Study On Preparation Of Co/Al₂O₃ By Solution Combustion And Its Selective Catalytic Oxidation Of Cyclohexane

Cyclohexanol and cyclohexanone?collectively referred to as KA oil?are important intermediates in chemical production,and the selective catalytic oxidation of cyclohexane is the main method for producing KA oil.The existing catalysts generally have some problems,such as low conversion of cyclohexane,poor selectivity of KA oil,and harsh reaction conditions.The purpose of this paper is to develop a catalyst for the selective catalytic oxidation of cyclohexane,which has excellent catalytic performance and can react in a mild environment.Alumina is an important inorganic nonmetallic material.It has low cost and stable structure and is widely used in the fields of catalysis,adsorption,ceramics and electronics.Two-dimensional nano-plate alumina has attracted wide attention because of its large specific surface area,more active sites exposed to the surface and excellent catalytic performance.Cobalt oxides and cobalt ions have high catalytic activity for the selective oxidation of cyclohexane.The combination of two-dimensional nano-plate alumina with cobalt oxides or cobalt ions can effectively solve the current problems of cyclohexane oxidation.In this paper,two-dimensional nano-plate alumina was synthesized by solution combustion method.It was used as a catalyst carrier to support Co₃O₄ or CoAc₂,which was applied to the catalytic oxidation of cyclohexane.The main research is as follows:Firstly,five-coordinated alumina was prepared by solution combustion method,and the influencing factors of five-coordinated Al were investigated.Then,complex metal oxide catalysts based on alumina were prepared.It was found that the Co₃O₄/Al₂O₃composite catalyst can improve the catalytic oxidation performance of cyclohexane,and the catalyst with 5%Co₃O₄ has the best catalytic activity.Secondly,two-dimensional nano-plate alumina was prepared by using mixed fuels?polyvinyl alcohol and glycine?.The effects of calcination reaction temperature on the morphology,structure and catalytic properties of the product were investigated.It was found that the proper calcination reaction temperature is beneficial to increase the crystallinity of alumina products and reduce the content of organic residue.CoAc₂/SCS-Al₂O₃?1273?catalyst has high catalytic activity for selective oxidation of cyclohexane.Finally,using urea as fuel,two-dimensional nano-plate?-Al₂O₃ was synthesized at a relatively low temperature.The effects of fuel to metal salt ratio,calcination temperature and metal ions in precursor on the product of alumina were investigated.The catalytic performance of two-dimensional nano-plate?-Al₂O₃ supported CoAc₂ for cyclohexane oxidation was also investigated.It has been found that increasing the ratio of fuel to metal salt or increasing the calcination reaction temperature can improve the crystallinity and change the phase compositions of alumina.The metal ions in the precursor can inhibit the formation of?-Al₂O₃ phase.CoAc₂/?-Al₂O₃?673?catalyst has the highest cyclohexane catalytic oxidation activity due to its high specific surface area,good dispersion and no internal diffusion resistance,and the conversion of cyclohexane is 7.9%and the selectivity of cyclohexanone is 42.7%.