Heterogeneous catalysis for bio-based polyester monomers from cellulosic biomass: advances, challenges and prospects
It is a 21st century challenge to develop a more sustainable chemical industry where fossil-based resources are, where possible, preferentially replaced by renewable alternatives. Bio-based polymers, in particular those derived from cellulose or other carbohydrates, are often considered benign alternatives for petrochemical plastics. The majority of bioplastic precursors are currently derived from fermentation or biotechnology. Chemocatalytic routes to both similar and new polymer building blocks are emerging in an effort to mitigate challenges related to carbohydrate fermentation, such as waste generation and costly product purification. This review critically surveys recent developments in applying heterogeneous catalysis for the production of bio-based polyester monomers from cellulose or cellulose-derived carbohydrates. Highlighted target molecules include various α-hydroxy acids or esters (e.g. lactic and glycolic acid, lactide and methyl vinyl glycolate), furandicarboxylic acid, ethylene glycol and isosorbide. The production of lactic acid from glycerol will exceptionally be included as well, as an oversupply of glycerol might contribute to non-negligible amounts of lactic acid in the future. Where possible, remaining challenges and future prospects are highlighted.