One-pot sol–gel synthesis of a CoMo catalyst for sustainable biofuel production by solvent- and hydrogen-free deoxygenation: effect of the citric acid ratio

Abstract

Deoxygenation by transition-metal-based catalysts is employed to produce a biofuel from fatty acids. In this study, the citric acid/CoMo ratio of an unsupported CoMo catalyst prepared by a sol–gel method was increased from 1 to 7 to investigate its effect on the physicochemical properties and performance of the catalyst. Deoxygenation was carried out at 300 °C under solvent- and hydrogen-free conditions. The CoMo-3 catalyst (e.g., citric acid/CoMo = 3) showed the highest oleic acid conversion rate, C₉–C₁₇ hydrocarbon selectivity, oxygen removal rate, and biofuel product quality. This catalyst exhibited the best catalytic performance because it had the highest amount of active species (CoMoO₄). Catalyst acidity considerably effected on the catalytic performance. Additionally, the citric acid/CoMo ratio affected the formation of single/mixed Co and Mo oxides.