Modified catalyst, preparation method thereof and application of modified catalyst in low-carbon olefin production from waste plastics

Abstract

The present application relates to the field of catalyst and the field of recycling of polymer materials, and discloses a modified catalyst, a preparation method thereof and application of the modified catalyst in a reaction of preparing low-carbon olefins from waste plastics. The modified catalyst comprises a composite molecular sieve and a modified oxide supported on the composite molecular sieve, the composite molecular sieve comprises an Hbeta molecular sieve and a high-specific-surface-area all-silicon mesoporous molecular sieve, and the content of the Hbeta molecular sieve is 24-55% by weight, the content of the high-specific-surface-area all-silicon mesoporous molecular sieve is 43-66% by weight, and the content of the modified oxide is 2-10% by weight, based on the total weight of the modified catalyst. The modified catalyst is applied in the reaction of preparing low-carbon olefins from waste plastics, which not only solves the problem of recycling of waste plastics, but also increases the yield of important chemical raw material, 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 modified catalyst, a preparation method thereof and application of the modified catalyst in a reaction of producing low-carbon olefins from waste plastics. BACKGROUND

[0002] Plastic products have the characteristics of light weight, high strength, corrosion resistance, good chemical stability, easy processing and aesthetic 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 chemical recycling scheme of waste plastics mainly includes 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 thermal chemical decomposition reaction occurs under high-temperature anaerobic conditions, and the macromolecular organic matter in waste plastic products is converted into small-molecular liquid matter, fuel gas and coke. 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, as an improvement of the catalytic cracking method, 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, and has good energy recovery, so it 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. If a large amount of low-carbon olefins is needed, a two-stage method of thermal cracking-catalytic upgrading method needs to be used.

[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 application aims to overcome the problem of low content of low-carbon olefins in the prior art waste plastic chemical recycling approach, and provides a modified catalyst, a preparation method thereof and application of the modified catalyst in a reaction of preparing low-carbon olefins from waste plastics.

[0007] To achieve the above-mentioned purpose, the application provides a modified catalyst in a first aspect, wherein the modified catalyst comprises a composite molecular sieve and a modified oxide supported on the composite molecular sieve, the composite molecular sieve comprises an Hβ molecular sieve and a high-specific-surface-area all-silicon mesoporous molecular sieve, and the content of the Hβ molecular sieve is 24-55 wt%, the content of the high-specific-surface-area all-silicon mesoporous molecular sieve is 43-66 wt%, and the content of the modified oxide is 2-10 wt% based on the total weight of the modified catalyst.

[0008] The application provides a preparation method of a modified catalyst in a second aspect, wherein the method comprises:

[0009] The Hβ molecular sieve, the high-specific-surface-area all-silicon mesoporous molecular sieve and a modified oxide precursor are mixed, ball milled and then calcined to obtain the modified catalyst.

[0010] The application provides a modified catalyst prepared by the preparation method in a third aspect.

[0011] The application provides application of the modified catalyst in a fourth aspect.

[0012] Through the above technical solution, the technical solution of the application has the following advantages:

[0013] (1) The modified catalyst provided by the application has raw materials that are easy to obtain, a simple preparation method, easy-to-control conditions and good product repeatability.

[0014] (2) The modified catalyst provided by the application comprises a zeolite molecular sieve (Hβ molecular sieve) with a certain surface acidity and a mesoporous material with a large pore size, has a stable structure, good high-temperature resistance and helps the diffusion of raw material and product molecules in the cracking reaction process.

[0015] (3) The modified catalyst provided by the application can convert waste plastics into low-carbon olefins in one step when used in the reaction of preparing low-carbon olefins from waste plastics by direct catalytic cracking, and is a new method for chemical recycling of waste plastics; the application solves the problem of recycling waste plastics and increases the production of important chemical raw material low-carbon olefins, and has good economic benefits.

[0016] (4) The modified catalyst provided by the present application has mild process conditions, is easy to operate, and has low requirements for the reaction device when used in the reaction of direct catalytic cracking of waste plastics to produce low-carbon olefins.

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

[0018] Figure 1 is a small-angle X-ray diffraction (XRD) spectrum of the modified catalyst A of Example 1;

[0019] Figure 2 is a wide-angle X-ray diffraction (XRD) spectrum of the modified catalyst A of Example 1. DETAILED DESCRIPTION

[0020] The endpoints of the ranges and any values claimed herein are not to be understood as being limited to the exact values recited as implicitly included within the range. The range format is used herein to literally describe a range from the one particular endpoint to the other particular endpoint. Any numeric range recited herein is inclusive of the values that are implicitly described as being between the recited range endpoints. Numeric ranges include endpoints unless specifically indicated otherwise. Numeric ranges include endpoints unless specifically indicated otherwise.

[0021] As described previously, the first aspect of the present application provides a modified catalyst, wherein the modified catalyst comprises a composite molecular sieve and a modified oxide supported on the composite molecular sieve, the composite molecular sieve comprises an Hβ molecular sieve and a high specific surface area all-silica mesoporous molecular sieve, and the content of the Hβ molecular sieve is 24-55 wt%, the content of the high specific surface area all-silica mesoporous molecular sieve is 43-66 wt%, and the content of the modified oxide is 2-10 wt% based on the total weight of the modified catalyst.

[0022] 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 the purpose of the present application is to solve this problem. According to the understanding of the physical and chemical properties of the heterogeneous catalyst by the inventors, the catalyst for directly preparing low-carbon olefins by catalytic cracking of waste plastics should have a certain acidity and good hydrothermal stability. Based on the above requirements, zeolite molecular sieves with stable framework structure and certain acidity are very suitable as the main component of the modified catalyst. However, because the pore size of the zeolite molecular sieve is small (less than 1.0 nm), and the molecular weight of the waste plastic product is large, the molecular chain is also relatively long. During the cracking reaction of the waste plastic product, the large-sized reactant molecules and product molecules have difficulty in diffusing in the narrow pores, which not only affects the contact of the reactants with 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 zeolite molecular sieve, the high specific surface area all-silicon mesoporous molecular sieve material has a larger pore size (greater than 2.0 nm) and a large pore volume, and is very suitable for catalytic reactions involving large molecules. However, the surface acidity of the all-silicon mesoporous molecular sieve material is extremely weak, and it is not suitable for being used alone as a catalyst for cracking reaction of waste plastics. The inventors of the present application found during the development and research of the modified catalyst for waste plastics that if the structural advantages of the all-silicon mesoporous inorganic material and the surface acid center of the zeolite molecular sieve are comprehensively utilized, a certain amount of high specific surface area all-silicon mesoporous molecular sieve is mixed with and modified by the acid Hβ molecular sieve, and is applied to the catalytic conversion reaction of waste plastics as a cracking catalyst, the activity of the cracking catalyst can be effectively improved, and the selectivity of low-carbon olefins can be increased.

[0023] According to the present application, preferably, the content of the Hβ molecular sieve is 29-51% by weight, the content of the high specific surface area all-silicon mesoporous molecular sieve is 46-62% by weight, and the content of the modified oxide is 3-9% by weight, based on the total weight of the modified catalyst; more preferably, the content of the Hβ molecular sieve is 34-46% by weight, the content of the high specific surface area all-silicon mesoporous molecular sieve is 50-58% by weight, and the content of the modified oxide is 4-8% by weight. In the present application, the use of the specific contents of the aforementioned components can make the prepared modified catalyst have better catalytic activity and higher selectivity of low-carbon olefins when used in the reaction of directly catalytic cracking of waste plastics to produce low-carbon olefins.

[0024] According to the present application, the modified oxide is selected from one or more of alkaline earth metal oxides, transition metal oxides, metalloid oxides and rare earth metal oxides; preferably, the modified oxide is selected from one or more of boron oxide, magnesium oxide, calcium oxide, strontium oxide, barium oxide, zinc oxide, copper oxide, cobalt oxide, cerium oxide, lanthanum oxide and zirconium dioxide. In the present application, the specific modified oxide selected from the present application can improve the surface electron distribution of the zeolite molecular sieve and mesoporous molecular sieve, and selectively cover part of the excessively strong acid centers, so that the surface properties of the catalyst are more suitable for the performance of waste plastic cracking reaction.

[0025] According to the present application, the specific surface area of the modified catalyst is 700-900 m 2 / g, and the pore volume is 0.5-1 cm 3 / g; preferably, the specific surface area of the modified catalyst is 720-872 m 2 / g, and the pore volume is 0.6-0.9 cm 3 / g.

[0026] According to the present application, the inventors of the present application use a mixture of Hβ molecular sieve with a SiO2 / Al2O3 molar ratio of 15-200 and high specific surface area full-silicon mesoporous molecular sieve as the main base component, and introduce a modified oxide as a modified component, so that the catalyst activity and low carbon olefin selectivity can be improved. Preferably, when the SiO2 / Al2O3 molar ratio of the Hβ molecular sieve is 40-100, the catalyst activity and low carbon olefin selectivity can be significantly improved.

[0027] According to the present application, the Hβ molecular sieve can be obtained by commercial purchase. In the present application, specifically, the Hβ molecular sieve is more preferably: Hβ molecular sieve with a SiO2 / Al2O3 molar ratio of 40 purchased from Nanjing Jicang Nanotechnology Co., Ltd.; Hβ molecular sieve with a SiO2 / Al2O3 molar ratio of 100 purchased from Nanjing Jicang Nanotechnology Co., Ltd.; Hβ molecular sieve with a SiO2 / Al2O3 molar ratio of 50 purchased from Shanghai Shenyuan New Material Technology Group Co., Ltd.

[0028] According to the present application, the high specific surface area full-silicon mesoporous molecular sieve has a specific surface area of 800-1400 m 2 / g, a pore volume of 0.7-1.7 cm 3 / g, and an average pore diameter of 2-4 nm; preferably, the high specific surface area full-silicon mesoporous molecular sieve has a specific surface area of 950-1300 m 2 / g, a pore volume of 1.1-1.6 cm 3The average pore size is 3-4 nm. In the present application, the high specific surface area full-silicon mesoporous molecular sieve with the specific parameters mentioned above can make the modified catalyst prepared for the direct catalytic cracking of waste plastics to produce low-carbon olefins have better catalytic activity and higher selectivity.

[0029] According to the present application, the preparation method of the high specific surface area full-silicon mesoporous molecular sieve comprises:

[0030] 1) mixing and contacting a template agent, tetraethyl orthosilicate and an aqueous ammonia solution under hydrolysis conditions to obtain a mixture;

[0031] 2) performing crystallization, filtration, washing and drying treatment on the mixture to obtain high specific surface area full-silicon mesoporous molecular sieve raw powder;

[0032] 3) removing the template agent in the high specific surface area mesoporous material raw powder to obtain the high specific surface area full-silicon mesoporous molecular sieve.

[0033] According to the present application, the template agent is a cationic surfactant, preferably hexadecyl trimethyl ammonium bromide.

[0034] According to the present application, the molar ratio of the tetraethyl orthosilicate, the template agent, ammonia and water is 1:(0.1-1):(0.5-5):(50-500), preferably 1:(0.2-0.6):(1-4):(100-300).

[0035] According to the present application, the hydrolysis conditions include a temperature of 20-60℃ and a time of 20-120min.

[0036] According to the present application, the crystallization conditions include a temperature of 40-140℃, preferably 70-120℃, and a time of 5-120h, preferably 24-72h.

[0037] According to the present application, the filtration method is not particularly required 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 comprises using a suction filter bottle, vacuumizing the bottom side of the funnel or using a centrifugal filter.

[0038] According to the present application, the method of washing the solid product is not particularly required, for example: deionized water can be used to wash the solid product, the volume ratio of deionized water to solid product can be 5-20, and the washing times can be 2-8 times.

[0039] According to the present application, the drying conditions include a temperature of 70-140℃ and a time of 4-20h.

[0040] According to the present application, the method for removing the template agent has no special requirements and can be various existing methods, such as a calcination method or an extraction method. The conditions of the calcination method can be a temperature of 400-650℃, preferably 450-600℃; and a time of 4-60h, preferably 8-30h.

[0041] The second aspect of the present application provides a preparation method of a modified catalyst, wherein the method comprises: mixing Hβ zeolite, high specific surface area all-silica mesoporous zeolite and a modified oxide precursor, ball milling and calcination treatment to obtain the modified catalyst.

[0042] According to the present application, the modified oxide precursor is selected from inorganic salts or inorganic acids containing alkaline earth metals, transition metals, metalloids and rare earth metals; preferably, the modified oxide precursor is selected from inorganic salts or inorganic acids containing boron, magnesium, calcium, strontium, barium, zinc, copper, cobalt, cerium, lanthanum and zirconium.

[0043] According to the present application, the weight ratio of the Hβ zeolite, the high specific surface area all-silica mesoporous zeolite and the modified oxide precursor is 1:(0.5-3):(0.05-1.2), preferably 1:(0.8-2.5):(0.15-0.8).

[0044] According to the present application, the ball milling is carried out in a ball mill, wherein the diameter of the grinding balls in the ball mill can be 2-3mm; the number of the 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 100-300mL, usually 2-8 grinding balls can be used; the material of the grinding balls is agate or polytetrafluoroethylene, preferably agate. The conditions of the ball milling include: the rotating speed of the grinding balls can be 200-600r / min, preferably 300-500r / min; the temperature in the ball mill jar can be 30-90℃, preferably 40-80℃; and the time of the ball milling can be 5-50h, preferably 8-24h.

[0045] According to the present application, the conditions of the calcination include: a temperature of 450-750℃, preferably 550-650℃; and a time of 2-30h, preferably 5-16h.

[0046] In the preparation method of the present application, the Hβ zeolite and the high specific surface area all-silica mesoporous zeolite are consistent with the foregoing description, which will not be repeated here.

[0047] The third aspect of the present application provides a modified catalyst prepared by the foregoing preparation method.

[0048] The fourth aspect of the present application provides an application of the foregoing modified catalyst in a reaction of direct catalytic cracking of waste plastics to produce low-carbon olefins.

[0049] According to the application, the application method of the catalyst comprises: reacting the waste plastic powder with the modified catalyst.

[0050] In the application, the conditions for contacting the waste plastic powder with the modified catalyst comprise: the temperature for contacting can be 420-580℃, preferably 450-540℃; the pressure for contacting can be 0.01-1.0Mpa, preferably 0.05-0.5Mpa; the time for contacting can be 0.5-12h, preferably 1-5h; and the weight ratio of the modified catalyst to the waste plastic powder can be 1:0.5-50, preferably 1:2-30.

[0051] The application will be described in detail below through examples.

[0052] In the following examples and comparative examples:

[0053] 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°.

[0054] 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°.

[0055] 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 4h before determination, the specific surface area of the sample was calculated by BET method, and the pore volume was calculated by BJH model.

[0056] 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.

[0057] The drying oven was produced by Shanghai Yiheng Scientific Instrument Co., Ltd., and the model was DHG-9030A.

[0058] The muffle furnace was produced by CARBOLITE Company, and the model was CWF1100.

[0059] The Hβ molecular sieve with a SiO2 / Al2O3 molar ratio of 40 used in the examples and comparative examples was purchased from Nanjing Jicang Nanometer Technology Co., Ltd.; the Hβ molecular sieve with a SiO2 / Al2O3 molar ratio of 100 was purchased from Nanjing Jicang Nanometer Technology Co., Ltd.; and the Hβ molecular sieve with a SiO2 / Al2O3 molar ratio of 50 was purchased from Shanghai Shenyuan New Material Technology Group Co., Ltd. The other reagents used in the examples and comparative examples were purchased from National Pharmaceutical Group Chemical Reagent Co., Ltd., and the reagent purity was analytical pure.

[0060] Example 1

[0061] (1) Preparation of high specific surface area all-silica mesoporous molecular sieve

[0062] At a temperature of 40°C, 25.5 g of template cetyltrimethylammonium bromide, 70 g of ammonia water with a concentration of 25 wt%, and 488 g of deionized water were mixed and stirred for 20 min, and 41.6 g of tetraethyl orthosilicate was slowly added to the above mixture, and stirring was continued for 40 min. The mixture was transferred to a hydrothermal reaction kettle with a polytetrafluoroethylene lining, and after crystallization at 100°C for 48 h, the solid product was separated from the mother liquor by filtration, and washed with deionized water for 5 times, and after suction filtration, it was dried at 110°C for 12 h to obtain high specific surface area all-silica mesoporous molecular sieve raw powder; the high specific surface area all-silica mesoporous molecular sieve raw powder was calcined at 500°C for 16 h in flowing air to obtain high specific surface area all-silica mesoporous molecular sieve A.

[0063] The specific surface area of the high specific surface area all-silica mesoporous molecular sieve A was 1182 m 2 / g, the pore volume was 1.4 cm 3 / g, and the average pore size was 3.5 nm.

[0064] (2) Preparation of modified catalyst

[0065] 20 g of Hβ molecular sieve (SiO2 / Al2O3 molar ratio of 50, specific surface area of 683 m 2 / g, pore size of 0.7 nm, purchased from Shanghai Shenyuan New Material Science and Technology Group Co., Ltd.), 27 g of high specific surface area all-silica mesoporous molecular sieve A, 12.2 g of magnesium nitrate hexahydrate, and 2.0 g of boric acid were added into a 300 ml ball mill jar, 6 maroon grinding balls with a diameter of 2 mm were put in, and ball milling was started. The temperature in the ball mill jar was controlled at 60°C, the rotation speed of the grinding balls was 400 r / min, and the ball milling time was 16 h. The powder obtained after ball milling was calcined at 600°C for 10 h to obtain modified catalyst A.

[0066] Based on the total weight of catalyst A, the content of Hβ molecular sieve was 40 wt%, the content of high specific surface area all-silica mesoporous molecular sieve was 54 wt%, the content of magnesium oxide was 3.8 wt%, and the content of boron oxide was 2.2 wt%.

[0067] The specific surface area of catalyst A was 831 m 2 / g, and the pore volume was 0.8 cm 3 / g.

[0068] Figure 1is the small angle XRD pattern of catalyst A. The pattern shows that the sample has three clear diffraction peaks at small angles below 5°, which proves that the material has a typical two-dimensional hexagonal mesoporous structure. It shows that the high specific surface area full-silica mesoporous molecular sieve still has a relatively regular mesoporous channel structure after being prepared into a catalyst, and the catalyst preparation process does not destroy the basic structure of the mesoporous molecular sieve.

[0069] Figure 2 is the wide angle XRD pattern of catalyst A. The pattern shows that the x-ray diffraction angle of the sample is mainly: 2θ = 7.7°, 13.1°, 22.5° and 25.1°. These four diffraction signals are consistent with the Hβ molecular sieve diffraction pattern, indicating that the Hβ molecular sieve crystal phase did not change significantly during catalyst preparation. In addition, there is no diffraction signal corresponding to the modified oxide in the wide angle XRD pattern, indicating that the modified component is in a uniform dispersed state on the catalyst.

[0070] (3) Performance evaluation of direct conversion of waste plastics to low-carbon olefins

[0071] The performance of the catalyst in the catalytic cracking of methyl tert-butyl ether was evaluated on a fixed bed reaction device. The catalyst loading was 10.0 g, the polyethylene waste plastic loading was 50.0 g, the reaction temperature was 480°C, the reaction pressure was 0.1 MPa, and 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 column and hydrogen flame detector (FID), using programmed temperature and correction factor for quantitative analysis; the liquid composition was analyzed by Agilent 6890 gas chromatograph equipped with PONA column. The reaction results are shown in Table 1.

[0072] Example 2

[0073] (1) Preparation of high specific surface area full-silica mesoporous molecular sieve

[0074] At a temperature of 20°C, 14.6 g of template cetyltrimethylammonium bromide, 28 g of 25wt% ammonia water and 339 g of deionized water were mixed and stirred for 40 min, and 41.6 g of tetraethyl orthosilicate was slowly added to the above mixture, and stirring was continued for 60 min. The mixture was transferred to a hydrothermal reaction kettle with a polytetrafluoroethylene liner, and after crystallization at 120°C for 24 h, the solid product was separated from the mother liquor by filtration and washed with deionized water 8 times, and after suction filtration, it was dried at 70°C for 20 h to obtain high specific surface area full-silica mesoporous molecular sieve raw powder; the high specific surface area full-silica mesoporous molecular sieve raw powder was calcined at 450°C for 30 h in flowing air to obtain high specific surface area full-silica mesoporous molecular sieve B.

[0075] The specific surface area of high specific surface area full-silica mesoporous molecular sieve B is 1169m 2 / g, pore volume 1.4 cm 3 / g, pore diameter 3.3 nm.

[0076] (2) Preparation of modified catalyst

[0077] 23 g of Hβ molecular sieve (molar ratio of SiO2 / Al2O3 100, specific surface area 669 m 2 / g, pore diameter 0.7 nm, purchased from Nanjing Jicang Nanometer Technology Co., Ltd.), 25 g of high specific surface area all-silica mesoporous molecular sieve B, 3.8 g of calcium nitrate and 1.2 g of boric acid were added into a 300 ml ball mill tank, 8 maroon balls with a diameter of 2 mm were put in, and ball milling was started. The temperature in the ball mill tank was controlled at 80°C, the rotation speed of the milling ball was 500 r / min, and the ball milling time was 8 h. The powder obtained after ball milling was calcined at 650°C for 5 h to obtain the modified catalyst B.

[0078] Based on the total weight of catalyst B, the content of Hβ molecular sieve was 46 wt%, the content of high specific surface area all-silica mesoporous molecular sieve was 50 wt%, the content of calcium oxide was 2.6 wt%, and the content of boric oxide was 1.4 wt%.

[0079] The specific surface area of catalyst B was 795 m 2 / g, pore volume 0.7 cm 3 / g.

[0080] The reaction performance of catalyst B was tested according to the method for evaluating the reaction performance of catalysts for direct conversion of waste plastics to low-carbon olefins in step (3) of Example 1, and the evaluation results are shown in Table 1.

[0081] Example 3

[0082] (1) Preparation of high specific surface area all-silica mesoporous molecular sieve

[0083] At a temperature of 60°C, 43.7 g of template hexadecyl trimethyl ammonium bromide, 112 g of 25 wt% ammonia water with a concentration of 25 wt% and 1000 g of deionized water were mixed and stirred for 10 min, and 41.6 g of tetraethyl orthosilicate was slowly added to the above mixture, and stirring was continued for 10 min. The mixture was transferred to a hydrothermal reaction kettle with a polytetrafluoroethylene liner, and after crystallization at 70°C for 72 h, the solid product was separated from the mother liquor by filtration, and washed with deionized water for 6 times, and after suction filtration, it was dried at 140°C for 8 h to obtain high specific surface area all-silica mesoporous molecular sieve raw powder; the high specific surface area all-silica mesoporous molecular sieve raw powder was calcined at 600°C in flowing air for 8 h to obtain high specific surface area all-silica mesoporous molecular sieve C.

[0084] The specific surface area of high specific surface area all-silica mesoporous molecular sieve C was 1147 m 2 / g, pore volume 1.3 cm 3 / g, and the pore volume was 0.7 cm

[0085] (2) Preparation of the modified catalyst

[0086] Hβ zeolite (SiO2 / Al2O3 molar ratio 40, specific surface area 651 m 2 / g, pore size 0.7 nm, purchased from Nanjing Jicang Nanometer Technology Co., Ltd.), 29 g of high specific surface area all-silica mesoporous molecular sieve C, 1.8 g of barium nitrate, 3.7 g of zinc nitrate hexahydrate, and 2.4 g of lanthanum nitrate hexahydrate were added into a 300 ml ball mill jar, 4 maroon grinding balls with a diameter of 2 mm were put into the jar, and the ball milling was started. The temperature in the ball mill jar was controlled at 40°C, the rotation speed of the grinding balls was 300 r / min, and the ball milling time was 24 h. The powder obtained after ball milling was calcined at 550°C for 16 h to obtain the modified catalyst C.

[0087] Based on the total weight of catalyst C, the content of Hβ zeolite was 34 wt%, the content of high specific surface area all-silica mesoporous molecular sieve was 58 wt%, the content of barium oxide was 4.2 wt%, the content of zinc oxide was 2.0 wt%, and the content of lanthanum oxide was 1.8 wt%.

[0088] The specific surface area of catalyst C was 847 m 2 / g, and the pore volume was 0.7 cm 3 / g.

[0089] The reaction performance of catalyst C was tested according to the method for evaluating the reaction performance of catalysts for direct conversion of waste plastics to low-carbon olefins in step (3) in Example 1, and the evaluation results are shown in Table 1.

[0090] Example 4

[0091] The high specific surface area all-silica mesoporous molecular sieve A was prepared according to the method in step (1) in Example 1.

[0092] The modified catalyst D was prepared according to the method in step (2) in Example 1. The preparation conditions were changed, and the specific process was as follows:

[0093] Hβ zeolite (SiO2 / Al2O3 molar ratio 50, specific surface area 683 m 2 / g, pore size 0.7 nm, purchased from Shanghai Shentan New Material Technology Group Co., Ltd.), 31 g of high specific surface area all-silica mesoporous molecular sieve A, 18.3 g of magnesium nitrate hexahydrate, and 3.0 g of boric acid were added into a 300 ml ball mill jar, 6 maroon grinding balls with a diameter of 2 mm were put into the jar, and the ball milling was started. The temperature in the ball mill jar was controlled at 60°C, the rotation speed of the grinding balls was 400 r / min, and the ball milling time was 16 h. The powder obtained after ball milling was calcined at 600°C for 10 h to obtain the modified catalyst D.

[0094] The content of the Hβ molecular sieve was 29% by weight, the content of the high specific surface area all-silica mesoporous molecular sieve was 62% by weight, the content of magnesium oxide was 5.7% by weight, and the content of boron oxide was 3.3% by weight, based on the total weight of catalyst D.

[0095] The specific surface area of catalyst D was 856 m 2 / g, and the pore volume was 0.9 cm 3 / g.

[0096] 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 (3) in Example 1, and the evaluation results are listed in Table 1.

[0097] Example 5

[0098] The high specific surface area all-silica mesoporous molecular sieve B was prepared according to the method in step (1) in Example 2.

[0099] The modified catalyst E was prepared according to the method in step (2) in Example 2. The preparation conditions were changed, and the specific process was as follows:

[0100] 25.5 g of Hβ molecular sieve (SiO2 / Al2O3 molar ratio was 100, specific surface area was 669 m 2 / g, pore size was 0.7 nm, and was purchased from Nanjing Jicang Nanometer Technology Co., Ltd.), 23 g of high specific surface area all-silica mesoporous molecular sieve B, 2.8 g of calcium nitrate, and 0.9 g of boric acid were added into a 300 ml ball mill tank, 8 maroon grinding balls with a diameter of 2 mm were put into the tank, and ball milling was started. The temperature in the ball mill tank was controlled at 80°C, the rotating speed of the grinding ball was 500 r / min, and the ball milling time was 8 h. After ball milling, the obtained powder was calcined at 650°C for 5 h to obtain the modified catalyst E.

[0101] The content of the Hβ molecular sieve was 51% by weight, the content of the high specific surface area all-silica mesoporous molecular sieve was 46% by weight, the content of calcium oxide was 1.9% by weight, and the content of boron oxide was 1.1% by weight, based on the total weight of catalyst E.

[0102] The specific surface area of catalyst E was 746 m 2 / g, and the pore volume was 0.6 cm 3 / g.

[0103] 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 (3) in Example 1, and the evaluation results are listed in Table 1.

[0104] Example 6

[0105] The high specific surface area all-silica mesoporous molecular sieve A was prepared according to the method in step (1) in Example 1.

[0106] Modified catalyst F was prepared according to the method of step (2) in Example 1. The preparation conditions were changed, and the specific process was as follows:

[0107] 12 g of Hβ molecular sieve (molar ratio of SiO2 / Al2O3 was 50, specific surface area was 683 m 2 / g, pore size was 0.7 nm, purchased from Shanghai Shengyan New Material Science and Technology Group Co., Ltd.), 33 g of high specific surface area all-silica mesoporous molecular sieve A, 20.2 g of magnesium nitrate hexahydrate, and 3.3 g of boric acid were added into a 300 ml ball mill tank, 6 maroon grinding balls with a diameter of 2 mm were put in, and the ball milling was started. The temperature in the ball mill tank was controlled at 60°C, the rotating speed of the grinding ball was 400 r / min, and the ball milling time was 16 h. The powder obtained after ball milling was calcined at 600°C for 10 h to obtain modified catalyst F.

[0108] Based on the total weight of catalyst F, the content of Hβ molecular sieve was 24 wt%, the content of high specific surface area all-silica mesoporous molecular sieve was 66 wt%, the content of magnesium oxide was 6.3 wt%, and the content of boron oxide was 3.7 wt%.

[0109] The specific surface area of catalyst F was 872 m 2 / g, and the pore volume was 0.9 cm 3 / g.

[0110] The reaction performance of catalyst F was tested according to the method of 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.

[0111] Example 7

[0112] High specific surface area all-silica mesoporous molecular sieve B was prepared according to the method of step (1) in Example 2.

[0113] Modified catalyst G was prepared according to the method of step (2) in Example 2. The preparation conditions were changed, and the specific process was as follows:

[0114] 27.5 g of Hβ molecular sieve (molar ratio of SiO2 / Al2O3 was 100, specific surface area was 669 m 2 / g, pore size was 0.7 nm, purchased from Nanjing Jicang Nanometer Technology Co., Ltd.), 21.5 g of high specific surface area all-silica mesoporous molecular sieve B, 1.8 g of calcium nitrate, and 0.7 g of boric acid were added into a 300 ml ball mill tank, 8 maroon grinding balls with a diameter of 2 mm were put in, and the ball milling was started. The temperature in the ball mill tank was controlled at 80°C, the rotating speed of the grinding ball was 500 r / min, and the ball milling time was 8 h. The powder obtained after ball milling was calcined at 650°C for 5 h to obtain modified catalyst G.

[0115] The content of Hβ molecular sieve was 55% by weight, the content of high specific surface area all-silica mesoporous molecular sieve was 43% by weight, the content of calcium oxide was 1.2% by weight, and the content of boron oxide was 0.8% by weight, based on the total weight of catalyst G.

[0116] The specific surface area of catalyst G was 720 m 2 / g, and the pore volume was 0.6 cm 3 / g.

[0117] The reaction performance of catalyst G 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.

[0118] Comparative Example 1

[0119] The high specific surface area all-silica mesoporous molecular sieve A was prepared according to the method in step (1) in Example 1.

[0120] The modified catalyst D1 was prepared according to the method in step (2) in Example 1. The preparation conditions were changed, and the specific process was as follows:

[0121] 6 g of Hβ molecular sieve (SiO2 / Al2O3 molar ratio was 50, specific surface area was 683 m 2 / g, pore size was 0.7 nm, and was purchased from Shanghai Shenyuan New Material Science and Technology Group Co., Ltd.), 36 g of high specific surface area all-silica mesoporous molecular sieve A, 29.4 g of magnesium nitrate hexahydrate, and 6.0 g of boric acid were added into a 300 ml ball mill tank, 6 maroon grinding balls with a diameter of 2 mm were put in, and the ball milling was started. The temperature in the ball mill tank was controlled at 60°C, the rotating speed of the grinding ball was 400 r / min, and the ball milling time was 16 h. The powder obtained after ball milling was calcined at 600°C for 10 h to obtain the modified catalyst D1.

[0122] The content of Hβ molecular sieve was 12% by weight, the content of high specific surface area all-silica mesoporous molecular sieve was 72% by weight, the content of magnesium oxide was 9.2% by weight, and the content of boron oxide was 6.8% by weight, based on the total weight of catalyst D1.

[0123] The specific surface area of catalyst D1 was 893 m 2 / g, and the pore volume was 1.0 cm 3 / g.

[0124] The reaction performance of catalyst D1 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.

[0125] Comparative Example 2

[0126] The high specific surface area all-silica mesoporous molecular sieve B was prepared according to the method in step (1) in Example 2.

[0127] Modified catalyst D2 was prepared according to the method of step (2) in Example 2. The preparation conditions were changed, and the specific process was as follows:

[0128] 37.5 g of Hβ molecular sieve (SiO2 / Al2O3 molar ratio of 100, specific surface area of 669 m 2 / g, pore size of 0.7 nm, purchased from Nanjing Jicang Nanometer Technology Co., Ltd.), 12 g of high specific surface area all-silica mesoporous molecular sieve B, 0.9 g of calcium nitrate, and 0.35 g of boric acid were added into a 300 ml ball mill jar, 8 maroon grinding balls with a diameter of 2 mm were put into the jar, and the ball milling was started. The temperature in the ball mill jar was controlled at 80°C, the rotation speed of the grinding balls was 500 r / min, and the ball milling time was 8 h. The powder obtained after ball milling was calcined at 650°C for 5 h to obtain modified catalyst D2.

[0129] The content of Hβ molecular sieve was 75 wt%, the content of high specific surface area all-silica mesoporous molecular sieve was 24 wt%, the content of calcium oxide was 0.6 wt%, and the content of boron oxide was 0.4 wt% based on the total weight of catalyst D2.

[0130] The specific surface area of catalyst D2 was 680 m 2 / g, and the pore volume was 0.5 cm 3 / g.

[0131] The reaction performance of catalyst D2 was tested according to the method for evaluating the reaction performance of direct conversion of waste plastics to light olefins in step (3) in Example 1, and the evaluation results are listed in Table 1.

[0132] Comparative Example 3

[0133] High specific surface area all-silica mesoporous molecular sieve A was prepared according to the method of step (1) in Example 1.

[0134] Modified catalyst D3 was prepared according to the method of step (2) in Example 1. The preparation conditions were changed, and no Hβ molecular sieve was used, and the specific process was as follows:

[0135] 47 g of high specific surface area all-silica mesoporous molecular sieve A, 12.2 g of magnesium nitrate hexahydrate, and 2.0 g of boric acid were added into a 300 ml ball mill jar, 6 maroon grinding balls with a diameter of 2 mm were put into the jar, and the ball milling was started. The temperature in the ball mill jar was controlled at 60°C, the rotation speed of the grinding balls was 400 r / min, and the ball milling time was 16 h. The powder obtained after ball milling was calcined at 600°C for 10 h to obtain modified catalyst D3.

[0136] The content of high specific surface area all-silica mesoporous molecular sieve was 94 wt%, the content of magnesium oxide was 3.8 wt%, and the content of boron oxide was 2.2 wt% based on the total weight of catalyst D3.

[0137] The reaction performance of catalyst D3 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.

[0138] Comparative Example 4

[0139] Step (1) in Example 1 was cancelled, and the modified catalyst D4 was prepared according to the method in step (2) in Example 1. The preparation conditions were changed, and no high specific surface area all-silica mesoporous molecular sieve was used, and the specific process was as follows:

[0140] 47 g of Hβmolecular sieve (SiO2 / Al2O3molar ratio of 50, specific surface area of 683 m 2 / g, pore size of 0.7 nm, purchased from Shanghai Shentan New Material Science and Technology Group Co., Ltd.), 12.2 g of magnesium nitrate hexahydrate, and 2.0 g of boric acid were added into a 300 ml ball mill tank, 6 maroon grinding balls with a diameter of 2 mm were put in, and the ball milling was started. The temperature in the ball mill tank was controlled at 60°C, the rotating speed of the grinding ball was 400 r / min, and the ball milling time was 16 h. The powder obtained after ball milling was calcined at 600°C for 10 h to obtain the modified catalyst D4.

[0141] Based on the total weight of catalyst D4, the content of Hβmolecular sieve was 94% by weight, the content of magnesium oxide was 3.8% by weight, and the content of boron oxide was 2.2% by weight.

[0142] The reaction performance of catalyst D4 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.

[0143] Comparative Example 5

[0144] The high specific surface area all-silica mesoporous molecular sieve A was prepared according to the method in step (1) in Example 1.

[0145] The modified catalyst D5 was prepared according to the method in step (2) in Example 1. The preparation conditions were changed, and no modification component was added, and the specific process was as follows:

[0146] 21 g of Hβmolecular sieve (SiO2 / Al2O3molar ratio of 50, specific surface area of 683 m 2 / g, pore size of 0.7 nm, purchased from Shanghai Shentan New Material Science and Technology Group Co., Ltd.) and 29 g of high specific surface area all-silica mesoporous molecular sieve A were added into a 300 ml ball mill tank, 6 maroon grinding balls with a diameter of 2 mm were put in, and the ball milling was started. The temperature in the ball mill tank was controlled at 60°C, the rotating speed of the grinding ball was 400 r / min, and the ball milling time was 16 h. The powder obtained after ball milling was calcined at 600°C for 10 h to obtain the modified catalyst D5.

[0147] The content of the Hβzeolite was 42 wt% and the content of the high specific surface area all-silica mesoporous molecular sieve was 58 wt% based on the total weight of catalyst D5.

[0148] The reaction performance of catalyst D5 was tested according to the method for evaluating the reaction performance of direct conversion of waste plastics to light olefins in step (3) in Example 1, and the evaluation results are listed in Table 1.

[0149] Comparative Example 6

[0150] The high specific surface area all-silica mesoporous molecular sieve A was prepared according to the method in step (1) in Example 1.

[0151] The modified catalyst D6 was prepared according to the method in step (2) in Example 1. The preparation conditions were changed, and the modified oxide was changed to sodium oxide, and the specific process was as follows:

[0152] 20 g of Hβzeolite (SiO2 / Al2O3molar ratio of 50, specific surface area of 683 m 2 / g, pore size of 0.7 nm, purchased from Shanghai Shenyuan New Material Science and Technology Group Co., Ltd.), 27 g of high specific surface area all-silica mesoporous molecular sieve A, and 8.2 g of sodium nitrate were added into a 300 ml ball mill tank, 6 maroon grinding balls with a diameter of 2 mm were put in, and the ball milling was started. The temperature in the ball mill tank was controlled at 60°C, the rotation speed of the grinding ball was 400 r / min, and the ball milling time was 16 h. The powder obtained after ball milling was calcined at 600°C for 10 h to obtain the modified catalyst D6.

[0153] The content of the Hβzeolite was 40 wt%, the content of the high specific surface area all-silica mesoporous molecular sieve was 54 wt%, and the content of sodium oxide was 6.0 wt% based on the total weight of catalyst D6.

[0154] The reaction performance of catalyst D6 was tested according to the method for evaluating the reaction performance of direct conversion of waste plastics to light olefins in step (3) in Example 1, and the evaluation results are listed in Table 1.

[0155] Comparative Example 7

[0156] The modified catalyst D7 was prepared according to the same method as in Example 1, except that the "high specific surface area all-silica mesoporous molecular sieve A" in Example 1 was replaced by "commercially available silica (purchased from Qingdao Hailang Silica Drier Factory, specific surface area of 329 m 2 / g, pore volume of 0.6 cm 3 / g)", and the specific surface area of the catalyst was 307 m 2 / g, and the pore volume was 0.4 cm 3 / g.

[0157] The reaction performance of catalyst D7 was tested according to the reaction performance evaluation method of direct conversion of waste plastics to light olefins in step (3) in embodiment 1, and the evaluation results are listed in table 1.

[0158] Comparative example 8

[0159] The modified catalyst D8 was prepared according to the same method as in embodiment 1, except that the "Hβ molecular sieve" in embodiment 1 was replaced by "full-silica silicalite-1 molecular sieve (purchased from Tianjin Nanhua Catalyst Co., Ltd., specific surface area 318 m 2 / g, pore volume 0.35 cm 3 / g)", and the specific surface area of the catalyst D8 was 601 m 2 / g, pore volume 0.6 cm 3 / g.

[0160] The reaction performance of catalyst D8 was tested according to the reaction performance evaluation method of direct conversion of waste plastics to light olefins in step (3) in embodiment 1, and the evaluation results are listed in table 1.

[0161] Table 1

[0162]

[0163]

[0164] From the above results, it can be seen that the modified catalyst provided by the present application can directly catalytically convert waste plastics to produce light olefins. The conversion rate of waste plastics is 100%, and the yield of light olefins is high.

[0165] In comparative example 1, the content of high specific surface area full-silica mesoporous molecular sieve is too high, the content of Hβ molecular sieve is too low, and the content of modified component is too high; due to the reasons of insufficient activation sites in the reaction process because of the small number of acid centers on the catalyst, the conversion rate of raw materials is low, and the yield of light olefins is low.

[0166] In comparative example 2, the content of high specific surface area full-silica mesoporous molecular sieve is too low, the content of Hβ molecular sieve is too high, and the content of modified component is too low; due to the reasons of blocked diffusion of reactants and product molecules in the reaction process because of the small number of large pore channels in the catalyst, the yield of light olefins is low.

[0167] In comparative example 3, the catalyst does not contain Hβ molecular sieve, but only contains high specific surface area full-silica mesoporous molecular sieve. Due to the reasons of serious lack of activation sites in the reaction process because of almost no acid centers on the catalyst, the conversion rate of raw materials is very low, and the yield of light olefins is low.

[0168] In the comparative example 4, the catalyst does not contain the high specific surface area all-silica mesoporous molecular sieve, but only contains the Hβ molecular sieve. Due to the fact that the catalyst almost does not contain the large pore diameter channel, the diffusion of the reactant and product molecules is seriously hindered during the reaction process, which results in a low yield of the low carbon olefins.

[0169] In the comparative example 5, the catalyst does not contain the modified oxide, which results in a low yield of the low carbon olefins.

[0170] In the comparative example 6, the modified oxide specified in the present application is not used, but sodium oxide is used. Due to the fact that the modified effect of the same weight of sodium oxide is low, which results in a low yield of the low carbon olefins.

[0171] In the comparative example 7, the "high specific surface area all-silica mesoporous molecular sieve A" is replaced by "commercially available silica". Although the channel of the commercially available silica also belongs to the mesoporous category, it belongs to the amorphous crystal phase structure, and the channel size is irregular. Compared with the high specific surface area all-silica mesoporous molecular sieve, the diffusion promoting effect is poor, which results in a low yield of the low carbon olefins.

[0172] In the comparative example 8, the "Hβ molecular sieve" is replaced by "all-silica silicalite-1 molecular sieve". The all-silica silicalite-1 molecular sieve also belongs to the microporous material, but since the molecular sieve does not contain Al element, the surface only contains a small amount of silicon hydroxyl, and the acidity is extremely weak. The catalyst D7 prepared has a small amount of acid sites on the surface and weak acidity, and the waste plastic catalytic cracking reaction process lacks active sites, which results in that the raw material only produces thermal cracking, so the conversion rate is low, and the yield of the low carbon olefins is low.

[0173] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present 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 present application, and all fall within the protection scope of the present application.

Claims

1. Use of a modified catalyst in a reaction of direct catalytic cracking of waste plastics to light olefins, the use comprising: The method comprises the following steps: contacting the plastic powder with the modified catalyst to carry out the reaction, wherein the plastic powder is polyethylene waste plastic, the modified catalyst comprises a composite molecular sieve and a modified oxide supported on the composite molecular sieve, the composite molecular sieve comprises Hbeta molecular sieve and high specific surface area full-silica mesoporous molecular sieve, and the content of the Hbeta molecular sieve is 24-55% by weight, the content of the high specific surface area full-silica mesoporous molecular sieve is 43-66% by weight, and the content of the modified oxide is 2-10% by weight based on the total weight of the modified catalyst; the modified oxide is selected from one or more of boron oxide, magnesium oxide, calcium oxide, strontium oxide, barium oxide, zinc oxide, copper oxide, cobalt oxide, cerium oxide, lanthanum oxide and zirconium dioxide. The specific surface area of the modified catalyst is 720-872 m 2 / g, and the pore volume is 0.6-0.9 cm 3 / g. The preparation method of the modified catalyst comprises the following steps: The Hbeta molecular sieve, the high specific surface area full-silica mesoporous molecular sieve and the modified oxide precursor are mixed and ball milled, and then subjected to calcination treatment to obtain the modified catalyst.

2. The use according to claim 1, wherein, The content of the Hbeta molecular sieve is 29-51% by weight, the content of the high specific surface area full-silica mesoporous molecular sieve is 46-62% by weight, and the content of the modified oxide is 3-9% by weight based on the total weight of the modified catalyst.

3. The use according to claim 2, wherein, The content of the Hbeta molecular sieve is 34-46% by weight, the content of the high specific surface area full-silica mesoporous molecular sieve is 50-58% by weight, and the content of the modified oxide is 4-8% by weight based on the total weight of the modified catalyst.

4. The use according to claim 1, wherein, The SiO2 / Al2O3 molar ratio of the Hbeta molecular sieve is 15-200.

5. Use according to claim 4, wherein, The SiO2 / Al2O3 molar ratio of the Hbeta molecular sieve is 40-100.

6. The use according to claim 1, wherein, The high specific surface area full-silica mesoporous molecular sieve has a specific surface area of 800-1400 m 2 / g, a pore volume of 0.7-1.7 cm 3 / g, and an average pore diameter of 2-4 nm.

7. Use according to claim 6, wherein, The high specific surface area full-silica mesoporous molecular sieve has a specific surface area of 950-1300 m 2 / g, a pore volume of 1.1-1.6 cm 3 / g, and an average pore diameter of 3-4 nm.

8. Use according to claim 1 or 7, wherein The preparation method of the high specific surface area full-silica mesoporous molecular sieve comprises the following steps: 1) under hydrolysis conditions, a template agent, tetraethyl orthosilicate and an aqueous ammonia solution are mixed and contacted to obtain a mixture; 2) the mixture is subjected to crystallization, filtration, washing and drying treatment to obtain high specific surface area full-silica mesoporous molecular sieve raw powder; 3) the template agent in the high specific surface area full-silica mesoporous material raw powder is removed to obtain high specific surface area full-silica mesoporous molecular sieve.

9. Use according to claim 8, wherein, The template agent is a cationic surfactant; And / or, the molar ratio of the tetraethyl orthosilicate, the template agent, ammonia and water is 1:(0.1-1):(0.5-5):(50-500); And / or, the hydrolysis conditions comprise that the temperature is 20-60 DEG C and the time is 20-120 min; And / or, the crystallization conditions comprise that the temperature is 40-140 DEG C and the time is 5-120 h; And / or, the template agent removal conditions comprise that the temperature is 400-650 DEG C and the time is 4-60 h.

10. Use according to claim 9, wherein, The template agent is cetyltrimethylammonium bromide; And / or, the molar ratio of the tetraethyl orthosilicate, the template agent, ammonia and water is 1:(0.2-0.6):(1-4):(100-300).

11. The use according to claim 1, wherein, The weight ratio of the Hbeta molecular sieve, the high specific surface area full-silica mesoporous molecular sieve and the modified oxide precursor is 1:(0.5-3):(0.05-1.2). And / or, the ball milling conditions include: the rotation speed of the grinding ball is 200-600 r / min, the temperature in the ball milling tank is 30-90 DEG C, and the ball milling time is 5-50 h; And / or, the calcination conditions include: the temperature is 450-750 DEG C, and the time is 2-30 h.

12. Use according to claim 11, wherein, The modified oxide precursor is selected from inorganic salts or inorganic acids containing boron, magnesium, calcium, strontium, barium, zinc, copper, cobalt, cerium, lanthanum and zirconium; And / or, the weight ratio of the Hbeta molecular sieve, the high specific surface area full-silica mesoporous molecular sieve and the modified oxide precursor is 1: (0.8-2.5): (0.15-0.8).

13. The use according to claim 1, wherein, The SiO2 / Al2O3 molar ratio of the Hbeta molecular sieve is 15-200; and / or, the high specific surface area all-silica mesoporous molecular sieve has a specific surface area of 800-1400 m 2 / g, and a pore volume of 0.7-1.7 cm 3 / g, and an average pore diameter of 2-4 nm.

14. Use according to claim 13, wherein, The SiO2 / Al2O3 molar ratio of the Hbeta molecular sieve is 40-100; and / or the high specific surface area all-silica mesoporous molecular sieve has a specific surface area of 950-1300 m 2 / g, and a pore volume of 1.1-1.6 cm 3 / g, and an average pore diameter of 3-4 nm.

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

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