Search Results (105)

In wet flue gas desulfurization and denitrification processes, nitrite accumulation inhibits denitrification efficiency and induces secondary pollution due to its acidic disproportionation. This study developed a Mn-modified ZSM-5 zeolite catalyst, achieving efficient resource conversion of nitrite in nitrogen-containing wastewater through an O₃ + Mn/ZSM-5 catalytic system. Mn/ZSM-5 catalysts with varying SiO₂/Al₂O₃ ratios (prepared by wet impregnation) were characterized by BET, XRD, and XPS. Experimental results demonstrated that Mn/ZSM-5 (SiO₂/Al₂O₃ = 400) exhibited a larger specific surface area, enhanced adsorption capacity, abundant surface Mn³⁺/Mn⁴⁺ species, hydroxyl oxygen species, and chemisorbed oxygen, leading to superior oxidation capability and catalytic activity. Under the optimized conditions of reaction temperature = 40 °C, initial pH = 4, Mn/ZSM-5 dosage = 1 g/L, and O₃ concentration = 100 ppm, the $\mathrm{N}{\mathrm{O}}_2^{-}$ oxidation efficiency reached 94.33%. Repeated tests confirmed that the Mn/ZSM-5 catalyst exhibited excellent stability and wide operational adaptability. The synergistic effect between Mn species and the zeolite support significantly improved ozone utilization efficiency. The O₃ + Mn/ZSM-5 system required less ozone while maintaining high oxidation efficiency, demonstrating better cost-effectiveness. Mechanism studies revealed that the conversion pathway of $\mathrm{N}{\mathrm{O}}_2^{-}$ followed a dual-path catalytic mechanism combining direct ozonation and free radical chain reactions. Practical spray tests confirmed that coupling the Mn/ZSM-5 system with ozone oxidation flue gas denitrification achieved over 95% removal of liquid-phase $\mathrm{N}{\mathrm{O}}_2^{-}$ byproducts without compromising the synergistic removal efficiency of NO_x/SO₂. This study provided an efficient catalytic solution for industrial wastewater treatment and the resource utilization of flue gas denitrification byproducts. Full article

The efficient simultaneous removal of NO_x and CO from sintering flue gas under low-temperature conditions (110–180 °C) in iron and steel enterprises remains a significant challenge in the field of environmental catalysis. In this study, we present an innovative strategy to enhance the performance of CuSmTi catalysts through silver modification, yielding a bifunctional system capable of oxygen structure regulation and demonstrating superior activity for the combined NH₃-SCR and CO oxidation reactions under low-temperature, oxygen-rich conditions. The modified AgCuSmTi catalyst achieves complete NO conversion at 150 °C, representing a 50 °C reduction compared to the unmodified CuSmTi catalyst (T_100% = 200 °C). Moreover, the catalyst exhibits over 90% N₂ selectivity across a broad temperature range of 150–300 °C, while achieving full CO oxidation at 175 °C. A series of characterization techniques, including XRD, Raman spectroscopy, N₂ adsorption, XPS, and O₂-TPD, were employed to elucidate the Ag-Cu interaction. These modifications effectively optimize the surface physical structure, modulate the distribution of acid sites, increase the proportion of Lewis acid sites, and enhance the activity of lattice oxygen species. As a result, they effectively promote the adsorption and activation of reactants, as well as electron transfer between active species, thereby significantly enhancing the low-temperature performance of the catalyst. Furthermore, in situ DRIFTS investigations reveal the reaction mechanisms involved in NH₃-SCR and CO oxidation over the Ag-modified CuSmTi catalyst. The NH₃-SCR process predominantly follows the L-H mechanism, with partial contribution from the E-R mechanism, whereas CO oxidation proceeds via the MvK mechanism. This work demonstrates that Ag modification is an effective approach for enhancing the low-temperature performance of CuSmTi-based catalysts, offering a promising technical solution for the simultaneous control of NO_x and CO emissions in industrial flue gases. Full article

Metal–organic frameworks (MOFs) are a novel type of porous crystalline materials assembled from metal ions and organic linkers. Their derivatives can inherit characteristics such as high specific surface area, tunable porosity, and unique topological structures, which make MOF-derived metal oxides ideal catalysts for the selective catalytic reduction (SCR) of NO_x. This review focuses on the synthetic strategies of MOF-derived metal oxides and the latest progress of oxides derived from various typical MOFs materials (including MILs, ZIFs, UiO, BTC series, MOF-74, MOF-5, and Prussian blue analogs, etc.) in the catalytic reduction in NO_x, and analyzes the mechanisms for the enhanced catalytic performance. In addition, the challenges and prospects of MOF derivatives in catalytic applications are discussed. It is hoped that this review will help researchers understand the latest research progress of MOF-derived metal oxide materials in the catalytic removal of NO_x pollution. Full article

Mesoporous silicas of MCM-41 and MCM-48 types were synthesized and modified with copper using the ammonia-driven deposition precipitation (ADP) method, resulting in highly dispersed copper species. Samples with varying copper loadings were thoroughly characterized in terms of their porous structure, metal content, copper species’ aggregation, and the stability of deposited forms under reaction conditions. Copper-modified mesoporous silicas exhibited excellent catalytic performance in the low-temperature NH₃-SCR process. Their activity in NO to NO₂ oxidation suggests that the fast-SCR pathway plays a significant role in NO_x conversion at low temperatures. However, direct ammonia oxidation limited SCR efficiency at higher temperatures. These findings demonstrate the potential of ADP-modified copper–silica catalysts for effective and selective NO_x removal under low-temperature conditions. Full article

In pursuing sustainable environmental solutions, the concept of ‘waste to treasure’ has emerged as a promising approach. In this study, a new process is proposed to combine solid copper slag with hydrogen peroxide (H₂O₂) to remove nitrogen oxides (NOx) from acidic exhaust gases, thus effectively utilizing waste materials. Firstly, different smelting slags were screened to determine the catalytic potential of copper slag for hydrogen peroxide. Subsequently, the catalytic activity of the copper slags at various stages of the copper smelting process was thoroughly evaluated and optimized. In addition, a multifactorial evaluation of slow-cooled copper slag catalysts for removing NOx was carried out. Preliminary indications are that the iron phase in the copper slag is identified as the main source of catalytic activity sites. The results suggest that Fe²⁺/Fe³⁺ sites on the surface of the Fe phase in the slow-cooled copper slag may be crucial in improving the NOx removal efficiency. The main reactive oxygen species detected in the system were ·OH, ·O₂⁻, and ¹O₂. In addition, the transformation products, formation pathways, and reaction mechanisms of NO in the liquid phase were initially investigated and determined. This study provides a green and sustainable path for the utilization of solid waste and management of atmospheric fumes in the non-ferrous metal industry and offers new perspectives to address environmental challenges in industrial processes. Full article

Ammonia has attracted much interest as a potential green and renewable hydrogen carrier or energy vector. Compared to hydrogen, ammonia offers several advantages. For example, ammonia has a significantly higher energy density and can be liquefied at room temperature at a moderate pressure of 8 bars. While ammonia can be cracked to supply hydrogen, it is also possible to convert it directly into high-temperature solid oxide fuel cells (SOFCs) to generate electricity. The Ship-FC project aims to install an ammonia-fed 2MW SOFC system on board the vessel Viking energy to demonstrate the feasibility of zero CO₂ emission shipping. For this NH₃ SOFC system, a catalytic afterburner is required to remove the hydrogen and ammonia present in the SOFC off-gas and to recover heat. The current study analysed the effects of different catalyst supports, with a focus on NO_X formation through the combustion of an SOFC off-gas surrogate. The study investigated the performance of catalysts based on the active metals, platinum and iridium, as well as the catalyst supports, Al₂O₃, SiO₂, and TiO₂. The results were correlated with catalyst characterisation data and ammonia TPD results. The investigations showed that the formation of NO_X was clearly affected by the nature of the catalyst support. The highest selectivity towards NO_X was observed for Al₂O₃, followed by SiO₂, and the lowest selectivity was observed for TiO₂. This trend was evident for the supported platinum and iridium catalysts and for the samples exclusively containing the support. The trend for N₂O formation was opposite to that of NO_X formation (TiO₂ > SiO₂ > Al₂O₃) in both the presence and absence of platinum or iridium. Full article

The alumina, in the form of α-Al₂O₃ tabular balls, considered in this study is a high-purity form of aluminum oxide that has been fired at high temperatures (well above 1900 °C), virtually removing porosity. However, the purity and inertness of the surface of the Al₂O₃ tabular balls minimize the catalytic activity, which is why lithium doping was tried. Thus, the target of this study was the effect of doping with lithium ions in some tabular balls of Al₂O₃ (the crystalline structure is corundum) on the improvement of the catalytic properties of alumina. This study examined the impact of a lithium catalyst on the combustion of various fuels within a porous inert medium (PIM) burner. This study specifically compared low calorific gaseous fuel (e.g., biogas) combustion in a PIM burner with and without the lithium catalyst. The experimental setup comprised a gas preparation unit for mixing CNG and CO₂ to simulate biogas and a PIM burner. The PIM burner comprised Al₂O₃ spheres (13 mm diameter, 45% porosity) in a random packing configuration. Three fuels, varying in composition and lower heating value (LHV ranging from 20.771 to 27.695 MJ/m³), were combusted at air ratios ranging from 1.67 to 1.79. The results indicated that the catalyst increased peak combustion temperatures by 23.2 °C to 51.4 °C, depending on the fuel type and air ratio. Significantly higher carbon monoxide (CO) concentrations were observed without the catalyst, particularly with fuel type F1, while nitrous oxide (NOx) levels remained consistently low. Upstream flame propagation was observed in the presence of the catalyst. These findings demonstrate the potential of lithium catalysts to enhance combustion stability and reduce emissions in porous media combustion burners. Following these studies, it can be stated that Li(I) has the role of promoter of the catalytic process. Full article

Nitrogen oxides (NOx) and chlorinated volatile organic compounds (CVOCs) are major environmental pollutants, posing severe risks to human health and ecosystems. Traditional single-component catalysts often fail to remove both pollutants efficiently, making synergistic catalytic technologies a critical research focus. In this study, a mesoporous HPW-CS-Ce-Ti oxide catalyst, modified with H₃PW₁₂O₄₀ (HPW) and chitosan (CS), was synthesized via self-assembly. The optimized 10HPW-CS-Ce_0.3-Ti catalyst achieved nearly 100% NO conversion at 167–288 °C and a T₉₀ of 291 °C for CVOC conversion, demonstrating superior dual-pollutant removal. HPW and chitosan facilitated mesoporous structure formation, enhancing mass transfer and active site availability. HPW doping also modulated the Ce⁴⁺/Ce³⁺ ratio, boosting redox capacity and surface-active oxygen species, while increasing acidity to promote NH₃ and CVOC adsorption. This study presents a novel catalyst and synthesis method with significant potential for environmental protection and human health. Full article

The removal of low-concentration NOx contamination in the urban atmosphere has been regarded as an urgent issue to be solved in the context of urbanization. In the past few decades, TiO₂ photocatalysis has been intensively investigated as an economical, efficient, and environmentally friendly means for the abatement of low-concentration NOx. Up to now, however, there have been few reviews focusing on TiO₂-based photocatalysts for photocatalytic NO removal. In this review article, we will summarize the latest advances in the photocatalytic removal of NOx contamination with TiO₂-based photocatalysts, which have been endowed with the reputation of being star catalysts for atmospheric environment remediation. We will begin with a survey of the mechanistic investigations of photocatalytic NOx removal, focusing on the in situ Fourier Transform Infrared Spectroscopy (in situ FTIR) and Electron Paramagnetic Resonance (EPR) studies and the theoretical calculation of reaction pathways with Density Functional Theory. We will then introduce the test methods and the ISO standards for photocatalytic NOx removal and discuss the effect of reaction parameters (catalyst mass, irradiation conditions, temperature, and humidity). Meanwhile, we also elaborate the latest modification methods to enhance photocatalytic efficiency and summarize the progress in recent years in modified TiO₂-based photocatalysts applied in NOx abatement. Lastly, we will put forward some feasible suggestions. In the end, this review may provide some inspiration in designing more effective TiO₂-based photocatalysts for removing NOx contamination from the ambient atmosphere. Full article

Nitrogen oxides (NO_x) and chlorobenzene (CB) released during waste incineration and iron ore sintering pose significant threats to both the atmosphere and human health, necessitating effective control measures. Vanadium-based catalysts are commonly employed for the simultaneous control of NO_x and CB; however, their catalytic performance requires further enhancement. In this study, the NH₃-SCR activity and CB catalytic oxidation (CBCO) activity were significantly enhanced by doping the V10W/Ti catalyst with Ce. During the multi-pollutant control (MPC) reaction, the optimized 15CeV10W/Ti catalyst demonstrated NO_x conversion approaching 100% and N₂ selectivity exceeding 95% at temperatures between 210 and 450 °C. Additionally, it achieved CB conversion nearing 100% and CO₂ selectivity above 80% at temperatures above 350 °C. These results were markedly superior to those of the conventional commercial 1%V₂O₅–10%WO₃/TiO₂ catalyst. Characterization studies indicated that the 15CeV10W/Ti catalyst possessed improved redox performance and more acidic sites. In the MPC reaction, the declined CBCO activity, compared to the CB separate oxidation, can be attributed primarily to the competitive adsorption of NH₃ with CB. Conversely, the observed decrease in NO_x conversion at lower temperatures was primarily due to the suppression of the oxidation of NO to NO₂ by CB. Full article

The problem of removing NO_x and carbon particle emissions from diesel engines has been a challenge in the field of environmental protection, which is prompting people to actively explore ways to improve the efficiency of pollutant emission treatment. Due to the high price of precious metals, developing an alternative catalytic material with high catalytic activity and stability is a difficult task. Perovskite, with its stable and flexibly variable crystal structure, has become a research hotspot in the field of catalysis. This paper discusses the structure of perovskite catalysts and the mechanism behind the simultaneous catalytic oxidation of diesel engine soot and NO_x. Meanwhile, it provides a comprehensive review of the preparation methods and A/B site modification strategies, establishing a foundation for the synthesis and A/B site modification of perovskite catalysts capable of catalyzing the oxidation of soot and NO_x simultaneously. Additionally, this article offers an outlook on the challenges and future development of perovskite catalysts in this field. Full article

Sintering flue gas contains significant amounts of harmful gases, such as carbon monoxide and nitrogen oxides (NO_x), which pose severe threats to the ecological environment and human health. Selective catalytic reduction (SCR) technology is widely employed for the removal of nitrogen oxides, with copper-cerium-based bimetallic catalysts and their derivatives demonstrating excellent catalytic efficiency in SCR reactions, primarily due to the significant synergistic effect between copper and cerium. This paper summarizes the main factors affecting the catalytic performance of Cu-Ce-based bimetallic catalysts and their derivatives in the selective catalytic reduction of ammonia and carbon monoxide. Key considerations include various preparation methods, doping of active components, and the effects of loading catalysts on different supports. This paper also analyzes the influence of surface oxygen vacancies, redox capacity, acidity, and specific surface area on catalytic performance. Additionally, the anti-poisoning performance and reaction mechanisms of the catalysts are discussed. Finally, the paper proposes strategies for designing high-activity and high-stability catalysts, considering the development prospects and challenges of Cu-Ce-based bimetallic catalysts and their derivatives, with the aim of providing theoretical guidance for optimizing Cu-Ce-based catalysts and promoting their industrial applications. Full article

Selective catalytic reduction of nitrogen oxides with NH₃ (NH₃-SCR) was investigated deeper and deeper with poisoning factors such as H₂O, SO₂, heavy metals, etc. In order to remove the reheating process before the SCR reactor, the application trend of NH₃-SCR technology in the non-power industry is concentrated on the condition of low temperature even ultra-low temperature. The present study summarizes the research process of SO₂ and H₂O resistance of NH₃-SCR catalysts under low temperatures related to the working conditions of municipal solid waste incineration plants. In detail, the effects of a high content of H₂O and low concentration of SO₂ are reviewed. Other factors such as heavy metals, alkali, or alkaline earth metals in the reaction system, synergistic removal of NO_x, polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) are addressed. Finally, the catalytic performance of assembled monolithic catalysts and pilot-scale experiments are also analyzed for the possibility of industrial application. Hopefully, in view of the questions outlined in this study, valuable insights could be taken into consideration for the development of NH₃-SCR in waste incineration. Full article

Nitrogen oxides are one of the main atmospheric pollutants and pose a threat to the ecological environment and human health. Selective catalytic reduction (NH₃-SCR) is an effective way of removing nitrogen oxides, with the catalyst being the key to this technology. Two-dimensional nanostructured layered double oxide (LDO) has attracted increasing attention due to the controllability of cations in the layers and the exchangeability of anions between layers. As a derivative of layered double hydroxide (LDH), LDO not only inherits the controllability and diversity inherent in the LDH structure but also exhibits excellent performance in the catalytic field. This article contains three main sections. It begins with a brief discussion of the development of LDO catalysts and analyzes the advantages of the LDO structure. The later section introduces the synthesis methods of LDH, clarifies the conversion relationship between LDH and LDO, and summarizes the modification impacts of the properties of LDO catalysts. The application of LDO catalysts used in NH₃-SCR under wild temperature conditions is discussed, and the different types, reaction processes, and mechanisms of LDO catalysts are described in the third section. Finally, future research directions and outlooks are also offered to assist the development of LDO catalysts and overcome the difficult points related to NH₃-SCR. Full article

The Special Issue “Exclusive Papers of the Editorial Board Members and Topical Advisory Panel Members of Catalysts in Section “Catalytic Materials” contains 14 peer-reviewed research articles and 1 review paper (Contributions 1–15), which broadly focus on the field of homogeneous and heterogeneous catalysis, with an emphasis on synthesis, physico-chemical characterizations, and applications in several environmental protection reactions, such as CO₂ valorization, NOx SCR, removal of VOCs, photocatalysis [...] Full article