A study of the mechanism for NOx reduction with ethanol on γ-alumina supported silver

A multistep mechanism has been elucidated for the reduction of NO, in the presence of added ethanol over Ag/gamma-Al2O3 at 320 degrees C. Under these conditions, ethanol principally reacts with oxygen to form acetaldehyde. Surface acetate ions, which are formed from adsorbed acetaldehyde, react with NO2 to yield nitromethane. Evidence is presented indicating that the aci-anion of nitromethane is an intermediate. In contrast, NOx reduction with ethanol over Ag/gamma-Al2O3 at 200 degrees C is inefficient, because surface acetate ions are much less reactive at 200 degrees C than at 320 degrees C. At 200 degrees C, the dominant pathway for ethanol oxidation is reaction with NO2, producing ethyl nitrite, which decomposes into a number of products, including N2O, which is stable under reaction conditions. On the basis of these mechanistic data, conditions can be defined under which NOx reduction with ethanol may be viable. (c) 2005 Elsevier Inc. All rights reserved.