Utilization of rice husk ash as silica source for the synthesis of mesoporous silicas and their application to CO2 adsorption through TREN/TEPA grafting

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. CO2 adsorption of branched amine TREN and straight chain amine TEPA at 25, 50 and 75 degrees C was obtained by Thermogravimetric Analyser (TGA) at atmospheric pressure. TREN grafted mesoporous silica showed 7% of CO2 adsorption while TEPA grafted mesoporous silicas showed less CO2 adsorption. which is due to the presence of isolated amine groups in TREN. TREN grafted mesoporous silicas were also observed to be selective towards CO2, thermally stable and recyclable. The order Of CO2 adsorption with respect to amount of amine grafting was observed to be MCM-48/TREN > MCM-41/TREN > SBA-15/TREN. (C) 2009 Elsevier B.V. All rights reserved.