Simulation of toluene decomposition in a pulse-periodic discharge operating in a mixture of molecular nitrogen and oxygen

The kinetic model of toluene decomposition in nonequilibrium low-temperature plasma generated by a pulse-periodic discharge operating in a mixture of nitrogen and oxygen is developed. The results of numerical simulation of plasma-chemical conversion of toluene are presented; the main processes responsible for C₆H₅CH₃ decomposition are identified; the contribution of each process to total removal of toluene is determined; and the intermediate and final products of C₆H₅CH₃ decomposition are identified. It was shown that toluene in pure nitrogen is mostly decomposed in its reactions with metastable N₂(A₃?? _u ⁺ ) and N₂(a??¹?? _u ^? ) molecules. In the presence of oxygen, in the N₂ : O₂ gas mixture, the largest contribution to C₆H₅CH₃ removal is made by the hydroxyl radical OH which is generated in this mixture exclusively due to plasma-chemical reactions between toluene and oxygen decomposition products. Numerical simulation showed the existence of an optimum oxygen concentration in the mixture, at which toluene removal is maximum at a fixed energy deposition.     

Polycrystal diamond growth in a microwave plasma torch

Diamond films of different structures were deposited on quartz, WC-Co, and molybdenum substrates in a microwave plasma torch discharge in an argon-hydrogen-methane gas mixture in a sealed chamber at pressures close to atmospheric by using the chemical vapor deposition technique. Images of diamond polycrystal films and separate crystals, as well as results of Raman spectroscopy, are presented. The spectra of optical plasma radiation recorded during film deposition demonstrate the presence of intense H_α hydrogen and C₂ radical bands known as Swan bands.     

Simulations of a longitudinal glow discharge in a hot air flow at atmospheric pressure

A one-dimensional axisymmetric time-dependent model of a discharge in a gas flow is developed. The model includes a fairly complete set of plasmochemical reactions and describes the heating and gasdynamic expansion of a plasma channel in air. The processes governing the distribution of nitrogen molecules in the N₂(C ³Π_u, v) state over vibrational levels are considered. The parameters of a longitudinal glow discharge in a hot (T ₀ = 1500?3000 K) air flow at atmospheric pressure are calculated. It is found that gas preheating considerably influences the parameters of the discharge channel. The results of calculations are compared with the experimental data.     

Protein modeling and molecular dynamics simulation of the two novel surfactant proteins SP-G and SP-H

The prospects of a control for a novel gallium nitride pseudo-halide vapor phase epitaxy (PHVPE) with HCN were thoroughly analyzed for hydrocarbons–NH₃–Ga gas phase on the basis of quantum chemical investigation with DFT (B3LYP, B3LYP with D3 empirical correction on dispersion interaction) and ab-initio (CASSCF, coupled clusters, and multireference configuration interaction including MRCI+Q) methods. The computational screening of reactions for different hydrocarbons (CH₄, C₂H₆, C₃H₈, C₂H₄, and C₂H₂) as readily available carbon precursors for HCN formation, potential chemical transport agents, and for controlled carbon doping of deposited GaN was carried out with the B3LYP method in conjunction with basis sets up to aug-cc-pVTZ. The gas phase intermediates for the reactions in the Ga-hydrocarbon systems were predicted at different theory levels. The located π-complexes Ga…C₂H₂ and Ga…C₂H₄ were studied to determine a probable catalytic activity in reactions with NH₃. A limited influence of the carbon-containing atmosphere was exhibited for the carbon doping of GaN crystal in the conventional GaN chemical vapor deposition (CVD) process with hydrocarbons injected in the gas phase. Our results provide a basis for experimental studies of GaN crystal growth with C₂H₄ and C₂H₂ as auxiliary carbon reagents for the Ga-NH₃ and Ga-C-NH₃ CVD systems and prerequisites for reactor design to enhance and control the PHVPE process through the HCN synthesis.     

Simulation of separation of C2H6 from CH4 using zeolitic imidazolate frameworks

Separation of important chemical feedstocks, such as C₂H₆ from natural gas, can greatly benefit the petrochemical industry. In this paper, the grand canonical Monte Carlo method has been used to study the adsorption and separation of CH₄ and C₂H₆ in zeolites, isoreticular metal-organic framework-1 (IRMOF-1) and zeolitic imidazolate frameworks (ZIFs) with different topology, including soadlite, gmelinite and RHO topologies. Compared with mordenite zeolite and IRMOF-1, ZIFs and mordenite framework inverted (MFI) zeolite have better separation performance for C₂H₆/CH₄ mixtures at different mole fractions of C₂H₆. From the study of equilibrium snapshots and density distribution profiles, adsorption sites could be grouped as (1) sites with strong interactions with adsorbent and (2) sites with strong interactions with surrounding adsorbates. The gas molecules occupied the first site and then went on to occupy the second site. In CH₄/C₂H₆ mixture adsorption/separation, the adsorption of CH₄ was confined by the existence of C₂H₆. Due to energetic effect, C₂H₆ selectivity was affected by temperature at a low-pressure range, but did not change as much in a high-pressure range because of packing effect in micropore. In binary adsorption, large C₂H₆ molecules favour sites with strong adsorbent interactions. At high pressures, packing effects played an important role and it became easy for small CH₄ molecules to access the sites with strong adsorbate interactions.     

Tertiary phosphine complexes of nickel(0) and nickel(I). New dinitrogen complexes of nickel(0)

The reduction of NiX₂(PCy₃)₂ (X = Cl, Br; PCy₃ = tricyclohexylphosphine) in toluene with sodium sand under argon affords [NiX(PCy₃)₂]₂ or Ni(PCy₃)₃. In the same way starting from NiX₂P₂ [X = Cl, Br; P = P(C₂H₅)₃, P(CH₂CH₂CH₂CH₃)₃, P(C₂H₅)₂ C₆H₅] the tetracoordinate Ni(0) complexes NiP₄ are obtained. These give NiP₃(N₂) under nitrogen. The electronic spectra of Ni(0) and Ni(I) complexes, both in the solid state and solution, are reported.     

N-substituted ethylcarbamate complexes of thorium(IV) and lanthanum(III) nitrates

N-substituted ethylcarbamates form with thorium nitrate the complexes Th(NO₃)₄·3RHNC(O)OC₂H₅ (where R = CH₃, C₂H₅, C₆H₅(CH₃)CH) and with lanthanum nitrate the complexes La(NO₃)₃· 2RR′NC(O)OC₂H₅·3H₂O (where R = CH₃, C₂H₅, C₆H₅(CH₃)CH; R′ = H and R = CH₃, C₆H₅; R′ = C₂H₅ or R = R′ = CH₃). In addition the anhydrous La(NO₃)₃·3(C₂H₅)₂NC(O)OC₂H₅ has been isolated. From the IR spectra it is deduced that the carbamates coordinate the metal through the carbonyl oxygen atom and that the nitrato groups act as chelated ligands. ¹H nmr spectral data of the complexes are reported and discussed.     

Synthesis of hydrocarbons under presumed prebiotic conditions using high-frequency discharge

Summary Various hydrocarbons were synthesized by high-frequency discharge in a primordial terrestrial model atmosphere. The products were extracted by benzene or methanol and analyzed by GC-MS. The mean carbon chain length of the hydrocarbons formed by the discharge through pure CH₄ gas was less than 6. Benzene was also obtained. Some isomers were obtained for each of the hydrocarbons containing a given number of carbons. When a small amount of C₂H₂ was added to the CH₄, longer chain compounds were formed, as compared with discharge in CH₄ only. However, when the amount of C₂H₂ was increased, unextractable high molecular weight compounds were produced. The amounts of products decreased as the mixing ratio of CO₂ to CH₄ increased. No hydrocarbons were detected when the ratio of CO₂/CH₄ exceeded 1.     

The Effect of Hydrophobicity of Ammonium Salts on Stability of Quasi‐2D Perovskite Materials in Moist Condition

With the potential of achieving high efficiency and low production costs, perovskite solar cells (PSCs) have attracted great attention. However, their unstableness under moist condition has retarded the commercial development. Recently, 2D perovskites have received a lot of attention due to their high moisture resistance. In this work, four quasi 2D quasi perovskites are prepared, then their stability under moist condition is investigated. The surface morphology, crystal structure, optical properties, and photovoltaic performance are measured. Among the four quasi‐2D perovskites, (C₆H₅CH₂NH₃)₂(FA)₈Pb₉I₂₈ has the best performance: uniform and dense film, extremely well‐oriented crystal structure, strong absorption, and a high power conversion efficiency (PCE) of 17.40%. The aging tests show that quasi‐2D perovskites are more stable under moist conditions than FAPbI₃ is. The (C₆H₅CH₂NH₃)₂(FA)₈Pb₉I₂₈ quasi‐2D perovskite devices exhibit high humidity stability, maintaining 80% of the starting PCE after 500 h under 80% relative humidity. Compared with other quasi‐2D perovskites, (C₆H₅CH₂NH₃)₂(FA)₈Pb₉I₂₈ has the highest humidity stability, due to their strongest hydrophobicity from C₆H₅CH₂NH₃⁺. This work demonstrates that the properties of perovskite materials can be modified by adding different ammonium salts into FAPbI₃. Thus, by introducing ammonium salts with high hydrophobic properties the fabrication of highly efficient and stable 2D PSCs may be possible.     

Simulation of ethylene conversion initiated by a streamer corona in an air flow

The conversion of ethylene (C₂H₄) at concentrations of 400 and 930 ppm in an air flow at a temperature of 295 K is simulated. Ethylene is added to air either upstream of the discharge chamber or in the reaction tube, downstream of a pulsed corona discharge. It is taken into account that the distribution of the gas components in the discharge zone is nonuniform due to the streamer nature of the discharge. In the reaction tube, all of the components are assumed to be uniform. Simulation results agree with the experiments carried out at voltage pulse amplitudes of 30 and 40 kV, a gas flow rate of 2–10 l/min, and a specific energy deposition of up to 0.15 J/cm³. It is shown that the ozone produced plays a governing role in the C₂H₄ conversion. It is found that it is possible to minimize the energy spent on conversion by choosing the optimum pulse repetition rate and the specific energy deposited per pulse. The presence of water vapor impedes the ethylene conversion and increases the concentration of formaldehyde and methane.     

Glow discharge in singlet oxygen

Currently, there is no experimental data on the plasma balance in gas mixtures with a high content of singlet delta oxygen O₂(¹Δ_g). These data can be obtained by studying the parameters of an electric discharge in singlet oxygen produced by a chemical generator. The O₂(¹Δ_g) molecules significantly change the kinetics of electrons and negative ions in plasma. Hence, the discharge conditions at low and high. O₂(¹Δ_g) concentrations are very different. Here, the parameters of the positive column of a glow discharge in a gas flow from a chemical singlet-oxygen generator are studied. It is experimentally shown that, at an O₂(¹Δ_g) concentration of 50% and at pressures of 1.5 and 2 torr, the electric field required to sustain the discharge is considerably lower than in the case when all of the oxygen molecules are in the ground state. A theoretical model of the glow discharge is proposed whose predictions are in good agreement with the experimental data.     

Far UV irradiation of model prebiotic atmospheres

UV light has been the most important energy source on the primitive Earth. However, very few experiments have been performed to test directly the possible role of this energy source on the chemical evolution of the primitive atmosphere, mainly on account of experimental difficulties. Experiments are generally performed with other excitations, mainly electric discharge, and it is frequently assumed that UV irradiation would give similar results.As theoretical considerations make this assumption questionable, direct experimental controls have been undertaken: Model primitive atmospheres have been submitted to 147 nm UV light and the gaseous phase has been analysed. Preliminary qualitative results concerning CH₄–NH₃ atmospheres are reported.Irradiation of pure CH₄ gives rise to the synthesis of a large number of hydrocarbons, mainly saturated hydrocarbons but including also unsaturated ones as, C₂H₂, C₂H₄, C₃H₆, C₃H₄. These insaturated hydrocarbons are synthetized at a very low rate when ammonia is present in the medium.Irradiations of CH₄–NH₃ mixtures give rise, in addition to hydrocarbons, to important amounts of HCN (about 0.1%) and to lesser amounts of CH₃CN and C₂H₅CN. No unsaturated nitriles such as acrylonitrile and cyanoacetylene have been detected. Search for amines is in progress.These results evidence that UV irradiation may contribute largely to synthesis of HCN in CH₄–NH₃ atmospheres and, consequently to the synthesis of many biochemical compounds that can be derivated from HCN. However, synthesis of other compounds, such as pyrimidines, which can derivate from other nitriles, such as cyanoacetylene, cannot be initiated only by UV light, contrary to electric discharges. In addition, if electric discharges are very efficient for synthesis of nitriles in CH₄–N₂ atmospheres, there is not yet evidence that UV light is able to do so.Presented at the 2nd ISSOL Meeting and the 5th ICOL in Kyoto, 5–10 April, 1977.     

Reactions of VCl3, VCl4 and TiX4 (XCl,Br) with benzofuroxan and its 5-methyl-, 5-chloro- and 5-methoxi-derivatives. I.

By means of the reaction between VCl₃ and benzofuroxan the compound VCl₃·2C₆H₄N₂O₂ was obtained, while in reaction with TiX₄ (XCl, Br) the compounds with stoichiometry TiX₄·C₆H₄N₂O₂ (X Cl, Br) were obtained.Furthermore, with some benzofuroxan derivatives (5-methyl, 5-chloro and 5-methoxi) the complexes MCl₄·2YC₆H₃N₂O₂ (MTi, V; YCH₃O, Cl, CH₃), TiCl₄·YC₆H₃N₂O₂ (YCH₃O, CH₃) and TiBr₄·YC₆H₃N₂O₂ (YCH₃O, Cl, CH₃) have been isolated.The compounds were characterized by elementary analysis, cryoscopic molecular weight determination in nitrobenzene, magnetic measurements and IR, Vis and EPR spectroscopy.     

Amidino-complexes of iron(II) and (III)

Lithioamidines {R′N(Li)C(R)NR′, I; R = CH₃, R′ = C₆H₅, p-CH₃,C₆H₄} react with iron(III) chloride

in monoglyme to produce navy-blue, high spin Fe{R′NC(R)NR′}₃ complexes which are extremely air and moisture sensitive. The corresponding reaction when R = R′ = C₆H₅ produces a soluble red complex and an air-stable green complex, whereas when R = H, R′ = C₆H₅ and R = R′ = C₆H₅ and the reaction is started at ca. ?20°, red and green complexes respectively are formed. Though all the complexes are formulated Fe{R′NC(R)NR′}₃, their properties reflect association through bridging amidino-groups. Iron(II) chloride reacts with I(R = CH₃, R′ = p-CH₃C₆H₄) to form two complexes, one crimson and soluble in organic solvents, and one brown and insoluble, which are fomulated [Fe{R′NC(R)NR′}₂]_n. The iron(III) complexes failed to react with, or were decomposed by, a variety of reducing, electrophilic and nucleophilic reagents, though blue Fe{p-CH₃C₆H₄NC(CH₃)N-p-CH₃C₆H₄}₃ reacts readily with nitric oxide to form a purple addition complex from which the N-nitroso-compound p-CH₃C₆H₄NC(CH₃)N(NO)-p-CH₃C₆H₄ was obtained in high yield. Treatment of the corresponding brown iron(II) complex with nitric oxide gave no reaction.     

Organic derivatives of aluminium. Part I. Reactions of alkanolamines with aluminium isopropoxide

Reactions of alkanolamines [R₁R₂NXOH; R₁ = H, CH₃, C₂H₅; R₂ = H, CH₃, C₂H₅ and X = -CH₂CH₂-, -CH₂CH₂CH₂-, -CH₂CHCH₃, -C₆H₄CH₂CH₂-] with aluminium isopropoxide in different molar ratios (1 to 3) yield compounds of the type Al(OPrⁱ)_3?n(OXNR₁R₂)_n, where ‘n’ can be 1, 2 and 3. Most of the derivatives are distillable liquids, soluble in common organic solvents and susceptible to hydrolysis even by atmospheric moisture. The new derivatives are characterized by elemental analysis, IR and ¹H NMR spectra. Molecular weight measurements of Al(OPrⁱ)_3?n(OXNR₁R₂)_n reveal them to be tetrameric in nature.     

Novel thermolytic products and their structures derived from thermolysis of isomerized products of spiro[4.4]nona-1,3-diene(dicarbonyl)[ethoxy(aryl)carbene]iron phosphine adducts [(η-C9H12)Fe{C(OC2H5)Ar}(CO)2PPh3]

Heating a benzene solution of the isomerized product of spiro[4.4]nona-1,3-diene(dicarbonyl)[ethoxy(aryl)carbene]iron phosphine adduct [(η³-C₉H₁₂)Fe{C(OC₂H₅)(C₆H₄CH₃-o)}(CO)₂PPh₃] (1) in a sealed quartz tube at 85-90 °C for 72 h gave the ring-opened η⁴ olefin-coordinated dicarbonyliron phosphine complex [Fe{η⁴-C₅H₇CHCHCH₂CHC(OC₂H₅)C₆H₄CH₃-o}(CO)₂PPh₃] (3) and cyclobutane derivative [C₂₄H₂₂O₇] (4). The thermal decomposition of analogous isomerized product [(η³-C₉H₁₂)Fe{C(OC₂H₅)(C₆H₄CH₃-p)}-(CO)₂PPh₃] (2) afforded the corresponding η⁴ olefin-coordinated dicarbonyliron phosphine complex [Fe{η⁴-C₅H₇CHCHCH₂CHC(OC₂H₅)C₆H₄CH₃-p}(CO)₂PPh₃] (6) and compound 4. The structures of products 3 and 4 have been established by X-ray diffraction studies.     

A theoretical study on the reaction mechanism of O<Subscript>2</Subscript> with C<Subscript>4</Subscript>H<Subscript>9</Subscript>• radical

Ab initio calculations have been performed using the complete basis set model (CBS-QB3) to study the reaction mechanism of butane radical (C₄H₉•) with oxygen (O₂). On the calculated potential energy surface, the addition of O₂ to C₄H₉• forms three intermediates barrierlessly, which can undergo subsequent isomerization or decomposition reaction leading to various products: HOO• + C₄H₈, C₂H₅• + CH₂CHOOH, OH• + C₃H₇CHO, OH• + cycle-C₄H₈O, CH₃• + CH₃CHCHOOH, CH₂OOH• + C₃H₆. Five pathways are supposed in this study. After taking into account the reaction barrier and enthalpy, the most possible reaction pathway is C₄H₉• + O₂ → IM1 → TS5 → IM3 → TS6 → IM4 → TS7 → OH• + cycle-C₄H₈O.     

Kinetics and mechanism of alkali-induced decomposition of 2-alkoxyethylcobaloximes

Kinetics of the base-induced decomposition of five 2-alkoxyethyl(aquo)cobaloximes, ROCH₂CH₂- Co(D₂H₂)OH₂ (R = C₆H₅, CF₃CH₂, CH₃, CH₃CH₂, (CH₃)₂CH), have been studied manometrically in aqueous base, ionic strength 1.0 M (KC1) at 25.0± 0.1 °C under an argon atmosphere. For the complexes with good leaving group alkoxide substituents (R = C₆H₅ and CF₃CH₂) the reactions are first- order in cobaloxime and first-order in hydroxide ion and produce stoichiometric amounts of ethylene and leaving group alcohol (ROH). NMR observation of decomposing solutions and workup of cobalt chelate products show that the reaction is initiated by hydroxide ion attack on an equatorial quaternary carbon leading to formation of an altered cobal- oxime product in which one of the Schiff's base linkages has become hydrated. For the remainer of the complexes the yield of ethylene is less than stoichiometric and pH-dependent, and the ethylene evolving reaction is second-order in hydroxide ion activity. The yield-limiting side reaction is shown to be base-catalyzed formation of a base-stable but photolabile alkoxyethylcobaloxime analog in which a Schiff's base linkage of the chelate has become hydrated, β-Elimination to form alkyl vinyl ethers was not observed for any of the alkoxyethylcobal- oximes. The second-order dependence of ethylene formation on hydroxide ion activity for R = CH₃, CH₂CH₃, and CH(CH₃)₂ is discussed at some length, but is not well understood at present.     

The spark discharge synthesis of amino acids from various hydrocarbons

The spark discharge synthesis of amino acids using an atmosphere of CH₄ + N₂ + H₂O + NH₃ has been investigated with variable pNH₃. The amino acids produced using higher hydrocarbons (ethane, ethylene, acetylene, propane, butane, and isobutane) instead of CH₄ were also investigated. There was considerable range in the absolute yields of amino acids, but the yields relative to glycine (or -amino-n-butyric acid) were more uniform. The relative yields of the C₃ to C₆ aliphatic -amino acids are nearly the same (with a few exceptions) with all the hydrocarbons. The glycine yields are more variable. The precursors to the C₃-C₆ aliphatic amino acids seem to be produced in the same process, which is separate from the synthesis of glycine precursors. It may be possible to use these relative yields as a signature for a spark discharge synthesis provided corrections can be made for subsequent decomposition events (e.g. in the Murchison meteorite).     

Comparative properties of fluorous phosphine ligand complexes: W(CO)5L. Crystal structure of W(CO)5P(C6H4-4-CH2CH2(CF2)7CF3)3

The compounds W(CO)₅P(C₆H₄-4-CH₂CH₂(CF₂)₇CF₃)₃ (1) and W(CO)₅P(CH₂CH₂(CF₂)₅CF₃)₃ (2) were synthesized in order to probe the electronic and physical effects of ligation by perfluorocarbon substituted tertiary phosphine ligands in a W(CO)₅L complex. The π-accepting ability of the fluorous phosphines was found to rank with non-fluorous comparators as P(CH₂CH₂(CF₂)₅CF₃)₃ > P(C₆H₄-4-CH₂CH₂(CF₂)₇CF₃)₃ > PPh₃ > P(p-tolyl)₃ > P(n-octyl)₃. The X-ray crystal structure of W(CO)₅P(C₆H₄-4-CH₂CH₂(CF₂)₇CF₃)₃ shows strong intermolecular association of fluorous components but confirms that the para fluorocarbon subtituents have an insignificant effect on the tungsten coordination environment. Partition coefficients (toluene/perfluoromethylcyclohexane) were measured for compounds 1 and 2.