(440a) Sulfur Species During Deactivation and Regeneration of Ni-Based Catalysts Used for Conditioning Biomass-Derived Syngas

For syngas conditioning catalysts used for hydrocarbon/tar steam reforming, short lifetimes are an obstacle that leads to high cost of the finished fuel product.  While there are many components of syngas that can contribute to catalyst deactivation, hydrogen sulfide (H₂S) is generally considered to be one of the most severe poisons. In order to overcome this deactivation challenge, it would be beneficial to have a catalyst that is i) resistant to deactivation and/or ii) can be readily regenerated. In the present work, we focus on the role of regeneration process on sulfur species found on the catalyst surface. We report sulfur surface chemistry during catalyst regeneration cycles on a Ni tar reforming catalysts used in real biomass-derived syngas with ~ 50 ppm H₂S. These results will be presented in terms of deactivation by sulfur poisoning, as well as other physical methods.  In the context of previous results for these samples, we will demonstrate the importance of the regeneration protocols, which we are in the process of developing. The appearance of sulfides that transform into sulfates using a steam/air regeneration will be shown, as well as the persistence of sulfates on the catalyst surface after they are formed. This work will be presented in the context of activity measurements, additional characterization, sulfur reaction mechanisms during regeneration, and schemes to more fully regenerate catalysts will be discussed.