Adsorption, Coadsorption, and Reaction of Acetaldehyde and NO2on Na−Y,FAU: An In Situ FTIR Investigation

The adsorption of acetaldehyde and its coadsorption and reaction with NO 2 were investigated on a Na−Y,FAU zeolite using in situ FTIR spectroscopy. Acetaldehyde adsorbs strongly over Na−Y and desorbs molecularly at around 400 K with very limited extent of condensation or polymerization. Reaction between CH 3 CHO and NO 2 takes place in coadsorption experiments even at 300 K. In the initial step, acetaldehyde is oxidized to acetic acid accompanied by the formation of NO, which can be observed as N 2 O 3 formed via a further reaction between NO and NO 2 . The key intermediates in the overall NO x reduction in this process are nitromethane and, possibly, nitrosomethane, which form in the next step. Their decomposition and further reaction with adsorbed NO x species lead to the formation of HCN, HNCO, N 2 O, CO 2, and organic nitrile species identified by their characteristic IR vibrational signatures. At 473 K, the reaction between adsorbed CH 3 CHO and NO 2 is very fast. The results seem to suggest a mechanism in which N−N bond formation takes place among ionic nitrogen containing species (NO + and CN - or NCO - ). No evidence has been found to suggest the participation of NH x + NO y - type species in the N−N bond formation under the experimental conditions of this study, although their role in the overall N 2 formation process cannot be ruled out under realistic catalytic conditions.