Fluidized bed catalyst composition for the one-step preparation of methyl methacrylate and use thereof

Abstract

The present application belongs to the technical field of catalysts, and particularly relates to a fluidized bed catalyst composition for preparing methyl methacrylate by one-step method and application thereof. The fluidized bed catalyst composition comprises catalyst A, a Ni-Al-Ti LDOs composite spherical catalyst, and catalyst B, a K / Mg-Al LDO composite spherical catalyst. Catalysts A and B are mixed in a mass ratio of 1: (1.5-3.0) and then uniformly mixed to form a fluidized bed catalyst composition which is loaded into a fluidized bed reactor. Methyl methacrylate is prepared by reacting methanol and methyl acetate as raw materials. The fluidized bed catalyst composition has excellent catalytic activity and selectivity for methyl methacrylate, greatly improves the problem of rapid deactivation of the catalyst, prolongs the service life of the catalyst, and the prepared catalyst can be regenerated and reused.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a fluidized bed catalyst composition for the one-step preparation of methyl methacrylate and its application. Background Technology

[0002] Methyl methacrylate (MMA) is a crucial monomer in polymerization reactions and plays a vital role in modern chemical engineering. Its polymer, polymethyl methacrylate (PMMA), boasts excellent optical properties, mechanical strength, and fire resistance, making it widely used in various fields such as acrylic glass, high-performance surface coatings, functional membrane materials, and modifiers. Furthermore, MMA, as a comonomer, demonstrates significant application potential in emerging fields such as adsorbent materials and polymer additives. With the continued growth in global demand for high-performance polymer materials, the market size and production capacity of MMA are rapidly expanding. Research and optimization of its efficient preparation technologies are not only of significant scientific importance but also crucial for improving the economic benefits of the chemical industry chain.

[0003] The industrial production of MMA mainly relies on routes such as the acetone cyanohydrin (ACH) method, the isobutylene oxidative carbonylation method, and the methacrylate esterification method. While the acetone cyanohydrin method is widely used, it uses toxic hydrogen cyanide as a raw material and produces numerous byproducts, posing serious environmental pollution and safety risks. The isobutylene oxidative carbonylation method relies on petroleum-based raw materials and is complex, requires high investment, and operates under harsh conditions. The methacrylate esterification method, on the other hand, has high requirements for raw material purity and catalyst selectivity, and has not yet achieved fully economical and efficient large-scale production. Therefore, developing green, low-carbon, and efficient MMA synthesis routes has become an important research direction in this field.

[0004] Currently, a novel one-step synthesis process for high-value-added esters based on methanol and methyl acetate has attracted widespread attention as a green, low-carbon, and efficient MMA synthesis route. The specific process involves the dehydrogenation of methanol (MeOH) to produce formaldehyde (FA) and hydrogen (H2). Formaldehyde then undergoes aldol condensation with methyl acetate (MeAc) to yield methyl acrylate (MA). Methyl acrylate is further hydrogenated with the hydrogen obtained in the first step to generate methyl propionate (MP). Finally, methyl propionate undergoes aldol condensation with formaldehyde to yield methyl methacrylate (MMA). The overall reaction equation is: 2MeOH + MeAc → MMA + H2 + 2H2O. This reaction involves aldol condensation, where aldehydes aromatize on the catalyst surface, leading to carbon deposition and rapid catalyst deactivation, resulting in a short catalyst lifetime. Furthermore, the commonly used fixed-bed reactors for this reaction often experience localized hot spots in the catalyst bed due to poor heat transfer, which undoubtedly exacerbates catalyst deactivation caused by carbon deposition.

[0005] Compared to fixed-bed reactors, fluidized-bed reactors have better bed temperature uniformity, which can improve the problem of local hot spots in the catalyst bed that exists in fixed-bed reactors. However, existing catalysts that are catalytically active in fixed beds have significantly reduced catalytic activity in fluidized beds, making it impossible to obtain excellent catalytic effects. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies, this invention provides a fluidized bed catalyst composition for the one-step preparation of methyl methacrylate, which greatly improves the problem of excessively rapid catalyst deactivation while achieving excellent catalytic performance.

[0007] To achieve the above objectives, the technical solution provided by the present invention is as follows: A fluidized bed catalyst composition for the one-step preparation of methyl methacrylate includes catalyst A and catalyst B; wherein, catalyst A is a Ni-Al-Ti LDOs composite spherical catalyst, comprising the following preparation process: first, Ni-Al-Ti LDHs material is prepared by precipitation method, then the Ni-Al-Ti LDHs material, silica sol and polyvinyl alcohol are mixed and emulsified, granulated, calcined and reduced to obtain the Ni-Al-Ti LDOs composite spherical catalyst, wherein the mass ratio of Ni-Al-Ti LDHs material, silica sol and polyvinyl alcohol is (70~80):(20~30):(1~3); The catalyst B is a K / Mg-Al LDO composite spherical catalyst, which includes the following preparation process: first, Mg-Al LDH material is prepared by precipitation method; then, Mg-Al LDH material, silica sol and polyvinyl alcohol are mixed and emulsified, granulated and calcined to obtain Mg-Al LDO composite spherical support; finally, Mg-Al LDO composite spherical support is impregnated in potassium metal salt solution, and after aging, drying and calcination, K / Mg-Al LDO composite spherical catalyst is obtained. The mass ratio of Mg-Al LDH material, silica sol and polyvinyl alcohol is (70~80):(20~30):(1~3). Catalyst A and catalyst B are mixed and then loaded into a fluidized bed reactor as a fluidized bed catalyst composition. Methyl methacrylate is prepared by reacting methanol and methyl acetate as raw materials. The mass ratio of catalyst A to catalyst B in the catalyst composition is 1:(1.5~3.0).

[0008] The present invention is further configured such that catalyst A specifically includes the following preparation steps: (1) Ni salt, Al salt, Ti salt and urea are dissolved in deionized water, and Ni-Al-Ti layered hydroxide aqueous solution is prepared by urea coprecipitation. After condensation and reflux, filtration and drying, Ni-Al-Ti LDHs material is obtained; wherein, in the mixed metal salt solution, the molar ratio of Ni:Al:Ti is (2~4):(0.85~0.95):(0.05~0.15); (2) After mixing the Ni-Al-Ti LDHs material and silica sol mentioned in step (1) with polyvinyl alcohol (PVA), deionized water is added and the mixture is emulsified into a uniform slurry in an emulsifier. The mixture is then granulated into spherical particles in a spray granulator, calcined in a muffle furnace, and sieved to obtain Ni-Al-Ti LDOs composite spherical catalyst. (3) The Ni-Al-Ti LDOs composite spherical catalyst was thermally reduced to prepare the Ni-Al-TiLDOs composite spherical catalyst.

[0009] The present invention is further configured such that, in step (1) of the catalyst A preparation process, the amount of urea added is such that the molar ratio of urea to the total molar amount of metals (Ni, Al and Ti) is (3~5):1.

[0010] The present invention is further configured such that, in step (1) of the catalyst A preparation process, the reflux temperature is 80~100℃ and the reflux time is 12~24 hours.

[0011] The present invention is further configured such that, in step (2) of the catalyst A preparation process, the mass ratio of Ni-Al-Ti LDHs, silica sol and polyvinyl alcohol is (70~80):(20~30):(1~3); the calcination temperature is 500~600℃; and the particle size range of the Ni-Al-Ti LDOs composite spherical catalyst obtained after sieving is 100~200 mesh.

[0012] The present invention is further configured such that, in step (3) of the catalyst A preparation process, the thermal reduction treatment conditions are reduction at 400~600℃ for 2~4 hours under H2 / Ar atmosphere.

[0013] The present invention further specifies that the catalyst B specifically includes the following preparation steps: (1) Using magnesium salt and aluminum salt as carrier precursors, a magnesium aluminum salt solution is prepared, and then a Mg-Al layered hydroxide aqueous solution is prepared by co-precipitation method. After filtration and drying, Mg-Al LDH material is obtained; wherein, in the magnesium aluminum salt solution, the Mg:Al molar ratio is (2~4):1; (2) After mixing the Mg-Al LDH material and silica sol mentioned in step (1) with polyvinyl alcohol (PVA), the mixture is emulsified into a uniform slurry by an emulsifier, granulated into spherical particles in a spray granulator, calcined in a muffle furnace, and sieved to obtain Mg-Al LDO composite spherical carrier. (3) Weigh potassium carbonate and dissolve it in deionized water to obtain a precursor solution of metal K. Use the equal volume impregnation method to impregnate the above precursor solution on the Mg-Al LDO composite spherical support. After aging, drying and calcination, K / Mg-AlLDO composite spherical catalyst is obtained.

[0014] The present invention is further configured such that, in step (1) of the catalyst B preparation process, the Mg:Al molar ratio is preferably (2.5~3.5):1; the Mg ion concentration in the salt solution is 0.1~0.3 mol / L; and the precipitant in the co-precipitation method is Na2CO3 solution with a molar concentration of 0.3~0.8 mol / L.

[0015] The present invention is further configured such that, in step (1) of the catalyst B preparation process, when the magnesium aluminum salt solution and the Na2CO3 solution are mixed, the pH of the mixed system is controlled to be 9.3-9.7.

[0016] The present invention is further configured such that, in step (2) of the catalyst B preparation process, the mass ratio of Mg-Al LDH, silica sol and polyvinyl alcohol is (70~80):(20~30):(1~3); the calcination temperature is 500~600℃; and the particle size range of the Mg-Al LDO composite spherical catalyst obtained by sieving is 100~200 mesh.

[0017] The present invention is further configured such that, in step (3) of the catalyst B preparation process, the loading of K is 3~7wt%; the aging time is 4~8 hours; and the calcination temperature is 500~600℃.

[0018] The present invention is further configured such that the fluidized bed catalyst composition further includes calcium oxide, and the mass ratio of catalyst A, catalyst B and calcium oxide is 1:(1.5~3.0):(1.0~4.0); preferably, the mass ratio of catalyst A, catalyst B and calcium oxide is 1:(1.5~3.0):(2.0~4.0); more preferably, it is 1:(1.5~3.0):(2.0~3.0).

[0019] This invention provides an application of the fluidized bed catalyst composition for the one-step preparation of methyl methacrylate in a fluidized bed reactor using methyl acetate and methanol as raw materials, wherein the molar ratio of methanol to methyl acetate is (1.8~2.2):1.

[0020] The present invention further specifies the reaction conditions as follows: the catalyst bed height-to-diameter ratio is 2-4; N2 is selected as the carrier gas, the carrier gas flow rate (operating gas velocity) is 40-60 sccm; and the volumetric hourly space velocity (LHSV) is 2-4 h⁻¹. - ¹; The reaction temperature is 340~360℃.

[0021] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a fluidized bed catalyst composition for one-step preparation of methyl methacrylate, which achieves excellent catalytic effect while greatly improving the problem of excessive catalyst deactivation, extending the service life of the catalyst, and the obtained catalyst can be regenerated and reused. Detailed Implementation

[0022] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0023] In the embodiments of the present invention, the silica sol is an ammonium silica sol with a particle size range of 10~20 nm; the polyvinyl alcohol is PVA 05-88 type.

[0024] Example 1 A fluidized bed catalyst composition for one-step preparation of methyl methacrylate includes catalyst A and catalyst B, wherein catalyst A is a Ni-Al-Ti LDOs composite spherical catalyst and catalyst B is a K / Mg-Al LDOs composite spherical catalyst; The catalyst A specifically includes the following preparation steps: (1) Add 8.82 g Ni(NO3)2·6H2O, 3.38 g Al(NO3)3·9H2O and 9.6 g urea to a round-bottom flask containing 200 mL of deionized water and turn on magnetic stirring until completely dissolved; slowly add 0.24 g Ti(SO4)2 and continue stirring to ensure no flocculent precipitate is formed; then reflux the reaction system at 95°C for 18 hours, and immediately remove the flask and immerse it in cold water for rapid cooling. Then filter until the pH of the filtrate is neutral, and put the washed filter cake into a vacuum oven at 80°C to dry overnight to obtain Ni-Al-Ti LDHs material.

[0025] (2) Ni-Al-Ti LDHs material, silica sol and PVA were mixed at a mass ratio of 70:30:2 and deionized water was added. The mixture was emulsified into a uniform slurry in an emulsifier and granulated into spherical particles in a spray granulator. The microspheres obtained by spraying were placed in a muffle furnace for calcination for 5 hours at a calcination temperature of 550℃. After sieving, 100~200 mesh Ni-Al-TiLDOs composite spherical catalysts were obtained.

[0026] (3) The prepared Ni-Al-Ti LDOs composite spherical catalyst was reduced at 500℃ in an H2 / Ar atmosphere (H2 and Ar volume ratio of 1:4) for 3 hours to obtain the Ni-Al-Ti LDOs composite spherical catalyst, denoted as A1.

[0027] The catalyst B specifically includes the following preparation steps: (1) Dissolve 11.54 g Mg(NO3)2·6H2O and 5.63 g Al(NO3)3·9H2O in 150 mL of deionized water. Under stirring, add the mixed salt solution and precipitant Na2CO3 dropwise to a round-bottom beaker containing 50 mL of water, keeping the pH stable at 9.5. After the addition is complete, age the suspension for 12 hours, then filter it until the pH of the filtrate is neutral. Place the washed filter cake in a vacuum oven at 80°C and dry it overnight to obtain Mg-Al LDH material.

[0028] (2) The obtained Mg-Al LDH material, silica sol and PVA are mixed at a mass ratio of 70:30:2 and deionized water is added. The mixture is emulsified into a uniform slurry in an emulsifier and granulated into spherical particles in a spray granulator. The microspheres obtained by spraying are placed in a muffle furnace for calcination for 5 hours at a calcination temperature of 550℃. After sieving, 100~200 mesh Mg-AlLDO composite spherical carriers are obtained.

[0029] (3) Weigh 10g of Mg-Al LDO composite spherical support into a crucible, dissolve 0.88g of K2CO3 in deionized water of the corresponding saturated water absorption volume to obtain a precursor solution, add it dropwise to the Mg-Al LDO composite spherical support, shake evenly, age for 6 hours, dry in an oven at 110℃ for 5 hours, take it out and grind it, calcine it in a muffle furnace at 550℃ for 5 hours to obtain K / Mg-Al LDO composite spherical catalyst, denoted as B1. Mix the catalyst A1 and catalyst B1 obtained above evenly as a fluidized bed catalyst composition (A1+B1) for one-step preparation of methyl methacrylate in a fluidized bed reactor. The specific process is as follows: The fluidized bed combined catalyst prepared above was mixed evenly and then loaded onto the quartz mesh in the middle section of the fluidized bed reactor reaction tube. The combined catalyst consisted of 1.5 g of catalyst A1 and 3 g of catalyst B1. The inner diameter of the reaction tube was 16 mm, resulting in a catalyst bed height-to-diameter ratio of 3 and a bed volume of 9.6 cm². 3 Set the N2 flow rate (operating gas velocity) to 50 sccm, raise the temperature to 350℃ at a rate of 20℃ / min, and maintain this temperature. Turn on the constant temperature water bath and set the temperature to -7℃. After the catalyst bed temperature and the constant temperature water bath temperature stabilize, turn on the horizontal flow pump and set the flow rate to 0.483 mL / min (LHSV = 3 h). -1 The raw materials methanol and methyl acetate are introduced, with a molar ratio of methanol to methyl acetate of 2:1. When the mixed gas comes into contact with the catalyst, the reaction begins, yielding products such as FA, MA, MP, and MMA (methyl methacrylate). The effluent gaseous product is condensed and stored in a condenser. After 1 hour of reaction, it is collected in a reagent bottle. The product is filtered through a 0.22 μm filter membrane, and approximately 0.8 g of the product is added dropwise to a 1.5 ml chromatographic sample vial. Approximately 0.8 g of n-propanol is then added for dilution, and four drops of n-butanol are added as an internal standard. The mixture is thoroughly mixed. A Fuli F70 chromatograph is used to analyze the components of the sample, detecting the target product MMA and other substances.

[0030] Product analysis yielded the MeAC conversion rate C in the above embodiments. MeAc Target product MMA selectivity MMA The following formula is used to evaluate the reaction performance of this invention:

[0031] ; The detection results for different reaction times are shown in Table 1.

[0032] Comparative Example 1 Compared with Example 1, the difference lies in the catalyst composition, specifically: The preparation process of catalyst A is as follows: 8.82 g Ni(NO3)2·6H2O, 3.38 g Al(NO3)3·9H2O, and 9.6 g urea are added to a round-bottom flask containing 200 mL of deionized water. Magnetic stirring is turned on until completely dissolved, forming a clear green solution. 0.24 g Ti(SO4)2 is slowly added, and stirring is continued for 30 minutes to ensure that no flocculent precipitate is formed. The round-bottom flask is placed in an oil bath or a thermostatic magnetic stirrer, equipped with a reflux condenser, and the temperature is set to 95°C. After reflux for 18 hours, the flask is immediately removed and immersed in cold water for rapid cooling. Filtering is then performed until the pH of the filtrate is neutral. The washed filter cake was dried overnight in a vacuum oven at 80°C. After grinding, Ni-Al-TiLDHs powder was obtained. The powder was calcined in a muffle furnace for 5 hours at 550°C to obtain Ni-Al-Ti LDOs powder. The obtained Ni-Al-Ti LDOs powder was reduced at 500°C in an H2 / Ar atmosphere (volume ratio 1:4) for 3 hours to obtain Ni-Al-Ti LDOs powder catalyst, denoted as A2.

[0033] The preparation process of catalyst B is as follows: 11.54 g of Mg(NO3)2·6H2O and 5.63 g of Al(NO3)3·9H2O were dissolved in 150 mL of deionized water to form a clear mixed salt solution. Under stirring, the mixed salt solution and precipitant Na2CO3 were added dropwise in parallel to a round-bottom beaker containing 50 mL of water, maintaining the pH at 9.5. After the addition was complete, the suspension was aged for 12 hours, followed by filtration until the pH of the filtrate was neutral. The washed filter cake was dried overnight in a vacuum oven at 80°C, and then ground to obtain Mg-Al LDH powder. The powder was calcined in a muffle furnace for 5 hours at 550°C to obtain Mg-Al LDO powder. Weigh 10g of Mg-Al LDO powder into a crucible, dissolve 0.88g of K2CO3 in deionized water of the corresponding saturated water absorption volume to obtain a precursor solution, add it dropwise to the Mg-Al LDO powder, shake evenly, age for 6 hours, dry in an oven at 110℃ for 5 hours, take it out and grind it, calcine it in a muffle furnace at 550℃ for 5 hours to obtain K / Mg-AlLDO powder catalyst, denoted as B2.

[0034] The fluidized bed catalyst composition (A2+B2) prepared above was used to prepare methyl methacrylate in a fluidized bed reactor in a one-step process. The specific process was the same as in Example 1. The catalyst composition was 1.5 g of catalyst A2 and 3 g of catalyst B2. The detection results at different reaction times are shown in Table 1.

[0035] Comparative Example 2 Compared with Example 1, the difference lies in the catalyst composition, specifically: The preparation process of catalyst A is as follows: 8.82 g Ni(NO3)2·6H2O, 3.38 g Al(NO3)3·9H2O, and 9.6 g urea are added to a round-bottom flask containing 200 mL of deionized water. Magnetic stirring is turned on until completely dissolved, forming a clear green solution. 0.24 g Ti(SO4)2 is slowly added, and stirring is continued for 30 minutes to ensure that no flocculent precipitate is formed. The round-bottom flask is placed in an oil bath or a thermostatic magnetic stirrer, equipped with a reflux condenser, and the temperature is set to 95°C. After reflux for 18 hours, the flask is immediately removed and immersed in cold water for rapid cooling. Filtering is then performed until the pH of the filtrate is neutral. The washed filter cake was mixed with aluminum sol at a mass ratio of 7:3, and deionized water was added. The mixture was emulsified into a homogeneous slurry in an emulsifier, and then granulated into spherical particles in a spray granulator. The microspheres obtained by spraying were placed in a muffle furnace and calcined for 5 hours at a temperature of 550℃. After sieving, 100~200 mesh Ni-Al-Ti LDOs aluminum sol spherical catalysts were obtained. The prepared Ni-Al-Ti LDOs aluminum sol spherical catalysts were reduced at 500℃ in an H2 / Ar atmosphere (volume ratio of 1:4) for 3 hours to obtain Ni-Al-Ti LDOs aluminum sol spherical catalysts, denoted as A3.

[0036] The preparation process of catalyst B is as follows: 11.54 g of Mg(NO3)2·6H2O and 5.63 g of Al(NO3)3·9H2O are dissolved in 150 mL of deionized water to form a clear mixed salt solution. Under stirring, the mixed salt solution and precipitant Na2CO3 are added dropwise in parallel to a round-bottom beaker containing 50 mL of water, maintaining the pH at 9.5. After the addition is complete, the suspension is aged for 12 hours, followed by filtration until the pH of the filtrate is neutral. The washed filter cake is mixed with alumina sol at a mass ratio of 7:3, and deionized water is added. The mixture is emulsified into a uniform slurry in an emulsifier, granulated into spherical particles in a spray granulator, and the spray-obtained microspheres are calcined in a muffle furnace for 5 hours at 550℃. After sieving, 100-200 mesh Mg-Al LDO alumina sol spherical carriers are obtained. Weigh 10g of Mg-Al LDO aluminum sol spherical support into a crucible, dissolve 0.88g of K2CO3 in deionized water of the corresponding saturated water absorption volume to obtain a precursor solution, add it dropwise to the Mg-Al LDO aluminum sol spherical support, shake evenly, age for 6 hours, dry in an oven at 110℃ for 5 hours, remove and grind, calcine in a muffle furnace at 550℃ for 5 hours to obtain K / Mg-Al LDO aluminum sol spherical catalyst, denoted as B3.

[0037] The fluidized bed catalyst composition (A3+B3) prepared above was used to prepare methyl methacrylate in a fluidized bed reactor in a one-step process, the specific process being the same as in Example 1. The catalyst composition consisted of 1.8 g of catalyst A3 and 3.6 g of catalyst B3. The detection results for different reaction times are shown in Table 1.

[0038] Comparative Example 3 Compared with Example 1, the difference lies in the catalyst composition, specifically: The preparation process of catalyst A is as follows: 8.82 g Ni(NO3)2·6H2O, 3.38 g Al(NO3)3·9H2O, and 9.6 g urea are added to a round-bottom flask containing 200 mL of deionized water. Magnetic stirring is turned on until completely dissolved, forming a clear green solution. 0.24 g Ti(SO4)2 is slowly added, and stirring is continued for 30 minutes to ensure that no flocculent precipitate is formed. The round-bottom flask is placed in an oil bath or a thermostatic magnetic stirrer, equipped with a reflux condenser, and the temperature is set to 95°C. After reflux for 18 hours, the flask is immediately removed and immersed in cold water for rapid cooling. Filtering is then performed until the pH of the filtrate is neutral. The washed filter cake and silica sol were mixed at a mass ratio of 7:3, and deionized water was added. The mixture was emulsified into a homogeneous slurry in an emulsifier, and then granulated into spherical particles in a spray granulator. The microspheres obtained by spraying were placed in a muffle furnace and calcined for 5 hours at a temperature of 550℃. After sieving, 100~200 mesh Ni-Al-Ti LDOs silica sol spherical catalysts were obtained. The prepared Ni-Al-Ti LDOs silica sol spherical catalysts were reduced at 500℃ in an H2 / Ar atmosphere (volume ratio of 1:4) for 3 hours to obtain Ni-Al-Ti LDOs silica sol spherical catalysts, denoted as A4.

[0039] The preparation process of catalyst B is as follows: 11.54 g of Mg(NO3)2·6H2O and 5.63 g of Al(NO3)3·9H2O are dissolved in 150 mL of deionized water to form a clear mixed salt solution. Under stirring, the mixed salt solution and precipitant Na2CO3 are added dropwise in parallel to a round-bottom beaker containing 50 mL of water, maintaining the pH at 9.5. After the addition is complete, the suspension is aged for 12 hours, followed by filtration until the pH of the filtrate is neutral. The washed filter cake is mixed with silica sol at a mass ratio of 7:3, and deionized water is added. The mixture is emulsified into a uniform slurry in an emulsifier, granulated into spherical particles in a spray granulator, and the spray-obtained microspheres are calcined in a muffle furnace for 5 hours at 550℃. After sieving, 100-200 mesh Mg-Al LDO silica sol spherical carriers are obtained. Weigh 10g of Mg-Al LDO silica sol spherical support into a crucible, dissolve 0.88g of K2CO3 in deionized water of the corresponding saturated water absorption volume to obtain a precursor solution, add it dropwise to the Mg-Al LDO silica sol spherical support, shake evenly, age for 6 hours, dry in an oven at 110℃ for 5 hours, remove and grind, calcine in a muffle furnace at 550℃ for 5 hours to obtain K / Mg-Al LDO silica sol spherical catalyst, denoted as B4.

[0040] The fluidized bed catalyst composition (A4+B4) prepared above was used to prepare methyl methacrylate in a fluidized bed reactor in a one-step process, the specific process being the same as in Example 1. The catalyst composition consisted of 1.5 g of catalyst A4 and 3.0 g of catalyst B4. The detection results for different reaction times are shown in Table 1.

[0041] Comparative Example 4 The combined catalyst (A1 + B1) prepared in Example 1 was used in a fixed-bed reactor to prepare methyl methacrylate. The specific process included: weighing 0.1875 g of A1 and 0.375 g of B1, mixing them thoroughly, and then loading them into a reaction tube. The catalyst was fixed at both ends with silica wool. The inner diameter of the reaction tube was 8 mm, resulting in a catalyst bed height-to-diameter ratio of 3 and a bed volume of 1.2 cm³. 3 The N2 flow rate was set to 10 sccm, the preheating furnace temperature to 340℃, and the reactor temperature was increased to 350℃ at a rate of 2℃ / min and then maintained. The constant temperature water bath was turned on and set to -7℃. After the catalyst bed temperature and the constant temperature water bath temperature stabilized, the horizontal flow pump was turned on and the flow rate was set to 0.06 mL / min (LHSV = 3 h). -1The raw materials methanol and methyl acetate were introduced, with a molar ratio of methanol to methyl acetate of 2:1. The reaction began upon contact with the catalyst, yielding products such as FA, MA, MP, and MMA. The effluent gaseous product was condensed and stored in a condenser. After 1 hour of reaction, it was collected in a reagent bottle. The product was filtered through a 0.22 μm filter membrane, and approximately 0.8 g of the product was added dropwise to a 1.5 ml chromatographic sample vial. Approximately 0.8 g of n-propanol was then added for dilution, and four drops of n-butanol were added as an internal standard. The mixture was thoroughly mixed. A Fuli F70 chromatograph was used to analyze the components of the sample, detecting the target product MMA and other substances. The detection results at different reaction times are shown in Table 1.

[0042] Comparative Example 5 The combined catalyst (A2 + B2) prepared in Comparative Example 1 was used in a fixed-bed reactor to prepare methyl methacrylate, and the reaction process was the same as in Comparative Example 4. The detection results at different reaction times are shown in Table 1.

[0043] Comparative Example 6 The combined catalyst (A3 + B3) prepared in Comparative Example 2 was used in a fixed-bed reactor to prepare methyl methacrylate. The mass of catalyst A3 was 0.225 g, and the mass of catalyst A4 was 0.45 g. The reaction process was the same as in Comparative Example 4. The results of different reaction times are shown in Table 1.

[0044] Comparative Example 7 The combined catalyst (A4 + B4) prepared in Comparative Example 3 was used in a fixed-bed reactor to prepare methyl methacrylate, and the reaction process was the same as in Comparative Example 4. The detection results at different reaction times are shown in Table 1.

[0045] Example 2 Compared with Example 1, the difference lies in the composition of catalysts A and B. In step (2) of preparing catalyst A, Ni-Al-Ti LDHs material, silica sol, and PVA are mixed in a mass ratio of 70:30:1; in step (2) of preparing catalyst B, the obtained Mg-Al LDHs material, silica sol, and PVA are mixed in a mass ratio of 70:30:1. The remaining operations are the same as in Example 1, and catalysts A5 and B5 are prepared respectively.

[0046] The fluidized bed catalyst composition (A5+B5) prepared above was used to prepare methyl methacrylate in a fluidized bed reactor in a one-step process, the specific process being the same as in Example 1. The catalyst composition consisted of 1.5 g of catalyst A5 and 3.0 g of catalyst B5. The detection results for different reaction times are shown in Table 1.

[0047] Example 3 Compared with Example 1, the difference lies in the composition of catalysts A and B. In step (2) of preparing catalyst A, Ni-Al-Ti LDHs material, silica sol, and PVA are mixed in a mass ratio of 70:30:3. In step (2) of preparing catalyst B, the obtained Mg-Al LDH material, silica sol, and PVA are mixed in a mass ratio of 70:30:3. The remaining operations are the same as in Example 1, and catalysts A6 and B6 are prepared respectively.

[0048] The fluidized bed catalyst composition (A6+B6) prepared above was used to prepare methyl methacrylate in a fluidized bed reactor in a one-step process, the specific process being the same as in Example 1. The catalyst composition consisted of 1.5 g of catalyst A6 and 3.0 g of catalyst B6. The detection results for different reaction times are shown in Table 1.

[0049] Comparative Example 8 Compared with Example 1, the difference lies in the composition of catalysts A and B. In step (2) of preparing catalyst A, Ni-Al-Ti LDHs material, silica sol, and PVA are mixed in a mass ratio of 70:30:0.5; in step (2) of preparing catalyst B, the obtained Mg-Al LDHs material, silica sol, and PVA are mixed in a mass ratio of 70:30:0.5. The remaining operations are the same as in Example 1, and catalysts A7 and B7 are prepared respectively.

[0050] The fluidized bed catalyst composition (A7+B7) prepared above was used to prepare methyl methacrylate in a fluidized bed reactor in a one-step process, the specific process being the same as in Example 1. The catalyst composition consisted of 1.5 g of catalyst A7 and 3.5 g of catalyst B7. The detection results for different reaction times are shown in Table 1.

[0051] Comparative Example 9 Compared with Example 1, the difference lies in the composition of catalysts A and B. In step (2) of preparing catalyst A, Ni-Al-Ti LDHs material, silica sol, and PVA are mixed in a mass ratio of 70:30:4. In step (2) of preparing catalyst B, the obtained Mg-Al LDH material, silica sol, and PVA are mixed in a mass ratio of 70:30:4. The remaining operations are the same as in Example 1, and catalysts A7 and B7 are prepared respectively.

[0052] The fluidized bed catalyst composition (A7+B7) prepared above was used to prepare methyl methacrylate in a fluidized bed reactor in a one-step process, the specific process being the same as in Example 1. The catalyst composition consisted of 1.5 g of catalyst A7 and 3.0 g of catalyst B7. The detection results for different reaction times are shown in Table 1.

[0053] Table 1. Evaluation results of the reaction performance of the catalyst compositions in Examples 1-3 and Comparative Examples 1-9

[0054] By comparing the catalytic effects of the same catalyst in fluidized beds and fixed beds, it can be seen that the same catalyst exhibits different catalytic performance in fixed beds and fluidized beds. Furthermore, all the catalyst compositions mentioned above show significantly worse stability and shorter catalyst lifetime when applied in fixed-bed reactors. Comparing Example 1 and Comparative Examples 1-3, it can be seen that using aluminum sol as a binder to form the catalyst provides more acidic sites, which is beneficial to the reaction and results in better initial activity than catalysts formed using silica sol. However, excessive acidic sites can also lead to the aromatization of substances such as formaldehyde on the catalyst surface, generating carbon deposits and resulting in a high deactivation rate. Using silica sol alone as a binder leads to insufficient active sites on the surface of the spherical catalyst, resulting in low initial reaction activity. When polyvinyl alcohol (PVA) is added as an additional binder, during the calcination of the support, PVA decomposes into numerous channels in the spherical catalyst, facilitating contact between active sites and reactants. The excellent mechanical strength of the silica sol binder after calcination also allows the composite spherical catalyst to operate stably in the fluidized bed reactor, largely unaffected by bed "hot spots." Comparing Examples 1 and 4, it can be seen that although the catalytic effects of fixed beds and fluidized beds are very similar in the initial stage of the reaction, the deactivation efficiency of the catalyst in the fixed bed is much higher than that in the fluidized bed. Comparing Examples 1-3 and 8, it can be seen that polyvinyl alcohol is oxidized and decomposed during calcination, forming pores on the surface of the spherical catalyst, directly affecting the number of active sites on the catalyst surface. When the amount of polyvinyl alcohol is small, it is not conducive to the reaction, resulting in low reaction activity, and the reaction rate decreases rapidly as the reaction proceeds. In Comparative Example 9, the larger amount of polyvinyl alcohol results in better catalytic activity, but it can be seen that the reaction activity decreases significantly as the reaction proceeds. This is because a large amount of shaped catalyst breaks down during the fluidization process, disrupting the fluidization state.

[0055] Example 4 Compared with Example 1, the difference is that calcium oxide is also added to the fluidized bed catalyst composition. The specific composition of the catalyst composition is: 1.5 g of catalyst A1, 3 g of catalyst B1, and 1 g of calcium oxide. The three are mixed evenly and then loaded into the fluidized bed reactor. The detection results for different reaction times are shown in Table 2.

[0056] Example 5 Compared with Example 1, the difference is that calcium oxide is also added to the fluidized bed catalyst composition. The specific composition of the catalyst composition is: 1.5 g of catalyst A1, 3 g of catalyst B1, and 2 g of calcium oxide. The three are mixed evenly and then loaded into the fluidized bed reactor. The detection results for different reaction times are shown in Table 2.

[0057] Example 6 Compared with Example 1, the difference is that calcium oxide is also added to the fluidized bed catalyst composition. The specific composition of the catalyst composition is: 1.5 g of catalyst A1, 3 g of catalyst B1, and 3 g of calcium oxide. The three are mixed evenly and then loaded into the fluidized bed reactor. The detection results for different reaction times are shown in Table 2.

[0058] Example 7 Compared with Example 1, the difference is that calcium oxide is also added to the fluidized bed catalyst composition. The specific composition of the catalyst composition is: 1.5 g of catalyst A1, 3 g of catalyst B1, and 4 g of calcium oxide. The three are mixed evenly and then loaded into the fluidized bed reactor. The detection results for different reaction times are shown in Table 2.

[0059] Comparative Example 10 Compared with Example 1, the difference is that calcium oxide is also added to the fluidized bed catalyst composition. The specific composition of the catalyst composition is: 1.5 g of catalyst A1, 3 g of catalyst B1, and 5 g of calcium oxide. The three are mixed evenly and then loaded into the fluidized bed reactor. The detection results for different reaction times are shown in Table 2.

[0060] Comparative Example 11 Compared with Comparative Example 4, the difference lies in the addition of calcium oxide to the fluidized bed catalyst composition. The specific composition of the catalyst composition is as follows: catalyst A1 is 0.1875 g, catalyst B1 is 0.375 g, and calcium oxide is 0.125 g. After being mixed evenly, the three are loaded into a fixed-bed reactor. The detection results at different reaction times are shown in Table 2.

[0061] Table 2. Fluidized bed reaction results of Examples 4-7 and Comparative Examples 10-11

[0062] Comparative Examples 1, 4-7, and Comparative Example 10 show that adding calcium oxide to the catalyst bed can further improve the selectivity of MMA and increase the stability of the catalyst. As the amount of calcium oxide added increases, the duration of water removal effect also increases. However, if the amount added is too large, excessive alkaline calcium hydroxide will accumulate in the system, which will aggravate the self-disproportionation reaction of the intermediate formaldehyde and is not conducive to the formation of MMA. Comparative Example 11 shows that calcium oxide is not suitable for addition in a fixed-bed reactor. The heat released by calcium oxide after absorbing water has a severe impact on the fixed bed with poor heat transfer, and the selectivity of MMA and the single-pass life of the catalyst will decrease significantly.

[0063] Example 8 Cyclic regeneration performance test of catalyst composition The catalyst composition (1.5 g Al + 3 g B1) and catalytic reaction process of Example 1 were used, except that the reaction was carried out for 10 h. After the reaction was completed, the catalyst was regenerated at 550 °C for 6 h using 1 vol% O2 / Ar mixed gas at a flow rate of 50 sccm. After the regeneration was completed, the reaction was carried out for another 5 h. The test results are shown in Table 3.

[0064] Table 3 Evaluation results of the cyclic regeneration test of the catalyst composition (A1+B1)

[0065] As can be seen from Table 3, the catalyst composition prepared using the technical solution of the present invention has good reaction activity in the fluidized bed, and the deactivated catalyst can be completely restored to its activity after regeneration.

[0066] Example 9 Cyclic regeneration performance test of catalyst composition The catalyst composition (1.5 g Al + 3 g B1 + 3 g CaO) and catalytic reaction process of Example 6 were used, except that the reaction was carried out for 10 h. After the reaction was completed, the catalyst was regenerated at 550 °C for 6 h using 1 vol% O2 / Ar mixed gas at a flow rate of 50 sccm. After the regeneration was completed, the reaction was carried out for another 5 h. The test results are shown in Table 4.

[0067] Table 4 Evaluation results of the cyclic regeneration test of the catalyst composition (A1+B1+CaO)

[0068] As can be seen from Table 4, the catalyst combination of K / Mg-Al LDO composite spherical catalyst, Ni-Al-Ti LDOs composite spherical catalyst and calcium oxide has better selectivity and stability in fluidized bed reaction compared with the combination without calcium oxide, and all three can be regenerated simultaneously, and their activity can be completely restored through regeneration.

[0069] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will be able to make various modifications based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, any modifications derived or inspired therefrom are still within the scope of protection of this invention.

Claims

1. A fluidized bed catalyst composition for the one-step preparation of methyl methacrylate, characterized in that, The catalyst includes catalyst A and catalyst B; wherein, catalyst A is a Ni-Al-Ti LDOs composite spherical catalyst, which includes the following preparation process: first, Ni-Al-Ti LDHs material is prepared by precipitation method, then the Ni-Al-Ti LDHs material, silica sol and polyvinyl alcohol are mixed and then emulsified, granulated, calcined and reduced to obtain the Ni-Al-Ti LDOs composite spherical catalyst, wherein the mass ratio of Ni-Al-Ti LDHs material, silica sol and polyvinyl alcohol is (70~80):(20~30):(1~3); The catalyst B is a K / Mg-Al LDO composite spherical catalyst, which includes the following preparation process: first, Mg-Al LDH material is prepared by precipitation method; then, Mg-Al LDH material, silica sol and polyvinyl alcohol are mixed and emulsified, granulated and calcined to obtain Mg-Al LDO composite spherical support; finally, Mg-Al LDO composite spherical support is impregnated in potassium metal salt solution, and after aging, drying and calcination, K / Mg-Al LDO composite spherical catalyst is obtained. The mass ratio of Mg-Al LDH material, silica sol and polyvinyl alcohol is (70~80):(20~30):(1~3). Catalyst A and catalyst B are mixed and then loaded into a fluidized bed reactor as a fluidized bed catalyst composition. Methyl methacrylate is prepared by reacting methanol and methyl acetate as raw materials. The mass ratio of catalyst A to catalyst B in the catalyst composition is 1:(1.5~3.0).

2. The fluidized bed catalyst composition according to claim 1, characterized in that, The catalyst A specifically includes the following preparation steps: (1) Ni salt, Al salt, Ti salt and urea are dissolved in deionized water, and Ni-Al-Ti layered hydroxide aqueous solution is prepared by urea coprecipitation. After condensation and reflux and filtration, Ni-Al-Ti LDHs material is obtained; wherein, in the mixed metal salt solution, the molar ratio of Ni:Al:Ti is (2~4):(0.85~0.95):(0.05~0.15); (2) After mixing the Ni-Al-Ti LDHs material and silica sol mentioned in step (1) with polyvinyl alcohol, deionized water is added and the mixture is emulsified into a uniform slurry in an emulsifier, granulated into spherical particles in a spray granulator, calcined in a muffle furnace, and sieved to obtain Ni-Al-Ti LDOs composite spherical catalyst. (3) The Ni-Al-Ti LDOs composite spherical catalyst was thermally reduced to prepare the Ni-Al-Ti LDOs composite spherical catalyst.

3. The fluidized bed catalyst composition according to claim 2, characterized in that, In step (1), the reflux temperature is 80~100℃ and the reflux time is 12~24 hours.

4. The fluidized bed catalyst composition according to claim 2, characterized in that, In step (2), the mass ratio of Ni-Al-TiLDHs, silica sol and polyvinyl alcohol is (70~80):(20~30):(1~3); the calcination temperature is 500~600℃; in step (3), the thermal reduction treatment conditions are reduction at 400~600℃ for 2~4 hours in H2 / Ar atmosphere.

5. The fluidized bed catalyst composition according to claim 1, characterized in that, The catalyst B specifically includes the following preparation steps: (1) Using magnesium salt and aluminum salt as carrier precursors, a magnesium aluminum salt solution is prepared, and then a Mg-Al layered hydroxide aqueous solution is prepared by co-precipitation method. After filtration and drying, Mg-Al LDH material is obtained; wherein, in the magnesium aluminum salt solution, the Mg:Al molar ratio is (2~4):1; (2) After mixing the Mg-Al LDH material and silica sol mentioned in step (1) with polyvinyl alcohol, the mixture is emulsified into a uniform slurry by an emulsifier, granulated into spherical particles in a spray granulator, calcined in a muffle furnace, and sieved to obtain Mg-Al LDO composite spherical carrier. (3) Weigh potassium carbonate and dissolve it in deionized water to obtain a precursor solution of metal K. Use the equal volume impregnation method to impregnate the above precursor solution on the Mg-Al LDO composite spherical support. After aging, drying and calcination, K / Mg-Al LDO composite spherical catalyst is obtained.

6. The fluidized bed catalyst composition according to claim 5, characterized in that, In step (1), the preferred Mg:Al molar ratio is (2.5~3.5):

1.

7. The fluidized bed catalyst composition according to claim 6, characterized in that, In step (2), the mass ratio of Mg-AlLDH, silica sol and polyvinyl alcohol is (70~80):(20~30):(1~3); the calcination temperature is 500~600℃; in step (3), the loading of K is 3~7wt%; the aging time is 4~8 hours; and the calcination temperature is 500~600℃.

8. The fluidized bed catalyst composition according to claim 6, characterized in that, The fluidized bed catalyst composition further includes calcium oxide, and the mass ratio of catalyst A, catalyst B and calcium oxide is 1:(1.5~3.0):(1.0~4.0).

9. The application of a fluidized bed catalyst composition according to any one of claims 1 to 8, characterized in that, This method is used to prepare methyl methacrylate in a fluidized bed reactor using methyl acetate and methanol as raw materials in a one-step process, with a molar ratio of methanol to methyl acetate of (1.8~2.2):

1.

10. The application according to claim 9, characterized in that, The reaction conditions were as follows: catalyst bed height-to-diameter ratio of 2-4; N2 as the carrier gas with a flow rate of 40-60 sccm; and volumetric space velocity of 2-4 h⁻¹. - ¹; The reaction temperature is 340~360℃.

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