Manganese oxide- based gold catalysts for low temperature CO conversion

Abstract

Initial investigations at Mintek, into the addition of gold to commercial hopcalite (CuxMnyOz), showed that it improved the activity of hopcalite. So this study was initially focused on investigating Aulhopcalite catalysts further. Also, since according to literature, MnxOy has catalytic potential, the study of AulMnxOy catalysts was included. Au/hopcalite and Aul/nxOy catalysts were made by means of deposition-precipitation, colloidal gold deposition and co-precipitation. Only one catalyst-type was highly active at room temperature - the co-precipitated Au/MnxOy catalysts. The optimised co-precipitated Au/MnxOy catalysts were more active than all the other catalysts by at least an order of magnitude. So the study focus changed, to make the optimisation of AulMnxOy catalysts a priority. Cerium is a well-known promoter on MnxOy catalysts, and so was also added to the co-precipitated Au/MnxOy catalysts. However, even small amounts of cerium had an adverse effect on the catalysts' activities. The compaction and crushing of a co-precipitated Au/MnxOy catalyst to obtain granules of larger particle size than the powders, was also carried out. The activities and surface areas of the catalysts were found to be comparable. This augers well for industrial purposes, since the use of powdered catalysts in industry is not viable.