Selective Hydrodeoxygenation of Lignin-Derived Phenols to Aromatics Catalyzed by Nb2O5-Supported Iridium

Abstract

The dominating catalytic approach to aromatic hydrocarbons from renewables, deoxygenation of phenol-rich depolymerized lignin bio-oils, is hard to achieve: Hydrodeoxygenation (HDO) of phenols typically leads to the loss of aromaticity and to non-negligible fractions of cyclohexanones and cyclohexanols. Here, we report a catalyst, niobia-supported iridium nanoparticles (Ir@Nb2O5), which combines full conversion in the HDO of lignin-derived phenols with appreciable and tunable selectivity for aromatics (25-95%) under mild conditions (200-300 °C, 2.5-10 bar of H2). A simple approach to the removal of Brønsted-acidic sites via Hünig's base prevents coking and allows reaction conditions (T > 225 °C, 2.5 bar of H2), promoting high yields of aromatic hydrocarbons.