Comparison of methane activation and catalytic ethylene formation on free gold and palladium dimer cations: product binding determines the catalytic turnover
Comparison of methane activation and catalytic ethylene formation on free gold and palladium dimer cations: product binding determines the catalytic turnover
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DOI：
10.1039/c3cy00286a
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发表时间：
2013-10
影响因子：
5
通讯作者：
S. M. Lang;A. Frank;T. Bernhardt
中科院分区：
文献类型：
--
作者：
S. M. Lang;A. Frank;T. Bernhardt
气相二聚体Au 2+和Pd 2+已被证明容易活化甲烷，并促进其脱氢，最终导致在Au 2+的情况下在室温下选择性地形成乙烯。在多碰撞条件下的离子阱质谱研究揭示了类似的产品离子分布在室温下的二聚体阳离子与甲烷的反应。然而，相应的动力学揭示了它们的催化性能有相当大的差异。与温度相关的反应性研究的各个催化反应步骤相关联的速率常数的详细评价允许确定周转频率，关键和速率决定的反应步骤，以及活化障碍。这些结果强调，所形成的产物从金属中心最终释放的倾向决定性地决定了金二聚体与钯相比的上级催化性能。
The gas-phase dimers Au2+ and Pd2+ have been shown to readily activate methane and to facilitate its dehydrogenation eventually leading to the selective formation of ethylene at room temperature in the case of Au2+. Ion trap mass spectrometric investigations under multi-collision conditions reveal similar product ion distributions at room temperature for both dimer cations in reaction with methane. Yet, the corresponding kinetics disclose considerable differences in their catalytic properties. A detailed evaluation of the rate constants associated with the individual catalytic reaction steps in conjunction with temperature dependent reactivity studies allow for the determination of turnover frequencies, critical and rate-determining reaction steps, as well as activation barriers. These results emphasize that the propensity for the final liberation of the formed product from the metal center decisively determines the superior catalytic properties of the gold dimer compared to palladium.