Interaction of water and ammonium in NaHY zeolite as detected by combined IR and gravimetric analysis (AGIR)

Qualitative as well as quantitative information is obtained simultaneously by combining thermogravimetry and operando IR spectroscopy with on line mass spectrometry. A microbalance has been adapted to an infrared reactor cell. The weight and IR spectra of a solid sample can be measured together in real time in operando conditions, in a gas flow at temperature between room temperature and 773 K. Molar absorbance coefficients epsilons can be obtained directly. The new technique was first applied to adsorbed water and ammonia on a solid acid catalyst, HY zeolite. Epsilon coefficients for water bands were measured. They are influence by the hydration level, and the nu+delta combination band is shown to be a much better option to determine the amount of adsorbed water on zeolites. Epsilon has also been measured for ammonium ions, and water was shown to greatly influence the spectral response of these ions.