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Title: Effect of ammonia on cobalt Fischer-Tropsch synthesis catalysts: A surface science approach
Authors: Kızılkaya, Ali Can
Niemantsverdriet, J. W.
Weststrate, C. J.
Keywords: Fischer-Tropsch synthesis
Catalyst poisoning
Ammonia adsorption
Cobalt nanoparticles
Issue Date: May-2019
Publisher: Royal Society of Chemistry
Source: Kızılkaya, A. C., Niemantsverdriet, J. W., and Weststrate, C. J. (2019). Effect of ammonia on cobalt Fischer-Tropsch synthesis catalysts: A surface science approach. Catalysis Science and Technology, 9(3), 702-710. doi:10.1039/c8cy01723a
Abstract: Ammonia adsorption and decomposition on defect-rich hcp-Co(0001) surfaces were investigated under ultra-high vacuum conditions in order to provide a fundamental explanation for industrially observed ammonia poisoning of cobalt based Fischer-Tropsch synthesis (FTS) catalysts. Temperature-programmed desorption, infrared spectroscopy and work function measurements indicate that undercoordinated sites bind ammonia stronger than sites on flat Co(0001), and they also induce its dehydrogenation. Density functional theory calculations were employed to explore the reactivity of defective Co surfaces using the fcc-Co(211) as a model. The results indicate that the decomposition products (NH x ) adsorb strongly on or around the step site on fcc-Co(211). We find that NH (+2H ad ), adsorbed in the threefold site on the upper terrace, is equally stable as NH 2 (+H ad ), adsorbed in the bridge position at the step edge, both being significantly more stable than the equivalent species adsorbed on the flat Co(0001). The calculated activation barriers for NH 3,ad dehydrogenation steps are in reasonable agreement with the barriers obtained by fitting experimental data. Based on these fundamental insights, poisoning of cobalt nanoparticles during FTS by NH 3 contaminants can be linked mainly to the blocking of undercoordinated sites by strongly adsorbed NH 2 species.
ISSN: 2044-4753
Appears in Collections:Chemical Engineering / Kimya Mühendisliği
Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection

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