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fff; International audience; Identifying the structure of the most active site is essential to improve the performance of supported metal catalysts. For structure-sensitive reactions, in silico design cannot be easily achieved combining the scaling relations and Brønsted–Evans–Polanyi relations, which are only built on energy-based descriptors. We used here the generalized coordination number as a structural descriptor and established that low-coordinated sites are desirable when using Co and Cu to perform the acceptor-less alcohol dehydrogenation reaction.

The synthesis of Co-Ru bimetallic nanoparticles was performed by co-reduction of Co(II) and Ru(III) salts in octan-1-ol, acting both as a solvent and a mild reducing agent. The metal composition was varied in the entire range, from pure Co to pure Ru. Although Co and Ru are miscible in the bulk, the formation of nanoalloys is not straightforward and requires selecting carefully reaction parameters such as the nature of the solvent and that of the metal precursors. The formation of nanoalloys was unambiguously evidenced by HAADF STEM–EDX analyses. The particle size and the size dispersity were found to decrease with increasing Ru amount, yielding very small and monodisperse particles for the richest compositions in Ru. The unsupported particles were tested for the acceptorless alcohol dehydrogenation using (±)-octan-2-ol and octan-1-ol as model substrates. The results clearly show a synergetic effect since the bimetallic particles exhibit better performances than their monometallic counterparts.

fff; International audience; Mo/TiO2 catalysts with atomic dispersion of molybdenum appear active and stable in the gas-phase hydrogenation of CO2. The comparison between various titania materials shows a crucial effect of the support surface structure on the methanol yield. Molybdenum supported at low coverage on rutile titania nanorods is the most active and methanol-selective system. From catalyst characterization by aberration-corrected scanning transmission electron microscopy, near-ambient pressure X-ray photoelectron spectroscopy, diffuse reflectance UV-vis spectroscopy, and temperature-programmed techniques, we suggest that the most active catalysts for methanol production involve atomically-dispersed oxomolybdate species with high reducibility and strong interaction with the rutile support.

Les pratiques numeriques ne sont pas innees et necessitent donc un accompagnement. Dans le secteur de la protection de l'enfance et plus particulierement de l'accompagnement des jeunes majeurs, la question du numerique est un enjeu educatif important. L'education au numerique est necessaire pour ces jeunes qui doivent etre independants precocement.L’independance vis-a-vis du systeme de protection de l’enfance ne peut etre transferee du cote des solidarites familiales puisque le soutien familial fait defaut et a justifie les mesures de protection. Aussi, seul le recours a d’autres aides sociales peut permettre de compenser la precocite de cette independance juvenile. Seulement quand l’acces a ces aides sous-tend des equipements numeriques et un savoir-faire « administrativo-numerique », comment faciliter la transition ? C’est pour repondre a cette question que nous avons decide de monter un projet associatif permettant l’accompagnement des jeunes majeurs au numerique. Ce projet passe par la mise en œuvre d’un bus itinerant proposant des ateliers numeriques. Ces ateliers ont pour objectif de permettre aux jeunes majeurs d’acceder a une culture informationnelle, de pouvoir faire les demarches administratives pour beneficier de prestations sociales et de favoriser le lien social.

The catalytic effect of nitrogen incorporation into Mo on hydrogenation (of –NO2 to –NH2 in nitrobenzene to aniline) and hydrogenolysis (of –CO in benzaldehyde to toluene) processes has been assessed. Bulk Mo was prepared by temperature programmed reduction of MoO3 (in H2 to 933 K) and β-Mo2N (confirmed by powder XRD) subsequently synthesised by Mo nitridation in N2/H2. Two intermediate samples (MoN-1 and MoN-2) with different Mo/N ratio were prepared by altering the duration (1 and 2 h) of the nitridation step. XPS analysis revealed a nitrogen surface enrichment (Mo/N = 2.2 → 0.9 from MoN-1 to β-Mo2N) relative to the bulk (Mo/N = 5.1 → 2.5). Incorporation of N did not affect morphology and each sample exhibited (by SEM analysis) aggregates (

This study describes the use of new ZnO/PAAH hybrid nanomaterials (PAAH = polyacrylic acid) as copper catalyst supports for the hydrogenolysis of glycerol. A study of the synthesis parameters (washing process, temperatures of synthesis and calcination) of these hybrid supports has allowed us to vary their morphology and specific surface area and ultimately the sizes and dispersion of the copper nanoparticles, and to perform a general analysis of their effects on the catalytic performance of the materials. All catalysts were synthesized by the urea deposition-precipitation method (DPU) and were fully characterized to establish a structure–activity relationship. Optimization of the synthesis and catalytic conditions allowed remarkable yields/conversions of the order of 70% for selectivities in 1,2 propanediol of 90%.

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.

SSCI-VIDE+CDFA:ECI2D+RCE:CPI:LPI:NPR; International audience; Catalysts based on molybdenum carbide or nitride nanoparticles (2–5 nm) supported on titania were prepared by wet impregnation followed by a thermal treatment under alkane (methane or ethane)/hydrogen or nitrogen/hydrogen mixture, respectively. The samples were characterized by elemental analysis, volumetric adsorption of nitrogen, X-ray diffraction, and aberration-corrected transmission electron microscopy. They were evaluated for the hydrogenation of CO2 in the 2–3 MPa and 200–300°C ranges using a gas-phase flow fixed bed reactor. CO, methane, methanol, and ethane (in fraction-decreasing order) were formed on carbides, whereas CO, methanol, and methane were formed on nitrides. The carbide and nitride phase stoichiometries were tuned by varying the preparation conditions, leading to C/Mo and N/Mo atomic ratios of 0.2–1.8 and 0.5–0.7, respectively. The carbide activity increased for lower carburizing alkane concentration and temperature, i.e., lower C/Mo ratio. Enhanced carbide performances were obtained with pure anatase titania support as compared to P25 (anatase/rutile) titania or zirconia, with a methanol selectivity up to 11% at 250°C. The nitride catalysts appeared less active but reached a methanol selectivity of 16% at 250°C.CO(2)hydrogenation

SSCI-VIDE+CDFA+ALI:CPI:NPR; International audience; Molybdenum carbides supported on TiO2 or ZrO2 were prepared by a temperature-programmed reduction–carburization method using mixtures of hydrogen and hydrocarbon (methane or ethane). All of the materials exhibited molybdenum carbide with a cubic crystallographic structure. The carbon content and the MoC lattice parameter increased with the increase of the hydrocarbon percentage (5–40%) and temperature (600–800 °C) during carburization. All catalysts were significantly active in the hydrogenation of succinic acid to butyric acid and γ-butyrolactone. For the first time, a correlation between the degree of carburization and the catalytic activity for succinic acid hydrogenation was established. The selectivity depends strongly on the support. MoC/TiO2 favored the formation of butyric acid, while MoC/ZrO2 and bulk MoC generated γ-butyrolactone primarily. The stability of MoC/TiO2 up to 50 h on stream in a continuous reactor was demonstrated, showing the interest of carbide catalysts for future biorefinery processes.

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.

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 production of cyclopentanone derivatives from 5-hydroxymethylfurfural (HMF) using non-noble metal based catalysts is reported for the first time. Five different mixed oxides containing Ni, Cu, Co, Zn and Mg phases on an Al-rich amorphous support were prepared and characterised (XRD, ICP, SEM, TEM, H2-TPR, NH3/CO2-TPD and N2 sorption). The synthesised materials resulted in well-dispersed high metal loadings in a mesoporous network, exhibiting acid/base properties. The catalytic performance was tested in a batch stirred reactor under H2 pressure (20–50 bar) in the range T = 140–180 °C. The Cu–Al2O3 and the Co–Al2O3 catalysts showed a highly selective production of 3-hydroxymethylcyclopentanone (HCPN, 86%) and 3-hydroxymethylcyclopentanol (HCPL, 94%), respectively. A plausible reaction mechanism is proposed, clarifying the role of the reduced metal phases and the acid/basic sites on the main conversion pathways. Both Cu–Al2O3 and Co–Al2O3 catalysts showed a loss of activity after the first run, which can be reversed by a regeneration treatment. The results establish an efficient catalytic route for the production of the diol HCPL (reported for the first time) and the ketone HCPN from bio-derived HMF over 3d transition metals based catalysts in an environmental friendly medium such as water.

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%).

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%).

TiO2-supported Mo carbides “MoC/TiO2” were prepared by impregnation of Mo salt followed by temperature programmed reduction-carburization using 20% v/v C2H6/H2. Catalysts were characterized by XRD, XPS, TEM, STEM, ICP, Raman, BET, and carbon elemental analysis. The catalytic activity was evaluated for aqueous phase hydrogenation of succinic acid at 160–240 °C, and 90–150 bar of H2 in batch reactor. MoC/TiO2 is active for this reaction. The main products after 24 h are γ-butyrolactone, and more remarkably butyric acid. These intermediates are then converted to tetrahydrofuran, butanol, 1,4-butanediol and butane. The reaction conditions (temperature, pressure) do not impact the products distribution. A larger amount of butyric acid is formed when catalysts were synthesized with a higher gas hourly space velocity. The deactivation observed while recycling the catalyst was mainly attributed to a decrease in the amounts of carbidic molybdenum and carbidic carbon, as demonstrated by XPS analysis.

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; We report the first synthesis of Mo2C-supported Au and Au–Pd catalysts (nominal Au/Pd = 10 and 30) obtained from colloidal nanoparticles stabilised by polyvinyl alcohol (PVA). Equivalent Au/Al2O3 and Au–Pd/Al2O3 were prepared and served as benchmarks. Residual PVA was removed by thermal treatment in N2, which was monitored by thermogravimetric analysis. The catalysts were characterised in terms of temperature-programmed reduction (TPR), BET surface area, H2 chemisorption, powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) measurements. The reduced catalysts exhibited an equivalent metal particle size range (1–8 nm) and mean size (4–5 nm). The carbide samples showed greater H2 chemisorption capacity than the Al2O3 systems where inclusion of Pd enhanced H2 uptake. XPS measurements suggest electron transfer from Al2O3 to Au while the Au binding energy for the carbide samples is close to that of the metallic Au reference. The catalysts were tested in the gas phase hydrogenation of nitrobenzene, p-chloronitrobenzene and p-nitrobenzonitrile and delivered 100% selectivity to the target amine in each case. Inclusion of Pd served to increase selective hydrogenation rates where Au–Pd/Mo2C outperformed Au–Pd/Al2O3, a response that is attributed to increased surface hydrogen.

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+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.

The role of the support in the gas phase hydrogenation of butyronitrile over Pd/Al2O3 and Pd/C (2.5–3.0 nm mean Pd size) has been studied, taking bulk Pd as benchmark. Catalyst activation by temperature programmed reduction was monitored and the metal and acid functions characterized by H2 and NH3 chemisorption/temperature programmed desorption and electron microscopy (STEM/TEM). Butyronitrile hydrogenation was stable with time on-stream to deliver butylamine where consecutive condensation with the intermediate butylidenimine generated dibutylamine and tributylamine. Condensation can occur on bulk Pd but selectivity is influenced by the support and reaction over Pd/Al2O3 generated dibutylamine as principal product. Preferential tertiary amine formation was observed over Pd/C and attributed to greater surface acidity that favors the condensation step. Increased hydrogen spillover and acidity (associated with Pd/C) elevated butyronitrile consumption rate.

Synthesis of phase pure Co3Mo3N and Fe3Mo3N by temperature programmed ammonolysis has been established by XRD and elemental analysis. The ternary nitrides are characterised by a η-6 structure and low surface area (4–9 m2 g−1). Pseudomorphic transformation of cobalt molybdate prepared using cobalt nitrate generated rod-shaped crystals while the use of iron chloride resulted in Fe3Mo3N aggregates with irregular morphology and wide size distribution. XPS measurements have revealed surface N enrichment relative to the bulk where the passivated samples show a range of oxidation states; Co3Mo3N exhibited Mo2+ and Con+ (0 ≤ n ≤ 3) whereas Fe3Mo3N was characterised by higher oxidation states (Fe3+ and Mo3+). Temperature programmed reduction (TPR) to 823 K served to remove the passivation layer where subsequent H2 chemisorption and temperature programmed desorption (TPD) has demonstrated greater uptake on Fe3Mo3N relative to Co3Mo3N, resulting in a higher nitrobenzene hydrogenation rate (to aniline). Fe3Mo3N promoted selective reduction of –NO2 in p-chloronitrobenzene to generate p-chloroaniline as sole product whereas Co3Mo3N favoured C-Cl scission with the formation of nitrobenzene (in addition to p-chloroaniline). Hydrodechlorination properties were further established for Co3Mo3N in the conversion of chlorobenzene (to benzene) under conditions where Fe3Mo3N was inactive. A temporal deactivation of both nitrides is associated with Cl poisoning of Co3Mo3N and structural changes to Fe3Mo3N.

The gas-phase hydrogenation of benzoic acid was studied over Au supported on CeO 2 and Ce 0.62 Zr 0.38 O 2 (CZ). HAADF-STEM has established formation of nanoscale (mean = 1.5–2 nm) Au particles, which is consistent with CO adsorption measurements. Incorporation of Au facilitated partial support reduction during TPR to 573 K where the presence of Zr increased oxygen mobility, resulting in a greater degree of Ce 4+ reduction (to Ce 3+ ) in Au/CZ, as demonstrated by oxygen storage capacity and XPS measurements. Hydrogenation of an aqueous benzoic acid feed generated benzaldehyde and benzyl alcohol with a higher rate over Au/CZ that is attributed to the action of oxygen vacancies, which activate the carboxyl function for hydrogen attack. A parallel/consecutive kinetic model has been applied to quantify catalytic selectivity. A concerted (single step) conversion is proposed for Au/CeO 2 that involves bridging interaction of the benzoate with Ce cations and Au nanoparticles with hydrogen addition. A stepwise conversion on Au/CZ is achieved via a Mars and van Krevelen mechanism with benzoic acid activation at an oxygen vacancy and reaction with surface hydrogen to generate benzaldehyde as a reactive intermediate that is converted to benzyl alcohol via nucleophilic C O attack. Switching from an aqueous to ethanolic feed increased rate due to greater oxygen vacancy availability with higher selectivity to benzaldehyde and appreciable toluene formation over Au/CZ.

Exclusive hydrogenation of benzaldehyde to benzyl alcohol in gas phase continuous operation (393–413 K, 1 atm) was achieved over Au/Al2O3, Au/TiO2 and Au/ZrO2. Synthesis of Au/Al2O3 by deposition–precipitation generated a narrower distribution (2–8 nm) of smaller (mean = 4.3 nm) Au particles relative to impregnation (1–21 nm, mean = 7.9 nm) with increased H2 uptake under reaction conditions and higher benzaldehyde turnover. Switching reactant carrier from ethanol to water resulted in a significant enhancement of selective hydrogenation rate over Au/Al2O3 with 100% benzyl alcohol yield, attributed to increased available reactive hydrogen. This response extends to reaction over Au/TiO2 and Au/ZrO2.

We report the first continuous (gas phase) hydrogenation of nitrocyclohexane over oxide (Al2O3, TiO2, CeO2 and ZrO2) supported Au catalysts. Thermochemical analysis has established possible thermodynamic constraints and product distribution at equilibrium. The catalysts have been characterised by temperature-programmed reduction (TPR), H2/O2 chemisorption/temperature-programmed desorption (TPD), BET surface area/porosity, X-ray diffraction (XRD) and scanning/transmission electron microscopy (STEM/TEM) measurements. The effects of space velocity (2–6 × 104 h−1), temperature (353 and 473 K) and H2 partial pressure (8 × 10−4–0.93 atm) on catalyst performance have been examined. Selectivity to the target cyclohexanone oxime is sensitive to H2 pressure, where an increase in temperature favours cyclohexanone with amine/ketone condensation and subsequent reduction to dicyclohexylamine. An increase in turnover frequency was observed with decreasing (surface area weighted) mean Au size (from 7.0 to 4.3 nm) but a lower value was obtained for 3.0 nm Au (on CeO2) that is linked to suppressed H2 chemisorption (under reaction conditions) resulting from strong interaction with the partially reduced support. We establish a critical surface interplay between imine, H and –OH that governs selectivity. Au/Al2O3 exhibited the highest activity and oxime selectivity (maximum = 95%), Au/CeO2 promoted near exclusive production of cyclohexanone whereas Au/TiO2 and Au/ZrO2 generated a cyclohexylamine/cyclohexanone mixture.

The use of nonreducible (Al2O3) and reducible (Ce0.62Zr0.38O2, CZ) carriers to support nanoscale Au has been studied in gas phase p-chloronitrobenzene hydrogenation. Reaction over Au/Al2O3 generated p-chloroaniline as the sole product, whereas Au/CZ catalyzed nitro-group reduction and dechlorination to aniline. A parallel/consecutive kinetic model has been applied to quantify selectivity for Au/CZ. Catalyst characterization has included temperature programmed reduction (TPR)/desorption (TPD), XPS, HAADF-STEM, CO adsorption-FTIR, and oxygen storage capacity (OSC) measurements. The incorporation of Au with CZ promoted reduction of the support with the generation of surface hydrogen and oxygen vacancies, where the latter was facilitated at higher reduction temperature (from 393 to 973 K). Strong Au–CZ interactions enhanced Au dispersion with a narrow size distribution (mean = 1.8–1.9 nm) and influenced adsorptive and catalytic properties. Sintering of Au (from 5.7 to 8.8 nm mean) on Al2O3 was observed with i...

The catalytic response of Ni on Al2O3 obtained from Ni-Al layered double hydroxides was studied for the liquid-phase hydrogenation of hydroxymethyl furfural to tetrahydrofuran-2,5-diyldimethanol (THFDM) in water. The successive calcination and reduction of the precursors caused the removal of interlayer hydroxyl and carbonate groups and the reduction of Ni(2+) to Ni(0). Four reduced mixed oxide catalysts were obtained, consisting of different amount of Ni metal contents (47-68 wt%) on an Al-rich amorphous component. The catalytic activity was linked to Ni content whereas selectivity was mainly affected by reaction temperature. THFDM was formed in a stepwise manner at low temperature (353 K) whereas 3-hydroxymethyl cyclopentanone was generated at higher temperature. Coke formation caused deactivation; however, the catalytic activity can be regenerated using heat treatment. The results establish Ni on Al2O3 as a promising catalyst for the production of THFDM in water.

Metal–Organic Frameworks (MOFs) are porous crystalline materials that have emerged as promising hosts\ud for the heterogenization of homogeneous organometallic catalysts, forming hybrid materials which\ud combine the benefits of both classes of catalysts. Herein, we report the encapsulation of the\ud organometallic cationic Lewis acidic catalyst [CpFe(CO)2(L)]+ ([Fp–L]+, Cp ¼ h5\ud -C5H5, L ¼ weakly bound\ud solvent) inside the pores of the anionic [Et4N]3[In3(BTC)4] MOF (H3BTC ¼ benzenetricarboxylic acid) via\ud a direct one-step cation exchange process. To conclusively validate this methodology, initially [Cp2Co]+\ud was used as an inert spatial probe to (i) test the stability of the selected host; (ii) monitor the\ud stoichiometry of the cation exchange process and (iii) assess pore dimensions, spatial location of the\ud cationic species and guest-accessible space by single crystal X-ray crystallography. Subsequently,\ud the quasi-isosteric [Fp–L]+ was encapsulated inside the pores via partial cation exchange to form\ud [(Fp–L)0.6(Et4N)2.4][In3(BTC)4]. The latter was rigorously characterized and benchmarked as\ud a heterogeneous catalyst in a simple Diels–Alder reaction, thus verifying the integrity and reactivity of\ud the encapsulated molecular catalyst. These results provide a platform for the development of\ud heterogeneous catalysts with chemically and spatially well-defined catalytic sites by direct exchange\ud of cationic catalysts into anionic MOFs.

The catalytic action of Mo2N and Au/Mo2N has been assessed in the selective gas phase hydrogenation of p-chloronitrobenzene (p-CNB) to p-chloroaniline (p-CAN). The nitrides were synthesised via temperature programmed treatment of MoO3 in H-2 + N-2 and Au introduced by deposition-precipitation with urea. We have examined the influence of nitride crystallographic phase (tetragonal beta-Mo2N vs. cubic gamma-Mo2N) and surface area (7-66 m(2) g(-1)) on the catalytic response. Catalyst activation by temperature programmed reduction has been monitored and the reduced catalysts characterised in terms of BET area/pore volume, H-2 chemisorption/temperature programmed desorption (TPD), powder X-ray diffraction (XRD), elemental analysis, scanning (SEM) and transmission (TEM) electron microscopy and X-ray photoelectron spectroscopy (XPS) measurements. The formation of beta- and gamma-Mo2N was confirmed by XRD and TEM. gamma-Mo2N exhibits a platelet morphology whereas beta-Mo2N is characterised by an aggregation of small crystallites. Hydrogen chemisorption and TPD analysis have established a greater hydrogen uptake capacity (per unit area) for beta-Mo2N relative to gamma-Mo2N, which is associated with surface nitrogen deficiency, i.e. higher surface Mo/N for beta-Mo2N. Incorporation of Au on both nitrides resulted in an increase in surface hydrogen. The Au phase takes the form of nano-scale particles with a mean size of 7 and 4 nm on beta-Mo2N and gamma-Mo2N, respectively. Both beta-Mo2N and gamma-Mo2N promoted the exclusive hydrogenation of p-CNB to p-CAN where the beta-form delivered a higher specific (per m(2)) rate; the specific rate for gamma-Mo2N was independent of surface area. The inclusion of Au on both nitrides served to enhance p-CAN production.

We provide the first evidence of exclusive benzyl alcohol production in the continuous gas phase hydrogenation of benzaldehyde (T = 393 K; P = 1 atm) over Au/Al2O3, where activity was largely maintained for up to 15 h on-stream. XRD and DRS UV–vis have established the presence of metallic Au post temperature programmed reduction to 473 K, with a surface area weighted mean Au particle size (from TEM analysis) of 7.9 nm. Under the same reaction conditions, Ni/Al2O3 and Pd/Al2O3 were non-selective, generating toluene as the principal product via hydrogenolysis of benzaldehyde and exhibiting an appreciable temporal loss of activity. The results establish Au/Al2O3 as a promising catalyst for the production of benzyl alcohol.

The use of renewable biomass, such as ethylene glycol (EG), for hydrogen production offers a more sustainable system compared to natural gas and petroleum reforming. For the first time, the reaction thermodynamics of steam reforming and sorption enhanced steam reforming of EG have been investigated. Gibbs free energy minimization method was used to study the effect of pressure (1–5 atm), temperature (500–1100 K) and water to EG ratio (WER 0–8) on the production of hydrogen and the formation of associated by-products (CH4, CO2, CO, C). The results suggest that hydrogen production is optimum when steam reforming occurs at atmospheric pressure, 925 K and with a WER of 8. Moreover, working at high temperature (>900 K) and with a WER above 6 inhibits almost entirely the production of methane and carbon. The main source of hydrogen in the system is found to be steam reforming of methane and water gas shift reaction by the analysis of the response reactions (RERs). Hydrogen production is governed by the former reaction at low temperatures while the latter one comes into prominence as temperature increases. By coupling with in situ CO2 capture using CaO, the formation of CO2 and CO can be avoided and high purity of hydrogen (>99%) can be achieved.

A tetragonal molybdenum nitride (beta-Mo2N) has been prepared by temperature programmed treatment of MoO3 in flowing N-2 + H-2 and for the first time shown to catalyze the liquid phase selective hydrogenation (T = 423 K; P-H2 = 11 bar) of a series of para-substituted (-H, -OH, -O-CH3, -CH3, -Cl, -I and -NO2) nitrobenzenes to give the corresponding aromatic amine. Reaction over Pd/Al2O3, as a benchmark catalyst (Pd particle size ca. 18 nm), resulted in a composite hydrodechlorination/hydrogenation of p-chloronitrobenzene (as a representative nitroarene) to generate nitrobenzene and aniline. beta-Mo2N has been characterized in terms of temperature-programmed reduction (TPR), H-2 chemisorption/temperature programmed desorption (TPD), BET surface area/pore volume, elemental analysis, powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning (SEM) and transmission (TEM) electronic microscopy. Elemental analysis, XRD, SEM and TEM have confirmed the formation of tetragonal beta-Mo2N, characterized by an agglomeration of flake-like crystallites. Post-synthesis, the nitride was passivated by contact with 1% (v/v) O-2/He at ambient temperature and XPS analysis has demonstrated the formation of a superficial passivating oxide overlayer without bulk oxidation. Pre-reaction, activation by TPR to 673 K was necessary to remove the passivating film. Hydrogen TPD has revealed significant hydrogen uptake (0.7 mu mol m(-2)) associated with beta-Mo2N. Nitro group reduction kinetics have been subjected to a Hammett treatment where the reaction constant (p = 0 4) is diagnostic of an increase in rate due to the presence of electron-withdrawing substituents on the aromatic ring, consistent with a nucleophilic mechanism. The results presented in this study establish the viability of beta-Mo2N to promote selective nitroarene hydrogenation. (C) 2011 Elsevier B.V. All rights reserved.

The catalytic continuous gas phase hydrogenation of p-chloronitrobenzene (P=1 atm;T=423 K) has been investigated over a series of oxide (Al2O3, TiO2, Fe2O3 and CeO2) supported Au (1 mol %) catalysts. The application of two catalyst synthesis routes,i.e. impregnation (IMP) and deposition-precipitation (DP), has been considered where the DP route generated smaller mean Au particle sizes (1.5-2.8 nm) compared with the IMP preparation (3.5-9.0 nm). The catalysts have been characterised in terms H2 chemisorption and BET area measurements where the formation of metallic Au post-activation has been verified by diffuse reflectance UV-Vis, XRD and HRTEM analyses.p-Chloroaniline was generated as the sole reaction product over all the Au catalysts with no evidence of C-Cl and/or C-NO2 bond scission and/or aromatic ring reduction. The specific hydrogenation rate increased with decreasing Au particle size (from 9 to 3 nm), regardless of the nature of the support. This response extends to a reference Au/TiO2 catalyst provided by the World Gold Council. A decrease in specific rate is in evidence for smaller particles (< 2 nm) and can be attributed to a quantum size effect. The results presented establish the basis for the design and development of a versatile catalytic system for the clean continuous production of high value amino compounds under mild reaction conditions.

International audience; The effects of Au particle size and support properties have been examined in the gas-phase hydrogenation of 4-nitrobenzaldehyde over Au/ZrO2, Au/TiO2 and Au/Al2O3. Gold particle size was varied using deposition-precipitation and impregnation syntheses. The catalysts have been characterised in terms of BET area/pore volume, temperature-programmed reduction (TPR), XRD, H2 chemisorption/TPD, TEM, XPS, and pyridine adsorption FTIR measurements. Reaction exclusivity to 4-aminobenzaldehyde was achieved over Au/ZrO2 and Au/TiO2 where a decrease in Au particle size (mean from 7.0 to 4.7 nm) generated a higher turnover frequency. Pyridine adsorption coupled with FTIR analysis has revealed stronger Lewis acidity associated with Au/Al2O3, which contributes to Cdouble bond; length as m-dashO reduction via the formation of a benzoate intermediate. Selectivity to the alcohol is sensitive to Au size and reaction temperature with 100% 4-nitrobenzyl alcohol selectivity over Au/Al2O3 (mean Au size = 7.8 nm) at 423-443 K. Our results demonstrate the viability of controlling selective single bondNO2 and Cdouble bond; length as m-dashO reduction using oxide-supported Au catalysts.

International audience; b-Mo2C and b-Mo2C/Al2O3 have been synthesised via temperature programmed carburisation and employed, for the first time, as supports for gold catalysts. 1%w/w Au/Mo2C and Au/Mo2C/Al2O3 were prepared by deposition-precipitation with urea and used to promote the gas phase hydrogenation of para-chloronitrobenzene (p-CNB) and meta-dinitrobenzene (m-DNB) where 1% w/w Au/Al2O3 served as a reference catalyst. The supports and supported Au catalysts have been characterised in terms of point of zero charge, temperature programmed reduction (TPR), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) measurements. Both Mo2C and Mo2C/Al2O3 exhibited hydrogenation activity that was significantly enhanced with the incorporation of Au. XPS and elemental analysis of Mo2C/Al2O3 revealed a lesser carbidic character and the presence of free surface carbon. Moreover, preparation of Au/Mo2C/Al2O3 was accompanied by a leaching of the Mo component into solution. The carbide-based catalysts were characterised by a broader distribution of larger Au particles compared with the reference Au/Al2O3, which can be attributed to weaker Au/carbide interactions resulting in Au agglomeration during synthesis and activation. Nevertheless, the carbide systems delivered higher hydrogenation rates relative to Au/Al2O3. All the Au catalysts tested exhibited 100% selectivity to the target p-chloroaniline product in p-CNB hydrogenation. In the case of m-DNB, both nitro groups were hydrogenated to generate m-phenylenediamine as principal product for reaction over Au/Al2O3 whereas Au/Mo2C promoted the exclusive production of m-nitroaniline at low conversions. The results demonstrate a synergistic effect between Au and Mo2C that can be exploited in the cleaner production of commercially important aromatic amines.

The catalytic gas phase hydrogenation of m-dinitrobenzene (1 atm, 423 K) over laboratory synthesised (1 mol%) Au supported on Al2O3, TiO2, Fe2O3 and CeO2 and a reference Au/TiO2 (World Gold Council) has been investigated. The catalysts were prepared by deposition-precipitation (DP) and impregnation (IMP), where the former route generated smaller (surface area weighted) mean Au particle sizes (1.5-2.8 nm) compared with the IMP synthesis (3.5-9.0 nm). The catalysts have been characterized in terms of temperature programmed reduction (TPR), H-2 chemisorption/temperature programmed desorption (TPD), BET area, powder X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) analyses. Hydrogen consumption over the T range 371-457 K during activation of Au on TiO2, Al2O3 and CeO2 can be associated with Au3+ -> Au-0 reduction. XRD analysis demonstrated the presence of metallic gold in Au/Fe2O3 pre-TPR. A partial and complete reduction of the hematite support to magnetite (Fe2O3 -> Fe3O4) was observed post-TPR to 423 and 673 K, respectively; H-2-TPD results suggest the participation of spillover hydrogen in this step. Exclusive -NO2 group reduction and time invariant conversions were observed for all the catalysts considered in this study. An increase in the specific hydrogenation rate with a decrease in the mean Au size (from 9 to 3 nm) was observed. m-Nitroaniline was generated as the sole product over Au/TiO2 and Au/Fe2O3 whereas Au/CeO2 promoted the exclusive formation of m-phenylenediamine and a mixture of both products was obtained over Au/Al2O3. Our findings establish a basis for the development of a sustainable (clean and continuous) process for the hydrogenation of m-dinitrobenzene where product composition can be controlled through the choice of the oxide support.

The batch liquid phase hydrogenation of p-chloronitrobenzene over MO2N resulted in the sole formation of p-chloroaniline. Incorporation of Au nanoparticles (mean size = 8 nm) enhanced hydrogen uptake with a fourfold increase in rate, retention of ultraselectivity with stability over repeated reaction cycles. Reaction exclusivity to p-chloroaniline extended to continuous gas phase operation where Au/MO2N outperformed Au/Al2O3 as a benchmark. Under the same conditions, Pd/MO2N was non-selective, generating nitrobenzene and aniline via combined hydrodechlorination and hydrogenation. These results demonstrate the viability of Au/MO2N as a new catalyst formulation in selective substituted nitroarene hydrogenation. (C) 2012 Elsevier B.V. All rights reserved.

A temperature programmed treatment of MoO3 in flowing N-2 + H-2 has been employed to prepare beta-phase molybdenum nitride (beta-Mo2N) which has been used to promote, for the first time, the catalytic hydrogenation of p-chloronitrobenzene. The reduction/nitridation synthesis steps have been monitored in situ and the starting oxide, reaction intermediates and nitride product have been identified and characterized by powder X-ray diffraction (XRD), diffuse reflectance UV-Vis (DRS UV-Vis), elemental analysis, scanning electron microscopy (SEM) and BET/pore volume measurements. Our results demonstrate that MoO3 -> beta-Mo2N is a kinetically controlled process where an initial reduction stage generates (sequentially) MoO2 and Mo as reaction intermediates with a subsequent incorporation of N to produce beta-Mo2N. SEM analysis has established that the transformation is non-topotactic with a disruption to the platelet morphology that characterizes MoO3 and an increase in BET area (from 1 m(2) g(-1) to 17 m(2) g(-1)). Moreover, temperature programmed desorption measurements have revealed a significant hydrogen uptake (0.71 mu mol m(-2)) on beta-Mo2N. This has been exploited in the hydrogenation of p-chloronitrobenzene where p-chloroaniline was generated as the sole product with an associated rate constant (k = 2.0 min(-1)) that is higher than values recorded for supported transition metals. Our study establishes the reaction mechanism involved in the synthesis of beta-Mo2N and demonstrates its viability to promote selective -NO2 group reduction as an alternative sustainable, high throughput route to commercially important haloamines.