Catalytic Effect of Ni and Fe Addition to Gasifier Bed Material in the Steam Reforming of Producer Gas
2014
Bambal, Ashish S. | Vecchio, Kenneth S. | Cattolica, Robert J.
The removal of tars from producer gas in a biomass gasification process is a challenging task, due mainly to the poor reforming activity of bed materials used in gasifiers. In this study, the steam reforming performance of Ni- and Fe-catalyzed gasifier bed materials is evaluated. Experiments are performed with the bimetallic catalysts, with overall metal loading as low as 1.00 wt %, in a lab-scale fixed-bed reactor between 700 and 900 °C. The addition of Fe to Ni results in smaller crystallites of NiO on the calcined catalysts. The reduced bimetallic catalysts show an improvement in the metal surface area and metal dispersion in comparison to the catalyst containing only Ni. The enhancement is possible with intimate contact of Ni and Fe, and it is found to be limited by their relative amounts. The catalyzed bed materials display higher conversion for C₇H₈ and C₂H₄ than the base material but lower CH₄ conversion. The steam reforming of the producer gas tars show strong dependence on the reaction temperature with the improved tar destruction performance at the higher reaction temperature. The catalytic steam reforming of tars also results in higher H₂-to-CO ratio. The higher turnover frequency (TOF) and the lower activation energy for the bimetallic catalysts than those for the Ni-only catalyst confirm the role of Fe in the activity enhancement of Ni catalysts. The spent catalysts characterization reveals that Fe assist in minimizing the sintering of the Ni crystallites during high-temperature calcination and steam reforming reactions.
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