Abstract
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 (600–850 °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.
Highlights
As it is expected [10], the use of the modified sol-gel synthesis allows a decrease in the calcination temperature required to achieve the perovskite-like structure from 850 ◦ C to 600 ◦ C
Note that BM-C700 shows the best catalytic performance as it features a high amount of oxygen vacancies and high reducibility that promote the highest lattice oxygen mobility
The use of carbon black during the sol-gel synthesis allows the decrease in the calcination temperature required to achieve the perovskite-like structure
Summary
Pollution generated by mobile sources is one of the main problems in urban areas as a consequence of the huge increase in the amount of on-road automobiles. The automotive exhaust is typically composed of nitrogen oxides (NOx ), hydrocarbons (HC), carbon monoxide (CO) and soot (PM) that cause some well-known negative effects on the environment and human health. To regulate the automotive exhaust composition, in Europe, the EuroVI protocol establishes that, since 2015, the levels of NOx and PM have to be reduced by. To meet this regulation, the reduction of NOx is performed by Selective Catalytic Reduction (SCR) and Lean NOx Traps (LNTs), catalytic after-treatment systems [1,2]. All the new vehicles must be equipped with a unit based on a Diesel
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