In situ Moessbauer investigation of iron oxide catalyst in water gas shift reaction - Impact of oxyreduction potential and temperature

The aim of the study is to obtain the exact state of iron oxide catalyst active phase in reaction conditions, as well as the correlation between the active phase and catalytic properties of iron-containing catalysts. In situ Moessbauer spectroscopy is the major investigation technique. It is established that the change of reaction conditions (temperature and gas reaction mixture) lead to redistribution of the relative weight of spectra components and influence mainly tetrahedrally and octahedrally coordinated cations in Fe3O4 phase. It was concluded, that the active sites of the catalyst in studied reaction are probably pairs of Fe3++Fe2+-(Fe2.5+) ions, i.e. the mixed valance iron ions. The obtained catalytic activity can be explained with combination of the natural thermo-activated and catalytically induced electron exchange and better synchronizing of oxidation and reduction steps of the catalytic reaction.