Fabrication and evaluation of nanocomposite membranes of polyethersulfone/α-alumina for hydrogen separation

Abstract

In this study, polyethersulfone (PES)-based nanocomposite membranes with the incorporation of inorganic filler of α-alumina were prepared via thermal phase inversion method. The fabricated flat sheet-mixed matrix membranes were characterized using X-ray diffraction, thermal gravimetric analysis, differential scanning calorimetry, scanning electron microscopy, and atomic force microscope analysis, and the permeation tests were performed for hydrogen, nitrogen and carbon dioxide. Also prepared α-alumina particles were identified by X-ray diffraction and the surface area, total pore volume and average pore diameter of particles were measured with a high-speed gas-sorption analyzer. The distribution and dispersion of α-alumina particles suspended in the polymer matrix were uniform and the surface roughness of the nanocomposite membranes was obviously lower than that of the pure membranes. The thermal analysis indicated that the glass transition temperature of the mixed matrix membranes was around 221.23 °C and the initial degradation temperature was up to 433 °C in air. The nanocomposite membranes increased the permeability of hydrogen, nitrogen and carbon dioxide gases and the hydrogen over nitrogen selectivity, simultaneously and shifted above the Robeson’s upper bound line-2008. The results showed that the nanocomposite membrane containing 8 wt % of α-alumina led to a considerable and simultaneous increase in the permeability of hydrogen (up to 8 times at pressure of 4 bar) and the selectivity of hydrogen over nitrogen (up to 2.4 times at pressure of 4 bar) in comparison to the neat polyethersulfone membranes. The pressure dependence of the gas permeability of the membranes was also investigated and based on selectivity versus permeability charts, the appropriate morphology of the nanocomposite membrane was suggested. Overall, the capability of α-alumina as an inorganic filler for hydrogen separation application has been shown.