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Topics in Catalysis

, Volume 9, Issue 3–4, pp 207–213 | Cite as

A density functional theory study of hydrogen recombination and hydrogen-deuterium exchange on Ga/H-ZSM-5

  • Nick O. Gonzales
  • Arup K. Chakraborty
  • Alexis T. Bell
Article

Abstract

Density functional theory calculations have been carried out to determine the thermodynamic stability of various Ga species in gallium-exchanged ZSM-5, the thermodynamics of H2 adsorption, and the most favorable pathway for H2/D2 exchange. The portion of the zeolite associated with Ga was represented by a cluster containing 7, 21, or 33 atoms. The B3LYP hybrid method was used to account for the effects of electron exchange and correlation. The most likely form of Ga expected in freshly exchanged and calcined ZSM-5 is ZGa(OH)2. H2 reduction of this species is projected to produce ZGa(H)(OH) and ZGa(H)2. While the thermodynamics of H2 desorption from ZGa(H)2 are favorable, the process is projected to be slow because of a high activation barrier. The most favorable pathway for H2/D2 exchange over ZGa(H)2 proceeds via Z(D)(Ga(H)2(D)) as an intermediate. Similar calculations have been carried out for H2/D2 exchange over H-ZSM-5.

Ga/H-ZSM-5 H2/D2 exchange density functional theory 

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Copyright information

© Kluwer Academic Publishers 1999

Authors and Affiliations

  • Nick O. Gonzales
    • 1
  • Arup K. Chakraborty
    • 1
  • Alexis T. Bell
    • 1
  1. 1.Material Sciences Division, Lawrence Berkeley National Laboratory and Department of Chemical EngineeringUniversity of CaliforniaBerkeley, CAUSA

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