The catalytic activity of CuO–CeO2 mixed oxides for diesel soot oxidation with a NO/O2 mixture

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

doi:10.1016/j.catcom.2007.04.023

Cited by 89 publications

(48 citation statements)

References 14 publications

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“…A number of copper-containing multi-component catalysts have also demonstrated to be active for soot oxidation, such us CuO/CeO 2 [5], copper-loaded MFI zeolite [6], Al 2 O 3 - [7] and CeO 2 - [8] [11]) and bimetallic Cu/K active phases supported on ZrO 2 [12], Al 2 O 3 [13] and beta zeolite [14], among others.…”

Section: -Introductionmentioning

confidence: 99%

Cu/Al2O3 catalysts for soot oxidation: Copper loading effect

López-Suárez

Bueno‐López

Illán-Gómez

2008

Applied Catalysis B: Environmental

172

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Cu/Al 2 O 3 catalysts with metal loading from 0.64 to 8.8 wt. % have been prepared and characterised by different techniques: N 2 adsorption at -196ºC (BET surface area), ICP (Cu loading), XRD, selective copper surface oxidation with N 2 O (Cu dispersion), TPR-H 2 (redox properties), and XPS (copper surface species). The catalytic activity for soot oxidation has been tested both in air and NOx/O 2 . The activity in air depends on the amount of easily-reduced Cu(II) species, which are reduced around 275ºC under TPR-H 2 conditions. The amount of the most active Cu(II) species increases with the copper loading from Cu_1% to Cu_5% and remains almost constant for higher copper loading.In the presence of NOx, the first step of the mechanism is NO oxidation to NO 2 , and the catalytic activity for this reaction depends on the copper loading. For catalysts with copper loading between Cu_1% and Cu_5%, the catalytic activity for soot oxidation in the presence of NOx depends on NO 2 formation. For catalysts with higher copper loading this trend is not followed because of the low reactivity of model soot at the temperature of maximum NO 2 production. Regardless the copper loading, all the catalysts improve the selectivity towards CO 2 formation as soot oxidation product both under air and NOx/O 2 .

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Section: -Introductionmentioning

confidence: 99%

Cu/Al2O3 catalysts for soot oxidation: Copper loading effect

López-Suárez

Bueno‐López

Illán-Gómez

2008

Applied Catalysis B: Environmental

172

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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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“…Herein, more attentions were focused on CuOx-CeO2 since its favorable properties in catalytic oxidation reactions, such as diesel soot, [22] volatile organic compounds [23] and carbon monoxide [24] etc. The reaction path follows a rodox mechanism, involving the change of the oxidation state of both copper (Cu 2+ ↔Cu + ) and cerium (Ce 4+ ↔Ce 3+ ).…”

Section: Introductionmentioning

confidence: 99%

Cerium doped copper/ZSM-5 catalysts used for the selective catalytic reduction of nitrogen oxide with ammonia

Dou

Wang

et al. 2015

Chemical Engineering Journal

124

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Abstract:The CuCe/ZSM-5 catalysts with different cerium loadings (0, 0.5, 1.0, 1.5 and 2.0 wt.%) was investigated to evaluate the correlation between structural characteristics and catalytic performance for the selective catalytic reduction (SCR) of NO by NH3. It was found that the addition of cerium increased copper dispersion and prevented its crystallization. According to the results of X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction by hydrogen (H2-TPR), copper species were enriched on the ZSM-5 grain surfaces and part of copper ions was incorporated into the cerium lattice. Addition of cerium improved the redox properties of the CuCe/ZSM-5 catalysts, owing to the higher valence of copper and mobility of lattice oxygen than those of Cu/ZSM-5 catalyst. Hence the introduction of * Corresponding author. Tel.: +86-22-60601278; Fax.: +86-22-60600320 E-mail address: haoqinglan@tust.edu.cn ** Corresponding author. Tel.: +822 2220 0441; fax: +822 2220 2299 (K. Hui)E -mail address: kshui@hanyang.ac.kr (K. Hui) 2 cerium in Cu/ZSM-5 improved significantly NO conversion. On the one hand, the cerium introduction into Cu-Z enhances their low-temperature activities. 95% NO conversion is reached around 197 ºC for Cu-Z while the corresponding temperature value decreases to 148 ºC for CuCe4-Z. On the other hand, the temperature range of efficient NO reduction (95%) also extends to higher temperature when the cerium are added to Cu/ZSM-5. Among the Cu-Ce/ZSM-5 catalysts tested, the CuCe4-Z sample exhibits the highest catalytic activity with the temperature range for 90% NO removal of 148-427 ºC.

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The catalytic activity of CuO–CeO2 mixed oxides for diesel soot oxidation with a NO/O2 mixture

Cited by 89 publications

References 14 publications

Cu/Al2O3 catalysts for soot oxidation: Copper loading effect

Cu/Al2O3 catalysts for soot oxidation: Copper loading effect

Diesel soot combustion ceria catalysts

Cerium doped copper/ZSM-5 catalysts used for the selective catalytic reduction of nitrogen oxide with ammonia

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