Model biogas reforming over Ni-Rh/MgAl2O4 catalyst. Effect of gas impurities

Autothermal biogas reforming is an attractive option for hydrogen production in small scale units. A Ni-Rh/ MgAl2O4 catalyst was developed that showed good long-term stability for autothermal model biogas reforming at 700 degrees C. The impact of different concentration of H2S or NH3 on the catalyst stability was studied for both autothermal and steam reforming conditions. The Ni-Rh/MgAl2O4 catalyst was characterized by TEM before and after exposure to H2S. The presence of H2S in the feed led to irreversible catalyst deactivation during autothermal reforming. During steam reforming, the catalyst activity can be restored by removing H2S or NH3 from the feed. A microkinetic model for steam reforming was adapted to take into account the catalyst deactivation by H2S or NH3. The model was validated against experimental data. The mechanism of H2S and NH3 adsorption on nickel could be deduced and described with physically meaningful parameters.