Showing results 1 to 20 of 22
  Tailor-made morphologies for Pd/SiO2 catalysts through sol-gel process with various silylated ligandsLambert, Stéphanie  ; ; et alin Microporous & Mesoporous Materials (2008), 115 Detailed reference viewed: 19 (6 ULg)Characterization of gels via solvent desorption measurementsGommes, Cédric ; Noville, Francis ; Pirard, Jean-Paul 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 ▲] Detailed reference viewed: 21 (9 ULg)Hydrodechlorination of 1,2-dichloroethane on Pd-Ag catalysts supported on tailored texture carbon xerogelsJob, Nathalie ; Heinrichs, Benoît ; et alin Catalysis Today (2005), 102 Porous carbon xerogels synthesized in a previous study were investigated as catalysts supports. The support chosen was a micro-mesoporous carbon xerogel obtained from the pyrolysis of a resorcinol ... [more ▼] Porous carbon xerogels synthesized in a previous study were investigated as catalysts supports. The support chosen was a micro-mesoporous carbon xerogel obtained from the pyrolysis of a resorcinol-formaldehyde resin whose synthesis variables were fixed at suitable values. Palladium and silver were deposited on this tailored texture carbon by co-impregnation using a solution of palladium and silver nitrates in nitric acid and water. Several catalysts were prepared with various Pd and Ag global contents, the latters being measured experimentally. Alloy particles, detected in all bimetallic samples, were studied by a combination of various techniques that enabled us to obtain their size as well as their bulk and surface composition. When present, the fraction of unalloyed silver was also calculated. The characterization data were related to the results of catalytic tests obtained for selective hydrodechlorination of 1,2-dichloroethane into ethylene. Results show that when the Ag content is too high, pure Ag particles are formed and the alloy composition remains constant. As a consequence, the surface composition of the alloy is constant as well and the catalytic tests lead to similar results. (c) 2005 Elsevier B.V. All rights reserved. [less ▲] Detailed reference viewed: 43 (6 ULg) Qualitative assessment of the purity of multi-walled carbon nanotube samples using krypton adsorptionGommes, Cédric ; Noville, Francis ; et alin 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 ▲] Detailed reference viewed: 36 (1 ULg)Palladium-silver sol-gel catalysts for selective hydrodechlorination of 1,2-dichloroethane into ethylene - IV. Deactivation mechanism and regenerationHeinrichs, Benoît ; Noville, Francis ; Schoebrechts, Jean-Paul et alin Journal of Catalysis (2003), 220(1), 215-225 The activity and selectivity of a 1.9% Pd-3.7% Ag/SiO2 catalyst during selective hydrodechlorination of 1,2-dichloroethane into ethylene have been followed in the course of time. The deactivation curves ... [more ▼] The activity and selectivity of a 1.9% Pd-3.7% Ag/SiO2 catalyst during selective hydrodechlorination of 1,2-dichloroethane into ethylene have been followed in the course of time. The deactivation curves show two distinct periods: an initial period at the very beginning of catalyst operation, that is, during the first 20 operating hours, characterized by a sharp decrease of the rates of both reactions involved in the process (1,2-dichloroethane hydrodechlorination and undesired ethylene hydrogenation) and a second period, after the first 20 operating hours and investigated for more than 600 h, characterized by a clearly slower deactivation. During the initial period, the hydrodechlorination rate decreases less quickly than the hydrogenation rate and this results in a fast increase of ethylene selectivity which reaches a maximum at the end of this period. After the initial period, the hydrodechlorination rate decreases faster than the hydrogenation rate and this results in a slow decrease of ethylene selectivity. A comparison between the physico-chemical properties of the fresh catalyst and of the deactivated one suggests a deactivation mechanism by poisoning or coking of silver sites at the surface of the active Pd-Ag alloy particles whereas palladium sites would remain intact. The selectivity evolution during the second period, that is, after the very first operating hours, is in agreement with such a mechanism. However, the sharp ethylene selectivity increase during the initial operating hours suggests, in addition to the deactivation by silver sites disappearance, the presence of a further nonidentified phenomenon. The characterization of the catalyst after a regeneration treatment including an oxidation step followed by a reduction step shows that this treatment allows restoration near to the physico-chemical properties of the fresh catalyst. (C) 2003 Elsevier Inc. All rights reserved. [less ▲] Detailed reference viewed: 57 (5 ULg)Is it possible to obtain a coherent image of the texture of a porous material?Noville, Francis ; Gommes, Cédric ; et alin Studies in Surface Science and Catalysis (2002), 144 This study consists in verifying the coherence of a few commonly used analysis methods of nitrogen adsorption-desorption isotherms. These methods were tested on model samples obtained by mechanically ... [more ▼] This study consists in verifying the coherence of a few commonly used analysis methods of nitrogen adsorption-desorption isotherms. These methods were tested on model samples obtained by mechanically mixing two micro- and mesoporous solids respectively with known, mass proportions. Although the individual analysis methods may lead to discrepancies in the interpretation of the isotherms, their systematic comparison allows drawing a coherent picture of the porous texture. [less ▲] Detailed reference viewed: 37 (9 ULg)Palladium-silver sol-gel catalysts for selective hydrodechlorination of 1,2-dichloroethane into ethylene II. Surface composition of alloy particlesHeinrichs, Benoît ; Noville, Francis ; et alin Journal of Catalysis (2000), 192(1), 108-118 The surface composition of alloy particles in Pd-Ag/SiO2 hydrodechlorination (HDC) sol-gel catalysts has been determined by combining three experimental techniques, carbon monoxide chemisorption, X-ray ... [more ▼] The surface composition of alloy particles in Pd-Ag/SiO2 hydrodechlorination (HDC) sol-gel catalysts has been determined by combining three experimental techniques, carbon monoxide chemisorption, X-ray diffraction, and transmission electron microscopy, Values obtained through this method show a very marked silver enrichment of the surface, as expected: as a consequence of the important gap between palladium and silver surface energies. These values are in complete agreement with surface composition curves calculated in other studies by means of Auger electron spectroscopy and infrared spectroscopy. The influence of sample pretreatment temperature as well as the influence of carbon monoxide on surface composition are discussed. (C) 2000 Academic Press. [less ▲] Detailed reference viewed: 30 (4 ULg)Deactivation mechanisms and regeneration of a bimetallic hydrodechlorination catalystHeinrichs, Benoît ; Noville, Francis ; et alin Studies in Surface Science and Catalysis (1999), 126 The temporal evolution of the activity and selectivity of a 1.9%Pd-3.7%Ag/SiO2 catalyst during selective hydrodechlorination of 1,2-dichloroethane into ethylene is examined. A comparison between the ... [more ▼] The temporal evolution of the activity and selectivity of a 1.9%Pd-3.7%Ag/SiO2 catalyst during selective hydrodechlorination of 1,2-dichloroethane into ethylene is examined. A comparison between the physico-chemical properties of the fresh catalyst and of the deactivated one suggests a deactivation mechanism by poisoning or coking of Ag sites at the surface of the active Pd-Ag particles. A regeneration treatment is proposed which allows to restore the initial properties of the fresh catalyst. [less ▲] Detailed reference viewed: 22 (6 ULg)Deactivation mechanisms and regeneration of a bimetallic hydrodechlorination catalystHeinrichs, Benoît ; Noville, Francis ; et alPoster (1999) Detailed reference viewed: 7 (0 ULg)Pd/SiO2-cogelled aerogel catalysts and impregnated aerogel and xerogel catalysts: Synthesis and characterizationHeinrichs, Benoît ; Noville, Francis ; Pirard, Jean-Paul in Journal of Catalysis (1997), 170(2), 366-376 Pd/SiO2 aerogel catalysts have been synthesized by cogelation of tetraethoxysilane with complex Pd2+[NH2-CH2-CH2-NH-(CH2)(3)-Si(OCH3)(3)](2) containing a hydrolysable silyl group. Pd catalysts have also ... [more ▼] Pd/SiO2 aerogel catalysts have been synthesized by cogelation of tetraethoxysilane with complex Pd2+[NH2-CH2-CH2-NH-(CH2)(3)-Si(OCH3)(3)](2) containing a hydrolysable silyl group. Pd catalysts have also been prepared by impregnation of silica aerogels and xerogels with solutions of this complex or Pd2+(NH3)(4) followed by drying under hypercritical conditions or under vacuum. It appears that, in cogelled samples, the Pd2+ complex acts as a nucleation agent in the formation of silica particles. The resulting catalysts are then composed of completely accessible palladium crystallites with a diameter of about 2.3 nm located inside silica particles with a monodisperse microporous distribution centered on a hydraulic radius of 0.43 nm. The continuous meso- and macropore distribution is located in voids between particles and between aggregates constituted of those particles. In impregnated samples, it appears that Pd particles are located outside SiO2 particles. The relation between the texture of cogelled and impregnated catalysts and their behavior toward sintering has been studied in detail. In cogelled samples, it has been shown that Pd crystallites cannot migrate because they are trapped in the pores of SiO2 particles. These catalysts are sinterproof during hypercritical drying, When Pd crystallites are not trapped inside SiO2 particles, hypercritical drying leads to an extensive sintering of metal particles. During calcination of impregnated catalysts dried under vacuum, sintering occurs to a various extent depending on the support texture. The Pd crystallites size decreases when the pore size distribution is shifted toward the small sizes. (C) 1997 Academic Press. [less ▲] Detailed reference viewed: 41 (15 ULg)Texture and sintering of zirconium dioxide-yttrium oxide ceramics; ; et al in Reactivity of Solids (1988), 4 Detailed reference viewed: 23 (1 ULg)Oceanic polymetallic nodules : a catalyst for hydrotreatment of petroleum residuaDodet, Claude ; Noville, Francis ; Crine, Michel et alin Acta Chimica Hungarica (1987), 124 Detailed reference viewed: 18 (5 ULg)OCEANIC POLYMETALLIC NODULES - A CATALYST FOR HYDROTREATMENT OF PETROLEUM RESIDUESDodet, Claude ; Noville, Francis ; Crine, Michel et alin Acta Chimica Hungarica-Models In Chemistry (1987), 124(1), 65-72 Detailed reference viewed: 9 (1 ULg)Study of the texture of monodisperse silica sphere samples in the nano size rangeDodet, Claude ; Noville, Francis ; Crine, Michel et alin Colloids and Surfaces A : Physicochemical and Engineering Aspects (1986), 19 Detailed reference viewed: 39 (1 ULg)Utilitation des nodules océaniques polymétalliques en hydrotraitement des coupes pétrolières lourdes avant leur valorisation métallurgiqueDodet, Claude ; Noville, Francis ; Crine, Michel et alin L'industrie minérale - Mines et Carrières - Les techniques (1986), 68 Detailed reference viewed: 29 (6 ULg)Hydrotreatment of petroleum atmospheric residua using oceanic polymetallic nodules in trickle bed reactorDodet, Claude ; Noville, Francis ; Crine, Michel et alin Bulletin des Sociétés Chimiques Belges (1985), 94 Detailed reference viewed: 4 (1 ULg)Etude de la réduction des nodules océaniques polymétalliques en vue deleur utilisation comme catalyseursDodet, Claude ; Noville, Francis ; Crine, Michel et alin Annales de Chimie Science des Materiaux (1985), 10 Detailed reference viewed: 7 (1 ULg)Texture of manganese nodules used as a catalyst for demetalizing and desulfurizing petroleum residuaDodet, Claude ; Noville, Francis ; Crine, Michel et alin Colloids and Surfaces A : Physicochemical and Engineering Aspects (1984), 11 Detailed reference viewed: 31 (0 ULg)Etude de la texture des nodules océaniques en vue de leur utilisation comme catalyseursDodet, Claude ; Noville, Francis ; Crine, Michel et alin Revue Roumaine de Chimie (1984), 29 Detailed reference viewed: 9 (3 ULg)Hydrodemetalation and hydrodesulfurization of petroleum residua using manganese nodules in trickle bed reactorDodet, Claude ; Noville, Francis ; Crine, Michel et alin Applied Catalysis (1984), 11 Detailed reference viewed: 9 (0 ULg)
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