Wang Yanqun, Tang Yizhen, Shao Youxiang
College of Chemistry and Environmental Engineering, Yangtze University, Jingzhou 434023, China.
School of Environmental and Municipal Engineering, Qingdao University of Technology, Qingdao 266033, China.
J Mol Graph Model. 2017 Sep;76:521-534. doi: 10.1016/j.jmgm.2017.05.009. Epub 2017 May 17.
Catalytic dehydration and dehydrogenation reactions of ethanol have been investigated systematically using the ab initio quantum chemistry methods The catalysts include water, hydrogen peroxide, formic acid, phosphoric acid, hydrogen fluoride, ammonia, and ethanol itself. Moreover, a few clusters of water and ethanol were considered to simulate the catalytic mechanisms in supercritical water and supercritical ethanol. The barriers for both dehydration and dehydrogenation can be reduced significantly in the presence of the catalysts. It is revealed that the selectivity of the catalytic dehydration and dehydrogenation depends on the acidity and basicity of the catalysts and the sizes of the clusters. The acidic catalyst prefers dehydration while the basic catalysts tend to promote dehydrogenation more effectively. The calculated water-dimer catalysis mechanism supports the experimental results of the selective oxidation of ethanol in the supercritical water. It is suggested that the solvent- and catalyst-free self-oxidation of the supercritical ethanol could be an important mechanism for the selective dehydrogenation of ethanol on the theoretical point of view.
采用从头算量子化学方法系统研究了乙醇的催化脱水和脱氢反应。催化剂包括水、过氧化氢、甲酸、磷酸、氟化氢、氨以及乙醇本身。此外，考虑了一些水和乙醇的团簇以模拟超临界水和超临界乙醇中的催化机理。在催化剂存在下，脱水和脱氢的势垒均可显著降低。结果表明，催化脱水和脱氢的选择性取决于催化剂的酸度和碱度以及团簇的大小。酸性催化剂更倾向于脱水，而碱性催化剂往往更有效地促进脱氢。计算得到的水二聚体催化机理支持了超临界水中乙醇选择性氧化的实验结果。从理论角度来看，超临界乙醇的无溶剂和无催化剂自氧化可能是乙醇选择性脱氢的一个重要机理。
