Reports: GB5

47206-GB5 Large-Scale Quantum Mechanical Calculations for the Catalytic Dehydrogenation of Alkanes: Chromium Supported on Transition Aluminas

Sanwu Wang, University of Tulsa

During the second year, we continue to employed large-scale first-principles quantum mechanical calculations to investigate the catalytic chemical reaction of the dehydrogenation of a selected alkane, propane (C3H8), with the presence of Cr (in the form of dispersed chromium oxide CrO3 species) supported on g-alumina (g-Al2O3). We used the model of periodic supercells and the method of density-functional theory with ultrasoft pseudopotentials, the generalized gradient-corrected exchange-correlation functionals, and the plane-wave basis set.

We reported in the first annual report that we found that when a propane (C3H8) molecule reacts with to a CrO4 species supported on the γ-Al2O3 surface, dissociation of propane occurs - two hydrogen atoms of the C3H8 molecule are trapped by the oxygen sites of the chrominm oxide species, and a propene (C3H6) molecule is simultaneously released. In the second year (the period covering this report), we investigated the role of a CrO3 species supported on the γ-Al2O3 surface and we found CrO3 acts as a catalyst in a way similar to the CrO4 species – the dissociation of C3H8 molecule (into a C3H6 molecule and two trapped hydrogen atoms) with the presence of CrO3/γ-Al2O3 is energetically favorable, and the energy gain is of ~0.2–1.1 eV.

However, the activation energy of the dissociation process has not yet determined. We are currently employing “nudged elastic band method” to determine the reaction pathways and the associated reaction barriers of dehydrogenation of propane. We expect to report the results in the next report.*

* This project was initially awarded for two years, but we requested for a no-cost extension, and a one-year extension was approved by PRF.