Synthesis Of Chabazite Membrane And Its Gas Separation Performance Of CO₂/N₂

According to statistics,the amount of CO2 emitted into the atmosphere has gradually increased in the past half of a century due to the massive combustion of fossil fuels such as coal,oil,and natural gas.The current CO2 emissions have reached 18.5 billion tons to 24.2 billion tons every year.With the continuous improvement of people’s awareness of energy conservation and environmental protection,people began to carry out technological reforms on industries with high pollution and high energy consumption.The recycling of CO2 in exhaust gas became a research focus in the world.Among many CO2 recovery and separation methods,membrane separation technology has many advantages over other technologies,such as energy-saving,high-efficiency,simple experimental operation,and convenient to use the equipment.Therefore,it became one of the most promising new technologies in the 21st century.The core of the membrane separation technology is the performance of membranes.Therefore,the preparation of dense and defect-free membranes which have a certain mechanical strength and low gas mass transfer resistance has become the research focus of membrane separation technology.Because chabazite has a unique molecular gate effect,the adsorption selectivity for CO2 and N2 is high.Therefore,this study mainly uses the secondary growth method to synthesize chabazite membrane on the macroporous alumina ceramic carries.Then,the optimal synthesis conditions of chabazite membranes were investigated,and structural properties of those membranes were characterized.Finally,This paper studies the separation performance of CO2 and N2 from those membranes.First,chabazite membrane was prepared by secondary growth synthesis method.Its microscopic morphology is obviously different from the zeolite membrane with CHA topology.This can prove that is a new kind of zeolite membrane material.The optimal synthesis conditions of the chabazite membrane are as follows:AHS-CHA seeds,crystallization time was 4 days,the concentration of the synthetic solution was 1:8,and the seed concentration was 10 g/L.The actual imaging,thermal imaging and SEM images of the cross-section of the chabazite membrane show that the membrane thickness of the chabazite membrane is about 20μm.The density of the membrane is significantly higher than that of the ceramic carries,and the membrane is dense and coherent.To obtain smoother membrane surface,5%PEG was added to the synthetic solution as a binder.The results show that the binder can promote higher flatness of the membrane and plays an important role in optimizing the membrane formation.The gas separation performance study of the chabazite membrane shows that the ideal separation coefficient of CO2 and N2 can reach 3.5 in the single component gas permeability test.In the separation performance test of mixed components,the actual separation coefficient of CO2 and N2 increased to 4.05 due to the intermolecular diffusion competition and the selective adsorption of chabazite.By comparison of the permeation separation test at different temperatures,pressures,we can conclude that as the pressure increases,the separation factor of the membrane decreases.As the temperature rises,the separation factor of the membrane decreases slightly.Finally,the stability of the chabazite membrane was tested.The separation coefficient of the chabazite membrane did not change significantly in a certain period of time,indicating that the prepared chabazite membrane has good stability.The chabazite membrane can be applied to the separation of CO2 and N2 in flue gas.