Promotional effect of microwave hydrothermal treatment on the low-temperature NH3-SCR activity over iron-based catalyst

Abstract

Microwave hydrothermal was introduced into the preparation of iron–cerium–titanium mixed oxide catalyst for NH3-SCR of NOx, and the catalysts after microwave hydrothermal treatment or not are characterized by X-ray diffraction (XRD), Infrared spectrum (IR), Transmission Electron Microscope (TEM), nitrogen adsorption–desorption and temperature programmed desorption (NH3/NO-TPD). Microwave hydrothermal treatment enhanced the low-temperature NH3-SCR activity of iron–cerium–titanium mixed oxide catalyst, and made its NH3-SCR reactive temperature window shift to the low-temperature region. Microwave hydrothermal treatment accelerated the crystallite rate of the precursors for iron–cerium–titanium mixed oxide catalysts, adjusted the microscopic pore structure of catalyst, and enlarged the pore diameter and the pore volume of catalyst. Microwave hydrothermal treatment increases Fe and Ce dispersion on the surface of catalyst, and the molar ratio of Ce3+/Ce4+ on the surface of mixed oxide catalyst could also be enhanced after microwave hydrothermal treatment, and improved the relative concentration of Ce3+, thereby enhanced the oxidation and reduction properties of catalyst. At the same time, microwave hydrothermal treatment enhanced the low-temperature adsorption intensity of NH3 over catalyst, thereby enhanced the low-temperature SCR activity of iron–cerium–titanium mixed oxide catalyst.