Decomposition of methane and its reaction with CO2 over Rh/ZSM-5 catalyst

The decomposition of methane, its conversion into higher hydrocarbons and t he reaction between CH4 and CO2 have been investigated on Rh/ZSM-5 in a fix ed 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 H -2, O-2 and CO2. The carbon exhibited less reactivity toward CO2. The react ion between CH4 and CO2 occurred rapidly above 673 K to give CO and H-2 wit h 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 responsi ble for the lack of carbon deposition. However, a significant amount of car bon 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 deacti vation can be decreased by using a large excess of CO2.