References of "Pirard, Jean-Paul"
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See detailSynthesis of SiO2 xerogels and Pd/SiO2 cogelled xerogel catalysts from silylated acetylacetonate ligands
Lambert, Stéphanie ULg; Sacco, Luigi; Ferauche, Fabrice et al

Conference (2005)

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See detailPreparation and characterization of xerogel catalyst microspheres
Alié, Christelle ULg; Ferauche, Fabrice; Heinrichs, Benoît ULg et al

in Journal of Non-Crystalline Solids (2004), 350

For easier handling and use in fixed bed reactors, Pd-Ag/SiO2 aerogel-like xerogel catalysts were shaped into microspheres using the microencapsulation process developed by BRACE GmbH. Before the bead ... [more ▼]

For easier handling and use in fixed bed reactors, Pd-Ag/SiO2 aerogel-like xerogel catalysts were shaped into microspheres using the microencapsulation process developed by BRACE GmbH. Before the bead production process, the xerogel catalyst was ground in water and mixed with ethylene glycol and sodium alginate, the latter of which is the gelation agent. The beads were formed at a vibrating nozzle and solidified during their fall in a water tank containing calcium ions, which induce cross-linking of the alginate and consequent bead hardening. Preliminary work was done using a syringe instead of the material-consuming BRACE unit. The beads were made from a suspension of dried only, dried and calcined, or dried, calcined, and reduced catalyst. The textural properties of the beads were analyzed by nitrogen adsorption-desorption isotherms and mercury porosimetry; and bead catalytic activity was tested for selective hydrodechlorination of 1,2-dichloroethane. The beads made from a suspension of dried catalyst appear to have properties the closest to that of the xerogel reference catalyst. Porosity and surface area are maintained at their level before bead formation. However conversion of 1,2-dichloroethane decreases after the production process, possibly due to poisoning by calcium ions. (C) 2004 Elsevier B.V. All rights reserved. [less ▲]

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See detailSynthesis of SiO2 xerogels and Pd/SiO2 cogelled xerogel catalysts from silylated acetylacetonate ligand
Lambert, Stéphanie ULg; Sacco, Luigi; Ferauche, Fabrice et al

in Journal of Non-Crystalline Solids (2004), 343(1-3), 109-120

SiO2 xerogels and Pd/SiO2 cogelled xerogel catalysts have been prepared in a mixture of tetrahydrofurane (THF) and ethanol containing tetraethoxysilane (TEOS), and an aqueous ammonia solution of 0.18 mol ... [more ▼]

SiO2 xerogels and Pd/SiO2 cogelled xerogel catalysts have been prepared in a mixture of tetrahydrofurane (THF) and ethanol containing tetraethoxysilane (TEOS), and an aqueous ammonia solution of 0.18 mol/l, from synthesized new silylated acetylacetonate ligands, respectively, 3-[3-(trimethoxysilyl)propyl]-2,4-pentanedione (MS-acac-H), 2,2,6,6-tetramethyl-4-[3-(trimethoxysilyl)propyl]-3,5-heptanedione (MS-dPvM), and 1,3-diphenyl-2-[3-(trimethoxysilyl)propyl]-1,3-propanedione (MS-dBzM), able to form a chelate with a metal ion such as Pd2+. All samples form homogeneous colored gels. The resulting catalysts are composed of palladium crystallites with a diameter of about 3.5 nm, located inside primary silica particles exhibiting a monodisperse microporous distribution as well as large palladium particles from 20 to 50 nm, situated outside the silica aggregates. The silylated organic ligand has a strong influence on the textural properties of xerogels and catalysts, both before and after calcination and reduction steps. Changing the nature of the silylated ligand permits tailoring textural properties such as pore volume, pore size and surface area. Although small palladium crystallites are located inside the silica particles, their complete accessibility, via the micropore network, has been shown. 1,2-Dichloroethane hydrodechlorination over Pd/SiO2 catalysts mainly produces ethane and the reaction rate increases linearly with palladium dispersion. Hydrodechlorination over Pd/SiO2 cogelled xerogel catalysts is a structure insensitive reaction compared to the ensemble size concept. (C) 2004 Elsevier B.V. All rights reserved. [less ▲]

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See detailDetermination of surface composition of alloy nanoparticles and relationships with catalytic activity in Pd-Cu/SiO2 cogelled xerogel catalysts
Lambert, Stéphanie ULg; Heinrichs, Benoît ULg; Brasseur, Alain et al

in Applied Catalysis A : General (2004), 270(1-2), 201-208

The combination of results from carbon monoxide chemisorption, X-ray diffraction, and transmission electron microscopy allowed calculating the surface composition of the palladium-copper nanoparticles in ... [more ▼]

The combination of results from carbon monoxide chemisorption, X-ray diffraction, and transmission electron microscopy allowed calculating the surface composition of the palladium-copper nanoparticles in Pd-Cu/SiO2 cogelled xerogel catalysts. Values obtained indicate a very pronounced surface enrichment with copper. Surface compositions obtained with this method, which combines three different experimental techniques, are in agreement with the literature data previously obtained for surface segregation in Pd-Cu/SiO2 catalysts by other techniques as low energy ion scattering and X-ray photoelectron spectroscopy. While 1,2-dichloroethane hydrodechlorination over pure palladium mainly produces ethane, increasing copper content in bimetallic catalysts results in an increase in ethylene selectivity, to reach 100% in ethylene selectivity for the sample containing 1.4 wt.% of palladium and 3.0 wt.% of copper. (C) 2004 Elsevier B.V. All rights reserved. [less ▲]

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See detailPd-Ag/SiO2 and Pd-Cu/SiO2 cogelled xerogel catalysts for selective hydrodechlorination of 1,2-dichloroethane into ethylene
Lambert, Stéphanie ULg; Ferauche, Fabrice; Brasseur, Alain et al

in CD-ROM of full texts of the 16th International Congress of Chemical and Process Engineering, CHISA (Paper A7.2, 11 p.) (2004, August 22)

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See detailStudy of textural properties and nucleation phenomenon in Pd/SiO2, Ag/SiO2 and Cu/SiO2 cogelled xerogel catalysts
Lambert, Stéphanie ULg; Alié, Christelle ULg; Pirard, Jean-Paul ULg et al

in Journal of Non-Crystalline Solids (2004), 342(1-3), 70-81

Pd/SiO2, Ag/SiO2 and CU/SiO2 xerogel catalysts have been synthesized by cogelation of tetraethoxysilane (TEOS) and chelates of Pd, Ag and Cu with 3-(2-aminoethylamino)propyltrimethoxysilane (EDAS). The ... [more ▼]

Pd/SiO2, Ag/SiO2 and CU/SiO2 xerogel catalysts have been synthesized by cogelation of tetraethoxysilane (TEOS) and chelates of Pd, Ag and Cu with 3-(2-aminoethylamino)propyltrimethoxysilane (EDAS). The resulting materials are composed of completely accessible metallic crystallites with a diameter of about 3 nm, located inside silica particles exhibiting a monodisperse microporous distribution centered on a pore width of about 0.8 nm. Voids between silica particles and between aggregates of silica particles constitute the material meso- and macroporous texture. The EDAS/TEOS ratio is the main operating variable to tailor the material morphology. When the EDAS/TEOS ratio decreases, metallic particle size decreases, whereas silica particle size increases. Thus the meso- and macropores between silica particles are larger. So the total pore volume can reach 5 cm(3)/g when the EDAS/TEOS ratio decreases. The remarkable morphology of these materials can be explained by the rule in which the EDAS metal complex acts as a nucleation agent in the formation of silica particles. A nucleation mechanism by EDAS-metal complex based on mass equations and the nuclei formation kinetics allows fitting the entire results. (C) 2004 Elsevier B.V. All rights reserved. [less ▲]

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See detailPhase separation during silica gel formation followed by time-resolved SAXS
Gommes, Cédric ULg; Goderis, Bart; Pirard, Jean-Paul ULg et al

Poster (2004, August)

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See detailHydrodechlorination of 1,2-dichloroethane on Pd-Ag catalysts supported on texture-tailored materials
Job, Nathalie ULg; Heinrichs, Benoît ULg; Ferauche, Fabrice et al

Conference (2004, July 19)

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See detailImage analysis of X-ray microtomograms of Pd-Ag/SiO2 xerogel catalysts supported on Al2O3 foams
Blacher, Silvia ULg; Léonard, Angélique ULg; Heinrichs, Benoît ULg et al

in Colloids and Surfaces A : Physicochemical and Engineering Aspects (2004), 241(1-mars Sp. Iss. SI), 201-206

In order to preshape and mechanically strengthen, Pd-Ag/SiO2 xerogel catalysts were carried out in Al2O3 foams (pore-sizes similar to40 mum). The final material consists of a Pd-Ag/SiO2 xerogel ... [more ▼]

In order to preshape and mechanically strengthen, Pd-Ag/SiO2 xerogel catalysts were carried out in Al2O3 foams (pore-sizes similar to40 mum). The final material consists of a Pd-Ag/SiO2 xerogel immobilized in the open cells of the alumina foam. The localization of the xerogel catalyst in alumina foams of various pore structure was studied by X-ray microtomography. The three-dimensional (3D) porous structure was reconstructed from the consecutive cross-sections obtained by this technique. Total porosity, porous density distribution, and pore-size distribution were determined by image analysis on the free and impregnated supports. Our results show that the success of the used impregnation technique depends on the pore structure of the support. (C) 2004 Elsevier B.V. All rights reserved. [less ▲]

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See detailIn situ SAXS analysis of silica gel formation with an additive
Gommes, Cédric ULg; Blacher, Silvia ULg; Goderis, Bart et al

in Journal of Physical Chemistry B (2004), 108(26), 8983-8991

Time-resolved small-angle X-ray scattering (SAXS) measurements performed during the formation of tetraethyl orthosilicate (TEOS) based silica gels in alcohol with 3-(2-aminoethylamino ... [more ▼]

Time-resolved small-angle X-ray scattering (SAXS) measurements performed during the formation of tetraethyl orthosilicate (TEOS) based silica gels in alcohol with 3-(2-aminoethylamino)propyltrimethoxysilane (EDAS) as an additive are reported. The measurements reveal no discontinuity of the nanostructure at the gel point. A chemically induced spinodal phase separation is found to give a coherent picture of the collected data. Increasing the amount of EDAS induces the phase separation on a smaller length scale, which finally leads to a modified gel morphology. The SAXS measurements and the electron micrographs associated with the dry gels could be interpreted in terms of the suggested wet gel formation mechanism. [less ▲]

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See detailSynthesis of Pd/SiO2, Ag/SiO2, and Cu/SiO2 cogelled xerogel catalysts: study of metal dispersion and catalytic activity
Lambert, Stéphanie ULg; Cellier, Caroline; Grange, Paul et al

in Journal of Catalysis (2004), 221(2), 335-346

Pd/SiO2, Ag/SiO2, and Cu/SiO2 xerogel catalysts have been synthesized by cogelation of tetraethoxysilane (TEOS) and chelates of Pd, Ag, and Cu with 3-(2-aminoethylamino)propyltrimethoxysilane (EDAS). It ... [more ▼]

Pd/SiO2, Ag/SiO2, and Cu/SiO2 xerogel catalysts have been synthesized by cogelation of tetraethoxysilane (TEOS) and chelates of Pd, Ag, and Cu with 3-(2-aminoethylamino)propyltrimethoxysilane (EDAS). It appears that the metal complex acts as a nucleation agent in the formation of silica particles. The resulting catalysts are then composed of completely accessible metallic crystallites with a diameter of about 3 nm located inside silica particles exhibiting a monodisperse microporous distribution. The metal dispersion has been determined from CO and O-2 chemisorption, TEM, and X-ray diffraction. Although metallic particles are located inside silica particles, their complete accessibility, via the micropore network, has been shown. 1,2-Dichloroethane hydrodechlorination over Pd/SiO2 catalysts mainly produces ethane and the specific hydrodechlorination rate per gram of Pd decreases when metal loading increases. Hydrodechlorination over Pd/SiO2 catalysts is a structure-insensitive reaction with regard to the ensemble size concept. Benzene oxidation over Ag/SiO2 and Cu/SiO2 catalysts produces H2O and CO2 only and specific oxidation rate per gram of metal decreases when silver and copper loadings increase. Furthermore, it is concluded that benzene oxidation is a structure-insensitive reaction. (C) 2003 Elsevier Inc. All rights reserved. [less ▲]

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See detailComparison of different methods for characterizing multi-walled carbon nanotubes
Gommes, Cédric ULg; Blacher, Silvia ULg; Dupont-Pavlovsky, N. et al

in Colloids and Surfaces A : Physicochemical and Engineering Aspects (2004), 241(1-3), 155-164

Four complementary and independent methods are used to characterize nanotube samples: (i) TEM observation coupled with image analysis, (ii) nitrogen and krypton adsorption isotherm analysis, (iii ... [more ▼]

Four complementary and independent methods are used to characterize nanotube samples: (i) TEM observation coupled with image analysis, (ii) nitrogen and krypton adsorption isotherm analysis, (iii) thermogravimetry and (iv) wide angle X-ray scattering. The methodology is discussed on the basis of two multi-walled carbon nanotube samples produced by the CCVD technique with very different reaction rates. It is shown that the total amount of deposited carbon is larger for the sample produced at the higher rate, that the fraction of nanotubes in the deposited carbon does not seem to be significantly different, but that the crystallinity of the nanotubes wall is larger for the sample produced at the lowest reaction rate. (C) 2004 Elsevier B.V. All rights reserved. [less ▲]

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See detailSynthesis of Pyrazolylpyridine Derivatives Bearing a Tethered Alkoxysilyl Group.
Sacco Luigi; Lambert, Stéphanie ULg; Pirard, Jean-Paul ULg et al

in Synthesis (2004), 5

A synthesis of a new serie of trimethoxysilyl-tethered N-substituted 3,5-dialkylpyrazolylpyridines is reported. The silyl spacers allow the grafting of ligands onto silica via formation of covalent bonds ... [more ▼]

A synthesis of a new serie of trimethoxysilyl-tethered N-substituted 3,5-dialkylpyrazolylpyridines is reported. The silyl spacers allow the grafting of ligands onto silica via formation of covalent bonds as well as the synthesis of xerogels. [less ▲]

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See detailElaboration of new formulations to remove micropollutants in MSWI flue gas
Brasseur, Alain; Gambin, Amandine; Laudet, Alain et al

in Chemosphere (2004), 56(8), 745-756

This study consists in identifying and testing potential inorganic substitutes to carbon based materials commonly used as adsorbents for the removal of organic pollutants such as dioxins and furans ... [more ▼]

This study consists in identifying and testing potential inorganic substitutes to carbon based materials commonly used as adsorbents for the removal of organic pollutants such as dioxins and furans released from Municipal Solid Waste Incinerators (MSWI). Although carbon materials enable to reach the current regulation in terms of dioxins and furans emissions, they exhibit a potential auto ignition risk when present in hot flue gases. Here, the adsorption potential of carbon based products is compared to the one of some inorganic materials. Chlorobenzene was chosen as a reference molecule to compare the removal performance of the different adsorbents. This comparison was based on the determination of the adsorption energies derived from temperature programmed desorption (TPD) experiments. In the first part of this study, five inorganic materials were selected according to their chlorobenzene adsorption performance compared to those of carbon based products currently used to remove micropollutants from MSWI flue gases. In the second part of the study, the influence of the inlet concentration of adsorbate on the adsorption potential of sorbents is investigated. Actually, the organic compound concentration was decreased in order to be closer to those met in MSWI. Furthermore, the adsorption experiments were performed with other adsorbates whose molecular mass or chlorine content are higher. Thanks to these adsorption results a new organic free formulation has been proposed for the removal of micropollutants. Tests carried out on an industrial scale, demonstrated that this product enables to reach the current norm concerning dioxins and furans emissions. (C) 2004 Elsevier Ltd. All rights reserved. [less ▲]

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See detailPorous carbon xerogels with texture tailored by pH control during sol-gel process
Job, Nathalie ULg; Pirard, René ULg; Marien, José ULg et al

in Carbon (2004), 42(3), 619-628

Despite commonly accepted ideas, evaporative drying does not always completely destroy the pore texture of phenolic gel. This work shows that very porous carbon materials can be synthesized by evaporative ... [more ▼]

Despite commonly accepted ideas, evaporative drying does not always completely destroy the pore texture of phenolic gel. This work shows that very porous carbon materials can be synthesized by evaporative drying and pyrolysis of aqueous resorcinol-formaldehyde gels provided that the operating variables are correctly chosen. Moreover, in this manner monoliths can be easily produced. The pore texture of the materials was studied before and after pyrolysis in order to determine which synthesis and/or pyrolysis variables have an influence on the final texture of the carbon. Results show that it is possible to tailor the morphology of these materials by varying the initial pH of the precursors solution in a narrow range. Micro-macroporous, micro-mesoporous, microporous or totally non-porous carbon materials were obtained. The specific surface area is independent from the initial pH whereas the total void volume varies from 0.4 to 1.4 cm(3)/g when the initial pH decreases from 6.25 to 5.45. These materials can be used as catalysts supports or for electrochemical applications, the texture control being an interesting advantage. (C) 2004 Elsevier Ltd. All rights reserved. [less ▲]

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