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Fly ash was converted to a Cancrinite‐type zeolite and then functionalized with various amines to investigate its ability to adsorb CO2. Fly ash was first subjected to thermal‐alkaline treatment followed by hydrothermal treatment to remove unburned carbon and transform it into a cancrinite‐type zeolite before being functionalized with either 3‐aminopropyltriethoxysilane (APTES), diethanolamine (DEA), or monoethanolamine (MEA). The resulting Cancrinite and its functionalized products were characterized by various techniques to confirm the success of fly ash to Cancrinite transformation and functionalization method. Cancrinite has significant improvement in surface area (77.7 m2 g−1) in comparison with original fly ash (11.2 m2 g−1), but its CO2 adsorption is very poor, about 6.6 mg g−1. Amine functionalization caused a reduction in the surface area and porosity of the fly ash Cancrinite, however, it enhanced the CO2 adsorption significantly. While the sorbents impregnated with DEA and MEA had higher CO2 adsorption capacities (49 and 84 mg CO2/g adsorbent respectively) than the sorbent grafted with APTES (24 mg CO2/g adsorbent), the grafted sorbent was more stable over multiple adsorption–desorption cycles. This study demonstrated that fly ash‐derived Cancrinite‐type zeolite has low CO2 adsorption in spite of its high surface area, however, its CO2 adsorption can be improved by amine‐functionalization. © 2018 American Institute of Chemical Engineers Environ Prog, 38: 77–88, 2019 [ABSTRACT FROM AUTHOR]

In this study, amine-bridged silsesquioxane (ABS) and ABS with dangling amino groups were synthesized by a facile method, without using any structure directing agents, and tested for CO2 adsorption. The covalent attachment of dangling aminopropyl groups into ABS improves CO2 adsorption significantly; CO2 loading at 30 °C increases from 83.7 to 129.6 mg g−1 by adding 3-aminopropyltriethoxysilane (APTES) to bis[3-(trimethoxysilyl)propyl]amine (BTMSPA) precursor at a molar ratio of APTES/BTMSPA = 0.5. The properties of CO2 adsorbent can be controlled by the solvent water content and aging conditions. The water content of 25 wt% produces optimal solvent conditions for a resulting adsorbent with the highest surface area (333 m2 g−1), pore volume (0.3 cm3 g−1), and CO2 loading (132 mg g−1 at 30 °C) with an aging time is 48 h in the same solvent at 60 °C. Aging in water has more effect on structural transition than ethanol; adsorbent possesses the highest pore volume (0.85 cm3 g−1) and largest pore size (15.5 nm) when it was aged in water but it has the largest surface area (447 m2 g−1) when it was aged in ethanol. Aging in ethanol results in the best sorbent with the high CO2 loading and stable CO2 adsorption activity. An adsorbent aged for 144 h in ethanol shows excellent CO2 adsorption performance in a packed bed reactor; it was relatively stable after 50 adsorption/desorption cycles with a CO2 loading capacity of 144.6 mg g−1. The success of this research offers a novel route for synthesize of ABS with minimized waste, while maintaining the quality of produced adsorbent. [ABSTRACT FROM AUTHOR]

In this study, we report the effect of the moisture of polyethylenimine (PEI) impregnated mesoporous precipitated silica used for CO2 adsorption on the heat capacity and the heat required to regenerate the adsorbent. The results indicate that the heat capacity of the absorbent increases as its moisture content increases. The increase in moisture results in the rise of the vaporization heat of water and the elevated heat capacity results in higher sensible heat. For these reasons, the total regeneration heat required for CO2 capture process increases significantly. The adsorbent has a maximum CO2 adsorption capacity at 75 °C. CO2 capture process using PEI impregnated mesoporous precipitated silica requires a minimum energy to regenerate the adsorbent; it reduces 46% of the energy compared to a process using an aqueous MEA 30 wt%, as the process operates at 75 °C. [ABSTRACT FROM AUTHOR]