Process for the oxidation of methylacrolein and oxidation catalysts, their preparation and use

Abstract

The application provides a method for oxidizing methyl propyl aldehyde, an oxidation catalyst and a preparation method and application thereof, the catalyst has an X-ray diffraction pattern shown in the following table, a relative intensity ratio is a peak height ratio of each peak to a highest peak, a highest peak position of the catalyst is 2theta = 26.30+0.09 degrees, and a d-spacing is 3.38 angstroms. By using the catalyst, the yield of the acrylic ester copolymer is reduced, a good technical effect is achieved, and the catalyst can be used in industrial production of methyl methacrylic acid.

Description

TECHNICAL FIELD

[0001] The present application relates to an oxidation catalyst and a method for preparing and using the same, and a method for oxidizing methacrolein. BACKGROUND

[0002] Methacrolein is an organic compound, mainly used for the manufacture of copolymer and resin, and is a raw material for the production of methacrylic acid and a monomer raw material for thermoplastic plastics. Methacrylic acid is an important organic chemical raw material and an intermediate of polymer, which is used in the fields of organic synthesis and polymer preparation, such as synthetic rubber, thermosetting paint, fabric treatment agent, insulating material, adhesive and ion exchange resin. In recent years, the market demand for methacrylic acid has been increasing worldwide, and the production of methacrylic acid has always been a research hotspot.

[0003] The commonly used production method is acetone cyanhydrin method, which has low atom utilization rate, needs to use strong corrosive sulfuric acid and highly toxic hydrocyanic acid, and also produces solid waste ammonium bisulfate. Oxidation of methacrolein to methacrylic acid is a relatively environmentally friendly green method, and is also a key step for the production of methyl methacrylate. At present, the synthesis of methacrylic acid by methacrolein oxidation method has been successfully applied in industry.

[0004] The catalyst used for the reaction of methacrolein oxidation to methacrylic acid is Keggin type heteropoly acid, such as phosphomolybdic acid, phosphomolybdic acid, etc. The reaction temperature is about 300℃. Heteropoly compounds contain tertiary structure, the primary structure is relatively stable, and the secondary and tertiary structures can be regulated by changing the type and category of catalyst adding elements, so that the specific surface area, acidity, redox property and catalytic activity, etc. are adjusted by changing the type and content of heteroatoms. SUMMARY

[0005] At present, Keggin type heteropoly acid as catalyst has the advantages of small environmental pollution, easy regeneration and low reaction temperature, and has special selectivity in unsaturated oxide reaction, so it has broad industrialization prospect. However, the problem of high content of acrylic ester copolymer (ACR) as one of the reaction by-products of the methacrylic acid catalyst obtained by the prior art still needs to be further solved. One of the technical problems to be solved by the present application is the problem of too much acrylic ester copolymer (ACR) in the synthesis process of the by-product alkyl acrylic acid of the existing catalyst, and a new catalyst is provided, which has the characteristic of less copolymer by-product.

[0006] To solve the above technical problems, according to the first aspect of the present application, an oxidation catalyst is provided, which has the X-ray diffraction pattern shown in the following table,

[0007]

[0008] The relative intensity ratio is the ratio of the height of each peak to the height of the highest peak, and the highest peak of the catalyst is at 2θ = 26.30 ± 0.09°, and the d-spacing is

[0009] The general formula of the catalyst is PMo a V b X c Z d O g ,

[0010] X is one or more selected from Sc, Ti, Y, Zr, Nb, Hf, and Ta;

[0011] Z is at least one selected from La, Ce, Pr, and Nd;

[0012] a is the molar ratio of Mo to P;

[0013] b is the molar ratio of V to P;

[0014] c is the molar ratio of X to P;

[0015] d is the molar ratio of Z to P;

[0016] g is the number of moles of oxygen atoms required to satisfy the valence of each element in the active component;

[0017] The ratio of d to c is (0.05-1):1.

[0018] According to a second aspect of the present application, a preparation method of the catalyst is provided, comprising the following steps: (1) mixing, dissolving, and bubbling an oxygen-containing atmosphere to obtain a premixing solution; then adding a Z element source to the premixing solution, mixing uniformly, and then adding an X element source to obtain a mixing solution I, and then performing a sealing and aging treatment;

[0019] (2) filtering the mixing solution I after aging, supplementing cold water during filtering, and then drying and calcining.

[0020] According to a third aspect of the present application, the catalyst is applied in the synthesis of alkyl acrylic acid, preferably C3-C6 alkyl acrylic acid, and more preferably methacrylic acid.

[0021] According to a fourth aspect of the present application, a method for oxidizing methacrolein is provided, which comprises oxidizing a methacrolein raw material in the presence of the catalyst.

[0022] The present application can well solve the problem of excessive by-product such as acrylic ester copolymer (ACR) in the existing catalyst.

[0023] Adopting the catalyst, the yield of by-product acrylic ester copolymer can be reduced, good technical effect is obtained, and the catalyst can be used in industrial production of methyl methacrylate. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a comparison of X-ray diffraction patterns. DETAILED DESCRIPTION

[0025] The endpoints of the ranges and any values claimed herein are not to be construed as limiting. Ranges can be expressed as from about one particular value to about another; however, when such a range is broader than or includes between about the minimum and maximum values, it is to be construed as specifically claimed. Values within a range are not to be construed as being "partited" unless specifically indicated otherwise. Any numerical values include increments of one unit plus or minus 0.5%, unless otherwise indicated. All ranges are inclusive of the numbers recited as being the limits of a range unless otherwise indicated.

[0026] The present application provides an oxidation catalyst, which has an X-ray diffraction pattern shown in the following table,

[0027]

[0028] The relative intensity ratio is the peak height ratio of each peak to the highest peak, the highest peak of the catalyst is at 2θ = 26.30 ± 0.09°, and the d-spacing is

[0029] The general formula of the catalyst is PMo a V b X c Z d O g ,

[0030] X is one or more selected from Sc, Ti, Y, Zr, Nb, Hf, and Ta;

[0031] Z is at least one selected from La, Ce, Pr, and Nd;

[0032] a is the molar ratio of Mo to P;

[0033] b is the molar ratio of V to P;

[0034] c is the molar ratio of X to P;

[0035] d is the molar ratio of Z to P;

[0036] g is the molar number of oxygen atoms required to satisfy the valence of each element in the active component;

[0037] The ratio of d to c is (0.05-1):1.

[0038] The present application can well solve the problem of excessive by-product acrylic ester copolymer (ACR) of the existing catalyst.

[0039] The yield of the by-product acrylic ester copolymer can be reduced by using the catalyst of the present application, and a good technical effect is achieved, which can be used in the industrial production of methyl methacrylate.

[0040] According to the preferred embodiment of the present application, the 2θ (°) position of peak 2 and peak 3 is in the range of 8.80-12.5, for example, 8.8, 9.0, 9.5, 10.1, 10.2, 10.7, 10.9, 11.5, 12.0, 12.5, and the relative intensity ratio of peak 2 and peak 3 is (1.1-1.4):1, for example, 1.1:1, 1.2:1, 1.3:1, 1.4:1. By using this preferred embodiment, the problem of excessive by-product such as acrylic ester copolymer (ACR) of the existing catalyst can be well solved.

[0041] According to the preferred embodiment of the present application, the 2θ (°) position of peak 4 and peak 5 is in the range of 1.55-1.89, for example, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.89, and the relative intensity ratio of peak 4 and peak 5 is (0.65-0.9):1, 0.65:1, 0.70:1, 0.75:1, 0.8:1, 0.85:1, 0.9:1. By using this preferred embodiment, the problem of excessive by-product such as acrylic ester copolymer (ACR) of the existing catalyst can be well solved.

[0042] In the present application, the catalysts with the aforementioned structure can all achieve the purpose of the present application, and there is no special requirement for their composition. The catalyst compositions commonly used in the art can all be used in the present application. For the present application, preferably

[0043] a is the molar ratio of Mo to P, and a is 2.0-12.0;

[0044] b is the molar ratio of V to P, and b is 0.1-1.2;

[0045] c is the molar ratio of X to P, and c is 0.1-1.2;

[0046] d is the molar ratio of Z to P, and d is 0.05-0.2;

[0047] g is the number of moles of oxygen atoms required to satisfy the valence of each element in the active component.

[0048] In the present application, the aforementioned X substances can all achieve the purpose of the present application. In the examples, Ce is used as an exemplary description of the purpose of the present application, but the present application is not limited to this range.

[0049] According to a preferred embodiment of the present application, preferably, the ratio of d to c is (0.05-1):1, preferably (0.05-0.5):1, for example 0.05:1, 0.1:1, 0.15:1, 0.2:1, 0.25:1, 0.3:1, 0.35:1, 0.4:1, 0.45:1, 0.5:1. With this preferred embodiment, the problem of excessive by-products of the existing catalyst, such as acrylic ester copolymer (ACR), can be well solved.

[0050] The present application does not have special requirements for the preparation method of the catalyst, and the catalyst with the aforementioned structure can achieve the purpose of the present application. For the present application, a preparation method of the catalyst is provided, which comprises the following steps:

[0051] (1) The phosphorus source, the molybdenum source and the vanadium source are mixed and dissolved, and a pre-mixed solution is obtained by bubbling in an oxygen-containing atmosphere. Then, the Z element source is added to the pre-mixed solution, and the X element source is added after uniform mixing to obtain the mixed solution I, and then the sealing and aging treatment is performed.

[0052] (2) The mixed solution I is filtered after aging, and cold water is supplemented during filtering, and then dried and calcined.

[0053] According to a preferred embodiment of the present application, step (1) comprises: the phosphorus source, the molybdenum source and the vanadium source are mixed and dissolved, and a pre-mixed solution is obtained by bubbling in an oxygen-containing atmosphere. Preferably, the bubbling temperature is 30-50°C, and in the examples of the present application, 40°C is used as a demonstrative to illustrate the advantages of the present application, but the scope of the present application is not limited thereto. The bubbling time is 1-12h, and the bubbling time is determined according to specific needs, and preferably 4-10h, and in the examples of the present application, 6h is used as a demonstrative to illustrate the advantages of the present application, but the scope of the present application is not limited thereto. Then, the Z element source is added to the pre-mixed solution, and the X element source is added after uniform mixing to obtain the mixed solution I. With this preferred embodiment, the problem of excessive by-products of the existing catalyst, such as acrylic ester copolymer (ACR), can be well solved.

[0054] In the present application, the concentration of the pre-mixed solution has no special requirements, and according to the present application, the total active component concentration of phosphorus, molybdenum and vanadium in the pre-mixed solution is preferably 0.1-5mol / L. However, the present application is not limited to this range.

[0055] In the present application, the Z element source has no special requirements, and according to a preferred embodiment of the present application, the Z element source is provided in the form of an aqueous solution with a temperature of 40-60°C.

[0056] In the present application, the X element source has no special requirements, and according to a preferred embodiment of the present application, the X element source is provided in the form of an aqueous solution with a temperature of 40-60°C.

[0057] In the present application, the concentration of the mixed solution I is not particularly limited, and according to one preferred embodiment of the present application, the total concentration of the active component elements in the mixed solution I is 0.5-5.5 mol / L.

[0058] In the present application, the dissolution is appropriately heated, for example, generally at 30-50°C, to ensure uniform dissolution, which is well known to those skilled in the art and will not be described in detail herein.

[0059] In the present application, the oxygen-containing atmosphere is air, oxygen or a mixture of inert gas and oxygen, and according to one preferred embodiment of the present application, the oxygen-containing atmosphere is preferably a mixture of nitrogen and oxygen, and the ratio of nitrogen to oxygen is preferably (1-3):1, for example, 1:1, 2:1 or 3:1, but the present application is not limited to this range. The use of this preferred embodiment can effectively solve the problem of excessive by-products such as acrylic ester copolymer (ACR) of the existing catalyst.

[0060] According to one preferred embodiment of the present application, the method further comprises: the mixed solution I is subjected to a sealing and aging treatment before drying, and the preferred temperature for standing is 60-100°C (for example, 60°C, 70°C, 80°C, 90°C or 100°C, and 80°C is used as an exemplary illustration in the embodiments of the present application, but the present application is not limited to this), and / or the standing time is 12-60h (for example, 12h, 15h, 20h, 25h, 30h, 35h or 40h, but the present application is not limited to this). The use of this preferred embodiment can effectively solve the problem of excessive by-products such as acrylic ester copolymer (ACR) of the existing catalyst.

[0061] According to one preferred embodiment of the present application, the mixed solution I is filtered after standing and aging, and cold water is supplemented during the filtering, and the preferred temperature of the cold water is not higher than 10°C, preferably 2-5°C, and the preferred ratio of the amount of the cold water to the mass of the mixed solution I is (0.05-0.15):1, for example, 0.05:1, 0.1:1 or 0.15:1. The use of this preferred embodiment can effectively solve the problem of excessive by-products such as acrylic ester copolymer (ACR) of the existing catalyst.

[0062] According to one preferred embodiment of the present application, the dispersion medium is selected from one or more of water, methanol, ethanol, propanol, acetone and formamide, and the use of this preferred embodiment can effectively solve the problem of excessive by-products such as acrylic ester copolymer (ACR) of the existing catalyst.

[0063] In the present application, the drying and calcination conditions are not particularly limited, and the commonly used conditions can be used in the present application.

[0064] According to a preferred embodiment of the present application, the drying temperature is 60-150℃, for example 60℃, 80℃, 100℃, 120℃, 140℃, 150℃.

[0065] According to a preferred embodiment of the present application, the drying time is 1-48 hours, for example 5h, 12h, 15h, 20h, 25h, 30h, 35h, 40h, etc., but the present application is not limited thereto.

[0066] In the present application, the calcination conditions are not particularly required, and the commonly used calcination conditions can achieve the purpose of the present application.

[0067] According to a preferred embodiment of the present application, the calcination temperature is 300-500℃, for example 300℃, 350℃, 400℃, 450℃, 500℃.

[0068] According to a preferred embodiment of the present application, the calcination time is 1-48 hours, for example 5h, 12h, 15h, 20h, 25h, 30h, 35h, 40h, etc., but the present application is not limited thereto.

[0069] According to a preferred embodiment of the present application, the calcination atmosphere is inert atmosphere or oxygen-containing atmosphere.

[0070] In the present application, the drying conditions are not particularly required, and the commonly used drying conditions can achieve the purpose of the present application, preferably the drying temperature is 60-150℃, and / or the drying time is 1-48 hours.

[0071] According to a preferred embodiment of the present application, the calcination temperature is 300-500℃, and / or the calcination time is 1-48 hours, and / or the calcination atmosphere is inert atmosphere or oxygen-containing atmosphere.

[0072] In the present application, in one technical solution, the phosphorus source, the molybdenum source and the vanadium source are preferably mixed and dissolved at the same time, and then air is introduced for bubbling, the bubbling temperature is 30-50℃, and the bubbling time is 1-12h.

[0073] In the present application, in one technical solution, the Z element source is preferably slowly added to the pretreated premix under stirring, and then the X element solution is slowly added after uniform stirring. In the present application, the slow operation method is not particularly required, and the main purpose is to make the Z element and the X element respectively act on the Keggin type heteropoly acid structure.

[0074] In the present application, in one technical solution, the mixed solution I is preferably sealed and aged before drying, preferably the standing temperature is 60-100℃, and the standing time is 12-60h.

[0075] In the present application, in one technical solution, the mixed solution I is filtered after standing and aging, and appropriate amount of cold water is supplemented during the filtering, the temperature of the cold water is not higher than 10 DEG C, and the mass ratio of the amount of the cold water to the mixed solution I is (0.05-0.15):1.

[0076] The present application provides the use of the catalyst described in the present application in the synthesis of alkyl acrylic acid, preferably the alkyl acrylic acid is C3-C6 alkyl acrylic acid, more preferably the alkyl acrylic acid is methacrylic acid.

[0077] The present application provides a method for oxidizing methacrolein, which comprises: oxidizing a methacrolein raw material with an oxidizing gas containing oxygen in the presence of the catalyst described in the present application.

[0078] In the above technical solution, in order to make the reaction more stable and controllable, it is preferred to be carried out in the presence of dilute gas phase materials.

[0079] In the above technical solution, the dilute gas phase materials are preferably water vapor.

[0080] In the above technical solution, the oxidizing gas can be pure oxygen, oxygen-enriched air, but from the economic aspect, air is preferred.

[0081] In the above technical solution, the reaction temperature can be selected from 100-500 DEG C.

[0082] In the above technical solution, in the raw material gas composed of methacrolein, air and water vapor, the volume ratio of methacrolein: air: water vapor is preferably 1:(10-30):(1-8).

[0083] In the above technical solution, the total space velocity of the raw material gas is preferably 1000-4000 h -1 .

[0084] According to the preferred embodiment of the present application, the conditions of the oxidation include:

[0085] The diluent is water vapor; and / or

[0086] The reaction temperature is 100-500 DEG C; and / or

[0087] The total space velocity of the raw material gas is preferably 1000-4000 h -1 .

[0088] The volume ratio of methacrolein: air: water vapor is 1:(10-30):(1-8).

[0089] The catalyst evaluation method of the present application is as follows:

[0090] Reactor: fixed bed micro-reactor, inner diameter 10 mm, reactor length 400 mm;

[0091] Catalyst loading: 2 grams;

[0092] Reaction temperature: 310°C;

[0093] Reaction time: 4 hours;

[0094] Raw material volume ratio: methacrolein: air: water vapor = 1:20:4;

[0095] Total raw gas space velocity: 2500h -1 .

[0096] Using the catalyst of the present application, the yield of by-product acrylic ester copolymer can be reduced to 0.25% or less at a total raw gas space velocity of 2500h -1 , achieving good technical effects, and can be used in the industrial production of methacrylic acid.

[0097] Example 1

[0098] 1. A mixed solution I is obtained by mixing active element solutions of the components;

[0099] Phosphoric acid containing 0.1 moles of phosphorus (molecular formula: H3PO4) is added to a three-necked flask, ammonium molybdate containing 1.0 moles of Mo (molecular formula: (NH4)2MoO4) and ammonium metavanadate containing 0.1 moles of V (molecular formula: NH4VO3) are added respectively, and then dissolved in water at 40°C, followed by continuous air bubbling, with a bubbling time of 6 hours and a temperature of 40°C, and the total active component concentration of phosphorus, molybdenum and vanadium being 1 mol / L. A cerium nitrate solution containing 0.01 moles of Ce (molecular formula: Ce(NO3)3) dissolved in hot water at 50°C is slowly added to the above-mentioned pretreated phosphorus source, molybdenum source and vanadium source mixed solution, and after stirring to uniformity, a yttrium nitrate solution containing 0.1 moles of Y (molecular formula: Y(NO3)3) dissolved in hot water at 50°C is slowly added. After stirring to uniformity, an active component mixed solution I is obtained (total concentration of active component elements being 1 mol / L).

[0100] 2. The mixed solution I is dried and calcined.

[0101] 200g of the above-mentioned active component mixed solution I is taken, sealed, placed in an 80°C oven, and left to stand for 24 hours. 20g of cold water at 5°C is added, stirred to uniformity, and then filtered using filter paper. After filtration is completed, drying is carried out in a 100°C oven for 12 hours, and then calcination is carried out in a muffle furnace at 360°C for 12 hours to obtain a catalyst with a composition of PMo 10 VYCe 0.1 O g , with the ratio of d to c being 0.1:1.

[0102] 3. Catalyst evaluation

[0103] The above catalyst was charged into a fixed bed reactor and the results of the evaluation are shown in Table 1.

[0104] Figure 1 is a comparison of X-ray diffraction patterns. The upper solid line is the XRD pattern of a catalyst prepared according to the prior art (Comparative Example 1) and the lower solid line is the XRD pattern of a catalyst prepared according to the present technology (Example 1).

[0105] From Figure 1 It can be seen that the XRD pattern of Example 1 includes a peak 1 at 2Θ = 9.46°, I / I 0＝ 16.8%; a peak 2 at 2Θ = 12.68°, I / I 0＝ 17.7%; a peak 3 at 2Θ = 23.28°, I / I 0＝ 14.1%; a peak 4 at 2Θ = 25.55°, I / I 0＝ 21.1%; a peak 5 at 2Θ = 27.25°, I / I 0＝ 27.0%. The positions of peak 2 and peak 3 differ by 10.60° and the relative intensity ratio of peak 2 to peak 3 is 1.26:1. The positions of peak 4 and peak 5 differ by 1.70° and the relative intensity ratio of peak 4 to peak 5 is 0.78:1.

[0106] Example 2

[0107] Example 1 except that the catalyst composition was PMo 10 VYCe 0.05 O g and the ratio of d to c was 0.05:1. The XRD pattern of Example 2 includes a peak 1 at 2Θ = 9.38°, I / I 0＝ 16.5%; a peak 2 at 2Θ = 12.61°, I / I 0＝ 17.4%; a peak 3 at 2Θ = 23.22°, I / I 0＝ 14.0%; a peak 4 at 2Θ = 25.50°, I / I 0＝ 20.8%; a peak 5 at 2Θ = 27.19°, I / I 0＝ 26.8%. The positions of peak 2 and peak 3 differ by 10.61° and the relative intensity ratio of peak 2 to peak 3 is 1.24:1. The positions of peak 4 and peak 5 differ by 1.69° and the relative intensity ratio of peak 4 to peak 5 is 0.78:1.

[0108] Example 3

[0109] The procedure of Example 1 was followed except that the catalyst composition was PMo5VYCeO 10 VYCeO g The ratio of d to c was 1 : 1. The XRD pattern of Example 3 included a peak 1 at 2Θ = 9.49°, I / I 0＝ 17.0%; a peak 2 at 2Θ = 12.75°, I / I 0＝ 18.0%; a peak 3 at 2Θ = 23.34°, I / I 0＝ 14.3%; a peak 4 at 2Θ = 25.60°, I / I 0＝ 21.4%; a peak 5 at 2Θ = 27.30°, I / I 0＝ 27.4%. The positions of peak 2 and peak 3 were separated by 10.59° and the relative intensity ratio of peak 2 to peak 3 was 1.26: 1. The positions of peak 4 and peak 5 were separated by 1.70° and the relative intensity ratio of peak 4 to peak 5 was 0.78: 1.

[0110] Example 4

[0111] The procedure of Example 1 was followed except that the catalyst composition was PMo5VYCeO 10 V 0.1 YCe 0.1 O g The ratio of d to c was 0.1 : 1. The XRD pattern of Example 4 included a peak 1 at 2Θ = 9.52°, I / I 0＝ 17.1%; a peak 2 at 2Θ = 12.72°, I / I 0＝ 18.1%; a peak 3 at 2Θ = 23.35°, I / I 0＝ 14.0%; a peak 4 at 2Θ = 25.61°, I / I 0＝ 21.3%; a peak 5 at 2Θ = 27.31°, I / I 0＝ 27.5%. The positions of peak 2 and peak 3 were separated by 10.63° and the relative intensity ratio of peak 2 to peak 3 was 1.29: 1. The positions of peak 4 and peak 5 were separated by 1.70° and the relative intensity ratio of peak 4 to peak 5 was 0.77: 1.

[0112] Example 5

[0113] The procedure of Example 1 was followed except that the catalyst composition was PMo5VYCe0.1 O g The ratio of d to c is 0.1:1. The XRD spectrum of Example 5 includes, peak 1 at 2-theta = 9.40°, I / I 0＝ 16.9%; peak 2 at 2-theta = 12.70°, I / I 0＝ 17.8%; peak 3 at 2-theta = 23.23°, I / I 0＝ 13.8%; peak 4 at 2-theta = 25.50°, I / I 0＝ 20.9%; peak 5 at 2-theta = 27.22°, I / I 0＝ 26.9%. The difference in position between peak 2 and peak 3 is 10.53°, and the relative intensity ratio of peak 2 to peak 3 is 1.29:1. The difference in position between peak 4 and peak 5 is 1.72°, and the relative intensity ratio of peak 4 to peak 5 is 0.78:1.

[0114] Example 6

[0115] The method of Example 1 was followed, except that the sparging gas was a mixture of nitrogen and oxygen in a ratio of 1:1. The XRD spectrum was similar to that of Example 1 and met the requirements of the present application.

[0116] Comparative Example 1

[0117] The method of Example 1 was followed, except that the catalyst composition was PMo 10 VYCe 0.01 O g The ratio of d to c was 0.01:1.

[0118] Comparative Example 2

[0119] The method of Example 1 was followed, except that the catalyst composition was PMo 10 VYCe2O g The ratio of d to c was 2:1.

[0120] Comparative Example 3

[0121] The method of Example 1 was followed, except that no air sparging was performed.

[0122] Comparative Example 4

[0123] The method of Example 1 was followed, except that the mixture I was not aged.

[0124] Comparative Example 5

[0125] The method of Example 1 was followed, except that no cold water was mixed during filtration.

[0126] Table 1

[0127]

[0128] ACR yield % = amount of methyl methacrolein consumed to produce ACR / total amount of methyl methacrolein fed * 100 %.

[0129] The above describes the preferred embodiments of the present application in detail, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including that each technical feature is combined in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application and belong to the protection scope of the present application.

Claims

1. An oxidation catalyst, characterized in that, The catalyst has the X-ray diffraction pattern shown in the table below. *The relative intensity ratio is the ratio of the peak height of each peak to the highest peak. The highest peak of the catalyst is 2θ = 26.30 ± 0.09°, and the d-interval is 3.3854 ± 0.06 Å. The catalyst is represented by the general formula: PMo a V b X c Z d O g , X is one or more selected from Sc, Ti, Y, Zr, Nb, Hf, and Ta; Z is selected from at least one of La, Ce, Pr, and Nd; 'a' represents the molar ratio of Mo to P; the value of 'a' ranges from 2.0 to 12.

0. b is the molar ratio of V to P; b ranges from 0.1 to 1.

2. c is the molar ratio of X to P; c takes values ​​from 0.1 to 1.

2. d is the molar ratio of Z to P; d ranges from 0.05 to 0.

2. g represents the number of moles of oxygen atoms required to satisfy the oxidation states of each element in the active component. The ratio of d to c is (0.05~1):

1.

2. The catalyst according to claim 1, wherein, The 2θ (°) position difference between peak 2 and peak 3 ranges from 8.80 to 12.5, and the relative intensity ratio between peak 2 and peak 3 is (1.1~1.4):1; and / or The 2θ (°) positions of peak 4 and peak 5 differ by a range of 1.55 to 1.89, and the relative intensity ratio of peak 4 to peak 5 is (0.65 to 0.9):

1.

3. The catalyst according to claim 1 or 2, wherein, The ratio of d to c is (0.05~0.5):

1.

4. The catalyst according to claim 3, wherein, The ratio of d to c is (0.05~0.2):

1.

5. A method for preparing the catalyst according to any one of claims 1-4, comprising the following steps: (1) The phosphorus source, molybdenum source and vanadium source are mixed and dissolved, and an oxygen-containing atmosphere is introduced for bubbling to obtain a premixed solution; then the Z element source is added to the premixed solution, mixed evenly, and then the X element source is added to obtain the mixed solution I, and then sealed and allowed to stand for aging treatment. (2) Mixture I is filtered after standing and aging, cold water is added during filtration, and then it is dried and calcined.

6. The preparation method according to claim 5, wherein, In step (1), The bubbling temperature is 30~50℃, and the bubbling time is 1~12h; and / or In the premixed solution, the total concentration of active components, including phosphorus, molybdenum, and vanadium, is 0.1-5 mol / L; and / or The oxygen-containing atmosphere is a mixture of nitrogen and oxygen; and / or The Z element source is provided by an aqueous solution at a temperature of 40-60°C; and / or The X element source is provided by an aqueous solution at a temperature of 40-60°C; and / or In mixture I, the total concentration of active component elements is 0.5-5.5 mol / L.

7. The preparation method according to claim 6, wherein, In step (1), The oxygen-containing atmosphere is a mixture of nitrogen and oxygen, with a nitrogen to oxygen ratio of (1~3):

1.

8. The preparation method according to claim 5, wherein, In step (1), Settling temperature 60-100℃ and / or settling time 12-60h.

9. The preparation method according to claim 5, wherein, In step (2), the temperature of the cold water should not exceed 10℃.

10. The preparation method according to claim 9, wherein, In step (2), the cold water temperature is 2-5℃.

11. The preparation method according to claim 9, wherein, In step (2), the ratio of cold water replenishment to the mass of mixed liquid I is (0.05~0.15):

1.

12. The preparation method according to claim 5, wherein, The drying temperature is 60~150℃, and / or the drying time is 1~48 hours; The roasting temperature is 300~500℃, and / or the roasting time is 1~48 hours, and / or the roasting atmosphere is an inert atmosphere or an oxygen-containing atmosphere.

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

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

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

16. A method for oxidizing methacrolein, characterized in that, The method includes: oxidizing a methacrolein feedstock with an oxygen-containing oxidizing gas in the presence of the catalyst described in any one of claims 1-4.

17. The method according to claim 16, wherein, The conditions for oxidation include: The diluent is water vapor; and / or The reaction temperature is 100~500℃; and / or The total space velocity of the feed gas is 1000~4000 h⁻¹ -1 ; By volume ratio, methacrolein: air: water vapor = 1:(10~30):(1~8).

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