首页|Long alkyl chain-containing organosilica/silicalite-1 composite membranes for alcohol recovery
Long alkyl chain-containing organosilica/silicalite-1 composite membranes for alcohol recovery
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NSTL
A long alkyl chain-containing organosilica layer obtained from 1,8-bis(triethoxysilyl)octane(BTESO)was used to modify silicalite-1 membranes via a sol-gel method to obtain bi-layered BTESO/silicalite-1 composite membranes on macroporous α-Al2O3 supports for the recovery of diluted ethanol by pervaporation.Silicalite-1 zeolite membranes were hydrothermally synthesized using two seeding methods: those prepared using wet-rubbing seeding method exhibited larger separation factors than those obtained using the dip-coating method in the pervaporation of ethanol/water due to the thinner seed layer in the former.After modified with BTESO,the surface became smoother and denser with higher hydrophobicity,and the thickness of BTESO layer was approximately 300 nm on both types of membranes.In pervaporation,two types of silicalite-1 membranes unexpectedly showed similar performances after BTESO modification.Ethanol flux increased or was maintained while water flux decreased greatly for silicalite-1 membranes after BTESO coating with increasing sol concentrations,and a higher separation factor was attained without sacrificing ethanol flux.The long alkyl chains in BTESO and silanols reacted with hydroxyl groups in silicalite-1 provided flexibility and hydrophobicity for ethanol transport with minor resistance.The optimized 2.0% BTESO/silicalite-1 membranes synthesized using wet-rubbing method showed a maximum flux of 6.84 kg m~(-2)h~(-1)and separation factor of 24.6 with overall pervaporation separation index of 161 in the pervaporation of 5.0 wt% ethanol/water mixture at 60 ℃.
NSTL
