Characterization of lithium and cesium modified zeolite catalysts in the oxidative conversion of methane Original Research Article

By ion exchange of the X zeolite with lithium and cesium it is shown that the performance of the resulting catalysts depends on the alkali cation type, the way of catalyst treating after the ion exchange procedure (washing or not), and the reaction conditions. The most effective catalyst as regards C2-selectivity is found to be CsX, left unwashed after the ion exchange. Short contact times, high CH4/O2 ratios, reaction temperatures of not more than 800°C are conditions favouring the C2 selectivity and stability of CsX-unwashed catalysts. The significant catalytic performance of the latter is related to the basicity, as well as to the stabilization of the zeolite framework, caused by the suitable alkali presence. This relation is revealed by TPD of CO2, DTA and IR spectroscopy.