Organo-NOx formation–decomposition as the origin of the changes in the low temperature NO-TPD profile in the presence of n-decane on Ag/γ-Al2O3

• Excess release of NO, instead of NO2, was observed with concomitant n-C10 activation.
• Indirect evidence for the Ag-assisted formation–decomposition of organo-NOx species.
• This suggests the involvement of organo-NOx species as intermediates of n-C10-SCR.

The NOx desorption profiles obtained in O2–He and n-C10–O2–He were compared on γ-Al2O3 and Ag/γ-Al2O3. On Ag/γ-Al2O3, the low-temperature NOx desorption profiles obtained in n-C10–O2–He were significantly different from those obtained in O2–He. In particular, at 190–220 °C excess release of NO, instead of NO2, was observed concomitantly with n-C10 consumption. This is interpreted as the result of the formation–decomposition of organo-NOx species issued from the interaction of NO2 and hydrocarbons initially chemisorbed on Al2O3 and activated on Ag species, respectively. The occurrence of such a phenomenon at temperatures close to those at which the n-C10-SCR reaction starts provides support for the involvement of the organo-NOx species as intermediates.