Synthesis and modification of micro and mesoporous materials as CO2 adsorbent

Abstract

Carbon dioxide (CO2) removal from natural gas attracts more attention than other impurities due to its corrosiveness and inert property. Amine based chemical absorption has been used commercially for CO2 separation. However, the liquid amine based processes pose operating difficulties due to high regeneration energy, large equipment size, solvent leakage and corrosion problem. Therefore, recent studies have introduced a promising approach which is the incorporation of organic amines into porous supports for CO2 adsorption. This research studies the modification of porous materials by grafting amine functional groups directly to the surface of a solid sorbents. Amines (MEA, DEA, TEA, MDEA, and PEI) have been chosen as modification agents for mesoporous supports (MCM-41 and SBA-15) and microporous supports (zeolites NaY and 13X). The structures of the modified adsorbents were characterized by powder X-Ray Diffraction (XRD), nitrogen adsorption at 77K and Fourier Transform Infrared (FTIR) spectroscopy. Gas adsorption measurements were carried out using Thermal Gravimetric Analyzer (TGA). Investigation on the physicochemical properties and gas CO2 adsorption characteristics of the amines modified adsorbents were thoroughly studied. Results revealed that types of amines and supports, amine loading concentration, metals loading, adsorption and heating temperatures significantly affect both structural and gas adsorption characteristics of the amine modified adsorbents. MEA modified MCM-41 shows the highest CO2 adsorption capacity (40.91 mg/g sorbent) which is 2.2 times higher than MCM-41 support itself (18.58 mg/g sorbent). Although zeolites NaY and 13X show high adsorption but after modification, the adsorption capacity was reduced by 50 %. Cu modified MCM-41 also shows moderate adsorption (25.11 mg/g sorbent) but not much increment can be observed after grafting of MEA. As of operating temperatures of the adsorption process, the adsorption temperature at 25°C and heating temperature at 100°C show the highest adsorption capacity. Furthermore, adsorption bands observed in FTIR spectra demonstrated that the CO2 interact strongly with the amine modified adsorbents.