Catalytic Hydrotreatment of β-O-4 Ether in Lignin: Cleavage of the C-O Bond and Hydrodeoxygenation of Lignin-Derived Phenols in One Pot

Selective hydrotreatment of beta-O-4 ether bonds in lignin is a key strategy for the lignin valorization. The current catalytic strategy can only transfer beta-O-4 model compounds to aromatics. Also, further upgrading was still needed to convert those aromatics/phenols into aviation fuels or chemicals (e.g., cycloalkanes, cycloalcohols) in a following step. Herein, a one-pot method for the hydrotreatment of lignin beta-O-4 ether to cycloalkanes/cycloalcohols over NiLa/CNT was reported due to the introduction of La. The dehydroxylation of 2-phenoxy-1-phenylethan-1-ol to phenethoxy-benzene was the key step during the hydrotreatment, followed by the beta-O-4 bond cleavage to ethylbenzene and phenol, which was then simultaneously hydrogenated to afford ethyl cyclohexane and cyclohexanol. The catalyst acidity was found to be important during the hydrotreatment process, especially the Bronsted acid sites. This was confirmed by control experiments using different reaction intermediates as reactants, as well as analysis of products distribution and DFT calculations. This work provides a novel and economical method for the selective hydrotreatment of lignin model compounds into aviation fuel.