Department of Chemistry and Applied Biosciences, ETH Zürich , Vladimir-Prelog-Weg 1-5, CH-8093 Zürich, Switzerland.
Department of Mechanical and Process Engineering, ETH Zürich , Leonhardstrasse 21, CH-8092 Zürich, Switzerland.
J Am Chem Soc. 2017 May 24;139(20):6919-6927. doi: 10.1021/jacs.7b01625. Epub 2017 May 9.
Syngas production via the dry reforming of methane (DRM) is a highly endothermic process conducted under harsh conditions; hence, the main difficulty resides in generating stable catalysts. This can, in principle, be achieved by reducing coke formation, sintering, and loss of metal through diffusion in the support. [{Ni(μ-OCHO)(OCHO)(tmeda)}(μ-OH)] (tmeda = tetramethylethylenediamine), readily synthesized and soluble in a broad range of solvents, was developed as a molecular precursor to form 2 nm Ni(0) nanoparticles on alumina, the commonly used support in DRM. While such small nanoparticles prevent coke deposition and increase the initial activity, operando X-ray Absorption Near-Edge Structure (XANES) spectroscopy confirms that deactivation largely occurs through the migration of Ni into the support. However, we show that Ni loss into the support can be mitigated through the Mg-doping of alumina, thereby increasing significantly the stability for DRM. The superior performance of our catalytic system is a direct consequence of the molecular design of the metal precursor and the support, resulting in a maximization of the amount of accessible metallic nickel in the form of small nanoparticles while preventing coke deposition.
通过甲烷的干重整（DRM）生产合成气是一个在苛刻条件下进行的高度吸热过程；因此，主要的困难在于生成稳定的催化剂。这原则上可以通过减少积碳形成、烧结和通过在载体中的扩散导致的金属损失来实现。[{Ni(μ-OCHO)(OCHO)(tmeda)}(μ-OH)]（tmeda = 四甲基乙二胺）是一种易于合成且在很宽的溶剂范围内可溶的分子前体，被开发为在氧化铝（DRM 中常用的载体）上形成 2nm Ni(0)纳米颗粒的前体。虽然这种小的纳米颗粒可以防止积碳沉积并提高初始活性，但operando X 射线吸收近边缘结构（XANES）光谱证实失活主要是通过 Ni 向载体中的迁移发生的。然而，我们表明，通过氧化铝的镁掺杂可以减轻 Ni 向载体中的损失，从而显著提高 DRM 的稳定性。我们的催化体系的优异性能是金属前体和载体的分子设计的直接结果，这导致了以小纳米颗粒形式存在的可用金属镍量的最大化，同时防止积碳沉积。
