CO₂ adsorption properties and thermal stability of different amine-impregnated MCM-41 materials

The adsorption properties of CO₂ on MCM-41 mesoporous materials impregnated with ethylenediamine (EDA), tetraethylenepentamine (TEPA) and two kinds of polyethylenimines (PEI600 and PEI1800), respectively, were studied with mass spectrometry (MS) and thermogravimetry (TG) techniques. The sample obtained by impregnating EDA (EDA-MCM-41) showed a low CO₂ adsorption capacity due to the ready volatilization of EDA, while those samples prepared by TEPA (TEPA-MCM-41), PEI600 (PEI600-MCM-41) or PEI1800 (PEI1800-MCM-41) exbibit higher adsorption capacity and thermal stability although the adsorption capacity decreased with increasing molecular weight of amines. A maximum CO₂ adsorption capacity of 2.7 mmol/g was achieved on the TEPA-MCM-41 with 40% TEPA. When this sample was regenerated at 100 ℃ under pure nitrogen atmosphere, its CO₂ adsorption capacity was decreased by 7.4% after ten recycles in contrast to less than 1% for both PEI600-MCM-41 and PEI1800-MCM-41. However, when the regeneration atmosphere was changed to 80% CO₂/20% N₂, the regeneration temperature should be be increased to more than 160 ℃ for all the samples despite that PEI-MCM-41 showed high thermal stability than TEPA-MCM-41.