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Ordered microporous carbons were synthesized by the nanocasting process using EMC-2 zeolite (EMT structure type) and acetylene as a mould and a carbon precursor, respectively. In this study, the conditions of the synthesis methods for preparing the ordered microporous carbons were examined. Temperature and duration parameters for the chemical vapour infiltration were optimized to yield an ordered carbon replica that displays up the three XRD diffraction peaks. This faithful replica exhibits also a high micropore volume (1.3–1.4 cm3/g) with mainly supermicroporosity, a high specific surface area (>2900 m2/g) and nearly no mesoporosity. The pore size distribution calculated with NLDFT method from nitrogen physisorption data shows three maxima at 0.6, 1.0 and 1.8 nm diameters. The second is due to the zeolite wall dissolution. The first and the third are attributed to different types of default. Compared to the classical two-step procedure, the direct infiltration with acetylene appears an interesting route for the preparation of ordered microporous carbon replicas with high micropore volume.

Nanosized EDI-type molecular sieve is prepared from aluminosilicate precursor solutions containing tetramethylammonium cations and copper amine complexes [Cu(NH 3 ) 4 ] 2+ as templates. The influence of chemical composition and various synthesis parameters on the size and degree of crystallinity of the EDI nanoparticles is investigated. The crystallization of nanosized EDI-type zeolite is shown to be directed by square planar [Cu(NH 3 ) 4 ] 2+ complexes used as co-templating species to the tetramethylammonium cations. The single addition of copper cations or ammonia leads to the crystallization of pure nanosized FAU zeolite, whereas the combination of both generates EDI-type microporous nanomaterial. Thus the [Cu(NH 3 ) 4 ] 2+ complexes offer new templating functions in addition to the classical quaternary ammonium additives for creation of nanosized molecular sieves.

The main types of nanoporous adsorbents for water are identified and described with emphasis on the mechanism of adsorption, modification, improvement of the water sorption capacity, possible regeneration, and stabilization. Among the three main groups of water sorbents, i.e. inorganic materials (zeolites, clays, silica), carbon based materials and organic polymers, the first one is described in details. The significance of their porosity, chemical and structural features relative to the water adsorptive properties of each inorganic type materials is reviewed. Important features for silicates, zeolites, aluminophosphates, mesoporous materials and clays are described, which define the interactions between the water and the porous structures. The significant improvements of the water sorption capacity of nanoporous materials under modification of their surface, particle size, morphology, and chemical specificity are explored for each type of inorganic porous compounds. The hydrophilic nanoporous materials are of significant importance for construction of regularly operating sorption equipments, reversible physi- or chemisorption reactors for generation of heat and cold, purification of lubricants, and sensing of water with different concentrations.

The synthesis and characterization of 2:1 phyllosilicates and organophyllosilicates belonging to the smectite group are reported. The fluorine medium was used both as mineralizing agent and as a local probe to determine directly the coordination of structural fluorine. This latter was found to be sensitive to the chemical nature of the octahedral elements and therefore to the type of the octahedral sequences. Fluorine atoms substituted part of hydroxyl groups in the layer creating defects in the lattice and therefore increased the thermal stability. Compared to the pure hydroxyl medium, the reaction time was decreased from 7 to 2 days. A hydrothermal treatment at 220 °C was necessary for the crystallization of 2:1 phyllosilicates, whereas room temperature was sufficient for the preparation of organophyllosilicates. In theses structures, organic groups are covalently bonded to each silicon atom. Organosilane are used as silica sources. A formation mechanism based on the different characterization results was proposed for both phyllosilicates and organophyllosilicates.

This paper deals with the synthesis results obtained mostly from pure silica systems in the presence of (CH3 )3 N+ (CH2 )n N+ (CH3 )3 ions (n = 5 , 6, 9 or 10) in fluoride media, but also in the presence of (CH3 )3 N+ (CH2 )n O(CH2 )n N+ (CH3 )3 ions (n = 2 or 4) in hydroxide or fluoride media. A variety of zeolites form, namely ZSM-48, MTW-type, BEA-type, MFI-type, ITH-type zeolites, but also, in case of pronounced degradation of the template into N(CH3 )4 + or N(CH3 )3 , AST-type, MTN-type and RUT-type materials. The samples are characterized by XRD, SEM, thermal and elementary analyses, 1 H liquid NMR (after dissolution of the sample in HF aqueous solution) and solid-state NMR (19 F, 13 C, 27 Al) spectroscopy.

We report a joint experimental and molecular simulation study of water condensation in silicalite-1 zeolite. A sample was synthesized using the fluoride route and was found to contain essentially no defects. A second sample synthesized using the hydroxide route was found to contain a small amount of silanol groups. The thermodynamics of water condensation was studied in these two samples, as well as in a commercial sample, in order to understand the effect of local defects on water adsorption. The molecular simulation study enabled us to qualitatively reproduce the experimentally observed condensation thermodynamics features. A shift and a rounding of the condensation transition was observed with an increasing hydrophilicity of the local defect, but the condensation transition was still observed above the water saturation vapor pressure P0. Both experiments and simulations agree on the fact that a small water uptake can be observed at very low pressure, but that the bulk liquid does not form from the gas phase below P0. The picture that emerges from the observed water condensation mechanism is the existence of a heterogeneous internal surface that is overall hydrophobic, despite the existence of hydrophilic "patches". This heterogeneous surface configuration is thermodynamically stable in a wide range of reduced pressures (from P/P0 = 0.2 to a few thousands), until the condensation transition takes place.

The in situ generation of the structure-directing agent is a new synthesis route developed in our laboratory since 1996. The alkylformamide molecules, used as main solvent, in our synthesis mixtures are unstable in acidic media and decompose at high temperature generating in situ the corresponding ethylamine molecules which act as structure-directing agents. In this paper, we report the influence of some synthesis parameters (temperature, heating time, etc.) on the in situ decomposition of ethylformamide. The influence on the nature of the synthesized products is also described and illustrated from the starting synthesis mixture of a 1-D gallophosphate named Mu-37. This compound, which is structurally related to two fluorogallophosphates reported in the literature, has the following chemical formula GaP 2 O 7 F[CH 3 CH 2 NH 3 ] 2 ( Z = 4), and consists of one-dimensional anionic gallium diphosphate chains containing GaO 4 F 2 units linked by diphosphate P 2 O 7 ones, and charge-balanced by protonated ethylamine molecules. Mu-37 was also characterized by powder XRD, SEM, elemental and thermal analyses, and solid state NMR spectroscopy ( 13 C, 31 P MAS and 1 H- 31 P CP MAS experiments).

Natural and synthetic clay minerals have been transformed into Si-pillared mesoporous structures and then grafted with SH functions, for heavy metal ion trapping in polluted soils. The techniques and the limits encountered were detailed, with assessments of transformations by FTIR spectrometry and X-ray diffraction analyses. Adsorption isotherms of Cd2+ and Ph2+ were measured after 1 day shaking in calcium nitrate suspensions. Tests of Cd and Ph plant uptake were pursued by ray-grass cultivation on polluted soil amended or not with a functionalized synthetic beidellite during 3 months. Natural beidellite, hectorite and vermiculite were transformed into SH-grafted pillared clays but difficulties were encountered to keep a regular and significant interlayer distance until the last step. The well crystalline high-charge vermiculite of Santa Olalla (Spain), after Li-saturation, exchange with alkyl-ammonium cations, formation and grafting of interlayer Si-pillars, showed the highest capacity of Cd2+ and Pb2+ fixation among the 3 functionalized tested clay minerals. The cadmium uptake by ray-grass grown on polluted soil has been quite depressed by amendments with 0.17 or 0.5% of functionalized synthetic beidellite, but these amendments were inefficient for lead. (C) 2006 Elsevier B.V. All rights reser

Dynamic light scattering (DLS) was used to characterize the micelles and particles in the reaction mixtures during the synthesis of SBA-3 type silica at different temperatures, acid and salt concentrations. The adsorption of the siliceous species on the micelles leads to their transformation into wormlike micelles which aggregate into “liquid particles” (gyroids or spheres, observed by optical microscopy) through the screening of the micellar charges. Their transformation into “solid particles” occurs through the replacement of the intermicellar hydrogen and Van der Waals bonds involving the silanol groups by siloxane bonds.

More than four boron per unit cell has been introduced into the framework of silicalite-1, using fluorine containing media. The initial gels were of composition 9MF–xH3BO3–10SiO2–1.25TPABr–330 H2O with M = NH4, Na, K and Cs and x = 0.1–10. The syntheses were carried out in hydrothermal conditions at 170°C. The amount of incorporated TPA+ ions remains quasi constant (3.5–3.8/u.c.) up to 4 B/u.c., while it decreases with increasing boron content. The amount of tetrahedral B/u.c. can be as high as 8 in presence of K+ or Cs+ ions in the as-synthesized samples. It is observed that the preferential countercations to framework negative charges related to the presence of tetrahedral boron, [SiOB]−, are TPA+, K+ and Cs+ ions. It is interpreted, that the −4.0 ppm versus BF3.OEt2 NMR line stems from tetrahedral framework boron, while the −2.9 ppm NMR line represents both extraframework and/or tetracoordinated deformed framework boron in the structure.

Mesostructured carbon materials were obtained by nanocasting MCM-48 and SBA-15 ordered mesoporous silica templates via two carbon infiltration routes: a liquid-phase process (LPI) using sucrose solution or a gas-phase chemical vapor infiltration (CVI) process using propene. The structural characteristics of the carbon replicas were investigated by synchrotron low-angle X-ray diffraction (LAXRD) analysis in combination with transmission electron microscopy (TEM). The materials obtained by the liquid-phase process demonstrated a long-range mesoscopic order at relatively low carbon loading (ca. 35 wt % in SiO2/C composite), with their structural elements being essentially shrunk compared to that of the templates. The CVI replicas at similar low infiltration content were found to be only partly organized within nanodomains, but at bigger carbon loading (ca. 50 wt %) highly ordered mesostructures displaying up to ten nonzero XRD reflections were obtained. Moreover, these materials were shown to have thicker frameworks faithfully replicating their templates. Particular features of the CVI replica of MCM-48 were an amorphous carbon shell on the external particle surface and a gradient of the nanoframework displacement. The carbon replicas of SBA-15 were characterized by a semitubular structure.

The porous structure of a series of micro/mesoporous composite materials synthesized from a mixture of precursor solutions generally used for preparation of Beta microporous molecular sieves and pure mesoporous MCM-48 silica has been investigated. A short crystallization time of the precursor solutions results in the formation of small crystalline zeolitic domains, while after prolonged synthesis the development of larger Beta zeolitic crystallites is observed. An analysis of nitrogen isotherms based on the α s -method has revealed a relationship between the synthesis conditions and the development of both micro- and mesoporosity of these materials. With increasing the size of the zeolitic domains the mesoporosity of the composite materials decreases while the microporosity is increased. The structural features of these composites determined by XRD corroborate with the nitrogen sorption results.

Mesoporous siliceous materials with MCM-41 and MCM-48 pore architecture were functionalized by the grafting of n-propyl groups to the silica network using two routes: post-synthesis treatment of pure silica and direct grafting by a co-condensation process. XRD, N2 adsorption–desorption measurements and 29Si solid state NMR were used to investigate the influence of the spatial pore arrangement (hexagonal and cubic, respectively) on the functionalization procedure. Different grafting rates were observed depending on the surfactant removal procedure, the nature of the material and the grafting process.

Highly ordered porous carbon materials obtained by a replica technique have been used for supercapacitor application and electrochemical hydrogen storage. For the preparation of the well-tailored carbons, MCM-48, SBA-15 and MSU-1 molecular sieves served as templates, whereas a sucrose solution, propylene and pitch were the carbon source. A careful physico-chemical characterization (CO2 and N2 adsorption, X-ray diffraction, electron microscopy observations) allowed to estimate the total surface area, the pore size distribution, the micro/mesopore volume as well as the structure and the microtexture of the investigated carbons. The specific capacitance (F/g) and the hydrogen adsorption capacity in the carbon nanopores were correlated with the microtextural properties. Especially, a linear dependence has been found between the capacitance or the amount of electrochemically stored hydrogen and the ultramicropores (pores smaller than 0.7 nm) volume. It clearly indicates that in these carbons: (a) the major part of the electrical double layer is charged with non-solvated ions; (b) ultramicropores play a determinant role for hydrogen storage.

A solid state 13C NMR study of hardened networks obtained by the reaction of blocked and nonblocked isocyanates (pMDI) with urea-formaldehyde (UF) resins in water showed different results according to the temperature of the reaction. At high temperature, in water, both a nonblocked or an emulsifiable, blocked isocyanate, appear to crosslink with UF resins through the formation both of traditional methylene bridges connecting urea to urea and of urethane bridges. The latter have been confirmed by 13C NMR to form in water by reaction of the isocyanate NCO group with the hydroxymethyl groups of the UF resin. At ambient temperature, UF/pMDI resins where the pMDI is a emulsifiable blocked isocyanate, do not appear to form urethanes to any great extent but rather to crosslink through the usual UF resin urea to urea methylene bridges. Even in this case, when urethane bridges appear to be absent, evidence of crosslinking in water through reaction of the isocyanate with the NH2 and NH amide of the UF resin has not been observed. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 589–596, 2006

Smooth and homogeneous monolayer Silicalite-1 seeds were deposited on silicon substrate surfaces via the Langmuir–Blodgett (LB) technique. The LB films were prepared by vertical dipping leaving part of the substrate uncoated. Neither substrate modification nor additives were required to produce densely packed monolayer seeds. The degree of coverage and packing of the seed layers were dependent on the target pressure used for film deposition. Dense Silicalite-1 films with controlled thickness in the range 100–650 nm were synthesized after secondary synthesis. The (0 k 0) reflections dominated in all the XRD patterns, suggesting that the prepared polycrystalline films were preferentially b-oriented perpendicular to the substrate surface. The degree of in-plane orientation was preserved with increasing film thickness. All secondary growth films were very smooth with a clear boundary between the seeded and non seeded substrate sections. The Silicalite-1 films were highly stable upon both ultrasonic treatment and calcination.

Congrès du 08 au 11 septembre 2008

Congrès du 02 au 06 septembre 2008

Congès du 07 au 09 juillet 2008; International audience

Congrès du 07 au 10 juillet 2008

Congrès du 25 au 28 mai 2008

Hydrothermal synthesis with hexamethylenediamine and ethylenediamine as structure directing agents and amorphous GeO 2 and SiO 2 as framework atoms sources in hydroxide or fluoride media led to IM-13, IM-14 and IM-15, three new materials. The structures of IM-14 and IM-13 were investigated using direct methods on powder X-ray diffraction data and the charge flipping method on a single crystal, respectively. Both materials are open framework structures displaying common structure building units.

The essential chemical modifications involving the polymeric constituents of wood in friction welding occur in the first 5–6 s slowing down or even stopping afterwards. FT-IR and CP-MAS 13C NMR of the welded area of wood have shown dehydration and an apparent increase in the crystallinity of cellulose. A certain level of hemicelluloses degradation occurs, accompanied by the generation of some furfural. Cellulose degradation is instead very slight. Both analytical techniques show an increase in the proportion of lignin in the welding interphase. A proportion of methoxy groups of lignin is de-etherified to phenolic hydroxy groups. Self-condensation of lignin occurs by internal rearrangement with the formation of Ar–Ar and Ar–CH2–Ar bridges. This progresses throughout the whole process of welding. The formation of C–O–C bridges, although stopping after 6 s welding, at the start of wood carbonisation, also appears to contribute to the increase in cross-linking of the lignin network.

International audience; The porous structure and the periodic array of cavities in ordered mesoporous materials with large, three-dimensionally arranged and interconnected pores is thoroughly described by combining electron tomography, small-angle X-ray diffraction, and nitrogen sorption techniques. We used the ability of the electron tomography to provide local three-dimensional information of a nano-object and compared the results to those of the other characterization techniques which furnish global information. We showed thus that the face-centered cubic (fcc) structure usually assigned to the FDU-12 materials is in fact an intergrowth of cubic and hexagonal close-packing structures. This agrees with small-angle X-ray scattering (SAXS) modeling, but for the first time a direct visualization of these stacking faults was achieved. Three-dimensional transmission electron microscopy (3D-TEM) provides also a direct and unique evidence of peculiar stacking defects ("z-shifted [111] areas"), as well as an estimate of their density, which have never been reported elsewhere. In addition, interstitial cavities were also observed, revealing the complex defective structure of this material. A direct observation of the nature of the connecting pores was also achieved for the first time, with a resolution limit of 2 nm. Finally, the characteristics of the porous network evidenced by 3D-TEM are used to explain and validate the results obtained by nitrogen sorption experiments.

Congrès du 06 au 09 septembre 2007; International audience

Zeolite Beta films were synthesized with the ultimate goal of preventing the organic contamination in spacecrafts in low earth orbit. The films were prepared in fluoride media in order to extend their thickness. Intergrown films ranging from 0.7 to 40 were obtained. Zeolite films characteristics were subjected to detail investigation.

International audience

New inorganic composite materials (ICM) were prepared combining a diatomite (Kieselguhr) from Algerian origin and charcoal from pine. After pyrolysis at 850 °C and chemical treatment with HCl, several techniques were used for the characterization of the obtained ICM. X-ray diffraction patterns and FT-Infrared spectroscopy showed that calcium carbonates, initially present as impurities in the natural Kieselguhr, have totally disappeared after treatment. A phase transition for diatomite was observed from quartz, dolomite and amorphous phase to cristobalite after mixture with charcoal. According to the nitrogen adsorption-desorption analysis, the surface properties of diatomite were found to be profoundly affected by the presence of charcoal. Indeed, the surface increased from 5 to 405 m2/g. The obtained products also exhibit a hydrophobic characteristic, contrary to the hydrophilic nature of the initially used diatomite material. These new ICM seem to be promising materials for use as industrial adsorbents in different applications like for the wastewater and air treatment, and for solvent recuperation.

Materials based on molecular sieves are investigated as an effective, environmentally-safe, economical and reusable alternative to traditional antioxidant additives. A substantial extension of lubricant lifetime is achieved by selective adsorption of oxidation by-products and water with nanoporous materials of controlled structure, morphology, size and chemical composition. Four types of materials, two hydrophobic and two hydrophilic, were used for purification of two commercial compressor oil formulations with different times of operation. After separation of the lubricants from the nanoporous materials, both were analyzed for trapped molecules, anti-oxidants, water content and color changes.

International audience

A comprehensive study including (i) the synthesis of colloidal zeolite-β nanoparticles with size below 100 nm from precursor suspensions, (ii) kinetics of the crystallization process of zeolite-β, (iii) stabilization of the β nanocrystals in coating suspensions, (iv) preparation of homogeneous thin films by a spin-coating approach, and (v) physicochemical characterizations of the films are the focus of this paper. It has been demonstrated that the crystallization process of β was completed within 7 days, and the final size and shape of the nanocrystals resemble the amorphous particles in the precursor suspensions. Next, the crystalline β particles were stabilized in colloidal suspensions under addition of inorganic silica-based binders and further applied for a spin-on process of films. It has been confirmed that the number of coating steps, speed of deposition, concentration of coating suspensions, and type of binders had a pronounced influence on the thickness, mechanical, and optical properties of the ...

Hydrothermal synthesis with ethylenediamine as structure-directing agent and amorphous GeO2 as framework atom source led to IM-14, a new open-framework material of formula |(enH2)2 (H2O)2.3|[Ge8O17(OH)2] of which the 3D-framework holds intersecting channels delimited by 8- and two distinct 10-membered rings. The structure of IM-14 was investigated using powder X-ray diffraction data: monoclinic, space group P21/a, a = 20.2023(13) A, b = 14.9647(8) A, c = 7.7017(4) A, β = 91.076(4)°, V = 2328.0(3) A3 and Z = 4. This material was also characterised by chemical and thermal analyses, SEM, 1H–13C MAS DEC NMR spectroscopy, 1H and 13C liquid NMR spectroscopies after dissolution in HF.

Glyoxalated soy flour adhesives for wood particleboard added with a much smaller proportion of glyoxalated lignin or tannin and without any addition of either formaldehyde or formaldehyde-based resin are shown to yield results satisfying the relevant standard specifications for interior wood boards. Adhesive resin formulations in which the total content of natural material is either 70 or 80% of the total resin solids content gave good results. The resins comprising 70% by weight of natural material can be used in a much lower proportion on wood chips and can afford pressing times fast enough to be significant under industrial panel pressing conditions. The best formulation of all the ones tried was the one based on glyoxalated precooked soy flour (SG), to which a condensed tannin was added in water solution and a polymeric isocyanate (pMDI), where the proportions of the components SG/T/pMDI was 54/16/30 by weight. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Catalytic Oxidative DeHydrogenation of Propane (ODHP) by N 2 O over Fe-BEA catalysts has been studied in continuous feed regime against time and with periodic changing of in-let feed composition under reaction-regeneration cycles. The influence of process parameters on the propylene production has been evaluated, namely N 2 O/propane ratio and crystal size of the parent zeolite. The particle size (micro- vs. nano-particles) of the catalyst has been shown to be a crucial parameter for propylene yields and catalyst selectivity at higher temperatures. The nano-sized catalyst exhibits superior propylene formation in comparison with micro-sized one. Time dependent performance of ODHP was carried out using reactant streams containing N 2 O or N 2 O with O 2 . Reactivation of the catalysts by oxidation pulses revealed that short pulses of oxygen are sufficient to regenerate the active sites and stabilize propylene yield.