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See detailMicrowave-Assisted Ruthenium-Catalyzed Reactions
Nicks, Francois ULg; Borguet, Yannick ULg; Delfosse, Sebastien et al

in Australian Journal of Chemistry (2009), 62(3), 184-207

Since the first reports on the use of microwave irradiation to accelerate organic chemical transformations, a plethora of papers has been published in this field. In most examples, microwave heating has ... [more ▼]

Since the first reports on the use of microwave irradiation to accelerate organic chemical transformations, a plethora of papers has been published in this field. In most examples, microwave heating has been shown to dramatically reduce reaction times, increase product yields, and enhance product purity by reducing unwanted side reactions compared with conventional heating methods. The present contribution aims at illustrating the advantages of this technology in homogeneous catalysis by ruthenium complexes and, when data are available, at comparing microwave-heated and conventionally heated experiments. Selected examples refer to olefin metathesis, isomerization reactions, 1,3-dipolar cycloadditions, atom transfer radical reactions, transfer hydrogenation reactions, and H/D exchange reactions. [less ▲]

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See detailMicrowave-Assisted Synthesis of 1,3-Dimesitylimidazolinium Chloride
Hans, Morgan ULg; Delaude, Lionel ULg

in Wipf, Peter (Ed.) Organic Syntheses. Volume 87 (2010)

A procedure for the microwave-assisted synthesis of 1,3-dimesitylimidazolinium chloride on a preparative scale is described starting from simple, commercially available reagents. Prior to a microwave ... [more ▼]

A procedure for the microwave-assisted synthesis of 1,3-dimesitylimidazolinium chloride on a preparative scale is described starting from simple, commercially available reagents. Prior to a microwave-assisted cyclization, it involves the formation of N,N'-dimesitylethane-1,2-diamine dihydrochloride via condensation of glyoxal with two equivalents of mesitylamine, followed by reduction of the intermediate Schiff base with sodium borohydride under acidic conditions. All three steps proceed readily under normal atmosphere. Laboratory grade solvents and reagents taken straight from the bottles do not require any additional purification. The two intermediates and the final product are isolated in high yield and purity by simple filtration and washing and may be used without any further purification for most applications. [less ▲]

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See detailMicrowave-assisted synthesis of D-glucuronic acid derivatives using cost-effective solid acid catalysts
Richel, Aurore ULg; Laurent, Pascal ULg; Wathelet, Bernard ULg et al

in Tetrahedron Letters (2010), 51

Monomode microwave-assisted coupling of D-glucuronic acid with alcohols, in the presence of various impregnated acid catalysts, was successfully performed, affording in almost quantitative yields the ... [more ▼]

Monomode microwave-assisted coupling of D-glucuronic acid with alcohols, in the presence of various impregnated acid catalysts, was successfully performed, affording in almost quantitative yields the corresponding monosubstituted b-D-glucofuranosidurono-6,3-lactones in less than 10 min at 85°C. This study evidences the synergy of microwaves and impregnated acid catalysts as a fast and clean strategy in the field of carbohydrate chemistry. [less ▲]

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See detailMicrowave-assisted synthesis of imidazolinium salts
Hans, Morgan; Demonceau, Albert ULg; Delaude, Lionel ULg

in Polymer Preprints (2008), 49(2), 942-943

Imidazolinium salts were prepd. via microwave-assisted cyclocondensation of ethanediamines with triethoxy alkanes or triethoxymethyl benzene. The synthesized imidazolinium salts may be used as NHC ... [more ▼]

Imidazolinium salts were prepd. via microwave-assisted cyclocondensation of ethanediamines with triethoxy alkanes or triethoxymethyl benzene. The synthesized imidazolinium salts may be used as NHC precursors or ionic liqs. [less ▲]

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See detailMicrowave-assisted synthesis of N-heterocyclic carbene precursors
Aidouni, Adila; Demonceau, Albert ULg; Delaude, Lionel ULg

in Synlett (2006), (3), 493-495

A very simple and efficient procedure is reported for the synthesis of 1,3-diarylimidazolinium chlorides by cyclization of N,N'-diarylethylenediamines dihydrochlorides with triethyl ortho-formate under ... [more ▼]

A very simple and efficient procedure is reported for the synthesis of 1,3-diarylimidazolinium chlorides by cyclization of N,N'-diarylethylenediamines dihydrochlorides with triethyl ortho-formate under microwave irradiation. [less ▲]

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See detailMicrowave-assisted synthesis of vinyl esters through ruthenium-catalyzed addition of carboxylic acids to alkynes
Nicks, Francois ULg; Libert, Lionel ULg; Delaude, Lionel ULg et al

in Polymer Preprints (2008), 49(2), 944-945

1-Hexen-2-yl 4-acetoxybenzoate was regioselectively prepd. via microwave-assisted ruthenium-catalyzed addn. of 4-acetoxybenzoic acid to 1-hexyne. Species of catalysts, reaction time and temp. play roles ... [more ▼]

1-Hexen-2-yl 4-acetoxybenzoate was regioselectively prepd. via microwave-assisted ruthenium-catalyzed addn. of 4-acetoxybenzoic acid to 1-hexyne. Species of catalysts, reaction time and temp. play roles in the reaction respect to yields and selectivity, therefore were examd. Microwave effect was obsd. and preferred to the generation of the Markovnikov-type product compared to traditional heating. [less ▲]

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See detailMicrowave-Assisted Synthesis of Vinyl Esters through Ruthenium-Catalyzed Addition of Carboxylic Acids to Alkynes
Nicks, Francois ULg; Libert, Lionel ULg; Delaude, Lionel ULg et al

in Australian Journal of Chemistry (2009), 62(3), 227-231

A rapid and efficient method is described for the selective synthesis of enol esters via the microwave-accelerated addition of carboxylic acids to terminal alkynes. The method employs the readily ... [more ▼]

A rapid and efficient method is described for the selective synthesis of enol esters via the microwave-accelerated addition of carboxylic acids to terminal alkynes. The method employs the readily available [RuCl2(p-cymene)(PPh3)] complex as catalyst without the need of bases, and reactions are complete in 20 min. [less ▲]

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See detailMicrowave-assisted thermochemical and primary hydrolytic conversions of lignocellulosic resources: a review
Richel, Aurore ULg; Jacquet, Nicolas ULg

in Biomass Conversion and Biorefinery (in press)

Faced with the inevitable depletion of fossil resources, agricultural productions have rapidly emerged as promising renewable alternatives. Particularly, the conversion of lignocellulosic materials has ... [more ▼]

Faced with the inevitable depletion of fossil resources, agricultural productions have rapidly emerged as promising renewable alternatives. Particularly, the conversion of lignocellulosic materials has nowadays opened new vistas for the production of energy, biofuels and chemicals. In this literature review, microwave technology is described as an original heating source either for the thermochemical conversions (at temperatures up to 400°C) of lignocellulose into biofuels or the pretreatment (below 400°C) and further hydrolysis of lignocellulose into bioethanol and other valuable chemicals. Advantages of microwave approaches include a commonly observed acceleration in reaction rate and improved selectivities and yields. [less ▲]

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See detailMicrowave-assisted transformations of agroresources: an example of green chemistry
Richel, Aurore ULg

in SciTopics-Research summarises by Experts (2010)

Faced with the inevitable depletion of fossil resources, agricultural productions have rapidly emerged as a promising renewable alternative. Alongside its traditional involvement in the agro-food, the ... [more ▼]

Faced with the inevitable depletion of fossil resources, agricultural productions have rapidly emerged as a promising renewable alternative. Alongside its traditional involvement in the agro-food, the biomass has nowadays opened new vistas in the non-food sector. Indeed, original products and structures, potentially biodegradable, are proposed as substitutes for conventional petrochemical derivatives. The steady rise of oil prices, on the one hand, and the implementation of a new European legislation (REACH: Registration, Evaluation and Authorization of Chemicals), on the other hand, have only help to boost the academic and industrial research in this area. In this context, microwave-mediated synthesis has progressively emerged as a green chemistry technology. Application of microwaves (MW) as a non conventional heating source finds a plethora of illustrations in the field of organic synthesis. Microwaves usually accelerate chemical processes, while offering improved yields and selectivities. MW heating enables reactions under solventless conditions, providing unique chemical pathways, with special advantages such as ease of manipulation and reduction (or prevention) of pollution "at source". Various reactions and processes can be applied to transform lignocellulosic raw materials into valuable fuels and chemicals. Selected examples of strategical modifications of renewable biomass feedstocks via activation by microwave irradiation are proposed herein. [less ▲]

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See detailMicrowave-assisted transformations of agroresources: an example of green chemistry
Richel, Aurore ULg; Laurent, Pascal ULg; Paquot, Michel ULg

Report (2010)

Faced with the inevitable depletion of fossil resources, agricultural productions have rapidly emerged as a promising renewable alternative. Alongside its traditional involvement in the agro-food, the ... [more ▼]

Faced with the inevitable depletion of fossil resources, agricultural productions have rapidly emerged as a promising renewable alternative. Alongside its traditional involvement in the agro-food, the biomass has nowadays opened new vistas in the non-food sector. Indeed, original products and structures, potentially biodegradable, are proposed as substitutes for conventional petrochemical derivatives. The steady rise of oil prices, on the one hand, and the implementation of a new European legislation (REACH: Registration, Evaluation and Authorization of Chemicals), on the other hand, have only help to boost the academic and industrial research in this area. In this context, microwave-mediated synthesis has progressively emerged as a green chemistry technology. Application of microwaves (MW) as a non conventional heating source finds a plethora of illustrations in the field of organic synthesis. Microwaves usually accelerate chemical processes, while offering improved yields and selectivities. MW heating enables reactions under solventless conditions, providing unique chemical pathways, with special advantages such as ease of manipulation and reduction (or prevention) of pollution "at source". Various reactions and processes can be applied to transform lignocellulosic raw materials into valuable fuels and chemicals. Selected examples of strategical modifications of renewable biomass feedstocks via activation by microwave irradiation are proposed herein. [less ▲]

Detailed reference viewed: 42 (7 ULg)
See detailMicrowave-assisted transformations of carbohydrates
Richel, Aurore ULg

Report (2010)

This reports deals with the involvment of microwaves for the conversion of renewable feedstocks, and in particlar for the tranfsormation of monosaccharides and cellulose into high added value materials.

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See detailMicrowave-assisted transformations of carbohydrates
Richel, Aurore ULg; Wathelet, Jean-Paul ULg; Paquot, Michel ULg

in SciTopics / Research Summaries by Experts (2010)

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See detailMicrowave-Enhanced Ruthenium Catalysed Atom Transfer Radical Additions
Richel, Aurore ULg; Leclerc, Alain; Demonceau, Albert ULg et al

Poster (2005)

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See detailMicrowave-enhanced ruthenium-catalysed atom transfer radical additions
Borguet, Yannick ULg; Richel, Aurore ULg; Delfosse, Sbastien et al

in Tetrahedron Letters (2007), 48(36), 6334-6338

The first monomode microwave-assisted atom transfer radical additions (ATRA) of carbon tetrachloride to various olefins were successfully performed, affording the adducts with almost quantitative yields ... [more ▼]

The first monomode microwave-assisted atom transfer radical additions (ATRA) of carbon tetrachloride to various olefins were successfully performed, affording the adducts with almost quantitative yields in less than 10 min at 160 'C. (c) 2007 Elsevier Ltd. All rights reserved. [less ▲]

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See detailMicrowave-treatment of frozen wood packaging material
Henin, Jean-Marc; Bauduin, Aline; Leyman, Michaël ULg et al

Conference (2012, July 12)

As part of the wood packaging material (WPM) regulation in international trade, the dielectric heating (DH) is soon to be included in ISPM15 (IPPC 2009) as an approved phytosanitary treatment. It has been ... [more ▼]

As part of the wood packaging material (WPM) regulation in international trade, the dielectric heating (DH) is soon to be included in ISPM15 (IPPC 2009) as an approved phytosanitary treatment. It has been considered that when using dielectric radiation (i.e. microwaves or radiofrequencies), reaching 60°C or more throughout the entire profile of the wood during at least 60s (i.e. 60°C/60s) ensures the eradication of any noxious organism present in the wood. Regarding the treatment itself, the main requirements mentioned in the draft of ISPM15 Annex 1 (IPPC 2011) concern the way to achieve “uniformity of heating” as well as the treatment duration, which must not exceed 30min. Concerning wood characteristics, the only restriction to the DH concerns the thickness of the wood pieces, which must not exceed 20cm; no other restriction exists regarding wood moisture content, density or initial temperature. As reported in the draft of ISPM15 Annex 1, it is generally considered that “when using microwaves as a heating source, the coldest part of the wood is the surface”. This statement implies that achieving 60°C (or more) during 60s at the surface of the wood should guarantee compliance with IPPC requirements (i.e. 60°C throughout the profile of the wood). However, since ice and liquid water exhibit very different properties towards microwaves, initially frozen wood (9cmX9cm and 17cmX17cm in cross-section) was irradiated in a 28.8 kW microwave oven (2.45GHz) in order to assess whether achieving 60°C/60s at the surface of less than 20cm-thick planks ensures higher core temperatures. The temperature pattern observed after the treatment was compared with the one observed after the treatment of initially thawed wood pieces. It was observed that, in some conditions, initially frozen pieces exhibit inside temperature (much) lower than 60°C, despite complying with 60°C/60s all over the surface of the wood. These results show that when wood is heated with microwaves, its coldest part may not be the surface. Our results also strongly suggest that the impact of wood properties on post-treatment temperature pattern should be further investigated in order to better identify the limits of the DH (at least on frozen wood). [less ▲]

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See detailMicrowear and Residue Analysis in Perspective: the contribution of ethnoarchaeological evidence
Rots, Veerle ULg; Williamson, Bonny

in Journal of Archaeological Science (2004), 31

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See detailA micro–macro approach of permeability evolution in rocks excavation damaged zones
Levasseur, Séverine ULg; Collin, Frédéric ULg; Charlier, Robert ULg et al

in Computers & Geotechnics (2013), 49

Excavation damaged zone, with significant irreversible deformations and nonnegligible changes in flow and transport properties generally occurs in indurated clay around underground structures. The stress ... [more ▼]

Excavation damaged zone, with significant irreversible deformations and nonnegligible changes in flow and transport properties generally occurs in indurated clay around underground structures. The stress perturbation around the excavation could lead to a significant increase of the permeability physically due to diffuse and/or localized microcracks growth in the material. In the present study, we investigate microcracks-induced damage processes together with the subsequent modification in permeability. The proposed approach is based on a homogenization-based upper bound extended to the context of micro-cracked media in presence of initial stress. Application of this approach is done on a borehole excavation problem related to the Selfrac in situ experiments on Opalinus Clay. Although, the model fails to quan-titatively account for the in situ permeability change (which may also originated from existing macro-fractures), its prediction shows a significant evolution of the material permeability around the borehole. This is in qualitative agreement with available data. [less ▲]

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See detailMid and late Holocene dust deposition in Western Europe: The Misten peat bog (Hautes Fagnes - Belgium)
Allan, Mouhamd ULg; Beghin, Jérémie ULg; le roux, Gael et al

in Climate of the Past (2013), 9(2889-2928,),

Dust deposition in southern Belgium is estimated from the geochemical signature of an ombrotrophic peatland. The Rare Earth Elements (REE) and lithogenic elements concentrations, as well as Nd isotopes ... [more ▼]

Dust deposition in southern Belgium is estimated from the geochemical signature of an ombrotrophic peatland. The Rare Earth Elements (REE) and lithogenic elements concentrations, as well as Nd isotopes, were determined by HR-ICP-MS and MC-ICP-MS respectively, along a  6 m peat section covering 5300 years, from 2000 to 7300 cal.BP dated by the 14C method. Changes in REE concentration in the peat correlate with those of Ti, Al, Sc and Zr that are lithogenic conservative elements, suggesting that REE are immobile in the studied peat bogs and can be used as tracers of dust deposition. Peat humification and testate amoebae were used to evaluate hydroclimatic conditions. The range of dust deposition varied from 0.03 to 4.0 g m-2 yr-1. The highest dust fluxes were observed from 2750 to 2550 cal.BP and from 5150 to 4750 cal.BP and correspond to cold periods. The Nd values show a large variability from -13 to –5, identifying three major sources of dusts: local soils, distal volcanic and desert particles. [less ▲]

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See detailMid and late Holocene dust deposition in Western Europe: The Misten peat bog (Hautes Fagnes - Belgium)
Allan, Mouhamd ULg; Le Roux, Gael; Piotrowska, Natalia et al

Poster (2012, June)

Multi-proxy climate recorded from peatlands have been used to tracer the climate change during the Holocene. The initiation of peatland may be related to a change to colder and or wetter climate, and the ... [more ▼]

Multi-proxy climate recorded from peatlands have been used to tracer the climate change during the Holocene. The initiation of peatland may be related to a change to colder and or wetter climate, and the variations in peat composition reflect changes in precipitation and temperature. Peat has been used as an archive to reconstruct climate change over the Holocene (e.g., Shotyk et al., 1998; Sapkota et al., 2006). To characterize the climate in Belgium, a 570 cm-long core from Misten peat bog was studied. Several radiocarbon ages allow to define an accurate age model, the peat core represents 5500 years of record. The analyses of REE and lithogenic element contents, as well as the Nd isotopes, were performed by HR-ICP-MS and MC-ICP-MS. Peat humification, C/N ratio, ash content and bulk density were used to evaluate local hydroclimatic conditions. The dust deposition ranges from 0.03 to 4 g m -2 yr -1. As a first observation the highest rates of atmospheric dust deposition correspond to cold periods. The Nd values show large variability, between +1 to –22, identifying three major sources of dusts falling into the peat: local soils, distal volcanic and desert particles. Further studies are in progress to better identify the main forcing factor on the evolution of the atmospheric dust deposition over the Holocene. [less ▲]

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See detailMid and late Holocene dust deposition in Western Europe: The Misten peat bog (Hautes Fagnes - Belgium)
Allan, Mouhamd ULg; Fagel, Nathalie ULg; Le Roux, Gael et al

Poster (2012, June 28)

The Misten peat bog representing 7.5 m of peat accumulation in the Hautes-Fagnes Plateau, Belgium, provides a record of Rare Earth Elements (REE) deposition since more than 7000 years. The analyses of REE ... [more ▼]

The Misten peat bog representing 7.5 m of peat accumulation in the Hautes-Fagnes Plateau, Belgium, provides a record of Rare Earth Elements (REE) deposition since more than 7000 years. The analyses of REE and lithogenic element concentrations, as well as the Nd isotopes, were performed by HR-ICP-MS and MC-ICP-MS, respectively in peat layers previously dated by 210Pb and 14C. REE concentration variations in peat samples are correlated with Ti, Zr and Sc that are lithogenic conservative elements, suggesting that REE are immobile in the studied peat bogs [1] and can be used as tracers of dust deposition. Peat humification, C/N ratio, ash content and bulk density were used to evaluate hydroclimatic conditions. The Nd values show large variability, between +1 to –22, identifying three major sources of dusts falling into the peat: local soils, distal volcanic and desert particles. More recently, industrial emissions provide a fourth source of dusts [2], which is also clearly recorded in the last 200 years of the Misten peat profile. [less ▲]

Detailed reference viewed: 34 (16 ULg)