CN117623329A

CN117623329A - Double-pore composite molecular sieve, preparation method thereof and application thereof in reaction for preparing low-carbon olefin by directly catalyzing and cracking waste plastics

Info

Publication number: CN117623329A
Application number: CN202210979515.5A
Authority: CN
Inventors: 刘红梅; 江珊; 亢宇; 徐向亚
Original assignee: Sinopec Beijing Chemical Research Institute Co ltd; China Petroleum and Chemical Corp
Current assignee: Sinopec Beijing Chemical Research Institute Co ltd; China Petroleum and Chemical Corp
Priority date: 2022-08-16
Filing date: 2022-08-16
Publication date: 2024-03-01

Abstract

The invention relates to the field of catalysts and the field of polymer material recycling, and discloses a double-pore composite molecular sieve, a preparation method thereof and application thereof in the reaction of preparing low-carbon olefin by directly catalyzing and cracking waste plastics. The double-pore composite molecular sieve comprises an SAPO-5 molecular sieve and a cubic single-crystal all-silicon mesoporous molecular sieve, wherein the content of the SAPO-5 molecular sieve is 50-74 wt% and the content of the cubic single-crystal all-silicon mesoporous molecular sieve is 26-50 wt% based on the total weight of the double-pore composite molecular sieve. In the reaction of preparing the low-carbon olefin by directly catalyzing and cracking the waste plastics, the double-pore composite molecular sieve solves the problem of recycling the waste plastics and increases the yield of the important chemical raw material low-carbon olefin.

Description

Double-pore composite molecular sieve, preparation method thereof and application thereof in reaction for preparing low-carbon olefin by directly catalyzing and cracking waste plastics

Technical Field

The invention relates to the field of catalysts and the field of polymer material recycling, in particular to a double-pore composite molecular sieve, a preparation method thereof and application thereof in the reaction of preparing low-carbon olefin by directly catalyzing and cracking waste plastics.

Background

The plastic product has the characteristics of light weight, high strength, corrosion resistance, good chemical stability, convenient processing, attractive appearance and practicability, and is widely applied to various fields worldwide. However, plastics are difficult to degrade naturally, and conventional landfill techniques, although they are low in investment and simple to operate, can encroach on a large amount of land, causing land pollution. Although the incineration technology can realize the reduction requirement and recover part of energy, the process is easy to release a large amount of hydrocarbons, nitrides, sulfides and highly toxic substances, which directly threatens the health of human beings and ecological environment. Therefore, the recovery and high-value utilization of waste plastics are widely regarded as a measure for saving energy and protecting environment in all countries of the world. The waste plastic recycling method mainly comprises the technologies of classified recycling, monomer raw material preparation, clean fuel oil production, power generation and the like.

In the prior art, the chemical recycling scheme of waste plastics is mainly waste plastic cracking technology. Waste plastic pyrolysis includes three basic methods, namely: thermal cracking (one-stage process), catalytic cracking (one-stage process) and thermal cracking-catalytic modification (two-stage process). The earliest waste plastic cracking technology developed was thermal cracking technology. The technology refers to a thermal conversion process of performing thermochemical decomposition reaction under the condition of high Wen Jue oxygen to convert macromolecular organic matters in waste plastic products into substances such as liquid matters with small molecular mass, fuel gas, coke and the like. The reaction temperature of the process is generally controlled between 350 and 900 ℃. If the catalyst is added in the thermal cracking process, the catalytic thermal cracking technology is adopted, so that the cracking temperature can be reduced, and the product performance can be improved. The improvement of thermal cracking-catalytic modification method is that after waste plastics are thermally cracked, the catalyst is used to make catalytic modification on the cracked gas.

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

It is therefore an important research direction for plastic waste treatment to explore a new chemical recycling process to produce a clean and high quality end product.

Disclosure of Invention

The invention aims at providing a double-pore composite molecular sieve and a preparation method thereof and application thereof in the reaction of preparing low-carbon olefin by directly catalyzing and cracking waste plastics, aiming at the current situation that the content of the low-carbon olefin recovered in the chemical recycling way of the waste plastics is low, and the double-pore composite molecular sieve not only solves the problem of recycling the waste plastics, but also increases the yield of the important chemical raw material low-carbon olefin, thereby being a novel way for one-step catalytic conversion and utilization of the waste plastics.

In order to achieve the above object, a first aspect of the present invention provides a double pore composite molecular sieve, wherein the double pore composite molecular sieve comprises a SAPO-5 molecular sieve and a cubic single crystal all-silicon mesoporous molecular sieve, and the content of the SAPO-5 molecular sieve is 50 to 74 wt% and the content of the cubic single crystal all-silicon mesoporous molecular sieve is 26 to 50 wt%, based on the total weight of the double pore composite molecular sieve.

The second aspect of the invention provides a preparation method of a double-pore composite molecular sieve, wherein the preparation method comprises the following steps:

(1) Mixing triethylamine, an aluminum source, a phosphorus source, a silicon source and water and carrying out contact reaction to obtain a gel mixture;

(2) Performing primary crystallization treatment on the gel mixture to obtain mixed slurry, adding a cubic single crystal all-silicon mesoporous molecular sieve, mixing, and performing secondary crystallization treatment; and separating, washing, drying and roasting the obtained product to obtain the double-pore composite molecular sieve.

The third aspect of the invention provides an application of the double-pore composite molecular sieve in a reaction for preparing low-carbon olefin by directly catalyzing and cracking waste plastics.

Compared with the prior art, the technical scheme of the invention has the following advantages:

(1) The double-pore composite molecular sieve provided by the invention comprises the SAPO-5 microporous molecular sieve with a proper amount of weak acid center on the surface and an all-silicon mesoporous material with larger pore diameter, and has the advantages of stable structure, good high temperature resistance and contribution to the diffusion of raw materials and product molecules in the cracking reaction process.

(2) In the preparation process of the double-pore composite molecular sieve, mother liquor after primary crystallization of the SAPO-5 molecular sieve is mixed with the cubic single crystal all-silicon mesoporous molecular sieve after ball milling, secondary crystallization is carried out, and micropore channels and mesoporous channels in the double-pore composite molecular sieve are uniformly distributed.

(3) The double-pore composite molecular sieve provided by the invention can be used for converting waste plastics into low-carbon olefin in one step when being used for the reaction of preparing low-carbon olefin by directly catalyzing and cracking the waste plastics, and is a novel method for chemical recycling of the waste plastics. Solves the problem of recycling waste plastics, increases the yield of important chemical raw materials, namely low-carbon olefin, and has good economic benefit.

(4) The double-hole composite molecular sieve provided by the invention is used for the reaction of preparing the low-carbon olefin by directly catalyzing and cracking waste plastics, and has the advantages of mild process conditions, easiness in operation and low requirements on reaction devices.

Additional features and advantages of the invention will be set forth in the detailed description which follows.

Drawings

The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate the invention and together with the description serve to explain, without limitation, the invention. In the drawings:

FIG. 1 is a small angle X-ray diffraction (XRD) spectrum of the double pore composite molecular sieve A prepared in example 1;

FIG. 2 is a wide-angle X-ray diffraction (XRD) spectrum of the double-pore composite molecular sieve A prepared in example 1;

FIG. 3 is a pore size distribution diagram of the double pore composite molecular sieve A prepared in example 1.

Detailed Description

The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein.

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

The inventors of the present invention found that: in the prior art, no process for producing low-carbon olefin (including ethylene, propylene and butylene) by directly catalytically cracking waste plastics exists, and one of the purposes of the present invention is to solve the problem. To the knowledge of the inventors of the physicochemical properties of heterogeneous catalysts, catalysts for the direct preparation of lower olefins by catalytic cracking of waste plastics should have a certain acidity but not be too acidic. In addition, the waste plastic catalytic cracking catalyst needs to have good thermal stability. The SAPO-5 molecular sieve not only has weaker acidity, but also has better thermal stability (crystalline phase can still be kept stable after being roasted at a high temperature of 650 ℃), and is a relatively applicable waste plastic catalytic cracking catalyst. However, the pore diameter of the SAPO-5 molecular sieve is generally less than 1.5nm, which severely limits the improvement of the catalytic performance of the SAPO-5 molecular sieve, mainly because the SAPO-5 is a microporous molecular sieve with smaller pore diameter and smaller pore volume The molecular weight of the waste plastic product is larger, and the molecular chain is longer. In the cracking reaction process of waste plastic products, reactant molecules and product molecules with larger sizes are difficult to diffuse between narrow pore channels, so that the contact between the reactant and an active center is influenced, side reactions such as deep dehydrogenation and the like are easy to occur, and the performance of the catalyst is reduced. Compared with microporous molecular sieve, the cubic monocrystalline all-silicon mesoporous molecular sieve material has larger pore canal size (aperture is 5-10 nm) and large pore volume (can reach 0.8 cm) ³ Above/g), is very suitable for catalytic reactions involving macromolecules. However, the cubic single-crystal all-silicon mesoporous molecular sieve is an all-silicon material, has a small amount of silicon hydroxyl groups on the surface, has extremely weak acidity, and is not suitable for being independently used as a catalyst for catalyzing waste plastic cracking reaction. The inventor of the invention finds that if the structural advantage of the all-silicon mesoporous inorganic material and the surface acid center of the microporous molecular sieve are comprehensively utilized when the waste plastic cracking catalyst is developed and researched, a certain amount of cubic single crystal all-silicon mesoporous molecular sieve is mixed with the SAPO-5 molecular sieve, the specific surface area and the pore volume of the catalyst can be effectively improved, and the internal diffusion performance in the reaction can be remarkably improved. When the cracking catalyst is applied to the catalytic conversion reaction of waste plastics, the activity of the cracking catalyst can be effectively improved, and the selectivity of low-carbon olefin can be increased.

According to the invention, the content of the SAPO-5 molecular sieve is 54 to 70 weight percent and the content of the cubic single crystal all-silicon mesoporous molecular sieve is 30 to 46 weight percent based on the total weight of the double-pore composite molecular sieve; more preferably, the SAPO-5 molecular sieve is contained in an amount of 58 to 66 wt.% and the cubic single crystal all-silicon mesoporous molecular sieve is contained in an amount of 34 to 42 wt.% based on the total weight of the double pore composite molecular sieve. In the invention, the prepared double-pore composite molecular sieve has better catalytic activity and higher low-carbon olefin selectivity when being used for the reaction of preparing the low-carbon olefin by directly catalyzing and cracking waste plastics by adopting the content of the specific components.

According to the invention, the specific surface area of the double-pore composite molecular sieve is 350-500m ² Per gram, the pore volume is 0.50-0.80mL/g, the pore size distribution is bimodal, andthe maximum several pore diameters corresponding to the double peaks are respectively 0.5-1.1nm and 5-10nm; preferably, the specific surface area of the double-pore composite molecular sieve is 380-470m ² The pore volume is 0.6-0.74mL/g, the pore size distribution is bimodal, and the most probable pore diameters corresponding to the bimodal are 0.6-0.9nm and 6-9nm respectively; more preferably, the specific surface area of the double-pore composite molecular sieve is 410-447m ² And/g, wherein the pore volume is 0.64-0.7mL/g, the pore size distribution is bimodal, and the most probable pore diameters corresponding to the bimodal are respectively 0.7-0.8nm and 7-8nm. In the invention, when the double-pore composite molecular sieve has the specific structural parameters, the double-pore composite molecular sieve can be used for preparing the low-carbon olefin by directly catalyzing and cracking waste plastics, and has better catalytic activity and higher low-carbon olefin selectivity.

According to the invention, the specific surface area of the cubic single crystal all-silicon mesoporous molecular sieve is 500-900m ² Per gram, the pore volume is 0.8-1.4ml/g, and the average pore diameter is 5-10nm; preferably, the specific surface area of the cubic single crystal all-silicon mesoporous molecular sieve is 679-734m ² Per gram, the pore volume is 1-1.2ml/g, and the average pore diameter is 7-8nm.

According to the invention, the preparation method of the cubic single crystal all-silicon mesoporous molecular sieve comprises the following steps:

(S1) under the condition of preparing an adhesive tape piece by hydrolysis, contacting and mixing a template agent, potassium sulfate, an acidic aqueous solution and a silicon source to obtain a gel mixture;

(S2) crystallizing the gel mixture, and then filtering, washing and drying to obtain cubic single crystal all-silicon mesoporous molecular sieve raw powder;

and (S3) sequentially carrying out template agent removal treatment and ball milling treatment on the cubic single crystal all-silicon mesoporous molecular sieve raw powder to obtain the cubic single crystal all-silicon mesoporous molecular sieve.

The templating agent according to the present invention may be any of the various triblock copolymer polyoxyethylene-polyoxypropylene-polyoxyethylene templating agents conventionally used in the art, preferably P108 (formula EO ₁₃₂ PO ₆₀ EO ₁₃₂ )。

According to the present invention, the acidic aqueous solution is preferably an aqueous solution of a mineral acid, including an aqueous solution of sulfuric acid, an aqueous solution of hydrochloric acid, an aqueous solution of hydrobromic acid and an aqueous solution of nitric acid, more preferably an aqueous solution of hydrochloric acid.

According to the present invention, the silicon source may be an organic compound or an inorganic compound containing silicon; preferably a silicon-containing organic compound; more preferably one or more of ethyl orthosilicate, methyl orthosilicate or butyl orthosilicate.

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

According to the invention, the conditions of the hydrolysis glue preparation conditions comprise: the temperature is 25-60 ℃ and the time is 10-200min; preferably, the temperature is 30-55deg.C for 10-60min. Preferably, in order to achieve better mixing effect, the mixing efficiency can be improved by rapid stirring or by means of ultrasonic means in the process of preparing the rubber by hydrolysis.

According to the invention, the crystallization process can be carried out in a hydrothermal reaction kettle with a polytetrafluoroethylene lining, and the crystallization conditions are as follows: the crystallization temperature is 25-60 ℃ and the crystallization time is 10-72h; preferably, the temperature is 30-55deg.C and the time is 10-40h.

According to the present invention, the washing conditions are not particularly limited, and for example, the washing process may include: after filtration, a solid product is obtained, which is repeatedly washed with distilled water (the number of washing times may be 2 to 10), and then suction filtration is performed.

According to the invention, the drying conditions are preferably: drying at 70-150deg.C for 3-20 hr; preferably, the temperature is 100-130 ℃ and the time is 5-16h.

According to the invention, the template removal treatment process comprises the following steps: roasting the cubic single crystal mesoporous molecular sieve raw powder in an air atmosphere; the template removing temperature is 400-700 ℃, and the template removing time is 8-50h; preferably, the temperature is 500-600 ℃ and the time is 10-30h.

According to the invention, 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 grinding balls can be reasonably selected according to the size of the ball milling tank, and for the ball milling tank with the size of 100-300mL, 2-8 grinding balls can be generally used; the material of the grinding ball is agate or polytetrafluoroethylene, and agate is preferred. The ball milling conditions include: the rotation speed of the grinding balls can be 200-600r/min, preferably 300-500r/min; the temperature in the ball milling tank may be 30-90 ℃, preferably 40-80 ℃; the ball milling time may be 5 to 50 hours, preferably 8 to 24 hours.

The inventors of the present invention found that: and a certain amount of cubic monocrystalline all-silicon mesoporous molecular sieve is mixed with the SAPO-5 molecular sieve, so that the specific surface area and the pore volume of the catalyst can be effectively improved, and the internal diffusion performance in the reaction is obviously improved. However, if the two prepared molecular sieves are mechanically mixed, the obtained mixed molecular sieves have uneven distribution of micropore channels and mesopore channels, and the effect of improving the diffusion performance is not obvious enough. In the invention, the inventor mixes mother liquor after primary crystallization of the SAPO-5 molecular sieve with the cubic single crystal all-silicon mesoporous molecular sieve after ball milling, and performs secondary crystallization to obtain the double-pore composite molecular sieve. The microporous pore canal and the mesoporous pore canal in the composite molecular sieve obtained by the method are uniformly distributed, and the catalyst has high catalytic activity and high low-carbon olefin selectivity when being used for waste plastic catalytic cracking reaction.

According to the invention, in step (1), the aluminium source is selected from one or more of pseudo-boehmite, aluminium hydroxide, alkaline aluminium sol, aluminium isopropoxide, basic aluminium acetate, gibbsite and boehmite, preferably one or more of pseudo-boehmite, aluminium hydroxide, alkaline aluminium sol or aluminium isopropoxide.

According to the present invention, in step (1), the phosphorus source may be an inorganic acid or an acid salt containing a phosphorus element, preferably one or more of phosphoric acid, phosphorous acid, monoammonium phosphate and monoammonium phosphate.

According to the invention, in step (1), the silicon source may be an organosilicon source or an inorganic silicon source, preferably one or more of tetramethyl silicate, tetraethyl silicate, tetraisopropyl silicate, tetrabutyl silicate, silica sol, water glass and white carbon black.

According to the invention, in step (1), the aluminum source (in Al ₂ O ₃ Meter), the phosphorus source (in P ₂ O ₅ Meter), the silicon source (in SiO ₂ Calculated as a mole ratio of triethylamine to water) of 1: (0.5-3): (0.05-2): (0.2-4): (10-200), preferably 1: (0.8-1.6): (0.1-1): (0.5-2): (20-100).

According to the present invention, in step (1), the conditions of the contact reaction include: the temperature is 10-80 ℃, preferably 20-60 ℃; the time is 0.1-10h, preferably 0.5-6h. Preferably, in order to achieve better mixing effect, the mixing efficiency can be improved by rapid stirring or by means of ultrasound during the contact reaction.

According to the present invention, in the step (2), the conditions for the first crystallization include: the temperature is 90-150 ℃, preferably 110-140 ℃; the time is 3-30 hours, preferably 5-20 hours.

According to the invention, in the step (2), the weight ratio of the cubic single crystal all-silicon mesoporous molecular sieve to the mixed slurry is 1: (4-24), preferably 1: (6-16).

According to the present invention, in the step (2), the conditions for the second crystallization include: the temperature is 140-230 ℃, preferably 160-210 ℃; the time is 10-100h, preferably 16-72h.

According to the present invention, in the step (2), there is no particular limitation on the separation method, and the separation method may be a separation method known in the art, including gravity filtration, pressure filtration, vacuum filtration or centrifugal filtration. Preferably, the separation process specifically includes: vacuum-pumping the bottom of the funnel by using a suction bottle or filtering by using a centrifugal filter.

According to the invention, in step (2), the method of washing the solid product is not particularly required, for example: the solid product may be washed with deionized water, the volume ratio of deionized water to solid product may be 5-20, and the number of washes may be 2-8.

According to the present invention, in step (2), the drying conditions include: the temperature is 60-150deg.C, preferably 80-130deg.C; the time is 1-30 hours, preferably 3-20 hours.

According to the present invention, in step (2), the conditions for firing include: the temperature is 450-650 ℃, preferably 500-600 ℃; the time is 5-30 hours, preferably 8-20 hours.

In a third aspect, the invention provides an application of a double-pore composite molecular sieve in a reaction for preparing low-carbon olefin by directly catalyzing and cracking waste plastics.

According to the invention, the application method of the double-pore composite molecular sieve comprises the following steps: under specific conditions, the waste plastic powder is contacted with the double-pore composite molecular sieve.

According to the present invention, the conditions under which the waste plastic powder is contacted with the double-pore composite molecular sieve include: the temperature of contact may be 420-580 ℃, preferably 450-540 ℃; the contact pressure may be 0.01-1Mpa, preferably 0.05-0.5Mpa; the contact time may be 0.5 to 12 hours, preferably 1 to 5 hours; the weight ratio of the double-hole composite molecular sieve to the waste plastic powder can be 1:0.5 to 50, preferably 1:2-30.

The present invention will be described in detail by examples.

In the following examples and comparative examples:

small angle XRD testing of the samples was performed on a high power, rotary target X-ray diffractometer, D8 ADVANCE, BRUKER AXS, germany, scan range: 0.5-10 deg..

Wide angle XRD testing of the samples was performed on an X' Pert MPD X-ray powder diffractometer, philips company, netherlands, cu ka target, scan range 2θ=5-90 °.

The pore structure parameter analysis of the samples was performed on an ASAP2020-M+C type adsorber available from Micromeritics, inc. The sample was vacuum degassed at 350 ℃ for 4 hours prior to measurement, the specific surface area of the sample was calculated using the BET method, and the pore volume was calculated using the BJH model.

Elemental analysis experiments of the samples were performed on an Eagle III energy dispersive X-ray fluorescence spectrometer manufactured by EDAX, inc. of America.

The drying oven is manufactured by Shanghai-Heng scientific instrument Co., ltd, and the model is DHG-9030A.

The muffle furnace is available from CARBOLITE company under the model CWF1100.

F108 used in examples and comparative examples was purchased from Aldrich, and the other reagents used in examples and comparative examples were purchased from national pharmaceutical systems chemical Co., ltd, and the purity of the reagents was analytically pure.

Example 1

This example is directed to illustrating a dual pore composite molecular sieve prepared in accordance with the present invention.

(1) Preparation of cubic single crystal all-silicon mesoporous molecular sieve

20g (0.0014 mol) of template F108, 52.4g (0.3 mol) of potassium sulfate are mixed with 600g of aqueous hydrochloric acid (which contains 1.2mol of HCl) and stirred at 38℃until F108 is completely dissolved; 41.6g (0.2 mol) of ethyl orthosilicate is added into the solution, stirring is continued for 15min at 38 ℃, and standing and crystallization are carried out for 24h at 38 ℃; washing the solid product obtained by filtration with deionized water for 4 times, and drying at 110 ℃ for 10 hours after suction filtration to obtain the cubic single crystal mesoporous molecular sieve raw powder. Calcining the cubic single crystal mesoporous molecular sieve raw powder for 30 hours at 500 ℃ in air atmosphere, removing the template agent, adding the calcined powder into a 200ml ball milling tank, putting 5 agate grinding balls with the diameter of 2mm, and starting ball milling. The temperature in the ball milling tank is controlled to be 50 ℃, the rotating speed of the grinding balls is 400r/min, and the ball milling time is 20h. The powder product obtained after ball milling is the cubic single crystal all-silicon mesoporous molecular sieve A.

The specific surface area of the cubic single crystal all-silicon mesoporous molecular sieve A is 734m ² Per g, pore volume of 1.2mL/g and average pore diameter of 7.6nm.

(2) Preparation of double-hole composite molecular sieve

Firstly, phosphoric acid is dissolved in distilled water to prepare phosphoric acid solution, then pseudo-boehmite powder (available in Shandong aluminum industry) with the model of P-DF-03-LS is prepared at the temperature of 40 DEG CProduced by Limited liability company, has a specific surface area of 257m ² Per gram, pore volume of 0.32cm ³ And/g) adding the mixture into the phosphoric acid aqueous solution, and continuously adding the tetraethyl silicate and the triethylamine after stirring uniformly. N (Al) ₂ O ₃ ):n(P ₂ O ₅ ):n(SiO ₂ ):n(TEA):n(H ₂ O) is 1:1.2:0.3:1.4:80. After the material feeding is completed, stirring is continued for 2 hours at 40 ℃; and transferring the gel mixture into a hydrothermal kettle with a polytetrafluoroethylene lining for primary crystallization. The temperature of the first crystallization treatment is 120 ℃ and the time is 8 hours. And uniformly mixing the mixed slurry obtained after the primary crystallization treatment with the cubic single crystal all-silicon mesoporous molecular sieve A (the weight ratio of the cubic single crystal all-silicon mesoporous molecular sieve to the mixed slurry is 1:13), and performing secondary crystallization treatment. The temperature of the second crystallization treatment is 180 ℃ and the time is 48 hours. The solid product obtained by filtration is washed by deionized water for 6 times, and the solid product is dried for 10 hours at 110 ℃, and then is roasted for 16 hours at 550 ℃ to obtain the double-pore composite molecular sieve A.

The content of the SAPO-5 molecular sieve is 62 weight percent and the content of the cubic single crystal all-silicon mesoporous molecular sieve is 38 weight percent based on the total weight of the double-pore composite molecular sieve A.

The specific surface area of the double-hole composite molecular sieve A is 429m ² Per gram, pore volume of 0.67cm ³ /g。

FIG. 1 is a small angle XRD spectrum of a double pore composite molecular sieve A; from the spectrum of fig. 1, it is shown that the cubic single-crystal all-silicon mesoporous molecular sieve a exhibits 1 diffraction peak (2θ=0.6°) of the (110) plane and 1 diffraction peak (2θ=1.2°) of the (200) plane corresponding to the cubic heart-like phase in the small angle region. (110) The diffraction peak intensity of the surface is high, the peak shape is narrow, and the material has a good long-range order structure. This shows that the cubic monocrystalline all-silicon mesoporous molecular sieve still has a regular mesoporous pore structure after being prepared into the catalyst, and the basic structure of the mesoporous molecular sieve is not damaged in the catalyst preparation process.

FIG. 2 is a wide angle XRD spectrum of a double pore composite molecular sieve A; from the spectrum of fig. 2, the wide angle x-ray diffraction angles of the sample are shown mainly: 2θ=8.1 °, 13.2 °, 14.9 °, 19.7 °, 21.0 °, and 22.3 °. The diffraction signals are consistent with the diffraction patterns of the SAPO-5 molecular sieve. This indicates that the SAPO-5 molecular sieve has a typical AFI crystalline phase in the double pore composite molecular sieve prepared by secondary crystallization.

FIG. 3 is a pore size distribution diagram of a double pore composite molecular sieve A; from the spectrum of FIG. 3, it is shown that the sample has a remarkable double-pore structure, and the pore diameters of the double pores are respectively 0.8nm and 7.6nm. Wherein, pore canal with the aperture of 0.8nm is provided by SAPO-5 molecular sieve, and pore canal with the aperture of 7.6nm is provided by cubic monocrystalline full-silicon mesoporous molecular sieve.

(3) Evaluation of reaction performance of preparing low-carbon olefin by directly converting waste plastics

And (3) carrying out the catalytic cracking reaction performance evaluation of the waste plastics of the double-pore composite molecular sieve A on a fixed bed reaction device. The double-hole composite molecular sieve A has 6.0 g of filling amount, 40.0g of filling amount of polyethylene waste plastics, the reaction temperature is 480 ℃, the reaction pressure is 0.1MPa, the reaction time is 2 hours, and after the product is cooled and gas-liquid separated, the gas composition is provided with Al ₂ O ₃ -agilent 6890 gas chromatograph analysis of S capillary chromatography column and hydrogen flame detector (FID), quantitative analysis with correction factor using temperature programming; the liquid composition was analyzed with an Agilent 6890 gas chromatograph equipped with a PONA column. The reaction results are shown in Table 1.

Example 2

(1) Preparation of cubic single crystal all-silicon mesoporous molecular sieve

20g (0.0014 mol) of template F108, 73.4g (0.42 mol) of potassium sulfate are mixed with 833g of aqueous hydrochloric acid (which contains 2.1mol of HCl) and stirred at 55℃until F108 is completely dissolved; 58.2g (0.28 mol) of ethyl orthosilicate is added into the solution, stirring is continued for 10min at 55 ℃, and standing and crystallization are carried out for 10h at 55 ℃; washing the solid product obtained by filtration with deionized water for 6 times, and drying at 130 ℃ for 5 hours after suction filtration to obtain the cubic single crystal mesoporous molecular sieve raw powder. Calcining the cubic single crystal mesoporous molecular sieve raw powder for 10 hours at 600 ℃ in air atmosphere, removing the template agent, adding the calcined powder into a 200ml ball milling tank, putting 8 agate grinding balls with the diameter of 2mm, and starting ball milling. The temperature in the ball milling tank is controlled to be 80 ℃, the rotating speed of the grinding balls is 500r/min, and the ball milling time is 8h. The powder product obtained after ball milling is the cubic single crystal all-silicon mesoporous molecular sieve B.

The specific surface area of the cubic single crystal all-silicon mesoporous molecular sieve B is 705m ² Per g, pore volume is 1.1. 1.1mLg and average pore diameter is 8nm.

(2) Preparation of double-hole composite molecular sieve

Firstly, phosphorous acid is dissolved in distilled water to prepare a phosphorous acid aqueous solution, then, the analytically pure aluminum isopropoxide is added into the phosphorous acid aqueous solution at the temperature of 20 ℃, and silica sol and triethylamine are continuously added after uniform stirring. N (Al) ₂ O ₃ ):n(P ₂ O ₅ ):n(SiO ₂ ):n(TEA):n(H ₂ O) is 1:0.8:1:2:100. After the material feeding is completed, stirring is continued for 6 hours at 20 ℃; and transferring the gel mixture into a hydrothermal kettle with a polytetrafluoroethylene lining for primary crystallization. The temperature of the first crystallization treatment is 140 ℃ and the time is 5 hours. And uniformly mixing the mixed slurry obtained after the primary crystallization treatment with the cubic single crystal all-silicon mesoporous molecular sieve B (the weight ratio of the cubic single crystal all-silicon mesoporous molecular sieve to the mixed slurry is 1:16), and performing secondary crystallization treatment. The temperature of the second crystallization treatment is 210 ℃ and the time is 16h. Washing the solid product obtained by filtration with deionized water for 8 times, drying the solid product at 80 ℃ for 20 hours, and roasting the solid product at 500 ℃ for 20 hours to obtain the double-pore composite molecular sieve B.

The content of the SAPO-5 molecular sieve is 58 weight percent and the content of the cubic single crystal all-silicon mesoporous molecular sieve is 42 weight percent based on the total weight of the double-pore composite molecular sieve B.

The specific surface area of the double-hole composite molecular sieve B is 448m ² Per gram, pore volume of 0.69cm ³ /g。

The reaction performance of the double pore composite molecular sieve B was tested according to the reaction performance evaluation method for directly converting the waste plastics of step (3) to low-carbon olefin in example 1, and the evaluation results are shown in table 1.

Example 3

(1) Preparation of cubic single crystal all-silicon mesoporous molecular sieve

20g (0.0014 mol) of template F108, 24.5g (0.14 mol) of potassium sulfate are mixed with 278g of aqueous hydrochloric acid (containing 0.7mol of HCl) and stirred at 30℃until F108 is completely dissolved; 29.1g (0.14 mol) of ethyl orthosilicate is added into the solution, stirring is continued for 60min at 30 ℃, and standing and crystallization are carried out for 40h at 30 ℃; washing the solid product obtained by filtration with deionized water for 8 times, and drying at 100 ℃ for 16 hours after suction filtration to obtain the cubic single crystal mesoporous molecular sieve raw powder. Calcining the cubic single crystal mesoporous molecular sieve raw powder for 15 hours at 550 ℃ in air atmosphere, removing the template agent, adding the calcined powder into a 200ml ball milling tank, putting 4 agate grinding balls with the diameter of 2mm, and starting ball milling. The temperature in the ball milling tank is controlled to be 40 ℃, the rotating speed of the grinding balls is 300r/min, and the ball milling time is 24 hours. The powder product obtained after ball milling is the cubic single crystal all-silicon mesoporous molecular sieve C.

The specific surface area of the cubic single crystal all-silicon mesoporous molecular sieve C is 679m ² Per g, pore volume of 1.0mL/g and average pore diameter of 7.0nm.

(2) Preparation of double-hole composite molecular sieve

Firstly, dissolving monoammonium phosphate in distilled water to prepare monoammonium phosphate aqueous solution, then adding aluminum hydroxide gel into the monoammonium phosphate aqueous solution at the temperature of 60 ℃, and continuously adding tetramethyl silicate and triethylamine after uniformly stirring. N (Al) ₂ O ₃ ):n(P ₂ O ₅ ):n(SiO ₂ ):n(TEA):n(H ₂ O) is 1:1.6:0.1:1.5:20. After the material feeding is completed, stirring is continued for 0.5h at 60 ℃; and transferring the gel mixture into a hydrothermal kettle with a polytetrafluoroethylene lining for primary crystallization. The temperature of the first crystallization treatment is 110 ℃ and the time is 20h. And uniformly mixing the mixed slurry obtained after the primary crystallization treatment with the cubic single crystal all-silicon mesoporous molecular sieve C (the weight ratio of the cubic single crystal all-silicon mesoporous molecular sieve to the mixed slurry is 1:6), and performing secondary crystallization treatment. The temperature of the second crystallization treatment is 160 ℃ and the time is 72 hours. Washing the solid product obtained by suction filtration with deionized water for 4 times, wherein the solid product is at 130 DEG CDrying for 3h, and roasting at 600 ℃ for 8h to obtain the double-pore composite molecular sieve C.

Based on the total weight of the double-pore composite molecular sieve C, the content of the SAPO-5 molecular sieve is 66 weight percent, and the content of the cubic single crystal all-silicon mesoporous molecular sieve is 34 weight percent.

The specific surface area of the double-hole composite molecular sieve C is 408m ² Per gram, pore volume of 0.64cm ³ /g。

The reaction performance of the double pore composite molecular sieve C was tested according to the reaction performance evaluation method for directly converting the waste plastics of step (3) to low-carbon olefin in example 1, and the evaluation results are shown in table 1.

Example 4

Cubic single crystal all-silicon mesoporous molecular sieve a was prepared according to the method of step (1) in example 1.

(2) Preparation of double-hole composite molecular sieve

Firstly, ammonium dihydrogen phosphate is dissolved in distilled water to prepare ammonium dihydrogen phosphate aqueous solution, then German original import pseudo-boehmite powder (purchased from Beijing Asia Taihua chemical auxiliary agent Co., ltd.) with model SB is prepared at 40 ℃ and the specific surface area is 241m ² Per gram, pore volume of 0.53cm ³ And/g) adding the mixture into an ammonium dihydrogen phosphate aqueous solution, stirring uniformly, and then continuously adding sodium silicate and triethylamine. N (Al) ₂ O ₃ ):n(P ₂ O ₅ ):n(SiO ₂ ):n(TEA):n(H ₂ O) is 1:0.7:1.5:3:150. After the material feeding is completed, stirring is continued for 2 hours at 40 ℃; and transferring the gel mixture into a hydrothermal kettle with a polytetrafluoroethylene lining for primary crystallization. The temperature of the first crystallization treatment is 120 ℃ and the time is 8 hours. And uniformly mixing the mixed slurry obtained after the primary crystallization treatment with the cubic single crystal all-silicon mesoporous molecular sieve A (the weight ratio of the cubic single crystal all-silicon mesoporous molecular sieve to the mixed slurry is 1:18), and performing secondary crystallization treatment. The temperature of the second crystallization treatment is 180 ℃ and the time is 48 hours. Filtering to obtain The solid product of (2) is washed by deionized water for 6 times, and the solid product is dried for 10 hours at 110 ℃, and then is roasted for 16 hours at 550 ℃ to obtain the double-pore composite molecular sieve D.

The content of the SAPO-5 molecular sieve is 54 weight percent and the content of the cubic single crystal all-silicon mesoporous molecular sieve is 46 weight percent based on the total weight of the double-pore composite molecular sieve D.

The specific surface area of the double-hole composite molecular sieve D is 467m ² Per gram, pore volume of 0.72cm ³ /g。

The reaction performance of catalyst D was tested according to the evaluation method for the reaction performance of the direct conversion of waste plastics to light olefins in step (3) of example 1, and the evaluation results are shown in Table 1.

Example 5

Cubic single crystal all-silicon mesoporous molecular sieve B was prepared according to the method of step (1) in example 2.

(2) Preparation of double-hole composite molecular sieve

Firstly, phosphorous acid is dissolved in distilled water to prepare a phosphorous acid aqueous solution, then alkaline aluminum sol is added into the phosphorous acid aqueous solution at the temperature of 30 ℃, and white carbon black and triethylamine are continuously added after uniform stirring. N (Al) ₂ O ₃ ):n(P ₂ O ₅ ):n(SiO ₂ ):n(TEA):n(H ₂ O) is 1:2.2:0.08:0.4:15. After the material feeding is completed, stirring is continued for 5 hours at 30 ℃; and transferring the gel mixture into a hydrothermal kettle with a polytetrafluoroethylene lining for primary crystallization. The temperature of the first crystallization treatment is 140 ℃ and the time is 5 hours. And uniformly mixing the mixed slurry obtained after the primary crystallization treatment with the cubic single crystal all-silicon mesoporous molecular sieve B (the weight ratio of the cubic single crystal all-silicon mesoporous molecular sieve to the mixed slurry is 1:5), and performing secondary crystallization treatment. The temperature of the second crystallization treatment is 210 ℃ and the time is 16h. Washing the solid product obtained by filtration with deionized water for 8 times, drying the solid product at 80 ℃ for 20 hours, and roasting the solid product at 500 ℃ for 20 hours to obtain the double-pore composite molecular sieve E.

The content of the SAPO-5 molecular sieve is 70 weight percent and the content of the cubic single crystal all-silicon mesoporous molecular sieve is 30 weight percent based on the total weight of the double-pore composite molecular sieve E.

The specific surface area of the double-hole composite molecular sieve E is 391m ² Per gram, pore volume of 0.61cm ³ /g。

The reaction performance of the double pore composite molecular sieve E was tested according to the reaction performance evaluation method for preparing low carbon olefin by directly converting the waste plastics of the step (3) in example 1, and the evaluation results are shown in Table 1.

Example 6

(2) Preparation of double-hole composite molecular sieve

Firstly, phosphoric acid is dissolved in distilled water to prepare a phosphoric acid solution, then aluminum hydroxide gel is added into the phosphoric acid solution at the temperature of 40 ℃, and after uniform stirring, tetraisopropyl silicate and triethylamine are continuously added. N (Al) ₂ O ₃ ):n(P ₂ O ₅ ):n(SiO ₂ ):n(TEA):n(H ₂ O) is 1:0.5:2:4:200. After the material feeding is completed, stirring is continued for 2 hours at 40 ℃; and transferring the gel mixture into a hydrothermal kettle with a polytetrafluoroethylene lining for primary crystallization. The temperature of the first crystallization treatment is 120 ℃ and the time is 8 hours. And uniformly mixing the mixed slurry obtained after the primary crystallization treatment with the cubic single crystal all-silicon mesoporous molecular sieve A (the weight ratio of the cubic single crystal all-silicon mesoporous molecular sieve to the mixed slurry is 1:24), and performing secondary crystallization treatment. The temperature of the second crystallization treatment is 180 ℃ and the time is 48 hours. The solid product obtained by filtration is washed by deionized water for 6 times, and the solid product is dried for 10 hours at 110 ℃, and then is roasted for 16 hours at 550 ℃ to obtain the double-pore composite molecular sieve F.

The content of the SAPO-5 molecular sieve is 50 weight percent and the content of the cubic single crystal all-silicon mesoporous molecular sieve is 50 weight percent based on the total weight of the double-pore composite molecular sieve F.

The specific surface area of the double-hole composite molecular sieve F is 485m ² Per gram, pore volume of 0.75cm ³ /g。

The reaction performance of the catalyst F was tested according to the evaluation method of the reaction performance of the waste plastics directly converted to light olefins in the step (3) of example 1, and the evaluation results are shown in Table 1.

Example 7

(2) Preparation of double-hole composite molecular sieve

Firstly, phosphorous acid is dissolved in distilled water to prepare a phosphorous acid aqueous solution, then aluminum isopropoxide is added into the phosphorous acid aqueous solution at the temperature of 30 ℃, and tetrabutyl silicate and triethylamine are continuously added after uniform stirring. N (Al) ₂ O ₃ ):n(P ₂ O ₅ ):n(SiO ₂ ):n(TEA):n(H ₂ O) is 1:3:0.05:0.2:10. After the material feeding is completed, stirring is continued for 5 hours at 30 ℃; and transferring the gel mixture into a hydrothermal kettle with a polytetrafluoroethylene lining for primary crystallization. The temperature of the first crystallization treatment is 140 ℃ and the time is 5 hours. And uniformly mixing the mixed slurry obtained after the primary crystallization treatment with the cubic single crystal all-silicon mesoporous molecular sieve B (the weight ratio of the cubic single crystal all-silicon mesoporous molecular sieve to the mixed slurry is 1:4), and performing secondary crystallization treatment. The temperature of the second crystallization treatment is 210 ℃ and the time is 16h. Washing the solid product obtained by filtration with deionized water for 8 times, drying the solid product at 80 ℃ for 20 hours, and roasting the solid product at 500 ℃ for 20 hours to obtain the double-pore composite molecular sieve G.

The content of the SAPO-5 molecular sieve is 74 weight percent and the content of the cubic single crystal all-silicon mesoporous molecular sieve is 26 weight percent based on the total weight of the double-pore composite molecular sieve G.

The specific surface area of the double-hole composite molecular sieve G is 372m ² Per gram, pore volume of 0.58cm ³ /g。

The reaction performance of the double pore composite molecular sieve G was tested according to the reaction performance evaluation method for directly converting the waste plastics of step (3) to low-carbon olefin in example 1, and the evaluation results are shown in table 1.

Comparative example 1

(2) Preparation of double-hole composite molecular sieve

Firstly, phosphoric acid is dissolved in distilled water to prepare phosphoric acid solution, then pseudo-boehmite powder (produced by Shandong aluminum company, inc. and having specific surface area of 257 m) with model number of P-DF-03-LS is prepared at 40 DEG C ² Per gram, pore volume of 0.32cm ³ And/g) adding the mixture into the phosphoric acid aqueous solution, and continuously adding the tetraethyl silicate and the triethylamine after stirring uniformly. N (Al) ₂ O ₃ ):n(P ₂ O ₅ ):n(SiO ₂ ):n(TEA):n(H ₂ O) is 1:1.2:0.3:1.4:80. After the material feeding is completed, stirring is continued for 2 hours at 40 ℃; and transferring the gel mixture into a hydrothermal kettle with a polytetrafluoroethylene lining for primary crystallization. The temperature of the first crystallization treatment is 120 ℃ and the time is 8 hours. And uniformly mixing the mixed slurry obtained after the primary crystallization treatment with the cubic single crystal all-silicon mesoporous molecular sieve A (the weight ratio of the cubic single crystal all-silicon mesoporous molecular sieve to the mixed slurry is 1:3), and performing secondary crystallization treatment. The temperature of the second crystallization treatment is 180 ℃ and the time is 48 hours. The solid product obtained by filtration is washed by deionized water for 6 times, and the solid product is dried for 10 hours at 110 ℃, and then is roasted for 16 hours at 550 ℃ to obtain the double-pore composite molecular sieve D1.

The content of the SAPO-5 molecular sieve is 30 weight percent and the content of the cubic single crystal all-silicon mesoporous molecular sieve is 70 weight percent based on the total weight of the double-pore composite molecular sieve D1.

The specific surface area of the double-hole composite molecular sieve D1 is 579m ² Per gram, pore volume of 0.89cm ³ /g。

The reaction performance of the double pore composite molecular sieve D1 was tested according to the reaction performance evaluation method for directly converting the waste plastics of step (3) to low-carbon olefin in example 1, and the evaluation results are shown in table 1.

Comparative example 2

Firstly, phosphorous acid is dissolved in distilled water to prepare a phosphorous acid aqueous solution, then, the analytically pure aluminum isopropoxide is added into the phosphorous acid aqueous solution at the temperature of 20 ℃, and silica sol and triethylamine are continuously added after uniform stirring. N (Al) ₂ O ₃ ):n(P ₂ O ₅ ):n(SiO ₂ ):n(TEA):n(H ₂ O) is 1:0.8:1:2:100. After the material feeding is completed, stirring is continued for 6 hours at 20 ℃; and transferring the gel mixture into a hydrothermal kettle with a polytetrafluoroethylene lining for primary crystallization. The temperature of the first crystallization treatment is 140 ℃ and the time is 5 hours. And uniformly mixing the mixed slurry obtained after the primary crystallization treatment with the cubic single crystal all-silicon mesoporous molecular sieve B (the weight ratio of the cubic single crystal all-silicon mesoporous molecular sieve to the mixed slurry is 1:90), and performing secondary crystallization treatment. The temperature of the second crystallization treatment is 210 ℃ and the time is 16h. Washing the solid product obtained by filtration with deionized water for 8 times, drying the solid product at 80 ℃ for 20 hours, and roasting the solid product at 500 ℃ for 20 hours to obtain the double-pore composite molecular sieve D2.

The content of the SAPO-5 molecular sieve is 90 weight percent and the content of the cubic single crystal all-silicon mesoporous molecular sieve is 10 weight percent based on the total weight of the double-pore composite molecular sieve D2.

The specific surface area of the double-hole composite molecular sieve D2 is 297m ² Per gram, pore volume of 0.47cm ³ /g。

The reaction performance of the double pore composite molecular sieve D2 was tested according to the reaction performance evaluation method for directly converting the waste plastics of step (3) to low-carbon olefin in example 1, and the evaluation results are shown in table 1.

Comparative example 3

Step (2) of example 1 was omitted.

The reactivity of the cubic single-crystal all-silicon mesoporous molecular sieve a was tested according to the method for evaluating the reactivity of the low-carbon olefin prepared by directly converting the waste plastics of step (3) in example 1, and the evaluation results are shown in table 1.

Comparative example 4

Step (1) of example 1 was omitted.

The preparation method of the SAPO-5 molecular sieve comprises the following specific steps:

firstly, phosphoric acid is dissolved in distilled water to prepare phosphoric acid solution, then pseudo-boehmite powder (produced by Shandong aluminum company, inc. and having specific surface area of 257 m) with model number of P-DF-03-LS is prepared at 40 DEG C ² Per gram, pore volume of 0.32cm ³ And/g) adding the mixture into the phosphoric acid aqueous solution, and continuously adding the tetraethyl silicate and the triethylamine after stirring uniformly. N (Al) ₂ O ₃ ):n(P ₂ O ₅ ):n(SiO ₂ ):n(TEA):n(H ₂ O) is 1:1.2:0.3:1.4:80. After the material feeding is completed, stirring is continued for 2 hours at 40 ℃; and transferring the gel mixture into a hydrothermal kettle with a polytetrafluoroethylene lining for primary crystallization. The temperature of the first crystallization treatment is 120 ℃ and the time is 8 hours. And carrying out secondary crystallization treatment on the mixed slurry obtained after the primary crystallization treatment. The temperature of the second crystallization treatment is 180 ℃ and the time is 48 hours. The solid product obtained by filtration is washed by deionized water for 6 times, and the solid product is dried for 10 hours at 110 ℃ and then baked for 16 hours at 550 ℃ to obtain the SAPO-5 molecular sieve.

The specific surface area of the SAPO-5 molecular sieve is 253m ² Per gram, pore volume of 0.41cm ³ /g。

The reaction performance of the SAPO-5 molecular sieves was tested according to the method for evaluating the reaction performance of the direct conversion of waste plastics to lower olefins in step (3) of example 1, and the evaluation results are shown in table 1.

Comparative example 5

Step (1) of example 1 was omitted.

The preparation of the composite material D3 comprises the following specific processes:

firstly, phosphoric acid is dissolved in distilled water to prepare phosphoric acid solution, then pseudo-boehmite powder (produced by Shandong aluminum company, inc. and having specific surface area of 257 m) with model number of P-DF-03-LS is prepared at 40 DEG C ² Per gram, pore volume of 0.32cm ³ And/g) adding the mixture into the phosphoric acid aqueous solution, and continuously adding the tetraethyl silicate and the triethylamine after stirring uniformly. N (Al) ₂ O ₃ ):n(P ₂ O ₅ ):n(SiO ₂ ):n(TEA):n(H ₂ O) is 1:1.2:0.3:1.4:80. After the material feeding is completed, stirring is continued for 2 hours at 40 ℃; and transferring the gel mixture into a hydrothermal kettle with a polytetrafluoroethylene lining for primary crystallization. The temperature of the first crystallization treatment is 120 ℃ and the time is 8 hours. The mixed slurry obtained after the first crystallization treatment was mixed with silica powder (laboratory self-made, specific surface area 274m ² Per gram, pore volume of 0.57cm ³ Uniformly mixing (weight ratio of silicon dioxide to mixed slurry is 1:13 And performing a second crystallization treatment. The temperature of the second crystallization treatment is 180 ℃ and the time is 48 hours. The solid product obtained by filtration was washed with deionized water 6 times, dried at 110℃for 10 hours, and then calcined at 550℃for 16 hours to obtain composite material D3.

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

The specific surface area of the composite material D3 is 259m ² Per gram, pore volume of 0.46cm ³ /g。

The reaction performance of the composite material D3 was tested according to the evaluation method of the reaction performance of the direct conversion of waste plastics to light olefins in the step (3) of example 1, and the evaluation results are shown in table 1.

Comparative example 6

The cubic single crystal all-silicon mesoporous molecular sieve was prepared according to the method of step (1) in example 1, the ball milling process was omitted, and the obtained product was cubic single crystal all-silicon mesoporous molecular sieve D4.

The double pore composite molecular sieve D4 was prepared according to the method of step (2) in example 1.

The content of the SAPO-5 molecular sieve is 62 weight percent and the content of the cubic single crystal all-silicon mesoporous molecular sieve is 38 weight percent based on the total weight of the double-pore composite molecular sieve D4.

The reaction performance of the double pore composite molecular sieve D4 was tested according to the reaction performance evaluation method for directly converting the waste plastics of step (3) to low-carbon olefin in example 1, and the evaluation results are shown in table 1.

TABLE 1

Project	Catalyst	Conversion of waste plastics (%)	Yield of lower olefins (%)
				Example 1	Double-hole composite molecular sieve A	100	44.6
Example 2	Double-hole composite molecular sieve B	100	44.4
				Example 3	Double-hole composite molecular sieve C	100	44.1
Example 4	Double-hole composite molecular sieve D	100	43.2
				Example 5	Double-hole composite molecular sieve E	100	43.0
Example 6	Double-hole composite molecular sieve F	100	41.5
				Example 7	Double-hole composite molecular sieve G	100	41.1
Comparative example 1	Double-hole composite molecular sieve D1	97	19.7
				Comparative example 2	Double-hole composite molecular sieve D2	100	26.8
Comparative example 3	Cubic single crystal all-silicon mesoporous molecular sieve A	59	13.1
				Comparative example 4	SAPO-5 molecular sieve	100	22.5
Comparative example 5	Double-hole composite molecular sieve D3	100	29.3
				Comparative example 6	Double-hole composite molecular sieve D4	100	34.2

From the results, the double-pore composite molecular sieve provided by the invention can directly catalyze and convert waste plastics into low-carbon olefin. The conversion rate of the waste plastics is 100 percent, and the yield of the low-carbon olefin is high.

In comparative example 1, the content of cubic single-crystal all-silicon mesoporous molecular sieve was too high and the content of SAPO-5 molecular sieve was too low. Because of the small number of acid centers on the catalyst and insufficient activation sites in the reaction process, the raw material conversion rate is low and the low-carbon olefin yield is low.

In comparative example 2, however, the content of cubic single-crystal all-silicon mesoporous molecular sieve was too low and the content of SAPO-5 molecular sieve was too high. The catalyst has fewer mesoporous channels, and the low-carbon olefin yield is lower due to the fact that the diffusion of reactant and product molecules is blocked in the reaction process.

In comparative example 3, only cubic single-crystal all-silicon mesoporous molecular sieve is used as a cracking catalyst, and SAPO-5 molecular sieve is not added, so that the catalyst has low raw material conversion rate and low carbon olefin yield because active acid centers hardly exist.

In comparative example 4, only the SAPO-5 molecular sieve is used as a cracking catalyst, and the cubic single crystal all-silicon mesoporous molecular sieve is not added, so that the low-carbon olefin yield is lower due to the fact that mesoporous pore channels are not contained in the catalyst and the diffusion of reactant and product molecules is blocked in the reaction process.

In comparative example 5, the cubic single-crystal all-silicon mesoporous molecular sieve is replaced by silicon dioxide powder, and the prepared composite material has lower low yield of low-carbon olefin due to the fact that the specific surface area of silicon dioxide is low, the pore volume is small, the pore structure is irregular, and the dispersion effect is obviously lower than that of the cubic single-crystal all-silicon mesoporous molecular sieve.

In comparative example 6, the ball milling process is omitted in the preparation of the cubic single crystal all-silicon mesoporous molecular sieve, so that the mesoporous molecular sieve and the microporous molecular sieve of the double-pore composite molecular sieve are not uniformly dispersed, the diffusion effect is affected, and the yield of the low-carbon olefin is lower.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, a number of simple variants of the technical solution of the invention are possible, including combinations of the individual technical features in any other suitable way, which simple variants and combinations should likewise be regarded as being disclosed by the invention, all falling within the scope of protection of the invention.

Claims

1. The double-pore composite molecular sieve is characterized by comprising an SAPO-5 molecular sieve and a cubic single-crystal all-silicon mesoporous molecular sieve, wherein the content of the SAPO-5 molecular sieve is 50-74 wt% and the content of the cubic single-crystal all-silicon mesoporous molecular sieve is 26-50 wt% based on the total weight of the double-pore composite molecular sieve.

2. The dual pore composite molecular sieve of claim 1, wherein the SAPO-5 molecular sieve is present in an amount of 54 to 70 wt.% and the cubic single crystal all silicon mesoporous molecular sieve is present in an amount of 30 to 46 wt.% based on the total weight of the dual pore composite molecular sieve;

preferably, the content of the SAPO-5 molecular sieve is 58 to 66 weight percent, and the content of the cubic single crystal all-silicon mesoporous molecular sieve is 34 to 42 weight percent based on the total weight of the double-pore composite molecular sieve.

3. The double pore composite molecular sieve according to claim 1 or 2, wherein the specific surface area of the double pore composite molecular sieve is 350-500m ² Per g, pore volume of 0.50-0.80mL/g, pore size distribution of bimodal distributionThe maximum several pore diameters corresponding to the double peaks are respectively 0.5-1.1nm and 5-10nm;

preferably, the specific surface area of the double-pore composite molecular sieve is 380-470m ² The pore volume is 0.6-0.74mL/g, the pore size distribution is bimodal, and the most probable pore diameters corresponding to the bimodal are 0.6-0.9nm and 6-9nm respectively;

more preferably, the specific surface area of the double-pore composite molecular sieve is 410-447m ² And/g, wherein the pore volume is 0.64-0.7mL/g, the pore size distribution is bimodal, and the most probable pore diameters corresponding to the bimodal are respectively 0.7-0.8nm and 7-8nm.

4. The dual pore composite molecular sieve of claim 1 or 2, wherein the cubic single crystal all-silicon mesoporous molecular sieve has a specific surface area of 500-900m ² Per gram, the pore volume is 0.8-1.4mL/g, and the average pore diameter is 5-10nm.

5. The double-pore composite molecular sieve according to claim 1 or 4, wherein the preparation method of the cubic single-crystal all-silicon mesoporous molecular sieve comprises the following steps:

6. The dual pore composite molecular sieve of claim 5, wherein the templating agent is a triblock copolymer polyoxyethylene-polyoxypropylene-polyoxyethylene templating agent;

and/or the acidic aqueous solution is an aqueous solution of an inorganic acid, preferably an aqueous solution of hydrochloric acid;

and/or the molar ratio of the template agent, potassium sulfate, the silicon source, water in the inorganic acid aqueous solution and inorganic acid in the inorganic acid aqueous solution is 1: (50-500): (50-300): (5000-50000): (200-2000);

And/or, the conditions of the hydrolysis glue making conditions comprise: the temperature is preferably 25-60deg.C, and the time is 10-200min;

and/or, the crystallization conditions include: the temperature is 25-60 ℃ and the time is 10-72h;

and/or, the process of template removal agent treatment comprises the following steps: calcining the cubic single crystal all-silicon mesoporous molecular sieve raw powder for 8-50 hours at 400-700 ℃ in air atmosphere;

and/or, the ball milling treatment conditions comprise: the rotating speed of the grinding balls is 200-600r/min, the temperature in the ball milling tank is 30-90 ℃, and the ball milling time is 5-50h.

7. A method of preparing the double pore composite molecular sieve of any one of claims 1 to 6, comprising:

8. The preparation method according to claim 7, wherein in the step (1), the aluminum source is selected from one or more of pseudo-boehmite, aluminum hydroxide, alkaline alumina sol, aluminum isopropoxide, basic aluminum acetate, gibbsite and boehmite, preferably one or more of pseudo-boehmite, aluminum hydroxide, alkaline alumina sol or aluminum isopropoxide;

And/or the phosphorus source is an inorganic acid or acid salt containing phosphorus element, preferably one or more of phosphoric acid, phosphorous acid, monoammonium phosphate and monoammonium phosphate;

and/or the silicon source is an organic silicon source or an inorganic silicon source, preferably one or more of tetramethyl silicate, tetraethyl silicate, tetraisopropyl silicate, tetrabutyl silicate, silica sol, water glass and white carbon black;

and/or the aluminum source is made of Al ₂ O ₃ Counting the number of the phosphorus sources by P ₂ O ₅ Meter, the silicon source is made of SiO ₂ The molar ratio of the triethylamine to the water is 1: (0.5-3): (0.05-2): (0.2-4): (10-200);

and/or, the conditions of the contact reaction include: the temperature is 10-80 ℃, preferably 20-60 ℃; the time is 0.1-10h, preferably 0.5-6h.

9. The production method according to claim 7, wherein in the step (2), the conditions for the first crystallization include: the temperature is 90-150 ℃, preferably 110-140 ℃; the time is 3-30h, preferably 5-20h;

and/or the weight ratio of the cubic single crystal all-silicon mesoporous molecular sieve to the mixed slurry is 1: (4-24), preferably 1: (6-16);

and/or, the conditions of the second crystallization include: the temperature is 140-230 ℃, preferably 160-210 ℃; the time is 10-100h, preferably 16-72h;

And/or, the roasting conditions include: the temperature is 450-650 ℃, preferably 500-600 ℃; the time is 5-30 hours, preferably 8-20 hours.

10. Use of the double-pore composite molecular sieve according to any one of claims 1-6 in a reaction for preparing low-carbon olefin by directly catalyzing and cracking waste plastics.

11. The application of claim 10, wherein the application comprises: the plastic powder is contacted with the novel catalyst to react;

and/or, the contacting conditions include: the temperature is 420-580 ℃, the pressure is 0.01-1MPa, and the contact time is 0.5-12h;

and/or the weight ratio of the novel catalyst to the amount of the waste plastic powder is 1: (0.5-50).