Pyrolysis of propane in the presence of propylene

Pyrolysis of propane in the presence of propylene and propylene labeled with C-14 has been studied in the temperature range of 833–1019 K. The strong inhibition effect of propylene on the thermal decomposition of propane has been confirmed.     

Pyrolysis of propane in the presence of ethylene

Pyrolysis of propane in the presence of ethylene and ethylene labeled with¹⁴C has been studied in the temperature range 773–1019 K. The disappearance of the inhibiting effect of ethylene on the thermal decomposition of propane with increasing temperature was observed.

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¹⁴C 773–1019 . .

     

Pyrolysis of propane in the presence of hydrogen

The pyrolysis of propane in the presence of hydrogen, deuterium and argon was studied in the temperature range 890–1019 K. The acceleration of the reaction in the presence of hydrogen has been observed.

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, 890–1019 . .

     

Pyrolysis of propane in the presence of14C2H4 studied by the kinetic isotope method

The kinetic isotope method was used to explain the role of ethylene in the pyrolysis of propane. The mechanism of the radioactivity appearance in methane and propylene is proposed.     

Pyrolysis of acetylene behind reflected shock waves

The thermal decomposition of acetylene has been studied in the temperature and pressure regimes of 1900–2500 K and 0.3–0.55 atm using a shock tube coupled to a time-of-flight mass spectrometer. A series of mixtures varying from 1.0–6.2% C₂H₂ diluted in a Ne-Ar mixture yielded a carbon atom density range of 0.24–2.0 × 10¹⁷ atoms cm^?3 in the reflected shock zone. Concentration profiles for C₂H₂, C₄H₂, and C₆H₂ were constructed during typical observation times of 750 μs. C₈H₂ and trace amounts of C₄H₃ were found in relatively low concentrations at the high-temperature end of this study. A mechanism for acetylene pyrolysis is proposed, which successfully models this work and the results obtained by several other groups employing a variety of analytical techniques. Two values of the heat of formation for C₂H(134 ± 2 and 127 ± 1 kcal/mol) were employed in the modeling process; superior fits to the data were attained using the latter value. The initial step of acetylene decomposition involves competition between two channels. In mixtures (<200 ppm) where the acetylene concentrations are less than 2.18 × 10^?9 mol cm^?3, the decay is predominantly first order with respect to C₂H₂; in mixtures >200 ppm, the dominant initial step is second order. The rate constant for the second-order reaction is described by the equation Benzene concentrations predicted by the model are below the TOF detectability limit. C₄H₃ was observed in the 6.2% C₂H₂ mixture in accordance with the proposed mechanism.     

Pyrolysis of trichlorosilane in the presence of chloroform

The pyrolysis of trichlorosilane in the presence of different amounts of chloroform and the copyrolysis of HSiCl₃ with buta-1,3-diene in the presence of 1 mol.% chloroform were studied. The enthalpies of formation of products resulting from the pyrolysis of HSiCl₃ in the presence of chloroform were calculated by the quantum chemical method. Based on the thermochemical data as well as data from GLC and mass spectrometry, it was concluded from the condensate composition that introduction of chloroform into the zone of pyrolysis of HSiCl₃ favors generation of silylenes.     

Mechanism and kinetics of the silane decomposition in the presence of acetylene and in the presence of olefins

Kinetic data and product studies are reported for the silane pyrolysis in the presence of olefins and acetylene. The kinetics of silane loss in the presence of acetylene was found to be identical to the initial gas phase silane decomposition step (SiH₄ + M → SiH₂ + H₂ + M) when corrected for pressure fall-off effects. This result and the absence of methane or ethane from the pyrolysis of SiH₄ in the presence of 1-butene or 1-pentene demonstrate that silyl radicals and H atoms are not involved in silane-olefin or silane-acetylene reactions. Qualitative aspects and kinetic data from the SiH₄ pyrolysis in the presence of propylene are in accord with propylsilane formation via propylsilylene formed by silylene addition to propylene.     

Dehydrogenation of propane in the presence of carbon dioxide over oxide-based catalysts

In the present study, we show the advantages of CO₂ use for the dehydrogenation of propane to propene on the basis of thermodynamic considerations and some experimental results. Several metal oxides Ga₂O₃, Cr₂O₃, Fe₂O₃ unsupported and supported on g- Al₂O₃ and SiO₂ were tested. Ga₂O₃ catalyst was found to be an effective agent for dehydrogenation of propane to propene. The yield of propene at 873 K was 30.1 %. This revised version was published online in June 2006 with corrections to the Cover Date.     

Oxidative polydehydrocondensation of p-diethynylbenzene and acetylene in the presence of p-substituted phenylacetylenes

Conclusions Oxidative polydehydrocondensation of diethynylbenzene and acetylene in the presence of p-iodo, p-bromo-,p-methoxy-, p-nitro, p-tert-butylphenylacetylene, and -naphthylacetylene, produced oligomers with functional groups.Translated from Izvestiya Akademii Nauk SSSR, Seria Khimicheskaya, No. 10, p. 1908, October, 1964     

Gas hydrate phase equilibria for propane in the presence of additive components

A proper discussion on the possibility and feasibility of technological applications for gas hydrates requires knowledge of the phase behaviour and its relation to the gas hydrate structure and its occupation. This paper presents experimental data on gas hydrate phase equilibria for the system water+propane and for various systems of the kind water+propane+additive. The additives considered are tetrahydropyran, cyclobutanone and cyclohexane, which are assumed to occupy the large cavity of structure II (sII) hydrate, and methylcyclohexane that is a typical structure H (sH) hydrate former. All additives have in common that they are very poorly soluble in water and, therefore, an additional liquid phase is present in these systems. The pressure for the equilibrium hydrate–liquid water–vapour (H–L_w–V) in the system water+propane is reduced upon addition of each of these components. Simultaneously, the hydrate equilibrium hydrate–liquid water–liquid propane (H–L_w–L_C3H8) is shifted to lower temperatures. These observations can be explained in terms of mutual miscibility of propane and the additive component. However, it cannot be excluded that propane molecules are exchanged by additive molecules in occupying the large cavity of sII.     

Thermal reactions of dialkyl disulfides with acetylene in the presence of methanol

Gas-phase reaction of diethyl disulfide or disulfide oil with acetylene performed in the presence of methanol provides an essentially more selective thiophene formation. The yield of thiophene increases by 20–30%, and the yield of by-products decreases by half.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 8, 2004, pp. 1318–1320.Original Russian Text Copyright © 2004 by Deryagina, Sukhomazova, Levanova, Korchevin, Russavskaya.This revised version was published online in April 2005 with a corrected cover date.     

Copolymerization of acetylene with ethylene in the presence of dibenzenetitanium(0)

The interaction between acetylene and dibenzenetitanium(0) at a room temperature results in the acetylene polymerization and its reduction to ethylene, ethane, and methane at the expense of H atoms of the acetylene molecule. The catalytically active species capable of copolymerizing acetylene with ethylene that are formed during the reaction or are added into the system originate from the interaction of dibenzenetitanium(0) with acetylene.     

Acylation of acetylene compounds in the presence of divalent copper salts and chelates

Conclusions Salts and chelates of bivalent copper effectively catalyze the formation of acetylenic ketones from terminal acetylene compounds and carboxylic acid chlorides in the presence of tertiary amines.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 855–858, April, 1986.The authors express gratitude to V. L. Varand for elemental analysis of the chelates.     

Reaction space organization effect on propane pyrolysis in the presence of a nickel-copper catalyst

Propane pyrolysis at atmospheric pressures and temperatures of 500–700°C in the presence of a bimetallic catalyst containing 50 wt % Ni, 40 wt % Cu, and a silicon dioxide textural promoter has been investigated. It has been established experimentally that the reactor geometry and the way the reactants are let in and out exert an effect on the catalytic pyrolysis. The overall process rate is mainly determined by the heterogeneous reaction occurring on the catalyst surface. The homogeneous constituent of the process has an effect on the propane conversion at the early stages of the reaction.     

Liquid-phase hydrogenation of acetylene on the Pd/sibunit catalyst in the presence of carbon monoxide

The liquid-phase catalytic hydrogenation of acetylene into ethylene in the presence of CO over palladium supported on the graphite-like material Sibunit has been investigated. Carbon monoxide is an effective modifier of the selective hydrogenation process, exerting its effect by competing with acetylene and ethylene for chemisorption sites on the palladium surface. Under the optimum conditions (T = 90°C; N-methylpyrrolidone solvent; feed consisting of 2 vol % C₂H₂, 90 vol % H₂, and He balance), the introduction of 2 vol % CO ensures a high ethylene selectivity of 89.6 ± 1.5% at an acetylene conversion of 95.8 ± 1.3%, with the acetylene converted into hydrooligomers taken into account.     

Electrochemical behaviors of adrenaline at acetylene black electrode in the presence of sodium dodecyl sulfate

The electrochemical behaviors of adrenaline at the acetylene black electrode in the presence of sodium dodecyl sulfate (SDS) were investigated by cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The results indicated that the electrochemical responses of adrenaline were apparently improved by SDS, due to the enhanced accumulation of protonated adrenaline via electrostatic interaction with negatively charged SDS at the hydrophobic electrode surface. This was verified by the influences of different kinds of surfactants on the electrochemical signals of adrenaline. The electrochemical parameters of the adrenaline oxidation were explored by chronocoulometry. Under optimal working conditions, the oxidation peak current at 0.57 V was proportional to adrenaline concentration in the range of 5.0x10(-8) to 7.0x10(-6) mol/L, with a low detection limit of 1.0x10(-8)mol/L for 70s accumulation by differential pulse voltammetry (DPV). This method was applied to determine adrenaline in the hydrochloride injection sample. The results are satisfying compared with that by the standardized method of high performance liquid chromatography (HPLC).     

Role of silica-alumina catalyst texture in the reaction of propane oxidative dehydrogenation in the presence of sulfur dioxide

The effects of preparation conditions, component ratio, and pretreatment temperature (1000–1550‡C) of silica-alumina samples on their phase composition, texture characteristics, and catalytic properties are studied in the reaction of the oxidative dehydrogenation of propane by sulfur dioxide. It is shown that the samples contain individual silicon and aluminum oxides. The product of their interaction (mullite) is formed only at 1550°C. Mesoporous and macroporous catalysts with monoand polydispersed pore distributions over sizes are obtained. It is found that the porous structure of the catalyst plays a key role in the process of the oxidative dehydrogenation of propane in the presence of sulfur dioxide at 600–700°C. The apparent rate of propylene formation increases with an increase in the pore volume with radii between 10 and 100 nm. Propane is transformed into propylene more selectively on the catalyst where the pores with radii of 10–100 nm dominate; narrower pores (< 10 nm) are favorable for the formation of coke and complete oxidation products.