Chemical Recycling Processes of Waste Polyethylene Terephthalate Using Solid Catalysts

Abstract

Polyethylene terephthalate (PET) is a non-degradable single-use plastic and a major component of plastic waste in landfills. Chemical recycling is one of the most widely adopted methods to transform post-consumer PET into PET's building block chemicals. Non-catalytic depolymerization of PET is very slow and requires high temperatures and/or pressures. Recent advancements in the field of material science and catalysis have delivered several innovative strategies to promote PET depolymerization under mild reaction conditions. Particularly, hetero-geneous catalysts assisted depolymerization of post-consumer PET to monomers and other value-added chemicals is the most industrially compatible method. This review includes current progresses on the heterogeneously catalyzed chemical recycling of PET. It describes four key pathways for PET depolymerization including, glycolysis, pyrolysis, alcoholysis, and reductive depolymerization. The catalyst function, active sites and structure-activity correlations are briefly outlined in each section. An outlook for future development is also presented.

Critical issues for the deployment of plastic waste pyrolysis

“…Interestingly, CaO, which is a basic oxide, also enhanced decarboxylation and produced even more benzene (7%) than ZSM-5 zeolite in the catalytic pyrolysis of PET at 600 °C, at the expense of generating less yields of benzene derivatives and indenes/naphthalenes. 76,77…”

Advances in solar-driven, electro/photoelectrochemical, and microwave-assisted upcycling of waste polyesters

“…Such polyesters are insensitive to hydrolysis and microbial degradation, resulting in a very long degradation period in the natural environment of 100 to 1000 years. 6 The rapid accumulation of polyester has posed serious environmental and health threats. On the other hand, polyesters, petroleum-based products, can provide raw materials for the production of new plastic products and reduce the demand for petroleum raw materials.…”

Guanidine functionalized porous SiO2 as heterogeneous catalysts for microwave depolymerization of PET and PLA

“…The method involves reacting PET, excess diol, usually ethylene glycol (EG) and a catalyst, with the product bis(2-hydroxyethyl) terephthalate (BHET) being obtained. Many catalysts are effective for this transformation such as metal oxides, 5,6 nanoparticles, 7–9 metal salts and metal-containing ionic liquids, 5,10,11 and organocatalysts. 12–18…”