(770a) A Simplified Route to Prepare Biomass-Derived Terephthalic Acid (TA)

Abstract : In response to diminishing oil reserves and increasing costs for petroleum-based products, there is a great need to develop new routes to chemicals intermediates from renewable resources. Here we reported a novel synthesis route to directly transform biomass-derived chemicals (isoprene and acrylic acid) to terephthalic acid (TA) through p-toluic acid (PTA). TA is an important monomer for synthesizing polyesters including polyethylene terephthalate (PET), polypropanediol terephthalate (PPT) or polybutylene terephthalate (PBT), which have broad applications from drink bottles to polyester fibers.  The starting chemicals can be produced from biomass through established chemical processes. Bio-based isoprene can be produced by the fermentation of biomass sugars. Acrylic acid can be produced either from dehydration of glucose-based lactic acid or dehydration and oxidation of glycerol (available in large quantity from biodiesel production). In this study, TA was converted from isoprene and acrylic acid through three simple reactions including Diels-Alder reaction, dehydro-aromatization, and oxidation. The simplified process is based on the efficient dehydro-aromatization reaction of cyclohexene carboxylic acid to PTA using a cost-effective catalyst (sulfuric acid). All three reactions were conducted under mild conditions.  Finally, pure TA was successfully synthesized with the overall yield of approximately 60% and its structure was confirmed by ¹H-NMR (Nuclear Magnetic Resonance). Theoretically, at the first time, we elucidated the dehydro-aromatization reaction mechanism of cyclohexene carboxylic acids using sulfuric acid as the catalyst.