Abragam A.

Alayon E. M. C.

Anita Godiksen

Atanasov M.

Bates S. A.

Bendix J.

Bersuker I. B.

Bridgeman A. J.

Broser I.

Carl P. J.

Chao C.-C.

Comba P.

Conesa J. C.

Deka U.

Doronkin D. E.

Fickel D. W.

Filippo Giordanino

Frederick N. Stappen

Gao F.

Giordanino F.

Glerup J.

Groothaert M. H.

Göltl F.

Iwamoto M.

Jahn H. A.

Kazanskii V. B.

Kivelson D.

Korhonen S. T.

Kucherov A.

Kwak J. H.

Lars F. Lundegaard

Larsen S. C.

LoJacono M.

Mikheikin I. D.

Narayana M.

Neese F.

Occhiuzzi M.

Palomino G. T.

Peisach J.

Peter N. R. Vennestrøm

Pierloot K.

Piligkos S.

Sakaguchi U.

Schaffer C. E.

Soria J.

Susanne Mossin

Søren Birk Rasmussen

Vanelderen P.

Verma A. A.

Wang D.

Woertink J. S.

Öpik U.

Cu-CHA combines high activity for the selective catalytic reduction (SCR) reaction with better hydrothermal stability and selectivity compared to other copper-substituted zeolites. At the same time Cu-CHA offers an opportunity for unraveling the coordination environment of the copper centers since the zeolite framework is very simple with only one crystallographically independent tetrahedral site (T-site). In this study the results of an X-band electron paramagnetic resonance (EPR) investigation of ion-exchanged Cu-CHA zeolite with a Si/Al ratio of 14 ± 1 is presented. Different dehydration treatments and rehydration experiments are performed in situ while monitoring with EPR. The results are compared with recent literature evidence from temperature-programmed reduction, X-ray methods, IR spectroscopic methods, and UV–visible spectroscopy. On the basis of these findings quantitative information is obtained for the different copper positions in dehydrated Cu-CHA. The well-defined copper sites in the six-membered ring of the CHA structure are found to be EPR active, to give two distinct sets of signals in an approximate 1:1 ratio, and to add up to 19 ± 2% of the total copper in the material. The long-standing question of the EPR silent monomeric Cu2+ in copper-substituted zeolites is suggested to be copper species with an approximate trigonal coordination sphere appearing during the dehydration. After complete dehydration at 250 °C the majority of the EPR silent Cu2+ is suggested to exist as Cu2+–OH– coordinated to two framework oxygen atoms located in the microenvironment of an isolated Al T-site

Godiksen, Anita

Stappen, Frederick N.

Vennestrøm, Peter N. R.

Giordanino, Filippo

Rasmussen, Søren Birk

Lundegaard, Lars F.

Mossin, Susanne

Online Research Database In Technology

Coordination Environment of Copper Sites in Cu-CHA Zeolite Investigated by Electron Paramagnetic Resonance

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The Journal of Physical Chemistry C

http://orbit.dtu.dk/ws/files/115643612/Coordination_Environment_of_Copper_Sites_in_Cu_CHA_Zeolite.pdf

Coordination Environment of Copper Sites in Cu-CHA Zeolite Investigated by Electron Paramagnetic Resonance

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