STUDIES OF THE CHANGES OCCURRING ON REDUCTION AND REOXIDATION OF CU-Y ZEOLITES

The possibility that Cu-Y zeolites are dealuminated during reduction with H-2 (at 473 K) or with CO (at 773 K) was investigated by XRD and by Si-29 and Al-27 MAS NMR. H-2/02 and CO/O2 cycles Were also examined. Stoichiometric determinations of the oxidation and reduction steps were determined separately to compare the chemistry occurring using CO or H-2 as the reducing agents. Although some dealumination was detected under certain conditions, the amount was much less than that required to charge-balance the lattice on the conversion of Cu2+ to Cu+. Evidence is presented that extralattice oxygen is introduced during the preparation steps.