CO2 adsorption by amine modified siliceous mesostructured cellular foam (MCF) in humidified gas

• Water addition increased the working capacity, at 105 °C, by 2–17% of its value.
• In wet CO2, PEI modified MCF’s sorption capacity remained stable over 10 cycles.
• Water fed with the CO2 reduced urea formation and stabilised the adsorbent.

A set of branched and linear polyethyleneimine (PEI) modified mesocellular siliceous foams (MCF) were evaluated as adsorbents for CO2 capture at modestly elevated temperatures under conditions that simulate the vacuum swing adsorption (VSA) process in humidified gas. Increasing the temperature was found to be beneficial for achieving reversible CO2 adsorption/desorption with reasonable capacities and rates. Under humid conditions, the materials lost 0–15% of their adsorption capacities in 0.5 atm CO2 compared to under dry conditions at 105–115 °C. The working capacity (0.025–0.15 atm CO2) at 105 °C was 2–17% higher under humid than under dry conditions. During cycling, the branched PEI adsorbent showed a gradual decrease in CO2 adsorption–desorption capacity under dry conditions, but the reduction in capacity was significantly reduced under wet conditions. The reduction in CO2 adsorption capacity was attributed to by-product formation, confirmed by IR, 13C CP-MAS NMR and EDS. In a humid environment, the formation of by-product was significantly reduced.

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