环烷酸催化脱羧机理的研究  

Study on the Mechanism of Catalytic Decarboxylation of Naphthenic Acid

作　　者：叶蔚甄 龙军[1] 赵毅[1] 代振宇[1] 周涵[1] 

机构地区：[1]中国石化石油化工科学研究院,北京100083

出　　处：《石油学报（石油加工）》2016年第5期943-950,共8页Acta Petrolei Sinica(Petroleum Processing Section)

基　　金：中国石化基础研究项目(YK515026)资助

摘　　要：为深入认识环烷酸催化脱羧的反应机理,选取具有代表性的带有较长侧链的9-环己基壬酸为模型化合物,采用基于密度泛函理论的量子化学从头计算方法研究了该分子的电荷分布和前线轨道分布,发现分子中的羰基O原子更易受到B酸和L酸进攻。在此基础上,进一步分析了该分子与B酸和L酸作用前后的键长、键级等变化,推演出了羧基β位碳碳键发生断裂生成小分子的石油酸和直接脱羧生成CO22条反应路径。比较2条反应路径的反应能垒后,提出了在B酸作用下,9-环己基壬酸分子更容易发生的是生成小分子石油酸的反应,而在L酸作用下,9-环己基壬酸分子更容易发生直接脱羧生成CO2反应的观点。To deeply elucidate the mechanism of catalytic decarboxylation of naphthenic acids, density functional theory based ab initio quantum method was selected, and 9-cyclohexylnonanoic acid with a long chain was used as model compound, to study the charge distributions and frontier orbital of molecule, and its elementary reaction steps under catalysis of Bronsted and Lewis acids. Calculated results showed that the carbonyl oxygen atom in the molecule was more susceptible to be attacked by B acid and L acid. Then the bond length and bond order of this molecule before and after being attacked by B acid and L acid were calculated and two reaction paths were deduced, in which one is the cracking of β C -C bond in carboxyl group to generate small acid molecule and the other is direct decarboxylation to generate CO2. From the comparison of energy barriers for the two reaction paths in the presence of B acid and L acid, it is found that 9-cyclohexylnonanoic acid was more likely to generate small acid in the presence of B acid, while more likely to generate C02 in the presence of L acid. These theoretical insights may greatly promote the development of more selective decarboxylation catalysts.

关 键 词：分子模拟 环烷酸 脱羧机理 B酸和L酸 电荷分布 前线轨道 

分 类 号：O641[理学—物理化学]