COALBED METHANE EVALUATION IN AUSTRALIAN COAL BASINS - A NEW LOOK AT COAL OPTICAL PROPERTIES
Dr. Sundaram Krishnamoorthy
University of California at Berkeley
Friday, May 11, 2001, 3:00 pm
Ben Bandy Conference Center
Center for Applied Energy Research
A step-by-step approach to the design of high activity Fe-based FisherTropsch synthesis (FTS) catalysts was applied by using promoters such as K, Cu and Ru to control the site density of active Fe carbide species. The presence of these promoters increased the reduction/carburization rates of Fe-Zn oxide precursors and also increased the FTS rates, which corresponded to an increase in the density of active sites.
The consistent correlation between the FTS rates and the density of CO binding sites on promoted Fe catalysts indicates that the effect of each promoter is essentially to produce a larger number of nucleation sites for the formation of smaller FeCx crystallites. These in turn led to higher density of active sites for CO adsorption/dissociation, promoted carburization, and hence increased FTS rates. In an effort to enhance the site density by increasing the surface area of the Fe oxide precursors, a high surface area Fe-Zn-K-Cu oxide catalyst was prepared using an alcohol instead of water as the surface-active component, to wash the Fe-Zn hydroxide precursors in order to minimize their decrease in surface areas due to the pore mouth pinching caused by the surface tension of intrapore liquids during the drying process.
The resulting highly dispersed Fe-Zn-K-Cu catalyst, when compared with a typical Co/SiO2 catalyst at conditions normally employed for Co-FTS catalysts, showed similar hydrocarbon productivities. This indicates that Fe-based catalysts, which are significantly less sensitive to FTS reaction conditions than Co catalysts, if prepared so as to be highly dispersed with appropriate choice of synthesis protocols, can provide active and selective alternative to Co catalysts.