Enhanced Tolerance to Flue Gas Contaminants on Carbon Dioxide Capture Using Amine-Functionalized Multiwalled Carbon Nanotubes

Abstract

The adsorption behavior of adsorbents for carbon dioxide can be significantly affected by flue gas contaminants. In this work, we examined the performance of tetraethylenepentamine (TEPA) impregnated industrial grade multiwalled carbon nanotubes (IG-MWCNTs) in trace amounts of flue gas contaminants such as H2O, NO, and SO2. It was observed that H2O and NO had a minimal impact on CO2 adsorption capacity, while the effect of SO2 on CO2 adsorption was influenced by adsorption temperature and SO2 concentration. Compared with silica-based adsorbents, i.e., TEPA-impregnated MCM-41, amine-functionalized IG-MWCNTs show significantly better tolerance to H2O and SO2. In addition, we examined the variation of CO2 adsorption with and without SO2 with various experimental methods (N2 adsorption/desorption isotherms, X-ray diffraction, and differential scanning calorimetry analysis) and molecular simulation. Experimental results show that irreversible sulfate/sulphite species deposited into the adsorbent contributes to the decrease on CO2 adsorption, while the results from simulation studies reveal that the enthalpy difference between the isolated TEPA with SO2 and TEPA···SO2 (ΔH(TEPA···SO2)) is larger than that of CO2 (ΔH(TEPA···CO2)), indicating that SO2 has a stronger reaction activity with TEPA than CO2. The increase of the ratio of ΔH(TEPA···SO2)/ΔH(TEPA···CO2) with increasing temperature illustrates that the difference of CO2 adsorption capacity with and without SO2 increases with elevated temperatures.