| abstract |
A NOx absorbent comprising a crystalline compound oxide of ZrO2 of the following formula having at least one element selected from the alkali metals and alkaline earth metals, MmZr1-mOn where M is a earth metal supported thereon Rare trivalent selected from Sc, Y, La, Nd, Pm, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu, or a divalent alkaline earth metal selected from Mg, Ca, Sr, Ba and Ra , or any combination thereof; where 0.01 <m <0.5; and 1, 5 <n <2, 0. |