Design of meso-TiO2@MnO(x)-CeO(x)/CNTs with a core-shell structure as DeNO(x) catalysts: promotion of activity, stability and SO2-tolerance

Synthesis of MnO2-CuO-Fe2O3/CNTs catalysts: low-temperature SCR activity and formation mechanism

MnO₂-CuO-Fe₂O₃/CNTs catalysts, as a low-dimensional material, were fabricated by a mild redox strategy and used in denitration reactions. A formation mechanism of the catalysts was proposed. NO conversions of 4% MnO₂-CuO-Fe₂O₃/CNTs catalyst of 43.1-87.9% at 80-180 °C were achieved, which was ascribed to the generation of amorphous MnO₂, CuO and Fe₂O₃, and a high surface-oxygen (O_s) content.

Dual Promotional Effects of TiO2-Decorated Acid-Treated MnO x Octahedral Molecular Sieve Catalysts for Alkali-Resistant Reduction of NO x

Alkali metals generated during waste incineration in power stations are not conducive to the control of nitrogen oxide (NO _x) emission. Hence, improved selective catalytic reduction of NO _x with ammonia (NH₃-SCR) in the presence of alkali metals is a major issue for practical NO _x removal. In this work, we developed a novel TiO₂-decorated acid-treated MnO _x octahedral molecular sieve (OMS-5(H)@TiO₂) catalyst with improved alkali-resistant NO _x reduction at low temperature, and the dual promotional effects of OMS-5(H)@TiO₂ catalysts were clarified. It was found that the special structure of the acid-treated MnO _x octahedral molecular sieve (OMS-5(H)) was responsible for the trapping of alkali metals and high deNO _x activity at low temperature. Subsequently, the decoration by TiO₂ further improved the redox properties by accelerating the high ratio of Mn⁴⁺ and O_α on the surface of the highly active (OMS-5(H)@TiO₂) catalyst. Moreover, a thorough mechanism study via in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTs) demonstrated that the acid treatment led to remarkable increment of acid sites, which enabled the catalyst to resist alkali metals in the form of ion exchange. Meanwhile, the decoration of TiO₂ further increased the strength of the Lewis acid sites, assisting more active intermediate species to effectively take part in the deNO _x reaction. Besides, a "fast SCR" process was observed to certify that the decoration of TiO₂ promoted the improvement of low-temperature activity in the presence of alkali metals. The dual effects combining OMS-5(H) with TiO₂ decoration in terms of alkali metal resistance and high catalytic activity at low temperature proved that the high-performance deNO _x catalyst was successfully developed in this work. The work paves a way for the development of superior low-temperature SCR catalysts with improved NO _x reduction efficiency in the presence of alkali metals.

Improved NO x Reduction in the Presence of SO2 by Using Fe2O3-Promoted Halloysite-Supported CeO2-WO3 Catalysts

Currently, selective catalytic reduction (SCR) of NO _x with NH₃ in the presence of SO₂ by using vanadium-free catalysts is still an important issue for the removal of NO _x for stationary sources. Developing high-performance catalysts for NO _x reduction in the presence of SO₂ is a significant challenge. In this work, a series of Fe₂O₃-promoted halloysite-supported CeO₂-WO₃ catalysts were synthesized by a molten salt treatment followed by the impregnation method and demonstrated improved NO _x reduction in the presence of SO₂. The obtained catalyst exhibits superior catalytic activity, high N₂ selectivity over a wide temperature range from 270 to 420 °C, and excellent sulfur-poisoning resistance. It has been demonstrated that the Fe₂O₃-promoted halloysite-supported CeO₂-WO₃ catalyst increased the ratio of Ce³⁺ and the amount of surface oxygen vacancies and enhanced the interaction between active components. Moreover, the SCR reaction mechanism of the obtained catalyst was studied using in situ diffuse reflectance infrared Fourier transform spectroscopy. It can be inferred that the number of Brønsted acid sites is significantly increased, and more active species could be produced by Fe₂O₃ promotion. Furthermore, in the presence of SO₂, the Fe₂O₃-promoted halloysite-supported CeO₂-WO₃ catalyst can effectively prevent the irreversible bonding of SO₂ with the active components, making the catalyst exhibit desirable sulfur resistance. The work paves the way for the development of high-performance SCR catalysts with improved NO _x reduction in the presence of SO₂.

A γ-Fe2O3-modified nanoflower-MnO2/attapulgite catalyst for low temperature SCR of NOx with NH3

A novel mesoporous γ-Fe₂O₃-modified nanoflower-MnO₂/attapulgite catalyst has been fabricated through a facile hydrothermal method and used for low temperature SCR of NO_x with NH₃.

MnO2–Graphene-oxide-scroll–TiO2 composite catalyst for low-temperature NH3-SCR of NO with good steam and SO2 resistance obtained by low-temperature carbon-coating and selective atomic layer deposition

Coating GO at low temperature and selectively depositing TiO₂ on oxygen-containing functional groups on GO.

The synergistic effects between Ce and Cu in CuyCe1−yW5Ox catalysts for enhanced NH3-SCR of NOx and SO2 tolerance

Non-manganese-based metal oxides are promising catalysts for the NH₃-SCR (selective catalytic reduction) of NO_x at low temperatures.

The transient reduction of NO with CO and naphthalene in the presence of oxygen using a core–shell SmCeO2@TiO2-supported copper catalyst

This work studied the reaction of common pollutants on a catalytic surface under oxidizing conditions.

Cerium and tin oxides anchored onto reduced graphene oxide for selective catalytic reduction of NO with NH3 at low temperatures

A series of cerium and tin oxides anchored on reduced graphene oxide (CeO2-SnO x /rGO) catalysts are synthesized using a hydrothermal method and their catalytic activities are investigated by selective catalytic reduction (SCR) of NO with NH3 in the temperature range of 120-280 °C. The results indicate that the CeO2-SnO x /rGO catalyst shows high SCR activity and high selectivity to N2 in the temperature range of 120-280 °C. The catalyst with a mass ratio of (Ce + Sn)/GO = 3.9 exhibits NO conversion of about 86% at 160 °C, above 97% NO conversion at temperatures of 200-280 °C and higher than 95% N2 selectivity at 120-280 °C. In addition, the catalyst presents a certain SO2 resistance. It is found that the highly dispersed CeO2 nanoparticles are deposited on the surface of rGO nanosheets, because of the incorporation of Sn4+ into the lattice of CeO2. The mesoporous structures of the CeO2-SnO x /rGO catalyst provides a large specific surface area and more active sites for facilitating the adsorption of reactant species, leading to high SCR activity. More importantly, the synergistic interaction between cerium and tin oxides is responsible for the excellent SCR activity, which results in a higher ratio of Ce3+/(Ce3+ + Ce4+), higher concentrations of surface chemisorbed oxygen and oxygen vacancies, more strong acid sites and stronger acid strength on the surface of the CeSn(3.9)/rGO catalyst.

Enhanced Oxygen Vacancies in a Two-Dimensional MnAl-Layered Double Oxide Prepared via Flash Nanoprecipitation Offers High Selective Catalytic Reduction of NOx with NH₃

A two-dimensional MnAl-layered double oxide (LDO) was obtained by flash nanoprecipitation method (FNP) and used for the selective catalytic reduction of NOx with NH₃. The MnAl-LDO (FNP) catalyst formed a particle size of 114.9 nm. Further characterization exhibited rich oxygen vacancies and strong redox property to promote the catalytic activity at low temperature. The MnAl-LDO (FNP) catalyst performed excellent NO conversion above 80% at the temperature range of 100⁻400 °C, and N₂ selectivity above 90% below 200 °C, with a gas hourly space velocity (GHSV) of 60,000 h-1, and a NO concentration of 500 ppm. The maximum NO conversion is 100% at 200 °C; when the temperature in 150⁻250 °C, the NO conversion can also reach 95%. The remarkable low-temperature catalytic performance of the MnAl-LDO (FNP) catalyst presented potential applications for controlling NO emissions on the account of the presentation of oxygen vacancies.

Fabrication of γ-MnO2-Ce Pillared Montmorillonite for Low Temperature NH3-SCR

A series of γ-MnO2-Ce/MMT catalyst materials synthesized by homogeneous precipitation method was investigated for the selective catalytic reduction (SCR) of NOx with NH3. X-ray diffraction and specific surface areas were utilized for micro structure and layer spacing investigation. And NH3-TPD, Pyridoxine IR, H2-TPR and XPS were used to investigate Brønsted acid and Lewis acid, redox properties, atomic concentrations and element chemical state for as-prepared catalysts. The results showed that the γ-MnO2-Ce/MMT had superior NOx conversion compared to the bulk particles, among which 6 wt.% γ-MnO2-Ce/MMT displayed the best deNOx of 95.3% for the low temperature selective catalytic reduction of NOx with NH3 (NH3-SCR) under the GHSV of 25,000 h−1, therefore it is a promising catalyst for low temperature NH3-SCR.

Performance of selective catalytic reduction of NO with NH3 over natural manganese ore catalysts at low temperature

Natural manganese ore catalysts for selective catalytic reduction (SCR) of NO with NH₃ at low temperature in the presence and absence of SO₂ and H₂O were systematically investigated. The physical and chemical properties of catalysts were characterized by X-ray diffraction, Brunauer-Emmett-Teller (BET) specific surface area, NH₃ temperature-programmed desorption (NH₃-TPD) and NO-TPD methods. The results showed that natural manganese ore from Qingyang of Anhui Province had a good low-temperature activity and N₂ selectivity, and it could be a novel catalyst in terms of stability, good efficiency, good reusability and lower cost. The NO conversion exceeded 85% between 150°C and 300°C when the initial NO concentration was 1000 ppm. The activity was suppressed by adding H₂O (10%) or SO₂ (100 or 200 ppm), respectively, and its activity could recover while the SO₂ supply is cut off. The simultaneous addition of H₂O and SO₂ led to the increase of about 100% in SCR activity than bare addition of SO₂. The formation of the amorphous MnO_x, high concentration of lattice oxygen and surface-adsorbed oxygen groups and a lot of reducible species as well as adsorption of the reactants brought about excellent SCR performance and exhibited good SO₂ and H₂O resistance.

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.

Selective catalytic reduction of NO with NH3 over MnO2/PDOPA@CNT catalysts prepared via poly(dopamine) functionalization

MnO₂/PDOPA@CNT catalysts were for the first time prepared via poly(dopamine) functionalization and applied in low-temperature NO reduction with NH₃.

Novel CeO2@TiO2 core-shell nanostructure catalyst for selective catalytic reduction of NOx with NH3

The CeO₂@TiO₂ core-shell nanostructure catalyst prepared by a two-step hydrothermal method was used for selective catalytic reduction (SCR) of NOx with NH₃ in this study. The catalyst presented the obvious core-shell structure, and the shell was amorphous TiO₂ which could protect the active center from the SO₂ erosion. The catalyst showed high activity and stability, excellent N₂ selectivity and superior SO₂ resistance and H₂O tolerance. Characterizations such as TEM, HR-TEM, XRD, BET, XPS, NH₃-TPD, and H₂-TPR were carried out. The results indicated that the catalyst had large surface area and the active sites were well dispersed on the surface. The NH₃-TPD, H₂-TPR and XPS results implied that its increased SCR activity might be due to the enhancement of NH₃ chemisorption and the increase of active oxygen species, both of which were conductive to NH₃ activation. The excellent catalytic performance suggests that it is a promising candidate for SCR catalyst.

Porous nanopeapod Pd catalyst with excellent stability and efficiency

Porous Pd@m-C/SiO₂ nanopeapods are prepared by a nanoconfinement method. The Pd nanoparticles show high efficiency and stability in chemical reactions such as reduction of nitrobenzene by H₂ and reduction of NO by NH₃. The high catalytic activity is attributed to the unique peapod structure, mesoporous wall, and large specific surface area on Pd@m-C/SiO₂ rendering the Pd nanoparticles highly active in chemical reactions.

Sc promoted and aerogel confined Ni catalysts for coking-resistant dry reforming of methane

Sc promoted and aerogel confined Ni catalysts were developed for coking-resistant dry reforming of methane.

Influence of transition metal (Fe, Co, and Ag) doping on the MnOx–CeO2/Ti-bearing blast furnace slag catalyst for selective catalytic reduction of NOx with NH3 at low temperature

Mn–Ce based catalysts supported on Ti-bearing blast furnace slag (industrial solid waste) and the doping of transition metals were studied.

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.

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.

Low-Temperature Selective Catalytic Reduction of NO with NH₃ over Mn₂O₃-Doped Fe₂O₃ Hexagonal Microsheets

Mn2O3-doped Fe2O3 hexagonal microsheets were prepared for the low-temperature selective catalytic reduction (SCR) of NO with NH3. These hexagonal microsheets were characterized by SEM, TEM, XRD, BET, XPS, NH3-TPD, H2-TPR, and in situ DRIFT and were shown to exhibit a considerable uniform hexagonal microsheet structure and excellent low temperature SCR efficiency. When doped with different Mn molar ratios, Mn2O3 was detected in the Fe2O3 hexagonal microsheets based on the XRD results without the presence of other MnOX species. In addition, the hexagonal microsheets with a Mn/Fe molar ratio of 0.2 showed the best SCR removal performance among the materials, where a 98% NO conversion ratio at 200 °C at a space velocity of 30,000 h(-1) was obtained. Meanwhile, excellent tolerances to H2O and SO2, as well as high thermal stability, were obtained in Mn2O3-doped Fe2O3 hexagonal microsheets. Moreover, on the basis of the XPS and in situ DRIFT results, it can be suggested that coupled Mn2O3 nanocrystals played a key role at low temperatures and produced a possible redox reaction mechanism in the SCR process.

Creating hierarchically macro-/mesoporous Sn/CeO2for the selective catalytic reduction of NO with NH3

Hierarchically macro-/mesoporous Sn/CeO₂was created for the selective catalytic reduction of NO with NH₃.

Activity and SO2 resistance of amorphous CeaTiOx catalysts for the selective catalytic reduction of NO with NH3: in situ DRIFT studies

Amorphous Ce_0.3TiO_x exhibits a high activity and sulfur resistance for NH₃-SCR of NO due to the strong interactions between Ce and Ti.

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.

Fabrication and formation mechanism of Ce2O3–CeO2–CuO–MnO2/CNTs catalysts and application in low-temperature NO reduction with NH3

Ce₂O₃–CeO₂–CuO–MnO₂/CNTs catalysts were synthesized via a redox strategy, and presented 58–85% NO conversion at 80–180 °C.

Promotional effect of iron oxide on the catalytic properties of Fe–MnOx/TiO2 (anatase) catalysts for the SCR reaction at low temperatures

The surface interaction of the iron-improved MnO_x/TiO₂ (anatase) catalyst for the selective catalytic reduction of nitric oxide was studied. The role of iron was investigated through detailed experiments.

Low-temperature selective catalytic reduction of NO with NH3 over Ni–Mn–Ox catalysts

A series of Ni(n)–MnO_x catalysts with high activity for the low temperature NH₃-SCR have been synthesized by a hard template method.

Preparation of novel CeMo(x) hollow microspheres for low-temperature SCR removal of NOx with NH3

A series of novel Mo doped CeO₂ hollow microspheres have been successfully synthesized using carbon microspheres as templates, which were characterized by XRD, SEM, TEM, BET and used to remove NO_x upon NH₃-SCR at lower temperature.

Structure–performance relationships of MnO2 nanocatalyst for the low-temperature SCR removal of NOX under ammonia

To investigate the corresponding relationship between catalytic efficiency and structure, MnO₂ nanomaterials (nanospheres, nanosheets, nanorods) have been prepared successfully, and were thoroughly characterized by SEM and TEM.

Morphology-dependent performance of Zr–CeVO4/TiO2 for selective catalytic reduction of NO with NH3

The morphology-dependent performance of Zr–CeVO₄/TiO₂ was demonstrated for the selective catalytic reduction of NO with NH₃.