基于密度泛函理论从分子层面分析原油中镍/钒卟啉化合物

基于密度泛函理论(DFT)，通过量子化学计算研究了主要的石油卟啉，包括ETIO、DPEP、DI-PEP、RHODO-TIO、RHODO-PEP或RHODO-I-PEP型和Ni²⁺/VO²⁺形成的金属卟啉配合物的分子结构、电子特性、解离能等。卟啉环的空腔尺寸、电荷分布、共轭特性均使其易于与Ni²⁺/VO²⁺发生络合，且配合物结构稳定。空间效应和竞争吸附使得VO²⁺卟啉配合物中的V原子和卟啉环不共面，VO²⁺卟啉环的配位作用弱于Ni²⁺卟啉环，因此Ni的脱除通常比V困难。Ni²⁺/VO²⁺卟啉配合物表现出显著的取代基效应：供电子的环烷基促进了卟啉环和Ni²⁺/VO²⁺的配位；吸电子的苯基削弱了卟啉环和Ni²⁺/VO²⁺的配位。对原油中Ni²⁺/VO²⁺卟啉化合物配位化学特性的研究，对于原油脱Ni/V技术的开发与改进具有一定的理论指导作用。

DFT Analysis for Ni/V-orphyrin Complexes in Petroleum at the Molecular Level

Different types of petroporphyrins, including the complexes of ETIO, DPEP, DI-PEP, RHODO-TIO, RHODO-PEP, or RHODO-I-PEP type porphyrin with Ni²⁺/VO²⁺, were studied by density functional theory (DFT), for their structure, electronic properties, and dissociation energy of petroporphyrins at the molecular level. The suitable size of the cavity, charge distribution, and conjunction effect of porphyrin make them bond tightly with Ni²⁺/VO²⁺. In comparison with VO²⁺, the bond of Ni²⁺ with porphyrin is stronger, which makes Ni more difficult to remove. The petroporphyrins show an evident substituent effect: the electron-onating group (cycloalkyl group) contributes to the complexation, while the electron withdrawing group (phenyl group) inhibits the complexation. The fundamental study of the coordination chemistry properties of porphyrins with Ni²⁺/VO²⁺ contributes to the development of the petroleum demetallization and supports the advancement of molecular refining.