1,8-Bis[3-(triethoxy­silyl)prop­yl]-1,8-diazo­niatricyclo­[9.3.1.14,8]hexa­decane diiodide

The organic mol­ecule of title compound, C30H66N4O6Si2 2+·2I−, is located around a centre of symmetry. The structure exhibits disorder of the trieth­oxy groups with the ratios 0.78 (1)/0.22 (1), 0.67 (1)/0.33 (1) and 0.58 (1)/0.42 (1)

Axisymmetric Implementation for 3D-Based DSMC Codes

The primary objective in developing NASA s DSMC Analysis Code (DAC) was to provide a high fidelity modeling tool for 3D rarefied flows such as vacuum plume impingement and hypersonic re-entry flows [1]. The initial implementation has been expanded over time to offer other capabilities including a novel axisymmetric implementation. Because of the inherently 3D nature of DAC, this axisymmetric implementation uses a 3D Cartesian domain and 3D surfaces. Molecules are moved in all three dimensions but their movements are limited by physical walls to a small wedge centered on the plane of symmetry (Figure 1). Unfortunately, far from the axis of symmetry, the cell size in the direction perpendicular to the plane of symmetry (the Z-direction) may become large compared to the flow mean free path. This frequently results in inaccuracies in these regions of the domain. A new axisymmetric implementation is presented which aims to solve this issue by using Bird s approach for the molecular movement while preserving the 3D nature of the DAC software [2]. First, the computational domain is similar to that previously used such that a wedge must still be used to define the inflow surface and solid walls within the domain. As before molecules are created inside the inflow wedge triangles but they are now rotated back to the symmetry plane. During the move step, molecules are moved in 3D but instead of interacting with the wedge walls, the molecules are rotated back to the plane of symmetry at the end of the move step. This new implementation was tested for multiple flows over axisymmetric shapes, including a sphere, a cone, a double cone and a hollow cylinder. Comparisons to previous DSMC solutions and experiments, when available, are made

Applied Aeroscience and CFD Branch Rarefied Gas Dynamics Discipline Overview

No abstract availabl

Synthesis and Characterization of Electrospun Nanofibers of Sr-La-Ce Oxides as Catalysts for the Oxidative Coupling of Methane

Catalytic nanofibers composed of La-Ce and Sr-La-Ce oxides were synthesized by the electrospinning method with 5 wt % Sr and different La/Ce molar ratios. The materials were obtained by calcining electrospun polymer composite fibers and were studied for the oxidative coupling of methane. The catalytic performance was compared with analogous Sr-La-Ce powder catalysts. SEM micrographs of Sr-La-Ce fibers (La/Ce: 0.1, 0.2, 1, and 3) showed nanostructures with homogeneous and uniform diameters (170-200 nm). In addition, the XRD patterns revealed the formation of crystalline solid solutions like LaxCeyOz. The strontium enhanced the CH4 conversion and C2 selectivity since it possibly generated structural defects that promote the formation of superoxide species. The SrLaCe3 nanofibers reached a CH4 conversion of 28.5% and C2 yield of 21.7% at 600 °C. The randomly packed nanofibers improved the heat and mass transfer properties due to their high geometric surface ratio with high bed porosity.Fil: Sollier, Brenda Maria del Valle. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Bonne, Magali. Université Haute-alsace.; FranciaFil: Khenoussi, Nabyl. Université Haute-alsace.; FranciaFil: Michelin, Laure. Université Haute-alsace.; FranciaFil: Miro, Eduardo Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Gómez, Leticia Ester. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Boix, Alicia Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Lebeau, Benedicte. Université Haute-alsace.; Franci

Encapsulation of a UV filter in a mesoporous silica for cosmetic applications

L’encapsulation de principes actifs connaît un intérêt croissant dans de nombreux domaines tels que la pharmacie, l’agrochimie, l’alimentaire, la cosmétique, le textile, le bâtiment... Selon les applications ciblées, une encapsulation permanente ou instable avec un relargage contrôlé du principe actif dans le temps et parfois l’espace est recherchée. La chimie permet de répondre à ces différentes attentes. Cet article décrit comment à partir d’une problématique propre au domaine de la cosmétique, un matériau hybride organique-inorganique a été imaginé, synthétisé, caractérisé pour mieux comprendre ses propriétés et testé dans des formulations cosmétiques

Deep hydrodesulfurization of 4,6-dimethydibenzothiophene over CoMoS/TiO2 catalysts: Impact of the TiO2 treatment

International audienceMesostructured titania as support for the CoMoS active phase in deep hydrodesulfurization (HDS) of 4,6-dimethydibenzothiophene (4,6-DMDBT) leads to an increase of the intrinsic HDS activity and a higher selectivity for direct desulfurization (DDS) for HDS reaction in contrast with the conventional CoMoS/alumina catalyst. The temperature treatment of the mesostructured TiO2 support, modifies the catalyst’s activity for the transformation of 4,6-DMDBT. The higher total and HDS activities were obtained after treatment at 380 °C corresponding to the higher specific surface area and to a mesostructured TiO2 material with a semi-crystalline anatase framework. Beyond 550 °C, the specific surface area decreases strongly corresponding to a complete crystallization of the mesopores walls into anatase structure. Moreover, the temperature under which the support is treated prior its impregnation has no impact on the selectivity of the transformation routes of the sulfur compound

Organic/Inorganic heterogeneous silica-based photoredox catalyst for Aza-Henry Reactions

The transformation of light into chemical energy is a leitmotiv in the development of sustainable and environmentally concerned chemical processes. Chemists invented original concepts to address this purpose, like photoredox catalysis, which became a wonderful tool to transform simple organic compounds into high-value products. Nevertheless, the most relevant transition metal based photocatalysts suffer from major disadvantages like toxicity, cost, and poor recyclability potential. To circumvent this, we propose a new generation of heterogeneous photoredox catalysts resulting from the combination of porous silica materials and Rose Bengal. They promote carbon–carbon bond formations under visible-light in environmentally benign solvent using air as the only stoichiometric redox partner. The pure covalent photocatalytic system provides a robust and recyclable system for greener catalysis. This report would be of broad significance because it addresses important sustainability issues: recycling, non-toxic metal-free photocatalysts, and less-waste-producing chemical process.Fil: Soria Castro, Silvia Mercedes. Université de Strasbourg; Francia. Université Haute-alsace. Institut de Science Des Matériaux de Mulhouse.; FranciaFil: Lebeau, Benedicte. Université de Strasbourg; Francia. Université Haute-alsace. Institut de Science Des Matériaux de Mulhouse.; FranciaFil: Cormier, Morgan. Université Haute-alsace.; FranciaFil: Neunlist, Serge. Université Haute-alsace.; FranciaFil: Daou, T. Jean. Université de Strasbourg; FranciaFil: Goddard, Jean-Philippe. Université Haute-alsace.; Franci

Synthesis of Binderless ZK-4 Zeolite Microspheres at High Temperature

Binderless zeolite macrostructures in the form of ZK-4 microspheres were prepared using anion-exchange resin beads as shape-directing macrotemplates. The particles were synthesized under hydrothermal conditions at different temperatures and treatment times. The influence of the different synthesis parameters was investigated by X-ray diffraction, scanning electron microscopy, fluorescence X, nitrogen adsorption measurements and 29Si solid-state NMR. Fully crystalline spheres similar in size and shape to the original resin beads were obtained by a hydrothermal treatment at the highest temperatures (150–180 °C) for a short treatment time of 24 h. The synthesized microspheres showed to be promising in the molecular decontamination of volatile organic compounds (VOCs)

Determination of Microporous and Mesoporous Surface Areas and Volumes of Mesoporous Zeolites by Corrected t ‐Plot Analysis

International audienceZeolites are well-known microporous catalysts, involved in many industrial applications. Their microporosity yet impedes diffusion of bulky molecules/feedstocks. To overcome this drawback, zeolites with bimodal porosity, e.g. micropores and mesopores were developed during the last decades. In this context, it is important to develop/use methods able to evaluate accurately the textural properties of micro-/mesoporous zeolites. t-Plot is commonly used for determining the micro-and mesopore surface areas and pore volumes. However, previously we showed that the classical t-plot analysis overestimates the mesopore surface areas and underestimates the micropore volumes for FAU-Y micro-/mesoporous zeolite. Measurements performed with mechanical mixtures of FAU-Y and MCM-41 allowed us to provide corrections to the t-plot analysis. These corrections were up to date limited to FAU structured zeolites. In the present work, we present specific corrections of the t-plot for a broader series of zeolites including MFI, *BEA and MOR, based on a set of mechanical mixtures of zeolites and MCM-41. Minor correction factors were required for MOR, whilst for MFI and *BEA similar corrections as for the FAU-Y were inferred for the micropore volume. As far as the surface area is concerned higher correction factors were required for MFI compared to *BEA. This corrected t-plot analysis was applied to characterize a great variety of mesoporous zeolites prepared by micelle-templating following a two-steps procedure