Fischer–Tropsch Synthesis: Effect of the Promoter’s Ionic Charge and Valence Level Energy on Activity

Date
2021-10-10
Authors
Ribeiro, Mirtha Z. Leguizamón León
Souza, Joice C.
Gnanamani, Muthu Kumaran
Martinelli, Michela
Upton, Gabriel F.
Jacobs, Gary
Ribeiro, Mauro C.
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Journal ISSN
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Abstract

In this contribution, we examine the effect of the promoter´s ionic charge and valence orbital energy on the catalytic activity of Fe-based catalysts, based on in situ synchrotron X-ray powder diffraction (SXRPD), temperature-programmed-based techniques (TPR, TPD, CO-TP carburization), and Fischer–Tropsch synthesis catalytic testing studies. We compared the promoting effects of K (a known promoter for longer-chained products) with Ba, which has a similar ionic radius but has double the ionic charge. Despite being partially “buried” in a crystalline BaCO3 phase, the carburization of the Ba-promoted catalyst was more effective than that of K; this was primarily due to its higher (2+) ionic charge. With Ba2+, higher selectivity to methane and lighter products were obtained compared to the K-promoted catalysts; this is likely due to Ba´s lesser capability of suppressing H adsorption on the catalyst surface. An explanation is provided in terms of a more limited mixing between electron-filled Ba2+ 5p and partially filled Fe 3d orbitals, which are expected to be important for the chemical promotion, as they are further apart in energy compared to the K+ 3p and Fe 3d orbitals.

Description
Keywords
Fischer–Tropsch synthesis, iron, alkali, ion valance, alkali-earth, promoter
Citation
Reactions 2 (4): 408-426 (2021)
Department
Biomedical Engineering and Chemical Engineering
Mechanical Engineering