DING Chunpu, ZHANG Yuecheng*, WANG Chunling, YANG Ruiyun, ZHAO Jiquan
(School of Chemical Engineering and Technology, Hebei University of Technology, Tianjin 300130, China)
Abstract: Three di-nitrogen Schiff base ligands were synthesized by the condensation of 2-pyridinecarboxaldehyde with aniline and its derivatives and their structures were characterized fully. The effects of the in situ coordination of methyltrioxorhenium (MTO) with Schiff bases on the epoxidation of alkenes with 30% H2O2 as an oxidant were studied. The results revealed that the ligand with an electron-withdrawing carboxy group has suitable coordination capacity and acidity, therefore, it can largely increase theselectivity of epoxides without concomitancy of the obvious decrease of reaction rate in the epoxidation of olefins catalyzed by MTO. For example, when the molar ratio of the Schiff base I to MTO was 2 and the reaction was run at 10 ℃ for 4 h, the conversion of cyclohexene and the selectivity of the epoxide were reached 94.6% and 99.0%, respectively. However, the ligands without electron-withdrawing group decreased the catalytic activity of MTO, though they could increase the selectivity of epoxides in some degree.
Key words: methyltrioxorhenium; carboxy group; Schiff base ligand; cyclohexene; epoxidation; 30% hydrogen peroxide
E-mail: zyctju@yahoo.com.cn
Journal of Molecular Catalysis, Vol. 24, Issue 5, 2010, 392~399
