Catalytic activity of alkali and transition metal salt mixtures for steam-char gasification

Abstract

The catalytic activities of pure and mixed catalysts of alkali and transition metal salts in steam-char gasification at 700-850 degrees C were measured with a thermobalance. The effects of catalyst loading (0-35 wt%) and composition, coal rank and steam partial pressure were determined. The initial rate increases with increasing steam partial pressure in non-catalytic gasification but is almost independent of it in catalytic gasification. The catalytic activities of single salts are in the order K2CO3 > Ni(NO3)(2) > K2SO4 approximate to Ba(NO3)(2) > FeSO4. The gasification rate with K2SO4 can be enhanced by addition of other salts and the order of catalytic activity of the salt mixtures tested is K2SO4 + Ni(NO3)(2) > K2SO4 + Ba(NO3)(2) = K2SO4 + FeSO4. The char reactivity increases with increasing catalyst loading for K2SO4 + Ni(NO3)(2) and with gasification temperature. The catalytic effectiveness of K2SO4 + Ni(NO3)(2) decreases with increasing coal rank. An equimolar mixture of K2SO4 and Ni(NO3)(2) exhibits the highest catalytic activity and a synergistic effect.