Speakers
Description
Abstract
Ammonia is industrially produced by the Haber-Bosch process over a fused, multi-promoted iron-based catalyst [1]. Current knowledge about this reaction has been derived from model systems with less structural complexity impeding a clear-cut structure-activity correlation [1,2]. Here, we explore the real structure and its structural evolution of complex, technical, multi-promoted ammonia synthesis catalysts using scale-bridging electron microscopy, complemented by X-ray diffraction, spectroscopy and near-ambient pressure X-ray photoelectron spectroscopy, respectively [3].
Our detailed analysis shows the presence of additional phases and disentangles different members of the ammonia iron family. Operando experiments unravel their interconnectedness suggesting that each component has to fulfill a distinct role in ensuring highly active and stable ammonia synthesis catalysts. These experiments further highlight that activation is the critical step in which the active catalyst structure is formed and decode the pivotal role of the promoters. The synergism between the different promoters contributes simultaneously to the structural stability, hierarchical architecture, catalytic activity, and poisoning resistance. We discuss that the confluence of these aspects is the key for the superior performance of technical catalyst formulations. The study demonstrates that catalysis science can only proceed if we openly explore the full complexity of catalytic systems [3].
References
- R. Schlögl, Catalytic Synthesis of Ammonia—A “Never-Ending Story”?, Angewandte Chemie International Edition, 42 (2003) 2004-2008.
- G. Ertl, Surface Science and Catalysis—Studies on the Mechanism of Ammonia Synthesis: The P. H. Emmett Award Address, Catalysis Reviews, 21 (1980) 201-223.
- L. Sandoval-Diaz, D. Cruz, M. Vuijk, G. Ducci, M. Hävecker, W. Jiang, M. Plodinec, A. Hammud, D. Ivanov, T. Götsch, K. Reuter, R. Schlögl, C. Scheurer, A. Knop-Gericke, T. Lunkenbein, Metastable nickel–oxygen species modulate rate oscillations during dry reforming of methane, Nature Catalysis, 7 (2024) 161-171.
