Selective catalytic reduction of NO by propane over CoOx/Al2O3: an investigation of the surface reactions using in situ infrared spectroscopy

Abstract

The partial oxidation of propane and the mechanism of the selective catalytic reduction (SCR) of NO by C₃H₈ over CoO_x/Al₂O₃ catalysts were investigated using in situ infrared spectroscopy. Emphases are placed on the formation and reactivity of surface oxygenates during the SCR reaction. The SCR reaction starts with partial oxidation of propane to adsorbed acetate and formate. Impregnation of cobalt onto alumina greatly enhanced this reaction. The as-formed acetate acts as an efficient reductant for NO reduction. Surface nitrates (nitrites) are also reactive to propane and to oxygenates generated from C₃H₈ + O₂ reaction. Surface –NCO species are formed over CoO_x/Al₂O₃ catalysts. These nitrogen containing organic species are believed to be the direct intermediates in the final formation of N₂. On the basis of these investigations, a proposed reaction mechanism explains the formation and roles of all intermediates detected by IR spectroscopy in this study.