Quantum-Chemical Investigation of Hydrocarbon Oxidative Dehydrogenation over Spin-Active Carbon Catalyst Clusters

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• 作者：Oleksiy V. Khavryuchenko ; Benjamin Frank ; Annette Trunschke ; Klaus Hermann ; Robert Schl枚gl
• 刊名：The Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：March 28, 2013
• 年：2013
• 卷：117
• 期：12
• 页码：6225-6234
• 全文大小：389K
• 年卷期：v.117,no.12(March 28, 2013)
• ISSN：1932-7455

文摘

Graphene-like carbon clusters with oxygen-saturated zigzag and armchair edges were used as models for density-functional theory investigations of the oxidative dehydrogenation (ODH) of hydrocarbon molecules over carbon catalysts. The product of the first elementary step of the reaction, which is either a hydrocarbon radical or a surface ether, is found to be strictly dependent on the spin multiplicity of the catalyst, although energies of the initial state are spin-degenerate. The barriers of the first step of the ODH of light hydrocarbons (methane, ethane, and propane) over zigzag-edge carbon clusters are higher (59鈥?04 kJ/mol) than those for ethylbenzene (18鈥?8 kJ/mol), and the barrier of the second H abstraction is generally rate-limiting (82鈥?06 kJ/mol). The armchair edge is passive toward reaction with hydrocarbons, but it reacts almost without a barrier with hydrocarbon radicals. The barrier of reoxidation by O₂ was found to decrease from 161 to 69 kJ/mol with an increasing level of saturation with H atoms.