Pillared laponite clays-supported palladium catalysts for the complete oxidation of benzene

Zr-, Ce-, and Al-pillared laponite clays (Al-Lap, Ce-Lap, Zr-Lap) were prepared and used as supports of palladium catalysts for the complete oxidation of benzene. The pillared clays and the supported Pd catalysts were characterized by N-2 adsorption/desorption, differential scanning calorimetry (DSC), hydrogen chemisorption and temperature-programmed reduction (TPR) techniques. The specific surface areas of the pillared clays exceed 430 m(2)/g, and the pore diameters are greater than 4 nm. DSC analysis revealed that the pillared clays have higher thermal stability in comparison with the parent clay. Palladium catalysts supported on the pillared clays are much more active than those supported on conventional alumina. Pd/Zr-Lap, in particular, could catalyze the complete oxidation of benzene at a temperature as low as 210degreesC. The effect of calcination temperature on the catalytic activity was investigated. The optimal calcination temperature was found to be 400degreesC for Pd/Al-Lap catalysts, and 600degreesC for Pd/Zr-Lap and Pd/Ce-Lap catalysts. At optimal calcination temperatures, palladium crystallites of proper size could be formed in pillared clays and showed a higher activity than those calcined at other temperatures. (C) 2004 Elsevier B.V. All rights reserved.