Synthesis and characterization of Al2O3 and ZrO2-TiO2 nano-composite as a support for NO, storage-reduction catalyst

To improve the thermal stability of NOx storage-reduction catalysts, a novel support containing Al2O3, ZrO2, and TiO2 was synthesized by the coprecipitation method. The XRD and TEM results indicated that primary particles of gamma-Al2O3 and a solid solution Of ZrO2-TiO2 coexisted as secondary particles, that is, the synthesized support was a nano-composite of gamma-Al2O3 and ZrO2-TiO2. The synthesized support had a characteristic single meso-pore, derived from the structure of the secondary particle. The basicity of the synthesized support was lower than that of the physically mixed oxide. After thermal treatment, aggregation of the ZrO2-TiO2 particles in the support was inhibited relative to that in the mixture of Al2O3 powder and ZrO2-TiO2 powder. This was attributed to the diffusion barrier (against ZrO2-TiO2) created by primary Al2O3 in the synthesized support. After a thermal aging test, the NO, storage-reduction catalyst containing the synthesized support had a larger NOx storage capacity than the catalyst containing the physically mixed oxide. (C) 2007 Elsevier Inc. All rights reserved.