References of "Pirard, Jean-Paul"
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See detailOlefin cyclopropanation and insertion into O-H bonds mediated by copper(I) and palladium(II) covalently anchored to silica xerogels
Sacco, Luigi; Lambert, Stéphanie ULg; Pirard, Jean-Paul ULg et al

in Journal of Catalysis (2005), 232(1), 51-59

Copper(I) and palladium(II) ligated to pyrazolylpyridine hearing a tethered (trimethoxysilyl)propyl group in position 4 of the pyrazole ring were chemically bonded to silica via a sol-gel process. The ... [more ▼]

Copper(I) and palladium(II) ligated to pyrazolylpyridine hearing a tethered (trimethoxysilyl)propyl group in position 4 of the pyrazole ring were chemically bonded to silica via a sol-gel process. The textural properties of the materials (Specific Surface area, porous volume, and pore size distribution) were characterized by nitrogen adsorption-desorption isotherms, mercury porosimetry, and TEM analysis. The hybrid materials were tested as catalysts in olefin cyclopropanation and as potential chemoselective catalysts in the reaction with unsaturated alcohols (double bond versus -OH group), with ethyl diazoacetate as a carbene precursor, and compared with the corresponding homogeneous complexes. © 2005 Elsevier Inc. All rights reserved. [less ▲]

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See detailFormation and structural characteristics of Pd-Ag/SiO2 and Pd-Cu/SiO2 catalysts synthesized by cogelation
Lambert, Stéphanie ULg; Gommes, Cédric ULg; Alié, Christelle ULg et al

in Journal of Non-Crystalline Solids (2005), 351(52-54), 3839-3853

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

Pd-Ag/SiO2 and Pd-Cu/SiO2 xerogel catalysts have been synthesized by cogelation of tetraethoxysilane (TEOS) and chelates of either Pd and Ag or Pd and Cu with 3-(2-aminoethylamino)propyltrimethoxysilane (EDAS). After an extensive study of the influences of synthesis operating variables over structural characteristics of gels, highly dispersed bimetallic Pd-Ag/SiO2 and Pd-Cu/SiO2 xerogel catalysts were obtained. These samples are then composed of completely accessible Pd-Ag and Pd-Cu alloy crystallites with sizes of 2-3.5 nm located inside silica particles exhibiting a monodisperse microporous distribution. It appears also that the metal complex acts as a nucleation agent in the formation of silica particles. (c) 2005 Elsevier B.V. All rights reserved. [less ▲]

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See detailQualitative assessment of the purity of multi-walled carbon nanotube samples using krypton adsorption
Gommes, Cédric ULg; Noville, Francis ULg; Bossuot, Christophe et al

in Studies in Surface Science and Catalysis (2005), 160

Krypton is a subcritical vapour at the nitrogen boiling temperature. As such, its adsorption on crystalline surfaces leads to condensation steps, typical of type VI isotherms according to IUPAC, while its ... [more ▼]

Krypton is a subcritical vapour at the nitrogen boiling temperature. As such, its adsorption on crystalline surfaces leads to condensation steps, typical of type VI isotherms according to IUPAC, while its adsorption on rough surfaces is BET-like. Based on this property of krypton adsorption at 77 K, a methodology is proposed to determine the purity of carbon nanotubes samples. The method is tested on model samples obtained by mixing mechanically purified multi-walled carbon nanotubes with various amounts of the same catalyst as used for their synthesis. [less ▲]

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See detailNitrogen Adsorption on Silica Xerogels or the Odd Look of a t Plot
Gommes, Cédric ULg; Blacher, Silvia ULg; Pirard, Jean-Paul ULg

in Langmuir (2005), 21

Nitrogen adsorption in some silica xerogels leads to t plots that cannot be interpreted by the occurrence of capillary condensation or by the filling of micropores. Their particular appearance stems from ... [more ▼]

Nitrogen adsorption in some silica xerogels leads to t plots that cannot be interpreted by the occurrence of capillary condensation or by the filling of micropores. Their particular appearance stems from the unique columnar structure of these samples at the nanometer scale, by which the adsorbent surface has a positive curvature. A standard thermodynamic approach allows the phenomenon to be exploited to characterize the samples. [less ▲]

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See detailAssessment of the 3D Localization of Metallic Nanoparticles in Pd/SiO2 Cogelled Catalysts by Electron Tomography
Gommes, Cédric ULg; de Jong, Krijn; Pirard, Jean-Paul ULg et al

in Langmuir (2005), 21

The purpose of this study is to analyze the localization of palladium nanoparticles within their silica support, in two heterogeneous catalysts synthesized by the sol-gel process, with different metal ... [more ▼]

The purpose of this study is to analyze the localization of palladium nanoparticles within their silica support, in two heterogeneous catalysts synthesized by the sol-gel process, with different metal loadings. Electron tomography demonstrates that the palladium particles are localized deep inside the silica skeleton. The use of digital image analysis further shows that the dispersion of palladium is optimal in the sample with the lowest loading. The particles are regularly spaced in the middle of the silica skeleton, with a distance between them comparable to the diameter of the struts of silica. [less ▲]

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See detailConvective drying of wastewater sludges: Influence of air temperature, superficial velocity, and humidity on the kinetics
Léonard, Angélique ULg; Blacher, Silvia ULg; Marchot, Pierre ULg et al

in Drying Technology (2005), 23(8), 1667-1679

The influence of air temperature, velocity, and humidity during convective drying of two different sludges (A and B) is investigated through a 3 3 factorial design. For sludge A, a constant drying flux ... [more ▼]

The influence of air temperature, velocity, and humidity during convective drying of two different sludges (A and B) is investigated through a 3 3 factorial design. For sludge A, a constant drying flux period is observed, while sludge B is characterized by a long decreasing drying flux phase. A sensitivity analysis shows that temperature is the main operating parameter affecting the drying kinetics. Mass and heat transfer coefficients as well as water evaporation capacities are calculated from drying curves. Transfer coefficients are related to operating conditions through dimensionless relations. For both sludges, a linear relation is found between water evaporation capacity and the maximal measured drying flux. [less ▲]

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See detailCarbon aerogels, cryogels and xerogels: Influence of the drying method on the textural properties of porous carbon materials
Job, Nathalie ULg; Thery, Alexandre; Pirard, René ULg et al

in Carbon (2005), 43(12), 2481-2494

Carbon materials with tailored texture can be obtained from drying and pyrolysis of resorcinol-formaldehyde gels. The pore texture of both dried and pyrolyzed material depends on the drying process ... [more ▼]

Carbon materials with tailored texture can be obtained from drying and pyrolysis of resorcinol-formaldehyde gels. The pore texture of both dried and pyrolyzed material depends on the drying process. Several more or less expensive methods (supercritical drying, freeze-drying, evaporative drying) were tested in order to determine which process is the most suitable for the synthesis of a porous carbon with a definite texture. Supercritical drying leads to the highest pore volume and the widest texture range, but residual surface tensions and shrinkage are not avoided when the pore size is small or when the material density is low; this hampers to fix both the pore volume and the pore size easily. Monoliths are very difficult to obtain by freeze-drying, and the appearance of huge channels due to ice crystal growth at high dilution ratio hinders the fabrication of low density materials. Moreover, gels with small pores do not remain frozen throughout drying, which leads to surface tensions and shrinkage. Although generally replaced by more complicated techniques, evaporative drying is suitable when dense carbons are needed or when the only selection criterion is the pore size: all pore sizes are reachable, but this parameter is in this case strongly correlated to the pore volume. (C) 2005 Elsevier Ltd. All rights reserved. [less ▲]

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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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