Preparation Of Mixed Matrix Membranes Based On MOF Materials And Performance Of Light Hydrocarbon Separation

As the feed gases of chemical products,light hydrocarbon gases play an important role.Reasonable and efficient utilization of light hydrocarbon gas is the key to improve the level of petrochemical production and economic benefits.The traditional cryogenic separation and pressure swing adsorption separation have high energy consumption and are easy to produce secondary pollution.Gas membrane separation method has the characteristics of simple equipment,energy saving and environmental protection.If it can be applied in industrialization,it is of great significance to ease resource tension and build an energy-saving and environment-friendly society.However,the common organic polymer membranes are limited by the material themselves,so it is difficult to achieve high permeability and selectivity of gas.Metal-organic framework materials（MOF）,as a new type of nanometer filling materials,have many advantages such as high specific surface area and specific adsorption of light hydrocarbons.The introduction of MOF nanoparticles into organic polymer membranes to prepare mixed matrix membranes is expected to break through the"trade-off"effect and achieve high-performance separation of light hydrocarbons.Aiming at the separation of C₂H₄/C₂H₆ and C₃H₆/C₃H₈,the application goal of this paper is to improve the permeability and separation performance of mixed matrix membranes materials for light hydrocarbon gases.ZIF-8/PDMS,Cu-MOF/PDMS mixed matrix membranes and ZIF-8-based,Cu-MOF-based mixed matrix carbon membranes based on MOFs were designed and prepared,respectively.The structure and performance of the prepared MOFs nanoparticles and mixed matrix membranes were characterized by XRD,SEM,TG,N₂adsorption,light hydrocarbon adsorption performance test and light hydrocarbon permeability test,etc.The effects of the addition amounts of MOF and carbonization temperature on the membrane performance were investigated,and the following conclusions were drawn:（1）Mixed matrix membranes of ZIF-8/PDMS and Cu-MOF/PDMS were prepared by physical blending,and good dispersity and interfacial structure were maintained.However,the loading of MOF only improves the light hydrocarbon permeability of the mixed matrix membranes,but does not play a positive role in promoting its separation performance.（2）ZIF-8-based mixed matrix carbon membranes were prepared by physical blending and high temperature carbonization.The dispersity of the two matrixes was good and the interfacial structure was uniform.After high temperature pyrolysis of ZIF-8,a porous carbon nanostructure containing Zn O was formed,which was embedded in the carbon matrix formed by carbonization of polymer precursor.The micro-pore structure and gas adsorption site of the mixed matrix membranes were increased,and the diffusion selectivity of olefin/alkane gases was improved.The ZIF-8-based mixed matrix carbon membranes prepared under the optimal process conditions showed excellent performance of light hydrocarbon permeation and separation,and the ideal selectivity of C₂H₄/C₂H₆ and C₃H₆/C₃H₈ are 15.8 and 14.4,respectively,which increases by 154.8%and 182.4%compared with the original membranes.（3）Cu-MOF-based mixed matrix carbon membranes were prepared.After high temperature pyrolysis of Cu-MOF,a porous carbon nanostructure containing Cu O was added into the carbon film,and the adsorption selectivity of olefin/alkane gases is improved under the action of Cu²⁺.The permeability and selectivity of light hydrocarbon in the mixed matrix membranes were improved successfully.The Cu-MOF-based matrix carbon membranes prepared under the optimal process conditions showed excellent performance of light hydrocarbon separation.The ideal selectivity of C₂H₄/C₂H₆ and C₃H₆/C₃H₈ are 10.6 and 14.9,respectively,which are 71.0%and 65.6%higher than those of the original membranes.