Role of oxygen in the SCR of NOx with propane over Co/ZSM-5: Reaction and TPD study

Abstract The roles of oxygen in selective catalytic reduction (SCR) of nitric oxide with propane were studied for Co/ZSM-5 catalysts with different cobalt loadings. The catalytic activities in the NO+C 3 H 8 +O 2 , NO+O 2 , and C 3 H 8 +O 2 reactions were compared in conjunction with catalyst characterization by TPD of NO and TPR. The data obtained reveals multiple roles of oxygen that depend on the structure of the catalyst. It was found that for the catalysts containing cobalt oxide species NO 2 formation plays important role in the SCR of NO. The catalysts that contain only isolated Co 2+ ions were found to be inactive in NO 2 formation. Nevertheless, these catalysts also exhibit relatively high NO x conversion albeit at higher temperature, and their SCR activity was found to be strongly promoted by oxygen. TPD of NO adsorbed on the catalyst precovered with oxygen indicates that oxygen preadsorption decreases the strength of NO adsorption, thus improving the activity.