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Tar Reforming in Model Gasifier Effluents: Transition Metal/Rare Earth Oxide Catalysts

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journal contribution
posted on 14.05.2014, 00:00 by Rui Li, Amitava Roy, Joseph Bridges, Kerry M. Dooley
The removal of tars from syngas generated in biomass or coal/biomass gasifiers plays an important role in syngas cleanup. Rare earth oxides (REOs, e.g., Ce/LaOx) mixed with transition metals (e.g., Mn, Fe) were synthesized by various methods and in some cases supported on a thermally stable alumina. These catalysts were applied to tar removal in the temperature range <1100 K using synthetic syngas mixtures with C10H8 as a tar model compound, both with and without H2S. Some commercial Ni reforming catalyst formulations were examined comparatively. Fresh and used catalysts were characterized by XANES, XAFS, XRD, TPO, and BET. We found that the C10H8 is reformed to at least methane, although further reforming to CO and H2 is not always achieved. While CO2, H2S, and coke formation all inhibited or deactivated the catalysts at certain temperatures and to different extents, it was determined that Fe- or Mn-doped supported REOs are promising tar cleanup catalysts. They exhibited higher sulfur tolerance, less coking, and less methanation than typical Ni-based high temperature reforming catalysts. This behavior is in part attributed to enhanced generation of oxygen vacancies in the doped REOs.