Preparation And Pervaporation Performance Of BTESE-derived Hybrid Silica Membrane

At present,the industrial pervaporation membrane is mainly zeolite membrane.However,in the diversified market demand,the extremely poor acid resistance of zeolite membrane restricts its pervaporation application range.Silica membrane is an excellent choice for membrane separation field,which has good acid and alkali resistance and heat resisting property.Nevertheless,hydrothermal reaction of pervaporation can destroy membrane layer structure of amorphous silica.In this dissertation,in view of problems existing in poor hydrothermal stability of silica material,silica composite membrane was prepared by sol-gel method,in which organosilane BTESE(1,2-bis(triethoxysilyl)ethane)was selected as the silicon source,and transition metal ion Zr was introduced to reaction system.The microstructure and mechanism of action of each layer of the silica composite membrane were deeply discussed,and the pervaporation performance of the silica composite membrane under different preparation conditions and environmental conditions was tested.The main research results were introduced as follows:(1)The design of silica composite membrane consists of particle layer,transition layer and separation layer.Particle layer was the pore structure mainly composed of?-Al2O3 particles.The surface of particle layer was flat and surface pore diameter was about 100 nm to 200 nm.The thickness of particle layer was about 2.5 ?m,which could provide quite reliable support for other layers.The transition layer and the separation layer with smooth and nonporous surfaces were compact structures formed by amorphous silica,and the total thickness of the two film layers was about 1 ?m.Plasticity and thermal stability of silica network in transition layer were significantly improved due to the introduction of Zr,which had contributed to the formation of a continuous and complete separation layer without cracks.(2)The preparation processes of the silica composite membrane were optimized by following conditions: the particle layer coating method was the combination of 1.9?m and 0.2 ?m particles,the transition layer coating method adopted wipe coating method,the separation layer coating times were 3 times,and the coating temperature was 160 ? to 180 ?.The pervaporation characteristics for isopropanol dehydration at75 ? of silica composite membrane were tested.The average flux was above 1kg·m-2·h-1,and the water concentration of permeate could reach 99.4 wt%.(3)The silica composite membrane had stable pervaporation performance and fine hydrothermal stability under different operating temperatures and feed concentration.The silica composite membrane still maintained stable pervaporation performance after soaking in different kinds of acidic environments with p H=2 for 15 days,which indicated that the silica composite membrane had excellent acid resistance and was more suitable for pervaporation in acidic systems.