Fixed bed reactor design for gas phase chain reactions catalysed by solids: The oxidative coupling of methane

A multitubular catalytic fixed bed reactor for the oxidative coupling of methane is designed. A heterogeneous two-dimensional reactor model taking into account axial dispersion of mass and enthalpy is applied. A reaction network consisting of 36 gas phase radical reactions and 10 catalytic reactions, based upon experiments with an Sn/Li/MgO catalyst at atmospheric pressure, temperatures of 923-1,023 K and methane-to-oxygen ratios of 2-12, is used. Intrapellet concentration profiles of molecules and, even more so, of radicals are shown to affect the selectivity towards ethane and ethylene. The importance of homogeneous reactions in the void space between the catalyst pellets is highlighted. The reactor dimensions are determined by heat removal considerations.