Oxidation catalysts, methods of making and using the same, and methods of synthesizing methylacrylic acid

Abstract

This invention relates to the field of catalysts, specifically to an oxidation catalyst, its preparation method and application, and a method for synthesizing methacrylic acid. The catalyst comprises a support and an active component, said active component comprising components having the general formula H... 3+a‑2b‑nc Q c Cu b [PV a Mo 12‑a O 40 The component Q is selected from at least one of Cs, Sb, Zn, Ca, Co, K, Na, and Fe; a = 0–6; b = 0–2; c is 0 to 4 / n; n is the valence state of Q; wherein the XRD pattern of the catalyst includes values ​​at 2θ = 9.5°±0.2°, 10.6°±0.2°, 13.0°±0.2°, 15.1°±0.2°, 18.5°±0.2°, and 21.4°±0.2°. Signal peaks are observed at 23.3°±0.2°, 23.9°±0.2°, 25.6°±0.2°, 26.3°±0.2°, 27.3°±0.2°, 30.5°±0.2°, 32.4°±0.2°, 35.9°±0.2°, 39.1°±0.2°, 43.7°±0.2°, 47.9°±0.2°, 55.4°±0.2°, and 62.4°±0.2°. Using the catalyst of this invention in the synthesis of alkyl acrylic acid, especially methacrylic acid, can significantly improve the product yield.

Description

Technical Field

[0001] This invention relates to the field of catalysts, specifically to an oxidation catalyst, its preparation method and application, and a method for synthesizing methacrylic acid. Background Technology

[0002] Methyl methacrylate (MMA) is an important organic chemical raw material, mainly used in the production of polymethyl methacrylate (PMMA), polyvinyl chloride (PVC) additive ACR, and as a second monomer in the production of acrylonitrile fibers. It can also be used in the production of coatings, adhesives, lubricants, and textile dyes. Its main downstream product, acrylic glass, is an important thermoplastic that was developed early on. It possesses characteristics such as beautiful appearance, excellent light transmittance, chemical stability, heat resistance, ease of dyeing, and ease of processing, and is widely used in the automotive, construction, sanitary ware, and public works industries. In recent years, polymer products synthesized from MMA have also been widely used in IT-related fields such as optical guide plates for LCD displays and DVD discs. With the diversification and development of downstream MMA products, global demand and production capacity for MMA are continuously increasing.

[0003] Currently, in industrialized MMA production processes, the traditional ACH process relies heavily on the acrylonitrile operating conditions for its feedstock, hydrogen cyanide, leading to higher production costs and diminishing its advantages. BASF's technology lacks significant economic benefits, and Alpha technology is still in its early stages of industrialization, requiring further evaluation for its maturity and overall economic viability. Compared to other processes, the direct oxidation method using C4 as a feedstock offers advantages such as a wide availability of raw materials and better economics. Furthermore, the abundant C4 resources resulting from the commissioning of numerous ethylene cracking units in China provide a reliable feedstock for isobutylene-to-MMA production, making C4-based MMA production a promising application prospect. The catalyst for the oxidation of methacrolein to methacrylic acid is a crucial step in the C4 route for MMA production.

[0004] Currently, Mo-P heteropolyacid catalysts have better catalyst performance, with high conversion and selectivity. However, due to the lack of stable crystal morphology in heteropolyacids, their service life is relatively short. Improving the stability of phosphomolybdenum heteropolyacids is a key technical challenge. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of short service life, low activity, and low product selectivity of existing oxidation catalysts, and to provide an oxidation catalyst, its preparation method and application, and a method for synthesizing methacrylic acid. This catalyst has the characteristics of long service life, high activity, and high product selectivity.

[0006] To achieve the above objectives, a first aspect of the present invention provides an oxidation catalyst comprising a support and an active component, said active component comprising a component having the general formula H... 3+a-2b-nc Q cCu b [PV a Mo 12-a O 40 The component Q is selected from at least one of Cs, Sb, Zn, Ca, Co, K, Na, and Fe; a = 0-6; b = 0-2; c is 0 to 4 / n; n is the valence state of Q; wherein the XRD pattern of the catalyst includes the following values ​​at 2θ = 9.5°±0.2°, 10.6°±0.2°, 13.0°±0.2°, 15.1°±0.2°, 18.5°±0.2°, and 21.4°±0. Signal peaks are observed at 2°, 23.3°±0.2°, 23.9°±0.2°, 25.6°±0.2°, 26.3°±0.2°, 27.3°±0.2°, 30.5°±0.2°, 32.4°±0.2°, 35.9°±0.2°, 39.1°±0.2°, 43.7°±0.2°, 47.9°±0.2°, 55.4°±0.2°, and 62.4°±0.2°.

[0007] A second aspect of the present invention provides a method for preparing the catalyst described herein, the method comprising:

[0008] (1) Dissolve molybdenum source and vanadium source in water, and add phosphorus source. Mix for the first time to obtain solution A. Then add solution B containing copper source and optional Q source for the second mixing. Finally, introduce reducing agent for the third mixing to obtain mixed solution H.

[0009] (2) Crystallize the mixture H and dry it to obtain the catalyst precursor;

[0010] (3) The catalyst precursor obtained after impregnation is mixed with the support source and optionally the binder, and then shaped and calcined to obtain the catalyst.

[0011] A third aspect of the present invention provides the application of the catalyst described herein in the synthesis of alkyl acrylic acid, wherein the alkyl acrylic acid is preferably a C3-C6 alkyl acrylic acid, and more preferably the alkyl acrylic acid is methacrylic acid.

[0012] A fourth aspect of this invention provides a method for synthesizing methacrylic acid, the method comprising: contacting a methacrolein-containing feedstock with the catalyst described herein; preferably, the contact reaction conditions include: a reaction temperature of 240-320°C, more preferably 270-305°C; and / or a volume hourly space velocity (VHSV) of methacrolein of 60-120 h⁻¹. -1 Preferably 80-100h -1 .

[0013] Through the above technical solution, the present invention has the following advantages:

[0014] The catalyst with the features of this invention has a stable large-grained Keggin-type heteropolyacid structure and large pores, and has a long service life, high activity, and high product selectivity.

[0015] Using the catalyst of this invention in the synthesis of alkyl acrylic acid, especially methacrylic acid, can significantly improve the product yield. Attached Figure Description

[0016] Figure 1 Here is an SEM image of the catalyst prepared in Example 1;

[0017] Figure 2 This is an SEM image of the catalyst prepared in Comparative Example 1. Detailed Implementation

[0018] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0019] A first aspect of the present invention provides an oxidation catalyst comprising a support and an active component, said active component comprising a component having the general formula H 3+a-2b-nc Q c Cu b [PV a Mo 12-a O 40The component (where H is hydrogen) is selected from at least one of Cs, Sb, Zn, Ca, Co, K, Na, and Fe; a = 0-6; b = 0-2; c is 0 to 4 / n; n is the valence state of Q; wherein the XRD pattern of the catalyst includes the following values ​​at 2θ = 9.5°±0.2°, 10.6°±0.2°, 13.0°±0.2°, 15.1°± 0.2°, 18.5°±0.2°, 21.4°±0.2°, 23.3°±0.2°, 23.9°±0.2°, 25.6°±0.2°, 26.3°±0.2°, 27.3°±0.2°, 30.5°±0.2°, 32.4°±0.2°, 35.9°±0.2°, 39.1°±0.2°, 43.7° Signal peaks are observed at ±0.2°, 47.9°±0.2°, 55.4°±0.2°, and 62.4°±0.2°, with preferred peaks at 2θ = 9.5°±0.1°, 10.6°±0.1°, 13.0°±0.1°, 15.1°±0.1°, 18.5°±0.1°, 21.4°±0.1°, 23.3°±0.1°, and 23.9°. Signal peaks are observed at ±0.1°, 25.6°±0.1°, 26.3°±0.1°, 27.3°±0.1°, 30.5°±0.1°, 32.4°±0.1°, 35.9°±0.1°, 39.1°±0.1°, 43.7°±0.1°, 47.9°±0.1°, 55.4°±0.1°, and 62.4°±0.1°.

[0020] According to a preferred embodiment of the present invention, the active component in the catalyst comprises a Keggin-type heteropolyacid structure with large hexahedral crystals. By adopting the aforementioned preferred embodiment, the stability, service life, and activity of the catalyst can be further improved.

[0021] According to a preferred embodiment of the present invention, the end face of the Keggin-type heteropolyacid structure is quadrilateral, and the side length is 100-3000 nm.

[0022] According to a preferred embodiment of the present invention, the end face of the Keggin-type heteropolyacid structure is rectangular, with a length-to-width ratio of 1-20. By adopting the aforementioned preferred embodiment, the stability, service life, and activity of the catalyst can be further improved.

[0023] In this invention, the carrier can be a conventional choice in the art. According to a preferred embodiment of the invention, the carrier is selected from at least one of SiO2, Al2O3, ZrO2 and TiO2.

[0024] In this invention, as long as the purpose of this invention can be achieved, there is no particular limitation on the amount of support and active component in the catalyst. According to a preferred embodiment of this invention, the catalyst contains 20-90 parts by mass of active component and 10-80 parts by mass of support.

[0025] A second aspect of the present invention provides a method for preparing the catalyst described herein, the method comprising:

[0026] (1) Dissolve molybdenum source and vanadium source in water, and add phosphorus source. Mix for the first time to obtain solution A. Then add solution B containing copper source and optional Q source for the second mixing. Finally, introduce reducing agent for the third mixing to obtain mixed solution H.

[0027] (2) Crystallize the mixture H and dry it to obtain the catalyst precursor;

[0028] (3) The catalyst precursor obtained after impregnation is mixed with the support source and optionally the binder, and then shaped and calcined to obtain the catalyst.

[0029] The catalyst prepared by the method of this invention can further improve the stability, service life and catalytic activity of the catalyst.

[0030] In this invention, the method of adding solution B includes adding solution B to solution A dropwise.

[0031] In this invention, as long as the purpose of this invention can be achieved, there are no special requirements for the type of reducing agent. According to a preferred embodiment of this invention, the reducing agent contains an organic aldehyde, preferably a C1-C5 aldehyde, and more preferably at least one of formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde and pentanal.

[0032] According to a preferred embodiment of the present invention, the reducing agent comprises formaldehyde and / or acetaldehyde. By adopting the aforementioned preferred embodiment, the stability, lifespan, and catalytic activity of the prepared catalyst can be further improved.

[0033] In this invention, the range of phosphorus sources is relatively wide. According to a preferred embodiment of this invention, the phosphorus source comprises a phosphorus compound, preferably at least one of phosphoric acid and phosphate.

[0034] In this invention, the range of molybdenum sources is relatively wide. According to a preferred embodiment of this invention, the molybdenum source comprises a molybdenum compound, preferably at least one of ammonium heptamolybdate, molybdenum trioxide, and ammonium tetramolybdate.

[0035] In this invention, the range of vanadium sources is relatively wide. According to a preferred embodiment of this invention, the vanadium source comprises a vanadium compound, preferably at least one of ammonium metavanadate, vanadium pentoxide, and vanadium trioxide.

[0036] In this invention, the range of selectable copper sources is relatively wide. According to a preferred embodiment of this invention, the copper source comprises a copper compound, preferably at least one selected from copper nitrate, copper chloride, copper oxide, and cuprous oxide; and / or

[0037] In this invention, the range of possible Q sources is relatively wide. According to a preferred embodiment of this invention, the Q source comprises an oxygen-containing salt and / or an oxygen-containing salt hydrate selected from at least one element selected from Cs, Sb, W, Ca, Te, K, Na, and Fe.

[0038] In this invention, the range of selectable carrier sources is relatively wide. According to a preferred embodiment of this invention, the carrier source is selected from at least one of SiO2 source, Al2O3 source, ZrO2 source and TiO2 source.

[0039] In this invention, the range of selectable adhesives is relatively wide. According to a preferred embodiment of this invention, the adhesive is selected from at least one of hydroxypropyl cellulose, graphite, and water.

[0040] In this invention, the conditions for the first mixing can be conventional choices in the art. According to a preferred embodiment of the invention, the conditions for the first mixing include: a temperature of 60-100°C and a time of 0.5-48h.

[0041] In this invention, the conditions for the second mixing can be conventional choices in the art. According to a preferred embodiment of the invention, the conditions for the second mixing include: a temperature of 60-100°C and a time of 0.5-48h.

[0042] In this invention, the conditions for the third mixing can be conventional choices in the art. According to a preferred embodiment of the invention, the conditions for the third mixing include: a temperature of 60-100°C and a time of 0.5-48h.

[0043] In this invention, the crystallization conditions can be conventionally chosen in the art. According to a preferred embodiment of this invention, the crystallization conditions include: a temperature of 60-200°C and a time of 2-200 hours.

[0044] In this invention, the drying conditions can be conventional choices in the art, as long as they can achieve the purpose of this invention.

[0045] In this invention, the calcination conditions can be conventionally selected in the art. According to a preferred embodiment of this invention, the calcination conditions include: a temperature of 250-400°C and / or a calcination time of 2-100 hours.

[0046] By applying the aforementioned preferred conditions of this invention, the stability, lifespan, and catalytic activity of the prepared catalyst can be further improved.

[0047] In this invention, the molding method can be a conventional choice in the art. According to a preferred embodiment of the invention, the molding method is selected from at least one of tableting, extrusion, and ball rolling.

[0048] In this invention, the catalyst is shaped into at least one of the following: a circular sheet, a Raschig ring, or a sphere.

[0049] A third aspect of the present invention provides the application of the catalyst described herein in the synthesis of alkyl acrylic acid, wherein the alkyl acrylic acid is preferably a C3-C6 alkyl acrylic acid, and more preferably the alkyl acrylic acid is methacrylic acid.

[0050] Using the catalyst of this invention in the synthesis of alkyl acrylic acid, especially methacrylic acid, can significantly improve the product yield.

[0051] A fourth aspect of the present invention provides a method for synthesizing methacrylic acid, the method comprising: reacting a raw material containing methacrolein with the catalyst described in the present invention.

[0052] In this invention, the contact conditions can be conventionally chosen in the art. According to a preferred embodiment of the invention, the contact reaction conditions include: a reaction temperature of 240-320°C, preferably 270-305°C; and / or a volume hourly space velocity (HSV) of methacrolein of 60-120 mL·h. -1 ·g -1 Preferably 80-100 mL·h -1 ·g -1 .

[0053] The present invention will be described in detail below through examples. In the following examples, the content of each component in the product (including CO) is specified. x The results were obtained by gas chromatography; unless otherwise specified, all raw materials are commercially available products.

[0054] The catalyst evaluation method used in the following examples is as follows:

[0055] The reactant methacrolein was passed into a fixed-bed reactor packed with the catalyst to be tested. The product was absorbed with dilute acid at 0°C and then analyzed by gas chromatography. During the analysis, the carbon balance was calculated, and data with a carbon balance of 95-105% were selected as valid data. The reaction conditions were as follows:

[0056] Reactor: Fixed-bed reactor, inner diameter 25.4 mm, length 750 mm;

[0057] Catalyst loading: 150 grams;

[0058] Reaction temperature: 300℃;

[0059] Reaction time: 500 hours;

[0060] Raw material volume ratio: Methacrolein:O2:water vapor:N2 = 1:2.5:5:18;

[0061] Methacrolein volume hourly space velocity: 80 mL·h -1 ·g -1 .

[0062] Conversion rate = (Methacrolein consumed in the reaction / Methacrolein added to the reaction) * 100%

[0063] Methacrylic acid yield = (number of moles of methacrylic acid produced in the reaction) / (theoretically number of moles of methacrylic acid produced) * 100%;

[0064] CO x (%) = CO generated in the reaction x Number of moles / theoretically generated CO x number of moles * 100%

[0065] Example 1

[0066] (1) Mix 6.6 g of ammonium metavanadate (NH4VO3) and 120 g of ammonium heptamolybdate ((NH4)6Mo7O 24 Dissolve 4H₂O in 300ml of deionized water, add 6.5g of phosphoric acid solution (85wt%), heat to 80°C, and stir continuously for 2 hours to obtain solution A. Dissolve 6.8g of copper nitrate trihydrate and 16.5g of cesium nitrate in 100ml of deionized water to obtain solution B. Add solution B dropwise to solution A, stir continuously at 80°C for 3 hours, and finally add 50g of formaldehyde to the mixture H, and stir continuously at 80°C for 3 hours.

[0067] (2) Transfer the mixture H to the crystallization vessel, heat it at 150°C for 100 hours, and then take it out and dry it to obtain the catalyst precursor.

[0068] (3) Take 100g of the obtained precursor (II), 5g of hydroxypropyl cellulose, 40g of SiO2, 1.6g of graphite and 3.2g of deionized water and mix them evenly. Set the tableting pressure to 3kN using a tablet press and press to form a circular tablet with a diameter of 5mm and a thickness of 4mm. Finally, calcine at 355℃ for 20 hours to obtain the catalyst for the synthesis of methacrylic acid.

[0069] In the XRD pattern of the catalyst, signal peaks are observed at 2θ = 9.5°, 10.6°, 13.0°, 15.1°, 18.5°, 21.4°, 23.3°, 23.9°, 25.6°, 26.3°, 27.3°, 30.5°, 32.4°, 35.9°, 39.1°, 43.7°, 47.9°, 55.4°, and 62.4°.

[0070] SEM images such as Figure 1 The catalyst contains a hexahedral structure with rectangular end faces, the rectangles being 700-1000 nm long and 300-480 nm wide.

[0071] The catalysts obtained were evaluated using the aforementioned catalyst evaluation methods, and the results are shown in Table 1.

[0072] Example 2

[0073] Use 100g of formaldehyde instead of 50g of formaldehyde, otherwise the same as in Example 1.

[0074] The XRD pattern of the catalyst is similar to that of Example 1, with an error of no more than ±0.2.

[0075] SEM analysis revealed that the catalyst contains a hexahedral structure with rectangular end faces, the rectangles being 1200-1500 nm long and 350-500 nm wide.

[0076] The catalysts obtained were evaluated using the aforementioned catalyst evaluation methods, and the results are shown in Table 1.

[0077] Example 3

[0078] Use 150g of formaldehyde instead of 50g of formaldehyde, otherwise the same as in Example 1.

[0079] The XRD pattern of the catalyst is similar to that of Example 1, with an error of no more than ±0.2.

[0080] SEM analysis revealed that the catalyst contains a hexahedral structure with rectangular end faces, the length of which is 1900-2200 nm and the width is 480-650 nm.

[0081] The catalysts obtained were evaluated using the aforementioned catalyst evaluation methods, and the results are shown in Table 1.

[0082] Example 4

[0083] Acetaldehyde was used instead of formaldehyde, and everything else was the same as in Example 2.

[0084] The XRD pattern of the catalyst is similar to that of Example 1, with an error of no more than ±0.2.

[0085] SEM analysis revealed that the catalyst contains a hexahedral structure with rectangular end faces, the length of which is 980-1200 nm and the width is 390-550 nm.

[0086] The catalysts obtained were evaluated using the aforementioned catalyst evaluation methods, and the results are shown in Table 1.

[0087] Example 5

[0088] Propionaldehyde was used instead of formaldehyde, and everything else was the same as in Example 2.

[0089] The XRD pattern of the catalyst is similar to that of Example 1, with an error of no more than ±0.2.

[0090] SEM analysis revealed that the catalyst contains a hexahedral structure with rectangular end faces, the length of which is 530-850 nm and the width is 470-600 nm.

[0091] The catalysts obtained were evaluated using the aforementioned catalyst evaluation methods, and the results are shown in Table 1.

[0092] Example 6

[0093] Butyraldehyde was used instead of formaldehyde, and everything else was the same as in Example 2.

[0094] The XRD pattern of the catalyst is similar to that of Example 1, with an error of no more than ±0.2.

[0095] SEM analysis revealed that the catalyst contains a hexahedral structure with rectangular end faces, the length of which is 450-780 nm and the width is 230-360 nm.

[0096] The catalysts obtained were evaluated using the aforementioned catalyst evaluation methods, and the results are shown in Table 1.

[0097] Example 7

[0098] The crystallization temperature was 200℃ instead of 150℃, and everything else was the same as in Example 2.

[0099] The XRD pattern of the catalyst is similar to that of Example 1.

[0100] SEM analysis revealed that the catalyst contains a hexahedral structure with rectangular end faces, the length of which is 2220-2800 nm and the width is 970-1300 nm.

[0101] The catalysts obtained were evaluated using the aforementioned catalyst evaluation methods, and the results are shown in Table 1.

[0102] Example 8

[0103] Replace 16.5g of cesium nitrate with 12.6g of zinc nitrate hexahydrate, otherwise the same as in Example 2.

[0104] The XRD pattern of the catalyst is similar to that of Example 1, with an error of no more than ±0.2.

[0105] SEM analysis revealed that the catalyst contains a hexahedral structure with rectangular end faces, the length of which is 1350-1720 nm and the width is 120-240 nm.

[0106] The catalysts obtained were evaluated using the aforementioned catalyst evaluation methods, and the results are shown in Table 1.

[0107] Comparative Example 1

[0108] Formaldehyde is not used; otherwise, it is the same as in Example 1.

[0109] The XRD pattern of the prepared catalyst differs from that of Example 1, and the SEM image is shown below. Figure 2 The catalyst does not have a hexahedral structure.

[0110] The catalysts obtained were evaluated using the aforementioned catalyst evaluation methods, and the results are shown in Table 1.

[0111] Table 1

[0112]

[0113] As can be seen from the results in Table 1, the catalysts prepared using the technical solutions of this invention have significantly better stability, activity, and selectivity.

[0114] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. An oxidation catalyst, characterized in that, The catalyst comprises a support and an active component, the active component comprising components having the general formula H 3+a-2b-nc Q c Cu b [PV a Mo 12-a O 40 The component Q is selected from at least one of Cs, Sb, Zn, Ca, Co, K, Na, and Fe; a = 0-6; b = 0-2; c is 0 to 4 / n; n is the valence state of Q; wherein the XRD pattern of the catalyst includes values ​​at 2θ = 9.5°±0.2°, 10.6°±0.2°, 13.0°±0.2°, 15.1°±0.2°, 18.5°±0.2°, and 21.4°±0.2°. Signal peaks are observed at the following locations: 23.3°±0.2°, 23.9°±0.2°, 25.6°±0.2°, 26.3°±0.2°, 27.3°±0.2°, 30.5°±0.2°, 32.4°±0.2°, 35.9°±0.2°, 39.1°±0.2°, 43.7°±0.2°, 47.9°±0.2°, 55.4°±0.2°, and 62.4°±0.2°. The active component in the catalyst includes a Keggin-type heteropolyacid structure with large hexahedral crystals, the end faces of which are quadrilateral and each side has a length of 100-3000 nm.

2. The catalyst according to claim 1, wherein, The end face of the Keggin-type heteropolyacid structure is rectangular, with a length-to-width ratio of 1-20.

3. The catalyst according to claim 1 or 2, wherein, The support is selected from at least one of SiO2, Al2O3, ZrO2 and TiO2.

4. The catalyst according to claim 1 or 2, wherein, The catalyst comprises, by weight, 20-90 parts of active component and 10-80 parts of support.

5. A method for preparing the catalyst according to any one of claims 1-4, characterized in that, The method includes: (1) Dissolve molybdenum source and vanadium source in water, add phosphorus source, mix for the first time to obtain solution A, add solution B containing copper source for the second mixing, and finally pass in reducing agent for the third mixing to obtain mixed solution H; (2) Crystallize the mixture H and dry it to obtain the catalyst precursor; (3) The obtained catalyst precursor is mixed with the third support source and then shaped and calcined to obtain the catalyst; The reducing agent contains organic aldehydes.

6. The preparation method according to claim 5, wherein, The method includes: (1) Dissolve molybdenum source and vanadium source in water, add phosphorus source, mix for the first time to obtain solution A, then add solution B containing copper source and Q source for the second mixing, and finally pass in reducing agent for the third mixing to obtain mixed solution H; (2) Crystallize the mixture H and dry it to obtain the catalyst precursor; (3) The obtained catalyst precursor is mixed with the support source and binder and then shaped and calcined to obtain the catalyst.

7. The preparation method according to claim 5 or 6, wherein, The reducing agent contains C1-C5 aldehydes; and / or The phosphorus source comprises a phosphorus compound; and / or The molybdenum source contains a molybdenum compound; and / or The vanadium source comprises a vanadium compound; and / or The copper source comprises a copper compound; and / or The carrier source is selected from at least one of SiO2 source, Al2O3 source, ZrO2 source and TiO2 source.

8. The preparation method according to claim 7, wherein, The reducing agent comprises at least one of formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, and valeraldehyde; and / or The phosphorus source comprises at least one of phosphoric acid and phosphate; and / or The molybdenum source comprises at least one of ammonium heptamolybdate, molybdenum trioxide, and ammonium tetramolybdate; and / or The vanadium source comprises at least one of ammonium metavanadate, vanadium pentoxide, and vanadium trioxide; and / or The copper source includes at least one of copper nitrate, copper chloride, copper oxide, and cuprous oxide.

9. The preparation method according to claim 7, wherein, The reducing agent contains formaldehyde and / or acetaldehyde.

10. The preparation method according to claim 6, wherein, The Q source comprises an oxygen-containing salt and / or oxygen-containing salt hydrate selected from at least one element selected from Cs, Sb, W, Ca, Te, K, Na, and Fe.

11. The preparation method according to claim 5 or 6, wherein, The conditions for the first mixing include: a temperature of 60-100°C and a time of 0.5-48 h; and / or The conditions for the second mixing include: a temperature of 60-100°C; a time of 0.5-48 h; and / or The conditions for the third mixing include: a temperature of 60-100℃; a time of 0.5-48h; and / or The crystallization conditions include: a temperature of 60-200℃ and a time of 2-200h; and / or The calcination conditions include a temperature of 250-400℃ and / or a time of 2-100h.

12. The use of the catalyst according to any one of claims 1-4 in the synthesis of alkyl acrylic acid.

13. The application according to claim 12, wherein, The alkyl acrylic acid is a C3-C6 alkyl acrylic acid.

14. The application according to claim 13, wherein, The alkyl acrylic acid is methacrylic acid.

15. A method for synthesizing methacrylic acid, characterized in that, The method includes: reacting a methacrolein-containing raw material with the catalyst described in any one of claims 1-4.

16. The method according to claim 15, wherein, The conditions for the contact reaction include: The reaction temperature is 240-320℃; and / or The volume hourly space velocity (VHSV) of methacrolein is 60-120 mL·h. -1 ·g -1 .

17. The method according to claim 16, wherein, The conditions for the contact reaction include: The reaction temperature is 270-305℃; and / or The volume hourly space velocity (VHSV) of methacrolein is 80-100 mL·h. -1 ·g -1 .

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