Role of catalysts precursor anions in coal gasification. Ninth quarterly report, (October--December 1993)

摘要

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. In the previous report, the influence of acetate, chloride and nitrate ions, when using the corresponding potassium compounds, were discussed. In this report, the influence of catalyst loading on char reactivity is reported for potassium chloride, potassium carbonate or potassium sulfate catalyst precursors. The thermograms for the char preparation in nitrogen show that rapid devolatilization ((approximately)65 %wt.) 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 (8 %wt.) of carbon gasification of the unloaded, demineralized coal. For KCl. char reactivities at 0.59 and 1.75 %wt. potassium were essentially the same, 70.0 and 68.2 %wt., respectively. However, when K(sub 2)SO(sub 4) was used, the gasification activities were 48.9 and 59.4 %wt., respectively, for potassium contents of 1.65 and 2.44 %wt. In contrast, a higher reactivity (59.8 %wt.) was obtained at a potassium loading of 2.76 %wt than at a higher catalyst loading of 3.18 %wt. which gave a char conversion of 48.1 % wt. Thus, whereas some of the catalyst activities increase with catalyst loading, others decreased as the catalyst content was increased. This suggests that catalyst dispersion is high for catalyst contents of 0.59 or 2.44 %wt. potassium. Reduced catalyst dispersion appears to exist at the highest potassium content of 3.18 %wt. Thus, cataltytic activity is influenced by catalyst precursor type, the level of catalyst loading and catalyst dispersion.