Oxidative coupling of methane using microwave dielectric heating

Abstract

Microwave heating was applied in the oxidative coupling of methane to higher hydrocarbons over alumina supported La 2 O 3 /CeO 2 catalysts. It was found that microwave heating had a dramatic effect on the reaction when methane was converted into C 2 hydrocarbons in the absence of oxygen, with products produced at measured temperatures about 250 • C lower than those observed with conventional heating. It was shown that the reaction in the absence of oxygen occurred primarily in the gas phase and it was the localised heating of the methane that was responsible for the increased reaction rate. However, it was observed that microwave heating did not produce significant "special microwave effects" which affected the product species formed when the oxidative coupling reaction occurred in the presence of oxygen.

Microwave assisted heterogeneous catalysis: effects of varying oxygen concentrations on the oxidative coupling of methane

“…The catalytic reaction was carried out with a laboratory-scale, continuous flow reactor system equipped with facilities for both microwave and conventional heating [6,17]. Briefly, a tubular packed-bed quartz reactor (inner diameter, 10 mm) was placed in either a cylindrical microwave cavity or a conventional furnace.…”

“…The main compounds analyzed by gas chromatography included methane, ethane and ethylene. The GC peaks were also calibrated using gas mixtures of known concentrations [6].…”

“…The conversion of methane, which is the major constituent of natural gas, into value-added chemicals has increasingly received attention in recent years [1][2][3][4][5][6][7][8][9]. Among the processes studied, oxidative coupling of methane (OCM) has shown a promising alternative route to convert methane directly into higher hydrocarbons [1][2][3][4][5][6][7], while extensive studies has been focused on converting methane into synthesis gas [8,9], which can then be converted to higher hydrocarbons through the Fischer-Tropsch chemistry [9].…”

“…Among the processes studied, oxidative coupling of methane (OCM) has shown a promising alternative route to convert methane directly into higher hydrocarbons [1][2][3][4][5][6][7], while extensive studies has been focused on converting methane into synthesis gas [8,9], which can then be converted to higher hydrocarbons through the Fischer-Tropsch chemistry [9]. In the OCM process, methane and oxygen are generally fed over a metal or metal oxide catalyst at moderate temperatures (500-800°C) to produce mainly ethane and ethylene.…”

“…In our previous study [6] the OCM reaction was investigated by comparing microwave dielectric heating and conventional heating methods. The catalysts used under different conditions were examined with a range of catalyst characterization techniques.…”