Gerd Dahlhoff

ϵ-Caprolactam: new by-product free synthesis routes

The production of the nylon precursor ϵ-caprolactam via the Beckmann rearrangement is one of the large industrial processes worldwide. In this work, the state-of-the-art processes are summarized and the two main pathways for new production capacities (the butadiene-based and especially the heterogeneously catalyzed routes starting from benzene/cyclohexanone oxime) are described. Additionally, the new recycling processes to recover caprolactam from waste carpets and some new approaches are described.

The use of MCM-22 as catalyst for the Beckmann rearrangement of cyclohexanone oxime to ε-caprolactam

A variety of catalysts have been applied to the Beckmann rearrangement of cyclohexanone oxime to e-caprolactam. Experiments with MFI structures yielded good results showing the importance of weak acidic sites, a large outer surface and pore structure accessible only through 10 MR channels. Recent reports on the discovery and characterisation of the MCM-22 catalyst with its large outer surface and special structure recommended this material for the use in the Beckmann rearrangement. In the present study the synthesis and brief characterisation of MCM-22 was carried out followed by the first in depth analysis of its applicability for the Beckmann rearrangement of cyclohexanone oxime to e-caprolactam. The performance of the material was compared to one of the established catalysts, the [B]-MFI, showing several drawbacks like lower yields and poor mechanical stability.

Improved evaporation methods for the system ethanol + cyclohexanone oxime

Abstract The heterogeneously catalyzed gas phase Beckmann rearrangement for the production of e -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%).