Simultaneous oxidation of Hg0 and NH3-SCR of NO by nanophase Ce x Zr y Mn z O2 at low temperature: the interaction and mechanism

Abstract

Simultaneous oxidation of Hg and NH-SCR of NO by catalyst is one of the key methods for co-purification of coal-fired flue gas. Till now, the interaction between the oxidation of Hg and NH-SCR of NO and its mechanism have not clarified. In this study, a series of nanophase Ce Zr Mn O was prepared for the simultaneous oxidation of Hg and NH-SCR of NO at low temperature. The catalysts were characterized using surface area analysis, X-ray diffraction, temperature-programmed techniques, and several types of microscopy and spectroscopy. The experimental results indicated that the CeZrMnO exhibited superior Hg removal efficiency (> 99%) and NO conversion efficiency (> 90%) even at 150 °C, and it also exhibited a good durability in the presence of SO and HO. The excellent performance of CeZrMnO on co-purifying Hg and NO was due to the stronger synergistic effects of Ce-Zr-Mn in CeZrMnO than that of the others, which was illustrated by the characterization results of XPS, XRD, and FT-IR. Moreover, it was found that the NO conversion of CeZrMnO could be slightly influenced by Hg and was decreased about 4% to the max, while that of Hg could rarely be affected by the selected catalytic reduction process of NO. It might be due to the co-purification mechanism of NO and Hg. The mechanism of the simultaneous oxidation of Hg and NH-SCR of NO was mainly due to the synergetic effect on the mobility of surface oxygen and the activation of lattice oxygen of CeZrMnO. The effect of the oxidation of Hg on the NH-SCR of NO was mainly due to the absorbed Hg/Hg on the surface of CeZrMnO, which attenuated the formation of NH, -NH, and NH on its acid sites. Similarly, the NH-SCR of NO process could hardly influence the oxidation of Hg when NO and Hg were co-purified.

Poisoning Effect Comparison of ZnCl2 and ZnSO4 on Mn‐Ce/AC Catalyst for Low‐Temperature SCR of NO

“…First, although both of ZnCl 2 and ZnSO 4 would lead to the bad property change of active component Mn, the decrease of Mn 4+ , reducibility of manganese oxide and acid sites was more serious on ZnC−Mn‐Ce/AC catalyst. Besides, loading ZnSO 4 could improve the content of Ce 3+ and O β on the catalyst surface (from XPS result), which was beneficial for enhancing the oxidation ability and the denitrification performance of the catalyst . This mitigated the poisoning effects of ZnSO 4 on Mn−Ce/AC catalyst.…”

“…spectra were made up of Ce 3d 3/2 and Ce3 d/2 , in which u1 and v1 were attributed to Ce 3 + and the others belonged to Ce 4 + . [25][26][27] According to the reference, [20] CeO 2 had the unique ability of storing and releasing oxygen because of the reaction CeO…”

Deactivation Effect of CaO on Mn-Ce/AC Catalyst for SCR of NO with NH3 at Low Temperature

“…More importantly, the peak of Mn 2 O 3 could be detected on CaO poisoning catalyst surface, indicating that part of MnO 2 in AC surface was converted to Mn 2 O 3 . MnO 2 participated in a main catalytic role and promoted the conversion rate of NO to NO 2 [21,22]. The decrease of MnO 2 would definitely cause the reduction of the SCR performance for the catalyst.…”

A Critical Review of Recent Progress and Perspective in Practical Denitration Application

“…The active components were dispersed at atomic level, and the conversion rate was over 90% in the temperature range of 240 to 360 °C (Figure 10c,d). MnOx-based catalysts are currently the focus of low-temperature NH3-SCR flue gas denitrification technology research [168][169][170]. As an active component, MnOx can provide free electrons, which play an important role in the SCR process [171].…”

“…As an active component, MnOx can provide free electrons, which play an important role in the SCR process [171]. Wang et al [172] prepared MnOx catalyst with Na2CO3 as precipitator has a high specific surface area and amorphous framework MnO x -based catalysts are currently the focus of low-temperature NH 3 -SCR flue gas denitrification technology research [168][169][170]. As an active component, MnO x can provide free electrons, which play an important role in the SCR process [171].…”