Low temperature oxidation of diesel soot particles over one-dimensional 2 × 3 tunnel-structured Na2Mn5O10 catalysts

Abstract

Tunnel-structured manganese oxides have drawn widespread research attention due to their excellent oxidation properties for the soot oxidation reaction. In this study, a series of romanechite Na2Mn5O10 catalysts with a 2 × 3 tunnel structure were synthesized via a facile hydrothermal method. The as-synthesized catalysts were investigated using X-ray diffraction, scanning and transmission electron microscopy, H2 and soot temperature-programmed reduction, O2 temperature-programmed desorption, NO temperature-programmed oxidation, X-ray photoelectron spectroscopy, and other measurements. Among all the catalysts, the Na1MnyOδ-120 catalyst exhibited the best catalytic performance for soot combustion, with T10, T50, and T90 values of 281 ℃, 317 ℃, and 343 ℃, respectively, which were considerably reduced to 271 ℃, 310 ℃, and 335 ℃ in the existence of 10% H2O. The results of multiple characterization methods indicated that the Na2Mn5O10 catalysts exhibit good reducibility, strong oxygen adsorption and activation capacity, and NO to NO2 oxidation ability. Moreover, the active sites (Mn and oxygen vacancies) and reaction mechanism (Langmuir–Hinshelwood) were also revealed by in-situ DRIFT and density functional theory calculations results. This study details a new strategy for the design and synthesis of efficient soot oxidation catalysts with practical application prospects.