Amine Distribution and Carbon Dioxide Sorption Performance of Amine Coated Silica Aerogel Sorbents: Effect of Synthesis Methods

Tetraethylenepentamine (TEPA) modified silica aerogel CO2 adsorbents were prepared by two methods: evaporative precipitation and wet-impregnation. The distribution of amine on the support and CO2 adsorption performance of these sorbents were studied by nitrogen porosimetry, thermogravimetric analysis, transmission electron microscopy, and CO2 gravimetric adsorption analysis to understand the synthesis-structure-CO2 adsorption property relationships of the silica aerogel supported amine sorbents. The sorbents prepared by evaporative precipitation showed slightly better distributions of TEPA and adsorption performance relative to the wet impregnated analogues. The enhancements observed, however, were unexpectedly small suggesting that the two methods of amine immobilization result in similar TEPA distributions. It appears that the thermodynamic limitation toward lowering the free energy of the system is causing the TEPA to consolidate inside the aerogel network, suggesting that methods of impregnation are of little influence on amine distribution within the pore network of the support.