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Sample records for n-pentane n-hexane n-heptane

  1. Binary chromatographic data and estimation of adsorbent porosities. [data for system n-heptane/n-pentane

    NASA Technical Reports Server (NTRS)

    Meisch, A. J.

    1972-01-01

    Data for the system n-pentane/n-heptane on porous Chromosorb-102 adsorbent were obtained at 150, 175, and 200 C for mixtures containing zero to 100% n-pentane by weight. Prior results showing limitations on superposition of pure component data to predict multicomponent chromatograms were verified. The thermodynamic parameter MR0 was found to be a linear function of sample composition. A nonporous adsorbent failed to separate the system because of large input sample dispersions. A proposed automated data processing scheme involving magnetic tape recording of the detector signals and processing by a minicomputer was rejected because of resolution limitations of the available a/d converters. Preliminary data on porosity and pore size distributions of the adsorbents were obtained.

  2. A model of reduced oxidation kinetics using constituents and species: Iso-octane and its mixtures with n-pentane, iso-hexane and n-heptane

    SciTech Connect

    Harstad, Kenneth; Bellan, Josette

    2010-11-15

    A previously described methodology for deriving a reduced kinetic mechanism for alkane oxidation and tested for n-heptane is here shown to be valid, in a slightly modified version, for iso-octane and its mixtures with n-pentane, iso-hexane and n-heptane. The model is still based on partitioning the species into lights, defined as those having a carbon number smaller than 3, and heavies, which are the complement in the species ensemble, and mathematically decomposing the heavy species into constituents which are radicals. For the same similarity variable found from examining the n-heptane LLNL mechanism in conjunction with CHEMKIN II, the appropriately scaled total constituent molar density still exhibits a self-similar behavior over a very wide range of equivalence ratios, initial pressures and initial temperatures in the cold ignition regime. When extended to larger initial temperatures than for cold ignition, the self-similar behavior becomes initial temperature dependent, which indicates that rather than using functional fits for the enthalpy generation due to the heavy species' oxidation, an ideal model based on tabular information extracted from the complete LLNL kinetics should be used instead. Similarly to n-heptane, the oxygen and water molar densities are shown to display a quasi-linear behavior with respect to the similarity variable, but here their slope variation is no longer fitted and instead, their rate equations are used with the ideal model to calculate them. As in the original model, the light species ensemble is partitioned into quasi-steady and unsteady species; the quasi-steady light species mole fractions are computed using the ideal model and the unsteady species are calculated as progress variables using rates extracted from the ideal model. Results are presented comparing the performance of the model with that of the LLNL mechanism using CHEMKIN II. The model reproduces excellently the temperature and species evolution versus time or versus

  3. n-Heptane

    Integrated Risk Information System (IRIS)

    n - Heptane ; CASRN 142 - 82 - 5 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Effec

  4. n-Hexane

    Integrated Risk Information System (IRIS)

    n - Hexane ; CASRN 110 - 54 - 3 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Effect

  5. Subchronic Inhalation Toxicity Study of n-pentane in Rats

    PubMed Central

    Cho, Hae-Won; Han, Jeong-Hee; Lee, Sung-Bae; Chung, Yong-Hyun; Rim, Kyung-Taek; Yang, Jeong-Sun

    2012-01-01

    Objectives This study was conducted in order to obtain information concerning the health hazards that may result from a 13 week inhalation exposure of n-pentane in Sprague-Dawley rats. Methods This study was conducted in accordance with the Organization for Economic Co-operation and Development (OECD) guidelines for the testing of chemicals No. 413 'Subchronic inhalation toxicity: 90-day study (as revised in 2009)'. The rats were divided into 4 groups (10 male and 10 female rats in each group), and were exposed to 0, 340, 1,530, and 6,885 ppm n-pentane in each exposure chamber for 6 hour/day, 5 days/week, for 13 weeks. All of the rats were sacrificed at the end of the treatment period. During the test period, clinical signs, mortality, body weights, food consumption, ophthalmoscopy, locomotion activity, urinalysis, hematology, serum biochemistry, gross findings, organ weights, and histopathology were assessed. Results During the period of testing, there were no treatment related effects on the clinical findings, body weight, food consumption, ophthalmoscopy, urinalysis, hematology, serum biochemistry, gross findings, relative organ weight, and histopathological findings. Conclusion The no-observable-adverse-effect level (NOAEL) of n-pentane is evaluated as being more than 6,885 ppm (20.3 mg/L) in both male and female rats. n-pentane was not a classified specific target organ toxicity in the globally harmonized classification system (GHS). PMID:23019535

  6. Polyneuropathy due to n-hexane.

    PubMed

    Paulson, G W; Waylonis, G W

    1976-08-01

    In 25 years, at least eight of 50 total exposed employees in a small plant developed a mild neuropathy. Studies of urine or blood for lead, arsenic, mercury, cadmium, thallium, and antimony revealed no sign of toxic agents, but the atmosphere in one room contained toxic levels of n-hexane. The sourse was the glue used in the plant. Serum cholinesterase levels were reduced, offering a possible laboratory tests to alert clinicians to the possibility of n-hexane exposure. All patients recovered completely. Mechanical and administrative adjustments should prevent such industrial accidents. PMID:182098

  7. Experimental study of boiling-up kinetics and superheat limit for n-hexane on solid powder-like structures

    NASA Astrophysics Data System (ADS)

    Gurashkin, A. L.; Perminov, S. A.; Ermakov, G. V.

    2006-12-01

    The experimental setup is described and results are presented for measuring average boiling-up lag time for superheated n-hexane mixed with solid structures (activated coal, cellulose, silica gel) as function of temperature under atmospheric pressure. The “aging” of the cell with the filler was carried out before measurements: this was about 600 1000 boiling events. We developed a new method for analysing of “aging” procedure: comparison of average flux (frequency) of boiling-up events (processing of experimental data) and the frequency of nucleation obtained from exponential model. By the end of aging of the cell with silica gel the average empirical flux reduces by factor of four relative to the “exponential” value. But for activated coal and cellulose the difference in these fluxes is about 20 %. In all experiments, the event flux was nonstationary. For n-hexane in tested systems, the margin of superheating was T n/T cr ≅ 0.873 0.875, although it was T n/T cr ≅ ≅ 0.883 for n-pentane in systems filled by nickel powder (sintered porous nickel with grains of 1.5 or 5.0 micron size) and in the presence of a smooth copper plate. The average time of boiling-up lag in n-hexane at low normalized temperatures was also smaller than for n-pentane. For all systems, the lag time is almost the same for the temperature range T n/T cr ≅ 0.860 0.874 (plateau). Thus, a smaller amount of superheated liquid or its division into smaller liquid elements does not result in longer liquid lifetime for superheat liquid and the maximal superheat temperature, as one could expect from the classical theory of homogeneous nucleation.

  8. N-hexane neuropathy in offset printers.

    PubMed Central

    Chang, C M; Yu, C W; Fong, K Y; Leung, S Y; Tsin, T W; Yu, Y L; Cheung, T F; Chan, S Y

    1993-01-01

    In an offset printing factory with 56 workers, 20 (36%) developed symptomatic peripheral neuropathy due to exposure to n-hexane. Another 26 workers (46%) were found to have subclinical neuropathy. The initial change in the nerve conduction study was reduced amplitude of the sensory action potentials, followed by reduced amplitude of the motor action potentials, reduction in motor conduction velocities and increase in distal latencies. These changes indicate primary axonal degeneration with secondary demyelination. Sural nerve biopsy in a severe case showed giant axonal swellings due to accumulation of 10nm neurofilaments, myelin sheath attenuation and widening of nodal gaps. The development of neuropathy bore no direct relationship to the duration of exposure, hence factors such as individual susceptibility may be important. Optic neuropathy and CNS involvement were uncommon and autonomic neuropathy was not encountered. Images PMID:8505647

  9. Extinction and Autoignition of n-Heptane in Counterflow Configuration

    SciTech Connect

    Seiser, R.; Pitsch, H.; Seshadri, K.; Pitz, W.J.; Curran, H.J.

    2000-01-12

    A study is performed to elucidate the mechanisms of extinction and autoignition of n-heptane in strained laminar flows under nonpremixed conditions. A previously developed detailed mechanism made UP of 2540 reversible elementary reactions among 557 species is the starting point for the study. The detailed mechanism was previously used to calculate ignition delay times in homogeneous reactors, and concentration histories of a number of species in plug-flow and jet-stirred reactors. An intermediate mechanism made up of 1282 reversible elementary reactions among 282 species and a short mechanism made up of 770 reversible elementary reactions among 160 species are assembled from this detailed mechanism. Ignition delay times in an isochoric homogeneous reactor calculated using the intermediate and the short mechanism are found to agree well with those calculated using the detailed mechanism. The intermediate and the short mechanism are used to calculate extinction and autoignition of n-heptane in strained laminar flows. Steady laminar flow of two counter flowing Streams toward a stagnation plane is considered. One stream made up of prevaporized n-heptane and nitrogen is injected from the fuel boundary and the other stream made up of air and nitrogen is injected from the oxidizer boundary. Critical conditions of extinction and autoignition given by the strain rate, temperature and concentrations of the reactants at the boundaries, are calculated. The results are found to agree well with experiments. Sensitivity analysis is carried out to evaluate the influence of various elementary reactions on autoignition. At all values of the strain rate investigated here, high temperature chemical processes are found to control autoignition. In general, the influence of low temperature chemistry is found to increase with decreasing strain. A key finding of the present study is that strain has more influence on low temperature chemistry than the temperature of the reactants.

  10. Industrial application of catalytic systems for n-heptane isomerization.

    PubMed

    Alemán-Vázquez, Laura Olivia; Cano-Domínguez, José Luis; Torres-García, Enelio; Villagómez-Ibarra, José Roberto

    2011-01-01

    The ideal gasoline must have a high pump octane number, in the 86 to 94 range, and a low environmental impact. Alkanes, as a family, have much lower photochemical reactivities than aromatics or olefins, but only the highly branched alkanes have adequate octane numbers. The purpose of this work is to examine the possibilities of extending the technological alternative of paraffin isomerization to heavier feedstocks (i.e., n-heptane) using non-conventional catalytic systems which have been previously proposed in the literature: a Pt/sulfated zirconia catalyst and a molybdenum sub-oxide catalyst. Under the experimental conditions at which these catalysts have been evaluated, the molybdenum sub-oxide catalyst maintains a good activity and selectivity to isomerization after 24 h, while the Pt/sulfated zirconia catalyst shows a higher dimethylpentanes/methylhexanes ratio, probably due to a lower operating temperature, but also a high formation of cracking products, and presents signs of deactivation after 8 h. Though much remains to be done, the performance of these catalysts indicates that there are good perspectives for their industrial application in the isomerization of n-heptane and heavier alkanes. PMID:21760573

  11. The Burning of Large N-Heptane Droplets in Microgravity

    NASA Technical Reports Server (NTRS)

    Manzello, Samuel L.; Choi, Mun Young; Kazakov, Andrei; Dryer, Frederick L.; Dobashi, Ritsu; Hirano, Toshisuke; Ferkul, Paul (Technical Monitor)

    2000-01-01

    Experimental results are presented on the burning and sooting behavior of large n-heptane droplets in air at atmospheric pressure under microgravity conditions. The experiments were performed at the Japanese Microgravity Center (JAMIC) 10 sec dropshaft in Hokkaido, Japan. Soot volume fraction, burning rate, flame standoff and luminosity were measured for droplets of 2.6 mm and 2.9 mm in initial diameter. These are the largest droplets for which soot volume fraction measurements have ever been performed. Previous measurements of soot volume fractions for n-heptane droplets, confined to smaller droplet sizes of less than 1.8 mm, indicated that maximum soot volume fraction increased monotonically with initial droplet size. The new results demonstrate for the first time that sooting tendency is reduced for large droplets as it has been speculated previously but never confirmed experimentally. The lower soot volume fractions for the larger droplets were also accompanied by higher burning rates. The observed phenomenon is believed to be caused by the dimensional influence on radiative heat losses from the flame. Numerical calculations confirm that soot radiation affects the droplet burning behavior.

  12. N-heptane adsorption and desorption in mesoporous materials

    NASA Astrophysics Data System (ADS)

    Zaleski, R.; Gorgol, M.; Błazewicz, A.; Kierys, A.; Goworek, J.

    2015-06-01

    Positron Annihilation Lifetime Spectroscopy (PALS) was used for an in situ monitoring of adsorption and desorption processes. The disordered and ordered porous silica as well as the porous polymer were used as adsorbents, while an adsorbate in all the cases was n-heptane. The lifetimes and particularly the intensities of the ortho-positronium(o-Ps) components depend strongly on the adsorbate pressure. The analysis of these dependencies allows us to identify several processes, which are taking place during sorption. At low pressure, an island-like growth of the first layers of the adsorbate on the silica, in a contrary to a swelling of the polymer, is observed. A size of the pores, which remain empty, is estimated at the subsequent stages of the adsorbate condensation and evaporation. The adsorbate thrusting into micropores is deduced at p/p0 > 0.6 whilst the mesopores are still not completely filled.

  13. n-Hexane polyneuropathy in a ball-manufacturing factory

    SciTech Connect

    Huang, C.C.; Shih, T.S.; Cheng, S.Y.; Chen, S.S.; Tchen, P.H. )

    1991-02-01

    Five overt and two occult cases of n-hexane polyneuropathy occurred in a ball-manufacturing factory in Taiwan. The severity of polyneuropathy was directly related to the index of n-hexane exposure that occurred during the processes of cement coating and nylon fiber winding in a poorly ventilated room. The n-hexane concentrations over eight hours of personal sampling of the air of the cement coating and nylon fiber winding areas were 109 ppm and 86 ppm, respectively. After installation of a new factory ventilation system, these seven patients recovered completely, and there were no new cases in the two-year follow-up.

  14. A New Exploration of the Torsional Energy Surface of N-Pentane Using Molecular Modeling Software

    ERIC Educational Resources Information Center

    Galembeck, Sergio E.; Caramori, Giovanni F.; Romero, Jose Ricardo

    2005-01-01

    The torsional potential energy surface of a chemical compounds, the accessible conformations at a specified temperature and the transition states that connect these confirmations establishes many chemical properties such as dynamic behavior, reactivity and biological activity. A conformational search of n-pentane is presented using computational…

  15. Selective optical detection of n-heptane/iso-octane vapors by polyimide lightguides

    NASA Astrophysics Data System (ADS)

    Podgorsek, R. P.; Franke, H.; Feger, C.

    1995-03-01

    The optical anisotropy of planar polyimide lightguides in an atmosphere of n-heptane / iso-octane is investigated in a transient experiment for pure and several mixed-vapor concentrations. The polymer sensor responds only to n-heptane and not to iso-octane vapors. However, the presence of the latter affects the dynamic behavior of the waveguide anisotropy, which can be fitted by a stretched exponential time dependence. The saturation values of the birefringence are an absolute measure for the n-heptane concentration and are not affected by the presence of the iso-octane vapors.

  16. Strategies for mechanism reduction for large hydrocarbons: n-heptane

    SciTech Connect

    Lu, Tianfeng; Law, Chung K.

    2008-07-15

    A 55-species reduced mechanism for n-heptane oxidation was derived from a 188-species skeletal mechanism, which was previously obtained from a detailed mechanism consisting of 561 species using a directed relation graph (DRG). This reduced mechanism was derived by first obtaining a skeletal mechanism with 78 species using DRG-aided sensitivity analysis. The unimportant reactions were eliminated by using the importance index defined in computational singular perturbation (CSP), with a newly posited restriction to treat each reversible reaction as a single reaction. An isomer lumping approach, also developed in the present study, then groups the isomers with similar thermal and diffusion properties so that the number of species transport equations is reduced. It was found that the intragroup mass fractions of the isomers can be approximated as constants in the present reduced mechanism, leading to a 68-species mechanism with 283 elementary reactions. Finally, 13 global quasi-steady-state species were identified using a CSP-based time-scale analysis, resulting in the 55-species reduced mechanism, with 283 elementary reactions lumped into 51 semiglobal steps. Validation of the reduced mechanism shows good agreement with the detailed mechanism for both ignition and extinction phenomena. The inadequacy of the detailed mechanism in predicting the experimental laminar flame speed is also demonstrated. (author)

  17. On the combustion chemistry of n-heptane and n-butanol blends.

    PubMed

    Karwat, Darshan M A; Wagnon, Scott W; Wooldridge, Margaret S; Westbrook, Charles K

    2012-12-27

    High-speed gas sampling experiments to measure the intermediate products formed during fuel decomposition remain challenging yet important experimental objectives. This article presents new speciation data on two important fuel reference compounds, n-heptane and n-butanol, at practical thermodynamic conditions of 700 K and 9 atm, for stoichiometric fuel-to-oxygen ratios and a dilution of 5.64 (molar ratio of inert gases to O(2)), and at two blend ratios, 80%-20% and 50%-50% by mole of n-heptane and n-butanol, respectively. When compared against 100% n-heptane ignition results, the experimental data show that n-butanol slows the reactivity of n-heptane. In addition, speciation results of n-butanol concentrations show that n-heptane causes n-butanol to react at temperatures where n-butanol in isolation would not be considered reactive. The chemical kinetic mechanism developed for this work accurately predicts the trends observed for species such as carbon monoxide, methane, propane, 1-butene, and others. However, the mechanism predicts a higher amount of n-heptane consumed at the first stage of ignition compared to the experimental data. Consequently, many of the species concentration predictions show a sharp rise at the first stage of ignition, a trend that is not observed experimentally. An important discovery is that the presence of n-butanol reduces the measured concentrations of the large linear alkenes, including heptenes, hexenes, and pentenes, showing that the addition of n-butanol affects the fundamental chemical pathways of n-heptane during ignition. PMID:23206273

  18. Process for the solvent deasphalting of asphaltene-containing hydrocarbons

    SciTech Connect

    Ikematsu, M.; Honzyo, I.; Sakai, K.

    1985-06-25

    A process for the solvent deasphalting of asphaltene-containing hydrocarbons which comprising mixing asphaltene-containing hydrocarbons with a metal compound such as aluminum carbonates or titanium (IV) oxide and also with a solvent such as n-heptane, n-hexane, n-heptane or a mixed n-pentane.n-butanol solvent, to form a mixture which is then allowed to stand still to precipitate and separate the asphaltene therefrom thereby obtaining a deasphalted oil.

  19. Process for the solvent deasphalting of asphaltene containing hydrocarbons

    SciTech Connect

    Ikematsu, M.; Honzyo, I.; Sakai, K.

    1985-04-30

    A process for the solvent deasphalting of asphaltene-containing hydrocarbons which comprising mixing asphaltene-containing hydrocarbons with a metal compound such as aluminum sulfate or titanium (IV) oxide and also with a solvent such as n-heptane, n-hexane, n-heptane or a mixed n-pentane.n-butanol solvent, to form a mixture which is then allowed to stand still to precipitate and separate the asphaltene therefrom thereby obtaining a deasphalted oil.

  20. Neuropathy associated with chronic low level exposure to n-hexane

    SciTech Connect

    Ruff, R.L.; Petito, C.K.; Acheson, L.S.

    1981-05-01

    Concentrations of n-hexane greater than the threshold limit value (TLV) of 500 ppm are known to produce peripheral neuropathy. This report describes the case of a worker who developed peripheral neuropathy, with a histologic pattern characteristic of n-hexane toxicity, after chronic on-the-job exposure to n-hexane at concentrations less than 450 ppm. We suggest that the current TLV for n-hexane be reevaluated.

  1. The simulation of organic rankine cycle power plant with n-pentane working fluid

    NASA Astrophysics Data System (ADS)

    Nurhilal, Otong; Mulyana, Cukup; Suhendi, Nendi; Sapdiana, Didi

    2016-02-01

    In the steam power plant in Indonesia the dry steam from separator directly used to drive the turbin. Meanwhile, brine from the separator with low grade temperature reinjected to the earth. The brine with low grade temperature can be converted indirectly to electrical power by organic Rankine cycle (ORC) methods. In ORC power plant the steam are released from vaporization of organic working fluid by brine. The steam released are used to drive an turbine which in connected to generator to convert the mechanical energy into electric energy. The objective of this research is the simulation ORC power plant with n-pentane as organic working fluid. The result of the simulation for brine temperature around 165°C and the pressure 8.001 bar optained the net electric power around 1173 kW with the cycle thermal efficiency 14.61% and the flow rate of n-pentane around 15.51 kg/s. This result enable to applied in any geothermal source in Indonesia.

  2. Ozone production by a dc corona discharge in air contaminated by n-heptane

    NASA Astrophysics Data System (ADS)

    Pekárek, S.

    2008-01-01

    Beneficial purposes of ozone such as elimination of odours, harmful bacteria and mildew can be used for transportation of food, fruits and vegetables with the aim to extend their storage life. To date the main technique used for this purpose in the transportation of these commodities, e.g. by trucks, was cooling. Here a combination of cooling together with the supply of ozone into containers with these commodities is considered. For these purposes we studied the effect of air contamination by n-heptane (part of automotive fuels) and humidity on ozone production by a dc hollow needle to mesh corona discharge. We found that, for both polarities of the needle electrode, addition of n-heptane to air (a) decreases ozone production; (b) causes discharge poisoning to occur at lower current than for air; (c) does not substantially influence the current for which the ozone production reaches the maximum. Finally the maximum ozone production for the discharge in air occurs for the same current as the maximum ozone production for the discharge contaminated by n-heptane. We also found that humidity decreases ozone production from air contaminated by n-heptane irrespective of the polarity of the coronating needle electrode. This dependence is stronger for the discharge with the needle biased positively.

  3. A model-free temperature-dependent conformational study of n-pentane in nematic liquid crystals

    NASA Astrophysics Data System (ADS)

    Burnell, E. Elliott; Weber, Adrian C. J.; Dong, Ronald Y.; Meerts, W. Leo; de Lange, Cornelis A.

    2015-01-01

    The proton NMR spectra of n-pentane orientationally ordered in two nematic liquid-crystal solvents are studied over a wide temperature range and analysed using covariance matrix adaptation evolutionary strategy. Since alkanes possess small electrostatic moments, their anisotropic intermolecular interactions are dominated by short-range size-and-shape effects. As we assumed for n-butane, the anisotropic energy parameters of each n-pentane conformer are taken to be proportional to those of ethane and propane, independent of temperature. The observed temperature dependence of the n-pentane dipolar couplings allows a model-free separation between conformer degrees of order and conformer probabilities, which cannot be achieved at a single temperature. In this way for n-pentane 13 anisotropic energy parameters (two for trans trans, tt, five for trans gauche, tg, and three for each of gauche+ gauche+, pp, and gauche+ gauche-, pm), the isotropic trans-gauche energy difference Etg and its temperature coefficient Etg ' are obtained. The value obtained for the extra energy associated with the proximity of the two methyl groups in the gauche+ gauche- conformers (the pentane effect) is sensitive to minute details of other assumptions and is thus fixed in the calculations. Conformer populations are affected by the environment. In particular, anisotropic interactions increase the trans probability in the ordered phase.

  4. Elucidating the key role of the fungal mycelium on the biodegradation of n-pentane as a model hydrophobic VOC.

    PubMed

    Vergara-Fernández, Alberto; Scott, Felipe; Moreno-Casas, Patricio; Díaz-Robles, Luis; Muñoz, Raúl

    2016-08-01

    The role of the aerial mycelium of the fungus Fusarium solani in the biodegradation of n-pentane was evaluated in a continuous fungal bioreactor (FB) to determine the contribution of the aerial (hyphae) and non-aerial (monolayer) fungal biomass. The experimental results showed that although the aerial biomass fraction represented only 25.9(±3)% on a dry weight basis, it was responsible for 71.6(±4)% of n-pentane removal. The FB attained a maximum elimination capacity (ECmax) of 680(±30) g m(-3) h(-1) in the presence of fungal hyphae (which supported an interfacial area of 5.5(±1.5) × 10(6) m(2) m(-3)). In addition, a mathematical model capable of describing n-pentane biodegradation by the filamentous fungus was also developed and validated against the experimental data. This model successfully predicted the influence of the aerial biomass fraction and its partition coefficient on the n-pentane removal, with EC decreasing from 680(±30) g m(-3) h(-1) to values of 200(±14) g m(-3) h(-1) when the dimensionless partition coefficient increased from 0.21(±0.09) with aerial biomass to 0.88(±0.06) without aerial biomass. PMID:27209557

  5. A model-free temperature-dependent conformational study of n-pentane in nematic liquid crystals

    SciTech Connect

    Burnell, E. Elliott; Weber, Adrian C. J.; Dong, Ronald Y.; Meerts, W. Leo; Lange, Cornelis A. de

    2015-01-14

    The proton NMR spectra of n-pentane orientationally ordered in two nematic liquid-crystal solvents are studied over a wide temperature range and analysed using covariance matrix adaptation evolutionary strategy. Since alkanes possess small electrostatic moments, their anisotropic intermolecular interactions are dominated by short-range size-and-shape effects. As we assumed for n-butane, the anisotropic energy parameters of each n-pentane conformer are taken to be proportional to those of ethane and propane, independent of temperature. The observed temperature dependence of the n-pentane dipolar couplings allows a model-free separation between conformer degrees of order and conformer probabilities, which cannot be achieved at a single temperature. In this way for n-pentane 13 anisotropic energy parameters (two for trans trans, tt, five for trans gauche, tg, and three for each of gauche{sub +} gauche{sub +}, pp, and gauche{sub +} gauche{sub −}, pm), the isotropic trans-gauche energy difference E{sub tg} and its temperature coefficient E{sub tg}{sup ′} are obtained. The value obtained for the extra energy associated with the proximity of the two methyl groups in the gauche{sub +} gauche{sub −} conformers (the pentane effect) is sensitive to minute details of other assumptions and is thus fixed in the calculations. Conformer populations are affected by the environment. In particular, anisotropic interactions increase the trans probability in the ordered phase.

  6. Asymptotic analysis with reduced chemistry for the burning of n-heptane droplets

    NASA Technical Reports Server (NTRS)

    Card, J. M.; Williams, F. A.

    1992-01-01

    The method of rate-ratio asymptotics is used with reduced chemistry to analyze the flame structure and extinction of an isolated n-heptane droplet burning under quasisteady, spherically symmetrical conditions. The outer transport zones are described by the classical Burke-Schumann solution. The inner reaction zone consists of a thin layer, on the rich side of the flame, where the fuel is consumed, and on the lean side, a broader but still asymptotically thin oxidation layer, where H2 and CO are consumed. Special attention is given to differences in predictions of extinction conditions, caused by different chemical-kinetic approximations in the reduced chemistry, including fuel-chemistry effects through molecules containing more than one carbon atom. From the analysis, extinction diameters for n-heptane droplets are estimated for different pressures and ambient oxygen concentrations. The results show that extinction diameters are extremely sensitive to the number of radicals consumed in breaking down each fuel molecule.

  7. Elasticity and phase behaviour of n-heptane and n-nonane in nanopores

    NASA Astrophysics Data System (ADS)

    Schappert, Klaus; Gemmel, Laura; Meisberger, Dennis; Pelster, Rolf

    2015-09-01

    Here we present an ultrasonic study on the elasticity of normal alkanes (n-heptane and n-nonane) in the nanopores of porous Vycor glass (average pore radius rP = 2.74 \\text{nm} ). Above the melting temperature we have found a non-zero shear modulus for both n-heptane and n-nonane, which is also typical for the rotator phases of bulk alkanes at temperatures below the melting temperature. This points to the formation of a special molecular order of the adsorbed alkanes. Furthermore, the alkanes undergo a continuous stiffening over a broad temperature range (of Δ T > 60 \\text{K} for heptane or Δ T > 120 \\text{K} for nonane). The results clearly indicate that nanoconfinement induces an extremely broad continuous transition of heptane and nonane into a crystalline low-temperature phase.

  8. Volume properties of reverse micellar systems AOT/ n-heptane/DMSO-water

    NASA Astrophysics Data System (ADS)

    Sargsyan, A. R.; Shahinyan, G. A.; Markarian, S. A.

    2014-05-01

    The volume properties of reverse micellar systems bis(2-ethylhexyl) sulfosuccinate sodium salt/ n-heptane/dimethyl sulfoxide-water are studied via densitometry. The presence of dimethyl sulfoxide and the increase in its amount in a dimethyl sulfoxide-water mixed solvent raise the apparent volume of the polar phase. This increase is also observed when the degree of hydration of the polar core and the temperature are raised.

  9. Electrical conductivity and permittivity of water-AOT-n-heptane microemulsions

    SciTech Connect

    Arcoleo, V.; Goffredi, M.; Liveri, V.T.

    1995-11-01

    Measurements of the electrical conductivity and of the complex permittivity of water-sodium bis(2-ethylhexyl) sulfosuccinate (AOT)-n-heptane microemulsions are reported. The experimental results are rationalized in terms of a hopping mechanism of AOT anions within clusters of reversed micelles. The dependence of the hopping rate and of the cluster dimensions upon the ratio [water]/[AOT] and temperature is discussed.

  10. Absorption and recovery of n-hexane in aqueous solutions of fluorocarbon surfactants.

    PubMed

    Xiao, Xiao; Yan, Bo; Fu, Jiamo; Xiao, Xianming

    2015-11-01

    n-Hexane is widely used in industrial production as an organic solvent. As an industrial exhaust gas, the contribution of n-hexane to air pollution and damage to human health are attracting increasing attention. In the present study, aqueous solutions of two fluorocarbon surfactants (FSN100 and FSO100) were investigated for their properties of solubilization and dynamic absorption of n-hexane, as well as their capacity for regeneration and n-hexane recovery by thermal distillation. The results show that the two fluorocarbon surfactants enhance dissolution and absorption of n-hexane, and their effectiveness is closely related to their concentrations in solution. For low concentration solutions (0.01%-0.30%), the partition coefficient decreases dramatically and the saturation capacity increases significantly with increasing concentration, but the changes for both are more modest when the concentration is over 0.30%. The FSO100 solution presents a smaller partition coefficient and a greater saturation capacity than the FSN100 solution at the same concentration, indicating a stronger solubilization for n-hexane. Thermal distillation is a feasible method to recover n-hexane from these absorption solutions, and to regenerate them. With 90sec heating at 80-85°C, the recovery of n-hexane ranges between 81% and 85%, and the regenerated absorption solution maintains its original performance during reuse. This study provides basic information on two fluorocarbon surfactants for application in the treatment of industrial n-hexane waste gases. PMID:26574100

  11. Distribution of pesticides in n-hexane/water and n-hexane/acetonitrile systems and estimation of possibilities of their extraction isolation and preconcentration from various matrices.

    PubMed

    Zayats, M F; Leschev, S M; Petrashkevich, N V; Zayats, M A; Kadenczki, L; Szitás, R; Szemán Dobrik, H; Keresztény, N

    2013-04-24

    Distribution of 150 most widely used pesticides of different chemical classes (amides, anilinopirimidines, aromatics, benzenesulfonates, carbamates, dicarboximides, organophosphorus compounds, phenyl esters, phenylureas, pyrazoles, pyrethroids, pyrimidines, strobilurins, sulfamides, triazines, triazoles, etc.) in n-hexane/water and n-hexane/acetonitrile systems was investigated at 25°C. Distribution constants of pesticides (P) have been calculated as ratio of pesticide concentration in n-hexane to its concentration in water or acetonitrile phase. HPLC and GC methods were used for pesticides determination in phases. It was found that the overwhelming majority of pesticides are hydrophobic, i.e. in n-hexane/water system LgP≫0, and the difference in LgP values can reach 9.1 units. Replacement of water for acetonitrile leads to dramatic fall of LgP values reaching 9.5 units. The majority of LgP values in this case are negative and their differences is strongly leveled in comparison with a hexane/water system. Thus, maximal difference in pesticides LgP values for n-hexane/acetonitrile system is 3.2 units. It is shown that n-hexane can be used for selective and efficient extraction and preconcentration of pesticides from water matrices. On the other hand, acetonitrile is effective for the isolation and preconcentration of pesticides from hydrocarbon and vegetable oil matrices. The distribution constants described in the paper may be effectively used for the estimation of possibilities of extraction isolation, preconcentration and separation of pesticides. PMID:23567114

  12. IRIS Toxicological Review and Summary Documents for N-Hexane (External Review Draft)

    EPA Science Inventory

    EPA's assessment of the noncancer health effects and carcinogenic potential of n-hexane was last prepared and added to the IRIS data base in 1990. The IRIS program is updating the IRIS assessment for n-hexane; this update will incorporate health effects information published sin...

  13. A numerical study of thermal and chemical effects in interactions of n-heptane flames with a single surface

    SciTech Connect

    Owston, Rebecca; Magi, Vinicio; Abraham, John

    2007-02-15

    The thermal and chemical effects of a one-dimensional, premixed flame quenching against a single surface are studied numerically. Fuels considered include n-heptane and molar-based mixtures of 95/5 and 70/30 percent n-heptane and hydrogen, respectively. A reduced gas-phase kinetic mechanism for n-heptane is employed. Wall boundary conditions investigated include both an adiabatic and an isothermal wall with temperatures ranging from 298 to 1200 K. The effects of equivalence ratio variations between 0.7 and 3 are investigated. The computations with n-heptane and n-heptane/hydrogen mixtures show that for wall temperatures greater than 400 K heat release rates have a higher value for the wall-interacting flame than for the freely propagating flame. It is also seen that the peak wall heat flux increases with increasing wall temperatures up to 1000 K. Chemical pathway analysis reveals the importance of radical recombination reactions at the surface to the heat release profiles of this study. The effect of H, O, and OH radical recombination near the inert wall is observed to lower the heat release spike on a 750 K isothermal boundary. The concentrations of intermediate hydrocarbons in the near-wall region are studied and related to unburned hydrocarbon formation in an engine cylinder. It is shown that a simple one-step global reaction rate expression for n-heptane fuel conversion cannot reproduce the flame-wall trends observed with the reduced n-heptane mechanism. (author)

  14. Experiments on combusion in reduced gravity and turbulent vaporization of n-heptane droplets

    NASA Astrophysics Data System (ADS)

    Gökalp, I.; Chauveau, C.; Monsallier, G.

    1990-01-01

    A Droplet Burning Facility which allows the investigation of droplet vaporization and burning under various dynamic and thermal conditions has been constructed. The system has been operated during the parabolic flights of the NASA KC135 aircraft. An important set of data has been collected on the low temperature turbulent vaporization and envelope burning of suspended n-heptane droplets at ground and reduced gravity conditions. From digitized images obtained by a rapid video camera, the time evolution of the droplet and the flame dimensions are determined with great accuracy. The information is used to deduce the vaporization rate constant, the flame diameter and the flame standoff ratio under various conditions.

  15. Experimental and modeling investigation of the low-temperature oxidation of n-heptane

    PubMed Central

    Herbinet, Olivier; Husson, Benoit; Serinyel, Zeynep; Cord, Maximilien; Warth, Valérie; Fournet, René; Glaude, Pierre-Alexandre; Sirjean, Baptiste; Battin-Leclerc, Frédérique; Wang, Zhandong; Xie, Mingfeng; Cheng, Zhanjun; Qi, Fei

    2013-01-01

    The low-temperature oxidation of n-heptane, one of the reference species for the octane rating of gasoline, was investigated using a jet-stirred reactor and two methods of analysis: gas chromatography and synchrotron vacuum ultra-violet photo-ionization mass spectrometry (SVUV-PIMS) with direct sampling through a molecular jet. The second method allowed the identification of products, such as molecules with hydroperoxy functions, which are not stable enough to be detected using gas chromatography. Mole fractions of the reactants and reaction products were measured as a function of temperature (500-1100K), at a residence time of 2s, at a pressure of 800 torr (1.06 bar) and at stoichiometric conditions. The fuel was diluted in an inert gas (fuel inlet mole fraction of 0.005). Attention was paid to the formation of reaction products involved in the low temperature oxidation of n-heptane, such as olefins, cyclic ethers, aldehydes, ketones, species with two carbonyl groups (diones) and ketohydroperoxides. Diones and ketohydroperoxides are important intermediates in the low temperature oxidation of n-alkanes but their formation have rarely been reported. Significant amounts of organic acids (acetic and propanoic acids) were also observed at low temperature. The comparison of experimental data and profiles computed using an automatically generated detailed kinetic model is overall satisfactory. A route for the formation of acetic and propanoic acids was proposed. Quantum calculations were performed to refine the consumption routes of ketohydroperoxides towards diones. PMID:23712100

  16. Statistical thermodynamics of the isomerization reaction between n-heptane and isoheptane.

    PubMed

    Yu, Tao; Zheng, Jingjing; Truhlar, Donald G

    2012-01-14

    We have employed electronic structure calculations and the recently proposed multi-structural (MS) anharmonicity method to calculate partition functions and thermodynamic quantities, in particular entropy and heat capacity, for n-heptane and isoheptane. We included all structures, of which there are 59 for n-heptane and 37 for isoheptane, and we carried out the calculations both in the local harmonic approximation and by including torsional (T) anharmonicity. In addition, ΔS°, ΔH, and ΔG° for the isomerization reaction between these two species were also calculated. It is found that all calculated thermodynamic quantities based on the MS-T approximation in the temperature range from 298 K to 1500 K agree well with experimental data from the American Petroleum Institute (API) tables or Thermodynamics Research Center (TRC) data series and with values obtained from Benson's empirical parameters fit to experiment. This demonstrates not only the high accuracy of the electronic structure calculations but also that the MS-T method can be used to include both multiple-structure anharmonicity and torsional anharmonicity in the calculation of thermodynamic properties for complex molecules that contain many torsions. It also gives us confidence that we can apply the MS-T statistical thermodynamic method to obtain thermodynamic properties (i) over a broader temperature range than that for which data are available in the API tables, TRC data series, or from empirical estimation and (ii) to the many molecules for which experimental data are not available at any temperature. PMID:22119933

  17. n-Hexane-related peripheral neuropathy among automotive technicians--California, 1999-2000.

    PubMed

    2001-11-16

    Solvents, glues, spray paints, coatings, silicones, and other products contain normal (n-) hexane, a petroleum distillate and simple aliphatic hydrocarbon. n-Hexane is an isomer of hexane and was identified as a peripheral neurotoxin in 1964. Since then, many cases of n-hexane-related neurotoxicity have occurred in printing plants, sandal shops, and furniture factories in Asia, Europe, and the United States. This report describes an investigation of n-hexane-associated peripheral neuropathy in an automotive technician, an occupation in which this condition has not been reported, and summarizes the results of two other case investigations in the automotive repair industry. The findings suggest that solvent manufacturers should avoid using hexane when producing automotive degreasing products, and automotive technicians should avoid regular contact with hexane-based cleaning solvents. PMID:11724159

  18. Rate-ratio asymptotic analysis of autoignition of n-heptane in laminar nonpremixed flows

    SciTech Connect

    Seshadri, K.; Peters, N.; Paczko, G.

    2006-07-15

    A rate-ratio asymptotic analysis is carried out to elucidate the mechanisms of autoignition of n-heptane (C{sub 7}H{sub 16}) in laminar, nonpremixed flows. It has been previously established that autoignition of n-heptane takes place in three distinct regimes. These regimes are called the low-temperature regime, the intermediate-temperature regime, and the high-temperature regime. The present analysis considers the high-temperature regime. A reduced chemical-kinetic mechanism made up of two global steps is used in the analysis. The reduced mechanism is deduced from a skeletal mechanism made up of 16 elementary reactions. The skeletal mechanism is derived from a short mechanism made up of 30 elementary reactions. The short mechanism is deduced from a detailed mechanism made up of 56 elementary reactions. In the reduced mechanism, the first global step represents a sequence of fast reactions starting from the rate-limiting elementary reaction between n-heptane and HO{sub 2}. In this global step C{sub 7}H{sub 16} is consumed and hydrogen peroxide (H{sub 2}O{sub 2}) is formed. The second global step represents a sequence of fast reactions starting from the rate-limiting elementary reaction in which H{sub 2}O{sub 2} is consumed and OH is formed. A key aspect of the second global step is that the sequence of fast reactions gives rise to consumption of fuel only without net consumption of H{sub 2}O{sub 2}. This makes the chemical system autocatalytic. The unsteady flamelet equations are used to predict the onset of autoignition. In the flamelet equations a conserved scalar quantity, Z, is used as the independent variable. On the oxidizer side of the mixing layer Z=0, and on the fuel side Z=1. The practical case where the temperature of the oxidizer stream, T{sub 2}, is much greater than the temperature of the fuel stream is considered. Therefore autoignition is presumed to take place close to Z=0. Balance equations are written for C{sub 7}H{sub 16} and H{sub 2}O{sub 2

  19. Microgravity combustion of isolated n-decane and n-heptane droplets

    NASA Technical Reports Server (NTRS)

    Choi, Mun Y.; Dryer, Frederick L.; Card, John M.; Williams, Forman A.; Haggard, John B.; Borowski, Brian A.

    1992-01-01

    This paper presents recent experimental results on n-heptane droplet combustion from a 5.0 second Zero-Gravity Facility. For these experiments, droplet sizes from 1 mm to 1.75 mm were studied, oxygen mole fractions in nitrogen ranged from 12 to 21 percent, and the pressure was varied from 0.25 to 1 atm. Disruptive burning mechanisms were observed in some of the experiments conducted in air environments. However, this behavior was inhibited by reducing the oxygen concentration and/or the system pressure. The above results suggest that combinations of lower oxygen indices and reduced ambient pressures are important to reducing the effects of sooting on droplet vaporization-rates.

  20. Phase equilibrium of sodium bis(2-ethylhexyl) phosphate/water/n-heptane/sodium chloride microemulsion

    SciTech Connect

    Shioi, Akihisada; Harada, Makoto; Matsumoto, Keishi )

    1991-09-19

    The microemulsion phase diagram for the sodium bis(2-ethylhexyl) phosphate (SDEHP)/water/n-heptane/sodium chloride system is reported. The salinity effects on the phase diagram are discussed in detail. Cylindrical aggregates were found to exist in the oil-rich region and disklike aggregates in the brine-rich region. The middle-phase microemulsion in equilibrium with both the excess brine and oil phases was concluded to be composed of these microstructures. Sodium bis(2-ethylhexyl) phosphate has a common hydrocarbon tail with sodium bis(2-ethylhexyl) sulfosuccinate (AOT), but the phase equilibrium and the structures of the microemulsion phases in SDEHP system were much different from those in the AOT case. The differences were attributed to those in the shapes of aggregates for the two cases.

  1. Spray evaporation and dispersion of n-heptane droplets within premixed flame

    NASA Astrophysics Data System (ADS)

    Chrigui, Mouldi; Zghal, Ali; Sadiki, Amsini; Janicka, Johannes

    2010-10-01

    A detailed numerical simulation of n-heptane droplets was carried out on a stationary three-dimensional configuration with complex geometry. The investigations focused on spray evaporation and dispersion within a carrier phase that featured operating conditions similar to those found in industrial applications, i.e. elevated pressure and temperature. The simulations were carried out using the Eulerian-Lagrangian approach with two-way coupling. There were two cases. The first dealt with spray characteristics within the preheated carrier phase without considering combustion. The second investigated the influence of combustion on droplet characteristics. Both cases had the same boundary conditions. The numerical simulations used two models to compute the progress variable mean reaction rate that governs the combustion process, which is captured by the Bray-Moss-Libby model.

  2. Measurement of asphaltene particle size distributions in crude oils diluted with n-heptane

    SciTech Connect

    Ferworn, K.A.; Svrcek, W.Y.; Mehrotra, A.K. )

    1993-05-01

    The formation and growth of asphaltene particles from heavy crude oils diluted with n-heptane at 22 C and atmospheric pressure was studied using a laser particle analyzer. The results obtained with six crude oil samples indicate that the asphaltene precipitation is an instantaneous process leading to a unimodal, log-normal distribution. At typical laboratory conditions, the particles remained essentially unaltered in size and population density. A vast majority of the particles were noted to be far from round in shape, with the mean particle size ranging from 4.5 to 291 [mu]m. It was found that the oil-to-diluent ratio is an important parameter in determining the size of the generated asphaltene particles; higher dilution ratios yielded larger particles. The mean asphaltene particle size was also found to increase with the average molar mass and the asphaltene content of crude oils.

  3. Quasi-isochoric pπT measurements and second virial coefficient of n-heptane

    NASA Astrophysics Data System (ADS)

    Millat, J.; Hendl, H.; Bich, E.

    1994-09-01

    Quasi-isochoric pπT measurements on n-heptane vapor were carried out in the low density region using an improved apparatus that was originally proposed by Opel and Schaffenger ( Wiss. Z. Univ. Rostock N18:871, 1969). The experimental results extend over the temperature range between 350 and 600 K and the density range between 11.5 and 52.2 mol · m-3. Above 473 K a small but significant influence of decomposition was found. Accordingly, a correction scheme assuming a trace of decomposition products was applied to these data. Second virial coefficients were derived with an assumed maximum uncertainty of ±3%.. The results are compared with others in the literature and used to develop an improved correlation function for the temperature dependence of B( T).

  4. Some Recent Observations on the Burning of Isolated N-Heptane and Alcohol Droplets

    NASA Technical Reports Server (NTRS)

    Dryer, F. L.; Kazakov, A.; Urban, B. D.

    2001-01-01

    In a joint program involving Prof. F.A. Williams of the University of California, San Diego and Dr. V. Nayagam of the National Center for Microgravity Research on Combustion and Fluid Dynamics, the combustion of liquid fuel droplets of n-heptane, n-decane, methanol, methanol-water, ethanol and ethanol-water having initial diameters between about 1 mm and 6 mm continues to be studied. The objectives of the work are to improve fundamental knowledge of droplet combustion dynamics for pure fuels and fuel-water mixtures through microgravity experiments and theoretical analyses. The Princeton contributions to the collaborative program supports the engineering design, data analysis, and data interpretation requirements for the study of initially single component, spherically symmetric, isolated droplet combustion studies through experiments and numerical modeling. The complementary UCSD contributions apply asymptotic theoretical analyses and are described in the published literature and in a companion communication in this conference. The combined program continues to focus on analyses of results obtained from Fiber Supported Droplet Combustion (FSDC) experiments (FSDC-2, STS- 94) conducted with the above fuels in shuttle cabin air and Droplet Combustion Experiment (DCE) data obtained for unsupported and fiber supported droplets of n-heptane in Helium-Oxygen mixtures and cabin air (STS-83, STS-94). The program is preparing for a second DCE experimental mission using methanol/methanol-water as fuels and helium-oxygen-nitrogen environments. DCE-2 is to be conducted aboard the International Space Station. Emphases of recent Princeton work are on the study of simple alcohols (methanol, ethanol) and alcohol/water mixtures as fuels, with time-dependent measurements of drop size, flame-standoff, liquid-phase composition, and finally, extinction. Ground based experiments have included bench-scale studies at Princeton and collaborative experimental studies in the 2.2 second drop

  5. EFFECTS OF EQUIVALENCE RATIO ON SPECIES AND SOOT CONCENTRATIONS IN PREMIXED N-HEPTANE FLAMES. (R828193)

    EPA Science Inventory

    The micro-structure of laminar premixed, atmospheric-pressure, fuel-rich flames of n-heptane/oxygen/argon has been studied at two equivalence ratios (C/O = 0.63 and C/O = 0.67). A heated quartz microprobe coupled to an online gas chromatography/mass spectrometry (HP 5890 Serie...

  6. An Experimental Study of n-Heptane and JP-7 Extinction Limits in an Opposed Jet Burner

    NASA Technical Reports Server (NTRS)

    Convery, Janet L.; Pellett, Gerald L.; O'Brien, Walter F., Jr.; Wilson, Lloyd G.; Williams, John

    2005-01-01

    Propulsion engine combustor design and analysis requires experimentally verified data on the chemical kinetics of fuel. Among the important data is the combustion extinction limit as measured by observed maximum flame strain rate. The extinction limit relates to the ability to maintain a flame in a combustor during operation. Extinction limit data can be obtained for a given fuel by means of a laminar flame experiment using an opposed jet burner (OJB). Laminar extinction limit data can be applied to the turbulent application of a combustor via laminar flamelet modeling. The OJB consists of two axi-symmetric tubes (one for fuel and one for oxidizer), which produce a flat, disk-like counter-flow diffusion flame. This paper presents results of experiments to measure extinction limits for n-heptane and the military specification fuel JP-7, obtained from an OJB. JP-7 is an Air Force-developed fuel that continues to be important in the area of hypersonics. Because of its distinct properties it is currently the hydrocarbon fuel of choice for use in Scramjet engines. This study provides much-desired data for JP-7, for which very little information previously existed. The interest in n-heptane is twofold. First, there has been a significant amount of previous extinction limit study and resulting data with this fuel. Second, n-heptane (C7H16) is a pure substance, and therefore does not vary in composition as does JP-7, which is a mixture of several different hydrocarbons. These two facts allow for a baseline to be established by comparing the new OJB results to those previously taken. Additionally, the data set for n-heptane, which previously existed for mixtures up to 26 mole percent in nitrogen, is completed up to 100% n-heptane. The extinction limit data for the two fuels are compared, and complete experimental results are included.

  7. Selective Oxidation of n-Hexane by Cu (II) Nanoclusters Supported on Nanocrystalline Zirconia Catalyst.

    PubMed

    Acharyya, Shankha Shubhra; Ghosh, Shilpi; Adak, Shubhadeep; Singh, Raghuvir; Saran, Sandeep; Bal, Rajaram

    2015-08-01

    Cu (II) nanoclusters supported on nanocrystalline zirconia catalyst (with size ~15 nm), was prepared by using cationic surfactant cetyltrimethylammonium in a hydrothermal synthesis method. The catalyst was characterized by XRD, XPS, TGA, SEM, TEM, FTIR and ICP-AES. The catalyst was found to be efficient in selective oxidation of n-hexane to 2-hexanol. An n-hexane conversion of 55%, with a 2-hexanol selectivity of 70% was achieved over this catalyst in liquid phase, without the use of any solvent. The catalyst can be reused several times without any significant activity loss. PMID:26369156

  8. Cloning of organic solvent tolerance gene ostA that determines n-hexane tolerance level in Escherichia coli.

    PubMed Central

    Aono, R; Negishi, T; Nakajima, H

    1994-01-01

    A variety of genes are involved in determining the level of organic solvent tolerance of Escherichia coli K-12. Gene ostA is one of the genes contributing to the level of organic solvent tolerance. This gene was cloned from an n-hexane-tolerant strain of E. coli, JA300. A JA300-based n-hexane-sensitive strain, OST4251, was converted to the n-hexane-tolerant phenotype by transformation with DNA containing the ostA gene derived from JA300. Thus, the cloned ostA gene complemented the n-hexane-sensitive phenotype of OST4251. Images PMID:7811102

  9. Investigation of Y/SBA Composite Molecular Sieves Morphology Control and Catalytic Performance for n-Pentane Aromatization.

    PubMed

    Shi, Chun-Wei; Wu, Wen-Yuan; Li, Shuai; Bian, Xue; Zhao, Shan-Lin; Pei, Ming-Yuan

    2016-01-01

    Using Y molecular sieve as the core, Y/SBA-15 composite molecular sieves were prepared by different crystallization methods in the paper. The growth process and morphologies of the composite molecular sieves were controlled by adjusting the synthesis factors. The structures and acidity of two kinds of composite molecular sieves were characterized by X-ray diffraction (XRD), N2 adsorption/desorption, transmission electron microscopy (TEM), and NH3-TPD. The catalysis performances of the composite molecular sieves were investigated in the aromatization reaction of n-pentane. The results indicated that the desired core-shell composite molecular sieves were obtained when the crystallization conditions were 36 hours, 100 °C and secondary crystallization. The aromatization results showed that core-shell composite molecular sieves had better selectivity for producing high application value xylenes compared to mixed-crystal composite molecular sieves. PMID:27029526

  10. Effects of temperature and pressure on asphaltene particle size distributions in crude oils diluted with n-pentane

    SciTech Connect

    Nielsen, B.B.; Svrcek, W.Y.; Mehrotra, A.K. . Dept. of Chemical and Petroleum Engineering)

    1994-05-01

    The effects of temperature (0--150 C) and pressure (0--5.6 MPa) on the size distribution of asphaltene particles (or agglomerates), formed as a result of diluting the crude oils with n-pentane, were studied using a modified laser particle analyzer. Four crude oils, ranging from an asphaltic condensate to a heavy oil-sand bitumen, were tested in this investigation. The average size of asphaltene agglomerates ranged from 266 to 495 Am. The results suggest that the mean asphaltene particle size increases with pressure and decreases slightly with temperature; however, no trends were evident with the molar mass of crude oils. Although the particle size distributions in most cases were unimodal and described adequately by the log-normal distribution function, bimodal distributions were also identified in certain cases.

  11. Investigation of Y/SBA Composite Molecular Sieves Morphology Control and Catalytic Performance for n-Pentane Aromatization

    PubMed Central

    Shi, Chun-Wei; Wu, Wen-Yuan; Li, Shuai; Bian, Xue; Zhao, Shan-lin; Pei, Ming-Yuan

    2016-01-01

    Using Y molecular sieve as the core, Y/SBA-15 composite molecular sieves were prepared by different crystallization methods in the paper. The growth process and morphologies of the composite molecular sieves were controlled by adjusting the synthesis factors. The structures and acidity of two kinds of composite molecular sieves were characterized by X-ray diffraction (XRD), N2 adsorption/desorption, transmission electron microscopy (TEM), and NH3-TPD. The catalysis performances of the composite molecular sieves were investigated in the aromatization reaction of n-pentane. The results indicated that the desired core-shell composite molecular sieves were obtained when the crystallization conditions were 36 hours, 100 °C and secondary crystallization. The aromatization results showed that core-shell composite molecular sieves had better selectivity for producing high application value xylenes compared to mixed-crystal composite molecular sieves. PMID:27029526

  12. Numerical investigation of kinetic energy dynamics during autoignition of n-heptane/air mixture

    NASA Astrophysics Data System (ADS)

    Lucena Kreppel Paes, Paulo; Brasseur, James; Xuan, Yuan

    2015-11-01

    Many engineering applications involve complex turbulent reacting flows, where nonlinear, multi-scale turbulence-combustion couplings are important. Direct representation of turbulent reacting flow dynamics is associated with prohibitive computational costs, which makes it necessary to employ turbulent combustion models to account for the effects of unresolved scales on resolved scales. Classical turbulence models are extensively employed in reacting flow simulations. However, they rely on assumptions about the energy cascade, which are valid for incompressible, isothermal homogeneous isotropic turbulence. A better understanding of the turbulence-combustion interactions is required for the development of more accurate, physics-based sub-grid-scale models for turbulent reacting flows. In order to investigate the effects of reaction-induced density, viscosity, and pressure variations on the turbulent kinetic energy, Direct Numerical Simulation (DNS) of autoignition of partially-premixed, lean n-heptane/air mixture in three-dimensional homogeneous isotropic turbulence has been performed. This configuration represents standard operating conditions of Homogeneous-Charge Compression-Ignition (HCCI) engines. The differences in the turbulent kinetic energy balance between the present turbulent reacting flow and incompressible, isothermal homogeneous isotropic turbulence are highlighted at different stages during the autoignition process.

  13. Direct numerical simulation of ignition in turbulent n-heptane liquid-fuel spray jets

    SciTech Connect

    Wang, Y.; Rutland, C.J.

    2007-06-15

    Direct numerical simulation was used for fundamental studies of the ignition of turbulent n-heptane liquid-fuel spray jets. A chemistry mechanism with 33 species and 64 reactions was adopted to describe the chemical reactions. The Eulerian method is employed to solve the carrier-gas flow field and the Lagrangian method is used to track the liquid-fuel droplets. Two-way coupling interaction is considered through the exchange of mass, momentum, and energy between the carrier-gas fluid and the liquid-fuel spray. The initial carrier-gas temperature was 1500 K. Six cases were simulated with different droplet radii (from 10 to 30 {mu}m) and two initial velocities (100 and 150 m/s). From the simulations, it was found that evaporative cooling and turbulence mixing play important roles in the ignition of liquid-fuel spray jets. Ignition first occurs at the edges of the jets where the fuel mixture is lean, and the scalar dissipation rate and the vorticity magnitude are very low. For smaller droplets, ignition occurs later than for larger droplets due to increased evaporative cooling. Higher initial droplet velocity enhances turbulence mixing and evaporative cooling. For smaller droplets, higher initial droplet velocity causes the ignition to occur earlier, whereas for larger droplets, higher initial droplet velocity delays the ignition time. (author)

  14. Giant rodlike reversed micelles formed by sodium bis(2-ethylhexyl) phosphate in n-heptane

    SciTech Connect

    Yu, Z.J.; Neuman, R.D. )

    1994-08-01

    The solution behaviors of sodium bis(2-ethylhexyl) phosphate (NaDEHP) in n-heptane were investigated by light-scattering and viscosity measurements. NaDEHP forms giant rodlike reversed micelles, with a radius of gyration as large as 53 nm, which violently contrasts with the literature view that the average micellar aggregation numbers in nonaqueous or apolar media are much smaller (seldom exceeding 20) than those in aqueous media. Significantly, a small amount of water plays the role of an antimicellar growth agent; i.e., the reversed micellar size decreases remarkably when [open quotes]dry[close quotes] solutions are exposed to humid air from which water vapor is absorbed or when bulk water is directly added - a behavior which is distinctly opposite to that for sodium bis(2-ethylhexyl) sulfosuccinate/apolar medium systems. Thus, the literature views that large micelles can only be found in aqueous media and that the surfactant headgroups in reversed micelles are linked together by hydrogen bonds are misleading. It is suggested that the primary contribution to the driving force for the growth of rodlike NaDEHP reversed micelles is long-range electrostatic interactions among the headgroups of the surfactant molecules and their counterions, and a possible mechanism for the effect of water is also discussed. 27 refs., 7 figs., 1 tab.

  15. Development of a reduced n-heptane oxidation mechanism for HCCI combustion modeling

    SciTech Connect

    Maroteaux, F.; Noel, L.

    2006-07-15

    Homogeneous charge compression ignition (HCCI) is one of the alternatives to reduce significantly engine emissions for future regulations. This new alternative combustion process is mainly controlled by chemical kinetics in comparison with the conventional combustion in internal combustion engines. The optimization of the engine over the complete engine operation range requires an accurate analysis of the combustion process under all operating conditions; detailed modeling of the HCCI process is an opportunity to realize the engine optimization at lower cost. The combination of CFD computations with detailed chemistry leads to excessive computation times, and is not achievable with current computer capabilities. In this paper, a reduced chemical model for n-heptane is described, in view of its implementation into a CFD simulation code. In the first part, the reduction process to get to the 61-step mechanism is detailed and then the 26-step mechanism is described; this further reduction is carried out under various conditions that include a range of interest in engine applications. The third part is dedicated to extensive validation work in reference to the original detailed mechanism and two reduced mechanisms published in the literature, focusing on the prediction of ignition delay times under constant as well as variable volume conditions. A good and accurate reproduction of both ignition delay times and heat release can be reached with the 26-step model. (author)

  16. Process for the solvent deasphalting of asphaltene-containing hydrocarbons

    SciTech Connect

    Ikematsu, M.; Honzyo, I.; Sakai, K.

    1985-03-05

    A continuous process for solvent deasphalting asphaltene-containing hydrocarbons which comprises mixing (A) 100 parts by weight of asphaltene-containing hydrocarbons with (B) 0.005-0.5 parts by weight of an amorphous silicon dioxide and/or a silicate compound and also with (C) 5-2000 parts by weight of a solvent such as n-heptane, n-hexane, n-heptane or a mixed n-pentane.n-butanol solvent, to form a mixture which is then allowed to stand still to precipitate and separate the asphaltene therefrom thereby obtaining a deasphalted oil.

  17. Kinetic modeling of autoignition of higher hydrocarbons: n-heptane, n-octane and iso-octane

    SciTech Connect

    Westbrook, C.K.; Pitz, W.J.

    1986-08-01

    In the present paper, the construction of reaction mechanisms for larger fuel molecules is described, drawing heavily on experience and trends established in previous studies of smaller fuel molecules. Sensitivity analysis shows which classes of reaction steps are likely to have the greatest influence on computed results and for which additional experimental information is needed. This process is illustrated for the cases of n-heptane, n-octane, and iso-octane. N-heptane and iso-octane are of interest since they are the reference fuels defining octane number, having octane numbers of 0 and 100, respectively. N-octane is included since it can be compared with n-heptane to illustrate the importance of fuel molecule size with the structure unchanged, and it can be compared with iso-octane to show the influence of molecular structure with molecular size unchanged. Computed results under shock tube and under internal combustion engine conditions will be described to demonstrate how initial pressure, temperature, fuel type, fuel structure, and other important parameters affect the rates of autoignition. These differences will be interpreted in terms of the detailed kinetic reaction mechanism, and strategies for modifying autoignition rates will be discussed. 27 refs., 4 figs., 1 tab.

  18. Fischer-Tropsch synthesis in near-critical n-hexane: Pressure-tuning effects

    SciTech Connect

    Bochniak, D.J.; Subramaniam, B.

    1998-08-01

    For Fe-catalyzed Fischer-Tropsch (FT) synthesis with near-critical n-hexane (P{sub c} = 29.7 bar; T{sub c} = 233.7 C) as the reaction medium, isothermal pressure tuning from 1.2--2.4 P{sub c} (for n-hexane) at the reaction temperature (240 C) significantly changes syngas conversion and product selectivity. For fixed feed rates of syngas (H{sub 2}/CO = 0.5; 50 std. cm{sup 3}/g catalyst) and n-hexane (1 mL/min), syngas conversion attains a steady state at all pressures, increasing roughly threefold in this pressure range. Effective rate constants, estimated assuming a first-order dependence of syngas conversion on hydrogen, reveal that the catalyst effectiveness increases with pressure implying the alleviation of pore-diffusion limitations. Pore accessibilities increase at higher pressures because the extraction of heavier hydrocarbons from the catalyst pores is enhanced by the liquid-like densities, yet better-than-liquid transport properties, of n-hexane. This explanation is consistent with the single {alpha} (= 0.78) Anderson-Schulz-Flory product distribution, the constant chain termination probability, and the higher primary product (1-olefin) selectivities ({approximately}80%) observed at the higher pressures. Results indicate that the pressure tunability of the density and transport properties of near-critical reaction media offers a powerful tool to optimize catalyst activity and product selectivity during FT reactions on supported catalysts.

  19. Communication: Molecular dynamics and {sup 1}H NMR of n-hexane in liquid crystals

    SciTech Connect

    Weber, Adrian C. J.; Burnell, E. Elliott; Meerts, W. Leo; Lange, Cornelis A. de; Dong, Ronald Y.; Muccioli, Luca Pizzirusso, Antonio Zannoni, Claudio

    2015-07-07

    The NMR spectrum of n-hexane orientationally ordered in the nematic liquid crystal ZLI-1132 is analysed using covariance matrix adaptation evolution strategy (CMA-ES). The spectrum contains over 150 000 transitions, with many sharp features appearing above a broad, underlying background signal that results from the plethora of overlapping transitions from the n-hexane as well as from the liquid crystal. The CMA-ES requires initial search ranges for NMR spectral parameters, notably the direct dipolar couplings. Several sets of such ranges were utilized, including three from MD simulations and others from the modified chord model that is specifically designed to predict hydrocarbon-chain dipolar couplings. In the end, only inaccurate dipolar couplings from an earlier study utilizing proton-proton double quantum 2D-NMR techniques on partially deuterated n-hexane provided the necessary estimates. The precise set of dipolar couplings obtained can now be used to investigate conformational averaging of n-hexane in a nematic environment.

  20. KINETICS AND SELECTIVITY OF DEEP CATALYTIC OXIDATION OF N-HEXANE AND BENZENE

    EPA Science Inventory

    Deep (complete) catalytic combustion (oxidation) of volatile organic compounds (VOCs) is emerging as an important emission control technique. A fundamental study was carried out for low-temperature deep oxidation of n-hexane and benzene over a 0.1% Pt, 3% Ni/gamma-Al2O3 catalyst....

  1. A Model of Reduced Kinetics for Alkane Oxidation Using Constituents and Species for N-Heptane

    NASA Technical Reports Server (NTRS)

    Harstad, Kenneth G.; Bellan, Josette

    2011-01-01

    The reduction of elementary or skeletal oxidation kinetics to a subgroup of tractable reactions for inclusion in turbulent combustion codes has been the subject of numerous studies. The skeletal mechanism is obtained from the elementary mechanism by removing from it reactions that are considered negligible for the intent of the specific study considered. As of now, there are many chemical reduction methodologies. A methodology for deriving a reduced kinetic mechanism for alkane oxidation is described and applied to n-heptane. The model is based on partitioning the species of the skeletal kinetic mechanism into lights, defined as those having a carbon number smaller than 3, and heavies, which are the complement of the species ensemble. For modeling purposes, the heavy species are mathematically decomposed into constituents, which are similar but not identical to groups in the group additivity theory. From analysis of the LLNL (Lawrence Livermore National Laboratory) skeletal mechanism in conjunction with CHEMKIN II, it is shown that a similarity variable can be formed such that the appropriately non-dimensionalized global constituent molar density exhibits a self-similar behavior over a very wide range of equivalence ratios, initial pressures and initial temperatures that is of interest for predicting n-heptane oxidation. Furthermore, the oxygen and water molar densities are shown to display a quasi-linear behavior with respect to the similarity variable. The light species ensemble is partitioned into quasi-steady and unsteady species. The reduced model is based on concepts consistent with those of Large Eddy Simulation (LES) in which functional forms are used to replace the small scales eliminated through filtering of the governing equations; in LES, these small scales are unimportant as far as the overwhelming part of dynamic energy is concerned. Here, the scales thought unimportant for recovering the thermodynamic energy are removed. The concept is tested by

  2. Some Recent Observations on the Burning of Isolated N-Heptane and Alcohol Droplets

    NASA Technical Reports Server (NTRS)

    Dryer, F. L.

    1999-01-01

    In a joint program involving Prof F.A. Williams of the University of California, San Diego and Dr. Vedha Nayagam of the National Center for Microgravity Research on Fluid and Combustion, the combustion of liquid fuel droplets having initial diameters between about 1 mm and 6 mm is being studied. The objectives of the work are to improve fundamental knowledge of droplet combustion dynamics through microgravity experiments and theoretical analyses. The Princeton contributions to the collaborative program supports the engineering design, data analysis, and data interpretation requirements for the study of initially single component, spherically symmetric, isolated droplet combustion studies through experiments and numerical modeling. The complementary UCSD contributions apply asymptotic theoretical analyses and are described in the published literature and in a companion communication in this volume. Emphases of the Princeton work are on the study of simple alcohols (methanol, ethanol), alcohol/water mixtures, and pure alkanes (n-heptane, n-decane) as fuels, with time dependent measurements of drop size, flame-stand-off, liquid-phase composition, and finally, extinction. Ground based experiments have included bench-scale studies at Princeton and collaborative experimental studies in the 2.2 and 5.18 second drop towers at NASA-Glenn Research Center. Spacelab studies have included fiber-supported droplet combustion (FSDC) experiments in the Glovebox facility with accompanying numerical analyses. Experiments include FSDC-1, performed on the USML-2 mission in October, 1995 (STS-73) and FSDC-2, on the second flight of the MSL-1 mission in July, 1997 (STS-94).

  3. Monte Carlo versus molecular dynamics simulations in heterogeneous systems: an application to the n-pentane liquid-vapor interface.

    PubMed

    Goujon, Florent; Malfreyt, Patrice; Simon, Jean-Marc; Boutin, Anne; Rousseau, Bernard; Fuchs, Alain H

    2004-12-22

    The Monte Carlo (MC) and molecular dynamics (MD) methodologies are now well established for computing equilibrium properties in homogeneous fluids. This is not yet the case for the direct simulation of two-phase systems, which exhibit nonuniformity of the density distribution across the interface. We have performed direct MC and MD simulations of the liquid-gas interface of n-pentane using a standard force-field model. We obtained density and pressure components profiles along the direction normal to the interface that can be very different, depending on the truncation and long range correction strategies. We discuss the influence on predicted properties of different potential truncation schemes implemented in both MC and MD simulations. We show that the MD and MC profiles can be made in agreement by using a Lennard-Jones potential truncated via a polynomial function that makes the first and second derivatives of the potential continuous at the cutoff distance. In this case however, the predicted thermodynamic properties (phase envelope, surface tension) deviate from experiments, because of the changes made in the potential. A further readjustment of the potential parameters is needed if one wants to use this method. We conclude that a straightforward use of bulk phase force fields in MD simulations may lead to some physical inconsistencies when computing interfacial properties. PMID:15606277

  4. Effect of Pressure on Absorption Spectra of Lycopene in n-Hexane and CS2 Solvents

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Liu, Wei-Long; Zheng, Zhi-Ren; Huo, Ming-Ming; Li, Ai-Hua; Yang, Bin

    2010-01-01

    The absorption spectra of lycopene in n-hexane and CS2 are measured under high pressure and the results are compared with β-carotene. In the lower pressure range, the deviation from the linear dependence on the Bayliss parameter (BP) for β-carotene is more visible than that for lycopene. With the further increase of the solvent BP, the 0-0 bands of lycopene and β-carotene red shift at almost the same rate in n-hexane; however, the 0-0 band of lycopene red shifts slower than that of β-carotene in CS2. The origins of these diversities are discussed taking into account the dispersion interactions and structures of solute and solvent molecules.

  5. Inhibition of residual n-hexane in anaerobic digestion of lipid-extracted microalgal wastes and microbial community shift.

    PubMed

    Yun, Yeo-Myeong; Shin, Hang-Sik; Lee, Chang-Kyu; Oh, You-Kwan; Kim, Hyun-Woo

    2016-04-01

    Converting lipid-extracted microalgal wastes to methane (CH4) via anaerobic digestion (AD) has the potential to make microalgae-based biodiesel platform more sustainable. However, it is apparent that remaining n-hexane (C6H14) from lipid extraction could inhibit metabolic pathway of methanogens. To test an inhibitory influence of residual n-hexane, this study conducted a series of batch AD by mixing lipid-extracted Chlorella vulgaris with a wide range of n-hexane concentration (∼10 g chemical oxygen demand (COD)/L). Experimental results show that the inhibition of n-hexane on CH4 yield was negligible up to 2 g COD/L and inhibition to methanogenesis became significant when it was higher than 4 g COD/L based on quantitative mass balance. Inhibition threshold was about 4 g COD/L of n-hexane. Analytical result of microbial community profile revealed that dominance of alkane-degrading sulfate-reducing bacteria (SRB) and syntrophic bacteria increased, while that of methanogens sharply dropped as n-hexane concentration increased. These findings offer a useful guideline of threshold n-hexane concentration and microbial community shift for the AD of lipid-extracted microalgal wastes. PMID:25966884

  6. Experimental study and chemical analysis of n-heptane homogeneous charge compression ignition combustion with port injection of reaction inhibitors

    SciTech Connect

    Lue, Xingcai; Ji, Libin; Zu, Linlin; Hou, Yuchun; Huang, Cheng; Huang, Zhen

    2007-05-15

    The control of ignition timing in the homogeneous charge compression ignition (HCCI) of n-heptane by port injection of reaction inhibitors was studied in a single-cylinder engine. Four suppression additives, methanol, ethanol, isopropanol, and methyl tert-butyl ether (MTBE), were used in the experiments. The effectiveness of inhibition of HCCI combustion with various additives was compared under the same equivalence ratio of total fuel and partial equivalence ratio of n-heptane. The experimental results show that the suppression effectiveness increases in the order MTBE < isopropanol << ethanol < methanol. But ethanol is the best additive when the operating ranges, indicated thermal efficiency, and emissions are considered. For ethanol/n-heptane HCCI combustion, partial combustion may be observed when the mole ratio of ethanol to that of total fuel is larger than 0.20; misfires occur when the mole ratio of ethanol to that of total fuel larger than 0.25. Moreover, CO emissions strongly depend on the maximum combustion temperature, while HC emissions are mainly dominated by the mole ratio of ethanol to that of total fuel. To obtain chemical mechanistic informations relevant to the ignition behavior, detailed chemical kinetic analysis was conducted. The simulated results also confirmed the retarding of the ignition timing by ethanol addition. In addition, it can be found from the simulation that HCHO, CO, and C{sub 2}H{sub 5}OH could not be oxidized completely and are maintained at high levels if the partial combustion or misfire occurs (for example, for leaner fuel/air mixture). (author)

  7. Inhalation developmental toxicology studies: Teratology study of n-hexane in rats: Final report

    SciTech Connect

    Mast, T.J.

    1987-12-01

    The straight chain hydrocarbon, n-hexane, is a volatile, ubiquitous solvent used in industrial, academic, and smaller commercial environments. The significant opportunity for women of child-bearing age to be exposed to this chemical prompted the undertaking of a study to assess the developmental toxicity of n-hexane in an animal model. Timed-pregnant (30 animals per group) and virgin (10 animals per group) Sprague-Dawley rats were exposed to 0 (filtered air), 200, 1000, and 5000 ppM n-hexane (99.9% purity) vapor in inhalation chambers for 20 h/day for a period of 14 consecutive days. Sperm-positive females were exposed for 6 to 19 days of gestation (dg) and virgins were exposed concurrently for 14 consecutive days. The day of sperm detection was designated as 0 dg for mated females. Adult female body weights were monitored prior to, throughout the exposure period, and at sacrifice. Uterine, placental, and fetal body weights were obtained for gravid females at sacrifice. Implants were enumerated and their status recorded as live fetus, early or late resorption, or dead. Live fetuses were sexed and examined for gross, visceral, skeletal, and soft-tissue craniofacial defects. 16 refs., 3 figs., 7 tabs.

  8. Inhalation developmental toxicology studies: Teratology study of n-hexane in mice: Final report

    SciTech Connect

    Mast, T.J.; Decker, J.R.; Stoney, K.H.; Westerberg, R.B.; Evanoff, J.J.; Rommereim, R.L.; Weigel, R.J.

    1988-05-01

    Gestational exposure to n-hexane resulted in an increase in the number of resorbed fetuses for exposure groups relative to the control group; however, the increases were not directly correlated to exposure concentration. The differences were statistically significant for the 200-ppM with respect to total intrauterine death (early plus late resorptions), and with respect to late resorptions for the 5000-ppM group. A small, but statistically significant, reduction in female (but not male) fetal body weight relative to the control group was observed at the 5000-ppM exposure level. There were no exposure-related increases in any individual fetal malformation or variation, nor was there any increase in the incidence of combined malformations or variations. Gestational exposure of CD-1 mice to n-hexane vapors appeared to cause a degree of concentration-related developmental toxicity in the absence of overt maternal toxicity, but the test material was not found to be teratogenic. This developmental toxicity was manifested as an increase in the number of resorptions per litter for all exposure levels, and as a decrease in the uterine: extra-gestational weight gain ratio at the 5000-ppM exposure level. Because of the significant increase in the number of resorptions at the 200-ppM exposure level, a no observable effect level (NOEL) for developmental toxicity was not established for exposure of mice to 200, 1000 or 5000-ppM n-hexane vapors. 21 refs., 3 figs., 9 tabs.

  9. Simulation of auto-ignition of iso-octane and n-heptane in an internal combustion engine

    SciTech Connect

    Basevich, V.Ya.; Belyaev, A.A.; Brandshteter, V.

    1994-05-01

    A detailed kinetic mechanism is proposed for the oxidation of iso-octane, n-heptane, and mixtures of them in air (number of particles 43, number of reactions 284), which satisfactorily describes the distinctive features of low-temperature and high-temperature oxidation at an initial temperature of 1200 K, pressure of 15-40 absolute atmospheres or higher, and a fuel excess ratio of 0.5-2. The abbreviated mechanisms obtained to describe the auto-ignition of fuel with an octane number of 90 involve 27 particles (38 reactions) and 18 particles (22 reactions).

  10. The oxidation of n-butane and n-heptane in a CFR engine; Isomerization reactions and delay of autoignition

    SciTech Connect

    Sahetchian, K.A.; Blin, N.; Rigny, R.; Seydi, A. ); Murat, M. )

    1990-03-01

    During the oxidation of {ital n}-butane in a flow system and also in a motored CFR engine (600 rpm) hydrogen peroxide, primary and secondary butylhydroperoxides, and peracetic acid are formed. In the CFR engine these peroxides appear only when the compression ratio is larger than 10:1 ({ital T}{sub max} = 650 K). No autoignition has been observed. A comparison of {ital n}-butane and {ital n}-heptane oxidation is presented. Isomerization reactions,which are correlated with the alkane structure and the octane number, account for the differences in the experimental results.

  11. Asymptotic analysis for the burning of n-heptane droplets using a four-step reduced mechanism

    NASA Technical Reports Server (NTRS)

    Card, J. M.

    1993-01-01

    A four-step reduced mechanism is obtained from a minimal chemical-kinetic description, where the effects of the elementary rates are treated as parameters in the expressions for the global rates. This mechanism is used to analyze the extinction characteristics of a single n-heptane droplet burning under quasi-steady, spherically symmetrical conditions. The reaction layer consists of a merged inner zone, on the fuel-rich side of the flame, where fuel and H atoms are consumed thereby producing H2 and CO along with H2O and CO2, and an oxygen-consumption zone, on the fuel-lean side, where H2 and CO are oxidized to produce additional H2O and CO2 along with H radicals. For the inner zone, a parameter mu is identified which describes the ratio of the thickness of a fuel-consumption layer to that of an H-recombination layer. Analytical solutions for the rate of scalar dissipation at extinction are obtained in the limiting cases of mu tending to 0 and mu tending to infinity. From the results of the analysis, extinction diameters for n-heptane droplets are estimated for different pressures and ambient oxygen concentrations.

  12. Reversed micellar solution-to-bicontinuous microemulsion transition in sodium bis(2-ethylhexyl) phosphate/n-heptane/water system

    SciTech Connect

    Yu, Z.J.; Neuman, R.D.

    1995-04-01

    The solution structures in the three-component system sodium bis(2-ethylhexyl) phosphate (NaDEHP)/n-heptane/water have been investigated by dynamic and static light-scattering, electrical conductivity, and {sup 31}P-NMR spectroscopic and viscometric measurements. A transition in the physicochemical properties was observed over a rather narrow range of W{sub o} (molar ratio of water to NaDEHP) values. Rodlike reversed micelles and swollen rodlike reversed micelles form when W{sub o}< 4. Beyond this W{sub o} range, phase separation occurs at low NaDEHP concentrations, and homogeneous one-phase microemulsions form at high NaDEHP concentrations. It is suggested that the n-heptane-continuous solution of water-swollen reversed micelles transforms to a bicontinuous microemulsion when W{sub o} increases beyond W{sub o} {approx} 4. The bicontinuous microemulsion region ranges between two local viscosity maxima at W{sub o}{approx} 4 and W{sub o}{approx} 100, and an oil-in-water (O/W) microemulsion exists when W{sub o}> 100. Local dynamic domain structures consistent with the bicontinuous microemulsion behaviors are proposed and discussed. 29 refs., 7 figs., 1 tab.

  13. In vitro antioxidant activity and HPTLC determination of n-hexane extract of Emilia sonchifolia (L.)DC.

    PubMed Central

    Sophia, D.; Ragavendran, P.; Arulraj, C.; Gopalakrishnan, V. K.

    2011-01-01

    The free radical scavenging activities of n-hexane extract of the whole plant of Emilia sonchifolia was evaluated by employing various in vitro assay systems like DPPH radical scavenging activity, superoxide radical scavenging activity and hydrogen peroxide scavenging activity with IC50 values 180, 160 and 160 μg/ml respectively. The results of the study indicate that the n-hexane extract of the whole plant of Emilia sonchifolia possess a significant scavenging effect with increasing concentrations probably due to its antioxidant potential. High performance thin layer chromatography (HPTLC) analysis in the n-hexane extract of Emilia sonchifolia showed the presence of terpenoids which probably may be responsible for the antioxidant activity. Thus, n-hexane extract of Emilia sonchifolia can be used potentially as a bioactive source of natural antioxidants due to the presence of terpenoids in it PMID:24826021

  14. Molecular dynamics simulations of n-hexane at 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide interface

    SciTech Connect

    Lisal, Martin; Izak, Pavel

    2013-07-07

    Molecular dynamics simulations of n-hexane adsorbed onto the interface of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([bmim][Tf{sub 2}N]) are performed at three n-hexane surface densities, ranged from 0.7 to 2.3 {mu}mol/m{sup 2} at 300 K. For [bmim][Tf{sub 2}N] room-temperature ionic liquid, we use a non-polarizable all-atom force field with the partial atomic charges based on ab initio calculations for the isolated ion pair. The net charges of the ions are {+-}0.89e, which mimics the anion to cation charge transfer and polarization effects. The OPLS-AA force field is employed for modeling of n-hexane. The surface tension is computed using the mechanical route and its value decreases with increase of the n-hexane surface density. The [bmim][Tf{sub 2}N]/n-hexane interface is analyzed using the intrinsic method, and the structural and dynamic properties of the interfacial, sub-interfacial, and central layers are computed. We determine the surface roughness, global and intrinsic density profiles, and orientation ordering of the molecules to describe the structure of the interface. We further compute the survival probability, normal and lateral self-diffusion coefficients, and re-orientation correlation functions to elucidate the effects of n-hexane on dynamics of the cations and anions in the layers.

  15. Effect of adamantane-containing additives on the isomerization of n-heptane in the ionic liquid trimethylammonium hydrochloride-aluminum chloride

    NASA Astrophysics Data System (ADS)

    Vasina, T. V.; Kustov, L. M.; Novakov, I. A.; Orlinson, B. S.

    2013-01-01

    We study the effect of adamantane-containing additives on the process of isomerization of n-heptane in the ionic liquid trimethylammonium hydrochloride-aluminum chloride (1 : 2 mol). It is shown that introducing 1-cyanomethyl-3-cyanoadamantane (5.0 wt %) into the reaction mixture slows conversion and lowers the yield of iso-products by a factor of more than 1.5, while adding adamantylpolyimide (0.5-5.0 wt %) substantially accelerates the isomerization of n-heptane and increases the yield of iso-products. In addition, this reaction proceeds under mild conditions at 40°C in the absence of hydrogen and precious metals.

  16. Adsorption of N-hexane, methanol and water vapor and binary mixtures of N-hexane/water vapor on super activated carbon nanoparticles

    NASA Astrophysics Data System (ADS)

    Prado, Jesus Antonio

    Recent times have seen a large rise in the utilization of engineered nanomaterials (ENMs) within a wide variety of industries due to their unique properties. Consequently, the fabrication, application and disposal of ENMs will inevitably lead to their release to the environment. Once ENMs are in the environment, they may undergo atmospheric transformations, such the sorption of hazardous air pollutants (HAPs) or water vapor. These transformed ENMs may then affect the general public through inhalation -- or other pathways of exposure -- and those employed by the ever-growing nanotechnology sector are of particular vulnerability. As a result, it is important to evaluate the adsorption characteristics of a common carbon-based ENM under the presence of HAPs or water vapor which may adsorb onto them. This study investigated the unary and binary gas-phase adsorption of n-hexane, methanol and water vapor on super activated carbon nanoparticles (SACNPs) with a bench-scale adsorption system. Removal efficiencies, breakthrough tests, throughput ratios, adsorption capacities and kinetics modeling were completed to assess the adsorption behavior of the SACNPs.

  17. NOx formation from the combustion of monodisperse n-heptane sprays doped with fuel-nitrogen additives

    NASA Technical Reports Server (NTRS)

    Sarv, Hamid; Cernansky, Nicholas P.

    1989-01-01

    A series of experiments with simulated synthetic fuels were conducted in order to investigate the effect of droplet size on the conversion of fuel-nitrogen to NOx. Pyridine and pyrrole were added to n-heptane as nitrogen-containing additives and burned as monodisperse fuel droplets under various operating conditions in a spray combustion facility. The experimental results indicate that under stoichiometric and fuel-rich conditions, reducing the droplet size increases the efficiency of fuel-N conversion to NOx. This observation is associated with improved oxidation of the pyrolysis fragments of the additive by better oxygen penetration through the droplet flame zone. The dominant reactions by which fuel-N is transformed to NOx were also considered analytically by a premixed laminar flame code. The calculations are compared to the small droplet size results.

  18. A molecular ;phase ordering; phase transition leading to a modulated aperiodic composite in n-heptane/urea

    SciTech Connect

    Mariette, C.; Huard, M.; Rabiller, P.; Nichols, Shane M.; Ecolivet, C.; Janssen, Ted; Alquist, III, Keith E.; Hollingsworth, Mark D.; Toudic, B.

    2012-07-11

    n-Heptane/urea is an aperiodic inclusion compound in which the ratio of host and guest repeats along the channel axis is very close to unity and is found to have a constant value (0.981) from 280 K to 90 K. Below 280 K, two phase transitions are observed. The first (T{sub c1} = 145 K) is a ferroelastic phase transition that generates superstructure reflections for the host while leaving the guest with 1D order. The second (T{sub c2} = 130 K) is a 'phase ordering' transition to a four-dimensional structure (P2{sub 1}11(0{beta}{gamma})) with pronounced host-guest intermodulation and a temperature dependent phase shift between guests in adjacent channels.

  19. [Effect of Acetonitrile and n-hexane on the Immunoassay of Environmental Representative Pollutants].

    PubMed

    Lou, Xue-ning; Zhou, Li-ping; Song, Dan; Yang, Rong; Long, Feng

    2016-01-15

    Based on indirect competitive immunoassay mechanism, bisphenol A (BPA) was detected by the evanescent wave all-fiber immunosensor previously developed with the detection limit of 0.2 microg x L(-1) and the linear detection range of 0.3-33.4 microg x L(-1). The effects of two commonly used organic solvents, including acetonitrile and n-hexane, on the immunosensing assay of BPA were investigated. The influence mechanism of organic solvents on immunosensing assay was discussed. The experimental results showed that the effect of n-hexane on immunosensing assay was negligible even at a high concentration of up to 10%, whereas the effect of acetonitrile on the immunosensing assay was relatively great. BPA could be detected in solutions containing a low concentration of acetonitrile. However, the specific binding reaction between antibody and antigen in homogeneous solution was completely inhibited by high concentrations of acetonitrile, and the quantitative analysis of BPA was not achieved. This might result from the changes of antibody conformation or binding capability between antibody and antigen because acetonitrile replaced a part of the water molecules on the antibody surface. PMID:27078982

  20. Ir/KLTL zeolites: Structural characterization and catalysis on n-hexane reforming

    SciTech Connect

    Triantafillou, N.D.; Gates, B.C.

    1996-03-01

    Ir/KLTL zeolite catalysts were prepared by incipient wetness impregnation of LTL zeolites with [Ir(NH{sub 3}){sub 5}Cl]Cl{sub 2}. The catalysts were characterized by extended X-ray absorption fine structure (EX-AFS) spectroscopy, infrared spectroscopy, and H{sub 2} chemisorption. EXAFS data show that the average Ir cluster size (after treatment at 300{degrees}C in H{sub 2}) increased from about 7 to 20 {Angstrom} as the zeolite K:Al atomic ratio increased from 0.34 to 1.56. Infrared spectra of adsorbed CO show that the electron donation to the Ir increased as the K:Al ratio increased. In contrast to the performance reported for Pt/KLTL zeolites with metal clusters as small as those observed in the present experiments, the Ir/KLTL catalyst has a low selectivity for dehydrocyclization of n-hexane at 440-480{degrees}C and 1 atm with a H{sub 2}: n-hexane feed molar ratio of 6. Instead, the catalysts are selective for hydrogenolysis. The selectivity is insensitive to the K:Al ratio, but the activity for dehydrocyclization is a maximum at a K:Al atomic ratio of about 1. The results show that even the smallest Ir clusters to which electron donation is significant still behave essentially like metallic Ir in the catalytic reactions. 49 refs., 4 figs., 7 tabs.

  1. n-Hexane hydro-isomerization over promoted Pd/HZSM-5 catalysts

    NASA Astrophysics Data System (ADS)

    Thoa Dao, Thi Kim; Loc Luu, Cam

    2015-09-01

    A series of Pd/HZSM-5 catalysts modified by various metallic species, including Co, Ni, Fe, Re, and Cu, was prepared by sequential impregnation. Contents of Pd and second metals in modified catalysts were 0.8 and 1.0 wt%, respectively. Physico-chemical characteristics of catalysts were investigated by nitrogen physi-sorption (BET), x-ray diffraction (XRD), transmission electron microscopy (TEM), ammonia temperature programmed desorption (NH3-TPD), temperature programmed reduction (TPR) and hydrogen pulse chemisorption (HPC). Coke formation was studied by the method of thermogravimetric analysis (TGA). The activities of catalysts in n-hexane isomerization were studied in a micro-flow reactor under atmospheric pressure at 250 °C, and molar ratio of H2: n-hexane of 5.92. It was found that Co, Ni, Fe, and Re additives exhibited geometric and electronic effects toward Pd/HZSM-5 catalyst, leading to an enhancement of its activity and stability. On the contrary, Cu additive caused Pd/HZSM-5 to become poorer in activity and stability.

  2. Hydraulic transport across hydrophilic and hydrophobic nanopores: Flow experiments with water and n -hexane

    NASA Astrophysics Data System (ADS)

    Gruener, Simon; Wallacher, Dirk; Greulich, Stefanie; Busch, Mark; Huber, Patrick

    2016-01-01

    We experimentally explore pressure-driven flow of water and n -hexane across nanoporous silica (Vycor glass monoliths with 7- or 10-nm pore diameters, respectively) as a function of temperature and surface functionalization (native and silanized glass surfaces). Hydraulic flow rates are measured by applying hydrostatic pressures via inert gases (argon and helium, pressurized up to 70 bar) on the upstream side in a capacitor-based membrane permeability setup. For the native, hydrophilic silica walls, the measured hydraulic permeabilities can be quantitatively accounted for by bulk fluidity provided we assume a sticking boundary layer, i.e., a negative velocity slip length of molecular dimensions. The thickness of this boundary layer is discussed with regard to previous capillarity-driven flow experiments (spontaneous imbibition) and with regard to velocity slippage at the pore walls resulting from dissolved gas. Water flow across the silanized, hydrophobic nanopores is blocked up to a hydrostatic pressure of at least 70 bar. The absence of a sticking boundary layer quantitatively accounts for an enhanced n -hexane permeability in the hydrophobic compared to the hydrophilic nanopores.

  3. Effects of anionic surfactant on n-hexane removal in biofilters.

    PubMed

    Cheng, Yan; He, Huijun; Yang, Chunping; Yan, Zhou; Zeng, Guangming; Qian, Hui

    2016-05-01

    The biodegradability of three anion surfactants by biofilm microorganisms and the toxicity of the most readily biodegradable surfactant to biofilm microorganisms were examined using batch experiments, and the optimal concentration of SDS for enhanced removal of hexane was investigated using two biotrickling filters (BTFs) for comparison. Results showed that SDS could be biodegraded by microorganisms, and its toxicity to microorganisms within the experimental range was negligible. The best concentration of SDS in biofiltration of n-hexane was 0.1 CMC and the elimination capacity (EC) of 50.4 g m(-3) h(-1) was achieved at a fixed loading rate (LR) of 72 g m(-3) h(-1). When an inlet concentration of n-hexane increased from 600 to 850 mg m(-3), the removal efficiency (RE) decreased from 67% to 41% by BTF2 (with SDS) and from 52% to 42% by BTF1 (without SDS). SDS could enhance hexane removal from 43% (BTF1) to 60% (BTF2) at gas empty-bed residence time (EBRT) of 7.5 s and an inlet concentration of 200 mg m(-3). PMID:26907592

  4. Antifungal activity of methanol and n-hexane extracts of three Chenopodium species against Macrophomina phaseolina.

    PubMed

    Javaid, Arshad; Amin, Muhammad

    2009-01-01

    Antifungal activity of methanol and n-hexane leaf, stem, root and inflorescence extracts (1, 2, 3 and 4% w/v) of three Chenopodium species (family Chenopodiaceae) namely Chenopodium album L., Chenopodium murale L. and Chenopodium ambrosioides L. was investigated against Macrophomina phaseolina (Tassi) G. Goid., a soil-borne fungal plant pathogen that has a broad host range and wide geographical distribution. All the extracts of the three Chenopodium species significantly suppressed the test fungal growth. However, there was marked variation among the various extract treatments. Methanol inflorescence extract of C. album exhibited highest antifungal activity resulting in up to 96% reduction in fungal biomass production. By contrast, methanol leaf extract of the same species exhibited least antifungal activity where 21-44% reduction in fungal biomass was recorded due to various employed extract concentrations. The various methanol extracts of C. murale and C. ambrosioides decreased fungal biomass by 62-90 and 50-84%, respectively. Similarly, various n-hexane extracts of C. album, C. murale and C. ambrosioides reduced fungal biomass by 60-94, 43-90 and 49-86%, respectively. PMID:19662577

  5. A comprehensive skeletal mechanism for the oxidation of n-heptane generated by chemistry-guided reduction

    SciTech Connect

    Zeuch, Thomas; Moreac, Gladys; Ahmed, Syed Sayeed; Mauss, Fabian

    2008-12-15

    Applied to the primary reference fuel n-heptane, we present the chemistry-guided reduction (CGR) formalism for generating kinetic hydrocarbon oxidation models. The approach is based on chemical lumping and species removal with the necessity analysis method, a combined reaction flow and sensitivity analysis. Independent of the fuel size, the CGR formalism generates very compact submodels for the alkane low-temperature oxidation and provides a general concept for the development of compact oxidation models for large model fuel components such as n-decane and n-tetradecane. A defined sequence of simplification steps, consisting of the compilation of a compact detailed chemical model, the application of linear chemical lumping, and finally species removal based on species necessity values, allows a significantly increased degree of reduction compared to the simple application of the necessity analysis, previously published species, or reaction removal methods. The skeletal model derived by this procedure consists of 110 species and 1170 forward and backward reactions and is validated against the full range of combustion conditions including low and high temperatures, fuel-lean and fuel-rich mixtures, pressures between 1 and 40 bar, and local (species concentration profiles in flames, plug flow and jet-stirred reactors, and reaction sensitivity coefficients) and global parameters (ignition delay times in shock tube experiments, ignition timing in a HCCI engine, and flame speeds). The species removal is based on calculations using a minimum number of parameter configurations, but complemented by a very broad parameter variation in the process of compiling the kinetic input data. We further demonstrate that the inclusion of sensitivity coefficients in the validation process allows efficient control of the reduction process. Additionally, a compact high-temperature n-heptane oxidation model of 47 species and 468 reactions was generated by the application of necessity

  6. Simultaneous realization of high catalytic activity and stability for catalytic cracking of n-heptane on highly exposed (010) crystal planes of nanosheet ZSM-5 zeolite.

    PubMed

    Xiao, Xia; Zhang, Yaoyuan; Jiang, Guiyuan; Liu, Jia; Han, Shanlei; Zhao, Zhen; Wang, Ruipu; Li, Cong; Xu, Chunming; Duan, Aijun; Wang, Yajun; Liu, Jian; Wei, Yuechang

    2016-08-01

    Nanosheet ZSM-5 zeolite with highly exposed (010) crystal planes demonstrates high reactivity and good anti-coking stability for the catalytic cracking of n-heptane, which is attributed to the synergy of high external surface area and acid sites, fully accessible channel intersection acid sites, and hierarchical porosity caused by the unique morphology. PMID:27458616

  7. Method 1664, Revision A: n-hexane extractable material (HEM; oil and grease) and silica gel treated n-hexane extractable material (SGT-HEM; non-polar material) by extraction and gravimetry

    SciTech Connect

    Not Available

    1999-02-01

    This method is for determination of n-hexane extractable material (HEM; oil and grease) and n-hexane extractable material that is not adsorbed by silica gel (SGT-HEM; non-polar material) in surface and saline waters and industrial and domestic aqueous wastes. Extractable materials that may be determined are relatively non-volatile hydrocarbons, vegetable oils, animal fats, waxes, soaps, greases, and related materials. This method is capable of measuring HEM and SGT-HEM in the range of 5 to 1000 mg/L, and may be extended to higher levels by analysis of a smaller sample volume collected separately.

  8. Reactive extraction of lactic acid with trioctylamine/methylene chloride/n-hexane

    SciTech Connect

    Han, D.H.; Hong, W.H.

    1996-04-01

    The trioctylamine (TOA)/methylene chloride (MC)/n-hexane system was used as the extraction agent for the extraction of lactic acid. Curves of equilibrium and hydration were obtained at various temperatures and concentrations of TOA. A modified mass action model was proposed to interpret the equilibrium and the hydration curves. The reaction mechanism and the corresponding parameters which best represent the equilibrium data were estimated, and the concentration of water in the organic phase was predicted by inserting the parameters into the simple mathematical equation of the modified model. The concentration of MC and the change of temperature were important factors for the extraction and the stripping process. The stripping was performed by a simple distillation which was a combination of temperature-swing regeneration and diluent-swing regeneration. The type of inactive diluent has no influence on the stripping. The stripping efficiencies were about 70%.

  9. Intermolecular dispersion interactions of normal alkanes with rare gas atoms: van der Waals complexes of n-pentane with helium, neon, and argon

    NASA Astrophysics Data System (ADS)

    Balabin, Roman M.

    2008-09-01

    Interaction energies of normal pentane with three rare gas atoms (helium, neon, and argon) were calculated using ab initio methods: the second-order Møller-Plesset (MP2), the fourth-order Møller-Plesset (MP4), and coupled cluster with single and double substitutions with noniterative triple excitation (CCSD(T)) levels of theory. Dunning's correlation consistent basis sets up to aug-cc-pVQZ were applied. Eight profiles (246 points for each rare gas atom) of potential energy surface (PES) of all-trans (anti-anti) conformation of n-pentane were scanned. Optimal distances for complex formation were found. MP2 interaction energies at the basis set limit were evaluated by three different methods (Feller's, Helgaker's, and Martin's). The MP2 interaction energy at the basis set limit for a global minimum of n-pentane complex with argon was more than 400 cm -1, so formation of a stable complex (at least at low temperature) can be expected. A comparison with previously published data on propane complexes with rare gas atoms (both computational and experimental) was done. The MP4 level of theory was found to be sufficient for a description of C 5H 12 complexes with helium, neon, and argon.

  10. Thermodynamics of cavity formation in water and n-hexane using the Widom particle insertion method

    NASA Astrophysics Data System (ADS)

    Tomás-Oliveira, Isabel; Wodak, Shoshana J.

    1999-11-01

    The Widom particle insertion (WPI) method is used to compute the free energy, enthalpy, and entropy associated with the creation of empty cavities of different sizes in water and n-hexane. These thermodynamic parameters are computed from the likelihood of encountering such cavities in thermally equilibrated configurations from 4 ns (1 ns=10-9 s) molecular dynamics trajectories of the neat liquids. The obtained free energy values are in excellent agreement with those computed previously, using the same or other methods. We find that the entropy term is large and unfavorable in both liquids, but more so in water than in hexane. The change in internal energy is, on the other hand, virtually zero in hexane and slightly favorable in water. Comparison with scaled particle theory (SPT) predictions shows good agreement for the free energy values for small cavities, but the theory systematically underestimates these values for large cavities. In contrast, the free energy components obtained by the two methods show several significant differences. With WPI, the entropy of cavity formation is unfavorable in both liquids for all cavity sizes. SPT yields an unfavorable entropy only for water. In hexane, however, the predicted entropy is negative for small cavities, but changes sign for cavity radii >1.1 Å. In addition, SPT yields an unfavorable enthalpy of cavity formation in water, whereas with WPI this term is small but favorable. Taking n-hexane as a model for organic solvents, our calculations thus suggest that the process of cavity formation is similar in water and these solvents, a conclusion which seems to make good physical sense. SPT reaches an opposite conclusion, which seems harder to rationalize, and probably arises from the highly simplified solvent model used by this theory.

  11. Complex formation between excited-state saturated amines and water in n-hexane solution

    SciTech Connect

    Halpern, A.M.; Ruggles, C.J.; Zhang, X.K.

    1987-06-10

    Fluorescence spectra and decay curves of dilute solutions (<3 x 10/sup -4/ M) of triethylamine (TEA), tri-n-propylamine (TPA), and 1,4-diazabicyclo(2.2.2)octane (DABCO) in H/sub 2/O- and D/sub 2/O-saturated n-hexane reveal the presence of a complex formed between the electronically excited amine and water. The decay curves, measured between 273 and 323 K (and at 280 and 360 nm; 300 and 400 nm for DABCO), conform to the standard monomer-excimer photokinetic scheme and are analyzed accordingly. These results indicate that the binding energy of the excited TEA-H/sub 2/O complex (B*) is ca. 7.8 kcal/mol, which is larger than that of the ground-state TEA hydrate. B* for the TPA and DABCO-H/sub 2/O complexes is estimated to be ca. 10 and 8.8 kcal/mol, respectively. Stationary-state measurements are consistent with these assignments. The activation energy for the diffusion of water in n-hexane (assumed to be monomeric) appears to be very small (<1 kcal/mol). The decay constants of the three complexes studied are ca. 3.4 x 10/sup 7/ s/sup -1/ for amine-H/sub 2/O and 2.9 x 10/sup 7/ s/sup -1/ for the amine-D/sub 2/O systems. Intrinsic fluorescence quantum efficiencies of the amine-H/sub 2/O complexes are 0.17, 0.23, and 0.28 for TEA, TPA, and DABCO, respectively, at 303 K. A Foerster cycle analysis of the dry and H/sub 2/O-saturated fluorescence spectra of TEA, when taking the ground-state hydrate into account indicates that the repulsion energy of the post-fluorescence (TEA-H/sub 2/O) complex is ca. 10 kcal/mol.

  12. THE STRUCTURE SENSITIVITY OF n-HEPTANE DEHYDROCYCLIZATION AND HYDROGENOLYSIS CATALYZED BY PLATINUM SINGLE CRYSTALS AT ATMOSPHERIC PRESSURE

    SciTech Connect

    Gillespie, W. D.; Herz, R. K.; Petersen, E. E.; Somorjai, G. A.

    1980-09-01

    The dehydrocyclization and hydrogenolysis of n~heptane catalyzed by platinum single crystal surfaces have been investigated at temperatures from 533 to 603 K in the range of one atmosphere total pressure, The flat (111), stepped (557), and kinked (10,8,7) and (25,10,7) surfaces used tn this study were characterized in ultrahigh vacuum by low energy electron diffraction and Auger electron spectroscopy before and after reaction experiments. The rate of dehydrocyclization to toluene on the four surfaces increased in the order (111) (25,10,7) (557) (10,8,7), Hydrogenolysis, however, increased in the order (557) (10,8,7) (111) (25,10,7), As a result, the selectivity of toluene production versus hydrogenolysis increased by an order of magnitude in the order (25,10,7) (111) (10,8,7) (557). The sum of the rates of hydrogenolysis and toluene production remains relatively constant. The effect of preoxidation of the single crystal catalysts was to increase the rate of hydrogenolysis and decrease the rate of dehydrocyclization, Iri general, the reaction rates decreased with increasing reaction time. This decrease was shown to be the result of the depositon of irreversibly adsorbed carbonaceous species.

  13. Environmentally friendly efficient coupling of n-heptane by sulfated tri-component metal oxides in slurry bubble column reactor.

    PubMed

    Ma, Hongzhu; Xiao, Jing; Wang, Bo

    2009-07-30

    SO(4)(2-)/M(x)O(y) is of the greatest interest in solid catalysts and green catalysts. Slurry bubble column reactors are of considerable interest in industrial processes and various biochemical processes. The cetane number (CN) has widely used diesel fuel quality parameter related to the ignition delay time (and combustion quality) of a fuel. CN improvement of diesel fuels is a difficult task that refiners will face in the near future. For that purpose, the tests were designed in which n-heptane is used as the reactant in the air or ozone atmosphere at room temperature (RT) and local atmospheric pressure (LAP) using different catalysts of sulfated tri-component metal oxides SO(4)(2-)/Fe(2)O(3)-TiO2-SnO(2) (SFTSn) and SO(4)(2-)/MnO(2)-TiO2-SnO(2) (SMTSn) in slurry bubble column reactor. The products distribution was analyzed by gas chromatography-mass spectrometry (GC-MS) method and the results show that the relative selectivity of long linear alkane (C(12)-C(28)) reaches the maximum (87.330%) when SMTSn is used as catalyst in flow air at 60 min. Diesel fuel components with higher cetane numbers can be easily obtained from this study. PMID:19124196

  14. Linear time reduction of large kinetic mechanisms with directed relation graph: n-Heptane and iso-octane

    SciTech Connect

    Lu, Tianfeng; Law, Chung K.

    2006-01-01

    The algorithm of directed relation graph recently developed for skeletal mechanism reduction was extended to overall linear time operation, thereby greatly facilitating the computational effort in mechanism reduction, particularly for those involving large mechanisms. Together with a two-stage reduction strategy and using the kinetic responses of autoignition and perfectly stirred reactor (PSR) with extensive parametric variations as the criteria in eliminating unimportant species, a detailed 561-species n-heptane mechanism and a detailed 857-species iso-octane mechanism were successfully reduced to skeletal mechanisms consisting of 188 and 233 species, respectively. These skeletal mechanisms were demonstrated to mimic well the performance of the detailed mechanisms, not only for the autoignition and PSR systems based on which the reduced mechanisms were developed but also for the independent system of jet-stirred reactor. It was further observed that the accuracy of calculated species concentrations was equivalently bounded by the user-specified error threshold value and that the reduction time for a single reaction state is only about 50 ms for the large iso-octane mechanism.

  15. Combustion of n-heptane in a shock tube and in a stirred reactor: A detailed kinetic modeling study

    SciTech Connect

    Gaffuri, P.; Curran, H.J.; Pitz, W.J.; Westbrook, C.K.

    1995-04-13

    A detailed chemical kinetic reaction mechanism is used to study the oxidation of n-heptane under several classes of conditions. Experimental results from ignition behind reflected shock waves and in a rapid compression machine were used to develop and validate the reaction mechanism at relatively high temperatures, while data from a continuously stirred tank reactor (cstr) were used to refine the low temperature portions of the reaction mechanism. In addition to the detailed kinetic modeling, a global or lumped kinetic mechanism was used to study the same experimental results. The lumped model was able to identify key reactions and reaction paths that were most sensitive in each experimental regime and provide important guidance for the detailed modeling effort. In each set of experiments, a region of negative temperature coefficient (NTC) was observed. Variation in pressure from 5 to 40 bars were found to change the temperature range over which the NTC region occurred. Both the lumped and detailed kinetic models reproduced the measured results in each type of experiments, including the features of the NTC region, and the specific elementary reactions and reaction paths responsible for this behavior were identified and rate expressions for these reactions were determined.

  16. A rapid compression machine investigation of oxidation and auto-ignition of n-heptane: Measurements and modeling

    SciTech Connect

    Minetti, R.; Carlier, M.; Ribaucour, M.; Therssen, E.; Sochet, L.R.

    1995-08-01

    n-Heptane oxidation and auto-ignition in a rapid compression machine is studied in the low and intermediate temperature regimes at high pressures. Experimental ignition delay times and some phenomenological aspects related to knock in engines are presented, providing additional information at lower temperatures on previously published delays from shock tube experiments. The products of oxidation are identified and time profiles are measured during a two-stage ignition process. Eight C{sub 7} heterocycles, heptenes, lower 1-alkenes, aldehydes, and carbon monoxide are the main species. Their origin is discussed in relation to the isomerization and decomposition of heptylperoxy radicals. The high selectivity observed in the formation of lower 1-alkenes is explained by the scission of the {beta} C-C bond of the {beta}-hydroperoxyheptyl radicals weakened by the presence of oxygen atoms. Numerical simulation of the experiments with Warnatz`a comprehensive chemical mechanism gives satisfactory results for cool flame and total ignition delays, but fails to reproduce the detailed chemistry before auto-ignition.

  17. Lipase-catalyzed synthesis of isoamyl acetate in an ionic liquid/n-heptane two-phase system at the microreactor scale.

    PubMed

    Pohar, Andrej; Plazl, Igor; Žnidaršič-Plazl, Polona

    2009-12-01

    A continuously operated psi-shaped microreactor was used for lipase-catalyzed synthesis of isoamyl acetate in the 1-butyl-3-methylpyridinium dicyanamide/n-heptane two-phase system. The chosen solvent system with dissolved Candida antarctica lipase B, which was attached to the ionic liquid/n-heptane interfacial area due to its amphiphilic properties, was shown to be highly efficient and enabled simultaneous esterification and product removal. At preliminarily selected conditions regarding the type of acyl donor, its molar ratio to alcohol and enzyme concentration, 48.4 g m(-3) s(-1) of isoamyl acetate was produced, which was almost three-fold better as compared to the intensely mixed batch process. This was mainly a consequence of efficient reaction-diffusion dynamics in the microchannel system, where the developed flow pattern comprising of intense emulsification provided a large interfacial area for the reaction and simultaneous product extraction. PMID:19904405

  18. Comparison of oil refining and biodiesel production process between screw press and n-hexane techniques from beauty leaf feedstock

    NASA Astrophysics Data System (ADS)

    Bhuiya, M. M. K.; Rasul, M. G.; Khan, M. M. K.; Ashwath, N.

    2016-07-01

    The Beauty Leaf Tree (Callophylum inophyllum) is regarded as an alternative source of energy to produce 2nd generation biodiesel due to its potentiality as well as high oil yield content in the seed kernels. The treating process is indispensable during the biodiesel production process because it can augment the yield as well as quality of the product. Oil extracted from both mechanical screw press and solvent extraction using n-hexane was refined. Five replications each of 25 gm of crude oil for screw press and five replications each of 25 gm of crude oil for n-hexane were selected for refining as well as biodiesel conversion processes. The oil refining processes consists of degumming, neutralization as well as dewaxing. The degumming, neutralization and dewaxing processes were performed to remove all the gums (phosphorous-based compounds), free fatty acids, and waxes from the fresh crude oil before the biodiesel conversion process carried out, respectively. The results indicated that up to 73% and 81% of mass conversion efficiency of the refined oil in the screw press and n-hexane refining processes were obtained, respectively. It was also found that up to 88% and 90% of biodiesel were yielded in terms of mass conversion efficiency in the transesterification process for the screw press and n-hexane techniques, respectively. While the entire processes (refining and transesterification) were considered, the conversion of beauty leaf tree (BLT) refined oil into biodiesel was yielded up to 65% and 73% of mass conversion efficiency for the screw press and n-hexane techniques, respectively. Physico-chemical properties of crude and refined oil, and biodiesel were characterized according to the ASTM standards. Overall, BLT has the potential to contribute as an alternative energy source because of high mass conversion efficiency.

  19. Theoretical Basis for Estimated Test Times and Conditions for Drop Tower and Space-Based Droplet Burning Experiments With Methanol and N-Heptane

    NASA Technical Reports Server (NTRS)

    Marchese, Anthony J.; Dryer, Fredrick L.; Choi, Mun Y.

    1994-01-01

    In order to develop an extensive envelope of test conditions for NASA's space-based Droplet Combustion Experiment (DCE) as well those droplet experiments which can be performed using a drop tower, the transient vaporization and combustion of methanol and n-heptane droplets were simulated using a recently developed fully time-dependent, spherically symmetric droplet combustion model. The transient vaporization of methanol and n-heptane was modeled to characterize the instantaneous gas phase composition surrounding the droplet prior to the introduction of an ignition source. The results for methanol/air showed that the entire gas phase surrounding a 2 mm methanol droplet deployed in zero-g .quickly falls outside the lean flammability limit. The gas phase surrounding an identically-sized n-heptane droplet, on the other hand, remains flammable. The combustion of methanol was then modeled considering a detailed gas phase chemical kinetic mechanism (168 steps, 26 species) and the effect of the dissolution of flame-generated water into the liquid droplet. These results were used to determine the critical ignition diameter required to achieve quasi-steady droplet combustion in a given oxidizing environment. For droplet diameters greater than the critical ignition diameter, the model predicted a finite diameter at which the flame would extinguish. These extinction diameters were found to vary significantly with initial droplet diameter. This phenomenon appears to be unique to the transient heat transfer, mass transfer and chemical kinetics of the system and thus has not been reported elsewhere to date. The extinction diameter was also shown to vary significantly with the liquid phase Lewis number since the amount of water present in the droplet at extinction is largely governed by the rate at which water is transported into the droplet via mass diffusion. Finally, the numerical results for n-heptane combustion were obtained using both 2 step and 96 step semi

  20. Studies of photoionization in liquids using a laser two-photon ionization conductivity technique. [Potoionization of pyrene, fluoranthene and TMPD in liquid n-pentane

    SciTech Connect

    Siomos, K.; Christophorou, L.G.

    1981-01-01

    One-photon ionization studies of solute molecules in a liquid medium are limited by the absorption of the host medium. A laser two-photon ionization (TPI) technique using a frequency tunable dye laser has been developed, whereby the photoionization threshold of a solute molecule was determined from the induced conductivity in the liquid medium under study due to electron-ion pair formation via two-photon ionization of the solute. The two-photon induced electron-ion current is measured as a function of the laser wavelength, lambda/sub laser/. In this paper, results are reported and discussed on the photoionization of N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD), pyrene and fluoranthene in liquid n-pentane (n-Pt).

  1. Experimental Study of the Density and Viscosity of n-Heptane at Temperatures from 298 K to 470 K and Pressure upto 245 MPa

    NASA Astrophysics Data System (ADS)

    Sagdeev, D. I.; Fomina, M. G.; Mukhamedzyanov, G. Kh.; Abdulagatov, I. M.

    2013-01-01

    The density and viscosity of n-heptane have been simultaneously measured over the temperature range from 298 K to 470 K and at pressures up to 245 MPa using the hydrostatic weighing and falling-body techniques, respectively. The expanded uncertainty of the density, pressure, temperature, and viscosity measurements at the 95 % confidence level with a coverage factor of k= 2 is estimated to be 0.15 % to 0.30 %, 0.05 %, 0.02 K, and 1.5 % to 2.0 % (depending on temperature and pressure ranges), respectively. The measured densities were used to develop a Tait-type equation of state for liquid n-heptane. Theoretically based Arrhenius-Andrade and Vogel-Tamman-Fulcher type equations with pressure-dependent coefficients were used to describe the temperature and pressure dependences of the measured viscosities for liquid n-heptane. The measured values of the density and viscosity were compared in detail with reported data and with the values calculated from a reference EOS and correlation models for the viscosity.

  2. Combustion Characteristics in a Non-Premixed Cool-Flame Regime of n-Heptane in Microgravity

    NASA Technical Reports Server (NTRS)

    Takahashi, Fumiaki; Katta, Viswanath R.; Hicks, Michael C.

    2015-01-01

    A series of distinct phenomena have recently been observed in single-fuel-droplet combustion tests performed on the International Space Station (ISS). This study attempts to simulate the observed flame behavior numerically using a gaseous n-heptane fuel source in zero gravity and a time-dependent axisymmetric (2D) code, which includes a detailed reaction mechanism (127 species and 1130 reactions), diffusive transport, and a radiation model (for CH4, CO, CO2, H2O, and soot). The calculated combustion characteristics depend strongly on the air velocity around the fuel source. In a near-quiescent air environment (< or = 2 mm/s), with a sufficiently large fuel injection velocity (1 cm/s), a growing spherical diffusion flame extinguishes at ˜1200 K due to radiative heat losses. This is typically followed by a transition to the low-temperature (cool-flame) regime with a reaction zone (at ˜700 K) in close proximity to the fuel source. The 'cool flame' regime is formed due to the negative temperature coefficient in the low-temperature chemistry. After a relatively long period (˜18 s) of the cool flame regime, a flash re-ignition occurs, associated with flame-edge propagation and subsequent extinction of the re-ignited flame. In a low-speed (˜3 mm/s) airstream (which simulates the slight droplet movement), the diffusion flame is enhanced upstream and experiences a local extinction downstream at ˜1200 K, followed by steady flame pulsations (˜0.4 Hz). At higher air velocities (4-10 mm/s), the locally extinguished flame becomes steady state. The present axisymmetric computational approach helps in revealing the non-premixed 'cool flame' structure and 2D flame-flow interactions observed in recent microgravity droplet combustion experiments.

  3. In Vitro Anti-Listerial Activities of Crude n-Hexane and Aqueous Extracts of Garcinia kola (heckel) Seeds

    PubMed Central

    Penduka, Dambudzo; Okoh, Anthony I.

    2011-01-01

    We assessed the anti-Listerial activities of crude n-hexane and aqueous extracts of Garcinia kola seeds against a panel of 42 Listeria isolates previously isolated from wastewater effluents in the Eastern Cape Province of South Africa and belonging to Listeria monocytogenes, Listeria grayi and Listeria ivanovii species. The n-hexane fraction was active against 45% of the test bacteria with zones of inhibition ranging between 8–17 mm, while the aqueous fraction was active against 29% with zones of inhibition ranging between 8–11 mm. The minimum inhibitory concentrations (MIC) were within the ranges of 0.079–0.625 mg/mL for the n-hexane extract and 10 to >10 mg/mL for the aqueous extract. The rate of kill experiment carried out for the n-hexane extract only, revealed complete elimination of the initial bacterial population for L. grayi (LAL 15) at 3× and 4× MIC after 90 and 60 min; L. monocytogenes (LAL 8) at 3× and 4× MIC after 60 and 15 min; L. ivanovii (LEL 18) at 3× and 4× MIC after 120 and 15 min; L. ivanovii (LEL 30) at 2, 3 and 4× MIC values after 105, 90 and 15 min exposure time respectively. The rate of kill activities were time- and concentration-dependant and the extract proved to be bactericidal as it achieved a more than 3log10 decrease in viable cell counts after 2 h exposure time for all of the four test organisms at 3× and 4× MIC values. The results therefore show the potential presence of anti-Listerial compounds in Garcinia kola seeds that can be exploited in effective anti-Listerial chemotherapy. PMID:22072929

  4. Analysis of petroleum contaminated soils by spectral modeling and pure response profile recovery of n-hexane.

    PubMed

    Chakraborty, Somsubhra; Weindorf, David C; Li, Bin; Ali, Md Nasim; Majumdar, K; Ray, D P

    2014-07-01

    This pilot study compared penalized spline regression (PSR) and random forest (RF) regression using visible and near-infrared diffuse reflectance spectroscopy (VisNIR DRS) derived spectra of 164 petroleum contaminated soils after two different spectral pretreatments [first derivative (FD) and standard normal variate (SNV) followed by detrending] for rapid quantification of soil petroleum contamination. Additionally, a new analytical approach was proposed for the recovery of the pure spectral and concentration profiles of n-hexane present in the unresolved mixture of petroleum contaminated soils using multivariate curve resolution alternating least squares (MCR-ALS). The PSR model using FD spectra (r(2) = 0.87, RMSE = 0.580 log10 mg kg(-1), and residual prediction deviation = 2.78) outperformed all other models tested. Quantitative results obtained by MCR-ALS for n-hexane in presence of interferences (r(2) = 0.65 and RMSE 0.261 log10 mg kg(-1)) were comparable to those obtained using FD (PSR) model. Furthermore, MCR ALS was able to recover pure spectra of n-hexane. PMID:24686115

  5. Inhalation reproductive toxicology studies: Male dominant lethal study of n-hexane in Swiss (CD-1) mice: Final report

    SciTech Connect

    Mast, T.J.; Rommereim, R.L.; Evanoff, J.J.; Sasser, L.B.; Decker, J.R.; Stoney, K.H.; Weigel, R.J.; Westerberg, R.B.

    1988-08-01

    The straight-chain hydrocarbon, n-hexane, is a volatile, ubiquitous solvent routinely used in industrial environments; consequently, the opportunity for industrial, environmental or accidental exposure to hexane vapors is significant. Although myelinated nerve tissue is the primary target organ of hexane, the testes have also been identified as being sensitive to hexacarbon exposure. The objective of this study was to evaluate male dominant lethal effects in Swiss (CD-1) mice after exposure to 0, 200, 1000, or 5000 ppM n-hexane, 20 h/day for 5 consecutive days. Each exposure concentration consisted of 30 randomly selected, proven male breeders; 4 groups. The mice were weighed just prior to the first day of exposure and at weekly intervals until sacrifice. Ten males in each dose group were sacrificed one day after the cessation of exposure, and their testes and epididymides were removed for evaluation of the germinal epithelium. The remaining male mice, 20 per group, were individually housed in hanging wire-mesh breeding cages where they were mated with unexposed, virgin females for eight weekly intervals; new females were provided each week. The mated females were sacrificed 12 days after the last day of cohabitation and their reproductive status and the number and viability of the implants were recorded. The appearance and behavior of the male mice were unremarkable throughout the study period and no evidence of n-hexane toxicity was observed. 18 refs., 3 figs., 11 tabs.

  6. High-temperature diffusion of hydrogen, carbon monoxide, and carbon dioxide in liquid n-heptane, n-dodecane, and n-hexadecane

    SciTech Connect

    Matthews, M.A.; Rodden, J.B.; Akgerman, A.

    1987-07-01

    Mutual diffusion coefficients at infinite dilution have been measured for hydrogen, carbon monoxide, and carbon dioxide in the solvents n-heptane, n-dodecane, and n-hexadecane. The data cover the temperature range from 25 to 293/sup 0/C and pressures of 1415 and 3450 kPa. The Taylor dispersion method was used for diffusion measurements. It was found that the Sovova correlation for diffusion of dissolved gases in liquids failed to predict diffusivities at temperatures above ambient. A free-volume approach to correlation is indicated instead.

  7. Determination of the boiling-point distribution by simulated distillation from n-pentane through n-tetratetracontane in 70 to 80 seconds.

    PubMed

    Lubkowitz, Joaquin A; Meneghini, Roberto I

    2002-01-01

    This work presents the carrying out of boiling-point distributions by simulated distillation with direct-column heating rather than oven-column heating. Column-heating rates of 300 degrees C/min are obtained yielding retention times of 73 s for n-tetratetracontane. The calibration curves of the retention time versus the boiling point, in the range of n-pentane to n-tetratetracontane, are identical to those obtained by slower oven-heating rates. The boiling-point distribution of the reference gas oil is compared with that obtained with column oven heating at rates of 15 to 40 degrees C/min. The results show boiling-point distribution values nearly the same (1-2 degrees F) as those obtained with oven column heating from the initial boiling point to 80% distilled off. Slightly higher differences are obtained (3-4 degrees F) for the 80% distillation to final boiling-point interval. Nonetheless, allowed consensus differences are never exceeded. Precision of the boiling-point distributions (expressed as standard deviations) are 0.1-0.3% for the data obtained in the direct column-heating mode. PMID:12049156

  8. Catalytic performance of V2O5-MoO3/γ-Al2O3 catalysts for partial oxidation of n-hexane1

    NASA Astrophysics Data System (ADS)

    Mahmoudian, R.; Khodadadi, Z.; Mahdavi, Vahid; Salehi, Mohammed

    2016-01-01

    In the current study, a series of V2O5-MoO3 catalyst supported on γ-Al2O3 with various V2O5 and MoO3 loadings was prepared by wet impregnation technique. The characterization of prepared catalysts includes BET surface area, powder X-ray diffraction (XRD), and oxygen chemisorptions. The partial oxidation of n-hexane by air over V2O5-MoO3/γ-Al2O3 catalysts was carried out under flow condition in a fixed bed glass reactor. The effect of V2O5 loading, temperature, MoO3 loading, and n-hexane LHSV on the n-hexane conversion and the product selectivity were investigated. The partial oxygenated products of n-hexane oxidation were ethanol, acetic anhydride, acetic acid, and acetaldehyde. The 10% V2O5-1%MoO3/γ-Al2O3 was found in most active and selective catalyst during partial oxidation of n-hexane. The results indicated that by increasing the temperature, the n-hexane conversion increases as well, although the selectivity of the products passes through a maximum by increasing the temperature.

  9. Reverse Micelle Formation of Triton X-100 in Butanol and n-Heptane Mixed Solvents Studied by the Positron Annihilation Technique

    PubMed

    Das; Ganguly

    1997-08-01

    The positron annihilation technique (PAT) has been applied to study the molecular association phenomenon of Triton X-100 (TX-100) and formation of reversed micelles in the mixed solvent of butanol and n-heptane. The results indicate the sensitivity of positronium (Ps) parameters to the phase transition region due to the self-aggregation phenomenon of TX-100 within the system. The intensity of the long-lived ortho-Ps component, I3, and its lifetime, tau3, show a remarkable change at a critical concentration of the surfactant at approximately 1.5 mM coined as the operational CMC of TX-100 in both (1:1) and (1:2) butanol-n-heptane (BuHp) systems. The narrow component/para-Ps intensity as computed from Doppler broadening of annihilation radiation indicates discernable changes at the same concentration region ( approximately 1.5 mM) of TX-100 in the system. Further, microphase changes due to the association of water molecules within the nonaqueous phase has been studied by Ps parameters, which reveals a clear demarcation of the polar and nonpolar zones. PMID:9268557

  10. A new organized media: glycerol:N,N-dimethylformamide mixtures/AOT/n-heptane reversed micelles. The effect of confinement on preferential solvation.

    PubMed

    Durantini, Andrés M; Falcone, R Dario; Silber, Juana J; Correa, N Mariano

    2011-05-19

    In this work we investigate the behavior of the glycerol (GY):N,N-dimethylformamide (DMF) mixture in homogeneous and sodium 1,4-bis(2-ethylhexyl)sulfosuccinate (AOT)/n-heptane reversed micelles (RMs) media. To achieve this goal we have used the solvatochromic behavior of 1-methyl-8-oxyquinolinium betaine (QB) as an absorption probe, and dynamic light scattering (DLS). QB shows strong preferential solvation when it is dissolved in the GY:DMF mixture, and, as QB is a good hydrogen bond acceptor molecular probe, it is preferentially solvated by the GY-DMF hydrogen-bonded (H-bonded) species. On the other hand, when the GY:DMF mixture was investigated in AOT RMs, the results show that the mixture is encapsulated in the polar core of the AOT RMs. DLS confirms the formation of the GY:DMF/AOT/n-heptane RMs since an increase in the W(s)=([GY]+[DMF])/[AOT] values causes an increment in the RMs droplets sizes. The solvatochromic behavior of QB, which resides at the AOT RMs interface, shows that QB is mostly solvated by GY molecules, especially at low W(s) values. Thus, it seems that upon encapsulation inside the polar core of the AOT RMs, the GY-DMF interaction diminishes due to the strong AOT-GY interaction. (1)H NMR chemical shifts of GY and DMF measured in the different AOT RMs investigated shows that GY and DMF behave practically as noninteracting solvents inside the RMs. PMID:21517031

  11. [An experimental study on the neurotoxicity of 2-octanone and 2-hexanol, a metabolite of n-hexane].

    PubMed

    Misumi, J; Nagano, M; Nomura, S

    1982-09-01

    An electrophysiological study of the neurotoxicity of 2-octanone (an analogue of methyl n-butyl ketone) and 2-hexanol (a metabolite of n-hexane) was conducted on rats as a part of the study to determine the specific molecular arrangement required for the development of peripheral neuropathy. The compound 2-octanone or 2-hexanol was administered subcutaneously in the daily dose of 400 mg/kg of each compound into the back of seven rats, weighing 290 g, 5 days per week for a period of 21 weeks. Animals treated with 2-octanone for 21 weeks failed to exhibit apparent clinical and neurophysiological evidence except a slight inhibition of weight gain and narcotic effects after treatment with the compound. The same doses of 2-hexanol for 21 weeks caused hypersalivation, gait disturbances, crossing phenomena of hind limbs and a failure of normal growth. Retardation of the conduction velocity in the motor and sensory nerve fibers and the prolonged motor latencies of the tail nerves (distal part) began to appear at the 14th week of the experiment when 9.6 g in the total dose had been given to each animal. These changes were intensified in the subsequent course of the experiment. Our previous experiments and the present results showed that n-hexane barely produced peripheral neuropathy in doses over 10.5 g, and that 2-hexanone (MBK), 2,5-hexanediol or 2,5-hexanedione never failed to produce a neuropathy even in doses less than 9.6 g of each compound. The above results suggest that the neurotoxic potency of 2-hexanol is greater than that of n-hexane but less than that of MBK, 2,5-hexanediol or 2,5-hexanedione. PMID:6296504

  12. cis-trans photoisomerization of 1,3,5,7-octatetraene in n-hexane at 4.2 K

    PubMed Central

    Granville, Mark F.; Holtom, Gary R.; Kohler, Bryan E.

    1980-01-01

    Photoisomerization of the linear polyene 1,3,5,7-octatetraene has been observed in an n-hexane matrix maintained at the boiling point of helium. To a good approximation, only the trans,trans and cis,trans isomers participate in the photochemistry. These compounds have been unambiguously identified by comparing the observed high-resolution fluorescence spectra to those of chromatographically purified reference compounds. Although the quantum yield of this process is probably low, its microscopic rate seems to compete favorably with vibrational deactivation. PMID:16592751

  13. Thermodiffusion, molecular diffusion and Soret coefficient of binary and ternary mixtures of n-hexane, n-dodecane and toluene.

    PubMed

    Alonso de Mezquia, David; Wang, Zilin; Lapeira, Estela; Klein, Michael; Wiegand, Simone; Mounir Bou-Ali, M

    2014-11-01

    In this study, the thermodiffusion, molecular diffusion, and Soret coefficients of 12 binary mixtures composed of toluene, n-hexane and n-dodecane in the whole range of concentrations at atmospheric pressure and temperatures of 298.15 K and 308.15 K have been determined. The experimental measurements have been carried out using the Thermogravitational Column, the Sliding Symmetric Tubes and the Thermal Diffusion Forced Rayleigh Scattering techniques. The results obtained using the different techniques show a maximum deviation of 9% for the thermodiffusion coefficient, 8% for the molecular diffusion coefficient and 2% for the Soret coefficient. For the first time we report a decrease of the thermodiffusion coefficient with increasing ratio of the thermal expansion coefficient and viscosity for a binary mixture of an organic ring compound with a short n-alkane. This observation is discussed in terms of interactions between the different components. Additionally, the thermogravitational technique has been used to measure the thermodiffusion coefficients of four ternary mixtures consisting of toluene, n-hexane and n-dodecane at 298.15 K. In order to complete the study, the values obtained for the molecular diffusion coefficient in binary mixtures, and the thermodiffusion coefficient of binary and ternary mixtures have been compared with recently derived correlations. PMID:25376978

  14. Reflectometric measurement of n-hexane adsorption on ZnO2 nanohybrid film modified by hydrophobic gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Sebők, Dániel; Csapó, Edit; Ábrahám, Nóra; Dékány, Imre

    2015-04-01

    Zinc-peroxide/poly(styrenesulfonate) nanohybrid thin films (containing 20 bilayers: [ZnO2/PSS]20, d ∼ 500 nm) were prepared using layer-by-layer (LbL) method. The thin film surface was functionalized by different surface modifying agents (silanes, alkylthiols and hydrophobized nanoparticles). Based on the experimental results of quartz crystal microbalance (QCM) and contact angle measurements (as prequalifications) the octanethiol covered gold nanoparticles (OT-AuNPs) were selected for further vapour adsorption studies. Reflectometric interference spectroscopy (RIfS) was used to measure n-hexane vapour adsorption on the original and modified nanohybrid films in a gas flow platform. The thin film provides only the principle of the measurement (by interference phenomenon), the selectivity and hydrophobicity is controlled and enhanced by surface functionalization (by dispersion interaction between the alkyl chains). The interference pattern shift (Δλ) caused by the increase of the optical thickness of the thin film due to vapour adsorption was investigated. It was found that due to the surface functionalization by hydrophobic nanoparticles the effect of water vapour adsorption decreased significantly, while for n-hexane opposite tendency was observed (the effective refractive index and thus the interference pattern shift increased drastically). The correlation between QCM technique and optical method (RIfS) was specified: linear specific adsorbed amount vs. wavelength shift calibration curves were determined in the pr = 0-0.4 relative vapour pressure range. The thin film is suitable for sensorial application (e.g. volatile organic compound/VOC sensor).

  15. Crystallization of thin water films on graphite: Effects of n-hexane, formaldehyde, acetone, and methanol additives

    NASA Astrophysics Data System (ADS)

    Souda, Ryutaro

    2015-12-01

    Interactions of molecular additives with amorphous solid water have been investigated using time-of-flight secondary ion mass spectrometry and temperature programmed desorption. The crystallization temperature of water on a clean graphite substrate decreases from the bulk value of 160 K to 150 K when water deposition temperature increases from 20 K to 100 K. This phenomenon is induced by the formation of a specifically oriented water layer at the interface, as evidenced by that a submonolayer of n-hexane adspecies on graphite quenches this behavior. Thermal desorption spectra of additives reflect their hydration forms. The n-hexane molecules are trapped in the interior of a porous water film via hydrophobic hydration and released explosively during crystallization. The thermal desorption spectra of methanol resemble those of water from multilayer films because methanol can enter the hydrogen-bond network of water via hydrophilic hydration. The hydration of formaldehyde is hydrophobic in nature despite the presence of the polar carbonyl group. Features of both hydrophilic and hydrophobic hydrations are identifiable in acetone-water interactions; the branching ratio depends on the water preparation method and substrate.

  16. Rate constant for OH with selected large alkanes : shock-tube measurements and an improved group scheme.

    SciTech Connect

    Sivaramakrishnan, R.; Michael, J. V.; Chemical Sciences and Engineering Division

    2009-04-06

    High-temperature rate constant experiments on OH with the five large (C{sub 5}-C{sub 8}) saturated hydrocarbons n-heptane, 2,2,3,3-tetramethylbutane (2,2,3,3-TMB), n-pentane, n-hexane, and 2,3-dimethylbutane (2,3-DMB) were performed with the reflected-shock-tube technique using multipass absorption spectrometric detection of OH radicals at 308 nm. Single-point determinations at {approx}1200 K on n-heptane, 2,2,3,3-TMB, n-hexane, and 2,3-DMB were previously reported by Cohen and co-workers; however, the present work substantially extends the database to both lower and higher temperature. The present experiments span a wide temperature range, 789-1308 K, and represent the first direct measurements of rate constants at T > 800 K for n-pentane. The present work utilized 48 optical passes corresponding to a total path length of {approx}4.2 m. As a result of this increased path length, the high OH concentration detection sensitivity permitted pseudo-first-order analyses for unambiguously measuring rate constants.

  17. Mesoporous Aluminosilicate Catalysts for the Selective Isomerization of n-Hexane: The Roles of Surface Acidity and Platinum Metal.

    PubMed

    Musselwhite, Nathan; Na, Kyungsu; Sabyrov, Kairat; Alayoglu, Selim; Somorjai, Gabor A

    2015-08-19

    Several types of mesoporous aluminosilicates were synthesized and evaluated in the catalytic isomerization of n-hexane, both with and without Pt nanoparticles loaded into the mesopores. The materials investigated included mesoporous MFI and BEA type zeolites, MCF-17 mesoporous silica, and an aluminum modified MCF-17. The acidity of the materials was investigated through pyridine adsorption and Fourier Transform-Infrared Spectroscopy (FT-IR). It was found that the strong Brönsted acid sites in the micropores of the zeolite catalysts facilitated the cracking of hexane. However, the medium strength acid sites on the Al modified MCF-17 mesoporous silica greatly enhanced the isomerization reaction. Through the loading of different amounts of Pt into the mesopores of the Al modified MCF-17, the relationship between the metal nanoparticles and acidic sites on the support was revealed. PMID:26168190

  18. Molecular motion of benzene, n-hexane, and cyclohexane in potassium zeolite L studied by deuterium NMR

    SciTech Connect

    Silbernagel, B.G.; Garcia, A.R.; Newsam, J.M.; Hulme, R. )

    1989-08-24

    The molecular motions of perdeuterated benzene, n-hexane, and cyclohexane sorbed at loading levels of 1 molecule per channel lobe (or, equivalently, per unit cell) in potassium zeolite L have been examined by {sup 2}H nuclear magnetic resonance (NMR) for 100 K {le} T {le} 350 K. Benzene (C{sub 6}D{sub 6}) gives a broad signal with, for T < {approx} 150 K, a quadrupolar splitting of half of the static value, interpreted in terms of rapid reorientation in the molecular plane. This mode of motion is consistent with the location of benzene in capping positions above channel wall site potassium cations observed at 78 K by powder neutron diffraction. For temperatures above {approx} 250 K, a less broad component (interpreted as indicating activated benzene site hopping) develops. Sorbed n-hexane (C{sub 6}H{sub 14}) also shows no evidence for isotropic motion. Two distinct spectral components, associated respectively with the methyl and methylene deuterons, are observed. The magnitudes of the {sup 2}H quadrupolar coupling strengths can be interpreted solely in terms of torsional rotations about the carbon-carbon bonds. The temperature dependence of the {sup 2}H spin-lattice relaxation processes suggests an activation energy of {approx} 2 kcal mol{sup {minus}1} for these C-C bond rotations, consistent with earlier studies of bond rotation in alkanes. Sorbed cyclohexane (C{sub 6}D{sub 12}) shows a transition in the dynamical behavior (on the time scale of the {sup 2}H NMR experiment) in the vicinity of 280 K. Close to 280 K , a narrow signal is observed consistent with effectively isotropic reorientations, but both above and below 280 K there is a significant residual quadrupole interaction. The narrow component decreases rapidly with temperature, becoming unobservable below 230 K.

  19. Triplet excitation dynamics of two keto-carotenoids in n-hexane and in methanol as studied by ns flash photolysis spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Li; Hu, Feng; Chang, Yu-Qiang; Zhou, Yan; Wang, Peng; Zhang, Jian-Ping

    2015-07-01

    Siphonaxanthin and siphonein are two keto-carotenoids. Upon anthracene-sensitizing, triplet excitation dynamics of these two carotenoids were studied in n-hexane and in methanol, respectively, by ns flash photolysis spectroscopy. In n-hexane, bleaching of the ground state absorption (GSB) and the excitation triplet (3Car*) absorption were observed. In methanol, upon the decay of the 3Car*, the cation dehydrodimer of carotenoid, #[Car]2+, generated by the same rate, while an additional GSB generated synchronously, a polar solvent assisted and anthracene-sensitized mechanism was addressed based on the discussion. The environment-sensitive triplet excitation dynamics imply their potential role in photo-protection in vivo.

  20. Supercritical SC-CO2 and Soxhlet n-Hexane Extract of Tunisian Opuntia ficus indica Seeds and Fatty Acids Analysis

    PubMed Central

    Yeddes, Nizar; Chérif, Jamila Kalthoum; Jrad, Amel; Barth, Danielle; Trabelsi-Ayadi, Malika

    2012-01-01

    The fatty acids profiles of Tunisian Opuntia ficus indica seeds (spiny and thornless form) were investigated. Results of supercritical carbon dioxide (SC-CO2) and soxhlet n-hexane extract were compared. Quantitatively, the better yield was obtained through soxhlet n-hexane: 10.32% (spiny) and 8.91% (thornless) against 3.4% (spiny) and 1.94% (thornless) by SC-CO2 extract (T = 40°C, P = 180 bar, time = 135 mn, CO2 flow rate = 15 mL·s−1). Qualitatively, the main fatty acids components were the same for the two types of extraction. Linoleic acid was the major compound, SC-CO2: 57.60% (spiny), 59.98% (thornless), soxhlet n-hexane: 57.54% (spiny), 60.66% (thornless), followed by oleic acid, SC-CO2: 22.31% (spiny), 22.40% (thornless), soxhlet n-hexane: 25.28% (spiny), 20.58% (thornless) and palmitic acid, SC-CO2: 14.3% (spiny), 12.92% (thornless), soxhlet n-hexane: 11.33% (spiny), 13.08% (thornless). The SC-CO2 profiles fatty acids showed a richness with other minority compounds such as C20:1, C20:2, and C22.The seeds oil was highly unsaturated (US = 4.44–5.25), and the rising temperatures donot affect the selectivity of fatty acids extract by SC-CO2: US = 4.44 (T = 40°C) and 4.13 (T = 70°C). PMID:22754699

  1. Antiestrogenic and Anti-Inflammatory Potential of n-Hexane Fraction of Vitex negundo Linn Leaf Extract: A Probable Mechanism for Blastocyst Implantation Failure in Mus musculus

    PubMed Central

    Jivrajani, Mehul; Ravat, Nirav; Anandjiwala, Sheetal; Nivsarkar, Manish

    2014-01-01

    The anti-implantation potential of different fractions of Vitex negundo Linn leaf extract was evaluated in female Swiss Albino mice. Animals from different groups were dosed orally either with 0.2% agar (vehicle) or with fractions of V. negundo leaf extract (n-hexane, chloroform, n-butanol, and remnant fractions) at 10:00 a.m., from day 1 to day 6 of pregnancy. The pregnant females from each group were sacrificed on different days of pregnancy (n = 6), and uterus was excised and used for estimation of lipid peroxidation and assay of superoxide dismutase activity as a marker for blastocyst implantation. Animals treated with n-hexane fraction showed altered level of superoxide anion radical and superoxide dismutase activity as compared to control animals. The probable mechanism by which this extract exhibits inhibition of blastocyst implantation is through the anti-inflammatory and antiestrogenic potential. PMID:27351007

  2. Effect of carriers on physico-chemical properties and activity of Pd nano-catalyst in n-hexane isomerization

    NASA Astrophysics Data System (ADS)

    Loc Luu, Cam; Thoa Dao, Thi Kim; Nguyen, Tri; Huong Bui, Thanh; Yen Dang, Thi Ngoc; Hoang, Minh Nam; Thoang Ho, Si

    2013-12-01

    In this work zeolites HY, HZSM-5 and mixes of zeolites with γ-Al2O3 in different ratios were taken as carriers for 0.8 wt% Pd catalysts. Physico-chemical characteristics of the catalysts were determined by methods of Brunauer-Emmett-Teller (BET)-N2 adsorption, x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), transmission electron microscopy (TEM), temperature-programmed reduction (TPR), hydrogen pulse chemisorption (HPC) and NH3 adsorption-desorption. The activity of catalysts was studied at 225-450 °C, at 0.1 and 0.7 MPa with molar ratio of H2:n-C6H14 = 5.92 and n-hexane concentration 9.2 mol%. Mixing of γ-Al2O3 with zeolite made acidity of catalyst weaken and led to a decrease of Pd cluster size, to an increase of Pd dispersity and a reduction of the extent of Pd in the case of catalyst Pd/HY; but for the catalyst Pd/HZSM-5 such mixing led to the reverse effect. That is why the increase of activity in the first case and the decrease of activity in the second case have been observed. It has been found that the optimal ratio of mixed carrier is γ-Al2O3:HY = 2.5:1 and the optimal calcined temperature of NH4ZSM-5 to obtain HZSM-5 is 500-550 °C. An increase of reaction pressure from 0.1 to 0.7 MPa remarkably increased the activity, selectivity and stability of Pd-based catalysts.

  3. Inhalation reproductive toxicology studies: Sperm morphology study of n-hexane in B6C3F1 mice: Final report

    SciTech Connect

    Mast, T.J.; Hackett, P.L.; Decker, J.R.; Westerberg, R.B.; Sasser, L.B.; McClanahan, B.J.; Rommereim, R.L.; Evanoff, J.J.

    1988-08-01

    The straight-chain hydrocarbon, n-hexane, is a volatile, ubiquitous solvent routinely used in industrial environments. Although myelinated nerve tissue is the primary target organ of hexane, the testes have also been identified as being sensitive to hexacarbon exposure. The objective of this study was to evaluate the epididymal sperm morphology of male B6D3F1 mice 5 weeks after exposure to 0, 200, 1000, or 5000 ppM n-hexane, 20 h/day for 5 consecutive days. Two concurrent positive control groups of animals were injected intraperitoneally with either 200 or 250 mg/kg ethyl methanesulfonate, a known mutagen, once each day for 5 consecutive days. The mice were weighed just prior to the first day of exposure and at weekly intervals until sacrifice. During the fifth post-exposure week the animals were killed and examined for gross lesions of the reproductive tract and suspensions of the epididymal sperm were prepared for morphological evaluations. The appearance and behavior of the mice were unremarkable throughout the experiment and there were no deaths. No evidence of lesions in any organ was noted at sacrifice. Mean body weights of male mice exposed to n-hexane were not significantly different from those for the 0-ppM animals at any time during the study. Analyses of the sperm morphology data obtained 5 weeks post-exposure (the only time point examined) indicated that exposure of male mice to relatively high concentrations of n-hexane vapor for 5 days produced no significant effects on the morphology of sperm relative to that of the 0-ppM control group. 24 refs., 2 figs., 7 tabs.

  4. Characterization of digestive enzymes from de-oiled mackerel (Scomber japonicus) muscle obtained by supercritical carbon dioxide and n-hexane extraction as a comparative study.

    PubMed

    Asaduzzaman, A K M; Chun, Byung-Soo

    2015-06-01

    The oil in mackerel muscle was extracted using an environmental friendly solvent, supercritical carbon dioxide (SC-CO2) at a semi-batch flow extraction process and an n-hexane. The SC-CO2 was carried out at temperature 45 °C and pressures ranging from 15 to 25 MPa. The flow rate of CO2 (27 g/min) was constant at the entire extraction period of 2 h. The highest oil extracted residues after SC-CO2 extraction was used for activity measurement of digestive enzymes. Four digestive enzymes were found in water soluble extracts after n-hexane and SC-CO2 treated samples. Amylase, lipase and trypsin activities were higher in water soluble extracts after SC-CO2 treated samples except protease. Among the four digestive enzymes, the activity of amylase was highest and the value was 44.57 uM/min/mg of protein. The water soluble extracts of SC-CO2 and n-hexane treated mackerel samples showed same alkaline optimum pH and pH stability for each of the digestive enzymes. Optimum temperature of amylase, lipase, protease and trypsin was 40, 50, 60 and 30 °C, respectively of both extracts. More than 80 % temperature stability of amylase, lipase, protease and trypsin were retained at mentioned optimum temperature in water soluble extracts of both treated samples. Based on protein patterns, prominent protein band showed in water soluble extracts after SC-CO2 treated samples indicates no denaturation of protein than untreated and n-hexane. PMID:26028731

  5. Enthalpy difference between conformations of normal alkanes: Intramolecular basis set superposition error (BSSE) in the case of n-butane and n-hexane

    NASA Astrophysics Data System (ADS)

    Balabin, Roman M.

    2008-10-01

    In this paper, an extra error source for high-quality ab initio calculation of conformation equilibrium in normal alkanes—intramolecular basis set superposition error (BSSE)—is discussed. Normal butane (n-butane) and normal hexane (n-hexane) are used as representative examples. Single-point energy difference and BSSE values of trans and gauche conformations for n-butane (and trans-trans-trans and gauche-gauche-gauche conformations for n-hexane) were calculated using popular electron correlation methods: The second-order Moller-Plesset (MP2), the fourth-order Moller-Plesset (MP4), and coupled cluster with single and double substitutions with noniterative triple excitation [CCSD(T)] levels of theory. Extrapolation to the complete basis set is applied. The difference between BSSE-corrected and uncorrected relative energy values ranges from ˜100 cal/mol (in case of n-butane) to more than 1000 cal/mol (in case of n-hexane). The influence of basis set type (Pople or Dunning) and size [up to 6-311G(3df,3pd) and aug-cc-pVQZ] is discussed.

  6. Antihyperglycemic and antihyperlipidemic effects of n-hexane fraction from the hydro-methanolic extract of sepals of Salmalia malabarica in streptozotocin-induced diabetic rats.

    PubMed

    De, Debasis; Ali, Kazi Monjur; Chatterjee, Kausik; Bera, Tushar Kanti; Ghosh, Debidas

    2012-01-01

    Bio-efficacy of n-hexane fraction of sepal of Salmalia malabarica was evaluated covering the biochemical sensors for the management of hyperglycemic and hyperlipidemic effects. Evaluation of n-hexane fraction of Salmalia malabarica (SMH) from hydro-methanolic (2:3) extract at the dose of 0.1 gm/kg body weight twice a day were investigated in normal and streptozotocin (STZ) induced diabetic rats. Normal and STZ-induced diabetic rats were divided into five groups. The effect of the fraction on fasting blood glucose (FBG), serum insulin, hemoglobin, glycated hemoglobin, total cholesterol (TC), triglyceride (TG), high density lipoprotein cholesterol (HDLc), low density lipoprotein cholesterol (LDLc), very low density lipoprotein cholesterol (VLDLc), phospholipids, free fatty acids, urea, uric acid, creatinine, albumin and transaminases were investigated in STZ-induced diabetic rat. A significant reduction of FBG level was observed after SMH treatment in STZ-induced diabetic rat. Treatment of diabetic rats with n-hexane fraction of this plant restored the levels of the above biochemical sensors significantly (p<0.001) in respect to the control. Histological studies of pancreas showed a qualitative diminution in the area of the islet's of Langerhans in diabetic group which was recovered by said fraction. Phytochemical screening of the fraction revealed the presence of flavonoids, terpenoids and steroids. PMID:22732718

  7. Influence of turbulence-chemistry interaction for n-heptane spray combustion under diesel engine conditions with emphasis on soot formation and oxidation

    NASA Astrophysics Data System (ADS)

    Bolla, Michele; Farrace, Daniele; Wright, Yuri M.; Boulouchos, Konstantinos; Mastorakos, Epaminondas

    2014-03-01

    The influence of the turbulence-chemistry interaction (TCI) for n-heptane sprays under diesel engine conditions has been investigated by means of computational fluid dynamics (CFD) simulations. The conditional moment closure approach, which has been previously validated thoroughly for such flows, and the homogeneous reactor (i.e. no turbulent combustion model) approach have been compared, in view of the recent resurgence of the latter approaches for diesel engine CFD. Experimental data available from a constant-volume combustion chamber have been used for model validation purposes for a broad range of conditions including variations in ambient oxygen (8‑21% by vol.), ambient temperature (900 and 1000 K) and ambient density (14.8 and 30 kg/m3). The results from both numerical approaches have been compared to the experimental values of ignition delay (ID), flame lift-off length (LOL), and soot volume fraction distributions. TCI was found to have a weak influence on ignition delay for the conditions simulated, attributed to the low values of the scalar dissipation relative to the critical value above which auto-ignition does not occur. In contrast, the flame LOL was considerably affected, in particular at low oxygen concentrations. Quasi-steady soot formation was similar; however, pronounced differences in soot oxidation behaviour are reported. The differences were further emphasised for a case with short injection duration: in such conditions, TCI was found to play a major role concerning the soot oxidation behaviour because of the importance of soot-oxidiser structure in mixture fraction space. Neglecting TCI leads to a strong over-estimation of soot oxidation after the end of injection. The results suggest that for some engines, and for some phenomena, the neglect of turbulent fluctuations may lead to predictions of acceptable engineering accuracy, but that a proper turbulent combustion model is needed for more reliable results.

  8. Role of the medium on the C343 inter/intramolecular hydrogen bond interactions. An absorption, emission, and 1HNMR investigation of C343 in benzene/n-heptane mixtures.

    PubMed

    Gutierrez, Jorge A; Falcone, R Darío; Silber, Juana J; Correa, N Mariano

    2010-07-15

    C343, a common molecular probe utilized in solvation dynamics experiments, was studied in homogeneous media. Absorption, emission, and (1)HNMR spectroscopies were used to investigate the behavior of C343 in benzene and in benzene/n-heptane mixtures. We demonstrate the implications of the medium polarity, measured as the Kamlet-Taft polarity-polarizability (pi*) parameter, in the C343 inter/intramolecular hydrogen bond (H-bond) interactions and the role that this interaction plays in the dimerization process of the dye. In pure benzene, the dimer prevails because the intermolecular H-bond interaction is favored. On the other hand, as the n-heptane content increases the intramolecular H-bond is the strongest and the C343 monomer is favored. As the polarity of the medium decreases, the solvophobic interaction makes that C343 monomer species experiences a more complicated aggregation process beyond the simple monomer dimer equilibrium present in pure benzene. Thus, the addition of n-heptane to the mixture yields a C343 higher-order aggregates species. Thus, our work reveals the importance that the medium has on the behavior of a widespread dye used as chromophore for very different systems such as homogeneous and microheterogenous media. This is very important since the use of chromophores without understanding its chemistry can induce artifacts into the interpretation of solvation dynamics in heterogeneous environments, in particular, those provided by biological systems such as proteins. Considerable care in choosing and characterizing the system is required to analyze the results fully. PMID:20565101

  9. Effect of total hydroalcholic extract of Nigella sativa and its n-hexane and ethyl acetate fractions on ACHN and GP-293 cell lines.

    PubMed

    Shahraki, Samira; Khajavirad, Abolfazl; Shafei, Mohammad Naser; Mahmoudi, Mahmoud; Tabasi, Nafisa Sadat

    2016-01-01

    Medicinal plants are noted for their many advantages including the ability to treat diseases such as cancer. In this study, we examined the antitumor effect of the medicinal plant Nigella sativa on the morphology, survival, and apoptosis of ACHN (human renal adenocarcinoma) and GP-293 (normal renal epithelial) cell lines. From a hydroalcoholic extract of N. sativa, n-hexane and ethyl acetate fractions were extracted. Cells were treated with various concentrations of total hydroalcholic extract and n-hexane and ethyl acetate fractions; cell viability, morphological changes, and apoptosis were then determined. Results were presented as mean ± standard error of the mean (SEM). One-way analysis of variance (ANOVA) was applied for the statistical analysis of the data. The total extract and the fractions in a dose- and time-dependent manner reduced the cell viability in ACHN with no effect on the GP-293 cell line. In addition, the total extract resulted in more morphological changes in the ACHN cells compared to the GP-293 cells. The effect of the total extract in inducing apoptosis after 48 hours in the ACHN cell line was greater than in GP-293. In addition, the effect of the two fractions was lower than the total extract at all used concentrations. Therefore, the effect of total extract and n-hexane and ethyl acetate fractions of N. sativa on cell viability and apoptosis in the ACHN cell line is greater than in the GP-293 cell line. However, the effect of the total extract is higher than either of the two fractions on their own. PMID:26870685

  10. Effect of total hydroalcholic extract of Nigella sativa and its n-hexane and ethyl acetate fractions on ACHN and GP-293 cell lines

    PubMed Central

    Shahraki, Samira; Khajavirad, Abolfazl; Shafei, Mohammad Naser; Mahmoudi, Mahmoud; Tabasi, Nafisa Sadat

    2015-01-01

    Medicinal plants are noted for their many advantages including the ability to treat diseases such as cancer. In this study, we examined the antitumor effect of the medicinal plant Nigella sativa on the morphology, survival, and apoptosis of ACHN (human renal adenocarcinoma) and GP-293 (normal renal epithelial) cell lines. From a hydroalcoholic extract of N. sativa, n-hexane and ethyl acetate fractions were extracted. Cells were treated with various concentrations of total hydroalcholic extract and n-hexane and ethyl acetate fractions; cell viability, morphological changes, and apoptosis were then determined. Results were presented as mean ± standard error of the mean (SEM). One-way analysis of variance (ANOVA) was applied for the statistical analysis of the data. The total extract and the fractions in a dose- and time-dependent manner reduced the cell viability in ACHN with no effect on the GP-293 cell line. In addition, the total extract resulted in more morphological changes in the ACHN cells compared to the GP-293 cells. The effect of the total extract in inducing apoptosis after 48 hours in the ACHN cell line was greater than in GP-293. In addition, the effect of the two fractions was lower than the total extract at all used concentrations. Therefore, the effect of total extract and n-hexane and ethyl acetate fractions of N. sativa on cell viability and apoptosis in the ACHN cell line is greater than in the GP-293 cell line. However, the effect of the total extract is higher than either of the two fractions on their own. PMID:26870685

  11. Steam reforming of n-hexane on pellet and monolithic catalyst beds. A comparative study on improvements due to heat transfer

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Monolithic catalysts with higher available active surface areas and better thermal conductivity than conventional pellets beds, making possible the steam reforming of fuels heavier than naphtha, were examined. Performance comparisons were made between conventional pellet beds and honeycomb monolith catalysts using n-hexane as the fuel. Metal-supported monoliths were examined. These offer higher structural stability and higher thermal conductivity than ceramic supports. Data from two metal monoliths of different nickel catalyst loadings were compared to pellets under the same operating conditions. Improved heat transfer and better conversion efficiencies were obtained with the monolith having higher catalyst loading. Surface-gas interaction was observed throughout the length of the monoliths.

  12. Sorption rate and thermal barriers in a gas-zeolite system: investigation of n-hexane sorption in MFI-type zeolite.

    PubMed

    Wloch, J; Kornatowski, J

    2004-02-17

    The nonequilibrium gravimetric sorption method was used to determine diffusion coefficient values for n-hexane in MFI-type materials. Improvements in the measurement device and experimental conditions resulted in high values of the corrected diffusion coefficient, which are comparable to the literature data obtained by the methods of pulsed field gradient nuclear magnetic resonance (PFG NMR) and frequency response (FR). The results indicate that thermal effects of sorption affect practically neither the rate of the sorption nor the diffusion coefficient. PMID:15803693

  13. Solid-liquid work of adhesion of coarse-grained models of n-hexane on graphene layers derived from the conditional reversible work method

    SciTech Connect

    Ardham, Vikram Reddy; Leroy, Frédéric E-mail: f.leroy@theo.chemie.tu-darmstadt.de; Deichmann, Gregor; Vegt, Nico F. A. van der E-mail: f.leroy@theo.chemie.tu-darmstadt.de

    2015-12-28

    We address the question of how reducing the number of degrees of freedom modifies the interfacial thermodynamic properties of heterogeneous solid-liquid systems. We consider the example of n-hexane interacting with multi-layer graphene which we model both with fully atomistic and coarse-grained (CG) models. The CG models are obtained by means of the conditional reversible work (CRW) method. The interfacial thermodynamics of these models is characterized by the solid-liquid work of adhesion W{sub SL} calculated by means of the dry-surface methodology through molecular dynamics simulations. We find that the CRW potentials lead to values of W{sub SL} that are larger than the atomistic ones. Clear understanding of the relationship between the structure of n-hexane in the vicinity of the surface and W{sub SL} is elucidated through a detailed study of the energy and entropy components of W{sub SL}. We highlight the crucial role played by the solid-liquid energy fluctuations. Our approach suggests that CG potentials should be designed in such a way that they preserve the range of solid-liquid interaction energies, but also their fluctuations in order to preserve the reference atomistic value of W{sub SL}. Our study thus opens perspectives into deriving CG interaction potentials that preserve the thermodynamics of solid-liquid contacts and will find application in studies that intend to address materials driven by interfaces.

  14. Kinetics of catalytic oxidation of benzene, n-hexane, and emission gas from a refinery oil/water separator over a chromium oxide catalyst.

    PubMed

    Wang, J B; Chou, M S

    2000-02-01

    With the advances made in the past decade, catalytic incineration of volatile organic compounds (VOCs) has become the technology of choice in a wide range of pollution abatement strategies. In this study, a test was undertaken for the catalytic incineration, over a chromium oxide (Cr2O3) catalyst, of n-hexane, benzene, and an emission air/vapor mixture collected from an oil/water separator of a refinery. Reactions were carried out by controlling the feed stream to constant VOC concentrations and temperatures, in the ranges of 1300-14,700 mg/m3 and 240-400 degrees C, respectively. The destruction efficiency for each of the three VOCs as a function of influent gas temperature and empty bed gas residence time was obtained. Results indicate that n-hexane and the oil vapor with a composition of straight- and branch-chain aliphatic hydrocarbons exhibited similar catalytic incineration effects, while benzene required a higher incineration temperature or longer gas retention time to achieve comparable results. In the range of the VOC concentrations studied, at a given gas residence time, increasing the operating temperature of the catalyst bed increased the destruction efficiency. However, the much higher temperatures required for a destruction efficiency of over 99% may be not cost-effective and are not suggested. A first-order kinetics with respect to VOC concentration and an Arrhenius temperature dependence of the kinetic constant appeared to be an adequate representation for the catalytic oxidation of these volatile organics. Activation energy and kinetic constants were estimated for each of the VOCs. Low-temperature destruction of the target volatile organics could be achieved by using the Cr2O3 catalyst. PMID:10680352

  15. Effect of Different Surfactants on the Interfacial Behavior of the n-Hexane-Water System in the Presence of Silica Nanoparticles.

    PubMed

    Biswal, Nihar Ranjan; Rangera, Naveen; Singh, Jayant K

    2016-07-28

    This paper presents the effect of negatively charged silica nanoparticles (NPs) on the interfacial tension of the n-hexane-water system at variable concentrations of four different surfactants, viz., an anionic surfactant, sodium dodecyl sulfate (SDS), a cationic surfactant, cetyltrimethylammonium bromide (CTAB), and two nonionic surfactants, Tween 20 and Triton X-100 (TX-100). The presence of negatively charged silica nanoparticles is found to have a different effect depending on the type of surfactant. In the case of ionic surfactants, SDS and CTAB, silica NPs reduce the interfacial tension of the system. On the contrary, for nonionic surfactants, Tween 20 and TX-100, silica NPs increase the interfacial tension. The increasing/decreasing nature of the interfacial tension in the presence of NPs is well supported by the calculated surface excess concentrations. The diffusion kinetic control (DKC) and statistical rate theory (SRT) models are used to understand the behavior of dynamic interfacial tension of the surfactant-NP-oil-water system. The DKC model is found to describe the studied surfactant-NP-oil-water systems more aptly. PMID:27367433

  16. Enzymatic hydrolysis of N-benzoyl-L-tyrosine p-nitroanilide by α-chymotrypsin in DMSO-water/AOT/n-heptane reverse micelles. A unique interfacial effect on the enzymatic activity.

    PubMed

    Moyano, Fernando; Setien, Evangelina; Silber, Juana J; Correa, N Mariano

    2013-07-01

    The reverse micelle (RM) media are very good as nanoreactors because they can create a unique microenvironment for carrying out a variety of chemical and biochemical reactions. The aim of the present work is to determine the influence of different water-dimethyl sulfoxide (DMSO) mixtures encapsulated in 1,4-bis-2-ethylhexylsulfosuccinate (AOT)/n-heptane RMs on the enzymatic hydrolysis of N-benzoyl-L-tyrosine p-nitroanilide (Bz-Try-pNA) by α-chymotrypsin (α-CT). The reaction was first studied in homogeneous media at different DMSO-water mixture compositions and in DMSO-water/AOT/n-heptane RMs. The hydrolysis rates of Bz-Try-pNA catalyzed by α-CT were determined by UV-vis spectroscopy. The reaction follows the Michaelis-Menten mechanism and the kinetic parameters: kcat, KM, and kcat/KM were evaluated under different conditions. In this homogeneous media, DMSO plays an important role in the solubilization process of the peptide which is almost insoluble in water, but it has a tremendous impact on the inactivation of α-CT. It is shown that the enzyme dissolved in a 20% molar ratio of the DMSO-water mixture does not present enzymatic activity. Dynamic light scattering has been used to assess the formation of DMSO-water/AOT/heptane RMs at different DMSO compositions. The results also show that there is preferential solvation of the AOT RM interface by water molecules. To test the use of these RMs as nanoreactors, the kinetic parameters for the enzymatic reaction in these systems have been evaluated. The parameters were determined at fixed W(S) {W(S) = ([water] + [DMSO])/[AOT] = 20} at different DMSO-water compositions. The results show that the Michaelis-Menten mechanism is valid for α-CT in all the RM systems studied and that the reaction takes place at the RM interface. Surprisingly, it was observed that the enzyme encapsulated by the RMs show catalytic effects with similar kcat/KM values at any DMSO composition investigated, which evidence that DMSO molecules are

  17. N,N'-(Hexane-1,6-diyl)bis(4-methyl-N-(oxiran-2-ylmethyl)benzenesulfonamide): Synthesis via cyclodextrin mediated N-alkylation in aqueous solution and further Prilezhaev epoxidation

    PubMed Central

    Fischer, Julian; Millan, Simon

    2013-01-01

    Summary N-alkylation of N,N'-(hexane-1,6-diyl)bis(4-methylbenzenesulfonamide) with allyl bromide and subsequent Prilezhaev reaction with m-chloroperbenzoic acid to give N,N'-(hexane-1,6-diyl)bis(4-methyl-N-(oxiran-2-ylmethyl)benzenesulfonamide) is described. This twofold alkylation was performed in aqueous solution, whereby α-, and randomly methylated β-cyclodextrin were used as adequate phase transfer catalysts and the cyclodextrin–guest complexes were characterized by 1H NMR and 2D NMR ROESY spectroscopy. Finally, the curing properties of the diepoxide with lysine-based α-amino-ε-caprolactam were analyzed by rheological measurements. PMID:24367447

  18. Changes in autonomic function as determined by ECG R-R interval variability in sandal, shoe and leather workers exposed to n-hexane, xylene and toluene.

    PubMed

    Murata, K; Araki, S; Yokoyama, K; Yamashita, K; Okajima, F; Nakaaki, K

    1994-01-01

    To clarify if autonomic nervous system effects might be associated with exposure to organic solvents, 30 sandal, shoe and leather workers exposed to n-hexane, xylene, and toluene, and 25 unexposed controls were examined using the coefficient of variation in electrocardiographic R-R intervals (CVRR), combined with the distribution of nerve conduction velocities (DCV). The C-CVRSA and C-CVMWSA (two component CVs of the CVRR reflecting parasympathetic and sympathetic activities, respectively) were also computed from component spectral powers using autoregressive spectral and component analyses. Concentrations of the metabolites of the solvents in urine samples taken in the morning before work were 0-3.18 (mean 1.39) mg/l for 2,5-hexanedione, 0.10-0.43 (mean 0.19) g/g creatinine (Cn) for methylhippuric acid, and 0.05-2.53 (mean 0.41) g/g Cn for hippuric acid. In the solvent workers, the CVRR and C-CVRSA were reduced significantly when compared with the unexposed controls. The faster velocities of the DCV as well as the sensory median nerve conduction velocity (SCV) were significantly slowed in the solvent-exposed workers. The SCV was significantly correlated with the CVRR and C-CVMWSA among the solvent workers. These data suggest that chronic exposure to some organic solvents may affect cardiac autonomic function (mainly, parasympathetic activity) in addition to faster myelinated fibers of the peripheral nerves. However, the absence of significant dose-effect relations among the solvent workers makes it difficult to definitively attribute the differences to specific solvent exposures. PMID:7715857

  19. Pollutant emissions from gasoline combustion. 1. Dependence on fuel structural functionalities.

    PubMed

    Zhang, Hongzhi R; Eddings, Eric G; Sarofim, Adel F

    2008-08-01

    To study the formation of air pollutants and soot precursors (e.g., acetylene, 1,3-butadiene, benzene, and higher aromatics) from aliphatic and aromatic fractions of gasoline fuels, the Utah Surrogate Mechanisms is extended to include submechanisms of gasoline surrogate compounds using a set of mechanism generation techniques. The mechanism yields very good predictions of species concentrations in premixed flames of n-heptane, isooctane, benzene, cyclohexane, olefins, oxygenates, and gasoline using a 23-component surrogate formulation. The 1,3-butadiene emission comes mainly from minor fuel fractions of olefins and cyclohexane. The benzene formation potential of gasoline components shows the following trends as functions of (i) chemical class: n-paraffins < isoparaffins < olefins < naphthalenes < alkylbenzenes < cycloparaffins < toluene; (ii) carbon number: n-butane < n-pentane < n-hexane; and (iii) branching: n-hexane < isohexane < 2,2,4-trimethylpentane < 2,2,3,3-tetramethylbutane. In contrast, fuel structure is not the main factor in determining acetylene formation. Therefore, matching the benzene formation potential of the surrogate fuel to that produced by the real fuel should have priority when selecting candidate surrogate components for combustion simulations. PMID:18754484

  20. Crystal structure of bis­(benzyl­amine-κN)[5,10,15,20-tetra­kis­(4-chloro­phen­yl)porphyrinato-κ4 N]iron(II) n-hexane monosolvate

    PubMed Central

    Dhifaoui, Selma; Harhouri, Wafa; Bujacz, Anna; Nasri, Habib

    2016-01-01

    In the title compound, [FeII(C44H24Cl4N4)(C6H5CH2NH2)2]·C6H14 or [FeII(TPP-Cl)(BzNH2)2]·n-hexane [where TPP-Cl and BzNH2 are 5,10,15,20-tetra­kis­(4-chloro­phen­yl)porphyrinate and benzyl­amine ligands, respectively], the FeII cation lies on an inversion centre and is octa­hedrally coordinated by the four pyrrole N atoms of the porphyrin ligand in the equatorial plane and by two amine N atoms of the benzyl­amine ligand in the axial sites. The crystal structure also contains one inversion-symmetric n-hexane solvent mol­ecule per complex mol­ecule. The average Fe—Npyrrole bond length [1.994 (3) Å] indicates a low-spin complex. The crystal packing is sustained by N—H⋯Cl and C—H⋯Cl hydrogen-bonding inter­actions and by C—H⋯π inter­molecular inter­actions, leading to a three-dimensional network structure. PMID:26870596

  1. Crystal structure of bis-(benzyl-amine-κN)[5,10,15,20-tetra-kis-(4-chloro-phen-yl)porphyrinato-κ(4) N]iron(II) n-hexane monosolvate.

    PubMed

    Dhifaoui, Selma; Harhouri, Wafa; Bujacz, Anna; Nasri, Habib

    2016-01-01

    In the title compound, [Fe(II)(C44H24Cl4N4)(C6H5CH2NH2)2]·C6H14 or [Fe(II)(TPP-Cl)(BzNH2)2]·n-hexane [where TPP-Cl and BzNH2 are 5,10,15,20-tetra-kis-(4-chloro-phen-yl)porphyrinate and benzyl-amine ligands, respectively], the Fe(II) cation lies on an inversion centre and is octa-hedrally coordinated by the four pyrrole N atoms of the porphyrin ligand in the equatorial plane and by two amine N atoms of the benzyl-amine ligand in the axial sites. The crystal structure also contains one inversion-symmetric n-hexane solvent mol-ecule per complex mol-ecule. The average Fe-Npyrrole bond length [1.994 (3) Å] indicates a low-spin complex. The crystal packing is sustained by N-H⋯Cl and C-H⋯Cl hydrogen-bonding inter-actions and by C-H⋯π inter-molecular inter-actions, leading to a three-dimensional network structure. PMID:26870596

  2. Rate Constants for the Reactions of Hydroxyl Radical with Several Alkanes, Cycloalkanes, and Dimethyl Ether

    NASA Technical Reports Server (NTRS)

    DeMore, W.; Bayes, K.

    1998-01-01

    Relative rate experiements were used to measure rate constants and temperature denpendencies of the reactions of OH with propane, n-butane, n-pentane, n-hexane, cyclopropane, cyclobutane, cyclopentane, and dimethyl ether.

  3. Comparative effect of organosulfur compounds on catalysts for the n-heptane isomerization reaction at medium pressure: Mo{sub 2}C-oxygen-modified, MoO{sub 3}-carbon-modified, Pt/{gamma}-Al{sub 2}O{sub 3}, and Pt/{beta}-zeolite catalysts

    SciTech Connect

    York, A.P.E.; Pham-Huu, C.; Del Gallo, P.; Ledoux, M.J.; Blekkan, E.A.

    1996-03-01

    Molybdenum oxycarbide formed from oxidized Mo{sub 2}C or reduced MoO{sub 3} is an active and very selective catalyst for the isomerization of n-heptane compared to supported Pt. Deactivation experiments performed on the catalysts with different concentrations of organosulfur compounds show that molybdenum oxycarbide exhibits a very high resistance to deactivation, whereas with platinum-based catalysts deactivation occurs even at low sulfur concentration in the feed. Deactivation can be slowed by increasing the hydrogen partial pressure from 6 to 20 bar. In these conditions, the molybdenum oxycarbide shows no deactivation with sulfur concentrations up to 120 ppm of S. In addition, the deactivated molybdenum catalysts can be easily regenerated by mild oxidative treatment under flowing air at atmospheric pressure and 723 K for 2 h followed by a reactivation period under the hydrogen and hydrocarbon mixture.

  4. Bis[3α,7α,12α-tris­(4-nitro­benzo­yloxy)-5β-cholan-24-yl] disulfide–ethyl acetate–n-hexane (4/4/1)

    PubMed Central

    Brzezinski, Krzysztof; Tomkiel, Aneta M.; Łotowski, Zenon; Morzycki, Jacek; Dauter, Zbigniew

    2011-01-01

    The crystal structure of the title compound, C90H100N6O24S2·C4H8O2·0.25C6H14, solved and refined against synchrotron diffraction data, contains two formula units in the asymmetric unit with the all-trans n-hexane mol­ecule having half-occupancy and one of the ethyl acetate mol­ecules disordered over two positions. The two symmetry-independent disulfide mol­ecules are assembled by approximate face-to-face and face-to-edge inter­actions between their 4-nitro­benzo­yloxy groups into an inter­twined dimer having a double-helix-type structure. The centrally placed disulfide bridges in the two symmetry-independent mol­ecules exhibit different helicity as shown by the C—S—S—C torsion angles of 71.0 (1) and −92.5 (1)°. PMID:21522786

  5. Enthalpy Differences of the n-Pentane Conformers.

    PubMed

    Csontos, József; Nagy, Balázs; Gyevi-Nagy, László; Kállay, Mihály; Tasi, Gyula

    2016-06-14

    The energy and enthalpy differences of alkane conformers in various temperature ranges have been the subject for both experimental and theoretical studies over the last few decades. It was shown previously for the conformers of butane [G. Tasi et al., J. Chem. Theory Comput. 2012, 8, 479-486] that quantum chemical results can compete with spectroscopic techniques and results obtained even from the most carefully performed experiments could be biased due to the improper statistical model utilized to evaluate the raw experimental data. In the current study, on one hand, the experimental values and their uncertainties for the enthalpy differences for pentane conformers are re-evaluated using the appropriate statistical model. On the other hand, a coupled-cluster-based focal-point analysis has been performed to calculate energy and enthalpy differences for the conformers of pentane. The model chemistry defined in this study includes contributions up to the perturbative quadruple excitations augmented with further small correction terms beyond the Born-Oppenheimer and nonrelativistic approximations. Benchmark quality energy and enthalpy differences for the pentane conformers are given at temperatures 0 and 298.15 K as well as for the various temperature ranges used in the gas-phase experimental measurements. Furthermore, a slight positive shift for the experimental enthalpy differences is also predicted due to an additional Raman active band belonging to the gauche-gauche conformer. PMID:27096811

  6. Isotope values of atmospheric halocarbons and hydrocarbons from Irish urban, rural, and marine locations

    NASA Astrophysics Data System (ADS)

    Redeker, K. R.; Davis, S.; Kalin, R. M.

    2007-08-01

    Stable carbon isotope ratios for 37 hydrocarbon, CFC and halocarbon compounds were determined over the course of 1 year (86 samples) from the urban Belfast environment, Northern Ireland (NI). A smaller number of samples were collected from rural locations at Crossgar and Hillsborough, NI, and one marine location at Mace Head, Republic of Ireland. Source δ13C "signatures" suggest that C5 alkanes and ≥C4 alkenes are most likely derived from vehicle emissions. C3-C5 hydrocarbons show significant enrichment of δ13C with iso-alkanes < n-alkanes < alkenes < alkynes. There is also significant enrichment of δ13C from propane to n-butane to n-pentane. There is no significant separation between n-pentane, n-hexane, n-heptane or methyl-butane, methyl pentane and methyl hexanes. Calculated hydroxyl reaction kinetic isotope effects and subsequent δ13C enrichment are insufficient to explain shifts in isotopic ratio relative to concentration for all compounds as is differences in origin of air mass. Very few compounds show significant diurnal shifts; however, alkanes and ≥C4 alkenes demonstrate consistent enrichment of isotopic ratios when summer samples are compared to winter samples. Benzene is the sole compound measured that appears to become more depleted in δ13C when summer samples are compared against winter samples. Urban air, sampled at Belfast, which has originated in Europe shows enriched values for hydrocarbons while air which has originated in the Arctic Ocean is most similar to marine air off the Atlantic, sampled at Mace Head, Ireland.

  7. Rate constants for OH with selected large alkanes : shock-tube measurements and an improved group scheme.

    SciTech Connect

    Sivaramakrishnan, R.; Michael, J. V.; Chemical Sciences and Engineering Division

    2009-04-30

    High-temperature rate constant experiments on OH with the five large (C{sub 5}-C{sub 8}) saturated hydrocarbons n-heptane, 2,2,3,3-tetramethylbutane (2,2,3,3-TMB), n-pentane, n-hexane, and 2,3-dimethylbutane (2,3-DMB) were performed with the reflected-shock-tube technique using multipass absorption spectrometric detection of OH radicals at 308 nm. Single-point determinations at {approx}1200 K on n-heptane, 2,2,3,3-TMB, n-hexane, and 2,3-DMB were previously reported by Cohen and co-workers; however, the present work substantially extends the database to both lower and higher temperature. The present experiments span a wide temperature range, 789-1308 K, and represent the first direct measurements of rate constants at T > 800 K for n-pentane. The present work utilized 48 optical passes corresponding to a total path length of {approx}4.2 m. As a result of this increased path length, the high OH concentration detection sensitivity permitted pseudo-first-order analyses for unambiguously measuring rate constants. The experimental results can be expressed in Arrhenius form in units of cm{sup 3} molecule{sup -1} s{sup -1} as follows: K{sub OH+n-heptane} = (2.48 {+-} 0.17) x 10{sup -10} exp[(-1927 {+-} 69 K)/T] (838-1287 K); k{sub OH+2,2,3,3-TMB} = (8.26 {+-} 0.89) x 10{sup -11} exp[(-1337 {+-} 94 K)/T] (789-1061 K); K{sub OH+n-pentane} = (1.60 {+-} 0.25) x 10{sup -10} exp[(-1903 {+-} 146 K)/T] (823-1308 K); K{sub OH+n-hexane} = (2.79 {+-} 0.39) x 10{sup -10} exp[(-2301 {+-} 134 K)/T] (798-1299 K); and k{sub OH+2,3-DMB} = (1.27 {+-} 0.16) x 10{sup -10} exp[(-1617 {+-} 118 K)/T] (843-1292 K). The available experimental data, along with lower-T determinations, were used to obtain evaluations of the experimental rate constants over the temperature range from {approx}230 to 1300 K for most of the title reactions. These extended-temperature-range evaluations, given as three-parameter fits, are as follows: k{sub OH+n-heptane} = 2.059 x 10{sup -5}T{sup 1.401} exp(33 K/T) cm{sup 3

  8. A moderate distortion of the `picket-fence' porphyrin (cryptand-222)potassium chlorido[meso-α,α,α,α-tetrakis(o-pivalamidophenyl)porphyrinato]ferrate(II) n-hexane monosolvate.

    PubMed

    Yu, Qiang; Liu, Diansheng; Li, Xiangjun; Li, Jianfeng

    2015-10-01

    As representative porphyrin model compounds, the structures of `picket-fence' porphyrins have been studied intensively. The title solvated complex salt {systematic name: (4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane)potassium(I) [5,10,15,20-tetrakis(2-tert-butanamidophenyl)porphyrinato]iron(II) n-hexane monosolvate}, [K(C18H36N2O6)][Fe(C64H64N8O4)Cl]·C6H14 or [K(222)][Fe(TpivPP)Cl]·C6H14 [222 is cryptand-222 or 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane, and TpivPP is meso-α,α,α,α-tetrakis(o-pivalamidophenyl)porphyrinate(2-)], [K(222)][Fe(TpivPP)Cl]·C6H14, is a five-coordinate high-spin iron(II) picket-fence porphyrin complex. It crystallizes with a potassium cation chelated inside a cryptand-222 molecule; the average K-O and K-N distances are 2.81 (2) and 3.05 (2) Å, respectively. One of the protecting tert-butyl pickets is disordered. The porphyrin plane presents a moderately ruffled distortion, as suggested by the atomic displacements. The axial chloride ligand is located inside the molecular cavity on the hindered porphyrin side and the Fe-Cl bond is tilted slightly off the normal to the porphyrin plane by 4.1°. The out-of-plane displacement of the metal centre relative to the 24-atom mean plane (Δ24) is 0.62 Å, indicating a noticeable doming of the porphyrin core. PMID:26422211

  9. Direct observation of metal nanoparticles as heterogeneous nuclei for the condensation of supersaturated organic vapors: Nucleation of size-selected aluminum nanoparticles in acetonitrile and n-hexane vapors

    SciTech Connect

    Abdelsayed, Victor; Samy El-Shall, M.

    2014-08-07

    This work reports the direct observation and separation of size-selected aluminum nanoparticles acting as heterogeneous nuclei for the condensation of supersaturated vapors of both polar and nonpolar molecules. In the experiment, we study the condensation of supersaturated acetonitrile and n-hexane vapors on charged and neutral Al nanoparticles by activation of the metal nanoparticles to act as heterogeneous nuclei for the condensation of the organic vapor. Aluminum seed nanoparticles with diameters of 1 and 2 nm are capable of acting as heterogeneous nuclei for the condensation of supersaturated acetonitrile and hexane vapors. The comparison between the Kelvin and Fletcher diameters indicates that for the heterogeneous nucleation of both acetonitrile and hexane vapors, particles are activated at significantly smaller sizes than predicted by the Kelvin equation. The activation of the Al nanoparticles occurs at nearly 40% and 65% of the onset of homogeneous nucleation of acetonitrile and hexane supersaturated vapors, respectively. The lower activation of the charged Al nanoparticles in acetonitrile vapor is due to the charge-dipole interaction which results in rapid condensation of the highly polar acetonitrile molecules on the charged Al nanoparticles. The charge-dipole interaction decreases with increasing the size of the Al nanoparticles and therefore at low supersaturations, most of the heterogeneous nucleation events are occurring on neutral nanoparticles. No sign effect has been observed for the condensation of the organic vapors on the positively and negatively charged Al nanoparticles. The present approach of generating metal nanoparticles by pulsed laser vaporization within a supersaturated organic vapor allows for efficient separation between nucleation and growth of the metal nanoparticles and, consequently controls the average particle size, particle density, and particle size distribution within the liquid droplets of the condensing vapor. Strong

  10. Kinetic modeling of hydrocarbon autoignition at low and intermediate temperatures in a rapid compression machine

    SciTech Connect

    Curran, H J; Pitz, W J; Westbrook, C K; Griffiths, J F; Mohamed, C

    2000-11-01

    A computer model is used to examine oxidation of hydrocarbon fuels in a rapid compression machine. For one of the fuels studied, n-heptane, significant fuel consumption is computed to take place during the compression stroke under some operating conditions, while for the less reactive n-pentane, no appreciable fuel consumption occurs until after the end of compression. The third fuel studied, a 60 PRF mixture of iso-octane and n-heptane, exhibits behavior that is intermediate between that of n-heptane and n-pentane. The model results indicate that computational studies of rapid compression machine ignition must consider fuel reaction during compression in order to achieve satisfactory agreement between computed and experimental results.

  11. Extents of alkane combustion during rapid compression leading to single and two stage ignition

    SciTech Connect

    Cox, A.; Griffiths, J.F.; Mohamed, C.; Curran, H.; Pitz, W.J.; Westbrook, C.K.

    1996-02-01

    Extents of reactant consumption have been measured during the course of spontaneous ignition following rapid compression of N-pentane and N-heptane and also of PRF 60 (N-heptane = i-octane, 2.2.4 trimethylpentane) in stoichiometric mixtures with air. Compressed gas temperatures of 720-750 K and 845-875 K were studied at reactant densities of 131 mol m{sup minus 3}. At the lower gas temperature there was no evidence of reactant consumption during the course of the compression stroke. Two-stage ignition occurred at these temperatures, but only modest proportions of n-pentane were consumed during the first stage (< 15%) whereas about 40% of proportions of n- heptane reacted under the same conditions. At the higher compressed gas temperature the oxidation of n-pentane began only after the piston had stopped, whereas more than 30% of the n-heptane had already been consumed in the final stage of the compression stroke. The behavior of the PRF 60 mixture differed somewhat from that of N- pentane despite the similarly of the research octane numbers. Although there was a preferential oxidation of n-heptane at T{sub c} = 850K, which persisted throughout the early development of spontaneous ignition during the post-compression period, oxidation of both components of the PRF 60 mixture began before the piston had stopped. Numerical simulations of the spontaneous ignition under conditions resembling those of the rapid compression experiments show that the predicted reactivity from detailed kinetics are consistent with the observed features. Insights into the kinetic interactions that give rise to the relative reactivities of the primary reference fuel components are established

  12. [Surface characterization of urushiol-titanium chelate polymers by inverse gas chromatography].

    PubMed

    Xu, Yanlian; Lin, Jinhuo; Xia, Jianrong; Hu, Binghuan

    2011-03-01

    Urushiol-titanium chelate polymer (UTP), the reaction product of urushiol with titanium compound, is a special eco-friendly polymer with excellent performances, such as strong acids-resistance, strong alkalis-resistance, salt solution-resistance and several organic solvent-resistance. Inverse gas chromatography (IGC) was used to measure the dispersive component of surface free energy (gamma(s)d) and the Lewis acid-base parameters of UTP in this work. The gamma(s)d and the acid/base characters of UTP' surfaces were estimated by the retention time with different non-polar and polar probes at infinite dilution region. n-Pentane (C5), n-hexane (C6), n-heptane (C7), n-octane (C8) and n-nonane (C9) were chosen as the non-polar probes to characterize the gamma(s)d. Trichloromethane (CHCl3), tetrahydrofuran (THF) and acetone were chosen as polar probes to detect the Lewis acid-base parameters. The specific free energy (deltaG(a)AB) and the enthalpy (deltaH(a)AB) of adsorption corresponding to acid-base surface interactions were determined. By correlating deltaH(a)AB with the donor and acceptor numbers of the probes, the acidic (K(a)) and the basic (K(b)) parameters of the samples were calculated. The results showed that the dispersive components of the free energy of UTP were 37.68, 33.53, 35.92, 24.01 and 31.32 mJ/m2 at 70, 80, 90, 100 and 110 degrees C, respectively. The Lewis acidic number K(a) of UTP was 0.185 3, and the Lewis basic number K(b) was 0.966 2. The results were of great importance to the study of the surface properties and the applications for urushiol-metal chelate polymers. PMID:21657056

  13. Viscometric determination of the onset of asphaltene flocculation: A novel method

    SciTech Connect

    Escobedo, J.; Mansoori, G.A.

    1995-05-01

    A new technique for the determination of the onset of asphaltene flocculation has been developed through accurate viscosity measurements of a crude oil being diluted with a precipitating agent (n-pentane, n-heptane, n-nonane). This detection method is based on experimental observations of an increase in the viscosity of a crude oil-asphaltene-precipitating agent suspension in which asphaltene particle aggregation occurs. The key point in this development is the phenomenon of asphaltene flocculation induced by the addition of a n-paraffin hydrocarbon (i.e. n-heptane, n-pentane, n-nonane) to crude oil. The onset of asphaltene flocculation is detected graphically, and its location is enhanced by comparison of the analyte curve with a reference system. The reference system was developed using polar and non-precipitating solvents (i.e. toluene, benzene, THF).

  14. An atmospheric pressure chemical ionization study of the positive and negative ion chemistry of the hydrofluorocarbons 1,1-difluoroethane (HFC-152a) and 1,1,1,2-tetrafluoroethane (HFC-134a) and of perfluoro-n-hexane (FC-72) in air plasma at atmospheric pressure.

    PubMed

    Marotta, Ester; Paradisi, Cristina; Scorrano, Gianfranco

    2004-07-01

    A report is given on the ionization/dissociation behavior of the title compounds within air plasmas produced by electrical corona discharges at atmospheric pressure: both positive and negative ions were investigated at different temperatures using atmospheric pressure chemical ionization mass spectrometry (APCI-MS). CHF(2)CH(3) (HFC-152a) undergoes efficient ionic oxidation to C(2)H(5)O(+), in which the oxygen comes from water present in the plasma. In contrast, CF(3)CH(2)F (HFC-134a) does not produce any characteristic positive ion under APCI conditions, its presence within the plasma being revealed only as a neutral ligand in ion-molecule complexes with ions of the background (H(3)O(+) and NO(+)). Analogously, the perfluorocarbon FC-72 (n-C(6)F(14)) does not produce significant positive ions at 30 degrees C: at high temperature, however, it undergoes dissociative ionization to form many product ions including C(3)F(6)(+), C(2)F(4)(+), C(n)F(2n+1)(+) and a few families of oxygen containing cations (C(n)F(2n+1)OH(2)(+), C(n)F(2n)OH(+), C(n)F(2n-1)O(+), C(n)F(2n-1)O(2)H(2)(+), C(n)F(2n-2)O(2)H(+)) which are suggested to derive from C(n)F(2n+1)(+) in a cascade of steps initiated by condensation with water followed by steps of HF elimination and H(2)O addition. Negative ions formed from the fluoroethanes CHF(2)CH(3) and CF(3)CH(2)F (M) include complexes with ions of the background, O(2)(-)(M), O(3)(-)(M) and some higher complexes involving also water, and complexes of the fluoride ion, F(-)(H(2)O), F(-)(M) and higher complexes with both M and H(2)O also together. The interesting product O(2)(-)(HF) is also formed from 1,1-difluoroethane. In contrast to the HFCs, perfluoro-n-hexane gives stable molecular anions, M(-), which at low source temperature or in humidified air are also detected as hydrates, M(-)(H(2)O). In addition, in humidified air F(-)(H(2)O)(n) complexes are also formed. The reactions leading to all major positive and negative product ions are discussed

  15. Preferential methanogenic biodegradation of short-chain n-alkanes by microbial communities from two different oil sands tailings ponds.

    PubMed

    Shahimin, Mohd Faidz Mohamad; Foght, Julia M; Siddique, Tariq

    2016-05-15

    Oil sands tailings ponds harbor diverse anaerobic microbial communities capable of methanogenic biodegradation of solvent hydrocarbons entrained in the tailings. Mature fine tailings (MFT) from two operators (Albian and CNRL) that use different extraction solvents were incubated with mixtures of either two (n-pentane and n-hexane) or four (n-pentane, n-hexane, n-octane and n-decane) n-alkanes under methanogenic conditions for ~600 d. Microbes in Albian MFT began methane production by ~80 d, achieving complete depletion of n-pentane and n-hexane in the two-alkane mixture and their preferential biodegradation in the four-alkane mixture. Microbes in CNRL MFT preferentially metabolized n-octane and n-decane in the four-alkane mixture after a ~80 d lag but exhibited a lag of ~360 d before commencing biodegradation of n-pentane and n-hexane in the two-alkane mixture. 16S rRNA gene pyrosequencing revealed Peptococcaceae members as key bacterial n-alkane degraders in all treatments except CNRL MFT amended with the four-alkane mixture, in which Anaerolineaceae, Desulfobacteraceae (Desulfobacterium) and Syntrophaceae (Smithella) dominated during n-octane and n-decane biodegradation. Anaerolineaceae sequences increased only in cultures amended with the four-alkane mixture and only during n-octane and n-decane biodegradation. The dominant methanogens were acetoclastic Methanosaetaceae. These results highlight preferential n-alkane biodegradation by microbes in oil sands tailings from different producers, with implications for tailings management and reclamation. PMID:26925736

  16. Utilization of n-Alkanes by Cladosporium resinae

    PubMed Central

    Teh, J. S.; Lee, K. H.

    1973-01-01

    Four different isolates of Cladosporium resinae from Australian soils were tested for their ability to utilize liquid n-alkanes ranging from n-hexane to n-octadecane under standard conditions. The isolates were unable to make use of n-hexane, n-heptane, and n-octane for growth. In fact, these hydrocarbons, particularly n-hexane, exerted an inhibitory effect on spore germination and mycelial growth. All higher n-alkanes from n-nonane to n-octadecane were assimilated by the fungus, although only limited growth occurred on n-nonane and n-decane. The long chain n-alkanes (C14 to C18) supported good growth of all isolates, but there was no obvious correlation between cell yields and chain lengths of these n-alkanes. Variation in growth responses to individual n-alkane among the different isolates was also observed. The cause of this variation is unknown. PMID:4735447

  17. Adsorption of n-alkane vapours at the water surface.

    PubMed

    Biscay, Frédéric; Ghoufi, Aziz; Malfreyt, Patrice

    2011-06-21

    Monte Carlo simulations are reported here to predict the surface tension of the liquid-vapour interface of water upon adsorption of alkane vapours (methane to hexane). A decrease of the surface tension has been established from n-pentane. A correlation has been evidenced between the decrease of the surface tension and the absence of specific arrangement at the water surface for n-pentane and n-hexane. The thermodynamic stability of the adsorption layer and the absence of film for longer alkanes have been checked through the calculation of a potential of mean force. This complements the work recently published [Ghoufi et al., Phys. Chem. Chem. Phys., 2010, 12, 5203] concerning the adsorption of methane at the water surface. The decrease of the surface tension has been interpreted in terms of the degree of hydrogen bonding of water molecules at the liquid-vapour interface upon adsorption. PMID:21584320

  18. Photocurrent enhancement in nonpolar liquids by the addition of electron scavengers

    SciTech Connect

    Howell, G.A.; Lee, K.; Tweeten, D.W.; Lipsky, S.

    1988-07-14

    The photocurrent from anthracene, triphenylamine, and N,N,N',N'-tetramethyl-p-phenylenediamine excited above their ionization thresholds in liquid n-pentane or n-hexane is found to be enhanced by the addition of low concentrations (/approx lt/0.02 M) of the electron scavengers perfluoromethylcyclohexane or perfluorodecalin. The enhancement is not observed in solvents of higher electron mobility (e.g.,. cyclohexane, isooctane, etc.) or for scavengers of lower electron affinity (e.g., n-perfluorohexane). For the solute naphthalene, no enhancement is observed under any conditions. The effects of excitation energy and applied electric field strength are reported.

  19. Total cross section of electron scattering by fluorocarbon molecules

    NASA Astrophysics Data System (ADS)

    Yamada, T.; Ushiroda, S.; Kondo, Y.

    2008-12-01

    A compact linear electron transmission apparatus was used for the measurement of the total electron scattering cross section at 4-500 eV. Total cross sections of chlorofluorocarbon (CCl2F2), hydrochlorofluorocarbon (CHClF2), perfluoropropane (C3F8), perfluoro-n-pentane (C5F12), perfluoro-n-hexane (C6F14) and perfluoro-n-octane (C8F18) were obtained experimentally and compared with the values obtained from a theoretical calculation and semi-empirical model calculation.

  20. Combustion of liquid fuels in a flowing combustion gas environment at high pressures

    NASA Technical Reports Server (NTRS)

    Canada, G. S.; Faeth, G. M.

    1975-01-01

    The combustion of fuel droplets in gases which simulate combustion chamber conditions was considered both experimentally and theoretically. The fuel droplets were simulated by porous spheres and allowed to gasify in combustion gases produced by a burner. Tests were conducted for pressures of 1-40 atm, temperatures of 600-1500 K, oxygen concentrations of 0-13% (molar) and approach Reynolds numbers of 40-680. The fuels considered in the tests included methanol, ethanol, propanol-1, n-pentane, n-heptane and n-decane. Measurements were made of both the rate of gasification of the droplet and the liquid surface temperature. Measurements were compared with theory, involving various models of gas phase transport properties with a multiplicative correction for the effect of forced convection.

  1. Study of asphalt/asphaltene precipitation during addition of solvents to West Sak crude

    SciTech Connect

    Jiang, J.C.; Patil, S.L.; Kamath, V.A. )

    1990-07-01

    In this study, experimental data on the amount of asphalt and asphaltene precipitation due to addition of solvents to West Sak crude were gathered. The first set of tests were conducted for two types of West Sak stock tank oils. Solvents used include: ethane, carbon dioxide, propane, n-butane, n-pentane, n-heptane, Prudhoe Bay natural gas (PBG) and natural gas liquids (NGL). Effect of solvent to oil dilution ratio on the amount of precipitation was studied. Alteration of crude oil composition due to asphalt precipitation was measured using gas-liquid chromatography. A second set of experiments were conducted to measure asphaltene precipitation due to addition of CO{sub 2} to live (recombined) West Sak crude.

  2. Coal surface control for advanced physical fine coal cleaning technologies

    SciTech Connect

    Morsi, B.I.; Chiang, S-H.; Sharkey, A.; Blachere, J.; Klinzing, G.; Araujo, G.; Venkatadri, R.; Bi, H.; Campbell, P.; Ciocco, M.; Hittle, L.; Kim, S.; Kim, Y.; Perez, L.

    1990-01-01

    Research continued on surface control of coal. This report describes Task 7 of the program. The following topics are discussed: quantitative distribution of iron species; surface functional groups; comparison of wet and dry ground samples; study of Illinois No. 6 coal wet ground using additives; study of wet grinding using tall oil; elemental distribution of coal samples wet ground without additives; elemental distribution of coal samples wet ground with tall oil; direct determination of pyrite by x-ray diffraction; electron microprobe measurements; morphology; zeta potential measurements; pyrite size distribution; statistical analysis of grinding study data; grinding using N-pentane; cyclohexane, and N-heptane; study of the effects of the grinding method and time; study of the effects of the agglomeration time; and the pentane to coal ratio. 13 refs.

  3. Trapping of Methanol, Hydrogen Cyanide, and n-Hexane in Water Ice, above Its Transformation Temperature to the Crystalline Form

    NASA Astrophysics Data System (ADS)

    Notesco, G.; Bar-Nun, A.

    1997-04-01

    HCN and n-C 6H 14were found experimentally to be trapped in water ice, when codeposited with water vapor on a cold plate, at 140 K and CH 3OH even at 160 K. At these temperatures at least part of the water ice is cystalline. These three gases have relatively high sublimation temperatures, whereas the gases studied earlier, Ar, Kr, Xe, CO, CH 4, and N 2, which have lower sublimination temperatures, are trapped only in amorphous water ice, up to ˜100 K. It seems that the major factor determining the efficiency of gas trapping by water ice, during codeposition of a gas-water vapor mixture on a cold plate, is the sublimation temperatures of the gases to be trapped. Those with a high sublimation temperature remain, during codeposition, longer in the pores of the water ice which are open to the surface, until they are covered by additional ice layers. Only methanol seems to form a clathrate hydrate, in agreement with the experimental results of D. Blake et al.(1991), Science254, 548-551), which points to the importance of the interaction of the gas molecules with the water molecules in the ice. Consequently, comets and icy satellites that were formed in the Jupiter-Saturn region and their subnebulae could trap CH 3OH, HCN, and heavy hydrocarbons, whereas comets and icy satellites that were formed in the Uranus-Neptune region, at the outskirts of the Saturnian subnebulae (Titan), and beyond the planets in the Kuiper belt could trap also gases having lower sublimation temperatures.

  4. Retama monosperma n-hexane extract induces cell cycle arrest and extrinsic pathway-dependent apoptosis in Jurkat cells

    PubMed Central

    2014-01-01

    Background Retama monosperma L. (Boiss.) or Genista monosperma L. (Lam.), locally named as “R’tam”, is an annual and spontaneous plant belonging to the Fabaceae family. In Morocco, Retama genus is located in desert regions and across the Middle Atlas and it has been widely used in traditional medicine in many countries. In this study, we show that Retama monosperma hexane extract presents significant anti-leukemic effects against human Jurkat cells. Methods Human Jurkat cells, together with other cell lines were screened with different concentrations of Retama monosperma hexane extract at different time intervals. Growth inhibition was determined using luminescent-based viability assays. Cell cycle arrest and apoptosis were measured by flow cytometry analysis. Combined caspase 3 and 7 activities were measured using luminometric caspase assays and immunoblots were performed to analyze expression of relevant pro- and anti-apoptotic proteins. GC-MS were used to determine the chemical constituents of the active extract. Results Retama monosperma hexane extract (Rm-HE) showed significant cytotoxicity against Jurkat cells, whereas it proved to be essentially ineffective against both normal mouse fibroblasts (NIH3T3) and normal lymphocytes (TK-6). Cytometric analysis indicated that Rm-HE promoted cell cycle arrest and apoptosis induction accompanied by DNA damage induction indicated by an increase in p-H2A.X levels. Rm-HE induced apoptosis was partially JNK-dependent and characterized by an increase in Fas-L levels together with activation of caspases 8, 3, 7 and 9, whereas neither the pro-apoptotic nor anti-apoptotic mitochondrial membrane proteins analyzed were significantly altered. Chemical identification analysis indicated that α-linolenic acid, campesterol, stigmasterol and sitosterol were the major bioactive components within the extract. Conclusions Our data suggest that bioactive compounds present in Rm-HE show significant anti leukemic activity inducing cell cycle arrest and cell death that operates, at least partially, through the extrinsic apoptosis pathway. PMID:24460687

  5. High pressure combustion of liquid fuels. [alcohol and n-paraffin fuels

    NASA Technical Reports Server (NTRS)

    Canada, G. S.

    1974-01-01

    Measurements were made of the burning rates and liquid surface temperatures for a number of alcohol and n-paraffin fuels under natural and forced convection conditions. Porous spheres ranging in size from 0.64-1.9 cm O.D. were emloyed to simulate the fuel droplets. The natural convection cold gas tests considered the combustion in air of methanol, ethanol, propanol-1, n-pentane, n-heptane, and n-decane droplets at pressures up to 78 atmospheres. The pressure levels of the natural convection tests were high enough so that near critical combustion was observed for methanol and ethanol vaporization rates and liquid surface temperature measurements were made of droplets burning in a simulated combustion chamber environment. Ambient oxygen molar concentrations included 13%, 9.5% and pure evaporation. Fuels used in the forced convection atmospheric tests included those listed above for the natural convection tests. The ambient gas temperature ranged from 600 to 1500 K and the Reynolds number varied from 30 to 300. The high pressure forced convection tests employed ethanol and n-heptane as fuels over a pressure range of one to 40 atmospheres. The ambient gas temperature was 1145 K for the two combustion cases and 1255 K for the evaporation case.

  6. Effects of light and copper ions on volatile aldehydes of milk and milk fractions

    SciTech Connect

    Jeno, W.; Bassette, R.; Crang, R.E.

    1988-09-01

    Raw, laboratory-pasteurized and plant-pasteurized homogenized milks were exposed to copper ions (5 ppm), to sunlight or fluorescent light and the effects determined on the composition of volatile aldehydes. The greatest change due to copper treatment was an increase in n-hexanal; acetaldehyde showed the least response in each of the sources of milk. The responses were similar from all three sources of milk with laboratory-pasteurized milk samples showing the greatest responses for each aldehyde analyzed. Similar milk samples exposed to sunlight also showed an increase in volatile aldehydes from all milk sources but with the greatest response being acetaldehyde and n-pentanal components. The milk fraction most susceptible to changes in the presence of light was neutralized whey, whereas resuspended cream was most susceptible to copper exposure. Overall, dialyzed whey appeared to be influenced more than other milk fractions by both light and copper ions.

  7. Combination process for high-octane gasoline production

    SciTech Connect

    Bagirov, R.A.; Dadashev, B.A.; Gasimov, B.A.; Naviev, N.I.

    1984-04-01

    This article describes the use of a combination unit for the catalytic isomerization of n-paraffins with continuous chromatography to increase the yield of high-octane gasoline. The feed, consisting of 44.6% n-pentane and n-hexane and 55.4% isoparaffins and cyclic hydrocarbons, enters the bottom of the adsorber in the vapor phase, and the adsorption of n-paraffins takes place in a fluidized bed of CaA zeolite. The recovery of n-paraffins from the pentane-hexane cut as a function of temperature was investigated in the 70-100/sup 0/C interval. It is determined that a combination of adsorption chromatography with catalytic isomerization of the straight-chain paraffins removed from the feed offers a means for increasing the octane number of the product by 18-20 units.

  8. Alternatives for Benzene in the Extraction of Bitumen Fume from Exposure Sample Media.

    PubMed

    Sutter, Benjamin; Ravera, Christel; Hussard, Caroline; Langlois, Eddy

    2016-01-01

    Benzene is frequently used to extract collected bitumen fumes from personal sampler substrates. However, this solvent is particularly dangerous because of its carcinogenicity (group 1 of the International Agency for Research on Cancer classification). Therefore, to prevent the exposure of laboratory technicians to benzene during the fume extraction step from samplers, a compromise had to be found to identify a less toxic solvent with the same extraction capacity. To compare the extraction capacities of selected solvents, bitumen fumes were generated in the laboratory from three different batches of road surfacing bitumen collected on dedicated bitumen fume samplers. The samplers were then extracted by benzene and the solvents tested. Of 11 selected solvents less toxic than benzene and used in studies on bitumen and bitumen fume analyses, n-hexane and n-heptane were identified as alternatives to benzene. In particular, the results demonstrated that n-heptane was the best candidate solvent for benzene replacement, due to its extraction efficiency comparable to benzene for the three bitumen fumes tested and its low toxicity, which is highly compatible with benzene replacement. PMID:26400870

  9. Re-Os dating of maltenes and asphaltenes within single samples of crude oil

    NASA Astrophysics Data System (ADS)

    Georgiev, Svetoslav V.; Stein, Holly J.; Hannah, Judith L.; Galimberti, Roberto; Nali, Micaela; Yang, Gang; Zimmerman, Aaron

    2016-04-01

    Re-Os geochronology of oil may constrain the timing of oil formation and improve oil-source and oil-oil correlations. Typically, asphaltene (ASPH), the heaviest and most Re-Os rich oil fraction, from multiple oils within an oil field or a larger petroleum system are analyzed to obtain sufficient spread in Re-Os isotopic ratios, a mathematical necessity for precise Re-Os isochrons. Here we offer a new approach for Re-Os geochronology of oil based on isotopic analyses of different fractions within a single sample of crude oil. We studied three oils from the Gela oil field, southern Sicily, Italy, recovered from Triassic-Jurassic stratigraphic intervals (Streppenosa, Noto, and Sciacca Formations) within the Gela-1 well. ASPH (insoluble in n-alkane) and maltene (MALT, soluble in n-alkane) fractions of oil were separated using n-pentane, n-hexane, n-heptane and n-decane solvents. The ASPH contents of the Sciacca and Noto oils (26-33 wt%) are notably higher compared to the Streppenosa oil (7-12 wt% ASPH). We present an optimized Re-Os procedure with sample digestion in a high-pressure asher, followed by isotopic measurements using negative thermal ionization mass spectrometry. Very high metal contents of Gela oils allowed acquisition of precise Re-Os data. Systematic variations between the type of solvent used for ASPH precipitation and the ASPH content of the oil (also known from the literature) and the Re-Os contents of the ASPH and MALT fractions (first observed in this study) provide important practical applications for Re-Os analyses of oil. Most Re and Os (∼96-98%) in the Noto oil are hosted in the ASPH fraction. In contrast, a significant portion of Re and Os (∼33-34%) is stored in the MALT fraction of the lighter, but heavily biodegraded Streppenosa oil. Collectively, our new data on alkane distribution, hopane and sterane biomarkers, major and trace element contents, and Re-Os concentrations and isotopic ratios of the oils and their fractions support the

  10. Analysis of polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins and dibenzofurans in particulate and oily films on impervious surfaces.

    PubMed

    Klees, Marcel; Hiester, Ernst; Schmidt, Torsten C

    2015-12-15

    During this study wipe sampling was applied to various impervious surfaces for the determination of polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/PCDFs) area concentrations. To that end, a wipe sampling method based on solvent wetted cotton wipes was evaluated and transfer efficiencies of PCBs and PCDD/PCDFs in particulate films (PFs) and oily liquid films (OFs) during sampling were investigated. For PFs sufficient transfer efficiencies of low concentrated PCB and PCDD/PCDF congeners in 1g/m(2) spiking surrogate were achieved after the first wipe using n-hexane as wetting solvent. Transfer efficiencies for OFs were the highest in the first wipe if n-hexane or n-heptane were used rather than toluene. The spiking experiments of OFs showed a log-linear correlation between the number of wiping procedures and transfer efficiency which indicates that transfer efficiencies were constant in subsequent wipes. Furthermore, it was successfully demonstrated that pressurized liquid extraction is a suitable tool for the extraction of wipe samples. Finally, the feasibility of this wipe sampling method was demonstrated on various impervious surfaces of different origin, and concentration levels of PCBs and PCDD/PCDFs in wipe samples are discussed. Hereby, remarkably high ∑CB6 concentrations of up to 1400μg/m(2) (taken at a transformer recycling site) were detected. PMID:26318221

  11. Fuel droplet burning rates at high pressures.

    NASA Technical Reports Server (NTRS)

    Canada, G. S.; Faeth, G. M.

    1973-01-01

    Combustion of methanol, ethanol, propanol-1, n-pentane, n-heptane, and n-decane was observed in air under natural convection conditions, at pressures up to 100 atm. The droplets were simulated by porous spheres, with diameters in the range from 0.63 to 1.90 cm. The pressure levels of the tests were high enough so that near-critical combustion was observed for methanol and ethanol. Due to the high pressures, the phase-equilibrium models of the analysis included both the conventional low-pressure approach as well as high-pressure versions, allowing for real gas effects and the solubility of combustion-product gases in the liquid phase. The burning-rate predictions of the various theories were similar, and in fair agreement with the data. The high-pressure theory gave the best prediction for the liquid-surface temperatures of ethanol and propanol-1 at high pressure. The experiments indicated the approach of critical burning conditions for methanol and ethanol at pressures on the order of 80 to 100 atm, which was in good agreement with the predictions of both the low- and high-pressure analysis.

  12. Gas-Phase Reaction of Hydroxyl Radical with p-Cymene over an Extended Temperature Range.

    PubMed

    Bedjanian, Yuri; Morin, Julien; Romanias, Manolis N

    2015-11-12

    The kinetics of the reaction of OH radicals with p-cymene has been studied in the temperature range of 243-898 K using a flow reactor combined with a quadrupole mass spectrometer: OH + p-cymene → products. The reaction rate constant was determined as a result of absolute measurements, from OH decay kinetics in excess of p-cymene and employing the relative rate method with OH reactions with n-pentane, n-heptane,1,3-dioxane, HBr, and Br2 as the reference ones. For the rate coefficient of the H atom abstraction channel, the expression k1b = (3.70 ± 0.42) × 10(-11) exp[-(772 ± 72)/T] was obtained over the temperature range of 381-898 K. The total rate constant (addition + abstraction) determined at T = 243-320 K was k1 = (1.82 ± 0.48) × 10(-12) exp[(607 ± 70)/T] or, in a biexponential form, k1 = k1a + k1b = 3.7 × 10(-11) exp(-772/T) + 6.3 × 10(-13) exp(856/T), independent of the pressure between 1 and 5 Torr of helium. In addition, our results indicate that the reaction pathway involving alkyl radical elimination upon initial addition of OH to p-cymene is most probably unimportant. PMID:26473634

  13. Theory of viscosity as a criterion for detection of onset of asphaltene flocculation

    SciTech Connect

    Escobedo, J.; Mansoori, G.A.

    1994-12-31

    Recently, the authors proposed a new technique for the determination of the onset of asphaltene flocculation. This method is based on viscosity measurements of a crude oil being diluted with a precipitating solvent (i.e., n-pentane, n-heptane, etc.). The onset of asphaltene flocculation is detected by a sharp increase in the relative viscosity of the suspension in which asphaltene particle aggregation occurs. The key point in this development is the changes which occur in the relative viscosity of the mixture and its relationship to the phenomenon of flocculation of asphaltene particles induced by the addition of a low-molecular-weight n-paraffin to crude oil. In this paper, they present a theoretical analysis of the proposed new technique for the onset of asphaltene flocculation and to estimate the background viscosity of the crude oil-precipitating solvent mixture. This in turn has allowed them to perform analyses of the trends of specific and relative viscosities as a function of precipitating solvent concentration, and hence particle concentration. These analyses have provided them information regarding the effect of the suspended asphaltene particles on the viscosity of the mixture. This effect becomes remarkable at a point which coincides with the previously predicted onset of asphaltene flocculation. The increase in the specific (or relative) viscosity after this point is very rapid.

  14. Quantitative analysis of volatile organic compounds released and consumed by rat L6 skeletal muscle cells in vitro

    PubMed Central

    Mochalski, Paweł; Al-Zoairy, Ramona; Niederwanger, Andreas; Unterkofler, Karl; Amann, Anton

    2016-01-01

    Knowledge of the release of volatile organic compounds (VOCs) by cells provides important information on the origin of VOCs in exhaled breath. Muscle cells are particularly important, since their release of volatiles during the exertion of an effort contributes considerably to breath concentration profiles. Presently, the cultivation of human skeletal muscle cells is encountering a number of obstacles, necessitating the use of animal muscle cells in in vitro studies. Rat L6 skeletal muscle cells are therefore commonly used as a model for studying the molecular mechanisms of human skeletal muscle differentiation and functions, and facilitate the study of the origin and metabolic fate of the endogenously produced compounds observed in breath and skin emanations. Within this study the production and uptake of VOCs by rat L6 skeletal muscle cells were investigated using gas chromatography with mass spectrometric detection, combined with head-space needle trap extraction as the pre-concentration technique (HS-NTE-GC-MS). Seven compounds were found to be produced, whereas sixteen species were consumed (Wilcoxon signed-rank test, p < 0.05) by the cells being studied. The set of released volatiles included two ketones (2-pentanone and 2-nonanone), two volatile sulphur compounds (dimethyl sulfide and methyl 5-methyl-2-furyl sulphide), and three hydrocarbons (2-methyl 1-propene, n-pentane and isoprene). Of the metabolized species there were thirteen aldehydes (2-propenal, 2-methyl 2-propenal, 2-methyl propanal, 2-butenal, 2-methyl butanal, 3-methyl butanal, n-pentanal, 2-methyl 2-butenal, n-hexanal, benzaldehyde, n-octanal, n-nonanal and n-decanal), two esters (n-propyl propionate and n-butyl acetate), and one volatile sulphur compound (dimethyl disulfide). The possible metabolic pathways leading to the uptake and release of these compounds by L6 cells are proposed and discussed. An analysis of the VOCs showed them to have huge potential for the identification and monitoring

  15. A predictive method for crude oil volatile organic compounds emission from soil: evaporation and diffusion behavior investigation of binary gas mixtures.

    PubMed

    Wang, Haijing; Fischer, Thomas; Wieprecht, Wolfgang; Möller, Detlev

    2015-05-01

    Due to their mobility and toxicity, crude oil volatile organic compounds (VOCs) are representative components for oil pipeline contaminated sites detection. Therefore, contaminated location risk assessment, with airborne light detection and ranging (LIDAR) survey, in particular, requires ground-based determinative methods for oil VOCs, the interaction between oil VOCs and soil, and information on how they diffuse from underground into atmosphere. First, we developed a method for determination of crude oil VOC binary mixtures (take n-pentane and n-hexane as examples), taking synergistic effects of VOC mixtures on polydimethylsiloxane (PDMS) solid-phase microextraction (SPME) fibers into consideration. Using this method, we further aim to extract VOCs from small volumes, for example, from soil pores, using a custom-made sampling device for nondestructive SPME fiber intrusion, and to study VOC transport through heterogeneous porous media. Second, specific surface Brunauer-Emmett-Teller (BET) analysis was conducted and used for estimation of VOC isotherm parameters in soil. Finally, two models were fitted for VOC emission prediction, and the results were compared to the experimental emission results. It was found that free diffusion mode worked well, and an empirical correction factor seems to be needed for the other model to adapt to our condition for single and binary systems. PMID:25572270

  16. Long-Term Incubation Reveals Methanogenic Biodegradation of C5 and C6 iso-Alkanes in Oil Sands Tailings.

    PubMed

    Siddique, Tariq; Mohamad Shahimin, Mohd Faidz; Zamir, Saima; Semple, Kathleen; Li, Carmen; Foght, Julia M

    2015-12-15

    iso-Alkanes are major components of petroleum and have been considered recalcitrant to biodegradation under methanogenic conditions. However, indigenous microbes in oil sands tailings ponds exposed to solvents rich in 2-methylbutane, 2-methylpentane, 3-methylpentane, n-pentane, and n-hexane produce methane in situ. We incubated defined mixtures of iso- or n-alkanes with mature fine tailings from two tailings ponds of different ages historically exposed to different solvents: one, ~10 years old, receiving C5-C6 paraffins and the other, ~35 years old, receiving naphtha. A lengthy incubation (>6 years) revealed iso-alkane biodegradation after lag phases of 900-1800 and ~280 days, respectively, before the onset of methanogenesis, although lag phases were shorter with n-alkanes (~650-1675 and ~170 days, respectively). 2-Methylpentane and both n-alkanes were completely depleted during ~2400 days of incubation, whereas 2-methylbutane and 3-methylpentane were partially depleted only during active degradation of 2-methylpentane, suggesting co-metabolism. In both cases, pyrotag sequencing of 16S rRNA genes showed codominance of Peptococcaceae with acetoclastic (Methanosaeta) and hydrogenotrophic (Methanoregula and Methanolinea) methanogens. These observations are important for predicting long-term greenhouse-gas emissions from oil sands tailings ponds and extend the known range of hydrocarbons susceptible to methanogenic biodegradation in petroleum-impacted anaerobic environments. PMID:26571341

  17. Modeling VOC Sorption and Transport in Glassy Polymeric Membranes

    NASA Astrophysics Data System (ADS)

    De Angelis, Maria Grazia; Olivieri, Luca; Sarti, G. C.

    2010-06-01

    In this work we evaluated the sorption, diffusion and permeation of a series of volatile organic compounds (VOCs) (acetone, n-butane, n-pentane, n-hexane, ethanol, methanol, chloroform and toluene) into glassy polymers of increasing fractional free volume (FFV): Polycarbonate (PC), Amorphous Teflon AF1600 and AF2400, poly-trimethylsilyl norbornene (PTMSN) and poly[1-(trimethylsilyl)-1-propyne] (PTMSP). Based on some experimental data of sorption and diffusion, and on theoretical and empirical models for the solubility and diffusion coefficients, the permeability for vapor/N2 mixtures was evaluated. These parameters are useful for the membrane separation processes and for other applications such as chemical sensors. The ideal separation factors of glassy polymeric membranes versus mixtures of VOCs and N2 were estimated at various pressures and compositions and at 25° C. The selectivity vs. permeability maps for the mixtures considered were plotted, showing that some of these materials show potentially the same selective ability of rubbery polymeric films. In particular it is shown that, the higher the FFV, the better the vapor/gas selectivity.

  18. High pressure droplet burning experiments in reduced gravity

    NASA Technical Reports Server (NTRS)

    Chauveau, Christian; Goekalp, Iskender

    1995-01-01

    A parametric investigation of single droplet gasification regimes is helpful in providing the necessary physical ideas for sub-grid models used in spray combustion numerical prediction codes. A research program has been initiated at the LCSR to explore the vaporization regimes of single and interacting hydrocarbon and liquid oxygen droplets under high pressure conditions. This paper summarizes the status of the LCSR program on the high pressure burning of single fuel droplets; recent results obtained under normal and reduced gravity conditions with suspended droplets are presented. In the work described here, parabolic flights of the CNES Caravelle is used to create a reduced gravity environment of the order of 10(exp -2) g(sub O). For all the droplet burning experiments reported here, the suspended droplet initial diameters are scattered around 1.5 mm; and the ambient air temperature is 300 K. The ambient pressure is varied between 0.1 MPa and 12 MPa. Four fuels are investigated: methanol (Pc = 7.9 MPa), n-heptane (Pc = 2.74 MPa), n-hexane (Pc = 3.01 MPa) and n-octane (Pc = 2.48 MPa).

  19. Comparative study of free and immobilized lipase from Bacillus aerius and its application in synthesis of ethyl ferulate.

    PubMed

    Saun, Nitin Kumar; Narwal, Sunil Kumar; Dogra, Priyanka; Chauhan, Ghanshyam Singh; Gupta, Reena

    2014-01-01

    In the present study, a purified lipase from Bacillus aerius immobilized on celite matrix was used for synthesis of ethyl ferulate. The celite-bound lipase exposed to glutaraldehyde showed 90.02% binding efficiency. It took two hours to bind maximally onto the support. The pH and temperature optima of the immobilized lipase were same as those of free enzyme i.e 9.5 and 55°C. Among different substrates both free and immobilized lipase showed maximum affinity towards p-nitrophenyl palmitate (p-NPP). The lipase activity was found to be stimulated in the presence of Mg(2+) in case of free enzyme while Zn(2+) and Fe(3+) showed stimulatory effect on immobilized lipase whereas salt ions as well as chelating agents inhibited activity of both free and immobilized lipase. Maximum enzyme activity was observed in n-hexane as organic solvent followed by n-heptane for both free and immobilized lipase, however CCl4, acetone and benzene inhibited the enzyme activity. Moreover, all the selected detergents (SDS, Triton X-100, Tween 80 and Tween 20) had an inhibitory effect on both free and immobilized enzyme activity. The celite bound lipase (1.5%) efficiently performed maximum esterification (2.51 moles/l) of ethanol and ferulic acid (100 mM each, at a molar ratio of 1:3) when incubated at 55°C for 48 h resulting in the formation of ester ethyl ferulate. PMID:25099909

  20. Biodiesel production using waste frying oil

    SciTech Connect

    Charpe, Trupti W.; Rathod, Virendra K.

    2011-01-15

    Research highlights: {yields} Waste sunflower frying oil is successfully converted to biodiesel using lipase as catalyst. {yields} Various process parameters that affects the conversion of transesterification reaction such as temperature, enzyme concentration, methanol: oil ratio and solvent are optimized. {yields} Inhibitory effect of methanol on lipase is reduced by adding methanol in three stages. {yields} Polar solvents like n-hexane and n-heptane increases the conversion of tranesterification reaction. - Abstract: Waste sunflower frying oil is used in biodiesel production by transesterification using an enzyme as a catalyst in a batch reactor. Various microbial lipases have been used in transesterification reaction to select an optimum lipase. The effects of various parameters such as temperature, methanol:oil ratio, enzyme concentration and solvent on the conversion of methyl ester have been studied. The Pseudomonas fluorescens enzyme yielded the highest conversion. Using the P. fluorescens enzyme, the optimum conditions included a temperature of 45 deg. C, an enzyme concentration of 5% and a methanol:oil molar ratio 3:1. To avoid an inhibitory effect, the addition of methanol was performed in three stages. The conversion obtained after 24 h of reaction increased from 55.8% to 63.84% because of the stage-wise addition of methanol. The addition of a non-polar solvent result in a higher conversion compared to polar solvents. Transesterification of waste sunflower frying oil under the optimum conditions and single-stage methanol addition was compared to the refined sunflower oil.

  1. n-Aldehydes (C6-C10) in snow samples collected at the high alpine research station Jungfraujoch during CLACE 5

    NASA Astrophysics Data System (ADS)

    Sieg, K.; Starokozhev, E.; Fries, E.; Sala, S.; Püttmann, W.

    2009-03-01

    Samples of freshly fallen snow were collected at the high alpine research station Jungfraujoch, Switzerland, during the Cloud and Aerosol Characterization Experiments (CLACE) 5 in February and March 2006. Sampling was carried out on the Sphinx platform. Headspace-solid-phase-dynamic extraction (HS-SPDE) combined with gas chromatography/mass spectrometry (GC/MS) was used to quantify C6-C10 n-aldehydes in the snow samples. The most abundant n-aldehyde was n-hexanal (median concentration 1.324 μg L-1) followed by n-nonanal, n-decanal, n-octanal and n-heptanal (median concentrations 1.239, 0.863, 0.460, and 0.304 μg L-1, respectively). A wide range of concentrations was found among individual snow samples, even for samples taken at the same time. Higher median concentrations of all n-aldehydes were observed when air masses reached Jungfraujoch from the north-northwest in comparison to air masses arriving from the southeast-southwest. Results suggest that the n-aldehydes detected most likely are of direct and indirect biogenic origin, and that they entered the snow through the particle phase.

  2. Observed trends in ambient concentrations of C 2-C 8 hydrocarbons in the United Kingdom over the period from 1993 to 2004

    NASA Astrophysics Data System (ADS)

    Dollard, G. J.; Dumitrean, P.; Telling, S.; Dixon, J.; Derwent, R. G.

    Hourly measurements of up to 26 C 2-C 8 hydrocarbons have been made at eight urban background sites, three urban-industrial sites, a kerbside and a rural site in the UK from 1993 onwards up until the end of December 2004. Average annual mean benzene and 1,3-butadiene concentrations at urban background locations have declined at about -20% per year and the observed declines have exactly mimicked the inferred declines in benzene and 1,3-butadiene emissions over the same period. Ninety-day rolling mean concentrations of ethylene, propylene, n- and i-butane, n- and i-pentane, isoprene and propane at urban and rural sites have also declined steadily by between -10% and -30% per year. Rolling mean concentrations of acetylene, 2- and 3-methylpentane, n-hexane, n-heptane, cis- and trans-but-2-ene, cis- and trans-pent-2-ene, toluene, ethylbenzene and o-, m- and p-xylene at a roadside location in London have all declined at between -14% and -21% per year. These declines demonstrate that motor vehicle exhaust catalysts and evaporative canisters have effectively and efficiently controlled vehicular emissions of hydrocarbons in the UK. Urban ethane concentrations arising largely from natural gas leakage have remained largely unchanged over this same period.

  3. CRADA Final Report: Optimized Catalysts for the Cracking of Heavier Petroleum Feedstocks

    SciTech Connect

    Somorjai, Gabor A.

    2003-01-02

    Catalysts lower the activation energy required for chemical reactions to proceed and are widely used in petroleum refining and chemical manufacturing. The useful lifetime and, thus, the value of an industrial catalyst are limited by a process known as deactivation in which the efficiency of the catalyst declines over time. Understanding this deactivation process is essential for developing new catalysts with longer useful lifetimes. In this project a new surface science tool, ultraviolet (UV) Raman spectroscopy, was used to identify chemical species on the surfaces of catalysts in-situ under actual reaction conditions. In collaboration with Catalytica this tool was applied to study deactivation in a series of important industrial catalysts. In the specific case of "reforming" catalysts are used to dehydrogenate and cyclize n-hexane and n-heptane to form benzene and toluene for the production of high octane gasoline, the buildup and polymerization of carbonaceous reaction byproducts on the surface of the catalyst was studied in-situ by this new method. The information on catalyst reaction and deactivation mechanisms has been found to be useful to the industrial partner in improving their catalysts. These improvements could have a major impact on the efficiency of petroleum refining and gasoline production. In addition, the new surface science tools developed by this project will have general applicability to the study of catalysis and to the field of surface science in general.

  4. Gas-Phase Reactions of Atomic Gold Cations with Linear Alkanes (C2-C9).

    PubMed

    Zhang, Ting; Li, Zi-Yu; Zhang, Mei-Qi; He, Sheng-Gui

    2016-06-30

    To develop proper ionization methods for alkanes, the reactivity of bare or ligated transition metal ions toward alkanes has attracted increasing interests. In this study, the reactions of the gold cations with linear alkanes from ethane up to nonane (CnH2n+2, n = 2-9) under mild conditions have been characterized by mass spectrometry and density functional theory calculations. When reacting with Au(+), small alkanes (n = 2-6) were confirmed to follow specific reaction channels of dehydrogenation for ethane and hydride transfer for others to generate product ions characteristic of the original alkanes, which indicates that Au(+) can act as a reagent ion to ionize alkanes from ethane to n-hexane. Strong dependence of the chain length of alkanes was observed for the rate constants and reaction efficiencies. Extensive fragmentation took place for larger alkanes (n > 6). Theoretical results show that the fragmentation induced by the hydride transfer occurs after the release of AuH. Moreover, the fragmentation of n-heptane was successfully avoided when the reaction took place in a high-pressure reactor. This implies that Au(+) is a potential reagent ion to ionize linear and even the branched alkanes. PMID:27266670

  5. Phase equilibria and modeling of pyridinium-based ionic liquid solutions.

    PubMed

    Domańska, Urszula; Królikowski, Marek; Ramjugernath, Deresh; Letcher, Trevor M; Tumba, Kaniki

    2010-11-25

    The phase diagrams of the ionic liquid (IL) N-butyl-4-methylpyridinium bis{(trifluoromethyl)sulfonyl}imide ([BM(4)Py][NTf(2)]) with water, an alcohol (1-butanol, 1-hexanol, 1-octanol, 1-decanol), an aromatic hydrocarbon (benzene, toluene, ethylbenzene, n-propylbenzene), an alkane (n-hexane, n-heptane, n-octane), or cyclohexane have been measured at atmospheric pressure using a dynamic method. This work includes the characterization of the synthesized compound by water content and also by differential scanning calorimetry. Phase diagrams for the binary systems of [BM(4)Py][NTf(2)] with all solvents reveal eutectic systems with regards to (solid-liquid) phase equilibria and show immiscibility in the liquid phase region with an upper critical solution temperature (UCST) in most of the mixtures. The phase equilibria (solid, or liquid-liquid) for the binary systems containing aliphatic hydrocarbons reported here exhibit the lowest solubility and the highest immiscibility gap, a trend which has been observed for all ILs. The reduction of experimental data has been carried out using the nonrandom two-liquid (NRTL) correlation equation. The phase diagrams reported here have been compared with analogous phase diagrams reported previously for systems containing the IL N-butyl-4-methylpyridinium tosylate and other pyridinium-based ILs. The influence of the anion of the IL on the phase behavior has been discussed. PMID:20964426

  6. A rapid and efficient method for directed screening of lipase-producing Burkholderia cepacia complex strains with organic solvent tolerance from rhizosphere.

    PubMed

    Shu, Zhengyu; Lin, Ruifeng; Jiang, Huan; Zhang, Yanfeng; Wang, Mingzi; Huang, Jianzhong

    2009-06-01

    Lipase from Burkholderia cepacia strain is one of the most versatile biocatalysts and is used widely in many biotechnological application fields including detergent additives, the resolution of racemic compounds, etc. Based on the known whole genomic information of B. cepacia strain, both ampicillin and kanamycin were added to the TB-T medium to screen B. cepacia complex stains from rhizosphere soil samples. The selected colonies from the modified TB-T medium were then qualitatively determined the ability to produce extracellular lipase on the rhodamine B-olive oil agar plates. A total of 35 lipolytic pseudo-B. cepacia complex strains were isolated and the positive rate of lipolytic bacteria was 65%. Among them, 15 pseudo-B. cepacia complex strains showed tolerance to benzene, n-hexane and n-heptane at concentration of 10% (V/V) and were identified by the recA gene sequence. All of the 14 lipolytic bacteria were identified as B. cepacia complex strains except that the recA gene sequence of one lipolytic bacterium, strain ZMB009, was not obtained. PMID:19447345

  7. Nitrogen incorporation in saturated aliphatic C6-C8 hydrocarbons and ethanol in low-pressure nitrogen plasma generated by a hollow cathode discharge ion source.

    PubMed

    Usmanov, Dilshadbek T; Chen, Lee Chuin; Hiraoka, Kenzo; Wada, Hiroshi; Nonami, Hiroshi; Yamabe, Shinichi

    2016-06-01

    Ion/molecule reactions of saturated hydrocarbons (n-hexane, cyclohexane, n-heptane, n-octane and isooctane) in 28-Torr N2 plasma generated by a hollow cathode discharge ion source were investigated using an Orbitrap mass spectrometer. It was found that the ions with [M+14](+) were observed as the major ions (M: sample molecule). The exact mass analysis revealed that the ions are nitrogenated molecules, [M+N](+) formed by the reactions of N3 (+) with M. The reaction, N3 (+) + M → [M+N](+) + N2 , were examined by the density functional theory calculations. It was found that N3 (+) abstracts the H atom from hydrocarbon molecules leading to the formation of protonated imines in the forms of R'R″CNH2 (+) (i.e. C-H bond nitrogenation). This result is in accord with the fact that elimination of NH3 is the major channel for MS/MS of [M+N](+) . That is, nitrogen is incorporated in the C-H bonds of saturated hydrocarbons. No nitrogenation was observed for benzene and acetone, which was ascribed to the formation of stable charge-transfer complexes benzene⋅⋅⋅⋅N3 (+) and acetone⋅⋅⋅⋅N3 (+) revealed by density functional theory calculations. Copyright © 2016 John Wiley & Sons, Ltd. PMID:27270868

  8. D/H Isotope Ratio Measurements of Atmospheric Volatile Organic Compounds

    NASA Astrophysics Data System (ADS)

    Meisehen, Thomas; Bühler, Fred; Koppmann, Ralf; Krebsbach, Marc

    2015-04-01

    Analysis of isotope ratios in atmospheric volatile organic compounds (VOC) is a reliable method to allocate their sources, to estimate atmospheric residence times and investigate physical and chemical processes on various temporal and spatial scales. Most investigations yet focus on carbon isotope ratios. Certainly more detailed information can be gained by the ratio of deuterium (D) to hydrogen (H) in VOC, especially due to the high mass ratio. Combining measurements of carbon and hydrogen isotopes could lead to considerable improvement in our understanding of atmospheric processes. For this purpose we set up and thoroughly characterised a gas chromatograph pyrolysis isotope ratio mass spectrometer to measure the D/H ratio in atmospheric VOC. From a custom-made gas standard mixture VOC were adsorbed on Tenax®TA which has the advantage that CO2 is not preconcentrated when measuring ambient air samples. Our results show that the pyrolysis method has significant impact on the D/H ratios. A pyrolysis temperature of at least 1723 K and conditioning of the ceramic tube on a regular basis is essential to obtain reproducible D/H isotope ratios. For an independent comparison D/H ratios of the pure VOC used in the gas standard were determined using elemental analysis by Agroisolab (Jülich, Germany). Comparisons of 10 VOC show perfect agreement within the standard deviations of our measurements and the errors given by Agroisolab, e.g. for n-pentane, toluene, 4-methyl-2-pentanone and n-octane. A slight mean difference of 5.1 o was obtained for n-heptane while significant mean differences of 15.5 o and 20.3 o arose for 1,2,4-trimethylbenzene and isoprene, respectively. We further demonstrate the stability of our system and show that the sample preparation does not affect the isotope ratios. Moreover the applicability of our system to ambient air samples is demonstrated.

  9. Stable Carbon Isotope Ratios and Mixing Ratios of Several VOC Including n-Hexane, Benzene, Toluene, p-Xylene, n-Octane, and n-Decane Measured During the Border Air Quality Study Campaign (June-July, 2007)

    NASA Astrophysics Data System (ADS)

    Kornilova, A.; Moukhtar, S.; Huang, L.; Rudolph, J.

    2008-12-01

    Many important secondary pollutants are formed during the oxidation of Volatile Organic Compounds (VOC) in the atmosphere. These organic compounds can contribute significant mass to atmospheric particulate matter (PM) and therefore impact physical properties and composition of aerosols. Despite numerous studies, the formation processes for atmospheric PM are still not well understood. While there have been very extensive laboratory investigations of PM formation, nearly all of these studies have been conducted at VOC concentrations which exceed ambient atmospheric levels by several orders of magnitude. Consequently there is substantial uncertainty in the extrapolation of laboratory results to the atmosphere. Recently it has been demonstrated that stable carbon isotopic composition measurements can be very valuable in providing increased insight into the chemical and transport processes of VOC in the troposphere. Studies showed that isotope ratio measurements could aid in the determination of photochemical processing of individual VOC. It is expected that applying isotope measurements to studies of VOC oxidation products in the atmosphere will allow to establish quantitative relationship between the amount of precursor oxidized and the concentration of secondary pollutants formed during this process. Thus, the yield of secondary organic aerosols (SOA) from this reaction can be calculated. A cartridge technique was developed for field sampling of VOC and subsequent laboratory analysis by gas chromatography coupled with isotope ratio mass spectrometry. It was first implemented during the BAQS field study (June-July, 2007) parallel to PM sampling. Stable carbon isotopic composition and concentrations of several VOC were determined and compared to those of PM. The results of these measurements will be presented and discussed.

  10. A new model for pressure-induced shifts of electronic absorption bands as applied to neat CS sub 2 and CS sub 2 in n-hexane and dichloromethane solutions

    SciTech Connect

    Agnew, S.F.; Swanson, B.I. )

    1990-01-25

    The authors propose a model for the pressure dependence of electronic absorption spectra and apply it to the authors data on CS{sub 2} both in neat phase and in hexane and dichloromethane solid solutions. They believe that their data represent a rather severe test of this model and argue that any model for the pressure dependence of electronic absorption spectra must include certain minimal effects - dispersive or dielectric and repulsive or volume effects - in order to adequately represent the data. They discuss previous models at some length in order to delineate the limits of their applicability. They further acknowledge and define the limits of the applicability of their model to solvent-induced shifts in general.

  11. n-Aldehydes (C6-C10) in snow samples collected at the high alpine research station Jungfraujoch during CLACE 5

    NASA Astrophysics Data System (ADS)

    Sieg, K.; Starokozhev, E.; Fries, E.; Sala, S.; Püttmann, W.

    2009-04-01

    C6-C10 n-aldehydes were analyzed in samples of freshly fallen snow collected at the high alpine research station Jungfraujoch, Switzerland, during the Cloud and Aerosol Characterization Experiments (CLACE) 5 in February and March 2006. Sampling was carried out on the Sphinx platform. Headspace - solid phase dynamic extraction (HS-SPDE) combined with gas chromatography/mass spectrometry (GC/MS) was used to quantify n-aldehydes in melted snow samples. n-Hexanal was identified as the most abundant n-aldehyde (median concentration 1.324 µg L-1) followed by n-nonanal, n-decanal, n-octanal and n-heptanal (median concentrations 1.239, 0.863, 0.460 and 0.304 µg L-1, respectively). A wide range of concentrations of n-aldehydes was found in snow samples from Jungfraujoch, even for samples collected at the same time during the same snowfall event. According to their physical and chemical characteristics, n-aldehydes are expected to be primarily linked to aerosol particles in the atmosphere suggesting the uptake of n-aldehydes into snow via the particle phase. Particle scavenging can occur during snow formation in clouds. The high concentration variations of the n-aldehydes among the snow samples can be explained assuming that aerosol particles, which are loaded with n-aldehydes, are heterogeneously distributed throughout the snow samples. Higher median concentrations of all n-aldehydes were observed when air masses reached Jungfraujoch from the north-northwest in comparison to air masses arriving from the southeast-southwest. The sources of atmospheric n-aldehydes present at Jungfraujoch are most likely to be related to direct and indirect biogenic emissions. The presence of n-aldehydes as semivolatile constituents of direct biogenic emissions from vegetation has been reported previously in studies of Ciccioli et al. [1], Yokouchi et al. [2] and Kesselmeier and Staudt [3]. The distribution pattern of the n-aldehydes in emissions from vegetation largely matches with the n

  12. Molecular dynamics averaging of Xe chemical shifts in liquids

    NASA Astrophysics Data System (ADS)

    Jameson, Cynthia J.; Sears, Devin N.; Murad, Sohail

    2004-11-01

    The Xe nuclear magnetic resonance chemical shift differences that afford the discrimination between various biological environments are of current interest for biosensor applications and medical diagnostic purposes. In many such environments the Xe signal appears close to that in water. We calculate average Xe chemical shifts (relative to the free Xe atom) in solution in eleven liquids: water, isobutane, perfluoro-isobutane, n-butane, n-pentane, neopentane, perfluoroneopentane, n-hexane, n-octane, n-perfluorooctane, and perfluorooctyl bromide. The latter is a liquid used for intravenous Xe delivery. We calculate quantum mechanically the Xe shielding response in Xe-molecule van der Waals complexes, from which calculations we develop Xe (atomic site) interpolating functions that reproduce the ab initio Xe shielding response in the complex. By assuming additivity, these Xe-site shielding functions can be used to calculate the shielding for any configuration of such molecules around Xe. The averaging over configurations is done via molecular dynamics (MD). The simulations were carried out using a MD technique that one of us had developed previously for the simulation of Henry's constants of gases dissolved in liquids. It is based on separating a gaseous compartment in the MD system from the solvent using a semipermeable membrane that is permeable only to the gas molecules. We reproduce the experimental trends in the Xe chemical shifts in n-alkanes with increasing number of carbons and the large chemical shift difference between Xe in water and in perfluorooctyl bromide. We also reproduce the trend for a given solvent of decreasing Xe chemical shift with increasing temperature. We predict chemical shift differences between Xe in alkanes vs their perfluoro counterparts.

  13. [Pollution characteristics and ozone formation potential of ambient VOCs in winter and spring in Xiamen].

    PubMed

    Xu, Hui; Zhang, Han; Xing, Zhen-yu; Deng, Jun-jun

    2015-01-01

    Air samples were collected at urban and rural sites in Xiamen from January to April 2014. The concentrations of 48 ambient volatile organic compounds (VOC) species were measured by the method of cryogenic pre-concentrator and gas chromatography-mass spectrometry (GC/MS). The ozone formation potential (OFP) of VOCs was also calculated with the method of maximum incremental reactivity (MIR). The results showed that the average mixing ratios of VOCs in winter were 11.13 x 10(-9) and 7.17 x 10(-9) at urban and rural sites, respectively, and those in spring were 24.88 x 10(-9) and 11.27 x 10(-9) at urban and rural sites, respectively. At both sites, alkanes contributed the most to VOCs, followed by aromatics and alkenes. The ratios of B/T showed that vehicle and solvent evaporation were the main sources of VOCs at urban site. While at rural site, transport of anthropogenic sources was another important source of VOCs besides local biomass emissions. Ten main components including propene, n-butane, i-butane, n-pentane, i-pentane, n-hexane, benzene, toluene, ethylbenzene and m/p-xylene accounted for 61.57% and 45.83% of total VOCs at urban and rural sites in winter, respectively, and 62.83% and 53.74% at urban and rural sites in spring, respectively. Aromatics contributed the most to total OFP, followed by alkenes. Alkanes contributed the least to OFP with the highest concentration. C3, C4 alkenes and aromatics were found to be the more reactive species with relatively high contributions to ozone formation in Xiamen. Comparing the average MIR of VOCs at the two sites, it was found that the reactivity of VOCs at rural site was higher than that at urban site. PMID:25898641

  14. Sampling, storage, and analysis of C2-C7 non-methane hydrocarbons from the US National Oceanic and Atmospheric Administration Cooperative Air Sampling Network glass flasks.

    PubMed

    Pollmann, Jan; Helmig, Detlev; Hueber, Jacques; Plass-Dülmer, Christian; Tans, Pieter

    2008-04-25

    An analytical technique was developed to analyze light non-methane hydrocarbons (NMHC), including ethane, propane, iso-butane, n-butane, iso-pentane, n-pentane, n-hexane, isoprene, benzene and toluene from whole air samples collected in 2.5l-glass flasks used by the National Oceanic and Atmospheric Administration, Earth System Research Laboratory, Global Monitoring Division (NOAA ESRL GMD, Boulder, CO, USA) Cooperative Air Sampling Network. This method relies on utilizing the remaining air in these flasks (which is at below-ambient pressure at this stage) after the completion of all routine greenhouse gas measurements from these samples. NMHC in sample aliquots extracted from the flasks were preconcentrated with a custom-made, cryogen-free inlet system and analyzed by gas chromatography (GC) with flame ionization detection (FID). C2-C7 NMHC, depending on their ambient air mixing ratios, could be measured with accuracy and repeatability errors of generally < or =10-20%. Larger deviations were found for ethene and propene. Hexane was systematically overestimated due to a chromatographic co-elution problem. Saturated NMHC showed less than 5% changes in their mixing ratios in glass flask samples that were stored for up to 1 year. In the same experiment ethene and propene increased at approximately 30% yr(-1). A series of blank experiments showed negligible contamination from the sampling process and from storage (<10 pptv yr(-1)) of samples in these glass flasks. Results from flask NMHC analyses were compared to in-situ NMHC measurements at the Global Atmospheric Watch station in Hohenpeissenberg, Germany. This 9-months side-by-side comparison showed good agreement between both methods. More than 94% of all data comparisons for C2-C5 alkanes, isoprene, benzene and toluene fell within the combined accuracy and precision objectives of the World Meteorological Organization Global Atmosphere Watch (WMO-GAW) for NMHC measurements. PMID:18355832

  15. Investigating the validity of the Knudsen prescription for diffusivities in a mesoporous covalent organic framework

    SciTech Connect

    Krishna, Rajamani; van Baten, Jasper M.

    2011-04-27

    Molecular dynamics (MD) simulations were performed to determine the self-diffusivity (Di,self) and the Maxwell–Stefan diffusivity (ÐI) of hydrogen, argon, carbon dioxide, methane, ethane, propane, n-butane, n-pentane, and n-hexane in BTP-COF, which is a covalent organic framework (COF) that has one-dimensional 3.4-nm-sized channels. The MD simulations show that the zero-loading diffusivity (ÐI(0)) is consistently lower, by up to a factor of 10, than the Knudsen diffusivity (Di,Kn) values. The ratio ÐI(0)/Di,Kn is found to correlate with the isosteric heat of adsorption, which, in turn, is a reflection of the binding energy for adsorption on the pore walls: the stronger the binding energy, the lower the ratio ÐI(0)/Di,Kn. The diffusion selectivity, which is defined by the ratio D1,self/D2,self for binary mixtures, was determined to be significantly different from the Knudsen selectivity (M2/M1)1/2, where MI is the molar mass of species i. For mixtures in which component 2 is more strongly adsorbed than component 1, the expression (D1,self/D2,self)/(M2/M1)1/2 has values in the range of 1–10; the departures from the Knudsen selectivity increased with increasing differences in adsorption strengths of the constituent species. The results of this study have implications in the modeling of diffusion within mesoporous structures, such as MCM-41 and SBA-15.

  16. METHYL KETONE METABOLISM IN HYDROCARBON-UTILIZING MYCOBACTERIA

    PubMed Central

    Lukins, H. B.; Foster, J. W.

    1963-01-01

    Lukins, H. B. (University of Texas, Austin) and J. W. Foster. Methyl ketone metabolism in hydrocarbon-utilizing mycobacteria. J. Bacteriol. 85: 1074–1087. 1963.—Species of Mycobacterium especially M. smegmatis 422, produced the homologous methyl ketones during the oxidation of propane, n-butane, n-pentane, or n-hexane. A carrier-trapping experiment demonstrated the formation of 2-undecanone, as well as 1,11-undecanedioic acid, during the oxidation of undecane-1-C14. Aliphatic alkane-utilizing mycobacteria were able to grow at the expense of several aliphatic methyl ketones as sole sources of carbon. Other ketones which did not support growth were oxidized by resting bacterial suspensions. M. smegmatis 422 cells grown on propane or acetone were simultaneously adapted to oxidize both substrates, as well as n-propanol. n-Propanol cells were unadapted to propane or acetone. Acetone produced from propane in a medium enriched in D2O contained a negligible quantity of D, presumably eliminating propylene as an intermediate in the oxidation. Cells grown at the expense of alkanes or methyl ketones in the presence of O218 had a higher content of O18 than did cells grown on terminally oxidized compounds, e.g., primary alcohols or fatty acids. An oxygenase reaction is postulated for the attack on methyl ketones. Acetol was isolated and characterized as an oxidation product of acetone by M. smegmatis 422. Acetol-grown cells had a higher O18 content than did n-propanol cells, and its utilization appears to involve at least one oxygenase reaction. Acetol produced from acetone in the presence of O218 was not enriched in the isotope, indicating the occurrence of exchange reactions or of oxygenation reactions at a later stage in the assimilation of acetone and acetol. PMID:14043998

  17. CARIBIC Observations of Non-Methane Hydrocarbons (NMHCs) in the UT/LS: Biomass Burning in the Tropics and Anthropogenic Pollution in the Extra-Tropics

    NASA Astrophysics Data System (ADS)

    Brenninkmeijer, C. A.; Rhee, T. S.; Slemr, F.; Mfühle, J.; Fischer, H.; Zahn, A.; van Velthoven, P. F.

    2003-12-01

    CARIBIC (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrumented Container) used a Boeing 767 on intercontinental flights to measure trace gases and aerosols between November 1997 and April 2002. From April 2004 onwards, a new Lufthansa Airbus A340-600 with a new inlet system and measurement container with 16 experiments will become operational. Here we discuss the results for NMHCs for a flight from the Maldives to Germany, June 2000. Twelve air samples of 350 L were collected and analyzed in the laboratory for NMHCs, halocarbons, CH4, CO, N2O, SF6, and isotopic compositions in CO and CO2. In the upper troposphere (UT) of the tropics, the concentrations of saturated NMHCs (C2 - C6) were significantly lower and less variable than in the extra-tropics, likely due to enhanced photo-oxidation in summer. A good correlation between long-lived NMHCs and CO, and their emission ratios imply that the air masses come from biomass burning regions. By contrast, the concentrations of all saturated NMHCs in the extra-tropics were greatly augmented. In particular, very high concentrations of several short-lived NMHCs, i.e., n-pentane, i-pentane, n-hexane, were observed near or even in the lowermost stratosphere (LS). Tight anti-correlations between CO and O3, the enhancement of ultra-fine particles, and the calculated backward trajectories indicate the occurrence of deep convection of highly polluted air from southern Europe into the lowermost stratosphere. The CARIBIC findings show a direct (fast) injection of polluted air to be a significant source of NMHCs observed in the lowermost stratosphere in the extra-tropics.

  18. Investigation of the impact of organic solvent type and solution pH on the extraction efficiency of naphthenic acids from oil sands process-affected water.

    PubMed

    Huang, Rongfu; McPhedran, Kerry N; Sun, Nian; Chelme-Ayala, Pamela; Gamal El-Din, Mohamed

    2016-03-01

    Naphthenic acids (NAs) from oil sand process-affected water (OSPW) were liquid-liquid extracted using six organic solvents (n-pentane, n-hexane, cyclohexane, dichloromethane, ethyl ether, and ethyl acetate) at three pHs (2.0, 8.5, and 12.0). The NAs exist in ionic (ions) and non-ionic (molecules) forms in the water phase depending on their dissociation constants and the solution pH. Results showed the extractability of NA molecules depends on the solvent polarity and the extractability of NA ions on the water solubility in solvent. The organic solvent type and solution pH were found to not only impact the extracted amounts of each NA species, but also the NAs distribution in terms of molecule carbon number and hydrogen deficiency. Overall, it is concluded that ethyl ether can be used as an alternative to dichloromethane (DCM) given their similar extraction efficiencies and extracted NA profiles. This is important since DCM is known to have metabolic toxicity and transitioning to the safer ethyl ether would eliminate laboratory DCM exposures and risk to human health. Despite the higher extraction efficiency of NAs at pH 2.0, extraction at pH 12.0 could be useful for targeted extraction of low-concentration nonpolar organic compounds in OSPW. This knowledge may assist in the determination of the specific NAs species that are known to have chronic, sub-chronic and acute toxicity to various organisms, and the potential targeting of treatment to these NAs species. PMID:26741553

  19. Characteristics of volatile organic compounds (VOCs) emitted from a petroleum refinery in Beijing, China

    NASA Astrophysics Data System (ADS)

    Wei, Wei; Cheng, Shuiyuan; Li, Guohao; Wang, Gang; Wang, Haiyan

    2014-06-01

    This study made a field VOCs (volatile organic compounds) measurement for a petroleum refinery in Beijing by determining 56 PAMS VOCs, which are demanded for photochemical assessment in US, and obtained the characteristics of VOCs emitted from the whole refinery and from its inner main devices. During the monitoring period, this refinery brought about an average increase of 61 ppbv in the ambient TVOCs (sum of the PAMS VOCs) at the refinery surrounding area, while the background of TVOCs there was only 10-30 ppbv. In chemical profile, the VOCs emitted from the whole refinery was characteristic by isobutane (8.7%), n-butane (7.9%), isopentane (6.3%), n-pentane (4.9%%), n-hexane (7.6%), C6 branched alkanes (6.0%), propene (12.7%), 1-butene (4.1%), benzene (7.8%), and toluene (5.9%). On the other hand, the measurement for the inner 5 devices, catalytic cracking units (CCU2 and CCU3), catalytic reforming unit (CRU), tank farm (TF), and wastewater treatment(WT), revealed the higher level of VOCs pollutions (about several hundred ppbv of TVOCs), and the individual differences in VOCs chemical profiles. Based on the measured speciated VOCs data at the surrounding downwind area, PMF receptor model was applied to identify the VOCs sources in the refinery. Then, coupling with the VOCs chemical profiles measured at the device areas, we concluded that CCU1/3 contributes to 25.9% of the TVOCs at the surrounding downwind area by volume, followed by CCU2 (24.7%), CRU (18.9%), TF (18.3%) and WT (12.0%), which was accordant with the research of US EPA (2008). Finally, ozone formation potentials of the 5 devices were also calculated by MIR technique, which showed that catalytic cracking units, accounting for about 55.6% to photochemical ozone formation, should be given the consideration of VOCs control firstly.

  20. Selective hydroxylation of alkanes by an extracellular fungal peroxygenase.

    PubMed

    Peter, Sebastian; Kinne, Matthias; Wang, Xiaoshi; Ullrich, René; Kayser, Gernot; Groves, John T; Hofrichter, Martin

    2011-10-01

    Fungal peroxygenases are novel extracellular heme-thiolate biocatalysts that are capable of catalyzing the selective monooxygenation of diverse organic compounds, using only H(2)O(2) as a cosubstrate. Little is known about the physiological role or the catalytic mechanism of these enzymes. We have found that the peroxygenase secreted by Agrocybe aegerita catalyzes the H(2)O(2)-dependent hydroxylation of linear alkanes at the 2-position and 3-position with high efficiency, as well as the regioselective monooxygenation of branched and cyclic alkanes. Experiments with n-heptane and n-octane showed that the hydroxylation proceeded with complete stereoselectivity for the (R)-enantiomer of the corresponding 3-alcohol. Investigations with a number of model substrates provided information about the route of alkane hydroxylation: (a) the hydroxylation of cyclohexane mediated by H(2)(18)(2) resulted in complete incorporation of (18)O into the hydroxyl group of the product cyclohexanol; (b) the hydroxylation of n-hexane-1,1,1,2,2,3,3-D(7) showed a large intramolecular deuterium isotope effect [(k(H)/k(D))(obs)] of 16.0 ± 1.0 for 2-hexanol and 8.9 ± 0.9 for 3-hexanol; and (c) the hydroxylation of the radical clock norcarane led to an estimated radical lifetime of 9.4 ps and an oxygen rebound rate of 1.06 × 10(11) s(-1). These results point to a hydrogen abstraction and oxygen rebound mechanism for alkane hydroxylation. The peroxygenase appeared to lack activity on long-chain alkanes (> C(16)) and highly branched alkanes (e.g. tetramethylpentane), but otherwise exhibited a broad substrate range. It may accordingly have a role in the bioconversion of natural and anthropogenic alkane-containing structures (including alkyl chains of complex biomaterials) in soils, plant litter, and wood. PMID:21812933

  1. Ultrafast molecular dynamics of biofuel extraction for microalgae and bacteria milking: blocking membrane folding pathways to damaged lipid-bilayer conformations with nanomicelles.

    PubMed

    Gillet, Jean-Numa

    2015-01-01

    Cell milking is a 100% renewable green energy for CO2 by extraction of biofuels inside the cytosol of photosynthetic micro-organisms as microalgae and bacteria. The cells are exposed to a hydrophobic solvent forming holes and cracks through their membranes from which the biofuels can leak out. In protein folding, the goal would be to find pathways to the unique functional protein conformer. However, in the lipid-bilayer interaction with the solvent for milking, the objective is to block the pathways for damaged membrane conformations of low free energy with undesired nanostructures, using the solvent properties, as shown with an ab initio structural bioinformatic model. Statistical thermodynamics is used to compute the free energy (including entropy) from the molecular dynamics trajectory of the biomolecular system with many conformational changes. This model can be extended to the general problem of biomolecules folding as for proteins and nucleic acids. Using an adaptation of the Einstein diffusion law, the conformational change dynamics of the lipid bilayer depends on the two diffusion coefficients of the solvent: D1 before the irreversible folding transition time and the much smaller D2 thereafter. In contrast to the n-hexane and n-heptane hydrocarbons of smaller size, the residual D2=4.7 × 10(-7)cm(2)/s of the n-decane solvent, with the highest partition coefficient among the three extractors, is the only to present a D2 value that is significantly below the critical threshold of 10(-6)cm(2)/s. Therefore, the membrane would resist to long hydrocarbons and the exposed cells would remain viable for milking. PMID:24735062

  2. Isolation and identification of some unknown substances in disposable nitrile-butadiene rubber gloves used for food handling.

    PubMed

    Mutsuga, M; Wakui, C; Kawamura, Y; Maitani, T

    2002-11-01

    In Japan, disposable gloves made from nitrile-butadiene rubber (NBR) are frequently used in contact with foods. In a previous paper, we investigated substances migrating from various gloves made of polyvinyl chloride, polyethylene, natural rubber and NBR. Zinc di-n-butyldithiocarbamate (ZDBC), diethyldithiocarbamate (ZDEC) used as vulcanization accelerators, di(2-ethylhexyl)phthalate (DEHP) used as a plasticizer and many unknown compounds that migrated from NBR gloves into n-heptane were detected by GC/MS. In this paper, six unknown compounds were obtained from one kind of NBR glove by n-hexane extraction and each was isolated by silica gel chromatography. From the results of NMR and mass spectral analysis of the six unknown compounds, their structures are proposed as 1,4-dione-2,5-bis(1,1-dimethylpropyl)cyclohexadiene (1), 2-(1,1-dimethylethyl)-4-(1,1,3,3-tetra methylbutyl)phenol (2), 2,6-bis(1,1-dimethylethyl)-4-(1,1,3,3-tetramethylbutyl)phenol (3), 2,4-bis(1,1,3,3-tetramethylbutyl)phenol (4), 2-(1,1-dimethylethyl)4,6-bis(1,1,3,3-tetramethylbutyl)phenol (5) and 2,4,6-tris(1,1,3,3-tetramethylbutyl)phenol (6). Compound 1 was observed in five of the seven kinds of NBR gloves, and compounds 2-4 and 6, which are not listed in Chemical Abstract (CA), were present in four kinds of gloves. PMID:12456282

  3. Growth of Rhodococcus sp. strain BCP1 on gaseous n-alkanes: new metabolic insights and transcriptional analysis of two soluble di-iron monooxygenase genes

    PubMed Central

    Cappelletti, Martina; Presentato, Alessandro; Milazzo, Giorgio; Turner, Raymond J.; Fedi, Stefano; Frascari, Dario; Zannoni, Davide

    2015-01-01

    Rhodococcus sp. strain BCP1 was initially isolated for its ability to grow on gaseous n-alkanes, which act as inducers for the co-metabolic degradation of low-chlorinated compounds. Here, both molecular and metabolic features of BCP1 cells grown on gaseous and short-chain n-alkanes (up to n-heptane) were examined in detail. We show that propane metabolism generated terminal and sub-terminal oxidation products such as 1- and 2-propanol, whereas 1-butanol was the only terminal oxidation product detected from n-butane metabolism. Two gene clusters, prmABCD and smoABCD—coding for Soluble Di-Iron Monooxgenases (SDIMOs) involved in gaseous n-alkanes oxidation—were detected in the BCP1 genome. By means of Reverse Transcriptase-quantitative PCR (RT-qPCR) analysis, a set of substrates inducing the expression of the sdimo genes in BCP1 were assessed as well as their transcriptional repression in the presence of sugars, organic acids, or during the cell growth on rich medium (Luria–Bertani broth). The transcriptional start sites of both the sdimo gene clusters were identified by means of primer extension experiments. Finally, proteomic studies revealed changes in the protein pattern induced by growth on gaseous- (n-butane) and/or liquid (n-hexane) short-chain n-alkanes as compared to growth on succinate. Among the differently expressed protein spots, two chaperonins and an isocytrate lyase were identified along with oxidoreductases involved in oxidation reactions downstream of the initial monooxygenase reaction step. PMID:26029173

  4. Growth of Rhodococcus sp. strain BCP1 on gaseous n-alkanes: new metabolic insights and transcriptional analysis of two soluble di-iron monooxygenase genes.

    PubMed

    Cappelletti, Martina; Presentato, Alessandro; Milazzo, Giorgio; Turner, Raymond J; Fedi, Stefano; Frascari, Dario; Zannoni, Davide

    2015-01-01

    Rhodococcus sp. strain BCP1 was initially isolated for its ability to grow on gaseous n-alkanes, which act as inducers for the co-metabolic degradation of low-chlorinated compounds. Here, both molecular and metabolic features of BCP1 cells grown on gaseous and short-chain n-alkanes (up to n-heptane) were examined in detail. We show that propane metabolism generated terminal and sub-terminal oxidation products such as 1- and 2-propanol, whereas 1-butanol was the only terminal oxidation product detected from n-butane metabolism. Two gene clusters, prmABCD and smoABCD-coding for Soluble Di-Iron Monooxgenases (SDIMOs) involved in gaseous n-alkanes oxidation-were detected in the BCP1 genome. By means of Reverse Transcriptase-quantitative PCR (RT-qPCR) analysis, a set of substrates inducing the expression of the sdimo genes in BCP1 were assessed as well as their transcriptional repression in the presence of sugars, organic acids, or during the cell growth on rich medium (Luria-Bertani broth). The transcriptional start sites of both the sdimo gene clusters were identified by means of primer extension experiments. Finally, proteomic studies revealed changes in the protein pattern induced by growth on gaseous- (n-butane) and/or liquid (n-hexane) short-chain n-alkanes as compared to growth on succinate. Among the differently expressed protein spots, two chaperonins and an isocytrate lyase were identified along with oxidoreductases involved in oxidation reactions downstream of the initial monooxygenase reaction step. PMID:26029173

  5. In Silico Calculation of Infinite Dilution Activity Coefficients of Molecular Solutes in Ionic Liquids: Critical Review of Current Methods and New Models Based on Three Machine Learning Algorithms.

    PubMed

    Paduszyński, Kamil

    2016-08-22

    The aim of the paper is to address all the disadvantages of currently available models for calculating infinite dilution activity coefficients (γ(∞)) of molecular solutes in ionic liquids (ILs)-a relevant property from the point of view of many applications of ILs, particularly in separations. Three new models are proposed, each of them based on distinct machine learning algorithm: stepwise multiple linear regression (SWMLR), feed-forward artificial neural network (FFANN), and least-squares support vector machine (LSSVM). The models were established based on the most comprehensive γ(∞) data bank reported so far (>34 000 data points for 188 ILs and 128 solutes). Following the paper published previously [J. Chem. Inf. Model 2014, 54, 1311-1324], the ILs were treated in terms of group contributions, whereas the Abraham solvation parameters were used to quantify an impact of solute structure. Temperature is also included in the input data of the models so that they can be utilized to obtain temperature-dependent data and thus related thermodynamic functions. Both internal and external validation techniques were applied to assess the statistical significance and explanatory power of the final correlations. A comparative study of the overall performance of the investigated SWMLR/FFANN/LSSVM approaches is presented in terms of root-mean-square error and average absolute relative deviation between calculated and experimental γ(∞), evaluated for different families of ILs and solutes, as well as between calculated and experimental infinite dilution selectivity for separation problems benzene from n-hexane and thiophene from n-heptane. LSSVM is shown to be a method with the lowest values of both training and generalization errors. It is finally demonstrated that the established models exhibit an improved accuracy compared to the state-of-the-art model, namely, temperature-dependent group contribution linear solvation energy relationship, published in 2011 [J. Chem

  6. Approach to estimation of absorption of aliphatic hydrocarbons diffusing from interior materials in an automobile cabin by inhalation toxicokinetic analysis in rats.

    PubMed

    Yoshida, Toshiaki

    2010-01-01

    The interior air of an automobile cabin has been demonstrated in our previous studies to be contaminated by high concentrations of a large variety of aliphatic hydrocarbons diffusing from the interior materials. In the present study, the amounts of seven selected aliphatic hydrocarbons absorbed by the car driver were estimated by evaluating their inhalation toxicokinetics in rats. Measured amounts of the substances were injected into a closed chamber system in which a rat had been placed, and the concentration changes in the chamber were examined. The toxicokinetics of the substances were evaluated based on concentration-time courses using a nonlinear compartment model. Their absorption amounts in humans at the levels of actual concentrations in the cabins without ventilation were extrapolated from the results found with the rats. The absorption amounts estimated for a driver during a 2 h drive were as follows: 6 microg/60 kg of human body weight for methylcyclopentane (interior concentration 23 microg/m(3) as median value in previous study), 5 microg for 2-methylpentane (36 microg/m(3)), 13 microg for n-hexane (65 microg/m(3)), 51 microg for n-heptane (150 microg/m(3)), 26 microg for 2,4-dimethylheptane (97 microg/m(3)), 17 microg for n-nonane (25 microg/m(3)) and 49 microg for n-decane (68 microg/m(3)). An inverse relationship was found between the exposure and absorption among the substances (e.g. between n-decane and 2,4-dimethylheptane). These findings suggest that not only the exposure concentrations but also the absorption amounts should be taken into account to evaluate the health effects of exposure to low concentrations of volatile compounds as environmental contaminants. PMID:19743389

  7. Volatile organic compound concentrations, emission rates, and source apportionment in newly-built apartments at pre-occupancy stage.

    PubMed

    Shin, Seung H; Jo, Wan K

    2012-10-01

    The present study investigated the indoor concentrations of selected volatile organic compounds (VOCs) and formaldehyde and their indoor emission characteristics in newly-built apartments at the pre-occupancy stage. In total, 107 apartments were surveyed for indoor and outdoor VOC concentrations in two metropolitan cities and one rural area in Korea. A mass balanced model was used to estimate surface area-specific emission rates of individual VOCs and formaldehyde. Seven (benzene, ethyl benzene, toluene, m,p-xylene, o-xylene, n-hexane, and n-heptane) of 40 target compounds were detectable in all indoor air samples, whereas the first five were detected in all outdoor air samples. Formaldehyde was also predominant in the indoor air samples, with a high detection frequency of 96%. The indoor concentrations were significantly higher than the outdoor concentrations for aromatics, alcohols, terpenes, and ketones. However, six halogenated VOCs exhibited similar concentrations for indoor and outdoor air samples, suggesting that they are not major components emitted from building materials. It was also suggested that a certain portion of the apartments surveyed were constructed by not following the Korean Ministry of Environment guidelines for formaldehyde emissions. Toluene exhibited the highest emission rate with a median value of 138 μg m(-2) h(-1). The target compounds with median emission rates greater than 20 μg m(-2) h(-1) were toluene, 1-propanol, formaldehyde, and 2-butanone. The wood panels/vinyl floor coverings were the largest indoor pollutant source, followed by floorings, wall coverings, adhesives, and paints. The wood panels/vinyl floor coverings contributed nearly three times more to indoor VOC concentrations than paints. PMID:22698369

  8. Fischer-Tropsch synthesis in supercritical reaction media. [Quarterly] progress report, July 1, 1993--September 30, 1993

    SciTech Connect

    Subramaniam, B.

    1993-10-01

    Figure 1 shows the physical appearance of the reactor and analytical units. The feed preparation section consists of a mass flow controller for syngas introduction, the BPLC pump for n-hexane introduction, preheaters, check valves, static mixer, and safety head has been completed. The stainless steel reactor was fabricated and was alonized to passivate the stainless steel surface. The fluidized sand bath surrounding the reactor was fabricated in house. Aluminum oxide (120 mesh) will be used as the fluidized medium. Stepping-motor-driven micrometering (Autoclave{reg_sign}) valves have been installed for pressure control of the reactor and of the syngas feed stream. The sample transfer lines connected to the gas sampling valves in the GC will be routed inside the valve oven and out through the front top of the GC, where they will be connected with the heated sample transfer lines from the reactor. The sample outlet line will be routed through a cold trap operated at 20{degrees}C or lower and the gases from the cold trap will be exhausted to the roof vent. The reactor unit is versatile and permits us to investigate the effect(s) of any of the following variables on syngas conversion, selectivity and reaction rate maintenance: (1) pressure (25--70) bars, (2) syngas flowrate (30--150) cc/min/g{center_dot}cat, (3) syngas ratio (H{sub 2}/CO of 0.5, 1.0 or 2.0) (4) ratio of syngas to reaction media (0.2--5.0), (5) catalyst type (Fe or Co), (6) direction of cocurrent flow (upflow or downflow), (7) cosolvent effects (such as n-pentane), and (8) sulfur content (1--50 mg{center_dot}/g{center_dot}Fe). Based on a literature review (Pennline et al., 1987; Baltrus et al., 1989; Bukur et al., 1990), the pretreatment of Fe catalysts will be performed with flowing CO at low pressure ({approximately}1 atm) and high temperatures ({approximately}280{degrees}C).

  9. Effects of biomass burning on summertime nonmethane hydrocarbon concentrations in the Canadian wetlands

    NASA Technical Reports Server (NTRS)

    Blake, D. R.; Smith, T. W., Jr.; Chen, T.-Y.; Whipple, W. J.; Rowland, F. S.

    1994-01-01

    Approximately 900 whole air samples were collected and assayed for selected C2-C10 hydrocarbons and seven halocarbons during the 5-week Arctic Boundary Layer Expedition (ABLE) 3B conducted in eastern Canadian wetland areas. In more than half of the 46 vertical profiles flown, enhanced nonmethane hydrocarbon (NMHC) concentrations attributable to plumes from Canadian forest fires were observed. Urban plumes, also enhanced in many NMHCs, were separately identified by their high correlation with elevated levels of perchloroethene. Emission factors relative to ethane were determined for 21 hydrocarbons released from Canadian biomass burning. Using these data for ethane, ethyne, propane, n-butane, and carbon monoxide enhancements from the literature, global emissions of these four NMHCs were estimated. Because of its very short atmospheric lifetime and its below detection limit background mixing ratio, 1,3-butadiene is an excellent indicator of recent combustion. No statistically significant emissions of nitrous oxide, isoprene, or CFC 12 were observed in the biomass-burning plumes encountered during ABLE 3B. The presence of the short-lived biogenically emitted isoprene at altitudes as high as 3000 m implies that mixing within the planetary boundary layer (PBL) was rapid. Although background levels of the longer-lived NMHCs in this Canadian region increase during the fire season, isoprene still dominated local hydroxyl radical photochemistry within the PBL except in the immediate vicinity of active fires. The average biomass-burning emission ratios for hydrocarbons from an active fire sampled within minutes of combustion were, relative to ethane, ethene, 2.45; ethyne 0.57; propane, 0.25; propene, 0.73; propyne, 0.06; n-butane, 0.09; i-butane, 0.01; 1-butene, 0.14; cis-2-butene, 0.02; trans-2-butene, 0.03; i-butylene, 0.07; 1,3-butadiene, 0.12; n-pentane, 0.05; i-pentane, 0.03; 1-pentene, 0.06; n-hexane, 0.05; 1-hexene, 0.07; benzene, 0.37; toluene, 0.16.

  10. Development and implementation of a stereoselective normal-phase liquid chromatography-tandem mass spectrometry method for the determination of intrinsic metabolic clearance in human liver microsomes.

    PubMed

    Zhang, Yingru; Caporuscio, Christian; Dai, Jun; Witkusa, Michael; Rose, Anne; Santella, Joseph; D'Arienzo, Celia; Wang-Iverson, David B; Tymiak, Adrienne A

    2008-11-01

    The stereoselective determination of stereoisomers in biological samples provides vital information on stereospecific metabolism and pharmacokinetic profiles of the drugs. Despite the unique advantage and the great success of normal-phase (NP) HPLC for the separations of drug stereoisomers using polysaccharide-type chiral stationary phases (CSPs), the technique is rarely applied to quantitative HPLC-MS-MS bioanalysis. This is, at least in part, due to the incompatibility between the usual mobile phase (n-hexane or n-heptane) in normal-phase HPLC and the MS ionization sources which poses a potential detonation hazard. An environmentally friendly and nonflammable alternative solvent, ethoxynonafluorobutane (ENFB), was reported previously to potentially provide an ideal solution for combining the powers of stereoselective NP chromatographic separation and MS-MS detection. In this study, a stereoselective NP-HPLC-MS-MS method was developed using ENFB to quantify a pair of Bristol Myers Squibb (BMS) proprietary drug stereoisomers and their ketone metabolite for an in vitro study, which demonstrated, for the first time, the practical applicability and utility of ENFB for bioanalysis in pharmaceutical industry. The effects of different organic modifiers and temperature, as well as the comparison between ENFB and the usual solvent, heptane, for the separation, are discussed. The resolution of the stereoisomers was achieved using 63% of 3:1 mixture of ethanol and methanol with 37% ENFB on a Chiralpak AD-H column at 50 degrees C. High sensitivity was obtained using the MS-MS detection in the positive ion atmospheric pressure chemical ionization (APCI) mode. The lower limit of quantitation (LLOQ) for the first stereoisomer and the ketone metabolite was 5 ng/mL, and was 10 ng/mL for the second isomer in the human liver microsome-potassium phosphate buffer matrix. The linear dynamic range of 5-1000 ng/mL for both isomers and 10-1000 ng/mL for the metabolite were demonstrated

  11. Cytotoxic activity of plants of family zygophyllaceae and euphorbiaceae.

    PubMed

    Dastagir, Ghulam; Hussain, Farrukh

    2014-07-01

    The methanolic and n-hexane extracts of studied plants showed significant toxicity to brine shrimps. The methanolic extract of Fagonia cretica had highest LD50 (117.72) value, while Peganum harmala showed low LD50 value (41.70) compared to n-hexane extract. The methanolic and n-hexane extracts of Tribulus terrestris showed similar LD50 values. The methanolic extract of Chrozophora tinctoria showed low LD50 value than the n-hexane extract. The methanolic extract of Ricinus communis showed highest LD50 value while the n-hexane extract showed lowest LD50 value. The LD50 value less than 100 was obtained for n-hexane extracts of Fagonia cretica, Peganum harmala and Ricinus communis. The n-hexane extracts of these plants also showed the highest toxicity as compare to methanolic extracts. The chemical constituents detected in the present investigation might be responsible for cytotoxic activity. PMID:25015443

  12. Pentane conversion on dealuminated H-Y and HZSM-5

    SciTech Connect

    Hong, Y.; Gruver, V.; Fripiat, J.J.

    1996-07-01

    Kinetics of n-pentane conversion was studied in relation to the acidity of Y zeolites. Selectivity to isomerization vs. cracking depends mainly on the zeolite structure and the partial clogging of the pores. 34 refs., 5 figs., 7 tabs.

  13. C-H\\ctdot O hydrogen bonding in a 4-fluorobenzoate multilayer induced by silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Perry, Donald A.; Schiefer, Elizabeth M.; Cordova, James S.; Bonde, Ashley M.; Razer, Taylor M.; Primm, Katherine M.; Chen, Tsung Yen; Biris, Alexandru S.

    2011-08-01

    SERS, SEIRA, and DFT calculations showed silver nanoparticles can stimulate C-H⋯O hydrogen bonding in 4-fluorobenzoate ion/ n-heptane multilayers. SERS/DFT demonstrated that 4-fluorobenzoic acid (4FBA) adsorbed as a 4-fluorobenzoate (4FBT) monolayer on nanosilver. Ionization of 4FBA to 4FBT occurred in the multilayer when 4FBA was deposited in n-heptane onto nanosilver. Frequency shifts in SEIRA bands of 4FBT COO stretch and n-heptane CH bend modes illustrated a change in the degree of C-H⋯O hydrogen bonding as more 4FBT/ n-heptane was adsorbed to the multilayer. This work will influence many research areas such as sensors formed from thin organic layers on metal nanoparticles.

  14. 21 CFR 177.1655 - Polysulfone resins.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... with the solvents—distilled water, 50 percent (by volume) ethyl alcohol in distilled water, 3 percent acetic acid in distilled water, and n-heptane, yield total extractives in each extracting solvent not...

  15. 21 CFR 177.1556 - Polyaryletherketone resins.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... temperature for 2 hours with the following solvents: Distilled water, 50 percent (by volume) ethyl alcohol in distilled water, 3 percent acetic acid (by weight) in distilled water, and n-heptane. (d) In testing...

  16. 21 CFR 177.1655 - Polysulfone resins.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... extracted at reflux temperatures for 6 hours with the solvents—distilled water, 50 percent (by volume) ethyl alcohol in distilled water, 3 percent acetic acid in distilled water, and n-heptane, yield...

  17. 21 CFR 177.1655 - Polysulfone resins.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... extracted at reflux temperatures for 6 hours with the solvents—distilled water, 50 percent (by volume) ethyl alcohol in distilled water, 3 percent acetic acid in distilled water, and n-heptane, yield...

  18. 21 CFR 177.1655 - Polysulfone resins.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... extracted at reflux temperatures for 6 hours with the solvents—distilled water, 50 percent (by volume) ethyl alcohol in distilled water, 3 percent acetic acid in distilled water, and n-heptane, yield...

  19. 21 CFR 177.2415 - Poly(aryletherketone) resins.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... milligrams per square inch of food contact surface: Distilled water, 50 percent (by volume) ethanol in distilled water, 3 percent acetic acid in distilled water, and n-heptane. In testing the final food...

  20. 40 CFR Appendix: Table 1 to... - List of Hazardous Air Pollutants (HAP) for Subpart HHH

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Acetaldehyde 71432 Benzene (includes benzene in gasoline) 75150 Carbon disulfide 463581 Carbonyl sulfide 100414 Ethyl benzene 107211 Ethylene glycol 75050 Acetaldehyde 50000 Formaldehyde 110543 n-Hexane...

  1. 40 CFR Appendix: Table 1 to... - List of Hazardous Air Pollutants (HAP) for Subpart HHH

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... Acetaldehyde 71432 Benzene (includes benzene in gasoline) 75150 Carbon disulfide 463581 Carbonyl sulfide 100414 Ethyl benzene 107211 Ethylene glycol 75050 Acetaldehyde 50000 Formaldehyde 110543 n-Hexane...

  2. Thermal Ignition

    NASA Astrophysics Data System (ADS)

    Boettcher, Philipp Andreas

    sufficiently rapidly undergoes only a moderate amount of thermal decomposition and explodes quite violently. This behavior can also be captured and analyzed using a one-step reaction model, where the heat release is in competition with the depletion of reactants. Hot surface ignition is examined using a glow plug or heated nickel element in a series of premixed n-hexane air mixtures. High-speed schlieren photography, a thermocouple, and a fast response pressure transducer are used to record flame characteristics such as ignition temperature, flame speed, pressure rises, and combustion mode. The ignition event is captured by considering the dominant balance of diffusion and chemical reaction that occurs near a hot surface. Experiments and models show a dependence of ignition temperature on mixture composition, initial pressure, and hot surface size. The mixtures exhibit the known lower flammability limit where the maximum temperature of the hot surface was insufficient at igniting the mixture. Away from the lower flammability limit, the ignition temperature drops to an almost constant value over a wide range of equivalence ratios (0.7 to 2.8) with large variations as the upper flammability limit is approached. Variations in the initial pressure and equivalence ratio also give rise to different modes of combustion: single flame, re-ignition, and puffing flames. These results are successfully compared to computational results obtained using a flamelet model and a detailed chemical mechanism for n-heptane. These different regimes can be delineated by considering the competition between inertia, i.e., flame propagation, and buoyancy, which can be expressed in the Richardson number. In experiments of hot surface ignition and subsequent flame propagation a 10 Hz puffing flame instability is visible in mixtures that are stagnant and premixed prior to the ignition sequence. By varying the size of the hot surface, power input, and combustion vessel volume, we determined that the

  3. Gravity Effects in Condensing and Evaporating Films

    NASA Technical Reports Server (NTRS)

    Hermanson, J. C.; Som, S. M.; Allen, J. S.; Pedersen, P. C.

    2004-01-01

    A general overview of gravity effects in condensing and evaporating films is presented. The topics include: 1) Research Overview; 2) NASA Recognizes Critical Need for Condensation & Evaporation Research to Enable Human Exploration of Space; 3) Condensation and Evaporation Research in Reduced Gravity is Enabling for AHST Technology Needs; 4) Differing Role of Surface Tension on Condensing/Evaporating Film Stability; 5) Fluid Mechanisms in Condensing and Evaporating Films in Reduced Gravity; 6) Research Plan; 7) Experimental Configurations for Condensing Films; 8) Laboratory Condensation Test Cell; 9) Aircraft Experiment; 10) Condensation Study Current Test Conditions; 11) Diagnostics; 12) Shadowgraph Images of Condensing n- pentane Film in Unstable (-1g) Configuration; 13) Condensing n-Pentane Film in Normal Gravity (-1g) at Constant Pressure; 14) Condensing n-Pentane Film in Normal Gravity (-1g) with Cyclic Pressure; 15) Non-condensing Pumped Film in Normal Gravity (-1g); 16) Heat Transfer Coefficient in Developing, Unstable Condensing Film in Normal Gravity; 17) Heat Transfer for Unsteady Condensing Film (-1g); 18) Ultrasound Measurement of Film Thickness N-pentane Film, Stable (+1g) Configuration; and 19) Ultrasound Measurement of Film Thickness N-pentane Film, Unstable (-1g) Configuration.

  4. Research on Volatile Organic Compounds in the Mexico City Metropolitan Area (MCMA) in two campaigns collected in the Winter-2011 and Spring-2012

    NASA Astrophysics Data System (ADS)

    Magaña, M.; González-Vargas, S.; Blanco, S.; Watanabe, T.; Maeda, T.; Cardenas, B.

    2013-05-01

    Because of the importance of information on the concentration and speciation of Volatile Organic Compounds (VOC) in the atmosphere for the development of regulatory programs or emission control, is necessary to determine the type and the concentrations of reactive and toxic VOC in atmospheric air. The aim of this study is to determine the speciation and quantification of VOC in the atmospheric air of the Mexico City Metropolitan Area (MCMA), from samples obtained in November-December 2011 (cold-dry) and March-April (warm-dry). This study presents the results of characterization of VOC in ambient air in the MCMA conducted during 2011-2012. Sampling of VOC was done in two sampling campaigns: from November 17th to December 11th, 2011, and March 1st to April 6th, 2012 through collection of ambient air each six days in six liters stainless steel SUMMA canisters of 24 hours integrated samples, in three sites (Merced: commercial area with vehicular sources, Pedregal: residential area with vehicular sources and San Agustin: industrial sources with heavy traffic), in the MCMA. The analysis of samples was carried out with two chromatographic systems: 1) method equivalent to the EPA's Method TO-14, and 2) GC/MSD coupled to a preconcentrator ENTECH, for the analysis of the compounds listed in EPA method TO15. It was investigated the concentration of 111 volatile organic compounds, (ozone precursors and toxic compounds). It was found that concentrations of 23 species, constitute 80% of the total VOC concentration tested: ethane, propane, isobutane, n-butane, n-pentane, n-hexane, isopentane, methylcyclopentane, ethylene, propylene, acetylene, benzene, toluene, ethylbenzene, m/p-xylene, o-xylene, 1,2,4-trimethylbenzene, ethyl and isopropyl alcohols, acetone, 2-butanone, MTBE and ethyl acetate. Both in 2011 and 2012, the highest concentrations measured in the three sites were for compounds associated with the combustion of LPG gas: propane, n-butane. The highest concentrations of

  5. Electron Transport in Paracoccus Halodenitrificans and the Role of Ubiquinone

    NASA Technical Reports Server (NTRS)

    Hochstein, L. I.; Cronin, S. E.

    1983-01-01

    The membrane-bound NADH oxidase of Paracoccus halodenitrificans was inhibited by dicoumarol, 2-n-heptyl-4-hydroxyquinoline-N-oxide (HQNO), and exposure to ultraviolet light (at 366 nm). When the membranes were extracted with n-pentane, NADH oxidase activity was lost. Partial restoration was achieved by adding the ubiquinone fraction extracted from the membranes. Succinate oxidation was not inhibited by dicoumarol or HQNO but was affected by ultraviolet irradiation or n-pentane extraction. However, the addition of the ubiquinone fraction to the n-pentane-extracted membranes did not restore enzyme activity. These observations suggested the reducing equivalents from succinate entered the respiratory chain on the oxygen side of the HQNO-sensitive site and probably did not proceed through a quinone.

  6. Electron transport in Paracoccus halodenitrificans and the role of Ubiquinone

    NASA Technical Reports Server (NTRS)

    Hochstein, L. I.; Cronin, S. E.

    1984-01-01

    The membrane-bound NADH oxidase of Paracoccus halodenitrificans was inhibited by dicoumarol, 2-n-heptyl-4-hydroxyquinoline-N-oxide (HQNO), and exposure to ultraviolet light (at 366 nm). When the membranes were extracted with n-pentane, NADH oxidase activity was lost. Partial restoration was achieved by adding the ubiquinone fraction extracted from the membranes. Succinate oxidation was not inhibited by dicoumarol or HQNO but was affected by ultraviolet irradiation or n-pentane extraction. However, the addition of the ubiquinone fraction to the n-pentane-extracted membranes did not restore enzyme activity. These observations suggested the reducing equivalents from succinate entered the respiratory chain on the oxygen side of the HQNO-sensitive site and probably did not proceed through a quinone.

  7. Low severity upgrading of F-T waxes with solid superacids. Quarterly report, March 1, 1993--May 31, 1993

    SciTech Connect

    Tierney, J.W.; Wender, I.

    1993-09-01

    The upgrading of Fischer-Tropsch waxes with solid superacids continued this quarter, the isomerization and hydrocracking of n-pentane were examined by in situ FT-IR. It was found that the intensity of protonic acid sites was weakened as n-pentane was introduced into the IR cell, indicating that protonic acid sites tend to donate a proton to n-paraffins. There was no evidence of olefinic intermediates. It is likely that, as we previously proposed, isomerization and hydrocracking over Pt/ZrO{sub 2}/SO{sub 4} catalyst proceed through initial protonation of n-alkanes to form carbonium ions which are then isomerized and hydrocracked.

  8. Modeling the Auto-Ignition of Biodiesel Blends with a Multi-Step Model

    SciTech Connect

    Toulson, Dr. Elisa; Allen, Casey M; Miller, Dennis J; McFarlane, Joanna; Schock, Harold; Lee, Tonghun

    2011-01-01

    There is growing interest in using biodiesel in place of or in blends with petrodiesel in diesel engines; however, biodiesel oxidation chemistry is complicated to directly model and existing surrogate kinetic models are very large, making them computationally expensive. The present study describes a method for predicting the ignition behavior of blends of n-heptane and methyl butanoate, fuels whose blends have been used in the past as a surrogate for biodiesel. The autoignition is predicted using a multistep (8-step) model in order to reduce computational time and make this a viable tool for implementation into engine simulation codes. A detailed reaction mechanism for n-heptane-methyl butanoate blends was used as a basis for validating the multistep model results. The ignition delay trends predicted by the multistep model for the n-heptane-methyl butanoate blends matched well with that of the detailed CHEMKIN model for the majority of conditions tested.

  9. Understanding nanofluid stability through molecular simulation

    SciTech Connect

    Dang, Liem X.; Annapureddy, Harsha V.; Sun, Xiuquan; Thallapally, Praveen K.; McGrail, B. Peter

    2012-11-01

    We performed molecular dynamics simulations to study solvation of a nanoparticle and nanoparticle-nanoparticle interactions in an n-hexane solution. Structural signatures are barely observed between the nanoparticle and n-hexane molecules because of weak binding and steric effects. The dynamic properties of the n-hexane molecule, on the other hand, are significantly influenced by the solvated nanoparticle. The diffusion of n-hexane molecules inside the nanoparticle is significantly decreased mainly because of the loss of dimensions of translation. Because one translational degree of freedom is lost by colliding with the wall of nanoparticle, the n-hexane molecules outside the nanoparticle diffuse 30% slower than the molecules in pure solution. The computed free energy profiles illustrate that the arrangement of the nanoparticles in bulk n-hexane solution are dependent on the orientation and functional group. We found that the n-hexane solvent exerts some effects on the interactions between the solvated nanoparticles. This work was supported by the US Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences and by the Office of Energy Efficiency and Renewable Energy, Geothermal Technologies Program. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for DOE by Battelle.

  10. Fiber Supported Droplet Combustion-2 (FSDC-2)

    NASA Technical Reports Server (NTRS)

    Colantonio, Renato; Dietrich, Daniel; Haggard, John B., Jr.; Nayagan, Vedha; Dryer, Frederick L.; Shaw, Benjamin D.; Williams, Forman A.

    1998-01-01

    Experimental results for the burning characteristics of fiber supported, liquid droplets in ambient Shuttle cabin air (21% oxygen, 1 bar pressure) were obtained from the Glove Box Facility aboard the STS-94/MSL-1 mission using the Fiber Supported Droplet Combustion - 2 (FSDC-2) apparatus. The combustion of individual droplets of methanol/water mixtures, ethanol, ethanol/water azeotrope, n-heptane, n-decane, and n-heptane/n-hexadecane mixtures were studied in quiescent air. The effects of low velocity, laminar gas phase forced convection on the combustion of individual droplets of n-heptane and n-decane were investigated and interactions of two droplet-arrays of n-heptane and n-decane droplets were also studied with and without gas phase convective flow. Initial diameters ranging from about 2mm to over 6mm were burned on 80-100 micron silicon fibers. In addition to phenomenological observations, quantitative data were obtained in the form of backlit images of the burning droplets, overall flame images, and radiometric combustion emission measurements as a function of the burning time in each experiment. In all, 124 of the 129 attempted experiments (or about twice the number of experiments originally planned for the STS-94/MSL-1 mission) were conducted successfully. The experimental results contribute new observations on the combustion properties of pure alkanes, binary alkane mixtures, and simple alcohols for droplet sizes not studied previously, including measurements on individual droplets and two-droplet arrays, inclusive of the effects of forced gas phase convection. New phenomena characterized experimentally for the first time include radiative extinction of droplet burning for alkanes and the "twin effect" which occurs as a result of interactions during the combustion of two-droplet arrays. Numerical modeling of isolated droplet combustion phenomenon has been conducted for methanol/water mixtures, n-heptane, and n-heptane/n-hexadecane mixtures, and results

  11. Photophysics of 4- N, N-dimethylamino cinnamaldehyde in AOT reverse micelles and exploration of its position and orientation

    NASA Astrophysics Data System (ADS)

    Panja, Subhasis; Chakravorti, Sankar

    2003-01-01

    An attempt has been made in this Letter to locate the position and orientation of 4- N, N-dimethylamino cinnamaldehyde (DMACA) inside sodium bis(2-ethylhexyl) sulfosuccinate (AOT)- n-heptane reverse micelle based on change in photophysical properties of DMACA compared to that in n-heptane. It has been proposed that the possibility of finding the donor moiety inside the small water pool of reverse micelle is maximum while the acceptor group straddles in the remaining part of the reverse micelle. The micropolarity in the vicinity of the donor moiety has been computed in terms of dielectric constant with varying water pool size.

  12. 21 CFR 178.3010 - Adjuvant substances used in the manufacture of foamed plastics.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... agent in polystyrene. Isopentane For use as a blowing agent in polystyrene. n-Pentane Do. 1,1,2,2-Tetra-chloroethylene For use only as a blowing agent adjuvant in polystyrene at a level not to exceed 0.3 percent by weight of finished foamed polystyrene intended for use in contact with food only of the types...

  13. 21 CFR 178.3010 - Adjuvant substances used in the manufacture of foamed plastics.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... agent in polystyrene. Isopentane For use as a blowing agent in polystyrene. n-Pentane Do. 1,1,2,2-Tetra-chloroethylene For use only as a blowing agent adjuvant in polystyrene at a level not to exceed 0.3 percent by weight of finished foamed polystyrene intended for use in contact with food only of the types...

  14. 21 CFR 178.3010 - Adjuvant substances used in the manufacture of foamed plastics.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... agent in polystyrene. Isopentane For use as a blowing agent in polystyrene. n-Pentane Do. 1,1,2,2-Tetra-chloroethylene For use only as a blowing agent adjuvant in polystyrene at a level not to exceed 0.3 percent by weight of finished foamed polystyrene intended for use in contact with food only of the types...

  15. 21 CFR 178.3010 - Adjuvant substances used in the manufacture of foamed plastics.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...-Difluoroethane (CAS Reg. No. 75-37-6) For use as a blowing agent in polystyrene. Isopentane For use as a blowing agent in polystyrene. n-Pentane Do. 1,1,2,2-Tetra-chloroethylene For use only as a blowing agent adjuvant in polystyrene at a level not to exceed 0.3 percent by weight of finished foamed...

  16. 21 CFR 178.3010 - Adjuvant substances used in the manufacture of foamed plastics.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... agent in polystyrene. Isopentane For use as a blowing agent in polystyrene. n-Pentane Do. 1,1,2,2-Tetra-chloroethylene For use only as a blowing agent adjuvant in polystyrene at a level not to exceed 0.3 percent by weight of finished foamed polystyrene intended for use in contact with food only of the types...

  17. Conservative and dissipative force field for simulation of coarse-grained alkane molecules: A bottom-up approach

    NASA Astrophysics Data System (ADS)

    Trément, Sébastien; Schnell, Benoît.; Petitjean, Laurent; Couty, Marc; Rousseau, Bernard

    2014-04-01

    We apply operational procedures available in the literature to the construction of coarse-grained conservative and friction forces for use in dissipative particle dynamics (DPD) simulations. The full procedure rely on a bottom-up approach: large molecular dynamics trajectories of n-pentane and n-decane modeled with an anisotropic united atom model serve as input for the force field generation. As a consequence, the coarse-grained model is expected to reproduce at least semi-quantitatively structural and dynamical properties of the underlying atomistic model. Two different coarse-graining levels are studied, corresponding to five and ten carbon atoms per DPD bead. The influence of the coarse-graining level on the generated force fields contributions, namely, the conservative and the friction part, is discussed. It is shown that the coarse-grained model of n-pentane correctly reproduces self-diffusion and viscosity coefficients of real n-pentane, while the fully coarse-grained model for n-decane at ambient temperature over-predicts diffusion by a factor of 2. However, when the n-pentane coarse-grained model is used as a building block for larger molecule (e.g., n-decane as a two blobs model), a much better agreement with experimental data is obtained, suggesting that the force field constructed is transferable to large macro-molecular systems.

  18. Mikrokristallbildung und intermolekulare Triplett-Triplett-Energieiibertragung in festen transparenten Glasern bei 77 K. Das System N-Methylcarbazol/Naphthalin / Microcrystal Formation and Intermolecular Triplet-Triplet Energy Transfer in Rigid Transparent Glasses at 77 K. The System N-Methyl-earbazole / Naphthalene

    NASA Astrophysics Data System (ADS)

    Zander, M.

    1984-05-01

    The efficient intermolecular triplet-triplet energy transfer between N-methylcarbazole (donor) and naphthalene (acceptor) observed at 10-2 ᴍ concentration of donor and acceptor in a rigid transparent methylcyclohexane/n-pentane glass at 77 K is shown to occur in microcrystals of the donor containing small amounts of the acceptor

  19. A predictive method for volatile organic compounds emission from soil: Evaporation and diffusion behavior investigation of a representative component of crude oil.

    PubMed

    Wang, Haijing; Fischer, Thomas; Wieprecht, Wolfgang; Möller, Detlev

    2015-10-15

    Pipelines are convenient, economical and widely used mode of transportation of crude oil. However, the inevitable or otherwise accidents during such transport of crude oil lead to large scale oil spills, which consequently result in both soil and air pollution. When such pollution occurs, crude oil VOC concentrations in air, soil pollution evaluation and VOC propagation in soil provide important evidence for airborne detection of oils spills. Therefore, several issues, including determination method for VOC, isotherm parameters of VOC sorption on soil surfaces, and VOC diffusion flux simulation, are significant. In our previous study, n-butane and n-pentane were proved to be the maximum VOCs in studied crude oils. Therefore, a predictive method using n-pentane as a representative component is proposed in this paper. Firstly, a headspace solid phase microextraction (SPME) method was developed for determination of n-pentane in non-equilibrium mass transfer conditions. Secondly, Brunauer-Emmett-Teller (BET) analysis with liquid nitrogen was carried out to predict isotherm parameters for n-pentane. Finally, two models were used to predict the emission process. Probably influenced by gas vapor density below and above the soil layer, the experimental data amounted to 74% of the deduced value from the simplified analytical model. However, the free diffusion model fitted well with the experimental results. PMID:26026407

  20. Immiscible Systems

    ERIC Educational Resources Information Center

    Eckelmann, Jens; Luning, Ulrich

    2013-01-01

    layers of liquids. The setup of both demonstrations is such that one homogeneous layer in a multiphasic mixture separates into two new layers upon shaking. The solvents used are methanol, toluene, petroleum ether or "n"-pentane, silicone oil, perfluoroheptanes,…

  1. Conservative and dissipative force field for simulation of coarse-grained alkane molecules: a bottom-up approach.

    PubMed

    Trément, Sébastien; Schnell, Benoît; Petitjean, Laurent; Couty, Marc; Rousseau, Bernard

    2014-04-01

    We apply operational procedures available in the literature to the construction of coarse-grained conservative and friction forces for use in dissipative particle dynamics (DPD) simulations. The full procedure rely on a bottom-up approach: large molecular dynamics trajectories of n-pentane and n-decane modeled with an anisotropic united atom model serve as input for the force field generation. As a consequence, the coarse-grained model is expected to reproduce at least semi-quantitatively structural and dynamical properties of the underlying atomistic model. Two different coarse-graining levels are studied, corresponding to five and ten carbon atoms per DPD bead. The influence of the coarse-graining level on the generated force fields contributions, namely, the conservative and the friction part, is discussed. It is shown that the coarse-grained model of n-pentane correctly reproduces self-diffusion and viscosity coefficients of real n-pentane, while the fully coarse-grained model for n-decane at ambient temperature over-predicts diffusion by a factor of 2. However, when the n-pentane coarse-grained model is used as a building block for larger molecule (e.g., n-decane as a two blobs model), a much better agreement with experimental data is obtained, suggesting that the force field constructed is transferable to large macro-molecular systems. PMID:24712786

  2. Method for removing sulfur compounds from C/sub 6/ and lower alkanes

    SciTech Connect

    Keyworth, D.A.

    1989-03-28

    A process is described for recovering a low sulfur content hydrocarbon fraction having a boiling point of n-hexane or less from a hydrocarbon stream containing hydrocarbons boiling at or below the boiling point of hexane and organic sulfur compounds comprising monosulfides boiling at or below the boiling point of n-hexane. It consists of contacting the hydrocarbon stream with a dilute aqueous solution of sodium hypochlorite for a time sufficient to convert a selected amount of monosulfide compounds present to compounds having boiling points above the boiling point of n-hexane, separating an aqueous phase and a hydrocarbon phase and fractionally distilling the hydrocarbon phase to recover a hydrocarbon fraction having a boiling point of n-hexane or less, and having a reduced amount of the organic sulfur compounds.

  3. 21 CFR 177.1610 - Polyethylene, chlorinated.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... chlorination of polyethylene conforming to the density, maximum n-hexane extractable fraction, and maximum... polyethylene is limited to use only as a modifier admixed at levels not exceeding 15 weight percent in...

  4. 21 CFR 177.1610 - Polyethylene, chlorinated.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... produced by the direct chlorination of polyethylene conforming to the density, maximum n-hexane extractable... percent in plastic articles prepared from polyvinyl chloride and/or from vinyl chloride...

  5. 40 CFR Table 2 to Subpart Ggg of... - Partially Soluble HAP

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...,4-) Chlorobenzene Trichloroethylene Chloroethane (ethyl chloride) Trimethylpentane Vinyl acetate Xylene (p) Vinyl chloride N-hexane Xylene (m) Xylene (o) ...-Tetrachloroethane Chloromethane 1,1,2-Trichloroethane Chloroprene 1,1-Dichloroethylene (vinylidene chloride)...

  6. 40 CFR 260.11 - References.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 1 CFR part 51. These materials are incorporated as they exist on the date of approval and a notice... Silica Gel Treated n-Hexane Extractable Material (SGT-HEM; Non-polar Material) by Extraction...

  7. 40 CFR Table 4 to Subpart Ppp of... - Known Organic HAP From Polyether Polyol Products

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Polyol Products Organic HAP/chemical name 1,3 Butadiene (106990) Epichlorohydrin (106898) Ethylene Oxide (75218) n-Hexane (110543) Methanol (67561) Propylene Oxide (75569) Toluene (108883) CAS No. = Chemical Abstracts Service Registry Number....

  8. 40 CFR Table 4 to Subpart Ppp of... - Known Organic HAP From Polyether Polyol Products

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Products Organic HAP/chemical name 1,3 Butadiene (106990) Epichlorohydrin (106898) Ethylene Oxide (75218) n-Hexane (110543) Methanol (67561) Propylene Oxide (75569) Toluene (108883) CAS No. = Chemical...

  9. Numerical investigation of spontaneous flame propagation under Reactivity Controlled Compression Ignition (RCCI) conditions

    NASA Astrophysics Data System (ADS)

    Bhagatwala, Ankit; Sankaran, Ramanan; Kokjohn, Sage; Chen, Jacqueline

    2014-11-01

    Results from one and two-dimensional direct numerical simulations under dual-fuel Reactivity Controlled Compression Ignition (RCCI) conditions will be presented. These simulations employ an improved model of compression heating through mass source/sink terms developed in a previous work, which incorporates feedback from the flow to follow a predetermined experimental pressure trace. One-dimensional simulations explored the effect of temperature and fuel concentration gradients on the combustion mode. Two-dimensional simulations explored parametric variation in temperature stratification, pressure profiles and n-heptane concentration. Statistics derived from analysis of local diffusion/reaction balances were used to elucidate combustion characteristics for the different cases. Both deflagration and spontaneous ignition modes were observed to co-exist. Higher n-heptane concentration and higher level of thermal stratification resulted in a greater degree of flame propagation, whereas lower n-heptane concentration (higher fraction of iso-octane) and higher pressure resulted in more prevalent autoignition. Starting with a uniform initial temperature and a stratified n-heptane concentration also resulted in a large fraction of combustion occurring through flame propagation.

  10. 21 CFR 177.1040 - Acrylonitrile/styrene copoly-mer.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... deionized water or reagent grade n-heptane at reflux temperature for 2 h.1 Minimum 10 pct solution viscosity... viscosity, titled: “Determination of Residual Acrylonitrile and Styrene Monomers-Gas Chromatographic... Copolymers,” and “Analytical Method for 10% Solution Viscosity of Tyril,” which are incorproated by...