Preparation Of HTPB-PU Pervaporation Membrane For Concentration Of Dilute Butanol Aqueous Solution

Pervaporation is a promising separation technique and becoming a research focus. For its unique structure and property, polyurethane pervaporation membrane has already widely used in the separation of organic mixture. According to solution diffusion theory of pervaporation, microphase separation structure is beneficial to the components dissolved and diffused in the membrane. As to improve the performance of pervaporation (PV) membranes, the HTPB-PU and HTPB-VTES-PU membranes were prepared and their pervaporation performance of butanol/water in dilute solution were investigated.Pervaporation membrane (HTPB-PU) was prepared by HTPB polyurethane which was synthesized by two steps. The HTPB-PU membrane was applied in separation of dilute butanol solution. The effects of proportion of soft and hard segments and operating temperature on pervaporation membrane performance were investigated. As shown in DSC study, HTPB-PU membrane had two glass transition temperatures; In addition, light and dark phases of the micro-area were shown in transmission electron microscope images. Therefore, the membrane has micro-phase separation structure. The solution and diffusion behaviors of water and butanol in the membrane were analyzed through the permeability and solubility parameters. The results showed that the membrane separation factor was elevated with-NCO/-OH ratio, but the flux was declined. When-NCO/-OH ratio was 2, the separation factor and permeation flux of membrane were 42.8 and 38.1 g/m2h respectively. The membrane flux and separation factor were both improved with increasing operating temperature.In the role of initiator, the HTPB polyurethane and the VTES reacted to produce new polymer by double bonds reaction and the HTPB-VTES-PU pervaporation membranes were obtained. These membranes were used in the separation of dilute butanol solution. The effects of content of VTES and the operation temperature on the performance of pervaporation were further studied. The DSC result showed that HTPB-VTES-PU had three glass transition temperatures, and the presence of three-phase region could be clearly observed in the TEM image. Therefore, after the addition of VTES, the micro-phase separation structure of the membrane began to change and the degree of phase separation increased. Through the calculation of permeability coefficient, HTPB-VTES-PU membrane also had a high selectivity towards butanol. As showed in the pervaporation experimental results, the membrane permeation flux was increased while the separation factor was decreased with increasing of VTES. The effect of operation temperature on the membrane permeation flux and separation factor was consistent with that of the HTPB-PU membrane.