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SSCI-VIDE+CARE+VML; International audience; In aircrafts, outside air is not directly fed to passengers, because it contains high ozone concentration at elevated altitudes. Catalytic converters are thus necessary to lower ozone concentration to authorized values. Such equipments already exist but have to evolve to take into account the energetic constraints of more electrical aircrafts. Concretely, ozone reduction has to be performed efficiently at temperatures lower than 100°C, so that the ozone concentration of fresh air entering the aircraft cabin does not exceed 100 ppb (for 3 hours) and 250 ppb instantly.To improve the ozone converter efficiency, different solutions car arise from catalyst and/or reactor optimisation, keeping in mind that the pressure drop must be kept very low.In this study, a focus was made on the reactor configuration, using a single commercial catalyst coated on different structures in order to find the best trade off between pressure drop and mass transfer efficiency.

International audience; The term LOHC stands for Liquid Organic Hydrogen Carriers. The term has been so well accepted by the scientific community that the studies published before the existence of this name are not very visible. In this mini-review, we have tried to rehabilitate various studies that deserve to be put back in the spotlight in the present context. Studies indeed began in the early 1980s and many publications have compared the use of various organic carriers, various catalysts and reactors. Recent reviews also include the economic aspects of this concept.

International audience; This work describes the development of easy to prepare cobalt nanoparticles (NPs) in solution as promising alternative catalysts for alkene hydrosilylation with the industrially relevant tertiary silane MDHM (1,1,1,3,5,5,5-heptamethyltrisiloxane). The Co NPs demonstrated high activity when used at 30 °C for 3.5-7 h in toluene, with catalyst loadings 0.05-0.2 mol%, without additives. Under these mild conditions, a set of terminal alkenes were found to react with MD H M, yielding exclusively the anti-Markovnikov product in up to 99% yields. Additionally, we demonstrated the possibility of using UV irradiation to further activate these cobalt NPs in order to enhance their catalytic performances, but also to promote tandem isomerization-hydrosilylation reactions using internal alkenes, among them unsaturated fatty ester (methyl oleate), to produce linear products in up to quantitative yields.

This article presents an experimental kinetic study of the Suzuki&ndash, Miyaura reaction of 4-iodoacetophenone with phenylboronic acid catalyzed by the Herrmann&ndash, Beller palladacycle. This catalyst, together with the solvent (ethanol) and the base (sodium methylate), were chosen to ensure catalyst stability and reactants solubility all along the reaction. Based on the study of initial reaction rates, a quasi-first-order was found for 4-iodoacetophenone with a first-order dependence on the initial concentration of palladium. A zero-order was found for the base and the phenylboronic acid. The oxidative addition step of the mechanism was thus considered as the rate determining step. A global rate law was derived and validated quantitatively. A global activation energy, with an average value of ca. 63 kJ/mol was determined.

International audience; (C.d.B.); Tel.: +33-4-72-43-1755 (V.M.) † These authors contributed equally to this work. Abstract: A critical review of conclusions about the putative heterogeneous mechanism in the Suzuki-Miyaura coupling by supported Pd solids is reported. In the first section, the turnover frequencies (TOF) of 20 well-established homogeneous catalysts are shown to be in the range 200 to 1,000,000,000 h −1. The evidences used to prove a heterogeneous mechanism are discussed and another interpretation is proposed, hypothesizing that only the leached species are responsible for the catalytic reaction, even at ppb levels. Considering more than 40 published catalytic systems for which liquid phase Pd content have been reported, activities have been computed based on leached Pd concentrations and are shown to be in the range TOF 150 to 70,000,000 h −1. Such values are compatible with those found for the well-established homogeneous catalysts which questions the validity of the conclusions raised by many papers about the heterogeneous (solid) nature of Suzuki-Miyaura catalysis. Last, a tentative methodology is proposed which involves the rational use of well-known tests (hot-filtration test, mercury test.. .) to help to discriminate between homogeneous and heterogeneous mechanisms.

International audience; The homogeneous vs heterogeneous contributions when using solid catalysts for the Suzuki-Miyaura coupling is still disputed. Leaching is often observed and quantified albeit with unclear conclusions about contributions of the leached species and of the solid catalyst to the global catalytic activity. In this work, a new flow reactor design to discriminate both contributions is proposed. With the help of a simple reactor model, it has been possible to conclude that the coupling of 4-iodoacetophenone with phenylboronic acid proceeded with the leached homogeneous species only, whatever the solid Pd/silica used, whereas chloro-derivatives behaves differently. This reactor is simple to build and could be of general use to reveal actual heterogeneous vs homogeneous catalysis for many reactions. Keywords Suzuki-Miyaura · Heterogeneous · Leaching · Palladium The knowledge of the reaction location is of prime importance both to design efficient industrial processes and to understand the underlying fundamental mechanisms. For example, many catalytic processes are operated with heterogeneous (solid) catalysts for easier separation and downstream treatments thus to lower operating costs. However, when the fluid phase is a liquid, it appears that the knowledge of the reaction location is not straightforward. Indeed, active catalytic species may leach from the solid, which is then a simple catalyst precursor, and solubilizes in the liquid phase in which it catalyzes the reaction. Several papers including recent reviews have analyzed such situations for many different type of catalytic processes.[1,2] One must realize that the design of a catalytic reactor is largely based on the assumption of the reaction location simply because the reaction time, i.e. the contact time between the

International audience; An Ir(NHC) supported catalyst is used in the selective hydrogenation of terpinen-4-ol to cis p-menthan-4-ol. Its activity, selectivity and stability are compared to those of a homogeneous homologue [IrCl(COD)MesImPr] and to a commercial Pd/C. The solid Ir catalyst is much more selective than the Pd catalyst (92 vs. 42% at 80°C) but also more active, more selective and more stable than the iridium complex in solution. For the first time, a supported catalyst shows an enhanced activity with respect to a complex in a diastereoselective hydrogenation reaction.

A catalyst containing small (ca. 2.5 nm) and crystalline Pt nanoparticles embedded into the walls of a mesostructured silica framework was found to be highly active in alkene hydrosilylation reaching TONs of ca. 105. More importantly, no Pt leaching was detected. This result is remarkable because Pt leaching is a recurrent problem in alkene hydrosilylation, which often prevents heterogeneous catalysts from being used industrially. This result is in contrast to the significant Pt leaching observed for other Pt/SiO2 catalysts.

The reverse flow adsorber (RFA) can be used as a catalytic reactor for homogeneous catalysis to avoid the issues of catalyst separation. The RFA combines the reverse flow circulation and the separation of the dissolved solute from the liquid homogeneous mixture. In this work, the RFA is modeled and simulated in order to evaluate its separation performances and its behavior. The studied adsorber is a single adsorption/desorption packed bed, and the reversal of flows is applied to keep the solute inside the bed as longer as possible while minimizing its outlet concentration (leaching). The chosen one dimensional model accounts for the axial dispersion and the non-equilibrium effects (mass transfer resistances, etc). The numerical method of lines (MOL) is used to solve the partial differential algebraic model equations (PDAEs). Two cases are studied; the first one is the dynamic of the homogeneous solute concentration starting from a pre-loaded column and without solute addition. The second case considers operations with continuous solute side stream addition. In the first case, leaching persists until the initially pre-loaded adsorption column with solute is completely emptied thus demonstrating unsteady-state operations in contrast with previous works. To compensate leaching, solute makeup is added at the center of the column. This leads, after priming a number of cycles, to a stationary periodic state operation.

International audience; tel: +33 (0)4 72 43 17 55 ­ Fax: +33 (0)4 72 43 16 73 The deposition of TiO 2 ­P25 on Pyrex glass is studied in order to propose a procedure for obtaining uniform and adherent thin films with a controlled thickness in the range between fractions of micrometer to a few tens of micrometers. Different deposition methods such as spray­coating, dip­coating and drop­coating of liquid suspensions of TiO 2 ­P25 powder are considered. The effect of pretreatment of the glass support, as well as post­deposition steps such as drying condition and thermal treatment are also reported. A basic glass pretreatment and an acidic TiO 2 suspension are chosen for an optimized adherence of the film. Drop­coating, associated with a slow drying under 55% relative humidity and a high temperature thermal treatment is the method of choice to prepare coated glass slides in a large range of film thicknesses.

The structure of polysiloxane copolymers obtained by hydrosilylation of 1-octene with polymethylhydrosiloxane (PMHS) was analyzed by 29Si NMR spectroscopy and revealed a tendency to form block copolymers. Although all the platinum catalysts that were used showed a tendency to form some block structures, only Karstedt catalyst led to well defined block copolymers. However, the tacticity of these copolymers could not be determined using Heteronuclear Multiple Bond Correlation (HMBC) 2D (1H/ 29Si) NMR technique. The following criteria were found to affect the structure of the hydrosilylation product: low SiH conversion, the “age” of the Karstedt catalyst (low TON) and high octene/SiH ratios.

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The deactivation and regeneration of Pd/carbon coated support catalysts, used during nitrobenzene hydrogenation, were studied. Three methods have been tested: electrochemical treatment, chemical oxidation and oxygen plasma treatment. The regenerated catalysts were characterized by physisorption of nitrogen (BET method) and were compared with the activities of fresh catalysts. It was found that the electrochemical treatment allows the complete regeneration of the catalyst, without any modification of textural properties. Simple chemical oxidation did not allow the activity recovery of Pd catalysts and led to modification of the textural properties of carbon. Finally, the catalyst may be regenerated also by plasma method, albeit with some increase of the pore diameter.

An original process based on cold plasma assisted polymerization of tetramethyldisiloxane (TMDSO) in the presence of O 2 was developed to cover substrates showing various shapes (plate and foam). In the frame of catalytic application, this coating has to act as a bonding layer for the deposition of active phase such as VO x/TiO 2 well-known for its properties in NO x and volatile organic compounds abatement and in the production of chemical intermediates. Good results were obtained by the deposition of a 5- lm thick polysiloxane film followed by a thermal treatment under air at 650 8C and by a remote nitrogen plasma post treatment. This procedure led to a silica-like layer allowing its coating in an aqueous suspension of TiO 2. Such a multilayered material can be obtained homogeneously on the whole surface of a sample showing a 3D open geometry like metallic foam. Characterizations of the different steps of the elaborated multilayer material were performed by Fourier transformed infrared spectroscopy, Raman spectrometry, X-ray photoelectron spectroscopy, and electron probe micro-analyzer. POLYM. ENG. SCI., 51:940– 947, 2011. a2011 Society of Plastics Engineers

Two model reactions were used to show the influence of catalytic foams on improving heat transfer. The catalytic performances were compared to those observed when using the same reactors packed with catalytic powder or beads. One reaction was the exothermic oxidative dehydrogenation of propane which was investigated on 7%V2O5/TiO2 coated on stainless steel foam. A silica layer was first deposited on the foam surface by Remote Plasma Enhanced Chemical Vapour Deposition to avoid poisoning of active phase by iron species, to favour the anchoring of TiO2 support and to accommodate the difference of dilatation coefficients. When comparing catalytic foams with powders in the same reactor, the selectivity to propene at isoconversion was higher by 12–45 mol% for the same amount and composition (7%V2O5/TiO2) of the active phase and in the same operating conditions (contact time, C3/O2 ratio, temperature range). The other reaction was the endothermic dehydrogenation of methylcyclohexane on 2%Pt/Al2O3 directly coated on foams and on molecular sieve beads. To study the influence of heat and mass transfers, the material (FeCrAlloy or alumina) and porosity (81–97%) of foams were varied. It was found that, even for highly exothermic or endothermic reactions not limited by external transport, the coated foams significantly increased the effective conductivity of catalytic beds, the denser foam leading to higher effective conductivity.

International audience; Viscosities of the ternary and binary mixtures of 1-octene, Rhodorsil H68, Rhodorsil 308V750 have been measured at different temperatures between 293.15 and 353.15 K and at atmospheric pressure. Two correlations were established to predict the viscosity of all mixtures. The first is a statistical expression deduced from an experimental design. The second is based on an additivity law and the temperature effect on binary mixtures.

Catalytic structured reactors are designed to improve both heat and mass transfers during reactions in the presence of catalytic layers. The know-how acquired in the coating of stainless steel walls by catalytic layers of VO x /TiO 2 , active in the abatement of volatile organic compounds and in the production of chemical intermediates, was extended to metallic foams. The preferred and original way was to first make a deposit of a silica-like primer by cold plasma assisted polymerization of tetramethyldisiloxane in the presence of oxygen. After mineralisation, this layer was supposed to act as a barrier against poisoning by elements of the metallic substrate, as well as a stabilizer of the catalyst layers. The cells of the foam were homogeneously covered by a 5 μm-thick polysiloxane film ending in ca. 1 μm thick silica after calcination. After studying the textural properties and zeta potential of aqueous suspensions of TiO 2 particles, the silica-coated foams were dipped in a 37 wt.% aqueous suspension of TiO 2 -anatase. The final VO x /TiO 2 /SiO 2 /foams were obtained by grafting polyvanadate specie in sol–gel medium. At every step of coating, the multilayer materials were studied mainly by X-ray Photoelectron Spectroscopy and Electron Probe Micro-Analysis. Moreover the mechanical and chemical stability of the successive coatings was checked.

International audience; The catalytic total oxidation of toluene is used to bring the required calories to restore hydrogen from methylcyclohexane (MCH). Two coupled reactions, both catalyzed by Pt/alumina, are thus considered in one autothermal heat-exchanger reactor (HER): endothermic dehydrogenation of methylcyclohexane and catalytic combustion of less than 10% of produced toluene (6% for the chemical reaction, about 4% for heat losses). Both reactions are carried out at 350 °C. Methylcyclohexane and toluene light-off curves have been performed in one elementary module. Methylcyclohexane combustion has been eliminated due to its safety drawbacks, although the MCH combustion provides best stability to autothermal HER.

International audience; Different types of aqueous TiO2-P25 suspensions were prepared and their properties, including rheological behaviour and zeta potential, were studied. Then, TiO2 suspensions were used to elaborate TiO2 coatings on various substrates (cordierite monolith, stainless steel plates and beta-SiC foam) using a dip-coating method. The relationship between the suspension stability and the coating adhesion has been considered. The structural and morphological characterisation of TiO2 coatings has been performed using scanning electron microscopy, X-ray diffraction and other methods. Finally, the photocatalytic properties of the materials have been determined by studying the photooxidation of aqueous ammonia.

International audience; The deposition of thick layers of -Al2O3 is often performed by the washcoating method consisting of immersing the object to coat in a slurry containing -Al2O3 powder and nitric acid. Although this method gives very satisfying results in terms of adherence and BET surface, it shows a bad reproducibility in terms of viscosity of the slurry and thus layer thickness. Characterizations of the slurry were performed at different preparation steps to try to understand and control the chemistry involved.

Bromination of (R)‐2,2′‐(diphenylphospnino)‐1,1′‐binaphthyl (BINAP) in [Hmim]PF6 ionic liquid was performed with N‐halosuccinimides at 110°C during 12 h, affording the 4,4′‐dibromoBINAP in high yield. The ionic liquid was recycled four times without modification of selectivity or efficiency.

International audience; When surface-supported chemical reactions are performed in microsystems, high production rate cannot be obtained due to the intrinsically low surface area. Increasing the active surface area of silicon microsystems is a challenge that is addressed in this paper using two original approaches: (i) modifying the structure of silicon by creating nanostructures (black silicon) using conventional etching processes of silicon micromachining or (ii) depositing a layer of porous _-alumina by washcoating a colloidal suspension of boehmite onto the silicon surface. The catalytic oxidation of carbon monoxide on platinum was chosen as a first test reaction in the domain of heterogeneous catalysis. In order to perform this reaction, platinum was either deposited by sputtering on silicon devices with black silicon nanostructuration, or impregnated inside the porosity of an alumina layer previously deposited on a silicon device. For specific biological applications, such as proteins analysis, some biological reactions could be advantageously achieved in microsystems using surface-supported species. As an example, an enzymatic reaction was carried out usingsilicon devices modified with black silicon nanostructuration and further functionalized with trypsin as a model enzyme. The catalytic activity was compared between silicon devices with the same two types of catalysts, comprising or not an enhancement of the surface activity. A minimum 10- fold increase in catalytic activity was estimated from kinetic measurements and represents the augmentation of the active surface really available for reactions. It was also shown how these catalytic materials were integrated in a microreactor increasing its catalytic active surface without modifying its global size.

International audience; A continuous micro-structured reactor equipped with a perforated (5 μm) membrane is used for the investigation of the gas–liquid–solid asymmetric hydrogenation of ethylpyruvate on a Pt/γ-Al2O3 catalyst modified with chiral inductors under high hydrogen pressure (45 bar). Up to eight chiral inductors have been evaluated, the best enantioselectivity (63%) being obtained with cinchonidine. The very low reaction volume (100 μl) offers short operating time. Solvent effect, deactivation studies and the effect of modifier leaching are also reported.

A library of 5,5′-disubstituted BINAP derivatives were synthesized in good yield from optically pure BINAP and evaluated for the Rh-catalyzed homogeneous asymmetric hydrogenation of (α)-acylaminoacrylate ester, with ee of up to 77% being obtained with the phenyl derivative. The enantiomeric excess variation was followed according to the groups introduced in the 5,5′-position of BINAP and for a range of pressure from 5 to 30 bar.

Electronic effects of electron-donating and electron-withdrawing substituents at the para position of the phenyl moieties of BINAP ligands were studied towards asymmetric hydrogenation of α-(acylamino)acrylic acids. Enantiomeric excesses varied as a linear relationship towards Hammett coefficients σ p of electron-donating groups between 0 and −0.63.

International audience; The methods used to deposit a catalyst on structured surfaces are reviewed. Physical methods such as PVD and chemical methods (sol–gel, CVD, direct synthesis, etc.) are described. The coating of catalysts based on oxide, zeolite or carbon support is detailed on various surfaces such as silicon or steel microstructured reactors, cordierite monoliths or foams, fibres, tubes, etc.

The enantiomeric excess (ee) in asymmetric hydrogenation may vary with the concentration of hydrogen dissolved in the liquid phase. This concentration is proportional to hydrogen pressure when the reactor operates in chemical regime, but depend on the stirring rate if mass transfer is limiting. For example, decrease of ee from 61 to 51% ee has been observed upon varying the stirring rate from 100 to 2000 rpm. A good characterisation of the reactor used is recommended to quantify the influence of hydrogen on ee.

International audience; The study concerns a catalytic micro-reactor with the goal of gas detection. The objectives are: (i) to develop a silicon “micro-reactor” with its heater, (ii) to deposit catalysts in the micro-channels of the device, and (iii) to study catalytic conversions of this system. The main results are related to the temperature control and to the deposition of the catalyst in the micro-channel by wash-coat for alumina and impregnation for platinum. This micro-reactor is evaluated for the conversion of CO into CO2 for gas sensor applications. The current experiments demonstrate the possibility to use such micro-component to improve the selectivity of CH4 detection devices with mixtures of CH4 and CO.

International audience; A silicon micro-structured reactor has been designed for gas-solid heterogeneous catalysis, in particular for the dehydrogenation of methylcyclohexane. Two types of catalyst deposition on silicon have been evaluated: the first consists of a washcoat deposition of a gamma-alumina layer followed by Pt impregnation, the second is a cathodic Pt film sputtering. The Pt/Al2O3 catalyst reveals a higher activity for this reaction and was selected for further investigation. Since the micro-structured reactor is composed of pillars of typical dimension 5 × 100 μm, a special washcoat method has been developed leading to the controlled deposition of a homogeneous gamma-alumina layer of thickness −1) and conducted at ca. 380 °C, heaters have been integrated using screen-printing methods. FEMLAB simulations have helped to integrate the hot reaction zone and a low temperature section for connectors (

The transformation mechanism of dibenzothiophene,4-methyl-dibenzothiophene, 4,6-dimethyldibenzothiophene, and 2,8-di-methyldibenzothiophene has been studied in a batch reactor overan industrial NiMo/Al2O3hydrotreating catalystat 573 K under 5 MPa of hydrogen pressure. A detailed mechanisticstudy including competitive catalytic experiments proved that theadsorption of the most refractory molecules at the catalyst surfacewas not the rate-determining step for their transformation. Ourresults imply that the hydrodesulfurization of these compounds occurson one single type of sites by a flat adsorption, leading to apreliminary partial hydrogenation of one aromatic ring. Variationsin reactivities of the dibenzothiophene derivatives were thus explainedby different reaction rates for the C–S bond scission due tosteric hindrance generated by the methyl substitution near the sulfur atom.

The synthesis of substituted dibenzothiophenes in the 4 and/or 6 positions has been optimized and pure 4,6-dimethyldibenzothiophene has been prepared by a new selective method; X-ray analysis of this compound is described.

The use of ligand-free supported Pd is an attractive idea because it avoids problems related to the presence of the ligands (cost and toxicity). Also the catalyst is easily recovered at the end of the reaction by conventional methods such as filtration or decantation. Thus, it is easier to meet regulations in Active Pharmaceutical Ingredients (

The use of ligand-free supported Pd is an attractive idea because it avoids problems related to the presence of the ligands (cost and toxicity). Also the catalyst is easily recovered at the end of the reaction by conventional methods such as filtration or decantation. Thus, it is easier to meet regulations in Active Pharmaceutical Ingredients (

Résumé confidentiel; Résumé confidentiel

Alkene hydrosilylation is a crucial method of forming carbon-silicon bonds. It is used industrially for the production of functional silicone fluids and silicone elastomers. The current industrial alkene hydrosilylation processes use platinum complexes as catalysts. Although these complexes are extremely efficient, they are usually not recovered at the end of the synthesis, making their use expensive and unsustainable, given the scarcity of platinum. In this work, we have synthesized and evaluated several kinds of metal nanoparticles as catalysts for alkene hydrosilylation, in a quest towards sustainable catalyts. First, we have synthesized platinum nanoparticles of 2 nm diameter and compared them with Karstedt's complex, the benchmark catatalyst in alkene hydrosilylation. It was shown that platinum nanoparticles were as efficient as Karstedt's complex in industrially relevant hydrosilylation conditions, despite their lower metal dispersion. These findings reactivated the debate on whether's Karstedt's complex was truly homogeneous or colloidal during catalysis. Then, a leaching-resistant heterogeneous platinum catalyst was developed, based on the embedding of platinum nanoparticles in the matrix of a mesostructured silica, SBA-15. Finally, other alternative catalytic systems were developed, based on other metals; L'hydrosilylation des alcènes est une méthode cruciale de formation de liaisons carbone-silicium. Elle est utilisée industriellement pour la production de fluides silicones fonctionnels et d'élastomères silicones. Les procédés actuels d'hydrosilylation des alcènes utilisent des complexes de platine comme catalyseurs. Bien que ces complexes soient extrêmement efficients, ils ne sont d'habitude pas récupérés en fin de réaction, ce qui rend leur utilisation coûteuse et peu durable, étant donnée la rareté du platine. Dans ce projet, nous avons synthétisé et testé plusieurs types de nanoparticules métalliques comme catalyseurs pour l'hydrosilylation des alcènes, dans un effort vers des catalyseurs durables. D'abord, nous avons synthétisé des nanoparticules de platine de 2 nm de diamètre et les avons comparées avec le complexe de Karstedt, le catalyseur de référence en hydrosilylation des alcènes. Nous avons montré que les nanoparticules de platine étaient aussi efficientes que le complexe de Karstedt dans des conditions proches des conditions industrielles, malgré leur dispersion métallique plus faible. Ces observations ont réactivé le débat sur la nature réellement homogène ou colloïdale du complexe de Karstedt pendant la catalyse. Ensuite, un catalyseur hétérogène à base de platine, résistant à la lixiviation, a été développé, basé sur l'encapsulation de nanoparticules de platine dans la matrice d'une silice mésostructurée, la SBA-15. Enfin, d'autres catalyseurs alternatifs ont été développés, basés sur d'autres métaux