On the hydrothermal-enhanced synthesis of highly selective Mo2C catalysts to fully deoxygenated products in the guaiacol HDO reaction

Abstract

We describe the hydrothermal synthesis of carbon nanofibers (CNF) supported Mo2C catalysts with improved efficiency in the hydrodeoxygenation (HDO) of guaiacol as compared to the conventional incipient wetness route. Different impregnation methods were evaluated after careful optimization of the surface chemistry of the support (by HCl wash, HNO3 wash, and N2 thermal treatments) to assist the impregnation of the Mo precursor. CNF pre-treated with HCl exhibited the surface freest of oxygenated groups according to the TPD analyses and resulted in catalysts with higher Mo loadings according to the ICP-OES analysis regardless of the impregnation method used. The Mo2C/CNF catalysts obtained by carbothermal hydrogen reduction of the impregnated supports presented different physicochemical characteristics depending on the impregnation method, as revealed by the characterization carried out by XRD, XPS, ICP-OES and STEM. The hydrothermal impregnation resulted in the highest surface atomic Mo/C ratio, as the evidence of a higher specific surface concentration of both the Mo precursor and carbide on the support, and the largest guaiacol conversion (97%) and HDO ratio (84%) in the HDO of guaiacol at 300 °C and 34 bar H2.