The application of inelastic neutron scattering to investigate iron-based Fischer-Tropsch to olefins catalysis

Alisha L. Davidson, Emma K. Gibson, Giannantonio Cibin, Hendrik van Rensburg, Stewart F. Parker, Paul B. Webb, David Lennon

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)

Abstract

The technique of inelastic neutron scattering (INS) is used to investigate how hydrogen is partitioned within a series of Na and S promoted iron-based Fischer-Tropsch-to-olefin catalysts. Two reaction test regimes are examined. First, reaction testing at elevated temperature and pressure demonstrate how Na/S additions enhance short chain olefin selectivity and reduce methane formation under industrially relevant reaction conditions. For a fixed level of Na incorporation (2000 ppm), sulfur concentrations of ≤ 100 ppm result in only a modest improvement in olefin selectivity. However, for sulfur values of ≥ 100 ppm there is a noticeable and systematic increase in C2-C4 olefin selectivity; rising from ∼30.0 % to 35.2% at 250 ppm. Second, using ambient pressure CO hydrogenation as a test reaction in INS and micro-reactor configurations, catalyst samples are further analysed by TPR, TPO, XRD and S K-edge XANES. INS shows the formation of a hydrocarbonaceous overlayer to be significantly attenuated by the presence of the promoters, with increasing S levels significantly reducing the intensity of the sp2 and sp3 hybridised ν(C-H) modes of the overlayer, albeit to differing degrees. A probable role for how this combination of promoters is perturbing the form of the hydrocarbonaceous overlayer to subsequently moderate the product distribution is considered.
Original languageEnglish
Pages (from-to)197-208
Number of pages12
JournalJournal of Catalysis
Volume392
Early online date8 Oct 2020
DOIs
Publication statusPublished - Dec 2020

Keywords

  • Fischer-Tropsch-to-olefins catalysis
  • Inelastic neutron scattering
  • XANES
  • Chemical modifiers

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