Preparation And Permeation Performance Of Layered Zirconium Phosphonate Membrane

Membrane separation technology can perfectly solve the energy burden and pollution problems caused by the traditional separation process due to its low energy consumption,high efficiency and no pollution.However,the trade-off effect between selectivity and permeability of traditional membrane materials restricts its performance improvement,so the development of new membrane materials has become an urgent task.As a typical two-dimensional membrane material,the layered molecular sieve membrane,owing to its regular and controllable transport channel and ultra-short mass transfer path,achieves accurate screening and rapid diffusion of guest molecules,and therefore,exhibits excellent separation performance.The ideal interlayer channels should be arranged perpendicular to the substrate,in order to shorten the diffusion path and reduce the mass transfer resistance.In addition,prepared membrane should have excellent stability to meet the needs of practical applications.This thesis has been carried out to solve the above problems.In this study,we synthesized a novel layered zirconium phenylphosphonate?ZrPP?membrane material and systematically studied its crystal structure.Then we prepared well-intergrown ZrPP membranes by facile in situ hydrothermal growth and investigated its gas separation performance as well as the thermal/chemical/mechanical stability.Main research results are as follows:?1?ZrPP powders were synthesized by fluorine coordination method,which were layered crystals formed by stacking of hexagonal lamellar plates.The crystal structure,thermal stability and adsorption properties of the powders were then characterized.The results showed that the interlayer height of ZrPP crystals was 3.2?,and ZrPP crystals had strong adsorption capacity for CO₂ and the crystal structure was stable until 400?.It is expected to be used to prepare H₂/CO₂ separation membrane with high separation performance and high stability.?2?Well-intergrown ZrPP membranes with vertically aligned interlayer galleries were prepared on t-ZrO₂ modified?-Al₂O₃ substrates by facile in situ hydrothermal growth.Due to"evolutionary selection",ZrPP crystals grew perpendicular to substrates,which greatly shortened the diffusion path length.Owing to the proper primary interlayer height?3.2??and the strong interaction between CO₂ and the polar ZrPP framework,prepared ZrPP membrane exhibited excellent H₂/CO₂ separation performance.At 1 bar and 200°C,the separation factor was 101.2,and H₂ permeance reached up to 482.7 barrer.As the operating temperature increased,the H₂/CO₂ separation performance further increased.?3?The durability of ZrPP membrane was systematically investigated.ZrPP membranes had partially penetrated substrate pores,which was very beneficial for enhancing their mechanical stability.Because of the high Zr-O bond strength and high coordination number of Zr⁴⁺ions,ZrPP membranes exhibited excellent mechanical,thermal and chemical stability.The morphology and crystal structure of the ZrPP membrane remained unchanged after ultrasonic treatment in deionized water for 1 h,calcination at 400°C for 24 h and treatment under extreme acidic/alkaline conditions for 24 h.Its separation performance also kept unchanged under long-term operation in harsh conditions.