Preparation And Gas Separation Properties Of The Siloxane/PEO Hybrid Membranes

Nowadays, global warming is one of the most serious environmental problems.The main reason is the large emissions of CO₂. So how to capture or absorb theCO₂efficiently is the focus of the scientific research.To capture the CO₂, the conventional methods have many problems, such astaking up large areas, operating cumbersome, and also, may cause the secondarypollution for the environment. In this case, the technology of membranes separationcomes into being, increasing year by year.In the material of PEO, they contain the polar ethylene oxide （EO） groups,which have a strong affinity with the quadrupolar CO₂. This material could separatethe CO₂with other non-polar gas molecules. But, the high crystallinity of PEO-based materials reduces the permeability and separation selectivity. So how toimprove the character of the materials, lowering the crystallinity, is one of keyresearch points.Silicones can be generally used as a modifier. The siloxanes, taking differentgroups, can react with a variety of substances. The modified materials improvedhave a good character of the mechanical strength.We choose the functional oligomers （O,O’-bis（2-aminopropyl） polypropyleneglycol-block-polyethylene glycol-block-polypropylene glycol） with epoxy-functional silanes （3-glycidyloxypropyltrimethoxysilane）（GOTMS）, and thetetraethoxy silane （TEOS） was added to the reacting medium to adjust theproportion of the three composition. Changes the silica content of the system, weprepared two series of the PEO-based hybrid membranes and tested thephysicochemical properties and the separation of the CO₂/H₂and CO₂/N₂.For the gas separation of hybrid membranes prepared is not satisfied, wechoose the PEG, with small molecular weight （Mw=200）, to treat the hybridmembranes. There are two kinds of PEG, one with the terminal hydroxyl group andthe other with the methoxy group. We also test the gas separation of the membranes.Using the test methods, such as FTIR-ATR, DSC, TG, XRD, SEM and AFM etal, we character the structure of the cross-linked organic-inorganic membranes, theresults of the gas separation test is as follows, the CO₂permeability could be cometo123.68Barrer with an attractive CO₂/H₂selectivity of2.66and the CO₂/N₂selectivity of50.94. After the treatment of the PEG, the permeability gets furtherimprovement.