Controllable Preparation And Ester/Water Separation Performance Of BTESE-Derived Microporous Silica Membranes

The separation and recovery of organic solvents is of great importance to the sustainable development of industry and ecological protection in areas such as chemicals,electronics and new energy.Permeation vaporisation offers an energy efficient separation method that has attracted a lot of attention from researchers in recent years.Microporous silica（Si O₂）membranes have great prospects for application in the field of membrane separation due to their acid resistance and fouling resistance,but the poor hydrothermal stability of inorganic silica membranes affects their application in liquid separation.Based on these two points,this study proposes to improve the hydrothermal stability of silica membranes by introducing boron,a non-metallic element,into silica by sol-gel method,and to modify them by hydrochloric acid curing in order to achieve pore size regulation of silica membranes and improve their selective separability by permeation vaporization.（1）The separation layer plays a decisive role in the structure of Si O₂ film derived from BTESE as silane precursor.The selective separability of the silicon dioxide membrane separation layer is achieved mainly by molecular sieving through the pores of the network structure.When the volume ratio of BTESE/ethanol is 1:1 and the film is coated 3 times,the membrane surface was smooth and compact,the highest water content was 90.35%,and the osmotic flux was 3.34 kg·m^-2·h^-1.（2）B was mainly incorporated into the silicon dioxide network in the form of Si-O-B bonds.When the ratio of BTESE:H₃BO₃:H₂O:H⁺=1:0.5:45:0.33,and the calcination temperature is 200°C,the boron-doped BTESE composite membrane has the best separation performance,and the pervaporation flux was 4.08 kg·m^-2·h^-1 with a water content of 97.64%.（3）The acid resistance and hydrothermal stability of the boron-doped Si O₂composite membrane were tested,and the composite membrane showed stable pervaporation performance.The prepared silicon dioxide composite membrane was applied to the pervaporation dehydration of ethyl acetate-ethanol-water ternary system with a flux of 3.08 kg·m^-2·h^-1 and a water content of 82.63%and a separation factor of48.08,the results showed that the membrane could be used in the ethyl acetate synthesis process to improve the purity of the product.（4）Hydrochloric acid treatment of the prepared boron-doped Si O₂ composite membrane for 100 min can effectively enhance the selectivity of the silica membrane,reduce the specific surface area and pore size of the membrane,the specific surface area of the membrane is only 32.59 m²·g^-1,the pore size was reduced to 0.354 nm.After pervaporation in ethyl acetate aqueous solution for 12 h,the flux of HCl cured modified boron doped Si O₂ membrane was stable at about 1.80 kg·m^-2·h^-1,and the separation factor was kept above 462.81.The membrane still had good separation performance.