Anewmethod for the preparation of y-alumina membranes from aluminium chloridewas investigated in this paper. Boehmite solwas synthesized by an anionic exchange method, which could offer OH−-ion and simultaneously remove Cl−-ion. Boehmite sols were then deposited on the inner surface of the hollow fiber supports by a filtration technique. The thermal evolution, phase transformation, structure, morphology and pore size distribution of the -alumina membranes were characterized by thermogravimetric analysis (TGA), differential thermal analysis (DTA), X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and nitrogen isothermal adsorption measurement. SEM images showed that the membranes were defect-free. Gas permeability tests suggested that the obtained membranes possessed gas selectivity, and its separation factor for H2/N2 and H2/CH4 were 3.31 and 2.25 at 0.1MPa, respectively. The most concentrative pore diameter, pore volume and specific surface area of an unsupported membrane calcinated at 600 ◦C were 3.7 nm, 0.18 ml/g and 176.9m2/g, respectively.

Taking advantage of Fourier transform infrared spectrum and X-ray photoelectron spectroscopy, the researcher has conducted a contrastive research on the surface molecular structure of porous PVDF membrane before and after modification. Research results indicate that, though the C-F characteristic peak of the PVDF membrane still exists after modification, the peak is obviously flat, which indicates that the content of F atom decreases evidently; the results also indicate that hydroxyl characteristic peak is sharper, which indicates the content of O atom increases evidently. This proves that chemical binding force has been produced by chemical reactions on the surface of PVDF membrane during the modification. The coexistence of C-F functional group with C-OH one on the surface of PVDF membrane after modification proves that the surface features of the PVDF membrane have been successfully altered. Combination of Fourier transform infrared spectrum with X-ray photoelectron spectroscopy is proved an effective approach for analyzing the surface structure of the membrane.

α-Al2O3 hollow fibers were prepared by a phase-inversion method combined with the reaction bonded aluminum oxide (RBAO) process. Next, -Al2O3 membranes, which were fabricated by a sol–gel process, were cast on the outer surface of the hollow fiber supports. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD), nitrogen isothermal absorption measurements and gas permeability testing were used to characterize the supports andα-Al2O3 membranes. The results showed that the mechanical strength of hollow fiber supports is better than that of non-RBAO hollow fiber, and their porosity and mean pore size were 50.1% and 0.88μm, respectively. SEM images ofα-Al2O3 membranes showed that the membranes were defect-free. The most concentrative pore diameter and the specific surface area ofα-Al2O3 membranes were about 4.5 nm and 228.9m2/g, respectively. Gas permeability tests suggested that theα-Al2O3 membranes possessed gas selectivity, and the separation factor for N2/Ar are 1.133 at 0.3MPa and 1.139 at 0.4MPa, respectively, which is slightly smaller than the value expected from the ideal Kundsen diffusion (α=1.194).

α-Al2O3 hollow fibers were prepared by a phase-inversion method combined with the reaction bonded aluminum oxide (RBAO) process. Next, γ-Al2O3 membranes, which were fabricated by a sol-gel process, were cast on the outer surface of the hollow fiber supports. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermo gravimetric analysis (TGA), X-ray diffraction (XRD), nitrogen isothermal absorption measurements and gas permeability testing were used to characterize the supports and γ-Al2O3 membranes. The results showed that the mechanical strength of hollow fiber supports is better than that of non-RBAO hollow fiber, and their porosity and mean pore size were 50.1% and 0.88μm, respectively. SEM images of γ-Al2O3 membranes showed that the membranes were defect-free. The most concentrative pore diameter and the specific surface area of γ-Al2O3 membranes were about 4.5 nm and 228.9 m2/g, respectively. Gas permeability tests suggested that the γ-Al2O3 membranes possessed gas selectivity, and the separation factor for N2/Ar are 1.133 at 0.3MPa and 1.139 at 0.4MPa, respectively, which is slightly smaller than the value expected from the ideal Kundsen diffusion (α=1.194).

A membrane gas absorption (MGA) process was evaluated in this work for CO2 capture from CO2/N2 gas-mixed streams at room temperature. The experimental study of a polypropylene (PP) hollow fiber membrane contactor in combination with the technique of CO2 absorption into aqueous solutions of activated methyl diethanolamine (MDEA) and MDEA as absorbents was carried out. A laboratory-scale setup, in which the solution with CO2 loading was able to be hot-regenerated into the solution without CO2 loading and used circularly, was established in this study. The effects of a variety of operation factors, such as gas and liquid flow rates, membrane pore-wetting, and liquid CO2 loading, on the separation performance of the membrane contactor were investigated. The absorption performances were compared between activated MDEA and MDEA. A mathematical model was developed to simulate the mass-transfer behavior of the membrane gas-liquid contactor. The experimental results show that the use of a membrane gas-liquid contactor with improved alkanol amines such as activated MDEA can be completely applied to CO2 capture. Low and steady liquid CO2 loading was able to be controlled by hot-regeneration. The CO2 absorption performance of activated MDEA was remarkably better than that of MDEA. The CO2 removal efficiency could reach more than 99% with activated MDEA. The average overall mass-transfer coefficient with activated MDEA was 2.25 times that with MDEA. The activator piperazine (PZ), even with a small quantity in the activated MDEA, plays a significant role in the improvement of mass transfer in MGA. A comparison of model estimations with experimental results indicates that estimations of the non wetting mode are divaricated from experimental data. Taking partial-wetting of the membrane into account, the model simulation is validated with experimental data. Partial-wetting can result in significant membrane resistance to mass transfer in MGA.