CO₂ adsorption performance for amine grafted particulate silica aerogels

A series of amine grafted CO₂ sorbents were prepared by functionalizing mono, di, and tri-amine substituted trialkoxysilanes on a particulate silica aerogel manufactured by Cabot Corp. The CO₂ adsorption performance, textural properties, and the nitrogen content of the functionalized aerogels were investigated using CO₂ gravimetric adsorption analysis, nitrogen porosimetry, and CHN elemental analysis. The synthesis variables involved in the grafting procedure were studied independently toward obtaining a high performing CO₂ capture sorbent. Of the mono, di, and tri-amine silanes, the tri-amine grafted aerogel obtained the highest adsorption capacity and was further investigated to determine the effects of synthesis conditions on adsorption performance. For anhydrous (dry) grafting the optimum conditions for the silica aerogel was 95°C and a 2:1 silane:silica ratio that resulted in an adsorption capacity of 1.76mmol/g. For hydrous (wet) grafting the optimum temperature was 95°C and a water addition of 300mg H₂O/g of silica where the sorbent achieved a capacity of 2.61mmol/g. The same sorbent also showed excellent cyclic stability maintaining a working capacity of 2.30mmol/g for 100 cycles.