Substitution of co with ni in Co/Al2O3 catalysts for fischer–tropsch synthesis

Michela Martinelli, Sai Charan Karuturi, Richard Garcia, Caleb D. Watson, Wilson D. Shafer, Donald C. Cronauer, A. Jeremy Kropf, Christopher L. Marshall, Gary Jacobs

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

The effect of cobalt substitution with nickel was investigated for the Fischer–Tropsch synthesis reaction. Catalysts having different Ni/Co ratios were prepared by aqueous incipient wetness co-impregnation, characterized, and tested using a continuously stirred tank reactor (CSTR) for more than 200 h. The addition of nickel did not significantly modify the morphological properties measured. XRD, STEM, and TPR-XANES results showed intimate contact between nickel and cobalt, strongly suggesting the formation of a Co-Ni solid oxide solution in each case. Moreover, TPR-XANES indicated that nickel addition improves the cobalt reducibility. This may be due to H2 dissociation and spillover, but is more likely the results of a chemical effect of intimate contact between Co and Ni resulting in Co-Ni alloying after activation. FTS testing revealed a lower initial activity when nickel was added. However, CO conversion continuously increased with time on-stream until a steady-state value (34%–37% depending on Ni/Co ratio) was achieved, which was very close to the value observed for undoped Co/Al2O3. This trend suggests nickel can stabilize cobalt nanoparticles even at a lower weight percentage of Co. Currently, the cobalt price is 2.13 times the price of nickel. Thus, comparing the activity/price, the catalyst with a Ni/Co ratio of 25/75 has better performance than the unpromoted catalyst. Finally, nickel-promoted catalysts exhibited slightly higher initial selectivity for light hydrocarbons, but this difference typically diminished with time on-stream; once leveling off in conversion was achieved, the C5 + selectivities were similar (≈ 80%) for Ni/Co ratios up to 10/90, and only slightly lower (≈ 77%) at Ni/Co of 25/75.

Original languageEnglish
Article number334
JournalCatalysts
Volume10
Issue number3
DOIs
StatePublished - Mar 2020

Bibliographical note

Publisher Copyright:
© 2020 by the authors. Licensee MDPI, Basel, Switzerland.

Keywords

  • Bimetallic catalyst
  • Cobalt-nickel alloys
  • Fischer
  • TPR-XANES/EXAFS
  • Tropsch synthesis

ASJC Scopus subject areas

  • Catalysis
  • General Environmental Science
  • Physical and Theoretical Chemistry

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