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Equilibrium molecular dynamics (EMD) simulations are used to model density ρL, dynamic viscosity ηL, and self-diffusivity Dself of liquid ethane at pressures close to saturation conditions and temperatures T between (184–298) K, close to the critical temperature Tc. To correct for a T-dependent drift of the simulated results from experimental data, a T-dependent force field modification from our previous studies is extended to a wider T-range. The modification is validated within this work by comparing predicted ρL, ηL, and Dself to experimental reference data. With the modification applied, EMD simulations are able to predict ρL, ηL, and Dself of liquid ethane at T = 298 K with relative deviations of 6.3%, 13%, and 28% from literature references, respectively. Simulations of binary mixtures of liquid ethane with different dissolved gases were performed to predict the Fick diffusivity D11. At a mole fraction of dissolved nitrogen xN2 = 0.03, a deviation of more than a factor of three is found between simulation results and experimental results determined using the dynamic light scattering method. This shows that EMD simulations are not able to predict the critical slowing down of D11 approaching Tc, despite excellent agreement between simulations and reference data for neat ethane. [ABSTRACT FROM AUTHOR]

The laminar burning velocity (SL) was measured at sub-atmospheric pressure (0.84 atm) and an environmental temperature of 295 ± 2 K for two high C2H6 content fuel mixtures, 75% CH4 – 25% C2H6 (mixture M1), and 50% CH4 – 50% C2H6 (mixture M2), as well as the pure constituent fuels. The equivalence ratios for the experiments ranged between 0.8 and 1.4. Numerical calculations predicting SL were performed using 3 detailed reaction mechanisms, finding GRI-Mech 3.0 to achieve the best agreement at the pressure conditions evaluated. The pre-exponential factor of reaction H + O2 = O + OH (R38) was modified in order to improve the numerical results at sub-atmospheric conditions. Kinetic analysis by means of the defined reaction factor ( F R , i ± j ) was carried out to identify the mechanism for SL changes at sub-atmospheric conditions. According to the experimental results, SL increased by 15.9% and 26.3% for mixtures M1 and M2, respectively, at 0.84 atm as compared to 1.0 atm. The reaction pathways elaborated employing FR indicate that the increase in SL at sub-atmospheric conditions is caused by increased CH3 radical production by reaction C2H5 + H = 2CH3 (R159), which increases the formation of H radical through reactions O + CH3 = H + CH2O (R10) and O + CH3 = H + H2 + CO (R284). The recombination reactions associated with the production of CH4 and C2H6 also contribute to SL increases at sub-atmospheric conditions. [ABSTRACT FROM AUTHOR]

Dual fueling is a successful model in the engine combustion area which perks up the performance and emission fronts. The combined effect of using biodiesel and gas dual fueling shall address the problem associated with emissions and depletion of fossil fuels. Fuel derived from Annona squamosa seeds is a creditable biofuel, which is resulted from waste seeds. This paper characterizes the gaseous exhaust emission and performance model of a dual-fueled, direct injection diesel engine fueled with ethane as gaseous fuel and Annona squamosa biodiesel as the base and liquid fuel. Ethane is supplied with air in the intake manifold at different flow rates (five lpm and ten lpm). Ethane supply at ten lpm lowered HC emissions by seven ppm, CO by 0.4% and smoke emission by 0.2 BSU for biodiesel. In addition, ethane supply to biodiesel lowered the BSFC by 13 kg/kW-h and enhanced the efficiency by 0.4%. Hence, dual-fueling ethane is an effective technique for improving the usage of biofuels in diesel engine applications. [ABSTRACT FROM AUTHOR]

We provide the first large field investigation of more than 20 gold deposits and sites along the Keraf suture zone, covering an area of ~15,000 km2. The area shows diverse structural settings for gold mineralization in greenschist, amphibolite, and hornfels metamorphosed rocks. The reverse fault and dyke-hosted settings appear to be the most favourable for forming gold deposits. Two major N-S-trending, ~300-km-long corridors of deformation are delineated (West and East) but only the West seems important for gold. From fluid inclusions, 6 types of fluids are distinguished based on specific volatile contents and proportions. Most types can be related to fluid evolution by hydrothermal reactions and phase separations from a primitive fluid of metamorphic origin, containing H2O, CO2, N2, CH4, C2H6, and H2. Regional hydrothermal fields are identified based on the combinations of structural settings and fluid types. The northern field is defined as a single large hydrothermal system accounting for the mineralization of the 3 gold deposits (WG-03, UTM and Central). For sites along the West Corridor, such as Toubi, Anas, NW and Shereik, multiple and overlapping hydrothermal systems are necessary to explain the various fluid types and structural settings, even at the deposit scale (Shereik). Conversely, other sites (SW, Yasmine, Korup, Saijd, Dardora, Negeim, and SE) formed by localized individual hydrothermal systems. The documentation of fluids containing ethane at numerous sites and deposits is the most significant outcome. Such ethane-bearing fluids are generated by the metamorphism of carbonaceous-pyritic sedimentary rocks. These rocks are considered one of the best sources for providing ligands and gold for the formation of orogenic gold deposits. Consequently, the Keraf suture zone, composed mainly of carbonaceous turbidites, is interpreted to have provided such source rocks in the suture zone and below the adjacent cratons during the collision, forming orogenic gold deposits (graphical abstract). [ABSTRACT FROM AUTHOR]

Soot formation from combustion devices, which tend to operate at high pressure, is a health and environmental concern, thus investigating the effect of pressure on soot formation is important. While most fundamental studies have utilised the co-flow laminar diffusion flame configuration to study the effect of pressure on soot, there is a lack of investigations into the effect of pressure on the flow field of diffusion flames and the resultant influence on soot formation. A recent work has displayed that recirculation zones can form along the centreline of atmospheric pressure diffusion flames. This present work seeks to investigate whether these zones can form due to higher pressure as well, which has never been explored experimentally or numerically. The CoFlame code, which models co-flow laminar, sooting, diffusion flames, is validated for the prediction of recirculation zones using experimental flow field data for a set of atmospheric pressure flames. The code is subsequently utilised to model ethane-air diffusion flames from 2 to 33 atm. Above 10 atm, recirculation zones are predicted to form. The reason for the formation of the zones is determined to be due to increasing shear between the air and fuel steams, with the air stream having higher velocities in the vicinity of the fuel tube tip than the fuel stream. This increase in shear is shown to be the cause of the recirculation zones formed in previously investigated atmospheric flames as well. Finally, the recirculation zone is determined as a probable cause of the experimentally observed formation of a large mass of soot covering the entire fuel tube exit for an ethane diffusion flame at 36.5 atm. Previously, no adequate explanation for the formation of the large mass of soot existed. [ABSTRACT FROM AUTHOR]

This study analyzed the effect of the shale boom on the olefin industries. We investigated the paths by which US natural gas prices are transferred to ethylene and propylene prices and identified the price determinants based on the supply and demand conditions of each commodity's market. By comparing with the Japanese markets, the understanding of the supply structure of the ethylene and propylene industries is broadened. A path analysis framework was constructed to reflect the supply chains and applied to 2009–2018 data. Results showed that the downward trend in ethane prices provoked by the US shale boom reduced ethylene prices and raised propylene prices. Propane still serves as a determinant of the latter, while naphtha has lost predictive power for both. The comparative data confirmed that the US produces most of its petrochemicals from natural gas and gas-based feedstocks, while Japan relies on crude oil and refined naphtha. [ABSTRACT FROM AUTHOR]

The growing demand for energy and lack of conventional natural resources has compelled researchers all around the world to pay great attention to the extraction of shale gas, an unconventional natural gas trapped within shale formations. To enhance the gas recovery process and minimise the environmental hazards requires improved technologies. It has been reported that most of the gases trapped in shale rock formations are adsorbed in complex nano-size heterogeneous pores. However, only an insignificant amount of information is available. It is desired to investigate the microscopic behaviour of these gases under nano-confinement for the advancement of enhanced gas recovery (EGR) technologies. In the proposed work, Molecular Dynamics (MD) simulation techniques are used to study the structural and dynamical behaviour of shale gas, which is roughly an 80-20% molar mixture of methane and ethane respectively, confined inside 2.2 nm, slit-like nanopores. The calcite [104] surface has been chosen, as it is the most stable calcite surface. The density profiles of gases are calculated at various temperatures to understand the structural behaviour. The mean square displacements (MSDs) and self-diffusion coefficients are calculated to understand the dynamical behaviour inside the nanopore. [ABSTRACT FROM AUTHOR]

Pyrolysis of lower alkanes is among the main industrial methods for the production of light olefins. In this paper, an artificial neural network (ANN) model was developed in order to predict production of ethylene from ethane pyrolysis based on data obtained from mathematical modeling of the process in a plug flow reactor. Results obtained from the mathematical models were validated using experimental data from the literature. According to the results, the linear regression between network outputs and corresponding targets are proven satisfactory with a correlation coefficient of 1. The optimum number of neurons of 10 was obtained at hidden layer. [ABSTRACT FROM AUTHOR]

Steam cracking of diverse hydrocarbon sources is nowadays the main technology used to produce ethene worldwide, however, it presents energetic and environmental limitations related to the large consumption of energy and production of carbon oxides. To overcome this, industry and academy have aimed their research at developing a new technology based on the oxidative dehydrogenation (ODH) of ethane. Main challenges for its industrial implementation are yet catalyst and industrial reactor design. In this sense, Ni based catalysts have been promising materials for the production of ethene out of ethane at laboratory scale, however there is a scarce amount of researching on engineering aspects related to the evaluation of their performance at industrial scale. This work is aimed at giving insights on the performance of a Ni-loaded Y zeolite catalyst (Ni/KY) during the ethene production via ODH of ethane in an industrial-scale wall-cooled fixed bed catalytic reactor with a lowdt/dp. To achieve this, an industrial reactor model that couples reaction kinetics to heat and mass transport phenomena is developed following reactor engineering fundamentals. To assess the kinetics of the ODH of ethane over the aforementioned catalyst, a detailed kinetic model is developed using published experiments [J. Catal.265 (2009) 54–62]. Then, this kinetics is coupled to the industrial-scale reactor model, a 2D heterogeneous model accounting for heat and mass transport. The kinetic model following a Langmuir–Hinshelwood–Hougen–Watson mechanism allows an accurate description of laboratory data. Activation energy, related to the formation of ethene, and enthalpy adsorption of ethene indicate that the production ethene is favored at larger reaction temperatures, however, once it is produced, this olefin is more strongly adsorbed on the catalyst surface than the other byproducts. However, from the parametric sensitivity study applied to the industrial reactor, a larger coolant temperature brings out a significant but positive effect on the yield of ethene whereas a lower concentration of ethane in the feedstock favors the oxydehydrogenation reaction rather than total oxidation reactions. To this end, the proposed industrial reactor technology, along with the Ni/KY material, overcomes the hot spot formation and enables operations at larger temperatures, hence, favoring the production of ethene rather than carbon oxides. [ABSTRACT FROM PUBLISHER]

The present study was purposed to model the hydrate formation temperature of the pure gas containing CH4and C2H6in a certain pressure range from 1 to 50 MPa by Peng–Robinson (PR). Hydrate forming temperature depends on pressure and composition of gases. Accuracy of this model was evaluated by data collected from other previously published research. Results from the model showed the hydrate formation temperatures have great agreement with reported values. High value ofR2(0.99) confirms its satisfactory performance. [ABSTRACT FROM AUTHOR]

Major advances in the ethane/ethylene separation will be related with the discovery of adsorbents that present preferential adsorption of ethane over ethylene. Metal-organic frameworks (MOFs) are crystalline materials consisting of metal ions, or ion clusters, and organic ligands. Gas chromatography (GC) is most informative for materials screening for the ethane/ethylene separation since it needs only few mg of sample and gives selectivity results at various temperatures. This is illustrated by the methodology presented in this work where materials from two types of families (zeolites and MOFs) were used to show the reversed selectivity that can be found towards the ethane/ethylene separation. [ABSTRACT FROM AUTHOR]

We studied the structural and dynamical properties of methane and ethane in montmorillonite (MMT) slit pore of sizes 10, 20  and 30 Å using grand canonical Monte Carlo and classical molecular dynamics (MD) simulations. The isotherm, at 298.15 K, is generated for pressures up to 60 bar. The molecules preferentially adsorb at the surface as indicated by the density profile. In case of methane, we observe only a single layer, at the pore wall, whose density increases with increasing pressure. However, ethane also displays a second layer, though of low density in case of pore widths 20  and 30 Å. In-plane self-diffusion coefficient,D‖, of methane and ethane is of the order of 10− 6 m2/s. At low pressure,D‖increases significantly with the pore size. However,D‖decreases rapidly with increasing pressure. Furthermore, the effect of pore size onD‖diminishes at high pressure. Ideal adsorbed solution theory is used to understand the adsorption behaviour of the binary mixture of methane (80%) and ethane (20%) at 298.15 K. Furthermore, we calculate the selectivity of the gases at various pressures of the mixture, and found high selectivity for ethane in MMT pores. However, selectivity of ethane decreases with increase in pressure or pore size. [ABSTRACT FROM PUBLISHER]

The effective separation of small hydrocarbon molecules (C1– C4) is an important process for the petroleum industry, determining the end price of many essential commodities in our daily lives. Current technologies for separation of these molecules rely on energy-intensive fractional distillation processes at cryogenic temperature, which is particularly difficult because of their similar volatility. In retrospect, adsorptive separation using solid-state adsorbents might be a cost-effective alternative. Several types of solid-state adsorbents (e.g., zeolite molecular sieves) were tested for separation of small hydrocarbon molecules as a function of pressure, temperature, or vacuum. Among different types of plausible adsorbents, metal organic frameworks (MOFs), a class of porous, crystalline, inorganic-organic hybrid materials, is particularly promising. In this brief comment article, we discuss the separation properties of different types of solid-state adsorbents, with a particular emphasis on MOF-based adsorbents for separation of C2hydrocarbon molecules. [ABSTRACT FROM AUTHOR]

In the present work, mass transfer coefficients of main natural-gas components, methane and ethane, are determined during the hydrate formation. A complete explanation is given to show that the liquid mass transfer resistance at the gas-liquid interface predominates in the process. A fast and precise model has been also proposed to predict the rate of gas consumption. The advantage of the developed model is that there is no need to use fugacity and flash calculations in water-hydrate phase. [ABSTRACT FROM AUTHOR]

An experimental reaction setup consisting of an electric furnace and a quartz reactor with metal coupons inside it was used to study the rate of coke formation on the metal surfaces in different ranges of temperature and diluent ratio. Nitrogen, instead of steam, was used as a diluent in order to exclude the potential effect of oxidation of coke in a steam cracking environment. A kinetic model for coke deposition is experimentally derived based on an expounded surface reaction mechanism for ethane pyrolysis over chromium, iron, and stainless steel coupons. The results of the model are in good agreements with the experimental data with a significant probability confidence. [ABSTRACT FROM AUTHOR]

Previous attempts to model elevated-pressure coflow laminar flames have been hindered by neglecting the preheating within the burner, caused by downward heat transfer to the burner. In the present work, the computational domain is extended below the exit plane of the fuel tube to account for the flame preheating effect. Conjugate heat transfer (CHT) is implemented by the harmonic mean method to model the heat transfer between the fluid streams and solid fuel tube. This extension of the domain allows for solutions to a high pressure ethane/air data set from 2 to 33 atm, which is an improvement over previous attempts where only pressures below 15 atm could be modeled. The extended model more accurately predicts centerline soot formation than the truncated model due to capturing fuel pyrolysis that occurs below the exit plane of the fuel tube. This increased fuel pyrolysis increases the contribution by polycyclic aromatic hydrocarbon (PAH) condensation to computed soot volume fractions. For pressures above 20 atm, the extended model predicts that PAH condensation is the dominant mechanism on the wings—a location where surface growth was thought to be heavily dominant regardless of flame characteristics. It is determined that the choice of fuel tube wall treatment does significantly affect numerical predictions, with the best experimental agreement obtained using a CHT model as oppose to an isothermal or adiabatic walls. The extended model with CHT is the only model that displays quantitative accuracy and is a significant advancement over previous qualitatively accurate models. [Supplementary materials are available for this article. Go to the publisher's online edition ofCombustion Science and Technologyfor the following free supplemental resource: Numerical details.] [ABSTRACT FROM AUTHOR]

Steady-state global chemistry calculations for 20 different flames were carried out using an axisymmetric Computational Fluid Dynamics (CFD) code. Computational results for 16 flames were compared with flame images obtained at the NASA Glenn Research Center. The experimental flame data for these 16 flames were taken from Sunderland et al. [4] which included normal and inverse diffusion flames of ethane with varying oxidiser compositions (21, 30, 50, 100% O2 mole fraction in N2) stabilised on a 5.5 mm diameter burner. The test conditions of this reference resulted in highly convective inverse diffusion flames (Froude numbers of the order of 10) and buoyant normal diffusion flames (Froude numbers ∼0.1). Additionally, six flames were simulated to study the effect of oxygen enhancement on normal diffusion flames. The enhancement in oxygen resulted in increased flame temperatures and the presence of gravity led to increased gas velocities. The effect of gravity-variation and oxygen enhancement on flame shape and size of normal diffusion flames was far more pronounced than for inverse diffusion flames. For normal-diffusion flames, their flame-lengths decreased (1 to 2 times) and flames-widths increased (2 to 3 times) when going from earth-gravity to microgravity, and flame height decreased by five times when going from air to a pure oxygen environment. [ABSTRACT FROM PUBLISHER]

MULTIMODE calculations of low-lying rovibrational energies are reported for C2H4 and C2D4 for total angular momentum J = 0 and 1. The calculations are compared with recent benchmark ones for C2H4 J = 0 [G. Avila and T. Carrington, Jr. J. Chem. Phys. 135, 064101 (2011)] and shown to be highly accurate and roughly two orders of magnitude faster. Calculations of rotation constants for the twelve fundamentals for both C2H4 and C2D4 are reported. [ABSTRACT FROM AUTHOR]

The room temperature high resolution infrared spectrum of C2H6 between 1330 and 1610 cm−1, the region of the ν6 and ν8 fundamentals, has been re-investigated owing to the relevance of this spectral region in atmospheric and planetary applied research. The assignments of transitions from the ground vibrational state to the upper states ν6, ν8, ν4 + ν12 and 2ν4 + ν9 (4592 in total) and from the lower state ν4 to the upper state ν4 + ν8 (1090 lines) have been considerably extended with respect to our previous work [F. Lattanzi, C. di Lauro and J. Vander Auwera, J. Mol. Spectrosc. 248 (2008) 134–145], especially for the hot transitions. In particular, three new series of perturbation activated transitions were found, with ΔK = ±2, made observable by the resonance of the type l(Δl = ±2, ΔK = ∓1) within ν8. Also, new P-transitions to ν6 were found, made observable by the x,y-Coriolis resonance with ν8, at the values of K from 15 to 18. The extension of the assignments in the high frequency wing of ν8 and their analysis allowed the discovery of two additional resonance interactions. The first interaction, a higher order Coriolis-type between ν8(±K, l = ±1) and ν6(±K ± 2, l = 0), induces a few detectable transitions to ν6 with ΔK = 3. The second interaction, of the type l(Δl = ±2, ΔK = ∓1), comes to resonance between ν8(k = ±19, l = ±1) and 2ν4 + ν9 (k = ±20, l = ∓1). This last resonance and the x,y-Coriolis resonance of ν6 and 2ν4 + ν9 allows one to observe several transitions to the 2ν4 + ν9 vibrational state. The extension of the assignments in the (ν4 + ν8) − ν4 hot band allowed discovery of a resonance interaction of the type l(Δl = ±2, ΔK = ∓1) between the states ν4 + ν8 and 2ν4 + ν12, in addition to their well known Fermi-type interaction. The K-values before and after the level crossing could be determined for both interactions. Better values were also determined for the J-structure parameters B, DJ and DJK in the ν4 state, from 410 selected combination differences. Least squares fit calculations, performed on 2084 upper state energy levels for the cold system (RMS of 3.69 × 10−3 cm−1) and 500 for the hot system (RMS of 6.62 × 10−3 cm−1), required a more sophisticated Hamiltonian model than in our previous work. [ABSTRACT FROM PUBLISHER]

Adsorption-based process for removal of ethane and ethylene, as the main products of oxidative coupling methane reaction from unreacted methane is discussed. The adsorption equilibrium of methane, ethane, and ethylene was determined experimentally on CaX, the calcium cation exchanged NaX zeolite, by the volumetric measurements in a high pressure setup at three different temperatures. The adsorption isotherms were well modeled by the extended Langmuir-Freundlich isotherm and the adsorbed capacity, adsorption constants, and surface heterogeneity parameter were determined by regression of the model to the isothermal experiments. The results indicated that CaX zeolite would be a selective adsorbent for the separation of ethane, ethylene, and methane from each other at moderate temperatures and pressures. The breakthrough curves of gases were determined in a dynamic adsorption experiment of the gaseous mixture in a fixed bed of CaX zeolites for a feed with similar molar composition of OCM hydrocarbon product. Significant difference of breakthrough times was observed for methane, ethane, and ethylene. It is concluded that construction of an adsorption unit from CaX zeolites at the OCM reactor downstream would be economic and useful for the separation of methane from the C2 products. [ABSTRACT FROM AUTHOR]

Uptake of acetylene and ethane molecules by a disperse aqueous system was simulated by molecular dynamics. The cluster (H2O)20 remains stable until the number of the captured C2H2 molecules becomes larger than 3 and the number of the C2H6 molecules becomes more than 4. Addition of acetylene molecules to the disperse aqueous system increases both the real and imaginary parts of the dielectric permittivity in the frequency range [image omitted] . However, capturing of ethane molecules decreases the dielectric permittivity in the same frequency range. The integral IR absorption coefficient of the disperse system containing C2H2 and C2H6 molecules increases. The heat-radiating power of the clusters decreases upon absorption of ethane molecules and increases when acetylene molecules are added to the water cluster. Absorbed C2H2 molecules are aligned with the tangent to the water core of the cluster, thus impeding their penetration into the aggregate and, hence, decreasing the solubility of acetylene. [ABSTRACT FROM AUTHOR]

The relationship of exhaled ethane and n-pentane to exhaled NO, carbonylated proteins, and indoor/outdoor atmospheric pollutants were examined in order to evaluate ethane and n-pentane as potential markers of airway inflammation and/or oxidative stress. Exhaled NO and carbonylated proteins were found to have no significant associations with either ethane (p = 0.96 and p = 0.81, respectively) or n-pentane (p = 0.44 and 0.28, respectively) when outliers were included. In the case where outliers were removed n-pentane was found to be inversely associated with carbonylated proteins. Exhaled hydrocarbons adjusted for indoor hydrocarbon concentrations were instead found to be positively associated with air pollutants (NO, NO2 and CO), suggesting pollutant exposure is driving exhaled hydrocarbon concentrations. Given these findings, ethane and n-pentane do not appear to be markers of airway inflammation or oxidative stress. [ABSTRACT FROM AUTHOR]

A custom-built, solvent recirculating, supercritical fluid extraction (SFE) apparatus was used to study the extraction of hydrocarbons from a crude oil tank bottom sludge (COTBS) with supercritical ethane. The SFE experiments were carried out varying the pressure (10 MPa and 17.20 MPa) and temperature (35°C and 65°C). The yield of the extracted hydrocarbon fraction increased with increase in extraction pressure at constant temperature, and decreased with increase in extraction temperature at constant pressure. The maximum extraction yield was obtained at the pressure and temperature conditions that lead to the highest solvent density. The extracted hydrocarbon fraction was a significantly upgraded liquid relative to the original untreated COTBS. [ABSTRACT FROM AUTHOR]

Experimental studies of adiabatic cellular flames of CH4 + O2 + CO2, C2H6 + O2 + CO2, and C3H8 + O2 + CO2 are presented. Visual and photographic observations of the flames were performed to quantify their cellular structure. Non-stretched flames of methane and propane were stabilized at atmospheric pressure on a perforated plate burner of improved design. New measurements are compared with recent results from this group. A Heat Flux method was used to determine propagation speeds under conditions when the net heat loss of the flame is zero. Under specific experimental conditions the flames become cellular; this leads to significant modification of the flame propagation speed. The onset of cellularity was observed throughout the stoichiometric range of the mixtures studied. Cellularity disappeared when the flames became only slightly sub-adiabatic. Increasing the oxygen content in the artificial air and increasing the temperature of the burner plate led to increase of the number of cells observed. No direct proportionality between the number of cells and propagation speeds in CH4 + O2 + CO2 flames was observed. Dependence of the number of cells as a function of equivalence ratio clearly showed a local minimum in the stoichiometric mixtures. [ABSTRACT FROM AUTHOR]

Scleroderma (systemic sclerosis) is a chronic multisystem autoimmune disease in which oxidative stress is suspected to play a role in the pathophysiology. Therefore, it was postulated that patients with scleroderma would have abnormally high breath ethane concentrations, which is a volatile product of free-radical-mediated lipid peroxidation, compared with a group of controls. There was a significant difference ( p –1 CO 2 (SEM=0.76) in the scleroderma patients ( n =36) versus the mean exhaled concentration of 2.72 pmol ml -1 CO 2 (SEM=0.71) in a group of healthy controls ( n =21). Within the scleroderma group, those subjects taking a calcium channel blocker had lower ethane concentrations compared with patients who were not taking these drugs ( p =0.05). There was a significant inverse association between lung diffusion capacity for carbon monoxide (per cent of predicted) and ethane concentration ( b =-2.8, p =0.026, CI=-5.2 to -0.35). These data support the presence of increased oxidative stress among patients with scleroderma that is detected by measuring breath ethane concentrations. [ABSTRACT FROM AUTHOR]

New experimental results were obtained for the mutual sensitization of the oxidation of NO and ethane and NO and ethylene in fuel-lean conditions. An atmospheric fused-silica jet-stirred reactor operating over the temperature range 700-1150 K was used. The initial carbon mole fraction was 2500 ppm whereas that of NO varied from 0 to 1200 ppm. Sonic quartz probe sampling followed by on-line Fourier transform infrared analyses and off-line gas chromatographythermal conductivity detection flame ionization detection analyses were used to measure the concentration profiles of the reactants, stable intermediates, and the final products. A detailed chemical kinetic modeling of the present experiments was performed (147 species, 1085 reversible reactions). An overall good agreement between the present data and modeling was obtained. Furthermore. the proposed model was able to simulate, better than in previous modeling efforts, plug-flow reactor experimental results available in the literature. According to the proposed model, the mutual sensitization of the oxidation of ethane or ethylene and NO proceeds mostly through the conversion of NO to NO2 by HO2 radicals. The NO-to-NO2 conversion is enhanced by the production of HO2 radicals from the oxidation of the fuel. The production of OH resulting from the oxidation of NO by the hydroperoxy radical promotes the oxidation of the fuel: NO + HO2 ⇒ OH + NO2 is followed by OH + C2H4 ⇒ C2H3 + H2O and OH + C2H6 ⇒ C2H5 + H2O. In the case of ethane, at low temperature, the reaction further proceeds via CH3 + O2 ⇒ CH3O2; CH3O2 + NO ⇒ CH3O + NO2; C2H5O2 + NO ⇒ C2H5O + NO2; C2H5 + O2 ⇒ C2H4 + HO2. At higher temperature, the sequence is followed by CH3O ⇒ CH2O + H; C2H5O ⇒ CH3CHO + H; C2H5O ⇒ CH3 + CH2O; CH2O + OH ⇒ HCO + H2O; HCO + O2 HO2 + CO; and H + O2 ⇒ HO2. In the case of ethylene, the reaction further proceeds via C2H3 + O2 ⇒ CH2O + HCO; CH2O + OH ⇒ HCO + H2O; HCO + O2 ⇒ HO2 + CO; and H + O2 + M ⇒ HO2 + M. The main chemical kinetic differences between the two fuels in presence of NO were analyzed. [ABSTRACT FROM AUTHOR]

Modulated Differential Scanning Calorimetry (MDSC) has been applied to the study of methane, ethane, and propane hydrates at different hydrate and ice concentrations. The reversing thermodynamical component of the MDSC curves, makes it possible to characterize such hydrates. Methane and ethane hydrates show the melting-decomposition peak at a temperatures higher than the ice contained in the sample, while propane hydrate melts and decomposes at a lower temperature than the ice present in the sample. The hydrate peaks tend to disappear if the hydrate is stored at atmospheric pressure. Guest size and cavity occupation fix the heat of dissociation and stability of the hydrates, as confirmed by parallel tests on tetrahydrofurane hydrates. [ABSTRACT FROM AUTHOR]

Adsorption of light hydrocarbons, such as ethane, ethylene, n-butane, isobutane, and isobutene, on zeolites 5A [LTA] and H-Beta [BEA] was investigated, in order to evaluate the possible use of these zeolites as adsorbents for reducing cold start emissions at engine exhaust. Equilibrium isotherms at 25°C were determined and analyzed by Langmuir and virial equations to estimate adsorption capacities at saturation and adsorption affinity for single hydrocarbons at low pressure. Good affinities of zeolites 5A and H-Beta for the tested light hydrocarbons were found either at saturation or at low pressure. Flow measurements were also carried out with a fixed-bed microreactor using a real engine exhaust gas. Reasonable performances of zeolite H-Beta in trapping hydrocarbons present in the emission at engine exhaust were obtained. Poor performances, obtained, on the contrary, with zeolite 5A, were interpreted as due to the preferential adsorption of water vapor, compared to hydrocarbons. On the basis of the present and of previously collected data, the possibility of use of zeolite H-Beta, coupled to zeolite H-Y or zeolite H-ZSM5, to realize a hydrocarbon adsorbent trap for reducing cold start emission is, at last, envisaged. [ABSTRACT FROM AUTHOR]

Oxidative dehydrogenation of ethane to ethylene was investigated using Mo 0.71 V 0.21 Nb 0.08 mixed-oxide catalyst, in powder form and coated over a monolith. At 570°C and with a feed stream containing an O 2 /C 2 H 6 mole ratio of one, ethylene selectivity value reaching to 96% was obtained at a conversion level of about 5% with the monolith-supported catalyst. DRIFTS studies indicated the presence of adsorbed ethoxide species. The proposed reaction scheme for the production of ethylene includes the elimination of β-hydrogen of adsorbed species by the lattice oxygen. [ABSTRACT FROM AUTHOR]

Attention deficit hyperactivity disorder (ADHD) comprises a range of behavioural problems including inattention, hyperactivity and impulsivity. Diagnosis and treatment of the disorder is made difficult due to its unknown biological basis. Several studies have identified abnormalities in membrane fatty acids in some subjects with ADHD, and some success has been reported using lipid therapies. We have measured exhalant ethane levels, a non-invasive measure of oxidative damage to n-3 fatty acids, to probe biochemical alterations in ADHD. Patients with ADHD ( N =10) had higher levels of ethane in exhalant than in healthy volunteers ( N =12) with approximately 50% of ADHD cases being above the control range. In contrast, levels of butane, a marker of protein oxidation, were unaltered. Our data, although preliminary, suggests that some patients with ADHD have higher rates of oxidative breakdown of n-3 polyunsaturated fatty acids (PUFAs). Such a biochemical abnormality may underlie the previously observed fatty acid deficiencies, as well as providing further rationale for the use of anti-oxidant and/or lipid supplementation therapy in the treatment of ADHD. Larger studies of ADHD using this non-invasive assessment of oxidative stress appear warranted. [ABSTRACT FROM AUTHOR]

Oxidative stress may initiate lipid peroxidation that generates ethane. Ethane, at low concentrations, is eliminated by pulmonary exhalation. Previous methods have not allowed frequent sampling, thus ethane kinetics has not been studied in man. A validated method over the range 3.8-100,000 ppb with a limit of quantitation of 3.8 ppb (CV 9.3%) based on cryofocusing technique of a 60 ml breath sample allowed frequent sampling. Due to a rapid analytical procedure batches of more than 100 samples may be analyzed. In human volunteers (24-55 years) uptake was studied for up to 23 min ( n =9) , elimination was studied for 210 min ( n =9). Ethane was inhaled (concentrations varied from 16 to 29 ppm (parts per million)) through a non-rebreathing system; sampling was performed with short intervals from the expiratory limb. Samples were also drawn from the inhalatory limb. Ninety-five percent of steady state (inspired) concentration was reached within 1.75 min. Five percent of the initially inhaled concentrations was found in exhaled air 1.5 min after termination of inhalation. A terminal mean half life of 31 min for ethane was also observed. The data indicate that frequent sampling will be necessary to capture relevant changes in breath ethane. [ABSTRACT FROM AUTHOR]

Mild oxidation is one of the promising techniques proposed to control pollutant emissions from combustion plants. It is characterized by high preheating of combustion air and massive recycle of burned gases before reaction. These requisites lead to high combustion efficiency and good control of thermal peaks and hot spots, lowering NOx thermal emissions. In this work, a laboratory-scale burner for mild combustion, which is an apparatus characterized by high internal recycle ratio, high back-mixing, and the possibility of also simulating external recycles of burned gases, is described, as well as the main experimental results achieved. These were carried out to demonstrate the possibility of reproducing the main phenomena observed in real-size flameless burners. Operating conditions for obtaining stable "mild" combustion with methane and ethane as fuels were investigated and operating parameters maps were obtained. [ABSTRACT FROM AUTHOR]

Ethane, 1,2-bis(pentabromophenyl) (EBP; CAS no. 8452-53-9) dose levels of 0, 100, 320 and 1000 mg/kg/day administered to rats by gavage in corn oil for 90 consecutive days produced no compound-related clinical signs of systemic toxicity, ocular lesions, or alterations in urinalysis, clinical chemistry, and hematology values in the treated or recovery groups. No biologically or toxicologically significant differences were observed in body weights, body weight gains, and food consumption. Statistically significant differences were found between control and high-dose animals in mean absolute or relative liver weights. Histomorphological evaluation showed in male rats low-grade liver changes consisting of minimal to slight hepatocellular vacuolation (high-dose males) and minimal to slight centrilobular hepatocytomegaly (high- and possibly mid-dose males). These changes had resolved by the end of the 28-day recovery period. No treatment-related changes were found in the livers of female rats. No treatment-related histomorphologic changes were present in any of the other tissues examined in either sex, except for evidence of aspirated test article in individual rats. The 90-day EBP no-adverse-effect level in the rat was ≥ 1000 mg/kg/day, and was consistent with that of the preceding 28-day study (no-effect level ≥ 1250 mg/kg/day). EBP's lack of toxicity is likely related to poor bioavailability due to its high molecular weight and low solubility. [ABSTRACT FROM AUTHOR]