| As a typical MOFs material,UiO has become an ideal membrane material for gas separation due to its good thermal and chemical stability,regular pore structure,and easy modification.UiO-66 has a theoretical pore size of 0.6 nm,which has a good application prospect in propylene/propane separation,but its ability to separate H2 small molecules is limited.Among the derivatives of UiO-66,UiO-66-NH2 has a unique advantage for the adsorption and separation of CO2 gas due to the strong interaction between amino groups and CO2.However,due to the problems of ligand deprotonation and poor grain symbiosis in the synthetic solution,it is still difficult to prepare highly efficient and stable UiO-66-NH2 membranes.In addition,the choice of supporting body also has an important effect on the permeability and separation performance of the MOFs membrane.Hollow fiber can be used as an excellent support for membrane materials because of its large specific surface area,high unit packing density,and thin tube wall.In this paper,combining the advantages of UiO-66-NH2 membrane and hollow fiber membrane,ZrO2-Al2O3 composite hollow fiber andα-Al2O3 hollow fiber were prepared by phase conversion method,and the growth of UiO-66-NH2 membrane was induced by homologous metal induction method with ZrO2.The synthesis time of the UiO-66-NH2membrane was greatly shortened by this method,and the prepared UiO-66-NH2 membrane had good gas permeability selectivity,stability,and reproducibility.The main research contents and results are as follows:（1）The ZrO2-Al2O3 composite hollow fiber was prepared by phase conversion/sintering technology.The influences of ZrO2 content and sintering temperature on the structural characteristics and permeability flux of the composite hollow fiber were investigated.Based on this,the influences of carrier activation conditions and crystallization conditions on the membrane formation of UiO-66-NH2 were explored.The results show that the N2 flux and pore size of 15 wt.%ZrO2-Al2O3 composite hollow fiber sintered at 1450℃is 5.5×10-7 mol·m-2·s-1·Pa-1 and 0.37μm,respectively.UiO-66-NH2 membranes with a thickness of 2.9μm were prepared after being activated by 2-amino-terephthalic acid solution and crystallization at 140℃for 48 h.The H2 permeation flux was 6.2×10-7 mol·m-2·s-1·Pa-1,and the ideal selectivity of H2/CH4 and H2/CO2 were 7.57 and 5.46,respectively.After continuous operation at 30-200℃for 80 h,the H2/CO2 separation performance of the membrane can still be maintained at about5.2,showing good thermal stability.In addition,the membrane also showed good preparative reproducibility.（2）The α-Al2O3 hollow fiber was prepared by phase conversion/sintering technology,and commercial ZrO2 powder was uniformly introduced into the carrier by the rotary impregnation method,and UiO-66-NH2 membrane was induced to be prepared.The effects of impregnation concentration,crystallization time,and crystallization temperature on UiO-66-NH2 membranes were investigated.The results show that a continuous UiO-66-NH2 membrane with a thickness of 5.7μm can be obtained by using 0.1 wt.%impregnation solution and crystallization at 140℃for 48 h.The ideal selectivity of H2/CO2 and H2/CH4 is 4.3 and 3.1,respectively.The pore size of the UiO-66-NH2 membrane modified by salicylaldehyde（P-UiO-66-NH2）was reduced from0.45 nm to 0.37 nm.The H2 flux is 1.5×10-7 mol·m-2·s-1·Pa-1,while the ideal selectivity of H2/CO2 and H2/CH4 is increased to 6.7 and 21.7,respectively.The membrane showed good thermal stability at 30-200℃for 80 h,and the separation coefficient of the H2/CH4 binary mixture was 20.2-23.8.The membrane showed good hydrothermal and mechanical stability under boiling water and high-temperature treatment.The gas permeation flux of the P-UiO-66-NH2 membrane prepared in different batches is similar,which proves that the prepared P-UiO-66-NH2 membrane has good stability and preparation reproducibility.This highly stable P-UiO-66-NH2 membrane can provide more possibilities for industrial applications of hydrogen separation and purification. |
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