Effect of Sequence of Impregnation on the Structure and Catalytic Properties of Cu-Co-Al-Oxide System

Twelve samples of Co-Cu/Al2O3 were prepared by impregnating Al2O3 with cobalt salt followed by copper salt or vice versa. The composition of the prepared samples varied in the molar ratios 1:1, 1:2 and 1:3 with respect to CuO:CoO or CoO:CuO, while Al2O3 content was kept at about 13-15 mol. The prepared solids were calcined at diflerent temperatures and the products were characterized by means of XRD-analysis. The catalytic activity of the calcined solids was tested in H2O2 decomposition. The XRD-analysis revealed that the sequence of impregnation affects much the structure of the samples. The loading of alumina with cobalt followed by copper salts produced sample with structure differs from that for sample firstly treated with copper followed by cobalt salts. XRD- analysis showed the formation of crystalline spinel Co1-x Cux Al2O4 with nearly the same crystal structure as CoAl2O4 even with high copper content. The examination of catalytic activity of these samples showed that catalysts with Co-loaded over Cu were more active than catalysts with Cu loaded over Co. In all cases the double oxides loaded over Al2O3 were more active than the single oxide over Al2O3.