(172b) Greening Paints, Plastics, and Fibers: Renewable Phthalic Anhydride from Biomass-Derived Sugars

Every year, 3 million tonnes of phthalic anhydride are manufactured worldwide for the production of paints, plasticizers, and fabrics.  However, phthalic anhydride is currently produced by the catalytic oxidation of o-xylene, a chemical derived from petroleum.  Here, we suggest a renewable route to phthalic anhydride from biomass-derived furan and maleic anhydride.  Furan and maleic anhydride were converted to phthalic anhydride in two reaction steps: Diels–Alder cycloaddition followed by dehydration. Excellent yields for the Diels–Alder reaction between furan and maleic-anhydride were obtained at room temperature and solvent-free conditions (SFC) yielding 96% exo-4,10-dioxa-tricyclo[5.2.1.0]dec-8-ene-3,5-dione (oxanorbornene dicarboxylic anhydride) after 4 h of reaction. It is shown that this reaction is resistant to thermal runaway because of its reversibility and exothermicity. Subsequently, the dehydration of the oxanorbornene was investigated using mixed-sulfonic carboxylic anhydrides in methanesulfonic acid (MSA). An 80% selectivity to phthalic anhydride (87% selectivity to phthalic anhydride and phthalic acid) was obtained after running the reaction for 2 h at 298 K to form a stable intermediate followed by 4 h at 353 K to drive the reaction to completion. The structure of the intermediate was determined. This result is much better than the 11% selectivity obtained in neat MSA using similar reaction conditions.