Oxidative coupling of methane in a corona discharge plasma reactor using HY zeolite as a catalyst

Abstract

Oxidative coupling of methane in the presence of corona discharge plasma has been studied for the production of higher hydrocarbons under the conditions of ambient temperature and atmospheric pressure. The corona discharge was created by applying 3 kV (DC) between a tip and a plate electrode, 1.5 and 2.5 mm apart, in a tubular reactor. The effects of variables such as methane to oxygen ratio, total flow rate, electric current and more importantly, electrode gap distance were investigated. The electrode gap distance affected the electric field strength and subsequent plasma reactions. Five electrodes shaped like needles in the tip plate were applied to create more discharge intensity. At CH4/O2 ratio = 4, total flow rate = 4 mL/min, electric current = 10 mA and electrode gap distance = 1.5 mm, 31.9, 58 and 55 % of C2 yield, C2 selectivity and methane conversion, respectively were achieved. The main products were ethane, ethylene, acetylene, while CO and CO2 were also observed. The corona discharge interaction with HY-zeolite catalyst has led to low temperature methane conversion. Thus, the effect of surface modified zeolite catalyst was also examined. At a CH4/O2 ratio of 4 and total flow rate of 4 mL/min, 59.4, 69.7 and 85.3 %, of C2 yield, C2 selectivity and methane conversion, respectively were achieved. Experimental results revealed that corona discharge techniques, in the presence of HY-zeolite catalyst, has potentials for improving methane conversion, C2 selectivity and C2 yield.