VOx/SBA-15催化剂上甲苯气相部分氧化

A series of vanadiumbased catalysts with SBA-15 as support were prepared by incipient wetness impregnation and characterized by XRD, BET, TPR, UV-Vis and NH3-TPD. The reaction of toluene oxidation over VOx/SBA15 was carried out in a fixedbed reactor under the conditions of 380℃~520℃, 0.15MPa, n(N2)/n(O2)/n(toluene) = 40/10/1, GHSV=600h－1. The results showed that there is an optimal vanadium loading to get highest benzaldehyde selectivity. Vanadium species existed mainly in the form of isolated and polymeric vanadium species at low vanadium loadings; increasing vanadium loadings would cause the formation of V2O5 crystalline. Isolated polymeric vanadium species were shown to be active in partial oxidation of toluene to benzaldehyde, whereas polymeric vanadium species, especially V2O5 crystalline, reduce greatly the selectivity of benzaldehyde in toluene oxidation. A better dispersion of vanadium species over VOx/SBA-15 surface was observed than those over VOx/MCM-41 and VOx/SiO2, this may contribute to its higher benzaldehyde selectivity in toluene oxidation.