HIGHLY RESOLVED H-1 MAS NMR-SPECTRA OF DEHYDRATED ZEOLITE HY

Highly resolved H-1 single-pulse MAS n.m.r. spectra of dried zeolite HY are presented and analyzed by Gaussian deconvolution to afford estimates of the absolute concentrations of the different types of OH groups present. The small line widths of many signals arise from the low hydrogen content of the dried samples. Measurements have been made of the OH:Al ratio of the nonlattice phase, which is observed to vary from less-than-or-equal-to 0.07 to 1.7. Changes were observed in the OH distribution between sites in dried samples allowed to age over a time scale of weeks in a water-free environment. In addition, the populations of all sites are shown to increase, although at unequal rates, when water is allowed to invade slowly from the atmosphere. The different affinities of sites for reaction with an incoming sorbate are discussed.