Affiliation:
1. Department of Material Science and Engineering, University of Ioannina, Ioannina, Greece GR-45110, Greece
2. Department of Chemistry, University of Ioannina, Ioannina, Greece GR-45110, Greece
Abstract
The adsorption of a series of alkyl halides, RX ( X = Cl , Br , I ) over acidic zeolite has been investigated by the ONIOM2 method. A 56T model cluster constructed from 55 Si atoms and one tetrahedral Al atom with one Brönsted acid site, has been used to represent the zeolite catalyst. Density functional theory (DFT) and specifically, the two layered schemes B3LYP/6-31+G(d,p)genECP:UFF and M06-2X/6-31+G(d,p)genECP:UFF have been employed, augmented with the addition of extra polarization functions for the proper treatment of the halogen atoms. Examination of selective structural changes and the computed adsorption enthalpies, ΔH ad , of the van der Waals 1:1 adsorption complexes assumingly formed, shows a strong dependence both on the theoretical method and the alkyl radical structure. A modest influence of the halogen atom involved is also observed. The comparison of the performance of the two functionals underlines the higher capacity of the M06-2X functional to provide a more satisfactory description of the adsorption process and the contribution of the van der Waals dispersion forces.
Publisher
World Scientific Pub Co Pte Lt
Subject
Computational Theory and Mathematics,Physical and Theoretical Chemistry,Computer Science Applications