Applied highlights.(Highlights)

Ionic liquid storage of toxic gases

Storing and handling highly toxic compounds at high pressures greatly increases risks of leaks and accidental releases compared with dangerous solids and liquids that have negligibly small vapour pressures. But some gases must be stored at high pressures, for example, those that cannot be liquefied by ordinary industrial processes and compressed liquefied gases that have high vapour pressures even at moderate temperatures. Traditionally the gas industry has managed the potential safety hazards associated with such high-pressure gases through judicious use of suitable gas cylinders, valves, and related equipment. An alternative approach is to incorporate toxic gases into a medium that can hold large enough quantities of the substances to be practical for industrial use and can readily release the compounds as needed. Researchers at Air Products have discovered that ionic liquids can help mitigate some of the hazards of storing and shipping toxic and reactive gases at high pressures, by reversibly taking up large quantities of poisonous substances, such as phosphine and boron trifluoride, by forming chemical complexes with them, while retaining the low vapours pressures that are characteristic of ionic liquids (DJ Tempel, P B Henderson, J R Brzozowski et al, J. Am. Chem. Soc. 2008, 130, 400). Using a combination of experimental and computational procedures, the Lewis acidities and basicities of hazardous gases and ionic liquids can be matched into pairs that reversibly

form chemical complexes. For example, the toxic gas phosphine, a Lewis base, binds to imidazolium trichorodicuprate ionic liquid, a Lewis acid, in a 2:1 molar ratio. Similarly, the toxic gas boron trifluoride binds in equimolar ratios to a basic imidazolium etrafluoroborate. In both cases, at the maximum gas capacity of the ionic liquids, the pressure remains near 1 atm, which is a tiny fraction of the pressures at which P[H.sub.3] and B[F.sub.3] are typically shipped and stored. The gases are extracted from the ionic liquids by simply connecting the container in which the complexed material is stored to a vacuum source.

[ILLUSTRATION OMITTED]

In brief

* Multiple electrically wired surface enzyme logic gates

* MOFs for high-density gas adsorption

* Self-cleaning and controlled release smart films

* Selective NOx optical sensing

* Water soluble magnetite nanoparticles

* Magnetic transition metal room temperature ionic liquids

* Biodegradable microcapsules

* Microporous Polymers

* Hydrogen sensing nanoparticles

* Ionic liquid storage of toxic gases

Nigel P Freestone; The University of Northampton

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