Kinetics of the water-gas shift reaction over Pt and Au supported bifunctional catalysts

internationa

Kinetics and Mechanism of the Water-Gas Shift Reaction Over Platinum Supported Catalysts

INGENIERIE+KRA:OTH:YSCNon

Spatially resolved catalysis in microstructured reactors by IR spectroscopy: CO oxidation over mono- and bifunctional Pt catalysts

A new experimental reactor concept is presented for spatially resolved DRIFTS surface analysis in a microstructured catalytic reactor. Both gas and surface adspecies concentration profiles can be established along the channels coated with a catalyst. The oxidation of carbon monoxide was studied from 25 to 300 degrees C over a Pt/Al2O3 and a Pt/CeO2-Al2O3 catalyst. For these operating conditions, nearly isothermal conditions were observed for the microstructured reactor, with a continuous linear increase in the reaction product along the micro-channels. In contrast, an important thermal effect with the characteristic light-off was obtained in a fixed bed DRIFTS reactor, underlining the unique behavior of the microstructured system. Modeling of the CO conversion and surface adspecies concentration as a function of the temperature along the channels was performed based on a mono-functional reaction mechanism for the case of the alumina-supported catalyst or a bifunctional one taking into account sites on the platinum particles and on the ceria support for the case of the ceria-supported system. The model permits an adequate description of the data along the reactor axis over both catalysts. It underlines the important role of ceria in the creation of an additional site for oxygen chemisorption and the transfer of oxygen to the active site on the Pt/support interface. It also provides new insights in the change of the rate-controlling step from being the oxygen chemisorption on platinum to the CO2 production at the platinum/ceria interface

The Central English Channel troughs: major source-to-sink remnants or giant tidal scours?

The Central English Channel troughs correspond to elongated incisions up to 250 m-deep, at several locations at the bottom of this sea corridor. Depending on their location, they are usually interpreted as part of the submerged quaternary paleovalley network or as resulting from megaflood events. Shedding light on these features, their age, and the processes underlying their development is key for understanding their significance in terms of event geology. The interpretation of a dense grid of high-resolution marine seismic data acquired in the Bay of Seine area reveals that the extensive Quaternary paleovalley and trough network commonly as associated to the “Channel River” system is actually subdivided into at least two superimposed and unrelated incised networks. The overlying network corresponds to fluvial incisions developing during low sea-level conditions of Pleistocene time and connects to the present day fluvial network. The underlying network corresponds to the troughs and appears as a complex, deeper, relatively discontinuous and isolated network. This older network shows unexpected local incision depth up to c.350-400 m-deep and complex sedimentary infill involving several sedimentary processes and environments from fluvial to tidal and shallow-marine. We discuss these observations and their implications for understanding the origin, age and development of the troughs all over the English Channel, from the Dangeard Troughs in the Dover Strait to the Hurd Deep at the western end. We also raise questions about the significance of these large incised features in terms of source-to-sink system of northwestern Europe

Une analyse des modalités de résolution des tensions liées aux différents usages des espaces ruraux

This work concerns conflicts which appear between various actors and various rural space uses. We study characteristics and possible modalities of outcome of conflicts, and we examine if environmental services (defined as operations on natural goods to improve environmental quality) can allow to assure repair, prevention or management of conflicts.Notre projet de recherche porte sur les tensions qui émergent entre différents acteurs et différents usages des espaces ruraux. L`idée de départ consiste à étudier les caractéristiques et les éventuelles modalités de dénouement des tensions (ou conflits), et à examiner en quoi les services environnementaux (entendus comme des opérations sur des biens de nature pour améliorer leur qualité environnementale) peuvent permettre d`assurer la réparation, la prévention ou la gestion des tensions

PSDR Rhône-Alpes Projet 2.8. : analyse des modalités de résolution des tensions liées aux différents usages des espaces ruraux

AutresThis work concerns conflicts which appear between various actors and various rural space uses. We study characteristics and possible modalities of outcome of conflicts, and we examine if environmental services (defined as operations on natural goods to improve environmental quality) can allow to assure repair, prevention or management of conflicts.Notre projet de recherche porte sur les tensions qui émergent entre différents acteurs et différents usages des espaces ruraux. L`idée de départ consiste à étudier les caractéristiques et les éventuelles modalités de dénouement des tensions (ou conflits), et à examiner en quoi les services environnementaux (entendus comme des opérations sur des biens de nature pour améliorer leur qualité environnementale) peuvent permettre d`assurer la réparation, la prévention ou la gestion des tensions

Premiers résultats de la Campagne Tore-Madère (26/09 au 19/10/2001 sur le N/O L'Atalante)

National audienc

Structure and evolution of a passive margin in a compressive environment : example of the south-western Alps-Ligurian basin junction during the Cenozoic

We focus on the northern Ligurian margin, at the geological junction of the subalpine domain and the Ligurian oceanic basin, in order (1) to identify the location of the southern limit of the Alpine compressive domain during the Cenozoic, and (2) to study the influence of a compressive environment on the tectonic and sedimentary evolution of a passive margin. Based on published onshore and offshore data, we first propose a chronology of the main extensional and compressional regional tectonic events. High-resolution seismic data image the margin structure down to similar to 3 km below seafloor. These data support that past rifting processes control the present-day margin structure, and that 2800-4000 m of synrift sediment was deposited on this segment of the margin in two steps. First, sub-parallel reflectors indicate sediment deposition within a subsident basin showing a low amount of extension. Then, a fan-shaped sequence indicates block tilting and a higher amount of extension. We do not show any influence of the Miocene Alpine compression on the present-day margin structure at our scale of investigation, despite the southern subalpine relief formed in the close hinterland at that time. The southern front of the Miocene Alps was thus located upslope from the continental margin. Finally, a comparison with the Gulf of Lions margin suggests that the tectonic influence of the Alpine compression on the rifting processes is restrited to an increase of the subsidence related to flexure ahead of the Alpine front, explaining abnormally high synrift thicknesses in the study area. The Alpine environment, however, has probably controlled the sedimentary evolution of the margin since the rifting. Indeed, sediment supply and distribution would be mainly controlled by the permanent building of relief in the hinterland and by the steep basin morphology, rather than by sea-level fluctuations, even during the Messinian sea-level low-stand