NO Conversion Research Articles

Analysis and prediction of denitration performance of Mn1Co0.5Cr0.5Ox catalyst based on CFD and BP-GA method

Based on the experimental data of Mn1Co0.5Cr0.5Ox catalysts and the component transport model in Computational Fluid Dynamics (CFD), a kinetic model for the standard NH3-SCR (NH3 selective catalytic reduction) process was effectively established. The objective of the model development was to predict the denitrification reaction rate of the catalyst, which incorporates various factors such as the Arrhenius parameters (Pre-exponential factor and activation energy), inertial resistance, viscous resistance, and surface-to-volume ratio. To verify the practicability of the model, simulation results were compared with actual experimental data. The effects of NH3, NO, O2 concentrations, and gas hourly space velocity (GHSV) on NO conversion were simulated and analyzed. Subsequently, the NO conversion prediction model was trained and established using a combination of numerical simulation results, back-propagation neural network, and genetic algorithm (BP-GA). Furthermore, the significance of the impact that various factors had on the denitrification activity of the catalyst was determined.

Reaction site-isolation for simultaneous removal of NOx and toluene: A reverse strategy to realize bifunctional catalysis

In this study, 3V5W/Cu@Ti catalyst with the function of reaction site-isolation was prepared to achieve the simultaneous removal of NO and toluene. The catalyst was prepared through the hard template and impregnation method, and V-W, and Cu species were introduced into the outer and inner layers of the hollow spherical shell TiO2, respectively. Under the coexistence of multi-pollutants, toluene was completely removed with NO conversions above 90% at 250 ℃. Even at high temperatures of 350-400 ℃, complete conversions of NO and toluene were maintained with apparent lower by-products than those for other catalysts. DFT calculations and activation energy(Ea) indicate that NH3 tends to adsorb and react at the V/W sites on the catalyst's outer layer, while toluene is more likely to adsorb and react at the Cu sites on the inner layer. The Ea and DFT results were well-consistent with the catalytic reactivity, revealing the achievement of reaction site-isolation.

Effect of modified Fe2O3/activated carbon catalysts for low-temperature CO selective catalytic reduction of NOx in underground diesel vehicle exhaust

The elimination of CO and NOx has practical significance for the control of exhaust pollutants from underground diesel vehicles. Catalytic reduction of NO by CO (CO-SCR) using activated carbon (AC) catalysts is considered a cost-effective and environmentally friendly denitrification method. In this study, Fe2O3/AC-based catalysts were prepared using an impregnation method and modified with different metals to investigate their impact on catalyst performance. The results demonstrated that the catalyst exhibited the highest denitrification efficiency when loaded with 10% Fe. The Mn-doped 10Fe/AC catalyst exhibited the best catalytic performance, with the highest NO conversion of 97.5% and CO removal rate of 83.3% at 240 °C. The effects of loading Mn, Ce, and La on the physical and chemical properties of the catalysts were analyzed using various characterization tools, and the reaction mechanism of the catalysts was investigated by in situ DRIFTS technique. The findings revealed that the strong synergistic interaction occurring between Mn and Fe led to an increase in the surface-adsorbed oxygen (Oα) and Fe3+, which produced more oxygen vacancies on the catalyst, thus improving the redox properties. The in-situ DRIFT results indicated that the addition of Mn enhanced the adsorption capacity of active NO and CO. For the CO-SCR reaction on Fe-Mn/AC catalyst, the E-R mechanism was followed at low temperature and the L-H mechanism was followed at high temperature.

Selective catalytic reduction of NO with NH3 over HZSM-5/CeO2 hybrid catalysts: Relationship between acid structure and reaction mechanism

CeO2 is active in the NH3 selective catalytic reduction of NO (NH3-SCR) reaction due to its excellent redox properties. However, the low surface acidity of CeO2 limits its NH3-SCR activity. In this study, highly active HZSM-5-modified HZSM-5/CeO2 (Z/Ce) mixed oxide catalysts were prepared by a simple physical milling method. The HZSM-5 modification stimulated many thermally stable Brønsted-acid structures and high oxygen mobility on the surface of the Z/Ce catalysts, promoting the acid cycling pathways driven by redox macrocycles, and accelerating NO removal. The NO conversion of 25Z/Ce at 200–400 °C is about 34.8 %-62.3 % higher than that of CeO2. A series of physicochemical and in situ interfacial reactions were analyzed to explore the medium- and high-temperature reaction mechanism on the CeO2 surface. The Eley-Rideal reaction mechanism on the Lewis-acid structure with NO(g) as the reactant is deduced. When HZSM-5 modified CeO2, more NO was activated to NO2(g) on the surface of the Z/Ce catalyst at medium and high temperatures (300 °C). This significantly enhanced the Eley-Rideal reaction mechanism with NO2(g) as the main reactant on the Brønsted-acid structure as well as the occurrence of the “Fast-SCR” reaction. This work provides a simple method to improve the performance of CeO2 in the NH3-SCR reaction and elucidates the reaction mechanism.

Unveiling the role of oxygen in ammonia coal combustion: A DFT study on NOx emission mechanism

Ammonia-coal combustion mitigates CO2 emissions, yet nitrogen oxide emissions and char nitrogen oxidation mechanisms require further study. Our research employs density functional theory to explore coal char interactions with NO, NH3, and the impact of hydroxyls (–OH) and oxygen on reduction–oxidation processes. Findings indicate oxygen aids in forming hydroxyls on coal char, facilitating NO to NO2 conversion, lowering the activation energy for ammonia-coal oxidation to NO2. Oxygen also promotes char nitrogen oxidation to NO, reducing its activation energy. In NH3/coal/O2 systems, NH3 oxidation initiates NO formation. With the increase of the temperature, the reduction rate of NO by ammonia is always higher than the production rate of NO.

Low temperature sintering flue gas NH3-SCR denitrification mechanism of embedded 7Mn3Ce/AC catalyst

Friction of catalyst in practical application and transportation leads to the metal oxides shedding, thus diminishing the lifetime. In order to inhibit the active component fallout, a series of embedded catalysts were prepared by activated carbon (AC) fabrication from coal as based, which were designed to remove NOx from sinter flue gas. Research results demonstrated that the denitrification activity of 7Mn3Ce/AC catalyst reached 81.3 % at 180 °C, and still maintained stable NO conversion after 44 h. MnO2 and CeO2 were added in catalyst could increase the Oα proportion, leading to an improvement the mobility of oxygen. Moreover, the formation of oxygen vacancies by Oβ in cerium oxide was facilitated by a high relative ratio of Ce3+, and Mn4+ favorable redox properties promoted the reduction of NO to N2, which advantaged the denitrification process. Furthermore, abundant Lewis acid and Brønsted acid sites were instrumental in the accumulation of NH3 on the catalyst surface. The reaction pathway of 7Mn3Ce/AC catalyst followed the E-R and L-H mechanisms.

Unprecedented N2O production by nitrate-ammonifying Geobacteraceae with distinctive N2O isotopocule signatures.

Dissimilatory nitrate reduction to ammonium (DNRA), driven by nitrate-ammonifying bacteria, is an increasingly appreciated nitrogen-cycling pathway in terrestrial ecosystems. This process reportedly generates nitrous oxide (N2O), a strong greenhouse gas with ozone-depleting effects. However, it remains poorly understood how N2O is produced by environmental nitrate-ammonifiers and how to identify DNRA-derived N2O. In this study, we characterize two novel enzymatic pathways responsible for N2O production in Geobacteraceae strains, which are predominant nitrate-ammonifying bacteria in paddy soils. The first pathway involves a membrane-bound nitrate reductase (Nar) and a hybrid cluster protein complex (Hcp-Hcr) that catalyzes the conversion of NO2- to NO and subsequently to N2O. The second pathway is observed in Nar-deficient bacteria, where the nitrite reductase (NrfA) generates NO, which is then reduced to N2O by Hcp-Hcr. These enzyme combinations are prevalent across the domain Bacteria. Moreover, we observe distinctive isotopocule signatures of DNRA-derived N2O from other established N2O production pathways, especially through the highest 15N-site preference (SP) values (43.0‰-49.9‰) reported so far, indicating a robust means for N2O source partitioning. Our findings demonstrate two novel N2O production pathways in DNRA that can be isotopically distinguished from other pathways.IMPORTANCEStimulation of DNRA is a promising strategy to improve fertilizer efficiency and reduce N2O emission in agriculture soils. This process converts water-leachable NO3- and NO2- into soil-adsorbable NH4+, thereby alleviating nitrogen loss and N2O emission resulting from denitrification. However, several studies have noted that DNRA can also be a source of N2O, contributing to global warming. This contribution is often masked by other N2O generation processes, leading to a limited understanding of DNRA as an N2O source. Our study reveals two widespread yet overlooked N2O production pathways in Geobacteraceae, the predominant DNRA bacteria in paddy soils, along with their distinctive isotopocule signatures. These findings offer novel insights into the role of the DNRA bacteria in N2O production and underscore the significance of N2O isotopocule signatures in microbial N2O source tracking.

Highly Efficient NO Conversion on Layered Photocatalysts: Surface Active Site Regulation and Molecule Activation

Highly Efficient NO Conversion on Layered Photocatalysts: Surface Active Site Regulation and Molecule Activation

Selective conversion of thermal decomposition products of ammonium perchlorate by amorphous CoSnOx

The directional transformation of products in the multiphase decomposition process of ammonium perchlorate (AP) still faces significant challenges, one of which is the conversion of greenhouse gas N2O. Furthermore, additional elucidation of the structure and potential catalytic mechanisms of catalysts with high thermal stability is imperative for the aforementioned process. This study proposes a cobalt-based amorphous oxide with high thermal stability for catalysing the thermal decomposition of AP and achieving the transformation of catalytic products from N2O to NO (and its derivatives). The results indicate that the type of catalytic decomposition products is related to the structural transformation of the catalyst, suggesting a synergistic oxidation mechanism by active oxygen and lattice oxygen. The peak decomposition temperature of AP has dropped to near the limit of 257.2 °C, TG-IR test and MD simulation results indicate the selective generation of NO under the lattice oxygen mechanism. In addition, kinetic calculations elucidated the transition of catalysts from amorphous to crystalline state in catalysis. Finally, suggestions were made for the current characterization techniques of catalysts. This study offers a reference point for the catalyst design of AP decomposition-oriented products, which is beneficial for the transition to more environmentally-friendly products.

The enhanced SO2 resistance of Fe-Ti catalyst by W/SO42− co-modification for NH3-SCR: A combined experimental and DFT study

It remains a great challenge to improve the low-temperature SO2 resistance of catalysts applied for selective catalytic reduction of NOx with NH3 (NH3-SCR). This work develops an outstanding SO2-tolerant Fe-Ti (FT) catalyst by W/SO42− co-modification via a sol–gel method using Fe(NO3)3·9H2O, tetrabutyl titanate, ammonium tungstate and thiourea as raw materials. The physicochemical characterizations, in-situ diffuse reflectance infrared Fourier transform (DRIFT) measurements and density functional theory (DFT) calculations were combined to reveal the underlying mechanisms. Although W doping can effectively enhance the surface acidity, NH3 adsorption on Lewis acid sites can still be restrained by competitive adsorption of SO2, whereas SO42− modification can enhance the adsorption stability of NH3 without being affected by SO2. Simultaneously, the NO adsorption ability on Fe sites can be significantly enhanced by W/SO42− co-modification. Furthermore, the W doping or SO42− modification can induce conversion of Fe3+ to Fe2+ to affect the redox property of Fe species. A proper amount of Fe2+ suppressed the oxidizability of FT catalyst to inhibit NH3 overoxidation to enhance N2 selectivity, and created more oxygen vacancies to generate larger amount of chemisorbed oxygen to facilitate NH3 dehydrogenation and NO oxidation. More importantly, the inhibition effect of SO2 adsorption on Fe sites was strengthened by W/SO42− co-modification. Consequently, the W/SO42− co-modified FT catalyst exhibited high activity with >90 % of NO conversion and >95 % of N2 selectivity within a broad window of 275–450 °C and possessed superior SO2 + H2O tolerance at 275 °C.

Thin Films of Bismuth Oxyhalides (BiOX, X = Cl, Br, I) Deposited by Thermal Evaporation for the Decontamination of Water and Air by Photocatalysis

Thin films of BiOCl, BiOBr, and BiOI (BiOX) were deposited by thermal evaporation for their potential application in the decontamination of water and air through their photocatalytic activity, which was compared among the three. The BiOX thin films were subjected to characterization through X-ray diffraction, high-resolution transmission electron microscopy, and scanning electron microscopy. Additionally, the optical properties were determined from the diffuse reflectance spectrum obtained with a spectrophotometer. To assess the efficacy of the semiconductor films in water decontamination, the evolution of rhodamine B discoloration and its mineralization was monitored by measuring total organic carbon. The decontaminating activity in the air was evaluated in a gas reactor, measuring the conversion of NOx-type gases. The results demonstrated that the thin films of the three oxides exhibited decontaminating photocatalytic activity in both water and air. However, notable distinctions were observed in the photocatalytic activities of the three bismuth oxyhalides in water, while in air, they exhibited similarities. In aqueous environments, the mineralization percentages exhibited notable variation after 96 h, with the BiOBr film displaying a value of 9.2%/mg and the BiOCl film a value of 3.9%/mg. In contrast, the NO conversion rate in the air was approximately 0.6%/mg for the three oxyhalide films.

Exploring the promotion effect of low MnCoOx doping for low-temperature NH3-SCR of 13X zeolite synthesized from coal fly ash

Using fly ash rich in SiO2 and Al2O3 to prepare heterogeneous zeolite catalysts is an efficacious pathway for the resource development of solid waste. Herein, 13X zeolite with a rich specific surface area was synthesized from fly ash, and low amount of active components (Mn and Co) was added during the preparation of the 13X zeolite. Finally, a series of low-load xMnyCo/13X denitration catalysts were successfully prepared. The results show that the low supported 1Mn2Co/13X zeolite catalyst exhibits excellent selective catalytic performance, with higher than 80 % NO conversion and more than 90 % N2 selectivity during 150–350 ℃. It also demonstrates excellent resistance to both water and sulfur. Physicochemical characterization analysis indicated that a little Mn and Co were doped on the surface of 13X zeolite did not have a detailed crystal structure. The element Co doping increased the proportion of Mn3+, Mn4+ and Ov on 13X zeolite. The results of in situ DRIFTs demonstrated that the NH3-SCR reaction on the surface of 1Mn2Co/13X zeolite followed both the E-R and L-H mechanisms. Additionally, process simulation results further show that using 1Mn2Co/13X zeolite as an industrial denitration agent can reduce material costs by 64.0 % and operating costs by nearly 20 %.

Selective photocatalytic reduction of nitric oxide to dinitrogen via bimetallic bond incorporation

In this study, we addressed the challenge of optimizing the first rate-limiting NO adsorbate state, which has received limited attention in previous research on the photoreduction of NO. We prepared BiFeWO6 (BFWO), which improved not only the NO removal rate under illumination but also the selectivity of photocatalytic NO conversion to N2. To further optimize the performance, we introduced platinum into BFWO, achieving a 57.5 % NO conversion rate with ∼80 % N2 selectivity under 425 nm light-emitting diode illumination (50 mW/cm2), which is optimal for converting NO into less harmful compounds at low concentrations. FeOBi bonds were identified as the key active sites of the first rate-limiting NO adsorbate state in BFWO through time-resolved operando infrared (IR) spectroscopy and density functional theory (DFT) analysis. The specific adsorption configuration of NO on the FeOBi group accelerated the photoreduction reaction kinetics, resulting in superior photocatalytic NO removal performance.

Multi-objective optimization of chemical reaction characteristics of selective catalytic reduction in denitrification of diesel engine using ELM-MOPSO methodology

This study systematically investigated the effects of structural parameters in a two-stage selective catalytic reduction (SCR) catalyst on ammonia storage, NO conversion efficiency, and ammonia slip using computational fluid dynamics (CFD) simulations. The rank ordering of the correlations between structural parameters and performance metrics was determined by gray relational analysis (GRA). Both the catalyst diameter and the upstream catalyst porosity had correlations exceeding 0.9, making them key parameters affecting SCR performance. An extreme learning machine (ELM) prediction model was trained using data obtained from CFD simulations. The prediction performance of this ELM model was then evaluated using statistical metrics. Finally, the optimized Pareto frontier diagram was obtained through the multi-objective particle swarm optimization (MOPSO) algorithm, and the optimal results were selected for further CFD modeling analysis. The results showed that the upstream NO conversion efficiency of the SCR system was improved by 7.7 %, the downstream NO conversion efficiency was improved by 18.67 %, the ammonia slip was reduced by 71.97 %, and the upstream ammonia storage capacity was improved by 6.83 % compared with the original model.

Synthesis of low-temperature NH3-SCR catalysts for MnOx with high SO2 resistance using redox-precipitation method with mixed manganese sources

It remains a big challenge to enhance the SO2 resistance of catalyst in low-temperature NH3-SCR reduction. In this work, a series of MnOx-a%Mn (a = 0, 1, 3, 5, 10) catalysts were prepared by introducing manganese acetylacetonate during the reaction between lactic acid and KMnO4, based on the molar ratio of manganese acetylacetonate to KMnO4. Notably, MnOx-5 %Mn exhibited more than 95 % NO conversion and 100 % N2 selectivity at 80–240 °C. Moreover, the catalyst demonstrated excellent sulfur resistance by sustaining over 90 % NO conversion at 140 °C at the presence of 100 ppm SO2 for more than 6 h. Furthermore, XPS characterization indicated that adding manganese acetylacetonate enhanced electron transfer efficiency and improved the reduction capacity of the catalyst due to the interconversion between Mn3+ and Mn4+, which improved electron transfer efficiency. The enhanced reduction capacity of the catalyst promoted the formation of oxygen vacancies and surface-adsorbed oxygen species (Oα), avoiding over-oxidation of NH3. The results elucidated that manganese acetylacetonate could optimize the overall performance by modulating the synergistic effect between the oxidizing ability and surface acidity of the catalyst. Therefore, the MnOx-5 %Mn catalyst possessed a broad operational temperature window (40–240 °C) and SO2 resistance in the NH3-SCR reaction, indicating its potential for practical application.

Improved surface acidity of CeO2/TiO2 catalyst by Cu doping to enhance the SCR catalytic activity

The catalyst is based on CeO2 cannot be widely used in SCR reaction because of its poor NH3 adsorption performance. In this study, Cu-doped CeTi catalyst was designed. The results show that the CeTiCu0.3 has a wide active temperature window of 200–450 °C in NH3-SCR reaction, and NO conversion is > 80%. This is mainly due to the fact that Cu doping provides more acidic sites on the surface of CeTi catalyst, especially the increase of Lewis acid sites is more obvious. NH3-TPD showed that CeTiCu0.3 had a large NH3 adsorption capacity and was mainly adsorbed at Lewis acid sites. In situ DRIFTs results show that NH3 first adsorbs on the Lewis acid site of catalyst in coordination state and reacts with gaseous NOx, while NOx adsorbed on catalyst surface has low reactivity. Therefore, the CeTiCu0.3 catalyst is mainly controlled by the Eley–Rideal mechanism. More Lewis acid sites, and abunda nt Cu2+/Cu+ and Ce4+/Ce3+ formed Cu2+, Ce3+ and surface reactive oxygen species are the main reasons for the excellent catalytic performance of CeTiCu.

Temperature-induced evolution of CuOx clusters in CuOx/TiO2 catalyst for boosting auto-exhaust oxidation

Developing non-noble metal oxides, replacing platinum group catalysts for auto-exhaust purification, where their usage amount exceeds 40 % of global demand, remains a challenge. Herein, we presented a combined approach on the synthesis and application of robust CuOx/TiO2 catalysts with ultra-fine CuOx clusters (ca. 1 nm). The strong interaction between CuOx and TiOx induces favorable interfacial charge accumulation, facilitating the extraction of the interfacial oxygen atoms in Cu2-x-O-Ti4-y chains and the surface lattice oxygen on CuOx clusters. Isotope 18O2 experiments and DFT calculations jointly confirmed that these oxygen atoms preferentially participate in the oxidation through the Mars-van Krevelen mechanism below 250 °C. The resulted oxygen vacancies facilitate the adsorption and activation of O2 molecules, which will participate the oxidation above 250 °C through Eley-Rideal mechanism. The increase in the temperature also drives the synergy of active oxygen species in the interfacial Cu2-x-O-Ti4-y bond chains and on CuOx clusters, cooperatively promoting the conversion of NO to NO2. As a result, the CuOx/TiO2 catalyst exhibits exceptional catalytic performance in soot oxidation, with a four-fold higher reaction rate (4.17 μmol g−1 min−1) than that of single-atom Cu₁-TiO2 catalyst. Such findings provide a novel strategy for the advancement of Cu-based cluster catalysts in environmental applications.

Efficient screening of single-atom Porphyrazine-coordinated transition metal catalysts for electrochemical nitric oxide reduction: Insights from first-principles calculations

The electrochemical conversion of NO to NH3 is gaining attention in green energy for its dual benefits of producing ammonia and eliminating toxic NO. However, the lack of efficient and durable electrocatalysts limits its application, highlighting the need for improved catalysts to advance this promising strategy. The emerging transition metal porphyrazine frameworks (TM − Pz), which combine the advantages of single-atom metal (SAC) centers with the coordination of surrounding 4 N ligands, present promising opportunities in the field of electrochemical catalysis. We have designed a series of 3d transition metal single-atom catalysts (SACs) and conducted high-throughput screening, based on first-principles computations, to identify effective catalysts for the electrocatalytic conversion of NO to NH3. Our findings reveal that the Ti − Pz, Fe − Pz, and V − Pz nanosheets exhibit significantly lower UL values of −0.11, −0.24, and −0.31 V, respectively, when compared to the experimentally and theoretically determined criterion of −0.32 V. The correlation between limiting potentials (UL) and a specific descriptor (φ) is particularly significant for constructing a volcano plot, which illustrates the intrinsic properties of metal atoms in various TM − Pz series and their associated remarkable nitric oxide reduction reaction (NORR) performance. Among the range of nanosheets evaluated, the Ti − Pz and Fe − Pz models emerge as particularly noteworthy, demonstrating significantly higher selectivity and NORR activity than their counterparts. This research deepens our comprehension of the distinctive and advantageous properties of SACs, presenting progressive perspectives that can directly facilitate the discovery and optimization of SACs for NORR applications.

Theoretical investigation of graphdiyne-supported single-cluster catalysts for electroreduction of nitric oxide

The electrochemical NO reduction reaction (NORR) to NH3 offers an efficient, environmentally friendly strategy for NO removal and NH3 production, but developing effective catalysts to facilitate the conversion of NO into NH3 remains a challenge. Single-cluster catalysts (SCCs) with multi-metallic sites show promise due to the synergistic interactions among the active atoms. Herein, utilizing density functional theory (DFT) and grand-canonical DFT (GC-DFT), we systematically investigated the potential of late transition metal (TM = Fe, Co, Ni, Cu, Ru, Rh, Pd, Pt) clusters on graphdiyne (TMx/GDY, x = 1–5) for NORR. Ni3/GDY, Pd3/GDY, and Pt3/GDY emerged as the most promising candidates, demonstrating stability, excellent NORR activity, and HER suppression. Their outstanding performance is attributed to the moderate adsorption of NO, with the dxz/dyz orbitals playing a key role in NO activation. GC-DFT results highlight nonlinear variation of intermediate grand free energies with the applied potential. Detailed electronic property analyses were conducted to reveal the charge effects induced by the applied chemical potential. This study provides valuable insights into SCC-catalyzed NO reduction and highlights the significance of potential effects in theoretical simulations of electrochemical systems.

In situ decorated Mn-FeOx amorphous oxides on filter felt by a polyphenol-assisted method for low-temperature NH3-SCR

The combination of dust filtration technology and selective catalytic reduction of nitrogen oxides can effectively reduce the energy consumption and footprint of the flue gas purification system. To fabricate the high efficiency and firmly bonded catalytic filter material, a novel polyphenol-assisted method was designed in this work for in situ decorating Mn-FeOx amorphous oxides onto the smooth polyphenylene sulfide (PPS) filter felt. The polyphenolic compounds are not only worked as the dispersant, but also the binder for Mn-FeOx catalysts to firmly anchor on PPS filter felts. The introduction of Fe3+ into catalyst precursors can increase the Mn4+ content, surface adsorbed oxygen, as well as surface acidity, which displays satisfactory denitration performance and SO2 tolerance at low temperatures. The Mn5Fe1-TA/PDA@PPS sample shows nearly 100 % NO conversion efficiency at 180 °C with only 10.11 % catalysts loading in the sulfur dioxide free flue gas. Furthermore, the green and efficient synthesis route makes the catalytic filter felts preserve the same gas permeability and thermal stability with the pristine PPS filter felt, which suggests that the Mn5Fe1-TA/PDA@PPS has great prospects for simultaneously removing of NOx and dust in practical applications.