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33 results on '"Nedez, C."'

1. Surface organometallic chemistry of tin: thermal transformation, under vacuum, of yields Si-O-Sn(n-Bu)3 supported on silica

Author

Nedez, C., Lefebvre, F., Choplin, A., Basset, J.M., and Benazzi, E.

Subjects
Organometallic compounds -- Research, Tin -- Analysis, Chemistry
Abstract

Dialkylated, monoalkylated and nonalkylated tin surface complexes were formed when a well-defined surface organometallic fragment was grafted at the surface of two silicas, SiO2(200) and SiO2(500). The degree of dehydroxylation differentiated the two silicas. The choice of a starting tin complex was crucial for the control of surface organostannic fragment structure.

Published
1994

2. Surface organometallic chemistry of germanium: evidence for the formation of highly thermally stable triple bond Si-O-GeR3 fragments by reaction of GeR4 complexes (R = n-Bu, Et) with the surface of silica

Author

Nedez, C., Choplin, A., and Basset, J.M.

Subjects
Germanium -- Research, Organometallic compounds -- Analysis, Silica -- Analysis, Nuclear magnetic resonance spectroscopy -- Analysis, Chemistry
Abstract

GeR4 complexes interaction with incompletely dehydroxylated silica surfaces is studied using infrared and NMR spectroscopies and analytical methods. At room temperature, physisorption of the complexes occurs through a hydrogen bonding between terminal methyl and surface silanol groups. The grafted complex is thermally stable as confirmed by experimental data.

Published
1994

3. Surface organometallic chemistry of tin: reactivity of tetraalkyltin complexes and tributyltin hydride toward silica

Author

Nedez, C., Theolier, A., Lefebre, F., Choplin, A., Basset, J.M., and Joly, J.F.

Subjects
Tin -- Research, Silica -- Research, Reactivity (Chemistry) -- Research, Chemistry
Abstract

The low-temperature reactivity of tetraalkyltin complexes and tributyltin hydride toward the suface of a high-specific-area silica is studied. Infrared spectrum analysis is performed on specially prepared samples to obtain the necessary measurements. Results show that the reaction between the tetraalkyltin or hydridotributyltin complexes and the surface of the silica leads to the clean formation of the related trialkyltin surface complexes.

Published
1993

4. Surface organometallic chemistry: reaction of tris-allyl rhodium with surfacesof silica, alumina, titania, and magnesia

Author

Dufour, P., Houtman, C., Santini, C.C., Nedez, C., Basset, J.M., Hsu, L.Y., and Shore, S.G.

Subjects
Surface chemistry -- Research, Rhodium -- Research, Silica -- Research, Aluminum oxide -- Research, Titanium dioxide -- Research, Chemistry
Abstract

A study was done on the reaction of tris-allyl rhodium with surfaces of silica, alumina, titania and magnesia using infrared spectroscopy, isotopic labelling experiments, quantitative analysis of gaseous products and elemental analysis. Results show that the interaction of tris-allyl rhodium with oxide varies with the nature of the support and degree of hydroxylation. No reactions were seen with magnesia but silica and titania partially dehydroxylated alumina and reacted rapidly at room temperature.

Published
1992

7. Surface organometallic chemistry of tin: formation of the grafted organometallic complex (***Si-O)2Sn(n-C4H9)2 by reaction of H2Sn(n-C4H9)2 with the surface of a partially dehydroxylated silica

Author

Nedez, C., Choplin, A., Lefebvre, F., Basset, J.M., and Benazzi, E.

Subjects
Tin compounds -- Research, Organometallic chemistry -- Analysis, Surface chemistry -- Analysis, Chemistry
Abstract

Surface microanalysis, quantitative analysis of evolved gases and spectroscopic studies of the reaction between H2Sn(n-C4H9)2 and the surface of Aerosil silica dehydroxylated at 200 or 500 degrees Celsius reveal the physisorption of the starting complex on the silica surface at room temperature soon after interaction. Surface silanols and CH groups of the butyl ligand and the tin hydride undergo two weak interactions.

Published
1994

12. Selective isomerization of xylenes

Author

Benazzi, E., De Tavernier, S., Beccat, P., Joly, J.P., Nedez, C., Choplin, A., Basset, J.M., Institut de recherches sur la catalyse (IRC), Centre National de la Recherche Scientifique (CNRS), and IRCELYON, ProductionsScientifiques

Subjects
[CHIM.CATA] Chemical Sciences/Catalysis, [CHIM.CATA]Chemical Sciences/Catalysis
Published
1994

16. Catalytic properties of small and large port mordenites, modified by surface organometallic chemistry, in C8 aromatics isomerization

Author

Benazzi, E., De Tavernier, S., Beccat, P., Joly, J.P., Nedez, C., Basset, J.M., Choplin, A., Institut de recherches sur la catalyse (IRC), Centre National de la Recherche Scientifique (CNRS), American Chemical Society, and IRCELYON, ProductionsScientifiques

Subjects
[CHIM.CATA] Chemical Sciences/Catalysis, [CHIM.CATA]Chemical Sciences/Catalysis
Published
1993

24. Surface organometallic chemistry of tin: Formation of the organometallic complex...

Author

Nedez, C. and Choplin, A.

Subjects
*TIN compounds, *SILICA, *REACTIVITY (Chemistry)
Abstract

Investigates the reaction of H2Sn(n-C4H9) with the surface of Aerosil silica dehydroxylated at 200 or 500 degrees Celsius. Surface microanalysis; Quantitative analysis of the evolved gases; Two types of weak interactions that occur between surface silanols and the CH groups of the butyl ligands and the tin hyddrides.

Published
1994
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25. Efficient Removal of Polymerization Inhibitors by Adsorption on the Surface of an Optimized Alumina

Author

Nedez, C. and Ray, J.-L.

Abstract

tert-Butylcatechol (TBC) is an efficient inhibitor of parasitic polymerization of many monomers during their transportation and storage. Just before the monomers are used, removal of the inhibitor is often necessary and can easily be achieved by adsorption on alumina. The influence of the main physical parameters of the alumina on its performance has been particularly studied. The accessibility of the TBC molecule into the internal porous network of the alumina beads or extrudates appears to be the key parameter, clearly more than the specific surface area. Procatalyse's specially optimized Spheralite 538E performs particularly well in removing TBC from hydrocarbon streams.

Published
1999

26. Optimization of the Textural Characteristics of an Alumina To Capture Contaminants in Natural Gas

Author

Nedez, C., Boitiaux, J.-P., Cameron, C. J., and Didillon, B.

Abstract

Capillary condensation of water can seriously impair the performance of an adsorbent intended for use in removing contaminants (mercury, arsenic, sulfur, etc.) in natural gas. Adsorption and desorption isotherms were used to determine how the nature and pore structure distribution of the adsorbent (alumina, active cabon) affect water adsorption. The contribution of the different phenomena involved (chemisorption, physisorption, capillary condensation) have been determined. The threshold of capillary condensation is reached much more rapidly on active carbon and microporous alumina (40% relative humidity) than on a highly mesoporous alumina (75−80% relative humidity).

Published
1996

27. Surface Organometallic Chemistry of Germanium:  Infrared, CP-MAS <SUP>13</SUP>C Solid State NMR, and Analytical Evidence for the Formation of Highly Thermally Stable −O−Ge(n-C<INF>4</INF>H<INF>9</INF>)<INF>3</INF> Grafted Fragments by Reaction of Ge(n-C<INF>4</INF>H<INF>9</INF>)<INF>4</INF> with the Surface of Partially Dehydroxylated Alumina and Silica−Alumina

Author

Nedez, C., Lefebvre, F., and Basset, J.-M.

Abstract

Interaction of Ge(n-C4H9)4 complex with partially dehydroxylated α- and η-alumina and silica−alumina surfaces has been investigated by 13C CP-MAS NMR, infrared spectroscopy, and analytical methods. At 25 °C, Ge(n-C4H9)4 interacts, via hydrogen bonds, by its butyl ligands, with hydroxyl groups of the surface. At 250 °C, Ge(n-C4H9)4 reacts with the hydroxyl groups to form >X-O-Ge(n-C4H9)3 (X = Si, Al) and 1 mol of butane/mol of grafted germanium. When the complex is grafted on silica−alumina the germanium atom is tetracoordinated, while on alumina it could adopt a tetra- or a pentacoordination. The grafted −O−Ge(n-C4H9)3 fragments exhibit, on both silica−alumina and alumina, extraordinary high thermal stability (until 400 °C in vacuo). This phenomenon had already been observed with &tbd1;SiOGe(n-C4H9)3 grafted on silica.

Published
1996

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