References of "Pirard, René"
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See detailPhysico-chemical properties and photocatalytic activity of calcined P-doped and P/Ag-doped TiO2 xerogels
Bodson, Céline; Pirard, Sophie ULg; Pirard, René ULg et al

Conference (2013, March 05)

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See detailSynthèse de MWNT dans un réacteur continu incliné rotatif à lit mobile par procédé CCVD
Douven, Sigrid ULg; Pirard, Sophie ULg; Chan, Fang-Yue et al

Conference (2012, October)

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See detailLarge-scale synthesis of multi-walled carbon nanotubes in a continuous inclined mobile-bed rotating reactor by the catalytic chemical vapour deposition process using methane as carbon source
Douven, Sigrid ULg; Pirard, Sophie ULg; Chan, Fang-Yue et al

in Chemical Engineering Journal (2012)

Multi-walled carbon nanotubes (CNTs) were produced in a continuous inclined mobile-bed rotating reactor by the catalytic chemical vapour deposition of methane on a bimetallic Ni-Mo/MgO catalyst whose ... [more ▼]

Multi-walled carbon nanotubes (CNTs) were produced in a continuous inclined mobile-bed rotating reactor by the catalytic chemical vapour deposition of methane on a bimetallic Ni-Mo/MgO catalyst whose activity remains constant in the course of time. Measurements performed on the continuous reactor were validated to ensure that the installation worked correctly and that measurements were precise enough. The performance of the reactor was simulated using a model based on the chemical reactor engineering approach. Hypotheses of the model were verified, and a kinetic study was performed to obtain a kinetic rate expression and to determine the catalytic activity as a function of time. The purity level of produced CNTs depends on the desired properties of the product, so the operating conditions are linked to the purity level that is required. A minimal purity level corresponds to high carbon production, and a maximal purity level corresponds to high specific productivity. It was shown that operating conditions had to be fixed to reach a given specific productivity or a given carbon production, and the optimized operating conditions leading to those two opposite purity level objectives were established. [less ▲]

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See detailSynthesis of very highly dispersed platinum catalysts supported on carbon xerogels by the strong electrostatic adsorption method
Lambert, Stéphanie ULg; Job, Nathalie ULg; D'Souza, Lawrence et al

in Journal of Catalysis (2009), 261

Highly dispersed Pt/carbon xerogel catalysts are obtained by applying the “Strong Electrostatic Adsorption” (SEA) of hexachloroplatinic acid to carbon xerogels (PZC = 9.4) and platinum tetraammine ... [more ▼]

Highly dispersed Pt/carbon xerogel catalysts are obtained by applying the “Strong Electrostatic Adsorption” (SEA) of hexachloroplatinic acid to carbon xerogels (PZC = 9.4) and platinum tetraammine chloride to oxidized carbon xerogels (PZC = 2.4). After the reduction step, all these Pt/carbon xerogel catalysts display a very high level of metal dispersion: very small platinum particles (1.1-1.3 nm) are observed by TEM. Pt particle sizes obtained by CO chemisorption are in good agreement with TEM micrographs, which shows that the metal is accessible to reactants. These Pt/carbon xerogel catalysts are very active for the hydrogenation of benzene into cyclohexane. [less ▲]

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See detailPolymer membrane by electrospinning
Aqil, Abdelhafid ULg; Grignard, Bruno ULg; Croisier, Florence ULg et al

Poster (2008, November 28)

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See detailEffect of the counter-ion of the basification agent on the pore texture of organic and carbon xerogels
Job, Nathalie ULg; Gommes, Cédric ULg; Pirard, René ULg et al

in Journal of Non-Crystalline Solids (2008), 354(40-41), 4698-4701

Organic and carbon xerogels were prepared by polycondensation of resorcinol with formaldehyde in water, followed by evaporative drying and, eventually, pyrolysis. The pH of the precursor's solution was ... [more ▼]

Organic and carbon xerogels were prepared by polycondensation of resorcinol with formaldehyde in water, followed by evaporative drying and, eventually, pyrolysis. The pH of the precursor's solution was fixed at 6.0 in all cases by adding various hydroxides as basification agent. Three alkali metal hydroxides (LiOH, NaOH and KOH) and three alkaline earth metals hydroxides (Ca(OH)(2), Ba(OH)(2), Sr(OH)(2)) were used. It was found that the pore texture of the organic and carbon xerogels is totally independent on the cation size, but depends on the charge and concentration of the counter-cation. Indeed, the pore size of the alkaline earth metal loaded samples is larger than that of the alkali metal-doped xerogels. As a matter of fact, to reach the same initial pH, the concentration in alkali metal hydroxide must be twice that of the alkaline earth metal base. The effect of ions on the pore texture was thus attributed to electrostatic effects on the microphase separation process that occurs prior to gelation. (C) 2008 Elsevier B.V. All rights reserved. [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 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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See detailMultigram scale synthesis and characterization of low-density silica xerogels
Alié, Christelle ULg; Tcherkassova, Natalia ULg; Ferauche, Fabrice et al

in Journal of Non-Crystalline Solids (2006), 352(26-27), 2763-2771

The synthesis of silica with preserved porosity and tailored morphology by sol-gel process can be achieved by hybrid organic-inorganic synthesis: a modified alkoxide, viz. 3-(2-aminoethylamino ... [more ▼]

The synthesis of silica with preserved porosity and tailored morphology by sol-gel process can be achieved by hybrid organic-inorganic synthesis: a modified alkoxide, viz. 3-(2-aminoethylamino)propyltrimethoxysilane (EDAS), is introduced during the base catalysed synthesis with TEOS as main silica precursor. Additives with methoxy groups induce a nucleation mechanism because of their higher reactivity compared to main reagents with ethoxy groups. The nucleation model presented in previous papers was refined by taking into account the porosity of the particles and calculating the number of additive molecules by nucleus for each value of the ratio of additive/main reagent. The extrapolation of the synthesis process to semi-industrial scale goes through the replacement of laboratory grade reagents by industrial grade reagents and the scaling up to the production of higher quantities. At each of these two steps, the morphology and porosity of the samples has been compared to those of laboratory grade samples. It was shown that the texture and particle size has quasi totally been preserved. (c) 2006 Elsevier B.V. All rights reserved. [less ▲]

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See detailMetal catalysts suppported on texture-tailored carbon xerogels
Job, Nathalie ULg; Léonard, Angélique ULg; Colomer, Jean-François et al

in Studies in Surface Science and Catalysis (2006), 162

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See detailLarge-scale synthesis and shaping of xerogel catalysts
Alié, Christelle ULg; Ferauche, Fabrice; Tcherkassova, Natalia et al

Poster (2006)

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See detailLarge-scale synthesis and forming of xerogel catalysts
Alié, Christelle ULg; Ferauche, Fabrice; Tcherkassova, Natalia et al

in Studies in Surface Science and Catalysis (2006), 162

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See detailNon intrusive mercury porosimetry: Pyrolysis of resorcinol-formaldehyde xerogels
Job, Nathalie ULg; Pirard, René ULg; Pirard, Jean-Paul ULg et al

in Particle & Particle Systems Characterization (2006), 23(1), 72-81

When submitted to mercury porosimetry, some materials are penetrated by mercury whereas others, among the most porous, are densified by the isostatic pressure. Notably, this is the case for materials ... [more ▼]

When submitted to mercury porosimetry, some materials are penetrated by mercury whereas others, among the most porous, are densified by the isostatic pressure. Notably, this is the case for materials whose structure is made of particles aggregated into filament-like clusters that are interconnected in a 3-D array. Indeed, that kind of material undergoes a volume variation due to hierarchical pore collapse. In the case of intrusion, the mercury porosimetry data are classically analyzed by the Washburn equation. In the case of hierarchical pore collapse, data can be correctly analyzed by the collapse model equation. Using an equation that does not correspond to the mechanism leads to large errors in the pore size distribution. Thus, an accurate data analysis requires prior determination of the mechanism leading to the volume variation recorded as a function of the pressure. The present work particularly examines the complex and unusual behavior of partially pyrolyzed resorcinol-formaldehyde gels when submitted to mercury porosimetry. The unusual behavior encountered complicates the mechanism identification and, therefore, the equation selection. However, the major part of the volume distribution as a function of the pore size can be determined with a good accuracy. [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 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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