Preliminary Tests for a Kinetic Study of the Oxidative Coupling of Methane Over a 25% Ba/La2O3 Catalyst

Abstract

Abstract To perform a kinetic study of a catalytic system, low reactant conversions and isothermality are required. Test runs made over a 25% Ba/La 2 O 3 catalyst at 830 ° C, CH 4 /O 2 =10, showed that these two conditions demand important dilution both of the reactant gases and of the catalyst. Efforts have been made to find the influence of the homogeneous gas phase reactions in the free volume made up of the precatalytic zone, the dilution of catalyst, and the postcatalytic zone of a fixed bed reactor. Blank tests of a quartz filled reactor showed that the precatalytic volume is of negligible importance under catalytic conditions. Variations of the catalyst to diluent ratio at different gas space velocities showed that the conversion of reactant gases are uninfluenced by the homogeneous gas phase. At complete oxygen conversion, only C 2 H 6 to C 2 H 4 reaction took place in the gas phase, while at lower oxygen conversions, the selectivities changed towards CO x products. Variation of the post-catalytic volume showed that a larger volume here led to a lower CH 4 conversion. This is probably due to a formation of CH 4 from the products in the postcatalytic gas phase. This interpretation is supported by the observation that the C 2 /CO x ratio decreased with increasing post-catalytic volume even at complete oxygen conversion.