Preparation and characterisation of activated Ni (Mn)/Mg/Al hydrotalcites for combustion catalysis

The Ni-Mg-Al and Mg-Mn-Al hydrotalcite-like compounds with various Ni and Mn contents (molar ratios Ni:Mg:Al in hydroxide layers of 4:0:2, 3:1:2, and 2:2:2 and Mg:Mn:Al of 4:2:0 and 4: 1: 1, respectively) were prepared by coprecipitation. The products were characterised by chemical analysis and X-ray diffraction (XRD) measurements. After calcination at different temperatures, the properties of the resulting oxides (surface area, porous structure and surface concentration of metals by XPS) were examined. From the catalysts calcined at 800degreesC the Ni(4)AI(2) sample showed the highest surface area and the highest catalytic activity. The oxidation activity in methane combustion (related to the surface area of mesopores) depended on the amount of surface nickel or manganese component linearly. The lower activity of manganese over nickel in methane combustion was proved. (C) 2002 Elsevier Science B.V. All rights reserved.