Fischer-Tropsch synthesis: Effect of pretreatment conditions of cobalt on activity and selectivity for hydrogenation of carbon dioxide

Muthu Kumaran Gnanamani, Gary Jacobs, Robert A. Keogh, Wilson D. Shafer, Dennis E. Sparks, Shelley D. Hopps, Gerald A. Thomas, Burtron H. Davis

Research output: Contribution to journalArticlepeer-review

70 Scopus citations

Abstract

The effect of pretreatment conditions of cobalt on activity and product selectivity for the hydrogenation of carbon dioxide was studied over a 1%Na/20%Co-SiO2 catalyst using a fixed-bed catalytic reactor operated at 220 °C and 1.89 MPa. The metallic form of cobalt was obtained from the reduction of cobalt oxide (Co3O4) by H2 at 350 °C and produced primarily methane and lower hydrocarbons (C2-C4) from CO2. Pretreatments with pure H2 or syngas (H2:CO) at 250 °C yield a fraction of partially reduced cobalt (CoO), which tends to suppress the hydrogenation activity of cobalt somewhat, reducing methane selectivity to a limited degree. After CO activation, partially reduced cobalt oxide (CoO) and cobalt carbide phases formed and produced significantly less methane (i.e., selectivity of 15.3%), and surprisingly, the selectivity for alcohols increased to 73.2%. In the absence of sodium, direct methanation is still a preferred reaction for CO2 for CO pretreated cobalt; the XRD results of used catalysts revealed that the cobalt carbide phase converted to metallic cobalt. The results indicate that Na doping and carbide are important for low methane and high oxygenate selectivities. However, further work is needed to determine whether the role of Na is merely to stabilize the cobalt carbide phase, or whether Na is involved in promoting the catalytic cycle.

Original languageEnglish
Pages (from-to)39-46
Number of pages8
JournalApplied Catalysis A: General
Volume499
DOIs
StatePublished - Jun 25 2015

Bibliographical note

Funding Information:
This research was conducted with financial support from the Commonwealth of Kentucky .

Publisher Copyright:
© 2015 Elsevier B.V. All rights reserved.

Keywords

  • Alcohols
  • Carbon dioxide
  • Cobalt
  • Cobalt carbide
  • Cobalt oxide
  • Hydrogenation

ASJC Scopus subject areas

  • Catalysis
  • Process Chemistry and Technology

Fingerprint

Dive into the research topics of 'Fischer-Tropsch synthesis: Effect of pretreatment conditions of cobalt on activity and selectivity for hydrogenation of carbon dioxide'. Together they form a unique fingerprint.

Cite this