Overwhelming low ammonia escape and low temperature denitration efficiency via MnO -decorated two-dimensional MgAl layered double oxides

Abstract

Low temperature catalysts are attracting increasing attention in the selective catalytic reduction (SCR) of NO with NH 3 . MnO x -decorated MgAl layered double oxide (Mn/MgAl-LDO) was synthesized via a facile fast pour assisted co-precipitation (FP-CP) process. Compared to the Mn/MgAl-LDO obtained via slow drop assisted co-precipitation (SD-CP) method, the Mn/MgAl-LDO (FP-CP) has excellent activity. The Mn/MgAl-LDO (FP-CP) catalyst was shown to possess a high NO conversion rate of 76%–100% from 25 to 150 °C, which is much better than the control Mn/MgAl-LDO (SD-CP) (29.4%–75.8%). In addition, the Mn/MgAl-LDO (FP-CP) offered an enhanced NO conversion rate of 97% and a N 2 selectivity of 97.3% at 100 °C; the NO conversion rate was 100% and the N 2 selectivity was 90% at 150 °C with a GHSV of 60,000 h −1 . The Mn/MgAl-LDO (FP-CP) catalyst exhibited a smaller fragment nano-sheet structure (sheet thickness of 7.23 nm). An apparent lattice disorder was observed in the HRTEM image confirming the presence of many defects. The H 2 -TPR curves show that the Mn/MgAl-LDO (FP-CP) catalyst has abundant reducing substances. Furthermore, the enhanced surface acidity makes the NH 3 concentration of the Mn/MgAl-LDO (FP-CP) catalyst lower than 100 ml·m −3 after the reaction from 25 to 400 °C. This can effectively reduce the ammonia escape rate in the SCR reaction. Thus, the Mn/MgAl-LDO (FP-CP) catalyst has potential applications in stationary industrial installations for environmentally friendly ultra-low temperature SCR.