Up-scaled flash nano-precipitation production route to develop a MnOx–CeO2–Al2O3 catalyst with enhanced activity and H2O resistant performance for NOx selective catalytic reduction with NH3

Abstract

The synthesis of a MnOx–CeO2–Al2O3 composite catalyst using the flash nano-precipitation (FNP) method and its application to the selective catalytic reduction of NOx with NH3 (NH3-SCR) was performed and compared with the same catalyst obtained via the impregnation method. Using the MnOx–CeO2–Al2O3 catalyst from FNP, 90% NOx conversion was achieved between 150 and 300°C with a gas hourly space velocity of 15,300h−1. When 5 vol% H2O was added to the simulated flue gases, the NOx conversion was maintained above 90%. Both catalysts were characterized using XRD, XPS, BET, SEM, TEM, element mapping, and H2-TPR. The characterization results showed that mixed crystals of cerium, aluminum, and manganese oxides were formed through the FNP method, and the ratio of Mn4+ and Ce3+ increased, which promoted the catalytic activity at lower temperature compared to the impregnation method. The MnOx–CeO2–Al2O3 catalyst exhibited an enhanced pore structure, with a BET surface area of approximately 207.5m2/g, a pore volume of approximately 0.23cm3/g, and an average pore diameter of approximately 8.2nm, while for the catalyst from the impregnation method the BET surface area was 125.3m2/g, pore volume was 0.17cm3/g and pore size was 5.4nm. The performance of the MnOx–CeO2–Al2O3 catalyst was significantly better, and the effects of some inhibitors on the reduction of NOx were less than with the reference catalysts from the impregnation method. The FNP method could be applicable at an industrial scale to produce cost-effective catalysts.