| Popis: |
A string of niobium–based transition metal composite oxides (named as Nb2O5-MOx, M = Cr, V, Ti, Cu, Co, Fe, Mn and Ni, respectively) were synthesized, and their catalytic performances for the elimination of monochlorobenzene/toluene as typical VOCs were studied. Research result of structure–property relationship showed that nanocrystalline/amorphous state and mesoporous structure were formed, and transition metal elements were highly dispersed into Nb2O5, which were conducive to adjusting the physico-chemical properties of Nb2O5-MOx and enhancing the synergistic catalysis effect. The mesoporous and surface acidity of material promoted the adsorption, sensitization and breakage of chemical bonds in the organic reactants, and then reaction intermediates were oxidized and transformed into CO2 and H2O by the redox sites of material. Oxidation properties and electron density of catalysts were the most important factors affecting the catalytic combustion reaction. The order of apparent catalytic activity for monochlorobenzene elimination was: Nb2O5–Cr2O3 > Nb2O5–CuO > Nb2O5–Co3O4 > Nb2O5–Fe2O3 > Nb2O5–V2O5 > Nb2O5–Mn3O4 > Nb2O5 > Nb2O5–NiO, and the order for toluene degradation was: Nb2O5–CuO > Nb2O5–Mn3O4 > Nb2O5–V2O5 > Nb2O5–Fe2O3 > Nb2O5–Cr2O3 > Nb2O5–Co3O4 > Nb2O5 > Nb2O5–NiO. Considering the toxicity of Cr and V, the by-products produced by Cu and the high price of Co, Nb2O5–Fe2O3 was selected as the most suitable catalyst. Its catalytic activity could reach 69% conversion for monochlorobenzene (320 °C), 80% for toluene (320 °C) and 81% for 1,2-dichloroethane elimination (270 °C), and also maintain 120 h without significant deactivation, indicating that the applicability of Nb2O5–Fe2O3 was worthy of more attention and further study. |
