Detailed Investigation of Sm2O3 Catalysts with Different Morphologies for Oxidative Coupling of Methane

Sm2O3 catalysts with different morphologies (nanoparticle, nanorod, hollow nanosphere, nanofiber, flower-like) were synthesized and tested for the oxidative coupling of methane. The results obtained showed that increasing specific surface area reduced the activity, C-2 selectivity and, thus the yield. It was observed that the reaction initiation temperature was dependent on the total or partial oxidation of methane, which produced the heat for the initiation of the reaction. The effect of temperature on catalytic performance was relatively low at lower temperatures (<600 degrees C) than at higher temperatures (>700 degrees C). High reaction temperatures (>700 degrees C) decreased the C-2 selectivity, lower temperatures were found beneficial to achieve higher C-2 selectivity and yield as expected. Hollow nanosphere morphology showed the highest activity and selectivity at 450 degrees C and yielded 10.5 % C-2 under high space velocity. The highest C-2 yield (11.8 %) was obtained at 600 degrees C with nanoparticle morphology. Considering the results at the conditions that full oxygen conversion was attained, it was found that the C-2 selectivity and yield decreased with the nanoparticle>flower-like>nanorod and nanosphere>nanofiber sequence.