Development of Ionic liquids for energy-saving type air conditioning system; origin of the moisture absorption capability of ionic liquids

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K05159
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 34030:Green sustainable chemistry and environmental chemistry-related
• Research Institution: Toyota Physical and Chemical Research Institute
• Principal Investigator: ITOH TOSHIYUKI 公益財団法人豊田理化学研究所, フェロー事業部門, フェロー (50193503)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: イオン液体 / 調湿材 / 液式調湿空調機 / 調湿機構解明 / 小角X線散乱スペクトル / MDシミュレーション

Outline of Final Research Achievements

We have been deeply interested in their moisture absorption capability because this makes ILs possible candidates for desiccants for the liquid desiccant-type air conditioners (LDAC). To gain insights into the origin of ILs’ dehumidification capability (DC), we systematically synthesized various types of ILs by combining dimethylphosphonium anions with various types of alkyl group-substituted cations and found that the DC was vary with the alkyl substituent of the cations. Among tested ILs, the best IL afforded 14-times higher DC (mol) than that of the popular solid desiccants CaCl2. We conducted small- and wide-angle X-ray scattering (SWAXS) analysis of 8 types of 1,2,4-triazolium dimethylphosphate and established that water from air is absorbed mainly into polar regions of nanostructured ILs. MD simulation experiments suggest that the introduction of an appropriate alkyl side chain in the cationic moiety can be the key to the design of efficient desiccant ILs for LDAC

Free Research Field

有機合成化学，イオン液体

Academic Significance and Societal Importance of the Research Achievements

液式調湿空調機は現在主流のコンプレッサー型空調機に較べて80％以下の消費電力で運転できる省エネ性能に加えて換気を行いつつ運転ができる．ところが現行の液式調湿空調機は調湿材として塩化リチウム水溶液を使用しているために普及が進んでおらず，塩化リチウムに替わる調湿材を開発することが地政学的観点からも求められていた．本研究では液式調湿空調機の調湿材に適したイオン液体の開発を目指して研究を進め，塩化リチウムを凌駕する調湿機能を持つイオン液体を見いだし，さらに従来未解明であったイオン液体の調湿機能の起源がイオン液体が形成するナノ集合体の構造に起因することを明らかにした．