Showing papers on "Dehydrogenation published in 1981"

A greatly improved procedure for ruthenium tetroxide catalyzed oxidations of organic compounds

Abstract: Addition of acetonitrile to the traditional CCl4/H2O solvent system for ruthenium tetraoxide catalyzed oxidations leads to a greatly improved system; some applications to olefins, alcohols, aromatic rings, and ethers are described. © 1981, American Chemical Society. All rights reserved.

Gas-phase reactions of iron(1+) with ketones and ethers

Abstract: A pulsed laser has been used in conjunction with an ion cyclotron resonance spectrometer to generate and study the gas-phase ion-molecule reactions of Fe/sup +/ with simple carbonyl compounds and ethers. Oxidative addition reactions are observed, producing alkyl acyl, and alkoxide intermediates which undergo intramolecular rearrangement by a ..beta..-hydride shift mechanism. Decarbonylation reactions are observed with only a few small ketones. The main reaction channel is dehydrogenation for unbranched ketones and reductive elimination of methane for those branched at the ..cap alpha.. carbon. Reactions of Fe/sup +/ with diisopropyl ketone, cyclohexanone, cyclopentanone, and tetrahydrofuran suggest the existence of intermediate and stable ..pi..-ally complexes resulting from sequential ..beta..-hydride shifts.

Dehydrogenation versus dehydration of aliphatic alcohols on metal oxides

Abstract: Dehydrogenation (—H2) of propan-2-ol and butan-2-ol to the corresponding ketones and/or their dehydration (—H2O) to alkenes have been compared over high purity powdered oxides of the fourth row transition metals. Activities of commercially available Al2O3, SiO2 and TiO2 catalyst supports were also determined. Quartz microcatalytic reactions with gas chromatographic analysis were used in both continuous-flow and pulsed-reactant model to study the dependence of sample activity to (—H2) and (—H2O) processes upon the state of oxidation–reduction of the surface, upon temperature and upon preadsorption of selective acidic or basic poisons. Sealed reactors with mass spectrometric analysis were also employed to monitor the growth of hydrogen product and its relationship to other products. Results are considered in the light of various two-electron and one-electron models for the selectivity and activity of metal oxide surfaces.

Tin-Antimony Oxide Catalysts

Abstract: Publisher Summary This chapter examines tin-antimony oxide catalyst which has been commercially developed for the oxidation of propylene to acrolein as well as for the ammoxidation of propylene to acrylonitrile and the oxidative dehydrogenation of butenes to 1,3-butadiene. The tin-antimony oxide catalyst is one that is most amenable to investigation by a wide range of spectroscopic and physical techniques. The properties of the system are very sensitive to composition, calcination temperature, and length of treatment. It is shown in the chapter that the coprecipitated catalyst is an initially homogenous and amorphous solid, which is slowly crystallized on heating. It seems that the range of compositions which give rise to the formation of solid solutions is small and only occurs when the materials are heated to high temperatures. The cationic species in the solid solution phase of antimony in tin oxide appear to be antimony and charge balance seems to be achieved by the delocalization of electrons into a conduction band.

Applications of the Vilsmeier reaction. 13. Vilsmeier approach to polycyclic aromatic hydrocarbons

Abstract: The Synthesis of three typical polycyclic hydrocarbons (PAH) has been described, wherein the Vilsmeier reaction plays a major role. Vilsmeier reaction of the tetraloll gives the dihydronaphthaldehyde 2 which on cyclodehydration gives the dihydroarene 3. Ita dehydrogenation affords 3-methoxybenz[a]anthracene (4). Vilsmeier reaction on the dimethoxydihydronaphthalene 5 gives the versatile dimethoxydihydronaphthaldehyde 6 which has been converted to the dimethoxybenzo[c]fluorene 7 by direct cyclodehydration and the fulvene 10 by cyclodehydration of allylic alcohol 8 derived from 6 followed by dehydrogenation. The saturated alcohol 12 corresponding to 8 undergoes cyclodehydration to give the dimethoxyhexahydrobenzo[c]phenanthrene (13). Some of the advantages of the Vilsmeier approach to PAH have been pointed out.

Ion-beam studies of the reactions of atomic cobalt ions with cycloalkanes in the gas phase. Formation and decomposition of chemically activated metallacycles

Abstract: An ion-beam apparatus is employed to study the reaction of singly charged cobalt positive ions with cyclopropane, cyclobutane, cyclopentane, and cyclohexane. In all cases, ring cleavage reactions are observed. These processes find analogy with the decompositions of solution-phase metallacycles by C-C bond cleavage. In all systems but cyclopropane, dehydrogenation of the cycloalkane is also observed. Multiple dehydrogenation occurs with cyclopentane (yielding Co(C/sub 5/H/sub 6/)/sup +/) and cyclohexae (yielding Co(Ct/sub 6/H/sub 8/)/sup +/ and Co(C/sub 6/H/sub 6/)/sup +/). The present results are contrasted with the reactions of Co/sup +/ with the isomeric alkenes.

Supported catalysts and process for their preparation

Abstract: A process for the preparation of a supported catalyst containing a catalytically active metal such as a noble metal is disclosed wherein the supported catalyst is prepared by initially contacting the inert support with a base and disposing an amount of base in the support corresponding to 0.01 to 50 gram equivalents of base per gram equivalent of catalytically active metal to be deposited thereon, drying the so-treated support to a residual moisture content of less than 10 percent of the maximum absorbency of the support and thereafter impregnating the same with a salt solution of a catalytically active metal, e.g., a salt of a catalytically active noble metal. The inert support is one having a BET surface area of less than 20 square meters per gram. The catalyst is useful in hydrogenation, dehydrogenation, hydrogenolysis, oxidation, polymerization, isomerization or cyclization reactions.

Isomerization, dehydrogenation and cracking of methylcyclohexane over HNaY zeolites

Abstract: On HNaY zeolites the fractions of acid sites which are active for cracking, isomerization and dehydrogenation of methylcyclohexane do not increase linearly with increasing degree of exchange. Isomerization and dehydrogenation seem to involve a similar activated complex, while cracking proceeds through a different one and requires stronger acid sites. Activation energies are independent of exchange degree.

Dehydrogenation of cyclohexane and chemisorption of H2 and O2 on supported Pt−Pb and Pt−Sn catalysts

Abstract: With increasing amounts of Pb or Sn the weak adsorption of hydrogen decreases, the adsorption of oxygen increases and the activity in the dehydrogenation of cyclohexane decreases. A correlation could be found between the amount of weakly adsorbed hydrogen and the dehydrogenation activity.

Process for conversion of propane or butane to gasoline

Abstract: A multi-step hydrocarbon conversion process for producing gasoline from propane or butane is disclosed. The feed hydrocarbon is passed into a dehydrogenation zone and the entire dehydrogenation zone effluent including hydrogen and light by-products is then passed into a catalytic condensation zone wherein the resulting olefins are converted into dimers and trimers. The condensation zone effluent stream is passed into a separation zone in which the dimers and trimers are concentrated into a product stream, with unconverted feed hydrocarbon and hydrogen being recycled to the dehydrogenation zone.

Catalyst and process for manufacturing a ketone by dehydrogenation of a secondary alcohol

Abstract: A secondary alcohol dissolved in a C12 to C20 paraffinic hydrocarbon substantially free of aromatics and of sulfur is dehydrogenated to the corresponding ketone at a temperature of 170°-230° C. in the presence of a catalyst of the Raney nickel type containing from 0.1 to 10% by weight of an additional metal consisting of copper, silver, gold, tin, lead, zinc, cadmium, indium or germanium, the ketone being preferably removed, as it is formed, from the reaction medium. A catalyst for use in the present process is provided.

Catalytic dehydrogenation process

Abstract: A process for the catalytic dehydrogenation of low molecular weight paraffinic hydrocarbons is disclosed. The process is particularly directed to the separation of hydrogen from the olefinic hydrocarbon products and unreacted paraffinic hydrocarbons.

The Cycloaddition of Nitrilimines with 1,2-Dibenzoylethylenes

Abstract: The cycloaddition of nitrilimines with 1,2-dibenzoylethylenes gave an unexpected 1,3-diaryl-4-benzoylpyrazole and benzoic acid, along with an expected cycloadduct, 1,3-diaryl-4,5-dibenzoyl-2-pyrazoline, and its dehydrogenated product, 1,3-diaryl-4,5-dibenzoylpyrazole. The elimination of the benzoyl group from the pyrazoline followed by dehydrogenation was shown to be the course of the unusual reaction.

Reaction of 4-methylpent-2-yne with dodecacarbonyltriruthenium. The structure of a novel alkyne dimerization dehydrogenation product

Abstract: Reaction of [Ru3(CO)12] with 4-methylpent-2-yne yields, as the major product, an open cluster [Ru3(CO)8(C12H18)], the result of an unusual type of dimerization and dehydrogenation of an internal alkyne. The crystal structure of [Ru3(CO)8(C12H18)] has been determined by X-ray methods. Crystals are triclinic, space group P, with Z= 2 in a unit cell of dimensions a= 9.719(8), b= 13.862(10), c= 9.039(8)A, α= 103.40(8), β= 103.60(7), and γ= 87.76(6)°. The structure has been solved from diffractometer data by Patterson and Fourier methods and refined by full-matrix least squares to R= 0.033 for 3 701 observed reflections. The complex consists of a bent arrangement of three Ru atoms (with Ru–Ru bonds of 2.661 and 2.645 A and Ru–Ru–Ru angle of 89.1°) co-ordinated by eight (six terminal and two bridging) carbonyls and by an organic ligand, derived from dimerization and dehydrogenation of 4-methylpent-2-yne. This organic ligand forms two σ bonds with the central Ru atom, giving rise to a metallocyclopentadiene ring in which the terminal Ru atoms are on opposite sides of this ring and are η interacting with its four carbon atoms.

Process for the preparation of bis(1-phenylethenyl) compounds

Abstract: A 1,1-diphenylethane and an aromatic compound such as benzene are reacted in the presence of a Friedel-Craft's catalyst to provide a compound having two 1,1-diaromatic substituted ethane groups, dehydrogenation provides a bis(1-phenylethenyl)aromatic compound.

Catalytic Properties of Zeolites Towards Oxidation Reactions

Abstract: We shall review experimental data on the catalytic properties of zeolites towards the oxidation and oxidative dehydrogenation of aliphatic, naphthene, and alkylaromatic hydrocarbons, and of inorganic or organic molecules containing hetero-atoms. The influence of the zeolite structure, of the nature and concentration of the exchangeable cations, and of the valency state of the transition metals on the activity and selectivity of the catalysts will be discussed, together with the effect of these factors on the course of the hydrocarbon oxidation reactions. Specific aspects of the interaction of molecular oxygen and of oxidisable compounds with various zeolites will be examined in the light of ESR, i.r. spectroscopy, and thermal desorption data. We shall show that variations in the structure and composition of the zeolite can lead to different types of reaction, yielding valuable products, and thus confirming the importance of zeolites among oxidation catalysts. 188 references.