Experimental And Simulation Study On Adsorption And Separation Of CF₄/N₂ By ETS-10

For nearly half a century,due to the continuous increase of industrial demand and production activities,especially the expansion of aluminum production capacity in developing countries,the emission of CF4 is increasing day by day.CF4 is a gas with high greenhouse effect potential and has a negative impact on the ozone layer.Therefore,it is urgent to seek an economic and reasonable CF4 adsorption technology.Titanosilicate ETS-10 has a unique microporous framework structure,and has good adsorption,ion exchange and catalytic activity.This multifunctional property makes it widely used in organic synthesis,catalysis,adsorption separation of CO2/N2 and dehydration,denitration and desulfurization.Combined with these characteristics and advantages of ETS-10,this paper carried out experimental and simulation studies on the adsorption and separation of CF4 using ETS-10,as follows:Firstly,ETS-10 molecular sieve was synthesized by hydrothermal method.The samples were characterized by XRD,SEM and FTIR to ensure that ETS-10 molecular sieve with high purity was obtained.The CF4 adsorption capacity of ETS-10 was studied.The results showed that the prepared ETS-10 had high CF4 adsorption capacity.The adsorption capacity of CF4 was 1.4 mmol/g,1.12 mmol/g and 0.94 mmol/g at 273 K,303 K and 333 K,respectively.Four models of Langmuir,Dual-site Langmuir(DSL),Freundlich and Toth,were used to fit the adsorption of CF4 on ETS-10.It was found that the Langmuir model had the best fitting effect.The CF4/N2 adsorption selectivity ratios of ETS-10 at different temperatures were calculated by IAST model.The overall adsorption selectivity factors at 273 K,303 K and 333 K were all greater than 5 at atmospheric pressure,indicating that ETS-10 could be used for CF4/N2 separation.The adsorption thermodynamics of CF4 and N2 on ETS-10 was studied.The results showed that ETS-10 adsorption of CF4 and N2 was physical adsorption,and the adsorption capacity of CF4 was greater than that of N2.The adsorption kinetics study showed that the Banham model had the best fitting effect.Based on the experimental study,Aspen Adsorption software was used to study the separation process of CF4/N2 by titanosilicate ETS-10.According to the experimental data of adsorption isotherm of single component gas,the Langmuir adsorption equilibrium model parameters related to temperature were fitted by Origin Software fitting tool,and the applicability of the fitting results was discussed.Based on thermodynamics,hydrodynamics and heat and mass transfer,the model of multicomponent gas in adsorption bed is established,and the initial and boundary conditions of the model are given.Then the mathematical model was established,and the simulation flow chart was established by using the mathematical model.The auxiliary design of adsorption process can be aided by Aspen Adsorption.Based on Aspen Adsorption,the breakthrough curve and the axial distribution of CF4 concentration in the adsorption bed of ETS-10 molecular sieve were obtained.The influence of pressure,mass transfer coefficient,temperature,adsorbent quantity and bulk density on the breakthrough curve of CF4 was observed.When the mass transfer coefficient is changed,the breakthrough curve becomes steep with the increase of mass transfer coefficient,the length of mass transfer zone and adsorption resistance decrease,and the utilization ratio of molecular sieve is improved.When the temperature changes,the breakthrough point begins to move,the adsorption capacity decreases with the increase of temperature,but the adsorption rate is accelerated.In a certain range,if we want to improve the utilization efficiency of molecular sieve,we can increase the pressure,reduce the temperature and increase the mass transfer coefficient.The faster the gas flow rate is,the faster the penetration is.However,if the gas flow rate is too fast,the adsorbate molecules can not fully contact with the adsorbent surface,which will reduce the adsorption efficiency.When changing the amount of adsorbent,the breakthrough time increases with the increase of the amount of adsorbent,and the adsorption capacity also increases.With the increase of the amount of adsorbent,the size of the adsorption bed will also change.Therefore,the appropriate adsorption bed should be selected according to the actual situation.The penetration time increases with the increase of the packing density,and the bulk density of the adsorbent should be controlled in real life in order to avoid the influence of bulk density on the breakthrough time and reduce the adsorption efficiency.In general,based on Aspen Adsorption,this paper carried out a shallow study on adsorption theory and simple application in the field of adsorption,which provides some basic data for pressure swing adsorption treatment of CF4,and has some reference value.Through this simulation,the influence of some factors on the adsorption and separation of CF4 was directly explored,which can guide and optimize the experiment,effectively reduce the number of experiments and improve the experimental accuracy.In this study,the optimal conditions for improving the adsorption performance were found,which laid a foundation for futher exploring the reaction mechanism and mass transfer process in the adsorption process.