Comparison of oxidizing agents for the oxidative coupling of methane over state-of-the-art catalysts

The synthesis of selected state-of-the-art catalysts providing high performances in the oxidative coupling of methane (OCM) with O-2 was reproduced according to the respective recipes reported in literature. A reference material with identical stoichiometric composition was further synthesized by applying the cellulose templating method. This method increases the surface area and affects the phase composition and crystallite size of the catalysts as determined by N-2-physisoprtion. X-ray diffraction and scanning electron microscopy. This, however, is in most cases detrimental to the catalytic OCM performance due to enhanced global activity resulting in hot spots in the catalyst bed. Catalysts were tested in the OCM under variation of temperature (973-1073 K), GHSV (3600-100,000h(-1)) and oxidizing agent (O-2 and N2O). In general, conversions of CH4 when using N2O are lower than in the presence of O-2, however, the selectivities to C-2 products ethane and ethylene are higher even at a similar level of CH4 conversion. This confirms the presence of different oxygen species formed by activation of these oxidizing agents. (C) 2011 Elsevier B.V. All rights reserved.