Beckmann rearrangement of cyclohexanone oxime over Al-MCM-41 and P modified Al-MCM-41 molecular sieves

► P modified Al-MCM-41 catalysts show better selectivity for caprolactam than Al-MCM-41. ► More weak acid sites with certain acid strength are favorable to vapor-phase Beckmann rearrangement of cyclohexanone oxime. ► The selectivity for side productions cyclohexanone and 2-cyclohexen-1-one over AM is very low (less than 1.3%) and are even barely detected 4 h later. ► The interaction of P with the Al-MCM-41 framework and its role in changing various types of acidity is explained.