Sorption and permeation study of polyetherimide/hydrophobic silica nanocomposite membrane for effective syngas (H2/CO/CO2) separation

Abstract

This study aimed to fabricate and investigate the nanocomposite membrane made of polyetherimide (PEI) and hydrophobic fumed silica as filler. Commercial nanosilica (0–20 wt%) was embedded into PEI (Ultem1000) to prepare PEI/Silica dense nanocomposite membranes. Permeability and solubility of H2, CO, and CO2, as the main gases in syngas mixture, was investigated at 2–6 bar and 25 ± 1 °C. The effect of feed pressure (2–6 bar) on the gas permeability and solubility was studied for the pure and nanocomposite membranes. The membrane characterization was examined by FTIR, XRD, DSC, SEM, and EDX analysis. It revealed that in the low percentage of nanosilica, the permeability increased and the selectivity decreased, as the permeability of H2 increased from 1.08 to 1.63 barrer at 6 bar, while H2/CO and H2/CO2 decreased from 19.6 to 15 and from 3.8 to 3.6, respectively. The SEM and EDX images showed that by the increase in nanosilica loading, the silica particles dispersed more uniformly in the polymer matrix and formed membranes without any defect. For the nanocomposite membrane containing 20 wt% nanosilica, in comparison with pure PEI membrane, the H2/CO selectivity increased by almost 350% and reached 66.4, while H2 and CO permeability reduced by 21% and 77%, respectively. Solubility and diffusivity obtained through gas sorption measurement experiments, confirmed these outcomes, as the hydrogen diffusivity increased by an increase in nanosilica loading but CO and CO2 diffusivity decreased.