Influence of gas atmosphere and role of tar on catalytic reforming of methane and tar model compounds: Special focus on syngas produced by sorption enhanced gasification

Abstract

Combining sorption enhanced gasification (SEG) of biomass with a downstream reformer leads to high-quality syngas for hydrogen production and synthesis applications. Reforming of methane and tar model compounds (toluene and naphthalene) at various parameters and in simulated SEG environments was thus examined for reaching maximum conversion of hydrocarbons to enhance H2/CO production. This was studied by means of thermodynamic analyses and experiments using a Ni-based catalyst in a fixed bed reformer. Simulation and experimentation indicate that the high steam-to-carbon ratio of SEG syngas promotes the high conversion of hydrocarbons. The high hydrogen concentration inhibits the methane-steam reaction but improves CO yield. Experimentally, the presence of tar model compounds at 600 °C reduced methane conversion by approximately 30%, and deactivation of catalysts by carbon formation was detected. The deactivation resulted in significant drops in toluene and naphthalene conversions over time, while methane conversion remained almost stable. Furthermore, the heavier tar compound, naphthalene, showed an inhibition effect on toluene and methane reforming. The results implicate the significance of studying different hydrocarbons in the reforming process. Overall, to completely convert all hydrocarbons in the SEG syngas for more H2/CO production, a high reforming temperature of 800 °C for the applied Ni-based catalyst is recommended. No additional steam is required in a reformer due to the typical composition of SEG syngas.