MnO_x-supported geopolymer pellets catalysts for low temperature NH₃-SCR: The effect of synthesized temperature

MnOx-supported geopolymer pellets catalysts with 10 wt.% MnOX were prepared by hydrothermal impregnation method at different temperatures. The samples were characterized by X-ray diffraction, Brunauer-Emmett-Teller, BSEM/EDS, X-ray photoelectron spectroscopy, H-2-temperature programmed reduction, NH3-temperature programmed desorption, in-situ Diffuse reflection Fourier transform infrared spectroscopy, and the deNO(x) performances for low-temperature NH3-SCR were tested. The results show that the catalyst synthesized at 120 & DEG;C (named as MG-120 & DEG;C) displays more excellent SCR activity than other catalysts. The NOx conversion efficiency of MG-120 & DEG;C catalyst is & SIM;90% at 120 & DEG;C and & SIM;98% at 280 & DEG;C, and more than 85% N-2 selectivity of MG-120 & DEG;C catalyst can be obtained in the temperature range of 120-200 & DEG;C. The MG-120 & DEG;C catalyst possesses better dispersion of MnOx, multivalent oxidation state of manganese on the surface, higher content of surface chemisorbed oxygen, and more Lewis acid sites and Bronsted acid sites, which promote the reduction of NOx efficiently to proceed simultaneously by the Eley-Rideal mechanism and the Langmuir-Hinshelwood mechanisms.