Zeolite supported palladium catalysts for hydroalkylation of phenolic model compounds

Abstract Bifunctional palladium-based catalysts with zeolite supports were investigated in phenol hydroalkylation, representing high-potential model reaction for transformation of lignocellulose-derived compounds to automotive and jet fuels. Conversion of phenol correlated with the amount of accessible acid sites and textural properties of the solid acid support: under the same reaction conditions and at the same Pd loading. The highest phenol conversions (99–100%) were obtained for large-pore zeolite Beta and mesopore-containing MCM-36/56 materials. The selectivity towards the targeted cyclohexylcyclohexane on different supports decreased in the following order Beta (57%) > MCM-36 (42%) ≈ MCM-56 (37%) > MCM-22 (20%), while the contribution of undesired reaction termination through formation of non-reactive cyclohexane was more pronounced for the expanded MCM-36/56 based catalysts. Substrate consumption after 60 min over the least active MCM-22-based catalysts increased with increasing Pd content as follows 27% (0.3 wt % Pd), 80% (0.5 wt % Pd) and 98% (0.7 wt % Pd). High activity of Pd/Beta catalysts was not vitiated even by sintering effects being the most pronounced for Beta as a support.