High deNOx performance of Mn/TiO2 catalyst by NH3

A High-Performance Mn/TiO2 Catalyst with a High Solid Content for Selective Catalytic Reduction of NO at Low-Temperatures

Mn/TiO2 catalysts with varying solid contents were innovatively prepared by the sol-gel method and were used for selective catalytic reduction of NO at low temperatures using NH3 (NH3-SCR) as the reducing agent. Surprisingly, it was found that as the solid content of the sol increased, the catalytic activity of the developed Mn/TiO2 catalyst gradually increased, showing excellent catalytic performance. Notably, the Mn/TiO2 (50%) catalyst demonstrates outstanding denitration performance, achieving a 96% NO conversion rate at 100 °C under a volume hourly space velocity (VHSV) of 24,000 h-1, while maintaining high N2 selectivity and stability. It was discovered that as the solid content increased, the catalyst's specific surface area (SSA), surface Mn4+ concentration, chemisorbed oxygen, chemisorption of NH3, and catalytic reducibility all improved, thereby enhancing the catalytic efficiency of NH3-SCR in degrading NO. Moreover, NH3 at the Lewis acidic sites and NH4+ at the Bronsted acidic sites of the catalyst were capable of reacting with NO. Conversely, NO and NO2 adsorbed on the catalyst, along with bidentate and monodentate nitrates, were unable to react with NH3 at low temperatures. Consequently, the developed catalyst's low-temperature catalytic reaction mechanism aligns with the E-R mechanism.

Preparation of Mn/TiO2 catalysts using recovered manganese from spent alkaline batteries for low-temperature NH3-SCR

Black mass (BM) from spent alkaline Zn-MnO2 batteries was used for the first time as a Mn source in the preparation of Mn/TiO2 catalysts for low-temperature NH3-selective catalytic reduction (SCR) of NOx. To recover Mn species and eliminate alkali and Zn species, BM powder underwent DI-water washing, followed by carbothermal reduction. The resulting slags were further dissolved in HNO3, loaded onto TiO2 particles with ball milling, and then subjected to calcination. Nearly 100% of Zn species were removed from the BM via carbothermal reduction at 950 °C for 4 h with 5.0 wt% activated carbon. The resulting catalyst, derived from the treated BM, achieved similar NOx conversion (97%) as the catalyst prepared using a reagent-grade Mn chemical at 160 °C but a higher NOx-to-N2 conversion rate at 78%. The promoted N2 selectivity was attributed to a high Mn4+/Ti ratio and the presence of impurities from BM, such as Fe3+ ions, which enhanced oxidation ability of the catalyst. Conversely, insufficient removal of Zn or carbon additives in the slags led to a decreased Mn concentration, an increased proportion of Mn2+/Mn3+ species, increased surface OH groups, and reduced oxidation ability on the surface, thus reducing NOx conversion and N2 selectivity.

A Review of Mn-Based Catalysts for Abating NOx and CO in Low-Temperature Flue Gas: Performance and Mechanisms

Mn-based catalysts have attracted significant attention in the field of catalytic research, particularly in NOx catalytic reductions and CO catalytic oxidation, owing to their good catalytic activity at low temperatures. In this review, we summarize the recent progress of Mn-based catalysts for the removal of NOx and CO. The effects of crystallinity, valence states, morphology, and active component dispersion on the catalytic performance of Mn-based catalysts are thoroughly reviewed. This review delves into the reaction mechanisms of Mn-based catalysts for NOx reduction, CO oxidation, and the simultaneous removal of NOx and CO. Finally, according to the catalytic performance of Mn-based catalysts and the challenges faced, a possible perspective and direction for Mn-based catalysts for abating NOx and CO is proposed. And we expect that this review can serve as a reference for the catalytic treatment of NOx and CO in future studies and applications.

Promoting effect of Ru-doped Mn/TiO2 catalysts for catalytic oxidation of chlorobenzene

Mn/TiO2 catalysts were synthesized using deposition-precipitation method. Ru-doped Mn/TiO2 catalysts were prepared by incipient-wetness impregnation method. To investigate the effect of Ru and Mn species, the catalytic performances of Mn/TiO2...

Theoretical Design of Transition Metal-Doped TiO2 for the Selective Catalytic Reduction of NO with NH3 by DFT Calculations

Many transition metal oxides supported on TiO2 have been studied for selective catalytic reduction (SCR) of NO with NH3. However, the trade-off exists between the low-temperature activity and N2 selectivity....

Improvement of the activity and SO2 tolerance of Sb-modified Mn/PG catalysts for NH3-SCR at a low temperature

A series of MnM/palygorskite (PG) (M = La, W, Mo, Sb, Mg) catalysts was prepared by the wetness co-impregnation method for low-temperature selective catalytic reduction (SCR) of NO with NH₃. Conversion efficiency followed the order Sb > Mo > La > W > Mg. A combination of various physico-chemical techniques was used to investigate the influence of Sb-modified Mn/PG catalysts. MnSb_0.156/PG catalyst showed highest NO conversion at low temperatures in the presence of SO₂ which reveals that addition of Sb oxides effectively enhances the SCR activity of catalysts. A SO₂ step-wise study showed that MnSb_0.156/PG catalyst displays higher durable resistance to SO₂ than Mn/PG catalyst, where the sulfating of active phase is greatly inhibited after Sb doping. Scanning electron microscopy and X-ray diffraction results showed that Sb loading enhances the dispersion of Mn oxides on the carrier surface. According to the results of characterization analyses, it is suggested that the main reason for the deactivation of Mn/PG is the formation of manganese sulfates which cause the permanent deactivation of Mn-based catalysts. For Sb-doped Mn/PG catalyst, SO_x ad-species formed were mainly combined with SbO_x rather than MnO_x. This preferential interaction between SbO_x and SO₂ effectively shields the MnO_x as active species from being sulfated by SO₂ resulting in the improvement of SO₂ tolerance on Sb-added catalyst. Multiple information support that, owing to the addition of Sb, original formed MnO_x crystallite has been completely transformed into highly dispersed amorphous phase accounting for higher SCR activity.

MnO2 -Based Materials for Environmental Applications

Manganese dioxide (MnO₂ ) is a promising photo-thermo-electric-responsive semiconductor material for environmental applications, owing to its various favorable properties. However, the unsatisfactory environmental purification efficiency of this material has limited its further applications. Fortunately, in the last few years, significant efforts have been undertaken for improving the environmental purification efficiency of this material and understanding its underlying mechanism. Here, the aim is to summarize the recent experimental and computational research progress in the modification of MnO₂ single species by morphology control, structure construction, facet engineering, and element doping. Moreover, the design and fabrication of MnO₂ -based composites via the construction of homojunctions and MnO₂ /semiconductor/conductor binary/ternary heterojunctions is discussed. Their applications in environmental purification systems, either as an adsorbent material for removing heavy metals, dyes, and microwave (MW) pollution, or as a thermal catalyst, photocatalyst, and electrocatalyst for the degradation of pollutants (water and gas, organic and inorganic) are also highlighted. Finally, the research gaps are summarized and a perspective on the challenges and the direction of future research in nanostructured MnO₂ -based materials in the field of environmental applications is presented. Therefore, basic guidance for rational design and fabrication of high-efficiency MnO₂ -based materials for comprehensive environmental applications is provided.

Performance Evaluation of a Novel Thermal Power Plant Process with Low-Temperature Selective Catalytic Reduction

We present the concept of a novel thermal power plant process in conjunction with low-temperature selective catalytic reduction (SCR). This process can be employed to achieve modern standards for NOx emissions and solve problems related to post-gas cleaning processes, such as thermal fatigue, catalyst damage, and an increase in differential pressure in the boiler. Therefore, this study is aimed at evaluating the performance of a novel flue-gas cleaning process for use in a thermal power plant, where a low-temperature SCR is implemented, along with the existing SCR. We developed a process model for a large-scale power plant, in which the thermal power plant was divided into a series of heat exchanger block models. The mass and energy balances were solved by considering the heat transfer interaction between the hot and cold sides to obtain the properties of each material flow. Using the process model, we performed a simulation of the new process. New optimal operating conditions were derived, and the effects that the new facilities have on the existing process were evaluated. The results show that the new process is feasible in terms of operating stability and cost, as well as showing an increase in the boiler thermal efficiency of up to 1.3%.

Mechanism and regeneration of sulfur-poisoned Mn-promoted calcined NiAl hydrotalcite-like compounds for C3H6-SCR of NO

The selective catalytic reduction of NO with propene (C₃H₆-SCR) in the presence of SO₂ was investigated over a series of Mn-promoted calcined NiAl hydrotalcite-like compounds. The obtained 5% MnNiAlO catalyst exhibits superior NO conversion efficiency (95%) at 240 °C, and excellent sulfur-poisoning resistance. The possible reaction pathways of the catalytic process were proposed according to several characterization measurements. It is demonstrated that Mn-promoted NiAlO catalysts enhance the Brønsted acid sites and surface active oxygen groups, and improve the redox properties by the redox cycle (Ni³⁺ + Mn²⁺ ↔ Ni²⁺ + Mn⁴⁺). Thus, the amount of the reaction intermediates is improved, and the reactivities between C_xH_yO_z species and nitrite/nitrate species are promoted. Furthermore, in the presence of SO₂, the MnNiAlO samples can give rise to minor formation of sulfate and inhibit the competitive adsorption effectively due to their nitrite/nitrate species being more abundant and stable. Finally, regeneration was studied using in situ FTIR and the water washing method showed the best performance on the regeneration of S-poisoned catalysts.

The selective catalytic reduction of NO with propene (C₃H₆-SCR) in the presence of SO₂ was investigated over a series of Mn-promoted calcined NiAl hydrotalcite-like compounds.

A superior Fe-V-Ti catalyst with high activity and SO2 resistance for the selective catalytic reduction of NOx with NH3

A series of Fe-V-Ti oxide catalysts were prepared by a co-precipitation method, among which the Fe_0.1V_0.1TiO_x catalyst showed the optimal NH₃-SCR performance and excellent SO₂ resistance. Fe_0.1V_0.1TiO_x achieved > 90% NO_x conversion at 225-450 °C under a GHSV of 200,000 h^-1. When introducing SO₂ and H₂O to the SCR reaction for 24 h, the NO_x conversion maintained a level above 93% at 250 °C. The Raman and Mössbauer spectra showed that FeVO₄ and Fe₂O₃ coexisted on the surface of TiO₂. In Fe-V-Ti catalysts, the charge interaction between Fe₂O₃ and FeVO₄ as well as the electronic inductive effect between Fe and V species resulted in the improvement of SCR activity and N₂ selectivity at high temperatures. The NH₃-SCR process on the Fe_0.1V_0.1TiO_x catalyst mainly followed the Eley-Rideal (E-R) reaction mechanism with gaseous NO reacting with adsorbed NH₃ adsorbed species.

Tourmaline-Modified FeMnTiO x Catalysts for Improved Low-Temperature NH3-SCR Performance

Low temperature NH₃ selective catalytic reduction (NH₃-SCR) technology is an efficient and economical strategy for cutting NO _x emissions from power-generating equipment. In this study, a novel and highly efficient NH₃-SCR catalyst, tourmaline-modified FeMnTiO _x is presented, which was synthesized by a simple one-step sol-gel method. We found that the amount of tourmaline has an important impact on the catalytic performance of the modified FeMnTiO _x-based catalysts, and the NO _x conversion exceeded 80% from 160 to 380 °C with the addition of 5 wt % tourmaline. Compared with the pure FeMnTiO _x, the catalytic efficiency at a temperature below 100 °C was increased by nearly 18.9%, and the operation temperature window was broadened significantly. The enhanced catalytic performance of the FeMnTiO _x catalyst was mainly attributed to the small spherical nanoparticles structure around the tourmaline powders, resulting in the increased content of Mn³⁺, Mn⁴⁺, and chemical oxygen on the catalytic surface. These as-developed tourmaline-modified FeMnTiO _x materials have been demonstrated to be promising as a new type highly efficient low temperature NH₃-SCR catalyst.

Effect of initial support particle size of MnO x /TiO2 catalysts in the selective catalytic reduction of NO with NH3

A series of manganese-based catalysts supported by 5-10 nm, 10-25 nm, 40 nm and 60 nm anatase TiO2 particles was synthesized via an impregnation method to investigate the effect of the initial support particle size on the selective catalytic reduction (SCR) of NO with NH3. All catalysts were characterized by transmission electron microscopy (TEM), N2 physisorption/desorption, X-ray diffraction (XRD), temperature programmed techniques, X-ray photoelectron spectroscopy (XPS) and in situ diffuse reflectance infrared transform spectroscopy (DRIFTS). TEM results indicated that the particle sizes of the MnO x /TiO2 catalysts were similar after the calcination process, although the initial TiO2 support particle sizes were different. However, the initial TiO2 support particle sizes were found to have a significant influence on the SCR catalytic performance. XPS and NH3-TPD results of the MnO x /TiO2 catalysts illustrated that the surface Mn4+/Mn molar ratio and acid amount could be influenced by the initial TiO2 support particle sizes. The order of surface Mn4+/Mn molar ratio and acid amount over the MnO x /TiO2 catalysts was as follows: MnO x /TiO2(10-25) > MnO x /TiO2(40) > MnO x /TiO2(60) > MnO x /TiO2(5-10), which agreed well with the order of SCR performance. In situ DRIFTS results revealed that the NH3-SCR reactions over MnO x /TiO2 at low temperature occurred via a Langmuir-Hinshelwood mechanism. More importantly, it was found that the bridge and bidentate nitrates were the main active substances for the low-temperature SCR reaction, and bridge nitrate adsorbed on Mn4+ showed superior SCR activity among all the adsorbed NO x species. The variation of the initial TiO2 support particle size over MnO x /TiO2 could change the surface Mn4+/Mn molar ratio, which could influence the adsorption of NO x species, thus bringing about the diversity of the SCR catalytic performance.

A study on the NH3-SCR performance and reaction mechanism of a cost-effective and environment-friendly black TiO2 catalyst

In this paper, black TiO2 without adding active components was developed for NH3-SCR-DeNOx. The catalytic activity tests showed that the NO removal efficiency of black TiO2 was always greater than 90% at 330-390 °C, which almost reached that of the commercial NH3-SCR-DeNOx catalyst. XRD, UV-vis, TG, EPR, XPS, H2-TPR, DFT and NH3-TPD analyses were carried out to study the structure-effectiveness relationship. We found that a large number of oxygen vacancies were formed over the black TiO2 surface. It was not only promoted the adsorption of NH3via direct (oxygen vacancies as Lewis acid sites for NH3 adsorption) and indirect (oxygen vacancies promote the formation of surface hydroxyl groups, which are Brønsted acid sites for NH3 adsorption) forms, but also improved the redox properties by promoting the reduction of Ti4+ to Ti3+. These changes lead to the superior catalytic activity of black TiO2 for NH3-SCR-DeNOx. Additionally, an in situ DRIFT study demonstrated that the NH3-SCR-DeNOx reaction over black TiO2 occurred via the Eley-Rideal (E-R) mechanism. Finally, the catalytic stability and resistance to H2O and SO2 of the black TiO2 catalyst were studied, and it showed good performances. This study offered new and important insights into the understanding of the role of oxygen vacancies in determining the physical and chemical properties of catalysts.

Low-temperature co-purification of NOx and Hg0 from simulated flue gas by CexZryMnzO2/r-Al2O3: the performance and its mechanism

In this study, series of Ce_xZr_yMn_zO₂/r-Al₂O₃ catalysts were prepared by impregnation method and explored to co-purification of NO_x and Hg⁰ at low temperature. The physical and chemical properties of the catalysts were investigated by XRD, BET, FTIR, NH₃-TPD, H₂-TPR, and XPS. The experimental results showed that 10% Ce_0.2Zr_0.3Mn_0.5O₂/r-Al₂O₃ yielded higher conversion on co-purification of NO_x and Hg⁰ than the other prepared catalysts at low temperature, especially at 200-300 °C. 91% and 97% convert rate of NO_x and Hg⁰ were obtained, respectively, when 10% Ce_0.2Zr_0.3Mn_0.5O₂/r-Al₂O₃ catalyst was used at 250 °C. Moreover, the presence of H₂O slightly decreased the removal of NO_x and Hg⁰ owing to the competitive adsorption of H₂O and Hg⁰. When SO₂ was added, the removal of Hg⁰ first increased slightly and then presented a decrease due to the generation of SO₃ and (NH₄)₂SO₄. The results of NH₃-TPD indicated that the strong acid of 10% Ce_0.2Zr_0.3Mn_0.5O₂/r-Al₂O₃ improved its high-temperature activity. XPS and H₂-TPR results showed there were high-valence Mn and Ce species in 10% Ce_0.2Zr_0.3Mn_0.5O₂/r-Al₂O₃, which could effectively promote the removal of NO_x and Hg⁰. Therefore, the mechanisms of Hg⁰ and NO_x removal were proposed as Hg (ad) + [O] → HgO (ad), and 2NH₃/NH₄⁺ (ad) + NO₂ (ad) + NO (g) → 2 N₂ + 3H₂O/2H⁺, respectively. Graphical abstract ᅟ.

A comparative study on the Mn/TiO2-M(M = Sn, Zr or Al) Ox catalysts for NH3-SCR reaction at low temperature

A series of TiO₂-M(M = Sn, Zr or Al) O_x were prepared and manganese oxide (MnO_x) was supported on the carrier by the traditional impregnation method for low-temperature selective catalytic reduction (SCR) of NO_x with ammonia as a reductant. The obtained catalysts were characterized by XRD, BET, high-resolution transmission electron microscope (HRTEM), H₂-TPR, NH₃-TPD, X-ray photoelectron spectroscopy (XPS) and in situ Fourier-transform infrared (FT-IR) and their catalytic activities for NO_x reduction with NH₃ in the presence of SO₂ were investigated comparatively. The results showed that the highest NO_x conversion of over 90% could be obtained with the Mn/Ti-Sn catalyst at a wide range of temperature window of 150-270°C. The combination of characterization techniques, such as BET, XRD and HRTEM, revealed that manganese oxides were well dispersed on Ti-Sn. H₂-TPR suggested that Ti-Sn and Ti-Zr supports could enhance the reduction ability of catalysts. Accordingly, Mn/Ti-Al exhibited worse activity at low temperature. XPS results were in good agreement with H₂-TPR results, and Mn/Ti-Sn had more surface-reducible species of Mn⁴⁺ ions and more surface-adsorbed oxygen species, which was conducive to SCR reaction. The in situ FT-IR spectra of NH₃ adsorption indicated that all the modified catalysts had more Lewis acid sites and the amide species at 1506 cm^-1 had a certain influence on the catalytic reaction at low temperature. Mn/Ti-Zr showed a stronger resistance to SO₂ but Mn/Ti-Al was affected more adversely and all the catalysts could not be restored to the initial catalytic activity after stopping feeding SO₂. NH₃-TPD revealed that the total acid amount of the Mn/Ti-Sn sample was larger than other samples, which indicated that the Ti-Sn solid solution could provide more surface acid sites over the catalyst.

Insight into the synergism between MnO2 and acid sites over Mn-SiO2@TiO2 nano-cups for low-temperature selective catalytic reduction of NO with NH3

The rational synthesis of low-temperature catalysts with high catalytic activity and stability is highly desirable for the selective catalytic reduction of NO with NH3. Here we synthesized a Mn-SiO2/TiO2 nano-cup catalyst via the coating of the mesoporous TiO2 layers on SiO2 spheres and subsequent inlay of MnO2 nanoparticles in the narrow annulus. This catalyst exhibited superior catalytic SCR activities and stability for low-temperature selective catalytic reduction of NO with NH3, with NO conversion of ∼100%, N2 selectivity above 90% at a temperature ∼140 °C. The characterization results, such as BET, XRD, H2-TPR, O2/NH3-TPD and XPS, indicated that this nano-cup structure catalyst possesses high concentration and dispersion of Mn4+ active species, strong chemisorbed O- or O2 2- species and highly stable MnO X active components over the annular structures of the TiO2 shell and SiO2 sphere, and thus enhanced the low-temperature SCR performance.

Promotional Effects of Ti on a CeO2-MoO3 Catalyst for the Selective Catalytic Reduction of NOx with NH3

In this study, Ti was doped to CeO₂-MoO₃ to promote the catalytic performance for the selective catalytic reduction of NO_x with NH₃ (NH₃-SCR). The preparation method for CeMo_0.5Ti_aO_x (a = 0, 1, 2, 5, 10) catalysts was a stepwise precipitation method. When Ti was doped, all of the Ce-Mo-Ti catalysts exhibited remarkably improved NO_x conversion and N₂ selectivity than the CeMo_0.5O_x without Ti. The CeMo_0.5Ti₅O_x with excellent activity in a broad temperature range was selected as an optimal catalyst to investigate the effects of Ti addition. The formation process analysis of the CeMo_0.5Ti₅O_x showed that, the Mo and Ti species first precipitated together from the mixed solution with the increase of pH, and then Ce species precipitated onto the Mo-Ti precipitates. The obtained catalyst exhibited remarkably facilitated NO_x and NH₃ adsorption, enhanced charge imbalance, promoted redox property, and improved surface acidity, which are all important reasons for the excellent catalytic performance of an NH₃-SCR catalyst.

Integrated removal of NO and mercury from coal combustion flue gas using manganese oxides supported on TiO2

A catalyst composed of manganese oxides supported on titania (MnO_x/TiO₂) synthesized by a sol-gel method was selected to remove nitric oxide and mercury jointly at a relatively low temperature in simulated flue gas from coal-fired power plants. The physico-chemical characteristics of catalysts were investigated by X-ray fluorescence (XRF), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analyses, etc. The effects of Mn loading, reaction temperature and individual flue gas components on denitration and Hg⁰ removal were examined. The results indicated that the optimal Mn/Ti molar ratio was 0.8 and the best working temperature was 240°C for NO conversion. O₂ and a proper ratio of [NH₃]/[NO] are essential for the denitration reaction. Both NO conversion and Hg⁰ removal efficiency could reach more than 80% when NO and Hg⁰ were removed simultaneously using Mn0.8Ti at 240°C. Hg⁰ removal efficiency slightly declined as the Mn content increased in the catalysts. The reaction temperature had no significant effect on Hg⁰ removal efficiency. O₂ and HCl had a promotional effect on Hg⁰ removal. SO₂ and NH₃ were observed to weaken Hg⁰ removal because of competitive adsorption. NO first facilitated Hg⁰ removal and then had an inhibiting effect as NO concentration increased without O₂, and it exhibited weak inhibition of Hg⁰ removal efficiency in the presence of O₂. The oxidation of Hg⁰ on MnO_x/TiO₂ follows the Mars-Maessen and Langmuir-Hinshelwood mechanisms.

Mechanistic Investigation into the Effect of Sulfuration on the FeW Catalysts for the Selective Catalytic Reduction of NOx with NH3

Iron tungsten (FeW) catalyst is a potential candidate for the selective catalytic reduction (SCR) of NO_x with ammonia because of its excellent performance in a wide operating window. Sulfur poisoning effects in SCR catalysts have long been recognized as a challenge in development of efficient catalysts for applications. In this paper, the impact of sulfuration on catalyst structure, NH₃-SCR reaction performance and mechanism was systematically investigated through spectroscopic and temperature-programmed approaches. The sulfuration inhibited the SCR activity at low temperatures (<300 °C), while no evident effect was observed at high temperatures (≥300 °C). After sulfuration for FeW oxides catalyst, the organic-like with covalent S═O bonds sulfate species were mainly formed over the FeW catalysts. Combining TPD with in situ DRIFTS results, it was found that the Lewis and the Brønsted acidity were enhanced by the interaction between metal species and sulfate species due to the strong electron withdrawing effect of the S═O double bonds. The in situ DRIFTS study showed that the formation of NO₂ was hindered, leading to the "fast-SCR" pathway was partly cut off by the sulfuration process and thereby the loss of SCR activity at low temperatures. However, the Langmuir-Hinshelwood reaction pathway between adsorbed NH₃/NH₄⁺ species and nitrate species was facilitated and dominated at high temperatures, making the as-synthesized FeW catalysts resistant to SO₂ poisoning.

The enhanced resistance to P species of an Mn–Ti catalyst for selective catalytic reduction of NOx with NH3 by the modification with Mo

The modification of Mn–Ti catalyst by Mo could enhance its resistance to P species.

A review of Mn-containing oxide catalysts for low temperature selective catalytic reduction of NOx with NH3: reaction mechanism and catalyst deactivation

The reactions over Mn-containing selective catalytic reduction (SCR) catalysts.

Influence of tungsten on the NH3-SCR activity of MnWOx/TiO2 catalysts

A series of bulk MnWO_x and supported MnWO_x/TiO₂ catalysts with MnWO₄ structure were prepared via self-propagating high-temperature synthesis (SHS), co-precipitation and impregnation methods.

In situ fabrication of porous MnCoxOy nanocubes on Ti mesh as high performance monolith de-NOx catalysts

Porous MnCo_xO_y nanocubes on Ti mesh as monolith catalysts present enhanced de-NO_x performance.

A highly efficient CeWOx catalyst for the selective catalytic reduction of NOx with NH3

Characterization was used to investigate the main reasons for the highly efficient NO_x abatement by the CeWO_x catalyst.

The enhanced performance of a CeSiOx support on a Mn/CeSiOx catalyst for selective catalytic reduction of NOx with NH3

A series of Mn/CeSiO_x catalysts were prepared by the wet impregnation method and used for selective catalytic reduction of NO with NH₃.

A mechanistic DFT study of low temperature SCR of NO with NH3 on MnCe1−xO2(111)

The mechanism of low temperature SCR of NO with NH₃ catalyzed by MnCe_1−xO₂(111) has been explored by density functional theory.

Highly dispersed MnOx nanoparticles supported on three-dimensionally ordered macroporous carbon: a novel nanocomposite for catalytic reduction of NOx with NH3 at low temperature

A novel MnO_x/3DOMC nanocomposite is fabricated via a simple multicomponent infiltration of three-dimensionally ordered templates, and exhibits superior NH₃-SCR of NO_x performance.

Promotion mechanism of CeO2addition on the low temperature SCR reaction over MnOx/TiO2: a new insight from the kinetic study

A new insight into CeO₂addition on the SCR reaction over MnO_x/TiO₂was drawn according to steady-state kinetic analysis.

Effects of different manganese precursors as promoters on catalytic performance of CuO–MnOx/TiO2 catalysts for NO removal by CO

Since the formation of the surface synergetic oxygen vacancy SSOV (Cu⁺–□–Mn³⁺) in the xCuyMn(N)/TiO₂ catalyst is easier than that (Cu⁺–□–Mn²⁺) in the xCuyMn(A)/TiO₂ catalyst, the activity of the xCuyMn(N)/TiO₂ catalyst is higher than that of the xCuyMn(A)/TiO₂ catalyst.

The mechanism of the effect of H2O on the low temperature selective catalytic reduction of NO with NH3 over Mn–Fe spinel

H₂O effect on NO reduction over Mn–Fe spinel was related to the competition adsorption and the decrease in oxidation ability.

Effect of SO2 on SCR activity of MnOx/PG catalysts at low temperature

Palygorskite (PG)-supported manganese oxide catalysts (MnOx/PG) were prepared for the selective catalytic reduction (SCR) of NO with ammonia in the presence of SO

A combinatorial chemistry method for fast screening of perovskite-based NO oxidation catalyst

A fast parallel screening method based on combinatorial chemistry (combichem) has been developed and applied in the screening tests of perovskite-based oxide (PBO) catalysts for NO oxidation to hit a promising PBO formulation for the oxidation of NO to NO2. This new method involves three consecutive steps: oxidation of NO to NO2 over a PBO catalyst, adsorption of NOx onto the PBO and K2O/Al2O3, and colorimetric assay of the NOx adsorbed thereon. The combichem experimental data have been used for determining the oxidation activity of NO over PBO catalysts as well as three critical parameters, such as the adsorption efficiency of K2O/Al2O3 for NO2 (α) and NO (β), and the time-average fraction of NO included in the NOx feed stream (ξ). The results demonstrated that the amounts of NO2 produced over PBO catalysts by the combichem method under transient conditions correlate well with those from a conventional packed-bed reactor under steady-state conditions. Among the PBO formulations examined, La0.5Ag0.5MnO3 has been identified as the best chemical formulation for oxidation of NO to NO2 by the present combichem method and also confirmed by the conventional packed-bed reactor tests. The superior efficiency of the combichem method for high-throughput catalyst screening test validated in this study is particularly suitable for saving the time and resources required in developing a new formulation of PBO catalyst whose chemical composition may have an enormous number of possible variations.

Mechanism of N2O formation during the low-temperature selective catalytic reduction of NO with NH3 over Mn-Fe spinel

The mechanism of N2O formation during the low-temperature selective catalytic reduction reaction (SCR) over Mn-Fe spinel was studied. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and transient reaction studies demonstrated that the Eley-Rideal mechanism (i.e., the reaction of adsorbed NH3 species with gaseous NO) and the Langmuir-Hinshelwood mechanism (i.e., the reaction of adsorbed NH3 species with adsorbed NOx species) both contributed to N2O formation. However, N2O selectivity of NO reduction over Mn-Fe spinel through the Langmuir-Hinshelwood mechanism was much less than that through the Eley-Rideal mechanism. The ratio of NO reduction over Mn-Fe spinel through the Langmuir-Hinshelwood mechanism remarkably increased; therefore, N2O selectivity of NO reduction over Mn-Fe spinel decreased with the decrease of the gas hourly space velocity (GHSV). As the gaseous NH3 concentration increased, N2O selectivity of NO reduction over Mn-Fe spinel increased because of the promotion of NO reduction through the Eley-Rideal mechanism. Meanwhile, N2O selectivity of NO reduction over Mn-Fe spinel decreased with the increase of the gaseous NO concentration because the formation of NH on Mn-Fe spinel was restrained. Therefore, N2O selectivity of NO reduction over Mn-Fe spinel was related to the GHSV and concentrations of reactants.