Synthesis and testing of active and water resilient low temperature methane combustion catalysts

We report on the synthesis and testing of robust nanocatalysts for low temperature methane combustion. The Pd-CeO2 based catalyst supported on Al2O3 was synthesized via a one-step solution-combustion synthesis (SCS) method and characterized by the analytical techniques of HRTEM, XRD, BET, XPS and TPDRO. Contrary to the catalyst prepared by core-shell and co-precipitation methods, the Pd-S catalyst synthesized by SCS method exhibited superior activity for methane decomposition and excellent resilience to water poisoning in the feed. The exceptional high activity of the Pd-S catalyst can be attributed to smaller well dispersed metal nanoparticles, stronger metal support interactions, presence of surface defects and induced phases resulting in excellent oxygen mobility. The light-off curves of the Pd-S catalyst were also different and revealed the presence of three distinctive regions: the high temperature region (above 400°C) was characterized by 100% activity presumably exhibiting the Mar-van Krevlen mechanism. The second region of the light off curves lied between ~300 and ~ 400°C, where the catalytic activity gradually decreased with decreasing the temperature. Methane oxidation in this region is believed to follow the Langmuir-Hinshelwood mechanism. The third region extends from ~200°C down to ~300°C, characterized by exponential decay in activity with decreasing temperature.