Solely Biomass-Derived Polyethylene Terephthalate (PET): Conversion of Bio-based Isoprene and Acrolein to p-Xylene and Terephthalic Acid

There exist significant challenges in the synthesis of solely biomass-derived p-xylene and terephthalic acid (TPA), the monomer precursors of polyethylene terephthalate (PET). Herein, we describe a flexible synthetic route to prepare either p-xylene or TPA from biomass-derived isoprene and acrolein, which avoids harsh reaction conditions such as high pressure or extreme low temperature. The route starts from 4-methylcyclohex- 3-enecarbaldehyde, the product of Diels-Alder reaction of isoprene and acrolein. Then p-xylene was successfully obtained by subsequent reduction and aromatization reactions using either environment-friendly solvents or in neat. In addition, this route was further modified for a process to prepare both p-xylene and TPA. By using the same intermediate after Diels-Alder reaction, an aromatization reaction was followed by a reduction to p-xylene or an oxidation to directly TPA in an overall yield of 32% over three steps.