Effect of calcination temperature on the structure and NO_x adsorption-reduction performance of Fe modified hydrotalcite-based Pt/BaO/MgFeO catalyst

In this paper, the iron-magnesium hydrotalcite-based catalysts with well dispersed noble metal for the lean NO_x trap (LNT) were prepared by co-precipitation and impregnation methods. The effects of different calcination temperatures on the catalyst structure and the adsorption-reduction performance for NO_x were investigated by analytical techniques. Results show that the crystalline structure of the catalysts remains stable when the calcination temperature is lower than 700℃. The sintering of the catalysts prepared and the conglobation of Pt particles appear on the catalyst surface after calcination at 800℃. With the increase in calcination temperature from 500 to 800℃, the desorption amounts of NO_x increases after an initial decrease, while the corresponding peak temperature show a marginal change. DRIFTs results indicate that the adsorbed NO_x species and the adsorption pathways over the catalyst after calcination at 800℃ differ from those at 500℃. The ratio of NH₃/N₂ released from the reduction of adsorbed NO_x species over the catalyst calcinated at 800℃ decreases in comparison with those calcinated at lower temperatures, which is responsible for the decrease in the NO_x conversion efficiency.