Infrared Characterisation of Cu-SAPO-STA-7 using CO and NO as probe molecules

B. MOULIN, A. VILMONT, M. DATURI, L. GAVEROVA, P. LLEWELLYN, A. L. PICONE, P. A. WRIGHT

Albena

Simposio; Third International Symposium on Advanced micro-and mesoporous materials; 2009

For many years, efforts have been made to obtain more effective and economical catalytic materials to reduce air pollution. Transition metal-containing zeolites have shown potential for the decomposition of NO and CO, and Cu-exchanged ZSM5 zeolite possesses high NO decomposition activity, although issues remain active site poisoning, regeneration and lifetime. Crystalline silicoaluminophosphates (SAPO) are a zeolite-like family of microporous solids with potential applications as catalysts and adsorbents. By using copper-containing macrocycles as templates for these solids, followed by calcination, it is possible to introduce copper cations in extra-framework positions in these materials without aqueous ion exchange. In one of these, Cu STA-7, a  highly crystalline and porous solid is prepared in this way and synchrotron XRD experiments have allowed us to locate the position of Cu2+ cations in the structure, showing four well defined sites. IR spectroscopy of adsorbed probe molecules is a powerful tool to obtain informations about the oxidation and the coordination state of the surface copper cations. In this work the copper sites within Cu STA-7 pre-treated under different conditions have been probed by IR and also adsorption microcalorimetry. At room temperature CO adsorbs strongly on Cu+ sites whereas NO is preferably adsorbed on Cu2+  sites. For Cu STA-7 the pre-treatment conditions strongly influence the oxidation state of the copper cations, which governs the CO adsorption modes at room temperature. Moreover, NO adsorption reveals that Cu2+ ions are present in various environments, which can be related to their locations deduced from XRD analysis.