Influence of Impregnation Processes on Ruthenium-Molybdenum Carbon Catalysts for Selective Hydrodeoxygenation of Biomass-Derived Sorbitol into Renewable Alkanes

Sorbitol, as a C6 sugar related compound derived from cellulose, is regarded as a promising biomass-derived substrate and has characteristically higher oxygen content than in fossil-based resources. In this work, ruthenium-molybdenum carbon catalysts prepared by different impregnation processes were employed and extensively studied in a trickle-bed reactor for sorbitol hydrodeoxygenation (HDO). Interestingly, these catalysts afforded remarkably different HDO performance. Ruthenium-molybdenum catalysts prepared by ultrasonic treatment and calcination obtained high HDO performance in sorbitol conversion with 79.8% carbon yield of C5/C6 alkanes (pentane and hexane), almost twice that of ruthenium-molybdenum catalysts prepared without using a calcination processes. Therefore, a series of characterization studies (N-2-adsorption, XRD, HRTEM, XPS, H-2-TPR, CO-TPD, NH3-TPD, Py-IR spectra, etc.) were performed over relevant catalysts to study the catalytic mechanism. The results suggest that prior calcination offers a better chance for the proximity between Ru and Mo precursors to produce the bimetallic catalytic structure Ru-MoOx, which produces high HDO performance.