Patent•
Olefin metathesis catalyst
11 Sep 1984-
TL;DR: In this article, a catalyst comprising an inorganic refractory oxide support containing at least one of tungsten oxide and molybdenum oxide and a promoting amount of at least a methylating agent under conditions suitable for the methylating agents to promote the activity of the oxides for the disproportionation reaction.
Abstract: Olefins are converted into other olefins having different numbers of carbon atoms by contact with a catalyst comprising an inorganic refractory oxide support containing at least one of tungsten oxide and molybdenum oxide and a promoting amount of at least one methylating agent under conditions suitable for the methylating agent compounds to promote the activity of tungsten and molybdenum oxides for the disproportionation reaction.
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TL;DR: In this paper, the fungus Fusarium oxysporum was challenged with aqueous anionic complexes SiF62− and TiF 62− respectively and extracellular protein-mediated hydrolysis of the anionic complex results in the facile room temperature synthesis of crystalline titania particles while calcination at 300 °C is required for crystallization of silica.
Abstract: The synthesis of inorganic materials by biological systems is characterized by processes that occur at close to ambient temperatures, pressures and neutral pH. This is exemplified by biosilicification in marine organisms such as diatoms while laboratory-based synthesis of silica involves extreme temperature and pH conditions. We show here that silica and titania particles may be produced by challenging the fungus Fusarium oxysporum with aqueous anionic complexes SiF62− and TiF62− respectively. Extra-cellular protein-mediated hydrolysis of the anionic complexes results in the facile room temperature synthesis of crystalline titania particles while calcination at 300 °C is required for crystallization of silica.
348 citations
TL;DR: The literature of olefin metathesis by heterogeneous supported catalysts, both industrial-type supported metal oxides (ReOx/Al2O3, ReOx/(SiO2−Al 2O3) and supported organometallic complexes, is comprehensively reviewed in this paper.
Abstract: The literature of olefin metathesis by heterogeneous supported catalysts, both industrial-type supported metal oxides (ReOx/Al2O3, ReOx/(SiO2–Al2O3), MoOx/SiO2, MoOx/Al2O3, MoOx/(SiO2–Al2O3), WOx/SiO2, and WOx/(SiO2–Al2O3)) and supported organometallic complexes, is comprehensively reviewed. The focus of this Review is supported metal oxide catalysts, but the well-defined supported organometallic catalyst literature is also covered because such model catalysts have the potential to bridge heterogeneous and homogeneous olefin metathesis catalysis. The recent world shortage of small olefin feedstocks has created renewed interest in olefin metathesis as a route to synthesizing small olefins and is reflected in the recent growth of the patent literature. Despite the extensive application of supported metal oxides in industry for metathesis of small and large olefins, the molecular structures and oxidation states of the catalytic active sites, surface reaction intermediates, and reaction mechanisms of this imp...
220 citations
Patent•
22 Jul 1997TL;DR: In this article, the authors proposed a process for the production of light olefins from an oxygenate feedstock using a metal aluminophosphate catalyst, which can provide the advantage of extended catalyst life and greater catalyst stability in the oxygenate conversion zone.
Abstract: The present invention relates to a process for the production of light olefins comprising olefins having from 2 to 4 carbon atoms per molecule from an oxygenate feedstock. The process comprises passing the oxygenate feedstock to an oxygenate conversion zone containing a metal aluminophosphate catalyst to produce a light olefin stream. A propylene stream and/or mixed butylene is fractionated from said light olefin stream and cracked to enhance the yield of ethylene and propylene products. This combination of light olefin product and propylene and butylene cracking in a riser cracking zone or a separate cracking zone provides flexibility to the process which overcomes the equilibrium limitations of the aluminophosphate catalyst. In addition, the invention provides the advantage of extended catalyst life and greater catalyst stability in the oxygenate conversion zone.
114 citations
TL;DR: In this article, supported Wox/SiO2 catalysts were investigated for propylene metathesis as a function of tungsten oxide loading and temperature, and they were synthesized by incipient-wetness impregnation of an aqueous ammonium metatungstate solution onto the silica support and calcined at elevated temperatures.
Abstract: Supported WOx/SiO2 catalysts were investigated for propylene metathesis as a function of tungsten oxide loading and temperature. The catalysts were synthesized by incipient-wetness impregnation of an aqueous ammonium metatungstate solution onto the silica support and calcined at elevated temperatures to form the supported tungsten oxide phase. In situ Raman spectroscopy under dehydrated conditions revealed that below 8% WOx/SiO2, only surface WOx sites are present on the silica support: dioxo (O═)2WO2 and mono-oxo O═WO4. The in situ XANES analysis showed that dioxo surface WO4 sites were the dominant surface WOx sites on SiO2 (>90%). The isolated nature of the surface WOx sites was confirmed with in situ UV–vis spectroscopy. The surface WOx sites are activated by exposure to propylene at elevated temperature that removes oxygen from these sites. The activation process produces a highly active surface WOx site that can perform olefin metathesis at ∼150–250 °C. For 8% WOx/SiO2 and higher tungsten oxide load...
78 citations
TL;DR: In this paper, the authors investigated the wear properties of diamond-like nanocomposite (DLN, Dylyn®) coatings and found that they are amorphous, hard and wear resistant coatings, deposited using a plasma-assisted CVD process.
67 citations
References
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TL;DR: In this article, the results of photoelectric cross-sections for the Kα lines of magnesium at 1254 eV and of aluminum at 1487 eV were given for Z values up to 96.
4,891 citations
TL;DR: In this paper, the authors presented new calculations of electron inelastic mean free paths (IMFPs) for 200-2000 eV electrons in 27 elements (C, Mg, Al, Si, Ti, V, Cr, Fe, Ni, Cu, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Hf, Ta, W, Re, Os, Ir, Pt, Au and Bi).
Abstract: We present new calculations of electron inelastic mean free paths (IMFPs) for 200–2000 eV electrons in 27 elements (C, Mg, Al, Si, Ti, V, Cr, Fe, Ni, Cu, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Hf, Ta, W, Re, Os, Ir, Pt, Au and Bi) and four compounds (LiF, SiO2, ZnS and Al2O3). These calculations are based on an algorithm due to Penn which makes use of experimental optical data (to represent the dependence of the inelastic scattering probability on energy loss) and the theoretical Lindhard dielectric function (to represent the dependence of the scattering probability on momentum transfer). Our calculated IMFPs were fitted to the Bethe equation for inelastic electron scattering in matter; the two parameters in the Bethe equation were then empirically related to several material constants. The resulting general IMFP formula is believed to be useful for predicting the IMFP dependence on electron energy for a given material and the material-dependence for a given energy. The new formula also appears to be a reasonable but more approximate guide to electron attenuation lengths.
829 citations
TL;DR: The model hydrodesulfurization catalysts studied in this article contained 1-30% MoO/sub 3/ on δ-gamma-alumina and were calcined at 400/sup 0/-700/sup 1 0/C for 1-32 hr and reduced at 500/sup 2 0 /C in hydrogen.
Abstract: The model hydrodesulfurization catalysts studied contained 1-30% MoO/sub 3/ on ..gamma..-alumina and were calcined at 400/sup 0/-700/sup 0/C for 1-32 hr and reduced at 500/sup 0/C in hydrogen. At low MoO/sub 3/ loadings (to approx. 8%), molybdenum in the tetrahedral lattice of alumina was the main species; at higher coverage of MoO/sub 3/, to monolayer coverage (approx. 20% MoO/sub 3/), molybdenum in the octahedral lattice of ..gamma..-alumina became more important; around monolayer concentration of MoO/sub 3/, Al/sub 2/(MoO/sub 4/)/sub 3/ started to form; and at higher molybdena concentration, bulk MoO/sub 3/ was also observed. An increase in calcination temperature and time favored formation of the tetrahedral lattice species and of Al/sub 2/(MoO/sub 4/)/sub 3/.
403 citations
TL;DR: In this article, laser Raman and Fourier transform infrared spectroscopies as well as X-ray diffraction were used to study the interactions of MoO3 with various metal oxide supports.
145 citations
TL;DR: In this paper, a combined Raman spectroscopy-X-ray absorption study showed a significantly altered structure of the molybdenum oxide phase after dehydration, the total Mo-Mo coordination number drops from 3.27 to 0.20 after anin situ thermal treatment at 673 K.
Abstract: In contrast to the frequently reported lack of interaction between hexavalent molybdenum and SiO2 and the tendency of silica-supported MoO3 to coalescence, it has been found that on dehydration small molybdenum oxide clusters spread over a silica support. A combined Raman spectroscopy-X-ray absorption study shows a significantly altered structure of the molybdenum oxide phase after dehydration. In EXAFS the total Mo-Mo coordination number drops from 3.27 to 0.20 after anin situ thermal treatment at 673 K. The increase of the peak in the XANES region (Is -→ 4d) indicates that the coordination sphere of the molybdenum atoms strongly alters after dehydration. The Raman spectra reflect the change of the structure through a shift of the position of the terminal Mo=O bond from 944 to 986 cm−1 and the disappearance of the bridged Mo-O-Mo vibration at 880 cm−1. It is concluded that dehydration produces almost isolated molybdenum sites in this highly dispersed sample. Water ligands stabilize the oligomeric clusters under ambient conditions; the removal of water causes spreading of these clusters.
116 citations