Adsorption of CO2, moisture and ethanol at low partial pressure using aminofunctionalised silica aerogels

Common applications for CO2 adsorption require the removal of CO2 at high partial pressures. Hence, a number of adsorbents have already been optimised for this task. Nonetheless, new fields for CO2 adsorption at low partial pressure are emerging, like the removal of CO2 from atmosphere or enclosed inhabited environments in submarines, space crafts or aircraft. One way to increase the energetic efficiency of the latter application would be to use tailor made adsorbents in the closed loop environmental control systems able to remove all desired species in one adsorption step. First off all these adsorbents should feature a high adsorption capacity at low CO2 partial pressures. Furthermore, the adsorbents should allow regeneration at low temperatures, have the ability to work in moist conditions and adsorb small amounts of VOCs like ethanol. In this work, the ability of silica aerogels functionalised with a mono- and a tri-aminosilane to fulfil the desired requirements was investigated. Both adsorption of pure components and adsorption from gas mixtures were used to characterise the adsorbents. The aerogels showed a high CO2 adsorption capacity at low partial pressure (250 Pa) despite a decreasing specific surface area due to functionalisation. In presence of humidity an increase in the CO2 adsorption capacity takes place. Both types of amino-functionalised aerogels are able to adsorb water, ethanol and CO2 simultaneously. The aerogels could be regenerated in an air flow at 70 degrees C and a mild vacuum (25,000 Pa) with negligible losses in adsorption capacity. Thus, functionalised silica aerogel possesses properties for an application as adsorbents in a closed loop environmental control system. (c) 2013 Elsevier B.V. All rights reserved.