Study On Lquid-phase Beckmann Rearrangement Of Cyclohexanone Oxime To Caprolactam Over Solid Sulfonic Acid

Caprolactam is an important organic chemical raw material. It is widely used to automobile, spinning, medicine, electron and machinery trades. The liquid acids such as concentrated sulfuric acid or oleum are homogeneous catalysts for the commercial process for producing ε-caprolactam, in which ammonia is used to neutralize the product mixture. This process leads to severe ecological concerns and economical drawbacks, such as the inevitable equipment corrosion, difficulty in product separation, and formation of large amount low value-added ammonium sulphates. The vapour-phase process is highly energy-consuming because it is usually conducted above 300℃, and often leads to low selectivity of lactams and fast catalyst deactivation arising from coke formation.Therefore, the liquid-phase Beckmann rearrangement has attracted growing attentions; yet, it is still one challenge to explore green and recyclable heterogeneous catalyst under mild conditions.In this work, we explored the liquid-phase Beckmann rearrangement of cyclohexanone oxime under mild condition by using solid sulfonic acid instead of liquid fuming sulfuric acid as catalysts.First of all, the liquid-phase Beckmann rearrangement over Nafion-H sulfonic acid resin and Amberstly-15 sulfonic acid resin had been researched. The influences of solvent, amount of catalyst reaction time, reaction temperature, concentration of sulfuric acid inregeneration process were examined.what is more, the optimized reaction conditions and the reuse of catalyst was investigated. Results indicate that conversion of oxime can reach 84.2% with 72.9% of selectivity to ε-caprolactam by using Nafion-H sulfonic acid resin under optimal reaction conditions.Catalytic effect of Amberetly-15 sulfonic acid resin is similar to Nafion-H, the conversion of oxime can reach to 75.3% with 70.9% of selectivity to ε-caprolactam. This catalytic system involved is environmentally harmless, easily separate, and the catalyst can be conveniently recovered for recycled use.Secondly, we design a simple continuity device, preliminary experimental researches by cyclohexanone oxime dissolved in a solvent DMSO reaction solution was configured by Nafion-H, Amberstly-15 two kinds of acid resin, while the completion of the feed side discharge reaction process. Experimental results show that acid resin the continuous catalyze cyclohexanone oxime rearrangement caprolactam, but the reaction time is shorter for about 16 h, and used again after regeneration, reflecting poor results.In addition, the liquid-phase Beckmann rearrangement of cyclohexanone oxime to caprolactam over amidosulfonic acid in the solvent phenol was researched. Some influence factors such as amount of catalyst, reaction time, reaction temperature et al. were investigated. It should be noted that the reaction rate of this catalyzed system is fast, and the material of cyclohexanone oxime can translate completely in 1h. However, it only gave the result with 49.8% of selectivity to caprolactam and formed many kinds of by-products.