THEORETICAL-STUDIES OF CO ADSORPTION ON H-ZSM-5 AND HYDROTHERMALLY TREATED H-ZSM-5

The adsorption of CO on H-ZSM-5 and hydrothermally treated H-ZSM-5 is studied by means of quantum mechanical calculations. Good agreement wi th experimental FTIR data is established. The Al(OH)(3) dimer is found to account for the new bands that appear in the hydroxyl region of th e FTIR spectra of H-ZSM-5 as a result of hydrothermal treatment. Effec ts of electron correlation (investigated through second-order Moller-P lesset perturbation and density-functional theory) are compared with H artree-Fock results. Red shifts in the stretching frequency of bridgin g OH groups due to the CO interaction are best described by the densit y-functional approach. Frequency shifts are found to correlate with ch anges in local geometry.