Catalytic Oxidation Of Cyclohexane To KA Oil Over Ce-based Composite Oxide Catalyst

Cyclohexanol and cyclohexanone（KA oil）are important intermediates in the synthesis of caprolactam,and the development of their preparation technology has an significant impact on downstream industries such as medicine,pesticides,coatings and detergents.At present,KA oil is mainly prepared by a two-step process of non-catalytic oxidation of cyclohexane in industry,cyclohexane is first oxidized to cyclohexyl hydrogen peroxide,and then cyclohexyl hydrogen peroxide is decomposed into KA oil in lye,it has a long process route,high energy consumption（the conversion of cyclohexane was 3-5%）,low yield of KA oil（82-83%）,and lots of saponified waste lye.Therefore,which is urgent to develop a new catalytic reaction system for green and efficient one-step catalytic oxidation of cyclohexane to prepare KA oil.CeO₂ is widely used in various catalytic oxidation reactions due to its strong oxygen storage and release ability and cerium ion coupling and valence change characteristics.In this work,three kinds of Ce-based composite metal oxide catalysts（CeMnCuO_x,CeMnO_x,and CeCrO_x）were prepared by taking transition metal-modified Ce-based catalysts.The main conclusions obtained are as follows:（1）The Ce-based composite oxide catalyst（CeMnCuO_x）was synthesized by co-precipitation method,and its catalytic performance for cyclohexane oxidation were investigated.It was found that under the conditions of catalyst dosage of 0.1 g,reaction temperature of 150℃,oxygen pressure of 0.5 MPa,and time of 1.5 h,the conversion of cyclohexane was 5.4%,and the selectivity to KA oil was 84.9%.After the catalyst was recycled for five times,the catalytic activity remained basically unchanged,and the CeMnCuO_x catalyst before and after use was characterized by N₂ physical adsorption and desorption,FT-IR,XRD,which showed that the catalyst had good repeatability and structural stability.（2）The CeMnO_x composite oxide catalysts were prepared by sol-gel method,and its catalytic performance for cyclohexane oxidation were investigated.It was found that under the conditions of catalyst dosage of 0.1 g,reaction temperature of 150℃,oxygen pressure of 0.55MPa,and time of 2 h,the conversion of cyclohexane was 7.7%,and the selectivity to KA oil was 85.6%.After the catalyst was recycled for five times,the catalytic activity remained basically unchanged,and the physicochemical properties of the catalysts were analyzed by N₂physical adsorption and desorption,FT-IR,XRD,XPS,TEM and other characterization methods,which showed that the catalyst had good repeatability and structural stability.（3）The CeCrO_x composite oxide catalyst was prepared by glycine-nitrate combustion method,and its catalytic performance were investigated.It was found that under the conditions of catalyst dosage of 0.1 g,reaction temperature of 150℃,oxygen pressure of 0.55 MPa,and time of 2 h,the conversion of cyclohexane was 5.4%,and the selectivity to KA oil was 87.0%,and it was found that the Ce-based catalyst modified by CrOx effectively improved the selectivity of cyclohexanone.After the catalyst was recycled for five times,the catalytic activity remained basically unchanged,and the microstructure of CeCrO_x composite oxide catalyst was studied by BET,FT-IR,XRD,UV-vis DRS,XPS and other characterization methods.The results showed that the physicochemical properties and microstructure of the catalyst did not change before and after using,which showed that the catalyst had good catalytic performance and stability.In this work,Ce-based composite oxide are used as a novel and inexpensive catalyst for the one-step catalytic oxidation of cyclohexane to KA oil,which shows good catalytic performance and potential application prospects.Meanwhile,it provides a new method for the selective oxidation of alkanes to oxygenates ideas and directions.