Preparation And Performance Of PEBA Gas Separation Membrane Modifed By Fumed Silica For Oil Vapor Separation

With the rapid development of industrial chemistry and the increasing apparent consumption of crude oil,volatile organic compounds(VOCs)have become the second largest category of atmospheric pollutants.Most volatile organic compounds have pungent smell and toxicity.However,VOCs have certain utilization value.Therefore,the separation and recovery of VOCs has become the best pollution control measure.Compared with other technologies,membrane separation technology has low cost,high selectivity and can recover volatile organic gases for reuse.In order to expand the application of membrane technology,it was usually necessary to modify the membrane material.Blending modification can combine the characteristics of multiple materials to give the membrane more functional characteristics and improve the gas separation effect of the membrane.Therefore,based on the principle of blending modification,combining the structure and performance of fumed silica and polyether block amide(PEBA),a gas separation composite membrane was prepared and its structure,performance and volatile organic gas separation ability were studied.Polyethersulfone(PES)was selected as the porous support layer,and polyether block amide(PEBA)was used as the separation layer.Flat composite membranes with PEBA content of 3wt%-11wt% were prepared by spin coating.SEM,FT-IR,and XPS were used to characterize the surface morphology and structure of the membranes,the influence of different content of PEBA on the performance of the membrane was analyzed.The gas separation ability of membranes were tested through a gas separation experiment.The results showed that when the PEBA content is 7wt%,the overall performance of the membrane is the best.Fumed silica was added to the separation layer,and modified PEBA gas separation membranes with fumed silica content of 0.2wt%-0.8wt% were prepared by blending.SEM,FT-IR,XPS,XRD,contact angle test and tensile strength test were used to characterize the modified membrane,and the influence of different content of fumed silica particles on the structure and performance of the membrane was analyzed.The modified membranes were used to separate VOCs,the gas flux is measured,and gas separation performance were analyzed by gas chromatography.The results showed that fumed silica and PEBA are physically blended,and the best addition amount is 0.6wt%.When the content of fumed silica is 0.6%wt,the hydrophobicity of the membrane is increased by 57%,the gas flux is increased by 153% compared with the pure PEBA membrane,the comprehensive gas separation coefficient is 30.77,and the separation capacity is increased by 335%.The separation effect of butane is the most significant,increasing by 193% and 405% respectively.The addition of fumed silica destroyed the chain packing of PEBA polymer and increased the movement and free volume of the inner chain of PEBA molecule.The gas entered through the amorphous region between PEBA and fumed silica particles,so the gas flux increased.On the other hand,hydrophobic groups in fumed silica particles increase their affinity to separated components.The adsorption reaction between fumed silica particles and PEBA played a barrier role in the passage of permeable gas,which can enhance the selective separation of PEBA membrane.