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Biorefineries, which utilize lignocellulosic biomass as renewable energy source and sustainable carbon feedstock, are a promising solution to alleviate the excessive dependence on the depleting fossil resources and address climate change and other environmental problems. Owing to the recalcitrance and over-functionalized nature of biomass, the conversion of biomass into desirable products requires a series of complex deconstruction, catalytic conversion, separation and purification processes. In the biorefinery roadmap, 5-hydroxymethylfurfural (HMF) stands out as a bridge connecting biomass raw materials to alternative fuels, chemicals and materials, which can displace petroleum-derived products. This review describes the recent advances in the design and development of catalytic systems for the conversion of biomass and their constituent carbohydrates to HMF via hydrolysis, isomerization and dehydration reactions, and the upgrading of HMF towards polymer monomers, fine chemicals, fuel precursors, fuel additives, liquid fuels, and other platform chemicals via hydrogenation, oxidation, esterification, etherification, amination and aldol condensation reactions, with emphasis on how the catalysts, solvents and reaction conditions determine the reaction pathway and product selectivity. We also attempt to provide a conceptual framework on how to evaluate the actual reaction efficiency, reusability, and economic and technical feasibility of different catalytic systems and highlight the key research challenges to be addressed.

Reaction efficiencies of biorefinery processes are universally low because of the severe side reactions at high substrate loading. Here, we show that the use of Sn-modified Al2O3 catalyst in ionic ...

Summary Various recycling technologies have been developed to deal with plastic problems, but they face considerable economic and technological challenges in practice. An attractive alternative is upcycling, which aims to dig out the embedded value to incentivize large-scale valorization of plastic wastes. The degradation of nonrecoverable plastic wastes is another necessity to treat the omnipresent pollution. This review presents an overview on the conversion of plastic wastes toward value-added products and the catalytic degradation of nonrecoverable plastic wastes. Based on an examination of traditional recycling technologies and products, we summarize the state-of-the-art design and development of plastic conversion to high-value and high-performance fuels, chemicals, and materials. Subsequently, we highlight the advances in catalytic degradation of plastics to environmentally benign or degradable products and mineralization into carbon dioxide and water. We conclude with our perspective on the ongoing challenge and opportunities.

5-Hydroxymethylfurfural (HMF) is an important intermediate in the utilization of lignocellulosic biomass. Ionic liquid 1-ethyl-3-methylimidazolium bromide (EMIMBr) containing a dissolved SnCl4 as catalyst was found to be capable to convert carbohydrates into HMF, as an alternative to the chromium-based catalytic system. Based on this, a biphasic system consisting of glycol dimethyl ether or dimethyl carbonate as the extraction phase, and EMIMBr/SnCl4 in combination with partial dissolved organic solvent as the reaction phase was developed for the production of HMF from carbohydrates (80 wt% with respect to the ionic liquid) at high concentrations. The biphasic system could obtain HMF yields (49.0–65.7%) comparable to or slightly higher than the monophasic system. The biphasic system could not only considerably displace ionic liquids with organic solvents, but also promote the separation of HMF from the reaction system owing to the excellent extraction ability and low boiling point of the organic solvents.