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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]

NH3 is a dangerous gas, posing significant threats to human health and the delicate equilibrium of the environment. It emerges as a primary contributor to the noxious gas emissions prevalent in the selective catalytic reduction (SCR) processes employed by marine diesel engines. Its deleterious impact extends beyond the immediate surroundings, permeating the air with potential health hazards and exacerbating environmental degradation. The repercussions of NH3 emissions are far-reaching, impacting respiratory health, ecosystem vitality, and overall air quality. In this paper, BaTiO3/Ti3C2Tx composites were synthesized by anchoring BaTiO3 nanospheres on multilayer Ti3C2Tx nanosheets. The shortcomings of low sensitivity and poor recovery of the pristine Ti3C2Tx MXene gas sensor were improved. The BaTiO3/MXene composite sensor exhibits an improved response (10.43) to 20 ppm NH3 at room temperature, which is about 3.5 times higher than that of the pure MXene sensor. Furthermore, the BaTiO3/MXene composite sensor greatly improves the recovery time and exhibits outstanding repeatability, stability, and high selectivity to NH3. The exceptional characteristics of these composites underscore the potential for advancing novel sensitive materials in the form of BaTiO3/MXene composites, specifically tailored for high-performance NH3 sensors. [ABSTRACT FROM AUTHOR]

To control the diesel engine urea SCR system with high accuracy, firstly, the partial differential equations of the SCR system are simplified through variable substitution and the method of characteristic lines to eliminate the partial derivative terms of the hyperbolic partial differential equations in the flow direction. The backward difference method is used to solve the problem, and the adaptive time step is adjusted to improve computational efficiency. Secondly, the Levenberg-Marquardt algorithm is applied to identify the model parameters per second based on the 1800-s test bench data. By combining the experimental data with the parameter identification results, this paper calculated the downstream NOx concentration with 99.5 % accuracy. Finally, the 1800s transient test data was applied to a commonly used single-state SCR control model, and cell numbers 1–4 of the cases were numerically simulated. It was found that the reduced-order model had a computation time of 1 s but was less accurate. When the test data was applied to the model presented in this study, the calculation time was 27s, and the model's calculation results show that the average error of the downstream NOx concentration is 16.95 ppm, which is 14.3 ppm lower than that of the two-cell one-state model.

Selective catalytic reduction (SCR) is an important method to control nitrogen oxides (NOx) emissions from diesel engines. Excellent SCR structural parameters are the key to effectively reduce NOx and back pressure. The dynamic reaction processes of NOx standard reaction, fast reaction and NO2-SCR reaction are deeply explored by establishing the Eley-Rideal model. The results show that the wall thickness and washcoat thickness of the SCR are the main determinants of the catalyst performance, while the CPSI has a great influence on the pressure drop. In addition, regression prediction analysis of experimental data by random forest (RF), particle swarm optimized backpropagation artificial neural network (PSOBP-ANN) and response surface methodology (RSM) was performed to explore the coupling relation functions of structural parameters, and optimal test results were solved and verified. The denitrification efficiency of the structure-optimized SCR system increased by 22 % and the pressure drop decreased by 23 %.

[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]

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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]

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]

Pollutants such as nitrogen oxides (NOx), sulfur oxides (SO2), and particulate matter (PM) in ship exhaust have a great impact on human health, environment and climate conditions. Combined selective catalytic reduction technology and dry exhaust gas cleaning technology, a test rig (SCR-DryEGCS system) for WD10C195-15 marine four-stroke high speed diesel engine was established to analyse the removal effect of NOx, SO2, and PM from exhaust gas. The SCR-DryEGCS system removed 89.03%, 99%, and 96% of NOx, SO2, and PM respectively. And also compared with low sulfur oil combined SCR method to verify the feasibility of the SCR-DryEGCS method. It shows that the SCR-DryEGCS system has its own advantages and has a good effect on the removal of NOx, SOx, and PM at the same time. [ABSTRACT FROM AUTHOR]

The SO2 poisoning of a heterobimetallic FeCu‐SSZ‐13 in selective catalytic reduction of NO with NH3 (NH3‐SCR) was systematically investigated in this study. It was shown that when SO2 is involved in the feeding flue gas, the losses in the redox ability of active metals (primary contributor to deactivation) and in the number of Brønsted acid sites both inhibit the formation of NH4NO2 intermediate, resulting in the rapid deactivation of FeCu‐SSZ‐13. The SO2 poisoning of FeCu‐SSZ‐13 at low temperature is more serious than at high temperature, because of the more severe loss of redox ability of active metals. Unlike that of monometallic Cu‐/Fe‐CHA, the SO2 poisoning of the bimetallic one is saliently featured by that partial SO2 is oxidized to SO3 and partial Brønsted acid sites are destroyed due to the formation of H2SO4. This work may provide a fundamental understanding on the SO2 poisoning of heterobimetallic zeolite‐based NH3‐SCR catalysts. [ABSTRACT FROM AUTHOR]

This study quantified emission factors of black carbon (BC) and nitrogen oxides (NOx) from 21 engines on in-use excursion vessels and ferries operating in California's San Francisco Bay, including EPA uncertified and Tier 1-4 engines and across engine operating modes. On average, ∼60 fuel-based emission factors per engine were measured using a novel combination of exhaust plume capture combined with GPS location and speed data that can be more readily deployed than common portable emissions measurement systems. BC and NOx emission factors (g kg-1) were lowest and least variable during fast cruising and highest during maneuvering and docked operation. Selective catalytic reduction (SCR) reduced NOx emissions by ∼80% when functional. However, elevated NOx emissions that exceeded corresponding exhaust standards were measured on most Tier 3 and Tier 4 engines sampled, which can be attributed to inactive SCR during frequent low engine load operation. In contrast, BC emissions exceeded the PM emission standard for only one engine, and SCR systems employed as a NOx reduction technology also reduced emitted BC. Using these measured emission factors to compare commuting options, we show that the CO2-equivalent emissions per passenger-kilometer are comparable when commuting by car and ferry, but BC and NOx emissions can be several to more than ten times larger when commuting by ferry.

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]

As society moves towards climate neutrality, hydrogen fuelled internal combustion engines (H2 ICEs) should be considered as a prime technology. These engines are valued for their robustness, superior lifetimes, manufacturing techniques and characteristics, which are already known from diesel or gasoline engines. Since an H2 ICE is run on hydrogen (H2), carbon-based emissions are only released on a very low level from the lube oil. Nitrogen oxides (NOx) emissions are de facto the only gaseous pollutant that must be processed by the exhaust aftertreatment system (EAS) of such engines. This paper provides an overview of the raw exhaust gas emission behaviour of a 2 l four-cylinder passenger car engine that is run solely on hydrogen. As already mentioned, the main challenge faced by the EAS is to reduce NOx. Thus, the inspected EAS includes a selective catalytic reduction (SCR) catalyst with ammonia (NH3) as a reductant. The species of NOx was reduced under stationary operation conditions at all of the considered engine load points at an efficiency of at least 98%. Strategies that could be applied to conduct a load change of an H2 ICE were experimentally investigated. To perform a load change under high performance conditions, H2 ICEs needed to be run on a richer air-fuel mixture than under stationary operation conditions in order to provide enough exhaust enthalpy for the turbocharger. If a richer air-fuel mixture was used, higher NOx emissions were detected, increasing the necessity of an EAS containing an SCR catalyst for H2 ICEs. A WLTC and two RDE cycles were investigated to determine their raw and tailpipe exhaust gas emissions. By applying a simple AdBlue® dosing strategy, the raw NOx exhaust gas emissions from the WLTC could be reduced from 79.9 mg/km to as low as 7.3 mg/km. Carbon-based and secondary emissions such as NH3 and nitrous oxides (N2O) were measured at levels well below 5 mg/km. [ABSTRACT FROM AUTHOR]

Pt/ZrP2O7 catalysts exhibiting high activity for catalytic NOx reduction by H2 in the presence of excess O2 were developed in this study. At a low temperature of 125 °C and a high space velocity of approximately 5 × 104 h–1, 0.4 wt % Pt/ZrP2O7 facilitated a higher NO conversion to N2 (51%) than 0.4 wt % Pt/ZrO2 (<5%) for a reaction mixture of 200 ppm NO, 5000 ppm H2, 10% O2, and He balance. However, N2O and NO2 production increased at temperatures lower than 100 °C and higher than 200 °C, thereby decreasing the N2 yield. High-resolution electron microscopy and X-ray photoelectron spectroscopy analyses of 0.4 wt % Pt/ZrP2O7 revealed the coexistence of large metallic Pt crystallites with sizes of ∼20 nm and highly dispersed Pt oxide nanoclusters. When Pt loading was decreased to 0.05 wt %, the large metallic Pt crystallites disappeared, and only the Pt oxide nanoclusters remained on ZrP2O7. Owing to this structural change, N2O/NO2 formation was significantly suppressed, enabling highly selective NO reduction to N2. Moreover, catalyst preparation by equilibrium adsorption instead of wet impregnation further improved the reaction, achieving >90% selective NO conversion to N2, which was nearly free of undesired byproducts (NH3, N2O, and NO2) at 175 °C. The Pt oxide nanocluster supported on ZrP2O7 was more tolerant to the presence of 10% water vapor in the exhaust gas than the metallic Pt particles. Therefore, the developed catalyst is suitable for applications in practical exhaust gas purification for H2-fueled internal combustion engines. [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]

The reduction of various nitrogen oxide (NOx) emissions from diesel engines is an important environmental issue due to their negative impact on air quality and public health. Selective catalytic reduction (SCR) has emerged as an effective technology to mitigate NOx emissions, but predicting the performance of SCR systems remains a challenge due to the complex chemistry involved. In this study, we propose using DNN models to predict NOx emission reductions in SCR systems. Four types of datasets were created; each consisted of five variables as inputs. We evaluated the models using experimental data collected from a diesel engine equipped with an SCR system. Our results indicated that the deep neural network (DNN) model produces precise estimates for exhaust gas temperature, NOx concentration, and De-NOx efficiency. Moreover, inclusion of additional input features, such as engine speed and temperature, improved the prediction accuracy of the DNN model. The mean absolute error (MAE) values for these parameters were 3.1 °C, 3.04 ppm, and 3.65%, respectively. Furthermore, the R-squared coefficient of determination values for the estimates were 0.912, 0.983, and 0.905, respectively. Overall, this study demonstrates the potential of using DNNs to accurately predict NOx emissions from diesel engines and provides insights into the impact of input features on the performance of the model. [ABSTRACT FROM AUTHOR]

This study aims to numerically analyze the ceramic and metallic monoliths as a catalyst substrate of selective catalytic reduction (SCR) system in marine applications. The representative elementary volume of each catalyst substrate was chosen and pressure drop through the volume was numerically calculated to estimate the parameters for the porous model. The fixed-bed experiment using a powder catalyst of 3V7MO/TiO2 was conducted in the way to estimate the global one-step reaction kinetics. Thus, the NO conversion from both ceramic and metallic monolith catalysts was calculated by a porous model with a simplified reaction mechanism to numerically investigate the flow and thermal characteristics within the two types of catalyst substrate. As an extreme condition, an external heat loss with an ambient temperature of 300 K was set to the reactor wall. Predicted results indicate that the NO conversion performance of ceramic monolith is better in general due to the lower heat loss from the cold wall. However, it is found that there is a trade-off relationship between the residence time and the external heat loss. Heat management such as thermal insulation plays an essential role to maximize the benefits of using metallic monolith as a catalyst substrate for practical marine applications. [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]

Featured Application: Catalytic NOx emission control. Cu-CHA zeolites have proven to be effective for NOx reduction, but a drawback in using CHA zeolites is the cost associated with using expensive organic structure-directing agents. To overcome this drawback, we are reporting here the synthesis of Cu-CHA zeolite catalysts in both their NH4-form as well as K-form that do not require the use of organic structure-directing agents. After comprehensive characterization by XRF, XRD, 27Al NMR spectroscopy, FE-SEM, SEM/EDS, N2-adsorption/desorption, NH3-TPD, H2-TPR, and XPS, the zeolite catalysts were tested for NOx conversion by NH3-selective catalytic reduction (NH3-SCR). Cu-NH4-CHA zeolite catalysts exhibited remarkable activity and thermal stability over a wide temperature window, outperforming their counterpart K-forms. Among the NH4-forms of CHA zeolite catalysts, the 0.1 M Cu-NH4-CHA showed the best catalytic performance, achieving 50% NOx conversion at a temperature as low as 192 °C, and reaching full conversion of NOx at 261 °C. These Cu-based CHA zeolite catalysts are promising thanks to their environmentally friendly synthesis and offer the opportunity of maximizing DeNOx strategies in applications for NOx pollution abatement. [ABSTRACT FROM AUTHOR]

Nitrogen oxides (NOx) are the primary air pollutant in China. The iron and steel industries have become the primary industrial sources of NOx emissions in China. The NOx emissions from iron and steel industries account for 27.3% of all industrial NOx emissions from sources nationwide, surpassing thermal power generation and cement manufacturing. Over the past ten years, China’s iron and steel industry has achieved tremendous results in flue gas desulfurization, but a huge gap in denitrogenate (deNOx) still remains. In 2019, the Ministry of Ecology and Environment and other departments jointly issued “Opinions on Promoting the Implementation of Ultra-low Emission in the Iron and Steel Industry”, which promoted the retrofitting of ultra-low emission in the iron and steel industry. Sintering, pelleting, coking, and other processes are the focus of retrofitting for NOx emissions. Because their low-temperature flue gas contains several contaminants that differ from the flue gas of thermal power plants, they cannot completely copy the existing deNOx technology for the coal-fired boiler flue gas of thermal power plants. At present, selective catalytic reduction (SCR), activated carbon (AC) adsorption catalysis, ozone (O3) oxidation and absorption, and other technologies are used in sintering, pelleting, and coking processes. These technologies have achieved good results. Herein, we investigated the existing flue gas deNOx technologies for sintering, pelleting, and coking processes in iron and steel industries and analyzed the advantages and disadvantages of SCR technology, AC adsorption catalysis, and O3 oxidation and absorption technologies. The SCR technology has high efficiency and reliable performance, but the operation process requires heating of the flue gas, which uses large amounts of blast furnace gas or coking oven gas, and the service life of the catalyst is typically approximately three years. The waste SCR catalysts are recognized as HW50 hazardous waste. AC adsorption catalytic technology can simultaneously desulfurize and deNOx; its operating temperature is low without flue gas reheating. The by-product of H2SO4 can be utilized, and the waste AC produced can be directly used for sintering or coking, while its deNOx efficiency is low. O3 oxidation and absorption technologies have a low initial investment cost and require little floor space. However, their operating cost is relatively high, and the coabsorption of NOx and SO2 makes the desulfurization ash mixed with nitrate, which increases the difficulty of comprehensive utilization. Finally, we analyzed the application possibilities of SCR and other technologies, providing a reference for the development and selection of deNOx technologies for flue gas from the iron and steel industry.

Al modified FDU-12 molecular sieve (Al–FDU-12) was successfully prepared by hydrothermal method and then Cu/Al–FDU-12 and Cu–Ce/Al–FDU-12 denitrification catalysts were synthesized using the impregnation process. Through experiment investigated was the impact on the NH3–SCR (selective catalytic reduction of NO with NH3 as the reductant) activity of different loadings of active component. The sulfur tolerance of the catalyst was also investigated. The results exhibited that the optimal loadings of Cu and Ce were 20 and 10%, respectively. The NOx conversion of Cu20Ce10/Al–FDU-12 reached 80%, while its N2 selectivity was over 99% at 250°C. The addition of Ce can improve the redox characteristics as well as the amount of surface chemisorbed oxygen, which facilitated the "FAST SCR" reaction. In addition, Cu+ is preferentially oxidized to form Cu2+, NOx is combined with Cu2+ to form the active intermediate Cu2+–NxOy and further reacts with NH3 to generate N2 and H2O, yet Cu+, thus promoting the catalytic cycle. What's more, the catalyst had good catalytic activity when SO2 was introduced. [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]

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Three kinds of Ce-based catalysts (CePO4, CeVO4, Ce2(SO4)3) were synthesized and used for the selective catalytic reduction (SCR) of NO by NH3. NH3-SCR performances were conducted in the temperature range of 80 to 400 °C. The catalytic efficiencies of the three catalysts are as follow: CePO4 > CeVO4 > Ce2(SO4)3, which is in agreement with their abilities of NH3 adsorption capacities. The highest NO conversion rate of CePO4 could reach about 95%, and the catalyst had more than 90% NO conversion rate between 260 and 320 °C. The effect of PO43−, VO43− and SO42− on NH3-SCR performances of Ce-based catalysts was systematically investigated by the X-ray photoelectron spectroscopy analysis, NH3 temperature programmed desorption, H2 temperature programmed reduction and field emission scanning electron microscopy tests. The key factors that can enhance the SCR are the existence of Ce4+, large NH3 adsorption capacity, high and early H2 consumptions, and suitable microstructures for gas adsorption. Finally, CePO4 and CeVO4 catalysts also exhibited relatively strong tolerance of SO2, and the upward trend about 8% was detected due to the sulfation enhancement by SO2 for Ce2(SO4)3. [ABSTRACT FROM AUTHOR]

The catalyst activity monitoring in the selective catalytic reduction (SCR) system is of great importance for safety and economic operation in the power plant. To address the problem, a framework based on clustering considering time delay has been proposed. A compound parameter, q, is put forward in this paper as a strategy to remove the influences from gas volume (power output), inlet NOx concentration, and outlet NOx concentration to the ammonia amount. A modified entropy‐based fuzzy clustering (EFC) method is proposed by a threshold varying model and then tested for its efficiency by four datasets from the University of California, Irvine (UCI) machine learning repository. With the maximum mutual information entropy coefficient (MIC) method for detecting time delay and the modified EFC method, process data from three working levels are handled for automatically obtained clustering centres. The proposed activity value, μ, is then calculated based on 1440 process data before and after the catalyst replacement shown in boxplot figures. The results of the framework are analyzed to be in accordance with the real working conditions, with μ values and fluctuation ranges starting to fall near first from the 721st sample in the 24th box. [ABSTRACT FROM AUTHOR]

The significance of the selective catalytic reduction system in vehicles increases in line with the high standards of emission control and enhanced selective catalytic reduction efficiency. This study aims to improve the performance of the selective catalytic reduction system through an optimization method using a metamodel. The objective function is defined as the ammonia uniformity index, and the design parameters are defined in relation to the pipe length and mixer related to the chemical reaction of the urea solution. The range of design parameters has been designated by a trial-and-error method in order to maintain the overall design drawings of the selective catalytic reduction system and prevent modeling errors. Three algorithms, namely, ensemble decision tree, Kriging, and radial basis function, are employed to develop the metamodel. The accuracy of the metamodel is verified based on three indicators: the normalized root mean square error, root mean square error, and maximum absolute error. The metamodel is generated using the Kriging model, which has the highest accuracy among the algorithms, and optimization is also performed. The predicted optimization results are confirmed by computational fluid dynamics numerical analysis with a 99.83% match. The ammonia uniformity index is improved by 1.38% compared to the base model, and it can be said that the NOx purification efficiency is improved by 30.95%. Consequently, optimizing the uniformity index performance through structural optimization is of utmost importance. Furthermore, this study reveals that the design variables related to the mixer play a crucial role in the performance. Therefore, using the metamodel to optimize the selectively catalytic reduction system's structure should be considered significant. Finally, in the future, the analysis model can be validated using test equipment based on the findings of this study. [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]

The following research presents a numerical evaluation of existing and conceptual urea-mixing devices used in close-coupled (to the engine) selective catalytic reduction (SCR) systems. The analysis was aimed at the assessment of urea-mixing devices that could considerably enhance the reduction of nitrogen oxides from the diesel-engine combustion process under a wide range of operating conditions, including cold starts. The analysis showed that replacing blade-equipped static mixers with perforated stationary mixing devices may provide a more uniform spatial distribution of ammonia at the inlet to the SCR catalyst and reduce pressure drops generated by mixing devices. Moreover, the conceptual mixing devices, based on combinations of the blade and perforated mixers to develop intensive turbulence, enabled the increase of the mixing length leading to effective decomposition of the urea-water solution (UWS), and provided uniform spatial distribution of ammonia, even for the small-sized mixing systems. However, the intensive mixing was often associated with a significant rise in the pressure drop.

The most commonly used method for industrial flue gas denitrification is selective catalytic reduction (SCR). However, the catalyst preparation is complex and expensive. The iron and steel industry produces large amounts of waste containing metal oxides that can be used as active catalytic components for SCR of nitrogen oxides. In this study, a novel catalyst for SCR of nitrogen oxides was prepared by roasting, sulfuric acid, and sulfuric acid-roasting modification of steelmaking sludge, which is used as the raw material. The physical and chemical properties of the catalysts from steelmaking sludge before and after modification were analyzed using Brunauer-Emmett-Teller analysis, scanning electron microscopy, X-ray diffraction, X-ray fluorescence, and temperature-programmed desorption of ammonia. It has been revealed that Fe, Mn, V, and Ti are the main active groups of the catalyst. Calcination can transform Fe3O4 to α-Fe2O3 with better denitrification activity, thus improving the catalyst reactivity. A high calcination temperature can cause a collapse of the pore structure of the catalyst, thereby decreasing the surface area and active sites and ultimately reducing the catalytic activity. The catalyst modified at the optimum calcination temperature of 400 °C has the highest catalytic activity at 350 °C and a denitrification efficiency of 57.6%. The sulfuric acid-modified catalyst has excellent catalytic activity. Sulfuric acid impregnation changes the surface morphology of the catalyst, reduces the grain size, generates numerous sulfate species, provides more acidic sites on the catalyst surface, and promotes catalyst performance. The 9 mol·L−1 sulfuric acid-modified catalyst has the highest denitrification efficiency at 300 °C. Compared with the unmodified catalyst, the denitrification efficiency significantly increased from 22.9% to 88.5%. Conversely, a denitrification efficiency of 72.9% is measured for the catalyst modified by sulfuric acid and roasting modification, which is lower than that of the sulfuric acid-modified catalyst at 300 °C. This may be explained by the fact that sulfuric acid and roasting modification causes not only structural changes in the catalyst but also the decomposition of the generated sulfate species, thereby leading to catalytic efficiency reduction. This work shows a feasible preparation of a low-cost SCR catalyst for denitrification by roasting and acid modification using steelmaking sludge as the raw material, provides a theoretical basis for developing low-cost denitrification catalysts using metallurgical solid wastes and promotes clean production in the metallurgical industry.

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.