Understanding of NOx storage property of impregnated Ba species after crystallization of mesoporous alumina powders

Abstract The regulation of automobile exhaust gas, especially that concerning hazardous nitrogen oxide (called as NOx) becomes stricter year-by-year, which should be urgently corresponded for cleaning the NOx containing emission. According to surface affinity of γ-alumina to metal catalysts and its thermal stability, crystalline γ-alumina has been frequently utilized as catalyst supports showing relatively high specific surface area. From the viewpoint, we consider that highly porous alumina powders prepared using amphiphilic organic molecules are potential as such a catalyst support for improving NOx removing property. In this study, we report surface property of the mesoporous alumina powders against NOx molecules after crystallizing to its γ-phase and NOx storage property after impregnation of barium (Ba) acetate in the mesopores. Adsorption of NO with O2 on mesoporous γ-alumina powders without Ba species were more likely to be bridging bidentate than chelating nitrates (NO3-) with comparing to commercially available γ-alumina powders. After impregnating the Ba species, admitted NO molecules were oxidized with enough O2 and stored very strongly as ionic nitrate (NO3-) onto the Ba species even after heating at 500 °C. This preliminary study is helpful for designing mesoporous deNOx catalysts combined with unique storage/adsorption property.