Interaction of water and methanol with a zeolite at high coverages

We investigate the interaction of small polar molecules such as water and methanol with a low-aluminum sodalite using first principles density functional molecular dynamics calculations and the projector augmented wave method. Whereas in the low coverage limit methanol is unprotonated, we find that at higher coverage the proton is transferred from the acid site to the adsorbed molecules. The derived vibrational spectra are consistent with infrared data. Our findings indicate that acid-catalyzed reactions in zeolites should parallel those in highly acidic solutions, while zeolites offer the additional advantages of higher acidity, temperature and selectivity due to steric effects.