Preparation Of Nano Au/Fe₂O₃ Catalyst And Its Microwave Catalytic Property Of Cyclohexane Oxidation

The selective oxidation of cyclohexane is one of the most representative reactions in alkanes oxidation because its products cyclohexanol and cyclohexanone(KA-oil)are the intermediate for nylon-66 and nylon-6.In the actual process,selective oxidation of cyclohexane usually uses soluble cobalt salts as catalyst or absence of catalyst,which generally requires high temperature and pressure(150-170?,0.8-2.5 MPa),simultaneously,it shows low cyclohexane conversion(?4%),poor KA-oil selectivity(75-80%),high-energy consumption and environmental pollution.therefore,it is a challenging subjects of academic and practical study to achieve the high conversion and selectivity of cyclohexane under mild conditions.Microwave(MW)has the characteristic of accelerating reaction rate,low energy cosumption and pullution,and the reaction which doesn't carry out in conventional method can be realized by the assistance of MW.MW has combined action with catalyst and can reduce the reaction activation energy obviously.In this paper,we used the Au-NPs which has high catalytic activity under low temperature and MW catalytic technology as catalyst together,we aimed at the selective oxidation of cyclohexane and got results as follow:We synthesized Au-NPs catalyst using Fe2O3 as the carrier,and investigated the influence of precipitation agent,baking temperature,gold load on the morphology and properties.The catalyst was characterized by TG-DSC,TEM,XRD,UV-Vis and BET and the catalytic performance was evaluated in the selective oxidation of cyclohexane.Using the unique properties of MW and the autocatalysis of nano gold catalyst,we achieved cyclohexane selective oxidation in a mild reaction conditions(?65 ?,solvent-free,atmospheric pressure),and the influence of different factors in the MW catalytic cyclohexane oxidation reaction was investigated.We got such conclusions:(1)The Fe2O3 in the gold catalyst can improve the activity of catalyst to cyclohexane oxidation;when Na2CO3 was used as precipitant,caking temperature was 300 ? and the amount of loading gold is 0.2%,the catalyst had the highest activity.As a carrier of gold catalyst,Fe2O3 can promote the selective oxidation of cyclohexane in a low temperature.(2)The interaction between MW and gold catalyst can promote cyclohexane selective oxidation under low pressure and low temperature condition;when 0.2%CP-Au/Fe2O3 was used as catalyst and cat.:TBHP:cyclohexane = 1 g:1 g:30 mL under the 400 W MW irradiation for 7 h in the reaction,we obtained 2.47%cyclohexane conversion and 100%KA-oil and CHHP selective;the irradiation of MW can activate O2 under mild conditions,so it can promote cyclohexane oxidation reaction.