Competitive adsorption of a binary CO2-CH4 mixture in nanoporous carbons: effects of edge-functionalization.
Competitive adsorption of a binary CO2-CH4 mixture in nanoporous carbons: effects of edge-functionalization.
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DOI：
10.1039/c4nr05128a
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发表时间：
2015-01
期刊：
影响因子：
6.7
通讯作者：
Xiaoqing Lu;Dongliang Jin;Shuxian Wei;Mingmin Zhang;Qing Zhu;Xiaofan Shi;Zhigang Deng;Wenyue Guo;W. Shen
中科院分区：
文献类型：
--
作者：
Xiaoqing Lu;Dongliang Jin;Shuxian Wei;Mingmin Zhang;Qing Zhu;Xiaofan Shi;Zhigang Deng;Wenyue Guo;W. Shen
采用密度泛函理论(DFT)和巨正则蒙特卡罗(GCMC)模拟相结合的方法，首次研究了边功能化对CO_2-CH_4二元混合物在纳米多孔炭中竞争吸附的影响。结果表明，在低压下，边功能化对CO2的单组分吸附比CH4有更大的促进作用，从而显著提高了CO2对CH4的选择性，其顺序为NH2-NPC>；COOH-NPC>；OH-NPC>；H-NPC>；NPC。吸附增强主要源于(1)具有大孔径和有效可接近表面积的有利环境，(2)高电负性/电正性，(3)强吸附能，和(4)由于嵌入的边功能化基团的诱导/直接相互作用而产生的大的静电贡献。这些影响的差异越大，二氧化碳在CO2-CH4二元混合物中的竞争吸附优势就越大。温度对气体吸附有负面影响，但对静电对选择性的贡献影响不明显。随着压力的增加，CO2对CH4的选择性先急剧下降，然后趋于平缓。这项工作突出了边功能化的NPC在竞争吸附、捕获和分离二元CO2-CH4混合物方面的潜力，并为设计和筛选用于碳捕获和储存的吸附材料提供了一种有效和优越的替代策略。
The effect of edge-functionalization on the competitive adsorption of a binary CO2-CH4 mixture in nanoporous carbons (NPCs) has been investigated for the first time by combining density functional theory (DFT) and grand canonical Monte Carlo (GCMC) simulation. Our results show that edge-functionalization has a more positive effect on the single-component adsorption of CO2 than CH4, therefore significantly enhancing the selectivity of CO2 over CH4, in the order of NH2-NPC > COOH-NPC > OH-NPC > H-NPC > NPC at low pressure. The enhanced adsorption originates essentially from the effects of (1) the conducive environment with a large pore size and an effective accessible surface area, (2) the high electronegativity/electropositivity, (3) the strong adsorption energy, and (4) the large electrostatic contribution, due to the inductive effect/direct interaction of the embedded edge-functionalized groups. The larger difference from these effects results in the higher competitive adsorption advantage of CO2 in the binary CO2-CH4 mixture. Temperature has a negative effect on the gas adsorption, but no obvious influence on the electrostatic contribution on selectivity. With the increase of pressure, the selectivity of CO2 over CH4 first decreases sharply and subsequently flattens out to a constant value. This work highlights the potential of edge-functionalized NPCs in competitive adsorption, capture, and separation for the binary CO2-CH4 mixture, and provides an effective and superior alternative strategy in the design and screening of adsorbent materials for carbon capture and storage.