Study On The Oxidation Of Tetralin

α-Tetralone as a chemical intermediate is widely used in pharmaceuticals,dyes,pesticides and other industries,its main production method is tetralin oxidation.The conversion rate of tetralin by the traditional oxidation method is 20%which involves the following condition:Chromium acetate and 2-methyl-5-ethylpyridine（Cr（Ac）₃-MEP）as composite catalysts,and air as the oxidant to react at 130°C.There are problems such as large amount of catalyst used,toxic and difficult to recycle,which cause pollution to the environment.Therefore,it is very important to develop green,pollution-free catalysts.Based on this,the research on ionic liquid-catalyzed air oxidation of tetralin was carried out in this paper.In this paper,a series of imidazole-based ionic liquids were first synthesized and their catalytic effects on the air oxidation of tetralin were evaluated.By comparing with NHPI catalysts,[Bmim]Br catalysts were screened out.Then,the tetralin oxidation process conditions were optimized,and the optimal conditions were 0.1 mol tetralin,0.25 mmol[Bmim]Br,150ml/min air flow rate,100℃,20 h.The results showed that the conversion rate of tetralin can reach 43.15%,and the main products wereα-tetralone andα-tetralol with selectivities of 64.75%and 21.8%,respectively.The[Bmim]Br catalyst could be recycled,and its activity did not decrease significantly after three cycles.The reaction solution was rectified under reduced pressure,and three substances,tetralin,α-tetralone andα-tetralol,could be separated by Aspen Plus simulation.Furthermore,the by-productα-tetralol in the tetralin oxidation reaction was further studied for H₂O₂oxidation.The effects of acetonitrile,ethanol and ethyl acetate as solvents on the reaction were investigated,and the results showed that acetonitrile was the best.The optimal reaction conditions were 0.01 molα-tetralol,0.04 mol H₂O₂,0.003 mol HBr,10 ml acetonitrile,and the yield ofα-tetralone was 86.95%.Finally,the kinetics and catalytic mechanism of ionic liquid-catalyzed tetralin oxidation were studied.The results showed that[Bmim]Br catalyst could reduce the activation energy of tetralin oxidation.In addition,the mechanism of[Bmim]Br-catalyzed tetralin oxidation is different from that of tetralin auto-oxidation.Under[Bmim]Br catalysis,there is no production of tetralin hydroperoxide,but the process of brominating tetralin intermediates.the brominated tetralin would be debrominated toα-tetralone,which would be further oxidized toα-tetralone.