Reaction conditions effect and pathways in the oxidative steam reforming of raw bio-oil on a Rh/CeO₂-ZrO₂ catalyst in a fluidized bed reactor

A reaction scheme has been proposed for the oxidative steam reforming (OSR) of raw bio-oil on a Rh/CeO₂-ZrO₂ catalyst, based on the study of the effect reaction conditions (temperature, space time, oxygen/carbon ratio and steam/carbon ratio) have on product yields (H₂, CO, CO₂, CH₄, hydrocarbons). The runs were performed in a two-step system, with separation of pyrolytic lignin (first step) followed by catalytic reforming in a fluidized bed reactor (second step), under a wide range of reaction conditions (600–750 °C; space time, 0.15–0.6 g_catalysth/g_bio-oil; oxygen to carbon molar ratio (O/C), 0–0.67; steam to carbon molar ratio (S/C), 3–9). The catalyst is very active for bio-oil reforming, and produces high H₂ yield (between 0.57 and 0.92), with low CO yield (0.035–0.175) and CH₄ yield (below 0.045) and insignificant light hydrocarbons formation. The proposed reaction scheme considers the catalyzed reactions (reforming, water gas shift (WGS) and combustion) and the thermal routes (decomposition/cracking and combustion). The deactivation of the catalyst affects progressively the reactions in the following order: CH₄ reforming, hydrocarbons reforming, oxygenates reforming, combustion and WGS.