Ceria-based oxides as supports for LaCoO3 perovskite; catalysts for total oxidation of VOC

摘要

Supported LaCoO3 perovskites with 10 and 20 wt.% loading were obtained by wet impregnation of different Ce1-xZrxO2 (x = 0-0.3) supports with a solution prepared from La and Co nitrates, and citric acid. Supports were also prepared using the "citrate method". All materials were calcined at 700 degrees C for 6 h and investigated by N-2 adsorption at -196 degrees C, XRD and XPS. XRD patterns and XPS measurements evidenced the formation of a pure perovskite phase, preferentially accumulated at the outer surface. These materials were comparatively tested in benzene and toluene total oxidation in the temperature range 100-500 degrees C. All catalysts showed a lower T-50 than the corresponding Ce1-xZrxO2 supports. Twenty weight percent LaCoO3 catalysts presented lower T-50 than bulk LaCoO3. In terms of reaction rates per mass unit of perovskite calculated at 300 degrees C, two facts should be noted (i) the activity order is more than 10 times higher for toluene and (ii) the reverse variation with the loading as a function of the reactant, a better activity being observed for low loadings in the case of benzene. For the same loading, the support composition influences drastically the oxidative abilities of LaCoO3 by the surface area and the oxygen mobility. (c) 2006 Elsevier B.V. All rights reserved.