Valorization of Quercus suber Bark toward Hydrocarbon Bio-Oil and 4-Ethylguaiacol

A reductive fractionation process for the valorization of Quercus suber bark toward hydrocarbons in gasoline and diesel ranges and optionally 4-ethylguaiacol has been developed. The procedure involves three steps: (1) tandem hydrogen-free Pd/C-catalyzed transfer hydrogenolysis of lignin where the carbohydrates serve as an inherent hydrogen donor under slightly alkaline conditions to also facilitate the depolymerization of suberin, (2) optional distillation, to isolate the 4-ethylguaiacol, (3) hydrodeoxygenation of the mixture from the first step by a Pt-MoO3/TiO2 catalyst generated hydrocarbons in gasoline and diesel ranges. The yield of 4-ethylguaiacol (90% purity) is 2.6% of dry bark weight (12% of acid insoluble lignin), and yield of hydrocarbon bio-oil is 42% of dry bark weight. This corresponds to a theoretical maximum yield of 77% for lignin and suberin. The carbon yield of the obtained bio-oil is thereby 64% from the total initial bark.