摘要
以氯化稀土为催化剂 ,以锌粉为还原剂 ,对不同羧酸和溶剂条件下的丙烯直接用氧气环氧化进行了研究 ,并对它的催化反应机理进行了初步探讨 ,.实验结果表明 ,氯化稀土中只有 Eu Cl3对丙烯直接环氧化起催化作用 ,并且要在锌粉和羧酸共同存在下才有效 ,所用羧酸中丙酸的效果最佳 ,使用有机溶剂比不用溶剂效果更好 ,但不能用碱性物质作为反应体系的溶剂 .反应气压力越高越有利于环氧丙烷 (PO)的生成 ,但反应温度不宜过高 .在 Eu Cl3、锌粉、羧酸催化体系中 ,Eu Cl3起电子传递的桥梁作用 ,锌粉提供电子 ,羧酸提供质子 。
The formation of propylene oxide from propylene by direct epoxidation with O 2 has been studied over rare earth chloride catalysts with different carboxylic acids and solvents, and a preliminary discussion on the mechanism of this reaction has been given. Significant PO formation was observed only over EuCl 3 catalyst and in the presence of zinc powder and carboxylic acids. As to the carboxylic acids, propanoic acid is the best for epoxidation of propylene. The yields of the epoxide were higher than those without solvents, but basic substance was not suitable as solvent. The higher the pressure used, the more TON obtained. However high reaction temperature was not suitable for epoxidation. In the catalytic system of EuCl 3, zinc powder and carboxylic acids, EuCl 3 plays a role in transferring electron; zinc powder is the e - donor and carboxylic acids is the H + donor. The mechanism given is consistent with the results of the experiments.
出处
《分子催化》
EI
CAS
CSCD
北大核心
2001年第1期25-28,共4页
Journal of Molecular Catalysis(China)
