Alumina supported aldol condensation catalyst as well as preparation method and application thereof

Abstract

The invention discloses an aluminum oxide supported aldol condensation catalyst as well as a preparation method and application thereof. The aluminum oxide supported aldol condensation catalyst takes cesium and niobium as active components, and an aluminum oxide carrier used by the catalyst is prepared by adopting one of a coprecipitation method, a hydrothermal synthesis method or an evaporation-induced self-assembly method, so that the prepared aldol condensation catalyst has relatively high surface area and pore volume; the catalyst prepared by the method is beneficial to dispersion of active components on the surface of the catalyst, accelerates conversion and diffusion of reactants, intermediate products and products, improves reaction activity, product selectivity and stability of aldol condensation, has a long service life and has a good industrial application prospect.

Description

Technical Field

[0001] The present application relates to the field of catalyst technology, and in particular to an alumina-supported aldol condensation catalyst and a preparation method and application thereof. Background Art

[0002] Methyl methacrylate (MMA) is a key basic chemical raw material, which is widely used in many fields such as organic glass manufacturing, plastic modification and surface coating, and has broad market prospects. At present, the mainstream process route is to produce MMA using the acetone cyanohydrin method (ACH). However, this process involves highly corrosive concentrated sulfuric acid and highly toxic raw material hydrocyanic acid, and produces a large amount of sulfate waste, which does not meet modern environmental protection requirements and is gradually facing elimination. In recent years, the green and environmentally friendly route of synthesizing methyl methacrylate through a one-step aldol condensation method using methyl propionate and formaldehyde as raw materials has gradually received attention. This method has high atomic economy, the raw materials can come from coal chemical products, and the reaction conditions are mild, and the industrialization prospects are broad.

[0003] At present, the catalysts used for the aldol condensation of methyl propionate and formaldehyde generally have low activity and poor stability, which hinders the industrial application of this process route. Therefore, it is necessary to provide an aldol condensation catalyst with high catalytic activity and high stability. Summary of the invention

[0004] The present application provides an alumina-supported aldol condensation catalyst, a preparation method and an application thereof. The alumina-supported aldol condensation catalyst provided in the present application has both high catalytic activity and high stability.

[0005] In a first aspect, an embodiment of the present application provides an alumina-supported aldol condensation catalyst, comprising an alumina carrier and an active component, wherein the alumina carrier is prepared by a co-precipitation method, a hydrothermal synthesis method or an evaporation-induced self-assembly method, and the active component comprises cesium and niobium.

[0006] In some embodiments, the alumina support is prepared by a co-precipitation method.

[0007] In some embodiments, the catalytic life of the alumina-supported aldol condensation catalyst is greater than 200 hours.

[0008] In some embodiments, the alumina-supported aldol condensation catalyst has a specific surface area greater than 150 m 2 / g, pore volume greater than 0.358cm 3 / g.

[0009] In some embodiments, the alumina-supported aldol condensation catalyst has a methyl propionate conversion rate of not less than 29.6%, and a methyl methacrylate selectivity of not less than 87.5%.

[0010] In some embodiments, the co-precipitation method is used to prepare the alumina carrier, comprising the following steps:

[0011] (1) Dissolve Al(NO3)3·9H2O in deionized water to form Al 3+ Aqueous solution with a concentration of 0.2-1.0 mol / L;

[0012] (2) Dissolve (NH4)2CO3 in an appropriate amount of deionized water to form NH 4+ Aqueous solution with a concentration of 1.0-3.0 mol / L;

[0013] (3) simultaneously dropping the aqueous solution obtained in step (1) and the aqueous solution obtained in step (2) into a container pre-filled with deionized water to obtain a mixed solution, and maintaining the pH in the range of 7.0-8.5 during the dropping process;

[0014] (4) aging the mixed solution obtained in step (3) at 30-80° C. for 3-5 h;

[0015] (5) The mixed solution obtained in step (4) is filtered, washed, dried at 100-150° C. for 10-18 h, and calcined at 400-600° C. for 5-8 h to obtain the alumina carrier.

[0016] In some embodiments, the hydrothermal synthesis method is used to prepare the alumina support, comprising the following steps:

[0017] (1) dissolving Al(NO3)3·9H2O in deionized water to obtain an aqueous solution;

[0018] (2) dissolving CO(NH2)2 in deionized water, and then adding the obtained solution to the aqueous solution of step (1) under stirring, and stirring for 20-60 minutes;

[0019] (3) transferring the mixed solution obtained in step (2) to a hydrothermal reactor and subjecting it to hydrothermal treatment at 100-200° C. for 8-16 h;

[0020] (4) Cooling the mixed solution obtained in step (3) to room temperature, filtering, washing, drying at 100-150° C. for 10-18 h, and calcining at 400-800° C. for 5-8 h to finally obtain the alumina carrier.

[0021] In some embodiments, the preparation of the alumina support by the evaporation-induced self-assembly method comprises the following steps:

[0022] (1) dissolving aluminum isopropoxide and glucose in deionized water to obtain an aqueous solution, and stirring for 4-12 hours;

[0023] (2) adjusting the pH of the aqueous solution obtained in step (1) to 4.0-6.0 using a dilute nitric acid solution, and continuing stirring for 12-48 hours;

[0024] (3) drying the solution obtained in step (2) in an oven at 100-150° C. to evaporate the water and organic volatiles to obtain a solid substance;

[0025] (4) calcining the solid material obtained in step (3) at 400-800° C. for 5-8 hours to obtain the alumina carrier.

[0026] In a second aspect, the present invention provides a method for preparing an alumina-supported aldol condensation catalyst, comprising the following steps:

[0027] (1) dissolving a niobium-containing compound in water to obtain an aqueous solution of the niobium-containing compound;

[0028] (2) adding the alumina carrier to the aqueous solution of the niobium compound by an equal volume impregnation method, standing for 1-18 hours, and then drying at 100-120° C. for 1-18 hours to obtain a niobium-containing solid;

[0029] (3) dissolving the cesium-containing compound in water to obtain an aqueous solution of the cesium-containing compound;

[0030] (4) adding the niobium-containing solid into the cesium-containing compound aqueous solution by an equal volume impregnation method, standing for 1-18 hours, then drying at 100-120° C. for 1-18 hours, and calcining at 400-600° C. for 5-8 hours to obtain the alumina-supported aldol condensation catalyst.

[0031] In a third aspect, an embodiment of the present application provides an application of an alumina-supported aldol condensation catalyst in the preparation of methyl methacrylate.

[0032] It can be seen from the above technical scheme that the present specification provides an alumina-supported aldol condensation catalyst, with cesium (Cs) and niobium (Nb) as active components, wherein Cs provides alkaline active sites and Nb provides acidic active sites, to obtain a highly efficient acid-base bifunctional catalyst; the alumina carrier used in the catalyst is prepared by one of the following methods: coprecipitation, hydrothermal synthesis or evaporation-induced self-assembly, so that the prepared aldol condensation catalyst has a higher surface area and pore volume, which is beneficial to the dispersion of active components on the catalyst surface, accelerates the conversion and diffusion of reactants, intermediates and products, improves the reaction activity, product selectivity and stability of the aldol condensation, has a longer service life, and has good prospects for industrial application. DETAILED DESCRIPTION

[0033] In order to facilitate the understanding of this specification, this specification will be described more comprehensively below. This specification can be implemented in many different forms without departing from the core spirit of this specification, and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of this specification more thorough and comprehensive.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which this specification belongs. The terms used herein in this specification are only for the purpose of describing specific embodiments and are not intended to limit this specification. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0035] In a first aspect, an embodiment of the present application provides an alumina-supported aldol condensation catalyst, comprising an alumina carrier and an active component, wherein the alumina carrier is prepared by a co-precipitation method, a hydrothermal synthesis method or an evaporation-induced self-assembly method, and the active component comprises cesium (Cs) and niobium (Nb).

[0036] In the embodiment of the present application, the mass of Cs accounts for 5wt%-20wt% of the total mass of the alumina-supported aldol condensation catalyst, and the mass of Nb accounts for 5wt%-20wt% of the total mass of the alumina-supported aldol condensation catalyst, in terms of mass percentage. Among them, Cs provides alkaline active sites and Nb provides acidic active sites in the active components, so that the alumina-supported aldol condensation catalyst provided in the embodiment of the present application is a highly efficient acid-base bifunctional catalyst. The Cs active component can be derived from at least one of cesium carbonate, cesium propionate, cesium acetate, and cesium nitrate, and the Nb active component can be derived from at least one of niobium pentachloride, ammonium niobate oxalate hydrate, and niobium pentaethoxide.

[0037] The alumina carrier used in the alumina-supported aldol condensation catalyst in the embodiments of the present application is prepared by one of the following methods: co-precipitation, hydrothermal synthesis or evaporation-induced self-assembly. The alumina prepared by the above method is used as a carrier, so that the prepared aldol condensation catalyst has a higher surface area and pore volume, which is beneficial to the dispersion of active components on the catalyst surface, accelerates the conversion and diffusion of reactants, intermediates and products, improves the reaction activity, product selectivity and stability of the aldol condensation, has a longer service life, and has good prospects for industrial application.

[0038] In some embodiments, the alumina support is prepared by a co-precipitation method.

[0039] After a large number of experiments, the inventors found that using alumina prepared by the co-precipitation method as a carrier can make the prepared catalyst have a higher specific surface area and pore volume. In the process of preparing methyl methacrylate by the aldol condensation reaction, the catalyst has a longer service life and can achieve a higher reactant conversion rate and product selectivity.

[0040] In some embodiments, the catalytic life of the alumina-supported aldol condensation catalyst is greater than 200 hours. For example, the catalytic life of the catalyst can reach 210 hours, 220 hours, 230 hours, 240 hours, 250 hours, 260 hours, 270 hours, 280 hours, 290 hours, 300 hours, or any other value greater than 200 hours.

[0041] In some embodiments, the specific surface area of ​​the alumina-supported aldol condensation catalyst is greater than 150 m 2 / g, pore volume greater than 0.358cm 3 / g.

[0042] In some embodiments, the alumina-supported aldol condensation catalyst has a methyl propionate conversion of not less than 29.6%, and a methyl methacrylate selectivity of not less than 87.5%.

[0043] In some embodiments, the co-precipitation method for preparing an alumina carrier comprises the following steps:

[0044] (1) Dissolve Al(NO3)3·9H2O in deionized water to form Al 3+ Aqueous solution with a concentration of 0.2-1.0 mol / L;

[0045] (2) Dissolve (NH4)2CO3 in an appropriate amount of deionized water to form NH 4+ Aqueous solution with a concentration of 1.0-3.0 mol / L;

[0046] (3) simultaneously dropping the aqueous solution obtained in step (1) and the aqueous solution obtained in step (2) into a container pre-filled with deionized water to obtain a mixed solution, and maintaining the pH in the range of 7.0-8.5 during the dropping process;

[0047] (4) aging the mixed solution obtained in step (3) at 30-80° C. for 3-5 h;

[0048] (5) The mixed solution obtained in step (4) is filtered, washed, dried at 100-150° C. for 10-18 h, and calcined at 400-600° C. for 5-8 h to obtain an alumina carrier.

[0049] In some embodiments, the hydrothermal synthesis method for preparing an alumina carrier comprises the following steps:

[0050] (1) dissolving Al(NO3)3·9H2O in deionized water to obtain an aqueous solution;

[0051] (2) dissolving CO(NH2)2 in deionized water, and then adding the obtained solution to the aqueous solution of step (1) under stirring, and stirring for 20-60 minutes;

[0052] (3) transferring the mixed solution obtained in step (2) to a hydrothermal reactor and subjecting it to hydrothermal treatment at 100-200° C. for 8-16 h;

[0053] (4) The mixed solution obtained in step (3) is cooled to room temperature, filtered, washed, dried at 100-150° C. for 10-18 h, and calcined at 400-800° C. for 5-8 h to finally obtain an alumina carrier.

[0054] In some embodiments, the preparation of an alumina support by evaporation-induced self-assembly method comprises the following steps:

[0055] (1) dissolving aluminum isopropoxide and glucose in deionized water to obtain an aqueous solution, and stirring for 4-12 hours;

[0056] (2) adjusting the pH of the aqueous solution obtained in step (1) to 4.0-6.0 using a dilute nitric acid solution, and continuing stirring for 12-48 hours;

[0057] (3) drying the solution obtained in step (2) in an oven at 100-150° C. to evaporate the water and organic volatiles to obtain a solid substance;

[0058] (4) Calcine the solid material obtained in step (3) at 400-800° C. for 5-8 hours to obtain an alumina carrier.

[0059] In a second aspect, the present invention provides a method for preparing an alumina-supported aldol condensation catalyst, comprising the following steps:

[0060] (1) dissolving a niobium-containing compound in water to obtain an aqueous solution of the niobium-containing compound;

[0061] (2) adding the alumina carrier to the aqueous solution of the niobium compound by an equal volume impregnation method, standing for 1-18 hours, and then drying at 100-120° C. for 1-18 hours to obtain a niobium-containing solid;

[0062] (3) dissolving the cesium-containing compound in water to obtain an aqueous solution of the cesium-containing compound;

[0063] (4) adding the niobium-containing solid into the cesium-containing compound aqueous solution by an equal volume impregnation method, standing for 1-18 hours, then drying at 100-120° C. for 1-18 hours, and calcining at 400-600° C. for 5-8 hours to obtain an alumina-supported aldol condensation catalyst.

[0064] In a third aspect, an embodiment of the present application provides an application of an alumina-supported aldol condensation catalyst in the preparation of methyl methacrylate.

[0065] In the process of applying an alumina-supported aldol condensation catalyst to the preparation of methyl methacrylate, a fixed bed reaction system can be used, operated at normal pressure, and the upper and lower ends of the catalyst are supported by quartz sand, wherein the amount of the catalyst used is 1-5 mL; the reaction raw materials are a mixed solution of methyl propionate, formaldehyde and methanol, wherein the formaldehyde comes from one or more of formalin solution, triformaldehyde, polyformaldehyde and methylal, and the carrier gas is nitrogen; the molar ratio of methyl propionate: formaldehyde: methanol is 1: (0.5-5): (2-5) (for example, it can be 1: 1: 3, 1: 2: 3, etc.), the reaction temperature is 300°C-400°C, and the feed liquid hourly space velocity is 1-5h -1 (For example, it can be 1.5h -1 , 2.0h -1 wait).

[0066] During the reaction, gas chromatography can be used to analyze the composition of the product. Gas chromatography conditions: Liquid product analysis is performed on a Shimadzu GC 2014 gas chromatograph, using an Inertcap 624 column (30m×0.32mm×1.8μm), a hydrogen flame ionization detector, and a heating program: 60°C for 1 minute, heating to 150°C at a heating rate of 25°C / min, and holding for 2 minutes.

[0067] The following are specific preparation examples involved in the above content of the present disclosure. It should be clear that the following examples are only for illustrating the above-disclosed alumina-supported aldol condensation catalyst and its preparation method and application, and the specific implementation methods and parameters used therein are only one or several methods in accordance with the numerous processes and methods described above. Those skilled in the art can use other parameters according to the content described in this specification to prepare the alumina-supported aldol condensation catalyst according to the above method without deviating from the core spirit disclosed in the application.

[0068] In the examples and comparative examples of the present application, the specific surface area and pore volume of the catalyst were determined using an ASAP 2020 fully automatic adsorption analyzer. The sample was vacuum degassed at 350°C for 6 hours before testing to completely remove internal gas, moisture and impurities. The specific surface area of ​​the catalyst was analyzed using the Brunauer-Emmett-Teller (BET) specific surface area detection method, and the pore volume of the catalyst was analyzed using the Barrett-Joyner-Halenda (BJH) method.

[0069] Example 1

[0070] The present embodiment provides an alumina-supported aldol condensation catalyst, and the preparation method of the alumina-supported aldol condensation catalyst comprises the following steps: weighing 2.28 g of ammonium niobate oxalate hydrate and dissolving it in an appropriate amount of deionized water, adding 10 g of alumina, standing for 12 hours, and then drying at 110°C for 12 hours; weighing 1.16 g of cesium carbonate and dissolving it in an appropriate amount of deionized water, immersing the dried solid again in an aqueous solution containing 1.16 g of cesium carbonate, standing for 12 hours, and then drying it again at 110°C for 12 hours, and then calcining the obtained sample at 600°C for 6 hours to obtain an alumina-supported aldol condensation catalyst.

[0071] The aluminum oxide used in this embodiment is prepared by a coprecipitation method, comprising the following steps: weighing 75 g of Al(NO3)3·9H2O and dissolving it in an appropriate amount of deionized water to form Al 3+ A 0.5 mol / L aqueous solution and a 1 mol / L (NH4)2CO3 solution were prepared at the same time; the two solutions were simultaneously dripped into a beaker with a small amount of deionized water prepared in advance, maintaining a constant dripping rate, and maintaining the pH stable at 7.5 during the dripping process; after aging at 50°C for 3h, the filtered solid was washed with ethanol and deionized water, dried at 110°C for 12h, and finally calcined at 600°C for 6h to obtain an alumina carrier.

[0072] The alumina-supported aldol condensation catalyst of this embodiment was tested using the aforementioned test method. The test results showed that the specific surface area of ​​the alumina-supported aldol condensation catalyst was 223.22 m 2 / g, pore volume is 0.45cm 3 / g.

[0073] Example 2

[0074] The present embodiment provides an alumina-supported aldol condensation catalyst, and the preparation method of the alumina-supported aldol condensation catalyst comprises the following steps: weighing 2.28 g of ammonium niobate oxalate hydrate and dissolving it in an appropriate amount of deionized water, adding 10 g of alumina, standing for 12 hours, and then drying at 110°C for 12 hours; weighing 1.16 g of cesium carbonate and dissolving it in an appropriate amount of deionized water, immersing the dried solid again in an aqueous solution containing 1.16 g of cesium carbonate, standing for 12 hours, and then drying it again at 110°C for 12 hours, and then calcining the obtained sample at 600°C for 6 hours to obtain an alumina-supported aldol condensation catalyst.

[0075] The aluminum oxide used in this embodiment is prepared by a coprecipitation method, comprising the following steps: weighing 75 g of Al(NO3)3·9H2O and dissolving it in an appropriate amount of deionized water to form Al 3+A 0.5 mol / L aqueous solution and a 1 mol / L (NH4)2CO3 solution are prepared at the same time; the two solutions are simultaneously dripped into a beaker with a small amount of deionized water prepared in advance, maintaining a constant dripping rate, and maintaining the pH stable at 8.5 during the dripping process; after aging at 50°C for 3h, the filtered solid is washed with ethanol and deionized water, dried at 110°C for 12h, and then calcined at 600°C for 6h to obtain an alumina carrier.

[0076] The alumina-supported aldol condensation catalyst of this embodiment was tested using the aforementioned test method. The test results showed that the specific surface area of ​​the alumina-supported aldol condensation catalyst was 153.25 m 2 / g, pore volume is 0.39cm 3 / g.

[0077] Example 3

[0078] The present embodiment provides an alumina-supported aldol condensation catalyst, and the preparation method of the alumina-supported aldol condensation catalyst comprises the following steps: weighing 2.28 g of ammonium niobate oxalate hydrate and dissolving it in an appropriate amount of deionized water, adding 10 g of alumina, standing for 12 hours, and then drying at 110°C for 12 hours; weighing 1.16 g of cesium carbonate and dissolving it in an appropriate amount of deionized water, immersing the dried solid again in an aqueous solution containing 1.16 g of cesium carbonate, standing for 12 hours, and then drying it again at 110°C for 12 hours, and then calcining the obtained sample at 600°C for 6 hours to obtain an alumina-supported aldol condensation catalyst.

[0079] The aluminum oxide used in this embodiment is prepared by a coprecipitation method, comprising the following steps: weighing 75 g of Al(NO3)3·9H2O and dissolving it in an appropriate amount of deionized water to form Al 3+ A 0.5 mol / L aqueous solution and a 1 mol / L (NH4)2CO3 solution were prepared at the same time; the two solutions were simultaneously dripped into a beaker with a small amount of deionized water prepared in advance, maintaining a constant dripping rate, and maintaining the pH stable at 6.5 during the dripping process; after aging at 50°C for 3h, the filtered solid was washed with ethanol and deionized water, dried at 110°C for 12h, and then calcined at 600°C for 6h to obtain an alumina carrier.

[0080] The alumina-supported aldol condensation catalyst of this embodiment was tested using the aforementioned test method. The test results showed that the specific surface area of ​​the alumina-supported aldol condensation catalyst was 108.37 m 2 / g, pore volume is 0.35cm 3 / g.

[0081] Example 4

[0082] The present embodiment provides an alumina-supported aldol condensation catalyst, and the preparation method of the alumina-supported aldol condensation catalyst comprises the following steps: weighing 2.28 g of ammonium niobate oxalate hydrate and dissolving it in an appropriate amount of deionized water, adding 10 g of alumina, standing for 12 hours, and then drying at 110°C for 12 hours; weighing 1.16 g of cesium carbonate and dissolving it in an appropriate amount of deionized water, immersing the dried solid again in an aqueous solution containing 1.16 g of cesium carbonate, standing for 12 hours, and then drying it again at 110°C for 12 hours, and then calcining the obtained sample at 400°C for 6 hours to obtain an alumina-supported aldol condensation catalyst.

[0083] The aluminum oxide used in this embodiment is prepared by a coprecipitation method, comprising the following steps: weighing 75 g of Al(NO3)3·9H2O and dissolving it in an appropriate amount of deionized water to form Al 3+ A 0.5 mol / L aqueous solution and a 1 mol / L (NH4)2CO3 solution were prepared at the same time; the two solutions were simultaneously dripped into a beaker with a small amount of deionized water prepared in advance, maintaining a constant dripping rate, and the pH was maintained stable at 6.5 during the dripping process; after aging at 50°C for 3h, the filtered solid was washed with ethanol and deionized water, dried at 110°C for 12h, and then calcined at 400°C for 6h to obtain an alumina carrier.

[0084] The alumina-supported aldol condensation catalyst of this embodiment was tested using the aforementioned test method. The test results showed that the specific surface area of ​​the alumina-supported aldol condensation catalyst was 169.24 m 2 / g, pore volume is 0.37cm 3 / g.

[0085] Example 5

[0086] The present embodiment provides an alumina-supported aldol condensation catalyst, and the preparation method of the alumina-supported aldol condensation catalyst comprises the following steps: weighing 2.28 g of ammonium niobate oxalate hydrate and dissolving it in an appropriate amount of deionized water, adding 10 g of alumina, standing for 12 hours, and then drying at 110°C for 12 hours; weighing 1.16 g of cesium carbonate and dissolving it in an appropriate amount of deionized water, immersing the dried solid again in an aqueous solution containing 1.16 g of cesium carbonate, standing for 12 hours, and then drying it again at 110°C for 12 hours, and then calcining the obtained sample at 600°C for 6 hours to obtain an alumina-supported aldol condensation catalyst.

[0087] The alumina used in this embodiment is prepared by a hydrothermal synthesis method, including the following steps: weigh 37.5gAl(NO3)3·9H2O and dissolve it in 300mL deionized water to obtain solution A; weigh 36gCO(NH2)2 and dissolve it in 50mL deionized water to obtain solution B; stir for 20-60min; slowly add solution B to solution A, stir for 30min, transfer to a 500mL hydrothermal kettle, and hydrothermally treat at 120°C for 12h. After cooling to room temperature, the mixed solution is filtered, washed with deionized water and ethanol, dried at 110°C for 12h, and finally calcined at 600°C for 6h to obtain an alumina carrier.

[0088] The alumina-supported aldol condensation catalyst of this embodiment was tested using the aforementioned test method. The test results showed that the specific surface area of ​​the alumina-supported aldol condensation catalyst was 120.24 m 2 / g, pore volume is 0.37cm 3 / g.

[0089] Example 6

[0090] The present embodiment provides an alumina-supported aldol condensation catalyst, and the preparation method of the alumina-supported aldol condensation catalyst comprises the following steps: weighing 2.28 g of ammonium niobate oxalate hydrate and dissolving it in an appropriate amount of deionized water, adding 10 g of alumina, standing for 12 hours, and then drying at 110°C for 12 hours; weighing 1.16 g of cesium carbonate and dissolving it in an appropriate amount of deionized water, immersing the dried solid again in an aqueous solution containing 1.16 g of cesium carbonate, standing for 12 hours, and then drying it again at 110°C for 12 hours, and then calcining the obtained sample at 600°C for 6 hours to obtain an alumina-supported aldol condensation catalyst.

[0091] Among them, the alumina used in this embodiment is prepared by evaporation-induced self-assembly, including the following steps: weighing 40.8g of aluminum isopropoxide and 36.0g of glucose, dissolving in 540mL of deionized water, and stirring for 6h; adjusting the solution pH to 5.5 with dilute nitric acid solution, and continuing to stir for 24h, then evaporating in a 120°C oven to remove water and organic volatiles, and finally calcining at 600°C for 6h to remove the template agent glucose to obtain an alumina carrier.

[0092] The alumina-supported aldol condensation catalyst of this embodiment was tested using the aforementioned test method. The test results showed that the specific surface area of ​​the alumina-supported aldol condensation catalyst was 219.17 m 2 / g, pore volume is 0.38cm 3 / g.

[0093] Comparative Example 1

[0094] The present comparative example provides an alumina-supported aldol condensation catalyst, and the preparation method of the alumina-supported aldol condensation catalyst comprises the following steps: weighing 2.28 g of ammonium niobate oxalate hydrate and dissolving it in an appropriate amount of deionized water, adding 10 g of alumina, standing for 12 hours, and then drying at 110°C for 12 hours; weighing 1.16 g of cesium carbonate and dissolving it in an appropriate amount of deionized water, immersing the dried solid again in an aqueous solution containing 1.16 g of cesium carbonate, standing for 12 hours, and then drying it again at 110°C for 12 hours, and then calcining the obtained sample at 800°C for 6 hours to obtain an alumina-supported aldol condensation catalyst.

[0095] The aluminum oxide used in this comparative example was prepared by a coprecipitation method, comprising the following steps: weighing 75 g of Al(NO3)3·9H2O and dissolving it in an appropriate amount of deionized water to form Al 3+ A 0.5 mol / L aqueous solution and a 1 mol / L (NH4)2CO3 solution were prepared at the same time; the two solutions were simultaneously dripped into a beaker with a small amount of deionized water prepared in advance, maintaining a constant dripping rate, and maintaining the pH stable at 6.5 during the dripping process; after aging at 50°C for 3h, the filtered solid was washed with ethanol and deionized water, dried at 110°C for 12h, and then calcined at 800°C for 6h to obtain an alumina carrier.

[0096] The alumina-supported aldol condensation catalyst of this comparative example was tested using the aforementioned test method. The test results showed that the specific surface area of ​​the alumina-supported aldol condensation catalyst was 121.17 m 2 / g, pore volume is 0.33cm 3 / g.

[0097] Comparative Example 2

[0098] The present comparative example provides an alumina-supported aldol condensation catalyst, and the preparation method of the alumina-supported aldol condensation catalyst comprises the following steps: weighing 2.28 g of ammonium niobate oxalate hydrate and dissolving it in an appropriate amount of deionized water, adding 10 g of commercial alumina (purchased from Shanghai MacLean Biochemical Technology Co., Ltd., brand A800251), standing for 12 hours, and then drying at 110°C for 12 hours; weighing 1.16 g of cesium carbonate and dissolving it in an appropriate amount of deionized water, immersing the dried solid again in an aqueous solution containing 1.16 g of cesium carbonate, standing for 12 hours, and then drying it again at 110°C for 12 hours, and then calcining the obtained sample at 600°C for 6 hours to obtain an alumina-supported aldol condensation catalyst.

[0099] The alumina-supported aldol condensation catalyst of this comparative example was tested using the aforementioned test method. The test results showed that the specific surface area of ​​the alumina-supported aldol condensation catalyst was 117.41 m 2 / g, pore volume is 0.35cm3 / g.

[0100] Test Case

[0101] The alumina-supported aldol condensation catalyst prepared in Examples 1-6 and Comparative Examples 1-2 was used to prepare methyl methacrylate. The application method included the following steps: loading the catalyst sample into a fixed bed reactor to evaluate the performance, the reaction pressure was normal pressure, the amount of catalyst used was 4 mL, the molar ratio of methyl propionate: formaldehyde (from trioxymethylene): methanol was 1:1:3, and the liquid hourly space velocity was 1.5 h -1 The reaction temperature was 350° C., and the liquid product analysis was performed on a Shimadzu GC 2014 gas chromatograph. The catalysts of each embodiment and comparative example were subjected to stability tests to determine the time when they became deactivated during operation.

[0102] The catalyst performance results of Examples 1-6 and Comparative Examples 1-2 are shown in Table 1 below.

[0103] Table 1. Catalyst performance results of Examples 1-6 and Comparative Examples 1-2

[0104]

[0105] It can be seen from Table 1 that, under the same active component loading, the specific surface area and pore volume of the alumina-supported catalysts prepared by the co-precipitation method, the hydrothermal synthesis method, and the evaporation-induced self-assembly method are higher than those of the commercial alumina-supported catalysts; under the same evaluation conditions, the activity and service life of the prepared catalysts are also higher than those of commercial alumina, especially the alumina-supported catalyst prepared by the co-precipitation method has the highest specific surface area and pore volume, the highest catalytic activity, so that the active components can be better dispersed, and the diffusion process of the reactants can be effectively accelerated, so that it obtains the optimal catalytic activity and the longest service life.

[0106] In summary, the alumina-supported aldol condensation catalyst provided by the present invention exhibits excellent catalytic activity and stability, a long service life, and a simple preparation process, and has great potential to meet the needs of large-scale industrial production.

[0107] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0108] The above-described embodiments only express several embodiments of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. It should be understood that, on the basis of the technical solutions provided by those skilled in the art in the present application, the technical solutions obtained through logical analysis, reasoning or limited experiments are all within the protection scope of the claims attached to the present application. Therefore, the protection scope of the patent of the present application shall be based on the attached claims, and the specification can be used to interpret the content of the claims.

Claims

1. An alumina-supported aldol condensation catalyst, characterized in that: The invention comprises an alumina carrier and an active component. The alumina carrier is prepared by a coprecipitation method, a hydrothermal synthesis method or an evaporation-induced self-assembly method. The active component comprises cesium and niobium.

2. The alumina-supported aldol condensation catalyst according to claim 1, characterized in that The alumina carrier is prepared by a co-precipitation method.

3. The alumina-supported aldol condensation catalyst according to claim 2, characterized in that: The catalytic life of the alumina-supported aldol condensation catalyst is greater than 200 hours.

4. The alumina-supported aldol condensation catalyst according to claim 3, characterized in that: The specific surface area of ​​the alumina-supported aldol condensation catalyst is greater than 150 m 2 / g, pore volume greater than 0.358cm 3 / g.

5. The alumina-supported aldol condensation catalyst according to claim 2, characterized in that: The alumina-supported aldol condensation catalyst has a methyl propionate conversion rate of not less than 29.6%, and a methyl methacrylate selectivity of not less than 87.5%.

6. The alumina-supported aldol condensation catalyst according to claim 1, characterized in that: The coprecipitation method for preparing the alumina carrier comprises the following steps: (1) Dissolve Al(NO3)3·9H2O in deionized water to form Al 3+ Aqueous solution with a concentration of 0.2-1.0 mol / L; (2) Dissolve (NH4)2CO3 in an appropriate amount of deionized water to form NH 4+ Aqueous solution with a concentration of 1.0-3.0 mol / L; (3) simultaneously dropping the aqueous solution obtained in step (1) and the aqueous solution obtained in step (2) into a container pre-filled with deionized water to obtain a mixed solution, and maintaining the pH in the range of 7.0-8.5 during the dropping process; (4) aging the mixed solution obtained in step (3) at 30-80° C. for 3-5 h; (5) The mixed solution obtained in step (4) is filtered, washed, dried at 100-150° C. for 10-18 h, and calcined at 400-600° C. for 5-8 h to obtain the alumina carrier.

7. The alumina-supported aldol condensation catalyst according to claim 1, characterized in that: The hydrothermal synthesis method is used to prepare the alumina carrier, comprising the following steps: (1) dissolving Al(NO3)3·9H2O in deionized water to obtain an aqueous solution; (2) dissolving CO(NH2)2 in deionized water, and then adding the obtained solution to the aqueous solution of step (1) under stirring, and stirring for 20-60 minutes; (3) transferring the mixed solution obtained in step (2) to a hydrothermal reactor and subjecting it to hydrothermal treatment at 100-200° C. for 8-16 h; (4) Cooling the mixed solution obtained in step (3) to room temperature, filtering, washing, drying at 100-150° C. for 10-18 h, and calcining at 400-800° C. for 5-8 h to finally obtain the alumina carrier.

8. The alumina-supported aldol condensation catalyst according to claim 1, characterized in that: The method of preparing the alumina carrier by the evaporation-induced self-assembly method comprises the following steps: (1) dissolving aluminum isopropoxide and glucose in deionized water to obtain an aqueous solution, and stirring for 4-12 hours; (2) adjusting the pH of the aqueous solution obtained in step (1) to 4.0-6.0 using a dilute nitric acid solution, and continuing stirring for 12-48 hours; (3) drying the solution obtained in step (2) in an oven at 100-150° C. to evaporate the water and organic volatiles to obtain a solid substance; (4) calcining the solid material obtained in step (3) at 400-800° C. for 5-8 hours to obtain the alumina carrier.

9. A method for preparing an alumina-supported aldol condensation catalyst, characterized in that: The following steps are involved: (1) dissolving a niobium-containing compound in water to obtain an aqueous solution of the niobium-containing compound; (2) adding the alumina carrier to the aqueous solution of the niobium compound by an equal volume impregnation method, standing for 1-18 hours, and then drying at 100-120° C. for 1-18 hours to obtain a niobium-containing solid; (3) dissolving the cesium-containing compound in water to obtain an aqueous solution of the cesium-containing compound; (4) adding the niobium-containing solid into the cesium-containing compound aqueous solution by an equal volume impregnation method, standing for 1-18 hours, then drying at 100-120° C. for 1-18 hours, and calcining at 400-600° C. for 5-8 hours to obtain the alumina-supported aldol condensation catalyst.

10. Use of the alumina-supported aldol condensation catalyst according to any one of claims 1 to 5 in the preparation of methyl methacrylate.

Images