Hierarchical ZSM-5 supported Ni catalysts for hydrodeoxygenation of phenolics: Effect of reactant volumes and substituents

Hydrodeoxygenation (HDO) is considered as one of the most efficient technologies for phenolics upgrading. To explore the effect of volumes and substituents on the phenolics, hierarchical nanosponge ZSM-5 supporting Ni catalyst (Ni/NPZ) is prepared and used in HDO reactions. The Ni/NPZ catalyst with hierarchical pores and highly dispersed metal species, shows enhanced adsorption of phenolics and adsorption/transfer of hydrogen, thus giving significantly higher catalytic activity than the reference micropores catalyst (Ni/CZ). Moreover, phenolics with large volumes such as 4-propylphenol give decreased conversion rates than phenol and anisole, through sequenced hydrogenation and deoxygenation procedures. Owing to the steric resistance, the deoxygenation occurs firstly on guaiacol and 2,6-dimethoxyphenol, following by hydrogenation of aromatic rings. Interestingly, the scission of C-C bonds occurs at 2,6-ditertbutylphenol by electron transfer between tertbutyl and aromatic ring, which improves their initial conversion.