The application of inelastic neutron scattering in the investigation of iron-based Fischer-Tropsch catalysts

Davidson, Alisha Louise (2019) The application of inelastic neutron scattering in the investigation of iron-based Fischer-Tropsch catalysts. PhD thesis, University of Glasgow.

Abstract

The main aim of this study was to expand on previous projects that have established the use of inelastic neutron scattering (INS) to investigate a range of iron-based Fischer-Tropsch catalysts applied to the hydrogenation of CO at elevated temperature. The project initially makes use of a standard reference hematite catalyst (α-Fe2O3) and analyses the temporal behaviour of the hydrocarbonaceous overlayer known to form on the catalyst for an extended period of time on stream (240 h). INS analysis was complemented by other techniques such as X-ray diffraction, Raman spectroscopy and temperature-programmed oxidation (TPO) measurements to establish the complete evolutionary profile of the standard hematite catalyst.

This methodology was also applied to a range of doubly promoted iron-based catalysts that have the potential to be Fischer-Tropsch to olefins (FTO) catalysts. FTO chemistry has gained significant interest over the past several years as it provides a means of supplying lower olefins (C2-C4) independently from crude oil. Five catalyst samples were tested over a range of sulfur concentrations (10 – 250 ppm) with a fixed concentration of sodium (2000 ppm). As well as the techniques utilised for the reference catalyst, XANES was applied to determine the form of the sulfur within the catalyst before and after exposure to CO hydrogenation conditions.

Of the five doubly promoted iron-based catalysts tested, one was selected to be analysed as a function of time on stream up to 24 h utilising INS and TPO to investigate how the rate of the hydrocarbonaceous overlayer formation was affected by the inclusion of promoters. Additionally, using the same catalyst, a preliminary measurement was carried out which involved the introduction of CO2 into the reactant mixture. Once more, INS was utilised to determine how the addition of a CO2 co-feed would affect the formation of the hydrocarbonaceous overlayer. From a combination of characterisation and reaction testing of the doubly promoted iron catalysts, a scheme is proposed to account for the addition of the promoters, sodium and sulfur, and the role in which these modifiers may play in the FTO process.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Subjects: Q Science > QD Chemistry
• Colleges/Schools: College of Science and Engineering > School of Chemistry
• Supervisor's Name: Lennon, Professor David
• Date of Award: 2019
• Depositing User: Alisha L. Davidson
• Unique ID: glathesis:2019-75143
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 01 Nov 2019 14:05
• Last Modified: 04 Nov 2024 08:39
• Thesis DOI: 10.5525/gla.thesis.75143
• URI: https://theses.gla.ac.uk/id/eprint/75143