| The flue gas and natural gas contain a varous amount of water vapor,and thus the impact of water vapor on the properties of adsorbents should be carefully considered during their industrial applications.It is well known that many adsorbents are greatly affected by the coexisting water vapor.However,less research has been carried out on this topic.Therefore,this thesis research has been focused on investigating the effects of the coexisting water vapor on the adsorption separation of CO2 on several adsorbents.Activated carbon is one of the adsorbents widely used in industry due to its reversible adsorption of CO2 at relatively low temperatures,large specific surface area,and low adsorption heat.Molecular sieves are a kind of common adsorbents,which have ordered pore structures and can selectively adsorb small molecules.Metal organic frameworks(MOFs)have large specific surface areas andadjustable apertures,and therefore they may have great applications in the field of gas separation and storage.This thesis research mainly focuses on investigating the effects of water vapor on the separation performance of the gas mixtures CO2/CH4 and CO2/N2 on several different adsorbents.1.The amino-functionalized metal organic frameworks(MOFs),NH2-MIL-125 and NH2-UiO-66,were successfully synthesized by a hydrothermal method.The single-component isotherms of CO2,CH4,and N2 on the synthesized MOFs were measured with a volumetric method.Then either Langmuir or dual-site Langmuir model was used to describe the measured isotherm data.The fitting results show that the used model can describe the experimental data well.Futhermore,a breakthrough-column technique was used to evaluate the adsorption separation performance of the two gas mixtures CO2/CH4 and CO2/N2.The results show that under a dry condition the separation efficiency is enhanced as the total pressure of the gas mixture is increased at a constant temperature while at a constant pressure,the separation efficiency is decreased as the temperature is increased.These results are in good agreement with the predictions by the ideal adsorbed-solution theory(IAST).In the presence of water vapour,the measured breakthrough curves are almost the same as those under the dry conditions.Additionally,based on the measured breakthrough curves,the estimated adsorbed amounts of the binary mixtures in the presence of water vapour are almost the same as those under the dry conditions,confirming that the coexisting water vapour hardly affects the adsorption separation of the binary mixtures on the amino-fuctionalized MOFs.2.The adsorption isotherms of the single-component gases CO2,CH4,and N2 on 13X zeolite were measured,and the measured adsorption data were described by a proper isotherm model.Then the breakthrough-column technique was used to investigate the separation performance of CO2/CH4 and CO2/N2 mixtures on 13X.The results show that under dry conditions,13X adsorbent possesses some excellent separation properties for the mixtures while the separation effiency of the mixtures is decreased as the relative humidity is increased or the adsorption-desorption cycle is increased in the presence of water vapor.Additionally,based on the measured breakthrough curves,the estimated adsorbed amounts of the binary mixtures in the presence of water vapour are decreased as the relative humidity is increased or the adsorption-desorption cycle is increased in the presence of water vapor,confirming that the coexisting water vapour significantly affects the adsorption separation of the binary mixtures on 13X zeolite.3.Kureha carbon,which is hydrophobic,was used as adsorbent for the sepration of CO2/CH4 and CO2/N2 mixtures with the breakthrough-column technique.After several adsorption-desorption cycles in the presence of water vapor,the breakthrough curves are hardly changed,indicating that the separation performance of Kureha carbon is not affected by the presence of water vapor.This implies the potential application of Kureha carbon on CO2 adsorption-based separations. |
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