Improved evaporation methods for the system ethanol + cyclohexanone oxime

The heterogeneously catalyzed gas phase Beckmann rearrangement for the production of ε-caprolactam — the precursor of the polyamid Nylon-6 — requires the evaporation of the reactant mixture cyclohexanone oxime + ethanol in such a way that the formation of thermodynamically preferred byproducts, which strongly influence the product quality, is minimized. To optimize the evaporation process a fluidized bed evaporator, a flash evaporator and a pipe evaporator are compared. The lowest average by product formation was observed with the fluidized bed evaporator (0.69%), followed by the flash evaporator (1.67%) and the pipe evaporator (2.75%).