Condensation Of Acetylene Research Articles

Effectiveness of dimethylethynylcarbinol and methyl tert-butyl ether on octane number increase of gasoline compositions

Despite the significant increase in requirements to the quality of motor fuel, harmful exhaust gases from gasoline combustion are still a major environmental problem. Today gasoline occupies one of the leading positions among primary energy sources. The problem of improving the quality of gasoline is one of the urgent problems of the chemical industry. In order to reduce harmful exhaust emissions from internal combustion engines, improve the detonation resistance of fuels and utilize renewable fuels, many different oxygen-containing additives are added to base gasoline. The research and development of new oxygen-containing additives for gasoline based on tertiary acetylene alcohols is an important and urgent task. The influence of dimethylethynylcarbinol (DMEC) and methyl tert-butyl ether (MTBE) on the increase of octane number of gasoline compositions was evaluated by the increase of octane number of straight-run gasoline and reforming gasoline blends in the ratios of 30:70 and 20:80. Aliphatic acetylene alcohol DMEС was obtained by condensation of acetone and acetylene under Favorsky reaction conditions. The physicochemical properties of the synthesized DMEС correspond to the literature data. Straight-run gasoline and reforming gasoline produced by “Atyrau Oil Refinery” LLP were used for the study. Determination of octane number of gasoline compositions containing the proposed additives was carried out by express method on the gasoline detonation resistance meter on the octanometer SHATOX SX-100K. It was determined that DMEС is an effective oxygenate additive for increasing the octane number of gasoline compositions compared to MTBE. The research of influence of oxygenates as MTBE and DMEС on increase of octane number of gasoline compositions consisting of straight-run gasoline and reforming gasoline in different ratios showed that increase of octane number at addition of DMEС is higher than at addition of MTBE. According to the results of research, tertiary acetylene alcohol - DMEС can be proposed as an oxygencontaining additive to motor gasoline.

Detailed kinetic modeling of acetylene decomposition/soot formation during quenching of coal pyrolysis in thermal plasma

A detailed chemical kinetic mechanism based on the Appel-Bockhorn-Frenklach (ABF) model was established to describe acetylene decomposition, ethylene formation, and soot formation during quenching in coal pyrolysis to acetylene process. The predictions agreed well with the reported acetylene pyrolysis experimental data. Numerical simulations were then performed to deeply understand the reaction behaviors during quenching of coal pyrolysis in thermal plasma, and to optimize the quenching design for better heat recovery. Two key operating parameters of quenching, i.e., the temperature after quenching and the quenching rate, were studied in detail and optimized after the kinetics were validated. The simulation results also proved that hydrogen can promote the formation of ethylene and inhibit the condensation of acetylene during quenching. In particular, in-depth discussion of acetylene decomposition and ethylene formation using this detailed kinetic mechanism combined with thermodynamic method provided a comprehensive understanding of the thermodynamics and kinetics interpreting pilot plant experimental data.

Soot predictions in premixed and non-premixed laminar flames using a sectional approach for PAHs and soot

A new soot model is presented, which has been developed for CFD applications, combining accuracy and efficiency. While the chemical reactions of small gas phase species are captured by a detailed chemical kinetic mechanism, polycyclic aromatic hydrocarbons (PAHs) and soot particles are represented by sectional approaches. The latter account for important mechanisms such as the formation of sections, their oxidation, the condensation of acetylene, and the collisions between sections. The model has been designed to predict soot for a variety of fuels with good accuracy at relatively low computational cost. Universal model parameters are applied, which require no tuning in dependence of test case or fuel. Soot predictions of ethylene, propylene, kerosene surrogate, and toluene flames are presented, which show good agreement with the experimental data. Furthermore, the importance of the correct choice for thermodynamic data of PAHs and soot is highlighted and the impact of heat radiation is discussed.

Synthesis of Polysubstituted Pyrroles by Condensation of Acetylenes and Amines

Synthesis of Polysubstituted Pyrroles by Condensation of Acetylenes and Amines

Controlled Synthesis of Dinuclear Acetylide-Bridged Ruthenium Complexes

A series of dinuclear and trinuclear, acetylide-bridged ruthenium(II) complexes was synthesized by the condensation of terminal acetylenes with methyl ruthenium complexes. Dinuclear ruthenium(II) complexes trans,trans-(RC≡C)Ru(dmpe)2(μ-C≡CC6H4C≡C)Ru(C≡CR′)(dmpe)2 (R = R′ = Ph; R = R′ = tBu; R = Ph, R′ = tBu; R = tBu, R′ = 3,5-tBu2-C6H3) were synthesized by the reaction of trans-(CH3)Ru(dmpe)2(C≡CR) with the unsymmetrical bis(acetylido)ruthenium(II) complex trans-(R′C≡C)Ru(dmpe)2(C≡CC6H4C≡CH) at ambient temperature and pressure. These complexes were fully characterized by NMR spectroscopy, and trans,trans-(tBuC≡C)Ru(dmpe)2(μ-C≡CC6H4C≡C)Ru(dmpe)2(C≡CtBu) was characterized crystallographically. The symmetrical trinuclear ruthenium(II) complexes trans,trans,trans-(RC≡C)Ru(dmpe)2(μ-C≡CC6H4C≡C)Ru(depe)2(μ-C≡CC6H4C≡C)-Ru(dmpe)2(C≡CR) (R = Ph, tBu, SiMe3) were also prepared and characterized, and the redox behavior of a subset of the complexes was studied using cyclic voltammetry.

Synthesis of Polysubstituted‐2‐naphthols.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis of polysubstituted-2-naphthols

Substituted 3-(triisopropylsilyl)-2-naphthols are prepared by an aluminum chloride catalyzed condensation of phenyl acetyl chloride derivatives and triisopropylsilyl acetylene. The yields obtained are in the range of 41% to 67%. The reaction is regiospecific and gives only the 3-(trialkylsilyl)-2-naphthol isomer.

Copper-catalyzed chlorination and condensation of acetylene and dichloroacetylene

The chlorination and condensation of acetylene at low temperatures is demonstrated using copper chlorides as chlorinated agents coated to model borosilicate surfaces. Experiments with and without both a chlorine source and borosilicate surfaces indicate the absence of gas-phase and gas-surface reactions. Chlorination and condensation occur only in the presence of the copper catalyst. C2 through C8 organic products were observed in the effluent; PCDD/F were only observed from extraction of the borosilicate surfaces. A global reaction model is proposed that is consistent with the observed product distributions. Similar experiments with dichloroacetylene indicate greater reactivity in the absence of the copper catalyst. Reaction is observed in the gas-phase and in the presence of borosilicate surfaces at low temperatures. The formation of hexachlorobenzene is only observed in the presence of a copper catalyst. PCDD/F were only observed from extraction of the borosilicate surfaces. A global reaction model is proposed for the formation of hexachlorobenzene from dichloroacetylene.

Highly regioselective palladium-catalyzed condensation of terminal acetylenes with 2,5-diiodobenzoic acid

Abstract Palladium-catalyzed coupling reactions between terminal alkynes and 2,5-diiodobenzoic acid have been shown to be highly regioselective, giving a rapid and efficient route for the synthesis of disymmetric 2,5-bis ethynyl benzoic acid derivatives.

Pyrolysis and molecular growth of chlorinated hydrocarbons

Abstract The high-temperature pyrolysis of chlorinated hydrocarbons is reviewed with a primary focus on the authors’ research on the gas-phase molecular growth chemistry and elementary reaction mechanisms leading to the formation of chlorinated benzenes and chlorinated polycyclic aromatic hydrocarbons. The authors’ recent heterogeneous mechanistic studies of the chlorination and condensation of acetylene at lower temperatures are also summarized. A pathway diagram suggesting a link between these heterogeneous reactions and the formation of polychlorinated dibenzo- p -dioxins and furans under post-combustion conditions is presented and discussed.

Influence of triphenylphosphine complexes on condensation of acetylenes with aryl halides

Efficient organic luminophores displaying a blue luminescence were obtained by the interaction of 4-iodonaphthalic anhydrides or the corresponding naphthalimides with phenylacetylene in the presence of triethylamine and using bis(triphenyl phosphine)palladium dichloride copper iodide systems as catalysts.

Interaction of acetylene molecules with the MgO(100) surface: LEED experiments and potential-energy calculations

Abstract Structural and thermodynamical low-energy electron diffraction experiments were performed on MgO(100) single crystals cleaved indashsitu under ultra-high vacuum conditions. Acetylene adsorption experiments were conducted within the temperature range 40–94 K and the C 2 H 2 pressure range 10 −9 –10 −6 Torr. We have determined experimentally a commensurate (2 × 2) herringbone structure containing two molecules and having two glide planes. Bulk condensation of acetylene has been studied and the latent heat of sublimation ΔH sub = 5.08 ± 0.3 kcal mol −1 determined. The isosteric heat of adsorption Q st = 6.9 ± 0.4 kcal mol −1 and lateral interaction energy Q ∥ = 3.1 ± 0.4 kcal mol −1 have been measured and compared with semi-empirical potential calculations which detail the nature of the various contributions to these physical quantities. The stable adsorption sites are the Mg atoms, and the calculated geometry is in good agreement with our LEED observations. Moreover, the influence of the molecular motions on the isosteric heat of adsorption is evaluated to take temperature effects into account.

ChemInform Abstract: Heterogeneously‐Catalyzed Synthesis of Six‐Membered N‐Heterocycles and Acetonitrile by Condensation of Acetylacetone, Acetylene and Ammonia.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

A ruthenium-catalyzed reconstitutive condensation of acetylenes and allyl alcohols

A ruthenium-catalyzed reconstitutive condensation of acetylenes and allyl alcohols

Synthesis of 9,10-diacetylenylanthracenes

Syntheses are reported for 9,10-bis(phenylethynyl)anthracene and its derivatives containing identical and different substituants in the phenyl groups by the acetylenic condensation of 9,10-dibromoanthracene. The introduction of a donor substituent into one phenyl group and a withdrawing substituent into the other leads to a significant shift of the fluorescence maximum toward longer wavelengths.

Nature of the stratospheric haze on Uranus: Evidence for condensed hydrocarbons

We have used a number of models to analyze Voyager images of Uranus obtained at several high phase angles to derive physical and chemical properties of particulate matter present in the planet's lower stratosphere. These models include a multiple‐scattering algorithm for plane parallel atmospheres, a spherical atmosphere code for performing limb inversions, a microphysical model of aerosol formation, growth, and sedimentation, and a photochemical model of methane photolysis. We obtain definitive evidence for the presence of aerosols at pressure levels ranging from a few millibars to about 100 mbar. There are two possible sets of particle properties that can fit radiances observed close to but somewhat interior to the limb at several phase angles in four visible wavelength bands. The low‐density solution is characterized by particles having a modal radius and number density equal to 0.13 ± 0.02 µm and 2 ± 1 particles/cm³, respectively, at a pressure level of 44 mbar. The alternative, high‐density solution is characterized by particles having a modal radius that is 0.6–0.7 times that of the low‐density solution at the reference level and a density that is 2 orders of magnitude larger. Since the high‐density solution implies a mass production rate for the stratospheric aerosols that is much larger than those that can plausibly be supplied by photochemically produced gases that condense, whereas the low‐density solution does not, we favor the low‐density solution. Inversion of narrow‐angle, high‐resolution images of the limb provides a definition of a variable that provides a measure of the amount of aerosol scattering at high phase angles. The vertical profile of this variable shows a decrease of several orders of magnitude from pressure levels of tens to a few millibars. This decrease is due chiefly to the particle size of the aerosols becoming small compared to a wavelength. Above the base of the stratosphere the aerosol optical depth is approximately 0.01 in the mid‐visible. A major source for the stratospheric aerosols is the condensation of ethane, acetylene, and diacetylene gas species at pressure levels of approximately 14, 2.5, and 0.1 mbar, respectively. These gases are produced at much higher altitudes by solar UV photolysis of methane and diffuse to the lower stratosphere, where they condense. In addition, diacetylene is also produced photochemically within its condensation region. Condensation of locally produced diacetylene may represent a significant fraction of the total hydrocarbon condensation. Such a local source of condensation may be required by the inversions to the limb profiles, which indicate that at least half of the ice condensation occurs at altitudes above the 5‐mbar level. The hypothesis that the stratospheric particles are made of hydrocarbon ices is supported by the approximate agreement between the total ice condensation rate predicted by the methane photochemical model and the aerosol mass production rate derived for the low‐density solution of the Voyager data. The aerosol mass production rate derived from the Voyager data is equal to 2–15 × 10−17 g/cm²/s. Additional but weaker support for this hypothesis is provided by the Voyager radio occultation temperature profiles. It is suggested that solar UV radiation promotes solid state chemistry within the lower order hydrocarbon ices, resulting in the production of polymers capable of absorbing at visible wavelengths. Thus this altered material could play a key role in the planet's heat budget. Ethane, acetylene, and diacetylene ices evaporate at approximately the 600‐, 900‐, and 3000‐mbar levels of the upper troposphere. The polymeric material is expected to evaporate at pressures in excess of the evaporation level for diacetylene.

Synthesis of ethynylanthraquinones

1. A method has been developed for synthesis of ethynylanthraquinones by condenstion of the corresponding iodo derivatives with 2-methyl-3-butyn-2-ol and base cleavage of the resulting anthraquinoylacetylenic alcohols. 2. Acetylenic condensation of iodo derivatives has been carried out for the first time in aqueous-organic media with a Pd-Cu catalyst and Na2CO3 leading to a considerable acceleration of the reaction.

Synthesis of acetylenic ketones from straight-chain acid chlorides

A method for the catalytic condensation of acetylenes with the acid chlorides of unbranched aliphatic acids was found.

Photolysis of methane and the ionosphere of Uranus

Photochemical calculations for Uranus predict an extensive region of condensation of acetylene, ethane and methane in the vicinity of the temperature inversion layer. This could explain why ethane was not detected on Uranus, unlike Neptune which has a much warmer inversion layer. Subsequent snow-out of the condensibles is expected to result in reduced visibility in the troposphere. Ionospheric calculations for the equatorial region to be probed by Voyager, indicate peak electron concentrations on the order of 5×10 3 cm −3 , if dynamical effects are important. Upper limit to the electron peak is 3×10 4 cm −3 . Exospheric temperatures as high as 200–250K are conceivable.

ChemInform Abstract: SYNTHESIS OF ACETYLENYL‐N‐METHYLPYRROLES

AbstractDie Trimethyl‐carbethoxy‐pyrrolyliodide (I) setzen sich mit den monosubstituierten Acetylenen (II) zu den Acetylenylpyrrolen (IV) um.