Fabrication Of Membranes And Process Evaluation Of Hollow Fiber Membranes For Gas Separation

In recent years,the increase of anthropogenic activities such as the burning of large amounts of fossil fuels has resulted in substantial increase emissions of greenhouse gases?mainly CO₂?.Greenhouse effect causes global warming,and the huge amounts of greenhouse gas emissions have an impact on global ecological environment.Development and application of carbon capture technologies can reduce carbon emissions effectively.Membrane separation technology,as a new and green technology among all carbon capture technologies,has been developed rapidly with its unique advantages.In this study,hybrid membranes,facilitated transport mixed matrix membranes?FT-MMMs?for carbon capture were fabricated.Moreover,the membrane process of hollow fiber membrane permeator for air separation was analyzed.PEBAX/ATP hybrid membranes and PEBAX/ATP-NH₂ FT-MMMs were prepared for CO₂/CH₄ separation,while hollow fiber membrane process evaluation aimed at O₂/N₂separation.The main research contents are as follows:PEBAX/ATP hybrid membranes were prepared by doping one-dimensional attapulgite nanorods into PEBAX 1657 which acted as a polymeric matrix.After acidification,the attapulgite surface and the inner walls of channels were rich with hydroxyl groups so that its hydrophilicity was enhanced.In humid conditions,attapulgite nanorods can maintain a favorable water environment within membranes to increase the solubility of CO₂.With the increase of the loading of attapulgite nanorods,the CO₂ permeability of the hybrid membranes increased continuously.Compared with the CO₂ permeability of the pristine PEBAX membrane,that of PEBAX/ATP?10?hybrid membranes increased from 46.9 to 61.6 Barrer without the decrease of CO₂/CH₄ selectivity in a dry condition.In a humid condition,the permeability increased from 440.8 Barrer to 498.4 Barrer with improved CO₂/CH₄ selectivity.PEBAX/ATP-NH₂ MMMs were prepared for the CO₂/CH₄ separation by doping 3-aminopropyltriethoxysilane modified attapulgite nanorods into PEBAX 1657.On one hand,amino-modified attapulgite nanorods introduced fixed carriers for CO₂permeation;on the other hand,the attapulgite nanorods modified with the silane coupling agent could improve the interface compatibility between polymer matrix and inorganic particles.Compared with those of PEBAX/ATP hybrid membranes,CO₂permeability and CO₂/CH₄ selectivity of PEBAX/ATP-NH₂?10?FT-MMM were both improved.PEBAX/ATP-NH₂?10?FT-MMM showed optimum gas separation performance with a CO₂ permeability of around 654 Barrer and a CO₂/CH₄ selectivity of around 24 under a wet condition.Compared with those of pristine membranes,CO₂permeability increased by 48%and CO₂/CH₄ selectivity increased by 26%.Through analyzing membrane process and optimizing operation conditions,cellulose acetate based hollow fiber membrane permeator can be used in the air separation system in the oxygen enriched combustion of carbon capture technology.Within a wide range of stage cut values,the relationships among product purity,recovery and productivity of hollow fiber membrane permeator were investigated.Under high pressure,high productivity could be obtained.Besides,the bore-side feed gave a better separation performance than the shell side feed.In a single-stage membrane separation operation,feed gas was composed of 20.5 mol%O₂ and 79.5 mol%N₂.After permeation through the hollow fiber membrane permeator,the purity of O₂ in the permeate gas could reach53.7 mol%;the purity of N₂ in the residue gas could reach 98.7 mol%.