The IR studies of the interaction of organic molecules with Ag+ ions in zeolites

We studied the properties of Ag+ ions in zeolites AgZSM-5, AgY and AgX with CO as a probe molecule. We studied also how Ag+ interacts with molecules of propene, acetylene, benzene and acetone. IR studies of CO sorption showed that Ag+ in zeolites were less electron donor than Cu+. In the case of zeolite AgX two kinds of Ag+ sites with various electron donor properties for example at various location (S-II and S-III) were found. The interaction of organic molecules with Ag+ ions in zeolites results in the weakening of C=C bond in propene, C C bond in acetylene, C-C bond in aromatic ring in benzene as well as C=O bond in acetone. This was realized by pi back donation of d electrons of Ag+ to antibonding pi* orbitals of multiple bonds. However, the effect of multiple bonds weakening by Ag+ ions is weaker than by Cu+ ions due to weaker electron donor properties of Ag+. The coadsorption of CO and organic molecules on the same Ag+ ion was also studied. (C) 2007 Elsevier Inc. All rights reserved.