Supported ionic liquid membranes with high carrier efficiency via strong hydrogen-bond basicity for the sustainable and effective olefin/paraffin separation

HaozhenDou, BinJiang, MiXu, JunhanZhou, YongliSun, LuhongZhang*

School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, People’s Republic of China

Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin University, Tianjin 300072, People’s Republic of China

Highlights

  • Supported ionic liquid membranes (SILMs) with high carrier efficiency were designed and fabricated.
  • The strong hydrogen-bond basicity of AILs greatly increased the number of carriers and enhanced the carrier efficiency.
  • The effect of interactions in membranes on the carrier activity were revealed at the molecular level.
  • The gas solubility was measured and described by a first-order equilibrium model quantitatively.
  • The SILMs obtained good C2H4 permeability, high C2H4/C2H6 selectivity and acceptable stability.

Abstract

Supported ionic liquid membranes (SILMs) constitute a radical advance in olefin/paraffin separation membranes. Unfortunately, the applications of SILMs are vastly hindered by low carrier efficiency. Herein, SILMs with high carrier efficiency via strong hydrogen-bond basicity were designed to carry out efficient ethylene/ethane separation. The strong hydrogen-bond basicity of ILs not only endowed the membranes with high carrier concentration, but also effectively favored for the good disassociation of carrier to form solvated free ions through coordinative interactions between IL and carrier, which greatly increased the number of carrier and enhanced the carrier efficiency. Benefiting from the high carrier efficiency, both ethylene permeability and ethylene/ethane selectivity were significantly elevated, which could reach up to 100 Barrers and 40, respectively, surpassing most of results reported in the open literature. Meanwhile, the ethylene and ethane solubility data in the carrier/ILs were measured in a pressure range from 0 to 3.5 bar at 298.15 K, a first-order equilibrium model based on the formation carrier-ethylene complex species has been developed to describe the physical and chemical dissolving behaviors of ethylene and the equilibrium constants were obtained accordingly. Moreover, the membrane separation process was optimized, confirming that ethylene permeability and ethylene/ethane selectivity increased with the increase of carrier concentration due to the combined effects of gas solubility and diffusion. It was notable that the selectivity of as-prepared SILMs was more effective at lower transmembrane pressures and operating temperatures, which contributed to designing the energy-efficient and sustainable membrane processes. This study opens a new route for the utilization of the IL properties to manipulate the carrier efficiency for developing high performance SILMs.

Graphical abstract

Keywords

Ionic liquids; Hydrogen bond basicity; Olefin/paraffin separations; Supported ionic liquid membranes; Thermodynamic analysis

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