Study On The Catalytic Oxidation Of Cyclohexanone To ε-Caprolactone

ε-Caprolactone is an important intermediate for organic synthesis and a novel polyester monomer. Polycaprolactone, the ring-opening polymerization product of s-caprolactone, has wide applications in the field of biomedical materials and environment friendly plastic. Currently, the industrial process route for the synthesis of ε-caprolactone has been realized mainly through the Baeyer-Villiger reaction, which involves the oxidation of cyclohexanone by peroxy acid. However, in practice there are still many issues demanding prompt solution, such as poor safety and many by-products. Therefore, developing a safe, economic, and clean new technology for the synthesis of ε-caprolactone holds great theoretical significance and prospect for industrial applications.In this paper, according to the disadvantages existing in the current technology for the synthesis of ε-caprolactone, the technology was investigated to prepare peroxyacetic acid by acetic anhydride and hydrogen peroxide at low temperature and then ε-caprolactone was synthesized by oxidation of cyclohexanone with use of hydrous peroxyacetic acid. The advantage of this technology was that the water in the peracetic acid intermediate didn’t need to be removed which improved the safety of the technology.First, different catalysts were tested to select the best catalyst for the oxidation of cyclohexanone to ε-caprolactone. The results showed that the catalyst A exhibited highest catalytic activity towards the reaction, compared with the zinc oxide, tin acetate and other catalysts. Second, the influences of the materials ratio, peracetic acid preparation time, cyclohexanone oxidation time, reaction temperature and catalyst loading upon the oxidation of cyclohexanone to ε-caprolactone over catalyst A were investigated. As a result, the optimum reaction conditions were as follows:the material molar ratio of cyclohexanone to hydrogen peroxide to acetic anhydride was1:1.2:1.15, the amount of the catalyst was2.5wt%of cyclohexanone, hydrogen peroxide and acetic anhydride reacted to prepare peracetic acid for1h at10℃and cyclohexanone was oxidated to s-caprolactone for3h at50℃.92.5%of the conversion of cyclohexanone and80.1%of the GC yield of ε-caprolactone were achieved under the optimum conditions.Furthermore, on the basis of a small-scale pilot study, we explored the feasibility of the amplification of cyclohexanone oxidation reaction. The conditions of cyclohexanone oxidation and post-processing were also explored. The results showed that the experiment of cyclohexanone oxidation could be successfully amplified and high purity ε-caprolactone was obtained with67.7%of separate yield and99.0%of purity. In the post-processing, as the by-products,78.3%of acetic acid and77.2%of sodium salt could be recovered. Besides, the chloroform used as extraction solvent was recyclable. The residue of the distillation was the oligomer of ε-caprolactone. In addition, the preliminary design of technological process of ε-caprolactone synthesis was also provided. The research results provided an important reference basis for the industrial production of ε-caprolactone by oxidation of cyclohexanone.