Surface species during catalytic reduction of NO by propene studied by in situ IR-spectroscopy over Pt supported on mesoporous Al2O3 with MCM-41 typestructure

The selective catalytic reduction of NO by propene (HC-SCR) in the presence of excess oxygen over Pt/MCM-41 (Al2O3) and MCM-41 (Al2O3) catalysts has b een studied by simultaneous in situ IR-spectroscopy and catalytic activity measurements. IR-spectra of Pt/MCM-41 (Al2O3) and MCM-41 (Al2O3) were compa red during the adsorption of the single reactants (NO and C3H6) and during the NO reduction With C3H6 in presence of excess O-2 (NO + C3H6 + O-2 react ion). The adsorption of NO resulted in the formation of surface nitrate spe cies on the Al2O3 support and surface NO species on Pt. Adsorption of prope ne led to the formation of carboxylate species on Al2O3. Under reaction con ditions nitrates, carboxylates, acetates, hydrocarbon fragments, isocyanate , cyanide species and CO were present on the catalyst surface. The surface concentration of the isocyanate species was found to be strongly correlated to the activity of the Pt/MCM-41 catalyst. Besides the formation of isocya nate, cyanide species were also observed on the surface. Both species incre ased in concentration with increasing oxygen concentration in the feed. The isocyanate species were found to be a reaction intermediate during the NO reduction, whereas the cyanide species were stable against further reaction . For the cyanide formation, a reaction pathway via isocyanate. by abstract ion of an oxygen atom by propene was observed. (C) 2001 Elsevier Science B. V. All rights reserved.