Mesostructured CMK-3 carbon supported Ni–ZrO2 as catalysts for the hydrodeoxygenation of guaiacol

Abstract

Abstract In this work, mesoporous carbon materials were obtained by using the nanocasting method starting from ordered mesoporous SBA-15 and commercial nonporous Cab-O-sil® M − 5 silica hard templates; materials were named CMK-3 and C-Cab, respectively. These carbon materials, displaying different porous structures (mesopore diameter, specific surface area and pore volume) were used to stabilize Ni and ZrO2 particles using different deposition methods for the nickel and zirconium phases. The catalysts were tested in the hydrodeoxygenation of guaiacol. The conversion varied from 40 to 100% depending on the textural properties of the carbon support and reaction time at 300 °C and under 50 bar of hydrogen pressure. The catalysts were selective toward the formation of the hydrogenation product (methoxycyclohexanol) and hydrogenated - partially deoxygenated product (cyclohexanol). The deposition of the Ni and ZrO2 precursors in mesoporous CMK-3 carbon replicas with a unimodal mesopore diameter, with respect to the use of non-ordered carbons, allows to obtain improved selectivity toward cyclohexanol and, more importantly, toward cyclohexane. Preparation using incipient-wetness impregnation favoured the formation of both monoclinic and tetragonal phases, while the deposition-precipitation method led to the formation of ZrO2 with a unique tetragonal structure. The presence of both monoclinic and tetragonal phases modified the density of catalyst acid sites, which allow to improve the selectivity toward cyclohexane and cyclohexanol while decreasing the selectivity toward the undesired methoxycyclohexanol and other oxygenated compounds.