Surface and catalytic properties of Cu–Ce–O composite oxides prepared by combustion method
30 Jun 2003-Colloids and Surfaces A: Physicochemical and Engineering Aspects (Elsevier)-Vol. 220, Iss: 1, pp 261-269
TL;DR: In this article, surface and catalytic properties of Cu-Ce-O composite materials prepared by solution combustion method have been investigated by X-ray diffraction, temperature programmed reduction and electron paramagnetic resonance spectroscopy.
About: This article is published in Colloids and Surfaces A: Physicochemical and Engineering Aspects.The article was published on 2003-06-30. It has received 103 citations till now. The article focuses on the topics: Copper oxide & Electron paramagnetic resonance.
Citations
More filters
TL;DR: In this article, a review discusses recent developments in catalytic systems for the destruction of volatile organic compounds (VOCs) and their sources of emission, mechanisms of catalytic destruction, the causes of catalyst deactivation, and catalyst regeneration methods.
1,014 citations
TL;DR: This Review focuses on the analysis of new approaches and results in the field of solution combustion synthesis (SCS) obtained during recent years, emphasizing the chemical mechanisms that are responsible for rapid self-sustained combustion reactions.
Abstract: Solution combustion is an exciting phenomenon, which involves propagation of self-sustained exothermic reactions along an aqueous or sol–gel media. This process allows for the synthesis of a variety of nanoscale materials, including oxides, metals, alloys, and sulfides. This Review focuses on the analysis of new approaches and results in the field of solution combustion synthesis (SCS) obtained during recent years. Thermodynamics and kinetics of reactive solutions used in different chemical routes are considered, and the role of process parameters is discussed, emphasizing the chemical mechanisms that are responsible for rapid self-sustained combustion reactions. The basic principles for controlling the composition, structure, and nanostructure of SCS products, and routes to regulate the size and morphology of the nanoscale materials are also reviewed. Recently developed systems that lead to the formation of novel materials and unique structures (e.g., thin films and two-dimensional crystals) with unusual...
841 citations
TL;DR: The article discusses oxidation catalysis by substitutional cation doping of binary oxides by assuming that the 'as-prepared' catalyst is a doped oxide that, under reducing reaction conditions, is converted to very small metallic dopant clusters supported on the host oxide.
Abstract: The article discusses oxidation catalysis by substitutional cation doping of binary oxides. Substitutional cation doping is not the only possibility. One can imagine that replacing some anions with other anions may also be beneficial. There is evidence that the presence of small amounts of halogen in the feed or on the oxide surface improves its catalytic activity. It is very likely that doped oxide catalysts have been used before the concept was formulated explicitly. Most oxide catalysts have low levels of impurities that may be substitutional dopants. If they segregate at the surface, they can affect the catalytic activity without our knowledge even though their net concentration is very low. It is also possible that the 'as-prepared' catalyst is a doped oxide that, under reducing reaction conditions, is converted to very small metallic dopant clusters supported on the host oxide. The physical and chemical properties of such clusters are different from those of a bulk metal, and it is difficult to distinguish them from a doped oxide.
668 citations
TL;DR: In this paper, a urea combustion method was used to evaluate the performance of a mixture of CuO and CeO 2 catalysts in the oxidation of ethanol, ethyl acetate and toluene.
Abstract: CuO–CeO 2 catalysts were prepared via a urea combustion method and their performance in the oxidation of ethanol, ethyl acetate and toluene was evaluated. XRD, H 2 -TPR and N 2 physisorption were employed in catalyst characterization. The specific surface area of mixed materials was higher than the one of single oxides. In ceria-rich materials, crystalline copper oxide phases are absent and segregation of a CuO phase takes place at atomic Cu/(Cu + Ce) ratios higher than 0.25. The mixed oxides get reduced by H 2 at lower temperatures than the corresponding single oxides and copper ions promote reduction of ceria. Ethanol gets more easily oxidized than ethyl acetate, which in turn gets more easily oxidized than toluene. CuO–CeO 2 catalysts of low copper content produce very low amounts of acetaldehyde during ethanol and ethyl acetate oxidation at all conversion levels. This is augmented by the presence of water in the feed. The specific activity of Cu x Ce 1− x catalysts in the oxidation of ethanol, ethylacetate and toluene (specific rate of volatile organic compound (VOC) consumption) is lower than the one of pure CuO and CeO 2 , i.e. combination of the two phases leads to suppression of intrinsic activity. On the other hand, the specific rate of CO 2 production during ethanol and ethyl acetate oxidation is also lower over CuO–CeO 2 than over CeO 2 , but higher than over CuO. The larger surface area of CuO–CeO 2 catalysts counterbalances their smaller specific activity allowing complete VOC conversion at lower temperatures compared to the single oxides.
488 citations
TL;DR: It is found that nearly monodisperse copper oxide nanoparticles prepared via the thermal decomposition of a Cu(I) precursor exhibit exceptional activity toward CO oxidation in CO/O2/N2 mixtures.
Abstract: We find that nearly monodisperse copper oxide nanoparticles prepared via the thermal decomposition of a Cu(I) precursor exhibit exceptional activity toward CO oxidation in CO/O2/N2 mixtures. Greater than 99.5% conversion of CO to CO2 could be achieved at temperatures less than 250 degrees C for over 12 h. In addition, the phase diagram and pathway for CO oxidation on Cu2O (100) is computed by ab initio methods and found to be in qualitative agreement with the experimental findings.
260 citations
References
More filters
TL;DR: In this article, the authors measured the oxygen removal at various temperatures using TPR traces of unsupported or alumina-supported ceria and showed that the reduction of surface capping oxygen and bulk oxygen anions is associated with reduction of the shared oxygen anion at the interface.
1,726 citations
TL;DR: In this paper, the use of CeO 2 -based materials in the automotive three-way catalysts (TWCs) is considered, and the multiple roles of COO 2 as a TWC promoter and in particular the oxygen storage/release capacity (OSC) are critically discussed.
1,632 citations
TL;DR: In this paper, the authors report on the activity of Cu-and Ni-containing cerium oxide catalysts for low-temperature water-gas shift (WGS) in nanocrystalline form by urea co-precipitation-gelation method.
Abstract: In this paper we report on the activity of Cu- and Ni-containing cerium oxide catalysts for low-temperature water-gas shift (WGS). Bulk catalysts were prepared in nanocrystalline form by the urea co-precipitation–gelation method. Lanthanum dopant (10 at.%) was used as a structural stabilizer of ceria, while the content of Cu or Ni was in the range of 5–15 at.% (2–8 wt.%). At low metal loadings, Cu or Ni were present in the form of highly dispersed oxide clusters, while at high loadings, clusters as well as particles of CuO or NiO (>10 nm in size) were present on ceria. Both Cu and Ni increased the reducibility of ceria, as evidenced by H2-TPR experiments. The WGS reaction activity of Ce(La)Ox was increased significantly by addition of a small amount (2 wt.%) of Cu or Ni. The catalysts were not activated prior to testing. Steady-state WGS kinetics were measured over the temperature range of 175–300 and 250–300°C, respectively, for Cu- and Ni–Ce(La)Ox. The activation energy of the reaction over Ce(La)Ox was 58.5 kJ/mol, while it was 38.2 and 30.4 kJ/mol, respectively, over the 5 at.% Ni–Ce(La)Ox and 5 at.% Cu–Ce(La)Ox catalysts in CO-rich conditions. A co-operative redox reaction mechanism, involving oxidation of CO adsorbed on the metal cluster by oxygen supplied to the metal interface by ceria, followed by H2O capping the oxygen vacancy on ceria, was used to fit the kinetics. Parametric studies were mainly performed with the 5 at.% Cu–(La)Ox catalyst. Notably, this material requires no activation and retains high WGS activity and stability at temperatures up to 600°C.
800 citations
TL;DR: In this paper, the reaction kinetics of CO and methane oxidation over the Cu-Ce-O catalysts were measured at a partial pressure of CO or oxygen from 0.001 to 0.06 bar, and at temperatures ranging from 40 to 200°C for CO oxidation and from 400 to 550°c for methane oxidation.
415 citations
394 citations