SOLID-STATE ION-EXCHANGE IN ZEOLITES .5. NH4-Y-IRON(II) CHLORIDE

Solid-state ion-exchange reactions proceeding upon grinding of hydrate d NH4-Y zeolite and FeCl2 . 4H2O in air and subsequent heating in vacu um have been followed by X-ray diffraction (XRD) and temperature-progr ammed evolution of volatile reaction products (H2O, NH, and HCl) monit ored by mass spectrometry (MS). Changes in valence state and coordinat ion environment of the exchanged iron ions upon heat treatment up to 7 20 K in vacuum and air, as well as in hydrogen after treatment in air, were studied by Mossbauer spectroscopy. Partial ion exchange and oxid ation to cationic hydroxy-iron(III) species proceed upon mere grinding . Heat treatment in vacuum results in partial autoreduction and charac teristic environmental changes of di- and tri-valent Fe species, espec ially in the temperature range between 620 and 720 K. In an oxidizing atmosphere, autoreduction is suppressed; however, at temperatures >520 K, iron(III) oxide is formed in increasing amounts. Reduction by hydr ogen subsequent to heat treatment in air at 720 K results in the forma tion of a magnetite-like oxide phase and some metallic alpha-iron.