A method of synthesizing 1-methylpentyl acetate

Abstract

The application discloses a method for synthesizing 1-methylpentyl acetate. The method uses a multi-metal MIL-53 or MIL-88 embedded modified heteropolyacid salt as a catalyst, the catalyst uses the multi-metal MIL-53 or MIL-88 as a carrier, and uses a transition metal salt modified heteropolyacid salt as an active component. The reaction is carried out under the condition that the temperature is 50 DEG C to 120 DEG C and the pressure is 0.1 to 5 MPa, and can be operated in a batch or continuous mode. The method effectively solves the problems of easy solution loss of the heteropolyacid, poor stability of the catalyst and equipment corrosion, waste water treatment and other problems existing in the traditional esterification process by using the unique structure of the catalyst. The method has the advantages of high atom utilization rate, excellent catalyst activity and stability, mild reaction condition, low production cost and the like, is suitable for addition esterification reaction of C5+ olefins and carboxylic acid, and has a good application prospect in industrial production.

Description

Technical Field

[0001] This invention relates to the field of esterification technology of olefins and carboxylic acids. Specifically, it relates to a green catalytic process for the direct addition synthesis of 1-methylpentyl acetate using C5+ olefin (hexene) and acetic acid as raw materials under the action of a multi-metallic MIL-53 (or MIL-88) embedded modified heteropolyacid salt catalyst. The core of this process lies in the use of a novel composite catalyst system to solve the problems of equipment corrosion and complex product separation in existing technologies for synthesizing carboxylic acid esters through alcohol-acid dehydration. Background Technology

[0002] Organic esters play an irreplaceable role in fine chemicals, with wide applications in fuel additives, environmentally friendly solvents, and fragrances. Currently, the traditional esterification reaction of carboxylic acids and alcohols is the main method for industrial production of organic esters. However, with the introduction of environmentally friendly and atom-economic concepts, the production method of organic esters through the addition esterification of olefins with carboxylic acids has received widespread attention. This method boasts 100% atom utilization and is a green production process. Moreover, compared to Fischer-Speier esterification, it overcomes problems such as ester hydrolysis caused by byproduct water, increased product separation costs, and catalyst deactivation. Furthermore, due to the rapid development of Fischer-Tropsch synthesis in recent years, olefins are gradually becoming a cheap and readily available resource; therefore, the preparation of olefin chemical products from olefins can enhance their practical application value. Currently, the complex product composition and low reactivity of the addition esterification of C5+ olefins and fatty acids have led most research to focus on C2-C4 olefins or cyclohexene. Technologies for producing carboxylic acid esters from C5+ olefins and fatty acids using olefinic acid addition reactions are rarely reported. Therefore, it is necessary to further strengthen the research and application of the addition esterification reaction of C5+ olefins and fatty acids.

[0003] Patent CN109456179A employs a fixed-bed process to co-feed dilute ethylene in dry gas with vaporized acetic acid for esterification to prepare ethyl acetate. Patents CN103044246A, CN101121656A, and CN106977398A disclose processes for synthesizing sec-butyl acetate using butene and acetic acid. None of these patents involve the reaction of C5+ olefins with carboxylic acids. Patent CN211896735U discloses a production system for preparing and separating pentyl (hexyl, heptyl) acetate using Fischer-Tropsch synthesis oil rich in α-olefins and acetic acid as raw materials under solid acid catalysis, but no reports have been found regarding its corresponding catalytic system. Summary of the Invention

[0004] The purpose of this invention is to provide a method for synthesizing 1-methylpentyl acetate from hexene and acetic acid, and its application. The catalyst is a multi-metallic MIL-53 (or MIL-88) embedded modified heteropolyacid acid salt catalyst, which overcomes the problems of equipment corrosion, difficult treatment of reaction waste liquid, and difficulty in water separation existing in traditional methods. At the same time, the method of this invention has good reaction performance, with excellent activity and stability.

[0005] This invention comprises the following: synthesizing 1-methylpentyl acetate from hexene and acetic acid, using a polymetallic MIL-53 (or MIL-88)-encapsulated modified heteropolyacid salt as a catalyst. The catalyst uses polymetallic MIL-53 (or MIL-88) as a support and a transition metal salt-modified heteropolyacid salt as the active component. The mass ratio of the active component to the support is 0.05:1 to 0.5:1, preferably 0.1:1 to 0.4:1, and more preferably 0.2:1 to 0.3:1.

[0006] In the catalyst used in the method of this invention, the active component is a modified heteropolyacid salt. The heteropolyacids used as modifying raw materials include one or more of the following: phosphotungstic acid, silicotungstic acid, arsostungstic acid, germanotungstic acid, phosphomolybdic acid, silicotungstic acid, arsostungstic acid, and germanotungstic acid, preferably phosphotungstic acid. The modified metal salts include one or more of the following: nitrates and chlorides of fourth and fifth period transition metals, such as manganese nitrate, iron nitrate, cobalt nitrate, nickel nitrate, copper chloride, zinc nitrate, ruthenium chloride, zirconium oxychloride, and cadmium nitrate, wherein the molar doping amount of the metal ions is 5% to 70%, preferably 10% to 50%, and more preferably 25% to 45%.

[0007] In the catalyst used in the method of this invention, the support is a MIL-53 (or MIL-88) metal-organic framework (MOF) material, and the substrate metal ion (i.e., the basic linker metal ion of the metal-organic framework material, which coordinates with the organic ligand) is specifically Al. 3+ Cr 3+ Fe 3+ One of them, preferably Al 3+ The doped metal ion is Mn. 2+ Co 2+ Ni 2+ Cu 2+ One or more of the following, wherein the molar amount of the doped metal ion is 10% to 300% of the base metal ion, preferably 30% to 250%, more preferably 60% to 200%.

[0008] In the catalyst used in this invention, a modified heteropolyacid salt is first prepared, then mixed with other raw materials, and finally synthesized in one step via a hydrothermal method to create a multi-metallic MIL-53 (or MIL-88) encapsulated modified heteropolyacid salt catalyst. The specific preparation steps are as follows: (1) Prepare an aqueous solution of an appropriate amount of heteropoly acid with deionized water, add a small amount of concentrated hydrochloric acid to ensure the stability of the solution, and obtain an anionic solution A. Prepare a solution of the corresponding mass of transition metal salt with deionized water according to the doping amount, add a small amount of concentrated hydrochloric acid to ensure the stability of the solution, and obtain a cationic solution B. Add solution B to solution A dropwise with slow stirring, increase the stirring speed, and stir for 1~12h until the mixed solution is clear. Dry at 70℃~150℃ for 6~24h, and calcine at 300℃~400℃ for 12~20h to obtain modified heteropoly acid salt.

[0009] (2) Metal salts, one or two of 1,4-benzenedicarboxylic acid (1,4-BDC) or fumaric acid, N,N-dimethylformamide (DMF), and modified heteropolyacid salts are mixed in the calculated required proportions and stirred for 0.5-4 h. The mixture is then heated in a high-pressure reactor at 60℃-200℃ for 6-24 h, cooled to room temperature, and centrifuged to obtain a solid. This solid is then vacuum dried at 50℃-90℃ for 4-16 h to obtain the final embedded catalyst. SEM and EDS analysis confirms successful catalyst preparation.

[0010] In this method, the reaction temperature for synthesizing the corresponding ester from hexene and acetic acid is 50℃~120℃, preferably 70℃~110℃, more preferably 80℃~100℃; the reaction pressure is 0.1~5MPa, preferably 0.6~3.4MPa, more preferably 0.8~3MPa; the molar ratio of olefin to acetic acid is 10:1~1:10, preferably 6:1~1:5, more preferably 3:1~1:2. The reaction can be carried out in a batch or continuous manner. In batch operation, the catalyst accounts for 0.5%~30% of the total weight of the reactants, preferably 1%~20%, more preferably 2%~10%; the reaction time is 0.5~10h, preferably 2~7h, more preferably 3~6h. In continuous operation, the liquid hourly space velocity (LHSV) of the total hexene and acetic acid reactants is 0.4~5h⁻¹. -1 Preferably 0.6~3h -1 More preferably 0.9~2h -1 .

[0011] The beneficial effects of this invention are: 1. The addition of metal ions solves the problem of reduced catalyst activity caused by the gradual dissolution of heteropolyacids from the catalyst. The heteropolyacid salts remain stable on the support, and the amount of acid in the catalyst does not decrease significantly. 2. The unique "breathing effect" of MIL-53 (or MIL-88) allows for reversible changes in pore size, providing favorable conditions for the diffusion of reactants and products. Furthermore, multimetallic MIL-53 (or MIL-88) can further enhance its resistance to carbon buildup through the synergistic effect of metals. 3. The preparation method provided by this invention is easy to operate, and the metal salts used are mostly inexpensive, making it easy to industrialize and reduce production costs, and has great application potential.

[0012] This invention utilizes the unique structure of the catalyst to effectively solve problems such as easy solubility and loss of heteropoly acids, poor catalyst stability, and equipment corrosion and wastewater treatment inherent in traditional esterification processes. This method offers advantages such as high atom utilization, excellent catalyst activity and stability, mild reaction conditions, and low production costs. It is suitable for the addition esterification reaction of C5+ olefins with carboxylic acids and has promising applications in industrial production. Attached Figure Description

[0013] Figure 1 This is a gas chromatogram of the reaction product of Example 1 of the present invention. Detailed Implementation

[0014] The present invention will be further described in detail below through embodiments.

[0015] Example 1 1) Dissolve 3.0 g of phosphotungstic acid in 30 mL of deionized water, add 4 drops (approximately 0.05 mL each) of concentrated hydrochloric acid (36-38 wt%) to acidify, and stir until homogeneous to obtain an anionic solution. Dissolve 50.2 mg of Mn(NO3)2·4H2O and 121.2 mg of Fe(NO3)3·9H2O in 30 mL of deionized water, add 4 drops of concentrated hydrochloric acid (36-38 wt%) to acidify, and stir until homogeneous to obtain a cation solution. Under stirring at 800 r / min, slowly add the cation solution to the anionic solution at a rate of 2 mL / min. Stir at the same speed for 8 h, then dry in an oven at 110 °C for 12 h. Scrape off the solid, grind it into powder, and calcine at 350 °C for 12 h to obtain Mn. 0.2 Fe 0.3 H 1.7 PW 12 O 40 The modified phosphotungstic acid salt has a metal ion doping amount of 50% of the molar amount of the raw material HPW.

[0016] 2) Combine 325mg FeCl3·6H2O, 158mg MnCl2·4H2O, 200mg 1,4-BDC, 70ml DMF, 330mgMn 0.2 Fe 0.3 H 1.7 PW 12 O 40The mixture was stirred at room temperature for 0.5 h, heated in an autoclave at 150 °C for 6 h, cooled to room temperature, and the orange solid product was collected by centrifugation at 6000 rpm for 2 min. The obtained product was vacuum dried at 60 °C for 12 h to obtain the final catalyst Mn with an active component content of approximately 6 wt%. 0.2 Fe 0.3 H 1.7 PW 12 O 40 @Fe / Mn 0.66 -MIL-53.

[0017] The successful preparation of the catalyst was confirmed by SEM and EDS analysis, and the active component modified heteropoly acid salt was embedded in the metal-organic framework material.

[0018] 3) Take 0.3g of catalyst and add it to a mixed solution of 10ml hexene and 10ml acetic acid (total mixed solution 17g, molar ratio of hexene to acetic acid 1:2). After sealing in a high-pressure reactor, react at 70℃, 1.0MPa, and 500r / min for 5h. Analyze the product by gas chromatography (using butyl acetate as an internal standard). Recover the catalyst and repeat the experiment. The reaction results are shown in Table 1.

[0019] Example 2 The process and conditions are the same as in Example 1, except that: the heteropoly acid in step 1) is replaced with silicomolybdic acid; the transition metal salts in steps 1) and 2) are replaced with Fe(NO3)3·9H2O and CoCl2·6H2O, and the required amounts are calculated to prepare 12wt% Fe 0.1 Co 0.3 H 2.1 SiMo 12 O 40 @Fe / Co2-MIL-53; In step 3), the amounts of hexene and acetic acid were 8 ml and 12 ml, respectively (hexene-acetic acid molar ratio 1:3). The reaction was carried out in a high-pressure reactor at 90℃, 2.0 MPa, and 500 r / min for 5 h. The products were analyzed and the catalyst was recovered for repeated experiments. The reaction results are shown in Table 1.

[0020] Example 3 The process and conditions are the same as in Example 1, except that in step 2), 200 mg of 1,4-BDF is replaced with 250 mg of fumaric acid, ultimately yielding 6 wt% Mn. 0.2 Fe 0.3 H 1.7 PW 12 O 40 @Fe / Mn 0.66In step 3 of MIL-88, the amounts of hexene and acetic acid were 8 ml and 16 ml, respectively (hexene-acetic acid molar ratio 1:4). The reaction was carried out in a high-pressure reactor at 85℃, 1.5 MPa, and 500 r / min for 2 h. The products were analyzed and the catalyst was recovered for repeated experiments. The reaction results are shown in Table 1.

[0021] Example 4 The process and conditions are the same as in Example 1, except that: in step 1), the heteropoly acid is replaced with germanomolybdic acid, and the transition metal salt is replaced with AgNO3 solution and ZrOCl2·8H2O; in step 2), the metal salt is replaced with Al(NO3)3·9H2O and NiCl2·6H2O. The required amounts are calculated to obtain 15wt% Zr. 0.2 Ag 0.2 H2GeMo 12 O 40 @Al / Ni 0.8 -MIL-53; In step 3), the amounts of hexene and acetic acid were 8 ml and 16 ml, respectively (hexene-acetic acid molar ratio 1:4). The reaction was carried out in a high-pressure reactor at 100℃, 3.2 MPa, and 500 r / min for 7 h. The products were analyzed and the catalyst was recovered for repeated experiments. The reaction results are shown in Table 1.

[0022] Example 5 The process and conditions are the same as in Example 1, except that: the heteropoly acid in step 1) is replaced with germanomolybdic acid; the transition metal salts in steps 1) and 2) are replaced with Cr(NO3)3·9H2O and NiCl2·6H2O, and the required amounts are calculated to obtain 30wt% Cr. 0.1 Ni 0.2 H 2.3 GeMo 12 O 40 @Cr / Ni2-MIL-53; In step 3), the amounts of hexene and acetic acid were 6 ml and 15 ml, respectively (molar ratio of 1:5). The reaction was carried out in a high-pressure reactor at 80℃, 0.8 MPa, and 500 r / min for 6 h. The products were analyzed and the catalyst was recovered for repeated experiments. The reaction results are shown in Table 1.

[0023] Example 6 Pure phosphotungstic acid was used as the catalyst, and other conditions were the same as in step 3) of Example 1. The reaction results are shown in Table 1.

[0024] Example 7 Mn prepared using step 1) of Example 1 0.2 Fe 0.3 H 1.7 PW 12 O 40Modified phosphotungsten was used as a catalyst, and other conditions were the same as in step 3) of Example 1. The reaction results are shown in Table 1.

[0025] Example 8 325 mg FeCl3·6H2O, 200 mg 1,4-BDC, and 70 ml DMF were mixed and stirred at room temperature for 0.5 h. The mixture was then heated in an autoclave at 150 °C for 6 h, cooled to room temperature, and the orange solid product was collected by centrifugation at 6000 rpm for 2 min. The obtained product was vacuum dried at 60 °C for 12 h to obtain pure MIL-53 (Fe), and the successful preparation was confirmed by SEM and EDS analysis. Using this as a catalyst, the remaining conditions were the same as in step 3) of Example 1, and the reaction results are shown in Table 1.

[0026] Example 9 325 mg FeCl3·6H2O, 158 mg MnCl2·4H2O, 200 mg 1,4-BDC, and 70 ml DMF were mixed and stirred at room temperature for 0.5 h. The mixture was then heated in an autoclave at 150 °C for 6 h, cooled to room temperature, and the orange solid product was collected by centrifugation at 6000 rpm for 2 min. The obtained product was then vacuum dried at 60 °C for 12 h to obtain Fe / MnCl2. 0.66 MIL-53 was successfully prepared, as confirmed by SEM and EDS analysis. It was used as a catalyst, and the remaining conditions were the same as in step 3) of Example 1. The reaction results are shown in Table 1.

[0027] Example 10 325 mg FeCl3·6H2O, 200 mg 1,4-BDC, 70 ml DMF, and 330 mg HPW were mixed and stirred at room temperature for 0.5 h. The mixture was then heated in an autoclave at 150 °C for 6 h, cooled to room temperature, and the orange solid product was collected by centrifugation at 6000 rpm for 2 min. The obtained product was vacuum dried at 60 °C for 12 h to obtain HPW@MIL-53, and the successful preparation was confirmed by SEM and EDS analysis. HPW was used as a catalyst, and the remaining conditions were the same as in Example 1. The reaction results are shown in Table 1.

[0028] Example 11 Using the Fe / Mn ratio in Example 9 0.66 -MIL-53 was used as a carrier, and Mn was prepared in step 1) of Example 1. 0.2 Fe 0.3 H 1.7 PW 12 O 40Modified phosphotungsten was used as the active component; 120 mg of the active component and 2 g of the carrier were weighed (6 wt%), poured into 10 ml of ethanol and mixed. After sonication for 1.5 h, the mixture was dried at 110 °C and ground to obtain the impregnated supported Mn. 0.2 Fe 0.3 H 1.7 PW 12 O 40 / Fe / Mn 0.66 -MIL-53. It was used as a catalyst, and the other conditions were the same as in step 3) of Example 1. The reaction results are shown in Table 1.

[0029] Example 12 The catalyst was the same as that used in Example 1 (i.e., the catalyst prepared using step 2 of Example 1), but a continuous reaction was employed. The reaction was carried out at a temperature of 100°C, a pressure of 2.5 MPa, and a total liquid hourly space velocity (LHSV) of 1 h⁻¹ for the hexene and acetic acid mixture. -1 The molar ratio of acetic acid to hexene was 2:1, and the catalyst dosage was 0.5 g. A 40-hour stability evaluation experiment was conducted on the catalyst. The reaction results are shown in Table 2.

[0030] Example 13 The catalyst was the same as that prepared in Example 2 (i.e., the catalyst prepared in step 2 of Example 2), but a continuous reaction was used instead. The reaction was carried out at a temperature of 70°C, a pressure of 1.5 MPa, and a total liquid hourly space velocity (LHSV) of 1.2 h⁻¹ for the hexene and acetic acid mixture. -1 The molar ratio of acetic acid to hexene was 1:1, and the catalyst dosage was 0.4 g. A 40-hour stability evaluation experiment was conducted on the catalyst. The reaction results are shown in Table 2.

[0031] Example 14 The catalyst was the same as that used in Example 3 (i.e., the catalyst prepared using step 2 of Example 3), but a continuous reaction was employed. The reaction was carried out at a temperature of 100°C, a pressure of 2 MPa, and a total liquid hourly space velocity (LHSV) of 1 h⁻¹ for the hexene and acetic acid products. -1 The molar ratio of acetic acid to hexene was 3:1, and the catalyst dosage was 0.5 g. A 40-hour stability evaluation experiment was conducted on the catalyst. The reaction results are shown in Table 2.

[0032] Example 15 The catalyst was the same as that used in Example 4 (i.e., the catalyst prepared in step 2 of Example 4), but a continuous reaction was employed. The reaction was carried out at a temperature of 110°C, a pressure of 2.5 MPa, and a total liquid hourly space velocity (LHSV) of 0.8 h⁻¹ for the hexene and acetic acid mixture. -1 The molar ratio of acetic acid to hexene was 2:1, and the catalyst dosage was 0.5 g. A 40-hour stability evaluation experiment was conducted on the catalyst. The reaction results are shown in Table 2.

[0033] Example 16 The catalyst was the same as that used in Example 5 (i.e., the catalyst prepared in step 2 of Example 5), but a continuous reaction was employed. The reaction was carried out at a temperature of 80°C, a pressure of 1 MPa, and a total liquid hourly space velocity (LHSV) of 1.5 h⁻¹ for the hexene and acetic acid products. -1 The molar ratio of acetic acid to hexene was 2:1, and the catalyst dosage was 0.4 g. A 40-hour stability evaluation experiment was conducted on the catalyst. The reaction results are shown in Table 2.

[0034] Example 17 The catalyst was the same as in Example 6, and the reaction conditions for the synthesis of 1-methylpentyl acetate were the same as in Example 12. The reaction results are shown in Table 2.

[0035] Example 18 The catalyst was the same as in Example 7, and the reaction conditions for the synthesis of 1-methylpentyl acetate were the same as in Example 12. The reaction results are shown in Table 2.

[0036] Example 19 The catalyst was the same as in Example 8, and the reaction conditions for the synthesis of 1-methylpentyl acetate were the same as in Example 12. The reaction results are shown in Table 2.

[0037] Example 20 The catalyst was the same as in Example 9, and the reaction conditions for the synthesis of 1-methylpentyl acetate were the same as in Example 12. The reaction results are shown in Table 2.

[0038] Example 21 The catalyst was the same as in Example 10, and the reaction conditions for the synthesis of 1-methylpentyl acetate were the same as in Example 12. The reaction results are shown in Table 2.

[0039] Example 22 The catalyst was the same as in Example 11, and the reaction conditions for the synthesis of 1-methylpentyl acetate were the same as in Example 12. The reaction results are shown in Table 2.

[0040] Table 1. Reactor Reaction Examples

[0041] The repetition of 5 times refers to the result of filtering and separating the catalyst after the reaction to synthesize 1-methylpentyl acetate, and then conducting the reaction to synthesize 1-methylpentyl acetate again under the same conditions for the 5th time. Table 2 Fixed-bed reaction examples

[0042] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept of the present invention, and these should also be considered within the scope of protection of the invention.

Claims

1. A method for synthesizing 1-methylpentyl acetate, characterized in that: This method uses one or two of the polymetallic MIL-53 or MIL-88 embedded modified heteropolyacid salts as catalysts to carry out a catalytic reaction at a reaction temperature of 50℃~120℃ and a reaction pressure of 0.1~5MPa to synthesize 1-methylpentyl acetate from hexene and acetic acid.

2. The method for synthesizing 1-methylpentyl acetate according to claim 1, characterized in that: The catalyst support is one or more of the multi-metallic MIL-53 or MIL-88 metal-organic framework materials, and the active component is a transition metal salt modified heteropoly acid salt; wherein the mass ratio of the active component to the support is 0.05:1 to 0.5:

1.

3. The method for synthesizing 1-methylpentyl acetate according to claim 1, characterized in that: The modified heteropolyacid salt is a heteropolyacid modified with transition metals from the fourth and fifth periods. The modified transition metals are one or more of manganese, iron, cobalt, nickel, copper, zinc, ruthenium, zirconium, silver, and cadmium. Furthermore, the molar doping amount of modified metal ions in the modified heteropolyacid salt is 5% to 70%.

4. The method for synthesizing 1-methylpentyl acetate according to claim 1, characterized in that: The substrate metal ion in the multimetallic MIL-53 or MIL-88 support is Al. 3+ Cr 3+ or Fe 3+ One or more of the following, and doped with Mn 2+ Co 2+ Ni 2+ Cu 2+ One or more metal ions are used, and the molar amount of the doped metal ion is 10% to 250% of that of the base metal ion.

5. The method for synthesizing 1-methylpentyl acetate according to claim 1, characterized in that: In the reaction, the molar ratio of hexene to acetic acid is 10:1 to 1:

10.

6. The method for synthesizing 1-methylpentyl acetate according to claim 1 or 5, characterized in that: The method employs an intermittent operation, with the catalyst dosage accounting for 0.5% to 30% of the total weight of the reactants, and the reaction time being 0.5 to 10 hours.

7. The method for synthesizing 1-methylpentyl acetate according to claim 6, characterized in that: The reaction temperature is 70℃~100℃, the reaction pressure is 0.6~3.4MPa; the catalyst dosage is 1%~12%, the reaction time is 2~7h; and the molar ratio of hexene to acetic acid is 3:1~1:

5.

8. The method for synthesizing 1-methylpentyl acetate according to claim 1 or 5, characterized in that: The method employs a continuous operation, with a liquid hourly space velocity (LHSV) of 0.4–5 h⁻¹ for the hexene and acetic acid mixture. -1 .

9. The method for synthesizing 1-methylpentyl acetate according to claim 8, characterized in that: The reaction temperature is 70℃~100℃, and the reaction pressure is 0.6~3.4MPa; the molar ratio of hexene to acetic acid is 3:1~1:5, and the liquid hourly space velocity is preferably 0.6~2h. -1 .

10. The method for synthesizing 1-methylpentyl acetate according to claim 1, characterized in that: The catalyst is prepared by a method comprising the following steps: (1) Synthesis of modified heteropoly acid salts: The raw heteropoly acid is prepared into an aqueous solution with water to obtain an anionic solution A. The required mass of transition metal salt is prepared into a solution with water according to the amount of modified transition metal ion doping to obtain a cationic solution B. Solution B is added dropwise to solution A under stirring, and the mixture is stirred for 1~12h until the mixed solution is clear. It is dried at 70℃~150℃ for 6~24h and calcined at 300℃~400℃ for 12~20h to obtain modified heteropoly acid salts. (2) Mix one or two of the following: metal salts, 1,4-phenylenediic acid or fumaric acid, N,N-dimethylformamide, and modified heteropoly acid salts in the required proportion and stir for 0.5-4h. Heat in a high-pressure reactor at 60℃-200℃ for 6-24h, cool and centrifuge to obtain a solid. Vacuum dry at 50℃-90℃ for 4-16h to obtain the final embedded catalyst. The raw material heteropolyacid of the active component is one or more of phosphotungstic acid, silicotungstic acid, arsostungstic acid, germanotungstic acid, phosphotomolybdic acid, silicotomolybdic acid, arsostomolybdic acid, or germanotomolybdic acid; the transition metal salt used for modification is one or more of the nitrates or chlorides of fourth and fifth period transition metals, and is one or more of manganese nitrate, iron nitrate, cobalt nitrate, nickel nitrate, copper chloride, zinc nitrate, ruthenium chloride, zirconium oxychloride, silver nitrate, and cadmium nitrate.

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