活性炭吸附二苯并噻吩过程中酚羟基作用的分子模拟和实验研究

A Molecular Simulation and Experimental Study of the Effect of Phenolic Hydroxyl on the Adsorption of Dibenzothiophene on Activated Carbon

采用密度泛函方法研究了酚羟基与二苯并噻吩的作用机理,根据"分子内原子理论"计算酚羟基与二苯并噻吩络合吸附体系的电荷密度及其拉普拉斯值,用"自然键轨道理论"计算酚羟基与二苯并噻吩之间的电荷转移,结果表明:酚羟基的反键轨道σ*O33-H34与二苯并噻吩的π体系πC1=C2存在交互作用(C1=C2σ*O33-H34);二苯并噻吩的π电子体系中约有5.29×10 22C的电荷转移至酚羟基(O-H)的反键轨道σ*O33-H34,H34与C1=C2之间形成了O-H...π芳香氢键,其结合能为7.97 kJ mol 1。实验测定了不同酚羟基含量的活性炭对二苯并噻吩的平衡吸附量,结果表明:活性炭对二苯并噻吩吸附量随着表面酚羟基含量增加而增强,当活性炭表面酚羟基含量从0.14 mmol g 1AC增加到0.38mmol g 1AC时,活性炭对DBT吸附量从9.3 mg S g 1AC增加到14.1 mg S g 1AC,提高了52%。这与分子模拟计算及分析结论一致,提高活性炭表面酚羟基含量,使得活性炭与二苯并噻吩有更多机会形成芳香氢键,利于提高活性炭对二苯并噻吩的吸附容量。

The interaction between phenolic hydroxyl on activated carbon and dibenzothiophene was investigated by using density function theory and by the absorption experiments. The theory of Atoms in Molecules was used to calculate the theoretical charge density and the Laplacian of the complex adsorption system. The electron distribution of the system was analyzed by performing the natural bond orbital calculations for the monomers and adsorption complex. Based on the theoretical study of the complex adsorption, it was found that there exists hydrogen bonds between the πelectron systems （πc1=c2） of dibenzothiophene and the anti-bond orbital （σo33-H34） of the phenolic hydroxyl. When the hydrogen bond is formed, some charge （5.29×10-22 C） is transferred from πc1-c2 to orσo33-H34 and the interaction energy is 7.97 kJ.mol-1. The adsorption amounts of dibenzothiophene on activated carbons with different amounts of phenolic hydroxyl were measured. The results show that the dibenzothiopheneon adsorption amount and the absorptive power of the activated carbon increase with the increase of the amount of phenolic hydroxyl on the activated carbon, which indicates that the increase of phenolic hydroxyl amount on activated carbon offers more adsorption sites for dibenzothiophene adsorption. When the phenolic hydroxyl on the oxidized activated carbon increases from 0.14 to 0.38 mmol-g-1AC, its dibenzothiophene adsorption amount increases by 52% （from 9.3 to 14.1 mgS-g-1AC）, which is in good agreement with the theoretical results. The investigation provides valuable information for developing novel adsorbents for ultra-deep desulfurization of liquid fuels.