| 摘要 |
PROBLEM TO BE SOLVED: To provide a catalytic trap for causing NOx included in an exhaust gas stream in which lean conditions and stoichiometric or rich conditions periodically appear alternately to undergo conversion.SOLUTION: A catalytic trap includes: (a) a catalytic trap material including (i) a refractory metal oxide support on which catalytic components effective in promoting reduction of NOx under the stoichiometric or rich conditions of the exhaust gas stream are dispersed and (ii) a NOx sorbent that includes one or more kinds of basic oxygen compounds of alkali metals selected from the group consisting of lithium, sodium, and potassium, which adsorbs NOx under the lean conditions of the exhaust gas stream, and which is effective in desorbing NOx under stoichiometric or rich conditions of the exhaust gas stream, wherein other components included in the catalytic trap material are inert to the basic oxygen compounds; and (b) a refractory carrier member the top of which is covered with the catalytic trap material and inert to the basic oxygen compound. |
