Double-hole composite molecular sieve, preparation method thereof and application of double-hole composite molecular sieve in direct catalytic cracking of waste plastics to produce low-carbon olefins

Abstract

The application relates to the field of catalysts and the field of recycling of high polymer materials, and discloses a double-hole composite molecular sieve, a preparation method thereof and application of the double-hole composite molecular sieve in a reaction of directly catalytically cracking waste plastics to prepare low-carbon olefins. The double-hole composite molecular sieve comprises SAPO-5 molecular sieve and cubic single-crystal full-silicon mesoporous molecular sieve, and the content of the SAPO-5 molecular sieve is 50-74% by weight and the content of the cubic single-crystal full-silicon mesoporous molecular sieve is 26-50% by weight based on the total weight of the double-hole composite molecular sieve. In the reaction of directly catalytically cracking waste plastics to prepare low-carbon olefins, the double-hole composite molecular sieve not only solves the problem of recycling of waste plastics, but also increases the yield of important chemical raw materials, i.e. low-carbon olefins.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalysts and the field of recycling of high molecular materials, in particular, to a double-pore composite molecular sieve, a preparation method thereof and application of the double-pore composite molecular sieve in a reaction of direct catalytic cracking of waste plastics to produce low-carbon olefins. BACKGROUND

[0002] Plastic products have the characteristics of light weight, high strength, corrosion resistance, good chemical stability, easy processing and aesthetic and practicality, and are widely used in various fields worldwide. However, plastics are difficult to degrade naturally, and conventional landfill technology, although it has low investment and simple operation, will occupy a large amount of land and cause land pollution. Incineration technology can achieve the requirement of reduction, and at the same time, part of the energy can be recovered, but this process can easily release a large amount of hydrocarbons, nitrogen compounds, sulfur compounds and toxic substances, which directly threaten the health of human beings and the ecological environment. Therefore, the recycling and high-value utilization of waste plastics, as a measure to save energy and protect the environment, have been widely valued by countries around the world. The main methods of waste plastic recycling and utilization include classification recycling, production of monomer raw materials, production of clean fuel and power generation.

[0003] In the prior art, the main scheme of chemical recycling of waste plastics is waste plastic cracking technology. Waste plastic cracking includes three basic methods, namely thermal cracking method (one-stage method), catalytic cracking method (one-stage method) and thermal cracking-catalytic upgrading method (two-stage method). The earliest developed waste plastic cracking technology is thermal cracking technology. This technology refers to a thermal conversion process in which the macromolecular organic matter in waste plastic products is converted into small molecular liquid matter, fuel gas and coke under high-temperature and anaerobic conditions. The reaction temperature of this process is generally controlled at 350-900℃. If a catalyst is added during the thermal cracking process, it is a catalytic thermal cracking technology, which can not only reduce the cracking temperature, but also improve the product performance. The thermal cracking-catalytic upgrading method is an improvement of the catalytic cracking method, which uses a catalyst to catalytically upgrade the cracking gas after thermal cracking of waste plastics. This method has higher product quality, flexible operation and low operating cost than the thermal cracking method and the catalytic cracking method, but the process is more complex.

[0004] The cracking technology has wide flexibility in treating waste plastics, good energy recovery, and is one of the waste plastic treatment technologies with wide application prospect. In the prior art, the products produced by one-step thermal cracking method and one-step catalytic cracking method are mainly fuel oil, and only a small amount of low-carbon olefins (ethylene, propylene, butene) can be obtained.

[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

[0006] The present application aims at the current situation that the low-carbon olefin content is less in the recycling of waste plastics by chemical recycling, and provides a dual-pore composite molecular sieve, a preparation method thereof and application of the dual-pore composite molecular sieve in a reaction of directly catalytic cracking of waste plastics to produce low-carbon olefin. The dual-pore composite molecular sieve solves the problem of recycling of waste plastics and increases the production of important chemical raw material low-carbon olefin in the reaction of directly catalytic cracking of waste plastics to produce low-carbon olefin, and is a new one-step catalytic conversion and utilization way of waste plastics.

[0007] In order to achieve the above-mentioned purpose, the present application provides a dual-pore composite molecular sieve, wherein the dual-pore composite molecular sieve comprises SAPO-5 molecular sieve and cubic single-crystal all-silica mesoporous molecular sieve, and the content of the SAPO-5 molecular sieve is 50-74 wt% and the content of the cubic single-crystal all-silica mesoporous molecular sieve is 26-50 wt% based on the total weight of the dual-pore composite molecular sieve.

[0008] The present application provides a preparation method of the dual-pore composite molecular sieve, wherein the preparation method comprises:

[0009] (1) mixing triethylamine, an aluminum source, a phosphorus source, a silicon source and water and performing contact reaction to obtain a gel mixture;

[0010] (2) performing first crystallization treatment on the gel mixture to obtain a mixed slurry, adding cubic single-crystal all-silica mesoporous molecular sieve, mixing and performing second crystallization treatment; and performing separation, washing, drying and calcination treatment on the obtained product to obtain the dual-pore composite molecular sieve.

[0011] The present application provides application of the aforementioned dual-pore composite molecular sieve in a reaction of directly catalytic cracking of waste plastics to produce low-carbon olefin.

[0012] Compared with the prior art, the technical scheme of the present application has the following advantages:

[0013] (1) The dual-pore composite molecular sieve provided by the present application comprises SAPO-5 microporous molecular sieve with appropriate weak acid centers on the surface and all-silica mesoporous material with large pore size, and has stable structure and good high-temperature resistance, which is helpful to diffusion of raw material and product molecules in the cracking reaction.

[0014] (2) In the preparation process of the dual-pore composite molecular sieve provided by the present application, the mother liquor after the first crystallization of the SAPO-5 molecular sieve is mixed with the cubic single-crystal all-silica mesoporous molecular sieve after ball milling, and the second crystallization is performed, so that the micropore channels and mesopore channels in the directly obtained dual-pore composite molecular sieve are uniformly distributed.

[0015] (3) The double-pore composite molecular sieve provided by the application can convert waste plastics into low-carbon olefins in one step in the reaction of waste plastics direct catalytic cracking to produce low-carbon olefins, and is a new method for chemical recycling of waste plastics. Both the problem of waste plastic recycling and the production of important chemical raw material low-carbon olefins are solved, and good economic benefits are obtained.

[0016] (4) The double-pore composite molecular sieve provided by the application has mild process conditions, is easy to operate, and has low requirements for the reaction device in the reaction of waste plastics direct catalytic cracking to produce low-carbon olefins.

[0017] Other features and advantages of the present application will be described in detail in the following specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0018] The accompanying drawings are included to provide a further understanding of the application, and constitute a part of the specification, and are used together with the following specific embodiments to explain the application, but do not constitute a limitation on the application. In the drawings:

[0019] Figure 1 is a small-angle X-ray diffraction (XRD) spectrum of the double-pore composite molecular sieve A prepared in Example 1;

[0020] Figure 2 is a wide-angle X-ray diffraction (XRD) spectrum of the double-pore composite molecular sieve A prepared in Example 1;

[0021] Figure 3 is a pore size distribution graph of the double-pore composite molecular sieve A prepared in Example 1. DETAILED DESCRIPTION

[0022] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The ranges or values should be construed to be approximations that allow for significant variation. Various ranges of values that are explicitly delineated in the specification as supplied herein are not to be limited to the specific numerical values stated. The endpoints of these ranges and any values between these endpoints are included as if explicitly written herein. Any numerical value, however, can only be approximations.

[0023] In a first aspect, the present application provides a double-pore composite molecular sieve, wherein the double-pore composite molecular sieve comprises SAPO-5 molecular sieve and cubic single-crystal all-silica mesoporous molecular sieve, and the content of the SAPO-5 molecular sieve is 50-74 wt%, and the content of the cubic single-crystal all-silica mesoporous molecular sieve is 26-50 wt% based on the total weight of the double-pore composite molecular sieve.

[0024] The inventors of the present application found that there is no process for directly catalytic cracking of waste plastics to produce low-carbon olefins (including ethylene, propylene, butene) in the prior art, and one of the purposes of the present application is to solve this problem. According to the understanding of the inventors on the physical and chemical properties of the heterogeneous catalyst, the catalyst for directly preparing low-carbon olefins by catalytic cracking of waste plastics should have a certain acidity but the acidity cannot be too strong. In addition, the waste plastics catalytic cracking catalyst needs to have good thermal stability. SAPO-5 molecular sieve not only has relatively weak acidity, but also has relatively good thermal stability (the crystal phase can still remain stable after high-temperature calcination at 650 DEG C), and is a relatively suitable waste plastics catalytic cracking catalyst. However, the pore size of SAPO-5 molecular sieve is generally below 1.5 nm, which seriously limits the improvement of the catalytic performance of SAPO-5 molecular sieve. The main reason is that SAPO-5 is a microporous molecular sieve, the pore size is small, and the pore volume is also small, while the molecular weight of the waste plastics product is large, and the molecular chain is also relatively long. During the cracking reaction of the waste plastics product, the large-sized reactant molecules and product molecules are difficult to diffuse in the narrow pore channel, which not only affects the contact between the reactants and the active centers, but also easily leads to the occurrence of deep dehydrogenation and other side reactions, thereby causing the performance of the catalyst to decrease. Compared with the microporous molecular sieve, the cubic single crystal all-silica mesoporous molecular sieve material has a larger pore size (the pore size is between 5-10 nm) and a larger pore volume (which can reach 0.8 cm 3 / g or more), and is very suitable for catalytic reactions involving macromolecules. However, the cubic single crystal all-silica mesoporous molecular sieve is an all-silica material, and the surface only contains a small amount of silicon hydroxyl groups, so the acidity is extremely weak, and it is not suitable for being used alone as a catalyst to catalyze the waste plastics cracking reaction. The inventors of the present application found during the development and research of the waste plastics cracking catalyst that if the structural advantages of the all-silica mesoporous inorganic material and the surface acid center of the microporous molecular sieve are comprehensively utilized, a certain amount of cubic single crystal all-silica mesoporous molecular sieve is mixed with SAPO-5 molecular sieve, the specific surface area and the pore volume of the catalyst can be effectively improved, and the internal diffusion performance in the reaction can be significantly improved. When applied to the catalytic conversion reaction of waste plastics as a cracking catalyst, not only the activity of the cracking catalyst can be effectively improved, but also the selectivity of low-carbon olefins can be increased.

[0025] According to the present application, preferably, the content of the SAPO-5 molecular sieve is 54-70 wt% and the content of the cubic single crystal all-silica mesoporous molecular sieve is 30-46 wt% based on the total weight of the dual-pore composite molecular sieve; more preferably, the content of the SAPO-5 molecular sieve is 58-66 wt% and the content of the cubic single crystal all-silica mesoporous molecular sieve is 34-42 wt% based on the total weight of the dual-pore composite molecular sieve. In the present application, the use of the specific content of each component can make the dual-pore composite molecular sieve prepared have better catalytic activity and higher selectivity of low-carbon olefins when used in the reaction of directly catalytic cracking of waste plastics to prepare low-carbon olefins.

[0026] According to the present application, the specific surface area of the dual-pore composite molecular sieve is 350-500 m 2 / g, the pore volume is 0.50-0.80 mL / g, the pore size distribution is bimodal distribution, and the most probable pore sizes corresponding to the bimodal distribution are 0.5-1.1 nm and 5-10 nm, respectively; preferably, the specific surface area of the dual-pore composite molecular sieve is 380-470 m 2 / g, the pore volume is 0.6-0.74 mL / g, the pore size distribution is bimodal distribution, and the most probable pore sizes corresponding to the bimodal distribution are 0.6-0.9 nm and 6-9 nm, respectively; more preferably, the specific surface area of the dual-pore composite molecular sieve is 410-447 m 2 / g, the pore volume is 0.64-0.7 mL / g, the pore size distribution is bimodal distribution, and the most probable pore sizes corresponding to the bimodal distribution are 0.7-0.8 nm and 7-8 nm, respectively. In the present application, when the dual-pore composite molecular sieve has the specific structural parameters described above, it can be used in the reaction of preparing low-carbon olefins by direct catalytic cracking of waste plastics, and has better catalytic activity and higher selectivity of low-carbon olefins.

[0027] According to the present application, the specific surface area of the cubic single-crystal full-silica mesoporous molecular sieve is 500-900 m 2 / g, the pore volume is 0.8-1.4 mL / g, and the average pore size is 5-10 nm; preferably, the specific surface area of the cubic single-crystal full-silica mesoporous molecular sieve is 679-734 m 2 / g, the pore volume is 1-1.2 mL / g, and the average pore size is 7-8 nm.

[0028] According to the present application, the preparation method of the cubic single-crystal full-silica mesoporous molecular sieve comprises:

[0029] (S1) mixing a template agent, potassium sulfate, an acidic aqueous solution and a silicon source under hydrolysis gel preparation conditions to obtain a gel mixture;

[0030] (S2) performing crystallization treatment on the gel mixture, and then performing filtration, washing and drying treatment to obtain a cubic single-crystal full-silica mesoporous molecular sieve raw powder;

[0031] (S3) sequentially performing a template removal treatment and a ball milling treatment on the cubic single-crystal full-silica mesoporous molecular sieve raw powder to obtain a cubic single-crystal full-silica mesoporous molecular sieve.

[0032] According to the present application, the template agent can be various kinds of triblock copolymer polyoxyethylene-polyoxypropylene-polyoxyethylene template agents commonly used in the art, and is preferably P108 (molecular formula: EO 132 PO 60 EO 132 ).

[0033] According to the present application, the acidic aqueous solution is preferably an aqueous inorganic acid solution, including an aqueous sulfuric acid solution, an aqueous hydrochloric acid solution, an aqueous hydrobromic acid solution and an aqueous nitric acid solution, and more preferably an aqueous hydrochloric acid solution.

[0034] According to the present application, the silicon source can be a silicon-containing organic compound or a silicon-containing inorganic compound; preferably a silicon-containing organic compound; and more preferably one or more of tetraethyl orthosilicate, tetramethyl orthosilicate or tetra-n-butyl orthosilicate.

[0035] According to the present application, the molar ratio of the template agent, potassium sulfate, silicon source, water and hydrogen chloride is 1:(50-500):(50-300):(5000-50000):(200-2000), and preferably 1:(100-300):(100-200):(10000-30000):(500-1500).

[0036] According to the present application, the conditions of the hydrolysis and gelation process include a temperature of 25-60℃ and a time of 10-200min; preferably a temperature of 30-55℃ and a time of 10-60min. In a preferred embodiment, in order to achieve better mixing effect, rapid stirring or ultrasonic means can be used to improve the mixing efficiency during the hydrolysis and gelation process.

[0037] According to the present application, the crystallization process can be carried out in a hydrothermal reactor equipped with a polytetrafluoroethylene lining, and the crystallization conditions are a crystallization temperature of 25-60℃ and a crystallization time of 10-72h; preferably a temperature of 30-55℃ and a time of 10-40h.

[0038] According to the present application, the washing conditions are not particularly limited, for example, the washing process can include repeatedly washing (the number of washing times can be 2-10) the solid product obtained after filtration with distilled water, and then performing suction filtration.

[0039] According to the present application, the drying conditions are preferably a drying temperature of 70-150℃ and a drying time of 3-20h; preferably a temperature of 100-130℃ and a time of 5-16h.

[0040] According to the present application, the template removal treatment process includes calcining the cubic single-crystal mesoporous molecular sieve raw powder in an air atmosphere; the template removal temperature is 400-700℃, and the template removal time is 8-50h; preferably the temperature is 500-600℃, and the time is 10-30h.

[0041] According to the application, the ball milling is carried out in a ball mill, wherein the diameter of the milling balls in the ball mill can be 2-3 mm; the number of the milling balls can be reasonably selected according to the size of the ball mill tank, and generally 2-8 milling balls can be used for a ball mill tank with a size of 100-300 mL; the material of the milling balls is agate or polytetrafluoroethylene, and preferably agate. The conditions of the ball milling include that the rotating speed of the milling balls can be 200-600 r / min, preferably 300-500 r / min; the temperature in the ball mill tank can be 30-90℃, preferably 40-80℃; and the time of the ball milling can be 5-50 h, preferably 8-24 h.

[0042] The second aspect of the application provides a preparation method of a dual-pore composite molecular sieve, wherein the preparation method comprises:

[0043] (1) mixing and contacting triethylamine, an aluminum source, a phosphorus source, a silicon source and water to obtain a gel mixture;

[0044] (2) carrying out a first crystallization treatment on the gel mixture to obtain a mixed slurry, adding a cubic single-crystal all-silica mesoporous molecular sieve, mixing and then carrying out a second crystallization treatment; and carrying out separation, washing, drying and calcination treatment on the obtained product to obtain the dual-pore composite molecular sieve.

[0045] The inventors of the application find that mixing a certain amount of cubic single-crystal all-silica mesoporous molecular sieve with SAPO-5 molecular sieve can effectively improve the specific surface area and pore volume of the catalyst and significantly improve the internal diffusion performance in the reaction. However, if the two prepared molecular sieves are mechanically mixed, the micropore channels and mesopore channels in the obtained mixed molecular sieve are not uniformly distributed, and the effect of improving the diffusion performance is not significant enough. In the application, the mother liquor after the initial crystallization of the SAPO-5 molecular sieve is mixed with the cubic single-crystal all-silica mesoporous molecular sieve after ball milling, and a secondary crystallization is carried out to obtain a dual-pore composite molecular sieve. The micropore channels and mesopore channels in the composite molecular sieve obtained by this method are uniformly distributed, and the composite molecular sieve has high catalytic activity and high selectivity of low-carbon olefins when used in waste plastic catalytic cracking reaction.

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

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

[0048] According to the present application, in step (1), the silicon source can be an organic silicon source 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.

[0049] According to the present application, in step (1), the molar ratio of the aluminum source (calculated as Al2O3), the phosphorus source (calculated as P2O5), the silicon source (calculated as SiO2), the triethylamine and water is 1:(0.5-3):(0.05-2):(0.2-4):(10-200), preferably 1:(0.8-1.6):(0.1-1):(0.5-2):(20-100).

[0050] According to the present application, in step (1), the conditions of the contact reaction include: temperature of 10-80℃, preferably 20-60℃; time of 0.1-10h, preferably 0.5-6h. 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.

[0051] According to the present application, in step (2), the conditions of the first crystallization include: temperature of 90-150℃, preferably 110-140℃; time of 3-30h, preferably 5-20h.

[0052] According to the present application, in step (2), the weight ratio of the cubic single-crystal full-silica mesoporous molecular sieve to the mixed slurry is 1:(4-24), preferably 1:(6-16).

[0053] According to the present application, in step (2), the conditions of the second crystallization include: temperature of 140-230℃, preferably 160-210℃; time of 10-100h, preferably 16-72h.

[0054] According to the present application, in step (2), 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, vacuumizing the bottom side of the funnel or using a centrifugal filter to filter.

[0055] According to the present application, in step (2), the method of 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 (2), 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 (2), the conditions of the calcination include: the temperature is 450-650℃, preferably 500-600℃; the time is 5-30h, preferably 8-20h.

[0058] In a third aspect, the present application provides an application of the dual-pore composite molecular sieve in a reaction of direct catalytic cracking of waste plastics to produce low-carbon olefins.

[0059] According to the present application, the application method of the dual-pore composite molecular sieve includes: contacting the waste plastic powder with the dual-pore composite molecular sieve under specific conditions.

[0060] According to the present application, the conditions of the contacting of the waste plastic powder with the dual-pore composite molecular sieve include: the temperature of the contacting can be 420-580℃, preferably 450-540℃; the pressure of the contacting can be 0.01-1Mpa, preferably 0.05-0.5Mpa; the time of the contacting can be 0.5-12h, preferably 1-5h; and the weight ratio of the dual-pore composite molecular sieve to the waste plastic powder can be 1:0.5-50, preferably 1:2-30.

[0061] The present application will be described in detail below through examples.

[0062] In the following examples and comparative examples:

[0063] The small-angle XRD test of the sample was performed on a high-power rotating target X-ray diffractometer of D8 ADVANCE type of BRUKER AXS company in Germany, and the scanning range was 0.5-10°.

[0064] The wide-angle XRD test of the sample was performed on an X-ray powder diffractometer of X’Pert MPD type of Philips company in the Netherlands, Cu Kα target, and the scanning range 2θ=5-90°.

[0065] The pore structure parameter analysis of the sample was performed on an adsorptometer of ASAP2020-M+C type purchased from Micromeritics company in the United States. The sample was vacuum degassed at 350℃ for 4 hours before determination, the specific surface area of the sample was calculated by BET method, and the pore volume was calculated by BJH model.

[0066] The elemental analysis experiment of the sample was performed on an energy dispersive X-ray fluorescence spectrometer of Eagle III produced by EDAX company in the United States.

[0067] The drying oven was produced by Shanghai Yiheng Scientific Instrument Co., Ltd., and the model was DHG-9030A.

[0068] The muffle furnace was produced by CARBOLITE company, and the model was CWF1100.

[0069] F108 used in the examples and comparative examples was purchased from Aldrich Company, and other reagents used in the examples and comparative examples were purchased from National Pharmaceutical Group Chemical Reagent Co., Ltd., and the purity of the reagents was analytical pure.

[0070] Example 1

[0071] This example is to illustrate the preparation of the dual-pore composite molecular sieve according to the present application.

[0072] (1) Preparation of cubic single-crystal all-silica mesoporous molecular sieve

[0073] 20 g (0.0014 mol) of template F108, 52.4 g (0.3 mol) of potassium sulfate, and 600 g of an aqueous hydrochloric acid solution (containing 1.2 mol of HCl) were mixed and stirred at 38°C until the F108 was completely dissolved; 41.6 g (0.2 mol) of tetraethyl orthosilicate was added to the above solution, and the stirring was continued at 38°C for 15 min, and the solution was left to stand at 38°C for crystallization for 24 h; the obtained solid product was washed with deionized water for 4 times, and after suction filtration, it was dried at 110°C for 10 h to obtain cubic single-crystal mesoporous molecular sieve raw powder. The above cubic single-crystal mesoporous molecular sieve raw powder was calcined at 500°C in air for 30 h to remove the template, and then was added to a 200 ml ball mill tank, 5 maroon grinding balls with a diameter of 2 mm were put into the tank, and the ball milling was started. The temperature in the ball mill tank was controlled at 50°C, the rotation speed of the grinding balls was 400 r / min, and the ball milling time was 20 h. The powder product obtained after ball milling was the cubic single-crystal all-silica mesoporous molecular sieve A.

[0074] The specific surface area of the cubic single-crystal all-silica mesoporous molecular sieve A was 734 m 2 / g, the pore volume was 1.2 mL / g, and the average pore size was 7.6 nm.

[0075] (2) Preparation of dual-pore composite molecular sieve

[0076] First, phosphoric acid was dissolved in distilled water to prepare a phosphoric acid solution, and then under the temperature condition of 40°C, pseudo-boehmite powder with a model number of P-DF-03-LS (produced by Shandong Aluminum Co., Ltd., with a specific surface area of 257 m 2 / g, a pore volume of 0.32 cm 3 / g) and triethylamine. The molar ratio of n(Al2O3):n(P2O5):n(SiO2):n(TEA):n(H2O) in the mixed system was 1:1.2:0.3:1.4:80. After the completion of the feeding, the stirring was continued at 40°C for 2h; then the gel mixture was transferred into a Teflon-lined autoclave for the first crystallization treatment. The temperature of the first crystallization treatment was 120°C, and the time was 8h. After the first crystallization treatment, the mixed slurry obtained was mixed with cubic single-crystal all-silica mesoporous molecular sieve A (the weight ratio of the cubic single-crystal all-silica mesoporous molecular sieve to the mixed slurry was 1:13) for the second crystallization treatment. The temperature of the second crystallization treatment was 180°C, and the time was 48h. The solid product obtained was washed with deionized water for 6 times, and the solid product was dried at 110°C for 10h, and then calcined at 550°C for 16h to obtain the dual-pore composite molecular sieve A.

[0077] The content of the SAPO-5 molecular sieve was 62% by weight, and the content of the cubic single-crystal all-silica mesoporous molecular sieve was 38% by weight based on the total weight of the dual-pore composite molecular sieve A.

[0078] The specific surface area of the dual-pore composite molecular sieve A was 429m 2 / g, and the pore volume was 0.67cm 3 / g.

[0079] Figure 1 is the small-angle XRD pattern of the dual-pore composite molecular sieve A; from Figure 1 The pattern shows that the cubic single-crystal all-silica mesoporous molecular sieve A has one diffraction peak of (110) plane (2θ = 0.6°) and one diffraction peak of (200) plane (2θ = 1.2°) in the small-angle region, which correspond to the cubic crystal phase. The diffraction peak of (110) plane is high in intensity and narrow in peak shape, which indicates that the material has a good long-range ordered structure. This indicates that the cubic single-crystal all-silica mesoporous molecular sieve still has a relatively regular mesoporous pore structure after being prepared into a catalyst, and the basic structure of the mesoporous molecular sieve is not destroyed during the catalyst preparation process.

[0080] Figure 2 is the wide-angle XRD pattern of the dual-pore composite molecular sieve A; from Figure 2 The pattern shows that the wide-angle x-ray diffraction angle of the sample is mainly: 2θ = 8.1°, 13.2°, 14.9°, 19.7°, 21.0° and 22.3°. The above diffraction signals are consistent with the diffraction pattern of the SAPO-5 molecular sieve. This indicates that the SAPO-5 molecular sieve in the dual-pore composite molecular sieve prepared by the second crystallization has a typical AFI crystal phase.

[0081] Figure 3 is the pore size distribution pattern of the dual-pore composite molecular sieve A; from Figure 3The spectrum shows that the sample has obvious double-channel structure, and the double-hole pore sizes are 0.8 nm and 7.6 nm respectively. Among them, the pore size of 0.8 nm is provided by SAPO-5 molecular sieve, and the pore size of 7.6 nm is provided by cubic single crystal full-silicon mesoporous molecular sieve.

[0082] (3) Performance evaluation of direct conversion of waste plastics to low-carbon olefins

[0083] The waste plastic catalytic cracking reaction performance evaluation of the double-hole composite molecular sieve A was carried out on a fixed bed reaction device. The loading amount of the double-hole composite molecular sieve A was 6.0 g, the loading amount of the polyethylene waste plastic was 40.0 g, the reaction temperature was 480℃, the reaction pressure was 0.1 MPa, the reaction time was 2 hours, after the product was cooled and gas-liquid separated, the gas composition was analyzed by Agilent 6890 gas chromatograph equipped with Al2O3-S capillary chromatographic column and hydrogen flame detector (FID), and the quantitative analysis was carried out by using correction factor; the liquid composition was analyzed by Agilent 6890 gas chromatograph equipped with PONA chromatographic column. The reaction results are shown in Table 1.

[0084] Example 2

[0085] The present embodiment is to illustrate the double-hole composite molecular sieve prepared by the present application.

[0086] (1) Preparation of cubic single crystal full-silicon mesoporous molecular sieve

[0087] 20 g (0.0014 mol) of template F108, 73.4 g (0.42 mol) of potassium sulfate and 833 g of hydrochloric acid aqueous solution (containing 2.1 mol of HCl) were mixed and stirred at 55℃ until F108 was completely dissolved; 58.2 g (0.28 mol) of tetraethyl orthosilicate was added to the above solution, and the stirring was continued at 55℃ for 10 min, and the crystallization was carried out at 55℃ for 10 h; the obtained solid product was washed with deionized water for 6 times, and after suction filtration, it was dried at 130℃ for 5 h to obtain the cubic single crystal mesoporous molecular sieve raw powder. The above cubic single crystal mesoporous molecular sieve raw powder was calcined at 600℃ for 10 h in air atmosphere, and after removing the template, it was added to a 200 ml ball mill tank, 8 maroon grinding balls with a diameter of 2 mm were put into the tank, and the ball milling was started. The temperature in the ball mill tank was controlled at 80℃, the rotating speed of the grinding ball was 500 r / min, and the ball milling time was 8 h. The powder product obtained after ball milling was the cubic single crystal full-silicon mesoporous molecular sieve B.

[0088] The specific surface area of the cubic single crystal full-silicon mesoporous molecular sieve B was 705 m 2 / g, the pore volume was 1.1 mLg, and the average pore size was 8 nm.

[0089] (2) Preparation of double-hole composite molecular sieve

[0090] Firstly, phosphorous acid was dissolved in distilled water to prepare an aqueous phosphorous acid solution, and then, at a temperature of 20°C, analytical reagent isopropyl aluminum alcohol was added to the aqueous phosphorous acid solution, and after stirring to uniformity, silica sol and triethylamine were added. The molar ratio of n(Al2O3):n(P2O5):n(SiO2):n(TEA):n(H2O) in the mixed system was 1:0.8:1:2:100. After the completion of the feeding, stirring was continued at 20°C for 6h; after which the gel mixture was transferred to an autoclave with a polytetrafluoroethylene liner for a first crystallization treatment. The temperature of the first crystallization treatment was 140°C, and the time was 5h. The mixed slurry obtained after the first crystallization treatment was uniformly mixed with cubic single-crystal all-silica mesoporous molecular sieve B (the weight ratio of the cubic single-crystal all-silica mesoporous molecular sieve to the mixed slurry was 1:16), and a second crystallization treatment was performed. The temperature of the second crystallization treatment was 210°C, and the time was 16h. The solid product obtained after filtration was washed with deionized water 8 times, the solid product was dried at 80°C for 20h, and then calcined at 500°C for 20h, to obtain the dual-pore composite molecular sieve B.

[0091] The content of the SAPO-5 molecular sieve was 58% by weight, and the content of the cubic single-crystal all-silica mesoporous molecular sieve was 42% by weight, based on the total weight of the dual-pore composite molecular sieve B.

[0092] The specific surface area of the dual-pore composite molecular sieve B was 448m 2 / g, and the pore volume was 0.69cm 3 / g.

[0093] (3) Performance evaluation of the reaction for directly converting waste plastics into low-carbon olefins

[0094] The reaction performance of the dual-pore composite molecular sieve B was tested according to the performance evaluation method of the reaction for directly converting waste plastics into low-carbon olefins in step (3) in Example 1, and the evaluation results are listed in Table 1.

[0095] Example 3

[0096] This example is directed to the dual-pore composite molecular sieve prepared by the present application.

[0097] (1) Preparation of a cubic single-crystal all-silica mesoporous molecular sieve

[0098] A mixture of 20 g (0.0014 mol) of template F108, 24.5 g (0.14 mol) of potassium sulfate and 278 g of an aqueous hydrochloric acid solution (containing 0.7 mol of HCl) was stirred at 30°C until the F108 was completely dissolved; 29.1 g (0.14 mol) of tetraethyl orthosilicate was added to the above solution, which was continuously stirred at 30°C for 60 min and left to stand at 30°C for crystallization for 40 h; the obtained solid product was washed with deionized water for 8 times, and then dried at 100°C for 16 h after suction filtration, to obtain a cubic single-crystal mesoporous molecular sieve raw powder. The above cubic single-crystal mesoporous molecular sieve raw powder was calcined at 550°C for 15 h in an air atmosphere to remove the template, and then added into a 200 ml ball mill tank, 4 maroon balls with a diameter of 2 mm were put into the tank, and the ball milling was started. The temperature in the ball mill tank was controlled at 40°C, the rotating speed of the milling balls was 300 r / min, and the ball milling time was 24 h. The powder product obtained after the ball milling was the cubic single-crystal all-silica mesoporous molecular sieve C.

[0099] The specific surface area of the cubic single-crystal all-silica mesoporous molecular sieve C was 679 m 2 / g, the pore volume was 1.0 mL / g, and the average pore size was 7.0 nm.

[0100] (2) Preparation of a dual-pore composite molecular sieve

[0101] First, ammonium dihydrogen phosphate was dissolved in distilled water to prepare an ammonium dihydrogen phosphate aqueous solution, and then aluminum hydroxide gel was added to the ammonium dihydrogen phosphate aqueous solution under the condition of a temperature of 60°C, and the mixture was stirred uniformly, and then tetramethyl orthosilicate and triethylamine were continuously added. The molar ratio of n (Al2O3) : n (P2O5) : n (SiO2) : n (TEA) : n (H2O) in the mixed system was 1:1.6:0.1:1.5:20. After the completion of the feeding, the gel mixture was continuously stirred at 60°C for 0.5 h; and then the gel mixture was transferred into a hydrothermal kettle with a polytetrafluoroethylene lining to perform a first crystallization treatment. The temperature of the first crystallization treatment was 110°C, and the time was 20 h. The mixed slurry obtained after the first crystallization treatment was uniformly mixed with the cubic single-crystal all-silica mesoporous molecular sieve C (the weight ratio of the cubic single-crystal all-silica mesoporous molecular sieve to the mixed slurry was 1:6), and a second crystallization treatment was performed. The temperature of the second crystallization treatment was 160°C, and the time was 72 h. The obtained solid product was washed with deionized water for 4 times, the solid product was dried at 130°C for 3 h, and then calcined at 600°C for 8 h, to obtain the dual-pore composite molecular sieve C.

[0102] The content of the SAPO-5 molecular sieve was 66% by weight, and the content of the cubic single-crystal all-silica mesoporous molecular sieve was 34% by weight, based on the total weight of the dual-pore composite molecular sieve C.

[0103] The specific surface area of the dual-pore composite molecular sieve C was 408 m 2 / g, the pore volume was 0.64 cm3 / g.

[0104] (3) Reaction performance evaluation of direct conversion of waste plastics to light olefins

[0105] The reaction performance of the dual-pore composite molecular sieve C was tested according to the reaction performance evaluation method of direct conversion of waste plastics to light olefins in step (3) of Example 1, and the evaluation results are listed in Table 1.

[0106] Example 4

[0107] This example is directed to the dual-pore composite molecular sieve prepared by the present application.

[0108] The cubic single-crystal all-silica mesoporous molecular sieve A was prepared according to the method in step (1) of Example 1.

[0109] (2) Preparation of dual-pore composite molecular sieve

[0110] First, ammonium dihydrogen phosphate was dissolved in distilled water to prepare an ammonium dihydrogen phosphate aqueous solution, and then a Germany original imported pseudo-boehmite powder (purchased from Beijing Yatai Aohua Chemical Auxiliary Co., Ltd., with a specific surface area of 241 m 2 / g, and a pore volume of 0.53 cm 3 / g) was added into the ammonium dihydrogen phosphate aqueous solution, and after stirring uniformly, water glass and triethylamine were continuously added. The molar ratio of n (Al2O3) : n (P2O5) : n (SiO2) : n (TEA) : n (H2O) in the mixed system was 1:0.7:1.5:3:150. After the completion of feeding, stirring was continued at 40°C for 2h; and 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 120°C, and the time was 8h. After the first crystallization treatment, the obtained mixed slurry was uniformly mixed with the cubic single-crystal all-silica mesoporous molecular sieve A (the weight ratio of the cubic single-crystal all-silica mesoporous molecular sieve to the mixed slurry was 1:18), and the second crystallization treatment was carried out. The temperature of the second crystallization treatment was 180°C, and the time was 48h. The obtained solid product was washed with deionized water for 6 times, and the solid product was dried at 110°C for 10h, and then calcined at 550°C for 16h, to obtain the dual-pore composite molecular sieve D.

[0111] Based on the total weight of the dual-pore composite molecular sieve D, the content of the SAPO-5 molecular sieve was 54wt%, and the content of the cubic single-crystal all-silica mesoporous molecular sieve was 46wt%.

[0112] The specific surface area of the dual-pore composite molecular sieve D was 467 m 2 / g, and the pore volume was 0.72 cm 3 / g.

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

[0114] Example 5

[0115] This example is to illustrate the preparation of the dual-pore composite molecular sieve of the present application.

[0116] The cubic single-crystal all-silica mesoporous molecular sieve B was prepared according to the method in step (1) in Example 2.

[0117] (2) Preparation of dual-pore composite molecular sieve

[0118] First, phosphorous acid was dissolved in distilled water to prepare an aqueous phosphorous acid solution, and then an alkaline aluminum sol was added to the aqueous phosphorous acid solution at a temperature of 30°C. After stirring uniformly, white carbon black and triethylamine were added. The molar ratio of n (Al2O3) : n (P2O5) : n (SiO2) : n (TEA) : n (H2O) in the mixed system was 1:2.2:0.08:0.4:15. After the completion of feeding, stirring was continued at 30°C for 5h; and then the gel mixture was transferred into a hydrothermal kettle with a polytetrafluoroethylene liner for a first crystallization treatment. The temperature of the first crystallization treatment was 140°C, and the time was 5h. The mixed slurry obtained after the first crystallization treatment was uniformly mixed with the cubic single-crystal all-silica mesoporous molecular sieve B (the weight ratio of the cubic single-crystal all-silica mesoporous molecular sieve to the mixed slurry was 1:5) for a second crystallization treatment. The temperature of the second crystallization treatment was 210°C, and the time was 16h. The solid product obtained by filtration was washed with deionized water for 8 times, the solid product was dried at 80°C for 20h, and then calcined at 500°C for 20h to obtain the dual-pore composite molecular sieve E.

[0119] The content of the SAPO-5 molecular sieve was 70wt%, and the content of the cubic single-crystal all-silica mesoporous molecular sieve was 30wt% based on the total weight of the dual-pore composite molecular sieve E.

[0120] The specific surface area of the dual-pore composite molecular sieve E was 391m 2 / g, and the pore volume was 0.61cm 3 / g.

[0121] (3) Reaction performance evaluation of direct conversion of waste plastics to light olefins

[0122] The reaction performance of the dual-pore composite molecular sieve E was tested according to the reaction performance evaluation method of direct conversion of waste plastics to light olefins in step (3) in Example 1, and the evaluation results are listed in Table 1.

[0123] Example 6

[0124] This example is to illustrate the preparation of the dual-pore composite molecular sieve of the present application.

[0125] Cubic single-crystal all-silica mesoporous molecular sieve A was prepared according to the method of step (1) in Example 1.

[0126] (2) Preparation of the dual-pore composite molecular sieve

[0127] First, phosphoric acid was dissolved in distilled water to prepare a phosphoric acid solution, and then aluminum hydroxide gel was added to the phosphoric acid solution at a temperature of 40°C, and after stirring to uniformity, tetraisopropyl silicate and triethylamine were added. The molar ratio of n(Al2O3):n(P2O5):n(SiO2):n(TEA):n(H2O) in the mixed system was 1:0.5:2:4:200. After the completion of the feeding, stirring was continued at 40°C for 2h; and 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 120°C, and the time was 8h. The mixed slurry obtained after the first crystallization treatment was uniformly mixed with cubic single-crystal all-silica mesoporous molecular sieve A (the weight ratio of the cubic single-crystal all-silica mesoporous molecular sieve to the mixed slurry was 1:24), and a second crystallization treatment was performed. The temperature of the second crystallization treatment was 180°C, and the time was 48h. The solid product obtained by filtration was washed with deionized water for 6 times, the solid product was dried at 110°C for 10h, and then calcined at 550°C for 16h to obtain the dual-pore composite molecular sieve F.

[0128] The content of the SAPO-5 molecular sieve was 50% by weight, and the content of the cubic single-crystal all-silica mesoporous molecular sieve was 50% by weight, based on the total weight of the dual-pore composite molecular sieve F.

[0129] The specific surface area of the dual-pore composite molecular sieve F was 485m 2 / g, and the pore volume was 0.75cm 3 / g.

[0130] The reaction performance of the catalyst F was tested according to the 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 listed in Table 1.

[0131] Example 7

[0132] This example is to illustrate the dual-pore composite molecular sieve prepared by the present application.

[0133] Cubic single-crystal all-silica mesoporous molecular sieve B was prepared according to the method of step (1) in Example 2.

[0134] (2) Preparation of the dual-pore composite molecular sieve

[0135] Firstly, phosphorous acid was dissolved in distilled water to prepare a phosphorous acid aqueous solution, then aluminum isopropoxide was added into the phosphorous acid aqueous solution under the temperature condition of 30℃, and after stirring uniformly, tetrabutyl orthosilicate and triethylamine were continuously added. The molar ratio of n(Al2O3):n(P2O5):n(SiO2):n(TEA):n(H2O) in the mixed system was 1:3:0.05:0.2:10. After the completion of feeding, stirring was continued at 30℃ for 5h; then the gel mixture was transferred into an autoclave with a polytetrafluoroethylene liner for the first crystallization treatment. The temperature of the first crystallization treatment was 140℃, and the time was 5h. The mixed slurry obtained after the first crystallization treatment was uniformly mixed with cubic single-crystal all-silica mesoporous molecular sieve B (the weight ratio of the cubic single-crystal all-silica mesoporous molecular sieve to the mixed slurry was 1:4) for the second crystallization treatment. The temperature of the second crystallization treatment was 210℃, and the time was 16h. The solid product obtained by filtration was washed with deionized water for 8 times, the solid product was dried at 80℃ for 20h, and then calcined at 500℃ for 20h to obtain the dual-pore composite molecular sieve G.

[0136] The content of the SAPO-5 molecular sieve was 74% by weight, and the content of the cubic single-crystal all-silica mesoporous molecular sieve was 26% by weight based on the total weight of the dual-pore composite molecular sieve G.

[0137] The specific surface area of the dual-pore composite molecular sieve G was 372m 2 / g, and the pore volume was 0.58cm 3 / g.

[0138] (3) Performance evaluation of the reaction of directly converting waste plastics into low-carbon olefins

[0139] The reaction performance of the dual-pore composite molecular sieve G was tested according to the performance evaluation method of the reaction of directly converting waste plastics into low-carbon olefins in step (3) of Example 1, and the evaluation results are listed in Table 1.

[0140] Comparative Example 1

[0141] The cubic single-crystal all-silica mesoporous molecular sieve A was prepared according to the method in step (1) of Example 1.

[0142] (2) Preparation of the dual-pore composite molecular sieve

[0143] Firstly, phosphorous acid was dissolved in distilled water to prepare a phosphorous acid aqueous solution, then aluminum isopropoxide was added into the phosphorous acid aqueous solution under the temperature condition of 30℃, and after stirring uniformly, tetrabutyl orthosilicate and triethylamine were continuously added. The molar ratio of n(Al2O3):n(P2O5):n(SiO2):n(TEA):n(H2O) in the mixed system was 1:3:0.05:0.2:10. After the completion of feeding, stirring was continued at 30℃ for 5h; then the gel mixture was transferred into an autoclave with a polytetrafluoroethylene liner for the first crystallization treatment. The temperature of the first crystallization treatment was 140℃, and the time was 5h. The mixed slurry obtained after the first crystallization treatment was uniformly mixed with cubic single-crystal all-silica mesoporous molecular sieve B (the weight ratio of the cubic single-crystal all-silica mesoporous molecular sieve to the mixed slurry was 1:4) for the second crystallization treatment. The temperature of the second crystallization treatment was 210℃, and the time was 16h. The solid product obtained by filtration was washed with deionized water for 8 times, the solid product was dried at 80℃ for 20h, and then calcined at 500℃ for 20h to obtain the dual-pore composite molecular sieve G. 2 / g, and the pore volume was 0.32cm 3(g) adding phosphoric acid aqueous solution, stirring uniformly, and then adding tetraethyl silicate and triethylamine. The molar ratio of n(Al2O3):n(P2O5):n(SiO2):n(TEA):n(H2O) in the mixed system was 1:1.2:0.3:1.4:80. After the completion of feeding, stirring was continued at 40°C for 2h; 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 120°C, and the time was 8h. After the first crystallization treatment, the mixed slurry obtained was uniformly mixed with cubic single-crystal all-silica mesoporous molecular sieve A (the weight ratio of the cubic single-crystal all-silica mesoporous molecular sieve to the mixed slurry was 1:3), and the second crystallization treatment was carried out. The temperature of the second crystallization treatment was 180°C, and the time was 48h. The solid product obtained by filtration was washed with deionized water for 6 times, the solid product was dried at 110°C for 10h, and then calcined at 550°C for 16h, to obtain the dual-pore composite molecular sieve D1.

[0144] The content of the SAPO-5 molecular sieve was 30% by weight, and the content of the cubic single-crystal all-silica mesoporous molecular sieve was 70% by weight, based on the total weight of the dual-pore composite molecular sieve D1.

[0145] The specific surface area of the dual-pore composite molecular sieve D1 was 579m 2 The pore volume was 0.89cm 3 / g.

[0146] The reaction performance of the dual-pore composite molecular sieve D1 was tested according to the 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 listed in Table 1.

[0147] Comparative Example 2

[0148] The cubic single-crystal all-silica mesoporous molecular sieve B was prepared according to the method in step (1) in Example 2.

[0149] Firstly, phosphorous acid was dissolved in distilled water to prepare an aqueous phosphorous acid solution, and then analytical pure aluminum isopropoxide was added into the aqueous phosphorous acid solution at a temperature of 20°C, and after stirring uniformly, silica sol and triethylamine were continuously added. The molar ratio of n(Al2O3):n(P2O5):n(SiO2):n(TEA):n(H2O) in the mixed system was 1:0.8:1:2:100. After the completion of feeding, stirring was continued at 20°C for 6h; and 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 140°C, and the time was 5h. The mixed slurry obtained after the first crystallization treatment was uniformly mixed with cubic single-crystal all-silica mesoporous molecular sieve B (the weight ratio of the cubic single-crystal all-silica mesoporous molecular sieve to the mixed slurry was 1:90) to perform a second crystallization treatment. The temperature of the second crystallization treatment was 210°C, and the time was 16h. The solid product obtained by filtration was washed with deionized water for 8 times, the solid product was dried at 80°C for 20h, and then calcined at 500°C for 20h to obtain the dual-pore composite molecular sieve D2.

[0150] The content of the SAPO-5 molecular sieve was 90% by weight, and the content of the cubic single-crystal all-silica mesoporous molecular sieve was 10% by weight, based on the total weight of the dual-pore composite molecular sieve D2.

[0151] The specific surface area of the dual-pore composite molecular sieve D2 was 297m 2 / g, and the pore volume was 0.47cm 3 / g.

[0152] The reaction performance of the dual-pore composite molecular sieve D2 was tested according to the reaction performance evaluation method of direct conversion of waste plastics to low-carbon olefins in step (3) in Example 1, and the evaluation results are listed in Table 1.

[0153] Comparative Example 3

[0154] The cubic single-crystal all-silica mesoporous molecular sieve A was prepared according to the method in step (1) in Example 1.

[0155] Step (2) in Example 1 was cancelled.

[0156] The reaction performance of the cubic single-crystal all-silica mesoporous molecular sieve A was tested according to the reaction performance evaluation method of direct conversion of waste plastics to low-carbon olefins in step (3) in Example 1, and the evaluation results are listed in Table 1.

[0157] Comparative Example 4

[0158] Step (1) in Example 1 was cancelled.

[0159] The SAPO-5 molecular sieve was prepared, and the specific process was as follows:

[0160] Firstly, phosphoric acid was dissolved in distilled water to prepare a phosphoric acid solution, and then a pseudo-boehmite powder (P-DF-03-LS, produced by Shandong Aluminum Co., Ltd., specific surface area 257 m 2 / g, pore volume 0.32 cm 3 / g) was added into the phosphoric acid aqueous solution, and after stirring uniformly, tetraethyl orthosilicate and triethylamine were added. The molar ratio of n(Al2O3):n(P2O5):n(SiO2):n(TEA):n(H2O) in the mixed system was 1:1.2:0.3:1.4:80. After the completion of feeding, stirring was continued at 40℃ for 2h; and then the gel mixture was transferred into a hydrothermal kettle with a polytetrafluoroethylene liner for a first crystallization treatment. The temperature of the first crystallization treatment was 120℃, and the time was 8h. The mixed slurry obtained after the first crystallization treatment was subjected to a second crystallization treatment. The temperature of the second crystallization treatment was 180℃, and the time was 48h. The solid product obtained by filtration was washed with deionized water for 6 times, the solid product was dried at 110℃ for 10h, and then calcined at 550℃ for 16h to obtain SAPO-5 molecular sieves.

[0161] The specific surface area of the SAPO-5 molecular sieves was 253 m 2 / g, and the pore volume was 0.41 cm 3 / g.

[0162] The reaction performance of the SAPO-5 molecular sieves was tested according to the method for evaluating the reaction performance of direct conversion of waste plastics to low-carbon olefins in step (3) of Example 1, and the evaluation results are listed in Table 1.

[0163] Comparative Example 5

[0164] Step (1) in Example 1 was cancelled.

[0165] The composite material D3 was prepared, and the specific process was as follows:

[0166] Firstly, phosphoric acid was dissolved in distilled water to prepare a phosphoric acid solution, and then a pseudo-boehmite powder (P-DF-03-LS, produced by Shandong Aluminum Co., Ltd., specific surface area 257 m 2 / g, pore volume 0.32 cm 3(g) adding phosphoric acid aqueous solution, stirring uniformly, and then adding tetraethyl silicate and triethylamine. The molar ratio of n(Al2O3):n(P2O5):n(SiO2):n(TEA):n(H2O) in the mixed system was 1:1.2:0.3:1.4:80. After the completion of feeding, stirring was continued at 40°C for 2h; 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 120°C, and the time was 8h. The mixed slurry obtained after the first crystallization treatment was mixed with silica powder (laboratory-made, specific surface area 274m2 / g, pore volume 0.57cm3 / g) at a weight ratio of 1:13, and the second crystallization treatment was carried out. The temperature of the second crystallization treatment was 180°C, and the time was 48h. The solid product obtained by filtration was washed with deionized water for 6 times, and the solid product was dried at 110°C for 10h, and then calcined at 550°C for 16h to obtain the composite material D3. 2 / g, pore volume 0.46cm3 / g. 3 / g, pore volume 0.46cm3 / g.

[0167] The content of SAPO-5 molecular sieve was 62wt% and the content of silica was 38wt% based on the total weight of the composite material D3.

[0168] The specific surface area of the composite material D3 was 259m2 / g, and the pore volume was 0.46cm3 / g. 2 / g, pore volume 0.46cm3 / g. 3 / g, pore volume 0.46cm3 / g.

[0169] The reaction performance of the composite material D3 was tested according to the method for evaluating the reaction performance of waste plastics in direct conversion to low-carbon olefins in step (3) in Example 1, and the evaluation results are listed in Table 1.

[0170] Comparative Example 6

[0171] The cubic single-crystal all-silica mesoporous molecular sieve was prepared according to the method in step (1) in Example 1, and the ball milling process was cancelled, and the product obtained was the cubic single-crystal all-silica mesoporous molecular sieve D4.

[0172] The dual-pore composite molecular sieve D4 was prepared according to the method in step (2) in Example 1.

[0173] The content of SAPO-5 molecular sieve was 62wt% and the content of cubic single-crystal all-silica mesoporous molecular sieve was 38wt% based on the total weight of the dual-pore composite molecular sieve D4.

[0174] The reaction performance of the dual-pore composite molecular sieve D4 was tested according to the method for evaluating the reaction performance of waste plastics in direct conversion to low-carbon olefins in step (3) in Example 1, and the evaluation results are listed in Table 1.

[0175] Table 1

[0176] Table 1 Item Catalyst Waste plastic conversion rate (%) Low carbon olefin yield (%) Example 1 Dual-pore composite molecular sieve A 100 44.6 Example 2 Dual-pore composite molecular sieve B 100 44.4 Example 3 Dual-pore composite molecular sieve C 100 44.1 Example 4 Dual-pore composite molecular sieve D 100 43.2 Example 5 Dual-pore composite molecular sieve E 100 43.0 Example 6 Dual-pore composite molecular sieve F 100 41.5 Example 7 Dual-pore composite molecular sieve G 100 41.1 Comparative Example 1 Dual-pore composite molecular sieve D1 97 19.7 Comparative Example 2 Dual-pore composite molecular sieve D2 100 26.8 Comparative Example 3 Cubic single-crystal all-silica mesoporous molecular sieve A 59 13.1 Comparative Example 4 SAPO-5 molecular sieve 100 22.5 Comparative Example 5 Dual-pore composite molecular sieve D3 100 29.3 Comparative Example 6 Dual-pore composite molecular sieve D4 100 34.2

[0177] From the above results, it can be seen that the double-hole composite molecular sieve provided by the application can directly catalytically convert waste plastics into low-carbon olefins. The conversion rate of waste plastics is 100%, and the yield of low-carbon olefins is high.

[0178] In Comparative Example 1, the content of the cubic single-crystal all-silica mesoporous molecular sieve is too high, and the content of the SAPO-5 molecular sieve is too low. Due to the small number of acid sites on the catalyst, the active sites are insufficient during the reaction, which leads to low conversion rate of raw materials and low yield of low-carbon olefins.

[0179] In Comparative Example 2, the content of the cubic single-crystal all-silica mesoporous molecular sieve is too low, and the content of the SAPO-5 molecular sieve is too high. Due to the small number of mesoporous channels in the catalyst, the diffusion of reactant and product molecules is hindered during the reaction, which leads to low yield of low-carbon olefins.

[0180] In Comparative Example 3, only the cubic single-crystal all-silica mesoporous molecular sieve is used as a cracking catalyst, and no SAPO-5 molecular sieve is added. Since there are almost no active acid sites on the catalyst, the conversion rate of raw materials is low, and the yield of low-carbon olefins is low.

[0181] In Comparative Example 4, only the SAPO-5 molecular sieve is used as a cracking catalyst, and no cubic single-crystal all-silica mesoporous molecular sieve is added. Since the catalyst does not contain mesoporous channels, the diffusion of reactant and product molecules is hindered during the reaction, which leads to low yield of low-carbon olefins.

[0182] In Comparative Example 5, silica powder is used instead of the cubic single-crystal all-silica mesoporous molecular sieve. Since the specific surface area of the silica is low, the pore volume is small, and the pore structure is irregular, the dispersion effect is significantly lower than that of the cubic single-crystal all-silica mesoporous molecular sieve, which leads to low yield of low-carbon olefins in the prepared composite material.

[0183] In Comparative Example 6, the ball milling process is cancelled in the preparation of the cubic single-crystal all-silica mesoporous molecular sieve, which leads to uneven dispersion of the mesoporous molecular sieve and the microporous molecular sieve in the double-hole composite molecular sieve, affecting the diffusion effect, and leading to low yield of low-carbon olefins.

[0184] The above describes the preferred embodiments of the application, but the application is not limited thereto. Within the technical concept of the application, various simple modifications can be made to the technical solutions of the application, including the combination of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as disclosed by the application and fall within the protection scope of the application.

Claims

1. Use of a dual-pore composite molecular sieve in a direct catalytic cracking of waste plastics to light olefins reaction, the use comprising: The plastic powder is contacted with a dual-pore composite molecular sieve catalyst, characterized in that the dual-pore composite molecular sieve comprises SAPO-5 molecular sieve and cubic single-crystal all-silica mesoporous molecular sieve, and the content of the SAPO-5 molecular sieve is 50-74% by weight based on the total weight of the dual-pore composite molecular sieve, and the content of the cubic single-crystal all-silica mesoporous molecular sieve is 26-50% by weight. The preparation method of the dual-pore composite molecular sieve comprises: (1) mixing and contacting triethylamine, an aluminum source, a phosphorus source, a silicon source and water to obtain a gel mixture; (2) after the gel mixture is subjected to a first crystallization treatment, a mixed slurry is obtained, a cubic single-crystal all-silica mesoporous molecular sieve is added, and after mixing, a second crystallization treatment is performed; the obtained product is subjected to separation, washing, drying and calcination treatment to obtain the dual-pore composite molecular sieve.

2. The use according to claim 1, wherein, The content of the SAPO-5 molecular sieve is 54-70% by weight based on the total weight of the dual-pore composite molecular sieve, and the content of the cubic single-crystal all-silica mesoporous molecular sieve is 30-46% by weight.

3. Use according to claim 2, wherein, The content of the SAPO-5 molecular sieve is 58-66% by weight based on the total weight of the dual-pore composite molecular sieve, and the content of the cubic single-crystal all-silica mesoporous molecular sieve is 34-42% by weight.

4. The use according to claim 1, wherein, The specific surface area of the double-pore composite molecular sieve is 350-500 m 2 / g, the pore volume is 0.50-0.80 mL / g, the pore size distribution is bimodal distribution, and the most probable pore sizes corresponding to the bimodal distribution are 0.5-1.1 nm and 5-10 nm, respectively.

5. Use according to claim 4, wherein, The specific surface area of the double-pore composite molecular sieve is 380-470 m 2 / g, the pore volume is 0.6-0.74 mL / g, the pore size distribution is bimodal distribution, and the most probable pore sizes corresponding to the bimodal distribution are 0.6-0.9 nm and 6-9 nm, respectively.

6. Use according to claim 5, wherein, The specific surface area of the double-pore composite molecular sieve is 410-447 m 2 / g, the pore volume is 0.64-0.7 mL / g, the pore size distribution is bimodal distribution, and the most probable pore sizes corresponding to the bimodal distribution are 0.7-0.8 nm and 7-8 nm, respectively.

7. The use according to claim 1, wherein, The specific surface area of the cubic single-crystal full-silica mesoporous molecular sieve is 500-900 m 2 / g, the pore volume is 0.8-1.4 mL / g, and the average pore size is 5-10 nm.

8. Use according to claim 1 or 7, wherein The preparation method of the cubic single-crystal all-silica mesoporous molecular sieve comprises: (S1) under hydrolysis gel preparation conditions, mixing a template agent, potassium sulfate, an acidic aqueous solution and a silicon source to obtain a gel mixture; (S2) after the gel mixture is subjected to a crystallization treatment, filtration, washing and drying treatment, a cubic single-crystal all-silica mesoporous molecular sieve raw powder is obtained; (S3) the cubic single-crystal all-silica mesoporous molecular sieve raw powder is subjected to a template agent removal treatment and a ball milling treatment in sequence to obtain the cubic single-crystal all-silica mesoporous molecular sieve.

9. Use according to claim 8, wherein, The template agent is a triblock copolymer polyoxyethylene-polyoxypropylene-polyoxyethylene template agent; And / or, the acidic aqueous solution is an inorganic acid aqueous solution; And / or, the molar ratio of the template agent, potassium sulfate, the silicon source, water in the inorganic acid aqueous solution and the inorganic acid in the inorganic acid aqueous solution is 1:(50-500):(50-300):(5000-50000):(200-2000); And / or, the conditions of the hydrolysis gel preparation conditions include: the temperature is 25-60℃, and the time is 10-200min; And / or, the conditions of the crystallization include: the temperature is 25-60℃, and the time is 10-72h; And / or, the process of the template agent removal treatment comprises: calcining the cubic single-crystal all-silica mesoporous molecular sieve raw powder in an air atmosphere at 400-700℃ for 8-50h; And / or, the conditions of the ball milling treatment include: the rotating speed of the grinding ball is 200-600r / min, the temperature in the ball milling tank is 30-90℃, and the ball milling time is 5-50h.

10. Use according to claim 9, wherein, The acidic aqueous solution is a hydrochloric acid aqueous solution.

11. The use according to claim 1, wherein, In step (1), the aluminum source is selected from one or more of pseudoboehmite, aluminum hydroxide, alkaline aluminum sol, aluminum isopropoxide, basic aluminum acetate, gibbsite and monohydrate soft aluminum. And / or, the phosphorus source is an inorganic acid or an acid salt containing phosphorus element; And / or, the silicon source is an organic silicon source or an inorganic silicon source; And / or, the molar ratio of the aluminum source calculated as Al2O3, the phosphorus source calculated as P2O5, the silicon source calculated as SiO2, the triethylamine and water is 1: (0.5-3): (0.05-2): (0.2-4): (10-200); And / or, the conditions of the contact reaction include: temperature is 10-80℃, time is 0.1-10h.

12. Use according to claim 11, wherein, The aluminum source is selected from one or more of pseudoboehmite, aluminum hydroxide, basic aluminum sol or aluminum isopropyl alcohol; And / or, the phosphorus source is one or more of phosphoric acid, phosphorous acid, ammonium dihydrogen phosphate and 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 conditions of the contact reaction include: temperature is 20-60℃; Time is 0.5-6h.

13. The use according to claim 1, wherein, In step (2), the conditions of the first crystallization include: temperature is 90-150℃, time is 3-30h; And / or, the weight ratio of the cubic single crystal full-silica mesoporous molecular sieve to the mixed slurry is 1: (4-24); And / or, the conditions of the second crystallization include: temperature is 140-230℃, time is 10-100h; And / or, the conditions of the calcination include: temperature is 450-650℃, time is 5-30h.

14. Use according to claim 13, wherein, In step (2), the conditions of the first crystallization include: temperature is 110-140℃; time is 5-20h; And / or, the weight ratio of the cubic single crystal full-silica mesoporous molecular sieve to the mixed slurry is 1: (6-16); And / or, the conditions of the second crystallization include: temperature is 160-210℃; time is 16-72h; And / or, the conditions of the calcination include: temperature is 500-600℃; time is 8-20h.

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

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