Polyethylenimine-impregnated siliceous mesocellular foam particles as high capacity CO2 adsorbents

Abstract

Siliceous mesostructured cellular foams (MCF) impregnated with polyethylenimine (PEI) of various molecular weights and structures were evaluated as CO 2 adsorbents. The MCF solid support consisted of a well-defined interconnected three-dimensional mesoporous structure with large cell diameter of 30.3 nm and large window diameter of 11.3 nm, filled with polyethylenimine up to 70 weight percent or about 22.3% nitrogen atom by weight of the adsorbents. While other mesoporous solid supports lost their porosity after PEI impregnation, our MCF solid support maintained its pore volume over the range of 1.12 to 1.64 cm 3 g 21 . The importance of the porosity of PEI-impregnated MCF adsorbents for high capacity CO 2 adsorbents was demonstrated. The highest CO 2 sorption capacity (180.6 mg-CO 2 /g-adsorbent or 393.6 mg-CO 2 /g-PEI at 75 uC) was obtained for silica supports loaded with 50 weight percent branched PEI with average molecular weight of 600 g mol 21 . Under dry atmospheric CO 2 gas, this adsorbent reached the theoretical CO 2 capacity of 0.50 mole-CO 2 per mole-nitrogen within less than about 8 min, making this adsorbent one of the most effective CO 2 adsorbents reported. Repeated multiple sorption cycles demonstrated good stability of this adsorbent for CO 2 capture. The initial sorption kinetics determined the overall CO 2 sorption capacity, which was limited by the formation of a carbamate layer as a result of the CO 2 -PEI complexation that due to inhibition of CO 2 diffusion; the kinetics of ''ionic'' gelation of the impregnated PEI by CO 2 controlled the overall performance of the CO 2 adsorbents. At 75 uC, the operating temperature favored the molecular mobility of PEI and unrestricted diffusion of CO 2 to allow the theoretical CO 2 capacity of the PEI to be attained. Lower temperatures limited the mobilities of PEI and CO 2 and the kinetics of ''ionic'' gel formation dominated, causing a lowered overall performance of the CO 2 adsorbents. Overall, this study points to the importance of interconnected porous channel networks to optimize the performance of PEI-impregnated mesoporous silica particles.

Carbon dioxide adsorption by zinc-functionalized ionic liquid impregnated into bio-templated mesoporous silica beads

“…The increase in k 2 despite the reduction in SSA and V p points out to the effect of the nature of interaction to be an additional factor that describes the kinetics in this intermediate step. The chemisorptive nature of the uptake by EZT3 compensated for the negative effect of impregnation on the textural properties resulting in an increase in the overall capacity of the sorbent, which is similarly observed in amine-impregnated porous silica supports[21,58,66,[68][69][70]. The rate constant at the extended region (k 3 ) is comparable with bulk EZT3 suggesting saturation of sorption sites.…”

Amine-modified ordered mesoporous silica: The effect of pore size on CO2 capture performance

“…[1,12,16] This type of Page 5 of 28 A c c e p t e d M a n u s c r i p t sorbents was named as "molecular basket" solid amine sorbent, which usually shows high selectivity and regenerability during CO 2 capture separation processes. Birbara et al [17,18] [25][26][27][28][29] and hexagonal mesoporous silica (HMS) [30,31] have been used as amines supports to improve CO 2 capture performance. It is increasingly realized that the structures of the supports, such as pore volume, [5,26] pore size, [19,29] and pore interconnection [32], can significantly influence the CO 2 capture performances of these sorbents.…”

Amine Functionalization of Microsized and Nanosized Mesoporous Carbons for Carbon Dioxide Capture

“…[13][14][19][20] We thus selected the impregnation method for amino-functionalization of mesoporous carbons in the present work. Ethylenediamine was selected for the chemical grafting via an amide route (-CONH-CH 2 NH 2 ) because (a) it is a well-established animo-functionalization method for carbon materials such as carbon nanotubes 21 and (b) ethylenediamine, similar to PEI, can provide a high content of amino groups that are active CO 2 -adsorption sites.…”