Abstract: | Bismuth tungstate catalysts with Bi/W ratios 2/3, 1/1, 2/1, and 6/1 have been investigated after various heat treatments by room temperature X-ray analysis. The activity and selectivity of Bi2WO6 catalyst are suggested to be connected with the presence of corner sharing W—O octhedra in the bulk of the solid that give rise to tetragonal pyramidal W—O sites at the surface. The very low activity of Bi2(WO4)3 is attributed to edge-shared octahedral coordination of W while the same of Bi6WO12 is due to tetrahedral coordination of W. The inactivity of Bi2W2O9 may be associated with its typically low oxidation power. The promoting influence of Bi2O3 is to enforce a structural situation on W—O so that W may be present in a tetragonal pyramidal 5-configuration. |