Synthesis Of Activated Carbon Immobilized Ionic Liquid And CO₂ Adsorption Properties

The immobilization of ionic liquids into activated carbon support were carried out with impregnation and grafting methods, and the modified particles were characteristics via FTIR, TG, XPS and SEM analysis. The effects regulation of granularity of AC, immobilization method and loading amount of ionic liquids on pore structure, CO2 adsorption capacity and CO2/N2 selectivity were investigated. Furthermore, the PSA properties of CO2 in mixed gas on immobilization of ionic liquid were tested in detail. The main findings are as follows:(1) According to the FTIR spectroscopy and X-ray photoelectron spectroscopy, the immobilization of ionic liquids into activated carbon support were synthesized successfully through impregnation and grafting methods. Thermogravimetric analysis showed that all prepared samples have high thermal stability. The scanning electron micrographs showed that the sample prepared by grafting method presents more developed porous structure.(2) The granularity of AC, immobilization method and loading amount of ionic liquids have significant effects on PSD and CO2 adsorption selectivity of adsorbents. The samples present the developed microporous structure and exhibit a higher pore size distribution(PSD) in the 0.4~0.6 nm range, which results a higher CO2 adsorption capacity. Sample GPH-3 prepared with the ionic liquids concentration of 19.3 % and grafted onto the granular activated carbon surface showes a better CO2 adsorption capacity(10.12 wt%) at 298 K and 0.1 MPa. The introduced IL phase on the activated carbon surface showes an improvement in the CO2/N2 selectivity and the sample IPH-3 exhibites the best selectivity.(3) The breakthrough curves of CO2 in mixed gas were determined on the immobilization of ionic liquids and the optimal pressures of PSA were calculated. The mass transfer process is controlled by gas membrane mass transfer in low mixture flow. With mixture flow increased, the control step gradually turnes to intraparticle diffusion mass transfer. Higher pressure in PSA process could improve the adsorption capacity of the immobilization of ionic liquids under low mixture flow(100 ml/min), and the most appropriate operating pressure is 0.5 MPa under 300 ml/min and 0.4 MPa under 500 ml/min. The activated carbon immobilized ionic liquids which carried with grafting method exhibits the better CO2 sorption/desorption cycle capacity.(4) An established model was used to fit CO2 breakthrough curves. Axial dispersion coefficient(DL) is affected less by the properties of samples and it increases with increasing mixture flow and decreases with increasing pressure. DL of AC-1, GPH-3 and IPH-1 are about the same level. Pore diffusion coefficient(D) is decided jointly by the properties of samples and operating pressure. D of three samples are very close in low flow. D of three samples increase with increasing flow, and D of AC-1 is higher than the GPH-3 and IPH-1. The data of D of sample GPH-3 is higher than IPH-1 under the same conditions. Vapor mass transfer coefficients(k) are mainly determined by external factors and affected less by the properties of samples. They are in the same level of magnitude and increas with mixture flow.