Gas-phase Beckmann rearrangement of cyclohexanone oxime to ϵ-caprolactam over silica supported niobia catalysts

In most of the industrial processes for the production of ϵ-caprolactam the final synthesis step comprises the homogeneous liquiq-phase Beckmann rearrangement of cyclohexanone oxime catalyzed by oleum. The substantial amount of ammonium sulphate generated as co-product as well as the corrosive process media can lead to certain disadvantages. Summarizing, this work contributes essentially to an increased understanding an improvement of the inexpensive, amorphous Nb0x / Si0x heterogeneous catalyst for the gas-phase Beckmann rearrangement to overcome the disadvantages of the homogeneously catalyzed reaction.