Search results for "Cerium"
showing 10 items of 140 documents
Screening of ceria-based catalysts for internal methane reforming in low temperature SOFC
2010
Gaudillere, Cyril Vernoux, Philippe Mirodatos, Claude Caboche, Gilles Farrusseng, David 6th World Congress on Oxidation Catalysis (6WCOC) JUL 05-10, 2009 Lille, FRANCE; International audience; Ceria-based catalysts have been assessed for internal methane reforming at low temperature (400-600 C) in Solid Oxide Fuel Cell (SOFC) A combinatorial library of 15 metal (Cu Pt Ni) supported ceria was prepared using wet impregnation method The ceria-based oxides are undoped or doped with metal transition (Zr) or by rare earth (Gd or Pr) The effect of the metal the dopant and the surface area on the catalytic performances was investigated in high-throughput manner using a 16-parallel reactor The catal…
The catalytic performance of mesoporous cerium oxides prepared through a nanocasting route for the total oxidation of naphthalene
2010
Cerium oxides have been prepared by nanocasting of a mesoporous siliceous KIT-6. Through this synthesis method a partially ordered mesoporous structure, as demonstrated by several characterization techniques (N2 adsorption, XRD and HRTEM) has been obtained. Accordingly, very high surface areas have been achieved (up to 163 m2/g), despite using high calcination temperatures (550 °C). We have demonstrated that the aging temperature of the siliceous template is of outstanding importance, as this parameter is directly responsible for both the pore size and the surface area of the catalysts. In addition, whilst a low preparation temperature (40 °C) makes the further removal of the silica templat…
The influence of various synthesis methods on the catalytic activity of cerium oxide in one-pot synthesis of diethyl carbonate starting from CO2, eth…
2013
Different synthesis methods such as homogeneous precipitation at room temperature and supercritical water (T > 647 K and P > 22.1 MPa) were employed for cerium oxide preparation. Additionally, deposition of ceria on silica mesoporous material, SBA-15, was carried out. The obtained materials were characterized by means of X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, nitrogen physisorption, X-ray photoelectron spectroscopy and CO2 temperature programmed desorption. Considerable variations in physico-chemical properties of the resulting materials were observed. The catalytic activities of pristine cerium oxide and ceria loaded on SBA-15 support were…
Cerium and cerium oxide: A brief introduction
2020
Abstract A short introduction on the history and main properties of cerium and cerium oxide is here provided. The main applications of cerium oxide, reported and discussed in this book, are also briefly summarized, with some final considerations on the future perspectives and the market outlooks of this outstanding oxide.
Photocatalytic and photothermocatalytic applications of cerium oxide-based materials
2020
Abstract Cerium dioxide (CeO2) presents unique properties as the special electronic and optical properties of the 4f electrons, the capacity to form nonstoichiometric oxygen-deficient CeO2 − x oxides, the high oxygen mobility, and the reversible transformation between Ce4 + and Ce3 + that make it interesting for photocatalytic applications. CeO2 is a wide bandgap semiconductor (3.0–3.4 eV), but different approaches as combination with oxides, deposition of noble metals, doping with metal and nonmetal species, and the formation of surface defects have been adopted to extend its absorption towards the visible region with the aim to improve its photocatalytic performance. Cerium oxide-based ma…
Isotope shifts in natural cerium
2003
High resolution crossed beam resonance fluorescence laser spectroscopy has been performed on an atomic beam of naturally occurring cerium, and isotope shifts have been measured in several transitions. Changes in mean square charge radius, δ〈r 2〉, have been extracted using the King plot technique and show the characteristic increase at the N = 82 neutron shell closure. The measurements form the basis for further investigations of radioactive isotopes and isomers on both sides of the shell closure.
Chaotic dynamics in an unstirred ferroin catalyzed Belousov–Zhabotinsky reaction
2009
Abstract The Belousov–Zhabotinsky (BZ) reaction is the best known example of far from equilibrium self-organizing chemical reaction. Among the many dynamical behaviors that this reaction can exhibit, spatio-temporal chaos attracted particular interest, both for the ferroin and cerium catalyzed systems. In recent years transient chaos was found in the cerium catalyzed BZ reaction, when conducted in batch and unstirred reactors. It was established that the chaotic oscillations, originated by the coupling among chemical kinetics and transport phenomena, appeared and disappeared following a Ruelle–Takens–Newhouse scenario. In this Letter, we show results about the ferroin catalyzed system condu…
Deuterium isotope effect on the induction period of the cerium catalyzed Belousov-Zhabotinsky reaction
2009
Abstract In this work we present results about the deuterium isotopic effect on the global kinetics of a cerium catalyzed Belousov–Zhabotinsky reaction. A nonlinear dependence of the induction period upon the percentage of deuterated reactants was found in batch conditions. In order to understand this result, we investigated two reaction pathways responsible for the length of the induction period, namely: (a) the reaction between the enolic form of the malonic acid with molecular bromine and (b) the oxidation of malonic acid by the Ce(IV) ion. In both cases we obtained a linear dependence of the kinetic constants on the percentage of deuterated reactants. Nevertheless, by inserting the expe…
Electrocatalysis of the oxidation of methylenedioxyamphetamines at electrodes modified with cerium-doped zirconias
2004
The catalytic effect of monoclinic and tetragonal cerium-doped zirconias (m-CexZr1−xO2 and t-CexZr1−xO2, 0<x<0.10, respectively), prepared from gel precursors, on the oxidation of methylenedioxyamphetamine (MDA) and methylenedioxymetamphetamine (MDMA) at pH 7.0 has been studied. Upon attachment of synthetic specimens to polymer film electrodes, an oxidation peak near to +1.05 V vs AgCl/Ag appears that is unaffected by chloride ions and common interfering compounds, namely, dopamine, norepinephrine and ascorbic acid. The catalytic effect appears to be strongly influenced by crystallinity of specimens and coordination of cerium, increasing from the amorphous starting material to t-CexZr1−xO2 …
Sol–Gel Synthesis of Tunable Cerium Titanate Materials
2008
Cerium titanate structures present a high technological interest because of their optical and catalytic properties. This work reports the synthesis of these materials by a sol–gel methodology that allows mixed oxides with TiIV/CeIII, TiIV/CeIV or TiIV/CeIII–CeIV species to be obtained. Crystallization of CeO2–TiO2 mixed oxides and Ce2Ti2O7 pyrochlore phase was corroborated by XRD and Raman spectroscopy. Magnetic and EPR measurements were performed in order to clarify the oxidation state of the cerium ions in the system as a result of the easy oxidation of CeIII. The firing atmosphere is crucial for the CeIII/CeIV ratio, which is responsible for the different structure, but it also affects t…