Abstract: NOx storage-reduction catalysts, Ba/(Pt/γ-Al2O3), were prepared by the impregnation method using Ba(NO3)2 and Ba(CH3COO)2 as the barium precursors. Characterization studies of the catalysts were performed by means ofX-raydiffraction,X-rayphotoelectron spectroscopy, temperature-programmed reaction desorption, and differential thermal analysis-thermogravimetry. The results indicate that the dispersion threshold of Ba(NO3)2 is 0.047 g/g (Ba/(Pt/γ-Al2O3) mass ratio), which is only about 1/3 of that ofBa(CH3COO)2. After the calcination treatment, the threshold of barium for the catalyst using Ba(CH3COO)2 as the precursor is larger than that using Ba(NO3)2 as the precursor. As a result, the Ba/(Pt/γ-Al2O3) catalyst prepared from Ba(CH3COO)2 has a higher NOx storage capacity than the catalyst prepared from Ba(NO3)2.

Key words: barium nitrate, barium acetate, nitrogen oxide, storage, monolayer dispersion, lean-burn