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US-20260125533-A1 - PLASTIC DEPOLYMERIZATION USING METAL ORGANIC FRAMEWORK BASED CATALYSTS

US20260125533A1US 20260125533 A1US20260125533 A1US 20260125533A1US-20260125533-A1

Abstract

A process for depolymerizing plastic waste, including the steps of: a) providing a melt plastic waste feedstock made from or containing recycled polypropylene and b) subjecting the melt product obtained in (a) to a temperature ranging from 280° C. to 600° C., thereby obtaining a depolymerization product; wherein the melt product, the depolymerization product, or both are contacted with a metal organic framework (MOF) catalyst.

Inventors

  • Diego Brita
  • Simona Guidotti
  • Dario Liguori
  • Francesco Menichelli

Assignees

  • BASELL POLIOLEFINE ITALIA S.R,I.

Dates

Publication Date
20260507
Application Date
20231005
Priority Date
20221007

Claims (15)

  1. 1 . A process for depolymerizing plastics, comprising the steps of: a) providing a melt plastic waste feedstock comprising recycled polypropylene; and b) subjecting the melt product obtained in (a) to a temperature ranging from 280° C. to 600° C., thereby obtaining a depolymerization product; wherein the melt product, the and depolymerization product, or both are contacted with a metal organic framework catalyst.
  2. 2 . The process according to claim 1 , wherein the amount of catalyst ranges from 0.1-20 wt. %, with respect to the total weight of plastic waste feedstock and catalyst.
  3. 3 . The process according to claim 1 , wherein the plastic waste feedstock comprises a mixture of polyethylene and polypropylene in a weight ratio 85:15 to 15:85.
  4. 4 . The process according to claim 1 , wherein the MOF has a 3D (cage) framework.
  5. 5 . The process according to claim 1 , wherein the MOF has a 2D (layered) framework.
  6. 6 . The process according to claim 1 , wherein the MOF catalyst is selected from the group consisting of MOFs with zeolitic topologies.
  7. 7 . The process according to claim 1 , wherein the organic linker of the MOF is selected from the group consisting of carboxylates, phosphonates, N-based groups and N—O-containing groups.
  8. 8 . The process according to claim 7 , wherein the organic linkers are selected from the group consisting of fumaric carboxylate (FA), benzene-1,4-dicarboxylate (BDC), 1,3,5-benzene tricarboxylate (BTC), and formic carboxylate.
  9. 9 . The process according to claim 8 , wherein in which the MOF is selected from the group consisting of Zr-MOF-808 (Zr based BTC linker), Ce-MOF-808 (Ce based BTC+FA linker), MOF-199 (Cu based, BTC linker), and MIL-88A (Fe 2 O 3 based, fumaric carboxylate ligand).
  10. 10 . The process according to claim 1 , wherein the MOF is MOF-5, based on Zn 4 O(1,4-benzodicarboxylate) 3 .
  11. 11 . The process according to claim 1 , wherein the MOF is used in association with a poison suppressing agent.
  12. 12 . The process according to claim 11 , wherein the poison suppressing agent is selected from the group consisting of Ca(OH) 2 , Mg(OH) 2 , Ba(OH) 2 , Sr(OH) 2 , CaO, Al 2 O 3 , and Zr(HPO 4 ) 2 .
  13. 13 . The process according to claim 1 , wherein the amount of liquid depolymerization product is higher than 60% wt. of the plastic waste feedstock.
  14. 14 . The process according to claim 1 , wherein the amount of the higher than C28 fraction in the liquid depolymerization product is equal to, or lower than, 4%, with respect to the total amount of liquid depolymerization product.
  15. 15 . The process according to claim 1 , wherein the Branch Index of the liquid depolymerization product is no more than 1% wt.

Description

FIELD OF THE DISCLOSURE In general, the present disclosure relates to the field of chemistry. More specifically, the present disclosure relates to polymer chemistry. In particular, the present disclosure relates to a catalytic method for depolymerizing plastic feedstock and to a catalyst for the depolymerization. BACKGROUND OF THE DISCLOSURE For some applications, plastics are inexpensive and durable materials for manufacturing a variety of products. As such, the production of plastics has increased dramatically over the last decades. In some instances, the durability of the plastics contributes to an increase in the amount of plastics are filling up landfill sites and natural habitats. In some instances, degradable and biodegradable plastics persist depending on environmental factors, such as ultraviolet light exposure, temperature, ant the presence of microorganisms. Currently, plastic recycling primarily includes mechanical recycling and chemical recycling. With mechanical recycling, plastics are transformed without changing their chemical structure and may be used to produce new materials. In some instances, mechanical recycling steps include: collecting plastic wastes; sorting plastic by type and color; pressing or milling plastics for packaging plastics; washing and drying plastics; and reprocessing plastics into pellets by agglutinating, extruding and cooling the plastics. In some instances, the plastics are polyolefins such as polyethylene (PE) and polypropylene (PP). Alternatively, chemical recycling modifies the structure of plastics, thereby permitting use of the resulting plastics as raw material for different industries or as a basic input or feedstock for manufacturing new plastic products. In some instances, chemical recycling steps include: collecting plastics and heating the plastics to a temperature at which the polymers break down into fragments. In some instances, this process is referred to as depolymerization and converts plastic waste material to liquid fuel by thermal degradation (cracking) in the absence of oxygen. In some instances, plastics waste is first melted within a stainless steel chamber, under an inert purging gas. Next, the molten material is heated to a gaseous state. Then, the gaseous material is drawn and condensed in one or more condensers, thereby yielding a hydrocarbon distillate made from or containing straight and branched chain aliphatic, cyclic aliphatic, and aromatic hydrocarbons. In some instances, the resulting mixture is used as a fuel. In some instances, the resulting mixture is used as a feedstock in a thermocatalytic process for obtaining refined chemicals such as monomers. SUMMARY OF THE DISCLOSURE In a general embodiment, the present disclosure provides a process for depolymerizing plastics including the steps of: a) providing a melt plastic waste feedstock made from or containing recycled polypropylene; andb) subjecting the melt product obtained in (a) to a temperature ranging from 280° C. to 600° C., thereby obtaining a depolymerization product;wherein the melt product, the depolymerization product, or both are contacted with a metal organic framework (MOF) catalyst. In some embodiments, the amount of catalyst used ranges from 0.1 to 20 wt. %, alternatively 0.1-10 wt. %, alternatively from 0.1 to 5 wt. %, with respect to the total weight of plastic waste feedstock and catalyst. In some embodiments, the plastic waste feedstock is made from or containing a mixture of polyethylene and polypropylene in a weight ratio 85:15 to 15:85, alternatively 80:20 to 20:80. In some embodiments, the polyethylene is selected from the group consisting of high density polyethylene (HDPE), low-density polyethylene (LDPE), and linear low density polyethylene (LLDPE). In some embodiments, the polypropylene (PP) is a propylene homopolymer or a propylene copolymer, having a lower amount of ethylene, butene, or both. In some embodiments, the feedstock is made from or containing other polyolefins like polybutene. In some embodiments, the feedstock is further made from or containing other polymeric materials. In some embodiments, the other polymeric materials are selected from the group consisting of polystyrene (PS), ethyl-vinyl acetate copolymer (EVA), ethyl-vinyl alcohol copolymer (EVOH), polyvinyl chloride (PVC), and mixtures thereof. In some embodiments, the feedstock is made from or containing more than 80% wt of a mixture between polyethylene and polypropylene, wherein polypropylene accounts for more than 50% wt of the polypropylene/polyethylene mixture. In some embodiments, the depolymerization process occurs in an oxygen-free environment. In some embodiments, an oxygen containing atmosphere is not introduced into the depolymerization system. In some embodiments, the barrier to the potentially oxygen-containing atmosphere is obtained with a series of expedients. In some embodiments, the series of expedients is selected from the group consisting of nitrogen blanketing and