The influence of potassium ions on the structure and catalytic properties of silica-supported vanadium oxide catalysts was studied in the epoxidation of propene using N2O as an oxidant. The combination of different techniques (XRD, DR UV-vis, Raman, FTIR, and H-2 TPR) for the characterization of potassium doped V/SBA-15 catalysts reveals the formation of various types of vanadate species, including polyvanadates. Potassium changes the acid-base characteristics of the system and decreases the acidic character of surface vanadia. A decrease in the acidic character accounts for better selectivity in propene epoxidation; however, neutralization of active vanadium forms results in lower propene conversion. Textural, XRD and SEM/TEM, results indicate that the ordered hexagonal mesoporous structure with large pore diameters of the support is retained upon vanadium incorporation, although further modification with potassium ions results in a partial structure damage. (C) 2016 Elsevier Inc. All rights reserved.