Abstract
A series of Mn/γ-Al2O3 and MnxMoy/γ-Al2O3 catalysts were prepared by using Incipient Wetness Impregnation (IWI) method. The catalytic performance tests showed that the Mn3Mo1.25/γ-Al2O3 demonstrated a higher SCR performance (NO conversion of around 96%) at a broad low temperature range (150–300 °C). The characterization showed that the addition of Mo to the Mn/γ-Al2O3 catalysts promoted the dispersion of MnOx on the surface of γ-Al2O3. The adsorption of NO could form two different species, i.e., nitrites and nitrates, on the surface of the catalyst. The presence of nitrites is beneficial to low temperature SCR. It is found that the existence of Mo in the catalyst favours the formation of Mn3+, which plays a critical role in the adsorption of NH3 and therefore improves NH3 adsorption capacity of the MnOx/γ-Al2O3 catalysts. The low temperature SCR of the Mn3Mo1.25/γ-Al2O3 catalyst was found to mainly follow L-H mechanism, but E-R mechanism also plays a role to some extent. Moreover, it is found that the addition of Mo not only mitigates the deactivation of the catalysts, but also broadens the effective temperature range of the SCR catalysts.
Highlights
The emission of nitrogen oxides (NOx) from combustion processes is associated with a series of severe environmental problems, such as acid rain and ozone depletion, has become an issue of great concern for decades [1,2,3]
There is a need for the development of low temperature selective catalytic reduction (SCR) catalysts, which has attracted a wide attention in recent years [10, 11]
The manganese-based catalyst is a good alternative to vanadium-based SCR catalysts, which has demonstrated high catalytic activity and selectivity at low temperature [9, 12,13,14,15,16,17,18,19,20]
Summary
The emission of nitrogen oxides (NOx) from combustion processes is associated with a series of severe environmental problems, such as acid rain and ozone depletion, has become an issue of great concern for decades [1,2,3] To address this problem, the selective catalytic reduction (SCR). The addition of transition and/or rare earth metals, such as Fe, Ce and Sb etc, has been found to have positive effects on the performance of these Mn-based catalysts [20, 23,24,25,26] To date, very little work has been carried out on the addition of molybdenum to manganese-based catalysts (MnMo/γ-Al2O3) to improve its low temperature SCR performance [30]. The mechanism of the SCR process over the Mo-modified catalyst at low temperature was investigated
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