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

DOI: 10.1016/j.jcat.2020.09.025 DOI Help

Authors: Alisha L. Davidson (University of Glasgow) , Emma K. Gibson (University of Glasgow) , Giannantonio Cibin (Diamond Light Source) , Hendrik Van Rensburg (Sasol Group Technology) , Stewart F. Parker (University of Glasgow; ISIS Facility) , Paul B. Webb (University of St Andrews) , David Lennon (University of Glasgow)
Co-authored by industrial partner: Yes

Type: Journal Paper
Journal: Journal Of Catalysis

State: Published (Approved)
Published: October 2020
Diamond Proposal Number(s): 15151 , 18431

Open Access Open Access

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.

Journal Keywords: Fischer-Tropsch-to-olefins catalysis; inelastic neutron scattering; XANES; chemical modifiers

Subject Areas: Chemistry


Instruments: B18-Core EXAFS

Added On: 13/10/2020 15:32

Documents:
1-s2.0-S0021951720303936-main.pdf

Discipline Tags:

Catalysis Physical Chemistry Chemistry

Technical Tags:

Spectroscopy X-ray Absorption Spectroscopy (XAS) X-ray Absorption Near Edge Structure (XANES)