Abstract: It has been shown by in situ XRD that V_2O_5 can disperse spontaneously onto the surface of silica gel, but the dispersion temperature is relatively high. The presence of H_2O vapour inhibits the dispersion of V_2O_5 to a certain extent, The dispersion process of V_2O_5 onto the surface of silica gel can be accelerated by using K_2SO_4 as an additive. The surface acidity of V_2O_5/SiO_2 is quite strong. However, K_2SO_4 can suppress the acidity by neutralizing strong acid sites. This may be one of the important reasons why K_2SO_4 can improve the selectivity of V_2O_5/SiO_2 for many selective oxidations.

Key words: V₂O₅/SiO₂ catalyst, Dispersion on surface, K₂SO₄ promoter