CO2 capture at low temperature by nanoporous silica modified with amine groups

Abstract

MCM-41 and SBA-15 were chosen as nanoporous materials based on silica for its modification with aminegroups. This modification was done by two methods: grafting method and wet impregnation method. The firstmethod grafted-amine groups by chemical reaction between surface silanol groups in the nanoporousmaterials and 3-aminopropyltrimetoxilane (APTMS).In the wet impregnation method, low molecular weightpolyethylenimine (PEI) is incorporated trough this method. These modified materials capture CO2 at lowtemperature. CO2 capture on the sorption sites by amine loading is believed to occur via chemisorptionmechanism by formation of ammonium carbamate. The evaluation and analysis of CO2 adsorption was carriedout by two methods: static mode and dynamic mode. The static mode is a pure CO2 adsorption-desorptionisotherms at 298K. The isotherms of the functionalized materials show a behavior by chemisorption, captureat low pressure, being the desorption branch almost horizontal, while nanoporous silica isotherms is due aphysical adsorption, low CO2 capture at low pressure and dependence with pressure, a complete reversibilityof the desorption process. The dynamic mode is a thermogravimetry study at different N2/CO2 concentrations.Isothermal CO2 captures at 298K were carried out to evaluate the suitability of the samples for cyclicoperation. The mass increase during the capture step was interpreted as CO2 adsorption capacity of thesamples. The results obtained by both methods were compared, and, its differences were analyzed.