Integrated electrocatalytic processing of levulinic acid and formic acid to produce biofuel intermediate valeric acid

Herein, we report integrated electrocatalytic processing of simulated acid-catalyzed cellulose hydrolysis downstream (levulinic acid + formic acid) to the biofuel intermediate valeric acid (VA). This green electro-biorefining process does not require complex steps to separate levulinic acid and formic acid (FA) from H2SO4; instead it couples electrocatalytic hydrogenation (ECH) of levulinic acid (LA) in a single electrocatalytic flow cell reactor and electrocatalytic oxidation of formic acid in a proton exchange membrane-direct formic acid fuel cell (DFAFC). The presence of FA has shown no negative effect on the ECH of LA and a high VA selectivity of >90% can be achieved on a non-precious Pb electrode while the Faradaic efficiency remains >47% during 8 hours of reaction in the single electrocatalytic flow cell reactor. This stream is fed directly to the DFAFC with a Pd/C anode catalyst to self-sustainably remove FA where 47% conversion of FA can be reached in 6 hours. However, electro-oxidation of FA over Pd/C appears to be reversibly inhibited by the product VA produced during ECH of LA. The electro-oxidation of FA + C-2-C-5 alkyl carboxylic acid in the half cell study shows that such an inhibition effect could have originated from the -COOH adsorption on the Pd surface. Higher carboxylic acid concentration and longer carbon chain lead to more serious loss of the electrocatalytic surface area (ECSA) of Pd/C.