LOCATION AND REDUCIBILITY OF NI IONS IN HEU-TYPE ZEOLITES

Starting from a well-characterized natural clinoptilolite (sample HC), the following samples were prepared by ionic exchange with the corres ponding cations: NaHC, KHC, CaHC, and MgHC. These samples were exchang ed with Ni2+ to obtain the samples NiNaHC, NiKHC, NiCaHC, and NiMgHC. Using absorption spectrometry, NH3 adsorption, thermoprogrammed reduct ion, and Mossbauer spectrometry we studied the reduction of iron in HC , the cationic composition and adsorption of NH3 in NaHC, KHC, CaHC, M gHC, NiNaHC, NiKHC, NiCaHC, and NiMgHC, and the thermoreduction in Ni- exchanged samples. (C) 1995 Academic Press, Inc.