The control of catalytic performance of rutile-type Sn/V/Nb/Sb mixed oxides, catalysts for propane ammoxidation to acrylonitrile

This paper describes the effect of the composition of rutile-type Sn/V/Nb/Sb mixed oxides catalysts on the catalytic performance in the gas-phase ammoxidation of propane to acrylonitrile. The variation in the atomic ratio between components in catalysts is the key for the control of activity and selectivity. In samples with atomic composition Sn/V/Nb/Sb 1/0.2/1/x (0 x 5) and 1/0.2/y/3 (0 y 3) several compounds formed, i.e., SnO2, Sb/Nbmixed oxide, Sb6O13 and non-stoichiometric rutile-type V/Nb/Sb/O; the latter segregated preferentially at the surface of the catalyst. Tin oxide provided the rutile matrix for the dispersion of the mixed oxides. The main role of Sb was shown to generate mixed oxides containing specific sites for the allylic ammoxidation of propylene intermediately formed. The presence of Nb enhanced the activity and selectivity of these sites

Controlled Growth of WO3Nanostructures with Three Different Morphologies and Their Structural, Optical, and Photodecomposition Studies

Tungsten trioxide (WO3) nanostructures were synthesized by hydrothermal method using sodium tungstate (Na2WO4·2H2O) alone as starting material, and sodium tungstate in presence of ferrous ammonium sulfate [(NH4)2Fe(SO4)2·6H2O] or cobalt chloride (CoCl2·6H2O) as structure-directing agents. Orthorhombic WO3having a rectangular slab-like morphology was obtained when Na2WO4·2H2O was used alone. When ferrous ammonium sulfate and cobalt chloride were added to sodium tungstate, hexagonal WO3nanowire clusters and hexagonal WO3nanorods were obtained, respectively. The crystal structure and orientation of the synthesized products were studied by X-ray diffraction (XRD), micro-Raman spectroscopy, and high-resolution transmission electron microscopy (HRTEM), and their chemical composition was analyzed by X-ray photoelectron spectroscopy (XPS). The optical properties of the synthesized products were verified by UV–Vis and photoluminescence studies. A photodegradation study on Procion Red MX 5B was also carried out, showing that the hexagonal WO3nanowire clusters had the highest photodegradation efficiency

A new physical mapping approach refines the sex-determining gene positions on the Silene latifolia Y-chromosome

Sex chromosomes are particularly interesting regions of the genome for both molecular genetics and evolutionary studies; yet, for most species, we lack basic information, such as the gene order along the chromosome. Because they lack recombination, Y-linked genes cannot be mapped genetically, leaving physical mapping as the only option for establishing the extent of synteny and homology with the X chromosome. Here, we developed a novel and general method for deletion mapping of non-recombining regions by solving "the travelling salesman problem", and evaluate its accuracy using simulated datasets. Unlike the existing radiation hybrid approach, this method allows us to combine deletion mutants from different experiments and sources. We applied our method to a set of newly generated deletion mutants in the dioecious plant Silene latifolia and refined the locations of the sex-determining loci on its Y chromosome map

Hydrodeoxygenation of guaiacol Part II: Support effect for CoMoS catalysts on HDO activity and selectivity

3-4 Van Ngoc Bui Laurenti, Dorothee Delichere, Pierre Geantet, ChristopheBio-oils coming from ligno-cellulosic biomass are suitable material for the production of second generation biofuels. The oxygenated compounds have to be eliminated to confer good properties to these bio-oils and to permit their addition to traditional fuels. Hydrodeoxygenation (HDO) process which allows O-elimination by C-O bond cleavage under H-2 can be realized with the same type of catalysts as those used in HDS, supported CoMoS or NiMoS phases. In this work, the support effect associated with CoMoS catalysts has been investigated in guaiacol HDO reaction. Zirconia and titania supports have been compared with the traditional industrially used gamma-alumina and it appeared that zirconia as support gave very efficient conversion of guaiacol into deoxygenated hydrocarbons with a totally different selectivity. The difference in selectivity allowed us to propose a different reaction scheme compared to gamma-alumina and titania supported CoMoS. (c) 2010 Elsevier B.V. All rights reserved

Development of V/Al/O-mixed oxides based catalysts for in the ammoxidation of propane

International @ RAFFINAGE+CLO:PDE:SLO:JMIInternational audienceAcrylonitrile is an important intermediate in industry that is currently produced by ammoxidation of costly and increasingly scarce propylene. This work aimed at developing novel catalysts allowing to use cheaper and abundant propane to produce acrylonitrile. These catalysts are based upon vanadium and aluminum oxi-nitrides prepared by nitridation under ammoniac or in catalytic reaction conditions. Various parameters were studied like reactant partial pressures or contact time in order to understand the catalytic reaction mechanism. After testing, catalysts were characterized using a multi-techniques approach to evidence possible transformations and relate catalytic and structural or textural properties. This allowed understanding the origin of the catalytic properties and proposing sites for alkane activation and N insertion. Synergetic effects with phases like Sb2O3 were searched allowing to develop catalysts as selective to acrylonitrile but leading to more propene as by-product, which can be ammoxidize to acrylonitrile in a second reactor or valorized

Heterogeneous reaction of sulphur dioxide on Eyjafjallajökulls volcanic ash from the 2010 eruption

International @ AIR+LBU:PDE:CGO:BDAInternational audienceVolcanic eruptions may induce important climatic and weather modifications. When volcanic ashes are emitted into the atmosphere they can travel for several weeks according to their size distribution and altitude of the ashes emission. The Eyjafjallajökull eruption, between April 14th and May 23th, is considered as a medium-size eruption with injection of the ashes plume at relative low altitude (troposphere). However, ash was widely dispersed because of upper-level winds that advected the plume over the UK and continental Europe, as well as into the translattalntic flight routes. During volcanic eruptions high amounts of SO2 were injected into the atmosphere (from 50 to 200 ppbv) [1]. Previous literature showed that SO2 could be convert into sulfate on mineral dust surfaces under dark conditions [2]. Sor far no conversion of SO2 has been studied with real volcanic ashes and under day conditions (light exposure). The present study focuses on SO2 kinetics on real Eyjafjallajökull's ash samples, collected the 20th of April 2010 at Seljavellir. The kinetics was investigated using a flow-tube set up at atmospheric pressure and simulating atmospheric conditions. The ashes were deposited on a horizontal cylindrical coated-wall flow tube reactor surrounded by 5 fluorescent lamps (emission from 320-420 nm, ?max=365nm). The kinetic studies revealed that the under UV-A irradiation conversion of SO2 into sulphates is enhanced on these ash samples (as shown in figure 1 below). Figure 1. Uptake of SO2 under darkness and weak UV-A irradiation on Eyjafjallajökull's ash sample. Moreover chemical analyses as, Ion Chromatography (IC) and Scanning Electron Microscopy (SEM) coupled to energy dispersion spectrometry (EDS) were performed on volcanic ashes before and after exposition to gaseous SO2. X-ray photoelectron spectroscopy (XPS) and ion chromatography (IC) analyses confirmed an enhanced SO2 uptake under irradiation with conversion of SO2 to sulphate. Beside SEM-EDS analysis suggested that the conversion takes place systematically on iron oxide site. Figure 1. Mapping of Sulfur and Iron on SEM picture. By combining kinetics and chemical analyses a new reaction mechanism for SO2 conversion on volcanic ashes under light conditions is proposed. Self, S., M. Widdowson, T. Thordarson, and A. E. Jay (2006), Earth Planet. Sci. Lett., 248(1-2), 518-532. Zhang, X. Y., G. S. Zhuang, J. M. Chen, Y. Wang, X. Wang, Z. S. An, and P. Zhang (2006), J. Phys. Chem. B, 110(25), 12588-12596

An alternative route to synthesize acrylic acid: dehydration of lactic acid and lactates over alkaline earth phosphates

RMN+ECI2D+CLO:PDE:JMI:SLONational audienceAcrylic acid is one of the major petrochemical intermediates. In near future, its production from renewable resources is required by clean process. Dehydration of lactic acid to acrylic acid corresponds to one of the alternative routes to investigate. In the present work, alkaline earth phosphates have been prepared and evaluated for this reaction and also dehydration of ethyl lactate to acrylic acid and ethyl acrylate that appeared as more interesting. Moreover, the reaction mechanisms were determined focusing the effect of water. Furthermore, a correlation between catalytic and acido-base properties was established. Finally, the active sites, selective or not, were identified from numerous techniques including in situ DRIFT spectroscopy

Evidence of anti-coking behavior of La0.8Sr0.2Cr0.98Ru0.02O3 as potential anode material for Solid Oxide Fuel Cells directly fed under methane

+PDELa0.8Sr0.2CrO3 (LSC) based Ru catalysts are very active in methane steam reforming. Nevertheless, they can be easily poisoned under water-deficient conditions. Ru can be deposited as metallic ruthenium particles decorating the LSC grains or be inserted as Ru ions in the perovskite structure. Both Ru-promoted LSC catalysts were studied in methane steam reforming under water-deficient conditions and characterized after testing. Catalytic activity tests showed that ruthenium metal species are deactivated under water-deficient atmosphere, while ruthenium species inserted in LSC presented a remarkable stability and catalytic activity where residual steam plays a key role. Very unreactive carbon species responsible for deactivation were detected by temperature-programmed oxidation and transmission electron microscopy over metallic ruthenium species. Such species were not observed when ruthenium species are inserted and stabilized into the LSC structure. La0.8Sr0.2Cr0.98Ru0.02O3 appears therefore as a highly promising anti-coking anode material for Solid Oxide Fuel Cells directly fed with methane or natural gas and operating under water-deficient conditions. (c) 2012 Elsevier Inc. All rights reserved

Dehydration of lactic acid to acrylic acid over alkaline earth phosphates

International @ RAFFINAGE+EBL:PDE:CLO:CPI:JMI:SLOInternational audienceAcrylic acid (AA) is a platform molecule produced at 4Mt/year by selective oxidation of propene, a petrochemical resource whose price is growing quickly because of increasing demand and rarefaction of petroleum. An alternative route consists in dehydration of lactic acid (LA) that can be yielded both by dehydrogenation of glycerol1 or fermentation of sugars2. However, AA is rarely obtained selectively from LA because of easy decarbonylation leading to acetaldehyde and CO. High yields to acrylic acid were obtained using modified zeolithes3,4 but they suffered from coking and probably hydrothermal instability. In the present work, the gas phase conversion of LA over different phosphates was investigated. A complete analysis of the products was obtained by GC completed by GC-MS and GC-2D data. Good catalytic performances were obtained for alkaline earth ortho, pyrophosphates and hydroxyapatites with selectivities to AA reaching 50% near complete conversion. The main by-products were acetaldehyde and CO. These catalysts were stable for at least 24 hours and only small amounts of carbonates and carboxylates were evidenced after reaction. The optimized temperature of 380°C was shown to favour AA desorption without thermal degradation. The presence of residual Na+ cations at the surface of catalysts inhibited the carbonylation route to the benefit of decarboxylation leading to by-producing of H2 that reacts with AA to form propionic acid. Finally, good catalytic performances were also obtained for alkaline earth phosphates using methyl lactate as reactant that yielded mainly methyl acrylate. Furthermore, NH3 and CO2-TPD curves achieved to characterize the acid-base properties revealed that the most efficient catalysts owned only weak and moderated sites. As very similar profiles of the curves were observed (Fig.1a) with molar acid/base balance around 2, it suggested the presence of high proportion of amphoteric sites that could be the active and selective sites for LA dehydration. The surface characterization obtained both from XPS, 1H-31P CP MAS NMR spectra (Fig.1b, c) evidenced the presence of hydroxylated phosphorous rich phase that is XRD amorphous. Its composition was very different to the bulk one with O/P molar ratio close to 3 and a proportion of oxygen involved in hydroxyl groups of 20%. This phase could correspond to polyphosphates in interaction with alkaline earth cations