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, heterogeneous 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.

We use infrared (IR) spectroscopy, gel permeation chromatography (GPC), and liquid chromatography-mass spectrometry (LC-MS) in multistage dissolution experiments in various solvents to investigate the solubility and molecular structure of humins formed during fructose dehydration. We demonstrate that the soluble fraction of humins correlates positively with the donor number of solvents resulting in significant dissolution at room temperature in solvents with high donor number. Most of the solubilized humins fragments have relatively low molecular weight (M_w), and the same species are present in different quantities as the residual solid is repeatedly dissolved in the same solvent. In contrast to the common belief of humins consisting of polymers of large M_w, we postulate for the first time that they are spatially and chemically heterogeneous and consist of insoluble macromolecules and small soluble species that are weakly associated within the structure. The solubility profiles of dissolved species in acetonitrile and methanol are different in terms of M_w but possess similar IR spectra, indicative of similar functional groups in dissolved species. Furthermore, we hypothesize that the identified humins fragments form through aldol condensation between 5-hydroxymethylfurfural and its hydrated products and through condensation of furanic species.

This article discusses the formation of robust C–C linkages in lignin and proposes ways to avoid it.

Glucaric acid, a promising bio-based chemical for the production of adipic acid, is produced on a commercial Pt/C catalyst via aerobic oxidation of glucose in water. Facile oxidation of gluconic acid, an intermediate oxidation product of glucose, under optimal conditions of an initial pH of 7.2, 80 °C, 13.8 bar O₂ and a glucose/Pt molar ratio of 54, enabled a maximum glucaric acid yield of 74%, the highest yield reported to date. It is found that in an acidic solution, gluconic acid is the major product while in a highly basic solution, selectivity to glucaric acid is poor due to its C–C bond cleavage to low carbon chain carboxylic acids. High temperatures and high Pt loadings result in lower selectivity to glucaric acid. Recyclability and characterization studies reveal that the catalyst is stable after five cycles with no sign of Pt leaching into the solution.