(558ba) Ionic Liquid-Based Gas Separation: From Material Design to Applications

Xiangping Zhang ^a,b, Haifeng Dong ^a, Shaojuan Zeng ^a, Yi Nie ^a

^a Institute of Process Engineering, Chinese Academy of Sciences, 100190, Beijing, China

^b University of Chinese Academy of Sciences, Beijing 100049, China

Email:xpzhang@ipe.ac.cn

Ionic liquids (ILs) have received burgeoning academic and industrial interests as promising alternatives in gas separation owing to the unique characteristics, such as extremely low vapor pressure, optimistic gas solubility and tunable properties¹. In our work, from an industrial viewpoint, a multi-scale (micro-meso-macro) research strategy was applied for IL-based gas separation (such as CO₂ and NH₃) through a parallel R&D mode, including IL screening and synthesis, unit design, engineering scale-up and process design.

Firstly, the structure-property relationship and absorption mechanism of ILs were revealed by combining molecular simulation with experimental characterization². For acidic gas, the stronger the H-bond interaction between ILs and CO₂/SO₂ and the larger the volume of the anion, the greater influence on CO₂/SO₂ capacity greatly. For alkaline NH₃, the H-bond and cations play important roles, and the introduction of metal ions can greatly improve NH₃ capacity over 30 times than conventional ILs³. Moreover, considering the diversity and complex molecular structures of ILs, a novel ionic fragment method combining with molecular simulation was proposed to predict structure-property relationship of pure and multicomponent systems with less depending on experimental data. Based on these results, the targeted ILs and IL-based materials were designed and prepared for gas separation. Then, considering novel units scale-up of IL-based system, the hydrodynamics and transport properties were obtained by experimental measurement and CFD calculations for the optimal structure of unit⁴. Finally, based on the establishment of thermodynamic models of IL-based system, the IL-based process simulation and assessment (such as energy consumption, environmental impact and economic performance) were further performed⁵, which will provide useful information to develop the energy-saving and cost-efficient gas separation technology with ILs. Based on the above studies, the pilot plants of CO₂ separation from biogas (capacity 80,000 standard cubic metre/a), SO₂ removal from flue gas (capacity 2400,000 standard cubic metre/a) and NH₃ recovery from ammonium molybdate tail gas (capacity 0.13 billion standard cubic metre/a) with IL-based systems were finally established, which show great potentials for industrial applications.

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