References of "Richel, Aurore"
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See detailProduction of surface-active agents and antioxidants from renewable resources under microwave heating
Richel, Aurore ULg

Conference (2012, November)

The non-energetic valorization of renewable resources using efficient and eco-friendly methodologies is the central axis of the “green chemistry” concept. In particular, the chemical conversion of ... [more ▼]

The non-energetic valorization of renewable resources using efficient and eco-friendly methodologies is the central axis of the “green chemistry” concept. In particular, the chemical conversion of carbohydrates arising from the hydrolysis of non-edible vegetable feedstock (i.e., lignocellulosic biomass and streams) is a widely explored thematic for the production of new high-added value materials. In this context, we report here on the development of a microwave heating methodology for the efficient production of carbohydrate-based and lignin-based chemicals with relevant antioxidant and surface-active properties. New effective synthetic protocols minimizing wastes and energy-consumption are proposed. Enhanced yields and selectivities are achieved after a few minutes of microwave heating using heterogeneous catalysts. The benefits of this microwave approach are highlighted in terms of yields, atom efficiency, environmental factor, and carbon efficiency. Up-scaling assays are also discussed. [less ▲]

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See detailOptimization of a formic/acetic acid treatment of beech wood for lignin extraction
Simon, Mathilde ULg; Richel, Aurore ULg; Vanderghem, Caroline ULg et al

Conference (2012, August)

Lignocellulosic substrates are a promising alternative resource for the sustainable production of energy (biofuels), bio-based products and organic compounds. In the past, the extraction and recycling of ... [more ▼]

Lignocellulosic substrates are a promising alternative resource for the sustainable production of energy (biofuels), bio-based products and organic compounds. In the past, the extraction and recycling of cellulose (into fermentable glucose) constituted the central axis of lignocellulosic biorefinery processes. Degraded hemicelluloses and lignins were recovered as side-products with no possibilities of high-added value applications. Within the context of an integrated biorefinery, and for economic reasons, the recovery and the non-energetic valorization of lignins have opened recently new horizons. Lignin is a cross-linked phenolic polymer and is considered as potential alternative to petrochemical polymers or as a source of antioxidants for cosmetics and food industry, resins, chelating agent... As the final application of lignin depends on both extraction process and type of lignocellulosic sources, the development of fast and efficient physicochemical characterization methods is thus a prerequisite to optimize extraction processing conditions. In this study, beech wood particles (Fagus sylvatica L.) are delignified at atmospheric pressure by a formic acid/acetic acid/water mixture. Firstly, response surface methodology is used to optimize cooking time and temperature for delignification, pulp yield and concentration of degradation products (2-furfural and 5-hydroxymethylfurfural). The results highlight that best delignification is obtained in the highest cooking times and temperatures and that 5-hydroxymethylfurfural is produced during the formic/acetic acid treatment but is also degraded into 2-furfural. With the aim to develop an integrated biorefinery approach, multi-criteria optimization is used to find ideal cooking time and temperature (5h07, 104.2°C) leading to the maximization of delignification and pulp yield and to the minimization of 2-furfural production Finally, physicochemical and chemical structures of extracted lignins are found dependent on treatment conditions harshness. [less ▲]

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See detailGreen synthesis and antioxidant activity of new PEGylated ferulic acids
Nicks, Francois ULg; Richel, Aurore ULg; Richard, Gaetan ULg et al

in Tetrahedron Letters (2012), 53(19), 2402-2405

PEGylation of ferulic acid is described through a green esterification process involving poly(ethylene glycol) (PEG) with three different average molecular weights (200, 400 and 1000 g/mol) as both ... [more ▼]

PEGylation of ferulic acid is described through a green esterification process involving poly(ethylene glycol) (PEG) with three different average molecular weights (200, 400 and 1000 g/mol) as both reactive and solvent. Esterification with PEG400 and PEG1000 leads to original compounds soluble in all proportions in water. These new compounds display an antioxidant activity similar to that of ferulic acid. [less ▲]

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See detailLa lignine, une molécule d'intérêt issue du bioraffinage
Richel, Aurore ULg

in Chimie Nouvelle (2012), 111

The implementation of lignocellulosic biorefinery initiatives generates significant amounts of underexploited lignins. Lignin, one of the most abundant renewable molecules on earth, is a highly branched ... [more ▼]

The implementation of lignocellulosic biorefinery initiatives generates significant amounts of underexploited lignins. Lignin, one of the most abundant renewable molecules on earth, is a highly branched biopolymer consisting of aromatic units. Generally intended for energy purposes, lignin has nowadays opened new vistas for higher added-value applications such as syngas, additive in the plastics industry or as a source of aromatic compounds dedicated to the chemical sector. This article provides an update on this molecule and its potential applications. [less ▲]

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See detailEvaluation of Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry for second-generation lignin analysis
Richel, Aurore ULg; Vanderghem, Caroline ULg; Simon, Mathilde ULg et al

in Analytical Chemistry Insights (2012), 7

Matrix-Assisted Laser Desorption/Ionization time-of-flight (MALDI-TOF) mass spectrometry is evaluated as an elucidation tool for structural features and molecular weights estimation of some extracted ... [more ▼]

Matrix-Assisted Laser Desorption/Ionization time-of-flight (MALDI-TOF) mass spectrometry is evaluated as an elucidation tool for structural features and molecular weights estimation of some extracted herbaceous lignins. Optimization of analysis conditions, using a typical organic matrix, namely CHCA (alpha-cyano-4-hydroxycinnamic acid), in combination with alpha-cyclodextrine, allows efficient ionization of poorly soluble lignin materials and suppression of matrix-related ions background. Analysis of low-mass fragments ions (m/z 100-600) in the positive ion mode offers a “fingerprint” of starting lignins that could be a fine strategy to qualitatively identify principal interunit linkages between phenylpropanoid units. The molecular weights of lignins are estimated using size exclusion chromatography and compared to MALDI-TOF-MS profiles. Miscanthus (Miscanthus x giganteus) and Switchgrass (Panicum Virgatum L.) lignins, recovered after a formic acid/acetic acid/water process or aqueous ammonia soaking, are selected as benchmarks for this study. [less ▲]

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See detailCatalytic hydroprocessing of lignin under thermal and ultrasound conditions
Finch, Kenneth B.; Richards, Ryan; Richel, Aurore ULg 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 detailConversion of carbohydrates under microwave heating
Richel, Aurore ULg; Paquot, Michel ULg

in Chang, C.F. (Ed.) Carbohydrates - Comprehensive Studies on Glycobiology and Glycotechnology (2012)

The non-energetic valorisation of renewable resources using efficient and eco-friendly methodologies is the central axis of the "green chemistry" concept. In particular, the chemical and chemo-enzymatical ... [more ▼]

The non-energetic valorisation of renewable resources using efficient and eco-friendly methodologies is the central axis of the "green chemistry" concept. In particular, the chemical and chemo-enzymatical transformations of carbohydrates arising from the hydrolysis of non-edible vegetal feedstock (i.e., lignocellulosic biomass) are a widely explored thematic for the production of new high-added value materials, synthons, and platform chemicals. Since the seminal works of Gedye and Giguere in 1986, the use of microwaves as a non-conventional heating source has gained large attention in organic chemistry. Due to commonly observed acceleration in reactions rates and improved selectvities and yields, microwave heating has progressively emerged as a green chemistry technology. Minimizing both energy consumption (via the reduction of temperature and reaction times) and wastes (by improvement of selectivity), microwaves has enjoyed significant adoption by the research community. This chapter describes the use of microwave processes to mediate key reactions in the field of carbohydrates chemistry. Some examples of typical carbohydrates reactions (glycosylations, hydroxyl groups’ protection, etc.) under microwave conditions are displayed and highlight the benefits of this microwave approach in terms of yields, atom efficiency, environmental factor, and carbon efficiency. [less ▲]

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See detailMediterranean lignocellulosic biomass delignification and lignin valorization into high-added value components
Manara, Panagiota; Richel, Aurore ULg; Zabaniotou, Anastasia

Conference (2012)

The present study approaches the extraction of lignin samples from several lignocellulosic renewable feedstocks, including raw materials from Greece. The valorization of these lignins samples into high ... [more ▼]

The present study approaches the extraction of lignin samples from several lignocellulosic renewable feedstocks, including raw materials from Greece. The valorization of these lignins samples into high-added value components will also be explored using chemical catalytic routes and “green chemistry” methodology. The present study is a collaboration of Biomass Group of Aristotle University of Thessaloniki, Greece and Gembloux Agro-Bio Tech, in the frame of UBIOCHEM COST ACTION C0903, performed at the Laboratories of Biological and Industrial Chemistry Unit, Gembloux Agro-Bio Tech, University of Liege with samples preparation at AUTh. The lignin extraction from lignocellulosic biomass takes place via chemical, thermal and mechanical routes, including acid or basic processes, steam cracking, steam explosion. Statistical approaches (i.e. response surface methodology) are used for the optimization of processing parameters. Physico-chemical characterization of lignin materials is considered using specific techniques developed by the research team of Agro-Bio-Tech Institute, including qualitative and quantitative mono- and bidimensionnal NMR spectroscopy, MALLS, FT-IR, TGA and chemical methods. The characterization of the lignocellulosic materials before and after pretreatment protocol is investigated regarding the determination of extractives, ash, total lignin contents, and structural carbohydrates as well as proteins contents. Chemical catalytic routes and “green chemistry” methodology is conducted in order to valorize lignin. [less ▲]

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See detailDe nouveaux débouchés pour petits bois et rémanents ?
Wertz, Jean-Luc ULg; de Moreau d'Andoy, Guillaume; Richel, Aurore ULg

in Silva Belgica (2012), 119(3), 24-29

Le pétrole coûtera de plus en plus cher. Les chimistes travaillent depuis de nombreuses années sur des alternatives à la pétrochimie. L'utilisation de produits ligneux- dont le bois- comme matière ... [more ▼]

Le pétrole coûtera de plus en plus cher. Les chimistes travaillent depuis de nombreuses années sur des alternatives à la pétrochimie. L'utilisation de produits ligneux- dont le bois- comme matière première de cette nouvelle chimie verte arrive au stade des usines pilotes. De quoi s'agit-il ? [less ▲]

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See detailLiquid Crystalline Phases Induced by the Hydroxyl Group Stereochemistry of Amphiphilic Carbohydrate Bicatenary Derivatives
Razafindralambo, Hary ULg; Richel, Aurore ULg; Paquot, Michel ULg et al

in Journal of Physical Chemistry B (2012), 116(13), 3998-4005

Liquid-crystals (LC) may exist in different phases depending upon the orientational and positional orders of molecules in the material. Here, we demonstrate that the class of LC state induced by ... [more ▼]

Liquid-crystals (LC) may exist in different phases depending upon the orientational and positional orders of molecules in the material. Here, we demonstrate that the class of LC state induced by amphiphilic carbohydrate bicatenary derivatives is strictly a hydroxyl group stereochemistry-dependent. This statement results from the experimental and theoretical investigations of surface film (2D) and bulk solid (3D) thermal behavior of synthetic stereoisomers n-tetradecyl (-D-n-tetradecyl) galacto- and gluco-pyranosiduronate, with an axial (GalA-C14/14) or equatorial (GlcA-C14/14) hydroxyl group at the fourth carbon, respectively. Surface pressure-area isotherms (283 K to 310 K), differential scanning calorimetry thermograms (223 K to 573 K), and polarized optical textures (298-363 K) reveal that GlcA-C14/14 organizes as a smectic LC-like phase (positional or lateral order) whereas the analogous stereoisomeric GalA-C14/14 behaves as a nematic LC-like phase (orientational order). Thermodynamic investigations and molecular dynamics models computed under similar temperature conditions provide consistent data with physical properties resulting from experimental approaches. [less ▲]

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See detailEfficient microwave-promoted synthesis of glucuronic and galacturonic acid derivatives using sulfuric acid impregnated on silica
Richel, Aurore ULg; Nicks, Francois ULg; Laurent, Pascal ULg et al

in Green Chemistry Letters & Reviews (2012), 5(2), 179-186

Monomode microwave-assisted syntheses of D-glucuronic and D-galacturonic acid derivatives are reported in the presence of a solid acid catalyst, consisting of sulfuric acid loaded onto silica. This ... [more ▼]

Monomode microwave-assisted syntheses of D-glucuronic and D-galacturonic acid derivatives are reported in the presence of a solid acid catalyst, consisting of sulfuric acid loaded onto silica. This approach affords a variety of surface-active monoglycosylated glucofuranosidurono-6,3-lactones and disubstituted galacturonic adducts in excellent yields in less than 10 min at 85 °C. This study illustrates the application of microwave heating mode, in combination with a cost-effective solid catalyst, as an efficient, selective and eco-friendly methodology in carbohydrate chemistry. [less ▲]

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See detailLa chimie verte. Principes généraux et illustration pour la valorisation des agroressources
Richel, Aurore ULg

Conference (2011, August)

Le concept de « chimie verte » se décrit comme un ensemble cohérent de 12 principes ayant pour objectif de réduire ou d’éliminer l’utilisation et la génération de substances dangereuses émanant de la ... [more ▼]

Le concept de « chimie verte » se décrit comme un ensemble cohérent de 12 principes ayant pour objectif de réduire ou d’éliminer l’utilisation et la génération de substances dangereuses émanant de la synthèse et de l’application des produits chimiques. Parmi ces 12 principes, la réduction des déchets à la source, la diminution de l’utilisation des réactifs toxiques, la conservation de l’énergie et l’exploitation de matières premières renouvelables sont présentés et discutés sur base de quelques exemples choisis. [less ▲]

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See detailMonolayer Properties of Uronic Acid Bicatenary Derivatives at the Air-Water Interface: Effect of Hydroxyl Group Stereochemistry Evidenced by Experimental and Computational Approaches
Razafindralambo, Hary ULg; Richel, Aurore ULg; Wathelet, Bernard ULg et al

in Physical Chemistry Chemical Physics [=PCCP] (2011), 13(33), 1529115298

By screening uronic acid-based surfactant interfacial properties, the effect of the hydroxyl group stereochemistry (OH-4) on the conformation of bicatenary (disubstituted) derivatives at the air–water ... [more ▼]

By screening uronic acid-based surfactant interfacial properties, the effect of the hydroxyl group stereochemistry (OH-4) on the conformation of bicatenary (disubstituted) derivatives at the air–water interface has been evidenced by experimental and computational approaches. Physical and optical properties of a monolayer characterized by Langmuirfilmbalance, Brewster angle microscopy, and ellipsometry at 20°C reveal that the derivative of glucuronate (C14/14–GlcA) forms a more expanded monolayer, and shows a transition state under compression, in the opposite to that of galacturonate (C14/14–GalA). Both films are very mechanically resistant (compression modulus > 300m Nm-1) and stable (collapse pressure exceeding 60mNm-1), while that of C14/14–GalA exhibits a very high compression modulus up to 600mNm-1 like films in the solid state. Computational approaches provide single and assembly molecular models that corroborate the molecule expansion degree and interactions data from experimental results. Differences in the molecular conformation and film behaviours of uronic acid bicatenary derivatives at the air–water interface are attributed to the intra-H-bonding formation, which is more favourable with an OH-4 in the axial (C14/14–GalA) than in the equatorial position (C14/14–GlcA). [less ▲]

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See detailDiallyl disulfides: comparison between classical and microwave assisted synthesis
DETHIER, Bérénice ULg; Richel, Aurore ULg; Laurent, Pascal ULg et al

Poster (2011, June)

Garlic contains organosulfur compounds, such as diallyl disulfides (DADS), diallyl monosulfides (DAMS) and diallyl trisulfides (DATS), which have potential health properties. The first objective of this ... [more ▼]

Garlic contains organosulfur compounds, such as diallyl disulfides (DADS), diallyl monosulfides (DAMS) and diallyl trisulfides (DATS), which have potential health properties. The first objective of this work is to conduct the synthesis of these molecules by heating in a classical oil bath or by microwave irradiation with a phase transfer catalyst. We concluded that the synthesis should be cnducted at 40°C in an oil bath, with a phase transfer catalyst. [less ▲]

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See detailStructure-Surface Activity Relationships Of Uronic Acid-Derivative Surfactants From Renewable Resources Applications
Razafindralambo, Hary ULg; Richel, Aurore ULg; Richard, Gaetan ULg et al

Poster (2011, June)

Introduction and Background: Uronic acid-derivative surfactants are amphiphilic compounds with growing interests owing to their potential applications in various areas [1]. This class of carbohydrate ... [more ▼]

Introduction and Background: Uronic acid-derivative surfactants are amphiphilic compounds with growing interests owing to their potential applications in various areas [1]. This class of carbohydrate-based surfactants can be easily prepared from renewable raw materials in a wide range of structure by modular synthesis thanks to the presence of one carboxylic and numerous hydroxyl groups. The polar head group configurations according to the stereochemistry of OH groups, and geometry (cyclic or not), the hydrophobic tail (number and length of alkyl chain), and the type of linker (ester, acetal and amide, etc) are among the main variables in their structural entities. Therefore, the investigation of their structure-surface activity relationships appears valuable for increasing backgrounds, and achieving a rational design for selecting the best structures to be used in different industrial fields [2]. Methodology: A few analogous of glucuronic acid-derivative surfactants have been synthesized by chemical or enzymatic routes. After purification, their structure has been confirmed by various spectroscopic techniques (RMN, MS, IR). Surface tensions of true aqueous solution have been then measured in dynamic and static modes using a series of complementary techniques. Critical micelle concentrations, minimum molecular areas, and maximum surface excesses have also been determined. Results and Discussion: Glucuronic acid derivative surfactants under investigation vary in the polar head group configuration including cyclic or non-cyclic structure and α or β anomeric form, in the hydrophobic tail regarding to the chain length (C8 to C14), the presence of a double bond, as well as an OH group at the terminal carbon, and in the type of linker, ester in C6 or acetal in C1. Results showed that all of these structural attributes affect both dynamic and equilibrium surface properties of glucuronic acid -based surfactants. Conclusion: A set of synthetic glucuronic acid-based surfactants varying in the polar head group, hydrophobic tail, and linker allow us to generate various surface-active properties at the air-water interface, and to increase the knowledge on relationships between their structure and surface-active properties. [1] Laurent, P.; Razafindralambo, H.; Wathelet, B.; Blecker, C.; Wathelet, J.-P.; Paquot, M., Synthesis and Surface-Active Properties of Uronic Amide Derivatives, Surfactants from Renewable Organic Raw Materials. Journal of Surfactants and Detergents 2010, in press. [2] Razafindralambo, H.; Blecker, C.; Mezdour, S.; Deroanne, C.; Crowet, J.; Brasseur, R.; Lins, L.; Paquot, M., Impacts of the Carbonyl Group Location of Ester Bond on Interfacial Properties of Sugar-Based Surfactants: Experimental and Computational Evidences. The Journal of Physical Chemistry B 2009, 113 (26), 8872-8877. Acknowledgment: This work was supported by Belgian Walloon Region within DGTRE research project of excellence (TECHNOSE). [less ▲]

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See detailLa chimie verte
Richel, Aurore ULg

Conference (2011, May)

Le concept de « chimie verte » se décrit comme un ensemble cohérent de 12 principes ayant pour objectif de réduire ou d’éliminer l’ulitisation et la génération de substrances dangereuses émanant de la ... [more ▼]

Le concept de « chimie verte » se décrit comme un ensemble cohérent de 12 principes ayant pour objectif de réduire ou d’éliminer l’ulitisation et la génération de substrances dangereuses émanant de la synthèse et de l’application des produits chimiques. Parmi ces 12 principes, la réduction des déchets à la source, la diminution de l’utilisation des réactifs toxiques, la conservation de l’énergie et l’exploitation de matières premières renouvelables seront présentés et discutés sur base de quelques exemples choisis. [less ▲]

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See detailCHIMIE THÉORIQUE ET PHYSIQUE APPLIQUÉE À L’ANALYSE STRUCTURALE DES BIOMOLÉCULES (CG 204) - Exercices
Gillet, Sébastien ULg; Richel, Aurore ULg; Wathelet, Bernard ULg

Learning material (2011)

Le cours est axé sur l'apprentissage de l'analyse spectrale (IR, MS, RMN, RMN2D) des molécules organiques ou biologiques.L'interprétation qui en découle permettra d'en retrouver la structure.

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See detailGreen Chemistry in Wallonia. Focus on lignocellulosic transformations.
Richel, Aurore ULg; Paquot, Michel ULg

Conference (2011, February 10)

In the context of the valorisation of agricultural resources, the development of new sustainable strategies has gained attention. In this sense, this speech describes some major actions and contributions ... [more ▼]

In the context of the valorisation of agricultural resources, the development of new sustainable strategies has gained attention. In this sense, this speech describes some major actions and contributions undertaken in Wallonia around both “green chemistry” and “biorefinery” concepts. [less ▲]

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See detailLipase-catalyzed synthesis of L-cysteine glucosyl esters in organic media
Valepyn, Emmanuel ULg; Nys, Joël ULg; Richel, Aurore ULg et al

in Biocatalysis & Biotransformation (2011), 29(1), 25-30

New sugar amino acids were synthesized by enzymatic esterification of D -glucose with L -cysteine using immobilized lipase B from Candida antarctica in a mixed solvent system composed of 2-methyl-2 ... [more ▼]

New sugar amino acids were synthesized by enzymatic esterification of D -glucose with L -cysteine using immobilized lipase B from Candida antarctica in a mixed solvent system composed of 2-methyl-2-butanol and dimethyl sulfoxide. Addition of small quantities of water to the medium improved the glucose conversion yield by a factor of two. [less ▲]

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