Development of Bifunctional Hydrodeoxygenation Catalyst Rh-HY for the Generation of Biomass-Derived High-Energy-Density Fuels

Liquid-phase hydrodeoxygenation (HDO) of phenol, anisole, and guaiacol over rhodium-doped, high-silica content zeolite catalysts (Si/Al = 15), HY, is investigated in a high-pressure-fixed bed reactor. These catalysts are characterized by inductively coupled plasma optical emission spectrometry, scanning electron microscopy with energy-dispersive spectroscopy, thermogravimetric analysis, X-ray diffraction, N₂ physisorption, ammonia temperature-programmed desorption, temperature-programmed oxidation, temperature-programmed reduction, ²⁷Al magic angle spinning nuclear magnetic resonance, and X-ray photoelectron spectroscopy. The effects of reaction temperature (150–250 °C) and weight hourly space velocity (WSHV = 1.0–2.8 h⁻¹) on activity, stability, and product distribution are investigated. The main products obtained from HDO reactions are methylcyclopentane, cyclohexane, methylcyclohexane, and bicyclohexyl. Cyclohexanone is the most abundant oxygenated product along with deactivation. For all tested catalysts, increasing the reaction temperature up to 250 °C improves the HDO reactions without significant activity or selectivity loss. Higher rhodium loading extends the catalyst life and increases the activity and cyclohexane selectivity for the guaiacol feed. The experiments indicate that anisole, phenol, and guaiacol undergo aromatic hydrogenation on rhodium particles first, followed by deoxygenation on the acid sites over zeolite combined with additional hydrogenation.