References of "Pirard, Jean-Paul"
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See detailInvestigation of the preparation and activity of gold catalysts in the total oxidation of n-hexane
Cellier Caroline; Lambert, Stéphanie ULg; Gaigneaux Eric et al

in Applied Catalysis B : Environmental (2007), 70

The factors affecting the preparation of Au/TiO2 catalysts and their activity in the total oxidation of n-hexane were investigated. The mechanism of gold deposition–precipitation is discussed through ... [more ▼]

The factors affecting the preparation of Au/TiO2 catalysts and their activity in the total oxidation of n-hexane were investigated. The mechanism of gold deposition–precipitation is discussed through comparison of the samples prepared by this method and others prepared by anion adsorption method. The influence of the pH and of the origin of TiO2 support used are additionally addressed. The difference of gold dispersion observed between the two methods is attributed to a difference of mobility of the gold precursors during the thermal treatment rather than to a difference of dispersion over the uncalcined samples. The mechanism of gold deposition–precipitation actually involves the reactions of gold hydroxy-chloride species with the surface. Another part of the work, thus, concerned the use of the deposition–precipitation method to prepare a Au/MnO2 catalyst. It is shown that the activity of g-MnO2 is directly proportional to its surface area and that the deposition–precipitation procedure decreases the surface and activity of MnO2. However, the deposition of gold allows to avoid a too deep sintering of g-MnO2 and, thus, helps to somehow preserve its activity. [less ▲]

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See detailInvestigation of the preparation and activity of gold catalysts in the total oxidation of n-hexane
Cellier, Caroline; Lambert, Stéphanie ULg; Gaigneaux, Eric M. et al

in Applied Catalysis B : Environmental (2007), 70(1-4), 406-416

The factors affecting the preparation of Au/TiO2 catalysts and their activity in the total oxidation of n-hexane were investigated. The mechanism of gold deposition-precipitation is discussed through ... [more ▼]

The factors affecting the preparation of Au/TiO2 catalysts and their activity in the total oxidation of n-hexane were investigated. The mechanism of gold deposition-precipitation is discussed through comparison of the samples prepared by this method and others prepared by anion adsorption method. The influence of the pH and of the origin of TiO2 support used are additionally addressed. The difference of gold dispersion observed between the two methods is attributed to a difference of mobility of the gold precursors during the thermal treatment rather than to a difference of dispersion over the uncalcined samples. The mechanism of gold deposition-precipitation actually involves the reactions of gold hydroxy-chloride species with the surface. Another pan of the work, thus, concerned the use of the deposition-precipitation method to prepare a Au/MnO2 catalyst. It is shown that the activity of gamma-MnO2 is directly proportional to its surface area and that the deposition-precipitation procedure decreases the surface and activity of MnO2. However, the deposition of gold allows to avoid a too deep sintering of gamma-MnO2 and, thus, helps to somehow preserve its activity. (c) 2006 Elsevier B.V. All rights reserved. [less ▲]

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See detailCompressing some sol-gel materials reduces their stiffness: a textural analysis
Gommes, Cédric ULg; Job, Nathalie ULg; Blacher, Silvia ULg et al

in Studies in Surface Science and Catalysis (2007), 160

The mechanical behaviour of two series of silica and of resorcinol xerogels is analyzed by mercury porosimetry. The data are expressed as pressure-density curves, which enables textural information to be ... [more ▼]

The mechanical behaviour of two series of silica and of resorcinol xerogels is analyzed by mercury porosimetry. The data are expressed as pressure-density curves, which enables textural information to be obtained. In particular, it is shown that some of the analyzed samples exhibit a marked lowering of their mechanical stiffness upon compression. This observation is analyzed in terms of the collapse of the sample’s porosity and of the heterogeneity of the microstructure. [less ▲]

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See detailAnalysis of kinetic models of multi-walled CNT synthesis
Pirard, Sophie ULg; Douven, Sigrid ULg; Pirard, Jean-Paul ULg

in Carbon (2007), 45(15), 3050-3052

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See detailCharacterization of gels via solvent desorption measurements
Gommes, Cédric ULg; Noville, Francis ULg; Pirard, Jean-Paul ULg

in Adsorption (2007), 13(5-6), 533-540

The present paper shows how a standard volumetric adsorption device can be used to measure solvent desorption isotherms on gels. As gels are very soft materials, they shrink significantly during the ... [more ▼]

The present paper shows how a standard volumetric adsorption device can be used to measure solvent desorption isotherms on gels. As gels are very soft materials, they shrink significantly during the measurement, and the data have to be analyzed in terms of the mechanical properties of the gel's skeleton. Methanol desorption isotherms are measured on a series of silica gels, and the results are compared with independent characterizations, notably beam bending. [less ▲]

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See detailHierarchical multimodal mesoporous carbon materials with parallel macrochannels
Su, Bao-Lian; Vantomme, Aurelien; Surahy, Lidwine et al

in Chemistry of Materials (2007), 19(13), 3325-3333

Hierarchically structured multimodal meso-macroporous carbon materials have been prepared by using the nanoreplication of the mesoporous walls of a meso-macroporous zirconia exotemplate. Like the zirconia ... [more ▼]

Hierarchically structured multimodal meso-macroporous carbon materials have been prepared by using the nanoreplication of the mesoporous walls of a meso-macroporous zirconia exotemplate. Like the zirconia exotemplate, the pure carbon material possesses funnel shaped straight macrochannels, parallel to each other and perpendicular to the tangent of the particles' dense mesoporous shell. As a result of the funnel-like shape, each macrochannel has a pore size gradient with a large opening centered at 300-700 nm. The walls of the macrochannels and the dense mesoporous shells are formed by a hierarchical mesostructured porous system with uniform mesopore sizes centered at 3, 15-17, and 25-50 nm. Macrochannels are interconnected with hierarchically mesostructured walls and shells. A high surface area of 950 m(2)/g with a mesopore volume of 0.44 cm(3)/g is obtained. The possibility of the nanoreplication of other meso-macroporous oxides such as aluminosilicates, titania, and niobium oxide with different macrochannel size, shape, and organization has also been studied to generate meso-macroporous carbon materials with different organizations of the macrochannels. [less ▲]

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See detailSynthesis of transition metal-doped carbon xerogels by cogelation
Job, Nathalie ULg; Pirard, René ULg; Vertruyen, Bénédicte ULg et al

in Journal of Non-Crystalline Solids (2007), 353(24-25), 2333-2345

The cogelation process, i.e. the co-polymerization of a metal complex with the gel precursors, was used for the synthesis of transition metal-doped resorcinol-formaldehyde gels. The aim of this process is ... [more ▼]

The cogelation process, i.e. the co-polymerization of a metal complex with the gel precursors, was used for the synthesis of transition metal-doped resorcinol-formaldehyde gels. The aim of this process is to anchor the metal to the polymer so that the former does not sinter during the pyrolysis step leading to porous carbon. Cu-, Ni-, Pd- or Pt-loaded gels were prepared by this technique. After drying and pyrolysis, Pd and Pt were obtained as metal nanoparticles (2-5 nm in diameter) inserted in the carbon nodules, when the complexing agent and the synthesis conditions were well chosen. These small metal particles were inaccessible to reactive gases, probably due to carbon deposit at the metal surface during pyrolysis: CO almost did not chemisorb. Oxidation of the support or pyrolysis under reductive atmosphere was applied to the metal-doped gels and carbons in order to make the surface of the metal particles accessible, but these treatments develop the macropores only. The cogelation process is then suitable to prepare metal nanoparticles protected from the outside by encapsulation in the carbon matrix. (C) 2007 Elsevier B.V. All rights reserved. [less ▲]

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See detailSynthesis of La0.9Sr0.1Ga0.8Mg0.2O2.85 by successive freeze-drying and self-ignition of a hydroxypropylmethyl cellulose solution
Traina, Karl ULg; Steil, M. C.; Pirard, Jean-Paul ULg et al

in Journal of the European Ceramic Society (2007), 27(12), 3469-3474

The present paper reports the synthesis of La0.9Sr0.1Ga0.8Mg0.2O2.85 perovskite powders by a method combining freeze-drying and self-ignition of an aqueous solution of metallic nitrates containing ... [more ▼]

The present paper reports the synthesis of La0.9Sr0.1Ga0.8Mg0.2O2.85 perovskite powders by a method combining freeze-drying and self-ignition of an aqueous solution of metallic nitrates containing hydroxypropylmethyl cellulose. The precursor powder obtained after self-ignition was submitted to various thermal treatments and the resulting powders were characterized by X-ray diffraction, electron microscopy, nitrogen adsorption-desorption isotherm analysis, mercury porosimetry and laser granulometry. It turns out that this synthesis method yields single-phase powders with good homogeneity and sinterability properties. The precursor powder treated at 1200 degrees C presents a coral-like structure which collapses under application of low uniaxial pressure, resulting in a narrow grain size distribution suitable for sintering (98.8% relative density for a pellet sintered at 1400 degrees C during 1 h). The fact that no milling step is necessary is an additional advantage of this method, which shows promising prospects for the synthesis of other multicationic oxides. (c) 2007 Elsevier Ltd. All rights reserved. [less ▲]

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See detailMultiscale image analysis of microcellular solids: application to hybrid silica xerogels
Gommes, Cédric ULg; Pirard, Jean-Paul ULg; Blacher, Silvia ULg

in Journal of Microscopy (2007), 226

A general methodology is proposed to characterize microcellular solids, the structure of which consists of a three-dimensional network of filamentary structures. The analysis is based on transmission ... [more ▼]

A general methodology is proposed to characterize microcellular solids, the structure of which consists of a three-dimensional network of filamentary structures. The analysis is based on transmission electron microscopy observation of the filaments individually and of their spatial arrangement. The micrographs are analyzed with greytone digital image analysis techniques, such as opening granulometry and correlation analysis. The methodology is applied to hybrid organic–inorganic low-density silica solids synthesized by the sol–gel method with an organically modified co-reactant. The quantitative impact of the coreactant on each structural level of the structure is assessed quantitatively. [less ▲]

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See detailA kinetic study of multi-walled carbon nanotube synthesis by catalytic chemical vapor deposition using a Fe-Co/Al2O3 catalyst
Pirard, Sophie ULg; Douven, Sigrid ULg; Bossuot, Christophe et al

in Carbon (2007), 45(6), 1167-1175

A kinetic study was performed to describe the initial specific rate of multi-walled carbon nanotube synthesis by catalytic chemical vapor deposition (CCVD) on a bimetallic cobalt-iron catalyst at high ... [more ▼]

A kinetic study was performed to describe the initial specific rate of multi-walled carbon nanotube synthesis by catalytic chemical vapor deposition (CCVD) on a bimetallic cobalt-iron catalyst at high temperature using ethylene decomposition to solid carbon and gaseous hydrogen. The study uses a mass spectrometer that allows reaction rate to be inferred from the exhaust gas composition measurements. The aim is to obtain a better understanding of the elementary steps involved in the production of carbon nanotubes so as to derive phenomenological kinetic models in agreement with experimental data. The best models assume the elimination of the first hydrogen atom from adsorbed ethylene as rate determining step and involve a hydrogen adsorption weak enough to be neglected. It was proved that hydrogen partial pressure has no influence on initial reaction rate of carbon nanotube synthesis with the catalyst used for this study. Activation energy and ethylene adsorption enthalpy were found to be equal to around 130 and - 130 kJ mol(-1), respectively. (C) 2007 Elsevier Ltd. All rights reserved. [less ▲]

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See detailAg/SiO2, Cu/SiO2 and Pd/SiO2 cogelled xerogel catalysts for benzene combustion: Relationships between operating synthesis variables and catalytic activity
Lambert, Stéphanie ULg; Cellier, Caroline; Gaigneaux, Eric M et al

in Catalysis Communications (2007), 8(8), 1244-1248

The aim of this work is to explore the applicability of the sol-gel method for the preparation of Ag/SiO2, Cu/SiO2 and Pd/SiO2 catalysts and to see whether such a method can yield silver, copper and ... [more ▼]

The aim of this work is to explore the applicability of the sol-gel method for the preparation of Ag/SiO2, Cu/SiO2 and Pd/SiO2 catalysts and to see whether such a method can yield silver, copper and palladium species stabilized by the carrier in the case of benzene oxidation. So Ag/SiO2, Cu/SiO2 and Pd/SiO2 xerogel catalysts were synthesized by cogelation of tetraethoxysilane (TEOS) and chelates of Ag, Cu and Pd with 3-(2-aminoethylamino)-propyltrimethoxysilane (EDAS). The resulting catalysts are composed of completely accessible metallic crystallites with a diameter of about 3 nm located inside silica particles. (c) 2006 Elsevier B.V. All rights reserved. [less ▲]

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See detailSol-gel synthesis of supported metals
Heinrichs, Benoît ULg; Lambert, Stéphanie ULg; Job, Nathalie ULg et al

in Regalbuto, John R. (Ed.) Catalyst Preparation : Science and Engineering (2007)

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See detailSynthesis of highly dispersed Pd/SiO2 cogelled xerogel catalysts from various silylated ligands
Lambert, Stéphanie ULg; Tran, Kim Yên; Arrachart, Guilhem et al

Poster (2007)

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See detailCarbon xerogels as catalyst supports for PEM fuel cell cathode
Job, Nathalie ULg; Marie, Julien; Lambert, Stéphanie ULg et al

Conference (2007)

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See detailTowards the production of carbon xerogel monoliths by optimizing convective drying conditions
Job, Nathalie ULg; Sabatier, Françoise; Pirard, Jean-Paul ULg et al

in Carbon (2006), 44(12), 2534-2542

Resorcinol-formaldehyde hydrogels prepared at various resorcinol/sodium carbonate ratios, R/C, were convectively air dried. The influence of the drying operating conditions, i.e. air temperature and ... [more ▼]

Resorcinol-formaldehyde hydrogels prepared at various resorcinol/sodium carbonate ratios, R/C, were convectively air dried. The influence of the drying operating conditions, i.e. air temperature and velocity, on the pore texture, shrinkage and cracking of the dried gels were investigated. Shrinkage was found to be isotropic. The shrinkage behaviour and the textural properties of the gels are independent of the drying operating conditions, but are completely determined by the value of the synthesis variables. The analysis of the drying kinetics shows two main drying periods. During the first phase, shrinkage occurs and the external surface of the material remains completely wet: heat and mass transfers are limited by external resistances located in a boundary layer. When shrinkage stops, the second period begins: the evaporation front recedes inside the solid and internal transfer limitations prevail. The drying time can be reduced by increasing the air temperature and/or velocity, but the temperature increase is limited when monolithicity is required, especially when the pores are small. For example, at a temperature of 160 degrees C and a velocity of 2 m/s, about 1 h is needed to dry a 2.8 cm in diameter and 1 cm in height cylinder containing macropores (pore width > 50 nm after drying). The same cylinder presenting small mesopores (pore width = 10-15 nm after drying) requires 20 h at 30 degrees C and 2 m/s to reach complete dryness without the development of cracks. (c) 2006 Elsevier Ltd. All rights reserved. [less ▲]

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See detailOptimized conditions for the preparation of Pt supported catalysts by deposition-precipitation
Cellier Caroline; Lambert, Stéphanie ULg; Ruaux Vincent et al

Poster (2006, September)

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See detailTime-resolved SAXS study of the formation of resorcinol-formaldehyde aqueous gels
Job, Nathalie ULg; Gommes, Cédric ULg; Goderis, B. et al

Poster (2006, August 06)

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