Fischer–Tropsch Synthesis: XANES Spectra of Potassium in Promoted Precipitated Iron Catalysts as a Function of Time On-stream

Gary Jacobs, Venkat Ramana Rao Pendyala, Michela Martinelli, Wilson D. Shafer, Muthu Kumaran Gnanamani, Syed Khalid, Aimee MacLennan, Yongfeng Hu, Burtron H. Davis

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

XANES K-edge spectra of potassium promoter in precipitated Fe catalysts were acquired following activation by carburization in CO and as a function of time on-stream during the course of a Fischer–Tropsch synthesis run for a 100Fe:2K catalyst by withdrawing catalysts, sealed in wax product, for analysis. CO-activated and end-of-run spectra of the catalyst were also obtained for a 100Fe:5K catalyst. Peaks representing electronic transitions and multiple scattering were observed and resembled reference spectra for potassium carbonate or potassium formate. The shift in the multiple scattering peak to higher energy was consistent with sintering of potassium promoter during the course of the reaction test. The catalyst, however, retained its carbidic state, as demonstrated by XANES and EXAFS spectra at the iron K-edge, suggesting that sintering of potassium did not adversely affect the carburization rate, which is important for preventing iron carbides from oxidizing. The method serves a starting point for developing better understanding of the chemical state and changes in structure occurring with alkali promoter. Graphical Abstract: [Figure not available: see fulltext.].

Original languageEnglish
Pages (from-to)1861-1870
Number of pages10
JournalCatalysis Letters
Volume147
Issue number8
DOIs
StatePublished - Aug 2017

Bibliographical note

Publisher Copyright:
© 2017, Springer Science+Business Media New York.

Keywords

  • Fischer–Tropsch synthesis
  • Iron-based catalyst
  • Olefin selectivity
  • Potassium promoter
  • XANES/EXAFS

ASJC Scopus subject areas

  • Catalysis
  • General Chemistry

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