Method for preparing high-selectivity olefin monomer through one-step microwave catalytic cracking of polyolefin

Abstract

The invention belongs to the technical field of catalytic cracking, and particularly relates to a method for preparing a high-selectivity olefin monomer through one-step microwave catalytic cracking of polyolefin. The method comprises the following steps: mixing polyolefin and a catalyst, and carrying out catalytic cracking under a microwave condition to obtain an olefin monomer; the ratio of the power of the microwaves to the mass of the catalyst is 10-2000W / g of the catalyst; the temperature of the catalytic cracking is 250 to 550 DEG C; the catalyst comprises a metal oxide, and the metal oxide has an alpha-phase structure; the selectivity of an olefin monomer corresponding to polyolefin in a gas-phase product is greater than or equal to 75%. Efficient conversion of polyolefin can be realized by adopting a microwave one-step method for catalytic cracking, the reaction time is remarkably shortened, the energy consumption is reduced, and the selectivity of the target monomer is high. The polyolefin is converted into the high-added-value monomer, the environmental pollution can be reduced, the process is simple, the raw material cost is low, and the economical efficiency is higher.

Description

Technical Field

[0001] This invention belongs to the field of catalytic cracking technology, specifically relating to a method for preparing highly selective olefin monomers by one-step microwave catalytic cracking of polyolefins. Background Technology

[0002] In existing technologies, the treatment of polyolefin waste typically employs methods such as pyrolysis, incineration, or landfill, which present the following problems: (1) Low efficiency: Traditional pyrolysis requires multiple steps (such as pre-cracking and catalytic reforming), which results in long reaction time, high energy consumption, and poor product selectivity (olefin monomer selectivity is only 20%~40%, syngas proportion ≥70% or hydrogen proportion ≥90%).

[0003] (2) Environmental pollution: Incineration and landfill will produce a large amount of harmful gases (such as dioxins) and solid residues (coke accounting for ≥30%), causing secondary pollution to the environment.

[0004] (3) Poor economic efficiency: Traditional methods involve multiple processes and require complex equipment, making it difficult to convert waste into high-value-added products in one step, resulting in low resource utilization.

[0005] Therefore, there is an urgent need to develop an efficient and environmentally friendly process that can convert polyolefins into high-value-added olefin monomers in a one-step reaction while reducing the generation of byproducts. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing highly selective olefin monomers by one-step microwave catalytic cracking of polyolefins, which solves the problems of low efficiency, numerous by-products, and serious environmental pollution of traditional processes.

[0007] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for one-step microwave catalytic cracking of polyolefins to prepare highly selective olefin monomers, comprising the following steps: After mixing polyolefins and catalysts, catalytic cracking is carried out under microwave conditions to obtain olefin monomers; The ratio of microwave power to catalyst mass is 10~2000W / g catalyst; The temperature for the catalytic cracking is 250~550℃; The catalyst comprises a metal oxide having an α-phase structure; The selectivity of the olefin monomer corresponding to the polyolefin in the gas phase product is ≥75%.

[0008] Preferably, the polyolefin includes polyethylene, polypropylene, polybutene, or polystyrene.

[0009] Preferably, the polyolefin includes solid particulate polyolefin or molten polyolefin; the average particle size of the solid particulate polyolefin is 0.1~5 mm.

[0010] Preferably, the metal oxide includes one or more of Al2O3, Cr2O3, Co2O3, Fe2O3, Mn2O3, Ni2O3, Ti2O3 and V2O3.

[0011] Preferably, the catalyst further includes an active component supported on the metal oxide, the active component comprising noble metals and / or rare earth metals; The precious metals include one or more of Pt, Pd, Rh, Ru, Ir, Au and Ag; The rare earth metals include one or more of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

[0012] Preferably, the active ingredient has a loading percentage on the catalyst of no more than 10%.

[0013] Preferably, the mass ratio of the polyolefin to the catalyst is 0.1 to 10000:1.

[0014] Preferably, the pressure for catalytic cracking is atmospheric pressure to 85 atm.

[0015] Preferably, the catalytic cracking time is 0.1~900s.

[0016] Preferably, the catalytic cracking process further includes introducing a carrier gas into the reaction system, the carrier gas including nitrogen, argon, hydrogen or CO2.

[0017] The advantages of this invention are as follows: (1) One-step high-efficiency conversion: No intermediate steps are required, the reaction time is short, and energy consumption is reduced by 50%~70%. (2) High selectivity: The selectivity of the olefin monomer corresponding to the polyolefin in the gas phase product is ≥75%, and the yield of other gases (including syngas, low-carbon alkanes, other olefins, etc.) is ≤25%, which is significantly better than the traditional process. (3) More gas phase products: The mass percentage of the gas phase products in the total reaction product is preferably ≥85%, and fewer by-products: The total mass percentage of the solid products and oil phase products in the total reaction product is preferably ≤15%. (4) The method provided by this invention does not produce harmful gases and can reduce environmental pollution. Attached Figure Description

[0018] Figure 1 A schematic flowchart of the method provided by the present invention (without carrier gas); Figure 2A schematic flowchart of the method provided by the present invention (with carrier gas). Detailed Implementation

[0019] This invention provides a method for one-step microwave catalytic cracking of polyolefins to prepare highly selective olefin monomers, comprising the following steps: After mixing polyolefins and catalysts, catalytic cracking is carried out under microwave conditions to obtain olefin monomers; The ratio of microwave power to catalyst mass is 10~2000W / g catalyst; The temperature for the catalytic cracking is 250~550℃; The catalyst comprises a metal oxide having an α-phase structure; The selectivity of the olefin monomer corresponding to the polyolefin in the gas phase product is ≥75%.

[0020] In this invention, the polyolefin preferably includes polyethylene, polypropylene, polybutene, or polystyrene. In this invention, the polyolefin is preferably polyolefin waste. In this invention, the polyolefin preferably includes solid particulate polyolefin or molten polyolefin; the average particle size of the solid particulate polyolefin is preferably 0.1~5 mm.

[0021] In this invention, the metal oxide preferably includes one or more of Al₂O₃, Cr₂O₃, Co₂O₃, Fe₂O₃, Mn₂O₃, Ni₂O₃, Ti₂O₃, and V₂O₃. In this invention, the catalyst further preferably includes an active component supported on the metal oxide, the active component preferably including noble metals and / or rare earth metals; the noble metal preferably includes one or more of Pt, Pd, Rh, Ru, Ir, Au, and Ag; the rare earth metal preferably includes one or more of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. In this invention, the mass percentage of the active component loaded on the catalyst is preferably no more than 10%, more preferably 0.1% to 10%.

[0022] The present invention does not impose any special limitations on the mixing process, as long as the polyolefin and the catalyst can be mixed evenly.

[0023] In this invention, the preferred mass ratio of the polyolefin to the catalyst is 0.1 to 10000:1. In this invention, the ratio of microwave power to catalyst mass is 10 to 2000 W / g catalyst, specifically 10 W / g catalyst, 100 W / g catalyst, 1000 W / g catalyst, 1100 W / g catalyst, 1200 W / g catalyst, 1300 W / g catalyst, 1400 W / g catalyst, 1500 W / g catalyst, 1600 W / g catalyst, 1700 W / g catalyst, 1800 W / g catalyst, 1900 W / g catalyst, and 2000 W / g catalyst.

[0024] In this invention, the catalytic cracking temperature is 250~550℃, specifically 250℃, 300℃, 350℃, 400℃, 450℃, 500℃, and 550℃. In this invention, the catalytic cracking pressure is preferably atmospheric pressure to 85 atm. In this invention, the catalytic cracking time is preferably 0.1~900s. In this invention, the catalytic cracking process preferably also includes introducing a carrier gas into the reaction system, the carrier gas including nitrogen, argon, hydrogen, or CO2. In this invention, introducing a carrier gas into the reaction system can better carry the generated olefin monomers out of the system.

[0025] In this invention, when the polyolefin is polyethylene, the corresponding olefin monomer is ethylene; when the polyolefin is polypropylene, the corresponding olefin monomer is propylene; when the polyolefin is polybutene, the corresponding olefin monomer is butene; and when the polyolefin is polystyrene, the corresponding olefin monomer is styrene.

[0026] In this invention, the conversion rate of the polyolefin is preferably ≥95%. In this invention, the products of the catalytic cracking preferably include gaseous products, solid products, and oil products.

[0027] In this invention, the gaseous products preferably account for ≥85% of the total mass of the reaction products, and the total mass of the solid products and oil-phase products preferably accounts for ≤15% of the total mass of the reaction products. In this invention, the gaseous products preferably include olefin monomers, syngas, and low-carbon alkanes; the syngas preferably includes CO and H2; and the alkanes preferably include CH4, C2H6, C3H8, and C4H6. 10 At least one of the following; the selectivity of the olefin monomer corresponding to the polyolefin in the gas phase product is preferably ≥75%, and the yield of other gases (including syngas, low-carbon alkanes, and other olefins besides the corresponding olefin monomer) is preferably ≤25%.

[0028] Unless otherwise specified, the materials and equipment used in this invention are all commercially available products in the field.

[0029] Figure 1A schematic flowchart of the method provided by the present invention (without carrier gas). Figure 2 A schematic flowchart of the method provided by the present invention (with carrier gas).

[0030] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0031] Example 1 Polyethylene waste with a particle size of 2 mm and a catalyst were mixed at a mass ratio of 3:1 to obtain a mixture. The catalyst was α-Al₂O₃ supported on Pd, and the mass percentage of Pd in ​​the catalyst was 5 wt%. The mixture obtained above was subjected to catalytic cracking under microwave conditions, wherein the ratio of microwave power to catalyst mass was 2000 W / g catalyst, the catalytic cracking temperature was 400℃, the pressure was 3 atm, and the carrier gas was nitrogen. The products of the catalytic cracking include gaseous products, solid products and oil products; In this embodiment, the raw material conversion rate is 95%, the mass percentage of the gaseous product is 85%, and the selectivity of the gaseous product ethylene is 75%.

[0032] Example 2 Polypropylene waste with a particle size of 3 mm and the catalyst were mixed at a mass ratio of 3:1 to obtain a mixture, wherein the catalyst was α-Co2O3 supported on Rh, and the mass percentage of Rh in the catalyst was 8 wt%. The mixture obtained above was subjected to catalytic cracking under microwave conditions, wherein the ratio of microwave power to catalyst mass was 2000 W / g catalyst, the catalytic cracking temperature was 450℃, the pressure was 2 atm, and the carrier gas was argon. The products of the catalytic cracking include gaseous products, solid products and oil products; In this embodiment, the raw material conversion rate is 96%, the mass percentage of gaseous products is 95%, and the selectivity of propylene in the gaseous products is 80%.

[0033] Example 3 Polybutene waste with a particle size of 0.5 mm and catalyst were mixed at a mass ratio of 8:1 to obtain a mixture, wherein the catalyst was α-Cr2O3 supported on Ce, and the mass percentage of Ce in the catalyst was 3 wt%. The mixture obtained above was subjected to catalytic cracking under microwave conditions, wherein the ratio of microwave power to catalyst mass was 1600 W / g catalyst, the catalytic cracking temperature was 420℃, the pressure was 5 atm, and the carrier gas was air. The products of the catalytic cracking include gaseous products, solid products and oil products; In this embodiment, the raw material conversion rate is 97%, the mass ratio of gaseous products is 90%, and the selectivity of butene in the gaseous products is 77%.

[0034] Example 4 Polystyrene waste with a particle size of 1 mm and a catalyst were mixed at a mass ratio of 10:1 to obtain a mixture. The catalyst was α-Fe2O3 supported on Rh, and the mass percentage of Rh in the catalyst was 6 wt%. The mixture obtained above was subjected to catalytic cracking under microwave conditions, wherein the ratio of microwave power to catalyst mass was 1200 W / g catalyst, the catalytic cracking temperature was 450℃, the pressure was 4 atm, and the carrier gas was hydrogen. The products of the catalytic cracking include gaseous products, solid products and oil products; In this embodiment, the raw material conversion rate is 97%, the mass percentage of gaseous products is 88%, and the selectivity of styrene in the gaseous products is 80%.

[0035] Comparative Example 1 Polyethylene waste with a particle size of 2 mm was pyrolyzed at a temperature of 550℃ and a pressure of 3 atm, with nitrogen as the carrier gas. The products of the catalytic cracking include gaseous products, solid products and oil products; In this comparative example, the raw material conversion rate was 96%, the mass percentage of gaseous products was 30%, and the mass percentage of solid and oil products reached 70%; the selectivity of ethylene among the gaseous products was 35%, and the proportion of other gases was 65%.

[0036] Comparative Example 2 Polyethylene waste with a particle size of 2 mm was subjected to catalytic cracking under microwave conditions, wherein the microwave power was 1500W, the catalytic cracking temperature was 450℃, the pressure was 3atm, and the carrier gas was nitrogen. In this comparative example, the raw material conversion rate was 96%, the mass percentage of gaseous products was 40%, and the mass percentage of solid and oil products was 60%. Among the gaseous products, the selectivity for ethylene was 45%, and the proportion of other gases was 55%.

[0037] Comparative Example 3 Polyethylene waste with a particle size of 2 mm and a catalyst were mixed at a mass ratio of 5:1 to obtain a mixture. The catalyst was α-Fe2O3 supported on Ru, and the mass percentage of Ru in the catalyst was 5 wt%. The mixture obtained above was pyrolyzed at a temperature of 500℃ and a pressure of 5 atm, with nitrogen as the carrier gas. The products of the catalytic cracking include gaseous products, solid products and oil products; In this comparative example, the raw material conversion rate was 96%, the mass percentage of gaseous products was 51%, and the mass percentage of solid and oil products was 49%. Among the gaseous products, the selectivity for ethylene was 45%, and the proportion of other gases was 55%.

[0038] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for one-step microwave catalytic cracking of polyolefins to prepare highly selective olefin monomers, characterized in that, Includes the following steps: After mixing polyolefins and catalysts, catalytic cracking is carried out under microwave conditions to obtain olefin monomers; The ratio of microwave power to catalyst mass is 10~2000W / g catalyst; The temperature for the catalytic cracking is 250~550℃; The catalyst comprises a metal oxide having an α-phase structure; The selectivity of the olefin monomer corresponding to the polyolefin in the gas phase product is ≥75%.

2. The method according to claim 1, characterized in that, The polyolefins include polyethylene, polypropylene, polybutene, or polystyrene.

3. The method according to claim 1 or 2, characterized in that, The polyolefin includes solid particulate polyolefin or molten polyolefin; the average particle size of the solid particulate polyolefin is 0.1~5 mm.

4. The method according to claim 1, characterized in that, The metal oxides include one or more of Al2O3, Cr2O3, Co2O3, Fe2O3, Mn2O3, Ni2O3, Ti2O3, and V2O3.

5. The method according to claim 1 or 4, characterized in that, The catalyst further includes an active component supported on the metal oxide, the active component comprising noble metals and / or rare earth metals; The precious metals include one or more of Pt, Pd, Rh, Ru, Ir, Au and Ag; The rare earth metals include one or more of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

6. The method according to claim 5, characterized in that, The active ingredient is loaded onto the catalyst at a mass percentage not exceeding 10%.

7. The method according to claim 1, characterized in that, The mass ratio of the polyolefin to the catalyst is 0.1~10000:

1.

8. The method according to claim 1, characterized in that, The pressure for catalytic cracking is atmospheric pressure to 85 atm.

9. The method according to claim 1, characterized in that, The catalytic cracking time is 0.1~900s.

10. The method according to claim 1, characterized in that, The catalytic cracking process also includes introducing a carrier gas into the reaction system, which includes nitrogen, argon, hydrogen, or CO2.

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