Amine-Functionalized Task-Specific Ionic Liquids: A Mechanistic Explanation for the Dramatic Increase in Viscosity upon Complexation with CO2 from Molecular Simulation
Amine-Functionalized Task-Specific Ionic Liquids: A Mechanistic Explanation for the Dramatic Increase in Viscosity upon Complexation with CO2 from Molecular Simulation
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DOI：
10.1021/ja804654b
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发表时间：
2008-11-05
影响因子：
15
通讯作者：
Maginn, Edward J.
中科院分区：
文献类型：
--
作者：
Gutowski, Keith E.;Maginn, Edward J.
从化石燃料燃烧中捕获CO2，特别是在燃煤发电厂中，是旨在稳定大气中温室气体水平的努力的关键组成部分。烷醇胺传统上用于此目的;然而，诸如挥发性、降解和再生成本的缺点已经成为开发新的、上级技术的驱动力。最近，一些开创性的研究与离子液体（IL），实验和计算，已经证明了他们的潜力作为CO2捕获剂。在传统的离子液体中，对CO2的实验研究揭示了其在这些介质中异常高的物理溶解度。补充模拟研究提供的证据表明，这是由于二氧化碳占据液体内的空隙空间，并有利地与阴离子相互作用。最近，一系列的第二代任务特定的离子液体（TSILs）含有胺官能团已被合成，并证明具有更高的容量CO2，由于它们与CO2的反应性，以及异常高的粘度在净和络合状态。目前的工作扩展了开创性的研究CO2捕获与离子液体提供洞察力，从模拟到机制负责的粘度急剧增加后，络合。模拟结果最终表明，缓慢的平移和旋转动力学，这是在高粘度的表现，可能是由于形成一个强大的，普遍的氢键网络。Serniquantitative估计的阳离子和阴离子的自扩散系数和旋转时间常数，以及详细的氢键分析，是一致的实验观察到的玻璃或凝胶状材料与CO2接触后形成。这对于利用这些先入为主的限制设计涉及离子液体的新方法或材料、合成或操纵用于CO2捕获的新TSIL框架以及持续异质环境中化学和动力学的新型实验研究具有重要意义。
The capture Of CO2 from fossil fuel combustion, particularly in coal-fired power plants, represents a critical component of efforts aimed at stabilizing greenhouse gas levels in the atmosphere. Alkanolamines have traditionally been used to this end; however, drawbacks such as volatility, degradation, and regeneration costs have been drivers for the development of new, superior technologies. Recently, several seminal studies with ionic liquids (ILs), both experimental and computational, have demonstrated their potential as CO2 capture agents. In traditional ILs, experimental studies with CO2 have revealed its unusually high physical solubility in these media. Complementary simulation studies have provided evidence that this is attributable to CO2 occupying void space within the liquid and favorably interacting with the anion. Recently, a series of second-generation task-specific ionic liquids (TSILs) containing amine functional groups have been synthesized and demonstrated to have much higher capacities for CO2 due to their reactivity with CO2, as well unusually high viscosities in both the neat and complexed states. The current work extends the seminal studies Of CO2 capture with ILs by providing insight from simulations into the mechanism responsible for the dramatic increase in viscosity upon complexation. Simulations conclusively demonstrate that the slow translational and rotational dynamics, which are manifest in the high viscosity, may be attributable to the formation of a strong, pervasive hydrogen-bonded network. Serniquantitative estimates of the cation and anion self-diffusion coefficients and rotational time constants, as well as detailed hydrogen bond analysis, are consistent with the experimentally observed formation of glassy or gel-like materials upon contact with CO2. This has significant implications for the design of new approaches or materials involving ILs that take advantage of these preconceived limitations, in the synthesis or manipulation of new TSIL frameworks for CO2 capture, and in novel experimental studies of chemistries and dynamics in persistent heterogeneous environments.