Valorization of Glycerol through Plasma-Induced Transformation into Formic Acid.

To cope with climate change issues, a significant shift is required in worldwide energy sources. Hydrogen and bioenergy are being considered as alternatives toward a carbon neutral society, making formic acid - a hydrogen carrying product of glycerol - of interest for the valorization of glycerol. Here we investigate the plasma-induced transformation of glycerol in an aqueous nanosecond repetitively pulsed discharge reactor. We found that the water content in the aqueous mixture fulfilled a crucial role in both the gas phase (as a source of OH radicals) and the liquid phase (as a promotor of the dissolved OH radical's mobility and reactivity). The formic acid produced was linearly proportional to the specific input energy, and the most cost-effective production of formic acid was found with 10 % v/v glycerol in the aqueous mixture. A plausible reaction pathway was proposed, consisting of the OH radical-driven dehydrogenation and dehydration of glycerol. The results provide a fundamental understanding of plasma-induced transformation of glycerol to formic acid and insights for future practical applications.