Influence of Brnsted acidity on the redox properties of silver species in zeolite mordenite

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H. Berndt, M. Richter, T. Gerlach and M. Baerns


Abstract

The redox behaviour of Ag+ ions exchanged into zeolites is strongly influenced by the presence and concentration of Brønsted acid sites (BS). This is demonstrated by a temperature programmed reduction study of various samples prepared by ion exchange into the Na+ form or by impregnation of the H+ form of mordenite with AgNO3 solution. The Brønsted acidity of the latter was varied by different ways of transforming the NH4+ form to the H+ form. High concentration of BS as well as a high Ag loading favours the reoxidation of A formed in the reduction process. On acidic, Ag-loaded mordenites, a complete reduction of Ag+ occurs only at relatively high temperatures (above 600°C) where the BS are progressively destroyed.


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