Selective ring opening of cyclic hydrocarbons during fuel upgrading: Mechanistic density functional studies of the metal catalyst
Final Report Abstract
Using results of density functional calculations, this computational chemistry project was successful at generating new insights on our fundamental understanding of elementary C-C and C-H activation mechanisms during catalytic hydrocarbon reforming. The thermal decomposition and hydrogenolysis of ethylene was addressed in several high-impact publications that resulted from this project. The surface chemistry of ethylene and related C2 H x species is not only a prototype system, from which important lessons, transferable to higher hydrocarbons, have been learned, but it is also in its own right an industrially relevant problem, e.g., in the context of selective hydrogenation of acetylene or synthesis of functionalized olefins. We exhaustively studied the transformation network of ethylene on Pt(111) and Pd(111). Our calculations overruled some of the earlier assumptions regarding the mechanism of ethylene dehydrogenation on Pt(111). With the help of kinetic Monte-Carlo simulations, we established new mechanisms for the transformation of ethylene to ethylidyne, on both Pt(111) and Pd(111). W e also studied the hydrogenolysis of the C-C bond in ethylene on M(111) for M = Pd, Pt, Rh, and Ni, and identified the most likely precursors to C-C bond cleavage as well as precursors to coke formation on various noble metal surfaces. Our publications motivated related theoretical studies on these and other metal surfaces as well as further experimental studies on reactions of C2 H x species. The second central topic of the project was the selective ring opening of cyclopentane derivatives over supported metal catalysts. This type of reaction is thought to be a key step during hydrorefining of diesel feedstocks by conversion of polycyclic hydrocarbons to hydrocarbons with structures that exhibit fewer rings. Our computational studies introduced a mechanism for methylcyclopentane ring opening that allowed us to rationalize the experimentally observed selectivity toward various ring-opening products. W e successfully explained the different selectivity with respect to linear and branched hexanes on small and large Pt particles and, on other noble-metal catalysts, the insensitivity of the product distribution on the particle size.
Publications
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Ethylene conversion to ethylidyne over the Pd(111) surface: Revisiting the mechanism with firstprinciples calculations, J. Phys. Chem. C (2009) 113, 2512-2520
Moskaleva, L. V.; Chen, Z.-X.; Basha Mohammed, A.; Sun, Q.; Aleksandrov, H. A.; Rösch, N.
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Transformations of Ethylene on the Pd(111) Surface: A Density Functional Study, J. Phys. Chem. C (2010) 114, 17683-17692
Chen, Z.-X.; Aleksandrov, H. A.; Basaran, D.; Rösch, N.
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Ethylene conversion to ethylidyne on Pd(111) and Pt(111): A first-principles-based kinetic Monte Carlo study, J. Catal. (2012) 285, 187-195
Aleksandrov, H. A.; Moskaleva, L. V.; Zhao, Z.-J.; Basaran, D.; Chen, Z.-X.; Mei, D.; Rösch, N.
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Tuning the selectivity for ring-opening reactions of methylcyclopentane over Pt catalysts: A mechanistic study from first-principles calculations, J. Catal. (2012) 285, 124-133
Zhao, Z.-J.; Moskaleva, L. V.; Rösch, N.
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Formation of n-hexane from methylcyclopentane via a metallacyclobutane intermediate at step sites of Pt surfaces: Mechanism from first-principles calculations, J. Catal. (2013) 299, 146-149
Zhao, Z.-J.; Moskaleva, L.; Rösch, N.
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Ring-opening reactions of methylcyclopentane over metal catalysts, M = Pt, Rh, Ir, and Pd: A mechanistic study from first-principles calculations, ACS Catal. (2013) 3, 196−205
Zhao, Z.-J.; Moskaleva, L.; Rösch, N.
