Characterizing the Influence of Mn and K Promoters On the Carburization Rates and Performance Parameters of Fe-Based FT Catalysts by TPR-EXAFS/XANES and Catalytic Testing

Promoters exert an important impact on both activity and selectivity of Fe catalysts for Fischer Tropsch Synthesis (FTS). While Si has been proposed to prevent Fe particle sintering during reaction, Cu is suggested to increase Fe reducibility, while K enhances the selectivity towards olefins and high molecular weight hydrocarbons. Besides those classical promoters used in commercial Fe FTS catalysts, Mn has also been claimed as a promoter for light olefin selectivity, as well as for improving the sulfur tolerance. The aim of this work is to investigate the influence of Mn on both the structure and activity of Fe based FTS catalysts, with or without small amounts of K. Iron based catalysts containing different amounts of Mn were prepared by coprecipitation and tested in a stirred tank slurry reactor, at 270 oC, 175 psig (H:CO=0.7). The effect of Mn and Mn/K promotion on the catalyst carburization rate during activation in CO/He has also been studied by in situ EXAFS/XANES. Correlations between the structure and catalytic performance will be made.