Selective hydrodeoxygenation of bio-oil model compounds and mixtures over CuCoOx catalysts under mild conditions

Abstract

Hydrodeoxygenation (HDO) is an effective technology for upgrading the quality of bio-oil. Despite the considerable research endeavors in recent years, the reaction conditions employed have been notably severe, and there remains a scarcity of investigations into the potential components in bio-oil. In the present study, a series of CuCoOx catalysts were synthesized for HDO reactions of guaiacol (GUA), vanillin (VAN), and levulinic acid (LA) using isopropanol as a hydrogen donor. Under mild reaction conditions (150–190 °C), the optimal CuCoOx catalyst exhibited good performance, yielding ∼99 % of the desired products from the respective model compounds. Notably, competitive HDO with esterification was observed at 150–170 °C when co-hydrotreating the mixtures of GUA, VAN, and LA over the CuCoOx catalyst. Upon increasing the reaction temperature to 190 °C, the esterification between compounds in the mixtures was inhibited, and all compounds were converted to products with low oxygen content. Further, various characterizations substantiated the robust adsorption capabilities of the optimal catalyst towards methoxy, carbonyl, and aromatic moieties. In addition, the Cu1Co10Ox-300 catalyst demonstrated the capacity to transform high-oxygen compounds present in pyrolysis oil into species with diminished oxygen content, and in some cases, into hydrocarbon compounds. The present study presents a promising approach for the efficient conversion of single model compounds and mixtures into value-added chemicals and fuels under mild conditions.