A study of the effect of sulphation on iron oxide catalysts for methane oxidation

Sulphated and non-sulphated iron oxides derived from goethite have been compared as methane oxidation catalysts. It has been observed that sulphation increases surface area, suppresses low temperature total oxidation and enhances the formation of partial oxidation products. Characterisation of these materials prior to activity testing demonstrates that, although transformed into haematite, both exhibit a relic morphology related to that of their precursor and that sulphation causes extensive pitting of crystallites. Analysis of powder X-ray diffraction patterns indicates that the relic morphology is multidomainic and that sulphation increases line widths in relation to the non-sulphated system. The post-reactor sulphated samples were found to have lost crystallinity and both catalysts had changed phase from haematite to maghemite.