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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

International audience; The catalytic conversion of dihydroxyacetone (DHA) to lactic acid (LA) via pyruvaldehyde (PA) in aqueous media was studied using different homogeneous metal salts. A kinetic model was developed and the parameters corresponding to each reaction steps were estimated. Agreement between experiments and simulated results was excellent and the performance of the different catalysts was consistent with previous studies described in the literature. Aluminium salts, which show the best performance, were tested in a whole range of concentrations and at different pH, in order to identify the catalytically active ionic species. It was confirmed that the DHA to pyruvaldehyde (PA) dehydration step is catalyzed by both Brønsted and Lewis acids whereas the consecutive reaction of PA to LA is solely catalyzed by Lewis acids. Moreover, comparing thermodynamic analysis of the reaction media and kinetic parameters demonstrated that cationic hydroxyl-aluminium complexes [Al(OH)h] (3-h)+ formed in situ by the hydrolysis of the aluminium aqua complexes like [Al(OH2)6] 3+ are the most active Lewis acids.

SSCI-VIDE+CDFA+ASD:NPR:CPI:MBE; International audience; Bimetallic Rh-ReOx (Re/Rh molar ratio 0.4-0.5) catalysts supported on TiO2 and ZrO2 were prepared by the successive impregnation of dried and calcined unreduced supported Rh catalysts. Their catalytic performances were evaluated in the hydrogenolysis of erythritol to butanetriols (BTO) and butanediols (BDO) in aqueous solution at 150-240 degrees C under 30-120 bar H-2. The activity depended on the nature of the support, and the highest selectivity to BTO and BDO at 80% conversion was 37 and 29 %, respectively, in the presence of 3.7 wt% Rh-3.5 wt% ReOx/ZrO2 at 200 degrees C under 120 bar. The characterization of the catalysts by CO chemisorption, TEM with energy-dispersive X-ray spectroscopy, thermogravimetric analysis with MS, and X-ray photoelectron spectroscopy suggests a different distribution and reducibility of Re species over the supported Rh nanoparticles, which depends on the support.

International audience; The aqueous-phase hydrogenolysis of xylitol into glycols over Ru/C was performed in the presence and absence of a wide range of concentrations of Ca(OH)2 to investigate the reaction pathway. Without base, epimerization and cascade decarbonylation were the predominant reactions with high selectivities to C5 and C4 alditols and light alkanes at full conversion. Glycol production was obtained by the addition of Ca(OH)2 to promote the retro-aldol reaction. It competed with reactions without base and became the main reaction for a OH−/ xylitol molar ratio Rmol(OH/xylitol) of 0.13, and high selectivities to glycols (56 %) and glycerol (16 %) were observed. However, lactate was a byproduct at up to 27 % with a high base amount (Rmol(OH/xylitol)=0.68). Bifunctional Ru/metal oxide/C catalysts (metal: Zn, Sn, Mn, Sr, W) were synthesized and were able to cleave the C−C bond into glycols without a base promoter. The 3.1 wt %Ru/MnO(4.5 %)/C catalyst was the most active (220 h−1) with reasonable selectivity to glycols (22 %) and glycerol (10 %) and a low production of lactate (

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%).

The kinetic stability of any material in water relies on the presence of surface weak spots responsible for chemical weathering by hydrolysis. Being able to identify the atomistic nature of these sites and the first steps of transformation is therefore critical to master the decomposition processes. This is the challenge that we tackle here: combining experimental and modeling studies we investigate the stability of alumina in water. Exploring the reactivity of shape-controlled crystals, we identify experimentally a specific facet as the location of the weak spots. Using biased ab initio molecular dynamics, we recognize this weak spot as a surface exposed tetra-coordinated Al atom and further provide a detailed mechanism of the first steps of hydrolysis. This understanding is of great importance to heterogeneous catalysis where alumina is a major support. Furthermore, it paves the way to atomistic understanding of interfacial reactions, at the crossroad of a variety of fields of research., Gaining atomistic level understanding of alumina/water interfaces is key to unraveling alumina decomposition processes. Here the authors combine the experimental synthesis of shape-controlled γ-Al2O3 samples with metadynamics simulations to identify the surface weak spots responsible for alumina decomposition.

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.

SSCI-VIDE+CDFA+EDE:CPI:MBE; International audience; The hydrolysate recovered after acid hydrolysis of the hemicellulose fraction of softwood represents a renewable and low-cost source of sugars which can be used for the production of chemicals such as glucaric acid. In this paper we first re-evaluated the metal-catalyzed aerobic oxidation of gluconate and one-step oxidation of glucose to glucarate in alkaline aqueous solution at 60 degrees C using air as oxidant. Then, we investigated the possible inhibitory effect of some inherent side (or by)-products liberated during the dilute mineral acid hydrolysis. High conversion efficiencies were obtained in glucose oxidation; however, the maximum glucarate yield was 54% over Pt/C since overoxidation products were formed under these conditions. As regards the residues in the hydrolysate, sodium salts (acetate and sulfate) or disaccharides (cellobiose and maltose) were without significant effect on the course of the reaction, whereas furan aldehydes (5-hydroxymethylfurfural and furfural) appeared to significantly slow down the reaction rates. Small phenolic residues from lignin showed a detrimental effect and should be eliminated prior to upgrading by catalytic oxidation of glucose in the hydrolysates.

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.

EAU:BIOVERT+PGA:CPI

This article presents the first systematic study concerning the effect of the oxidative treatment conditions on the surface chemical composition and the catalytic properties in the deep wet oxidation of organic ecotoxicants of a Sibunit type carbon material (S4) which was earlier identified as promising for the oxidative treatment of industrial wastewaters. The influence of the surface chemistry of the carbon materials oxidized under different conditions on the catalytic performances in the wet air oxidation of phenol of the bare carbon materials as well as the ruthenium-containing catalysts (3 wt % Ru) supported on the oxidized carbon samples was studied. The catalytic activity of the bare carbon samples appeared to be moderate and either (i) increased with the total number of carbonyl and phenolic surface groups or (ii) decreased with the total concentration of surface carboxylic and lactonic species. However, the catalytic performances of the Ru-containing catalysts were significantly higher. Based on our results, an optimum pretreatment of the carbon support could be identified to obtain the most stable and active Sibunit-supported ruthenium catalysts in the wet air oxidation of phenols.

Pt/C and PtBi/C catalysts prepared on a synthetic mesoporous carbon were evaluated in the oxidation of secondary aromatic alcohols (1-phenylethanol, α-methyl or phenyl pyridinemethanol) with air in different dioxane/water mixtures at 100 °C under 10 bar air. The observed activity for all substrates over both types of catalysts was strongly improved with the addition of water to the dioxane solvent as a result of different interactions of the alcohols with the metallic surface in the apolar dioxane solvent or polar aqueous medium. A promoting effect of bismuth was observed for all substrates. However, the reaction rate was also dramatically influenced by the nature of the aromatic moiety, the nature of the α-group, and the position of the substituent on the pyridine moiety. As a general rule the reactivity was meta

The influence of the surface chemical composition of carbon catalysts prepared by oxidative treatment on the basis of the Sibunit-4 carbon material of the Sibunit family on their catalytic properties in the liquid-phase oxidation of formic acid by hydrogen peroxide was studied for the first time. Pure carbon samples were found to be active in the destruction of hydrogen peroxide and the oxidation of an organic substrate, and their activity decreased with an increase in the number of carboxyl and lactone groups on the surface of a carbon catalyst. Nevertheless, the rates of such processes on carbon catalysts are lower than in the presence of even small amounts of homogeneous Fe3+. It was shown that carbon samples accelerate or (to the contrary) inhibit the Fe3+-catalyzed peroxide oxidation of an organic substance, depending on the quantitative ratio of surface carboxyl and lactone groups and Fe3+ ions in the reaction solution. Possible acceleration and inhibition mechanisms for peroxide oxidation on carbon catalysts are discussed. The established influence of the surface chemical properties of carbon catalysts must be taken into account in the development of catalysts and processes for the oxidative purification of industrial wastewater.

This article presents the first systematic study of the effect of oxidation under various conditions on the surface composition and catalytic properties of a carbon material of the Sibunit family (which is promising for oxidative treatment of industrial wastewater) in deep oxidation of organic ecotoxicants in aqueous solution. Modification of the surface properties and texture of Sibunit-4 by various oxidative treatment procedures using nitric acid, sodium hypochlorite, hydrogen peroxide, or oxygen as the oxidant is reported. The chemical state of the surface of oxidized Sibunit and its texture have been investigated by a combination of physical and chemical methods (XPS, acid-base titration with bases differing in strength, pH slurry measurements, determination of pH at the point of zero charge, and low-temperature N2 adsorption). By using different oxidation procedures, it is possible to obtain oxidized Sibunit samples with variable concentrations and natures of oxygen-containing surface groups.

Bernardi, Marco Cretenot, Didier Deleris, Stephane Descorme, Claude Chauzy, Julien Besson, Michele 6th World Congress on Oxidation Catalysis (6WCOC) JUL 05-10, 2009 Lille, FRANCE; International audience; Various soluble transition metal salts were compared in the wet air oxidation of industrial and municipal sewage sludges (2 5-25 g L-1 total organic carbon) at 200-250 degrees C under 4-15 bar O-2 partial pressure The evolution of the TOC content in both the liquid and solid phases and the overall TOC conversion were monitored While copper sulphate prevented the dissolution of the suspended organic matter due to strong bounding of copper to a fraction of the organic matter in sludge and showed high activity in the mineralization of the solubilized organic compounds (liquid phase) the implementation of iron sulphate resulted in a higher transfer of the organic matter to the liquid phase but in a moderate activity in the oxidation of solubilized molecules When used in combination a synergetic effect between these two salts was evidenced (C) 2010 Elsevier BV All rights reserved

Taran, Oxana Polyanskaya, Elena Ogorodnikova, Olga Kuznetsov, Vladimir Parmon, Valentin Besson, Michele Descorme, Claude; The catalytic behavior of five different carbon materials (mesoporous graphite-like carbon Sibunit, catalytic filamentous carbon (CFC), nano-diamonds (ND) and onion-like carbon (OLC)) in the catalytic wet peroxide oxidation of model organic compounds with different sorption capacities and stability towards oxidation (phenol, ethanol and formic acid) has been examined, in the absence and in the presence of Fe3+ ions. All the bare carbons showed extremely low catalytic activity in the oxidation of phenol. ethanol and formic acid in the absence of iron. The homogeneous Fe-catalyzed oxidation of all substrates was much faster. Furthermore, in the Fe-promoted catalytic oxidation over carbons, the presence of ND inhibited the oxidation of the model substrates compared to the homogeneous Fe3+-catalyzed oxidation. On the contrary, the other carbon samples (OLC, CFC. Sibunit) accelerated the oxidation of ethanol and formic acid under the same reaction conditions. More complex effects were observed for OLC. CFC and Sibunit in the oxidation of phenol. A tentative mechanism is discussed. (C) 2010 Elsevier B.V. All rights reserved.

Olive oil mill wastewater (OMW) generated by the olive oil extraction industry constitutes a major pollutant, posing severe environmental threats. It contains a high organic load and phytotoxic and antibacterial phenolic compounds which resist biological degradation. Platinum and ruthenium supported titania or zirconia were studied in the catalytic wet air oxidation (CWAO) of OMWs in a batch reactor and in a continuous trickle-bed reactor. CWAO experiments at 190 °C and 70 bar total air pressure confirmed the effective elimination of the TOC (total organic carbon) and of the phenolic content of actual diluted OMW. Simultaneously, toxicity towards Vibrio fischeri was reduced and a decrease in phytotoxicity occurred. The ruthenium catalysts were found stable over a long period of operation in a trickle-bed reactor. The biodegradability of the oxidized waste has been enhanced and this study also examined the feasibility of coupling CWAO and an anaerobic digestion treatment. The pretreatment of the OMW in the presence of a ruthenium catalyst reduced considerably the total phenolic contents of the wastewater, and produced an effluent suitable to be treated by anaerobic treatment with increased biomethane production compared to the untreated effluent.

International audience; A series of noble metal (Pt, Pd, Ru) loaded Ce0.33Zr0.63Pr0.04O2 catalysts were used in the Catalytic Wet Air Oxidation (CWAO) of 2- chlorophenol (2-CP) at relatively low temperature (393 K). Among the investigated noble metals, Ru exhibited the best activity. To optimize the reaction conditions, the effects of different parameters, such as the nature of the ruthenium precursor, the reaction temperature, the total pressure, the initial 2-CP concentration and the initial pH of the 2-CP solution on the catalytic performances of 3 wt.% Ru/Ce0.33Zr0.63Pr0.04O2 were evaluated. It was confirmed that the nature of the ruthenium precursor had nearly no effect on the activity of Ru/Ce0.33Zr0.63Pr0.04O2. The activation energy for the 2-CPCWAO over Ru/Ce0.33Zr0.63Pr0.04O2 was calculated to be 34 kJ mol-1. Unexpectedly, the 2-CP removal rate was 0.5 order with respect to the initial 2-CP concentration. Furthermore, the CWAO of 2-CP changed from first order (‘‘oxygen diffusion control'') to zero order (‘‘kinetic control'') with respect to the oxygen partial pressure, when the total pressure was higher than 4 MPa. The 2-CP conversion increased with the pH of the initial 2-CP solution. The dechlorination reaction is promoted at higher pH. However, too high pH hindered the total mineralization of 2-CP due to the possible poisoning effect of adsorbed carbonate and hydroxycarbonate species. The optimum initial pH was about 6.

International audience; Abstract We report for the first time the use of CexZr1−xO2 solid solutions as supports for Ru catalysts to be implemented in the catalytic wet air oxidation of 2-chlorophenol. Such catalytic systems appeared to be very efficient, even at low temperature (393 K) and low pressure (3 MPa), and exhibited a great advantage over Ru/CeO2 or Ru/ZrO2.

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.

The objective of this work was to investigate the catalytic wet air oxidation of p-coumaric acid, a biorecalcitrant phenolic compound typically found in olive oil wastewaters in the presence of Pt and Ru supported catalysts. The influence of the operating variables were established. The most important intermediates determined by HPLC measurements suggest a rapid attack by oxygen of the side-chain of p-coumaric acid, and the mineralization proceeds through different aromatic compounds reacting further to aliphatic intermediates (mainly acids). Important mineralization yields were achieved in the presence of the catalysts at 140 °C and 50 bar air. The importance of the nature of the support (TiO2, ZrO2) on the adsorption of p-coumaric acid was demonstrated.

Pt and Ru catalysts on mesoporous (MSP) TiO2 and ZrO2 were developed using sonochemical irradiation. The catalysts were characterized by XRD, TEM, HR TEM, EDX, and BET methods. The high homogeneity of the active metal phase was confirmed by electron microscopy. The catalysts were examined for the removal of organic pollutants from model wastewaters using the wet air oxidation (WAO) process of acetic, succinic and p-coumaric acids in an autoclave reactor at 140 and 190 °C and 50 bar total air pressure. The high activity and stability of Pt supported on a TiO2 (MSP) catalyst in the removal of succinic and p-coumaric acids, and intermediates of their oxidation was demonstrated. The catalytic performances of Ru/TiO2 (MSP) were similar to those of the catalysts prepared by incipient-wetness impregnation of commercial TiO2 supports.

This paper gives three examples of applications of activated carbons, including synthetic carbons obtained from polymers, in selective liquid phase organic reactions. It is shown that ruthenium supported on activated carbon cloths (ACC) obtained by carbonisation of woven rayon fabric are very selective in the hydrogenation of glucose to sorbitol. This is attributed to an easy mass transfer from the micropores to the liquid phase which favours the fast desorption of sorbitol avoiding epimerisation to mannitol. Synthetic carbons obtained by carbonisation of cross-linked phenolic resins are active in the oxidation with air of cyclic ketones (cyclohexanone, cyclododecanone, 3,3,5-trimethylcyclohexanone) to the corresponding dicarboxylic acids. The activity and selectivity depend upon treatments favouring the presence of surface functional groups, particularly quinone/carbonyl groups. This paper also shows that activated carbons obtained from natural sources can be modified by thermal treatments favouring the presence of basic sites which improve the rate of the oxidative decarboxylation of N-phosphonomethyl iminodiacetic acid to glyphosate. The nitrogen-containing basic functions generated by high temperatures thermal treatment of the activated carbon in NH3 are particularly active.

The stability of ruthenium catalysts supported on TiO2 and ZrO2 were studied in the wet air oxidation of aqueous solution of succinic and p-hydroxybenzoic acids taken as model effluent and on real effluents from the paper-pulp industry. Catalyst recycling experiments were conducted in batch reactor and long-term stability tests were conducted in trickle-bed reactor. In all experiments, ruthenium and support materials were perfectly stable to leaching, sintering and fouling. Ruthenium catalysts experienced a weak deactivation as they were exposed to air, e.g., in recycling experiments however the loss of activity occurred only after the first exposure and was completely reversible upon catalyst reduction. The deactivation was attributed to an over-oxidation of the catalyst surface particularly noticeable in the case of very small Ru-clusters (1 nm).

The hydrogenation of 9,10-dihydro-12-hydroxymethylene-9,10-ethanoanthracene-11-one was studied over ruthenium- and platinum-supported catalysts. The influence of several parameters on the activity and the diastereoselectivity of the reaction was studied and it was shown that the nature of the metal played a significant role. In the presence of platinum, both carbonyl groups were reduced with low diastereoselectivity towards the cis diol, while in the presence of ruthenium the diastereoselectivity could reach 60% in favour of the trans diol.

Catalytic wet-air oxidation of acidic and alkaline Kraft bleach plant effluents was investigated in a batch slurry reactor over TiO2 and Ru(3 wt.%)/TiO2 solids. At 463 K and 5.5 MPa total pressure, a drastic extent of total organic carbon (TOC) removal was observed with addition of the titanium dioxide support (TOC conversions up to 87%). The rate of TOC removal was further enhanced by deposition of metallic ruthenium on the TiO2 support. In that case, the decolorized liquid effluents were produced, with very low TOC values (TOC removal >99.6%), constituted of traces of acetic acid. No leaching of Ru or Ti was detected by ICP–AES analysis to the detection limits of 0.2 and 0.1 mg l−1, respectively. The overall kinetics of TOC removal was described by a simplified lumped kinetic model, assuming second-order kinetics for all reaction steps in a triangular reaction scheme. This model and its calculated parameters successfully predicted the time course and distribution of carbon lumps involved in the reactions.