H-1 MAS NMR-STUDIES OF HYDROXYL-GROUPS IN ALUMINUM-FREE H-BORALITES

H-1 MAS NMR spectra of H-boralites contain seven lines at 1.0, 1.4, 1. 7, 2.3, 2.6, 4.7 and 6.7 ppm with intensities dependent on the activat ion temperature. The lines at 6.7, 4.7 and 1.7 ppm are assigned to res idual ammonium ions, residual water and terminal Si-OH groups, respect ively. The prominent line at 2.3 ppm comes from bridging Si-O(H)-B hyd roxyls. The lines at 1.0, 1.4 and 2.6 ppm are tentatively assigned to B-OH, B-OH...O and Si-OH...O protons, respectively. The assignment has been assisted by the proton spectra of partially hydrated B2O3 and Si O2, and by infrared measurements.