Microporous-mesoporous composite catalyst, preparation method thereof, and application in the reaction of waste plastics to produce light olefins

Abstract

The present invention relates to the field of catalysts and the field of polymer material recycling, and discloses a kind of microporous mesoporous composite catalyst and its preparation method and application in waste plastics light olefins reaction.The microporous mesoporous composite catalyst includes modified microporous molecular sieve and macroporous mesoporous molecular sieve, and the modified microporous molecular sieve includes SAPO-11 zeolite molecular sieve and modified oxide loaded on SAPO-11 zeolite molecular sieve, based on the total weight of the microporous mesoporous composite catalyst, the content of modified microporous molecular sieve is 42-67 weight %, and the content of macroporous mesoporous molecular sieve is 33-58 weight %; Based on the total weight of the modified microporous molecular sieve, the content of SAPO-11 zeolite molecular sieve is 92-99 weight %, and the content of modified oxide is 1-8 weight %.The microporous mesoporous composite catalyst solves the problem of waste plastics recycling and increases the production of important chemical raw material light olefins in the direct catalytic cracking of waste plastics.

Description

Technical Field

[0001] The present invention relates to the field of catalysts and the field of polymer material recycling, and in particular to a microporous-mesoporous composite catalyst, a preparation method thereof, and application in the reaction of producing low-carbon olefins from waste plastics. Background Art

[0002] Plastic products are widely used in various fields worldwide. However, plastics are difficult to degrade naturally. Conventional landfill technology, while requiring minimal investment and simple to operate, occupies significant land and causes land pollution. While incineration can achieve waste reduction requirements and recover some energy, this process easily releases large amounts of hydrocarbons, nitrogen compounds, sulfides, and highly toxic substances, posing a direct threat to human and ecological health. Therefore, the recycling and high-value utilization of waste plastics, as a measure to conserve energy and protect the environment, is gaining widespread attention worldwide. Methods for recycling and utilizing waste plastics primarily include classified recycling, the production of monomer raw materials, the production of clean fuels, and power generation.

[0003] In existing technologies, the primary chemical recycling solution for waste plastics is waste plastic pyrolysis technology. This includes three basic methods: thermal pyrolysis (a single-stage process), catalytic pyrolysis (a single-stage process), and thermal pyrolysis-catalytic reforming (a two-stage process). Thermal pyrolysis is the earliest developed technology for waste plastic pyrolysis. This process involves a thermochemical decomposition reaction at high temperature and in the absence of oxygen, converting the high-molecular-weight organic matter in waste plastic products into low-molecular-weight liquids, fuel gas, and coke. The reaction temperature is generally controlled between 350°C and 900°C. Adding a catalyst to the thermal pyrolysis process, known as catalytic pyrolysis, not only lowers the pyrolysis temperature but also improves product performance. Thermal pyrolysis-catalytic reforming, an improvement on catalytic pyrolysis, involves catalytically reforming the pyrolysis gas after the pyrolysis of the waste plastic. This method offers higher-quality products, greater operational flexibility, and lower operating costs than both thermal and catalytic pyrolysis methods, but it is more complex.

[0004] Pyrolysis technology offers broad flexibility and good energy recovery in treating waste plastics, making it a promising technology for waste plastics treatment. Existing methods, such as one-step thermal cracking and one-step catalytic cracking, primarily produce fuel oil, yielding only small amounts of light olefins (ethylene, propylene, and butene). To obtain larger quantities of light olefins, a two-stage process involving thermal cracking and catalytic reforming is required.

[0005] Therefore, exploring a new chemical recycling process to produce pure and high-quality final products is an important research direction for plastic waste treatment. Summary of the Invention

[0006] The purpose of the present invention is to overcome the problem of low content of light olefins recovered in the existing chemical recycling of waste plastics, and to provide a microporous-mesoporous composite catalyst and a preparation method thereof, as well as an application in the reaction of producing light olefins from waste plastics. The microporous-mesoporous composite catalyst solves the problem of waste plastic recycling and increases the production of light olefins, an important chemical raw material, in the reaction of directly catalyzing and cracking waste plastics to produce light olefins.

[0007] To achieve the above-mentioned object, the first aspect of the present invention provides a microporous-mesoporous composite catalyst, wherein the microporous-mesoporous composite catalyst comprises a modified microporous molecular sieve and a macroporous mesoporous molecular sieve, the modified microporous molecular sieve comprises a SAPO-11 zeolite molecular sieve and a modified oxide supported on the SAPO-11 zeolite molecular sieve, and based on the total weight of the microporous-mesoporous composite catalyst, the content of the modified microporous molecular sieve is 42-67% by weight, and the content of the macroporous mesoporous molecular sieve is 33-58% by weight;

[0008] Based on the total weight of the modified microporous molecular sieve, the content of the SAPO-11 zeolite molecular sieve is 92-99 weight %, and the content of the modified oxide is 1-8 weight %.

[0009] A second aspect of the present invention provides a method for preparing a microporous-mesoporous composite catalyst, wherein the preparation method comprises:

[0010] The modified microporous molecular sieve and the macroporous mesoporous molecular sieve raw powder are mixed and ball-milled, and then calcined to obtain a microporous-mesoporous composite catalyst.

[0011] The third aspect of the present invention provides a microporous-mesoporous composite catalyst prepared by the aforementioned preparation method.

[0012] A fourth aspect of the present invention provides an application of the aforementioned microporous-mesoporous composite catalyst in the direct catalytic cracking of waste plastics to produce light olefins.

[0013] Through the above technical solution, the technical solution of the present invention has the following advantages:

[0014] (1) The raw materials of the microporous-mesoporous composite catalyst provided by the present invention are easily available, the preparation method is simple, the conditions are easy to control, and the product has good reproducibility.

[0015] (2) The microporous-mesoporous composite catalyst provided by the present invention includes a modified zeolite molecular sieve with a certain acidity on the surface and a mesoporous material with a larger pore size. It has a stable structure and good high-temperature resistance, and facilitates the diffusion of raw material and product molecules during the cracking reaction. In addition, the surface modification of the SAPO-11 zeolite molecular sieve using a specific oxide can effectively improve its surface properties. The microporous-mesoporous composite catalyst prepared by mixing the modified SAPO-11 zeolite molecular sieve with the large-pore mesoporous molecular sieve has high catalytic activity and high selectivity for light olefins in the catalytic cracking reaction of waste plastics.

[0016] (3) The microporous-mesoporous composite catalyst provided by the present invention can convert waste plastics into light olefins in a single step when used in the direct catalytic cracking of waste plastics to produce light olefins, thus providing a new method for chemical recycling of waste plastics. This not only solves the problem of waste plastic recycling, but also increases the production of light olefins, an important chemical raw material, and has good economic benefits.

[0017] (4) When the microporous-mesoporous composite catalyst provided by the present invention is used for the direct catalytic cracking of waste plastics to produce light olefins, the process conditions are mild, the operation is easy, and the requirements for the reaction device are not high.

[0018] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a small-angle X-ray diffraction (XRD) spectrum of the microporous-mesoporous composite catalyst A prepared in Example 1;

[0020] Figure 2 is the wide-angle X-ray diffraction (XRD) spectrum of the microporous-mesoporous composite catalyst A prepared in Example 1. DETAILED DESCRIPTION

[0021] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0022] As described above, the first aspect of the present invention provides a microporous-mesoporous composite catalyst, wherein the microporous-mesoporous composite catalyst comprises a modified microporous molecular sieve and a macroporous mesoporous molecular sieve, the modified microporous molecular sieve comprises a SAPO-11 zeolite molecular sieve and a modified oxide supported on the SAPO-11 zeolite molecular sieve, and based on the total weight of the microporous-mesoporous composite catalyst, the content of the modified microporous molecular sieve is 42-67% by weight, and the content of the macroporous mesoporous molecular sieve is 33-58% by weight;

[0023] Based on the total weight of the modified microporous molecular sieve, the content of the SAPO-11 zeolite molecular sieve is 92-99 weight %, and the content of the modified oxide is 1-8 weight %.

[0024] The inventors of the present invention have found that: in the prior art, there is no process for directly catalytically cracking waste plastics to produce light olefins (including ethylene, propylene, and butene). The purpose of the present invention is to solve this problem. According to the inventors' understanding of the physicochemical properties of heterogeneous catalysts, the catalyst used for the catalytic cracking of waste plastics to directly prepare light olefins should have a certain acidity and good hydrothermal stability. Based on the above requirements, the SAPO-11 zeolite molecular sieve, which has a stable skeleton structure and a certain acidity, is very suitable as the main component of the waste plastic cracking catalyst. However, because the pore size of the SAPO-11 zeolite molecular sieve is relatively small (0.4nm*0.65nm elliptical pores) and the pore volume is also relatively small (approximately 0.2-0.3cm 3 / g), while the molecular weight of waste plastic products is relatively large and the molecular chain is relatively long. During the cracking reaction of waste plastic products, it is difficult for the larger reactant molecules and product molecules to diffuse between the narrow channels, which not only affects the contact between the reactants and the active centers, but also easily leads to the occurrence of side reactions such as deep dehydrogenation, which in turn leads to a decrease in catalyst performance. Compared with zeolite molecular sieves, large-pore mesoporous molecular sieve materials have larger pore sizes (greater than 10.0nm, about 20 times larger than the pore size of SAPO-11 zeolite molecular sieves) and larger pore volumes (can reach 1.0cm 3 / g or more), which is very suitable for catalytic reactions involving macromolecules. However, the macropore mesoporous molecular sieve material is an all-silicon material with extremely weak surface acidity, which is not suitable for being used alone as a catalyst to catalyze the cracking reaction of waste plastics. The inventors of the present invention found during the development and research of waste plastic cracking catalysts that if the structural advantages of all-silicon mesoporous inorganic materials and the surface acidic centers of zeolite molecular sieves are comprehensively utilized, and a certain amount of macropore mesoporous molecular sieves are mixed with SAPO-11 zeolite molecular sieves, the specific surface area and pore volume of the catalyst can be effectively increased, and the internal diffusion performance in the reaction can be significantly improved. When used as a cracking catalyst in the catalytic conversion reaction of waste plastics, it can not only effectively improve the activity of the cracking catalyst, but also increase the selectivity of light olefins.

[0025] The inventors of the present invention also found that: because the acid centers on the surface of SAPO-11 zeolite molecular sieve are relatively dense, deep dehydrogenation may occur during the cracking reaction of waste plastic raw materials, which in turn causes problems such as catalyst deactivation and severe carbon deposition during the reaction. Therefore, it is necessary to modify the surface of SAPO-11 zeolite molecular sieve in an appropriate manner to reduce the density of surface acid centers to a certain extent, so as to make it more suitable for the catalytic cracking reaction of waste plastics. During the catalyst development research, the inventors of the present invention found that if the SAPO-11 zeolite molecular sieve is surface-modified using specific oxides, its surface properties can be effectively improved. The microporous-mesoporous composite catalyst prepared by mixing the modified SAPO-11 zeolite molecular sieve with a macroporous mesoporous molecular sieve has high catalytic activity and high selectivity for light olefins in the catalytic cracking reaction of waste plastics.

[0026] According to the present invention, preferably, based on the total weight of the microporous-mesoporous composite catalyst, the content of the modified microporous molecular sieve is 47-63% by weight, and the content of the macroporous mesoporous molecular sieve is 37-53% by weight; more preferably, the content of the modified microporous molecular sieve is 51-59% by weight, and the content of the macroporous mesoporous molecular sieve is 41-49% by weight. In the present invention, the use of the aforementioned specific contents of each component enables the prepared microporous-mesoporous composite catalyst to have better catalytic activity and higher selectivity for light olefins when used in the direct catalytic cracking of waste plastics to produce light olefins.

[0027] According to the present invention, the modified microporous molecular sieve comprises a SAPO-11 zeolite molecular sieve and a modified oxide. Preferably, based on the total weight of the modified microporous molecular sieve, the SAPO-11 zeolite molecular sieve comprises 93-98% by weight, and the modified oxide comprises 2-7% by weight; more preferably, the SAPO-11 zeolite molecular sieve comprises 94-97% by weight, and the modified oxide comprises 3-6% by weight. In the present invention, the modified microporous molecular sieve employs the aforementioned specific contents of each component, enabling the prepared microporous-mesoporous composite catalyst to exhibit better catalytic activity and higher selectivity for light olefins when used in the direct catalytic cracking of waste plastics to produce light olefins.

[0028] According to the present invention, the modified oxide is selected from one or more of alkaline earth metal oxides, transition metal oxides, and rare earth metal oxides; preferably, the modified oxide is selected from one or more of magnesium oxide, calcium oxide, strontium oxide, barium oxide, zinc oxide, cerium oxide, and lanthanum oxide. In the present invention, the specific modified oxide selected from the present invention has the advantage of improving the surface electron distribution of the SAPO-11 zeolite molecular sieve and selectively covering some of the overcrowded acidic centers, making the catalyst surface properties more suitable for the waste plastic cracking reaction.

[0029] According to the present invention, the molar ratio of Al2O3 / SiO2 / P2O5 of the SAPO-11 zeolite molecular sieve is 1:(0.1-1.5):(0.3-2), preferably 1:(0.4-0.8):(0.7-1).

[0030] According to the present invention, SAPO-11 zeolite molecular sieve can be obtained by commercial means. In the present invention, specifically, the SAPO-11 zeolite molecular sieve is more preferably: SAPO-11 zeolite molecular sieve (specific surface area 186m2) with Al2O3 / SiO2 / P2O5 molar ratio of 1:0.4:0.7 purchased from Nanjing Jicang Nano Technology Co., Ltd. 2 / g, pore volume 0.26cm 3 / g); SAPO-11 zeolite molecular sieve (specific surface area of ​​204 m2) with Al2O3 / SiO2 / P2O5 molar ratio of 1:0.8:1.0 purchased from Nanjing Jicang Nano Technology Co., Ltd. 2 / g, pore volume 0.28cm 3 / g).

[0031] According to the present invention, the preparation method of the modified microporous molecular sieve comprises: mixing SAPO-11 zeolite molecular sieve with a modifying component aqueous solution and reacting the mixture; and then removing water, drying and calcining the mixture to obtain the modified microporous molecular sieve.

[0032] According to the present invention, the aqueous solution of the modifying component includes a metal salt and water; the metal salt is selected from nitrates of one or more of alkaline earth metals, transition metals and rare earth metals, preferably nitrates of one or more of magnesium, calcium, strontium, barium, zinc, cerium and lanthanum.

[0033] According to the present invention, the mass concentration of the aqueous solution of the modifying component is 0.5-15%, preferably 1-8%.

[0034] According to the present invention, the weight ratio of the SAPO-11 zeolite molecular sieve to the aqueous solution of the modifying component is 1:(3-30), preferably 1:(5-20).

[0035] According to the present invention, the reaction conditions include: a temperature of 10-100°C, preferably 30-80°C; and a reaction time of 0.5-50 hours, preferably 2-20 hours. Preferably, to achieve better mixing, rapid stirring or ultrasonication can be used during the mixing of the SAPO-11 zeolite molecular sieve and the aqueous solution of the modifying component to improve mixing efficiency.

[0036] According to the present invention, the water removal method is not particularly limited and can be a water removal method known in the art, such as: using a rotary evaporator to evaporate water, or using a heating and stirring method to remove water.

[0037] According to the present invention, the drying conditions include: a temperature of 60-150° C., preferably 80-130° C.; and a drying time of 1-30 h, preferably 3-20 h.

[0038] According to the present invention, the calcination conditions include: a temperature of 400-700° C., preferably 500-600° C.; and a calcination time of 2-20 h, preferably 3-10 h.

[0039] The second aspect of the present invention provides a method for preparing a microporous-mesoporous composite catalyst. The specific operation process of the method is as follows: the modified microporous molecular sieve and the macroporous mesoporous molecular sieve raw powder are mixed and ball-milled, and the mixture is calcined to obtain a microporous-mesoporous composite catalyst.

[0040] According to the present invention, the weight ratio of the modified microporous molecular sieve to the macroporous mesoporous molecular sieve raw powder is 1: (0.5-2.5), preferably 1: (0.7-2).

[0041] According to the present invention, the ball milling is performed in a ball mill, wherein the diameter of the grinding balls in the ball mill can be 2-3 mm. The number of grinding balls can be appropriately selected based on the size of the ball mill jar; for a ball mill jar of 100-300 mL, 2-8 grinding balls can generally be used. The grinding balls are made of agate or polytetrafluoroethylene, preferably agate. The ball milling conditions include: a grinding ball rotation speed of 200-600 rpm, preferably 300-500 rpm; a temperature within the ball mill jar of 30-90°C, preferably 40-80°C; and a ball milling time of 5-50 hours, preferably 8-24 hours.

[0042] According to the present invention, the calcination conditions include: a temperature of 450-750° C., preferably 550-650° C.; and a calcination time of 5-40 h, preferably 8-20 h.

[0043] According to the present invention, the preparation method of the macroporous mesoporous molecular sieve raw powder includes: mixing and contacting a template, tetraethyl orthosilicate and a hydrochloric acid aqueous solution to obtain a mixture, and crystallizing, filtering, washing and drying the mixture to obtain the macroporous mesoporous molecular sieve raw powder.

[0044] According to the present invention, the template agent is a nonionic surfactant; in the present invention, preferably, the template agent is a polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer; more preferably, the template agent is P123 (molecular formula EO 20 PO 70 EO 20 ).

[0045] According to the present invention, the molar ratio of the template, tetraethyl orthosilicate, hydrochloric acid and water is 1: (20-200): (100-500): (7000-15000); preferably 1: (40-100): (200-300): (9000-13000).

[0046] According to the present invention, the mixing contact conditions include: temperature of 25-60°C and time of 20-120 min. In order to facilitate uniform mixing of the substances, according to a preferred embodiment of the present invention, the hydrolysis process is carried out under stirring conditions.

[0047] According to the present invention, the crystallization conditions include: temperature of 90-180° C., time of 5-120 h; preferably, the crystallization conditions include: temperature of 120-160° C., time of 10-40 h.

[0048] According to the present invention, there are no special requirements for the filtration method, and it can be any filtration method known in the art, including gravity filtration, pressure filtration, vacuum filtration, or centrifugal filtration. Preferably, the filtration process specifically includes: using a suction bottle, vacuuming the bottom side of the funnel or filtering using a centrifugal filter.

[0049] According to the present invention, the washing conditions are not particularly limited. For example, the washing process may include: obtaining a solid product after filtration, repeatedly washing the solid product with distilled water (the number of washings may be 2-10), and then filtering.

[0050] According to the present invention, the drying process can be carried out in a drying oven, and the drying conditions may include: temperature of 70-150°C and time of 4-30h; under preferred conditions, the drying conditions include: temperature of 100-130°C and time of 8-20h.

[0051] The third aspect of the present invention provides a microporous-mesoporous composite catalyst prepared by the aforementioned preparation method.

[0052] A fourth aspect of the present invention provides an application of the aforementioned microporous-mesoporous composite catalyst in the direct catalytic cracking of waste plastics to produce light olefins.

[0053] According to the present invention, the application method comprises: contacting waste plastic powder with the microporous-mesoporous composite catalyst to react.

[0054] In the present invention, the conditions for contacting the waste plastic powder with the microporous-mesoporous composite catalyst include: the contact temperature can be 420-580°C, preferably 450-540°C; the contact pressure is 0.01-1Mpa, preferably 0.05-0.5Mpa; and the contact time is 0.5-12h, preferably 1-5h.

[0055] According to the present invention, the weight ratio of the microporous-mesoporous composite catalyst to the waste plastic powder is 1:0.5-50, preferably 1:2-30.

[0056] The present invention will be described in detail below through examples.

[0057] In the following examples and comparative examples:

[0058] The small-angle XRD test of the samples was carried out on a D8 ADVANCE high-power rotating target X-ray diffractometer from BRUKER AXS, Germany, with a scanning range of 0.5-10°.

[0059] The wide-angle XRD test of the sample was carried out on an X'Pert MPD X-ray powder diffractometer produced by Philips of the Netherlands, using a Cu Kα target and a scanning range of 2θ=5-90°.

[0060] The pore structure parameters of the samples were analyzed using an ASAP2020-M+C adsorption instrument purchased from Micromeritics, Inc., USA. The samples were vacuum degassed at 350°C for 4 hours before measurement. The specific surface area of ​​the samples was calculated using the BET method, and the pore volume was calculated using the BJH model.

[0061] The elemental analysis experiments of the samples were carried out on an EagleⅢ energy dispersive X-ray fluorescence spectrometer produced by EDAX Company in the United States.

[0062] The drying oven was produced by Shanghai Yiheng Scientific Instrument Co., Ltd., model DHG-9030A.

[0063] The muffle furnace is produced by CARBOLITE, model CWF1100.

[0064] The P123 used in the Examples and Comparative Examples was purchased from Aldrich. The SAPO-11 zeolite molecular sieve with a SiO2 / Al2O3 molar ratio of 0.4 used in the Examples and Comparative Examples was purchased from Nanjing Jicang Nanotechnology Co., Ltd.; the SAPO-11 zeolite molecular sieve with a SiO2 / Al2O3 molar ratio of 0.8 was purchased from Nanjing Jicang Nanotechnology Co., Ltd. All other reagents used in the Examples and Comparative Examples were purchased from Sinopharm Chemical Reagent Co., Ltd. and were of analytical grade.

[0065] Example 1

[0066] (1) Preparation of macroporous mesoporous molecular sieve powder

[0067] Mix 58g of P123, 238g of 37wt% hydrochloric acid and 1856g of deionized water, and stir at 40°C until P123 is completely dissolved; then slowly add 135g of ethyl orthosilicate to the above solution, continue stirring at 40°C for 60min, and then transfer the obtained solution to a polytetrafluoroethylene-lined reactor, crystallize at 150°C for 20h, then filter and wash with deionized water 5 times, and then filter to obtain a solid product, which is dried at 100°C for 12h to obtain macroporous mesoporous molecular sieve powder A.

[0068] (2) Preparation of modified microporous molecular sieves

[0069] 2.9 g of magnesium nitrate hexahydrate was dissolved in 150 g of distilled water to prepare a modified component aqueous solution. 9.6 g of SAPO-11 zeolite molecular sieve (Al2O3 / SiO2 / P2O5 = 1 / 0.4 / 0.7) was added to the modified component aqueous solution and stirred at 60°C for 5 h. The water was then removed using a rotary evaporator. The solid product was dried at 110°C for 8 h and then calcined at 550°C for 6 h to obtain modified microporous molecular sieve A.

[0070] Based on the total weight of the modified microporous molecular sieve A, the content of SAPO-11 zeolite molecular sieve was 95.5% by weight, and the content of magnesium oxide was 4.5% by weight.

[0071] (3) Preparation of microporous-mesoporous composite catalysts

[0072] 28g of modified microporous molecular sieve A and 31g of raw macroporous mesoporous molecular sieve A were added to a 300ml ball mill. Six 2mm diameter agate grinding balls were placed and ball milling began. The temperature in the mill was controlled at 50°C, the ball speed was 400 rpm, and the milling time was 10 hours. The resulting powder was calcined at 600°C for 16 hours to obtain microporous-mesoporous composite catalyst A.

[0073] Based on the total weight of catalyst A, the content of the modified microporous molecular sieve is 55% by weight, and the content of the macroporous mesoporous molecular sieve is 45% by weight.

[0074] The specific surface area of ​​catalyst A is 275m 2 / g, pore volume 0.66cm 3 / g.

[0075] Figure 1 is the small-angle XRD spectrum of catalyst A. Figure 1 The spectra show three clearly visible diffraction peaks at small angles below 2°, demonstrating that the mesoporous material in the catalyst has a typical two-dimensional hexagonal mesoporous structure. This indicates that the macroporous mesoporous molecular sieve retains a relatively regular mesoporous channel structure after being prepared into a catalyst, and the catalyst preparation process does not destroy the basic structure of the mesoporous molecular sieve.

[0076] Figure 2 This is the wide-angle XRD spectrum of catalyst A. Figure 2 The wide-angle X-ray diffraction pattern of the sample shows the following main wide-angle X-ray diffraction angles: 2θ = 8.1°, 9.4°, 13.1°, 15.6°, 20.4°, 21.0°, and 22.1-23.2°. These diffraction signals are consistent with the diffraction pattern of SAPO-11 zeolite molecular sieve, indicating that the SAPO-11 zeolite sieve crystalline phase did not undergo significant changes during the catalyst preparation process, maintaining a well-defined AEL topology. Furthermore, the wide-angle XRD pattern shows no diffraction signals corresponding to the modified oxide, indicating that the modified component is uniformly dispersed on the catalyst.

[0077] (4) Evaluation of the reaction performance of direct conversion of waste plastics to light olefins

[0078] The catalyst's performance in the direct catalytic cracking of waste plastics to light olefins was evaluated in a fixed-bed reactor. Catalyst A was loaded at 10.0 g, polyethylene waste plastic at 50.0 g, and the reaction temperature was 480°C, the pressure at 0.1 MPa, and the reaction time was 2 hours. After cooling and gas-liquid separation, the product was analyzed for gas composition using an Agilent 6890 gas chromatograph equipped with an Al2O3-S capillary column and a flame ion detector (FID) using a temperature program and correction factors for quantitative analysis. Liquid composition was analyzed using an Agilent 6890 gas chromatograph equipped with a PONA column. The reaction results are shown in Table 1.

[0079] Example 2

[0080] (1) Preparation of macroporous mesoporous molecular sieves

[0081] Mix 58g P123, 197g 37wt% hydrochloric acid and 1496g deionized water, and stir at 60°C until P123 is completely dissolved; then slowly add 83.2g ethyl orthosilicate to the above solution, continue stirring at 60°C for 20min, and then transfer the obtained solution to a polytetrafluoroethylene-lined reactor, crystallize at 120°C for 40h, then filter and wash with deionized water 5 times, and then filter to obtain a solid product, which is dried at 80°C for 30h to obtain macroporous mesoporous molecular sieve raw powder B.

[0082] (2) Preparation of modified microporous molecular sieves

[0083] 1.8 g of calcium nitrate was dissolved in 100 g of distilled water to prepare a modified component aqueous solution. 9.4 g of SAPO-11 zeolite molecular sieve (Al2O3 / SiO2 / P2O5 = 1 / 0.8 / 1.0) was added to the modified component aqueous solution and stirred at 80°C for 2 h. The water was then removed using a rotary evaporator. The solid product was dried at 130°C for 3 h and then calcined at 600°C for 3 h to obtain modified microporous molecular sieve B.

[0084] Based on the total weight of the modified microporous molecular sieve B, the content of SAPO-11 zeolite molecular sieve was 94 weight %, and the content of calcium oxide was 6 weight %.

[0085] (3) Preparation of microporous-mesoporous composite catalysts

[0086] 30g of modified microporous molecular sieve B and 29g of raw macroporous mesoporous molecular sieve B were added to a 300ml ball mill. Eight 2mm diameter agate grinding balls were placed and ball milling began. The temperature in the mill was controlled at 80°C, the ball speed was 500 rpm, and the milling time was 8 hours. The resulting powder was calcined at 650°C for 8 hours to obtain microporous-mesoporous composite catalyst B.

[0087] Based on the total weight of the catalyst B, the content of the modified microporous molecular sieve was 59% by weight, and the content of the macroporous mesoporous molecular sieve was 41% by weight.

[0088] The specific surface area of ​​catalyst B is 269m 2 / g, pore volume 0.62cm 3 / g.

[0089] The reaction performance of Catalyst B was tested according to the reaction performance evaluation method for direct catalytic cracking of waste plastics to produce light olefins in step (4) of Example 1. The evaluation results are listed in Table 1.

[0090] Example 3

[0091] (1) Preparation of macroporous mesoporous molecular sieves

[0092] 58g P123, 296g 37wt% hydrochloric acid and 2153g deionized water were mixed and stirred at 25°C until P123 was completely dissolved; then 208g ethyl orthosilicate was slowly added to the above solution and stirred at 25°C for 120min. The obtained solution was then transferred to a polytetrafluoroethylene-lined reactor and crystallized at 160°C for 10h. The solution was then filtered and washed with deionized water 5 times. The solid product was then filtered to obtain a solid product. The solid product was dried at 120°C for 8h to obtain macroporous mesoporous molecular sieve powder C.

[0093] (2) Preparation of modified microporous molecular sieves

[0094] 0.8 g of lanthanum nitrate hexahydrate was dissolved in 80 g of distilled water to prepare a modified component aqueous solution. 9.7 g of SAPO-11 zeolite molecular sieve (Al2O3 / SiO2 / P2O5 = 1 / 0.4 / 0.7) was added to the modified component aqueous solution and stirred at 30°C for 20 h. The water was then removed using a rotary evaporator. The solid product was dried at 80°C for 20 h and then calcined at 500°C for 10 h to obtain modified microporous molecular sieve C.

[0095] Based on the total weight of the modified microporous molecular sieve C, the content of SAPO-11 zeolite molecular sieve is 97 weight %, and the content of lanthanum oxide is 3 weight %.

[0096] (3) Preparation of microporous-mesoporous composite catalysts

[0097] 26g of modified microporous molecular sieve C and 30g of raw macroporous mesoporous molecular sieve C were added to a 300ml ball mill. Four 2mm diameter agate grinding balls were placed and ball milling began. The temperature in the mill was controlled at 40°C, the ball speed was 300 rpm, and the milling time was 24 hours. The resulting powder was calcined at 550°C for 20 hours to obtain microporous-mesoporous composite catalyst C.

[0098] Based on the total weight of the catalyst C, the content of the modified microporous molecular sieve was 51% by weight, and the content of the macroporous mesoporous molecular sieve was 49% by weight.

[0099] The specific surface area of ​​catalyst C is 281m 2 / g, pore volume 0.70cm 3 / g.

[0100] The reaction performance of Catalyst C was tested according to the reaction performance evaluation method for direct catalytic cracking of waste plastics to produce light olefins in step (4) of Example 1. The evaluation results are listed in Table 1.

[0101] Example 4

[0102] Macroporous mesoporous molecular sieve raw powder A was prepared according to the method of step (1) in Example 1.

[0103] (2) Preparation of modified microporous molecular sieves

[0104] 4.5 g of magnesium nitrate hexahydrate was dissolved in 150 g of distilled water to prepare a modified component aqueous solution. 9.3 g of SAPO-11 zeolite molecular sieve (Al2O3 / SiO2 / P2O5 = 1 / 0.4 / 0.7) was added to the modified component aqueous solution and stirred at 60°C for 5 h. The water was then removed using a rotary evaporator. The solid product was dried at 110°C for 8 h and then calcined at 550°C for 6 h to obtain modified microporous molecular sieve D.

[0105] Based on the total weight of the modified microporous molecular sieve D, the content of SAPO-11 zeolite molecular sieve was 93 wt %, and the content of magnesium oxide was 7 wt %.

[0106] (3) Preparation of microporous-mesoporous composite catalysts

[0107] 32g of modified microporous molecular sieve D and 25g of raw macroporous mesoporous molecular sieve A were added to a 300ml ball mill. Six 2mm diameter agate grinding balls were placed in the mill and ball milling began. The temperature in the mill was controlled at 50°C, the ball speed was 400 rpm, and the milling time was 10 hours. The resulting powder was calcined at 600°C for 16 hours to obtain microporous-mesoporous composite catalyst D.

[0108] Based on the total weight of catalyst D, the content of the modified microporous molecular sieve is 63% by weight, and the content of the macroporous mesoporous molecular sieve is 37% by weight.

[0109] The specific surface area of ​​catalyst D is 263m 2 / g, pore volume 0.59cm 3 / g.

[0110] The reaction performance of Catalyst D was tested according to the reaction performance evaluation method for direct catalytic cracking of waste plastics to produce light olefins in step (4) of Example 1. The evaluation results are listed in Table 1.

[0111] Example 5

[0112] According to the method of step (1) in Example 2, macroporous mesoporous molecular sieve raw powder B was prepared.

[0113] (2) Preparation of modified microporous molecular sieves

[0114] 0.7 g of zinc nitrate hexahydrate was dissolved in 60 g of distilled water to prepare a modified component aqueous solution. 9.8 g of SAPO-11 zeolite molecular sieve (Al2O3 / SiO2 / P2O5 = 1 / 0.8 / 1.0) was added to the modified component aqueous solution and stirred at 80°C for 2 h. The water was then removed using a rotary evaporator. The solid product was dried at 130°C for 3 h and then calcined at 600°C for 3 h to obtain modified microporous molecular sieve E.

[0115] Based on the total weight of the modified microporous molecular sieve E, the content of SAPO-11 zeolite molecular sieve was 98 weight %, and the content of zinc oxide was 2 weight %.

[0116] (3) Preparation of microporous-mesoporous composite catalysts

[0117] 24g of modified microporous molecular sieve E and 37g of macroporous mesoporous molecular sieve powder B were added to a 300ml ball mill. Eight 2mm diameter agate grinding balls were placed and ball milling began. The temperature in the mill was controlled at 80°C, the ball speed was 500 rpm, and the milling time was 8 hours. The resulting powder was calcined at 650°C for 8 hours to obtain microporous-mesoporous composite catalyst E.

[0118] Based on the total weight of the catalyst E, the content of the modified microporous molecular sieve was 47% by weight, and the content of the macroporous mesoporous molecular sieve was 53% by weight.

[0119] The specific surface area of ​​catalyst E is 286m 2 / g, pore volume 0.73cm 3 / g.

[0120] The reaction performance of Catalyst E was tested according to the reaction performance evaluation method for direct catalytic cracking of waste plastics to produce light olefins in step (4) of Example 1. The evaluation results are listed in Table 1.

[0121] Example 6

[0122] Macroporous mesoporous molecular sieve raw powder A was prepared according to the method of step (1) in Example 1.

[0123] (2) Preparation of modified microporous molecular sieves

[0124] 5.1 g of magnesium nitrate hexahydrate was dissolved in 160 g of distilled water to prepare a modified component aqueous solution. 9.2 g of SAPO-11 zeolite molecular sieve (Al2O3 / SiO2 / P2O5 = 1 / 0.4 / 0.7) was added to the modified component aqueous solution and stirred at 60°C for 5 h. The water was then removed using a rotary evaporator. The solid product was dried at 110°C for 8 h and then calcined at 550°C for 6 h to obtain modified microporous molecular sieve F.

[0125] Based on the total weight of the modified microporous molecular sieve F, the content of SAPO-11 zeolite molecular sieve is 92 weight %, and the content of magnesium oxide is 8 weight %.

[0126] (3) Preparation of microporous-mesoporous composite catalysts

[0127] 34g of modified microporous molecular sieve F and 22g of macroporous mesoporous molecular sieve powder A were added to a 300ml ball mill. Six 2mm diameter agate grinding balls were placed and ball milling began. The temperature in the mill was controlled at 50°C, the ball speed was 400 rpm, and the milling time was 10 hours. The resulting powder was calcined at 600°C for 16 hours to obtain microporous-mesoporous composite catalyst F.

[0128] Based on the total weight of the catalyst F, the content of the modified microporous molecular sieve is 67% by weight, and the content of the macroporous mesoporous molecular sieve is 33% by weight.

[0129] The specific surface area of ​​catalyst F is 258m 2 / g, pore volume 0.55cm 3 / g.

[0130] The reaction performance of Catalyst F was tested according to the reaction performance evaluation method for direct catalytic cracking of waste plastics to produce light olefins in step (4) of Example 1. The evaluation results are listed in Table 1.

[0131] Example 7

[0132] According to the method of step (1) in Example 2, macroporous mesoporous molecular sieve raw powder B was prepared.

[0133] (2) Preparation of modified microporous molecular sieves

[0134] 0.3g of calcium nitrate was dissolved in 60g of distilled water to prepare an aqueous solution of the modified component. 9.9g of SAPO-11 zeolite molecular sieve (Al2O3 / SiO2 / P2O5 = 1 / 0.8 / 1.0) was added to the aqueous solution of the modified component. After stirring at 80°C for 2h, the water was removed using a rotary evaporator. The solid product was dried at 130°C for 3h and then calcined at 600°C for 3h to obtain modified microporous molecular sieve G.

[0135] Based on the total weight of the modified microporous molecular sieve G, the content of SAPO-11 zeolite molecular sieve was 99 weight %, and the content of calcium oxide was 1 weight %.

[0136] (3) Preparation of microporous-mesoporous composite catalysts

[0137] 21g of modified microporous molecular sieve G and 40g of macroporous mesoporous molecular sieve powder B were added to a 300ml ball mill. Eight 2mm diameter agate grinding balls were placed and ball milling began. The temperature in the mill was controlled at 80°C, the ball speed was 500 rpm, and the milling time was 8 hours. The resulting powder was calcined at 650°C for 8 hours to obtain microporous-mesoporous composite catalyst G.

[0138] Based on the total weight of the catalyst G, the content of the modified microporous molecular sieve was 42% by weight, and the content of the macroporous mesoporous molecular sieve was 58% by weight.

[0139] The specific surface area of ​​catalyst G is 292m 2 / g, pore volume 0.78cm 3 / g.

[0140] The reaction performance of Catalyst G was tested according to the reaction performance evaluation method for direct catalytic cracking of waste plastics to produce light olefins in step (4) of Example 1. The evaluation results are listed in Table 1.

[0141] Comparative Example 1

[0142] Macroporous mesoporous molecular sieve raw powder A was prepared according to the method of step (1) in Example 1.

[0143] (2) Preparation of modified microporous molecular sieves

[0144] 7.7 g of magnesium nitrate hexahydrate was dissolved in 200 g of distilled water to prepare a modified component aqueous solution. 8.8 g of SAPO-11 zeolite molecular sieve (Al2O3 / SiO2 / P2O5 = 1 / 0.4 / 0.7) was added to the modified component aqueous solution and stirred at 60°C for 5 h. The water was then removed using a rotary evaporator. The solid product was dried at 110°C for 8 h and then calcined at 550°C for 6 h to obtain modified microporous molecular sieve F.

[0145] Based on the total weight of the modified microporous molecular sieve F, the content of SAPO-11 zeolite molecular sieve is 88 weight %, and the content of magnesium oxide is 12 weight %.

[0146] (3) Preparation of microporous-mesoporous composite catalysts

[0147] 41g of modified microporous molecular sieve F and 13g of macroporous mesoporous molecular sieve powder A were added to a 300ml ball mill. Six 2mm diameter agate grinding balls were placed in the mill and ball milling began. The temperature in the mill was controlled at 50°C, the ball speed was 400 rpm, and the milling time was 10 hours. The resulting powder was calcined at 600°C for 16 hours to obtain microporous-mesoporous composite catalyst F.

[0148] Based on the total weight of the catalyst F, the content of the modified microporous molecular sieve was 81% by weight, and the content of the macroporous mesoporous molecular sieve was 19% by weight.

[0149] The specific surface area of ​​catalyst F is 239m 2 / g, pore volume 0.43cm 3 / g.

[0150] The reaction performance of catalyst D1 was tested according to the reaction performance evaluation method for direct conversion of waste plastics to light olefins in step (4) of Example 1. The evaluation results are listed in Table 1.

[0151] Comparative Example 2

[0152] According to the method of step (1) in Example 2, macroporous mesoporous molecular sieve raw powder B was prepared.

[0153] (2) Preparation of modified microporous molecular sieves

[0154] 0.1 g of calcium nitrate was dissolved in 60 g of distilled water to prepare a modified component aqueous solution. 10.0 g of SAPO-11 zeolite molecular sieve (Al2O3 / SiO2 / P2O5 = 1 / 0.8 / 1.0) was added to the modified component aqueous solution and stirred at 80°C for 2 h. The water was then removed using a rotary evaporator. The solid product was dried at 130°C for 3 h and then calcined at 600°C for 3 h to obtain modified microporous molecular sieve D2.

[0155] Based on the total weight of the modified microporous molecular sieve D2, the content of SAPO-11 zeolite molecular sieve was 99.5% by weight, and the content of calcium oxide was 0.3% by weight.

[0156] (3) Preparation of microporous-mesoporous composite catalysts

[0157] 14g of modified microporous molecular sieve D2 and 50g of macroporous mesoporous molecular sieve powder B were added to a 300ml ball mill. Eight 2mm diameter agate grinding balls were placed in the mill and ball milling began. The temperature in the mill was controlled at 80°C, the ball speed was 500 rpm, and the milling time was 8 hours. The resulting powder was calcined at 650°C for 8 hours to obtain the microporous-mesoporous composite catalyst D2.

[0158] Based on the total weight of the catalyst D2, the content of the modified microporous molecular sieve was 28% by weight, and the content of the macroporous mesoporous molecular sieve was 72% by weight.

[0159] The specific surface area of ​​catalyst D2 is 311m 2 / g, pore volume 0.90cm 3 / g.

[0160] The reaction performance of catalyst D2 was tested according to the reaction performance evaluation method for direct conversion of waste plastics to light olefins in step (4) of Example 1. The evaluation results are listed in Table 1.

[0161] Comparative Example 3

[0162] Macroporous mesoporous molecular sieve raw powder A was prepared according to the method of step (1) in Example 1.

[0163] Eliminate step (2) in Example 1.

[0164] The microporous-mesoporous composite catalyst D3 was prepared according to the method of step (3) in Example 1, except that the preparation conditions were changed and unmodified zeolite molecular sieve was used instead of modified zeolite molecular sieve. The specific process is as follows:

[0165] 28g of SAPO-11 zeolite molecular sieve (Al2O3 / SiO2 / P2O5 = 1 / 0.4 / 0.7) and 31g of macroporous mesoporous molecular sieve raw powder A were added to a 300ml ball mill. Six 2mm diameter agate grinding balls were placed in the mill and ball milling began. The temperature in the mill was controlled at 50°C, the ball speed was 400 rpm, and the milling time was 10 hours. The resulting powder was calcined at 600°C for 16 hours to obtain microporous-mesoporous composite catalyst D3.

[0166] Based on the total weight of the catalyst D3, the content of the SAPO-11 zeolite molecular sieve was 55% by weight, and the content of the macroporous mesoporous molecular sieve was 45% by weight.

[0167] The specific surface area of ​​catalyst D3 is 270m 2 / g, pore volume 0.65cm 3 / g.

[0168] The reaction performance of catalyst D3 was tested according to the reaction performance evaluation method for direct conversion of waste plastics to light olefins in step (4) of Example 1. The evaluation results are listed in Table 1.

[0169] Comparative Example 4

[0170] Catalyst D4 was prepared according to the method of Example 1, except that:

[0171] Eliminate step (1) in Example 1 and step (3) in Example 1;

[0172] Prepare modified microporous molecular sieve A according to the method of step (2) in Example 1;

[0173] Using modified microporous molecular sieve A as catalyst D4, the reaction performance of catalyst D4 was tested according to the reaction performance evaluation method for direct conversion of waste plastics to light olefins in step (4) of Example 1. The evaluation results are listed in Table 1.

[0174] Comparative Example 5

[0175] Catalyst D5 was prepared according to the method of Example 1, except that:

[0176] Prepare macroporous mesoporous molecular sieve raw powder A according to the method of step (1) in Example 1;

[0177] The modified microporous molecular sieve D5 was prepared according to the method of step (2) in Example 1, except that the preparation conditions were changed and the modified oxide was replaced with sodium oxide. The specific process is as follows:

[0178] 1.2 g of sodium nitrate was dissolved in 150 g of distilled water to prepare a modified component aqueous solution. 9.6 g of SAPO-11 zeolite molecular sieve (Al2O3 / SiO2 / P2O5 = 1 / 0.4 / 0.7) was added to the modified component aqueous solution and stirred at 60°C for 5 h. The water was then removed using a rotary evaporator. The solid product was dried at 110°C for 8 h and then calcined at 550°C for 6 h to obtain modified microporous molecular sieve D5.

[0179] Based on the total weight of the modified microporous molecular sieve D5, the content of SAPO-11 zeolite molecular sieve was 95.5% by weight, and the content of sodium oxide was 4.5% by weight.

[0180] (3) Preparation of microporous-mesoporous composite catalysts

[0181] 28g of modified microporous molecular sieve D5 and 31g of macroporous mesoporous molecular sieve powder A were added to a 300ml ball mill. Six 2mm diameter agate grinding balls were placed and ball milling began. The temperature in the mill was controlled at 50°C, the ball speed was 400 rpm, and the milling time was 10 hours. The resulting powder was calcined at 600°C for 16 hours to obtain the microporous-mesoporous composite catalyst D5.

[0182] Based on the total weight of the catalyst D5, the content of the modified microporous molecular sieve is 55% by weight, and the content of the macroporous mesoporous molecular sieve is 45% by weight.

[0183] The reaction performance of catalyst D5 was tested according to the reaction performance evaluation method for direct conversion of waste plastics to light olefins in step (4) of Example 1. The evaluation results are listed in Table 1.

[0184] Comparative Example 6

[0185] Catalyst D4 was prepared according to the method of Example 1, except that:

[0186] According to the method of step (1) in Example 1, macroporous mesoporous molecular sieve raw powder A was prepared and calcined at 600° C. for 16 h to obtain macroporous mesoporous molecular sieve A.

[0187] Eliminate step (2) in Example 1 and step (3) in Example 1;

[0188] Using macroporous mesoporous molecular sieve A as catalyst D6, the reaction performance of catalyst D6 was tested according to the reaction performance evaluation method for direct conversion of waste plastics to light olefins in step (4) of Example 1. The evaluation results are listed in Table 1.

[0189] Comparative Example 7

[0190] Catalyst D7 was prepared according to the method of Example 1, except that the modified microporous molecular sieve A was replaced by all-silicon silicalite-1 molecular sieve (purchased from Tianjin Nanhua Catalyst Co., Ltd., with a specific surface area of ​​318 m 2 / g, pore volume 0.35cm 3 / g)", and the specific surface area of ​​the catalyst is 332m 2 / g, pore volume 0.71cm 3 / g.

[0191] The reaction performance of catalyst D7 was tested according to the reaction performance evaluation method for direct conversion of waste plastics to light olefins in step (4) of Example 1. The evaluation results are listed in Table 1.

[0192] Comparative Example 8

[0193] Catalyst D8 was prepared according to the method of Example 1, except that the "macroporous mesoporous molecular sieve powder A" was replaced by "commercially available alumina (purchased from Qingdao Hailang Silica Gel Desiccant Factory, with a specific surface area of ​​147m 2 / g, pore volume 0.43cm 3 / g, average pore size 8.7nm)", and the specific surface area of ​​the catalyst is 125m 2 / g, pore volume 0.31cm 3 / g.

[0194] The reaction performance of catalyst D8 was tested according to the reaction performance evaluation method for direct conversion of waste plastics to light olefins in step (4) of Example 1. The evaluation results are listed in Table 1.

[0195] Table 1

[0196]

[0197]

[0198] The above results show that the microporous-mesoporous composite catalyst provided by the present invention can directly catalyze the conversion of waste plastics into light olefins. The waste plastic conversion rate is 100%, and the light olefin yield is high.

[0199] In Comparative Example 1, the content of macroporous mesoporous molecular sieve was too low, the content of modified microporous molecular sieve was too high, and the content of modified components was too high. Due to the small number of macropores in the catalyst, the diffusion of reactant and product molecules during the reaction was hindered, resulting in a low yield of light olefins.

[0200] In Comparative Example 2, the content of the macroporous mesoporous molecular sieve was too high, the content of the modified microporous molecular sieve was too low, and the content of the modified component was too low. Due to the small number of acidic sites on the catalyst and insufficient activation sites during the reaction, the feedstock conversion rate and the yield of light olefins were low.

[0201] In Comparative Example 3, the zeolite molecular sieve was not modified, resulting in a low yield of light olefins.

[0202] In Comparative Example 4, only modified microporous molecular sieve was used as the catalyst without adding macroporous mesoporous molecular sieve. Since the catalyst contained almost no macropore channels, the diffusion of reactant and product molecules during the reaction was severely hindered, resulting in a low yield of light olefins.

[0203] In Comparative Example 5, the modified oxide specifically defined in the present invention was not used, but sodium oxide was used. Since the modification effect of the same weight of sodium oxide was lower, the yield of light olefins was lower.

[0204] In Comparative Example 6, only a large-pore mesoporous molecular sieve was used as the catalyst without the addition of a modified microporous molecular sieve. Since the catalyst contained almost no acidic sites, the lack of activation sites during the reaction resulted in only thermal cracking of the feedstock, resulting in a lower conversion rate and yield of light olefins.

[0205] In Comparative Example 7, "Modified Microporous Molecular Sieve A" was replaced with "All-Silica Silicalite-1 Molecular Sieve." Although all-silica Silicalite-1 is also a microporous material, its surface acidity is extremely weak and has almost no catalytic activity. Therefore, the prepared catalyst D7 contains almost no acidic centers on its surface. This lacks activation sites during the catalytic cracking of waste plastics, resulting in only thermal cracking of the feedstock, resulting in a low conversion rate and low yield of light olefins.

[0206] In Comparative Example 8, "large-pore mesoporous molecular sieve powder A" was replaced with "commercial alumina." Although the pores of commercial alumina also fall into the mesoporous category, the pore structure of alumina is irregular, and compared with large-pore mesoporous molecular sieve, the diffusion effect of alumina is poor, resulting in a lower yield of light olefins.

[0207] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. Application of a microporous-mesoporous composite catalyst in the direct catalytic cracking of waste plastics to produce light olefins, characterized in that: The plastic powder is contacted with a microporous-mesoporous composite catalyst for reaction, wherein the microporous-mesoporous composite catalyst comprises a modified microporous molecular sieve and a macroporous mesoporous molecular sieve, the modified microporous molecular sieve comprises a SAPO-11 zeolite molecular sieve and a modified oxide supported on the SAPO-11 zeolite molecular sieve, and based on the total weight of the microporous-mesoporous composite catalyst, the content of the modified microporous molecular sieve is 42-67% by weight, and the content of the macroporous mesoporous molecular sieve is 33-58% by weight; Based on the total weight of the modified microporous molecular sieve, the content of the SAPO-11 zeolite molecular sieve is 92-99 weight %, and the content of the modified oxide is 1-8 weight %.

2. The use according to claim 1, wherein The contact conditions include: temperature of 420-580° C., pressure of 0.01-1 MPa, and contact time of 0.5-12 h; And / or, the weight ratio of the microporous-mesoporous composite catalyst to the waste plastic powder is 1:(0.5-50).

3. The use according to claim 1, wherein: Based on the total weight of the microporous-mesoporous composite catalyst, the content of the modified microporous molecular sieve is 47-63% by weight, and the content of the macroporous mesoporous molecular sieve is 37-53% by weight.

4. The use according to claim 3, wherein: Based on the total weight of the microporous-mesoporous composite catalyst, the content of the modified microporous molecular sieve is 51-59% by weight, and the content of the macroporous mesoporous molecular sieve is 41-49% by weight.

5. The use according to claim 1, wherein Based on the total weight of the modified microporous molecular sieve, the content of the SAPO-11 zeolite molecular sieve is 93-98 weight %, and the content of the modified oxide is 2-7 weight %.

6. The use according to claim 5, wherein: Based on the total weight of the modified microporous molecular sieve, the content of the SAPO-11 zeolite molecular sieve is 94-97 weight %, and the content of the modified oxide is 3-6 weight %.

7. The use according to claim 1, wherein: The modified oxide is selected from one or more of alkaline earth metal oxides, transition metal oxides and rare earth metal oxides; And / or, the molar ratio of Al2O3 / SiO2 / P2O5 of the SAPO-11 zeolite molecular sieve is 1:(0.1-1.5):(0.3-2).

8. The use according to claim 7, wherein: The modified oxide is selected from one or more of magnesium oxide, calcium oxide, strontium oxide, barium oxide, zinc oxide, cerium oxide and lanthanum oxide.

9. The use according to any one of claims 1 to 8, wherein: The preparation method of the modified microporous molecular sieve comprises: The SAPO-11 zeolite molecular sieve is mixed with a modified component aqueous solution and reacted; and then subjected to water removal, drying and calcination to obtain a modified microporous molecular sieve.

10. The use according to claim 9, wherein: The modified component aqueous solution comprises a metal salt and water; the metal salt is selected from nitrates of one or more of alkaline earth metals, transition metals and rare earth metals; and / or, the mass concentration of the aqueous solution of the modifying component is 0.5-15%; and / or, the weight ratio of the SAPO-11 zeolite molecular sieve to the aqueous solution of the modifying component is 1:(3-30); And / or, the reaction conditions include: temperature of 10-100° C., time of 0.5-50 h; And / or, the calcination conditions include: temperature of 400-700° C. and time of 2-20 h.

11. The use according to claim 10, wherein: The metal salt is selected from one or more nitrates of magnesium, calcium, strontium, barium, zinc, cerium and lanthanum.

12. The use according to claim 1, wherein: The preparation method of the macroporous mesoporous molecular sieve raw powder comprises: The template, ethyl orthosilicate and hydrochloric acid aqueous solution are mixed and contacted to obtain a mixture, and the mixture is crystallized, filtered, washed and dried to obtain macroporous mesoporous molecular sieve raw powder.

13. The use according to claim 12, wherein: The template agent is a nonionic surfactant; and / or, the molar ratio of the template, tetraethyl orthosilicate, hydrochloric acid and water is 1:(20-200):(100-500):(7000-15000); And / or, the mixing contact conditions include: temperature of 25-60° C., time of 20-120 min; And / or, the crystallization conditions include: temperature of 90-180° C. and time of 5-120 h.

14. The use according to claim 13, wherein: The molar ratio of the template, tetraethyl orthosilicate, hydrochloric acid and water is 1: (40-100): (200-300): (9000-13000).

15. The use according to any one of claims 1 to 8, wherein: The preparation method of the microporous-mesoporous composite catalyst comprises: The modified microporous molecular sieve and the macroporous mesoporous molecular sieve raw powder are mixed and ball-milled, and then calcined to obtain a microporous-mesoporous composite catalyst.

16. The use according to claim 15, wherein: The weight ratio of the modified microporous molecular sieve to the macroporous mesoporous molecular sieve powder is 1: (0.5-2.5); And / or, the ball milling conditions include: a grinding ball rotation speed of 200-600 r / min, a temperature in the ball milling jar of 30-90° C., and a ball milling time of 5-50 h; And / or, the calcination conditions include: temperature of 450-750° C. and time of 5-40 h.

17. The use according to claim 16, wherein: The weight ratio of the modified microporous molecular sieve to the macroporous mesoporous molecular sieve powder is 1:(0.7-2); And / or, the calcination conditions include: a temperature of 550-650°C; The time is 8-20h.

Images