Decomposition of methane and its reaction with CO 2 over Rh/ZSM-5 catalyst

Abstract

The decomposition of methane, its conversion into higher hydrocarbons and the reaction between CH4 and CO2 have been investigated on Rh/ZSM-5 in a fixed bed continuous-flow reactor. Independently of the temperature at 523–973 K, the decomposition of methane gave hydrogen, surface carbon and a small amount of ethane: ethylene and benzene were not detected. The reactivity of surface carbon formed at different temperatures has been examined toward H2, O2 and CO2. The carbon exhibited less reactivity toward CO2. The reaction between CH4 and CO2 occurred rapidly above 673 K to give CO and H2 with a ratio of 1.3–1.6. Very little carbon was deposited during the reaction. It is concluded that the facile reactions between CHx and CO2 are responsible for the lack of carbon deposition. However, a significant amount of carbon deposition and the deactivation of the catalyst occurred when more than 4–5% of ethane was added to the reacting gas mixture. The extent of deactivation can be decreased by using a large excess of CO2.