VAM oxidation over palladium loaded on high silica BEA and MFI zeolites

![CDATA[The catalytic combustion of lean air methane in the presence of water vapour is investigated. High silica zeolites with MFI and BEA topology are used as support for the Pd-based catalyst. The thermal stability of 1% Pd/H-BEA (Si/Al=175), 1% Pd/H-ZSM-5 (Si/Al=140) and 1%Pd/Silicalite (Si/Al=1100) during methane conversion as a function of time on stream is examined. The results display slight reduction in activity for H-BEA, moderate deactivation for MFI silicalite and rapid deactivation for HZSM-5 catalyst over 40 hours’ time on stream. The deactivation indicates the presence of water vapour in the feed could be the primary factor of catalyst deactivation. BEA zeolite was shown to be more stable compared to the MFI structure catalyst over 40 h of time on stream. It is suggested that that the nature of BEA support facilitates a higher level of palladium particle distribution in compare to MFI. Also, the silicalite-supported catalyst demonstrated superior activity and stability to the HZSM-5, suggesting that increasing the ratio of Si/Al leads to a reduction in aluminium concentration and a more neutral framework which results in higher hydrophobicity and thermal stability. In order to have better understanding of catalyst performance, the stability results were supported by catalyst characterization such as N2-adsorption and desorption, ICP, XRD and TEM analyses.]]