CN111939952B - Hierarchical pore catalyst and preparation method and application thereof - Google Patents

Abstract

The invention relates to a hierarchical porous catalyst, which is made of active components accounting for 30% to 60% of the total mass and a SiO ₂ carrier with three-dimensional ordered hierarchical pores as the balance; in parts by weight, the Active components consist of _17.66g / _35.32g ( _NH4 ) _{6Mo7O24 ·} 4H2O, 0.25g _NH4VO3 , 0.42g Cu( _{CH3C00 ) 2 ·} 2H2O, 0.48g _SbCl3 , 0.30 It consists of g H ₃ AsO ₄ , 1.09 g H ₃ PO ₄ , 0.35 g La(CH ₃ COO) ₃ . 1.5H ₂ O, 0.45 g Ce(NO ₃ ) ₃ .6H ₂ O and 2.12 g CsOH .H ₂ O. Meanwhile, the invention also discloses the preparation method and application of the catalyst. The invention can significantly improve the catalytic activity of the reaction, and it can be used to catalyze the oxidative dehydrogenation of isobutyraldehyde to prepare methacrylic acid, which can be carried out under the condition of normal pressure under the condition of air as an oxidant. based on acrylic acid yield and lower CO _x generation rate.

Description

A kind of hierarchical porous catalyst and its preparation method and application

technical field

The invention relates to the field of isobutyraldehyde conversion and utilization, in particular to a multi-level porous catalyst and a preparation method and application thereof.

Background technique

Methacrylic acid (MAA) is the basic raw material for the production of methyl methacrylate (MMA) and other higher esters. MAA and methanol are esterified to obtain MMA monomer. The polymerized product of MMA monomer is commonly known as plexiglass. It has excellent transparency, mechanical strength, machinability and weather resistance. It has the largest output and the most widely used acrylic products. species.

The production of methacrylic acid (MAA) from isobutyraldehyde is the most economical process route for the production of organic glass monomers. The process route was mainly developed by Nippon Chemical Co., Ltd. (Japanese Patent Publication No. Sho 50-149611). Jilin University and others carried out one-step oxidation of isobutyraldehyde based on the research on the catalyst for the oxidative dehydrogenation of isobutyric acid to methacrylic acid heteropolyacid. Research work on dehydrogenation to MAA, developed heteropolyacid catalysts and their supported catalysts (Wu Tonghao et al., Research on Heteropolyacid Catalysts for Oxidation of Isobutyraldehyde to Methacrylic Acid, Chinese Journal of Advanced Chemistry, 1985, vol. 6 , No.3: 265; Wu Tonghao et al., Research on the catalyst of one-step oxidation of isobutyraldehyde to methacrylic acid heteropolyacid, Petrochemical, 1985, 6:313). Due to the high reaction temperature and the participation of oxygen in this process, the reactants and products are prone to side reactions such as deep oxidation, which limits the improvement of the selectivity of methacrylic acid.

Since the reaction process of isobutyraldehyde oxidative dehydrogenation to methacrylic acid is a strong exothermic reaction, hot spots are easily formed in the reaction bed. In order to effectively improve the selectivity of methacrylic acid and control the temperature of the reaction bed, the preparation of catalysts and the selection of supports are particularly important. Composite oxide catalysts and traditional carrier-supported catalysts, such as amorphous SiO ₂ , Al ₂ O ₃ , etc., have poor thermal conductivity, hot spots are easily formed in the reaction bed, and the reaction process is difficult to control effectively, which limits their industrial application and promotion.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a multi-level porous catalyst with improved catalytic activity and a preparation method and application thereof.

Another technical problem to be solved by the present invention is to provide a preparation method of the hierarchical porous catalyst.

The third technical problem to be solved by the present invention is to provide the application of the hierarchical porous catalyst.

In order to solve the above problems, a kind of hierarchical porous catalyst according to the present invention is characterized in that: the catalyst is composed of active components accounting for 30% to 60% of the total mass and the balance is SiO ₂ with three-dimensional ordered hierarchical pores. The carrier is made; in parts by weight, the active component consists of 17.66g/35.32g (NH ₄ ) ₆ Mo ₇ O ₂₄ ·4H ₂ O, 0.25g NH ₄ VO ₃ , 0.42g Cu(CH ₃ C00) ₂ 2H ₂ O, 0.48g SbCl ₃ , 0.30g H ₃ AsO ₄ , 1.09g H ₃ PO ₄ , 0.35g La(CH ₃ COO) ₃ 1.5H ₂ O, 0.45g Ce(NO ₃ ) ₃ 6H ₂ O and 2.12 g CsOH·H ₂ O constituted.

The SiO ₂ carrier refers to the use of silicon source, macroporous template agent and mesoporous template agent to synthesize SiO ₂ precursor through volatilization and self-assembly method. After calcining at 600℃ for 4~8h, SiO ₂ with three-dimensional ordered macroporous-mesoporous structure is obtained; the macroporous template is polymethyl methacrylate (PMMA); the mesoporous template is polyoxyethylene Polyoxypropylene ether block copolymer (Pluronic F127).

The mass concentrations of the H ₃ AsO ₄ and the H ₃ PO ₄ are both 85%.

The preparation method of a kind of hierarchical porous catalyst as above, comprises the following steps:

⑴Weighing according to the proportion;

(2) Dissolve (NH ₄ ) ₆ Mo ₇ O ₂₄ ·4H ₂ O and NH ₄ VO ₃ in deionized water to obtain immersion solution A; dissolve Cu(CH ₃ C00) ₂ ·2H ₂ O and SbCl ₃ in deionized water water to obtain immersion solution B; dissolve H ₃ AsO ₄ and H ₃ PO ₄ in deionized water to obtain immersion solution C; mix La(CH ₃ COO) ₃ ·1.5H ₂ O with Ce(NO ₃ ) ₃ ·6H ₂ O was dissolved in deionized water to obtain dipping solution D; CsOH·H ₂ O was dissolved in deionized water to obtain dipping solution E;

(3) Impregnate the impregnation solution A on the SiO ₂ carrier at 80°C to 100°C, and dry it at 120°C for 3 to 12 hours; similarly, the impregnation solution B, the impregnation solution C, the impregnation solution C and the Liquid D and the impregnation liquid E are impregnated on the SiO ₂ carrier to obtain a sample;

(4) After drying the sample at 120°C overnight, it is obtained by calcining at 350-450°C for 4-6 hours.

The impregnation is an equal volume impregnation, and the impregnation is carried out in multiple times.

The application of the above-mentioned hierarchical porous catalyst is characterized in that: the catalyst catalyzes the reaction of oxidative dehydrogenation of isobutyraldehyde to prepare methacrylic acid in the preparation of methacrylic acid from isobutyraldehyde.

Compared with the prior art, the present invention has the following advantages:

1. In the present invention, SiO ₂ with a three-dimensional ordered macroporous-mesoporous structure is used as a carrier, and the macroporous channels in the carrier can make the raw materials and gases quickly reach the active sites on the mesoporous surface, thereby promoting the rapid progress of the reaction; In addition, the ordered mesoporous structure enables better dispersion of active species and improves catalyst activity; at the same time, the macroporous structure can speed up the rate and capacity of fluid diffusion, and the reaction products can quickly detach from the reactive center to avoid further deep oxidation, thereby reducing CO _X generation rate.

2. The present invention uses SiO ₂ with a multi-level pore structure as a carrier, which has an important influence on improving the reaction process of isobutyraldehyde oxidative dehydrogenation to methacrylic acid. The thermal conductivity can avoid the formation of hot spots in the reaction bed, and the reaction process can be effectively controlled, which is more conducive to its industrial application.

3. The carrier used in the catalyst obtained by the present invention has the characteristics of hierarchical pore structure and large specific surface area. The catalyst can be prepared by loading the active components on the surface of the catalyst and in the pores by the impregnation method. According to the requirements of different reaction conditions on the reactivity of the catalyst, the content and ratio of active components can be adjusted flexibly.

4. The catalyst obtained in the present invention can adapt to a wide range of operating conditions, and has excellent performance in oxidative dehydrogenation of isobutyraldehyde to produce methacrylic acid.

Description of drawings

The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

Figure 1 is a transmission electron microscope image (50 nm) of the carrier three-dimensionally ordered macroporous-mesoporous SiO ₂ in Example 1 of the present invention.

FIG. 2 is a transmission electron microscope image (100 nm) of the carrier three-dimensional ordered macroporous-mesoporous SiO ₂ in Example 1 of the present invention.

Figure 3 is a scanning electron microscope image (1.00 µm) of the carrier three-dimensional ordered macroporous-mesoporous SiO ₂ in Example 1 of the present invention.

Detailed ways

Example 1 A hierarchical porous catalyst, the catalyst is made of 23.12g active component and 53.95g SiO ₂ carrier with three-dimensional ordered hierarchical pores; the active component is 17.66g (NH ₄ ) ₆ Mo ₇ O ₂₄ · 4H ₂ O, 0.25g NH ₄ VO ₃ , 0.42g Cu(CH ₃ C00) ₂ · 2H ₂ O, 0.48g SbCl ₃ , 0.30g H ₃ AsO ₄ , 1.09g H ₃ PO ₄ , 0.35g La(CH 3 3COO) ₃ ·1.5H2O, 0.45g Ce( _{NO3 )3 · 6H2O} and 2.12g CsOH _{· H2O} .

Among them: SiO ₂ carrier refers to the use of silicon source, macroporous template agent and mesoporous template agent to synthesize SiO ₂ precursor by volatilization self-assembly method. After calcination at 600℃ for 4~8h, SiO ₂ with three-dimensional ordered macropore-mesoporous structure was obtained. The specific method is as follows:

① Dissolve 50 g of methyl methacrylate (MMA) in 500 g of water to obtain an aqueous solution of methyl methacrylate; slowly add 0.05 g of dimethacrylate to the aqueous solution of methyl methacrylate at 80°C under nitrogen atmosphere and stirring conditions Potassium sulfite, continue stirring for 12h, the solution gradually turned milky white to obtain an emulsion; the emulsion was purified by centrifugation, washed with distilled water to remove unreacted monomers and impurities, and dried at 80°C for 24h to obtain the macroporous template PMMA.

② Mix 65 g of F127 with 40 g of 0.2 mol/L HCl solution and 300 mL of absolute ethanol to obtain a mixed solution; add 100 g of tetraethyl silicate to the mixed solution, raise the temperature to 60°C, stir for 1 hour, and let stand overnight.

③ Add all the macroporous template PMMA synthesized in step ① to the solution after standing overnight in step ②, volatilize at 60°C, dry at 100-120°C for 12-24 hours, and then calcinate at not less than 600°C For 4-8h, SiO ₂ with three-dimensional ordered macropore-mesoporous structure was obtained.

The _SiO2 with three-dimensional ordered macropore-mesoporous structure was tested by transmission electron microscopy and scanning electron microscopy, and the results are shown in Figures 1 to 3. The three-dimensional ordered macropore-mesoporous structure of SiO ₂ has a specific surface area of 320 m ² ·g ^-1 , the average pore diameter of the macropores is 170 nm, the wall thickness of the macropores is 8 nm, and the average pore diameter of the mesopores is 6 nm.

The preparation method of this hierarchical porous catalyst comprises the following steps:

⑴Weighing according to the proportion;

(2) Dissolve 17.66g (NH ₄ ) ₆ Mo ₇ O ₂₄ ·4H ₂ O and 0.25g NH ₄ VO ₃ in 100 mL of deionized water to obtain immersion solution A; dissolve 0.42g Cu(CH ₃ C00) ₂ ·2H ₂ O Dissolve 0.48g SbCl ₃ in 100 mL of deionized water to obtain dipping solution B; dissolve 0.30 g H ₃ AsO ₄ and 1.09 g H ₃ PO ₄ in 100 mL of deionized water to obtain dipping solution C; 0.35 g La(CH ₃ COO) ₃ ·1.5H ₂ O and 0.45g Ce(NO ₃ ) ₃ ·6H ₂ O were dissolved in 100 mL of deionized water to obtain impregnation solution D; 2.12 g of CsOH·H ₂ O were dissolved in 100 mL of deionized water to obtain impregnation solution D liquid E;

(3) Using the equal volume impregnation method, impregnate the impregnating liquid A on the 53.95g SiO ₂ carrier (screening 40-60 mesh carrier) at 80 °C, and dry it at 120 °C for 12 hours; Impregnating liquid D and impregnating liquid E are impregnated on the SiO ₂ carrier to obtain a sample;

(4) After drying the sample at 120°C overnight, it was calcined at 400°C for 6 hours to obtain catalyst A1.

Example 2 A hierarchical porous catalyst, the catalyst is made of 40.78g active component and 95.15g SiO ₂ carrier with three-dimensional ordered hierarchical pores; the active component is 35.32g (NH ₄ ) ₆ Mo ₇ O ₂₄ 4H2O, 0.25g _NH4VO3 , 0.42g Cu( _{CH3C00 )2 2H2O} , 0.48g _SbCl3 , _{0.30g H3AsO4} , _{1.09g H3PO4} , _0.35g La( _CH 3COO) ₃ ·1.5H2O, 0.45g Ce( _{NO3 )3 · 6H2O} and 2.12g CsOH _{· H2O} .

Wherein: the SiO ₂ carrier is the same as in Example 1.

The preparation method of the hierarchical porous catalyst comprises the following steps:

⑴Weighing according to the proportion;

(2) Dissolve 35.32g (NH ₄ ) ₆ Mo ₇ O ₂₄ ·4H ₂ O and 0.25g NH ₄ VO ₃ in 100 mL of deionized water to obtain dipping solution A; dipping solution B, dipping solution C, dipping solution D, dipping solution E is with embodiment 1;

(3) Using the equal volume impregnation method, impregnate the impregnating liquid A on the 95.15g SiO ₂ carrier (screening 40-60 mesh carrier) at 100 °C, and dry it at 120 °C for 3 hours; Impregnating liquid D and impregnating liquid E are impregnated on the SiO ₂ carrier to obtain a sample;

(4) After drying the sample at 120°C overnight, it was calcined at 350°C for 6 hours to obtain catalyst B1.

Example 3 A hierarchical porous catalyst made from 23.12g active component and 28.25g SiO ₂ carrier with three-dimensional ordered hierarchical pores; the active component was 17.66g (NH ₄ ) ₆ Mo ₇ O ₂₄ 4H2O, 0.25g _NH4VO3 , 0.42g Cu( _{CH3C00 )2 2H2O} , 0.48g _SbCl3 , _{0.30g H3AsO4} , _{1.09g H3PO4} , _0.35g La( _CH 3COO) ₃ ·1.5H2O, 0.45g Ce( _{NO3 )3 · 6H2O} and 2.12g CsOH _{· H2O} .

Wherein: the SiO ₂ carrier is the same as in Example 1.

The preparation method of the hierarchical porous catalyst comprises the following steps:

⑴Weighing according to the proportion;

(2) Dissolve 17.66g (NH ₄ ) ₆ Mo ₇ O ₂₄ ·4H ₂ O and 0.25g NH ₄ VO ₃ in 50 mL of deionized water to obtain immersion solution A; dipping solution B, dipping solution C, dipping solution D, dipping solution E is with embodiment 1;

(3) Using the equal volume impregnation method, impregnate the impregnating liquid A on the 28.25g SiO ₂ carrier (screening 40-60 mesh carrier) at 90 °C, and dry it at 120 °C for 8 hours; Impregnating liquid D and impregnating liquid E are impregnated on the SiO ₂ carrier to obtain a sample;

(4) After drying the sample at 120°C overnight, it was calcined at 450°C for 4 hours to obtain catalyst A2.

Example 4 A hierarchical porous catalyst made from 40.78g active component and 49.84g SiO ₂ support with three-dimensionally ordered hierarchical pores; the active component was 35.32g (NH ₄ ) ₆ Mo ₇ O ₂₄ 4H2O, 0.25g _NH4VO3 , 0.42g Cu( _{CH3C00 )2 2H2O} , 0.48g _SbCl3 , _{0.30g H3AsO4} , _{1.09g H3PO4} , _0.35g La( _CH 3COO) ₃ ·1.5H2O, 0.45g Ce( _{NO3 )3 · 6H2O} and 2.12g CsOH _{· H2O} .

Wherein: the SiO ₂ carrier is the same as in Example 1.

The preparation method of the hierarchical porous catalyst comprises the following steps:

⑴Weighing according to the proportion;

(2) Dissolve 35.32g (NH ₄ ) ₆ Mo ₇ O ₂₄ ·4H ₂ O and 0.25g NH ₄ VO ₃ in 50 mL of deionized water to obtain dipping solution A; dipping solution B, dipping solution C, dipping solution D, dipping solution E is with embodiment 1;

(3) Using the equal volume impregnation method, impregnate the impregnating liquid A on the 49.84g SiO ₂ carrier (screening 40-60 mesh carrier) at 90 °C, and dry it at 120 °C for 8 hours; Impregnating liquid D and impregnating liquid E are impregnated on the SiO ₂ carrier to obtain a sample;

(4) After the sample was dried at 120°C overnight, it was calcined at 450°C for 4 hours to obtain catalyst B2.

Example 5 A hierarchical porous catalyst, the catalyst is made of 23.12g active component and 15.41g SiO ₂ carrier with three-dimensional ordered hierarchical pores; the active component is 17.66g (NH ₄ ) ₆ Mo ₇ O ₂₄ 4H2O, 0.25g _NH4VO3 , 0.42g Cu( _{CH3C00 )2 2H2O} , 0.48g _SbCl3 , _{0.30g H3AsO4} , _{1.09g H3PO4} , _0.35g La( _CH 3COO) ₃ ·1.5H2O, 0.45g Ce( _{NO3 )3 · 6H2O} and 2.12g CsOH _{· H2O} .

Wherein: the SiO ₂ carrier is the same as in Example 1.

The preparation method of the hierarchical porous catalyst comprises the following steps:

⑴Weighing according to the proportion;

(2) Dissolve 17.66g (NH ₄ ) ₆ Mo ₇ O ₂₄ ·4H ₂ O and 0.25g NH ₄ VO ₃ in 50 mL of deionized water to obtain immersion solution A; dipping solution B, dipping solution C, dipping solution D, dipping solution E is with embodiment 1;

(3) Using the equal volume impregnation method, impregnate the impregnating liquid A on the 15.41g SiO ₂ carrier (screening 40-60 mesh carrier) at 85 °C, and dry it at 120 °C for 12 hours; Impregnating liquid D and impregnating liquid E are impregnated on the SiO ₂ carrier to obtain a sample;

(4) After drying the sample at 120°C overnight, it was calcined at 400°C for 5h to obtain catalyst A3.

Example 6 A hierarchical porous catalyst made from 40.78g active component and 27.19g SiO ₂ support with three-dimensional ordered hierarchical pores; the active component was 35.32g (NH ₄ ) ₆ Mo ₇ O ₂₄ 4H2O, 0.25g _NH4VO3 , 0.42g Cu( _{CH3C00 )2 2H2O} , 0.48g _SbCl3 , _{0.30g H3AsO4} , _{1.09g H3PO4} , _0.35g La( _CH 3COO) ₃ ·1.5H2O, 0.45g Ce( _{NO3 )3 · 6H2O} and 2.12g CsOH _{· H2O} .

Wherein: the SiO ₂ carrier is the same as in Example 1.

The preparation method of the hierarchical porous catalyst comprises the following steps:

⑴Weighing according to the proportion;

(2) Dissolve 35.32g (NH ₄ ) ₆ Mo ₇ O ₂₄ ·4H ₂ O and 0.25g NH ₄ VO ₃ in 50 mL of deionized water to obtain dipping solution A; dipping solution B, dipping solution C, dipping solution D, dipping solution E is with embodiment 1;

(3) Using the equal volume impregnation method, impregnate the impregnating liquid A on the 27.19g SiO ₂ carrier (screening 40-60 mesh carrier) at 85 °C, and dry it at 120 °C for 12 hours; Impregnating liquid D and impregnating liquid E are impregnated on the SiO ₂ carrier to obtain a sample;

(4) After drying the sample at 120°C overnight, it was calcined at 400°C for 5 hours to obtain catalyst B3.

In the above-mentioned embodiments 1 to 6, the mass concentrations of H ₃ AsO ₄ and H ₃ PO ₄ are both 85%.

Application of the multi-level porous catalyst obtained in the above-mentioned embodiments 1 to 6: the catalyst catalyzes the reaction of isobutyraldehyde oxidative dehydrogenation to methacrylic acid in the preparation of methacrylic acid from isobutyraldehyde. The specific process is as follows:

In a normal-pressure quartz fixed-bed reactor with an inner diameter of 12 mm, catalyst A1, catalyst B1, catalyst A2, and catalyst B2 were used to catalyze the oxidative dehydrogenation of isobutyraldehyde to produce methacrylic acid, thereby realizing the production of methyl methacrylate from isobutyraldehyde. acrylic acid. The reaction conditions are that the pressure is normal pressure, the air is the oxidant, the liquid raw materials (isobutyraldehyde and water) are pumped in by two liquid injection pumps (liquid space velocity 0.8h ^-1 ), and then preheated and vaporized at 200 °C to enter the In the reaction system, the control temperature of the reaction furnace is 285°C, the molar ratio of the reaction materials isobutyraldehyde, water and air is 1:7:12.5, and the total gas space velocity is 1300h ^-1 .

The gas phase composition in the reaction product is analyzed online by gas chromatograph equipped with thermal conductivity detector, O ₂ , N ₂ , CO, CO ₂ , etc. The liquid product is collected by condensation, and isobutyl is analyzed by gas chromatograph equipped with FID (flame ion detector) Aldehyde, acetic acid, methacrolein, methacrylic acid and other products. The correction factor area normalization method was used to calculate the conversion rate of isobutyraldehyde and the selectivity of methacrylic acid, etc. The performance evaluation results are shown in Table 1 below.

Table 1

It can be seen from Table 1 that the isobutyraldehyde conversion rate of the catalyst obtained by the present invention is ≈ 100%, the selectivity of methacrylic acid is greater than or equal to 70%, the selectivity of methacrolein is greater than or equal to 5%, the selectivity of acetic acid is greater than or equal to 9%, and the selectivity of CO _x <8%, showing excellent reaction performance, indicating that the catalyst can be used to catalyze the oxidative dehydrogenation of isobutyraldehyde to prepare methacrylic acid with air as the oxidant under normal pressure conditions. A higher yield of methacrylic acid and a lower generation rate of CO _X are obtained, which are suitable for industrial application and promotion.

Claims (4)

1. A multi-stage pore catalyst, characterized by: the catalyst comprises active components accounting for 30-60% of the total mass and the balance of SiO with three-dimensional ordered hierarchical pore canals₂Preparing a carrier; the active component is composed of 17.66g or 35.32g (NH) by weight part₄)₆Mo₇O₂₄·4H₂O、0.25g NH₄VO₃、0.42g Cu(CH₃COO )₂·2H₂O、0.48g SbCl₃、0.30g H₃AsO₄、1.09g H₃PO₄、0.35g La(CH₃COO)₃·1.5H₂O、0.45g Ce(NO₃)₃·6H₂O and 2.12g CsOH. H₂O is formed; the SiO₂The carrier is SiO synthesized by using a silicon source, a macroporous template and a mesoporous template through a volatilization self-assembly method₂Drying the precursor at 100-120 ℃ for 12-24 h, and roasting at not less than 600 ℃ for 4-8 h to obtain the SiO with the three-dimensional ordered macroporous-mesoporous structure₂(ii) a The macroporous template agent is polymethyl methacrylate; the mesoporous template is a polyoxyethylene polyoxypropylene ether block copolymer;

the preparation method of the hierarchical pore catalyst comprises the following steps:

weighing in proportion;

good effect on the treatment of (NH)₄)₆Mo₇O₂₄·4H₂O and NH₄VO₃Dissolving in deionized water to obtain a steeping liquor A; mixing Cu (CH)₃COO )₂·2H₂O and SbCl₃Dissolving in deionized water to obtain a steeping liquor B; h is to be₃AsO₄And H₃PO₄Dissolving in deionized water to obtain a steeping liquor C; la (CH)₃COO)₃·1.5H₂O and Ce (NO)₃)₃·6H₂Dissolving O in deionized water to obtain a steeping liquor D; reacting CsOH.H₂Dissolving O in deionized water to obtain an impregnation solution E;

thirdly, dipping the dipping solution A into the SiO at the temperature of 80-100 DEG C₂Drying the carrier for 3-12 h at 120 ℃; in the same way, the impregnation liquid B, the impregnation liquid C, the impregnation liquid D and the impregnation liquid E are sequentially impregnated into the SiO₂Obtaining a sample on the carrier;

and fourthly, drying the sample at 120 ℃ overnight, and roasting the sample at 350-450 ℃ for 4-6 hours to obtain the product.

2. The multiwell catalyst of claim 1 wherein: said H₃AsO₄And said H₃PO₄The mass concentration of (A) is 85%.

3. The multiwell catalyst of claim 1 wherein: the impregnation is equal-volume impregnation, and the impregnation is carried out for multiple times.

4. The use of a multiwell catalyst as claimed in claim 1, wherein: the catalyst is used for catalyzing isobutyraldehyde to perform oxidative dehydrogenation to prepare methacrylic acid in the process of preparing methacrylic acid from isobutyraldehyde.

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