Catalytic combustion of soot over Cu, Mn substitution CeZrO2- nanocomposites catalysts prepared by self-propagating high-temperature synthesis method

A review of regeneration mechanism and methods for reducing soot emissions from diesel particulate filter in diesel engine

With the global emphasis on environmental protection and the proposal of the climate goal of "carbon neutrality," countries around the world are calling for reductions in carbon dioxide, nitrogen oxide, and particulate matter pollution. These pollutants have severe impacts on human lives and should be effectively controlled. Engine exhaust is the most serious pollution source, and diesel engine is an important contributor to particulate matter. Diesel particulate filter (DPF) technology has proven to be an effective technology for soot control at the present and in the future. Firstly, the exacerbating effect of particulate matter on human infectious disease viruses is discussed. Then, the latest developments in the influence of key factors on DPF performance are reviewed at different observation scales (wall, channel, and entire filter). In addition, current soot catalytic oxidant schemes are presented in the review, and the significance of catalyst activity and soot oxidation kinetic models are highlighted. Finally, the areas that need further research are determined, which has important guiding significance for future research. Current catalytic technologies are focused on stable materials with high mobility of oxidizing substances and low cost. The challenge of DPF optimization design is to accurately calculate the balance between soot and ash load, DPF regeneration control strategy, and exhaust heat management strategy.

Effect of regeneration method and ash deposition on diesel particulate filter performance: a review

As countries around the world pay more attention to environmental protection, the corresponding emission regulations have become more stringent. Exhaust pollutants cause great harm to the environment and people, and diesel engines are one of the most important sources of pollution. Diesel particulate filter (DPF) technology has proven to be the most effective way to control and treat soot. In this paper, we review the latest research progress on DPF regeneration and ash. Passive regeneration, active regeneration, non-thermal plasma-assisted DPF regeneration and regeneration mechanism, DPF regeneration control assisted by engine management, and uncontrolled DPF regeneration and its control strategy are mainly introduced. In addition, the source, composition, and deposition of ash are described in detail, as well as the effect of ash on the DPF pressure drop and catalytic performance. Finally, the issues that need to be further addressed in DPF regeneration research are presented, along with challenges and future work in ash research. Over all, composite regeneration is still the mainstream regeneration method. The formation of ash is complex and there are still many unanswered questions that require further in-depth research.

Nano-oxides washcoat for enhanced catalytic oxidation activity toward the perovskite-based monolithic catalyst

In order to explore a superior washcoat material to give full play to the catalytic activity of perovskite active components on the monolithic catalysts, three novel types of LaCoO₃/washcoat/cordierite monolith catalysts were prepared by a facile two-step procedure which employed the cordierite honeycomb ceramic as the monolith substrate, the nano-oxides (ZrO₂, ɤ-Al₂O₃, TiO₂) as the washcoat, and the perovskite of LaCoO₃ as the active components. The blank cordierite, powdered LaCoO₃, semi-manufactured monolithic catalysts (washcoat/cordierite), and manufactured monolithic catalysts (LaCoO₃/washcoat/cordierite) were characterized by XRD, SEM, XPS, N₂ adsorption-desorption, H₂-TPR, and ultrasonic test, and their catalytic activities and catalytic stability were evaluated by the toluene oxidation test. The research results indicate that the nanoparticles coated on the cordierite substrate as the washcoat can give full play to the catalytic ability of the LaCoO₃ active components and also showed high catalytic stability. However, the catalytic properties of the monolithic catalysts vary notably with the species of nano-washcoat. Among all the catalysts, the porous honeycomb surface structure, uniform distribution, high ratio of surface adsorbed oxygen, and strong reducing ability together give the LaCoO₃/ZrO₂/cordierite monolithic catalyst the highest catalytic activity on the oxidation of toluene at low temperature, which could be attributed to the excellent interactions of perovskite and nano-ZrO₂ washcoat. Therefore, the nano-oxides, especially the nano-ZrO₂, have a broad practical application potential for toluene oxidation at low temperature as the washcoat of perovskite-based monolithic catalysts.

Catalytic Combustion of Dimethyl Disulfide on Bimetallic Supported Catalysts Prepared by the Wet-Impregnation Method

In this paper, the catalytic combustion of DMDS (dimethyl disulfide, CH3SSCH3) over bimetallic supported catalysts were investigated. It was confirmed that Cu/γ-Al2O3-CeO2 showed best catalytic performance among the five single-metal catalysts. Furthermore, six different metals were separately added into Cu/γ-Al2O3-CeO2 to investigate the promoting effect. The experiments revealed Pt as the most effective promoter and the best catalytic performance was achieved as the adding amount of 0.3 wt%. The characterization results indicated that high activity and resistance to sulfur poisoning of Cu-Pt/γ-Al2O3-CeO2 could be attributed to the synergistic effect between Cu and Pt.

Catalytic Combustion of Diesel Soot on Ce/Zr Series Catalysts Prepared by Sol-Gel Method

Cerium-zirconium (Ce-Zr) solid solutions have been extensively used in a wide variety of catalytic processes due to their unique catalytic features in conjunction with lower cost compared to noble metal-based systems. A series of Ce-Zr-based catalysts was prepared by the sol-gel method. The structure and morphology of these catalysts were characterized by X-ray diffraction, thermogravimetric-differential scanning calorimetry, scanning electron microscopy, energy dispersive spectroscopy, and X-ray photoelectron spectroscopy. Furthermore, investigation on catalytic performance was carried out by constructing a test platform, and the result indicated that the catalysts apparently decreased the soot ignition temperature. These catalysts exhibited higher catalytic activity for soot oxidation under narrow contact conditions. The results revealed that some soot particles could react with adsorbed oxygen, and other part of diesel soot reacted with lattice oxygen. The activity of these catalysts was attributed to synergistic effect arising from the combination of K/Co/Zr and Ce-Zr solid solution, which led to the decrease in the ignition temperature to 294 °C (data from the test platform). The catalyst still keeps good stability and catalytic activity after the cycle oxidation experiment. A reaction pathway was proposed to explain catalytic combustion process of soot, i.e., combination of K/Co/Zr with Ce-Zr solid solution reduced the binding energy of Ce-Zr solid solution, which was conducive to provide more active sites to release the active oxygen (O2−) or lattice oxygen (O2−).

Highly enhanced soot oxidation activity over 3DOM Co3O4-CeO2 catalysts by synergistic promoting effect

Three-dimensionally ordered macroporous (3DOM) Co₃O₄-CeO₂ catalysts with controllable Co/Ce molar ratios synthesized by colloidal crystal template method were developed to catalyze the NO_x-assisted soot oxidation for the first time, and the obtained 3DOM Co₃O₄-CeO₂ catalysts exhibited highly enhanced soot oxidation activity. Detailed characterizations of 3DOM Co₃O₄-CeO₂ catalysts revealed that the highly enhanced soot oxidation activity was originated from the synergistic promoting effect by combining the macroporous effect resulted from the unique 3DOM framework, the chemical nature associated with more Co³⁺ reactive sites, the surface enrichment of Ce species and the improved redox properties. Meanwhile, the high NO_x storage and oxidation capacity resulted from the integrated respective merits of Co₃O₄ and CeO₂ also accounted for the enhanced soot oxidation activity via NO_x-assisted mechanism. Furthermore, the 3DOM Co₃O₄-CeO₂ catalysts demonstrated strong stability because of the surface enrichment of Ce species improving the thermal stability and the robust 3DOM framework inhibiting the structural collapse, showing their potential applications under practical conditions.

Construction of a hollow structure in La0.9K0.1CoO3−δ nanofibers via grain size control by Sr substitution with an enhanced catalytic performance for soot removal

The hollow structure is formed by Sr²⁺ doping in La_0.9K_0.1CoO_3−δ nanofibers for decreasing the grain size, which can improve the contact efficiency of soot–catalyst–gas as well as the intrinsic activity, responsible for the enhancement in activity.