Investigation of the fluid dynamic of the modified Hartmann tube equipment by high-speed video processing

Hartmann tube equipment is used in the dust explosion experimental test to screen the flammability of powdered materials (according to ISO 80079-20) and to determine the Minimum ignition energy of dust (UNI EN 13824:2004). For the test, the nominal concentration, as the ratio between the dust sample mass and the chamber test volume (1.2 liters), is considered, assuming a uniform concentration distribution. Even though adopted as standard procedure, this approach does not consider the dust cloud's non-stationary conditions inside the tube: The effect of turbulence decrease and dust sedimentation during the test duration will affect the dust concentration locally and globally within the test enclosure. Moreover, it is well known that the turbulence intensity influences Minimum Ignition Energy. This work derives from previous investigation on describing the dust cloud behavior within dust explosibility laboratory apparatuses. High-speed video recordings have recently been adopted to support the dust cloud dynamic analysis and visualize the cloud dispersion within a standard test setup, as the 20 L sphere and the modified Hartmann tube. This work intends to use different high-speed videos of dust dispersions in the modified Hartmann tube, with different injection pressure and sample mass, to focus on the behavior of the cloud at the typical delay time of the MIE measurement, i.e., 60-180 ms. Each video is processed frame by frame to reveal information on the cloud dynamics, otherwise hidden. The dust dynamic is accounted for calculating the variation in time of the brightness of pixels. This way, it is possible to obtain a set of data that incorporate the effects of the dust cloud distribution and the velocity of the particles clusters. The experimental data processing will help to focus on the time-scale and the length scale of the turbulence. The next study will focus on evaluating the time and space scale of the dust cloud and identifying the effect of ignition time delay on the MIE measurement to provide indications to operate at the most conservative conditions (higher concentration) and to avoid issues and under/overestimates due to agglomeration, sedimentation or segregation of dust particles

Sequestration of Martian CO2 by mineral carbonation

Carbonation is the water-mediated replacement of silicate minerals, such as olivine, by carbonate, and is commonplace in the Earth’s crust. This reaction can remove significant quantities of CO2 from the atmosphere and store it over geological timescales. Here we present the first direct evidence for CO2 sequestration and storage on Mars by mineral carbonation. Electron beam imaging and analysis show that olivine and a plagioclase feldspar-rich mesostasis in the Lafayette meteorite have been replaced by carbonate. The susceptibility of olivine to replacement was enhanced by the presence of smectite veins along which CO2-rich fluids gained access to grain interiors. Lafayette was partially carbonated during the Amazonian, when liquid water was available intermittently and atmospheric CO2 concentrations were close to their present-day values. Earlier in Mars’ history, when the planet had a much thicker atmosphere and an active hydrosphere, carbonation is likely to have been an effective mechanism for sequestration of CO2

On the influence of Si:Al ratio and hierarchical porosity of FAU zeolites in solid acid catalysed esterification pretreatment of bio-oil

A family of faujasite (FAU) zeolites with different Si:Al ratio, and/or hierarchical porosity introduced via post-synthetic alkaline desilication treatment, have been evaluated as solid acid catalysts for esterification pretreatments of pyrolysis bio-oil components. Acetic acid esterification with aliphatic and aromatic alcohols including methanol, anisyl alcohol, benzyl alcohol, p-cresol and n-butanol was first selected as a model reaction to identify the optimum zeolite properties. Materials were fully characterised using N2 porosimetry, ICP, XRD, XPS, FT-IR, pyridine adsorption, NH3 TPD, In-situ ATR and inverse gas chromatography (IGC). IGC demonstrates that the surface polarity and hence hydrophobicity of FAU decreases with increased Si:Al ratio. Despite possessing a higher acid site loading and acetic acid adsorption capacity, high Al-content FAU possess weaker acidity than more siliceous catalysts. Esterification activity increases with acid strength and decreasing surface polarity following the order FAU30>FAU6>FAU2.6. The introduction of mesoporosity through synthesis of a hierarchical HFAU30 material further enhances esterification activity through improved acid site accessibility and hydrophobicity. Methanol was the most reactive alcohol for esterification, and evaluated with HFAU30 for the pretreatment of a real pyrolysis bio-oil, reducing the acid content by 76% under mild conditions

Carbonylative Sonogashira Coupling in the Synthesis of Ynones: A Study of "Boomerang" Phenomena

BIOVERT+MGE:LDJThe behaviour of several organophosphino-palladium complexes immobilized on mesoporous silica during the palladium-catalyzed synthesis of propynone by carbonylative Sonogashira coupling was studied, particularly concerning leaching/redeposition phenomena. The results demonstrated that this cross-coupling reaction is catalyzed by soluble species. Furthermore, it is shown that the palladium leaching is not initiated by the oxidative addition step but rather by palladium-decoordination from grafted ligand. Despite this decoordination, catalyst performance after recycling is adequate. Additionally, several parameters linked either to catalyst preparation or reaction procedures were shown to reduce leaching allowing one to achieve metal contamination levels close to the recommendation of the European Agency for the Evaluation of Medicinal Products. Interestingly, this heterogeneous palladium-catalyzed procedure is fully selective toward the formation of ynones, allowing the preparation of various target compounds

Enhanced cooperative, catalytic behavior of organic functional groups by immobilization

International audienc

Heterogeneous metallo-organocatalysis for the selective one-pot synthesis of 2-benzylidene-indoxyl and 2-phenyl-4-quinolone

5 Genelot, Marie Dufaud, Veronique Djakovitch, LaurentOne-pot tandem heterogeneously catalyzed procedures for the selective synthesis of 2-benzylidene-indoxyl and 2-phenyl-4-quinolone have been developed. For this purpose, heterogeneous palladium-, amine-, and phosphine-catalysts were prepared by post-synthetic grafting onto SBA silica. The state of the hybrid materials was characterized using a wide variety of molecular and solid-state techniques. These materials exhibit high activities as 2-benzylidene-indoxyl was obtained in 81% yields through {[Pd]@SBA-15+PPh3} catalysis while 2-phenyl-4-quinolone was prepared by a fully heterogeneous if {[Pd]@SBA-15+[AMINE]@SBA-3} protocol in 61-75% isolated yield. For the later, we demonstrated that the catalysts mixture could be reused up to three runs without strong deactivation. (C) 2010 Elsevier Ltd. All rights reserved

Matériaux hybrides "complexes de palladium@silice mésoporeuse" pour l'obtention sélective de N-hétérocycles carbolylés

nationa

Selective synthesies of 2 types of N-heterocycles through heterogeneous multi-catalysis.

internationa