Diesel soot oxidation over supported vanadium oxide and K-promoted vanadium oxide catalysts

Several systems of vanadium oxide and K-promoted vanadium oxide catalysts which supported on different carries with the variations of V contents and K contents were prepared by incipient-wetness impregnation method. Their catalytic performances for diesel soot catalytic oxidation were investigated with temperature-programmed oxidation reaction (TPO). Spectroscopic techniques (FT-IR and UV–vis DRS) were utilized to determine the structure of VOx species for vanadia supported on γ-Al2O3, SiO2, TiO2, and ZrO2. Thermal analysis techniques, including thermogravimetrical (TG-DTA) analyses and temperature-programmed reduction (TPR), were used to characterize the thermal behavior and redox properties of K promoting vanadium oxide catalysts, respectively. The results showed that the structure of supported-vanadia catalysts depends on the support materials and also on the V loading. At high V loading, VOx species exists predominantly as polyvanadate species and V2O5. The catalytic activities of the catalysts for soot oxidation are correlated to their redox property and the mobility of surface atoms. The catalytic activity for soot oxidation orders as Ti > Zr > Si > Al, and the sequence for selectivity to CO2 formation (SCO2) is Ti > Zr > Si ∼ Al for the catalysts over different supports. Adding potassium into supported vanadia catalysts can improve the catalytic activity of soot oxidation. And when n(K):n(V):n(Ti) = 4:4:100 the catalyst of K4V4/TiO2 gives the best activity for soot combustion, i.e., the lowest reaction temperature.