170,387 research outputs found
Continuous hydrogen production by sequential catalytic cracking of acetic acid. Part II. Mechanistic features and characterisation of catalysts under redox cycling
No full textDavidian, Thomas Guilhaume, Nolven Provendier, Helene Mirodatos, ClaudeIn this study, the mechanism of sequential cracking of acetic acid (AA) over Ni-based catalysts was investigated. During AA cracking, both thermal and catalytic reactions take place. Acetic acid is thermally decomposed into CH4, CO, CO2 and H-2, which further react on Ni through WGS and steam reforming reactions, whereas some coke accumulates on the catalyst. The statistical distribution of labelled C*O-2 species suggests fast isotopic exchange between CO2 and surface carbonates. During the regeneration, the coke deposited during cracking is fully burnt, and carbonates are thermally decomposed. O-18(2) isotopic labelling experiments coupled with physico-chemical characterisations of catalysts, after cracking and regeneration steps, reveal that the nickel is reduced by cracking products at the beginning of each cracking step, and oxidized during the regeneration. This redox cycling progressively extracts metallic Ni, initially present as Ni2+ species incorporated in spinel-type structures. (c) 2007 Elsevier B.V. All rights reserved
Screening of ceria-based catalysts for internal methane reforming in low temperature SOFC
No full textGaudillere, Cyril Vernoux, Philippe Mirodatos, Claude Caboche, Gilles Farrusseng, David 6th World Congress on Oxidation Catalysis (6WCOC) JUL 05-10, 2009 Lille, FRANCEInternational audienceCeria-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 catalysts were assessed in two different conditions (i) in CH4 rich condition and (ii) in model reformate condition Catalytic performances are very metal depending In dry conditions Cu-based catalysts do not produce H-2 whereas NI-catalysts are very active despite low carbon balance However when water and CO2 are added in the feed the nature of the ceria plays an important role in the catalytic performances At low temperature (T < 550 C) most of Ni/ceria catalysts are not active under reformate conditions at low temperature while Pt catalysts appear more robust with respect to the conditions From unsteady state parallel studies we suggest that surface hydroxyl on ceria are the active species (C) 2010 Elsevier B V All rights reserve
Conversion catalytique de la biomasse : cas du reformage de l’éthanol et du craquage d’huiles depyrolyse pour illustrer des couplages ‐ réactivité, diffusion et vieillissement de catalyseurs.C. Mirodatos
No full textING+CMIInternational audienceNon
Acidity Characterization of Catalyst Libraries by High-Throughput Testing
No full textMorra, G. Farrusseng, D. Guillon, E. Morin, S. Bouchy, C. Mirodatos, C. 1st International Combinatorial Catalysis Symposium (ICCS) JUL 20-22, 2008 Daejeon, SOUTH KOREAThe development of acid and bi-functional catalysts with controlled properties is a matter of high interest for refinery applications. The issues of characterization and quantification of catalyst acidity in the frame of high throughput (HT) screening are outlined. The present study deals with the development of a HT method for the characterization of the Bronsted acidity of 80 bifunctional catalysts library by means of isomerization of 3,3-dimethylbutene testing. Catalytic results are validated with literature data. The choice of probe molecules, the operating conditions and deactivation issues upon testing are addressed. This method allows quantifying very accurately the acid strength. Catalyst ranking from large library can be achieved an acidity scale in conditions similar to the practical applications. The pros and cons of the use of model reactions for HT quantitative characterization are discussed
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Conversion catalytique de la biomasse : cas du reformage de l’éthanol et du craquage d’huiles depyrolyse pour illustrer des couplages ‐ réactivité, diffusion et vieillissement de catalyseurs.C. Mirodatos
No full textING+CMIInternational audienceNon
Conversion catalytique de la biomasse : cas du reformage de l’éthanol et du craquage d’huiles depyrolyse pour illustrer des couplages ‐ réactivité, diffusion et vieillissement de catalyseurs.C. Mirodatos
No full textING+CMIInternational audienceNon
Natural gas treating by selective adsorption: Material science and chemical engineering interplay
No full textTagliabue, Marco Farrusseng, David Valencia, Susana Aguado, Sonia Ravon, Ugo Rizzo, Caterina Corma, Avelino Mirodatos, ClaudeThe paper addresses current needs in Natural Gas (NG) treating. Basic principles of Pressure Swing Adsorption (PSA) separation processes are described. A state of the art of microporous adsorbents in the frame of NG treating is given. It includes reference and advanced zeolites, carbon based materials and Metal-Organic Frameworks (MOFs). The pros and cons of each material category are discussed. Guidelines to develop on-purpose materials are given from thermodynamics and material state of the art. Finally, PSA applicability to inert (nitrogen and carbon dioxide) rejection from NG is discussed. (C) 2009 Elsevier B. V. All rights reserved
Tap study of the impact of the oxidation state of Pt/PrCeZrO and Pt/GdCeZrO catalysts on their reactivity in the partial/deep oxidation of methane
No full textGubanova, Elena L. Sadykov, Vladislav A. van Veen, Andre C. Mirodatos, ClaudeThe temporal analysis of products (TAP) technique coupled with the oxygen TPD was used to elucidate the effects of the Pt-supported fluorite-like doped ceria-zirconia oxide chemical composition and the type of pretreatment on their oxygen bonding strength, mobility, and reactivity as related to catalytic properties in the partial oxidation of methane into synthesis gas. A rapid evolution of hydrogen under CH4 pulse observed for oxidized catalysts agrees with the direct route of the methane selective oxidation into syngas. This route is favored by the Pt-support interaction and a moderate bonding strength of surface oxygen species along with a high lattice oxygen mobility
Mitomycin C in highly myopic eyes - Author reply
No full textOphthalmology. 2005 Feb;112(2):208-18; discussion 219.
Mitomycin C modulation of corneal wound healing after photorefractive keratectomy in highly myopic eyes.
Gambato C, Ghirlando A, Moretto E, Busato F, Midena E.
SourceRefractive Surgery Service and Antimetabolite Therapy Research Unit, Department of Ophthalmology, University of Padova, Padova, Italy.
Abstract
PURPOSE: To evaluate the role of topical mitomycin C in corneal wound healing (CWH) after photorefractive keratectomy (PRK) in highly myopic eyes.
DESIGN: Prospective, double-masked, randomized clinical trial.
PARTICIPANTS: Seventy-two eyes of 36 patients affected by high (>7 diopters) myopia.
METHODS: In each patient, one eye was randomly assigned to PRK with intraoperative topical 0.02% mitomycin C application, and the fellow eye was treated with a placebo. Postoperatively, mitomycin C-treated eyes received artificial tears (3 times daily, tapered in 3 months), whereas the fellow eye was treated with fluorometholone sodium 2% and artificial tears (3 times daily, tapered in 3 months).
MAIN OUTCOME MEASURES: Uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA), contrast sensitivity, manifest refraction, and biomicroscopy. Contrast sensitivity was determined using the Pelli-Robson chart. Corneal confocal microscopy documented CWH.
RESULTS: Mean follow-up was 18 months (range, 12-36). No side effects or toxic effects were documented. At 12-month follow-up examination, UCVAs (logarithm of the minimum angle of resolution) were 0.4+/-0.48 and 0.5+/-0.53 (P = .03) in mitomycin C-treated eyes and corticosteroid-treated eyes, respectively. At 1 year, corneal haze developed in 20% of corticosteroid-treated eyes, versus 0% of mitomycin C-treated eyes. At 12, 24, and 36 months, corneal confocal microscopy showed activated keratocytes and extracellular matrix significantly more evident in untreated eyes (Ps = 0.004, 0.024, and 0.046, respectively).
CONCLUSION: Topical intraoperative application of 0.02% mitomycin C can reduce haze formation in highly myopic eyes undergoing PRK.
Comment in
Ophthalmology. 2006 Feb;113(2):357; author reply 357-8
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