Modification of chlorine-free alkali metal ion (K+, Rb+, or Cs+)-containing FeOx/SBA-15 catalysts with boron enhanced their catalytic performances in propylene epoxidation by nitrous oxide. A B-K+-FeOx/SBA-15 catalyst (K/Fe = 2.5, B/Fe = 0.5) showed the best propylene oxide (PO) formation activity, providing PO selectivities of 79 and 55% at propylene conversions of 4.8 and 13% at 350 and 400 degrees C, respectively.