Utilization of rice husk ash as silica source for the synthesis of mesoporous silicas and their application to CO_2 adsorption through TREN/TEPA grafting

摘要

Mesoporous MCM-41, MCM-48 and SBA-15 were synthesized using Rice husk ash (RHA) as the silica source and their defective Si-OH sites were functionalized by 3-cholropropyltrimethoxysilane (CPTMS) which was subsequently grafted with amine compounds, Tris(2-aminoethyl)amine (TREN) and Tetraethylenepentamine (TEPA). X-ray powder diffraction (XRD) and BET results of the parent mesoporous silica suggested their closeness of structural properties to those obtained from conventional silica sources. CO_2 adsorption of branched amine TREN and straight chain amine TEPA at 25,50 and 75 ℃ was obtained by Thermogravimetric Analyser (TGA) at atmospheric pressure.TREN grafted mesoporous silica showed 7% of CO_2 adsorption while TEPA grafted mesoporous silicas showed less CO_2 adsorption, which is due to the presence of isolated amine groups in TREN. TREN grafted mesoporous silicas were also observed to be selective towards CO_2. thermally stable and recyclable. The order of CO_2 adsorption with respect to amount of amine grafting was observed to be MCM-48/TREN > MCM-41 /TREN > SBA-15/TREN.