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The Synthesis Of Several Metal-Organic Frameworks And Their Adsorption Performances Of CO2 Capture And Olefin/Paraffin Separations

Posted on:2021-11-11Degree:DoctorType:Dissertation
Country:ChinaCandidate:Y W ChenFull Text:PDF
GTID:1481306464482084Subject:Chemical Engineering
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The efficient CO2 capture as well as high-efficiency and energy-saving olefin/paraffin(C2H6/C2H4 and C3H6/C3H8)separations are highly important for chemical industries,and also are hot topics in the field of science and technology in chemical separations to date.In this thesis,several metal-organic frameworks(MOFs)have been designed and investigated in their adsorption and separation performances for CO2 capture from flue gas and natural gas,olefin/paraffin separations.This work mainly involves the synthesis and characterizations of several MOFs,CO2/N2,CO2/CH4,C2H4/C2H6 and C3H6/C3H8 adsorption and separation performances and mechanisms.It belongs to the interdisciplinary fields of chemical engineering and material science,which is of great importance for scientific research and practical applications.In this thesis,we reported a new MOF-505@GO composite with high selectivities for CO2/CH4 and CO2/N2 separation.The copper-based MOF-505 and graphite oxide(GO)were selected for the synthesis of moisture stable MOF-505@GO composite.At 298 K and 100k Pa,MOF-505@5GO exhibited the CO2 uptake of 3.94 mmol/g and the CO2/CH4 and CO2/N2selectivities of MOF-505@5GO were calculated up to 8.6 and 37.2,respectively.Compared with the parent MOF,the CO2 uptake of of MOF-505@5GO had an increase of 37.3%and the CO2/CH4 and CO2/N2 selectivities of MOF-505@5GO separately increased by13.2%and33.8%.It provided an efficient method for improving CO2 adsorptive separation performance through utilizing the enhanced dispersive force and steric effect by incorporating MOFs with GO.In this thesis,we reported an unusual moisture-enhanced CO2 capture within microporous PCN-250 frameworks.Compared with the parent PCN-250(Fe3),PCN-250(Fe2Co)showed an improved CO2 adsorption performance due to the partial Co2+ions substitution in PCN-250 framework.The two materials showed an unusual moisture-enhanced adsorption of CO2 by converting the negative competitive coadsorption of water into the positive effect on CO2 adsorption.Under 50%RH humid condition,the CO2adsorption capacities of PCN-250(Fe3)and PCN-250(Fe2Co)increased by 54.2%and 68.9%compared to dry condition,respectively;even up to 90%RH,obvious increases of 43.7 and70.2%in the CO2 adsorption capacities were also observed.Molecular simulations indicated that the hydroxo functional groups(?3-O)within the framework played a crucial role in improving CO2 uptake in the presence of water vapor,which is the novelty of this work.In this thesis,we reported an C2H6-trapping MOF PCN-250 for highly selective adsorption of C2H6 over C2H4.At 298 K and 100 k Pa,adsorption capacities of C2H6 and C2H4were 5.21 and 4.22 mmol/g,respectively;the adsorption selectivities of C2H6/C2H4 mixtures(1:15 and 1:1,v/v)were 1.9.Meanwhile,its separation performance was also corroborated by the breakthrough experiments,indicating the potential of C2H4 purification from C2H6/C2H4mixtures.Computational simulation revealed that both the pore effect and the van der Waals adsorption energy governed the separation of C2H6 over C2H4 for PCN-250,especially at low pressures.It can provide some useful theory for designing C2H6-selective MOFs.In this thesis,we reported an efficient adsorptive separation of C3H6 over C3H8 on a flexible and thermoresponsive CPL-1.It can achieve the adsorptive separation of C3H6 over C3H8 via the gate opening adsorption for C3H6 whereas not for C3H8 on the flexible CPL-1 at273 K.Since CPL-1 had only surface adsorption for both C3H6 and C3H8 at 298 K and up to100 k Pa.Thus,we developed an efficient regeneration of CPL-1 at 298 K based on its thermoresponsive gate opening effect.Molecular dynamics simulation revealed that the hydrogen bonding was a key factor governing the selective adsorption of C3H6 over C3H8 in CPL-1.It was because C3H6 molecules could be more preferentially adsorbed to form hydrogen bonds due to the slight rotation of the pyrazine ligand and then its structural transformation triggered the consequence of opening the pores.In this thesis,we reported a pillar-layer metal-organic framework for efficient adsorption separation of C3H6 over C3H8.There is an unsaturated metal site within the Zn(II)center for[Zn2(5-aip)2(bpy)]·(DMF)·(H2O)2(Zn-aip-bpy)framework,which can selectively form specific interaction between the?-orbital of C3H6 molecule and the vacant s-orbital of unsaturated Zn(II)atom.Although Zn-aip-bpy had C3H6 adsorption capacity of 1.91 mmol/g at 100 k Pa and 298 K,it exhibited preferential adsorption of C3H6 over C3H8 with high C3H6/C3H8 adsorption selectivity up to 19.8,outperforming most widely investigated MOFs.Furthermore,breakthrough experiments demonstrated the efficient separation of C3H6 over C3H8 on Zn-aip-bpy.This material could be readily regenerated at 423 K within 20 min.
Keywords/Search Tags:metal-organic frameworks, carbon dioxide capture, olefin/paraffin separation, moisture-enhanced CO2 adsorption, C2H6-selective adsorbent
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