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Conversion of CO2 to fuels using supported Cu catalysts

Tariq, Anisa 2022. Conversion of CO2 to fuels using supported Cu catalysts. PhD Thesis, Cardiff University.
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Abstract

Amid global warming concerns and skyrocketing CO2 emissions in the atmosphere, mainly associated with the combustion of fossil fuels to produce energy, the research community has gained a large interest in CO2 capture and reutilization to produce renewable fuels such as methanol (MeOH), dimethylether (DME) and additional hydrocarbons. MeOH is currently produced from syngas (H2 + CO + CO2) over a Cu/ZnO/Al2O3 (CZA) catalyst at mild temperature (200 - 270 °C) and high pressure (50 - 100 bar) and has a global demand exceeding 98 Mt/annum. Syngas is produced from the steam reforming of hydrocarbons, predominantly methane, and consequently the overall process has a great environmental cost (ca. 88 Mt GHG eq). Therefore, a more effective approach such as CO2 hydrogenation to MeOH is required to enable the synthesis of CO2-neutral fuels whilst mitigating anthropogenic emissions. The catalytic conversion of CO2 into methanol and DME bears a strong potential to transform large amounts of CO2 in a short span of time due to the commonly reported high reaction rates. In order for the process to be sustainable in the light of the carbon cycle, H2 should be produced in a greener way, e.g., photocatalytic water splitting and water electrolysis sourced by natural/renewable energy sources. The literature surrounding the synthesis of methanol from CO2 hydrogenation has predominately been based on Cu catalysts and this is due to its remarkable hydrogenation activity and abundance. Although many new active catalyst formulations have been developed, they still carry the problem of incorporating harmful/expensive elements, making them less valuable for commercial use. As such this thesis explores the use of various supported Cu catalysts; Chapter 3 investigates the effect of various supported Cu catalysts prepared via the oxalate gel synthesis method, with a particular focus on Cu/ZrO2, towards the conversion of CO2 to MeOH. The role of various promoters (Pd, Pt, Ce, Ni and Ag) and the stability of these catalysts is also investigated. Chapter 4 explores the impact of varying the calcination temperature and reduction temperature of the Cu/ZrO2 catalysts prepared via oxalate gel, towards their hydrogenation of carbon dioxide to methanol. The deposition of Cu onto the ZrO2 polymorphs by oxalate gel and wet impregnation is also investigated to understand the effects of preparation method and support phase on catalytic activity. Finally, Chapter 5 investigates the synthesis of MeOH, DME and higher chain hydrocarbon between various CuZn or CuZr Zeolite integrated catalysts prepared via chemical vapour impregnation (CVI) and oxalate gel precipitation. Physical mixtures of the catalysts, as well as changes to the catalyst bed, are also explored in order to compare the catalyst activity

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Chemistry
Date of First Compliant Deposit: 31 October 2022
Last Modified: 10 Jun 2023 01:52
URI: https://orca.cardiff.ac.uk/id/eprint/153859

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