Study On The Liquid-phase Catalytic Oxidation Of Cyclohexylamine To Its Oxime

Cyclohexanone omixe is one of the most important intermediate in the production of Caprolactam.Conventionally it is synthesized in the cyclohexanone-hydroxylamine way.Montedipe S.P.A of Italy successfully developed a new technology in which the ammoxidation of cyclohexanone was catalyzed by titanium silicalite-1.Although this process has the mild reaction conditions,the use of cheaper and safe diluted hydrogen peroxide solution for oxidants,high conversion rate and selectivity,non-poluting process and no vice-thiamin merits,the titanium silicalite expensive production costs and demanding harsh conditions limit its large-scale industrial applications.Therefore investigators pay more attention on seeking a more efficient process for the production of cyclohexanone oxime route.The other route of preparation of cyclohexanone oxime includs:hydrogenation of nitro-cyclohexene,the partial hydrogenation of nitro-cyclohexane into cyclohexanone oxime,and oxidation of cyclohexylamine into cyclohexanone oxime.In this paper,we report a simple process for liquid-phase oxidation of cyclohexylamine to cyclohexanone oxime.The results are as follows:(1)A series of MOx-SiO2 catalysts were synthesized by sol-gel and impregnation method.The effect of additives(Na,K or P)on the oxidation of cyclohexylamine with H2O2 was studied in this thesis.The catalysts were characterized by FT-IR,XRD,UV-Vis and BET.The results indicated that the catalytic performance prepared by hydrothermal synthesis method and adding Na,K,P in the oxidation effect of cyclohexylamine was worse than the catalystby prepared sol-gel methed.(2)The influence of reaction temperature,reaction time,the amount of catalyst and the reuse of the catalyst on the oxidation of cyclohexylaime was investigated over the Al2O3-SiO2 catalyst with the 48 molar ratio of silica to alumina.The fresh Al2O3-SiO2 catalyst used Al2O3-SiO2 catalyst and the catalyst washed by methanol were characterized by FT-IR.Under the condition of V(acetonitrile):V(cyclohexylamine)=3,V(H2O2):V(cyclohexylamine)=3,0.8 g Al2O3-SiO2 catalyst,75?,and 5 h,the conversion of cyclohexylamine reached up to 99.9%and the selectivity for cyclohexanone oxime was 83.6%.A possible proposed reaction mechanism was proposed.(3)The catalytic performance of NaY Zeolite and modified NaY zeolite in oxidation of cyclohexylamine with H2O2 was also investigated.The catalysts were characterized by BET and XRD.It was suggested that modified NaY zeolite is in essential beneficial to the selective oxidation of cyclohexylamine to cyclohexanone oxime.The selectivity for cyclohexanone oxime reached up to 54.3%with the modified NaY as the catalyst,howerer it was only 28.8%over unmodified NaY catalyst.