Operating strategies for the oxidative steam reforming (OSR) of raw bio-oil in a continuous two-step system

This work aimed to establish a suitable O ₂ feeding strategy for the hydrogen production by oxidative steam reforming (OSR) of raw bio-oil in a reaction system with two-steps: thermal treatment (at 500 °C, for the controlled deposition of pyrolytic lignin) followed by the reforming of the volatile stream in a fluidized bed reactor. Specifically, the effect of co-feeding O ₂ before or after the thermal step was analyzed for oxygen-tocarbon molar ratio (O/C) in the 0.34-0.67 range. The catalytic step was kept at 700 °C, steam-to-carbon molar ratio (S/C) = 6.0, and space-time = 0.6 g _catalyst h(g _bio-oil) ^-1. When O ₂ is co-fed before the thermal step, there is a partial combustion of both, pyrolytic lignin and oxygenates, thus resulting a lower amount of oxygenated compounds entering the reforming reactor, although the composition of these oxygenates is not affected by the presence of O ₂ in the thermal step. As a result, a noticeable lower H ₂ yield was obtained when O ₂ is fed before the thermal treatment, although catalyst deactivation rate was similar to that obtained when co-feeding O ₂ after thermal treatment. Consequently, in the OSR of bio-oil in a two-step system, O ₂ must be co-fed after the thermal treatment step; in order to avoid bio-oil oxygenates oxidation prior to the reforming reaction.