Catalytic Performances Of Composite Catalysts On One-step Synthesis Of ε-caprolactam From Cyclohexane Nitrosation

ε-Caprolactam is an important organic chemical raw material and widely used to synthesize nylon-6 fibers and resins. All current commercial processes for caprolactam production are based on benzene, phenol or toluene.ε-Caprolactam is obtained by Beckmann rearrangement of cyclohexanone oxime using oleum or sulfuric acid as a reaction medium, and cyclohexanone oxime is producted from the reaction of cyclohexanone. The conventional method of preparation ofε-caprolactam from cyclohexanone oxime via Beckmann rearrangement results in the formation of a large amount of ammonium sulfate as by-products. So the emphasis of caprolactam production and research is to adopt green technics and reduce environmental pollution. From both synthetic and industrial points of view, it has profound realistic meaning and capacious applied foreground that the cyclohexane can be used as the starting material for one-step synthesis ofε-caprolactam from cyclohexane nitrosation reaction.We put forward the reaction of NOHSO₄ and cyclohexane under normal pressure as the probe reaction by the results obtained from one-step synthesis ofε-caprolactam from cyclohexane nitrosation reaction, and research the function of transition metal compound adjust and control the reaction. The effects of M-Al-O catalysts and M₁-M₂-Al-O catalysts, which contain part of the 4th period transition metal element and the aluminium isopropoxide was used as source on the cyclohexane liquid-phase nitrosation reactions were researched. The effects of supported way of the catalysts, the ratio of the transition metal element in the catalysts, the processing method and the calcination temperature of the catalyst were examined, and the better reaction conditions were obtained in this work.In addition, the effects on the capability of supported metallic oxide catalysts were researched by using different kind of Al₂O₃ and active carbon as the carriers in this work. The result showed that the performance of 10%M/γ-Al₂O₃catalyst effectively restrain the high conversion of cyclohexane and raise the selectivity of caprolactam. 10%M/γ-Al₂O₃catalyst was chosen as the example for researching the nitrosation reaction, and the optimal reaction conditions are as follows: the conversion of cyclohexane and the selectivity to caprolactam are 28.0% and 21.8% respectively when the reaction was carried out at temperature 81℃for 24h. The final products were analyzed by using an Agilent-1100 high performance liquid chromatograph (HPLC), GC-MS and LC-MS. On the basis of the results in this work, we proposed the possible reaction mechanism for the nitrosation of cyclohexane with nitrosyl sulfuric acid over catalyst.