A ZSM-5 / SAPO-34 composite molecular sieve catalyst, its preparation method and its application

Abstract

This invention discloses a ZSM-5 / SAPO-34 composite molecular sieve catalyst, its preparation method, and its application. The preparation method includes: Step 1, preparing a ZSM-5 seed solution: dissolving ZSM-5 molecular sieve in an alkaline solution to prepare a ZSM-5 seed solution; Step 2, preparing a SAPO-34 precursor solution: dissolving an organic template agent in deionized water, adding a silicon source dropwise, mixing well, adding a phosphorus source and an aluminum source, stirring to obtain a SAPO-34 molecular sieve catalyst precursor solution; Step 3, mixing the ZSM-5 seed solution and the SAPO-34 molecular sieve catalyst precursor solution and then crystallizing; filtering, washing, drying, and calcining the crystallized product to obtain a ZSM-5 / SAPO-34 composite molecular sieve; Step 4, pressing the composite molecular sieve into tablets and sieving to obtain the final product. The product of this invention has high crystallinity, high specific surface area, hierarchical porosity (adjustable micro-mesopore ratio), and suitable acid strength. It increases the active sites in contact with pyrolysis raw materials, effectively improves the selectivity of the target product 2,3-dihydrobenzofuran, reduces the types of final products, lowers subsequent processing costs, has simple preparation conditions, and has a wide range of applications.

Description

Technical Field

[0001] This invention belongs to the field of biomass energy utilization technology, specifically relating to a ZSM-5 / SAPO-34 composite molecular sieve catalyst, its preparation method, and its application. Background Technology

[0002] With the depletion of fossil fuel resources and environmental degradation worldwide, the conversion of renewable resources into chemicals and fuels is receiving increasing attention. Biomass is a potential renewable resource whose effective utilization can bring economic benefits. Biomass resources include agricultural and forest residues, aquatic plants and algae, municipal solid waste, and food waste. However, most biomass is discarded as waste and cannot be effectively utilized. The effective utilization of biomass is crucial for protecting the environment from the degradation caused by waste pollution. Bagasse is a major byproduct of the sugarcane industry. It can serve as an ideal base material for producing value-added chemicals and fuels through pyrolysis. Furthermore, bagasse is renewable and carbon-neutral. Compared to biomass such as corn cobs, rice husks, and straw, the yield of bio-oil obtained from the pyrolysis of bagasse is relatively high. Catalytically pyrolyzing bagasse using molecular sieves to produce high-value chemicals is one of the pathways for the effective utilization of biomass.

[0003] Composite molecular sieves are composite crystals possessing the structural features of two or more molecular sieves. They often exhibit properties different from single molecular sieves, displaying synergistic effects and unique catalytic performance. Composite molecular sieves overcome the limitations of single microporous or mesoporous molecular sieves, combining the advantages of each pore size structure. ZSM-5 molecular sieve has a unique MFI structure, providing abundant diffusion channels for reactants and products in catalytic reactions. SAPO-34 molecular sieve has a CHA topology and belongs to the microporous molecular sieve category. The synergistic effect of the two molecular sieves gives it suitable pores and acid centers, suppresses side reactions, and reduces diffusion resistance. Composite molecular sieves have attracted widespread attention from researchers due to their abundant active centers, multi-channel structure, and the synergistic effect of composite phase interfaces.

[0004] Patent CN118289775A discloses a ZSM-5 / Y composite molecular sieve and its preparation method. This catalyst possesses cooperative acidic centers and a pore structure, and its preparation process reduces water usage and significantly improves product yield. However, its preparation process is complex, and it suffers from low crystallinity and instability. Patent CN104492475B discloses a method for preparing a micro-mesoporous ZSM-5 / Pd-γ-Al2O3 composite catalyst. This catalyst combines the pore advantages of mesoporous material γ-Al2O3 with the strong acidity and high hydrothermal stability of microporous molecular sieve ZSM-5, but the prepared catalyst suffers from low crystallinity and low specific surface area. Patent CN118142572A discloses a Ni@β / MCM-41 modified composite molecular sieve. The preparation process modifies the morphology, structure, and size of this catalyst, resulting in high activity and a large specific surface area. However, its preparation method is not conducive to adjusting the acidity of the molecular sieve.

[0005] Therefore, it is crucial to develop a catalyst with multiple advantages, such as high crystallinity, high specific surface area, hierarchical porosity (adjustable micro-mesopore ratio), and suitable acid strength, and with high selectivity for 2,3-dihydrobenzofuran, for use in the process of biomass pyrolysis to 2,3-dihydrobenzofuran. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the purpose of this application is to provide a ZSM-5 / SAPO-34 composite molecular sieve catalyst, its preparation method and its application, to solve the problems of low crystallinity, low specific surface area, and difficulty in adjusting the pore size distribution and acid strength of the current catalysts.

[0007] To solve the above problems, the technical solution adopted in this application is:

[0008] This invention provides a method for preparing a ZSM-5 / SAPO-34 composite molecular sieve catalyst, characterized by comprising the following steps:

[0009] Step 1: Preparation of ZSM-5 seed solution: Dissolve ZSM-5 molecular sieve in alkaline solution to prepare ZSM-5 seed solution;

[0010] Step 2: Preparation of SAPO-34 precursor solution: Dissolve the organic template agent in deionized water, add the silicon source dropwise, mix well, then add the phosphorus source and aluminum source, stir well to obtain a white gel, which is the SAPO-34 molecular sieve catalyst precursor solution.

[0011] Step 3: Mix the ZSM-5 seed solution with the SAPO-34 molecular sieve catalyst precursor solution and then crystallize it. The crystallized product is filtered, washed, dried and calcined to obtain ZSM-5 / SAPO-34 composite molecular sieve.

[0012] Step 4: The ZSM-5 / SAPO-34 composite molecular sieve is shaped, pressed, and sieved to obtain the final product.

[0013] As a preferred embodiment of this application, in step 2, the silicon source is selected from at least one of silica sol, water glass, active silica, and tetraethyl orthosilicate; the aluminum source is selected from at least one of boehmite, aluminum isopropoxide, aluminum hydroxide, and aluminum salts; and the phosphorus source is selected from at least one of orthophosphoric acid, phosphorous acid, and phosphates.

[0014] As a preferred embodiment of this application, in step 2, the silicon source is tetraethyl orthosilicate; the aluminum source is aluminum hydroxide; and the phosphorus source is orthophosphoric acid.

[0015] As a preferred embodiment of this application, the silicon source, aluminum source and phosphorus source in step 2 are expressed in the form of oxide molar ratios, with the following composition ratio: n(SiO2):n(Al2O3):n(P2O5)=1:(0.5~3):(0.5~4).

[0016] As a preferred embodiment of this application, the silicon source, aluminum source and phosphorus source in step 2 are expressed in the form of oxide molar ratio, and the composition ratio is as follows: n(SiO2):n(Al2O3):n(P2O5)=1:(1~2):(1~2).

[0017] As a preferred embodiment of this application, the silicon source, aluminum source and phosphorus source in step 2 are expressed in the form of oxide molar ratios, with the following composition ratio: n(SiO2):n(Al2O3):n(P2O5) = 1:1.67:1.67.

[0018] As a preferred embodiment of this application, the alkaline solution in step 1 is an aqueous solution of sodium hydroxide with a mass concentration of 1% to 10%.

[0019] As a preferred embodiment of this application, the alkaline solution in step 1 is an aqueous solution of sodium hydroxide with a mass concentration of 2% to 8%.

[0020] As a preferred embodiment of the present invention, the solid-liquid ratio of ZSM-5 molecular sieve to alkaline solution in step 1 is 0.5~2g:20mL.

[0021] As a preferred embodiment of the present invention, the solid-liquid ratio of ZSM-5 molecular sieve to alkaline solution in step 1 is 1g:20mL.

[0022] As a preferred embodiment of the present invention, the organic template agent in step 2 is selected from at least one of diethanolamine, triethylamine, and tetraethylammonium hydroxide.

[0023] As a preferred embodiment of the present invention, the organic template agent in step 2 is diethanolamine.

[0024] As a preferred embodiment of the present invention, the stirring time in step 2 is 2-8 hours, the temperature is 40-60°C, and the stirring speed is 400-800 r / min.

[0025] As a preferred embodiment of the present invention, the stirring time in step 2 is 4 hours.

[0026] As a preferred embodiment of the present invention, the crystallization temperature in step 3 is 150~210℃ and the crystallization time is 12~72h.

[0027] As a preferred embodiment of the present invention, the crystallization temperature in step 3 is 200°C and the crystallization time is 24 hours.

[0028] As a preferred embodiment of the present invention, in step 3, the solid product after filtration of the crystallized product is washed with water and ethanol until the pH is 6-9, and then calcined in air at a rate of 5°C / min, with a calcination temperature of 500-700°C and a calcination time of 3-7 hours.

[0029] As a preferred embodiment of the present invention, in step 3, the solid product after filtration of the crystallized product is washed with water and ethanol until the pH is 6-9, and then calcined in air at a rate of 5°C / min, with a calcination temperature of 600°C and a calcination time of 5h.

[0030] Steps 1 and 2 can be interchanged and have no effect on the preparation of ZSM-5 / SAPO-34 composite molecular sieve catalysts.

[0031] The present invention also provides a ZSM-5 / SAPO-34 composite molecular sieve catalyst prepared according to the preparation method described above.

[0032] The present invention also provides an application of the ZSM-5 / SAPO-34 composite molecular sieve catalyst in the rapid catalytic pyrolysis of biomass to produce 2,3-dihydrobenzofuran.

[0033] As a preferred embodiment of the present invention, the application method includes:

[0034] The ZSM-5 / SAPO-34 composite molecular sieve catalyst was mixed with biomass and uniformly packed into the constant temperature zone of a vertical tube furnace.

[0035] N2 is introduced to purge and remove air. After purging, a pyrolysis reaction is carried out under N2 atmosphere. The temperature is increased to the reaction temperature of 400-600℃ at a rate of 30-60℃ / min, and held at a constant temperature for 1-25 minutes. The liquid phase products generated by pyrolysis are collected.

[0036] As a preferred embodiment of the present invention, the isothermal time for the pyrolysis reaction is 5 to 10 minutes.

[0037] As a preferred embodiment of the present invention, the biomass is a lignocellulosic biomass, such as sugarcane bagasse.

[0038] Compared with the prior art, the beneficial effects of the present invention are:

[0039] (1) This invention is a ZSM-5 / SAPO-34 composite molecular sieve suitable for the rapid catalytic pyrolysis of biomass to produce 2,3-dihydrobenzofuran. The composite molecular sieve of this invention has a hierarchical porous structure, overcoming the disadvantage of the single pore size distribution of a single molecular sieve. At the same time, by adjusting the proportion of micropores and mesopores and the acid strength in the composite molecular sieve, the pore distribution can be effectively adjusted and the decarboxylation of intermediate products can be facilitated, thus significantly improving the catalyst performance.

[0040] (2) The present invention uses a hydrothermal synthesis method to tightly combine two molecular sieves, which improves the crystallinity and specific surface area of ​​the catalyst, can better realize the spatial confinement effect of the reaction, and the preparation process is mild, easy to operate, low in production cost, and has little environmental pollution.

[0041] (3) Compared with existing catalysts for biomass catalytic cracking, the composite molecular sieve catalyst of the present invention reduces the reaction activation energy, reduces the types of products, and reduces the types of liquid phase products to within fifteen, and the selectivity of 2,3-dihydrobenzofuran can reach 48.15%. Attached Figure Description

[0042] Figure 1 The XRD patterns of the ZSM-5 / SAPO-34 composite molecular sieves obtained in Examples 1-6 are shown.

[0043] Figure 2 The image shows the SEM spectrum of the ZS-Al(OH)3 composite molecular sieve obtained in Example 1.

[0044] Figure 3 The images show the nitrogen adsorption-desorption isotherms of the composite molecular sieves obtained in Examples 1 and 4.

[0045] Figure 4 The pore size distribution diagrams are for the composite molecular sieves obtained in Examples 1 and 4. Detailed Implementation

[0046] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0047] It should be noted that the process equipment or apparatus not specifically mentioned in the following embodiments are all conventional equipment or apparatus in the art.

[0048] Furthermore, it should be understood that the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, does not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, unless otherwise stated. It should also be understood that the combined connection relationship between one or more devices / apparatus mentioned in this invention does not preclude the existence of other devices / apparatus before or after the combined devices / apparatus, or the insertion of other devices / apparatus between these explicitly mentioned devices / apparatus, unless otherwise stated. Moreover, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or limiting the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0049] In the following embodiments of the present invention, the reagents used are shown in Table 1:

[0050]

[0051] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0052] Example 1

[0053] Step 1: Prepare ZSM-5 seed solution: Take 1g of ZSM-5 molecular sieve and 1g of sodium hydroxide and place them in 20mL of deionized water and stir at room temperature for 1h to obtain ZSM-5 seed solution.

[0054] Step 2: Preparation of SAPO-34 precursor solution: Weigh 9.73g of diethanolamine (DEA) and dissolve it in 50mL of deionized water and stir at room temperature for 10min. Then add 5.79g of tetraethyl orthosilicate, 9.07g of phosphoric acid and 7.22g of aluminum hydroxide in sequence and stir at room temperature for 4h to obtain a white gel, which is the SAPO-34 molecular sieve catalyst precursor solution.

[0055] Step 3: Add the ZSM-5 seed solution to the SAPO-34 molecular sieve catalyst precursor solution and stir at room temperature for 4 hours. Then, transfer the mixture to a hydrothermal reactor and crystallize at 200°C in an oven for 24 hours. Wash the crystallized product with anhydrous ethanol and deionized water until neutral. Dry the resulting white crystals at 80°C in an oven for 12 hours, and then calcine at 600°C for 5 hours in air at a rate of 5°C / min to obtain the ZSM-5 / SAPO-34 composite molecular sieve.

[0056] Step 4: The ZSM-5 / SAPO-34 composite molecular sieve is shaped, pressed, and sieved to obtain the final product, which is the ZS-Al(OH)3 composite molecular sieve.

[0057] The catalyst prepared in this embodiment was characterized and tested as follows:

[0058] (1) Morphological characteristics:

[0059] SEM characterization was performed using a Zeiss G500 scanning electron microscope at an accelerating voltage of 5 kV using a field emission scanning electron microscope to observe the surface morphology of the samples at different magnifications. Samples were prepared as thinly as possible. Due to the poor conductivity of the samples, an 80-second gold sputtering process was performed before imaging to better aid in electron microscopy. Specific reagent preparation and testing procedures were performed according to the instruction manual. Figure 2 It can be seen that the ZS-Al(OH)3 composite molecular sieve catalyst prepared by this invention is a stacked spherical shape formed by small cubic stacking, and the ZS-Al(OH)3 molecular sieve has obvious pores and irregular cracks.

[0060] (2) Composition characterization:

[0061] XRD analysis of the sample's phase structure was performed using a PNAlytical Empyrean X-ray diffractometer with an X-ray wavelength of 0.1541 nm and a PIXcel 1D array detector. The tube current was 40 mA, the tube voltage was 40 kV, the scan step size was 0.02°, the scan rate was 5° / min, and the scan range was 5°–50°. Specific reagent preparation and testing procedures were performed according to the manufacturer's instructions. The X-ray diffraction parameters of the ZS-Al(OH)3 composite molecular sieve catalyst prepared in this invention are as follows: relative crystallinity is 92.68%.

[0062] (3) N2 physical adsorption (N2-BET)

[0063] The specific surface area (BET) and pore size distribution of the samples were determined using an ASAP-2010 (Micromeritics) automated physical adsorption analyzer. During testing, approximately 300–600 mg of sample was weighed and degassed at 160 °C under high vacuum for 8 h to reduce testing errors. The N2 adsorption-desorption curves of the samples were then measured at -196 °C. The pore size distribution of the samples was calculated using the Barrett-Joyner-Halenda model, and the specific surface area of ​​the catalyst was calculated using the Brunauer-Emmett-Teller equation. The ZS-Al(OH)3 composite molecular sieve catalyst prepared in this invention achieved a specific surface area of ​​435 m². 2 / g, pore volume 0.10cm 3 / g, average pore size 3.77nm.

[0064] Example 2

[0065] Step 1: Prepare ZSM-5 seed solution: Take 1g of ZSM-5 molecular sieve and 1g of sodium hydroxide and place them in 20mL of deionized water and stir at room temperature for 1h to obtain ZSM-5 seed solution.

[0066] Step 2: Preparation of SAPO-34 precursor solution: Weigh 9.73g of diethanolamine (DEA) and dissolve it in 50mL of deionized water. Stir at room temperature for 10min. Then add 5.79g of tetraethyl orthosilicate, 9.07g of phosphoric acid, and 18.91g of aluminum isopropoxide in sequence and stir at room temperature for 4h to obtain a white gel, which is the SAPO-34 molecular sieve catalyst precursor solution.

[0067] Step 3: Add the ZSM-5 seed solution to the SAPO-34 molecular sieve catalyst precursor solution and stir at room temperature for 4 hours. Then, transfer the mixture to a hydrothermal reactor and crystallize at 200°C in an oven for 24 hours. Wash the crystallized product with anhydrous ethanol and deionized water until neutral. Dry the resulting white crystals at 80°C in an oven for 12 hours, and then calcine at 600°C for 5 hours in air at a rate of 5°C / min to obtain the ZSM-5 / SAPO-34 composite molecular sieve.

[0068] Step 4: The ZSM-5 / SAPO-34 composite molecular sieve is shaped, pressed, and sieved to obtain the final product, ZS-C9H. 21 AlO3 composite molecular sieve catalyst.

[0069] Example 3

[0070] Step 1: Prepare ZSM-5 seed solution: Take 1g of ZSM-5 molecular sieve and 1g of sodium hydroxide and place them in 20mL of deionized water and stir at room temperature for 1h to obtain ZSM-5 seed solution.

[0071] Step 2: Preparation of SAPO-34 precursor solution: Weigh 9.73g of diethanolamine (DEA) and dissolve it in 50mL of deionized water and stir at room temperature for 10min. Then add 5.79g of tetraethyl orthosilicate, 9.07g of phosphoric acid, and 6.59g of high-purity boehmite in sequence and stir at room temperature for 4h to obtain a white gel, which is the SAPO-34 molecular sieve catalyst precursor solution.

[0072] Step 3: Add the ZSM-5 seed solution to the SAPO-34 molecular sieve catalyst precursor solution and stir at room temperature for 4 hours. Then, transfer the mixture to a hydrothermal reactor and crystallize at 200°C in an oven for 24 hours. Wash the crystallized product with anhydrous ethanol and deionized water until neutral. Dry the resulting white crystals at 80°C in an oven for 12 hours, and then calcine at 600°C for 5 hours in air at a rate of 5°C / min to obtain the ZSM-5 / SAPO-34 composite molecular sieve.

[0073] Step 4: The ZSM-5 / SAPO-34 composite molecular sieve is shaped, pressed, and sieved to obtain the final product, which is the ZS-AlOOH composite molecular sieve catalyst.

[0074] Example 4

[0075] Step 1: Prepare ZSM-5 seed solution: Take 0.5g of ZSM-5 molecular sieve and 1g of sodium hydroxide and place them in 20mL of deionized water and stir at room temperature for 1h to obtain ZSM-5 seed solution.

[0076] Step 2: Preparation of SAPO-34 precursor solution: Weigh 9.73g of diethanolamine (DEA) and dissolve it in 50mL of deionized water and stir at room temperature for 10min. Then add 5.79g of tetraethyl orthosilicate, 9.07g of phosphoric acid and 7.22g of aluminum hydroxide in sequence and stir at room temperature for 4h to obtain a white gel, which is the SAPO-34 molecular sieve catalyst precursor solution.

[0077] Step 3: Add the ZSM-5 seed solution to the SAPO-34 molecular sieve catalyst precursor solution and stir at room temperature for 4 hours. Then, transfer the mixture to a hydrothermal reactor and crystallize at 200°C in an oven for 24 hours. Wash the crystallized product with anhydrous ethanol and deionized water until neutral. Dry the resulting white crystals at 80°C in an oven for 12 hours, and then calcine at 600°C for 5 hours in air at a rate of 5°C / min to obtain the ZSM-5 / SAPO-34 composite molecular sieve.

[0078] Step 4: The ZSM-5 / SAPO-34 composite molecular sieve is shaped, pressed, and sieved to obtain the final product, which is the ZS-Al(OH)3-1 composite molecular sieve.

[0079] Example 5

[0080] Step 1: Prepare ZSM-5 seed solution: Take 1.5g of ZSM-5 molecular sieve and 1g of sodium hydroxide and place them in 20mL of deionized water and stir at room temperature for 1h to obtain ZSM-5 seed solution.

[0081] Step 2: Preparation of SAPO-34 precursor solution: Weigh 9.73g of diethanolamine (DEA) and dissolve it in 50mL of deionized water and stir at room temperature for 10min. Then add 5.79g of tetraethyl orthosilicate, 9.07g of phosphoric acid and 7.22g of aluminum hydroxide in sequence and stir at room temperature for 4h to obtain a white gel, which is the SAPO-34 molecular sieve catalyst precursor solution.

[0082] Step 3: Add the ZSM-5 seed solution to the SAPO-34 molecular sieve catalyst precursor solution and stir at room temperature for 4 hours. Then, transfer the mixture to a hydrothermal reactor and crystallize at 200°C in an oven for 24 hours. Wash the crystallized product with anhydrous ethanol and deionized water until neutral. Dry the resulting white crystals at 80°C in an oven for 12 hours, and then calcine at 600°C for 5 hours in air at a rate of 5°C / min to obtain the ZSM-5 / SAPO-34 composite molecular sieve.

[0083] Step 4: The ZSM-5 / SAPO-34 composite molecular sieve is shaped, pressed, and sieved to obtain the final product, which is the ZS-Al(OH)3-2 composite molecular sieve.

[0084] Example 6

[0085] Step 1: Prepare ZSM-5 seed solution: Take 2g of ZSM-5 molecular sieve and 1g of sodium hydroxide and place them in 20mL of deionized water and stir at room temperature for 1h to obtain ZSM-5 seed solution.

[0086] Step 2: Preparation of SAPO-34 precursor solution: Weigh 9.73g of diethanolamine (DEA) and dissolve it in 50mL of deionized water and stir at room temperature for 10min. Then add 5.79g of tetraethyl orthosilicate, 9.07g of phosphoric acid and 7.22g of aluminum hydroxide in sequence and stir at room temperature for 4h to obtain a white gel, which is the SAPO-34 molecular sieve catalyst precursor solution.

[0087] Step 3: Add the ZSM-5 seed solution to the SAPO-34 molecular sieve catalyst precursor solution and stir at room temperature for 4 hours. Then, transfer the mixture to a hydrothermal reactor and crystallize at 200°C in an oven for 24 hours. Wash the crystallized product with anhydrous ethanol and deionized water until neutral. Dry the resulting white crystals at 80°C in an oven for 12 hours, and then calcine at 600°C for 5 hours in air at a rate of 5°C / min to obtain the ZSM-5 / SAPO-34 composite molecular sieve.

[0088] Step 4: The ZSM-5 / SAPO-34 composite molecular sieve is shaped, pressed, and sieved to obtain the final product, which is the ZS-Al(OH)3-3 composite molecular sieve.

[0089] Example 7

[0090] Step 1: Prepare ZSM-5 seed solution: Take 1g of ZSM-5 molecular sieve and 1g of sodium hydroxide and place them in 10mL of deionized water and stir at room temperature for 1h to obtain ZSM-5 seed solution.

[0091] Step 2: Preparation of SAPO-34 precursor solution: Weigh 9.73g of diethanolamine (DEA) and dissolve it in 50mL of deionized water. Stir at room temperature for 10min. Then add 5.79g of tetraethyl orthosilicate, 9.07g of phosphoric acid, and 4.33g of aluminum hydroxide in sequence and stir at room temperature for 4h to obtain a white gel, which is the SAPO-34 molecular sieve catalyst precursor solution.

[0092] Step 3: Add the ZSM-5 seed solution to the SAPO-34 molecular sieve catalyst precursor solution and stir at room temperature for 4 hours. Then, transfer the mixture to a hydrothermal reactor and crystallize at 200°C in an oven for 24 hours. Wash the crystallized product with anhydrous ethanol and deionized water until neutral. Dry the resulting white crystals at 80°C in an oven for 12 hours, and then calcine at 600°C for 5 hours in air at a rate of 5°C / min to obtain the ZSM-5 / SAPO-34 composite molecular sieve.

[0093] Step 4: The ZSM-5 / SAPO-34 composite molecular sieve is shaped, pressed, and sieved to obtain the final product, which is the ZS-Al(OH)3-4 composite molecular sieve.

[0094] Example 8

[0095] Step 1: Prepare ZSM-5 seed solution: Take 1g of ZSM-5 molecular sieve and 1g of sodium hydroxide and place them in 20mL of deionized water and stir at room temperature for 1h to obtain ZSM-5 seed solution.

[0096] Step 2: Preparation of SAPO-34 precursor solution: Weigh 9.73g of diethanolamine (DEA) and dissolve it in 50mL of deionized water. Stir at room temperature for 10min. Then add 5.79g of tetraethyl orthosilicate, 9.07g of phosphoric acid, and 8.66g of aluminum hydroxide in sequence and stir at room temperature for 4h to obtain a white gel, which is the SAPO-34 molecular sieve catalyst precursor solution.

[0097] Step 3: Add the ZSM-5 seed solution to the SAPO-34 molecular sieve catalyst precursor solution and stir at room temperature for 4 hours. Then, transfer the mixture to a hydrothermal reactor and crystallize at 200°C in an oven for 24 hours. Wash the crystallized product with anhydrous ethanol and deionized water until neutral. Dry the resulting white crystals at 80°C in an oven for 12 hours, and then calcine at 600°C for 5 hours in air at a rate of 5°C / min to obtain the ZSM-5 / SAPO-34 composite molecular sieve.

[0098] Step 4: The ZSM-5 / SAPO-34 composite molecular sieve is shaped, pressed, and sieved to obtain the final product, which is ZS-Al(OH)3-5 composite molecular sieve.

[0099] Comparative Example 1

[0100] 7.76 g of sodium hydroxide and 7.22 g of aluminum hydroxide were dissolved in 100 mL of deionized water and stirred at room temperature for 0.5 h. Then, 4.23 g of tetrapropylammonium bromide and 5.79 g of tetraethyl orthosilicate were added sequentially and stirred at room temperature for 4 h. 1 g of SAPO-34 molecular sieve was added and stirred at room temperature for 4 h. The mixture was then placed in a hydrothermal reactor and crystallized at 200 °C for 24 h in an oven. The crystallized product was then washed with anhydrous ethanol and deionized water until neutral. The resulting white crystals were dried at 80 °C for 12 h in an oven, and then heated to 600 °C at a rate of 5 °C / min under air atmosphere. The mixture was calcined for 5 h, pressed into tablets, and sieved to obtain SZ-Al(OH)3 composite molecular sieve.

[0101] Comparative Example 2

[0102] 9.73 g of diethanolamine (DEA) was dissolved in 50 mL of deionized water and stirred at room temperature for 10 min. Then, 5.79 g of tetraethyl orthosilicate, 9.07 g of phosphoric acid, and 7.22 g of aluminum hydroxide were added sequentially and stirred at room temperature for 4 h. The mixture was then placed in a hydrothermal reactor and crystallized in an oven at 200 °C for 24 h. The crystallized product was then washed with anhydrous ethanol and deionized water until neutral. The resulting white crystals were dried in an oven at 80 °C for 12 h, and then calcined at 600 °C for 5 h under air atmosphere to obtain SAPO-34 molecular sieve. 1 g of ZSM-5 molecular sieve and 1 g of SAPO-34 molecular sieve were placed in 10 mL of deionized water and stirred at room temperature for 3 h. After filtration, drying, and calcination, the mixture was pressed into tablets and sieved to obtain ZS-1 composite molecular sieve.

[0103] Comparative Example 3

[0104] Take 0.5g of ZSM-5 molecular sieve and 1g of SAPO-34 molecular sieve obtained in Comparative Example 2, place them in 10mL of deionized water, stir at room temperature for 3h, filter, dry and calcine, press into tablets and sieve to obtain ZS-2 composite molecular sieve.

[0105] Comparative Example 4

[0106] Take 1.5g of ZSM-5 molecular sieve and 1g of SAPO-34 molecular sieve obtained in Comparative Example 2, place them in 10mL of deionized water, stir at room temperature for 3h, filter, dry and calcine, press into tablets and sieve to obtain ZS-3 composite molecular sieve.

[0107] The catalysts prepared in Examples 2 to 6 were characterized using the same methods and results as in Example 1, and will not be repeated here.

[0108] Example 9

[0109] The performance of the catalysts prepared in Examples 1-8 and Comparative Examples 1-4 was evaluated using the following methods:

[0110] The performance evaluation of the catalyst was carried out in a vertical tube furnace. The catalytic pyrolysis process was as follows: 0.5 g of catalyst and sugarcane bagasse were weighed out at a 1:1 ratio, mixed evenly, and placed in a quartz crucible, which was then placed in the temperature-controlled zone of the tube furnace. Before the reaction, nitrogen gas was purged for 30 min to remove the air from the tube furnace. After the nitrogen purging was completed, the temperature was increased to 550℃ at a rate of 50℃ / min, and then the reaction was kept at a constant temperature for 5 min. The gaseous products generated by pyrolysis were discharged and condensed and collected. The distribution of organic matter in the collected liquid products was analyzed by GC-MS. The results are shown in Table 2.

[0111] Table 2 Distribution of liquid phase products from sugarcane bagasse pyrolysis with different catalysts

[0112]

[0113] Table 2 shows that, comparing the liquid phase products of Example 1 with those of Examples 2-3, the yield of furans in the liquid phase product of Example 1 was increased, and all of them were the target product 2,3-dihydrobenzofuran (i.e., approximately 100% of the furan compounds in the liquid phase product were in the form of 2,3-dihydrobenzofuran). Comparing Examples 1, 7, and 8, adjusting the amount of aluminum source, the yield of furans in the liquid phase product initially increased and then decreased with the increase of aluminum source amount. In Example 1, 2,3-dihydrobenzofuran accounted for 48.15% of the liquid phase product. In summary, the ZS-Al(OH)3 composite molecular sieve synthesized from aluminum hydroxide has high stability, suitable acid strength, and a relative crystallinity of 92.68%, which can effectively improve catalytic activity and catalyst reactivity.

[0114] In summary, the ZS-Al(OH)3 composite molecular sieve synthesized from aluminum hydroxide exhibits high stability, suitable acid strength, and a relative crystallinity of 92.68%, effectively improving catalytic activity and catalyst reactivity. Combined with... Figure 3 and Figure 4 Comparative calculations show that the catalysts corresponding to Examples 1 and 4 exhibit type I and type IV composite isotherms, indicating that the ZSM-5 / SAPO-34 composite molecular sieve possesses typical micro-mesoporous composite channels. However, Example 1 exhibits the largest isotherm slope and hysteresis loop, indicating a higher number of mesopores. Example 1 achieves a specific surface area of ​​435 m². 2 / g, pore volume 0.10cm 3 / g, average pore size 3.77nm. Example 4 has a specific surface area of ​​419m². 2 / g, pore volume is 0.09cm 3 / g, average pore size 3.21nm.

[0115] Comparing Examples 1-3, it was found that the ZS-Al(OH)3 composite molecular sieve synthesized using aluminum hydroxide as the aluminum source exhibits high crystallinity and suitable acid strength. The catalyst more readily adsorbs glucose molecules from sugarcane bagasse, allowing them to first adsorb onto Lewis acid Al... 3+ Isomerization at the site transforms into fructose, and finally, dehydration of fructose to furan is catalyzed at the Brønsted acid Si-OH-Al site. Comparing Examples 4-6 with Comparative Examples 1-4 shows that with the introduction of ZSM-5 molecular sieves, the combination... Figure 2 It can be seen that the composite molecular sieve has obvious pores and irregular cracks. The presence of the layered structure provides better accessibility from the raw material to the inner surface of the crystal and from the product to the outer surface of the crystal, thereby achieving increased selectivity for 2,3-dihydrobenzofuran in the liquid phase product.

[0116] The above embodiments are for illustrating the implementation schemes disclosed in this invention and should not be construed as limiting the invention. Furthermore, various modifications listed herein, as well as variations in the methods and compositions of the invention, will be apparent to those skilled in the art without departing from the scope and spirit of the invention. Although the invention has been specifically described in conjunction with various specific preferred embodiments, it should be understood that the invention should not be limited to these specific embodiments. In fact, various modifications as described above that are obvious to those skilled in the art to obtain the invention should be included within the scope of this invention.

Claims

1. Application of a ZSM-5 / SAPO-34 composite molecular sieve catalyst in the rapid catalytic pyrolysis of biomass to produce 2,3-dihydrobenzofuran.

2. The application as described in claim 1, characterized in that, The application method includes: The ZSM-5 / SAPO-34 composite molecular sieve catalyst was mixed with biomass and uniformly packed into the constant temperature zone of a vertical tube furnace. N2 is introduced to purge and remove air. After purging, a pyrolysis reaction is carried out under N2 atmosphere. The temperature is increased to the reaction temperature of 400-600℃ at a rate of 30-60℃ / min, and held at a constant temperature for 1-25 minutes. The liquid phase products generated by pyrolysis are collected.

3. The application according to claim 1, characterized in that, The preparation method of the ZSM-5 / SAPO-34 composite molecular sieve catalyst includes the following steps: Step 1: Preparation of ZSM-5 seed solution: Dissolve ZSM-5 molecular sieve in alkaline solution to prepare ZSM-5 seed solution; Step 2: Preparation of SAPO-34 precursor solution: Dissolve the organic template agent in deionized water, add the silicon source dropwise, mix well, then add the phosphorus source and aluminum source, stir well to obtain a white gel, which is the SAPO-34 molecular sieve catalyst precursor solution. Step 3: Mix the ZSM-5 seed solution with the SAPO-34 molecular sieve catalyst precursor solution and then crystallize it. The crystallized product is filtered, washed, dried and calcined to obtain ZSM-5 / SAPO-34 composite molecular sieve. Step 4: The ZSM-5 / SAPO-34 composite molecular sieve is shaped, pressed, and sieved to obtain the final product.

4. The application according to claim 3, characterized in that, In step 2, the silicon source is selected from at least one of silica sol, water glass, active silica, and tetraethyl orthosilicate; the aluminum source is selected from at least one of boehmite, aluminum isopropoxide, aluminum hydroxide, and aluminum salts; and the phosphorus source is selected from at least one of orthophosphoric acid, phosphorous acid, and phosphates.

5. The application according to claim 4, characterized in that, In step 2, the silicon source is tetraethyl orthosilicate; the aluminum source is aluminum hydroxide; and the phosphorus source is phosphoric acid.

6. The application according to claim 5, characterized in that, The silicon source, aluminum source and phosphorus source in step 2 are expressed in the form of oxide molar ratio, and the composition ratio is as follows: n(SiO2):n(Al2O3):n(P2O5)=1:(0.5~3):(0.5~4).

7. The application according to claim 3, characterized in that, The alkaline solution mentioned in step 1 is a sodium hydroxide aqueous solution with a mass concentration of 0.01~1%, and the solid-liquid ratio of ZSM-5 molecular sieve to alkaline solution is 0.5~2g:20mL.

8. The application according to claim 3, characterized in that, The organic template agent mentioned in step 2 is selected from at least one of diethanolamine, triethylamine, and tetraethylammonium hydroxide.

9. The application according to claim 3, characterized in that, In step 3, the solid product after filtration of the crystallized product is washed with water and ethanol until pH=6~9, and then calcined in air at a rate of 5℃ / min, with a calcination temperature of 500~700℃ and a calcination time of 3~7h.

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