Enhancement of CO2 Adsorption/Desorption Properties of Solid Sorbents Using Tetraethylenepentamine/Diethanolamine Blends

Mesocellular silica foam was impregnated with tetraethylenepentamine (TEPA), diethanolamine (DEA), and their mixtures and examined as sorbents for CO2 capture. The sorbents were characterized by N-2 physisorption, elemental analysis, and Fourier transform infrared spectroscopy. The effects of amine blending on the CO2 uptake, working capacity, and heat of adsorption were investigated and discussed. The experimental results showed that the heat of adsorption decreased with increasing DEA-to-TEPA ratios, but the CO2 uptake improved by the blending of TEPA and DEA. Furthermore, the DEA/TEPA blend considerably improved the regeneration properties of the sorbents. Mesocellular silica foam loaded with a mixture of 40 wt % TEPA and 30 wt % DEA exhibited a CO2 adsorption uptake of 5.91 mmol/g at 50 degrees C and 100 kPa with a heat of adsorption of 80 kJ/mol. Additionally, these sorbents demonstrated high cyclic stability and high selectivity toward CO2/N-2 separation. In situ infrared spectroscopy investigations revealed that CO2 adsorption occurred predominantly through the formation of carbamate species for both TEPA and DEA.