An exploratory study of diesel soot oxidation with NO2 and O2 on supported metal oxide catalysts

A number of supported metal oxide catalysts were screened for their catalytic performance for the oxidation of carbon black (CB; a model diesel soot) using NO2 as the main oxidant. It was found that contact between the carbon and catalyst was a key factor in determining the rate of oxidation by NO2. Oxides with low melting points, such as Re2O7, MoO3 and V2O5 showed higher activities than did Fe3O4 and Co3O4. The activities Of MoO3 and V2O5 on various supporting materials were also examined. MoO3/SiO2 was the most active catalyst among the supported MoO3 examined, whereas, V2O5/MCM-41 showed the highest activity among the supported V2O5, Different performances of the supported MoO3 catalysts were explained by the interaction Of Moo(3) with the supports: a strong MoO3/support interaction may result in a poor mobility Of MoO3 and a poor activity for oxidation of carbon by NO2. The high activity Of V2O5/MCM-41 was associated with its catalysis of the oxidation Of SO2 by NO2 to form SO3, which substantially promotes oxidation of carbon by NO2. Addition of transition metal oxides or sulfates to supported MoO3 and V2O5 was also investigated. Combining MoO3 or V2O5 with CuO on SiO2, adding VOSO4 to MoO3/SiO2 or MoO3/Al2O3 and adding TiOSO4 or CuSO4 to V2O5/Al2O3 improved the catalytic performance. (C) 2002 Elsevier Science B.V. All rights reserved.