褐煤分子吸附水分子多聚体的机理

Mechanism of water polymer adsorption on lignite molecule

为研究水分在褐煤中的赋存规律,应用包含色散矫正的密度泛函理论(DFT-D3)研究了水分子多聚体在褐煤分子表面的吸附机理。对褐煤分子表面吸附水分子多聚体的平衡构型进行结构优化,通过约化密度梯度(RDG)图形化显示和判断水分子多聚体在褐煤分子表面的吸附作用类型,通过AIM理论得到吸附作用的拓扑参数并判断吸附作用的类型及强度,通过能量分解分析(EDA)得到各项能量在总吸附能中所占的比重。研究结果表明:水分子多聚体主要通过氢键作用吸附在褐煤分子表面,范德华力在吸附过程中的贡献较小。褐煤分子表面的羧基和羟基官能团为水分子多聚体提供主要的吸附位点。水分子多聚体吸附在褐煤分子表面会形成多个氢键,且吸附能大于单个水分子。水分子与褐煤分子在排斥力与吸引力的共同作用下形成稳定的平衡构型,且静电作用在吸引作用中占据主导地位。

In order to study the storage pattern of mositure in lignite,the adsorption mechanism of water polymer on lignite molecular surface was studied by density functional theory with dispersion correction（ DFT-D3）. The structure of equilibrium geometry of water polymer adsorption on lignite molecular surface was optimized. Reduced density gradient（ RDG） was carried out to visualize and judge the type of adsorption interaction between water polymer and lignite molecule,the AIM theory was used to obtain the topological parameters of adsorption interaction and then determine the type and strength of adsorption interaction, and the Energy decomposition analysis（ EDA） was applied to acquire the proportion of different energy to total adsorption energy. The results show that： water polymer adsorbed on lignite molecular surface mainly via hydrogen bond, and van der Waals forces make little contribution to the adsorption. Carboxyl and hydroxyl functional group in lignite provide the primary adsorption sites. More hydrogen bonds formed between water polymer and lignite molecule,and adsorption energy of water polymer on lignite is larger than that of single water. Water molecule adsorbed on lignite to form equilibrium configuration under the effect of repulsive and attractive interaction,and electrostatic interaction plays a dominant role in the attractive interactions.