Preparation method and application of a catalyst for co-thermal pyrolysis of waste plastics and biomass

Abstract

This invention provides a method for preparing and applying a catalyst for co-thermal pyrolysis of waste plastics and biomass, comprising the following steps: Step 1, mixing FCC waste catalyst, sodium carbonate, and a metal oxide precursor uniformly to form a powder; Step 2, modifying HZSM-5 molecular sieve with phosphorus; Step 3, mixing the mixture obtained in Step 1, the phosphorus-modified ZSM-5 molecular sieve from Step 2, a binder, and water to form microspheres, calcining to obtain the catalyst for co-thermal pyrolysis of waste plastics and biomass. The catalyst prepared by this invention has a large pore size and pore volume, and when used for co-thermal pyrolysis of waste plastics and biomass, the liquid yield is greater than 70%.

Description

Technical Field

[0001] This invention relates to a method for preparing a catalyst for co-thermal pyrolysis of waste plastics and biomass, and the application of this preparation method in the co-thermal pyrolysis process of waste plastics and biomass. Background Technology

[0002] Waste plastics, as part of urban solid waste, damage environmental sanitation and harm ecosystems. Common disposal methods include landfill, incineration, and recycling. However, landfill and incineration both cause secondary pollution. Therefore, focusing on the recycling and resource utilization of waste plastics is a green path towards sustainable development.

[0003] In addition, most of the energy and chemical raw materials available today come from fossil resources. Faced with severe challenges in energy reserves and environmental issues, the development of renewable energy sources such as biomass energy has attracted widespread attention from researchers.

[0004] Patent CN111876177A discloses a process where biomass is dried, pulverized, and sieved. Biomass with a particle size ≤3nm is then subjected to further drying. Waste plastics are ground and sieved, with particles <80 mesh being dried. The treated biomass and waste plastics are then mixed evenly at a mass ratio of 1:1-10 and placed in a reaction apparatus for heating, yielding bio-oil with a yield of 30%-70%. However, this technology has a liquid yield of less than 70% and requires staged heating, making the process relatively complex.

[0005] Patent CN103920526B discloses a composite catalyst using HZSM-5 molecular sieve as the catalyst support. The catalyst support is first loaded with the non-metallic element phosphorus, followed by the transition metal elements nickel, zinc, or copper. This technology uses HZSM-5 molecular sieve as the catalyst support, which has a small pore size, hindering the diffusion of large molecules.

[0006] Patent CN107118793B describes a method for preparing hierarchical HZSM-5 by treating HZSM-5 with an alkali, followed by atomic layer deposition (ALD) to deposit a metal source onto the hierarchical HZSM-5. This catalyst is used for co-pyrolysis of biomass and oils, effectively mitigating deactivation due to carbon buildup and improving aromatic yield. However, although this technique prepares hierarchical HZSM-5 through alkali treatment, its pore size distribution peaks are less than 1 nm, and the mesopore size in electron micrographs is 2-3 nm, which still falls short of the required pore size.

[0007] Patent CN103691429B discloses a catalyst consisting of two parts: a support and an active component. The active component is loaded onto the support via an impregnation method. The support is rapidly pyrolyzed carbon, a byproduct of the rapid pyrolysis and liquefaction process of biomass. After treatments such as degreasing, deashing, activation, and oxidation, the rapidly pyrolyzed carbon is formed into a mesoporous and macroporous channel structure with a main pore size of 20-80 nm. The active component is a transition metal, which is impregnated onto the support through loading and reduction steps to prepare a catalyst for rapid pyrolysis and liquefaction of biomass. The preparation of the support in this technology requires treatments such as degreasing, deashing, activation, and oxidation, which are complex steps, and the thermal stability of the catalyst needs to be improved.

[0008] Therefore, further research is needed in this field on catalysts for co-thermal pyrolysis of waste plastics and biomass. Summary of the Invention

[0009] The main objective of this invention is to provide a method for preparing and applying a catalyst for co-thermal pyrolysis of waste plastics and biomass, so as to overcome the defects of existing co-thermal pyrolysis catalysts, such as small pore size and insufficient activity, resulting in low yield of catalytic liquid.

[0010] To achieve the above objectives, the present invention provides a method for preparing a catalyst for co-thermal pyrolysis of waste plastics and biomass, comprising the following steps:

[0011] Step 1: Mix the FCC waste catalyst, sodium carbonate and metal oxide precursor evenly to form a powder;

[0012] Step 2: Modify the HZSM-5 molecular sieve with phosphorus;

[0013] Step 3: Mix the mixture obtained in Step 1, the phosphorus-modified ZSM-5 molecular sieve from Step 2, the binder, and water to form microspheres, and calcine them to obtain a catalyst for co-thermal pyrolysis of waste plastics and biomass.

[0014] The method for preparing a catalyst for co-thermal pyrolysis of waste plastics and biomass according to the present invention, wherein the metal in the metal oxide precursor is a Group IIA metal or a transition metal.

[0015] The method for preparing the catalyst for co-thermal pyrolysis of waste plastics and biomass according to the present invention, wherein the metal oxide precursor is calculated as metal oxide, and the dry basis mass ratio of sodium carbonate, the metal oxide precursor and the FCC waste catalyst is 0.01-0.05∶0.05-0.2∶1.

[0016] The method for preparing the catalyst for co-thermal pyrolysis of waste plastics and biomass according to the present invention, wherein in step 1, the powder is formed by ball milling for 10-20 minutes.

[0017] The method for preparing the catalyst for co-thermal pyrolysis of waste plastics and biomass according to the present invention, wherein in step 2, the method for phosphorus modification of HZSM-5 molecular sieve is as follows: impregnating HZSM-5 molecular sieve with a solution containing phosphorus precursor, drying at 120-140℃ for 2-3 hours, and calcining at 500-600℃ for 1-3 hours to obtain phosphorus-modified ZSM-5 molecular sieve.

[0018] The method for preparing the catalyst for co-thermal pyrolysis of waste plastics and biomass according to the present invention, wherein the phosphorus-containing precursor is at least one of phosphoric acid, diammonium hydrogen phosphate and ammonium phosphate; the phosphorus is calculated as P2O5 and the mass ratio of phosphorus to the dry basis of HZSM-5 molecular sieve is 1%-5%.

[0019] The method for preparing the catalyst for co-thermal pyrolysis of waste plastics and biomass according to the present invention, wherein the amount of phosphorus-modified ZSM-5 molecular sieve added in step 3 is 5%-20% of the dry basis mass of the FCC waste catalyst.

[0020] The method for preparing the catalyst for co-thermal pyrolysis of waste plastics and biomass according to the present invention, wherein the binder is selected from at least one of aluminum sol, neutral silica sol, and acidic silica sol; the amount of binder added in step 3 is 2%-10% of the dry basis mass of the FCC waste catalyst.

[0021] The method for preparing the catalyst for co-thermal pyrolysis of waste plastics and biomass according to the present invention, wherein, in step 1, the metal oxide precursor is selected from at least one of calcium carbonate, magnesium carbonate, and zinc carbonate; and in step 3, the calcination temperature is 830-900℃ and the calcination time is 1-3 hours.

[0022] To achieve the above objectives, the present invention also provides the application of the catalyst obtained by the above preparation method in the co-thermal pyrolysis of waste plastics and biomass, characterized in that the mass ratio of waste plastics to biomass is 1:1-10:1; the co-thermal pyrolysis conditions are: pyrolysis temperature 400-550℃, pressure 0.1-1.0MPa, and the amount of catalyst added is 2wt%-15wt% of the total mass of waste plastics and biomass.

[0023] The beneficial effects of this invention are:

[0024] This invention uses FCC spent catalyst as a carrier and metal oxide and phosphorus-modified ZSM-5 molecular sieve as active components. The original pore structure of the FCC spent catalyst and the pore-bursting effect of CO2 give the catalyst a large pore size and pore volume, thus improving the accessibility of the active components and making the liquid yield greater than 70%.

[0025] The catalyst of this invention uses FCC waste catalyst, which not only solves the problem of FCC waste catalyst treatment, but also realizes the reuse of FCC waste catalyst. Moreover, the process is simple and easy to industrialize. Detailed Implementation

[0026] The technical solution of the present invention will be described in detail below. The following embodiments are implemented under the premise of the technical solution of the present invention and a detailed implementation process is given. However, the protection scope of the present invention is not limited to the following embodiments. Structures or experimental methods that do not specify specific conditions in the following embodiments are generally performed under conventional conditions.

[0027] This invention provides a method for preparing a catalyst for co-thermal pyrolysis of waste plastics and biomass, comprising the following steps:

[0028] Step 1: Mix the FCC waste catalyst, sodium carbonate and metal oxide precursor evenly to form a powder;

[0029] Step 2: Modify the HZSM-5 molecular sieve with phosphorus;

[0030] Step 3: Mix the mixture obtained in Step 1, the phosphorus-modified ZSM-5 molecular sieve from Step 2, the binder, and water to form microspheres, dry and calcine them to obtain a catalyst for co-thermal pyrolysis of waste plastics and biomass.

[0031] Currently, most FCC waste catalysts are disposed of by landfill. The few FCC waste catalyst regeneration and revival processes mainly include acid washing, carbonylation-chlorination, sulfidation-oxidation and magnetic rotation, etc., to remove heavy metals and restore the activity of FCC waste catalysts. However, these methods have problems such as complicated processes and high revival costs.

[0032] This invention uses FCC waste catalyst as a carrier and metal oxide and phosphorus-modified ZSM-5 molecular sieve as active components. Sodium carbonate is added during the catalyst preparation process. During the calcination process, the catalyst will have a CO2 pore-bursting effect. Combined with the original pore structure of the FCC waste catalyst, the resulting catalyst has a large pore size and pore volume. This improves the accessibility of the active components dispersed on the pore surface, promotes the co-thermal pyrolysis conversion efficiency of waste plastics and biomass, and makes the liquid yield obtained by the catalyst greater than 70%.

[0033] In addition, the ball milling of the FCC waste catalyst and sodium carbonate in this invention can activate the metal, promote the synergistic effect of different metal ions, and help increase the number of reactive sites, thereby further improving the cracking reaction efficiency of the obtained catalyst.

[0034] In detail, step 1 of the present invention is: mixing FCC waste catalyst, sodium carbonate and metal oxide precursor evenly to form powder.

[0035] This invention does not impose any particular limitation on FCC waste catalysts; any catalytic cracking catalyst discarded from the catalytic cracking process can be used. This invention also does not impose any particular limitation on the structure and elemental content of FCC waste catalysts.

[0036] In one embodiment, the metal in the metal oxide precursor of the present invention is a Group IIA metal or a transition metal, such as calcium, magnesium, zinc, etc., and the metal oxide precursor can be a metal carbonate, such as at least one of calcium carbonate, magnesium carbonate, and zinc carbonate.

[0037] This invention does not specifically limit the method of forming the powder from the mixture of FCC waste catalyst, sodium carbonate, and metal oxide precursor. Preferably, the powder is formed by ball milling, more specifically by mechanical ball milling, which can activate the metals on the FCC waste catalyst, increase the number of active centers in the resulting catalyst, and realize the resource utilization of FCC waste catalyst. In one embodiment, the ball milling time is 10-20 minutes.

[0038] In one embodiment, the mass ratio of sodium carbonate, the metal oxide precursor, and the FCC waste catalyst (dry basis) is 0.01-0.05:0.05-0.2:1, based on the metal oxide. In another embodiment, the mass ratio of the metal oxide precursor to the FCC waste catalyst (dry basis) is 0.08:1-0.15:1.

[0039] Step 2 of this invention is: modifying HZSM-5 molecular sieve with phosphorus.

[0040] This invention does not specifically limit the use of HZSM-5 molecular sieves; commercially available HZSM-5 molecular sieves can be used, or they can be prepared using existing techniques. In one embodiment, the silica-alumina ratio of the HZSM-5 molecular sieve is 25-50.

[0041] In this invention, the HZSM-5 molecular sieve is first modified with phosphorus before being prepared into a catalyst. In one embodiment, the phosphorus modification is carried out by impregnation, such as impregnating the HZSM-5 molecular sieve in a solution containing a phosphorus precursor, and then drying and calcining it to obtain the phosphorus-modified HZSM-5 molecular sieve.

[0042] The phosphorus-containing precursor can be at least one of phosphoric acid, diammonium hydrogen phosphate, and ammonium phosphate. The solution of the phosphorus-containing precursor can be an aqueous solution of at least one of phosphoric acid, diammonium hydrogen phosphate, and ammonium phosphate. The impregnation method can be equal-volume impregnation, excess impregnation, etc. After impregnation, the ZSM-5 molecular sieve is dried and calcined. The drying temperature can be 120-140℃, and the drying time can be 2-3 hours. The calcination temperature can be 500-600℃, and the calcination time can be 1-3 hours.

[0043] In one embodiment, in the phosphorus-modified ZSM-5 molecular sieve, phosphorus, calculated as P2O5, accounts for 1%-5% of the dry basis of the ZSM-5 molecular sieve by mass.

[0044] Step 3 of this invention is as follows: the mixture obtained in step 1, the phosphorus-modified ZSM-5 molecular sieve from step 2, the binder, and water are mixed and pulped to form microspheres, which are then calcined to obtain a catalyst for co-thermal pyrolysis of waste plastics and biomass.

[0045] The binder of this invention is a conventional binder in the art. In one embodiment, the binder of this invention is selected from one or more mixtures of aluminum sol, neutral silica sol, and acidic silica sol. The amount of binder added is 2%-10% of the dry basis mass of the FCC waste catalyst.

[0046] In one embodiment, the amount of phosphorus-modified ZSM-5 molecular sieve added is 5%-20% of the dry basis mass of the FCC waste catalyst.

[0047] The present invention does not particularly limit the amount of water added in step 3, as long as a slurry can be formed. The method of forming microspheres is, for example, spray drying. The calcination temperature in step 3 is, for example, 830-900°C, and the calcination time is, for example, 1-3 hours.

[0048] The catalyst prepared by the method of this invention has a large pore size and pore volume, making it suitable as a catalyst for the co-thermal pyrolysis of waste plastics and biomass. In one embodiment, the mass ratio of waste plastics to biomass is 1:1 to 10:1. In another embodiment, the co-thermal pyrolysis conditions are: pyrolysis temperature 400-550℃, pressure 0.1-1.0 MPa, and catalyst addition amount of 2-15 wt% of the sum of the masses of waste plastics and biomass.

[0049] The present invention does not particularly limit the source of waste plastics and biomass. In one embodiment, the waste plastics are one or a mixture of several of waste low-density polyethylene (relative molecular weight of 0.910 to 0.925), high-density polyethylene (relative molecular weight of 0.941 to 0.965), polypropylene, and polystyrene, and the biomass is one or a mixture of several of sawdust, straw, and waste residue.

[0050] The technical solution of the present invention will be described below through specific embodiments.

[0051] Source of raw materials or equipment:

[0052] FCC spent catalyst (specific surface area 113.7 μm) 2 / g, pore volume is 0.127cm³ 3Sodium carbonate, calcium carbonate, magnesium carbonate, zinc carbonate, phosphoric acid, diammonium hydrogen phosphate, and ammonium phosphate were all analytical grade and produced by Sinopharm Group; aluminum sol (Al2O3 19.4wt%), neutral silica sol (SiO2 30wt%), acidic silica sol (SiO2 30wt%), and HZSM-5 (90% crystallinity, 30% silicon-aluminum ratio) were produced by Lanzhou Petrochemical Company.

[0053] Evaluation and analysis methods:

[0054] The catalyst pore volume and pore size were determined by low-temperature nitrogen adsorption-desorption method (analytical method is described in "Analytical Methods in Petrochemical Industry (RIPP Experimental Methods)", edited by Yang Cuiding et al., Science Press, 1990). The catalyst reaction performance was evaluated using a small fixed bed.

[0055] Example 1

[0056] 1021g of dry FCC waste catalyst, 21g of sodium carbonate, and 306g of calcium carbonate were mixed evenly and mechanically ball-milled for 12 minutes. 200g of HZSM-5 molecular sieve was impregnated with a solution containing 7.6g of diammonium hydrogen phosphate, dried at 130℃ for 3 hours, and then calcined at 570℃ for 1.5 hours to obtain phosphorus-modified ZSM-5 molecular sieve. The ball-milled product was mixed with 101g of dry phosphorus-modified ZSM-5 molecular sieve, 82g of alumina sol, and 3403g of deionized water, slurried, spray-dried to form microspheres, and calcined at 870℃ for 1.5 hours to obtain catalyst C-1 for the pyrolysis of waste plastics, with an average pore size of 9.2nm and a total pore volume of 0.59cm³. 3 / g.

[0057] Using waste plastics and biomass as raw materials (polypropylene and straw by mass percentage: 80% and 20%, respectively), co-thermal pyrolysis was carried out at a temperature of 450℃, a pressure of 0.7 MPa, and a catalyst ratio of (waste plastics and biomass) of 5 wt%, with a liquid yield of 79.7%.

[0058] Example 2

[0059] 1434g of dry FCC waste catalyst, 43g of sodium carbonate, and 243g of magnesium carbonate were mixed evenly and mechanically ball-milled for 15 minutes. An equal volume of 330g of HZSM-5 molecular sieve was impregnated with a solution containing 13.6g of phosphoric acid, dried at 139℃ for 2 hours, and then calcined at 530℃ for 2.5 hours to obtain phosphorus-modified ZSM-5 molecular sieve. The ball-milled product was mixed with 215g of dry phosphorus-modified ZSM-5 molecular sieve, 72g of acidic silica sol, and 4780g of deionized water, slurried, spray-dried to form microspheres, and calcined at 835℃ for 2.5 hours to obtain the catalyst C-2 for co-thermal pyrolysis of waste plastics and biomass, with an average pore size of 8.7nm and a total pore volume of 0.60cm³. 3 / g.

[0060] Using waste plastics and biomass as raw materials (polystyrene and wood chips by mass percentage: 90% and 10%, respectively), co-thermal pyrolysis was carried out at a temperature of 410℃, a pressure of 0.3 MPa, and a catalyst ratio of (waste plastics and biomass) of 5.7 wt%, with a liquid yield of 83.5%.

[0061] Example 3

[0062] 1507g of FCC waste catalyst (dry basis), 16g of sodium carbonate, and 302g of zinc carbonate were mixed evenly and mechanically ball-milled for 19 minutes. An equal volume of 350g of HZSM-5 molecular sieve was impregnated with a solution containing 7.4g of ammonium phosphate, dried at 130℃ for 2.2 hours, and then calcined at 510℃ for 2.8 hours to obtain phosphorus-modified ZSM-5 molecular sieve. The ball-milled product was mixed with 121g of phosphorus-modified ZSM-5 molecular sieve (dry basis), 106g of neutral silica sol, and 5023g of deionized water, slurried, spray-dried to form microspheres, and calcined at 895℃ for 1.1 hours to obtain the catalyst C-3 for co-thermal pyrolysis of waste plastics and biomass, with an average pore size of 9.3nm and a total pore volume of 0.65cm³. 3 / g.

[0063] Using waste plastics and biomass as raw materials (low-density polyethylene, high-density polyethylene, and straw by mass percentage: 30%, 30%, and 40%), co-thermal pyrolysis was carried out at a temperature of 465℃, a pressure of 0.6 MPa, and a catalyst ratio of (waste plastics and biomass) of 9 wt%, with a liquid yield of 77.3%.

[0064] Example 4

[0065] 1556g of FCC waste catalyst (dry basis), 78g of sodium carbonate, 125g of zinc carbonate, and 125g of calcium carbonate were mixed evenly and mechanically ball-milled for 11 minutes. 150g of HZSM-5 molecular sieve was impregnated with a solution containing 14g of diammonium hydrogen phosphate, dried at 133℃ for 2.6 hours, and then calcined at 570℃ for 2.3 hours to obtain phosphorus-modified ZSM-5 molecular sieve. The ball-milled product was mixed with 94g of phosphorus-modified ZSM-5 molecular sieve (dry basis), 31g of neutral silica sol, 47g of acidic silica sol, and 5932g of deionized water, slurried, spray-dried to form microspheres, and calcined at 850℃ for 2 hours to obtain the catalyst C-4 for co-thermal pyrolysis of waste plastics and biomass, with an average pore size of 9.2nm and a total pore volume of 0.63cm³. 3 / g.

[0066] Using waste plastics and biomass as raw materials (polypropylene, high-density polyethylene, straw, and waste residue in mass percentages of 20%, 40%, 20%, and 20%), co-thermal pyrolysis was carried out at a temperature of 525℃, a pressure of 0.9 MPa, and a catalyst ratio of 9 wt% (waste plastics and biomass), with a liquid yield of 75.1%.

[0067] Example 5

[0068] 1197g of FCC waste catalyst (dry basis), 48g of sodium carbonate, 239g of magnesium carbonate, and 132g of calcium carbonate were mixed evenly and mechanically ball-milled for 15 minutes. An equal volume of 300g of HZSM-5 molecular sieve was impregnated with a solution containing 25g of ammonium phosphate, dried at 127℃ for 2.9 hours, and then calcined at 540℃ for 2 hours to obtain phosphorus-modified ZSM-5 molecular sieve. The ball-milled product was mixed with 239g of phosphorus-modified ZSM-5 molecular sieve (dry basis), 36g of alumina sol, 48g of acidic silica sol, and 3721g of deionized water, slurried, spray-dried to form microspheres, and calcined at 880℃ for 1 hour to obtain the catalyst C-5 for co-thermal pyrolysis of waste plastics and biomass, with an average pore size of 8.1nm and a total pore volume of 0.59cm³. 3 / g.

[0069] Using waste plastics and biomass as raw materials (polypropylene, high-density polyethylene, polystyrene, wood chips, straw, and waste residue in the following mass percentages: 20%, 30%, 20%, 10%, 10%, 10%), co-thermal pyrolysis was carried out at a temperature of 495℃, a pressure of 0.5 MPa, and a catalyst ratio of (waste plastics and biomass) of 4.5 wt%, with a liquid yield of 77.4%.

[0070] Example 6

[0071] 1867g of FCC waste catalyst (dry basis), 55g of sodium carbonate, 260g of magnesium carbonate, and 112g of zinc carbonate were mixed evenly and mechanically ball-milled for 10 minutes. An equal volume of 380g of HZSM-5 molecular sieve was impregnated with a solution containing 21g of diammonium hydrogen phosphate, dried at 131℃ for 2.4 hours, and then calcined at 590℃ for 1.8 hours to obtain phosphorus-modified ZSM-5 molecular sieve. The ball-milled product was mixed with 243g of phosphorus-modified ZSM-5 molecular sieve (dry basis), 19g of alumina sol, 37g of neutral silica sol, and 6216g of deionized water, slurried, spray-dried to form microspheres, and calcined at 840℃ for 2.4 hours to obtain the catalyst C-6 for co-thermal pyrolysis of waste plastics and biomass, with an average pore size of 9.3nm and a total pore volume of 0.69cm³. 3 / g.

[0072] Using waste plastics and biomass as raw materials (polypropylene, low-density polyethylene, high-density polyethylene, polystyrene, wood chips, straw, and waste residue in the following mass percentages: 20%, 15%, 20%, 20%, 5%, 10%, 10%), co-thermal pyrolysis was carried out at a temperature of 470℃, a pressure of 0.3 MPa, and a catalyst ratio of (waste plastics and biomass) of 5.5 wt%, with a liquid yield of 79.3%.

[0073] Example 7

[0074] 1587g of FCC waste catalyst (dry basis), 78g of sodium carbonate, 126g of calcium carbonate, 64g of magnesium carbonate, and 95g of zinc carbonate were mixed evenly and mechanically ball-milled for 16 minutes. 410g of HZSM-5 molecular sieve was impregnated with a solution containing 38g of diammonium hydrogen phosphate, dried at 137℃ for 2.3 hours, and then calcined at 530℃ for 2.6 hours to obtain phosphorus-modified ZSM-5 molecular sieve. The ball-milled product was mixed with 285g of phosphorus-modified ZSM-5 molecular sieve (dry basis), 47g of alumina sol, and 7568g of deionized water, slurried, spray-dried to form microspheres, and calcined at 860℃ for 2.2 hours to obtain the catalyst C-7 for co-thermal pyrolysis of waste plastics and biomass, with an average pore size of 9.7nm and a total pore volume of 0.67cm³. 3 / g.

[0075] Using waste plastics and biomass as raw materials (low-density polyethylene, high-density polyethylene, polystyrene, straw, and waste residue by mass percentage: 30%, 5%, 30%, 20%, and 15%), co-thermal pyrolysis was carried out at a temperature of 540℃, a pressure of 0.2 MPa, and a catalyst content of 6 wt% (waste plastics and biomass). The liquid yield was 76.8%.

[0076] Example 8

[0077] 1289g of FCC waste catalyst (dry basis), 49g of sodium carbonate, and 384g of magnesium carbonate were mixed evenly and mechanically ball-milled for 18 minutes. 220g of HZSM-5 molecular sieve was impregnated with a solution containing 16g of diammonium hydrogen phosphate, dried at 137℃ for 2.3 hours, and then calcined at 555℃ for 2.5 hours to obtain phosphorus-modified ZSM-5 molecular sieve. The ball-milled product was mixed with 116g of phosphorus-modified ZSM-5 molecular sieve (dry basis), 25g of alumina sol, 38g of neutral silica sol, 51g of acidic silica sol, and 7027g of deionized water, slurried, spray-dried to form microspheres, and calcined at 850℃ for 2 hours to obtain the catalyst C-8 for co-thermal pyrolysis of waste plastics and biomass, with an average pore size of 8.7nm and a total pore volume of 0.59cm³. 3 / g.

[0078] Using waste plastics and biomass as raw materials (low-density polyethylene, high-density polyethylene, straw, and wood chips in mass percentages of 30%, 20%, 30%, and 20%), co-thermal pyrolysis was carried out at a temperature of 440℃, a pressure of 0.8 MPa, and a catalyst ratio of 8 wt% (waste plastics and biomass), resulting in a liquid yield of 72.1%.

[0079] Example 9

[0080] 1397g of dry FCC waste catalyst, 28g of sodium carbonate, and 195g of calcium carbonate were mixed evenly and mechanically ball-milled for 15 minutes. 270g of HZSM-5 molecular sieve was impregnated with a solution containing 8g of phosphoric acid, dried at 126℃ for 2.7 hours, and then calcined at 535℃ for 2.9 hours to obtain phosphorus-modified ZSM-5 molecular sieve. The ball-milled product was mixed with 153g of dry phosphorus-modified ZSM-5 molecular sieve, 73g of acidic silica sol, and 4642g of deionized water, slurried, spray-dried to form microspheres, and calcined at 870℃ for 1.5 hours to obtain the C-9 catalyst for co-thermal pyrolysis of waste plastics and biomass, with an average pore size of 9.1nm and a total pore volume of 0.66cm³. 3 / g.

[0081] Using waste plastics and biomass as raw materials (low-density polyethylene and waste residue by mass percentage: 60% and 40%, respectively), co-thermal pyrolysis was carried out at a temperature of 525℃, a pressure of 0.5 MPa, and a catalyst ratio of (waste plastics and biomass) of 7 wt%, with a liquid yield of 75.1%.

[0082] Comparative Example 1

[0083] 1021g of dry FCC waste catalyst and 21g of sodium carbonate were mixed evenly and mechanically ball-milled for 12 minutes. 200g of HZSM-5 molecular sieve was impregnated with a solution containing 7.6g of diammonium hydrogen phosphate, dried at 130℃ for 3 hours, and then calcined at 570℃ for 1.5 hours to obtain phosphorus-modified ZSM-5 molecular sieve. The ball-milled product was mixed with 101g of dry phosphorus-modified ZSM-5 molecular sieve, 82g of alumina sol, and 3403g of deionized water, slurried, spray-dried to form microspheres, and calcined at 870℃ for 1.5 hours to obtain the waste plastic pyrolysis catalyst D-1, with an average pore size of 7.6nm and a total pore volume of 0.47cm³. 3 / g.

[0084] Using waste plastics and biomass as raw materials (polypropylene and straw by mass percentage: 80% and 20%, respectively), co-thermal pyrolysis was carried out at a temperature of 450℃, a pressure of 0.7 MPa, and a catalyst ratio of (waste plastics and biomass) of 5 wt%, with a liquid yield of 62.7%.

[0085] Comparative Example 2

[0086] 1507g of dry FCC waste catalyst and 302g of zinc carbonate were mixed evenly and mechanically ball-milled for 19 minutes. An equal volume of 350g of HZSM-5 molecular sieve was impregnated with a solution containing 7.4g of ammonium phosphate, dried at 130℃ for 2.2 hours, and then calcined at 510℃ for 2.8 hours to obtain phosphorus-modified ZSM-5 molecular sieve. The ball-milled product was mixed with 121g of dry phosphorus-modified ZSM-5 molecular sieve, 106g of neutral silica sol, and 5023g of deionized water, slurried, spray-dried to form microspheres, and calcined at 895℃ for 1.1 hours to obtain catalyst D-2 for co-thermal pyrolysis of waste plastics and biomass, with an average pore size of 8.1nm and a total pore volume of 0.55cm³. 3 / g.

[0087] Using waste plastics and biomass as raw materials (low-density polyethylene, high-density polyethylene, and straw by mass percentage: 30%, 30%, and 40%), co-thermal pyrolysis was carried out at a temperature of 465℃, a pressure of 0.6 MPa, and a catalyst ratio of (waste plastics and biomass) of 9 wt%, with a liquid yield of 67.8%.

[0088] Comparative Example 3

[0089] 536g of dry FCC waste catalyst was calcined at 870℃ for 1.5 hours to obtain the waste plastic pyrolysis catalyst D-3, which has an average pore size of 6.1nm and a total pore volume of 0.13cm³. 3 / g. Using waste plastics and biomass as raw materials (polypropylene, high-density polyethylene, straw, and waste residue by mass percentage: 20%, 40%, 20%, 20%), co-thermal pyrolysis was carried out at a temperature of 525℃, a pressure of 0.9 MPa, and a catalyst ratio of (waste plastics and biomass) of 9 wt%, with a liquid yield of 47.2%.

[0090] Comparative Example 4

[0091] 1867g of dry FCC waste catalyst, 55g of sodium carbonate, 260g of magnesium carbonate, and 112g of zinc carbonate were mixed evenly and mechanically ball-milled for 10 minutes. This mixture was then mixed with 19g of aluminum sol, 37g of neutral silica sol, and 6216g of deionized water to form a slurry. The slurry was spray-dried to form microspheres, which were then calcined at 840℃ for 2.4 hours to obtain catalyst D-4 for co-thermal pyrolysis of waste plastics and biomass. The catalyst has an average pore size of 9.7nm and a total pore volume of 0.63cm³. 3 / g.

[0092] Using waste plastics and biomass as raw materials (polypropylene, low-density polyethylene, high-density polyethylene, polystyrene, wood chips, straw, and waste residue in the following mass percentages: 20%, 15%, 20%, 20%, 5%, 10%, and 10%), co-thermal pyrolysis was carried out at a temperature of 470℃, a pressure of 0.3 MPa, and a catalyst ratio of 5.5 wt% (waste plastics and biomass). The liquid yield was 67.9%.

[0093] Comparative Example 5

[0094] 1587g of dry FCC waste catalyst, 78g of sodium carbonate, 296g of calcium carbonate, 234g of magnesium carbonate, and 165g of zinc carbonate were mixed evenly and mechanically ball-milled for 16 minutes. The mixture was then mixed with 47g of aluminum sol and 7568g of deionized water to form a slurry. The slurry was spray-dried to form microspheres, which were then calcined at 860℃ for 2.2 hours to obtain the catalyst D-5 for co-thermal pyrolysis of waste plastics and biomass. The catalyst has an average pore size of 11.3nm and a total pore volume of 0.71cm³. 3 / g.

[0095] Using waste plastics and biomass as raw materials (low-density polyethylene, high-density polyethylene, polystyrene, straw, and waste residue in mass percentages of 30%, 5%, 30%, 20%, and 15%), co-thermal pyrolysis was carried out at a temperature of 540℃, a pressure of 0.2 MPa, and a catalyst concentration of 6 wt% (waste plastics and biomass). The liquid yield was 68.1%.

[0096] As shown in the above examples and comparative examples, the catalyst prepared by the method of the present invention has a large pore size and pore volume, and uses metal oxides and phosphorus-modified ZSM-5 molecular sieves as active components. It is used to catalyze the co-thermal cracking of waste plastics and biomass, and has a high liquid yield.

[0097] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a catalyst for co-thermal pyrolysis of waste plastics and biomass, characterized in that, Includes the following steps: Step 1: Mix the FCC waste catalyst, sodium carbonate and metal oxide precursor evenly to form a powder; Step 2: Modify the HZSM-5 molecular sieve with phosphorus; Step 3: Mix the mixture obtained in Step 1, the phosphorus-modified ZSM-5 molecular sieve from Step 2, the binder, and water to form microspheres, and calcine them to obtain a catalyst for co-thermal pyrolysis of waste plastics and biomass. The metal in the metal oxide precursor is at least one of calcium, magnesium, and zinc.

2. The method for preparing the catalyst for co-thermal pyrolysis of waste plastics and biomass according to claim 1, characterized in that, The metal oxide precursor, calculated as a metal oxide, has a dry basis mass ratio of sodium carbonate, the metal oxide precursor, and the FCC waste catalyst of 0.01-0.05:0.05-0.2:

1.

3. The method for preparing the catalyst for co-thermal pyrolysis of waste plastics and biomass according to claim 1, characterized in that, In step 1, the powder is formed by ball milling for 10-20 minutes.

4. The method for preparing the catalyst for co-thermal pyrolysis of waste plastics and biomass according to claim 1, characterized in that, In step 2, the method for phosphorus modification of HZSM-5 molecular sieve is as follows: HZSM-5 molecular sieve is impregnated with a solution containing phosphorus precursor, dried at 120-140℃ for 2-3 hours, and then calcined at 500-600℃ for 1-3 hours to obtain phosphorus-modified ZSM-5 molecular sieve.

5. The method for preparing the catalyst for co-thermal pyrolysis of waste plastics and biomass according to claim 4, characterized in that, The phosphorus-containing precursor is at least one of phosphoric acid, diammonium hydrogen phosphate, and ammonium phosphate; phosphorus is calculated as P2O5, and the mass ratio of phosphorus to the dry basis of HZSM-5 molecular sieve is 1%-5%.

6. The method for preparing the catalyst for co-thermal pyrolysis of waste plastics and biomass according to claim 1, characterized in that, The amount of phosphorus-modified ZSM-5 molecular sieve added in step 3 is 5%-20% of the dry basis mass of the FCC waste catalyst.

7. The method for preparing the catalyst for co-thermal pyrolysis of waste plastics and biomass according to claim 1, characterized in that, The binder is selected from at least one of aluminum sol, neutral silica sol, and acidic silica sol; the amount of binder added in step 3 is 2%-10% of the dry basis mass of the FCC waste catalyst.

8. The method for preparing the catalyst for co-thermal pyrolysis of waste plastics and biomass according to claim 1, characterized in that, In step 1, the metal oxide precursor is selected from at least one of calcium carbonate, magnesium carbonate, and zinc carbonate; in step 3, the calcination temperature is 830-900℃ and the calcination time is 1-3 hours.

9. The application of the catalyst obtained by the preparation method according to any one of claims 1-8 in the co-thermal pyrolysis of waste plastics and biomass, characterized in that, The mass ratio of waste plastics to biomass is 1:1 to 10:1; the conditions for co-thermal pyrolysis are: pyrolysis temperature 400-550℃, pressure 0.1-1.0MPa, and catalyst addition amount is 2wt%-15wt% of the total mass of waste plastics and biomass.