Catalysts and their preparation methods and methods for preparing methacrolein by isobutylene oxidation

Abstract

This invention discloses a catalyst, its preparation method, and a method for preparing methacrolein by isobutylene oxidation. The catalyst contains a silica support and an active metal component. The catalyst has a hollow microsphere structure, and the active metal component has the following general formula: Mo 10 Bi a X b Y c O x Wherein, X is selected from at least one of Fe, Ca, Mn, Co, Ni, Mg, Cr, W, Zr, and V, and Y is selected from at least one of Li, Na, K, Rb, and Cs; the value of a ranges from 0.03 to 8.0; the value of b ranges from 0.10 to 12.0; the value of c ranges from 0.02 to 2.0; and x is the number of oxygen atoms necessary to satisfy the valence of other elements. The catalyst for the preparation of methacrolein of this invention has suitable pore size and particle size, high specific surface area, and the hollow structure of the catalyst particles allows for more complete contact between the substrate and the catalyst, thereby improving the conversion rate of the reactants and giving the catalyst good activity.

Description

Technical Field

[0001] This invention relates to the field of catalysts, and particularly to a highly active catalyst for the oxidation of isobutylene to prepare methacrolein, a method for preparing the catalyst, and a method for the oxidation of isobutylene to prepare methacrolein. Background Technology

[0002] Methacrolein / methacrylic acid is a basic organic chemical raw material. As an organic chemical intermediate, it is mainly used to produce plexiglass. It can also be used in the manufacture of functional materials such as resins, coatings, adhesives, and lubricants, making its applications very wide-ranging. The method of selectively oxidizing C4 raw materials such as isobutylene / isobutanol / isobutane to prepare methacrolein / methacrylic acid, and further obtaining methyl methacrylate (MMA), has advantages such as low process cost and minimal environmental pollution, and is currently one of the main methods for preparing MMA.

[0003] CN105498795A discloses a methacrolein catalyst and its preparation method. The method adjusts the physical properties of the catalyst, such as specific surface area and pore size, by adding organic pore-forming agents such as urea and polyvinyl alcohol to the slurry. However, the catalyst obtained by this method has a low specific surface area, too large pore size, and low stability, which is not conducive to the full contact between the reaction raw materials and the active components of the catalyst and the long-term reaction.

[0004] CN102091634A discloses a method for preparing a catalyst for the selective oxidation of isobutylene / tert-butanol to prepare methacrolein. The method involves stirring and mixing silicon micropowder, silica, and precursor compounds of active components to obtain a mixed slurry, thereby obtaining the catalyst. The catalyst support used in this method is a solid powder, which lacks a good pore structure, has a low specific surface area, and is not conducive to the loading of active components.

[0005] CN113546636A describes a catalyst for the selective oxidation of isobutylene or tert-butanol to methacrolein via primary precipitation, filtration, secondary precipitation, drying, and calcination. This method can reduce evaporation energy consumption and improve the safety of the preparation process. The resulting product has the advantages of high catalyst yield, high catalyst activity, and high selectivity. However, the process steps are complex and the production cost is high.

[0006] Obtaining catalysts that simultaneously possess good catalytic activity, high selectivity, and high stability under high loads has always been an important research direction in the field of methacrolein catalysts. Summary of the Invention

[0007] The purpose of this invention is to overcome the problems of poor heat dissipation under high load, easy sublimation loss of molybdenum components, poor stability, and low selectivity, and to provide a catalyst for the preparation of methacrolein with more adsorption and desorption sites, good catalytic activity, good heat dispersion on the catalyst surface, less sublimation loss of active molybdenum components, and long catalyst life, as well as its preparation method and application.

[0008] The first aspect of this invention provides a catalyst for the preparation of methacrolein, the catalyst comprising: a silica support and an active metal component, the catalyst having a cavity microsphere structure, and the active metal component having the following general formula: Mo 10 Bi a X b Y c O x Wherein, X is selected from at least one of Fe, Ca, Mn, Co, Ni, Mg, Cr, W, Zr, and V, and Y is selected from at least one of Li, Na, K, Rb, and Cs; the value of a ranges from 0.03 to 8.0; the value of b ranges from 0.10 to 12.0; the value of c ranges from 0.02 to 2.0; and x is the number of oxygen atoms necessary to satisfy the valence of other elements.

[0009] A second aspect of the present invention provides a method for preparing the catalyst of the present invention, the method comprising:

[0010] (a) Dissolve the precursor containing Mo to obtain solution I;

[0011] (b) Add the inorganic silicon source dispersion to solution I obtained in step (a) to obtain mixed solution II;

[0012] (c) Dissolve the precursor containing Bi, X, and Y elements to obtain solution III, add it to mixed solution II and stir to obtain a mixed slurry;

[0013] (d) Add an organic solution of organosilicon source and an alkaline solution to the mixed slurry obtained in step (c), and then boil the slurry;

[0014] (e) The slurry obtained in step (d) is dried and calcined.

[0015] A third aspect of the present invention provides a method for preparing methacrolein by oxidation of isobutylene, the method comprising: in the presence of the catalyst described in the present invention, isobutylene undergoing an oxidation reaction in the presence of a mixture of oxygen and an inert gas and water.

[0016] The catalyst of this invention forms a hollow microsphere structure by adding an organic solvent solution containing an organosilicon source during the slurry preparation process. It is speculated that the hollow microsphere structure of this catalyst can provide more adsorption and desorption sites for the reaction substrate, enhancing catalytic activity. Simultaneously, it facilitates the dispersion of heat on the catalyst surface, reducing the sublimation loss of the active molybdenum component, thereby extending the catalyst's lifespan.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] The catalyst for the preparation of methacrolein of this invention has suitable pore size and particle size, high specific surface area, and the hollow structure of the catalyst particles allows for more thorough contact between the substrate and the catalyst, thereby improving the conversion rate of the reactants and giving the catalyst good activity. Simultaneously, this structure also promotes heat transfer and dispersion within the catalyst, avoiding localized overheating, thus reducing the sublimation loss of molybdenum components and improving the long-term operational stability of the catalyst. Under high loads, the catalyst maintains a high single-pass yield of methacrolein for extended periods; after 800 hours of operation, the isobutylene conversion can reach over 97.3%, and the methacrolein yield can reach over 82.0%. Attached Figure Description

[0019] Figure 1 This is a scanning electron microscope image of Embodiment 1 of the present invention. Detailed Implementation

[0020] 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.

[0021] This invention provides a catalyst for the preparation of methacrolein, the catalyst comprising: a silica support and an active metal component, the catalyst having a cavity microsphere structure, and the active metal component having the following general formula: Mo 10 Bi a X b Y c O x Wherein, X is selected from at least one of Fe, Ca, Mn, Co, Ni, Mg, Cr, W, Zr, and V, and Y is selected from at least one of Li, Na, K, Rb, and Cs; the value of a ranges from 0.03 to 8.0; the value of b ranges from 0.10 to 12.0; the value of c ranges from 0.02 to 2.0; and x is the number of oxygen atoms necessary to satisfy the valence of other elements.

[0022] According to a preferred embodiment of the present invention, the catalyst hollowness ratio is 30-70%. The hollowness ratio refers to the percentage of catalyst microspheres with cavity structures out of the total number of catalyst microspheres, and can be calculated using selective area scanning electron microscopy.

[0023] According to a preferred embodiment of the present invention, the catalyst has a specific surface area of ​​50–110 m². 2 / g.

[0024] According to a preferred embodiment of the present invention, the catalyst has an average pore size of 4 to 8 nm.

[0025] According to a preferred embodiment of the present invention, the particle size of the catalyst is 30 μm to 80 μm.

[0026] According to a preferred embodiment of the present invention, the silica support accounts for 20% to 80% of the total weight of the catalyst, and the total content of the active metal component accounts for 20% to 80% of the total weight of the catalyst.

[0027] This invention does not impose special requirements on the preparation method of the catalyst, as long as it meets the aforementioned requirements for the catalyst. According to a preferred embodiment of this invention, this invention provides a method for preparing the catalyst of this invention, the method comprising:

[0028] (a) Dissolve the precursor containing Mo to obtain solution I;

[0029] (b) Add the inorganic silicon source dispersion to solution I obtained in step (a) to obtain mixed solution II;

[0030] (c) Dissolve the precursor containing Bi, X, and Y elements to obtain solution III, add it to mixed solution II and stir to obtain a mixed slurry;

[0031] (d) Add an organic solution of organosilicon source and an alkaline solution to the mixed slurry obtained in step (c), and then boil the slurry;

[0032] (e) The slurry obtained in step (d) is dried and calcined.

[0033] According to a preferred embodiment of the present invention, the mass ratio of inorganic silicon source to organosilicon source is 120:1 to 80:1, preferably 105:1 to 95:1.

[0034] According to a preferred embodiment of the present invention, the inorganic silicon source dispersion is one or more of the following: inorganic sol of inorganic silicide, inorganic gel, and organic solution of inorganic silicide.

[0035] According to a preferred embodiment of the present invention, the inorganic silicon source dispersion is preferably a silica sol with a particle size of 5-15 nm and a mass concentration of 15%-40% by weight.

[0036] According to a preferred embodiment of the present invention, the organosilicon source is at least one of tetraethyl orthosilicate and methyl orthosilicate.

[0037] According to a preferred embodiment of the present invention, the organic solvent of the organic solution of the organosilicon source is selected from one or more of n-hexane, cyclohexane, acetone, and tetrahydrofuran, preferably one or more of n-hexane and cyclohexane.

[0038] According to a preferred embodiment of the present invention, the concentration of the organic solution of the organosilicon source is 5% to 40% by weight, preferably 20% to 30% by weight.

[0039] According to a preferred embodiment of the present invention, in step (d), the alkaline solution is selected from at least one of urea solution, sodium hydroxide solution and ammonia water; preferably, the concentration of the alkaline solution is 2-30 wt%.

[0040] According to a preferred embodiment of the present invention, in step (d), an organic solution of an organosilicon source and an alkaline solution are added sequentially, and the time interval between adding the organosilicon source solution and the alkaline solution is 2 to 10 minutes, preferably 3 to 5 minutes.

[0041] According to a preferred embodiment of the present invention, in step (d), the alkaline solution is added dropwise to the slurry to adjust the pH of the slurry to 2-5, preferably 3-4.

[0042] According to a preferred embodiment of the present invention, the conditions for boiling the slurry include: a temperature of 100-150°C, preferably 120-130°C; a time of 10-50 min, preferably 20-40 min; and a stirring speed of 200-400 rpm, preferably 250-300 rpm.

[0043] According to a preferred embodiment of the present invention, in step (e), the drying is spray drying, and the drying conditions include: the drying heat source is air, the drying temperature is 200-480°C, the drying time is 0.5-4h, and the average diameter of the spray droplets is 40-200μm.

[0044] According to a preferred embodiment of the present invention, in step (e), the calcination conditions include: being carried out in an oxygen-containing atmosphere, with a calcination temperature of 200–700°C and a calcination time of 3–8 hours.

[0045] This invention provides a method for preparing methacrolein by oxidation of isobutylene, the method comprising: isobutylene undergoing an oxidation reaction in the presence of a mixture of oxygen and an inert gas and water;

[0046] According to a preferred embodiment of the present invention, the preferred contact conditions include a molar ratio of isobutylene: oxygen: water: inert gas of 1:2-2.5:1-1.5:11-14, preferably 1:2.1-2.2:1-1.2:12.3-12.8.

[0047] According to a preferred embodiment of the present invention, the reaction temperature is 320–400°C, preferably 360–380°C.

[0048] According to a preferred embodiment of the present invention, the reaction pressure is 80-150 kPa, preferably 100-120 kPa.

[0049] According to a preferred embodiment of the present invention, the weight hourly space velocity is 0.06–0.12 h⁻¹. -1 Preferably 0.08–0.10 h -1 .

[0050] According to a preferred embodiment of the present invention, the inert gas is preferably nitrogen.

[0051] In this invention, in step (a), the Mo-containing precursor is not particularly limited and can be an oxide of Mo or any substance that can generate such an oxide after calcination. Preferably, it is one or more of water-soluble inorganic acid salts, water-soluble organic acid salts, or oxyacid ammonium salts of Mo, and more preferably, it is an oxyacid ammonium salt of Mo, such as (NH4)6Mo7O. 24 .

[0052] In this invention, the precursor containing Bi, X, and Y elements in step (c) is not particularly limited and can be an oxide of the corresponding element or any substance that can generate the oxide after calcination, such as an oxide, hydroxide, inorganic acid salt, or organic acid salt of the corresponding element. Preferably, it is a water-soluble inorganic acid salt and / or a water-soluble organic acid salt, and more preferably, it is one or more of a halide, alkoxide, nitrate, or acetate, and more preferably, it is a nitrate.

[0053] In this invention, in steps (a), (b), and (c), the mixing is carried out under conventional mixing conditions, and the mixture is simply mixed evenly.

[0054] In this invention, the specific surface area and pore size are measured using a Tristar physical adsorption instrument. Before testing, the samples undergo heating and vacuum degassing. Porosity was measured at 77 K, and the specific surface area was calculated using the Brunauer-Emmett-Teller (BET) method. The pore size distribution and pore volume can be calculated from the isothermal adsorption branch using the Barrettner-Joyner-Halenda (BJH) model.

[0055] In this invention, gas chromatography is used for online analysis of the product gas. The conversion rate of isobutylene, the selectivity of methacrolein, and the single-pass yield are used as indicators to evaluate the catalyst performance. The definitions of these indicators are as follows:

[0056] Isobutylene conversion rate (%) = (moles of isobutylene reacted / moles of isobutylene fed) × 100%;

[0057] Methacrolein selectivity (%) = (moles of methacrolein produced / moles of isobutylene reacted) × 100%;

[0058] Methacrolein single-pass yield (%) = (moles of methacrolein produced / moles of isobutylene fed) × 100%.

[0059] Example 1

[0060] 882.77 grams of (NH4)6Mo7O 24 • 4H₂O was dissolved in water to obtain solution I. 1990.24 g of 30% silica sol (particle size 10 nm) was added to solution I and mixed thoroughly to obtain solution II. 242.54 g of Bi(NO₃)₃·5H₂O, 145.41 g of Ni(NO₃)₂·6H₂O, 40.40 g of Fe(NO₃)₃·9H₂O, and 19.49 g of CsNO₃ were dissolved in water to obtain solution III. Solution III was added to solution II and stirred thoroughly to obtain a mixture. 19.90 g of 30% tetraethyl orthosilicate (5.97 g) in n-hexane was added to the mixture, and after mixing thoroughly for 5 min, 60 mL of 28% ammonia solution was added to adjust the pH to 3–4. The mixture was then stirred at 250 rpm for 40 min at 120°C and boiled to obtain a slurry. Slurry III was spray-dried at 340℃ for 40 minutes, resulting in an average droplet diameter of 100 μm, yielding particulate matter. Finally, the obtained particulate matter was calcined at 600℃ for 3 hours under an oxygen-containing atmosphere (21% oxygen by volume) to obtain oxidation catalyst particles for the preparation of methacrolein (active component: Mo). 10 Bi 1.0 Fe 0.2Ni 1.0 Cs 0.2 O 32.9 With a cavity ratio of 62% and an active component content of 60% by weight, this catalyst has a specific surface area of ​​68 m². 2 / g, with an average pore size of approximately 5.2nm and uniform distribution, and an average particle size of 45μm. Scanning electron microscopy revealed a distinct hollow microsphere structure (e.g., ...). Figure 1 ).

[0061] The reaction tube was filled with the oxidation catalyst for the preparation of methacrolein obtained in the above steps, and the oxidation reaction conditions for the preparation of methacrolein were as follows: In a millimeter-scale fluidized bed reactor, the reaction conditions were: reaction temperature: 365℃; reaction pressure: 100 kPa; catalyst loading: 300 g; catalyst isobutylene loading (WWH): 0.08 h. -1 Raw material ratio (moles): Isobutylene / Oxygen / Water / Nitrogen = 1:2.2:1:12.5.

[0062] Catalyst samples were analyzed after 3 hours of operation, showing a 97.6% conversion rate of isobutylene and a single-pass yield of 82.4% for methacrolein. The reaction was continued, and samples were analyzed again 800 hours after the start of the reaction. The 97.3% conversion rate of isobutylene and a single-pass yield of methacrolein were observed.

[0063] The hollow microsphere structure facilitates the dispersion of heat on the catalyst surface and reduces the sublimation loss of active molybdenum components. The molybdenum content before and after the reaction was characterized by inductively coupled plasma (ICP) elemental analysis. After 800 hours of reaction, the molybdenum content of the catalyst decreased by only 0.23%, thus improving the catalyst's lifespan and significantly enhancing its stability.

[0064] Example 2

[0065] 882.77 grams of (NH4)6Mo7O 24• 4H₂O was dissolved in water to obtain solution I. 1990.24 g of 30% silica sol (particle size 10 nm) was added to solution I and mixed thoroughly to obtain solution II. 242.54 g of Bi(NO₃)₃·5H₂O, 145.41 g of Ni(NO₃)₂·6H₂O, 40.40 g of Fe(NO₃)₃·9H₂O, and 19.49 g of CsNO₃ were dissolved in water to obtain solution III. Solution III was added to solution II and stirred thoroughly to obtain a mixture. 23.88 g of 25% methyl orthosilicate (5.97 g) in cyclohexane solution was added to the mixture, and after mixing thoroughly for 5 min, 60 mL of 28% ammonia solution was added to adjust the pH to 3–4. The mixture was then stirred at 250 rpm for 40 min at 120℃ and boiled to obtain a slurry. Slurry III was spray-dried at 340℃ for 40 minutes, resulting in an average droplet diameter of 100 μm, yielding particulate matter. Finally, the obtained particulate matter was calcined at 600℃ for 3 hours under an oxygen-containing atmosphere (21% oxygen by volume) to obtain oxidation catalyst particles for the preparation of methacrolein (active component: Mo). 10 Bi 1.0 Fe 0.2 Ni 1.0 Cs 0.2 O 32.9 With a cavity ratio of 58% and an active component content of 60% by weight, this catalyst has a specific surface area of ​​66 m². 2 / g, with an average pore size of about 5.8nm and uniform distribution, and an average particle size of 48μm. Its morphology was observed by scanning electron microscopy, and it has a distinct hollow microsphere structure.

[0066] The reaction tube was filled with the oxidation catalyst for the preparation of methacrolein obtained in the above steps, and the oxidation reaction conditions for the preparation of methacrolein were as follows: In a millimeter-scale fluidized bed reactor, the reaction conditions were: reaction temperature: 365℃; reaction pressure: 100 kPa; catalyst loading: 300 g; catalyst isobutylene loading (WWH): 0.08 h. -1 Raw material ratio (moles): Isobutylene / Oxygen / Water / Nitrogen = 1:2.2:1:12.5.

[0067] Catalyst samples were analyzed after 3 hours of operation, showing a 97.5% conversion rate of isobutylene and a 82.2% single-pass yield of methacrolein. The reaction was continued, and samples were analyzed again 800 hours after the start of the reaction. The 97.1% conversion rate of isobutylene and the 81.8% single-pass yield of methacrolein were observed.

[0068] The molybdenum content before and after the reaction was characterized by inductively coupled plasma (ICP) elemental analysis. After 800 hours of reaction, the molybdenum content of the catalyst decreased by only 0.28%.

[0069] Example 3

[0070] 882.77 grams of (NH4)6Mo7O 24 • 4H₂O was dissolved in water to obtain solution I. 1990.24 g of 30% silica sol (particle size 12 nm) was added to solution I and mixed thoroughly to obtain solution II. 485.07 g of Bi(NO₃)₃·5H₂O, 407.14 g of Ni(NO₃)₂·6H₂O, 303.00 g of Fe(NO₃)₃·9H₂O, and 19.49 g of CsNO₃ were dissolved in water to obtain solution III. Solution III was added to solution II and stirred thoroughly to obtain a mixture. 19.90 g of 30% tetraethyl orthosilicate (5.97 g) in n-hexane was added to the mixture, and after mixing thoroughly for 5 min, 30 mL of 10% sodium hydroxide solution was added to adjust the pH to 3–4. The mixture was then stirred at 250 rpm for 40 min at 120°C and boiled to obtain a slurry. Slurry III was spray-dried at 350℃ for 40 minutes, resulting in an average droplet diameter of 90 μm, yielding particulate matter. Finally, the obtained particulate matter was calcined at 600℃ for 3 hours under an oxygen-containing atmosphere (21% oxygen by volume) to obtain oxidation catalyst particles for the preparation of methacrolein (active component: Mo). 10 Bi 2.0 Fe 1.5 Ni 2.8 Cs 0.2 O 32.9 With a cavity ratio of 55% and an active component content of 65% by weight, this catalyst has a specific surface area of ​​60 m². 2 / g, with an average pore size of about 6.1nm and uniform distribution, and an average particle size of 44μm. Its morphology was observed by scanning electron microscopy, and it has a distinct hollow microsphere structure.

[0071] The reaction tube was filled with the oxidation catalyst for the preparation of methacrolein obtained in the above steps, and the oxidation reaction conditions for the preparation of methacrolein were as follows: In a millimeter-scale fluidized bed reactor, the reaction conditions were: reaction temperature: 365℃; reaction pressure: 100 kPa; catalyst loading: 300 g; catalyst isobutylene loading (WWH): 0.08 h. -1 Raw material ratio (moles): Isobutylene / Oxygen / Water / Nitrogen = 1:2.2:1:12.5.

[0072] Catalyst samples were analyzed after 3 hours of operation, showing a 97.3% conversion rate of isobutylene and a 82.1% single-pass yield of methacrolein. The reaction was continued, and samples were analyzed again 800 hours after the start of the reaction. The 96.9% conversion rate of isobutylene and the 81.7% single-pass yield of methacrolein were observed.

[0073] The molybdenum content before and after the reaction was characterized by inductively coupled plasma (ICP) elemental analysis. After 800 hours of reaction, the molybdenum content of the catalyst decreased by only 0.32%.

[0074] Example 4

[0075] 882.77 grams of (NH4)6Mo7O 24 • 4H₂O was dissolved in water to obtain solution I. 1990.24 g of 30% silica sol (particle size 10 nm) was added to solution I and mixed thoroughly to obtain solution II. 242.54 g of Bi(NO₃)₃·5H₂O, 145.41 g of Ni(NO₃)₂·6H₂O, 40.40 g of Fe(NO₃)₃·9H₂O, and 19.49 g of CsNO₃ were dissolved in water to obtain solution III. Solution III was added to solution II and stirred thoroughly to obtain a mixture. 16.59 g of 30% tetraethyl orthosilicate (4.98 g) in n-hexane was added to the mixture, and after mixing thoroughly for 5 min, 20 mL of 28% ammonia solution was added to adjust the pH to 3–4. The mixture was then stirred at 250 rpm for 40 min at 120°C and boiled to obtain a slurry. Slurry III was spray-dried at 340℃ for 40 minutes, resulting in an average droplet diameter of 100 μm, yielding particulate matter. Finally, the obtained particulate matter was calcined at 600℃ for 3 hours under an oxygen-containing atmosphere (21% oxygen by volume) to obtain oxidation catalyst particles for the preparation of methacrolein (active component: Mo). 10 Bi 1.0 Fe 0.2 Ni 1.0 Cs 0.2 O 32.9 With a cavity ratio of 35% and an active component content of 60% by weight, this catalyst has a specific surface area of ​​58 m². 2 / g, with an average pore size of about 6.5nm and an average particle size of 56μm. Its morphology was observed by scanning electron microscopy, and it has a hollow microsphere structure.

[0076] The reaction tube was filled with the oxidation catalyst for the preparation of methacrolein obtained in the above steps, and the oxidation reaction conditions for the preparation of methacrolein were as follows: In a millimeter-scale fluidized bed reactor, the reaction conditions were: reaction temperature: 365℃; reaction pressure: 100 kPa; catalyst loading: 300 g; catalyst isobutylene loading (WWH): 0.08 h. -1 Raw material ratio (moles): Isobutylene / Oxygen / Water / Nitrogen = 1:2.2:1:12.5.

[0077] Catalyst samples were analyzed after 3 hours of operation, showing a 97.0% conversion rate of isobutylene and a 81.7% single-pass yield of methacrolein. The reaction was continued, and samples were analyzed again 800 hours after the start of the reaction. The 96.3% conversion rate of isobutylene and the 80.8% single-pass yield of methacrolein were observed.

[0078] The molybdenum content before and after the reaction was characterized by inductively coupled plasma (ICP) elemental analysis. After 800 hours of reaction, the molybdenum content of the catalyst decreased by 0.46%.

[0079] Example 5

[0080] 882.77 grams of (NH4)6Mo7O 24 • 4H₂O was dissolved in water to obtain solution I. 1990.24 g of 30% silica sol (particle size 10 nm) was added to solution I and mixed thoroughly to obtain solution II. 242.54 g of Bi(NO₃)₃·5H₂O, 145.41 g of Ni(NO₃)₂·6H₂O, 40.40 g of Fe(NO₃)₃·9H₂O, and 19.49 g of CsNO₃ were dissolved in water to obtain solution III. Solution III was added to solution II and stirred thoroughly to obtain a mixture. 19.90 g of 30% tetraethyl orthosilicate (5.97 g) in acetone solution was added, and after mixing thoroughly for 5 min, 60 mL of 28% ammonia solution was added to adjust the pH to 3–4. The mixture was then stirred at 250 rpm for 40 min at 120°C and boiled to obtain a slurry. Slurry III was spray-dried at 340℃ for 40 minutes, resulting in an average droplet diameter of 100 μm, yielding particulate matter. Finally, the obtained particulate matter was calcined at 600℃ for 3 hours under an oxygen-containing atmosphere (21% oxygen by volume) to obtain oxidation catalyst particles for the preparation of methacrolein (active component: Mo). 10 Bi 1.0 Fe 0.2 Ni 1.0 Cs 0.2 O 32.9 With a cavity ratio of 38% and an active component content of 60% by weight, this catalyst has a specific surface area of ​​62 m². 2 / g, with an average pore size of about 5.6nm and uniform distribution, and an average particle size of 58μm. Its morphology was observed by scanning electron microscopy, and it has a hollow microsphere structure.

[0081] The reaction tube was filled with the oxidation catalyst for the preparation of methacrolein obtained in the above steps, and the oxidation reaction conditions for the preparation of methacrolein were as follows: In a millimeter-scale fluidized bed reactor, the reaction conditions were: reaction temperature: 365℃; reaction pressure: 100 kPa; catalyst loading: 300 g; catalyst isobutylene loading (WWH): 0.08 h. -1 Raw material ratio (moles): Isobutylene / Oxygen / Water / Nitrogen = 1:2.2:1:12.5.

[0082] Catalyst samples were analyzed after 3 hours of operation, showing a 97.1% conversion rate of isobutylene and a single-pass yield of 81.6%. The reaction was continued, and samples were analyzed again 800 hours after the start of the reaction. The 96.4% conversion rate of isobutylene and a single-pass yield of 81.0% of methacrolein were observed.

[0083] The molybdenum content before and after the reaction was characterized by inductively coupled plasma (ICP) elemental analysis. After 800 hours of reaction, the molybdenum content of the catalyst decreased by 0.42%.

[0084] Example 6

[0085] 882.77 grams of (NH4)6Mo7O 24 • 4H₂O was dissolved in water to obtain solution I. 1990.24 g of 30% silica sol (particle size 10 nm) was added to solution I and mixed thoroughly to obtain solution II. 242.54 g of Bi(NO₃)₃·5H₂O, 145.41 g of Ni(NO₃)₂·6H₂O, 40.40 g of Fe(NO₃)₃·9H₂O, and 19.49 g of CsNO₃ were dissolved in water to obtain solution III. Solution III was added to solution II and stirred thoroughly to obtain a mixture. 12.45 g of 40% tetraethyl orthosilicate (4.98 g) in n-hexane was added to the mixture, and after mixing thoroughly for 5 min, 60 mL of 28% ammonia solution was added to adjust the pH to 3–4. The mixture was then stirred at 250 rpm for 40 min at 120°C and boiled to obtain a slurry. Slurry III was spray-dried at 340℃ for 40 minutes, resulting in an average droplet diameter of 100 μm, yielding particulate matter. Finally, the obtained particulate matter was calcined at 600℃ for 3 hours under an oxygen-containing atmosphere (21% oxygen by volume) to obtain oxidation catalyst particles for the preparation of methacrolein (active component: Mo). 10 Bi 1.0 Fe0.2 Ni 1.0 Cs 0.2 O 32.9 With a cavity ratio of 33% and an active component content of 60% by weight, this catalyst has a specific surface area of ​​53 m². 2 / g, with an average pore size of about 7.5nm and uniform distribution, and an average particle size of 53μm. Its morphology was observed by scanning electron microscopy, and it has a hollow microsphere structure.

[0086] The reaction tube was filled with the oxidation catalyst for the preparation of methacrolein obtained in the above steps, and the oxidation reaction conditions for the preparation of methacrolein were as follows: In a millimeter-scale fluidized bed reactor, the reaction conditions were: reaction temperature: 365℃; reaction pressure: 100 kPa; catalyst loading: 300 g; catalyst isobutylene loading (WWH): 0.08 h. -1 Raw material ratio (moles): Isobutylene / Oxygen / Water / Nitrogen = 1:2.2:1:12.5.

[0087] Catalyst samples were analyzed after 3 hours of operation, showing a 96.9% conversion rate of isobutylene and a single-pass yield of 81.4%. The reaction was continued, and samples were analyzed again 800 hours after the start of the reaction. The 96.4% conversion rate of isobutylene and the single-pass yield of methacrolein were observed.

[0088] The molybdenum content before and after the reaction was characterized by inductively coupled plasma (ICP) elemental analysis. After 800 hours of reaction, the molybdenum content of the catalyst decreased by 0.84%.

[0089] Example 7

[0090] 882.77 grams of (NH4)6Mo7O 24• 4H₂O was dissolved in water to obtain solution I. 1990.24 g of 30% silica sol (particle size 10 nm) was added to solution I and mixed thoroughly to obtain solution II. 242.54 g of Bi(NO₃)₃·5H₂O, 145.41 g of Ni(NO₃)₂·6H₂O, 40.40 g of Fe(NO₃)₃·9H₂O, and 19.49 g of CsNO₃ were dissolved in water to obtain solution III. Solution III was added to solution II and stirred thoroughly to obtain a mixture. 14.93 g of 40% tetraethyl orthosilicate (5.97 g) in n-hexane was added to the mixture, and after mixing thoroughly for 5 min, 60 mL of 28% ammonia solution was added to adjust the pH to 3–4. The mixture was then stirred at 250 rpm for 40 min at 120°C and boiled to obtain a slurry. Slurry III was spray-dried at 340℃ for 40 minutes, resulting in an average droplet diameter of 100 μm, yielding particulate matter. Finally, the obtained particulate matter was calcined at 600℃ for 3 hours under an oxygen-containing atmosphere (21% oxygen by volume) to obtain oxidation catalyst particles for the preparation of methacrolein (active component: Mo). 10 Bi 1.0 Fe 0.2 Ni 1.0 Cs 0.2 O 32.9 With a cavity ratio of 35% and an active component content of 60% by weight, this catalyst has a specific surface area of ​​55 m². 2 / g, with an average pore size of about 7.8nm and uniform distribution, and an average particle size of 66μm. Its morphology was observed by scanning electron microscopy, and it has a hollow microsphere structure.

[0091] The reaction tube was filled with the oxidation catalyst for the preparation of methacrolein obtained in the above steps, and the oxidation reaction conditions for the preparation of methacrolein were as follows: In a millimeter-scale fluidized bed reactor, the reaction conditions were: reaction temperature: 365℃; reaction pressure: 100 kPa; catalyst loading: 300 g; catalyst isobutylene loading (WWH): 0.08 h. -1 Raw material ratio (moles): Isobutylene / Oxygen / Water / Nitrogen = 1:2.2:1:12.5.

[0092] Catalyst samples were analyzed after 3 hours of operation, showing a 97.0% conversion rate of isobutylene and a 81.6% single-pass yield of methacrolein. The reaction was continued, and samples were analyzed again 800 hours after the start of the reaction. The 96.5% conversion rate of isobutylene and the 81.0% single-pass yield of methacrolein were observed.

[0093] The molybdenum content before and after the reaction was characterized by inductively coupled plasma (ICP) elemental analysis. After 800 hours of reaction, the molybdenum content of the catalyst decreased by 0.35%.

[0094] Comparative Example 1

[0095] 882.77 grams of (NH4)6Mo7O 24 • 4H₂O was dissolved in water to obtain solution I. 1990.24 g of 30% silica sol was added to solution I and mixed thoroughly to obtain solution II. 242.54 g of Bi(NO₃)₃·5H₂O, 145.41 g of Ni(NO₃)₂·6H₂O, 40.40 g of Fe(NO₃)₃·9H₂O, and 19.49 g of CsNO₃ were dissolved in water to obtain solution III. Solution III was added to solution II and stirred thoroughly to obtain a mixture. 60 mL of 28% ammonia solution was added to adjust the pH to 3–4. The mixture was then stirred at 250 rpm for 40 minutes at 120°C and boiled to obtain a slurry. Slurry III was spray-dried at 340°C for 40 minutes, with an average droplet diameter of 100 μm, to obtain particulate matter. Finally, the obtained particles were calcined at 600°C for 3 hours in an oxygen-containing atmosphere (oxygen volume fraction 21%) to obtain oxidation catalyst particles for the preparation of methacrolein (active component is Mo). 10 Bi 1.0 Fe 0.2 Ni 1.0 Cs 0.2 O 32.9 The catalyst has an active component content of 60% by weight and a specific surface area of ​​34 m². 2 / g, with an average pore size of about 11.6nm and an average particle size of 50μm. The morphology of the particles was observed by scanning electron microscopy, and no obvious hollow microsphere structure was found.

[0096] The reaction tube was filled with the oxidation catalyst for the preparation of methacrolein obtained in the above steps, and the oxidation reaction conditions for the preparation of methacrolein were as follows: In a millimeter-scale fluidized bed reactor, the reaction conditions were: reaction temperature: 365℃; reaction pressure: 100 kPa; catalyst loading: 300 g; catalyst isobutylene loading (WWH): 0.08 h. -1 Raw material ratio (moles): Isobutylene / Oxygen / Water / Nitrogen = 1:2.2:1:12.5.

[0097] Catalyst samples were analyzed after 3 hours of operation, showing a 92.6% conversion rate of isobutylene and a 76.0% single-pass yield of methacrolein. The reaction was continued, and samples were analyzed again 800 hours after the start of the reaction. The 87.4% conversion rate of isobutylene and the 69.2% single-pass yield of methacrolein were observed.

[0098] The molybdenum content before and after the reaction was characterized by inductively coupled plasma (ICP) elemental analysis. After 800 hours of reaction, the molybdenum content of the catalyst decreased by 6.15%.

[0099] Comparative Example 2

[0100] 882.77 grams of (NH4)6Mo7O 24 • 4H₂O was dissolved in water to obtain solution I. 1990.24 g of 30% silica sol was added to solution I and mixed thoroughly to obtain solution II. 242.54 g of Bi(NO₃)₃·5H₂O, 145.41 g of Ni(NO₃)₂·6H₂O, 40.40 g of Fe(NO₃)₃·9H₂O, and 19.49 g of CsNO₃ were dissolved in water to obtain solution III. Solution III was added to solution II and stirred thoroughly to obtain a mixture. 5.97 g of ZSM-5 molecular sieve uniformly dispersed in 20 mL of water was added to the mixture, and after mixing thoroughly for 5 min, 60 mL of 28% ammonia solution was added to adjust the pH to 3–4. The mixture was then stirred at 250 rpm for 40 min at 120℃ and boiled to obtain a slurry. Slurry III was spray-dried at 340℃ for 40 minutes, resulting in an average droplet diameter of 100 μm, yielding particulate matter. Finally, the obtained particulate matter was calcined at 600℃ for 3 hours under an oxygen-containing atmosphere (21% oxygen by volume) to obtain oxidation catalyst particles for the preparation of methacrolein (active component: Mo). 10 Bi 1.0 Fe 0.2 Ni 1.0 Cs 0.2 O 32.9 The catalyst has an active component content of 60% by weight and a specific surface area of ​​38 m². 2 / g, with an average pore size of about 10.5nm and uniform distribution, and an average particle size of 56μm. The morphology of the particles was observed by scanning electron microscopy, and no obvious hollow microsphere structure was found.

[0101] The reaction tube was filled with the oxidation catalyst for the preparation of methacrolein obtained in the above steps, and the oxidation reaction conditions for the preparation of methacrolein were as follows: In a millimeter-scale fluidized bed reactor, the reaction conditions were: reaction temperature: 365℃; reaction pressure: 100 kPa; catalyst loading: 300 g; catalyst isobutylene loading (WWH): 0.08 h. -1 Raw material ratio (moles): Isobutylene / Oxygen / Water / Nitrogen = 1:2.2:1:12.5.

[0102] Catalyst samples were analyzed after 3 hours of operation, showing a 91.8% conversion rate of isobutylene and a 75.2% single-pass yield of methacrolein. The reaction was continued, and samples were analyzed again 800 hours after the start of the reaction. The 85.8% conversion rate of isobutylene and the 68.1% single-pass yield of methacrolein were observed.

[0103] The molybdenum content before and after the reaction was characterized by inductively coupled plasma (ICP) elemental analysis. After 800 hours of reaction, the molybdenum content of the catalyst decreased by 4.30%.

[0104] Comparative Example 3

[0105] 882.77 grams of (NH4)6Mo7O 24 • 4H₂O was dissolved in water to obtain solution I. 597.07 g of ZSM-5 molecular sieve was added to 1393.16 g of water and stirred until evenly dispersed. Solution I was then added and mixed thoroughly to obtain solution II. 242.54 g of Bi(NO₃)₃·5H₂O, 145.41 g of Ni(NO₃)₂·6H₂O, 40.40 g of Fe(NO₃)₃·9H₂O, and 19.49 g of CsNO₃ were dissolved in water to obtain solution III. Solution III was added to solution II and stirred thoroughly to obtain a mixture. 19.90 g of a 30% tetraethyl orthosilicate solution (5.97 g) in n-hexane was added to the mixture. After mixing thoroughly for 5 min, 60 mL of 28% ammonia solution was added to adjust the pH to 3–4. The mixture was then stirred at 250 rpm for 40 min at 120°C and boiled to obtain a slurry. Slurry III was spray-dried at 340℃ for 40 minutes, resulting in an average droplet diameter of 100 μm, yielding particulate matter. Finally, the obtained particulate matter was calcined at 600℃ for 3 hours under an oxygen-containing atmosphere (21% oxygen by volume) to obtain oxidation catalyst particles for the preparation of methacrolein (active component: Mo). 10 Bi 1.0 Fe 0.2 Ni 1.0 Cs 0.2 O 32.9 The catalyst has an active component content of 60% by weight and a specific surface area of ​​21 m². 2 / g, with an average pore size of about 16.2nm and an average particle size of 69μm. The morphology of the particles was observed by scanning electron microscopy, and no hollow microsphere structure was found.

[0106] The reaction tube was filled with the oxidation catalyst for the preparation of methacrolein obtained in the above steps, and the oxidation reaction conditions for the preparation of methacrolein were as follows: In a millimeter-scale fluidized bed reactor, the reaction conditions were: reaction temperature: 365℃; reaction pressure: 100 kPa; catalyst loading: 300 g; catalyst isobutylene loading (WWH): 0.08 h. -1 Raw material ratio (moles): Isobutylene / Oxygen / Water / Nitrogen = 1:2.2:1:12.5.

[0107] Catalyst samples were analyzed after 3 hours of operation, showing an isobutylene conversion of 86.2% and a single-pass yield of 68.1%. The reaction was continued, and samples were analyzed again 800 hours after the start of the reaction, showing an isobutylene conversion of 77.0% and a single-pass yield of 56.7% for methacrylaldehyde.

[0108] The molybdenum content before and after the reaction was characterized by inductively coupled plasma (ICP) elemental analysis. After 800 hours of reaction, the molybdenum content of the catalyst decreased by 8.63%.

[0109] Tables 1 and 2 summarize the catalyst-related data and evaluation data for the examples and comparative examples.

[0110] Table 1. Structural parameters of catalysts in Examples 1-7 and Comparative Examples 1-3

[0111]

[0112]

[0113] Table 2. Catalyst performance test results of Examples 1-7 and Comparative Examples 1-3

[0114]

[0115] As shown in Tables 1 and 2, the oxidation catalyst for the preparation of methacrolein prepared according to the method of the present invention has suitable pore size and particle size, exhibits a distinct hollow microsphere structure, high specific surface area, low sublimation loss of active molybdenum component, and a longer catalyst lifespan. Under high load, the catalyst maintains a high single-pass yield of methacrolein for a long period; after 800 hours of catalyst operation, the isobutylene conversion rate can reach over 97.3%, and the methacrolein yield can reach over 82.0%. The molybdenum content of the oxidation catalyst for the preparation of methacrolein in Example 1 decreased by only 0.23% after 800 hours of reaction.

[0116] 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 combinations of 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. A catalyst for the preparation of methacrolein, characterized in that, The catalyst contains a silica support and an active metal component. The catalyst has a hollow microsphere structure, and the active metal component has the following general formula: Mo 10 Bi a X b Y c O x Wherein, X is selected from at least one of Fe, Ca, Mn, Co, Ni, Mg, Cr, W, Zr, and V; Y is selected from at least one of Li, Na, K, Rb, and Cs; the value of a ranges from 0.03 to 8.0; the value of b ranges from 0.10 to 12.0; and the value of c ranges from 0.02 to 2.

0. x The number of oxygen atoms required to satisfy the valence of other elements; The catalyst has a cavity ratio of 30-70%; The silica support accounts for 20% to 80% of the total weight of the catalyst, and the total content of the active metal component accounts for 20% to 80% of the total weight of the catalyst. The method for preparing the catalyst includes: (a) Dissolve the precursor containing Mo to obtain solution I; (b) Add the inorganic silicon source dispersion to solution I obtained in step (a) to obtain mixed solution II; (c) Dissolve the precursor containing Bi, X, and Y elements to obtain solution III, add it to mixed solution II and stir to obtain a mixed slurry; (d) Add an organic solution of organosilicon source and an alkaline solution to the mixed slurry obtained in step (c), and then boil the slurry; (e) The slurry obtained in step (d) is dried and calcined.

2. The catalyst according to claim 1, wherein, The catalyst has a specific surface area of ​​50~110m². 2 / g; The catalyst has an average pore size of 4-8 nm; The catalyst has a particle size of 30μm to 80μm.

3. The catalyst according to claim 1, wherein, The inorganic silicon source dispersion is one or more of the following: inorganic sol of inorganic silicides, inorganic gel of inorganic silicides, and organic solution of inorganic silicides; The organosilicon source is at least one of tetraethyl orthosilicate and methyl orthosilicate; The organic solvent of the organic solution of the organosilicon source is selected from one or more of n-hexane, cyclohexane, acetone, and tetrahydrofuran; The concentration of the organic solution of the organosilicon source is 5% to 40% by weight. The mass ratio of inorganic silicon source to organic silicon source is 120:1 to 80:

1.

4. The catalyst according to claim 3, wherein, The inorganic silicon source dispersion is a silica sol with a particle size of 5-15 nm and a mass concentration of 15%-40% by weight. The organosilicon source is at least one of tetraethyl orthosilicate and methyl orthosilicate; The organic solvent of the organic solution of the organosilicon source is one or more of n-hexane and cyclohexane; The concentration of the organic solution of the organosilicon source is 20% to 30% by weight. The mass ratio of inorganic silicon source to organic silicon source is 105:1 to 95:

1.

5. The catalyst according to claim 1, wherein, In step (d), the alkaline solution is selected from at least one of urea solution, sodium hydroxide solution and ammonia water.

6. The catalyst according to claim 5, wherein, In step (d), the concentration of the alkaline solution is 2-30 wt%.

7. The catalyst according to claim 1, wherein, In step (d), the organic solution and alkaline solution of the organosilicon source are added sequentially, with a time interval of 2 to 10 minutes between the addition of the organosilicon source solution and the alkaline solution.

8. The catalyst according to claim 7, wherein, In step (d), the time interval between adding the organosilicon source solution and the alkaline solution is 3 to 5 minutes.

9. The catalyst according to claim 1, wherein, In step (d), the alkaline solution is added dropwise to the slurry to adjust the pH of the slurry to 2-5; The conditions for boiling the soy milk include: a temperature of 100~150℃; The time is 10-50 minutes; The stirring speed is 200~400 rpm.

10. The catalyst according to claim 9, wherein, In step (d), adjust the pH of the slurry to 3-4; The conditions for boiling the soy milk include: a temperature of 120~130℃; The time is 20-40 minutes; The stirring speed is 250~300 rpm.

11. The catalyst according to claim 1, wherein, In step (e), The drying method is spray drying, and the drying conditions include: the drying heat source is air, the drying temperature is 200~480℃, the drying time is 0.5~4h, and the average diameter of the spray droplets is 40~200μm.

12. The catalyst according to claim 1, wherein, In step (e), the calcination conditions include: calcination is carried out in an oxygen-containing atmosphere, the calcination temperature is 200~700℃, and the calcination time is 3~8h.

13. A method for preparing methacrolein by oxidation of isobutylene, characterized in that, The method comprises: in the presence of a catalyst according to any one of claims 1-12, isobutylene undergoes an oxidation reaction in the presence of a mixture of oxygen and an inert gas and water.

14. The method according to claim 13, wherein, Exposure conditions include: The molar ratio of isobutylene:oxygen:water:inert gas is 1:2~2.5:1~1.5:11~14; and / or The reaction temperature is 320~400℃; The reaction pressure is 80~150 kPa; The weight hourly space velocity is 0.06–0.12 h. -1 ; The inert gas is nitrogen.

15. The method according to claim 14, wherein, Exposure conditions include: The molar ratio of isobutylene:oxygen:water:inert gas is 1:2.1~2.2:1~1.2:12.3~12.8; and / or The reaction temperature is 360~380℃; The reaction pressure is 100~120 kPa; The weight hourly space velocity is 0.08~0.10 h. -1 .

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