氮杂冠醚取代非对称双Schiff碱配合物催化氧化对二甲苯研究

将一系列苯并-10-氮杂-15-冠-5或吗啉基取代的不对称双Schiff碱配合物作为催化剂,在常压和120℃条件下用于催化氧化对二甲苯研究。探讨了Schiff配合物中心金属离子、Schiff碱配体中挂接的氮杂冠醚环、配体芳环上取代基等对催化氧化对二甲苯反应活性及其氧化产物选择性的影响。实验结果表明:配合物中氮杂冠醚的存在能显著缩短反应诱导期、提高催化活性和选择性;Schiff碱Mn(Ⅲ)配合物比Schiff碱Co(Ⅱ)和Schiff碱Cu(Ⅱ)具有更高的催化活性;氮杂冠醚Schiff碱Mn(Ⅲ)配合物催化氧化二甲苯的转化率和产物选择性分别达75%和90%。

Study on catalytic oxidation for p-xylene to p-toluic acid by unsymmetrical Schiff base complexes with pendant aza-crown ether

Unsymmetrical Schiff base complexes with pendant aza-crown or morpholino groups had been studied as catalysts in aerobic oxidation of p-xylene to p-toluic acid(PTA)with air at 120℃ under normal atmospheric pressure.The effects of central metal of Schiff base complexes,the aza-crown ether group pendant and substituents group in Schiff base ligands on the oxidation of p-xylene were also investigated.The results revealed that the catalytic activity of Schiff base complexes binding benzo-10-aza-crown ether pendants could be visibly improved and the induce period of the oxidation for p-xylene to p-toluic acid was shortened.Schiff base manganese(Ⅲ) complexes had higher catalytic activity than both cobalt(Ⅱ)and copper(Ⅱ) complexes.Significant selectivity(up to 90%)and conversion levels(up to~75%)were obtained in the presence of aza-crown ether substituted unsymmetrical Schiff base Mn(Ⅲ)complexes.