Impregnation of Amines Onto Porous Precipitated Silica for CO2 capture

AbstractIn this study, porous precipitated silica (PPS) was synthesized using sodium silicate as an inexpensive silica precursor and then impregnated with various amines such as 2-aminomethylpropanol (AMP), monoethanolamine (MEA), diethanolamine (DEA) and polyethyleneimine (PEI) to produce amine-impregnated solid adsorbents, which will be evaluated as a sorbent for CO2 capture. Major parameters and performances of adsorbents including thermal stability, adsorption capacity, heat capacity, and adsorption heat were investigated. The results indicated that MEA impregnated PPS (60 wt%) has the highest CO2 adsorption capacity; up to 233mg/g, while the adsorption capacity of PEI impregnated PPS (60 wt%) is 136mg/g. The heat capacity of PEI impregnated PPS (50 wt%) is relatively low (1.68J/gC) compared to that of aqueous MEA 30 wt% (3.98J/go·C). Obtained results were used to calculate the energy requirement for adsorbent regeneration. The calculated results revealed that PEI impregnated PPS (50 wt%) requires the least energy for regeneration, only 2080kJ/kg of CO2 and it is 44.7% lower than energy requirement for aqueous MEA 30 wt%. Thermal stability of the adsorbents was confirmed by thermal gravity analyses, which showed that AMP and MEA start vaporizing at very low temperature and complete at 110 and 120 oC, DEA vaporizes at temperature from 100200oC, and PEI vaporizes and decomposes at about 250400 oC. The study on adsorption/desorption performance at the regeneration temperature of 90 oC indicated that the stability of the sorbent is greatly varied with the vaporization temperature. PEI impregnated PPS shows a no significant loss in CO2 adsorption capacity, while DEA impregnated PPS lost 12% of adsorption capacity after 10 cycles