Steam Gasification of Residues Catalyzed by Alumina-supported Potassium Carbonate and Calcium Oxide

Steam reforming of atmospheric, vacuum and solvent-deasphalting residues was investigated using a fluidized bed reactor, where alumina-supported potassium and calcium oxide catalysts were packed. Atmospheric residues were gasified with high efficiency on GaO above 850°C. The catalytic activity, however, decreased markedly with increasing Conradson carbon residue (CGR) of the feed residues. On the other hand, high activity of potassium catalyst was attained even in the gasification of very heavy residues from solvent deasphalting. The decrease in catalytic activity of CaO was not due to sulfur-poisoning of active sites, but was attributed to increasing carbon deposition or to decreasing reactivity of the deposited carbon. Carbon deposited on CaO, especially from residues having large CCR, was less reactive than carbon on the potassium catalyst. The mobility of catalytically active species in deposited carbon layers is a possible explanation for the superior catalytic activity of potassium to CaO.