Micropore-mesopore dual-hole composite catalyst, preparation method thereof and application thereof in direct catalytic cracking reaction of waste plastics

Abstract

This invention relates to the fields of catalyst preparation and polymer material recycling, and discloses a microporous-mesoporous dual-pore composite catalyst, its preparation method, and its application in the direct catalytic cracking reaction of waste plastics. The microporous-mesoporous dual-pore composite catalyst comprises ZRP-5 molecular sieve and HMS all-silica mesoporous molecular sieve. The pore size of the microporous-mesoporous dual-pore composite catalyst exhibits a bimodal distribution, with micropores having a diameter of 0.3-0.6 nm and mesopores having a diameter of 2-5 nm. Based on the total weight of the microporous-mesoporous dual-pore composite catalyst, the content of ZRP-5 molecular sieve is 20-50% by weight, and the content of HMS all-silica mesoporous molecular sieve is 50-80% by weight. Applying this microporous-mesoporous dual-pore composite catalyst to the direct catalytic cracking reaction of waste plastics to produce low-carbon olefins not only solves the problem of waste plastic recycling but also increases the production of important chemical raw materials such as low-carbon olefins.

Description

Technical Field

[0001] This invention relates to the fields of catalyst preparation and polymer material recycling, specifically to a microporous-mesoporous dual-pore composite catalyst, its preparation method, and its application in the direct catalytic cracking reaction of waste plastics. Background Technology

[0002] Plastic products are widely used in various fields worldwide. However, plastics are difficult to degrade naturally. While conventional landfill technology requires less investment and is simpler to operate, it occupies a large amount of land and causes soil pollution. Incineration technology, although it can reduce waste volume and recover some energy, easily releases large amounts of hydrocarbons, nitrogen oxides, sulfides, and highly toxic substances, directly threatening human and environmental health. Therefore, the recycling and high-value utilization of waste plastics is a widely recognized measure for energy conservation and environmental protection. Methods for recycling and utilizing waste plastics mainly include sorting and recycling, producing monomer raw materials, producing clean fuels, and using them for power generation.

[0003] In existing technologies, the main chemical recycling scheme for waste plastics is waste plastic pyrolysis technology. Waste plastic pyrolysis includes three basic methods: thermal pyrolysis (one-stage method), catalytic pyrolysis (one-stage method), and thermal pyrolysis-catalytic modification (two-stage method). The earliest developed waste plastic pyrolysis technology was thermal pyrolysis. This technology refers to a thermal conversion process in which a thermochemical decomposition reaction occurs under high-temperature, oxygen-free conditions, converting the large molecular weight organic matter in waste plastic products into small molecular weight liquids, fuel gas, and coke. The reaction temperature in this process is generally controlled between 350-900℃. Adding a catalyst during the thermal pyrolysis process results in catalytic thermal pyrolysis, which not only lowers the pyrolysis temperature but also improves product performance. The thermal pyrolysis-catalytic modification method, an improvement on catalytic pyrolysis, uses a catalyst to catalytically modify the pyrolysis gas after the waste plastic pyrolysis. This method produces higher quality products, is more flexible in operation, and has lower operating costs than thermal pyrolysis and catalytic pyrolysis, but the process is more complex.

[0004] Cracking technology for treating waste plastics offers great flexibility and good energy recovery, making it one of the most promising waste plastic treatment technologies. In existing technologies, one-step thermal cracking and one-step catalytic cracking primarily produce fuel oil, yielding only small amounts of low-carbon olefins (ethylene, propylene, butene). If a large quantity of low-carbon olefins is required, a two-stage process of thermal cracking followed by catalytic reforming is necessary.

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

[0006] The purpose of this invention is to address the problem of low low-carbon olefin content recovered in current chemical recycling of waste plastics by providing a microporous-mesoporous dual-pore composite catalyst, its preparation method, and its application in the direct catalytic cracking reaction of waste plastics. By applying this microporous-mesoporous dual-pore composite catalyst to the direct catalytic cracking reaction of waste plastics to produce low-carbon olefins, the problem of waste plastic recycling is solved, and the production of important chemical raw material low-carbon olefins is increased.

[0007] To achieve the above objectives, the first aspect of the present invention provides a microporous-mesoporous dual-pore composite catalyst, wherein the microporous-mesoporous dual-pore composite catalyst comprises ZRP-5 molecular sieve and HMS all-silica mesoporous molecular sieve, and the pore size of the microporous-mesoporous dual-pore composite catalyst exhibits a bimodal distribution, with micropore pore size of 0.3-0.6 nm and mesopore pore size of 2-5 nm;

[0008] Based on the total weight of the microporous-mesoporous dual-pore composite catalyst, the content of ZRP-5 molecular sieve is 20-50% by weight, and the content of HMS all-silica mesoporous molecular sieve is 50-80% by weight.

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

[0010] (I) The ZRP-5 molecular sieve was ball-milled to obtain the ball-milled ZRP-5 molecular sieve;

[0011] (II) Mix HMS all-silica mesoporous molecular sieve with water to obtain HMS all-silica mesoporous molecular sieve slurry;

[0012] (III) The ball-milled ZRP-5 molecular sieve and the HMS all-silica mesoporous molecular sieve slurry are contacted and pulped to obtain a microporous-mesoporous dual-pore composite catalyst slurry.

[0013] (IV) The microporous-mesoporous dual-pore composite catalyst slurry was filtered, dried and calcined to obtain the microporous-mesoporous dual-pore composite catalyst.

[0014] A third aspect of the present invention provides a microporous-mesoporous dual-pore composite catalyst prepared by the preparation method described above.

[0015] The fourth aspect of this invention provides an application of the aforementioned microporous-mesoporous dual-pore composite catalyst in the direct catalytic cracking of waste plastics to produce low-carbon olefins.

[0016] The technical solution of the present invention has the following advantages through the above technical solution:

[0017] (1) The microporous-mesoporous dual-pore composite catalyst provided by the present invention has readily available raw materials, a simple preparation method, easy-to-control conditions, and good product repeatability.

[0018] (2) The microporous-mesoporous dual-pore composite catalyst provided by this invention includes both ZRP-5 molecular sieve with a certain degree of surface acidity and HMS all-silica mesoporous molecular sieve with a large pore size. It has a stable structure and good high-temperature resistance. During the pyrolysis reaction, the acidic sites of the microporous molecular sieve serve as active centers for the pyrolysis of waste plastic molecules, while the mesoporous channels facilitate the diffusion of raw material and product molecules.

[0019] (3) The microporous-mesoporous dual-pore composite catalyst provided by this invention can convert waste plastics into low-carbon olefins in one step when used in the direct catalytic cracking reaction of waste plastics to produce low-carbon olefins. This is a new method for the chemical recycling of waste plastics. It not only solves the problem of waste plastic recycling, but also increases the production of important chemical raw materials such as low-carbon olefins, thus having good economic benefits.

[0020] (4) The microporous-mesoporous dual-pore composite catalyst provided by the present invention has mild process conditions, is easy to operate and has low requirements for reaction equipment when used for direct catalytic cracking of waste plastics to produce low-carbon olefins.

[0021] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0022] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof.

[0023] Figure 1 This is the small-angle X-ray diffraction (XRD) pattern of the microporous-mesoporous dual-pore composite catalyst A in Example 1;

[0024] Figure 2 This is the wide-angle X-ray diffraction (XRD) pattern of the microporous-mesoporous dual-pore composite catalyst A of Example 1;

[0025] Figure 3 This is a pore size distribution diagram of the microporous-mesoporous dual-pore composite catalyst A in Example 1. Detailed Implementation

[0026] The endpoints and any values ​​of the ranges 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 endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0027] As mentioned above, the first aspect of the present invention provides a microporous-mesoporous dual-pore composite catalyst, wherein the microporous-mesoporous dual-pore composite catalyst comprises ZRP-5 molecular sieve and HMS all-silica mesoporous molecular sieve, and the pore size of the microporous-mesoporous dual-pore composite catalyst exhibits a bimodal distribution, with micropore pore size of 0.3-0.6 nm and mesopore pore size of 2-5 nm;

[0028] Based on the total weight of the microporous-mesoporous dual-pore composite catalyst, the content of ZRP-5 molecular sieve is 20-50% by weight, and the content of HMS all-silica mesoporous molecular sieve is 50-80% by weight.

[0029] The inventors of this invention have discovered that, in the prior art, there is no process for the direct catalytic cracking of waste plastics to produce low-carbon olefins (including ethylene, propylene, and butene). The microporous-mesoporous dual-pore composite catalyst developed by the inventors of this invention can solve this problem.

[0030] On the one hand, the inventors of this invention discovered that catalysts for the direct preparation of low-carbon olefins from waste plastics through catalytic cracking should possess a certain degree of acidity and good hydrothermal stability. ZRP-5 molecular sieves, possessing both a stable MFI-type topological framework and mild acidity, are very suitable as the main component of waste plastic cracking catalysts. However, because ZRP-5 molecular sieves have relatively small pore sizes (average pore diameter around 0.5 nm) and small pore volumes (approximately 0.2 cm³), they are less suitable for use as the main component of such catalysts. 3 The molecular weight of waste plastics is approximately 1 / g, while the molecular weight and molecular chain of waste plastic products are relatively large. During the pyrolysis reaction of waste plastics, the larger reactant and product molecules have difficulty diffusing within the narrow channels, which not only affects the contact between reactants and active sites but also easily leads to side reactions such as deep dehydrogenation, thus causing a decline in catalyst performance. Compared with microporous molecular sieves, HMS all-silica mesoporous molecular sieve materials have larger pore sizes (approximately 6-10 times the pore size of ZRP-5 molecular sieves) and larger pore volumes (up to 0.8 cm³). 3 HMS all-silica mesoporous molecular sieves (with a surface acidity of over / g) are highly suitable for catalytic reactions involving large molecules. However, as an all-silica material, HMS has extremely weak surface acidity, resulting in poor activity and low catalytic efficiency when used alone as a catalyst for the pyrolysis of waste plastics. During their research and development of catalysts for the pyrolysis of waste plastics, the inventors of this invention discovered that by comprehensively utilizing the pore advantages of HMS all-silica mesoporous molecular sieves and the suitable surface acidity centers of ZRP-5 microporous molecular sieves, the specific surface area and pore volume of the catalyst can be effectively increased, significantly improving the internal diffusion performance in the reaction. When used as a pyrolysis catalyst in the catalytic conversion reaction of waste plastics, it not only effectively improves the activity of the pyrolysis catalyst but also increases the selectivity for low-carbon olefins.

[0031] On the other hand, the inventors of this invention discovered that simply mixing ZRP-5 molecular sieve with HMS all-silica mesoporous molecular sieve is insufficient to fully utilize the catalytic activity of the acidic centers on the surface of the microporous molecular sieve ZRP-5 and the advantages of the pore structure of the HMS all-silica mesoporous molecular sieve. In the preparation of the cracking catalyst, if the ball-milled ZRP-5 molecular sieve powder is added to the HMS all-silica mesoporous molecular sieve slurry, and the two molecular sieves are uniformly mixed by slurrying, followed by filtration, drying, and calcination to remove the template agent from the HMS all-silica mesoporous molecular sieve, the microporous-mesoporous dual-porous composite catalyst obtained by this preparation method exhibits high catalytic activity and high selectivity for low-carbon olefins in the catalytic cracking reaction of waste plastics.

[0032] According to the present invention, the pore size of the microporous-mesoporous dual-pore composite catalyst is bimodal, with the micropore size being 0.4-0.5 nm and the mesopore size being 3-4 nm; preferably, the pore size of the microporous-mesoporous dual-pore composite catalyst is bimodal, with the micropore size being 0.43-0.47 nm and the mesopore size being 3.2-3.8 nm.

[0033] According to the present invention, preferably, based on the total weight of the microporous-mesoporous dual-porous composite catalyst, the content of ZRP-5 molecular sieve is 25-45% by weight, and the content of HMS all-silica mesoporous molecular sieve is 55-75% by weight; preferably, based on the total weight of the microporous-mesoporous dual-porous composite catalyst, the content of ZRP-5 molecular sieve is 30-40% by weight, and the content of HMS all-silica mesoporous molecular sieve is 60-70% by weight. In the present invention, by using the aforementioned specific contents of each component, the prepared microporous-mesoporous dual-porous composite catalyst can exhibit better catalytic activity and higher low-carbon olefin selectivity when used in the direct catalytic cracking of waste plastics to prepare low-carbon olefins.

[0034] According to the present invention, the SiO2 / Al2O3 molar ratio of the ZRP-5 molecular sieve is 70-300.

[0035] According to the present invention, the ZRP-5 molecular sieve is selected from one or more of ZRP-5A, ZRP-5B, and ZRP-5C molecular sieves. In this invention, the ZRP-5 molecular sieve can be obtained commercially. Specifically, the ZRP-5 molecular sieve is more preferably: ZRP-5A molecular sieve with a SiO2 / Al2O3 molar ratio of 70; ZRP-5B molecular sieve with a SiO2 / Al2O3 molar ratio of 100; and ZRP-5C molecular sieve with a SiO2 / Al2O3 molar ratio of 300. All three molecular sieves were purchased from Wuhan Hezhong Biochemical Manufacturing Co., Ltd.

[0036] According to the present invention, the specific surface area of ​​the microporous-mesoporous dual-pore composite catalyst is 650-800 m².2 / g, with a pore volume of 0.58-0.79 ml / g; preferably, the specific surface area of ​​the microporous-mesoporous biporous composite catalyst is 690-780 m² / g. 2 / g, with a pore volume of 0.62-0.75ml / g; more preferably, the specific surface area of ​​the microporous-mesoporous biporous composite catalyst is 725-776m². 2 The pore volume is 0.66-0.72 ml / g. In this invention, the microporous-mesoporous biporous composite catalyst has the above structural parameters and exhibits better catalytic activity and higher low-carbon olefin selectivity when used in the direct catalytic cracking of waste plastics to prepare low-carbon olefins.

[0037] A second aspect of the present invention provides a method for preparing a microporous-mesoporous dual-pore composite catalyst, wherein the preparation method includes:

[0038] (I) The ZRP-5 molecular sieve was ball-milled to obtain the ball-milled ZRP-5 molecular sieve;

[0039] (II) Mix HMS all-silica mesoporous molecular sieve raw powder with water to obtain HMS all-silica mesoporous molecular sieve raw slurry;

[0040] (III) The ball-milled ZRP-5 molecular sieve and the HMS all-silica mesoporous molecular sieve slurry are contacted and pulped to obtain a microporous-mesoporous dual-pore composite catalyst slurry.

[0041] (IV) The microporous-mesoporous dual-pore composite catalyst slurry was filtered, dried and calcined to obtain the microporous-mesoporous dual-pore composite catalyst.

[0042] According to the present invention, in step (I), the ball milling is carried out 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 reasonably selected according to the size of the ball mill jar, and for a ball mill jar with a size of 100-300 mL, 2-8 grinding balls can usually be used; the material of the grinding balls is agate or polytetrafluoroethylene, preferably agate. The ball milling conditions include: the rotational speed of the grinding balls can be 200-600 r / min, preferably 300-500 r / min; the temperature inside the ball mill jar can be 30-90℃, preferably 40-80℃; the ball milling time can be 5-50 h, preferably 8-24 h.

[0043] According to the present invention, after washing the HMS all-silica mesoporous molecular sieve prepared above, a certain amount of distilled water is added to obtain the HMS all-silica mesoporous molecular sieve slurry.

[0044] According to the present invention, the weight ratio of the ZRP-5 molecular sieve and the HMS all-silica mesoporous molecular sieve slurry is 1:(20-250), preferably 1:(50-180). It should be noted that the HMS all-silica mesoporous molecular sieve slurry contains not only water but also the template agent used in the preparation of the mesoporous molecular sieve. Both the template agent and water are removed by calcination in the final step of the preparation of the microporous-mesoporous dual-porous composite catalyst.

[0045] According to the present invention, in step (III), the pulping process may include: adding ZRP-5 molecular sieve powder to the HMS all-silica mesoporous molecular sieve slurry and rapidly stirring with a stirring paddle. The stirring speed may be greater than or equal to 100 rpm, preferably greater than or equal to 300 rpm; the stirring time may be 1-24 h, preferably 5-12 h.

[0046] According to the present invention, in step (IV), the filtration process has no special requirements and can be a filtration method known in the art, including gravity filtration, pressure filtration, vacuum filtration, or centrifugal filtration. Preferably, the filtration process specifically includes: using a vacuum flask to create a vacuum at the bottom of the funnel or using a centrifugal filter.

[0047] According to the present invention, in step (IV), the drying conditions include: a temperature of 50-150°C, preferably 60-120°C; and a time of 1-24 hours, preferably 3-16 hours.

[0048] According to the present invention, in step (IV), the calcination conditions include: a temperature of 450-700°C, preferably 500-650°C; and a time of 4-30 h, preferably 6-20 h.

[0049] According to the present invention, the preparation method of the HMS all-silica mesoporous molecular sieve raw powder includes:

[0050] (1) Under hydrolytic gelation conditions, a template agent, alcohol and water are mixed and brought into contact to obtain a mixture; wherein the template agent is a neutral surfactant;

[0051] (2) The silicon source is added dropwise to the mixture to obtain a gel mixture;

[0052] (3) The gel mixture is crystallized; then the crystallized product is filtered and washed to obtain HMS all-silica mesoporous molecular sieve powder.

[0053] According to the present invention, in step (1), preferably, the template agent is selected from one or more of dodecylamine, tetradecylamine, hexadecylamine and octadecylamine.

[0054] According to the present invention, in step (1), the alcohol is ethanol.

[0055] According to the present invention, in step (1), the silicon source is a silicon-containing organic compound and / or a silicon-containing inorganic compound; preferably a silicon-containing organic compound; more preferably one or more of tetraethyl orthosilicate, methyl orthosilicate and butyl orthosilicate.

[0056] According to the present invention, in step (1), the weight ratio of the template agent, the alcohol, the water and the silicon source is 1:(1-30):(2-20):(1-12); preferably 1:(3-15):(4-10):(2-8).

[0057] According to the present invention, in step (1), the contact conditions include: a temperature of 10-80°C, preferably 20-60°C; and a time of 0.5-5 h, preferably 1-3 h. Preferably, in order to ensure that the template agent, ethanol, water, and silicon source are mixed evenly, the contact process can be carried out under stirring conditions.

[0058] According to the present invention, in step (1), the crystallization conditions include: a temperature of 10-80°C, preferably 20-60°C; and a time of 3-48h, preferably 5-30h.

[0059] According to the present invention, in step (1), the washing process may include: after filtration, obtaining a solid product, repeatedly washing the solid product with distilled water or ethanol (the number of washing times may be 5-10 times), and then performing vacuum filtration.

[0060] A third aspect of the present invention provides a microporous-mesoporous dual-pore composite catalyst prepared by the preparation method described above.

[0061] The fourth aspect of this invention provides an application of the aforementioned microporous-mesoporous dual-pore composite catalyst in the direct catalytic cracking of waste plastics to produce low-carbon olefins.

[0062] According to the present invention, the waste plastic is waste polyethylene plastic (waste polyethylene plastic).

[0063] According to the present invention, the method of applying the catalyst includes: contacting waste polyethylene plastic particles with a microporous-mesoporous dual-porous composite catalyst under specific conditions.

[0064] In this invention, the contact conditions between the waste polyethylene plastic particles and the microporous-mesoporous dual-pore composite catalyst include: the contact temperature can be 420-580℃, preferably 450-540℃; the contact pressure can be 0.01-1.0 MPa, preferably 0.05-0.5 MPa; the contact time can be 0.5-12 h, preferably 1-5 h; and the weight ratio of the microporous-mesoporous dual-pore composite catalyst to the waste polyethylene plastic particles can be 1:0.5-50, preferably 1:2-30.

[0065] The present invention will be described in detail below through embodiments.

[0066] In the following examples and comparative examples:

[0067] (1) Small-angle XRD tests of the samples were performed on a D8 ADVANCE high-power rotating target X-ray diffractometer from BRUKER AXS GmbH, Germany, with a scanning range of 0.5-10°.

[0068] (2) Wide-angle XRD tests of the samples were performed on a Philips X'Pert MPD X-ray powder diffractometer with Cu Kα target and a scanning range of 2θ = 5-90°.

[0069] (3) The pore structure parameters of the samples were analyzed using an ASAP2020-M+C adsorption analyzer manufactured by Micromeritics, USA. Before the analysis, the samples were degassed under vacuum at 350℃ for 4 hours. The specific surface area of ​​the samples was calculated using the BET method, and the pore volume was calculated using the BJH model.

[0070] (4) Scanning electron microscope images of the samples were obtained on an XL-30 field emission environmental scanning electron microscope manufactured by FEI Corporation in the United States.

[0071] (5) Elemental analysis of the samples was performed on an Eagle III energy-dispersive X-ray fluorescence spectrometer manufactured by EDAX Corporation in the United States.

[0072] (6) The drying oven was manufactured by Shanghai Yiheng Scientific Instruments Co., Ltd., model DHG-9030A.

[0073] (7) The muffle furnace was manufactured by CARBOLITE, model CWF1100.

[0074] (8) All other reagents used in the examples and comparative examples were purchased from Sinopharm Chemical Reagent Co., Ltd., and the reagent purity was analytical grade.

[0075] Example 1

[0076] This embodiment illustrates the microporous-mesoporous dual-pore composite catalyst prepared according to the present invention and its application in the direct conversion of waste plastics to low-carbon olefins.

[0077] (1) Preparation of microporous-mesoporous dual-pore composite catalysts

[0078] 10.0 g of dodecylamine was dissolved in a mixed solution of 72.0 g ethanol and 63.0 g distilled water. The solution was heated to 40 °C and stirred for 30 minutes. Then, 42.0 g of tetraethyl orthosilicate (TEOS) was added dropwise. Stirring continued during the dropwise addition, which lasted for 2 hours. After the addition was complete, the solution was stirred at 40 °C for 20 hours to crystallize. After crystallization, the solid product was separated from the mother liquor by filtration. The solid product was washed eight times with anhydrous ethanol, filtered, and then an appropriate amount of distilled water was added to obtain 400 g of HMS mesoporous molecular sieve slurry A.

[0079] 50g of ZRP-5B molecular sieve (SiO2 / Al2O3 molar ratio of 100, specific surface area of ​​342m²) was used. 2 / g, pore volume is 0.18cm³ 3 (g) was added to a 300ml ball mill jar, along with six 2mm diameter agate grinding balls, and milling began. The temperature inside the ball mill jar was controlled at 60℃, the grinding speed was 400r / min, and the milling time was 16h. 6.2g of the resulting ZRP-5B molecular sieve powder was added to an HMS all-silica mesoporous molecular sieve slurry and stirred at 500 rpm for 10h to obtain a microporous-mesoporous dual-pore composite catalyst slurry. The white solid obtained by filtration of the microporous-mesoporous dual-pore composite catalyst slurry was dried at 90℃ for 5h and calcined at 600℃ for 12h to obtain microporous-mesoporous dual-pore composite catalyst A.

[0080] Based on the total weight of the microporous-mesoporous dual-pore composite catalyst A, the content of ZRP-5 molecular sieve is 36% by weight, and the content of HMS all-silica mesoporous molecular sieve is 64% by weight.

[0081] The specific surface area of ​​the microporous-mesoporous dual-pore composite catalyst A is 776 m². 2 / g, pore volume is 0.72cm³ 3 / g.

[0082] Figure 1 This is the small-angle XRD pattern of catalyst A, from Figure 1 It can be seen that, Figure 1 A relatively broad single diffraction peak appeared, with the peak value between 2θ = 2-3°, which is a characteristic diffraction peak of the (100) crystal plane. This indicates that the sample has a typical hexagonal worm-like pore structure. This shows that after calcination at 600℃, the HMS mesoporous molecular sieve crystal phase did not change significantly and still maintained a typical hexagonal mesoporous structure.

[0083] Figure 2 This is the wide-angle XRD pattern of catalyst A, from... Figure 2The X-ray diffraction patterns of the sample are shown to be mainly 2θ = 7.8°, 8.9°, 14.9°, 23.1°, and 24.0°. These five diffraction signals are consistent with the diffraction patterns of ZRP-5 molecular sieves, indicating that the ZRP-5 molecular sieve in catalyst A still maintains the typical MFI crystal phase structure, and that the ball milling, pulping, and calcination processes in catalyst preparation did not destroy the basic structure of the ZRP-5 molecular sieve.

[0084] Figure 3 This is the pore size distribution diagram of catalyst A, from... Figure 3 The spectrum shows that the sample has a distinct dual-channel structure, indicating that the pore size of the microporous-mesoporous composite catalyst exhibits a bimodal distribution, with micropores having a diameter of 0.45 nm and mesopores having a diameter of 3.4 nm. The 0.45 nm pores are provided by ZRP-5 molecular sieves, and the 3.4 nm pores are provided by HMS all-silica mesoporous molecular sieves.

[0085] (2) Evaluation of the reaction performance of direct conversion of waste plastics to low carbon olefins

[0086] The performance of the catalyst in the catalytic cracking of waste plastics was evaluated using a fixed-bed reactor. The catalyst loading was 10.0 g, and the waste polyethylene plastic granules loading was 50.0 g. The reaction temperature was 500℃, the reaction pressure was 0.1 MPa, and the reaction time was 1 hour. After product cooling and gas-liquid separation, the gas composition was analyzed using an Agilent 6890 gas chromatograph equipped with an Al2O3-S capillary column and a flame ionization detector (FID), with programmed temperature ramping and quantitative analysis using correction factors. The liquid composition was analyzed using an Agilent 6890 gas chromatograph equipped with a PONA column. The reaction results are shown in Table 1.

[0087] Example 2

[0088] This embodiment illustrates the microporous-mesoporous dual-pore composite catalyst prepared according to the present invention and its application in the direct conversion of waste plastics to low-carbon olefins.

[0089] (1) Preparation of microporous-mesoporous dual-pore composite catalysts

[0090] 10.0 g of hexadecylamine was dissolved in a mixed solution of 30.0 g ethanol and 40.0 g distilled water. The solution was heated to 60 °C and stirred for 20 minutes. Then, 20.0 g of methyl orthosilicate (TMOS) was added dropwise. Stirring continued during the dropwise addition, which lasted for 40 minutes. After the addition was complete, the solution was stirred at 60 °C for 5 hours to crystallize. After crystallization, the solid product was separated from the mother liquor by filtration. The solid product was washed 10 times with distilled water, filtered, and then distilled water was added to obtain 300 g of HMS mesoporous molecular sieve slurry B.

[0091] 50g of ZRP-5A molecular sieve (SiO2 / Al2O3 molar ratio of 70, specific surface area of ​​329m²) was used. 2 / g, pore volume is 0.16cm³ 3 (g) was added to a 300ml ball mill jar, along with eight 2mm diameter agate grinding balls, and milling began. The temperature inside the ball mill jar was controlled at 80℃, the grinding speed was 500r / min, and the milling time was 8h. 3.0g of the ZRP-5A molecular sieve powder obtained after milling was added to an HMS all-silica mesoporous molecular sieve slurry and stirred at 300 rpm for 12h to obtain a microporous-mesoporous dual-pore composite catalyst slurry. The white solid obtained by filtration of the microporous-mesoporous dual-pore composite catalyst slurry was dried at 120℃ for 3h and calcined at 500℃ for 20h to obtain microporous-mesoporous dual-pore composite catalyst B.

[0092] Based on the total weight of the microporous-mesoporous dual-pore composite catalyst B, the content of ZRP-5 molecular sieve is 30% by weight, and the content of HMS all-silica mesoporous molecular sieve is 70% by weight.

[0093] The specific surface area of ​​the microporous-mesoporous dual-pore composite catalyst B is 747 m². 2 / g, pore volume is 0.71cm³ 3 / g; and the microporous-mesoporous dual-pore composite catalyst has a bimodal pore size distribution and a dual-channel structure, wherein the micropore size is 0.43nm and the mesopore size is 3.6nm.

[0094] The reaction performance of catalyst B was tested according to the reaction performance evaluation method for direct conversion of waste plastics to low-carbon olefins in step (2) of Example 1. The evaluation results are listed in Table 1.

[0095] Example 3

[0096] This embodiment illustrates the microporous-mesoporous dual-pore composite catalyst prepared according to the present invention and its application in the direct conversion of waste plastics to low-carbon olefins.

[0097] (1) Preparation of microporous-mesoporous dual-pore composite catalysts

[0098] 10.0 g of octadecylamine was dissolved in a mixed solution of 150.0 g of ethanol and 100.0 g of distilled water. After stirring at 20 °C for 1 h, 80.0 g of butyl orthosilicate was added dropwise. Stirring continued during the dropwise addition, which lasted for 2 h. After the dropwise addition was complete, crystallization was carried out at 20 °C for 30 h with stirring. After crystallization, the solid product was separated from the mother liquor by filtration. The solid product was washed five times with ethanol, filtered, and then distilled water was added to obtain 500 g of HMS mesoporous molecular sieve slurry C.

[0099] 50g of ZRP-5C molecular sieve (SiO2 / Al2O3 molar ratio of 300, specific surface area of ​​354m²) was used. 2 / g, pore volume 0.20cm³ 3 (g) was added to a 300ml ball mill jar, along with four 2mm diameter agate grinding balls, and milling began. The temperature inside the ball mill jar was controlled at 40℃, the grinding speed was 300r / min, and the milling time was 24h. 9.3g of the ZRP-5C molecular sieve powder obtained after milling was added to an HMS all-silica mesoporous molecular sieve slurry and stirred at 600 rpm for 6h to obtain a microporous-mesoporous dual-pore composite catalyst slurry. The white solid obtained by filtration of the microporous-mesoporous dual-pore composite catalyst slurry was dried at 60℃ for 16h and calcined at 650℃ for 6h to obtain microporous-mesoporous dual-pore composite catalyst C.

[0100] Based on the total weight of the microporous-mesoporous dual-pore composite catalyst C, the content of ZRP-5 molecular sieve is 40% by weight, and the content of HMS all-silica mesoporous molecular sieve is 60% by weight.

[0101] The specific surface area of ​​the microporous-mesoporous dual-pore composite catalyst C is 725 m². 2 / g, pore volume is 0.66cm³ 3 / g; and the microporous-mesoporous dual-pore composite catalyst has a bimodal pore size distribution and a dual-channel structure, wherein the micropore size is 0.47nm and the mesopore size is 3.3nm.

[0102] The reaction performance of catalyst C was tested according to the reaction performance evaluation method for direct conversion of waste plastics to low-carbon olefins in step (2) of Example 1. The evaluation results are listed in Table 1.

[0103] Example 4

[0104] This embodiment illustrates the microporous-mesoporous dual-pore composite catalyst prepared according to the present invention and its application in the direct conversion of waste plastics to low-carbon olefins.

[0105] (1) Preparation of microporous-mesoporous dual-pore composite catalysts

[0106] 10.0 g of hexadecylamine was dissolved in a mixed solution of 30.0 g ethanol and 40.0 g distilled water. The solution was heated to 60 °C and stirred for 20 minutes. Then, 20.0 g of methyl orthosilicate (TMOS) was added dropwise. Stirring continued during the dropwise addition, which lasted for 40 minutes. After the addition was complete, the solution was stirred at 60 °C for 5 hours to crystallize. After crystallization, the solid product was separated from the mother liquor by filtration. The solid product was washed 10 times with distilled water, filtered, and then distilled water was added to obtain 400 g of HMS mesoporous molecular sieve slurry D.

[0107] 50g of ZRP-5A molecular sieve (SiO2 / Al2O3 molar ratio of 70, specific surface area of ​​329m²) was used. 2 / g, pore volume is 0.16cm³ 3 (g) was added to a 300ml ball mill jar, along with eight 2mm diameter agate grinding balls, and milling began. The temperature inside the ball mill jar was controlled at 80℃, the grinding speed was 500 rpm, and the milling time was 8 hours. 2.4g of the resulting ZRP-5A molecular sieve powder was added to an HMS all-silica mesoporous molecular sieve slurry and stirred at 300 rpm for 12 hours to obtain a microporous-mesoporous dual-pore composite catalyst slurry. The white solid obtained by filtration of the microporous-mesoporous dual-pore composite catalyst slurry was dried at 120℃ for 3 hours and calcined at 500℃ for 20 hours to obtain microporous-mesoporous dual-pore composite catalyst D.

[0108] Based on the total weight of the microporous-mesoporous dual-pore composite catalyst D, the content of ZRP-5 molecular sieve is 25% by weight, and the content of HMS all-silica mesoporous molecular sieve is 75% by weight.

[0109] The specific surface area of ​​the microporous-mesoporous dual-pore composite catalyst D is 780 m². 2 / g, pore volume 0.75cm³ 3 / g; The microporous-mesoporous dual-pore composite catalyst has a bimodal pore size distribution and a dual-channel structure, wherein the micropore size is 0.43nm and the mesopore size is 3.5nm.

[0110] The reaction performance of catalyst D was tested according to the reaction performance evaluation method for direct conversion of waste plastics to low-carbon olefins in step (2) of Example 1. The evaluation results are listed in Table 1.

[0111] Example 5

[0112] This embodiment illustrates the microporous-mesoporous dual-pore composite catalyst prepared according to the present invention and its application in the direct conversion of waste plastics to low-carbon olefins.

[0113] (1) Preparation of microporous-mesoporous dual-pore composite catalysts

[0114] 10.0 g of octadecylamine was dissolved in a mixed solution of 150.0 g of ethanol and 100.0 g of distilled water. After stirring at 20 °C for 1 h, 80.0 g of butyl orthosilicate was added dropwise. Stirring continued during the dropwise addition, which lasted for 2 h. After the addition was complete, crystallization was carried out at 20 °C for 30 h with stirring. After crystallization, the solid product was separated from the mother liquor by filtration. The solid product was washed five times with ethanol, filtered, and then distilled water was added to obtain 600 g of HMS mesoporous molecular sieve slurry E.

[0115] 50g of ZRP-5C molecular sieve (SiO2 / Al2O3 molar ratio of 300, specific surface area of ​​354m²) was used. 2 / g, pore volume 0.20cm³ 3 (g) was added to a 300ml ball mill jar, along with four 2mm diameter agate grinding balls, and milling began. The temperature inside the ball mill jar was controlled at 40℃, the grinding speed was 300r / min, and the milling time was 24h. 11.0g of the ZRP-5C molecular sieve powder obtained after milling was added to an HMS all-silica mesoporous molecular sieve slurry and stirred at 600 rpm for 6h to obtain a microporous-mesoporous dual-pore composite catalyst slurry. The white solid obtained by filtration of the microporous-mesoporous dual-pore composite catalyst slurry was dried at 60℃ for 16h and calcined at 650℃ for 6h to obtain microporous-mesoporous dual-pore composite catalyst E.

[0116] Based on the total weight of the microporous-mesoporous dual-pore composite catalyst E, the content of ZRP-5 molecular sieve is 45% by weight, and the content of HMS all-silica mesoporous molecular sieve is 55% by weight.

[0117] Among them, the specific surface area of ​​the microporous-mesoporous dual-pore composite catalyst E is 690 m². 2 / g, pore volume is 0.62cm³ 3 / g; and the microporous-mesoporous dual-pore composite catalyst has a bimodal pore size distribution and a dual-channel structure, wherein the micropore size is 0.47nm and the mesopore size is 3.2nm.

[0118] The reaction performance of catalyst E was tested according to the reaction performance evaluation method for direct conversion of waste plastics to low-carbon olefins in step (2) of Example 1, and the evaluation results are listed in Table 1.

[0119] Example 6

[0120] This embodiment illustrates the microporous-mesoporous dual-pore composite catalyst prepared according to the present invention and its application in the direct conversion of waste plastics to low-carbon olefins.

[0121] (1) Preparation of microporous-mesoporous dual-pore composite catalysts

[0122] 10.0 g of hexadecylamine was dissolved in a mixed solution of 30.0 g ethanol and 40.0 g distilled water. The solution was heated to 60 °C and stirred for 20 minutes. Then, 30.0 g of tetraethyl orthosilicate (TEOS) was added dropwise. Stirring continued during the dropwise addition, which lasted for 40 minutes. After the addition was complete, the solution was stirred at 60 °C for 5 hours to crystallize. After crystallization, the solid product was separated from the mother liquor by filtration. The solid product was washed 10 times with distilled water, filtered, and then distilled water was added to obtain 500 g of HMS mesoporous molecular sieve slurry F.

[0123] 50g of ZRP-5A molecular sieve (SiO2 / Al2O3 molar ratio of 70, specific surface area of ​​329m²) was used. 2 / g, pore volume is 0.16cm³ 3 (g) was added to a 300ml ball mill jar, along with eight 2mm diameter agate grinding balls, and ball milling began. The temperature inside the ball mill jar was controlled at 80℃, the grinding speed was 500r / min, and the milling time was 8h. 2.0g of the ZRP-5A molecular sieve powder obtained after ball milling was added to an HMS all-silica mesoporous molecular sieve slurry and stirred at 300 rpm for 12h to obtain a microporous-mesoporous dual-pore composite catalyst slurry. The white solid obtained by filtration of the microporous-mesoporous dual-pore composite catalyst slurry was dried at 120℃ for 3h and calcined at 500℃ for 20h to obtain microporous-mesoporous dual-pore composite catalyst F.

[0124] Based on the total weight of the microporous-mesoporous dual-pore composite catalyst F, the content of ZRP-5 molecular sieve is 20% by weight, and the content of HMS all-silica mesoporous molecular sieve is 80% by weight.

[0125] Among them, the specific surface area of ​​the microporous-mesoporous dual-pore composite catalyst F is 800 m². 2 / g, pore volume is 0.79cm³ 3 / g; and the microporous-mesoporous dual-pore composite catalyst has a bimodal pore size distribution and a dual-channel structure, wherein the micropore size is 0.43nm and the mesopore size is 3.5nm.

[0126] The reaction performance of catalyst F was tested according to the reaction performance evaluation method for direct conversion of waste plastics to low-carbon olefins in step (2) of Example 1. The evaluation results are listed in Table 1.

[0127] Example 7

[0128] This embodiment illustrates the microporous-mesoporous dual-pore composite catalyst prepared according to the present invention and its application in the direct conversion of waste plastics to low-carbon olefins.

[0129] (1) Preparation of microporous-mesoporous dual-pore composite catalysts

[0130] 10.0 g of octadecylamine was dissolved in a mixed solution of 150.0 g of ethanol and 100.0 g of distilled water. After stirring at 20 °C for 1 h, 60.0 g of methyl orthosilicate was added dropwise. Stirring continued during the dropwise addition, which lasted for 2 h. After the dropwise addition was complete, crystallization was carried out at 20 °C for 30 h with stirring. After crystallization, the solid product was separated from the mother liquor by filtration. The solid product was washed five times with ethanol, filtered, and then distilled water was added to obtain 400 g of HMS mesoporous molecular sieve slurry G.

[0131] 50g of ZRP-5C molecular sieve (SiO2 / Al2O3 molar ratio of 300, specific surface area of ​​354m²) was used. 2 / g, pore volume 0.20cm³ 3 (g) was added to a 300ml ball mill jar, along with four 2mm diameter agate grinding balls, and ball milling began. The temperature inside the ball mill jar was controlled at 40℃, the grinding speed was 300r / min, and the milling time was 24h. 20.0g of the ZRP-5C molecular sieve powder obtained after ball milling was added to an HMS all-silica mesoporous molecular sieve slurry and stirred at 600 rpm for 6h to obtain a microporous-mesoporous dual-pore composite catalyst slurry. The white solid obtained by filtration of the microporous-mesoporous dual-pore composite catalyst slurry was dried at 60℃ for 16h and calcined at 650℃ for 6h to obtain microporous-mesoporous dual-pore composite catalyst G.

[0132] Based on the total weight of the microporous-mesoporous dual-pore composite catalyst G, the content of ZRP-5 molecular sieve is 50% by weight, and the content of HMS all-silica mesoporous molecular sieve is 50% by weight.

[0133] Among them, the specific surface area of ​​the microporous-mesoporous dual-pore composite catalyst G is 650 m². 2 / g, pore volume is 0.58cm³ 3 / g; and the microporous-mesoporous dual-pore composite catalyst has a bimodal pore size distribution and a dual-channel structure, wherein the micropore size is 0.47nm and the mesopore size is 3.8nm.

[0134] The reaction performance of catalyst G was tested according to the reaction performance evaluation method for direct conversion of waste plastics to low-carbon olefins in step (2) of Example 1, and the evaluation results are listed in Table 1.

[0135] Comparative Example 1

[0136] (1) Preparation of microporous-mesoporous dual-pore composite catalysts

[0137] 10.0 g of hexadecylamine was dissolved in a mixed solution of 30.0 g ethanol and 40.0 g distilled water. The solution was heated to 60 °C and stirred for 20 minutes. Then, 20.0 g of methyl orthosilicate (TMOS) was added dropwise. Stirring continued during the dropwise addition, which lasted for 40 minutes. After the addition was complete, the solution was stirred at 60 °C for 5 hours to crystallize. After crystallization, the solid product was separated from the mother liquor by filtration. The solid product was washed 10 times with distilled water, filtered, and then distilled water was added to obtain 300 g of HMS mesoporous molecular sieve slurry D1.

[0138] 50g of ZRP-5A molecular sieve (SiO2 / Al2O3 molar ratio of 70, specific surface area of ​​329m²) was used. 2 / g, pore volume is 0.16cm³ 3 (g) was added to a 300ml ball mill jar, along with eight 2mm diameter agate grinding balls, and milling began. The temperature inside the ball mill jar was controlled at 80℃, the grinding speed was 500 rpm, and the milling time was 8 hours. 0.8g of the resulting ZRP-5A molecular sieve powder was added to an HMS all-silica mesoporous molecular sieve slurry and stirred at 300 rpm for 12 hours to obtain a microporous-mesoporous dual-pore composite catalyst slurry. The white solid obtained by filtration of the microporous-mesoporous dual-pore composite catalyst slurry was dried at 120℃ for 3 hours and calcined at 500℃ for 20 hours to obtain microporous-mesoporous dual-pore composite catalyst D1.

[0139] Based on the total weight of the microporous-mesoporous dual-pore composite catalyst D1, the content of ZRP-5 molecular sieve is 10% by weight, and the content of HMS all-silica mesoporous molecular sieve is 90% by weight.

[0140] Among them, the specific surface area of ​​the microporous-mesoporous dual-porous composite catalyst D1 is 953 m². 2 / g, pore volume is 0.94cm³ 3 / g, with dual-channel pore sizes of 0.43nm and 3.6nm, respectively.

[0141] The reaction performance of catalyst D1 was tested according to the reaction performance evaluation method for direct conversion of waste plastics to low-carbon olefins in step (2) of Example 1, and the evaluation results are listed in Table 1.

[0142] Comparative Example 2

[0143] (1) Preparation of microporous-mesoporous dual-pore composite catalysts

[0144] 10.0 g of octadecylamine was dissolved in a mixed solution of 150.0 g of ethanol and 100.0 g of distilled water. After stirring at 20 °C for 1 h, 80.0 g of butyl orthosilicate was added dropwise. Stirring continued during the dropwise addition, which lasted for 2 h. After the dropwise addition was complete, crystallization was carried out at 20 °C for 30 h with stirring. After crystallization, the solid product was separated from the mother liquor by filtration. The solid product was washed five times with ethanol, filtered, and then distilled water was added to obtain 600 g of HMS mesoporous molecular sieve slurry D2.

[0145] 50g of ZRP-5C molecular sieve (SiO2 / Al2O3 molar ratio of 300, specific surface area of ​​354m²) was used. 2 / g, pore volume 0.20cm³ 3(g) was added to a 300ml ball mill jar, along with four 2mm diameter agate grinding balls, and ball milling began. The temperature inside the ball mill jar was controlled at 40℃, the grinding speed was 300r / min, and the milling time was 24h. 54.0g of the ZRP-5C molecular sieve powder obtained after ball milling was added to an HMS all-silica mesoporous molecular sieve slurry and stirred at 600 rpm for 6h to obtain a microporous-mesoporous dual-pore composite catalyst slurry. The white solid obtained by filtration of the microporous-mesoporous dual-pore composite catalyst slurry was dried at 60℃ for 16h and calcined at 650℃ for 6h to obtain microporous-mesoporous dual-pore composite catalyst D2.

[0146] Based on the total weight of the microporous-mesoporous dual-pore composite catalyst D2, the content of ZRP-5 molecular sieve is 80% by weight, and the content of HMS all-silica mesoporous molecular sieve is 20% by weight.

[0147] Among them, the specific surface area of ​​the microporous-mesoporous dual-porous composite catalyst D2 is 478 m². 2 / g, pore volume 0.35cm³ 3 / g, with dual-channel pore sizes of 0.47nm and 3.3nm, respectively.

[0148] The reaction performance of catalyst D2 was tested according to the reaction performance evaluation method for direct conversion of waste plastics to low-carbon olefins in step (2) of Example 1. The evaluation results are listed in Table 1.

[0149] Comparative Example 3

[0150] The cracking catalyst was prepared using the same method as in Example 1, except that:

[0151] Step (1) in Example 1 was omitted, and ZRP-5 molecular sieve was used as the cracking catalyst instead, without the addition of HMS all-silica mesoporous molecular sieve.

[0152] The reaction performance of ZRP-5B molecular sieve was tested according to the reaction performance evaluation method for direct conversion of waste plastics to low-carbon olefins in step (2) of Example 1. The evaluation results are listed in Table 1.

[0153] Comparative Example 4

[0154] The cracking catalyst was prepared using the same method as in Example 1, except that:

[0155] The pyrolysis catalyst was prepared according to step (1) of Example 1, except that the preparation conditions were changed and HMS mesoporous molecular sieve was used instead of ZRP-5 molecular sieve. The specific process is as follows:

[0156] 10.0 g of dodecylamine was dissolved in a mixed solution of 72.0 g ethanol and 63.0 g distilled water, heated to 40 °C, and stirred for 30 minutes. Then, 42.0 g of tetraethyl orthosilicate (TEOS) was added dropwise. Stirring continued during the dropwise addition, which lasted for 2 hours. After the addition was complete, crystallization was carried out at 40 °C for another 20 hours with stirring. After crystallization, the solid product was separated from the mother liquor by filtration. The solid product was washed 8 times with anhydrous ethanol, dried at 90 °C for 5 hours, and calcined at 600 °C for 12 hours to obtain 11.5 g of HMS all-silica mesoporous molecular sieve A.

[0157] The specific surface area of ​​HMS all-silica mesoporous molecular sieve A is 1021 m². 2 / g, pore volume is 1.02cm³ 3 / g.

[0158] The reaction performance of HMS all-silica mesoporous molecular sieve A was tested according to the reaction performance evaluation method for direct conversion of waste plastics to low-carbon olefins in step (2) of Example 1. The evaluation results are listed in Table 1.

[0159] Comparative Example 5

[0160] The cracking catalyst was prepared using the same method as in Example 1, except that:

[0161] The ball milling process of ZRP-5B molecular sieve in step (1) of Example 1 and the slurrying process in catalyst preparation were cancelled. Instead, 3.5g of ZRP-5B molecular sieve and 6.5g of HMS all-silica mesoporous molecular sieve A were directly mixed to obtain catalyst D3.

[0162] The reaction performance of catalyst D3 was tested according to the reaction performance evaluation method for direct conversion of waste plastics to low-carbon olefins in step (2) of Example 1. The evaluation results are listed in Table 1.

[0163] Comparative Example 6

[0164] The cracking catalyst was prepared using the same method as in Example 1, except that:

[0165] The HMS all-silica mesoporous molecular sieve was replaced with commercially available silica powder, and a microporous-mesoporous dual-porous composite catalyst was prepared by ball milling. The specific process is as follows:

[0166] 18g of ZRP-5B molecular sieve (SiO2 / Al2O3 molar ratio of 100, specific surface area of ​​342m²) was used. 2 / g, pore volume is 0.18cm³ 3 / g) and 32g of commercially available silica powder (specific surface area of ​​274m²) 2 / g, pore volume is 0.54cm³ 3(g) was added to a 300ml ball mill jar, and six agate grinding balls with a diameter of 2mm were placed inside. Ball milling was then started. The temperature inside the ball mill jar was controlled at 60℃, the rotation speed of the grinding balls was 400r / min, and the ball milling time was 16h, to obtain the microporous-mesoporous dual-pore composite catalyst D4.

[0167] Based on the total weight of catalyst D4, the ZRP-5 molecular sieve content is 36 wt% and the silica content is 64 wt%.

[0168] Catalyst D4 has a specific surface area of ​​296 m². 2 / g, pore volume is 0.40cm³ 3 / g, with dual-channel pore sizes of 0.45nm and 17nm respectively.

[0169] The reaction performance of catalyst D4 was tested according to the reaction performance evaluation method for direct conversion of waste plastics to low-carbon olefins in step (2) of Example 1. The evaluation results are listed in Table 1.

[0170] Comparative Example 7

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

[0172] The microporous-mesoporous biporous composite catalyst D5 was prepared according to the method in step (1) of Example 1.

[0173] The difference is that the ZRP-5B molecular sieve is replaced with a ZSM-5 molecular sieve. The specific process is as follows:

[0174] 10.0 g of dodecylamine was dissolved in a mixed solution of 72.0 g ethanol and 63.0 g distilled water. The solution was heated to 40 °C and stirred for 30 minutes. Then, 42.0 g of tetraethyl orthosilicate (TEOS) was added dropwise. Stirring continued during the dropwise addition, which lasted for 2 hours. After the addition was complete, the solution was stirred at 40 °C for 20 hours to crystallize. After crystallization, the solid product was separated from the mother liquor by filtration. The solid product was washed eight times with anhydrous ethanol, filtered, and then distilled water was added to obtain 400 g of HMS mesoporous molecular sieve slurry A.

[0175] 50g of ZSM-5 molecular sieve (SiO2 / Al2O3 molar ratio of 25, specific surface area of ​​337m²) was used. 2 / g, pore volume is 0.27cm³ 3(g) was added to a 300ml ball mill jar, along with six 2mm diameter agate grinding balls, and milling began. The temperature inside the ball mill jar was controlled at 60℃, the grinding speed was 400 rpm, and the milling time was 16 hours. 6.2g of the resulting ZSM-5 molecular sieve powder was added to an HMS all-silica mesoporous molecular sieve slurry and stirred at 500 rpm for 10 hours to obtain a microporous-mesoporous dual-pore composite catalyst slurry. The white solid obtained by filtration of the microporous-mesoporous dual-pore composite catalyst slurry was dried at 90℃ for 5 hours and calcined at 600℃ for 12 hours to obtain the microporous-mesoporous dual-pore composite catalyst D5.

[0176] Based on the total weight of catalyst D5, the content of ZSM-5 molecular sieve is 36% by weight, and the content of HMS all-silica mesoporous molecular sieve is 64% by weight.

[0177] The reaction performance of catalyst D5 was tested according to the reaction performance evaluation method for direct conversion of waste plastics to low-carbon olefins in step (2) of Example 1. The evaluation results are listed in Table 1.

[0178] The reaction performance of catalyst D5 was tested according to the reaction performance evaluation method for direct conversion of waste plastics to low-carbon olefins in step (2) of Example 1. The evaluation results are listed in Table 1.

[0179] Table 1

[0180]

[0181]

[0182] The results above demonstrate that the microporous-mesoporous dual-porous composite catalyst provided by this invention can directly catalytically convert waste plastics into low-carbon olefins. The waste plastic conversion rate is 100%, and the low-carbon olefin yield is high.

[0183] In Comparative Example 1, the content of HMS all-silica mesoporous molecular sieve was too high, while the content of ZRP-5 molecular sieve was too low. Due to the limited number of acidic centers on the catalyst and insufficient activation sites during the reaction, the feed conversion rate and the yield of low-carbon olefins were low.

[0184] In Comparative Example 2, the content of HMS all-silica mesoporous molecular sieve was too low, while the content of ZRP-5 molecular sieve was too high. The low yield of low-carbon olefins was due to the limited number of mesoporous channels in the catalyst, which hindered the diffusion of reactant and product molecules during the reaction.

[0185] In Comparative Example 3, only ZRP-5 molecular sieve was used as the cracking catalyst, and HMS all-silica mesoporous molecular sieve was not added. Because the catalyst does not contain mesoporous channels, the diffusion of reactant and product molecules is hindered during the reaction, resulting in a low yield of low-carbon olefins.

[0186] In Comparative Example 4, only HMS all-silica mesoporous molecular sieve was used as the cracking catalyst, without the addition of ZRP-5 molecular sieve. Since there are almost no active acidic centers on the catalyst, the feed conversion rate is low and the yield of low-carbon olefins is low.

[0187] In Comparative Example 5, the ball milling process of ZRP-5 molecular sieve and the slurry preparation process in catalyst preparation were omitted, and ZRP-5 molecular sieve was directly mixed with HMS all-silica mesoporous molecular sieve. Due to insufficient uniformity in the mixing of the microporous molecular sieve with acidic centers and the HMS molecular sieve with mesoporous structure, the yield of low-carbon olefins was relatively low.

[0188] In Comparative Example 6, commercially available silica powder was used to replace HMS all-silica mesoporous molecular sieve. Due to the irregular mesoporous channel structure of commercially available silica, the yield of low-carbon olefins was relatively low.

[0189] In Comparative Example 7, ZSM-5 molecular sieve with a SiO2 / Al2O3 molar ratio of 25 was used instead of ZRP-5 molecular sieve. Due to the greater acidity of the acid centers of ZSM-5 molecular sieve, more reaction byproducts were produced, resulting in a lower yield of low-carbon olefins.

[0190] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. The application of a microporous-mesoporous dual-porous composite catalyst in the direct catalytic cracking of waste plastics to produce low-carbon olefins, the application including: The microporous-mesoporous dual-pore composite catalyst is reacted with waste plastic, characterized in that the waste plastic is waste polyethylene plastic particles, the microporous-mesoporous dual-pore composite catalyst comprises ZRP-5 molecular sieve and HMS all-silica mesoporous molecular sieve, the pore size of the microporous-mesoporous dual-pore composite catalyst exhibits a bimodal distribution, with micropore pore size of 0.3-0.6 nm and mesopore pore size of 2-5 nm; the specific surface area of ​​the microporous-mesoporous dual-pore composite catalyst is 650-800 m². 2 / g, with a pore volume of 0.58-0.79mL / g; and based on the total weight of the microporous-mesoporous biporous composite catalyst, the content of ZRP-5 molecular sieve is 20-50% by weight, and the content of HMS all-silica mesoporous molecular sieve is 50-80% by weight. The preparation method of the microporous-mesoporous dual-pore composite catalyst includes: (I) The ZRP-5 molecular sieve was ball-milled to obtain the ball-milled ZRP-5 molecular sieve; (II) Mix HMS all-silica mesoporous molecular sieve raw powder with water to obtain HMS all-silica mesoporous molecular sieve raw slurry; (III) The ball-milled ZRP-5 molecular sieve and the HMS all-silica mesoporous molecular sieve slurry are brought into contact and pulped to obtain a microporous-mesoporous dual-pore composite catalyst slurry; (IV) The microporous-mesoporous dual-pore composite catalyst slurry is filtered, dried and calcined to obtain the microporous-mesoporous dual-pore composite catalyst.

2. The application according to claim 1, wherein, The micropore-mesopore dual-pore composite catalyst has a micropore diameter of 0.4-0.5 nm and a mesopore diameter of 3-4 nm.

3. The application according to claim 2, wherein, The micropore-mesopore dual-pore composite catalyst has a micropore diameter of 0.43-0.47 nm and a mesopore diameter of 3.2-3.8 nm.

4. The application according to claim 1, wherein, Based on the total weight of the microporous-mesoporous dual-pore composite catalyst, the content of ZRP-5 molecular sieve is 25-45% by weight, and the content of HMS all-silica mesoporous molecular sieve is 55-75% by weight.

5. The application according to claim 4, wherein, Based on the total weight of the microporous-mesoporous dual-pore composite catalyst, the content of ZRP-5 molecular sieve is 30-40% by weight, and the content of HMS all-silica mesoporous molecular sieve is 60-70% by weight.

6. The application according to claim 1, wherein, The SiO2 / Al2O3 molar ratio of the ZRP-5 molecular sieve is 70-300.

7. The application according to claim 6, wherein, The ZRP-5 molecular sieve is selected from one or more of ZRP-5A molecular sieve, ZRP-5B molecular sieve, and ZRP-5C molecular sieve.

8. The application according to claim 1, wherein, The specific surface area of ​​the microporous-mesoporous dual-pore composite catalyst is 690-780 m². 2 / g, with a pore volume of 0.62-0.75mL / g.

9. The application according to claim 8, wherein, The specific surface area of ​​the microporous-mesoporous dual-pore composite catalyst is 725-776 m². 2 / g, with a pore volume of 0.66-0.72mL / g.

10. The application according to claim 1, wherein, The conditions for ball milling include: a ball rotation speed of 200-600 r / min, a ball milling jar temperature of 30-90℃, and a milling time of 5-50 h.

11. The application according to claim 1, wherein, The conditions for pulping include: stirring speed ≥ 100 rpm and stirring time 1-24h.

12. The application according to claim 11, wherein, The pulping conditions include: stirring speed ≥ 300 rpm and stirring time 5-12 h.

13. The application according to claim 1, wherein, The weight ratio of the ZRP-5 molecular sieve to the HMS all-silica mesoporous molecular sieve slurry is 1:(20-250).

14. The application according to claim 13, wherein, The weight ratio of the ZRP-5 molecular sieve to the HMS all-silica mesoporous molecular sieve slurry is 1:(50-180).

15. The application according to claim 1, wherein, The preparation method of the HMS all-silica mesoporous molecular sieve raw powder includes: (1) Under hydrolytic gelation conditions, the template agent, alcohol and water are mixed and contacted to obtain a mixture; wherein the template agent is a neutral surfactant; (2) The silicon source is added dropwise to the mixture to obtain a gel mixture; (3) The gel mixture is crystallized; then the crystallized product is filtered and washed to obtain HMS all-silica mesoporous molecular sieve powder.

16. The application according to claim 15, wherein, The template agent is selected from one or more of dodecylamine, tetradecylamine, hexadecylamine, and octadecylamine.

17. The application according to claim 15, wherein, The alcohol is ethanol.

18. The application according to claim 15, wherein, The silicon source is a silicon-containing organic compound and / or a silicon-containing inorganic compound.

19. The application according to claim 18, wherein, The silicon source is a silicon-containing organic compound.

20. The application according to claim 19, wherein, The silicon source is one or more of tetraethyl orthosilicate, methyl orthosilicate, and butyl orthosilicate.

21. The application according to claim 15, wherein, The weight ratio of the template agent, the alcohol, the water and the silicon source is 1:(1-30):(2-20):(1-12); And / or, the crystallization conditions include: a temperature of 10-80°C and a time of 3-48 hours.

22. The application according to claim 21, wherein, The weight ratio of the template agent, the alcohol, the water and the silicon source is 1:(3-15):(4-10):(2-8).

23. The application according to claim 1, wherein, In the reaction of the microporous-mesoporous dual-pore composite catalyst with the waste plastic, the contact conditions include: temperature of 420-580℃, pressure of 0.01-1MPa, and time of 0.5-12h. And / or, the weight ratio of the microporous-mesoporous dual-pore composite catalyst to the waste polyethylene plastic particles is 1:(0.5-50).

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