Determination of active site densities and mechanisms for soot combustion with O2 on Fe-doped CeO2 mixed oxides

Zhang, Zhaoliang; Han, Dong Suk; Wei, Shaojie; Zhang, Yexin

doi:10.1016/j.jcat.2010.08.017

Cited by 229 publications

(123 citation statements)

References 39 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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“…The soot was mixed with the catalyst in a weight ratio of 1:9 in an agate mortar for 30 min, which results in a tight contact between soot and catalyst. Isothermal reactions and isothermal anaerobic titrations were carried out to obtain the number of active redox sites (O* amount) and turnover frequency (TOF) [32]. Soot-TPR experiments were performed as the carbothermal reduction in the absence of gas phase oxygen in a fixed-bed flow reactor.…”

Section: Activity Measurementmentioning

confidence: 99%

“…8), suggesting that the free K species might activate gaseous oxygen. This was further studied by isothermal anaerobic titrations using soot as a probe material on K/Al 2 O 3 [32] at 240 • C (K/TiO 2 is not active at this temperature), in which the O 2 flow was turned on at the start and then turned off during the catalytic soot combustion process (Fig. S2).…”

Section: Activitymentioning

confidence: 99%

K-supported catalysts for diesel soot combustion: Making a balance between activity and stability

Wang

Chen

et al. 2016

Catalysis Today

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“…The combination of traps and oxidation catalysts in the continuously regenerating particulate trap (CRT) appears to be one efficient after-treatment technique for diesel engines [5,6]. The key challenge is to find effective catalysts for soot combustion that operates at low temperatures [7][8][9][10][11]. The catalytic combustion of diesel soot is a typical reaction of heterogeneous catalysis containing solid particle as reactant.…”

Section: Introductionmentioning

confidence: 99%

“…However, the catalytic performances of 3DOM oxides are limited by their intrinsic activity, i.e., the catalytic combustion of soot over perovskite-type oxides requires a higher temperature (ca. 350-450 • C) than that of exhaust gas from a diesel engine (150-400 • C) [5][6][7][8][9][10][11][12][13][14][15][16][17][18]. It is generally known that the addition of metal (active site) to oxides can modify the intrinsic catalytic properties of themselves due to the establishment of an interaction between metal and support, which can enhance the redox properties of the modified materials [26].…”

Section: Introductionmentioning

confidence: 99%