Four supported catalysts with the same tungsten loading were prepared by depositing decatungstate species W10O4− 32, through wet impregnation, on the surface of γ-alumina and silica at different pH values. The prepared samples were characterized using BET measurements as well as XRD, UV–vis DR, and XP spectroscopies. Higher dispersion of W (VI) oxo-species was obtained in the silica-supported catalysts compared with the ...