Density functional theoretical investigations on various nanostructural zeolite surfaces

Through density functional calculations, the Bronsted acidities on various nanostructural ZSM-5 zeolite surfaces were studied as well as the hydrogen exchanging processes with adsorbed H2O monomer or dimer. The Bronsted acidities on the four nanostructural surfaces show differences, although slightly, with their strengths increasing as (100) < (210) < (410) < (001). For hydrogen exchanging processes with H2O monomer or dimer, the reaction rate increases in the order (210) < (100) < (001) < (410) or (210) < (410) < (001). No transition-state structure is present on H2O dimer/(100) surface system. The introduction of a second H2O molecule accelerates the hydrogen exchanging processes and meanwhile influences the nanostructural geometries such that they are more evident. Besides the activation barrier, the adsorption energy and reaction heat display differences from one surface to another, which results in the preference of catalytic reactions to a specific nanostructural zeolite surface, such as the hydrogen exchanging processes studied in this paper