Trinity Study on the Zeolite Acidity using Thermal Measurements, Spectroscopy, and Density Functional Theory Calculation

Abstract

Our recent progress in the study on zeolite acidity is reviewed. An IRMS-TPD (infrared spectroscopy/mass spectroscopy-temperature programmed desorption) of ammonia experiment provides us not only number and strength of the acid site, but the structure of Brønsted or Lewis character. When more than two kinds of the Brønsted acid sites exist, these acid sites can be measured individually and directly. This is an important advantage of the method, because any other methods cannot provide such precise characterization data. Furthermore, these findings are supported by the DFT (density functional theory) calculation. Three techniques, i.e., TPD, IR, and DFT, therefore, are combined into a powerful technique to study the zeolite acidity. Studies on four kinds of Brønsted acid sites in HY and cation exchanged HY zeolites, known as catalysts for the cracking of hydrocarbons, are explained as examples.