Abstract
This research uses three techniques to study catalyzed gasification of carbon in an effort to determine the concentration of catalyst sites on a carbon surface and thus determine how effectively a catalyst is utilized for steam gasification. Both alkali and alkaline earth oxides are effective catalysts for accelerating the gasification rate of coal chars, but in many cases only a fraction of the catalyst is in a form that is effective for gasification. We will study the steam gasification of carbon in order to determine the concentration of active catalyst sites, the composition of the catalyst, and the location of the catalyst on the surface. Transient isotope tracing (switching reactant feed gases between H{sub 2}{sup 16}O and H{sub 2}{sup 18}O) will be used to measure the concentration of sites at steady-state reaction conditions. A steady flow of H{sub 2}{sup 16}O in He, will be replaced by H{sub 2}{sup 18}O in He, while maintaining the same reaction rate, and the change in product signals will be detected with a computer-controlled mass spectrometer. Secondary ion mass spectrometry (SIMS) will be used for both high surface area samples of carbon/carbonate mixtures that are heated in steam to various temperatures and for model surfaces with deposited ions. Scanning tunneling microscopy (STM), will be used to determine catalyst dispersion and the location of catalyst on the surface. Carbon black, graphite, and coal char will be used in the transient tracing experiments. Both K and Ca catalysts will be used.
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