Abstract
Applying a density functional approach to slab models of planar, (111), and rough, (110), Pd surfaces, we determined the isomerization free energy barriers of 1-butene to be significantly lower than the hydrogenation barriers. Microkinetic modeling allows one to mirror the kinetic experiments on conversions of 1-butene at the corresponding single-crystal surfaces in a qualitative fashion. Despite the inherent limitations of such kinetic modeling, theoretical predictions are fully supported by experimental data using Pd model catalysts: i.e., Pd(111) and Pd(110) surfaces. The isomerization mechanism was calculated to proceed via an initial dehydrogenation of 1-butene to 1-buten-3-yl as an intermediate—in contrast to the commonly proposed 2-butyl intermediate, associated with the Horiuti–Polanyi mechanism. Our modeling results rule out the original assumption that isomerization has to start with a hydrogenation step to rationalize the dependence of isomerization on hydrogen. However, this hydrogen dependenc...
Published Version
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