Production of renewable gasoline from aqueous phase hydrogenation of lignin pyrolysis oil

The hydrogenation of biomass pyrolysis oils to upgraded biofuels, especially the aliphatic compounds with a low boiling range has attracted significant research attention. However, compared with the water soluble phase of pyrolysis oils, the water insoluble parts are relatively difficult to upgrade due to the complex high molecular weight aromatic structures. To solve this problem, a two step hydrogenation of water insoluble pyrolysis oil (heavy oil) produced from pyrolysis of pine wood ethanol organosolv lignin (EOL) at 600 °C for 30 min was examined. Ru/C was used as the catalyst and water was used as the dispersant for the heavy oil and hydrogenation products. The carbon conversion yields for the first and second step hydrogenation are 35% and 33% (overall molar% of carbon content in the heavy oil), respectively. The products of first step of hydrogenation are primarily aromatic molecules which are produced from the hydrolytic cleavage of ether bond and methoxy groups in the heavy oils. Further hydrogenation was shown to covert the insoluble heavy oils (weight average molecular weight is 265 g/mol) to the aliphatic alcohols and other aliphatic components which could be used as renewable gasoline. As far as we know, this is the first reported effort to upgrade water insoluble parts of lignin pyrolysis oil to the total aliphatic components by aqueous phase hydrogenation.