Halloysite-Supported Ru-Based Bifunctional Catalysts for the Hydrodeoxygenation of Guaiacol

This study investigates the effects of the active-phase deposition method on the properties and performance of Ru-based catalysts supported on halloysite nanotubes (HNTs) in the model hydrodeoxygenation (HDO) of guaiacol. Among the loading methods tested—incipient wetness impregnation, vacuum impregnation, and microwave-assisted impregnation—the last provided the highest dispersion of the resulting ruthenium nanoparticles and their preferential location inside the lumen of the nanotubes. For the Ru/HNT catalyst synthesized by microwave-assisted impregnation, optimal reaction conditions were established: 180°C, 3 MPa H2, a guaiacol/Ru molar ratio of 200, and water as a solvent. Under these conditions, guaiacol conversion reached 100% with a turnover frequency (TOF) of 278 h–1; moreover, the selectivity toward the product of exhaustive HDO, cyclohexane, did not exceed 6% due to the low acidity of halloysite.