Zhihua Qiao,Zhi Wang,Shuangjie Yuan,Jixiao Wang,Shichang Wang
Small molecular amines (SMAs) (ethanediamine (EDA), piperazine (PIP), monoethanolamine (MEA) and diethanol amine (DEA)) were separately used to modify the polyvinylamine (PVAm). ATR-FTIR, elemental analyzer, XRD and SEM were employed to characterize the SMA interacted PVAm. The PVAm–SMA/polysulfone (PS) membranes were developed by coating PVAm–SMA mixed solutions on the PS ultrafiltration membrane. CO 2 permeance and CO 2 /H 2 selectivity of the PVAm–SMA/PS membranes were investigated. Among different PVAm–SMA/PS membranes, the PVAm–MEA/PS membrane shows the highest CO 2 /H 2 separation performance. Moreover, the effect of the selective layer thickness on the CO 2 /H 2 separation performance of the PVAm–MEA/PS membrane was studied. With increasing the PVAm–MEA selective layer thickness, the CO 2 /H 2 separation performance of the membrane apparently decreases. Finally, the CO 2 /H 2 separation performance stability of the PVAm–MEA/PS membranes was investigated and no deterioration in the membrane permselectivity was observed.
Xiaochang Cao,Haoqing Xu,Songlin Dong,Jiayou Xu,Zhihua Qiao,Song Zhao,Jixiao Wang,Zhi Wang
In this work, we proposed a simple method to prepare high-performance and pressure-resistant mixed matrix membranes (MMMs) for CO 2 /H 2 separation. The groups or segments of poly-(vinylamine) (PVAm) were used to modify covalent organic frameworks (COFs), and COFs with similar frameworks but different surfaces were obtained. Then, modified COFs were mixed with PVAm matrix and used to coat the modified-polysulfone (mPSf) to prepare MMMs for CO 2 /H 2 separation. Modified COFs and the PVAm matrix were highly compatible because COF surfaces possessed the same groups or segments as PVAm. Meanwhile, in the coating solution, COF surfaces were found to induce penetration of PVAm molecules into COF pores, narrowing the pore size of the COFs and providing an amino environment for CO 2 preferential absorption and transport. The penetration degree was affected by the hydrogen bond between COF surfaces and the PVAm molecules. In addition, the incorporated COFs effectively restricted the mobility of the PVAm matrix, increasing the pressure resistance for MMMs under high pressure. In the gas permeation test, the optimal MMMs could achieve a CO 2 permeance of 957 GPU and a CO 2 /H 2 selectivity of 17.1 at 2.0 MPa because of the high compatibility and size of the channels (0.94 nm).
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