The valorization of waste biomass is a resource for the current energy transition and a pillar of circular economy. In particular, the short-term evolution of the mobility sector requires a suitable green liquid fuel, especially for aviation and shipping market. Pyrolysis is a promising technology to convert lignocellulosic biomass into valuable fuels and chemicals, but several negative features of bio-oil (poor stability, acidity, coking tendency, high oxygen content) limit both its direct use and its upgrading processes. These negative factors are mainly caused by the presence of C2-C4 oxygenates in bio-oil (aldehydes, ketones, acids). A possible solution to improve bio-oil quality is the addition of a catalytic upgrading stage, aiming to convert these detrimental light oxygenates from the vapor-phase. C-C coupling reactions - like ketonization and aldol condensation - can increase the C-chain length of bio-oil species while reducing the overall O/C ratio. Catalysis is necessary to improve the kinetics (rate and selectivity) of these processes. In this work, acetic acid chain-growth reactions are studied on TiO2 and Ru/TiO2 catalysts, proving relevant performances in promoting not only ketonization but also secondary growth reactions with the formation of C8+ species.