アンモニアによる高活性な低温還元脱硝触媒の開発

―主にNH₄Br-Cu (II) -NaYゼオライト触媒の選定とその作用機構について―

抄録

For the purpose to develop high active catalysts for low temperature reduction of NO with NH₃, the effect of addition of halogenides (NH₄Br, NH₄I, NH₄Cl, HBr) to Cu (II) -exchanged Y-type zeolite, V₂O_x-activated carbon and V₂O_x-TiO₂ catalysts, etc. and the reduction mechanism were studied by the temperature programmed reaction and desorption methods.
The experiments on the reduction of NO were carried out by using a flow re'actor (I.D.: 12.0 mm) under atmospheric pressure and at 90-220°C. The average diameter of the granular catalysts was 1.0 mm. Inlet gas concentration was mainly 470 ppmNO-30 ppmNO₂-667 ppmNH₃-5%O₂-0 or 10%H₂O-N₂ and the total gas flow rate was 1000 Ncm³/min (space velocity: 4.0×104hr^-1) toward 1.5 ml (bulk volume) of the catalysts.
These results showed that NH₄Br-Cu (II) -NaY was found to be highly active and stable catalyst. Furthermore, the reduction mechanism over Cu (II) -NaY and NH₄Br-Cu (II) -NaY, the contribution of surface oxygen (= adsorbed oxygen+lattice oxygen) and adsorbed NH₃ to the promotion of reaction rate was clarified.