REDUCTION OF NI-2+ CATIONS IN Y-ZEOLITES .1. EFFECT OF SAMPLE PRETREATMENT

A range of NiNa-Y and NiK-Y zeolites was prepared by ion exchange. The location of Ni2+ cations within the zeolite framework was monitored after various stages of thermal treatment and the reduction process of the transition metal ion in a flowing hydrogen atmosphere was investigated and correlated with such factors as the hydrogen flow rate, reduction time, reduction temperature, sample precalcination, and NH3 pretreatment. Cation location was probed by means of Cs+ back exchange and confirmed by the observation of the IR spectra of CO adsorbed on the activated zeolites. Iodometric titrations and Na+ back-exchange techniques were used to measure the levels of Ni2+ reduction. The data generated reveal how the interrelated Ni2+ ion location and the nature of the charge-balancing alkali metal co-cation serve to influence the level of Ni2+ reduction. © 1990.