Porous cracking catalyst, preparation method thereof and application of porous cracking catalyst in low-carbon olefin production from waste plastics

Abstract

The present application relates to the field of catalyst and the field of recycling of polymer materials, and discloses a porous cracking catalyst, a preparation method thereof and application of the porous cracking catalyst in a reaction of preparing low-carbon olefins from waste plastics. The porous cracking catalyst comprises SAPO-18 molecular sieve, super-large pore silica gel and modified oxide, wherein, based on the total weight of the porous cracking catalyst, the SAPO-18 molecular sieve accounts for 28-60 wt%, the super-large pore silica gel accounts for 30-70 wt%, and the modified oxide accounts for 2-10 wt%; the specific surface area of the porous cracking catalyst is 380-450 m 2 / g, the pore volume is 0.68-1.05 mL / g, and the pore size distribution is a three-peak distribution, and the most probable pore sizes corresponding to the three peaks are 0.38-0.45 nm, 2-4.5 nm and 15-45 nm, respectively. The porous cracking catalyst is applied in waste plastics, which not only solves the problem of recycling of waste plastics, but also increases the production of important chemical raw material, i.e. low-carbon olefins.

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 porous cracking catalyst, a preparation method thereof, and an application thereof in the reaction of producing light olefins from waste plastics. Background Art

[0002] Since their advent in the 20th century, plastic products have been widely used in various fields worldwide due to their lightweight, high strength, corrosion resistance, good chemical stability, easy processing, and aesthetic and practical features. However, plastics are difficult to degrade naturally. Conventional landfill technology, while requiring low investment and simple operation, occupies a large amount of land and causes land pollution. While incineration technology can achieve waste reduction requirements and recover some energy, it 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 has received widespread attention worldwide. Methods for recycling and utilizing waste plastics mainly include classified recycling, preparation of monomer raw materials, production of clean fuel, and use for power generation.

[0003] Large-scale, well-regulated waste plastic recycling companies will gradually refine the classification of recycled waste plastics, continuously develop and apply new technologies and products for waste plastics, gradually expand the application areas of waste plastics, and increase the added value of recycled plastic products. Existing chemical recycling solutions for waste plastics primarily rely on waste plastic cracking technology. There are three basic methods for waste plastic cracking: thermal cracking (a single-stage process), catalytic cracking (a single-stage process), and thermal cracking-catalytic modification (a two-stage process). Thermal cracking is the earliest developed technology for waste plastic cracking. This technology involves a thermal conversion process under high-temperature, anaerobic conditions, where a thermochemical decomposition reaction occurs, converting the high-molecular-weight organic matter in waste plastic products into low-molecular-weight liquids, fuel gas, and coke. The reaction temperature for this process is generally controlled between 350 and 900°C. Adding a catalyst to the thermal cracking process, known as catalytic thermal cracking, not only reduces the cracking temperature but also improves product performance. The thermal cracking-catalytic reforming method is an improvement of the catalytic cracking method. After the waste plastics are thermally cracked, the cracking gas is catalytically reformed with a catalyst. This method produces higher quality products than the thermal cracking and catalytic cracking methods, is more flexible to operate, and has lower operating costs, but the process is more complicated.

[0004] Cracking technology offers extensive flexibility and good energy recovery in treating waste plastics, making it a promising technology for waste plastics treatment. Existing technologies primarily produce fuel oil through one-step thermal cracking and one-step catalytic cracking, yielding only small amounts of light olefins (ethylene, propylene, and butene). To obtain larger quantities of light olefins, a two-stage thermal cracking-catalytic reforming process is required. Therefore, exploring new chemical recovery processes to produce pure, high-quality end products is an important research area for plastic waste treatment. Summary of the Invention

[0005] The purpose of the present invention is to address the current problem of low content of light olefins recovered in the chemical recycling of waste plastics, and to provide a porous cracking catalyst and a preparation method thereof, as well as an application in the reaction of producing light olefins from waste plastics. The porous cracking catalyst is applied to waste plastics, providing a new approach for the one-step catalytic conversion and utilization of waste plastics, thereby solving the problem of waste plastic recycling and increasing the production of light olefins, an important chemical raw material.

[0006] To achieve the above-mentioned object, the first aspect of the present invention provides a porous cracking catalyst, wherein the porous cracking catalyst comprises SAPO-18 molecular sieve, ultra-large pore silica gel and modified oxide, and based on the total weight of the porous cracking catalyst, the content of the SAPO-18 molecular sieve is 28-60% by weight, the content of the ultra-large pore silica gel is 30-70% by weight, and the content of the modified oxide is 2-10% by weight;

[0007] The specific surface area of ​​the porous cracking catalyst is 380-450m 2 / g, the pore volume is 0.68-1.05mL / g, the pore size distribution is trimodal distribution, and the most probable pore sizes corresponding to the three peaks are 0.38-0.45nm, 2-4.5nm and 15-45nm, respectively.

[0008] A second aspect of the present invention provides a method for preparing the aforementioned porous cracking catalyst, wherein the preparation method comprises:

[0009] (1) mixing a template, an aluminum source, a phosphorus source, a silicon source, and water and performing a contact reaction to obtain a gel mixture; performing a first crystallization treatment on the gel mixture to obtain a mixed slurry; mixing the mixed slurry with ultra-large pore silica gel and performing a second crystallization treatment; and separating, washing, drying, and calcining the crystallized product to obtain a mixed molecular sieve;

[0010] (2) The mixed molecular sieve is immersed in an aqueous solution containing a modified oxide precursor, and the solid product after removing moisture is dried and calcined to obtain a porous cracking catalyst.

[0011] A third aspect of the present invention provides an application of the aforementioned porous cracking catalyst in the direct catalytic cracking of waste plastics to produce light olefins.

[0012] Through the above technical solution, compared with the prior art, the technical solution of the present invention has the following advantages:

[0013] (1) The porous cracking catalyst provided by the present invention includes SAPO-18 zeolite molecular sieve with acidic centers on the surface and ultra-large porous silica gel with double-pore mesoporous channels. It has a stable structure and good high-temperature resistance, and helps the diffusion of raw material and product molecules during the cracking reaction.

[0014] (2) During the preparation of the porous cracking catalyst provided by the present invention, the mother liquor after the primary crystallization of SAPO-18 molecular sieve is mixed with the ultra-large-pore silica gel after ball milling, and then subjected to secondary crystallization. The micropores and mesopores in the porous cracking catalyst directly obtained are evenly distributed.

[0015] (3) The porous cracking catalyst provided by the present invention can convert waste plastics into light olefins in a single step when used in the direct catalytic cracking reaction 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.

[0016] (4) When the porous cracking 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.

[0017] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following detailed description, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings:

[0019] Figure 1 is a pore size distribution diagram of ultra-macroporous silica gel A prepared in Example 1 of the present invention;

[0020] Figure 2 This is a pore size distribution diagram of the porous cracking catalyst A prepared in Example 1 of the present invention. 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 mentioned above, the first aspect of the present invention provides a porous cracking catalyst, wherein the porous cracking catalyst comprises SAPO-18 molecular sieve, ultra-large pore silica gel and modified oxide, and based on the total weight of the porous cracking catalyst, the content of the SAPO-18 molecular sieve is 28-60% by weight, the content of the ultra-large pore silica gel is 30-70% by weight, and the content of the modified oxide is 2-10% by weight;

[0023] The specific surface area of ​​the porous cracking catalyst is 380-450m 2 / g, the pore volume is 0.68-1.05mL / g, the pore size distribution is trimodal distribution, and the most probable pore sizes corresponding to the three peaks are 0.38-0.45nm, 2-4.5nm and 15-45nm, respectively.

[0024] The inventors of the present invention have discovered 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 address this problem. Based on the inventors' understanding of the physicochemical properties of heterogeneous catalysts, catalysts used for the catalytic cracking of waste plastics to directly produce light olefins should have a certain acidity, but the acidity should not be too strong. In addition, the catalyst for the catalytic cracking of waste plastics needs to have good thermal stability. SAPO-18 molecular sieve not only has surface acidic sites, but also has relatively good thermal stability (the crystalline phase can still remain stable after high-temperature roasting at 550°C). After appropriate modification, it can be used as a catalyst for the catalytic cracking reaction of waste plastics. However, the pore size of SAPO-18 molecular sieve is generally around 0.4nm, which seriously limits the practical application of SAPO-18 molecular sieve catalysts. This is mainly because SAPO-18 is a microporous molecular sieve with a small pore size and pore volume, while the molecular weight of the waste plastic product is large and the molecular chain is relatively long. During the cracking reaction of waste plastic products, larger reactant molecules and product molecules have difficulty diffusing between narrow pores, which not only affects the contact between reactants and active centers, but also easily leads to side reactions such as deep dehydrogenation, which in turn leads to a decrease in catalyst performance. Compared with microporous molecular sieves, ultra-large pore silica gel materials have double pores with larger pore sizes (the most probable pore diameters are 2-5nm and 20-50nm respectively) and large pore volumes (up to 1.0cm 3 / g or more), very suitable for catalytic reactions involving macromolecules. However, ultra-large pore silica gel is a fully silicon material with only a small amount of silanol groups on the surface, which is extremely weak in acidity and 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 ultra-large pore silica gel and the surface acidic centers of zeolite molecular sieves are comprehensively utilized, a certain amount of ultra-large pore silica gel is mixed with SAPO-18 molecular sieves, the 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] According to the present invention, preferably, based on the total weight of the porous cracking catalyst, the content of the SAPO-18 molecular sieve is 32-56% by weight, the content of the ultra-large pore silica gel is 35-65% by weight, and the content of the modified oxide is 3-9% by weight; more preferably, based on the total weight of the porous cracking catalyst, the content of the SAPO-18 molecular sieve is 36-52% by weight, the content of the ultra-large pore silica gel is 40-60% by weight, and the content of the modified oxide is 4-8% by weight. In the present invention, the use of the aforementioned specific contents of each component can enable the prepared porous cracking 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.

[0026] According to the present invention, preferably, the specific surface area of ​​the porous cracking catalyst is 388-445m 2 / g, the pore volume is 0.76-1mL / g, the pore size distribution is trimodal, and the most probable pore sizes corresponding to the three peaks are 0.39-0.44nm, 2.5-4nm and 20-38nm respectively; more preferably, the specific surface area of ​​the porous cracking catalyst is 394-440m 2 / g, a pore volume of 0.84-0.93 mL / g, a trimodal pore size distribution, and the most probable pore sizes corresponding to the three peaks are 0.4-0.42 nm, 2.8-3.4 nm, and 25-32 nm, respectively. In the present invention, when the porous cracking catalyst has the aforementioned specific structural parameters, it can be used in the direct catalytic cracking of waste plastics to produce light olefins with better catalytic activity and higher light olefin selectivity.

[0027] According to the present invention, the modified oxide is selected from alkaline earth metal oxides; preferably, the modified oxide is selected from one or more of calcium oxide, magnesium oxide, strontium oxide and barium oxide.

[0028] According to the present invention, the specific surface area of ​​the ultra-macroporous silica gel is 200-500m2 / g, the pore volume is 1-2mL / g, the pore size is bimodal distribution, the first most probable pore size is 2-5nm, and the second most probable pore size is 20-50nm.

[0029] According to the present invention, the method for preparing the ultra-macroporous silica gel comprises:

[0030] In the presence of butanol and glycerol, an inorganic silicon source is contacted with an acid agent, and the resulting mixture is filtered and washed to obtain a silica gel filter cake; the silica gel filter cake is then dried, calcined and ball-milled to obtain ultra-macroporous silica gel.

[0031] According to the present invention, the butanol may be one or more of n-butanol, sec-butanol and isobutanol; preferably n-butanol.

[0032] According to the present invention, the inorganic silicon source is selected from one or more of water glass, sodium metasilicate and silica sol, preferably water glass.

[0033] According to the present invention, the acid agent can be any substance or mixture (such as a solution) that can be conventionally used to adjust the pH value; preferably, the acid agent is an aqueous solution of at least one selected from hydrochloric acid, sulfuric acid, nitric acid and hydrobromic acid; more preferably, the acid agent is an aqueous solution of sulfuric acid.

[0034] According to the present invention, the weight ratio of the inorganic silicon source, acid agent, butanol and glycerol is 1: (0.05-0.5): (0.02-0.6): (0.02-0.6), preferably 1: (0.1-0.3): (0.06-0.4): (0.06-0.4).

[0035] According to the present invention, the conditions for contacting the inorganic silicon source with the acid agent may include: a temperature of 15-40° C. and a time of 1-3 hours; preferably, in order to achieve a better mixing effect, rapid stirring or ultrasonic means may be used to improve the mixing efficiency during the contact (hydrolysis and gel preparation) of the inorganic silicon source with the acid agent.

[0036] 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.

[0037] 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.

[0038] According to the present invention, the drying conditions include: drying temperature of 60-150° C., and drying time of 1-30 h; preferably, the temperature is 90-130° C., and the drying time is 5-16 h.

[0039] According to the present invention, the calcination conditions include: calcination temperature of 450-700° C., calcination time of 3-20 h; preferably, the temperature is 500-650° C., and the calcination time is 6-12 h.

[0040] 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.

[0041] A second aspect of the present invention provides a method for preparing the aforementioned porous cracking catalyst, wherein the preparation method comprises:

[0042] (1) mixing a template, an aluminum source, a phosphorus source, a silicon source, and water and performing a contact reaction to obtain a gel mixture; performing a first crystallization treatment on the gel mixture to obtain a mixed slurry; mixing the mixed slurry with ultra-large pore silica gel and performing a second crystallization treatment; and separating, washing, drying, and calcining the crystallized product to obtain a mixed molecular sieve;

[0043] (2) The mixed molecular sieve is immersed in an aqueous solution containing a modified oxide precursor, and the solid product after removing moisture is dried and calcined to obtain a porous cracking catalyst.

[0044] The inventors discovered that mixing a certain amount of ultra-large pore silica gel with SAPO-18 molecular sieve can increase the pore volume of the catalyst and improve the internal diffusion performance during the reaction. However, if the two prepared molecular sieves are mechanically mixed, the resulting mixed molecular sieve has an uneven distribution of micropores and mesopores, and the improvement in diffusion performance is not significant enough. In the present invention, the inventors mixed the mother liquor after the primary crystallization of SAPO-18 molecular sieve with ball-milled ultra-large pore silica gel and performed a secondary crystallization to obtain a porous cracking catalyst. The composite molecular sieve obtained by this method has a uniform distribution of micropores and mesopores, and exhibits high catalytic activity and high selectivity for light olefins when used in the catalytic cracking reaction of waste plastics.

[0045] According to the present application, in step (1), the template agent is N,N-diisopropylethylamine.

[0046] According to the present application, in step (1), the aluminum source is selected from one or more of pseudoboehmite, aluminum hydroxide, basic aluminum sol, aluminum isopropoxide, aluminum hydroxide acetate, gibbsite and bayerite, preferably one or more of pseudoboehmite, aluminum hydroxide, basic aluminum sol and aluminum isopropoxide, more preferably pseudoboehmite.

[0047] According to the present application, in step (1), the phosphorus source is an inorganic acid or acid salt containing phosphorus element, preferably one or more of phosphoric acid, phosphorous acid, ammonium dihydrogen phosphate and monohydrogen phosphate, more preferably phosphoric acid.

[0048] According to the present application, in step (1), the silicon source is an organic silicon source and / or an inorganic silicon source, preferably one or more of tetramethyl silicate, tetraethyl silicate, tetraisopropyl silicate, tetrabutyl silicate, silica sol, water glass and white carbon black, more preferably silica sol.

[0049] According to the present application, in step (1), the molar ratio of the aluminum source (calculated as Al2O3), the silicon source (calculated as SiO2), the phosphorus source (calculated as P2O5), the template agent and water is 1:(0.1-2):(0.2-2.5):(0.5-3):(10-150), preferably 1:(0.3-1):(0.5-1.2):(1-2):(30-80).

[0050] According to the present application, in step (1), the conditions of the contact reaction include: temperature of 20-100℃, preferably 40-80℃; time of 1-10h, preferably 2-6h. Preferably, in order to achieve better mixing effect, fast stirring or ultrasonic means can be used to improve the mixing efficiency during the contact reaction.

[0051] According to the present application, in step (1), the conditions of the first crystallization include: temperature of 140-200℃, preferably 160-180℃; time of 2-24h, preferably 6-16h.

[0052] According to the present application, in step (1), the weight ratio of the superlarge-pore silica gel to the amount of the mixed slurry is 1:(2-15), preferably 1:(3-10).

[0053] According to the present application, in step (1), the conditions of the second crystallization include: temperature of 140-200℃, preferably 160-180℃; time of 20-100h, preferably 48-72h.

[0054] According to the present application, in step (1), the separation method is not particularly required, and can be a separation method known in the art, including gravity filtration, pressure filtration, vacuum filtration or centrifugal filtration. Preferably, the separation process specifically includes: using a suction filter bottle, vacuum suction on the bottom side of the funnel or using a centrifugal filter to filter.

[0055] According to the present application, in step (1), the method for washing the solid product is not particularly required, for example: the solid product can be washed with deionized water, the volume ratio of deionized water to solid product can be 5-20, and the washing times can be 2-8 times.

[0056] According to the present application, in step (1), the drying conditions include: temperature of 60-150℃, preferably 80-130℃; time of 1-30h, preferably 3-20h.

[0057] According to the present application, in step (1), the calcination conditions include: temperature of 450-650℃, preferably 500-600℃; time of 5-50h, preferably 8-30h.

[0058] According to the present application, in step (2), the modified oxide precursor includes an inorganic salt of an alkaline earth metal; preferably, the alkaline earth metal is selected from one or more of calcium, magnesium, strontium, and barium.

[0059] According to the present application, in step (2), the mass concentration of the aqueous solution containing the modified oxide precursor is 0.3-5%, preferably 0.5-4%.

[0060] According to the present application, in step (2), the weight ratio of the mixed molecular sieve to the aqueous solution containing the modified oxide precursor is 1:(5-20), preferably 1:(8-16).

[0061] According to the present application, in step (2), the impregnation conditions include: temperature of 10-100℃, preferably 20-90℃; time of 0.5-20h, preferably 2-12h. Preferably, in order to achieve better mixing effect, rapid stirring or ultrasonic means can be used to improve the mixing efficiency during the contact reaction.

[0062] According to the present application, in step (2), the method for removing water is not particularly required, and can be a method known in the art, for example: using a rotary evaporator or heating and evaporating during stirring.

[0063] According to the present application, in step (2), the drying conditions include: temperature of 70-150℃, preferably 90-120℃; time of 2-30h, preferably 4-20h.

[0064] According to the present invention, in step (2), the calcination conditions include: a temperature of 500-700° C., preferably 550-650° C.; and a calcination time of 3-20 h, preferably 5-12 h.

[0065] A third aspect of the present invention provides an application of the aforementioned porous cracking catalyst in the direct catalytic cracking of waste plastics to produce light olefins.

[0066] According to the present invention, the application comprises: under specific conditions, contacting waste plastic powder or particles with the porous cracking catalyst to react.

[0067] According to the present invention, the contact conditions include: temperature of 420-580° C., pressure of 0.01-1 MPa, and contact time of 0.5-12 h.

[0068] According to the present invention, the weight ratio of the porous cracking catalyst to the waste plastic powder or particles is 1:(0.5-50).

[0069] The present invention will be described in detail below through examples.

[0070] In the following examples and comparative examples:

[0071] 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.

[0072] 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.

[0073] The drying oven was produced by Shanghai Yiheng Scientific Instrument Co., Ltd., model DHG-9030A.

[0074] The muffle furnace is produced by CARBOLITE, model CWF1100.

[0075] Other reagents used in the examples and comparative examples were purchased from Sinopharm Chemical Reagent Co., Ltd. and were of analytical grade.

[0076] Example 1

[0077] This embodiment is intended to illustrate the porous cracking catalyst prepared by the present invention and its application in the reaction of producing light olefins from waste plastics.

[0078] (1) Preparation of ultra-macroporous silica gel

[0079] A mixture of water glass with a concentration of 15 wt% 50 g, aqueous solution of sulfuric acid with a concentration of 12 wt% 10 g, n-butanol 10 g and glycerol 10 g were mixed at 25 °C and contacted under stirring for 2.0 h. White solid material was obtained by suction filtration, and the solid material was washed with distilled water for 8 times to obtain silica gel filter cake. The silica gel filter cake was dried at 110 °C for 12 h and calcined at 550 °C for 8 h, and then put into a 100 mL ball mill tank, wherein the material of the ball mill tank was polytetrafluoroethylene, the material of the grinding ball was agate, the diameter of the grinding ball was 3 mm, the number of the grinding ball was 4, and the rotating speed was 400 r / min. The ball mill tank was closed, and the ball milling was carried out at 60 °C for 16 h to obtain the superlarge-pore silica gel A.

[0080] The specific surface area of the superlarge-pore silica gel A was 361 m 2 / g, and the pore volume was 1.7 ml / g.

[0081] Figure 1 The average pore size distribution of the superlarge-pore silica gel A prepared in Example 1 is shown in FIG. 1, and it can be seen that the pore size of the material is bimodal distribution, the first most probable pore size is 3.3 nm, and the second most probable pore size is 32 nm. Figure 1

[0082] (2) Preparation of porous cracking catalyst

[0083] Firstly, pseudo-boehmite powder (produced by Shandong Aluminum Co., Ltd., specific surface area 257 m 2 / g, pore volume 0.32 cm 3 / g) with a model number of P-DF-03-LS was mixed with deionized water at a temperature of 60 °C, stirred for 1 h, then phosphoric acid was added, stirred for 1 h, then silica sol was added, and after uniform stirring, the template N, N-diisopropyl ethylamine was slowly added dropwise. The molar ratio of n (Al2O3) : n (SiO2) : n (P2O5) : n (C8H 19 N) : n (H2O) in the mixed system was 1:0.6:0.9:1.6:60. After the template was added dropwise, the mixed system was continuously stirred at 60 °C for 1 h to obtain a gel mixture. Then the gel mixture was transferred into a hydrothermal kettle with a polytetrafluoroethylene liner for the first crystallization treatment. The temperature of the first crystallization treatment was 170 °C, and the time was 12 h. The mixed slurry obtained after the first crystallization treatment was uniformly mixed with the superlarge-pore silica gel A (the weight ratio of the superlarge-pore silica gel to the mixed slurry was 1:6.4), and the second crystallization treatment was carried out. The temperature of the second crystallization treatment was 170 °C, and the time was 60 h. After the crystallization was completed, the solid product obtained by centrifugal filtration was washed with deionized water for 6 times, the solid product was dried at 110 °C for 10 h, and then calcined at 550 °C for 16 h to obtain the mixed molecular sieve A.

[0084] ​1.8 g of calcium nitrate was dissolved in 100 g of deionized water, 9.4 g of the above-mentioned mixed molecular sieve A was added, and the mixture was stirred at 50°C for 6 h. The solid product obtained after removing moisture using a rotary evaporator was dried at 110°C for 12 hours and calcined at 600°C for 8 hours to obtain a porous cracking catalyst A.

[0085] Based on the total weight of the porous cracking catalyst A, the content of SAPO-18 molecular sieve is 44% by weight, the content of ultra-large pore silica gel is 50% by weight, and the content of calcium oxide is 6%.

[0086] The specific surface area of ​​porous cracking catalyst A is 420m 2 / g, pore volume 0.91cm 3 / g.

[0087] Figure 2 is the pore size distribution diagram of the porous cracking catalyst A prepared in Example 1, Figure 2 It can be seen that the sample has a distinct three-pore channel structure, with most probable pore diameters of 0.41nm, 3.1nm, and 28nm, respectively. Among them, the channel with a most probable pore diameter of 0.41nm is provided by the SAPO-18 molecular sieve, and the two types of mesoporous channels with most probable pore diameters of 3.1nm and 28nm are provided by ultra-large pore silica gel. Compared with the most probable pore diameter of ultra-large pore silica gel A, the two types of mesoporous channels of porous cracking catalyst A are slightly smaller. This is mainly due to a small amount of smaller SAPO-18 molecular sieve particles entering the ultra-large pore silica gel channels during the secondary crystallization process, causing slight blockage.

[0088] (3) Evaluation of the reaction performance of direct conversion of waste plastics to light olefins

[0089] The catalytic cracking performance of porous cracking catalyst A for waste plastics was evaluated in a fixed-bed reactor. The loading of porous cracking catalyst A was 6.0 g, and the loading of polyethylene waste plastic was 40.0 g. The reaction temperature was 480°C, the pressure was 0.1 MPa, and the reaction time was 2 hours. After cooling and gas-liquid separation, the gas composition was analyzed using an Agilent 6890N gas chromatograph equipped with an Al2O3-S capillary column and a flame ion detector (FID) using a programmed temperature ramp and correction factors for quantitative analysis. The liquid composition was analyzed using an Agilent 7890A gas chromatograph equipped with a PONA column. The reaction results are shown in Table 1.

[0090] Example 2

[0091] This embodiment is intended to illustrate the porous cracking catalyst prepared by the present invention and its application in the reaction of producing light olefins from waste plastics.

[0092] (1) Preparation of ultra-macroporous silica gel

[0093] 100 g of 15 wt% water glass, 30 g of 12 wt% aqueous sulfuric acid solution, 6 g of n-butanol, and 40 g of glycerol were mixed at 15°C and stirred for 3.0 hours. A white solid was obtained by filtration and washed four times with distilled water to obtain a silica gel filter cake. The silica gel filter cake was dried at 90°C for 16 hours, calcined at 500°C for 12 hours, and placed in a 200 ml ball mill. Eight 2 mm diameter agate grinding balls were added, the mill was sealed, and ball milling began. The temperature in the mill was controlled at 80°C, the grinding balls rotated at 300 rpm, and the milling time was 8 hours to obtain ultra-macroporous silica gel B.

[0094] The specific surface area of ​​ultra-macroporous silica gel B is 381m 2 / g, the pore volume is 1.8 ml / g, the first most probable pore diameter is 3.5 nm, and the second most probable pore diameter is 36 nm.

[0095] (2) Preparation of porous cracking catalyst

[0096] At a temperature of 40°C, the German imported pseudo-boehmite powder of model SB (purchased from Beijing Asia Pacific Aohua Chemical Additives Co., Ltd., with a specific surface area of ​​241m 2 / g, pore volume 0.53cm 3 / g) was mixed with deionized water, stirred for 1 hour, and then phosphoric acid was added. After stirring for another 1 hour, silica sol was added. After stirring evenly, the template agent N,N-diisopropylethylamine was slowly added dropwise. In the mixed system, n(Al2O3):n(SiO2):n(P2O5):n(C8H 19 The molar ratio of (N):n(H2O) was 1:0.4:0.7:1.3:50. After the template was added, the mixture was stirred at 40°C for 3 hours to obtain a gel mixture. The gel mixture was then transferred to a polytetrafluoroethylene-lined hydrothermal autoclave for the first crystallization treatment. The first crystallization treatment was performed at 160°C for 16 hours. The mixed slurry obtained after the first crystallization treatment was uniformly mixed with ultraporous silica gel B (the weight ratio of ultraporous silica gel to mixed slurry was 1:9.2) and then subjected to a second crystallization treatment. The second crystallization treatment was performed at 160°C for 72 hours. After the crystallization, the solid product obtained by centrifugation was washed eight times with deionized water, dried at 130°C for 3 hours, and then calcined at 600°C for 8 hours to obtain mixed molecular sieve B.

[0097] 1.4 g of barium nitrate was dissolved in 80 g of deionized water, 9.2 g of the above-mentioned mixed molecular sieve B was added, and the mixture was stirred at 90°C for 2 h. The solid product obtained after removing moisture using a rotary evaporator was dried at 120°C for 4 hours and calcined at 650°C for 5 hours to obtain a porous cracking catalyst B.

[0098] The content of SAPO-18 molecular sieve is 52% by weight, the content of the ultra-large pore silica gel is 40% by weight, and the content of barium oxide is 8% based on the total weight of the porous cracking catalyst B.

[0099] The specific surface area of the porous cracking catalyst B is 440 m 2 / g, the pore volume is 0.84 cm 3 / g, and the most probable pore diameters are 0.42 nm, 3.2 nm and 31 nm, respectively.

[0100] (3) Performance evaluation of direct conversion of waste plastics to low-carbon olefins

[0101] The reaction performance of the porous cracking catalyst B was tested according to the performance evaluation method of direct conversion of waste plastics to low-carbon olefins in step (3) of Example 1, and the evaluation results are shown in Table 1.

[0102] Example 3

[0103] This example is to illustrate the porous cracking catalyst prepared by the present application and its application in the reaction of converting waste plastics to low-carbon olefins.

[0104] (1) Preparation of ultra-large pore silica gel

[0105] 100 g of water glass with a concentration of 15% by weight, 10 g of sulfuric acid aqueous solution with a concentration of 12% by weight, 40 g of n-butanol and 6 g of glycerol were mixed at 40°C and contacted under stirring for 1.0 h. White solid material was obtained by suction filtration, and the solid material was washed with distilled water for 8 times to obtain a silica gel filter cake. The silica gel filter cake was dried at 130°C for 5 h and then calcined at 650°C for 6 h, and then placed in a 200 ml ball mill tank, 6 maroon grinding balls with a diameter of 2.5 mm were added, the ball mill tank was closed, and the ball milling was started. The temperature in the ball mill tank was controlled at 40°C, the rotation speed of the grinding balls was 500 r / min, and the ball milling time was 24 h to obtain the ultra-large pore silica gel C.

[0106] The specific surface area of the ultra-large pore silica gel C is 338 m 2 / g, the pore volume is 1.5 ml / g, the first most probable pore diameter is 3.0 nm, and the second most probable pore diameter is 31 nm.

[0107] (2) Preparation of porous cracking catalyst

[0108] First, pseudo-boehmite powder (produced by Zibo Hengqi Powder New Material Co., Ltd., with a specific surface area of 250 m 2 / g, and a pore volume of 0.42 cm 3 / g) was mixed with deionized water, stirred for 0.5h, and then phosphoric acid was added. After stirring for 0.5h, silica sol was added. After stirring evenly, the template agent N,N-diisopropylethylamine was slowly added dropwise. In the mixed system, n(Al2O3):n(SiO2):n(P2O5):n(C8H 19 The molar ratio of (N):n(H2O) was 1:0.8:1.0:1.8:70. After the template was added, the mixture was stirred at 80°C for 1.0 h to produce a gel mixture. The gel mixture was then transferred to a polytetrafluoroethylene-lined hydrothermal autoclave for a first crystallization treatment at 180°C for 6 h. The resulting mixed slurry was uniformly mixed with ultraporous silica gel C (the weight ratio of ultraporous silica gel to mixed slurry was 1:4.6) for a second crystallization treatment at 180°C for 48 h. After crystallization, the solid product obtained by centrifugation was washed four times with deionized water, dried at 80°C for 20 h, and then calcined at 500°C for 30 h to produce mixed molecular sieve C.

[0109] 0.8 g of strontium nitrate was dissolved in 120 g of deionized water, 9.6 g of the above-mentioned mixed molecular sieve C was added, and the mixture was stirred at 90°C for 2 h. The solid product obtained after removing moisture using a rotary evaporator was dried at 120°C for 4 hours and calcined at 650°C for 5 hours to obtain a porous cracking catalyst C.

[0110] Based on the total weight of the porous cracking catalyst C, the content of SAPO-18 molecular sieve is 36% by weight, the content of ultra-large pore silica gel is 60% by weight, and the content of strontium oxide is 4%.

[0111] The specific surface area of ​​porous cracking catalyst C is 394m 2 / g, pore volume 0.93cm 3 / g, and the most probable pore diameters are 0.40nm, 2.8nm and 26nm respectively.

[0112] (3) Evaluation of the reaction performance of direct conversion of waste plastics to light olefins

[0113] The reaction performance of the porous cracking catalyst C was tested according to the reaction performance evaluation method for direct conversion of waste plastics to light olefins in step (3) of Example 1. The evaluation results are listed in Table 1.

[0114] Example 4

[0115] This embodiment is intended to illustrate the porous cracking catalyst prepared by the present invention and its application in the reaction of producing light olefins from waste plastics.

[0116] Ultra-macroporous silica gel A was prepared in the same manner as in step (1) of Example 1.

[0117] (2) Preparation of porous cracking catalyst

[0118] At 60 °C, firstly, the pseudo-boehmite powder of model P-DF-03-LS (produced by Shandong Aluminum Co., Ltd., with a specific surface area of ​​257m 2 / g, pore volume 0.32cm 3 / g) was mixed with deionized water, stirred for 1 hour, and then phosphoric acid was added. After stirring for another 1 hour, silica sol was added. After stirring evenly, the template agent N,N-diisopropylethylamine was slowly added dropwise. In the mixed system, n(Al2O3):n(SiO2):n(P2O5):n(C8H 19 The molar ratio of (N):n(H2O) was 1:0.3:0.5:1.0:30. After the template was added, the mixture was stirred at 60°C for 1 hour to produce a gel mixture. The gel mixture was then transferred to a polytetrafluoroethylene-lined hydrothermal autoclave for a first crystallization treatment. The first crystallization treatment was performed at 170°C for 12 hours. The resulting mixed slurry was uniformly mixed with ultraporous silica gel A (the weight ratio of ultraporous silica gel to mixed slurry was 1:9.1) and then subjected to a second crystallization treatment. The second crystallization treatment was performed at 170°C for 60 hours. After crystallization, the solid product obtained by centrifugation was washed six times with deionized water, dried at 110°C for 10 hours, and then calcined at 550°C for 16 hours to produce mixed molecular sieve D.

[0119] 2.6 g of calcium nitrate was dissolved in 70 g of deionized water, 9.1 g of the above-mentioned mixed molecular sieve D was added, and the mixture was stirred at 50°C for 6 h. The solid product obtained after removing moisture using a rotary evaporator was dried at 110°C for 12 hours and calcined at 600°C for 8 hours to obtain a porous cracking catalyst D.

[0120] Based on the total weight of the porous cracking catalyst D, the content of SAPO-18 molecular sieve was 56% by weight, the content of ultra-large pore silica gel was 35% by weight, and the content of calcium oxide was 9%.

[0121] The specific surface area of ​​porous cracking catalyst D is 445m 2 / g, pore volume 0.76cm 3 / g, and the most probable pore diameters are 0.41nm, 3.2nm and 29nm respectively.

[0122] The reaction performance of Catalyst D was tested using the same reaction performance evaluation method for direct conversion of waste plastics to light olefins as in step (3) of Example 1. The evaluation results are listed in Table 1.

[0123] Example 5

[0124] This embodiment is intended to illustrate the porous cracking catalyst prepared by the present invention and its application in the reaction of producing light olefins from waste plastics.

[0125] Ultra-macroporous silica gel B was prepared in the same manner as in step (1) of Example 2.

[0126] (2) Preparation of porous cracking catalyst

[0127] At a temperature of 40°C, the German imported pseudo-boehmite powder of model SB (purchased from Beijing Asia Pacific Aohua Chemical Additives Co., Ltd., with a specific surface area of ​​241m 2 / g, pore volume 0.53cm 3 / g) was mixed with deionized water, stirred for 1 hour, and then phosphoric acid was added. After stirring for another 1 hour, silica sol was added. After stirring evenly, the template agent N,N-diisopropylethylamine was slowly added dropwise. In the mixed system, n(Al2O3):n(SiO2):n(P2O5):n(C8H 19 The molar ratio of (N):n(H2O) was 1:1.0:1.2:2.0:80. After the template was added, the mixture was stirred at 40°C for 3 hours to obtain a gel mixture. The gel mixture was then transferred to a polytetrafluoroethylene-lined hydrothermal autoclave for a first crystallization treatment. The first crystallization treatment was performed at 160°C for 16 hours. The resulting mixed slurry was uniformly mixed with ultraporous silica gel B (the weight ratio of ultraporous silica gel to mixed slurry was 1:3.8) and then subjected to a second crystallization treatment. The second crystallization treatment was performed at 160°C for 72 hours. After crystallization, the solid product obtained by centrifugation was washed eight times with deionized water, dried at 130°C for 3 hours, and then calcined at 600°C for 8 hours to obtain mixed molecular sieve E.

[0128] 1.9 g of magnesium nitrate hexahydrate was dissolved in 150 g of deionized water, 9.7 g of the above-mentioned mixed molecular sieve E was added, and the mixture was stirred at 90° C. for 2 h. The solid product obtained after removing moisture using a rotary evaporator was dried at 120° C. for 4 hours and calcined at 650° C. for 5 hours to obtain a porous cracking catalyst E.

[0129] Based on the total weight of the porous cracking catalyst E, the content of SAPO-18 molecular sieve is 32 weight %, the content of ultra-large pore silica gel is 65 weight %, and the content of magnesium oxide is 3%.

[0130] The specific surface area of ​​porous cracking catalyst E is 388m 2 / g, pore volume 1.0cm 3 / g, and the most probable pore diameters are 0.42nm, 3.3nm and 32nm respectively.

[0131] The reaction performance of the porous cracking catalyst E was tested according to the same reaction performance evaluation method for direct conversion of waste plastics to light olefins as in step (3) of Example 1. The evaluation results are listed in Table 1.

[0132] Example 6

[0133] This embodiment is intended to illustrate the porous cracking catalyst prepared by the present invention and its application in the reaction of producing light olefins from waste plastics.

[0134] Ultra-macroporous silica gel A was prepared in the same manner as in step (1) of Example 1.

[0135] (2) Preparation of porous cracking catalyst

[0136] At 60 °C, firstly, the pseudo-boehmite powder of model P-DF-03-LS (produced by Shandong Aluminum Co., Ltd., with a specific surface area of ​​257m 2 / g, pore volume 0.32cm 3 / g) was mixed with deionized water, stirred for 1 hour, and then phosphoric acid was added. After stirring for another 1 hour, silica sol was added. After stirring evenly, the template agent N,N-diisopropylethylamine was slowly added dropwise. In the mixed system, n(Al2O3):n(SiO2):n(P2O5):n(C8H 19 The molar ratio of (N):n(H2O) was 1:0.2:0.4:0.8:25. After the template was added, the mixture was stirred at 60°C for 1 hour to produce a gel mixture. The gel mixture was then transferred to a polytetrafluoroethylene-lined hydrothermal autoclave for a first crystallization treatment. The first crystallization treatment was performed at 170°C for 12 hours. The resulting mixed slurry was uniformly mixed with ultraporous silica gel A (the weight ratio of ultraporous silica gel to mixed slurry was 1:10.7) and then subjected to a second crystallization treatment. The second crystallization treatment was performed at 170°C for 60 hours. After crystallization, the solid product obtained by centrifugation was washed six times with deionized water, dried at 110°C for 10 hours, and then calcined at 550°C for 16 hours to produce mixed molecular sieve F.

[0137] 2.9 g of calcium nitrate was dissolved in 60 g of deionized water, 9.0 g of the above-mentioned mixed molecular sieve F was added, and the mixture was stirred at 50°C for 6 h. The solid product obtained after removing moisture using a rotary evaporator was dried at 110°C for 12 hours and calcined at 600°C for 8 hours to obtain a porous cracking catalyst F.

[0138] Based on the total weight of the porous cracking catalyst F, the content of SAPO-18 molecular sieve is 60% by weight, the content of ultra-large pore silica gel is 30% by weight, and the content of calcium oxide is 10%.

[0139] The specific surface area of ​​porous cracking catalyst F is 450m2 / g, pore volume 0.68cm 3 / g, and the most probable pore diameters are 0.41nm, 3.1nm and 28nm respectively.

[0140] The reaction performance of Catalyst F was tested using the same reaction performance evaluation method for direct conversion of waste plastics to light olefins as in step (3) of Example 1. The evaluation results are listed in Table 1.

[0141] Example 7

[0142] This embodiment is intended to illustrate the porous cracking catalyst prepared by the present invention and its application in the reaction of producing light olefins from waste plastics.

[0143] Ultra-macroporous silica gel B was prepared in the same manner as in step (1) of Example 2.

[0144] (2) Preparation of porous cracking catalyst

[0145] At a temperature of 40°C, the German imported pseudo-boehmite powder of model SB (purchased from Beijing Asia Pacific Aohua Chemical Additives Co., Ltd., with a specific surface area of ​​241m 2 / g, pore volume 0.53cm 3 / g) was mixed with deionized water, stirred for 1 hour, and then phosphoric acid was added. After stirring for another 1 hour, silica sol was added. After stirring evenly, the template agent N,N-diisopropylethylamine was slowly added dropwise. In the mixed system, n(Al2O3):n(SiO2):n(P2O5):n(C8H 19 The molar ratio of (N):n(H2O) was 1:1.2:1.5:2.4:85. After the template was added, the mixture was stirred at 40°C for 3 hours to obtain a gel mixture. The gel mixture was then transferred to a polytetrafluoroethylene-lined hydrothermal reactor for the first crystallization treatment. The first crystallization treatment was performed at 160°C for 16 hours. The resulting mixed slurry was uniformly mixed with ultraporous silica gel B (the weight ratio of ultraporous silica gel to mixed slurry was 1:2.9) and then subjected to a second crystallization treatment. The second crystallization treatment was performed at 160°C for 72 hours. After crystallization, the solid product obtained by centrifugation was washed eight times with deionized water, dried at 130°C for 3 hours, and then calcined at 600°C for 8 hours to obtain mixed molecular sieve G.

[0146] 1.3 g of magnesium nitrate hexahydrate was dissolved in 180 g of deionized water, 9.8 g of the above-mentioned mixed molecular sieve G was added, and the mixture was stirred at 90°C for 2 h. The solid product obtained after removing moisture using a rotary evaporator was dried at 120°C for 4 hours and calcined at 650°C for 5 hours to obtain a porous cracking catalyst G.

[0147] Based on the total weight of the porous cracking catalyst G, the content of SAPO-18 molecular sieve is 28 weight percent, the content of ultra-large pore silica gel is 70 weight percent, and the content of magnesium oxide is 2 percent.

[0148] The specific surface area of ​​porous cracking catalyst G is 380m 2 / g, pore volume 1.05cm 3 / g, and the most probable pore diameters are 0.42nm, 3.3nm and 33nm respectively.

[0149] The reaction performance of the porous cracking catalyst G was tested according to the same reaction performance evaluation method for direct conversion of waste plastics to light olefins as in step (3) of Example 1. The evaluation results are listed in Table 1.

[0150] Comparative Example 1

[0151] Ultra-macroporous silica gel A was prepared in the same manner as in step (1) of Example 1.

[0152] (2) Preparation of porous cracking catalyst

[0153] At 60 °C, firstly, the pseudo-boehmite powder of model P-DF-03-LS (produced by Shandong Aluminum Co., Ltd., with a specific surface area of ​​257m 2 / g, pore volume 0.32cm 3 / g) was mixed with deionized water, stirred for 1 hour, and then phosphoric acid was added. After stirring for another 1 hour, silica sol was added. After stirring evenly, the template agent N,N-diisopropylethylamine was slowly added dropwise. In the mixed system, n(Al2O3):n(SiO2):n(P2O5):n(C8H 19 The molar ratio of (N):n(H2O) was 1:0.6:0.9:1.6:60. After the template was added, the mixture was stirred at 60°C for 1 hour to produce a gel mixture. The gel mixture was then transferred to a polytetrafluoroethylene-lined hydrothermal autoclave for a first crystallization treatment at 170°C for 12 hours. The resulting mixed slurry was uniformly mixed with ultraporous silica gel A (the weight ratio of ultraporous silica gel to mixed slurry was 1:0.5) and then subjected to a second crystallization treatment at 170°C for 60 hours. After crystallization, the solid product obtained by centrifugation was washed six times with deionized water, dried at 110°C for 10 hours, and then calcined at 550°C for 16 hours to produce mixed molecular sieve D1.

[0154] Porous cracking catalyst D1 was prepared by the following steps: 2.4 g of strontium nitrate was dissolved in 50 g of deionized water, 8.8 g of the mixed molecular sieve D1 prepared in the above step was added, and the mixture was stirred at 50 °C for 6 h. After removing the water by using a rotary evaporator, the obtained solid product was dried at 110 °C for 12 h and calcined at 600 °C for 8 h to obtain the porous cracking catalyst D1.

[0155] The content of SAPO-18 molecular sieve was 6 wt%, the content of the ultra-large pore silica gel was 82 wt%, and the content of strontium oxide was 12% based on the total weight of the porous cracking catalyst D1.

[0156] The specific surface area of the porous cracking catalyst D1 was 318 m 2 / g, and the pore volume was 1.33 cm 3 / g.

[0157] The reaction performance of the porous cracking catalyst D1 was tested according to the same method of direct conversion of waste plastics to light olefins in step (3) of Example 1, and the evaluation results are shown in Table 1.

[0158] Comparative Example 2

[0159] The ultra-large pore silica gel B was prepared according to the same method as in step (1) of Example 2.

[0160] (2) Preparation of the porous cracking catalyst

[0161] Firstly, the pseudo-boehmite powder of SB type (purchased from Beijing Yatopu Aohua Chemical Auxiliary Co., Ltd., the specific surface area was 241 m 2 / g, and the pore volume was 0.53 cm 3 / g) was mixed with deionized water at a temperature of 40 °C, and stirred for 1 h. Then, phosphoric acid was added, and the mixture was stirred for another 1 h. Subsequently, silica sol was added, and the mixture was stirred uniformly. Then, the template N, N-diisopropyl ethylamine was slowly added dropwise. The molar ratio of n (Al2O3) : n (SiO2) : n (P2O5) : n (C8H 19 N) : n (H2O) in the mixed system was 1:0.4:0.7:1.3:50. After the template was added dropwise, the mixed system was continuously stirred at 40 °C for 3 h to obtain a gel mixture. Then, the gel mixture was transferred into a hydrothermal kettle with a polytetrafluoroethylene liner to perform a first crystallization treatment. The temperature of the first crystallization treatment was 160 °C, and the time was 16 h. The mixed slurry obtained after the first crystallization treatment was uniformly mixed with the ultra-large pore silica gel B (the weight ratio of the ultra-large pore silica gel to the mixed slurry was 1:32) to perform a second crystallization treatment. The temperature of the second crystallization treatment was 160 °C, and the time was 72 h. After the crystallization was completed, the solid product obtained by centrifugal filtration was washed with deionized water for 8 times. The solid product was dried at 130 °C for 3 h, and then calcined at 600 °C for 8 h to obtain the mixed molecular sieve D2.

[0162] 0.2 g of barium nitrate was dissolved in 200 g of deionized water, 9.9 g of the above-mentioned mixed molecular sieve D2 was added, and the mixture was stirred at 90°C for 2 h. The solid product obtained after removing moisture using a rotary evaporator was dried at 120°C for 4 hours and calcined at 650°C for 5 hours to obtain a porous cracking catalyst D2.

[0163] Based on the total weight of the porous cracking catalyst D2, the content of SAPO-18 molecular sieve was 81% by weight, the content of ultra-large pore silica gel was 18% by weight, and the content of barium oxide was 1%.

[0164] The specific surface area of ​​porous cracking catalyst D2 is 511m 2 / g, pore volume 0.45cm 3 / g.

[0165] The reaction performance of the porous cracking catalyst D2 was tested using the same reaction performance evaluation method for direct conversion of waste plastics to light olefins as in step (3) of Example 1. The evaluation results are listed in Table 1.

[0166] Comparative Example 3

[0167] Ultra-macroporous silica gel A was prepared in the same manner as in step (1) of Example 1.

[0168] Eliminate step (2) in Example 1.

[0169] The reaction performance of ultra-large pore silica gel A was tested using the same reaction performance evaluation method for direct conversion of waste plastics to light olefins as in step (3) of Example 1. The evaluation results are listed in Table 1.

[0170] Comparative Example 4

[0171] The catalyst was prepared in the same manner as in Example 1, except that:

[0172] Eliminate step (1) in Example 1.

[0173] Preparation of SAPO-18 molecular sieve, the specific process is as follows:

[0174] At 60 °C, firstly, the pseudo-boehmite powder of model P-DF-03-LS (produced by Shandong Aluminum Co., Ltd., with a specific surface area of ​​257m 2 / g, pore volume 0.32cm 3 / g) was mixed with deionized water, stirred for 1 hour, and then phosphoric acid was added. After stirring for another 1 hour, silica sol was added. After stirring evenly, the template agent N,N-diisopropylethylamine was slowly added dropwise. In the mixed system, n(Al2O3):n(SiO2):n(P2O5):n(C8H 19The molar ratio of N):n(H20):n(Na20):n(TPAOH):n(H2O) was 1:0.6:0.9:1.6:60. After the template was added dropwise, the mixed system was continuously stirred at 60°C for 1 h to obtain a gel mixture. Then the gel mixture was transferred into a hydrothermal kettle with a polytetrafluoroethylene liner for crystallization treatment. The crystallization treatment was carried out at a temperature of 170°C for 72 h. After the crystallization was completed, the obtained solid product was centrifugally filtered, washed with deionized water for 6 times, dried at 110°C for 10 h, and then calcined at 550°C for 16 h to obtain SAPO-18 molecular sieves.

[0175] The specific surface area of the SAPO-18 molecular sieves was 558 m 2 / g, and the pore volume was 0.24 cm 3 / g.

[0176] The reaction performance of the SAPO-18 molecular sieves was tested according to the same method of Example 1, step (3) for the direct conversion of waste plastics to light olefins, and the evaluation results are shown in Table 1.

[0177] Comparative Example 5

[0178] The SAPO-18 molecular sieves were prepared according to the method of Comparative Example 4.

[0179] 1.8 g of calcium nitrate was dissolved in 100 g of deionized water, 9.4 g of the above SAPO-18 molecular sieves was added, and the mixture was stirred at 50°C for 6 h. After removing the water by using a rotary evaporator, the obtained solid product was dried at 110°C for 12 h, and then calcined at 600°C for 8 h to obtain a cracking catalyst D3.

[0180] The content of the SAPO-18 molecular sieves was 94% by weight, and the content of calcium oxide was 6% based on the total weight of the cracking catalyst D3.

[0181] The specific surface area of the cracking catalyst D3 was 518 m 2 / g, and the pore volume was 0.21 cm 3 / g.

[0182] The reaction performance of the cracking catalyst D3 was tested according to the same method of Example 1, step (3) for the direct conversion of waste plastics to light olefins, and the evaluation results are shown in Table 1.

[0183] Comparative Example 6

[0184] The catalyst was prepared according to the same method of Example 1, except that:

[0185] Step (1) in Example 1 was cancelled.

[0186] The cracking catalyst D4 was prepared, and the specific process was as follows:

[0187] Pseudo-boehmite powder (produced by Shandong Aluminum Co., Ltd., specific surface area 257 m 2 / g, pore volume 0.32 cm 3 / g) was first mixed with deionized water at a temperature of 60°C, stirred for 1 h, then phosphoric acid was added, stirred for another 1 h, then silica sol was added, stirred uniformly, and then the template N,N-diisopropyl ethylamine was slowly added dropwise. The molar ratio of n(Al2O3):n(SiO2):n(P2O5):n(C8H 19 N):n(H2O) in the mixed system was 1:0.6:0.9:1.6:60. After the template was added dropwise, the mixed system was stirred at 60°C for 1 h to obtain a gel mixture. The gel mixture was then transferred into a hydrothermal kettle with a polytetrafluoroethylene liner to perform a first crystallization treatment. The temperature of the first crystallization treatment was 170°C, and the time was 12 h. The mixed slurry obtained after the first crystallization treatment was uniformly mixed with silica powder (laboratory-made, specific surface area 274 m 2 / g, pore volume 0.57 cm 3 / g) (the weight ratio of the large-pore silica gel to the mixed slurry was 1:6.4) to perform a second crystallization treatment. The temperature of the second crystallization treatment was 170°C, and the time was 60 h. After the crystallization was completed, the solid product obtained by centrifugal filtration was washed with deionized water for 6 times, the solid product was dried at 110°C for 10 h, and then calcined at 550°C for 16 h to obtain a mixed molecular sieve.

[0188] 1.2 g of calcium nitrate was dissolved in 100 g of deionized water, 9.6 g of the above mixed molecular sieve was added, stirred at 50°C for 6 h, and then the solid product obtained after water was removed using a rotary evaporator was dried at 110°C for 12 h and calcined at 600°C for 8 h to obtain a cracking catalyst D4.

[0189] Based on the total weight of the cracking catalyst D4, the content of the SAPO-18 molecular sieve was 45 wt%, the content of the silica was 51 wt%, and the content of the calcium oxide was 4%.

[0190] The reaction performance of the composite material D4 was tested according to the same method for evaluating the reaction performance of the direct conversion of waste plastics to low-carbon olefins in step (3) in Example 1, and the evaluation results are shown in Table 1.

[0191] Table 1

[0192]

[0193]

[0194] The above results show that the porous cracking 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.

[0195] In Comparative Example 1, the ultra-large pore silica gel content was too high, the SAPO-18 molecular sieve content was too low, and the modified oxide content was also outside the range specified in the present invention. Due to the small number of acidic sites on the catalyst, insufficient activation sites during the reaction resulted in low feedstock conversion and low light olefin yields.

[0196] In Comparative Example 2, the ultra-large pore silica gel content was too low, the SAPO-18 molecular sieve content was too high, and the modified oxide content was significantly below the range specified in the present invention. Due to the limited number of mesopores in the catalyst, the diffusion of reactant and product molecules during the reaction was hindered, making it impossible to effectively suppress side reactions, resulting in a low yield of light olefins.

[0197] In Comparative Example 3, only ultra-large pore silica gel was used as the cracking catalyst without adding SAPO-18 molecular sieve. Since there were almost no active acidic centers on the catalyst, the raw material conversion rate and the yield of light olefins were low.

[0198] In Comparative Example 4, only SAPO-18 molecular sieve was used as the cracking catalyst, without the addition of ultra-macroporous silica or modification. Because the catalyst lacks mesoporous channels, diffusion of reactant and product molecules is hindered during the reaction, and the distribution of surface acidic sites is irrational, resulting in a low yield of light olefins.

[0199] In Comparative Example 5, only the modified SAPO-18 molecular sieve was used as the cracking catalyst without the addition of ultra-macroporous silica. Because the catalyst lacked mesoporous channels, diffusion of reactant and product molecules was hindered during the reaction, resulting in a low yield of light olefins.

[0200] In Comparative Example 6, silica powder was used instead of ultra-large pore silica gel. Since silica has a lower specific surface area, a smaller pore volume, and an irregular pore structure, its dispersion effect is significantly lower than that of ultra-large pore silica gel, resulting in a lower yield of light olefins in the cracking catalyst prepared.

[0201] 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 porous cracking catalyst in the direct catalytic cracking of waste plastics to produce light olefins, wherein: The application comprises: contacting waste plastic powder or particles with a porous cracking catalyst for reaction, wherein the porous cracking catalyst comprises SAPO-18 molecular sieve, ultra-large pore silica gel and modified oxide, and based on the total weight of the porous cracking catalyst, the content of the SAPO-18 molecular sieve is 28-60% by weight, the content of the ultra-large pore silica gel is 30-70% by weight, and the content of the modified oxide is 2-10% by weight; The specific surface area of ​​the porous cracking catalyst is 380-450m 2 / g, the pore volume is 0.68-1.05mL / g, the pore size distribution is trimodal distribution, and the most probable pore sizes corresponding to the three peaks are 0.38-0.45nm, 2-4.5nm and 15-45nm, respectively.

2. The use according to claim 1, wherein Based on the total weight of the porous cracking catalyst, the content of the SAPO-18 molecular sieve is 32-56 weight %, the content of the ultra-large pore silica gel is 35-65 weight %, and the content of the modified oxide is 3-9 weight %.

3. The use according to claim 2, wherein: Based on the total weight of the porous cracking catalyst, the content of the SAPO-18 molecular sieve is 36-52 weight %, the content of the ultra-large pore silica gel is 40-60 weight %, and the content of the modified oxide is 4-8 weight %.

4. The use according to any one of claims 1 to 3, wherein: The specific surface area of ​​the porous cracking catalyst is 388-445m 2 / g, the pore volume is 0.76-1.00 mL / g, the pore size distribution is trimodal, and the most probable pore sizes corresponding to the three peaks are 0.39-0.44 nm, 2.5-4 nm and 20-38 nm, respectively.

5. The use according to claim 4, wherein: The specific surface area of ​​the porous cracking catalyst is 394-440m 2 / g, the pore volume is 0.84-0.93 mL / g, the pore size distribution is trimodal, and the most probable pore sizes corresponding to the three peaks are 0.4-0.42 nm, 2.8-3.4 nm and 25-32 nm, respectively.

6. The use according to claim 1 or 3, wherein: The modifying oxide is selected from alkaline earth metal oxides.

7. The use according to claim 6, wherein: The modified oxide is selected from one or more of calcium oxide, magnesium oxide, strontium oxide and barium oxide.

8. The use according to any one of claims 1 to 3, wherein: The specific surface area of ​​the ultra-large pore silica gel is 200-500m 2 / g, the pore volume is 1-2mL / g, the pore size is bimodal distribution, the first most probable pore size is 2-5nm, and the second most probable pore size is 20-50nm.

9. The use according to any one of claims 1 to 3, wherein: The preparation method of the ultra-macroporous silica gel comprises: In the presence of butanol and glycerol, an inorganic silicon source is contacted with an acid agent, and the resulting mixture is filtered and washed to obtain a silica gel filter cake; the silica gel filter cake is then dried, calcined and ball-milled to obtain ultra-macroporous silica gel.

10. The use according to claim 9, wherein: The inorganic silicon source is selected from one or more of water glass, sodium metasilicate and silica sol; And / or, the weight ratio of the inorganic silicon source, acid agent, butanol and glycerol is 1: (0.05-0.5): (0.02-0.6): (0.02-0.6).

11. The use according to claim 10, wherein: The weight ratio of the inorganic silicon source, the acid agent, butanol and glycerol is 1: (0.1-0.3): (0.06-0.4): (0.06-0.4).

12. The use according to any one of claims 1 to 3, wherein: The preparation method of the porous cracking catalyst comprises: (1) mixing a template, an aluminum source, a phosphorus source, a silicon source and water and performing a contact reaction to obtain a gel mixture; performing a first crystallization treatment on the gel mixture to obtain a mixed slurry; mixing the mixed slurry with ultra-large pore silica gel and performing a second crystallization treatment; separating, washing, drying and calcining the product after the crystallization treatment to obtain a mixed molecular sieve; (2) The mixed molecular sieve is immersed in an aqueous solution containing a modified oxide precursor, and the solid product after removing moisture is dried and calcined to obtain a porous cracking catalyst.

13. The use according to claim 12, wherein: In step (1), the template is N,N-diisopropylethylamine; And / or, the aluminum source is selected from one or more of pseudo-boehmite, aluminum hydroxide, basic aluminum sol, aluminum isopropoxide, basic aluminum acetate, gibbsite and boehmite; And / or, the phosphorus source is an inorganic acid or acid salt containing phosphorus; And / or, the silicon source is an organic silicon source and / or an inorganic silicon source; And / or, the aluminum source is calculated as Al2O3, the silicon source is calculated as SiO2, the phosphorus source is calculated as P2O5, and the molar ratio of the template to water is 1: (0.1-2): (0.2-2.5): (0.5-3): (10-150); And / or, the weight ratio of the ultra-macroporous silica gel to the mixed slurry is 1:(2-15).

14. The use according to claim 13, wherein: The phosphorus source is one or more of phosphoric acid, phosphorous acid, ammonium dihydrogen phosphate and ammonium monohydrogen phosphate; And / or, the silicon source is one or more of tetramethyl silicate, tetraethyl silicate, tetraisopropyl silicate, tetrabutyl silicate, silica sol, water glass and white carbon black; And / or, the weight ratio of the ultra-macroporous silica gel to the mixed slurry is 1:(3-10).

15. The use according to claim 13, wherein: The conditions of the contact reaction include: a temperature of 20-100°C; And / or, the conditions for the first crystallization include: temperature of 140-200° C., time of 2-24 h; And / or, the conditions for the second crystallization include: temperature of 140-200° C., time of 20-100 h; And / or, the calcination conditions include: temperature of 450-650° C. and time of 5-50 h.

16. The use according to claim 15, wherein: The conditions for the contact reaction include: a temperature of 40-80°C.

17. The use according to claim 13, wherein: In step (2), the modified oxide precursor is an inorganic salt of an alkaline earth metal; and / or, the mass concentration of the aqueous solution containing the modified oxide precursor is 0.3-5%; and / or, the weight ratio of the mixed molecular sieve to the aqueous solution containing the modified oxide precursor is 1:(5-20); And / or, the calcination conditions include: temperature of 500-700° C. and time of 3-20 h.

18. The use according to claim 17, wherein: The alkaline earth metal is selected from one or more of calcium, magnesium, strontium and barium.

19. 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 porous cracking catalyst to the waste plastic powder or particles is 1:(0.5-50).

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