It　was　found　that　Ti-modified　MoO3-Bi2SiO5/SiO2　exhibited　excellent　catalytic　performance　for　the　epoxidation　of　propylene　by　molecular　oxygen.　The　effect　of　Ti　on　the　performance　of　the　catalysts　was　investigated,　and　the　results　showed　that　the　high　surface　area,　greater　pore　size,　and　moderate　acidity　of　the　Ti-modified　catalyst　were　favorable　to　the　selective　formation　of　propylene　oxide　(PO).　Interactions　between　MoO3,　bismuth　oxide　clusters,　and　Ti　species　were　proposed　to　favor　PO　formation.　The　presence　of　Ti　not　only　enhanced　the　dispersion　of　MoO3　nanoparticles　but　also　inhibited　the　reactivity　of　the　lattice　oxygen　and　reduced　the　strong　acidity　of　the　catalyst,　contributing　to　the　increase　in　C3H6　conversion　and　PO　selectivity,　respectively.　Kinetic　studies　indicated　that　a　high　space　velocity　or　low　reaction　temperature　was　beneficial　for　improving　the　selectivity　to　PO　by　decreasing　the　deep　oxidation　of　PO.　(c)　2014　Elsevier　Inc.　All　rights　reserved.