Enhancing CO₂/N₂ and CO₂/CH₄ separation in mixed matrix membrane: A comprehensive study on Pebax®1657 with SSMMP/IL for improved efficiency

Abstract

Mixed matrix membranes (MMMs) have been proposed as a solution to surmount Robeson's trade‐off curves and have demonstrated efficacy in gas separation processes, particularly for CO2 capture. In this study, MMMs based on Pebax®1657 were obtained utilizing synthetic silico‐metallic mineral particles (SSMMP) functionalized with ionic liquids (ILs). The objective was to attain enhanced CO2 separation performance, thereby showcasing the potential to mitigate the environmental repercussions of industrial processes that entail greenhouse gas emissions. For membrane production, an ethanol/water mixture was used as solvent, with the SSMMP/IL content varying from 0.5 to 20% by weight of the polymer. The primary aim of this study was to assess the effect of filler addition on permeability and selectivity for CO2, CH4, and N2. Comprehensive analyses, including SEM, FTIR, TGA, DSC, and DMA were conducted to evaluate the properties of the produced membranes. Gas permeability and ideal selectivity were measured at 25°C and different pressures, ranging from 1 to 7 bar. Characterization results demonstrate that the glass transition temperature (Tg) of MMMs increased compared to pure Pebax®1657, indicating that the addition of SSMMP/IL reduces the flexibility of the PEO chains, forming a rigid interface at the polymer/filler, which may enhance selectivity. This effect, corroborated by gas permeation, was observed for both CO2/N2 and CO2/CH4. For CO2/N2, the highest selectivity was achieved at lower filler concentrations, gradually decreasing as the filler load increased. MMM‐0.5 wt% achieved the highest selectivity of 91.96. The membrane CO2 permeability rose with an elevated filler content, rising from 84.21 for pure Pebax®1657 to 192.17 Barrer for MMM‐20 wt% at 4 bar. The permeability results were influenced by the gas diffusion coefficients of the MMMs, which increased with increasing SSMMP/IL content. The effect of feed pressure on MMM‐5 wt% was also assessed, revealing that CO2 permeability increased with increasing pressure, from 126.72 Barrer at 1 bar to 165.56 Barrer at 7 bar. This work showcased the viability of MMMs incorporating SSMMP/IL for industrial use, as they displayed separation capabilities that exceeded the 2008 Robeson upper bound.Highlights Mixed matrix membranes based on Pebax®1657 and SSMMP‐20%‐[bmim][Tf2N] were prepared. CO2 permeability of the MMMs was increased by 128% and CO2/N2 selectivity by 83%. Higher CO2 pressures increase MMMs permeability. The obtained MMMs have separation performances above the Robeson upper Bound.