| Membrane separation has advantages which is energy saving, environment-friendly as a kind of new separation technology, compared to traditional separation technology. Membrane can be divided into organic membrane and inorganic membrane. Inorganic membrane has advantages that good chemical stability, anti acid, alkali and organic solvents, high mechanical strength, high thermal stability, pore size molecular level (<0.8 nm) and uniform pore size, different strengths hydrophilic/hydrophobic properties,compared to origanic membrane which is easy to swelling and has low high thermal stability. Metal organic frameworks compounds (MOFs) become a new type of microporous membrane materials after carbon and molecular sieve membrane with the rapid development of coordination chemistry of transition metal ions and organic ligands via the complex self-assembled. Zeolitic imidazolate frameworks (ZIFs) is MOFs in a major branch, ZIFs have similar high stability to zeolite and a large pore volume and a high specific surface area, ZIFs can adjust aperture and functionality which is modified or selecting different imidazole ligands.In this paper, ZIF-78 for the study, the use of traditional solvent hot, dynamic crystallization, and added triethylamine prepared legal ZIF-78 crystals were prepared by secondary synthesis ZIF-78 crystals, synthesis of ZIF-78 membrane,the main research is as follows:(1) Added to the reaction mixture deprotonated agent triethylamine, can even synthesize perfect crystals of ZIF-78 crystals. When Zn (NO3) 2· 6H2O:2-nIM:5-nbIM:triethylamine: DMF= 4:5:5:5:904, the products of 2～4 μm umbrella hexagonal prismatic crystals.(2) The molar ratio of metal ions and organic ligands, concentration of the reaction solution, formosa regent temperature and time on the ZIF-78 crystals will have a huge impact, according to a molar ratio of Zn (NO3) 2 · 6H2O:2-nIM:5-nbIM:DMF=4:5:5:904,regent synthesis reaction mixture was prepared to adopt ZIF-78,110 ℃ rotating regent 12 h,140℃ rotation regent synthesis 3 h obtained ZIF-78 of the best crystal morphology.(3) Different size particles of α-Al2O3 macroporous α-Al2O3 have some modification, the selection of α-Al2O3 particles of 600-700 nm modified macroporous carrier can fill the big hole big hole carrier surface defects providing more heterogeneous nucleation density.(4) The effect of temperature on crystal growth is particularly significant, in favor of low-temperature-induced nucleation and crystal growth requires a lot of energy.100℃ and 24 h is the best conditions during deposition regent, which can synthesis good crystals,.(5) Configuring a seed crystal was added an amount of polyethylene glycol can help enhancing the binding force between the carrier and the seed layer. Experiments confirmed that the amount of 4% PEG, the effect is best.(6) Regent deposition time has critical effects to the final ZIF-78 membrane, the membrane-forming synthetic time is shorter than 12 h, which can lead to the poor growth crystal membrane surface, the degree of crystallinity is not high; the membrane-forming composition time is longer than 24 h, which can make the growth of crystal grains too large, the connection between the grain does not close, no symbiotic growth, will lead to large intergranular holes. |
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