バリウムヘキサアルミノガレートのNO_x浄化特性

抄録

NO/O₂ and NO/C₃H₆/O₂ reactions were investigated over barium hexaaluminogallate (Ba (Al, Ga)₁₂O₁₉ and BaCo (Al, Ga)₁₁O₁₉) with Al/Ga=9/3, 6/6 and 3/9 ratios. BaCo(Al, Ga)₁₁O₁₉ was synthesized by crystallization at 1100°C via the coprecipitation precursor powders prepared by aqueous metal nitrates and ammonium carbonate. The NO_x conversion amount in the NO/O₂ reaction over all hexaaluminogallates was less than 10%. The addition of C₃H₆ as a reductant gas significantly improved the NO_x conversion over BaCo(Al, Ga)₁₁O₁₉ in excess oxygen compared with that in the case of Ba(Al, Ga)₁₂O₁₉. The Al/Ga ratio influenced the morphologies and catalytic activities of hexaaluminogallate powders. With increasing Al/Ga ratio, the NO_x reduction with C₃H₆ to N₂ increased up to 40% and 28% for BaCo(Al, Ga)₁₁O₁₉ powders and Ba(Al, Ga)₁₂O₁₉ powders, respectively. Highly dispersed Co species are effective in accelerating the NO activation step in selective reduction with C₃H₆.