Ultra-stable and cost-efficient protic ionic liquid based facilitated transport membranes for highly selective olefin/paraffin separation

• Published in: Journal of membrane science 2018-07, Vol.557, p.76-86
• Main Authors: Dou, Haozhen, Jiang, Bin, Xiao, Xiaoming, Xu, Mi, Wang, Baoyu, Hao, Li, Sun, Yongli, Zhang, Luhong
• Format: Article
• Language: English
• Subjects: Facilitated transport membranes; Long-term stability; Protic ionic liquids, olefin/paraffin separation
• ISSN: 0376-7388; 1873-3123
• DOI: 10.1016/j.memsci.2018.04.015

Facilitated transport membranes (FTMs) for olefin/paraffin separations have failed to achieve commercial success due to the instability of carriers although great efforts have been made. In this work, ultra-stable and cost-efficient protic ionic liquid based FTMs (PIL-FTMs) were firstly prepared by utilizing the Brönsted acidic property of PILs to stabilize the carrier. The gas solubility in the carrier/PILs was measured and the separation performances of PIL-FTMs were evaluated systemically. The results indicated that the structure of PILs affected the C2H4 permeability and the presence of ether group and hydroxyl group in PILs significantly enhanced the C2H4/C2H6 selectivity. The carrier concentration led to structural variation of PIL-FTMs, thus manipulating the gas separation performances of PIL-FTMs. The increase of transmembrane pressure decreased C2H4 permeability and C2H4/C2H6 selectivity, indicating a typical feature of FTMs. The increase of temperature increased the C2H4 permeability but decreased C2H4/C2H6 selectivity. The separation performances of PIL-FTMs were much higher than other results in the literature. Furthermore, the PIL-FTMs exhibited excellent stability during the long-term experiments carried out for six months. Finally, the investigation of separation mechanism revealed that the hydrogen-bonding and coordinative interactions between PILs and carrier accounted for the high separation efficiency of PIL-FTMs. In all, the excellent long-term stability, outstanding separation performances and economic feasibility of PIL-FTMs could play an important role in moving these membranes toward industrial application. [Display omitted] •PILs-FTMs were firstly employed for the C2H4/C2H6 separation.•The long-term stability of carrier was obtained by the Brönsted acidic property of PILs.•The activity of carrier was enhanced by the hydrogen-bonding and coordinative interactions.•PILs-FTMs exhibited excellent separation performances and long-term stability.