HALOGENILS · New Halogenated Ionic Liquids as novel task-specific fluids

New halogenated ionic liquids as novel task-specific fluids

Ionic liquids (ILs) are organic salts with melting points below 100 degrees of Celsius. ILs gained prominence since 2001 when it was realised that room-temperature molten salts could be used to replace volatile organic solvents, as witnessed by the exponential growth of the number of publications in the field. Fluorinated organic compounds display many exceptional physicochemical properties that have been used in many commercial applications as refrigerants, surfactants, polymers, components of pharmaceuticals, fire retardants, lubricants and insecticides. The above-mentioned aspects motivated us to seek for the possibility of developing neoteric ILs with halogenated alkyl chains. This challenging project is mainly based on two scientific ideas. On one hand, these news ILs can be applied as solvents with improved extraction properties. The understanding at a molecular level of their nature and interactions can drive this research project a step forward into the industrial application of these compounds. On the other hand, the introduction of halogenated atoms on specific positions of the resonance ring cation of an IL can induce unique properties, such as lower viscosity or lower enthalpies of vaporisation, compared to the already available ILs. These general goals have been caught up with the following work. Firstly, to enlarge the understanding of halogenated ILs thermodynamic behaviour and thus to expand their possible applications, eight new halogenated ILs have been selected to study the effect of the halogenations' effect on the following properties: melting and decomposition temperature, density, refractive index, dynamic viscosity and ionic conductivity in a temperature range from 283.15 to 353.15 K at atmospheric pressure. The toxicity was also evaluated since it is an important property regarding the industrial applications. On the other hand, this work also explored the possibility of increasing the ionicity of ILs via the solubilisation of inorganic salts in their midst. The resulting purely ionic media - distinct IL plus inorganic salt mixtures - are liquid in an extensive concentration range and can be aptly denominated High Ionicity ILs (HIILs). Secondly, solid-liquid and liquid-liquid equilibria of the 17 binary mixtures were studied, at atmospheric pressure in a wide temperature range. Data were interpreted using molecular dynamic simulations. The study illustrates, once again, the unique structural and solvent properties of ILs. Furthermore, separations in alternative extraction schemes of fluorinated gases, carbon dioxide and separation of olefin / paraffin mixtures were also developed using as solvent two supported fluorinated ILs. This work provides results for understanding the factors that influence gas permeation, gas diffusion, gas solubility and separation selectivity in fluorinated ILs. Besides, a study of the thermodynamic (solubility) and transport (diffusivities) phenomena in the fluorinated ILs is important in the context of being working fluids in a chemical process. The inclusion of fluorinated groups in ILs can be very interesting for expanding the capabilities of ILs. The numbers of applications of these new fluorinated ILs are outstanding. Finally, eight new imidazolium and pyridinium ILs with one or two inductive groups were synthesised with good levels of purity for physicochemical studies. Viscosity measurements were performed for the bistriflimide ILs which showed a marked increase in viscosity due to the size of the halogen substituents. Molecular dynamic simulation data were performed to obtain a structural explanation for this behaviour. New ILs with distinct anions will also be tested to analyse if the flexibility of the bistriflimide anion is also playing a predominant role in these results. This research project exploited a new scientific branch of the field of ILs that is almost unexplored. With this work, significant fundamental results have been achieved and can be of relevant importance to this booming area. The results of this innovative research project shed light on the cutting-edge halogenated ILs branch, as well as the development of environmentally benign halogenated ILs applications. Other aims justify the development of this project, including novel greener processes with environmental and economic sustainability based on the almost null volatility of ILs, their ease of recovery and consequent recyclability. Over the last years, environmental concerns have highlighted the extensive and increasing importance of implementation of industrial processes using greener solvents. As European Union (EU) is set to play a major role in the global development of sustainable policies, the approach to investigations tackling the basis of future environmentally friendly processes is a crucial objective to be pursued. The development of new extractive process technologies using the research carried out under this submission was also evaluated. These technologies are more sustainable from the point of view of the environment, as well as economic, due to the almost null volatility of ILs (less air pollution compared to conventional volatile organic solvents used in today's industry) and recyclability. The specific design of the proposed ILs will also contribute for an increasing efficiency of extraction of halogenated compounds that are toxic to the environment. The project aims to introduce, in the EU, technology based on novel, non-volatile, recyclable ILs, as alternatives to volatile organic compounds (VOCs) currently used widely in all chemical sectors. At atmosphere conditions, ILs do not produce vapour emissions, thus reducing levels of VOCs. The great importance of reducing emissions of greenhouse gases is the priority goal of Kyoto Protocol, which has been signed by the EU. As a consequence, this project is moving into the direction of helping to fulfil these ambitious requirements.

Data: CORDIS, © European Union