The development of new heterogeneous catalytic processes for the production of ε-caprolactam Original Research Article

Two catalytic methods emerging newly for the production of ε-caprolactam are reviewed: the ammoximation, and the vapor phase Beckmann rearrangement. These processes do not produce any ammonium sulfate as a by-product. The key for the processes are the catalysts used. The TS-1 zeolite comprising Ti and Si oxides with the structure of MFI is applied as an effective catalyst in the ammoximation reaction. This work reviews its catalysis and the features of the reaction. Although many solid acid catalysts have been tested for the Beckmann rearrangement, recently high silica MFI zeolites without so-called acidic sites are developed for the reaction. A brief history of the catalyst development on the rearrangement is presented, and the catalysis of high silica MFI zeolite is reviewed.