Studies On The Separation Of Hydrocarbons With Ionic Hybrid Porous Materials

Gas separation is one of the most important processes of the production of high purity chemicals and clean energy.However,the trade-off between adsorption selectivity and uptake capacity has caused huge consumption of energy.In this dissertation,for the highly efficient production of polymer-grade ethylene and acetylene,a novel method for the separation of C₂H₄ and C₂H₂ using ionic hybrid porous materials was proposed.Adsorption properties and separation mechanism were studied in order to promote the progress of the gas separation process.In this dissertation,C₂H₂ and C₂H₄ single-component gas sorption isotherms were measured on ionic hybrid porous（SIFSIX,SiF62-）materials,the influence of pore structure and geometry of SiF62-anions on separation selectivity and uptake capacity were systematically studied.It was found that SIFSIX materials showed excellent C₂H₂/C₂H₄ separation performance.In particular,the separation selectivity and uptake capacity of SIFSIX materials were significantly affected by the pore structure of SIFSIX materials.SIFSIX-1-Cu（1=4,4’-bipyridine）,with the pore size of 8 A,adsorbed as high as 8.5 mmol/g C₂H₂ at 298 K and 1.0 bar,and exhibited a high C₂H₂/C₂H₄ separation selectivity（7.1-10.6）.Interpenetrated SIFSIX-2-Cu-i（2=4,4’-bipyridylacetylene,pore size of 5.2 A）showed the highest Qst（41.8-37.7 kJ/mol）of acetylene.SIFSIX-2-Cu-i adsorbed 2.1 mmol/g C₂H₂ at 298 K and a low pressure of 0.025 bar and exhibited the record C₂H₂/C₂H₄ selectivity（39.7 to 44.8）.Therefore,this study addressed the trade-off problem between physical adsorption capacity and selectivity.The excellent C₂H₂/C₂H₄（1/99,50/50）separation performance of SIFSIX materials（SIFSIX-1-Cu,SIFSIX-2-Cu-i and SIFSIX-3-Zn）were examined by the experimental breakthrough studies.Breakthrough experiments for the 1/99 mixture with trace amount of CO₂,O₂,and H2O on SIFSIX-2-Cu-i were conducted.Meanwhile,the cycling performance and stability of SIFSIX materials were investigated.The results showed that SIFSIX materials showed excellent C₂H₂/C₂H₄ separation performance.In the important separation process of C₂H₂/C₂H₄（1/99,v/v）,fixed-bed of SIFSIX-2-Cu-i adsorbed as high as 0.73 mmol/g C₂H₂,higher than the benchmark materials ever reported.The concentration of residual C₂H₂ in the purified C₂H₄ was less than 1 ppm.Water stability and recycle tests both confirmed the excellent stability of SIFSIX-2-Cu-i.High-revolution neutron powder diffraction and supported by first-principles density functional theory calculations provide a deeper insight into the nature of the interaction of acetylene/ethylene within SIFSIX ionic hybrid porous materials.In SIFSIX materials,hydrogen bonding（C-H…F）between SiFe2-anion and acetylene were formed.By tuning the pore size and geometry of SiF62-anions,synergistic host-guest and guest-guest interactions were formed.In SIFSIX-1-Cu,four acetylene molecules formed the uacetylene clusters"through multiple diplo-diplo interactions.In SIFSIX-2-Cu-i,one C₂H₂ molecule can be simultaneously bound by two F atoms from different nets through cooperative Hδ+…Fδ-interactions,which enabled the recognition of acetylene and enhanced the uptake capacity of acetylene.The separation mechanism of SIFSIX materials is also applicable to the separation of other gases.In this dissertation,high efficient separation of SO₂ with high capacity and selectivity were realized by using the ionic hybrid porous materials as adsorbent.SO₂ adsorption isotherms,separation mechanism and breakthrough experiments were studied on SIFSIX materials.Results showed that SIFSIX-1-Cu adsorbed as high as 11.01 mmol/g SO₂ at 298 K and 1.0 bar,which was higher than all the reported materials measured at the same conditions.SIFSIX-2-Cu-i adsorbed as high as 2.31 and 4.16 mmol/g SO₂ at 0.002 bar and O.Olbar respectively.Meanwhile,SIFSIX materials exhibited outstanding SO₂/CO₂（54-70 for SIFSIX-1-Cu,87-89 for SIFSIX-2-Cu-i）and S02/N2（2513-3145 for SIFSIX-1-Cu,1285-3103 for SIFSIX-2-Cu-i）selectivity.DFT calculation showed that SIFSIX-1-Cu and SIFSIX-2-Cu-i grasp every atoms of SO₂ through Sδ+…Fδ-electrostatic and Oδ-…Hδ+ diplo-diplo interactions.The strong interactions enforced the formation of "SO₂ clusters".The stability of SIFSIX materials were tested by X-ray powder diffraction.The excellent separation performance of SIFSIX materials were confirmed by the experimental breakthrough studies.