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The selective catalytic reduction (SCR) system plays a crucial role in reducing diesel exhaust emissions. To further enhance the performance of the SCR system, a three-dimensional numerical simulation model was established and experimentally validated for its reliability. Subsequently, the length (L1) and porosity (ε1) of carrier 1, as well as the length (L2) and porosity (ε2) of carrier 2, were varied to achieve an axial non-uniform distribution of the catalysts. The impact of this axial non-uniform distribution on the SCR system's performance was investigated. Finally, a fuzzy grey relational analysis method was employed to evaluate and optimize the influence of the aforementioned four individual parameters on the SCR system's denitrification (de-NOx) efficiency and pressure drop. The results indicate that variations of L1 have the greatest impact on de-NOx efficiency, while changes of ε2 have the most significant effect on pressure drop. The fuzzy grey relational degrees of L1, L2, ε1, and ε2 on de-NOx efficiency are 0.8267, 0.6288, 0.7457, and 0.8233, respectively. Similarly, the fuzzy grey relational degrees of L1, L2, ε1, and ε2 on pressure drop are 0.3552, 0.4894, 0.1045, and 0.7931, respectively. Compared with uniformly distributed catalysts, axially non-uniform distributed catalysts can improve de-NOx efficiency by 2.22% and reduce pressure drop by 46 Pa. This study provides theoretical and engineering references for improving the SCR catalyst coating process. [ABSTRACT FROM AUTHOR]

Selective catalytic reduction of nitrogen oxides with NH3 at low temperatures remains a crucial goal for industrial applications. However, effective catalysts operating at 70–90 °C are rarely reported, limiting SCR scenarios to high‐temperature conditions. Herein, we report a unique MnO2 nanofilament catalyst grown on activated semi‐coke synthesized via a one‐step in situ hydrothermal approach, which exhibits a stable and marked 100 % conversion rate of NO to N2 with 100 % selectivity at 90 °C, superior to the other prepared structures (nanowires, nanorods, and nanotubes). Temperature‐programmed desorption shows a large number of acid sites on MnO2(NFs)/ASC, benefiting the formation of NH4+ ions. Meanwhile, diffuse reflectance infrared Fourier transform spectroscopy reveals the activation of NO with O2 to form bidentate nitrate/bridging nitrate NO2 intermediates via bidentate nitrate species, triggering the Fast SCR with NH3 at low temperatures. Such an effective, easy‐to‐prepare, and low‐cost catalyst paves a new pathway for low‐temperature SCR for a wide range of application scenarios. [ABSTRACT FROM AUTHOR]

Nitrogen oxides (NOx) are produced during the high‐temperature combustion process of fossil fuels, which are considered as an atmospheric pollutant that can lead to significant environmental issues such as acid rain and photochemical smog. Therefore, it is essential to minimize the concentration of NOx in the atmosphere in order to protect the ecological environment upon which human beings depends. The integrated utilization of NOx removal technology results in environmentally harmless compounds, such as N2 and H2O, through the processes like adsorption, separation, catalytic reduction and other methods. Metal‐organic frameworks (MOFs) are seen as ideal candidates for addressing NOx pollution issues in the atmosphere due to their high specific surface area, ultrahigh porosity and unlimited modifiability. Herein, the latest research progress in MOFs and MOFs‐derived materials related to NOx adsorption, separation and catalytic reduction is presented and summarized. Besides, some opportunities and problems need to be solved in this field are proposed and discussed. [ABSTRACT FROM AUTHOR]

Nanowire‐MnO2 and a series of Zr‐doped MnO2 catalysts with different Zr/Mn molar ratios were successively prepared by hydrothermal and impregnation methods. The Zr‐doped MnO2 catalyst with Zr/Mn molar ratio of 0.04 and calcination temperature of 400 °C, proved to be the optimal that possessed the highest low‐temperature denitration efficiency. It showed the NO conversion of ~92 % and N2 selectivity of ~80 % at 150 °C. Characterization results demonstrated that the main active phase of the catalyst was β‐MnO2, Zr atoms interacted with Mn atoms, and Zr doping increased the structural defects, oxygen vacancies and weak acid sites, which effectively enhanced the low‐temperature denitration activity and N2 selectivity of β‐MnO2, also improved the water and sulphur resistance to some extent. [ABSTRACT FROM AUTHOR]

The present study conducts a comparative analysis between selective catalytic reduction (SCR) using a Cu-zeolite catalyst and selective non-catalytic reduction (SNCR) for the removal of NO x from industrial waste gas. The primary objective of this investigation is to computationally explore the removal of NO x using NH3 at various reactor conditions, along with the study of different hydrodynamic aspects. The study revealed the impact of different porosity of the catalyst (in SCR) and the number of baffles (in SNCR) on the reaction and fluid flow profile. Distinct geometries were employed to model each process, incorporating a turbulent model and kinetic parameters with an eddy-dissipation model (EDM) for simulations. Analyzing the effect of the NH3/NO ratio on NO conversion efficiency is a crucial component of the study. With diminishing efficiency at higher ratios, the SCR process demonstrated nearly complete NO conversion at a certain NH3/NO ratio, and this value changes with the inlet gas temperature. In contrast, SNCR produced less favorable conversion rates than SCR, indicating that the amount of NH3 supply affects conversion efficiency. At the SCR system’s optimum NH3/NO ratio, SNCR achieved an 83 % conversion, and the conversion rate remained relatively constant as the ratio was increased. The results highlight the various possibilities for optimization of the reactor systems in terms of efficiency and economic feasibility. [ABSTRACT FROM AUTHOR]

To eliminate the harm of nitrogen oxides to human health and ecological environment, selective catalytic denitrification using methane as a reducing agent (CH4-SCR) has received widespread attention. Developing highly active CH4-SCR denitrification catalysts has become a research focus of this technology. In this article, Co(x)/ZRP catalysts were prepared by impregnation method, and the effects of Co(x)/ZRP catalysts with different cobalt loading amounts on the denitrification performance of CH4-SCR were investigated. The physicochemical properties of Co (x)/ZRP catalysts were characterized using XRD, H2-TPR, Py-IR, NH3-TPD and NO-TPD methods. The CH4-SCR denitrification performance of Co(x)/ZRP catalysts was evaluated on fixed bed micro-reactor under atmospheric pressure. The results showed that the cobalt species in the Co(x)/ZRP catalyst were Co3O4. With the increase of cobalt loading, the Co3O4 grains became larger, the redox ability and NO adsorption and desorption performance of the catalyst were improved. With the increase of cobalt loading, the denitrification activity of Co(x)/ZRP catalyst first increased and then decreased, which was consistent with the variation of medium strong acid amount in the total acid of the catalyst. Among them, the Co(20)/ZRP catalyst had a higher amount of medium strong acid, and the CH4-SCR denitrification performance was good, with Tm of 342 °C, XNomax of 39.2%. The L-acid and medium strong acid content of the catalyst played an important role in the CH4-SCR catalytic denitrification activity of the catalyst. [ABSTRACT FROM AUTHOR]

With the acceleration of industrialization and the increasing prominence of environmental pollution problems, the emission of nitrogen oxides (NOx) in the atmosphere has become a global concern. These emissions are not only hazardous to human health, but also one of the main factors leading to acid rain, photochemical smog and global climate change. Therefore, the development and implementation of efficient denitrification technologies are an important issue for environmental protection. The present review focuses on the research progress of the denitrification technology in the recent years, including the traditional denitrification methods and common technologies. At the same time, the advantages, limitations and application prospects of each method are analyzed. The mechanisms, influencing factors, advantages and disadvantages of the denitrification catalysts are also discussed. In addition, the future research trends and potential challenges of denitrification technology are discussed. It is expected that this review will provide useful references for promoting the development and application of denitrification technology, which may help researchers to choose high‐performance and cost‐effective methods. [ABSTRACT FROM AUTHOR]

Selective catalytic reduction of NOx with hydrogen (H2‐SCR‐DeNOx) is applied among other techniques (i. e., SCR‐DeNOx by applying NH3 or hydrocarbons as reducing agents) to control nitrogen oxides from mobile and stationary sources. As a zero carbon technology, which efficiently reduces NOx below 200 °C, H2‐SCR‐DeNOx has gained attention in installations and plants with H2 availability. The catalytic properties of platinum‐based catalysts with the main focus on the applied supports (i. e., inorganic oxides and zeolites) are given in detail. Another focus concerns on how the feed composition affects catalytic properties, specifically the levels of oxygen, water vapor, sulfur, and carbon oxides present in the exhausts. The major challenges are presented in enhancing the N2 selectivity and stability of catalysts at low temperatures without affecting their activity. Promising research prospects in this area include the development of catalysts with improved dispersion and distribution of Pt particles. In addition, the proposed bi‐functional (dual‐function) reaction mechanism over Pt‐containing catalysts, together with the adsorption/dissociation mechanism and NO oxidation/reduction mechanism, is described and critically reviewed. Also, Pd‐based catalysts are briefly discussed. It is expected that the review will provide broad insights into the design and optimization of catalysts in the H2‐SCR‐DeNOx. [ABSTRACT FROM AUTHOR]

This study aims to investigate the NOx/CO reduction characteristics of harmful gases according to the loading amount of active Ag, which plays the most important role in H2-SCR, and the type of support. H2-SCR with Ag loaded on support of TiO2 was reduced to Ag+ at about 140 °C in AgO oxide, and H2-SCR with Ag loaded on support of Al2O3 was reduced to Ag clusters (Agnδ+) at about 260 °C in AgO oxide. Because it is more unstable than AgO oxide, it promoted the chemical reaction of Ag. 0.5Ag/TiO2 H2-SCR showed the highest NOx conversion rate of about 18% at 200 °C, and the window width was also widened. 2Ag/Al2O3 H2-SCR improved the low-temperature activity of the catalyst due to its large specific surface area and the loading amount of active catalyst Ag. Although the harmful gas reduction performance has decreased significantly compared to the active material Pt used in the H2-SCR, research on active materials considering the performance the improvement and economic feasibility must be continued. [ABSTRACT FROM AUTHOR]

The preparation of two‐dimensional (2D) materials often requires complicated exfoliation procedures having low yields. The exfoliated nanosheets are prone to thermal aggregation and unsuitable for thermocatalysis. Herein, a scalable approach produces 2D catalyst precursors well‐distributed and mixed at the nanoscale. Using continuous microfluidization and single‐layer layered double hydroxide (LDH) synthesis, the prepared suspension contained exfoliated hexagonal boron nitride (h‐BN) nanosheets and single‐layer LDHs. The increased contact area between h‐BN and LDHs enables the formation of highly dispersed MnCoAl mixed metal oxide nanoparticles anchored on h‐BN nanosheets after calcination. In the selective catalytic reduction of NOx with NH3 (NH3‐SCR, a representative thermocatalytic application), this nanocomposite demonstrates a record turnover frequency of 0.772 h−1 among reported Mn‐based NH3‐SCR catalysts, with high NOx conversion and high N2 selectivity at low temperatures. By creating 2D precursors mixed at the nanoscale, this new synthetic approach can realize the scalable production of highly efficient thermocatalysts. [ABSTRACT FROM AUTHOR]

The denitrification efficiency of carbon‐based zero valent iron catalyst (C‐ZFe) for low‐temperature selective catalytic reduction (SCR) (<140°C) highly depends on the structural species of iron oxide (FexOy) and the physicochemical properties of the catalyst. In the study, we investigated the main factors affecting the low‐temperature denitrification efficiency of C‐ZFe such as temperature, iron content and O2. The results showed that the average NOX conversion was 72.6 % at 135°C when the space velocity was 459 h−1 and the mass ratio of carbon to iron was 15 % to 85 %. The surface morphology and structure of C‐ZFe were characterized by the surface area and pore size distribution measurements, X‐ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR) and X‐ray photoelectron spectroscopy (XPS). The results indicated that the iron on the catalyst surface was oxidized by O2 to Fe2O3, which could retain NO and then formed intermediate products. NO entered the mesoporous structure along C‐ZFe surface and proceeded a catalytic reduction reaction with the adjacent carbon. [ABSTRACT FROM AUTHOR]

A literature review on oxide compositions developed to modify ceramic aluminosilicate fibers-based filter elements for the selective catalytic reduction of nitrogen oxides during the purification of high-temperature industrial gases is presented. Methods for preparing the catalytic compositions and methods for their introduction into the structure of the ceramic filter elements are also discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Gd-modified Mn-Co LDOs derived from LDHs are developed for the SCR de-NO x. • Gd-modified Mn-Co LDOs exhibit excellent activity and high H 2 O/SO 2 tolerance. • The physicochemical properties inherited from LDHs and Gd-modification promote activity. • Both E-R and L-H mechanisms are included in SCR de-NO x over Gd-modified Mn-Co LDOs. Metal oxides derived from layered double hydroxides (LDHs) are expected to obtain low-temperature denitrification (de-NO x) catalysts with high catalytic activity and H 2 O/SO 2 tolerance in the selective catalytic reduction (SCR) of NO x with NH 3. In current work, we successfully prepared Gd-modified Mn-Co metal oxides derived from Gd-modified Mn-Co LDHs. The resultant Gd-modified Mn-Co metal oxides exhibit excellent catalytic activity and high H 2 O/SO 2 tolerance in the NH 3 -SCR de-NO x reaction. The reasons for the enhancement can be ascribed to the unique surface physicochemical properties inherited from LDHs and the modification of Gd, which increase the specific surface area, improve the relative content of Mn4+ and Co3+ on the surface, enhance the number of acidic sites, strengthen the reducibility of catalyst, resulting in the enhanced catalytic activity and H 2 O/SO 2 tolerance. Additionally, it is demonstrated that the NH 3 -SCR de-NO x reaction occurred on the surface of Gd-modified Mn-Co oxides followed both Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) mechanisms. This study provides us with a design approach to promote catalytic activity and H 2 O/SO 2 tolerance through morphology control and rare earth modification. [ABSTRACT FROM AUTHOR]

Barium and iridium supported on Zeolite Socony Mobil-5 (ZSM-5) are efficient catalysts for the selective catalytic reduction of nitric oxide by carbon monoxide (CO-SCR), with enhanced cyclic stability. The introduction of Ba hindered the oxidation of metallic Ir active species and enabled Ir to maintain an active metallic state, thereby preventing a decrease in catalytic activity in the CO-SCR reaction. Moreover, the Ba modification increased the NO adsorption of the catalyst, further improving the catalytic activity. Owing to the better anti-oxidation ability of Ir0 in IrBa0.2/ZSM-5(27) than in Ir/ZSM-5(27), IrBa0.2/ZSM-5(27) showed better stability than Ir/ZSM-5(27). Considering that all samples in the present study were tested to simulate actual flue gases (such as sintering flue gas and coke oven flue gas), NH3 was introduced into the reaction system to serve as an extra reductant for NOx. The NOx conversion to N2 (77.1%) was substantially improved using the NH3-CO-SCR system. The proposed catalysts and reaction systems are promising alternatives for treating flue gas, which contains considerable amounts of NOx and CO in oxygen-enriched environments. [ABSTRACT FROM AUTHOR]

Organic–inorganic hybrid materials with highly ordered pore structure are based on the introduction of organic bridging groups on the channel walls of the pore structure. The introduction of organic bridging groups not only modulates the physical and chemical properties of the prepared mesoporous materials, but also improves the functionalization of the mesoporous materials. In this thesis, we mainly prepared TNU-9 catalysts containing copper by organic–inorganic hybrid method and investigated the NH3-SCR properties of the materials. The results showed that the NOx conversion of Cu@PMO-TNU-9-2% was more than 99% at 350 °C, and N2 selectivity was nearly 99% at 300–450 °C. In addition, the resistance test results showed that the conversion of NOx could still reach more than 90% within 7 h with the introduction of 100 ppm SO2 at 300 °C and a gas flow rate of 100 ml/min. Furthermore, the NOx conversion of Cu@PMO-TNU-9–2% catalyst decreased to 90.5% and then was stabilized when 100 ppm water vapor was introduced. [ABSTRACT FROM AUTHOR]

Mn–La0.5/TiO2 denitration catalysts were prepared by impregnation, combustion, coprecipitation, reverse coprecipitation, and in situ deposition method, and their catalytic activities were compared. The catalyst prepared by the in situ deposition method had the highest catalytic activity and N2 selectivity with a T80 of 104.8 °C, a NO conversion of up to 100%, and a temperature window of 104.8–365.6 °C. The water and sulfur resistance of the catalysts prepared by the in situ deposition method and the coprecipitation method were compared. The elemental valence state, composition, redox ability, and surface acidic sites of the catalysts were analyzed by XPS, XRF, H2-TPR and NH3-TPD. The adsorption behavior and NH3-SCR reaction of the catalysts were investigated by in situ diffuse reflectance infrared Fourier transform spectroscopy. Results showed the catalyst prepared by the in situ deposition method had better water and sulfur resistance, higher Mn4+ content, H2 consumption and medium acidic sites, and faster adsorption rate of NH3 and NO when compared with those prepared by other methods. The NH3-SCR reaction on two catalysts followed the Eley–Rideal mechanism, and "fast SCR" played a key role in the reaction. [ABSTRACT FROM AUTHOR]

The selective catalytic reduction (SCR) system features with integrated high-pressure urea dosing pump to regulate the urea spray injection pressure for pertinent mixing of evaporated ammonia with exhaust gas mixtures in the diesel engine. This paper is a contribution to numerical simulation studies of external gear pumps using the immersed solid method for better understanding of continuously changing fluid fields and transient flow characteristics. A comprehensive set of data gained by the investigations from KATECH institute was executed in the present study, which led to an optimized CFD setup for realistic numerical simulation. Parametric analyses have been carried out for the gear speed and supplied urea liquid mass flow rate to find the behavior of pressure, mass flow rate, and velocity fluctuations in the domain. As a result, the pressure at the outlet reached its maximum with the increase in rotational speed, and the fluctuations grew. [ABSTRACT FROM AUTHOR]

x W/MnCe nanorod catalysts with various tungsten contents were synthesised using the incipient wetness impregnation method for selective catalytic reduction (SCR) of nitrogen oxides with NH 3 (i.e. NH 3 -SCR reaction). Tungsten addition considerably widened the active temperature window and enhanced the SO 2 /H 2 O tolerance of the catalysts. The optimum catalytic performance was achieved when the tungsten content was 15 wt% with NO x conversion being ≥ 80% in the range of 175–450 °C. The MnCe nanorods approximately retained their morphology after tungsten loading. Microcrystalline WO 3 formed when the W content was 15%, resulting in increments in the amount of Ce3+ and Mn4+, which is in favour of the NH 3 -SCR reaction on the catalyst surface. Moreover, the broad active temperature windows of the tungsten-modified MnCe nanorod catalysts were related to the balance between the redox and acidic properties. Tungsten addition enhanced the acidity of the MnCe catalyst while suppressing its reducibility. Both the Brønsted and Lewis acid sites are active, and the formation of reactive bridging nitrate species promote the performance of 15 W/MnCe catalyst. Overall, this study provided an easy method of adjusting the active temperature window of Mn–Ce nanorod catalysts through W modification. [Display omitted] [ABSTRACT FROM AUTHOR]

With increasingly stringent emissions legislation, such as that stipulated by the International Maritime Organization, for nitrogen oxide emission reduction in marine diesel engines, the imperative of curtailing nitrogen oxide emissions from marine diesel engines is intensifying. Consequently, the significance of aftertreatment technologies, including diesel particulate filters (DPFs) and selective catalytic reduction (SCR), is poised to grow substantially. In particular, a redesign is required to reduce the size of DPF and SCR systems for application in small ships. In this study, we varied the shape of the filters in DPF and SCR systems, aiming to achieve a distinct flow pattern and enable overall miniaturization. The performance metrics, including the nitric oxide (NO) reduction rate, NH3 slip rate, and pressure drop, of the redesigned models were compared with those of the conventional model. Computational fluid dynamics simulations were used to compare the performance of the redesigned model with that of the conventional model in terms of NO reduction and pressure drop. The redesigned system achieved a NO reduction rate of 6.9% below that of the conventional system, offering additional noteworthy benefits such as a 50% reduction in both pressure and overall length. [ABSTRACT FROM AUTHOR]

Cu-SSZ-39 zeolite with an AEI structure exhibits excellent hydrothermal stability and can be a potential alternative to Cu-SSZ-13 zeolite SCR catalysts for NOx removal in diesel vehicles. However, the inferior low-temperature performance of Cu-SSZ-39 leads to substantial NOx emissions during the cold-start period, impeding its practical application. In this study, Ce-Mn oxide-modified Cu-SSZ-39 catalysts (CeMnOx/Cu-SSZ-39) and references (CeO2/Cu-SSZ-39 and MnOx/Cu-SSZ-39) were prepared by the ion-exchange of Cu ions followed by impregnation of the oxide precursors, with the aim of enhancing the NH3-SCR performance at low temperatures. The modified catalysts exhibited improved low-temperature activity and hydrothermal stability compared to the unmodified counterpart. In particular, CeMnOx/Cu-SSZ-39 showed the highest activity among the three catalysts and achieved NOx conversions above 90% within the temperature range of 180 °C to 600 °C, even after undergoing hydrothermal aging at 800 °C. Experimental results indicated that the synergistic effect between Ce and Mn in CeMnOx improves the redox properties and acidity of the catalyst due to the presence of Ce3+, Mn4+, and abundant adsorbed oxygen species, which facilitate low-temperature SCR reactions. Furthermore, the interaction of CeMnOx with Cu-SSZ-39 stabilizes the zeolite framework and hinders the agglomeration of Cu species during the hydrothermal aging process, contributing to its exceptional hydrothermal stability. The kinetics and NO oxidation experiments demonstrated that CeMnOx provides access to fast SCR reaction pathways by oxidizing NO to NO2, resulting in a significant increase in low-temperature activity. This study provides novel guidelines for the design and preparation of Cu-SSZ-39 zeolite with outstanding SCR performance over a wide temperature range. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fe doping improved the low-temperature activity and SO 2 durability of Ce-W oxides. • Doping Fe facilitated the "fast SCR" reaction, thereby improving the SCR activity. • Introducing Fe species could effectively prevent sulfate deposition. • Doping Fe accelerated the decomposition of ammonium bisulfate. Ceria-based catalysts for the selective catalytic reduction of NO x with NH 3 (NH 3 -SCR) are always subject to deactivation by sulfur poisoning. In this study, Fe-doped Ce-W mixed oxides, which were synthesized by the co-precipitation method, improved the SCR activity and SO 2 durability at low temperatures of undoped Ce-W oxides. The improved low-temperature activity was mainly due to the enhancement of redox properties at low temperatures and more active oxygen species, together with the adsorption and activation of more abundant NO x species, facilitating the "fast SCR" reaction. In the presence of SO 2 , doping with Fe species effectively prevented sulfate deposition on the CeW catalyst, due to the interaction between Fe, Ce, and W species inducing electron transfer among different metal sites and altering the electron distribution. The competitive adsorption behavior between NO and SO 2 was changed by Fe doping, in which the adsorption and oxidation of SO 2 were restrained. Besides, the elevated NO oxidation accelerated the decomposition of ammonium bisulfate, causing the SCR reaction to not be greatly suppressed. Hence, Fe-doped Ce-W oxides catalysts showed excellent sulfur resistance. This study provides an in-depth understanding of efficient Ce-based catalysts for SO 2 -tolerance strategies. [ABSTRACT FROM AUTHOR]

In this paper, the NOx conversion efficiency of Mo-Cu-Ag/TiO2/Cordierite catalyst at low temperatures was investigated by using fusel oil as a reductant. The properties of Mo-Cu-Ag/TiO2/Cordierite catalyst prepared by the impregnation method were analyzed by Brunauer-Emmett-Teller, scanning electron microscopy with energy dispersive spectroscopy, Fourier-transform infrared spectroscopy analyses, and X-ray diffraction. The SCR performance tests were performed under real diesel exhaust gas conditions in a temperature range from 200 °C to 290 °C with a rise of 10 °C, five different engine loads, and three different space velocities. The minimum and maximum NOx conversion rates were determined as 78,99% at 5 kW and 85.94% at 1 kW engine load, respectively. [ABSTRACT FROM AUTHOR]

It's a big challenge to use commercial catalysts in the non‐electric industries because complex flue gas containing alkali metals, heavy metals and SO2 could deactivate catalysts. In this study, we demonstrate that inherent SO42− modified V2O5/CeO2 catalysts exhibit remarkable resistance to multi‐poisons including K, Pb and SO2. The mechanisms of multiple poisoning resistance are revealed, and the evolutions of interactions between various poisons and different catalysts are elucidated. It is evidenced that K or Pb could bond on the inherent SO42− sites of catalysts; the interaction of K with Pb could impair the poisoning effects of K&Pb on catalysts; the newly formed surface SO42− species with the introduction of SO2 could bond with K dominantly, decrease the interaction between K and Pb, and relieve the effects of Pb on catalysts. K&Pb&SO2 co‐poisoned catalysts still maintain high adsorption of NH3/NH4+ and NOx species and a superior NOx reduction efficiency via the Langmuir‐Hinshelwood reaction pathway, leading to the ultra‐strong resistance of multi‐poisons. This work successfully achieves efficient and stable NOx removal in the presence of K&Pb&SO2, and sheds light on the interactions between various poisons and different catalysts, which is significant to abate NOx emissions for non‐electric industries. [ABSTRACT FROM AUTHOR]

Nitrogen oxides (NOx) are major contaminant causing environmental pollution in atmosphere. The most effective method for NOx removal is ammonia selective catalytic reduction (NH3-SCR), and catalysts play a crucial role. Cu-based zeolite catalysts are commonly used for the removal of NOx from diesel engine exhaust, but the complex composition of diesel exhaust and the harsh operating environment of catalysts make zeolite catalysts susceptible to deactivation, thus limiting their practical application. This manuscript focuses on the negative effects of actual working conditions associated with diesel vehicle exhausts and analyses the influence of composition structure that Cu-based zeolite catalysts have on NH3-SCR reaction, which refers mainly to the effects brought by topology, Si/Al ratio and Cu species. The strategies for developing Cu-based zeolite catalysts are summarized, and the current development bottlenecks such as improving catalytic performance, reducing synthesis cost and enhancing production efficiency are discussed, and the future research directions of Cu-based zeolite are prospected. [ABSTRACT FROM AUTHOR]

Polyoxymethylene dimethyl ethers (OME) produced from methanol are considered as potential substitutes of Diesel fuel. Emissions of formaldehyde and other components have been observed, particularly under cold-start conditions in engine test-bench experiments with OME fuel. In this study, the reactivity of OME3 (CH3O(CH2O)3CH3) and its decomposition products was studied in the temperature range 80–450 °C in a model gas test bench over V2O5/WO3/TiO2 and Cu-CHA SCR catalysts, a platinum-coated V2O5/WO3/TiO2 ammonia slip catalyst (ASC) and two diesel oxidation catalysts (DOC), based on platinum and platinum-palladium. Already at 80 °C, OME3 was largely hydrolyzed to methanol and formaldehyde over all catalysts. At temperatures above 150 °C, V2O5/WO3/TiO2 oxidized methanol and formaldehyde to CO via formic acid as intermediate. The platinum ASC showed a similar behavior but oxidized the decomposition products to CO2. Whereas Cu-CHA hydrolyzed OME3 quantitatively to methanol and formaldehyde, it did not show oxidation activity in the studied temperature range. The data indicate that the release of significant amounts of OME from a catalytic converter can be virtually ruled out under cold start conditions, but also that low temperature hydrolysis produces formaldehyde and methanol emissions. [ABSTRACT FROM AUTHOR]

Using sintering dust as a raw material, selective catalytic reduction (SCR) catalysts were pretreated with water and acid washing (HF, HCl, HNO3 and H2SO4) and then modified by different metal oxides (Ce, Cu, Eu, Nd and Mn) with an impregnation method. Based on this, the catalyst was supported by ZrO2, Al2O3 and TiO2. The catalysts were ascertained by various characterization techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and N2 adsorption–desorption analysis. The results showed that the main component of sintering dust was iron oxide (> 50 wt%), which is a feasible material for fabricating SCR catalysts. The catalysts pretreated by HF and modified by CeO2 improve the denitration efficiency. When modified with 10 wt% CeO2, the Ce10-PSDCHF catalyst sample exhibited the best NOx conversion rate, reaching 76.4% at 280 °C. The catalyst modified by ZrO2 was dispersed well and had best denitration efficiency. The denitration efficiency of SCR increased with the increase in ZrO2 loading and the NOx conversion rate of 0.25-Ce10-PSDCHF/ZrO2 catalyst reached 85% at 280 °C. The modification and support of metal oxides improve the denitration efficiency, which makes the sintering dust have promising industrial application prospects. This work would be timely technical guidance and valuable insights for the application of sintering dust. [ABSTRACT FROM AUTHOR]

Selective catalytic reduction (SCR) system is considered to be the most effective control method for reducing NOx in exhaust gas post-treatment of the diesel engine. Catalysts are the main factors affecting de-NOx efficiency in SCR reactions. In recent years, due to the excellent characteristics of copper zeolite catalysts, they have been widely studied as low-temperature NH3-SCR catalysts. However, the development of low-temperature SCR catalysts with high removal efficiency still faces severe challenges. This paper reviewed the latest research progress with copper zeolite catalysts at low temperature and compared the action mechanism of various copper zeolite catalysts in NH3-SCR reactions. Copper zeolite catalysts were studied from the aspects of catalytic performance, preparation strategy, broadening the operating temperature window, hydrothermal deactivation and resistance to H2O and SO2. Several solutions to the problems existing in low-temperature NH3-SCR reactions were discussed. In addition, this paper also puts forward some views on the future research direction of copper zeolite catalysts. Finally, the summaries and prospects of the development of low-temperature SCR copper zeolite catalysts were presented. Hopefully, more researchers can understand the current research status of copper zeolite catalysts and obtain better research achievements from copper zeolite catalysts in the future. This review could pave the way for similar studies to enable a wider variety of copper zeolite catalysts to be commercially available. [ABSTRACT FROM AUTHOR]

Chlorine species, widely presented in industrial flue gas such as the waste incineration plants, can poison the catalysts and affect the selective catalytic reduction (SCR) performance. In this work, effects of Cl on the SCR performance of V2O5–WO3/TiO2 (VW/Ti) catalysts were investigated by NH4Cl deposition. The results showed that the NOx conversion efficiency at low reaction temperature (< 300 °C) decreased with the loading of NH4Cl after calcination. It was found that instead of causing the chlorination of VW/Ti catalyst the NH4Cl decomposed into volatile Cl species due to the weak V–Cl bonding. Such decomposition reduced significantly the surface non-lattice oxygen species to inhibit NO adsorption and activation, but hardly affected the redox ability and acidity of VW/Ti catalyst. Time–resolved in situ DRIFTs results indicated that NH3 activation and the SCR process predominated by Eley–Rideal mechanism were not influenced with NH4Cl impregnation, while the SCR at low temperature following a Langmuir–Hinshelwood path was limited by the decreased and weaker binding sites for NO activation. [ABSTRACT FROM AUTHOR]

The power generation sector is considered one of the major contributors to nitrogen oxides (NOx) emissions which have serious impacts on air quality. An optimization model is developed to help decision‐makers determine the best strategy or mix of strategies for the electricity sector to meet a given NOx reduction target and electricity demand at a minimum cost. The model recommended the selective catalytic reduction (SCR) technology to be applied at higher NOx emissions and the reduction reached up to 80 %. This potential option provides promising prospects for NOx emissions control, which is in line with the economic demand for sustainable energy and environmentally friendly technologies. [ABSTRACT FROM AUTHOR]

Different spinel composite oxide catalysts, LiMn2O4, ZnMn2O4 and CrMn2O4 are prepared and activities of the catalysts for selective catalytic reduction of NOx by NH3 (NH3-SCR) are tested at 50~450 ℃. The effects of catalyst structure, metal elements and valence states on NH3-SCR activity are investigated. The catalysts are characterized by physical adsorption instrument (BET), X-ray diffractometer (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), NH3 temperature-programmed desorption (NH3-TPD) and H2 temperature-programmed reduction (H2-TPR), etc. The structure-activity relationship of spinel catalyst is also studied. The results show that： The LiMn2O4 spinel catalyst has the best activity with more than 90% NO conversion at the space velocity of 6×104 mL/(g∙h) at 150 ℃, and it shows more than 80% NO conversion at 100~400 ℃, demonstrating good low temperature activity and wide temperature range. However, the denitrification activity of ZnMn2O4 and CrMn2O4 is relative poor, and the two have similar activities. In the presence of water, the activity of LiMn2O4 decreased greatly, while the activities of ZnMn2O4 and CrMn2O4 decreases slightly, showing better water resistance. The conversion rate of ZnMn2O4 reach 90% at 150 ℃, which is better than that of CrMn2O4 in the presence of water. Spinel ZnMn2O4 has a good NO conversion rate in a wide temperature range and strong water resistance. [ABSTRACT FROM AUTHOR]

Novel yttrium-doped CeO2, MnOx, and CeMnOx composites are investigated as catalysts for low-temperature NH3-SCR. The study involves the preparation of unmodified oxide supports using a citrate method followed by modification with Y (2 wt.%) using two approaches, including the one-pot citrate method and incipient wetness impregnation of undoped oxides. The NH3-SCR reaction is studied in a fixed-bed quartz reactor to test the ability of the prepared catalysts in NO reduction. The gas reaction mixture consists of 800 ppm NO, 800 ppm NH3, 10 vol.% O2, and He as a balance gas at a WHSV of 25,000 mL g−1 h−1. The results indicate that undoped CeMnOx mixed oxide exhibits significantly higher deNOx performance compared with undoped and Y-doped MnOx and CeO2 catalysts. Indeed, yttrium presence in CeMnOx promotes the competitive NH3-SCO reaction, reducing the amount of NH3 available for NO reduction and lowering the catalyst activity. Furthermore, the physical-chemical properties of the prepared catalysts are studied using nitrogen adsorption/desorption, XRD, Raman spectroscopy, temperature-programmed reduction with hydrogen, and temperature-programmed desorption of ammonia. This study presents a promising approach to enhancing the performance of NH3-SCR catalysts at low temperatures that can have significant implications for reducing NO emissions. [ABSTRACT FROM AUTHOR]

γ-Fe2O3 is considered to be a promising catalyst for the selective catalytic reduction (SCR) of nitrogen oxide (NOx). In this study, first-principle calculations based on the density function theory (DFT) were utilized to explore the adsorption mechanism of NH3, NO, and other molecules on γ-Fe2O3, which is identified as a crucial step in the SCR process to eliminate NOx from coal-fired flue gas. The adsorption characteristics of reactants (NH3 and NOx) and products (N2 and H2O) at different active sites of the γ-Fe2O3 (111) surface were investigated. The results show that the NH3 was preferably adsorbed on the octahedral Fe site, with the N atom bonding to the octahedral Fe site. Both octahedral and tetrahedral Fe atoms were likely involved in bonding with the N and O atoms during the NO adsorption. The NO tended to be adsorbed on the tetrahedral Fe site though the combination of the N atom and the Fe site. Meanwhile, the simultaneous bonding of N and O atoms with surface sites made the adsorption more stable than that of single atom bonding. The γ-Fe2O3 (111) surface exhibited a low adsorption energy for N2 and H2O, suggesting that they could be adsorbed onto the surface but were readily desorbed, thus facilitating the SCR reaction. This work is conducive to reveal the reaction mechanism of SCR on γ-Fe2O3 and contributes to the development of low-temperature iron-based SCR catalysts. [ABSTRACT FROM AUTHOR]

The thermal analysis kinetic method was employed to solve the activation energies of the thermal decomposition reactions of urea and cyanuric acid, with the purpose of understanding the formation of deposits in the diesel engine SCR system. The deposit reaction kinetic model was established by optimizing the reaction paths and reaction kinetic parameters based on the thermal analysis test data of the key components in the deposit. The result shows that the established deposit reaction kinetic model can accurately describe the decomposition process of the key components in the deposit. Compared to the Ebrahimian model, the simulation precision of the established deposit reaction kinetic model is significantly improved above 600 K. The activation energies of the urea and cyanuric acid decomposition reactions are 84 kJ/mol and 152 kJ/mol, respectively, after model parameters identification. The identified activation energies were closest to those of the Friedman one-interval method indicating that the Friedman one-interval method is reasonable to solve the activation energies of deposit reactions. [ABSTRACT FROM AUTHOR]

The SCR performance of V2O5-WO3/TiO2 SCR-catalysts characterized by different surface W density (2.1W/nm2 and 9.5W/nm2) and different surface V density varying in the range 1–8V/nm2 has been investigated in order to clarify existing controversies on the preferential involvement of electronic and geometric effects in the catalytic properties. It was found that tungsten has a weak effect on the VOx cluster size distribution through contraction of dilution effect. In contrast, the optimal interaction between W and V, when both reach their highest composition, appears to be a relevant parameter that can enhance their acidic properties and improve the catalytic efficiency in dry conditions. On the other hand, an absence of significant interaction leads to discontinuity due to deactivation. In the presence of steam, acidic properties are averaged, lowering the impact of the V to W ratio. Finally, the critical importance of acidic properties which outperform redox properties in the definition of active site is pointed out in the light of this study. [ABSTRACT FROM AUTHOR]

This paper proposes a gain-scheduling (GS) control strategy for selective catalytic reduction (SCR) systems in diesel engines, to minimize both nitrogen oxides (NOx) emissions and ammonia (NH3) slip downstream of the SCR catalyst. The proposed GS controller switches among multiple linear time-invariant H∞ controllers based on the engine's operating condition, and adopts three measurable GS parameters, that is, the amount of NOx entering the SCR catalyst, exhaust gas temperature in the catalyst, and ammonia slip measurement. While switching surfaces for the first two GS parameters are determined by simply dividing their operating ranges, to find optimal switching surfaces for the ammonia slip GS parameter, a novel method called Violation-Time-based Decision method is proposed. The efficiency of the proposed GS SCR controller is validated in simulations using real experimental data obtained from a diesel engine in the Non-Road-Transient Cycle (NRTC). [ABSTRACT FROM AUTHOR]

In this experimental investigation, a procreation approach was used to produce a catalyst based on SnO2@rGO nanocomposite for use in a selective catalytic reduction (SCR) system. Plastic waste oil is one such alternative that helps to ensure the survival of fossil fuels and also lessens the negative impacts of improper waste disposal. The SnO2@rGO nanocomposite was prepared by fine dispersion of SnO2 nanoparticles on monolayer-dispersed reduced graphene oxide (rGO) and carefully investigated for its potential in adsorbing CO, CO2, NOX, and hydrocarbon (HC). The as-synthesized SnO2@rGO nanocomposite was characterized by Fourier transform infrared spectroscopy, high-resolution transmission electron microscopy, scanning electron microscopy, X-ray diffraction spectroscopy, thermogravimetry, and surface area analyses. Then, the impact of catalysts inside the exhaust engine system was evaluated in a realistic setting with a single-cylinder, direct-injection diesel engine. As a result, the catalysts reduced harmful pollution emissions while marginally increasing brake-specific fuel consumption. The nanocomposite was shown to exhibit higher NOX adsorption efficiencies when working with different toxic gases. Maximum reductions in the emission of NOX, hydrocarbons, and CO were achieved at a rate of 78%, 62%, and 15%, respectively. These harmful pollutants were adsorbed on the active sites of catalyst and are converted to useful fuel gases through catalytic reduction thereby hindering the trajectory of global warming. [ABSTRACT FROM AUTHOR]

Vessel emissions have contributed a great deal to air quality deterioration in China. Hence, the Chinese government has promulgated a series of stringent emission regulations. It is in this context that vessel emission control technology research is in full swing. In particular, during the 13th Five-Year Plan, the air pollution control technology of vessels has greatly improved. Vessel emission control has followed two main governance routes: source emission reduction and aftertreatment technology. Source control focuses on alternative fuels, with two main directions, the development of new fuels and the modification of existing fuels. Moreover, after-treatment technologies have also been developed, including wet desulfurization technology using seawater or alkaline liquids as wet washing liquids and selective catalytic reduction (SCR) for the control of NO x emission. Due to China's increasingly stringent emissions standards and regulations, work on the development of clean alternative fuels and further upgrading the collaborative application of after-treatment technologies to meet the near-zero-emissions requirements of vessels is still necessary. [Display omitted] [ABSTRACT FROM AUTHOR]

Effective adsorption and speedy surface reactions are vital requirements for efficient active sites in catalysis, but it remains challenging to maximize these two functions simultaneously. We present a solution to this issue by designing a series of atom‐pair catalytic sites with tunable electronic interactions. As a case study, NO selective reduction occurring on V1−W1/TiO2 is chosen. Experimental and theoretical results reveal that the synergistic electron effect present between the paired atoms enriches high‐energy spin charge around the Fermi level, simultaneously rendering reactant (NH3 or O2) adsorption more effective and subsequent surface reactions speedier as compared with single V or W atom alone, and hence higher reaction rates. This strategy enables us to rationally design a high‐performance V1−Mo1/TiO2 catalyst with optimized vanadium(IV)‐molybdenum(V) electronic interactions, which has exceptional activity significantly higher than the commercial or reported catalysts. [ABSTRACT FROM AUTHOR]

Effective adsorption and speedy surface reactions are vital requirements for efficient active sites in catalysis, but it remains challenging to maximize these two functions simultaneously. We present a solution to this issue by designing a series of atom‐pair catalytic sites with tunable electronic interactions. As a case study, NO selective reduction occurring on V1−W1/TiO2 is chosen. Experimental and theoretical results reveal that the synergistic electron effect present between the paired atoms enriches high‐energy spin charge around the Fermi level, simultaneously rendering reactant (NH3 or O2) adsorption more effective and subsequent surface reactions speedier as compared with single V or W atom alone, and hence higher reaction rates. This strategy enables us to rationally design a high‐performance V1−Mo1/TiO2 catalyst with optimized vanadium(IV)‐molybdenum(V) electronic interactions, which has exceptional activity significantly higher than the commercial or reported catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Manganese-based catalysts are characterized by electron paramagnetic resonance. • Superoxide radical (O 2 *) is observed in all samples. • O 2 * is born of accepting electrons through overlapped orbits of Mn-d and O-p. • O 2 * produces nitrogen-containing free radicals during SCR. • Ce and La doping increase the number of O 2 *, thus increasing SCR performances. Manganese-based catalysts attract extensive attentions in low-temperature selective catalytic reduction (SCR) of nitrogen oxide (NO x). However, seldom work focuses on the existence of free radicals and their roles in SCR. In this work, electron paramagnetic resonance spectrometer and density functional theory are combined to reveal surface characterizations of manganese oxide and Ce/La-doped manganese oxides. As a result, superoxide radical (O 2 *) exists on manganese-oxide surface, produces nitrogen-containing free radical, and functions as electron transfer between NO x and NH 3 at 100 °C, resulting in good NO x conversion as well as N 2 selectivity at the same time. The O 2 * is born of accepting electrons on adsorbed oxygen through overlapped orbits of Mn-d and O-p. Additional metal doping increases the percentage of O 2 * among all oxygen species from 2.9 % to 6.9 % (Ce doping) and 5.1 % (La doping). The order of O 2 * percentage is consistent with the NO x -conversion order at 100 °C, i.e., Ce doping (91.6 %) > La doping (55.7 %) > catalyst without doping (27.5 %). Above result helps to understand interface behaviors of manganese-based catalyst in SCR. This work is also in favor of developing more effective low-temperature catalysts. [ABSTRACT FROM AUTHOR]

The purpose of this study is to improve the simultaneous reduction of NOX and CO, harmful gases emitted from internal combustion engines, at low temperatures using a Pt/TiO2 H2-SCR catalyst. A better NOX/CO reduction performance was observed upon loading 2 wt% of the additive catalyst CeO2 on the main catalyst Pt because the oxygen storage capacity improved. In the presence of CO, the water gas reaction was promoted, resulting in the NOX conversion rate by the 0.5Pt−2CeO2/TiO2 SCR catalyst of 42 % at 75 °C and 70 % at 100 °C; this was a 15 ∼ 20 % higher NOX conversion as compared to without CO at low temperatures. The NOX reduction performance by the 0.5Pt−2CeO2−2ZrO2/TiO2 SCR catalyst was the highest at temperatures below 100 °C. At an appropriate amount of the additive catalyst ZrO2, the reaction rate improved because the acid point of the catalyst surface and the intensity of adsorption are adjusted. The optimum reduction temperature for NOX/CO reduction performance by the H2-SCR catalyst was 400 °C. Our results also indicate that the Pt species has a significant impact. [ABSTRACT FROM AUTHOR]

The conversion of nitrogen oxides (NO x) by hydrothermally aged copper (Cu)–based selective catalytic reduction (SCR) is an irreversible phenomenon. Tail exhaust NO x emission control and on-board diagnostics (OBD) monitoring are difficult with hydrothermally aged Cu–based SCR because the on-board NO x sensor has cross sensitivity to NH 3 in the exhaust. In this study, the performance and diagnosis of hydrothermally aged SCR under real engine exhaust were studied. The influence of hydrothermally aged SCR on NH 3 storage, tail exhaust NO x , urea injection, and OBD diagnosis were quantitatively analyzed under the World Harmonized Transient Cycle (WHTC). The results show that hydrothermally aged SCR had a great influence on the NH 3 storage capacity. In terms of SCR conversion efficiency and OBD detection, compared with fresh SCR, hydrothermally aged SCR was more sensitive to space velocity than to temperature. Under different OBD monitored release conditions, the NO x conversion efficiency was greatly different; hence, the occurrence of a false diagnosis can be avoided through the selection of appropriate release conditions. These research results provide a reference for SCR size design, NO x control, and diagnostic strategies. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • V 2 O 5 /TiO 2 catalysts with specific vanadyl species were synthesized. • The effect of water on vanadyl was investigated via operando Raman spectroscopy. • Different sensitivities of various vanadyl species to water were revealed. • Sensitivity of vanadyl species to water is temperature-dependent. Vanadia-based catalysts are widely used in the selective catalytic reduction of NO x with NH 3 (NH 3 -SCR) for NO x abatement. However, the effect of water on specific vanadyl species is still unclear. Herein, the temperature-dependent sensitivity of vanadyl species to water has been originally elucidated via operando Raman spectroscopy. Interestingly, the stronger competitive adsorption of NH 3 on polymeric vanadyl species in the presence of H 2 O dominants the NH 3 -SCR reaction above 250 °C despite the polymeric vanadyl show stronger adsorption to H 2 O than the monomeric ones. By contrast, the association of water molecules via hydrogen bonding dominants the activity degeneration to both monomeric and polymeric vanadyl species at temperatures below 250 °C. Furthermore, the stronger adsorption of water on polymeric vanadyl will give rise to even worse degeneration. This work elucidates the interaction of vanadyl species with water, which is essential for the development of high-performance catalysts for water-tolerant NO x abatement. [ABSTRACT FROM AUTHOR]

Benefiting from the exceptional selective catalytic reduction of NOx with ammonia (NH3-SCR) activity, excellent N2 selectivity, and superior hydrothermal durability, the Cu2+-exchanged zeolite catalyst with a chabazite structure (Cu-CHA) has been considered the predominant SCR catalyst in nitrogen oxide (NOx) abatement. However, sulfur poisoning remains one of the most significant deterrents to the catalyst in real applications. This review summarizes the NH3-SCR reaction mechanism on Cu-CHA, including the active sites and the nature of hydrothermal aging resistance. On the basis of the NH3-SCR reaction mechanism, the review gives a comprehensive summary of sulfate species, sulfate loading, emitted gaseous composition, and the impact of exposure temperature/time on Cu-CHA. The nature of the regeneration of sulfated catalysts is also covered in this review. The review gives a valuable summary of new insights into the matching between the design of NH3-SCR activity and sulfur resistance, highlighting the opportunities and challenges presented by Cu-CHA. Guidance for future sulfur poisoning diagnosis, effective regeneration strategies, and a design for an efficient catalyst for the aftertreatment system (ATS) are proposed to minimize the deterioration of NOx abatement in the future. Finally, we call for more attention to be paid to the effects of PO43- and metal co-cations with sulfur in the ATS. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cu-SSZ-13 catalysts with different Cu2+ species were synthesized successfully. • The balance between Cu2+-2Z and [Cu(OH)]+-Z exhibited optimal DeNOx performance. • The optimal ratio of Cu2+ species can promote the rapid formation of intermediates. In diesel vehicle exhaust after-treatment systems, high silica Cu-SSZ-13 has received increasing attention as a commercialized catalyst owing to its high efficiency in selective catalytic reduction reactions with NH 3 (NH 3 -SCR). However, research on the regulation of Cu2+ species within metal active centers in the pore structure of chabazite (CHA)-type zeolite to improve catalytic performance lacks sufficient depth. Herein, SSZ-13 zeolite with various Al distributions was prepared by adjusting the proportion of N,N,N-Trimethyl-1-adamantanaminiumhydroxide (TMAdaOH) and Na in the initial gel. Moreover, three representative Cu-SSZ-13 catalysts with different Cu2+ species were synthesized via an ion exchange method. 23Na MAS NMR and NO adsorption infrared spectroscopy results revealed that with increasing Na content and decreasing TMAdaOH concentration in the initial gel, the number of paired Al in the CHA framework gradually increased. Consequently, this increased the number of Cu2+-2Z sites near six-membered ring (MR) and reduced the amount of [Cu(OH)]+-Z sites near eight-MR. The fresh Cu-SSZ-13 catalyst, with a moderate amount of Cu2+-2Z and [Cu(OH)]+-Z, exhibited optimal catalytic performance across the entire temperature window. After hydrothermal aging, Cu-SSZ-13 with a higher concentration of Cu2+-2Z species featured optimal performance among all Cu-SSZ-13 catalysts above 400 °C. These findings indicated the significance of balancing the amount of both Cu2+-2Z and [Cu(OH)]+-Z in the Cu-SSZ-13 zeolite. Additionally, the results elucidated the reaction intermediates involved in the NH 3 -SCR process catalyzed by Cu-SSZ-13 with various Cu species. [ABSTRACT FROM AUTHOR]

Selective catalytic reduction (SCR) systems are an effective way of treating NO x emissions to meet increasingly stringent international emission standards. However, the difference of reaction temperature and catalyst location will restrict the reaction of SCR to some extent. Therefore, considering the different reaction conditions, it is necessary to analyze the relationship between them for the study of SCR reaction. In this paper, Cu-ZSM-5 is selected as the catalyst in the SCR reaction, and the effects of different temperatures and catalyst locations on NH 3 molar concentration and NO x conversion under three different SCR are investigated. Firstly, a dynamic model of NH 3 -SCR is established and verified by the experimental data of fast SCR, standard SCR, and NO 2 -SCR in steady state. Then, the RSM (Response Surface Methodology) is used to further optimize NO x conversion rate. The optimal reaction conditions under the three SCR reactions were obtained by RSM optimization. The results indicate that both reaction temperature and catalyst location exert significant effects on NO x conversion under the three SCR reactions. Finally, the performance of NH 3 -SCR over Cu zeolite catalyst is predicted and further evaluated to provide combinations and frameworks for improved performance. • A dynamic model of NH 3 -SCR is established and verified by the experimental results. • The fast SCR, standard SCR, and NO 2 -SCR are compared in steady state. • The effects of different structure parameters on NH 3 molar concentration and NO x conversion are investigated. • The optimal reaction conditions under the three SCR reactions were obtained by RSM optimization. [ABSTRACT FROM AUTHOR]

In the selective catalytic reduction (SCR) of NO x with NH 3 , a catalyst usually exhibits a seesaw effect on de-NO x activity and N 2 selectivity at low temperatures. Herein, we designed metal-organic frameworks (MOFs) with dual-ligand coordination to regulate the electronic and morphological structure for a breakthrough of the seesaw effect. The developed catalyst attained a noteworthy NO x conversion exceeding 90% within 60–330 ℃ with increased N 2 selectivity. The dual-ligand coordination leads to more defects and a more uniform electron distribution for delocalization of electrons, thereby improving de-NO x activity. Furthermore, the dual-ligand coordination manifests a Si-O-Mn bond for amplifying both de-NO x activity and thermal stability. Additionally, the dual ligands and Mn produce a hollow sea-urchin-like morphology with more exposed active sites for concentrating reactants and intermediates to improve electron transfer efficiency in N 2 selectivity. This work clarifies the mechanism of dual-ligand regulation for electron-morphology to simultaneously enhance de-NO x activity and N 2 selectivity. [Display omitted] • TEOS&Mn-BTC with more defects and structure tunability is designed by dual-ligand coordination. • Si-O-Mn bond formed by dual ligands leads to electron-metal-carrier coordination structure. • Self-assembly of block copolymers with ligands and Mn forms hollow sea-urchin-like microsphere. • The electron-morphology regulation breaks the seesaw effect between activity and selectivity. [ABSTRACT FROM AUTHOR]

Two‐dimensional (2D) catalysts are highly attractive for their great potential in environment remediation and energy conversion. In this work, a novel layered manganese silicate (MnSiO3) catalyst was synthesized by hydrothermal method using silica in vermiculite, a layered silicate clay mineral, as the lattice‐matching matrix and silicon source. The epitaxial growth of MnSiO3 is confined in the 2D directions, resulting in the morphology of vermiculite crystal thin nanosheets. The physichemical characterization results showed that MnSiO3 possessed higher Mn4+ content, acidic sites and reducing substances than that of MnOx/SiO2. The MnSiO3 therefore exhibited 100 % NO conversion rate with 85 % N2 selectivity at 150 °C in the NH3−SCR process. In situ DRIFTS studies show that MnSiO3 has strong NO adsorption capacity and NH3 activation capacity, which is beneficial to the improvement of NH3−SCR activity. [ABSTRACT FROM AUTHOR]

Many coking plants have adopted the process of preheating flue gas to apply medium and low temperature selective catalytic reduction (SCR) denitrification technology, which increases the NOx treatment cost, fuel consumption, and generates secondary pollutants. Based on the unique temperature distribution characteristics of the coke oven regenerator, this work proposes a method for synergizing SCR inside the regenerator to remove NOx. A 3-D numerical model of the synergy between heat storage and SCR reaction was constructed to study the influence of mixing parameters (atomization angle, injection velocity, nozzles number) on the NO reduction and NH3 distribution. The validity of the model was verified. The results showed that the uneven distribution of NH3 near the catalytic layer and the small SCR coating area limited the NO reduction efficiency. Increasing the number of nozzles was more beneficial than the injection velocity and atomization angle for improving the NH3 distribution uniformity and NO reduction efficiency, achieving a maximum NO reduction efficiency of 37.1% (reduced to 251.6 mg/m³). Further research found that the NO reduction capacity of the co-operative SCR model cannot exceed 36% without changing the thermal storage brick structure. When the inlet NO concentration is less than 235 mg/m3, the reaction model ensures that the outlet NO concentration meets the national emission standards. [ABSTRACT FROM AUTHOR]

The Co-Mn-LDH catalyst was synthesized by the hydrothermal method. Then the catalyst was calcined and modified to prepare the Co-Mn-LDO catalyst, which was applied to low-temperature NH3-SCR denitration. The results show that the overall denitration performance of the Co-Mn-LDH catalyst is general, the optimal denitration efficiency is only 45%.However, the optimal denitration conversion of the modified Co-Mn-LDO catalyst is 90% at 250 ℃.The analysis shows that the Co-Mn-LDO catalyst has larger specific surface area, more Co3+,Mn4+ species and surface adsorbed oxygen, which result in more excellent denitrification performance. [ABSTRACT FROM AUTHOR]