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NH3 selective catalytic reduction (NH3-SCR) is the most prevalent and effective method for removing nitrogen oxides. Over the past few decades, manganese (Mn)-based catalysts have demonstrated strong catalytic activity and have been extensively studied for low-temperature NH3-SCR reactions. This paper provides an in-depth introduction to four forms of Mn-based catalysts: single manganese oxide-based catalysts, binary Mn-based metal oxide catalysts, ternary and multivariate Mn-based metal oxide catalysts, and nano-Mn-based catalysts. Advances have been made in enhancing Mn-based catalysts' redox performance and acidity, increasing the active component's dispersion, lowering binding energy, enlarging specific surface area, raising the Mn4+/Mn3+ ratio, and enriching surface adsorbed oxygen by optimizing preparation methods, altering the oxidation state of active components, modifying crystal phases, and adjusting morphology and dispersion, along with various metal modifications. The mechanism of low-temperature NH3-SCR reactions has been elucidated using various characterization techniques. Finally, the research directions and future prospects of Mn-based catalysts for low-temperature NH3-SCR reactions are discussed, aiming to accelerate the commercial application of new Mn-based catalysts. [ABSTRACT FROM AUTHOR]

Catalytic ozonation is a potential technology to eliminate refractory organic contaminants with the low concentration in secondary effluent from industrial park wastewater treatment plants (IPWWTPs). In this study, the catalytic ozonation over the Mn-based catalyst significantly improved the chemical oxygen demand (COD), total organic carbon (TOC), and UV254 removals of secondary effluent from IPWWTPs. The Mn-based catalyst/O3 system achieved 84.8%, 69.8%, and 86.4% removals of COD, TOC, and UV254, which were 3.3, 5.7, and 1.1 times that in ozonation alone, respectively. Moreover, the Mn-based catalytic ozonation process exhibited excellent pH tolerance ranging from pH 4.0 to 9.0. Additionally, the depth analysis based on fluorescence excitation-emission matrix (EEM) confirmed that the catalytic ozonation process preferred to degrade toxic aromatic hydrocarbons. The existence of the Mn-based catalyst/O3 system enhanced 21.4%–38.3% more fluorescent organic matters removal, compared to that in ozonation alone. Mechanistic studies proved that the abundant Lewis acid sites (Mnn+/Mn(n+1)+ and adsorbed oxygen) on the surface of the Mn-based catalyst effectively promoted O3 decomposition into reactive oxygen species (ROS), and ·O2−/HO2· and 1O2 were the main ROS for degrading refractory organic contaminants. The contributions of ROS oxidation (91.2%) was much higher than that of direct O3 oxidation (8.8%). Thus, this work provides an effective advanced treatment process for purifying secondary effluent from IPWWTPs. [ABSTRACT FROM AUTHOR]

NH3 selective catalytic reduction (NH3-SCR) is the most prevalent and effective method for removing nitrogen oxides. Over the past few decades, manganese (Mn)-based catalysts have demonstrated strong catalytic activity and have been extensively studied for low-temperature NH3-SCR reactions. This paper provides an in-depth introduction to four forms of Mn-based catalysts: single manganese oxide-based catalysts, binary Mn-based metal oxide catalysts, ternary and multivariate Mn-based metal oxide catalysts, and nano-Mn-based catalysts. Advances have been made in enhancing Mn-based catalysts’ redox performance and acidity, increasing the active component’s dispersion, lowering binding energy, enlarging specific surface area, raising the Mn4+/Mn3+ ratio, and enriching surface adsorbed oxygen by optimizing preparation methods, altering the oxidation state of active components, modifying crystal phases, and adjusting morphology and dispersion, along with various metal modifications. The mechanism of low-temperature NH3-SCR reactions has been elucidated using various characterization techniques. Finally, the research directions and future prospects of Mn-based catalysts for low-temperature NH3-SCR reactions are discussed, aiming to accelerate the commercial application of new Mn-based catalysts.

Mn/TiO2 series selective catalytic reduction (SCR) catalysts with regular spherical shape could be obtained by ultrasonic spray pyrolysis method. The investigation of experimental parameters, such as decomposition temperature and the type and flow rate of carrier gas, showed that a high and stable NOx conversion at 70% could be achieved at 180 °C when the ultrasonic spray pyrolysis temperature was 500 °C and N2 was used as a carrier gas with a flow rate of 2 L/min. The physical and chemical properties of the catalysts were characterized by X-ray diffraction, SEM, and H2-TPR, revealing that a regular spherical structure, a small amount of Mn2O3 crystals, and high redox ability were the important factors affecting the activity of the catalyst. With these properties, Mn(0.5)/TiO2 (500 °C, N2, 2 L/min) exhibited more than 90% conversion at 240 °C with N2 selectivity above 96%.

The CO-SCR technology based on transition metal is of great significance for NO x removal in large-scale industrial production. However, excess oxygen usually hinders the deNO x reaction in the actual industrial process. In this paper, a series of Mn-based catalysts modified by transition metals (Fe, Ni, Cu) were prepared using the co-precipitation method, which aimed to obtain good CO-SCR performance under O 2 -rich condition. The results showed that the Cu-Mn 2 sample exhibited excellent deNO x performance. Regardless of the presence or absence of oxygen, the NO conversion of Cu-Mn 2 catalyst was remain about 60% and 95% at 350 and 400 ℃, respectively. Differently, the NO conversion of Fe-Mn 2 catalyst significantly increased from approximately 10% to 61% at 400 ℃ after introducing oxygen, which proved that excess oxygen could promote the CO-SCR process over Fe-Mn 2 sample. The varied physical and chemical properties of the prepared materials were thoroughly evaluated through BET, SEM, XRD, XPS and in situ DRIFTS technologies. The results demonstrated that perovskite α-Mn 2 O 3 , decahedral Mn 5 O 8 , Fe 2 O 3 and Fe 3 O 4 crystals were the dominant structures promoting deNO x reaction on the Fe-Mn 2 catalyst. The oxidation of low valence nitrogen oxides by decahedral Mn 5 O 8 on Fe-Mn 2 catalyst was an important factor for oxygen resistance. And the various spinel structures over Ni-Mn 2 , and Cu-Mn 2 indicated strong synergistic effects. For the Cu-Mn 2 catalyst, the strong synergistic effect of Cu-□-Mn species could promote the dissociation of intermediate -NONO. O 2 tended to occupy the surface synergetic oxygen vacancies in Cu-□-Mn species at high temperatures, which could inhibit the dissociation of -NONO and enhance the CO oxidation reaction. The possible reaction mechanisms for CO-SCR over Mn-based catalysts were discussed specifically. [ABSTRACT FROM AUTHOR]

A series of xSm–4Ce–10Mn/TiO2 (x = 0, 2, 4, 6, 8, 10) catalysts were prepared by a reverse co-precipitation method. The catalysts were characterized by XRD, TEM, IR and XPS, and the effects of Sm loading on NO conversion and H2O/SO2 resistance were investigated. Results showed the xSm–4Ce–10Mn/TiO2 exhibited the best low-temperature catalytic activity, N2 selectivity and H2O/SO2 resistance at x = 10. The electronic interactions between Sm and other metals caused the decrease of Mn4+ and Ce3+ content on the surface of the Sm modified catalysts, which was not favorable for the low-temperature activity. However, the increase of surface adsorbed oxygen content contributed to improving the low-temperature activity. In addition, the introduction of Sm resulted in less deposition and easy decomposition of (NH4)2SO4 on the catalyst surface, which improved the H2O/SO2 resistance of the catalyst. [ABSTRACT FROM AUTHOR]

As the crucial role of zeolite catalysts becomes increasingly prominent in refining and petrochemical industries, this study introduces a novel application of xMn / HY catalysts in ethane catalytic dehydrogenation via Chemical Looping Oxidative Dehydrogenation (CL-ODH). The synergistic effect of manganese oxides on the HY framework and a moderate amount of acidic sites within the catalyst facilitates the cleavage of C-H bonds and the desorption of olefins, which are vital for advancing ethane CL-ODH. We identified the reasons for maintaining high ethylene selectivity using advanced characterization techniques such as XRD, SEM, TEM, BET, H 2 -TPR, NH 3 -TPD, and Py-IR. Notably, under optimized conditions at 700 °C with a gas time-space velocity (GHSV) of 1800 mL·h−1·g−1, the 3Mn/HY catalyst achieved approximately 97.1 % selectivity for ethylene and a 22.7 % conversion of ethane. These findings present a scalable route for ethylene production, showcasing significant industrial relevance by potentially reducing energy costs and improving yield. [Display omitted] • New 3Mn/HY catalyst improves ethane CL-ODH efficiency, achieving 97 % ethylene selectivity. • Optimised 3Mn/HY catalyst maintains stable performance after 20 redox cycles at 700°C. • Manganese was added to optimise the acid centre. • Synergistic effect of manganese metal oxides and Lewis acid sites facilitates C-H bond breaking. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nanolaminated MAB phase Mn 2 AlB 2 is discovered for PI activation. • Mn 2 AlB 2 exhibits excellent catalytic activity toward PI activation. • IO 3 , O 2 − and e− co-contributes to TC degradation in Mn 2 AlB 2 /PI system. • Degradation pathways of TC and biotoxicity of intermediates are evaluated in detail. Periodate (PI) is emerged as a chemically stable, ecofriendly and safe solid-oxidant to execute advanced oxidation process (AOP) for water decontamination. Nevertheless, the robust catalytic system to efficiently trigger PI activation still remains scarce. The nanolaminated MAB phase Mn 2 AlB 2 consisting of the MnB bilayer interspersed with Al monolayers has been explored for the first time as a new Mn-based catalyst to activate PI for tetracycline (TC) elimination from water. The Mn 2 AlB 2 catalyst exhibits outstanding catalytic performance, achieving a considerable kinetic rate constant (k) of 0.1732 min−1 within 30 min, which is 5.99 times that of PI alone and even superior to counterparts of Al3+/PI, Mn2+/PI, H 3 BO 3 /PI, Mn 3 O 4 /PI and α-MnO 2 /PI systems. The free radicals of IO 3 and O 2 − combined with nonradical pathway (1O 2 and electron transfer) are responsible for the TC elimination, as evidenced by quenching experiments, electron paramagnetic resonance (EPR) spectroscopy and in situ electrochemical tests. Besides, the TC degradation intermediates are determined and their related toxicities are assessed. This work unveils the PI activation on a new catalytic platform of nanolaminated MAB phase Mn 2 AlB 2 and provides new avenues for the rational design of advanced catalysts for PI-based AOPs. [ABSTRACT FROM AUTHOR]

[Display omitted] NO x and toluene have been identified as the dominant air pollutants in solid wasted combustion, and it is of great importance to remove these two pollutants simultaneously. Here, we found that Mn/CeO 2 and Mn/TiO 2 exhibited a bifunctional property in both NO reduction and toluene oxidation, and both of which could achieve 80% of conversion rate in NO reduction and toluene oxidation processes. However, the activity of both Mn/CeO 2 and Mn/TiO 2 decreased in simultaneous removal of NO x and toluene compared with separate NO x reduction and toluene oxidation. This indicates that there is a mutual inhibition between NO x reduction and toluene oxidation in simultaneous removal process over Mn-based catalysts, attributing to the competitive adsorption and utilization of active oxygen. In detail, the adsorption of toluene occupied the Lewis acid sites and restrained the NH 3 adsorption. Meanwhile, the competitive utilization of active oxygen by NH 3 /NO x inhibited toluene oxidation to CO 2 by active oxygen species as the reaction between NH 3 /NO x and active oxygen species would occur more easily. [ABSTRACT FROM AUTHOR]

The combination of non-thermal plasma (NTP) and catalyst characterized by high energy efficiency, enhanced volatile organic compounds (VOCs) removal efficiency, high product selectivity, and low production of unwanted and/or toxic by-products possesses a great promise for the abatement of VOCs. This work reviews the state of knowledge regarding Mn-based catalysts for VOCs abatement in the post-plasma-catalytic (PPC) system. First, the development and the performance of different Mn-based catalysts such as pure manganese oxide, mixed manganese oxide-based catalysts, and supported Mn-based catalysts in terms of VOCs abatement and O3 decomposition are summarized. Then, the mechanism of the VOCs decomposition in the NTP and PPC system is discussed. Finally, the modeling and simulation of VOCs abatement in the NTP and PPC system are overviewed. This review aims at providing a reference guide for the development and optimization of VOCs abatement in the PPC system using Mn-based catalysts. [ABSTRACT FROM AUTHOR]

The utilization of manganese oxide catalysts in the thermal catalytic degradation of formaldehyde (HCHO) is widespread due to their beneficial catalytic activity, variable structure, and ease of preparation. This study delves into the oxidation reaction of HCHO on the surface of manganese(Ⅲ) oxide(Mn 2 O 3) series catalysts through a combination of experimental and theoretical simulation methods. The influence of alumina (Al 2 O 3) loading and doping with Fe, Ce, Ni, Co, and Cu on the catalyst performance was investigated. Various methods such as X-ray diffraction (XRD), N 2 -adsorption-desorption, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) were used to investigate the structure-activity relationship between the physical morphology and chemical state of catalyst activity and active components. In situ diffuse reflectance infrared Fourier transform spectra (in situ DRIFTS) was used to characterize the intermediates during the reaction and it was found that the major intermediates during formaldehyde oxidation include formate and dioxymethylene (DOM). Throughout the entire reaction process, H 2 O formation had the highest reaction energy barrier (E b = 192.70 kJ/mol), which acted as the rate-determining step of the reaction. The pore structure of the Al 2 O 3 -loaded catalysts was more complex, and the relative content of (O α +O γ) increased, improving the conversion of HCHO. Still, the morphology changed from honeycomb to granular, and the agglomeration phenomenon was obvious, resulting in a decrease in the selectivity of CO 2. In addition, Fe/Ce doping improved the agglomeration phenomenon of the catalyst and promoted the further oxidation of formaldehyde to CO 2. [Display omitted] • Incorporation of Al 2 O 3 loading can effectively improve the problem of CO 2 selectivity lagging. • The possible oxidation pathways of HCHO on the Mn 2 O 3 (110) surface were obtained by Density Functional Theory. • Al 2 O 3 loading and doping with metal ions can significantly increase the specific surface area of catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Catalyst with strong EMSI effect was developed exploiting the confinement effect. • Mn@M2 demonstrates optimal redox performance and the most pronounced EMSI effect. • The electron-rich/poor centers on the Si-O-Mn-O bond facilitate oxygen cycling. • The mechanism of toluene degradation with EMSI effect has been investigated. The non-thermal plasma catalysis holds great promise for VOCs removal, and the development of catalysts with electronic metal-support interaction (EMSI) effect is beneficial for VOCs removal. In this study, we prepared three Mn@M catalysts with EMSI coordination structures by encapsulating MnO x particles within the mesoporous molecular sieve (MCM-41) with different pore size (2.9 nm, 4.4 nm, and 7.9 nm), and investigated the effect of pore size on EMSI and non-thermal plasma catalytic performance of Mn@M for toluene. Among three catalysts, Mn@M2 with an average pore size of 4.38 nm exhibited the strongest EMSI and superior redox capabilities, thus demonstrating the highest mineralization rate, carbon balance, and CO 2 selectivity for plasma catalytic oxidation of toluene. The EMSI effect leads to the formation of electron-rich and electron-poor centers on the Si-O-Mn-O bond, facilitating the generation of reactive oxygen species and enhancing the oxygen cycle. In addition, the reaction degradation pathway was investigated using in situ DRIFTS and GC–MS. This study provides valuable insights for designing highly effective supported catalysts by pore confinement to degrade VOCs in adsorption-plasma catalysis system. [ABSTRACT FROM AUTHOR]

Designing suitable catalysts for efficiently degrading volatile organic compounds (VOCs) is a great challenge due to the distinct variety and nature of VOCs. Herein, the suitability of different typical VOCs (toluene and acetone) over Pt-based catalysts and Mn 2 O 3 was investigated carefully. The activity of Mn 2 O 3 was inferior to Pt-loaded catalysts in toluene oxidation but showed superior ability for destroying acetone, while Pt loading could boost the catalytic activity of Mn 2 O 3 for both acetone and toluene. This suitability could be determined by the physicochemical properties of the catalysts and the structure of the VOC since toluene destruction activity is highly reliant on Pt 0 in the metallic state and linearly correlated with the amount of surface reactive oxygen species (O ads ), while the crucial factor that affects acetone oxidation is the mobility of lattice oxygen (O lat ). The Pt/Mn 2 O 3 catalyst shows highly active Pt-O-Mn interfacial sites, favoring the generation of O ads and promoting Mn-O lat mobility, leading to its excellent performance. Therefore, the design of abundant active sites is an effective means of developing highly adaptive catalysts for the oxidation of different VOCs.

Achieving no or low polychlorinated byproduct selectivity is essential for the chlorinated volatile organic compounds (CVOCs) degradation, and the positive roles of water vapor may contribute to this goal. Herein, the oxidation behaviors of chlorobenzene over typical Mn-based catalysts (MnO 2 and acid-modified MnO 2 ) under dry and humid conditions were fully explored. The results showed that the presence of water vapor significantly facilitates the deep mineralization of chlorobenzene and restrains the formation of Cl 2 and dichlorobenzene. This remarkable water vapor-promoting effect was conferred by the MnO 2 substrate, which could suitably synergize with the postconstructed acidic sites, leading to good activity, stability, and desirable product distribution of acid-modified MnO 2 catalysts under humid conditions. A series of experiments including isotope-traced (D 2 O and H 2 18 O) CB-TPO provided complete insights into the direct involvement of water molecules in chlorobenzene oxidation reaction and attributed the root cause of the water vapor-promoting effect to the proton-rich environment and highly reactive water-source oxygen species rather than to the commonly assumed cleaning effect or hydrogen proton transfer processes (generation of active OOH). This work demonstrates the application potential of Mn-based catalysts in CVOCs elimination under practical application conditions (containing water vapor) and provides the guidance for the development of superior industrial catalysts.

Thermal catalytic degradation of formaldehyde (HCHO) over manganese-based catalysts is garnering significant attention. In this study, both theoretical simulations and experimental methods were employed to elucidate the primary reaction pathways of HCHO on the MnO 2 (110) surface. Specifically, the effects of doping MnO 2 with elements such as Fe, Ce, Ni, Co, and Cu on the HCHO oxidation properties were evaluated. Advanced characterization techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), and X-ray photoelectron spectroscopy (XPS), were employed to discern the physical properties and chemical states of the active components on the catalyst surface. The comprehensive oxidation pathway of HCHO on the MnO 2 (110) surface includes O 2 adsorption and dissociation, HCHO adsorption and dehydrogenation, CO 2 desorption, H 2 O formation and desorption, oxygen vacancy supplementation, and other elementary reactions. The pivotal rate-determining step was identified as the hydrogen migration process, characterized by an energy barrier of 234.19 kJ mol−1. Notably, HCHOO and *CHOO emerged as crucial intermediates during the reaction. Among the doped catalysts, Fe-doped MnO 2 outperformed its counterparts doped with Ce, Ni, Co, and Cu. The optimal degradation rate and selectivity were achieved at a molar ratio of Fe: Mn = 0.1. The superior performance of the Fe-doped MnO 2 can be ascribed to its large specific surface area, conducive pore structure for HCHO molecular transport, rich surface-adsorbed oxygen species, and a significant presence of oxygen vacancies. • Thermal catalytic degradation of HCHO by metal atom-doped Mn-based catalysts. • The degradation pathway of HCHO on the catalyst surface was simulated. • Connection between catalyst physicochemical properties and CO 2 selectivity. [ABSTRACT FROM AUTHOR]

• Mn-Ce/Ti-H exhibits over 80% NO x conversion at 160–330 °C for NH 3 -SCR. • H 2 O 2 addition improve dispersion of Ce, mn species on TiO 2 and increase Mn4+ Ce3+ and surface active o. • Mn-Ce synergism improve redox capability and facilitate electron transfer of the catalysts. • Mn4+and surface active o facilitate the low-temperature activity via fast SCR route. • The addition of w can significantly increase the amount of intermediate-strong acidic sites of the catalyst. A series of MnO x /TiO 2 based NO x reduction catalyst was prepared by excessive impregnation method. The catalyst was modified by Ce, W and oxidizing agent H 2 O 2. Mn-Ce/Ti-H and Mn-Ce-W/Ti-H catalysts exhibit the best low temperature activity (nearly 80% NO x conversion at 155–325 °C) and the widest active temperature range (nearly 80% NO x conversion at 180–420 °C), respectively. Property and structure of the modified catalyst were characterized by XRD, TEM, XPS, H 2 -TPR, NH 3 -TPD, etc. It is found that oxidizing agent H 2 O 2 , as well as the high dispersion and specific surface area, can increase the amount of Mn4+, Ce3+ and active oxygen sites on catalyst surface, and the synergistic interaction between Mn and Ce facilitated redox process of the catalysts. These can improve the low temperature activity of the catalyst by facilitating "fast SCR" reaction. The addition of W increased acidity of the catalyst and improved high temperature catalytic activity of the catalyst. [Display omitted] [ABSTRACT FROM AUTHOR]

A new type of low-temperature NH 3 -SCR catalyst with a chemical composition of Cu w Mn y Ti 1-y O x was prepared from layered double hydroxides precursors for the first time. The purpose of this novel design is to improve the De-NO x efficiency and SO 2 resistance of Mn-based catalysts. The Cu 1 Mn 0.5 Ti 0.5 O x catalyst achieved a NO x conversion as high as 90% at 200 °C, which is much higher than that of the control catalysts Cu-Mn/TiO 2 (86.1%) and Mn/TiO 2 (80.7%). The properties of catalysts were characterized in detail using a series of physico-chemical techniques including XRD, BET, FTIR, SEM, TEM, H 2 -TPR, NH 3 -TPD, TGA, and XPS analyses. The excellent catalytic performance of Cu 1 Mn 0.5 Ti 0.5 O x catalyst can be associated with its higher specific surface area and surface acidity, and more active MnO 2 and CuO species. Besides, when copper oxide is introduced, the catalysts showed significant resistance to 100 ppm SO 2 and 5% H 2 O. Finally, the poisoning mechanism and the regenerability of Cu 1 Mn 0.5 Ti 0.5 O x catalyst was proposed. In short, the newly designed Cu 1 Mn 0.5 Ti 0.5 O x catalyst was found to have higher catalytic activity and excellent SO 2 and H 2 O resistance compared to the control catalysts of Cu-Mn/TiO 2 and Mn/TiO 2 . [ABSTRACT FROM AUTHOR]

Different location Cu species on the SiO 2 @Mn catalysts surface was prepared to form well-defined core-shell material for enhancing the catalytic efficiency of degrading Na 2 S in waste water. The modified location of Cu species was tuned through changing the order of impregnation. The species of Cu in the middle layer perform the best activity and selectivity. Integrating XRD, HAADF-STEM, H 2 -TRP, UV–vis, XPS, CV and Na 2 S removal tests, the decisive factor for improved the catalytic efficiency for Na 2 S removal probably is the unique structural advantages of Cu species in the middle layer, which produces higher ratio of Mn 4+ /(Mn 4+  + Mn 3+ ) and provides rich surface active oxygen. And Na 2 S in waste water could be degraded as high as 92.77% in 4 h with air as an oxidant at ambient conditions. Recycling experiments indicate that no significant deactivation occurred for the catalysts during tests in seven times. This work provides a novel sight for preparing high-efficient and stable catalysts for Na 2 S degradation. [ABSTRACT FROM AUTHOR]

We report a novel NH 3 -SCR catalyst Cu 0.5 Mg 1.5 Mn 0.5 Al 0.5 O x synthesized from layered double hydroxides with superior activity in a wide temperature range and improved SO 2 and H 2 O resistance comparing to conventional doped Mn/γ-Al 2 O 3 . This catalyst results in a high NO x removal efficiency of 87.0–96.6% in the low temperature range of 100–250 °C, much better than Mn/γ-Al 2 O 3 (35.0–67.2%). Besides, it exhibits significant resistance to SO 2 and H 2 O due to the existence of Cu and Mg. The promoting effects of Cu and Mg are thoroughly investigated using various physico-chemical techniques. The superior NH 3 -SCR activity of Cu 0.5 Mg 1.5 Mn 0.5 Al 0.5 O x catalyst can be associated with its high specific surface area, high reducibility of MnO 2 and CuO species, abundance of acid sites, and the well dispersion of MnO 2 and CuO species. The interactions between SO 2 and NH 3 , and the degradation mechanism caused by SO 2 were investigated using in-situ DRIFT analysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • Effect of SO 2 over Hg0 oxidation on MnO 2 (1 1 0) surface was studied by DFT method. • SO 2 could be retained on the MnO 2 surface in a chemisorption type. • Hg0 adsorption was inhibited by adsorbed SO 2 due to the competitive repulsion. • Hg0 oxidation at the active site adjacent to adsorbed SO 2 was obviously restrained. • Hg0 oxidation at the nonadjacent site to adsorbed SO 2 was little influenced. The inferior sulfur resistance is a major technical bottleneck of Mn-based catalysts to be employed as low-temperature selective catalytic reduction (SCR) catalyst for elemental mercury (Hg0) oxidation. The first-principle calculation based on density functional theory was adopted to investigate the influence of SO 2 on mercury adsorption and oxidation over the MnO 2 surface. The results indicated that Hg0 preferred to adsorb at the hollow and O br bridge sites on the surface, and the adsorption of HgO was a strong chemisorption behavior. SO 2 could be retained on the MnO 2 surface through chemisorption. The adsorbed SO 2 generated inhibition on Hg0 adsorption by the competitive and repulsive effects, while the effect of SO 2 on HgO adsorption was negligible. SO 2 showed almost no impact on the adsorption and dissociation of O 2. Hg0 adsorption and oxidation at the active sites adjacent to the adsorbed SO 2 was apparently restrained on the SO 2 -covered surface, and the desorption of generated HgO became easier compared to that on the clean surface. By contrast, Hg0 oxidation at the nonadjacent sites to SO 2 was little influenced by the adsorbed SO 2. The study results would offer guidance for impairing the inhibitory effect of SO 2 and improving the SO 2 resistance of Mn-based catalysts. [ABSTRACT FROM AUTHOR]

Mn-based catalysts have excellent deNO x performance, but they suffer from the toxic effects of SO 2 and H 2 O easily. Ni and Ce doping can enhance SO 2 and H 2 O resistance of Mn-based catalysts, while the microscopic mechanism of modification remains unclear and needs further investigation. In this study, the effects of Ni and Ce doping on SO 2 and H 2 O resistance over the β-MnO 2 (1 1 0) surface was explored by a density functional theory. Results indicate that Ni and Ce doping can limit the adsorption of SO 2 and H 2 O at the main sites, especially Ce doping. Although Ce cannot prevent SO 2 from occupying the Ce-top site, it promotes the production of Brønsted acid sites on the surface, which is conducive to SCR deNO x reaction. The presence of Ce has a greater inhibitory effect on SO 2 oxidation than Ni, which can inhibit the formation of (NH 4) 2 SO 4 and NH 4 HSO 4. In addition, Ce can significantly promote the dissociation of *H 2 O and thus re-expose the Lewis active sites to the NH 3 -SCR process. These results offer insights into the mechanism of modification at the molecular level not available experimentally and provide theoretical guidance for the development of Mn-based catalysts with improved SO 2 and H 2 O resistance. [Display omitted] • Ni and Ce doping can limit the adsorption of SO 2 and H 2 O at the main active sites. • Ce inhibits the oxidation of SO 2 on the β-MnO 2 (1 1 0) surface more strongly than Ni • Lewis active sites are re-exposed due to *H 2 O successive dissociation promoted by Ce. • Mechanisms of Ni and Ce to improve SO 2 and H 2 O resistance of β-MnO 2 is revealed. [ABSTRACT FROM AUTHOR]

Mn 2 O 3 as a typical Mn based semiconductor has attracted growing attention due to its peculiar 3 d electron structure and stability, and the multi-valence Mn on the surface is the key to peroxydisulfate activation. Herein, an octahedral structure of Mn 2 O 3 with (111) exposed facet was synthesized by a hydrothermal method, which was further sulfureted to obtained a variable-valent Mn oxide for the high activation efficiency of peroxydisulfate under the light emitting diode irradiation. The degradation experiments showed that under the irradiation of 420 nm light, S modified manganese oxide showed an excellent removal for tetracycline within 90 min, which is about 40.4% higher than that of pure Mn 2 O 3. In addition, the degradation rate constant k of S modified sample increased 2.17 times. Surface sulfidation not only increased the active sites and oxygen vacancies on the pristine Mn 2 O 3 surface, but also changed the electronic structure of Mn due to the introduce of surface S2−. This modification accelerated the electronic transmission during the degradation process. Meanwhile, the utilization efficiency of photogenerated electrons was greatly improved under light. Besides, the S modified manganese oxide had an excellent reuse performance after four cycles. The scavenging experiments and EPR analyses showed that •OH and 1O 2 were the main reactive oxygen species. This study therefore provides a new avenue for further developing manganese-based catalysts towards high activation efficiency for peroxydisulfate. [Display omitted] • The S-modified manganese oxide were synthesized by hydrothermal process. • ·OH and 1O 2 were the main ROS in the M-1S-90/PDS/LED light system. • The introduction of S greatly promoted the LED light response and valence cycle of Mn. • A reasonable PDS activation mechanism was put forward. [ABSTRACT FROM AUTHOR]

Herein, two simple model catalysts (Mn 3 O 4 and MnFeO x) were fabricated and operated under different temperatures (100, 150, 200, 250 °C) in SCR atmosphere with the presence of SO 2 , followed by thermal regeneration and characterizations to reveal the deactivation mechanism and the role of FeO x. The results indicated both catalysts exhibited temperature-dependent deactivation behavior, where the total activity loss displayed volcano-type SO 2 resistance tendency within 100–250 °C and the most severe activity loss (98 % for Mn 3 O 4 and 81 % for MnFeO x) was found at 150 °C. Meanwhile, the higher relative proportion of irreversible activity loss was found at lower temperatures, which is associated with the more easily saturated chemical adsorption of SO 2 as evidenced by SO 2 +O 2 breakthrough test. At higher temperatures, the SO 2 oxidation and its further transformation into NH 4 HSO 4 could be favored, thus resulting in increased reversible activity loss. The FeO x modification can protect MnO x species from sulfation to a certain degree and lower the irreversible deactivation, which is evidenced by the binding energy upshift and downshift of Fen+ species after being poisoned and regenerated, as well as the slightly changed binding energy of Mnn+ species from the XPS analysis. [Display omitted] • The impact of test temperature on SO 2 resistance over Mn-based catalysts was studied. • Volcano-type SO 2 resistance was found over Mn-based catalysts within 100–250 °C. • The most severe deactivation of the catalyst occurred at 150 °C. • Irreversible deactivation at low temperature is related to SO 2 adsorption saturation. • The formation of NH 4 HSO 4 favors reversible deactivation at higher temperatures. [ABSTRACT FROM AUTHOR]

The development of a cost-effective and eco-friendly catalyst with superior activity for low-temperature selective catalytic reduction of NO X with NH 3 (NH 3 -SCR) is an urgent issue. In this work, a series of CeMn- supported montmorillonite (MMT) were synthesized via a cation exchange reaction. The effects of the valence state of the Mn precursor, acid or base pretreatment of MMT, and the molar ratio of Ce/Mn on zCeMn(x)-MMT(y) were examined. The XRD results revealed that the layer spacing of MMT increased due to Mn3+ of acetate manganese showing the highest cation exchange efficiency. Therefore, Mn(C)-MMT has stronger electronegative and abundant acidic sites, which facilitates the adsorption of NH 3. In addition, the dispersion and uniformity of Mn(C)-MMT(12) were improved under the base pretreatment with pH = 12, as confirmed by TEM. To further improve the redox ability, the coexistence of CeO 2 favors the production of Mn4+, Ce3+, and adsorbed oxygen species, as confirmed by XPS analysis, thereby facilitating NO oxidation and improving NO X conversion by fast-SCR. Accordingly, 2CeMn(C)-MMT(12) with high dispersion and acidity and abundant Mn species exhibited a NO X conversion of 41% at 100 °C and 85% at 250 °C, invoking an applicable and efficient performance for low-temperature SCR. [Display omitted] • MMT shows higher NO X conversion than other supports commonly used in SCR. • Mn3+ of acetate manganese shows the highest cation exchange efficiency with MMT. • Base pretreatment of MMT improves the dispersion and uniformity of Mn(C)-MMT(12). • 2CeMn(C)-MMT(12) with abundant Mn4+, Ce3+, and O Ads increases NO X conversion. [ABSTRACT FROM AUTHOR]

[Display omitted] • Adsorption behavior of gas molecules at the main active sites adjacent to Pb and Zn and the doping sites were revealed. • Pb and Zn dopings have a negative effect on the generation of *NH 2 and *O. • The detrimental effect on the deNO x of Pb is severer than that of Zn. • The inhibition mechanisms of Pb and Zn on the deNOx were discussed. Mn-based catalysts are promising materials for the removal of NO x by NH 3 -SCR reaction. Heavy metals can cause the deactivation of deNO x of catalysts. However, the inactivation mechanism of catalysts requires further research. In this paper, the effects of Pb and Zn doping on the deNO x reaction over the β-MnO 2 catalyst were investigated by the DFT method, and the poisoning mechanism of heavy metals on the catalyst was revealed. Pb and Zn can not only inhibit the adsorption of NH 3 and O 2 at the peripheral sites, but also weaken the adsorption properties of NH 3 at the doping sites, leading to a decrease in the activity of the β-MnO 2 catalyst. Meanwhile, Pb and Zn can limit the formation and decomposition of *NH 2 NO intermediates, which is detrimental to the SCR reaction. In addition, the production of hydroxyl groups is restricted due to Pb and Zn preventing the formation of *H and *O. Although Pb and Zn can make the conversion of hydroxyl groups to *H 2 O easier, it is not enough to compensate for the restricted *H 2 O generation caused by the large reduction in the number of hydroxyl groups, and the deNO x reaction is ultimately inhibited. [ABSTRACT FROM AUTHOR]

Herein, MnOx catalysts were prepared by in situ pyrolysis of Mn metal organic frameworks (Mn-MOF). The Mn-5TA with proper doping of tartaric acid (Mn-MOF/ tartaric acid mass ratio of 5), exhibited superior catalytic activity and stability towards catalytic removal of toluene under simulated real-exhaust conditions. Mn3+ and oxygen vacancies were beneficial for toluene degradation, whereas Mn3+ can generate oxygen vacancies to maintain charge conservation and then responsible for toluene adsorption and generation of intermediates. In addition, the oxygen vacancies were explored by EPR, Raman and O 2 -TPD. Compared with other catalysts, Mn-5TA has higher oxygen vacancy contents. Meanwhile, in-situ DRIFTS also indicated that oxygen vacancies could play a key role in the adsorption-oxidation process of toluene. Therefore, the present study provides a simple method to introduce and control the content of oxygen vacancies, and the obtained results provide a new strategy for the rational design of efficient catalytic materials for the elimination of volatile organic compounds. • The oxygen vacancy-rich MnOx catalysts were prepared by in situ pyrolysis of Mn metal organic frameworks (Mn-MOF). • The Mn-5TA with proper doping of tartaric acid exhibited superior catalytic activity and stability towards catalytic removal of toluene. • Low-valence Mn can be generated oxygen vacancies to maintain charge conservation. • Oxygen vacancies could play a key role in the adsorption-oxidation process of toluene. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mn, Ce, W, and Fe were co-doped on cordierite honeycomb. • Ce, W, and Fe doping regulated and maintained ratio between Mn3+ and Mn4+. • SCR performances were thus significantly improved. • Low-temperature catalytic activity was increased. • Hydrothermal stability was enhanced. Mn-based catalyst is widely investigated in selective catalytic reduction (SCR) of nitrogen oxide (NO), and shows high NO conversion at low temperatures. However, most reports emphasize on powder catalyst instead of monolithic one. In this work, Mn-containing cordierite honeycomb and CeWFe co-doping comparisons were synthesized and applied in SCR. As a result, MnCeWFe showed the best catalytic activity, selectivity, temperature window, and hydrothermal stability. It removed 90.4% of NO together with a selectivity of 97.7% at 150 °C, and removed over 90% of NO from 150 °C to 250 °C. Even after a hydrothermal treatment, the activity of MnCeWFe was only decreased from 90.4% to 75.4% at 150 °C. In comparison, the activity of Mn was decreased from 60.7% to 32.4%. According to X-ray photoelectron spectroscopy and Diffuse Reflection Fourier Transform Infrared, CeWFe co-doping made the ratio between Mn3+ and Mn4+ close to 1:1, maintained this ratio under hydrothermal environment, and carried out SCR by both Eley-Rideal and Langmuir-Hinshelwood mechanisms, thus resulting in good performances. This work is in favor of developing an effective catalyst for industrial application. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mn-based catalyst with hollow spherical structure was prepared by hydrothermal method. • The coating of TiO 2 layer expanded the operating temperature window of the catalysts. • The deposition of hydrophobic layer effectively improved the water resistance. The Mn-based catalyst with hollow spherical structure was prepared by hydrothermal method and used for selective catalytic reduction (SCR) of NO with NH 3. Mn-based catalysts exhibit excellent de-NO x performance at low-temperature, but narrow operating temperature window and poor water resistance restrict its application. Effectively expanding the operating temperature window and improving the H 2 O resistance of the Mn-based catalyst are the keys to industrial application. In this article, the H-MnO 2 catalyst was prepared by hydrothermal method and modified by kinetic adsorption and vapor deposition methods. The TiO 2 layer can effectively limit the excessive redox performance and improve the acidity of the catalyst surface, the NO conversion above 90% at 140–380 °C of H-MnO 2 @TiO 2 catalyst. The phenyltrimethoxysilane was deposited on the surface of the H-MnO 2 @TiO 2 catalyst by vapor deposition method. The NO conversion rate of the H-MnO 2 @TiO 2 @HL catalyst exceeds 80% in the temperature range of 180–380 °C. When the H 2 O was introduced, the NO conversion rate increases from 70% to 85% at 180 °C. The in situ DRIFTs results showed NH 3 and NO could be adsorbed and activated on the catalyst surface, and the catalytic reaction follows Langmuir-Hinshelwood (L-H) mechanism. Under the presence of H 2 O, the NH 4 + bonding to Brønsted acid sites were inhibited but the NH 3 bonding to Lewis acid site was almost unaffected. In summary, through two-step modification, the operating temperature window and water resistance of Mn-based catalysts are effectively improved. It can be seen that a reasonable structure design can effectively improve the comprehensive performance of the catalyst. [ABSTRACT FROM AUTHOR]

• The doping of Si increased the surface acidity and inhibited the NH 3 oxidation. • The 0.3Mn/Ce 8 Si 2 O x -R exhibited large amount of Mn4+, Ce3+, and oxygen vacancies. • The interaction between Mn and Ce-SiO x was improved by the citric acid method. • The 0.3Mn/Ce 8 Si 2 O x -R-CA exhibited excellent Fast-SCR reaction via [NO]/[NO 2 ] = 1. A series of Mn/CeSiO x catalysts were synthesized to investigate the Ce/Si ratios and morphology effect of Ce/SiO x support for the selective catalytic reduction (SCR) of NO with NH 3 at low temperature. The characterization and catalytic test showed that the 0.3Mn/Ce 8 Si 2 O x -R catalyst exhibits high NO x conversion at low temperature. The Ce/Si ratio was 8/2 over the 0.3Mn/Ce 8 Si 2 O x -R catalyst, increasing the surface acidity and inhibiting the side reaction of NH 3. The {1 1 0} and {1 0 0} facts of the nanorod structure are rich in Ce3+ species and oxygen vacancies for the SCR reaction. Moreover, the citric acid method was employed on 0.3Mn/Ce 8 Si 2 O x -R-CA to improve the interaction between Mnn+ and Ce 8 Si 2 O x -R and enhance the strength of surface acidity, leading to the highest NO x conversion and Fast-SCR process. During the suppression effect of SO 2 or HCl on catalytic activity, the 0.3Mn/Ce 8 Si 2 O x -R-CA catalyst shows higher poison resistance to HCl than SO 2. [ABSTRACT FROM AUTHOR]

• The oxygen vacancy defect engineering can be fine-manipulated via a double-complexation-assisted strategy. • Tailoring oxygen vacancy defects on these catalysts can greatly improve the activation and generation of products. • The C C cleavage of benzoate species could be the rate-controlling step in the toluene oxidation process. • Quasi in situ XPS confirms that increasing Mn4+ content plays the crucial role in the toluene oxidation. • Both lattice oxygen and adsorbed oxygen species can participate in the activation-oxidation process of toluene. To elucidate the role of oxygen vacancy defects, various Mn-based oxides with oxygen vacancy defects are employed to the toluene oxidation, which are synthesized by adjusting solvent and double-complexation routes. The MnO x -ET catalyst shows the highest catalytic activity (T 90 = 225 °C) for toluene oxidation. Compared with other Mn-based oxides, the as-prepared MnO x -ET catalyst has more surficial oxygen vacancies and good oxygen storage capacity (OSC), which is the reason on its remarkable activity for toluene oxidation. In addition, in situ DRIFTS study reveals that both lattice oxygen and adsorbed oxygen species can participate in the activation-oxidation process of toluene, which results in two reaction routes for the toluene oxidation. The rich oxygen-vacancy concentration of catalysts accelerates the key steps for the activation and generation of oxidized products. Quasi-in situ XPS results further confirm that enrich adsorbed-oxygen species as active oxygen and increasing Mn4+ concentration enhance the superior activity for toluene oxidation. [ABSTRACT FROM AUTHOR]