煤与水的表面相互作用是洁净煤技术领域的重要科学问题之一。然而,褐煤与水的相互作用是一个复杂的物理化学过程,其微观机制在原子尺度和电子结构方面仍不明确。尤其缺乏褐煤中不同官能团与水之间相互作用能量、稳定性结构特征、相互作用本质的系统考察。基于多尺度分子模拟研究了褐煤与水微观相互作用的分子机制。基于量子化学计算重点考察典型褐煤模型结构中不同官能团与单分子水的相互作用,获得水分子在褐煤不同位点吸附的局域极小构象,以及稳定吸附构象的几何结构特征。基于独立梯度模型的直观绘景阐释了褐煤与水分子之间的相互作用形式主要为范德华作用和氢键。借助能量分解分析方法定量描述并确定了静电作用是稳定煤-水相互作用的最主要因素。此外,还基于分子动力学模拟揭示了不同数量褐煤分子与大量水分子相互作用的组装行为和演化特征,阐明了褐煤分子结构在大量水中的团聚现象。分子动力学模拟结果同样印证了褐煤和水分子主要以静电作用结合。

Coal-water interfacial interactions are one of the key scientific issues in clean coal technology. However, the microscopic mechanism of lignite-water interaction is still unclear in terms of atomic scale structure and electronic properties. There is a lack of systematicinvestigation on the interaction energy, stable structural features, and interaction nature of different functional groups in lignite with water molecules. Herein, the molecular mechanism of lignite-water microscopic interaction based on multi-scale molecular simulations wasinvestigated. The interaction between representative model structures of lignite and a single water molecule was investigated by quantum chemical calculations. The localized minima configurations of different adsorption sites on lignite and corresponding stable adsorption configurations are obtained. The interaction forms between lignite and water molecules were intuitively illustrated by independent gradient model ( IGM ), which mainly included van der Waals interactions and hydrogen bonds. The electrostatic interaction wasquantitatively described and identified as the dominant factor stabilizing the lignite-water interaction by energy decomposition analysis.Furthermore, the assembly behaviors and evolution characteristics of different numbers of lignite molecules interacting with a large numberof water molecules were revealed based on molecular dynamics simulations. The aggregation phenomena of lignite molecules in bulk waterwere elucidated. The molecular dynamics simulation results also confirm that lignite bind to H2O mainly through electrostatic interaction.

0 引言

1 模型及计算方法

   1.1 计算模型

   1.2 量子化学计算细节

   1.3 分子动力学模拟计算细节

2 结果与讨论

   2.1 褐煤与水单分子相互作用的量子化学分析

   2.2 褐煤与大量水相互作用的分子动力学模拟分析

3 结论