La and Co Addition to Mn/TiO<sub>2</sub> Catalysts for Enhancing Low-Temperature Denitrification Activity and H<sub>2</sub>O/SO<sub>2</sub> Tolerance
Yan Wang, Huidong Xie, Hu Liu, Ge Mu, Chang Yang, Shouning Chai
Abstract
Manganese oxide-based denitrification catalysts supported by anatase with active components of Mn, Mn–La, Mn–Co, and Mn–La–Co oxides were prepared by a coprecipitation approach, and comparisons of their catalytic activities were made. The influences of Co and La addition on the NO removal and H 2 O/SO 2 tolerance of the MnO x catalysts were investigated. The reasons for the different catalytic performances were investigated by using XRD, XPS, H 2 -TPR, and NH 3 -TPD experiments. The reaction mechanism of selective catalytic reduction of NO x with ammonia was determined by in situ diffuse reflectance infrared Fourier transform spectroscopy. Experiments proved that the addition of Co and La expanded the active temperature window (120–369 °C) and improved the sulfur tolerance due to the increase in the contents of Mn 4+ and surface-active oxygen, along with the enhancement of the redox capacity of the catalyst. Different NH 3 –SCR reaction mechanisms were found over the catalysts Mn–La–Co/TiO 2 and Mn/TiO 2: the former was both the Eley–Rideal and Langmuir–Hinshelwood mechanisms, while the latter followed only the Langmuir–Hinshelwood mechanism. In addition, a “fast SCR” reaction mechanism was active for all catalysts. This work provides useful insights for improving the sulfur tolerance of manganese-based denitrification catalysts.