An integrated ZnO–SnO2 n–n heterostructure strategy of catalysts and ash for promoting diesel soot combustion
Effective removal of soot deposited in diesel particulate filter by catalysts has attracted great attention in the aftertreatment field to achieve environment protection, but the problem is short by incomplete and poor soot combustion. Herein, an integrated ZnO–SnO 2 semiconductor n–n heterostructure strategy of catalysts and ash is proposed for promoting diesel soot combustion. The integrated effects of different catalysts and ZnO ash on soot oxidation are studied with thermogravimetric analysis and gas emission analysis. The diesel soot is simulated by Printex U (PU) particles, and the catalysts include SnO 2 , ZrO 2 , TiO 2 , CeO 2 and Pt/Al 2 O 3 nanoparticles. Compared with other catalysts, the best catalytic effect on soot oxidation is achieved when SnO 2 catalyst is mixed with PU/ZnO at 1:1:1 mass ratio in tight contact method. The S and R w indexes reach the largest values of 9.33 × 10 –8 % 2 min −2 ℃ −3 and 38.64 × 10 5 , and the CO 2 amount reaches the maximum value at 3462 ppm, which is correspondingly with the XRD and XPS spectrum results of PU/ZnO/SnO 2 with ZnO–SnO 2 heterojunction structure having more adsorbed oxygen. The excessive catalyst is negative to the heat and oxygen transfer among the nanoparticles. When the mass ratio of PU/ZnO/SnO 2 is 1:1:1, the soot combustion presents the comparatively superior state. The results of this study innovate the soot oxidation influenced by catalyst and ash, which benefits the optimization of passive regeneration strategy in DPF application.
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