Mixed Catalyst SmMn₂O₅/Cu-SAPO34 for NH₃-Selective Catalytic Oxidation.

ABSTRACT: Low-temperature selective catalytic oxidation (SCO) is crucial for removing the NH₃ slip from the upstream of NH₃-selective catalytic reduction (NH₃-SCR). Herein, combining zeolite Cu-SAPO34 and the active oxidant mullite SmMn₂O₅, we developed mixed-phase catalysts SmMn₂O₅/Cu-SAPO34 by grinding powder mixtures to achieve a low-temperature activity and a reasonable N₂ selectivity. The physicochemical properties of the catalysts were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) measurement, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The evaluation of NH₃ oxidation activity showed that for 30 wt % SmMn₂O₅/Cu-SAPO34, 90% NH₃ conversion was at a temperature of 215 °C in the presence of 500 ppm NH₃ and 21% O₂ balanced with N₂. The in situ DRIFTS spectra reveal the internal SCR mechanism (i-SCR), i.e., NH₃ oxidizing to NO _x on mullite and NO _x subsequently to proceed with SCR reactions, leading to higher conversion and selectivity over the mixed catalysts. This work provides a strategy to design the compound catalyst to achieve low-temperature NH₃ oxidation via synergistic utilization of the advantages of each individual catalyst.

SUBMITTER: Dong A 

PROVIDER: S-EPMC8928535 | biostudies-literature | 2022 Mar

REPOSITORIES: biostudies-literature