Abstract
Non-thermodynamical CO2 adsorption behavior for amine-modified nanoporous silica is clarified by evaluating the mobility of organic functional group inside mesopores by using pulsed NMR technique. CO2 adsorption behavior of nanoporous silica modified with amino-propyl silane (AP) changes significantly depending on the amount of AP loaded. A low AP loaded sample shows normal adsorption behavior; the amount of CO2 adsorbed decreases with increasing temperature. In contrast, a high AP loaded sample possesses non-thermodynamic CO2 adsorption behavior in which the amount of CO2 adsorbed increases with increasing temperature in within a certain temperature range. To address the mechanism, a pulsed NMR technique was employed to clarify the mobility of AP molecules, and it was found that the mobility of mobile components in a high AP loaded sample increased drastically with increasing temperature while the mobility in a low AP loaded sample remained unchanged. It is understood that the enhancement of the diffusion of CO2 inside nanopores leads to the non-thermodynamic adsorption behavior.
Highlights
Global warming caused by the increase of the amount of CO2 emission is a serious problem to be solved immediately
CO2 adsorption behavior of nanoporous silica modified with amino-propyl silane (AP) changes significantly depending on the amount of AP loaded
A pulsed NMR technique was employed to clarify the mobility of AP molecules, and it was found that the mobility of mobile components in a high AP loaded sample increased drastically with increasing temperature while the mobility in a low AP loaded sample remained unchanged
Summary
Global warming caused by the increase of the amount of CO2 emission is a serious problem to be solved immediately. If the selectivity for water vapor is higher than that for CO2, it is required to remove water vapor from the emission This process consumes a lot of energy, and developing the adsorbent with higher CO2 selectivity is crucial. Opposite CO2 adsorption behavior was observed for polyethyleneimine-impregnated materials [26] and amino-modified porous silicas [27] [28]. A porous material with this non-thermodynamic adsorption behavior is expected to be a high CO2 selection adsorbent for the emission gases of factories. The amount of CO2 adsorbed decreases with increasing temperature for a low AP loaded material To understand this behavior difference, a pulsed NMR technique is adopted to clarify the mobility of AP molecules in AP loaded nanoporous silicas at different temperature. A distinct difference is observed in the mobility
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