Gas Drying Using Supported Ionic Liquids

Abstract

Supported ionic liquids are promising pseudo-adsorbents for gas drying processes. They are produced by impregnation of hygroscopic ionic liquids with low vapor pressures on silica surfaces. A screening of potential alternatives to [EMIM][MeSO3] revealed that [EMIM][TFA] is sufficiently hygroscopic but not thermally stable enough for technical use. [EMIM]Cl shows, compared to [EMIM][MeSO3], a higher affinity for water absorption, but is less stable as well as corrosive. [EMIM][OTF] shows high thermal stability, but has an insufficient low activity coefficient of water, so that [EMIM][MeSO3] remains most promising. Water sorption isotherms and measurements of breakthrough curves in a bench scale fixed-bed adsorber confirmed, that depending on the operating conditions, the capacity for water can be increased in a supported system of [EMIM][MeSO3] impregnated on Silica 90, compared to adsorption at the pure silica surface. Exceptionally for medium to low partial pressures of water, supported systems appear to be favourable for adsorption processes. The shapes of the breakthrough curves of pure silica and the supported system are similar, what indicates similar or only slightly increased mass transport resistances due to the impregnation.