Catalytic oxidation of toluene promoted by Mn-Ce solid solutions with multiple active sites and high oxygen mobility

Abstract

In this study, the active site density and lattice oxygen mobility on the surface of (MnCe)O_x solid solution catalysts were synchronously optimized by controlling the ratio and sequence of the addition of tetrapropylammonium hydroxide and dextran. This led to the exceptional performance of co-modified Mn-Ce solid solution catalysts in efficiently degrading toluene. The best catalytic performance of toluene oxidation was achieved after applying 0.1 mol/L tetrapropylammonium hydroxide followed by 2 % dextran modified (MnCe)O_x (0.1T-2 % D-MC). The toluene conversion rate reached 90 % at 211 °C. As observed by scanning electron microscopy (SEM) and Raman spectroscopy (Raman), tetrapropylammonium hydroxide tends to interact with CeO₂, thus generating oxygen vacancies. Meanwhile, the porous structure on the catalyst surface was induced to form, the specific surface area was increased, the active component grain size was reduced, and the active site density was increased. Oxygen temperature programmed desorption (O₂-TPD) and X-ray photoelectron spectroscopy (XPS) results showed that dextran interacted with MnO_x to produce lattice defects, and complexed with metal ions, thus the rate of cycling of lattice oxygen species was increased. The Mn-CeO₂ (111)-O_v-OH model exhibits excellent adsorption capacity for toluene and oxygen molecules (-0.9025 eV, −5.9739 eV). A new approach to utilize organic substances and auxiliary agents with targeting properties as modifiers is proposed in this paper. The limitations of MnCe binary catalysts in practical applications were successfully broken through. A new idea and method for solving related scientific problems are provided by the research results.