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Diesel particulate filter (DPF) is considered as an effective method to control particulate matter (PM) emissions from diesel engines, which is included in the mandatory installation list by more and more national/regional laws and regulations, such as CHINA VI, Euro VI, and EPA Tier3. Due to the limited capacity of DPF to contain PM, the manufacturer introduced a method of treating deposited PM by oxidation, which is called regeneration. This paper comprehensively summarizes the most advanced regeneration technology, including filter structure, new catalyst formula, accurate soot prediction, safe and reliable regeneration strategy, uncontrolled regeneration and its control methods. In addition, due to the change of working conditions in the regeneration process, the additional emissions during regeneration are discussed in this paper. The DPF is not only the aftertreatment device but also can be combined with diesel oxidation catalyst (DOC), selective catalytic reduction (SCR) and exhaust recirculation (EGR). In addition, the impact of DPF modification on the original system of some old models has been reasonably discussed in order to achieve emission targets. [ABSTRACT FROM AUTHOR]

Electron paramagnetic resonance (EPR) is the only technique that provides direct detection of free radicals and samples that contain unpaired electrons. Thus, EPR had an important potential application in the field of selective catalytic reduction of nitrogen oxide (SCR). For the first time, this work reviewed recent developments of EPR in charactering SCR. First, qualitative analysis focused on recognizing Cu, Fe, V, Ti, Mn, and free-radical (oxygen vacancy and superoxide radical) species. Second, quantification of the active species was obtained by a double-integral and calibration method. Third, the active species evolved because of different thermal treatments and redox-thermal processes under reductants (NH3 and NO). The coordination information of the active species in catalysts and their effects on SCR performances were concluded from mechanism viewpoints. Finally, potential perspectives were put forward for EPR developments in characterizing the SCR processes in the future. After all, EPR characterization will help to have a deep understanding of structure–activity relationship in one catalyst. [ABSTRACT FROM AUTHOR]

Solid oxide fuel cells (SOFCs) are highly promising energy conversion devices. However, the performance and efficiency of current SOFC devices are still limited by inadequate oxygen reduction activity in the cathode, which has been recognized as a great challenge for SOFCs to achieve high power output at low operating temperatures. This has stimulated intensive efforts to develop more efficient cathodes for enhanced catalytic oxygen reduction. This article reviews recent advances in design and fabrication of cathodes for efficient SOFCs, with emphasis on (1) engineering cathode microstructures, (2) fabrication techniques to prepare cathode layers, and (3) strategies to address segregation and poisoning issues. [Display omitted] • Recent progress in SOFC cathodes with efficient catalytic O 2 reduction is reviewed. • Design principles of efficient cathodes are summarized. • Engineering microstructures and fabrication techniques of cathodes are discussed. • Critical technical challenges, strategies and solutions in this topic are highlighted. [ABSTRACT FROM AUTHOR]

The usage of zero valent iron (Fe) nanoparticles for various organic transformations has been extensively reported in the last decade because of high natural abundance, low toxicity and low cost of Fe metal. The development of synthetic strategies used for fabrication of iron nanoparticles and their stabilization using various supporting materials has made a significant contribution to their use in catalysis. This critical review gives research progress of synthesis, stabilization and characterization of zero valent Fe nanoparticles. It specially emphasizes on their use as reducing agent and as catalyst in various reduction reactions in the last ten years. Catalytic reductions of different organic substrates in the presence of Fe nanoparticles using different hydrogen sources have been mainly described critically in this review. Challenges and future perspectives for further development in the field of Iron nanoparticles catalyzed reduction reactions have been described. [ABSTRACT FROM AUTHOR]

[Display omitted] • Various NH 3 -SCR catalysts have been developed. • The theory and practice of designing metal oxide catalysts for NH 3 -SCR. • The close coupling of redox and acid sites is imperative for the design of NH 3 -SCR catalysts. For NO x control in the presence of excess oxygen, selective catalytic reduction with ammonia (NH 3 -SCR) has been successfully applied in the purification of coal-fired flue gas and diesel vehicle exhaust on a large scale. For both cases, various NH 3 -SCR catalysts have been developed, with the incorporation of desirable catalytic properties being the central issue. However, the fundamental principle for designing NH 3 -SCR catalysts with high activity, selectivity, and stability remain unclear. Generally, in the NH 3 -SCR reaction, the redox and acid sites on the catalyst are prerequisites that need to work together. Therefore, the close coupling of these dual functional sites is imperative for the design of NH 3 -SCR catalysts with high NO x removal efficiency. Taking this intrinsic principle into account, we successfully designed and developed various novel catalysts with excellent NH 3 -SCR performance. This review will focus on the theory and practice of designing metal oxide catalysts for NH 3 -SCR. [ABSTRACT FROM AUTHOR]

It is crucial to control NOx emission into the atmosphere because it can make several harmful health and environmental effects. Many techniques are available for NOx reduction, and among them, selective catalytic reduction (SCR) is one of the most efficient techniques for NOx removal in flue gas cleaning process. The reduction of NOx by CO offers a simple and low-cost technology for reducing NOx emissions from mobile or stationary sources. In this review, NOx emission, different NOx control technologies, and the challenges for the SCR process are studied. This paper reviews various types of catalysts, including supported and unsupported metal oxide catalysts as efficient catalysts for NOx reduction by CO. The reported experimental researches are analyzed to make an overview of the NOx reduction through CO-SCR process. Moreover, catalytic performances in the presence of oxygen, water steam, and sulfur dioxide, which usually exist in exhaust gases produced in the combustion process, are discussed. Moreover, this paper reviews the possible reaction mechanisms for the CO–SCR. [ABSTRACT FROM AUTHOR]

Cu-exchanged zeolites are one kind of effective catalysts to eliminate NOx for Selective catalytic reduction with NH3(NH3-SCR) in oxygen-rich exhaust from diesel engines. The microstructure–performance relationships between supports and active sites is crucial to rationally design excellent catalysts for the effective elimination of NOx. Therefore, the effect of topology and element ratio on active species and performance, the new progress in reaction and chemical poisoning mechanism to clarify the nature of the catalytic reactions are reviewed in this article. Furthermore, some new research methods to further promote SCR performance are summarized, which is helping in guiding the rational design of Cu-zeolites catalysts. From the reviewed data, the following important viewpoints emerged: (i) topologies exert different influence on acid properties and the nature of Cu species, which further effect the NH3-SCR performance; (ii) the Si/Al and Cu/Al compositional ratios are key factors in effecting the performance of the Cu-zeolites catalysts; (iii) the degree of chemical inactivation depends on the content and type of impurities; (iv) the common modification methods include the doping of foreign cations or metal oxides and core–shell structures; (v) the active site in the low temperature NH3-SCR catalyst is a mobile transient ion pairs ([(NH3)2CuI-O2-CuI(NH3)2]).Only in the high temperature regime do the NH3-solvated Cu ions decompose to isolated Cu2+ ions that anchor on the zeolite framework and become immobilized. [ABSTRACT FROM AUTHOR]

Nitrophenol is common carcinogenic pollutant known for its adverse effects on human beings and aquatic life. During the last few decades, the chemical reduction of nitrophenol compounds has been widely reported as the advanced removal methodology for such hazardous dyes from aqueous reservoirs. Many researchers have utilized different nanocatalytic systems using sodium borohydride (NaBH4) as the reducing agent for acquiring industrially useful reduction product of aminophenol by carrying out the chemical reduction of nitrophenols. Polymeric material supported monometallic nanoparticles are widely reported catalyst for the degradation of 2-nitrophenol (2-NP) and 4-nitrophenol (4-NP). This review critically discusses the pros and cons of numerous supporting mediums of nanocatalytic assemblies used for the immobilization of nanomaterials. Mechanism and kinetic analysis of the reduction reaction of 2-NP and 4-NP have also been explained in this study. In addition, recent literature has also been effectively summarized in the tabular form for developing a better understanding of the reader. Pictorial representation of key nanocatalytic assemblies and catalytic reduction mechanism has also been narrated in this study. [ABSTRACT FROM AUTHOR]