Praveen C S, Borosy A P, Copéret C, Comas-Vives A
Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir Prelog-Weg 1-5, CH-8093 Zürich, Switzerland.
Department of Chemistry, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Catalonia, Spain.
Inorg Chem. 2021 May 17;60(10):6865-6874. doi: 10.1021/acs.inorgchem.0c03135. Epub 2021 Feb 5.
Well-defined Ga(III) sites on SiO are highly active, selective, and stable catalysts in the propane dehydrogenation (PDH) reaction. In this contribution, we evaluate the catalytic activity toward PDH of tricoordinated and tetracoordinated Ga(III) sites on SiO by means of first-principles calculations using realistic amorphous periodic SiO models. We evaluated the three reaction steps in PDH, namely, the C-H activation of propane to form propyl, the β-hydride (β-H) transfer to form propene and a gallium hydride, and the H-H coupling to release H, regenerating the initial Ga-O bond and closing the catalytic cycle. Our work shows how Brønsted-Evans-Polanyi relationships are followed to a certain extent for these three reaction steps on Ga(III) sites on SiO and highlights the role of the strain of the reactive Ga-O pairs on such sites of realistic amorphous SiO models. It also shows how transition-state scaling holds very well for the β-H transfer step. While highly strained sites are very reactive sites for the initial C-H activation, they are more difficult to regenerate. The corresponding less strained sites are not reactive enough, pointing to the need for the right balance in strain to be an effective site for PDH. Overall, our work provides an understanding of the intrinsic activity of acidic Ga single sites toward the PDH reaction and paves the way toward the design and prediction of better single-site catalysts on SiO for the PDH reaction.
SiO 上定义明确的 Ga(III) 位点是丙烷脱氢（PDH）反应中高活性、高选择性和稳定的催化剂。在本论文中，我们通过使用实际的非晶态周期性 SiO 模型进行第一性原理计算，评估了 SiO 上三配位和四配位 Ga(III) 位点对 PDH 的催化活性。我们评估了 PDH 中的三个反应步骤，即丙烷的 C-H 活化形成丙基、β-氢化物（β-H）转移形成丙烯和氢化镓，以及 H-H 偶联释放 H，再生初始的 Ga-O 键并完成催化循环。我们的工作表明，在 SiO 上的 Ga(III) 位点上，这三个反应步骤在一定程度上遵循了布朗斯特-埃文斯-波拉尼关系，并突出了实际非晶态 SiO 模型此类位点上反应性 Ga-O 对的应变作用。它还表明了过渡态标度在 β-H 转移步骤中表现得非常好。虽然高度应变的位点对于初始 C-H 活化是非常活泼的位点，但它们更难再生。相应地，应变较小的位点活性不足，这表明需要在应变方面达到适当的平衡才能成为有效的 PDH 位点。总体而言，我们的工作有助于理解酸性 Ga 单位点对 PDH 反应的本征活性，并为设计和预测用于 PDH 反应的 SiO 上更好的单位点催化剂铺平了道路。
