Investigation of the influence of reaction parameters on Mn/Na2WO4/SiO2 catalyst for the oxidative coupling of methane

The influence of reaction parameters on the 2Mn/5Na(2)WO(4)/SiO2 catalyst for the oxidative coupling of methane was investigated and compared with the results of non-catalytic reaction. The effects of oxidant type (O-2 and N2O), CH4/O (1/1-4/1) ratio, GHSV (7500-37500 L kg(-1) h(-1)) and temperature (740-820 degrees C) were evaluated by using one variable at a time procedure. Activity tests showed that high C2 yields could be obtained at low CH4/O ratios and space velocities independent of the oxidant type (O-2 or N2O) and reaction medium (catalytic or non-catalytic) within the selected range of parameters. Continuous increase in temperature enhanced the C-2 yield especially when N2O was used during the reactions performed without catalyst. The highest C-2 yield was 16.4% with the catalyst at CH4/O=1, 7500 L kg(-1) h(-1) and 780 degrees C using O-2. It was found that the highest C-2 yield without the catalyst use was 10.1% at CH4/0=1, 7500 L kg(-1) h(-1) and 820 degrees C using N2O. The catalyst activity towards O-2 dissociation is well but poor for N2O decomposition. It was observed that the catalyst did not deactivate despite some sintering and phase changes during 8 hours.