Revealing the size effect of P-coated carbon-supported palladium nanoparticles in complete hydrodeoxygenation of bio-based aromatic alcohols

The rational design of highly efficient catalysts for the selective hydrodeoxygenation (HDO) of aromatic alcohols is imperative for advancing the sustainable synthesis of biofuels and high-value fine chemicals. Palladium nanoparticles (NPs) have emerged as a promising catalytic system for facilitating C-OH bond cleavage. Herein, a series of Pd NPs with uniform sizes (2.2-7.2 nm) were prepared on phosphorus-coated carbon to probe the size effect in the HDO of bio-based aromatic alcohols. A strong linear correlation was observed between the enhancement in catalytic activity and the decrease in Pd particle size, while alkane selectivity remained consistently high at 99.9%. The catalyst achieves a remarkable >99.9% yield of ethylbenzene from phenylethanol through a one-pot hydrogenation-deoxygenation pathway under mild conditions (25 °C and 10 bar H₂) with a high turnover frequency (TOF) of 645 h^-1. Furthermore, the catalyst demonstrates excellent generality for converting various benzyl alcohols into corresponding alkanes under identical conditions. A key finding is that a decrease in Pd particle size strengthens the metal-support interaction (MSI) with the P-containing support, resulting in electron-enriched Pd NPs. This electronic modification promotes the adsorption and activation of the C-OH bond, thereby enhancing the catalytic efficiency. This knowledge can guide the synthesis of highly active catalysts, enabling the efficient HDO of bio-based aromatic alcohols with reduced precious metal loadings.