Role of the type of grafting solvent and its removal process on APTES functionalization onto SBA-15 silica for CO2 adsorption

In this work, silica-based CO2 adsorbents were successfully prepared by the sol-gel method. These materials were chemically modified with 3-aminopropyltriethoxysilane (APTES) using the grafting technique. Two synthesis parameters were investigated in this study, namely the solvent used in the grafting step (toluene against ethanol) and the process employed for removing the solvent (filtration against evaporation). The influence of these parameters on pore structure, surface chemistry and CO2 capture performance were evaluated and discussed on the basis of a series of experimental tests, including FTIR, TG-MS, nitrogen adsorption tests, XRD, TEM and CO2 adsorption. The use of ethanol led to samples with a NH2 concentration of about 1.20 +/- 0.05 mmol g(-1). On the other hand, samples obtained using toluene showed amine concentrations two times higher than the specimens prepared with ethanol. Samples obtained by evaporation exhibited blocked pores and a low CO2 adsorption capacity when compared to those obtained by filtration. The sample prepared using toluene as the solvent and a filtration step displayed a CO2 adsorption capacity as high as 6.3 wt% at 30 degrees C and 1 bar.