FTIR STUDY OF WEAK HYDROGEN-BONDING OF BRONSTED HYDROXYLS IN ZEOLITES AND ALUMINOPHOSPHATES

FTIR spectroscopy is used for the investigation of hydrogen bonding of the Bronsted hydroxyls: in H-ZSM-5-zeolite with a number of weak bases (Ar, H-2, O-2, N-2, CH4, C2H6, C3H8, CO, C2H4). The following correlation for the increase in intensity of the hydroxyl band, due to its shift resulting from perturbation, is observed: Delta A/A(0) = 0.018 Delta nu(OH). Applying this correlation to the HF-LF pair in the infrared spectra of H-Y, H-EMT, and H-EMO zeolites, it is shown that the distribution of Bronsted hydroxyls between super and P cages is approximately 1:1 whereas in SAPO-37 samples this ratio is close to 3:1. This is in agreement with results for the deconvolution of the hydroxyl region of the H-1 MAS NMR spectra. The estimated values of the extinction coefficients for the HF and LF band in H-Y zeolite (Si/Al = 2.7) are 3.2 and 8.5 cm.mu mol(-1), respectively.