COMPETITION BETWEEN THE GAS AND SURFACE REACTIONS FOR THE OXIDATIVE COUPLING OF METHANE 2. 'ISOTHERMAL' RESULTS IN CATALYTIC JET-STIRRED REACTOR

摘要

The reaction of methane oxidative coupling has been investigated through a jet-stirred and well-mixed catalytic reactor system over La_2O_3 catalyst. The reaction conditions are favorable for the obtaining of information on the initiation steps of the reactions, as low partial pressure of reactants and products, and low space time are employed. The catalytic surface performed as the generator of free radicals and hence the initiator of the free radical chain reactions. Experimental results show that there exists considerable competition between the catalytic and gas phase processes, and that the importance of gas phase reactions increases with the temperature. The results also lead us to conclude that the CO_2 mainly comes from the surface catalytic process in the temperature range below 750 °C, and that C_2H_4 is a secondary product coming from the oxidative dehydrogenation of ethane which most probably happens in the gas phase.