P-cresol oxidation catalyst and preparation method thereof

Abstract

The invention provides a p-cresol oxidation catalyst and a preparation method thereof. The preparation method comprises the following steps: S1, adding a first active metal source, a second active metal source and a carrier source into water to obtain a first solution; s2, adding a precipitator into water to obtain a second solution; s3, mixing the first solution with the second solution to obtain a third solution with the pH value of 9-10; s4, carrying out hydrothermal reaction on the third solution at 100-140 DEG C to obtain a first product; s5, sequentially washing, drying and calcining the first product to obtain the p-cresol oxidation catalyst, the first active metal source is a cobalt source and a copper source, the second active metal source comprises a cerium source, and the carrier source is an aluminum source. The p-cresol oxidation catalyst with high activity and selectivity is prepared by accurately controlling the conditions of the hydrothermal reaction and the proportion of each active metal source and simultaneously forming the carrier in situ in the reaction and generation process of the catalyst.

Description

Technical Field

[0001] The invention relates to the field of fine chemicals, and in particular to a p-cresol oxidation catalyst and a preparation method thereof. Background Art

[0002] p-Hydroxybenzaldehyde is a very important fine chemical intermediate in the fields of medicine, pesticides, petrochemicals, and fragrances. It can be used in the synthesis of antibiotics such as methoxybenzylamine, hydroxyampicillin, and trimethoxybenzaldehyde. It can also be used in the synthesis of herbicides such as azobenzil and dichlorvos in pesticides, as well as dichloro-p-hydroxybenzaldehyde, a reagent that inhibits the growth of microorganisms.

[0003] In the prior art, the routes for synthesizing p-hydroxybenzaldehyde mainly include Gattermann method, chloroacetaldehyde method, phenol formaldehyde method, p-nitrotoluene method, Mn2O3 method, microbial method and p-cresol catalytic oxidation method.

[0004] Among them, the catalytic oxidation method of p-cresol uses green and clean oxygen or air as an oxidant. This method first reacts p-cresol with sodium hydroxide to generate sodium p-cresol to protect the phenolic hydroxyl group, and then catalytically oxidizes the methyl group in p-cresol. After the reaction is completed, it is acidified to obtain p-hydroxybenzaldehyde. This method has a simple process, a high purity target product, is relatively environmentally friendly, and has strong industrial advantages.

[0005] At present, the catalysts used for the catalytic oxidation of p-cresol to prepare p-hydroxybenzaldehyde are mainly divided into homogeneous catalysts and heterogeneous catalysts. Homogeneous catalysts mainly use organic metal compounds such as acetates, nitrates, phthalocyanines of transition metals such as cobalt, copper, manganese, iron, nickel, and chromium as the main catalyst, and add sodium bromide, potassium bromide, copper chloride, etc. as auxiliary agents (CN 143066 A, US4929766 A, CN 201351147 Y) to catalyze the oxidation of p-cresol to synthesize p-hydroxybenzaldehyde in the system. However, this type of catalyst has the problems of long oxidation reaction time, difficult product separation, and low conversion rate of p-cresol. The active components of heterogeneous catalysts are mainly cobalt nitrate, cobalt acetate, cobalt trioxide, etc., and the carriers are mostly selected from aluminum oxide, silicon oxide, titanium dioxide, activated carbon, and ion exchange resin (CN 1218780 C, CN 113831228A, CN115850043 A, CN 116803501 A). However, this type of catalyst has the disadvantages of easy loss of active components, easy over-oxidation of the product during the reaction, complex synthesis route, long synthesis cycle and poor strength.

[0006] Based on this, how to provide a new p-cresol oxidation catalyst to improve the yield of the obtained p-hydroxybenzaldehyde product in the catalytic oxidation reaction of p-cresol is one of the important technical problems that need to be solved in this field. Summary of the invention

[0007] The main purpose of the present invention is to provide a p-cresol oxidation catalyst and a preparation method thereof, so as to solve the problem that the catalyst used for the catalytic oxidation of p-cresol in the prior art cannot catalyze the preparation of p-hydroxybenzaldehyde product with high yield.

[0008] In order to achieve the above-mentioned purpose, the first aspect of the present invention provides a method for preparing a p-cresol oxidation catalyst, comprising: step S1, adding a first active metal source, a second active metal source and a carrier source into water to obtain a first solution; step S2, adding a precipitant into water to obtain a second solution; step S3, mixing the first solution with the second solution to obtain a third solution with a pH of 9 to 10; step S4, subjecting the third solution to a hydrothermal reaction at 100°C to 140°C to obtain a first product; step S5, washing, drying and calcining the first product in sequence to obtain a p-cresol oxidation catalyst; wherein the first active metal source is a cobalt source and a copper source, the second active metal source includes a cerium source, and the carrier source is an aluminum source.

[0009] Furthermore, the molar ratio of the first active metal source to the second active metal source is 1:(0.1-0.5), preferably 1:(0.18-0.20); in the first active metal source, the molar ratio of the cobalt source to the copper source is (0.2-10):1, preferably (1-2):1.

[0010] Furthermore, based on the total weight of the first active metal source and the second active metal source as 100%, the amount of the carrier source is 5% to 100%, preferably 30% to 80%.

[0011] Furthermore, the second active metal source is a cerium source and an iron source, and the molar ratio of the cerium source to the iron source is (1-5):1, preferably (2-3):1.

[0012] Furthermore, the first active metal source, the second active metal source and the carrier source are each independently added in the form of one or more of nitrate, phosphate, sulfate, acetate and chloride; and / or the precipitant is selected from one or more of sodium carbonate, sodium hydroxide and sodium bicarbonate.

[0013] Furthermore, in step S4, the temperature of the hydrothermal reaction is 120±5° C., and the time is 5 h to 6 h.

[0014] Furthermore, in step S5, the drying is vacuum drying, and the temperature of the vacuum drying is 70° C. to 80° C., and the time is 12 h to 24 h.

[0015] Further, in step S5, the heating rate of calcination is 12°C / min~15°C / min, the holding temperature is 500°C~550°C, and the holding time is 3h~4h; preferably, calcination is carried out under a protective atmosphere, and the amount of protective atmosphere introduced is 100mL / min~300mL / min; more preferably, the protective atmosphere is nitrogen and / or argon.

[0016] The second aspect of the present invention provides a p-cresol oxidation catalyst, which is prepared by the preparation method of the p-cresol oxidation catalyst.

[0017] Furthermore, the specific surface area of ​​the p-cresol oxidation catalyst is 160 m 2 / g ~240m 2 / g.

[0018] By applying the technical solution of the present invention, the conditions of the hydrothermal reaction and the ratio of each active metal source are precisely controlled, and a carrier is formed in situ during the reaction generation process of the catalyst, thereby preparing a p-cresol oxidation catalyst with high activity and selectivity. The obtained catalyst exhibits excellent catalytic performance in the p-cresol oxidation reaction, which not only improves the reaction rate, but also significantly improves the yield and purity of the hydroxybenzaldehyde product. DETAILED DESCRIPTION

[0019] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0020] As described in the background technology, the catalyst used for the catalytic oxidation of p-cresol in the prior art has the problem that it is unable to catalyze the production of p-hydroxybenzaldehyde products with high yield. In order to solve the above technical problems, the first aspect of the present invention provides a method for preparing a p-cresol oxidation catalyst, comprising: step S1, adding a first active metal source, a second active metal source and a carrier source into water to obtain a first solution; step S2, adding a precipitant into water to obtain a second solution; step S3, mixing the first solution with the second solution to obtain a third solution with a pH of 9 to 10; step S4, subjecting the third solution to a hydrothermal reaction at 100°C to 140°C to obtain a first product; step S5, washing, drying and calcining the first product in sequence to obtain a p-cresol oxidation catalyst; wherein the first active metal source is a cobalt source and a copper source, the second active metal source includes a cerium source, and the carrier source is an aluminum source.

[0021] By applying the technical solution of the present invention, the reaction conditions and the types of active metal sources are precisely controlled, and the carrier is formed in situ during the reaction generation process of the catalyst, thereby preparing a p-cresol oxidation catalyst with high activity and selectivity.

[0022] Specifically, the above-mentioned preparation method provided by the present invention is to mix the first active metal component with the second active metal ion salt and the carrier precursor salt and then prepare the p-cresol oxidation catalyst by a hydrothermal method. In particular, in the process of the valence state of each active metal source changing and forming a catalytic active center, the added carrier precursor salt, that is, the carrier source, simultaneously forms a layered catalyst carrier structure in situ, and this special layered structure can significantly reduce the metal ion interlayer distance, improve the electron transfer efficiency of each active variable valence metal, thereby enhancing the oxidation activity of the obtained p-cresol oxidation catalyst. The aluminum source, a specific carrier source, acts as a structural stabilizer, plays a role in enhancing the structural stability in the obtained layered structure, prevents the collapse of the layered structure, and maintains the high activity and long-term stability of the catalyst. At the same time, it does not participate in the redox reaction in the catalytic process, thereby helping to extend the life of the catalyst. In the above preparation process, the pH value of the third solution obtained by mixing the first solution and the second solution is strictly controlled because the above pH value range can ensure the formation of a stable precursor structure, thereby generating a catalyst with higher activity in the subsequent hydrothermal reaction, thereby improving the reaction conversion rate and product purity in the industrial production process of p-cresol oxidation reaction.

[0023] The p-cresol oxidation catalyst prepared by the method provided by the present invention has a second active metal Ce. 4+ , which is conducive to the formation of more effective catalytic activation center CeO2, which is easily oxidized to CeO2-x oxide in an oxidizing environment. CeO2 loses oxygen atoms to generate oxygen vacancies (Ov). When CeO2-x is exposed to an oxygen-containing environment, it can be rapidly oxidized to the original CeO2. Therefore, the obtained CeO2 has excellent oxygen storage and release properties. As a second active metal doping, it is more conducive to the oxidation of p-cresol to generate p-hydroxybenzaldehyde. At the same time, by in-situ generating a carrier with a layered structure, compared with the catalyst system obtained by direct loading, the in-situ generated structure is more stable and has better binding properties with each active metal. At the same time, the layered carrier structure also provides a larger specific surface area, which is conducive to the dispersion of each active metal component, increases the opportunity for reactants to contact active sites, and improves the catalytic efficiency.

[0024] In the actual catalytic reaction process, the obtained catalyst introduces the first active metal component (i.e., Co 3+ 、Co 2 + , Cu 2+ ) and the second active metal component (i.e. Ce 4+), the variable valence metal achieves the conversion of different oxidation states by gaining and losing electrons, so that the catalyst in which it is located can transfer electrons at different stages of the reaction, promoting the activation of the reactant p-cresol. At the same time, due to the multiple oxidation states and electron transfer ability of the variable valence metal, the obtained p-cresol oxidation catalyst can highly selectively activate the CH chemical bond in the reaction, making it easier to oxidize it to an aldehyde group, providing higher reaction selectivity and reducing the occurrence of side reactions. Thirdly, since the first active metal and the second active metal component contain different metal elements, namely Ce 4+ , Cu 2+ , whose introduction can change Co 3+ 、Co 2+ The electron cloud density around the catalyst. The above-mentioned active metals form more effective activation centers through the synergistic effect between metal ions, and the synergistic effect of multiple metal centers can significantly enhance the overall catalytic activity of the catalyst, making its catalytic product show better yield and selectivity.

[0025] In summary, the present invention designs a special process route and condition parameters, and the catalyst obtained by the preparation method exhibits excellent catalytic performance in the oxidation reaction of p-cresol, which not only improves the reaction rate, but also significantly improves the yield and purity of the product p-hydroxybenzaldehyde.

[0026] With respect to the above-mentioned preparation process, the inventors have, after a large number of experiments, preferably selected the molar ratio of the first active metal source to the second active metal source to be 1:(0.1~0.5), and more preferably 1:(0.18~0.20). By continuously optimizing the dosage of the two active metal sources, a more effective synergistic effect can be formed between the metals, the electronic structure of the catalyst is optimized, the comprehensive performance of the catalyst is improved, and its catalytic efficiency in the oxidation reaction of cresol is significantly enhanced. The molar ratio of the cobalt source to the copper source in the preferred first active metal source is (0.2~10):1, and more preferably (1~2):1, which can make Cu 2+ Better match with the second active metal source to change Co 3+ / Co 2+ The surrounding electron cloud density promotes the more effective formation of active sites on the catalyst surface, improves the selectivity of the p-cresol oxidation reaction, makes the obtained catalyst more suitable for the fine control of the p-cresol oxidation reaction, reduces the generation of by-products, and thereby increases the yield of the target product p-hydroxybenzaldehyde.

[0027] In several typical embodiments, the amount of the carrier source is 5% to 100%, preferably 30% to 80%, based on the total weight of the first active metal source and the second active metal source as 100%. This preferred and more preferred amount of the carrier source can promote the in-situ construction of the catalyst carrier during the formation of the active metal center, thereby obtaining a more stable layered structure. At the same time, it can also provide sufficient support for the active metal center in the obtained catalyst to prevent it from aggregating during subsequent catalytic applications, thereby maintaining the activity and stability of the catalyst, so that the obtained p-cresol oxidation catalyst exhibits more efficient catalytic performance in a more stringent application environment.

[0028] In order to better optimize the overall electronic structure of the obtained catalyst and make the electron transfer in the catalytic reaction more efficient, the inventors, after a large number of experiments, further introduced an iron source into the second active metal source, that is, the second active metal source is preferably a cerium source and an iron source, and the molar ratio of the cerium source to the iron source is (1-5):1, more preferably (2-3):1. This preferred second active metal combination can further enhance the activity of the obtained catalyst, increase the conversion rate of the p-cresol oxidation reaction, and thus achieve highly selective catalysis at a high conversion rate. In particular, the second active metal source component, Fe3O4, has reversible redox properties because it has Fe 3+ / Fe 4+ This mutually convertible electronic structure can provide electrons during the reaction and promote redox. At the same time, in the redox reaction, the surface of Fe3O4 can adsorb and activate oxygen molecules, converting them into highly reactive oxygen species to further promote the reaction. Therefore, it can act as a synergistic catalyst with CeO2, thereby more efficiently transferring electrons and activated oxygen molecules, and ultimately improving the yield and purity of the target product p-hydroxybenzaldehyde.

[0029] In several typical embodiments, the first active metal source, the second active metal source and the carrier source are each independently added in the form of one or more of nitrate, phosphate, sulfate, acetate and chloride. The precipitant is preferably selected from one or more of sodium carbonate, sodium hydroxide and sodium bicarbonate, and the concentration of the second solution is preferably 1.0M~1.1M. Compared with other precipitants that show alkalinity and can increase the pH of the third solution, the above precipitant type can more effectively control the precipitation process of each active metal ion in the form of a solution of the above concentration, forming a more uniform precursor, thereby more effectively improving the structural stability and catalytic activity of the obtained catalyst.

[0030] With respect to the hydrothermal reaction in step S4 of the preparation method provided by the present invention, the inventors further preferred the hydrothermal reaction temperature to be 120±5°C and the time to be 5h~6h after a large number of experiments. The hydrothermal reaction under this condition can more effectively promote the in-situ generation of a stable layered structure carrier and make the active metal ions more evenly distributed on the carrier, so as to significantly improve the catalytic activity of the obtained catalyst.

[0031] In order to effectively remove moisture from the catalyst before calcination, avoid the influence of water evaporation at high temperature on the catalyst structure and the generation of impurities, and thereby make the catalyst exhibit higher stability and activity, it is preferred that in step S5, the drying is vacuum drying, and the vacuum drying temperature is 70°C~80°C, and the time is 12h~24h.

[0032] At the same time, in order to promote the crystallization of the catalyst, form a stable crystalline phase structure, and improve the thermal stability and catalytic efficiency of the catalyst during subsequent use, it is further preferred that in step S5, the heating rate of calcination is 12°C / min~15°C / min, the insulation temperature is 500°C~550°C, and the insulation time is 3h~4h. It is more preferred that the calcination is carried out under a protective atmosphere, and the amount of the protective atmosphere introduced is 100mL / min~300mL / min, and the protective atmosphere is more preferably nitrogen and / or argon. Introducing a protective atmosphere into the calcination system with a specific amount of introduction can more effectively avoid oxidation of the catalyst during high temperature crystallization, thereby maintaining its reducibility, so that it has higher structural stability and longer service life during use.

[0033] The second aspect of the present invention provides a p-cresol oxidation catalyst, which is prepared by the preparation method of the p-cresol oxidation catalyst. The obtained p-cresol oxidation catalyst has high activity, high selectivity and good stability, is conducive to the adsorption and oxidation reaction of p-cresol molecules on its surface, so that hydroxybenzaldehyde can be obtained by catalytic oxidation with high yield and high selectivity, and is also suitable for the catalytic mechanism research of p-cresol oxidation reaction, providing a theoretical basis for the development of more efficient catalysts.

[0034] It should be emphasized that the carrier source introduced in the present invention generates an aluminum oxide carrier with a special layered structure in situ during the above-mentioned preparation reaction, and its conversion rate is close to 100%. Therefore, in the final p-cresol oxidation catalyst, the active metal loading on the carrier is 5% to 50%, preferably 10% to 20%.

[0035] Furthermore, the specific surface area of ​​the p-cresol oxidation catalyst is 160 m 2 / g ~240m 2 / g. That is, the obtained catalyst exhibits a high specific surface area, thereby being able to provide more active sites, enhancing its catalytic activity, being suitable for improving the catalyst performance of p-cresol oxidation reaction, and realizing a more efficient catalytic conversion process.

[0036] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0037] Unless otherwise defined, all professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0038] Example 1

[0039] A preparation method of p-cresol oxidation catalyst:

[0040] (1) Weigh 53.1g (0.3mol) of cobalt acetate and 37.5g (0.2mol) of anhydrous copper nitrate as the first active metal source (wherein the molar ratio of the cobalt source to the copper source is 1.5:1); weigh 26g (0.06mol) of cerium nitrate hexahydrate and 8.1g (0.03mol) of ferric chloride hexahydrate as the second active metal source (wherein the molar ratio of the cerium source to the iron source is 2:1); at this time, the ratio of the total molar amount of the first active metal source to the total molar amount of the second active metal source is 1:0.18. Then weigh 43g of aluminum nitrate nonahydrate as the carrier source (which accounts for 34.5% of the total weight of the first active metal source and the second active metal source). Mix the above raw materials and add them to 500mL of deionized water, and heat and stir in a water bath to fully dissolve to obtain a first solution;

[0041] (2) Weigh 106 g of sodium carbonate as a precipitant and add deionized water to prepare a 1 M second solution;

[0042] (3) The first solution is placed in a neutralization reaction kettle and heated and stirred to preheat. After a period of time, the second solution is added dropwise until the pH of the system is 9. The heating and stirring are continued for 30 minutes to obtain a third solution.

[0043] (4) placing the third solution in a hydrothermal kettle and subjecting it to a hydrothermal reaction at 120° C. for 6 h, opening the kettle after the kettle has cooled, and filtering to obtain a precipitate, i.e., the first product;

[0044] (5) washing the first product with deionized water until it is neutral; vacuum drying the product after washing and filtration at 80°C for 12 h; calcining the dried product under nitrogen gas protection conditions, with the nitrogen gas flow rate maintained at 200 mL / min; calcination conditions: heating rate of 15°C / min, holding temperature of 550°C, and calcination time of 3 h;

[0045] (6) The calcined product is crushed and ground, granulated, and pressed into tablets to obtain a catalyst, which is a heterogeneous cresol oxidation catalyst.

[0046] During the calcination process, the support source was completely converted into a layered alumina support with a loading of 10 wt% of active metal sites thereon.

[0047] Example 2

[0048] A preparation method of p-cresol oxidation catalyst:

[0049] (1) Weigh 53.1g (0.3mol) of cobalt acetate and 37.5g (0.2mol) of anhydrous copper nitrate as the first active metal source (wherein the molar ratio of the cobalt source to the copper source is 1.5:1); weigh 32.6g (0.075mol) of cerium nitrate hexahydrate and 6.5g (0.025mol) of ferric chloride hexahydrate as the second active metal source (wherein the molar ratio of the cerium source to the iron source is 3:1); at this time, the ratio of the total molar amount of the first active metal source to the total molar amount of the second active metal source is 1:0.2. Then weigh 100.7g of aluminum nitrate nonahydrate as the carrier source (which accounts for 77.6% of the total weight of the first active metal source and the second active metal source). Mix the above raw materials and add them to 500mL of deionized water, and heat and stir in a water bath to fully dissolve to obtain a first solution;

[0050] (2) Weigh 106 g of sodium carbonate as a precipitant and add deionized water to prepare a 1 M second solution;

[0051] (3) The first solution is placed in a neutralization reaction kettle and heated and stirred to preheat. After a period of time, the second solution is added dropwise until the pH of the system is 10. The heating and stirring are continued for 30 minutes to obtain a third solution.

[0052] (4) placing the third solution in a hydrothermal kettle and subjecting it to a hydrothermal reaction at 125°C for 5 hours, opening the kettle after the kettle has cooled, and filtering to obtain a precipitate, i.e., the first product;

[0053] (5) washing the first product with deionized water until it is neutral; vacuum drying the product after washing and filtration at 70°C for 24 hours; calcining the dried product under nitrogen gas protection conditions, with the nitrogen gas flow rate maintained at 200 mL / min; calcination conditions: heating rate of 12°C / min, holding temperature of 500°C, and calcination time of 4 hours;

[0054] (6) The calcined product is crushed and ground, granulated, and pressed into tablets to obtain a catalyst, which is a heterogeneous cresol oxidation catalyst.

[0055] During the calcination process, the support source was completely converted into a layered alumina support with a loading of 20 wt% of active metal sites thereon.

[0056] Example 3

[0057] A preparation method of p-cresol oxidation catalyst:

[0058] The difference between this embodiment and embodiment 1 is only that:

[0059] The amount of the copper source, i.e., anhydrous copper nitrate, in the first active metal source was changed to 84.4 g (0.45 mol).

[0060] At this time, the molar ratio of the cobalt source and the copper source in the first active metal source is changed to 0.67:1, and the ratio of the total molar amount of the first active metal source to the total molar amount of the second active metal source is changed to 1:0.12. Based on the total weight of the first active metal source and the second active metal source as 100%, the amount of the carrier source is changed to 25%.

[0061] Example 4

[0062] A preparation method of p-cresol oxidation catalyst:

[0063] The difference between this embodiment and embodiment 2 is only that:

[0064] The amount of the copper source, i.e., anhydrous copper nitrate, in the first active metal source was changed to 14 g (0.075 mol).

[0065] At this time, the molar ratio of the cobalt source and the copper source in the first active metal source is changed to 4:1, and the ratio of the total molar amount of the first active metal source to the total molar amount of the second active metal source is changed to 1:0.27. Based on the total weight of the first active metal source and the second active metal source as 100%, the amount of the carrier source is changed to 94.8%.

[0066] Example 5

[0067] A preparation method of p-cresol oxidation catalyst:

[0068] The difference between this embodiment and embodiment 1 is only that:

[0069] No iron source is added to the second active metal source, but cerium nitrate of equal weight is used to replace ferric chloride.

[0070] That is, the second active metal source is only a cerium source.

[0071] Example 6

[0072] A preparation method of p-cresol oxidation catalyst:

[0073] The difference between this embodiment and embodiment 1 is only that:

[0074] In the second active metal source, the amount of cerium source, cerium nitrate hexahydrate, was changed to 13 g (0.03 mol), and the amount of iron source, ferric chloride hexahydrate, was changed to 16.2 g (0.06 mol).

[0075] At this time, the molar ratio of the cerium source to the iron source in the second active metal source was changed to 0.5:1.

[0076] Example 7

[0077] A preparation method of p-cresol oxidation catalyst:

[0078] The difference between this embodiment and embodiment 1 is only that:

[0079] In the second active metal source, the amount of cerium source, cerium nitrate hexahydrate, was changed to 37.2 g (0.086 mol), and the amount of iron source, ferric chloride hexahydrate, was changed to 3.8 g (0.014 mol).

[0080] At this time, the molar ratio of the cerium source to the iron source in the second active metal source was changed to 6.1:1.

[0081] Example 8

[0082] A preparation method of p-cresol oxidation catalyst:

[0083] The difference between this embodiment and embodiment 1 is that the condition in step (4) is changed to:

[0084] The third solution was placed in a hydrothermal kettle and subjected to hydrothermal reaction at 100°C for 8 hours. The kettle was opened after cooling down and the precipitate, i.e. the first product, was obtained by filtration.

[0085] Example 9

[0086] A preparation method of p-cresol oxidation catalyst:

[0087] The difference between this embodiment and embodiment 1 is that the condition in step (4) is changed to:

[0088] The third solution was placed in a hydrothermal kettle and subjected to hydrothermal reaction at 140° C. for 4 h. After the kettle was cooled, the kettle was opened and the precipitate, i.e., the first product, was obtained by filtration.

[0089] Example 10

[0090] A preparation method of p-cresol oxidation catalyst:

[0091] The only difference between this embodiment and embodiment 1 is that the drying conditions in step (5) are changed to:

[0092] Dry under vacuum at 100°C for 8 h.

[0093] Embodiment 11

[0094] A preparation method of p-cresol oxidation catalyst:

[0095] The only difference between this embodiment and embodiment 1 is that the calcination conditions in step (5) are changed to:

[0096] The heating rate was 10°C / min, the holding temperature was 400°C, and the calcination time was 5h.

[0097] Example 12

[0098] A preparation method of p-cresol oxidation catalyst:

[0099] The only difference between this embodiment and embodiment 1 is that the calcination conditions in step (5) are changed to:

[0100] The heating rate was 18°C / min, the holding temperature was 700°C, and the calcination time was 1h.

[0101] Comparative Example 1

[0102] A preparation method of p-cresol oxidation catalyst:

[0103] The difference between this comparative example and Example 1 is that in step (1), no carrier source, i.e., aluminum nitrate, is added. Instead, an equal weight of Al2O3 powder (purchased from Innochem, model A47917) is used instead.

[0104] That is, the carrier in this comparative example was not generated in situ during the reaction.

[0105] Comparative Example 2

[0106] A preparation method of p-cresol oxidation catalyst:

[0107] The only difference between this comparative example and Example 1 is that in step (1), an equal weight of zirconium nitrate is used instead of aluminum nitrate as the carrier source.

[0108] Comparative Example 3

[0109] A preparation method of p-cresol oxidation catalyst:

[0110] The only difference between this comparative example and Example 1 is that no cerium source is added to the second active metal source, and an equal weight of ferric chloride is used to replace cerium nitrate.

[0111] That is, the second active metal source is only an iron source.

[0112] Comparative Example 4

[0113] A preparation method of p-cresol oxidation catalyst:

[0114] The only difference between this comparative example and Example 1 is that no cobalt source is added to the first active metal source, and an equal weight of copper nitrate is used to replace cobalt acetate.

[0115] That is, the first active metal source is only a copper source.

[0116] Comparative Example 5

[0117] A preparation method of p-cresol oxidation catalyst:

[0118] The only difference between this comparative example and Example 1 is that no copper source is added to the first active metal source, and an equal weight of cobalt acetate is used to replace copper nitrate.

[0119] That is, the first active metal source is only a cobalt source.

[0120] The specific surface area of ​​the obtained catalyst can be obtained based on the low-temperature nitrogen adsorption-desorption curve test.

[0121] Catalytic performance evaluation method: 50 g of the catalysts obtained in the above embodiments and comparative examples were respectively weighed and added into a fixed bed reactor, and a continuous reaction of oxidizing p-cresol to generate hydroxybenzaldehyde was carried out under the conditions of a reaction temperature of 80°C and a pressure of 0.5 MPa. After the reaction stabilized, samples were taken and sent to liquid chromatography to test the purity of p-hydroxybenzaldehyde, and then the yield of the p-hydroxybenzaldehyde product was calculated by liquid external standard.

[0122] The results of the above tests are shown in Table 1.

[0123] Table 1

[0124]

[0125] From the above description, it can be seen that the above embodiments of the present invention achieve the preparation of a p-cresol oxidation catalyst with a high specific surface area. When the obtained catalyst is used to catalyze the continuous reaction of p-cresol oxidation to generate hydroxybenzaldehyde, a high-purity hydroxybenzaldehyde product can be prepared with a high yield.

[0126] Specifically, compared with Example 1, Examples 3 and 4 changed the molar ratio of the first active component cobalt and copper, the ratio of the first active component to the second active component, and the proportion of the carrier. According to the continuous experimental results, the catalyst reaction effect is slightly lower than the catalyst prepared in Example 1, so the molar ratio of the cobalt source to the copper source is preferably (1-2): 1; Compared with Example 1, Examples 6 and 7 changed the molar ratio of the second active component cerium and iron, and Example 5 replaced the loaded iron source in the second active component with a cerium source. The comparison results showed that the catalyst reaction effects prepared in Examples 6 and 7 were lower than those in Example 1, and the reaction effect of Example 5 was relatively worse, indicating that the doping of the auxiliary agents cerium and iron was beneficial to the reaction, and the two elements synergistically promoted the reaction. Forward; Compared with Example 1, Examples 8 and 9 changed the conditions of the hydrothermal treatment. The hydrothermal step acts as a process for the growth of active components and carrier crystals. According to the results, the growth of active components and carrier crystals needs to be carried out at appropriate temperature and time; Example 10 changed the drying conditions in the preparation process. Compared with other examples, the change in drying conditions had a slight effect on the material properties; Compared with Example 1, Examples 11 and 12 respectively selected different calcination processes for post-treatment of the materials. According to the results, the calcination temperature is too low and the time is too short, which may lead to insufficient pyrolysis of the material. The calcination temperature is too high, which may lead to agglomeration of the active components, reducing the dispersion of the active components. At the same time, too high a temperature will lead to a reduction in the specific surface area of ​​the carrier.

[0127] In the comparative examples, the carrier in comparative example 1 uses non-in-situ generated γ-alumina, which has poor dispersibility of active components compared with the layered carrier structure of embodiment 1, and the synergistic catalytic effect between multiple metal ions is poor, so the catalyst effect is significantly worse; in comparative example 2, zirconium nitrate is used instead of aluminum nitrate as the catalyst carrier, and the specific surface area of ​​the carrier is low, so the reaction effect is poor; comparative examples 3, 4, and 5 show that the catalyst is the result of the synergistic catalytic reaction of the first and second active component metals during the reaction process, so changing to a single metal component has poor actual evaluation results.

[0128] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those described herein, for example.

[0129] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a p-cresol oxidation catalyst, characterized in that: include: Step S1, adding a first active metal source, a second active metal source and a carrier source into water to obtain a first solution; Step S2, adding a precipitant into water to obtain a second solution; Step S3, mixing the first solution with the second solution to obtain a third solution with a pH of 9 to 10; Step S4, subjecting the third solution to a hydrothermal reaction at 100° C. to 140° C. to obtain a first product; Step S5, washing, drying and calcining the first product in sequence to obtain the p-cresol oxidation catalyst; Wherein, the first active metal source is a cobalt source and a copper source, the second active metal source includes a cerium source, and the carrier source is an aluminum source.

2. The method for preparing a p-cresol oxidation catalyst according to claim 1, characterized in that: The molar ratio of the first active metal source to the second active metal source is 1:(0.1-0.5); In the first active metal source, the molar ratio of the cobalt source to the copper source is (0.2-10):

1.

3. The method for preparing a p-cresol oxidation catalyst according to claim 2, characterized in that: Based on the total weight of the first active metal source and the second active metal source being 100%, the amount of the carrier source used is 5% to 100%.

4. The method for preparing a p-cresol oxidation catalyst according to any one of claims 1 to 3, characterized in that: The second active metal source is the cerium source and the iron source, and the molar ratio of the cerium source to the iron source is (1-5):

1.

5. The method for preparing a p-cresol oxidation catalyst according to any one of claims 1 to 3, characterized in that: The first active metal source, the second active metal source and the carrier source are each independently added in the form of one or more of nitrate, phosphate, sulfate, acetate and chloride; And / or, the precipitating agent is selected from one or more of sodium carbonate, sodium hydroxide and sodium bicarbonate.

6. The method for preparing a p-cresol oxidation catalyst according to any one of claims 1 to 3, characterized in that: In step S4, the temperature of the hydrothermal reaction is 120±5° C., and the time is 5 h to 6 h.

7. The method for preparing a p-cresol oxidation catalyst according to any one of claims 1 to 3, characterized in that: In step S5, the drying is vacuum drying, and the temperature of the vacuum drying is 70° C. to 80° C., and the time is 12 h to 24 h.

8. The method for preparing a p-cresol oxidation catalyst according to any one of claims 1 to 3, characterized in that: In step S5, the calcination temperature rise rate is 12°C / min to 15°C / min, the holding temperature is 500°C to 550°C, and the holding time is 3h to 4h; And / or, the calcination is carried out under a protective atmosphere, and the amount of the protective atmosphere introduced is 100 mL / min to 300 mL / min.

9. A p-cresol oxidation catalyst, characterized in that: The p-cresol oxidation catalyst is prepared by the preparation method of the p-cresol oxidation catalyst according to any one of claims 1 to 8.

10. The p-cresol oxidation catalyst according to claim 9, characterized in that: The specific surface area of ​​the p-cresol oxidation catalyst is 160 m 2 / g ~240m 2 / g.

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