An investigation of the NO/H-2/O-2 reaction on noble-metal catalysts at low temperatures under lean-burn conditions

The NO/H-2/O-2 reaction has been studied under lean-burn conditions at low temperatures. Maxima in the NO conversions have been observed for a Pt/Al2O 3 catalyst at 140 degrees C (50% conversion) and for a 1% Pt/SiO2 catalyst at 90 degrees C (75% conversion). The selectivity to N2O is sensitive to th e reaction conditions and decreases as the temperature is raised. Addition of water has a noticeable effect on both the activity and the selectivity f or the NO reduction reaction, with N-2 formation being significantly decrea sed when water is introduced into the reaction mixture. The effect of varyi ng the NO and H-2 concentrations has been examined. In general, increasing the NO concentration lowers the activity, whereas increasing the H-2 concen tration increases the activity for NO reduction. The effect of these concen tration changes on the selectivity to N2O is complex. (C) 1999 Elsevier Sci ence B.V. All rights reserved.