Abstract
A wide variety of solid sorbents has recently been synthesized for application in CO2 adsorption. Among them, mesoporous silicas deserve attention because of their ability to accommodate large concentrations of different chemicals as a consequence of their surface chemistry and tunable pore structure. Functionalized materials exhibit promising features for CO2 adsorption at high temperatures and low CO2 concentrations. This work aimed to assess the influence of the textural properties on the performance of CO2 adsorption on functionalized mesoporous silica. With this goal, several mesoporous silica foams were synthesized by varying the aging temperature, obtaining materials with larger pore diameter. Thus, the synthesized materials were functionalized by grafting or impregnation with 3-aminopropyltriethoxysilane, polyethylenimine, and tetraethylenepentamine as amine sources. Finally, the amino functionalized materials were assessed for CO2 capture by means of equilibrium adsorption isotherms at 25, 45, and 65°C. Among the most outstanding results, high aging temperatures favor the performance of impregnated materials by exposing greater pore diameters. Low or intermediate temperatures favor grafting by preserving an appropriate density of silanol groups.
Highlights
In the last centuries, the increase in world population along with the industrial developments have caused an exponential increase in energy consumption, mainly from the use of fossil fuels as oil and coal
APTES-grafting of these structures enhances CO2 adsorption, even though the amount of loaded amino groups is restricted by the low density of silanols on the surface
Despite the chemical interaction brought about by grafted primary amines from APTES, physisorption has a leading role over chemisorption in these mesocellular foams (MCFs) and increasing temperature has an adverse effect on CO2 uptakes
Summary
The increase in world population along with the industrial developments have caused an exponential increase in energy consumption, mainly from the use of fossil fuels as oil and coal. As MCFs have a very wide pore diameter, this pore filling is less pronounced than in other porous materials with a smaller pore size (Cecilia et al, 2018, 2020) in which case the amine-rich polymer stacks on the surface of the silica blocking the porous structure and decreasing the access to chemisorption sites This is probably due to the regeneration conditions (110◦C and 10−4 mbar), which can remove a small proportion of N-species that are not sufficiently bound to the support by electrostatic interactions
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