A DRIFT spectroscopic study of the N2 adsorption and acidic properties of H- and Pt/H-zeolites

The N 2 adsorption on zeolite H- and Pt/H-mordenite and Beta (Pt/Al F =0.04–0.08) was studied by DRIFT spectroscopy at room temperature and 1 to 9 bar N 2 pressures. The H-bonding of N 2 to the OH groups induced shift of the v OH band to lower frequencies. The v OH shift was taken as a measure of the intrinsic acid strength of the sorption site hydroxyl groups. Results suggested that the intrinsic Bronsted acidity of the H- and the Pt, H-forms were about the same regardless of the amount and oxidation state of the Pt in the sample. In the spectrum of the H 2 -reduced Pt, H-mordenite, having relatively high Pt content (>1.5 wt%), as a new spectral feature, a v NN absorption band appeared at ≈2232–2245 cm −1 . The band was attributed to the v NN vibration of nitrogen, bound to relatively large Pt-clusters. This assignment was supported by the results of the DRIFT examination of the adsorbed CO.