Preparation and CO2 Sorption/Desorption of N-(3-Aminopropyl)Aminoethyl Tributylphosphonium Amino Acid Salt Ionic Liquids Supported into Porous Silica Particles

Abstract

To search for robust CO2 capture materials, several N-(3-aminopropyl)aminoethyl tributylphosphonium amino acid salts ([apaeP444][AA])-type task specific ionic liquids (TSILs) were synthesized and immobilized into porous silica support through a facile impregnation–vaporization method. The ILs and thus prepared sorbents, Sorb-AA, were well characterized, and their CO2 sorption and desorption behaviors under temperature- and vacuum-swing conditions were investigated. The ILs can be immobilized facilely into silica up to 1/1 IL/SiO2 weight ratio. After IL loading, the sorbents retain reasonably high specific surface area and porosity and therefore exhibit rapid sorption and desorption rates as well as excellent sorption capacity and selectivity and can be used repeatedly. Among them, Sorb-Lys has the highest CO2 sorption capacity. It can capture 1.54 mmol or 67.9 mg CO2 per gram sorbent from a simulated flue gas containing 14% CO2 in each cycle of sorption and desorption. Sorb-Gly has slightly less CO2 sorption capacity, 1.37 mmol or 60.4 mg CO2 per gram sorbent from the simulated flue gas, and much better long-term durability. It is estimated that it can retain 90% sorption capacity even after 1.38 × 103 cycles. These robust sorbents, especially Sorb-Gly, exhibit excellent potential in CO2 capture applications.