Evaluation of the Impact of H2O, O2, and SO2 on Postcombustion CO2 Capture in Metal鈥揙rganic Frameworks

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• 作者：Jiamei Yu ; Yuguang Ma ; Perla B. Balbuena
• 刊名：Langmuir
• 出版年：2012
• 出版时间：May 29, 2012
• 年：2012
• 卷：28
• 期：21
• 页码：8064-8071
• 全文大小：482K
• 年卷期：v.28,no.21(May 29, 2012)
• ISSN：1520-5827

文摘

Molecular modeling methods are used to estimate the influence of impurity species: water, O₂, and SO₂ in flue gas mixtures present in postcombustion CO₂ capture using a metal organic framework, HKUST-1, as a model sorbent material. Coordinated and uncoordinated water effects on CO₂ capture are analyzed. Increase of CO₂ adsorption is observed for both cases, which can be attributed to the enhanced binding energy between CO₂ and HKUST-1 due to the introduction of a small amount of water. Density functional theory calculations indicate that the binding energy between CO₂ and HKUST-1 with coordinated water is 1 kcal/mol higher than that without coordinated water. It is found that the improvement of CO₂/N₂ selectivity induced by coordinated water may mainly be attributed to the increased CO₂ adsorption on the hydrated HKUST-1. On the other hand, the enhanced selectivity induced by uncoordinated water in the flue gas mixture can be explained on the basis of the competition of adsorption sites between water and CO₂ (N₂). At low pressures, a significant CO₂/N₂ selectivity increase is due to the increase of CO₂ adsorption and decrease of N₂ adsorption as a consequence of competition of adsorption sites between water and N₂. However, with more water molecules adsorbed at higher pressures, the competition between water and CO₂ leads to the decrease of CO₂ adsorption capacity. Therefore, high pressure operation should be avoided in HKUST-1 sorbents for CO₂ capture. In addition, the effects of O₂ and SO₂ on CO₂ capture in HKUST-1 are investigated: The CO₂/N₂ selectivity does not change much even with relatively high concentrations of O₂ in the flue gas (up to 8%). A slightly lower CO₂/N₂ selectivity of a CO₂/N₂/H₂O/SO₂ mixture is observed compared with that in a CO₂/N₂/H₂O mixture, especially at high pressures, due to the strong SO₂ binding with HKUST-1.