A catalyst for preparing p-hydroxybenzaldehyde by oxidizing p-cresol and a method for using the catalyst

Abstract

The present application belongs to the field of catalyst preparation technology, specifically a catalyst for the oxidation of p-cresol to prepare p-hydroxybenzaldehyde and its use method, the catalyst is a composite metal oxide catalyst, the carrier is γ-Al2O3, the active component is a bimetallic oxide, the auxiliary agent is one or more metal oxides of variable valence metals Ce, Mn, Au, La, and the metal element in the bimetallic catalyst contains at least one of Cu and Co. The catalyst disclosed in the present application has high catalytic activity and strong stability, and the preparation method of the catalyst is simple and the catalytic conditions are mild, which solves the problems of high cost, complex preparation process and harsh reaction process conditions of traditional oxidation catalysts; the CuCoM-Al2O3 (M=Ce, Mn, Au, La) catalyst prepared by the deposition precipitation method in the present application has a p-cresol conversion rate of 80% and a p-hydroxybenzaldehyde selectivity of 99%.

Description

Technical Field

[0001] The present application belongs to the technical field of catalyst preparation, and specifically relates to a catalyst for preparing p-hydroxybenzaldehyde by oxidizing p-cresol and a method for using the catalyst. Background Art

[0002] p-Hydroxybenzaldehyde (p-PHB) is a widely used fine chemical intermediate. Its molecular structure contains active hydroxyl and aldehyde groups, exhibiting exceptional reactivity and enabling the synthesis of a wide range of functional compounds. It plays a crucial role in organic synthesis, pharmaceutical synthesis, pesticides, and fragrances. Market demand for p-HBA continues to increase, and high-purity products are in short supply.

[0003] There are currently several reported synthesis routes for p-hydroxybenzaldehyde, including (1) the phenol method; (2) the p-aminobenzaldehyde method; (3) the p-nitrotoluene method; (4) the p-cresol method; and (5) the microbial method.

[0004] The direct oxidation of p-cresol with air or oxygen in the presence of a catalyst to synthesize p-hydroxybenzaldehyde is a current mainstream process, characterized by a short process path, high yield, and minimal environmental pollution. Liu Yumin et al. used Co(OAc)2·4H2O as the main catalyst, Cu(OAc)2·H2O as the cocatalyst, and methanol as the solvent to synthesize PHBA under strong alkaline conditions in the liquid phase. The product yield reached 95.0%. However, the catalyst was a homogeneous catalyst, which remained in the reaction solution after the reaction, making it difficult to separate, recover, and reuse it in subsequent separation operations. Homogeneous catalysts also suffer from partial loss after use, resulting in low utilization and uneconomical efficiency. Shao Junquan et al. prepared a series of supported catalysts using a cobalt-copper main catalyst, nickel-zirconium cocatalysts, and TiO2 as a support by an impregnation method. Using oxygen as the oxidant and a molar ratio of sodium hydroxide to p-cresol of 5, the yield of PHBA, based on p-cresol, was 92.58%. However, the high amount of alkali used during the experiment caused some corrosion to the equipment. Patent CN201710058656.2 discloses a mesoporous composite metal oxide catalyst in which two or more of Co, Cu, Mn, Fe, and Ni are loaded on porous silicon KIT-6 by an impregnation method, wherein the conversion rate of p-cresol is as high as 99.6%, and the yield of p-hydroxybenzaldehyde is as high as 82%; Patent CN202211586946.1 discloses a method for synthesizing p-hydroxybenzaldehyde, in which metal oxides such as iron oxide, cobalt trioxide, and copper oxide are loaded on porous titanium dioxide to prepare a catalyst, a solution of the p-cresol salt and the catalyst are added to a reactor, and an oxygen source (air or oxygen) is introduced into the reactor so that the pressure in the reactor reaches 0.1 to 3.0 MPa. During the reaction, an oxygen source is continuously or intermittently introduced into the reactor to maintain a stable pressure in the reactor, the p-cresol conversion rate is maintained at about 80%, and the p-hydroxybenzaldehyde selectivity is maintained at about 98%. Although the raw material conversion rate and product selectivity are very high in the above two patents, the experimental process needs to be carried out in a pressure vessel, which is complicated to operate and requires high experimental conditions. Summary of the Invention

[0005] In order to solve the problems of the prior art, the present application provides a method for using a catalyst for oxidizing p-cresol to prepare p-hydroxybenzaldehyde, which is achieved through the following scheme:

[0006] A catalyst for preparing p-hydroxybenzaldehyde by oxidizing p-cresol, wherein the catalyst is a composite metal oxide catalyst, the carrier is γ-Al2O3, the active component is a bimetallic oxide, and the auxiliary agent is one or more metal oxides of variable valence metals Ce, Mn, Au, and La.

[0007] Furthermore, the metal element in the bimetallic catalyst contains at least one of Cu and Co.

[0008] Furthermore, the preparation method is as follows: (1) placing the carrier in a reaction vessel, and controlling the temperature in the reaction vessel to 70°C under stirring; (2) preparing an aqueous solution of a soluble salt of the active component and / or the auxiliary agent, and preparing an aqueous solution of a precipitant; (3) simultaneously dropping the aqueous solution of the soluble salt and the aqueous solution of the precipitant into the reaction vessel, and adjusting the dropping speed to ensure that the pH value of the mixed system in the reaction vessel is 9.5-10.5; (4) after the dropwise addition of the aqueous solution of the soluble salt is completed, heating and maintaining the temperature at 80°C, continuing to drop the aqueous solution of the precipitant to adjust the pH value of the mixed system in the reaction vessel to 10.8-11.2, and then aging at 80°C for 12-20 hours; (5) filtering the liquid obtained in step (4) while hot until the filtrate is washed to neutrality, drying the filter cake at 80-100°C for 8-12 hours, and then calcining at 450-650°C for 3-4 hours to obtain a catalyst; (6) pressing the catalyst obtained in step (5) into tablets for standby use.

[0009] Furthermore, the concentration of the aqueous solution of the soluble salt of the active component and / or the auxiliary agent in step (2) is 4.18-6.05 wt %; and the solution of the soluble salt in step (3) is added dropwise completely within 4-6 hours.

[0010] Furthermore, in the step (2), the atomic molar ratio of Co to Cu in the aqueous solution of the soluble salt of the active component or / and the auxiliary agent is 3:0.6-1.36.

[0011] Furthermore, in the step (2), the molar ratio of the total number of atoms of Co and Cu to the total number of atoms of the variable valence metal in the aqueous solution of the soluble salt of the active component or / and the auxiliary agent is 10:0.25-1.

[0012] Furthermore, the soluble salt in step (2) is one or more of nitrate, oxalate, and sulfate.

[0013] Furthermore, the precipitant in step (2) is an aqueous solution of ammonia with a mass concentration of 5.82 to 6.52 wt%.

[0014] Furthermore, in step (6), the tableting pressure is 15-20 MPa, and the holding time is 15-30 min.

[0015] A method for using a catalyst for preparing p-hydroxybenzaldehyde by oxidizing p-cresol comprises the following steps: pressing the catalyst into tablets, crushing the tablets, and passing the tablets through a 20-40 mesh sieve; loading the crushed catalyst into a constant temperature section of a fixed bed reactor; and filling and fixing both ends with 2-4 mesh quartz sand; loading the crushed catalyst into the constant temperature section of a fixed bed reactor; and filling and fixing both ends with 2-4 mesh quartz sand; loading the crushed catalyst into the constant temperature section of a fixed bed reactor; and filling and fixing both ends with 2-4 mesh quartz sand; and ... -1 .

[0016] The invention discloses an apparatus for preparing p-hydroxybenzaldehyde by oxidizing p-cresol. The apparatus comprises a fixed-bed reactor, wherein a fixed-bed reactor feed pipe is provided above the fixed-bed reactor, a fixed-bed reactor discharge pipe is provided below the fixed-bed reactor, the fixed-bed reactor feed pipe is connected to an air bottle via an air inlet pipe, a first stop valve, a mass flow meter and a one-way valve are provided on the air inlet pipe, the mass flow meter is located between the first stop valve and the one-way valve, the first stop valve is close to the air bottle, the one-way valve is close to the fixed-bed reactor feed pipe, the fixed-bed reactor feed pipe is connected to a raw material bottle via a raw material pipe, a horizontal flow pump is provided on the raw material pipe, the fixed-bed reactor discharge pipe is connected to a collecting bottle via a pipeline, a water bath condensing device is provided outside the collecting bottle, the collecting bottle is connected to a liquid chromatograph via a liquid phase pipe, a second stop valve is provided on the liquid phase pipe, and a collecting bottle outlet is provided on the collecting bottle.

[0017] Beneficial effects: (1) The catalyst disclosed in this application has high catalytic activity and strong stability, and the preparation method of the catalyst is simple and the catalytic conditions are mild, which solves the problems of high cost, complex preparation process and harsh reaction process conditions of traditional oxidation catalysts;

[0018] (2) The catalyst disclosed in this application is a heterogeneous catalyst with high catalytic activity, easy separation of the product and the catalyst, and the catalyst can be recycled and reused, thereby reducing costs;

[0019] (3) The CuCoM-Al2O3 (M = Ce, Mn, Au, La) catalyst prepared by the deposition precipitation method in this application has a conversion rate of 80% for p-cresol and a selectivity of 99% for p-hydroxybenzaldehyde;

[0020] (4) The oxidant used in the preparation process of this application is air, which is stable in nature, safe in operation, easy to control, inexpensive, highly competitive, and environmentally friendly, making it an ideal oxidant source for green catalytic oxidation;

[0021] (5) The present application adopts a fixed bed reactor for the preparation of p-hydroxybenzaldehyde, which has a fast reaction rate. When achieving the same production capacity, the amount of catalyst and the reactor volume required are smaller. In addition, the catalyst is not easily worn and can be used continuously for a long time, which is beneficial to improving the conversion rate of p-cresol and the selectivity of p-hydroxybenzaldehyde. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] To more clearly illustrate the technical solutions in the embodiments of this application, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some preferred embodiments of this application, not all embodiments. Regarding the preferred embodiments of this application, it is clear that those skilled in the art can derive other embodiments and drawings based on these embodiments and drawings without inventive effort, and all of them fall within the scope of protection of this application.

[0023] Figure 1 This is the equipment for preparing p-hydroxybenzaldehyde by oxidizing cresol in the embodiment of the present application;

[0024] In the figure, 1 is an air bottle, 2 is a raw material bottle, 3 is a stop valve 1, 4 is a mass flow meter, 5 is a one-way valve, 6 is a horizontal flow pump, 7 is a fixed bed reactor, 8 is a collecting bottle, 9 is a water bath condensation device, 10 is a liquid chromatograph, 11 is a stop valve 2, 12 is an air inlet pipe, and 13 is a raw material pipe. DETAILED DESCRIPTION

[0025] To make the objectives, technical solutions, and advantages of this application more clear, the embodiments of this application will be described in further detail below. It should be understood that the terms "upper," "lower," "top," "bottom," "inner," "outer," and the like indicate positions or location relationships based on the positions or location relationships shown in the accompanying drawings. The foregoing definitions are merely for the purpose of describing this application and simplifying the description, and do not indicate or imply that the structures referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0026] Example 1

[0027] A catalyst for preparing p-hydroxybenzaldehyde by oxidizing p-cresol, wherein the catalyst is a composite metal oxide catalyst, the carrier is γ-Al2O3, and the active component is a bimetallic oxide;

[0028] The metal elements in the bimetallic catalyst are Cu and Co;

[0029] A catalyst for preparing p-hydroxybenzaldehyde by oxidizing p-cresol is prepared by the following preparation method: (1) placing a carrier in a reaction container and controlling the temperature in the reaction container to 70°C under stirring; (2) preparing an aqueous solution of a soluble salt of an active component and / or an auxiliary agent, and preparing an aqueous solution of a precipitant; (3) simultaneously dropping the aqueous solution of the soluble salt and the aqueous solution of the precipitant into the reaction container, and adjusting the dropping speed to ensure that the pH value of the mixed system in the reaction container is between 9.5 and 10.5; (4) after the dropwise addition of the aqueous solution of the soluble salt is completed, heating and maintaining the temperature at 80°C, continuing to dropwise add the aqueous solution of the precipitant to adjust the pH value of the mixed system in the reaction container to 10.8-11.2, and then aging at 80°C for 12 hours; (5) filtering the liquid obtained in step (4) while hot until the filtrate is washed to neutrality, drying the filter cake at 80°C for 12 hours, and then calcining at 600°C for 4 hours to obtain a catalyst Cu 0.8 Co-Al2O3 (6) The catalyst obtained in step (5) is pressed into tablets for later use;

[0030] The concentration of the aqueous solution of the soluble salt of the active component and / or the auxiliary agent in step (2) is 4.18 wt %; the solution of the soluble salt in step (3) is added dropwise completely within 4 to 6 hours;

[0031] In step (2), the atomic molar ratio of Co to Cu in the aqueous solution of the soluble salt of the active component or / and the auxiliary agent is 3:0.8;

[0032] The Co is derived from Co(NO3)2·6H2O, and the Cu is derived from Cu(NO3)2·3H2O;

[0033] The tableting pressure in step (6) is 18 MPa, and the holding time is 25 min;

[0034] The precipitant in step (2) is an aqueous solution of ammonia with a mass concentration of 5.82 to 6.52 wt%.

[0035] Example 2

[0036] The aqueous solution concentration of the soluble salt of the active component in step (2) is 5.28 wt %, wherein the atomic molar ratio of Co to Cu is 3:1; the prepared catalyst is CuCo-Al2O3, and the rest is the same as in Example 1.

[0037] Example 3

[0038] The concentration of the aqueous solution of the soluble salt of the active component in step (2) is 5.66 wt %, wherein the atomic molar ratio of Co to Cu is 3:1.36, and the catalyst is Cu 1.36 Co-Al2O3, the rest are the same as in Example 1.

[0039] Example 4

[0040] A catalyst for preparing p-hydroxybenzaldehyde by oxidizing p-cresol, wherein the catalyst is a composite metal oxide catalyst, the carrier is γ-Al2O3, the active component is a bimetallic oxide; and the auxiliary agent is a metal oxide of a variable valence metal Ce.

[0041] The metal elements in the bimetallic catalyst are Cu and Co;

[0042] A catalyst for preparing p-hydroxybenzaldehyde by oxidizing p-cresol is prepared by the following preparation method: (1) placing a carrier in a reaction container and controlling the temperature in the reaction container to 70° C. under stirring; (2) preparing an aqueous solution of a soluble salt of an active component and / or an auxiliary agent and an aqueous solution of a precipitant; (3) simultaneously dropping the aqueous solution of the soluble salt and the aqueous solution of the precipitant into the reaction container, and adjusting the dropping speed to ensure that the pH value of the mixed system in the reaction container is between 9.5 and 10.5; (4 ) After the addition of the aqueous solution of the soluble salt is completed, the temperature is raised and maintained at 80°C, and the aqueous solution of the precipitant is continued to be added to adjust the pH value of the mixed system in the reaction vessel to 10.8-11.2, and then aged at 80°C for 12 hours; (5) the liquid obtained in step (4) is filtered while hot until the filtrate is washed to neutrality, the filter cake is dried at 80°C for 12 hours, and then calcined at 600°C for 4 hours to obtain a catalyst of CuCoCe-Al2O3 (6) the catalyst obtained in step (5) is pressed into tablets for use;

[0043] The concentration of the aqueous solution of the soluble salt of the active component and / or the auxiliary agent in step (2) is 6.05 wt %; the solution of the soluble salt in step (3) is added dropwise completely within 4 to 6 hours;

[0044] In step (2), the atomic molar ratio of Co to Cu in the aqueous solution of the soluble salt of the active component or / and the auxiliary agent is 3:1;

[0045] In step (2), the molar ratio of the total number of atoms of Co and Cu to the number of atoms of the variable-valence metal Ce in the aqueous solution of the soluble salt of the active component or / and the auxiliary agent is 10:1;

[0046] The Co is derived from Co(NO3)2·6H2O, the Cu is derived from Cu(NO3)2·3H2O, and the Ce is derived from Ce(NO3)2·6H2O;

[0047] The tableting pressure in step (6) is 18 MPa, and the holding time is 25 min;

[0048] The precipitant in step (2) is an aqueous solution of ammonia with a mass concentration of 5.82 to 6.52 wt%.

[0049] Example 5

[0050] The auxiliary agent is a metal oxide of the variable valence metal La;

[0051] The concentration of the aqueous solution of the soluble salt of the active component and / or the auxiliary agent in step (2) is 6.05 wt%;

[0052] In step (2), the molar ratio of the total number of atoms of Co and Cu to the number of atoms of the variable valence metal La in the aqueous solution of the soluble salt of the active component or / and the auxiliary agent is 10:1;

[0053] The La is derived from La(NO3)2.6H2O;

[0054] The prepared catalyst is CuCoLa-Al2O3, and the rest is the same as in Example 4.

[0055] Example 6

[0056] The auxiliary agent is the oxide of the variable valence metal Au;

[0057] The concentration of the aqueous solution of the soluble salt of the active component and / or the auxiliary agent in step (2) is 5.36 wt%;

[0058] In step (2), the molar ratio of the total number of atoms of Co and Cu to the number of atoms of the variable valence metal Au in the aqueous solution of the soluble salt of the active component or / and the auxiliary agent is 10:1;

[0059] The Au is derived from chloroauric acid;

[0060] The prepared catalyst is CuCoAu-Al2O3, and the rest is the same as in Example 4.

[0061] Example 7

[0062] The auxiliary agent is a metal oxide of the variable valence metal La;

[0063] The concentration of the aqueous solution of the soluble salt of the active component and / or the auxiliary agent in step (2) is 6.05 wt%;

[0064] In step (2), the molar ratio of the total number of atoms of Co and Cu to the number of atoms of the variable valence metal La in the aqueous solution of the soluble salt of the active component or / and the auxiliary agent is 10:1;

[0065] The La is derived from La(NO3)2.6H2O;

[0066] The molar ratio of Co to Cu is 3:1;

[0067] The prepared catalyst is CuCoLa-Al2O3, and the rest is the same as in Example 4.

[0068] Example 8

[0069] The calcination temperature of the filter cake is 450°C, the prepared catalyst is CuCoAu-Al2O3, and the rest is the same as Example 7.

[0070] Example 9

[0071] The calcination temperature of the filter cake is 500°C, the prepared catalyst is CuCoAu-Al2O3, and the rest is the same as Example 7.

[0072] Example 10

[0073] The calcination temperature of the filter cake is 550°C, the prepared catalyst is CuCoAu-Al2O3, and the rest is the same as Example 7.

[0074] Example 11

[0075] The calcination temperature of the filter cake is 650°C, the prepared catalyst is CuCoAu-Al2O3, and the rest is the same as Example 7.

[0076] Example 12

[0077] A device for preparing p-hydroxybenzaldehyde by oxidizing p-cresol, the device comprising a fixed-bed reactor 7, a fixed-bed reactor feed pipe provided above the fixed-bed reactor 7, a fixed-bed reactor discharge pipe provided below the fixed-bed reactor 7, the fixed-bed reactor feed pipe being connected to an air bottle 1 via an air inlet pipe 12, a stop valve 3, a mass flowmeter 4 and a one-way valve 5 provided on the air inlet pipe 12, the mass flowmeter 4 being located between the stop valve 3 and the one-way valve 5, the stop valve 3 being close to the air bottle 1, the one-way valve 5 being close to the fixed-bed reactor feed pipe, the fixed-bed reactor feed pipe being connected to a raw material bottle 2 via a raw material pipe 13, a horizontal flow pump 6 being provided on the raw material pipe 13, the fixed-bed reactor discharge pipe being connected to a collecting bottle 8 via a pipeline, a water bath condensation device 9 being provided outside the collecting bottle 8, the collecting bottle 8 being connected to a liquid chromatograph 10 via a liquid phase pipe, the liquid phase pipe being provided with a stop valve 2 11, and the collecting bottle 8 being provided with a collecting bottle outlet.

[0078] test

[0079] The tableted catalyst obtained in Example 1 was crushed to pass through a 20-40 mesh sieve. The crushed catalyst was loaded into the constant temperature section of a fixed bed reactor. The temperature of the constant temperature section was 65° C. and the pressure was normal pressure. Both ends were filled and fixed with 2-4 mesh quartz sand. The amount of catalyst filled was 4 mL, with the upper end quartz sand filling amount being 17 mL and the lower end quartz sand filling amount being 27 mL. A mixed gas of oxygen and nitrogen was introduced, and the oxygen concentration in the mixed gas was 50% vol. The reaction temperature was 65° C. After stabilization, the raw material liquid was pumped in, and the liquid volume space velocity was 0.045 h -1, reaction time 12h, calculation of conversion rate and selectivity, the results are shown in Table 1;

[0080] The performance of the catalysts obtained in Examples 2-11 was tested in the same manner as that of the catalyst obtained in Example 1. The conversion and selectivity were calculated. The results are shown in Table 1.

[0081] Table 1 Catalyst reaction evaluation results

[0082]

[0083]

[0084]

[0085]

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the preferred embodiments, ordinary technicians in this field should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present application, which should be included in the scope of the claims of the present application.

Claims

1. A catalyst for the oxidation of p-cresol to prepare p-hydroxybenzaldehyde, characterized in that: The catalyst is a composite metal oxide catalyst, the carrier is γ-Al2O3, the active components are Co and Cu, and the auxiliary agent is one or more of variable valence metals Au and La; the atomic molar ratio of Co to Cu is 3:0.6-1.

36.

2. A catalyst for preparing p-hydroxybenzaldehyde by oxidation of p-cresol as claimed in claim 1, characterized in that The molar ratio of Co to Cu is 3:0.8 or 3:1.36 or 3:

1.

3. A catalyst for preparing p-hydroxybenzaldehyde by oxidation of p-cresol as claimed in claim 2, characterized in that The preparation method is as follows: (1) placing the carrier in a reaction vessel, and controlling the temperature in the reaction vessel to 70°C under stirring; (2) preparing an aqueous solution of a soluble salt of an active component or / and an auxiliary agent, and preparing an aqueous solution of a precipitant; (3) simultaneously dropping the aqueous solution of the soluble salt and the aqueous solution of the precipitant into the reaction vessel, and adjusting the dropping speed to ensure that the pH value of the mixed system in the reaction vessel is 9.5-10.5; (4) after the dropwise addition of the aqueous solution of the soluble salt is completed, heating and maintaining the temperature at 80°C, continuing to drop the aqueous solution of the precipitant to adjust the pH value of the mixed system in the reaction vessel to 10.8-11.2, and then aging at 80°C for 12-20 hours; (5) filtering the liquid obtained in step (4) while hot until the filtrate is washed to neutrality, drying the filter cake at 80-100°C for 8-12 hours, and then calcining at 450-650°C for 3-4 hours to obtain a catalyst; (6) pressing the catalyst obtained in step (5) into tablets for standby use.

4. A catalyst for preparing p-hydroxybenzaldehyde by oxidation of p-cresol as claimed in claim 3, characterized in that The concentration of the aqueous solution of the soluble salt of the active component and / or the auxiliary agent in step (2) is 4.18-6.05 wt %; the solution of the soluble salt in step (3) is completely added dropwise within 4-6 hours.

5. A catalyst for preparing p-hydroxybenzaldehyde by oxidation of p-cresol as claimed in claim 3, characterized in that In the step (2), the molar ratio of the total number of atoms of Co and Cu to the total number of atoms of the variable valence metal in the aqueous solution of the soluble salt of the active component or / and the auxiliary agent is 10:0.25-1.

6. A catalyst for preparing p-hydroxybenzaldehyde by oxidation of p-cresol as claimed in claim 3, characterized in that The soluble salt in step (2) is one or more of nitrate, oxalate and sulfate.

7. A catalyst for preparing p-hydroxybenzaldehyde by oxidation of p-cresol as claimed in claim 3, characterized in that In the step (2), the precipitant is an aqueous solution of ammonia with a mass concentration of 5.82-6.52 wt%.

8. A catalyst for preparing p-hydroxybenzaldehyde by oxidation of p-cresol as claimed in claim 3, characterized in that The tableting pressure in step (6) is 15-20 MPa, and the pressure holding time is 15-30 minutes.

9. The method for using the catalyst for preparing p-hydroxybenzaldehyde by oxidation of p-cresol as claimed in claim 1, characterized in that: The steps are as follows: the catalyst is pressed into tablets and then crushed through a 20-40 mesh sieve, the crushed catalyst is loaded into the constant temperature section of a fixed bed reactor, and both ends are filled and fixed with 2-4 mesh quartz sand, the crushed catalyst is loaded into the constant temperature section of a fixed bed reactor, and both ends are filled and fixed with 2-4 mesh quartz sand, the amount of catalyst filled is 4 mL, the amount of quartz sand filled at the upper end is 17 mL, and the amount of quartz sand filled at the lower end is 27 mL, a mixture of oxygen and nitrogen is introduced, the oxygen concentration in the mixture is 5-50% vol, the reaction temperature is 45-75°C, and the raw material liquid is pumped in after stabilization, and the liquid volume space velocity is 0.01-0.1h -1 .

10. The method for using the catalyst for preparing p-hydroxybenzaldehyde by oxidation of p-cresol according to claim 9, characterized in that: The equipment for preparing p-hydroxybenzaldehyde by oxidizing p-cresol includes a fixed bed reactor, wherein a fixed bed reactor inlet pipe is provided above the fixed bed reactor, a fixed bed reactor discharge pipe is provided below the fixed bed reactor, the fixed bed reactor inlet pipe is connected to an air bottle through an air inlet pipe, a stop valve 1, a mass flow meter and a one-way valve are provided on the air inlet pipe, the mass flow meter is between the stop valve 1 and the one-way valve, the stop valve 1 is close to the air bottle, the one-way valve is close to the fixed bed reactor inlet pipe, the fixed bed reactor inlet pipe is connected to the raw material bottle through a raw material pipe, a horizontal flow pump is provided on the raw material pipe, the fixed bed reactor discharge pipe is connected to a collecting bottle through a pipeline, a water bath condensing device is provided on the outside of the collecting bottle, the collecting bottle is connected to a liquid chromatograph through a liquid phase pipe, a stop valve 2 is provided on the liquid phase pipe, and a collecting bottle outlet is provided on the collecting bottle.

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