Synthesis of chloropropylamine grafted mesoporous MCM-41, MCM-48 and SBA-15 from rice husk ash: their application to CO2 chemisorption

Abstract

Mesoporous siliceous MCM-41, MCM-48 and SBA-15 were synthesized using Rice Husk Ash (RHA) as the silica source. Their defective –OH sites were then grafted with 3-chloropropyl amine hydrochloride (3-CPA) and characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and BET techniques. Those results portrayed their resemblance with that synthesized from conventional silica sources. 3-CPA grafted mesoporous silicas were tested for CO2 chemisorption over fixed bed reactor at different temperatures. The maximum adsorption of 1.7 mmol/g of CO2 was observed on 3-CPA grafted SBA-15 (SBA-15/CPA) at 25°C. The chemisorbed CO2 on amine grafted mesoporous silica was stabilized by weak hydrogen bonds formed during the nucleophilic attack between lone pair of electrons in amine groups and quadrupolar CO2 with more degree of positive charge to form carbamates. The rapid steep slope which arises due to CO2 adsorption illustrated a minimal mass transfer effect and extreme fast kinetics. Performance tests such as reproducibility, stability and selectivity towards CO2 adsorption were also carried out over 3-CPA grafted mesoporous silica and the results were in line with that of well established CO2 sorbent.