Lignin pyrolytic oil conversion to biofuel via in-situ hydrodeoxygenation process using alcohols as liquid hydrogen donor as an efficient industrial technique
Abstract
Abstract In-situ hydrodeoxygenation (HDO) of methoxybenzene (anisole) was investigated over a refinery-grade Ni/MgSiO3 catalyst (Z503), chosen to emphasize direct industrial applicability and compatibility with existing hydroprocessing units. Reactions were carried out in a 100 mL stainless-steel batch reactor using methanol as solvent and hydrogen donor, while systematically varying methanol/anisole and water/methanol molar ratios, catalyst loading, temperature (200–300 °C), and time (2–6 h). The product spectrum could be steered between aromatic oxygenates and fully or partially saturated hydrocarbons. Low water content and moderate temperatures favored demethylation/transalkylation pathways that yielded phenol, o-cresol, and 2,6-xylenol. Increasing temperature, residence time, or catalyst loading promoted hydrogenation–hydrogenolysis sequences, producing methoxycyclohexane as a key intermediate and, ultimately, cyclohexane via HDO. The addition of water suppressed over-alkylation and shifted selectivity toward phenolic products, whereas higher methanol ratios enhanced methyl transfer. A mechanistic scheme is proposed in which anisole interconverts with phenol through trans-alkylation, while parallel hydrogenation opens a route to methoxycyclohexane and subsequent deoxygenation. Reusability tests revealed gradual catalyst deactivation during repeated batches, mainly attributed to coke deposition, partial oxidation or blockage of Ni sites, and possible hydrothermal modification of the Mg–Si–O surface. Therefore, although the fresh refinery-grade Ni/MgSiO3 catalyst showed promising activity for in-situ HDO, further regeneration or structural stabilization strategies are required to improve long-term durability. Overall, the study maps operating windows that enable controlled upgrading of anisole via a commercially deployed Ni/MgSiO3 catalyst and an internal hydrogen source, providing a plant-ready approach to HDO without external H2.