Plasma assisted oxidative coupling of methane (OCM) over Ag/SiO2 and subsequent regeneration at low temperature

Abstract In this study, oxidative coupling of methane (OCM) was carried out to produce C 2 and C 3 hydrocarbons directly from methane in a plasma-catalyst hybrid system. Since catalyst only reaction requires high temperature above 700 °C, dielectric barrier discharge (DBD) plasma was applied as plasma source to lower the reaction temperature. Among various supports, only SiO 2 showed the higher yield than plasma only reaction when combined with DBD plasma, which led us to focus on the SiO 2 -based catalyst. It was found that Ag/SiO 2 demonstrated the highest C 2+ hydrocarbon yield of about 9.7% at 385 °C. In this process, oxygen was proved to play an essential role in the coupling of methane to C 2+ hydrocarbons over Ag/SiO 2 catalyst. However, Ag/SiO 2 catalyst under plasma condition became deactivated with time-on-stream because of coking. It was demonstrated that plasma regeneration at 378 °C gave rise to the full recovery of activity while thermal regeneration did not due to the partial removal of coke and the sintering of Ag.