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CN116371455A - Catalyst for waste plastic cracking, preparation method thereof and waste plastic cracking method - Google Patents

Catalyst for waste plastic cracking, preparation method thereof and waste plastic cracking method Download PDF

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Publication number
CN116371455A
CN116371455A CN202310488563.9A CN202310488563A CN116371455A CN 116371455 A CN116371455 A CN 116371455A CN 202310488563 A CN202310488563 A CN 202310488563A CN 116371455 A CN116371455 A CN 116371455A
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catalyst
rare earth
molecular sieve
waste plastic
pyrolysis
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CN202310488563.9A
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郭方旭
李俊莱
季宇晨
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Ningbo Meioxygen New Material Technology Co ltd
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Ningbo Meioxygen New Material Technology Co ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J29/00—Catalysts comprising molecular sieves
    • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
    • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
    • B01J29/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively
    • B01J29/405—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively containing rare earth elements, titanium, zirconium, hafnium, zinc, cadmium, mercury, gallium, indium, thallium, tin or lead
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G1/00—Production of liquid hydrocarbon mixtures from oil-shale, oil-sand, or non-melting solid carbonaceous or similar materials, e.g. wood, coal
    • C10G1/10—Production of liquid hydrocarbon mixtures from oil-shale, oil-sand, or non-melting solid carbonaceous or similar materials, e.g. wood, coal from rubber or rubber waste
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G2300/00—Aspects relating to hydrocarbon processing covered by groups C10G1/00 - C10G99/00
    • C10G2300/10—Feedstock materials
    • C10G2300/1003—Waste materials
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G2300/00—Aspects relating to hydrocarbon processing covered by groups C10G1/00 - C10G99/00
    • C10G2300/70—Catalyst aspects
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/62—Plastics recycling; Rubber recycling

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Materials Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Wood Science & Technology (AREA)
  • General Chemical & Material Sciences (AREA)
  • Catalysts (AREA)

Abstract

The invention discloses a catalyst for waste plastic pyrolysis, which is a rare earth MOFs coated modified ZSM molecular sieve obtained by high-temperature calcination, wherein the rare earth MOFs accounts for 0.1-40% of the catalyst by mass; the specific surface area of the catalyst is 550-650 m 2 And/g. The catalyst for waste plastic pyrolysis has the catalytic effects of rare earth materials and ZSM molecular sieves, effectively increases and enriches the active sites of the catalyst, improves the catalytic efficiency of the catalyst on waste plastic, reduces the risk of blocking the catalyst by coke, and meets the long-term use requirement of waste plastic catalytic pyrolysis. The invention also discloses a preparation method of the catalyst for waste plastic pyrolysis and a waste plastic pyrolysis method.

Description

Catalyst for waste plastic cracking, preparation method thereof and waste plastic cracking method
Technical Field
The invention relates to the technical field of waste plastics, in particular to a catalyst for waste plastic pyrolysis, a preparation method thereof and a waste plastic pyrolysis method.
Background
Plastics are widely used in various industries, such as household appliances, automobiles, textiles, construction, agriculture, etc.; with the continuous development of society, the consumption of various plastic products is also increased, so that the waste plastics are increased, and the damage to the ecological environment is aggravated. The waste plastics are difficult to be automatically classified by a machine due to the physical properties of the waste plastics, the recovery rate is low for a long time, and thus huge resource waste is caused, and the garbage generated by the use of a large number of plastic products can cause serious environmental pollution problems if being treated by burying, burning and other methods. Therefore, disposal of waste plastics has been the focus of research in the industry.
Disclosure of Invention
In view of the shortcomings of the prior art, one aspect of the invention is to provide a catalyst for waste plastic pyrolysis, which solves the problems of single pore structure, easy blockage, low catalytic efficiency and the like of the existing catalyst for waste plastic pyrolysis, so that the catalyst can meet the long-term use requirement of waste plastic catalytic pyrolysis, and the catalytic pyrolysis efficiency of waste plastic is improved.
In order to achieve the above purpose, the invention adopts the following technical scheme:
the catalyst for waste plastic pyrolysis is a rare earth MOFs coated modified ZSM molecular sieve obtained by high-temperature calcination, wherein the rare earth MOFs accounts for 0.1-40% of the catalyst by mass; the specific surface area of the catalyst is 150-250 m 2 And/g. According to the invention, the rare earth MOFs after high-temperature calcination is used for coating the modified ZSM molecular sieve, so that on one hand, the rare earth MOFs and the ZSM molecular sieve are organically combined into a whole, the active sites of the ZSM molecular sieve are further enriched, the specific surface area of the catalyst is increased, and the catalytic activity of the catalyst on waste plastics is further improved; on the other hand, the structural design of the rare earth MOFs coated modified ZSM molecular sieve is beneficial to improving the treatment efficiency of the catalytic pyrolysis of the macromolecule waste plastics and reducing the coke yield and the risk of catalyst blockage.
Preferably, the rare earth MOFs are metal organic framework materials formed by carrying out molecular self-assembly on lanthanide series salt substances and MOF organic ligands through hydrothermal reaction. The lanthanide series salt substances are mainly cerium nitrate and lanthanum nitrate, and the cerium ions and the lanthanum ions are combined with active functional groups in the MOF organic ligand to form a network structure through molecular self-assembly, so that the metal organic framework material is obtained, the rare earth materials are uniformly distributed on the surface of the ZSM molecular sieve, and the overall catalytic performance of the catalyst is improved.
Preferably, the modified ZSM molecular sieve is an alkaline earth metal modified ZSM molecular sieve. The ZSM molecular sieve is at least one of ZSM5, ZSM22 and ZSM 35. The alkaline earth metal is mainly one or more than one of metal oxides of calcium, magnesium and barium; preferably, the alkaline earth metal is magnesium oxide.
Preferably, the high temperature calcination is performed under an inert gas atmosphere at a calcination temperature of 500 to 600 ℃.
In another aspect, the present invention provides a method for preparing a catalyst for pyrolysis of waste plastics, the method comprising the steps of:
s1: adding a certain amount of ZSM molecular sieve into 0.1-0.5 mol/L sodium hydroxide solution, adding magnesium oxide, heating to 70 ℃, reacting for 0.5-1.5 h, cooling to room temperature, and then sequentially filtering, washing and drying to obtain a modified ZSM molecular sieve; the ZSM molecular sieve is modified by adopting the alkaline earth metal magnesium oxide, so that on one hand, the pore structure in the ZSM molecular sieve is enriched; on the other hand, the acidity of the ZSM molecular sieve is reduced by utilizing the alkalinity of alkaline earth metals, so that the hydrogen transfer reaction of generated olefin is inhibited, and the catalytic cracking efficiency of waste plastics is improved.
S2: placing the modified ZSM molecular sieve obtained in the step S1 into a tubular reactor, preparing MOF organic ligand solution with the molar concentration of 0.1-0.5 mol/L and rare earth nitrate solution with the molar concentration of 0.1-0.5 mol/L, then introducing the MOF organic ligand solution and the rare earth nitrate solution into the tubular reactor at a first flow rate and a second flow rate respectively, and performing microwave hydrothermal reaction for 5-30 min to obtain a rare earth MOFs once coated modified ZSM molecular sieve intermediate; the rare earth MOFs are metal organic framework materials formed by carrying out molecular self-assembly on lanthanide series salt substances and MOF organic ligands through hydrothermal reaction.
S3: introducing MOF organic ligand solution and rare earth nitrate solution with the same molar concentration into the tubular reactor at a third flow rate and a fourth flow rate respectively, and continuing the microwave hydrothermal reaction on the rare earth MOFs once coated modified ZSM molecular sieve intermediate obtained in the step S2 to obtain a rare earth MOFs twice coated modified ZSM molecular sieve intermediate; according to the invention, by controlling the MOF organic ligand solution and the rare earth nitrate solution with different flow rates, the surface of the ZSM molecular sieve is enabled to obtain the rare earth material with concentration gradient change along the surface vertical direction, so that the catalytic effect of the catalyst is improved, the usage amount of the rare earth material is reduced, and the catalytic cracking performance of waste plastics is further ensured.
S4: and (3) filtering and drying the rare earth MOFs secondary coating modified ZSM molecular sieve intermediate obtained in the step (S3), and then calcining at a high temperature in an inert gas atmosphere to obtain the catalyst for waste plastic pyrolysis, which is abbreviated as rare earth MOFs coating modified ZSM molecular sieve.
Preferably, the preparation method of the MOF organic ligand solution comprises the following steps: a quantity of tetrakis (p-vinylphenyl) silane was dissolved in a solvent and 3- (trimethylsilyl) -4-pentenoic acid was added in a molar ratio of tetrakis (p-vinylphenyl) silane to 3- (trimethylsilyl) -4-pentenoic acid of 1:4, obtaining MOF organic ligand after reaction, and dissolving the MOF organic ligand obtained by separation in a solvent to obtain MOF organic ligand solution. According to the invention, through the addition reaction of tetra (p-vinylphenyl) silane and 3- (trimethylsilyl) -4-pentenoic acid, on one hand, MOF organic ligands have carboxyl active functional groups, and on the other hand, the molecular pores of the MOF material are favorably regulated and controlled, and the catalytic cracking of macromolecular waste plastics is more favorable.
Preferably, the rare earth nitrate solution is one solution or a mixed solution of two solutions of lanthanide nitrate; preferably, the rare earth nitrate solution is one solution or a mixed solution of two solutions of cerium nitrate and lanthanum nitrate.
Preferably, the first flow rate is less than the third flow rate, and the second flow rate is less than the fourth flow rate; preferably, the third flow rate is 1.1 to 1.5 times the first flow rate, and the fourth flow rate is 1.1 to 1.5 times the second flow rate.
The invention also provides a waste plastic cracking method, wherein the catalyst for waste plastic cracking is used in the waste plastic cracking process, the cracking condition is that the cracking temperature is 300-500 ℃, the pressure is 0.05-0.5 MPa, the airspeed is 1-10 h < -1 >, and the catalyst accounts for 2-15 wt% of the waste plastic.
Preferably, the waste plastic is one or more of waste low-density polyethylene, high-density polyethylene, polypropylene and polystyrene.
The invention has the beneficial effects that:
the catalyst for waste plastic pyrolysis prepared by the invention takes the rare earth MOFs coated modified ZSM molecular sieve as the catalyst, has the catalytic effects of rare earth materials and ZSM molecular sieves, effectively increases and enriches the active sites of the catalyst, improves the catalytic efficiency of the catalyst on waste plastic, reduces the risk of coke blocking the catalyst, and prolongs the service life of the catalyst.
Detailed Description
The following description is presented to enable one of ordinary skill in the art to make and use the invention. The preferred embodiments in the following description are by way of example only and other obvious variations will occur to those skilled in the art.
Example 1
The preparation method of the catalyst for waste plastic pyrolysis in the embodiment comprises the following steps:
s1: adding 100g of ZSM-5 molecular sieve into 150ml of 0.2mol/L sodium hydroxide solution, adding 12.5g of magnesium oxide, heating to 70 ℃, reacting for 1h, cooling to room temperature, and then sequentially filtering, washing and drying to obtain a modified ZSM molecular sieve;
s2: placing 80g of the modified ZSM molecular sieve obtained in the step S1 into a tubular reactor, preparing MOF organic ligand solution with the molar concentration of 0.1mol/L and rare earth nitrate solution with the molar concentration of 0.1mol/L, then introducing the MOF organic ligand solution and the rare earth nitrate solution into the tubular reactor at a first flow rate and a second flow rate respectively, heating the tubular reactor to 80 ℃ in a microwave heating mode, and performing microwave hydrothermal reaction for 10min to obtain a rare earth MOFs once coated modified ZSM molecular sieve intermediate; the first flow rate is 2.5mL/min, and the second flow rate is 10mL/min; the rare earth nitrate solution is a mixed solution of cerium nitrate and lanthanum nitrate, and the mass ratio of the cerium nitrate to the lanthanum nitrate is 2:3, a step of;
s3: introducing MOF organic ligand solution and rare earth nitrate solution with the same molar concentration into the tubular reactor at a third flow rate and a fourth flow rate respectively, and continuing the microwave hydrothermal reaction on the rare earth MOFs once coated modified ZSM molecular sieve intermediate obtained in the step S2 to obtain a rare earth MOFs twice coated modified ZSM molecular sieve intermediate; the third flow rate is 3mL/min, and the fourth flow rate is 12mL/min; the reaction temperature of the microwave hydrothermal reaction is 80 ℃ and the reaction time is 10min;
s4: and (3) filtering and drying the rare earth MOFs secondary coating modified ZSM molecular sieve intermediate obtained in the step (S3), and then calcining at a high temperature in an inert gas nitrogen atmosphere at a calcining temperature of 550 ℃ to obtain the catalyst for waste plastic pyrolysis, which is abbreviated as rare earth MOFs coating modified ZSM molecular sieve. The specific surface area of the catalyst is 192m 2 /g。
The preparation method of the MOF organic ligand solution comprises the following steps: 20g of tetrakis (p-vinylphenyl) silane, in a molar ratio of 1, to 3- (trimethylsilyl) -4-pentenoic acid, were dissolved in 100mL of solvent toluene, 3- (trimethylsilyl) -4-pentenoic acid were added: 4, adding 0.2g of sodium persulfate, heating to 60 ℃, reacting for 0.5h to obtain MOF organic ligand, and dissolving the separated MOF organic ligand in a solvent (the solvent is prepared by compounding water and ethanol in a volume ratio of 1:1) to obtain the MOF organic ligand solution.
The catalyst for waste plastic pyrolysis prepared in the embodiment is used in the waste plastic pyrolysis process, the pyrolysis temperature is 350 ℃, the pressure is 0.15MPa, and the airspeed is 2.5h -1 The catalyst accounts for 5wt% of the waste plastics; the waste plastic is waste low-density polyethylene; the gas phase yield of the low-carbon olefin after the reaction was 25.2% (wherein the olefin content was 21.5%), the liquid phase light oil yield was 67.2%, and the remainder was a solid phase. After the catalyst of this example was reused 5 times, the gas phase yield of the light olefins was 20.1% (wherein the olefin content was 15.4%) and the liquid phase light oil yield was 62.5%, the remainder being a solid phase.
Example 2
The preparation method of the catalyst for waste plastic pyrolysis in the embodiment comprises the following steps:
s1: adding 100g of ZSM-5 molecular sieve into 150ml of 0.2mol/L sodium hydroxide solution, adding 15g of magnesium oxide, heating to 70 ℃, reacting for 1h, cooling to room temperature, and then sequentially filtering, washing and drying to obtain a modified ZSM molecular sieve;
s2: placing 80g of the modified ZSM molecular sieve obtained in the step S1 into a tubular reactor, preparing MOF organic ligand solution with the molar concentration of 0.15mol/L and rare earth nitrate solution with the molar concentration of 0.15mol/L, then introducing the MOF organic ligand solution and the rare earth nitrate solution into the tubular reactor at a first flow rate and a second flow rate respectively, heating the tubular reactor to 80 ℃ in a microwave heating mode, and performing microwave hydrothermal reaction for 10min to obtain a rare earth MOFs once coated modified ZSM molecular sieve intermediate; the first flow rate is 2mL/min, and the second flow rate is 8mL/min; the rare earth nitrate solution is a mixed solution of cerium nitrate and lanthanum nitrate, and the mass ratio of the cerium nitrate to the lanthanum nitrate is 2:3, a step of;
s3: introducing MOF organic ligand solution and rare earth nitrate solution with the same molar concentration into the tubular reactor at a third flow rate and a fourth flow rate respectively, and continuing the microwave hydrothermal reaction on the rare earth MOFs once coated modified ZSM molecular sieve intermediate obtained in the step S2 to obtain a rare earth MOFs twice coated modified ZSM molecular sieve intermediate; the third flow rate is 3mL/min, and the fourth flow rate is 12mL/min; the reaction temperature of the microwave hydrothermal reaction is 80 ℃ and the reaction time is 10min;
s4: and (3) filtering and drying the rare earth MOFs secondary coating modified ZSM molecular sieve intermediate obtained in the step (S3), and then calcining at a high temperature in an inert gas nitrogen atmosphere at a calcining temperature of 600 ℃ to obtain the catalyst for waste plastic pyrolysis, which is abbreviated as rare earth MOFs coating modified ZSM molecular sieve. The specific surface area of the catalyst was 223m 2 /g。
The MOF organic ligand solution was prepared in the same manner as in example 1.
The catalyst for waste plastic pyrolysis prepared in the embodiment is used in the waste plastic pyrolysis process, the pyrolysis temperature is 420 ℃, the pressure is 0.15MPa, and the airspeed is 2h -1 The catalyst accounts for 3wt% of the waste plastics; the waste plastic is waste high-density polyethylene; containing low carbon after the reactionThe gas phase yield of olefins was 28.4% (wherein the olefin content was 21.4%), the liquid phase light oil yield was 63.1%, and the remainder was solid phase.
Example 3
The preparation method of the catalyst for waste plastic pyrolysis in the embodiment comprises the following steps:
s1: adding 100g of ZSM-5 molecular sieve into 150ml of 0.2mol/L sodium hydroxide solution, adding 10g of magnesium oxide, heating to 70 ℃, reacting for 1h, cooling to room temperature, and then sequentially filtering, washing and drying to obtain a modified ZSM molecular sieve;
s2: placing 80g of the modified ZSM molecular sieve obtained in the step S1 into a tubular reactor, preparing MOF organic ligand solution with the molar concentration of 0.2mol/L and rare earth nitrate solution with the molar concentration of 0.2mol/L, then introducing the MOF organic ligand solution and the rare earth nitrate solution into the tubular reactor at a first flow rate and a second flow rate respectively, heating the tubular reactor to 80 ℃ in a microwave heating mode, and performing microwave hydrothermal reaction for 10min to obtain a rare earth MOFs once coated modified ZSM molecular sieve intermediate; the first flow rate is 1.5mL/min, and the second flow rate is 6mL/min; the rare earth nitrate solution is a mixed solution of cerium nitrate and lanthanum nitrate, and the mass ratio of the cerium nitrate to the lanthanum nitrate is 2:3, a step of;
s3: introducing MOF organic ligand solution and rare earth nitrate solution with the same molar concentration into the tubular reactor at a third flow rate and a fourth flow rate respectively, and continuing the microwave hydrothermal reaction on the rare earth MOFs once coated modified ZSM molecular sieve intermediate obtained in the step S2 to obtain a rare earth MOFs twice coated modified ZSM molecular sieve intermediate; the third flow rate is 1.7mL/min, and the fourth flow rate is 6.8mL/min; the reaction temperature of the microwave hydrothermal reaction is 80 ℃ and the reaction time is 10min;
s4: and (3) filtering and drying the rare earth MOFs secondary coating modified ZSM molecular sieve intermediate obtained in the step (S3), and then calcining at a high temperature in an inert gas nitrogen atmosphere at a calcining temperature of 580 ℃ to obtain the catalyst for waste plastic pyrolysis, which is abbreviated as rare earth MOFs coating modified ZSM molecular sieve. The specific surface area of the catalyst is 211m 2 /g。
The MOF organic ligand solution was prepared in the same manner as in example 1.
The catalyst for waste plastic pyrolysis prepared in the embodiment is used in the waste plastic pyrolysis process, the pyrolysis temperature is 450 ℃, the pressure is 0.25MPa, and the airspeed is 3.5h -1 The catalyst accounts for 10wt% of the waste plastics; the waste plastic is waste polypropylene; the gas phase yield of the low-carbon olefin after the reaction was 25.5% (wherein the olefin content was 21.6%), the liquid phase light oil yield was 67.2%, and the remainder was a solid phase.
Comparative example 1
The catalyst for pyrolysis of waste plastics and the preparation method thereof of this comparative example are basically the same as those of example 1 in the raw material composition and preparation steps, except that step S3 is not included in the preparation method of this comparative example. The catalyst of this comparative example was subjected to waste plastic cracking reaction under the same conditions as in example 1, and the gas phase yield of the low-carbon olefin after the reaction was 23.2% (wherein the olefin content was 19.3%), the liquid phase light oil yield was 61.6%, and the remainder was a solid phase. After the catalyst of this comparative example was reused 5 times, the gas phase yield of the light olefins was 17.2% (wherein the olefin content was 12.7%) and the liquid phase light oil yield was 58.7%, with the remainder being a solid phase.
Comparative example 2
The catalyst for pyrolysis of waste plastics and the preparation method thereof of this comparative example are basically the same as those of example 1 in the raw material composition and preparation steps, except that in the preparation method of this comparative example, no MOF organic ligand solution was added in steps S2 and S3. The catalyst of this comparative example was subjected to waste plastic cracking reaction under the same conditions as in example 1, and the gas phase yield of the low-carbon olefin after the reaction was 20.4% (wherein the olefin content was 16.8%), the liquid phase light oil yield was 57.9%, and the remainder was a solid phase. After the catalyst of this comparative example was reused 5 times, the gas phase yield of the light olefins was 14.1% (wherein the olefin content was 10.5%) and the liquid phase light oil yield was 47.5%, with the remainder being a solid phase.
Comparative example 3
The catalyst for pyrolysis of waste plastics and the preparation method thereof of this comparative example are basically the same as those of example 1 in the raw material composition and preparation steps, except that step S4 is not included in the preparation method of this comparative example. The catalyst of this comparative example was subjected to waste plastic cracking reaction under the same conditions as in example 1, and the gas phase yield of the low-carbon olefin after the reaction was 20.7% (wherein the olefin content was 17.2%), the liquid phase light oil yield was 59.3%, and the remainder was a solid phase. After the catalyst of this comparative example was reused 5 times, the gas phase yield of the light olefins was 14.7% (wherein the olefin content was 10.7%) and the liquid phase light oil yield was 46.5%, the remainder being a solid phase.
The foregoing has shown and described the basic principles, principal features and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that the above embodiments and descriptions are merely illustrative of the principles of the present invention, and various changes and modifications may be made therein without departing from the spirit and scope of the invention, which is defined by the appended claims.

Claims (10)

1. The catalyst for waste plastic pyrolysis is characterized in that the catalyst is a rare earth MOFs coated modified ZSM molecular sieve obtained by high-temperature calcination, and the rare earth MOFs accounts for 0.1-40% of the catalyst by mass; the specific surface area of the catalyst is 150-250 m 2 /g。
2. The catalyst for pyrolysis of waste plastics according to claim 1, wherein the rare earth MOFs are metal organic framework materials obtained by molecular self-assembly of lanthanide series salt substances and MOF organic ligands through hydrothermal reaction.
3. The catalyst for pyrolysis of waste plastics according to claim 1, wherein the modified ZSM molecular sieve is an alkaline earth metal modified ZSM molecular sieve.
4. The catalyst for pyrolysis of waste plastics according to claim 1, wherein the high-temperature calcination is carried out under an inert gas atmosphere at a calcination temperature of 500 to 600 ℃.
5. A method for preparing a catalyst for cracking waste plastics, which is characterized by comprising the following steps:
s1: adding a certain amount of ZSM molecular sieve into 0.1-0.5 mol/L sodium hydroxide solution, adding magnesium oxide, heating to react for 0.5-1.5 h, cooling to room temperature, and then sequentially filtering, washing and drying to obtain a modified ZSM molecular sieve;
s2: placing the modified ZSM molecular sieve obtained in the step S1 into a tubular reactor, preparing MOF organic ligand solution with the molar concentration of 0.1-0.5 mol/L and rare earth nitrate solution with the molar concentration of 0.1-0.5 mol/L, then introducing the MOF organic ligand solution and the rare earth nitrate solution into the tubular reactor at a first flow rate and a second flow rate respectively, and performing microwave hydrothermal reaction for 5-30 min to obtain a rare earth MOFs once coated modified ZSM molecular sieve intermediate;
s3: introducing MOF organic ligand solution and rare earth nitrate solution with the same molar concentration into the tubular reactor at a third flow rate and a fourth flow rate respectively, and continuing the microwave hydrothermal reaction on the rare earth MOFs once coated modified ZSM molecular sieve intermediate obtained in the step S2 to obtain a rare earth MOFs twice coated modified ZSM molecular sieve intermediate;
s4: and (3) filtering and drying the rare earth MOFs secondary coating modified ZSM molecular sieve intermediate obtained in the step (S3), and then calcining at a high temperature in an inert gas atmosphere to obtain the catalyst for waste plastic pyrolysis, which is abbreviated as rare earth MOFs coating modified ZSM molecular sieve.
6. The method for preparing a catalyst for pyrolysis of waste plastics according to claim 5, wherein the preparation method of the MOF organic ligand solution is as follows: a quantity of tetrakis (p-vinylphenyl) silane was dissolved in a solvent and 3- (trimethylsilyl) -4-pentenoic acid was added in a molar ratio of tetrakis (p-vinylphenyl) silane to 3- (trimethylsilyl) -4-pentenoic acid of 1:4, obtaining MOF organic ligand after reaction, and dissolving the MOF organic ligand obtained by separation in a solvent to obtain MOF organic ligand solution.
7. The method for preparing a catalyst for pyrolysis of waste plastics according to claim 5, wherein the rare earth nitrate solution is one solution or a mixed solution of two solutions of lanthanide nitrate.
8. The method for preparing a catalyst for pyrolysis of waste plastics according to claim 5, wherein the first flow rate is smaller than the third flow rate, and the second flow rate is smaller than the fourth flow rate.
9. A waste plastic cracking method, characterized in that the catalyst for waste plastic cracking according to any one of claims 1 to 4 is used in the waste plastic cracking process under the cracking conditions of 300 to 500 ℃ of cracking temperature, 0.05 to 0.5MPa of pressure and 1 to 10 hours of airspeed -1 The catalyst accounts for 2-15 wt% of the waste plastics.
10. The method for cracking waste plastics according to claim 9, wherein the waste plastics are one or more of waste low density polyethylene, high density polyethylene, polypropylene and polystyrene.
CN202310488563.9A 2023-05-04 2023-05-04 Catalyst for waste plastic cracking, preparation method thereof and waste plastic cracking method Withdrawn CN116371455A (en)

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