Role of acetate and nitrates in the selective catalytic reduction of NO bypropene over alumina catalyst as investigated by FTIR

The mechanism of the selective catalytic reduction (SCR) of NO by C3H6 On A l2O3 was investigated using in situ IR spectroscopy. Attention was focused on the reactivity of the adsorbed acetate and nitrates on the Al2O3 surface . IR spectra showed that the reaction starts with the nitrates formation fr om NO + O-2 followed by its reaction with C3H6 to form acetate, which becom es the predominant surface species in the steady-state condition. The aceta te band, which was stable in He or NO, significantly decreased when the flo wing gas was switched to NO + O-2 A complementary set of experiments monito ring gas composition showed that N-2 and COx were produced by the reaction of acetate with NO + Oz. The rate of acetate consumption in NO + O-2 exhibi ted the same order of magnitude as the NO reduction rate, indicating that t he acetate is active as a reductant and takes part in the N-2 formation. Ni trates can oxidize both C3H6 and acetate, and are mostly reduced to N-2. A proposed reaction scheme explains the role of O-2 in facilitating SCR of NO .