(281e) Single Step Conversion of Short Carboxylic Acid Mixtures Obtained from Fermentation to Aromatics and α-Olefins over a Cu/ZrO2 Catalyst

Biomass represents an attractive feedstock for producing petrochemical substitutes. However, the high variety of functional groups found in biomass often reduces selectivity and yields during biomass conversion reactions. To overcome this problem, biological funneling can be used to drastically reduce the amount of functional groups. Using bioprocessing, biomass polysaccharides, which contain many functional groups can be converted to carboxylic acid mixtures that contain a single functional carboxylic acid group.

In this work, short carboxylic acids obtainable from a fermentation process were converted into aromatic compounds and/or alpha-olefins in a single step catalytic process with a near theoretical carbon yield. The experiments were carried out from 623 K to 673 K under hydrogen atmosphere using Cu/ZrO₂ catalyst. The combination of copper and zirconia oxide allowed full conversion of carboxylic acids via cascade C-C coupling reactions resulting in higher molecular weight (C8-C15) products, which form a water immiscible organic phase, and light alpha-olefins in the gas phase. Remaining oxygen functionalities are selectively removed by hydrogenation-dehydration reactions over copper while avoiding the hydrogenation of unsaturated C-C bonds reducing hydrogen consumption. Moreover, by tuning reaction conditions, selectivity can be controlled to favor the increased production of short alpha-olefins or heavier products.