Enhancement of hydrodeoxygenation catalytic performance through the addition of copper to molybdenum oxide-based catalysts

Abstract

The role of copper promoter and carbon support on the activity, selectivity, and stability of molybdenum oxide was determined for bulk and carbon-supported molybdenum oxide catalysts in phenol hydrodeoxygenation (HDO). The catalytic performance was correlated to the physicochemical properties determined using ICP-AES, XRD, XPS, Raman, TPR, H2O-TPD, and oxygen chemisorption. The results showed that at the studied reaction conditions (atmospheric pressure, 330 ºC, gas phase), the employment of activated carbon as support and the addition of copper improved phenol conversion from 1 (with MoO3) to 28% (with CuMo/C), maintaining high selectivity to benzene (around 100%) while characterization studies evidence the formation of mainly CuMoO4 species in bulk samples and metallic copper, Cu2O, and MoO2 on carbon-supported ones. The incorporation of copper in the molybdenum oxide catalysis promoted the reduction of molybdenum, the creation of oxygen vacancies, and the H• formation, all factors favoring the selective CO bond cleavage. Stability tests of the most active catalysts, Mo/C_H2 and CuMo_H2, showed that deactivation happened, but the direct deoxygenation route remained preferential throughout the reaction time with high selectivity to benzene (up to 98%). Deactivation was related to the lower concentration of available active sites (oxygen vacancies).