Addition of manganese to iron catalysts supported on silicalite-1 and its effect on CO hydrogenation

Abstract

The addition of manganese to iron catalysts supported on silicalite-1 increases the selectivity of the catalysts to alkenes in CO hydrogenation. The catalysts were prepared by impregnating the support with metal nitrates followed by calcination and in situ reduction in hydrogen. The Mössbauer spectra of the calcined samples showed that the addition of manganese reduced the size of the α-Fe₂O₃ particles. This was confirmed by XRD and TPR results. The active phase consists of Hägg carbide and some oxides of Fe^{I I I}, the latter being responsible for the increased alkene formation. The role of manganese is to reduce the particle size of the iron oxide precursor, making carburization unfavourable. This leads to an increase in the amount of the oxide phase in the catalyst, thereby increasing the selectivity to alkenes.