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We report first principles numerical discovery of hydrostatic pressure driven tetragonal to collapsed tetragonal transition in 1111-type material ThMnAsN accompanied by simultaneous magneto-structural, insulator to metal transition together with complete collapse of Mn moment. We present detailed evolution of various structural parameters, magnetism and electronic structures of ThMnAsN with increasing hydrostatic pressure. All the structural parameters show anomalies at a critical pressure P$_c \sim$ 9 GPa; c-lattice parameter, out of plane As-As bond length, anion height (h$_{As}$) undergo drastic modification compared to the in-plane parameters which is manifested in an iso-structural phase transition from tetragonal to a collapsed tetragonal (cT) phase. These modifications in "local structural correlations" due to pressure destroys usually localized nature of Mn moments and gets completely quenched. Apart from that the elastic constant, the electronic structures also bear the finger prints of insulator-metal and magneto-structural transition at higher pressures accompanying a total collapse of magnetic moment at the vicinity of 9 GPa. The critical value of the pressure P$_c$ at which tetragonal to collapse tetragonal phase transition occurs, remains robust with respect to the on-site Hubbard correlation (U). The dynamical stability of the compound at higher pressures are affirmed through detailed computations of phonon dispersion curves endowed with positive phonon frequency through out the Brillouin zone. The effect of magnetic spin structure on the electronic band structures are obtained through band unfolding. The electronic structure of ThMnAsN at higher pressures "orbital selectively" influences bands, band gap and closely resembles with the electronic structure of Fe-based superconductors with the occurrences of orbital selective Lifshitz transition., Comment: 13 pages, 21 figures

International audience; We report on the crystallite growth of nanometric NpO2 and UO2 powders. The AnO2 nanoparticles (An = U and Np) were synthesized by hydrothermal decomposition of the corresponding actinide(IV) oxalates. NpO2 powder was isothermally annealed between 950 °C and 1150 °C and UO2 between 650 °C and 1000 °C. The crystallite growth was then followed by high-temperature X-ray diffraction (HT-XRD). The activation energies for the growth of crystallites of UO2 and NpO2 were determined to be 264(26) kJ mol−1 and 442(32) kJ mol−1, respectively, with a growth exponent n = 4. The value of the exponent n and the low activation energy suggest that the crystalline growth is rate-controlled by the mobility of the pores, which migrate by atomic diffusion along the pore surfaces. We could thus estimate the cation self-diffusion coefficient along the surface in UO2, NpO2 and PuO2. While data for surface diffusion coefficients for NpO2 and PuO2 are lacking in the literature, the comparison with literature data for UO2 supports further the hypothesis of a surface diffusion controlled growth mechanism.

International audience; The powerful combination of steady state isotopic transient kinetic analysis (SSITKA) and operando infrared spectroscopy (IR) was applied to study the CO oxidation reaction on Pd-supported Al2O3 catalyst at low temperature. The aim was to reveal the true role of hydrogen‑carbonate species in the reaction mechanism. The SSITKA-IR experiments, conducted in presence and absence of CO2 in the gas feed, have confirmed that hydrogen‑carbonate species behave as spectator species in the reaction. Its formation was due to re-adsorption of the CO2 product itself on the alumina surface as confirmed by the direct 12CO2/13CO2 exchange observed on the bare support.

Aqueous hydroaminomethylation (HAM) is an atom economical route for the efficient production of amines in one reaction step, starting from basic chemicals like alkenes. Herein we present the first successful establishment of a continuous process for HAM in an aqueous multiphase system. The green mass transfer agents randomly methylated-β-cyclodextrins (CD) enabled the catalytic system consisting of rhodium/sulfoXantphos to achieve high yields of up to 70% with selectivities of up to 80% in several continuous experiments with a total run time of more than 220 h. The key here is that water and products have large polarity differences, but the reaction still proceeds effectively due to the addition of cyclodextrin, which made the application of solvents obsolete. The main achievements in this way were the investigation of the influence of the randomly methylated-β-cyclodextrin concentration on the reaction rate and the selectivity in batch studies and finding promising operating points in the first continuous experiments. In a final experiment, the separation temperature was investigated. It was shown that the catalyst loss in the product phase is enormously small at 0.003% h−1 of the initial mass (0.24% in total), which is the lowest ever reported value for the HAM on this scale. Within a run time of 78 hours, 2.87 kg of tertiary amine were produced using only 0.2 g (>14 000 : 1) of transition metal, while the loss of rhodium per kg of product produced was mostly around 0.15 mg kg−1, suggesting possible economical applicability. 25;9

International audience; Modulating the interaction between Mo nanoparticles and their support is an elegant approach to finely tune the structural, physico-chemical, redox and electronic properties of the active site. In this work, a series of molybdenum nitride catalysts supported on TiO2, and SBA-15 has been prepared and fully characterized. The results of characterization confirmed the high dispersion of Mo and the formation of small molybdenum nanoparticles in both the 10-Mo-N/SBA-15 and 10-Mo-N/TiO2 catalysts. In this context, we have shown that the catalytic activity of Mo species was strongly impacted by the nature of the catalytic support. Amongst the studied supports, SBA-15 was found to be the most appropriate for Mo dispersion. In comparison, when supported on a reducible oxide (TiO2), Mo species showed poor catalytic activity in both ammonia synthesis and decomposition and were prone to quick deactivation in the ammonia synthesis reaction. Evidence of charge transfer from the reducible support to the active phase, indicative of possible SMSI behaviour, has been observed by XPS and EPR. Differences in the oxidation states, redox behaviours, and electronic properties have been further studied by means of EPR, H2-TPR and H2-TPD.

International audience; We report bulk dilatometry and diffraction data through the T MIT = 427 K metal-insulator transition of the n = 3 member of the V n O 2n-1 Magnéli series. Besides VO 2 , V 3 O 5 is the only other vanadium oxide with a potentially useful MIT transition above room temperature. A narrow (ΔT = 10 K) abrupt negative thermal expansion of α L =-21.4 x 10-6 (dilatometry) and α V =-213 x 10-6 K-1 (crystallographic) is observed. We argue that the combination of the MIT along with the simultaneous vanadium charge ordering are responsible for such large values. The low temperature magnetic properties are also clarified and neutron diffraction measurements show a k = [½ ½ 0] magnetic structure at 1.5 K. DFT calculations of the exchange interactions support the low dimensionality and allow modelling the magnetic susceptibility.

International audience; In this work, zeolitic imidazolate framework-67 (ZIF-67)/chitosan composite beads were prepared by immersing chitosan beads incorporating cobalt (hydr)oxide into a solution containing the organic linker (2-methylimidazole). Compared to the conventional preparation protocols for metal-organic framework/polymer beads, the in-situ growth approach developed herein allows obtaining higher surface area with the shaped composites, up to 1200 m2/g for ZIF-67/CS2:1. The CO2 adsorption capacity of these ZIF-67/chitosan beads was investigated and reached 1.21 mmol/g at 273 K, which represents almost 100% of the adsorption capacity of pure ZIF-67, in line with the preserved surface area despite the incorporation of the 19% of additives included. Importantly, the ZIF-67/chitosan beads with an average bulk (crush) strength of 1.57 N could be easily regenerated, with a retained efficiency above 97% after 6 cycles. Furthermore, a possible mechanism for CO2 adsorption is discussed.

International audience; α-carbonyl homoallylic alcohols have been synthesized in a one-pot reaction from benzaldehyde and allylic alcohols. The nickel-catalyzed allylation of α-hydroxyketones has first been studied and allowed the identification of Ni(cod)2/dppf as the most suitable catalytic system. The tandem reaction that combines the benzoin condensation of aldehydes (synthesis of α-hydroxyketones) promoted by the 1,3-dimethylimidazolium chloride/DBU system and the nickel-catalyzed allylic alkylation with allylic alcohol has been realized in EtOH as green solvent. The reaction is 100 % atom-economical and water is formed as sole by-product. A broad scope of different benzaldehyde derivatives as well as various allylic alcohols is also described.

Maximizing the electrochemical performance of 3D micro-supercapacitors based on pseudocapacitive films is crucial for powering the next generation of miniaturized IoT devices. The films have to be nanostructured, must conform the 3D template, and have uniform deposition. To study the growth mechanism of nanostructured MnO2 films obtained by a pulsed electrodeposition method, in situ Atomic Force Microscopy methods operating in liquid mode, Scanning Electron Microscopy, and electrochemical characterization techniques were used. The impact of ON and OFF times during the pulsed electrodeposition process was investigated. The deposition mechanism in Volmer Weber Island growth mode provided some guidelines to tune the deposit morphology to enhance the electrochemical performance of the 3D electrode based on nanostructured MnO2 films.

International audience; Hydroxyl groups of several industrial grade lignins are esterified thanks to palladium-catalyzed hydroesterification reactions with CO and olefins, fatty esters or 1,3-butadiene. The reaction is efficient, salt-free and allows introducing aliphatic chains to lignin through ester linkage. Technical and modified lignins are characterized by NMR, IR, SEC and thermal properties are evaluated by DSC. The esterified lignins show modified glass transition temperatures that depend on the substitution degree of the hydroxyl groups and on the nature of the aliphatic chains that have been introduced. The implementation of this catalysis also opens up the possibility of inserting new reactive functionalities such as esters or unsaturations from abundant and/or biobased reactants.

International audience; The SCR performance of V2O5-WO3/TiO2 SCR-catalysts characterized by different surface W density (2.1W/nm2 and 9.5W/nm2) and different surface V density varying in the range 1–8V/nm2 has been investigated in order to clarify existing controversies on the preferential involvement of electronic and geometric effects in the catalytic properties. It was found that tungsten has a weak effect on the VOx cluster size distribution through contraction of dilution effect. In contrast, the optimal interaction between W and V, when both reach their highest composition, appears to be a relevant parameter that can enhance their acidic properties and improve the catalytic efficiency in dry conditions. On the other hand, an absence of significant interaction leads to discontinuity due to deactivation. In the presence of steam, acidic properties are averaged, lowering the impact of the V to W ratio. Finally, the critical importance of acidic properties which outperform redox properties in the definition of active site is pointed out in the light of this study.

Global pollution by plastics derived from petroleum has fostered the development of carbon–neutral, biodegradable bioplastics synthesized from renewable resources such as modern biomass, yet knowledge on the impact of bioplastics on ecosystems is limited. Here we review the polylactic acid plastic with focus on synthesis, biodegradability tuning, environmental conversion to microplastics, and impact on microbes, algae, phytoplankton, zooplankton, annelids, mollusk and fish. Polylactic acid is a low weight semi-crystalline bioplastic used in agriculture, medicine, packaging and textile. Polylactic acid is one of the most widely used biopolymers, accounting for 33% of all bioplastics produced in 2021. Although biodegradable in vivo, polylactic acid is not completely degradable under natural environmental conditions, notably under aquatic conditions. Polylactic acid disintegrates into microplastics faster than petroleum-based plastics and may pose severe threats to the exposed biota.

Numerous studies expose the potential of brannerite to become a good matrix, concentrating fission products and actinides. Minerals can complement the data collected from the synthetic materials and offer an advantage of a long-time exposure to radiation. Natural metamict brannerite from Akchatau, Kazakhstan, and its annealed sample were studied by EPMA, Raman spectroscopy, TGA, DSC, XRD and HTXRD. The radioactivity of pristine and annealed samples of brannerite was measured. Brannerite from Akchatau is characterized by the absence of significant amounts of REE and yttrium. The studied brannerite regains its structure at a temperature ~650 °C, revealed by the HTXRD and DSC. HTXRD was also performed on the annealed recrystallized brannerite. The thermal expansion for brannerite has been determined for the first time. The brannerite structure expands anisotropically with temperature increase. All the thermal expansion coefficients are positive except for αβ. The decreasing beta parameter indicates a “shear structural deformation“. The angle between the 1st axis of the tensor and the crystallographic a axis decreases with the increase of the temperature. The structure expands mostly in the α11 direction, approaching the bisector of the β angle. Brannerite has a low CTE at room temperature—αv = 16 × 10−6 °C−1, which increases up to 39.4 × 10−6 °C−1 at 1100 °C. In general, the thermal stability of brannerite is comparable to that of the other perspective oxide radioactive waste-immobilizing matrices (e.g., Ln2Zr2O7, CePO4, CaTiO3, CaZrTi2O7). The calculated thermal expansion of brannerite and the understanding of its underlying crystal chemical mechanisms may contribute to the behavior prediction of the material (both metamict and crystalline) at high temperatures.

International audience; Mesoporous silica (MPS) carriers are considered as a promising strategy to increase the solubility of poorly soluble drugs and to stabilize the amorphous drug delivery system. The development by the authors of a solvent-free method (milling-assisted loading, MAL) made it possible to manipulate the physical state of the drug within the pores. The present study focuses on the effects of the milling intensity and the pore architecture (chemical surface) on the physical state of the confined drug and its release profile. Ibuprofen (IBP) and SBA-15 were used as the model drug and the MPS carrier, respectively. It was found that decreasing the milling intensity promotes nanocrystallization of confined IBP. Scanning electron microscopy and low-frequency Raman spectroscopy investigations converged into a bimodal description of the size distribution of particles, by decreasing the milling intensity. The chemical modification of the pore surface with 3-aminopropyltriethoxisylane also significantly promoted nanocrystallization, regardless of the milling intensity. Combined analyses of drug release profiles obtained on composites prepared from unmodified and modified SBA-15 with various milling intensities showed that the particle size of composites has the greatest influence on the drug release profile. Tuning drug concentration, milling intensity, and chemical surface make it possible to easily customize drug delivery.

International audience; In this work, surface properties evaluated by catalytic conversion of isopropanol and by ammonia Temperature Programmed Reduction (NH3-TPD) over ferrite spinel nanoparticles was investigated. Bulk NiFe2O4 with specific surface area 114 m2/g and crystallites size 6 nm was prepared by hydrothermal synthesis using nitrates as precursors. X-ray diffraction (XRD), Raman spectroscopy, specific surface area by B.E.T, Scanning Electron Microscopy (SEM) and X-ray energy dispersive microanalysis (EDS), Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS) techniques were used for their structural and textural characterizations. The reducibility by hydrogen at variable temperatures was investigated by Temperature Programmed reduction (H2-TPR) and Thermal Gravimetric Analysis-Differential Scanning Calorimetry (TGA-DSC). The total acidity and acid strength distribution was determined by NH3-TPD. The synthesized oxide showed the presence of mixed phases containing the inverse spinel structure NiFe2O4 as the major phase and iron oxide α- Fe2O3 as an additional phase. It was shown that the surface of the powder was richer in Ni2+ species. The surface acidity (Brönsted and Lewis) determined by NH3-TPD showed that the number of acidic sites increased dramatically with the temperature. The catalytic conversion of isopropanol yields both acidic and redox/basic sites were available. A good correlation between textural, structural, redox and acid-base properties of catalyst is established.; Dans ce travail, les propriétés de surface évaluées par conversion catalytique de l'isopropanol et par réduction programmée en température de l'ammoniac (NH3-TPD) sur des nanoparticules de ferrite spinelle ont été étudiées. Le NiFe2O4 massif avec une surface spécifique de 114 m2/g et des cristallites de 6 nm a été préparé par synthèse hydrothermale en utilisant des nitrates comme précurseurs. La diffraction des rayons X (XRD), la spectroscopie Raman, la surface spécifique par B.E.T, la microscopie électronique à balayage (SEM) et la microanalyse dispersive en énergie (EDS), la microscopie électronique à transmission (TEM) et la spectroscopie photoélectronique à rayons X (XPS) ont été utilisées pour leurs caractérisations structurelles et texturales. La réductibilité par l'hydrogène à des températures variables a été étudiée par réduction programmée en température (H2-TPR) et par analyse thermogravimétrique et calorimétrie à balayage différentiel (TGA-DSC). L'acidité totale et la distribution de la force acide ont été déterminées par NH3-TPD. L'oxyde synthétisé a montré la présence de phases mixtes contenant la structure spinelle inverse NiFe2O4 comme phase principale et l'oxyde de fer α- Fe2O3 comme phase supplémentaire. Il a été montré que la surface de la poudre était plus riche en espèces Ni2+. L'acidité de surface (Brönsted et Lewis) déterminée par NH3-TPD a montré que le nombre de sites acides augmentait considérablement avec la température. La conversion catalytique de l'isopropanol donne lieu à la présence de sites acides et de sites redox/basiques. Une bonne corrélation entre les propriétés texturales, structurelles, redox et acide-base du catalyseur est établie.

International audience; Phosphate tungsten and molybenum bronzes represent an outstanding class of materials displaying textbook examples of charge-density-wave (CDW) physics among other fundamental properties. Here we report on the existence of a novel structural branch with the general formula [Ba(PO4)2][WmO3m−3] (m=3, 4 and 5) denominated ′layered monophosphate tungsten bronzes′ (L-MPTB). It results from thick [Ba(PO4)2]4− spacer layers disrupting the cationic metal-oxide 2D units and enforcing an overall trigonal structure. Their symmetries are preserved down to 1.8 K and the compounds show metallic behaviour with no clear anomaly as a function of temperature. However, their electronic structure displays the characteristic Fermi surface of previous bronzes derived from 5d W states with hidden nesting properties. By analogy with previous bronzes, such a Fermi surface should result into CDW order. Evidence of CDW order was only indirectly observed in the low-temperature specific heat, giving an exotic context at the crossover between stable 2D metals and CDW order.

International audience; The conversion of biomass as a sustainable path to access valuable chemicals and fuels is very attractive for the chemical industry, but catalytic conversions still often rely on the use of noble metals. Sustainability constraints require developing alternative catalysts from abundant and low-cost metals. In this context, NiFe nanoparticles are interesting candidates. In their reduced and supported form, they have been reported to be more active and selective than monometallic Ni in the hydrogenation of the polar functions of organic molecules, and the two metals are very abundant. However, unlike noble metals, Ni and Fe are easily oxidized in ambient conditions, and understanding their transformation in both oxidative and reductive atmospheres is an important though seldom investigated issue to be addressed before their application in catalysis. Three types of NiFe nanoparticles were prepared by an organometallic approach to ensure the formation of ultrasmall nanoparticles (

International audience; The use of an extrusion-spheronization process was investigated to prepare robust and highly porous extrudates and granules starting from UiO-66 and UiO-66_NH2 metal–organic framework powders. As-produced materials were applied to the capture of gaseous iodine and the adsorption of xenon and krypton. In this study, biosourced chitosan and hydroxyethyl cellulose (HEC) are used as binders, added in low amounts (less than 5 wt % of the dried solids), as well as a colloidal silica as a co-binder when required. Characterizations of the final shaped materials reveal that most physicochemical properties are retained, except the textural properties, which are impacted by the process and the proportion of binders (BET surface area reduction from 5 to 33%). On the other hand, the mechanical resistance of the shaped materials toward compression is greatly improved by the presence of binders and their respective contents, from 0.5 N for binderless UiO-66 granules to 17 N for UiO-66@HEC granules. UiO-66_NH2-based granules demonstrated consequent iodine capture after 48 h, up to 527 mg/g, in line with the pristine UiO-66_NH2 powder (565 mg/g) and proportionally to the retaining BET surface area (−5% after shaping). Analogously, the shaped materials presented xenon and krypton sorption isotherms correlated to their BET surface area and high predicted xenon/krypton selectivity, from 7.1 to 9.0. Therefore, binder-aided extrusion-spheronization is an adapted method to produce shaped solids with adequate mechanical resistance and retained functional properties.

Growing CO2 emissions lead to global warming, which is currently one of the most challenging environmental phenomena. Direct catalytic hydrogenation to dimethyl ether over hybrid catalysts enables CO2 utilization, hydrogen and energy storage and produces sustainable fuels and an important platform molecule. In this paper, we evaluated structure–performance correlations in the bifunctional hybrid copper–zinc SAPO-34 catalysts for direct synthesis of dimethyl ether via CO2 prepared using zirconia, alumina and ceria used as oxide carriers. Higher copper dispersion and higher CO2 conversion rate were uncovered over the alumina and zirconia supported catalysts followed by ceria supported counterpart. The CO2 hydrogenation seems to be principally favoured by higher copper dispersion and to a lesser extent depends on the concentration of Bronsted acid sites in the studied catalysts. Because of lower reverse water gas-shift activity, the alumina supported catalyst exhibited a higher dimethyl ether yield compared to the zirconia and ceria supported counterparts. 57;5

International audience; Several aryl polycarboxylic ligands (pyromellitic acid, 4,4′-azobenzenedicarboxylic acid and 3,3′,5,5′- azobenzenetetracarboxylic acid) have been used to react with the pentavalent ethoxide niobium(V) precursor Nb(OEt)5. Three new crystalline molecular compounds (1 with pyromellitate, 2 with 4,4′- azobenzenedicarboxylate and 3 with 3,3′,5,5′-azobenzenetetracarboxylate) were isolated from slowcrystallization at room temperature from the mother liquid containing the precursor Nb(OEt)5. They are composed of one polycarboxylate ligand fully coordinated to mononuclear or dinuclear octahedrally- coordinated niobium(V) units. For the dimers, the two adjacent niobium centers are bridged by one μ-O and one μ-OEt groups and complexed by only one of the syn–syn bidentate carboxylate function arms from the polytopic ligand. Compounds 1–3 were characterized in solid state by single-crystal and powder X-ray diffraction analysis. Insight into the formation of the three compounds was supported by the help of infrared and liquid 1H NMR spectroscopy.; Plusieurs ligands aryl polycarboxyliques (acide pyromellitique, acide 4,4′-azobenzènedicarboxylique et acide 3,3′,5,5′-azobenzènetétracarboxylique) ont été utilisés pour réagir avec l'éthoxyde pentavalent niobium(V) précurseur Nb(OEt)5. Trois nouveaux composés moléculaires cristallins (1 avec du pyromellitate, 2 avec du 4,4′-azobenzènedicarboxylate et 3 avec du 3,3′,5,5′-azobenzènetétracarboxylate) ont été isolés à partir decristallisation à température ambiante à partir du liquide mère contenant le précurseur Nb(OEt)5. Ils sont composés d'un ligand polycarboxylate entièrement coordonné à des unités de niobium (V) octaédriquement coordonnées mononucléaires ou dinucléaires. Pour les dimères, les deux centres de niobium adjacents sont pontés par un groupe μ-O et un groupe μ-OEt et complexés par un seul des bras de la fonction carboxylate syn – syn ​​bidentate du ligand polytopique. Les composés 1 à 3 ont été caractérisés à l'état solide par analyse par diffraction des rayons X sur monocristal et sur poudre. La compréhension de la formation des trois composés a été étayée par l'aide de la spectroscopie RMN 1H infrarouge et liquide.

International audience; Ternary Co3Mo3N nitrides are reported to exhibit high catalytic activity in ammonia synthesis. However, synthesis of ternary nitrides requires thermal treatments at elevated temperatures and reactive atmospheres that lead to unavoidable surface reduction (~ 10 m2 g-1). In this work, we have developed a novel approach to improve the catalytic activity of Co3Mo3N through its dispersion into a high surface area silica-based support (SBA-15). During ammonolysis and ammonia synthesis conditions reaction, SBA-15 demonstrated good thermal and chemical stability maintaining an ordered porous structure and high surface area (> 500 m2 g-1). For application in ammonia synthesis, SBA-15 supported cobalt molybdenum catalysts with different metal loading (10, 20 and 30 wt.%) were prepared by a modified impregnation-infiltration protocol and their catalytic activity studied. The dispersion of CoMo nitride nanoparticles into SBA-15 structures resulted in the improvement of their structural and textural properties of nitrides as evidenced by XRD analysis, STEM-EDS, and N2- physisorption (e.g. 10-CoMo-N/SBA-15: 348 m2 g-1). Nevertheless, the surface composition of CoMo-N/SBA-15 catalysts was found to be similar to the non-supported Co3Mo3N. Furthermore, supported CoMo-N/SBA-15 displayed enhanced catalytic activity in ammonia synthesis (1714, 1429 and 810 μmol gactive phase-1 h-1 corresponding to the CoMo oxide loadings of 10, 20, 30 wt.% respectively) that outperform the classical Co3Mo3N catalyst (298 μmol gcatalyst-1 h-1). The results reported in this work highlights a novel approach for the design of nitride-based catalysts with superior catalytic properties in ammonia synthesis.; Les nitrures ternaires de Co3Mo3N présentent une activité catalytique élevée dans la synthèse d'ammoniac. Cependant, la synthèse de nitrures ternaires nécessite des traitements thermiques à des températures élevées et des atmosphères réactives qui conduisent à une réduction de surface inévitable (~ 10 m2 g-1). Dans ce travail, nous avons développé une nouvelle approche pour améliorer l'activité catalytique du Co3Mo3N grâce à sa dispersion dans un support à base de silice à surface élevée (SBA-15). Au cours de la réaction dans les conditions d'ammonolyse et de synthèse d'ammoniac, le SBA-15 a démontré une bonne stabilité thermique et chimique en maintenant une structure poreuse ordonnée et une surface spécifique élevée (> 500 m2 g-1). Pour une application dans la synthèse d'ammoniac, des catalyseurs au cobalt-molybdène sur support SBA-15 avec différentes charges métalliques (10, 20 et 30 % en poids) ont été préparés par un protocole d'imprégnation-infiltration modifié et leur activité catalytique étudiée. La dispersion des nanoparticules de nitrure de CoMo dans les structures SBA-15 a entraîné l'amélioration de leurs propriétés structurelles et texturales des nitrures, comme en témoignent l'analyse XRD, le STEM-EDS et la physisorption N2 (par exemple 10-CoMo-N/SBA-15 : 348 m2 g-1). Néanmoins, la composition de surface des catalyseurs CoMo-N/SBA-15 s'est avérée similaire à celle du Co3Mo3N non supporté. De plus, le CoMo-N/SBA-15 supporté a affiché une activité catalytique améliorée dans la synthèse d'ammoniac (1714, 1429 et 810 μmol gactive phase-1 h-1 correspondant aux charges d'oxyde CoMo de 10, 20, 30 % en poids respectivement) qui surpassent le catalyseur classique Co3Mo3N (298 μmol gcatalyst-1 h-1). Les résultats rapportés dans ce travail mettent en évidence une nouvelle approche pour la conception de catalyseurs à base de nitrure avec des propriétés catalytiques supérieures dans la synthèse d'ammoniac.

International audience; Two hydroxyapatite supported CuO (10 wt% Cu) catalysts were prepared using the wet impregnation method via the conventional process and with the addition of native β-cyclodextrin using Cu(NO3)2.3H2O as copper precursor and adopting a ratio of β-cyclodextrin to copper of 0.1. After the impregnation step, the materials were dried at 80 °C and calcined in flowing dry air at 400 °C. The copper supported materials were characterized in the dried state and after calcination by means of conventional methods including X-ray diffraction, TG-MS, H2-TPR-MS, Raman spectroscopy, UV-vis-DR, ToF-SIMS and XPS. It was found that β-cyclodextrin hasd a profound impact on the final properties of the catalysts, both in terms of reducibility and dispersion of active species. It is suggested that at the early stages of the calcination, some hydroxyl groups of the β-CD units in close contact with Ca2+ of hydroxyapatite could play the role of spacers between the copper-based entities thus minimizing the aggregation process of the CuO nanoparticles. Finally, these copper oxide catalysts prepared from β-cyclodextrin were able to oxidize toluene more efficiently than the conventional catalyst. The copper oxide particles generated by the thermal decomposition of Cu2(OH)3(NO3) were smaller than those formed with copper nitrate alone and exhibited a higher reducibility, two key determinants for VOC total oxidation on transition metal oxides.

International audience; Bimetallic layered double oxide (LDO) NiM (M = Cr, Fe) catalysts with nominal compositions of Ni/M = 2 or 3 were tailored from layered double hydroxides (LDH) using a coprecipitation method to investigate the effects of the trivalent metal (Cr or Fe) and the amount of Ni species on the structural, textural, reducibility, and catalytic properties for CH4/CO2 reforming. The solids before (LDH) and after (LDO) thermal treatment at 500 °C were characterized using TGA-TD-SM, HT-XRD, XRD, Raman, and IR-ATR spectroscopies; N2 physical adsorption; XPS; and H2-TPR. According to the XRD and Raman analysis, a hydrotalcite structure was present at room temperature and stable up to 250 °C. The interlayer space decreased when the temperature increased, with a lattice parameter and interlayer space of 3.018 Å and 7.017 Å, respectively. The solids fully decomposed into oxide after calcination at 500 °C. NiO and spinel phases (NiM2O4, M = Cr or Fe) were observed in the NiM (M = Cr, Fe) catalysts, and Cr2O3 was detected in the case of NiCr. The NiFe catalysts show low activity and selectivity for DRM in the temperature range explored. In contrast, the chromium compound demonstrated interesting CH4 and CO2 conversions and generally excellent H2 selectivity at low reaction temperatures. CH4 and CO2 conversions of 18–20% with H2/CO of approx. 0.7 could be reached at temperatures as low as 500 °C, but transient behavior and deactivation were observed at higher temperatures or long reaction times. The excellent activity observed during this transient sequence was attributed to the stabilization of the metallic Ni particles formed during the reduction of the NiO phase due to the presence of NiCr2O4, opening the path for the use of these materials in periodic or looping processes for methane reforming at low temperature.; Des catalyseurs bimétalliques oxyde double lamellaire (LDO) NiM (M = Cr, Fe) avec des compositions nominales de Ni/M = 2 ou 3 ont été fabriqués à partir d'hydroxydes doubles lamellaires (LDH) en utilisant une méthode de coprécipitation pour étudier les effets du métal trivalent (Cr ou Fe) et de la quantité d'espèces de Ni sur la structure, la texture, la réductibilité et les propriétés catalytiques pour le reformage de CH4/CO2. Les solides avant (LDH) et après (LDO) traitement thermique à 500 °C ont été caractérisés par des spectroscopies TGA-TD-SM, HT-XRD, XRD, Raman, et IR-ATR ; adsorption physique de N2 ; XPS ; et H2-TPR. Selon l'analyse XRD et Raman, une structure hydrotalcite était présente à la température ambiante et stable jusqu'à 250 °C. L'espace intercouche diminue lorsque la température augmente, avec un paramètre de réseau et un espace intercouche de 3,018 Å et 7,017 Å, respectivement. Les solides se sont entièrement décomposés en oxyde après calcination à 500 °C. Des phases NiO et spinelles (NiM2O4, M = Cr ou Fe) ont été observées dans les catalyseurs NiM (M = Cr, Fe), et Cr2O3 a été détecté dans le cas de NiCr. Les catalyseurs NiFe présentent une faible activité et sélectivité pour le DRM dans la gamme de température explorée. En revanche, le composé de chrome a montré des conversions intéressantes de CH4 et de CO2 et une sélectivité généralement excellente pour H2 à des températures de réaction basses. Des conversions de CH4 et de CO2 de 18 à 20 % avec H2/CO d'environ 0,7 ont pu être atteintes à des températures aussi basses que 500 °C, mais un comportement transitoire et une désactivation ont été observés à des températures plus élevées ou à des temps de réaction longs. L'excellente activité observée pendant cette séquence transitoire a été attribuée à la stabilisation des particules métalliques de Ni formées pendant la réduction de la phase NiO en raison de la présence de NiCr2O4, ouvrant la voie à l'utilisation de ces matériaux dans des processus périodiques ou en boucle pour le reformage du méthane à basse température.

International audience; 106Ru is a radioactive isotope usually generated by the nuclear industry within power plant reactors. During a nuclear accident, 106Ru reacts with oxygen, leading to the production of highly volatile ruthe- nium tetroxide RuO4. The combination of volatility and radioactivity makes 106RuO4, one of the most radiotoxic species and justifies the development of a specific setup for its capture and immobilization. In this study, we report for the first time the capture and immobilization of gaseous RuO4 within a porousmetal–organic framework (UiO-66-NH2). We used specific installation for the production of gaseous RuO4 as well as for the quantification of this gas trapped within the filtering medium. We proved that UiO-66-NH2 has remarkable affinity for RuO4 capture, as this MOF exhibited the worldwide highest RuO4 decontamination factor (DF of 5745), hundreds of times higher than the DF values of sorbents daily used by the nuclear industry (zeolites or activated charcoal). The efficiency of UiO-66-NH2 can be explained by its pore diameters well adapted to the capture and immobilization of RuO4 as well as its conversion into stable RuO2 within the pores. This conversion corresponds to the reactivity of RuO4 with the MOF organic sub-network, leading to the oxidation of terephthalate ligands. As proved by powder X-ray diffr- action and NMR techniques, these modifications did not decompose the MOF structure.; 106Ru est un isotope radioactif généralement généré par l'industrie nucléaire dans les réacteurs des centrales électriques. Lors d'un accident nucléaire, le 106Ru réagit avec l'oxygène, conduisant à la production de tétroxyde de ruthénium très volatil RuO4. La combinaison de la volatilité et de la radioactivité fait du 106RuO4 l'une des espèces les plus radiotoxiques et justifie le développement d'un montage spécifique pour sa capture et son immobilisation. Dans cette étude, nous rapportons pour la première fois la capture et l'immobilisation de RuO4 gazeux au sein d'uncharpente organométallique (UiO-66-NH2). Nous avons utilisé des installations spécifiques pour la production de RuO4 gazeux ainsi que pour la quantification de ce gaz piégé dans le média filtrant. Nous avons prouvé que UiO-66-NH2 a une affinité remarquable pour la capture de RuO4, car ce MOF présentait le facteur de décontamination RuO4 le plus élevé au monde (DF de 5745), des centaines de fois supérieur aux valeurs DF des sorbants utilisés quotidiennement par l'industrie nucléaire (zéolithes ou charbon activé). L'efficacité de UiO-66-NH2 s'explique par ses diamètres de pores bien adaptés à la capture et à l'immobilisation de RuO4 ainsi que sa conversion en RuO2 stable au sein des pores. Cette conversion correspond à la réactivité du RuO4 avec le sous-réseau organique MOF, conduisant à l'oxydation des ligands téréphtalates. Comme le prouvent les techniques de diffraction des rayons X sur poudre et de RMN, ces modifications n'ont pas décomposé la structure MOF.

International audience; Methane oxidation has been studied on Rh/CexZr1−xO2. Catalytic performances were found highly sensitive to the preparation method of CexZr1−xO2 support. Coprecipitation method leads to the highest conversion and the lowest activation barrier suggesting improved metal-support interaction. In contrast, weak resistance to thermal aging is observed. Finally aged coprecipitated Rh/CexZr1−xO2 mimics the kinetic behavior of catalysts prepared by crystal templating method. Kinetic measurements performed on this latter catalyst show that a single site reaction mechanism is more appropriate compared to dual site mechanism which agrees with the assumption that deactivation of coprecipitated samples would be related to the suppression of the metal-support interface.

International audience; The reactivity of aryl monocarboxylic acids (benzoic, 1- or 2-naphtoic, 4’-methylbiphenyl-4-carboxylic and anthracene-9-carboxylic acids) has been investigated as complexing agent toward the ethoxide niobium(V) (Nb(OEt)5 precursor. A total of 8 coordination complexes has been isolated with distinct niobium(V) nuclearities as well as carboxylates complexation states. The use of benzoic acid gives to a tetranuclear core Nb4(μ2-O)4(L)4(OEt)8] (L = benzoate (1)) exhibiting four Nb-(μ2-O)-Nb linkages in a square plane configuration. A similar tetramer (7) is obtained with 2-naphtoic acid by using a 55% humidity atmosphere synthetic route. Two types of dinuclear bricks has been identified with one central Nb-(μ2-O)-Nb linkages, and differ by the complexation state, with one bridging carboxylate ([Nb2(μ2-O)(μ2-OEt)(L)(OEt)6], with L = 1-naphtoate (3) & L = anthracene-9-carboxylate (5)) or two bridging carboxylate groups ([Nb2(μ2-O)(L)2(OEt)6], with L = 4’-methylbiphenyl-4-carboxylic (4) & L = anthracene-9-carboxylate (6)). An octanuclear moiety [Nb8(μ2-O)12(L)8(η1-L)4-x(OEt)4+x] (with L = 2-naphtoate, x = 0 or 2; 8) has been obtained by using solvothermal route in acetonitrile, and possesses a cubic configuration with niobium centers at each node, linked through 12 μ2-O groups. The formation of the niobium oxo clusters has been characterized by infrared and liquid 1H NMR spectroscopy in order to analyze the esterification reaction, which induce the release of water molecule, which further reacts through oxolation process with niobium atoms, in different {Nb2O}, {Nb4 O4} and {Nb8O12} nuclearities.; a réactivité des acides aryl monocarboxyliques (acides benzoïque, 1- ou 2-naphtoïque, 4'-méthylbiphényl-4-carboxylique et anthracène-9-carboxylique) a été étudiée comme agent complexant vis-à-vis de l'éthoxyde niobium(V) (Nb(OEt) 5 précurseur. Au total, 8 complexes de coordination ont été isolés avec des nucléarités distinctes du niobium(V) ainsi que des états de complexation des carboxylates. L'utilisation de l'acide benzoïque donne à un noyau tétranucléaire Nb4(μ2-O)4(L)4(OEt) 8] (L = benzoate (1)) présentant quatre liaisons Nb-(μ2-O)-Nb dans une configuration de plan carré. Un tétramère similaire (7) est obtenu avec l'acide 2-naphtoïque en utilisant une voie de synthèse en atmosphère à 55 % d'humidité Deux types de briques dinucléaires ont été identifiées avec une liaison centrale Nb-(μ2-O)-Nb, et diffèrent par l'état de complexation, avec un carboxylate pontant ([Nb2(μ2-O)(μ2-OEt)(L) (OEt)6], avec L = 1-naphtoate (3) & L = anthracène-9-carboxylate (5)) ou deux groupes carboxylate pontants ([Nb2(μ2-O)(L)2(OEt)6], avec L = 4'-méthylbiphényl-4-carboxylique (4) & L = anthracène-9-carboxylate (6)). Une fraction octanucléaire [Nb8(μ2-O)12(L)8(η1-L)4-x(OEt)4+x] (avec L = 2-naphtoate, x = 0 ou 2 ; 8) a été obtenue par utilisant la voie solvothermique dans l'acétonitrile, et possède une configuration cubique avec des centres de niobium à chaque nœud, liés par 12 groupes μ2-O. La formation des agrégats oxo de niobium a été caractérisée par spectroscopie RMN 1H infrarouge et liquide afin d'analyser la réaction d'estérification, qui induit la libération de la molécule d'eau, qui réagit ensuite par le processus d'oxolation avec les atomes de niobium, dans différents {Nb2O}, {nucléarités Nb4O4} et {Nb8O12}.

International audience; The reactivity of 2,3-pyridine-dicarboxylic (known as quinolinic or H2qui) acid and 2,5-pyridine-dicarboxylic (known as isocinchomeronic or H2icc) acid has been investigated as a complexing agent toward the niobium(IV) tetrachloride precursor (NbCl4· 2THF) in different organic solvent mixtures. It resulted in the isolation of four crystalline assemblies of mononuclear coordination complexes 1−4 [Nb(HL)4·solvent], where HL is the monoprotonated quinolinate (Hqui) ligand (complexes 1−3) or the monoprotonated isocinchomeronate ligand (complex 4). For each complex, the discrete niobium(IV) center is eightfold coordinated to four oxygen atoms from the deprotonated carboxylate arm and four nitrogen atoms from the pyridine part of the dicarboxyl ligand with a dodecahedral environment [NbO4N4]. The remaining carboxyl arm (either in 3 or in 5 position) remained under its protonated form, leading to neutral [Nb(HL)4] moieties for compounds 1, 2, and 4, or the anionic [Nb(qui)(Hqui)3]− moiety for compound 3. The complexes are observed in various molecular arrangements, involving intercalated solvent molecules such as acetonitrile in compound 1 ([Nb(Hqui)4·0.8(CH3CN)], obtained at room temperature), a mixture of acetonitrile and pyridine in compound 2 ([Nb(Hqui)4·0.7CH3CN·2PYR], obtained via the solvothermal reaction at 80 °C), a mixture of pyridine and triethylamine, in addition with water and chloride species, in compound 3 ([Nb(qui)(Hqui)3·Cl·HPYR·HTEA·1.5H2O], obtained via solvothermal reaction at 80 °C), and N,N-dimethylformamide in compound 4 ([Nb(Hicc)4·6DMF], obtained at room temperature). The d1 configuration expected for the niobium(IV) centers has been analyzed by magnetic measurements, as well as by EPR and XPS. An anti-ferromagnetism transition has been observed at very low temperatures for complexes 1 (3.6 K) and 4 (3.3 K), for which the shortest Nb···Nb interatomic lengths occur.; La réactivité de l'acide 2,3-pyridine-dicarboxylique (appelé quinolinique ou H2qui) et de l'acide 2,5-pyridine-dicarboxylique (appelé isocinchomérone ou H2icc) a été étudiée en tant qu'agent complexant vis-à-vis du précurseur du tétrachlorure de niobium(IV) ( NbCl4· 2THF) dans différents mélanges de solvants organiques. Elle a abouti à l'isolement de quatre assemblages cristallins de complexes de coordination mononucléaire 1−4 [Nb(HL)4·solvant], où HL est le ligand quinoléinate monoprotoné (Hqui) (complexes 1−3) ou le ligand isocinchoméronate monoprotoné (complexe 4 ). Pour chaque complexe, le centre discret du niobium (IV) est coordonné huit fois à quatre atomes d'oxygène du bras carboxylate déprotoné et à quatre atomes d'azote de la partie pyridine du ligand dicarboxylique avec un environnement dodécaédrique [NbO4N4]. Le bras carboxyle restant (soit en position 3 soit en position 5) est resté sous sa forme protonée, conduisant aux groupements neutres [Nb(HL)4] pour les composés 1, 2 et 4, ou anionique [Nb(qui)(Hqui) 3]− groupement pour le composé 3. Les complexes sont observés dans divers arrangements moléculaires, impliquant des molécules de solvant intercalées telles que l'acétonitrile dans le composé 1 ([Nb(Hqui)4.0.8(CH3CN)], obtenu à température ambiante), un mélange d'acétonitrile et de pyridine dans le composé 2 ([Nb(Hqui)4.0.7CH3CN.2PYR], obtenu via le réaction solvothermique à 80 °C), un mélange de pyridine et de triéthylamine, en plus d'eau et d'espèces chlorure, dans le composé 3 ([Nb(qui)(Hqui)3·Cl·HPYR·HTEA·1,5H2O], obtenu par réaction solvothermique réaction à 80 °C), et le N,N-diméthylformamide dans le composé 4 ([Nb(Hicc)4·6DMF], obtenu à température ambiante). La configuration d1 attendue pour les centres de niobium(IV) a été analysée par des mesures magnétiques, ainsi que par EPR et XPS. Une transition anti-ferromagnétique a été observée à très basse température pour les complexes 1 (3,6 K) et 4 (3,3 K), pour lesquels les longueurs interatomiques Nb···Nb les plus courtes se produisent.

Aluminas are strategic materials used in many major industrial processes, either as catalyst supports or as catalysts in their own right. The transition alumina γ-Al2O3 is a privileged support, whose reactivity can be tuned by thermal activation. This study provides a qualitative and quantitative assessment of the hydroxyl groups present on the surface of γ-Al2O3 at three different dehydroxylation temperatures. The principal [AlOH] configurations are identified and described in unprecedented detail at the molecular level. The structures were established by combining information from high-field 1H and 27Al solid-state NMR, IR spectroscopy and DFT calculations, as well as selective reactivity studies. Finally, the relationship between the hydroxyl structures and the molecular-level structures of the active sites in catalytic alkane metathesis is discussed. 61;37

International audience; A non-thermal plasma (NTP) discharge is used in this study for the activation and regeneration of MS-13X pellets packed in a MS-13X & glass beads packed bed dielectric barrier discharge (DBD) reactor. NTP activation (in-situ) of MS-13X efficiently removes the adsorbed carbonaceous compounds and moisture resulting in an improved VOC adsorption. In addition, NTP exposure is used for the regeneration of the used MS-13X for cycled storage and discharge (CSD) removal of VOC from air. The amount of adsorbed toluene, products formed and the surface and bulk properties of the regenerated used MS-13X shows complete regeneration of used MS-13X. Finally, the stability of MS-13X during 10 cycles of CSD shows no degradation in performance. Thus, NTP exposure is proven to be successful for both the activation and regeneration of MS-13X pellets used for cyclic CSD process.

Light olefins are important feedstocks and platform molecules for the chemical industry. Their synthesis has been a research priority in both academia and industry. There are many different approaches to the synthesis of these compounds, which differ by the choice of raw materials, catalysts and reaction conditions. The goals of this review are to highlight the most recent trends in light olefin synthesis and to perform a comparative analysis of different synthetic routes using several quantitative characteristics: selectivity, productivity, severity of operating conditions, stability, technological maturity and sustainability. Traditionally, on an industrial scale, the cracking of oil fractions has been used to produce light olefins. Methanol-to-olefins, alkane direct or oxidative dehydrogenation technologies have great potential in the short term and have already reached scientific and technological maturities. Major progress should be made in the field of methanol-mediated CO and CO2 direct hydrogenation to light olefins. The electrocatalytic reduction of CO2 to light olefins is a very attractive process in the long run due to the low reaction temperature and possible use of sustainable electricity. The application of modern concepts such as electricity-driven process intensification, looping, CO2 management and nanoscale catalyst design should lead in the near future to more environmentally friendly, energy efficient and selective large-scale technologies for light olefin synthesis. 51

International audience; Coordination compounds Pd(L1)Cl2, Pd(L2)Cl2, and Pd(L3)Cl2 have been synthesized fromoptically pure α-amino-oxime ligands L1–L3 based on (R)-limonene. Structures of the new palladiumcomplexes are characterized and described by NMR spectroscopy and X-rays. These α-amino-oximeligands were then evaluated in the palladium-catalysed allylation of 1,3-dioxo compounds.; Les complexes Pd(L1)Cl2, Pd(L2)Cl2, et Pd(L3)Cl2 ont été synthétisés à partir des ligands α-amino-oxime L1-L3 issus du (R)-limonene. Ces nouveaux complexes de palladium ont été carracté-risés par RMN et diffraction aux rayons X. Les ligands α-amino-oxime associés à des précurseurs depalladium ont été évalués sur des réactions d’alkylation allylique.

International audience; The uranium and plutonium co-conversion process constitutes a continuous subject of interest for MOx fuel fabrication. Among the various routes considered, chemical coprecipitation by the salt effect has been widely investigated regarding its simplicity of integration between the partitioning and purification steps of the PUREX process, and the straightforward recovery of precursors that are easily converted into oxide phases by thermal decomposition. The present study focuses on the coprecipitation behavior of U–Th and U–Pu actinide peroxide mixed systems by examining the precipitation yields and settling properties for nitric acidity in the range of 1 to 3 M and hydrogen peroxide concentration in the range of 4.5 to 7 M. The precipitated solids have been characterized by powder XRD, IR and Raman spectroscopy, laser granulometry and SEM-EDS analyses revealing the synthesis of studtite and actinide(IV) peroxo-nitrates as aggregated particles. The actinide solid phases are uniformly distributed within the filtered cakes. The precursor thermal decomposition results in the formation of oxide phases at low temperature according to a sequential release of water molecules, peroxide ligands and nitrate ions. The calcination step has a limited effect on the morphology of the powders which remain highly divided. The high precipitation rate of actinides makes this chemical route potentially interesting as a co-precipitation process.

International audience; The hydrophobicity of oils is a key parameter to design surfactant/oil/water (SOW) macro-, micro-, or nano-dispersed systems with the desired features. This essential physicochemical characteristic is quantitatively expressed by the equivalent alkane carbon number (EACN) whose experimental determination is tedious since it requires knowledge of the phase behavior of the SOW systems at different temperatures and for different surfactant concentrations. In this work, two mathematical models are proposed for the rapid prediction of the EACN of oils. They have been designed using artificial intelligence (machine-learning) methods, namely, neural networks (NN) and graph machines (GM). While the GM model is implemented from the SMILES codes of a 111-molecule training set of known EACN values, the NN model is fed with some σ-moment descriptors computed with the COSMOtherm software for the 111-molecule set. In a preliminary step, the leave-one-out algorithm is used to select, given the available data, the appropriate complexity of the two models. A comparison of the EACNs of liquids of a fresh set of 10 complex cosmetic and perfumery molecules shows that the two approaches provide comparable results in terms of accuracy and reliability. Finally, the NN and GM models are applied to nine series of homologous compounds, for which the GM model results are in better agreement with the experimental EACN trends than the NN model predictions. The results obtained by the GMs and by the NN based on σ-moments can be duplicated with the demonstration tool available for download as detailed in the Supporting Information.

The glycerol oxidation reaction was developed leading to selective catalysts and optimum conditions for the production of carboxylic acids such as glycolic acid. However, carboxylic acids are produced in highly diluted mixtures, challenging the recovery and purification, and resulting in high production costs, polymerization, and thermal degradation of some of the products. The protection of the acid function by esterification reaction is one of the most promising alternatives through reactive distillation (RD); this technique allows simultaneously the recovery of carboxylic acids and the elimination of most part of the water. The reactive distillation, experimental and simulation, of glycolic acid was performed, based on kinetic and thermodynamic models developed. For the thermodynamic model, binary parameters of the missing couples were determined experimentally, and the non-random two-liquid (NRTL) model was selected as the most suitable to represent the binary behavior. The kinetic study of the esterification in the presence of homogeneous and heterogeneous catalysis concluded that the heterogeneous reaction can be accurately described either by a pseudo-homogeneous model or the Langmuir–Hinshelwood (L-H) adsorption model. Reactive distillation was conducted in a distillation column filled with random packing sulfonated ion-exchange resin, Nafion NR50®, or with extruded TiO2-Wox. The conversion rate of glycolic acid in reactive distillation increases from 14% without catalyst to 30% and 36% using Nafion NR50® and TiO2-Wox, respectively. As opposed to the batch reactor study, the conversion rate of glycolic acid was better with TiO2-Wox than with sulfonated ion-exchange resin. The better performance was related to an increase in the hydrodynamics inside the column. Tests using water in the feed confirm the hypothesis by increasing the conversion rate because of the decrease in the mass transfer resistance by reducing the average diffusion coefficient. The simulation of the reactive distillation column with ProSim® Plus showed that the yield of the ester increased operating at a low feed rate with reactive stripping. In the presence of water in the feed, nonreactive stages are required, including an enrichment region to separate water vapor.

International audience; The effect of metal and support acidity on the hydroconversion of dimeric aryl ethers, used as model molecules for lignin, is still under debate, both in terms of hydrogenolysis (cleavage of the ether bond) and formation of by-products (coupling of aromatic monomers to dimers by alkylation reaction). Their role is investigated here in the conversion of three typical molecules representative of the α-O-4, β-O-4, and 4-O-5 ether linkages of lignin, respectively, benzyl phenyl ether (BPE), phenethoxybenzene (PEB), and diphenyl ether (DPE), at 503 K, under 18 bar of H2 in decalin. Ru- and Pd-based catalysts were synthesized on non-acidic SiO2 and on acidic HZSM5. Under these reaction conditions, the conversion of the ethers over the bare supports was observed in the presence of acidic sites; the effect decreased as the ether bond strength increased. The results also suggest that the product distribution is directly affected both by the support acidity and by the oxophilicity of Ru. Alkylated products from isomerization reactions, which are reported to be formed only over acidic sites, were also produced on the surface of the Ru nanoparticles.

International audience; The present work reports the impregnation of palladium (Pd) or platinum (Pt) on hierarchical porous zeolite catalysts for Volatile Organic Compounds (VOCs) oxidation. The hierarchical porous zeolite (NaYmod) was synthesized via a top-down approach to incorporate mesoporosity into the microporous zeolite NaY. This process was achieved through a three steps synthesis: dealumination, desilication and alkaline treatment. 0.5 wt% of Pd and Pt precursors were then added to NaY and NaYmod supports by wet impregnation in order to elaborate efficient catalysts for the total oxidation of two types of VOCs, ethanol and toluene, which are probe molecules for oxygenated VOCs and BTEX compounds respectively. The supported and unsupported samples were characterized by X-Ray Diffraction (XRD), N2-physisorption, Transmission Electron Microscopy (TEM), and X-Ray Photoelectron Spectroscopy (XPS). The modified mesostructured support ensures a better dispersion of the active phases and led to a partial presence of highly reactive Pt(II) species in the case of platinum-based samples. Whatever the oxidation reaction, these latter demonstrate higher conversions compared to palladium-based ones. The presence of Pt(II) species provided a high catalytic performance, with a total degradation of both VOC probe molecules at temperatures lower than 170 °C. Such temperatures have not been recorded before for NaY supported materials.; Le présent travail rapporte l'imprégnation de palladium (Pd) ou de platine (Pt) sur des catalyseurs zéolitiques poreux hiérarchiques pour l'oxydation des composés organiques volatils (COV). La zéolithe poreuse hiérarchique (NaYmod) a été synthétisée via une approche descendante pour incorporer la mésoporosité dans la zéolithe microporeuse NaY. Ce processus a été réalisé par une synthèse en trois étapes : désalumination, désilication et traitement alcalin. 0,5 % en poids de précurseurs de Pd et Pt ont ensuite été ajoutés aux supports NaY et NaYmod par imprégnation humide afin d'élaborer des catalyseurs efficaces pour l'oxydation totale de deux types de COV, l'éthanol et le toluène, qui sont des molécules sondes pour les COV oxygénés et les composés BTEX respectivement. Les échantillons supportés et non supportés ont été caractérisés par diffraction des rayons X (XRD), physisorption du N2, microscopie électronique à transmission (TEM) et spectroscopie photoélectronique à rayons X (XPS). Le support mésostructuré modifié assure une meilleure dispersion des phases actives et a conduit à une présence partielle d'espèces Pt(II) hautement réactives dans le cas des échantillons à base de platine. Quelle que soit la réaction d'oxydation, ces derniers présentent des conversions plus élevées par rapport aux échantillons à base de palladium. La présence d'espèces de Pt(II) a fourni une performance catalytique élevée, avec une dégradation totale des deux molécules sondes de COV à des températures inférieures à 170 °C. De telles températures n'ont pas été enregistrées auparavant pour les échantillons de Pt(II). De telles températures n'ont pas été enregistrées auparavant pour les matériaux supportés par le NaY.

International audience; Redox-flow batteries are relevant to store energy from intermittent sources such as solar panels or wind turbines, thereby smoothing their energy supply. Up to now, most redox-flow batteries are based on vanadium. Vanadium is a rare and expensive material, thus recent research has focused on redox-flow batteries based on organic compounds and, in particular, anthraquinones as electroactive materials. However, the tunability of organic chemistry poses a needle-in-haystack challenge as the structures exhibiting the most desirable electrochemical properties may be hard to pinpoint. Moreover, the low water solubility of the most readily available anthraquinones may hinder their use as battery electrolytes. To aid in such endeavor, a theoretical approach is proposed to predict Pourbaix diagrams of redox-active organic compounds, allowing in silico anticipation of their electrochemical behavior in the entire pH range. DFT/COSMO-RS predicted pKa and reduction potentials are in good agreement with experimental data, and the resulting calculated Pourbaix diagrams are also in agreement with 4 experimental ones from literature, proving the reliability of the method. Finally, the effect of nature and position of some functional groups on the anthraquinone backbone is discussed, illustrating the power of the method to both understand and quantify the electrochemical activity of redox active organic materials.

International audience; Herein we report the original Ba10Fe7.75Zn5.25S18Si3O12 oxysulfide which crystallizes in a new structural type. Contrary to the usual oxychalcogenides, it crystallizes with a non-centrosymmetric 3D spatial network structure built from large magnetic clusters consisting of twelve (Fe2+/3+/Zn)S3O tetrahedra decorating a central Fe2+S6 octahedron and exhibiting a spin glass state

International audience; In recent years, the hydrothermal conversion of actinide (IV) oxalates into nanometric actinide dioxides (AnO2) has begun to be investigated as an alternative to the widely implemented thermal decomposition method. We present here a comparison between the hydrothermal and the conventional thermal decomposition of Pu(IV) oxalate in terms of particle size, morphology and residual carbon content. A parametric study was carried out in order to define the temperature and time applied in the hydrothermal conversion of tetravalent Pu-oxalate into PuO2 and to optimize the reaction conditions

International audience

Hydrogenation into light olefins is an attractive strategy for CO2fixation into chemicals. In this article, high throughput experimentation and extended characterization were employed to identify the most efficient promoters and to elucidate structure-performance correlations and reaction paths in the CO2hydrogenation to light olefins over zirconia-supported iron catalysts. K, Cs, Ba, Ce, Nb, Mo, Mn, Cu, Zn, Ga, In, Sn, Sb, Bi, and V were added in the same molar concentrations to zirconia-supported iron catalyst and evaluated as promoters. The CO2hydrogenation proceeds via intermediate formation of CO followed by surface polymerization. Over the iron catalysts containing alkaline promoters, initially higher selectivity to light olefins shows a significant decrease with the CO2conversion, because of further surface polymerization and the formation of longer chain hydrocarbons. A relatively low selectivity to light olefins over the promoted catalysts, without potassium, is not much affected by the CO2conversion. Essential characteristics of iron catalysts to obtain a higher yield of light olefins seem to be a higher iron dispersion, a higher extent of carbidization, and optimized basicity. The strongest promoting effect is reported for the alkaline metals. A further increase in the light olefin selectivity is observed after simultaneous addition of potassium with copper, molybdenum, gallium, or cerium.

International audience; Topoisomerases, targets of inhibitors used in chemotherapy, induce DNA breaks accumulation leading to cancer cell death. A newly synthesized copper(II) indenoisoquinoline complex WN197 exhibits a cytotoxic effect below 0.5 µM, on MDA-MB-231, HeLa, and HT-29 cells. At low doses, WN197 inhibits topoisomerase I. At higher doses, it inhibits topoisomerase IIα and IIβ, and displays DNA intercalation properties. DNA damage is detected by the presence of γH2AX. The activation of the DNA Damage Response (DDR) occurs through the phosphorylation of ATM/ATR, Chk1/2 kinases, and the increase of p21, a p53 target. WN197 induces a G2 phase arrest characterized by the unphosphorylated form of histone H3, the accumulation of phosphorylated Cdk1, and an association of Cdc25C with 14.3.3. Cancer cells die by autophagy with Beclin-1 accumulation, LC3-II formation, p62 degradation, and RAPTOR phosphorylation in the mTOR complex. Finally, WN197 by inhibiting topoisomerase I at low concentration with high efficiency is a promising agent for the development of future DNA damaging chemotherapies.

Two new oxyfluorides with a pyrochlore-type structure, Na2Nb2O5F2 and Na2Ta2O5F2, have been obtained, and for which the XRD crystallographic study coupled with 19F solid state NMR reveals an unusual O/F distribution.

International audience; Monolith-shaped three-way catalysts (TWC) are always at the edge of science and technology as a response to the stringent updates on the emission standards worldwide. In spite of rapid research on TWC materials, the exact compositions adapted by major automotive companies are not fully known. This study focuses on comparing two fresh commercial monolithic catalysts for gasoline engines, namely, monolith-A and monolith-B, to highlight the significance of their manufacturing strategies by its characterization and catalytic evaluation under realistic lean/rich/stoichiometric regimes. Firstly, monolith-A demonstrates a zoning on its front and back side with high Pd and Rh loading to enhance CO/HC oxidation and NOx reduction, respectively, having higher amounts of trace dopants like La, Y, Pr and S. Whereas, monolith-B has a homogeneous composition with much lower noble metal/trace elements content without any Pr and S. Secondly, the double-layer washcoating is employed by following different routes with distinct compositions of alumina and ceria-zirconia. Monolith-B showed better low temperature CO oxidation performance while monolith-A performed better for NOx reduction owing to higher Rh loading. Overall, the zoning strategy of monolith-A raises question on its cost effectiveness in regards to its performance while poor reduction capabilities is exhibited by monolith-B. This study highlights that the latest TWC strategies have a scope of further development particularly with respect to the catalytic performance/expense ratio.

Les cyclodextrines (CD) sont des oligosaccharides cycliques utilisées dans de nombreux domaines. Le greffage de polymères sur les CD permet d'obtenir de nouvelles structures et applications. Le polylactide (PLA) est un polyester aliphatique biosourcé et biocompatible qui peut être greffé sur des CD par polymérisation par ouverture de cycle initiée par -OH. En utilisant la 4-diméthylaminopyridine (DMAP) comme organocatalyseur, une fonctionnalisation quantitative est atteinte sur les α-, β-, γ- et 2,3-diméthyl- β-cyclodextrines natives. Des distributions étroites de poids moléculaire sont obtenues avec les CD natifs (dispersité < 1.1). La combinaison DMAP/β-CD est utilisée comme étude de cas, et la formation d'un complexe d'inclusion (1/1) est montrée pour la première fois dans la littérature, qui est entièrement caractérisé par RMN. L'inclusion du DMAP dans la cavité se produit via le bord secondaire du β-CD et la constante d'association (Ka) est estimée à 88,2 M-1. Son utilisation comme initiateur de polymérisation par ouverture de cycle conduit à une efficacité de fonctionnalisation partielle, et donc à un conjugué β-CD-PLA plus hydrophile que celui obtenu à partir de β-CD natif. Les résultats de la polymérisation incluant également l'utilisation du complexe d'inclusion adamantane/β-CD comme initiateur suggèrent que l'inclusion du catalyseur DMAP dans le CD ne peut pas se produire pendant les réactions de polymérisation. Le rac-lactide ne forme pas de complexe d'inclusion avec le β-CD. Cyclodextrins (CDs) are cyclic oligosaccharides used in many fields. Grafting polymers onto CDs enables new structures and applications to be obtained. Polylactide (PLA) is a biobased, biocompatible aliphatic polyester that can be grafted onto CDs by -OH-initiated ring-opening polymerization. Using 4-dimethylaminopyridine (DMAP) as an organocatalyst, a quantitative functionalization is reached on native α-, β-, γ- and 2,3-dimethyl- β-cyclodextrins. Narrow molecular weight distributions are obtained with the native CDs (dispersity < 1.1). The DMAP/β-CD combination is used as a case study, and the formation of an inclusion complex (1/1) is shown for the first time in the literature, which is fully characterized by NMR. The inclusion of DMAP into the cavity occurs via the secondary rim of the β-CD and the association constant (Ka) is estimated to be 88.2 M−1. Its use as an initiator for ring-opening polymerization leads to a partial functionalization efficiency, and thus a more hydrophilic β-CD-PLA conjugate than that obtained starting from native β-CD. Polymerization results including also the use of the adamantane/β-CD inclusion complex as an initiator suggest that inclusion of the DMAP catalyst into the CD may not occur during polymerization reactions. Rac-lactide does not form an inclusion complex with β-CD. 27;3

BaCoX 2O7 (X = As, P) are built on magnetic 1D units in which strong aperiodic undulations originate from incommensurate structural modulations with large atomic displacive amplitudes perpendicular to the chain directions, resulting in very unique multiferroic properties. High-pressure structural and vibrational properties of both compounds have been investigated by synchrotron X-ray powder diffraction and Raman spectroscopy at room temperature and combined with density functional calculations. A structural phase transition is observed at 1.8 GPa and 6.8 GPa in BaCoAs2O7 and BaCoP2O7, respectively. Sharp jumps are observed in their unit-cell volumes and in Raman mode frequencies, thus confirming the first-order nature of their phase transition. These transitions involve the disappearance of the modulation from the ambient-pressure polymorph with clear spectroscopic fingerprints, such as reduction of the number of Raman modes and change of shape on some peaks. The relation between the evolution of the Raman modes along with the structure are presented and supported by density functional theory structural relaxations.

Le développement des futures bioéconomies françaises et européennes passe par la mise au point de nouveaux procédés de chimie verte dans lesquels les transformations catalytiques sont essentielles. L'équipe VAALBIO (valorisation des alcanes et de la biomasse) du laboratoire UCCS (Unité de Catalyse et Chimie du Solide) travaille sur différents procédés catalytiques, soit en développant de nouveaux catalyseurs et/ou en concevant l'ensemble des procédés catalytiques. Nos recherches portent à la fois sur les aspects fondamentaux et appliqués de ces procédés. Dans cet article de revue, nous présentons les principaux sujets développés par notre équipe en nous concentrant principalement sur les procédés liés à l'oxygène et à l'hydrogène, ainsi que sur la production d'hydrogène vert et la catalyse hybride. Les impacts sociaux de la bioéconomie sont également abordés en appliquant le concept de la boussole institutionnelle. The development of the future French and European bioeconomies will involve developing new green chemical processes in which catalytic transformations are key. The VAALBIO team (valorization of alkanes and biomass) of the UCCS laboratory (Unité de Catalyse et Chimie du Solide) are working on various catalytic processes, either developing new catalysts and/or designing the whole catalytic processes. Our research is focused on both the fundamental and applied aspects of the processes. Through this review paper, we demonstrate the main topics developed by our team focusing mostly on oxygen- and hydrogen-related processes as well as on green hydrogen production and hybrid catalysis. The social impacts of the bioeconomy are also discussed applying the concept of the institutional compass. 27;12

International audience; COF-LZU1 with nanotube-like morphology has been synthesized with high crystallinity and pore volume in the presence of trimesic acid as a template. The as-synthesized COF nanotubes consist of a stack of plates with a diameter of about 100 nm with a hollow channel inside of about 20 nm.

International audience; Among all the proposed catalytic systems (new supports, synthesis post-treatment, change of transition metal, multi-metallic catalysts, etc.) for the methane dehydroaromatization, the initial Mo/ZSM-5 has remained one of the best suitable catalysts, despite its lack of deep understanding. The catalyst evolves throughout four successive stages: calcination, activation, induction, and deactivation. By studying the balance influence between the acid and metal functions throughout its lifetime, the molybdenum and carbon species could be localized, quantified, and identified as well as their roles. An optimal compromise was then established where the catalyst is composed of 4 wt% Mo with the highest possible acidity. Below these targets, the catalysts with minimal Mo content and low Brønsted acidity display poor catalytic performances, whereas zeolite amorphization occurs during the early stages of the reaction independently of the zeolite acidity once the Mo loading exceeds the optimal value.

International audience; This work investigates batch and continuous-flow heterogeneous catalytic hydrogenation of a mixture of cafestol and kahweol (C&K) to obtain pure cafestol. These diterpenes were extracted from green coffee beans, and hydrogenation was performed using well-established palladium catalysts (Pd/C, Pd/CaCO3, Pd/BaSO4, and Pd/Al2O3) and a carbon black-supported Pd catalyst coated by a covalently tethered SiO2 shell with mesoporous texture (Pd/CB@SiO2), all partially deactivated with quinoline. Pd/C 10% poisoned with 1 wt % quinoline gave the best result for batch reaction, producing cafestol from kahweol with high selectivity (>99%) after 10 min. Excellent selectivity was also obtained with the catalyst Pd/CB@SiO2 with only 1% Pd. In addition, Pd/C-quinoline adapted for continuous-flow experiments exhibited the best catalytic activity, also providing cafestol with excellent selectivity (>99%) after 9.8 s.