A comparative investigation of the reduction of NO by CH4 on Pt, Pd, and Rh catalysts

The effect of sodium on the Pd-catalyzed reduction of NO by methane

“…5(a) shows the`worst' case where the CO rate was $6 times less than the CO 2 rate. Here, our observations differ from those of Burch and Ramli [18] who found that over a wide temperature range CO was the principal carbon oxide, perhaps re¯ecting different support effects in the two cases.…”

“…For temperatures above $770 K, trace amounts of NH 3 were formed at high [CH 4 ] : [NO] ratios, in agreement with the ®ndings of Burch and Ramli for Pd/alumina and Pd/silica catalysts [18]. We also found that under all conditions used here, the main combustion product was CO 2 rather than CO.…”

“…5). However, in agreement with Burch and Ramli [18], we conclude that simultaneous elimination of NO and methane in exhaust gas under the same conditions is likely to be a dif®cult optimization problem.…”

“…Subramanian et al [17] reported high conversion efficiencies for Pd-based catalysts, and recent systematic studies of silica or alumina supported Pd, Pt and Rh catalysts have been reported by Burch et al [18,19]. Measurements were made both in the absence and in the presence of oxygen.…”

“…Burch et al concluded that Pt is effective for the removal of both reactants, although it may be difficult to optimize the simultaneous conversion of both under the same conditions. They also observed an influence of the support on the activity of all three metals, the effect being most pronounced in the case of Pd [18]. Electrochemical promotion (EP) [20] provides an alternative approach to the improvement of catalyst performance in NO x reduction.…”