Abstract: A pretreatment-transient reaction product analysis method was applied to study the surface intermediate species in the selective catalytic reduction of NOx with C2H4 over the Co-ZSM-5 catalyst. The reactions of the surface species NCaObHc, formed by the pretreatment of Co-ZSM-5 in a NO/C2H4/O2 gas mixture at 275 ℃, with a NO/O2 flow produce much more N2 than that with a single NO or O2 flow. Apart from the oxygen content that cannot be determined under the experimental conditions, the average atomic ratio of N∶C∶H in the surface species was measured to be about 1.0∶1.8∶5.0 based on the product analysis by mass spectrometry, infrared absorption spectroscopy, and gas chromatography-mass spectrometry.

Key words: surface intermediate species, nitrogen oxide, ethylene, selective catalytic reduction, cobalt, ZSM-5 zeolite