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See detailHeterogenization of a cyclocarbonation catalyst: optimization and kinetic study
Léonard, Géraldine L.-M.; Belet, Artium ULiege; Grignard, Bruno ULiege et al

in Catalysis Today (in press)

Different types of heterogeneous catalysts designed for a cyclocarbonation reaction between an epoxidized source and CO2 under supercritical conditions have been synthesized. The process implied a ... [more ▼]

Different types of heterogeneous catalysts designed for a cyclocarbonation reaction between an epoxidized source and CO2 under supercritical conditions have been synthesized. The process implied a quaternization step where a (haloalkyl)trimethoxysilane reacted with tributylamine leading to a tributyl(trimethoxysilylalkyl)ammonium halide, with iodine and bromine as halogens. Then, a grafting step onto commercial fumed silica through condensation reaction between the silane part and Si-OH surficial groups provided the immobilized catalyst. The efficiency of grafting has been validated by liquid 1H NMR, solid 29Si NMR and TG-DSC-MS analyzes. The benchmark cyclocarbonation reaction of polyethylene glycol diglycidylether at 80 °C and 100 bar during 4 h showed that the best immobilized catalyst was tributylpropylammonium iodide (IC3Q-EH5). It has also been shown that immobilization provided -surprisingly !- better conversions than the corresponding homogeneous catalyst’s: this phenomenon has been explained through an epoxide-ring-opening activating effect thanks to Si-OH surficial groups. Furthermore, kinetic studies performed by in situ Raman spectroscopy on IC3Q-EH5 showed that temperature had a strong influence on the yield of the reaction while CO2 pressure had only a small effect. Recycling of the catalyst has also been considered, but no precise conclusions could be conducted because of the high catalyst dispersion. Finally, the addition of a fluorinated alcohol co-catalyst allowed obtaining a similar yield but at 80 °C and 55 bar during only 2,5 h with the best candidate. [less ▲]

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See detailInsights on palladium decorated nitrogen-doped carbon xerogels for the hydrogen production from formic acid
Navlani-Garcia, Miriam; Salinas-Torres, David; Mori, Kohsuke et al

in Catalysis Today (2019), 324

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See detailPhosphine- and ammonium-functionalized ordered mesoporous carbons as supports for cluster-derived metal nanoparticles
Vidick, Deborah; Léonard, Alexandre ULiege; Poleunis, Claude et al

in Catalysis Today (2014), 235

An ordered mesoporous carbon (OMC) was functionalized with ammonium or chelating phosphine ligands. In both cases, the functionalization procedure started by oxidation by nitric acid treatment, followed ... [more ▼]

An ordered mesoporous carbon (OMC) was functionalized with ammonium or chelating phosphine ligands. In both cases, the functionalization procedure started by oxidation by nitric acid treatment, followed by activation of surface carboxylic acid groups with thionyl chloride, then formation of amide bonds with diamines. The pendant amine groups were then either quaternized or further reacted with phosphine. The introduced functions were used as anchors for molecular mixed-metal clusters. These organometallic grafted species could then be thermally transformed into hetero-metallic nanoparticles (NP) embedded within the mesoporous framework. The NP/OMC nanocomposites could find application in hydrogenation, heterogeneous catalysis or as electrodes in fuel cells. [less ▲]

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See detailLignin extraction from Mediterranean agro-wastes: Impact of pretreatment conditions on lignin chemical structure and thermal degradation behavior
Manara, Panagiota; Zabaniotou, Anastasia; Vanderghem, Caroline ULiege et al

in Catalysis Today (2014), 223

Three different types of Mediterranean, agro-industrial wastes (olive kernels, grape pomace/seeds, peach kernels), were subjected to two pretreatment processes, a chemical/organosolv and a physicochemical ... [more ▼]

Three different types of Mediterranean, agro-industrial wastes (olive kernels, grape pomace/seeds, peach kernels), were subjected to two pretreatment processes, a chemical/organosolv and a physicochemical one. The organosolv process included lignocellulosic biomass treatment with formic acid/acetic acid/water (30/50/20, v/v%), for 3 h at 107 °C, while the physicochemical method was conducted by immersing the biomass in a water/ethanol (8/92, v/v%), H2SO4 0.32 M, solvent and further exposing the slurry to microwave irradiation (maximum 250 W) for 1/2 h at 150 °C. Both processes were evaluated regarding the achieved delignification and the purity of the extracted lignins. The effect of the pretreatment processes onto the structure and thermal decomposition behavior of the extracted lignins was investigated via FT-IR and TGA analysis, respectively. The objective of the research work was to investigate potential valorization routes for these biomass agro-residues in the context of a biorefinery, focusing on lignin extraction. The pretreatment results showed that the obtained lignins, derived from both procedures, were of high purity (>82 wt%). Under the organosolv procedure, peach kernel delignification showed the maximum value (∼16 wt%), while under microwave pretreatment, olive kernel delignification showed the maximum value (∼35 wt%). Grape pomace/seeds appeared to be the most resistant in both treatments. [less ▲]

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See detailCatalytic hydroprocessing of lignin under thermal and ultrasound conditions
Finch, Kenneth B.; Richards, Ryan; Richel, Aurore ULiege et al

in Catalysis Today (2012), 196

Lignin isolated from Miscanthus x giganteus using acidic (FAL) and alkali (AL) conditions was thereafter subjected to the catalytic depolymerization under thermal or ultrasounds activation. The ... [more ▼]

Lignin isolated from Miscanthus x giganteus using acidic (FAL) and alkali (AL) conditions was thereafter subjected to the catalytic depolymerization under thermal or ultrasounds activation. The characterization of lignins was achieved by thermogravimetric analysis and FTIR. Three different classes of catalysts, containing nickel as active species, have been prepared in this scope: (i) nano-Ni by reduction of NiCl2 with NaBH4 under ultrasonication, (ii) Fe3O4-(NiMgAlO)x and (NiAlO)x by calcination of Mg(Ni)–Al hydrotalcite incorporated Fe3O4 followed by reduction with hydrogen, and (iii) NiO(111) nanosheets by reduction of Ni(NO3)2 with urea in benzyl alcohol. The catalysts were characterized by XRD and XPS techniques. Reduced mixed oxides displayed a moderate activity while a significant increase in conversion (up to 90%) was observed in the presence of nano-Ni(0). NiO(111) nanosheets catalysts performed very close to nano-Ni(0). The conversion and the mass distribution of the reaction products were strongly related to the procedure used for the extraction of ligning. In all the case AL led to a better depolymerization. The performances of the tested catalysts under ultrasound conditions were inferior to those tested under conventional heating conditions. The nature of the solvent was also found to be very important in this process. Thus, ionic liquid [BMIM]OAc led to the best results in autoclave conditions, and methanol under ultrasounds. [less ▲]

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See detailGenesis of active and inactive species during the preparation of MoO3/SiO2-Al2O3 metathesis catalysts via wet impregnation
Debecker, D. P.; Stoyanova, M.; Rodemerck, U. et al

in Catalysis Today (2011), 169(1), 60-68

The wet impregnation of ammonium heptamolybdate onto silica-alumina is used to prepare MoO3/SiO2-Al2O3 heterogeneous metathesis catalysts. The preparation is inspected in details in conjunction with ... [more ▼]

The wet impregnation of ammonium heptamolybdate onto silica-alumina is used to prepare MoO3/SiO2-Al2O3 heterogeneous metathesis catalysts. The preparation is inspected in details in conjunction with physico-chemical characterization tools with the aim to identify the parameters that dictate the genesis of active and inactive metathesis species. The effects of the MoO3 loading and of the calcination temperature are systematically explored. The samples are characterized by N2-physisorption, ICP-AES, XRD, Raman, 27Al MAS-NMR and XPS and evaluated in the metathesis of propene to butene and ethene. Particular attention is brought to the interaction of the mesoporous silica-alumina support with the active component, to the decomposition of the precursor salt and to the location of the molybdenum oxide phase with respect to the pores of the support. It is shown that the temperature of calcination influences markedly the performances of the catalyst. High temperature treatments are necessary to decompose efficiently the Mo salt precursor. In the metathesis of propylene, the performances are levelling off when the MoO 3 loading is increased above ∼8 wt.%. This effect is correlated to the build up of MoO 3 crystals and of Al2(MoO4)3 at relatively high loading. © 2010 Elsevier B.V. All rights reserved. [less ▲]

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See detailCurrent perspectives on microwave-enhanced reactions of monosaccharides promoted by heterogeneous catalysts.
Richel, Aurore ULiege; Laurent, Pascal ULiege; Wathelet, Bernard ULiege et al

in Catalysis Today (2011), 167

Involvment of heterogeneous catalysts as promoters of carbohydrate conversions, in synergy with microwaves as the heating source, is reported. This paper deals with the application of ion-exchange resins ... [more ▼]

Involvment of heterogeneous catalysts as promoters of carbohydrate conversions, in synergy with microwaves as the heating source, is reported. This paper deals with the application of ion-exchange resins, zeolites, clays and metal oxides as convenient mediators for key transformations of carbohydrates. A special emphasis is placed on the use of (doped) mineral supports, in solventless conditions, as clean promoters in combination with microwave dielectric heating. [less ▲]

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

in 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 ▲]

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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 ULiege; Ferauche, Fabrice; Brasseur, Alain et al

in Catalysis Today (2005), 100(3-4), 283-289

While 1,2-dichloroethane hydrodechlorination over pure palladium mainly produces ethane, increasing silver or copper content in bimetallic catalysts results in an increase in ethylene selectivity. The ... [more ▼]

While 1,2-dichloroethane hydrodechlorination over pure palladium mainly produces ethane, increasing silver or copper content in bimetallic catalysts results in an increase in ethylene selectivity. The specific consumption rate of 1,2-dichloroethane decreases when silver or copper loading increases. The turnover frequency, that is, the number of catalytic cycle per active site (palladium atom and its surrounding silver or copper atoms) and per second, seems to be independent of surface composition of alloy particles and 1,2-dichloroethane hydrodechlorination is insensitive to the atom's nature (silver or copper). (c) 2004 Elsevier B.V. All rights reserved. [less ▲]

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