Soot oxidation over V/ZSM-5 catalysts in a dielectric barrier discharge (DBD) reactor: Performance enhancement by transition metal (Mn, Co and Fe) doping

The oxidation of soot particles over a series of M-V/ZSM-5 (M = Mn, Co and Fe) catalysts was examined in a cylindrical dielectric barrier discharge (DBD) plasma reactor. Soot particles were completely removed in plasma reactor at 60th minute of reaction. The Mn-V/ZSM-5 catalyst showed higher catalytic activity of soot particles than Co-V/ZSM-5, Fe-V/ZSM-5 and VOx/ZSM-5 catalyst in the plasma reactor. However, the variation in CO2 selectivity was opposite to the change in soot oxidation rate. Catalyst characterizations of N2 adsorption-desorption, X-ray diffraction (XRD), X-ray photoelectron spectrometry (XPS) and temperature programmed reduction of hydrogen (H2-TPR) were performed to gain insights of the relationships between catalyst properties and performance of plasma-catalytic soot oxidation. The results substantiated that the concentration of Oads had the most significant effect on the soot oxidation process, while the specific surface area of the M-V/ZSM-5 catalysts showed only minor influence. Moreover, the relative contents of oxygen and V5+ species of the M-V/ZSM-5 catalysts were also the major factors affecting soot oxidation. In addition, higher discharge power and oxygen content were conducive to accelerating soot oxidation. The stability tests showed that the Mn-V/ZSM-5 catalyst maintained good catalytic activity after three cycles of plasma-induced experiments.