The ZIF-8 membrane has emerged as a promising candidate for C 3 H 6 /C 3 H 8 separation. However, the feasibility of ZIF-8 membranes for applications has rarely been investigated with gas provided directly by the industry sector. Herein, the C 3 H 6 /C 3 H 8 mixture collected from the backend of the Hydrogen Peroxide to Propylene Oxide (HPPO) process was applied as feed gas to examine the separation performance of tubular ZIF-8 membranes. The membranes exhibited excellent separation performance and long-term stability under 9 bar and 50 °C. Noticeably, upon scaling up to a membrane area of 452.16 cm 2 by connecting six three-channel modules in series (multi-step membrane), its separation performance satisfied the C 3 H 6 circulation requirements during the HPPO process (purity ≥97.5 % and recovery rate ≥85 %). Furthermore, a simulation of membrane operation under industrial working conditions (22 bar and 56.3 °C) was performed. By fixing the separation factor at 15, a minimum membrane area of 800 m 2 met the requirements at the cost of membrane permeance with 120 GPU. The corresponding economic calculation indicated a maximum of 91.8 % annual capital cost saving compared with the distillation process, paving the way for the practical application of membranes.
Xueting Zhao,Lingling Liu,Xinliang Zhang,Xinhao Cheng,Jinshan Sun,Jiefeng Pan
The inherent two-phase structure of heterogeneous ion exchange membranes leads to defects in high area resistance and powder, which has greatly limited the application in electrodialysis. In this research, we have prepared a series of semihomogeneous cation exchange membranes from polyethylene-polystyrene (PE–PS) resin particles, which were synthesized via monomer absorption and PE particle-confined polymerization. The processing of semihomogeneous cation exchange membranes was conducted via thermoforming the PE–PS resin particles into films and subsequent sulfonation. The influence of the monomer content on water uptake, IEC, membrane area resistance, and electrodialysis performance was studied. The results proved that due to the excellent mechanical and film-forming characteristics of PE, the sulfonated membranes were still endowed with great mechanical properties, and the heating conditions enhanced the monomer absorption in polyethylene particles, which ensured high IEC for excellent electrodialysis performance after sulfonation. It was observed that the semihomogeneous cation exchange membrane (CEM-60) showed the highest NaCl desalination ratio (92.3%) and exhibited higher current efficiency (97.68%) and lowest surface area resistance (1.82 Ω·cm2), which exceeded the commercial cation exchange membrane CAM (6.96 Ω·cm2). These results suggested a promising future of semihomogeneous membranes.
Xiaoling Duan,Cunwen Wang,Tielin Wang,Xiaolin Xie,Xingping Zhou,Yunsheng Ye
Comb-shaped polysulfone anion exchange membranes (AEMs) containing various pendant alkyl side chains were synthesized and characterized. Ionic clusters aggregation is observed in transmission electron microscopy (TEM) image and small-angle X-ray scattering (SAXS). The comb-shaped quaternized ammonium polysulfone (Cx-QAPSU) membranes show enhanced dimensional stability and ultra-low membrane area resistance ( R m ). Notably, the C16-QAPSU with 16 carbon atoms has the best hydrophilic-hydrophobic phase separation structure and lowest R m of 2.5 Ω cm 2 despite low ion exchange capacity ( IEC ) of 1.55 mmol/g and swelling ratio of 5.3%. Moreover, comb-shaped AEMs show much higher tensile strength ( TS ) compared to QAPSU membrane under the same IEC level. The C16-QAPSU with lowest R m of 2.5 Ω cm 2 exhibits the highest TS of 16.7 MPa. These results indicate that the long alkyl side chains especially the length of the pendant side chain of Cx-QAPSU up to C16 achieve an electrochemical-mechanical balance of AEMs. In electro-electrodialysis systems, the comb-shaped AEMs exhibit higher purification efficiency of wet phosphoric acid than non-comb-shaped AEMs.
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