Effect of Indium Addition on the Low-Temperature Selective Catalytic Reduction of NO x by NH3 over MnCeO x Catalysts: The Promotion Effect and Mechanism.

Abstract

A MnCeInOx catalyst was prepared by a coprecipitation method for denitrification of NH3-SCR (selective catalytic reduction). The catalysts were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry, scanning electron microscopy, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller analysis, H2 temperature-programmed reduction, and NH3 temperature-programmed desorption. The NH3-SCR activity and H2O and SO2 resistance of the catalysts were evaluated. The test results showed that the SCR and water resistance and sulfur resistance were good in the range of 125–225 °C. The calcination temperature of the Mn6Ce0.3In0.7Ox catalyst preparation was studied. The crystallization of the Mn6Ce0.3In0.7Ox catalyst was poor when calcined at 300 °C; however, the crystallization is excessive at a 500 °C calcination temperature. The influence of space velocity on the performance of the catalyst is great at 100–225 °C. FTIR test results showed that indium distribution on the surface of the catalyst reduced the content of sulfate on the surface, protected the acidic site of MnCe, and improved the sulfur resistance of the catalyst. The excellent performance of the Mn6Ce0.3In0.7Ox catalyst may be due to its high content of Mn4+, surface adsorbed oxygen species, high specific surface area, redox sites and acid sites on the surface, high turnover frequency, and low apparent activation energy.