Preparation And Application Of Inorganic Microporous Membranes

With the development of socio-economy, the demand for new technology and newenergy is increasing nowadays, which gives new requirements on the performance ofmaterials. As an evergreen in the field of materials, the inorganic porous material has beenextensively studied during the past decades owing to the excellent thermal stability,chemical stability and the unique pore structure. Many kinds of such materials have beenconverted into porous membranes, which exhibit advantages in the following respects:recycling, organic solvents resistance, no aging, fixed pore size. Furthermore, inorganicporous materials also have great application prospects in gas separation, wastewatertreatment, organics separation and membrane catalysis, etc.Desalination is the dream that human pursuits for hundreds of years. In the20thcentury, the development of desalination technology accelerated rapidly because of thewater crisis. There are nearly twenty kinds of desalination methods that have reachedindustrial scale production levels and are widely used throughout the world, such asdistillation, electrodialysis, reverse osmosis, etc. The reverse osmosis approach has beenextensively studied in recent years and is considered to be the most efficient way.However, the most important part of this approach is the reverse osmosis membrane.Based on a large number of experiments and tests, we selected the porous SiO2as supportto prepare the pure silica MFI-type zeolite membrane, which was applied for seawater desalination with the pressure condition of500psi. If the concentrations of the motherliquid for secondary growth were relatively low, the silicate-1zeolite membranes wouldshow high permeating flows and excellent separation factors. In addition, similar resultscould be obtained by using the aqueous polyethylene imine （PEI） solution as a functionalagent for the substrate with spin-coated seeds.In chemical industry, the largest fraction of production costs is related to theseparation and purifcation of product streams. The separation of mixed xylene isomers isone of the most challenging issues since xylene isomers are important chemicalintermediates. Metal organic frameworks （MOF） or porous coordination polymers （PCPs）are hybrid inorganic-organic materials made from an assembly of metal ions and organiclinkers. A large scale continuous MOF [Zn₂（BDC）₂（Dabco）] membrane has beensuccessfully synthesized by second growth approach on the modified porous SiO2substrate surface. The seed crystals were prepared using acetic acid as tapped agent. Thethickness of the membrane can be varied by adjusting the repetitions of growing process.The separation performance tests of xylene isomer mixtures were taken out on thesemembranes. Comparing with the conventional zeolite type membranes, separationproperties of [Zn₂（BDC）₂（Dabco）] membrane for xylene isomers are derived from theselective adsorption effect of the framework.Nowadays considerable attention is being paid to chiral resolution on account ofsignificant difference in biological and pharmacological properties of the isomers of chiralcompounds. One has desired affects while the other may be inert or even harmful. Theoption resolution of racemic mixture is possible through various separation techniques,including thin layer chromatography （TLC）, gas chromatography （GC）, High PerformanceLiquid Chromatography （HPLC） etc. However, all these methods suffer from setbacks ofsmall separation amounts per run, batch processing or high cost. We successfullysynthesized a homochiral MOF membrane by utilizing a “single nickel source” method,which had the advantages of using low-cost starting materials and simple operation. TheMOF membrane possesses chiral channels and has excellent thermal stability. So it can be applied for chiral resolution. A kind of diols isomer mixtures was used to test theirseparation efficiency. The temperature/pressure-related performance of the chiralmembrane was observed, which has been extensively studied in the feld of gas separationand should also be an important issue in the development of chiral resulation.As a clean energy, hydrogen holds promising hopes to replace petroleum-basedenergy to provide power to the people’s daily production and life. Hydrogen purificationand separation ensure the efficient use of energy and environmental protection. Manyinorganic porous membrane materials have been studied for hydrogen separation. A seriesof the nickel net supported [Ni₂（L-asp）₂P] membranes with different length of pillars havebeen successfully synthesized by second growth method. Compared with conventionalzeolite membranes, the family of MOF membranes possesses tunable pore size anddesignable structure, which makes the membranes suitable for gas separations. For themembranes building with longer ligands, high permeation flux for H2and desiredselectivity for binary gases permeations of H2/CH4, H2/N2and H2/CO2can be obtained.The membrane with ultra-micropore size showed a great preferential permeation of H2over other gas molecules.The ambient temperature around the world is rising, increasing awareness of peoplefor greenhouse gas controlling. The researchers around the world are trying to developmaterials with large amount adsorption on carbon dioxide. MOF materials with openskeleton structures and large surface area give great hope. We introduced nanotubes thattend to adsorb CO2into the original structure of MOF. The MOFs/carbon nanotubeshost-guest hybrid materials were obtained through the in-situ growth method. And wefound signifcant improvement in both CO₂storage capacity and isosteric heats ofadsorption with changed fluorescence spectroscopy. These very useful results suggest anew approach to increasing MOF gas adsorption enthalpy.