Coadsorption of ammonia and methanol on H-zeolites and alkaline-exchanged zeolites

Abstract

The interactions of methanol and ammonia on H-zeolites (H-Z) and alkaline-exchanged zeolites (Na-Z) have been investigated using Hartree-Fock (HF) and density functional theory (DFT) approaches. Full optimization of all clusters and their complexes has been optimized at B3 LYP 6-31 G∗ and HF 6-31 G∗ theoretical levels. The reaction mechanism of coadsorption of methanol and ammonia on H-Z is that the ammonia is found to bound to the Brønsted acid site of H-Z, yielding ammonium cation, which in turn operates as an active site for methanol. The result of coadsorption processes indicates that the stronger base ammonia is preferentially bonded to the Brønsted acid sites of H-Z, while methanol is interacted with the Lewis acid of Na-Z. Our findings are in excellent agreement with very recently reported data (Kogelbauer, A., Grundling, G., Lercher, J.A., J. Phys. Chem. 100 (1996) 1852-1837).