Improved CO₂ separation performance of Matrimid®5218 membrane by addition of low molecular weight polyethylene glycol

Abstract

Polyethylene glycols have received worldwide attention as a highly permeable CO2‐philic polymer in carbon dioxide separation applications. In this study, we investigated the influence of a low molecular weight polyethylene glycol (PEG 200) on physicochemical, morphological, and gas separation properties of Matrimid®5218 as a novel polymer blend. Both symmetric and asymmetric Matrimid flat sheet membranes with 0–20 wt.% PEG were prepared via a dense film‐casting method. The miscibility of blends at low PEG concentrations (3–5 wt.%) was confirmed by differential scanning calorimetry (DSC) and polarized light microscopy (PLM). Moreover, the blends were partially miscible at higher PEG concentrations (10–20 wt.%). Matrimid/PEG molecular interactions were further studied by FTIR and XRD analysis. SEM images indicated an impressive influence of PEG on the symmetric structure of Matrimid membrane. An asymmetric structure with a dense thin skin layer and a highly porous sub‐layer was observed for the blends containing 10–20 wt.% PEG. The CO2 permeability and CO2/CH4 selectivity of the best‐yield CO2‐selective blend membrane (Matrimid/PEG (95:5)) incvreased about 25% (from 7.68 to 9.62 Barrer) and 15% (from 35 to 40) compared to pure Matrimid, respectively. Furthermore studying the plasticization pressures of the membranes revealed that the more PEG content in blend the less the plasticization pressure obtained. © 2015 Society of Chemical Industry and John Wiley & Sons, Ltd

Preparation and characterization of Matrimid® 5218 based binary and ternary mixed matrix membranes for CO2 separation

“…The existence and strength of hydrogen bonding can be employed as a criterion for miscibility (Ahn et al, 1977). Moreover, the miscibility of blends containing small portions of PEG due to the formation of hydrogen bonds properly is in agreement with the previous DSC results (Loloei et al, 2015).…”

“…6 As FTIR analysis showed, the formation of the hydrogen bonding between the silanol groups of calcined ZSM-5 and OH group of the PEG seems to be the source of adsorption of PEG 200 on the ZSM-5 zeolite surface. In other words, PEG additive creates stronger interactions with ZSM-5 compared with Matrimid (Loloei et al, 2015). This raises the possibility that by increasing the PEG concentration, particles agglomeration and a non-uniform distribution of ZSM-5 will be observed.…”

“…6E, the simultaneous addition of PEG200 and ZSM-5 to the Matrimid modifies its semi crystalline nature to amorphous, which the contribution of the PEG in this modification is certainly more than the calcined ZSM-5. Based on our previous study (Loloei et al, 2015), by increasing the PEG concentration the fractional free volume of blends increased from 0.268 for pure Matrimid to 0.338 for membrane containing 15 wt.% PEG. Moreover, the density of these membranes decreased from 1.173 to 1.162 g/cm 3 .…”

“…According to (Loloei et al, 2015) it is approved that although PEG exhibits a strong affinity for CO 2 due to dipole-quadrupole interactions (Yave et al, 2009;Li et al, 1995), further increase in its concentration in polymer matrix (10-20 wt.% PEG) leads to a complete loss of CO 2 /CH 4 selectivity. Increase in PEG content results in enhancing local segmental motions of polymer and a significant increase in CH 4 permeability due to enhanced transport of all gases (Visser et al, 2007).…”

“…These membranes have lower permeability than solid-polymer mixed matrix membranes due to the existence of liquid filler on the solid filler surface, which hindered the path of gas molecules diffusion (Liu et al, 2008). In our pervious study (Loloei et al, 2015) a series of Matrimid ® 5218/Polyethylene glycol 200 blend membranes were investigated and the potential of LMW PEG as a CO 2 -philic polymer for CO 2 separation over CH 4 molecules was explored. Additionally, the ZSM-5 nanoparticles with pore aperture of 0.55 nm were embedded in a continuous phase.…”