Catalytic combustion of soot over Ru-doped mixed oxides catalysts

We employed modified substrates as outer heterogeneous catalysts to reduce the soot originating from the incomplete diesel combustion. Here, we proposed that ceria (CeO₂)-based catalysts could lower the temperature at which soot combustion occurred from 610 °C to values included in the operation range of diesel exhausts (270–400 °C). Here, we used the sol-gel method to synthesize catalysts based on mixed oxides (ZnO:CeO₂) deposited on cordierite substrates, and modified by ruthenium nanoparticles. The presence of ZnO in these mixed oxides produced defects associated with oxygen vacancies, improving thermal stability, redox potential, sulfur resistance, and oxygen storage. We evaluated the morphological and structural properties of the material by X-ray diffraction (XRD), Brumauer-emmett-teller method (BET), temperature programmed reduction (H₂-TPR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). We investigated how the addition of Ru (0.5 wt.%) affected the catalytic activity of ZnO:CeO₂ in terms of soot combustion. Thermogravimetric analysis (TG/DTA) revealed that presence of the catalyst decreased the soot combustion temperature by 250 °C, indicating that the oxygen species arose at low temperatures, which was the main reason for the high reactivity of the oxidation reactions. Comparative analysis of soot emission by diffuse reflectance spectroscopy (DRS) showed that the catalyst containing Ru on the mixed oxide-impregnated cordierite samples efficiently oxidized soot in a diesel stationary motor: soot emission decreased 80%.