Promotion effect and mechanism of the addition of Mo on the enhanced low temperature SCR of NOx by NH3 over MnOx/γ-Al2O3 catalysts

Abstract

A series of Mn/γ-Al2O3 and MnMo/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 to 300°C). The characterization showed that the addition of Mo to the Mn/γ-Al2O3 catalysts could promote the dispersion of MnOx on the surface of γ-Al2O3. The adsorption of NO could form two different species, nitrites and nitrates on the surface of the catalyst. The presence of nitrites is beneficial to low temperature SCR. It is also found that the existence of Mo in the catalyst favours the formation of Mn 3+ , 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 also found that the addition of Mo not only mitigates the deactivation of catalysts, but also broadens the effective temperature range of the SCR catalyst.

Effect of Ordered Mesoporous Alumina Support on the Structural and Catalytic Properties of Mn−Ni/OMA Catalyst for NH3−SCR Performance at Low‐temperature

“…The peak at 640.0 eV represented Mn 2+ (MnO) . The finally peak around 644.5 eV can be correlated to the satellite peak of Mn …”

“…For supported manganese‐based catalysts, the supports is supposed to own a large surface area that makes a critical difference to a better dispersion of manganese oxides, preventing the particles aggregation, and the synergistic effect between the supports and MnO x should be take into consideration. It is well known that γ‐Al 2 O 3 have been extensively exploited as the supports for the immobilization of MnO x or composite MnO x . Compared with γ‐Al 2 O 3 , ordered mesoporous alumina (OMA) owns many admirable characters including large surface area, extremely uniform channels, centralized pore‐size distribution, adjustable pore‐size on a large‐scale, and especially a great deal of Lewis acid sites .…”

A Review of Low Temperature NH3-SCR for Removal of NOx

“…One strategy is to modify the transition metal oxide with one or multiple metal oxides, which could enhance the active sites for the reaction by inducing the synergistic effect [30][31][32][33]. The other approach is to synthesize the supported materials to disperse the transition metal-based oxides which can increase the activity by metal-support interactions [26,[34][35][36][37]. Recently, many supported and mixed transition metal catalyst formulations have been studied to improve the low-temperature SCR performance, as well as resistance to SO 2 /H 2 O.…”

Catalytic Performance of MIL‐88B(V) and MIL‐101(V) MOFs for the Selective Catalytic Reduction of NO with NH3

“…Investigation of the adsorption properties of the materials on the reactants NH 3 and NO will help to further clarify the characteristics of the materials on the SCR reaction [37] . Figure 9 showed the NH 3 ‐TPD desorption diagram of MIL‐88B(V) and MIL‐101(V).…”