Redox behaviour of transition metal ions in zeolites. Part 6.—Reversibility of the reduction reaction in silver zeolites

Abstract

In this paper is shown that hydrogen is formed by oxidative thermal desorption from Y-zeolite or mordenite containing highly dispersed silver metal in the cages. Upon thermal degassing above 573 K, hydrogen is desorbed from previously reduced Ag zeolites. At the same time, silver metal is reoxidized and located as Ag⁺ ions in lattice positions and lattice hydroxyl groups disappear.

The following methods are used to characterize the system; isothermal and temperature programmed consumption or desorption of hydrogen in a volumetric system; i.r. spectroscopy of the hydroxyl region; i.r. spectroscopy of adsorbed carbon monoxide and pyridine; X-ray diffraction of Ag⁰ crystallites.