Shape-selective dissociative adsorption of alcohols on 1-butyl-3-methylimidazolium-exchanged mordenite zeolite

Abstract

Dissociative alcohol adsorption was investigated on 1-butyl-3-methylimidazolium ([bmim]) exchanged mordenite ([bmim]M20) by Fourier transform infrared spectroscopy (FT-IR). Methanol, ethanol, 1-propanol and 2-propanol were adsorbed onto [bmim]M20. Although acidic OH groups were almost completely absent on [bmim]M20, bands attributed to hydrogen-bonded νOH of acidic OH groups (the so-called ABC triplet) were apparent for alcohol adsorption on [bmim]M20. This indicates the generation of acidic OH groups on [bmim]M20 by the dissociative adsorption of alcohols. Methanol and ethanol could diffuse into the [bmim]M20 micropores in the absence of observable energy barriers at room temperature, while energy barriers for diffusion into the micropores were observed for 1-propanol and 2-propanol at room temperature. The activation energy for diffusion of 2-propanol into the [bmim]M20 micropores was estimated as 25 kJ mol −1. Shape-selective adsorption into the [bmim]M20 micropores was revealed for the alcohols examined.