Catalyst for preparing low-carbon aromatic hydrocarbon through co-pyrolysis of coal and waste plastics and preparation method of catalyst

Abstract

The invention discloses a catalyst for preparing low-carbon aromatic hydrocarbon through co-pyrolysis of coal and waste plastics and a preparation method thereof, and the catalyst is prepared according to the following steps: (1) pretreatment and surface modification of microporous USY, (2) preparation of USY-coated silica-alumina xerogel, (3) steam-assisted crystallization, and (4) template removal and post-treatment. According to the method, commercial micropore USY serves as a core, mesoporous USY deposited on the outer layer serves as a shell, active metal Ni and Ti are added, the mesoporous shell mainly plays a role in pre-cracking and transmission, super-molecules are pre-cracked on the surface, even if a small amount of carbon is deposited in a pore channel, the carbon deposition mainly occurs in a mesoporous channel, and therefore the performance of the catalyst is greatly improved. A key active center cannot be blocked, and deposited carbon in mesopores is easier to remove through scorching. A product generated by a catalyst core layer can also be quickly transferred to mesopores, so that excessive reaction is avoided, and the content of low-carbon aromatic hydrocarbon in a co-pyrolysis tar product is increased.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalysts, in particular to a catalyst for preparing low-carbon aromatic hydrocarbons through coal and waste plastic co-pyrolysis and a preparation method thereof. BACKGROUND

[0002] The coal and waste plastic co-pyrolysis technology can convert low-value coal and waste plastic into high-value oil and gas products, thereby simultaneously addressing the two difficult problems of white pollution control and clean coal utilization. This process has low raw material cost, high product value, good profit prospects, and meets the development direction of the "double carbon" target and circular economy.

[0003] The hydrogen-carbon molar ratio of coal is 0.5-1.1, and 50%-60% of the pyrolysis tar product is heavy components with a boiling point >360℃, and there are few high-value products. The hydrogen-carbon molar ratio of waste plastic is between 1.5 and 2.0, and the single waste plastic pyrolysis technology can obtain more light tar, but the current development is relatively slow, and it has the characteristics of unstable raw materials, small oil production scale, and strong regionalism. Adding waste plastic as a hydrogen source to coal for co-pyrolysis has a synergistic effect of increasing oil and reducing water, and at the same time, it improves the yield and quality of tar. However, the coal and waste plastic co-pyrolysis tar product still contains some heavy components, and the product composition is uncontrollable.

[0004] The currently disclosed catalysts are mostly hydrogenation cracking or bio-oil hydrogenation deoxidization catalysts for petroleum fractions, which need to complete the catalytic reaction under high temperature and high pressure, and the composition of petroleum fractions is relatively simple. In the coal and waste plastic coexistence system, the pyrolysis process converts the raw materials into oil products under relatively mild conditions. However, due to the extremely complex composition of coal, the existing commercial FCC catalysts have insufficient ability to break the bonds of large molecules in coal pyrolysis tar, and the mass transfer at the core-shell boundary of the disclosed core-shell structure catalyst is poor, which is prone to carbon deposition and deactivation. SUMMARY

[0005] To solve the above technical problems, the first purpose of the present application is to provide a preparation method of a catalyst for preparing low-carbon aromatic hydrocarbons through coal and waste plastic co-pyrolysis, and the second purpose is to provide a catalyst for preparing low-carbon aromatic hydrocarbons through coal and waste plastic co-pyrolysis prepared by the preparation method. The content of low-carbon aromatic hydrocarbons (benzene, toluene, xylene, styrene, ethylbenzene, naphthalene, abbreviated as BTESXN) in the co-pyrolysis tar product is increased, and the content of heavy components is reduced.

[0006] To achieve the above first purpose, the present application is implemented by the following technical solution: a preparation method of a catalyst for preparing low-carbon aromatic hydrocarbons through coal and waste plastic co-pyrolysis, characterized by being prepared according to the following steps:

[0007] Step (one) pretreatment and surface modification of microporous USY

[0008] (1) Calcination of USY powder at 550-600°C in a muffle furnace to remove the adsorbed organics and moisture in its pores;

[0009] (2) Surface charge modification: dispersing the activated USY in dilute NaOH solution, stirring at 60-65°C, then centrifuging, washing with deionized water until neutral, drying to obtain USY powder;

[0010] Step (two) Preparation of USY-encapsulated silica-alumina xerogel

[0011] (1) Preparation of solution A: dissolving cetyltrimethylammonium bromide and alkali source in a mixed solution of anhydrous ethanol and deionized water, magnetically stirring until completely clear;

[0012] (2) Preparation of solution B: mixing tetraethyl orthosilicate and aluminum source in anhydrous ethanol, stirring to initiate hydrolysis;

[0013] (3) Mixing and encapsulation: slowly adding solution B to solution A under vigorous stirring, continuing to stir to form a uniform transparent sol, slowly adding the pretreated and dried USY powder from step (one) to the above sol, continuing to stir at room temperature to ensure that the USY particles are fully and uniformly infiltrated and encapsulated;

[0014] (4) Solvent evaporation and drying: transferring the above slurry to a petri dish and placing it in a forced air drying oven to slowly evaporate the ethanol and water, forming a xerogel, after complete drying, grinding the obtained solid powder in a mortar to re-disperse it into a powder with good flowability, obtaining the precursor of USY@xerogel;

[0015] Step (three) Steam-assisted crystallization

[0016] (1) Filling: adding deionized water and alkali source solution to the bottom of the high-pressure reaction kettle, placing the USY@xerogel powder in a quartz boat or ceramic crucible, then suspending it in the lining;

[0017] (2) Crystallization: placing the reaction kettle in an oven at 50-100°C for crystallization, then increasing the temperature to 100-220°C for continued crystallization;

[0018] Step (four) Template removal and post-treatment

[0019] (1) Cooling and collection: after the crystallization is completed, naturally cooling to room temperature, taking out the powder sample,

[0020] (2) Washing: centrifugal washing with deionized water and ethanol alternately until there is no bromide ion in the supernatant detected by silver nitrate solution, drying the washed filter cake;

[0021] (3) Calcination: The washed powder is calcined in a muffle furnace at 550-600℃ to completely remove the hexadecyltrimethylammonium bromide template agent and the base source to obtain the core-shell structure @USY; the base source is one of tetramethylammonium hydroxide or tetrapropylammonium hydroxide;

[0022] Step (5) Synthesis of Ti / Ni-@USY with core-shell structure by ethanol impregnation method

[0023] (1) Impregnation of Ti: Add anhydrous ethanol to a container, inject the titanium source into the bottom of the container, add the core-shell structured @USY molecular sieve, stir slowly with a small rotor to prevent oxidation, knead in a sealed bag until uniform, then place the sealed bag open in a fume hood to dry, and then calcine in a muffle furnace at 500-650℃ to obtain Ti-@USY;

[0024] (2) Impregnating Ni: Dissolve nickel nitrate in anhydrous ethanol, knead it in a sealed bag until uniform, add Ti-@USY, knead it in a sealed bag until uniform, then place the sealed bag open in a fume hood to dry, and calcine it in a muffle furnace at 500-650℃ for 1-5 hours.

[0025] (3) Catalyst reduction: Reduced in a hydrogen atmosphere at 500~600℃ for 1-3 hours, the resulting catalyst is a core-shell Ti / Ni-@USY with a hierarchical pore structure.

[0026] Introducing commercial USY into a strongly alkaline, high-temperature hydrothermal aqueous synthesis system leads to severe dissolution and structural damage of the USY core. Therefore, this method pre-coats the silica-alumina source required for synthesizing mesoporous USY onto the surface of commercial USY particles in the form of a dry gel (dry gel method). Under conditions where only a small amount of water and template agent vapor are present, the surface gel layer is induced to crystallize and form mesoporous USY. This process involves very little liquid phase, which greatly inhibits the dissolution of the USY core (vapor-assisted crystallization).

[0027] The core of this invention's "Ti-first, Ni-later" strategy—impregnating Ti first and then Ni—lies in introducing a functionalized TiO2 interfacial layer between the USY support and the active metal Ni. This is not merely a change in order, but a fundamental alteration of the catalyst's structure-activity relationship. Ti has a large atomic radius and its oxide crystal structure is more loosely packed, resulting in a highly dispersed TiO2 layer on the USY surface after calcination. TiO2 itself possesses excellent oxygen affinity and abundant surface hydroxyl groups, making it suitable as a substrate for subsequent Ni impregnation. 2+The ideal anchoring point. The post-impregnated Ni precursor solution preferentially adsorbs onto the TiO2 layer, utilizing the anchoring effect of Ti-O bonds to achieve a high degree of monolayer or sub-monolayer dispersion of Ni species on the TiO2 surface. During subsequent high-temperature calcination and use, the TiO2 layer acts as a physical barrier, effectively preventing the migration and aggregation of Ni particles, resembling Ti nano-islands that protect Ni and improve the thermal stability of the catalyst. This is crucial for the harsh process of co-pyrolysis of coal and waste plastics to produce aromatics. In addition, the pyrolysis of coal and waste plastics produces poisons containing heteroatoms such as S, N, and Cl, as well as heavy metals. The TiO2 surrounding the active metal Ni can preferentially adsorb or react with some of the poisons, acting as a "sacrificial layer" to protect the acidity of the inner USY layer and the core Ni active center, thereby improving the overall anti-poisoning ability of the catalyst. In contrast, the catalyst prepared by "Ni first, then Ti" has lower Ni dispersion, Ni is prone to agglomeration and clogging of pores, and the re-covering of Ti will mask the Ni active sites and aggravate clogging.

[0028] In Ni / Ti-USY catalysts, the catalytic effects of Ni and Ti vary significantly depending on the reaction system (coal / waste plastic co-pyrolysis, heavy petroleum oil hydrotreating, and bio-oil hydrodeoxygenation) because their reaction mechanisms, target products, and reaction conditions differ greatly. Ni's core role is always related to hydrogenation / dehydrogenation, but in heavy petroleum oil modification systems, it tends towards deep hydrogenation to remove heteroatoms and saturate aromatics; in bio-oil catalytic systems, it tends towards selective hydrogenolysis of CO bonds; and in coal and waste plastic co-pyrolysis systems, it tends towards cyclization and dehydrogenation to generate aromatics. Ti mainly acts as a structural aid, modulating the acidity of USY, stabilizing Ni dispersion, and assisting oxygen treatment, but its specific function varies depending on the reaction chemical environment. For example, in heavy petroleum oil hydrotreating, Ti enhances the hydrothermal stability of USY and delays deactivation under high temperature and pressure; in bio-oil catalysis, TiOx species donate electrons to Ni, enhancing its activation of CO bonds; in coal and waste plastic co-pyrolysis, Ti oxides may anchor Ni particles, improving their dispersibility and thermal stability.

[0029] This invention uses commercially available microporous USY as the core and an outer layer of deposited mesoporous USY as the shell, with the addition of active metals Ni and Ti. The mesoporous shell mainly serves for pre-cracking and transport, pre-cracking large molecules on the surface. Even if there is a small amount of carbon buildup in the channels, it mainly occurs within the mesoporous channels and will not block key active centers. Furthermore, the carbon buildup within the mesopores is more easily removed by coking. Products generated in the catalyst core layer can also be rapidly transferred to the mesopores, avoiding over-reaction. Figure 8As shown, fragments detached from the shell (mesoporous region) by thermal decomposition diffuse along the mesopores into the interior of the sphere. At the active sites in the mesopores, continuous β-cleavage, isomerization, and dehydrogenation reactions occur, generating hydrocarbon intermediates with medium carbon numbers. In the core region, even smaller molecules continue to enter the innermost microporous region, undergoing deep cleavage and aromatization at the high-density, strongly acidic active sites, ultimately generating light, small-molecule products. This increases the content of low-carbon aromatics (benzene, toluene, xylene, styrene, ethylbenzene, naphthalene, abbreviated as BTESXN) in the co-pyrolysis tar products.

[0030] The cracking of macromolecular polycyclic aromatic hydrocarbons (PAHs) requires the activation of C–C bonds at strongly acidic sites. The resulting small-molecule free radicals rapidly combine and stabilize each other, preventing repolymerization to form higher-ring-number PAHs or carbon deposits, thus reducing the impact of carbon deposits on catalyst activity. This invention focuses on overcoming key catalytic barriers in the co-pyrolysis of coal and waste plastics. In traditional microporous USY catalysts, the diffusion of macromolecular reactants is hindered within the narrow channels, making them prone to excessive condensation and dehydrogenation within the channels, especially near active sites. This leads to dense and difficult-to-remove internal carbon deposits that directly cover the active centers and block the pore openings. To address this, we have developed a USY core-shell catalyst with a mesoporous-microporous hierarchical structure. The large pore size of the mesoporous shell layer of the core-shell catalyst preferentially traps macromolecular reactants for pre-cracking, while the inner microporous core maintains shape-selective catalytic function. The high diffusion rate of the mesoporous channels reduces the overall residence time of reactant molecules within the catalyst, thereby suppressing the opportunity for deep dehydrogenation, polymerization, and other carbon deposit-forming side reactions. Therefore, the mesoporous shell layer acts as a "sacrificial carbon deposit buffer" and a "rapid channel for unblocking." Compared to traditional microporous USY, the catalyst of this invention can significantly reduce carbon buildup. Even if carbon buildup occurs, most of it is generated on the inner wall of the mesoporous channel, while the key microporous active centers located in the core are preserved.

[0031] Specifically, the core-shell USY stepped porous catalyst prepared in this invention consists of a shell of mesoporous USY support with a pore size of 2-5 nm, and a core of commercially available microporous USY. Ni and Ti are loaded onto this core. When Ti is incorporated into the USY support, it protects the active component Ni and prevents its sintering. The shell pre-cracks macromolecules such as asphaltene, allowing more pre-cracked products to enter the core layer. The abundant pores in the core layer result in a longer residence time for reactants, thereby promoting the breaking of C–O bonds in phenols and alkyl rearrangement, producing light aromatics. The presence of the shell significantly reduces the impact of carbon deposition on catalyst performance.

[0032] In the above scheme: in step (i), the calcination time of USY powder is 5-6 hours, the concentration of sodium hydroxide solution is 1M, and the stirring time is 2-3 hours.

[0033] In the above scheme: in step (ii) (1), the mass ratio of hexadecyltrimethylammonium bromide to the alkali source is 2:1, and in the mixed solution of anhydrous ethanol and deionized water, the volume ratio of anhydrous ethanol to deionized water is 4:1.

[0034] In the above scheme: in step (ii) (2), the aluminum source is at least one of aluminum isopropoxide, aluminum sulfate, and boehmite, and the mass ratio of tetraethyl orthosilicate to aluminum source is 0.1~10:0.05~20. In step (ii) (4), the drying temperature is 60-70℃.

[0035] In step (1), the USY powder is calcined for 5-6 hours and stirred for 1-3 hours.

[0036] In step (ii) (1), the mass ratio of hexadecyltrimethylammonium bromide to the alkali source is 2:1, and the volume ratio of anhydrous ethanol to deionized water in the mixed solution of anhydrous ethanol and deionized water is 4:1.

[0037] In step (ii) (2), the aluminum source is at least one of aluminum isopropoxide, aluminum sulfate, and boehmite, and the mass ratio of tetraethyl orthosilicate to the aluminum source is 0.1~10:0.05~20. In step (ii) (4), the drying temperature is 60-70℃. Preferably, the mass ratio of tetraethyl orthosilicate to the aluminum source is 2-5g:0.1-10g.

[0038] In step (iii), the concentration of the alkali source solution is 0.1 g / mL, the volume ratio of deionized water to alkali source solution is 5:1, the crystallization time at 50-100℃ is 24-30 h, and the crystallization time at 100-220℃ is 45-50 h.

[0039] In step (four), the calcination time is 6-7 hours.

[0040] In step (5), the mass ratio of nickel nitrate to USY powder is 2~15g nickel nitrate: 1g USY powder, and the titanium source is at least one of tetrabutyl titanate, titanium butoxide or titanium chloride, with a mass ratio of titanium source to USY powder of 1~10g titanium source: 1g USY powder.

[0041] In step (5), the calcination time during Ti impregnation is 1-5 hours.

[0042] A method for preparing a catalyst for the co-pyrolysis of coal and waste plastics to produce low-carbon aromatics.

[0043] Beneficial Effects: This catalyst can directly replace existing catalysts in fluidized bed or fixed bed reactors without requiring large-scale modifications to the equipment. By employing a post-synthetic method to modify commercial USY, the raw material cost is reduced by approximately 60% compared to fully synthetic mesoporous molecular sieves. By suppressing excessive cracking reactions, this catalyst can improve the yield of light fuel oil and chemical feedstocks, enhance the adaptability of existing co-pyrolysis units to feedstocks, increase light oil yields, and extend operating cycles, demonstrating significant industrialization potential. This catalyst will provide key material support for the efficient co-conversion of coal and waste plastics, offering both significant economic and environmental benefits. Attached Figure Description

[0044] Figure 1 It is a raw material for bituminous coal.

[0045] Figure 2 It is a raw material from waste plastics.

[0046] Figure 3 Images of the various powders prepared: (a) USY, (b) @USY, (c) Ni-@USY, (d) Ti / Ni-@USY.

[0047] Figure 4 Comparison of tar quality after co-pyrolysis of coal and waste plastics using different catalysts.

[0048] Figure 5 These are low-carbon aromatic hydrocarbons obtained by co-pyrolysis catalyzed by different catalysts.

[0049] Figure 6 This is a schematic diagram of a two-stage fixed-bed catalytic waste plastic pyrolysis reactor.

[0050] Figure 7 This is a crystal composition test diagram of Ti / Ni-@USY.

[0051] Figure 8 This is a schematic diagram of a core-shell molecular sieve. Detailed Implementation

[0052] The present invention will now be further described with reference to the accompanying drawings and embodiments.

[0053] Example 1

[0054] A hierarchical porous core-shell structured Ti / Ni-@USY catalyst, the preparation steps of which are as follows:

[0055] (1) Take 1g of commercial microporous USY powder and calcine it in a muffle furnace at 550℃ for 5 hours to remove the organic matter and water adsorbed in the pores; disperse the calcined USY (silicon-aluminum ratio 5~80) in a dilute NaOH (concentration 1M) solution, stir at 60℃ for 2 hours, centrifuge, wash with deionized water until neutral, and dry at 110℃ overnight to obtain activated and modified USY-cores.

[0056] (2) Preparation of Solution A: Dissolve 1.0 g of hexadecyltrimethylammonium bromide (CTAB) and 0.5 g of tetramethylammonium hydroxide (TMAOH) in a mixture of 20 mL of anhydrous ethanol and 5 mL of deionized water, and stir magnetically until completely clear. Separately prepare Solution B (aluminum-silicon source): Add 2 g of tetraethyl orthosilicate (TEOS) and 0.10 g of aluminum source aluminum isopropoxide to 20 mL of anhydrous ethanol and mix, stirring for 40 minutes to allow for initial hydrolysis.

[0057] (3) Slowly add solution B to solution A which is being vigorously stirred, and continue stirring for 4 hours to form a uniform transparent sol; add the USY-cores obtained in step (1) to the sol, and stir at room temperature for 12 hours until the USY particles are fully coated; transfer the slurry to a petri dish, place it in a 60°C drying oven, and dry until the ethanol and water are completely evaporated. After it is completely dry, place it in a mortar and grind it gently to redisperse it into a free-flowing powder to obtain the "USY@dry gel" precursor. The dry gel layer is the "raw material" for the subsequent formation of the mesoporous shell.

[0058] (4) Add 1.0 mL of deionized water and 0.2 mL of TMAOH solution (0.5 g dissolved in 5 mL of water) to the bottom of the high-pressure reactor. Place the precursor obtained in step (3) into a quartz boat or ceramic crucible and suspend it in the reactor liner. First, place the reactor in an oven at 50~100℃ for 24 hours to crystallize, and then raise the temperature to 100~220℃ to continue crystallizing for 48 hours to complete the steam-assisted crystallization.

[0059] (5) After crystallization, the powder sample was naturally cooled to room temperature and removed. It was washed several times by alternating centrifugation with deionized water and ethanol until no bromide ions were detected in the supernatant of silver nitrate solution. It was then dried at 100°C overnight. The dried powder was placed in a muffle furnace and calcined at 550°C for 6 hours to remove CTAB and TMAOH template agents, thus obtaining the core-shell structure @USY molecular sieve.

[0060] (6) Pour ethanol into a beaker, and use a syringe to extract 10g of tetrabutyl titanate, the titanium source, and then inject the titanium source into the bottom of the beaker. Add the obtained core-shell structured @USY molecular sieve to the mixed solution. During the stirring process, use a small rotor to stir slowly to prevent oxidation. Knead the mixture in a sealed bag until uniform, then place the sealed bag open in a fume hood to dry for 10 h, and then calcine it in a muffle furnace at 550℃ for 5 h to obtain Ti-@USY.

[0061] (7) Impregnating Ni: Dissolve 2g of nickel nitrate in anhydrous ethanol solution and knead it in a sealed bag until uniform. Add Ti-@USY molecular sieve to the ethanol mixture and knead until uniform. Then, place the sealed bag open in a fume hood to dry for 10 h and calcine it in a muffle furnace at 550℃ for 5 h.

[0062] (8) After reduction in a hydrogen atmosphere at 550°C for 3 hours, the resulting catalyst is a core-shell Ti / Ni-@USY with a hierarchical pore structure.

[0063] (9) Take 0.5g of waste plastic (insulation boards, packaging materials, electrical appliance shells, toys, stationery, disposable tableware, transparent shells, experimental instruments, scraps of rigid packaging materials, etc. found in a certain waste treatment plant), 4.5g of bituminous coal and 1g of core-shell Ti / Ni-@USY catalyst respectively and place them in the pyrolysis section and catalytic section of a two-stage fixed bed reactor for catalytic pyrolysis experiment. The temperatures of the pyrolysis section and catalytic section are 550℃ and 500℃ respectively. After pyrolysis for 30min, collect the bottom liquid phase product pyrolysis oil, extract and separate the light oil and heavy oil and weigh them respectively.

[0064] Example 2

[0065] Same as Example 1, except for step (9), 0.5g of waste plastic, 4.5g of bituminous coal and 1g of Ni-@USY catalyst were placed in the pyrolysis section and catalytic section sleeve of the two-stage fixed bed reactor for catalytic pyrolysis experiment. The temperatures of the pyrolysis section and catalytic section were 550℃ and 500℃, respectively. After pyrolysis for 30min, the bottom liquid phase product pyrolysis oil was collected, and the light oil and heavy oil were extracted and separated and weighed.

[0066] Example 3

[0067] Same as Example 1, except in step (9): 0.5g of waste plastic, 4.5g of bituminous coal, and 1g of @USY were placed in the pyrolysis section and catalytic section sleeves of a two-stage fixed-bed reactor for catalytic pyrolysis experiments. The temperatures of the pyrolysis section and catalytic section were 550℃ and 500℃, respectively. After pyrolysis for 30 minutes, the bottom liquid phase product, pyrolysis oil, was collected, and the light oil and heavy oil were extracted and weighed separately.

[0068] Example 4

[0069] Same as Example 1, except for step (9), 0.5g of waste plastic, 4.5g of bituminous coal and 1g of USY were placed in the pyrolysis section and catalytic section sleeve of the two-stage fixed bed reactor respectively for catalytic pyrolysis experiment. The temperatures of the pyrolysis section and catalytic section were 550℃ and 500℃ respectively. After pyrolysis for 30min, the bottom liquid phase product pyrolysis oil was collected, and the light oil and heavy oil were extracted and separated and weighed respectively.

[0070] Example 5

[0071] Same as Example 1, except for step (9), 0.5g of waste plastic and 4.5g of bituminous coal are placed in the pyrolysis section of a two-stage fixed-bed reactor, and the catalytic section sleeve is left empty. A catalytic pyrolysis experiment is carried out. The temperatures of the pyrolysis section and the catalytic section are 550℃ and 500℃, respectively. After pyrolysis for 30 minutes, the bottom liquid phase product pyrolysis oil is collected, and the light oil and heavy oil are extracted and separated and weighed.

[0072] The two-stage fixed-bed reactor used is a current technology, such as Figure 6 As shown, the reactor includes an air inlet 1, a quartz tube reactor 2, a pyrolysis sleeve 3, a support tube 4, a catalytic sleeve 5, an ice-salt bath 6, a gas bag 7, a temperature controller 8, and an insulation layer 9. The pyrolysis atmosphere N2 enters the reactor through the air inlet. The two temperature controllers 8 control the pyrolysis temperature and the catalytic temperature (3 and 5) respectively. The support tube 4 provides space for the diffusion of pyrolysis volatiles and facilitates the separation of waste plastics and catalysts. The catalytic pyrolysis device collects liquid phase products through the external ice-salt bath 6, while non-condensable gases are collected by the gas bag 7. The external insulation layer 9 of the reactor prevents heat loss through heat exchange with the environment.

[0073] Table 1 Catalyst Description

[0074]

[0075] Table 2 Comparative Analysis of the Performance of USY Molecular Sieves Composite Materials

[0076]

[0077] As can be seen from the data in Table 2, after coating with a shell, the mesopore volume and specific surface area increased significantly, while the amount of carbon deposits on the catalyst decreased significantly.

[0078] Table 3 Catalytic effects of Ti / Ni-@USY on different types of waste plastics

[0079]

[0080] The experimental results of Examples 1-5 are as follows: Figure 4 As shown, from Figure 4 As can be seen from the data, the Ti / Ni-@USY method using this invention has the lowest heavy oil content.

[0081] In Table 3, under the columns for insulation boards, packaging materials, and appliance casings, the mass ratio of insulation boards to packaging materials to appliance casings is 4:3:3; the raw materials for the reaction system are 90% bituminous coal + toys, stationery, and disposable tableware (10%), and the mass ratio of reactants to catalyst is 5:1. Under the columns for toys, stationery, and disposable tableware, the mass ratio of toys to stationery to disposable tableware is 4:3:3; the raw materials for the reaction system are 90% bituminous coal + toys, stationery, and disposable tableware (10%), and the mass ratio of reactants to catalyst is 5:1. Under the columns for transparent casings, testing instruments, and rigid packaging materials, the mass ratio of transparent casings to testing instruments to rigid packaging materials is 4:3:3; the raw materials for the reaction system are 90% bituminous coal + 10% transparent casings, testing instruments, and rigid packaging materials, and the mass ratio of reactants to catalyst is 5:1.

[0082] Example 6

[0083] A hierarchical porous core-shell structured Ti / Ni-@USY catalyst, the preparation steps of which are as follows:

[0084] (1) Take 1g of commercial microporous USY powder and calcine it in a muffle furnace at 600℃ for 6 hours to remove the organic matter and moisture adsorbed in the pores; disperse the calcined USY (silicon-aluminum ratio 5~80) in a dilute NaOH (concentration 1M) solution, stir at 65℃ for 3 hours, centrifuge, wash with deionized water until neutral, and dry at 110℃ overnight to obtain activated and modified USY-cores.

[0085] (2) Preparation of solution A: Dissolve 1.0g CTAB and 0.5g TMAOH in a mixture of 20mL anhydrous ethanol and 5mL deionized water, and stir magnetically until completely clear. Prepare solution B separately: Add 5g TEOS and 10g aluminum sulfate to 50mL anhydrous ethanol and mix, stirring for 60 minutes to allow for initial hydrolysis.

[0086] (3) Slowly drop solution B into solution A which is being stirred vigorously, and continue stirring for 2 hours to form a uniform transparent sol; add USY-cores obtained in step (1) to the sol, and stir at room temperature for 6 hours until the USY particles are fully coated; transfer the slurry to a petri dish, dry it at 60°C until the ethanol and water are completely evaporated, and then grind it gently to obtain the "USY@dry gel" precursor.

[0087] (4) Add 1.0 mL of deionized water and 0.2 mL of TMAOH solution (0.5 g dissolved in 5 mL of water) to the bottom of the high-pressure reactor. Place the precursor obtained in step (3) into a quartz boat or ceramic crucible and suspend it in the reactor liner. First, place the reactor in an oven at 50~100℃ for 30 hours to crystallize, and then raise the temperature to 100~220℃ to continue crystallizing for 50 hours to complete the steam-assisted crystallization.

[0088] (5) After crystallization, the powder sample was naturally cooled to room temperature and removed. It was washed several times by alternating centrifugation with deionized water and ethanol until no bromide ions were detected in the supernatant of silver nitrate solution. It was then dried at 100°C overnight. The dried powder was placed in a muffle furnace and calcined at 600°C for 7 hours to remove CTAB and TMAOH template agents, thus obtaining the core-shell structure @USY molecular sieve.

[0089] (6) Impregnation of Ti: First, pour an appropriate amount of ethanol into a beaker. Use a syringe to draw 1g of titanium source (titanium butoxide) and then inject the titanium source into the bottom of the beaker. Add the core-shell structure @USY molecular sieve obtained in step (5) to the ethanol mixture. During the stirring process, use a small rotor to stir slowly to prevent oxidation. Rub the mixture in a sealed bag until uniform, then place the sealed bag open in a fume hood to dry for 10 h, and then calcine it in a muffle furnace at 650℃ for 1 h to obtain Ti-@USY.

[0090] (7) Impregnating Ni: Dissolve 15g of nickel nitrate in anhydrous ethanol solution and knead it in a sealed bag until uniform. Add Ti-@USY molecular sieve to the ethanol mixture and knead until uniform. Then, open the sealed bag and place it in a fume hood to dry for 10 h. Then, calcine it in a muffle furnace at 650℃ for 1 h.

[0091] (8) After reduction in a hydrogen atmosphere at 600℃ for 1 hour, the resulting catalyst is a core-shell Ti / Ni-@USY with a hierarchical pore structure.

[0092] (9) Take 0.5g of waste plastic (insulation boards, packaging materials, electrical appliance casings, toys, stationery, disposable tableware, transparent casings, experimental instruments, scraps of rigid packaging materials, etc., found in a waste treatment plant, with the same proportions as in Example 1), 4.5g of bituminous coal, and 1g of core-shell Ti / Ni-@USY catalyst, respectively, and place them in the pyrolysis section and catalytic section sleeves of a two-stage fixed-bed reactor for catalytic pyrolysis experiments. The temperatures of the pyrolysis section and catalytic section are 550℃ and 500℃, respectively. After pyrolysis for 30 minutes, collect the bottom liquid phase product, pyrolysis oil, and extract and separate light oil and heavy oil, weighing them separately. Light oil: 94.93%, heavy oil: 5.07%.

[0093] Example 7

[0094] A hierarchical porous core-shell structured Ti / Ni-@USY catalyst, the preparation steps of which are as follows:

[0095] (1) Take 1g of commercial microporous USY powder and calcine it in a muffle furnace at 550℃ for 5 hours to remove the organic matter and moisture adsorbed in the pores; disperse the calcined USY (silicon-aluminum ratio 5~80) in a dilute NaOH (1M) solution, stir at 60℃ for 1 hour, centrifuge, wash with deionized water until neutral, and dry at 110℃ overnight to obtain activated and modified USY-cores.

[0096] (2) Preparation of solution A: Dissolve 1.0g CTAB and 0.5g TPAOH in a mixture of 20mL anhydrous ethanol and 5mL deionized water, and stir magnetically until completely clear. Prepare solution B separately: Add 5g TEOS and 1g boehmite to 40mL anhydrous ethanol and mix, stirring for 60 minutes to allow for initial hydrolysis.

[0097] (3) Slowly drop solution B into solution A which is being vigorously stirred, and continue stirring for 2 hours to form a uniform transparent sol; add USY-cores obtained in step (1) to the sol, and stir at room temperature for 6 hours until the USY particles are fully coated; transfer the slurry to a petri dish, dry it at 60°C until the ethanol and water are completely evaporated, and grind it to obtain the "USY@dry gel" precursor.

[0098] (4) Add 1.0 mL of deionized water and 0.2 mL of TPAOH solution (concentration 0.5 g / 5 mL deionized water) to the bottom of the high-pressure reactor. Place the precursor obtained in step (3) into a quartz boat or ceramic crucible and suspend it in the reactor liner. First, place the reactor in an oven at 50~100℃ for crystallization for 26 hours, then raise the temperature to 100~220℃ and continue crystallization for 48 hours to complete the steam-assisted crystallization.

[0099] (5) After crystallization, the powder sample was naturally cooled to room temperature and removed. It was washed several times by alternating centrifugation with deionized water and ethanol until no bromide ions were detected in the supernatant of silver nitrate solution. It was then dried at 100°C overnight. The dried powder was placed in a muffle furnace and calcined at 600°C for 6 hours to remove CTAB and TPAOH template agents, thus obtaining the core-shell structure @USY molecular sieve.

[0100] (6) Impregnation of Ti: First, pour an appropriate amount of ethanol into a beaker. Use a syringe to draw 5g of titanium source (titanium chloride) and then inject the titanium source into the bottom of the beaker. Add the core-shell structure @USY molecular sieve obtained in step four to the ethanol mixture. During stirring, use a small rotor and control the speed and stirring time to prevent oxidation. Knead the mixture in a sealed bag until uniform, then place the sealed bag open in a fume hood to dry for 10 h, and then calcine it in a muffle furnace at 500℃ for 3 h to obtain Ti-@USY.

[0101] (7) Impregnating Ni: Dissolve 8g of nickel nitrate in anhydrous ethanol solution and knead it in a sealed bag until uniform. Add Ti-@USY molecular sieve to the ethanol mixture and knead until uniform. Then, open the sealed bag and place it in a fume hood to dry for 10 h. Then, calcine it in a muffle furnace at 500℃ for 3 h.

[0102] (8) After reduction in a hydrogen atmosphere at 500°C for 3 hours, the resulting catalyst is a core-shell Ti / Ni-@USY with a hierarchical pore structure.

[0103] (9) Take 0.5g of waste plastic (insulation boards, packaging materials, electrical appliance casings, toys, stationery, disposable tableware, transparent casings, experimental instruments, scraps of rigid packaging materials, etc., found in a waste treatment plant, with the same proportions as in Example 1), 4.5g of bituminous coal, and 1g of core-shell Ti / Ni-@USY catalyst, respectively, and place them in the pyrolysis section and catalytic section sleeves of a two-stage fixed-bed reactor for catalytic pyrolysis experiments. The temperatures of the pyrolysis section and catalytic section are 550℃ and 500℃, respectively. After pyrolysis for 30 minutes, collect the bottom liquid phase product, pyrolysis oil, and extract and separate light oil and heavy oil, weighing them separately. Light oil 95.22%, heavy oil 4.78%.

[0104] Example 8

[0105] The rest is the same as in Example 1, except that steps (6) and (7) are interchanged. The obtained Ni / Ti-@USY was subjected to catalytic pyrolysis experiment according to step (9), and the light oil and heavy oil were extracted and separated by mass. The light oil was 91.35% and the heavy oil was 8.65%.

[0106] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a catalyst for co-pyrolysis of coal and waste plastics to produce low-carbon aromatic hydrocarbons, characterized by, Preparation according to the following steps: Step (one) pretreatment and surface modification of microporous USY (1) Calcination of USY powder at 550-600℃ in a muffle furnace to remove organic matter and water adsorbed in the pores; (2) Surface charge modification: disperse the activated USY in a dilute NaOH solution, stir at 60-65℃, then centrifuge, wash with deionized water until neutral, dry to obtain USY powder; Step (two) preparation of USY-coated silica-alumina xerogel (1) Preparation of solution A: dissolve cetyltrimethylammonium bromide and alkali source in a mixed solution of anhydrous ethanol and deionized water, magnetically stir until completely clear; (2) Preparation of solution B: mix tetraethyl orthosilicate and aluminum source in anhydrous ethanol, stir to initiate hydrolysis; (3) Mixing and coating: slowly add solution B to solution A under vigorous stirring, continue stirring to form a uniform transparent sol, slowly add the pretreated and dried USY powder from step (one) to the above sol, continue stirring at room temperature to ensure that the USY particles are fully and uniformly infiltrated and coated; (4) Solvent evaporation and drying: transfer the above slurry to a petri dish and place it in a forced air drying oven to slowly evaporate ethanol and water, forming a xerogel, after complete drying, grind the obtained solid powder in a mortar to re-disperse it into a powder with good flowability, obtaining the precursor of USY@xerogel; Step (three) steam-assisted crystallization (1) Reactor loading: add deionized water and alkali source solution to the bottom of the high-pressure reaction kettle, place the USY@xerogel powder in a quartz boat or ceramic crucible, then suspend it in the lining; (2) Crystallization: place the reaction kettle in a 50-100℃ oven for crystallization, then increase the temperature to 100-220℃ for continued crystallization; Step (four) template removal and post-treatment (1) Cooling and collection: after crystallization is complete, cool naturally to room temperature, remove the powder sample; (2) Washing: centrifugal washing with deionized water and ethanol alternately until there is no bromide ion in the supernatant detected by silver nitrate solution, dry the washed filter cake; (3) Calcination: calcine the washed powder in a 550-600℃ muffle furnace to completely remove the cetyltrimethylammonium bromide template and alkali source, obtaining the core-shell structured @USY; the alkali source is one of tetramethylammonium hydroxide or tetrapropylammonium hydroxide; Step (five) synthesis of Ti / Ni-@USY with core-shell structure by ethanol impregnation method (1) Ti impregnation: add anhydrous ethanol to a container, pour the titanium source into the bottom of the container, add the core-shell structured @USY molecular sieve, use a small rotor to stir slowly to prevent oxidation, knead evenly in a sealed bag, then air dry the sealed bag in a fume hood, then calcine at 500-650℃ in a muffle furnace to obtain Ti-@USY; (2) Ni impregnation: dissolve nickel nitrate in anhydrous ethanol, knead evenly in a sealed bag, add Ti-@USY, knead evenly in a sealed bag, then air dry the sealed bag in a fume hood, calcine at 500-650℃ for 1-5h; (3) Catalyst reduction: reduction in hydrogen atmosphere at 500-600℃ for 1-3 hours, and the obtained catalyst is a core-shell Ti / Ni-@USY with hierarchical pore structure.

2. The method for preparing the catalyst for co-pyrolysis of coal and waste plastics to produce low-carbon aromatics according to claim 1, characterized in that: In step (one), the calcination time of the USY powder is 5-6h, and the stirring time is 1-3h.

3. The method for preparing the catalyst for co-pyrolysis of coal and waste plastics to produce low-carbon aromatic hydrocarbons according to claim 1 or 2, characterized in that: In (1) of step (two), the mass ratio of cetyltrimethylammonium bromide to alkali source is 2:1, and the volume ratio of anhydrous ethanol to deionized water in the mixed solution of anhydrous ethanol and deionized water is 4:

1.

4. The method for preparing the catalyst for co-pyrolysis of coal and waste plastics to produce low-carbon aromatics according to claim 3, characterized in that: In (2) of step (two), the aluminum source is at least one of aluminum isopropoxide, aluminum sulfate, and pseudo-boehmite, and the mass ratio of tetraethyl orthosilicate to the aluminum source is 0.1-10:0.05-20, and the drying temperature in (4) of step (two) is 60-70℃.

5. The method of claim 4, wherein the catalyst is prepared by the following steps: (1) mixing the metal oxide and the metal salt to form a mixture; (2) heating the mixture to form a catalyst precursor; and (3) calcining the catalyst precursor to form the catalyst. In step (three), the concentration of the alkali source solution is 0.1g / mL, the volume ratio of deionized water to the alkali source solution is 5:1, the crystallization time at 50-100℃ is 24-30h, and the crystallization time at 100-220℃ is 45-50h.

6. The method of claim 5, wherein the catalyst is prepared by the following steps: (1) mixing the metal oxide and the metal salt to form a mixture; (2) heating the mixture to form a catalyst precursor; and (3) calcining the catalyst precursor to form the catalyst. In step (four), the calcination time is 6-7h.

7. The method according to claim 6, wherein the catalyst is prepared by the following steps: (1) mixing the metal oxide and the metal salt to form a mixture; (2) adding the mixture into the solvent to form a solution; (3) adding the solution into the coal and waste plastic to form a mixture; (4) drying the mixture; and (5) calcining the mixture. In step (five), the mass ratio of nickel nitrate to USY powder is 2-15g of nickel nitrate:1g of USY powder, the titanium source is at least one of tetrabutyl titanate, titanium butoxide, or titanium chloride, and the mass ratio of the titanium source to USY powder is 1-10g of titanium source:1g of USY powder.

8. The method for preparing the catalyst for co-pyrolysis of coal and waste plastics to produce low-carbon aromatics according to claim 7, characterized in that: In step (five), the calcination time for impregnating Ti is 1-5h.

9. A coal and waste plastic co-pyrolysis catalyst for producing low-carbon aromatic hydrocarbons prepared by the preparation method of the coal and waste plastic co-pyrolysis catalyst for producing low-carbon aromatic hydrocarbons according to any one of claims 1-8.

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