Halometallate-based ionic liquid catalysts

Leu, Meike K. (2022) Halometallate-based ionic liquid catalysts. PhD thesis, University of Nottingham.

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Abstract

This work focuses on the synthesis and characterisation of halometallate ionic liquids (ILs), including Co(II), Ni(II), Cu(II), Zn(II), In(III), and Fe(III) metal halides. Due to their Lewis acidic nature, halometallate ILs are promising candidates as catalysts. In addition, ILs show advantageous properties (e.g. low vapour pressure and good ionic conductivity) for their use in catalytic applications using inductive heating methods such as microwave (MW) radiation or magneto-thermal heating. As for any catalyst the understanding of the catalytically active species and the properties of the respective catalyst are fundamental to explain the catalytic process. As to the best of our knowledge, no phase diagram has been reported for mixtures of [C1C4Im]Cl/CoCl2 and [C1C4Im]Cl/NiCl2, these were prepared to further understanding of discrete anion formation. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to prepare the phase diagram and it is demonstrated how small changes in mole fraction lead to significant changes in thermal behaviour. In addition, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to find additional evidence for anions formed. However only the formation of [MCl4]- could be observed.

Furthermore, dielectric properties are investigated as they are crucial to a future application of halometallate IL catalysts in MW radiation. The data was analysed and showed dependency regarding change with temperature and frequency. Conductivity was calculated from the obtained data and was confirmed by impedance spectroscopy. The observed dielectric constants vary depending on the metal and are in a range from ɛ’ = 3.4-13.9.

Finally, mechanistic and kinetic studies were carried out to determine the catalytically active species of the novel IL [C1C4Im][Fe(NO)2Cl2], which was used as a catalyst for carbon dioxide (CO2) conversion. Full conversion with good selectivity to the desired product was observed at optimised reaction parameters (neat, 40°C, 2 bar CO2, 24h, 5 mol% catalyst loading).

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Licence, Peter
Alves Fernandes, Jesum
Dimitrakis, Georgios
Keywords: Halometallate ionic liquids, Catalysts
Subjects: Q Science > QD Chemistry > QD450 Physical and theoretical chemistry
Faculties/Schools: UK Campuses > Faculty of Science > School of Chemistry
Item ID: 60712
Depositing User: Leu, Meike
Date Deposited: 28 Jul 2020 10:16
Last Modified: 28 Jul 2020 10:30
URI: http://eprints.nottingham.ac.uk/id/eprint/60712

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