Toshiyuki ITOH1, Toshiki NOKAMI2, Hyung KIM3
1Toyota Physical and Chemical Research Institute, Nagakute, Japan
2Tottori University, Tottori, Japan
3Carnegie Mellon University, Pittsburgh, United States
Liquid desiccant air-conditioners are expected to contributing sustainable living by reducing the electricity consumption . They can be driven with continuous ventilation, and thus can prevent airborne transmission of infectious diseases like COVID-19. In order to develop efficient desiccant materials for liquid desiccant air-conditioners, we have been investigating the dehumidification capability of ionic liquids (ILs) and discovered that several ILs, i. e.,tributylmethylphosphonium demethylphosphate , choline dimethylphosphate , and N1,N1,N1,N6,N6,N6-hexamethylhexane-1,6-diaminium bis(dimethylphosphate) ([HMC6][DMPO4]2) exhibited high dehumidification capability (DC) . Among them, DC per gram and dehumidification rate of the dicationic quaternary ammonium salts were superior to all popular solid desiccants. The DC depended on the carbon chain length of the spacer group -(CH2)n- that bridges the two terminal cationic moieties as order of (CH2)2 < (CH2)3 < (CH2)6. Importantly, favorable equilibrium water vapor pressures for the liquid desiccant air-conditioning system were attained for 80%(w/w)-60%(w/w) aqueous solutions of dicationic quaternary ammonium salts . We will report our further study to design IL type desiccant materials, in particular, investigation for clarifying the origin of dehumidification properties of imidazolium, triazolium, and pyrazolium salts.
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