 mmol of 2,3,6-trimethylphenol (TMP) and catalyst C4 (the mass of catalyst C4 is 8% of the mass of TMP) were added, and then oxygen was introduced at a rate of 5 mL·min -1 , and the mixture was stirred and heated to 80 °C. After reacting for 6 h, heating was stopped and the mixture was cooled to room temperature. The conversion rate of 2,3,6-trimethylphenol was detected to be 99.5%, and the selectivity of 2,3,5-trimethyl-1,4-benzoquinone was 99.2%. Finally, the catalyst was magnetically separated, washed with ethanol, dried, and then could be reused.

[0040] Example 5:

[0041] First, dissolve 282.6 mg of CoCl2·6H2O (1.19 mmol) and 187.8 mg of CuCl2·2H2O (1.10 mmol) in 30 mL of water. Then, add 1273.1 mg of sucrose and 424.4 mg of dicyandiamide and stir at 60 °C for 9 h. Next, add 100 mg of magnetic nano-Fe3O4 with an average diameter of 2 nm and stir at 60 °C for 3 h. Then, add 1000 mg of a molten salt mixture of ZnCl2 and NaCl, freeze-dry at -30 °C, and sublime under a vacuum pressure of 100 Pa. After drying at 110 °C, calcine in an inert gas helium atmosphere at 600 °C for 7 h to obtain a magnetic bimetallic carbon nitride material; wash 5 times with 0.01 mol·L -1 hydrochloric acid solution and deionized water to wash away the remaining metal particles and ZnCl2 and NaCl, and then calcine the obtained catalyst C5 again under the same conditions.

[0042] In 10 mL of ethanol, add 3 mmol of 2,3,6-trimethylphenol (TMP) and catalyst C5 (the mass of catalyst C5 is 7% of the mass of TMP), then pass oxygen with an oxygen rate of 10 mL·min -1 , and stir and heat up to 70 °C. After reacting for 4 h, stop heating and cool to room temperature. The conversion rate of 2,3,6-trimethylphenol is detected to be 99.0%, and the selectivity of 2,3,5-trimethyl-1,4-benzoquinone is 98.8%. Finally, suck out the catalyst with a magnet, wash and dry the catalyst with ethanol, and then it can be reused.

[0043] Example 6:

[0044] First, dissolve 282.6 mg of CoCl2·6H2O (1.19 mmol) and 187.8 mg of CuCl2·2H2O (1.10 mmol) in 30 mL of water. Then, add 636.5 mg of lactose, 636.5 mg of cellulose, and 424.4 mg of melamine and stir at 40 °C for 10 h. Next, add 100 mg of magnetic nano-Fe3O4 with an average diameter of 50 nm and stir at 40 °C for 3 h. Then, add 1000 mg of a molten salt mixture of LiCl and KCl, freeze-dry at -30 °C, and sublime under a vacuum pressure of 80 Pa. After drying at 150 °C, calcine in an inert gas nitrogen atmosphere at 600 °C for 8 h to obtain a magnetic bimetallic carbon nitride material; wash 4 times with 0.005 mol·L -1 hydrochloric acid solution and deionized water to wash away the remaining metal particles and LiCl and KCl, and then calcine the obtained catalyst C6 again under the same conditions.

[0045] In 10 mL of methanol, 3 mmol of 2,3,6-trimethylphenol (TMP) and catalyst C6 (the mass of catalyst C6 is 9% of the mass of TMP) were added, and then oxygen was passed through at a rate of 10 mL·min -1 , and the mixture was stirred and heated to 30 °C. After reacting for 10 h, heating was stopped and the mixture was cooled to room temperature. The conversion rate of 2,3,6-trimethylphenol was detected to be 98.0%, and the selectivity of 2,3,5-trimethyl-1,4-benzoquinone was 98.0%. Finally, the catalyst was magnetically removed, and after being washed with ethanol and dried, the catalyst could be reused.

[0046] Example 7:

[0047] First, 282.6 mg of CoCl2·6H2O (1.19 mmol) and 187.8 mg of CuCl2·2H2O (1.10 mmol) were dissolved in 30 mL of water. Then, 636.5 mg of glucose, 636.5 mg of sucrose, and 424.4 mg of urea were added and stirred at 40 °C for 6 h. Then, 100 mg of magnetic nano-Fe3O4 with an average diameter of 18 nm was added and stirred at 40 °C for 4 h. Then, 1000 mg of a molten salt mixture of NaCl and KCl was added, freeze-dried at -30 °C, sublimated under a vacuum pressure of 80 Pa, dried at 150 °C, and then calcined at 400 °C for 8 h in an inert gas nitrogen atmosphere to obtain a magnetic bimetallic carbon nitride material; it was washed 4 times with 0.008 mol·L -1 hydrochloric acid solution and deionized water to wash away the remaining metal particles and NaCl and KCl, and then the obtained catalyst C7 was calcined again under the same conditions.

[0048] In 10 mL of methanol, 3 mmol of 2,3,6-trimethylphenol (TMP) and catalyst C7 (the mass of catalyst C7 is 6% of the mass of TMP) were added, and then oxygen was passed through at a rate of 10 mL·min -1 , and the mixture was stirred and heated to 20 °C. After reacting for 13 h, heating was stopped and the mixture was cooled to room temperature. The conversion rate of 2,3,6-trimethylphenol was detected to be 99.0%, and the selectivity of 2,3,5-trimethyl-1,4-benzoquinone was 98.8%. Finally, the catalyst was magnetically removed, and after being washed with ethanol and dried, the catalyst could be reused.

[0049] Example 8:

[0050] First, dissolve 282.6 mg of CoCl₂·6H₂O (1.19 mmol) and 362.1 mg of FeCl₃·6H₂O (1.34 mmol) in 30 mL of water. Then, add 1273.1 mg of glucose and 424.4 mg of urea and stir at 30 °C for 6 h. Next, add 100 mg of magnetic nano-Fe₃O₄ with an average diameter of 10 nm and stir at 30 °C for 2 h. Then, add 1000 mg of NaCl molten salt and mix. Freeze-dry at -30 °C and sublime under a vacuum pressure of 60 Pa. After drying at 120 °C, calcine at 400 °C for 4 h in an inert gas nitrogen atmosphere to obtain a magnetic bimetallic carbon nitride material; wash 4 times with 0.005 mol·L -1 hydrochloric acid solution and deionized water to wash away the remaining metal particles and NaCl, and then calcine the obtained catalyst C8 under the same conditions again.

[0051] In 10 mL of methanol, add 3 mmol of 2,3,6-trimethylphenol (TMP) and catalyst C8 (the mass of catalyst C8 is 6% of the mass of TMP), then pass oxygen with an oxygen rate of 10 mL·min -1 , and stir and heat up to 60 °C. After reacting for 8 h, stop heating and cool to room temperature. The conversion rate of 2,3,6-trimethylphenol is detected to be 98.0%, and the selectivity of 2,3,5-trimethyl-1,4-benzoquinone is 98.4%. Finally, use a magnet to suck out the catalyst. After washing and drying the catalyst with ethanol, it can be reused.

[0052] Example 9:

[0053] First, dissolve 282.6 mg of CoCl₂·6H₂O (1.19 mmol) and 364.2 mg of NiCl₂·6H₂O (1.48 mmol) in 30 mL of water. Then, add 1273.1 mg of glucose and 424.4 mg of urea and stir at 30 °C for 6 h. Next, add 100 mg of magnetic nano-Fe₃O₄ with an average diameter of 10 nm and stir at 30 °C for 2 h. Then, add 1000 mg of NaCl molten salt and mix. Freeze-dry at -30 °C and sublime under a vacuum pressure of 60 Pa. After drying at 120 °C, calcine at 400 °C for 4 h in an inert gas nitrogen atmosphere to obtain a magnetic bimetallic carbon nitride material; wash 4 times with 0.005 mol·L -1 hydrochloric acid solution and deionized water to wash away the remaining metal particles and NaCl, and then calcine the obtained catalyst C9 under the same conditions again.

[0054] In 10 mL of methanol, add 3 mmol of 2,3,6-trimethylphenol (TMP) and catalyst C9 (the mass of catalyst C9 is 6% of the mass of TMP), then pass oxygen with an oxygen rate of 10 mL·min-1 Stir and heat up to 60 °C. After reacting for 8 h, stop heating and cool to room temperature. The conversion rate of 2,3,6-trimethylphenol is detected to be 99.0%, and the selectivity of 2,3,5-trimethyl-1,4-benzoquinone is 98.8%. Finally, the catalyst is magnetically attracted, and after being washed with ethanol and dried, it can be reused.

[0055] Example 10:

[0056] First, dissolve 283.4 mg of NiCl₂·6H₂O (1.15 mmol) and 187.8 mg of CuCl₂·2H₂O (1.10 mmol) in 30 mL of water. Continuously add 1273.1 mg of glucose and 424.4 mg of urea and stir at 30 °C for 6 h. Continuously add 100 mg of magnetic nano-Fe₃O₄ with an average diameter of 10 nm and stir at 30 °C for 2 h. Then continue to add 1000 mg of NaCl molten salt and mix. Freeze-dry at -30 °C and sublime under a vacuum pressure of 60 Pa. After drying at 120 °C, calcine at 400 °C for 4 h in an inert gas nitrogen atmosphere to obtain a magnetic bimetallic carbon nitride material; wash 4 times with 0.005 mol·L -1 hydrochloric acid solution and deionized water to wash away the remaining metal particles and NaCl, and then calcine the obtained catalyst C10 again under the same conditions.

[0057] In 10 mL of methanol, add 3 mmol of 2,3,6-trimethylphenol (TMP) and catalyst C10 (the mass of catalyst C10 is 6% of the mass of TMP), and then pass oxygen at an oxygen rate of 10 mL·min -1 Stir and heat up to 60 °C. After reacting for 8 h, stop heating and cool to room temperature. The conversion rate of 2,3,6-trimethylphenol is detected to be 98.0%, and the selectivity of 2,3,5-trimethyl-1,4-benzoquinone is 98.8%. Finally, the catalyst is magnetically attracted, and after being washed with ethanol and dried, it can be reused.

[0058] Example 11:

[0059] First, dissolve 283.4 mg of NiCl2·6H2O (1.15 mmol) and 362.1 mg of FeCl3·6H2O (1.34 mmol) in 30 mL of water. Then, add 1273.1 mg of glucose and 424.4 mg of urea and stir at 30 °C for 6 h. Next, add 100 mg of magnetic nano-Fe3O4 with an average diameter of 10 nm and stir at 30 °C for 2 h. Then, add 1000 mg of NaCl molten salt and mix. Freeze-dry at -30 °C and sublime under a vacuum pressure of 60 Pa. After drying at 120 °C, calcine in an inert gas nitrogen atmosphere at 400 °C for 4 h to obtain a magnetic bimetallic carbon nitride material; wash 4 times with 0.005 mol·L -1 hydrochloric acid solution and deionized water to wash away NaCl and remaining metal particles, and then calcine the obtained catalyst C11 again under the same conditions.

[0060] In 10 mL of methanol, add 3 mmol of 2,3,6-trimethylphenol (TMP) and catalyst C11 (the mass of catalyst C11 is 6% of the mass of TMP), then introduce oxygen with an oxygen rate of 10 mL·min -1 , and stir and heat up to 60 °C. After reacting for 8 h, stop heating and cool to room temperature. The conversion rate of 2,3,6-trimethylphenol is detected to be 97.0%, and the selectivity of 2,3,5-trimethyl-1,4-benzoquinone is 97.8%. Finally, use a magnet to suck out the catalyst. After washing and drying the catalyst with ethanol, it can be reused.

[0061] Control Example 1:

[0062] Repeat the preparation steps of the catalyst in Example 1 for the control example 1, with the only difference being that "the dosage of CuCl2·2H2O is 0", and finally obtain catalyst D1.

[0063] Apply catalyst D1 to the catalytic reaction for preparing 2,3,5-trimethyl-1,4-benzoquinone. Repeat the reaction steps in Example 1. After reacting for 8 h, the conversion rate of 2,3,6-trimethylphenol is 90.0%, and the selectivity of 2,3,5-trimethyl-1,4-benzoquinone is 85.0%.

[0064] Control Example 2:

[0065] Repeat the preparation steps of the catalyst in Example 1 for the control example 2, with the only difference being that "the dosage of CoCl2·6H2O is 0", and finally obtain catalyst D2.

[0066] Catalyst D2 was applied to the catalytic reaction for preparing 2,3,5-trimethyl-1,4-benzoquinone. The reaction steps were repeated as in Example 1. After reacting for 8 h, the conversion rate of 2,3,6-trimethylphenol was 80.0%, and the selectivity for 2,3,5-trimethyl-1,4-benzoquinone was 55.0%.

[0067] Comparative Example 3:

[0068] The preparation steps of the catalyst in Comparative Example 3 were repeated as in Example 1, with the only difference being that "CoCl2·6H2O was replaced with the same molar amount of MnCl2·4H2O, and CuCl2·2H2O was replaced with the same molar amount of ZnCl2·6H2O", and finally catalyst D3 was obtained.

[0069] Catalyst D3 was applied to the catalytic reaction for preparing 2,3,5-trimethyl-1,4-benzoquinone. The reaction steps were repeated as in Example 1. After reacting for 8 h, the conversion rate of 2,3,6-trimethylphenol was 45.8%, and the selectivity for 2,3,5-trimethyl-1,4-benzoquinone was 23.6%.

[0070] Comparative Example 4:

[0071] The preparation steps of the catalyst in Comparative Example 3 were repeated as in Example 1, with the only difference being that "CuCl2·2H2O was replaced with the same molar amount of ZnCl2·6H2O", and finally catalyst D4 was obtained.

[0072] Catalyst D4 was applied to the catalytic reaction for preparing 2,3,5-trimethyl-1,4-benzoquinone. The reaction steps were repeated as in Example 1. After reacting for 8 h, the conversion rate of 2,3,6-trimethylphenol was 49.8%, and the selectivity for 2,3,5-trimethyl-1,4-benzoquinone was 29.4%.

[0073] The above embodiments are only used to illustrate the specific implementation manners of the present invention and should not be construed as limiting the scope of the invention patent. For those skilled in the art, various modifications and improvements can still be made without departing from the core concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A method for preparing a magnetic bimetallic carbonitride solid catalyst, characterized in that It includes the following steps: Step 1: Magnetic nano Fe3O4 is added to a solution of metal M1 salt, metal M2 salt, carbon source and nitrogen source dissolved in water, stirred evenly, then molten salt is added, mixed and freeze-dried, and water is sublimated under vacuum; Among them, metal M1 is one of Co and Ni, and metal M2 is one of Fe and Cu; or the metal M1 and metal M2 are Co and Ni respectively; Step 2: Then it is dried at 110-150 °C and calcined in an inert gas atmosphere at 400-600 °C for 4-8 h to obtain a magnetic bimetallic nitrogen-carbon material. The remaining metal M1-M2 salts and molten salts in the material are washed away, dried, and then calcined again under the same conditions to obtain a catalyst product.

2. The preparation method of a magnetic bimetallic carbonitride solid catalyst according to claim 1, characterized in that The molar ratio of the metal M1 salt to the metal M2 salt is 0.5-2:1, preferably 0.75-1.1:1; both the metal M1 salt and the metal M2 salt are metal chlorides.

3. The preparation method of a magnetic bimetallic carbonitride solid catalyst as claimed in claim 1, wherein The carbon source is one or more of glucose, sucrose, lactose, cellulose, starch, and the molar ratio of the total amount of metal M1-M2 salts to the mass of the carbon source is 1-3 mmol: 1 g.

4. The preparation method of a magnetic bimetallic carbonitride solid catalyst as claimed in claim 1, wherein The nitrogen source is one or more of urea, dicyandiamide, and melamine, and the mass ratio of the nitrogen source to the carbon source is 0.2-0.4:

1.

5. The preparation method of a magnetic bimetallic carbonitride solid catalyst according to claim 1, characterized in that The mass ratio of magnetic nano Fe3O4 to the carbon source is 0.05-0.1:1, the average particle size of magnetic nano Fe3O4 is 5-50 nm, and the molten salt is one or more of LiCl, NaCl, KCl, ZnCl2.

6. The preparation method of a magnetic bimetallic carbonitride solid catalyst according to claim 1, characterized in that The stirring temperature in Step 1 is 20-60 °C, and the stirring time is 1-5 h; the freeze-drying temperature is -50 to -20 °C, and the vacuum pressure in the sublimation stage is 10-100 Pa.

7. The preparation method of a magnetic bimetallic carbonitride solid catalyst as described in claim 1, characterized in that Step 2 washing is carried out by washing successively with a dilute acid solution with a concentration of 0.001 - 0.01 mol·L -1 and deionized water, and the acid is one or more of nitric acid, hydrochloric acid, sulfuric acid, and phosphoric acid.

8. A magnetic bimetallic carbon-nitrogen solid catalyst prepared by the method according to any one of claims 1-7.

9. Use of a magnetic bimetallic carbonitride solid catalyst as described in claim 8 in the reaction for catalytic preparation of 2,3,5-trimethyl-1,4-benzoquinone, characterized in that In a solvent, raw material 2,3,6-trimethylphenol and the catalyst are added, and then oxygen is introduced, and the reaction is heated under normal pressure to obtain the product 2,3,5-trimethyl-1,4-benzoquinone; after the reaction is completed, it is cooled to room temperature, and the catalyst is sucked out with a magnet. After the catalyst is washed and dried with an alcohol solvent, it can be reused.

10. Use of a magnetic bimetallic carbonitride solid catalyst as described in claim 9 in the reaction for catalytic preparation of 2,3,5-trimethyl-1,4-benzoquinone, characterized in that The solvent described above is one of water, methanol, acetonitrile, DMF or ethanol. The dosage of the catalyst is 5% - 10% of the mass of raw material 2,3,6-trimethylphenol. The feeding rate of the oxygen is 5 - 20 mL·min -1 , the stirring reaction temperature is 20 - 80 °C, and the reaction time is 4 - 15 h.

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