Recent Progress in the Chemical Upcycling of Plastic Wastes

Abstract

The massive generation of plastic wastes without satisfactory treatment has induced severe environmental problems and gained increasing attentions. In this Minireview, recent progresses in the chemical upcycling of plastic wastes by using various methods (mainly in the past three to five years) is summarized. The chemical upcycling of plastic wastes points out a "plastic-based refinery" concept, which is to use the plastic wastes as platform feedstocks to produce highly valuable monomeric or oligomeric compounds, putting the plastic wastes back into a circular economy. The different chemical methods to upcycle plastic wastes, including hydrogenolysis, photocatalysis, pyrolysis, solvolysis, and others, are introduced in each section to valorize diverse plastic feedstocks into value-added chemicals, materials, or fuels. In addition, other emerging technologies as well as the new generation of plastic thermosets are covered.

Recent Advancements in Plastic Packaging Recycling: A Mini-Review

“…Mechanical recycling is the main and most widely used technology for plastic recycling, consisting of several steps, including collection, screening, automatic or manual sorting, washing, shredding, extrusion, and granulation [83][84][85][86] (Scheme 2). Mechanical recycling is classified as primary or secondary according to the type of starting material being processed.…”

“…Millions of euros are being invested to enhance chemical recycling and other cutting-edge technological solutions with the aim of producing 1.2 Mt of recycled plastic in EU by 2025 and 3.4 Mt by 2030 [9]. Chemical recycling methods are classified according to reaction conditions into solvolysis (hydrolysis, methanolysis, and glycolysis), catalytic depolymerization, and enzymatic depolymerization [83,84,[118][119][120][121][122][123][124][125][126][127]. Only main innovative solutions devised in the last year for plastic packaging chemical recycling are analyzed below i.e., PE, PP, PET, and PS.…”

“…Solvolysis involves the breaking of the hydrolyzable bonds of a polymer in the presence of an alcohol or water. It is rather frequent that, to improve reaction conditions, product selectivity, and yield, catalysts are used to promote solvolysis reactions [83,84,119,128].…”

A High‐Throughput Approach to Repurposing Olefin Polymerization Catalysts for Polymer Upcycling

“…Durability and resistance to degradation, the desirable properties of plastics, also pose significant endof-life-cycle problems. Paradoxically, plastic waste is also a largely untapped commodity resource, [9][10][11][12][13][14][15][16][17][18] though hydro-carbon polymers such as polyolefins or polydienes are challenging to recycle. A desirable outcome to close the end-of-life cycle of plastics is revalorization.…”

“…A desirable outcome to close the end-of-life cycle of plastics is revalorization. Catalytic plastic waste hydrogenolysis [9][10][11][19][20][21][22][23][24] produces liquid products (diesel), which can re-enter the polymer production cycle using already existing transportation and refinery infrastructure, [3] leading to a circular plastics economy. [3,13,18,25,26] For polyolefins however, depolymerization to reacquire the alkene monomer is endergonic and reaching high selectivities/ conversions is challenging.…”