(473c) Phthalic Anhydride Production From Renewable Carbon Sources

Increasing exploitation of fossil fuel feedstocks for the production of energy and materials has led to an increase in the price of crude oil as well as increasing levels of CO₂ in the atmosphere ^[1]. Therefore, there has been an accelerated research effort invested in the conversion of renewable biomass feedstocks into fuels and chemicals. One important chemical at risk for future shortages is phthalic anhydride because of its dependence on petroleum production.  Phthalic anhydride is used for the production of plasticizers, polyesters, and resins. In 2000, the worldwide production of phthalic anhydride was 3.23 million tons ^[2]. The objective of this study is to investigate a renewable route for the production of phthalic anhydride from lignocellulosic biomass.

A renewable route to phthalic anhydride from biomass-derived furan and maleic anhydride is investigated using quantitative NMR spectroscopy to identify products and byproducts.  Furan and maleic anhydride can be converted to phthalic anhydride in two steps: Diels Alder cycloaddition followed by dehydration.  Here the two reactions were investigated independently. Good yields of the Diels-Alder reaction between furan and maleic-anhydride were obtained at room temperature and solvent-free conditions (SFC) to yield ~81% to the cycloadduct after 1 hr of reaction.  The dehydration of the Diels-Alder cycloadduct was carried out using a number of promoters and reaction conditions. Ultimately, optimal yields for this dehydration were identified under reaction conditions containing mixed sulfonic-carboxylic anhydrides at room temperature as the key reagent.  The NMR investigations show a yield of 57% to phthalic anhydride (81% conversion, 70% selectivity) after 1 hour of reaction can be obtained.

References:
[1] Climent, M., Corma, A., & Iborra, S. (2011). Green Chemistry , 520-540.
[2] Phthalic Anhydride. Retrieved from http://www.inchem.org/documents/sids/sids/85449.pdf