Transport, Zwitterions, and the Role of Water for CO2 Adsorption in Mesoporous Silica-Supported Amine Sorbents

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• 作者：David S. Mebane ; Joel D. Kress ; Curtis B. Storlie ; Daniel J. Fauth ; McMahan L. Gray ; Kuijun Li
• 刊名：Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：December 19, 2013
• 年：2013
• 卷：117
• 期：50
• 页码：26617-26627
• 全文大小：531K
• 年卷期：v.117,no.50(December 19, 2013)
• ISSN：1932-7455

文摘

The uptake of CO<sub>2sub> in highly loaded, silica-supported, polyethylenimine (PEI)-impregnated sorbents was investigated in a reaction-diffusion model of the CO<sub>2sub> adsorption process. The model successfully replicated the pseudoequilibrium behavior experimentally observed in thermogravimetry (TGA) experiments. A parametric study and sensitivity analysis of the model revealed that the stability and mobility of diffusive intermediates鈥攁ssumed in the model to be zwitterions鈥攅ffectively control the observable capacity of the sorbent. A subsequent quantum chemical study called into question the stability of zwitterions in PEI but suggested that physically bonded moieties involving water, amines, and CO<sub>2sub> may be better candidates for diffusive intermediates. The implications are a strong dependence of the observable CO<sub>2sub> capacity of the sorbent on the presence of water in the gas stream, which was found to be consistent with TGA results.