CO<sub>2</sub> Gasification of Petroleum Coke with Metal Hydroxide Catalysts

Abstract

Gasification of petroleum coke with metal hydroxide catalysts has been carried out in CO2 at 850°C with a thermobalance. KOH is impregnated with coke, and Ca(OH)2 and fine particles of FeOOH are separately mixed with coke in water, metal loading being 3wt% in every case. Fixed carbon conversion excluding volatile matter was 7% and 55% after 120min without and with Fe, respectively, and it reaches 100% after 60min and 70min with K and Ca, respectively. Thus, K and Ca catalysts can promote the gasification remarkably. Initial rates per remaining carbon with K and Ca are as great as 50 and 100 times that without catalyst, respectively. The extent of rate enhancement by K addition is larger at the latter part of reaction, because the rate of K-catalyzed gasification increases exponentially with increasing fixed carbon conversion. When the samples after 50% conversion are subjected to X-ray diffraction measurements, the K is most highly dispersed among the three catalysts, and their presence lowers carbon crystallinity, irrespective of type of catalyst. Since inexpensive Ca(OH)2 is remarkably effective by simple mixing with coke in water, and is higher in thermal stability than KOH, which is known to vaporize readily as metal as the gasification proceeds, it can be concluded that the Ca is the most promising catalyst in coke gasification.