OXIDATION CATALYSIS OVER THE NANO-SUPPORTED METAL OXIDE CATALYSTS

摘要

Nanoscale supported metal oxide catalysts were synthesized by hydrothermal method using γ-Al2O3 TiO2, ZrO2 and CeO2 as the supports, and impregnated 5% of V2O5, MoO3, and CrO3 on each supports. The physical properties and structural information were characterized by TEM, BET, XRD, EDS and in situ Raman spectroscopy. Raman results have revealed that the desired molecular arrangements of the active surface metal oxide phases have been achieved. The reactivity/selectivity properties of the nano- catalysts are chemically probed with steady-state catalytic studies of propane oxidative dehydrogenation and methanol oxidation reactions. The results of methanol oxidation reaction have indicated that there are redox sites and acid sites on the surface of the MoO_x/Al2O3 and VO_x/Al2O3catalysts, and only redox sites on the surface of the other catalysts. The results of propane oxidation reaction have revealed that the nano-supported chromia catalyst possesses the highest activity, however, the selectivity of propene decreases with increasing reaction temperature. The nano-supported vanadia catalyst possesses the lower activity and higher selectivity. In addition, 5% VO_x/ZrO2 remains the high selectivity under high reaction temperature of 550°C.