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

Abstract

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 ºC; space time, 0.15-0.6 gcatalysth/gbio-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.