Enhanced incorporation of α-olefins in the fischer-tropsch synthesis chain-growth process over an alumina-supported cobalt catalyst in near-critical and supercritical hexane media

Nimir O. Elbashir, Christopher B. Roberts

Research output: Contribution to journalArticle

45 Citations (Scopus)

Abstract

Operating Fischer-Tropsch synthesis (FTS) in supercritical fluid (SCF) media offers advantages over conventional gas-phase FTS operation including in situ extraction of heavy hydrocarbons from the catalyst pores coupled with enhanced incorporation of α-olefins in the chain growth process. In this study, hydrocarbon product distributions in near-critical and supercritical hexane phase FTS (SCH-FTS) was studied over a 15% Co/Al2O3 in a high-pressure fixed-bed reactor system. The critical point of the hexane-syngas-products reaction mixture as collected from the reactor outlet was measured using a variable-volume view cell apparatus. All reactions were carried out in near-critical and supercritical regimes by tuning either the reaction temperature (230-260°C) or the reaction pressure (30-80 bar). Deviations from the standard Anderson-Schultz-Flory (ASF) chain growth model were observed in most cases; however, the degree of deviation depends on the reaction conditions within the near-critical and supercritical regions and varies from gaslike density to liquidlike density within the supercritical region. As an attempt to understand this phenomenon, a modification to the chain growth model in SCH-FTS, is presented. The model attributes the deviation from the standard ASF model to enhanced α-olefin incorporation within the middle distillate hydrocarbon products due to enhanced adsorption/ desorption dynamic in the SCF medium. The proposed enhanced olefin incorporation model was found to be in a good agreement with our experimental results.

Original languageEnglish
Pages (from-to)505-521
Number of pages17
JournalIndustrial and Engineering Chemistry Research
Volume44
Issue number3
Publication statusPublished - 2 Feb 2005
Externally publishedYes

Fingerprint

Fischer-Tropsch synthesis
Aluminum Oxide
Alkenes
Hexanes
Cobalt
Hexane
cobalt
aluminum oxide
Olefins
Alumina
catalyst
Hydrocarbons
Catalysts
Supercritical fluids
hydrocarbon
fluid
Reaction products
Desorption
desorption
Tuning

ASJC Scopus subject areas

  • Polymers and Plastics
  • Environmental Science(all)
  • Chemical Engineering (miscellaneous)

Cite this

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abstract = "Operating Fischer-Tropsch synthesis (FTS) in supercritical fluid (SCF) media offers advantages over conventional gas-phase FTS operation including in situ extraction of heavy hydrocarbons from the catalyst pores coupled with enhanced incorporation of α-olefins in the chain growth process. In this study, hydrocarbon product distributions in near-critical and supercritical hexane phase FTS (SCH-FTS) was studied over a 15{\%} Co/Al2O3 in a high-pressure fixed-bed reactor system. The critical point of the hexane-syngas-products reaction mixture as collected from the reactor outlet was measured using a variable-volume view cell apparatus. All reactions were carried out in near-critical and supercritical regimes by tuning either the reaction temperature (230-260°C) or the reaction pressure (30-80 bar). Deviations from the standard Anderson-Schultz-Flory (ASF) chain growth model were observed in most cases; however, the degree of deviation depends on the reaction conditions within the near-critical and supercritical regions and varies from gaslike density to liquidlike density within the supercritical region. As an attempt to understand this phenomenon, a modification to the chain growth model in SCH-FTS, is presented. The model attributes the deviation from the standard ASF model to enhanced α-olefin incorporation within the middle distillate hydrocarbon products due to enhanced adsorption/ desorption dynamic in the SCF medium. The proposed enhanced olefin incorporation model was found to be in a good agreement with our experimental results.",
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