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Title: Spectroscopic studies of the Fischer-Tropsch process and gas sorption in metal organic frameworks
Author: Davies, Andrew James
Awarding Body: University of Nottingham
Current Institution: University of Nottingham
Date of Award: 2013
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An introduction to reaction intermediates and the techniques used to identify them in this Thesis is outlined. Additionally the Fischer-Tropsch reaction is also described. This reaction is the subject of the work presented in Chapters 2 to 4. Chapter 2 The development of a gas pulse initiated time-resolved lA rig is summarised in this Chapter. The effect of various experimental conditions on the duration of the pulse of gas within the IR cell was explored with the use of a KBr sample. Additionally, a repeat of two relevant studies from the literature was performed in order to validate the results obtained on this new rig. Chapter 3 This Chapter focuses on the Fischer-Tropsch reaction over Co/Ab03. A combination of both rapid-scan FTIA and point-by-point quantum cascade laser spectroscopy was used to elucidate the intermediates involved in the reaction. Transient lA bands in the organic carbonyl region were observed and tentatively assigned to the formation of formyl units on the Co surface, based upon the lA spectra of organometallic analogues. Additionally, 13CO pulsing, as well as studies into the effect of H2 on these bands, were performed in order to further support this identification. Kinetic traces were obtained at variable temperatures in order to obtain the activation energy parameters, which were then compared to the calculated barriers for possible intermediates reported in the literature. The reproducibility of the transients with successive pulses of CO was also probed. Due to the limited IR window, product formation was not observed and, therefore, these intermediates have yet to be definitively linked to the Fischer-Tropsch Reaction. This Chapter also investigates the effect of CO pulsing over two reduced Fe catalysts. Chapter 4 Investigations into the reaction of CO over Fe particles supported in a matrix at low temperature are reported in this Chapter. Metallic Fe nanoparticles embedded in a silica disc were cooled to 100 K under inert conditions and then exposed to CO gas. Rapid formation of carbonyls was observed. Despite being stable at 100 K, warming by a few degrees caused a rapid, partial dissociation of the carbonyl species. Further warming resulted in further dissociation. Chapter 5 This Chapter reports infrared investigations into the gas uptake of Metal Organic Frameworks (MOFs). Unusual behaviour in the uptake of CO2 by a bifunctional MOF, Co(HL de), which exhibited a two-step uptake isotherm, was probed with FTIR. This was originally proposed to be due to two distinct forms of CO2, however IR spectra indicated that a single species of adsorbed CO2 was present within the pores of the MOF before and after the step. Additionally, S02 uptake in NOTT-202 and CO2, S02 and N02 in NOTT-300 was also probed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available