Boosting bio-lipids deoxygenation via tunable metal-support interaction in nickel/ceria-based catalysts

Ni-catalysts usually experienced quick deactivation during bio-lipids deoxygenation due to metal sintering and coke. Here we prepared a series of Ni/CeO2-Al2O3 catalysts, denoted as NiCeAl-EISA, NiCeAl-WI and NiCeAl-CP, prepared by evaporation-induced self-assembly (EISA), wetness impregnation (WI), co-precipitation (CP) methods, respectively, aiming at tuning metal-support interaction (MSI) in Ni/CeO2-Al2O3 catalysts for the deoxygenation of bio-lipids to hydrocarbons. The porosity and surface properties of the catalysts are systematically studied by BET, XRD, H2-TPR, HR-TEM, FT-IR, O2-TPD, NH3-TPD, RPR, Py-FTIR, XPS and in situ XPS. The NiCeAl-EISA catalyst afforded 92.2% n-C11 yield at full methyl laurate conversion, and efficiently deoxygenated different FAMEs, yielding corresponding alkanes yields of 97.8% (n-C9), 96.4% (n-C13), 94.3% (n-C15) and 92.9% (n-C17). The TOFs were calculated as 426-719, 241-343 and 148-243 h-1 for NiCeAl-EISA, NiCeAl-WI and NiCeAl-CP catalysts, respectively. Jatropha oil and waste cooking oil were also converted into liquid alkanes (C13-18) with a total yield of 95.4% and 93.7%, respectively. The NiCeAl-EISA catalyst exhibits superior catalytic activity and remained stable with 92.2% n-C11 yield after 11 consecutive runs, as compared with NiCeAl-WI and NiCeAl-CP. This significant increase in catalyst activity and stability is closely correlated with the tunable SMSI of Ni/CeO2-Al2O3 catalyst, which facilely forms abundant oxygen vacancies and interfacial sites (Ni delta+-OV-CeOx). This suppresses strong Ni-Al interaction, thus exposing more active and robust Ni sites to promote R-COOH -> RCHO reduction to produce more alkanes. The weakened Ni-Al interaction also reduces the strong acidity and consequently inhibits the coke formation and simultaneously restrains C-C bond cleavage of hydrocarbons.

Automated summary

In this study, a series of Ni/CeO2-Al2O3 catalysts were prepared by different methods and used for the deoxygenation of bio-lipids to hydrocarbons. Among them, the NiCeAl-EISA catalyst showed the best catalytic activity and stability, possibly due to its unique metal-support interaction.