Catalytic Performance of B2O3/TiO2–ZrO2 for Vapor-Phase Beckmann Rearrangement of Cyclohexanone Oxime: The Effect of Boria Loading

Abstract

A series of boria catalysts supported on titania–zirconia mixed oxide (B₂O₃/TiO₂–ZrO₂) with different boria loadings (8–20 wt%) were prepared and characterized by X-ray diffraction, adsorption of nitrogen, ¹¹B magic angle spinning (MAS) NMR measurements and temperature-programmed desorption (TPD) of ammonia. The catalytic performance of B₂O₃/TiO₂–ZrO₂ for vapor-phase Beckmann rearrangement of cyclohexanone oxime to ε-caprolactam was studied at 300°C. It was found that the lactam selectivity increased with increasing of boria loading, whereas a maximum oxime conversion was obtained at the boria loading of 12 wt%. The acid sites of medium strength on the surface of the catalyst play an important role in the selective formation of lactam.