Hydroxyl exchange on H–CaY and Pt/H–CaY zeolites with deuterium

Abstract

The kinetics of the exchange of zeolite hydroxyl groups with deuterium gas was studied on H–CaY and Pt/H–CaY zeolites using quantitative infrared spectroscopy to follow the 3 640 cm^–1 hydroxyl band. The rate of exchange on H–CaY is first order between 500 and 700 K while that on the Pt containing material, studied from 250 to 400 K, decreased exponentially with time. The exchange rate on Pt/H–CaY was 10⁵ faster than that on H–CaY alone. In both cases, however, the exchange mechanism is similar; the hydroxyl hydrogen migrates to the exchange site where exchange occurs. Pressure dependence of the rate, kinetic isotope effects and the rate increase due to water were also measured.