Preparation And Hydrogen Permeation Of SiO₂/Al₂O₃ Composite Hollow Fiber Membranes

Al2O3 hollow fiber ceramic membrane (AHFCM) with asymmetric structure was prepared by the phase-inversion and sintering technique. Its structure and air permeability was also examined. The result indicates that the controlled direction and thickness of finger-like voids of AHFCM was achieved by using different internal coagulant; the thickness of the sponge-like voids increased with the increase in air-gap. Different pore-forming agents were used to study the effect of pore-forming agent on the air permeability of AHFCM. The test result indicates that starch is the best pore-forming agent for preparation of AHFCM among the tested agents. Besides, the He/N2 separation coefficient of AHFCM was tested. The test result indicates that the prepared AHFCM showed good gas separation performance.Different solutions were used to modify the surfaces of AHFCM. The microstructure of surfaces of the modified membranes was characterized with SEM measurements. Besides, the effect of solution, coating times and sintering temperatures on the microstructure of membrane surface and air permeability was surveyed. The result indicates that both solutions could be used to modify the AHFCM. Compare with Alumina ball-milling solution, Al2O3 sol could form smooth layer at low temperature, the modification layer is thinner owing to its petty viscosity. For these reasons, Al2O3 sol was selected to modify the self-made Al2O3 hollow fiber ceramic membrane.SiO2/Al2O3 composite hollow fiber membrane was prepared by sol-gel method, dip coating and sintering technique. The surface of SiO2/Al2O3 composite hollow fiber membrane had been modified by cobalt-doped technique. The microstructure of surfaces of the modified membranes was characterized with SEM measurements. The phase composition of the powders dried from sol was observed by XRD. Besides, the effect of coating times, reduction and temperature on the gas separation performance of membrane was surveyed. The test result indicates that the gas separation performance of membrane was improved after cobalt-doped, the H2/CO2 separation coefficient was about 1.82 times of the original; the thickness of molecular sieving membrane and the gas separation performance could be increased by increasing coating times, while excessive coating times would also increase the risk of fracture. The best coating times was 10 through the experiment results. The Co3O4had been reduced to Co metal phase as the peaks of CO3O4 were no longer present. The high hydrogen permeability of SiO2/Al2O3 composite hollow fiber membrane after reduction was also demonstrated by the test of hydrogen permeability. Besides, low pressure and high temperature could improve hydrogen permeability of SiO2/Al2O3 composite hollow fiber membrane.