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International audience; Acceptor-less alcohol dehydrogenation reaction allows the co-production of added-value carbonyl compounds and H 2 from alcohols. Focusing on supported Ru and Cu catalysts, we evaluated the support effect on the dehydrogenation of 2-octanol and 1-octanol and identified the side products as resulting from aldolisation coupling. The most active and selective catalysts were then tested on the aliphatic vicinal-diol octan-1,2-diol and the highest conversion was reached using Cu/ZrO 2 (60%) with a high selectivity (94%) towards 1-hydroxy-2-octanone.

International audience; Cobalt nanorods and cobalt nanoplatelets, prepared by the same organometallic route with two different metal precursors, were tested for the first time in the acceptor-less dehydrogenation of 2-octanol. The nature of the metal precursor determines not only nanoparticle morphology but also their surface chemistry. While cobalt nanorods showed high conversions (up to 85% after 24 h) and complete selectivity toward 2-octanone with concomitant molecular hydrogen production, cobalt nanoplatelets were practically inactive. Here, we show that this striking difference in the catalytic properties is not associated with facet-dependent differences in reactivity, but rather with different surface chemistry. The activity critically depends on the coordinating ability of the adsorbed species under catalytic reaction conditions and to a smaller degree on their concentration, as evidenced by ligand exchange experiments at room temperature as well as by direct addition of ligands in the reaction during catalysis by cobalt nanorods. This study shows that to optimize performances with unsupported metal nanocatalysts, the capping ligands should be selected by considering their ability to reversibly dissociate from the metal surface during catalysis.

International audience; γ-alumina, a widely used industrial catalyst support, undergoes irreversible transformation into various aluminum hydroxides under hydrothermal conditions, resulting in strong modification of its intrinsic properties. Most of the strategies that have been proposed to prevent or at least minimize its transformation into oxy-hydroxides consist in covering the alumina surface by a hydrophobic carbon layer, making it less sensitive to modifications induced by water. However, such methods necessitate high carbon contents, which significantly modifies structural and chemical properties of alumina. Here, we propose a new method based on a series of adsorption/pyrolysis cycles using sorbitol molecules previously adsorbed on specific hydration sites of (110) faces of γ-alumina crystals. Those sites, which are responsible for the dissolution f γ-alumina crystals in water, are thus selectively protected by carbon clusters, the rest of the surface being totally exposed and accessible to adsorbates. Under hydrothermal conditions (10 hours in water at 200°C), the formation of hydroxides is almost totally suppressed by covering less than 25% of the surface with only 7 wt. % carbon, which is far below the amount necessary to get similar results with more conventional carbon deposition methods.  INTRODUCTION Molecules derived from existing biomass treatment processes such as fermentation and hydrolysis (sugars, alcohols, polyols, carboxylic acids, etc.) are platform molecules for bio-based products manufacture. They consist of oxygen-rich, highly functionalized and generally water soluble molecules and reactions to convert them into valuable bio-products in aque-ous media may require relatively high temperatures and sometimes high pressures. These particular conditions, which combine water and temperature, are called hydrothermal conditions (HT) and they represent a serious challenge in the field of today's heterogeneous catalysis. 1,2 Indeed, conventional catalysts used in the petroleum refining industry generally consist of an active metal phase deposited onto an inorganic support and they may not be appropriate for applications involving water as solvent under such HT conditions. For exam-γ-alumina, a widely used industrial catalyst support, undergoes irreversible transformation into various aluminum hydroxides by a dissolution/re-precipitation process when placed in a water-rich medium at moderate temperature, resulting in strong modification of its intrinsic properties. 3,4,5-8 The stability of alumina materials in water has been a matter of great interest during the last years and many strategies have been proposed to prevent or at least minimize their transformation into hydroxides. The approach generally consists in modifying the alumina surface in order to make it less sensitive to the modifications produced by water under hydrother-mal conditions. The benefits of organic additives (such as carbon 9,10), inorganic additives (such as silicon 11,12 or phosphorus 13) and metallic additives 14 on the HT stability of alumina have been reported. However, the main parameters that govern the dissolution of alumina remain poorly known, which makes difficult the development of rational methods to improve the stability of this material. Ravenelle and coworkers first noticed that alumina transformation did not occur when polyols were present in the aqueous medium during a hydrothermal process. 15,16 The effect is supposed to result from the chemisorp-tion of the organic molecules on alumina, which avoids direct contact between water molecules and the surface and significantly improves water resistance. 17 This result can be compared with the work of Pham et al. who increased alumina stability in water by covering its surface with an oxygenated carbonaceous layer resulting from sucrose pyrolysis at 400°C. 9 They showed that 10 wt. % of carbonaceous deposit on the alumina surface was enough to prevent the transformation of the solid into boehmite. In another study, the same group used methane as a carbon source to produce graphitic carbon on alumina surface by gas phase carbonization. In this case, a higher amount of carbon was required to effectively protect alumina (35 wt. %), leading to a complete modification of its original properties (textural properties and surface chemistry). 10 Despite a growing number of articles dedicated to the improvement of alumina based materials in hydrothermal conditions, rationalization of predominant parameters that control hydrothermal stability remain unclear. In a previous work, we proposed a mechanism of the first steps of alumina dissolution based on experimental and theoretical approaches. 18 This mechanism involves some specific surface sites located on basal (110) planes of alumina platelets which are particularly reactive towards liquid water. We also showed

The present study is concerned with the preparation of ordered mesoporous carbons containing uniform dispersions of ruthenium nanoparticles by a hard-template method, based on the use of RuCl3 and cyclodextrin as respective sources of metal and carbon. The influence of chemical structure of the parent CD [randomly methylated-β-CD (RAME-β-CD) and 2-hydroxypropyl-β-CD (HP-β-CD)] and loading of the ruthenium source are studied in detail. The catalysts are carefully characterized by N2-adsorption, TEM, XRD, CO pulse chemisorption, TG-MS and H2-TPR. The most outstanding effect is obtained when HP-β-CD is used, allowing to stabilize small and reactive Ru particles (1–2 nm) in the carbon matrix, with a good compromise between immobilization, surface availability and hydrogen spillover effect. The catalytic systems prepared from HP-β-CD display remarkably high catalytic activities in the liquid-phase hydrogenation of various substrates while their reusability and robustness are also demonstrated.

SSCI-VIDE+CDFA+MBE:NPR; International audience; Metal catalysts are essential in the production of fuels and chemicals. Nonetheless, tailoring the exposed active sites to achieve the maximal theoretical conversion is still a great challenge. In the case of structure-sensitive reactions, such as the attractive acceptor-less alcohol dehydrogenation, playing on the exposed metallic sites appears as an appealing strategy. Still, this approach requires advanced preparation protocols and is even more difficult to implement for supported non-noble metal catalysts which easily undergo sintering. Using the polyol method, we synthesized fourteen different cobalt catalysts, which consist of unsupported shaped nanoparticles stabilized by adsorbed carboxylate ligands. Their shape and the amount of ligands were characterized by combining TEM and TGA-N2 measurements. These catalysts were found to be active in the 2-octanol dehydrogenation conditionally upon an organic layer limited to 1 to 2 monolayers. Moreover, they were fully selective towards the desired ketone and H2. The active catalysts were stable, with no leaching or modification of the shape during the reaction. Periodic DFT computations predict a greater activity of the pristine open-type facet than of the compact one, but this is not confirmed experimentally with no clear correlation between the activity expressed in turnover number and the amount of a given type of site as quantified by TEM. Further modeling including the organic layer shows that the presence of ligands reduces the sensitivity to the metallic structure. Nonetheless, these ligands generate a catalytic pocket, similar to the one found in enzymes, that interacts with the alcohol substrate through H-bonding. This pocket is the most adapted to the alcohol dehydrogenation on the open-type facet, which is mainly exposed on rods. This detailed understanding paves the way to an improved design of bespoke unsupported catalysts considering simultaneously the structure and the nature of the ligand.

SSCI-VIDE+CDFA:ECI2D+CPI:SLO:MBE:NPR; International audience; The acceptor-less dehydrogenation of 2-octanol was tested over Co supported on Al2O3, C, ZnO, ZrO2 and various TiO2. The catalysts were characterized by ICP, XRD and TGA-H2. For Co/TiO2 P25, the effects of passivation, aging (storage at room temperature), and in situ activation under H2 were investigated. The catalysts have to be tested shortly after synthesis, in order to prevent deactivation. Co supported onTiO2 P25 was the most active and 69% yield of 2-octanone was obtained, using decane as a solvent. Selectivity to 2-octanone in the range of 90% to 99.9% were observed. Small amounts of C16 compounds were also formed due to aldol condensation/dehydration reactions. The catalysts exhibited higher conversion for the dehydrogenation of secondary alcohol (65-69%), in comparison to primary alcohol (2-10%). The dehydrogenation of 1,2-octanediol led principally to 1-hydroxy-2-octanone, with a selectivity of 90% and 69% for Co/TiO2 P25 and Co/TiO2 P90, respectively.

International audience; Re–Pd catalysts supported on TiO2 (P25 or DT51) prepared by successive impregnation (SI) or by Re deposition on Pd/TiO2 by catalytic reduction (CR) were characterized by XANES and EXAFS at the Pd and Re edges. These samples were shown to be efficient for the selective hydrogenation in aqueous solution of succinic acid (SUC) to 1,4-butanediol (BDO) (T = 160 °C, P(H2) = 150 bar). This study clearly highlights the need for in situ re-activation of Re-based systems before their characterization or use, since Re species are fully re-oxidized (Re7+) by contact with air. The XANES quantitative analysis at the Re LIII-edge reveals that after in situ reduction, the Re average reduction state is in most cases inferior or equal to +3, indicating the presence of a mixture of Re3+ and Re0 species in all reduced catalysts. EXAFS study indicates that the Re species are mainly located at the Pd-support interface for the CR sample, whereas a part of Re entities is also deposited as isolated forms on the support in the case of the SI catalyst. The Re–Pd/DT51-SI system leading to the best BDO yield displays a specific arrangement of the Pd and Re species (Re deposit on Pd sites of high coordination). In this sample, the Re0 species, present in none negligible proportion, would contribute similarly as Pd metal to the efficient transformation of SUC towards GBL, which is further converted to BDO on sites involving Pd0 and oxidized Re3+ species nearby

The recovery and upgrade of hemicelluloses, a family of heteropolysaccharides in wood, is a key step to making lignocellulosic biomass conversion a cost-effective sustainable process in biorefinery. The comparative selective catalytic C-O bond hydrogenolysis of C5-C6 polyols, sugars, and their mixtures for the production of valuable C6 and C5 deoxygenated products was studied at 200 &deg, C under 80 bar H2 over ReOx-Rh/ZrO2 catalysts. The sugars were rapidly converted to the polyols or converted into their hydrogenolysis products. Regardless of the reactants, C-O bond cleavage occurred significantly via multiple consecutive deoxygenation steps and led to the formation of linear deoxygenated C6 or C5 polyols. The distribution of products depended on the nature of the substrate and C-C bond scission was more important from monosaccharides. In addition, we demonstrated effective hydrogenolysis of a hemicellulose-extracted liquor from delignified maritime pine containing monosaccharides and low MW oligomers. Compared with the sugar-derived polyols, the mono- and oligosaccharides in the liquor were more rapidly converted to hexanediols or pentanediols. C-O bond scission was significant, giving a yield of desired deoxygenated products as high as 65%, higher than in the reaction of the synthetic mixture of glucose/xylose of the same C6/C5 sugar ratio (yield of 30%).

International audience; TiO2-supported Re-Pd catalysts were evaluated for the selective hydrogenation of succinic acid (SUC) to 1,4-butanediol (BDO) in aqueous solution at 160 °C under 150 bar of H2. Rhenium immobilized on Pd/TiO2 catalysts by ex situ preparation methods, namely successive impregnation (SI) or deposition by catalytic reduction (CR), was partially leached after handling in air and introduction into the SUC aqueous solution in the batch reactor; it was then re-deposited under H2 pressure. It was demonstrated in this study that Re can be deposited by CR on a monometallic Pd catalyst directly in situ in the autoclave under hydrogen pressure before the catalytic test. The Re loading and the activation time under reducing atmosphere in the autoclave were optimized. Finally, the best bimetallic catalysts synthesized in situ demonstrated an intermediate selectivity to BDO compared to the systems prepared ex situ from the same parent monometallic catalyst, in the following order: ex situ CR < in situ CR < ex situ SI.

Oxidation of aliphatic α,ω-diols is a potentially interesting route to the production of valuable α,ω-diacids or ω-hydroxy acids for various polymer synthesis. 1,4-Butanediol (BDO), 1,5-pentanediol (PDO) and 1,6-hexanediol (HDO) are particularly attractive since they may be obtained from lignocellulosic biomass. The aqueous aerobic oxidation of these diols to the corresponding diacids was investigated in water over a set of Au, Pt, Au–Pt and Au–Pd catalysts supported on zirconia at 70 °C or 90 °C under 40 bar air. The nature of the metallic catalyst influenced the distribution of products as oxidation proceeded. The longer the carbon chain linking the terminal alcohol groups, the higher the yield of the diacid. The best yields of succinic acid, glutaric acid and adipic acid reached 83, 84 and 96% from BDO, PDO and HDO, respectively, over Au–Pt/ZrO2. There was some evidence of decarbonylation of the α,ω-hydroxyaldehyde at the early stage of the reaction. The presence of the hydroxyl substituent in 1,2,6-hexanetriol significantly slowed the oxidation rates compared with HDO. Besides, oxidation of PDO or HDO was highly selective to the ω-hydroxycarboxylate in moderate alkaline medium (NaOH/diol = 2) over Au/ZrO2 (90–93%).

SSCI-VIDE+CDFA:ING+FRM:NPA:NPR:MBE; International audience; Understanding platinum (Pt) speciation on catalysts is crucial for the design of atom-efficient materials and optimized formulations. The adsorption of carbon monoxide (CO) as a probe molecule is widely used to reveal Pt dispersion and structures, yet the assignment of IR bands is not straightforward, hindering determination of the nature of the surface sites or ensemble involved. CO adsorption was studied here over a zirconia-supported Pt catalyst. Specific sites at the interface between Pt and the support were highlighted, giving rise to an unusual band around 1660 cm–1 that could be confidently assigned to a Pt2–CO bridging carbonyl interacting head-on with a support surface hydroxyl. This adduct was yet unstable in the present conditions and was converted into a linear and bridged carbonyl bound only to Pt. Such sites are potentially important for bifunctional reactions requiring both metal and acid/base properties, particularly those occurring at the metal–support perimeter. Such adducts have probably been mistaken for carbonate-type species in many past contributions and could potentially represent crucial reaction intermediates for CO oxidation and the water–gas shift reaction.

Production of linear deoxygenated C4 (butanetriols, -diols, and butanols), C5 (pentanetetraols, -triols, -diols, and pentanols), and C6 products (hexanepentaols, -tetraols, -triols, -diols, and hexanols) is achievable by hydrogenolysis of erythritol, xylitol, and sorbitol over supported-bimetallic Rh-ReOx (Re/Rh molar ratio 0.5) catalyst, respectively. After validation of the analytical methodology, the effect of some reaction parameters was studied. In addition to C O bond cleavage by hydrogenolysis, these polyols can undergo parallel reactions such as epimerization, cyclic dehydration, and C C bond cleavage. The time courses of each family of linear deoxygenated C4, C5, and C6 products confirmed that the sequence of appearance of the different categories of deoxygenated products followed a multiple sequential deoxygenation pathway. The highest selectivity to a mixture of linear deoxygenated C4, C5, and C6 products at 80% conversion was favoured under high pressure in the presence of 3.7wt.%Rh-3.5wt.%ReOx/ZrO2 catalysts (54–71% under 80 bar) at 200 °C.

International audience; Oxidation of alcohols is a key-reaction for the valorization of biomass compounds, and green processes are preferred to avoid the use or production of toxic compounds. In this context, unsupported nanometer-sized catalysts have emerged as very promising materials for heterogeneous catalysis. In this paper we explore the catalytic activity of unsupported cobalt nanoparticles towards the dehydrogenation of aliphatic primary and secondary alcohols under solvent-free conditions. The unsupported particles are found to be highly active for the conversion of secondary alcohol to the corresponding ketone vs. the primary alcohol. The oxidation process is following an acceptorless dehydrogenation mechanism, where the only by-product of the reaction is the highly valuable H2 molecule. DFT calculations evidence that the chemoselectivity of secondary vs. primary alcohols originates from a more favorable desorption of the ketone reaction product compared to the aldehyde. It is also found that the morphology of the particles has a strong influence on the catalyst efficiency and stability: Co nanorods can be recycled at least three times without a loss in catalytic performances.

SSCI-VIDE+CDFA+EDE:CPI:MBE; International audience; The hemicellulose-derived aqueous solution of C6 and C5 sugars (D-mannose, D-galactose, D-glucose, D-xylose, L-arabinose), obtained from the extraction and hydrolysis of the hemicellulosic polymers in softwoods prior to the production of pulp, was catalytically converted to the corresponding aldaric acids under alkaline (Pt/C) or native (Au-Pt/ZrO2) aqueous conditions with air. The inhibiting effect of some residual impurities and degraded compounds in the hydrolysate was confirmed, such as colored unsaturated compounds and 5-hydroxymethylfurfural. A combined purification process consisting of filtration, demineralization by ion-exchange resins, evaporation, and active carbon treatment of the raw aqueous-stream gave a purified hydrolysate of aldoses that was oxidized to hexaric and pentaric acids. The yields were dose to those of a synthetic solution of the pure sugars with the same distribution. The yields of aldaric acids accounted for ca. 50% of hexaric acids and up to 70% of pentaric acids.

SSCI-VIDE+CDFA+NPR:CPI:MBE; International audience; The hydrogenolysis reaction of biomass-derived xylitol to glycols and glycerol has been carried out in different water/organic solvent mixtures over a bifunctional Ru/MnO/C catalyst under alkaline-free conditions at 60 bar H2 and 200 °C. In pure water, the retro-aldol reaction takes place. However, decarbonylation and epimerization are the dominant reactions and produce C4 and C5 alditols, which limits the overall selectivity to glycols and glycerol (30%). When 90:10 vol % water/1,4-dioxane and water/2-PrOH solutions are used as solvents, the product distribution is very similar to the one in water. Meanwhile, in 90:10 vol % water/primary alcohol (ROH with R = Me, Et, nPr, nBu), the overall selectivity to glycols and glycerol is greatly enhanced (up to 70%), whereas the selectivity to C4 and C5 alditols is reduced. In a solution with a higher MeOH proportion of 20 vol %, the glycols are detected with even higher selectivity; however, some deactivation of the catalyst is observed. TGA analysis of the used catalysts shows that during the process some coke is deposited on the catalyst via a dehydrogenation step of ROH. The coke selectively inhibits the Ru sites that are active for the undesired reactions of decarbonylation and epimerization.

SSCI-VIDE+CDFA+NPR:CPI:MBE; International audience; 1,6-Hexanediol is an emerging building-block chemical, which may be derived from biomass and can produce adipic acid for the synthesis of polymers. A series of supported Pt, Bi-Pt, Au, Pd, Au-Pd, and Au-Pt catalysts were prepared and evaluated in the aerobic oxidation of 1,6-hexanediol to adipic acid in aqueous solution without the addition of a base or an acid. The influences of various molar ratios of the metals in the bimetallic systems and the support (C, ZrO2) were studied. Under the conditions used, bismuth did not promote the catalytic performance of Pt catalysts. On the other hand, formation of an alloy of Au-Pd or Au-Pt made the catalysts very effective. A yield of adipic acid of ca. 96% was achieved at 70 °C under 40 bar of air over the Au-Pt catalyst supported on zirconia with a Au/Pt molar ratio of about 1. Recycling tests revealed the possibility to use the catalyst up to 6 times without significant changes in its catalytic performance.

A series of Ru-(Mn-M)OX catalysts (M: Al, Ti, Zr, Zn) prepared by co-precipitation were investigated in the hydrogenolysis of xylitol in water to ethylene glycol, propylene glycol and glycerol at 200 &deg, C and 60 bar of H2. The catalyst promoted with Al, Ru-(Mn-Al)OX, showed superior activity (57 h&minus, 1) and a high global selectivity to glycols and glycerol of 58% at 80% xylitol conversion. In comparison, the catalyst prepared by loading Ru on (Mn-Al)OX, Ru/(Mn-Al)OX was more active (111 h&minus, 1) but less selective (37%) than Ru-(Mn-Al)OX. Characterization of these catalysts by XRD, BET, CO2-TPD, NH3-TPD and TEM showed that Ru/(Mn-Al)OX contained highly dispersed and uniformly distributed Ru particles and fewer basic sites, which favored decarbonylation, epimerization and cascade decarbonylation reactions instead of retro-aldol reactions producing glycols. The hydrothermal stability of Ru-(Mn-Al)OX was improved by decreasing the xylitol/catalyst ratio, which decreased the formation of carboxylic acids and enabled recycling of the catalyst, with a very low deactivation.

Au–Pt and Au–Pd bimetallic catalysts were prepared over various supports using different preparation methods and were compared in the base-free selective aerobic catalytic oxidation of glucose to glucaric acid. The method of preparation of the bimetallic catalysts, the support material for the Au–Pt bimetallic nanoparticles, and the metal molar ratios have a strong influence on the activity and the maximum yield of glucaric acid. The Au–Pt/ZrO2 catalyst with a molar ratio for Au/Pt = 1 provides a 50% yield of glucaric acid at complete conversion of glucose and gluconic acid at 100 °C, under 40 bar air, using a glucose/metal ratio of 80. The catalyst was stable upon sequential recycling in a batch reactor and in long-term use in a continuous reactor. The influence of possible residual impurities has been studied. Furan derivatives or lignin residues might be problematic for catalytic oxidation of glucose in hemicellulose hydrolysates.

MICROSCOPIE+CDFA+BKL:MAO:PDE:CPI:MBE; International audience; ReOx-Pd/TiO2 catalysts prepared from different 2wt%Pd/TiO2 catalysts using two protocols for the deposition of the Re promoter (successive impregnation and catalytic reduction) were characterized by different techniques to better understand the nature of the active and selective sites implied in the aqueous-phase hydrogenation of succinic acid to 1,4-butanediol. Regardless of the support and Re introduction method, it was established that varying amounts of Pd and Re were in very close proximity without electronic interaction in the reduced catalysts. A high fraction of Re always remained partially oxidized to generate a bimetallic catalyst that can provide the necessary bifunctional sites to enable the selective hydrogenolysis of the intermediate -butyrolactone to 1,4-butanediol. Depending on the method of promotion, the ReOx species that interact with Pd were deposited as clusters with different spatial Re-Re interactions

SSCI-VIDE+CDFA+FKE:CPI:MBE; International audience; Different oxygen- and nitrogen-containing carbons were studied as supports of ruthenium catalysts for the alkaline aqueous-phase oxidation of 5-hydroxymethylfurfural (HMF) to the corresponding diacid 2,5-furandicarboxylic acid FDCA. The surface properties of catalyst support (active carbon or mesoporous carbon replicated from mesostructured silica) were suggested to be a key factor deeply influencing the oxidation rates of the different steps of this reaction of ruthenium nanoparticles. The results highlight that the HMF oxidation reaction in water does not well tolerate O-functional groups, which strongly adsorb water and then block access of the substrate to the active metal sites and decrease the reaction rates. N-containing carbons were anticipated to be beneficial for the acceleration of the first step of ruthenium-alcoholate species formation. The result was the opposite, with a detrimental effect on the reaction rate when the Ru precursor was reacted with the amine-functionalized surface. (C) 2015 Elsevier B.V. All rights reserved.

SSCI-VIDE+CDFA+JFT:NVI:FAU:MBE:LDJ:CPI; International audience; In this work, it was shown that glycerol (Gly) can be effectively converted to lactic acid (LA) under inert atmosphere using a Pt/ZrO2 catalyst. Starting from pure glycerol, at 180 degrees C and under a He pressure of 30 bar, we were able to achieve up to 80% yield of LA after a reaction time of 8 h. The catalysts performance of Pt/TiO2, Pt/C and Pt/ZrO2 were compared showing that using Pt/ZrO2 high conversion and stable LA selectivity were achieved during all the process. Further, using Pt/ZrO2 the LA selectivity was less sensitive to the nature of the reaction atmosphere while using either H-2 or He. While using crude Gly (85% purity), a lower reaction rate was obtained in the presence of Pt/ZrO2, however high selectivity to LA (similar to 80%) was maintained. (C) 2014 Elsevier B.V. All rights reserved.

SSCI-VIDE+CDFA+NES:MBE; International audience; Pt catalysts prepared over different metallic oxide supports were investigated in the oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) in alkaline aqueous solutions with air, to examine the combined effect of the support and base addition. The base (nature and amount) played a significant role in the degradation or oxidation of HMF. Increasing amounts of the weak NaHCO3 base improved significantly the overall catalytic activity of Pt/TiO2 and Pt/ZrO2 by accelerating the oxidation steps, especially for the aldehyde group. This was highlighted by a proposed kinetic model that gave very good concentration-time fittings. Moreover, the promotion of the catalyst with bismuth yielded a PtBi/TiO2 catalytic system with improved activity and stability. Y2 O3  and La2 O3 ZrO2 -supported catalysts exhibited lower activity than Pt/ZrO2 , which suggests no cooperative effect of the weakly basic properties introduced and the homogeneous base. Quantitative oxidation of HMF (0.1M) and high yields of FDCA (>99%) were obtained in less than 5 h by using an HMF/Pt molar ratio of 100 and Na2 CO3 as a weak base over PtBi/TiO2 (Bi/Pt=0.22). 2015 WILEY-VCH Verlag GmbH

SSCI-VIDE+CARE:CDFA+CLS:MBE:CDS; International audience; Highly active and selective supported noble metal catalysts were studied in the catalytic wet air oxidation of ammonia. Under the applied reaction conditions (200 C, 50 bar total pressure) only nitrites and molecular nitrogen were detected as primary products. Nitrates formed upon oxidation of nitrites. Platinum-based catalysts were shown to be the most active and among the most selective toward molecular nitrogen. The control of the oxygen coverage at the catalyst surface (metal-oxygen bond energy) was evidenced to have a key impact on both the activity and the selectivity. The retro-disproportionation and nitrous acid decomposition reactions appeared to impact the selectivity upon the conversion of nitrites to nitrates. (C) 2014 Elsevier B.V. All rights reserved.

EAU:BIOVERT:RAFFINAGE+FAU:MBC:GAU:CPI:MBR:LDF; The hydrogenolysis of an alkaline aqueous solution of xylitol to mainly ethylene- and propylene-glycols was studied over a Ru/C catalyst in a high pressure fixed-bed reactor run in the trickle-bed mode with co-current downflow of liquid feed and hydrogen. The effects of reaction parameters including H-2 pressure (40-80 bar), temperature (190-200 degrees C) and pH values (NaOH/xylitol molar ratio in the range 0.1-0.2, pH 9-12) and residence time have been explored to increase the selectivity of this reaction to the desired ethyleneglycol product. The activity and final products distribution were much influenced by the hydrogen pressure. An optimum to afford a high conversion and a high selectivity to ethyleneglycol at different space times was found at 60 bar. The effects observed are in agreement with the reaction pathways previously proposed and the relative reaction rates of the dehydrogenation/hydrogenation and base-catalyzed reactions of the intermediates are affected by the hydrogen pressure and the concentration of the alkaline promoter. (C) 2014 Elsevier B.V. All rights reserved.

SSCI-VIDE+CDFA+TGE:MBE:CPI; International audience; Dehydrogenation of geraniol into geranial in the presence of a hydrogen acceptor (alkene) was studied. Supported palladium catalysts were not suitable for this transformation, but supported copper catalysts showed promising results at 150 degrees C; selectivity to the expected geranial was strongly dependent on the support and the calcinations/reduction procedure (>50 % in the presence of Mg-La hydrotalcite-supported copper).

BIOVERT+BKL:CPI; International audience; Bimetallic Re-Pd catalysts were prepared by addition of Re onto a Pd/TiO2 monometallic catalyst, either by a catalytic reduction method or by successive impregnation. The physical and chemical properties of the bimetallic catalysts were evaluated by several characterization techniques, including analysis by transmission electronic microscopy, hydrogen chemisorption, temperature programmed reduction and X-ray photoelectron spectroscopy to explain their different catalytic performances in the selective hydrogenation of succinic acid to 1,4-butanediol in aqueous solution. The localization of the Re deposit on the parent Pd catalyst surface varied according to the Re introduction mode. The catalytic reduction method induced a selective Re deposit at the Pd-TiO2 interface compared to a random distribution obtained by successive impregnation. The oxidation state of the Re species (Re3+, Re-0) on the reduced bimetallic samples was also linked to their preparation mode. (C) 2014 Elsevier B.V. All rights reserved.

International audience

BIOVERT+LCD:BKL:CPI; Supported noble-metal catalysts (Ru, Pd or Pt) and the corresponding Re-promoted catalysts exhibit a high activity for the hydrogenation of biobased carboxylic acids. Levulinic acid and succinic acid are converted into the lactones or the diols depending on the nature of the catalyst and the reaction conditions. The highest selectivity to 1,4-pentanediol of 82% is achieved at 140 degrees C in the presence of the 1.9%Ru-3.6%Re/C catalyst.

BIOVERT+BKL:CPI; A series of 2 wt % Pd/TiO2 monometallic catalysts were prepared by varying some parameters, such as the nature of the precursor salt, the titania support, and the preparation method. The structural and textural properties of the catalytic systems were fully characterized by several physical and chemical techniques (inductively coupled plasma optical emission spectrometry, N-2 physisorption, H-2 chemisorption, transmission.electron microscopy coupled with energy dispersive X-ray spectroscopy, powder X-ray diffraction, temperature programmed reduction, X-ray photoelectron spectroscopy, and gas phase reaction of cyclohexane dehydrogenation). The catalytic performances were further estimated for the hydrogenation of an aqueous solution of succinic acid (SUC) performed in a batch reactor at 160 degrees C and under 150 bar total pressure. The results showed that all the Pd catalysts are very Selective to produce gamma-butyrolactone, the first hydrogenated product. However, the rate of succinic acid conversion is a function of both the Pd dispersion and the preparation method. The deposition-precipitation method allows one to obtain the highest performing 2 wt % Pd/TiO2 samples during SUC hydrogenation in terms of activity and stability.

BIOVERT+NES; 5-Hydroxymethylfurfural (HMF) was quantitatively oxidized to 2,5-furandicarboxylic acid (FDCA) at 100 degrees C under 40 bar air in moderately basic aqueous solution in the presence of active carbon supported platinum and bismuth-platinum catalysts. The transformation of HMF into FDCA proceeded via the 5-hydroxymethyl-2-furancarboxylic acid (HMFCA) and 2,5-diformylfuran (DFF) intermediates; both of these were very reactive and rapidly oxidized to 5-formylfurancarboxylic acid (FFCA), the subsequent oxidation of which was found to be the rate-limiting step. The preparation method of the platinum catalysts influenced the particle size of metallic platinum and modified the surface of the support, therefore determining the activity. The addition of a carbonate base (Na2CO3/HMF molar ratio = 2) led to faster overall conversion than bicarbonate (NaHCO3/HMF = 4) by maintaining an appropriate pH for the oxidation reaction. The ex situ or in situ addition of a bismuth promoter still accelerated the reaction; the highest activity was observed for a Bi/Pt molar ratio of ca. 0.2. Furthermore, the promoter helped to prevent some deactivation of the Pt catalyst upon recycling experiments. Quantitative conversion of HMF (0.1 M) and >99% yield of FDCA were achieved using a molar ratio of HMF to Pt of 100 and Na2CO3 as the homogeneous base in less than 2 h.

BIOVERT+CPI; In the aerobic selective oxidation of alcohols in aqueous medium in a batch reactor, it was observed that the addition of water to dioxane solvent (10-50 vol%) substantially increased the activity of a Pt/C catalyst. Periodic density functional theory (DFT) calculations were carried out to compare the reactivity of alcohols on the bare Pt(111) surface and in the presence of adsorbed water or hydroxyl groups, to explain the effect of water. The calculations indicate that the presence of adsorbed hydroxyl groups promotes the catalytic activity by participating directly in the catalytic pathways and reducing the activation barrier. Good agreement was found between the experiments in aqueous phase and these calculations. Further, decarbonylation of the aldehyde may be involved in the deactivation during oxidation of a primary alcohol.

International audience; Hydrogenation of succinic acid aqueous solutions was performed using TiO2-supported 2 wt% Pd and 2 wt%Pd–x wt%Re catalysts, using either impregnation method or surface redox reduction of the monometallic catalyst. The former catalysts were superior in terms of activity and selectivity to 1,4-butanediol than the latter ones. However, higher Re loadings (3.4–3.6 wt% compared to 0.6–0.8 wt%) were necessary to initiate this synergy.

EAU+MBR:MLD:IDO:CDS; The selective removal of ammonia from industrial waste streams and the conversion of the organic matter to biodegradable compounds, without excessive mineralization of the carbon has been investigated over powder and pelletized titania- and zirconia-supported Pt catalysts in the wet air oxidation (WAO) of aqueous solutions at 200 degrees C under 36 bar of air, in batch and trickle-bed reactors. Ammonium acetate was chosen as a model compound (58 mmol L-1, Total Organic Carbon, TOC = 1392 mg L-1, Total Nitrogen, TN = 812 mg L-1). In the absence of any catalyst, very little ammonium was removed. With addition of a Pt catalyst supported, NH4+ was completely eliminated from the reaction mixture and converted to dinitrogen with a selectivity higher than 97.5%. The treated effluent contained very low concentration of nitrates as a by-product. Interestingly, the platinum catalysts were very little active in the mineralization of the organic carbon, so that the effluent could be post-treated in a conventional biological plant. The catalysts showed the same performances over recycling experiments in a batch reactor. Moreover, the pelletized catalysts were shown to be stable upon preliminary continuous experiments in a trickle-bed reactor over a period of 350 h. The 3%Pt/TiO2 catalysts were significantly more active than the 3%Pt/ZrO2 catalysts in batch and continuous experiments. (C) 2012 Elsevier B.V. All rights reserved.

EAU+CDS; p-Nitrophenol (PNP) is widely used as a raw material in several industries, therefore it can be released to the environment, being mandatory the treatment of the PNP-contaminated industrial wastewaters. In this sense, the influence of temperature, oxygen partial pressure, type of catalyst, pH and ionic strength on the wet air oxidation (WAO) of a highly concentrated PNP wastewater was studied. Several 480 min batch tests have been performed and four Pt and Ru-based catalysts have been tested. The PNP elimination, total organic carbon (TOC) abatement and the intermediates distribution were monitored. Moreover, respirometric screening tests were completed after each experiment to assess the biodegradability enhancement of the catalytic WAO (CWAO) treated effluents. The results showed that PNP elimination was higher than 90% in most cases, being the temperature the most important operating parameter upon CWAO. Additionally, all the catalysts showed a similar behaviour in terms of PNP and TOC conversions. Besides. CWAO increased the biodegradability by more than 50% in most of the tested conditions, being the carboxylic acid fraction the key factor to be taken into account, as the best biodegradability enhancement was observed when this fraction was the highest. The partial pressure of oxygen had a negligible effect on the biodegradability enhancement. The ionic strength influence over the CWAO was studied and even though it did not affect the CWAO performances, the presence of NaCl in the solution resulted in a decrease of the effluent biodegradability. In terms of pH, the most suitable scenario was the one with no pH adjustment. Conclusively, this work demonstrated that an integrated CWAO and biological treatment would allow an easy removal of PNP and the intermediates formed during the first step of the treatment, being the best CWAO conditions for this pre-treatment to work at 180 degrees C under stoichiometric oxygen pressure (i.e. 7.6 bar of oxygen partial pressure) with a Ru/TiO2 catalyst. (C) 2012 Elsevier B.V. All rights reserved.

BIOVERT+FAU:LDJ:CPI; Significant yields of lactic acid (LA) are obtained during the treatment of glycerol solution under inert gas with supported metallic catalysts under basic conditions. The nature of the atmosphere and the metal affected the activity and the selectivity of the reaction. Iridium-based catalysts are efficient for LA synthesis.

EAU+AGC; Catalytic wet air oxidation (CWAO) of a Basic Yellow 11 (BY11) aqueous solution, chosen as a model of a hardly biodegradable non-azo dye was carried out in a continuous-flow trickle-bed reactor, using nickel supported over hydrotalcite precursor calcined at 550 degrees C. An increase in the reaction temperature (120-180 degrees C), and a decrease in dye concentration (1000-3000 ppm) or liquid flow rate (0.1-0.7 mL min(-1)) enhanced the CWAO performance in a 30 and 19% for the variation of the temperature and concentration respectively. After a small leaching observed within the first hours, the catalyst proved to be very stable during the 65-day reaction. The CWAO process was found to be very efficient, achieving BY11 conversion up to 95% and TOC conversion up to 85% at 0.1 mL min(-1) and 180 degrees C under 5 MPa air. (C) 2012 Elsevier B.V. All rights reserved.

International audience; Two series of ceria-supported gold catalysts (1 and 4 wt.% Au) were prepared by deposition-precipitation with urea. Depending on the gold loading, the pretreatment of the Au/CeO2 catalysts (calcination in air vs. reduction in hydrogen) had a great influence on the oxidation state of gold, and in turn, on the activity of the Au/CeO2 catalysts in the Catalytic Wet Air Oxidation (CWAO) of model carboxylic acids. The higher the fraction in metallic gold is, the better the catalytic performances are.

Titania-supported gold catalysts were prepared via the so-called deposition–precipitation method, using either urea or ammonia as the precipitation agent and evaluated in the catalytic wet air oxidation of succinic acid (a model pollutant often found in the degradation pathway of phenolic compounds) at 463 K under 0.75 MPa oxygen partial pressure. The preparation parameter with the strongest impact on the gold particle size, the gold deposition yield, the chlorine removal efficiency and the gold catalyst performances was shown to be the final pH of the preparation, which strongly influenced the gold precursor speciation in solution and the interaction of the gold precursor with the titania support. Gold catalysts were shown to be very active, with about 80% of the succinic acid which is converted being directly mineralized. Furthermore, gold catalysts appeared to be somehow very selective in acetic acid with only traces of acrylic acid being intermediately produced upon succinic acid degradation. The most active catalyst was prepared via deposition–precipitation using ammonia and was shown to be only 3 times less active than the best performing ruthenium catalysts. Unfortunately, the gold catalyst rapidly deactivated upon time on stream, probably due to the intrinsic gold instability under the applied reaction conditions.

In the selective oxidation with air of 1-octanol and 2-octanol in 1,4-dioxane at 100 °C and 10 bar in the presence of carbon supported platinum catalysts, the catalytic activity could be impressively boosted by substitution of pure dioxane by increasing amounts of water. Changing the polarity of the solvent strongly influences the adsorption equilibrium of substrates and products at the catalyst surface and hence plays an influential role on the reaction rate.

Here, we report the transformation of glycerol alkaline solutions in the presence of supported iridium catalysts under either reductive or inert atmosphere at 453 K. It was shown that under H2, the expected 1,2-PDO issued from hydrogenolysis of the triol was the main product while under He, lactic acid was formed predominantly via Cannizzaro rearrangement.

SSCI-VIDE+CARE:CDFA+SYA:MBE:CDS; International audience; Different CexZr1 - xO2 mixed oxides, prepared by co-precipitation and Ce(x)Zri(1 - x)O(2)-supported platinum and ruthenium catalysts, synthesised by impregnation, were investigated in the catalytic wet air oxidation (CWAO) of succinic acid at 190 degrees C under 50 bar total pressure. The catalytic activity of these solids, was demonstrated to be strongly influenced by the Ce content in the CexZr1 - O-x(2) support. The higher the Ce content in the mixed oxide support, the higher the succinic acid removal rate. The ruthenium catalysts exhibited the best performances in terms of succinic conversion at a given time of reaction; but, when the activity was expressed per mole of metal, the platinum catalysts were observed to perform better (435 mol(acid) h(-1) mol(pt)(-1)). Upon recycling reactions, the Ce0.9Zr0.1O2 support and the 0.5 wt% Ru/Ce0.9Zr0.1O2 catalyst maintained some good performances even though the conversion of succinic acid gradually decreased. It was demonstrated that the leaching of the metallic phase, the formation of carbonaceous deposits on the catalyst surface and the decrease of the specific surface area did not play a major role in the deactivation, which was more likely related to modifications of the chemical state of the active phase. Finally, the reaction was shown to be +0.1 order with respect to succinic acid and +0.4 order with respect to oxygen, indicating some major changes in the reaction kinetics and mechanism of the reaction over such catalysts containing ceria. (C) 2014 Elsevier B.V. All rights reserved.

Minh, Doan Pham Besson, Michele Pinel, Catherine Fuertes, Patrick Petitjean, Carole; The effect of addition of Re to activated carbon-supported Ru and Pd catalysts in the hydrogenation of 15 wt% succinic acid aqueous solutions to 1,4-butanediol (BDO) was examined. The yield and selectivity were in the range 62-66% at 160 A degrees C and 150 bar over the Re promoted catalysts. Bio-succinic acid from a fermentation process could be efficiently hydrogenated on 4 wt%Re-2 wt%Pd/C without significant loss of selectivity.

Yang, Shaoxia Besson, Michele Descorme, Claude; CexZr1-xO2-based Pt catalysts were investigated in the catalytic wet air oxidation (CWAO) of formic acid at low temperature (294-326 K) under atmospheric pressure in order to evaluate the impact of the high oxygen mobility over the ceria-zirconia supports on the catalytic performances. The effect of the support composition, the Pt loading and the reaction conditions (reaction temperature, formic acid concentration, oxygen partial pressure) was studied. The bare supports, in the absence of any active metal, appeared to be only slightly active. The 0.080 wt.%Pt/Ce0.9Zr0.1O2 catalyst (0.5 g L-1) exhibited the best performances: 100% formic acid (5 g L-1) conversion was achieved after 360 min at 326 K under atmospheric pressure. The reaction apparent activation energy was ca. 36 +/- 4 kJ mol(-1). In the lowest temperature range (T

Grosjean, Nicolas Descorme, Claude Besson, Michele; N,N-dimethylformamide (DMF) is largely used as versatile solvent in various processes It is thus present in large quantities in many industrial effluents Oxidation of aqueous solutions of DMF with air was conducted at 180-230 degrees C under 50-70 bar total pressure in a batch reactor, in the absence or in the presence of heterogeneous noble metal catalysts (platinum, palladium, and ruthenium) supported on TiO2 or ZrO2 Under the examined reaction conditions. DMF decomposition and oxidation produced dimethylamine (DMA). methylamine (MA), and ammonium as the major N-containing products Formic acid was also intermediately formed from the scission of the C-N bond Nitrites and nitrates were only present in very low amounts. The addition of a catalyst accelerated the initial rates of DMF and TOC (total organic carbon) conversions. but the selectivity to N-2 was low. The production of DMA and MA was demonstrated to be very much detrimental to the chemical stability of these catalysts A dramatic leaching of the noble metals occurred because of the complexation with the free lone pair electrons on the nitrogen atom of these amines. (C) 2010 Elsevier B V All rights reserved

Carrier, M. Besson, M. Guillard, C. Gonze, E.; The Catalytic Wet Air Oxidation (CWAO) of diuron (N-(3,4-dichlorophenyl)-N,N-dimethylurea), a herbicide widely used in agriculture and belonging to the phenylurea family, has been investigated in aqueous solution in the presence of a Ru/TiO2 catalystat 140-180 degrees C and 5 MPa total air pressure. Diuron and Total Organic Carbon (TOC) have been analyzed. Some reaction products were identified by LC-ES/MS, and the amount of the inorganic ions and organic products generated during the process have been measured. Thermal degradation is the main initial process yielding mainly 3.4-dichloroaniline (DCA) and dimethylamine (DMA). Further oxidations lead to ring opening and smaller organic molecules from DCA, but the DMA fragment was more difficult to eliminate. Reactions between DCA and carboxylic acids conducted to the formation of condensation products. On the other hand, dechlorination was fast and complete. The work points out that CWAO over Ru supported catalysts may not a viable technique for degradation of diluted aqueous solutions of diuron. The mineralization is incomplete compared to other Advanced Oxidation Processes, and a possible leaching of the metal by the amines formed by thermal degradation of diuron may be critical. (C) 2009 Elsevier B.V. All rights reserved.

International audience; The wet air oxidation of p-hydroxybenzoic acid, chosen as a model compound of olive mills wastewaters was carried out at 140 degrees C and 50 bar air over Ru catalysts supported on TiO2 prepared by sol-gel method. These catalysts were characterized by means of N-2 adsorption-desorption, XRD and TEM. Optimization of the catalytic performances was obtained by studying some parameters such as the catalyst preparation method, the solvent evacuation way, the nature of the hydrolysis agent, the influence of the ruthenium salt used as the metal precursor (Ru(NO)(NO3)(3) or Ru(acac)(3)) and the catalyst pretreatment. The pre-calcination of the catalyst precursor at 300 degrees C under oxygen, before the reduction step under hydrogen, was detrimental to the activity. The results showed that the use of nitric acid as hydrolysis agent, drying under supercritical conditions and the use of Ru(NO)(NO3)(3) leads to the more efficient catalyst with high TOC abatement.

A series of Ce x Zr 1− x O 2 mixed-oxide-supported Ru catalysts were unprecedentedly evaluated in the catalytic wet air oxidation (CWAO) of 2-chlorophenol (2-CP) solutions (2 g L −1 ). They were shown to exhibit higher performances than the corresponding CeO 2 or ZrO 2 -supported catalysts. The ceria–zirconia solid solution structure appeared to be crucial for the higher activity of the 3 wt.% Ru/Ce x Zr 1− x O 2 catalysts. After introduction of praseodymium or neodymium in the Ce x Zr 1− x O 2 lattice, the activity of the 3 wt.% Ru/Ce x Zr 1− x O 2 catalysts was further improved. Pr was shown to have a greater effect than Nd, especially at low Pr concentration. Further investigations indicated that Ce x Zr 1− x O 2 solid solutions loaded Ru catalysts could maintain outstanding catalytic performances even at low temperature (393 K) and low pressure (3 MPa).