Oxidative pyrolysis of natural gas in a spouted-bed reactor: reaction stoichiometry and experimental reactor design

ii simple reaction network is developed to understand methane oxidative pyr olysis in a spouted-bed reactor. Oxidative pyrolysis for converting natural gas is attractive because it gives high methane conversions (80-90% per pa ss) at high selectivities to C2+ (40%) and carbon monoxide (40%). Based on results reported in a British Petroleum patent, our analysis shows that oxi dative pyrolysis is a combination of methane partial oxidation to carbon mo noxide which produces heat and of methane pyrolysis to C2+ (mostly ethylene and acetylene) which consumes heat. The methane pyrolysis reaction is ther modynamically Limited and requires temperatures above 1000 degrees C for si gnificant conversion. A pilot-plant oxidative pyrolysis reactor was designed from cold flow studi es to verify the BP results obtained at atmospheric pressure and to establi sh process feasibility at higher pressures. Scoping economic studies show t hat higher pressure operation is needed to avoid costly product compression in downstream upgrading processes. The pilot-plant spouted-bed reactor evo lved from a fragile quartz tube to a more robust one of stainless steel. Th e stainless steel performs similarly to the quartz reactor when the walls a re coated with an aluminum oxide layer to passivate inherent catalytic acti vity. Although a number of experimental challenges remain, initial runs hav e been successful in demonstrating that our method of preheating the feed s uccessfully ignites the reaction and that our analytical technique gives ex cellent closure in detailed material balances. Based on results presented in this paper ways are needed to improve on BP C 2+ yields, such as by process variable optimization and rapid thermal quenc h to minimize undesirable secondary pyrolysis reactions. (C) 1998 Elsevier Science B.V. All rights reserved.