Preparation Of Mixed-matrix Membranes Based On Metal-Organic Framework For Hydrogen Separation

Fossil fuels are the most important sources of energy today,but under the pressure of oil crisis and environmental protection,we urgently need to develop sustainable and clean energy.As a renewable and sustainable energy source,hydrogen is combustible and pollution-free.Thanks to high energy conversion efficiency,high energy density(1.43×10⁸ J kg^-1)and the richest potential source,hydrogen will be the most attractive and promising energy source in the future.Steam reforming（CH4+H2O→CO（CO2）+H2）is the main technology in the technologies of hydrogen production.The raw materials are methane and water vapor,and the products inevitably contain impurities such as CH₄,CO,CO₂,N₂ and H₂O.In general,H₂content in syngas is generally between 60%and 80%,depending on raw material quality and process conditions.When hydrogen is used in fuel cells,impurities can cause serious poisoning of fuel cell catalysts.In order to increase the calorific value of H₂,the remaining components of the steam flow must be removed.Therefore,the purification of hydrogen from impurities is extremely important.Membrane separation is an efficient,energy-saving,low-cost technology.The mixed-matrix membrane（MMM）can simultaneously possess the properties of fillers（such as Metal-organic Frameworks）which can sieve gas molecules according to the pore size as well as the good machinability of polymers.It has great prospect in the industrial application of gas separation.In this paper,we selected the Metal-organic Framework material CAU-21-ODB with pore size of 3.3?,which lies between 3.64?and 2.9?.The material with smaller size and more uniform distribution were successfully synthesized by solvothermal synthesis and microwave-assisted method.The thermogravimetric analysis,X-ray powder diffraction,scanning electron microscopy and gas adsorption test were used to characterize the stability and adsorption properties of this material.A series of mixed-matrix membranes based on PIM-1 with different loading were prepared with the help of"priming"technique.The membranes were also characterized by the above methods and gas permeations.In the series of mixed matrix membranes,the gas separation test shows that the best separation is obtained from the membrane with loading of 15.2wt%.The hydrogen permeability can reach about 7200 Barrer,the ideal separation ratio for H2 over N2 is 39,and the selectivity for H₂/N₂ mixture gas is about 127.This result not only reflects the high selectivity brought by CAU-21-ODB,but also reflects the high permeability of polymer PIM-1 as matrix.Moreover,the separation performance of the membrane shows high stability in cycle test.The separation performance is above the Robeson curve reported in 2008 and far exceeds the performance of other mixed-matrix membranes of the same type.It is a promising material for practical application and production.