BaMn0.7Cu0.3O3 is the most active catalyst for NO2 generation and soot oxidation. This behavior is a result of the enhancement of the redox properties of the catalyst due to the replacement of Mn(iii)/Mn(iv) by Cu(ii) in the perovskite structure.

A series of BaMnO3 solids (BM-CX) were prepared by a modified sol-gel method in which a carbon black (VULCAN XC-72R), and different calcination temperatures (600 °C–850 °C) were used. The fresh and used catalysts were characterized by ICP-OES, XRD, XPS, FESEM, TEM, O2-TPD and H2- TPR-. The characterization results indicate that the use of low calcination temperatures in the presence of carbon black allows decreasing the sintering effects and achieving some improvements regarding BM reference catalyst: (i) smaller average crystal and particles size, (ii) a slight increase in the BET surface area, (iii) a decrease in the macropores diameter range and, (iv) a lower temperature for the reduction of manganese. The hydrogen consumption confirms Mn(III) and Mn(IV) are presented in the samples, Mn(III) being the main oxidation state. The BM-CX catalysts series shows an improved catalytic performance regarding BM reference catalyst for oxidation processes (NO to NO2 and NO2-assisted soot oxidation), promoting higher stability and higher CO2 selectivity. BM-C700 shows the best catalytic performance, i.e., the highest thermal stability and a high initial soot oxidation rate, which decreases the accumulation of soot during the soot oxidation and, consequently, minimizes the catalyst deactivation.

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BaFe1−xCuxO3 perovskites (x = 0, 0.1, 0.3 and 0.4) have been synthetized, characterized and tested for soot oxidation in both Diesel and Gasoline Direct Injection (GDI) exhaust conditions. The catalysts have been characterized by BET, ICP-OES, SEM-EDX, XRD, XPS, H2-TPR and O2-TPD and the results indicate the incorporation of copper in the perovskite lattice which leads to: (i) the deformation of the initial hexagonal perovskite structure for the catalyst with the lowest copper content (BFC1), (ii) the modification to cubic from hexagonal structure for the high copper content catalysts (BFC3 and BFC4), (iii) the creation of a minority segregated phase, BaOx-CuOx, in the highest copper content catalyst (BFC4), (iv) the rise in the quantity of oxygen vacancies/defects for the catalysts BFC3 and BFC4, and (v) the reduction in the amount of O2 released in the course of the O2-TPD tests as the copper content increases. The BaFe1−xCuxO3 perovskites catalyze both the NO2-assisted diesel soot oxidation (500 ppm NO, 5% O2) and, to a lesser extent, the soot oxidation under fuel cuts GDI operation conditions (1% O2). BFC0 is the most active catalysts as the activity seems to be mainly related with the amount of O2 evolved during an. O2-TPD, which decreases with copper content.

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