Research On Pathway Of Cyclohexanone Ammoximation With Microemulsions

Cyclohexanone ammoximation reaction has been used in industry for many years, however, the mechanism of the reaction needs further study. On the other hand, as a new reaction medium for cyclohexanone ammoximation reaction, microemulsion is also needs further study.By using microemulsion as a reaction medium, and a reaserch tools for discovering cyclohexanone ammoximation reaction. In order to describe the mechanism of cyclohexanone ammoximation reaction, fluorescence spectrometry was used to measure the parameters of microemulsion, such as the critical micelle concentration (CMC) and micellar aggregation number (N). Finally, combining the microemulsion parameters and data from cyclohexanone ammoximation reaction, the mechanism of cyclohexanone ammoximation reaction was derived.It was found that CTAB/cyclohexanone/n-butanol/water and SDS/ cyclohexanone/n-butanol/water could construct microemulsions, when mass ratio of cyclohexanone/n-butanol/water was 1:2:7, at 60℃, the CMC of CTAB microemulsion was 3×10-3M, the CMC of SDS microemulsion was 2.5×10-3M. Experimental studies showed the higher concentration of surfactant, the greater micellar aggregation number. CTAB microemulsion had higher N and micellar diameters than the SDS microemulsion.Using microemulsion as a reaction medium, under an optium reaction conditions, up to 92.82% conversion of cyclohexanone and 61.89% selectivity of cyclohexanone oxime could be achieved.Conversion and selectivity of the reaction in microemulsion system were lower than non-microemulsion system, and CTAB microemulsion had lower conversion than the SDS microemulsion. Due to the phenomenon, base on models of the collision frequence, the fence layer of the sufactant and the free reaction phase, the conclusion were that the reaction was influenced by the combined effect of above three models. The reaction pathway of cyclohexanone ammoximation reaction was analysed based on above three models. The hydroxylamine mechanism was considered more suitable to describe cyclohexanone ammoximation reaction.