Preparation Of PVA/PVP Crosslinked Blend Membranes And Study On Their Dehydration Performance To 2-Methyltetrahydrofuran Solution

In recent years,with the increasing demand for anhydrous-grade organic solvents in the fields of petrochemicals,pharmaceuticals and chemicals,dehydration of organic solvents drawn more and more attention.2-Methyltetrahydrofuran?2-MeTHF?is considered to be an excellent alternative to tetrahydrofuran and dichloromethane as a new industrial solvent.However,it can form an azeotrope with water and then it was difficult to remove water from2-MeTHF solution.Pervaporation is a novel membrane separation technology in the field of organic dehydration with the advantages of energy saving,high efficiency,simple operation,no secondary pollution,easy coupling with other processes,etc.In this paper,PVA/PVP crosslinked blend membrane was prepared by crosslinked blend method,and this membrane and commercial PVA 4155composite membrane were applied to remove water from 2-MeTHF solution.The effects of parameters including the water content in 2-MeTHF solution,circulation flow and operation temperature on dehydration separation performance of the membrane were investigated in detail.The continuous separation process of the membrane material for 2-MeTHF solution was also explored,and the membrane materials were characterized by scanning electron microscopy?SEM?,X-ray diffraction?XRD?,contact angle measuring instrument?CAM?and microcomputer controlled electronic universal testing machine?MCEUTM?.The specific results were as follows:1.Using commercial PVA 4155 composite membrane as separating membrane on the 2-MeTHF solution.The effects of parameters including the water content in 2-MeTHF solution?1.90³.90 wt%?,circulation flow?15⁵5L/h?and operation temperature?26⁶8°C?on dehydration separation performance of the membrane were investingated in detail.The results showed that the permeated total flux,water flux and permeated side water concentration of PVA 4155 composite membrane increased with the increasing of water content in 2-MeTHF solution,circulation flow and operation temperature;the separation factor increased first and then decreased with the increasing of water content in 2-MeTHF solution,and the separation factor increased with the increasing of circulation flow and operation temperature.The permeated total flux and separation factor of the membrane were 848.47 g/?m²·h?and 513.37,respectively,under the condition that the water content in the 2-MeTHF solution was 3.90 wt%,circulation flow was 55 L/h,and operation temperature is 68°C.The 2-MeTHF solution with water content of 3.90 wt%was dehydrated continuously,and the 2-MeTHF solution was concentrated to 98.84 wt%after operation 30 hours.2.A series of PVA/PVP blend membranes were prepared by blending method to separate 2-MeTHF solution and the optimum PVA and PVP content(V_PVA:V_PVP=8:2)in the blend membrane were selected according to the dehydration separation performance of the membrane.Then,baesd on the above-mentioned optimum PVA and PVP content,PVA/PVP blend crosslinked membrane was prepared with the solution obtained by directly mixing cross-linking agent MAH,PVA and PVP by crosslinked blend method and was considered as separating membrane on the 2-MeTHF solution.The effects of parameters including the water content in 2-MeTHF solution?2.10³.90 wt%?,circulation flow?15⁵5 L/h?,membrane thickness?30⁷0 um?and operation temperature?26⁶8°C?on dehydration separation performance of the membrane was investingated in detail.The results showed that the permeated total flux,water flux,permeated side water concentration and the separation factor of PVA/PVP crosslinked blend membrane increased with the increasing of water content in 2-MeTHF solution,circulation flow and operation temperature,in contrast,the permeated total flux and water flux decreased with the increasing of membrane thickness and the permeated side water concentration and the separation factor increased with the increasing of membrane thickness.The permeated total flux and separation factor of membrane were 431.64 g/?m²·h?and 272.96,respectively,under the condition that the water content in the 2-MeTHF solution was 3.90 wt%,circulation flow was 55 L/h,membrane thickness was 60 um and operation temperature is 68°C.The 2-MeTHF solution with water content of 3.90 wt%was dehydrated continuously,and the 2-MeTHF solution was concentrated to 97.79 wt%after operation 30 hours.3.The membrane materials were characterized by scanning electron microscopy?SEM?,X-ray diffraction?XRD?,contact angle measuring instrument?CAM?and microcomputer controlled electronic universal testing machine?MCEUTM?.The results showed that PVP played an important role in final PVA/PVP membrane with the ratio of V_PVA/V_PVP equal to 8:2.The crystallinity of this membrane was reduced significantly,the contact angle was also reduced,the hydrophilicity was enhanced remarkably,and the mechanical strength was also improved;the addition of maleic anhydride had no obvious effect on the crystallinity of the final membrane,the hydrophilicity was enhanced slightly,and the mechanical strength was increased remarkably and the final membrane was uniform and dense.