22 research outputs found
Hydrodeoxygenation of guaiacol Part II: Support effect for CoMoS catalysts on HDO activity and selectivity
No full text3-4 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
The control of catalytic performance of rutile-type Sn/V/Nb/Sb mixed oxides, catalysts for propane ammoxidation to acrylonitrile
No full textArcozzi, Elena Ballarini, Nicola Cavani, Fabrizio Cimini, Massimo Lucarelli, Carlo Trifiro, Ferruccio Delichere, Pierre Millet, Jean-Marc M. Marion, PhilippeInternational audienceThis 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/Nb mixed 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. (C) 2008 Elsevier B.V. All rights reserved
Revisiting the physical processes of vapodeposited thin gold films on chemically modified glass by atomic force and surface plasmon microscopies
No full textRoland, Thibault Khalil, Andre Tanenbaum, Aaron Berguiga, Lotfi Delichere, Pierre Bonneviot, Laurent Elezgaray, Juan Arneodo, Alain Argoul, FrancoiseThe preparation of very thin (at the scale of a few tens of nanometers) gold films by thermal evaporation and deposition on a solid substrate (glass) remains a key step for the elaboration of transparent and sensitive optical biosensors. We study the influence of the glass surface treatment and its thermal conductivity on the structure and composition of evaporated gold films. Using a combination of atomic force microscopy (AFM), high resolution surface plasmon resonance (SPR) imaging, and X-ray photoelectrom spectroscopy (XPS), we demonstrate that the grafting of a layer of long chain mercaptant, using 11-mercaptoundecyltrimethoxysilane (S xi Si), prior to gold deposition produces a drastic modification of gold inner and surface textures. A thorough investigation of AFM image topography by 2D wavelet-based segmentation method reveals the flat conical shape of the gold surface grains and their shape invariance with the glass surface chemical treatment. However, this treatment leads to a drastic decrease of the mean size and polydispersity of these grains by a factor of 2, thereby lowering the gold surface roughness. The rationale is that the combination of surface forces and thermal transfer drives the formation of homogeneous and flatter gold films. (C) 2009 Elsevier B.V. All rights reserve
ChemInform Abstract: A New Approach to the Preparation of Nitrogen‐Doped Titania Visible Light Photocatalyst.
No full textGold Nanoparticles Supported on Passivated Silica: Access to an Efficient Aerobic Epoxidation Catalyst and the Intrinsic Oxidation Activity of Gold
No full textWell-defined and perfectly dispersed [(square SiO)Au(1)] surface species supported on silica have been obtained via surface organometallic chemistry and transformed upon mild reduction (H(2), 300 degrees C) into small (1.8 +/- 0.6 nm) Au particles supported on silica passivated with SiMe(3) functionalities. improved performance in liquid-phase aerobic epoxidation has been achieved, and the intrinsic activity of gold in oxidation is revealed.LR
CATL 37-Gold nanoparticles supported on passivated silica: Access to the intrinsic oxidation activity of gold
No full textLR
A new approach to the preparation of nitrogen-doped titania visible light photocatalyst
No full textA new simple method is described, allowing introduction of nitrogen into the TiO 2 lattice at low temperatures. The technique is based on the introduction of oxophilic molecules, such as CCl 4, into the reaction mixture. The treatment of titanium dioxide powders by NH 3-CCl 4 mixtures leads to highly dispersed N-doped TiO 2. As compared to bare TiO 2 or to the same oxide treated with sole NH 3, the solids treated with NH 3-CCl 4 mixtures showed a stronger red shift in optical absorption and enhanced photocatalytic activity under visible light, as demonstrated for two reactions of formic acid oxidation and photocatalytic production of hydrogen from methanol. The nitridation temperature can be significantly decreased by introducing CCl 4, because of a favorable change of the reaction thermodynamics. Not only can higher specific surface area of materials be obtained as a result of avoiding sintering but a higher amount of nitrogen is introduced in a position beneficial for the enhanced catalytic activity. The X-ray photoelectron spectroscopy study demonstrated increased surface concentration of nitrogen having N 1s binding energy near 399 eV. As established by ESR, the nature of paramagnetic species generated by treatments is strongly dependent on the titania polymorph variety and crystallinity as well as on the treatment conditions, but in all cases the major part of introduced nitrogen remains ESR-silent. © 2012 American Chemical Society.The authors gratefully acknowledge the King Abdullah University of Science and Technology for support of this research through the CADENCED project
