Supported phosphotungstic acid catalyst as well as preparation method and application thereof
By encapsulating phosphotungstic acid in situ on hydrogen-type β molecular sieve to form a supported phosphotungstic acid catalyst, the problems of the existing catalysts producing acidic wastewater during the acylation reaction and high requirements for equipment materials are solved, and efficient catalytic activity is achieved and environmentally friendly.
Patent Information
- Application Number
- CN202411448408.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-16
- Publication Date
- 2025-02-14
AI Technical Summary
There are problems in the selection of catalysts in the existing acylation reaction. Although the Lewis acid catalyst AlCl3 has high catalytic efficiency, the post-treatment produces acidic wastewater and has high requirements for the equipment material; while phosphotungstic acid has excellent catalytic properties, its specific surface area is small. , difficult to recycle.
By encapsulating phosphotungstic acid in situ on a hydrogen-type β molecular sieve, a supported phosphotungstic acid catalyst is formed, and the activity and life of the catalyst are improved by utilizing the high specific surface area of the molecular sieve and the selective channel selectivity of the molecular sieve.
The efficient catalytic activity and type selectivity of the catalyst are achieved, the generation of acidic wastewater is avoided, the corrosion of the equipment is reduced, and the catalyst can be reused, with good environmental protection and application prospects.
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Figure CN119425792A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of acylation synthesis catalyst preparation, and in particular to a supported phosphotungstic acid catalyst and a preparation method and application thereof. Background Art
[0002] 2-Methyl-6-acylanthanaphthalene is an important organic chemical raw material. Polyethylene naphthalate (PEN) obtained by polymerization of its oxidation product with ethylene glycol is a polyester compound with superior chemical and physical properties than polyethylene terephthalate (PET). PEN has broad application prospects in the fields of fibers, films, packaging containers and electronic components. Usually, 2-methyl-6-acylanthanaphthalene is prepared by Friedel-Crafts acylation reaction. In Friedel-Crafts acylation reaction, the selection of catalyst is particularly important. At present, Lewis acid catalyst AlCl3 is the one with the highest catalytic efficiency in the acylation reaction process in industrial production, but the post-processing of the catalyst will produce a large amount of acidic aluminum-containing wastewater, which is contrary to the existing green and clean production concept, and has high requirements on the material of the equipment.
[0003] Phosphotungstic acid is a heteropolyacid with strong acidity and high thermal stability, and has unique redox and acid properties. It exhibits excellent catalytic performance in a variety of acylation reactions. However, phosphotungstic acid has disadvantages such as small specific surface area and difficult recovery. Loading phosphotungstic acid on a suitable carrier can effectively improve its specific surface area and catalytic performance.
[0004] The high uniformity, easy tunability and shape selectivity of zeolite molecular sieve catalyst pores are unmatched by other catalysts. In particular, β-zeolite, with its unobstructed three-dimensional macroporous structure and suitable acid center strength, has shown excellent catalytic performance in the acylation reaction of various substrates. Summary of the invention
[0005] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.
[0006] To this end, the embodiments of the present invention provide a supported phosphotungstic acid catalyst and a preparation method and application thereof.
[0007] In a first aspect, the present invention provides a supported phosphotungstic acid catalyst, wherein the supported phosphotungstic acid catalyst is obtained by in-situ encapsulating phosphotungstic acid on a molecular sieve, wherein the supported amount of the phosphotungstic acid is less than 30%.
[0008] The in-situ encapsulation is a process of synthesizing phosphotungstic acid directly on the molecular sieve. The loading amount of phosphotungstic acid is below 30% to avoid blocking the molecular sieve pores when the loading amount is too high.
[0009] Furthermore, the molecular sieve is a hydrogen-type β molecular sieve.
[0010] The hydrogen-type β molecular sieve has a large specific surface area and selective pore selectivity. The phosphotungstic acid catalyst has low hydrothermal stability and a small specific surface area. Loading the phosphotungstic acid catalyst on the hydrogen-type β molecular sieve can not only expand the contact surface between the phosphotungstic acid catalyst and the reaction system, but also improve the reaction activity. At the same time, the phosphotungstic acid loaded in the molecular sieve pores further modifies the pore configuration, which is beneficial to the selective selectivity of the molecular sieve. In addition, the active component is loaded in the molecular sieve pores using in-situ synthesized phosphotungstic acid, which avoids the problem of rapid loss of phosphotungstic acid on the loaded catalyst prepared by the conventional impregnation method and increases the life of the catalyst.
[0011] Furthermore, the phosphotungstic acid is obtained by reacting disodium hydrogen phosphate and sodium tungstate in a molar ratio of 1:12.
[0012] In the present invention, disodium hydrogen phosphate and sodium tungstate are reacted in situ on a molecular sieve to prepare phosphotungstic acid, so that the phosphotungstic acid is encapsulated in situ on the molecular sieve, thereby avoiding the problem of rapid loss of phosphotungstic acid and improving the life of the catalyst.
[0013] In a second aspect, the present invention provides a method for preparing a supported phosphotungstic acid catalyst, comprising the following steps:
[0014] (a) adding molecular sieve, disodium hydrogen phosphate and sodium tungstate into deionized water and stirring to mix uniformly to obtain a slurry;
[0015] (b) adding an acidic solution to adjust the pH value of the slurry to below 3, and reflux with stirring;
[0016] (c) drying and calcining after centrifugal washing to obtain a supported phosphotungstic acid catalyst powder;
[0017] (d) molding the supported phosphotungstic acid catalyst powder to obtain a molded supported phosphotungstic acid catalyst.
[0018] Furthermore, in the step (a), the molar ratio of disodium hydrogen phosphate to sodium tungstate is 1:12, and the molecular sieve is a hydrogen-type β molecular sieve.
[0019] Disodium hydrogen phosphate and sodium tungstate react in a molar ratio of 1:12 to generate phosphotungstic acid, and in the subsequent calcination process, the calcination temperature is controlled below 300°C, so that the active component phosphotungstic acid always maintains a Keggin-type structure, which has high acidity and high catalytic activity. The loading amount of phosphotungstic acid is below 30%, that is, the ratio of the mass of phosphotungstic acid to the mass of the molecular sieve is below 30%, avoiding the pore blocking phenomenon caused by excessive loading.
[0020] The purpose of stirring in step (a) is to mix the materials evenly, and stirring at room temperature for more than 4 hours is sufficient. In addition, it is understood that the stirring rate can be selected according to the specific situation.
[0021] Furthermore, in the step (b), the reflux stirring temperature is 80-90° C. and the time is more than 4 hours.
[0022] The reflux stirring process is the process of in-situ encapsulation of phosphotungstic acid on the molecular sieve, and the reflux stirring temperature is 80-90°C, which increases the reaction rate while ensuring that the slurry does not boil. The reflux stirring temperature can be 80°C, 85°C, 90°C, or any value within the range of the two.
[0023] In some embodiments, the acidic solution in step (b) is hydrochloric acid or phosphoric acid, or other feasible acids. The acidic solution is added to adjust the pH value of the slurry to below 3, so that the slurry reacts under acidic conditions to produce phosphotungstic acid and avoid the generation of by-products.
[0024] Furthermore, in step (c), the drying temperature is 100-120° C., and the drying time is more than 12 hours; the calcination temperature is below 300° C., and the calcination time is more than 3 hours.
[0025] The purpose of drying is to remove part of the water first to avoid the influence of direct calcination on the structure of the molecular sieve. The drying temperature can be 100°C, 110°C, 120°C or any value within the range of the two.
[0026] The calcination temperature can be 200°C, 250°C, 280°C, 300°C, or a value within a range consisting of any two values. The temperature is kept below 300°C during calcination, so that the phosphotungstic acid supported on the molecular sieve maintains a Keggin-type structure, which has high acidity and catalytic activity, and avoids the influence of the calcination temperature on the structure of the phosphotungstic acid, thereby further avoiding the activity reduction of the catalyst.
[0027] The purpose of the centrifugal washing in step (c) is to clean the phosphotungstic acid on the surface of the molecular sieve. It is understood that the washing method can be water washing or other feasible solvent washing.
[0028] Further, the step (d) comprises:
[0029] S1: mixing the supported phosphotungstic acid catalyst powder, peptizing agent, binder and deionized water and kneading them into a blank;
[0030] S2: After the blank is sealed and aged, it is extruded to obtain a formed blank;
[0031] S3: drying and calcining the molded blank to obtain a molded supported phosphotungstic acid catalyst.
[0032] The purpose of step (d) is to shape the prepared supported phosphotungstic acid catalyst powder. The shaped catalyst is suitable for fixed bed reaction and can achieve continuous and efficient production.
[0033] Wherein, the peptizing agent is at least one of nitric acid, acetic acid and citric acid.
[0034] In some embodiments, the amount of the peptizing agent added is 5% to 15% of the weight of the supported phosphotungstic acid catalyst powder.
[0035] In some embodiments, the amount of the peptizing agent added is 8% of the weight of the supported phosphotungstic acid catalyst powder.
[0036] The binder is SB or other suitable binders, and the amount of the binder added is 25% to 30% of the weight of the supported phosphotungstic acid catalyst powder.
[0037] In some embodiments, the water-to-powder ratio of deionized water to supported phosphotungstic acid catalyst powder is 70% to 90%.
[0038] The process of kneading into a blank in step S1 is to put all materials into a kneading machine and knead them into a blank at a rotation speed of 300 r / min.
[0039] In step S2, the blank is sealed and aged, and then extruded to obtain a molded blank. The prepared blank is sealed with a plastic film, aged at room temperature for 10 hours, and then placed in an extruder for extrusion molding. The mold is selected to be clover-shaped or columnar.
[0040] Furthermore, the forming blank is dried and calcined by first shaping and drying the forming blank at room temperature for more than 24 hours, then placing it in an oven at 100-120° C. for more than 2 hours, and finally calcining it at less than 300° C. for more than 6 hours.
[0041] The purpose of first drying the formed blank at room temperature for more than 24 hours is to shape and remove some moisture, and then drying it in an oven at 100-120°C for more than 2 hours is to remove some moisture. Both of these processes of removing moisture are done at low temperatures to avoid the influence of temperature on the structure of the molecular sieve. The calcination temperature is below 300°C, so that the phosphotungstic acid loaded on the molecular sieve maintains a Keggin-type structure.
[0042] In a third aspect, the present invention provides the use of a supported phosphotungstic acid catalyst prepared by the method provided in the second aspect or a supported phosphotungstic acid catalyst provided in the first aspect in an acylation synthesis fixed bed reactor.
[0043] Compared with the prior art, the beneficial effects of the present invention are:
[0044] The phosphotungstic acid supported molecular sieve catalyst obtained by the method of the present invention has good acidic catalytic activity and high selectivity in acylation synthesis. The used catalyst can be reused after regeneration treatment. At the same time, the product and the catalyst can achieve solid-liquid separation without hydrolysis quenching, and a large amount of acidic wastewater is not generated. The catalyst is environmentally friendly and has low corrosion to equipment, and has good application prospects.
[0045] The present invention provides a relatively green and environmentally friendly catalytic system and a method for preparing the catalyst. The supported phosphotungstic acid catalyst avoids the generation of acidic wastewater in the traditional Lewis acid catalytic system and can efficiently achieve solid-liquid separation. The catalyst can be used in a fixed bed reactor to simplify the reaction steps, improve atomic economy, and reduce pollution.
[0046] The present invention loads phosphotungstic acid heteropolyacid on a molecular sieve, which can effectively improve its specific surface area and catalytic performance, and facilitates product separation. At the same time, the catalyst is modified by utilizing the adjustable denaturation of the molecular sieve catalyst pores and acidity to prepare a carrier-type catalyst suitable for a fixed bed reactor. BRIEF DESCRIPTION OF THE DRAWINGS
[0047] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:
[0048] Figure 1 The process flow chart of the preparation method of the supported phosphotungstic acid catalyst of the present invention is as follows;
[0049] Figure 2 This is a SEM image of the catalyst prepared in Example 1;
[0050] Figure 3 This is a SEM image of the catalyst prepared in Example 2;
[0051] Figure 4 This is a SEM image of the catalyst prepared in Example 3;
[0052] Figure 5 This is a chromatogram of the product obtained by carrying out a fixed bed acylation synthesis reaction using the catalyst prepared in Example 3. DETAILED DESCRIPTION
[0053] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.
[0054] The process flow of the preparation method of the supported phosphotungstic acid catalyst of the present invention is as follows: Figure 1As shown, Figure 1 The process flow shown is not described in detail here.
[0055] The following is a detailed description in conjunction with the examples and comparative examples. All chemical raw materials used are commercially available industrial products, methylnaphthalene is purchased from Maclean, purity> 97%; butyric anhydride is purchased from Sinopharm, purity 98%; Hβ molecular sieve is purchased from Tianjin Nankai Catalyst Factory, silicon-aluminum ratio (molar ratio) 25:1, Na content less than 0.5%. Sodium tungstate, disodium hydrogen phosphate, nitric acid, etc. are all purchased from Sinopharm.
[0056] The test materials and reagents used in the following examples, unless otherwise specified, can be obtained from commercial sources.
[0057] Example 1
[0058] Weigh 10.000g of hydrogen β molecular sieve, 0.032g of disodium hydrogen phosphate dihydrate and 0.715g of sodium tungstate dihydrate (the molar ratio of P (disodium hydrogen phosphate) to W (sodium tungstate) is 1:12) and add them into 200mL of deionized water, stir at room temperature for 4h, then add 3mol / L hydrochloric acid to pH=2.0, reflux the slurry at 90℃ with stirring for 4h, then filter and centrifuge to wash, wash the phosphotungstic acid on the surface of the molecular sieve, dry the sample at 110℃ for 15h, calcine at 280℃ for 3h, grind at room temperature to obtain 5%-PW / Hβ molecular sieve powder.
[0059] Weigh 10g of 5%-PW / Hβ molecular sieve powder modified by phosphotungstic acid, add 3g of pseudo-boehmite powder, 8mL of deionized water, and then add 0.6mL of concentrated nitric acid to stir evenly, and put the stirred material into a kneader (speed 300r / min) for kneading to form a blank. The obtained blank is sealed with a plastic film and aged at room temperature for 10h; the blank is placed in an extruder for extrusion molding, and the mold is selected as a clover-shaped mold; the molded blank is placed at room temperature for shaping and drying for 24h, and then placed in a vacuum oven at 105℃ for drying for 2h; and then baked in a muffle furnace at 290℃ for 6h to obtain a molded catalyst, which is marked as a 5%-PW / Hβ molecular sieve catalyst.
[0060] Example 2
[0061] Weigh 10.000g of hydrogen β molecular sieve, 0.109g of disodium hydrogen phosphate dihydrate and 2.419g of sodium tungstate dihydrate (the molar ratio of P (disodium hydrogen phosphate) to W (sodium tungstate) is 1:12) and add them into 200mL of deionized water, stir at room temperature for 4h, then add 3mol / L hydrochloric acid to pH=2.0, reflux the slurry at 90℃ with stirring for 4h, then filter and centrifuge to wash, wash the phosphotungstic acid on the surface of the molecular sieve, dry the sample at 110℃ for 15h, calcine at 280℃ for 3h, grind at room temperature to obtain 15%-PW / Hβ molecular sieve powder.
[0062] Weigh 10g of 15%-PW / Hβ molecular sieve powder modified by phosphotungstic acid, add 2.8g of pseudo-boehmite powder, 8mL of deionized water, and then add 0.6mL of concentrated nitric acid to stir evenly, and put the stirred material into a kneader (speed 300r / min) for kneading to form a blank. The obtained blank is sealed with a plastic film and aged at room temperature for 10h; the blank is placed in an extruder for extrusion molding, and the mold is selected as a clover-shaped; the molded blank is placed at room temperature for shaping and drying for 25h, and then placed in a vacuum oven at 105℃ for drying for 3h; and then baked in a muffle furnace at 290℃ for 6h to obtain a molded catalyst, which is marked as a 15%-PW / Hβ molecular sieve catalyst.
[0063] Example 3
[0064] Weigh 10.000g of hydrogen β molecular sieve, 0.265g of disodium hydrogen phosphate dihydrate and 5.881g of sodium tungstate dihydrate (the molar ratio of P (disodium hydrogen phosphate) to W (sodium tungstate) is 1:12) and add them into 200mL of deionized water, stir at room temperature for 4h, then add 3mol / L hydrochloric acid to pH=2.0, reflux the slurry at 90℃ with stirring for 4h, then filter and centrifuge to wash, wash the phosphotungstic acid on the surface of the molecular sieve, after the sample is at 110℃ for 15h, calcine at 280℃ for 3h, grind at room temperature to obtain 30%-PW / Hβ molecular sieve powder.
[0065] Weigh 10g of 30%-PW / Hβ molecular sieve powder modified by phosphotungstic acid, add 2.5g of pseudo-boehmite powder, 7mL of deionized water, and then add 0.5mL of concentrated nitric acid to stir evenly, and put the stirred material into a kneader (speed 300r / min) for kneading to form a blank. The obtained blank is sealed with a plastic film and aged at room temperature for 10h; the blank is placed in an extruder for extrusion molding, and the mold is selected as a clover-shaped mold; the molded blank is placed at room temperature for shaping and drying for 25h, and then placed in a vacuum oven at 105℃ for drying for 3h; and then baked in a muffle furnace at 290℃ for 6h to obtain a molded catalyst, which is marked as a 30%-PW / Hβ molecular sieve catalyst.
[0066] Comparative Example 1
[0067] Weigh 10.000g of hydrogen β molecular sieve, 0.265g of disodium hydrogen phosphate dihydrate and 5.881g of sodium tungstate dihydrate (the molar ratio of P (disodium hydrogen phosphate) to W (sodium tungstate) is 1:12) and add them into 200mL of deionized water, stir at room temperature for 4h, then add 3mol / L hydrochloric acid to pH=2.0, reflux the slurry at 90℃ with stirring for 4h, then filter and centrifuge to wash, wash the phosphotungstic acid on the surface of the molecular sieve, dry the sample at 110℃ for 15h, calcine at 550℃ for 3h, grind at room temperature to obtain 30%-PW / Hβ molecular sieve powder-1.
[0068] Weigh 10g of 30%-PW / Hβ molecular sieve powder-1 modified with phosphotungstic acid, add 2.5g of pseudo-boehmite powder, 8mL of deionized water, and then add 0.6mL of concentrated nitric acid to stir evenly, and put the stirred material into a kneader (speed 300r / min) for kneading to form a blank. The obtained blank is sealed with a plastic film and aged at room temperature for 10h; the blank is placed in an extruder for extrusion molding, and the mold is selected as a clover-shaped mold; the molded blank is placed at room temperature for shaping and drying for 25h, and then placed in a vacuum oven at 105℃ for drying for 3h; and then baked in a muffle furnace at 550℃ for 6h to obtain a molded catalyst, which is marked as 30%-PW / Hβ molecular sieve catalyst-1.
[0069] Comparative Example 2
[0070] Impregnation method for loading phosphotungstic acid: weigh 10.000g of hydrogenated β molecular sieve, add 4.285g of dried and dehydrated phosphotungstic acid and 200mL of deionized water, and ultrasonically pretreat at 80°C for 1 hour, filter to remove water, dry at 105°C for 4h, calcine at 280°C for 3h, and grind at room temperature to obtain 30%-PW / Hβ molecular sieve powder-2.
[0071] Weigh 10g of 30%-PW / Hβ molecular sieve powder-2 modified with phosphotungstic acid, add 2.5g of pseudo-boehmite powder, 8mL of deionized water, and then add 0.6mL of concentrated nitric acid to stir evenly, and put the stirred material into a kneader (speed 300r / min) for kneading to form a blank. The obtained blank is sealed with a plastic film and aged at room temperature for 10h; the blank is placed in an extruder for extrusion molding, and the mold is selected as a clover-shaped mold; the molded blank is placed at room temperature for shaping and drying for 25h, and then placed in a vacuum oven at 105℃ for drying for 3h; and then baked in a muffle furnace at 290℃ for 6h to obtain a molded catalyst, which is marked as 30%-PW / Hβ molecular sieve catalyst-2.
[0072] Comparative Example 3
[0073] Catalyst molding of molecular sieve powder: weigh 10g hydrogen-type β molecular sieve, add 3g pseudo-boehmite powder, 8mL deionized water, and then add 0.6mL concentrated nitric acid and stir evenly, put the evenly stirred material into a kneading machine (speed 300r / min) for kneading to form a blank. The obtained blank is sealed with a plastic film and aged at room temperature for 10h; the blank is placed in an extruder for extrusion molding, and the mold is selected as a clover-shaped mold; the molded blank is placed at room temperature for shaping and drying for 24h, and then placed in a vacuum oven at 105℃ for 2h; and then baked in a muffle furnace at 280℃ for 6h to obtain a molded catalyst, which is marked as Hβ molecular sieve catalyst.
[0074] Test Example 1
[0075] The supported phosphotungstic acid catalysts prepared in Examples 1 to 3 were tested by SEM scanning electron microscope. The test results are as follows: Figures 2 to 4 As shown. Figures 2 to 4 It can be seen that phosphotungstic acid is uniformly loaded on the hydrogen-type β molecular sieve.
[0076] Test Example 2
[0077] The activity of the catalyst was evaluated in a 10 ml fixed bed reactor. 10 ml of the catalyst prepared in the above examples and comparative examples were respectively loaded in a constant temperature section. Both ends were filled with inert alumina ceramic balls. The catalyst bed was heated to 200 ° C under nitrogen protection. Then, a mixed solution of 2-methylnaphthalene and butyric anhydride was input into the fixed bed reactor. The molar ratio of 2-methylnaphthalene to butyric anhydride in the mixed raw material was 1:2. The reaction temperature was controlled at 200 ° C and the liquid hourly space velocity was 1.0 h -1 Acylation reaction is carried out, and the product is cooled to room temperature by air heat exchange to obtain an acylated product. After the device is running stably, a small amount of product is taken and directly analyzed by gas chromatography. The peak area percentage method is used to calculate the butyric anhydride (BA) conversion rate and the selectivity of 2-methyl-6-acylnaphthalene. Among them, the butyric anhydride conversion rate is the ratio of the amount of butyric anhydride reacted to the amount of butyric anhydride added, and the selectivity of 2-methyl-6-acylnaphthalene is the ratio of the amount of 2-methyl-6-acylnaphthalene in the product to the amount of all methylbutyrylnaphthalene isomers in the product. The test results are shown in Table 1. The chromatogram of the product obtained using the catalyst of Example 3 is shown in Table 1. Figure 5 shown.
[0078] from Figure 5 It can be seen that the supported phosphotungstic acid catalyst has good acidic catalytic activity and high selectivity, and mainly produces 2,6- and 2,7-acylnaphthalene products.
[0079] Table 1:
[0080] item Calcination temperature / ℃ BA reaction conversion rate / % 2,6-reaction selectivity / % Example 1 280 89％ 62.8 Example 2 280 95％ 68.0 Example 3 280 93％ 63.0 Comparative Example 1 550 85％ 60.5 Comparative Example 2 280 86％ 62.5 Comparative Example 3 280 80％ 58.8
[0081] Comparative Examples 1 to 3 show that the catalyst prepared in the examples of the present application has a good BA conversion rate and selectivity for 2-methyl-6-acylnaphthalene, and has good catalytic performance.
[0082] By comparing Example 3 and Comparative Example 1, it can be seen that when the loading amount of phosphotungstic acid is at the same level, when the calcination temperature is higher, the BA conversion rate and the selectivity of 2-methyl-6-acylnaphthalene decrease.
[0083] By comparing Example 3 and Comparative Example 2, it can be seen that under the same level of loading of phosphotungstic acid, the BA conversion rate and selectivity of 2-methyl-6-naphthalene of the catalyst prepared by in-situ loading of phosphotungstic acid are higher than those of the catalyst prepared by loading phosphotungstic acid by impregnation.
[0084] By comparing Examples 1 to 3 and Comparative Example 3, it can be seen that when phosphotungstic acid is not loaded, the BA conversion rate and the selectivity of 2-methyl-6-acylnaphthalene of the Hβ molecular sieve catalyst are relatively low.
[0085] Test Example 3
[0086] The catalyst prepared in Example 2 in the above Test Example 2 was taken and the recovered catalyst was subjected to the catalyst activity evaluation test in a 10 ml fixed bed reactor. The catalyst was replaced by centrifugation with dichloromethane 4 times, then washed with a small amount of dichloromethane and dried at room temperature for 12 h, then dried at 105 ° C for 2 h, and finally calcined at 300 ° C for 2 h to obtain a regenerated catalyst.
[0087] The regenerated catalyst was used to perform an activity evaluation test of the catalyst according to Test Example 2, and the BA reaction conversion rate was calculated to be 85%, and the 2,6-reaction selectivity was 68%. Compared with Example 2, it can be seen that the recycled and regenerated catalyst still maintains good activity.
[0088] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms may be for different embodiments or examples. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.
[0089] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.
[0090] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.
Claims
1. A supported phosphotungstic acid catalyst, characterized in that: The phosphotungstic acid is obtained by in-situ encapsulating the phosphotungstic acid on a molecular sieve, wherein the loading amount of the phosphotungstic acid is less than 30%.
2. The supported phosphotungstic acid catalyst according to claim 1, characterized in that The molecular sieve is a hydrogen-type beta molecular sieve.
3. The supported phosphotungstic acid catalyst according to claim 1, characterized in that The phosphotungstic acid is obtained by reacting disodium hydrogen phosphate and sodium tungstate in a molar ratio of 1:
12.
4. A method for preparing a supported phosphotungstic acid catalyst, characterized in that: The method for preparing the supported phosphotungstic acid catalyst according to any one of claims 1 to 3 comprises the following steps: (a) adding molecular sieve, disodium hydrogen phosphate and sodium tungstate into deionized water and stirring to mix uniformly to obtain a slurry; (b) adding an acidic solution to adjust the pH value of the slurry to below 3, and reflux with stirring; (c) drying and calcining after centrifugal washing to obtain a supported phosphotungstic acid catalyst powder; (d) molding the supported phosphotungstic acid catalyst powder to obtain a molded supported phosphotungstic acid catalyst.
5. The method according to claim 4, characterized in that In the step (a), the molar ratio of disodium hydrogen phosphate to sodium tungstate is 1:12, and the molecular sieve is a hydrogen-type β molecular sieve.
6. The method according to claim 4, characterized in that In the step (b), the reflux stirring temperature is 80-90° C. and the time is more than 4 hours.
7. The method according to claim 4, characterized in that In the step (c), the drying temperature is 100-120° C., and the drying time is more than 12 hours; the calcination temperature is below 300° C., and the calcination time is more than 3 hours.
8. The method according to claim 4, characterized in that The step (d) comprises: The supported phosphotungstic acid catalyst powder, peptizing agent, binder and deionized water are mixed and kneaded into a blank; After the blank is sealed and aged, it is extruded to obtain a formed blank; The molded blank is dried and calcined to obtain a molded supported phosphotungstic acid catalyst.
9. The method according to claim 8, characterized in that The forming blank is dried and calcined by first shaping and drying the forming blank at room temperature for more than 24 hours, then placing it in an oven at 100-120° C. and drying it for more than 2 hours, and finally calcining it at less than 300° C. for more than 6 hours.
10. Use of a supported phosphotungstic acid catalyst prepared by the method according to any one of claims 4 to 9 or a supported phosphotungstic acid catalyst according to any one of claims 1 to 3 in an acylation synthesis fixed bed reactor.