Evaluation On The Adsorption And Separetion Properties Of Several CO₂ Adsorbents

CO₂ is one of the main greenhouse gases.Its excessive emissions will lead to carbon imbalances in the natural world,causing a series of environmental problems such as global warming and sea level rise,which will result in adverse effects on the survival and development of human society.Solid-phase adsorption is one of the most promising methods for CO₂ adsorption,separation,and capture.In recent years,researchers have found that metal-organic frameworks?MOFs?,zeolites,and activated carbons possess potential applications in CO₂ adsorption and separation.However,there has been a lack of an effective method to evaluate the adsorption and separation efficiency of CO₂ adsorbents.In this thesis,the adsorption and separation of CO₂,CH₄,and their mixtures on five adsorbents?metal-organic frameworks NH₂-MIL-125and NH₂-UiO-66,zeolites NaY and MOR,microporous activated carbon Kureha carbon?were investigated and an attempt was to develop a method to evaluate the adsorption and separation efficiency of CO₂ adsorbents.The main research contents are given as follows:1)The unary adsorption isotherms of CO₂ and CH₄ on five different adsorbents were determined by a volumetric method.These measured adsorption isotherms were described by suitable isothermal adsorption models,from which their adsorption thermodynamic parameters were determined as well.The adsorption selectivities for CO₂ over CH₄ were predicted by the ideal adsorption solution theory?IAST?.The results show that under the isothermal condition,the adsorption selectivity for CO₂ decreases first and then increases with increasing pressure while under the isobaric condition,the adsorption selectivity for CO₂ decreases with increasing temperature.In addition,the adsorption separation performance of a CO₂/CH₄ mixture on the five different adsorbents was investigated by a breakthrough-column technique.The results show that the adsorption selectivity for CO₂ as a function of temperature or pressure is consistent with the IAST prediction.2)Based on the principles of energy,material,and momentum conservation,an adsorption and separation engineering model of CO₂/CH₄ mixtures on the five different adsorbents was established and the measured breakthrough curves were fitted with the developed model.The results show that the established adsorption separation engineering model can describe the experimental breakthrough curves very well.When the CO₂/CH₄ mixture passes through a Kureha carbon or MOR bed,there is a significant"rolling-up"phenomenon in the CH₄ breakthrough curve.3)The adsorbents were evaluated with two different methods,the so-called "separation potential"and"parasitic energy".Although NaY has the best performance on the adsorption-based separation of CO₂/CH₄ mixtures,the energy consumption for the adsorbent regeneration is also the largest.Although the energy consumption of NH₂-MIL-125 regeneration is the smallest,the performance on the adsorption-based separation of CO₂/CH₄ mixtures is the worst.The comprehensive comparison shows that Kureha carbon has a higher separation efficiency of CO₂/CH₄ mixtures,meanwhile the energy consumption of the adsorbent regeneration is lower.Therefore,Kureha carbon can be considered as an ideal adsorbent.