Performance of PEI/BMI semi-IPN membranes for separations of various binary gaseous mixtures☆

Abstract

Synthesis of polyetherimide-bismaleimide (PEI-BMI) semi-interpenetrating polymer networks (semi-IPNs) combined with solvent phase inversion was used to prepare asymmetric flat membranes, which were coated with silicon rubber. These membranes were evaluated for production of O 2 -enriched air and separation of CO 2 from its mixture with CH 4 as well as with N 2 . Using different preparation schemes membranes with varying skin and supported layer characteristics were prepared. These different morphologies of membranes were responsible for a trade-off performance between gas permeance and permselectivity. These new composite, PEI-BMI semi-IPN membranes showed suitable performance for production of O 2 -enriched air and separation of CO 2 from natural gas or flue gas relevant to greenhouse gas emission control. Membrane performance was explained in terms of the intrinsic gas transport properties of the coated silicon layer and membrane glassy material, which determine the limitations of permeance-permselectivity trade-off. It was also found that the permselectivity for CO 2 over CH 4 or N 2 increases with increasing CO 2 feed concentration. This might be exploited to arrange for more cost-efficient multistage gas separation systems. Crown

Synthesis and characterization of bis (4-maleimidophenyl) fluorene and its semi interpenetrating network membranes with polyether imide (Ultem® 1000)

“…Asymmetric membranes of polyetherimide (PEI) with and without cardo-BMI were prepared as reported earlier [20,21] using the casting solution compositions given in Table 1. The calculated quantity of PEI was dissolved in anhydrous NMP by rolling the bottles at 60 • C. To the completely dissolved PEI solution, the calculated amount of anhydrous ethanol was added and mixed again until a homogeneous solution was obtained.…”

“…9. Phase separation was found to adversely affect the membrane performance for gas separation and hence the material composition was selected based on a previous work [21] to avoid phase separation. However, in the present study there was no obvious phase separation detected in microscopic and DSC studies.…”

“…Despite these salient properties, the permeance of the polyether imides should be substantially increased in order to compete with conventional separation processes. Recently our group reported asymmetric semi-IPN membranes with increased permeance [20][21][22]. Semi-IPN membranes of thermoplastic polymer and bismaleimide (BMI) increased the permeance by a factor of 15 without compromising the selectivity [20].…”

“…Semi-IPN membranes of thermoplastic polymer and bismaleimide (BMI) increased the permeance by a factor of 15 without compromising the selectivity [20]. The in situ polymerization of BMI led to the formation of thermoset BMI domains inside the polyimide matrix that gave rise to increased fractional free volume [20,21] resulting in higher permeances.…”

“…Our group reported a novel synthetic route with increased control over the semi-IPN formation [20][21][22].B M I was polymerized at ambient conditions in the presence of a proton donor, polar aprotic solvent and polyetherimide without the need for an initiator or catalyst [20,21]. At ambient conditions the polymerization occurs at a slower rate and hence it is possible to arrest the reaction at the required stage to control the phase separation and morphology [20,21]. In this work, the synthesis of BMI with a bisphenyl fluorene group and its use to make novel semi-IPN asymmetric membranes with commercial PEI (Ultem ® 1000) are reported.…”