Lean methane combustion over palladium loaded on alumina and HBETA zeolite : the role of the support on water vapour inhibition

Catalytic combustion of ventilation air methane is a potential solution for abatement of this greenhouse gas (GHG) source. A leading hypothesis for the observed catalyst deactivation of palladium-based catalysts when operating at low temperature is water poisoning. In this research, high silica BETA and alumina solids were used as supports for the Pd-based catalyst. The long term stability of methane conversion is significantly improved over HBETA compared to alumina supported Pd. TEM and chemisorption analyses confirms a greater level of dispersion of Pd in the HBETA compared to alumina support. TPD results shows that the Pd/Alumina catalyst adsorbs more water vapour at lower temperatures compared to Pd/HBETA resulting in an enhancement in the extent of water inhibition. Evidence for the presence of stored oxygen was observed in oxygen desorption results, where oxygen and water were co-adsorbed over the samples. This feature is also consistent with the supposition that Pd/HBETA has greater lattice oxygen mobility and a higher potential storage capacity compared to that of Pd/Al2O3. In addition, it was found that at lower temperatures, the effective surface coverage of oxygen was higher for Pd/HBETA compared to Pd/Alumina which was confirmed by TPD analysis