Gaseous Heterogeneous Catalytic Reactions over Mn-Based Oxides for Environmental Applications: A Critical Review

Abstract

Manganese oxide has been recognized as one of the most promising gaseous heterogeneous catalysts due to its low cost, environmental friendliness, and high catalytic oxidation performance. Mn-based oxides can be classified into four types: (1) single manganese oxide (MnOx), (2) supported manganese oxide (MnOx/support), (3) composite manganese oxides (MnOx-X), and (4) special crystalline manganese oxides (S-MnOx). These Mn-based oxides have been widely used as catalysts for the elimination of gaseous pollutants. This review aims to describe the environmental applications of these manganese oxides and provide perspectives. It gives detailed descriptions of environmental applications of the selective catalytic reduction of NOx with NH, the catalytic combustion of volatile organic compounds, Hg oxidation and adsorption, and soot oxidation, in addition to some other environmental applications. Furthermore, this review mainly focuses on the effects of structure, morphology, and modified elements and on the role of catalyst supports in gaseous heterogeneous catalytic reactions. Finally, future research directions for developing manganese oxide catalysts are proposed.

Simultaneous Control of NOx-Soot by Substitutions of Ag and K on Perovskite (LaMnO3) Catalyst

“…Generally, the A site is lanthanum and the B-site is a transition metal like Co, Mn, Cu, etc. Catalysts with Mn at B-site have been reported with considerable activity for the simultaneous soot-NOx reaction [20]. Also, as reported by Wang et al [16], silver substitution at A site enhances the activity of LaMnO3 by lowering the soot ignition temperature (Ti), the temperature for maximum soot combustion (Tp) and increasing the %NOx reduction.…”

Effect of Crystal Phase of MnO2 with Similar Nanorod‐Shaped Morphology on the Catalytic Performance of Benzene Combustion

“…The transition and rare earth metal oxides (Fe 2 O 3 , MnO 2 [11 ‐ 13] and Co 3 O 4 [14 ‐ 16] ), which show high activity on the VOCs catalytic combustion, are regarded as an alternative to noble‐metal catalysts due to their low price. Manganese oxides (MnO x ), because of variable oxidation states from +2 to +7, are one of the most active oxide catalysts in the abatement of VOCs . In the past years, extensive efforts have been paid on the effect of crystal structures and morphology on the oxidation reactions through adjusting the synthetic conditions.…”

Facet‐Dependent Activity of Co3O4 Catalyst for C3H8 Combustion

“…Therefore, much attention has been paid to the non-noble metal oxide catalysts, for example Co 3 O 4 , [13] MnO x , [14] CeO 2 [15,16] and mixed oxides such as spinels [17,18] and perovskites. [19] Among them, Co 3 O 4 is one of the most active catalysts towards catalytic combustion.…”