Dynamics of Mn/Na2WO4/SiO2 catalyst in oxidative coupling of methane

The dynamics of Mn-Na2WO4/SiO2 catalyst in oxidative coupling of methane (OCM) was investigated by transient experiments at a temperature range of 700-850 degrees C. Both the on-line analyses by GC-MS and off-line analyses by multi-port sampling valve were employed. The fully oxidized catalyst was exposed to concentration step-change of CH4 from 0.0% to 10% in Ar and the rate of consumption of CH4 and the rate of formation of OCM products were monitored. The results reveal that the catalyst has stable redox properties and provides its lattice oxygen for the reaction. Both hydrocarbon products and carbon oxides are formed in the absence of gas-phase oxygen. The reduced catalyst gets fully oxidized when exposed to gas-phase oxygen and recovers its activity to initial activity quite fast. The catalyst does not deactivate during consecutive reduction-oxidation cycles and can be used for cyclic mode of operation to obtain high C yield. (C) 2007 Elsevier Ltd. All rights reserved.