Selective oxidation of soot over Cu doped ceria/ceria–zirconia catalysts

Liang, Qionglin; Wu, Xiaodong; Weng, Duan; Lu, Zhenxiang

doi:10.1016/j.catcom.2007.06.007

Cited by 73 publications

(39 citation statements)

References 18 publications

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“…According to the catalysts screening compiled in Figure 3, ceria-base catalysts are among the most effective for soot combustion, and this has promoted an intense research activity during the last years on different ceria-based catalysts for Diesel soot combustion like, among others, ceria doped with Zr [25,[35][36][37][38], Fe [36,39], La [21,36,38], Pr [21,36], Sm [21,36], Tb [36], Cu [40][41][42], Mn [40,43], and Mo [44] and different compounds supported on ceria such as K/Ceria [34,45], Co/Ceria [45][46][47][48][49], Ba,K/Ceria [50,51], Cu-V/Ceria [52], Ag/Ceria [53,54] or Cu/Ceria [55].…”

Section: -Why Ceria Catalysts For Soot Combustion?mentioning

confidence: 99%

Diesel soot combustion ceria catalysts

Bueno‐López

2014

Applied Catalysis B: Environmental

393

243

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This review article summarizes the contents of the keynote lecture with the same tittle presented at the 7 th edition of the International Conference on Environmental Catalysis hold in Lyon (France) in September 2012. Different aspects of the ceria-catalyzed Diesel soot combustion reactions have been critically discussed, such as the high catalytic activity of ceria for Diesel soot combustion in comparison to some other potential catalysts, the potential ceria-catalyzed Diesel soot combustion mechanisms (the so-called NO 2 -assisted mechanism and the active oxygen mechanism) and the effect of ceria doping with suitable cations like those of Pr, La or Zr. Ceria must be doped in order to enhance thermal stability, but ceria doping also changes different physicochemical and catalytic properties of ceria. Zr-doping, for instance, has a double role on ceria as soot combustion catalyst: enhances ceria oxidation capacity of the adsorbed NOx species (positive effect) but stabilizes NO 2 on surface (negative effect). The surface properties of a ceria catalyst are usually more important than those of bulk: high surface area/small crystal size usually has a positive effect on the catalyst performance and, in mixed oxides, the surface composition also plays a role. The optimal dopant loading depends on the foreign cation being, for instance, around 5-10%, 20-30% and 50 mole % for La 3+ , Zr 4+ , and Pr 3+ / 4+ , respectively.Keywords: DPF regeneration; soot; ceria; doped-ceria; Diesel engine contamination. 2This review article summarizes the contents of the keynote lecture with the same tittle presented at the 7 th edition of the International Conference on Environmental Catalysis hold in Lyon (France) in September 2012. 1.-The problem.Soot particles are formed as undesired by-products in combustion process, being one of the main pollutants emitted by Diesel engines together with NOx, CO and unburned hydrocarbons [1]. Typical gas exhaust composition of a Diesel car, which is summarized in Table 1, is 30-80 ppm hydrocarbons, 200-1500 ppm CO, 300-1650 ppm NO (~ 0 ppm NO 2 ), 5-18% O 2 , > 2% H 2 O and > 2% CO 2 .Soot particles consist of a carbon nucleus with some inorganic material and adsorbed hydrocarbons, SO x , and water [2]. Figure 1 shows TEM images of a real soot sample. The single particles of few nanometers present an amorphous core surrounded by a graphitic shell, and such single particles agglomerate in larger entities with size typically in the range 0.1-10 µm [3].Several adverse effects on health have been attributed to soot. A fraction of these particles (the so-called PM-10, with size smaller than 10 m) can penetrate the respiratory tract and are deposited on lungs increasing cancer risk, asthma and bronchitis. The adsorbed hydrocarbons are mutagenic substances and SO x in contact with water form strong acid compounds.Diesel particle traps with different designs can be used for soot removal from gas streams, wall-flow monoliths being the most popular [3,4]. Figure 2 shows a commercial SiC Diesel Part...

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Section: -Why Ceria Catalysts For Soot Combustion?mentioning

confidence: 99%

Diesel soot combustion ceria catalysts

Bueno‐López

2014

Applied Catalysis B: Environmental

393

243

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“…Among the several catalysts used for soot combustion, the most common are: molten salts [14][15][16][17], Pt-based oxides [18][19][20][21], ceria-based oxides [18,19,[22][23][24][25][26][27][28], and others based on transition metals (such as copper or iron) [20,24,26,[29][30][31][32][33][34]. Although those catalysts containing Pt show a very high activity in the NO oxidation to NO 2 (and thus, promoting soot combustion), some other catalysts are being developed, whose NO 2 production activities are becoming closer to those of Pt-based catalysts, but with lower costs.…”

Section: Introductionmentioning

confidence: 99%

Opportunities for ceria-based mixed oxides versus commercial platinum-based catalysts in the soot combustion reaction. Mechanistic implications

Giménez-Mañogil¹,

Garcı́a-Garcı́a²

2015

Fuel Processing Technology

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The aim of this paper is to study the activities of ceria-zirconia and copper/ceriazirconia catalysts, comparing with a commercial platinum/alumina catalyst, for soot combustion reaction under different gas atmospheres and loose contact mode (simulating diesel exhaust conditions), in order to analyse the kinetics and to deduce mechanistic implications.Activity tests were performed under isothermal and TPR conditions. The NO oxidation to NO 2 was studied as well. It was checked that mass transfer limitations were not influencing the rate measurements. Global activation energies for the catalysed and non-catalysed soot combustion were calculated and properly discussed.The results reveal that ceria-based catalysts greatly enhance their activities under NOx/O 2 between 425ºC and 450ºC, due to the "active oxygen"-assisted soot combustion. Remarkably, copper/ceria-zirconia shows a slightly higher soot combustion rate than the Pt-based catalyst (under NOx/O 2 , at 450ºC).

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“…CuO-CeO2 catalysts were prepared via the citric acid sol-gel method as described elsewhere [42]. Ultrapure water having specification: pH 7.1, conductivity 140 µm/cm were used for dissolving copper and cerium nitrate according to the desired molar ratio.…”

Section: Citric Acid Sol-gel Methodsmentioning

confidence: 99%