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International audience; We recently reported (R. Castro Contreras, B. Guicheret, B. F. Machado, C. Rivera-Cárcamo, M. A. Curiel Alvarez, B. Valdez Salas, M. Ruttert, T. Placke, A. Favre Réguillon, L. Vanoye, C. de Bellefon, R. Philippe and P. Serp, J. Catal., 2019, 372, 226–244) that a structure/activity correlation exists in Pd/C catalysts for myrcene hydrogenation, which integrates the Pd dispersion, and the surface concentration of oxygen groups and defects of the support. Here, through a combined experimental–theoretical study, we provide an explanation of the influence of these three structural characteristics of Pd/C catalysts for alkene hydrogenation. Highly dispersed Pd nanoparticles (PdNP) are necessary to activate dihydrogen. A high concentration of surface defects on the support is necessary to stabilize Pd single atoms (PdSA), which coexist with PdNP on Pd/C catalysts. A high concentration of oxygenated surface groups is also necessary on the support to allow hydrogen spillover. We demonstrate that such a combination allows cooperative catalysis to operate between PdNP and PdSA that involves the formation of PdSA–H species, which are much more active than PdNP–H for alkene hydrogenation but also isomerization. Importantly, we also report an efficient method to control the ratio between PdSA and PdNP in Pd/C catalysts of similar loadings and show that the control of this ratio allows the development of a new generation of stable and highly active catalysts integrating the ultra-rational use of precious metals in short supply. Indeed, for myrcene hydrogenation, activity variations of several orders of magnitude were measured as a function of the value of this ratio.

International audience; Alternated slug flow in capillaries is an efficient way to separate droplets with different compositions for applications in various fields. This paper describes how to solve the main issue, i.e. droplets coalescence, by using a gas bubble as a separator and demonstrates quantitatively how the mass transfer between resulting liquid-(gas-liquid)-liquid flow is negligibly impacted by the gas bubble size distribution generated. Thus residence time of up to 30 min could be achieved avoiding coalescence. The conditions to generate and maintain the alternated flow such as the superficial velocities, viscosities and surface tensions, are provided. The mechanism for mass transfer between droplets is shown to occur mainly through the film at the wall of the capillaries explaining the negligible impact of the gas. Mastering such alternated slug flow opens the door for many applications requiring compartmentation of several reactions. 2

A kinetic study concerning the self-metathesis of methyl oleate and methyl elaidate was performed, using a variety of NHC-ruthenium pre-catalysts, bearing either mesityl groups or di-isopropyl-phenyl groups on the NHC ligand and various trans ligands with respect to the NHC unit. We showed that the system can be satisfactorily described using one initiation constant per pre-catalyst and four propagation constants that, conversely, do not depend on the pre-catalyst. The difference of reactivity with oleate (Z) and elaidate (E) can be fully explained by the propagation parameters; the studied pre-catalysts initiate with the same rate starting from the Z or the E olefin. The ranking of the propagation parameters is driven by the thermodynamic equilibrium. The transformation rates of Z and E isomers is only driven by these propagation constants and nothing differentiates the initiation step.

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.

An extractive-reaction process for the synthesis of HMF from fructose was implemented in microreactor. Experimental conditions were 10 wt.% fructose in water, MIBK as extracting solvent and HCl as catalyst in a temperature window of 120–160 °C, a MIBK/H2O ratio 1 to 9 and an HCl concentration of 0.25–2 M. The dehydration of fructose to HMF is achieved in less than 40s with a total HMF yield higher than 90% at 150 °C. Aqueous and organic phase spontaneously separate at the outlet of the reactor and HMF is obtained in MIBK with a yield of 80% and a purity of 92%.

An improved method for the oxidation of benzylic and aliphatic alcohols using concentrated bleach (1.6 M NaOCl) using 2-step continuous flow microreactors is reported herein. Enhancement of the reaction rate was obtained by on-line pH adjustment. In the first step, the pH of the bleach was precisely decreased to pH 8.5 using CO2. Such pH is a compromise between oxidative properties, chemical stability and unwanted precipitation. The aqueous bleach solution was subsequently used for the oxidation of benzyl alcohols in EtOAc using catalytic amounts of TBAB (n-Bu4N+Br−) in a segmented flow microreactor. The total conversion of benzyl alcohols was obtained in less than 1 min using 2 eq. of NaOCl at r.t. without any metal catalysts. Selective benzyl alcohol oxidation (>98%) was demonstrated on primary and secondary alcohols. For aliphatic alcohols, 0.1 mol% TEMPO was used as a co-catalyst in synergy with TBAB and a total conversion with high selectivity (>98%) was achieved in less than 2 min.

The organocatalyzed aerobic oxidation of aldehydes to acids was reproduced from the original report. In- and ex-situ analysis of the reaction mixture as the function of time reveals that, unlike the claim in the publication, the aerobic oxidation of aromatic and aliphatic aldehydes leads predominantly to the formation of peracids. The latter are transformed into the corresponding carboxylic acids during the workup procedure. The buildup of peracids in solution poses safety problems that should not be overlooked. This finding has also an influence on the way new catalysts are investigated to improve this reaction as well as on aerobic aldehyde-mediated co-oxidation.

International audience; The influence of the carbon support characteristics on Pd loading, dispersion and activity in Pd/C catalysts has been analyzed. Several carbon nanomaterials, including multi-walled CNTs, nitrogen-doped CNTs, sulfur-doped CNTs, large- and small-diameter nanofibers, few-layer graphene, and a fibrous carbon have been produced, functionalized, defunctionalized and characterized using several techniques (e.g., nitrogen adsorption, Raman spectroscopy, XPS, TGA, and elemental analysis). These supports present different surface chemistry, arising from different features (defect concentration, inter-defect distances, long-range order, and orientation of the graphene layers) and specific surface areas. The most relevant parameters were obtained by characterization of the materials by Raman, XPS, nitrogen adsorption, and XRD. Twenty-four palladium catalysts with the same nominal loading (2%w/w) were prepared by wet impregnation using an acetone solution of Pd nitrate. These 24 catalysts were characterized by ICP, XRD, XPS and TEM. The final Pd loading varied between 1 and 2%w/w and the Pd particle size ranged from 1.5 to 3.3 nm, depending on the nature of the support. The parameters influencing both Pd loading and dispersion are discussed, and their very high activity for the myrcene complete hydrogenation are reported.

The continuous selective aerobic oxidation of benzyl alcohol in flow was developed using an immobilized Ru0 catalyst. After optimization of the reaction conditions, the stability and productivity of the equipment were examined over time using tert-amyl alcohol as solvent, and no deactivation occurred. A cumulative TON close to 15 000 was obtained with a constant activity (TOF = 4 min−1). A semi-empirical kinetic rate expression was proposed.

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.

Stainless steel open-cell solid foams of various linear pore densities (20, 40, 60 PPI) are wash-coated with a commercial catalyst and are evaluated as internals for G-L-S reactions in co-current up-flow configuration. Hydrodynamics parameters such as liquid mean residence time, axial dispersion and pressure drop have been determined for an air/water system with superficial velocities between 0.8 mm/s and 25 mm/s for liquid and between 100 and 900 mm/s for gas. A generic piston-dispersion model represents well the liquid hydrodynamics and is used to estimate axial Peclet number and mean residence time for this phase. The Peclet number appears to increase with liquid velocity and foam linear pore density (5 Pe Pe Pe ɛ L −1 were obtained at low Re numbers, which is one order of magnitude higher than in up-flow fixed beds. A set of correlations is derived for the calculation of the gas/liquid and liquid/solid contributions to external mass transfer and allows explaining the unique bell-shaped Re dependence displayed by the overall mass transfer coefficient.

The Mukaiyama epoxidation was studied using a segmented flow reactor. Full conversion of cis-cyclooctene (0.67 M) with high selectivity (>99%) towards cyclooctene oxide was reached in 5 minutes using 2-ethylhexanal (2 M) as a sacrificial co-reductant, 100 ppm of Mn(II) as catalyst and 5 bar of oxygen. To gain further insights into the Mukaiyama reaction we have investigated the influence of the cis-cyclooctene/2-ethylhexanal ratio and cis-cyclooctene concentration. It was shown that after an induction period during which time aldehyde was oxidised faster than the alkene, the theoretical stoichiometry of the Mukaiyama reaction (1 mole of epoxide per mole of oxidised aldehyde) was observed. Then, different metal catalysts and catalyst loading were evaluated. The best results were obtained with Mn(II). We can suspect that the differences in productivity described in the literature for Mukaiyama epoxidation reaction could be explained by oxygen mass transfer resistance rather than catalytic efficiency. Surprisingly the selectivity of 2-ethylhexanal oxidation toward 2-ethylhexanoic acid was not improved by the co-oxidation of cis-cyclooctene. These results raised questions regarding the activated oxygen specie(s) responsible for the epoxidation and the exact mechanism of this reaction.

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; The electrochemical in situ regeneration of spent Pd/C/foam catalysts was investigated using a modified Mahoney-Robinson reactor (RM). The same reactor was used for reaction and regeneration experiments with and without removal/weighing of the catalyst between each measurement. The feasibility of the electrochemical regeneration was assessed by monitoring the catalyst activity versus cumulative turnover number (TON). The results showed that the catalyst activity was fully recovered after regeneration and that the catalyst had the same deactivation rate after several reaction/regeneration cycles. The influence of the foam pretreatment step and of the pH electrolyte solution on the catalyst loss was also studied. A basic pretreatment of the foam before the catalyst coating led to a significant improvement of the catalyst adherence on the foam.

Why would the pressure of hydrogen affect the enantioselectivity of hydrogenation in an opposite way for two enamide reactants, M-acrylate (methyl 2-acetamidoacrylate) and E-emap (ethyl 4-methyl-3-acetamido-2-pentanoate), with rhodium (I) complexes coordinated to a diphosphine ligand? This question was answered by a combination of experiments and DFT calculations. The activation free energies, the kinetic constants and the enantiomeric excess ee have been calculated. In the static pathways, the two substrates show significant differences. From the square-planar substrate-metal complex, M-acrylate (resp. E-emap) prefers the attack of the hydrogen on the side opposite to (resp. of) the amide group. Both substrates however show lower transition states on the pathway starting from the minor stereoisomer of the substrate-metal complex. The turnover-limiting step for M-acrylate is the oxidative addition of hydrogen on the substrate-metal complex, while it is the migratory insertion of the substrate in the Rh-H bond for E-emap. However, the energy profiles are not sufficient to understand the enantioselectivity of the reaction: the kinetic simulations lead to different conclusions and show a marked influence of the hydrogen pressure. For both substrates, the R isomer is obtained in the realistic pressure range, coming from the minor isomer for M-acrylate and from the major isomer for E-emap. Hence, depending on the reactant, the preferred pathway follows either the major/minor or the lock-and-key concept. The importance of combining DFT calculations with kinetic simulations in unraveling the mechanism is underlined. In particular, they reveal that the rate of formation of the metal-substrate complex plays a key role for the enantioselectivity.

Continuous-flow technology with channel dimension in the millimeter region found widespread applications in numerous applications. The epoxidation of methyl oleate with molecular oxygen using an aldehyde as sacrificial reductant (Mukaiyama reaction) was implemented in a segmented flow microreactor. The effect of aldehyde structure and aldehyde/methyl oleate molar ratio on the conversion to epoxides was studied. Total conversion of methyl oleate (0.67 M in heptane) with a selectivity higher than 99% and a cis/trans ratio ∼75/25 was reach in less than 4 min, at room temperature, using three equivalents of 2-ethylhexanal, 100 ppm of Mn(II) as catalyst and five bar of oxygen. Practical applications: As the result of the small reactor volumes, very high surface-to-volume ratio and high heat exchange efficiency compared to classical batch reactors, the overall safety of oxidation processes is significantly improved using continuous-flow technology. Microreactors also provide better mass transfer, and thus, improve the productivity of the aerobic epoxidation of methyl oleate using aldehyde as sacrificial reductant while maintaining the high selectivity of the process. (i) Epoxidation of methyl oleate with molecular oxygen is performed safely using continuous-flow technology. (ii) Total conversion is obtained in 4 min at r.t. using 100 ppm of Mn(II) and a sacrificial reductant. (iii) The selectivity and cis/trans ratio are comparable to batch.

International audience; Aldol-condensation of furfural with acetone catalysed by activated dolomite was investigated at temperatures from 306 to 413 K. The process of activation by calcination and hydration produced catalytically active calcium and magnesium hydroxides with improved surface area and surface basicity. The aldolcondensation mechanism began with a deprotonation of acetone forming a carbanion intermediate by hydroxyl ions, which then reacted with the carbonyl group of furfural to form a water soluble C-8 monomer (4-(furan-2-yl)-4-hydroxybutan-2-one). This C-8 monomer readily dehydrated to form selectively alpha,beta-unsaturated ketone (4-(2-furyl)-3-buten-2-one), which in turn, reacted with furfural forming a C-13 dimer (1,4-pentadien-3-one,1,5-di-2-furanyl). Compared with conventional sodium hydroxide catalyst, activated dolomite was less selective towards lumped C-8 monomers and C-13 dimers owing to carbon losses and deactivation, particularly at high temperatures. Activated dolomite was more selective to C-13 dimer owing to higher adsorption enthalpy of C-8 monomer compared with acetone competitor. Activated dolomite is therefore a promising catalyst to produce C-13 dimers which can be transformed upon hydrogenation and deep hydrodeoxygenation in high-quality diesel fuels. The first-order kinetic model with respect to furfural and acetone fitted well with actual experimental results with an average normalised standard deviation of 6.2%. (C) 2013 Elsevier B.V. All rights reserved.

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International audience; Commercially available H-Y (Faujasite) and H-ZSM5 zeolites with various SiO2/Al2O3 ratio (from 5 to 280) were used as acid catalyst for vapour phase methanol dehydration in mild condition (T\textless250 degrees C; P\textless5 bar). All tested catalysts were giving very high selectivity while conversion was highly dependent on both acid content and surface hydrophobicity expressed as Weitkamp hydrophobicity index (HI index). For H-Y and H-ZSM5 zeolites, a correlation was found between catalysts productivity expressed in kg of DME per hour per concentration of acid sites and HI index. Such results could rise to the design of more efficient catalyst for gas-phase DME synthesis from methanol.

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.

An efficient and metal-free method for the oxidation of aldehydes to the corresponding carboxylic acids has been developed. In a simple continuous-flow photochemical reactor, the use of camphorquinone (CQ) irradiated with a white light-emitting diode (LED) source enhanced the autoxidation of aldehydes. Under 5 bar of oxygen, visible light, and 0.3 mol% of CQ, the rate of oxidation was increased from 6 times with 2-ethylhexanal to 30 times for n-nonanal. The large interfacial area generated by a segmented flow apparatus associated with radicals formed by photooxidation of CQ ensures metal-free high throughput of carboxylic acids under safe conditions.

Resume Pour le traitement de l’eau contre les composes azotes nocifs (NH4+, NO2– et NO3–), une nouvelle approche est envisagee basee sur le couplage de deux reactions catalytiques ; l’hydrogenation de NO3– et NO2– et la photoxydation de NH4+. Le present travail est consacre a l’etude de la degradation photocatalytique de NH3/NH4+. L’effet d’ajouts metalliques sur l’activite et la selectivite du photocatalyseur a base de TiO2 en suspension a ete evalue. L’effet du pH, de la teneur en TiO2, de la temperature et la concentration en ammoniaque et en hydroxyde sur l’activite photocatalytique ont ete mesures.

A continuous-flow microreactor is applied for the selective aerobic neat oxidation of 2-ethylhexanal. Under 7.5 bar of O2 and 10 ppm of Mn(II) as catalyst, a production of up to 130 g/h of 2-ethylhexanoic acid can be obtained with a PFA tubing of 7 m (O 1.65 mm, reactor volume ca. 15 mL). The synergistic use of alkali metal salts and Mn(II) as catalyst improve the selectivity up to 94% under those conditions. We show that the productivity of this simple tube microreactor is limited by the thermal management.

Aerobic oxidation using a combination of copper salts and 2,2,6,6-tetramethylpiperidine N-oxyl (TEMPO) represent useful tools for organic synthesis and several closely related catalyst systems have been reported. To gain further insights, these catalytic systems were evaluated in a gas–liquid segmented flow device. The improvement of oxygen mass transfer has a significant influence on the turnover-limiting step. Hence, an improved catalytic system using copper(II) as copper source was implemented in a microreactor for the safe and efficient oxidation of primary alcohol.

A safe, straightforward, and atom economic approach for the oxidation of aliphatic aldehydes to the corresponding carboxylic acids within a continuous flow reactor is reported. Typically, the reaction is performed at room temperature using 5 bar of oxygen in PFA tubing and does require neither additional catalysts nor radical initiators except for those already contained in the starting materials. In some cases, a catalytic amount of a Mn(II) catalyst is added. Such a flow process may prove to be a valuable alternative to traditionally catalyzed aerobic processes.

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.

The purpose of these comments is to express some concern regarding the choice of the test reaction used to characterize the activity of some nanoporous aluminosilicate catalysts produced using an evaporation-induced self-assembly approach described in the recent Catal. Sci. Technol. paper of A. E. Graham et al. [2012, 2, 2258–2263].

The hydroformylation of olefins (oxo synthesis) is the most important process for the production of higher aldehydes (>C4). The liquid phase oxidation of the latter to carboxylic acids by molecular oxygen or air has been known for more than 150 years and is an industrially important process. However, in the recent literature, several different oxidizing reagents and catalytic processes have been reported for this oxidation but most of them have limitations as they use environmentally unacceptable reagents or unnecessarily sophisticated conditions. Herein, we re-evaluated the air oxidation of aldehydes. We show that under mild conditions (air or oxygen and non-optimized stirring), reactions are transfer limited and thus catalyst has no effect on reaction rate. Using efficient stirring (self-suction turbine), uncatalysed air oxidation of 0.8 M aldehyde is possible in 50 min at room temperature whereas less than 10 min was necessary with 10 ppm Mn(II). Thus, recommendations for avoiding common pitfalls that may rise during the evaluation of new catalysts are made.

International audience; The catalytic system prepared from [Rh(COD)(2)]BF4 and (R,R)-Me-BPE provides a spectacular detrimental hydrogen pressure effect on ee from 94% down to 56% in the hydrogenation of methylacrylate, whereas it has a strong beneficial effect on the hydrogenation of E-emap (from 42% up to 72%). The kinetic parameters have been determined for both systems and have helped to identify the most enantioselective controlling steps (MECS). Accordingly, further explanations for the structure-ee and hydrogen pressure relationship are proposed. (c) 2012 Elsevier B.V. All rights reserved.

International audience; A methodology that may be applied to help in the choice of a continuous reactor is proposed. In this methodology, the chemistry is first described through the use of eight simple criteria (rate, thermicity, deactivation, solubility, conversion, selectivity, viscosity, and catalyst). Then, each reactor type is also analyzed from their capability to answer each of these criteria. A final score is presented using "spider diagrams." Lower surfaces indicate the best reactor choice. The methodology is exemplified with a model substrate nitrobenzene and a target pharmaceutical intermediate, N-methyl-4-nitrobenzenemethanesulphonamide, and for three different continuous reactors, i.e., stirred tank, fixed bed, and an advanced microstructured reactor. Comparison with the traditional batch reactor is also provided.

International audience; Vapor-liquid equilibria of two compounds, glycerol (or 1,2,3-propanetriol) and 1,3-propanediol, and two mixtures, glycerol + water and glycerol + 1,3-propanediol, were determined using a static apparatus. The obtained pressure values range from 6 Pa to 45 kPa for the compounds and from (32 to 163) kPa for the mixtures. From the temperature dependence of the vapor pressures, the molar enthalpies of vaporization at the mean temperature of the experimental range were derived from the Clausius-Clapeyron equation. From these results the standard enthalpies of vaporization at T = 298.15 K were calculated. The experimental data of the mixtures were correlated using the nonrandom two-liquid (NRTL) model.

International audience; The liquid-phase dehydration of ethanol to diethylether over heterogeneous sulfonic-acid catalysts was carried out in a stirred batch reactor. The different Amberlyst catalysts were found to have similar activities for this reaction; even though Amberlyst 70 showed a lower acid capacity compensated by a higher specific activity. By comparing the conversion of ethanol as a function of reaction mixture composition, it was found that reaction rates greatly depended on ethanol concentration but also on reaction mixture polarity. The swelling of the used resins could not explain the observed variations of initial reaction rate since this effect was observed both with resins and with homogeneous catalyst, i.e. ptoluenesulfonic acid. The initial ethanol concentration has a complex effect on initial reaction rates that could not be correlated by usual kinetic models. Taking account of the intrinsic reactivity trends of the SN(2) etherification reaction, a strong dependence was found between solvent properties and initial reaction rate.

International audience; A library of 117 ligands was combined with three transition metals Ru, Rh and Ir and screened with three different operating conditions for the asymmetric H-transfer reduction of acetophenone into phenylethanol. The combinatorial approach was based on evolution of a first library containing 60 ligands. For the evolution, operators such as replication, regression, cross-over and mutation were used. The study was performed with a XYZ robot and fast chiral GC analysis. Over only 4 generations, the average targeted criterion, enantioselectivity, was increased from 20% to ca. 80% for the 4th generation. The best results provided enantiomeric excess up to 93%.

Depollution processes are based on a dual approach that combines catalyst design (formulation) and reactor design. This paper illustrates the interest of this approach to get innovative depollution solutions using three examples: depollution of water containing chlorophenols at trace level by hydrogenation; destruction of nitrates by hydrogenation and oxidation; combustion of diluted VOC with no extra heat supply.

A library of catalysts was designed for asymmetric-hydrogen transfer to acetophenone. At first, the whole library was submitted to evaluation using high-throughput experiments (HTE). The catalysts were listed in ascending order, with respect to their performance, and best catalysts were identified. In the second step, various simulated evolution experiments, based on a genetic algorithm, were applied to this library. A small part of the library, called the mother generation (G0), thus evolved from generation to generation. The goal was to use our collection of HTE data to adjust the parameters of the genetic algorithm, in order to obtain a maximum of the best catalysts within a minimal number of generations. It was namely found that simulated evolution's results depended on the selection of G0 and that a random G0 should be preferred. We also demonstrated that it was possible to get 5 to 6 of the ten best catalysts while investigating only 10 % of the library. Moreover, we developed a double algorithm making this result still achievable if the evolution started with one of the worst G0.

The synthesis of methyl chloride from methanol and hydrogen chloride catalysed by zinc chloride was investigated in water and in two room temperature ionic liquids in a CSTR reactor. Both Aliquat336 and BMICl drive to similar rate of reactions as the traditional process albeit at lower temperatures. More importantly, the formation of the side product Me2O is decreased in ionic liquids. From the reactor point of view and on the basis of kinetics and simulations, a new process involving plug flow behaviour using ionic liquids is proposed which would lead to process intensification, i.e. (50×) productivity increase.

International audience; The gas-liquid oxidation of cyclohexane is performed at high temperature (>200 degrees C) and pressure (up to 25 bar) using pure oxygen in a Pyrex capped silicon etched microreactor which allows convenient screen reaction conditions well above the flammability limit.

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.

International audience; A novel stopped flow reactor system is described in the current work, along with the underlying design philosophy. While the concept of stopped flow technology is not recent, this system is the first to be designed with the objective of studying particle morphology, and to work at extremely short (40 ms) residence times. It is shown that traditional chemical engineering principles are required to properly design and operate this type of reactor, and that when correctly design, it is a very flexible tool for the study of nascent polymerisation of olefins.

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.

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 (

A micro-structured single channel falling film is used for gas–liquid contacting. A small falling angle of 7.5° is used to ensure long residence time in the range 3–22 min, even with low viscosity solvents such as methanol. Using this device, a screening of molecular catalysts of the type rhodium/chiral diphosphines for the asymmetric hydrogenation of Methyl-Z-(α)-acetamidocinamate and similar substrates has been performed. The very small reacting volume of 14 μl leads to an average inventory of Rh/test as low as 0.1 μg. Comparisons with traditional batch experiments are provided.