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Selective catalytic reduction of NO

Pavlo I. Kyriienko

《化学科学与工程前沿（英文）》 2020年第14卷第4期页码 471-491 doi: 10.1007/s11705-019-1847-7

摘要： Research results regarding selective catalytic reduction (SCR) of NO with ethanol and other C oxygenates as reductants over silver-alumina catalysts are summarized. The aspects of the process mechanism, nature of active sites, role of alumina and silver (especially in the formation of bifunctional active sites), effects of reductants and reaction conditions are discussed. It has been determined that key stages of the process include formation of reactive enolic species, their interaction with NO and formation of nitroorganic compounds which transform to NCO species and further to N . The results obtained over various silver-alumina catalysts demonstrate the perspectives of their application for reducing the level of nitrogen oxides in engine emissions, including in the presence of water vapor and sulfur oxides. Ways to improve the catalysts for the SCR of NO with C oxygenates are outlined.

关键词： SCR nitrogen oxides silver-alumina catalyst silver species ethanol oxygenates

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Precise regulation of acid pretreatment for red mud SCR catalyst: Targeting on optimizing the acidity and reducibility

《环境科学与工程前沿（英文）》 2022年第16卷第7期 doi: 10.1007/s11783-021-1447-x

摘要：

• The optimum SCR activity was realized by tuning the acid pretreatment.

关键词： Air pollution control Nitrogen oxides Selective catalytic reduction Red mud Solid waste utilization

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₄ on HZSM-5 support: designing applicable catalysts for selective catalytic reduction of nitrogenoxides by ammonia

《化学科学与工程前沿（英文）》 2023年第17卷第11期页码 1741-1754 doi: 10.1007/s11705-023-2332-x

摘要： Based on monolayer dispersion theory, Co₃O₄/ZSM-5 catalysts with different loadings have been prepared for selective catalytic reduction of nitrogen oxides by ammonia. Co₃O₄ can spontaneously disperse on HZSM-5 support with a monolayer dispersion threshold of 0.061 mmol 100 m^–2, equaling to a weight percentage around 4.5%. It has been revealed that the quantities of surface active oxygen (O₂^–) and acid sites are crucial for the reaction, which can adsorb and activate NO_x and NH₃ reactants effectively. Below the monolayer dispersion threshold, Co₃O₄ is finely dispersed as sub-monolayers or monolayers and in an amorphous state, which is favorable to generate the two kinds of active sites, hence promoting the performance of ammonia selective catalytic reduction of nitrogen oxide. However, the formation of crystalline Co₃O₄ above the capacity is harmful to the reaction performance. 4% Co₃O₄/ZSM-5, the catalyst close to the monolayer dispersion capacity, possesses the most abundant active O₂^– species and acidic sites, thereby demonstrating the best reaction performance in all the samples. It is proposed the optimal Co₃O₄/ZSM-5 catalyst can be prepared by loading the capacity amount of Co₃O₄ onto HZSM-5 support.

关键词： Co₃O₄/ZSM-5 NO_x-SCR by NH₃ monolayer dispersion threshold effect surface acid sites surface active O₂^– anions

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Catalytic combustion of volatile organic compounds using perovskite oxides catalysts—a review

《化学科学与工程前沿（英文）》 2023年第17卷第11期页码 1649-1676 doi: 10.1007/s11705-023-2324-x

摘要： With the rapid development of industry, volatile organic compounds (VOCs) are gaining attention as a class of pollutants that need to be eliminated due to their adverse effects on the environment and human health. Catalytic combustion is the most popular technology used for the removal of VOCs as it can be adapted to different organic emissions under mild conditions. This review first introduces the hazards of VOCs, their treatment technologies, and summarizes the treatment mechanism issues. Next, the characteristics and catalytic performance of perovskite oxides as catalysts for VOC removal are expounded, with a special focus on lattice distortions and surface defects caused by metal doping and surface modifications, and on the treatment of different VOCs. The challenges and the prospects regarding the design of perovskite oxides catalysts for the catalytic combustion of VOCs are also discussed. This review provides a reference base for improving the performance of perovskite catalysts to treat VOCs.

关键词： perovskite oxides volatile organic compounds catalytic combustion reaction mechanism

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Design and operational considerations for selective catalytic reduction technologies at coal-fired boilers

Jeremy J. SCHREIFELS, Shuxiao WANG, Jiming HAO

《能源前沿（英文）》 2012年第6卷第1期页码 98-105 doi: 10.1007/s11708-012-0171-4

摘要： By the end of 2010, China had approximately 650 GW of coal-fired electric generating capacity producing almost 75% of the country’s total electricity generation. As a result of the heavy reliance on coal for electricity generation, emissions of air pollutants, such as nitrogen oxides (NO ), are increasing. To address these growing emissions, the Ministry of Environmental Protection (MEP) has introduced new NO emission control policies to encourage the installation of selective catalytic reduction (SCR) technologies on a large number of coal-fired electric power plants. There is, however, limited experience with SCR in China. It is therefore useful to explore the lessons from the use of SCR technologies in other countries. This paper provides an overview of SCR technology performance at coal-fired electric power plants demonstrating emission removal rates between 65% and 92%. It also reviews the design and operational challenges that, if not addressed, can reduce the reliability, performance, and cost-effectiveness of SCR technologies. These challenges include heterogeneous flue gas conditions, catalyst degradation, ammonia slip, sulfur trioxide (SO ) formation, and fouling and corrosion of plant equipment. As China and the rest of the world work to reduce greenhouse gas emissions, carbon dioxide (CO ) emissions from parasitic load and urea-to-ammonia conversion may also become more important. If these challenges are properly addressed, SCR can reliably and effectively remove up to 90% of NO emissions at coal-fired power plants.

关键词： nitrogen oxides (NO_x) coal selective catalytic reduction (SCR) air pollution control

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Multi-stage ammonia production for sorption selective catalytic reduction of NO

Chen ZHANG, Guoliang AN, Liwei WANG, Shaofei WU

《能源前沿（英文）》 2022年第16卷第5期页码 840-851 doi: 10.1007/s11708-021-0797-1

摘要： Sorption selective catalytic reduction of nitrogen oxides (NO_x) (sorption-SCR) has ever been proposed for replacing commercial urea selective catalytic reduction of NO_x (urea-SCR), while only the single-stage sorption cycle is hitherto adopted for sorption-SCR. Herein, various multi-stage ammonia production cycles is built to solve the problem of relative high starting temperature with ammonia transfer (AT) unit and help detect the remaining ammonia in ammonia storage and delivery system (ASDS) with ammonia warning (AW) unit. Except for the single-stage ammonia production cycle with MnCl₂, other sorption-SCR strategies all present overwhelming advantages over urea-SCR considering the much higher NO_x conversion driven by the heat source lower than 100°C and better matching characteristics with low-temperature catalysts. Furthermore, the required mass of sorbent for each type of sorption-SCR is less than half of the mass of AdBlue for urea-SCR. Therefore, the multifunctional multi-stage sorption-SCR can realize compact and renewable ammonia storage and delivery with low thermal energy consumption and high NO_x conversion, which brings a bright potential for efficient commercial de-NO_x technology.

关键词： selective catalytic reduction (SCR) nitrogen oxides (NO_x) ammonia composite sorbent chemisorption

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Multivalent manganese oxides with high electrocatalytic activity for oxygen reduction reaction

Xiangfeng Peng, Zhenhai Wang, Zhao Wang, Yunxiang Pan

《化学科学与工程前沿（英文）》 2018年第12卷第4期页码 790-797 doi: 10.1007/s11705-018-1706-y

摘要： A noble-metal-free catalyst based on both Mn O and MnO was prepared by using the dielectric barrier discharge technique at moderate temperature. The prepared catalyst shows a higher electrocatalytic activity towards the oxygen reduction reaction than the catalyst prepared by using the traditional calcination process. The enhanced activity could be due to the coexistence of manganese ions with different valences, the higher oxygen adsorption capacity, and the suppressed aggregation of the catalyst nanoparticles at moderate temperature. The present work would open a new way to prepare low-cost and noble-metal-free catalysts at moderate temperature for more efficient electrocatalysis.

关键词： oxygen reduction reaction manganese oxides mixed valences of manganese oxygen adsorption dielectric barrier discharge

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Redox reactions of iron and manganese oxides in complex systems

Jianzhi Huang, Huichun Zhang

《环境科学与工程前沿（英文）》 2020年第14卷第5期 doi: 10.1007/s11783-020-1255-8

摘要： • Mechanisms of redox reactions of Fe- and Mn-oxides were discussed. • Oxidative reactions of Mn- and Fe-oxides in complex systems were reviewed. • Reductive reaction of Fe(II)/iron oxides in complex systems was examined. • Future research on examining the redox reactivity in complex systems was suggested. Conspectus Redox reactions of Fe- and Mn-oxides play important roles in the fate and transformation of many contaminants in natural environments. Due to experimental and analytical challenges associated with complex environments, there has been a limited understanding of the reaction kinetics and mechanisms in actual environmental systems, and most of the studies so far have only focused on simple model systems. To bridge the gap between simple model systems and complex environmental systems, it is necessary to increase the complexity of model systems and examine both the involved interaction mechanisms and how the interactions affected contaminant transformation. In this Account, we primarily focused on (1) the oxidative reactivity of Mn- and Fe-oxides and (2) the reductive reactivity of Fe(II)/iron oxides in complex model systems toward contaminant degradation. The effects of common metal ions such as Mn2+ , Ca2+, Ni2+, Cr3+ and Cu2+, ligands such as small anionic ligands and natural organic matter (NOM), and second metal oxides such as Al, Si and Ti oxides on the redox reactivity of the systems are briefly summarized.

关键词： Iron oxides manganese oxides reduction oxidation complex systems reaction kinetics and mechanisms

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以氮氧化物深度减排为抓手，推动细颗粒物和臭氧协同控制 Views & Comments

楚碧武, 丁焰, 高翔, 李俊华, 朱廷钰, 余运波, 贺泓

《工程（英文）》 2022年第15卷第8期页码 13-16 doi: 10.1016/j.eng.2021.09.006

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The role of manganese oxides in the activation of peroxymonosulfate (PMS)

Jianzhi Huang, Huichun Zhang

《环境科学与工程前沿（英文）》 2019年第13卷第5期 doi: 10.1007/s11783-019-1158-8

摘要： Manganese oxides (MnOx) have been demonstrated to be effective materials to activate Oxone (i.e., PMS) to degrade various contaminants. However, the contribution of direct oxidation by MnOx to the total contaminant degradation under acidic conditions was often neglected in the published work, which has resulted in different and even conflicting interpretations of the reaction mechanisms. Here, the role of MnOx (as both oxidants and catalysts) in the activation of Oxone was briefly discussed. The findings offered new insights into the reaction mechanisms in PMS-MnOx and provided a more accurate approach to examine contaminant degradation for water/wastewater treatment.

关键词： Peroxymonosulfate Manganese oxides Catalyst Oxidant

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Review on research and application of mesoporous transitional metal oxides in water treatment

Minghao SUI, Lei SHE

《环境科学与工程前沿（英文）》 2013年第7卷第6期页码 795-802 doi: 10.1007/s11783-013-0521-4

摘要： This paper reviews the application of mesoporous transitional metal oxides in water treatment on basis of the catalysis and adsorption. Mesoporous transitional metal oxides are characterized by their intrinsic features, such as a high surface area, a highly ordered array of unidimensional pores with a very narrow pore size distribution, and highly dispersed active sites. Finally, the suggestions of further study on application are proposed.

关键词： mesoporous materials transitional metal oxides catalysis adsorption water treatment

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Ultrasound-assisted co-precipitation synthesis of mesoporous Co3O4–CeO2 composite oxides for highly selective

《化学科学与工程前沿（英文）》 2022年第16卷第8期页码 1211-1223 doi: 10.1007/s11705-022-2145-3

摘要： The one-step highly selective oxidation of cyclohexane into cyclohexanone and cyclohexanol as the essential intermediates of nylon-6 and nylon-66 is considerably challenging. Therefore, an efficient and low-cost catalyst must be urgently developed to improve the efficiency of this process. In this study, a Co₃O₄–CeO₂ composite oxide catalyst was successfully prepared through ultrasound-assisted co-precipitation. This catalyst exhibited a higher selectivity to KA-oil, which was benefited from the synergistic effects between Co³⁺/Co²⁺ and Ce⁴⁺/Ce³⁺ redox pairs, than bulk CeO₂ and/or Co₃O₄. Under the optimum reaction conditions, 89.6% selectivity to KA-oil with a cyclohexane conversion of 5.8% was achieved over Co₃O₄–CeO₂. Its catalytic performance remained unchanged after five runs. Using the synergistic effects between the redox pairs of different transition metals, this study provides a feasible strategy to design high-performance catalysts for the selective oxidation of alkanes.

关键词： Co₃O₄–CeO₂ composite oxides cyclohexanone cyclohexanol ultrasonic-assisted co-precipitation selective oxidation solvent-free

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Fluoride ions adsorption from water by CaCO enhanced Mn–Fe mixed metal oxides

《化学科学与工程前沿（英文）》 2023年第17卷第2期页码 236-248 doi: 10.1007/s11705-022-2193-8

摘要： Novel CaCO₃-enhanced Mn–Fe mixed metal oxides (CMFC) were successfully prepared for the first time by a simple-green hydrothermal strategy without any surfactant or template combined with calcination process. These oxides were then employed as an adsorbent for adsorptive removal of excess fluoride ions. The adsorbent was characterized by SEM, XPS, XRD, FTIR, and BET analysis techniques. The adsorption property of CMFC toward fluoride ion was analyzed by batch experiments. In fact, CMFC exhibited adsorption capacity of 227.3 mg∙g^‒1 toward fluoride ion. Results showed that ion exchange, electrostatic attraction and chemical adsorption were the main mechanism for the adhesion of large amount of fluoride ion on the CMFC surface, and the high adsorption capacity responded to the low pH of the adsorption system. When the fluoride ion concentration was increased from 20 to 200 mg∙L^‒1, Langmuir model was more in line with experimental results. The change of fluoride ion adsorption with respect to time was accurately described by pseudo-second-order kinetics. After five cycles of use, the adsorbent still maintains a performance of 70.6% of efficiency, compared to the fresh adsorbent. Therefore, this material may act as a potential candidate for adsorbent with broad range of application prospects.

关键词： mesoporous materials metal oxides fluoride ion adsorption mechanism

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Application of metal oxides-based nanofluids in PV/T systems: a review

《能源前沿（英文）》 2022年第16卷第3期页码 397-428 doi: 10.1007/s11708-021-0758-8

摘要： Having the wide application of metal oxides in energy technologies, in recent years, many researchers tried to increase the performance of the PV/T system by using metal oxide-based nanofluids (NFs) as coolants or optical filters or both at the same time. This paper summarizes recent research activities on various metal oxides (Al₂O₃, TiO₂, SiO₂, Fe₃O₄, CuO, ZnO, MgO)-based NFs performance in the PV/T system regarding different significant parameters, e.g., thermal conductivity, volume fraction, mass flowrate, electrical, thermal and overall efficiency, etc. By conducting a comparative study among the metal oxide-based NFs, Al₂O₃/SiO₂-water NFs are mostly used to achieve maximum performance. The Al₂O₃-water NF has a prominent heat transfer feature with a maximum electrical efficiency of 17%, and a maximum temperature reduction of PV module of up to 36.9°C can be achieved by using the Al₂O₃-water NF as a coolant. Additionally, studies suggest that the PV cell’s efficiency of up to 30% can be enhanced by using a solar tracking system. Besides, TiO₂-water NFs have been proved to have the highest thermal efficiency of 86% in the PV/T system, but TiO₂ nanoparticles could be hazardous for human health. As a spectral filter, SiO₂-water NF at a size of 5 nm and a volume fraction of 2% seems to be very favorable for PV/T systems. Studies show that the combined use of NFs as coolants and spectral filters in the PV/T system could provide a higher overall efficiency at a cheaper rate. Finally, the opportunities and challenges of using NFs in PV/T systems are also discussed.

关键词： metal oxide nanofluids (NFs) nanoparticles (NPs) optical filter PV/T systems solar energy

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Crystalline mesoporous transition metal oxides: hard-templating synthesis and application in environmental

Zhen MA, Bei ZHOU, Yu REN

《环境科学与工程前沿（英文）》 2013年第7卷第3期页码 341-355 doi: 10.1007/s11783-012-0472-1

摘要： Mesoporous silicas such as MCM-41 and SBA-15 possess high surface areas, ordered nanopores, and excellent thermal stability, and have been often used as catalyst supports. Although mesoporous metal oxides have lower surface areas compared to mesoporous silicas, they generally have more diversified functionalities. Mesoporous metal oxides can be synthesized via a soft-templating or hard-templating approach, and these materials have recently found some applications in environmental catalysis, such as CO oxidation, N O decomposition, and elimination of organic pollutants. In this review, we summarize the synthesis of mesoporous transition metal oxides using mesoporous silicas as hard templates, highlight the application of these materials in environmental catalysis, and furnish some prospects for future development.

关键词： mesoporous materials silica metal oxide hard-templating environmental catalysis