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
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.