Coprecipitation, perovskite preparation

Copper high Miller index, 26 12 Copper oxide, 27 184-187, 199 as adsorbent, 21 44 on alumina, 27 80-85 -manganese oxide, 27 91, 92 oxidation of CO over, 24 86 -platinum catalyst, 27 86-88 propylene oxidation, 30 141 Coprecipitation, perovskite preparation, 36 247-250... 

Wachowski et al. (42,43) have compared the surface areas of a series of eight perovskites prepared by different methods ceramic (<2.4 m2/g), coprecipitation as oxalates (4.5-11 m2/g), explosion (21-37 m2/g), and freeze-drying (22-39 m2/g). Again, surface areas clearly depended on the minimum temperature necessary for complete reaction. The greatest losses in surface area by sintering were observed in the temperature range 700-930°C. 

Calcination of the oxalate coprecipitates readily yielded phase-pure perovskite-type complex metal oxides. The required calcinations for the microemulsion-derived mixed oxalates were 100-250"C below the temperatures used for oxalates prepared in homogeneous aqueous solutions. 

The general formula of perovskites is ABO3, and soot combustion perovskite catalysts with many different cations have been reported for both A and B positions [7]. For instance, DoggaU et al. [8] prepared BaRuOs perovskites by coprecipitation method and its catalytic activity was tested for diesel soot oxidation with O2. The catalytic activity was attributed to the dissociative adsorption of oxygen on the catalyst surface, and was postulated that the 120 planes of BaRuOs can have abundant Ru atoms that can facilitate the O2 dissociation. The advantage of using this perovskite with regard to pure ruthenium oxide was attributed to the thermal stability of Ru within the BaRuOs matrix as well as basicity offered by Ba. 

---