Precursor-Support Interactions in Silica-Supported Manganese Oxide Catalysts

Summary. Catalyst materials investigated in this study were obtained by calcination of impregnated silica with Mn(CH₃COO)₂·4H₂O and MnC₂O₄·2H₂O, so as to yield 10wt% Mn/SiO₂. The precursor compounds as well as pure and impregnated silica support were calcined at 600 and 1000°C in a static air atmosphere for 5h. Structural characteristics of the catalysts thus obtained were investigated by DTA, TG, XRD, IR and DRS. N₂ adsorption at –195°C was used for the assessment of surface texture of the test materials. Results of structural characterisation of catalysts obtained by calcination of manganese acetate-impregnated silica at 1000°C indicated the presence of strong silica-precursor interactions. Species of manganese silicates were detectable. Moreover, the decomposition of manganese acetate enhanced the transformation of amorphous silica into well crystallised -quartz. In contrast, Mn₂O₃, Mn₃O₄, and minor proportions of MnO were detected in the catalysts derived from the manganese oxalate-impregnated silica. This has been ascribed to much weaker precursor/support interactions in the oxalate-impregnated silica than the acetate-impregnated one.