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We introduce here the engineering of nanobiosensors designed from gold nanorods coated with an ultrathin layer of silica (AuNR@SiO

"Ce travail a bénéficié d'une aide de l'Etat gérée par l'Agence Nationale de la Recherche au titre du programme Investissements d'Avenir portant la référence ANR-11-IDEX-0004-02, dans le cadre du Laboratoire d'Excellence MATISSE porté par Sorbonne Universités". "This work was supported by French state funds managed by the ANR within the Investissements d'Avenir programme under reference ANR-11-IDEX-0004-02, and more specifically within the framework of the Cluster of Excellence MATISSE led by Sorbonne Universités".; International audience; Formic acid oxidation reaction (FAOR) was studied using different platinum-zeolites hybrid catalysts. The catalysts were prepared by addition of two different forms of the ZSM-5 zeolite (ZSM-5-H+ and ZSM-5-NH4+) to an ink containing Vulcan carbon support and Pt nanoparticles (NPs). TEM images demonstrate a proper mixture of the components in the ink and a good dispersion of the Pt NPs mainly over the carbon. Both zeolites (ZSM-5-NH4+ and ZSM-5-H+) are stable under electrochemical conditions for FAOR, but ZSM-5-NH4+ undergoes fast conversion into ZSM-5-H+ due to the exchange between the compensator cation in the zeolite and protons in solution.A significant enhancement on the catalytic activity was found for both zeolite hybrid catalysts, being the ink containing ZSM-5-H+ the more stable over time. In particular, 7 and 10 times larger current densities than on 9 wt% Pt/C were achieved by the (7 wt% Pt/18.5 wt% ZSM-5-NH4+/C) and the (7 wt% Pt/18.5 wt% ZSM-5-H+/C) catalysts in chronoamperometry, respectively. The results demonstrated the beneficial and synergetic effect of the addition of zeolites in order to improve the catalytic activity of Pt NPs. The addition of zeolite ZSM-5 within the electrocatalyst did not provoke any relevant modification in the type of features displayed in cyclic voltammetry, but provoked a significant enhancement of the peak current density associated with the CO stripping. We propose that the mechanism for this improvement lies in a more efficient distribution of Pt nanoparticles on the catalytic ink thanks to the presence of zeolites and in the preconcentration of the reactant (HCOOH) within the zeolite microporosity occurring in solution. Moreover, local pH modifications associated with the NH4+/H+ exchange could have some impact on the kinetics of the FAOR by the direct via.

Vanadium based catalysts with the following compositions: 30%V2O5–70%MgO, 30%V2O5–70%SiO2 and 30%V2O5–40%MgO–30%SiO2 were prepared by the wet impregnation method using MgO and/or SiO2 as support. The structure, texture and morphology of the active phase strongly depend on the choice of support: for 30%V2O5–70%MgO, thin particles of Mg3V2O8 were identified with TEM (associated to EDS) together with MgO particles while large V2O5 particles beside silica particles bearing vanadium species on their surface (EDS) were observed in the case of the 30%V2O5–70%SiO2. For the 30%V2O5–40%MgO–30%SiO2, three crystalline phases were detected by XRD: Mg3V2O8, Mg2SiO4 and MgO. Mg3V2O8 and Mg2SiO4 were also identified with TEM-EDS with a silica-rich phase corresponding to the silica support bearing Mg and V species on its surface. The acid–base properties of the prepared materials were evaluated by the isopropanol decomposition test. The 30%V2O5–70%SiO2 displays only acidic properties (formation of propene) that can be assigned to the V2O5 phase and/or to the vanadium species dispersed on silica; the 30%V2O5–70%MgO presents mainly basic properties (formation of acetone) while the 3-components catalyst (30%V2O5–40%MgO–30%SiO2) displays both acid and basic properties. The catalytic activity was investigated in the oxidehydrogenation of n-butane. The selectivity to reaction products (butenes, COx, cracking, isobutane) is affected by the nature of surface vanadium and oxygen species, acid–base character and the operating conditions. The best selectivities to butenes (with low COx production) were obtained on the catalysts containing magnesium, probably a consequence of basic properties of MgO and highly dispersed magnesium-vanadium mixed phase. The decrease of contact time favors the dehydrogenation of n-butane to butenes especially for the V2O5–SiO2 catalyst.

International audience; Supported transition metal materials have been identified as ideal candidates for decades to catalyze various reactions of interest in the fields of hydrocarbon refining, energy and environmental catalysis. As the resources in transition metals on earth are known to be limited, it appears to be of the utmost interest to improve the efficiency of the catalytic materials in achieving the best use of these transition metals, in other words the highest metal accessibility when supported on oxide carriers. The present study demonstrates that the deposition of oxotungstates (with a W surface density of 1.3 W/nm2) coupled with the selective deposition of Rh on the CeO2 surface (via successive strong electrostatic adsorptions of an anionic [RhCl6]3- precursor) significantly reduces Rh sintering after reduction at 600 °C under H2 compared to a W-free CeO2 support. Oxotungstates are found to decrease the number of nucleation sites of CeO2 and, therefore, to act as spacers leading to the isolation of the nucleation sites. Oxotungstates may also act as a physical barrier preventing the sintering of the Rh metallic phase in the course of the reduction step at high temperature. Various morphologies of subnanometric Rh clusters exhibiting a limited atomicity (4 to 13 Rh atoms) were considered and most were found to be consistent with the very low coordination numbers of 4.0 ± 0.2 determined experimentally by EXAFS. The coordination numbers and the H2 chemisorption data led the conclusion that the Rh subnanometric clusters must be at the maximum two to three Rh layers thick and not larger than 5 Rh atoms. The benzene hydrogenation turnover frequencies at 50 °C were found to be similar on both the subnanometric Rh clusters and the 2.5 nm Rh nanoparticles (0.12 ± 0.3 s-1).

International audience; The coating of gold nanorods with a silica shell (AuNR@SiO2) is an effective way to extend their use in a wide variety of biomedical applications. A silica shell offers numerous advantages as it provides more stability, frees the surface from toxic cetyltrimethylammonium bromide (CTAB), and preserves the rod shape under photothermal conditions. We introduce herein a new strategy to perform this coating based on dissociation of tetraethylorthosilicate (TEOS) hydrolysis and condensation reactions. This dissociation is achieved by a pH modulation of the reaction medium, and, depending on selected pH conditions, AuNR@SiO2 with thick silica shell having an organized mesoporosity aligned either parallel (AuNR@//m-SiO2) or perpendicular (AuNR@⊥m-SiO2) to the AuNR surface were generated. Moreover, when mercaptopropyltrimethoxysilane (MPTMS) was used as a surface primer prior to TEOS condensation, ultrathin and homogeneous silica shells (AuNR@t-SiO2) of controllable thickness in the range 2-6 nm, are produced. These protocols proved robust enough to prevent contamination with core-free silica particles. While formation, at high TEOS concentration of these nanoparticles, is evidenced by TEM analysis before the purification procedure, their total elimination during the purification step was achieved by addition of a suitable amount of CTAB to ensure the colloidal stability of the core-free and core-shell nanoparticles. Complete elimination of CTAB was demonstrated by SERS when ligand exchange of CTAB by MPTMS is first carried out. In a preliminary study, AuNR@t-SiO2 particles were used to build up a nanoprobe aimed at the label-free plasmonic immunodetection of a model target in solution.

International audience; Nanoparticles made of coinage metals are well known to display unique optical properties stemming from the localized surface plasmon resonance (LSPR) phenomenon, allowing their use as transducers in various biosensing configurations. While most of the reports initially dealt with spherical gold nanoparticles owing to their ease of synthesis, the interest in gold nanorods (AuNR) as plasmonic biosensors is rising steadily. These anisotropic nanoparticles exhibit, on top of the LSPR band in the blue range common with spherical nanoparticles, a longitudinal LSPR band, in all respects superior, and in particular in terms of sensitivity to the surrounding media and LSPR-biosensing. However, AuNRs synthesis and their further functionalization are less straightforward and require thorough processing. In this paper, we intend to give an up-to-date overview of gold nanorods in LSPR biosensing, starting from a critical review of the recent findings on AuNR synthesis and the main challenges related to it. We further highlight the various strategies set up to coat AuNR with a silica shell of controlled thickness and porosity compatible with LSPR-biosensing. Then, we provide a survey of the methods employed to attach various bioreceptors to AuNR. Finally, the most representative examples of AuNR-based LSPR biosensors are reviewed with a focus put on their analytical performances.

We investigated different strategies to prepare Mn(salen) complexes supported on a silica/clay-mineral composite. The silica/clay-mineral surfaces were modified by grafting aminosilane groups, then Mn(salen) complexes were either grafted through a cross-linker, or deposited on the surface through interactions between amino group and manganese center. Two additional strategies, based on hydrogen bonds and electrostatic interactions, were also considered for comparison. The resulting materials were characterized using IR in diffuse reflectance mode, thermogravimetric analysis and elemental analysis in order to determine the manganese content and to establish the nature of the interaction between Mn(salen) complexes and silica/clay-mineral material surface for the different preparation protocols. These catalysts, were used for cyclohexene oxidation by tert-Butyl hydroperoxide with the objective of correlating the nature of the interaction between the metallic complex and the support to the catalytic activity. They were also compared to similar systems prepared using fumed silica as support, evidencing the input of this silica/clay-mineral composite in the catalytic performances. The obtained materials exhibited differences in both reactivity and selectivity that can be related to the nature of the interaction between the metallic center and the oxide support. The highest conversions were observed when the Mn complexes were immobilized with rigidness on the support. Interestingly, the resulting materials exhibited a remarkable stability, as evidenced by the absence of leaching of Mn(salen) in the reaction batch, and hence an excellent reusability.

Summary The electrocatalytic conversion of CO2 into valuable chemical feedstocks is a highly sought-after route to recycle CO2 emissions. Among the expected products, CO is a valuable synthon for organic syntheses and fuel generation. Nevertheless, most current electrocatalytic systems do not generate CO at a sufficient rate or purity for its subsequent direct conversion. Herein, we report the rational design of novel and highly active Ag-alloyed Zn dendritic electrodes with remarkable CO2-to-CO selectivity. Through fine-tuning of the individual electrodeposition parameters, the Ag content, porosity, thickness, and surface area of the electrodes were optimized, leading to a CO2-to-CO selectivity as high as 91%, which could be sustained above an average of 90% over 40 h. Increase of the CO2 pressure (up to 9.5 bar) to enhance the CO2 concentration allowed CO partial current densities as high as –286 mA.cm−2 to be achieved, setting a new record for predominantly Zn-based electrodes operating in neutral pH.

International audience; The influence of dealumination of two commercial amorphous silica-aluminas (ASAs) with acetylacetone on their textural properties, acidity and catalytic activity was studied by N2-sorption, NH3-TPD, FTIR of adsorbed pyridine as well as 1 H and 27 Al MAS NMR. Acetylacetone treatment increases the pore volume and surface area (+20+30%) of commercial ASA without changing the pore size. More than half of the Al species are extracted from ASA but the total acidity is preserved or even slightly increased (for the ASA with higher Al content). The percentage of acidic Al is increased by a factor 2. Dealumination results in a better access to acid sites and an increase of medium Brønsted acid sites (BAS), leading to a 1.5 higher catalytic activity for 3,3-Dimethyl-1-butene (33DMB1) isomerization.

A cheap, reproducible and facile method for synthesis of 1D high specific surface area biomorphic NiO crystalline microstructures by using natural fibers (cotton, hemp and flax) as templates, is reported. The effect of synthesis temperature and of fiber type on the structural and functional properties of biomorphic oxide in comparison with one produced without template is presented. A comparative (HR)TEM study performed on the ultrasonicated samples evidenced that, irrespective of the kind of fibers, fractions of tubular morphologies, fractions of mesoporous walls and fine nanoparticles populations are found. Such morphologies are never obtained in the absence of biotemplates and were induced by the carbonization and thermal decomposition of organic fiber constituents. A remarkable increase of the specific surface (between 20 and 50 times higher) than for template-free NiO (0.64 m2g-1) was reached when using fibers templates for synthesis at 600 °C/2 h. Due to the peculiar generated nanoporosity and ultrafine particle population, gas sensing tests demonstrated a higher sensitivity when templates were employed. The magnetic properties of tubular structures depend on their nanoscale arrangement and the magnetization values confirmed the Ni/NiO ratio determined by structural analysis.

New niobium-based oxygen carriers were prepared adopting polyol-mediated process. Four different polyols were used (diethylene glycol, triethylene glycol, tetraethylene glycol, and 1,2-propanediol) and four different quantities of water (0 mL, 1 mL, 10 mL, 30 mL, with a total volume of 80 mL of solution). Series of bulk and alumina-supported materials were prepared. Different structural and textural properties were obtained, depending on polyol type and hydrolysis ratio. After thermal treatment at 1000 °C, alumina-supported materials were evaluated in a lab-scaled fixed bed reactor. Despite a low conversion of methane due to a low content of active phase AlNbO4, they presented a high selectivity to syngas (a mixture of H2 and CO) during the first few seconds of reaction with CH4, indicating a high selectivity towards chemical-looping reforming process.

Molybdenum catalysts supported on titania and zirconia have been prepared via the impregnation on the corresponding hydroxides and oxides. The solids have been characterized by surface area measurements, XR-Fluorescence analysis, XRD and Raman Spectroscopy. The isopropanol decomposition reaction has been used to probe their acidic properties. These analyses revealed that introduction of molybdenum on the surfaces of the hydroxides and the oxides results in an increase of the specific surface area. Impregnation on the hydroxide leads to a comparatively better molybdenum dispersion and to a greater surface acidity. This indicates that the acid sites on hydroxide derived solids are stronger and more numerous than on their oxide derived counterpart.

International audience; The rational synthesis of metal-acid bifunctional catalysts based on aluminosilicates will involve control over which domain – alumina or silica – the metal can be deposited on, as well as the control of particle size. These factors determine the ratio and proximity of the metal and acid sites. The control of adsorption selectivity and particle size has been studied by measuring the uptake of anionic and cationic Pt precursors as a function of pH over various types of silica-alumina composites and pure oxide supports, followed by characterization of the nanoparticles resulting from reduction of the precursors.Results indicate that electrostatic adsorption can be exploited to achieve selective deposition. Ion exchange of cationic precursors also appears to occur over the acid sites. Cationic tetraammine Pt precursors, either electrostatically adsorbed onto silica domains at high pH, or ion exchanged at the acidic alumina-silica adlineation (interface between two oxides) at neutral pH, lead to small (1.7–3.0 nm) nanoparticles. The size of Pt nanoparticles resulting from anionic Pt hexachloride electrostatically deposited onto alumina domains at low pH depends on the size of the alumina domain; a critical domain size is needed to anchor the Pt precursors against sintering.In the companion paper, the factors controlling metal-acid site intimacy and ratio are demonstrated for the isomerization of n-heptane.

International audience; Oxide-promoted SBA-15 materials have been shown to be profitable in a wide variety of catalytic reactions of environmental interest. Zr-SBA-15 materials have been found to be of particular interest in hydrotreating, biomass conversion and Fisher–Tropsch synthesis. In these studies, the accessibility of ZrO2 located inside the silica mesoporosity has been hardly characterized, despite the fact that this may be critical in determining the best catalyst formulation. This can be accounted for by the lack of methods available for the characterization of oxides, in particular when these oxides are located in the porosity of another oxide. Recently, we have shown that ZrO2 particles dispersed in the porosity of an SBA-15 support could be characterized via a NOx-TPD methodology. In the present work Zr-SBA-15 materials were prepared with various loadings of Zr and thoroughly characterized through N2-sorption coupled with advanced pore size analysis, SEM, TEM, EDS, XRD, Raman spectroscopy and NOx-TPD. It was found that ZrO2 accessibility decreased to a significant extent up to a Zr surface density of about 2 Zr atoms/nm2 and then more slightly at higher Zr surface densities. It was also found for the first time that ZrSiO4 was formed above 2 Zr atoms/nm2. The fact that ZrSiO4 also chemisorbed NOx species, although to a much lower extent than ZrO2, paves the way for a method to characterize Zr-SBA-15 samples prepared by direct synthesis for which Zr should be mainly located in the silica walls.

International audience; The influence of the support on the nucleation of ZSM-5 nanoparticles has been studied for three supports: γ-alumina, zirconia and carbon nanotubes (CNT). While zeolite nucleation was suppressed in presence of alumina and strongly delayed in presence of zirconia, it occurred without delay in presence of CNT. These differences are explained by the partial dissolution of the support (for alumina and zirconia supports) that modify the composition of the zeolite nucleation solution. For the CNT/zeolite sample, the obtained composite contains about 60 wt% of zeolite and develops a surface area of 776 m 2 .g-1 .

International audience; Alloying strategies are commonly used to design electrocatalysts that take on properties of their constituent elements. Herein, we explore the use of such a strategy to develop Zn-Cu alloyed electrodes with unique hierarchical porosity and tunable selectivity for CO2 vs. H + reduction. By varying the Zn:Cu ratio, tailored syngas mixtures were attained with no other gaseous products, which we assign to preferential CO and H2 forming pathways on the alloys. The syngas ratios were also significantly less sensitive to the applied potential in the alloys relative to pure metal equivalents; an essential quality when coupling electrocatalysis to renewable power sources of fluctuating intensity. As such, industrially-relevant syngas ratios were achieved at large currents (-60 mA) for extensive operating times (> 9 h), demonstrating the potential of this strategy for fossil-free fuel production.

Alloying strategies are commonly used to design electrocatalysts that take on properties of their constituent elements. Herein, such a strategy is used to develop Zn-Cu alloyed electrodes with unique hierarchical porosity and tunable selectivity for CO

This paper reports the study of physicochemical, surface, and catalytic properties of two series of VMgO catalysts prepared by two different methods: wet impregnation and sol–gel. The characterizat...

We successfully prepared bifunctional catalysts with the distance between metallic and acid sites tuned at the nanometer scale. Sols of β-zeolite nanoparticles were synthesized and mixed in optimized conditions with a γ-AlOOH boehmite suspension to yield alumina/zeolite aggregates with a nanometer scale intimacy. The composition of the aggregate could be tuned from pure alumina to pure zeolite. Then, by carefully choosing the Pt precursor and the pH conditions, we were able to selectively deposit platinum, either on alumina or in zeolite domains. A subsequent, soft thermo-reduction step was applied that produced well-dispersed Pt nanoparticles either on alumina or in the zeolite nanodomains as confirmed by 3D tomography microscopy experiments. The catalytic properties of the obtained nanostructured catalysts were studied through n-heptane conversion. Comparison of these original bifunctional catalysts with monofunctional or conventional bifunctional catalysts showed the impact of the location of the metal...

International audience; Two series of V–Mg–O catalysts with vanadium contents of 30 and 60 wt % were synthesized using sol–gel (SG) and wet impregnation (IMP). The elaborated catalysts were characterized by X-ray diffraction, Fourier transform infrared, X-ray fluorescence, Brunauer–Emmett–Teller, NH3–temperature-programmed desorption, transmission electron microscopy and energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The preparation method and the vanadium content strongly influenced the textural, structural, and surface properties, as well as the reactivity of catalysts. The increase in the vanadium content leads to the formation of V–Mg mixed phases, which decreased the specific surface area. The lowest crystallite size and the highest surface area were obtained with the SG solids. The morphology of our catalysts is immensely affected by the preparation procedure; so the SG method leads to a smooth surface compared to the impregnation method. The NH3–temperature-programmed desorption analysis showed a weak acid character of the catalytic surface, the weakest of which was found in SG series. The X-ray photoelectron spectroscopy analysis revealed an enrichment of the catalytic surface with magnesium and the presence of three types of oxygen surface species (O2−, O2−, and O−). For both methods, the catalytic performances evaluated in the selective oxidation of n-butane are enhanced by the increase in the vanadium loading. The higher activity and selectivity to butenes were obtained with the SG solids.

International audience; In the preparation of supported catalysts by deposition, in solution, of a transition metal complex (TMC) on an oxide support, the interactions occurring at the solid/liquid interface between the TMC and the oxide have a crucial impact on the properties of the final catalyst. However, these interactions remain difficult to investigate and monitor as most of the spectroscopic characterization techniques can only be used once the solvent has been removed, which eliminates an essential partner of the interaction. In this paper, we show that Quartz Crystal Microbalance with dissipation monitoring (QCM-D), a highly sensitive technique operating in situ at the solid/liquid interface, can be used to undo this technical lock. QCM-D was used to study two well-known systems: the adsorption of [Pt(NH3)4]2+ on silica at high pH and the adsorption of [PtCl6]2− on alumina at low pH, in order to demonstrate that QCM-D can be a very useful tool for the investigation of the interaction between a TMC and an oxide surface in solution.

66-3 FIELD Section Title:Surface Chemistry and Colloids UMR 7197, Laboratoire de ReactiVite de Surface, UPMC Univ Paris 06, Paris, Fr. FIELD URL: written in English; NOx adsorption-desorption experiments were carried out on a series of W-free and W-containing ZrO2 samples. To the best of our knowledge, this study establishes for the first time NOx-TPD (temperature-programmed desorption of NOx) as a reliable method to estimate the accessible ZrO2 surface of complex oxides. The NOx uptake by ZrO2 was found to be 5.8 ( 0.2 μmol/m2. On the tungstated zirconia series of samples, the NOx uptake decreases linearly with W density up to about 5 W/nm2, which is in excellent agreement with literature data for which the pseudo monolayer coverage was obtained by spectroscopic methods. The accessible ZrO2 surface area of ZrO2/SBA-15 materials, which cannot be ascertained through common spectroscopic methods, was estimated by WO3 thermal spreading and the NOx-TPD method. Both values compare very well but NOx-TPD, unlike WO3 thermal spreading, does not alter the integrity of the investigated sample as the sample is pretreated at lower temperatures (500 instead of 700 °C). [on SciFinder(R)]

Blanchard, Juliette Bando, Kyoko K. Breysse, Michele Geantet, Christophe Lacroix, Michel Yoshimura, Yuji Sp. Iss. SI; In situ XAS at the Ru K edge was used to investigate the thiotolerance of metallic ruthenium supported on partially dealuminated acidic Y zeolite (Ru degrees/HYd, obtained by reduction at 673 K of Ru(NH3)(6)(3+)/HYd). After 3 h at 523 K under 350 ppm H2S in H-2 the formation of 1.9 Ru-S bond per Ru atoms is observed without modification of the core of the metallic particles (the number of Ru neighbors is unchanged). These results are compared to those obtained after reductive sulfidation of the same sample in order to understand the origin of the high hydrogenation activity of metallic ruthenium in the presence of H2S. (C) 2008 Elsevier B.V. All rights reserved.

There is limited knowledge on the influence of the pore size on surface phenomena (adsorption, dissolution, precipitation, etc.) at the oxide/water interface and a better understanding of the space confinement in nanoscale pores should have practical implications in different areas, such as transport of contaminants in the environment or heterogeneous catalyst preparation, to name a few. To investigate the modifications of the oxide adsorption properties at the oxide/water interface in a confined environment, the surface acidobasic and ion adsorption properties of six different aluminas (5 porous commercial aluminas with pore diameters ranging from 25 to 200 A and 1 non-porous alumina) were determined by means of acid-base titration and Ni(II) adsorption. It is shown that the confinement has a moderate impact on the alumina adsorption capacity because all materials have similar surface charging behaviours and ion saturation coverages. However, a confined geometry has a much larger impact on the ion adsorption constants, which decrease drastically when the average pore diameter decreases below 200 A. These results are discussed in terms of nanoscale pore space confinement.

International audience; Hydroxyapatites are increasingly used as heterogeneous catalysts since they present atypical behaviours for many acid base reactions. The aim of this study was to discuss the possible involvement of Ca2+ Lewis and/or PO–H Brønsted acid sites belonging to the hydroxyapatite system in the conversion of 2-methylbut-3-yn-1-ol, a model molecule that is known to account for the acid base properties, and of ethanol into n-butanol. A series of hydroxyapatite samples with similar bulk properties was prepared from a lone precipitation batch, but by varying the conditions of the washing and drying steps. Although the surface depth probed by XPS exhibited similar average composition, ISS analysis revealed a gradient of calcium concentration in the first surface layers. In fact, the different conditions of drying and washing resulted in a modulation of the relative amount of Ca2+ and PO–H accessible on the top surface, as revealed by the adsorption of the CO molecule monitored by FTIR. The conversion in the two alcohol molecules is linearly dependent on the nature of the acid base pairs involved: when accessible on the top surfaces, due to their stronger acidity, the Ca2+ Lewis acid sites are preferentially involved, but they are less efficient than PO–H, as illustrated by the linear decrease of the conversion levels with the increasing relative amount of accessible Ca2+ cations. It is thus concluded that PO–H sites enhance the performances of the catalysts for the two reactions, and that washing and drying conditions allowing us to decrease the calcium accessibility at the benefit of PO–H should be favoured.

International audience; Several series of metal-acid bifunctional catalysts with controlled metal:acid ratios and metal site-acid site proximity were evaluated for n-heptane isomerization. Through the study of metal deposition reported in the companion paper, proximity could be achieved at four distinct scales: atomic, nano-, micro-, and millimeter scales. In the first two catalyst series, atomic and nanometer scale intimacy was obtained by depositing Pt onto acidic silica-alumina supports (Pt/Al-Si). It is demonstrated that poorly dispersed Pt/silica-alumina catalysts with nanometer-scale proximity displayed a greater degree of bifunctionality than highly dispersed catalysts with atomic-scale proximity. In the latter two series of catalysts the scale of intimacy was stretched to micrometers using physical mixtures, and to millimeters by separating layers of nonacidic Pt/silica and metal free silica-alumina. Good bifunctionality is maintained at micrometer-scale intimacy and breaks down only at the millimeter scale. The best bifunction-ality is achieved at very high acid to metal site ratios; results indicated that a single metal site can supply several hundred acid sites. Optimized bifunctional performance of Pt/silica-alumina catalysts for n-heptane isomerization requires a high acid-to-metal site ratio with nanometer to micrometer scale site proximity. The control of the numbers and proximities of metal and acid sites achieved in this work can be extended to many other metal-acid bifunctional reactions.

Al-SBA-15 supports were prepared by post-synthesis alumination in aqueous solution of a pure silica SBA-15 material. The effects of the aluminium concentration [Al], and of the hydrolysis ratio h = [TMAOH]/[Al] on the speciation of aluminium ([Al(H2O)6]3+, [Al13O4(OH)24(H2O)20]7+, aluminium polymers) in the solution were examined. Depending on h and [Al], samples with various Si/Al ratios and acidities were obtained. The effects of h and [Al] on the characteristics of the final material were assigned to the speciation of the aluminium in the alumination solution: a correlation between the species present in solution and the Si/Al ratio in the final materials leads us to propose that [Al13O4(OH)24(H2O)20] is the most reactive and effective species toward grafting on the silica surface.

MCM-41 aluminosilicate mesostructures (Si/Al = 18) with hexagonal long-range order were assembled from protozeolitic nanoclusters (zeolite seeds) that normally nucleate the crystallization of β-zeolite (BEA). Depending on the duration of the thermal treatment leading to the zeolite seeds, different acidic materials can be obtained. For short pre-treatment duration, the material presents the main characteristics of the MCM-41, whereas for longer pre-treatment duration, there is a gradual transition to a mostly zeolitic one. Hydrocracking of n -decane was carried out on catalysts composed of a sulfided nickel tungsten phase supported on various β-MCM-41 supports as well as on an amorphous silica–alumina and an AlSBA-15 material. The hydrocracking properties of the catalysts are related to the nature of the β-МCМ-41 and vary from the comportment of silica–alumina materials to the one of a zeolite. The nickel-tungsten catalyst supported on β-MCM-6 (6 h pre-treatment for the zeolite seeds solution) is more active and more selective toward isomerization than the catalyst supported on a commercial silica–alumina support.

PtAl/MCM-41 and PtAl/SBA-15 materials were prepared by post-synthesis alumination followed by introduction of platinum by ion exchange. The samples were characterized by pyridine adsorption followed by FTIR and TPR of hydrogen. The catalytic behavior was explored in the transformation of n-hexane.

Hydrogenating catalysts were prepared by inserting Ru into the pores of mesoporous Al-MCM-41 materials by selective adsorption of [Ru(NH 3 ) 6 ] 3+ . Ru/support catalysts were obtained after reduction with H 2 . The activities of these catalysts in hydrogenation reactions were compared to those of Ru/HY and Ru/SiO 2 . The catalytic properties in the absence of sulfur were tested in benzene hydrogenation, and the intrinsic activities of all the catalysts (either supported on mesoporous materials or on zeolites) were identical. It was concluded from this result that the dispersion of the Ru metallic phase was similar for all these catalysts. These samples were tested in the tetralin hydrogenation in pure H 2 and in the presence of H 2 S (330 ppm of H 2 S in H 2 ). They were found to be much less active than the zeolite-supported catalysts in the presence of H 2 S. It is proposed that the lower activity of the catalysts supported on mesoporous materials is either due to their milder acidity, as evidenced by NH 3 -TPD, cumene cracking and pyridine desorption experiments, or to the localization of the Ru nanoparticles on alumina islands.

The effects of the addition of two different types of cosurfactants, n-alkylamine and n-alkyl alcohol, on the phase behavior of silicate-surfactant mesophases and the pore size of the calcined materials have been investigated using X-ray diffraction, N2-sorption, TG-MS, and solid state 1H and 13C NMR spectroscopy. The cosurfactants were added to a standard room-temperature synthesis, which results in a MCM-41 type, hexagonally ordered material in the absence of cosurfactant. Their addition led either to an increase or a decrease of the pore size and d spacing of the hexagonal mesophase, depending on the nature of the polar headgroup and on the chain length of the cosurfactant. For high cosurfactant/surfactant ratios, however, a transition to a lamellar phase was usually observed. The d spacing and the pore size of the hexagonal mesophase can be decreased considerably down to the supermicropore range by addition of butylamine without a marked decrease in the long-range order of the material. The addition o...

Cs-Pt/MCM-41 catalysts with basic character have been prepared by selective adsorption of Pt(NH3)4(OH)2 at pH = 8 on pure silica MCM-41 followed by incipient-wetness impregnation of CsNO3, then oxidation and reduction. The influence of the amount of Cs (0, 2 and 4 wt%) on the size of the reduced Pt particles and on their catalytic behavior in the conversion of n-hexane has been investigated. Whatever the Pt content (0.7 or 2.0 wt% Pt), the addition of Cs results in a higher Pt dispersion, a higher initial activity and a higher selectivity for aromatization. On the more basic Pt-richest MCM-41 sample (4 wt% Cs, 2 wt% Pt) the selectivity to benzene reaches values close to those obtained on Cs-enriched Pt/Cs-BEA zeolite. However, the catalytic stability is lower. The catalytic trends are discussed in view of the physicochemical properties of the solids determined by chemical analysis, N2 physisorption, XRD and TEM before and after catalytic test.

International audience; Understanding the interactions between metal complexes and oxide surfaces is crucial to the synthesis of supported metal catalysts. Recently developed in situ techniques have made it possible to closely characterize the solid/liquid interface. For the first time, the adsorption of platinum complexes on alumina and silica has been probed using a quartz crystal microbalance; we were able to observe the adsorption of metal complexes in real time, and to observe the reversibility of this adsorption.

The synthesis of a hexagonally packed porous titanium oxo-phosphate from titanium isopropoxide, sulfuric acid and alkyltrimethylammonium bromide is reported. XRD and TEM have been used to characterize the mesostructure that forms at ambient temperature as well as the calcined material. The effect of the alkyl chain length of the surfactant has also been studied. The N2-sorption isotherms of the samples calcined at 350°C are characteristic of super-microporous materials. The pore diameters and the surface areas of the materials, evaluated from the N2-sorption isotherms and unit cell parameters, indicate pore diameters of about 2–3 nm and surface areas around 350 m2/g.

The phase behavior of Zr(SO4)2/CTAB composite mesophases was investigated as a function of surfactant chain length, temperature, and salt concentration by XRD. It was shown that the initial step is a rapid formation of either a pure lamellar, hexagonal, or a mixed hexagonal/lamellar phase with a low degree of condensation (room temperature), depending on the chain length of the surfactant as well as on the ionic strength of the solution. The observed features may be qualitatively explained by expected variations in the packing parameter. TiOSO4/CTAB composite mesophases were shown to form in a similar manner as Zr(SO4)2/CTAB. A model accounting for changes in the inorganic framework with increasing degree of intraaggregate condensation was developed. Furthermore, using a tubular reactor setup connected to an in situ XRD cell it was shown that the mesophase formation occurred immediately (

The influence of added short-chain amines, n-butylamine, BA, and n-octylamine, OA, on the mesophase formation of surfactant−silicate composite structures in a room-temperature synthesis has been investigated in situ by synchrotron small-angle X-ray scattering. For BA a marked decrease in the d spacing of the hexagonal phase was observed with increasing amine concentration, while a slight increase in d spacing was initially observed for OA. However, the d spacing of the hexagonal phase went through a maximum with increasing concentration. Furthermore, two coexisting hexagonal phases or a purely lamellar phase was observed if the concentration of OA was increased further. The results are discussed in terms of two competing mechanisms of amine incorporation: solubilization within the CTAB−silicate mesophase and competitive adsorption of the amine to the silicate.

The NO x desorption profiles obtained in O 2 –He and n -C 10 –O 2 –He were compared on γ-Al 2 O 3 and Ag/γ-Al 2 O 3 . On Ag/γ-Al 2 O 3 , the low-temperature NO x desorption profiles obtained in n -C 10 –O 2 –He were significantly different from those obtained in O 2 –He. In particular, at 190–220 °C excess release of NO, instead of NO 2 , was observed concomitantly with n -C 10 consumption. This is interpreted as the result of the formation–decomposition of organo-NO x species issued from the interaction of NO 2 and hydrocarbons initially chemisorbed on Al 2 O 3 and activated on Ag species, respectively. The occurrence of such a phenomenon at temperatures close to those at which the n -C 10 -SCR reaction starts provides support for the involvement of the organo-NO x species as intermediates.

The influence of the addition of W to Al2O3, promoted or not by Ag, on the n-C10 SCR of NOx was investigated. It was shown that the addition of W was detrimental to the n-C10 SCR reaction. Based on the NOx- TPD, the XPS and the n-C10 SCR measurements, it was concluded that the loss of activity observed at temperatures lower than 400 C on the Ag/W(5)–Al2O3 catalyst compared with the Ag/Al2O3 sample is likely due to the preferential deposition of Ag on the tungstate phase, making it inactive for the n-C10 SCR reaction which requires the active silver species to be in close contact with the Al2O3. At higher temperatures, the occupation, by the tungstates, of the Al2O3 sites responsible for the n-C10-SCR reaction is proposed to be an additional drawback accounting for the detrimental effect of W on Al2O3-supported catalysts promoted or not by Ag.

International audience; The role of the aluminum source on the insertion of Al in the silicate layers during the hydrothermal crystallization of magadiite (NaSi7O13(OH),4H2O), a lamellar silicate, was investigated. Three aluminum sources were compared: aluminum isopropoxide, aluminum sulfate and aluminum hydroxide We observed that aluminum isopropoxide leads to the presence of mordenite impurities, aluminum sulfate to an only partial insertion of aluminum, whereas aluminum hydroxide allows preparing at 150 °C in 3 days, well crystallized Al-magadiite samples with Si/Al ratios of 20 or 40. Characterization by 29Si and 27Al NMR of the Al-magadiite samples obtained with aluminum hydroxide as Al source indicates that the samples retain the main characteristics of magadiite and all the aluminum atoms are in tetrahedral substitution in the silicate framework. The presence of acid sites is evidenced by the activities of these samples in cumene cracking, a model reaction for strong Brønsted acidity.

International audience; Layered silicates can be used for the preparation of high surface area materials by intercalation with organic cations followed by ultrasonication. The relevant parameters for delamination (exfoliation) of cetyltrimethylammonium bromide exchange magadiite are investigated. Using a magadiite wet cake, performing the delamination in water and recovering the solid phase by acidification allow increasing the surface area of the final material by a factor of ca. 20 (553 vs. 30 m2 g−1) compared to the standard procedure. The role of each step is analysed and the material resulting from the optimised procedure can be described as creased silicate layers. This results in a microporous-mesoporous material with about 60% of the surface in pores larger than 2.0 nm.

Three Pt catalysts exhibiting similar metal particles size ( C bond was favored with Pt/SBA-15 and Pt/Al-SBA-15, with significantly higher reaction rates on the latter catalyst. The acidic support changes the adsorptive properties of the platinum nanoparticles, modifying their surface electron density and possibly their morphology. In contrast, Pt/Al2O3 was the most selective catalyst of the series toward cinnamyl alcohol, with C C and C O hydrogenations taking place at the same rate. The presence of Lewis acidic sites close to the particles is assumed to favor the adsorption of molecules via their polar C O bond. Even if cinnamaldehyde hydrogenation does not require acidic sites to be performed, the composition and acidity of the support significantly influence the reaction rate and selectivity.

66-4 FIELD Section Title:Surface Chemistry and Colloids Research Institute of Petroleum Processing, SINOPEC, Beijing, Peop. Rep. China. FIELD URL: written in English; In this paper, a new delaminated mesoporous material was prepd. by swelling the lamellar phyllosilicate Magadiite using cetyltrimethylammonium bromide and tetrapropylammonium hydroxide soln., followed by delamination under the cavitation of ultrasonic treatment. Various characterization tools including XRD, N2 adsorption, NMR, IR, SEM and TEM were employed to observe its structure and morphol. XRD results show that the delaminated material has no long-range cryst. order. Furthermore, not only high surface area is obtained, but almost half of it is external surface. The observation for the morphol. further reveals that it is made up of the random stacking of single or few layers. All these characters show that this delaminated mesoporous material meets the requirements for application as support in the hydrotreatment of heavy mols. [on SciFinder(R)]

67-1 FIELD Section Title:Catalysis, Reaction Kinetics, and Inorganic Reaction Mechanisms 49, 66 Laboratoire de Reactivite de Surface, UMR 7197, UPMC Universite Paris 06, Paris, Fr. FIELD URL: written in English; Titania-coated SBA-15 materials (Ti-SBA-n with n = 1-4) were synthesized by successive grafting of titanium isopropoxide in iso-propanol. The investigation of the nature and localization of the TiO2 overlayer allowed us to conclude that there was formation of very small (UV-visible, EXAFS, XANES), ca. 2 nm or smaller (XRD and TEM) TiO2 domains that cover only partially the silica surface (CO adsorption). These nano TiO2 domains are located on or close to the mesopore surface (EELS, XRD and N2-sorption) rather than in the micropores as previously reported. [on SciFinder(R)]