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Exploring the influence of magnesium addition on the catalytic performance of Cu–Al mixed oxides in benzaldehyde reduction
No full textInternational audienceThe study investigates the impact of magnesium on the physicochemical properties of CuAlOx oxide and its catalytic behavior in the benzaldehyde reduction reaction. A series of catalysts, including CuAlO and CuAl1-xMgxO (x = 0.05; 0.1), were synthesized through a hydrothermal method, characterized using multiple techniques: Brunauer–Emmett–Teller (BET) surface area analysis, X-ray diffraction (XRD), laser Raman spectroscopy (LRS), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDX), temperature-programmed reduction (RTP), and X-ray photoelectron spectroscopy (XPS). Their catalytic performance in the reduction of benzaldehyde to benzyl alcohol was evaluated under atmospheric pressure within a temperature range of 150–200 °C. Their structural properties during reduction and re-oxidation were examined through in situ X-ray diffraction (HT-DRX) and X-ray photoelectron spectroscopy (HT-XPS) following specific pretreatments. The baseline CuAlOx system exhibits catalytic activity in the benzaldehyde reduction reaction, and these capabilities are significantly enhanced in the presence of magnesium. Indeed, with a high magnesium content, the CuAl0.9MgO.1 system achieves a conversion rate exceeding 83% and an impressive benzyl alcohol selectivity of up to 95%. The exact role of magnesium remains unclear. However, its presence appears to influence the reducibility of the system, which is slowed down, as observed in temperature-programmed reduction (RTP). Additionally, XRD results suggest the formation of a Cu–Mg–O mixed phase during preparation, while X-ray photoelectron spectroscopy (XPS) indicates the stabilization of copper in the Cu(I) oxidation state on the material’s surface. During the catalytic reaction, a synergistic effect between CuO, Cu–Mg–O, and Cu2O phases likely enhances the performance of CuAl0.9Mg0.1O compared to CuAlO.Cette étude examine l'impact du magnésium sur les propriétés physicochimiques de l'oxyde CuAlOx et son comportement catalytique dans la réaction de réduction du benzaldéhyde. Une série de catalyseurs, comprenant CuAlO et CuAl1-xMgxO (x = 0,05 ; 0,1), ont été synthétisés par une méthode hydrothermale et caractérisés à l'aide de plusieurs techniques : Analyse de la surface Brunauer-Emmett-Teller (BET), diffraction des rayons X (XRD), spectroscopie Raman laser (LRS), microscopie électronique à balayage couplée à la spectroscopie X à dispersion d'énergie (SEM-EDX), réduction programmée en température (TPR) et spectroscopie photoélectronique à rayons X (XPS). Leurs performances catalytiques pour la réduction du benzaldéhyde en alcool benzylique ont été évaluées sous pression atmosphérique dans une plage de température de 150 à 200 °C. Leurs propriétés structurelles au cours de la réduction et de la réoxydation ont été examinées par diffraction des rayons X in situ (HT-DRX) et par spectroscopie photoélectronique à rayons X (HT-XPS) à la suite de prétraitements spécifiques. Le système CuAlOx de base présente une activité catalytique dans la réaction de réduction du benzaldéhyde, et ces capacités sont considérablement renforcées en présence de magnésium. En effet, avec une teneur élevée en magnésium, le système CuAl0.9MgO.1 atteint un taux de conversion supérieur à 83 % et une sélectivité remarquable de l'alcool benzylique allant jusqu'à 95 %. Le rôle exact du magnésium n'est pas encore établi. Cependant, sa présence semble influencer la réductibilité du système, qui est ralentie, comme cela a été observé lors de la réduction programmée en température (RTP). En outre, les résultats de la XRD suggèrent la formation d'une phase mixte Cu-Mg-O pendant la préparation, tandis que la spectroscopie photoélectronique à rayons X (XPS) indique la stabilisation du cuivre dans l'état d'oxydation Cu(I) à la surface du matériau. Au cours de la réaction catalytique, un effet synergique entre les phases CuO, Cu-Mg-O et Cu2O améliore probablement les performances de CuAl0.9Mg0.1O par rapport à CuAlO
L’espace marionnettique comme microcosme des enjeux de patrimonialisation
No full textInternational audienc
How fake news effects spread in an oligopolistic market — Evidence from the insulin market
No full textInternational audienceThis study analyzes the impact of an event on November 11, 2022, when a fake “certified” Twitter account falsely claimed that Eli Lilly's insulin would be provided for free. We examine spillover effects on competitors within the insulin market oligopoly. Our findings reveal that while competitors experienced short-term impacts, these were weaker and of shorter duration compared to Eli Lilly. Spillovers within the broader pharmaceutical sector were limited to the immediate aftermath. No anticipatory behavior was detected. The effects were confined to American stock exchanges, suggesting an absence of spillovers in European markets
Chapitre XII : Vers la décarbonation des transports en Afrique. Utopie ou Réalité ?
No full textNational audienc
Lithium in Portland cement clinker: absence of evidence is not evidence of absence
No full textInternational audienceLithium (Li) is a challenging element to analyse in mineral matrixes. The very low energy (54 eV) of its X-ray emission line makes it almost impossible to analyse by common methods such as energy dispersive spectroscopy. Hence, its localisation within cementitious phases is poorly known. Based on glow-discharge mass spectrometry and time-of-flight secondary ion mass spectrometry, the present paper shows for the first time the repartition of Li at the scale of a microstructure of clinker with a 200 nm lateral resolution. Li is correlated to both Al and Fe in the interstitial phase, but also to Mg in periclase
Déceler le genre dans les textes juridiques. Outils méthodologiques
No full textInternational audienceUnlike other disciplines, legal history has largely overlooked gender studies. Seeking to address this gap, the ANR HLJPGenre team has developed an analytical framework for examining legal discourse through the lens of gender and intersectionality. The aim of this article is to describe this tool, its foundations, and the way it was developed and refined to provide an effective resource for researchers wishing to incorporate these fields into their work.Contrairement à d’autres disciplines, l’histoire du droit ne s’est que trop peu emparée des études de genre. Désireuse de pallier ce manque, l’équipe de l’ANR HLJPGenre a élaboré une grille de lecture permettant d’analyser le discours juridique au prisme du genre et de l’intersectionnalité. L’objet de l’article est de décrire cet instrument, ses fondements et la manière dont il a été élaboré et modifié afin de proposer un outil opérant aux chercheurs et chercheuses souhaitant intégrer ces champs à leurs travaux
Mechanosynthesis and Polymerization of Styrene Derivatives Based on Building Blocks of Lignin
No full textInternational audienceGiven the constraints dictated by the environment and the current policies, it is urgent to conceive and developnovel molecular building blocks and materials from bio-sourced platforms in order to compete and replace thoseobtained from petroleum sources (styrene, bisphenol A, etc.). Bio-sourced monomers can be obtained from thetransformation of molecules extracted from five main sources, namely terpenes, carbohydrates, lignin, proteins andlipids from animal, plant, or sea origin. Thanks to the presence of alcohol, acid or amine functional groups, thesebio-sourced molecules can often be polymerized by condensation reaction and yield bio-based polyesters orpolyamides with mechanical properties that can compete with their petroleum-based counterparts.Step-growth polymerization remains therefore the most explored pathway to produce bioplastics nowadays.Recently, the number of publications reporting free-radical chain-reaction polymerization (FRP) of bio-monomershas strongly increased. However, it remains still limited, probably due to the little number of readily availableradically polymerizable bio-sourced structures. In this context, lignin, the second most abundant natural polymericconstituent of wood, accounting for around 20% of the lignocellulosic biomass11 and currently discarded as wasteby the paper industry, appears to be a suitable candidate. Indeed, the controlled degradation of lignin allows toproduce biofuels, precursors for organic synthesis or oligomers that can be applied to prepare functional materials.Among those examples, the compounds obtained from lignin degradation represent a promising alternative todesign bio-sourced polymers displaying interesting thermo-mechanical properties thanks to the presence ofaromatic cycles.In this communication, we report the synthesis of polystyrenes prepared in three steps from vanillin, 4-hydrobenzaldehyde, and syringaldehyde, compounds that can be obtained through lignin depolymerization underoxidative conditions. The synthesis involves the conversion of these biosourced platforms into polymerizablestyrene derivatives through a methylation of the hydroxyl group followed by an olefination of the aldehyde function.The monomers were first synthesized under conventional conditions using solvents. Then, the synthesis wasimproved from the sustainability point of view by using a ball mill under solventless conditions, generating muchless waste in the process. Mechanochemistry has successfully been transposed from material sciences to organicchemistry in the past decades. Compared to conventional procedures and solvent-based reactions, it usesmechanical energy to induce a chemical reaction in solvent-free conditions and can afford shorter reaction times,higher yields and more sustainable process.The three monomers were then converted into biosourced homopolymers through free radical polymerization inbulk, providing functional polystyrene derivatives with thermal properties comparable to those of common petrosourced polystyrene
« Quelles recherches à venir sur la fantasy ? Un exercice d’imagination prospective »
No full textInternational audienc
L’activité physique et les enfants de milieux populaires : une revue de littérature des programmes internationaux d’interventions en contexte scolaire
No full textThis literature review examines sixteen physical activity intervention programs conducted in disadvantaged school settings. The analysis explores the logic behind school selection, the involvement of key stakeholders, and the degree of adaptation to social and cultural contexts. The findings highlight that an intervention’s effectiveness depends less on its intensity than on its ability to anchor locally, engage teachers and families, and respond to real-world constraints. Hybrid approaches—combining institutional targeting with contextual flexibility—emerge as the most promising. The study advocates for co-constructed, adaptable, and sustained interventions to effectively combat social inequalities in access to physical activity from early primary education onward.Cette revue de littérature examine seize programmes d'intervention en activité physique menés en milieu scolaire défavorisé. L’analyse croise la logique de sélection des écoles, l’implication des acteurs, et le niveau d’adaptation aux contextes sociaux et culturels. Les résultats soulignent que l’efficacité d’une intervention repose moins sur son intensité que sur sa capacité à s’ancrer localement, à mobiliser les enseignants et les familles, et à répondre aux contraintes du terrain. Les dispositifs hybrides, combinant ciblage institutionnel et flexibilité contextuelle, apparaissent les plus prometteurs. L’étude appelle à construire des interventions co-construites, adaptables et soutenues, pour lutter durablement contre les inégalités sociales d’accès à l’activité physique dès l’école primaire
