Preparation method and application of octahedron-like hierarchical pore SAPO-20 zeolite molecular sieve

Abstract

The invention relates to a preparation method and application of an octahedron-like hierarchical porous SAPO-20 zeolite molecular sieve, and the preparation process is as follows: pseudo-boehmite is taken as an aluminum source, an 85 wt% phosphoric acid aqueous solution is taken as a phosphorus source, white carbon black is taken as a silicon source, raw materials are added according to the molar ratio of Al2O3: H2O: P2O5: SiO2 = (0.8-1.2): 63: 18: 1.0, hydrochloric acid is used for controlling the pH value to 6.6-7.8, stirring continues for 12 hours, hydrothermal crystallization reaction is performed at 185-235 DEG C for 60-108 hours, and the molecular sieve is obtained. And taking out the product, washing with water until the product is neutral, drying, and calcining at 450 DEG C for 6 hours to obtain the hierarchical porous SAPO-20 zeolite molecular sieve with octahedral morphology. The synthesis method disclosed by the invention is simple, the raw materials are low in price, the requirement on equipment is not high, and the synthesized hierarchical pore SAPO-20 zeolite has a microporous structure of about 8.35 nm and mesoporous structure distribution of 25.85 nm. The porous structure, morphology and surface properties are promoted to be effectively adjusted, especially when the catalyst acts on a hydrogenation reaction of oxycarbide, unique molecular recognition characteristics are shown, and the catalytic efficiency of a corresponding catalytic process and the selectivity of a target product are greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of molecular sieve synthesis, and particularly relates to a preparation method and application of an octahedron-like hierarchical pore SAPO-20 zeolite molecular sieve. Background Art

[0002] Silicoaluminophosphate molecular sieves (abbreviated as SAPO molecular sieves), such SAPOs are a kind of silicoaluminophosphate with a new crystal structure obtained by introducing Si atoms into the aluminophosphate framework. Its framework is composed of PO4, AlO4, and SiO4 tetrahedrons as primary structure units connected to each other by oxygen bridge bonds to form a three-dimensional crystal structure. This unique framework composition and structural characteristics endow the aluminosilicate phosphate zeolite molecular sieves with rich pore structures, high specific surface areas, strong ion exchange properties, and surface acidity. And SAPO-20 zeolite molecular sieve is an aluminophosphate molecular sieve with an SOD-type topological structure. It is isomorphous with AlPO-20 and sodalite, belonging to the cubic crystal system. Its pore size is 9.8 nm (six-membered ring), and in the pore channels within the crystal, Si 4+ partially replaces P 5+ or Al 3+ to generate acidity, so it has been widely studied and applied in catalysis, adsorption, separation, etc.

[0003] Developing and designing special zeolite catalysts has always faced challenges in dealing with their inherent microporous characteristics, stability in aqueous solutions, and adjusting their corresponding composition, morphology, and acidity / basicity. Through research, it has been found that the introduction of secondary pores can not only effectively solve the problems of contact and diffusion limitations of active sites, but also promote the transformation of the morphology and other physical and chemical properties of zeolite molecular sieves. In current research reports, most of the obtained SAPO-20 zeolite molecular sieves have microporous structures, and their morphology is single cubic grains. The dense cubic structure and small pore size on the surface will cause disadvantages such as hindering the adsorption and diffusion of molecules during actual application, greatly limiting its industrial application. It should be noted that for zeolite molecular sieves, morphology can not only affect their structural integrity, active specific surface area, and distribution of active species, thereby changing their adsorption and catalytic efficiency, but also different morphologies are beneficial to exposing more surface active sites, which can promote the optimization of the diffusion paths of reactants and products in the zeolite pores, thereby improving the selectivity and adsorption efficiency of specific reactions.

[0004] Therefore, we attempted to develop a method for directly synthesizing an octahedron-like hierarchical pore SAPO-20 zeolite molecular sieve using inexpensive silica white as the silicon source through simple hydrothermal crystallization. By continuously narrowing the ranges of the raw material molar ratio, system pH, reaction time, and temperature, a low-cost synthesis route was found. The obtained octahedron-like highly crystalline SAPO-20 zeolite molecular sieve with a hierarchical pore structure has a micropore structure of approximately 8.35 nm and a mesopore structure distribution of 25.85 nm. It not only effectively regulates the pore structure, morphology, and surface properties, but especially when used as a catalyst support to load transition metals in the reaction of hydrogenating carbon oxides to prepare alcohol compounds, it can effectively catalyze the conversion of carbon oxides to alcohol, and the carbon dioxide conversion rate can reach over 93%. Summary of the Invention

[0005] To solve the problems that most SAPO-20 zeolite molecular sieves have a relatively small micropore size and a single morphology, the present invention provides a method for synthesizing an octahedron-like hierarchical pore SAPO-20 zeolite molecular sieve and its application. The SAPO-20 zeolite molecular sieve synthesized by the method of the present invention has a hierarchical pore structure and high crystallinity. When used as a support to load transition metals to prepare a catalyst for use in the reaction of hydrogenating carbon oxides to alcohol compounds, the carbon oxides have a relatively high conversion rate.

[0006] To achieve the above object, the present invention is realized through the following technical solutions:

[0007] A method for preparing an octahedron-like hierarchical pore SAPO-20 zeolite molecular sieve, comprising the following process: using pseudoboehmite as the aluminum source, 85 wt% phosphoric acid aqueous solution as the phosphorus source, and inexpensive silica white as the silicon source to add raw materials, controlling the pH at 6.6 - 7.8 with hydrochloric acid, then continuing to stir for 10 - 14 h (preferably 12 h), carrying out a hydrothermal crystallization reaction at 185 - 235 °C for 60 - 108 h, preferably 84 h, washing the product with water until neutral after taking it out, drying, and calcining at 420 - 460 °C (preferably 450 °C) for 5 - 7 h (preferably 6 h) to obtain the hierarchical pore SAPO-20 zeolite molecular sieve;

[0008] The feeding amounts of the raw materials of the aluminum source, the phosphorus source, the silicon source, and the seed crystal are calculated based on Al2O3, P2O5, and SiO2, and are added according to the molar ratio of Al2O3:H2O:P2O5:SiO2 = (0.8 - 1.2):63:1.8:1.0, and the system pH is controlled at 7.0. More preferably, it is added according to the molar ratio of Al2O3:H2O:P2O5:SiO2 = 1.1:63:1.8:1.0.

[0009] Further, hydrochloric acid is used to control the acidity and alkalinity of the system within the range of pH 6.6 - 7.8.

[0010] More preferably, hydrochloric acid is used to control the pH of the system at 7.2.

[0011] Furthermore, the temperature of the hydrothermal crystallization reaction is 195 - 235 °C; the time of the crystallization reaction is 60 - 108 h.

[0012] More preferably, the temperature of the hydrothermal crystallization reaction is 205 - 215 °C; the time of the crystallization reaction is 84 h.

[0013] In the last aspect of the present invention, there is provided the use of the octahedron-like hierarchical pore SAPO-20 zeolite molecular sieve obtained by the above preparation method in the reaction of hydrogenating carbon oxides to prepare alcohol compounds. The hierarchical pore SAPO-20 zeolite molecular sieve is loaded with a transition metal or a transition metal oxide and used as a catalyst.

[0014] Furthermore, the transition metal is one or more of Zr, Ni, Co, Zn, Cu, Ce, and preferably the transition metal is a Co-containing metal or a Co-containing metal oxide.

[0015] Beneficial technical effects: The present invention uses inexpensive silica as a silicon source and directly synthesizes an octahedron-like hierarchical pore SAPO-20 zeolite molecular sieve through simple hydrothermal crystallization. Compared with the prior art, by continuously narrowing the ranges of the raw material molar ratio, system pH, reaction time, and temperature range, a low-cost synthesis route has been found. The octahedron-like high-crystallinity SAPO-20 zeolite molecular sieve with a hierarchical pore structure obtained in the present invention has a micropore structure of about 8.35 nm and a mesopore structure distribution of 25.85 nm. It not only effectively regulates the pore structure, morphology, and surface properties, but especially as a catalyst support for loading transition metals in the reaction of hydrogenating carbon oxides to prepare alcohol compounds, it can effectively catalyze the conversion of carbon oxides into alcohols, and the carbon dioxide conversion rate can reach more than 93%. Description of the Drawings

[0016] Figure 1 SEM image of an octahedron-like hierarchical pore SAPO-20 zeolite molecular sieve prepared in Example 25.

[0017] Figure 2 N2 adsorption-desorption isotherm and pore size distribution curve of an octahedron-like hierarchical pore SAPO-20 zeolite molecular sieve prepared in Example 25.

[0018] Figure 3XRD patterns of SAPO-20 zeolite molecular sieves synthesized at different Al2O3:P2O5 ratios; among them, Example 1 represents Al2O3:P2O5 = 0.8:1.8, Example 2 represents Al2O3:P2O5 = 0.9:1.8, Example 3c represents Al2O3:P2O5 = 1.0:1.8, Example 4 represents Al2O3:P2O5 = 1.1:1.8, and Example 5 represents Al2O3:P2O5 = 1.2:1.8.

[0019] Figure 4 XRD patterns of SAPO-20 zeolite molecular sieves synthesized at different system pH values; among them, Example 6 represents the system with pH = 6.6, Example 7 represents the system with pH = 6.8, Example 8 represents the system with pH = 7.0, Example 9 represents the system with pH = 7.2, Example 10 represents the system with pH = 7.4, Example 11 represents the system with pH = 7.6, and Example 12 represents the system with pH = 7.8.

[0020] Figure 5 XRD patterns of SAPO-20 zeolite molecular sieves synthesized at different crystallization reaction temperatures; among them, Example 13 represents 185°C, Example 14 represents 195°C, Example 15 represents 205°C, Example 16 represents 215°C, Example 17 represents 225°C, and Example 18 represents 235°C.

[0021] Figure 6 XRD patterns of SAPO-20 zeolite molecular sieves synthesized at different crystallization reaction times; among them, Example 19 represents 60 h, Example 20 represents 72 h, Example 21 represents 84 h, Example 22 represents 96 h, and Example 23 represents 108 h.

[0022] Figure 7 XRD patterns of spherical multi-porous SAPO-20 zeolite molecular sieves prepared in Comparative Examples 1-2 and octahedron-like multi-porous SAPO-20 zeolite molecular sieves in Example 21.

[0023] Figure 8 Catalytic activity diagrams of each catalyst for carbon dioxide conversion in Application Example 1. Detailed implementation manners

[0024] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments and drawings of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and in no way limits the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0025] Unless otherwise specifically stated, the numerical values set forth in these examples do not limit the scope of the present invention. Technologies and methods known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, such technologies and methods should be regarded as part of the specification. In all examples shown and discussed herein, any specific values should be construed as merely exemplary and not as limiting. Thus, other examples of the exemplary embodiments may have different values.

[0026] For the experimental methods without specific conditions noted in the following examples, they are generally determined according to national standards; if there are no corresponding national standards, they are carried out according to general international standards or the standard requirements proposed by relevant enterprises. Unless otherwise specified, all parts are by weight and all percentages are by weight percentage.

[0027] In the description of "molar ratio of each material Al2O3:H2O:P2O5:SiO2" in the following examples and comparative examples: Al2O3 refers to the aluminum source, and the number of moles of the aluminum source is the number of moles of aluminum element in pseudo-boehmite; SiO2 refers to the silicon source, and the number of moles of the silicon source is the number of moles of silicon element in silica; P2O5 refers to the phosphorus source, and the number of moles of the phosphorus source is the number of moles of phosphorus element in phosphoric acid.

[0028] Calculation method of conversion rate: Conversion rate = (amount of initial reactant (mol) - amount of unreacted substance (mol)) / amount of initial reactant (mol) × 100%;

[0029] Calculation method of yield: Yield = amount of target product (mol) / amount of initial reactant (mol) × 100%.

[0030] Test and calculation method of crystallinity (%): Crystallinity is tested using an X-ray diffractometer, and the calculation formula is: Crystallinity = (diffraction peak intensity / total intensity) * 100%, and data processing is carried out using jade software.

[0031] S BET Measured by nitrogen adsorption using a physical adsorption instrument.

[0032] Example 1

[0033] Solution A: Obtained by dissolving 0.89 g of silica in 8.0 mL of H2O;

[0034] Dissolve 1.6 g of high-purity pseudo-boehmite AlOOH·nH2O in 9.0 mL of H2O and mix evenly. Add 2.8 mL of 85 wt% phosphoric acid aqueous solution, stir for 30 min, then add solution A drop by drop. After stirring for another 30 min, add 6.7 mL of N,N,N’,N’-tetramethyl-1,6-hexanediamine, and stir for 12 h to obtain a mixture. Add hydrochloric acid dropwise to the mixed solution to control the system pH = 7.0. Load the obtained mixture into a high-pressure reaction kettle, place it in an oven at 225 °C for hydrothermal crystallization reaction for 72 h. After filtration, washing, and drying, calcine at 450 °C for 6 h to obtain SAPO-20 zeolite molecular sieve with an octahedron-like morphology. The molar ratio of each material in the system is Al2O3:H2O:P2O5:SiO2:TMHD = 0.8:63:1.8:1.0:1.6.

[0035] The crystallinity and morphology of the prepared SAPO-20 zeolite molecular sieve are shown in Table 1.

[0036] Example 2

[0037] Solution A: Obtained by dissolving 0.89 g of silica white in 8.0 mL of H2O.

[0038] Dissolve 1.8 g of high-purity pseudo-boehmite AlOOH·nH2O in 9.0 mL of H2O and mix evenly. Add 2.8 mL of 85 wt% phosphoric acid aqueous solution, stir for 30 min, then add solution A drop by drop. After stirring for another 30 min, add 6.7 mL of N,N,N’,N’-tetramethyl-1,6-hexanediamine, and stir for 12 h to obtain a mixture. Add hydrochloric acid dropwise to the mixed solution to control the system pH = 7.0. Load the obtained mixture into a high-pressure reaction kettle, place it in an oven at 225 °C for hydrothermal crystallization reaction for 72 h. After filtration, washing, and drying, calcine at 450 °C for 6 h to obtain SAPO-20 zeolite molecular sieve with an octahedron-like morphology. The molar ratio of each material in the system is Al2O3:H2O:P2O5:SiO2:TMHD = 0.9:63:1.8:1.0:1.6.

[0039] The crystallinity and morphology of the prepared SAPO-20 zeolite molecular sieve are shown in Table 1.

[0040] Example 3

[0041] Solution A: Obtained by dissolving 0.89 g of silica white in 8.0 mL of H2O.

[0042] Dissolve 2.0 g of high-purity pseudo-boehmite AlOOH·nH2O in 9.0 mL of H2O and mix evenly. Add 2.8 mL of 85 wt% phosphoric acid aqueous solution, stir for 30 min, then add solution A drop by drop. After stirring for another 30 min, add 6.7 mL of N,N,N’,N’-tetramethyl-1,6-hexanediamine, and stir for 12 h to obtain a mixture. Add hydrochloric acid dropwise to the mixed solution to control the system pH = 7.0. Load the obtained mixture into a high-pressure reaction kettle, place it in an oven at 225 °C for hydrothermal crystallization reaction for 72 h. After filtration, washing, and drying, calcine at 450 °C for 6 h to obtain SAPO-20 zeolite molecular sieve with an octahedron-like morphology. The molar ratio of each material in the system is Al2O3:H2O:P2O5:SiO2:TMHD = 1.0:63:1.8:1.0:1.6.

[0043] The crystallinity and morphology of the prepared SAPO-20 zeolite molecular sieve are shown in Table 1.

[0044] Example 4

[0045] Solution A: Obtained by dissolving 0.89 g of silica white in 8.0 mL of H2O;

[0046] Dissolve 2.2 g of high-purity pseudo-boehmite AlOOH·nH2O in 9.0 mL of H2O and mix evenly. Add 2.8 mL of 85 wt% phosphoric acid aqueous solution, stir for 30 min, then add solution A drop by drop. After stirring for another 30 min, add 6.7 mL of N,N,N’,N’-tetramethyl-1,6-hexanediamine, and stir for 12 h to obtain a mixture. Add hydrochloric acid dropwise to the mixed solution to control the system pH = 7.0. Load the obtained mixture into a high-pressure reaction kettle, place it in an oven at 225 °C for hydrothermal crystallization reaction for 72 h. After filtration, washing, and drying, calcine at 450 °C for 6 h to obtain SAPO-20 zeolite molecular sieve with an octahedron-like morphology. The molar ratio of each material in the system is Al2O3:H2O:P2O5:SiO2:TMHD = 1.1:63:1.8:1.0:1.6.

[0047] The crystallinity and morphology of the prepared SAPO-20 zeolite molecular sieve are shown in Table 1.

[0048] Example 5

[0049] Solution A: Obtained by dissolving 0.89 g of silica white in 8.0 mL of H2O;

[0050] Dissolve 2.0 g of high-purity pseudoboehmite AlOOH·nH2O in 9.0 mL of H2O and mix evenly. Add 2.8 mL of 85 wt% phosphoric acid aqueous solution, stir for 30 min, then add solution A drop by drop. After stirring for another 30 min, add 6.7 mL of N,N,N’,N’-tetramethyl-1,6-hexanediamine, and stir for 12 h to obtain a mixture. Add hydrochloric acid dropwise to the mixed solution to control the system pH = 7.0. Load the obtained mixture into a high-pressure reaction kettle, place it in an oven at 225 °C for hydrothermal crystallization reaction for 72 h. After filtration, washing, and drying, calcine at 450 °C for 6 h to obtain SAPO-20 zeolite molecular sieve with an octahedron-like morphology. The molar ratio of each material in the system is Al2O3:H2O:P2O5:SiO2:TMHD = 1.2:63:1.8:1.0:1.6.

[0051] The crystallinity and morphology of the prepared SAPO-20 zeolite molecular sieve are shown in Table 1.

[0052] Example 6

[0053] Solution A: Obtained by dissolving 0.89 g of silica white in 8.0 mL of H2O;

[0054] Dissolve 2.2 g of high-purity pseudoboehmite AlOOH·nH2O in 9.0 mL of H2O and mix evenly. Add 2.8 mL of 85 wt% phosphoric acid aqueous solution, stir for 30 min, then add solution A drop by drop. After stirring for another 30 min, add 6.7 mL of N,N,N’,N’-tetramethyl-1,6-hexanediamine, and stir for 12 h to obtain a mixture. Add hydrochloric acid dropwise to the mixed solution to control the system pH = 6.6. Load the obtained mixture into a high-pressure reaction kettle, place it in an oven at 225 °C for hydrothermal crystallization reaction for 72 h. After filtration, washing, and drying, calcine at 450 °C for 6 h to obtain SAPO-20 zeolite molecular sieve with an octahedron-like morphology. The molar ratio of each material in the system is Al2O3:H2O:P2O5:SiO2:TMHD = 1.1:63:1.8:1.0:1.6.

[0055] The crystallinity and morphology of the prepared SAPO-20 zeolite molecular sieve are shown in Table 1.

[0056] Example 7

[0057] Solution A: Obtained by dissolving 0.89 g of silica white in 8.0 mL of H2O;

[0058] Dissolve 2.2 g of high-purity pseudo-boehmite AlOOH·nH2O in 9.0 mL of H2O and mix evenly. Add 2.8 mL of 85 wt% phosphoric acid aqueous solution. After stirring for 30 min, add solution A dropwise. After stirring for another 30 min, add 6.7 mL of N,N,N’,N’-tetramethyl-1,6-hexanediamine, and then stir for 12 h to obtain a mixture. Add hydrochloric acid dropwise to the mixed solution to control the system pH = 6.8. Load the obtained mixture into a high-pressure reactor and place it in an oven at 225 °C for hydrothermal crystallization reaction for 72 h. After filtration, washing, and drying, calcine it at 450 °C for 6 h to obtain SAPO-20 zeolite molecular sieve with an octahedron-like morphology. The molar ratio of each material in the system is Al2O3:H2O:P2O5:SiO2:TMHD = 1.1:63:1.8:1.0:1.6.

[0059] The crystallinity and morphology of the prepared SAPO-20 zeolite molecular sieve are shown in Table 1.

[0060] Example 8

[0061] Solution A: Obtained by dissolving 0.89 g of silica white in 8.0 mL of H2O.

[0062] Dissolve 2.2 g of high-purity pseudo-boehmite AlOOH·nH2O in 9.0 mL of H2O and mix evenly. Add 2.8 mL of 85 wt% phosphoric acid aqueous solution. After stirring for 30 min, add solution A dropwise. After stirring for another 30 min, add 6.7 mL of N,N,N’,N’-tetramethyl-1,6-hexanediamine, and then stir for 12 h to obtain a mixture. Add hydrochloric acid dropwise to the mixed solution to control the system pH = 7.0. Load the obtained mixture into a high-pressure reactor and place it in an oven at 225 °C for hydrothermal crystallization reaction for 72 h. After filtration, washing, and drying, calcine it at 450 °C for 6 h to obtain SAPO-20 zeolite molecular sieve with an octahedron-like morphology. The molar ratio of each material in the system is Al2O3:H2O:P2O5:SiO2:TMHD = 1.1:63:1.8:1.0:1.6.

[0063] The crystallinity and morphology of the prepared SAPO-20 zeolite molecular sieve are shown in Table 1.

[0064] Example 9

[0065] Solution A: Obtained by dissolving 0.89 g of silica white in 8.0 mL of H2O.

[0066] Dissolve 2.2 g of high-purity pseudo-boehmite AlOOH·nH2O in 9.0 mL of H2O and mix evenly. Add 2.8 mL of 85 wt% phosphoric acid aqueous solution, stir for 30 min, then add solution A drop by drop. After stirring for another 30 min, add 6.7 mL of N,N,N’,N’-tetramethyl-1,6-hexanediamine, and stir for 12 h to obtain a mixture. Add hydrochloric acid dropwise to the mixed solution to control the system pH = 7.2. Load the obtained mixture into a high-pressure reaction kettle, place it in an oven at 225 °C for hydrothermal crystallization reaction for 72 h. After filtration, washing, and drying, calcine it at 450 °C for 6 h to obtain SAPO-20 zeolite molecular sieve with an octahedron-like morphology. The feeding molar ratio of each material in the system is Al2O3:H2O:P2O5:SiO2:TMHD = 1.1:63:1.8:1.0:1.6.

[0067] The crystallinity and morphology of the prepared SAPO-20 zeolite molecular sieve are shown in Table 1.

[0068] Example 10

[0069] Solution A: Obtained by dissolving 0.89 g of silica white in 8.0 mL of H2O.

[0070] Dissolve 2.2 g of high-purity pseudo-boehmite AlOOH·nH2O in 9.0 mL of H2O and mix evenly. Add 2.8 mL of 85 wt% phosphoric acid aqueous solution, stir for 30 min, then add solution A drop by drop. After stirring for another 30 min, add 6.7 mL of N,N,N’,N’-tetramethyl-1,6-hexanediamine, and stir for 12 h to obtain a mixture. Add hydrochloric acid dropwise to the mixed solution to control the system pH = 7.4. Load the obtained mixture into a high-pressure reaction kettle, place it in an oven at 225 °C for hydrothermal crystallization reaction for 72 h. After filtration, washing, and drying, calcine it at 450 °C for 6 h to obtain SAPO-20 zeolite molecular sieve with an octahedron-like morphology. The feeding molar ratio of each material in the system is Al2O3:H2O:P2O5:SiO2:TMHD = 1.1:63:1.8:1.0:1.6.

[0071] The crystallinity and morphology of the prepared SAPO-20 zeolite molecular sieve are shown in Table 1.

[0072] Example 11

[0073] Solution A: Obtained by dissolving 0.89 g of silica white in 8.0 mL of H2O.

[0074] Dissolve 2.2 g of high-purity pseudo-boehmite AlOOH·nH2O in 9.0 mL of H2O and mix evenly. Add 2.8 mL of 85 wt% phosphoric acid aqueous solution, stir for 30 min, then add solution A dropwise. After stirring for another 30 min, add 6.7 mL of N,N,N’,N’-tetramethyl-1,6-hexanediamine, and stir for 12 h to obtain a mixture. Add hydrochloric acid dropwise to the mixed solution to control the system pH = 7.6. Load the obtained mixture into a high-pressure reaction kettle, place it in an oven at 225 °C for hydrothermal crystallization reaction for 72 h. After filtration, washing, and drying, calcine at 450 °C for 6 h to obtain SAPO-20 zeolite molecular sieve with an octahedron-like morphology. The molar ratio of each material in the system is Al2O3:H2O:P2O5:SiO2:TMHD = 1.1:63:1.8:1.0:1.6.

[0075] The crystallinity and morphology of the prepared SAPO-20 zeolite molecular sieve are shown in Table 1.

[0076] Example 12

[0077] Solution A: Obtained by dissolving 0.89 g of silica white in 8.0 mL of H2O.

[0078] Dissolve 2.2 g of high-purity pseudo-boehmite AlOOH·nH2O in 9.0 mL of H2O and mix evenly. Add 2.8 mL of 85 wt% phosphoric acid aqueous solution, stir for 30 min, then add solution A dropwise. After stirring for another 30 min, add 6.7 mL of N,N,N’,N’-tetramethyl-1,6-hexanediamine, and stir for 12 h to obtain a mixture. Add hydrochloric acid dropwise to the mixed solution to control the system pH = 7.8. Load the obtained mixture into a high-pressure reaction kettle, place it in an oven at 225 °C for hydrothermal crystallization reaction for 72 h. After filtration, washing, and drying, calcine at 450 °C for 6 h to obtain SAPO-20 zeolite molecular sieve with an octahedron-like morphology. The molar ratio of each material in the system is Al2O3:H2O:P2O5:SiO2:TMHD = 1.1:63:1.8:1.0:1.6.

[0079] The crystallinity and morphology of the prepared SAPO-20 zeolite molecular sieve are shown in Table 1.

[0080] Examples 13 - 18

[0081] The preparation method of the products in Examples 13 - 18 is the same as that in Example 9, except that the crystallization reaction temperature is different.

[0082] The crystallization reaction temperature in Example 13 is 185 °C.

[0083] The crystallization reaction temperature in Example 14 is 195 °C.

[0084] The crystallization reaction temperature of Example 15 is 205 °C.

[0085] The crystallization reaction temperature of Example 16 is 215 °C.

[0086] The crystallization reaction temperature of Example 17 is 225 °C.

[0087] The crystallization reaction temperature of Example 18 is 235 °C.

[0088] The crystallinity and morphology of the prepared SAPO-20 zeolite molecular sieve are shown in Table 1.

[0089] Examples 19 - 23

[0090] The preparation method of the products of Examples 19 - 23 is the same as that of Example 16, except that the crystallization reaction time is different.

[0091] The crystallization reaction time of Example 19 is 60 h.

[0092] The crystallization reaction time of Example 20 is 72 h.

[0093] The crystallization reaction time of Example 21 is 84 h.

[0094] The crystallization reaction time of Example 22 is 96 h.

[0095] The crystallization reaction time of Example 23 is 108 h.

[0096] The crystallinity and morphology of the prepared SAPO-20 zeolite molecular sieve are shown in Table 1.

[0097] Comparative Example 1

[0098] Prepared by the method reported in the patent "A Preparation Method of High-Crystallinity SAPO-20 Zeolite Molecular Sieve": (1) Dissolve the aluminum source in water, add the phosphorus source, stir evenly, add the water glass solution, continue to stir evenly, and then add the amine template agent, and stir for another 24 h; the aluminum source is calculated as Al2O3, the phosphorus source is calculated as P2O5, the water glass is calculated as SiO2, and the molar ratio of the feed amounts of each raw material is Al2O3:H2O:P2O5:SiO2:amine template agent = 0.8:40:1.0:(0.8 - 1):(1.1 - 1.5); (2) Transfer to a high-pressure reaction kettle and carry out a crystallization reaction at 180 - 220 °C for 36 - 96 h to obtain a high-crystallinity SAPO-20 zeolite molecular sieve.

[0099] Comparative Example 2

[0100] Prepared by the method reported in the patent "Preparation Method and Application of Spherical Multistage Pore SAPO-20 Zeolite Molecular Sieve": Aluminum source, phosphorus source, silicon source, inorganic structure directing agent, and organic amine structure directing agent are sequentially added to water. After all raw materials are added, stirring is continued for at least 6 h, and then crystallization reaction is carried out at 190-220 °C for at least 24 h to obtain spherical multistage pore SAPO-20 zeolite molecular sieve; wherein, the inorganic structure directing agent is a compound with alkali metal element or alkaline earth metal element, and the alkali metal element or alkaline earth metal element is represented by M; the molar ratio of each raw material feed is calculated as Al2O3:H2O:P2O5:SiO2:M2O:organic amine structure directing agent = 0.8:40:1.0:0.6:(0.8-1.5):(0.1-1).

[0101] The crystallinity (%) and nitrogen adsorption test were carried out on the above examples. Calculation method of crystallinity: Crystallinity was tested using an X-ray diffractometer, and the calculation formula is: crystallinity = (diffraction peak intensity / total intensity) * 100%, and data processing was carried out using jade software. Nitrogen adsorption was measured with a physical adsorption instrument to obtain S BET . The reaction parameters and specific crystallinity data of the above examples are shown in Table 1.

[0102] The products of the above examples and comparative examples were subjected to XRD test and crystallinity was calculated, and the results are shown in Table 1.

[0103] Table 1 Preparation parameters and crystallinity of the products of the above examples and comparative examples

[0104]

[0105]

[0106] Table 1 Preparation parameters, crystallinity and morphology of the products of the above examples and comparative examples

[0107] Results and discussion:

[0108] The SEM image of the high-crystallinity SAPO-20 zeolite product obtained in Example 21 is as Figure 1 shown, and its N2 adsorption-desorption isotherm and pore size distribution curve are as Figure 2 shown. It can be seen that the SAPO-20 zeolite product obtained by the method of the present invention is octahedron-like, has a multistage pore distribution, and the pore size distribution is around 8.35 nm and 25.85.

[0109] Examples 1-5 compared whether SAPO-20 zeolite could be synthesized under different Al2O3:P2O5 ratios. Through the crystallinity in Table 1 and Figure 3From the XRD patterns, it can be seen that porous SAPO-20 zeolite can be hydrothermally synthesized when the aluminum-phosphorus ratio is in the range of (0.8 - 1.2):1.8. However, when Al2O3:P2O5 = 1.1:1.8, the crystallinity is the highest. Therefore, when Al2O3:P2O5 = 1.1:1.8, it is beneficial to the synthesis of porous SAPO-20.

[0110] Examples 6 - 12 compared whether the acidity or alkalinity of the system was beneficial to the synthesis of SAPO-20 zeolite. Through the crystallinity in Table 1 and Figure 4 From the XRD patterns, it can be seen that SAPO-20 zeolite can be synthesized when the system pH is in the range of 6.8 - 7.6. And when the pH is about 7.2, the crystallinity is the highest. However, SAPO-20 zeolite cannot be synthesized under conditions of excessive acidity or alkalinity. Therefore, pH = 7.2 is beneficial to the synthesis of SAPO-20.

[0111] Examples 13 - 18 compared whether SAPO-20 zeolite could be synthesized in the system at different crystallization temperatures. Through the crystallinity in Table 1 and Figure 5 From the XRD patterns, it can be seen that as the crystallization temperature increases, the crystallinity of SAPO-20 zeolite gradually increases. However, at too high temperatures, such as exceeding 225 °C, the intensity of the characteristic peaks in the XRD pattern is lower and the corresponding crystallinity is also quite low. Therefore, the crystallization temperature of 215 °C is selected as the optimal temperature.

[0112] Examples 19 - 23 compared whether SAPO-20 zeolite could be synthesized in the system at different crystallization times. Through the crystallinity in Table 1 and Figure 6 From the XRD patterns, it can be seen that SAPO-20 can be synthesized when the crystallization time is in the range of 60 - 108 h. As the crystallization time extends, the crystallinity of SAPO-20 zeolite first increases and then decreases. Therefore, the crystallization time of 84 h is selected as the optimal time.

[0113] Examples 1 - 23 compared the relationship between crystallinity and morphology. Through the crystallinity in Table 1 and the morphology in Table 1, it can be seen that the formation of SAPO-20 with an octahedron-like morphology is related to the crystallinity. The higher the crystallinity, the more beneficial it is to the synthesis of SAPO-20 with an octahedron-like morphology. When the crystallinity is lower than 80%, the morphology of SAPO-20 is amorphous.

[0114] Comparative Examples 1 - 2 and Example 21 compared the crystallinity and morphology of SAPO-20 zeolite prepared by the prior art synthesis method and the optimal synthesis scheme of the present invention. Through the crystallinity in Table 1 and Figure 7From the XRD patterns, it can be seen that under different formulations and material ratios, the crystallinity of SAPO-20 zeolite does not show obvious differences. However, compared with the experimental scheme in the literature, the present invention proposes a new octahedron-like morphology, and the synthesized octahedron-like hierarchical pore SAPO-20 zeolite has a microporous structure of about 8.35 nm and a mesoporous structure distribution of 25.85 nm.

[0115] Application Example 1

[0116] The highly crystalline SAPO-20 zeolite molecular sieves with an octahedron-like morphology prepared in the above Examples 4, 8, 12, 13, 19-20, Examples 24, and 25 were all loaded with metal Co to prepare Co-SAPO-20 molecular sieve catalysts for the catalytic hydrogenation of carbon oxides to alcohol compounds, and the activity of the Co-SAPO-20 molecular sieve catalysts was measured.

[0117] Specific preparation process of the Co-SAPO-20 molecular sieve catalyst: Take a certain amount of octahedron-like SAPO-20 zeolite sample as the catalyst support, and introduce metal species by the equal-volume impregnation method according to 5 wt.% of the support mass. Prepare a solution according to the measured water inlet rate and uniformly drop it onto the surface of the zeolite molecular sieve. The metal precursor is mainly nitrate (cobalt nitrate selected in this application example). After the impregnated sample is dried in air at room temperature overnight, it is dried in an oven at 80-120 °C, and finally calcined at 450 °C for 6 h. Before use, the catalyst needs to be reduced: Take a certain amount of the catalyst, screen it to the target mesh number, and reduce it at 400 °C in a hydrogen atmosphere for 4 h. Then the 5% Co-SAPO-20 molecular sieve catalyst can be obtained.

[0118] In addition, 5% Zn / SAPO-20, 5% Cu / SAPO-20, 5% Ni / SAPO-20, 5% Zr / SAPO-20, and 5% Ce / SAPO-20 with different metals supported on octahedron-like hierarchical pore SAPO-20 zeolite molecular sieves were prepared according to the aforementioned method.

[0119] In order to test whether octahedron-like SAPO-20 as a support has higher catalytic activity than spherical-like SAPO-20 as a support, in the present invention, spherical-like hierarchical pore SAPO-20 zeolite molecular sieves were hydrothermally synthesized as supports to load transition metals to prepare catalysts 5% Co / SAPO-20, 5% Zn / SAPO-20, 5% Cu / SAPO-20, 5% Ni / SAPO-20, 5% Zr / SAPO-20, and 5% Ce / SAPO-20 catalysts according to the patent "A Preparation Method of High-Crystallinity SAPO-20 Zeolite Molecular Sieve". The catalytic activities of the above catalysts for carbon dioxide were tested, and the catalyst activity data and data graphs are shown in Table 2 and Figure 8 .

[0120] It can be seen that regardless of the morphology, 5% Co / SAPO-20 has the highest CO2 conversion rate and the best selectivity among single-metal catalysts. Moreover, octahedron-like SAPO-20 as the support has higher catalytic activity for the hydrogenation of CO2 to methanol than sphere-like SAPO-20 as the support.

[0121] Table 2. Activity comparison of the catalytic activity of different catalysts for the hydrogenation of CO2 to methanol

[0122]

[0123] As described above, only the preferred specific embodiments of the present invention are given, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A method for preparing octahedral multi-level pore SAPO-20 zeolite molecular sieve, characterized in that: The steps include: (1) Add aluminum source, phosphorus source and silicon source to water in sequence, stir evenly after adding each raw material, and then add other raw materials; (2) After all the raw materials are added, continue stirring, control the pH of the system to 6.6-7.8 with hydrochloric acid, and continue stirring for 10-14 hours; (3) subjecting the mixture to a hydrothermal crystallization reaction at 185-235° C. for 60-108 hours; (4) After the crystallization reaction is completed, the product is taken out, washed with water until neutral, dried, and calcined at 420-460° C. for 5-7 h to obtain a multi-level porous SAPO-20 zeolite molecular sieve with an octahedral morphology; Among them, the aluminum source is measured as Al2O3, the phosphorus source is measured as P2O5, and the silicon source is measured as SiO2, and the molar ratio of each raw material is Al2O3:H2O:P2O5:SiO2=(0.8-1.2):63:1.8:1.

0.

2. The method for preparing a ping-pong chrysanthemum-like SAPO-15 zeolite molecular sieve according to claim 1, characterized in that: The aluminum source is pseudo-boehmite.

3. The method for preparing a ping-pong chrysanthemum-like SAPO-15 zeolite molecular sieve according to claim 1, characterized in that: The phosphorus source is an 85% wt phosphoric acid aqueous solution.

4. The method for preparing a ping-pong chrysanthemum-like SAPO-15 zeolite molecular sieve according to claim 1, characterized in that: The silicon source is white carbon black.

5. The method for preparing the octahedral multi-level pore SAPO-20 zeolite molecular sieve according to claim 1, characterized in that: The temperature of the hydrothermal crystallization reaction in step (3) is 215° C. and the time is 84 hours.

6. The octahedral multi-level pore SAPO-20 zeolite molecular sieve according to any one of claims 1 to 5, characterized in that: The hierarchical pore SAPO-20 zeolite has a micropore structure of about 8.35 nm and a mesopore structure distribution of 25.85 nm.

7. Application of octahedral multi-level pore SAPO-20 zeolite molecular sieve in the reaction of preparing alcohol compounds by hydrogenation of carbon oxides, characterized in that: The octahedral multi-level pore SAPO-20 zeolite molecular sieve is loaded with transition metal or transition metal oxide to prepare a catalyst for use.

8. The use according to claim 7, characterized in that: The spherical multi-level pore SAPO-20 zeolite molecular sieve is used as a catalyst to catalyze the hydrogenation of oxygen-containing compounds to produce alcohols.

9. The use according to claim 7, characterized in that: The transition metal is one or more of Zr, Ni, Co, Zn, Cu, and Ce.

10. The use according to claim 9, characterized in that: The transition metal is a metal containing Co or a metal oxide containing Co.

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