Effect of Ethylene Oxide Functional Groups in PEBA-CNT Membranes on CO2/CH4 Mixed Gas Separation

Abstract

Poly (ether-block-amide) /poly (ethylene glycol)/ carbon nanotubes mixed matrix membranes have been successfully fabricated using solvent evaporation method to determine the effect of ethylene oxide groups on the performance of produced membranes. The effects of CNTs (2-8 wt%) and PEG (up to 50 wt%)were investigated in both single and mixed gas test setup in different temperature and pressure. Finally the membranes were structurally characterized using Scanning Electron Microscopy, X-Ray Diffraction, Fourier Transform Infrared Spectroscopy, and Atomic Force Microscopy.Results showed that addition of carbon nanotubes enhanced the gas separation performance of membranes and presences of ether groups in poly ethylene glycol improved the CO2 permeability. Membrane containing 8 wt % carbon nanotubes and 50 wt % poly ethylene glycol showed the best performance with CO2/CH4 selectivity of 45 and CO2permeability of 302 at pressure of 14 bars. Also, mixed gas permeation experiments were carried out and results showed dramatic decrease in CO2 selectivity due to membrane plasticizing. The permeability of CO2 in mixed gas test for membrane containing 50 wt% pol ethylene glycol and 8 wt% was 193 with CO2/CH4 selectivity of 19 in room temperature. Furthermore, membranes produced by 6 and 8 wt% carbon nanotubes and 50 wt% poly ethylene glycol placed above Robeson’s trade-off line. The effect of temperature on performance of fabricated membrane was finally investigated. Results showed an increase in permeability and decrease in selectivity for all membranes.