Study On CO₂ Capture Used Supported Amino Acid Ionic Liquids

CO₂ is the main component of greenhouse gases. Therefore, the development of the green, efficient and economical CO₂ capture technology is of great significance to alleviate the problem of global warming. Amino acid ionic liquids（AAILs） are potential green substitutes for CO₂ capture because of their negligible vapor pressures, tunable physicochemical properties, biodegradable characteristics and superior dissolved ability. But the relatively high viscous of AAILs result in low sorption and desorption rates greatly hinder their further development in CO₂ capture applications. However, immobilization of AAILs into porous supports can solve this problem.In this paper, Two amino acid ionic liquids（AAILs）, viz., tetramethyl ammonium glycinate（[N1111][Gly]） and tetramethyl ammonium lysine（[N1111][Lys]） were supported on porous silica gel, activated carbon through the impregnation evaporation method and used as the adsorbents for carbon dioxide. For these Supported sorbents, their structures and properties were characterized and their CO₂ capture performances were studied. ASPEN ADSIM software was used to simulate the adsorption process.The results indicated that:1) AAILs were successfully immobilized into porous silica gel and activated carbon with various weight ratios. AAILs were well distributed onto/into the surface/interior of the porous support. The supported sorbents retained high specific surface area and porosity, and exhibited good thermal stability.2) AAILs/SG avoided the disadvantage of high viscosity and exhibited rapid sorption desorption rates and excellent sorption capacity. As to AAILs/SG, 303.15 K to 323.15 K of temperature, adsorption capacity reduced with increasing temperature. 5% to 60% of ionic liquids loading, the CO₂ capture behaviors depended on the AAILs weight ratios in the sorbents, whereas there was a optimal loading of ionic liquids to get highest adoption capacity towards CO₂. Pressures up to 0.1 MPa,adsorption capacity increased with increasing pressures. The adsorption performance of [N1111][Gly]/SG was superior to [N1111][Lys]/SG. Then exposed to CO₂ at 0.1 MPa and T=303.15 K, the sorbents with [N1111][Gly] loading of 22.4 wt % achieved the highest CO₂ capture capacity, i.e. 41 mg CO₂/g sorbent, equivalent to 0.62 mol CO₂/mol AAIL; moreover, 90% of the equilibrium adsorption amount can be achieved in 20 min.3) [N1111][Gly]/SG was regenerated at 353.15 K under N2 atmosphere, the sorbents retained the advantageous properties and exhibited good recyclability after recycling six times. The adsorption of CO₂ by [N1111][Gly]/SG belonged to Chemical adsorption. The pseudo-second order model matched the CO₂ adsorption kinetics.4) One-bed Breakthrough and two-bed adsorption separation process were simulated with ASPEN ADSIM. [N1111][Gly]/SG had a good CO₂/N2 separation performance, which provided basic design parameters for the Industrial design for CO₂ capture.This work provided experimental and theoretical basis for developing environment friendly, efficient and economical CO₂ capture technology.