A hydroxy aldehyde condensation catalyst, a preparation method and a method for preparing methyl methacrylate using the same

Abstract

The present application relates to a kind of aldol condensation catalyst, preparation method and the method for preparing methyl methacrylate with it.The catalyst is composed of hydrophobic polymer carrier of doping zirconium modified spinel, and active component supported on the carrier, the carrier is composed of two parts of hydrophobic polymer and zirconium modified spinel, while the process for preparing methyl methacrylate using the catalyst includes two stages of hydrophobic balance and condensation reaction.The catalyst provided by the present application can reduce the carbon deposition and active component aggregation of catalyst, and at the same time, water in the reaction system can be removed, and the conversion of reaction is improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of catalysts, and particularly relates to a hydroxy aldehyde condensation catalyst, a preparation method thereof and a method for preparing methyl methacrylate by using the same. BACKGROUND

[0002] Methyl methacrylate (MMA) is mainly used to produce polymethyl methacrylate (PMMA) and acrylic resin materials, and can also be used to manufacture resins, plastics, paints, adhesives, lubricants, impregnants, glossing agents, insulating pouring materials and medical functional polymer materials, and is an important organic chemical raw material.

[0003] At present, the main routes for producing methyl methacrylate at home and abroad are the acetone cyanhydrin method and the isobutene method. Lucite improved the process and proposed an alpha-process in which no toxic substances are involved in the production process, no large amount of by-products, the environment is friendly, and the raw materials are easy to obtain. In the alpha-process, the second step is the reaction of methyl propionate and formaldehyde to produce methyl methacrylate, and many patent literatures have reported related catalysts at home and abroad.

[0004] CN106423159A discloses an anti-coking hydroxy aldehyde condensation catalyst, which comprises an active component, an anti-coking agent, an active additive and a carrier. The active component Cs is loaded on SiO2, the anti-coking agent is selected from one or more of Pt, Rh, Ru, Pd, Ir, Fe, Co and Ni, and one or more of La, Ce, Nd, Pr and Pm is added as an active additive, thereby improving the anti-coking capacity of the catalyst.

[0005] CN107175094A discloses a composite carrier catalyst for hydroxy aldehyde condensation and a preparation method thereof. The catalyst uses a composite oxide of SiO2 and TiO2 as a carrier, Cs as an active component, and one or more of Na, K, Mg, Ca, Ba, La, Zr, Sr or Sb as an additive. The catalyst can delay coking and improve the stability of the catalyst.

[0006] CN113751011A discloses a hydroxy aldehyde condensation catalyst composition, a preparation method thereof and a method for preparing methyl methacrylate by using the same. The catalyst uses SiO2 as a carrier, Cs as an active component, Ce as an additive, and Bi, Zr, La, Cu, Mn and Fe as a polymerization inhibitor. The catalyst inhibits the polymerization of double bonds in the reaction system, significantly reduces the speed of coking carbonization, and prolongs the single-pass service life of the catalyst.

[0007] In the condensation reaction of methyl propionate and formaldehyde, the reaction system contains substances with carbon-carbon and carbon-oxygen double bonds, which have natural polymerization coking tendency under the reaction conditions. The coking and carbon deposition on the surface of the catalyst not only affect the activity of the reaction, but also seriously affect the single-pass service life of the catalyst, resulting in frequent regeneration of the catalyst. Water is also generated in the reaction system, and as the reaction continues, water will continue to accumulate in the catalyst bed in the reactor. The presence of water not only causes the reaction to proceed in the reverse direction, reducing the conversion rate of the reaction, but also reduces the activity and service life of the catalyst. Therefore, improving the anti-coking and carbon deposition ability and hydrothermal stability of the catalyst and extending the single-pass service life of the catalyst are extremely important for the stable operation of the industrialization of the technology. SUMMARY

[0008] The technical problem to be solved by the present application is that in the process of aldol condensation reaction, on the one hand, the double bond substances in the reaction system will aggregate and deposit carbon, and the active components on the catalyst will also aggregate, reducing the activity and stability of the reaction of methyl propionate and formaldehyde; on the other hand, the water produced in the reaction will continue to accumulate in the reaction system, reducing the conversion rate of the reaction and reducing the service life of the catalyst.

[0009] To solve the above technical problems, the technical solution of the present application is as follows:

[0010] The present application provides a kind of aldol condensation catalyst, which can reduce the carbon deposition and active component aggregation of the catalyst in the process of methyl propionate and formaldehyde aldol condensation reaction, remove the water in the reaction system, improve the conversion rate of the reaction, and solve the problems of easy carbon deposition, poor stability, high requirement for the hydrothermal stability and strength of the catalyst, and low conversion rate in the whole reaction process.

[0011] The aldol condensation catalyst is composed of a hydrophobic polymer carrier doped with zirconium modified spinel and an active component loaded on the carrier.

[0012] In the present application, the carrier is composed of a hydrophobic polymer and a zirconium modified spinel, and the BET specific surface area of the carrier is 50-350 m 2 / g, the pore volume is 1-50 cm 3 / g, and the average pore size is 5-15 nm.

[0013] The hydrophobic polymer is a copolymer of divinylbenzene and monomer 2, wherein monomer 2 is one of C1-C8 alkyl acrylate, vinyl ester of linear or branched carboxylic acid, styrene and its derivatives, conjugated diene, (methyl) acrylamide and acrylonitrile, and chloroethylene.

[0014] Further, the mass ratio of the sum of the mass of divinylbenzene and monomer 2 to the mass of zirconium modified spinel is 1:(2-20).

[0015] The zirconium modified spinel is prepared by modifying spinel with zirconium, wherein the spinel has a general chemical formula of AB2O4 (wherein A and B are different divalent or trivalent metals), and has a hexagonal or nearly hexagonal crystal structure, and further has a cubic lattice to place oxygen atoms to form a cubic packing; further, the spinel includes but is not limited to MnAl2O4, FeAl2O4, MgAl2O4, ZnAl2O4, and ZnFe2O4.

[0016] The BET specific surface area of the spinel is 100-300 m 2 / g, the pore volume is 2-15 cm 3 / g, and the average pore size is 4-10 nm.

[0017] In the present application, the active component of the catalyst is Cs.

[0018] Preferably, the content of the zirconium element is 0.05-2 wt%, preferably 0.05-1 wt%, and more preferably 0.1-0.5 wt%, and the content of the active component Cs element is 1-15 wt%, preferably 3-8 wt%, and more preferably 5-8 wt%, based on the mass of the spinel.

[0019] In a second aspect of the present application, a preparation method of the above aldol condensation catalyst is provided, comprising the following steps:

[0020] (1) Preparation of zirconium modified spinel:

[0021] The zirconium source is dissolved in deionized water or an organic solvent under ultrasonic, the spinel is impregnated by the impregnation method, and the zirconium modified spinel is obtained by light-proof standing and drying.

[0022] (2) Preparation of catalyst carrier:

[0023] a. 400 parts by mass of deionized water, 6 parts by mass of hydroxymethyl cellulose, and 6 parts by mass of sodium dodecylbenzenesulfonate are added to a reactor, and the solid is dissolved by heating to 50°C under stirring to obtain a mixture a;

[0024] b. 10 parts by mass of divinylbenzene and 10 parts by mass of monomer 2 are uniformly mixed to obtain a mixture b, wherein the monomer 2 is one of C1-C8 alkyl acrylate, vinyl ester of linear or branched carboxylic acid, styrene and its derivatives, conjugated diene, (methyl) acrylamide, and acrylonitrile, and chloroethylene;

[0025] c. The zirconium modified spinel obtained in step (1) is added to the mixture b, and then added to the mixture a in the reactor after ultrasonic for 30-40 min;

[0026] d. Add 3 parts by mass of benzoyl peroxide, 10 parts by mass of toluene, 10 parts by mass of n-heptane and 8 parts by mass of dichloroethane into the mixture obtained in step c, heat to 70-90°C, stir for 7-9 h and then filter;

[0027] e. Wash the solid obtained by filtration in step d with deionized water and anhydrous ethanol, then extract the solid in a Soxhlet extractor with 1000 parts by mass of acetone for 48 h, filter, wash, dry and sieve the solid to obtain the catalyst carrier.

[0028] (3) Catalyst precursor preparation: weigh a certain amount of Cs source and prepare a solution, then immerse the catalyst carrier obtained in step (2), stand, dry to obtain the catalyst precursor.

[0029] (4) Catalyst activation: dry and calcine the catalyst precursor.

[0030] Preferably, in the preparation of the zirconium-modified spinel in step (1), the organic solvent is used to dissolve the zirconium source, so any organic solvent that can achieve the above purpose can be used, such as methanol, ethanol, carbon tetrachloride, acetone, DMF, etc.

[0031] The zirconium source is selected from one or more of zirconium dichloride, zirconium acetylacetone, zirconium tetrachloride, zirconium trifluoroacetylacetone, zirconium hexafluoroacetylacetone, zirconium n-propyl alcohol, zirconium isopropoxy isopropyl alcohol, zirconium bis-cyclopentadienyl dichloride, zirconium bis-cyclopentadienyl dimethyl, preferably zirconium dichloride, zirconium tetrachloride, zirconium trifluoroacetylacetone, zirconium hexafluoroacetylacetone, zirconium bis-cyclopentadienyl dichloride.

[0032] The immersion time is controlled to be 2-3 h, the immersion temperature is 30-50°C, the immersion is placed in the dark for 10-20 h, and then dried at 200°C for 8 h.

[0033] In step (2), the vinyl ester of the linear or branched carboxylic acid in step b includes but is not limited to vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, etc.; the conjugated diene includes but is not limited to 1,3-butadiene, isoprene, etc.; the derivative of styrene includes but is not limited to 1,2-styrene, 1,4-styrene, bromostyrene, etc.; the screen used for sieving in step e is 8-20 mesh;

[0034] In the preparation of the catalyst precursor in step (3), equal-volume impregnation or excess impregnation can be used to complete the loading of the active component. In the impregnation process, the immersion time is 0.5-2 h, preferably 1-1.5 h, the immersion temperature is 20-30°C, the immersion is placed in the dark for 10-20 h, and then dried at 50-100°C for 12 h-48 h, preferably 24-36 h.

[0035] In step (3), the source of Cs is selected from one or more of cesium nitrate, cesium carbonate, cesium chloride, cesium silicate, cesium hydroxide, cesium acetate, cesium propionate and cesium oxalate; more preferably, from one or more of cesium carbonate, cesium nitrate, cesium hydroxide and cesium acetate;

[0036] Preferably, in the process of activating the catalyst in step (4), the catalyst is first dried at 120-160°C for 4h, and then calcined in a muffle furnace at a temperature rising rate of 1-10°C / min, preferably at a temperature rising rate of 5-8°C / min, and the calcination temperature is 400-500°C. After reaching the end of the calcination temperature, the temperature is maintained for 4-8h, and then reduced to room temperature at a temperature reduction rate of 5-20°C / min under a nitrogen atmosphere.

[0037] In a third aspect of the present application, a method for preparing methyl methacrylate by catalyzing the aldol condensation of methyl propionate and formaldehyde using the above-mentioned catalyst is provided. The process for preparing methyl methacrylate using the catalyst includes two stages of water removal and condensation reaction.

[0038] 1) Water removal stage

[0039] In a fixed bed reactor, water vapor is introduced at normal pressure and 150°C for 2h, so that the catalyst surface in the catalyst bed layer reaches a water removal state, so that the water generated in the subsequent condensation reaction stage can be removed from the catalyst surface at the fastest speed.

[0040] 2) Condensation reaction stage

[0041] In a fixed bed reactor, the molar ratio of methyl propionate: formaldehyde: methanol is (1-10):1:(1-10), preferably (4-6):1:(4-6); the reaction temperature is 200-400°C, the pressure is 0.5-2Mpa, the reaction liquid space velocity is 2-10h -1 , and the reaction time is 2-500h.

[0042] The reaction equation is as follows: CH3CH2COOCH3+HCHO→C(CH3)2COOCH3+H2O.

[0043] Compared with the prior art, the present application has the following beneficial effects:

[0044] (1) The hydrophobic polymer carrier can change the water balance of the catalyst surface, quickly remove the water generated in the reaction from the catalyst, and expose more active sites for reaction;

[0045] (2) The zirconium-modified spinel doped on the carrier can improve the structural strength of the hydrophobic polymer carrier, improve the service life of the catalyst, and the spinel can also disperse the active component well to inhibit the polymerization of substances in the reaction system, so that the coking and carbonization rate of the catalyst surface is significantly reduced, thereby improving the anti-coking and carbonization capacity of the catalyst;

[0046] (3) The catalyst is applied in the process of preparing methyl methacrylate by aldol condensation, and can reduce the initial reaction temperature in the hydrophobic balance stage, reduce the generation of carbon deposition, and also make the water generated in the reaction stage leave the catalyst surface at the fastest speed, thereby improving the catalyst activity. The catalyst provided by the application has high utilization rate of active components, high reaction activity and stability, strong polymerization inhibition and anti-coking capacity, high conversion rate, low requirements for the hydrothermal stability and strength of the catalyst, and high industrial application value. DETAILED DESCRIPTION

[0047] Raw materials:

[0048] Magnesium aluminate spinel: Inoceram, ALFA, purity 99%.

[0049] Other raw materials appearing in this text are all conventional commercially available raw materials unless otherwise specified.

[0050] Test instruments and methods:

[0051] Thermogravimetric analysis: Mettler Toledo TGA-2 thermogravimetric analyzer.

[0052] Muffle furnace: Nabether L3 / 11-LT60 / 20 muffle furnace.

[0053] Tubular reactor: tube diameter 2.5 cm, tube length 80 cm, electric heating furnace heating.

[0054] Screening is carried out by two layers of screen mesh, the first layer of screen mesh is 8 mesh, the second layer of screen mesh is 20 mesh, and the carrier with the intermediate particle size is taken as the target catalyst carrier.

[0055] Example 1

[0056] 0.8115 g of zirconium acetylacetone was dissolved in 30 g of acetone, and 300 g of magnesium aluminate spinel was immersed in the above solution at room temperature, and after being immersed at 50°C for 2 h, it was taken out and placed at room temperature in the dark for 10 h, and finally dried at 200°C for 8 h to obtain zirconium-modified spinel 1.

[0057] Take 9 g of hydroxymethyl cellulose and 9 g of sodium dodecyl benzene sulfonate and 600 g of deionized water into a reactor and heat stirring at 50 °C to dissolve the solids. Take 15 g of divinyl benzene and 15 g of methyl methacrylate and add to the zirconium modified spinel 1 above and sonicate for 30 min and then add to the reactor. Take 4.5 g of benzoyl peroxide, 15 g of toluene, 15 g of n-heptane and 12 g of dichloroethane and add to the reactor. Heat to 70 °C and stir for 9 h and then filter. Wash the solids from the above filtration with deionized water, absolute ethanol and then extract the solids in a soxhlet extractor with 1500 g of acetone for 48 h and then filter. Wash, dry and sieve the solids to obtain the catalyst support.

[0058] Take 12.9554 g of CsNO3 and dissolve in 100 g of deionized water. Dissolve completely and then immerse the support in the solution at room temperature. Immerse for 1 h and then seal from light and let stand for 16 h. Then dry at 100 °C for 24 h to obtain precursor 1.

[0059] Place the precursor 1 in a muffle furnace and dry at 160 °C for 4 h. Then heat at a rate of 5 °C / min to 450 °C and calcine at 450 °C for 6 h. Then cool at a rate of 20 °C / min to room temperature to obtain catalyst 1.

[0060] In a fixed bed reactor, before the start of the reaction, by passing water vapor at atmospheric pressure and 150 °C for 2 h, the catalyst is allowed to reach a state of loose equilibrium. Then carry out the reaction at a molar ratio of methyl propionate: formaldehyde: methanol of 5:1:6, a catalyst dosage of 200 g, a reaction liquid space velocity of 4.0 h -1 , and a temperature of 330 °C. After 30 h of reaction, the single pass conversion of methyl propionate is 10.85% and the selectivity of methyl methacrylate is 85.67%. After 200 h of reaction, the single pass conversion of methyl propionate is 10.56% and the selectivity of methyl methacrylate is 86.08%. The catalyst sample is analyzed by thermogravimetry and the weight loss is measured to be 8.64 wt%.

[0061] Example 2

[0062] Take 1.7436 g of zirconium dichloride and dissolve in 50 g of methanol. After complete dissolution, take 900 g of magnesium aluminum spinel and immerse in the above solution at room temperature. Immerse for 2 h at 50 °C, then remove and let stand in the dark at room temperature for 15 h. Finally, dry at 200 °C for 8 h to obtain zirconium modified spinel 2.

[0063] 18g of hydroxymethyl cellulose and 18g of sodium dodecylbenzenesulfonate were weighed and added to 1200g of deionized water, and heated and stirred at 50°C to dissolve the solids. 30g each of divinylbenzene and acrylamide were weighed and added to the zircon-modified spinel 2 obtained above, and sonicated for 30 minutes before being placed into the reactor. 9g of benzoyl peroxide, 30g of toluene, 30g of n-heptane, and 24g of dichloroethane were weighed and added to the reactor, heated to 70°C, stirred for 9 hours, and then filtered. The filtered solid was washed with deionized water and anhydrous ethanol, then extracted with 3000g of acetone in a Soxhlet extractor for 48 hours, filtered, and then washed, dried, and sieved to obtain the catalyst support.

[0064] Weigh 26.5545g of Cs2CO3 and dissolve it in 200g of deionized water. After complete dissolution, immerse the carrier in the above solution at room temperature for 1 hour. After immersion, seal and protect from light and let stand for 16 hours. Then dry at 100℃ for 24 hours to obtain precursor 2.

[0065] Precursor 2 was placed in a muffle furnace and dried at 160°C for 4 hours. Then, it was heated to 450°C at a rate of 5°C / min and calcined at 450°C for 6 hours. Finally, it was cooled to room temperature at a rate of 20°C / min to obtain catalyst 2.

[0066] In a fixed-bed reactor, before the reaction began, water vapor was introduced at atmospheric pressure and 150°C for 2 hours to allow the catalyst to reach a hydrophobic equilibrium. After this initial reaction, the reaction proceeded with methyl propionate:formaldehyde:methanol in a molar ratio of 2:1:7, using 200g of catalyst, and with a liquid hourly space velocity (LISH) of 4.0 h⁻¹. -1 The reaction was carried out at 330℃. After 30 h of reaction, the single-pass conversion of methyl propionate was 9.79% and the selectivity of methyl methacrylate was 84.53%. After 200 h of reaction, the single-pass conversion of methyl propionate was 9.08% and the selectivity of methyl methacrylate was 84.78%. Thermogravimetric analysis of the catalyst sample showed a weight loss of 7.90 wt%.

[0067] Example 3

[0068] 0.6945 g of dicyclopentadienyl zirconium dichloride was weighed and dissolved in 50 g of carbon tetrachloride. After complete dissolution, 150 g of magnesium aluminum spinel was weighed and immersed in the above solution at room temperature. After immersion at 50 °C for 1 h, it was taken out and left to stand at room temperature in the dark for 12 h. Finally, it was dried at 200 °C for 8 h to obtain zircon-modified spinel 3.

[0069] 9g of hydroxymethyl cellulose and 9g of sodium dodecylbenzenesulfonate were weighed and added to 600g of deionized water, and heated and stirred at 50℃ to dissolve the solids. 15g each of divinylbenzene and methyl methacrylate were weighed and added to the zircon-modified spinel 2 obtained above, and sonicated for 30 minutes before being placed into the reactor. 4.5g of benzoyl peroxide, 15g of toluene, 15g of n-heptane, and 12g of dichloroethane were weighed and added to the reactor, heated to 70℃, stirred for 9 hours, and then filtered. The filtered solid was washed with deionized water and anhydrous ethanol, then extracted with 1500g of acetone in a Soxhlet extractor for 48 hours, filtered, washed, dried, and sieved to obtain the catalyst support.

[0070] Weigh 14.8345g of Cs2CO3 and dissolve it in 200g of deionized water. After complete dissolution, immerse the carrier in the above solution at room temperature for 2 hours. After immersion, seal and protect from light and let stand for 16 hours. Then dry at 80℃ for 24 hours to obtain precursor 3.

[0071] Precursor 3 was placed in a muffle furnace and dried at 120°C for 4 hours. Then, it was heated to 500°C at a rate of 5°C / min and calcined at 500°C for 8 hours. Finally, it was cooled to room temperature at a rate of 20°C / min to obtain catalyst 3.

[0072] In a fixed-bed reactor, before the reaction began, water vapor was introduced at atmospheric pressure and 150°C for 2 hours to allow the catalyst to reach a hydrophobic equilibrium. After this initial reaction, the reaction proceeded with methyl propionate:formaldehyde:methanol in a molar ratio of 4:1:9, using 200g of catalyst, and with a liquid hourly space velocity (LISH) of 4.0 h⁻¹. -1 The reaction was carried out at 330℃. After 36 h of reaction, the single-pass conversion of methyl propionate was 10.68%, and the selectivity of methyl methacrylate was 82.19%. After 200 h of reaction, the single-pass conversion of methyl propionate was 11.09%, and the selectivity of methyl methacrylate was 82.18%. Thermogravimetric analysis of the catalyst sample showed a weight loss of 9.38 wt%.

[0073] Example 4

[0074] 2.1793 g of zirconium tetrachloride was weighed and dissolved in 100 g of deionized water. After complete dissolution, 250 g of magnesium aluminum spinel was weighed and immersed in the above solution at room temperature. After immersion at 50 °C for 2 h, it was taken out and left to stand at room temperature in the dark for 20 h. Finally, it was dried at 200 °C for 8 h to obtain zirconium-modified spinel 4.

[0075] 15g of hydroxymethyl cellulose and 15g of sodium dodecylbenzenesulfonate were weighed and added to 1000g of deionized water, and heated and stirred at 50℃ to dissolve the solids. 25g each of divinylbenzene and butyl methacrylate were weighed and added to the zircon-modified spinel 2 obtained above, and sonicated for 30 minutes before being placed into the reactor. 7.5g of benzoyl peroxide, 25g of toluene, 25g of n-heptane, and 20g of dichloroethane were weighed and added to the reactor, heated to 70℃, stirred for 9 hours, and then filtered. The filtered solid was washed with deionized water and anhydrous ethanol, then extracted with 2500g of acetone in a Soxhlet extractor for 48 hours, filtered, and then washed, dried, and sieved to obtain the catalyst support.

[0076] Weigh 14.1436g of Cs2CO3 and dissolve it in 100g of deionized water. After complete dissolution, immerse the carrier in the above solution at room temperature for 1 hour. After immersion, seal and protect from light and let stand for 16 hours. Then dry at 100℃ for 24 hours to obtain precursor 4.

[0077] Precursor 4 was placed in a muffle furnace and dried at 160°C for 4 hours. Then, it was heated to 450°C at a rate of 5°C / min and calcined at 450°C for 6 hours. Finally, it was cooled to room temperature at a rate of 20°C / min to obtain catalyst 4.

[0078] In a fixed-bed reactor, before the reaction began, water vapor was introduced at atmospheric pressure and 150°C for 2 hours to allow the catalyst to reach a hydrophobic equilibrium. After the reaction, the molar ratio of methyl propionate:formaldehyde:methanol was 2:1:6, the catalyst dosage was 225 g, and the liquid hourly space velocity was 4.5 h⁻¹. -1 The reaction was carried out at 340℃. After 30 h of reaction, the single-pass conversion of methyl propionate was 11.56% and the selectivity of methyl methacrylate was 88.15%. After 250 h of reaction, the single-pass conversion of methyl propionate was 11.86% and the selectivity of methyl methacrylate was 86.19%. Thermogravimetric analysis of the catalyst sample showed a weight loss of 8.10 wt%.

[0079] Comparative Example 1

[0080] 2.1793 g of zirconium tetrachloride was dissolved in 100 g of deionized water. After complete dissolution, 250 g of magnesium aluminum spinel support was immersed in the solution at room temperature for 2 hours. The solution was then removed and allowed to stand in the dark at room temperature for 10 hours. Finally, it was dried at 200°C for 8 hours to obtain zirconium-modified spinel 5. 14.1436 g of Cs₂CO₃ was dissolved in 100 g of deionized water. The zirconium-modified spinel 5 was immersed in the solution at room temperature for 1 hour. After immersion, it was sealed and allowed to stand overnight in the dark. Finally, it was dried at 100°C for 12 hours to obtain precursor 5.

[0081] The precursor 5 was placed in a muffle furnace, dried at 160°C for 4h, then raised to 450°C at a rate of 5°C / min, and calcined at 450°C for 6h, then lowered to room temperature at a rate of 20°C / min to obtain catalyst 5.

[0082] In a fixed bed reactor, the catalyst was made to reach a loose water balance reaction by passing water vapor at atmospheric pressure and 150°C for 2h before the reaction started, then the reaction was carried out at a molar ratio of methyl propionate: formaldehyde: methanol of 5:1:6, a catalyst dosage of 200g, and a liquid hourly space velocity of 4.0h -1 After 30h of reaction, the single-pass conversion rate of methyl propionate was 10.33%, and the selectivity of methyl methacrylate was 85.98%; after 200h of reaction, the single-pass conversion rate of methyl propionate was 9.12%, and the selectivity of methyl methacrylate was 83.79%; the catalyst sample was subjected to thermogravimetric analysis, and the weight loss was 13.78wt%.

[0083] Comparative Example 2

[0084] Catalyst 6 was prepared according to Example 1, and in a fixed bed reactor, a loose water balance reaction was not carried out, and the reaction was directly carried out at a molar ratio of methyl propionate: formaldehyde: methanol of 5:1:6, a catalyst dosage of 200g, and a liquid hourly space velocity of 4.0h -1 After 30h of reaction, the single-pass conversion rate of methyl propionate was 10.33%, and the selectivity of methyl methacrylate was 85.98%; after 200h of reaction, the single-pass conversion rate of methyl propionate was 9.12%, and the selectivity of methyl methacrylate was 83.79%; the catalyst sample was subjected to thermogravimetric analysis, and the weight loss was 13.78wt%.

[0085] Comparative Example 3

[0086] Take 12g hydroxymethyl cellulose and 12g sodium dodecyl benzene sulfonate and 800g deionized water and add to the reactor and heat and stir at 50°C to dissolve the solids. Take 20g of divinyl benzene and 20g of methyl methacrylate and add to 200g of spinel 2 and sonicate for 30min and then add to the reactor. Take 6g of benzoyl peroxide, 20g of toluene, 20g of n-heptane and 16g of dichloroethane and add to the reactor. Heat to 70°C and stir for 9h and then filter. Wash the solids obtained by filtration with deionized water, anhydrous ethanol, and then extract the solids in a soxhlet extractor with 2000g of acetone for 48h, filter, wash, dry and sieve to obtain the catalyst carrier.

[0087] Take 19.7862g of Cs2CO3 and dissolve in 200g of deionized water, completely dissolved at room temperature, immerse the carrier in the above solution, immerse for 2h, after immersion, seal and avoid light for 16h, then dry at 90°C for 24h to obtain the precursor 7.

[0088] The precursor 7 was dried at 120°C for 4h, then heated to 500°C at a rate of 5°C / min and calcined at 500°C for 8h, and then cooled to room temperature at a rate of 20°C / min to obtain catalyst 7.

[0089] The catalyst was made to reach a state of loose water balance by passing water vapor at atmospheric pressure and 150°C for 2h before the reaction started, and then the reaction was carried out at a molar ratio of methyl propionate: formaldehyde: methanol of 5:1:6, a catalyst dosage of 200g, a reaction liquid space velocity of 4.0h -1 -1, and a reaction temperature of 330°C. After 36h of reaction, the single-pass conversion rate of methyl propionate was 10.19%, and the selectivity of methyl methacrylate was 80.39%. After 100h of reaction, the single-pass conversion rate of methyl propionate was 8.26%, and the selectivity of methyl methacrylate was 75.30%. Thermogravimetric analysis of the catalyst sample showed a weight loss of 12.87wt%.

Claims

1. A hydroxyl condensation catalyst, characterized in that: The catalyst consists of a hydrophobic polymer support made of zirconium-doped spinel and an active component loaded on the support; the hydrophobic polymer is a copolymer of divinylbenzene and monomer 2, wherein monomer 2 is one of C1-C8 alkyl acrylates, vinyl esters of linear or branched carboxylic acids, styrene and its derivatives, conjugated dienes, (meth)acrylamide and acrylonitrile, and vinyl chloride; the spinel is AB2O4, including MnAl2O4, FeAl2O4, MgAl2O4, ZnAl2O4, and ZnFe2O4; the active component is Cs; The method for preparing the catalyst support includes the following steps: (1) Preparation of zirconium-modified spinel: Zirconium source is ultrasonically dissolved in deionized water or organic solvent, and spinel is impregnated by impregnation method. After being left to stand in the dark, it is dried to obtain zirconium-modified spinel. (2) Preparation of catalyst support: a. Deionized water, hydroxymethyl cellulose, and sodium dodecylbenzene sulfonate are added to a reactor in a certain proportion, stirred and heated to dissolve the solids, and mixture a is obtained; b. Mix divinylbenzene and monomer 2 thoroughly to obtain mixture b; c. Take the zircon-modified spinel obtained in step (1) and add it to mixture b, and then add it to mixture a in the reactor; d. Add benzoyl peroxide, toluene, n-heptane, and dichloroethane to the mixture obtained in step c in a certain proportion, heat, stir and react, and then filter. e. After washing the solid obtained by filtration in step d with deionized water and anhydrous ethanol, the solid is extracted with acetone and filtered. The solid is then washed, dried and sieved to obtain the catalyst support.

2. The catalyst according to claim 1, characterized in that, Based on the quality of spinel, the Cs content is 1-15 wt%.

3. The catalyst according to claim 2, characterized in that, Based on the quality of spinel, the Cs content is 3-8 wt%.

4. The catalyst according to claim 2, characterized in that, Based on the quality of spinel, the Cs content is 5-8 wt%.

5. The catalyst according to claim 1, characterized in that, Based on the quality of spinel, the zirconium content is 0.05-2 wt%.

6. The catalyst according to claim 5, characterized in that, Based on the quality of spinel, the zirconium content is 0.05-1 wt%.

7. The catalyst according to claim 5, characterized in that, Based on the quality of spinel, the zirconium content is 0.1-0.5 wt%.

8. A method for preparing the catalyst according to any one of claims 1-7, comprising the following steps: (1) Preparation of zirconium-modified spinel: Zirconium source is ultrasonically dissolved in deionized water or organic solvent, and spinel is impregnated by impregnation method. After being left to stand in the dark, it is dried to obtain zirconium-modified spinel. (2) Preparation of catalyst support: a. Deionized water, hydroxymethyl cellulose, and sodium dodecylbenzene sulfonate are added to a reactor in a certain proportion, stirred and heated to dissolve the solids, and mixture a is obtained; b. Mix divinylbenzene and monomer 2 thoroughly to obtain mixture b; c. Take the zircon-modified spinel obtained in step (1) and add it to mixture b, and then add it to mixture a in the reactor; d. Add benzoyl peroxide, toluene, n-heptane, and dichloroethane to the mixture obtained in step c in a certain proportion, heat, stir and react, and then filter. e. After washing the solid obtained by filtration in step d with deionized water and anhydrous ethanol, the solid is extracted with acetone and filtered. The solid is then washed, dried and sieved to obtain the catalyst support. (3) Preparation of catalyst precursor: A certain amount of Cs source was weighed and prepared into a solution, and then the catalyst support obtained in step (2) was impregnated, allowed to stand, and dried to obtain the catalyst precursor. (4) Catalyst activation: The catalyst precursor is dried and calcined.

9. The preparation method according to claim 8, characterized in that, Step (1) The organic solvents are methanol, ethanol, carbon tetrachloride, acetone, and DMF; And / or: the impregnation time is 2-3 hours, the impregnation temperature is 30-50℃, after impregnation, it is left to stand in a dark place for 10-20 hours, and then dried at 200℃ for 8 hours.

10. The preparation method according to claim 8, characterized in that, The zirconium source is selected from one or more of zirconium dichloride, zirconium acetylacetonate, zirconium tetrachloride, zirconium trifluoroacetylacetonate, zirconium hexafluoroacetylacetonate, zirconium n-propoxide, zirconium isopropoxyisopropoxide, dicyclopentadienyl zirconium dichloride, and dicyclopentadienyl dimethyl zirconium.

11. The preparation method according to claim 8, characterized in that, The Cs source is selected from one or more of cesium nitrate, cesium carbonate, cesium chloride, cesium silicate, cesium hydroxide, cesium acetate, cesium propionate, and cesium oxalate.

12. A method for preparing methyl methacrylate using the catalyst according to any one of claims 1-7 or the catalyst obtained by the preparation method according to any one of claims 8-11, characterized in that: It includes two stages: hydrophobic equilibrium and condensation reaction. 1) Hydrophobic balance stage In a fixed-bed reactor, steam was introduced at atmospheric pressure and 150°C for 2 hours. 2) Condensation reaction stage In a fixed-bed reactor, the molar ratio of methyl propionate:formaldehyde:methanol is (1-10):1:(1-10), the temperature is 200-400℃, the pressure is 0.5-2 MPa, and the liquid hourly space velocity is 2-10 h⁻¹. -1 The reaction time is 2-500 hours.