Search results for "Hydrogenation"
showing 10 items of 155 documents
Density Functional Theory Study on Propane and Propene Adsorption on Pt(111) and PtSn Alloy Surfaces
2011
Density functional theory calculations were performed to investigate the adsorption of propane, propene, and C and H atoms on Pt and PtSn surfaces employing the revised Perdew–Burke–Ernzerhof (RPBE) and vdW-DF functionals. Propane adsorption was found to be mediated by van der Waals interactions without significant site preference on any of the studied surfaces. The adsorption characteristics of propene are different: On the Pt(111) and Pt3Sn(111) surfaces, propene adsorption is covalent, and the molecule prefers a di-σ site to a π site. Alloying Pt(111) with Sn leads to weaker adsorption owing to geometric and relaxation effects, whereas electronic effects are found to be small. On the PtS…
Oxidative dehydrogenation of propane and n-butane on V-Mg based catalysts
1994
Abstract The catalytic properties of vanadium supported catalysts for the oxidative dehydrogenation of propane and n-butane has been studied. Natural Sepiolite and magnesium oxalate were used as starting support materials. Large differences in the type of crystalline phases were detected on the calcined catalysts depending on the vanadium content and nature of the support. The active and selective sites for the oxidative dehydrogenation of propane and n-butane, are related with isolated V 5+ with atetrahedral coordination. The presence of vanadium species with coordination higher than 4 negatively influence the selectivity to dehydrogenation products.
Oxidative dehydrogenation of isobutane over Co-MCM-41 catalysts
2004
Abstract Cobalt-containing mesoporous silicates with MCM-41-like structure, with Si/Co≥49, are active and selective catalysts for the oxidative dehydrogenation (ODH) of isobutane. The formation of dehydrogenation products is analysed in terms of the nature of the cobalt species, tetrahedral Co(II), and heterogeneously initiated gas-phase reactions inside the mesopores.
Synthesis of non-k-region -quinones of polycyclic aromatic hydrocarbons from cyclic ketones
1982
Abstract Non-K-region o -quinones of polycyclic aromatic hydrocarbons are prepared in four steps from cyclic ketones via dehydrogenation of tetrahydrodiols with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone.
The role of metal oxides as promoters of V2O5/γ-Al2O3 catalysts in the oxidative dehydrogenation of propane
1997
Summary The physicochemical properties of potassium-, bismuth-, phosphorous- and molybdenum-doped (Me/V atomic ratios of 0 to 1) V 2 O 5 /γ-Al 2 O 3 catalysts and their catalytic behavior in the oxidative dehydrogenation of propane have been compared. The incorporation of metal oxides modifies the catalytic behavior of alumina-supported vanadia catalysts by changing both their redox and their acid-base properties. In this way, the addition of potassium leads to the best increase in the selectivity to propylene. This performance can be related to the modification of the acid character of the surface of the catalysts. The possible role of both redox and acid-base properties of catalysts on th…
Selective homogeneous hydrogenation of cycloocta-1,5, and cycloocta-1,3-diene to cyclooctene in the presence of (η4-cycloocta-1,5-diene)(η6-cycloocta…
1983
Cyclooctadiene isomers (1,3- and 1,5-COD) are selectively, homogenously hydrogenated to cyclooctene (C8H14) in tetrahydrofuran (THF) solution, under mild conditions of temperature (20 °C) and hydrogen pressure (1 atm), in the presence of catalytic amounts of (cycloocta-1,5-diene)(cycloocta-1,3,5,-triene)ruthenium(0), [Ru(η4-COD)(η6-C8H10)] (1). The rate of hydrogenation is higher when 1,3-COD is the substrate. Evidence for the isomerization 1,5-COD → 1,3-COD is reported. Similar studies carried out in several alcoholic solutions, although showing a decreased selectivity in the hydrogenation, confirm the isomerization 1,5-COD → 1,3-COD, and allow a discrimination between the isomerization an…
Transition Metal Compound Oxide Catalysts for Lowering the Light Off-Temperature of Particles from Diesel Exhaust
1993
Publisher Summary It has been realized that particle emissions from diesel engines are a severe environmental problem, which is difficult to solve by engine modifications alone. Even if the combustion occurs in a high excess of air, appreciable amounts of soot particles are found. Cracking processes, dehydrogenation, and polymerization play an important role in the formation of soot. To reduce soot fraction, several methods have been developed in the past, but most of them have fundamental disadvantages. Thus, a new procedure based on the catalytic burning of the soot in the exhaust gas is becoming important. This chapter describes the effect of several compound oxides. Further investigatio…
Cycloaddition reactions of 2-vinylthiophen
1985
Abstract Cycloaddition reactions between 2-vinylthiophen and the dienophiles maleic anhydride, dimethyl acetylenedicarboxylate,' methyl propiolate, and methyl acrylate, are reported. Products include simple benzo[b]thiophen carboxylates (6, 13, 17) and reduced derivatives (3, 4, 18). The acetylenic dienophiles also gave a dihydrobenzthienyl-acrylate (16) or -fumarate (11), and the dithienylcyclohexene esters (7) and (14).
ChemInform Abstract: Diels-Alder Reactions of Methyl- and π-Acceptor-Substituted 2- Vinylindoles with Dimethyl Acetylenedicarboxylate and Tetracyanoe…
2010
The Diels-Alder reactions of the 2-vinylindoles 1a-1d, which are now readily accessible, with dimethyl acetylenedicarboxylate and tetracyanoethylene give rise to the novel 1,2-dihydro- and 1,2,3,4-tetrahydrocarbazoles 2, 4, and 5 as well as the fully aromatized carbazoles 3. With regard to the product spectrum, the mechanistic rationale comprises a Diels-Alder step, formal 1,3-hydrogen shift, ene reaction, and dehydrogenation. Conformational aspects of the 1,2-dihydrocarbazoles 2b and 2c are also discussed.
Diels-alder reactions of methyl- and π-acceptor-substituted 2-vinylindoles with dimethyl acetylenedicarboxylate and tetracyanoethylene: Novel functio…
1991
The Diels-Alder reactions of the 2-vinylindoles 1a-1d, which are now readily accessible, with dimethyl acetylenedicarboxylate and tetracyanoethylene give rise to the novel 1,2-dihydro- and 1,2,3,4-tetrahydrocarbazoles 2, 4, and 5 as well as the fully aromatized carbazoles 3. With regard to the product spectrum, the mechanistic rationale comprises a Diels-Alder step, formal 1,3-hydrogen shift, ene reaction, and dehydrogenation. Conformational aspects of the 1,2-dihydrocarbazoles 2b and 2c are also discussed.