Hydrodeoxygenation of Guaiacol over Carbon-Supported Metal Catalysts

Catalytic bio-oil upgrading to produce renewable fuels has attracted increasing attention in response to the decreasing oil reserves and the increased fuel demand worldwide. Herein, the catalytic hydrodeoxygenation (HDO) of guaiacol with carbon-supported non-sulfided metal catalysts was investigated. Catalytic tests were performed at 4.0MPa and temperatures ranging from 623 to 673K. Both Ru/C and Mo/C catalysts showed promising catalytic performance in HDO. The selectivity to benzene was 69.5 and 83.5% at 653K over Ru/C and 10Mo/C catalysts, respectively. Phenol, with a selectivity as high as 76.5%, was observed mainly on 1Mo/C. However, the reaction pathway over both catalysts is different. Over the Ru/C catalyst, the OCH3 bond was cleaved to form the primary intermediate catechol, whereas only traces of catechol were detected over Mo/C catalysts. In addition, two types of active sites were detected over Mo samples after reduction in H-2 at 973K. Catalytic studies showed that the demethoxylation of guaiacol is performed over residual MoOx sites with high selectivity to phenol whereas the consecutive HDO of phenol is performed over molybdenum carbide species, which is widely available only on the 10Mo/C sample. Different deactivation patterns were also observed over Ru/C and Mo/C catalysts.