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Title: Iron and cobalt based heterogeneous catalysts for the conversion of CO2 to hydrocarbons
Author: Owen, R. E.
ISNI:       0000 0004 5357 1632
Awarding Body: University of Bath
Current Institution: University of Bath
Date of Award: 2014
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Hydrocarbons, currently derived from crude oil, represent a vital source of fuel as well as an important feedstock in many chemical processes. As a result the dwindling crude oil supply is likely to have a significant impact on society. When combined with the long timescale and large cost associated with their substitution it becomes obvious that a new route for hydrocarbon production is essential. CO2 has been gaining significant attention as a possible feedstock due, in part, to its low cost and renewable nature. The work reported within this thesis focuses on the development of catalysts that are active for both the reverse water gas shift (RWGS) reaction and the Fischer-Tropsch (FT) process simultaneously allowing the direct conversion of CO2 to hydrocarbons. Chapter 1 outlines the research carried out to date on the conversion of CO2 to hydrocarbon products as reported in the literature. A more detailed discussion on the motivation behind this work is given along with an introduction to both the reverse water-gas shift reaction and the Fischer-Tropsch process with a review of the literature associated with both processes. The aims of the work conducted within this thesis are contained at the end of this chapter. Chapter 2 details the experimental procedures used for the reported catalyst studies. The construction of each of the reactors used is given along with information on the components used. The characterisation methods utilised are introduced and the equipment and conditions used are detailed. Full information on the product analysis is also reported within this chapter. Chapter 3 reports the results obtained from an investigation into the utilisation of magnesium oxide as a possible catalyst support for iron, cobalt and nickel based catalysts for CO2 hydrogenation. The use of both palladium and potassium as potential promoters for Fe-MgO and Co-MgO catalysts was also investigated and reported along with the use of mixed MgOSiO2 supports for a potassium and palladium promoted iron system. Chapter 4 investigates in the use of palladium as a potential promoter for use in conjunction with an iron-silica catalyst. This three component system was further optimised for the production of heavier hydrocarbons and a higher CO2 conversion by the variation of both iron and palladium loading. The environmental impact associated with the preparation of each catalyst was assessed and compared relative to the improved performance through the use of life cycle assessment. Chapter 5 looks at the use of copper, zinc and gallium as possible promoters for the formation of hydrocarbons from CO2 over an iron-silica catalyst system. The study was extended to include further metals from Group 11 and Group 13 in order to determine how their promotional ability varied as you descend each group. The effect of promoter loading was also studied for the indium and gold containing systems. Chapter 6 includes further studies into the effects of the silica support properties on the performance of an iron-silica catalyst. Further investigations included the influence of reaction conditions such as WHSV, pressure and temperature. From these studies information on activation energies, mass transfer limitations and reaction mechanisms was derived. Chapter 7 outlines the investigations into the use of cobalt as the main catalyst component for CO2 hydrogenation. The influence of support properties as well as the effects of introducing a range of different noble, alkali and transition metal promoters was studied. These systematic studies allowed the development and optimisation of a cobalt-based CO2 hydrogenation catalyst that showed a high CO2 conversion combined with a good selectivity towards C2+ hydrocarbons.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available