The Preparation Of GO/ZIF-8 Composites And Membrane For Propylene And Propane Separation

Propylene?C₃H₆?is an important basic chemical material,it is commonly used in the production of a variety of important organic chemical materials such as synthetic resin,synthetic rubber and a variety of fine chemicals.The separation of propylene and propane is a very important problem in the petrochemical industry.With the development of research,membrane-based propylene/propane separation is getting a promising technology for its low energy consumption.ZIF-8 has attracted much attention due to its unique excellent high porosity,structured and adjustable pore structure.In particular,the effective window size is 0.4 nm,which makes the ZIF-8-based film a good choice for the separation of propylene and propane.But a pure inorganic ZIF-8 film is brittle with poor mechanical properties,so it cannot be widely used for application.ZIF-8 crystals are so large by in situ synthesis or secondary preparation methods,which can easily form gaps between ZIF-8 nanocrystals and even cracks in the membrane.In addition,the brittle substrates such as AAO and SiO₂ were usually used in the preparation of MOF membranes.It is so difficult to scale up in chemical and petrochemical industry.In this paper,a GO/ZIF-8 membrane was prepared on a flexible PTFE substrate by vacuum filtration,and a good propylene/propane separation performance was obtained.We first synthesized graphite oxide and ZIF-8,and then prepared the GO/ZIF-8 2D nanosheets with sandwich structure by regulating the ratio of metal center and organic ligand.ZIF-8 crystals are arranged regularly on both sides of graphite oxide.We regulated the GO contents to get GO/ZIF-8 composites with different GO weight ratio.There is little difference in their morphologies among 5.5%,11%and16.5%GO/ZIF-8 composites.The GO/ZIF-8 composite film was obtained by a simple vacuum suction method and the film was stabilized by Zn²⁺which was used as a crosslinking agent to prevent its crimp cracking.Finally,a series of membranes with different thicknesses were obtained and the membrane separation tests were carried out.The membranes show excellent properties in the mixture C₃H₆/C₃H₈ separation,the propylene permeance of the membrane with the thickness of 600 nm was8.3×10^-9mol·Pa^-1·m^-2·s^-1,and the separation coefficient was 100.