(462h) Efficient and Reversible Separation of Ammonia with Ionic Liquid-Based Materials

Authors: 
Zeng, S., Chinese Academy of Sciences
Dong, H., Institute of Process Engineering, Chinese Academy of Sciences
Zhang, X., Beijing Key Laboratory of Ionic Liquids Clean Process,CAS Key Labroratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences
Shang, D., Institute of Process Engineering, Chinese Academy of Sciences, 100190, Beijing, China
Zhang, S., Beijing Key Laboratory of Ionic Liquids Clean Process,CAS Key Labroratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences
Efficient and Reversible Separation of Ammonia with Ionic Liquid-based Materials

Shaojuan Zeng a, Dawei Shang a, Haifeng Dong a,Xiangping Zhang a,*, Suojiang Zhang a,*

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

*Corresponding author: xpzhang@ipe.ac.cn; sjzhang@ipe.ac.cn

As one typical alkaline and poisonous gas, NH3 emission inevitably causes serious air pollution problems, such as fog and haze, which has raised extensive attentions worldwide. The commercial methods, like water scrubbing and acid scrubbing, can purify the NH3-containing gas mixtures, but they substantially transfer the NH3 pollute from gas phase to liquid or solid phase, which doesnot mean total elimination1. Therefore, how to efficiently separate NH3 and simultaneously recover high purity of NH3 easily is the most fundamental way but also a great challenge. The emerging of Ionic liquids (ILs) provides a promising way to efficient separation of NH3 owing to their peculiar properties, like nonvolatility, designability and high stability2.

In this work, the interaction between NH3 and ILs and the structure-property relationship was firstly revealed by combining simulation calculations and experimental characterizations. The results indicated that the H-bond and cations play an important role in NH3 absorption, and the stronger H-bond means higher NH3 capacity. Meanwhile, the introduction of the metal center into ILs greatly improves NH3 absorption through chemical complexion. Based on these results, a series of functionalized Lewis-acid ILs with the metal center on anions and Brønsted-acid ILs with the acidic H groups on cations were designed for efficient and reversible absorption of NH3, respectively. For example, the Brønsted-acid IL [Bim][Tf2N] can absorb 2.69 molNH3·molIL-1 at 40℃ and 0.10 MPa through the strong hydrogen bonding between NH3 and cations3. The cobalt ILs [Cnmim]2[Co(NCS)4] not only have exceptional NH3 capacity and high NH3/CO2 selectivity, but also excellent recyclability. The maximal NH3 capacity is up to 6.09 molNH3·molIL-1 at 30℃ and 0.10 MPa, which is over 30 times higher than the conventional ILs4. On the other hand, considering the higher viscosity of these ILs, the ILs and porous materials were combined to form new adsorbents for NH3 separation. Compared with pure silica gel, NH3 adsorption capacity of IL-based materials increases by 70-100%, and the adsorption and desorption process is also very fast. These findings will provide significant theoretical basis to develop efficient and reversible IL-based technologies for NH3separation.

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  2. S. J. Zeng, X. P. Zhang, L. Bai, X. C. Zhang, H. Wang, J. J. Wang, D. Bao, M. D. Li, X. Y. Liu and S. J. Zhang, Chem Rev, 2017, 117, 9625-9673.
  3. D. W. Shang, X. P. Zhang, S. J. Zeng, K. Jiang, H. S. Gao, H. F. Dong, Q. Y. Yang and S. J. Zhang, Green Chem, 2017, 19, 937-945.
  4. S. J. Zeng, L. Liu, D. W. Shang, J. P. Feng, H. F. Dong, Q. X. Xu, X. P. Zhang and S. J. Zhang, Green Chem, 2018, DOI: 10.1039/c8gc00215k.