Technology And Terminal Reaction Kinetics Of Heterogeneous Ammoximation Of Cyclohexanone

Cyclohexanone oxime is the most important precursors ofε-caprolactam for nylon production, 90% of caprolactam is produced by it in the world. The novel process based on the direct ammoximation of cyclohexanone with ammonia and hydrogen peroxide over TS-1 catalyst has showed a lot of advantages compared with the traditional process. Without complex synthesis of hydroxylamine, ammoximation process has no byproduct of ammonium sulfate, as well as no ,NOx or SOx pollutants. So it is regarded as a relatively environmental friendly process. It is specially noted that t-butanol is used as the solvent in ammoximation for the well solubility of oxime. However, the solvent should be separated from oxime for its instability in oleum for Beckmann rearrangement, which leads to additional separation process, higher mass and power cost and more impurities. In order to solve this problem, n-hexane instead of t-butanol is used as solvent not only of liquid-liquid-solid 3-phase ammoximation, but also to remove reaction heat of Beckmann rearrangement.This reformation shows simple process flow and less energy consumption.in cyclohexanone oxime production.In this thesis, the influences of essential technological parameters on 3-phase ammoximation are studied. Effect of reaction tempture, reaction time , mole ratio of NH₃/cyclohexanone, mole ratio of H2O2/cyclohexanone, and concentration of catalyst on the conversion and selectivity are inverstigated. The result shows the optimum reaction conditions are following: reaction temperature 70-80℃; prolonged reaction time 20-40min; NH₃ /cyclohexanone molar ratio 1.7-2.2; H₂O₂ /cyllcohexanone molar ratio 1.0-1.1; TS-1 content 1.5%-3.0%(wt%). Under the above conditions, the conversion of cyclohexanone and the selectivity of oxime can both reach 98%.GC-MS has been used in analysising the byproducts of liquid-liquid-solid 3-phase and liquid-solid 2-phase ammoximation.The most important byproducts of 3-phase reaction are cyclohexanol and nitrocyclohexane, the number of macromolecules byproducts is less in 3-phase system compared with 2-phase system. At the same time, the cyclohexanone via oxidation of cyclohexane and the cyclohexanone produced by hydration of cyclohexene are used in 3-phase ammoximation, which aimed to compare the effect of different material. The results show that the ammoximation of cyclohexanone from oxidation process has higher selectivity of cyclohexanone oxime, as well as less byproducts.Finally, using experiment design, the terminal reaction kinetics for ammoximation of cyclohexanone is measured. The power type raction rate equation is used for match the experiment datas and the parameters are estimated by Gauss-Newtonian algorithm. Residual analysis and F inspection show that this model can reflect the terminal reaction characters of heterogenous ammoximation catalysed by TS-1. It also can be used for pilot-plant research and process design.