Chloe Cannon

Alkali Metal Halide Supported Alkali Metals as Gas Purification Agents

Gas purification gives access to gas feedstocks for uses such as industrial processes, transportation fuels, and cryogenics. Perhaps of greater daily impact is the importance of gas purification in the remediation of waste gases from e.g., internal combustion or semiconductor manufacture. Such approaches are essential to the removal of gases that are inherently toxic (e.g., carbon monoxide), corrosive (e.g., hydrogen chloride), or smog-generating (e.g., oxides of nitrogen). Remediation of many of these are well established, usually via neutralisation, adsorption and/or combustion or by oxidative catalytic processes that provide lower harm products (e.g., toxic carbon monoxide to inert carbon dioxide). In contrast, there are a large number of gases where current remediation methods are unattractive, costly or otherwise limited. One particularly challenging class of compounds are highly fluorinated main group species such carbon tetrafluoride and sulfur hexafluoride. These gases are integral to the semiconductor and battery industries, and their use cannot be obviated at current. They also represent a grave environmental threat; perfluorinated main group compounds are potent greenhouse gases and less fluorinated systems are often ozone depleting. Emission to the atmosphere must be eliminated by gas-purification engineering controls. At current, this is done through high temperature combustion, an energy intensive and industrially unattractive process.

The major challenge in developing alternative remediation methods is the high thermodynamic stability of S-F and C-F bonds which are inert to most conditions. The alkali metals, lithium, sodium, and potassium have been shown to activate C-F and S-F bonds. In the case of sodium, high abundance and low cost also make it an attractive remediation agent. At current, however, the physical properties of sodium, a bulk metal, preclude its application. The Liptrot lab has recently developed a new route to alkali metals which have been deposited onto alkali metal salts. These species have significant potential as gas remediation agents, and can be synthesised in a sufficiently scaleable fashion to allow widespread exploitation.

In this project, Chloe will optimise the generation of Na/NaCl and related systems; tune the loading of alkali metal present; and manipulate the physical properties of these materials to ensure they can react with gas streams. Chloe will then explore their reactivity towards usually unreactive bonds, initially using solution phase model compounds and ultimately towards the identified gas waste streams. In doing so, Chloe will add an important gas abatement solution which will enhance the sustainability of processes that underpin a huge swathe of modern technology in the form of batteries and semiconductors.