| The three kinds of immobilized ionic liquids that is 1-butyl-3-methyl imidazolium chloride([BMIM]Cl),1-butyl-3-methyl imidazolium tetrafluoroborate([BMIM]BF4)and 1-butyl-3-imidazolium glycine salt([BMIM]Gly)were systhesized,and the microcapsule-type immobilized ionic liquids were prepared by the high-speed shear method.The structural characterization and microstructure analysis of each samples were carried out and the adsorption capacity of CO2 and N2 were tested.The effects of the kind and ration of gas-phase silica gel and ionic liquids on the particle size,microstructure,CO2 adsorption capacity and CO2/N2 selectivity of ionic liquid microcapsules were investigated.On the basis of this,the diffusion behavior of CO2 adsorbed by ionic liquid microcapsules was discussed.The main conclusions are as follows:(1)According to the FTIR spectroscopy,the gas-phase silica gel coated imidazodium ionic liquids were successfully prepared.Thermogravimetric analysis showed that all prepared samples have high thermal stability.The surface morphology analysis showed that the prepared samples are micro-level and present a complete microcapsule structure.(2)The microstructure integrity and grain size are the main factors influencing the CO2 adsorption capacity for the gas-phase silica-coated ionic liquid-water microparticles,while the species of ionic liquids are the main factors affecting the selectivity of CO2/N2.Under the pressure of 0.1 MPa and 293 K,BC30 preparaed with [BMIM]Cl-water having a ratio of 3:7 has a smaller particles size and gives the better comprehensive performance.The sample reaches the adsorption equilibrium only 5 min,and the CO2 adsorption capacity is 6.84 %,while the selectivity is 25.33.[BMIM]Gly is the highest selectivity and BG30 almost has no adsorption N2.The prepared microparticle samples also have good recyclability.(3)For the gas-phase silica gel coated ionic liquid-ethylene glycol-water microparticle samples,the addition of ethylene glycol can result in the less volatilization of water and smaller particle size,while the selectivity changes a little,and the time for reaching adsorption equilibrium increases obviously,but the adsorption capacity decreases.Under the condition of 0.1 MPa and 293 K,the sample BCE30 reaches the adsorption equilibrium was 115 min,and the CO2 adsorption capacity is 2.89 wt%,while the selectivity is 20.25.The increasing of water content can bring about smaller particle size,less CO2 adsorption and higher CO2/N2 adsorption selectivity.BCE24-11 with the water content of 8.71 % can get equilibrium time 60 min and CO2 quilibrium adsorption capacity is 3.41 %,while the CO2/N2 selectivity is 17.05.The sample BCE24-12 with11.69 % water content,can achieve equilibrium time 230 min and CO2 adsorption capacity is 2.73 %,while the selectivity is 19.01.(4)The adsorption kinetic curves of samples were fitted by the diffusion model and the kinetic diffusion coefficients(DS)of CO2 in the microparticles were obtained.Compared with Ds(10-10m2/s)of pure ionic liquids,the diffusion rate of ionic liquid silica particles is faster which Ds is in the order of 10-7 ~10-8 m2/s,quitting to that of bare silica gel.Indicating that the structure of immobilized ionic liquid microcapsule is more conducive to the transfer of CO2,greatly reducing the adsorption desorption equilibrium time. |
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