Mixed-matrix membranes (MMMs) have aroused great attention for CO2 capture due to high gas separation properties and good processability. However, besides high cost, poor interfacial compatibility and inorganic particles aggregation in MMMs hinder their further development. Herein, we chose microporous sodium zeolite-Y (NaY) as a filler, which was added into sulfonated poly (ether ether ketone) (SPEEK) to engineer the MMMs for CO2/N2 separation. We deeply studied the influence of NaY incorporation on microstructure and separation properties of the membrane. It is obvious that NaY particles were evenly distributed in the SPEEK matrix due to strong interfacial interaction by hydrogen bonding, which was verified by ATR-FTIR and SEM results, and the string-like nanochannels were formed from the SAXS observation. MMM incorporated with 20 wt% NaY exhibited the separation properties (CO2 permeability of 765 Barrer; CO2/N2 selectivity of 63) at 1 bar under the pure gas conditions, which were superior to the pristine SPEEK membrane as well as the MMMs incorporated with other zeolites, transcending the 2008 Robeson's upper bound. The enhancement in separation properties is due to the fact that CO2 molecules preferentially pass through the string-like nanochannels faster than N2 molecules under elevated relative humidity owing to selective surface flow effect. Moreover, an increase in total water of MMMs loaded with NaY also contributed to enhanced CO2 permeability, while improved CO2/N2 selectivity resulted from high bound water. More importantly, stability studies reveal that the MMM (with 20 wt% NaY loading) held outstanding CO2 separation properties for over 360 h, demonstrating outstanding stability under a gas mixture testing condition.

为了获得高性能的气体分离膜,实现烟道气中CO2/N2高效分离回收,以磺化聚醚醚酮(SPEEK)和聚琥珀酰亚胺(PSI)为原料,己二胺为交联剂,原位交联反应制备富含氨基的半互穿网络共混膜,在膜内构建CO2传递通道和亲和位点,并采用红外光谱对共混膜的结构进行表征.研究水含量、PSI用量和进料气压力对膜气体分离性能的影响,在混合气条件下考察其气体分离性能和长时间运行稳定性.研究结果表明:SPEEK与PSI两相界面相容性较好,它们之间存在较强的相互作用,且呈半互穿网络微结构;PSI含量为60％(质量)时,纯气和混合气条件下CO2渗透性分别为652和601 Barrer,对应的CO2/N2选择性为67.6和60.3,优于纯SPEEK膜,且超过2008年的Robeson上限;共混膜运行360 h后,CO2渗透性和CO2/N2选择性仍然稳定.这主要是因为SPEEK与PSI形成富含氨基的半互穿网络微结构后,一方面提供了CO2促进传递载体;另一方面,增强了共混膜的保水性能,形成大量CO2传递水通道.

Polyaniline-decorated halloysite nanotubes (PANI-d-HNTs) having a multilayer hollow tubular structure were incorporated into sulfonated poly(ether ether ketone) (SPEEK) to prepare high-performance mixed matrix membranes (MMMs) for CO2/N-2 separation. Scanning electron microscopy images revealed that PANI-d-HNTs were tightly wrapped by SPEEK chains. The strong interfacial interaction between PANI-d-HNTs and SPEEK, as confirmed by attenuated total-reflectance Fourier-transform infrared spectroscopy and differential scanning calorimetry, led to excellent miscibility between the polymer and halloysite nanotubes, which in turn, resulted in improved mechanical properties for the MMMs. The highest CO2 permeability of 1260 Barrer and a CO2/N-2 selectivity of 87 were achieved for MMMs loaded with 0.9 wt% PANI-d-HNTs; these values exceeded the Robeson's upper bound proposed in 2008, and were also much higher than those of MMMs containing 0.9 wt% HNTs, for which, a CO2 permeability of 1093 Barrer and CO2/N-2 selectivity of 74 were observed. It is proposed that PANI-d-HNTs with a multilayer hollow tubular structure can be used as high-speed facilitated channels for CO2 transport, where densely arranged secondary amine groups readily reacted with CO2 to facilitate transport in the MMMs. Importantly, durability testing indicated that MMMs loaded with 0.9 wt% PANI-d-HNTs maintained outstanding CO2 permselectivity for over 120 h, suggesting the superior stability of the membranes under mixed gas feed conditions.