Kinetic effect of oxygen incorporation into the catalytic steam reforming of biomass fast pyrolysis volatiles

Continuous steam reforming of biomass pyrolysis volatiles has been approached under oxidative conditions in a bench scale lab unit, and a kinetic model has been proposed for the assessment of the results obtained and prediction of process performance. The pyrolysis and in-line oxidative steam reforming (P-OSR) has been performed in a two-step system consisting of a conical spouted bed reactor (CSBR) for the pyrolysis process and a fluidized bed (FBR) for the reforming one. The OSR process was carried out on a commercial Ni based catalyst, in the 600-700 degrees C temperature range, with space time values between 2.5 and 20 gcat min gvolatiles-1 , a steam/biomass ratio of 3 and an equivalence ratio (defined based on the volatiles fed into the reforming step) of 0.12. The reaction scheme considered for the kinetic modeling accounted for five reactions, which are the steam reforming of bio-oil oxygenate compounds, C2-C4 hydrocarbons and methane, the WGS reaction and the oxidation of hydrogen. A comparison of the kinetic results obtained in this study with those in a previous one dealing with the steam reforming of biomass pyrolysis volatiles (P-SR) under non-oxidative conditions shows substantial differences. Thus, the kinetic constant determined for bio-oil steam reforming is from 2.6 and 4.1 times higher when the process is conducted with oxygen. By contrasting the experimental conversion and H2 production values obtained in P-SR with those obtained in P-OSR, a synergistic effect of O2 addition on the reforming process is evident when operation is conducted under partial conversion conditions.