Study On Synthesis Of ε-Caprolactam By Liquid-Beckmann Rearrangement

ε-caprolactam(CPL) is an important organic chemical intermediates. It is widely used to spinning, electron, automobile, shipping, machinery trades and medicine. At present, the last step of commercial processes for nearly 95% caprolactam is Beckmann rearrangement of cyclohexanone oxime, which is catalyzed by concentrated sulfuric acid or fuming sulfuric acid. The process brings serious corrosion of the equipment, forms a large amount of low-value ammonium sulfate as by-product with a high cost, and causes environmental pollution seriouly. In this work, we explored the liquid-phase Beckmann rearrangement of cyclohexanone oxime and improved the traditional process. The catalyzed systems of H2SO4/Cr/Si O2 and cyanuric chloride(CNC) were examined.The main worksare as follows:First of all, the liquid-phase Beckmann rearrangement over H2SO4/Cr/Si O2 had been researched. The influences of reaction temperature, amount of catalyst, reaction time and amount of solvent were examined, and obtained the optimized reaction conditions. Results indicate that under the condition of cyclohexanone oxime 1.0g, H2SO4/Cr/Si O2 0.6g, reaction temperature 40 ℃ reaction time 5 h, amount of solvent12 ml, cyclohexanone oxime conversion is 96.9% and selectivity of caprolactam reaches 92.5%. Cyclohexanone is the main by-product under this catalyzed system.Moreover, the liquid-phase Beckmann rearrangement over cyanuric chloridehad been researched. The influences of reaction temperature, amount of catalyst, reaction time, solvent ratio, amount of solvent and cocatalyst were examined, and obtained the optimized reaction conditions. Results indicate that under the condition of cyclohexanone oxime 2.76 g, cyanuric chloride 36 mg, reaction temperature 80℃reaction time 2.5h, solvent ratio 1.25, amount of solvent20 ml, cyclohexanone oxime conversion can reach 98.4% and selectivity of caprolactam can reach97.2%. Cyclohexanone is the main by-product under this catalyzed system, and at the same time, it also puts forward the possible reaction route of the liquid-phase Beckmann rearrangement. This method has mild reaction condition, cheap and easy available catalyst, no by-product ammonium sulfate, and the solvent can be completely recycled, so this process has a very good application prospect.Finally, in order to reduce the loss of cyanuric chloride in the reaction process,the modified chloromethylated bead(PS)was prepared by the reaction of one of ethanediamine(EDA)、ethanolamine(ETA) or ethylene glycol(EG) with PS, And then, cyanuric chloride was loaded to the modified PS. The liquid-phase Beckmann rearrangement over the polystyrene chlorotriazine resin had been researched. Results indicate that the catalytic properties of polystyrene chlorotriazine resin for liquid-phase Beckmann rearrangement were still in a higher level,cyclohexanone oxime conversion can reach 97.6% and selectivity of caprolactam can reach94.8%.