Abstract: | On pulsing CH4 over MgO containing various amounts of praseodymium oxide (PrOx) at 1023 K, the CH4 conversion decreased with increasing pulse number, and both the initial activity and selectivity to C2 products (corresponding to the first pulse) decreased with increasing PrOx content. Characterization by XRD, SEM-EDX and XPS showed calcined materials to contain well-dispersed PrOx (x = 1·83–2) at low Pr concentrations, but only crystalline PrO1·83 at high (10 wt%) Pr concentration. A PrO1·83 phase was present at all Pr concentrations after the He treatment at 1023 K, and PrO1·83, PrO1·75 and PrO1·5 after reaction. © 1997 SCI |