| 摘要 |
PROBLEM TO BE SOLVED: To efficiently remove NOx in dilute combustion exhaust gas. SOLUTION: Exhaust gas of an internal combustion engine operated in a dilute air/fuel ratio is brought into contact with a catalyst-containing bed. The catalyst-containing bed is constituted by arranging a catalyst A containing silica, an acidic anion, alumina, calcium, magnesium, strontium and/or barium and a catalyst B consisting of alumina and silver having a pore structure wherein Y is 70% of X or more and Z is 20% of X or less when the sum value of pore vol. occupying pores with a pore radius of 300Å or less is X, the sum value of pare vol. with a pore radius of 25-100Å is Y and the sum value of pore vol. with a pare radius of 100-300Åis Z so that the catalyst A and the catalyst B are arranged in an exhaust gas flow direction so as to be devided into front and rear stages. |
