A multi-technique analytical approach has been used to show that carbonaceous material entrapped in the channels system of Cu- ZSM-5 catalysts may contribute to maintain the copper ions in the oxidation state +1. This suggests that the reduction of Cu2+ to Cu+ does not only occur via water elimination from CuOH+ species or via oxygen evolution from [Cu-O-Cu](2+) species, but also via oxidation of the carbonaceous materials to give CO and CO2. This mechanism occurs under high temperature (>300 degrees C) treatments in vacuo or He of Cu-ZSM-5 catalysts containing carbonaceous species and strongly adsorbed water molecules in the first coordination shell of the Cu2+. Our results may support the hypothesis about the roles of O-2 and hydrocarbons in the SCR of NOx; O-2 maintains together with hydrocarbons the optimal valence state of copper (Cu+) necessary to have the maximum conversion of NOx and hydrocarbons into N-2 and CO2. (C) 1999 Elsevier Science B.V. All rights reserved.
On the role of carbonaceous material in the reduction of Cu2+ to Cu+ in Cu-ZSM-5 catalysts / Carlo, Dossi; Achille, Fusi; Moretti, Giuliano; Sandro, Recchia; Rinaldo, Psaro. - In: APPLIED CATALYSIS A: GENERAL. - ISSN 0926-860X. - 188:1-2(1999), pp. 107-119. [10.1016/s0926-860x(99)00240-9]
On the role of carbonaceous material in the reduction of Cu2+ to Cu+ in Cu-ZSM-5 catalysts
MORETTI, GIULIANO;
1999
Abstract
A multi-technique analytical approach has been used to show that carbonaceous material entrapped in the channels system of Cu- ZSM-5 catalysts may contribute to maintain the copper ions in the oxidation state +1. This suggests that the reduction of Cu2+ to Cu+ does not only occur via water elimination from CuOH+ species or via oxygen evolution from [Cu-O-Cu](2+) species, but also via oxidation of the carbonaceous materials to give CO and CO2. This mechanism occurs under high temperature (>300 degrees C) treatments in vacuo or He of Cu-ZSM-5 catalysts containing carbonaceous species and strongly adsorbed water molecules in the first coordination shell of the Cu2+. Our results may support the hypothesis about the roles of O-2 and hydrocarbons in the SCR of NOx; O-2 maintains together with hydrocarbons the optimal valence state of copper (Cu+) necessary to have the maximum conversion of NOx and hydrocarbons into N-2 and CO2. (C) 1999 Elsevier Science B.V. All rights reserved.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
