Preparation Of Porous Functionalized Polymeric Ionic Liquid And Its Application In CO₂ Adsorption

The increase of CO₂ content in the atmosphere caused a huge threat to the environment.At the same time,CO₂is an important C1 resource.Therefore,capturing CO₂is an important measure to protect the environment and achieve sustainable development.Ionic liquids have a strong affinity for CO₂and have been used for CO₂capture.However,the high viscosity of ionic liquids limits their efficiency in capturing CO₂.Polymeric ionic liquids can be prepared as solid adsorbents for CO₂to overcome the shortcomings of ionic liquids.Moreover,compared with traditional CO₂solid adsorbents such as molecular sieve and activated carbon,polymeric ionic liquids have both chemical functional groups and solid-state microstructures and thus can integrate physical adsorption and chemical adsorption.Polymeric ionic liquids have the advantages of high CO₂adsorption capacity,low energy consumption and easy regeneration.Based on the above,this thesis introduced amino acid-based functionalized anions into the structures of polymeric ionic liquids and applied supercritical foaming technology to prepare porous functionalized polymeric ionic liquids for CO₂adsorption.Ionic liquid 1-（p-vinylbenzyl）-3-methylimidazolium glycinate,ionic salt1-（p-vinylbenzyl）-3-methylimidazolium arginine polymeric ionic liquids poly[1-（p-vinylbenzyl）-3-methylimidazolium glycinate]（P（[VBMI][Gly]））and poly[1-（p-vinylbenzyl）-3-methylimidazolium arginine]（P（[VBMI][Arg]））were primarily synthesized by two-step method.The structures of products were confirmed by NMR and FT-IR spectra.Field emission electron microscopy observed that the micro-morphology of the polymeric ionic liquids were looser than that of the corresponding monomers,and X-ray diffraction analysis indicated that synthesized products were amorphous.TGA analysis showed that the thermal decomposition temperature of polymeric ionic liquids was higher than that of corresponding monomers,and the thermal decomposition temperature of all products was higher than 150 ℃.The capture performance of the polymeric ionic liquids was better than that of the corresponding monomers,and P（[VBMI][Arg]）had the best capture performance.The maximum CO₂equilibrium adsorption capacity of P（[VBMI][Arg]）was 118 mg CO₂/g PIL at 25 ℃ and 10 m L·min^-1CO₂flow rate.P（[VBMI][Arg]）had good recycling performance,and the CO₂equilibrium adsorption capacity of P（[VBMI][Arg]）only decreased by 10%after six-cycle adsorption-desorption experiments.The pseudo-second order model fitted well with the kinetic data of CO₂adsorption on P（[VBMI][Arg]）.Porous polymeric ionic liquid porous-P（[VBMI][Gly]）was prepared by supercritical foaming method.FT-IR spectra and TG analysis showed that the structure and thermal stability of polymeric ionic liquid kept unchanged after supercritical foaming.The effects of supercritical foaming conditions on the morphology of the porous polymeric ionic liquid were investigated.The results showed that the cell size first increased and then decreased with the increase of the foaming temperature.As the foaming pressure increased,the cell size decreased.As the saturation time increased,the cell size increased.The porous polymeric ionic liquid was used for CO₂adsorption,and it was found that the small pore size was beneficial to improve the CO₂adsorption capacity.The CO₂equilibrium adsorption capacity of porous-P（[VBMI][Gly]）prepared at a foaming temperature of 110 ℃,a foaming pressure of 30 MPa,and a saturation time of 2 h was increased from 104 mg CO₂/g PIL to 165 mg CO₂/g PIL.The pore volume,porosity,average pore diameter and specific surface area of the above-mentioned porous-P（[VBMI][Gly]）can reach3.37 cm³·g^-1,82.89%,3μm,and 24 m²·g^-1,respectively.And its CO₂adsorption capacity decreased by 21%after eight-cycle adsorption-desorption experiments.