Copper-Containing Ionic Liquids for the Separation of Carbon Monoxide from Gas Mixtures

Chapter 1 introduces the usefulness of CO as a feedstock for industrial catalytic reactions and outlines some of the current CO purification techniques. The use of copper(l) salts in ILs as a purification technology is explored and the reversible binding of CO to Cu(I) is discussed. The aims of the project are outlined. Chapter 2 reports the methods used to synthesise various ionic liquids and copper(l) salts and their subsequent combination to form the target copper(l)-containing ILs. The methodology of the instrumentation was recorded and characterisation details obtained. Chapter 3 details the synthesis of copper(l)-containing ILs from 1-alkyl-3-methyl imidazolium salts with weakly coordinating anions. Their physical properties such as density and viscosity are assessed and reversible reactions with CO are demonstrated using high-pressure infrared spectroscopy. The formation of copper monocarbonyl and dicarbonyl complexes formed is discussed. Chapter 4 outlines the synthesis of copper(l)-containing ILs based on imidazolium cations functionalised with ether or highly fluorinated substituents. Properties such as viscosity, density and CO uptake of these systems are compared to the non-functionalised analogues. Chapter 5 describes the use of copper-containing ILs with weakly coordinating anions to separate CO from gas mixtures containing H2 and N2. Comparisons to the free halide systems are drawn and ii implications for potential commercial use are discussed. Their ability to separate CO from other gases such as CH4 and CO2 is also discussed with reference to literature solubility data. Chapter 6 explores the use of high-boiling point co-solvents (e.g. dimethyl malonate or dimethyl glutarate) in conjunction with the copper-containing ILs to reduce the viscosity of the mixture. The stability of the copper species and the effect on properties such as viscosity, copper concentration and density are investigated. The use of these mixtures to separate CO from H2 and N2 is explored. Chapter 7 gives the overall conclusions to the project and suggestions for future work. Appendices include supplementary spectroscopic and experimental data.