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1

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

NASA Technical Reports Server (NTRS)

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.

Meisch, A. J.

1972-01-01

2

The thermal conductivity of n -hexane, n -heptane, and n -decane by the transient hot-wire method  

Microsoft Academic Search

New absolute measurements of the thermal conductivity of liquid n-hexane, n-heptane, and n-decane are reported. The measurements have been carried out in the temperature range 300–370 K at atmospheric pressure in a transient hotwire instrument. The accuracy of the measurements is estimated to be ±0.5%. The density dependence of the thermal conductivity of n-hexane and n-heptane is found to be

M. J. Assael; E. Charitidou; C. A. Nieto de Castro; W. A. Wakeham

1987-01-01

3

Thermal conductivity of n-hexane, n-heptane, and n-decane by the transient hot-wire method  

SciTech Connect

New absolute measurements of the thermal conductivity of liquid n-hexane, n-heptane, and n-decane are reported. The measurements have been carried out in the temperature range 300-370 K at atmospheric pressure in a transient hot-wire instrument. The accuracy of the measurements is estimated to be +/- 0.5%. The density dependence of the thermal conductivity of n-hexane and n-heptane is found to be well described by a universal equation for the hydrocarbons based on a rough hard-sphere model. The measurements of the three hydrocarbons studied are also employed to generate more accurate effective core volumes, which are the only parameters characteristic of the fluid required for the application of the proposed universal scheme.

Assael, M.J.; Charitidou, E.; Nieto de Castro, C.A.; Wakeham, W.A.

1987-11-01

4

Determination of the adsorption heat of n-hexane and n-heptane on zeolites beta, L, 5A, 13X, Y and ZSM-5 by means of quasi-equilibrated temperature-programmed desorption and adsorption (QE-TPDA)  

Microsoft Academic Search

Measurements of temperature-programmed desorption and adsorption of n-hexane and n-heptane under quasi-equilibrium conditions (QE-TPDA) were performed for several zeolites in TPD apparatus equipped with a TCD detector. One-step adsorption profiles for zeolites X and Y and two-step adsorption profiles for beta, L, 5A and ZSM-5 were observed. Approximate adsorption isobars calculated from the QE-TPDA profiles did not depend on the

Wac?aw Makowski; ?ukasz Ogorza?ek

2007-01-01

5

Thermodynamics of acrylic esters containing binary liquid mixtures. I. Excess volumes and isentropic compressibilities of alkyl methacrylates + n-hexane, + n-heptane, + carbon tetrachloride, + chlorobenzene, and o-dichlorobenzene at 303.15 K  

NASA Astrophysics Data System (ADS)

Excess volumes and isentropic compressibilities of 15 binary liquid mixtures containing methyl methacrylate (MMA). ethyl methacrylate (EMA), and butyl methacrylate (BM) and n-Hexane, n-heptane, carbon tetrachloride chlorobenzene and o-dichlorobenzene are derived from the measured densities and speeds of sound at 303.15 K. The dependence of the excess volumes and the isentropic compressibilities both on the alkyl chain length and on the nature of the solvent shots the dominance of dispersing interactions in the mixtures of aliphatic hydrocarbons and specific interactions im the chlorinated solvent mixtures. The speeds of sound of binary mixtures of MMA were found to be reasonably predicted by free length and collision factor theories. An attempt is also made to estimate the individual contributions of interactional. free volume and P * effects to the overall excess volumes of binary mixtures containing MMA. The results indicate that the three factors are equally responsible for the observed values.

Sastry, N. V.; Dave, P. N.

1996-11-01

6

Vapour pressures of n-pentane determined by comparative ebulliometry  

Microsoft Academic Search

The vapour pressures of n-pentane have been measured using comparative ebulliometry with water as the reference substance. The measurements cover the temperature and pressure ranges 309 K and 102 kPa to 456 K and 2728 kPa. When combined with selected literature results, the range was extended downwards to a temperature and pressure of 268.8 K and 19.9 kPa and the

Michael B. Ewing; Jesus C. Sanchez Ochoa

2006-01-01

7

Excess enthalpies for the ternary mixtures phenol-1-hexanol- n-heptane and phenol-cyclohexanol- n-heptane, and their constituent binaries at 318.15 K  

Microsoft Academic Search

Excess molar enthalpies HE as a function of composition for the two ternary systems, phenol-1-hexanol-n-heptane and phenol-cyclohexanol-n-heptane, and five constituent binaries have been measured with a Calvet-type microcalorimeter at 318.15 K. All the excess enthalpies of binary systems containing n-heptane are positive, including those for a partially miscible system, phenol-n-heptane. The HE values of phenol-alcohol systems are negative. The results

H. Kirss; M. Kuus; E. Siimer; L. Kudryavtseva

1995-01-01

8

Effect of methanol on the biofiltration of n-hexane.  

PubMed

This study investigated the removal of recalcitrant compounds in the presence of a hydrophilic compound. n-Hexane is used as a model compound to represent hydrophobic compounds. Methanol has been introduced in mixture with n-hexane in order to increase the bioavailability of n-hexane in trickle-bed-air-biofilters (TBABs). The mixing ratios investigated were: 70% methanol:30% n-hexane, and 80% methanol:20% n-hexane by volume. n-Hexane loading rates (LRs) ranged from 0.9 to 13.2 g m(-3) h(-1). Methanol LRs varied from 4.6 to 64.5 g m(-3) h(-1) and from 2.3 to 45.2 g m(-3) h(-1) depending upon the mixing ratio used. Biofilter performance, effect of mixing ratios of methanol to n-hexane, removal profile along biofilter depth, COD/nitrogen consumption and CO(2) production were studied under continuous loading operation conditions. Results have shown that the degradation of n-hexane is significantly enhanced by the presence of methanol for n-hexane LRs less than 13.2 g m(-3) h(-1). For n-hexane LR greater than 13.2 g m(-3) h(-1), even though methanol had impacted n-hexane biodegradation, its removal efficiency was higher than our previous study for biodegradation of n-hexane alone, in presence of surfactant, or in presence of benzene. On the other hand, the degradation of methanol was not impacted by the presence of n-hexane. PMID:22516522

Zehraoui, Abderrahman; Hassan, Ashraf Aly; Sorial, George A

2012-06-15

9

Extinction and autoignition of n-heptane in counterflow configuration  

Microsoft Academic Search

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

R. Seiser; H. Pitsch; K. Seshadri; W. J. Pitz; H. J. Gurran

2000-01-01

10

Aromatization of n-hexane by platinum-containing molecular sieves. 2. n-Hexane reactivity  

Microsoft Academic Search

Pt\\/KL, Pt\\/BaKL, Pt\\/KBaKL, Pt\\/NaY, Pt\\/CsNaY, Pt\\/NaFAU(C), Pt\\/hex, Pt\\/SSZ-24, Pt\\/silica, and Pt\\/carbon were tested as catalysts for the aromatization of n-hexane at 460-510 C and atmospheric total pressure in order to study the influence of Pt cluster size and support acidity\\/basicity, microstructure, and chemical composition on activity and selectivity. Analysis of the catalytic and NHâ temperature-programmed desorption results from Pt\\/KL, Pt\\/BaKL,

E. Mielczarski; Suk Bong Hong; M. E. Davis; R. J. Davis

1992-01-01

11

Dielectric constant measurements on n-heptane and 2-heptanone  

SciTech Connect

A liquid transfer station has been built and installed in a fume hood. The dielectric properties of n-heptane and 2-heptanone have been measured using the coaxial structure of the Model 100-1, S/N 1 as the liquid measurement cell. The low (10 kHz to 1 Mhz) frequency value of the relative dielectric constant {epsilon} r was measured with a HP 4275 Multifrequency LCR Meter. Also time domain reflection (TDR) and insertion time domain transmission (TDT) measurements were made using a HP 54120/54121A oscilloscope. The value of the quasi-static relative dielectric constant for n-heptane was found to be 1.923 while that for 2-heptanone was 11.735.

Nahman, N.S. [Nahman (Norris S.), Boulder, CO (United States)

1994-01-12

12

A Comprehensive Modeling Study of n-Heptane Oxidation  

Microsoft Academic Search

A detailed chemical kinetic mechanism has been developed and used to study the oxidation of n-heptane in flow reactors, shock tubes, and rapid compression machines. Over the series of experiments numerically investigated, the initial pressure ranged from 1–42 atm, the temperature from 550–1700 K, the equivalence ratio from 0.3–1.5, and nitrogen-argon dilution from 70–99%. The combination of ignition delay time

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

1998-01-01

13

n-Hexane polyneuropathy in a ball-manufacturing factory  

SciTech Connect

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.

Huang, C.C.; Shih, T.S.; Cheng, S.Y.; Chen, S.S.; Tchen, P.H. (Chang Gung Medical College, Taipei (Taiwan))

1991-02-01

14

A kinetic modeling study of n-pentane oxidation in a well-stirred reactor  

Microsoft Academic Search

Oxidation of n-pentane in a well-stirred reactor is examined, using a numerical model and a detailed chemical kinetic reaction mechanism, including 53 chemical species and 326 elementary reactions. Temperatures studied range from 1068K to 1253K, and the pressure is atmospheric. The major reaction paths consuming n-pentane are H-atom abstraction by OH radicals, followed in importance by H-atom abstraction by H

Charles K. Westbrook; William J. Pitz; Mark M. Thornton; Philip C. Malte

1988-01-01

15

n-Hexane metabolism in occupationally exposed workers.  

PubMed Central

Lung uptake and excretion of n-hexane were studied in ten workers in a shoe factory. Simultaneous samples of inhaled and alveolar air were collected with the aid of a Rhan-Otis valve, personal samplers, and charcoal tubes. Alveolar excretion was monitored during a six hour postexposure period. Uptake was calculated from lung ventilation, the retention coefficient, and environmental concentrations. The amount of exhaled n-hexane was calculated from the decay curve. According to the experimental data, alveolar retention was about 25% of the inhaled n-hexane, corresponding to a lung uptake of about 17%. The postexposure alveolar excretion was about 10% of the total uptake. The main metabolites of n-hexane were identified and measured by capillary GC/MS in spot urine samples collected before, at the end, and 15 hours after the same working shift. Urinary concentrations were low, though related to n-hexane in the air. 2,5-Hexanedione in the end of shift samples gave the best estimate of overall exposure. About 3 mg/g creatinine of 2,5-hexanedione would correspond to about 50 ppm of n-hexane in the air (mean daily exposure).

Mutti, A; Falzoi, M; Lucertini, S; Arfini, G; Zignani, M; Lombardi, S; Franchini, I

1984-01-01

16

Extinction and Autoignition of n-Heptane in Counterflow Configuration  

SciTech Connect

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.

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

2000-01-12

17

The Burning of Large N-Heptane Droplets in Microgravity  

NASA Technical Reports Server (NTRS)

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.

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

2000-01-01

18

Rich n-heptane and diesel combustion in porous media  

SciTech Connect

Rich n-heptane and diesel flames in two-layer porous media are experimentally investigated in the context of syngas production. The stable operating points of n-heptane reforming have been determined and the mole fractions of H{sub 2}, CO, CO{sub 2} and light hydrocarbons have been measured in the exhaust gas at an equivalence ratio of 2 for different thermal input values. The reformer performance has been assessed also from the point of view of the heat losses and the mixture homogeneity. The pre-vapouriser produces an approximately uniform vapour-air mixture upstream of the flame front. The range of flow rates for stable flames decreased with increasing equivalence ratio. Heat losses were about 10% of the thermal input at high firing rates. A 77.2% of the equilibrium H{sub 2} was achieved at a flame speed of 0.82 m/s. The same reactor with a different porous matrix for the reforming stage demonstrates diesel reforming to syngas with a conversion efficiency of 77.3% for a flame speed of 0.65 m/s. (author)

Pastore, A.; Mastorakos, E. [Department of Engineering, University of Cambridge, Cambridge CB2 1PZ (United Kingdom)

2010-04-15

19

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

ERIC Educational Resources Information Center

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…

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

2005-01-01

20

A comprehensive modeling study of n-heptane oxidation  

SciTech Connect

A detailed chemical kinetic mechanism has been developed and used to study the oxidation of n-heptane in flow reactors, shock tubes, and rapid compression machines. Over the series of experiments numerically investigated, the initial pressure ranged from 1--42 atm, the temperature from 550--1,700 K, the equivalence ratio from 0.3--1.5, and nitrogen-argon dilution from 70--99%. The combination of ignition delay time and species composition data provide for a stringent test of the chemical kinetic mechanism. The reactions are classed into various types, and the reaction rate constants are given together with an explanation of how the rate constants were obtained. Experimental results from the literature of ignition behind reflected shock waves and in a rapid compression machine were used to develop and validate the reaction mechanism at both low and high temperatures. Additionally, species composition data from a variable pressure flow reactor and a jet-stirred reactor were used to help complement and refine the low-temperature portions of the reaction mechanism. A sensitivity analysis was performed for each of the combustion environments. This analysis showed that the low-temperature chemistry is very sensitive to the formation of stable olefin species from hydroperoxy-alkyl radicals and to the chain-branching steps involving ketohydroperoxide molecules. 89 refs.

Curran, H.J.; Gaffuri, P.; Pitz, W.J.; Westbrook, C.K. [Lawrence Livermore National Lab., CA (United States)] [Lawrence Livermore National Lab., CA (United States)

1998-07-01

21

Transition region ignition characteristics of n-heptane fuel sprays  

NASA Technical Reports Server (NTRS)

Ignition studies were perferred on monodisperse n-heptane sprays at atmospheric pressure over a range of equivalence ratios and droplet diameters. A capacitive discharge spark ignition system was used as the ignition source, providing independent control of spark energy and duration. Preliminary measurements were made to optimize spark duration and spark gap, optimum conditions being those at which the maximum frequency or probability of ignition was observed. The effect of spark duration on ignition frequency for several spark energies was determined for equivalence ratios of 0.5 and 1.0 and initial droplet diameters of 28 and 68 microns. Spark duration had little effect on ignition frequency over the entire 15 to 170 mu s range examined. Spark durations of 70 to 80 mu s were used for all subsequent work. The spark gap was optimized at equivalence ratios of 0.6, 0.8 and 1.0 and initial droplet diameters of 30, 40, 50, 60 and 70 microns by varying the electrode spacing from 0.5 to 5.0 mm while maintaining a constant spark energy. The optimum gap was determined to be 3.0 mm for nearly all conditions.

Danis, A. M.; Cernansky, N. P.; Namer, I.

1985-01-01

22

Methyl butanoate inhibition of n-heptane diffusion flames through an evaluation of transport and chemical kinetics  

Microsoft Academic Search

The extinction limits of methyl butanoate, n-heptane, and methyl butanoate\\/n-heptane diffusion flames have been measured as a function of fuel mole fraction with nitrogen dilution in counterflow with air. On a mole fraction basis, methyl butanoate diffusion flames are observed to have a much lower extinction strain rate than n-heptane diffusion flames and the extinction strain rate of n-heptane\\/methyl butanoate

Stephen Dooley; Mruthunjaya Uddi; Sang Hee Won; Frederick L. Dryer; Yiguang Ju

23

Photophysical anomalies of acridine in n-hexane  

SciTech Connect

The picosecond risetime of the 430 nm T/sub n/reverse arrowT/sub 1/ transient absorption and the T/sub 1/ formation quantum yield for acridine in n-hexane are temperature independent within experimental error between -51 and 25/sup 0/C, in sharp contrast to the large temperature dependence of the fluorescing state of acridine in n-hexane is not a kinetic precursor to T/sub 1/. The absence of marked tempertaure dependence in the T/sub 1/ formation yield presents and exception to the general observation that fluorescence and T/sub 1/ yields both decrease with increasing temperature in N-heterocycles and aromatic carbonyls with closely spaced lowest--energy n, ..pi..( and ..pi.., ..pi..( singlet states. (AIP)

Struve, W.S.; Hedstrom, J.H.; Morgante, C.G.; Jameson, A.K.; Lim, E.C.

1983-06-01

24

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

NASA Astrophysics Data System (ADS)

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.

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

1995-03-01

25

Adsorption of n-pentane on mesoporous silica and adsorbent deformation.  

PubMed

Development of quantitative theory of adsorption-induced deformation is important, e.g., for enhanced coalbed methane recovery by CO2 injection. It is also promising for the interpretation of experimental measurements of elastic properties of porous solids. We study deformation of mesoporous silica by n-pentane adsorption. The shape of experimental strain isotherms for this system differs from the shape predicted by thermodynamic theory of adsorption-induced deformation. We show that this difference can be attributed to the difference of disjoining pressure isotherm, responsible for the solid-fluid interactions. We suggest the disjoining pressure isotherm suitable for n-pentane adsorption on silica and derive the parameters for this isotherm from experimental data of n-pentane adsorption on nonporous silica. We use this isotherm in the formalism of macroscopic theory of adsorption-induced deformation of mesoporous materials, thus extending this theory for the case of weak solid-fluid interactions. We employ the extended theory to calculate solvation pressure and strain isotherms for SBA-15 and MCM-41 silica and compare it with experimental data obtained from small-angle X-ray scattering. Theoretical predictions for MCM-41 are in good agreement with the experiment, but for SBA-15 they are only qualitative. This deviation suggests that the elastic modulus of SBA-15 may change during pore filling. PMID:23758155

Gor, Gennady Yu; Paris, Oskar; Prass, Johannes; Russo, Patrícia A; Ribeiro Carrott, M Manuela L; Neimark, Alexander V

2013-07-01

26

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

PubMed

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

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

2012-12-27

27

Catalytic cracking of n-hexane over MoO 2  

Microsoft Academic Search

Catalytic cracking reactions of n-hexane over molybdenum oxide (MoO2) grown on a polycrystalline molybdenum foil (?1cm2) were studied in the temperature range 830–913K at a low conversion (<2%). The n-hexane pressure was 7.3Torr. The reactions were carried out in a batch reactor and no hydrogen or water vapor (steam) was used. The cracking products of n-hexane were mostly alkenes—ethylene (29mol%),

Jae Hee Song; Peilin Chen; Seong Han Kim; G. A. Somorjai; Robert J. Gartside; Frits M. Dautzenberg

2002-01-01

28

[Effect of Cordyceps militaris on the damage of rats induced by n-hexane].  

PubMed

Acutely inhaling n-hexane model was adopted to study the effect of Cordyceps militaris and the damage induced by n-hexane. The results showed that Cordyceps militaris was effective on the resisting lipid peroxidation. The results also showed that acutely inhaling n-hexane could lead to or enhance the damage reaction of oxygen free radicals, which could lead to injure of lipid peroxidation. That may be one of the mechanism of n-hexane toxicity effect on living things. PMID:11402725

Shen, Q; Chen, S

2001-02-01

29

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

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

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

2013-04-24

30

Distribution of neutral organic compounds between n-heptane and methanol or N,N-dimethylformamide.  

PubMed

Partition coefficients for a number of varied compounds were determined for the n-heptane-methanol and n-heptane-DMF partition systems and used to derive a general model for the distribution of neutral compounds in the biphasic systems. The partition coefficient, log Kp, was correlated through the solvation parameter model giving log Kp = -0.056 + 0.164E-0.620S-1.337A-0.957B + 0.507V for the n-heptane-methanol system with a multiple correlation coefficient of 0.986, standard error of the estimate 0.086, and Fischer statistic 413 for 65 compounds. For n-heptane-DMF, the model is log Kp = 0.065 + 0.030E-1.405S-2.039A-0.806B + 0.721V with a multiple correlation coefficient of 0.991, standard error of the estimate 0.080, and Fischer statistic 560 for 59 compounds. In the models the solute descriptors are excess molar refraction E, dipolarity/polarizability S, overall hydrogen bond acidity, and basicity A and B, respectively, and McGowan's characteristic volume V. Either model is expected to be able to estimate further values of the partition coefficient to about 0.08 log units and is applicable to a wide range of compounds. Applications include the choice of partitioning systems for sample clean-up, countercurrent chromatography, and estimation of solute descriptors for water insoluble or unstable compounds. PMID:17069245

Ahmed, Hamid; Poole, Colin F

2006-09-01

31

Urinary excretion of the metabolites of n-hexane and its isomers during occupational exposure.  

PubMed Central

Environmental exposure to commercial hexane (n-hexane, 2-methylpentane, and 3-methylpentane) was tested in several work places in five shoe factories by taking three grap-air samples during the afternoon shift. Individual exposure ranges were 32-500 mg/m3 for n-hexane, 11-250 mg/m3 for 2-methylpentane, and 10-204 mg/m3 for 3-methylpentane. The metabolites of commercial hexane in the urine of 41 workers were measured at the end of the work shift. 2-Hexanol, 2,5-hexanedione, 2,5-dimethylfuran, and gamma-valerolactone were found as n-hexane metabolites and 2-methyl-2-pentanol and 3-methyl-2-pentanol as 2-methylpentane and 3-methylpentane metabolites. The presence of metabolites in the urine was correlated with occupational exposure to solvents. n-Hexane exposure was correlated more positively with 2-hexanol and 2,5-hexanedione than with 2,5-dimethylfuran and gamma-valerolactone. A good correlation was also found between total n-hexane metabolites and n-hexane exposure. 2-Methyl-2-pentanol and 3-methyl-2-pentanol were highly correlated with 2-methylpentane and 3-methylpentane exposure. The results suggest that the urinary excretion of hexane metabolites may be used for monitoring occupational exposure to n-hexane and its isomers.

Perbellini, L; Brugnone, F; Faggionato, G

1981-01-01

32

Distribution of neutral organic compounds between n-heptane and fluorine-containing alcohols.  

PubMed

Partition coefficients for a number of varied compounds were determined for n-heptane-2,2,2-trifluoroethanol and n-heptane-1,1,1,3,3,3-hexafluoro-2-propanol and used to derive a general model for the distribution of neutral compounds in the biphasic systems. The partition coefficient, log K(p), was correlated through the solvation parameter model giving log K(p) = 0.160 + 1.190V + 0.856E - 1.538S - 1.325A - 2.965B for the n-heptane-2,2,2-trifluoroethanol system with a multiple correlation coefficient of 0.988, standard error of the estimate 0.136, and Fischer statistic 599 for 77 compounds. For n-heptane-1,1,1,3,3,3-hexafluoro-2-propanol, the model is log K(p) = -0.225 + 1.161V + 0.720E - 1.357S - 0.577A - 2.819B with a multiple correlation coefficient of 0.982, standard error of the estimate 0.148, and Fischer statistic 421 for 84 compounds. In the models, the solute descriptors are excess molar refraction E, dipolarity/polarizability S, overall hydrogen bond acidity and basicity A and B, respectively, and McGowan's characteristic volume V. Either model is expected to be able to estimate further values of the partition coefficient to about 0.13 log units and is applicable to a wide range of compounds. Applications include the choice of partitioning systems for sample clean-up and countercurrent chromatography and for estimating solute descriptors for water insoluble or reactive compounds. PMID:17266967

Qian, Jing; Poole, Colin F

2007-03-01

33

CHARACTERISTICS OF HOMOGENEOUS CHARGE COMPRESSION IGNITION (HCCI) COMBUSTION AND EMISSIONS OF n-HEPTANE  

Microsoft Academic Search

This paper reports the outcome from a systematic investigation carried out on HCCI (Homogeneous Charge Compression Ignition) combustion of a diesel type fuel. The n-heptane was chosen in this study to study the HCCI combustion characteristics of diesel engines with premixed charge by port fuel injection. Measurements were carried out in a single-cylinder, 4-stroke and variable compression ratio engine. Premixed

ZHIJUN PENG; HUA ZHAO; TOM MA; NICOS LADOMMATOS

2005-01-01

34

Ignition of n-heptane pool by heated stagnating oxidizing flow  

Microsoft Academic Search

The ignition temperature of a liquid pool of n-heptane by heated oxidizer in a stagnation flow was experimentally determined for system pressures of 0.61–3atm and pressure-weighted strain rates of 60–350s?1. The surface of the liquid pool was maintained at a fixed location through continuous replenishment. The state of ignition was brought about, and monitored, by gradually increasing the oxidizer temperature.

Wei Liu; Delin Zhu; Ning Wu; Chung K. Law

2010-01-01

35

Potassium-containing calcium aluminate catalysts for pyrolysis of n-heptane  

Microsoft Academic Search

The effectiveness of potassium promoted calcium aluminate to catalyze the steam pyrolysis of n-heptane has been investigated at 1023 K and atmospheric pressure. Various amounts of potassium were incorporated on calcium aluminate (12CaO?7Al2O3) by three different methods. Compared to thermal pyrolysis, addition of the calcium aluminate catalyst (either promoted or unpromoted) significantly increased the conversion as well as the yields

V. Anil Kumar; K. K. Pant; D. Kunzru

1997-01-01

36

Catalytic pyrolysis of n-heptane on unpromoted and potassium promoted calcium aluminates  

Microsoft Academic Search

Steam pyrolysis of n-heptane has been studied over different calcium aluminates and potassium impregnated calcium aluminate in a fixed bed reactor at atmospheric pressure. Various calcium aluminate catalysts were prepared by changing the precursor salt for obtaining CaO, which was subsequently used with Al2O3 for catalyst preparation. Depending on the source of CaO, the catalytic properties such as X-ray diffraction

K. K. Pant; D. Kunzru

2002-01-01

37

A SemiEmpirical Reaction Mechanism for n-Heptane Oxidation and Pyrolysis  

Microsoft Academic Search

A new semi-empirical mechanism for n-heptane oxidation and pyrolysis has been developed and validated against several independent data sets, including new flow reactor experiments. Previous semi-empirical chemical kinetic mechanisms assumed that a generic n-alkyl radical, formed by abstraction of an H-atom from the parent fuel, thermally decomposes into a fixed ratio of methyl and propene. While such an approach has

T. J. Held; A. J. Marchese; F. L. Dryer

1997-01-01

38

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

39

Model for the partition of neutral compounds between n-heptane and formamide.  

PubMed

Partition coefficients for 84 varied compounds were determined for n-heptane-formamide biphasic partition system and used to derive a model for the distribution of neutral compounds between the n-heptane-rich and formamide-rich layers. The partition coefficients, log K(p), were correlated through the solvation parameter model giving log K(p)=0.083+0.559E-2.244S-3.250A-1.614B+2.387V with a multiple correlation coefficient of 0.996, standard error of the estimate 0.139, and Fisher statistic 1791. In the model, the solute descriptors are excess molar refraction, E, dipolarity/polarizability, S, overall hydrogen-bond acidity, A, overall hydrogen-bond basicity, B, and McGowan's characteristic volume, V. The model is expected to be able to estimate further values of the partition coefficient to about 0.13 log units for the same descriptor space covered by the calibration compounds (E=-0.26-2.29, S=0-1.93, A=0-1.25, B=0.02-1.58, and V=0.78-2.50). The n-heptane-formamide partition system is shown to have different selectivity to other totally organic biphasic systems and to be suitable for estimating descriptor values for compounds of low water solubility and/or stability. PMID:20187036

Karunasekara, Thushara; Poole, Colin F

2010-04-01

40

N-heptane decomposition in multi-needle to plate electrical discharge  

NASA Astrophysics Data System (ADS)

Plasma based technologies are becoming more and more important for destruction of volatile organic compounds in air streams. The most frequent electrical discharges tested for VOC decomposition are corona and dielectric barrier discharge. We proposed [1] multi-hollow needles to plate atmospheric pressure discharge enhanced by the flow of the mixture of air with VOC through the needles. In this case all reactive mixture will pass through the active zone of the discharge. The high-speed gas flow near the exit of the needle will also efficiently cool the electrodes. Hence the higher values of the discharge current can be obtained without the danger of the discharge transition to the spark. The chemical reactions leading to the VOC decomposition can therefore be enhanced [2]. We performed an experimental study of the n-heptane decomposition efficiency on its concentration in air in the input of the discharge. We choose n-heptane, an important part of organic solvents and part of automotive fuels, as a representative of saturated alkanes. We found that with decreasing n-heptane concentration the decomposition efficiency increases. Acknowledgement: This work was supported by the research program No: J04/98:212300016 "Pollution control and monitoring of the Environment" of the Czech Technical University in Prague. References [1] S. Pekárek, V. Køíha, M. Pospíil - J. Physics D, Appl. Physics, 34, 117 (2001). [2] O. Goosens, T. Callebaut, Y. Akishev, C. Leys - IEEE Trans. Plasma Sc. 30, 176 (2002).

Pekarek, Stanislav; Pospisil, Milan

2003-10-01

41

Vapor–liquid equilibria for the system 1-propanol+ n-hexane near the critical region  

Microsoft Academic Search

Vapor–liquid equilibria and critical point data for the system 1-propanol+n-hexane at 483.15, 493.15, 503.15 and 513.15K are reported. The critical pressures determined from the critical opalescence of the mixture were compared with published data for the system 2-propanol+n-hexane. Phase behavior measurements were made in a modified circulating type apparatus with a view cell. These mixtures are highly nonideal because of

Byung Chul Oh; Youngdae Kim; Hun Yong Shin; Hwayong Kim

2004-01-01

42

Identification of intermediates in an n-heptane\\/oxygen\\/argon low-pressure premixed laminar flame using synchrotron radiation  

Microsoft Academic Search

This study was performed with the use of tunable vacuum ultraviolet (VUV) lasers for molecular beam sampling mass spectrometry (MBMS) to detect the intermediates of a premixed n-heptane\\/oxygen\\/argon laminar low-pressure flame. In this experiment, 24 intermediate species were identified and quantified by the photoionization mass and efficiency spectra at a stoichiometric mixture of n-heptane\\/oxygen highly diluted by argon gas. The

Chunde Yao; Chuanhui Cheng; Shiyu Liu; Zhenyu Tian; Jing Wang

2009-01-01

43

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

Microsoft Academic Search

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

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

2004-01-01

44

What can we learn about dispersion from the conformer surface of n-pentane?  

PubMed

In earlier work [Gruzman, D. ; Karton, A.; Martin, J. M. L. J. Phys. Chem. A 2009, 113, 11974], we showed that conformer energies in alkanes (and other systems) are highly dispersion-driven and that uncorrected DFT functionals fail badly at reproducing them, while simple empirical dispersion corrections tend to overcorrect. To gain greater insight into the nature of the phenomenon, we have mapped the torsional surface of n-pentane to 10-degree resolution at the CCSD(T)-F12 level near the basis set limit. The data obtained have been decomposed by order of perturbation theory, excitation level, and same-spin vs opposite-spin character. A large number of approximate electronic structure methods have been considered, as well as several empirical dispersion corrections. Our chief conclusions are as follows: (a) the effect of dispersion is dominated by same-spin correlation (or triplet-pair correlation, from a different perspective); (b) singlet-pair correlation is important for the surface, but qualitatively very dissimilar to the dispersion component; (c) single and double excitations beyond third order are essentially unimportant for this surface; (d) connected triple excitations do play a role but are statistically very similar to the MP2 singlet-pair correlation; (e) the form of the damping function is crucial for good performance of empirical dispersion corrections; (f) at least in the lower-energy regions, SCS-MP2 and especially MP2.5 perform very well; (g) novel spin-component scaled double hybrid functionals such as DSD-PBEP86-D2 acquit themselves very well for this problem. PMID:23452230

Martin, Jan M L

2013-04-11

45

Treatment of benzene and n-hexane mixtures in trickle-bed air biofilters.  

PubMed

Trickle-bed air biofilters (TBABs) are suitable for treatment of hydrophilic volatile organic compounds, but they pose a challenge for hydrophobic compounds. Three laboratory-scale TBABs were used for the treatment of an airstream contaminated with different ratios of n-hexane and benzene mixtures. The ratios studied were 1:1, 2:1, and 1:3 n-hexane:benzene by volume. Each TBAB was operated at a pH of 4 and a temperature of 20 degrees C. The use of acidic-buffered nutrient solution was targeted for changing the microorganism consortium to fungi as the main biodegradation element. The experimental plan was designed to investigate the long-term performance of the TBABs with an emphasis on different mixture loading rates, removal efficiency with TBAB depth, volatile suspended solids, and carbon mass balance closure. n-Hexane loading rate was kept constant in the TBABs for comparison reasons and ranged from 4 to 22 g/(m3 x hr). Corresponding benzene loadings ranged from 4 to 43 g/(m3 x hr). Generally, benzene behavior in the TBAB was superior to that of n-hexane because of its higher solubility. n-Hexane showed improved performance in the 2:1 mixing ratio as compared with the other two ratios. PMID:21387937

Hassan, Ashraf Aly; Serial, George A

2011-02-01

46

Neurophysiological studies of n-hexane polyneuropathy in the sandal factory.  

PubMed

Among 93 cases of n-hexane polyneuropathy during a large outbreak in 1968 44 cases were studied by conventional electromyogram and measurement of peripheral nerve conduction velocities, both of which showed remarkable changes, especially in the lower rather than the upper extremities. Over a few years since 1968 most of the cases completely recovered, except for a few with mild sensory impairment, after providing for 100 ppm as the maximal allowable concentration of n-hexane and well equipped ventilation systems in individual houses. During the rescreening in 1981, before which there occurred only 2 patients, 21 cases with mild n-hexane polyneuropathy were clinically and neurophysiologically observed, revealing mostly the same features as in the previous outbreak in 1968. From these data it may be suggested that, in spite of less than 50 ppm of n-hexane concentration in a room, the sandal workers have suffered from neurotoxicity from this organic solvent and the appropriateness of the present regulation on n-hexane has to be reconsidered. PMID:6297875

Iida, M

1982-01-01

47

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

PubMed Central

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.

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

2013-01-01

48

An experimental study on the combined effects of n-hexane and toluene on the peripheral nerve of the rat.  

PubMed Central

An electrophysiological study was undertaken to determine whether toluene affected the neurotoxicity of n-hexane. Separate groups of eight rats were exposed to 1000 ppm n-hexane, 1000 ppm toulene, 1000 ppm n-hexane plus 1000 ppm toluene, of fresh air in an exposure chamber for 12 hours a day for 16 weeks. The body weight, MCV, DL, MNCVs were measured before exposure, after four, eight 12, and 16 weeks exposure; and four weeks after exposure was discontinued. Exposure to 1000 ppm n-hexane considerably impaired the function of the peripheral nerve, but exposure to a mixture of 1000 ppm n-hexane plus 1000 ppm toluene resulted in only slight impairment; 1000 ppm toluene had little effect. These results strongly suggest that toluene decreases the toxic effects of n-hexane on the peripheral nerve.

Takeuchi, Y; Ono, Y; Hisanaga, N

1981-01-01

49

Rotator Phases of n-Heptane under High Pressure: Raman Scattering and X-ray Diffraction Studies  

SciTech Connect

We performed high-pressure Raman scattering and angle-dispersive synchrotron X-ray diffraction measurements on n-heptane at room temperature. It has been found that n-heptane undergoes a liquid to rotator phase III (R{sub III}) transition at 1.2 GPa and then transforms into another rotator phase R{sub IV} at about 3 GPa. As the pressure reaches 7.5 GPa, a transition from an orientationally disordered R{sub IV} phase to an ordered crystalline state starts and is completed around 14.5 GPa. Our results clearly present the high-pressure phase transition sequence (liquid-R{sub III}-R{sub IV}-crystal) of n-heptane, similar to that of normal alkanes.

C Ma; Q Zhou; F Li; J Hao; J Shu; L Huang; F Huang; Q Cui

2011-12-31

50

Measurement of the surface tensions and the interfacial tensions of n-pentane-water and R 113-water systems  

NASA Astrophysics Data System (ADS)

The surface and the interfacial tensions of mutually immiscible liquid systems were experimentally studied. The measured systems are n-pentane-water and R 113-water, which are proposed as heat transfer fluids for a direct-contact heat exchanger to be used for geothermal and waste heat recovery plants. The experimental apparatus was constructed based on the principle of the pendant drop method. Measurements were performed in the temperature range from 20 to 150°C. Based on the correlation of the surface and the interfacial tensions, the temperature dependences of the spreading coefficient, the film pressure, and the work of adhesion in each system were calculated.

Matsubara, H.; Murase, M.; Mori, Y. H.; Nagashima, A.

1988-05-01

51

Comparison of lipase-catalysed esterification in supercritical carbon dioxide and in n-hexane  

Microsoft Academic Search

Summary Oleic acid esterification by ethanol has been performed by an immobilized lipase fromMucor miehei in supercritical carbon dioxide and in n-hexane as solvents. In both media, determination of apparent kinetic constants has been achieved and influence of water content has been shown to be different due to various rates of water solubilities. Stability of the lipase has been proved

A. Marty; W. Chulalaksananukul; J. S. Condoret; R. M. Willemot; G. Durand

1990-01-01

52

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

SciTech Connect

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.

Bochniak, D.J.; Subramaniam, B. [Univ. of Kansas, Lawrence, KS (United States). Dept. of Chemical and Petroleum Engineering] [Univ. of Kansas, Lawrence, KS (United States). Dept. of Chemical and Petroleum Engineering

1998-08-01

53

Antifungal activity of n-hexane extracts of Datura metel against Ascochyta rabiei  

Microsoft Academic Search

The antimycotic potential of Datura metel (syn. Datura alba Nees.) was investigated in vitro against Ascochyta rabiei, the cause of chickpea blight disease. The pathogen was exposed to various n-hexane concentrations (1, 2, 3 and 4% w\\/v) of shoot and root extracts of D. metel using poisoning food technique. All the employed concentrations of both root and shoot extracts significantly

Shazia Shafique; Sobiya Shafique

2008-01-01

54

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

NASA Technical Reports Server (NTRS)

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.

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

1992-01-01

55

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

SciTech Connect

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. 24 refs.

Choi, M.Y.; Dryer, F.L.; Card, J.M.; Williams, F.A.; Haggard, J.B.; Borowski, B.A. (Princeton University, NJ (United States) California, University, La Jolla (United States) NASA, Lewis Research Center, Cleveland, OH (United States))

1992-01-01

56

Characterization of n-Hexane sub-fraction of Bridelia micrantha (Berth) and its antimycobacterium activity  

PubMed Central

Background Tuberculosis, caused by Mycobacterium tuberculosis (MTB), is the most notified disease in the world. Development of resistance to first line drugs by MTB is a public health concern. As a result, there is the search for new and novel sources of antimycobacterial drugs for example from medicinal plants. In this study we determined the in vitro antimycobacterial activity of n-Hexane sub-fraction from Bridelia micrantha (Berth) against MTB H37Ra and a clinical isolate resistant to all five first-line antituberculosis drugs. Methods The antimycobacterial activity of the n-Hexane sub-fraction of ethyl acetate fractions from acetone extracts of B. micrantha barks was evaluated using the resazurin microplate assay against two MTB isolates. Bioassay-guided fractionation of the ethyl acetate fraction was performed using 100% n-Hexane and Chloroform/Methanol (99:1) as solvents in order of increasing polarity by column chromatography and Resazurin microtiter plate assay for susceptibility tests. Results The n-Hexane fraction showed 20% inhibition of MTB H37Ra and almost 35% inhibition of an MTB isolate resistant to all first-line drugs at 10 ?g/mL. GC/MS analysis of the fraction resulted in the identification of twenty-four constituents representing 60.5% of the fraction. Some of the 24 compounds detected included Benzene, 1.3-bis (3-phenoxyphenoxy (13.51%), 2-pinen-4-one (10.03%), N(b)-benzyl-14-(carboxymethyl) (6.35%) and the least detected compound was linalool (0.2%). Conclusions The results show that the n-Hexane fraction of B. micrantha has antimycobacterial activity.

2011-01-01

57

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...

58

A numerical study of supercritical forced convective heat transfer of n-heptane inside a horizontal miniature tube  

Microsoft Academic Search

Supercritical convective heat transfer of hydrocarbon propellants plays a key role in the regenerative cooling technology development in aerospace applications. In this paper, a numerical study of the supercritical forced convective heat transfer of a typical hydrocarbon fuel, n-heptane, has been conducted based on a complete set of conservation equations of mass, momentum, and energy with accurate evaluations of the

Yi-Xin Hua; Ya-Zhou Wang; Hua Meng

2010-01-01

59

Numerical simulations of the ignition of n-heptane droplets in the transition diameter range from heterogeneous to homogeneous ignition  

Microsoft Academic Search

Spontaneous ignition of single n-heptane droplets in a constant volume filled with air is numerically simulated with the spherical symmetry. The volume is closed against mass, species, and energy transfer. The numerical model is fully transient. It continues calculation even after the droplet has completely vaporized, and therefore can predict pre-vaporized ignition. Initial pressure and initial air temperature are fixed

Osamu Moriue; Masato Mikami; Naoya Kojima; Christian Eigenbrod

2005-01-01

60

Evidence for an Elongation/Reduction/C1-Elimination Pathway in the Biosynthesis of n-Heptane in Xylem of Jeffrey Pine.  

PubMed Central

The biosynthetic pathway to n-heptane was investigated by examining the effect of the [beta]-keto acyl-acyl carrier protein synthase inhibitor (2R,3S)-2,3-epoxy-4-oxo-7E,10E-dodecadienamide (cerulenin), a thiol reagent ([beta]-mercaptoethanol), and an aldehydetrapping reagent (hydroxylamine) on the biosynthesis of n-[14C]heptane and putative intermediates in xylem sections of Jeffrey pine (Pinus jeffreyi Grev.& Balf.) incubated with [14C]acetate. Cerulenin inhibited C18 fatty acid biosynthesis but had relatively little effect on radiolabel incorporation into C8 fatty acyl groups and n-heptane. [beta]-Mercaptoethanol inhibited n-heptane biosynthesis, with a corresponding accumulation of radiolabel into both octanal and 1-octanol, whereas hydroxylamine inhibited both n-heptane and 1-octanol biosynthesis, with radiolabel accumulation in octyl oximes. [14C]Octanal was converted to both n-heptane and 1-octanol when incubated with xylem sections, whereas [14C]1-octanol was converted to octanal and n-heptane in a hydroxylamine-sensitive reaction. These results suggest a pathway for the biosynthesis of n-heptane whereby acetate is polymerized via a typical fatty acid synthase reaction sequence to yield a C8 thioester, which subsequently undergoes a two-electron reduction to generate a free thiol and octanal, the latter of which alternately undergoes an additional, reversible reduction to form 1-octanol or loss of C1 to generate n-heptane.

Savage, T. J.; Hristova, M. K.; Croteau, R.

1996-01-01

61

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

NASA Technical Reports Server (NTRS)

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.

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

2005-01-01

62

Scaling function of critical binary mixtures: Nitrobenzene- n-hexane data revisited  

NASA Astrophysics Data System (ADS)

Ultrasonic attenuation spectra of the nitrobenzene- n-hexane mixture of critical composition have been analysed. Data between 50 kHz and 1 GHz from different sources have been included to show that at a given temperature the spectra, in addition to the critical contribution, reveal a non-critical relaxation term. Taking this additional term into account inconsistencies in the scaling function reported in the literature are avoided. In the final analysis the scaling function of the nitrobenzene- n-hexane system follows the predictions of the Bhattacharjee-Ferrell theory with critical amplitude and relaxation rate of concentration fluctuations in nice agreement with determinations from independent methods. The low-frequency attenuation data are briefly discussed with a view to a bulk viscosity approach which yields a slightly different proportionality constant in the linear regime of the scaling function than the Bhattacharjee-Ferrell theory. Evidence in favour of the latter is obtained.

Mirzaev, Sirojiddin Z.; Kaatze, Udo

2012-01-01

63

Fluorescence vesicles by self-assembly of oligo(biphenylene vinylene) bolaamphiphiles in n-hexane  

NASA Astrophysics Data System (ADS)

Self-assembly of an oligo(biphenylene vinylene); OBPV bolaamphiphile with two polar coils of significantly long poly(propylene oxide); PPO (n = 21) at each end generated a fluorescent vesicle in apolar n-hexane. The vesicle efficiently produced trans-stilbene-like OBPV excimer emissions, as evidenced by an intense, redshifted, structured fluorescence spectrum with a long decay time of 5.0 ± 0.1 ns. An OBPV chromophore bound at both sides via a polar coil-to-coil interaction in apolar n-hexane was conducive to OBPV excimer emission, as evident from analysis of the spectroscopic data obtained from OBPVs with different PPO coil lengths (n = 13, 21, 34).

Hwang, In-Wook; Kim, Yong-Rok

2013-09-01

64

Equilibrium and Fixed?Bed Adsorption of n?Hexane on Activated Carbon  

Microsoft Academic Search

Equilibrium and fixed?bed adsorption of n?hexane on pelletized activated carbon (SLG?2PS) was studied between 298.15°K and 318.15°K. Equilibrium data was obtained in a gravimetric method. Adsorption isotherms were predicted by various model equations. Based on a comprehensive comparison of various single component isotherm models, the Langmuir–Freundlich isotherm was found to provide the best fit overall for the adsorption of the

W. G. Shim; J. W. Lee; H. Moon

2003-01-01

65

Anti-inflammatory Active Compounds from the n-Hexane Extract of Euphorbia hirta  

Microsoft Academic Search

The n-hexane extract of the aerial parts of Euphorbia hirta L. (Euphorbiaceae) and its main triterpenes, ?-amyrin (1), 24-methy- lencycloartenol (2), and ?-sitosterol (3) were evaluated for anti- inflammatory effects in mice. Both the extract and the triterpenes exerted significant and dose-dependent anti-inflammatory activity in the TPA-induced ear model. Some dual and triplet combinations of the triterpenes were tested as

Mariano Martínez-Vázquez; Teresa O. Ramírez Apan; María Eugenia Lazcano; Robert Bye; D. F. México

1999-01-01

66

Studies on the equilibrated thermodesorption of n -hexane from ZSM-5 zeolite  

Microsoft Academic Search

Equilibrated thermodesorption (TPED) and quasi-equilibrated temperature programmed desorption and adsorption (QE-TPDA) were\\u000a employed as methods for studying the influence of different extraframework cations (Na+, K+, Li+, Cu2+, Zn2+, or Mg2+) on adsorption of n-hexane on ZSM-5 zeolite with high Al content (Si\\/Al = 15). Considerable influence of the cations on both\\u000a initial adsorption in the micropores and ordering of the adsorbed molecules,

Dorota MajdaWacaw Makowski; Wac?aw Makowski

2010-01-01

67

Aromatization of n-hexane by platinum-containing molecular sieves. 3. Reactivity of platinum aluminophosphates  

Microsoft Academic Search

In accompanying reports, the authors describe a vapor phase impregnation procedure for loading highly dispersed platinum into the intracrystalline voids of molecular sieves and the catalytic behavior of platinum-containing aluminosilicate and silicate materials for the aromatization of n-hexane. Here they report on the reactivity of platinum-containing aluminophosphate molecular sieves and compare the results to those obtained from platinum-impregnated zeolites. All

E. Mielczarski; Suk Bong Hong; M. E. Davis

1992-01-01

68

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

SciTech Connect

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.

Nielsen, B.B.; Svrcek, W.Y.; Mehrotra, A.K. (Univ. of Calgary, Alberta (Canada). Dept. of Chemical and Petroleum Engineering)

1994-05-01

69

Pervaporation separation of n-heptane/thiophene mixtures by polyethylene glycol membranes: Modeling and experimental.  

PubMed

Gasoline desulfurization by membrane processes is a newly emerged technology, which has provided an efficient new approach for sulfur removal and gained increasing attention of the membrane and petrochemical field. A deep understanding of the solution/diffusion of gasoline molecules on/in the membrane can provide helpful information in improving or optimizing membrane performance. In this study, a desulfurization mechanism of polyethylene glycol (PEG) membranes has been investigated by the study of sorption and diffusion behavior of typical sulfur and hydrocarbon species through PEG membranes. A solution-diffusion model based on UNIFAC and free volume theory has been established. Pervaporation (PV) and sorption experiments were conducted to compare with the model calculation results and to analyze the mass transport behavior. The dynamic sorption curves for pure components and the sorption experiments for binary mixtures showed that thiophene, which had a higher solubility coefficient than n-heptane, was the preferential sorption component, which is key in the separation of thiophene/hydrocarbon mixtures. In all cases, the model calculation results fit well the experimental data. The UNIFAC model was a sound way to predict the solubility of solvents in membranes. The established model can predict the removal of thiophene species from hydrocarbon compounds by PEG membranes effectively. PMID:19666173

Lin, Ligang; Zhang, Yuzhong; Kong, Ying

2009-11-01

70

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

SciTech Connect

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)

Maroteaux, F.; Noel, L. [University Pierre et Marie Curie, INRIA Rocquencourt, B.P. 105, 78153 Le Chesnay Cedex (France)

2006-07-15

71

Ignition characteristics of rich n-heptane fuel sprays in the transition region  

NASA Technical Reports Server (NTRS)

Ignition studies were performed on monodisperse n-heptane sprays at atmospheric pressure over a range of equivalence ratios and droplet diameters. A capacitive discharge spark ignition system was used as the ignition source, providing independent control of spark energy and duration. Preliminary measurements were made to optimize spark duration and spark gap, optimum conditions being those at which the maximum frequency or probability of ignition was observed. Using the optimum electrode spacing and spark duration, the frequency of ignition was determined as a function of spark energy for three overall equivalence ratios (0.6, 0.8, and 1.0) and for initial droplet diameters of 25, 40, 50, 60, and 70 microns. An LDA system was used to determine the actual equivalence ratio at the spark gap, which varied from 1.5 to 4.7. The spark energy at which the frequency of ignition was 90 percent was defined as the minimum ignition energy. These data indicated that the ignitability of the sprays was enhanced as the equivalence ratio was increased, but was diminished as the droplet size was increased. The increase in minimum ignition energy with increasing droplet size and fixed equivalence ratio was nearly linear over the range of parameters studied. However, the effect became smaller with increasing equivalence ratio.

Danis, A. M.; Cernansky, N. P.; Namer, I.

1985-01-01

72

Simulating adsorption of n-heptane in the Pt/Al2O3 model: influence of platinum.  

PubMed

The molecular modeling method refered to in the literature as Grand Canonical Monte Carlo was used to analyze the phenomenon of n-heptane adsorption on the Pt/gamma-Al(2)O(3) catalyst. In order to describe relevant interactions, use was made of the forcefield methods (UFF and CVFF). With the conditions adopted for the purpose of the study, Pt was found to exert an advantageous effect on the adsorption of n-heptane. The number of adsorbed molecules was related to the content of the noble metal, and the relation was directly proportional, when temperature and pressure were constant. The contribution of Pt was most distinct at 573 K and 100 kPa. PMID:15886033

Szyja, Bart?omiej; Szczygie?, Jerzy

2005-06-01

73

Numerical study of flame spread in an n -heptane droplet array in different ambient temperature and microgravity conditions  

Microsoft Academic Search

Flame spread in an n-heptane droplet array under conditions of microgravity, different ambient temperatures, and droplet spacing is studied numerically.\\u000a The dimensionless distance, fuel type, and ambient temperature are characteristic parameters that could change the flame spread\\u000a modes. Variations of the droplet spacing change the amount of the gas fuel on the centerline of droplets, and the flame can\\u000a either

S. Ranjbaran; S. Tabejamaat

2011-01-01

74

Light Absorption by Hydrocarbon Molecules at 3.392 mum of He-Ne Laser  

Microsoft Academic Search

The decadic molar extinction coefficients of various hydrocarbon molecules at the wavelength of 3.392 mum of the infrared He-Ne laser were measured at temperatures between 292 and 1100 K using the shock-tube technique. Methane, ethane, propane, n-pentane, n-hexane, n-heptane, n-octane, n-nonane, iso-octane, methanol, ethanol, butanol, acetone and benzene absorbed the laser light. No Doppler-or pressure-broadening of these molecules was observed

Takao Tsuboi; Katsumi Inomata; Yutaka Tsunoda; Akihito Isobe; Koh-ichi Nagaya

1985-01-01

75

Excess molar volumes and dynamic viscosities for binary mixtures of toluene + n-alkanes (C 5–C 10) at T = 298.15 K – Comparison with Prigogine–Flory–Patterson theory  

Microsoft Academic Search

Densities ?, dynamic viscosities ?, for binary mixtures of toluene with some n-alkanes, namely, n-pentane, n-hexane, n-heptane, n-octane, n-nonane, and n-decane have been measured over the complete composition range. Excess molar volumes VE, viscosity deviations ??, and excess Gibbs free energy of activation ?G?E, were calculated there from and were correlated by Redlich–Kister type function in terms of mole fractions.

Hossein Iloukhani; Mahdi Rezaei-Sameti; Jalal Basiri-Parsa

2006-01-01

76

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

NASA Technical Reports Server (NTRS)

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 using tabular information from the LLNL skeletal mechanism in conjunction with CHEMKIN II utilized as surrogate ideal functions replacing the necessary functional forms. The test reveals that the similarity concept is indeed justified and that the combustion temperature is well predicted, but that the ignition time is over-predicted, a fact traced to neglecting a detailed description of the processes leading to the heavies chemical decomposition. To palliate this deficiency, functional modeling is incorporated into this conceptual reduction in addition to the modeling the evolution of the global constituent molar density, the enthalpy evolution of the heavies, the contribution to the reaction rate of the unsteady lights from other light species and from the heavies, the molar density evolution of oxygen and water, and the mole fractions of the quasisteady light species. The model is compact in that there are only nine species-related progress variables. Results are presented showing the performance of the model for predicting the temperature and species evolution. The model reproduces the ignition time over a wide range of equivalence ratios, initial pressure, and initial temperature.

Harstad, Kenneth G.; Bellan, Josette

2011-01-01

77

Effect of surface-active additives on the temperature behavior of interfacial tension in water- n-hexane systems  

NASA Astrophysics Data System (ADS)

The temperature dependence of interface tension in a water- n-hexane system without additives and after addition of stearic acid was experimentally studied at four different concentrations. A method for determining the excess surface chemical potential from experimental data on the temperature dependence of interfacial or surface tension is proposed for a diluted solution of surface-active impurity. The excess surface chemical potential of stearic acid at the interface of a water- n-hexane binary mixture is determined.

Ataev, G. M.

2012-03-01

78

In Situ 13C MAS NMR Study of n-Hexane Conversion on Pt and Pd Supported on Basic Materials  

Microsoft Academic Search

n-Hexane conversion was studiedin situon Pt and Pd supported on aluminum-stabilized magnesium oxide and Pt on Zeoite KL catalysts (Pt\\/Mg(Al)O, Pd\\/Mg(Al)O and Pt\\/KL) by means of13C MAS NMR spectroscopy.n-Hexane 1-13C was used as a labelled reactant. Forty NMR lines corresponding to 14 different products were resolved and identified. The NMR line assignments were confirmed by adsorption of model compounds. The

Irina I. Ivanova; Anne Pasau-Claerbout; Michaèl Seirvert; Niels Blom; Eric G. Derouane

1996-01-01

79

Designed catalysts from Pt nanoparticles supported on macroporous oxides for selective isomerization of n-hexane.  

PubMed

Selective isomerization toward branched hydrocarbons is an important catalytic process in oil refining to obtain high-octane gasoline with minimal content of aromatic compounds. Colloidal Pt nanoparticles with controlled sizes of 1.7, 2.7, and 5.5 nm were deposited onto ordered macroporous oxides of SiO2, Al2O3, TiO2, Nb2O5, Ta2O5, and ZrO2 to investigate Pt size- and support-dependent catalytic selectivity in n-hexane isomerization. Among the macroporous oxides, Nb2O5 and Ta2O5 exhibited the highest product selectivity, yielding predominantly branched C6 isomers, including 2- or 3-methylpentane, as desired products of n-hexane isomerization (140 Torr n-hexane and 620 Torr H2 at 360 °C). In situ characterizations including X-ray diffraction and ambient-pressure X-ray photoelectron spectroscopy showed that the crystal structures of the oxides in Pt/oxide catalysts were not changed during the reaction and oxidation states of Nb2O5 were maintained under both H2 and O2 conditions. Fourier transform infrared spectra of pyridine adsorbed on the oxides showed that Lewis sites were the dominant acidic site of the oxides. Macroporous Nb2O5 and Ta2O5 were identified to play key roles in the selective isomerization by charge transfer at Pt-oxide interfaces. The selectivity was revealed to be Pt size-dependent, with improved isomer production as Pt sizes increased from 1.7 to 5.5 nm. When 5.5 nm Pt nanoparticles were supported on Nb2O5 or Ta2O5, the selectivity toward branched C6 isomers was further increased, reaching ca. 97% with a minimum content of benzene, due to the combined effects of the Pt size and the strong metal-support interaction. PMID:24773412

An, Kwangjin; Alayoglu, Selim; Musselwhite, Nathan; Na, Kyungsu; Somorjai, Gabor A

2014-05-14

80

Dynamic biological exposure indexes for n-hexane and 2,5-hexanedione, suggested by a physiologically based pharmacokinetic model  

SciTech Connect

Biological exposure index (BEI) of n-hexane was studied for accuracy using a physiologically based pharmacokinetic (PB-PK) model. The kinetics of n-hexane in alveolar air, blood, urine, and other tissues were simulated for different values of alveolar ventilations and also for constant and variable exposures. The kinetics of 2,5-hexanedione, the toxic n-hexane metabolite, were also simulated. The ranges of n-hexane concentrations in biological media and the urinary concentrations of 2,5-hexanedione are discussed in connection with a mean n-hexane exposure of 180 mg/m3 (50 ppm) (threshold limit value (TLV) suggested by American Conference of Governmental Industrial Hygienists (ACGIH) for 1988-89). The experimental and field data as well as those predicted by simulation with the PB-PK model were comparable. The physiological-pharmacokinetic simulations are used to propose the dynamic BEIs of n-hexane and 2,5-hexanedione. The use of simulation with PB-PK models enables a better understanding of the limits, advantages, and issues associated with biological monitoring of exposures to industrial solvents.

Perbellini, L.; Mozzo, P.; Olivato, D.; Brugnone, F. (Univ. of Verona, Policlinico Borgo, Roma (Italy))

1990-07-01

81

Viscosities of nonelectrolyte liquid mixtures. II. Binary mixtures of n-hexane with alkanoates and bromoalkanoates  

NASA Astrophysics Data System (ADS)

Viscosity measurements are reported for mixtures of ethyl ethanoate, ethyl propionate, ethyl butyrate, ethyl-2-bromopropionate, ethyl-3-bromopropionate, ethyl-2-bromobutyrate, and ethyl-4-bromobutyrate with n-hexane at 303.15 K. The viscosity data have been correlated with equations of Grunberg and Nissan, of McAllister, and of Auslaender. Furthermore, excess Gibbs energies of activation ?G * E of viscous flow have been calculated with Eyring's theory of absolute reaction rates and values of ?G * E for the present binary mixtures have been explained in terms of the dipole-dipole interaction in alkanoates and the intramolecular Br...O interaction in bromoalkanoates.

Oswal, S. L.; Dave, J. P.

1992-11-01

82

Formation of volatile compounds and brown products in the model system n-hexanal-glycine.  

PubMed

During the boiling of a mixture of n-hexanal and glycine in aqueous medium, pH value 9, both soluble and insoluble brown colored pigments and volatile compounds were formed. The following volatile compounds were identified by gas chromatography and mass spectrometry; hexanone, decenone, undecenone, undecan-5-one, undecenedione, dodecenone, tridecanone, dodecanedione, tridecenone, dodecenedione, hexenyl hexanoate, caproic, valeric and butyric acids. The brown coloured pigments insoluble in water contained 0.57% of nitrogen. The presence of conjugated double-bonds, carbonyl and carboxyl groups was confirmed by spectral methods. The pigments were also separated by thin-layer chromatography on silica gel. PMID:1229723

Davídek, J; Jirou?ová, J

1975-11-12

83

1Butanol + hexylamine + n-heptane at temperature range (288.15–323.15 K): Experimental density data, excess molar volumes determination and modeling with cubic EOS  

Microsoft Academic Search

Densities ? of the ternary system 1-butanol+hexylamine+n-heptane and binaries: 1-butanol+hexylamine and hexylamine+n-heptane within the temperature range (288.15–323.15K) and atmospheric pressure are reported. Excess molar volumes VE were calculated from the density data and fitted by the Redlich–Kister and Nagata and Tamura equations. The results are analyzed in terms of the molecular interactions between the components of mixtures.Several empirical relationships (Radojkovic,

Ivona R. Radovi?; Mirjana Lj. Kijev?anin; Slobodan P. Šerbanovi?; Bojan D. Djordjevi?

2010-01-01

84

Model for the distribution of neutral organic compounds between n-hexane and acetonitrile.  

PubMed

Partition coefficients for 69 varied compounds were determined for the n-hexane-acetonitrile partition system and combined with 74 partition coefficients for (largely) terpenes, esters and alkylaromatic compounds determined by Isidorov and coworkers and 27 extraction p-values determined by Bowman and Beroza to derive a general model for the distribution of neutral compounds in the biphasic system. The partition coefficients, logK(p), were correlated through the solvation parameter model giving logK(p) = 0.097(+/- 0.049) + 0.189(+/-0.041)E - 1.332(+/-0.056)S - 1.649(+/-0.055)A - 0.966(+/-0.074)B + 0.773(+/-0.040)V with a multiple correlation coefficient of 0.985, standard error of the estimate 0.114, and Fischer statistic 1087. The solute descriptor E is the excess molar refraction, S is the dipolarity/polarizability, A and B are the overall hydrogen-bond acidity and basicity, respectively, and V is McGowan's characteristic volume. The model is expected to be able to estimate further values of the partition coefficient to about 0.1 log units and is applicable to a wide range of compounds except for n-alkylcarboxylic acids, which have higher partition coefficients than predicted, most likely due to the formation of oligomers (e.g. dimers) in the n-hexane layer. PMID:16337209

Ahmed, Hamid; Poole, Colin F

2006-02-01

85

Ignition of turbulent swirling n-heptane spray flames using single and multiple sparks  

SciTech Connect

This paper examines ignition processes of an n-heptane spray in a flow typical of a liquid-fuelled burner. The spray is created by a hollow-cone pressure atomiser placed in the centre of a bluff body, around which swirling air induces a strong recirculation zone. Ignition was achieved by single small sparks of short duration (2 mm; 0.5 ms), located at various places inside the flow so as to identify the most ignitable regions, or larger sparks of longer duration (5 mm; 8 ms) repeated at 100 Hz, located close to the combustion chamber enclosure so as to mimic the placement and characteristics of a gas turbine combustor surface igniter. The air and droplet velocities, the droplet diameter, and the total (i.e. liquid plus vapour) equivalence ratio were measured in inert flow by phase Doppler anemometry and sampling respectively. Fast camera imaging suggested that successful ignition events were associated with flamelets that propagated back towards the spray nozzle. Measurements of ignition probability with the single spark showed that localised ignition inside the spray is more likely to result in successful flame establishment when the spark is located in a region of negative velocity, relatively small droplet Sauter mean diameter, and mean equivalence ratio within the flammability limits. Ignition with the single spark was not possible at the location where the multiple spark experiments were performed. For those, the multiple spark sequence lasted approximately 1 to 5 s. It was found that a long spark sequence increases the ignition efficiency, which reached a maximum of 100% at the axial distance where the recirculation zone had maximum width. Ignition was not feasible with the spark downstream of about two burner diameters. Visualisation showed that small flame kernels emanate very often from the spark, which can be stretched as far as 20 mm from the electrodes by the turbulent velocity fluctuations. These kernels survive very little time. Successful overall ignition occurs at a random time from the spark initiation and, as in the case of the single spark, success is associated with kernels that move without getting extinguished towards the bluff body. The results demonstrate that the energy deposited by multiple sparks and spark stretching in a turbulent flow can have a spatially far-reaching effect to initiate combustion. (author)

Marchionea, T.; Ahmeda, S.F.; Mastorakos, E. [Department of Engineering, University of Cambridge (United Kingdom)

2009-01-15

86

Determination of low concentrations of aromatic hydrocarbons in multicomponent mixtures with iso-octane and n-heptane  

NASA Astrophysics Data System (ADS)

We have experimentally studied the absorption spectra of hydrocarbon mixtures based on n-heptane and isooctane with small (1%-2%) additions of aromatic hydrocarbons (benzene, toluene, xylene). The study was conducted in the region of the first overtones of the vibrational spectra for the hydrocarbon groups CH3, CH2, CH. We show that four-component modeling of the absorption spectrum of the hydrocarbon mixture and minimization of the deviation of the model spectrum from the experimental spectrum allow us to separately determine the content of the aromatic additives for concentrations from 1%.

Vesnin, V. L.; Muradov, V. G.

2011-11-01

87

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

SciTech Connect

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%.

Han, D.H.; Hong, W.H. [Korea Advanced Inst. of Science and Technology, Tajeon (Korea, Democratic People`s Republic of)

1996-04-01

88

Kinetics of enzyme-catalyzed alcoholysis of soybean oil in n-hexane.  

PubMed

This work investigated the production of fatty acid ethyl esters (FAEEs) from soybean oil using n-hexane as solvent and two commercial lipases as catalysts, Novozym 435 and Lipozyme IM. A Taguchi experimental design was adopted considering the variables temperature (35-65 degrees C), addition of water (0-10 wt/wt%), enzyme (5-20 wt/wt%) concentration, and oil-to-ethanol molar ratio (1:3-1:10). It is shown that complete conversion in FAEE is achieved for some experimental conditions. The effects of process variables on reaction conversion and kinetics of the enzymatic reactions are presented for all experimental conditions investigated in the factorial design. PMID:15917602

de Oliveira, Débora; do Nascimento Filho, Irajá; Di Luccio, Marco; Faccio, Carina; Dalla Rosa, Clarissa; Bender, João Paulo; Lipke, Nádia; Amroginski, Cristiana; Dariva, Cláudio; de Oliveira, José Vladimir

2005-01-01

89

Determination of dipole-dipole couplings in oriented n-hexane by two-dimensional NMR  

SciTech Connect

We give here a preliminary report of a method to analyze spectra and determine structures of molecules dissolved in liquid crystals. The basic idea is the use of randomly deuterated samples (a synthetically facile undertaking) which contain a mixture of all possible isotopomers of a molecule. This approach has been used before in the analysis of some cyclic compounds in nematic liquid crystals. A highly deuterated sample will contain mostly isotopomers with just a few protons. Thus, the task of interpreting one complex spectrum is reduced to one of analyzing a large number of simple but overlapping spectra. The crucial point is the ability to recognize the individual signals which derive from the same spin system (arise from one isotopomer). This can be achieved by the combined application of two-dimensional NMR and multiple-quantum NMR techniques as is shown for the case of n-hexane.

Gochin, M.; Schenker, K.V.; Zimmermann, H.; Pines, A.

1986-10-15

90

N-hexane inhalation during pregnancy alters DNA promoter methylation in the ovarian granulosa cells of rat offspring.  

PubMed

The N-hexane-induced impact on the reproductive system of the offspring of animals exposed to n-hexane has caused great concern. Pregnant Wistar rats inhaled 500, 2 500 or 12 500?ppm n-hexane during gestational days 1-20. Clinical characteristics and developmental indices were observed. Ovarian granulosa cells were extracted from F1 rats, the number of follicles was determined in ovarian slices and promoter methylation was assessed using MeDIP-Chip. Several methods were used to analyze the scanned genes, including the Gene Ontology Consortium tools, the DAVID Functional Annotation Clustering Tool, hierarchical clustering and KEGG pathway analysis. The results indicated that the live pups/litter ratio was significantly lowest in the 12 500?ppm group. A significant decrease in secondary follicles and an increase in atresic follicles were observed in the 12 500?ppm group. The number of shared demethylated genes was higher than that of the methylated genes, and the differentially methylated genes were enriched in cell death and apoptosis, cell growth and hormone regulation. The methylation profiles of the offspring from the 500?ppm and control groups were different from those of the 2500 and 12 500?ppm groups. Furthermore, the methylation status of genes in the PI3K-Akt and NF-kappa B signaling pathways was changed after n-hexane exposure. The Cyp11a1, Cyp17a1, Hsd3b1, Cyp1a1 and Srd5a1 promoters were hypermethylated in the n-hexane-exposed groups. These results indicate that the developmental toxicity of n-hexane in F1 ovaries is accompanied by the altered methylation of promoters of genes associated with apoptotic processes and steroid hormone biosynthesis. Copyright © 2013 John Wiley & Sons, Ltd. PMID:23740543

Li, Hong; Liu, Jin; Sun, Yan; Wang, Wenxiang; Weng, Shaozheng; Xiao, Shihua; Huang, Huiling; Zhang, Wenchang

2014-08-01

91

Sensitive determination of n-hexane and cyclohexane in human body fluids by capillary gas chromatography with cryogenic oven trapping.  

PubMed

A sensitive method was developed for determination of n-hexane and cyclohexane in human body fluids by headspace capillary gas chromatography (GC) with cryogenic oven trapping. Whole blood and urine samples containing n-hexane and cyclohexane were heated in a 7.5 mL vial at 70 degrees C for 15 min, and 5 mL of the headspace vapor was drawn into a glass syringe. All vapor was introduced through an injection port of a GC instrument in the splitless mode into an Rtx-Volatiles middle-bore capillary column at an oven temperature of -40 degrees C for trapping volatile compounds. The oven temperature was programmed to 180 degrees C for GC with flame ionization detection. These conditions gave sharp peaks for both n-hexane and cyclohexane, a good separation of each peak, and low background impurities for whole blood and urine. The extraction efficiencies of n-hexane and cyclohexane were 13.2-30.3% for whole blood and 12.7-20.7% for urine. The coefficients of within-day variation in terms of extraction efficiency of both compounds were 5.0-9.5% for whole blood and 3.8-10.8% for urine; those of day-to-day variation for the compounds were not greater than 16.6%. The regression equations for n-hexane and cyclohexane showed good linearity in the range of 5-500 ng/0.5 mL for whole blood and urine. The detection limits (signal-to-noise ratio = 3) for both compounds were 1.2 and 0.5 ng/0.5 mL for whole blood and urine, respectively. The data on n-hexane or cyclohexane in rat blood after inhalation of each compound are also presented. PMID:11234809

Kondo, K; Lee, X P; Kumazawa, T; Sato, K; Watanabe-Suzuki, K; Seno, H; Suzuki, O

2001-01-01

92

Plasma-enhanced chemical vapor deposition of n-heptane and methyl methacrylate for potential cell alignment applications.  

PubMed

Plasma-enhanced chemical vapor deposited polymers (plasma polymers) are promising candidates for biomaterials applications. In the present study, plasma deposition as a fast and easily scalable method was adapted to deposit coatings from n-heptane and methyl methacrylate monomers onto glass substrates. Linear patterns with line and groove widths between 1.25 and 160 ?m were introduced by degrative UV-lithography for cell alignment. Differential interference contrast optical microscopy, profilometry and atomic force microscopy revealed that the patterned surfaces had a smooth, homogeneous appearance and a pattern height of 8 and 45 nm for plasma deposited n-heptane and methyl methacrylate, respectively. UV-lithography increased the oxygen content on the surface drastically as shown by X-ray photoelectron spectroscopy. After immersion in simulated body fluid for 21 days, the pattern was still intact, and the ester groups were also maintained for the most part as shown by infrared spectroscopy. To test the coatings' potential applicability for biomaterial surfaces in a preliminary experiment, we cultured murine preosteoblastic MC3T3-E1 cells on these coatings. Light and electron microscopically, a normal spindle-shaped and aligned cell morphology was observed. At the mRNA level, cells showed no signs of diminished proliferation or elevated expression of apoptosis markers. In conclusion, plasma-enhanced chemical vapor deposited polymers can be patterned with a fast and feasible method and might be suitable materials to guide cell alignment. PMID:22992135

Steinbach, Annina; Tautzenberger, Andrea; Schaller, Andreas; Kalytta-Mewes, Andreas; Tränkle, Sebastian; Ignatius, Anita; Volkmer, Dirk

2012-10-24

93

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

NASA Technical Reports Server (NTRS)

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.

Card, J. M.

1993-01-01

94

Novel platinum/KL catalysts for the aromatization of N-hexane  

NASA Astrophysics Data System (ADS)

A number of studies were conducted to understand the underlying reasons for the uniqueness of Pt/KL for its high activity and selectivity for benzene production. Catalytic screening of basic supported Pt catalysts revealed that aromatization passes through dehydrogenated intermediates, including hexenes. Pt/KL was found to more efficiently convert hexenes to benzene than nonmicroporous basic supported Pt catalysts. The role of L-zeolite was found to protect the Pt clusters from bimolecular pathways leading to the deposition of coke on the surface of the Pt. Sulfur deactivates Pt/KL by agglomeration of Pt clusters and the formation of Pt-S, breaking up Pt ensembles required for aromatization. The role of morphology of Pt inside the L-zeolite channels was found to play an important role on catalytic stability. Series of catalysts were prepared by incipient wetness and vapor phase impregnation and characterized by a variety of techniques, including H2 chemisorption, EXAFS, FTIR of adsorbed CO, MCP ring opening, and TEM and tested by both pulse and flow mode n-hexane reaction. While both catalysts exhibited small Pt clusters inside the channels of the L-zeolite, the IWI had a fraction near the surface region large enough to block channels. Under reaction, the IWI catalysts deactivated to about half the initial activity. However, VPI had Pt clusters small enough to reside in the lobes of the ellipsoid cages of the channels; these catalysts were remarkably stable. Addition of a small amount of thulium to KL was found to aid in dispersing the Pt. Using TPO, thulium was found to act a sulfur getter. Electronic modification to Pt by exchanging the zeolite cation from potassium to lithium was studied by shape resonance XANES, microcalorimetry, and pulse neopentane hydrogenolysis. Addition of lithium resulted in a shift of the Fermi level of Pt away from the antibonding state of Pt-H, strengthening the chemisorption bond. Increased hydrogenolysis rates were observed for both neopentane and n-hexane aromatization experiments at the expense of aromatization. Finally, regeneration of Pt/KL catalysts was studied for sulfur poisoned catalysts. While air effectively burned off coke deposits, sintering of Pt resulted. An oxychlorination treatment effectively redispersed the Pt.

Jacobs, Gary

95

On the properties of methylbenzoate/n-hexane mixed solvents: a theoretical and experimental study.  

PubMed

This paper reports on an experimental and theoretical study of methylbenzoate/n-hexane mixed solvents as a function of pressure and temperature in the whole composition range. We have measured the pressure-volume-temperature (PVT) behavior of these fluids over wide temperature and pressure ranges; from the experimental data, relevant derived coefficients required for the fluid's characterization were calculated. The structure of mixed fluids was analyzed from macroscopic data according to excess and mixing properties. The statistical associating fluid theory (SAFT) and perturbed chain (PC)-SAFT molecularly based equations of state were used to predict the PVT behavior with model parameters for pure fluids fitted from correlation of available saturation literature data. The results provided by the PC-SAFT equation of state were clearly superior. Using the fitted PC-SAFT parameters, the global phase behavior of the mixture was predicted, and a type I pattern was inferred according to the van Konynenburg systematic. The molecular level structure was studied through classical molecular dynamics simulations in the NPT ensemble using the optimized potential for liquid simulations (all atom version) (OPLS-AA) force field. Molecular dynamics provides, on one hand, theoretical values of thermophysical properties, which are compared with the experimental ones to check the quality of simulations, and, on the other hand, valuable molecular level structural and dynamic information. Based on both macroscopic and microscopic studies, fluid structure was inferred. PMID:18373359

Aparicio, Santiago; Alcalde, Rafael; Davila, María J; García, Begoña; Leal, José M

2008-04-24

96

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

NASA Technical Reports Server (NTRS)

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.

Sarv, Hamid; Cernansky, Nicholas P.

1989-01-01

97

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

SciTech Connect

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.

Mariette, C.; Huard, M.; Rabiller, P.; Nichols, Shane M.; Ecolivet, C.; Janssen, Ted; Alquist, III, Keith E.; Hollingsworth, Mark D.; Toudic, B. (CNRS-UMR); (Nijmegen); (KSU)

2012-07-11

98

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

SciTech Connect

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 analysis to the skeletal mechanism. (author)

Zeuch, Thomas [Institut fuer Physikalische Chemie, Tammannstrasse 6, 37077 Goettingen (Germany); Moreac, Gladys [Renault, 1, avenue du Golf, 78288 Guyancourt cedex (France); Ahmed, Syed Sayeed; Mauss, Fabian [Lehrstuhl fuer Thermodynamik und Thermische Verfahrenstechnik, Sielower Strasse 12, 03044 Cottbus (Germany)

2008-12-15

99

Distortion and Orientation for Triplet Coronene in Different n-Heptane Shpol'skii Sites Using Phosphorescence-Polarized Microwave Double Resonance Techniques.  

National Technical Information Service (NTIS)

Using phosphorescence microwave double resonance techniques, the type of distortion and the orientation of the magnetic axes are determined for triplet coronene molecules in different Shpol'skii sites in n-heptane single crystals at 1.6 K. Coronene triple...

A. M. Merle W. M. Pitts M. A. El-Sayed

1977-01-01

100

Spectroscopic Investigation of the Origin of Distortion of Guest Coronene in Various Sites of n-Heptane Shpol'skii Matrix.  

National Technical Information Service (NTIS)

n-Heptane was chosen as a matrix because the spectra are sharp (Shpol'skii effect) and because this lattice offers various modes of insertion to the aromatic as evidenced by a multiplet of at least five components, one of them occurring in polycrystals on...

W. M. Pitts A. M. Merle M. A. El-Sayed

1978-01-01

101

Physiologically Based Modeling of n-Hexane Kinetics in Humans Following Inhalation Exposure at Rest and Under Physical Exertion: Impact on Free 2,5-Hexanedione in Urine and on n-Hexane in Alveolar Air  

Microsoft Academic Search

We used a modified physiologically based pharmacokinetic (PBPK) to describe\\/predict n-hexane (HEX) alveolar air concentrations and free 2,5-HD urinary concentrations in humans exposed to n-HEX by inhalation during a typical workweek. The effect of an increase in workload intensity on these two exposure indicators was assessed and, using Monte Carlo simulation, the impact of biological variability was investigated. The model

G. Hamelin; G. Charest-Tardif; G. Truchon; R. Tardif

2005-01-01

102

Solvent effect on the formation of self-assembled monolayer on DLC surface between n-hexane and Vertrel XF  

NASA Astrophysics Data System (ADS)

Self-assembled monolayers of 1 H,1 H,2 H,2 H-perfluorodecyltrichloro-silane (FDTS) have been deposited on the diamond-like carbon (DLC) film-coated magnetic heads with two different solvents, n-hexane and Vertrel XF. In order to investigate the solvent effect on the monolayer formation, a series of FDTS monolayers were prepared by varying the solution concentrations which were respectively characterized by time-of-flight mass spectroscopy, contact angle measurements and atomic force microscopy. Results showed that high density of aggregations were present for the FDTS monolayers using the n-hexane solvent, while the monolayer formed on the DLC surface using the Vertrel XF solvent exhibited excellent quality and reproducibility and no aggregations were observed.

Tan, Manlin; Zhang, Huayu; Wang, Yulei; Ma, Hongtao; Zhu, Jiaqi; Han, Jiecai

2008-08-01

103

Solubility of ethane in n-hexane at pressures to 5. 4 MPa and temperatures from 311 to 394 K  

SciTech Connect

Solubility data are presented for ethane in n-hexane at temperatures from 311 to 394 K (100 to 250{sup 0}F) at pressures to 5.4 MPa (780 psia). These data are in significant disagreement with earlier measurements. The new data can be described with average deviations of less than 0.001 mole fraction by the Soave-Redlich-Kwong or Peng-Robinson equations when two interaction parameters per isotherm are used in the equation.

Gasem, K.A.M.; Raff, A.M.; Darwish, N.; Robinson, R.L. Jr. (Oklahoma State Univ., School of Chemical Engineering, Stillwater, OK (US))

1989-10-01

104

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

Microsoft Academic Search

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 ²H nuclear magnetic resonance (NMR) for 100 K ⤠T ⤠350 K. Benzene (CâDâ) gives a broad signal with, for T < â 150 K, a quadrupolar

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

1989-01-01

105

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

PubMed Central

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.

Penduka, Dambudzo; Okoh, Anthony I.

2011-01-01

106

In vitro anti-listerial activities of crude n-hexane and aqueous extracts of Garcinia kola (heckel) seeds.  

PubMed

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 3log(10) 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

Penduka, Dambudzo; Okoh, Anthony I

2011-01-01

107

Isothermal vapor–liquid equilibria for the system ethanol and n-hexane in the near critical region  

Microsoft Academic Search

Isothermal VLE data of the n-hexane and ethanol system were obtained at near-critical temperatures. A circulating type equipment with a view cell has been used and compared with the data reported by [Fluid Phase Equilibria 145 (1998) 269] for the same system at 473.15K. The critical pressure was also determined from the critical opalescence of the mixtures. This mixture is

Jungha Seo; Jongcheon Lee; Hwayong Kim

2001-01-01

108

The effect of voids and dilution on n-hexane oxidation over a VMgO catalyst  

Microsoft Academic Search

The conversion of n-hexane has been studied over magnesium orthovanadate (Mg3V2O8). This work illustrates some of the problems associated with alkane activation and subsequent conversion to more valuable products with respect to location of voids and the catalyst in the reactor. The effect of differently packed reactors and dilution factors on the product profile was investigated at a constant gas

Holger B. Friedrich; Nishlan Govender; Mfanwenkosi R. Mathebula

2006-01-01

109

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

PubMed

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

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

2014-07-01

110

Measurements and simulations of mixing and autoignition of an n-heptane plume in a turbulent flow of heated air  

SciTech Connect

The autoignition of a gaseous n-heptane plume in heated turbulent air has been investigated experimentally and numerically with the conditional moment closure and a CFD code. It has been demonstrated that, consistent with previous experimental results for hydrogen and acetylene, the increased scalar dissipation rate created by faster co-flowing air delays autoignition, as revealed by a disproportionate increase of ignition length with air velocity. The predicted mean and variance of the mixture fraction, the mixture fraction PDF and the conditional scalar dissipation rate are in good agreement with experimental results obtained with acetone-tracer PLIF. The first-order, spatially averaged CMC model reproduces the experimental trends quite well, despite the neglect of conditional fluctuations and spatial dependence of the conditional averages. This is attributed to the fact that for a significant period of time before autoignition the conditional scalar dissipation rate at the most reactive mixture fraction is much smaller than the critical value above which autoignition is precluded. (author)

Markides, C.N.; De Paola, G.; Mastorakos, E. [Hopkinson Laboratory, Department of Engineering, University of Cambridge, Trumpington Street, Cambridge CB2 1PZ (United Kingdom)

2007-04-15

111

Liquid–liquid equilibrium data of water with neohexane, methylcyclohexane, tert-butyl methyl ether, n-heptane and vapor–liquid–liquid equilibrium with methane  

Microsoft Academic Search

Liquid–liquid equilibrium (LLE) data for non-aqueous liquid (neohexane [NH], tert-butyl methyl ether [TBME], methylcyclohexane [MCH], or n-heptane [nC7]) and water have been measured under atmospheric pressure at 275.5, 283.15, and 298.15K. It was found that TBME is the most water soluble followed by NH, MCH, and nC7. As the temperature increased, the solubility of the non-aqueous liquids (NALs) in water

R. Susilo; J. D. Lee; P. Englezos

2005-01-01

112

Isobaric vapor–liquid equilibria for the n-heptane + ethylene glycol monopropyl ether and n-octane + ethylene glycol monopropyl ether systems  

Microsoft Academic Search

Vapor–liquid equilibria (VLE) for the n-heptane+ethylene glycol monopropyl ether and n-octane+ethylene glycol monopropyl ether systems were measured. Isobaric VLE measurements of the associating fluid mixtures were conducted at several pressures (60kPa, 80kPa and 100kPa) using Fischer VLE 602 equipment. The experimental data were correlated using a two-term virial equation for vapor-phase fugacity coefficients and the three suffix Margules equation, Wilson,

Sunghyun Jang; Seonghoon Hyeong; Moon Sam Shin; Hwayong Kim

2010-01-01

113

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)

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-emperical chemical kinetic mechanisms. Neither mechanism exhibited the variation of extinction diameter with initial diameter.

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

1994-01-01

114

Synthesis and optical properties of nanosized CdS prepared in a quaternary CTAB\\/ nhexanol\\/n-heptane\\/water reverse micelle  

Microsoft Academic Search

Quaternary water-in-oil reverse micelles consisting of cetyltrimethylammonium bromide (CTAB), nhexanol, n-heptane and water\\u000a were prepared and characterized. The optimized reaction conditions were determined, and monodispersed droplets of the reverse\\u000a micelles were used as microreactors to synthesize CdS nanoparticles. By using transmission electron microscopy (TEM), UV-Vis\\u000a spectroscopy and fluorescence spectroscopy, the influences of the reverse micelle components on the size, size

Jun Zhang; Lingdong Sun; Cheng Qian; Chunsheng Liao; Chunhua Yan

2001-01-01

115

Determination of urinary 2,5-hexanedione concentration by an improved analytical method as an index of exposure to n-hexane.  

PubMed Central

2,5-Hexanedione is a main metabolite of n-hexane and is considered as the cause of n-hexane polyneuropathy. Therefore, it is useful to measure 2,5-hexanedione for biological monitoring of exposure to n-hexane. The analytical methods existing for n-hexane metabolites, however, were controversial and not established enough. Hence, a simple and precise method for determination of urinary 2,5-hexanedione has been developed. Five ml of urine was acidified to pH 0.5 with concentrated hydrochloric acid and heated for 30 minutes at 90-100 degrees C. After cooling in water, sodium chloride and dichloromethane containing internal standard were added. The sample was shaken and centrifuged. 2,5-Hexanedione concentration in an aliquot of dichloromethane extract was quantified by gas chromatography using a widebore column (DB-1701). Urinary concentration of 2,5-hexanedione showed a good correlation with exposure to n-hexane (n = 50, r = 0.973, p less than 0.001). This method is simple and precise for analysis of urinary 2,5-hexanedione as an index of exposure to n-hexane.

Saito, I; Shibata, E; Huang, J; Hisanaga, N; Ono, Y; Takeuchi, Y

1991-01-01

116

Pyrrole und 2,5-Heptandion im Urin der Ratte und 2,5-Heptandion im Urin des Menschen: Analytische Bestimmung der Ausscheidung nach Exposition gegn n-Heptan. (Pyrrole and 2,5-heptanedione in the urine of rats and 2,5-heptanedione in the urine of man: analytical determination of excretion upon exposure to n-heptane).  

National Technical Information Service (NTIS)

A method for quantifying levels of the neurotoxic metabolite 2,5-heptanedione in rats and man after experimental exposure to n-heptane was developed. It consisted in determining the quantity of 2,5-heptanedione excreted in urine and the relevant excretion...

A. G. C. Stoermer

1997-01-01

117

Grand Rounds: Could Occupational Exposure to n-Hexane and Other Solvents Precipitate Visual Failure in Leber Hereditary Optic Neuropathy?  

PubMed Central

Context Leber hereditary optic neuropathy (LHON) is a maternally inherited loss of central vision related to pathogenic mutations in the mitochondrial genome, which are a necessary but not sufficient condition to develop the disease. Investigation of precipitating environmental/occupational (and additional genetic) factors could be relevant for prevention. Case presentation After a 6-month period of occupational exposure to n-hexane and other organic solvents, a 27-year-old man (a moderate smoker) developed an optic neuropathy. The patient had a full ophthalmologic and neurologic investigation, including standardized cycloergometer test for serum lactic acid levels and a skeletal muscle biopsy. His exposure history was also detailed, and he underwent genetic testing for LHON mitochondrial DNA mutations. The patient suffered a sequential optic neuropathy with the hallmarks of LHON and tested positive for the homoplasmic 11778G ? A/ND4 mutation. Routine laboratory monitoring revealed increased concentrations of urinary 2.5 hexandione (n-hexane metabolite) and hippuric acid (toluene metabolite) in the period immediately preceding the visual loss. Discussion In a subject carrying an LHON mutation, the strict temporal sequence of prolonged appreciable occupational exposure followed by sudden onset of visual loss must raise a suspicion of causality (with a possible further interaction with tobacco smoke). Relevance In this article, we add to the candidate occupational/environmental triggers of LHON and highlight the need for appropriate case–control (and laboratory) studies to validate the causal effect of mixed toxic exposures.

Carelli, Valerio; Franceschini, Flavia; Venturi, Silvia; Barboni, Piero; Savini, Giacomo; Barbieri, Giuseppe; Pirro, Ettore; La Morgia, Chiara; Valentino, Maria L.; Zanardi, Francesca; Violante, Francesco S.; Mattioli, Stefano

2007-01-01

118

Solvent systems with n-hexane and/or cyclohexane in countercurrent chromatography-Physico-chemical parameters and their impact on the separation of alkyl hydroxybenzoates.  

PubMed

Countercurrent chromatography (CCC) is an efficient preparative separation technique based on the liquid-liquid distribution of compounds between two phases of a biphasic liquid system. The crucial parameter for the successful application is the selection of the solvent system. Especially for nonpolar analytes the selection options are limited. On the search for a suitable solvent system for the separation of an alkyl hydroxybenzoate homologous series, we noted that the substitution of cyclohexane with n-hexane was accompanied with unexpected differences in partitioning coefficients of the individual analytes. In this study, we investigated the influence of the subsequent substitution of n-hexane with cyclohexane in the n-hexane/cyclohexane/tert-butylmethylether/methanol/water solvent system family. Exact phase compositions and polarity, viscosity and density differences were determined to characterize the different mixtures containing n-hexane and/or cyclohexane. Findings were confirmed by performing CCC separations with different mixtures, which led to baseline resolution for positional isomers when increasing the amount of cyclohexane while the resolution between two pairs of structural isomers decreased. With the new methodology described, structurally similar compounds could be resolved by choosing a certain ratio of n-hexane to cyclohexane. PMID:24731544

Englert, Michael; Vetter, Walter

2014-05-16

119

Volumetric study of the mixtures n-hexane + isomeric chlorobutane: experimental characterization and volume translated Peng-Robinson predictions.  

PubMed

The p?Tx behavior of the binary mixtures n-hexane + isomeric chlorobutane has been studied over the whole composition range at temperatures between 283.15 and 323.15 K and pressures from 0.1 to 65.0 MPa. Experimental densities have been used to obtain different excess properties: excess molar volume, excess isobaric expansibility, excess isothermal compressibility, and excess internal pressure. These excess properties have been analyzed in terms of molecular interactions and structural effects. Finally, experimental densities of the binary mixtures have been compared with the predictions of the volume translated Peng-Robinson (VTPR) model. The overall average deviation between experimental and calculated densities is 0.00427 g·cm(-3), which can be considered reasonably good predictions. PMID:23931182

Guerrero, Hernando; Cea, Pilar; Gascón, Ignacio; Royo, Félix M; Lafuente, Carlos

2013-09-01

120

Ultrafast formation of I 2 following 350-nm photodissociation of CF 2I 2 in n-hexane  

NASA Astrophysics Data System (ADS)

This study presents the photodissociation dynamics of difluorodiiodomethane (CF 2I 2) in n-hexane by femtosecond pump-probe spectroscopy. Following 350-nm excitation of CF 2I 2 into the lowest-lying excited electronic state, the transient absorption spectra are measured between 355 and 785 nm up to a time delay of 1200 ps. The results suggest that electronically excited CFI2? molecules undergo a step-wise decay giving rise to two iodine fragments. The majority of the nascent iodine fragments combine on a 2-ps timescale to form molecular iodine. The spectral evolution is complete within 500 ps where the quantum yield of I 2 formation is measured to be 32%.

El-Khoury, Patrick Z.; Tarnovsky, Alexander N.

2008-03-01

121

Synthesis and Characterization Hydrophobic FePt@Au Core-Shell Nanoparticles in a Quaternary CTAB\\/n-Butanol\\/n-Heptane\\/Water Reverse Micelle  

Microsoft Academic Search

In this article, hydrophobic FePt@Au nanoparticles (NPs) were synthesized in Quaternary water in oil (W\\/O) reverse micelle consisting of cetyltrimethylammonium bromide (CTAB), n-butanol, n-heptane and water by aqueous sodium borohydride (NaBH4) and hydrazine hydrate (N2H4·H2O) as reductant on surface of the seed FePt NPs. The NPs are characterized by UV-vis spectroscopy, transmission electron microscopy (TEM) and energy dispersive x-ray analysis

Yun Zhi Fu; Xiu Dong Xiang

2008-01-01

122

How TOPO affects the interface of the novel mixed water/AOT:TOPO/n-heptane reverse micelles: dynamic light scattering and Fourier transform infrared spectroscopy studies.  

PubMed

In this work we report for the first time the formation of two reverse micelle (RM) media produced by the nonionic surfactant tri-n-octyl phosphine oxide (TOPO) in n-heptane and the one produced by mixing the anionic sodium 1,4-bis-2-ethylhexylsulfosuccinate (AOT) with different TOPO contents dissolved in n-heptane. Dynamic light scattering (DLS) experiments reveal the formation of water/TOPO/n-heptane RMs (TOPO RMs) and water/AOT:TOPO/n-heptane RMs (mixed RMs) since the droplet sizes increase as the water content increases. The addition of TOPO to the system at constant W0 (W0 = [water]/([AOT] + [TOPO])) causes the droplet sizes of mixed RMs to decrease compared with the AOT RMs. In addition, the decrease is larger when the water content is low (W0 = 0.5) but the effect is negligible at the maximum W0 value analyzed (W0 = 2). These results are not expected for mixtures of different nonionic surfactants with AOT and were explained considering the unique TOPO structure. Thus, at W0 = 0.5, we suggest that the percentage of TOPO molecules at the mixed RM interface is higher than those corresponding to the bulk solution. On the other hand, at W0 = 2 the RM interface is comprised mainly of AOT molecules. The FT-IR experiments performed by monitoring monodeuterated water frequency (?OD) in TOPO RMs show bound and "bulk-like" water structure even at very low water content. On the other hand, for mixed RMs the water structure depends on the water content. At low W0 value, there are two kinds of water molecules, and at W0 value around 2 only bound water exists. The Fourier transform infrared (FT-IR) experiments performed on the symmetric (?sSO3) and asymmetric (?aSO3) sulfonate stretching bands of AOT reveal the existence of a strong Na(+)?TOPO complex in the mixed RMs. The results show that adding TOPO to form mixed surfactant RMs with AOT reduces their size, changes the nature of water to have a "bulk-like" character and diminishes the ion pairing of the sulfonate group with Na(+). PMID:24947471

Odella, Emmanuel; Falcone, R Darío; Silber, Juana J; Correa, N Mariano

2014-07-01

123

Light Absorption by Hydrocarbon Molecules at 3.392 ?m of He-Ne Laser  

NASA Astrophysics Data System (ADS)

The decadic molar extinction coefficients of various hydrocarbon molecules at the wavelength of 3.392 ?m of the infrared He-Ne laser were measured at temperatures between 292 and 1100 K using the shock-tube technique. Methane, ethane, propane, n-pentane, n-hexane, n-heptane, n-octane, n-nonane, iso-octane, methanol, ethanol, butanol, acetone and benzene absorbed the laser light. No Doppler-or pressure-broadening of these molecules was observed except in the case of methane and ethane. The values of the decadic molar exctinction coefficients give information on a temperature-measurement technique which utilizes Beer-Lambert’s law.

Tsuboi, Takao; Inomata, Katsumi; Tsunoda, Yutaka; Isobe, Akihito; Nagaya, Koh-ichi

1985-01-01

124

X-ray Study of the Electric Double Layer at the n-Hexane/Nanocolloidal Silica Interface  

SciTech Connect

The spatial structure of the transition region between an insulator and an electrolyte solution was studied with x-ray scattering. The electron-density profile across the n-hexane/silica sol interface (solutions with 5, 7, and 12 nm colloidal particles) agrees with the theory of the electrical double layer and shows separation of positive and negative charges. The interface consists of three layers, i.e., a compact layer of Na{sup +}, a loose monolayer of nanocolloidal particles as part of a thick diffuse layer, and a low-density layer sandwiched between them. Its structure is described by a model in which the potential gradient at the interface reflects the difference in the potentials of 'image forces' between the cationic Na{sup +} and anionic nanoparticles and the specific adsorption of surface charge. The density of water in the large electric field ({approx}10{sup 9}-10{sup 10} V/m) of the transition region and the layering of silica in the diffuse layer is discussed.

Tikhonov,A.

2006-01-01

125

Thermal reactions of aromatics with CaO. Technical progress report, September 1, 1980-April 30, 1981. [Compounds tested -1-methylnaphthalene, toulene, benzene, n-heptane  

SciTech Connect

Experiments were performed near atmospheric pressure for the temperature range 550 to 950/sup 0/C. Helium carrier gas containing 3 mole % of the vapor phase reactant was passed through approximately 5.5-cm-deep, 0.7-cm-ID packed beds containing calcium oxide or quartz (for comparison studies). Contact times were approximately 2 s and around 5 mg of pure compound were fed in each run. Reaction products and unreacted feed were collected and analyzed. Carbon balances were performed on selected runs. The effects of CaO source and the method of CaO preparation were also investigated. Extents of conversion, and product distributions for n-heptane cracking were similar for calcium oxide and for quartz. However, the temperature for removal of aromatic hydrocarbons from the helium hydrocarbon mixtures in the presence of calcium oxide was reduced 140 to 180/sup 0/C from that with quartz. The temperature required for 20% conversion of each compound in the presence of calcium oxide and quartz respectively were: 1 - methylnaphthalene - 570 and 750/sup 0/C; toluene - 685 and 825/sup 0/C; benzene 750 and 890/sup 0/C; and n-heptane 585 and 610/sup 0/C. The reactivity of the aromatics increased with addition of a methyl group or a second aromatic ring to the molecule. Coke is the major product from the reaction of each aromatic. Methane yields from 1-methylnaphthalene and toluene were lower in the reactions over calcium oxide. On a unit weight basis calcium oxide obtained by calcining calcium hydroxide at final reaction temperatures was more active for benzene cracking than CaO obtained by calcining limestone. Calcium oxide cracking activity declines as coke is deposited on its surface but may be at least partially regenerated by burning off the coke. Apparent activation energies obtained by fitting a single reaction first order decomposition model to the data were lower for aromatics cracking over CaO compared to quartz but the opposite effect was found for n-heptane.

Longwell, J.P.; Ellig, D.L.; Krasniak, S.; Lai, S.C.K.; Williams, G.C.; Peters, W.A.

1981-07-01

126

Optically Detected Magnetic Resonance Study of Pyrene in Cationic Micelles and the Spin-Lattice Relaxation Pathways for Pyrene in N-Hexane and 3-METHYL Pentane Hosts  

NASA Astrophysics Data System (ADS)

The pyrene micro-environment in cationic micelles was probed using optically-detected magnetic resonance (ODMR) and phosphorescence lifetimes (at low temperatures, 1.65 and 77 K, respectively). These systems were also studied by fluorescence quenching and lifetime measurements at room temperature. As the surfactant's n-alkyl chain length increases, pyrene is situated more deeply within the micelle but experiences a more polar, less polarizable medium. The Shpol'skii effect (SE) was studied by ODMR. The linewidths for both ODMR transitions reach a minimum for pyrene in n-hexane versus shorter or longer n-alkanes. The (0-0) phosphorescence wavelength red shifted and the |D| zero-field splitting (zfs) parameter decreased within a series of n-alkane solvents with increasing n. We conclude that (1) there is a SE in ODMR transitions, with linewidths comparable to those in single crystals and (2) within a class of structurally related solvents there appears to be a correlation between phosphorescence energy, zfs parameters and chain length. We also studied the zero-field optically-detected triplet electron spin coherence for pyrene in n-hexane. Results show that optically-detected electron spin-echo coherence experiments in zero-field are feasible for randomly oriented triplet chromophores. The transient nutation is strongly damped but reasonably strong two-pulse echoes were seen when the pi/2 pulse length is approximately one-third the length corresponding to the first maximum in the nutation. Investigations of the triplet spin-lattice relaxation (SLR) were performed on pyrene in n-hexane, n-octane, n -decane and 3-methylpentane (3MP) using Microwave Saturated Phosphorescence Decay (MSPD) and Fast-Passage (FP) techniques. Results were (1) SLR rates decrease in the hosts studied in the order: n-decane > n-octane >= n-hexane, (2) in these systems and 3MP, the x, y sublevels are in the fast relaxation regime (SLR fast compared to sublevel lifetimes), whereas the x, z and y, z sublevels are in the intermediate relaxation regime (SLR comparable to sublevel lifetimes) and (3) relaxation in n-hexane proceeds via a direct process, W_ {D} ~ T^1, whereas for 3MP a direct-TLS (two-level system) phonon process is operative. At any given temperature in the range 2.52 to 4.2 K relaxation is faster in 3MP (glass) than in n-hexane (polycrystal). (Abstract shortened by UMI.).

Tringali, Arthur Emil

1992-01-01

127

Characterization of water\\/sodium bis(2-ethylhexyl) sulfosuccinate\\/sodium bis(amyl) sulfosuccinate\\/ n-heptane mixed reverse micelles and w\\/o microemulsion systems: The influence of water and sodium bis(amyl) sulfosuccinate content  

Microsoft Academic Search

The unique properties of reverse micelles, microemulsions, enable a variety of applications, from oil recovery to pharmaceuticals. For an effective process development for a targeted application, systems with specific ionic and molecular transport properties are needed. In this work, experiments were carried out to study microstructures of mixed reverse micelles, microemulsions (water\\/n-heptane), obtained with the use of anionic surfactants, sodium

Alen Kljaji?; Marija Bešter-Roga?; Sabina Trošt; Rok Zupet; Stane Pejovnik

2011-01-01

128

Calorimetric investigation of the solubilization of water-in-sodium dodecylbenzenesulfonate reversed micelles and water-in-oil microemulsions in mixed solvent of n-heptane and n-pentanol  

Microsoft Academic Search

Thermal behavior of sodium dodecylbenzenesulfonate (DDBS) reversed micelles with n-pentanol and n-heptane as mixed apolar solvents was studied by titrating water into anhydrous reversed micelles with a Tronac model 450 calorimeter. The solubilization of water can be described in terms of deformation of molecular structure of water, adsorption of water, ionization of surfactant, dilution of counterions, and swelling of droplets.

G. Gu; W. Wang; H. Yan

1994-01-01

129

Isobaric vapor–liquid equilibrium for binary mixtures of 1-hexene + n-hexane and cyclohexane + cyclohexene at 30, 60 and 101.3 kPa  

Microsoft Academic Search

Consistent vapor–liquid equilibria (VLE) data were determined for the binary systems 1-hexene+n-hexane and cyclohexane+cyclohexene at 30, 60 and 101.3kPa, with the purpose of studying the influence of the pressure in the separation of these binary mixtures. The two systems show a small positive deviation from ideality and do not present an azeotrope. VLE data for the binary systems have been

Beatriz Marrufo; Antonio Aucejo; Margarita Sanchotello; Sonia Loras

2009-01-01

130

Effect of Physical Exertion on the Biological Monitoring of Exposure to Various Solvents Following Exposure by Inhalation in Human Volunteers: II. n-Hexane  

Microsoft Academic Search

This study evaluated the impact of physical exertion on two n-hexane (HEX) exposure indicators in human volunteers exposed under controlled conditions in an inhalation chamber. A group of four volunteers (two women, two men) were exposed to HEX (50 ppm; 176 mg\\/m) according to several scenarios involving several periods when volunteers performed either aerobic (AERO), muscular (MUSC), or both AERO\\/MUSC

Robert Tardif; Véronique Nadeau; Ginette Truchon; Martin Brochu

2007-01-01

131

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

PubMed

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

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

2012-01-01

132

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

SciTech Connect

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.

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

2009-04-06

133

An experimental and numerical investigation of n-heptane/air counterflow partially premixed flames and emission of NO{sub x} and PAH species  

SciTech Connect

An experimental and numerical investigation of counterflow prevaporized partially premixed n-heptane flames is reported. The major objective is to provide well-resolved experimental data regarding the detailed structure and emission characteristics of these flames, including profiles of C{sub 1}-C{sub 6}, and aromatic species (benzene and toluene) that play an important role in soot formation. n-Heptane is considered a surrogate for liquid hydrocarbon fuels used in many propulsion and power generation systems. A counterflow geometry is employed, since it provides a nearly one-dimensional flat flame that facilitates both detailed measurements and simulations using comprehensive chemistry and transport models. The measurements are compared with predictions using a detailed n-heptane oxidation mechanism that includes the chemistry of NO{sub x} and PAH formation. The reaction mechanism was synergistically improved using pathway analysis and measured benzene profiles and then used to characterize the effects of partial premixing and strain rate on the flame structure and the production of NO{sub x} and soot precursors. Measurements and predictions exhibit excellent agreement for temperature and major species profiles (N{sub 2}, O{sub 2}, n-C{sub 7}H{sub 16}, CO{sub 2}, CO, H{sub 2}), and reasonably good agreement for intermediate (CH{sub 4}, C{sub 2}H{sub 4}, C{sub 2}H{sub 2}, C{sub 3}H{sub x}) and higher hydrocarbon species (C{sub 4}H{sub 8}, C{sub 4}H{sub 6}, C{sub 4}H{sub 4}, C{sub 4}H{sub 2}, C{sub 5}H{sub 10}, C{sub 6}H{sub 12}) and aromatic species (toluene and benzene). Both the measurements and predictions also indicate the existence of two partially premixed regimes; a double flame regime for f<5.0, characterized by spatially separated rich premixed and nonpremixed reaction zones, and a merged flame regime for f>5.0. The NO{sub x} and soot precursor emissions exhibit strong dependence on partial premixing and strain rate in the first regime and relatively weak dependence in the second regime. At higher levels of partial premixing, NO{sub x} emission is increased due to increased residence time and higher peak temperature. In contrast, the emissions of acetylene and PAH species are reduced by partial premixing because their peak locations move away from the stagnation plane, resulting in lower residence time, and the increased amount of oxygen in the system drives the reactions to the oxidation pathways. The effects of partial premixing and strain rate on the production of PAH species become progressively stronger as the number of aromatic rings increases. (author)

Berta, Paolo; Aggarwal, Suresh K. [Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, Chicago, IL (United States); Puri, Ishwar K. [Department of Engineering Science and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, VA (United States)

2006-06-15

134

Auto-ignition of toluene-doped n-heptane and iso-octane/air mixtures: High-pressure shock-tube experiments and kinetics modeling  

SciTech Connect

Toluene is often used as a fluorescent tracer for fuel concentration measurements, but without considering whether it affects the auto-ignition properties of the base fuel. We investigate the auto-ignition of pure toluene and its influence on the auto-ignition of n-heptane and iso-octane/air mixtures under engine-relevant conditions at typical tracer concentrations. Ignition delay times {tau}{sub ign} were measured behind reflected shock waves in mixtures with air at {phi}=1.0 and 0.5 at p=40 bar, over a temperature range of T=700-1200 K and compared to numerical results using two different mechanisms. Based on the models, information is derived about the relative influence of toluene on {tau}{sub ign} on the base fuels as function of temperature. For typical toluene tracer concentrations {<=}10%, the ignition delay time {tau}{sub ign} changes by less than 10% in the relevant pressure and temperature range. (author)

Hartmann, M.; Fikri, M.; Schulz, C. [Institute for Combustion and Gasdynamics (IVG), University of Duisburg-Essen, Duisburg (Germany); Gushterova, I.; Schiessl, R.; Maas, U. [Institute for Technical Thermodynamics (ITT), Karlsruhe Institute of Technology (KIT), Karlsruhe (Germany)

2011-01-15

135

Oxidation of n-hexane over Pt and Cu–Co oxide catalysts supported on a thin-film zirconia\\/stainless steel carrier  

Microsoft Academic Search

The complete oxidation of n-hexane in air over a stainless steel foil (SS) coated with a thin film of ZrO2 (SS\\/ZrO2), SS\\/ZrO2\\/Pt, SS\\/ZrO2\\/La2O3\\/CuCo and SS\\/ZrO2\\/La2O3\\/CuCo\\/Pt catalysts has been investigated. The ZrO2 films were deposited on the SS substrate by electrochemical and spray pyrolysis (SP) methods. Among electrochemically prepared samples, Pt containing catalysts exhibited the highest activity. The presence of La,

Tatjana Novakovi?; Nenad Radi?; Boško Grbi?; Tsvetana Marinova; Plamen Stefanov; Dimitar Stoychev

2008-01-01

136

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)

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.

1981-01-01

137

Experimental determination and modelling of densities and excess molar volumes of ternary system (1-butanol + cyclohexylamine + n-heptane) and corresponding binaries from 288.15 to 323.15 K  

Microsoft Academic Search

Experimental densities ? and excess molar volumes VE of one ternary and three binary systems containing 1-butanol, cyclohexylamine and n-heptane at temperatures from 283.15 to 323.15K are reported. Density measurements were performed by an Anton Paar DMA 5000 vibrating tube densimeter. The obtained VE of binary systems were fitted to the Redlich–Kister equation, and to the Nagata–Tamura equation for the

Mirjana Lj. Kijev?anin; Ivona R. Radovi?; Slobodan P. Šerbanovi?; Aleksandar Ž. Tasi?; Bojan D. Djordjevi?

2009-01-01

138

Validation of an analytical method for quality control of residual solvents (n-hexane and acetone) in D-002: new active ingredient from beeswax.  

PubMed

D-002 is a new natural product consisting of a mixture of aliphatic fatty alcohols, which shows antioxidant and anti-ulcer effects in experimental models. A new validated methodology for determining simultaneously residual n-hexane and acetone in D-002 using the headspace gas chromatography (HS/GC) is described. The very poor solubility of D-002 in most solvents did necessary sample preparations in solid state. Limit test conditions allowed a detection of residual n-hexane and acetone more sensitively than that recommended for such purposes in the general method of the European Pharmacopoeia. Validation assays, applied to both D-002 residual solvents, proved: suitable sensitivity; very high linearity (correlation coefficients > or =0.999, R.S.D. of slopes < or =0.8% and R.S.D. of response factors < or =5% and no biases) and accuracy (average recoveries between 94.7 and 100.1%); and precision was < or =2.1%. The method was found suitable for quality control and stability studies of this new product. PMID:18462903

Antolín, Ernesto Méndez; Quiñónez, Yaisme Balcinde; Canavaciolo, Víctor González; Cruz, Esperanza Rodríguez

2008-07-15

139

Removal of saturated aliphatic hydrocarbons (gasoline components) from air via bacterial biofiltration.  

PubMed

Two-stage biofilters (using perlite and granular activated carbon, GAC, as packing materials) were used for the removal of several linear, branched, and cyclic C(5)-C(8)saturated aliphatic hydrocarbons from air, both as individual chemicals and in mixtures. The acclimation of biofilters from styrene to n-heptane was complete in 14-18 days. The substrate switch resulted in significant changes in pH and microbial composition of biofilters. Subsequent experiments were conducted under steady state conditions at a constant EBRT of 123 s and near-neutral pH, assuring the predominantly bacterial (as opposed to fungal) biofilter population. n-Heptane was removed with consistently high, 87-100%, removal efficiencies (RE) for up to 16 g x m(-3) x h(-1) critical substrate loads in the perlite biofilter, while n-hexane and n-pentane exhibited significantly lower RE under similar conditions. The REs for iso-octane and cyclohexane were less than 10% under similar loads; n-heptane biodegradation was consistently ca. 10% lower in the presence of iso-octane than in its absence. The GAC biofilter showed a significantly lower efficiency than the perlite biofilter (the critical load, yielding RE > 90%, was only 5 g x m(-3) x h(-1) for n-heptane). Evidence obtained indicates that the rate limiting step for mixed culture biofiltration of aliphatic hydrocarbon mixtures is biodegradation rather than mass transfer. PMID:20560085

Paca, Jan; Halecky, Martin; Vanek, Tomas; Kozliak, Evguenii; Jones, Kim

2010-01-01

140

The UV absorption spectra of the trichlorobenzenes and the higher chlorinated benzenes in the gas phase and in n-hexane solution  

NASA Astrophysics Data System (ADS)

Absolute absorption cross sections are determined for the three isomeric trichlorobenzenes in the gas phase in the region from 33 000 to 60 000 cm -1, and relative absorption cross sections of the tetrachlorobenzenes, pentachlorobenzene, and hexachlorobenzene are presented in the region from 40 000 to 60 000 cm -1. Spectra in n-hexane solution are determined for comparison. The spectra in the gas phase are compared to the spectra in solution and to spectra of the analogous fluoro compounds. With respect to band shifts a comparison is made to theoretical considerations (developed for spectra in solution) and a revised set of parameters for gas-phase spectra is derived. Vapor pressures for the tetrachlorobenzenes and for pentachlorobenzene are estimated at room temperature from the observed absorption intensities.

Scharping, Heike; Zetzsch, Cornelius; Dessouki, Hassan A.

1987-06-01

141

In vitro effects of straight-chain alkanes (n-hexane through n-dodecane) on rat liver and lung cytochrome P-450  

SciTech Connect

To evaluate the effect of straight-chain alkanes on normal detoxication reactions a study was made of the in vitro effect of the homologous series n-hexane through n-dodecane on two cytochrome P-450 (EC 1.14 14.1) enzyme activities. Benzo(a)pyrene hydroxylase (BaPOHase) and 7-ethyoxycoumarin deethylase activities were measured in liver and lung microsomes of control and ..beta..-naphthoflavone-treated rats. In the presence of 2 mM n-hexane through n-dodecane, liver BaPOHase activity decreased from 67% of control with n-dodecane to 21% of control with octane. Lung benzo(a)pyrene hydroxylase was insensitive to all tested alkanes at 2 mM. In the presence of 2 mM alkanes, liver 7-ethoxycoumarin deethylase activity decreased from 73% of control with n-octane to 28% with n-octane. Lung 7-ethoxycoumarin deethylase was also sensitive to the alkane series. In the presence of 2 mM alkane the greatest effect was obtained with n-octane and represented a 56% loss in activity. Alkane concentration-dependent measurements showed 0.02-0.20 mM as the sensitive region of the curve for n-octane with maximal loss of activity achieved at 0.20 mM. Liver ethyoxycoumarin deethylase activity from ..beta..-naphthoflavone-treated rats was less sensitive towards the reactive alkane, n-octane, than the activity from control rats: Double-reciprocal-plot analysis revealed the maximal velocity (V/sub max/) was decreased in the presence of 0.2 mM n-octane. Hence this hydrocarbon did not exert its effect solely as an alternate substrate.

Rabovsky, J.; Judy, D.J.; Pailes, W.H.

1986-01-01

142

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

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 ?-, and randomly methylated ?-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 ?-amino-?-caprolactam were analyzed by rheological measurements.

Fischer, Julian; Millan, Simon

2013-01-01

143

Densities and bubble points of ternary mixtures of methane, n-butane and n-hexadecane and quaternary mixtures of methane, n-butane, n-heptane and n-hexadecane  

Microsoft Academic Search

The densities of three ternary mixtures of methane, n-butane and n-hexadecane and three quaternary mixtures of methane, n-butane, n-heptane and n-hexadecane were measured. The ternary mixtures were studied over the temperature range 295–350K and the pressure range 8.3–49.3MPa at the following methane mole fractions: 0.0185, 0.0358 and 0.0478 and corresponding n-butane mole fractions: 0.8680, 0.8527 and 0.8422. The quaternary mixtures

A Fenghour; J. P. M Trusler; W. A Wakeham

2001-01-01

144

Thermal diffusion and molecular diffusion values for some alkane mixtures: a comparison between thermogravitational column and thermal diffusion forced rayleigh scattering.  

PubMed

In the present work we studied the thermal diffusion behavior of n-decane in various alkanes by thermogravitational column (TC) technique and the thermal diffusion forced Rayleigh scattering (TDFRS) method. The investigated lighter alkanes compared to n-decane are n-pentane, n-hexane, n-heptane, n-octane, and the heavier ones are n-tetradecane, n-pentadecane, n-hexadecane, n-heptadecane, n-octadecane, and n-eicosane. The binary mixture n-decane/ n-pentane we investigated at several different concentrations; all other mixtures were only investigated at a mass fraction of 50%. Even for the volatile n-pentane/ n-decane mixture the deviations between the thermal diffusion coefficients determined by the different methods agreed within the error bars. Typically the agreement between the two methods was in the order of 5%. In comparison to recently published TC and TDFRS data we found deviations in the order of 30% up to 40%. We analyze and discuss the possible reasons for the discrepancies for the present and the past publications. PMID:18570400

Blanco, Pablo; Polyakov, Pavel; Bou-Ali, M Mounir; Wiegand, Simone

2008-07-17

145

Kinetics of cracking of n-decane and n-hexane on zeolites H-ZSM-5 and HY in the temperature range 500 to 780 K  

SciTech Connect

The kinetics of cracking of n-decane and n-hexane were investigated by observing the composition of the gas phase in contact with zeolite catalysts H-ZSM-5 and HY in a well-mixed closed system (gradientless batch-reactor). Catalyst temperature was varied from 473 K to 773 K, partial pressures of reactant paraffin between 0.5 and 20 mbar. For ZSM-5 the influence of crystal size and of Si/Al-ratio on the kinetics was investigated. At temperatures above 673 K, the rates of cracking on H-ZSM-5 are first order in the partial pressures of paraffin; an estimate of diffusivity under reaction conditions is obtained from the influence of crystal size on observed rates at T > 700 K. Between 473 K and 673 K, the rate of reaction of pure n-decane on H-ZSM-5 exhibits a maximum near 300 C and decreases with temperature to a minimum near 630 K. An induction period followed by autocatalysis was observed with n-decane as reactant in this temperature-range, depending on Si/Al ratio and degree of deactivation of the zeolite. It can be suppressed by addition of olefin to reactant paraffin. These phenomena are also observed in a less pronounced way with dealuminated HY, which deactivates more rapidly. A mathematical model based on a dual pathway of carbenium ion and protolytic cracking as postulated by Haag and Dessau represents the observations qualitatively and in an approximate way also quantitatively.

Riekert, L.; Zhou, J.-Q. (Univ. Karlsruhe (Germany))

1992-10-01

146

Determination of absolute photoionization cross-sections of alkanes and cyclo-alkanes.  

PubMed

Absolute photoionization and dissociative photoionization cross-sections of eleven n-alkanes (n-pentane, n-hexane, n-heptane, n-nonane, n-decane, n-undecane, n-dodecane, n-tridecane, n-tetradecane, n-pentadecane and n-hexadecane), three cyclo-alkanes (cyclopentane, methylcyclohexane and trans-decahydronaphthalene) and iso-octane were measured for photon energies from the ionization thresholds to 11.5 eV. The measurements were performed with the binary-liquid-mixture method utilizing the photoionization cross-sections of benzene as a calibration standard. The ionization energies of n-alkanes and cyclo-alkanes were also calculated at the B3P86/6-31 + +G(d,p) level and by the G3B3 method. PMID:20391606

Zhou, Zhongyue; Zhang, Lidong; Xie, Mingfeng; Wang, Zhandong; Chen, Dongna; Qi, Fei

2010-05-15

147

Excess enthalpies for 1,1,1-trichloroethane with alkanes, ketones, and esters  

SciTech Connect

Excess enthalpies provide quantitative information about the temperature dependence of the excess Gibbs energy G[sup E]. This information should therefore be used together with other results (vapor-liquid equilibria, liquid-liquid equilibria, limiting activity coefficients, and azeotropic data) for fitting simultaneously temperature-dependent G[sup E] model parameters or interaction parameters of group contribution methods. Although a large number of H[sup E] measurements have been published, results at temperatures other than 298.15 K are scarce. In this paper a flow calorimeter is described, and excess enthalpy data are given for the test systems n-hexane + cyclohexane, benzene + cyclohexane, and methanol + water at 298.15 K as well as for 1,1,1-trichloroethane + n-pentane, + n-heptane, + acetone, + 2-butanone, + methyl acetate, and + ethyl acetate at 363.15 K. These results were used for the systematic development of the group contribution method (modified UNIFAC) developed at Dortmund.

Gmehling, J. (Univ. Oldenburg, Oldenburg (Germany). Technische Chemie)

1993-01-01

148

Impact of choice of alkane deposition solvent on 4-fluorobenzoic acid layers adsorbed on silver nanostructures  

NASA Astrophysics Data System (ADS)

Surface-enhanced infrared absorption (SEIRA) experiments revealed that the chain length and evaporation rate of alkane deposition solvents altered 4-fluorobenzoic acid (4FBA) adsorption. 4FBA did not dissociate in the multilayer with the fast-evaporating n-pentane deposition solvent. However, with n-hexane and heavier solvents, the evaporation rate was slow enough to allow significant formation of 4-fluorobenzoate ions (4FBI) in the multilayer. Strong intermolecular attractions were present with heavier deposition solvents as evidenced by the incorporation of n-heptane into the 4FBI multilayer. This work will apply to many synthetic, biological, and environmental areas involving the interaction of metal nanostructures with oxygenated or halogenated hydrocarbons.

Cordova, Scott; Schiefer, Elizabeth; Bonde, Ashley; Razer, Taylor; Chen, TsungYen; Perry, Donald

2010-09-01

149

Some effects of aliphatic hydrocarbons on the electrical capacity and ionic currents of the squid giant axon membrane.  

PubMed Central

1. The electrical properties of squid giant axons were examined by means of admittance bridges at frequencies from 0.5 to 300 kHz. A simple equivalent circuit was used to estimate the membrane capacity. 2. The calculated membrane capacities decreased monotonically over the whole frequency range. 3. At 100 kHz and higher frequencies the membrane capacity was independent of potential. 4. At frequencies greater than 20 kHz, exposure of the axons to saturated or 0.9 saturated solutions of n-pentane (275-306 micrometer) reduced the capacity per unit area by 0.1-0.15 micro F cm-2. 5. At 1 kHz the effect of the saturated pentane solutions depended on the membrane potential. In axons having potentials between -60 and zero mV the pentane solutions lowered the capacity, whereas for potentials between -160 and -60 mV they produced little or no change. 6. Saturated solutions of n-hexane, n-heptane and n-octane exhibited qualitatively similar, but quantitatively smaller influences on the membrane capacity, the changes declining as the chain length increased. 7. Under voltage clamp, the peak inward and steady-state outward currents were partially suppressed by the hydrocarbons. Saturated solutions of n-pentane usually reduced the former (reversibly) by 60-80% and the latter by 20-40%. Solutions of n-hexane, n-heptane and n-octane appeared to have successively less effect. Except in deteriorating axons, none of the hydrocarbons produced any consistent changes in the passive membrane resistance, the resting potential or in the reversal potential of the transient inward current. 8. Both the changes in the clamp currents and in the membrane capacity were largely, though not usually completely, reversible. In the hydrocarbon solution the axons deteriorated more rapidly than normal. 9. The responses of axons of Doryteuthis plei to the hydrocarbons were very similar to those of Loligo forbesi with the exception that for the former all observed changes were some five times faster. 10. The time courses of the peak inward and steady-state outward currents on exposure of the axons to n-pentane resembled the time course of the change in membrane capacity at 100 kHz. 11. The simplest interpretation of the high frequency capacity results is suggested to be that, as for lipid bilayers, the membranes become thicker through adsorption of the hydrocarbon.

Haydon, D A; Requena, J; Urban, B W

1980-01-01

150

Effect of electron scavengers to reduce the ionization current of photoexcited N,N,N',N'-tetramethyl-p-phenylenediamine in nonpolar organic liquids  

SciTech Connect

The effects of perfluoro-n-hexane, perfluoro-n-heptane, perfluoromethylcyclohexane, and perfluorodecalin to reduce the ionization current of photoexcited N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) have been studied in the solvents tetramethylsilane, 2,2-dimethylbutane (2,2-DMB), isooctane, cyclohexane, n-hexane, and n-pentane. Results are reported over a range of excitation energies from 5.2 to 6.7 eV and, for selected systems, over a temperature range from -78 to 25/sup 0/C. At quencher concentrations, c/sub q/ less than or equal to 0.2 M, the ratio of the photocurrent without quencher, J/sub 0/, to that with quencher, J, is found to be concave upward, linear, or concave downward in its dependence on c/sub q/, depending on the system studied. At higher c/sub q/, J/sub 0//J is always concave upward. Both J/sub 0/ and J increase to about the same extent as the excitation energy increases, thus maintaining J/sub 0//J constant. As the temperature increases, J increases somewhat more rapidly than does J/sub 0/ and increasingly so the larger is c/sub q/. An attempt is made to explain these results with a model based on interaction of the quencher with an epithermal electron.

Lee, K.; Lipsky, S.

1982-05-27

151

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

NASA Astrophysics Data System (ADS)

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 ?13C "signatures" suggest that C5 alkanes and ?C4 alkenes are most likely derived from vehicle emissions. C3-C5 hydrocarbons show significant enrichment of ?13C with iso-alkanes < n-alkanes < alkenes < alkynes. There is also significant enrichment of ?13C 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 ?13C 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 ?13C 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.

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

2007-08-01

152

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

Microsoft Academic Search

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

H. J. Curran; W. J. Pit; C. K. Westbrook; W. J. Pitz

1996-01-01

153

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

SciTech Connect

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.

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

2000-11-01

154

n-Hexane Biodegradation in Trickle Bed Air Biofilters  

Microsoft Academic Search

While hydrophilic compounds are degraded easily in Trickling bed air biofilters (TBABs), hydrophobic compounds are retarded\\u000a until biological cultures produce a sufficient RNA or enzyme\\/protein to utilize this compound. Hydrophobic compounds are not\\u000a readily bio-available which makes them reluctant to biodegradation as mass transfer between the gas and liquid phases is a\\u000a rate limiting step. To enhance the destruction of

Ashraf Aly Hassan; George A. Sorial

2008-01-01

155

Experimental study of miscibility, density and isobaric vapor-liquid equilibrium values for mixtures of methanol in hydrocarbons (C5, C6)  

Microsoft Academic Search

Isobaric vapor-liquid equilibrium data at 141.3 kPa for the mixtures of methanol with n-pentane and n-hexane are reported. The miscibility of methanol + n-hexane is also measured in order to get the UCSP (upper critical solubility point), then the experimental curves of vE are obtained at temperatures with total miscibility. The equilibrium data are correlated with different equations and the

Ana Maria Blanco; Juan Ortega

1996-01-01

156

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

SciTech Connect

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

Cox, A.; Griffiths, J.F.; Mohamed, C. [Leeds Univ. (United Kingdom). School of Chemistry; Curran, H.; Pitz, W.J.; Westbrook, C.K. [Lawrence Livermore National Lab., CA (United States)

1996-02-01

157

Characteristics of atmospheric non-methane hydrocarbons in Foshan City, China.  

PubMed

Foshan is the most air-polluted city in Pearl River Delta. Non-methane hydrocarbons (NMHCs) were investigated for the first time in Foshan in winter 2008. Ethene, ethane, ethyne, propane, i-pentane, and toluene were the most abundant hydrocarbons and observed to be higher in Foshan than those in many other cities in China. Different from other cities, ethene and ethane were observed to be the two highest compounds in Foshan. Generally, the most abundant hydrocarbons showed high mixing ratios in the morning (0930-1030 hours), decreased to the lowest level in the afternoon (1430-1530 hours), and increased to higher value in the evening (1930-2030 hours). But i-pentane exhibited a different diurnal pattern with the highest level (13.4 ± 5.8 ppbv) in the afternoon, implying the acceleration of solvent evaporation resulting from higher temperature. Correlation coefficients (R(2)?= 66% for n = 6 at 95% confidence level) of the individual hydrocarbons with ethyne and i-pentane indicated vehicular emissions were the main sources of ethene, propene, i-butene, isoprene, benzene and toluene, while gasoline evaporation was responsible for n-pentane, n-hexane, and n-heptane. The good correlation of most of the hydrocarbons with ethyne, indicating vehicular emissions, were the main sources of NMHCs. B/T ratio was 0.36 ± 0.06, implying vehicular emissions acted as the major contributors as well as additional emissions of toluene emitted from solvent usage. According to investigation, it also suggested that LPG leakage was the main source of propane, while NG leakage was responsible for ethane in Foshan City. PMID:21380924

Tan, Jihua; Guo, Songjun; Ma, Yongliang; He, Kebin; Yang, Fumo; Yu, Yongchang; Wang, Jiewen

2011-12-01

158

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

PubMed

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

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

2011-03-01

159

Vapor-liquid equilibria for three aldehyde/hydrocarbon mixtures  

SciTech Connect

Isothermal vapor-liquid equilibrium (VLE) data were measured for the mixtures n-pentane/propionaldehyde, n-heptane/n-butyraldehyde, and isobutyraldehyde/n-heptane at low pressures (100-1000 mmHg) by using a dynamic still. The data reported here are thermodynamically consistent according to the point-to-point consistency test. These data are correlated with five activity coefficient models with parameters estimated from the maximum likelihood method. Also, UNIFAC parameters were estimated for the aldehyde/hydrocarbon functional-group interactions based on the new data.

Eng, R.; Sandler, S.I.

1984-04-01

160

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

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 also with reference to available thermochemical data and relevant literature reports. The effects on both positive and negative APCI spectra due to ion activation via increasing V(cone) are also reported and discussed: several interesting endothermic processes are observed under these conditions. The results provide important information on the role of ionic reactions in non-thermal plasma processes. PMID:15282758

Marotta, Ester; Paradisi, Cristina; Scorrano, Gianfranco

2004-07-01

161

The first overtone of CH stretchings in polymethylene chains: A conformationally dependent spectrum  

NASA Astrophysics Data System (ADS)

The infrared spectra of n-butane, n-pentane, n-heptane and n-hexatriacontane are given in the region 3500-6500 cm -1, corresponding to CH stretching-bending combination transitions (herein called ??= 3/2) and first overtone CH-stretching transitions (gD?= 2). A simple quantum mechanical model derived from that elaborated to explain the 3000 cm -1 Raman spectrum is applied.

Ricard-Lespade, L.; Longhi, G.; Abbate, S.

1990-04-01

162

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

Microsoft Academic Search

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).

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

1990-01-01

163

Modeling of NO sensitization of IC engines surrogate fuels auto-ignition and combustion  

Microsoft Academic Search

This paper presents a new chemical kinetic model developed for the simulation\\u000aof auto-ignition and combustion of engine surrogate fuel mixtures sensitized by\\u000athe presence of NOx. The chemical mechanism is based on the PRF auto-ignition\\u000amodel (n-heptane\\/iso-octane) of Buda et al. [1] and the NO\\/n-butane\\/n-pentane\\u000amodel of Glaude et al. [2]. The later mechanism has been taken as a

Jörg Anderlohr; A. Pires Da Cruz; Roda Bounaceur; F. Battin Leclerc

2009-01-01

164

Synthesis and characterization of fluorinated polyimides for pervaporation of n-heptane\\/thiophene mixtures  

Microsoft Academic Search

Soluble fluoro-polyimides have been synthesized by reacting of a fluorine-containing aromatic dianhydride, 2,2?-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride, with aromatic diamine to yield poly(amic acid)s which were then cyclized to yield polyimide by chemical imidization method. The polyimides have excellent solubility both in strong bipolar solvents, such as NMP and DMAc, and in common organic solvents, such as THF and dioxane, etc. The glass

Lihua Wang; Zhiping Zhao; Jiding Li; Cuixian Chen

2006-01-01

165

N-heptane decomposition in multi-needle to plate electrical discharge  

Microsoft Academic Search

Plasma based technologies are becoming more and more important for destruction of volatile organic compounds in air streams. The most frequent electrical discharges tested for VOC decomposition are corona and dielectric barrier discharge. We proposed [1] multi-hollow needles to plate atmospheric pressure discharge enhanced by the flow of the mixture of air with VOC through the needles. In this case

Stanislav Pekarek; Milan Pospisil

2003-01-01

166

Solubility and diffusion of organic vapors in silicone polymers  

NASA Astrophysics Data System (ADS)

Study of solubility and diffusion of organic vapors in polymer membranes is important for the development of membrane processes for the removal of organic vapors from air for environmental applications. The solubility and absorption/desorption kinetics of seven organic vapors, namely, n-pentane, n-hexane, n-heptane, benzene, cyclohexane, methanol, and 1-propanol in two polymer membranes, i.e. poly(dimethyl siloxane), PDMS, and poly(trifluoropropyl methyl siloxane), PTFPMS, have been studied at 35.0sp°C at different vapor activities. Solubilities of seven vapors in both polymers increase exponentially with increasing vapor activity. S(0) of the nonpolar vapors in PDMS are considerably higher than the corresponding values of these vapors in PTFPMS because of the lower glass-transition temperature, Tsb{g}, and hence the larger mean free volume of the former polymer. S(0) of polar vapors (methanol and propanol) are of similar magnitude for both silicones polymers. The Flory-Huggins equation describes satisfactorily the solubilities of nonpolar penetrant vapors but fails to describe the solubilities of polar vapors in both polymers. However, solubilities of all vapors in both polymers can be represented by either Flory-Rehner equation or modified Flory-Huggins equation. Values of the Flory interaction parameters for seven organic vapors in both polymers decrease with increasing solubility of these vapors. Diffusion coefficients obtained from absorption measurements were corrected for heat and swelling effects caused by the very high solubilities of the penetrant vapors in both polymers. Diffusion coefficients determined from the desorption measurements were corrected only for swelling effects, because the heat effects were negligible under the experimental conditions of this study. Heat-effect corrections were made using theory of Armstrong et al. with pertinent initial and boundary conditions. Corrected mutual diffusion coefficients of nonpolar vapors increase exponentially with increasing vapor concentration. By contrast, diffusion coefficients of polar vapors decrease with increasing concentration because of the clustering. Temperature changes of membrane sample (increase during absorption and decrease during desorption) obtained from measurements and those obtained from heat-effect models are in satisfactory agreement. The magnitude of the heat effects decreases with increasing membrane thickness. The correlation of diffusion coefficients and concentration using Fujita's and Vrentas and Duda's free-volume models must be considered as semiempirical.

Pimsamarn, Jindarat

167

Corona discharge of Titan's troposphere.  

PubMed

The atmosphere of Titan is constantly bombarded by galactic cosmic rays and Saturnian magnetospheric electrons causing the formation of free electrons and primary ions, which are then stabilized by ion cluster formation and charging of aerosols. These charged particles accumulate in drops in cloud regions of the troposphere. Their abundance can substantially increase by friction, fragmentation or collisions during convective activity. Charge separation occurs with help of convection and gravitational settling leading to development of electric fields within the cloud and between the cloud and the ground. Neutralization of these charge particles leads to corona discharges which are characterized by low current densities. These electric discharges could induce a number of chemical reactions in the troposphere and hence it is of interest to explore such effects. We have therefore, experimentally studied the corona discharge of a simulated Titan's atmosphere (10% methane and 2% argon in nitrogen) at 500 Torr and 298 K by GC-FTIR-MS techniques. The main products have been identified as hydrocarbons (ethane, ethyne, ethene, propane, propene + propyne, cyclopropane, butane, 2-methylpropane, 2-methylpropene, n-butene, 2-butene, 2,2-dimethylpropane, 2-methylbutane, 2-methylbutene, n-pentane, 2,2-dimethylbutane, 2-methylpentane, 3-methylpentane, n-hexane, 2,2-dimethylhexane, 2,2-dimethylpentane, 2,2,3-trimethylbutane, 2,3-dimethylpentane and n-heptane), nitriles (hydrogen cyanide, cyanogen, ethanenitrile, propanenitrile, 2-methylpropanenitrile and butanenitrile) and an uncharacterized film deposit. We present their trends of formation as a function of discharge time in an ample interval and have derived their initial yields of formation. These results clearly demonstrate that a complex organic chemistry can be initiated by corona processes in the lower atmosphere. Although photochemistry and charged particle chemistry occurring in the stratosphere can account for many of the observed hydrocarbon species in Titan, the predicted abundance of ethene is to low by a factor of 10 to 40. While some ethene will be produced by charged-particle chemistry, its production by corona processes and subsequent diffusion into the stratosphere appears to be an adequate source. Because little UV penetrates to the lower atmosphere to destroy the molecules formed there, the corona-produced species may be long-lived and contribute significantly to the composition of the lower atmosphere and surface. PMID:11541341

Navarro-Gonzalez, R; Ramirez, S I

1997-01-01

168

Isothermal vapor–liquid equilibria and excess molar volumes for 2-methyl pyrazine (2MP) containing binary mixtures  

Microsoft Academic Search

2-Methyl pyrazine (2MP) has led to significant interest for its industrial and pharmaceutical uses. The new vapor–liquid equilibria (VLE) at 353.15K and excess molar volumes (VE) at 298.15K over the whole mole fraction range for seven binaries (water, n-hexane, cyclohexane, n-heptane, methylcyclopentane (MCP), methylcyclohexane (MCH) and ethyl acetate (EA) with 2MP) have been measured. VLE were measured by using headspace

So-Jin Park; Hyun-Hee Kim; Kyu-Jin Han; Dong-Bok Won; Sang Bong Lee; Myoung-Jae Choi

2001-01-01

169

Volatile organic compounds in the air of Izmir, Turkey  

Microsoft Academic Search

A sampling program was conducted to determine the ambient VOC levels in the city of Izmir, Turkey during daytime and overnight periods between mid-August and mid-September 1998. Sampling sites were selected at high-density traffic roads and junctions far from stationary VOC sources. Samples were analyzed for benzene, toluene, m,p-xylene and o-xylene (BTX), alkylbenzenes (ethylbenzene, 1,3,5-trimethylbenzene, 1,2,4-trimethylbenzene), n-hexane and, n-heptane. Results

Aysen Muezzinoglu; Mustafa Odabasi; Levent Onat

2001-01-01

170

Emulsification of oil in water as affected by different parameters  

Microsoft Academic Search

The aim of this investigation was to develop a basic understanding of the emulsification process by considering simple systems such as n-hexane, n-heptane, n-decane, and kerosene oil in water. The technique employed for the purpose was ultrasonification. The effect of ultrasonification time, chain length, viscosity, surface tension, oil content, and ionic strength of the media on the quality of emulsion

Musa Kaleem Baloch; Gulzar Hameed

2005-01-01

171

Excited state proton transfer reaction of two new intramolecularly hydrogen bonded Schiff bases at room temperature and 77K  

Microsoft Academic Search

Two new orthohydroxy Schiff bases, 7-phenylsalicylidene benzylamine (PSBA) and 7-ethylsalicylideneaniline (ESA) have been synthesized. The excited state intramolecular proton transfer (ESIPT) and the structure of PSBA and ESA in its crystalline form and in the solvents n-hexane, n-heptane and 1,4-dioxane have been investigated by means of absorption, emission and nanosecond spectroscopy at room temperature and 77K. One ground state species

A. Koll; A Filarowski; D Fitzmaurice; E Waghorne; A Mandal; S Mukherjee

2002-01-01

172

Comparison of analytical methods and calibration methods for correction of detector response drift in arrays of carbon black-polymer composite vapor detectors  

Microsoft Academic Search

The responses of 15 carbon black-polymer composite chemiresistors have been analyzed during exposure to eight different analytes (n-hexane, tetrahydrofuran, ethanol, ethyl acetate, cyclohexane, n-heptane, n-octane, and isooctane) in random order at low concentration (0.5% of the vapor pressure of analyte at room temperature) over 4 months (8000 total analyte exposures) of data collection. Data were collected for periods during which

Brian C. Sisk; Nathan S. Lewis

2005-01-01

173

COMBUSTION REACTIONS OF PARAFFIN COMPONENTS IN LIQUID TRANSPORTATION FUELS USING GENERIC RATES  

Microsoft Academic Search

The approach of mechanism generation is the accepted one of assigning generic rates to reactions in the same class. The procedure has been successfully applied to higher paraffins that include detailed sub-models of n-hexane, cyclohexane, n-heptane, n-decane, n-dodecane, and n-hexadecane and semi-detailed sub-models of iso-octane and methyl cyclohexane, in addition to reactions of aromatic formation and oxidation. Comparison between predictions

HONGZHI R. ZHANG; ERIC G. EDDINGS; ADEL F. SAROFIM

2007-01-01

174

Removal of n-hexane by Fusarium solani with a gas-phase biofilter.  

PubMed

A gas-phase biofilter inoculated with the fungus Fusarium solani, isolated from a consortium grown on hexane vapors, was used to degrade this compound. The biofilter, packed with perlite and operated with an empty bed residence time of 60 s, was supplied with hexane concentrations between 0.5 gm(-3) and 11 gm(-3). Biofilter performance was evaluated over 100 days of operation. Several strategies for supplying the nutritive mineral medium were assayed to maintain favorable conditions for the fungal growth and activity. The Fusarium system was able to sustain an average elimination capacity of 90 gm(-3)(reactor) h(-1) with a maximum of 130 gm(-3)(reactor) h(-1) . The mass transfer limitations due to high biomass development in the biofilter were confirmed in batch experiments. Bacterial contamination was observed, but experiments in the biofilter and in batch reactors using selective inhibitors and controlled pH confirmed the predominant role of the fungus. Results indicate that fungal biofilters can be an effective alternative to conventional abatement technologies for treating hydrophobic compounds. PMID:15933872

Arriaga, Sonia; Revah, Sergio

2005-12-01

175

Estimated MP2 and CCSD(T) interaction energies of n-alkane dimers at the basis set limit: Comparison of the methods of Helgaker et al. and Feller  

NASA Astrophysics Data System (ADS)

The MP2 (the second-order Møller-Plesset calculation) and CCSD(T) (coupled cluster calculation with single and double substitutions with noniterative triple excitations) interaction energies of all-trans n-alkane dimers were calculated using Dunning's [J. Chem. Phys. 90, 1007 (1989)] correlation consistent basis sets. The estimated MP2 interaction energies of methane, ethane, and propane dimers at the basis set limit [EMP2(limit)] by the method of Helgaker et al. [J. Chem. Phys. 106, 9639 (1997)] from the MP2/aug-cc-pVXZ (X=D and T) level interaction energies are very close to those estimated from the MP2/aug-cc-pVXZ (X=T and Q) level interaction energies. The estimated EMP2(limit) values of n-butane to n-heptane dimers from the MP2/cc-pVXZ (X=D and T) level interaction energies are very close to those from the MP2/aug-cc-pVXZ (X=D and T) ones. The EMP2(limit) values estimated by Feller's [J. Chem. Phys. 96, 6104 (1992)] method from the MP2/cc-pVXZ (X=D, T, and Q) level interaction energies are close to those estimated by the method of Helgaker et al. from the MP2/cc-pVXZ (X=T and Q) ones. The estimated EMP2(limit) values by the method of Helgaker et al. using the aug-cc-pVXZ (X=D and T) are close to these values. The estimated EMP2(limit) of the methane, ethane, propane, n-butane, n-pentane, n-hexane, n-heptane, n-octane, n-nonane, and n-decane dimers by the method of Helgaker et al. are -0.48, -1.35, -2.08, -2.97, -3.92, -4.91, -5.96, -6.68, -7.75, and -8.75 kcal/mol, respectively. Effects of electron correlation beyond MP2 are not large. The estimated CCSD(T) interaction energies of the methane, ethane, propane, and n-butane dimers at the basis set limit by the method of Helgaker et al. (-0.41, -1.22, -1.87, and -2.74 kcal/mol, respectively) from the CCSD(T)/cc-pVXZ (X=D and T) level interaction energies are close to the EMP2(limit) obtained using the same basis sets. The estimated EMP2(limit) values of the ten dimers were fitted to the form m0+m1X (X is 1 for methane, 2 for ethane, etc.). The obtained m0 and m1 (0.595 and -0.926 kcal/mol) show that the interactions between long n-alkane chains are significant. Analysis of basis set effects shows that cc-pVXZ (X=T, Q, or 5), aug-cc-pVXZ (X=D, T, Q, or 5) basis set, or 6-311G** basis set augmented with diffuse polarization function is necessary for quantitative evaluation of the interaction energies between n-alkane chains.

Tsuzuki, Seiji; Honda, Kazumasa; Uchimaru, Tadafumi; Mikami, Masuhiro

2006-03-01

176

Estimated MP2 and CCSD(T) interaction energies of n-alkane dimers at the basis set limit: comparison of the methods of Helgaker et al. and Feller.  

PubMed

The MP2 (the second-order Møller-Plesset calculation) and CCSD(T) (coupled cluster calculation with single and double substitutions with noniterative triple excitations) interaction energies of all-trans n-alkane dimers were calculated using Dunning's [J. Chem. Phys. 90, 1007 (1989)] correlation consistent basis sets. The estimated MP2 interaction energies of methane, ethane, and propane dimers at the basis set limit [EMP2(limit)] by the method of Helgaker et al. [J. Chem. Phys. 106, 9639 (1997)] from the MP2/aug-cc-pVXZ (X=D and T) level interaction energies are very close to those estimated from the MP2/aug-cc-pVXZ (X=T and Q) level interaction energies. The estimated EMP2(limit) values of n-butane to n-heptane dimers from the MP2/cc-pVXZ (X=D and T) level interaction energies are very close to those from the MP2/aug-cc-pVXZ (X=D and T) ones. The EMP2(limit) values estimated by Feller's [J. Chem. Phys. 96, 6104 (1992)] method from the MP2/cc-pVXZ (X=D, T, and Q) level interaction energies are close to those estimated by the method of Helgaker et al. from the MP2/cc-pVXZ (X=T and Q) ones. The estimated EMP2(limit) values by the method of Helgaker et al. using the aug-cc-pVXZ (X=D and T) are close to these values. The estimated EMP2(limit) of the methane, ethane, propane, n-butane, n-pentane, n-hexane, n-heptane, n-octane, n-nonane, and n-decane dimers by the method of Helgaker et al. are -0.48, -1.35, -2.08, -2.97, -3.92, -4.91, -5.96, -6.68, -7.75, and -8.75 kcal/mol, respectively. Effects of electron correlation beyond MP2 are not large. The estimated CCSD(T) interaction energies of the methane, ethane, propane, and n-butane dimers at the basis set limit by the method of Helgaker et al. (-0.41, -1.22, -1.87, and -2.74 kcal/mol, respectively) from the CCSD(T)/cc-pVXZ (X=D and T) level interaction energies are close to the EMP2(limit) obtained using the same basis sets. The estimated EMP2(limit) values of the ten dimers were fitted to the form m0+m1X (X is 1 for methane, 2 for ethane, etc.). The obtained m0 and m1 (0.595 and -0.926 kcal/mol) show that the interactions between long n-alkane chains are significant. Analysis of basis set effects shows that cc-pVXZ (X=T, Q, or 5), aug-cc-pVXZ (X=D, T, Q, or 5) basis set, or 6-311G** basis set augmented with diffuse polarization function is necessary for quantitative evaluation of the interaction energies between n-alkane chains. PMID:16555885

Tsuzuki, Seiji; Honda, Kazumasa; Uchimaru, Tadafumi; Mikami, Masuhiro

2006-03-21

177

Biochemistry of Short-Chain Alkanes (Tissue-Specific Biosynthesis of n-Heptane in Pinus jeffreyi).  

PubMed Central

Short-chain (C7-C11) alkanes accumulate as the volatile component of oleoresin (pitch) in several pine species native to western North America. To establish the tissue most amenable for use in detailed studies of short-chain alkane biosynthesis, we examined the tissue specificity of alkane accumulation and biosynthesis in Pinus jeffreyi Grev. & Balf. Short-chain alkane accumulation was highly tissue specific in both 2-year-old saplings and mature trees; heart-wood xylem accumulated alkanes up to 7.1 mg g-1 dry weight, whereas needles and other young green tissue contained oleoresin with monoterpenoid, rather than paraffinic, volatiles. These tissue-specific differences in oleoresin composition appear to be a result of tissue-specific rates of alkane and monoterpene biosynthesis; incubation of xylem tissue with [14C]sucrose resulted in accumulation of radiolabel in alkanes but not monoterpenes, whereas incubation of foliar tissue with 14CO2 resulted in the accumulation of radiolabel in monoterpenes but not alkanes. Furthermore, incubation of xylem sections with [14C]acetate resulted in incorporation of radiolabel into alkanes at rates up to 1.7 nmol h-1 g-1 fresh weight, a rate that exceeds most biosynthetic rates reported with other plant systems for the incorporation of this basic precursor into natural products. This suggests that P. jeffreyi may provide a suitable model for elucidating the enzymology and molecular biology of short-chain alkane biosynthesis.

Savage, T. J.; Hamilton, B. S.; Croteau, R.

1996-01-01

178

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

Microsoft Academic Search

Molecular dynamics (MD) simulations were performed to determine the self-diffusivity (Di,self) and the Maxwell–Stefan diffusivity (?i) 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 (?i(0)) is consistently lower, by up to a factor of

R. Krishna; Baten van J. M

2011-01-01

179

Rapid determination of the synthetic pyrethroid insecticide, deltamethrin, in rat plasma and tissues by HPLC  

Microsoft Academic Search

Deltamethrin (DLM), [(S)-?-cyano-d-phenoxybenzyl-(1R,3R)-e-(2,2 dibromovinyl)-2,2-dimethylcyclo-propane-1-carboxylate], is a pyrethroid insecticide widely used in agriculture and households. There are several methods for analysis of DLM in biological fluids and tissues, but these methods are time consuming. They generally involve the extraction of DLM with lipid-soluble solvents such as n-pentane, n-hexane, diethylether or acetone, and subsequent evaporation of the solvent. A more rapid and

Kyu Bong Kim; Michael G. Bartlett; Sathanandam S. Anand; James V. Bruckner; Hyo Jung Kim

2006-01-01

180

Total cross section of electron scattering by fluorocarbon molecules  

NASA Astrophysics Data System (ADS)

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.

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

2008-12-01

181

Adsorption of vapors of argon, nitrogen, n-hexane, and benzene on boron nitride and molybdenum sulfide  

Microsoft Academic Search

1.The values of the adsorption of argon vapor per unit surface of adsorbents of different kinds differ sharply, since in this case only electrokinetic (dispersion) interactions are manifested, which depend basically upon the concentration, dimensions, and polarizability of the atoms on the surface of the adsorbent. The values of the adsorption of nitrogen vapor on adsorbents of different kinds are

L. D. Belyakova; A. V. Kiselev

1966-01-01

182

Aromatization of n-hexane by platinum-containing molecular sieves. 1. Catalyst preparation by the vapor phase impregnation method  

Microsoft Academic Search

A vapor phase impregnation method with Pt(acac)â has been developed and used to load Pt into aluminosilicate (KL, BaKL, NaY, CsNaY, cubic and hexagonal polytypes of faujasite, ZSM-12, and SSZ-24) and aluminophosphate (AlPOâ-5 and VPI-5) molecular sieves. Pt-containing molecular sieves are characterized by XRD,TPD, elemental analysis, ¹³C MAS NMR, TEM, and Hâ chemisorption. ¹³C MAS NMR, TEM, and Hâ chemisorption

Suk Bong Hong; E. Mielczarski; M. E. Davis

1992-01-01

183

Monte Carlo simulations of vapor–liquid–liquid equilibrium of some ternary petrochemical mixtures  

Microsoft Academic Search

The aim of this study was to determine the capability and accuracy of Monte Carlo simulations to predict ternary vapor–liquid–liquid equilibrium (VLLE) for some industrial systems. Hence, Gibbs ensemble Monte Carlo simulations in the isobaric–isothermal (NpT) and isochoric–isothermal (NVT) ensembles were performed to determine vapor–liquid–liquid equilibrium state points for three ternary petrochemical mixtures: methane\\/n-heptane\\/water (1), n-butane\\/1-butene\\/water (2) and n-hexane\\/ethanol\\/water (3).

Suren Moodley; Kim Bolton; Deresh Ramjugernath

2010-01-01

184

On the use of two-photon absorption for determination of femtosecond pump probe cross-correlation functions  

NASA Astrophysics Data System (ADS)

We have investigated the applicability of two-photon absorption signals ( h?pump+ h?probe) in common solvents for determination of the pump-probe cross-correlation function in transient absorption experiments. Ten different solvents, including water, lower alcohols, n-hexane, n-heptane, acetonitrile, dichloromethane, chloroform and tetrachloromethane, were studied with UV excitation and UV-visible probe pulses. We report on how the signals are influenced by the relative polarization of the pump and probe beams, the excitation intensity and the detection bandwidth. Other contributions to the signals are also discussed.

Rasmusson, Marcus; Tarnovsky, Alexander N.; Åkesson, Eva; Sundström, Villy

2001-02-01

185

Pressure dependence of the density of n-alkanes  

SciTech Connect

Accurate density data for n-alkanes are essential for the measurement of interfacial tension of liquid-liquid systems as a function of pressure. The variation of density with pressure for three n-alkanes, n-hexane, n-heptane, and n-decane, was measured at 21.2[degrees]C and pressures ranging from 0.1 to 35 MPa with a digital density meter. The Tait equation of the form ([rho] [minus] [rho][sub 0])/[rho] = C log[(B + P)/(B + P[sub 0])] was used to represent the experimental data. 20 refs., 2 figs., 4 tabs.

Susnar, S.S.; Budziak, C.J.; Neumann, A.W. (Univ. of Toronto, Ontario (Canada)); Hamza, H.A. (CANMET, Devon, Alberta (Canada))

1992-05-01

186

Cavitation, primary break-up and flash boiling of gasoline, iso-octane and n-pentane with a real-size optical direct-injection nozzle  

Microsoft Academic Search

Improvements to the direct-injection spark-ignition combustion system are necessary if the potential reductions in fuel consumption and emissions are to be fully realized in the near future. One critical link in the optimization process is the design and performance of the injectors used for fuel atomization. Multi-hole injectors have become the state-of-the-art choice for gasoline direct-injection engines due to their

J. Serras-Pereira; Z. van Romunde; P. G. Aleiferis; D. Richardson; S. Wallace; R. F. Cracknell

2010-01-01

187

Fuel property effects on engine combustion processes. Final report  

SciTech Connect

A major obstacle to improving spark ignition engine efficiency is the limitations on compression ratio imposed by tendency of hydrocarbon fuels to knock (autoignite). A research program investigated the knock problem in spark ignition engines. Objective was to understand low and intermediate temperature chemistry of combustion processes relevant to autoignition and knock and to determine fuel property effects. Experiments were conducted in an optically and physically accessible research engine, static reactor, and an atmospheric pressure flow reactor (APFR). Chemical kinetic models were developed for prediction of species evolution and autoignition behavior. The work provided insight into low and intermediate temperature chemistry prior to autoignition of n-butane, iso-butane, n-pentane, 1-pentene, n-heptane, iso-octane and some binary blends. Study of effects of ethers (MTBE, ETBE, TAME and DIPE ) and alcohols (methanol and ethanol) on the oxidation and autoignition of primary reference fuel (PRF) blends.

Cernansky, N.P.; Miller, D.L.

1995-04-27

188

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

NASA Technical Reports Server (NTRS)

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.

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

1975-01-01

189

Dynamics of pyrenesemicarbazide and pyrenethiosemicarbazide in reverse micelle of AOT in n-heptane: Probing critical penetration of water molecules toward the palisade  

NASA Astrophysics Data System (ADS)

In the present work, we have introduced two similar probe molecules with pyrene tags that can reside in different positions in the reverse micelles and show opposite dynamism on excitation. Herein, we have changed the concentration of water in the reverse micellar core gradually and monitored the spectrochemical changes in the dynamism of the two designed probe molecules. The results indicate that water molecules penetrate through the interface of the reverse micelles up a certain critical amount.

Maity, Arnab; Das, Shrabanti; Ghosh, Prasun; Das, Tarasankar; Seth, Sourav Kanti; Mondal, Somen; Gupta, Parna; Purkayastha, Pradipta

2013-11-01

190

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

Microsoft Academic Search

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 andn-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-livedortho-Ps component,I3,

Subir Kumar Das; B. Nandi Ganguly

1997-01-01

191

Characterizing the cyclic variability of ignition timing in a homogeneous charge compression ignition engine fuelled with n-heptane\\/iso-octane blend fuels  

Microsoft Academic Search

The cyclic variations of homogeneous charge compression ignition (HCCI) ignition timing is studied for a range of charge properties by varying the equivalence ratio, intake temperature, intake pressure, exhaust gas recirculation (EGR) rate, engine speed, and coolant temperature. Characterization of cyclic variations of ignition timing in HCCI at over 430 operating points on two single-cylinder engines for five different blends

M Shahbakhti; C R Koch

2008-01-01

192

Kinetic inhibitor effects on methane\\/propane clathrate hydrate-crystal growth at the gas\\/water and water\\/ n-heptane interfaces  

Microsoft Academic Search

The influence of the kinetic inhibitor poly(N-vinylpyrrolidone) or PVP on hydrate methane\\/propane hydrate formation was studied in pre-saturated liquid water with and without the presence of heptane under different undercooling conditions. It was found that when the inhibitor concentration was 0.1wt%, hydrate formation started as a film at the gas\\/water interface similar to the crystal behavior without inhibitor. When the

Rajnish Kumar; Ju Dong Lee; Myungho Song; Peter Englezos

2008-01-01

193

Glucose transport and its inhibition by short-chain n-alkanes in Cladosporium resinae.  

PubMed Central

Glucose transport in Cladosporium resinae was studies with the aid of the non-metabolizable glucose analogue 3-O-methyl-D-glucose (3-O-MG). 3-O-MG, transported as a free sugar without phosphorylation, was found to inhibit glucose uptake competitively. Conversely, glucose was a competitive inhibitor of 3-O-MG uptake. Moreover, both glucose and 3-O-MG were able to bring about rapid counterflow intracellular 3-O-MG. Thus, glucose and 3-O-MG share the same entry and exit systems. The transport of 3-O-MG is carrier mediated and energy dependent as shown by saturation kinetics, strong temperature dependence, accumulation of unaltered 3-O-MG against a concentration gradient, and inhibition of uptake by NaN3, NaCN, and 2,4-dinitrophenol. The glucose transport system appeared to be constitutive for glucose transport in cells grown on fructose, galactose, mannose, xylose, or glucose. There was no derepressible low-Km glucose transport system in C. resinae. n-Hexane and n-heptane were found to inhibit 3-O-MG uptake rapidly at temperatures above 20 C. Over 50% inhibition of the uptake rate occurred after only 10 min of incubation with n-hexane at 30 C. The percentage of inhibition in the presence of n-hexane, compared to controls in the absence of n-hexane, was found to increase with increasing temperature. Longer-chain n-alkanes (C8 to C18) had no significant effect on uptake. The efflux of intracellular 3-O-MG, which appeared to occur by facilitated diffusion, was not affected by any of the n-alkanes tested including n-hexane.

Teh, J S

1975-01-01

194

Applications of the Soave-Redlich-Kwong Equations of State Using Mathematic  

NASA Astrophysics Data System (ADS)

The application of the Peng-Robinson equations of state (PR EOS) using Matlab and Mathematic has already been demonstrated. In this paper, using Mathematic to solve Soave-Redlich-Kwong (SRK) EOS, as well as the estimation of pure component properties, plotting of vapor-liquid equilibrium (VLE) diagram and calculation of chemical equilibrium, is presented. First the SRK EOS is used to predict several pure-component properties, such as liquid and gas molar volumes for isobutane. The vapor-liquid isobaric diagram is then plotted for a binary mixture composed of n-pentane and n-hexane under the pressures of 2*10^5 and 8*10^5 Pa respectively.

Sun, Lanyi; Zhai, Cheng; Zhang, Hui

195

Effects on sorption and diffusion in PTMSP and TMSP/TMSE copolymers of free volume changes due to polymer ageing  

NASA Astrophysics Data System (ADS)

Solubility isotherms for n-pentane and n-hexane were measured in pure poly[1-(trimethylsilyl)-1-propyne] (PTMSP) and in 1-trimethylsilyl-1-propyne/1-trimethylsilyl-1- n-hexyne 70/30 copolymer, using freshly prepared samples as well as aged films, at different temperatures. The experimental values of penetrant diffusivity, mobility and heat of mixing have been reported and discussed, based on direct positron annihilation lifetime spectroscopy information, Dual Mode Sorption Model and Non-Equilibrium Lattice Fluid model. The ageing effect is more pronounced in PTMSP, where it leads to a significant solubility and diffusivity reduction, than in the copolymer where the effect is less important. In the activity range inspected the diffusion coefficient and the heat of mixing are almost concentration independent for PTMSP, while they increase appreciably with concentration in the copolymer, as an effect of the great difference in the free volume present in the two matrices.

Baschetti, M. Giacinti; Ghisellini, M.; Quinzi, M.; Doghieri, F.; Stagnaro, P.; Costa, G.; Sarti, G. C.

2005-04-01

196

Adsorption and reaction behavior of perfluoro-n-alkanes on Al{sub 2}O{sub 3}  

SciTech Connect

The adsorption of perfluoro-n-pentane and perfluoro-n-hexane on {gamma}-Al{sub 2}O{sub 3} at the solid/vapor interface has been studied by infrared spectroscopy and temperature-programmed desorption (TPD). At ambient beam temperature perfluorocarbons are adsorbed as intact, unchanged molecules and undergo chemical transformations leading to the formation of adsorbed, unsaturated carboxylate species. With increasing temperature further reactions occur, finally resulting in deep oxidation of all adsorbed species (indicated by desorption of CO and CO{sub 2}). These reactions are initiated by the formation of coordination bonds between perfluorocarbons and Lewis-acidic surface sites (coordinatively unsaturated cations) of Al{sub 2}O{sub 3}, followed by abstraction of fluorine from the adsorbed molecules.

Sokoll, R.; Tiller, H.J. [Friedrich-Schiller-Univ. Jena (Germany). Inst. fuer Physikalische Chemie] [Friedrich-Schiller-Univ. Jena (Germany). Inst. fuer Physikalische Chemie

1998-09-15

197

Vacuum ultraviolet absorption spectra of aromatic molecules in solution  

SciTech Connect

The absorption spectra of benzene, naphthalene, azulene, N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD), pyrene, and fluoroanthene were measured in liquid perfluoro-n-hexane (PFn-H) in the range 35,000 to 65,000 cm/sup -1/ and in liquid n-pentane (n-Pt) in the range 35,000 to 59,000 cm/sup -1/, using a 150-..mu..m-thick cell. The absorption spectra in PFn-H show more structure than those in n-Pt and because they are extended in the Rydberg transition region may be used to separate Rydberg from core transitions in the gaseous spectra of the molecules studied. The transmission spectra for PFn-H, n-Pt, and some of the most commonly used hydrocarbon solvents are presented also. 5 figures, 6 tables.

Kourouklis, G.A.; Siomos, K.; Christophorou, L.G.

1982-01-01

198

Photoconductivity induced by single-proton excitation of aromatic molecules in liquid hydrocarbons  

SciTech Connect

The spectral dependence of the photoconductivity of several aromatic solutes (anthracene, 1,2-benzanthracene, perylene, pyrene, azulene, ..cap alpha..-methylnaphthalene, and triphenylamine) in liquid hydrocarbon solvents (neopentane, 2,2,4-trimethylpentane(2,2,4-TMP), 2,2,4,4-tetramethylpentane (2,2,4,4-TMP), and n-pentane) are reported. In liquids which exhibit high thermal electron mobilities, relative maxima or shoulders are detected in the photoconductivity spectra. The corresponding transitions are thought to involve the formation of Rydberg states as precursors of separated charges. For anthracene and azulene, the transitions occur at approximately the same energy where Rydberg lines are observed in the gas phase. Quenching of the photoconductivity by perfluoromethylcyclohexane and by perfluoro-n-hexane supports this hypothesis.

Holroyd, R.A.; Preses, J.M.; Boettcher, E.H.; Schmidt, W.F.

1984-02-16

199

Explosion pressures of hydrocarbon-air mixtures in closed vessels.  

PubMed

An experimental study on pressure evolution during closed vessel explosions of several gaseous fuel-air mixtures was performed, at various initial pressures within 0.3-1.2 bar and ambient initial temperature. Explosion pressures and explosion times are reported for methane-, n-pentane-, n-hexane-, propene-, butene-, butadiene-, cyclohexane- and benzene-air mixtures. The explosion pressures measured in a spherical vessel (Phi=10 cm) and in three cylindrical vessels with different diameter/height ratios are examined in comparison with the adiabatic explosion pressures, computed by assuming chemical equilibrium within the flame front. The influence of initial pressure, fuel concentration and heat losses during propagation (determined by the size and shape of the explosion vessel and by the position of the ignition source) on explosion pressures and explosion times are discussed for some of the examined systems. PMID:16386834

Razus, Domnina; Movileanu, Codina; Brinzea, Venera; Oancea, D

2006-07-31

200

The viscosity of five liquid hydrocarbons at pressures up to 250 MPa  

SciTech Connect

This paper reports new measurements of the viscosity of toluene, n-pentane, n-hexane, n-octane, and n-decane at pressures up to 250 MPa in the temperature range 303 to 348 K. The measurements were performed with a vibrating-wire viscometer and with a relative method of evaluation. Calibration of the instrument was carried out with respect to reference values of the viscosity of the same liquids at their saturation vapour pressure. The viscosity measurements have a precision of [+-] 0.1% but the accuracy is limited by that of the calibration data to be [+-] 0.5%. The experimental data have been represented by polynomial functions of pressure for the purposes of interpolation. The data are also used as the most precise test yet applied to a representation of the viscosity of liquids based upon hard-sphere theory. 23 refs., 6 figs., 7 tabs.

Oliveira, C.M.B.P.; Wakeham, W.A. (Imperial College, London (United Kingdom))

1992-09-01

201

Thermodiffusion in ternary hydrocarbon mixtures. Part 1: n-dodecane/isobutylbenzene/tetralin  

NASA Astrophysics Data System (ADS)

Experiments are to be performed on board the ISS to understand the thermodiffusion behavior in ternary hydrocarbon mixtures of n-dodecane/isobutylbenzene/tetralin. This will be followed by additional experiments with these components as well as mixtures of n-hexane/n-heptane/n-dodecane and n-decane/isobutylbenzene/tetralin. For these additional experiments, the temperature of the mixture is yet to be determined. In a three part series, by applying the theory in the literature, thermodiffusion coefficients of all these mixtures have been determined. The predictions have been made using the thermodiffusion model of Firoozabadi as well as two correlations from the literature. In this first part, thermodiffusion coefficients of twelve mixtures of n-dodecane/isobutylbenzene/tetralin have been estimated. From the results it is proposed that the future experiments be performed at 318 K and 1 atm. Certain mixtures have also been identified as important experiments due to conflicting predictions by the theoretical methods.

Srinivasan, Seshasai; Saghir, M. Ziad

2011-09-01

202

Solvent effect on the charge-transfer complexes of chloranil with mesitylene and benzene  

NASA Astrophysics Data System (ADS)

The thermodynamic and spectrophotometric properties of the charge-transfer (CT) complexes of chloranil with mesitylene and benzene have been studied in different solvents such as n-hexane, cyclohexane, n-heptane, carbon tetrachloride, chloroform, dichloromethane and in addition, the properties of the former complex have been studied in benzene. The results show that the oscillator strengths ( f) of the CT absorption bands of these complexes in different solvents increase with the heats of formation (- ? H°). The role of the solvent in changing both thermodynamic as well as spectrophotometric properties of these complexes is assumed to be due to the solvent interaction with chloranil. An attempt has been made to calculate the thermodynamic and spectrophotometric properties of the solvent—chloranil interaction. Moreover, the CT absorption band positions of chloranil complexes with mesitylene and benzene in the gas phase have been determined from the corresponding values in different solvents.

Bhowmik, Benoy B.; Bhattacharyya, Amar

203

Vapor-liquid equilibrium constants at infinite dilution determined by a gas stripping method: ethane, propane, n-butane, n-pentane in the methane-n-decane system  

SciTech Connect

A new apparatus to measure partition coefficients Kinfinity /SUB s/ at infinite dilution up to 200 10/sup 5/ Pa and 423 K is described. Measurements of the systems: (1) methane-ethane-n-decane and methane-propane-n-decane at 294.25 K; and (2) methane-n-butane-n-decane at 344.25 K illustrate the reproducibility and good agreement with literature data. In addition, new data were obtained for the system methane-npentane-n-decane at 344.25 K up to 101 10/sup 5/ Pa.

Legret, D.; Desteve, J.; Renon, H.; Richon, D.

1983-01-01

204

Determination of descriptors for organosilicon compounds by gas chromatography and non-aqueous liquid-liquid partitioning.  

PubMed

Measurements of retention factors by gas chromatography on up to 10 complementary stationary phases at up to 5 temperatures for each stationary phase and liquid-liquid partition coefficients in three biphasic organic solvent systems (n-hexane-acetonitrile, n-heptane-N,N-dimethylformamide and n-heptane-2,2,2-trifluoroethanol) were used to estimate solute descriptors for 54 organosilicon compounds for use in the solvation parameter model. Many of the E descriptor values (electron lone pair interactions) are negative for simple siloxanes and silanes indicating that these compound bind electron lone pairs more tightly than n-alkanes. Silanes and siloxanes with alkyl groups have near zero dipolarity/polarizability (S descriptor). The S descriptor is only modest for simple phenylsilanes, silazanes, silanols, orthosilicates, and alkoxides. All organosilicon compounds with silicon-oxygen bonds are reasonably strong hydrogen-bond bases (B descriptor) but only the silanol group is a reasonably strong hydrogen-bond acid (A descriptor). Silanes (SiH) and silazanes (SiNHSi) are weak hydrogen-bond acids. Cavity formation and dispersion interactions (V or L descriptor) are often the main component of solvation models for siloxanes and silanes that have simple alkyl and aromatic substituents. A number of physicochemical properties (vapor pressure, aqueous solubility, biphasic partition coefficients, sorption coefficients, etc.) for linear and cyclic dimethylsiloxanes can be reliably predicted from their descriptors in established models for organic compounds. PMID:17888932

Ahmed, Hamid; Poole, Colin F; Kozerski, Gary E

2007-10-26

205

Determination of descriptors for semivolatile organosilicon compounds by gas chromatography and non-aqueous liquid-liquid partition.  

PubMed

The measurement of retention factors by gas chromatography on up to 15 stationary phases at several temperatures in the range 60-240 degrees C for each stationary phase and liquid-liquid partition coefficients in three biphasic organic solvent systems (n-hexane-acetonitrile, n-heptane-N,N-dimethylformamide, and n-heptane-2,2,2-trifluoroethanol) were used to calculate solute descriptors for 28 semivolatile linear and cyclic organosilicon compounds for use in the solvation parameter model. Regression analysis for oligomeric compounds allowed the descriptor values for the dimethylsiloxane, diethylsiloxane, methylvinylsiloxane, and methylhydrosiloxane monomer groups to be estimated. These monomer groups contribute significantly to the hydrogen-bond basicity (B descriptor) and cavity formation and dispersion interactions (L and V descriptors) of oligomeric organosilicon compounds, are non-hydrogen-bond acidic (A descriptor=0), are slightly less dipolar/polarizable than an n-alkane (S descriptors are negative and close to zero), and bind electron lone pairs more tightly than an n-alkane (E descriptor is small and negative). The semivolatile organosilicon compounds with polar functional groups in their side chain demonstrate a much wider range of selective intermolecular interactions than alkylsiloxanes and have solvation properties closer to those of polar organic compounds. PMID:19766233

Atapattu, Sanka N; Poole, Colin F

2009-11-01

206

2,5-Hexandion und Pyrrole im Urin des Menschen: Analytische Bestimmung und Untersuchung der Ausscheidung nach Exposition gegen n-Hexan. (2,5-hexandione and pyrroles in human urine: Analytical determination and examination of excretion after exposure to n-hexane).  

National Technical Information Service (NTIS)

Biological monitoring of persons exposed to hexane used to rely on the concentration level of 2,5-hexanedione (HDO) in urine after acid hydrolysis (total HDO). However, severely acidic conditions (<1pH) cause 4,5-dihydroxy-2-hexanon, another hexane metabo...

W. G. Dietz

1994-01-01

207

The Measurement of Laminar Burning Velocities and Markstein Numbers for Iso-octane–Air and Iso-octane–n-Heptane–Air Mixtures at Elevated Temperatures and Pressures in an Explosion Bomb  

Microsoft Academic Search

Spherically expanding flames have been employed to measure flame speeds, from which have been derived corresponding laminar burning velocities at zero stretch rate. Two burning velocities are defined, one based upon the rate of propagation of the flame front, the other on the rate of formation of burned gas. To express the effects of flame stretch upon burning velocity, Markstein

D. Bradley; R. A. Hicks; M. Lawes; C. G. W. Sheppard; R. Woolley

1998-01-01

208

Fuel droplet burning rates at high pressures.  

NASA Technical Reports Server (NTRS)

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.

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

1973-01-01

209

Characterization of de-emulsification capabilities of a Micrococcus species.  

PubMed

Effect of post harvest washing as well as cell concentration on de-emulsification characteristics of an isolated Micrococcus species has been tested with Tween 60 Span 60 stabilised oil in water (o/w) and L-92 pluronic surfactant stabilised water in oil (w/o) model emulsions (kerosene water). The cells used were 140 h old and grown under submerged conditions at 37 degrees C in a medium containing n-tetradecane (4% v/v) as the carbon source. The harvested bacterial cells when in an unwashed condition (at a cell concentration of 2 mg/ml of emulsion) were found to de-emulsify the o/w system at a much faster rate than the w/o system exhibiting half-life values for the respective system as 10.2 and 127.7 h. Post harvest washing of the cells with any lipid solubilising solvent (n-pentane, n-hexane, kerosene, chloroform-methanol-water (CMW)) yielded a decrease in their de-emulsification power for w/o emulsion. But the decay of o/w emulsion became faster with n-pentane- and kerosene-washed cells as evident from their corresponding half-life values of 3.3 and 4.6 h. Compared to the w/o system, an increase in the concentration of kerosene-washed cell had a direct effect on de-emulsification for the o/w system. For cell concentrations of 2, 3 and 4 mg/ml of the emulsion, the half-life values for the w/o system were 364.8, 442.0 and 454.9 h, respectively. For 2 and 4 mg/ml cell contents, the half-life values for the o/w system were 4.6 and 1.0 h. The decay of both the emulsions was very slow or even incomplete for cell concentrations less than 2 mg/ml. De-emulsifying capacity of the n-tetradecane grown Micrococcus species towards o/w model emulsion improved considerably after washing the cells with n-pentane and kerosene, and use of kerosene-washed cells (4 mg/ml) reduced the half-life to 1 h. PMID:11396902

Das, M

2001-08-01

210

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

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.

Agnew, S.F.; Swanson, B.I. (Los Alamos National Lab., NM (USA))

1990-01-25

211

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)  

Microsoft Academic Search

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

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

2008-01-01

212

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)

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.

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

2008-12-01

213

Adsorption structures of non-aromatic hydrocarbons on silicalite-1 using the single-crystal X-ray diffraction method.  

PubMed

The actual adsorption structures of non-aromatic hydrocarbons on the MFI-type zeolites have not yet been determined. This is due to the presence of twinning, which makes crystallographic analysis difficult. We recently overcame this problem, and now report the various adsorption structures of n-butane, n-pentane, n-hexane, 1-butene, cis and trans-2-butene, 2-butyne and isopentane on silicalite-1 (MFI-type zeolite) as determined via single-crystal X-ray diffraction. The structures were elucidated for both low and high loadings of each guest molecule in order to clarify the adsorption process. The low-loaded structures provide valuable insight into guest-framework interactions and initial adsorption behavior. The n-alkanes are initially adsorbed in the sinusoidal channel, while 2-butyne is adsorbed in the straight channel. In the case of the normal hydrocarbons, the molecular configuration (bent or linear) of the compound determines which channel is the preferred adsorption site. Bent molecules prefer the sinusoidal channel and linear molecules prefer the straight channel. In contrast, isopentane is initially adsorbed at the intersection, since the channels are too narrow to maintain the preferred distance between the framework and the bulky isopentane molecule. In the high-loaded structures, the guest molecules occupy additional sites, such that the normal hydrocarbons are located in both channels and isopentane is found at the intersection and the sinusoidal channel. PMID:24954128

Fujiyama, Shinjiro; Seino, Shintaro; Kamiya, Natsumi; Nishi, Koji; Yoza, Kenji; Yokomori, Yoshinobu

2014-07-01

214

Verification of diffusive and pumped samplers for volatile organic compounds using a controlled atmosphere test facility  

NASA Astrophysics Data System (ADS)

There is a requirement to verify the performance of sorbent-based passive or active samplers and to extend their use, where possible, to monitor volatile organic compounds (VOCs) that are known to be photochemical ozone pre-cursors or are relevant to the activities of the petrochemical industry. We report measurements of the 14-day diffusive uptake rates for the VOCs: i-butane (2-methyl propane), n-butane, i-pentane (2-methyl butane), n-pentane, n-hexane, benzene, toluene, and m-xylene (at environmental level concentrations) for industry standard axial samplers (Perkin-Elmer-type samplers) containing the sorbents Carbopack-X, -Z, -B or Tenax-TA. We also present data on back-diffusion, blank levels, and storage for the above sorbents, and describe the simultaneous use of the sorbent Carbopack-X for pumped sampling of certain VOCs. The results were obtained by dosing samplers in a controlled atmosphere test facility (CATFAC) operating under well-defined conditions of concentration, nominal temperature of 20 °C, wind speed of 0.5 m s -1, and relative humidities of 0% and 80%. Field measurements were also obtained to provide supplementary data to support the laboratory study. Results are compared to existing published data, where these are available.

Martin, Nicholas A.; Leming, Edward J.; Henderson, Malcolm H.; Lipscombe, Robert P.; Black, John K.; Jarvis, Scott D.

2010-09-01

215

Structural properties and catalytic activity in selective oxidation of In-containing ZSM-5 catalysts  

NASA Astrophysics Data System (ADS)

The characteristics of In-containing ZSM-5 zeolites prepared by different method have been investigated in the correlation of catalytic activity in the oxidative reaction of pentane and hexane. The zeolite catalysts have been prepared using four different methods: (i) ion-exchange in In(NO 3) 3 solution; (ii) solid state ion-exchange in oxidative atmosphere; (iii) solid state ion-exchange in reductive atmosphere; (iv) isomorphous substitution of aluminum for indium in the synthesis. The catalysts have been characterized by thermal analytical, XRD, nitrogen adsorption, IR, UV-VIS, 29Si MAS NMR, 27Al MAS NMR spectroscopic methods. Conversion of n-pentane and n-hexane has been studied in a fixed bed flow reactor in the presence or in the absence of dioxygen. High cracking activity is characteristic of the catalysts with high surface Brönsted acidity due to the oxidative treatment, while the catalyst pre-treated in reductive atmosphere having Lewis acidity are effective in the dehydrogenation and aromatization reactions of pentane and hexane. However, the significant increase of aromatic selectivity in the case of the catalyst prepared by solid state ion-exchange could be accounted to rapid dehydrogenation caused by isolated In 2O particles formed in reductive atmosphere. Synergism, namely intimate contact between these particles and the framework silicate structure can be assumed as active sites for the dehydrogenation and aromatization of alkenes.

Halász, János; Nyári, Wanda; Meretei, Edit; Hannus, István; Nagy, János B.; Kiricsi, Imre

2003-06-01

216

Monitoring of Selected Skin-Borne Volatile Markers of Entrapped Humans by Selective Reagent Ionization Time of Flight Mass Spectrometry in NO+ Mode  

PubMed Central

Selective reagent ionization time-of-flight mass spectrometry with NO+ as the reagent ion (SRI-TOF-MS (NO+)) was applied for near real-time monitoring of selected skin-borne constituents which are potential markers of human presence. The experimental protocol involved a group of 10 healthy volunteers enclosed in a body plethysmography chamber mimicking the entrapment environment. A total of 12 preselected omnipresent in human scent volatiles were quantitatively monitored. Among them there were six aldehydes (n-propanal, n-hexanal, n-heptanal, n-octanal, n-nonanal, and 2 methyl 2-propenal), four ketones (acetone, 2-butanone, 3-buten-2-one, and 6-methyl-5-hepten-2-one), one hydrocarbon (2-methyl 2-pentene), and one terpene (DL-limonene). The observed median emission rates ranged from 0.28 to 44.8 nmol × person–1 × min–1 (16–1530 fmol × cm–2 × min–1). Within the compounds under study, ketones in general and acetone in particular exhibited the highest abundances. The findings of this study provide invaluable information about formation and evolution of a human-specific chemical fingerprint, which could be used for the early location of entrapped victims during urban search and rescue operations (USaR).

2014-01-01

217

Volatile organic compounds in the air of Izmir, Turkey  

NASA Astrophysics Data System (ADS)

A sampling program was conducted to determine the ambient VOC levels in the city of Izmir, Turkey during daytime and overnight periods between mid-August and mid-September 1998. Sampling sites were selected at high-density traffic roads and junctions far from stationary VOC sources. Samples were analyzed for benzene, toluene, m, p-xylene and o-xylene (BTX), alkylbenzenes (ethylbenzene, 1,3,5-trimethylbenzene, 1,2,4-trimethylbenzene), n-hexane and, n-heptane. Results were compared with similar data from other cities around the world and for probable health dangers and sources of the compounds. Results of this study indicated that Izmir has rather high ambient BTX concentrations compared to many polluted cities in the world. Toluene was the most abundant VOC in Izmir air and was followed by xylenes, benzene and alkylbenzenes, respectively. All were strongly dependent on the expected daily variations of traffic flow in the city. The concentrations of other VOCs correlated well with benzene concentration at most sampling sites, excluding Gumuldur station indicating that ambient VOC levels were mainly affected by motor vehicle emissions. The toluene-to-benzene ratios for urban and non-urban sites were in good agreement with previously reported values, indicating a good relationship between the motor vehicle emissions and ambient VOC levels.

Muezzinoglu, Aysen; Odabasi, Mustafa; Onat, Levent

218

Enhancement of the spectral selectivity of complex samples by measuring them in a frozen state at low temperatures in order to improve accuracy for quantitative analysis. Part I. Raman spectroscopic compositional analysis of synthetic hydrocarbon mixtures.  

PubMed

A simple strategy for enhancing the Raman spectral selectivity of complex mixture samples by measuring them in a frozen state at low temperatures has been demonstrated and proven to improve the accuracy for compositional analysis. For evaluation, the Raman spectra of synthetic hydrocarbon mixtures that were composed of eleven hydrocarbons (n-hexane, n-heptane, n-octane, n-nonane, isooctane, cyclohexane, methylcyclohexane, benzene, toluene, xylene, and indan) were continuously collected during the elevation of their temperature from cryogenic to near room temperature. The accuracy of determination of n-paraffin concentrations improved significantly when the samples were measured at the temperature range between approximately -175 and -155 °C in comparison to the measurements at room temperature. However, the improvement of accuracy was relatively marginal for the concentration determination of naphthenic and aromatic components. Since n-paraffins are easily compressible and deformable in frozen conditions, the subsequent spectral variations could be diverse depending on their molecular structures. Due to this fact, the spectral discrimination among the paraffin components, as well as in comparison to other components, was enhanced and the improved spectral selectivity eventually led to more accurate determination of concentrations. Overall, the proposed strategy is simple and effective, so it is applicable for analysis of real complex mixture samples. PMID:23340768

Hwang, Jinyoung; Chung, Hoeil

2013-03-01

219

Viscosities of nonelectrolyte liquid mixtures. III. Selected binary and quaternary mixtures  

NASA Astrophysics Data System (ADS)

This paper is the final in a series of three viscosity and density studies of pure n-alkanes and selected binary and quaternary mixtures. A standard U-tube viscometer was used for viscosity measurements, and a Pyrex flask-type pycnometer was used for density determinations. Results are given here for pure alkane and selected binary mixtures of n-tetradecane + n-octane, for selected quaternary mixtures of n-hexadecane + n-dodecane + n-decane + n-hexane, and for pure and selected quaternary mixtures of n-hexadecane + n-dodecane + n-nonane + n-heptane at 303.16 and 308.16 K. The principle of congruence was tested, as was the Grunberg and Nissan equation, as they have been shown to be useful as prediction techniques for other n-alkane binary mixtures. Comparisons were made between the two groups of quaternary alkane mixtures and the binary n-tetradecane + n-octane mixtures of the same “pseudo” composition to understand better the dependence of mixture viscosities on the composition parameter.

Wakefield, D. L.

1988-05-01

220

Monitoring of selected skin-borne volatile markers of entrapped humans by selective reagent ionization time of flight mass spectrometry in NO+ mode.  

PubMed

Selective reagent ionization time-of-flight mass spectrometry with NO(+) as the reagent ion (SRI-TOF-MS (NO(+))) was applied for near real-time monitoring of selected skin-borne constituents which are potential markers of human presence. The experimental protocol involved a group of 10 healthy volunteers enclosed in a body plethysmography chamber mimicking the entrapment environment. A total of 12 preselected omnipresent in human scent volatiles were quantitatively monitored. Among them there were six aldehydes (n-propanal, n-hexanal, n-heptanal, n-octanal, n-nonanal, and 2 methyl 2-propenal), four ketones (acetone, 2-butanone, 3-buten-2-one, and 6-methyl-5-hepten-2-one), one hydrocarbon (2-methyl 2-pentene), and one terpene (DL-limonene). The observed median emission rates ranged from 0.28 to 44.8 nmol × person(-1) × min(-1) (16-1530 fmol × cm(-2) × min(-1)). Within the compounds under study, ketones in general and acetone in particular exhibited the highest abundances. The findings of this study provide invaluable information about formation and evolution of a human-specific chemical fingerprint, which could be used for the early location of entrapped victims during urban search and rescue operations (USaR). PMID:24611620

Mochalski, Pawe?; Unterkofler, Karl; Hinterhuber, Hartmann; Amann, Anton

2014-04-15

221

Hot Surface Ignition and Flame Propagation of Hydrocarbon Air Mixtures  

NASA Astrophysics Data System (ADS)

To mitigate the risk of accidental explosions in industrial facilities and in the aviation industry, the mechanisms and parameters leading to ignition must be investigated. Of particular are isolated hot surfaces in contact with gaseous hydrocarbon fuels, and thus ignition of premixed n-hexane air and n-heptane air mixtures is examined using a high temperature glow plug. Measurements include schlieren visualization, particle streaks, pressure, and temperature measurements in the plume created by the hot surface. These measurements are performed for experiments in both air and combustion mixtures ranging in equivalence ratio from 0.5 (near the lower flammability limit) to 3.0. This allows for comparison of ignition temperature, flame speed, pressure rise, and temperature distribution with a computational flame model. For equivalence ratios above 0.7 the ignition temperature was observed to be insensitive to increasing fuel concentration and showed good agreement with the model. Three distinct combustion modes are observed that scale with the Richardson number: single flame, multiple flames, and puffing. These behaviors show the transition from flame propagation dominated to buoyancy dominated behavior, with puffing cycles of the order 10 Hz.

Boettcher, Philipp; Ventura, Brian; Blanquart, Guillaume; Shepherd, Joseph

2010-11-01

222

Infrared band intensities of saturated hydrocarbons  

NASA Technical Reports Server (NTRS)

Kramers-Kronig analysis is applied to measured values of spectral reflectance at near-normal incidence to determine the real and the imaginary parts of the complex index of refraction for methane, ethane, propane, n-butane, n-hexane, n-heptane, and n-decane in the liquid state. The results indicate that the strengths of the characteristic bands as measured by the integral of the imaginary part are roughly constant for all the liquid alkanes except for methane. The intensity of the CH valence vibration bands in the spectra of the alkanes except methane is directly proportional to the number of CH groups per unit volume. The relations for the intensity of the bands due to CH2 and CH3 deformations are examined. Characteristic band intensities of the type established for NH4(+) and SO4(2-) groups in solutions and crystals cannot be extended to the more closely coupled CH2 and CH3 groups in alkane molecules.

Pinkley, L. W.; Sethna, P. P.; Williams, D.

1978-01-01

223

Transferable Potentials for Phase Equilibria. 4. United-Atom Description of Linear and Branched Alkenes and Alkylbenzenes  

SciTech Connect

The Transferable Potentials for Phase Equilibria-United Atom (TraPPE-UA) force field for hydrocarbons is extended to alkenes and alkylbenzenes by introducing the following pseudo-atoms: CH{sub 2}(sp{sup 2}), CH(sp{sup 2}), CH(aro), R-C(aro) for the link to aliphatic side chains, and C(aro) for the link of two benzene rings. In this united-atom force field, the nonbonded interactions of the hydrocarbon pseudo-atoms are solely governed by Lennard-Jones 12-6 potentials, and the Lennard-Jones well depth and size parameters for the new pseudo-atoms were determined by fitting to the single-component vapor-liquid phase equilibria of a few selected model compounds. Configurational-bias Monte Carlo simulations in the NVT version of the Gibbs ensemble were carried out to calculate the single-component vapor-liquid coexistence curves for ethene, propene, 1-butene, trans- and cis-2-butene. 2-methylpropene, 1,5-hexadiene, 1-octene, benzene, toluene, ethylbenzene, propylbenzene, isopropylbenzene, o-, m-, and p-xylene, and naphthalene. The phase diagrams for the binary mixtures of (supercritical) ethene/n-heptane and benzene/n-pentane were determined from simulations in the NpT Gibbs ensemble. Although the TraPPE-UA force field is rather simple and makes use of relatively few different pseudo-atoms, its performance, as judged by comparisons to other popular force fields and available experimental data, is very satisfactory.

WICK,COLLIN D.; MARTIN,MARCUS G.; SIEPMANN,J. ILJA

2000-07-12

224

The speciation of volatile organic compounds (VOCs) from motorcycle engine exhaust at different driving modes  

NASA Astrophysics Data System (ADS)

This study investigated the emissions of volatile organic compound (VOC) from motorcycle engine exhaust at different driving modes on a dynamometer. The speciations and the ozone formation potential of VOC samples also had been investigated by GC/MS and maximum increment reactivity (MIR), respectively. Both brand new and in-use motorcycles were tested in this study. The tested motorcycles include 2-stroke and 4-stroke engines. There are totally 48 VOC compounds identified in this study. Only the VOC species with C 3-C 9 were identified successfully. Experimental results indicated that isopentane, toluene, m, p-xylene, n-pentane, 2-methylpentane, 3-methylpentane, benzene, n-heptane and methylheptane were the major VOC speciations in the motorcycle engine exhaust. The amount of VOC emissions of the in-use 2-stroke motorcycles was 5 times that of the new 2-stroke motorcycles and the in-use 4-stroke motorcycles was 15 times that of the new 4-stroke motorcycles during the whole cycle. The amount of VOC speciation concentration during idle and deceleration stages was higher than those during the acceleration and cruising modes. However, the emission rate of VOCs at various driving modes tested on a dynamometer had not been precised enough due to the inconsistent variation of volume efficiency of motorcycle engine. These data shows a clear distinct emission rate of VOC at various driving modes. Besides, alkanes and aromatics were the major VOC speciation groups in the motorcycle engine exhaust. The amount of VOCs contributed from 23% to 76% THC for the four types motorcycle. Great variation of VOC/THC were found among new and in-use motorcycle. The ozone formation potential of a 2-strokes engine was higher than that of a 4-stroke engine. The ozone formation potential of in-use motorcycles were also clear higher than those of new motorcycles.

Tsai, Jiun-Horng; Chiang, Hung-Lung; Hsu, Yi-Chun; Weng, Hung-Cheng; Yang, Chang-Yu

225

Vapor pressure, heat capacity, and density along the saturation line, measurements for cyclohexanol, 2-cyclohexen-1-one, 1,2-dichloropropane, 1,4-di-tert-butylbenzene, ({+-})-2-ethylhexanoic acid, 2-(methylamino)ethanol, perfluoro-n-heptane, and sulfolane  

SciTech Connect

Vapor pressures were measured to a pressure limit of 270 kPa or lower decomposition point for eight compounds using a twin ebulliometric apparatus. Liquid-phase densities along the saturation line were measured for each compound over a range of temperatures (ambient to a maximum of 548 K). A differential scanning calorimeter (DSC) was used to measure two-phase (liquid + vapor) heat capacities for each compound in the temperature region ambient to the critical temperature or lower decomposition point. Where possible, the critical temperature and critical density for each compound were determined experimentally. The results of the measurements were combined to derive a series of thermophysical properties including critical temperature, critical density, critical pressure, acentric factor, enthalpies of vaporization [within the temperature range ({+-}50 K) of the vapor pressures], enthalpies of fusion if solid at ambient temperature, solubility parameter, and heat capacities along the saturation line. Wagner-type vapor-pressure equations were derived for each compound. In addition, the liquid-phase densities were compared with values derived using a four-term power series in either T or [(1 {minus} T{sub r}){sup 1/3}]. All measured and derived values were compared with those obtained in a search of the literature. Recommended critical parameters are listed for each of the compounds studied. A Rule-Of-Thumb derived in the 1992 Project Year was used to estimate thermal decomposition temperatures by radical scission from a knowledge of the bond dissociation energy or vice versa.

Steele, W.V.; Chirico, R.D.; Knipmeyer, S.E.; Nguyen, A. [National Inst. for Petroleum and Energy Research, Bartlesville, OK (United States)] [National Inst. for Petroleum and Energy Research, Bartlesville, OK (United States)

1997-11-01

226

Vapor pressure, heat capacity, and density along the saturation line, measurements for cyclohexanol, 2-cyclohexen-1-one, 1,2-dichloropropane, 1,4-di-tert-butylbenzene, ({+-})-2-ethylhexanoic acid, 2-(methylamino)ethanol, perfluoro-n-heptane, and sulfolane  

Microsoft Academic Search

Vapor pressures were measured to a pressure limit of 270 kPa or lower decomposition point for eight compounds using a twin ebulliometric apparatus. Liquid-phase densities along the saturation line were measured for each compound over a range of temperatures (ambient to a maximum of 548 K). A differential scanning calorimeter (DSC) was used to measure two-phase (liquid + vapor) heat

W. V. Steele; R. D. Chirico; S. E. Knipmeyer; A. Nguyen

1997-01-01

227

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

NASA Astrophysics Data System (ADS)

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-aldehyde pattern found in snow collected at Jungfraujoch. One exception is the significantly higher proportion of n-hexanal in the Jungfraujoch samples compared to vegetation emission. Additionally, indirect biogenic emissions can contribute to the atmospheric concentrations of n-aldehydes through oxidation of precursor compounds of biogenic origin. In this context, Moise and Rudich [4] and Thornberry and Abbatt [5] proposed the preferential formation of n-nonanal and n-hexanal from the cleavage by ozonolysis of double bonds in unsaturated fatty acids (namely oleic acid and linoleic acids). The predominance of n-hexanal and n-nonanal among the C6-C10 n-aldehydes in the snow samples collected at Jungfraujoch during CLACE 5 is therefore an argument for the formation of the aldehydes through oxidation of unsaturated fatty acids in the atmosphere. Anthropogenic emissions of n-aldehydes i.e. from fossil fuel burning are thought to be negligible in the air masses reaching Jungfraujoch. References: [1] P. Ciccioli, E. Brancaleoni, M. Frattoni, A. Cecinato, A. Brachetti, Atmos. Environ., Part A 27 (1993) 1891. [2] Y. Yokouchi, H. Mukai, K. Nakajima, Y. Ambe, Atmos. Environ., Part A 24 (1990) 439. [3] J. Kesselmeier, M. Staudt, J. Atmos. Chem. 33 (1999) 23. [4] T. Moise, Y. Rudich, J. Phys. Chem. 106 (2002) 6469. [5] T. Thornberry, J.P.D. Abbatt, Phys. Chem. Chem. Phys. 6 (2004) 84.

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

2009-04-01

228

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

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

229

Temporal variation of volatile organic compounds and their major emission sources in Seoul, Korea.  

PubMed

This study examines the characteristics of volatile organic compounds (VOCs) and their major emission sources at the Bulgwang site in Seoul, Korea. The annual levels of VOCs (96.2-121.1 ppb C) have shown a decreasing trend from 2004 to 2008. The most abundant component in Seoul was toluene, which accounted for over 23.5 % of the total VOCs on the parts per billion on a carbon basis, and the portions of alkanes with two to six carbons constituted the largest major lumped group, ranging from 40.1 to 48.4 % (45.3 ± 3.7 %) of the total VOCs. Major components of the solvent (toluene, m/p-xylene, o-xylene, and ethylbenzene) showed high in daytime and summer and low in nighttime and winter due mainly to the variation of the ambient temperature. The species mostly emitted from gasoline vapor (i/n-butane, i/n-pentane, n-hexane, and 2-methylpentane) and vehicular exhaust (ethylene, acetylene, and benzene) showed bimodal peaks in the diurnal variation around the commuting hours because of the high traffic volume. For the 14 out of 15 highest concentration species, the weekend effect was only evident on Sundays because of the stepwise implementation of the 5-day work-week system. Principal components analysis (PCA) was applied in order to identify the sources of the 15 highest concentration VOCs and, as a result, three principal components such as gasoline vapor (48.9 %), vehicular exhaust (17.9 %), and evaporation of solvents (9.8 %) were obtained to explain a total of 76.6 % of the data variance. Most influential contributing sources at the sampling site were traffic-related ones although the use of solvent was the dominant emission source based on the official emission inventory. PMID:23728967

Shin, H J; Roh, S A; Kim, J C; Lee, S J; Kim, Y P

2013-12-01

230

13C NMR studies of hydrocarbon guests in synthetic structure H gas hydrates: experiment and computation.  

PubMed

(13)C NMR chemical shifts were measured for pure (neat) liquids and synthetic binary hydrate samples (with methane help gas) for 2-methylbutane, 2,2-dimethylbutane, 2,3-dimethylbutane, 2-methylpentane, 3-methylpentane, methylcyclopentane, and methylcyclohexane and ternary structure H (sH) clathrate hydrates of n-pentane and n-hexane with methane and 2,2-dimethylbutane, all of which form sH hydrates. The (13)C chemical shifts of the guest atoms in the hydrate are different from those in the free form, with some carbon atoms shifting specifically upfield. Such changes can be attributed to conformational changes upon fitting the large guest molecules in hydrate cages and/or interactions between the guests and the water molecules of the hydrate cages. In addition, powder X-ray diffraction measurements revealed that for the hexagonal unit cell, the lattice parameter along the a-axis changes with guest hydrate former molecule size and shape (in the range of 0.1 Å) but a much smaller change in the c-axis (in the range of 0.01 Å) is observed. The (13)C NMR chemical shifts for the pure hydrocarbons and all conformers were calculated using the gauge invariant atomic orbital method at the MP2/6-311+G(2d,p) level of theory to quantify the variation of the chemical shifts with the dihedral angles of the guest molecules. Calculated and measured chemical shifts are compared to determine the relative contribution of changes in the conformation and guest-water interactions to the change in chemical shift of the guest upon clathrate hydrate formation. Understanding factors that affect experimental chemical shifts for the enclathrated hydrocarbons will help in assigning spectra for complex hydrates recovered from natural sites. PMID:21329330

Lee, Jong-Won; Lu, Hailong; Moudrakovski, Igor L; Ratcliffe, Christopher I; Ohmura, Ryo; Alavi, Saman; Ripmeester, John A

2011-03-10

231

Carbon isotope fractionation during volatilization of petroleum hydrocarbons and diffusion across a porous medium: a column experiment.  

PubMed

The study focuses on the effect of volatilization, diffusion, and biodegradation on the isotope evolution of volatile organic compounds (VOCs) in a 1.06 m long column filled with alluvial sand. A liquid mixture of 10 VOCs was placed at one end of the column, and measurements of VOC vapor concentrations and compound-specific isotope ratios (delta(13)C) were performed at the source and along the column. Initially, the compounds became depleted in 13C by up to -4.8% per hundred along the column axis, until at 26 h, uniform isotope profiles were observed for most compounds, which is expected for steady-state diffusion. Subsequently, several compounds (n-pentane, benzene, n-hexane) became enriched in 13C throughout the column. For the same compounds, a significant decrease in the source vapor concentration and a gradual enrichment of 13C by up to 5.3% per hundred at the source over a period of 336 h was observed. This trend can be explained by a larger diffusive mass flux for molecules with light isotopes compared to those with a heavy isotope, which leads to a depletion of light isotopes in the source. The isotope evolution of the source followed closely a Rayleigh trend and the obtained isotope enrichment factor corresponded well to the ratio between the diffusion coefficients for heavy and light molecules as expected based on theory. In contrastto diffusion, biodegradation had generally only a small effect on the isotope profiles, which is expected because in a diffusion-controlled system the isotope shift per decrease of mass flux is smaller than in an advection-controlled system. These findings open interesting perspectives for monitoring source depletion with isotope and have implications for assessing biodegradation and source variability in the unsaturated zone based on isotopes. PMID:19031863

Bouchard, Daniel; Höhener, Patrick; Hunkeler, Daniel

2008-11-01

232

METHYL KETONE METABOLISM IN HYDROCARBON-UTILIZING MYCOBACTERIA  

PubMed Central

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.

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

1963-01-01

233

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

PubMed

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 ?g m(-2) h(-1). The target compounds with median emission rates greater than 20 ?g 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

Shin, Seung H; Jo, Wan K

2012-10-01

234

Multidrug resistance in hydrocarbon-tolerant Gram-positive and Gram-negative bacteria.  

PubMed

New Gram-positive and Gram-negative bacteria were isolated from Poeni oily sludge, using enrichment procedures. The six Gram-positive strains belong to Bacillus, Lysinibacillus and Rhodococcus genera. The eight Gram-negative strains belong to Shewanella, Aeromonas, Pseudomonas and Klebsiella genera. Isolated bacterial strains were tolerant to saturated (i.e., n-hexane, n-heptane, n-decane, n-pentadecane, n-hexadecane, cyclohexane), monoaromatic (i.e., benzene, toluene, styrene, xylene isomers, ethylbenzene, propylbenzene) and polyaromatic (i.e., naphthalene, 2-methylnaphthalene, fluorene) hydrocarbons, and also resistant to different antimicrobial agents (i.e., ampicillin, kanamycin, rhodamine 6G, crystal violet, malachite green, sodium dodecyl sulfate). The presence of hydrophilic antibiotics like ampicillin or kanamycin in liquid LB-Mg medium has no effects on Gram-positive and Gram-negative bacteria resistance to toxic compounds. The results indicated that Gram-negative bacteria are less sensitive to toxic compounds than Gram-positive bacteria, except one bacteria belonging to Lysinibacillus genus. There were observed cellular and molecular modifications induced by ampicillin or kanamycin to isolated bacterial strains. Gram-negative bacteria possessed between two and four catabolic genes (alkB, alkM, alkB/alkB1, todC1, xylM, PAH dioxygenase, catechol 2,3-dioxygenase), compared with Gram-positive bacteria (except one bacteria belonging to Bacillus genus) which possessed one catabolic gene (alkB/alkB1). Transporter genes (HAE1, acrAB) were detected only in Gram-negative bacteria. PMID:21478643

Stancu, Mihaela Marilena; Grifoll, Magdalena

2011-01-01

235

[Characterization of surface properties of 1-allyl-3-methylimidazolium chloride ionic liquid by inverse gas chromatography].  

PubMed

The determination of the dispersive component of surface free energies (gamma(s)d) at different temperatures and Lewis acid-base parameters of 1-allyl-3-methylimidazolium chloride ionic liquid ([AMIM]Cl) were investigated by means of inverse gas chromatography (IGC). Four n-alkanes, including n-hexane (C6), n-heptane (C7), n-octane (C8) and n-nonane (C9), were chosen as the apolar probes to characterize the dispersive component of the surface free energies at 343.15, 353.15, 363.15 and 373.15 K, respectively; and dichloromethane (DCM), trichloromethane (TCM), tetrahydrofuran (THF), ethyl acetate (EtAc), acetone (Acet) as the polar probes to estimate the Lewis acid-base parameters to judge the interactions between [AMIM] Cl and the solvents. The IGC characterizations encompassed the adsorption thermodynamic parameters to acid-base surface interactions, including the standard enthalpy (deltaHa(s)) and the free energy change of adsorption (deltaGa(s)) at different temperatures. The results showed that the Lewis acid parameter Ka of [AMIM] Cl was 0.34, and the base parameter Kb was 1.68, which indicated it was Lewis amphoteric with predominantly basic character. Furthermore, the free energy of adsorption deltaGa(s) was also figured out. It was found that the gamma(s)d of the [AMIM] Cl were 52.26, 50.82, 46.08 and 42.05 mJ/m2 at 343.15, 353.15, 363.15 and 373.15 K, respectively. The results are of great importance to the study of the surface properties and the application of ionic liquid. PMID:23697180

Chen, Yali; Wang, Qiang; Deng, Lishuang; Zhang, Zhengfang; Tang, Jun

2013-02-01

236

Selective hydroxylation of alkanes by an extracellular fungal peroxygenase  

PubMed Central

Fungal peroxygenases are novel extracellular heme-thiolate biocatalysts that are capable of catalyzing the selective monooxygenation of diverse organic compounds, using only H2O2 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 H2O2-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 H218O2 resulted in complete incorporation of 18O into the hydroxyl group of the product cyclohexanol; (b) the hydroxylation of n-hexane-1,1,1,2,2,3,3-D7 showed a large intramolecular deuterium isotope effect [(kH/kD)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 × 1011 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 (> C16) 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.

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

2013-01-01

237

Phase equilibria study of the binary systems (N-hexylisoquinolinium thiocyanate ionic liquid + organic solvent or water).  

PubMed

Liquid-liquid phase equilibria (LLE) of binary mixtures containing a room-temperature ionic liquid N-hexylisoquinolinium thiocyanate, [HiQuin][SCN] with an aliphatic hydrocarbon (n-hexane, n-heptane), aromatic hydrocarbon (benzene, toluene, ethylbenzene, n-propylbenzene), cyclohexane, thiophene, water, and 1-alcohol (1-ethanol, 1-butanol, 1-hexanol, 1-octanol, 1-decanol) have been determined using a dynamic method from room temperature to the boiling-point of the solvent at ambient pressure. N-hexylisoquinolinium thiocyanate, [HiQuin][SCN] has been synthesized from N-hexyl-isoquinolinium bromide as a substrate. Specific basic characterization of the new compound including NMR spectra, elementary analysis, and water content have been done. The density and viscosity of pure ionic liquid were determined over a wide temperature range from 298.15 to 348.15 K. The mutual immiscibility with an upper critical solution temperature (UCST) for the binary systems {IL + aliphatic hydrocarbon, cyclohexane, or water} was detected. In the systems of {IL + aromatic hydrocarbon or thiophene} an immiscibility gap with a lower critical solution temperature (LCST) was observed. Complete miscibility in the liquid phase, over a whole range of ionic liquid mole fraction, was observed for the binary mixtures containing IL and an 1-alcohol. For the tested binary systems with immiscibility gap {IL + aliphatic hydrocarbon, aromatic hydrocarbon, cyclohexane, thiophene, or water}, the parameters of the LLE correlation have been derived using the NRTL equation. The basic thermal properties of the pure IL, that is, the glass-transition temperature as well as the heat capacity at the glass-transition temperature, have been measured using a differential scanning microcalorimetry technique (DSC). Decomposition of the IL was detected by simultaneous thermogravimetric/differential thermal analysis (TG/DTA) experiments. PMID:22424076

Królikowska, Marta; Karpi?ska, Monika; Zawadzki, Maciej

2012-04-12

238

Progress in the development of an electronic nose using arrays of chemically sensitive carbon black-polymer resistors  

NASA Astrophysics Data System (ADS)

Response data were collected for a carbon black-polymer composite electronic nose array during exposure to homologous series of alkanes and alcohols. At a fixed partial pressure of odorant in the vapor phase, the mean response intensity of the electronic nose signals varied significantly for members of each series of odorants. However, the mean response intensity of the electronic nose detectors, and the response intensity of the most strongly-driven set of electronic nose detectors, was essentially constant for members of a chemically homologous odorant series when the concentration of each odorant in the gas phase was maintained at a constant fraction of the odorant's vapor pressure. Because the thermodynamic activity of an odorant at equilibrium in a sorbent phase is equal to the partial pressure of the odorant in the gas phase divided by the vapor pressure of the odorant, and because the activity coefficients are similar within these homologous series of odorants for sorption of the vapors into specific polymer films, the data imply that the trends in detector response can be understood based on the thermodynamic tendency to establish a relatively constant concentration of sorbed odorant into each of the polymeric films of the electronic nose at a constant fraction of the odorant's vapor pressure. This phenomenon provides a natural mechanism for enhanced sensitivity to low vapor pressure compounds, like TNT, in the presence of high vapor pressure analytes, such as diesel fuel. In a related study to evaluate the target recognition properties of the electronic nose, a statistical metric based on the magnitudes and standard deviations along Euclidean projections of clustered array response data, was utilized to facilitate an evaluation of the performance of detector arrays in various vapor classification tasks. This approach allowed quantification of the ability of a fourteen-element array of carbon black-insulating polymer composite chemiresistors to distinguish between members of a set of nineteen solvent vapors, some of which vary widely in chemical properties (e.g. methanol and benzene) and others of which are very similar (e.g. n-pentane and n-heptane). The data also facilitated evaluation of questions such as array performance as a function of the number of detectors in the system.

Doleman, Brett J.; Severin, Erik J.; Sanner, Robert D.; Lewis, Nathan S.

1998-09-01

239

Polymerization of Vinylcyclohexane with TICL3-al(C2H5)3 Catalysts.  

National Technical Information Service (NTIS)

The polymerization of vinylcyclohexane was followed dilatometrically in cyclohexane and n-heptane solvents with TiCl3-Al(C2H5)3 as catalyst. In n-heptane constant rates were obtained, while in cyclohexane a slow change of the initial rate to a lower stead...

W. H. McCarty G. Parravano

1965-01-01

240

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

NASA Astrophysics Data System (ADS)

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.

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

1994-01-01

241

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

NASA Technical Reports Server (NTRS)

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.

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

1994-01-01

242

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

SciTech Connect

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).

Subramaniam, B.

1993-10-01

243

Enhancing chemical identification efficiency by SAW sensor transients through a data enrichment and information fusion strategy—a simulation study  

NASA Astrophysics Data System (ADS)

The paper proposes a new approach for improving the odor recognition efficiency of a surface acoustic wave (SAW) transient sensor system based on a single polymer coating. The vapor identity information is hidden in transient response shapes through dependences on specific vapor solvation and diffusion parameters in the polymer coating. The variations in the vapor exposure and purge durations and the sensor operating frequency have been used to create diversity in transient shapes via termination of the vapor-polymer equilibration process up to different stages. The transient signals were analyzed by the discrete wavelet transform using Daubechies-4 mother wavelet basis. The wavelet approximation coefficients were then processed by principal component analysis for creating feature space. The set of principal components define the vapor identity information. In an attempt to enhance vapor class separability we analyze two types of information fusion methods. In one, the sensor operation frequency is fixed and the sensing and purge durations are varied, and in the second, the sensing and purge durations are fixed and the sensor operating frequency is varied. The fusion is achieved by concatenation of discrete wavelet coefficients corresponding to various transients prior to the principal component analysis. The simulation experiments with polyisobutylene SAW sensor coating for operation frequencies over [55-160] MHz and sensing durations over [5-60] s were analyzed. The target vapors are seven volatile organics: chloroform, chlorobenzene, o-dichlorobenzene, n-heptane, toluene, n-hexane and n-octane whose concentrations were varied over [10-100] ppm. The simulation data were generated using a SAW sensor transient response model that incorporates the viscoelastic effects due to polymer coating and an additive noise source in the output. The analysis reveals that: (i) in single transient analysis the class separability increases with sensing duration for a given frequency of operation, and also with frequency for a given sensing duration, and (ii) the information fusion based on both the multiple sensing cycles and the multiple sensing frequencies enhances the class separability by nearly an order of magnitude.

Singh, Prashant; Yadava, R. D. S.

2013-05-01

244

Immiscible Systems  

ERIC Educational Resources Information Center

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,…

Eckelmann, Jens; Luning, Ulrich

2013-01-01

245

Eucalyptus camaldulensis: volatiles from immature flowers and high production of 1,8-cineole and ?-pinene by in vitro cultures  

Microsoft Academic Search

Calli of Eucalyptus camaldulensis Dehn were induced, for the first time, from immature flowers and stamens and established in the presence of 2,4-D and BA, under dark and light conditions. Immature flowers, of the same type used for callus induction, were submitted to hydrodistillation while the induced calli were extracted with n-pentane. The constituents of the n-pentane extracts and of

Andreas Giamakis; Ourania Kretsi; Ioanna Chinou; Caroline G. Spyropoulos

2001-01-01

246

Dynamical solvent effects on conformational isomerization of cyclohexane and 1,1-difluorocyclohexane  

Microsoft Academic Search

The effect of pressure on the conformational isomerization of cyclohexane in n-pentane-d12 solvent has been investigated by using the high-resolution, high-pressure nuclear magnetic resonance (NMR) technique. The isomerization rate of cyclohexane increases with increasing pressure at 218 K. The experimental data are interpreted in terms of stochastic models for isomerization reactions, and the results show that cyclohexane isomerization in n-pentane-d12

Joseph Ashcroft; Chuan-Liang Xie; Jiri Jonas

1989-01-01

247

Measurement and correlation of liquid-liquid equilibria of binary and ternary systems containing methanol and hydrocarbon  

SciTech Connect

Liquid-liquid equilibrium relations (LLE) have been measured using double-walled glass celles and are reported for four binary systems containing methanol (methanol - n-heptane, n-octane, n-nonane, and n-decane) in the 25 - 60/sup 0/C region. Further, LLE data of eight ternary systems containing methanol (methanol - benzene - n-heptane, n-octane, n-nonane, and n-decane; methanol - toluene - n-heptane, n-octane, n-nonane, and n-decane) have been determined at 25/sup 0/C. The results have been correlated using a modified Wilson equation.

Higashiuchi, H.; Sakuragi, Y.; Iwai, Y.; Arai, Y.; Nagatani, M.

1987-01-01

248

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

NASA Astrophysics Data System (ADS)

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.

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

249

21 CFR 180.22 - Acrylonitrile copolymers.  

Code of Federal Regulations, 2010 CFR

...appropriate to the intended conditions of use. The food-simulating solvents shall include, where applicable, distilled water, 8 percent or 50 percent ethanol, 3 percent acetic acid, and either n -heptane or an appropriate oil or...

2010-01-01

250

21 CFR 181.32 - Acrylonitrile copolymers and resins.  

Code of Federal Regulations, 2010 CFR

...appropriate to the intended conditions of use. The food-simulating solvents shall include, where applicable, distilled water, 8 percent or 50 percent ethanol, 3 percent acetic acid, and either n -heptane or an appropriate oil or fat....

2010-01-01

251

21 CFR 181.32 - Acrylonitrile copolymers and resins.  

Code of Federal Regulations, 2010 CFR

...appropriate to the intended conditions of use. The food-simulating solvents shall include, where applicable, distilled water, 8 percent or 50 percent ethanol, 3 percent acetic acid, and either n -heptane or an appropriate oil or fat....

2009-04-01

252

Measurement of Leachables from Tampons.  

National Technical Information Service (NTIS)

A water and n-heptane extraction of several brands of highly absorbent tampons have been examined by various analytical methods. Many inorganic elements such as sodium, silicon, boron, magnesium, iron, aluminum and titanium have been found in trace amount...

N. Lao

1981-01-01

253

Autoignition chemistry in a motored engine: An experimental and kinetic modeling study.  

National Technical Information Service (NTIS)

Autoignition of isomers of pentane, hexane, and primary reference fuel mixture of n-heptane and iso-octane has been studied experimentally under motored engine conditions and computationally using a detailed chemical kinetic reaction mechanism. Computed a...

H. J. Curran W. J. Pitz C. K. Westbrook P. Gaffuri W. R. Leppard

1996-01-01

254

HCCI combustion: Effect of NO in EGR  

Microsoft Academic Search

Experiments were performed for the oxidation of mixtures of n-heptane and iso-octane and of n-heptane and toluene in a jet-stirred reactor (JSR) under dilute conditions, at 10atm. The effect of the addition of variable initial NO concentration was also studied. A detailed kinetic model was performed to rationalize the results. Experiments were also performed using a homogeneous charge compression ignition

Anthony Dubreuil; Fabrice Foucher; Guillaume Dayma; Philippe Dagaut

2007-01-01

255

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)

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 25.2±14.5 ppbV and 16.6±9 ppbV for butane and propane respectively, was achieved in Merced in 2011 and 14.7±3.5 ppbV and 28.4±6.7 ppbV for the same compounds, in San Agustin in 2012). In the case of vehicular emissions, in both campaigns, 2011 and 2012, Merced showed the highest levels: 12.3±4.8 ppbV, 2.7±1.1 ppbV and 4.3±3.3 ppbV for toluene, benzene and MTBE respectively in 2011 and 9.48±6.5 ppbV, 1.5±0.9 ppbV and 2.4±1.0 ppbV for the same compounds in 2012. The compounds which comes from industrial emissions, have the lowest average concentrations in all stations. The VOCs measurement in atmospheric air, allowed determinate that the main source of VOC in the three studied sites of the MCMA are emissions of LPG gas and vehicular emissions. The highest concentrations were found during the cold-dry period in 2011. These data are consistent with continuous measurements determined in the southeastern MCMA during 2000-2007.

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

2013-05-01

256

Solvent dependent reductive defluorination of aliphatic C-F bonds employing Sm(HMDS)2.  

PubMed

Sm(HMDS)(2) in n-hexane mediates fast cleavage of primary, secondary and tertiary alkyl fluorides in good to excellent yields. In n-hexane Sm(HMDS)(2) exhibits uniquely enhanced reductive ability towards the C-F bond compared to when using THF as solvent. PMID:23358653

Janjetovic, Mario; Träff, Annika M; Ankner, Tobias; Wettergren, Jenny; Hilmersson, Göran

2013-03-01

257

A Mixture Suitable for an Aerostat.  

National Technical Information Service (NTIS)

A balloon filled with a gas mixture of ammonia and n-hexane will stay at a constant altitude due to condensation at altitude of the n-hexane. Since both components are liquid below about 50 meters in the ocean and together with the load are buoyant, the a...

R. M. Dunlap

1978-01-01

258

40 CFR 264.1063 - Test methods and procedures.  

Code of Federal Regulations, 2013 CFR

...this section. (b) Leak detection monitoring, as required in...40 CFR part 60. (2) The detection instrument shall meet the...air). (ii) A mixture of methane or n-hexane and air at a...but less than, 10,000 ppm methane or n-hexane. (5)...

2013-07-01

259

40 CFR 265.1063 - Test methods and procedures.  

Code of Federal Regulations, 2013 CFR

...this section. (b) Leak detection monitoring, as required in...40 CFR part 60. (2) The detection instrument shall meet the...air). (ii) A mixture of methane or n-hexane and air at a...but less than, 10,000 ppm methane or n-hexane. (5)...

2013-07-01

260

Electron Transport in Paracoccus Halodenitrificans and the Role of Ubiquinone  

NASA Technical Reports Server (NTRS)

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.

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

1983-01-01

261

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

SciTech Connect

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.

Tierney, J.W.; Wender, I.

1993-09-01

262

Understanding nanofluid stability through molecular simulation  

SciTech Connect

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.

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

2012-11-01

263

Thermal Ignition  

NASA Astrophysics Data System (ADS)

Accidental ignition of flammable gases is a critical safety concern in many industrial applications. Particularly in the aviation industry, the main areas of concern on an aircraft are the fuel tank and adjoining regions, where spilled fuel has a high likelihood of creating a flammable mixture. To this end, a fundamental understanding of the ignition phenomenon is necessary in order to develop more accurate test methods and standards as a means of designing safer air vehicles. The focus of this work is thermal ignition, particularly auto-ignition with emphasis on the effect of heating rate, hot surface ignition and flame propagation, and puffing flames. Combustion of hydrocarbon fuels is traditionally separated into slow reaction, cool flame, and ignition regimes based on pressure and temperature. Standard tests, such as the ASTM E659, are used to determine the lowest temperature required to ignite a specific fuel mixed with air at atmospheric pressure. It is expected that the initial pressure and the rate at which the mixture is heated also influences the limiting temperature and the type of combustion. This study investigates the effect of heating rate, between 4 and 15 K/min, and initial pressure, in the range of 25 to 100 kPa, on ignition of n-hexane air mixtures. Mixtures with equivalence ratio ranging from 0.6 to 1.2 were investigated. The problem is also modeled computationally using an extension of Semenov's classical auto-ignition theory with a detailed chemical mechanism. Experiments and simulations both show that in the same reactor either a slow reaction or an ignition event can take place depending on the heating rate. Analysis of the detailed chemistry demonstrates that a mixture which approaches the ignition region slowly undergoes a significant modification of its composition. This change in composition induces a progressive shift of the explosion limit until the mixture is no longer flammable. A mixture that approaches the ignition region 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 instability is a function of the interaction of the flame with the fluid flow induced by the combustio

Boettcher, Philipp Andreas

264

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

NASA Astrophysics Data System (ADS)

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.

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

2014-04-01

265

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

PubMed

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

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

2014-04-01

266

Accelerated molecular dynamics simulation of the thermal desorption of n-alkanes from the basal plane of graphite  

Microsoft Academic Search

We utilize accelerated molecular dynamics to simulate alkane desorption from the basal plane of graphite. Eight different molecules, ranging from n-pentane to n-hexadecane, are studied in the low coverage limit. Acceleration of the molecular dynamics simulations is achieved using two different methods: temperature acceleration and a compensating potential scheme. We find that the activation energy for desorption increases with increasing

Kelly E. Becker; Kristen A. Fichthorn

2006-01-01

267

Explosion characteristics of flammable organic vapors in nitrous oxide atmosphere  

Microsoft Academic Search

Despite unexpected explosion accidents caused by nitrous oxide have occurred, few systematic studies have been reported on explosion characteristics of flammable gases in nitrous oxide atmosphere compared to those in air or oxygen. The objective of this paper is to characterize explosion properties of mixtures of n-pentane, diethyl ether, diethylamine, or n-butyraldehyde with nitrous oxide and nitrogen using three parameters:

Yusuke Koshiba; Tomihisa Takigawa; Yusaku Matsuoka; Hideo Ohtani

2010-01-01

268

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

Code of Federal Regulations, 2013 CFR

...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...only as a blowing agent adjuvant in polystyrene at a level not to exceed 0.3...

2013-04-01

269

Excess molar volumes, excess viscosities and refractive indices of a quaternary liquid mixture at 298.15 K  

Microsoft Academic Search

Density, viscosity and refractive index values for the propan-2-ol + methylacetate + dichloromethane + n-pentane mixture have been measured at 298.15 K, over the whole concentration range. Excess molar volumes and viscosities have been calculated. Flory's statistical theory has been applied to predict the excess molar volumes and compare then to the experimental data. We have also applied Grunberg and

Ernesto Caner; Graciela C. Pedrosa; Miguel Katz

1996-01-01

270

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

SciTech Connect

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.

Keyworth, D.A.

1989-03-28

271

Complex Formation between Dimethyl Methylphosphonate and Hexafluoroisopropanol.  

National Technical Information Service (NTIS)

A solvent/water partitioning method was used to measure the complex formation between dimethyl methylphosphonate (DMMP) and hexafluoroisopropanol (HFIP). The highest formation constant was obtained when n-hexane was used as the partitioning solvent. Other...

D. C. Leggett

1990-01-01

272

[Chemical constituents of Eupolyphaga sinensis Walker].  

PubMed

Five compounds were isolated from the n-hexane extract and n-butanol of extract Eupolyphaga sinensis. These compounds were identified as octacosanol, beta-sitosterol, batyl alcohol, 2,4-pyrimidinedione and allantoin. PMID:1482536

Lu, Y; Jiang, P

1992-08-01

273

Fischer-Tropsch synthesis in supercritical reaction media. (Quarterly) progress report, July 1, 1993--September 30, 1993.  

National Technical Information Service (NTIS)

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 safet...

B. Subramaniam

1993-01-01

274

Comparison of the Rationale Used in Setting Occupational Exposure Standards for Ionizing Radiation and Hazardous Chemical Substances.  

National Technical Information Service (NTIS)

Ten chemicals which create significant occupational hazard are reviewed. They are toluene diisocyanate, hydrogen fluoride, n-hexane, carbon disulphide, cadmium, inorganic mercury, cobalt, nitroglycerol, silica and vinyl chloride. Each is discussed under t...

D. M. Halton

1986-01-01

275

Preparative isolation and purification of coumarins from Angelica dahurica (Fisch. ex Hoffn) Benth, et Hook. f (Chinese traditional medicinal herb) by high-speed counter-current chromatography.  

PubMed

A preparative high-speed counter-current chromatography (HSCCC) method for isolation and purification of coumarins from Angelica dahurica (Fisch. ex Hoffin) Benth, et Hook. f(Baizhi in Chinese) was successfully established by using n-hexane-methanol-water as the two-phase solvent system in gradient elution mode. The upper phase of n-hexane-methanol-water (5:5:5, v/v) was used as the stationary phase of HSCCC. The mobile phase used in HSCCC was the lower phase of n-hexane-methanol-water (5:5:5, v/v) and n-hexane-methanol-water (5:7:3, v/v) that was changed in gradient. Three major components including imperatorin, isoimperatorin and oxypeucedanine were isolated, each at over 98% purity as determined by high-performance liquid chromatography (HPLC). The peak fractions of HSCCC were identified by 1H-NMR and 13C-NMR. PMID:15527142

Liu, Renmin; Li, Aifeng; Sun, Ailing

2004-10-15

276

ONE-STEP PURIFICATION OF ASTILBIN FROM SMILAX GLABRA BY HIGH PERFORMANCE CENTRIFUGAL PARTITION CHROMATOGRAPHY  

Microsoft Academic Search

In this study, a preparative high performance centrifugal partition chromatography (CPC) method for isolation and purification of the bioactive component astilbin from the crude extract of Smilax glabra was successfully established by using n-hexane-ethyl acetate-methanol-water as the two-phase solvent system. The upper phase of n-hexane-ethyl acetate-methanol-water (1:10:1:10, v\\/v) was used as the stationary phase of CPC. Under the optimum conditions,

Jianbing Wu; Zhe Chen; Yingmei Zhao; Huizhong Wang

2012-01-01

277

In vitro cytotoxic effects of Senecio stabianus Lacaita (Asteraceae) on human cancer cell lines  

Microsoft Academic Search

This study is aimed to evaluate the in vitro cytotoxicity of Senecio stabianus Lacaita (Asteraceae) against renal adenocarcinoma ACHN, hormone-dependent prostate carcinoma LNCaP, amelanotic melanoma C32 and human breast adenocarcinoma MCF-7 cell lines. The n-hexane extract showed an interesting activity with IC50 values of 62.7 and 71.1 ?g mL against C32 and LNCaP, respectively. Two compounds identified in the n-hexane

Rosa Tundis; Monica R. Loizzo; Marco Bonesi; Federica Menichini; Daniela Dodaro; Nicodemo G. Passalacqua; Giancarlo Statti; Francesco Menichini

2009-01-01

278

Indirect and direct-acting mutagenicity of diesel, coal and wood burning-derived particulates and contribution of polycyclic aromatic hydrocarbons and nitropolycyclic aromatic hydrocarbons  

Microsoft Academic Search

Particulates exhausted from two types of diesel engines (DEPs), burning-derived particulates from three types of coal (CBPs) and burning-derived particulates from three types of wood (WBPs) were separated into four fractions by silica-gel column chromatography using n-hexane, n-hexane–dichloromethane (3:1, v\\/v), dichloromethane and methanol, as the corresponding eluents. The indirect-acting mutagenicity of each fraction was assayed by the Ames test using

Xiao-Yang Yang; Kazuhiko Igarashi; Ning Tang; Jin-Ming Lin; Wei Wang; Takayuki Kameda; Akira Toriba; Kazuichi Hayakawa

2010-01-01

279

Toxic polyneuropathy due to glue sniffing  

Microsoft Academic Search

Four cases of toxic polyneuropathy due to glue-sniffing were reported. Neurological examination revealed motor predominant mixed type polyneuropathy. The cause of polyneuropathies in these cases was considered to be due to the inhalation of the vaporized elements of the adhesive agent, which contain mainly n-hexane and toluene. N-hexane is considered to be chiefly responsible for the polyneuropathy, though toluene also

Ikuo Goto; Mutsuro Matsumura; Naohide Inoue; Yoshiyuki Murai; Kenshiro Shida; Tetsuji Santa; Yoshigoro Kuroiwa

1974-01-01

280

Control of charcoal rot fungus Macrophomina phaseolina by extracts of Datura metel  

Microsoft Academic Search

Methanolic leaf and fruit extracts of Datura metel were found highly effective in suppressing against Macrophomina phaseolina, the cause of charcoal rot disease. These extracts were further subjected to successive fractionation with n-hexane, chloroform, ethyl acetate and n-butanol. All the concentrations (3.125–200?mg?mL) of chloroform, ethyl acetate and n-butanol fractions of leaf extract, and n-hexane fraction of fruit extract completely inhibited

Arshad Javaid; Amna Saddique

2011-01-01

281

Control of charcoal rot fungus Macrophomina phaseolina by extracts of Datura metel  

Microsoft Academic Search

Methanolic leaf and fruit extracts of Datura metel were found highly effective in suppressing against Macrophomina phaseolina, the cause of charcoal rot disease. These extracts were further subjected to successive fractionation with n-hexane, chloroform, ethyl acetate and n-butanol. All the concentrations (3.125–200?mg?mL) of chloroform, ethyl acetate and n-butanol fractions of leaf extract, and n-hexane fraction of fruit extract completely inhibited

Arshad Javaid; Amna Saddique

2012-01-01

282

Continuous and Batch Distillation in an Oldershaw Tray Column  

ERIC Educational Resources Information Center

The importance of distillation in the separation field prompts the inclusion of distillation experiments in the chemical engineering curricula. This work describes the performance of an Oldershaw column in the rectification of a cyclohexane/n-heptane mixture. Total reflux distillation, continuous rectification under partial reflux, and batch…

Silva, Carlos M.; Vaz, Raquel V.; Santiago, Ana S.; Lito, Patricia F.

2011-01-01

283

Detailed chemical kinetic oxidation mechanism for a biodiesel surrogate  

Microsoft Academic Search

A detailed chemical kinetic mechanism has been developed and used to study the oxidation of methyl decanoate, a surrogate for biodiesel fuels. This model has been built by following the rules established by Curran and co-workers for the oxidation of n-heptane and it includes all the reactions known to be pertinent to both low and high temperatures. Computed results have

Olivier Herbinet; William J. Pitz; Charles K. Westbrook

2008-01-01

284

Removal of dyes and their mixtures from aqueous solution using liquid emulsion membrane  

Microsoft Academic Search

Extraction of dyes from aqueous solution was studied using liquid emulsion membrane. Study was carried out using two dyes, namely, crystal violet (CV) and methylene blue (MB). Extraction of single component system of each dye and their binary mixture were investigated. Liquid emulsion membrane was formed using n-heptane as membrane phase, sodium hydroxide solution as the internal phase and dye

Chandan Das; Meha Rungta; Gagandeep Arya; Sunando DasGupta; Sirshendu De

2008-01-01

285

ASPHALTENE PRECIPITATION AND SOLVENT PROPERTIES OF CRUDE OILS  

Microsoft Academic Search

Improved prediction of the onset of asphaltene precipitation may be achieved using refractive index (RI) to characterize crude oils and their mixtures with precipitants and solvents. Experimental measurements of RI for mixtures of several crude oils with the precipitant n-heptane, are reported at ambient conditions. Theoretical developments are described that will permit extension of these observations to reservoir conditionsMeasurements of

J. S. BUCKLEY; G. J. HIRASAKI; Y. LIU; S. VON DRASEK; J. X. WANG; B. S. GILL

1998-01-01

286

Using Nuclear Magnetic Resonance Spectroscopy for Measuring Ternary Phase Diagrams  

ERIC Educational Resources Information Center

A laboratory experiment is presented for the upper-level undergraduate physical chemistry curriculum in which the ternary phase diagram of water, 1-propanol and n-heptane is measured using proton nuclear magnetic resonance (NMR) spectroscopy. The experiment builds upon basic concepts of NMR spectral analysis, typically taught in the undergraduate…

Woodworth, Jennifer K.; Terrance, Jacob C.; Hoffmann, Markus M.

2006-01-01

287

Numerical study of a butanol\\/heptane fuelled Homogeneous Charge Compression Ignition (HCCI) engine utilizing negative valve overlap  

Microsoft Academic Search

► The calibration and comparison to experimental data of a parallel computing multizone combustion model. ► Simulation of operational characteristics of an n-butanol\\/n-heptane fuelled HCCI engine. ► Advanced engine design with the negative valve overlap (NVO) technology.

Sona Visakhamoorthy; John Z. Wen; Siva Sivoththaman; Charles Robert Koch

2012-01-01

288

Chemical flooding of oil reservoirs 7. Oil expulsion by spontaneous imbibition of brine with and without surfactant in mixed-wet, low permeability chalk material  

Microsoft Academic Search

Experiments are performed in four cores in order to study the effect of interfacial tension (IFT), wettability, and core length on the imbibition of water in an oil-saturated chalk material. Different wettability conditions are obtained by mixing different fractions of n-heptane with crude oil and by aging the chalk material in the oil mixture over different time intervals. In the

Jess Milter; Tor Austad

1996-01-01

289

Separation of Selected Bile Acids by TLC. I  

Microsoft Academic Search

Seven of the selected bile acids were investigated: cholic acid (C), chenodeoxycholic acid (CDC), deoxycholic acid (DC), lithocholic acid (LC), glycocholic acid (GC), glycodeoxycholic acid (GDC), and glycolithocholic acid (GLC). The retardation factor (RF), ?RF values, the separation factors (?), resolution factors (RS), as well as the constants of the pair separation (RF ), indicate that the mobile phase n?heptane–ethyl

A. Pyka; M. Do?owy

2003-01-01

290

Elimination of hydrophobic volatile organic compounds in fungal biofilters: reducing start-up time using different carbon sources.  

PubMed

Fungal biofilters have been recently studied as an alternative to the bacterial systems for the elimination of hydrophobic volatile organic compounds (VOC). Fungi foster reduced transport limitation of hydrophobic VOCs due to their hydrophobic surface and extended gas exchange area associated to the hyphal growth. Nevertheless, one of their principal drawbacks is their slow growth, which is critical in the start-up of fungal biofilters. This work compares the use of different carbon sources (glycerol, 1-hexanol, wheat bran, and n-hexane) to reduce the start-up period and sustain high n-hexane elimination capacities (EC) in biofilters inoculated with Fusarium solani. Four parallel experiments were performed with the different media and the EC, the n-hexane partition coefficient, the biomass production and the specific consumption rate were evaluated. Biofilters were operated with a residence time of 1.3?min and an inlet n-hexane load of 325?g?m(-3) (reactor) h(-1). The time to attain maximum EC once gaseous n-hexane was fed was reduced in the three experiments with alternate substrates, as compared to the 36 days needed with the control where only n-hexane was added. The shortest adaptation period was 7 days when wheat bran was initially used obtaining a maximum EC of 160?g?m(-3) (reactor) h(-1) and a critical load of 55?g?m(-3) (reactor) h(-1). The results were also consistent with the pressure drop, the amount of biomass produced and its affinity for the gaseous n-hexane, as represented by its partition coefficient. PMID:21404250

Vergara-Fernández, Alberto; Hernández, Sergio; Revah, Sergio

2011-04-01

291

Investigation of coal structure  

SciTech Connect

The method was applied to standard polymers under the same condition above. The particle size distribution with volume diameters of polyvinylpyrrolidone (average molecular mass; 10,000) was measured at sample/solvent = 0.50 g/100 ml. This polymer readily dissolve in methanol and water, while the polymer does not dissolve in n-hexane and toluene, and toluene is a slightly better solvent than n-hexane. Figure 3 shows the particle size distributions in n-hexane (a) and toluene (b-1 and -2). The distribution in toluene changed time to time, and two representative distributions are shown. The mean volume diameters-were 14 [mu]m in n-hexane and 18 and 31 [mu]m in toluene. The particle size distribution of cross-linked polyvinylpyrrolidone was further examined in methanol and n-hexane. Figure 4 compares these distributions with scanned counts at sample/solvent = 0.50 g/100 ml. As a significant portion of particles was over 250 [mu]m with volume diameters, the distributions are presented with scanned counts. Figure 4 compared the specific swelling ratio (Q') versus sample/solvent (w/w %) in the same solvents for this sample. It is seen that methanol is a good solvent than n-hexane and swells the sample. It is also seen that the swelling is dependent on the sample concentration. Therefore, the particle size in good solvent methanol is expected to be larger due to swelling. However, the particle size was smaller in methanol than in n-hexane (Figure 4). The dependence of sample concentration on solvent swelling in methanol (Figure 5) is interpreted as follows: Polymer particles disaggregated at low sample concentration and the interparticle voidage of the swollen polymer after centrifugation changed depending upon disaggregation.

Not Available

1993-01-01

292

Investigation of coal structure. Quarterly report, October 1, 1992--December 31, 1992  

SciTech Connect

The method was applied to standard polymers under the same condition above. The particle size distribution with volume diameters of polyvinylpyrrolidone (average molecular mass; 10,000) was measured at sample/solvent = 0.50 g/100 ml. This polymer readily dissolve in methanol and water, while the polymer does not dissolve in n-hexane and toluene, and toluene is a slightly better solvent than n-hexane. Figure 3 shows the particle size distributions in n-hexane (a) and toluene (b-1 and -2). The distribution in toluene changed time to time, and two representative distributions are shown. The mean volume diameters-were 14 {mu}m in n-hexane and 18 and 31 {mu}m in toluene. The particle size distribution of cross-linked polyvinylpyrrolidone was further examined in methanol and n-hexane. Figure 4 compares these distributions with scanned counts at sample/solvent = 0.50 g/100 ml. As a significant portion of particles was over 250 {mu}m with volume diameters, the distributions are presented with scanned counts. Figure 4 compared the specific swelling ratio (Q`) versus sample/solvent (w/w %) in the same solvents for this sample. It is seen that methanol is a good solvent than n-hexane and swells the sample. It is also seen that the swelling is dependent on the sample concentration. Therefore, the particle size in good solvent methanol is expected to be larger due to swelling. However, the particle size was smaller in methanol than in n-hexane (Figure 4). The dependence of sample concentration on solvent swelling in methanol (Figure 5) is interpreted as follows: Polymer particles disaggregated at low sample concentration and the interparticle voidage of the swollen polymer after centrifugation changed depending upon disaggregation.

Not Available

1993-01-01

293

Coal-water interaction and preparation of dewatered ultrafine clean coal  

SciTech Connect

The mandate of this project was to understand the mechanism responsible for coal-water interactions and to understand why coal holds water. In addition, we were to develop a bench-scale dewatering technique, based on heavy crude oil (< 20{degrees} API) treatments. Consequently, we undertook electron paramagnetic resonance (EPR), in situ desorption kinetics via Fourier transform infrared (ISDK-FTIR), specific heat, and in situ air-drying measurements on Hagel lignite coal, Illinois No. 2 bituminous coal, and oxidized Illinois No. 2 bituminous coal to understand how water interacts with coal. Attempts were also made to dewater Homer City bituminous coal cake and Illinois No. 2 coal-water slurry by treating these coals with (1) n-pentane, (2) petrolene {plus} n-pentane, (3) asphaltene {plus} benzene, (4) crude oil, and (5) crude oil {plus} asphaltene {plus} benzene. 34 refs., 34 figs., 11 tabs.

Malhotra, V.M.; Zitter, R.N.

1990-03-01

294

Chemical class separation of organics in shale oil by thin-layer chromatography  

SciTech Connect

Thin-layer chromatography (TLC) has been applied to the chemical class fractionation of shale oil. The chromatographic procedure gives rapid and reproducible separation of the oil into 14 fractions, without requiring prior extraction of asphaltenes, acids, or bases. The oil was adsorbed on silica-coated TLC plates and eluted with n-pentane and n-pentane/diethyl ether to separate the nonpolar and polar components, respectively. The principal compound types resolved included n-alkanes, alkenes, mono-, hydro-, di-, and polyaromatics, nitriles and ketones, hydroxyl aromatic hydrocarbons, and nitrogen heterocyctes. Compound identification was by gas chromatography/mass spectroscopy supplemented by ir spectrometry. The method significantly decreases the analysis time required for chemical class fractionation. 33 references, 4 figures, 1 table.

Harvey, T.G.; Matheson, T.W.; Pratt, K.C.

1984-01-01

295

Branched vs. linear hydrocarbon separations with novel modified zeolites.  

SciTech Connect

The conclusions of this paper are: (1) Adsorption/desorption on bulk unmodified zeolites showed isoprene adsorbed by zeolite-L and n-pentane adsorbed by zeolite-Y and ZSM-5; (2) Bulk carbonization is used to passivate zeolite activity toward organic adsorption/decomposition; (3) Based on the bulk modified zeolite separation results, we have determined that the MFI type has the most potential for isoprene enrichment; (4) Modified MFI type membrane are jointly made by Sandia and the Univ. of Colorado. Separation experiments are performed by Goodyear Chemical; (5) Isoprene/n-pentane separations have been demonstrated by using both zeolite membranes and modified bulk zeolites at various temperatures on the Goodyear Pilot-scale unit; and (6) Target zeolite membrane separations values of 6.7% isoprene enrichment have been established by economic analysis calculations by Burns & McDonnell.

Gray, Gary R.; Noble, Richard D.; Nenoff, Tina Maria; Arruebo, Manuel; Ulutagay-Kartin, Mutlu; Johnston, Kaylynn; Anderson, Thomas M.

2005-06-01

296

Branched vs. linear hydrocarbon separations with novel modified zeolites.  

SciTech Connect

Conclusions of this paper are: (1) Adsorption/desorption on bulk unmodified zeolites showed isoprene adsorbed by zeolite-L and n-pentane adsorbed by zeolite-Y and ZSM-5; (2) Bulk carbonization is used to passivate zeolite activity toward organic adsorption/decomposition; (3) Based on the bulk modified zeolite separation results, we have determined that the MFI type has the most potential for isoprene enrichment; (4) Modified MFI type membranes are jointly made by Sandia and the Univ. of Colorado. Separation experiments are performed by Goodyear Chemical; (5) Isoprene/n-pentane separations have been demonstrated by using both zeolite membranes and modified bulk zeolites at various temperatures on the Goodyear Pilot-scale unit; and (6) Target zeolite membrane separations values of 6.7% isoprene enrichment have been established by economic analysis calculations by Burns & McDonnell.

Gray, Gary R.; Noble, Richard D.; Nenoff, Tina Maria; Arruebo, Manuel; Ulutagay-Kartin, Mutlu; Anderson, Thomas M.

2004-08-01

297

Stable Isotopic Studies of n-Alkane Metabolism by a Sulfate-Reducing Bacterial Enrichment Culture  

PubMed Central

Gas chromatography-mass spectrometry and nuclear magnetic resonance spectroscopy were used to study the metabolism of deuterated n-alkanes (C6 to C12) and 1-13C-labeled n-hexane by a highly enriched sulfate-reducing bacterial culture. All substrates were activated via fumarate addition to form the corresponding alkylsuccinic acid derivatives as transient metabolites. Formation of d14-hexylsuccinic acid in cell extracts from exogenously added, fully deuterated n-hexane confirmed that this reaction was the initial step in anaerobic alkane metabolism. Analysis of resting cell suspensions amended with 1-13C-labeled n-hexane confirmed that addition of the fumarate occurred at the C-2 carbon of the parent substrate. Subsequent metabolism of hexylsuccinic acid resulted in the formation of 4-methyloctanoic acid, and 3-hydroxy-4-methyloctanoic acid was tentatively identified. We also found that 13C nuclei from 1-13C-labeled n-hexane became incorporated into the succinyl portion of the initial metabolite in a manner that indicated that 13C-labeled fumarate was formed and recycled during alkane metabolism. Collectively, the findings obtained with a sulfate-reducing culture using isotopically labeled alkanes augment and support the previously proposed pathway (H. Wilkes, R. Rabus, T. Fischer, A. Armstroff, A. Behrends, and F. Widdel, Arch. Microbiol. 177:235-243, 2002) for metabolism of deuterated n-hexane by a denitrifying bacterium.

Davidova, Irene A.; Gieg, Lisa M.; Nanny, Mark; Kropp, Kevin G.; Suflita, Joseph M.

2005-01-01

298

Open Cell Isocyanurate Foams for Vacuum Insulation Panels  

Microsoft Academic Search

This paper describes the preparation, processing, properties and applications of open cell rigid isocyanurate foams. A mechanism for the formation of open cell rigid foams is discussed. The open cell foams were blown by using a blend of methylene chloride and n-pentane at specific ratios between 95\\/5 and 50\\/50 by weight. The resulting foams had open cell contents of about

Kaneyoshi Ashida; Josho Kashiwame

1995-01-01

299

Development of a prototype low-temperature Rankine cycle electricity generation system  

Microsoft Academic Search

This paper describes the development of a small-scale system designed to generate electricity from low temperature heat (e.g., solar energy). The system operates on the Rankine cycle and uses n-pentane as the working fluid. A prototype system has been designed, constructed and tested. It is capable of delivering 1.5 kW of electricity with a thermal efficiency of 4.3%. Laboratory test

V. M. Nguyen; P. S. Doherty; S. B. Riffat

2001-01-01

300

Coupling Kernel Principal Component Analysis with ANN for improving analysis accuracy of seven-component alkane gaseous mixture  

Microsoft Academic Search

To further improving the analysis accuracy of Artificial Neural Networks (ANN) model for quantitative analysis of seven-component alkane gaseous mixtures composed of methane, ethane, propane, isobutane, n-butane, isopentane, and n-pentane, the Kernel Principal Component Analysis (KPCA) technique was proposed to couple with it. The gaseous mixtures were measured by a novel Acousto-Optic Tunable Filter Near Infrared (AOTF-NIR) spectrometer. KPCA mapped

Huimin Hao; Jianan Cao; Hongliang Wang; Zhiqiang Yu; Junhua Liu

2008-01-01

301

Kinetics and Products of the Gas-Phase Reaction of OH Radicals with 5Hydroxy2Pentanone at 296± 2 K  

Microsoft Academic Search

The 1,4-hydroxycarbonyl 5-hydroxy-2-pentanone is an important product of the gas-phase reaction of OH radicals with n-pentane in the presence of NO. We have used a relative rate method with 4-methyl-2-pentanone as the reference compound to measure the rate constant for the reaction of OH radicals with 5-hydroxy-2-pentanone at 296 ± 2 K. The carbonyls were sampled by on-fiber derivatization using

Sara M. Aschmann; Janet Arey; Roger Atkinson

2003-01-01

302

The effects of pressure, temperature, and concentration on the reactivity of alkanes: Experiments and modeling in a rapid compression machine  

Microsoft Academic Search

Experiments in a rapid compression machine have examined the influences of variations in pressure, temperature, and equivalence ratio on the autoignition of n-pentane. Equivalence ratios included values from 0.5 to � 2.0, compressed gas initial temperatures were varied between 675K and 980K, and compresed gas initial pressures varied from 8 to 20 bar. Numerical simulations of the same experiments were

C. K. Westbrook; H. J. Curran; W. J. Pitz; J. F. Griffiths; C. Mohamed; S. K. Wo

1998-01-01

303

Heat transfer with vaporization of a liqud by direct contact in another immiscible liquid: Experimental and numerical study  

Microsoft Academic Search

An experimental setup was designed to study direct-contact evaporators using a liquid dispersed in another immiscible liquid. The study was carried out on an n-pentane-water system to determine the influence of different parameters on these systems, and consequently to construct a model for this type of evaporator. An optical probe was used to measure the local void fraction. At different

L. Tadrist; J. Sun; R. Santini; J. Pantaloni

1991-01-01

304

Cometabolism of Methyl tertiary Butyl Ether and Gaseous n-Alkanes by Pseudomonas mendocina KR-1 Grown on C5 to C8 n-Alkanes  

PubMed Central

Pseudomonas mendocina KR-1 grew well on toluene, n-alkanes (C5 to C8), and 1° alcohols (C2 to C8) but not on other aromatics, gaseous n-alkanes (C1 to C4), isoalkanes (C4 to C6), 2° alcohols (C3 to C8), methyl tertiary butyl ether (MTBE), or tertiary butyl alcohol (TBA). Cells grown under carbon-limited conditions on n-alkanes in the presence of MTBE (42 ?mol) oxidized up to 94% of the added MTBE to TBA. Less than 3% of the added MTBE was oxidized to TBA when cells were grown on either 1° alcohols, toluene, or dextrose in the presence of MTBE. Concentrated n-pentane-grown cells oxidized MTBE to TBA without a lag phase and without generating tertiary butyl formate (TBF) as an intermediate. Neither TBF nor TBA was consumed by n-pentane-grown cells, while formaldehyde, the expected C1 product of MTBE dealkylation, was rapidly consumed. Similar Ks values for MTBE were observed for cells grown on C5 to C8 n-alkanes (12.95 ± 2.04 mM), suggesting that the same enzyme oxidizes MTBE in cells grown on each n-alkane. All growth-supporting n-alkanes (C5 to C8) inhibited MTBE oxidation by resting n-pentane-grown cells. Propane (Ki = 53 ?M) and n-butane (Ki = 16 ?M) also inhibited MTBE oxidation, and both gases were also consumed by cells during growth on n-pentane. Cultures grown on C5 to C8 n-alkanes also exhibited up to twofold-higher levels of growth in the presence of propane or n-butane, whereas no growth stimulation was observed with methane, ethane, MTBE, TBA, or formaldehyde. The results are discussed in terms of their impacts on our understanding of MTBE biodegradation and cometabolism.

Smith, Christy A.; O'Reilly, Kirk T.; Hyman, Michael R.

2003-01-01

305

Vapour-liquid coexistence curves of the united-atomand anisotropic united-atom force fields for alkane mixtures  

Microsoft Academic Search

The performances of two categories of force field for mixtures of alkanes are compared. Configurational-bias Monte Carlo simulations in the Gibbs ensemble were carried out to compute the vapour-liquid coexistence curves (VLCC) for pure n-pentane and n-dodecane and for binary mixtures of these components with methane. The united-atom (UA) force field (Siepmann and coworkers) and the anisotropic united-atom (AUA) force

Jerome Delhommelle; Anne Boutin; Bernard Tavitian; Allan D. Mackie; Alain H. Fuchs

1999-01-01

306

Vapour-Liquid Phase Equilibria Predictions of Methane–Alkane Mixtures by Monte Carlo Simulation  

Microsoft Academic Search

We report molecular simulations of methane–alkane mixtures using the Gibbs ensemble technique combined with the configurational-bias Monte Carlo method. The intermolecular interactions are modeled using both the united atom model with parameters proposed by Smit et al. and the anisotropic united atom model by Toxvaerd. Liquid-vapour phase diagrams are calculated for methane-n-pentane and methane-n-dodecane mixtures using these two potential models

Allan D. Mackie; Bernard Tavitian; Anne Boutin; Alain H. Fuchs

1997-01-01

307

A coupled implicit method for chemical non-equilibrium flows at all speeds  

NASA Technical Reports Server (NTRS)

The present time-accurate coupled-solution procedure addresses the chemical nonequilibrium Navier-Stokes equations over a wide Mach-number range uses, in conjunction with the strong conservation form of the governing equations, five unknown primitive variables. The numerical tests undertaken address steady convergent-divergent nozzle flows with air dissociation/recombination, dump combustor flows with n-pentane/air chemistry, and unsteady nonreacting cavity flows.

Shuen, Jian-Shun; Chen, Kuo-Huey; Choi, Yunho

1993-01-01

308

Explicit photochemical mechanism for atmospheric oxidation of n-butane  

Microsoft Academic Search

Alkanes, being an important component of atmosphere, serve as precursors to ozone formation in urban and rural air masses. An explicit photochemical oxidation mechanism for n-butane, which is the major hydrocarbon component of automobile exhaust, is created in this work. The yields of organic nitrates from n-butane, n-pentane, and methyl ethyl ketone photooxidations were studied in Teflon bag and smog

Wen

1992-01-01

309

Gas solubilities, vapor-liquid equilibria, and partial molal volumes in some hydrogen-hydrocarbon systems  

SciTech Connect

Gas solubilities were measured for hydrogen in n-pentane, 2,3-dimethylbutane, cyclohexane, n-decane, m-xylene, 1,4-diethylbenzene, and 1-methylnaphthalene. Vapor-liquid equilibrium ratios (K's) were measured for the second, third, fifth, and sixth of these systems. Partial molal volumes of hydrogen dissolved in the liquid hydrocarbons were measured for all systems except methylnaphthalene. Temperatures and pressures fell in the ranges 35-320/sup 0/C and 200-2400 psi.

Connolly, J.F.; Kandalic, G.A.

1986-10-01

310

High-Pressure Gas Chromatography and Chromatography with Supercritical Fluids. III. Fluid-Liquid Chromatography  

Microsoft Academic Search

High-boiling substances can be separated by partition chromatography, using n-pentane and isopropanol under supercritical conditions as mobile carriers. At moderate temperatures (200–250°C) the volatility of heavy substances may be enhanced by a factor of as much as 10 by increasing the pressure from atmospheric to about 50 kg\\/cm. This enables the analysis of compounds which are too heavy for ordinary

S. T. Sie; G. W. A. Rijnders

1967-01-01

311

Pseudotenfold symmetry in pentane-solvated C60 and C70  

Microsoft Academic Search

Crystals of C60 or C70 cocrystallized with n-pentane grow as elongated, ten-sided columns. X-ray diffraction shows ordering of C60 or C70 molecules along the column and a remarkable tenfold symmetry normal to the column. The ratio of the x-ray-diffraction vectors of the two lowest-order diffraction spots is nearly equal to the ``golden ratio,'' tau. Despite these similarities with decagonal, quasicrystalline

R. M. Fleming; A. R. Kortan; B. Hessen; T. Siegrist; F. A. Thiel; P. Marsh; R. C. Haddon; R. Tycko; G. Dabbagh; M. L. Kaplan; A. M. Mujsce

1991-01-01

312

Direct synthesis of Zr-SBA-15 mesoporous molecular sieves with high zirconium loading: Characterization and catalytic performance after sulfated  

Microsoft Academic Search

The Zr-SBA-15 mesoporous materials with high Zr\\/Si ratio (0–2.32) were first synthesized directly using zirconium nitrate and tetraethyl orthosilicate as precursor, displaying higher thermal stability after activated at 600°C. 29Si NMR spectra revealed the part existance of ZrO2 in the framework of SBA-15. After sulfated, the SO42-\\/Zr-SBA-15 exhibited high activity in the isomerization of n-pentane at 35°C, and the conversion

Li Fuxiang; Yu Feng; Li Yongli; Li Ruifeng; Xie Kechang

2007-01-01

313

Hydrogen production. [production from light hydrocarbon paraffins, separating the hydrogen from the effluent product, and, if desired, hydrogenating heavy unsaturated hydrocarbons with the hydrogen  

Microsoft Academic Search

A process is claimed for the production of hydrogen, including contacting a light paraffinic hydrocarbon such as ethane, propane, n-butane, iso-butane, n-pentane, isopentane, etc., with a catalyst comprising an active metal selected from the group consisting of a Group VIII metal, and a Group VIB metal, in an amount between about 0.5 and 15 percent by weight of the finished

R. A. Kmecak; S. M. Kovach

1976-01-01

314

Experimental analysis of local void fractions measurements for boiling hydrocarbons in complex geometry  

Microsoft Academic Search

The present paper is part of a research program on two-phase flows and heat transfer studies in tube bundles. An experimental study was carried out to analyse the void fraction for vertical two-phase flows. Boiling across a horizontal tube bundle for three hydrocarbons (n-pentane, propane and iso-butane) under saturated conditions is investigated. The experiments were performed on a tube bundle

L. Aprin; P. Mercier; L. Tadrist

2007-01-01

315

Adsorption of hydrocarbons on carbon molecular sieve  

Microsoft Academic Search

Tokyo Metropolitan University's Dept. of Industrial Chemistry gravimetrically measured the adsorption equilibria of methane, ethane, ethylene, propane, propylene, n-butane,, n-pentane, benzene, and cyclohexane on commercially available carbon molecular sieves at the temperature range of 5.4°⁻⁵°sup 0\\/C and pressures up to 1 atm. The experiment, part of a continuing study of the adsorption of gases and vapor on microporous solids, reports

Tomoko Nakahara; Mitsuho Hirata; Toshiaki Omori

1974-01-01

316

Expandable graphite as an intumescent flame retardant in polyisocyanurate–polyurethane foams  

Microsoft Academic Search

Flame retarded polyisocyanurate–polyurethane (FR PIR–PUR) foams have been synthesized by the use of a new flame retardant, expandable graphite (EG foams), never used on industrial scale in polyurethane rigid foams, and a mixture of expandable graphite and triethylphosphate (EG–TEP foams). FR PIR–PUR foams, blown with n-pentane, have been prepared with a constant NCO index (250) in order to achieve greater

M Modesti; A Lorenzetti; F Simioni; G Camino

2002-01-01

317

A kinetic model for the hexane cracking reaction over H-ZSM-5  

SciTech Connect

A kinetic model for the n-hexane cracking reaction over H-ZSM-5 has been developed. This model describes hydrocarbon transformations in the following reaction steps: protolytic cracking of n-hexane, hydrogen transfer between-hexane and light olefins, oligomerization, and cracking of olefins. The activation energy of the protolytic cracking steps is 75.6-152.4 kJ/mol, depending on the reaction products, and that of the hydrogen transfer steps is 4.1-8.9 kJ/mol, depending on the olefin involved in the reaction step. It is demonstrated that a considerable contribution from hydrogen transfer to n-hexane cracking manifests itself in the autocatalytic character for the reaction at 400[degrees]C. At 538[degrees]C (the temperature of the [alpha]-test) hydrogen transfer does not play an appreciable role in hexane cracking over H-ZSM-5 zeolites. 19 refs., 4 figs., 4 tabs.

Lukyanov, D.B.; Shtral, V.I. (Karpov Institute of Physical Chemistry, Moscow (Russian Federation)); Khadzhiev, S.N. (Groznyi Petroleum Institute, (Russian Federation))

1994-03-01

318

Allelopathic potential of Artemisia arborescens: isolation, identification and quantification of phytotoxic compounds through fractionation-guided bioassays.  

PubMed

The aerial part of Artemisia arborescens L. (Asteraceae) was extracted with water and methanol, and both extracts were fractionated using n-hexane, chloroform, ethyl acetate and n-butanol. The potential phytotoxicity of both crude extracts and their fractions were assayed in vitro on seed germination and root growth of lettuce (Lactuca sativa L.), a sensitive species largely employed in the allelopathy studies. The inhibitory activities were analysed by dose-response curves and the ED 50 were estimated. Crude extracts strongly inhibited both germination and root growth processes. The fraction-bioassay indicated the following hierarchy of phytotoxicity for both physiological processes: ethyl acetate ? n-hexane > chloroform ? n-butanol. On the n-hexane fraction, GC-MS analyses were carried out to characterise and quantify some of the potential allelochemicals. Twenty-one compounds were identified and three of them, camphor, trans-caryophyllene and pulegone were quantified. PMID:22687059

Araniti, Fabrizio; Lupini, Antonio; Sorgonà, Agostino; Conforti, Filomena; Marrelli, Mariangela; Statti, Giancarlo Antonio; Menichini, Francesco; Abenavoli, Maria Rosa

2013-01-01

319

Isolation of Aurantiamides from Gomphrena Celosioides C. Mart  

PubMed Central

In West Africa and Nigeria in particular, many virgin plants are still waiting to be evaluated for their medicinal importance. Claims of plants with folk medicinal applications need to be evaluated and verified. Gomphrena celosioides (family – Amaranthaceae) is a weed grown in lawns and the biological activity of the extract had earlier been established. In the present study, the plant was collected, air dried, ground and soxhlet extracted with n-hexane and two compounds were isolated from the flakes that were recovered from the n-hexane extract on cooling. Column chromatography using 5% chloroform in n-hexane effected the separation. The structures of the isolated compounds were elucidated by spectroscopic analysis using IR, NMR (1H and 13C) and EI-MS. The compounds were found to be aurantiamide and aurantiamide acetate. This is the first report of isolation of these compounds in Gomphrena celosioides.

Olutola Dosumu, Omotayo; Onocha, Patricia; Ekundayo, Olusegun; Ali, Muhammad

2014-01-01

320

Simple solvothermal synthesis of hydrophobic magnetic monodispersed Fe{sub 3}O{sub 4} nanoparticles  

SciTech Connect

Graphical abstract: A facile method to produce monodispersed magnetite nanoparticles is based on the solvothermal reaction of iron acetylacetonate (Fe(acac)3) decomposition. The sizes ranged from 7 to 12 nm, which could be controlled by adjusting the volume ratio of oleylamine to n-hexane. Display Omitted Highlights: ? The solvethermal reaction of Fe(acac){sub 3} decomposition was carried out at mild temperature in the presence of oleylamine and n-hexane. ? The size of nanocrystals is controlled by adjusting the volume ratio of oleylamine to n-hexane. ? The low-boiling-point solvent n-hexane offered autogenous pressure parameter after gasified in the reaction temperature. ? The as prepared hydrophobic monodisperse Fe{sub 3}O{sub 4} NPs can be used to prepare the magnetic micelles for future biomedical applications. -- Abstract: A new solvothermal method is proposed for the preparation of Fe{sub 3}O{sub 4} nanoparticles (NPs) from iron acetylacetonate in the presence of oleylamine and n-hexane. The products are characterized by X-ray powder diffraction, infrared (IR) spectroscopy, transmission electron microscopy, thermogravimetry/differential thermogravimetry (TG/DTG) analysis, and vibrating sample magnetometery. The new procedure yields superparamagnetic monodispersed Fe{sub 3}O{sub 4} particles with sizes ranging from 7 nm to 12 nm. The nanocrystal sizes are controlled by adjusting the volume ratio of oleylamine to n-hexane. IR and TG/DTG analyses indicate that the oleylamine molecules, as stabilizers, are adsorbed on the surface of Fe{sub 3}O{sub 4} NPs as bilayer adsorption models. The surface adsorption quantities of oleylamine on 7.5 and 10.4 nm-diameter Fe{sub 3}O{sub 4} NPs are 18% and 11%, respectively. The hydrophobic surface of the obtained nanocrystals is passivated by adsorbed organic solvent molecules. These molecules provide stability against agglomeration, enable solubility in nonpolar solvents, and allow the formation of magnetic polymer micelles.

Liu, Jing; Wang, Lu [School of Pharmaceutical Sciences, Hebei Medical University, Shijiazhuang 050017 (China)] [School of Pharmaceutical Sciences, Hebei Medical University, Shijiazhuang 050017 (China); Wang, Jing, E-mail: Jingwang@home.ipe.ac.cn [School of Pharmaceutical Sciences, Hebei Medical University, Shijiazhuang 050017 (China)] [School of Pharmaceutical Sciences, Hebei Medical University, Shijiazhuang 050017 (China); Zhang, Lantong, E-mail: zhanglantong@263.net [School of Pharmaceutical Sciences, Hebei Medical University, Shijiazhuang 050017 (China)] [School of Pharmaceutical Sciences, Hebei Medical University, Shijiazhuang 050017 (China)

2013-02-15

321

Evidence for the contribution of methane in the formation of aromatics and soot in fuel-rich pre-mixed combustion.  

PubMed

Experimental results from an isothermal laminar flow reactor at atmospheric pressure are presented on the chemical composition in the post-oxidative region of two sooting fuel-rich pre-mixed mixtures diluted in nitrogen. A base case composed of n-heptane and O2 in N2 at 1425 K with a C/O of 2.85 was perturbed by substituting 10% of the carbon in n-heptane with carbon as CH4. While these changes would intuitively reduce aromatics and soot formation by increasing H2 and decreasing C2H2 concentrations, we observe the opposite. The concentrations of individual aromatic species are observed to actually increase by up to 50% and the soot yield increases by 80%. PMID:11219708

Roesler, J F; de Tessan, M A; Montagne, X

2001-01-01

322

Reduction of Large Detailed Chemical Kinetic Mechanisms for Autoignition Using Joint Analyses of Reaction Rates and Sensitivities  

SciTech Connect

A new technique of reduction of detailed mechanisms for autoignition, which is based on two analysis methods is described. An analysis of reaction rates is coupled to an analysis of reaction sensitivity for the detection of redundant reactions. Thresholds associated with the two analyses have a great influence on the size and efficiency of the reduced mechanism. Rules of selection of the thresholds are defined. The reduction technique has been successfully applied to detailed autoignition mechanisms of two reference hydrocarbons: n-heptane and iso-octane. The efficiency of the technique and the ability of the reduced mechanisms to reproduce well the results generated by the full mechanism are discussed. A speedup of calculations by a factor of 5.9 for n-heptane mechanism and by a factor of 16.7 for iso-octane mechanism is obtained without losing accuracy of the prediction of autoignition delay times and concentrations of intermediate species.

Saylam, A; Ribaucour, M; Pitz, W J; Minetti, R

2006-11-29

323

Synthesis of 4-nitrophenyl acetate using molecular sieve-immobilized lipase from Bacillus coagulans.  

PubMed

Extracellular lipase from Bacillus coagulans BTS-3 was immobilized on (3 A x 1.5 mm) molecular sieve. The molecular sieve showed approximately 68.48% binding efficiency for lipase (specific activity 55 IU mg(-1)). The immobilized enzyme achieved approx 90% conversion of acetic acid and 4-nitrophenol (100 mM each) into 4-nitrophenyl acetate in n-heptane at 65 degrees C in 3 h. When alkane of C-chain length other than n-heptane was used as the organic solvent, the conversion of 4-nitrophenol and acetic acid was found to decrease. About 88.6% conversion of the reactants into ester was achieved when reactants were used at molar ratio of 1:1. The immobilized lipase brought about conversion of approximately 58% for esterification of 4-nitrophenol and acetic acid into 4-nitrophenyl acetate at a temperature of 65 degrees C after reuse for 5 cycles. PMID:19104860

Raghuvanshi, Shilpa; Gupta, Reena

2009-03-01

324

Two-dimensional thin layer chromatographic separation of phenolic compounds from Eupatorium cannabinum extracts and their antioxidant activity.  

PubMed

Two dimensional thin layer chromatography on DIOL polar bonded stationary phase was performed to optimize the separation of some anioxidant phenolic compounds from Eupatorium cannabinum extracts. Ethyl-methyl ketone mixed with n-heptane and ethyl acetate mixed with n-heptane were used as non-aqueous mobile phases in normal phase separations (1st direction of development in 2D-HPTLC mode) and methanol mixed with water was used as a mobile phase in reversed phase (2nd direction of development in 2D-HPTLC mode). The plates were sprayed by use of Merck TLC sprayer using 2-(diphenylboryoxy)-ethylamine and PEG4000 (Merck, Darmstadt, Germany) or DPPH and photographed in Camag Cabinet UV lamp at 254 nm and 365 nm by use of Fuji 8 mpx camera. Satisfactory separations of antioxidant phenolic compounds in Eupatorium cannabinum extracts were obtained by use of optimized 2D-HPTLC systems. PMID:22420560

Hawry?, Miroslaw A; Nowak, Renata; Waksmundzka-Hajnos, Monika; Swieboda, Ryszard; Robak, Monika

2012-01-01

325

Determination of organosilicon oxide polymers in tissue by atomic absorption spectroscopy using HGA graphite furnace.  

PubMed

A simple method of extraction and determination of organosilicon oxide polymers (silicones) in 0.1-0.5 g of formalin fixed tissue by atomic absorption spectroscopy is described. Before the tissue is extracted with n-heptane, it is dried in a desiccator containing concentrated sulphuric acid. The graphite tubes in the HGA graphite furnace are tubes with L'vov platform. The evaporation of n-heptane and a part of the charing of the tissue extract in the tube are done in the presence of oxygen (air). The significance of the employment of L'vov platform and the presence of oxygen are discussed. The methods detection limit (2 X S.D.) is about 0.009 microgram silicon/ml tissue extract which corresponds to about 0.5 microgram polydimethylsiloxane/g tissue. PMID:3770602

Felby, S

1986-01-01

326

Autoignition of gasoline surrogates mixtures at intermediate temperatures and high pressures  

SciTech Connect

Ignition times were determined in high-pressure shock-tube experiments for various stoichiometric mixtures of two multicomponent model fuels in air for the validation of ignition delay simulations based on chemical kinetic models. The fuel blends were n-heptane (18%)/isooctane (62%)/ethanol (20%) by liquid volume (14.5%/44.5%/41% by mole fraction) and n-heptane (20%)/toluene (45%)/isooctane (25%)/diisobutylene (10%) by liquid volume (17.5%/55%/19.5%/8.0% by mole fraction). These fuels have octane numbers comparable to a standard European gasoline of 95 RON and 85 MON. The experimental conditions cover temperatures from 690 to 1200 K and pressures at 10, 30, and 50 bar. The obtained ignition time data are scaled with respect to pressure and compared to previous results reported in the literature. (author)

Fikri, M.; Herzler, J.; Starke, R.; Schulz, C.; Roth, P. [IVG, Universitaet Duisburg-Essen, D-47048 Duisburg (Germany); Kalghatgi, G.T. [Shell Global Solutions U.K., P.O. Box 1, Chester CH1 3SH (United Kingdom)

2008-01-15

327

Formation of mesoporous alumina via hydrolysis of modified aluminum isopropoxide in presence of CTAB cationic surfactant  

NASA Astrophysics Data System (ADS)

Formation of mesoporous alumina at room temperature via combined utilization of acetic acid (as an organic modifier) and cetyl trimethyl ammonium bromide (CTAB) as a cationic surfactant has been investigated in n-heptane medium. The reactants molar ratio was aluminum isopropoxide:acetic acid:water:CTAB:n-heptane, as 1:1:3: x:15, where x was 1 or 3. The calcined materials (at 600 °C for 3 h) were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and N 2 adsorption/desorption techniques. Thus, amorphous (weakly crystalline ?-phase) mesoporous aluminas of possible hexagonal symmetry, high surface area and relatively narrow pore size distribution were obtained. The enhancement of surface area and retardation of crystallization were found to increase with the increasing of CTAB ration in the reaction mixture.

Khalil, Kamal M. S.

2008-12-01

328

Combined small-angle x-ray scattering/extended x-ray absorption fine structure study of coated Co nanoclusters in bis(2-ethylhexyl)sulfosuccinate  

NASA Astrophysics Data System (ADS)

Chemically stable cobalt nanostructures have been prepared with Co(II) reduction in the confined space of cobalt bis(2-ethylhexyl)sulfosuccinate, Co(AOT)2, reverse micelles dispersed in n-heptane. The reaction was carried out by adding a solution of sodium borohydride in ethanol (1% weight) to a 0.2M micellar solution of Co(AOT)2 in n-heptane at a reductant to Co(II) molar ratio of 4. This procedure involves the rapid formation of surfactant-coated Co nanoparticles followed by their slow separation as nanostructures embedded in a sodium bis(2-ethylhexyl)sulfosuccinate matrix. The resulting composites, characterized by extended x-ray absorption fine structure and small-angle x-ray scattering, showed the presence of subnanometer sized cobalt nanoparticles aggregated together to form elongated structures coated by the surfactant molecules.

Longo, A.; Giordano, F.; Giannici, F.; Martorana, A.; Portale, G.; Ruggirello, A.; Turco Liveri, V.

2009-06-01

329

Calibration of a Harwood DWT-1000 controlled-clearance piston gauge  

NASA Astrophysics Data System (ADS)

To meet growing demands for higher pressure measurements and measurement accuracies up to 200,000 psig, the Physical Metrology Laboratory (PML) at Rocky Flats Plant, Golden, Colorado, purchased and calibrated a Harwood Model DWT-1000, controlled-clearance piston gauge. Calibration of the DWT-1000 followed guidelines established by the National Bureau of Standards (NBS). The pressure medium used during operation and calibration of the system was n-Heptane. Due to the flammability of n-Heptane, safety enclosure was designed and constructed around the DWT-1000 which, when used in conjunction with a data acquisition console, monitors both safety and calibration equipment while protecting the surrounding environment in the event of a sudden pressure release. Calibration results and procedures are compiled in this report to assist those who will be or are presently confronted with the challenge of calibrating a similar type controlled-clearance piston gauge.

Shain, D. I.; Deitesfeld, C. A.

1987-09-01

330

Investigation of atmospheric pressure capillary non-thermal plasmas and their applications to the degradation of volatile organic compounds  

NASA Astrophysics Data System (ADS)

Atmospheric pressure capillary non-thermal plasma (AP-CNTP) has been investigated as a potential technology far the removal of volatile organic compounds (VOCs) in Advanced Life Support Systems (ALS). AP-CNTP is a destructive technology far the removal of VOCs from air streams by active plasma species, such as electrons, ions, and excited molecules. Complete VOC destruction ideally results in the formation of water, carbon dioxide (CO2), and other by-product's may also form, including ozone (O3), nitrous oxide (N2O), nitrogen dioxide (NO2), and decomposed hydrocarbons. Several organic compounds, such as BTEX, ethylene, n-heptane, isooctane, methanol and NH3, were tested in an AP-CNTP system. Parametric experiments were carried out by varying plasma discharge power, flowrates, and initial concentrations. The degradation efficiency varied depending on the chemical nature of the compounds. A plasmochemical kinetic model was derived for toluene, ethylbenzene, and m-xylene and n-heptane.

Yin, Shu-Min

331

Rotational Isomers, Intramolecular Hydrogen Bond, and IR Spectra of o-Vinylphenol  

NASA Astrophysics Data System (ADS)

Absorption bands of OH stretching vibrations in IR spectra of o-vinylphenol ( o-VP) in the weakly polar solvents CCl4 and n-hexane were studied. Several rotamers of the free OH group were observed for o-VP in n-hexane. The fraction of o-VP rotamers with an O-H…? intramolecular hydrogen bond (IHB) was less than 20% according to experimental estimates for CCl4 solutions and calculations in the gas phase and cyclohexane. The theoretical effective enthalpy of the o-VP IHB was estimated for rotamer A (-?H = 0.20 kcal/mol).

Glazunov, V. P.; Berdyshev, D. V.; Balaneva, N. N.; Radchenko, O. S.; Novikov, V. L.

2014-03-01

332

A Pretreatment Method for GC–MS Determination of Endocrine Disrupting Chemicals in Mollusk Tissues  

Microsoft Academic Search

Automatic soxhlet extraction followed by silica gel cartridge cleanup process was developed as a pretreatment method for GC–MS\\u000a determination of seven endocrine disrupting chemicals in mollusk tissues. Operation parameters including extraction time,\\u000a adsorption flow rate and elution flow rate were optimized as 140 min, 2 mL min?1 and 2 mL min?1, respectively. Thirty percent dichloromethane in n-hexane and 70% dichloromethane in n-hexane were used as

Ying Liu; Yuntao Guan; Tadao Mizuno; Hiroshi Tsuno; Wapeng Zhu

2009-01-01

333

Fast solid-phase extraction–gas chromatography–mass spectrometry procedure for oil fingerprinting  

Microsoft Academic Search

A rapid and simple fractionation procedure using solid-phase extraction (SPE) cartridges was developed for an accurate determination of aliphatic and polycyclic aromatic hydrocarbons in petroleum residues and further application in chemical fingerprinting of oil spills by gas chromatography–mass spectrometry (GC–MS). Among the adsorbents evaluated, SiO2\\/C3?CN exhibited the best selectivity, providing, by elution with n-hexane (4ml) and n-hexane–CH2Cl2 (1:1) (5ml), two

Roberto Alzaga; Paolo Montuori; Laura Ortiz; Josep M Bayona; Joan Albaigés

2004-01-01

334

Selective hydrogenation of chloronitrobenzene to chloroaniline in supercritical carbon dioxide over Ni\\/TiO 2: Significance of molecular interactions  

Microsoft Academic Search

The hydrogenation of chloronitrobenzene to chloroaniline was investigated over Ni\\/TiO2 at 35°C in supercritical CO2 (scCO2), ethanol, and n-hexane. The reaction rate followed the order of scCO2>n-hexane>ethanol. In scCO2, the selectivity to chloroaniline and to aniline over Ni\\/TiO2 were 97–99.5% and <1%, respectively, in the conversion range of 9–100%. The high chemoselectivity to chloroaniline cannot be achieved over Ni\\/TiO2 in

Xiangchun Meng; Haiyang Cheng; Shin-ichiro Fujita; Yufen Hao; Yanjiao Shang; Yancun Yu; Shuxia Cai; Fengyu Zhao; Masahiko Arai

2010-01-01

335

Isolation of substances from glossy privet (Ligustrum lucidum Ait.) inhibiting the mutagenicity of benzo[a]pyrene in bacteria.  

PubMed

Methanol and hot-water extracts of glossy privet (Ligustrum lucidum Ait.) inhibited the mutagenic activity of benzo[a]pyrene in Salmonella typhimurium TA98 with S9 mix. The methanol extract was fractionated with ether and n-hexane. As the active components, oleanolic and ursolic acids were isolated, which were soluble in ether and insoluble in n-hexane. The hot-water extract was fractionated to water, 60% and 100% methanol fractions. Nuezhenide was isolated from the 60% methanol fraction as the active component. PMID:7690454

Niikawa, M; Hayashi, H; Sato, T; Nagase, H; Kito, H

1993-09-01

336

Premixed ignition behavior of alternative diesel fuel-relevant compounds in a motored engine experiment  

Microsoft Academic Search

A motored engine study using premixed charges of fuel and air at a wide range of diesel-relevant equivalence ratios was performed to investigate autoignition differences among surrogates for conventional diesel fuel, gas-to-liquid (GTL) diesel fuel, and biodiesel, as well as, n-heptane. Experiments were performed by delivering a premixed charge of vaporized fuel and air and increasing the compression ratio in

James P. Szybist; André L. Boehman; Daniel C. Haworth; Hibiki Koga

2007-01-01

337

Premixed ignition behavior of alternative diesel fuel-relevant compounds in a motored engine experiment  

Microsoft Academic Search

A motored engine study using premixed charges of fuel and air at a wide range of diesel-relevant equivalence ratios was performed to investigate autoignition differences among surrogates for conventional diesel fuel, gas-to-liquid (GTL) diesel fuel, and biodiesel, as well as n-heptane. Experiments were performed by delivering a premixed charge of vaporized fuel and air and increasing the compression ratio in

James P. Szybist; Andre L. Boehman; Daniel C. Haworth; Hibiki Koga

2007-01-01

338

On the Collision of a Droplet with a Solid Surface  

Microsoft Academic Search

The collision dynamics of a liquid droplet on a solid metallic surface were studied using a flash photographic method. The intent was to provide clear images of the droplet structure during the deformation process. The ambient pressure (0.101 MPa), surface material (polished stainless steel), initial droplet diameter (about 1.5 mm), liquid (n-heptane) and impact Weber number (43) were fixed. The

S. Chandra; C. T. Avedisian

1991-01-01

339

ULTRA-DILUTE COMBUSTION OF PRIMARY REFERENCE FUELS  

Microsoft Academic Search

Using n-heptane and iso-octane as gasoline surrogate fuels, the laminar flame speeds, flame thicknesses, reaction zone thicknesses, and flammability limits of fuel\\/air\\/residual gas mixtures are computationally studied over ranges of pressures, temperatures, and dilution levels representative of unthrottled HCCI operation. These calculations are further used to characterize the combustion regime for spark-initiated HCCI combustion. In a turbulent premixed combustion regime

YIMIN HUANG; CHIH-JEN SUNG; KAMAL KUMAR

2007-01-01

340

On The Impact of the Ideal Gas Assumption to High-Pressure Combustion Phenomena in Engines  

Microsoft Academic Search

The effect of the ideal gas law assumption on auto-ignition and NOx-formation in a rapid compression machine is studied. For both processes the simulations are compared to a reference simulation using a Redlich-Kwong equation-of-state based on the critical properties of all constituents.Auto-ignition is studied for several n-heptane\\/air mixtures and the results show that the ideal gas assumption can impose large

A. Evlampiev; L. M. T. Somers; R. S. G. Baert; L. P. H. de Goey

2007-01-01

341

Measurement of activities of solvents in binary polymer solutions  

Microsoft Academic Search

Vapor liquid equilibrium data of nine binary solvent+polymer systems were measured by a vacuum electro-microbalance cell. Tested solvents were n-heptane, n-octane, n-nonane, methanol, ethanol, n-propanol and water. Polymers were poly (dimethylsiloxane, Mn: 26,000), poly (propylene oxide, Mn: 2000) and poly (ethylene glycol, Mn: 600). Data obtained in the present study together with existing literature data were correlated by UNIQUAC model.

Jisoo Kim; Eun-hyun Choi; Ki-Pung Yoo; Chul Soo Lee

1999-01-01

342

LASER IGNITION IN A LEAN PREMIXED PREVAPORIZED INJECTOR  

Microsoft Academic Search

Laser-induced spark ignition has proved to be an alternative way of achieving ignition. In this paper, we demonstrate the feasibility of laser spark ignition at the outlet of a lean premixed prevaporized injector, similar to those used in low-NOx air jet engines. This injector uses liquid n-heptane as fuel in preheated air with a high level of turbulence. After a

H. EL-RABII; K. ZÄHRINGER; J.-C. ROLON; F. LACAS

2004-01-01

343

Multi-species detection in spray flames with tunable excimer lasers  

Microsoft Academic Search

Planar imaging with tunable excimer-laser sheet illumination is used to determine spatial distributions of different species in liquid-fuelled spray flames of commercial oil burning furnaces. Two burner configurations, which differ only in the fuel\\/air mixing devices, are investigated to understand why one configuration yields 30% less NOx emission. Iso-octane and n-heptane fuels are used. To understand the origin for NOx

A. Koch; A. Chryssostomou; P. Andresen; W. Bornscheuer

1993-01-01

344

CATALYTIC HYDROTREATMENT OF PETROLEUM RESIDUE  

Microsoft Academic Search

Iraqi reduced crude (350°C+) with a sulfur content of 4.3 wt% and a total metal content (Ni+V) of 141 WPPM was n-heptane deasphalted at specified conditions. The deasphalted oil (97.2 wt% of original residue) contains 4.1 wt% of sulfur and 103 ppm of metal. The original reduced crude and deasphalted oil were hydrotreated on a commercial Ni-Mo-alumina catalyst presulfided at specified

Abdul-Halim A-K Mohammed; Abdullah A. Abbas; Ayad B. Ahmed; Abdul-Salam K. Al. Mayah

1987-01-01

345

Excess properties of binary mixtures of an alkanol or an alkane with butyl-vinyl ether or iso -butyl-vinyl ether  

Microsoft Academic Search

Experimental results are reported of excess molar volumesVmE and excess molar enthalpiesHmE at T= 298.15 K for twelve binary mixtures of alkanols (ethanol, 1-butanol, or iso -butanol) or alkanes { n -heptane, iso -octane (2,2,4-trimethylpentane), or n -octane} with butyl-vinyl ether or iso -butyl-vinyl ether. A vibrating-tube densitometer was used to determine VmE. The quantityHmE was measured by using a

Elena N. Rezanova; Rüdiger N. Lichtenthaler

2000-01-01

346

EXTRACTION OF RARE EARTH METALS WITH 2-ETHYLHEXYL PHOSPHONIC ACID MONO2-ETHYLHEXYL ESTER IN THE PRESENCE OF DIETHYLENETRIAMINEPENTAACETIC ACID IN AQUEOUS PHASE  

Microsoft Academic Search

The extraction equilibria of rare earth metals with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (commercial name, PC-88A, henceforth abbreviated as HR) dissolved in n-heptane were measured at 303 K. It was found that rare earth metals are extracted with the dimer of the extractant, (HR)2, as follows.The extraction equilibrium constants of metals were obtained and compared with the extraction equilibrium constants

Fukiko Kubota; Masahiro Goto; Fumiyuki Nakashio

1993-01-01

347

Extraction Kinetics of Rare Earth Metals with 2-Ethylhexyl Phosphonic Acid Mono2-ethylhexyl Ester Using a Hollow Fiber Membrane Extractor  

Microsoft Academic Search

A kinetic study concerning chemical complexation-based solvent extraction of rare earth metals with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester dissolved as an extractant in n-heptane was carried out using a microporous hydrophobic hollow fiber membrane extractor. The effects of concentration of chemical species in aqueous and organic feed solutions on the apparent permeabilities of metal species for extraction and stripping, respectively,

Fukiko Kubota; Masahiro Goto; Fumiyuki Nakashio; Tadashi Hano

1995-01-01

348

Transformation of steroids by gel-entrapped Nocardia rhodocrous cells in organic solvent  

Microsoft Academic Search

Whole cells of Nocardia rhodocrous were immobilized by entrapment with photo-crosslinkable resin prepolymers or urethane prepolymers of either hydrophilic or hydrophobic character, and their activity in converting 3ß- hydroxy-?5 to corresponding 3-keto-?4 in an appropriate organic solvent system (e.g., a water-saturated mixture of benzene and n-heptane (1:1 by volume)) was studied. Although both hydrophilic gel-entrapped cells and hydrophobic gel-entrapped cells

Tetsuo Omara; Takamitsu Iida; Atsuo Tanaka; Saburo Fukui

1979-01-01

349

Efficient High-Pressure State Equations  

NASA Technical Reports Server (NTRS)

A method is presented for a relatively accurate, noniterative, computationally efficient calculation of high-pressure fluid-mixture equations of state, especially targeted to gas turbines and rocket engines. Pressures above I bar and temperatures above 100 K are addressed The method is based on curve fitting an effective reference state relative to departure functions formed using the Peng-Robinson cubic state equation Fit parameters for H2, O2, N2, propane, methane, n-heptane, and methanol are given.

Harstad, Kenneth G.; Miller, Richard S.; Bellan, Josette

1997-01-01

350

Solubility of CO 2 in branched alkanes in order to extend the PPR78 model (predictive 1978, Peng–Robinson EOS with temperature-dependent k ij calculated through a group contribution method) to such systems  

Microsoft Academic Search

A high pressure, variable-volume visual cell was used to perform static measurements of phase equilibria involving carbon dioxide and four different alkanes: n-heptane, 2,2,4-trimethyl pentane (isooctane), 2,5-dimethyl hexane and 3-methyl pentane. Different temperatures ranging from 278.15 to 413.15K were selected. The bubble point pressures, ranging from 12 to 134bar were measured at carbon dioxide mole fractions between 0.23 and 0.91.

Fabrice Mutelet; Stéphane Vitu; Romain Privat; Jean-Noël Jaubert

2005-01-01

351

Study of absorption spectra of gasolines and other hydrocarbon mixtures in the second overtone region of the CH3, CH2, CH groups  

NASA Astrophysics Data System (ADS)

We have obtained experimental and model absorption spectra for individual hydrocarbons (toluene, benzene, n-heptane, and iso-octane) and their mixtures in the near IR range (? = 1080 1220 nm). We model the spectra of nonsynthetic gasolines obtained under the same conditions by combining the spectra of three pure hydrocarbons. We show that the octane number of the studied gasoline is linearly related to the toluene (or benzene) concentrations in the model mixture.

Muradov, V. G.; Sannikov, D. G.

2007-03-01

352

Intersystem crossing of single pentacene molecules in Shpol'skii matrices  

Microsoft Academic Search

We have measured the fluorescence decays of pentacene (Pc) dispersed in Shpol'skii matrices of n-heptane, n-tetradecane and n-hexadecane in the temperature range 1.7–200 K. In all of these matrices the decay times were about 25 ns at 1.7 K and shortened to less than 15 ns at high temperatures. This result suggests a low value of the intersystem crossing (ISC),

B. Kozankiewicz; M. Banasiewicz; J. Dresner; M. Orrit

2001-01-01

353

Selective liquid sorption properties of hydrophobized graphite oxide nanostructures  

Microsoft Academic Search

Hydrophilic graphite oxide (GO) of lamellar structure was prepared by oxidation of graphite; the thickness of the individual\\u000a lamellae was 6.1??. GO was hydrophobized by n-alkylammonium cations, and the GO-organocomplex nanocomposites were swollen in organic solvents of various polarities (ethanol,\\u000a toluene, cyclohexane, n-heptane) and their binary mixtures. The binary liquid composition determined the size (15–45??) of the lamellar GO nanostructures.

I. Dékány; R. Krüger-Grasser; A. Weiss

1998-01-01

354

The development of gas sensor for carbon monoxide monitoring using nanostructure of Nb–TiO 2  

Microsoft Academic Search

The development of titanium dioxide (TiO2) as a gas sensor for combustion and exhaust air pollutants monitoring is strongly dependent on its properties such as thermal stability, grain size and surface area. In this study, nanostructure TiO2 with its thermal stability enhanced by niobium dopant (Nb–TiO2) was synthesized using the water-in-oil (w\\/o) microemulsion system of n-heptane\\/water\\/sodium bis (2-ethylhexyl) sulfosuccinate (AOT)

T. Anukunprasert; C. Saiwan; E. Traversa

2005-01-01

355

Evaluation of hepatoprotective activity of Cassia fistula leaf extract.  

PubMed

Hepatoprotective activity of the n-heptane extract of Cassia fistula leaves was investigated in rats by inducing hepatotoxicity with carbon tetrachloride:liquid paraffin (1:1). The extract has been shown to possess significant protective effect by lowering the serum levels of transminases (SGOT and SGPT), bilirubin and alkaline phosphatase (ALP). The extract of C. fistula at a dose of 400 mg/kg showed significant hepatoprotective activity which was comparable to that of a standard hepatoprotective agent. PMID:10473173

Bhakta, T; Mukherjee, P K; Mukherjee, K; Banerjee, S; Mandal, S C; Maity, T K; Pal, M; Saha, B P

1999-09-01

356

Hepatoprotective activity of Cassia fistula leaf extract.  

PubMed

Hepatoprotective activity of the n-heptane extract of Cassia fistula leaves was investigated by inducing hepatotoxicity with paracetamol in rats. The extract at a dose of 400 mg/kg body wt. exhibited orally, significant protective effect by lowering the serum levels of transaminases (SGOT and SGPT), bilirubin and alkaline phosphatase (ALP). The effects produced were comparable to that of a standard hepatoprotective agent. PMID:11417916

Bhakta, T; Banerjee, S; Mandal, S C; Maity, T K; Saha, B P; Pal, M

2001-05-01

357

Thermochemical mass-spectrometric investigation under reducing conditions of [Pd(acac) 2] adsorbed on magnesium oxide  

Microsoft Academic Search

The thermochemical behavior of [Pd(acac)2] adsorbed onto different magnesium oxides has been studied under reducing conditions by means of the TPRD (temperature-programmed reductive decomposition) technique coupled to mass spectrometry. The thermal profiles of the different decomposition products have been rationalized in terms of chemical interactions with the support, and correlated with the catalytic properties in the dehydrocyclization reaction of n-heptane.The

Carlo Dossi; Rinaldo Psaro; Achille Fusi; Sandro Recchia; Vladimiro Dal Santo; Laura Sordelli

1998-01-01

358

Monodisperse monocomponent fuel droplet heating and evaporation  

Microsoft Academic Search

The results of numerical and experimental studies of heating and evaporation of monodisperse acetone, ethanol, 3-pentanone, n-heptane, n-decane and n-dodecane droplets in an ambient air of fixed temperature and atmospheric pressure are reported. The numerical model took into account the finite thermal conductivity of droplets and recirculation inside them based on the effective thermal conductivity model and the analytical solution

T. Kristyadi; V. Deprédurand; G. Castanet; F. Lemoine; S. S. Sazhin; A. Elwardany; E. M. Sazhina; M. R. Heikal

2010-01-01

359

Sensitized extraction spectrophotometric determination of Hg(II) with dithizone after its flotation as ion-associate using iodide and ferroin  

Microsoft Academic Search

This paper describes a simple and highly selective method for the separation, preconcentration and spectrophotometric determination of extremely low concentration of mercury. The method is based on the flotation of an ion-associate of HgI42? and ferroin between aqueous and n-heptane interface at pH 5. The ion-associate was then separated and treated with ammonia and dithizone solutions to extract only the

Mohammad Saeid Hosseini; Hamid Hashemi-Moghaddam

2005-01-01

360

A fundamental study on the control of the HCCI combustion and emissions by fuel design concept combined with controllable EGR. Part 1. The basic characteristics of HCCI combustion  

Microsoft Academic Search

This article investigates the basic combustion parameters including start of the ignition timing, burn duration, cycle-to-cycle variation, and carbon monoxide (CO), unburned hydrocarbon (UHC), and nitric oxide (NOx) emissions of homogeneous charge compression ignition (HCCI) engines fueled with primary reference fuels (PRFs) and their mixtures. Two primary reference fuels, n-heptane and iso-octane, and their blends with RON25, RON50, RON75, and

Xing-Cai Lü; Wei Chen; Zhen Huang

2005-01-01

361

[Selective separation of cinnamic and p-methoxycinnamic acids. The study on reactive extraction from mixture].  

PubMed

Cinnamic and p-methoxycinnamic acids have been separated from their mixture by reactive extraction with Amberlite LA-2 dissolved in n-heptane. The efficiency and the selectivity of their separation is controlled by the pH-value and extractant concentration, the optimum conditions being the pH-value of aqueous phase of 2 and the extractant concentration into the organic phase of 10 g/l. PMID:18389811

C?m?ru?, Maria; Galaction, Anca-Irina; Ca?caval, D

2007-01-01

362

Studies on emulsion liquid membrane extraction of cephalexin  

Microsoft Academic Search

An experimental study on batch extraction of cephalexin using an emulsion liquid membrane system has been reported. The effects of surfactant, carrier and solute concentrations, phase volume ratio, stirring speed, and counterion concentration on the extraction rate were examined. Surfactant, carrier and diluent used were Span-80, Aliquat-336 and n-heptane–kerosene (1:1), respectively. Under the optimised experimental conditions, emulsion swelling was found

G. C Sahoo; N. N Dutta

1998-01-01

363

Photoionization of Alkanes. Dissociation of Excited Molecular Ions  

Microsoft Academic Search

This report describes studies of photoionization and subsequent dissociation of all saturated paraffins from C2 to C6, plus n-heptane and n-octane, as a function of photon energy. The studies include data on all processes which occur below a photon energy of 11.9 ev. The instrument used was a mass spectrometer, combined with a Seya-Namioka monochromator. The direct experimental data are

Bruce Steiner; Clayton F. Giese; Mark G. Inghram

1961-01-01

364

Spectroscopic Determination of Ternary Phase Diagrams  

Microsoft Academic Search

Ternary phase diagrams describe phase equilibria among three components as a function of composition at constant temperature and pressure. The system of n-propanol, n-heptane, and water exhibits a simple ternary diagram with two well-demarcated regions. One region represents complete liquid miscibility at high proportions of n-propanol. The second region delineates the compositions where two immiscible liquid phases coexist--a water-rich layer

Kerry K. Karukstis; Sara K. Avrantinis; Stephanie L. Boegeman; Jeanie N. Conner; Blaine M. Hackman; Jennifer M. Lindsay; Alexander L. Mandel; Elizabeth J. Miller

2000-01-01

365

Shock tube determination of ignition delay times in full-blend and surrogate fuel mixtures  

Microsoft Academic Search

Autoignition characteristics of n-heptane\\/air, gasoline\\/air, and ternary surrogate\\/air mixtures were studied behind reflected shock waves in a high-pressure, low-temperature regime similar to that found in homogeneous charge compression ignition (HCCI) engine cycles. The range of experiments covered combustion of fuel in air for lean, stoichiometric, and rich mixtures (?=0.5, 1.0, 2.0), two pressure ranges (15–25 and 45–60 atm), temperatures from

B. M. Gauthier; D. F. Davidson; R. K. Hanson

2004-01-01

366

Soot Formation in a Shock Tube under Elevated Pressure Conditions  

Microsoft Academic Search

High pressure soot formation from methane, ethylene, acetylene, propane and n-heptane was studied at rich burning conditions applying the shock tube technique. Pressure behind reflected shock was varied between 15 and 100 bar. Time resolved measurements of soot particle diameter and number density were carried out using an extinction-scattering technique at 488?nm. It could be shown that soot formation at

H. KELLERER; A. MÜLLER; H.-J. BAUER; S. WITTIG

1996-01-01

367

Self-ignition of S.I. engine model fuels: A shock tube investigation at high pressure  

Microsoft Academic Search

The self-ignition of several spark-ignition (SI) engine fuels (iso-octane, methanol, methyl tert-butyl ether and three different mixtures of iso-octane and n-heptane), mixed with air, was investigated experimentally under relevant engine conditions by the shock tube technique. Typical modes of the self-ignition process were registered cinematographically. For temperatures relevant to piston engine combustion, the self-ignition process always starts as an inhomogeneous,

K. Fieweger; R. Blumenthal; G. Adomeit

1997-01-01

368

Fire Smoke Particle Size Measurement Based on the Multiwavelength and Multiangle Light Scattering Method  

NASA Astrophysics Data System (ADS)

A multiwavelength and multiangle mathematical model (MWMA) is developed, and the corresponding influence factors of the model are analysed by the numerical calculation. Combined with measurement data of radiation flux and the curve in theoretical calculation, particle sizes of different materials can be obtained. It is found that smoke particle size gradually decreases from land plaster, cotton wick, beech wood, polyurethane, sandalwood, decahydronaphthalene, to N-heptane.

Shu, Xue-Ming; Fang, Jun; Shao, Quan; Yuan, Hong-Yong; Fan, Wei-Cheng

2006-02-01

369

“Coulomb Staircase” at Room Temperature in a Self-Assembled Monolayer of Hydrophobic Fe\\/Pt@Au Core-Shell Nanoparticle  

Microsoft Academic Search

Hydrophobic Fe\\/Pt@Au core-shell nanoparticles (NPs) were synthesized in a quaternary CTAB\\/n-butanol\\/n-heptane\\/water reverse micelle. Dodecylthiol coated around the NPs as functional agent could be help the NPs to form a self-assembled monolayer of which can be viewed clearly by transmission electron microscopy (TEM). A scanning tunneling microscope (STM) was used to find the subtle self-assembled monolayer of the NPs and to

Yun Zhi Fu; Jin Ru Li

2011-01-01

370

Preparation of hydrophobic gold nanoparticles with safe organic solvents by microwave irradiation method  

Microsoft Academic Search

A safe organic solvent mixture n-heptane\\/ethanol was used as dispersion medium in reversal micelle to replace the commonly used toxic and highly volatile organic solvent such as chloroform and other solvents. This method overcame the obstacle for preparing hydrophobic nanoparticles by microwave irradiation method. The hydrophobic gold nanoparticles capped with octadecylamine (C18NH2) were prepared by using ethanol reduction in reverse

Ming Shen; Yu-kou Du; Hui-lin Rong; Jin-ru Li; Long Jiang

2005-01-01

371

Exploitation of reversed micelles as a medium in mimetic peroxidase-catalyzed fluorogenic reaction between hydrogen peroxide and l-tyrosine  

Microsoft Academic Search

The peroxidase activity of mimetic enzyme, iron tetrasulfonatophthalocyanine (FeTSPc), was characterized in reversed micelles of hexadecyltrimethylammonium bromide (CTAB) formed in n-heptane–n-pentanol solution (2:1, V:V). The assay is based on its catalytic effect on the oxidation reaction of l-tyrosine (l-tyr) by hydrogen peroxide. The influences of environmental factors, such as the water content, CTAB concentration and pH, on the peroxidase activity

Xiao-Lan Chen; Ling Wei; Huang-Hao Yang; Qing-Zhi Zhu; Jin-Gou Xu

2002-01-01

372

Kinetics of electron transfer reaction in micellar and reverse micellar media  

Microsoft Academic Search

Electron transfer reaction of pentaammineazidocobalt(III)chloride with ferrous salt has been investigated in cationic normal micellar media of N-cetyl-N,N,N trimethyl ammonium bromide (CTAB) and also in well-characterized, monodispersed biomimicking nanocavities formed by anionic surfactant, sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in n-heptane\\/water using spectrophotometric methods. The rate law and mechanism of the reaction is same in both continuous water pool, in presence of

Tapas Majumdar; Ambikesh Mahapatra

2007-01-01

373

Determination of Planck Mean Absorption Coefficients for Hydrocarbon Fuels  

Microsoft Academic Search

Infrared transmission of propane, n-heptane and propylene samples was measured using Fourier transform infrared spectroscopy (FTIR) for temperatures ?1000 K to facilitate calculation of absorption coefficients of fuel molecules at temperatures representative of non-premixed flame interiors. Spectrally resolved fits of the absorption coefficient data using a semi-empirical quantum-based expression provide a basis for calculating infrared spectra at any temperature. Experimentally-derived Planck

Kaoru Wakatsuki; Gregory S. Jackson; Jungho Kim; Anthony Hamins; Marc R. Nyden; Stephen P. Fuss

2008-01-01

374

VAPORIZATION AND OXIDATION OF LIQUID FUEL DROPLETS AT HIGH TEMPERATURE AND HIGH PRESSURE: APPLICATION TO N-ALKANES AND VEGETABLE OIL METHYL ESTERS  

Microsoft Academic Search

Vaporization and oxidation of liquid fuel droplets are basic mechanisms in spray combustion for various industrial applications. In this work, coupled effects of temperature and pressure on n-alkane droplet vaporization are investigated in experiments conducted in a high-pressure and high-temperature gasification facility equipped with the fiber-suspended droplet technique. The influence of temperature and pressure on n-heptane and n-decane vaporization rates

CÉLINE MORIN; CHRISTIAN CHAUVEAU; PHILIPPE DAGAUT; ISKENDER GÖKALP; MICHEL CATHONNET

2004-01-01

375

Effect of fuel composition and manifold conditions upon spray formation from an SI engine pintle injector  

Microsoft Academic Search

The performance of a pintle-type gasoline injector has been studied. Observations performed on test-rigs and running engines suggest that under conditions of low manifold pressure a `pencil-jet` formation may replace the well atomized spray normally produced by the injector. Importantly, this phenomenon was not observed when using substitute fuels such as n-heptane. It is concluded that both the mechanical design

P. Williams; P. Beckwith

1994-01-01

376

Cracked and repaired concrete subject to fluid penetration  

Microsoft Academic Search

Test series have been performed on concrete specimens containing bending cracks. The specimens were subject to fluid penetration.\\u000a Organic fluids (acetone, n-decane, n-heptane) have been used. In a second series, beams were precracked. The cracks were injected\\u000a by epoxy or polyurethane resin. After 10,000 loading cycles, organic fluids could penetrate into the concrete. Results are\\u000a presented and discussed. Suggestions for

Hans-Wolf Reinhardt; Massimo Sosoro; Xiao-feng Zhu

1998-01-01

377

Fundamentals of fuel stability. Technical Report No. 13  

Microsoft Academic Search

An investigation was conducted to evaluate some of the factors associated with the precision of measuring the quantity and the radioactivity of residues formed in binary mixtures of pure compounds during storage. The mixtures consisted of a sulfur compound and an unsaturated hydrocarbon blended with n-heptane as a diluent. The mixtures were stored in glass bottles at 43.3° C (110°

C. C. Ward; F. G. Schwartz; B. H. Eccleston

1963-01-01

378

Application and Perspective of Ionic Liquids on Rare Earths Green Separation  

Microsoft Academic Search

This review summarizes recent applications of ionic liquids (ILs) as ‘green’ solvents and extractants in the extraction and separation of Rare Earths (REs), which are widely used in a variety of high-tech products in mining, separation, and smelting can greatly damage the environment. Conventional imidazolium-based ILs as diluents are more active than non-coordinating solvents such as kerosene and n-heptane in

Yinghui Liu; Ji Chen; Deqian Li

2012-01-01

379

Application and Perspective of Ionic Liquids on Rare Earths Green Separation  

Microsoft Academic Search

This review summarizes recent applications of ionic liquids (ILs) as ‘green’ solvents and extractants in the extraction and separation of Rare Earths (REs), which are widely used in a variety of high-tech products in mining, separation, and smelting can greatly damage the environment. Conventional imidazolium-based ILs as diluents are more active than non-coordinating solvents such as kerosene and n-heptane in

Yinghui Liu; Ji Chen; Deqian Li

2011-01-01

380

Numerical and experimental study of water\\/oil emulsified fuel combustion in a diesel engine  

Microsoft Academic Search

Numerical and experimental studies were made on some of the chemical and physical properties of water\\/oil emulsified fuel (W\\/OEF) combustion characteristics. Numerical investigations of W\\/OEF combustion's chemical kinetic aspects have been performed by simulation of water\\/n-heptane mixture combustion, assuming a model of a homogenous reactor's concentric shells. The injection and fuel spray characteristics are analyzed numerically also in order to

Niko Samec; Breda Kegl; Robert W. Dibble

2002-01-01

381

Critical heat flux of binary mixtures in pool boiling and its correlation in terms of Marangoni number  

Microsoft Academic Search

Critical heat flux (CHF) in nucleate pool boiling of binary mixtures was newly measured with a horizontal platinum wire, 0.5 mm in diameter, and heated by DC, over the full range of concentrations. Seven mixtures were selected with the intent to cover various types of mixtures: methanol\\/water, ethanol\\/water, methanol\\/ethanol, ethanol\\/n-butanol, methanol\\/benzene, benzene\\/n-heptane and water\\/ethylene glycol, each in the saturated state

Yasunobu Fujita; Qiang Bai

1997-01-01

382

Gas-Phase Propylene Epoxidation over Ag\\/TS1 Prepared in W\\/O Microemulsion: Effects of the Molar Ratio of Water to Surfactant and the Reaction Temperature  

Microsoft Academic Search

Ag\\/TS-1 was prepared by microemulsion method in which dioctyl sulfosuccinate sodium salt (AOT) was used as the surfactant and n-heptane as the organic solvent. The synthesized Ag\\/TS-1 was characterized by UV–Vis and TEM and its catalytic properties in gas-phase propylene epoxidation were carried out in a fixed bed reactor. The results show that Ag is highly dispersed on TS-1 and

Chuanfu Wang; Xinwen Guo; Xiangsheng Wang; Ruipu Wang; Jingquan Hao

2004-01-01

383

Adsorption from the liquid phase on silica gels of various structural heterogeneity  

SciTech Connect

Competition of liquid components for silica gel surface was tested for binary liquid mixtures: methanol + benzene and 2-propanol + n-heptane. The adsorption isotherms were measured using silica gels for column chromatography Si-40 and Si-100 from Merck. On the basis of specific surface excess isotherms the surface layer capacities were calculated. Taking into account the properties of the bulk solutions, the influence of geometrical structure of silicas on the composition of the surface phase is discussed.

Goworek, J.; Derylo-Marczewska, A.; Borowka, A.

1999-08-31

384

Chemical flooding of oil reservoirs 6. Evaluation of the mechanism for oil expulsion by spontaneous imbibition of brine with and without surfactant in water-wet, low-permeable, chalk material  

Microsoft Academic Search

Experiments are performed in order to study the effect of interfacial tension, IFT, and core length on the imbibition of a surfactant solution into an oil-saturated chalk material. The wetting phases are synthetic brine and a 1.0 wt.% solution of an alkyl propoxyethoxysulfate dissolved in the brine. The non-wetting phase is n-heptane. The IFT between the surfactant solution and the

Jess Milter; Tor Austad

1996-01-01

385

Isolation of strontium-90, yttrium-90, promethium-147, and cerium-144 from wet ashed urine by calcium oxalate coprecipitation and sequential solvent extraction  

Microsoft Academic Search

A method has been developed for separating low-level activities of the ..beta..-emitting isotopes strontium-90, yttrium-90, promethium-147, and cerium-144 from urine and aqueous solutions. They are subsequently estimated by direct counting of sources on planchets or by liquid scintillation counting. The radionuclides are separated from each other and from interfering elements by solvent extraction with HDEHP (di-2-ethylhexyl)phosphoric acid) in n-heptane. It

Gary H. Kramer; Janet M. Davies

1982-01-01

386

Stability and aerosolization of pressurized metered dose inhalers containing thymopentin nanoparticles produced using a bottom-up process.  

PubMed

The objective of this study was to investigate the stability and aerosolization of pressurized metered dose inhalers (pMDIs) containing thymopentin nanoparticles. Thymopentin nanoparticles, fabricated by a bottom-up process, were suspended in hydrofluoroalkane (HFA) 134a together with cineole and/or n-heptane to produce pMDI formulations. The stability study of the pMDIs obtained was carried out at ambient temperature for 6 months. The amount of thymopentin and the aerosolization properties of pMDIs were determined using high-performance liquid chromatography (HPLC) and a twin-stage impinger (TSI), respectively. Based on the results, thymopentin nanoparticles were readily suspended in HFA 134a with the aid of cineole and/or n-heptane to form physically stable pMDI formulations, and more than 98% of the labeled amount of thymopentin and over 50% of the fine particle fraction (FPF) of the pMDIs were achieved. During storage, it was found that for all pMDIs more than 97% of the labeled amount of thymopentin and FPF greater than 47% were achieved. Moreover, the size of thymopentin nanoparticles in propellant containing cineole and n-heptane showed little change. It is, therefore, concluded that the pMDIs comprising thymopentin nanoparticles developed in this study were stable and suitable for inhalation therapy for systemic action. PMID:22343132

Tan, Yinhe; Yang, Zhiwen; Pan, Xin; Chen, Meiwan; Feng, Min; Wang, Lili; Liu, Hu; Shan, Ziyun; Wu, Chuanbin

2012-05-10

387

The oxidation of a gasoline surrogate in the negative temperature coefficient region  

SciTech Connect

This experimental study investigated the preignition reactivity behavior of a gasoline surrogate in a pressurized flow reactor over the low and intermediate temperature regime (600-800 K) at elevated pressure (8 atm). The surrogate mixture, a volumetric blend of 4.6% 1-pentene, 31.8% toluene, 14.0% n-heptane, and 49.6% 2,2,4-trimethyl-pentane (iso-octane), was shown to reproduce the low and intermediate temperature reactivity of full boiling range fuels in a previous study. Each of the surrogate components were examined individually to identify the major intermediate species in order to improve existing kinetic models, where appropriate, and to provide a basis for examining constituent interactions in the surrogate mixture. n-Heptane and 1-pentene started reacting at 630 K and 640 K, respectively, and both fuels exhibited a strong negative temperature coefficient (NTC) behavior starting at 700 and 710 K, respectively. Iso-octane showed a small level of reactivity at 630 K and a weak NTC behavior starting at 665 K. Neat toluene was unreactive at these temperatures. The surrogate started reacting at 630 K and exhibited a strong NTC behavior starting at 693 K. The extent of fuel consumption varied for each of the surrogate constituents and was related to their general autoignition behavior. Most of the intermediates identified during the surrogate oxidation were species observed during the oxidation of the neat constituents; however, the surrogate mixture did exhibit a significant increase in intermediates associated with iso-octane oxidation, but not from n-heptane. While neat toluene was unreactive at these temperatures, in the mixture it reacted with the radical pool generated by the other surrogate components, forming benzaldehyde, benzene, phenol, and ethyl-benzene. The observed n-heptane, iso-octane, and surrogate oxidation behavior was compared to predictions using existing kinetic models. The n-heptane model reasonably predicted the disappearance of the fuel, but overpredicted the formation of several of the smaller intermediates. The iso-octane model significantly overpredicted the reaction of the fuel and formation of the intermediates. The 1-pentene model reasonably predicted the fuel consumption, but underestimated the importance of radical addition to the double bond. The results of this study provide a critical experimental foundation for the investigation of surrogate mixtures and for validation of kinetic models. (author)

Lenhert, David B.; Miller, David L.; Cernansky, Nicholas P. [Department of Mechanical Engineering and Mechanics, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104-2875 (United States); Owens, Kevin G. [Department of Chemistry, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104-2875 (United States)

2009-03-15

388

In vitro antiprotozoal activity of the lipophilic extracts of different parts of Turkish Pistacia vera L  

Microsoft Academic Search

Thirteen lipophilic extracts prepared with n-hexane from various parts of Pistacia vera L. tree (Anacardiaceae) growing in Turkey were screened for their in vitro activity against four parasitic protozoa, Trypanosoma brucei rhodesiense, Trypanosoma cruzi, Leishmania donovani and Plasmodium falciparum. Melarsoprol, benznidazole, miltefosine, artemisinin and chloroquine were used as reference drugs. The cytotoxic potentials of the extracts on rat skeletal myoblast

I. Orhan; M. Aslan; B. Sener; M. Kaiser; D. Tasdemir

2006-01-01

389

Antioxidative activity of the crude extract of lignan glycosides from unroasted Burma black sesame meal  

Microsoft Academic Search

Sesame seed contains lignans and lignan glycosides. The antioxidative activity of the crude extract of lignan glycosides obtained from unroasted defatted black sesame seeds was investigated in this study. The components responsible for the antioxidative activity were also studied. The unroasted black sesame seeds, after defatted with n-hexane, were extracted with 80% methanolic solution to prepare for the crude extract

Yung-Shin Shyu; Lucy Sun Hwang

2002-01-01

390

ANTIPROLIFERATIVE AND APOPTOTIC EFFECT OF FENOLIC FRACTION OF ETHANOLIC EXTRACT OF Gynura procumbens (Lour.) Merr. AGAINST HeLa CELLS  

Microsoft Academic Search

Gynura procumbens (Lour.) Merr., also known as Sambung Nyawa, has traditionally used as antipyretic, hypotensive, hypoglycemic and anticancer. Screening for fenolik compounds was done to the chemoprevention potency of Sambung Nyawa leaves. In the present work, the leaves crude extract was subjected to silica gel column chromatography and then eluted with n-hexane containing increasing amounts of ethyl acetate. Thin layer

Edy Meiyanto dan Endah; P. Septisetyani

391

Cancer-suppressive potential of extracts of endemic plant Helichrysum zivojinii: effects on cell migration, invasion and angiogenesis.  

PubMed

Helichrysum zivojinii Cernjavski & Soska is an endemic plant species that grows in the National Park Galicica in Macedonia. Five extracts were isolated as fractions from the aerial parts of the plant: a n-hexane extract (1), a dichloromethane extract (2), an ethyl-acetate extract (3), a n-butanol extract (4) and a methanol extract (5). A dose-dependent cytotoxic activity of the extracts on MDA-MB-231 and EA.hy926 cells was observed. Extracts exhibited more pronounced cytotoxic actions on MDA-MB-231 cells than on EA.hy926 cells. The n-hexane extract (1), at a non-toxic concentration, exhibited an inhibitory effect on the migration as well the invasiveness of MDA-MB-231 cells. The dichloromethane extract (2), at a non-toxic concentration, demonstrated inhibition of MDA-MB-231 cells invasion. Each of the five extracts applied at non-toxic concentrations inhibited migration of EA.hy926 cells. The prominent inhibitory effect of the n-hexane extract on EA.hy926 cells migration was associated with a notable anti-angiogenic action of this extract. The other four tested extracts demonstrated mild anti-angiogenic activity. Our data highlight the prominent anticancer potential of n-hexane (1) and dichloromethane (2) extracts, which could be attributed to their very pronounced and selective cytotoxic activities as well as their anti-invasive and anti-angiogenic properties. PMID:24273869

Mati?, Ivana Z; Aljanci?, Ivana; Vajs, Vlatka; Jadranin, Milka; Gligorijevi?, Nevenka; Milosavljevi?, Slobodan; Jurani?, Zorica D

2013-09-01

392

Stability During Frying of Moringa oleifera Seed Oil Variety “Periyakulam 1”  

Microsoft Academic Search

The frying performance of the Moringa oleifera seed oil variety Periyakulam 1 (PKM 1) from India, extracted using cold press (CP) and n -hexane (H), during frying of potatoes and cod was studied especially as regards repeated frying operations. The oils were used for intermittent frying of potato slices and cod filets at a temperature of 175±5°C for 5 consecutive

John Tsaknis; Stavros Lalas

2002-01-01

393

COMPATIBILITY OF ORGANIC SOLVENTS WITH THE MICROSCREEN PROPHAGE-INDUCTION ASSAY: SOLVENT-MUTAGEN INTERACTIONS  

EPA Science Inventory

The following solvents did not induce prophage lambda in the Escherichia coli WP2 s (Microscreen assay: cetone, benzene, chloroform, ethanol, n-hexane, isopropanol methanol, toluene, and a mixture of the three isomers of xylene. imethyl sulfoxide was genotoxic in the presence and...

394

Detonability of hydrocarbon fuels in air  

Microsoft Academic Search

Liquid hydrocarbon fuels are used extensively in propulsion systems, and explosion hazards associated with fuel vapors mixed with air must be assessed. In this paper, the detonation of gas phase mixtures of n-hexane and the commercial fuel, JP-4, with oxidizers varying from pure oxygen to air, have been studied both experimentally and theoretically via kinetic modeling. Experiments were carried out

H. D. Beeson; R. D. McClenagan; F. J. Benz; W. J. Pitz; C. K. Westbrook; J. H. S. Lee

1989-01-01

395

Effects of lemon balm ( Melissa officinalis L.) extract on germination and seedling growth of six plants  

Microsoft Academic Search

The n-hexane-, acetone- and water-soluble fractions obtained from an aqueous acetone extract of lemon balm (Melissa officinalis L.) shoots inhibited the germination and the growth of roots and shoots of cockscomb (Amaranthus caudatus L.), cress (Lepidium sativum L.), crabgrass (Digitaria sanguinalis L.), timothy (Phleum pratense L.), lettuce (Lactuca sativa L.) and ryegrass (Lolium multiflorum Lam.). The inhibitory activity of the

Hisashi Kato-Noguchi

2001-01-01

396

High energy ionization in liquids: The free ion yield  

SciTech Connect

This paper considers some recent experimental results (n-hexane, neopentane, 2,2,4,4-tetramethylpentane, 2,2,4-trimethylpentane) which show how G{sub fi}(number of ion pairs or free ions per 100 eV absorbed) depends on conditions. The results provide insight into factors which determine free ion yield: molecular structure, field, temperature, tracks, density.

Holroyd, R.

1993-09-01

397

Herbicidal activity of Withania somnifera against Phalaris minor  

Microsoft Academic Search

Herbicidal activity of Withania somnifera (L.) Dunal. was studied against Phalaris minor Retz., one of the most problematic weeds of wheat in Pakistan. In laboratory bioassays the aqueous, methanol and n-hexane extracts of 5, 10 and 15% w\\/v (fresh weight basis) of the roots and shoots of W. somnifera were applied. Extracts in the different solvents exhibited markedly variable herbicidal

Arshad Javaid; Shazia Shafique; Sobiya Shafique

2010-01-01

398

Management of Parthenium hysterophorus (Asteraceae) by Withania somnifera (Solanaceae)  

Microsoft Academic Search

This study was designed to evaluate the herbicidal activity of Withania somnifera (L.) Dunal against the noxious weed parthenium (Parthenium hysterophorus L.). In a laboratory bioassay, the effect of aqueous, methanol and n-hexane shoot and root extracts of 5%, 10%, 15% and 20% w\\/v concentrations (on a fresh weight basis) of W. somnifera were tested against the germination and seedling

Arshad Javaid; Shazia Shafique; Sobiya Shafique

2011-01-01

399

Hazardous organic compounds in urban municipal solid waste from a developing country  

Microsoft Academic Search

Fresh and partially decomposed municipal solid waste (MSW) collected from three places in Chennai city, viz., a residential collection point and two dumping grounds (Kodungaiyur and Perungudi) were screened for hazardous organic pollutants. Toxicity Characteristics Leaching Procedure (TCLP) using a Zero Headspace Extractor (ZHE) followed by further extraction by solvent separation using n-hexane containing 15% di-ethyl ether was performed and

M. Swati; T. Rema; Kurian Joseph

2008-01-01

400

Adsorption competition study between oxygenated compounds and hydrocarbons on molecular sieves.  

National Technical Information Service (NTIS)

The aim of this study is to determine the competitive behavior of methanol and l -hexene in an n-hexane solvent system using a 13-x and a molecular sieves as the adsorbent. Adsorption was carried out in liquid phase. Parameters such as concentration, flow...

L. Kong Ming

1996-01-01

401

The influence on enzyme activity of storage of tissue blocks at ?70° C  

Microsoft Academic Search

Blocks of tissue from various organs of the rat have been chilled by precipitate immersion in n-hexane cooled to -70° C, and then stored at -70° C. At various intervals (up to 14 days) after chilling, cryostat sections were prepared from these blocks and assayed for the activity of a variety of enzymes. Enzyme activity was measured by scanning and

B. Henderson; N. Loveridge; W. R. Robertson; M. T. Smith

1981-01-01

402

Coumarins from Zosima absinthifolia seeds, with allelopatic effects  

Microsoft Academic Search

Zosima absinthifolia belongs to the Apiaceae family and is found in Iran, Turkey, Iraq and different countries of the Caucasus, Middle East and Central Asia. The fruits are used as food flavoring and as a food spice in Iran. In the present work, an n-hexane extract of the plant seeds was purified by vacuum liquid chromatography and preparative TLC for

Seyed Mehdi RAZAVI; Gholamhassan IMANZADEH; Mahdi DAVARI

2010-01-01

403

Neuropathy in a petrol sniffer.  

PubMed

A 4 year old boy developed a profound motor neuropathy after repeated deliberate inhalation of petroleum vapour. The condition was characterised by extreme slowing of the nerve conduction velocity. He made a gradual recovery over six months. The neuropathy was attributed to the N-hexane component of petroleum. PMID:3021070

Hall, D M; Ramsey, J; Schwartz, M S; Dookun, D

1986-09-01

404

Neuropathy in a petrol sniffer  

Microsoft Academic Search

A 4 year old boy developed a profound motor neuropathy after repeated deliberate inhalation of petroleum vapour. The condition was characterised by extreme slowing of the nerve conduction velocity. He made a gradual recovery over six months. The neuropathy was attributed to the N-hexane component of petroleum.

D M Hall; J Ramsey; M S Schwartz; D Dookun

1986-01-01

405

Adsorption of volatile organic compounds onto activated carbon cloths derived from a novel regenerated cellulosic precursor  

Microsoft Academic Search

Activated carbon cloths (ACC) were prepared from lyocell, a novel regenerated cellulose nanofibre fabric, by phosphoric acid activation in inert atmosphere at two different final thermal treatment temperatures (864 and 963°C). Benzene, toluene and n-hexane isotherms at 298 and 273K were measured in order to gain insight into the porous structure of the ACC and to evaluate their performance for

M. E. Ramos; P. R. Bonelli; A. L. Cukierman; M. M. L. Ribeiro Carrott; P. J. M. Carrott

2010-01-01

406

Chemisorption of Organic Compounds on a Clean Aluminum Surface Prepared by Cutting Under High Vacuum  

Microsoft Academic Search

The chemisorption of organic compounds as model compounds of lubrication additives has been studied at room temperature on a clean aluminum surface which was prepared by cutting under high-vacuum conditions. Hydrocarbons such as n-hexane, butene, and cyclohexene did not adsorb, but alkyl halides, organic acid, and alcohols adsorbed on the clean aluminum surface. The adsorption activity was monitored with a

Shigeyuki Mori; Mitsuru Suginoya; Yasukatsu Tamai

1982-01-01

407

VANADIUM PHOSPHORUS OXIDE AS AN EFFICIENT CATALYST FOR HYDROCARBON OXIDATIONS USING HYDROGEN PEROXIDE  

EPA Science Inventory

Calcined vanadium phosphorus oxide (VPO) prepared by an organic route is found to be an efficient catalyst for the oxidation of various alkanes such as cyclopentane, cyclohexane, n-hexane, cycloheptane, cyclooctane, cyclodecane and adamantane in acetonitrile solvent using the env...

408

Molecular mechanics and quantum mechanical modeling of hexane soot structure and interactions with pyrene  

Microsoft Academic Search

: Molecular simulations (energy minimizations and molecular dynamics) of an n-hexane soot model developed by Smith and co-workers (M. S. Akhter, A. R. Chughtai and D. M. Smith, Appl. Spectrosc., 1985, 39, 143; ref. 1) were performed. The MM+ (N. L. Allinger, J. Am. Chem. Soc., 1977, 395, 157; ref. 2) and COMPASS (H. Sun, J. Phys. Chem., 1998, 102,

J. D. Kubicki

2000-01-01

409

2D NMR spectroscopic analyses of archangelicin from the seeds of Angelica archangelica.  

PubMed

A total of six coumarins, bergapten (1), xanthotoxin (2), imperatorin (3), isoimperatorin (4), phellopterin (5) and archangelicin (6), have been isolated from an n-hexane extract of the seeds of Angelica archangelica. The results of comprehensive 2D NMR analyses of archangelicin are discussed. PMID:15634612

Muller, Melanie; Byres, Maureenx; Jaspars, Marcel; Kumarasamy, Yashodharan; Middleton, Moira; Nahar, Lutfun; Shoeb, Mohammad; Sarker, Satyajit D

2004-12-01

410

RATE CONSTANTS FOR THE REACTION OF OH RADICALS WITH A SERIES OF ALKENES AND DIALKENES AT 295 + OR - 1 K  

EPA Science Inventory

Using a relative rate technique, rate constants for the gas phase reactions of the OH radical with n-butane, n-hexane and a series of alkenes and dialkenes, relative to that for propene, have been determined in one atmosphere of air at 295 + or - 1K. The resulting rate constant d...

411

A simple sample preparation with HPLC–UV method for estimation of tiropramide from plasma: Application to bioequivalence study  

Microsoft Academic Search

A simple, rapid and selective method was developed for estimation of tiropramide from human plasma. The method involves extracting the tiropramide with n-hexane using diphenhydramine hydrochloride as internal standard. Chromatographic separation was carried out on a reversed phase C18 column using mixture of water and acetonitrile as mobile phase with UV detection set at 230nm. The retention time of internal

Khan Imran; Loya Punnamchand; Saraf Madhusudan Natvarlal

2007-01-01

412

40 CFR 63.945 - Test methods and procedures.  

Code of Federal Regulations, 2013 CFR

...closed position. (3) The detection instrument shall meet the...constituent. (4) The detection instrument shall be calibrated...and (ii) A mixture of methane or n-hexane in air at a...to adjust or not adjust the detection instrument readings to...

2013-07-01

413

40 CFR 63.905 - Test methods and procedures.  

Code of Federal Regulations, 2013 CFR

...closed position. (3) The detection instrument shall meet the...constituent. (4) The detection instrument shall be calibrated...and (ii) A mixture of methane or n-hexane in air at a...to adjust or not adjust the detection instrument readings to...

2013-07-01

414

40 CFR 63.1046 - Test methods and procedures.  

Code of Federal Regulations, 2013 CFR

...closed position. (3) The detection instrument shall meet the...constituent. (4) The detection instrument shall be calibrated...and (ii) A mixture of methane or n-hexane in air at a...to adjust or not adjust the detection instrument readings to...

2013-07-01

415

40 CFR 63.925 - Test methods and procedures.  

Code of Federal Regulations, 2013 CFR

...closed position. (3) The detection instrument shall meet the...constituent. (4) The detection instrument shall be calibrated...and (ii) A mixture of methane or n-hexane in air at a...to adjust or not adjust the detection instrument readings to...

2013-07-01

416

Herbicidal effects of extracts and residue incorporation of Datura metel against parthenium weed  

Microsoft Academic Search

The present study was designed to evaluate the herbicidal activity of Datura metel against the noxious weed parthenium (Parthenium hysterophorus L.). In a laboratory bioassay, the effect of aqueous, methanol and n-hexane shoot and root extracts of 5, 10, 15 and 20% w\\/v (on a fresh weight basis) concentration of D. metel were tested against the germination and seedling growth

Arshad Javaid; Sobiya Shafique; Shazia Shafique

2010-01-01

417

Control of charcoal rot fungus Macrophomina phaseolina by extracts of Datura metel.  

PubMed

Methanolic leaf and fruit extracts of Datura metel were found highly effective in suppressing against Macrophomina phaseolina, the cause of charcoal rot disease. These extracts were further subjected to successive fractionation with n-hexane, chloroform, ethyl acetate and n-butanol. All the concentrations (3.125-200?mg?mL?¹) of chloroform, ethyl acetate and n-butanol fractions of leaf extract, and n-hexane fraction of fruit extract completely inhibited the target fungal growth. Two compounds A and B from the n-hexane fraction of fruit extract and compound C from n-butanol fraction of leaf extract were obtained by TLC. Compound B exhibited the best antifungal activity with an MIC value of 7.81?µg?mL?¹ that was at par with that of commercial fungicide mancozeb (80% w/w). This study concludes that M. phaseolina can be effectively controlled by natural antifungal compounds in n-hexane fraction of methanolic fruit extract of D. metel. PMID:22004473

Javaid, Arshad; Saddique, Amna

2012-01-01

418

Separation and quantification of organic micropollutants (PAH, PCB) in sediments. Toxicity of extracts towards vibrio fisheri  

Microsoft Academic Search

Vibrio fisheri test has been used to evaluate the toxicity of contaminated sediment of the Venice lagoon. The following classes of organic microcontaminants were considered in this study: aliphatic hydrocarbons (AHs), polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and chlorinated pesticides. Contaminants were extracted from samples with n?hexane\\/dichloromethane in a sonication bath. Extracts were then purified and fractionated with column

M. Salizzato; M. Rigoni; B. Pavoni; A. Volpi Ghirardini; P. F. Ghetti

1997-01-01

419

Relaxant effects of different fractions from Tymus vulgaris on guinea-pig tracheal chains.  

PubMed

In previous studies, the relaxant effect of Tymus vulgaris has been demonstrated on guinea pig tracheal chains. Therefore, in the present study, the relaxant effects of n-hexane, dichloromethane, methanol and aqueous fractions of Tymus vulgaris on tracheal chains of guinea pigs were examined. The relaxant effects of four cumulative concentrations of each fraction (0.4, 0.8, 1.2 and 1.6 g%) in comparison to saline as negative control and four cumulative concentrations of theophylline (0.2, 0.4, 0.6 and 0.8 mM) were examined for their relaxant effects on precontracted tracheal chains of guinea pig by 60 mM KCl (group 1) and 10 ìÌ methacholine (group 2, n = 7 for each group). In group 1, all concentrations of the n-hexane fraction and theophylline and three last concentrations (0.8, 1.2 and 1.6 g%) of dichloromethane and two higher concentrations (1.2 and 1.6 g%) of methanol fractions showed significant relaxant effects compared to that of saline (p<0.05 to p<0.001). In group 2, all concentrations of theophylline, n-hexane and dichloromethane fractions and three concentrations (0.8, 1.2 and 1.6 g%) of methanol and two higher concentrations (1.2 and 1.6 g%) of aqueous fractions showed significant relaxant effects compared to that of saline (p<0.05 to p<0.001). In addition, with group 1, the relaxant effect of all concentrations of all fractions except the n-hexane fraction, were significantly less than those of theophylline (p<0.05 to p<0.001). The n-hexane fraction showed higher relaxant effect than theophylline. The relaxant effect of all concentrations of the n-hexane fraction and the three last concentrations (0.8, 1.2 and 1.6 g%) of dichloromethane and aqueous fractions were significantly greater in group 2 than in group 1 (p<0.05 to p<0.001). There were significant positive correlations between the relaxant effects and concentrations for theophylline and all fractions (except aqueous fraction in group 1) in both groups, but a negative correlation for the aqueous fraction in group 1 (p<0.05 to p<0.001). These results showed a potent relaxant effect for n-hexane and weaker relaxant effect for other fractions from Tymus vulgaris on tracheal chains of guinea pigs. PMID:22688986

Keyhanmanesh, Rana; Boskabady, Mohammad H

2012-01-01

420

Probing the adsorption characteristic of metal-organic framework MIL-101 for volatile organic compounds by quartz crystal microbalance.  

PubMed

As volatile organic compounds (VOCs) are a major group of air pollutants, development of materials for efficient adsorption and removal of VOCs is of great significance in both environmental and analytical sciences. Here we report metal-organic frameworks (MOFs) MIL-101 for the effective adsorption of VOCs at atmospheric pressure. A simple device was designed for quartz crystal microbalance (QCM), and six VOCs with various functional groups and polarities, i.e., n-hexane, toluene, methanol, butanone, dichloromethane, and n-butylamine, were chosen as targets to probe the adsorption properties of MIL-101. The developed device allows measurement of the adsorption isotherms and monitoring of the dynamic process for the adsorption of VOCs on MOFs, and also provides a useful tool for characterization of MOFs. The adsorption isotherms of the VOCs on MIL-101 followed the Dubinin-Astakhov equation with the characteristic energy from 5.70 (methanol) to 9.13 kJ mol(-1) (n-butylamine), Astakhov exponent from 0.50 (n-butylamine) to 3.03 (n-hexane), and the limiting adsorption capacity from 0.08 (n-hexane) to 12.8 (n-butylamine) mmol g(-1). MIL-101 exhibited the strongest affinity to n-butylamine, but the weakest affinity to n-hexane. The determined Astakhov exponents and the isosteric heats of adsorption revealed the energetic heterogeneity of MIL-101. MIL-101 showed the most energetically homogeneous for n-hexane, but the most energetically heterogeneous for n-butylamine. The dynamic process of adsorption monitored by the QCM system demonstrated the distribution of the sorption sites within MIL-101. The metal sites within the MIL-101 were vital in adsorption process. MIL-101 gave much higher affinity and bigger adsorption capacity to VOCs than activated carbon, offering great potential for real applications in the adsorption and removal of VOCs. PMID:21500773

Huang, Chan-Yuan; Song, Ming; Gu, Zhi-Yuan; Wang, He-Fang; Yan, Xiu-Ping

2011-05-15

421

Solvothermal Synthesis and Supported Catalysis of Polyanion-derived Metal Oxide Nanoparticles  

NASA Astrophysics Data System (ADS)

Supported metal oxides (SMOs) are important catalytic materials that find numerous applications in important industrial processes. Improving the structural properties of SMOs is a challenging objective due to material synthesis and characterization limitations. Recent developments in the characterization of SMOs, specifically tungstated zirconia (WOx/ZrO2), have revealed structural information that renewed scientific interest in developing more sophisticated synthetic protocols for SMOs. The current work aims to provide a robust characterization of WO x/ZrO2 by using different characterization techniques and probe reactions. Conventional and non-conventional synthetic methods are investigated to cover the whole spectrum of published methods in order to understand the properties and limitations of these techniques. In the second part of this work, a new synthetic approach is presented that successfully produces ultrasmall (smaller than 2 nm) tungsten oxide nanoparticles (WOx NPs). By using conventional tungsten precursors and oleylamine, WOx NPs are synthesized, characterized, and finally supported to test their propene metathesis activity. Conventional WOx/ZrO2 catalysts were prepared and extensively studied by probing their n-pentane isomerization activity and methanol dehydration activity. WOx/ZrO2 prepared via incipient wetness impregnation shows maximum n-pentane isomerization turnover rates (TOR) at intermediate surface densities (rhosurf). This method delivers the most active n-pentane isomerization WOx/ZrO 2 catalysts since it maximizes the number density of the active sub-nm slightly distorted Zr-WOx sites at rhosurf between 5.2-6.2 W/nm2. By comparing the n-pentane isomerization activity with the methanol dehydration activity of WOx /ZrO2, n-pentane isomerization is shown to be an excellent probe reaction for qualitatively identifying the relative (to the other species) population density of Zr-WOx clusters. Bimolecular n-pentane isomerization is the prevailing mechanism and requires a higher population density of Zr-WOx clusters than methanol dehydration. In the second part of this work, a new solvothermal synthesis route for the preparation of ultrasmall tungsten oxide nanoparticles (WOx NPs) is introduced. By using ammonium polyanionic salts and oleylamine, high yields (92+/-5%) of oleylaminecoated WOx NPs were consistently synthesized. The co-addition of an organic oxidant during the synthesis led to smaller WOx NPs thereby providing insight into the NP synthesis mechanism. Deposition and activation of the NPs on SiO2 support by removal of oleylamine allows better control over the WOx domain size than conventional methods. Oleylamine suppresses WOx NP sintering during calcination and prevents the formation of larger polytungstates present in conventional catalysts. The supported WOx NPs were found to be up to 3 times more selective for metathesis products than conventionally prepared tungstated silica likely due to their controlled structure.

Soultanidis, Nikolaos

422

Hydrostatic limits of 11 pressure transmitting media  

NASA Astrophysics Data System (ADS)

We present a systematic and comparative study of the pressure-induced solidification of 11 frequently used pressure transmitting fluids using the ruby fluorescence technique in a diamond anvil cell. These fluids are 1 : 1 and 5 : 1 iso-n pentane, 4 : 1 deuterated methanol-ethanol, 16 : 3 : 1 deuterated methanol-ethanol-water, 1 : 1 FC84-FC87 Fluorinert, Daphne 7474, silicone oil, as well as nitrogen, neon, argon and helium. The data provide practical guidelines for the use of these fluids in high pressure experiments up to 50 GPa.

Klotz, S.; Chervin, J.-C.; Munsch, P.; LeMarchand, G.

2009-04-01

423

Competitive chain transfer by [beta]-hydrogen and [beta]-methyl elimination for the model Ziegler-Natta olefin polymerization system [Me[sub 2]Si([eta][sup 5]-C[sub 5]Me[sub 4])[sub 2  

Microsoft Academic Search

The reaction of OpSc(H)(PMe[sub 3]) (Op = (([eta][sup 5]-C[sub 6]Me[sub 4])[sub 2]SiMe[sub 2])) with isobutene produces OpSc(CH[sub 3])(PMe[sub 3]) along with isobutene, 2-methylpentane, isobutene, 2-methyl-1-pentene, propane, and n-pentane. These products arise from a series of reactions involving olefin insertion, [beta]-CH[sub 3] and (faster) [beta]-H elimination which proceed until only the 2-methyl-1-alkenes (C[sub 4]H[sub 8], C[sub 6]H[sub 12], etc.) and the

S. Hajela; J. E. Bercaw

1994-01-01

424

Comparative study of choleretic agents in anesthetized rats as well as in restrained and and unrestrained rats, with or without compensation for biliary loss  

NASA Technical Reports Server (NTRS)

Tests were conducted on Wistar rats by using 3 control choleretic agents: 1-phenyl-1-hydroxy n-pentane, dehydrocholic acid, and phenyl-dimethylacetic acid. The effects of these agents were compared in different experimental conditions. The comparative study of choleretic agents in anesthetized rats, in restrained and unrestrained rats, with or without compensation for biliary loss by the biliary secretion of restrained or unrestrained rats does not show, in systematic pharmecodynamic investigations, an obvious superiority over the methods based on the simple technique.

Labrid, C.; Dureng, G.; Tachon, J.; Duchene-Marullaz, P.

1980-01-01

425

Intermolecular stretching vibrations of H-complexes in solution at low temperatures  

SciTech Connect

The long-wave IR spectra were measured in the study in solutions of Xe and n-pentane in the region of the frequency of intramolecular stretching vibrations nu/sub sigma/ for a series of complexes with an H bond, previously investigated in the nu(AH) frequency region in solutions of liquid xenon and freons to determine whether the nu/sub sigma/ band is as sensitive to the type of solvent as nu(AH). The spectra of H complexes of perfluoro-tert-butanol (PFTB), trifluoroethanol, and HCl with dimethyl ether, HCl with acetonitrile, and stronger complexes of PFTB with di- and trimethylamines were recorded.

Iskanderov, T.A.; Kazaryan, S.G.; Kimel'fel'd, Ya.M.; Lokshin, B.V.; Smirnova, E.M.

1987-05-01

426

Hydrodésazotation de la pyridine sous pression atmosphérique catalysée par des oxynitrures de Ni, Mo, et des oxynitrures mixtes MoNi, MoPNi, AlNi et AlPNi  

NASA Astrophysics Data System (ADS)

Hydrodenitrogenation of pyridine has been realised, under atmospheric pressure, in the presence of oxynitride catalysts of molybdenum, nickel and their solid solutions as well as on mixed catalysts MoNi, MoPNi, AlNi and AlPNi. In all cases, the main reaction products are n-pentane and N-pentylpiperidine, at any conversion. Kinetic results suggest that the conversion of pyridine, on nickel oxynitride, proceeds through successive steps with hydrogenation as rate-limiting. Molybdenum oxynitride and Mo-Ni-N solid solutions tested in the temperature range 500 circC-450 circC, showed a good structural and catalytic stability, but a low catalytic activity. On the other hand, nickel oxynitride catalyst yielded higher activity at much lower temperatures (190 circC-250 circC). X-rays analysis indicates that the used catalyst was entirely reduced to metallic nickel, which is the active phase. Under the same experimental conditions, mixed catalysts are relatively less active but more selective than nickel oxynitride into n-pentane formation. La réaction d'hydrodésazotation de la pyridine a été réalisée, sous pression atmosphérique, en présence de catalyseurs oxynitrures de molybdène, de nickel et leurs solutions solides ainsi que sur les catalyseurs mixtes MoNi, MoPNi, AlNi et AlPNi. Dans tous les cas, les principaux produits de réaction observés sont le n-pentane et la N- pentylpipéridine, quel que soit le taux de conversion. Les résultats cinétiques obtenus en régime intégral, en présence de l'oxynitrure de nickel, suggèrent un schéma réactionnel successif où l'hydrogénation de la pyridine serait l'étape limitante. L'oxynitrure de molybdène et les solutions solides Mo-Ni-N, testés à des températures supérieures ou égales à 500 circC, ont montré une bonne stabilité catalytique et structurale mais une faible activité catalytique. En revanche, l'oxynitrure de nickel présente une activité catalytique plus importante à des températures de réaction beaucoup plus basses (190 circC 250 circC). Cependant, l'analyse aux rayons X du catalyseur usagé, indique qu'il est entièrement réduit à l'état métallique; ceci laisse supposer que le nickel métallique est la phase active. Dans les mêmes conditions expérimentales, les catalyseurs mixtes sont relativement moins actifs que l'oxynitrure de nickel, mais plus sélectifs vis-à-vis de la formation du n-pentane.

Elkamel, K.; Elidrissi, M.; Yacoubi, A.; Nadiri, A.; Abouarnadasse, S.

1998-11-01

427

Reaktionen von Trimethylsiloxychlorsilanen (Me 3SiO)Me 2? n Ph n SiCl ( n=0, 1, 2) mit Lithium—Bildung von Trimethylsiloxy-substituierten Silyl- und Disilanyllithiumver- bindungen sowie Di und Trisilanen  

Microsoft Academic Search

The trimethylsiloxychlorosilanes (Me3SiO)Me2?nPhnSiCl (1: n=0; 2: n=1; 3: n=2) were allowed to react with lithium metal in tetrahydrofuran (THF) and in a mixture of THF–diethylether–n-pentane in volume ratio 4:1:1 (Trapp mixture). The reaction of 1 with lithium metal in THF under refluxing leads to the homo-coupling product [(Me3SiO)Me2Si]2 (4). A mixture of 1 and Me3SiCl in molar ratio 1:2 reacts

Jörg Harloff; Eckhard Popowski; Hans Fuhrmann

1999-01-01

428

Molecular dynamics simulation study of solvent effects on conformation and dynamics of polyethylene oxide and polypropylene oxide chains in water and in common organic solvents  

NASA Astrophysics Data System (ADS)

In this paper, the conformation and dynamics properties of polyethylene oxide (PEO) and polypropylene oxide (PPO) polymer chains at 298 K have been studied in the melt and at infinite dilution condition in water, methanol, chloroform, carbon tetrachloride, and n-heptane using molecular dynamics simulations. The calculated density of PEO melt with chain lengths of n = 2, 3, 4, 5 and, for PPO, n = 7 are in good agreement with the available experimental data. The conformational properties of PEO and PPO show an increasing gauche preference for the O-C-C-O dihedral in the following order water>methanol>chloroform>carbon tetrachloride = n-heptane. On the contrary, the preference for trans conformation has a maximum in carbon tetrachloride and n-heptane followed in the order by chloroform, methanol, and water. The PEO conformational preferences are in qualitative agreement with results of NMR studies. PEO chains formed different types of hydrogen bonds with polar solvent molecules. In particular, the occurrence of bifurcated hydrogen bonding in chloroform was also observed. Radii of gyration of PEO chains of length larger than n = 9 monomers showed a good agreement with light scattering data in water and in methanol. For the shorter chains the observed deviations are probably due to the enhanced hydrophobic effects caused by the terminal methyl groups. For PEO the fitting of end-to-end distance distributions with the semi-flexible chain model at 298 K provided persistence lengths of 0.375 and 0.387 nm in water and methanol, respectively. Finally, the radius of gyration of Pluronic P85 turned out to be 2.25 +/- 0.4 nm at 293 K in water in agreement with experimental data.

Hezaveh, Samira; Samanta, Susruta; Milano, Giuseppe; Roccatano, Danilo

2012-03-01

429

A comprehensive detailed chemical kinetic reaction mechanism for combustion of n-alkane hydrocarbons from n-octane to n-hexadecane  

SciTech Connect

Detailed chemical kinetic reaction mechanisms have been developed to describe the pyrolysis and oxidation of nine n-alkanes larger than n-heptane, including n-octane (n-C{sub 8}H{sub 18}), n-nonane (n-C{sub 9}H{sub 20}), n-decane (n-C{sub 10}H{sub 22}), n-undecane (n-C{sub 11}H{sub 24}), n-dodecane (n-C{sub 12}H{sub 26}), n-tridecane (n-C{sub 13}H{sub 28}), n-tetradecane (n-C{sub 14}H{sub 30}), n-pentadecane (n-C{sub 15}H{sub 32}), and n-hexadecane (n-C{sub 16}H{sub 34}). These mechanisms include both high temperature and low temperature reaction pathways. The mechanisms are based on previous mechanisms for the primary reference fuels n-heptane and iso-octane, using the reaction classes first developed for n-heptane. Individual reaction class rules are as simple as possible in order to focus on the parallelism between all of the n-alkane fuels included in the mechanisms. These mechanisms are validated through extensive comparisons between computed and experimental data from a wide variety of different sources. In addition, numerical experiments are carried out to examine features of n-alkane combustion in which the detailed mechanisms can be used to compare reactivities of different n-alkane fuels. The mechanisms for these n-alkanes are presented as a single detailed mechanism, which can be edited to produce efficient mechanisms for any of the n-alkanes included, and the entire mechanism, with supporting thermochemical and transport data, together with an explanatory glossary explaining notations and structural details, is available for download from our web page. (author)

Westbrook, Charles K.; Pitz, William J.; Herbinet, Olivier; Silke, Emma J. [Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); Curran, Henry J. [Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); University College of Ireland, Galway (Ireland)

2009-01-15

430

Structure and dynamics of 1,2-dimethoxyethane and 1,2-dimethoxypropane in aqueous and non-aqueous solutions: A molecular dynamics study  

NASA Astrophysics Data System (ADS)

Herein, we report a comparative modelling study of 1,2-dimethoxyethane (DME) and 1,2-dimethoxypropane (DMP) at 298 K and 318 K in the liquid state, water mixtures, and at infinite dilution condition in water, methanol, carbon tetrachloride, and n-heptane. Both DME and DMP are united-atom models compatible with GROMOS/OPLS force fields. Calculated thermodynamic and structural properties of the pure DME and DMP liquids resulted in excellent agreement with the experimental data. In aqueous solutions, densities, diffusion coefficients, and concentration dependent conformers of DME, were in agreement with experimental data. The calculated free energy of solvation (?Ghyd) at 298 K is equal to -22.1 +/- 0.8 kJ mol-1 in good agreement with the experimental value of 20.2 kJ mol-1. In addition, the free energy of solvation of DME in non-aqueous solvents follows the trend methanol ~ water < carbon tetrachloride < n-heptane, consistently with the dielectric constant of the solvents. On contrary, the presence of an extra methyl group on chiral carbon makes DMP less soluble than DME in water (?Ghyd = -16.0 +/- 1.1 kJ mol-1) but more soluble in non-polar solvents as n-heptane. Finally, for the DMP the chiral discrimination of the two enantiomers was calculated as solvation free energy difference of one DMP isomer in the solution of the other. The obtained value of ??GRS = -3.7 +/- 1.4 kJ mol-1 indicates a net chiral discrimination of the two enantiomers.

Hezaveh, Samira; Samanta, Susruta; Milano, Giuseppe; Roccatano, Danilo

2011-10-01

431

Recent Advances In Science Support For Isolated Droplet Combustion Experiments  

NASA Technical Reports Server (NTRS)

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, the combustion characteristics of isolated 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 investigated. 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 support 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. UCSD contributions are described in a companion communication in this conference. The Princeton effort also addresses the analyses of Fiber Supported Droplet Combustion (FSDC) experiments conducted with the above fuels and collaborative work with others who are investigating droplet combustion in the presence of steady convection. A thorough interpretation of droplet burning behavior for n-heptane and n-decane over a relatively wide range of conditions also involves the influences of sooting on the combustion behavior, and this particular aspect on isolated burning of droplets is under consideration in a collaborative program underway with Drexel University. This collaboration is addressed in another communication at this conference. The one-dimensional, time-dependent, numerical modeling approach that we have continued to evolve for analyzing isolated, quiescent droplet combustion data has been further applied to investigate several facets of isolated droplet burning of simple alcohols, n-heptane, and n-decane. Some of the new results are described below.

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

2003-01-01

432

Premixed ignition behavior of alternative diesel fuel-relevant compounds in a motored engine experiment  

SciTech Connect

A motored engine study using premixed charges of fuel and air at a wide range of diesel-relevant equivalence ratios was performed to investigate autoignition differences among surrogates for conventional diesel fuel, gas-to-liquid (GTL) diesel fuel, and biodiesel, as well as n-heptane. Experiments were performed by delivering a premixed charge of vaporized fuel and air and increasing the compression ratio in a stepwise manner to increase the extent of reaction while monitoring the exhaust composition via Fourier transform infrared (FTIR) spectrometry and collecting condensable exhaust gas for subsequent gas chromatography/mass spectrometry (GC/MS) analysis. Each fuel demonstrated a two-stage ignition process, with a low-temperature heat release (LTHR) event followed by the main combustion, or high-temperature heat release (HTHR). Among the three diesel-relevant fuels, the magnitude of LTHR was highest for GTL diesel, followed by methyl decanoate, and conventional diesel fuel last. FTIR analysis of the exhaust for n-heptane, the conventional diesel surrogate, and the GTL diesel surrogate revealed that LTHR produces high concentrations of aldehydes and CO while producing only negligible amounts of CO{sub 2}. Methyl decanoate differed from the other two-stage ignition fuels only in that there were significant amounts of CO{sub 2} produced during LTHR; this was the result of decarboxylation of the ester group, not the result of oxidation. GC/MS analysis of LTHR exhaust condensate for n-heptane revealed high concentrations of 2,5-heptanedione, a di-ketone that can be closely tied to species in existing autoignition models for n-heptane. GC/MS analysis of the LTHR condensate for conventional diesel fuel and GTL diesel fuel revealed a series of high molecular weight aldehydes and ketones, which were expected, as well as a series of organic acids, which are not commonly reported as products of combustion. The GC/MS analysis of the methyl decanoate exhaust condensate revealed that the aliphatic chain acts similarly to n-paraffins during LTHR, while the ester group remains intact. Thus, although the FTIR data revealed that decarboxylation occurs at significant levels for methyl decanoate, it was concluded that this occurs after the aliphatic chain has been largely consumed by other LTHR reactions. (author)

Szybist, James P.; Boehman, Andre L.; Haworth, Daniel C. [Pennsylvania State University, Fuel Science Program, 405 Academic Activities Building, University Park, PA 16802 (United States); Koga, Hibiki [Honda R and D Company, Ltd., Asaka-shi, Saitama 351-0024 (Japan)

2007-04-15

433

Velocity profiles in laminar diffusion flames  

NASA Technical Reports Server (NTRS)

Velocity profiles in vertical laminar diffusion flames were measured by using laser Doppler velocimetry (LDV). Four fuels were used: n-heptane, iso-octane, cyclohexane, and ethyl alcohol. The velocity profiles were similar for all the fuels, although there were some differences in the peak velocities. The data compared favorably with the theoretical velocity predictions. The differences could be attributed to errors in experimental positioning and in the prediction of temperature profiles. Error in the predicted temperature profiles are probably due to the difficulty in predicting the radiative heat losses from the flame.

Lyons, Valerie J.; Margle, Janice M.

1986-01-01

434

Detailed chemical kinetic modeling of diesel combustion with oxygenated fuels  

SciTech Connect

The influence of oxygenated hydrocarbons as additives to diesel fuels on ignition, NOx emissions and soot production has been examined using a detailed chemical kinetic reaction mechanism. N-heptane was used as a representative diesel fuel, and methanol, ethanol, dimethyl ether and dimethoxymethane were used as oxygenated fuel additives. It was found that addition of oxygenated hydrocarbons reduced NOx levels and reduced the production of soot precursors. When the overall oxygen content in the fuel reached approximately 25% by mass, production of soot precursors fell effectively to zero, in agreement with experimental studies. The kinetic factors responsible for these observations are discussed.

Pitz, W J; Curran, H J; Fisher, E; Glaude, P A; Marinov, N M; Westbrook, C K

1999-10-28

435

The preparation and characterization of Li 4Ti 5O 12\\/carbon nano-tubes for lithium ion battery  

Microsoft Academic Search

Li4Ti5O12\\/carbon nano-tubes (CNTs) composite was prepared by sol–gel method while Ti(OC4H9)4, LiCH3COO·2H2O and the n-heptane containing CNTs were used as raw materials. The characters of Li4Ti5O12\\/CNTs composite were determined by XRD, SEM, and TG methods. Its electrochemical properties were measured by charge–discharge cycling and impedance tests. It was found that the prepared Li4Ti5O12\\/CNTs presented an excellent rate capability and capacity

Junjie Huang; Zhiyu Jiang

2008-01-01

436

Flame Extinguishment Properties of Dry Chemicals: Extinction Weights for Small Diffusion Pan Fires and Additional Evidence for Flame Extinguishment by Thermal Mechanisms  

Microsoft Academic Search

An experimental study was made of the extinguishment of a small n-heptane diffusion flame (25.5 cm dia. pan) by a number of dry-chemical powders — KHCO3, NH 4H2PO4, Na2B4O7 . 10H2O, (NH4)2SO4, K2CO 3, K4Fe(CN)6 . 3H2O, Na2CO 3, K2SO4, NaCl, Na2C2O 4, K2C2O4 . H2O, and Monnex. The minimum weight of each required for flame extinction was determined as

Curtis T. Ewing; Francis R. Faith; James B. Romans; J. Thomas Hughes; Homer W. Carhart

1992-01-01

437

Investigations on Soot Formation in Heptane Jet Diffusion Flames by Optical Techniques  

Microsoft Academic Search

Two-dimensional optical measurements were performed for the investigation of soot formation of n-heptane laminar gas-jet diffusion\\u000a flames under buoyant and non-buoyant conditions utilizing the Bremen Drop Tower. Techniques employed were laser-induced incandescence\\u000a for the determination of soot concentration and primary particle sizes and two-color emission pyrometry with a three-point\\u000a Abel inversion for the measurement of temperature fields. In line with

Jörg Reimann; Stephan-André Kuhlmann; Stefan Will

2010-01-01

438

Spontaneous ignition characteristics of gaseous hydrocarbon-air mixtures  

NASA Technical Reports Server (NTRS)

Experiments are conducted to determine the spontaneous ignition delay times of gaseous propane, kerosine vapor, and n-heptane vapor in mixtures with air, and oxygen-enriched air, at atmospheric pressure. Over a range of equivalence ratios from 0.2 to 0.8 it is found that ignition delay times are sensibly independent of fuel concentration. However, the results indicate a strong dependence of delay times on oxygen concentration. The experimental data for kerosine and propane demonstrate very close agreement with the results obtained previously by Mullins and Lezberg respectively.

Freeman, G.; Lefebvre, A. H.

1984-01-01

439

The impact of asphaltenes removal on the kinetics of residuum hydrotreating  

SciTech Connect

Reduced crude (above 350{degrees} C) prepared in a laboratory distillation unit containing 15 trays was solvent deasphaltened at specified conditions using n-heptane as the precipitant. Both the original and deasphaltened reduced crude was hydrotreated on a commercial Ni-Mo- alumina catalyst in a laboratory trickle bed reactor. This investigation was undertaken to understand the role of asphaltenes removal in the kinetics of the desulphurization, demetallization and deasphaltening processes. Kinetic analysis shows that the hydrotreating reactions of the deasphaltened reduced crude followed a first order kinetics. Rate constants calculated for the above reactions are higher than those obtained in the HDS process for the original full residuum.

Abbas, A.A.; Ahmed, A.B.-A. (Baghdad Univ. (Iraq). Coll. of Engineering); Mohammed, A.-H.A.-K.; Abbas, K. (Petroleum Research Centre, Scientific Research Centre, P.O. Box 10039, Jadiriyah, Baaghdad, (IQ))

1990-01-01

440

Excess molar volumes and enthalpies of binary mixtures of an alkanol or an alkane with butyl-vinyl ether or iso-butyl-vinyl ether at 313.15 K  

Microsoft Academic Search

Experimental results are reported of excess molar volumes VmE and excess molar enthalpies HmE at T=313.15K for twelve binary mixtures of alkanols (ethanol, 1-butanol or iso-butanol) or alkanes (n-heptane, iso-octane (2,2,4-trimethylpentane) or n-octane) with butyl-vinyl ether or iso-butyl-vinyl ether. A vibrating-tube densitometer was used to determine VmE. The quantity HmE was measured using a quasi-isothermal flow calorimeter. The applicability of

E. N Rezanova; R. N Lichtenthaler

2001-01-01

441

Bioconversion of lipophilic compounds in non-aqueous solvent. Effect of gel hydrophobicity on diverse conversions of testosterone by gel-entrapped Nocardia rhodocrous cells  

Microsoft Academic Search

The bioconversion of testosterone (TS) in water-saturated benzene-n-heptane (4:1 by volume) was mediated by Nocardia rhodocrous cells whose steroid ?1-dehydrogenase and 17ß-hydroxysteroid dehydrogenase were induced by TS. TS was transformed into 4-androstene-3,17-dione (4-AD), dehydrotestosterone (DTS) and 1,4-androstadiene-3, 17-dione (ADD) by incubating with the cell suspensions in the presence of phenazine methosulfate (PMS). Time-courses of TS transformation revealed that DTS and

Saburo Fukui; Syed Ashrafudin Ahmed; Tetsuo Omata; Atsuo Tanaka

1980-01-01

442

Efficient High Pressure MixtureState Equations  

NASA Technical Reports Server (NTRS)

A method is presented for an accurate noniterative, computationally efficient calculation of high pressure fluid mixture equations of state, especially targeted to gas turbines and rocket engines. Pressures above 1 bar and temperatures above 100 K are addressed. The method is based on curve fitting an effective reference state relative to departure funcitons formed using the Peng-Robinson cubic state equation. Fit parameters for H(sub 2), O(sub 2), N(sub 2), propane, n-heptane and methanol are given.

Harstad, K. G.; Miller, R. S.; Bellan, J.

1996-01-01

443

Analysis of aromatic constituents in multicomponent hydrocarbon mixtures by infrared spectroscopy using multiple linear regression  

NASA Astrophysics Data System (ADS)

Absorption spectra of multicomponent hydrocarbon mixtures based on n-heptane and isooctane with addition of benzene (up to 1%) and toluene and o-xylene (up to 20%) were investigated experimentally in the region of the first overtones of the hydrocarbon groups (? = 1620-1780 nm). It was shown that their concentrations could be determined separately by using a multiple linear regression method. The optimum result was obtained by including four wavelengths at 1671, 1680, 1685, and 1695 nm, which took into account absorption of CH groups in benzene, toluene, and o-xylene and CH3 groups, respectively.

Vesnin, V. L.; Muradov, V. G.

2012-09-01

444

A Detailed Chemical Kinetic Reaction Mechanism for n-Alkane Hydrocarbons From n-Octane to n-Hexadecane  

Microsoft Academic Search

Detailed chemical kinetic reaction mechanisms have been developed to describe the pyrolysis and oxidation of nine n-alkanes larger than n-heptane, including n-octane (n-CH), n-nonane (n-CH), n-decane (n-CH), n-undecane (n-CH), n-dodecane (n-CH), n-tridecane (n-CH), n-tetradecane (n-CH), n-pentadecane (n-CH), and n-hexadecane (n-CH). These mechanisms include both high temperature and low temperature reaction pathways. The mechanisms are based on our previous mechanisms for

C K Westbrook; W J Pitz; O Herbinet; H J Curran; E J Silke

2008-01-01

445

A Detailed Chemical Kinetic Reaction Mechanism for n-Alkane Hydrocarbons from n-Octane to n-Hexadecane  

Microsoft Academic Search

Detailed chemical kinetic reaction mechanisms have been developed to describe the pyrolysis and oxidation of the n-alkanes, including n-octane (n-CH), n-nonane (n-CH), n-decane (n-CH), n-undecane (n-CH), n-dodecane (n-CH), n-tridecane (n-CH), n-tetradecane (n-CH), n-pentadecane (n-CH), and n-hexadecane (n-CH). These mechanisms include both high temperature and low temperature reaction pathways. The mechanisms are based on previous mechanisms for n-heptane, using the same

C K Westbrook; W J Pitz; O Herbinet; E J Silke; H J Curran

2007-01-01

446

Low and intermediate temperature oxidation of ethanol and ethanol-PRF blends: An experimental and modeling study  

SciTech Connect

In this brief communication, we present new experimental species profile measurements for the low and intermediate temperature oxidation of ethanol under knock-prone conditions. These experiments show that ethanol exhibits no global low temperature reactivity at these conditions, although we note the heterogeneous decomposition of ethanol to ethylene and water. Similar behavior is reported for an E85 blend in n-heptane. Kinetic modeling results are presented to complement these experiments and elucidate the interaction of ethanol and primary reference fuels undergoing cooxidation. (author)

Haas, Francis M.; Chaos, Marcos; Dryer, Frederick L. [Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544 (United States)

2009-12-15

447

Solid–liquid and liquid–liquid equilibria for 1,3,5-trioxane, or 1,4,7,10,13,16-hexaoxacyclooctadecane + selected n-alkane mixtures  

Microsoft Academic Search

Solid–liquid and liquid–liquid equilibrium temperatures for mixtures of 1,3,5-trioxane, or 1,4,7,10,13,16-hexaoxacyclooctadecane with n-heptane, or with n-tridecane, or with n-hexadecane are reported. The equilibrium temperatures were measured by a dynamic method. Mixtures with n-tridecane, or n-hexadecane show a eutectic point. 1,4,7,10,13,16-Hexaoxacyclooctadecane present a transition point in solid phase, which depends on the solvent. Dipole–dipole interactions are stronger in solutions with 1,3,5-trioxane.Mixtures

U. Domanska; J. A. González

2003-01-01

448

Hydrophobic layered double hydroxides (LDHs): Selective adsorbents for liquid mixtures  

Microsoft Academic Search

The external and internal surface area of the calcium aluminum double hydroxide [Ca2Al(OH)6] NO3 · 2H2O were hydrophobized by the anionic surfactants sodium dodecylsulfate and sodium dodecylbenzene sulfonate. The adsorption\\u000a behavior towards liquid mixtures (benzene\\/n-heptane and n-propanol\\/toluene) was studied by determining the surface excess adsorption isotherms, the heats of immersion in these liquids,\\u000a and the basal spacing, i.e. the expansion

I. Dékány; F. Berger; K. Imrik; G. Lagaly

1997-01-01

449

An experimental investigation of the burning characteristics of water-oil emulsions  

SciTech Connect

An experimental investigation was conducted on the combustion characteristics of droplets of n-heptane, n-decane, n-dodecane, n-hexadecane and iso-octane emulsified with various amount of water and freely falling in a furnace of controlled temperature. Results demonstrate the intricate influences of water emulsification on the ignition, extinction and micro-explosion of the droplet response, and that the droplet burning time can be significantly reduced through judicious fuel blending so as to minimize the ignition delay and advance the onset of micro-explosion.

Wang, C.H.; Chen, J.T. [National Taiwan Univ., Taipei (Taiwan, Province of China). Dept. of Mechanical Engineering] [National Taiwan Univ., Taipei (Taiwan, Province of China). Dept. of Mechanical Engineering

1996-10-01

450

Fatty and resinic acids extractions from crude tall oil  

SciTech Connect

The separation of fatty and resinic acidic fractions from crude tall-oil soap solutions with n-heptane by the technique of dissociation extraction is discussed. The theory of the overall process is supported by a systematic study developed to cover the high selectivity demonstrated in the differential solubility and the aptness between fatty and diterpenic acids to both liquids phases. To study the main factors affecting those liquid-liquid extraction systems and the amphiphilic behavior of such molecules involved, sodium salts aqueous solutions of crude tall oil and synthetic mixtures as molecular acidic models were used.

Nogueira, J.M.F. [Univ. of Lisbon (Portugal)

1996-11-01

451

Chemical kinetic mechanism for the oxidation of paraffinic hydrocarbons needed for primary reference fuels  

SciTech Connect

A detailed chemical kinetic reaction mechanism is described which simulates the oxidation of the primary reference fuels n-heptane and iso-octane. The high temperature subset of these mechanisms is identified, and the extensions to deal with low temperature conditions are also explained. The algorithms used to assign reaction rates to elementary steps in the reaction mechanism are described, and the means of identifying the different chemical species and the relevant reactions are outlined. Finally, we show how interested kinetic modeling researchers can obtain copies of this reaction mechanism.

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

1993-03-01

452

Structural studies on residua  

SciTech Connect

Within the authors ongoing program aimed at the elucidation of the molecular structure of the heavy ends of petroleum, they have recently explored the chemistry of the non-distillable, high molecular weight portions of Athabasca and other Alberta tar sand bitumens. The bitumen was deasphaltened by {und n}-pentane precipitation and the resultant maltene separated into five fractions by column chromatography according to polarity. The residua were then obtained by distillation at 230{degree}C and 10{sup {minus}3} torr of the fractions, M-1 through M-5. The M-1 fraction was considered to be comprised of the saturates and the subsequent fractions of monoaromatics, polyaromatics, resins I and resins II. The {und n}-pentane precipitated asphaltene was fractionated according to molecular weight into five fractions, A-1 through A-5, ranging from 17,000 to 1,200 in mw by gel permeation chromatography. Four methods were employed for the structural investigation of these residua: (a) Thermolysis (300-400{degree}C); (b) ruthenium (VIII) catalyzed oxidation; (c) thermolysis of the non-distillable portion of the Ru(VIII)oxidized acids after esterification with diazomethane, and (d) high resolution {sup 13}C and {sup 1}H NMR spectroscopy.

Strausz, O.P. (Univ. of Alberta, Edmonton (Canada))

1987-04-01

453

Evaluation of a locally homogeneous flow model of spray combustion  

NASA Technical Reports Server (NTRS)

A model of spray combustion which employs a second-order turbulence model was developed. The assumption of locally homogeneous flow is made, implying infinitely fast transport rates between the phase. Measurements to test the model were completed for a gaseous n-propane flame and an air atomized n-pentane spray flame, burning in stagnant air at atmospheric pressure. Profiles of mean velocity and temperature, as well as velocity fluctuations and Reynolds stress, were measured in the flames. The predictions for the gas flame were in excellent agreement with the measurements. The predictions for the spray were qualitatively correct, but effects of finite rate interphase transport were evident, resulting in a overstimation of the rate development of the flow. Predictions of spray penetration length at high pressures, including supercritical combustion conditions, were also completed for comparison with earlier measurements. Test conditions involved a pressure atomized n-pentane spray, burning in stagnant air at pressures of 3, 5, and 9 MPa. The comparison between predictions and measurements was fair. This is not a very sensitive test of the model, however, and further high pressure experimental and theoretical results are needed before a satisfactory assessment of the locally homogeneous flow approximation can be made.

Mao, C. P.; Szekely, G. A., Jr.; Faeth, G. M.

1980-01-01

454

Coupled-cluster, Möller Plesset (MP2), density fitted local MP2, and density functional theory examination of the energetic and structural features of hydrophobic solvation: Water and pentane  

NASA Astrophysics Data System (ADS)

The interaction potentials between immiscible polar and non-polar solvents are a major driving force behind the formation of liquid:liquid interfaces. In this work, the interaction energy of water-pentane dimer has been determined using coupled-cluster theory with single double (triple) excitations [CCSD(T)], 2nd order Möller Plesset perturbation theory (MP2), density fitted local MP2 (DF-LMP2), as well as density functional theory using a wide variety of density functionals and several different basis sets. The M05-2X exchange correlation functionals exhibit excellent agreement with CCSD(T) and DF-LMP2 after taking into account basis set superposition error. The gas phase water-pentane interaction energy is found to be quite sensitive to the specific pentane isomer (2,2-dimethylpropane vs. n-pentane) and relative orientation of the monomeric constituents. Subsequent solution phase cluster calculations of 2,2-dimethylpropane and n-pentane solvated by water indicate a positive free energy of solvation that is in good agreement with available experimental data. Structural parameters are quite sensitive to the density functional employed and reflect differences in the two-body interaction energy calculated by each method. In contrast, cluster calculations of pentane solvation of H2O solute are found to be inadequate for describing the organic solvent, likely due to limitations associated with the functionals employed (B3LYP, BHandH, and M05-2X).

Ghadar, Yasaman; Clark, Aurora E.

2012-02-01

455

On sub-T(g) dewetting of nanoconfined liquids and autophobic dewetting of crystallites.  

PubMed

The glass transition temperature (T(g)) of thin films is reduced by nanoconfinement, but it is also influenced by the free surface and substrate interface. To gain more insights into their contributions, dewetting behaviors of n-pentane, 3-methylpentane, and toluene films are investigated on various substrates as functions of temperature and film thickness. It is found that monolayers of these molecules exhibit sub-T(g) dewetting on a perfluoro-alkyl modified Ni substrate, which is attributable to the evolution of a 2D liquid. The onset temperature of dewetting increases with film thickness because fluidity evolves via cooperative motion of many molecules; sub-T(g) dewetting is observed for films thinner than 5 monolayers. In contrast, monolayers wet substrates of graphite, silicon, and amorphous solid water until crystallization occurs. The crystallites exhibit autophobic dewetting on the substrate covered with a wetting monolayer. The presence of premelting layers is inferred from the fact that n-pentane crystallites disappear on amorphous solid water via intermixing. Thus, the properties of quasiliquid formed on the crystallite surface differ significantly from those of the 2D liquid formed before crystallization. PMID:22337324

Souda, Ryutaro

2012-03-28

456

Coupled-cluster, Möller Plesset (MP2), Density Fitted Local MP2, and Density Functional Theory Examination of the Energetic and Structural Features of Hydrophobic Solvation: Water and Pentane  

SciTech Connect

The interaction potentials between immiscible polar and non-polar solvents are a major driving force behind the formation of liquid:liquid interfaces. In this work, the interaction energy of water–pentane dimer has been determined using coupled-cluster theory with single double (triple) excitations [CCSD(T)], 2nd order Möller Plesset perturbation theory (MP2), density fitted local MP2 (DF-LMP2), as well as density functional theory using a wide variety of density functionals and several different basis sets. The M05-2X exchange correlation functionals exhibit excellent agreement with CCSD(T) and DF-LMP2 after taking into account basis set superposition error. The gas phase water–pentane interaction energy is found to be quite sensitive to the specific pentane isomer (2,2- dimethylpropane vs. n-pentane) and relative orientation of the monomeric constituents. Subsequent solution phase cluster calculations of 2,2-dimethylpropane and n-pentane solvated by water indicate a positive free energy of solvation that is in good agreement with available experimental data. Structural parameters are quite sensitive to the density functional employed and reflect differences in the two-body interaction energy calculated by each method. In contrast, cluster calculations of pentane solvation of H2O solute are found to be inadequate for describing the organic solvent, likely due to limitations associated with the functionals employed (B3LYP, BHandH, and M05-2X).

Ghadar, Yasaman; Clark, Aurora E.

2012-02-02

457

Screening and evaluation of biosurfactant-producing strains isolated from oilfield wastewater.  

PubMed

The six biosurfactant-producing strains, isolated from oilfield wastewater in Daqing oilfield, were screened. The production of biosurfactant was verified by measuring the diameter of the oil spreading, measuring the surface tension value and emulsifying capacity against xylene, n-pentane, kerosene and crude oil. The experimental result showed three strains (S2, S3, S6) had the better surface activity. Among the three strains, the best results were achieved when using S2 strain. The diameter of the oil spreading of the biosurfactant produced by S2 strain was 14 cm, its critical micelle concentration (CMC) was 21.8 mg/l and the interfacial tension between crude oil and biosurfactant solution produced by S2 strain reduced to 25.7 mN/m. The biosurfactant produced by S2 strain was capable of forming stable emulsions with various hydrocarbons, such as xylene, n-pentane, kerosene and crude oil. After S2 strain treatment, the reduction rate of oil viscosity was 51 % and oil freezing point reduced by 4 °C. PMID:24426104

Liu, Jianghong; Chen, Yitong; Xu, Ruidan; Jia, Yunpeng

2013-06-01

458

Adsorption of selected volatile organic vapors on multiwall carbon nanotubes.  

PubMed

Carbon nanotubes are expected to play an important role in sensing, pollution treatment and separation techniques. This study examines the adsorption behaviors of volatile organic compounds (VOCs), n-hexane, benzene, trichloroethylene and acetone on two multiwall carbon nanotubes (MWCNTs), CNT1 and CNT2. Among these VOCs, acetone exhibits the highest adsorption capacity. The highest adsorption enthalpies and desorption energies of acetone were also observed. The strong chemical interactions between acetone and both MWCNTs may be the result from chemisorption on the topological defects. The adsorption heats of trichloroethylene, benzene, and n-hexane are indicative of physisorption on the surfaces of both MWCNTs. CNT2 presents a higher adsorption capacity than CNT1 due to the existence of an exterior amorphous carbon layer on CNT2. The amorphous carbon enhances the adsorption capacity of organic chemicals on carbon nanotubes. The morphological and structure order of carbon nanotubes are the primary affects on the adsorption process of organic chemicals. PMID:17980962

Shih, Yang-hsin; Li, Mei-syue

2008-06-15

459

Antioxidant and anti-cholinesterase activity of Globularia meridionalis extracts and isolated constituents.  

PubMed

The antioxidant and anti-cholinesterase properties of Globularia meridionalis (Podp.) O. Schwarz (Globulariaceae) were investigated. G. meridionalis aerial parts and roots were extracted with methanol, and the total extract successively partitioned with n-hexane. The methanol fraction of the roots showed the highest antioxidant activity with IC50 values of 8.0 and 2.1 microg/mL in the DPPH and beta-carotene bleaching tests, respectively. From this fraction, three flavonoids, namely pectolinarigenin 7-O-beta-glucoside, apigenin 7-O-beta-glucoside and luteolin, and two phenylethanoids, namely acteoside and isoacteoside, were isolated. Potential anti-cholinesterase effects were assessed through the acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes inhibition assay. The n-hexane fraction of the roots exhibited the highest activity against both AChE and BChE with IC50 values of 65.5 and 70.4 microg/mL, respectively. PMID:22978219

Tundis, Rosa; Bonesi, Marco; Menichini, Federica; Loizzo, Monica R; Conforti, Filomena; Statti, Giancarlo; Pirisi, Filippo M; Menichini, Francesco

2012-08-01

460

Phenomenological model of fungal biofilters for the abatement of hydrophobic VOCs.  

PubMed

This work describes the growth of filamentous fungi in biofilters for the degradation of hydrophobic VOCs. The study system was n-hexane and Fusarium solani B1. The system is mathematically described and the main physical, kinetic data and morphological parameters were obtained by independent experiments and validated with data from laboratory experiments. The model describes the increase in the transport area by the growth of the filamentous cylindrical mycelia and its relation with n-hexane elimination in quasi-stationary state in a biofilter. The model describing fungal growth includes Monod-Haldane kinetic and hyphal elongation and ramification. A specific surface area of transport (SSAT) of 1.91 x 10(5) m(2) m(-3) and a maximum elimination capacity (EC) of 248 g m(-3) h(-1) were obtained by the mathematical model simulation, with a 10% of error with respect to the experimental