Preparation and characterisation of Mn- and Co-supported catalysts derived from Al-pillared clays and Mn- and Co-complexes

Abstract

Mn and Co catalysts (≈10wt.% as MnO2 or Co3O4) supported on Al-pillared clays (two saponites and a montmorillonite) have been prepared by wetness impregnation, using complex salts of the metals (Co(II) acetylacetonate, tris(ethylenediamine) Co(III) chloride, Mn(II) acetylacetonate and Mn(III) acetate dihydrate) as precursors. The incorporation of these metals onto the clays by co-intercalation of AlMn and AlCo solutions was also considered, but this method was not useful to prepare the catalysts since only very small amounts of Mn or Co were fixed. All the solids have been thoroughly characterised (elemental chemical analysis, XRD, TG-DTA, FT-IR and UV-Vis spectroscopies, nitrogen adsorption, TPR and SEM). Impregnation led to solids which, in most cases, maintained the layered structure of the supports. However, their specific surface area markedly decreased due to blocking of the layered galleries by the organic moieties of the ligands. The surface area of some impregnated solids increased upon calcination at 500°C due to removal of the organic moieties. Dispersed Mn2O3, Mn3O4 and Co3O4 particles were present in the calcined catalysts.