Adipic acid (AA) is a widely produced industrial dicarboxylic acid used mainly in the production of Nylon-66 and other polymers. Current methods of petrochemical production of AA result in nitrous oxide (N2O) gas, a greenhouse gas much more potent than CO2. Biomass-derived furans derived from C6 sugars offer an alternative to petroleum as a feedstock for AA, thereby eliminating N2O production and creating a more sustainable route to AA. Tetrahydrofuran-2,5-dicarboxylic acid (THFDCA) is an excellent starting point for AA production due to its structural similarity (C6 dicarboxylic acid) and the ability to form it selectively from platform chemical 5-hydroxymethylfurfural (HMF). It has been proposed that ring opening of THFDCA to AA can be conducted by employment of hydriodic acid (HI) in combination with molecular H2 and Pd/C in acetic acid. In this work, we show that solid acid catalysts can be utilized as a proton source in combination with an iodide source in a weak organic acid as a solvent, achieving an AA yield of ~90% in the absence of any metal catalyst. We attribute these high yields to the multifunctional nature of iodide, which acts not only to activate molecular H2 in solution, but also to selectively remove C-O bonds without overhydrogenation of carboxylic acid groups. Advantages to solid acid catalysts include their less corrosive nature by controlling HI formation in situ. Through a series of reactivity studies, we have identified key mechanistic insights into the interactions between solid acids, iodides, and molecular H2. Although iodide decomposes over the course of reaction, solid acids can be regenerated and recycled, providing additional benefits in employing solid acids over homogeneous ones.

Adipic acid production from biomass-derivatived tetrahydrofuran-2,5-dicarboxylic acid via the combination of solid acids and iodide

254th National Meeting (2017)

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