Research Update: January 2015


This month, Brian had a paper accepted for publication by Topics in Catalysis. In this work, we employed in-situ transmission Fourier transform infrared (FTIR) spectroscopy is to investigate the ion exchange between acidic hydrogen in organic molecules adsorbed on a surface from the gas phase and sodium cations in zeolites. We demonstrated that this process produces Brønsted acid sites and the corresponding adsorbed salt species by identifying signature spectroscopic bands. Furthermore, the gas-phase deprotonation enthalpy (GPDE) of the organic compounds is identified as a key descriptor in determining the feasibility and extent of the exchange process. FTIR data for acetic acid is shown above, and the bands at 3645 wavenumbers (Brønsted acid sites) and 1585 wavenumbers (sodium acetate) are of particular interest. These data indicate that the degree of dissociation of the acidic hydrogen is a key element in the ion exchange. The generality of this process in zeolites was established by the observation of similar results on zeolites with differing topologies (FAU, MFI, *BEA, and MOR).