Venegas Juan M, Zhang Zisheng, Agbi Theodore O, McDermott William P, Alexandrova Anastassia, Hermans Ive
Department of Chemical and Biological Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI, 53706, USA.
Present address: Performance Silicones Process R&D, The Dow Chemical Company, 2651 W. Salzburg Road, Midland, MI, 48640, USA.
Angew Chem Int Ed Engl. 2020 Sep 14;59(38):16527-16535. doi: 10.1002/anie.202003695. Epub 2020 Jul 14.
Boron-containing materials, and in particular boron nitride, have recently been identified as highly selective catalysts for the oxidative dehydrogenation of alkanes such as propane. To date, no mechanism exists that can explain both the unprecedented selectivity, the observed surface oxyfunctionalization, and the peculiar kinetic features of this reaction. We combine catalytic activity measurements with quantum chemical calculations to put forward a bold new hypothesis. We argue that the remarkable product distribution can be rationalized by a combination of surface-mediated formation of radicals over metastable sites, and their sequential propagation in the gas phase. Based on known radical propagation steps, we quantitatively describe the oxygen pressure-dependent relative formation of the main product propylene and by-product ethylene. Free radical intermediates most likely differentiate this catalytic system from less selective vanadium-based catalysts.
含硼材料，尤其是氮化硼，最近被确定为丙烷等烷烃氧化脱氢的高选择性催化剂。迄今为止，尚无一种机制能够解释这种前所未有的选择性、观察到的表面氧官能化以及该反应独特的动力学特征。我们将催化活性测量与量子化学计算相结合，提出了一个大胆的新假设。我们认为，显著的产物分布可以通过表面介导的亚稳位点上自由基的形成以及它们在气相中的顺序传播来合理解释。基于已知的自由基传播步骤，我们定量描述了主要产物丙烯和副产物乙烯的氧压依赖性相对生成。自由基中间体很可能使该催化体系与选择性较低的钒基催化剂区分开来。
