Synthesis and characterization of CuO/Nb2O5/MCM-41 for the catalytic oxidation of diesel soot

This work deals with the preparation and application of new catalysts based on CuO, Nb2O5, and Si-MCM-41 for the abatement of diesel soot particulates. The properties of Si-MCM-41 mesoporous material were enhanced by studying the effect of the template removal method on specific surface area, terminal silanol groups, and long-range ordering. Template removal experiments indicated that thermal decomposition by double-step calcination at 300 °C for 3 h and 550 °C for 3 h produced a material with the best morphological characteristics. This material was used to prepare CuO/Nb2O5/MCM-41 catalysts with a 1:1 mass ratio (CuO:Nb2O5) and 2, 5, 10, 15, and 25 wt.% loadings. The incorporation of CuO and Nb2O5 leads to the formation of well-dispersed small crystallites and an amorphous phase, respectively, for the samples with lower oxide loadings. For the samples with higher oxide loadings, the crystallites increase in size, leading to the formation of copper–niobium mixed oxide phases and agglomerates. All the prepared materials presented considerable activity towards the oxidation of diesel soot particulates, shifting the maximum oxidation temperature (Tox) to lower values. The most promising catalyst was CuO/Nb2O5/MCM-41 with 25 wt.% of each oxide, which presented an onset temperature of 388 °C and appreciable activity at temperatures as low as 450 °C without the addition of any chemical promoter.