Mixed Catalyst SmMn(2)O(5)/Cu-SAPO34 for NH(3)-Selective Catalytic Oxidation

[Image: see text] Low-temperature selective catalytic oxidation (SCO) is crucial for removing the NH(3) slip from the upstream of NH(3)-selective catalytic reduction (NH(3)-SCR). Herein, combining zeolite Cu-SAPO34 and the active oxidant mullite SmMn(2)O(5), we developed mixed-phase catalysts SmMn(2)O(5)/Cu-SAPO34 by grinding powder mixtures to achieve a low-temperature activity and a reasonable N(2) 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 NH(3) oxidation activity showed that for 30 wt % SmMn(2)O(5)/Cu-SAPO34, 90% NH(3) conversion was at a temperature of 215 °C in the presence of 500 ppm NH(3) and 21% O(2) balanced with N(2). The in situ DRIFTS spectra reveal the internal SCR mechanism (i-SCR), i.e., NH(3) 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 NH(3) oxidation via synergistic utilization of the advantages of each individual catalyst.