密度泛函理论与分子力学方法研究沥青质分子间的π-π堆积作用  

Study on π-π stacking between asphaltene molecules by DFT and MM methods

作　　者：罗辉[1] 吕慧栋 周嘉安琪 邓文安[1] 李传[1] 南国枝[1] LUO Hui;LÜHuidong;ZHOU Jiaanqi;DENG Wenan;LI Chuan;NAN Guozhi(State Key Laboratory of Heavy Oil Processing in China University of Petroleum(East China),Qingdao 266580,China)

机构地区：[1]中国石油大学(华东)重质油国家重点实验室,山东青岛266580

出　　处：《中国石油大学学报（自然科学版）》2023年第1期189-196,共8页Journal of China University of Petroleum(Edition of Natural Science)

基　　金：国家自然科学基金联合基金项目(U20B6003);中央高校基本科研业务费专项(20CX02201A)。

摘　　要：为准确描述沥青质分子间的π-π堆积作用,采用密度泛函理论(DFT)和分子力学(MM)方法研究π-π堆积的势能面、质心距离(Re)和相互作用能(ΔEe)。结果表明,DFT-D、DFT/mGGA、MM以及采用DNP+基组的DFT/GGA方法在描述苯和沥青质的S型、T型和PD型二聚体时均可得到典型的势能面;DFT/mGGA-M06L方法的精确度最高,得到的Re和ΔEe与苯的参考值相比,误差均小于4.60%;S型沥青质二聚体的Re与苯的非常接近,均为0.388 nm,但ΔEe比苯的大十余倍;T型沥青质二聚体中近距离作用的原子数越多,ΔEe越大,但近距离作用的原子数只有一个或几个,导致ΔEe明显小于S型;PD型沥青质二聚体的ΔEe大于S型,且质心垂直距离(Rv)在约0.35 nm时ΔEe最大(接近S型的2倍),此时二聚体的片层间距明显小于S型,结构最稳定。To gain insight about the π-π stacking in asphaltene molecular aggregates, density functional theory(DFT) and molecular mechanics(MM) methods were adopted to study the potential energy surface(PES), the equilibrium center of mass distance(Re) and the equilibrium interaction energy(ΔEe). The results show that the typical PES are obtained to describe the S-type(sandwich), T-type(T-shaped) and PD-type(parallel-displaced) dimers of benzene or asphaltenes by using DFT-D, DFT/mGGA, MM, or DFT/GGA with DNP+ basis set, where the DFT/mGGA-M06L method has the highest accuracy. The ΔEeand Recalculated by mGGA-M06L are consistent with those reported in the literature for benzene dimers, and the errors are less than 4.60%. The Reof the S-type asphaltene dimer is very close to that of benzene, both are 0.388 nm, and ΔEeis more than ten times larger than that of benzene. For the T-type asphaltene dimers, the more atoms in the short-distance, the greater the ΔEe, but there is only one or several atoms in the short-distance, resulting in the ΔEesignificantly smaller than that of the S-type dimer. The ΔEeof the PD-type asphaltene dimers are greater than that of the S-type, and the ΔEeis the largest when the vertical distance(Rv) is about 0.35 nm, which is close to twice that of the S-type. In this case, the interlamellar spacing of the dimer is significantly smaller than that of the S-type, resulting in the most stable structural conformation.

关 键 词：沥青质聚集体 Π-Π堆积作用 密度泛函理论 分子力场 

分 类 号：TE622.1[石油与天然气工程—油气加工工程]