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Journal articles
Dehydrogenation Mechanisms of Methyl-cyclohexane on Al 2 O 3 Supported Pt 13 : Impact of Cluster Ductility
Abstract : By using density functional theory (DFT) and ab initio molecular dynamics, we investigate the dehydrogenation reactivity of 13 atoms platinum cluster supported on the γ-alumina (1 0 0) surface. We provide a detailed free energy profile and structural analysis of the dehydrogenation mechanisms of methyl-cyclohexane (MCH) into toluene. We highlight the quantitative impact of dispersion corrections on the free energy profile and on the adsorption configurations of the intermediates exhibiting a dual interaction with the cluster and with the alumina surface. During the step by step dehydrogenation of MCH, several reconstructions of the Pt cluster and hydrogen migrations occur. Due to the cluster ductility, they are moderately activated and provide optimal active sites catalyzing the CH bond cleavages. According to a preliminary kinetic analysis based either on energetic spans or on activation free energies of elementary steps, we found that many states and/or steps may be considered as determining ones. This may explain some diverging interpretations brought by previous experimental kinetic studies. We finally discuss how the cluster ductility challenges the historical concept of structure sensitivity/insensitivity for a given reaction in the case of nanometer-size metallic clusters dispersed on a support.
Cited literature [112 references]
https://hal-ifp.archives-ouvertes.fr/hal-01999587
Contributor : Catherine Belli Connect in order to contact the contributor
Submitted on : Wednesday, January 30, 2019 - 10:58:14 AM
Last modification on : Wednesday, November 20, 2019 - 8:05:37 AM
Contributor : Catherine Belli Connect in order to contact the contributor
Submitted on : Wednesday, January 30, 2019 - 10:58:14 AM
Last modification on : Wednesday, November 20, 2019 - 8:05:37 AM