STRUCTURAL TRANSITIONS IN ZEOLITE-P - AN IN-SITU FTIR STUDY

In situ FTIR spectroscopy is applied to characterise structural transi tions occurring in zeolites NaP and NaA upon hydration-dehydration in conjunction with adsorption measurements. Little spectral variation is observed in the region of structural vibrations of zeolite NaA. By co ntrast, NaP shows prominent reversible changes in the region of asymme tric stretching T-O vibrations, 900-1150 cm(-1), including both 'inter nal' and 'external' linkages, although the former are usually consider ed as structure insensitive. Based on regression analysis of our IR da ta and on XRD results reported previously, phase composition of NaP is determined and four stages in the hydration of P zeolite are outlined .