褐煤表面吸附水分子的微观机理

Micro-mechanism of Water Molecule Adsorption on Lignite Surfaces

应用密度泛函理论在分子水平上研究了水在褐煤表面的微观吸附机理,在B3LYP/6-311G+(d,p)优化基础上,采用Gaussian09软件程序包计算得到褐煤表面构型及其不同煤水吸附构型,采用完全均衡校正法对其相互作用能校正重叠误差.运用Multiwfn程序和VMD软件,应用静电势分布图、散点图和约化密度梯度(RDG)填色等值图对不同褐煤表面模型进行图形化分析.结果表明:褐煤表面对水分子的吸附为物理吸附,属于弱相互作用,这些弱相互作用力以氢键作用为主,其余为范德华弱相互作用;羟基、羧基对水的吸附性最强,其他含氧基团(如醚键、甲氧基等)次之,苯环最弱;水分子吸附形成的相互作用区域并不简单地集中于某个基团或某个原子,而是与褐煤局部区域都形成一定的相互作用,这不仅增强了水分子的吸附作用,而且对褐煤结构产生较大影响.

The micro-mechanism of water molecule adsorption on lignite surfaces was investigated by using density functional theory, following which different lignite surface models and coal-water adsorption mod- els were obtained through calculation by Gaussian09 program at the level of B3LYP/6 311G＋（d,p）, while the interaction energies were corrected by complete counterpoise method considering the basis set superposition error （BSSE）. Moreover, graphical analyses were also conducted for different lignite surface models using electrostatic potential diagram, scatter diagram and reduced density gradient （RDG） color-filled iso surface map with Muhiwfn program and VMD software. Results show that the water adsorption on lignite surface is of the weak interaction physical adsorption kind, the major part of which is hydrogen bonding in- teraction while the rest is Van Edward interaction. The adsorbability of hydroxyl and carboxyl to water is the strongest, followed by other oxygen functional groups such as the ether bond and methoxy, etc. , and that of benzene ring is the weakest. The interaction region formed through water adsorption does not simply concentrate on some groups or an atom but somewhat interacts with Local lignite areas. Thus the water adsorption is reinforced and the structure of lignite is impacted obviously.