基于密度泛函理论的2-乙基蒽醌在Pd催化剂上的加氢机理

Hydrogenation Mechanism of 2-Ethylanthraquinone on Pd Catalyst Based on Density Functional Theory

采用密度泛函理论方法研究了2-乙基蒽醌(eAQ)和H_(2)分子在Pd(111)催化剂上的吸附行为。结果表明,eAQ平行吸附在Pd(111)表面,金属Pd转移了部分电子给eAQ;H_(2)分子在Pd(111)面上发生了解离吸附,且解离能垒较低,表明金属Pd具有较强的H_(2)催化解离能力。在此基础上,根据eAQ的Fukui(0)指数和前线轨道等电子结构性质分析,研究了eAQ加氢机理,提出了eAQ加氢生成2-乙基蒽氢醌(eAQH_(2))的2条可能的反应路径,路径1是H自由基先进攻离乙基近的羰基O原子,路径2是H自由基先进攻离乙基远的羰基O原子。研究发现,Pd催化剂催化蒽醌加氢选择性较高的原因,一是与eAQ自身电子结构性质相关,二是生成副产物的反应能垒远高于主反应。

The adsorption behavior of 2-ethylanthraquinone(eAQ)and H_(2) on Pd(111)catalyst were studied by density functional theory.The results show that eAQ is absorbed on the Pd(111)surface in parallel,and partial electrons have been transferred from Pd(111)to eAQ;dissociative adsorption of H_(2) occurs on Pd(111)surface,with only a small energy barrier,indicating that Pd has a strong ability to promote H_(2) dissociation.On this basis,based on the analyzing electronic structural properties of the Fukui(0)index and frontier orbitals of eAQ,the paper investigates the eAQ hydrogenation mechanism,and proposes two possible reaction paths for 2-ethylanthrahydroquinone(eAQH_(2))generation from eAQ:Path 1 is where the H radical first attacks the carbonyl O atom near the ethyl group,while Path 2 is where the H radical first attacks the carbonyl O atom far from the ethyl group.It can be concluded that the high selectivity of anthraquinone hydrogenation on Pd catalyst is related to the electronic structure of eAQ and the energy barrier of by-products formation is much higher than that of the main reactions.