An experimental study on the oxidative coupling of methane in a direct current corona discharge reactor over Sr/La2O3 catalyst

The homogeneous and catalytic oxidative coupling of methane (OCM) for converting methane directly into higher hydrocarbons has been the subject of a large body of research. The present study on conversion of methane in de corona discharge packed bed reactors may significantly improve the process economics. Experimental investigations have been conducted in which all the reactive gases pass through a catalyst bed which is situated within the corona-induced plasma zone. In this study, a typical OCM catalyst, Sr/La2O3, was used to investigate experimentally the corona discharge OCM reactions. Experiments were conducted over a wide range of temperatures (823-1023 K) and input powers (0-6 W) with both positive and negative corona processes. Compared to the catalytic process in the absence of corona discharge, the corona discharge results in higher methane conversion and larger yield of C-2 products even at temperatures at which there is no C-2 activity for the catalyst alone. The methane conversion and C-2 yield increase with O-2 partial pressure during the corona-enhanced catalytic reactions, while the selectivity decreases slightly with increasing O-2 partial pressure. Compared to results obtained in the absence of corona discharges, methane conversion in the presence of the de corona was nearly five times larger and the selectivity for C-2 over eight times higher at 853 K. A great enhancement in catalytic activity has also been achieved at a temperature at which the catalyst alone shows no C-2 activity. The conversion at higher temperature (more than 953 K) is limited by the poor corona performance and the availability of active oxygen species.