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CN-122012135-A - Process for producing oil products by distilling and degrading waste plastics through molten salt

CN122012135ACN 122012135 ACN122012135 ACN 122012135ACN-122012135-A

Abstract

The invention belongs to the technical field of recycling and heterogeneous catalytic distillation of waste plastics, and discloses a process for preparing oil products by distilling and degrading waste plastics by using molten salt. Polyolefin waste plastics are used as raw materials, and under the synergistic effect of catalysis and heat transfer of a molten salt system, the oriented cracking of polyolefin is realized through distillation degradation reaction, and the sectional separation of oil products is synchronously completed. The process has the advantages of realizing the efficient degradation of the polyolefin waste plastics under the relatively mild reaction condition by means of the high-efficiency catalytic activity and the excellent heat transfer performance of the molten salt system, directionally preparing the high-quality oil product, along with simple and controllable preparation process of the molten salt system, recycling, greatly reducing the process cost and easily realizing large-scale production. The method provides a brand new technical path for the recycling conversion of the polyolefin waste plastics, has double values of environmental protection treatment and resource recovery, and has important application prospects in the fields of solid waste treatment and energy chemical industry.

Inventors

  • HUANG RUI
  • CHEN XI

Assignees

  • 大连理工大学

Dates

Publication Date
20260512
Application Date
20260130

Claims (10)

  1. 1. A process for preparing oil products from waste plastics by distillation and degradation of molten salt is characterized by comprising the following steps: The polyolefin waste plastics are used as reaction substrates, distillation catalytic degradation reaction is carried out in inert atmosphere and normal pressure environment in the presence of a molten salt system, the oriented cracking of the polyolefin waste plastics is realized to generate oil products, and the sectional distillation separation of the products is completed.
  2. 2. The process of claim 1, wherein the temperature of the distillative catalytic degradation reaction is 400 o C ~ 600 o C and the reaction time is 0.5h to 4 h.
  3. 3. The process according to claim 1, wherein the mass ratio of the molten salt system to the polyolefin waste plastics is 1:1 to 1:5.
  4. 4. The process according to claim 1, wherein the molten salt system is mixed with the polyolefin waste plastics and then ground, optionally with 1-5 mL absolute ethyl alcohol as a dispersing agent, and after grinding 5-10 min, the mixture is placed in a vacuum oven 40 o C ~ 60 o C for 1 h removal of the ethyl alcohol.
  5. 5. The process of claim 1, wherein the molten salt system is composed of one or two of alkali metal nitrate salts, and alkali metal chloride or alkaline earth metal chloride is added simultaneously, wherein the alkali metal chloride is NaCl, KCl, liCl, the alkaline earth metal chloride is CaCl 2 、MgCl 2 、BaCl 2 , and the alkali metal nitrate salt is NaNO 3 、KNO 3 、LiNO 3 .
  6. 6. The process according to claim 1, wherein the polyolefin waste plastics comprise one or more of low density polyethylene, high density polyethylene, polypropylene, polybutene-1, polyisobutene.
  7. 7. The process of claim 1, wherein a catalytic aid is added to the molten salt system to regulate the surface activity and the thermal stability of the molten salt system, wherein the catalytic aid is one or a combination of more than two of transition metal oxides, nitrides and carbides, the transition metal oxides are one of ZnO, fe 2 O 3 、Co 3 O 4 , niO and CuO, the nitrides are one of h-BN, si 3 N 4 , alN and ZrN, the nitrides are one of WC and Mo 2 C, tiC, siC, and the addition amount of the catalytic aid is 1% -15% of the total mass of the molten salt system.
  8. 8. The process of claim 1 wherein the inert atmosphere is nitrogen or argon.
  9. 9. The process according to claim 1, wherein the specific method of the fractional distillation separation is that the temperature gradient in the fractionation device is controlled to be 120 o C~360 o ℃, the gasoline fraction is collected at 120 o C ~180 o ℃, the diesel fraction is collected at 180 o C ~360 o ℃, and the residue at the bottom of the tube is wax oil and undegraded polyolefin residue.
  10. 10. The process according to claim 1, wherein the molten salt system is prepared by mixing one or more of alkali metal chloride, alkaline earth metal chloride and alkali metal nitrate, heating to 350 o C ~ 500 o C to completely melt, and stirring 60-240 min under inert atmosphere to obtain a uniform and stable molten salt system.

Description

Process for producing oil products by distilling and degrading waste plastics through molten salt Technical Field The invention belongs to the technical field of recycling and heterogeneous catalytic distillation of waste plastics, and relates to a process for preparing oil products by distilling and degrading waste plastics by using molten salt. Background Polyolefin plastics are widely used in various fields such as packaging, building materials and automobiles due to excellent physical and chemical properties, but the characteristic of difficult degradation of the polyolefin plastics results in a large amount of white pollution after being abandoned, which has become a global environmental challenge. Meanwhile, the oil product is taken as a core energy carrier, is indispensable in industrial production and daily life, converts waste polyolefin plastics into high-quality oil products, realizes the dual purposes of solid waste recycling and energy supplementing, and is an important technical direction taking both environmental protection and efficient resource utilization into consideration. At present, the main technical route for converting waste plastics into oil products covers thermal cracking, catalytic cracking, solvent depolymerization and the like, wherein the thermal cracking and the catalytic cracking have outstanding industrialization potential to be research hot spots, but the existing technical bottleneck needs to break through, firstly, the thermal cracking process needs to maintain a high-temperature environment of 600- o ℃ or higher, the energy consumption is large, the product system is complex, besides the oil-phase products, a large amount of cracked gas and carbon deposition are generated, the comprehensive yield of the oil products is usually lower than 60%, the heavy components in the oil-phase products account for more than 30%, the impurity contents of sulfur, nitrogen and the like are unstable, the subsequent process needs to be treated by a plurality of working procedures such as hydrofining, rectifying separation and the like, so that the total production cost is remarkably improved, secondly, the traditional catalytic cracking process mostly adopts solid acidic catalytic materials such as ZSM-5, Y-type molecular sieves and the like, although the reaction temperature can be reduced to 450- oC ~ 550o ℃, the carbon deposition generated in the polyolefin cracking process is easy to be deposited in the active center of the catalyst, the catalytic activity is fast attenuated, the catalyst is regenerated through complex working procedures such as roasting, the acid washing and the like, the active components are lost, the acid components are also generated, and the like are difficult to be generated, and the existing part of the solvent is introduced into the solvent, the complex solvent is suitable for the industrial process, the large-scale is difficult to be required to be recycled, and the industrial waste water is difficult to be required, and the large-scale, and the industrial waste water is difficult to be recycled, and the industrial waste is required to be increased, and the large-scale and the industrial waste is required and the technological cost is required to be increased. In the related research of oil products produced by catalytic degradation of waste plastics, part of the technologies adopt a homogeneous catalytic system or a composite catalytic system, and the method can improve the oil product yield, but has the defects of difficult separation of a catalyst and a product, serious catalyst loss, complicated subsequent purification procedures and the like. In order to improve the reaction efficiency, part of the system is also required to be hydrofined by introducing hydrogen, so that not only are the consumption of hydrogen raw materials and equipment investment increased, but also the process safety risk is improved. Meanwhile, part of processes depend on special heating equipment such as microwaves and ultrasound, and the bottlenecks such as high equipment investment, poor heating uniformity, difficulty in large-scale amplification and the like exist. As can be seen by comparing the prior art, the related drawbacks are further highlighted: Although the patent CN113502174 realizes the directional preparation of aviation grade fuel, the problems of complex reaction flow and multi-step hydrofining are caused to improve the quality of the product, so that the process cost is higher. Patent CN118546429 realizes low-temperature degradation of 350 oC ~ 450o C by introducing a specific metal oxide catalyst, reduces energy consumption, but a homogeneous catalytic system adopted by the process has the defects of difficult separation and recovery of the catalyst and easy pollution of products, and is limited in scale application. The selectivity of the product is improved by virtue of the shape selective catalytic performance of ZSM-5 in the patent CN117186926, but the trad