Catalytic oxidation for carbon-black simulating diesel particulate matter over promoted Pt/Al2O3 catalysts

Catalytic oxidation activity of carbon-black (CB) simulating the soot of diesel particulate matters to CO2 over 3Pt/Al2O3, 3Pt5Mn/Al2O3 and 3Pt/30Ba–Al2O3 catalysts is investigated with model gases of diesel emission. In case of the large amount of CB compared to the amount of catalyst (3/1, w/w) in the mixture sample, insufficient oxygen at the point of sudden increase in the amount of CO2 is leaded to the partial oxidation using the lattice oxygen of the catalyst. And the peaks of CO2 after the first peak were attributed to the regional combustion of the CB, which was not in contact with catalyst particles. The fresh 3Pt5Mn was estimated to the oxidation states on the catalyst surface by XPS. For used sample at 700 °C, the BEs of Pt 4d5 was revealed to metallic state Pt(0) (314.4 eV) in a predominant levels compared with Pt(II) (317.3 eV). While BEs of Mn 2p were similar to that obtained from the fresh 3Pt5Mn. It is suggested that Pt is in charge of the roles in CB-oxidation, using the lattice oxygen of the catalyst. Two-stage catalytic system with the strategies of promoting the soot oxidation and NOx reduction, simultaneously, were composed of the CB oxidation catalyst and the diesel oxidation catalyst. The catalytic oxidation of CB was accelerated by activated oxidants and exothermic reaction resulted from the diesel oxidation catalyst, which lies in upstream of two-stage. But the system with the CB oxidation catalyst sited in the upstream showed the initiation of CB oxidation at a lower temperature than the other case. Two-stage catalytic system composed of 3Pt5Mn with CB in the upstream and DOC in the downstream showed high oxidation activity with 95% consumption rate of CB to the total loaded CB in the range of 100–500 °C during the TPR process.