Climate change has significantly increased demand for renewable fuels, especially those derived from waste, such as waste cooking oil (WCO). However, highly efficient catalytic systems are needed to convert these low-quality feedstocks completely. In this context, we presented a rapid, solvent-free, and efficient process for WCO upgrading to produce green-diesel-range hydrocarbons, using Ru/NbOPO 4 catalysts. The in situ activation of needle-like RuO 2 nanocrystals promoted the complete conversion of WCO within 30 min, achieving 96% green diesel selectivity and 78 wt% liquid yield, with a catalyst containing 2.4 wt% Ru. The presence of oxophilic NbO x acid sites facilitated deoxygenation reactions in nitrogen (N 2 ) atmosphere; however, their effectiveness was reduced under hydrogen (H 2 ) conditions. Conversely, the metallic Ru 0 nanocrystals significantly enhanced hydrogenation and hydrogenolysis reactions, in the presence of H 2 , thereby minimizing the undesirable cracking of free fatty acids. Regardless of the atmosphere (H 2 or N 2 ), niobium-based catalysts favored the decarboxylation and decarbonylation reactions, resulting in the C n-1 hydrocarbons. The strong synergy between Ru and NbOPO 4 enabled the development of a rapid process for converting low-quality waste feedstocks into drop-in biofuels, thereby supporting the decarbonization of the industrial sector. • Fast solvent-free deoxygenation of WCO to green diesel production in 30 min. • Ru/NbOPO 4 catalyst delivers 96% green diesel selectivity with 78 wt% liquid yield. • NbOPO 4 drives catalytic deoxygenation under N 2 via oxophilic NbO x sites. • Higher Ru loading enhances hydrogenation reactions, increasing C n-1 hydrocarbons selectivity. • NbOPO 4 intrinsically promoted DCO x regardless of Ru loading or reaction atmosphere.
Rosa et al. (Fri,) studied this question.