活性炭表面钴羰基物种稳定性的理论研究

A theoretical study on the stability of cobalt carbonyl species on activated carbon under syngas reaction conditions

为探究在反应气氛CO的作用下,钴催化剂在活性炭表面各位点的稳定形态,采用密度泛函理论计算方法研究Co原子及Co的羰基络合物在活性炭表面多种活性位点上的吸附稳定性,分别考察了原子Co及Co与多个CO络合形成的羰基络合物在活性炭碳环平面和面内缺陷、带状边界及边界上含氧活性基团吸附构型,对比了各个吸附构型的形成吉布斯自由能随CO温度压力条件的变化.结果表明:活性炭表面不同位点上Co物种的稳定性有显著差异,CO的络合能极大促进Co原子在表面的稳定性;低温高压有利于Co羰基物种的稳定;在典型的合成气制高碳醇反应条件下,所考察的活性炭表面碳空位、带状边界及含氧基团(边界氧原子、边界取代氧原子)等位点上形成Co羰基物种是热力学有利的.研究为合成气反应制备高碳醇中活性炭表面上钴物种的稳定存在形式提供了理论依据.

In order to explore the stable morphology of the cobalt catalyst on the activated carbon(AC)surface under the interaction of CO in the reaction atmosphere,through density functional theory the stability of Co atom and cobalt carbonyls adsorbed on various active sites of AC was studied and compared the formation Gibbs free energy of different adsorption configuration.The results showed that the stability of CO species at different sites on the AC surface was different.Formation of cobalt carbonyls could significantly facilitate the stabilization of Co on AC surface and cobalt carbonyls prefer lower temperature and higher pressure.Under typical syngas conversion reaction to synthesis higher alcohols,formation of cobalt carbonyls were thermodynamically favorable on carbon vacancy,strip edge and oxygen-containing group.It provided a theoretical basis for the stable existence of cobalt species on the surface of AC in the synthesis of high-carbon alcohols by synthesis gas reaction.