Designing And Property Investigation Of Novel PIMs Membranes For High Performance Gas Separation

The gas separation membrane technology has the unique advantages of low energy consumption,high efficiency,simple operation,easy scale and environmental friendliness,and has great application potential in the field of industrial separation.However,conventional gas separation membrane materials have low gas permeability and are increasingly unable to meet the growing industrial production demand.The development of high permeability,high selectivity membrane materials has been one of the research hotspots in the field of chemical separation.Polymer of intrinsic microporosity?PIMs?are a class of high-permeability and medium-selective polymer materials developed in recent years.Their high permeability to gases is derived from the inefficient folding of rigid twisted molecular chains.Microporous structure.However,its permeability still cannot meet the requirements of actual industrial production.Designing and developing high-performance PIMs membrane has great and far-reaching significance for the development of membrane separation technology.This paper is based on the design and construction of high performance gas separation membranes,which are divided into the following three parts:?1?Synthesis of Polymer of Intrinsic Microporosity?PIM-1?.A large number of domestic and foreign literatures on PIM-1 research are Investigated,and PIM-1polymer material with good physical and chemical properties,high specific surface area and controlled microporous structure was prepared by high and low temperature methods,and their molecular structure information and thermal stability are studied.The advantages and disadvantages of high and low temperature methods are also discussed.It lays a good foundation for the subsequent work.?2?Polymers of gas separation membranes based on post-modified PIM-1typically have high gas selectivity but have relatively low gas permeability.Freeman theory provides guidance for the design of PIMs.The theory points out that increasing the molecular chain spacing and the rigidity of the molecular structure can improve the gas separation performance of the polymer.In this work,adamantane is grafted onto amidoxime-functionalized PIM-1?AOPIM-1?mainchain through a simple acyl chloride-substitution reaction.As a side group,adamantane is used to adjust the chain packing of AOPIM-1 and thus affect the permeability of gases,especially CO₂ permeability.Its results show that the d-spacing of adamantane-grafted AOPIM-1 membranes could be finely tuned by adjusting the mole ratio of grafted adamantane moiety on the polymer.The obtained membrane exhibits significantly enhanced CO₂ permeability from 980.7 Barrer in the case of AOPIM-1 membranes to 2483.6 Barrer in the case of adamantane-grafted AOPIM-1membranes,while the selectivity of CO2/N2 and CO2/CH4 gas pairs decrease slightly from 36.0 to 31.2 and from 33.8 to 30.1,correspondingly.The comprehensive separation performance of adamantane-grafted AOPIM-1membrane for CO2/N2 and CO2/CH4 largely surpasses the 2008 upper bound.?3?Mixed matrix membranes have showed improved propylene/propane selectivity compared to the pristine polymer membrane,but the industrial-scale propylene purification projects based on membrane separation technology is still restrained by its low permeability.In this work,a new fluorinated MOF-based mixed matrix membrane is developed by incorporating the SIFSIX-3-Zn nanoparticles into the polymer of intrinsic microporosity?PIM-1?matrix.The robust SIFSIX-3-Zn with high surface area and suitable aperture size can create new delivery channels to facilitate transport of propylene.10 wt%SIFSIX-3-Zn/PIM-1 MMMs shows an optimal enhancement of C3H6 permeability from 1699.9 Barrer to 3641.9 Barrer with the ideal C₃H₆/C₃H₈ selectivity simultaneously increasing by nearly 100%.This performance is placed in unpopulated high permeability area of the trade-off plot and surpasses the upper bound.The novel fluorinated MOF-based mixed matrix membrane may have great potential for industrial C₃H₆/C₃H₈ separation.