Abstract
The pyrolysis and hydrogasification behavior of ion-exchanged nickel species supported on Loy Yang brown coal was studied. The evolution profiles of volatile components during pyrolysis and hydrogasification were affected by the amount of exchanged nickel species. For pyrolysis, two peaks of CO evolution appeared, one at 650-770K, depending on the amount of exchanged nickel species and the other at ca. 880K, comparable to a broader peak at 870K for an acid washed coal. The CO evolution peaks became larger with increasing nickel loading. The CO_2 evolution peak appeared at 650K and it became larger with increasing nickel loading, and a new CO_2 evolution peak appeared at 850K for the nickel loadings more than 4.2wt%, which was negligible for the acid-washed coal. The decomposition behavior of Loy Yang coal is explained by the aggregation behavior of nickel species. For hydrogasification, the peak of CH_4 evolution appeared at 860-1010K, depending on the amount of exchanged nickel species, became larger with increasing nickel loading. The total amounts of CO evolved were not enhanced by the presence of nickel, however, the maximum temperature shifted to 640-700K, depending on the amounts of exchanged nickel species, comparable to a broader peak at 810K for the acid washed coal. The CO_2 evolution peak at 650K became slightly greater with nickel loadings, but the peak top temperature did not change. Larger nickel metal particles catalyzed the CH_4 formation from the Loy Yang coal under hydrogen atmosphere.
