The role of catalyst precursor anions in coal gasification. Eighth quarterly report, [July--September 1993

Abstract

This project investigates the roles of various aqueous soluble catalyst precursor anions, specifically acetate, chloride, nitrate, sulfate, and carbonate anions on the surface electrical properties of coal and seeks to understand the effects of these anions on the adsorption, dispersion and activities of calcium and potassium. The effects of the various anions on coal char gasification is currently under investigation. The influence of acetate, chloride and nitrate ions, when using the corresponding potassium compounds, are discussed in this report. The thermograms for the char preparation in nitrogen show that rapid devolatilization of moisture and other volatile materials occurs in the first 30 min. The rate of weight loss decreases significantly thereafter up to about 70 min. when char preparation was complete. Introduction of carbon dioxide after this time resulted in only a small amount of carbon gasification of the unloaded, demineralized coal. However, the chars containing the acetate, chloride or nitrate of potassium gave reactivities of 24.8, 30.4 or 24.3 %wt., respectively. The catalysts were ion-exchanged with the salt solutions and the corresponding potassium content were 2.9, 2.6 and 2.3 %wt. The higher reactivities of the catalyzed chars compared to the unloaded char correlates the high degree of demineralization and the resultant low catalytic activity by the inherent inorganic materials. It is observed that the potassium acetate and the potassium nitrate have similar reactivities, while the reactivity in the presence of KCl is higher. This finding contrasts some of the previous literature reports which show that oxygen-containing catalytic salts are more active catalysts due to the formation of carbon-oxygen-metal bonds which have been postulated as pre-requisites to carbon gasification.