Catalytic reduction of N2O over steam-activated FeZSM-5 zeolite: Comparison of CH4, CO, and their mixtures as reductants with or without excess O2

The catalytic reduction of N₂O by CH₄, CO, and their mixtures has been comparatively investigated over steam-activated FeZSM-5 zeolite. The influence of the molar feed ratio between N₂O and the reducing agents, the gas-hourly space velocity, and the presence of O₂ on the catalytic performance were studied in the temperature range of 475–850 K. The CH₄ is more efficient than CO for N₂O reduction, achieving the same degree of conversion at significantly lower temperatures. The apparent activation energy for N₂O reduction by CH₄ was very similar to that of direct N₂O decomposition (140 kJ mol^?1), being much lower for the N₂O reduction by CO (60 kJ mol^?1). This suggests that the reactions have a markedly different mechanism. Addition of CO using equimolar mixtures in the ternary N₂O + CH₄ + CO system did not affect the N₂O conversion with respect to the binary N₂O + CH₄ system, indicating that CO does not interfere in the low-temperature reduction of N₂O by CH₄. In the ternary system, CO contributed to N₂O reduction when methane was the limiting reactant. The conversion and selectivity of the reactions of N₂O with CH₄, CO, and their mixtures were not altered upon adding excess O₂ in the feed.