Preparation And Pervaporation Performance Of Alcohol Perm-selective Organic-inorganic Hybrid Membrane

It is very important to recover ethanol from fermentation broths to ensure the continuous fuel ethanol production. Distillation is the conventional methods that separate ethanol from water, but it surfers from high energy consumption, great installation cost and poor economic performance. Pervaporation (PV) is a new membrane separation technique to separate liquid mixtures, which based on the membrane's different selectivity towards the various components in the mixture, especially in the use of the separation of homogeneous mixtures such as azeotropic, closing-boiling and isomeric mixtures, which are difficult to separate by conventional methods.In this paper, we prepared such three different membranes: PDMS/silicalite-1(organized) membrane, PMDS/VTES membrane and PMDS/VTES-DVB membrane.Firstly, the average particle size of the prepared silicalite-1 is 0.466μm, they were modifided by coupling agent, then the modifided silicalite-1 were incorporated into polydimethysiloxane (PDMS) to form plat membranes, with polyacrylonitrile ultrofiltration membrane as a supporting layer. The pervaporation experiments of the separation of ethanol from dilute ethanol aqueous solution through PDMS/silicalite-1(organized) membranes were carried out. It is found that the pervaporation performance of PDMS/silicalite-1(organized) membranes is much better than that of PDMS/silicalite-1 membrane. The flux and selectivity do not take a persistent climbing tendency with the content of silicalite-1(organized) in PDMS from 1 to 8wt%. Both total flux and separation factor reach the maximal values (total flux: 921.11 g.m-2.h-1, separation factor: 11.7) with approximately 4.0 wt% silicalite-1(organized) in PDMS/silicalite-1(organized) membranes. The total flux and separation factor increased with increasing of temperature. The relationship between temperature and flux was accorded with Arrhenius equation.Then, PDMS/VTES membranes were crosslinked by vinyltriethoxysilane (VTES) to separate ethanol(EtOH) from aqueous solution by pervaporation(PV). The effects of crosslinking temperature, the content of crosslinking agent and feed temperature on the PV performance of PDMS/VTES membranes were investigated. For 6 wt% ethanol aqueous solution, the highest separation factor and total flux reached 15.5 and 421.67 g.m^-2.h^-1, respectively at 40℃, H-PDMS: VTES: DBTDL= 1: 0.2: 0.02, crosslinking temperature was 80℃. It was shown that the membranes had high EtOH permselectivity.Lastly, Add DVB and azobisisobutyronitrile(AIBN) to prepare PDMS/VTES-DVB membrane in order to improve the performance of PDMS membrane. The effects of crosslinking temperature, the content of DVB, the concentration of PDMS and feed temperature on the PV performance of PDMS/VTES-DVB membranes were investigated. For 6 wt% ethanol aqueous solution, when feed temperature was 40℃, H-PDMS: VTES: DBTDL: DVB: AIBN= 1: 0.2: 0.02: 0.02: 0002, crosslinking temperature was 60℃, the PDMS membrane had the high separation factor of 12.956 and total flux of 799.11 g.m^-2.h^-1, respectively.We found that the pervaporation performance of PDMS/silicalite-1(organized) membrane was better than that of PDMS/silicalite-1 membrane, and the PDMS/VTES membrane had the best pervaporation performance, the PDMS/VTES-DVB was more stable than PDMS/VTES membrane.