Significant Effects of Adding Mode on Low-Temperature De-NOx Performance and SO2 Resistance of a MnCeTiOx Catalyst Prepared by the Co-Precipitation Method

Three MnCeTiOx catalysts with the same composition were prepared by conventional co-precipitation (MCT-C), reverse co-precipitation (MCT-R), and parallel co-precipitation (MCT-P), respectively, and their low-temperature SCR performance for de-NOx was evaluated. The textural and structural properties, surface acidity, redox capacity, and reaction mechanism of the catalysts were investigated by a series of characterizations including N2 adsorption and desorption, XRD, SEM, XPS, H2-TPR, NH3-TPD, NO-TPD, and in situ DRIFTs. The results revealed that the most excellent catalytic performance was achieved on MCT-R, and more than 90% NOx conversion can be obtained at 100–300 °C under a high GHSV of 80,000 mL/(gcat·H). Furthermore, MCT-R possessed optimal tolerance to H2O and SO2 poisoning. The excellent catalytic performance of MCT-R can be attributed to its larger BET specific surface area; higher contents of Mn4+, Ce3+, and adsorbed oxygen species; and more adsorption capacity for NH3 and NO. Moreover, in situ DRIFTs results indicated that the NH3-SCR reaction follows simultaneously the Langmuir–Hinshelwood and Eley–Rideal mechanisms at 100 °C. By adjusting the adding mode during the co-precipitation process, excellent low-temperature de-NOx activity of MCT-R can be obtained simply and conveniently, which is of great practical value for the preparation of a MnCeTiOx catalyst for denitrification.