Abstract: We have examined the role of support oxygen vacancies in the gas phase hydrogenation of furfural over Au/TiO2 and Au/CeO2 prepared by deposition-precipitation. Both catalysts exhibited a similar Au particle size distribution (1-6 nm) and mean (2.8-3.2 nm). Excess H2 consumption during TPR is indicative of partial support reduction, which was confirmed by O2 titration. Gold on CeO2 with a higher redox potential exhibited a greater oxygen vacancy density. A lower furfural turnover frequency (TOF) was recorded over Au/CeO2 than Au/TiO2 and is linked to suppressed H2 chemisorption capacity and strong -C=O interaction at oxygen vacancies that inhibited activity. Gold on non-reducible Al2O3 as benchmark exhibited greater H2 uptake and delivered the highest furfural TOF. Full selectivity to the target furfuryl alcohol was achieved over Au/TiO2 and Au/Al2O3 at 413 K and over Au/CeO2 at 473 K with hydrogenolysis to 2-methylfuran at higher reaction temperature (523 K). A surface reaction mechanism is proposed to account for the activity/selectivity response.
Keywords: Furfural; Furfuryl alcohol; Oxygen vacancies; Selective hydrogenation; Supported Au.