Applied Catalysis, 62 (1990) 253-269 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJI Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands 253 zyxwvuts Effect of Pressure on the Oxidative Coupling Reaction of Methane ALFRED EKSTROM*, ROBERT REGTOP and SURESH BHARGAVA CSIRO Division of Fuel Technology, Private Mail Bag 7, P.0. Menai, NSW, 2234 (Australia), fax (+61-2) 543 6774. (Received 2 October 1989, revised manuscript received 6 February 1990) ABSTRACT Increasing the pressure in the oxidative coupling reaction of methane significantly increases the importance of the blank or uncatalysed reaction. The effect is so large that, at 0.4-0.6 MPa and low gas velocities, the only significant effect of the catalyst is to alter the CO/CO, ratio in the product stream. The importance of the blank reaction can be reduced by using high linear veloc- ities, but increasing pressure under these conditions still depresses the C,, selectivity of the catalysts. Keywords: methane oxidative coupling, pressure effect, blank reactor studies, selectivity (C2+ hydrocarbons). INTRODUCTION The oxidative coupling of methane to produce ethane, ethylene, small amounts of higher hydrocarbons, carbon dioxide, and carbon monoxide has recently attracted wide attention [l-5], because it offers the potential for de- velopment of a new process for the conversion of remote natural gas to liquid fuels, or, perhaps, ethylene [6-S]. Several comprehensive process and eco- nomic analyses of this reaction have stressed the importance of achieving both high per pass methane conversion and C 2 + selectivity [9-l 13. Implicit in these analyses has been the assumption that the high conversions and selectivities would be achieved at elevated pressures. Despite its apparent importance for process development, no detailed stud- ies of the effect of reaction pressure on the methane conversion and C,, selec- tivity appear to have been described. Hutchings et al. [ 121 reported that if the oxidative coupling reaction was carried out at 0.59 MPa at low (560°C maxi- mum) temperatures, the presence of a Li/MgO catalyst made little difference zyxwvuts 0166-9834/90/$03.50 0 1990 Elsevier Science Publishers B.V.