Abstract
We used a grand canonical Monte Carlo simulation to study the influence of impurities including water vapor, SO2, and O2 in the flue gas on the adsorption of CO2/N2 mixture in carbon nanotubes (CNTs) and carboxyl doped CNT arrays. In the presence of single impure gas, SO2 yielded the most inhibitions on CO2 adsorption, while the influence of water only occurred at low pressure limit (0.1 bar), where a one-dimensional chain of hydrogen-bonded molecules was formed. Further, O2 was found to hardly affect the adsorption and separation of CO2. With three impurities in flue gas, SO2 still played a major role to suppress the adsorption of CO2 by reducing the adsorption amount significantly. This was mainly because SO2 had a stronger interaction with carbon walls in comparison with CO2. The presence of three impurities in flue gas enhanced the adsorption complexity due to the interactions between different species. Modified by hydrophilic carboxyl groups, a large amount of H2O occupied the adsorption space outside the tube in the carbon nanotube arrays, and SO2 produced competitive adsorption for CO2 in the tube. Both of the two effects inhibited the adsorption of CO2, but improved the selectivity of CO2/N2, and the competition between the two determined the adsorption distribution of CO2 inside and outside the tube. In addition, it was found that (7, 7) CNT always maintained the best CO2/N2 adsorption and separation performance in the presence of impurity gas, for both the cases of single CNT and CNT array.
Highlights
Carbon capture and storage (CCS) [1] technologies have been extensively developed to minimized the influence of CO2 emission on the global warming effect
carbon nanotubes (CNTs), the results show that the ad-s2orption(6,c6a) pCNaTcity o(bf)various adsorbents is reduced, in comparison with of defect groups the (or simulation the lac-k2of res-u4l(t6s, f6o)rCu(N1nT0,m10o)dCiNfiTed carbon ato(m12,s1)2w) C(hNbiT)ch
A grand canonical Monte Carlo simulation is used to investigate the influence of impurity gases, including water, SO2, and O2, on the adsorption of CO2 in singe CNTs and functionalized CNT bundles
Summary
Carbon capture and storage (CCS) [1] technologies have been extensively developed to minimized the influence of CO2 emission on the global warming effect. To explore the influence of impurity gases on the adsorption and separation of CO2 from flue gas in a practical manner, the adsorption of gas mixtures (CO2/N2/X, X denotes the impurity gases, H2O, SO2, and O2) in the functionalized CNT bundles are required. Little is known about how the cooperative effects between adsorbate-CNT interaction and interaction between impurity and adsorbate affect CO2/N2 selectivity Discussions related to these and other related issues will be obtained in detail in this work. GCMC and density functional theory (DFT) simulations were conducted to investigate the adsorption separation of CO2 from flue gases using carbon nanotubes in the presence of impurity species (H2O, O2 and SO2), in order to fundamentally reveal the impacts of impurity gases on the adsorption behaviors and separation performance of CO2. The optimized ssttrruuccttuurree ooff CCNNTT uunniittcceelllwwiitthhddeeffeeccttss,,aannddtthheeccoonnssttrruucctteedd22×× 2 CNT array (b)
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