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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  

NASA Astrophysics Data System (ADS)

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 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.; de Castro, C. A. Nieto; Wakeham, W. A.

1987-11-01

3

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

SciTech Connect

A previously described methodology for deriving a reduced kinetic mechanism for alkane oxidation and tested for n-heptane is here shown to be valid, in a slightly modified version, for iso-octane and its mixtures with n-pentane, iso-hexane and n-heptane. The model is still based on partitioning the species into lights, defined as those having a carbon number smaller than 3, and heavies, which are the complement in the species ensemble, and mathematically decomposing the heavy species into constituents which are radicals. For the same similarity variable found from examining the n-heptane LLNL mechanism in conjunction with CHEMKIN II, the appropriately scaled total constituent molar density still exhibits a self-similar behavior over a very wide range of equivalence ratios, initial pressures and initial temperatures in the cold ignition regime. When extended to larger initial temperatures than for cold ignition, the self-similar behavior becomes initial temperature dependent, which indicates that rather than using functional fits for the enthalpy generation due to the heavy species' oxidation, an ideal model based on tabular information extracted from the complete LLNL kinetics should be used instead. Similarly to n-heptane, the oxygen and water molar densities are shown to display a quasi-linear behavior with respect to the similarity variable, but here their slope variation is no longer fitted and instead, their rate equations are used with the ideal model to calculate them. As in the original model, the light species ensemble is partitioned into quasi-steady and unsteady species; the quasi-steady light species mole fractions are computed using the ideal model and the unsteady species are calculated as progress variables using rates extracted from the ideal model. Results are presented comparing the performance of the model with that of the LLNL mechanism using CHEMKIN II. The model reproduces excellently the temperature and species evolution versus time or versus the similarity variable, with the exception of very rich mixtures, where the predictions are still very good but the multivalued aspect of these functions at the end of oxidation is not captured in the reduction. The ignition time is predicted within percentages of the LLNL values over a wide range of equivalence ratios, initial pressures and initial temperatures. (author)

Harstad, Kenneth; Bellan, Josette [California Institute of Technology, Jet Propulsion Laboratory, 4800 Oak Grove Drive, M/S 125-109, Pasadena, CA 91109-8099 (United States)

2010-11-15

4

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

5

Viscosity and thermal conductivity of binary n-heptane + n-alkane mixtures  

NASA Astrophysics Data System (ADS)

New absolute measurements of the viscosity of binary mixtures of n-heptane with n-hexane and n-nonane are presented. The measurements, performed in a vibrating-wire instrument, cover a temperature range 290 335 K and pressures up to 75 MPa. The concentrations studied are 40 and 70% by weight of n-heptane. The accuracy of the reported viscosity data is estimated to be ±0.5%. The present measurements, together with other n-heptane + n-alkane viscosity and thermal-conductivity measurements, are used to develop a consistent semiempirical scheme for the correlation and prediction of these mixture properties from those of the pure components.

Assael, M. J.; Charitidou, E.; Dymond, J. H.; Papadaki, M.

1992-03-01

6

Occupational ototoxicity of n-hexane.  

PubMed

The ability of chemicals to produce hearing loss themselves or to promote noise-induced hearing loss has been reported for some organic solvents. The objective of this study was to review the literature on the effects of low-level exposure to n-hexane on the auditory system and consider its relevance for occupational settings. Both human and animal investigations were evaluated only for realistic exposure concentrations based on the permissible inhalation exposure limits. In Quebec, the time-weighted average exposure value (TWAEV) for 8 h is 50 ppm. In humans, the upper limit for considering ototoxicity data relevant to the occupational exposure situation was set at five times the TWAEV. Animal data were evaluated only for exposure concentrations up to 100 times the TWAEV. There is no convincing evidence of n-hexane-induced hearing loss in workers. In rats, n-hexane seems to affect auditory function; however, the site of these alterations cannot be determined from the present data. Further studies with sufficient data on the exposure of workers to n-hexane are necessary to make a definitive conclusion. In the interim, we recommend considering n-hexane as a possibly ototoxic agent. PMID:18784199

Vyskocil, A; Leroux, T; Truchon, G; Gendron, M; El Majidi, N; Viau, C

2008-06-01

7

Reaction zone visualisation in swirling spray n-heptane flames  

E-print Network

) = 268.4 Total = 5925 words Colloquium: Spray and droplet combustion (7) Alternative Colloquium: IC engine and Gas Turbine Combustion (11) Supplemental Material: no 2 Reaction zone visualisation in swirling spray n-heptane flames R... . (2013). To appear. [20] A. Dowlut, T. Hussain, R. Balachandran, 19th International Congress on Sound and Vibration, Lithuania (2012). [21] R. J. Santoro, AD REPORTS -NTIS- AD A, (1994) 40-43. [22] L. Petarca, F. Marconi, Combust. Flame, 78 (1989...

Yuan, R.; Kariuki, J.; Dowlut, A.; Balachandran, R.; Mastorakos, E.

2014-06-26

8

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

9

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

10

Industrial application of catalytic systems for n-heptane isomerization.  

PubMed

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

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

2011-01-01

11

Ethane and n-pentane in exhaled breath are biomarkers of exposure not effect  

PubMed Central

The relationship of exhaled ethane and n-pentane to exhaled NO, carbonylated proteins, and indoor/outdoor atmospheric pollutants were examined in order to evaluate ethane and n-pentane as potential markers of airway inflammation and/or oxidative stress. Exhaled NO and carbonylated proteins were found to have no significant associations with either ethane (p = 0.96 and p = 0.81, respectively) or n-pentane (p = 0.44 and 0.28, respectively) when outliers were included. In the case where outliers were removed n-pentane was found to be inversely associated with carbonylated proteins. Exhaled hydrocarbons adjusted for indoor hydrocarbon concentrations were instead found to be positively associated with air pollutants (NO, NO2 and CO), suggesting pollutant exposure is driving exhaled hydrocarbon concentrations. Given these find-ings, ethane and n-pentane do not appear to be markers of airway inflammation or oxidative stress. PMID:19283520

Gorham, Katrine A.; Sulbaek Andersen, Mads P.; Meinardi, Simone; Delfino, Ralph J.; Staimer, Norbert; Tjoa, Thomas; Rowland, F. Sherwood; Blake, Donald R.

2013-01-01

12

Evoked potentials in chronic n-hexane intoxication  

SciTech Connect

Somatosensory, brainstem auditory and pattern-reversal visual evoked potentials (SEP, BAEP and PVEP) were studied in 5 patients with n-hexane polyneuropathy to determine if the CNS was affected. In SEPs, the median central conduction (N13-to-N20) was normal but the tibial central conduction (N22-to-P40) was delayed. The central conduction time (I-to-V interval) of the BAEP was also prolonged. However, the P100 latency of the PVEP was normal. The present data indicate that the spinal cord and the brainstem are primarily affected in chronic n-hexane intoxication.

Huang, C.C.; Chu, N.S. (Chang Gung Medical College, Taipei, Taiwan (China))

1989-07-01

13

The critical crossover at the n-hexane-water interface  

SciTech Connect

According to estimates of the parameters of the critical crossover in monolayers of long-chain alcohol molecules adsorbed at the n-hexane-water interface, all systems in which this phenomenon is observed are characterized by the same value of the critical exponent {nu} {approx} 1.8.

Tikhonov, A. M., E-mail: tikhonov@kapitza.ras.r [Russian Academy of Sciences, Kapitza Institute for Physical Problems (Russian Federation)

2010-06-15

14

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

15

Effects of Equivalence Ratio on Species and Soot Concentrations in Premixed N-Heptane Flames  

E-print Network

octane number. The oxida- tion of n-heptane has been investigated in shock tubes [1, 2], jet, respectively. Soot particle diameters, number densities, and volume fractions were determined using classical

Senkan, Selim M.

16

Whole-cell double oxidation of n-heptane.  

PubMed

Biocascades allow one-pot synthesis of chemical building blocks omitting purification of reaction intermediates and expenses for downstream processing. Here we show the first whole cell double oxidation of n-heptane to produce chiral alcohols and heptanones. The concept of an artificial operon for co-expression of a monooxygenase from Bacillus megaterium (P450 BM3) and an alcohol dehydrogenase (RE-ADH) from Rhodococcus erythropolis is reported and compared to the widely used two-plasmid or Duet-vector expression systems. Both catalysts are co-expressed on a polycistronic constructs (single mRNA) that reduces recombinant DNA content and metabolic burden for the host cell, therefore increasing growth rate and expression level. Using the artificial operon system, the expression of P450 BM3 reached 81mgg(-1) cell dry weight. In addition, in situ cofactor regeneration through the P450 BM3/RE-ADH couple was enhanced by coupling to glucose oxidation by E. coli. Under optimized reaction conditions the artificial operon system displayed a product formation of 656mgL(-1) (5.7mM) of reaction products (heptanols+heptanones), which is 3-fold higher than the previously reported values for an in vitro oxidation cascade. In conjunction with the high product concentrations it was possible to obtain ee values of >99% for (S)-3-heptanol. Coexpression of a third alcohol dehydrogenase from Lactobacillus brevis (Lb-ADH) in the same host yielded complete oxidation of all heptanol isomers. Introduction of a second ADH enabled further to utilize both cofactors in the host cell (NADH and NADPH) which illustrates the simplicity and modular character of the whole cell oxidation concept employing an artificial operon system. PMID:24925696

Müller, Christina A; Dennig, Alexander; Welters, Tim; Winkler, Till; Ruff, Anna Joelle; Hummel, Werner; Gröger, Harald; Schwaneberg, Ulrich

2014-12-10

17

Neuropathy associated with chronic low level exposure to n-hexane  

SciTech Connect

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

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

1981-05-01

18

Phase behavior of propane and n-pentane aerosol particles under conditions relevant to Titan  

NASA Astrophysics Data System (ADS)

The phase behavior of propane and n-pentane aerosols was studied under conditions relevant to Titan's atmosphere. Pure propane or n-pentane aerosols and mixed aerosols (mixed with either acetylene, carbon dioxide, or water aerosols) were generated in a bath gas cooling cell. The phase behavior of the aerosols was studied using infrared spectroscopy. Pure propane aerosols remained in a disordered phase during the timescale of the experiment, whereas n-pentane aerosols underwent a phase transition from an initially disordered phase into a crystalline phase. For the homogeneous crystallization of n-pentane aerosols in a nitrogen bath gas the surface and volume nucleation constants were found to range from 1012 to 1014cm-2s-1 and from 1011 to 1013cm-3s-1, respectively. The presence of solid acetylene, carbon dioxide, or water aerosols did not affect the phase behavior of propane aerosols but significantly accelerated the crystallization of n-pentane aerosols with acetylene aerosols acting as the most efficient crystallization nuclei.

Kathrin Lang, E.; Knox, Kerry J.; Signorell, Ruth

2013-01-01

19

Isochoric heat capacity of an n-hexane + water system  

NASA Astrophysics Data System (ADS)

The isochoric heat capacity of an n-hexane + water system at water contents of 0.121, 0.166, 0.2, 0.234, 0.256, and 0.3 mole fraction is studied along different isochors at different temperatures in the 140 to 550 kg/m3 range of densities using a high-temperature adiabatic calorimeter designed at the Amirkhanov Institute of Physics. The tabulated values of isochoric heat capacity C v, x are presented for an H2O concentration of 0.3 mole fraction. The curves of liquid-liquid and liquid-gas phase equilibria are constructed.

Bezgomonova, E. I.; Saidov, S. M.; Stepanov, G. V.

2015-01-01

20

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

21

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

NASA Astrophysics Data System (ADS)

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

Pekárek, S.

2008-01-01

22

Peripheral neuropathy and visual evoked potential changes in workers exposed to n-hexane  

Microsoft Academic Search

The aim of this study was to evaluate patients who had peripheral neuropathy and changes to their visual evoked responses resulting from exposure to n-hexane. Eighteen patients with acute or subacute neuropathy, who were working in a shoe factory, were investigated clinically and electrophysiologically. These evaluations were then repeated 9 months to 12 months after cessation of exposure to n-hexane.

Gulnihal Kutlu; Yasemin B. Gomceli; Tolga Sonmez; Levent E. Inan

2009-01-01

23

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

24

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

25

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

Microsoft Academic Search

A detailed numerical simulation of n-heptane droplets was carried out on a stationary three-dimensional configuration with complex geometry. The investigations\\u000a focused on spray evaporation and dispersion within a carrier phase that featured operating conditions similar to those found\\u000a in industrial applications, i.e. elevated pressure and temperature. The simulations were carried out using the Eulerian–Lagrangian\\u000a approach with two-way coupling. There were

Mouldi Chrigui; Ali Zghal; Amsini Sadiki; Johannes Janicka

2010-01-01

26

Shocktube investigation of self-ignition of n-heptane - Air mixtures under engine relevant conditions  

Microsoft Academic Search

To determine self-ignition characteristics under conditions relevant to piston engines combustion, n-heptane - air mixtures have been investigated in a high-pressure shock tube without use of the customary heat bath dilution. The initial pressure has been varied between 3.2 and 42 bar and the initial temperature between 660 and 1,350 K while the equivalence ratio covers the region between 0.5

H. K. Ciezki; G. Adomeit

1993-01-01

27

[Spectroscopic measurement of intermediate free radicals of n-heptane in the combustion reaction].  

PubMed

Using an intensified spectroscopic detector CCD and a chemical shock tube, transient emission spectra of n-heptane during the reaction process of combustion were measured, with exposure time of 6 micros and a spectral range of 200 - 850 nm Experiments were conducted at an ignition temperature of 1 408 K and pressure of 2.0 atmos, with an initial fuel mole fraction of 1.0% and an equivalence ratio of 1.0. Measured emission bands were determined to be produced by OH, CH and C2 free radicals, which reveals that small OH, CH and C2 radicals are important intermediate products in the combustion process of n-heptane. Time-resolved spectra indicate that radical concentrations of OH, CH and C2 reached their peaks sharply; however, CH and C2 reduced and disappeared rapidly while the duration of OH was much longer in the reaction. This work provides experimental data for understanding the microscopic process and validating the mechanism of n-heptane combustion reaction. PMID:22715748

Ye, Bin; Li, Ping; Zhang, Chang-hua; Wang, Li-dong; Tang, Hong-chang; Li, Xiang-yuan

2012-04-01

28

Olefin Chemistry in a Premixed n-Heptane Flame Hongzhi R. Zhang,* Eric G. Eddings, and Adel F. Sarofim  

E-print Network

A complete understanding of carbon flow through the major reaction pathways of normal alkane combustion mea- sured the concentration profiles of six 1-alkene species (C2- C7) in their n-heptane oxidation

Utah, University of

29

Esterification kinetics of triglycerides in n-hexane catalyzed by an immobilized lipase  

E-print Network

The kinetics of enzyme-catalyzed esterification of triglycerides over immobilized lipase in n-hexane was investigated. The reaction kinetics were described in terms of a mechanism developed following the Langmuir-Hinshelwood-Hougen-Watson (LHHW...

Gomez Ruiz, Alejandro

1998-01-01

30

The Modes of Decomposition of n-Pentane. III. Fate of Ethane at Low Pressures  

Microsoft Academic Search

In the nitric-oxide-inhibited decompositions of n-butane and n-pentane respectively, the reactions C4H10\\\\ -> \\\\ C2H6 + C2H4 and C5H12\\\\ -> \\\\ C2H6 + C3H6 give place as the initial pressure drops to the reactions C4H10\\\\ -> \\\\ (C2H4 + H2) + C2H4 and C5H12\\\\ -> \\\\ (C2H4 + H2) + C3H6. It is now shown that ethane added to the

B. C. Spall; F. J. Stubbs; C. J. Danby; Cyril Hinshelwood

1954-01-01

31

[Measurements of the ignition delay times of n-heptane by using characteristic emission from OH radical].  

PubMed

Using a measurement system consisting of a monochromator, a photomultiplier tube (PMT), piezoelectric pressure sensors and a digital oscilloscope, the ignition delay times of n-heptane/O2 mixture were measured behind reflected shock waves in a chemical shock tube, the onset of ignition was indicated by the steepest rise of the characteristic emission from OH radical at 306.4 nm. The experimental conditions cover temperatures from 1 170 to 1 730 K, pressures at (1.0 +/- 0.1) and (0.75 +/- 0.05) atm, and equivalence ratio of 1.0. Under these experimental conditions, the correlation formulas of ignition delay time dependence on the temperature for n-heptane have been obtained. Present results indicate that the ignition delay times of n-heptane decreases exponentially with the increase in temperatures. While temperature increases, the change rate of ignition delay time of n-heptane under the pressure of 0.75 atm is less than that of 1.0 atm. Present ignition delay data are important for constructing the kinetic model of the combustion reaction and provide an experimental criterion for validating the combustion reaction mechanism of n-heptane. PMID:21510410

Xie, Wei; Li, Ping; Zhang, Chang-Hua; Niu, Na; Nie, Xiao-Fei; Li, Cong-Shan

2011-02-01

32

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. PMID:23712100

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

2013-01-01

33

Vibrational spectra, ab initio calculations, and assignments of the fundamentals of the C2v conformer of n-pentane  

NASA Astrophysics Data System (ADS)

Ab initio calculations of the relative energies, optimized geometries and vibrational spectrum of the four conformers of n-pentane have been completed, and a normal coordinate calculation performed to establish the nature of the observed molecular vibrations. From the Raman spectrum of the annealed crystal, in which only aa conformer bands are observable, an assignment of the observed bands to the fundamental vibrations of the aa conformer of C2v symmetry is proposed. The relative energy in the liquid of the ag conformer to the aa conformer is measured in the CCC bending region near 400 cm-1 using both n-pentane and n-pentane-d12, and is found to be 164 ± 10 cm-1, corresponding to 460 ± 28 cal mol-1 in excellent agreement with the results of earlier workers obtained by other measurements, but roughly half the value calculated ab initio at the highest level of approximation available in this investigation.

LaPlante, Arthur J.; Stidham, Howard D.; Guirgis, Gamil A.; Dukes, Horace W.

2012-09-01

34

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

SciTech Connect

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

Seshadri, K. [Center for Energy Research, Department of Mechanical and Aerospace Engineering, University of California at San Diego, La Jolla, CA 92093-0411 (United States); Peters, N.; Paczko, G. [Institut fuer Technische Verbrennung, Rhein.-Westf. Technische Hochschule Aachen, 52058 Aachen (Germany)

2006-07-15

35

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

36

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

PubMed

The proton NMR spectra of n-pentane orientationally ordered in two nematic liquid-crystal solvents are studied over a wide temperature range and analysed using covariance matrix adaptation evolutionary strategy. Since alkanes possess small electrostatic moments, their anisotropic intermolecular interactions are dominated by short-range size-and-shape effects. As we assumed for n-butane, the anisotropic energy parameters of each n-pentane conformer are taken to be proportional to those of ethane and propane, independent of temperature. The observed temperature dependence of the n-pentane dipolar couplings allows a model-free separation between conformer degrees of order and conformer probabilities, which cannot be achieved at a single temperature. In this way for n-pentane 13 anisotropic energy parameters (two for trans trans, tt, five for trans gauche, tg, and three for each of gauche+ gauche+, pp, and gauche+ gauche-, pm), the isotropic trans-gauche energy difference Etg and its temperature coefficient Etg(') are obtained. The value obtained for the extra energy associated with the proximity of the two methyl groups in the gauche+ gauche- conformers (the pentane effect) is sensitive to minute details of other assumptions and is thus fixed in the calculations. Conformer populations are affected by the environment. In particular, anisotropic interactions increase the trans probability in the ordered phase. PMID:25591384

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

2015-01-14

37

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

38

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

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

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

2001-01-01

39

On the Combustion Chemistry of n-Heptane and n-Butanol Blends Darshan M. A. Karwat,*,  

E-print Network

On the Combustion Chemistry of n-Heptane and n-Butanol Blends Darshan M. A. Karwat,*, Scott W, for stoichiometric fuel-to-oxygen ratios and a dilution of 5.64 (molar ratio of inert gases to O2), and at two blend). There is an immediate need to understand how biofuels change the chemistry of conventional fuels in terms of global

Wooldridge, Margaret S.

40

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...

41

Soot formation modelling of n-heptane sprays under diesel engine conditions using the Conditional Moment Closure  

E-print Network

1 Soot formation modelling of n-heptane sprays under diesel engine conditions using the Conditional-volume vessel under diesel engine conditions under different ambient densities (14.8 and 30 kg/m3 ) and ambient that the conditional moment closure approach is a promising framework for soot modelling under Diesel engine conditions

Daraio, Chiara

42

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

EPA Science Inventory

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

43

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

44

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. PMID:21481267

2011-01-01

45

Effect of electrode shape, material and chemical structure on electric strength of some liquid hydrocarbons  

Microsoft Academic Search

The power frequency insulation breakdown phenomena in pure hydrocarbon liquids including straight, branched, and ring-type chemical structures is investigated. The electric strength of n-pentane, n-hexane, n-heptane, benzene, toluene, xylene, and 2,2,4-trimethyl pentane was determined using 13-mm-diameter spheres of brass, copper, and aluminium. In order to study the effect of electrode material and shape on breakdown strength, different shapes of electrodes

E. Husain; S. M. Islam

1990-01-01

46

Skeletal isomerization of n-heptane and hydroisomerization of benzene over bifunctional heteropoly compounds  

Microsoft Academic Search

Hydroisomerization of benzene and skeletal isomerization of n-heptane have been studied using various 2wt.% Pt-promoted solid acids such as Pt–Cs2.5H0.5PW12O40 (Pt–Cs2.5), SiO2 supported Pt–Cs2.5H0.5PW12O40 (Pt–Cs2.5\\/SiO2), Pt–SO42?\\/ZrO2, Pt–WO3\\/ZrO2, and Pt–H-? zeolite. The catalytic activity for the formation of methylcyclopentane in the hydroisomerization of benzene was in order of Pt–Cs2.5\\/SiO2>Pt–Cs2.5>Pt–WO3\\/ZrO2>Pt–SO42?\\/ZrO2. The highest activity of Pt–Cs2.5\\/SiO2 among these bifunctional catalysts would be due

Atsuyuki Miyaji; Toshio Okuhara

2003-01-01

47

Adsorption from n-heptane/benzene liquid mixture on acid leached bentonite powders  

NASA Astrophysics Data System (ADS)

In this study, adsorption excess isotherms of n-heptane/benzene liquid mixture on hydrochloric acid leached bentonite powders were determined. Adsorptions were conducted at 25 °C for 48 h. Experimental results were evaluated with both Schay-Nagy (SN) and Everett (E) methods. Specific surface areas (SSN and SE) of the powders were calculated regarding monolayer adsorption capacity of the preferentially adsorbed benzene. Adsorption equilibrium constants (K ? 1) were obtained by the E-method. The SE and SSN values are closed to each other. SE-values were found much lower than the corresponding Brunauer, Emmett and Teller (BET)-values. This difference was discussed with respect to the interaction of adsorbed molecules with solid surface, their collision diameter, molar cross sectional surface area and orientation in dense monolayer. Even the maximum for the SE was not associated with the maxima for K and nanopore volume (V), their values changed approximately parallel to each other with respect to the HCl% by the leaching.

Sar?kaya, Yüksel; Baykal, Mehmet; Önal, Mü?erref; Yener, Nilgün

2013-10-01

48

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

Microsoft Academic Search

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 DeltaG * E of viscous flow have been calculated with Eyring's theory of absolute

S. L. Oswal; J. P. Dave

1992-01-01

49

Extraction of aromatic hydrocarbons from lube oil using n-hexane as a co-solvent  

Microsoft Academic Search

Liquid–liquid extraction is the most common method for extraction of aromatics from lube oil. Aromatic content of vacuum distillate is reduced by solvent extraction, frequently with furfural. The solvent power and selectivity of furfural can be further increased by using n-hexane as co-solvent. The aromatics in lube oil were extracted at different temperatures (ranging from 323.15 to 343.15K) and different

S. M. Fakhr Hoseini; T. Tavakkoli; M. S. Hatamipour

2009-01-01

50

Batch polymerization of isoprene in n-hexane by n-butyllithium initiation  

E-print Network

was polymerized in n-hexane using n-butyl- lithium as an initiator. The polymerizations were con- 0 ducted in batch reactors at 30, 40, and 50 C. Initial monomer and initiator concentrations were varied from approximately 1 to 5 molar and 0. 005 to 0. 03 molar... conditions. Two runs were conducted at each temperature. These data were used in the development of a mathematical model which described monomer conversions, initiator conversions, and polymer molecular weight distri- butions. Rate expressions...

Porter, Raymond Eugene

1972-01-01

51

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

52

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

SciTech Connect

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

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

1988-05-01

53

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

SciTech Connect

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

Mast, T.J.

1987-12-01

54

Enhancements of methane, benzene, and n-pentane by oil and gas fields observed from the DC-3 aircraft campaign: A case study  

NASA Astrophysics Data System (ADS)

Observations in the boundary layer from the 1 June flight in Colorado of the 2012 Deep Convective Clouds and Chemistry campaign shows enhancements of n-pentane, methane, and benzene near oil and gas wells that are not correlated with enhancements in carbon monoxide. To further investigate the source of methane emissions, an i-pentane:n-pentane ratio is compared to surface measurements from the Denver-Julesberg Basin and found to be similar. Measurements of n-pentane, methane, benzene and CO are also shown with proximity to Denver to compare an urban signature with an oil and gas well emissions signature. Elevated n-pentane, methane, and benzene mixing ratios without enhancements in CO from the 1 June flight are considered to be strongly influenced by emissions from oil and natural gas fields located near the sampling locations.

Farris, Carolyn Michelle

55

High Pressure Oxidation of Liquid Fuels From Low to High Temperature. 1. n-Heptane and iso-Octane  

Microsoft Academic Search

Abstract–Normal heptane and iso-octane oxidations in a high-pressure jet-stirred reactor have been investigated experimentally in a wide range of conditions covering the low and high temperature oxidation regimes (550· 1150K, 10atm, 0.3 ?? ? 1.5). Reactants, intermediates and final products have been measured providing a useful picture of n-heptane oxidation. The relatively high level of oxygenated compounds formed in the

Philippe Dagaut; Marcelline Reuillon; Michel Cathonnet

1993-01-01

56

Comparative evaluation of blood and urine analysis as a tool for biological monitoring of n -hexane and toluene  

Microsoft Academic Search

Summary Blood and urine samples were collected from 57 male Japanese solvent workers [exposed to n-hexane (Hex-A), ethyl acetate, and toluene (Tol-A) at 1.5, 2.3, and 2.3 ppm as GM-TWA, respectively] and also from 20 male nonexposed workers at the end of a 8-h shift, and analyzed for n-hexane (Hex-B) and toluene (Tol-B) in blood, and n-hexane (Hex-U), toluene (Tol-U),

Toshio Kawail; Tomojiro Yasugil; Kazunori Mizunuma; Shun'ichi Horiguchi; Masayuki Ikeda

1993-01-01

57

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

SciTech Connect

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

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

1986-08-01

58

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

59

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

NASA Technical Reports Server (NTRS)

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

Dryer, F. L.

1999-01-01

60

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

PubMed

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

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

2011-09-01

61

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

PubMed Central

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

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

2011-01-01

62

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

63

On the characterization of NaDEHP/n-heptane nonaqueous reverse micelles: the effect of the polar solvent.  

PubMed

The behavior of two polar solvents, ethylene glycol (EG) and dimethylformamide (DMF), entrapped in sodium bis-(2-ethylhexyl) phosphate (NaDEHP)/n-heptane reverse micelles (RMs) was investigated using dynamic light scattering (DLS), molecular probe absorption and FT-IR spectroscopy. DLS results reveal the formation of RMs containing EG and DMF as a polar component. To the best of our knowledge this is the first report where both polar solvents are entrapped by the NaDEHP surfactant to effectively create RMs. We use the solvatochromism behavior of the molecular probe, 1-methyl-8-oxyquinolinum betaine (QB), and FT-IR spectroscopy to investigate the physicochemical properties of the non-aqueous RMs. Our results demonstrate that the NaDEHP surfactant interacts through hydrogen bonds with EG at the EG/NaDEHP interface and this interaction is responsible for destroying the bulk structure of pure solvent EG when entrapped in NaDEHP RMs. On the other hand, when DMF is incorporated inside the RMs the bulk structure of DMF is destroyed upon encapsulation by the Na-DMF interaction at the DMF/NaDEHP interface. Our results are completely different than the one observed for DMF/n-heptane/AOT. Our results show how the physicochemical properties, such as micropolarity, microviscosity and hydrogen bond interaction, of nonaqueous NaDEHP/n-heptane RMs interfaces can be dramatically changed by simply using different non-aqueous polar solvents. Thus, these results can be very useful to employ these novel RMs as nanoreactors since the dimensions of the RMs are around 10 to 20 nm. PMID:25684091

Quintana, Silvina S; Dario Falcone, R; Silber, Juana J; Moyano, Fernando; Mariano Correa, N

2015-02-25

64

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

PubMed

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

Javaid, Arshad; Amin, Muhammad

2009-01-01

65

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

SciTech Connect

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

Basevich, V.Ya.; Belyaev, A.A.; Brandshteter, V. [N.N. Semenov Institute of Chemical Physics, Moscow (Russian Federation)] [and others

1994-05-01

66

Metabolism of n-hexane by rat liver and extrahepatic tissues and the effect of cytochrome P-450 inducers.  

PubMed

1. The in vitro metabolism of n-hexane was studied in rat liver, lung, brain and skeletal muscle microsomes and in microsomes prepared from cell lines expressing human cytochrome P-450 2E1 or 2B6. The hydroxylated metabolites of n-hexane were quantified by gas chromatography-mass spectometry. 2. Rat liver and extensor digitorum longus (EDL, fast-twitch skeletal muscle) microsomes and the CYP 2B6 microsomes produced the pre-neurotoxic metabolite of n-hexane, 2-hexanol as a major metabolite in contrast to the other rat tissues examined. 3. Inhibition of 2- and 3-hexanol production from n-hexane by rat lung microsomes using metyrapone, an inhibitor of cytochrome P-450 2B1 activity, resulted in almost complete inhibition of lung microsomal activity. 4. Production of all three hexanols was significantly increased with phenobarbital-induced rat liver microsomes, with a 10-fold increase in 2- and 3-hexanol production. A slight increase in 2-hexanol production with phenobarbital-induced rat EDL and brain microsomes was observed. No increase in n-hexane metabolism was noted following induction with beta-naphthoflavone or with ethanol. PMID:9088965

Crosbie, S J; Blain, P G; Williams, F M

1997-03-01

67

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

68

Exploring the effect of fluid dynamics and kinetic mechanisms on n-heptane autoignition in transient jets  

SciTech Connect

The influence of physical parameters and of flow patterns on the prediction of n-heptane ignition dynamic in transient reacting n-heptane jets, in high pressure environment under laminar conditions, has been explored by using different kinetic mechanisms. Some preliminary transient laminar flamelet computations have been performed, thus showing that the sensitivity of the ignition time to strain rate depends on the kinetic mechanism used. Therefore, the structure of the reacting jet, in particular the localization of ignition spots, is investigated. The results show that, if the initial temperature of the reacting mixture is out of the intermediate range (800-1000 K) towards lower values, the fluid dynamics has an essential role. In this case, the ignition delay time is almost insensitive to the specific kinetic mechanism adopted, conversely it is severely shortened by increasing the streamwise velocity. The burning spot is located in the core of fuel roll-up, where low values of scalar dissipation rate occur. Nevertheless, the most reactive mixture fraction conditions are well predicted by chemical kinetics, as they are in good agreement with those computed for the one-dimensional diffusion layer. When the initial temperature of fuel and air is increased in the intermediate range, ignition is strongly dependent on the kinetic mechanism used. In these cases, the choice of an accurate chemical scheme is fundamental in order to obtain reliable results. (author)

Viggiano, Annarita [Department of Environmental Engineering and Physics, University of Basilicata, viale dell'Ateneo Lucano 10, 85100 Potenza (Italy)

2010-02-15

69

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

70

Absolute measurement of the thermal conductivity of alcohol + n-hexane mixtures  

NASA Astrophysics Data System (ADS)

New absolute measurements, by the transient hot-wire technique, of the thermal conductivity of binary mixtures of n-hexane with methanol, ethanol, and hexanol are presented. The temperature range examined was 295 345 K and the pressure atmospheric. The concentrations studied were 75% by weight of methanol and 25, 50, and 75% by weight of ethanol and hexanol. The overall uncertainty in the reported thermal conductivity data is estimated to be ±0.5%, an estimate confirmed by the measurement of the thermal conductivity of water. A recently extended semiempirical scheme for the prediction of the thermal conductivity of mixtures from the pure components is used to correlate and predict the thermal conductivity of these mixtures, as a function of both composition and temperature.

Assael, M. J.; Charitidou, E.

1990-11-01

71

1,4-hydroxycarbonyl products of the OH radical initiated reactions of C5-C8 n-alkanes in the presence of NO.  

PubMed

Alkanes account for approximately 50% of nonmethane organic compounds present in urban atmospheres. Previous studies have shown that hydroxycarbonyls are important products ofthe OH radical initiated reactions of > or = C5 n-alkanes, but isomer-specific identifications and quantifications of these products have not been carried out. In this work, we have used solid-phase microextraction fibers precoated with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine for on-fiber derivatization of carbonyl-containing compounds with subsequent analyses by combined gas chromatography-mass spectrometry (GC-MS) and GC with flame ionization detection (GC-FID). GC-MS analyses showed the presence of the oximes of 5-hydroxy-2-pentanone and 4-hydroxypentanal from the n-pentane reaction; 5-hydroxy-2-hexanone, 6-hydroxy-3-hexanone, and 4-hydroxyhexanal from the n-hexane reaction; 5-hydroxy-2-heptanone, 6-hydroxy-3-heptanone, 1-hydroxy-4-heptanone, and 4-hydroxyheptanal from the n-heptane reaction; and 5-hydroxy-2-octanone, 6-hydroxy-3-octanone, 7-hydroxy-4-octanone, and 4-hydroxyoctanal from the n-octane reaction. The formation yields of these 1,4-hydroxycarbonyls were determined from GC-FID analyses. By use of the yields of 1,4-hydroxycarbonyls formed from n-hexane, n-heptane, and n-octane at 50% relative humidity (and those from n-pentane at both 5 and 50% relative humidity), then formation of 1,4-hydroxycarbonyls accounts for 54% of the reaction products from n-pentane, 57% from n-hexane, 51% from n-heptane, and 53% from n-octane. Combined with previously measured yields of carbonyls, alkyl nitrates, and hydroxyalkyl nitrates, we can now accountfor approximately 74-118% of the products formed from the n-pentane through n-octane reactions. PMID:16047780

Reisen, Fabienne; Aschmann, Sara M; Atkinson, Roger; Arey, Janet

2005-06-15

72

Influence of zeolite pore structure on product selectivities for protolysis and hydride transfer reactions in the cracking of n-pentane.  

PubMed

The conversion of n-pentane was carried out to examine the effects of reaction conditions on changes in product selectivities at 823 K, using zeolites with 10- and 12-membered rings. We also investigated the influence of the pore structure of these zeolites on their catalytic activities for both protolysis and hydride transfer reactions. In the first half of this work, we examined the influence of acidic proton concentration and n-pentane pressure on the reaction rates for protolysis and hydride transfer reactions using ZSM-5 zeolites. The rates of hydride transfer reactions were more influenced by pentane pressure compared to protolysis reactions, and were proportional to the square of n-pentane pressure and the concentration of acidic protons. In the second half of this work, the influence of the zeolite pore structure on changes in product selectivities with n-pentane conversion and that on the rates of protolysis and the hydride transfer reactions were revealed using various zeolites with 10- and 12-membered rings. The catalytic activities of zeolites for the protolysis and hydride transfer reactions were influenced more by the spatial volume of the zeolite cavity than the acid strength of protons on the zeolite. PMID:25598271

Miyaji, Akimitsu; Iwase, Yasuyoshi; Nishitoba, Toshiki; Long, Nguyen Quang; Motokura, Ken; Baba, Toshihide

2015-02-21

73

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

74

Infrared Absorption Studies of n-Heptane under High Pressure Masashi Yamaguchi, Scott V. Serafin, Thomas Hellman Morton, and Eric L. Chronister*  

E-print Network

Infrared Absorption Studies of n-Heptane under High Pressure Masashi Yamaguchi, Scott V. Serafin increases the population of globular conformers with gauche bonds. Schoen et al.15 reported high-pressure.17 Investiga- tion under high pressure is desirable to further understand the phase behavior as well

Morton, Thomas Hellman

75

A model of reduced kinetics for alkane oxidation using constituents and species: Proof of concept for n-heptane  

SciTech Connect

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 in 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 skeletal mechanism in conjunction with CHEMKIN II, it is shown that a similarity variable can be formed such that the appropriately scaled 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 concept is tested by using tabular information from the LLNL skeletal mechanism in conjunction with CHEMKIN II. The test reveals that the similarity concept is indeed justified and that the combustion temperature is well predicted, but that the ignition time is overpredicted. To palliate this deficiency, functional modeling is incorporated into our conceptual reduction. Due to the reduction process, models are also included for the global constituent molar density, the kinetics-induced enthalpy evolution of the heavy species, the contribution to the reaction rate of the unsteady lights from the heavies, the molar density evolution of oxygen and water, the mole fractions of the quasi-steady light species and the mean molar heat capacity of the heavy species. The model is compact in that there are only nine species-related progress variables. Results are presented comparing the performance of the model for predicting the temperature and species evolution with that of the skeletal mechanism. The model reproduces the ignition time over a wide range of equivalence ratios, initial pressure and initial temperature. (author)

Harstad, Kenneth; Bellan, Josette [4800 Oak Grove Drive, M/S 125-109, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109-8099 (United States)

2010-08-15

76

Calculating the Krichevsky function and parameter for an n-hexane + water system from direct densitometric measurements  

NASA Astrophysics Data System (ADS)

Based on experimental pVTx data, a theoretical study of the thermodynamic properties of a binary n-hexane + water system is performed for ten water concentrations (0.166, 0.201, 0.234, 0.237, 0.347, 0.615, 0.827, 0.918, 0.935, and 0.964 mole fractions of H2O) along different isochors. Constant volume piezometer measurements are made in the temperature, density, and pressure intervals of 303.65-690.55 K, 66.87-801.20 kg/m3, and 65.7 MPa. Based on the pVTx data and using different methods, the Krichevsky parameter is determined near the critical properties of the pure solvent ( n-hexane or water).

Rasulov, S. M.; Orakova, S. M.; Abdulagatov, I. M.

2015-01-01

77

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

78

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

79

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

SciTech Connect

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

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

1988-08-01

80

Small-angle X-ray scattering study on the fluctuations of supercritical aqueous solution of n-pentane along the critical isotherm of water  

NASA Astrophysics Data System (ADS)

Fluctuation terms of the supercritical aqueous solutions of n-pentane, i.e., those of densities, concentrations, and their correlation terms, were evaluated by small-angle X-ray scattering intensity in combination with isothermal compressibility and partial molar volumes. The fluctuations increased significantly with the fluid density up to the region of middle density, ˜0.2 g cm-3, and then decreased at higher density. In the region where the fluctuations took maxima or minima, the density was lower than those of water critical density. The particle-number fluctuations of individual components obtained from the fluctuation terms show that water molecules are distributed more inhomogeneously than n-pentane, especially in the region of ˜0.3 g cm-3.

Morita, Takeshi; Murai, Hiromi; Kase, Syunsuke; Nishikawa, Keiko

2012-08-01

81

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

SciTech Connect

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

Lu, Tianfeng; Law, Chung K. [Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544 (United States)

2006-01-01

82

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

83

A complex chemical kinetic mechanism for the oxidation of gasoline surrogate fuels: n heptane, iso octane and toluene - Mechanism development and validation  

E-print Network

The development and validation against experimental results of a new gasoline surrogate complex kinetic mechanism is presented in this paper. The surrogate fuel is a ternary mixture of n heptane, iso octane and toluene. The full three components mechanism is based on existing n heptane/iso octane (gasoline PRF) and toluene mechanisms which were modified and coupled for the purpose of this work. Mechanism results are compared against available experimental data from the literature. Simulations with the PRF plus toluene mechanism show that its behavior is in agreement with experimental results for most of the tested settings. These include a wide variety of thermodynamic conditions and fuel proportions in experimental configurations such as HCCI engine experiments, rapid compression machines, a shock tube and a jet stirred reactor.

Da Cruz, A Pires; Anderlohr, Jörg; Bounaceur, Roda; Battin-Leclerc, Frédérique

2009-01-01

84

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

85

Droplet-droplet interactions investigated using a combination of electrochemical and dynamic light scattering techniques. The case of water/BHDC/benzene:n-heptane system.  

PubMed

In this contribution the electrochemistry of [Fe(CN)6](4-/3-) as the probe molecule was investigated in benzyl-n-hexadecyldimethylammonium chloride (BHDC) reverse micelles (RMs) varying the composition of the external solvent (benzene:n-heptane mixtures) and the surfactant concentration, at a fixed water content and probe concentration. The electrochemical and dynamic light scattering results show that in water/BHDC/benzene:n-heptane systems the aggregate sizes increase on increasing BHDC concentration. This behavior was unexpected since it is known that for water/BHDC/benzene RM systems keeping the water content constant and the surfactant concentration below 0.2 M, the droplet sizes are independent of the concentration of the surfactant. We explain the results considering that on changing the external solvent to benzene:n-heptane mixtures, RMs tend to associate in clusters and equilibrium between free RMs and droplet clusters is established. A model is presented which, using electrochemical and dynamic light scattering data, allows calculating the aggregation number of the RMs, the number of RMs that form the droplet clusters and the standard electron transfer heterogeneous rate constant. PMID:25727358

Florez Tabares, Juán Sebastián; Correa, N Mariano; Silber, Juana J; Sereno, Leonides E; Molina, Patricia G

2015-04-01

86

A mass spectrometry study of alkanes in air plasma at atmospheric pressure  

Microsoft Academic Search

The positive APCI-mass spectra in air of linear (n-pentane, n-hexane, n-heptane, n-octane), branched [2,4-dimethylpentane, 2,2-dimethylpentane and 2,2,4-trimethylpentane (i-octane)], and cyclic (cyclohexane) alkanes were analyzed at different mixing ratios and temperatures. The effect of air humidity\\u000a was also investigated. Complex ion chemistry is observed as a result of the interplay of several different reagent ions, including\\u000a atmospheric ions O2+•, NO+, H3O+,

Ester Marotta; Cristina Paradisi

2009-01-01

87

The absorption spectrum of C60 in n-hexane solution revisited: Fitted experiment and TDDFT/PCM calculations  

NASA Astrophysics Data System (ADS)

The UV absorption spectrum of C60 in n-hexane solvent has been revised by means of numerical analysis and time-dependent density functional theory (TDDFT). The absorption spectrum in the range 3-7 eV has been fitted by a spectral function that includes fourteen transitions with Gaussian lineshape, providing reference transition energies and intensities. The agreement between the experimental and theoretical UV absorption intensities has been considerably improved with respect to previous calculations, by including the solvent dielectric response via the polarizable continuum model (PCM).

Menéndez-Proupin, E.; Delgado, Alain; Montero-Alejo, Ana L.; García de la Vega, J. M.

2014-02-01

88

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

PubMed

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

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

2014-11-01

89

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

90

ArF excimer laser-induced deposition of Ag/C nanocomposite thin films in the presence of n-Hexane  

NASA Astrophysics Data System (ADS)

Ag/C nanocomposite thin films with different Ag/C molar ratios have been prepared using ArF excimer laser-induced ablation process and silver target under n-Hexane atmosphere. The morphology, crystal structure and composition of as-deposited Ag/C nanocomposite thin films were investigated with high resolution electronic microscopic techniques (including scanning electron microscopy and transmission electron microscopy) and energy-dispersive X-ray spectroscopy, respectively. Laser Raman spectroscopy and Fourier transform infrared spectroscopy techniques were also applied to characterize the final carbonaceous products generated from n-Hexane under laser ablation process. The optical emission of the plume caused by the interaction between excimer laser and silver target in the presence of n-Hexane was studied to understand the possible reaction process. The UV-vis absorption of as-deposited Ag/C thin films, which is attributed to the surface plasmonic excitation, was also investigated in the present work.

Gondal, Mohammed Ashraf; Fajgar, Radek; Chang, Xiaofeng; Shen, Kai; Xu, Qingyu

2014-08-01

91

Chemical surface modification of polycrystalline platinum thin-films to promote preferential chemisorption of n-hexane, piperidine, and cyclohexane  

SciTech Connect

In this study, hard/soft Lewis acid-base (HSAB) principles are used to modify a thin-polycrystalline platinum film to promote preferential chemisorption of molecules such as piperidine, n-hexane, and cyclohexane. Specifically, the particle size and electron density distribution of the platinum surface is modified using thermal treatment and co-adsorption of electro-positive and negative species. These studies are conducted in an ultra-high vacuum chamber. The platinum surface is characterized, before and after modification protocols, using a variety of in-situ and ex-situ techniques. These include temperature programmed desorption (TPD), both resistance change and work function measurements, and both X-ray photoelectron spectroscopy and diffraction.

Thomas, V.; Schwank, J.; Gland, J. [Univ. of Michigan, Ann Arbor, MI (United States)

1994-12-31

92

Comparison of the effects of nitrogen poisoning on molybdenum oxycarbide and Pt/{beta}-zeolite catalysts in the isomerization of n-heptane  

SciTech Connect

The effect of nitrogen-containing compounds was studied over MoO{sub 3}-carbon-modified and Pt-(1.5 wt %)/{beta}-zeolite catalysts using n-heptane isomerization as the test reaction and piperidine and pyridine as the poisoning molecules. n-Heptane isomerization performed over both catalysts under pure feed showed no deactivation as a function of time on stream. At a pressure of 6 bar the MoO{sub 3}-carbon-modified catalyst exhibited a high resistance to deactivation up to 10 ppm of nitrogen, while the Pt-based catalyst was strongly deactivated down to 30% of its initial activity after 20 h. At higher concentrations of nitrogen ({ge}40 wt ppm) deactivation occurred over both catalysts as a function of time. Results obtained after different regeneration regimes on the MoO{sub 3}-carbon-modified deactivated catalyst led to the conclusion that the deactivation observed was essentially due to coke formation. Finally, increasing the total pressure allowed a better resistance to deactivation by hydrogenating the coke residues over the MoO{sub 3}-carbon-modified catalyst.

Del Gallo, P.; Pham-Huu, C.; York, A.P.E.; Ledoux, M.J. [Univ. Louis Pasteur, Strasbourg (France)

1996-10-01

93

Spectroscopic evidence on the absence of trapped chemical dimer cations (1) after irradiation of n-pentane in the solid state  

NASA Astrophysics Data System (ADS)

Absorption spectra were recorded after irradiation of a number of decane isomers in n-pentane and 3-methylpentane (with CO 2 added as electron acceptor) and in 1,1,2-trichlorotrifluoroethane at 77 K. Absorption bands, with band maxima ranging from 595 to 760 nm were observed in all cases, except after irradiation of 2,6-, 3,5- and 3,6-dimethyloctane and 3,4-diethylhexane in pentane and after irradiation of n-decane and 3,4-diethylhexane in 3-methylpentane. No absorption in the same spectral region was observed after irradiation of pentane with CO 2 or 2-chlorobutane added as electron acceptor. The results specifically rule out the presence of trapped condensation ions, formed by "direct dimerization" (RH + + RH ? R +2 + H 2) or pentane cations with pentane molecules, after irradiation of pentane at 77 K. Arguments against direct "ionic dimerization" in the radiolysis of alkanes are presented and discussed.

Wolput, Greta; Neyens, Marleen; Strobbe, Marc; Ceulemans, Jan

94

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

SciTech Connect

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

Siomos, K.; Christophorou, L.G.

1981-01-01

95

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

PubMed Central

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

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

2012-01-01

96

Modulation of carbon tetrachloride-induced nephrotoxicity in rats by n-hexane extract of Sonchus asper.  

PubMed

Sonchus asper is traditionally used in the treatment of renal dysfunction. In the present study, protective effects of S. asper against carbon tetrachloride (CCl4)-induced nephrotoxicity of rats were determined. In this study, 24 male albino rats (190-200 g) were equally divided into four groups. Group I (control group) was given saline (1 ml/kg body weight (b.w.), 0.85% NaCl) and dimethyl sulfoxide (1 ml/kg b.w.); group II was treated with CCl4 (1 ml/kg b.w. intraperitoneally); groups III and IV were administered with CCl4 and after 48 h with S. asper n-hexane extract (SHE; 100 and 200 mg/kg b.w.). All the treatments were given twice a week for 4 weeks. The results revealed that CCl4-induced oxidative stress as evidenced by the significant depletion of antioxidant enzymes, namely, superoxide dismutase, catalase, peroxidase, glutathione-S-transferase, glutathione peroxidase, glutathione reductase, and glutathione contents, while increased lipid peroxidation (thiobarbituric acid-reactive substances contents). Administration of SHE significantly ameliorated (p < 0.01) the activity of antioxidant enzymes and reduced lipid peroxides. Coadministration revealed that S. asper extract can protect the kidney against CCl4-mediated oxidative damage by restoring the activity of antioxidant enzyme, due to the presence of plant bioactive constituents. PMID:23589407

Khan, Rahmat Ali; Khan, Muhammad Rashid; Shah, Naseer Ali; Sahreen, Sumaira; Siddiq, Pakiza

2013-04-15

97

A detailed chemical kinetic reaction mechanism for the oxidation of iso-octane and n-heptane over an extended temperature range and its application to analysis of engine knock  

Microsoft Academic Search

A detailed chemical kinetic reaction is developed to describe the oxidation of n-heptane, iso-octane, and their mixtures over a wide range of operating conditions. In addition to a high temperature submechanism, reaction paths are included to describe the lower temperature regimes in which the rate and intermediate products of oxidation are controlled by addition of molecular oxygen to alkyl and

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

1988-01-01

98

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

99

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

100

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

SciTech Connect

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

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

1988-08-01

101

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

102

Multi-timescale modeling of ignition and flame regimes of n-heptane-air mixtures near spark assisted homogeneous charge compression ignition conditions  

SciTech Connect

The flame regimes of ignition and flame propagation as well as transitions between different flame regimes of n-heptane-air mixtures in a one-dimensional, cylindrical, spark assisted homogeneously charged compression ignition (HCCI) reactor are numerically modeled using a multi-timescale method with reduced kinetic mechanism. It is found that the initial mixture temperature and pressure have a dramatic impact on flame dynamics. Depending on the initial temperature gradient, there exist at least six different combustion regimes, an initial single flame front propagation regime, a coupled low temperature and high temperature double-flame regime, a decoupled low temperature and high temperature double-flame regime, a low temperature ignition regime, a single high temperature flame regime, and a hot ignition regime. The results show that the low temperature and high temperature flames have distinct kinetic and transport properties as well as flame speeds, and are strongly influenced by the low temperature chemistry. The pressure and heat release rates are affected by the appearance of different flame regimes and the transitions between them. Furthermore, it is found that the critical temperature gradient for ignition and acoustic wave coupling becomes singular at the negative temperature coefficient (NTC) region. The results show that both the NTC effect and the acoustic wave propagation in a closed reactor have a dramatic impact on the ignition front and acoustic interaction.

Ju, Yiguang; Sun, Wenting; Burke, M. P.; Gou, Xiaolong; Chen, Zheng

2011-01-01

103

Antifungal and herbicidal properties of essential oils and n-hexane extracts of Achillea gypsicola Hub-Mor. and Achillea biebersteinii Afan. (Asteraceae)  

Microsoft Academic Search

The chemical composition of essential oils isolated by hydrodistillation from the aerial parts of Achillea gypsicola Hub-Mor., Achillea biebersteinii Afan. and n-hexane extracts obtained from the flowers of A. gypsicola and A. biebersteinii Afan. was analyzed by GC and GC–MS. Camphor (40.17–23.56%, respectively), 1,8-cineole (22.01–38.09%, respectively), piperitone (11.29–0.37%, respectively), borneol (9.50–5.88%, respectively) and ?-terpineol (1.56–5.15%, respectively) were found to be

Saban Kordali; Ahmet Cakir; Tulay Aytas Akcin; Ebru Mete; Adnan Akcin; Tuba Aydin; Hamdullah Kilic

2009-01-01

104

The pathway to total isomer selectivity: n-hexane conversion (reforming) on platinum nanoparticles supported on aluminum modified mesoporous silica (MCF-17).  

PubMed

When pure mesoporous silica (MCF-17) was modified with aluminum (Al modified MCF-17), Lewis acid sites were created, but this material was inactive for the catalytic conversion (reforming) of n-hexane to isomers. When colloidally synthesized platinum nanoparticles were loaded onto traditional MCF-17, the catalyst showed very low activity toward isomer production. However, when Pt nanoparticles were loaded onto Al modified MCF-17, isomerization became the dominant catalytic pathway, with extremely high activity and selectivity (>90%), even at high temperatures (240-360 °C). This highly efficient catalytic chemistry was credited to the tandem effect between the acidic Al modified MCF-17 and the Pt metal. PMID:25387226

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

2014-11-26

105

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

NASA Astrophysics Data System (ADS)

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.

1981-10-01

106

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

107

Heterogeneous nitration reactions of polycyclic aromatic hydrocarbons and n-hexane soot by exposure to NO 3/NO 2/N 2O 5  

NASA Astrophysics Data System (ADS)

Although heterogeneous reactions of polycyclic aromatic hydrocarbons (PAHs) with atmospheric oxidants may be important loss processes for PAHs, our understanding of their kinetics and products is incomplete. A product study of the reaction of two PAHs (i.e., anthracene and pyrene) and n-hexane soot with NO 3 and N 2O 5 using a variety of analytical techniques (XPS, DRIFTS, GC-MS, optical absorption) was undertaken. The goal was to characterize the products of these heterogeneous nitration reactions to aid in reaction mechanism development. NitroPAHs were found to be the products of the nitration of anthracene and pyrene whereas evidence of both nitro and carbonyl functional groups were observed on the surface of n-hexane soot samples following exposure to a mixed flow of NO 3 and N 2O 5. Absorption experiments indicate that the nitration of PAHs alter the optical properties of the particles to which they are adsorbed, giving rise to absorption intensity in the near UV and visible portions of the spectrum.

Kwamena, N.-O. A.; Abbatt, J. P. D.

108

Reference Correlation of the Thermal Conductivity of n-Hexane from the Triple Point to 600 K and up to 500 MPa  

NASA Astrophysics Data System (ADS)

This paper contains new, representative reference equations for the thermal conductivity of n-hexane. The equations are based in part upon a body of experimental data that has been critically assessed for internal consistency and for agreement with theory whenever possible. In the case of the dilute-gas thermal conductivity, a theoretically based correlation was adopted in order to extend the temperature range of the experimental data. Moreover, in the critical region, the experimentally observed enhancement of the thermal conductivity is well represented by theoretically based equations containing just one adjustable parameter. The correlations are applicable for the temperature range from the triple point to 600 K and pressures up to 500 MPa. The overall uncertainty (considered to be estimates of a combined expanded uncertainty with a coverage factor of 2) of the proposed correlation is estimated, for pressures less than 500 MPa and temperatures less than 600 K, to be less than 6%.

Assael, M. J.; Mylona, S. K.; Tsiglifisi, Ch. A.; Huber, M. L.; Perkins, R. A.

2013-03-01

109

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. PMID:24367447

Fischer, Julian; Millan, Simon

2013-01-01

110

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

111

A molecular dynamics investigation of the unusual concentration dependencies of Fick diffusivities in silica mesopores  

SciTech Connect

Molecular Dynamics (MD) simulations were carried out to determine the self-diffusivitiy, D{sub i,self}, the Maxwell–Stefan diffusivity, Ð{sub i}, and the Fick diffusivity, D{sub i}, for methane (C1), ethane (C2), propane (C3), n-butane (nC4), n-pentane (nC5), n-hexane (nC6), n-heptane (nC7), and cyclohexane (cC6) in cylindrical silica mesopores for a range of pore concentrations. The MD simulations show that zero-loading diffusivity Ð{sub i}(0) is consistently lower, by up to a factor of 20, than the values anticipated by the classical Knudsen formula. The concentration dependence of the Fick diffusivity, D{sub i} is found to be unusually complex, and displays a strong minimum in some cases; this characteristic can be traced to molecular clustering.

Krishna, Rajamani; van Baten, Jasper M

2011-01-01

112

Skeletal isomerization of n-heptane over Pd-H 4SiW 12O 40 supported on SiO 2: comparative study with typical bifunctional catalysts  

Microsoft Academic Search

Skeletal isomerization of n-heptane in the presence of hydrogen has been studied over silica-supported bifunctional catalysts, Pd-H4SiW12O40\\/SiO2 with different loadings of H4SiW12O40. The catalytic performances of these catalysts have been compared with those of typical bifunctional catalysts such as Pd-H-? zeolite, Pt-SO42?\\/ZrO2, and Pd-WO3\\/ZrO2. The Pd catalysts with low loadings of H4SiW12O40, such as 2wt.% Pd-10, 15 and 20wt.% H4SiW12O40\\/SiO2,

Atsuyuki Miyaji; Ryuichiro Ohnishi; Toshio Okuhara

2004-01-01

113

Determination of vapor liquid equilibrium for the ternary iso-propanol/atactic-polypropylene/n-heptane mixture at 105C and 140C, and the binary iso-propanol/atactic-polypropylene mixture at 85C using perturbation gas chromatography / cby Lamar Lane Joffrion  

E-print Network

to Bondi's recommendation (1964). Using Bondi's work s;/sf is 1. 13 for the IPA/APP mixture and 1. 06 for the n-heptane/APP mixture. In Figure 6, composition isotherms are shown for the IPA/APP mixture using interpolation and integration results...

Joffrion, Lamar Lane

1984-01-01

114

The correlation of nucleate boiling burn-out data  

E-print Network

A dimensionless correlation is developed for nucleate boiling buzrnout data including the following ranges of variables. Fluids - Water Bensene n - Heptane n - Pentane Ethanol Pressure - 0.0045 to 0.96 of critical pressure ...

Griffith, P.

1957-01-01

115

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

PubMed

The reverse micelle (RM) media are very good as nanoreactors because they can create a unique microenvironment for carrying out a variety of chemical and biochemical reactions. The aim of the present work is to determine the influence of different water-dimethyl sulfoxide (DMSO) mixtures encapsulated in 1,4-bis-2-ethylhexylsulfosuccinate (AOT)/n-heptane RMs on the enzymatic hydrolysis of N-benzoyl-L-tyrosine p-nitroanilide (Bz-Try-pNA) by ?-chymotrypsin (?-CT). The reaction was first studied in homogeneous media at different DMSO-water mixture compositions and in DMSO-water/AOT/n-heptane RMs. The hydrolysis rates of Bz-Try-pNA catalyzed by ?-CT were determined by UV-vis spectroscopy. The reaction follows the Michaelis-Menten mechanism and the kinetic parameters: kcat, KM, and kcat/KM were evaluated under different conditions. In this homogeneous media, DMSO plays an important role in the solubilization process of the peptide which is almost insoluble in water, but it has a tremendous impact on the inactivation of ?-CT. It is shown that the enzyme dissolved in a 20% molar ratio of the DMSO-water mixture does not present enzymatic activity. Dynamic light scattering has been used to assess the formation of DMSO-water/AOT/heptane RMs at different DMSO compositions. The results also show that there is preferential solvation of the AOT RM interface by water molecules. To test the use of these RMs as nanoreactors, the kinetic parameters for the enzymatic reaction in these systems have been evaluated. The parameters were determined at fixed W(S) {W(S) = ([water] + [DMSO])/[AOT] = 20} at different DMSO-water compositions. The results show that the Michaelis-Menten mechanism is valid for ?-CT in all the RM systems studied and that the reaction takes place at the RM interface. Surprisingly, it was observed that the enzyme encapsulated by the RMs show catalytic effects with similar kcat/KM values at any DMSO composition investigated, which evidence that DMSO molecules are localized far from the RM interface. PMID:23734596

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

2013-07-01

116

HEALTH EFFECTS ASSESSMENT FOR N-PENTANE  

EPA Science Inventory

The report summarizes and evaluates information relevant to a preliminary interim assessment of adverse health effects associated with specific chemicals or compounds. The Office of Emergency and Remedial Response (Superfund) uses these documents in preparing cost-benefit analyse...

117

Evidence for Alkane Coordination to an Electron-Rich Uranium Center Ingrid Castro-Rodriguez, Hidetaka Nakai, Peter Gantzel, Lev N. Zakharov, Arnold L. Rheingold, and  

E-print Network

. Recrystallization of highly reactive 1 from neat n-pentane, n-hexane, benzene, and/or toluene, or mixtures thereof an additional solvent molecule in the crystal lattice that is distant from the uranium atom and often disordered

Meyer, Karsten

118

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

NASA Technical Reports Server (NTRS)

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

DeMore, W.; Bayes, K.

1998-01-01

119

40 CFR Appendix A to Part 439 - Tables  

Code of Federal Regulations, 2014 CFR

... Treatability class Amyl alcohol Alcohols. Ethanol 1 Isopropanol 1 Methanol 1 Phenol Isobutyraldehyde 1 Aldehydes. n-Heptane 1 Alkanes. n-Hexane 1 Diethylamine 1 Amines. Triethylamine Benzene Aromatics....

2014-07-01

120

40 CFR Appendix A to Part 439 - Tables  

Code of Federal Regulations, 2011 CFR

... Treatability class Amyl alcohol Alcohols. Ethanol 1 Isopropanol 1 Methanol 1 Phenol Isobutyraldehyde 1 Aldehydes. n-Heptane 1 Alkanes. n-Hexane 1 Diethylamine 1 Amines. Triethylamine Benzene Aromatics....

2011-07-01

121

40 CFR Appendix A to Part 439 - Tables  

Code of Federal Regulations, 2013 CFR

... Treatability class Amyl alcohol Alcohols. Ethanol 1 Isopropanol 1 Methanol 1 Phenol Isobutyraldehyde 1 Aldehydes. n-Heptane 1 Alkanes. n-Hexane 1 Diethylamine 1 Amines. Triethylamine Benzene Aromatics....

2013-07-01

122

40 CFR Appendix A to Part 439 - Tables  

Code of Federal Regulations, 2012 CFR

... Treatability class Amyl alcohol Alcohols. Ethanol 1 Isopropanol 1 Methanol 1 Phenol Isobutyraldehyde 1 Aldehydes. n-Heptane 1 Alkanes. n-Hexane 1 Diethylamine 1 Amines. Triethylamine Benzene Aromatics....

2012-07-01

123

STRUCTURAL CHARACTERIZATION OF ASPHALTENES AND ETHYL ACETATE INSOLUBLE FRACTIONS OF PETROLEUM VACUUM RESIDUES  

Technology Transfer Automated Retrieval System (TEKTRAN)

Asphaltenes and insoluble fractions of vacuum residues (VRs) of two Indian crude oils (viz. Heera and Jodhpur) of different specific gravity were obtained by precipitation of VRs in n-hexane, n-heptane and ethyl acetate, and also by subsequent reprecipitation of n-heptane and ethyl acetate soluble f...

124

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

SciTech Connect

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

York, A.P.E.; Pham-Huu, C.; Del Gallo, P.; Ledoux, M.J. [Univ. Louis Pasteur, Strasbourg (France). Lab. de Chimie des Materiaux Catalytiques] [Univ. Louis Pasteur, Strasbourg (France). Lab. de Chimie des Materiaux Catalytiques; Blekkan, E.A. [Univ. of Trondheim (Norway)] [Univ. of Trondheim (Norway)

1996-03-01

125

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

NASA Astrophysics Data System (ADS)

This work reports the direct observation and separation of size-selected aluminum nanoparticles acting as heterogeneous nuclei for the condensation of supersaturated vapors of both polar and nonpolar molecules. In the experiment, we study the condensation of supersaturated acetonitrile and n-hexane vapors on charged and neutral Al nanoparticles by activation of the metal nanoparticles to act as heterogeneous nuclei for the condensation of the organic vapor. Aluminum seed nanoparticles with diameters of 1 and 2 nm are capable of acting as heterogeneous nuclei for the condensation of supersaturated acetonitrile and hexane vapors. The comparison between the Kelvin and Fletcher diameters indicates that for the heterogeneous nucleation of both acetonitrile and hexane vapors, particles are activated at significantly smaller sizes than predicted by the Kelvin equation. The activation of the Al nanoparticles occurs at nearly 40% and 65% of the onset of homogeneous nucleation of acetonitrile and hexane supersaturated vapors, respectively. The lower activation of the charged Al nanoparticles in acetonitrile vapor is due to the charge-dipole interaction which results in rapid condensation of the highly polar acetonitrile molecules on the charged Al nanoparticles. The charge-dipole interaction decreases with increasing the size of the Al nanoparticles and therefore at low supersaturations, most of the heterogeneous nucleation events are occurring on neutral nanoparticles. No sign effect has been observed for the condensation of the organic vapors on the positively and negatively charged Al nanoparticles. The present approach of generating metal nanoparticles by pulsed laser vaporization within a supersaturated organic vapor allows for efficient separation between nucleation and growth of the metal nanoparticles and, consequently controls the average particle size, particle density, and particle size distribution within the liquid droplets of the condensing vapor. Strong correlation is found between the seed nanoparticle's size and the degree of the supersaturation of the condensing vapor. This result and the agreement among the calculated Kelvin diameters and the size of the nucleating Al nanoparticles determined by transmission electron microscopy provide strong proof for the development of a new approach for the separation and characterization of heterogeneous nuclei formed in organic vapors. These processes can take place in the atmosphere by a combination of several organic species including polar compounds which could be very efficient in activating charged nanoparticles and cluster ions of atmospheric relevance.

Abdelsayed, Victor; Samy El-Shall, M.

2014-08-01

126

Fully atomistic molecular-mechanical model of liquid alkane oils: Computational validation.  

PubMed

Fully atomistic molecular dynamics simulations were performed on liquid n-pentane, n-hexane, and n-heptane to derive an atomistic model for middle-chain-length alkanes. All simulations were based on existing molecular-mechanical parameters for alkanes. The computational protocol was optimized, for example, in terms of thermo- and barostat, to reproduce properly the properties of the liquids. The model was validated by comparison of thermal, structural, and dynamic properties of the normal alkane liquids to experimental data. Two different combinations of temperature and pressure coupling algorithms were tested. A simple differential approach was applied to evaluate fluctuation-related properties with sufficient accuracy. Analysis of the data reveals a satisfactory representation of the hydrophobic systems behavior. Thermodynamic parameters are close to the experimental values and exhibit correct temperature dependence. The observed intramolecular geometry corresponds to extended conformations domination, whereas the intermolecular structure demonstrates all characteristics of liquid systems. Cavity size distribution function was calculated from coordinates analysis and was applied to study the solubility of gases in hexane and heptane oils. This study provides a platform for further in-depth research on hydrophobic solutions and multicomponent systems. © 2014 Wiley Periodicals, Inc. PMID:24554590

Zahariev, Tsvetan K; Slavchov, Radomir I; Tadjer, Alia V; Ivanova, Anela N

2014-02-19

127

Determination of thermodynamic properties of poly (cyclohexyl methacrylate) by inverse gas chromatography.  

PubMed

In this work, some thermodynamic properties of poly (cyclohexyl methacrylate) were studied by inverse gas chromatography (IGC). For this purpose, the polymeric substance was coated on Chromosorb W and which was filled into a glass column. The retention times (t(r)) of the probes were determined from the interactions of poly (cyclohexyl methacrylate) with n-pentane, n-hexane, n-heptane, n-octane, n-decane, methanol, ethanol, 2-propanol, butanol, acetone, ethyl methyl ketone, benzene, toluene and o-xylene by IGC technique. Then, the specific volume (Vg(0)) was determined for each probe molecule. By using (1/T; lnVg(0)) graphics, the glass transition temperature of poly (cyclohexyl methacrylate) was found to be 373 K. The adsorption heat under the glass transition temperature (deltaH(a)), and partial molar heat of sorption above the glass transition (deltaH1(S)), partial molar free energy of sorption (deltaG1(S)) and partial molar entropy of sorption (deltaS1(S)) belonging to sorption for every probe were calculated. The partial molar heat of mixing at infinite dilution (deltaH1(infinity)), partial molar free energy of mixing at infinite dilution (deltaG1(infinity)), Flory-Huggins interaction parameter (chi12(infinity)) and weight fraction activity coefficient (a1/w1)(infinity) values of polymer-solute systems were calculated at different column temperatures. The solubility parameters (delta2) of the polymer were obtained by IGC technique. PMID:25255568

Kaya, Ismet; Pala, Cigdem Yigit

2014-07-01

128

Rate constants 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. The experimental results can be expressed in Arrhenius form in units of cm{sup 3} molecule{sup -1} s{sup -1} as follows: K{sub OH+n-heptane} = (2.48 {+-} 0.17) x 10{sup -10} exp[(-1927 {+-} 69 K)/T] (838-1287 K); k{sub OH+2,2,3,3-TMB} = (8.26 {+-} 0.89) x 10{sup -11} exp[(-1337 {+-} 94 K)/T] (789-1061 K); K{sub OH+n-pentane} = (1.60 {+-} 0.25) x 10{sup -10} exp[(-1903 {+-} 146 K)/T] (823-1308 K); K{sub OH+n-hexane} = (2.79 {+-} 0.39) x 10{sup -10} exp[(-2301 {+-} 134 K)/T] (798-1299 K); and k{sub OH+2,3-DMB} = (1.27 {+-} 0.16) x 10{sup -10} exp[(-1617 {+-} 118 K)/T] (843-1292 K). The available experimental data, along with lower-T determinations, were used to obtain evaluations of the experimental rate constants over the temperature range from {approx}230 to 1300 K for most of the title reactions. These extended-temperature-range evaluations, given as three-parameter fits, are as follows: k{sub OH+n-heptane} = 2.059 x 10{sup -5}T{sup 1.401} exp(33 K/T) cm{sup 3} molecule{sup -1} s{sup -1} (241-1287 K); k{sub OH+2,2,3,3-TMB} = 6.835 x 10{sup -17}T{sup 1.886} exp(-365 K/T) cm{sup 3} molecule{sup -1} s{sup -1} (290-1180 K); k{sub OH+n-pentane} = 2.495 x 10{sup -16}T{sup 1.649} exp(80 K/T) cm{sup 3} molecule{sup -1} s{sup -1} (224-1308 K); k{sub OH+n-hexane} = 3.959 x 10{sup -18}T{sup 2.218} exp(443 K/T) cm{sup 3} molecule{sup -1} s{sup -1} (292-1299 K); and k{sub OH+2,3-DMB} = 2.287 x 10{sup -17}T{sup 1.958} exp(365 K/T) cm{sup 3} molecule{sup -1} s{sup -1} (220-1292 K). The experimental data and the evaluations obtained for these five larger alkanes in the present work were used along with prior data/evaluations obtained in this laboratory for H abstractions by OH from a series of smaller alkanes (C{sub 3}?C{sub 5}) to devise rate rules for abstractions from various types of primary, secondary, and tertiary H atoms. Specifically, the current scheme was applied with good success to H abstractions by OH from a series of n-alkanes (n-octane through n-hexadecane). The total rate constants using this group scheme for reactions of OH with selected large alkanes are given as three-parameter fits in this article. The rate constants for the various abstraction channels in any large n-alkane can also be obtained using the groups listed in this article. The present group scheme serves to reduce the uncertainties in rate constants for OH + alkane reactions.

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

2009-04-30

129

[1,2-Bis(diphenyl­phosphan­yl)ethane-?2 P,P?]{2-[(4-nitro­benzoyl­meth­yl)diphenyl­phosphan­yl]phenyl-?2 C,C?}palladium(II) trifluoro­methane­sulfonate–dichloro­methane–n-hexane (1/1/0.5)  

PubMed Central

In the cation of the title compound, [Pd(C26H19NO3P)(C26H24P2)]CF3O3S·CH2Cl2·0.5C6H14, the PdII atom has a slightly tetra­hedrally distorted square-planar coordination geometry. The PdC3P and PdC2P2 five-membered metallacycles adopt envelope and twist conformations, respectively. In the crystal, inter­molecular C—H?O hydrogen bonds link cations and anions into a three-dimensional network. The dichloro­methane solvent mol­ecule is disordered over three orientations with a site-occupancy ratio of 0.5/0.3/0.2. The n-hexane solvent mol­ecule has a crystallographically imposed centre of symmetry. PMID:21753947

Rizzoli, Corrado; Karami, Kazem; Borzooie, Farzaneh

2011-01-01

130

[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

131

Plasma desorption mass spectrometry of organics at low temperatures  

E-print Network

of structural features, i.e., the length of the alkane chains, and the size, saturation and nature of the substitution groups on aliphatic or aromatic rings. Specifically, the following compounds were studied: n-decane, n-octane, n-hexane, n-pentane, cyclooctane...

Shirey, Eldon Lynn

1993-01-01

132

Production of flavor esters by immobilized lipase  

Microsoft Academic Search

Summary Candidacylindracea lipase adsorbed to silica gel produced a variety of flavor esters when hydrated and shaken in n-heptane containing substrates. Scale-up production of ethyl butyrate was examined in a packed column with recycling of n-hexane containing substrates. Increased substrate concentrations were stimulatory up to a point after which inhibition and enzyme destabilization in repeated runs occurred.

Bruce Gillies; Hiroshi Yamazaki; David W. Armstrong

1987-01-01

133

Criteria for selection of components for surrogates of natural gas and transportation fuels q  

E-print Network

Mechanism) includes detailed sub-models of n-bu- tane, n-hexane, n-heptane, n-decane, n-dodecane, n-tetradecane 585 5607. E-mail address: westshanghai@yahoo.com (H.R. Zhang). 1 Presenting author. Proceedings

Utah, University of

134

The preparation of polymeric carbon from PTFE in the suspension of alkali metals  

Microsoft Academic Search

Partly or almost totally defluorinated carbonaceous materials were prepared by reaction of a PTFE powder with alkali metal (Li, Na, K) suspensions in toluene, n-pentane, n-hexane or n-octane at room temperature. The reactivity of the alkali metals increased in the series Li

Jarom??r Hlavatý; Ladislav Kavan

1999-01-01

135

Testing of the abiotic degradation of chemicals in the atmosphere: the smog chamber approach  

Microsoft Academic Search

Methods for measuring the hydroxyl-, ozone-, and direct photochemical reactivity of a substance in one specially designed medium size smog chamber are described. Rate coefficients for the reaction of OH with n-hexane, n-heptane, ethene, ethyne, chloroform, trichloroethene, methanol, 2-propanol, benzene, o-xylene, 1,4-dichlorobenzene, 1,2,4-trichlorobenzene, p-chloroaniline, naphthalene, acenaphthene, 1,4-dichloronaphthalene, biphenyl, and fluorenone are given and discussed. An upper limit of 5 X

W. H. Kloepffer; F. Haag; E. G. Kohl; R. Frank

1988-01-01

136

Enthalpy of dilution of poly(isobutylene) in n-heptane  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume D2 'Polymer Solutions - Physical Properties and their Relations I (Thermodynamic Properties: PVT -Data and miscellaneous Properties of polymer Solutions) of Volume 6 `Polymers' of Landolt-Börnstein - Group VIII `Advanced Materials and Technologies'.

Wohlfarth, Ch.

137

pVT data of poly(isobutylene) in n-heptane  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume D2 'Polymer Solutions - Physical Properties and their Relations I (Thermodynamic Properties: PVT -Data and miscellaneous Properties of polymer Solutions) of Volume 6 `Polymers' of Landolt-Börnstein - Group VIII `Advanced Materials and Technologies'.

Wohlfarth, Ch.

138

Liquid-liquid equilibrium in the- n-heptane- n-perfluorohexane system  

NASA Astrophysics Data System (ADS)

The shape of the liquid-liquid coexistence curve in the C7H16-C6F14 system in the molar concentration-temperature coordinates close to the critical solution point was studied by narrow-beam gamma-raying of two-phase samples. The molar volumes of the coexisting liquid phases and critical point coordinates (critical temperature T c = 316.266 ± 0.03 K and critical concentration x c = 39.0 ± 0.4 mol % C6F14) were determined. The critical index ? of the coexistence curve was found to be 0.322 ± 0.005. The diameter of the coexistence curve did not obey the classic “rectilinear diameter rule.”

Khairulin, R. A.; Stankus, S. V.; Gruzdev, V. A.; Bityutskii, V. A.

2009-01-01

139

Effects of oxygenate concentration on species mole fractions in premixed n-heptane flames  

E-print Network

for the determination of gasoline octane number which rates fuel's tendency to knock in an engine under standardized in these emissions is the improvement in motor vehicle fuel properties. Fuel oxygenates were first used as an octane

Senkan, Selim M.

140

Sustained degradation of n-pentane and isobutane in a gas-phase bioreactor  

Microsoft Academic Search

Microorganisms were able to remove hydrocarbons (pentane and isobutane) from air by biological action in a columnar bioreactor with ceramic packing. The reactor was operated in a liquid continuous mode with gas recirculation and a slow addition of the organic-containing air. After a period of acclimation, the reactor has operated for 12 months with only pentane and isobutane as carbon

Brian H. Davison; James E. Thompson

1993-01-01

141

pVT data of poly(isobutylene) in n-pentane  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume D2 'Polymer Solutions - Physical Properties and their Relations I (Thermodynamic Properties: PVT -Data and miscellaneous Properties of polymer Solutions) of Volume 6 `Polymers' of Landolt-Börnstein - Group VIII `Advanced Materials and Technologies'.

Wohlfarth, Ch.

142

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

Microsoft Academic Search

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 withn-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

S. L. Oswal; J. P. Dave

1992-01-01

143

pVT data of poly(isobutylene) in n-hexane  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume D2 'Polymer Solutions - Physical Properties and their Relations I (Thermodynamic Properties: PVT -Data and miscellaneous Properties of polymer Solutions) of Volume 6 `Polymers' of Landolt-Börnstein - Group VIII `Advanced Materials and Technologies'.

Wohlfarth, Ch.

144

n Hexane isomerization on Pt\\/HMOR: effect of platinum content  

Microsoft Academic Search

Current specifications for gasoline impose strong restrictions on the content of aromatic compounds. Isomerization of normal\\u000a paraffins to isoparaffins is considered an important petroleum reaction for the production of clean gasoline to improve its\\u000a Research Octane Number (RON) and Motor Octane Number (MON). The isoparaffins are considered as an alternative to the use of\\u000a oxygenated and aromatic compounds, whose maximum

Bianca V. SousaKaroline; Karoline D. Brito; José J. N. Alves; Meiry G. F. Rodrigues; Carlos M. N. Yoshioka; Dilson Cardoso

2011-01-01

145

Aerobic/anaerobic/aerobic sequenced biodegradation of a mixture of chlorinated ethenes, ethanes and methanes in batch bioreactors.  

PubMed

A novel aerobic/anaerobic/aerobic treatment was implemented in batch reactors containing aquifer materials from a site contaminated by tetrachloroethylene (PCE), trichloroethylene (TCE), vinyl chloride (VC), 1,1,2-trichloroethane (1,1,2-TCA) and chloroform (CF). Consortia grown aerobically on methane, propane, n-pentane and n-hexane completely biodegraded the chlorinated solvent mixture, via aerobic cometabolism of VC, CF, TCE and 1,1,2-TCA, followed by PCE reductive dechlorination (RD) to 1,2-cis-dichlorothylene (cis-DCE) or TCE, and cis-DCE/TCE cometabolism in a further aerobic phase. n-Hexane was the best substrate. No electron donor was supplied for RD, which likely utilized cellular material produced during the aerobic phase. Chloride release was stoichiometric with chlorinated solvent biodegradation. According to the Lepidium sativum ecotoxicity test, a decreased toxicity was observed with propane, n-pentane and n-hexane, but not methane. A kinetic study of PCE RD allowed to estimate the PCE maximum specific rate (0.57 ± 0.07 mg mg(protein)(-1) day(-1)) and half-saturation constant (6.7 ± 1.5 mg L(-1)). PMID:23201903

Frascari, Dario; Fraraccio, Serena; Nocentini, Massimo; Pinelli, Davide

2013-01-01

146

Mechanism Reduction and Generation Using Analysis of Major Fuel Consumption Pathways for n-Heptane in Premixed and Diffusion  

E-print Network

-Heptane in Premixed and Diffusion Flames Hongzhi R. Zhang,* Eric G. Eddings, and Adel F. Sarofim Department of Chemical Engineering, UniVersity of Utah, Salt Lake City, Utah 84112 Charles K. Westbrook Chemical heptane premixed flame ( ) 1.9) and a normal heptane opposed diffusion flame, in order to identify

Utah, University of

147

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. PMID:12226177

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

1996-01-01

148

Sooting behaviour of n-heptane laminar diffusion flames at high Ahmet E. Karatas, Gorngrit Intasopa, mer L. Glder  

E-print Network

range considered in this work. Ó 2013 The Combustion Institute. Published by Elsevier Inc. All rights combustion systems, such as diesel and aircraft gas turbine engines, and in fires the combustion is turbu at pressures above atmospheric in a high pressure combustion chamber. The fuel is diluted with either nitrogen

Gülder, Ömer L.

149

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

Microsoft Academic Search

SO42?\\/MxOy is of the greatest interest in solid catalysts and green catalysts. Slurry bubble column reactors are of considerable interest in industrial processes and various biochemical processes. The cetane number (CN) has widely used diesel fuel quality parameter related to the ignition delay time (and combustion quality) of a fuel. CN improvement of diesel fuels is a difficult task that

Hongzhu Ma; Jing Xiao; Bo Wang

2009-01-01

150

Proceedings of the Combustion Institute, Volume 28, 2000/pp. 20292037 EXTINCTION AND AUTOIGNITION OF n-HEPTANE  

E-print Network

for octane rating in internal combustion engines. It has a cetane number of ap- proximately 56, which reactors, and concentration histories of a number of species in plug-flow and jet-stirred reactors

Pitsch, Heinz

151

Modelling of heating and evaporation of n-Heptane droplets: Towards a generic model for fuel droplet/particle conversion  

E-print Network

. The droplets are discretized into a number of control volumes along the radial, polar and azimuthal direc in the droplet. A similar Hill spherical vortex is therefore formed, enhancing the heat and mass transfer

Yin, Chungen

152

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

153

A molecular simulation study of commensurate–incommensurate adsorption of n-alkanes in cobalt formate frameworks  

Microsoft Academic Search

The channels of the cobalt formate frameworks consist of one-dimensional channels that have a zig-zag configuration. Propane (C3) has a length that commensurates with the channel segment length; longer n-alkanes such as n-butane (nC4), n-pentane (nC5) and n-hexane (nC6) have conformations that straddle two channel segments. Configurational-bias Monte Carlo (CBMC) simulations show that the adsorption strength of C3 is higher

R. Krishna; J. M. van Baten

2009-01-01

154

Photocurrent enhancement in nonpolar liquids by the addition of electron scavengers  

SciTech Connect

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

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

1988-07-14

155

Process Engineering Thermodynamics 424304 E (4 sp)  

E-print Network

. A mixture of n-hexane (n-C6) and n-octane (n-C8) is fed into a distillation column at atmospheric pressure. Estimate the number of theoretical stages for the column. (2+4+1½ p.) F mol/min xF = ? D = 500 mol/min xF = 0.5 mol/mol) of n-pentane (n-C5) and n-octane (n-C8) is separated at atmospheric pressure

Zevenhoven, Ron

156

A study of PVT relations for carbon dioxide, n-pentane, and n-octane mixtures using a recombination apparatus  

E-print Network

the hydrocarbon. Immiscible displacement in COz flooding happens with heavy and moderately viscous oils at pressures less than 6. 895 MPa (1, 000 psi). Klins and Alii?l discussed this mechanism in their paper. At a pressure less than 6. 895 MPa (1, 000 psi), i... graphical correlation to an equation form. He further extended the correlation to COz experimentally. He found that the solubility of COz in hydrocarbon is equivalent to a mixture of 58 mole percent methane and 42 mole percent of propane in hydrocarbon...

Wirawan, Januar Fitri Santo

1993-01-01

157

Spectral-luminescence investigation of 9,10-anthraquinone in various states of aggregation  

SciTech Connect

A scheme of the electron level configuration of anthraquinone in three states of aggregation is constructed on the bases of experimental data obtained. A class of inert solvents, namely normal hydrocarbons, was employed as a matrix for producing quasiline spectra of absorption and emission of organic molecules. The spectra were also obtained for anthraquinone; optimal resolution was observed in matrices of n-hexane and n-heptane. The emission and excitation spectra of the luminescence and the kinetics of phosphorescence attentuation were measured on setups produced in the laboratory; the absorption spectra were recorded with a Spectral-185 spectrophotometer.

Oginets, V.Y.

1986-02-01

158

Scattering properties of salt-free wormlike micellar solutions  

NASA Astrophysics Data System (ADS)

Static and dynamic light scattering and conductivity experiments were carried out on salt-free aqueous micellar solutions of cetyltrimethylammonium n-hexane sulfonate (CTAC_6SO_3) and cetyltrimethylammonium n-heptane sulfonate (CTAC_7SO_3) as a function of surfactant concentration. This study confirms the analogy between the behavior in the semi-dilute regime of elongated micellar systems and "classical" polyelectrolyte solutions. Time-resolved scattering experiments performed after a variation of concentration from about twice the overlap volume fraction ?^* to less than half of it revealed the existence of a structural relaxation with a characteristic time of several hours.

Bellour, M.; Knaebel, A.; Munch, J. P.; Candau, S. J.

2000-10-01

159

Catalytic reactions of n-alkanes on. beta. -W sub 2 C and WC: The effect of surface oxygen on reaction pathways  

SciTech Connect

Tungsten carbide powders with WC and {beta}-W{sub 2}C structures catalyze alkane hydrogenolysis reactions. Alkanes adsorb on fresh carbide surfaces strongly leading to rapid deactivation by carbon fragments and to high selectivity to hydrogenolysis products. n-Hexane isomerization or dehydrocyclization products were not observed on fresh carbides. Chemisorbed oxygen lowers the binding energy of adsorbed intermediates and decreases both hydrogenolysis and deactivation rates. Oxygen-exposed carbides catalyze n-hexane and n-heptane isomerization with high selectivity (74-99%). Isomerization involves methyl-shift pathways that require alkene intermediates. These results and the well-known acid properties of WO{sub x} surface species suggest that oxygen-exposed tungsten carbides catalyze bifunctional (dehydrogenation/carbenium-ion) alkane isomerization pathways.

Ribeiro, F.H.; Boudart, M.; Dalla Betta, R.A. (Stanford Univ., CA (United States)); Iglesia, E. (Exxon Research and Engineering Co., Annandale, NJ (United States))

1991-08-01

160

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

Microsoft Academic Search

HCN andn-C6H14were found experimentally to be trapped in water ice, when codeposited with water vapor on a cold plate, at 140 K and CH3OH even at 160 K. At these temperatures at least part of the water ice is cystalline. These three gases have relatively high sublimation temperatures, whereas the gases studied earlier, Ar, Kr, Xe, CO, CH4, and N2,

G. Notesco; A. Bar-Nun

1997-01-01

161

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

162

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

163

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

E-print Network

This paper presents a new chemical kinetic model developed for the simulation of auto-ignition and combustion of engine surrogate fuel mixtures sensitized by the presence of NOx. The chemical mechanism is based on the PRF auto-ignition model (n-heptane/iso-octane) of Buda et al. [1] and the NO/n-butane/n-pentane model of Glaude et al. [2]. The later mechanism has been taken as a reference for the reactions of NOx with larger alcanes (n-heptane, iso-octane). A coherent two components engine fuel surrogate mechanism has been generated which accounts for the influence of NOx on auto-ignition. The mechanism has been validated for temperatures between 700 K and 1100 K and pressures between 1 and 10 atm covering the temperature and pressure ranges characteristic of engine post-oxidation thermodynamic conditions. Experiments used for validation include jet stirred reactor conditions for species evolution as a function of temperature, as well as diesel HCCI engine experiments for auto-ignition delay time measurements...

Anderlohr, Jörg; Bounaceur, Roda; Battin-Leclerc, Frédérique

2009-01-01

164

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

NASA Technical Reports Server (NTRS)

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

Canada, G. S.

1974-01-01

165

A Journey from n-Heptane to Liquid Transportation Fuels. 1. The Role of the Allylic Radical and Its Related Species in Aromatic  

E-print Network

Department of Chemical Engineering, UniVersity of Utah, Salt Lake City, Utah 84112 ReceiVed August 31, 2007-heptane flames with good numerical accuracy. The concentrations of these species are closely related to those

Utah, University of

166

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

SciTech Connect

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

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

1988-09-01

167

A viscometric study of tuning micellar morphology by organic additives  

Microsoft Academic Search

The micellar morphology in aqueous 0.2 M sodium dodecyl sulfate (SDS) solutions has been studied in the simultaneous presence\\u000a of organic salts (anilinium hydrochloride, AHC; ortho-toluidine hydrochloride, oTHC; para-toluidine hydrochloride, pTHC) and aliphatic alcohols (n-butanol, C4OH; n-pentanol, C5OH; n-hexanol, C6OH; n-heptanol, C7OH), aliphatic amines (n-butylamine, C4NH2; n-pentylamine, C5NH2; n-hexylamine, C6NH2; n-heptylamine, C7NH2), or hydrocarbons (n-hexane, C6H; n-heptane, C7H) by viscosity measurements

Ziya Ahmad Khan; Sanjeev Kumar; Tanweer Ahmad

2008-01-01

168

Purification and characterization of the enantioselective nitrile hydratase from Rhodococcus equi A4.  

PubMed

The nitrile hydratase from Rhodococcus equi A4 consisted of two kinds of subunits which slightly differed in molecular weight (both approximately 25 kDa) and showed a significant similarity in the N-terminal amino acid sequences to those of the nitrile hydratase from Rhodococcus sp. N-774. The enzyme preferentially hydrated the S-isomers of racemic 2-(2-, 4-methoxyphenyl)propionitrile, 2-(4-chlorophenyl)propionitrile and 2-(6-methoxynaphthyl)propionitrile (naproxennitrile) with E-values of 5-15. The enzyme functioned in the presence of 5-98% (v/v) of different hydrocarbons, alcohols or diisopropyl ether. The addition of 5% (v/v) of n-hexane, n-heptane, isooctane, n-hexadecane, pristane and methanol increased the E-value for the enzymatic hydration of 2-(6-methoxynaphthyl)propionitrile. PMID:11330707

Prepechalová, I; Martínková, L; Stolz, A; Ovesná, M; Bezouska, K; Kopecký, J; Kren, V

2001-03-01

169

Molecular dynamics of n-hexane: A quasi-elastic neutron scattering study on the bulk and spatially nanochannel-confined liquid  

E-print Network

, Departamento de Física, Santiago, Chile 7 Institute of Materials Physics and Technology, Hamburg University Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9, France 6 Pontificia Universidad Católica de Chile of Technology, D-21073 Hamburg, Germany (Received 14 December 2011; accepted 5 March 2012; published online 26

170

The effect of varying oven temperatures and residence times on thermal desorption of n-hexane and 1-hexene from diffusive organic vapor dosimeters  

E-print Network

. Lawrence Vanell of Foxboro Analytical, Inc. for his technical advice concerning several aspects of the research. A special thanks goes to the 3M Company for their ex- treme generosity in donating the monitors used for this s tudv ~ Finally, I would... Temperatures Averaged Over Three Days and Three Residence Times 54 LIST OF FIGURES 1. Breakdown of 3M Organic Vapor Monitor 2. Removing Draft Shield and Retaining Ring from 3M Organic Vapor Monitor 3. Elutriation Cap in place on 3M Monitor 4. Inserting 3...

Steele, Kenneth Garnett

1981-01-01

171

Hydrochloroethers in the troposphere: Kinetics with Cl atoms, lifetimes and atmospheric acceptability indices  

NASA Astrophysics Data System (ADS)

Rate constants for the gas-phase reactions of chlorine atoms with 2-chloroethyl ethyl ether ( k1) and bis(2-chloroethyl) ether ( k2) were determined for the first time using a conventional relative rate technique. Experiments were carried out at (298 ± 2) K and atmospheric pressure using synthetic air as bath gas. The decay rates of the hydrochloroethers were measured relative to those of n-pentane and n-heptane. The following rate constants were derived in units of cm 3 molecule -1 s -1: k1 = (1.7 ± 0.5) × 10 -10 and k2 = (1.0 ± 0.3) × 10 -10. The rate constants obtained are compared with previous literature data to indicate reactivity trends and are used to estimate the global atmospheric lifetimes ( ?global) of the studied hydrochloroethers. Radiative forcing efficiencies (RE) of the ethers were determined from their integrated IR absorption cross-sections. Using ?global and RE, estimations were made of atmospheric hazard indices of the two chlorinated ethers such as the ozone depletion potential (ODP) and the global warming potential (GWP).

Dalmasso, Pablo R.; Taccone, Raúl A.; Nieto, Jorge D.; Cometto, Pablo M.; Lane, Silvia I.

2012-02-01

172

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

173

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

PubMed

Knowledge of the release of volatile organic compounds (VOCs) by cells provides important information on the origin of VOCs in exhaled breath. Muscle cells are particularly important, since their release of volatiles during the exertion of an effort contributes considerably to breath concentration profiles. Presently, the cultivation of human skeletal muscle cells is encountering a number of obstacles, necessitating the use of animal muscle cells in in vitro studies. Rat L6 skeletal muscle cells are therefore commonly used as a model for studying the molecular mechanisms of human skeletal muscle differentiation and functions, and facilitate the study of the origin and metabolic fate of the endogenously produced compounds observed in breath and skin emanations. Within this study the production and uptake of VOCs by rat L6 skeletal muscle cells were investigated using gas chromatography with mass spectrometric detection, combined with head-space needle trap extraction as the pre-concentration technique (HS-NTE-GC-MS). Seven compounds were found to be produced, whereas sixteen species were consumed (Wilcoxon signed-rank test, p < 0.05) by the cells being studied. The set of released volatiles included two ketones (2-pentanone and 2-nonanone), two volatile sulphur compounds (dimethyl sulfide and methyl 5-methyl-2-furyl sulphide), and three hydrocarbons (2-methyl 1-propene, n-pentane and isoprene). Of the metabolized species there were thirteen aldehydes (2-propenal, 2-methyl 2-propenal, 2-methyl propanal, 2-butenal, 2-methyl butanal, 3-methyl butanal, n-pentanal, 2-methyl 2-butenal, n-hexanal, benzaldehyde, n-octanal, n-nonanal and n-decanal), two esters (n-propyl propionate and n-butyl acetate), and one volatile sulphur compound (dimethyl disulfide). The possible metabolic pathways leading to the uptake and release of these compounds by L6 cells are proposed and discussed. An analysis of the VOCs showed them to have huge potential for the identification and monitoring of some molecular mechanism and conditions. PMID:25307263

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

2014-12-01

174

Possible effect of carbon nanotube diameter on gas–surface interactions – The case of benzene, water, and n-pentane adsorption on SWCNTs at ultra-high vacuum conditions  

Microsoft Academic Search

Effect of carbon nanotubes (CNT) crystal structure on chemical activity (SAR) has been studied extensively in CNT suspension. However, these effects are experimentally underexplored for gas–CNT interactions (heterogeneous catalysis). We report about ultra-high vacuum kinetics experiments on metallic, semiconducting, and mixed CNTs. A weak and probe molecule specific SAR is present for adsorption inside the CNTs but not for the

M. Komarneni; A. Sand; J. Goering; U. Burghaus; M. Lu; L. Monica Veca; Ya-Ping Sun

2009-01-01

175

Rate constants and H atom branching ratios of the gas-phase reactions of methylidyne CH(X2Pi) radical with a series of alkanes.  

PubMed

The reactions of the CH radical with several alkanes were studied, at room temperature, in a low-pressure fast-flow reactor. CH(X2Pi, v = 0) radicals were obtained from the reaction of CHBr(3) with potassium atoms. The overall rate constants at 300 K are (0.76 +/- 0.20) x 10(-10) [Fleurat-Lessard, P.; Rayez, J. C.; Bergeat, A.; Loison, J. C. Chem. Phys. 2002, 279, 87],1 (1.60 +/- 0.60) x 10(-10)[Galland, N.; Caralp, F.; Hannachi, Y.; Bergeat, A.; Loison, J.-C. J. Phys. Chem. A 2003, 107, 5419],2 (2.20 +/- 0.80) x 10(-10), (2.80 +/- 0.80) x 10(-10), (3.20 +/- 0.80) x 10(-10), (3.30 +/- 0.60) x 10(-10), and (3.60 +/- 0.80) x 10(-10) cm3 molecule(-1) s(-1), (errors refer to +/-2sigma) for methane, ethane, propane, n-butane, n-pentane, neo-pentane, and n-hexane respectively. The experimental overall rate constants correspond to those obtained using a simple classical capture theory. Absolute atomic hydrogen production was determined by V.U.V. resonance fluorescence, with H production from the CH + CH4 reaction being used as a reference. Observed H branching ratios were for CH4, 1.00[Fleurat-Lessard, P.; Rayez, J. C.; Bergeat, A.; Loison, J. C. Chem. Phys. 2002, 279, 87];1 C(2)H(6), 0.22 +/- 0.08 [Galland, N.; Caralp, F.; Hannachi, Y.; Bergeat, A.; Loison, J.-C. J. Phys. Chem. A 2003, 107, 5419];2 C(3)H(8), 0.19 +/- 0.07; C(4)H(10) (n-butane), 0.14 +/- 0.06; C(5)H(12) (n-pentane), 0.52 +/- 0.08; C(5)H(12) (neo-pentane), 0.51 +/- 0.08; C(5)H(12) (iso-pentane), 0.12 +/- 0.06; C(6)H(14) (n-hexane), 0.06 +/- 0.04. PMID:17165876

Loison, Jean-Christophe; Bergeat, Astrid; Caralp, Françoise; Hannachi, Yacine

2006-12-21

176

Separations of cyclic, branched, and linear hydrocarbon mixtures through silicalite membranes  

SciTech Connect

Binary and ternary mixtures of organic vapors were separated at elevated temperatures with a silicalite zeolite membrane on a porous, tabular, alumina support. Linear alkanes, branched alkanes, aromatics, and saturated ring compounds were used as feeds, and permeances of pure compounds and mixtures were measured between 360 and 510 K. Pure compound permeances of the linear alkanes strongly decrease with increasing chain length, whereas the branched and cyclic compounds permeate at rates similar to those of n-hexane and n-heptane. Almost all permeances increase with increasing temperature. Mixtures of branched or cyclic molecules with small linear alkanes were readily separated with high selectivities (over 200 for n-hexane/benzene), even though the ratios of pure component permeances were small. The separation behavior is not due to molecular sieving but instead appears to be due to preferential adsorption (adsorption on external surface, pore entering, adsorption in pores) of one species, which prevents the other organics from adsorbing and transporting through the membrane. Mixtures of cyclic or branched molecules showed small or no separations. For all systems, separations factors decrease as temperature increases apparently because preferential adsorption becomes less important at elevated temperatures. For mixtures of benzene or methylyclohexane with 2,2,4-trimethylpentane and for mixtures of 2,2-dimethylbutane with 3-methylpentane, both compounds permeated at similar rates and no separations were obtained. Single-file transport in the zeolite channels is suspected to limit transport. The membranes have intercrystalline regions in parallel with the zeolite pores that may also permeate the organics.

Funke, H.H.; Argo, A.M.; Falconer, J.L.; Noble, R.D. [Univ. of Colorado, Boulder, CO (United States). Dept. of Chemical Engineering] [Univ. of Colorado, Boulder, CO (United States). Dept. of Chemical Engineering

1997-01-01

177

First steps in photophysics. I. Fluorescence yield and radiative rate coefficient of 9,10-bis(phenylethynyl)anthracene in paraffins.  

PubMed

The fluorescence quantum yield of 9,10-bis(phenylethynyl)anthracene (BPEA) is almost unity in every examined solvent. Using different hydrocarbons, one can make a convenient and sufficiently accurate experimental test for determination of the extent of the refractive index correction needed in fluorescence quantum yield determination on a given fluorometer. By comparison of the measurements in n-pentane-cis-decaline or n-hexane-toluene solvent pairs, the requirement of the n(2) correction is confirmed for most of the fluorometers; however, for one of the examined pieces of equipment the necessary correction proved to be slightly lower. By excited state's lifetime measurements, the refractive index dependence of the fluorescence rate coefficient was reexamined. At 25 °C for BPEA the relationship is in agreement with Bakhshiev's prediction: the experimentally determined exponent of n in the rate coefficient deriving equation is around 1.32 using different paraffins as solvents. The negative temperature coefficient of the radiative rate in part originates from the temperature dependence of the refractive index, while also a small intrinsic contribution has been found. PMID:25296291

Demeter, Attila

2014-10-30

178

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

2014-08-14

179

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

180

Identification of environmentally acceptable low-sound speed liquids  

NASA Astrophysics Data System (ADS)

Liquids with unusually low sound speeds are required as filling fluids for sonar targets and acoustic lenses. In this paper, we report on the search for environ mentally acceptable fluids for these purposes. A precision variable pathlength interferometer, incorporating some novel features, has been constructed and used to make sound speed measurements on a number of liquids with low speeds of sound. The measurements were made. with a precision of ±0.05 % and an uncertainty of ±0.2%. at atmospheric pressure and at various temperatures in the range 273.15 to 303.15 K. The most promising low-sound speed liquid identified was n-perlluorohexane, which has a sound speed below 600 m · s-1 in the temperature range of interest here. This liquid forms homo geneous mixtures over at least part of the temperature range with several alkanes including n-pentane, n-hexane, and 2,2-dimethylbutane. Experimental results for binary mixtures of perfluorohexane isomers with each of the aforementioned alkanes are reported.

Cuscó, L.; Trusler, J. P. M.

1995-05-01

181

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

182

Separation and aquatic toxicity of enantiomers of the organophosphorus insecticide trichloronate.  

PubMed

Many of the organophosphorus pesticides (OPs) currently used are chiral and therefore consist of mixture of enantiomers. Despite the fact that the biological processes of chiral pesticides are enantioselective, the acute aquatic toxicity of chiral OPs with respect to enantioselectivity has so far received limited research. In this study, the enantiomeric separation and acute aquatic toxicity of trichloronate were investigated. Baseline enantioseparation of trichloronate was successfully achieved using high-performance liquid chromatography on a Chiralcel OJ column, with a mobile phase of n-hexane/n-heptane/ethanol (90/5/5, v/v/v) at the flow rate of 1.0 ml min(-1) and room temperature. The resolved enantiomers were characterized for their optical rotation and by gas chromatography coupled with mass spectrometry. Significant differences were found between the enantiomers in acute aquatic toxicity to Ceriodaphnia dubia and Daphnia magna. The (-)-trichloronate was 8-11 times more toxic to the test organisms than its (+)-form, while the racemate showed intermediate toxicity. These results suggest that assessment of the environmental safety of chiral OPs should take stereospecificity into consideration. PMID:16845672

Liu, Weiping; Lin, Kunde; Gan, Jianying

2006-09-01

183

Biodiesel production using waste frying oil  

SciTech Connect

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

Charpe, Trupti W. [Chemical Engineering Department, Institute of Chemical Technology, Matunga, Mumbai 400 019 (India); Rathod, Virendra K., E-mail: vk.rathod@ictmumbai.edu.in [Chemical Engineering Department, Institute of Chemical Technology, Matunga, Mumbai 400 019 (India)

2011-01-15

184

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

185

[Cloning and expression of organic solvent tolerant lipase gene from Staphylococcus saprophyticus M36].  

PubMed

Lipases are important biocatalysts that are widely used in food processing and bio-diesel production. However, organic solvents could inactivate some lipases during applications. Therefore, the efficient cloning and expression of the organic solvent-tolerant lipase is important to its application. In this work, we first found out an organic solvent-tolerant lipase from Staphylococcus saprophyticus M36 and amplified the 741 bp Lipase gene lip3 (GenBank Accession No. FJ979867), by PCR, which encoded a 31.6 kD polypeptide of 247 amino acid residues. But the lipase shared 83% identity with tentative lip3 gene of Staphylococcus saprophyticus (GenBank Accession No. AP008934). We connected the gene with expression vector pET-DsbA, transformed it into Escherichia coli BL21 (DE3), and obtained the recombinant pET-DsbA-lip3. With the induction by 0.4 mmol/L of isopropyl beta-D-thiogalactopyranoside at pH 8.0, OD600 1.0, 25 degrees C for 12 h, the lipase activity reached up to 25.8 U/mL. The lipase expressed was stable in the presence of methanol, n-hexane, and isooctane, n-heptane. PMID:20352979

Tang, Yanchong; Lu, Yaping; Lü, Fengxia; Bie, Xiaomei; Guo, Yao; Lu, Zhaoxin

2009-12-01

186

Diluent and extractant effects on the enthalpy of extraction of uranium(VI) and americium(III) nitrates by trialkyl phosphates  

SciTech Connect

The effect of various diluents such as n-hexane, n-heptane n-octane, isooctane, n-decane, n-undecane, n-dodecane, n-tetradecane, n-hexadecane, cyclohexane, benzene, toluene, p-xylene, mesitylene and o-dichlorobenzene on the enthalpy of extraction of uranyl nitrate by tri-n-amyl phosphate (TAP) over the temperature range 283 K--333 K has been studied. The results indicate that the enthalpy of extraction does not vary significantly with the diluents studied. Also enthalpies of extraction of uranyl nitrate and americium(III) nitrate by neutral organo phosphorous extractants such as tri-n-butyl phosphate (TBP), tri-n-amyl phosphate (TAP), tri-sec-butyl phosphate (TsBP), tri-isoamyl phosphate (TiAP) and tri-n-hexyl phosphate (THP) have been studied. An attempt has been made to explain the trends, on the basis of the nature of the solvate formed and the different terms which contribute to the overall enthalpy change.

Srinivasan, T.G.; Vasudeva Rao, P.R. [Indira Gandhi Centre for Atomic Research, Kalpakkam (India). Fuel Chemistry Div.; Sood, D.D. [Bhabha Atomic Research Centre, Mumbai (India). Radiochemistry and Isotope Group

1998-11-01

187

High pressure droplet burning experiments in reduced gravity  

NASA Technical Reports Server (NTRS)

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

Chauveau, Christian; Goekalp, Iskender

1995-01-01

188

Syntheses and structural characterizations of anionic borane-capped ammonia borane oligomers: evidence for ammonia borane H2 release via a base-promoted anionic dehydropolymerization mechanism.  

PubMed

Studies of the activating effect of Verkade's base, 2,8,9-triisobutyl-2,5,8,9-tetraaza-1-phosphabicyclo[3.3.3]undecane (VB), on the rate and extent of H(2) release from ammonia borane (AB) have led to the syntheses and structural characterizations of three anionic aminoborane chain-growth products that provide direct support for anionic dehydropolymerization mechanistic steps in the initial stages of base-promoted AB H(2) release reactions. The salt VBH(+)[H(3)BNH(2)BH(2)NH(2)BH(3)](-) (1) containing a linear five-membered anionic aminoborane chain was produced in 74% yield via the room-temperature reaction of a 3:1 AB/VB mixture in fluorobenzene solvent, while the branched and linear-chain seven-membered anionic aminoborane oligomers VBH(+)[HB(NH(2)BH(3))(3)](-) (2a) and VBH(+)[H(3)BNH(2)BH(2)NH(2)BH(2)NH(2)BH(3)](-) (2b) were obtained from VB/AB reactions carried out at 50 °C for 5 days when the AB/VB ratio was increased to 4:1. X-ray crystal structure determinations confirmed that these compounds are the isoelectronic and isostructural analogues of the hydrocarbons n-pentane, 3-ethylpentane, and n-heptane, respectively. The structural determinations also revealed significant interionic B-H···H-N dihydrogen-bonding interactions in these anions that could enhance dehydrocoupling chain-growth reactions. Such mechanistic pathways for AB H(2) release, involving the initial formation of the previously known [H(3)BNH(2)BH(3)](-) anion followed by sequential dehydrocoupling of B-H and H-N groups of growing borane-capped aminoborane anions with AB, are supported by the fact that 1 was observed to react with an additional AB equivalent to form 2a and 2b. PMID:21961893

Ewing, William C; Marchione, Allegra; Himmelberger, Daniel W; Carroll, Patrick J; Sneddon, Larry G

2011-10-26

189

Thermochemistry of C7H16 to C10H22 alkane isomers: primary, secondary, and tertiary C-H bond dissociation energies and effects of branching.  

PubMed

Standard enthalpies of formation (?H°f 298) of methyl, ethyl, primary and secondary propyl, and n-butyl radicals are evaluated and used in work reactions to determine internal consistency. They are then used to calculate the enthalpy of formation for the tert-butyl radical. Other thermochemical properties including standard entropies (S°(T)), heat capacities (Cp(T)), and carbon-hydrogen bond dissociation energies (C-H BDEs) are reported for n-pentane, n-heptane, 2-methylhexane, 2,3-dimethylpentane, and several branched higher carbon number alkanes and their radicals. ?H°f 298 and C-H BDEs are calculated using isodesmic work reactions at the B3LYP (6-31G(d,p) and 6-311G(2d,2p) basis sets), CBS-QB3, CBS-APNO, and G3MP2B3 levels of theory. Structures, moments of inertia, vibrational frequencies, and internal rotor potentials are calculated at the B3LYP/6-31G(d,p) level for contributions to entropy and heat capacities. Enthalpy calculations for these hydrocarbon radical species are shown to have consistency with the CBS-QB3 and CBS-APNO methods using all work reactions. Our recommended ideal gas phase ?H°f 298 values are from the average of all CBS-QB3, CBS-APNO, and for G3MP2B3, only where the reference and target radical are identical types, and are compared with literature values. Calculated values show agreement between the composite calculation methods and the different work reactions. Secondary and tertiary C-H bonds in the more highly branched alkanes are shown to have bond energies that are several kcal mol(-1) lower than the BDEs in corresponding smaller molecules often used as reference species. Entropies and heat capacities are calculated and compared to literature values (when available) when all internal rotors are considered. PMID:25180943

Hudzik, Jason M; Bozzelli, Joseph W; Simmie, John M

2014-10-01

190

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

191

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

192

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

PubMed

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

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

2008-04-25

193

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

SciTech Connect

Molecular dynamics (MD) simulations were performed to determine the self-diffusivity (D{sub i,self}) and the Maxwell–Stefan diffusivity (?{sub 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 (?{sub I}(0)) is consistently lower, by up to a factor of 10, than the Knudsen diffusivity (D{sub i,Kn}) values. The ratio ?{sub I}(0)/D{sub i,Kn} is found to correlate with the isosteric heat of adsorption, which, in turn, is a reflection of the binding energy for adsorption on the pore walls: the stronger the binding energy, the lower the ratio ?{sub I}(0)/D{sub i,Kn}. The diffusion selectivity, which is defined by the ratio D{sub 1,self}/D{sub 2,self} for binary mixtures, was determined to be significantly different from the Knudsen selectivity (M{sub 2}/M{sub 1}){sup 1/2}, where M{sub I} is the molar mass of species i. For mixtures in which component 2 is more strongly adsorbed than component 1, the expression (D{sub 1,self}/D{sub 2,self})/(M{sub 2}/M{sub 1}){sup 1/2} has values in the range of 1–10; the departures from the Knudsen selectivity increased with increasing differences in adsorption strengths of the constituent species. The results of this study have implications in the modeling of diffusion within mesoporous structures, such as MCM-41 and SBA-15.

Krishna, Rajamani; van Baten, Jasper M.

2011-01-01

194

Molecular dynamics averaging of Xe chemical shifts in liquids  

NASA Astrophysics Data System (ADS)

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

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

2004-11-01

195

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

PubMed

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

Yoshida, Toshiaki

2010-01-01

196

Determination of thermodynamic properties of isotactic poly(1-butene) at infinite dilution using density and inverse gas chromatography.  

PubMed

The partial molar volumes, V1(M), and the molar volume of isotactic crystalline low-molecular-weight poly(1-butene), iPBu-1, V1, have been calculated from the measured density of {iPBu-1 + solvent (n-hexane, n-heptane, n-nonane, n-decane, p-xylene, cyclohexane and chloroform)} systems. Some of the thermodynamic quantities were also obtained for the iPBu-1 with eight hydrocarbons (n-octane, n-decane, n-undecane, n-dodecane, n-tridecane, o-xylene, m-xylene, p-xylene) by the method of inverse gas chromatography at various temperatures. The weight fraction activity coefficients of the solvent at infinite dilution, omega2(infinity) and the Flory-Huggins thermodynamic interaction parameters, chi21(infinity), between polymer and solvents were determined. The partial molar free energy, deltaG2(infinity), the partial molar heat of mixing, deltaH2(infinity), at infinite dilution and the polymer solubility parameter, delta1, were calculated. Additionally, the (solid + liquid) binary mixtures equilibria, SLE, of iPBu-1 with three hydrocarbons (n-octane, n-decane and m-xylene) were studied by a dynamic method. By performing these experiments over a large concentration range, the T-x phase diagrams of the polymer-solvent systems were constructed. The excess Gibbs energy models were used to describe the nonideal behaviour of the liquid phase. The omega2(infinity) were determined from the solubility measurements and were predicted by using the UNIFAC FV model. PMID:15830936

Koz?owska, Marta Karolina; Doma?ska, Urszula; Lempert, Ma?gorzata; Rogalski, Marek

2005-03-18

197

Recovery of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) from Ralstonia eutropha cultures with non-halogenated solvents.  

PubMed

Reduced downstream costs, together with high purity recovery of polyhydroxyalkanoate (PHA), will accelerate the commercialization of high quality PHA-based products. In this work, a process was designed for effective recovery of the copolymer poly(hydroxybutyrate-co-hydroxyhexanoate) (P(HB-co-HHx)) containing high levels of HHx (>15?mol%) from Ralstonia eutropha biomass using non-halogenated solvents. Several non-halogenated solvents (methyl isobutyl ketone, methyl ethyl ketone, and butyl acetate and ethyl acetate) were found to effectively dissolve the polymer. Isoamyl alcohol was found to be not suitable for extraction of polymer. All PHA extractions were performed from both dry and wet cells at volumes ranging from 2?mL to 3?L using a PHA to solvent ratio of 2% (w/v). Ethyl acetate showed both high recovery levels and high product purities (up to 99%) when using dry cells as starting material. Recovery from wet cells, however, eliminates a biomass drying step during the downstream process, potentially saving time and cost. When wet cells were used, methyl isobutyl ketone (MIBK) was shown to be the most favorable solvent for PHA recovery. Purities of up to 99% and total recovery yields of up to 84% from wet cells were reached. During polymer recovery with either MIBK or butyl acetate, fractionation of the extracted PHA occurred, based on the HHx content of the polymer. PHA with higher HHx content (17-30?mol%) remained completely in solution, while polymer with a lower HHx content (11-16?mol%) formed a gel-like phase. All PHA in solution could be precipitated by addition of threefold volumes of n-hexane or n-heptane to unfiltered PHA solutions. Effective recycling of the solvents in this system is predicted due to the large differences in the boiling points between solvent and precipitant. Our findings show that two non-halogenated solvents are good candidates to replace halogenated solvents like chloroform for recovery of high quality PHA. PMID:22903730

Riedel, Sebastian L; Brigham, Christopher J; Budde, Charles F; Bader, Johannes; Rha, Chokyun; Stahl, Ulf; Sinskey, Anthony J

2013-02-01

198

Selective hydroxylation of alkanes by an extracellular fungal peroxygenase.  

PubMed

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

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

2011-10-01

199

Kinetics of fast reactions of excited species. Final report  

Microsoft Academic Search

This report contains brief summaries of findings in the following areas: gamma radiation induced decomposition of chloroform; proton transfer and ion neutralization reactions in gaseous hydrocarbons; kinetics of thremal D-atom reactions with CHâ CâHâ; the gamma radiation induced decomposition of liquid n-pentane; pulse radiolysis of rare gases and liquid n-pentane and n-pentane-Oâ solutions; rate constants and activation energies for second

Firestone

1986-01-01

200

Chain branching and termination in the low-temperature combustion of n-alkanes: 2-pentyl radical + O2, isomerization and association of the second O2.  

PubMed

Association of alkyl radicals with ground-state oxygen (3)Sigma(g)(+)(O(2)) generates chemically activated peroxy intermediates, which can isomerize or further react to form new products before collisional stabilization. The lowest-energy reaction (approximately 19 kcal mol(-1)) for alkylperoxy derivatives of C(3) and larger n-hydrocarbons is an isomerization (intramolecular H-atom transfer) that forms a hydroperoxide alkyl radical, and there is a approximately 30 kcal mol(-1) barrier path to olefin plus HO(2), which is a termination step at lower temperatures. The low-energy-barrier product, hydroperoxide alkyl radical intermediate, can experience additional chemical activation via association with a second oxygen molecule, where there are three important paths that result in chain branching. The competition between this HO(2) + olefin termination step of the first O(2) association and the chain branching processes from the second chemical activation step plays a dominant role at temperatures below 1000 K. Secondary n-pentyl radicals are used in this study as surrogates to analyze the thermochemistry and detailed kinetics of the chemical activation and stabilized adduct reactions important to chain branching and termination. As these radicals provide six- member ring transition states for H-atom transfer between secondary carbons, they represent the detailed kinetics of larger alkane radicals, such as the common fuel components n-heptane and n-decane. Comprehensive potential energy diagrams developed from multilevel CBS-QB3, G3MP2, and CBS-APNO and single-level ab initio and density functional theory methods are used to analyze secondary 2-pentyl (n-pentan-2-yl) and interrelated 2-hydroperoxide-pentan-4-yl radical interactions with O(2). The thermochemistry and kinetics of the chemical activation and stabilized adduct reactions important to chain branching and termination are reported and discussed. Results show that the chain branching reactions have faster kinetics in this system because the barriers are lower than those observed in ethyl and propyl radical plus O(2) reactions; consequently, the branching is predicted to be more important. The lower barriers for branching result in less competition from the termination (HO(2) + olefin) path in this larger radical. Several nontraditional reaction channels not previously considered in the literature are identified. A pathway is suggested to explain the formation of a unique trioxane product observed experimentally. PMID:20604539

Asatryan, Rubik; Bozzelli, Joseph W

2010-07-29

201

NISTIR 5780 Enhancement of R123 Pool Boiling by the  

E-print Network

NISTIR 5780 Enhancement of R123 Pool Boiling by the Addition of N-Hexane Mark A. Kedzierski Enhancement of R123 Pool Boiling by the Addition of N-Hexane Mark A. Kedzierski March 1996 00, Ct of pool boiling performance of a GEWA-TTM surface for three fluids: (1) pure R123, (2) R123/n-hexane (99

Oak Ridge National Laboratory

202

COMBUSTION REACTIONS OF PARAFFIN COMPONENTS IN LIQUID TRANSPORTATION  

E-print Network

-hexadecane and semi-detailed sub- models of iso-octane and methyl cyclohexane, in addition to reac- tions of aromatic for n-heptane, iso-octane, n-decane and gasoline premixed flames. The mechanism was also able mechanism for n-heptane as reviewed by Simmie (2003). For higher hydrocarbons the number of reactions

Utah, University of

203

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

204

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

205

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

206

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

Microsoft Academic Search

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.

Timothy G. Harvey; Trevor W. Matheson; Kerry C. Pratt

1984-01-01

207

Maximization of argon-hydrocarbon Penning mixtures  

Microsoft Academic Search

Townsend's primary and secondary ionization coefficients have been measured in 0·003, 0·03, 0·3 and 3% of n-pentane, ethylene and acetylene mixed in argon for a total pressure in the range 0·5 to 500 torr and for a uniform field gap up to 1 cm. For n-pentane, a concentration of 15% was also employed. A marked Penning effect is again observed

A E D Heylen

1970-01-01

208

Process Simulation and Evaluation of Alternative Solvents for Jatropha Curcas L. Seed Oil Extraction in Biodiesel Production  

E-print Network

-case flowsheet is synthesized for oil extraction. Then, the base-case extraction process and each solvent Fire and Explosion Index (F & EI) and the Solvent Safety Index (SSI). Eight solvents, including n-heptane, toluene, xylene, dichloromethane, chloroform, 1...

Chiou, Ming-Hao

2012-10-19

209

ICDERS July 23-27, 2007 Poitiers, France Correspondence to : Jorg.ANDERLOHR@ifp.fr 1  

E-print Network

conditions. Experiments used for validation include jet stirred reactor conditions for species evolution for the reactions of NOx with larger alcanes (n-heptane, iso-octane). A coherent two components engine fuel

Paris-Sud XI, Université de

210

Vrme-och strmningsteknik / Thermal and flow engineering Massverfring & separationsteknik /  

E-print Network

.4.2011 Obs: matrikelnummer = a b c d e och z = max(c,d,e) Note: input data depends on matriculation number content of A (n-heptane) and a residue with a higher content of B (n-octane)) with a batch distillation faction x0 in the distillate at the point where the stillpot contains z mol n-heptane + (a+e) mol n-octane

Zevenhoven, Ron

211

Continuous enzymatic transesterification of high oleic sunflower oil in a packed bed reactor: influence of the glycerol production  

Microsoft Academic Search

The transesterification of high oleic sunflower oil with butanol by the immobilized Lipozyme® in n-hexane was carried out in a continuous packed bed reactor, oleic acid, butyl ester, and glycerol being formed as the main products. It was found that glycerol, insoluble in n-hexane, remained in the reactor adsorbed onto the enzymatic support, leading to a drastic decrease in enzymatic

Valérie Dossat; Didier Combes; Alain Marty

1999-01-01

212

DOI: 10.1002/chem.200501053 Micelle-to-Vesicle Transition Induced by Organic Additives in Catanionic  

E-print Network

in a number of practical applica- tions[2] and of fundamental interest as well.[3] For catanionic surfactant, n-hexane, n-octane, and n-dodecane) and polar organ- ic additives, such as n-octanol and n hydrocarbons (n-bu- tylbenzene, n-hexane, n-octane, and n- dodecane) to the catanionic surfactant system n

Huang, Jianbin

213

Effect of film thickness and viscoelasticity on separability of vapour classes by wavelet and principal component analyses of polymer-coated surface acoustic wave sensor transients  

NASA Astrophysics Data System (ADS)

The transient response of a polymer-coated surface acoustic wave (SAW) vapour sensor depends on partitioning and diffusion of vapour species into the polymer in conjunction with its thickness and viscoelastic properties. The shapes of transient signals carry information about vapour identities due to specificity of the partition coefficient and the diffusion coefficient. The analysis of transient signals therefore offers a simpler approach for vapour identification in comparison to conventional electronic nose systems that employ a broadly selective sensor array. The transient response-based methods are however not developed to a similar level of maturity as their sensor array counterparts. The main reason for this is associated with complex signal generation kinetics and polymer viscoelasticity. The latter is independent of vapour identities (assuming low concentrations) but influences sensor response through nonlinear dependences on polymer thickness and viscoelastic coefficients. In this paper, we endeavour to find out whether viscoelasticity and its manifestation through thickness dependences could be turned into an advantage for transient-based vapour identification. Using an established SAW sensor model with additive noise we analyse sensor transients by wavelet decomposition and principal component analysis (PCA) for various combinations of polymer thickness, viscoelastic storage and loss moduli and noise level. We calculate vapour class separability measures defined on the basis of scatter matrices of principal components of wavelet coefficients to determine the discrimination ability of sensor transients for various combinations of film thickness and viscoelastic parameters. The simulation experiments are performed by considering a polyisobutylene-coated SAW oscillator sensor under exposure to seven volatile organic compounds (chloroform, chlorobenzene, o-dichlorobenzene, n-heptane, toluene, n-hexane and n-octane). The film thicknesses are varied from thin film (where mass loading dominates) to thick film through fundamental film resonance (where viscoelastic effects dominate) to very thick film regions spanning over a few higher order resonances. The storage and loss shear moduli are varied to simulate conditions of glassy, glassy-rubbery and rubbery phases of polymer. The transient response generation incorporates an additive noise source with uniform distribution over a specified range. Effect of noise variation on class separability is also studied. A comparison of the wavelet transform method is made with the phase space-based partial-least-squares regression method for feature extraction. In conclusion, it is found that (i) vapour class separability increases with polymer thickness for all viscoelastic conditions from glassy to rubbery, except near film resonances, (ii) near resonance class separability dramatically declines for films with no or low loss, (iii) by imparting finite viscoelastic losses to polymer coatings, not only are the detrimental effects of film resonance eliminated but also the sensor performance improves, and (iv) viscoelastic effects produce better noise immunity in thick film sensors. This analysis provides a new perspective for designing high-performance transient sensors through optimization of film thickness for specific polymer selections.

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

2011-02-01

214

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.

1984-01-01

215

Kinetics of fast reactions of excited species. Final report  

SciTech Connect

This report contains brief summaries of findings in the following areas: gamma radiation induced decomposition of chloroform; proton transfer and ion neutralization reactions in gaseous hydrocarbons; kinetics of thremal D-atom reactions with CH/sub 4/ C/sub 2/H/sub 6/; the gamma radiation induced decomposition of liquid n-pentane; pulse radiolysis of rare gases and liquid n-pentane and n-pentane-O/sub 2/ solutions; rate constants and activation energies for second order decay of pentyl and peroxypentyl radicals; pulse radiolysis fo aromatic solutes in halogenated solvents; the gamma radiation induced decomposition of nitromethane; the radiolysis of heavy water vapor; pulse radiolysis of solvated electrons in binary liquid solutions; collisional quenching of rare gas excimers by small foreign molecules; kinetics and mechanism for decay of Paschen-1s argon atoms; detection and monitoring of excited atoms in pulse irradiated rare gases.

Firestone, R.F.

1986-09-01

216

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

217

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

SciTech Connect

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

Toulson, Dr. Elisa [Michigan State University, East Lansing; Allen, Casey M [Michigan State University, East Lansing; Miller, Dennis J [Michigan State University, East Lansing; McFarlane, Joanna [ORNL; Schock, Harold [Michigan State University, East Lansing; Lee, Tonghun [Michigan State University, East Lansing

2011-01-01

218

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

219

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

Microsoft Academic Search

Extracellular lipase from Bacillus coagulans BTS-3 was immobilized on (3 Å × 1.5 mm) molecular sieve. The molecular sieve showed approximately 68.48% binding efficiency\\u000a 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\\u000a acetate in n-heptane at 65°C in 3 h. When alkane of C-chain length other than n-heptane was used as the

Shilpa Raghuvanshi; Reena Gupta

2009-01-01

220

Isotropic tensile strength of molecular glasses  

Microsoft Academic Search

The relationship between the bulk density and pressure of configurations corresponding to local minima on the potential energy surface of molecular models of ethane, n-pentane, and cyclopentane (the equation of state of their energy landscape) has been explored. Like simpler, atomic fluids, these systems exhibit a limiting bulk density below which minimum energy configurations are no longer spatially homogeneous, but

Marcel Utz; Pablo G. Debenedetti; Frank H. Stillinger

2001-01-01

221

Thermodynamic analysis of a solar thermal water pump  

Microsoft Academic Search

The principle of the workings of a solar thermal water pump with n-pentane as the working fluid is described briefly. The performance of the pump is predicted from the thermodynamic analysis of the cycle of events. Experiments were carried out with a small solar thermal pump having a collector area of 1 m2. The experimental and theoretical results were compared.

K. Sumathy; A. Venkatesh; V. Sriramulu

1996-01-01

222

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

SciTech Connect

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; Rousseau, Bernard, E-mail: bernard.rousseau@u-psud.fr [Laboratoire de Chimie-Physique, UMR 8000 CNRS, Université Paris-Sud, Orsay (France)] [Laboratoire de Chimie-Physique, UMR 8000 CNRS, Université Paris-Sud, Orsay (France); Schnell, Benoît; Petitjean, Laurent; Couty, Marc [Manufacture Française des Pneumatiques MICHELIN, Centre de Ladoux, 23 place des Carmes, 63000 Clermont-Ferrand (France)] [Manufacture Française des Pneumatiques MICHELIN, Centre de Ladoux, 23 place des Carmes, 63000 Clermont-Ferrand (France)

2014-04-07

223

21 CFR 177.1620 - Polyethylene, oxidized.  

Code of Federal Regulations, 2010 CFR

...density, maximum n- hexane extractable fraction, and maximum xylene...article, when extracted with the solvent or solvents characterizing the type of...test sample for each extracting solvent.) (c) The provisions...

2010-04-01

224

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

Code of Federal Regulations, 2010 CFR

...Organic HAP From Polyether Polyol Products Organic HAP/chemical name [CAS No.] 1,3 Butadiene (106990) Epichlorohydrin (106898) Ethylene Oxide (75218) n-Hexane (110543) Methanol (67561) Propylene Oxide...

2010-07-01

225

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

Code of Federal Regulations, 2014 CFR

...Organic HAP From Polyether Polyol Products Organic HAP/chemical name[CAS No.] 1,3 Butadiene (106990) Epichlorohydrin (106898) Ethylene Oxide (75218) n-Hexane (110543) Methanol (67561) Propylene Oxide...

2014-07-01

226

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

Code of Federal Regulations, 2013 CFR

...Organic HAP From Polyether Polyol Products Organic HAP/chemical name[CAS No.] 1,3 Butadiene (106990) Epichlorohydrin (106898) Ethylene Oxide (75218) n-Hexane (110543) Methanol (67561) Propylene Oxide...

2013-07-01

227

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

Code of Federal Regulations, 2011 CFR

...Organic HAP From Polyether Polyol Products Organic HAP/chemical name [CAS No.] 1,3 Butadiene (106990) Epichlorohydrin (106898) Ethylene Oxide (75218) n-Hexane (110543) Methanol (67561) Propylene Oxide...

2011-07-01

228

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

Code of Federal Regulations, 2012 CFR

...Organic HAP From Polyether Polyol Products Organic HAP/chemical name [CAS No.] 1,3 Butadiene (106990) Epichlorohydrin (106898) Ethylene Oxide (75218) n-Hexane (110543) Methanol (67561) Propylene Oxide...

2012-07-01

229

A Rapid Method for Hydrocarbon-type Analysis of Heavy Oils and Synthetic Fuels by Pyrolysis Thin Layer Chromatography  

Microsoft Academic Search

Hydrocarbon-type fractions (saturates, aromatics, polynuclear aromatics, and polar compounds) from heavy crude oils and synthetic fuels were separated by thin layer chromatography (TLC) on chromarods, using an Iatroscan TH-10 analyzer. The best results were obtained on a silica gel chromarod when n-hexane, 10 percent benzene in n-hexane, and 5 percent ethyl acetate in benzene were used as developing solvent. A

M. A. Poirier; A. E. George

1983-01-01

230

Pressurized liquid extraction of polychlorinated dibenzo- p-dioxins, polychlorinated dibenzofurans and coplanar polychlorinated biphenyls from contaminated soil  

Microsoft Academic Search

Extraction solvents for pressurized liquid extraction (PLE) used to extract polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans (PCDD\\/PCDFs), and coplanar polychlorinated biphenyls (Co-PCBs) from contaminated soil were investigated. The PCDD\\/PCDFs and Co-PCBs in Certified Reference Material: CRM 0422 (Forest soil) were extracted using toluene, n-hexane, acetone, acetone\\/toluene and acetone\\/n-hexane (1:1, v\\/v). Soxhlet extraction was the reference method. Results demonstrated that PLE using mixed

Osamu Kiguchi; Takashi Kobayashi; Katsumi Saitoh; Nobuaki Ogawa

2006-01-01

231

An investigation into lowest acceptable combustion temperatures for hydrocarbon fuels in HCCI engines  

Microsoft Academic Search

The combustion temperatures required for complete combustion in homogeneous charge compression ignition engines have been investigated computationally and experimentally. Fuels from several different hydrocarbon classes are covered including: iso-octane, n-heptane, toluene, and methylcyclohexane. Over a wide range of conditions, it was found that the temperature requirements are well described by the peak cycle temperature. For operation with a compression ratio

Magnus Sjöberg; John E. Dec

2005-01-01

232

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 et al. 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

O Herbinet; W J Pitz; C K Westbrook

2007-01-01

233

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

234

Development of a reduced chemical kinetic mechanism for a gasoline surrogate for gasoline HCCI combustion  

Microsoft Academic Search

A reduced chemical kinetic mechanism consisting of 48 species and 67 reactions is developed and validated for a gasoline surrogate fuel. The surrogate fuel is modeled as a blend of iso-octane, n-heptane, and toluene. The mechanism reduction is performed using sensitivity analysis, investigation of species concentrations, and consideration of the main reaction path. Comparison between ignition delay times calculated using

Kyeonghyeon Lee; Yongrae Kim; Kyoungdoug Min

2010-01-01

235

Reduced chemical kinetic mechanisms for hydrocarbon fuels  

Microsoft Academic Search

Using CARM (Computer Aided Reduction Method), a computer program that automates the mechanism reduction process, a variety of different reduced chemical kinetic mechanisms for ethylene and n-heptane have been generated. The reduced mechanisms have been compared to detailed chemistry calculations in simple homogeneous reactors and experiments. Reduced mechanisms for combustion of ethylene having as few as 10 species were found

C J Montgomery; M A Cremer; M P Heap; J-Y Chen; C K Westbrook; L Q Maurice

1999-01-01

236

Detailed chemical kinetic modeling of diesel combustion with oxygenated fuels  

Microsoft Academic Search

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

W J Pitz; H J Curran; E Fisher; P A Glaude; N M Marinov; C K Westbrook

1999-01-01

237

Chemical kinetic mechanism for the oxidation of paraffinic hydrocarbons needed for primary reference fuels  

Microsoft Academic Search

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

C. K. Westbrook; W. J. Pitz

1993-01-01

238

21 CFR 177.1330 - Ionomeric resins.  

Code of Federal Regulations, 2012 CFR

...both, and including oil-in-water emulsions of low- or high-fat content Water...both, and including oil-in-water emulsions of low- or high-fat content n -heptane...salt, and including water-in-oil emulsions of low- or high-fat content...

2012-04-01

239

21 CFR 177.1330 - Ionomeric resins.  

Code of Federal Regulations, 2014 CFR

...both, and including oil-in-water emulsions of low- or high-fat content Water...both, and including oil-in-water emulsions of low- or high-fat content n -heptane...salt, and including water-in-oil emulsions of low- or high-fat content...

2014-04-01

240

21 CFR 177.1330 - Ionomeric resins.  

Code of Federal Regulations, 2013 CFR

...both, and including oil-in-water emulsions of low- or high-fat content Water...both, and including oil-in-water emulsions of low- or high-fat content n -heptane...salt, and including water-in-oil emulsions of low- or high-fat content...

2013-04-01

241

A new comprehensive semiempirical approach to calculate three-phase water/hydrocarbons equilibria  

E-print Network

parameters, i.e. vapor phase composition (vi). In this study, the CSA has been used to run the data from Billman (1989) and Beladi (1995). These data include two ternary systems of n-heptane/n-dodecane/water, for which their initial overall compositions...

Tandia, Bagus Krisna

1995-01-01

242

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

243

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

244

21 CFR 177.1330 - Ionomeric resins.  

Code of Federal Regulations, 2010 CFR

...both, and including oil-in-water emulsions of low- or high-fat content Water...both, and including oil-in-water emulsions of low- or high-fat content n -heptane...salt, and including water-in-oil emulsions of low- or high-fat content...

2010-04-01

245

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

246

2007-01-0175 Development of an Experimental Database and Chemical  

E-print Network

ratings, also find widespread use as convenient surrogates for variable octane number fuel. Ternary of a fully-blended fuel. The simplest surrogate fuels consist of single components, e.g., the use of iso-octane as a gasoline surrogate. Binary blends of n-heptane and iso- octane, the primary reference fuels for octane

Pitsch, Heinz

247

Kinetic effects of toluene blending on the extinction limit of n-decane diffusion flames  

E-print Network

by using n-hep- tane and iso-octane as the primary reference fuels (PRF) [2]. The overall combustion speeds by adjusting the mixing ratio of n-heptane and iso- octane [2]. However, the PRF model does the stoichiometric air/fuel ratio (and thus the Reynolds number and turbulent flow intensity), in order to mimic

Ju, Yiguang

248

Twenty-Seventh Symposium (International) on Combustion/The Combustion Institute, 1998/pp. 20692076 PLANAR LASER-INDUCED FLUORESCENCE IMAGING OF CREVICE  

E-print Network

-induced fluorescence (PLIF) from iso-octane/n-heptane fuel blends doped with 3-pentanone. The fluorescence was imaged with lower octane ratings were shown to enhance flame penetration due to their increased reactivity source of crevice emissions, and a number of studies have been undertaken in an at- tempt to minimize

Long, Marshall B.

249

Experimental and modeling investigation of the low temperature oxidation of nheptane  

E-print Network

for gasolines with an octane number of 0 [33]. This species is also a possible surrogate for the nalkanes oxidation of nheptane, one of the reference species for the octane rating of gasoline, was investigated [132]. nHeptane is one of the two primary reference fuels which are used for the octane rating

Paris-Sud XI, Université de

250

A Generalized Interaction Method for the Prediction of Octane Numbers for Gasoline Blends  

Microsoft Academic Search

This paper presents an interaction method for predicting the research and motor octane numbers of gasoline blends. The proposed method and correlation has the following characteristics: (1) The blending correlation blends exactly the octane numbers of isooctane and n-heptane.(2) The blended octane number is unchanged when blending identical components. (3) The blending equation describes blending behavior accurately throughout the entire

Chorng H. Twu; John E. Coon

251

LAMINAR BURNING VELOCITY OF GASOLINES WITH ADDITION OF ETHANOL  

E-print Network

-heptane, iso-octane, and toluene mixture) of close research octane number have been measured at 358 K. Non with a research octane number (RON) of 87. However, while the agreement was very good for lean mixtures, and for pure n-heptane, iso-octane, toluene and ethanol, have been satisfactorily simulated using a detailed

Boyer, Edmond

252

This article was published in an Elsevier journal. The attached copy is furnished to the author for non-commercial research and  

E-print Network

components for use in high-performance gasoline fuels. ``Octane'' or, more precisely the octane number''. The most common measure of the octane number is the RON (research octane number). By definition iso-octane (2,2,4- trimethyl pentane) is given an octane number (RON) of 100 and n-heptane an octane number of 0

Skogestad, Sigurd

253

Modelling a Dual-fuelled Multi-cylinder HCCI Engine Using a PDF based Engine Cycle Simulator  

Microsoft Academic Search

Operating the HCCI engine with dual fuels with a large difference in auto-ignition characteristics (octane number) is one way to control the HCCI operation. The effect of octane number on combustion, emissions and engine performance in a 6 cylinder SCANIA truck engine, fuelled with n-heptane and isooctane, and running in HCCI mode, are investigated numerically and compared with measurements taken

Amit Bhave; Markus Kraft; Luca Montorsi; Fabian Mauss

2004-01-01

254

DETAILED CHEMICAL KINETIC MODELS FOR THE LOW TEMPERATURE COMBUSTION OF HYDROCARBONS WITH APPLICATION TO  

E-print Network

: motor octane number MTBE: methyl-tert-butyl-ether NTC: negative temperature coefficient P: pressure Pc,2,4-trimethylpentane) R: gas constant RCM: rapid compression machine RON: research octane number ST: shock tube T: pressure after compression in a RCM PRF: primary reference fuels, i.e. n-heptane and iso-octane (1

Paris-Sud XI, Université de

255

Hydroisomerization of Pentane, Hexane, and Heptane for Improving the Octane Number of Gasoline  

Microsoft Academic Search

The hydroisomerization of n-heptane to dibranched and tribranched products for producing high octane gasoline has been studied using unidirectional 12 Membered Ring (MR) zeolites with different pore diameters, and zeolites with other pore topologies including one with connected 12×10 MR pores and two tridirectional 12 MR zeolites. Besides the pore topology, the crystallite size of the zeolite was seen to

A. Chica; A. Corma

1999-01-01

256

HCCI experiments with toluene reference fuels modeled by a semidetailed chemical kinetic model  

SciTech Connect

A semidetailed mechanism (137 species and 633 reactions) and new experiments in a homogeneous charge compression ignition (HCCI) engine on the autoignition of toluene reference fuels are presented. Skeletal mechanisms for isooctane and n-heptane were added to a detailed toluene submechanism. The model shows generally good agreement with ignition delay times measured in a shock tube and a rapid compression machine and is sensitive to changes in temperature, pressure, and mixture strength. The addition of reactions involving the formation and destruction of benzylperoxide radical was crucial to modeling toluene shock tube data. Laminar burning velocities for benzene and toluene were well predicted by the model after some revision of the high-temperature chemistry. Moreover, laminar burning velocities of a real gasoline at 353 and 500 K could be predicted by the model using a toluene reference fuel as a surrogate. The model also captures the experimentally observed differences in combustion phasing of toluene/n-heptane mixtures, compared to a primary reference fuel of the same research octane number, in HCCI engines as the intake pressure and temperature are changed. For high intake pressures and low intake temperatures, a sensitivity analysis at the moment of maximum heat release rate shows that the consumption of phenoxy radicals is rate-limiting when a toluene/n-heptane fuel is used, which makes this fuel more resistant to autoignition than the primary reference fuel. Typical CPU times encountered in zero-dimensional calculations were on the order of seconds and minutes in laminar flame speed calculations. Cross reactions between benzylperoxy radicals and n-heptane improved the model predictions of shock tube experiments for {phi}=1.0 and temperatures lower than 800 K for an n-heptane/toluene fuel mixture, but cross reactions had no influence on HCCI simulations. (author)

Andrae, J.C.G. [Department of Chemical Engineering and Technology, Royal Institute of Technology (KTH), SE-100 44 Stockholm (Sweden); Brinck, T. [Department of Physical Chemistry, Royal Institute of Technology (KTH), SE-100 44 Stockholm (Sweden); Kalghatgi, G.T. [Shell Global Solutions (UK), P.O. Box 1, Chester CH1 3SH (United Kingdom)

2008-12-15

257

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

258

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

259

Cavitation in the vicinity of the high-voltage electrode as a key step of nanosecond breakdown in liquids  

NASA Astrophysics Data System (ADS)

Fast shadowgraphy of nanosecond discharge in liquids with different dielectric permittivity, namely in water, ethanol and n-pentane, has been performed. Formation of a gas cavity at a nanosecond time scale was observed as a pre-breakdown phenomenon at amplitudes of the high-voltage pulse close to the breakdown threshold. This phenomenon is considered as a possible key step of high-voltage breakdown in polar liquids.

Marinov, I.; Guaitella, O.; Rousseau, A.; Starikovskaia, S. M.

2013-08-01

260

Supporting Information Copyright Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, 2007  

E-print Network

-Aldrich) in n-pentane (BDH Omnisolv) with a low pressure mercury lamp in a water- cooled immersion well.1% of the of diene. The pump pulses (196 nm, 150 fs, 109 W cm-2) were generated from a Ti-sapphire laser system of the laser (805 nm, 45 fs, 1­3×1013 W cm-2, polarization 55° versus the pump) served for probing

Leigh, William J.

261

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

262

MEASURING CONTAMINANT FLUX THROUGH PLANTS BY FOURIER TRANSFORM INFRARED (FT-IR) SPECTROMETRY  

Microsoft Academic Search

Plants have a large capacity to transfer water and associated contaminants from soil to atmosphere. We measured the transfer rate for a range of constituents of gasoline that vary in volatility, solubility, and octanol\\/water partition coefficient. We tested benzene, toluene, ethyl benzene, meta-xylene, 1,2,4-trimethyl benzene, cyclohexene, n-pentane, ethyl ether, n-propyl ether, and t-butyl methyl ether. Aliphatic hydrocarbon constituents of gasoline

V. D. Makepeace; L. C. Davis; J. Dana; K. Selk; K. Smith; R. M. Hammaker; W. G. Fateley; L. E. Erickson

263

Numerical study of multicomponent droplet vaporization at near critical conditions  

NASA Technical Reports Server (NTRS)

A comprehensive numerical analysis of multicomponent droplet vaporization at near critical conditions has been carried out. The model is based on the full time-dependent conservation equations and accommodates various important high-pressure phenomena. As an example, the case involving a two-component (n-pentane and n-octane) fuel droplet in nitrogen gas is studied. The influences of transient effects, surface regression, ambient gas solubility, and phase-equilibrium relations on vaporization mechanisms are examined in detail.

Hsieh, Kwang-Chung; Shuen, Jian-Shun; Yang, Vigor

1988-01-01

264

Modification of the surface pathways in alkane oxidation by selective doping of Bronsted acid sites of vanadyl pyrophosphate  

Microsoft Academic Search

The modification of Bronsted POH groups of (VO)âPâOâ by selective doping with K in an anhydrous medium causes a considerable modification of the surface oxidation pathways in Câ- and Câ-alkane oxidative transformation, with (i) a considerable decrease in the selective formation of maleic anhydride from n-butane and of maleic and phthalic anhydrides from n-pentane, (ii) an increase in the relative

G. Centi; G. Golinelli; G. Busca

1990-01-01

265

Liquid CO2 extraction of Jasminum grandiflorum and comparison with conventional processes.  

PubMed

The concrete (0.35%) of Jasminum grandiflorum L. flowers was prepared by extraction in n-pentane, and the absolute (0.27%) by fractionation of the n-pentane extract (concrete) with cold methanol. Direct extraction of flowers with liquid CO2 gave a relatively fat-free product in 0.26% yield. The liquid CO2 extract was enriched with terpenoids and benzenoids, thus providing the organoleptically accepted product. The major compounds, such as benzyl acetate, (E,E)-alpha-farnesene and (Z)-3-hexenyl benzoate, along with compounds like indole, methyl anthranilate, (Z)-jasmone, (Z)-methyl jasmonoate and (Z)-methyl epi-jasmonoate, are responsible for the high diffusivity of the jasmine fragrance. These compounds have been obtained with improved recoveries in the liquid CO2 extract. On the other hand, the yield of the essential oil was poor (0.05%), and some polar compounds (oxygenated terpenoids) were recovered in less amounts in comparison with either the n-pentane or liquid CO2 extract. PMID:22428256

Prakash, Om; Sahoo, Deeptanjali; Rout, Prasant Kumar

2012-01-01

266

Instrumental studies on silicone oil adsorption to the surface of intraocular lenses  

NASA Astrophysics Data System (ADS)

The purpose of this study was to examine the degree of adherence of silicone oil to various intraocular lenses (IOLs) through comparison of the physico-chemical properties of the oil and IOLs. Four kinds of IOLs comprising various biomaterials were examined: PMMA (720A™), PHEMA (IOGEL 1103™), Acrysof (MA60BM™), and silicone (SI30NB™). Each lens was immersed in silicone oil or carboxylated silicone (CS-PDMS) oil for 72 h. For determination of the changes in chemical and elemental compositions on the surfaces of IOLs caused by the contact with silicone oil, IOLs were washed and rinsed with n-pentane to remove as much of the adsorbed silicone oil as possible, then subjected to Fourier transform infrared spectroscopic (FTIR) and X-ray photoelectron spectroscopic (XPS) analyses. The results of FTIR studies strongly indicate that washing with n-pentane completely removed the adhered silicone oil on the surfaces of PHEMA and Acrysof IOLs, whereas the residual silicone oil was detected on the surfaces of PMMA and silicone IOLs. XPS studies showed that silicone oil coverage of PMMA lenses was 12%, even after washing with n-pentane. In the case of silicone IOLs, the relative O1s peak area of carboxyl group in the residual CS-PDMS oil was found to be ˜2.7%. Considering that 2.8% carboxyl group-substituted silicone oil was used in the present study, CS-PDMS oil covered the entire surface of the silicone IOLs.

Kim, Chun Ho; Joo, Choun-Ki; Chun, Heung Jae; Yoo, Bok Ryul; Noh, Dong Il; Shim, Young Bock

2012-12-01

267

Influence of EGR compounds on the oxidation of an HCCI-diesel surrogate  

E-print Network

This paper presents an experimental and numerical study of the impact of various additives on the oxidation of a typical automotive surrogate fuel blend, i.e. n-heptane and toluene. It examines the impact of engine re-cycled exhaust has compounds on the control of an Homogeneous Charge Compression-Ignition (HCCI) engine. Series of experiments were performed in a hihly diluted Jet-Stirred Reactor (JDR) at pressures of 1 and 10 atm (1 atm = 101,325 Pa). The chosen thermo-chemical conditions were close to those characteristices of the pre-ignition period in an HCCI engine. The influence of various additives, namely nitric oxide (NO), ethylene (C2H4) and methanol (CH3OH), on the oxidation of a n-heptane/toluene blend was studied over a wide range of temperatures (550-1100 K), including the zone of the Negative Temperature Coefficient (NTC).

Anderlohr, Jörg; Da Cruz, A Pires; Bounaceur, Roda; Battin-Leclerc, Frédérique; Dagaut, Philippe; Montagne, X; 10.1016/j.proci.2008.06.019

2009-01-01

268

Laser extinction technique for measurements of carbon particles concentration during combustion  

NASA Astrophysics Data System (ADS)

Particulate matter (PM) from diesel engines originate from soot particles which form during combustion and is notoriously a major source of concern as an airborne contaminant in the environment. The mechanisms by which soot is generated in diesel engines are still not completely understood and the use of optical techniques in a controllable environment is crucial for this purpose. This work focuses on the development and application of the laser extinction technique to the study of soot formation evolution in a rapid compression machine (RCM). A suitable optical arrangement to determine soot kinetics with high temporal resolution is presented together with the results obtained in the case of rich n-heptane, toluene and toluene/n-heptane mixtures under different conditions of pressure and temperature. The experimental investigation is focused on the fuel-rich premixed turbulent flame.

Di Sante, R.

2013-06-01

269

Possible room temperature superconductivity in conductors obtained by bringing alkanes into contact with a graphite surface.  

PubMed

Electrical resistances of conductors obtained by bringing alkanes into contact with a graphite surface have been investigated at room temperatures. Ring current in a ring-shaped container into which n-octane-soaked thin graphite flakes were compressed did not decay for 50 days at room temperature. After two HOPG plates were immersed into n-heptane and n-octane at room temperature, changes in resistances of the two samples were measured by four terminal technique. The measurement showed that the resistances of these samples decrease to less than the smallest resistance that can be measured with a high resolution digital voltmeter (0.1?V). The observation of persistent currents in the ring-shaped container suggests that the HOPG plates immersed in n-heptane and n-octane really entered zero-resistance state at room temperature. These results suggest that room temperature superconductor may be obtained by bringing alkanes into contact with a graphite surface. PMID:23826513

Kawashima, Yasushi

2013-05-01

270

Possible room temperature superconductivity in conductors obtained by bringing alkanes into contact with a graphite surface  

NASA Astrophysics Data System (ADS)

Electrical resistances of conductors obtained by bringing alkanes into contact with a graphite surface have been investigated at room temperatures. Ring current in a ring-shaped container into which n-octane-soaked thin graphite flakes were compressed did not decay for 50 days at room temperature. After two HOPG plates were immersed into n-heptane and n-octane at room temperature, changes in resistances of the two samples were measured by four terminal technique. The measurement showed that the resistances of these samples decrease to less than the smallest resistance that can be measured with a high resolution digital voltmeter (0.1?V). The observation of persistent currents in the ring-shaped container suggests that the HOPG plates immersed in n-heptane and n-octane really entered zero-resistance state at room temperature. These results suggest that room temperature superconductor may be obtained by bringing alkanes into contact with a graphite surface.

Kawashima, Yasushi

2013-05-01

271

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

272

Molecular structure and component blending effects on knock related chemistry  

SciTech Connect

Atmospheric pressure flow reactor experiments were conducted on the oxidation and pyrolysis of n-octane and iso-octane and the oxidation of blends of iso-octane and n-heptane have led to the conclusions that a) the difference in knocking tendency of fuels may result primarily from the comparative oxidation rates of the intermediates rather than the rate of attack on the initial fuel molecule, b) certain small unsaturated hydrocarbons interfere with the oxidation of other intermediates and serve as model compounds for the development of octane number enhancers, c) high temperature homogeneous oxidation chemistry of n-heptane/iso-octane mixtures and single component paraffin fuels can be correlated with the global phenomena of octane number measurement in a test engine, d) the contribution of thermal and oxidative processes to the rapid decay of the initial fuel can be evaluated from rate parameters from pyrolysis studies of pure hydrocarbon fuels.

Brezinsky, K.; Dryer, F.L.

1987-01-01

273

Detailed kinetic models for the low-temperature auto ignition of gasoline surrogates  

E-print Network

In the context of the search for gasoline surrogates for kinetic modeling purpose, this paper describes a new model for the low-temperature auto-ignition of n-heptane/iso-octane/hexene/toluene blends for the different linear isomers of hexene. The model simulates satisfactory experimental results obtained in a rapid compression machine for temperatures ranging from 650 to 850 K in the case of binary and ternary mixtures including iso octane, 1-hexene and toluene. Predictive simulations have also been performed for the autoignition of n heptane/iso octane/hexene/toluene quaternary mixtures: the predicted reactivity is close to that of pure iso octane with a retarding effect when going from 1- to 3-alkene.

Bounaceur, Roda; Fournet, René; Warth, Valérie; Battin-Leclerc, Frédérique

2009-01-01

274

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

275

Separation of Nickel and Copper by Solvent Extraction Using Di?2 Ethylhexylphosphoric Acid?Based Synergistic Mixture  

Microsoft Academic Search

Solvent extraction of copper(II) and nickel(II) from aqueous acetate solutions with di(2?ethylhexyl)phosphoric acid (D2EHPA), dissolved in n?heptan has been investigated. The extraction of Cu(II) was found to be quantitative in neutral, acetic acid, and acetate buffer media 96%, 95%, and 85% respectively. On the other hand, the extraction efficiency of Cu(II) decreases with the increase of the salt concentration in

Mohamed Amine Didi; Didier Villemin

2005-01-01

276

Magnetic field effect on pyrene–DMA exciplex luminescence in non-aqueous AOT reverse micelle  

Microsoft Academic Search

Magnetic field effect (MFE) on pyrene–DMA exciplex luminescence and exciplex lifetime have been studied in reverse micelle of Aerosol-OT in n-heptane in presence of N,N-dimethylformamide and methanol as the polar solvent at different Ws (Ws=[polar solvent]\\/[surfactant]) values. It is found that two types of exciplexes are residing at different locations of the non-aqueous reverse micelle. Out of these only the

Doyel Das; Deb Narayan Nath; Partha Pratim Parui; Mihir Chowdhury

2006-01-01

277

Flame-extinguishing concentrations and peak concentrations of N 2, Ar, CO 2 and their mixtures for hydrocarbon fuels  

Microsoft Academic Search

Fire-extinguishing efficiency of inert gas mixtures was investigated by measuring flame-extinguishing concentrations and peak concentrations for hydrocarbon fuels, because new fire-extinguishing agents composed of inert gas mixtures have been developed as halon alternatives. The flame-extinguishing concentrations of nitrogen, argon, carbon dioxide and their mixtures for n-heptane were measured with the FRI glass cup burner. The peak concentrations of the agents

Naoshi Saito; Yoshio Ogawa; Yuko Saso; Chihong Liao; Ryuta Sakei

1996-01-01

278

Hydrocarbon fuel cooling technologies for advanced propulsion  

Microsoft Academic Search

Storable hydrocarbon fuels that undergo endothermic reaction provide an attractive heat sink for future high-speed aircraft. An investigation was conducted to explore the endothermic potential of practical fuels, with inexpensive and readily available catalysts, under operating conditions simulative of high-speed flight applications. High heat sink capacities and desirable reaction products have been demonstrated for n-heptane and Norpar 12 fuels using

D. R. Sobel; L. J. Spadaccini

1997-01-01

279

Detailed Chemical Kinetic Reaction Mechanisms for Primary Reference Fuels for Diesel Cetane Number and Spark-Ignition Octane Number  

Microsoft Academic Search

For the first time, a detailed chemical kinetic reaction mechanism is developed for primary reference fuel mixtures of n-hexadecane and 2,2,4,4,6,8,8-heptamethyl nonane for diesel cetane ratings. The mechanisms are constructed using existing rules for reaction pathways and rate expressions developed previously for the primary reference fuels for gasoline octane ratings, n-heptane and iso-octane. These reaction mechanisms are validated by comparisons

C K Westbrook; W J Pitz; M Mehl; H J Curran

2010-01-01

280

Detailed chemical kinetic reaction mechanisms for primary reference fuels for diesel cetane number and spark-ignition octane number  

Microsoft Academic Search

A detailed chemical kinetic reaction mechanism is developed for primary reference fuel mixtures of n-hexadecane and 2,2,4,4,6,8,8-heptamethyl nonane for diesel cetane ratings. The mechanisms are constructed using existing rules for reaction pathways and rate expressions developed previously for the primary reference fuels for gasoline octane ratings, n-heptane and iso-octane. These reaction mechanisms are validated by comparisons between computed and experimental

C. K. Westbrook; W. J. Pitz; M. Mehl; H. J. Curran

2011-01-01

281

A path flux analysis method for the reduction of detailed chemical kinetic mechanisms  

Microsoft Academic Search

A direct path flux analysis (PFA) method for kinetic mechanism reduction is proposed and validated by using high temperature ignition, perfect stirred reactors, and steady and unsteady flame propagations of n-heptane and n-decane\\/air mixtures. The formation and consumption fluxes of each species at multiple reaction path generations are analyzed and used to identify the important reaction pathways and the associated

Wenting Sun; Yiguang Ju; Zheng Chen; Xiaolong Gou

2010-01-01

282

Estimation of octanol–water partition coefficients for neutral and weakly acidic compounds by microemulsion electrokinetic chromatography using dynamically coated capillary columns  

Microsoft Academic Search

Microemulsion electrokinetic chromatography (MEEKC) using dynamically coated capillary columns is shown to be suitable for estimating the octanol–water partition coefficient (log P) for neutral and weakly acidic compounds at pH 3. The solvation parameter model is used to demonstrate that the retention properties of sodium dodecyl sulfate (1.4% w\\/v), n-butanol (8% v\\/v) and n-heptane (1.2% v\\/v) microemulsion are strongly correlated

Salwa K. Poole; Sneha Patel; Karen Dehring; Heather Workman; Jessica Dong

2003-01-01

283

Molecular interaction studies of acrylic esters with 1-alcohols  

Microsoft Academic Search

Hydrogen bonding between 1-alcohols and acrylic esters in n-heptane has been studied by FTIR spectroscopic method. The formation constant of the 1:1 complexes has been calculated using Nash method. The values of formation constant and free energy change vary with alcohol and ester chain length, which suggests that the strengths of the intermolecular O–H?OC bonds are shown to be dependent

P. Sivagurunathan; K. Dharmalingam; K. Ramachandran

2006-01-01

284

Molecular interactions in alcohol–ethyl methacrylate mixtures  

Microsoft Academic Search

Molecular interaction between alcohols (1-propanol, 1-butanol, s-butanol, t-butanol, 1-pentanol, 1-heptanol, 1-octanol and 1-decanol) with ethyl methacrylate has been studied in n-heptane, CCl4 and benzene at 298K using FTIR spectroscopic and dielectric methods. The result obtained from both the methods indicates only the existence of most likely 1:1 complex formation between the alcohol and ethyl methacrylate in these systems. The alkyl

K. Dharmalingam; K. Ramachandran; P. Sivagurunathan; G. M. Kalamse

2008-01-01

285

Hydrogen bonding interaction between acrylic esters and monohydric alcohols in non-polar solvents: An FTIR study  

Microsoft Academic Search

The association between acrylic esters (methyl methacrylate, ethyl methacrylate and butyl methacrylate) and some monohydric (primary, secondary and tertiary) alcohols in non-polar solvents, viz. n-heptane, CCl4 and benzene has been investigated by means of FTIR spectroscopy. The most likely association complex between alcohol and acrylic ester is 1:1 stoichiometric complex through the hydroxyl group of alcohol and the carbonyl group

K. Dharmalingam; K. Ramachandran; P. Sivagurunathan

2007-01-01

286

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

287

Autoignition quality of gasoline fuels in partially premixed combustion in diesel engines  

Microsoft Academic Search

A single-cylinder diesel engine has been run on gasolines of different octane numbers and on model fuels, mixtures of iso-octane, n-heptane and toluene, at different operating conditions. The autoignition quality of the fuel is best described by an Octane Index, OI=(1?K)·RON+K·MON for fuels in the gasoline autoignition range where RON and MON are, respectively, the Research and Motor Octane numbers

G. T. Kalghatgi; L. Hildingsson; A. J. Harrison; B. Johansson

2011-01-01

288

Radical formation in ethanol and heptane following the nuclear transformation of ⁵⁷Co  

Microsoft Academic Search

A radiochromatographic method was used to determine the relative yields of alkyl iodides formed as a result of electron capture by ⁵⁷Co in ethanol and n-heptane containing radioactive iodine at room temperature. In both systems the usual radiolysis due to Auger electrons is accompanied by a more severe fragmentation connected with the formation of highly ionized solvent molecules in Auger

V. B. Torshin; E. S. Filatov; Yu. D. Perfilev

1987-01-01

289

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

290

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

291

Structure characterization of petroleum vacuum residues by in-beam EI Fourier transform ion cyclotron resonance mass spectrometry  

Microsoft Academic Search

A n-heptane soluble fraction (AH-VR-Sa) of Arabian heavy vacuum residues (AH-VR) has been analyzed by in-beam electron ionization Fourier transform ion cyclotron resonance mass spectrometry (EI FT-ICR MS). The probe temperature and the ionization energy of in-beam EI were independently adjusted to expand the detectable range of peaks originating from components of AH-VR-Sa and to prevent fragmentation of the molecular

Keiko Miyabayashi; Yasuhide Naito; Kazuo Tsujimoto; Mikio Miyake

2002-01-01

292

Selective pressurized liquid extraction of polychlorinated dibenzo- p-dioxins, dibenzofurans and dioxin-like polychlorinated biphenyls from food and feed samples  

Microsoft Academic Search

Selective pressurized liquid extraction (PLE) of polychlorinated dibenzo-p-dioxins\\/dibenzofurans (PCDD\\/Fs) and dioxin-like polychlorinated biphenyls (dl-PCBs) from various food and feed samples was performed with a selective PLE method previously developed for bulk PCBs. The method utilizes sulfuric acid impregnated silica inside the extraction cell to oxidize coextracted fat. Extractions were performed at 100°C with n-heptane for 5min in two cycles. Data

Karin Wiberg; Sune Sporring; Peter Haglund; Erland Björklund

2007-01-01

293

Synthesis and studies on spectroscopic as well as electron donating properties of the two alkoxy benzo[ b]thiophenes  

Microsoft Academic Search

Synthesis, characterization, steady state and time resolved, using time correlated single photon counting as well as laser flash photolysis techniques, spectroscopic investigations were made for two alkoxy benzo[b]thiophene molecules: 5-methoxy benzo[b]thiophene (5MBT) and 5-methoxymethyl benzo[b]thiophene (5MMBT). In both non-polar n-heptane (NH) and polar acetonitrile (ACN) solvents and at ambient temperature the electronic absorption spectra of these thiophenes exhibit different band

T. Misra; T Ganguly; S Kamila; C Basu; A De

2001-01-01

294

Involvements of phenyldibenzophosphole and 9-phenylcarbazole in electron transfer reactions with photoexcited 9-cyanoanthracene  

Microsoft Academic Search

9-Cyanoanthracene (9CNA), used as an electron acceptor, has been subjected to photoexcitation in the presence of both the electron donors, phenyldibenzophosphole (PDP) and 9-phenylcarbazole (9PC). Steady state and time resolved (fluorescence lifetime by time correlated single photon counting and laser flash photolysis) spectroscopic measurements were made both in non-polar n-heptane (NH) and polar aprotic acetonitrile (ACN) at the ambient temperature.

T. Sahu; S. K. Pal; T. Misra; T. Ganguly

2005-01-01

295

Transition from cool flame to thermal flame in compression ignition process  

SciTech Connect

The mechanism that initiates thermal flames in compression ignition has been studied. Experimentally, a homogeneous charge compression ignition (HCCI) engine was used with DME, n-heptane, and n-decane. Arrhenius plots of the heat release rate in the HCCI experiments showed that rates of heat release with DME, n-heptane, and n-decane exhibited a certain activation energy that is identical to that of the H{sub 2}O{sub 2} decomposition reaction. The same feature was observed in diesel engine operation using ordinary diesel fuel with advanced ignition timing to make ignition occur after the end of fuel injection. These experimental results were reproduced in nondimensional simulations using kinetic mechanisms for DME, n-heptane, and n-decane, the last being developed by extending the n-heptane mechanism. Methanol addition, which suppresses low-temperature oxidation (LTO) and delays the ignition timing, had no effect on the activation energy obtained from the Arrhenius plot of heat release rate. Nevertheless, methanol addition lowered the heat release rates during the prethermal flame process. This is because H{sub 2}O{sub 2} formation during cool flame was reduced by adding methanol. The mechanism during the transition process from cool flame to thermal flame can be explained quantitatively using thermal explosion theory, in which the rate-determining reaction is H{sub 2}O{sub 2} decomposition, assuming that heat release in this period is caused by partial oxidation of DME and HCHO initiated with the reaction with OH produced though H{sub 2}O{sub 2} decomposition. (author)

Yamada, Hiroyuki; Suzaki, Kotaro; Goto, Yuichi [National Traffic Safety and Environment Laboratory, 7-42-27 Jindaiji-Higashimachi, Chofu, Tokyo 182-0012 (Japan); Tezaki, Atsumu [Department of Mechanical and Intellectual Systems Engineering, University of Toyama, Gofuku 3190, Toyama-shi, Toyama 930-8555 (Japan)

2008-07-15

296

Experiments on the effect of initial diameter in spherically symmetric droplet combustion of sooting fuels  

NASA Technical Reports Server (NTRS)

The effect of initial droplet diameter on the burning rate of sooting fuels (n-heptane and 1-chloro-octane) is studied experimentally at low gravity. A 1.2 s drop tower provided a low gravity environment to minimize buoyancy and achieve spherically symmetric flames for stationary droplets. Free-floating and fiber supported droplets were burned, and both methods gave matching results for droplets of similar initial diameter.

Jackson, G. S.; Avedisian, C. T.

1993-01-01

297

TLC Profiling of Impurities of 1?(3,4?Methylenedioxyphenyl)?2?nitropropene an Intermediate in MDMA Synthesis. Influence of Sample Preparation Methods and Conditions  

Microsoft Academic Search

Thin?layer chromatography (TLC) was employed for screening profiling of impurities of 1?(3,4?methylenedioxyphenyl)?2?nitropropene, an intermediate product of (3,4?methylenedioxy)methamphetamine (MDMA) synthesis (from piperonal). Liquid–liquid extraction (LLE) and solid phase extraction (SPE) were applied to isolate impurities from the drug matrix. The SPE extraction process was performed on C8 columns and LLE was carried out using n?heptane. The influence of buffer solutions (pH

J. Kochana; J. Wilamowski; A. Parczewski

2004-01-01

298

Study on octane number dependence of PRF\\/air weak flames at 1–5 atm in a micro flow reactor with a controlled temperature profile  

Microsoft Academic Search

Combustion and ignition characteristics of a stoichiometric gaseous Primary Reference Fuel (blended fuel of n-heptane and iso-octane, PRF)\\/air mixture were investigated by using a micro flow reactor with a controlled temperature profile.By changing the mixture flow velocity at the inlet of the reactor, three kinds of flames were observed: normal propagating flame in a high flow velocity region; unstable flames,

Mikito Hori; Akira Yamamoto; Hisashi Nakamura; Takuya Tezuka; Susumu Hasegawa; Kaoru Maruta

299

Mapping surrogate gasoline compositions into RON\\/MON space  

Microsoft Academic Search

In this paper, new experimentally determined octane numbers (RON and MON) of blends of a tri-component surrogate consisting of toluene, n-heptane, i-octane (called toluene reference fuel TRF) arranged in an augmented simplex design are used to derive a simple response surface model for the octane number of any arbitrary TRF mixture. The model is second-order in its complexity and is

Neal Morgan; Andrew Smallbone; Amit Bhave; Markus Kraft; Roger Cracknell; Gautam Kalghatgi

2010-01-01

300

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

301

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

302

A study of Fischer-Tropsch model compounds reacting over ZSM-5  

E-print Network

then dehydrated to form 1-decene. Decanal was seen to decompose by three different mechanisms, aldol condensation, cleavage of CO to form n-nonane, and reduction to 1-decanol. Heptane was seen to follow classical carbonium ion chemistry. First order rate... 10 Liquid Partial Product Distribution For Cracking of n-Heptane on Ni-ZSM-5 at 680 K 36 11 Mechanism for Decanal Decomposition to n-Nonane and CO 12 Mechanism for Decanal Aldol Condensation. . . . . . . . . . . 40 CHAPTER INTRODUCTION Since...

Riley, Mark Garner

1984-01-01

303

Gas Dynamic Features of Self Ignition of Non Diluted Fuel\\/Air Mixtures at High Pressure  

Microsoft Academic Search

– The self ignition of several non diluted fuel\\/air mixtures at high pressureis studied. Hydrogen,rsc-ocrane and n-heptane have been used as fuels. Experimentshave been performedusing the shock tube technique. Various observation methods, such as recording of pressure and of light band emission and shadow cinematography have been applied. The type of self ignition 35 well as the ignition delay times

R. BLUMENTHAL; K. FIEWEGER; K. H. KOMP; G. ADOMEIT

1997-01-01

304

Gas Dynamic Features of Self Ignition of Non Diluted Fuel\\/Air Mixtures at High Pressure  

Microsoft Academic Search

The self ignition of several non diluted fuel\\/air mixtures at high pressure is studied. Hydrogen, iso-octane and n-heptane have been used as fuels. Experiments have been performed using the shock tube technique. Various observation methods, such as recording of pressure and of light band emission and shadow cinematography have been applied. The type of self ignition as well as the

R. BLUMENTHAL; K. FIEWEGER; K. H. KOMP; G. ADOMEIT

1996-01-01

305

LARGE-ACTIVATION-ENERGY ASYMPTOTIC ANALYSIS OF MULTICOMPONENT-FUEL DIFFUSION FLAMES  

Microsoft Academic Search

This analysis addresses some aspects of the internal structure and extinction of diffusion flames established by burning of multicomponent fuel (n-heptane diffusion flame enriched with hydrogen). By presuming one-global-step reactions with large activation energy, the zone where all reactions take place is described by large-activation-energy asymptotics. In this study, it is also supposed that the values of the Damköhler numbers

FERNANDO F. FACHINI

2005-01-01

306

Experiments And Model Development For The Investigation Of Sooting And Radiation Effects In Microgravity Droplet Combustion  

NASA Technical Reports Server (NTRS)

This study involves flight experiments (for droplets between 1.5 to 5 mm) and supportive ground-based experiments, with concurrent numerical model development and validation. The experiments involve two fuels: n-heptane, and ethanol. The diagnostic measurements include light extinction for soot volume fraction, two-wavelength pyrometry and thin-filament pyrometry for temperature, spectral detection for OH chemiluminescence, broadband radiometry for flame emission, and thermophoretic sampling with subsequent transmission electron microscopy for soot aerosol property calculations.

Yozgatligil, Ahmet; Choi, Mun Young; Dryer, Frederick L.; Kazakov, Andrei; Dobashi, Ritsu

2003-01-01

307

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

308

Application of solvent engineering to optimize lipase-catalyzed 1,3-diglyacylcerols by mixture response surface methodology.  

PubMed

1,3-Diacylglycerol (DAG) has been introduced in Japan as a cooking oil under the trade name of Econa to reduce body fat accumulation. Solvent engineering was applied to determine the optimum solvent mixtures for the lipase-catalyzed synthesis of 1,3-DAG by mixture response surface methodology. n-Hexane was required to maintain the lipase activity and the product selectivity could be adjusted by changing the hydrophobicity of reaction medium. The optimum yield (approximately 40%) of 1,3-DAG synthesis was obtained with n-hexane/octane (1:1, v/v). PMID:14677712

Liao, Hui-Fen; Tsai, Wei-Chuan; Chang, Shu-Wei; Shieh, Chwen-Jen

2003-11-01

309

A tabulated chemistry approach for numerical modeling of diesel spray evaporation in a 'stabilized cool flame' environment  

SciTech Connect

Droplet evaporation in a 'stabilized cool flame' environment leads to a homogeneous, heated air-fuel vapor mixture that can be subsequently either burnt or utilized in fuel-reforming applications for fuel cell systems. The paper investigates the locally occurring physico-chemical phenomena in an atmospheric pressure, diesel spray, stabilized cool flame reactor, utilizing a tabulated chemistry approach in conjunction with a two-phase, Eulerian-Lagrangian computational fluid dynamics code. Actual diesel oil physical properties are used to model spray evaporation in the two-phase simulations, whereas the corresponding chemistry is represented by n-heptane. A lookup table is constructed by performing a plethora of perfectly stirred reactor simulations, utilizing a semidetailed n-heptane oxidation chemical kinetics mechanism. The overall exothermicity of the preignition n-heptane oxidation chemistry and the fuel consumption rates are examined as a function of selected independent parameters, namely temperature, fuel concentration, and residence time; their influence on cool flame reactivity is thoroughly studied. It is shown that the tabulated chemistry approach allows accurate investigation of the chemical phenomena with low computational cost. The two-phase flow inside the stabilized cool flame reactor is simulated, utilizing the developed lookup table. Predictions are presented for a variety of test cases and are compared to available experimental data, with satisfactory agreement. Model validation tests indicate that prediction quality improves with increasing values of air temperature at the reactor's inlet. (author)

Kolaitis, D.I.; Founti, M.A. [Heterogeneous Mixtures and Combustion Systems, Thermal Engineering Section, School of Mechanical Engineering, National Technical University of Athens, Heroon Polytechniou 9, Polytechnioupoli Zografou, 15780 Athens (Greece)

2006-04-15

310

Observations of soot during droplet combustion at low gravity - Heptane and heptane/monochloroalkane mixtures  

NASA Technical Reports Server (NTRS)

Experimental observations of the combustion of sooting fuel droplets, performed in a drop tower to create a low gravity environment, are reported. Free n-heptane droplets and suspended droplets of heptane, monochloroalkanes, and mixtures of monochloro-octane and heptane were studied. Initial droplet diameters ranged from 0.4 to 1.1. mm. The results suggest that soot may influence droplet vaporization rates. Spherical symmetry of the flame allowed for extended observation of soot agglomerates inside the droplet flame. Effects of slight convective flows were also observed, both through variations of natural convection around the suspended droplets and through variations in the drift velocities of the unsupported droplets. Slight convective flows around the suspended droplets reduced flame luminosity as well as soot accumulation inside the flame and increased droplet vaporization rates. Mixing monochloro-octane with n-heptane demonstrated the effectiveness of n-heptane in reducing soot emissions from the flames of the chlorinated fuels. Finally, trends of initial droplet diameter with burning rate were observed and may be linked to the effect of droplet size upon soot formation inside the flame.

Jackson, G. S.; Avedisian, C. T.; Yang, J. C.

1992-01-01

311

Structural and phase transformations during ball milling of titanium in medium of liquid hydrocarbons  

NASA Astrophysics Data System (ADS)

It has been shown using X-ray diffraction, scanning electron microscopy, and chemical analysis that, upon ball milling of ?-titanium in liquid organic media (toluene and n-heptane), a nanocrystalline fcc phase is formed that is a metastable carbohydride Ti(C,H) deficient in hydrogen and carbon compared to stable carbohydrides. The dimensions of powder particles after milling in toluene and n-heptane differ substantially (are 5-10 and 20-30 ?m, respectively. It has been shown that the kinetics of the formation of Ti(C,H) is independent of the milling medium. The atomic ratios H/C in the products of mechanosynthesis agree well with those corresponding to the employed organic media, i.e., H/C = 1.1 for toluene and 2.3 for n-heptane. A solid-liquid mechanism of mechanosynthesis is suggested, which includes repeated processes of particle fracturing with the formation of fresh surfaces, adsorption of liquid hydrocarbons on these surfaces, and subsequent cold welding of the newly formed particles. It is assumed that the formation of the fcc phase in the process of milling is connected with the generation of stacking faults in ?-Ti. Upon annealing at 550°C, the fcc phase decomposes with the formation of stable titanium carbide TiC (annealing in a vacuum) or stable titanium carbohydride and a ?-Ti(H) solid solution (annealing in argon) with a partial reverse transformation Ti(C,H) ? ?-Ti in both cases.

Dorofeev, G. A.; Lubnin, A. N.; Lad'yanov, V. I.; Mukhgalin, V. V.; Puskkarev, B. E.

2014-02-01

312

Fuel-Specific Effect of Exhaust Gas Residuals on HCCI Combustion: A Modeling Study  

SciTech Connect

A modeling study was performed to investigate fuel-specific effects of exhaust gas recirculation (EGR) components on homogeneous charge compression ignition (HCCI) combustion at conditions relevant to the negative valve overlap (NVO) strategy using CHEMKIN-PRO. Four single-component fuels with well-established kinetic models were chosen: n-heptane, iso-octane, ethanol, and toluene. These fuels were chosen because they span a wide range of fuel chemistries, and produce a wide compositions range of complete stoichiometric products (CSP). The simulated engine conditions combined a typical spark ignition engine compression ratio (11.34) and high intake charge temperatures (500-550 K) that are relevant to NVO HCCI. It was found that over the conditions investigated, all the fuels had overlapping start of combustion (SOC) phasing, despite the wide range in octane number (RON = 0 to 120). The effect of the EGR components CO2 and H2O was to suppress the compression temperature because of their higher heat capacities, which retarded SOC. For a concentration of O2 higher than the stoichiometric amount, or excess O2, there was an effect of advancing SOC for n-heptane, iso-octane, and toluene, but SOC for ethanol was not advanced. Low temperature heat release (LTHR) for n-heptane was also found to be highly dependent on excess O2, and mild endothermic reaction was observed for cases when excess O2 was not present.

Szybist, James P [ORNL

2008-01-01

313

Screening seeds of Scottish plants for antibacterial activity  

Microsoft Academic Search

Based on ethnopharmacological and taxonomic information, seeds of 21 Scottish plant species from 14 different families were obtained from authentic seed suppliers. Their n-hexane, dichloromethane and methanol extracts were assessed for antibacterial activity against 11 pathogenic bacterial species. Methanol extracts of 11 plant species showed significant antibacterial activity. Malva moschata and Prunus padus were active against five bacterial species, Reseda

Yashodharan Kumarasamy; Philip John Cox; Marcel Jaspars; Lutfun Nahar; Satyajit Dey Sarker

2002-01-01

314

Fischer-Tropsch synthesis in supercritical reaction media. Progress report, October 1, 1992--December 31, 1992  

SciTech Connect

Our goals for this quarter were to complete construction of the reactor and analytical units for carrying out Fischer-Tropsch (F-T) synthesis in liquid (n-hexadecane) and in supercritical n-hexane phases. Progress during this quarter was slower than expected.

Subramaniam, B.; Bochniak, D.; Snavely, K.

1993-01-01

315

Fischer-Tropsch synthesis in supercritical reaction media  

SciTech Connect

Our goals for this quarter were to complete construction of the reactor and analytical units for carrying out Fischer-Tropsch (F-T) synthesis in liquid (n-hexadecane) and in supercritical n-hexane phases. Progress during this quarter was slower than expected.

Subramaniam, B.; Bochniak, D.; Snavely, K.

1993-01-01

316

Synthesis of ethyl butyrate in organic media catalyzed by Candida rugosa lipase immobilized in polyurethane foams: A kinetic study  

Microsoft Academic Search

A kinetic study on the synthesis of ethyl butyrate in n-hexane, catalyzed by Candida rugosa lipase immobilized in two hydrophilic polyurethane foams (“HYPOL FHP 2002” and “HYPOL FHP 5000”) was performed. With the “FHP5000” foams, esterification rates and conversion were always higher than those obtained with “FHP2002”. For both immobilized preparations, BA did not cause any inhibition on the enzymatic

P. Pires-Cabral; M. M. R. da Fonseca; S. Ferreira-Dias

2009-01-01

317

Modelling the production of ethyl butyrate catalysed by Candida rugosa lipase immobilised in polyurethane foams  

Microsoft Academic Search

Response surface methodology was used to model and optimise the esterification of ethanol with butyric acid in n-hexane, catalysed by Candida rugosa lipase immobilised in two hydrophilic polyurethane foams (“FHP 2002™” and “FHP 5000™”). Experiments were carried out following central composite rotatable designs (CCRD), as a function of the initial water activity of the biocatalyst (aw), initial butyric acid concentration

P. Pires-Cabral; M. M. R. da Fonseca; S. Ferreira-Dias

2007-01-01

318

Esterification activity and operational stability of Candida rugosa lipase immobilized in polyurethane foams in the production of ethyl butyrate  

Microsoft Academic Search

Ethyl butyrate is a fruity flavor ester widely used in food and pharmaceutical products. The synthesis of ethyl butyrate in n-hexane, catalyzed by Candida rugosa lipase immobilized in two hydrophilic polyurethane foams (“HYPOL FHP 2002” and “HYPOL FHP 5000”) was performed. In this study, the effects of (i) the immobilization supports, (ii) the initial substrate concentrations and (iii) the water

P. Pires-Cabral; M. M. R. da Fonseca; S. Ferreira-Dias

2010-01-01

319

Environmental Hydrocarbons Produce Degeneration in Cat Hypothalamus and Optic Tract  

Microsoft Academic Search

2,5-Hexanedione, the principal neurotoxic metabolite of the industrial solvents n-hexane and methyl n-butyl ketone causes axonal degeneration in the mammillary body and visual nuclei of cats. Prolonged, low-level exposure to hydrocarbons in the environment may cause premature deterioration in areas of the human brain vital for perception and behavior.

Herbert H. Schaumburg; Peter S. Spencer

1978-01-01

320

A new ester coumarin from Ferula Persica wild, indigenous to Iran.  

PubMed

Ferula persica wild (Apiaceae) is a perennial herb indigenous to Iran. It has been used in folk medicine for treatment of diabetes, lowering of blood pressure and for antispasmodic, carminative, laxative and expectorant effects in central Iran. Dried ground roots of F. persica (150 g) were extracted sequentially with n-hexane, dichloromethane and methanol (MeOH), 500 ml each, using a Soxhlet apparatus. The n-hexane extract of the roots (3 g) was subjected to vacuum liquid chromatography on silica gel, eluting with solvent mixtures of increasing polarity: 100% n-hexane-ethyl acetate (EtOAc), to yield a number of fractions, Fraction 4 (80% EtOAc in n-hexane) was further analysed by preparative TLC (mobile phase was 12% acetone in chloroform) to yield a coumarin ester (10.1 mg, Rf = 0.31, blue florescent). The structure of the isolated compound was elucidated by spectroscopic means. The compound is 7-O-(4,8,12 -trihydroxy-4,8,12-trimethyl-tridecanoyl)-coumarin, named, ferulone C as a new natural product. PMID:25427054

Razavi, Seyed Mehdi; Janani, Mehrnoush

2014-11-26

321

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

322

SPECTROFLUOROMETRIC AND HIGH-PERFORMANCE LIQUID CHROMATOGRAPHIC DETERMINATION OF a-TOCOPHEROL ACETATE IN OLIVE OIL  

Technology Transfer Automated Retrieval System (TEKTRAN)

A high performance liquid chromatographic (HPLC) method was developed for the quantitative determination of '-acetate tocopherol in olive oil. After extracts in n-hexane, acetate '- tocopherol were quantitatively analyzed by HPLC with fluorimetric detector. The presence of acetate '- tocopherol in...

323

INHIBITORY EFFECTS OF TABEBUIA IMPETIGINOSA INNER BARK EXTRACT ON PLATELET AGGREGATION AND VASCULAR SMOOTH MUSCLE CELL PROLIFERATION THROUGH SUPPRESSIONS OF ARACHIDONIC ACID LIBERATION AND ERK1/2 MAPK ACTIVATION  

Technology Transfer Automated Retrieval System (TEKTRAN)

The antiplatelet and antiproliferation activities of Tabebuia impetiginosa Martius ex DC (taheebo) were investigated using washed rabbit platelets and rat aortic vascular smooth muscle cells (VSMCs) in vitro. The methanol extract of taheebo was separated into five sub-fractions using n-hexane, chlo...

324

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...

325

40 CFR 60.696 - Performance test methods and procedures and compliance provisions.  

Code of Federal Regulations, 2010 CFR

...60.693, the owner or operator shall inspect such equipment...emissions, defects, or other problems that may cause the requirements...plugs. (b) The owner or operator of each source that is...n-hexane. (c) The owner or operator shall conduct a...

2010-07-01

326

Frying Stability of Moringa stenopetala Seed Oil  

Microsoft Academic Search

The frying performance of Moringa stenopetala seed oil (extracted with cold press or n-hexane) 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 C for 5 consecutive days (5 fryings per day). The chemical changes occurring in oils were evaluated. Free fatty acid content,

Stavros Lalas; Olga Gortzi; John Tsaknis

2006-01-01

327

Studies on Achras sapota L; part III. Isolation and identification of some triterpenoids from the leaves of Achras sapota L.  

PubMed

The triterapenoids present in the leaves of Achras sapota L belongs mainly to alpha/beta-Amyrin and Lupenol series. A long straight chain hydrocarbon, tritriacontane was also found to be present in the n-Hexane extract of the leaves. PMID:16414645

Ahmed, R; Tabassum, S; Ifzal, S M

1989-07-01

328

[Chromatographic separation of aminoglutethimide enantiomers on cellulose tris(3,5-dimethylphenylcarbamate) chiral stationary phase].  

PubMed

Aminoglutethimide (AG) has been used clinically as a drug in the treatment of hormone-dependent metastatic breast cancer. It was reported that S-(-)-AG enantiomer had small activity and sometimes might cause side effects. Therefore, it was of great significance to obtain the high-purity R-(+)-AG by enantioseparation. In this work, aminoglutethimide enantiomers were separated by high performance liquid chromatography (HPLC) using an analytical column which was packed with cellulose tris(3,5-dimethylphenylcarbamate) stationary phase (Chiralcel OD-H). The solubilities of racemic AG in two different solvent compositions, n-hexane/ethanol and n-hexane/isopropanol, were measured, separately. The effects of alcohol content and monoethanolamine additive on the separation performance of racemic AG by HPLC were investigated. According to the experiments, n-hexane-ethanol (30:70, v/v) with 0.1% monoethanolamine additive was selected as the mobile phase. The separation factor, resolution, asymmetry factor, number of theoretical plates and maximum column capacity were measured and analyzed for the chromatographic separation of racemic AG at a flow-rate of 0. 6 mL/min and column temperature of 25-40 °C, with Chiralcel OD-H as stationary phase and n-hexane-ethanol (30:70, v/v) with 0. 1% monoethanolamine as mobile phase. This work provides the basic information of chromatographic separation for the batch and continuous production of aminoglutethimide enantiomers. PMID:25507724

Lin, Xiaoiian; Gong, Rujin; Li, Ping; Yu, Jianguo

2014-08-01

329

[Chromatographic separation of aminoglutethimide enantiomers on cellulose tris(3,5-dimethylphenylcarbamate) chiral stationary phase].  

PubMed

Aminoglutethimide (AG) has been used clinically as a drug in the treatment of hormone-dependent metastatic breast cancer. It was reported that S-(-)-AG enantiomer had small activity and sometimes might cause side effects. Therefore, it was of great significance to obtain the high-purity R-(+)-AG by enantioseparation. In this work, aminoglutethimide enantiomers were separated by high performance liquid chromatography (HPLC) using an analytical column which was packed with cellulose tris(3,5-dimethylphenylcarbamate) stationary phase (Chiralcel OD-H). The solubilities of racemic AG in two different solvent compositions, n-hexane/ethanol and n-hexane/isopropanol, were measured, separately. The effects of alcohol content and monoethanolamine additive on the separation performance of racemic AG by HPLC were investigated. According to the experiments, n-hexane-ethanol (30:70, v/v) with 0.1% monoethanolamine additive was selected as the mobile phase. The separation factor, resolution, asymmetry factor, number of theoretical plates and maximum column capacity were measured and analyzed for the chromatographic separation of racemic AG at a flow-rate of 0. 6 mL/min and column temperature of 25-40 °C, with Chiralcel OD-H as stationary phase and n-hexane-ethanol (30:70, v/v) with 0. 1% monoethanolamine as mobile phase. This work provides the basic information of chromatographic separation for the batch and continuous production of aminoglutethimide enantiomers. PMID:25434126

Lin, Xiaoiian; Gong, Rujin; Li, Ping; Yu, Jianguo

2014-08-01

330

REMOVAL OF HYDROPHOBIC MICRO?ORGANIC POLLUTANTS FROM MUNICIPAL WASTEWATER TREATMENT PLANT EFFLUENTS BY SORPTION ONTO SYNTHETIC POLYMERIC ADSORBENTS: UPFLOW COLUMN EXPERIMENTS  

Microsoft Academic Search

Continuous upflow bench?scale column experiments were carried out to investigate the use of a synthetic form polymer, polypropylene, and polypropylene coated with a thin layer of n?hexane as sorbents for hydrophobic organic compounds present in the effluent of municipal wastewater treatment plant. Two polycyclic aromatic hydrocarbons, namely, phenanthrene and fluorene, were selected as representative hydrophobic organic compounds for experimental purposes.

V. S. Muhandiki; Y. Shimizu; Y. A. F. Adou; S. Matsui

2008-01-01

331

NMR Imaging as a Tool for Studying the Diffusion and Co-Diffusion of Gases in Zeolite Catalysts  

Microsoft Academic Search

H NMR imaging is a powerful technique for studying the diffusion of pure hydrocarbons (for example benzene and n-hexane) during their adsorption in or desorption from a fixed bed of zeolite crystallites. This technique is used to visualize the progression of the diffusing molecules in the zeolite bed and to determine their intracrystallite diffusion coefficients. More importantly, NMR imaging is

J. Fraissard

332

Chemical composition, antimicrobial and antioxidant activities of Centaurea ensiformis Hub.Mor. (Asteraceae), a species endemic to Mugla (Turkey)  

Microsoft Academic Search

The n-hexane, chloroform, ethyl acetate and ethyl alcohol extracts of the aerial parts of Centaurea ensiformis, endemic to Turkey, have been assessed for antimicrobial and antioxidant activities. The chemical composition of the hexane extract of this plant was determined. The antimicrobial activities on microorganisms, including multiple antibiotic resistant bacteria, were evaluated using the disc diffusion method. The antioxidant activities were

Aysel Ugur; Mehmet Emin Duru; Ozgur Ceylan; Nurdan Sarac; Omer Varol; Ibrahim Kivrak

2009-01-01

333

21 CFR 177.1520 - Olefin polymers.  

Code of Federal Regulations, 2012 CFR

...9003-07-0), resulting from the reaction of a mixture of methyl methacrylate...6 to 37 kilopoise at a shear rate of 100?1 seconds at 232...12 to 27 kilopoise at a shear rate of 100?1 seconds at 232...give a smooth and uniform stir rate. Allow the n -hexane...

2012-04-01

334

21 CFR 177.1520 - Olefin polymers.  

Code of Federal Regulations, 2013 CFR

...9003-07-0), resulting from the reaction of a mixture of methyl methacrylate...6 to 37 kilopoise at a shear rate of 100?1 seconds at 232...12 to 27 kilopoise at a shear rate of 100?1 seconds at 232...give a smooth and uniform stir rate. Allow the n -hexane...

2013-04-01

335

21 CFR 177.1520 - Olefin polymers.  

Code of Federal Regulations, 2014 CFR

...9003-07-0), resulting from the reaction of a mixture of methyl methacrylate...6 to 37 kilopoise at a shear rate of 100?1 seconds at 232...12 to 27 kilopoise at a shear rate of 100?1 seconds at 232...give a smooth and uniform stir rate. Allow the n -hexane...

2014-04-01

336

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

337

Cytotoxicity and modulation of cancer-related signaling by (Z)- and (E)- 3,4,3´,5´ tetramethoxystilbene isolated from Eugenia rigida  

Technology Transfer Automated Retrieval System (TEKTRAN)

The leaves of E. rigida DC (Myrtaceae) were collected from Puerto Rico in March, 2006. The sample was identified by Mr. F. Axelrod and a voucher specimen (3008783) was deposited at the Herbarium of Missouri Botanical Garden, St. Louis, MO. Air-dried powdered leaves (107 g) were soaked in n-hexane an...

338

Determination of assay and impurities of gamma irradiated chloramphenicol in eye ointment  

Microsoft Academic Search

A sample preparation method was developed to isolate chloramphenicol and its radiolytic products from an oily ointment base. The isolation method suspended the eye ointment in n-hexane at 45°C, and isolated the target compounds as residue by centrifugation. It was found that the main element to ensure a satisfactory isolation was keeping the sample solution at 45°C during sample preparation.

Lan Hong; Hans Altorfer

2001-01-01

339

Classification of edible oils using synchronous scanning fluorescence spectroscopy  

Microsoft Academic Search

Total luminescence and synchronous scanning fluorescence spectroscopy techniques were tested as regards their ability to characterize and differentiate edible oils, including soybean, sunflower, rapeseed, peanut, olive, grapeseed, linseed and corn oils. Total luminescence spectra of all oils studied as n-hexane solutions exhibit an intense peak, which appears at 290 nm in excitation and 320 nm in emission, attributed to tocopherols.

Ewa Sikorska; Tomasz Górecki; Igor V Khmelinskii; Marek Sikorski; Jacek Kozio?

2005-01-01

340

In vitro antioxidant activity and inhibitory effect, on oleic acid-induced hepatic steatosis, of fractions and subfractions from oat (Avena sativa L.) ethanol extract  

Technology Transfer Automated Retrieval System (TEKTRAN)

Oats (Avena sativa L.) were extracted with 80% aqueous ethanol and the extract was successively isolated by liquid-liquid partition to yield n-hexane, ethyl acetate, n-butanol and water layers. Among these extractions the ethyl acetate (EA) layer exhibited the highest total phenolic content (TPC), t...

341

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

342

Protective effect of Emilia sonchifolia (L.) against high protein diet induced oxidative stress in pancreas of Wistar rats  

PubMed Central

Objectives: The present study was undertaken to investigate the oxidative damage, the biochemical and histopathological changes in the pancreas of the Wistar rats which was fed high protein diet and the recovery after the oral administration of the n-hexane extract of the herb, Emilia sonchifolia. Materials and Methods: The rats fed with high protein diet for a period of 30 days and treated with n-hexane extract of Emilia sonchifolia (250 mg/kg body weight). Body weight, pancreatic weight, serum amylase, lipase, aspartate transaminase, alanine transaminase, urea, uric acid, creatinine, DNA and RNA content of the pancreas, pancreatic enzymatic and non-enzymatic antioxidants such as superoxide dismutase, catalase, glutathione peroxidase, reduced glutathione, and vitamin C were evaluated. Results and Discussion: At the end of the study the rats gained less body weight and showed a significant (P < 0.05) increase in serum levels of amylase, lipase, aspartate transaminase, alanine transaminase, urea, uric acid, creatinine, tissue DNA, and RNA content and showed a significant (P < 0.05) decrease in the pancreatic antioxidants. Treatment with the n-hexane extract ameliorated the damage caused by high protein diet. This was also evidenced by histopathological studies. Conclusion: From the results, it was suggested that the n-hexane extract of Emilia sonchifolia has an effective medicinal property and can act as a pancreato-protective herb. PMID:22368400

Sophia, Dominic; Ragavendran, Paramasivam; Raj, Chinthamony Arul; Gopalakrishnan, Velliyur Kanniappan

2012-01-01

343

KINETICS AND SELECTIVITY OF DEEP CATALYTIC OXIDATION OF VOLATILE ORGANIC COMPOUND MIXTURES  

EPA Science Inventory

The paper gives results of a fundamental study of low-temperature deep (complete) oxidation of n-hexane, benzene, and ethyl-acetate over a 0.1% Pt, 3% Ni/gamma-AL203 catalyst. (NOTE: Deep catalytic combustion of volatile organic compounds--VOCs--is emerging as an important emissi...

344

SIGMA-ALDRICH MATERIAL SAFETY DATA SHEET  

E-print Network

N-HEXANE 110-54-3 Yes Formula C6H14 Synonyms Esani (Italian) * Gettysolve-B * Heksan (Polish) * n is difficult, give oxygen. DERMAL EXPOSURE In case of contact, immediately wash skin with soap and copious spray. Carbon dioxide, dry chemical powder, or appropriate foam. FIREFIGHTING Protective Equipment: Wear

Choi, Kyu Yong

345

Processing of commercial peanut cake into food-grade meal and its utilization in preparation of cookies  

Microsoft Academic Search

The commercial cake produced during expeller pressing of peanuts was extracted with n-hexane, and 80% ethanol followed by sieving through 80 mesh, to remove residual oil, pigments, bitter taste and fibrous material. The processed meal exhibited comparable composition with defatted peanut flour prepared in the laboratory by solvent extraction of full-fat peanut meal. However, the processed cake meal exhibited low

P. V. Tate; J. K. Chavan; P. B. Patil; S. S. Kadam

1990-01-01

346

Antimicrobial and antioxidant activities of Swietenia macrophylla leaf extracts  

Microsoft Academic Search

The antimicrobial and antioxidant activities of methanol, dichloromethane and n-hexane extracts of S. macrophylla leaves were evaluated. The antimicrobial activity of the extracts was tested against four species of bacteria, Staphylococcus aureus, Bacillus subtilis, Escherichia coli and Pseudomonas aeruginosa, and a fungus, Candida albicans. The methanol and the dichloromethane extracts were found to be active against the Gram- positive bacteria

Seok-Keik Tan; Hasnah Osman; Keng-Chong Wong; Peng-Lim Boey; Padzilah Ibrahim

347

Ethyl acetate-n-butanol gradient solvent system for high-speed countercurrent chromatography to screen bioactive substances in okra.  

PubMed

High-speed countercurrent chromatographic separation (HSCCC) possesses the property of zero-loss of sample, which is very useful for the screening of bioactive components. In the present study, the ethyl acetate-n-butanol gradient HSCCC solvent system composed of n-hexane-ethyl acetate-n-butanol-water was investigated for the screening of bioactive substances. To screen the antiproliferative compounds in okra extract, we used the stationary phase ethyl acetate-n-butanol-water (1:1:10) as the stationary phase, and eluted the antiproliferative components by 6-steps of gradient using mobile phases n-hexane-ethyl acetate (1:2), n-hexane-ethyl acetate (1:4), n-hexane-ethyl acetate (0:4), n-butanol-ethyl acetate (1:4) n-butanol-ethyl acetate (1:2), n-butanol-ethyl acetate (2:2), and n-butanol-ethyl acetate (2:1). The fractions collected from HSCCC separation with the gradient solvent system were assayed for antiproliferative activity against cancer cells. Bioactive components were identified: a major anti-cancer compound, 4'-hydroxy phenethyl trans-ferulate, with middle activity, and a minor anti-cancer compound, carolignan, with strong activity. The result shows that the gradient solvent system is potential for the screening of bioactive compounds from natural products. PMID:25069743

Ying, Hao; Jiang, Heyuan; Liu, Huan; Chen, Fangjuan; Du, Qizhen

2014-09-12

348

Effect of OH radical scavengers on secondary organic aerosol formation from reactions of isoprene with ozone  

NASA Astrophysics Data System (ADS)

In order to understand the effect of OH radical scavengers on secondary organic aerosol formation, aerosol yields from the isoprene ozonolysis were measured in the presence of sufficient amounts of OH radical scavengers. Cyclohexane, CO, n-hexane, and diethyl ether were used as the OH radical scavengers. The aerosol yield was determined to be 0.002-0.023 for experiments without OH radical scavengers in the aerosol mass range 2-120 ?g m-3. Similar aerosol yields were observed in experiments using cyclohexane. The aerosol yield observed with n-hexane was close to that observed without scavengers at 120 ?g m-3, but this aerosol yield was slightly lower than those observed in reactions without scavengers in the range 3-83 ?g m-3. The offline aerosol samples obtained in experiments with cyclohexane or n-hexane contained oxygenated hydrocarbons with six or more carbon atoms. Aerosol formation in experiments that used cyclohexane or n-hexane as the scavenger was enhanced. This was caused by the oxidation products of the OH radical scavengers, although the increase in the yield could not be quantified. The aerosol yields were 0.002-0.014 for experiments with CO and diethyl ether in the aerosol mass range 4-120 ?g m-3. The reaction of CO with OH radicals forms HO2 radicals, whereas the reactions of cyclohexane, n-hexane, and diethyl ether, respectively, with OH radicals form organic peroxy (RO2) radicals. Present results show that the aerosol yield is independent of the HO2/RO2 ratio or that it decreases with increasing HO2/RO2 ratio. Since the HO2 concentration is much higher than the RO2 concentration in the atmosphere, the results obtained using CO in this study will be a good approximation of the aerosol yield from the ozonolysis of isoprene in the atmosphere.

Sato, Kei; Inomata, Satoshi; Xing, Jia-Hua; Imamura, Takashi; Uchida, Risa; Fukuda, Sayaka; Nakagawa, Kazumichi; Hirokawa, Jun; Okumura, Motonori; Tohno, Susumu

2013-11-01

349

Separation of flavonoids from Millettia griffithii with high-performance counter-current chromatography guided by anti-inflammatory activity.  

PubMed

Millettia griffithii is a unique Chinese plant located in the southern part of Yunnan Province. Up to now, there is no report about its phytochemical or related bioactivity research. In our previous study, the n-hexane crude extract of Millettia griffithii revealed significant anti-inflammatory activity at 100 ?g/mL, inspiring us to explore the anti-inflammatory constituents. Four fractions (I, II, III, and A) were fractionated from n-hexane crude extract by high-performance counter-current chromatography with solvent system composed of n-hexane/ethyl acetate/methanol/water (8:9:8:9, v/v) and then were investigated for the potent anti-inflammatory activity. Fraction A, with the most potent inhibitory activity was further separated to give another four fractions (IV, V, VI, and B) with solvent system composed of n-hexane/ethyl acetate/methanol/water (8:4:8:4, v/v). Compound V and fraction B exhibited remarkable anti-inflammatory activity with nitric oxide inhibitory rate of 80 and 65%, which was worth further fractionation. Then, three fractions (VII, VIII, and IX) were separated from fraction B with a solvent system composed of n-hexane/ethyl acetate/methanol/water (8:1:8:1, v/v), with compound VIII demonstrating the most potent inhibitory activity (80%). Finally, the IC50 values of compound V and VIII were tested as 38.2 and 14.9 ?M. The structures were identified by electrospray ionization mass spectrometry and(1)H and (13)C NMR spectroscopy. PMID:25413585

Tang, Huan; Wu, Bo; Chen, Kai; Pei, Heying; Wu, Wenshuang; Ma, Liang; Peng, Aihua; Ye, Haoyu; Chen, Lijuan

2015-02-01

350

Novel modified zeolites for energy-efficient hydrocarbon separations.  

SciTech Connect

We present synthesis, characterization and testing results of our applied research project, which focuses on the effects of surface and skeletal modification of zeolites for significant enhancements in current hydrocarbon (HC) separations. Zeolites are commonly used by the chemical and petroleum industries as catalysts and ion-exchangers. They have high potential for separations owing to their unique pore structures and adsorption properties and their thermal, mechanical and chemical properties. Because of zeolites separation properties, low cost, and robustness in industrial process, they are natural choice for use as industrial adsorbents. This is a multidisciplinary effort to research, design, develop, engineer, and test new and improved materials for the separation of branched vs. linear organic molecules found in commercially important HC streams via adsorption based separations. The focus of this project was the surface and framework modification of the commercially available zeolites, while tuning the adsorption properties and the selectivities of the bulk and membrane separations. In particular, we are interested with our partners at Goodyear Chemical, on how to apply the modified zeolites to feedstock isoprene purification. For the characterization and the property measurements of the new and improved materials powder X-ray diffraction (PXRD), Residual Gas Analyzer-Mass Spectroscopy (RGA-MS), Electron Microscopy (SEM/EDAX), temperature programmed desorption (TPD) and surface area techniques were utilized. In-situ carbonization of MFI zeolite membranes allowed for the maximum separation of isoprene from n-pentane, with a 4.1% enrichment of the binary stream with n-pentane. In four component streams, a modified MFI membrane had high selectivities for n-pentane and 1-3-pentadiene over isoprene but virtually no separation for the 2-methyl-2-butene/isoprene pair.

Arruebo, Manuel (University of Colorado, Boulder, CO); Dong, Junhang; Anderson, Thomas (Burns and McDonnell, Kansas City, MO); Gu, Xuehong; Gray, Gary (Goodyear Chemical Company, Akron, OH); Bennett, Ron (Goodyear Chemical Company, Akron, OH); Nenoff, Tina Maria; Kartin, Mutlu; Johnson, Kaylynn (Goodyear Chemical Company, Akron, OH); Falconer, John (University of Colorado, Boulder, CO); Noble, Richard (University of Colorado, Boulder, CO)

2006-11-01

351

A remarkable solvent effect on the nuclearity of neutral titanium(IV)-based helicate assemblies.  

PubMed

The spontaneous self-assembly of a neutral circular trinuclear Ti(IV) -based helicate is described through the reaction of titanium(IV) isopropoxide with a rationally designed tetraphenolic ligand. The trimeric ring helicate was obtained after diffusion of n-pentane into a solution with dichloromethane. The circular helicate has been characterized by using single-crystal X-ray diffraction study, (13) C CP-MAS NMR and (1) H?NMR DOSY solution spectroscopic, and positive electrospray ionization mass-spectrometric analysis. These analytical data were compared with those obtained from a previously reported double-stranded helicate that crystallizes in toluene. The trimeric ring was unstable in a pure solution with dichloromethane and transformed into the double-stranded helicate. Thermodynamic analysis by means of the PACHA software revealed that formation of the double-stranded helicates was characterized by ?H(toluene)=-30?kJ?mol(-1) and ?S(toluene)=+357?J?K(-1) ?mol(-1) , whereas these values were ?H(CH2 Cl2 )=-75?kJ?mol(-1) and ?S(CH2 Cl2 )=-37?J?K(-1) ?mol(-1) for the ring helicate. The transformation of the ring helicate into the double-stranded helicate was a strongly endothermic process characterized by ?H(CH2 Cl2 )=+127?kJ?mol(-1) and ?H(n-pentane)=+644?kJ?mol(-1) associated with a large positive entropy change ?S=+1115?J?K(-1) ?mol(-1) . Consequently, the instability of the ring helicate in pure dichloromethane was attributed to the rather high dielectric constant and dipole moment of dichloromethane relative to n-pentane. Suggestions for increasing the stability of the ring helicate are given. PMID:24644255

Weekes, David Michael; Diebold, Carine; Mobian, Pierre; Huguenard, Clarisse; Allouche, Lionel; Henry, Marc

2014-04-22

352

Photoconductivity of nonpolar liquids induced by vacuum-ultraviolet light  

NASA Astrophysics Data System (ADS)

The intrinsic photoconductivity (pc) of 11 liquid hydrocarbons and silanes induced by VUV light was measured. From the onset of the pc the following thresholds were estimated in eV at T=(294±2) K: isopentane 9.15; n-pentane 9.1; neohexane 8.75; 3-methyl pentane 8.85; cyclohexane 8.75; n-tridecane 9.25; n-pentene-1 8.33; cyclopentene 7.4; tetramethylethylene 6.8; hexamethyldisilane 6.75; triethylsilane 8.25. Absolute quantum yields were determines at 120 nm for a field strength of 2.5 kV cm-1.

Böttcher, Ernst-Holger; Schmidt, Werner F.

1984-02-01

353

Testing the performance of a VUV photoionization source on a double focussing mass spectrometer using alkanes and thiophenes  

Microsoft Academic Search

The performance of a newly developed photoionization source in combination with a high resolution mass spectrometer is tested. The total ion currents for several linear alkanes (n-pentane to n-decane) and for some thiophenes (2-methylthiophene, 2,5-dimethylthiophene and 2-ethylthiophene) are measured at three fixed wavelengths: the Kr I (10.03 eV and 10.64 eV), Ar I (11.62 eV and 11.83 eV) and Ne

M. Bobeldijk; P. G. Kistemaker; J. J. Boon

1991-01-01

354

Efficient analysis of highly complex nuclear magnetic resonance spectra of flexible solutes in ordered liquids by using molecular dynamics  

NASA Astrophysics Data System (ADS)

The NMR spectra of n-pentane as solute in the liquid crystal 5CB are measured at several temperatures in the nematic phase. Atomistic molecular dynamics simulations of this system are carried out to predict the dipolar couplings of the orientationally ordered pentane, and the spectra predicted from these simulations are compared with the NMR experimental ones. The simulation predictions provide an excellent starting point for analysis of the experimental NMR spectra using the covariance matrix adaptation evolutionary strategy. This shows both the power of atomistic simulations for aiding spectral analysis and the success of atomistic molecular dynamics in modeling these anisotropic systems.

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

2012-05-01

355

Characterization of road asphalt using Gel Permeation Chromatography  

E-print Network

. 31 in Toluene MacMillan AC-20 Dickens 1984 Core 3. 9. LNS, NNS, and SNS Regions of the GPC Chromatograms ~ ~ Dorchester AC-5 ~ . 33 4. 1. Variability of Chevron AC-10 Over Time. . . . . . . . . . . . . . . 500 and 50 Angstrom Columns/THF/100.... Nitro en Bases + 1st Acidaffins Rostler Ratio Paraffins + 2nd Acidaffins Asphalt n-Pentane Precipitate Asphaltenes Nitrogen Bases Solution H2$04 8Ss&s 1st Acidaffins H2SO4 H2SO4 2nd Acldaffins 2 ParaNns Figure 2. 1. Rosrler Analysis Better...

Donaldson, Guy Randal

1987-01-01

356

Influence of the preparative method on the activity of highly acidic WO{sub x}/ZrO{sub 2} and the relative acid activity compared with zeolites  

SciTech Connect

The acid activity of the solid tungsten/zirconia can be affected by the catalyst preparation method. Reflux of the hydrous zirconia prior to tungsten impregnation gives a catalyst with higher surface area than the nonrefluxed material, 62 vs 32 m{sup 2}/g, but with the same strong acid site density, as determined by n-pentane isomerization activity. It is also shown that the simultaneous coprecipitation of tungsten with the formation of hydrous zirconia yields a catalyst with about two times the strong acid site density of WO{sub x}/ZrO{sub 2} catalysts prepared by impregnation. 30 refs., 6 figs., 12 tabs.

Santiesteban, J.G.; Vartuli, J.C.; Han, S. [Mobil Technology Company, Paulsboro, NJ (United States)] [and others] [Mobil Technology Company, Paulsboro, NJ (United States); and others

1997-06-01

357

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

358

Self-ignition of S.I. engine model fuels: A shock tube investigation at high pressure  

SciTech Connect

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, deflagrative mild ignition. This instant is defined by the ignition delay time, {tau}{sub defl}. The deflagration process in most cases is followed by a secondary explosion (DDT). This transition defines a second ignition delay time, {tau}{sub DDT}, which is a suitable approximation for the chemical ignition delay time, if the change of the thermodynamic conditions of the unburned test gas due to deflagration is taken into account. For iso-octane at p = 40 bar, a NTC (negative temperature coefficient), behavior connected with a two step (cool flame) self-ignition at low temperatures was observed. This process was very pronounced for rich and less pronounced for stoichiometric mixtures. The results of the {tau}{sub DDT} delays of the stoichiometric mixtures were shortened by the primary deflagration process in the temperature range between 800 and 1,000 K. Various mixtures of iso-octane and n-heptane were investigated. The results show a strong influence of the n-heptane fraction in the mixture, both on the ignition delay time and on the mode of self-ignition. The self-ignition of methanol and MTBE (methyl tert-butyl ether) is characterized by a very pronounced initial deflagration. For temperatures below 900 K (methanol: 800 K), no secondary explosion occurs. Taking into account the pressure increase due to deflagration, the measured delays {tau}{sub DDT} of the secondary explosion are shortened by up to one order of magnitude.

Fieweger, K.; Blumenthal, R.; Adomeit, G. [RWTH, Aachen (Germany). Inst. fuer Allegemeine Mechanik] [RWTH, Aachen (Germany). Inst. fuer Allegemeine Mechanik

1997-06-01

359

Theoretical study of binding and permeation of ether-based polymers through interfaces.  

PubMed

We present a molecular dynamics simulation study on the interactions of poly(ethylene oxide) (PEO), poly(propylene oxide) (PPO), and their ABA-type block copolymer, poloxamers, at water/n-heptane and 1,2-dimyristoyl-sn-glycero-3-phospatidycholine (DMPC) lipid bilayer/water interfaces. The partition coefficients in water/1-octanol of the linear polyethers up to three monomers were calculated. The partition coefficients evidenced a higher hydrophobicity of the PPO in comparison to PEO. At the water/n-heptane interface, the polymers tend to adopt elongated conformations in agreement with similar experimental ellipsometry studies of different poloxamers. In the case of the poloxamers at the n-heptane/water interface, the stronger preference of the PPO block for the hydrophobic phase resulted in bottle-brush-type polymer conformations. At lipid bilayer/water interface, the PEO polymers, as expected from their hydrophilic nature, are weakly adsorbed on the surface of the lipid bilayer and locate in the water phase close to the headgroups. The free energy barriers of permeation calculated for short polymer chains suggest a thermodynamics propensity for the water phase that increase with the chain length. The lower affinity of PEO for the hydrophobic interior of the lipid bilayer resulted in the spontaneous expulsion within the simulation time. On the contrary, PPO chains and poloxamers have a longer residence time inside the bilayer, and they tend to concentrate in the tail region of the bilayer near the polar headgroups. In addition, polymers with PPO unit length comparable to the thickness of the hydrophobic region of the bilayer tend to span across the bilayer. PMID:24219592

Samanta, Susruta; Hezaveh, Samira; Roccatano, Danilo

2013-11-27

360

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

361

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

362

The role of water in the formation of reversed micelles: An antimicellization agent  

USGS Publications Warehouse

Micellization of sodium bis(2-ethylhexyl) phosphate in n-heptane has been studied under controlled environmental conditions by dynamic and static light scattering. The results clearly show that a trace amount of water has a very dramatic effect on reversed micellization. In contrast with results in the literature, water can function as an antimicellization agent. The generality of and the evidence for supporting the current view that water is a prerequisite for the formation of reversed micelles are discussed and criticized. ?? 1992 American Chemical Society.

Yu, Z.-J.; Zhou, N.-F.; Neuman, R.D.

1992-01-01

363

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

364

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

365

Kinetic modelling of a surrogate diesel fuel applied to 3D auto-ignition in HCCI engines  

E-print Network

The prediction of auto-ignition delay times in HCCI engines has risen interest on detailed chemical models. This paper described a validated kinetic mechanism for the oxidation of a model Diesel fuel (n-decane and ?-methylnaphthalene). The 3D model for the description of low and high temperature auto-ignition in engines is presented. The behavior of the model fuel is compared with that of n-heptane. Simulations show that the 3D model coupled with the kinetic mechanism can reproduce experimental HCCI and Diesel engine results and that the correct modeling of auto-ignition in the cool flame region is essential in HCCI conditions.

Bounaceur, Roda; Fournet, René; Battin-Leclerc, Frédérique; Jay, S; Da Cruz, A Pires

2007-01-01

366

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

367

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

368

Photoisomerization and reorientational mobility of symmetric carbocyanines in AOT/alkane/polar solvent microemulsions  

NASA Astrophysics Data System (ADS)

Molecular motion of carbocyanine fluorophores DOCI, DODCI and DTDCI were studied in AOT/n-heptane microemulsions containing added polar solvents: water, methanol or acetonitrile. The response varied remarkably depending on the nature of the fluorophore and polar solvent. When the amount of added polar solvent was low, molecular mobility was invariably retarded, due to a combination of electrostatic and hydrophobic forces that induce the guest fluorophore to cling to the AOT molecules of the host reverse micelle. However, at high amounts of added methanol or water, these interactions diminished considerably, causing increase in the mobility of the guest fluorophores up to different extents.

Dandapat, Manika; Basu, Saswati; Ghosh, Deborin; Mandal, Debabrata

2014-07-01

369

A Ternary Phase Diagram for a Less Hazardous System  

NASA Astrophysics Data System (ADS)

The ternary phase diagram for the partially miscible liquid system n-propanol-n-heptane-water can be determined readily in an undergraduate laboratory experiment. The coexistence curve is obtained from titration results. Tie lines are then estimated from the compositions of pairs of phases in equilibrium, the propanol concentrations being determined by gas chromatography. The reagents are less hazardous than those of the classic acetic acid-chloroform-water system, and the gas chromatographic analysis has more interest for students than the acid-base titrations of the older experiment.

Udale, Barbara A.; Wells, John D.

1995-12-01

370

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

371

Testing of high-octane fuels in the single-cylinder airplane engine  

NASA Technical Reports Server (NTRS)

One of the most important properties of aviation fuels for spark-ignition engines is their knock rating. The CFR engine tests of fuels of 87 octane and above does not always correspond entirely to the actual behavior of these fuels in the airplane engine. A method is therefore developed which, in contrast to the octane number determination, permits a testing of the fuel under various temperatures and fuel mixture conditions. The following reference fuels were employed: 1) Primary fuels; isooctane and n-heptane; 2) Secondary fuels; pure benzene and synthetic benzine.

Seeber, Fritz

1940-01-01

372

The Potential of Using Natural Gas in HCCI Engines: Results from Zero- and Multi-dimensional Simulations  

E-print Network

greenhouse emissions. However, natural gas also brings a few challenges for HCCI engine operations. Natural gas is known for its high octane number and therefore is hard to auto-ignite. To enable the use of natural gas in HCCI engines, higher compression... and Checkel [18] have pointed out that the addition of reforming gases (i.e., CO and H2) advances SOC for the high-octane fuel (CNG) and retards SOC for the low-octane fuel (n-heptane). The SOC 13 change in the high-octane fuels mainly results from...

Zheng, Junnian

2012-07-16

373

The effect of initial diameter in sperically symmetric droplet combustion of sooting fuels  

NASA Technical Reports Server (NTRS)

The effect of initial droplet diameter on the burning rate of sooting fuels - n-heptane and 1-chloro-octane - was examined experimentally at low gravity. A 1.2s drop tower provided a low gravity environment to minimize buoyancy and achieve spherically symmetric flames for stationary droplets. Free-floating and fiber-supported droplets were burned, and both techniques gave matching results for droplets of similar initial diameter. Burning rate constants for both fuels were measured for a large number of droplets ranging from 0.4 to 1.1mm in initial diameter.

Jackson, G. S.; Avedisian, C. T.

1994-01-01

374

Fluorescent spectra of chromatographic fractions of crude oils  

E-print Network

. For this investigation, n-heptane, cyclohexane, iso-octane, benzene, chloroform, ether, and methanol were used in that order. The volume of eluent depended upon the size of the charged crude. Splitting sess eluent charges into two or three fractions gave a... better fractionat. '. on. hecovery of the oil raried from BO. Q to 89. 5 per cent on tests on four different crudes. Analysis of the fractions in iso-prapyl ether 'by spectrographic means revealed a distinct di ference between the crude oils...

Dixon, William Samuel

1952-01-01

375

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

376

Oxidations catalyzed by osmium compounds. Part 1: Efficient alkane oxidation with peroxides catalyzed by an olefin carbonyl osmium(0) complex  

Microsoft Academic Search

A carbonyl osmium(0) complex with ?-coordinated olefin, (2,3-?-1,4-diphenylbut-2-en-1,4-dione)undecacarbonyl triangulotriosmium (1), efficiently catalyzes oxygenation of alkanes (cyclohexane, cyclooctane, n-heptane, isooctane, etc.) with hydrogen peroxide, as well as with tert-butyl hydroperoxide and meta-chloroperoxybenzoic acid in acetonitrile solution. Alkanes are oxidized to corresponding alcohols, ketones (aldehydes) and alkyl hydroperoxides. Thus, heating cyclooctane with the 1–H2O2 combination at 70°C gave products with turnover number

Georgiy B. Shul’pin; Aleksandr R. Kudinov; Lidia S. Shul’pina; Elena A. Petrovskaya

2006-01-01

377

Use of detailed kinetic mechanisms for the prediction of autoignitions  

E-print Network

This paper describes how automatically generated detailed kinetic mechanisms are obtained for the oxidation of alkanes and how these models could lead to a better understanding of autoignition and cool flame risks at elevated conditions. Examples of prediction of the occurrence of different autoignition phenomena, such as cool flames or two-stage ignitions are presented depending on the condition of pressure, temperature and mixture composition. Three compounds are treated, a light alkane, propane, and two heavier ones, n-heptane and n-decane.

Buda, Frédéric; Battin-Leclerc, Frédérique; Porter, Richard; Hughes, Kevin J; Griffiths, John F

2006-01-01

378

High-performance liquid chromatographic determination of primary amines in aqueous solutions after extraction and derivatization with 2,2-diphenyl-1-oxa-3-oxonia-2-boratanaphthalene (DOOB).  

PubMed

Aqueous solutions of tryptamine, tyramine and ethanolamine are extracted and derivatizated to azomethine chelates using a solution of DOOB in diethyl ether. The extraction takes about 2 h. Diisopropyl ether and toluol have also been tested as extractants. The separation of the azomethine chelates is realized by a gradient program on a Si 60 column using a mixture of n-heptane/tert-butyl methyl ether. UV detection is carried out at 280 nm. The concentration of these three amines has been determined in a Chianti wine sample. PMID:15045446

Sanchez-Rodas, D; Hohaus, E; Wenclawiak, B

1996-05-01

379

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

380

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

381

Removal of dilute volatile organic contaminants from gaseous waste streams using trickling biofilters  

SciTech Connect

As increasingly stringent environmental regulations and oversight force emission reduction, dilute gaseous hydrocarbon waste streams remain the focus of remediation efforts for many industries. Advances in biotechnology hold promise for providing low-cost alternatives to more traditional, energy intensive treatment methods such as incineration and adsorption. Elucidation of engineering principles governing the behavior of such systems, combined with successful predictive modeling, will broaden their applicability. Oak Ridge National Laboratory has developed processes which exploit a microbial consortium to treat a mixture of 0.5% n-pentane and 0.5% isobutane in air. Since hydrocarbon gases are sparingly soluble in water, good mixing and high surface area between the gas and liquid phases are essential properties for biodegradation to be effective. A trickle-bed bioreactor (or trickling biofilter) has been operated continuously using n-pentane and isobutane as sole carbon and energy sources for over fifteen months to provide a high surface area (using a structured packing) with increased rates. Maximum degradation rates achieved thus far have been {approximately}60 g VOC/h/m{sup 3} in a single pass in this gas-continuous columnar system. Mass transfer coefficients comparable to literature values have also been measured for this reactor, with values being two to three times higher than those found in gas-recycle reactors.

Barton, J.W.; Klasson, K.T.; Koran, L.J. Jr. [Oak Ridge National Lab., TN (United States)] [and others

1995-12-31

382

Seasonal behavior of non-methane hydrocarbons in the firn air at Summit, Greenland  

NASA Astrophysics Data System (ADS)

Non-methane hydrocarbons (NMHC) were measured in the ambient air and in the snowpack interstitial firn air at ?1 m depth continuously for nearly two years at Summit, Greenland, from fall 2008 through summer 2010. Additionally, five firn air depth profiles were conducted to a depth of 3 m spanning winter, spring, and summer seasons. Here we report measurements of ethane, ethene, ethyne, propane, propene, i-butane, n-butane, i-pentane, n-pentane, and benzene and discuss the seasonal behavior of these species in the ambient and firn air. The alkanes, ethyne, and benzene in the firn air closely reflect the ambient air concentrations during all the seasons of the year. In spring and summer seasons, ethene and propene were enhanced in the near-surface firn over that in the ambient air, indicating a photochemical production mechanism for these species within the snowpack interstitial air. Evaluation of the NMHC ratios of i-butane/n-butane, i-pentane/n-pentane, and benzene/ethyne in both ambient and firn air does not provide evidence for chlorine or bromine radical chemistry significantly affecting these gases, except in a few summer samples, where individual data points may suggest bromine oxidation influence.

Helmig, D.; Stephens, C. R.; Caramore, J.; Hueber, J.

2014-03-01

383

A delicate balance of complexation vs. activation of alkanes interacting with [Re(Cp)(CO)(PF3)] studied with NMR and time-resolved IR spectroscopy  

PubMed Central

The organometallic alkane complexes Re(Cp)(CO)(PF3)(alkane) and Re(Cp)(CO)2(alkane) have been detected after the photolysis of Re(Cp)(CO)2(PF3) in alkane solvent. NMR and time-resolved IR experiments reveal that the species produced by the interaction of n-pentane with [Re(Cp)(CO)(PF3)] are an equilibrium mixture of Re(Cp)(CO)(PF3)(pentane) and Re(Cp)(CO)(PF3)(pentyl)H. The interaction of cyclopentane with [Re(Cp)(CO)(PF3)] most likely results in a similar equilibrium between cyclopentyl hydride and cyclopentane complexes. An increasing proportion of alkane complex is observed on going from n-pentane to cyclopentane to cyclohexane, where only a small amount, if any, of the cyclohexyl hydride form is present. In general, when [Re(Cp)(CO)(PF3)] reacts with alkanes, the products display a higher degree of oxidative cleavage in comparison with [Re(Cp)(CO)2], which favors alkane complexation without activation. Species with the formula Re(Cp)(CO)(PF3)(alkane) have higher thermal stability and lower reactivity toward CO than the analogous Re(Cp)(CO)2(alkane) complexes. PMID:17435163

Ball, Graham E.; Brookes, Christopher M.; Cowan, Alexander J.; Darwish, Tamim A.; George, Michael W.; Kawanami, Hajime K.; Portius, Peter; Rourke, Jonathan P.

2007-01-01

384

Cobalt and nickel supported on HY zeolite: Synthesis, characterization and catalytic properties  

SciTech Connect

Bifunctional catalysts consisting of cobalt and nickel supported on HY zeolite were synthesized by solvent excess impregnation and characterized by X-ray diffraction, Fourier-transformed infrared spectroscopy, scanning electron microscopy, atomic absorption spectroscopy, thermogravimetric analysis and nitrogen adsorption. The profiles of metal reduction on zeolite were obtained by temperature-programmed reduction. The catalytic properties of the bifunctional catalysts were verified by n-hexane hydroconversion. X-ray diffraction and microstructural analyses showed the presence of crystalline phases in HY zeolite and in samples after impregnation. A decrease in the micropore surface area was observed by nitrogen adsorption experiments and attributed to a reduction in the accessibility to micropores. The catalysts showed catalytic activity in the hydroconversion of n-hexane with selectivity to branched hydrocarbons. Such catalytic activity was related to the acid and metallic properties of the bifunctional catalysts used.

Garrido Pedrosa, Anne M. [Federal University of Rio Grande do Norte, Department of Chemistry, CP 1692, 59078-970 Natal-RN (Brazil)]. E-mail: annemgp@yahoo.com; Souza, Marcelo J.B. [Federal University of Sergipe, Department of Chemical Engineering, 49100-000 Sao Cristovao-SE (Brazil); Melo, Dulce M.A. [Federal University of Rio Grande do Norte, Department of Chemistry, CP 1692, 59078-970 Natal-RN (Brazil); Araujo, Antonio S. [Federal University of Rio Grande do Norte, Department of Chemistry, CP 1692, 59078-970 Natal-RN (Brazil)

2006-06-15

385

Biological activity of Spatoglossum asperum: a brown alga.  

PubMed

Chloroform and methanol fractions of an ethanol extract of Spatoglossum asperum showed antifungal activity against the highly destructive plant pathogen, Macrophomina phaseolina while the n-hexane fraction showed activity against Rhizoctonia solani and Fusarium solani. n-Hexane and methanol fractions also showed nematicidal activity against the plant parasitic nematode, Meloidogyne javanica. Column chromatography of the ethanol extract of seaweed yielded oily fractions named SA-I to SA-VI. GC-MS data of these oily fractions showed the presence of various fatty acid esters. Some of these oily fractions exhibited strong antifungal and nematicidal activities. Oily fractions of S. asperum also showed hypolipidaemic activity in normal, triton-induced and high fat diet-induced hyperlipidaemic rats without producing any ill effect on cardiac and liver enzymes. PMID:16161033

Ara, Jehan; Sultana, Viqar; Qasim, Rashida; Ehteshamul-Haque, Syed; Ahmad, Viqar Uddin

2005-07-01

386

Optimization of the LC enantioseparation of chiral pharmaceuticals using cellulose tris(4-chloro-3-methylphenylcarbamate) as chiral selector and polar non-aqueous mobile phases.  

PubMed

The resolving power of a new commercial polysaccharide-based chiral stationary phase, Sepapak-4, with cellulose tris(4-chloro-3-methylphenylcarbamate) coated on silica microparticles as chiral selector, was evaluated toward the enantioseparation of ten basic drugs with widely different structures and hydrophobic properties, using ACN as the main component of the mobile phase. A multivariate approach (experimental design) was used to screen the factors (temperature, n-hexane content, acidic and basic additives) likely to influence enantioresolution. Then, the optimization was performed using a face-centered central composite design. Complete enantioseparation could be obtained for almost all tested chiral compounds, demonstrating the high chiral discrimination ability of this chiral stationary phase using polar organic mobile phases made up of ACN and containing an acidic additive (TFA or formic acid), 0.1% diethylamine and n-hexane. These results clearly illustrate the key role of the nature of the acidic additive in the mobile phase. PMID:20432231

Dossou, Katina S S; Chiap, Patrice; Chankvetadze, Bezhan; Servais, Anne-Catherine; Fillet, Marianne; Crommen, Jacques

2010-06-01

387

Vitiquinolone--a quinolone alkaloid from Hibiscus vitifolius Linn.  

PubMed

Phytochemical investigations of the powdered root of Hibiscus vitifolius Linn. (Malvaceae) was extracted successively with n-hexane and chloroform. Analysis of the n-hexane extract by GC-MS led to the identification of twenty-six components by comparison of their mass spectra with GC-MS library data. A novel quinolone alkaloid, vitiquinolone (5) together with eight known compounds viz. ?-Amyrin acetate (1), n-octacosanol (2), ?-Amyrin (3), stigmasterol (4), xanthyletin (6), alloxanthoxyletin (7), xanthoxyletin (8) and betulinic acid (9) were isolated from chloroform extract by column chromatography over silica gel. The structure of vitiquinolone was established on the basis of spectroscopic methods including UV, IR, 1D, 2D NMR and ESI-MS. The known compounds were identified on the basis of their physical and spectroscopic data as reported in the literature. PMID:24128571

Ramasamy, D; Saraswathy, A

2014-02-15

388

Release of volatile mercury from vascular plants  

NASA Technical Reports Server (NTRS)

Volatile, organic solvent soluble mercury has been found in leaves and seeds of several angiosperms. Leaves of garlic vine, avocado, and haole-koa release mercury in volatile form rapidly at room temperature. In garlic vine, the most active release is temperature dependent, but does not parallel the vapor-pressure temperature relationship for mercury. Mercury can be trapped in nitric-perchloric acid digestion fluid, or n-hexane, but is lost from the hexane unless the acid mixture is present. Seeds of haole-koa also contain extractable mercury but volatility declines in the series n-hexane (90%), methanol (50%), water (10%). This suggests that reduced volatility may accompany solvolysis in the more polar media.

Siegel, S. M.; Puerner, N. J.; Speitel, T. W.

1974-01-01

389

Ferulaldehyde and lupeol as direct and indirect antimicrobial compounds from Cordia gilletii (Boraginaceae) root barks.  

PubMed

Cordia gilletii De Wild (Boraginaceae), a medicinal plant used against infectious diseases in the Democratic Republic of Congo, was investigated for direct and indirect antimicrobial properties. On one hand, the methanol extract is active against many pathogenic bacteria, including resistant strains. Its bio-guided fractionation led to the isolation of ferulaldehyde; this compound showed antimicrobial and antioxidant properties that may support the activity we observed for the methanol extract and some of the traditional uses of C. gilletii. On the other hand, the n-hexane extract of root barks possesses indirect antimicrobial properties, enhancing the activity of antibiotics against methicillin-resistant Staphylococcus aureus (MRSA). The fractionation of this extract led to the isolation of lupeol, which decreases the minimum inhibitory concentration of several antibiotics (4 to 8 fold) against MRSA and contributes to the effects observed for the raw n-hexane extract. PMID:25026702

Okusa, Philippe N; Stévigny, Caroline; Névraumont, Marie; Gelbcke, Michel; Van Antwerpen, Pierre; Braekman, Jean Claude; Duez, Pierre

2014-05-01

390

Separation of hexane isomers in a metal-organic framework with triangular channels.  

PubMed

Metal-organic frameworks can offer pore geometries that are not available in zeolites or other porous media, facilitating distinct types of shape-based molecular separations. Here, we report Fe2(BDP)3 (BDP(2-) = 1,4-benzenedipyrazolate), a highly stable framework with triangular channels that effect the separation of hexane isomers according to the degree of branching. Consistent with the varying abilities of the isomers to wedge along the triangular corners of the structure, adsorption isotherms and calculated isosteric heats indicate an adsorption selectivity order of n-hexane > 2-methylpentane > 3-methylpentane > 2,3-dimethylbutane ? 2,2-dimethylbutane. A breakthrough experiment performed at 160°C with an equimolar mixture of all five molecules confirms that the dibranched isomers elute first from a bed packed with Fe2(BDP)3, followed by the monobranched isomers and finally linear n-hexane. Configurational-bias Monte Carlo simulations confirm the origins of the molecular separation. PMID:23704568

Herm, Zoey R; Wiers, Brian M; Mason, Jarad A; van Baten, Jasper M; Hudson, Matthew R; Zajdel, Pawel; Brown, Craig M; Masciocchi, Norberto; Krishna, Rajamani; Long, Jeffrey R

2013-05-24

391

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

PubMed

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 the Salmonella typhimurium TA100 strain with S9 mix and the direct-acting mutagenicity was assayed using the S. typhimurium TA98 strain without S9 mix. The polycyclic aromatic hydrocarbons (PAHs) and nitropolycyclic aromatic hydrocarbons (NPAHs) of each fraction were determined by high-performance liquid chromatography (HPLC). Both direct- and indirect-acting of mutagenicities were the highest in samples of DEPs. The contributions of PAHs in samples of WBPs and NPAHs in DEPs were the largest, respectively. PMID:19896557

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

2010-01-01

392

A developed determination of midazolam and 1?-hydroxymidazolam in plasma by liquid chromatography–mass spectrometry: Application of human pharmacokinetic study for measurement of CYP3A activity  

Microsoft Academic Search

This paper describes sensitive and reliable determination of midazolam (MDZ) and its major metabolite 1?-hydroxymidazolam (1-OHMDZ) in human plasma by liquid chromatography–mass spectrometry (LC–MS) with a sonic spray ionization (SSI) interface. MDZ, 1-OHMDZ and diazepam as an internal standard were extracted from 1ml of alkalinized plasma using n-hexane–chloroform (70:30, v\\/v). The extract was injected into an analytical column (YMC-Pak Pro

Mikiko Shimizu; Tsukasa Uno; Hiro-omi Tamura; Hideko Kanazawa; Isao Murakami; Kazunobu Sugawara; Tomonori Tateishi

2007-01-01

393

Neutral lipid classes of black cumin ( Nigella sativa L.) seed oils  

Microsoft Academic Search

n-Hexane (H) and chloroform:methanol (CM) were used to extract the oils of Nigella sativa L. seeds. A combination of column and thin-layer chromatography procedures on silica gel were performed to fractionate the main neutral lipid classes of seed oils. The fatty acid pattern of neutral lipid (NL) fractions, triacylglycerol (TAG) and sterol content were determined. NLs constituted 97.2% and 96.1%

Mohamed F. Ramadan; Jörg-Thomas Mörsel

2002-01-01

394

Preparative isolation and purification of lutein from the microalga chlorella vulgaris by high-speed counter-current chromatography.  

PubMed

High-speed counter-current chromatography (HSCCC) was applied to the isolation and purification of lutein from microalgae. Analytical HSCCC was used for the preliminary selection of a suitable solvent system composed of n-hexane-ethanol-water (4:3:1, v/v). Using the above solvent system, preparative HSCCC was successfully performed yielding lutein at 98% purity from 200 mg of the crude extract in a one-step separation. PMID:11206781

Li, H B; Chen, F; Zhang, T Y; Yang, F Q; Xu, G Q

2001-01-01

395

Antioxidant activities of methanolic and hot-water extracts from leaves of three cultivars of Mai-Men-Dong (Liriope spicata L.)  

Microsoft Academic Search

dipheny-2-picrylhydrazyl (DPPH) scavenging activities of the 80% methanolic leaf extracts of three cultivars (small leaf, SL; big leaf, BL; thin leaf, TL) of Mai-Men-Dong (Liriope spicata L.) are analyzed by spectrophotometry. The concentrations required for 50% inhibition (IC50) of DPPH radicals were 81.08, 96.97, and 53.78 µg\\/mL, respectively. The methanolic extracts were further partitioned into three n-hexane-, ethylacetate-, and water-soluble

Wen-Chi HOU; Wen-Chung WU; Chih-Yuan YANG; Hsien-Jung CHEN; Sin-Yie LIU

2004-01-01

396

Liquid-Liquid Extraction for Recovery of Paclitaxel from Plant Cell Culture: Solvent Evaluation and Use of Extractants for Partitioning and Selectivity  

PubMed Central

A major challenge in the production of metabolites by plant cells is the separation and purification of a desired product from a number of impurities. An important application of plant cell culture is the biosynthesis of the anti-cancer agent paclitaxel. Liquid-liquid extraction plays a critical role in the recovery of paclitaxel and other valuable plant-derived products from culture broth. In this study, the extraction of paclitaxel and a major unwanted by-product, cephalomannine, from plant cell culture broth into organic solvents is quantified. Potential solvent mixtures show varying affinity and selectivity for paclitaxel over cephalomannine. The partition coefficient of paclitaxel is highest in ethyl acetate and dichloromethane, with measured values of 28 and 25, respectively; however selectivity coefficients are less than 1 for paclitaxel over cephalomannine for both solvents. Selectivity coefficient increases to 1.7 with extraction in n-hexane but the partition coefficient decreases to 1.9. Altering the pH of the aqueous phase results in an increase in both recovery and selectivity using n-hexane, but does not change the results for other solvents significantly. The addition of extractants trioctyl amine (TOA) or tributyl phosphate (TBP) to n-hexane gives significantly higher partition coefficients for paclitaxel (8.6 and 23.7, respectively), but no selectivity. Interestingly, when 20% hexafluorobenzene (HFB) is added to n-hexane, the partition coefficient remains approximately constant but the selectivity coefficient for paclitaxel over cephalomannine improves to 4.5. This significant increase in selectivity early in the purification process has the potential to simplify downstream processing steps and significantly reduce overall purification costs. PMID:22581674

McPartland, Timothy J.; Patil, Rohan A.; Malone, Michael F.; Roberts, Susan C.

2012-01-01

397

Lipase-catalyzed methanolysis of triricinolein in organic solvent to produce 1,2(2,3)-diricinolein  

Microsoft Academic Search

The objective of this study was to find the optimal parameters for lipase-catalyzed methanolysis of triricinolein to produce\\u000a 1,2(2,3)-diricinolein. Four different immobilized lipases were tested, Candida antarctica type B (CALB), Rhizomucor miehei (RML), Pseudomonas cepacia (PCL), and Penicillium roquefortii (PRL). n-Hexane and diisopropyl ether (DIPE) were examined as reaction media at three different water activities (a\\u000a w), 0.11, 0.53, and

Charlotta Turner; Xiaohua He; Tasha Nguyen; Jiann-Tsyh Lin; Rosalind Y. Wong; Robert E. Lundin; Leslie Harden; Thomas McKeon

2003-01-01

398

Comparative evaluation of urinalysis and blood analysis as means of detecting exposure to organic solvents at low concentrations  

Microsoft Academic Search

One hundred and forty-three workers exposed to one or more of toluene, xylene, ethylbenzene, styrene, n-hexane, and methanol at sub-occupational exposure limits were examined for the time-weighted average intensity of exposure by diffusive sampling, and for biological exposure indicators by means of analysis of shift-end blood for the solvent and analysis of shift-end urine for the corresponding metabolite(s). Urinalysis was

Toshio Kawail; Tomojiro Yasugi; Kazunori Mizunuma; Shun'ichi Horiguchi; Hiroshi Iguchi; Yoko Uchida; Okujou Iwami; Masayuki Ikeda

1992-01-01

399

Enzymatic esterification in organic media: role of water and organic solvent in kinetics and yield of butyl butyrate synthesis  

Microsoft Academic Search

The respective roles of organic solvent and of water in butyl butyrate synthesis from n-butanol and n-butyric acid in n-hexane by Mucor miehei lipase have been investigated by analysis of the kinetics and the reaction balances. Esterificaton was found to take place in both low water systems containing solid enzyme in hexane and in biphasic aqueous enzyme solution\\/hexane systems. In

Frédéric Monot; Frédérique Borzeix; Marc Bardin; Jean-Paul Vandecasteele

1991-01-01

400

Development and validation of a method for determination of corticosteroids in pig fat using liquid chromatography–tandem mass spectrometry  

Microsoft Academic Search

A new method was developed to determine five corticosteroids (prednisolone, methylprednisone, flumethasone, dexamethasone, and methylprednisolone) in pig fat samples by liquid chromatography–tandem mass spectrometry (LC–MS\\/MS) utilizing an optimized liquid–liquid extraction (LLE) and subsequent solid-phase extraction (SPE) for sample clean-up. In the sample preparation, a pig fat sample was dissolved in n-hexane and then extracted into the methanol–water (50\\/50, v\\/v) mixture

Ádám Tölgyesi; Virender K. Sharma; Jen? Fekete

2011-01-01

401

An interesting thinner intoxication case: Intrathoracic injection  

Microsoft Academic Search

Thinners, including aromatic hydrocarbons such as toluene, xylene, and N-hexane, are widely used in industry for the production\\u000a of plastics, varnish, paint, and glue. Use of these toxic agents frequently leads to chronic intoxication caused by abuse\\u000a or misuse of solvents, which are usually taken in through inhalation. Thinners may have neurotoxic, myotoxic, hepatotoxic,\\u000a nephrotoxic, and cardiotoxic systemic effects. The

Ilhami Solak; Ilkin Cankayali; Hasim Aksu; Ali Resat Moral

2006-01-01

402

Pyrene-POSS nanohybrid as a dispersant for carbon nanotubes in solvents of various polarities: its synthesis and application in the preparation of a composite membrane  

PubMed Central

In this study we report the preparation of nanohybrid dispersant molecules based on pyrene and polyhedral oligomeric silsesquioxanes for non-covalent functionalization of multi-walled carbon nanotubes (MWCNTs). The prepared dispersant improves the dispersion of MWCNTs in organic solvents with very different polarities such as tetrahydrofuran, toluene, and n-hexane. The functionalized MWCNTs were used to introduce conductivity into polydimethylsiloxane membranes which can be used for electrostatic discharge applications. PMID:22676373

2012-01-01

403

Antidermatophyte and antimelanogenesis compound from Eleutherine americana grown in Indonesia  

Microsoft Academic Search

An active compound from the bulb of Eleutherine americana L. Merr. (Iridaceae) collected from East Kalimantan, Indonesia, was tested for its antidermatophyte and antimelanogenesis\\u000a activity. Antifungal assay-directed fractionation of the n-hexane-soluble fraction of the methanolic extract of the bulb of E. americana led to the isolation of 1 as an active compound. The compound was identified as the naphthoquinone eleutherin

Irawan Wijaya Kusuma; Enos Tangke Arung; Enih Rosamah; Sri Purwatiningsih; Harlinda Kuspradini; Syafrizal; Juli Astuti; Yong-Ung Kim; Kuniyoshi Shimizu

2010-01-01

404

Fraction of Pt surface covered with coke following hydrogenolysis of hexane  

Microsoft Academic Search

This paper reports that following hydrogenolysis of n-hexane on an alumina-supported platinum catalyst, the surface of the metal is covered partially with carbonaceous residues or coke. The fraction of surface platinum not covered with coke has been found to be about one half by four independent techniqu3s: titration of preadsorbed oxygen by dihydrogen, chemisorption of carbon monoxide, infrared spectroscopy of

F. J. Rivera-Latas; R. A. Dalla Betta; M. Boudart

1992-01-01

405

Determination of chlorophenoxy acid herbicides in water by in situ esterification followed by in-vial liquid–liquid extraction combined with large-volume on-column injection and gas chromatography–mass spectrometry  

Microsoft Academic Search

A new approach for rapidly analysing chlorophenoxy acid herbicides in water is presented. The chlorinated acids are derivatised with dimethyl sulphate in the water sample itself (800 ?l) and, next, the methyl esters are extracted with 800 ?l of n-hexane. A 200-?l volume of the extract is injected into the GC–MS system. The miniaturisation of both the methylation and extraction

M. Isabel Catalina; Jens Dallüge; René J. J Vreuls; Udo A. Th Brinkman

2000-01-01

406

High-performance liquid chromatography method to measure ?- and ?-tocopherol in leaves, flowers and fresh beans from Moringa oleifera  

Microsoft Academic Search

A high-performance liquid chromatography method for the microscale determination of ?- and ?-tocopherol in leaves, flowers and fresh beans from Moringa oleifera is reported. The method includes microscale saponification and extraction with n-hexane. Optimized conditions for reversed-phase HPLC with UV detection were as follows: column, 25cm×0.46cm, Exil ODS 5-?m; column temperature, 25°C; mobile phase, a 20:80 (v\\/v) mixture of methanol:acetonitrile;

D. I. Sánchez-Machado; J. López-Cervantes; N. J. Ríos Vázquez

2006-01-01

407

In vitro and in vivo anti-angiogenesis effect of shallot ( Allium ascalonicum): A heat-stable and flavonoid-rich fraction of shallot extract potently inhibits angiogenesis  

Microsoft Academic Search

This study has been undertaken to elucidate the anti-angiogenic properties of shallot extract in vitro and in vivo and also to define the responsible fraction and its stability. After preparation of the extract of shallot bulbs with 50% ethanol, the extract was successively fractionated into n-hexane, ethyl acetate, n-butanol and aqueous fractions. The ethyl acetate fraction was further fractionated to

Parivash Seyfi; Ali Mostafaie; Kamran Mansouri; Delnia Arshadi; Hamid-Reza Mohammadi-Motlagh; Amir Kiani

2010-01-01

408

Purification of icariin from the extract of Epimedium segittatum using high-speed counter-current chromatography  

Microsoft Academic Search

Icariin was purified from the extract of Epimedium segittatum by high-speed counter-current chromatography with a two-phase solvent system composed of n-hexane–n-butanol–methanol–water (1:4:2:6, v\\/v). We used two multilayer coil planet centrifuges with different capacities. A 300 mg amount of the extract was separated using a semipreparative instrument equipped with a 230-ml capacity column to yield 103 mg of icariin at 86.2%

Qizhen Du; Ming Xia; Yoichiro Ito

2002-01-01

409

Simultaneous Determination of Fluoroquinolones, Tetracyclines and Sulfonamides in Chicken Muscle by UPLC–MS–MS  

Microsoft Academic Search

A rapid and sensitive analytical method for the simultaneous determination of four fluoroquinolones, four tetracyclines and\\u000a six sulfonamides in chicken muscle using ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC–MS–MS)\\u000a has been developed and validated. Samples were extracted with McIlvaine buffer-acetonitrile, defatted with n-hexane, and analyzed by UPLC–MS–MS. Solvent delay technique was applied in the analysis to remove the

Jianzhong Shen; Liming Guo; Fei Xu; Qinxiong Rao; Xi Xia; Xiaowei Li; Shuangyang Ding

2010-01-01

410

Silver-alumina catalysts for selective reduction of NO by higher hydrocarbons: structure of active sites and reaction mechanism  

Microsoft Academic Search

Silver-alumina catalysts prepared by sol–gel method (Ag-Al2O3) and impregnation method (Ag\\/Al2O3) were studied for the selective catalytic reduction (SCR) of NO by higher alkanes (n-hexane and n-octane). UV–VIS and Ag K-edge XAFS results established the structure of the catalysts; below 2wt.%, highly dispersed Ag+ ions are predominant Ag species, while at higher Ag loading, Agn clusters are predominant. A relationship

Ken-ichi Shimizu; Junji Shibata; Hisao Yoshida; Atsushi Satsuma; Tadashi Hattori

2001-01-01

411

Synthesis and characterization of high-silica EMT and FAU zeolites prepared in the presence of crown-ethers with either ethylene glycol or 1,3,5-trioxane  

Microsoft Academic Search

EMT- and FAU-type zeolites were prepared by using a mixture of organic molecules, i.e., crown-ether + ethylene glycol or crown-ether + 1,3,5-trioxane. The products were characterized by elemental analysis, XRD, SEM, thermal analysis, n-hexane adsorption, and n.m.r. spectroscopy. Depending on the method used to prepare the starting gel, the solids obtained showed different characteristics. D.t.a. proved to be a good

P. Schulz

1995-01-01

412

The Effect of Air\\/Fuel Ratio on Properties and Reactivity of Combustion Soots  

Microsoft Academic Search

The dependence of specific properties of black carbon (BC) soots on fuel type and combustion conditions has been studied, and the effects of these properties on soot particle hydration and reaction with ozone determined. Series of soots were prepared from n-hexane, diesel and JP8 aircraft fuels, utilizing a flow combustion system designed for accurate control of the air\\/fuel ratio in

A. R. Chughtai; J. M. Kim; D. M. Smith

2002-01-01

413

Evaluation of the antioxidant activity of Ruellia tuberosa  

Microsoft Academic Search

The antioxidant activity of Ruellia tuberosa L. (Acanthaceae) was investigated by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical-scavenging assay and the hydrogen peroxide-induced luminol chemiluminescence assay. The methanolic extract (ME) and its four fractions of water (WtF), ethyl acetate (EaF), chloroform (CfF), and n-hexane (HxF) were prepared and then subjected to antioxidant evaluation. The results of both methods revealed that R. tuberosa

Fu-An Chen; An-Bang Wu; Pochuen Shieh; Daih-Huang Kuo; Chi-Ying Hsieh

2006-01-01

414

Excited-state Raman spectroscopy with and without actinic excitation: S1 Raman spectra of trans-azobenzene  

NASA Astrophysics Data System (ADS)

We show that femtosecond stimulated Raman spectroscopy can record excited-state spectra in the absence of actinic excitation, if the Raman pump is in resonance with an electronic transition. The approach is illustrated by recording S1 and S0 spectra of trans-azobenzene in n-hexane. The S1 spectra were also measured conventionally, upon n?* (S0 ? S1) actinic excitation. The results are discussed and compared to earlier reports.

Dobryakov, A. L.; Quick, M.; Ioffe, I. N.; Granovsky, A. A.; Ernsting, N. P.; Kovalenko, S. A.

2014-05-01

415

Fluorous Metal Organic Frameworks as Superhydrophobic Adsorbents for Oil Spill Cleanup and Hydrocarbons Storage  

Microsoft Academic Search

We demonstrate that fluorous metal-organic frameworks (FMOFs) are highly hydrophobic porous materials with a high capacity and affinity to C-C hydrocarbons of oil components. FMOF-1 exhibits reversible adsorption with a high capacity for n-hexane, cyclohexane, benzene, toluene, and p-xylene, with no detectable water adsorption even at near 100% relative humidity, drastically outperforming activated carbon and zeolite porous materials. FMOF-2, obtained

Chi Yang; Qian Mather; Xiaoping Wang; Ushasree Kaipa; Vladimir Nesterov; Augustin Venero; Mohammad A Omary

2011-01-01

416

Microwave roasting effects on the physico-chemical composition and oxidative stability of sunflower seed oil  

Microsoft Academic Search

The purpose of the present study was to explore the influences of microwave heating on the composition of sunflower seeds\\u000a and to extend our knowledge concerning the changes in oxidative stability, distribution of FA, and contents of tocopherols\\u000a of sunflower seed oil. Microwaved sunflower seeds (Helianthus annuus L.) of two varieties, KL-39 and FH-330, were extracted using n-hexane. Roasting decreased

Fozia Anjum; Farooq Anwar; Amer Jamil; M. Iqbal

2006-01-01

417

An experimental study of induction electrohydrodynamic pumping in a horizontal axisymmetric configuration  

E-print Network

. Four fluids were also doped to alter their electrical conductivity to determine the optimum electrical conductivity range. N-Hexane bulk fluid velocities as high as 38. 5 cm/s (at 12 kilovolts and 8. 0 Hz with a corresponding mass flow rate of 0. 487... of Different Dielectric Fluids. . . . . . Doping Comparison, . Theoretical Results Comparison. . VI. CONCLUSIONS AND RECOMMENDATIONS. . . . Conclusions. Recommendations. . . REFERENCES . . APPENDIX A. . . . . . . . VITA. Page 49 49 67 67 106...

Bohinsky, Brian Joseph

1991-01-01

418

Purification and thermal analysis of perfluoro- n-alkanoic acids  

Microsoft Academic Search

Purification of perfluoro-n-alkanoic acids (CnF2n+1COOH, n=7, 9, 11, 13, 15 and 17) was made by repeated recrystallizations from n-hexane\\/acetone mixed solvent, and their purity was found to be more than 99.5% by GC–MS, NMR, and elemental analysis. The thermal behaviors such as melting point and enthalpy change of fusion were investigated using differential scanning calorimetry (DSC). The melting point monotonously

Minami Tsuji; Tohru Inoue; Osamu Shibata

2008-01-01

419

Imaging of hydrocarbon reactions in zeolite packed-bed reactors using positron emission profiling  

Microsoft Academic Search

The ability of positron emission profiling (PEP) to measure concentration profiles of molecules labelled with positron-emitting\\u000a nuclei, such as 11C, 13N, and 15O, inside chemical reactors has been demonstrated for the system n-hexane–Pt\\/H-zeolites under conditions typical of the hydroisomerization reaction. Data obtained in the absence of reaction\\u000a were first measured and used to model mass transport processes in these biporous,

B. G. Anderson; N. J. Noordhoek; D. Schuring; F. J. M. M. de Gauw; A. M. de Jong; M. J. A. de Voigt; R. A. van Santen

1998-01-01

420

Desorption of high-molecular n-paraffins from CaA zeolite beds  

Microsoft Academic Search

1.The desorption of n-dodecane and n-pentadecane in the liquid phase from CaA beds was studied with n-paraffin eluants of various molecular weights (n-hexane, n-octane, n-decane). A high zeolite operating capacity for n-paraffin (8–9 wt.%) is achieved with any of the eluants studied. The molecular weight of the n-paraffin eluant has a marked influence on its consumption in the desorption process.

L. V. Borisova; Ya. V. Mirskii; A. Z. Dorogochinskii

1971-01-01

421

Cationic polymerization of isobutylene with H 2O\\/TiCl 4 initiating system in the presence of electron pair donors  

Microsoft Academic Search

Cationic polymerization of isobutylene (IB) in a mixture of methylene dichloride (CH2Cl2) and n-hexane (n-Hex) was conducted by using H2O as initiator, TiCl4 as co-initiator in the presence of strong external electron pair donor (ED), such as pyridine (Py), dimethylacetamide (DMA) or triethylamine (TEA). The effects of ED concentration, TiCl4 concentration, solvent polarity, polymerization temperature (T) and time on IB

Ying-xin Qiu; Yi-xian Wu; Xiao-lu Gu; Xu Xu; Guan-ying Wu

2005-01-01

422

Antimicrobial activity and chemical composition of endemic Centaurea cariensis subsp. niveo-tomentosa  

Microsoft Academic Search

The antimicrobial activity of the n-hexane, chloroform, ethyl acetate and ethyl alcohol extracts of the aerial parts of Centaurea cariensis subsp. niveo-tomentosa was evaluated against microorganisms, including multi-antibiotic resistant bacteria, using the paper disc diffusion method. The chemical composition of the chloroform extract of this plant was determined by gas chromatography and gas chromatography-mass spectrometry. The chloroform extract exhibited significant

Aysel Ugur; Nurdan Sarac; Ozgur Ceylan; M. Emin Duru

2010-01-01

423

Characterization of racemization of chiral pesticides in organic solvents and water  

Microsoft Academic Search

Eight chiral pesticides, which were selected to cover different pesticide species and origins of chirality, were investigated to explore their chiral stability in organic solvents and water. Profenophos, fenamiphos, quizalofop-ethyl, dichlorprop-methyl (DCPP-methyl) and acetochlor were showed stable under all test conditions. However, significant racemization was observed for malathion, phenthoate and fenpropathrin in methanol, ethanol and water, but not in n-hexane,

Zhaoyang Li; Tong Wu; Qiaoling Li; Bingzhu Zhang; Weixiao Wang; Jingyin Li

2010-01-01

424

Nutrient Limitation in a Compost Biofilter Degrading Hexane  

Microsoft Academic Search

A laboratory-scale compost-based biofilter was operated over a six-month period to study the requirements for removal of n-hexane from air. Hexane is a relatively short chain aliphatic hydrocarbon with a high Henry's coefficient and a low water solubility. Acclimation of the biofilter was slow, but removal efficiencies around 80% were achieved after one month of operation. However, performance decreased during

Eberhard Morgenroth; Edward D. Schroeder; Daniel P. Y. Chang; Kate M. Scow

1996-01-01

425

Antifungal activity of Syzygium cumini against Ascochyta rabiei–the cause of chickpea blight  

Microsoft Academic Search

Aqueous, ethanol and n-hexane extracts from leaves, fruit, root-bark and stem-bark of Syzygium cumini (L.) Skeels were tested for their antifungal activity against Ascochyta rabiei (Pass.) Lab., the cause of blight disease of the chickpea (Cicer arietinum L.). Different concentrations, namely 1, 2, …, 5% of both aqueous and the two organic solvent extracts were used in this study. Aqueous

Khajista Jabeen; Arshad Javaid

2010-01-01

426

Chemical composition, anti-inflammatory, molluscicidal and free-radical scavenging activities of the leaves of Ficus radicans ‘Variegata’ (Moraceae)  

Microsoft Academic Search

The methanol crude extract of the leaves of Ficus radicans Roxb. ‘Variegata’ (Moraceae) and the n-hexane, ethyl acetate and aqueous methanol fractions resulting from its fractionation were evaluated for their anti-inflammatory, molluscicidal and free-radical scavenging activities. The crude extract and fractions exhibited significant inhibition of inflammation in both croton oil (CO)-induced ear oedema in mice (p?

Maria Augusta Naressi; Marcos Alessandro dos Santos Ribeiro; Ciomar Aparecida Bersani-Amado; Maria Lucilia M. Zamuner; Willian Ferreira da Costa; Clara M. Abe Tanaka; Maria Helena Sarragiotto

2011-01-01

427

Chemical composition, anti-inflammatory, molluscicidal and free-radical scavenging activities of the leaves of Ficus radicans ‘Variegata’ (Moraceae)  

Microsoft Academic Search

The methanol crude extract of the leaves of Ficus radicans Roxb. ‘Variegata’ (Moraceae) and the n-hexane, ethyl acetate and aqueous methanol fractions resulting from its fractionation were evaluated for their anti-inflammatory, molluscicidal and free-radical scavenging activities. The crude extract and fractions exhibited significant inhibition of inflammation in both croton oil (CO)-induced ear oedema in mice (p?

Maria Augusta Naressi; Marcos Alessandro dos Santos Ribeiro; Ciomar Aparecida Bersani-Amado; Maria Lucilia M. Zamuner; Willian Ferreira da Costa; Clara M. Abe Tanaka; Maria Helena Sarragiotto

2012-01-01

428

HPTLC-densitometric method for simultaneous determination of salmeterol xinafoate and fluticasone propionate in dry powder inhalers  

Microsoft Academic Search

A high performance thin layer chromatography (HPTLC) method was developed and validated for determination of two anti-asthmatic drugs, salmeterol xinafoate and fluticasone propionate in co-formulations. Study was performed on pre-coated silica gel HPTLC plates using n-hexane:ethyl acetate:acetic acid (5:10:0.2) as a mobile phase. A TLC scanner set at 250nm was used for direct evaluation of the chromatograms in reflectance\\/absorbance mode.

Lantider Kasaye; Ariaya Hymete; Abdel-Maaboud I. Mohamed

2010-01-01

429

Simultaneous extraction of polychlorinated dibenzo- p-dioxins, polychlorinated dibenzofurans and coplanar polychlorinated biphenyls from contaminated soil using pressurized liquid extraction  

Microsoft Academic Search

Pressurized liquid extraction (PLE) was studied for simultaneous extractions of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD\\/PCDFs), and of coplanar polychlorinated biphenyls (Co-PCBs) from a tightly bounded condition in the soil matrix. Temperatures were maintained at 175 and 200°C, respectively, and two or three static cycles for single PLE with toluene and acetone\\/n-hexane were studied using a certified reference material to compare

Osamu Kiguchi; Katsumi Saitoh; Nobuaki Ogawa

2007-01-01

430

Resolution of racemic trans-2-methyl-1-cyclohexanol by lipase-catalysed transesterification in a membrane reactor  

Microsoft Academic Search

A kinetic resolution of trans-2-methyl-1-cyclohexanol with transesterification was studied using a membrane reactor. The highest enantioselectivity was observed for the reaction with vinyl acetate in an n-hexane solution, which was catalysed by lipase from Pseudomonas sp. It was also found that the use of both native lipase and that immobilised in a polyamide hollow-fibre membrane leads to conversion of the

Józef Ceynowa; Marta Rauchfleisz

2001-01-01

431

Biosurfactants from Acinetobacter calcoaceticus BU03 enhance the solubility and biodegradation of phenanthrene  

Microsoft Academic Search

A thermophilic bacterial strain, Acinetobacter calcoaceticus BU03, with a biosurfactant?producing capability, was isolated from petroleum?contaminated soil with an improved procedure which employed the solubilization of polycyclic aromatic hydrocarnons (PAHs), i.e. naphthalene in agar plate, as a selection criterion. Crude biosurfactant was recovered from the culture of BU03 by extraction with n?hexane, and its properties were investigated. Biosurfactants from A. calcoaceticus

Zhenyong Zhao; Jonathan W. C. Wong

2009-01-01

432

Electrochemical performances of poly(3,4-ethylenedioxythiophene)–NiFe 2O 4 nanocomposite as electrode for supercapacitor  

Microsoft Academic Search

Poly 3,4-ethylenedioxythiophene (PEDOT)-based NiFe2O4 conducting nanocomposites were synthesized and their electrochemical properties were studied in order to find out their suitability as electrode materials for supercapacitor. Nanocrystalline nickel ferrites (5–20nm) have been synthesized by sol–gel method. Reverse microemulsion polymerization in n-hexane medium for PEDOT nanotube and aqueous miceller dispersion polymerization for bulk PEDOT formation using different surfactants have been adopted.

Pintu Sen; Amitabha De

2010-01-01

433

Europium bis(dimethylsilyl)amides including mixed-valent Eu3[N(SiHMe2)2]6[?-N(SiHMe2)2]2.  

PubMed

Trivalent Eu[N(SiHMe2)2]3(THF)2 can easily be synthesized by applying a routine salt metathesis protocol (EuCl3(THF)2 and 3 equiv. of Li[N(SiHMe2)2] in n-hexane) which crystallizes isotypically to its analogues of the rare-earth metal series (space group P21/c). Transsilylamination of Eu[N(SiMe3)2]2(THF)2 with a slight excess of HN(SiHMe2)2 in n-hexane-THF yields the divalent trinuclear compound Eu{[?-N(SiHMe2)2]2Eu[N(SiHMe2)2](THF)}2, the solid-state structure of which differs significantly from the samarium and ytterbium analogues by showing three unique molecules in the asymmetric unit of which one is related to the two others by an inversion. Using crude Eu[N(SiMe3)2]3 in transsilylamination reactions with HN(SiHMe2)2 in n-hexane afforded n-hexane-insoluble trivalent ate complexes {MEu[N(SiHMe2)2]4}n (M = Na, K) depending on the synthesis conditions of Eu[N(SiMe3)2]3. Performing the transsilylamination of Eu[N(SiMe3)2]3 with a large excess of HN(SiHMe2)2 at elevated temperatures gave reproducibly the donor-free, mixed-valent, trinuclear compound Eu(II){[?-N(SiHMe2)2]Eu(III)[N(SiHMe2)2]3}2 in good yield. PMID:25318830

Bienfait, André M; Schädle, Christoph; Maichle-Mössmer, Cäcilia; Törnroos, Karl W; Anwander, Reiner

2014-12-14

434

Application of preparative high-speed counter-current chromatography\\/preparative high-performance liquid chromatography mode in rapid separation of saponins  

Microsoft Academic Search

Combined with preparative high-performance liquid chromatography, high-speed counter-current chromatography was employed for isolation and purification of saponins from Gypsophila paniculata L. n-Hexane–n-butanol–methanol–0.02% TFA (1:9:1:9, v\\/v) was employed as solvent system and 210nm was chosen as the wavelength of ultraviolet detection for the first time. The research tried to compare HSCCC with prep-HPLC, and further integrated their advantages to improve separation

Shun Yao; Jianguang Luo; Xuefeng Huang; Lingyi Kong

2008-01-01

435

Isolation of anti-ulcerogenic sesquiterpene lactones from Centaurea solstitialis L. ssp. solstitialis through bioassay-guided fractionation procedures in rats  

Microsoft Academic Search

The fresh spiny flowers of Centaurea solstitialis ssp. solstitialis (CSS) are used for the treatment of peptic ulcers in Turkey. Ethanol (80%) extract of CSS exhibited significant anti-ulcerogenic effect on the ethanol-induced ulcerogenesis model in rats. The ethanol extract was further fractionated by successive solvent extractions with n-hexane, chloroform, ethyl acetate and n-butanol. All fractions showed significant anti-ulcerogenic activity, however,

Erdem Yesilada; Ilhan Gürbüz; Erdal Bedir; Irem Tatli; Ikhlas A. Khan

2004-01-01

436

Catalytic combustion of volatile organic compounds on gold\\/titanium oxynitride catalysts  

Microsoft Academic Search

Catalytic oxidation of n-hexane, benzene and 2-propanol was investigated on Au\\/TiOxNy and Au\\/TiO2 catalysts prepared by the deposition–precipitation method and characterized by XRD, TEM and XPS techniques. The dispersion and average size of the gold particles are dependent on the nitrogen content of the support. Calcination of samples leads to a decrease in the nitrogen content of the samples and

M. A. Centeno; M. Paulis; M. Montes; J. A. Odriozola

2005-01-01

437

Syngas in millisecond reactors: higher alkanes and fast lightoff  

Microsoft Academic Search

Steady-state and transient catalytic partial oxidation of hydrocarbons (methane, butane, cyclohexane, n-hexane, isooctane, decane) has been carried out on rhodium-coated alumina monoliths in an effort to determine whether higher alkanes can be successfully converted to H2 and CO in short contact time reactors. This process is also necessary to determine the feasibility of on-board hydrogen generation for fuel cell and

L. D. Schmidt; E. J. Klein; C. A. Leclerc; J. J. Krummenacher; K. N. West

2003-01-01

438

Attraction of the Parasitic Mite Varroa to the Drone Larvae of Honey Bees by Simple Aliphatic Esters  

Microsoft Academic Search

An important parasitic threat to honey bees, the mite Varroa jacobsoni, is attracted to its major prey, drone larvae, by methyl and ethyl esters of straight-chain fatty acids, in particular methyl palmitate. These esters were extracted from drone larvae with n-hexane and were identified by gas chromatography-mass spectrometry. Their behavioral effect was evaluated with the use of a four-arm airflow

Yves Le Conte; Gerard Arnold; Jerome Trouiller; Claudine Masson; Bertrand Chappe; Guy Ourisson

1989-01-01

439

Detection of aroclor, DDT, malathion and HCB using semipermeable membranes as concentration method  

Microsoft Academic Search

Semipermeable membrane devices (SPMDs) containing 1 g of triolein were used to extract pp'-DDT (DDT), hexachlorobenzene (HCB), malathion and aroclor 1254 from aqueous samples. Recoveries higher than 95% were analytically confirmed for DDT and HCB using GC-MS after an extraction with n-hexane or methylene chloride. Different approaches were made to combine this concentration method with biological detection systems using toxicity

A. I. De la Torre; C. Fernández; J. V. Tarazona; M. J. Muñoz

1995-01-01

440

Single-step separation of organochlorine pesticide residues from fatty materials by combined use of solid-matrix partition and C 18 cartridges  

Microsoft Academic Search

A rapid single-step partition step between n-hexane and acetonitrile on a two-cartridge system composed of Extrelut-3 with a C18 cartridge connected downstream has been developed for the separation of organochlorine (OC) pesticide residues from oils and fats. The extract is cleaned up by Florisil minicolumn chromatography before gas chromatography with electron-capture detection. Carry over of fatty material through the partition

Alfonso Di Muccio; Tiziana Generali; Danilo Attard Barbini; Patrizia Pelosi; Antonella Ausili; Fabio Vergori; Silvana Girolimetti

1997-01-01

441

Thin Residual Films Between Steel-Mercury Surfaces  

Microsoft Academic Search

Several models for adsorbed films on metal surfaces have been proposed, such as monolayers and multilayers. For these films, the effect of solvent molecule is not sufficiently taken into consideration.In this study, a steel ball and mercury surfaces were used as electrodes, and the oil-film thickness between the electrodes was estimated by measuring the capacitance of the film. n-Hexane and

Heihachiro Okabe; Yasuyuki Watanabe

1982-01-01

442

Preparative separation of rhein from Chinese traditional herb by repeated high-speed counter-current chromatography  

Microsoft Academic Search

High-speed counter-current chromatography (HSCCC) was repeatedly used for isolation and purification of rhein from Rheum officinale Baill (Dahuang) with a two-phase solvent system composed of n-hexane–ethyl acetate–methanol–water (3:7:5:5, v\\/v), which had been selected by analytical (HSCCC). Using two preparative units of the HSCCC centrifuge, about a 500mg amount of the crude extract was separated, yielding 6.7mg of rhein at a

Yun Wei; Tianyou Zhang; Yoichiro Ito

2003-01-01

443

Supercritical fluid extraction of dandelion leaves  

Microsoft Academic Search

?-Amyrin and ?-sitosterol were extracted from dandelion in preparative scale using supercritical carbon dioxide. A 32 full-factorial design was carried out to map the effects of extraction pressure and temperature (over the ranges 150–450 bar and 35–65°C, respectively) on the yields and recoveries of the active components. The supercritical fluid extraction (SFE) was compared to Soxhlet extraction with n-hexane and

B. Simándi; Sz. T. Kristo; Á. Kéry; L. K. Selmeczi; I. Kmecz; S. Kemény

2002-01-01

444

Minor components responsible for flavor reversion of soybean oil  

Microsoft Academic Search

Edible refined, bleached and deodorized (RBD) soybean oil was fractionated by silicic acid column chromatography to identify\\u000a minor components responsible for flavor reversion. Minor components from oil eluted with diethyl ether\\/n-hexane (1:1) were\\u000a compared with those from corn and canola oils. All vegetable oils contain free fatty acids, diglycerides and sterols as major\\u000a ingredients in this fraction. However, unusual triglycerides

Yasushi Endo; Hiromi Endo; Kenshiro Fujimoto; Takashi Kaneda

1991-01-01

445

A validated chiral HPLC method for the determination of mebeverine HCl enantiomers in pharmaceutical dosage forms and spiked rat plasma  

Microsoft Academic Search

A new, precise, simple and accurate HPLC method was developed for the first time to separate and determine mebeverine enantiomers. Enantiomeric resolution was achieved on a cellulose Tris (3,5-dimethylphenyl carbamate) column known as Chiralcel OD, with UV detection at 263 nm. The mobile phase consisted of n-hexane, isopropyl alcohol and triethylamine (90:9.9:0.1 v\\/v\\/v). Sample run time was 18 min. On

Mahasen A. Radwan; Heba H. Abdine; Hassan Y. Aboul-Enein

2006-01-01

446

Characterization of Terebinth Fruit Oil and Optimization of Acidolysis Reaction with Caprylic and Stearic Acids  

Microsoft Academic Search

Characterization of the fatty acid and triacylglycerol composition of terebinth fruit oil and the synthesis of structured\\u000a lipids (SL) were performed in this study. Interesterification reaction of terebinth fruits oil (Pistacia terebinthus L.) with caprylic acid (CA) and stearic acid (SA) to produce a SL was performed in n-hexane using immobilized sn-1,3 specific lipase from Mucor miehei. The effect of

Derya KocakHasene; Hasene Keskin; Sibel Fad?lo?lu; Boleslaw Kowalski; Fahrettin Gö?ü?

447

HPLC analysis of coumarins in Turkish Seseli species (Umbelliferae)  

Microsoft Academic Search

The n-hexane extracts of aerial and underground parts of three Seseli species, S. gummiferum subsp. corymbosum, S. resinosum, and S. hartvigii growing in Turkey were investigated concerning the presence of coumarins by normal-phase HPLC (high-performance liquid chromatography).\\u000a In this respect, two coumarins, osthol (1) and corymbocoumarin (2) [(?)-(3?S, 4?S)-3?-acetoxy-4?-isovaleryloxy-3?, 4?-dihydroseselin] isolated from aerial parts of S. gummiferum subsp. corymbosum, were

Alev Tosun; Masaki Baba; Toru Okuyama

2007-01-01

448

Decay dynamics of the triplet state of 2,6-dimethyl-4H-1-benzothiopyran-4-thione in solution  

Microsoft Academic Search

The phosphorescence decay kinetics and transient triplet-triplet absorption of 2,6-dimethyl-4H-1-benzothiopyran-4-thione (DMBTPT) were recorded in deoxygenated n-hexane, n-hexadecane and 3-methylpentane solutions. The measurements of DMBTPT in the triplet state were performed using a flash photolysis system with an excimer laser as excitation source. The triplet state decay constant at infinite dilution (k0) and teh self-quenching rate constant (ksq) for DMBTPT at

Marek Sikorski; W?odzimierz Augustyniak; Igor V. Khmelinskii

1996-01-01

449

A comparative study of the WO x dispersion on Mn-promoted tungstated zirconia catalysts prepared by conventional and high-throughput experimentation  

Microsoft Academic Search

Conventional and high-throughput experimentation (HTE) techniques were used for the synthesis, characterization, and catalytic testing of Pt\\/Mn–WOx–ZrO2 materials. The catalysts were prepared by surfactant-assisted coprecipitation and screened for catalytic activity in a multi-channel fixed bed (MCFB) micro-reactor for the hydroisomerization of n-hexane. Conventional coprecipitation route leads mainly to the segregation of the WO3 crystalline phase (XRD). On the other hand,

M. L. Hernández-Pichardo; J. A. Montoya; P. del Angel; A. Vargas; J. Navarrete

2008-01-01

450

Estimation of effective diffusion coefficients in porous catalysts  

E-print Network

diffusion of n- hexane in a type II crystalline titanate, and the intracrystalline diffusivities were found to be independent of the adsorbate concentration. sv ACKNOWLEDGEMENT I would like to acknowledge my research advisor, Dr. R. G. Anthony... Concentration Results Obtained for LaZSM-5, FeZSM-5 and BZSM-5 . Results Obtained for Zeolite HY . Analysis of the Two Phase Model . Results Obtained for Type II Crystalline Titanate. . . . . 40 53 53 61 63 63 70 83 CHAPTER VI CONCLUSION . 89...

Kulkarni, Shrikant Ulhas

1991-01-01

451

Esterification of phenolic acids catalyzed by lipases immobilized in organogels  

Microsoft Academic Search

Lipases from Rhizomucor miehei and Candida antarctica B were immobilized in hydroxypropylmethyl cellulose organogels based on surfactant-free microemulsions consisting of n-hexane,\\u000a 1-propanol and water. Both lipases kept their catalytic activity, catalyzing the esterification reactions of various phenolic\\u000a acids including cinnamic acid derivatives. High reaction rates and yields (up to 94%) were obtained when lipase from C. antarctica was used. Kinetic

M. Zoumpanioti; E. Merianou; T. Karandreas; H. Stamatis; A. Xenakis

2010-01-01

452

Carica papaya lipase-catalyzed synthesis of terpene esters  

Microsoft Academic Search

An efficient approach to synthesize terpene esters using plant lipase-Carica papaya lipase (CPL) as the biocatalyst was developed in this work. The effects of chain length of acyl donor and solvent type on the CPL-catalyzed transesterification reaction were investigated firstly. It was found that CPL showed the highest activity in n-hexane with vinyl octanoate as the best acyl donor. To

Pengyong You; Erzheng Su; Xuepeng Yang; Duobin Mao; Dongzhi Wei

2011-01-01

453

Comparative bioactivity studies on two Mimosa species (Estudios comparativos de dos especies de Mimosa)  

Microsoft Academic Search

Comparative antioxidant, antibacterial activities and general toxicity studies on the n-hexane, dichloromethane (DCM) and methanol (MeOH) extracts of Mimosa pudica and Mimosa rubicaulis, two Bangladeshi medicinal plants, were carried out, using the 2,2-diphenyl- 1-picryl-hydrazyl (DPPH) assay, the resazurin microtitre plate based assay, and the brine shrimp lethality assay, respectively. The DCM and MeOH extracts of both M. pudica and M.

Samuel GENEST; Conor KERR; Ankit SHAH; M. Mukhlesur RAHMAN; Gadria M. M. SAIF-E-NASER; Poonam NIGAM; Lutfun NAHAR; Satyajit D. SARKER

2008-01-01

454

Physiochemical Properties of Jatropha curcas Seed Oil from Different Origins and Candidate Plus Plants (CPPs)  

Microsoft Academic Search

The physicochemical properties of Jatropha seed oil from 9 geographical origins and 24 candidate plus plants (CPPs) were evaluated. The yield of seed oil obtained by\\u000a Soxhlet extraction using n-hexane as solvent varied from 40.0% (Malaysia) to 48.4% (Vietnam) among seeds from different origins and 32.1% (CPP-17) to\\u000a 48.8% (CPP-01) (w\\/w) among CPPs. Density, specific gravity, and refractive index of

A. K. M. Aminul Islam; Z. Yaakob; N. Anuar; S. R. P. Primandari; M. Osman

455

Optimierung der dünnschichtchromatographischen Trennung der Inhaltsstoffe der Extrakte von Digitalis purpurea auf Kieselgelschichten  

Microsoft Academic Search

The separation of the glycosides of Digitalis purpurea by thin-layer chromatography (TLC) on dry silica gel plates has been optimized. It was found that a complete assessment of the extracts can only be obtained if the polar primary glycosides are developed with ethylmethylketone; water (94.6?5.4) and the lower polar secondary glycosides and the aglycones with ethyl acetate: n-hexane: ethanol (65?15?10).

A. Janßen; D. Sopczak

1980-01-01

456

Isochoric thermal conductivity of solid n-alkanes: Hexane C6H14  

NASA Astrophysics Data System (ADS)

The isochoric thermal conductivity of solid n-hexane C6H14 is studied using three samples with different densities for temperatures ranging from 100 K to the onset of melting. In all cases, the isochoric thermal conductivity varies more weakly than ??1/T. The present results are compared with the thermal conductivities of other representatives of the n-alkanes. The contributions of low-frequency phonons and "diffuse modes" to the thermal conductivity are calculated.

Konstantinov, V. A.; Revyakin, V. P.; Sagan, V. V.

2011-05-01

457

Antioxidant Potential ofEcklonia cavaon Reactive Oxygen Species Scavenging, Metal Chelating, Reducing Power and Lipid Peroxidation Inhibition  

Microsoft Academic Search

The antioxidative potential of different fractions (respective organic and aqueous fractions of n-hexane, chloroform and ethyl acetate) of 70% methanol extract of Ecklonia cava(a brown seaweed) was evaluated using 1,1-diphenyl-2-picrylhydrazyl (DPPH), superoxide anion, hydrogen peroxide, hydroxyl radical, nitric oxide, ferrous ion chelating, reducing power and lipid peroxidation inhibition (conjugated diene hydroperoxide and thiobarbituric acid-reactive substances production) assays. The 70% methanol

Mahinda Senevirathne; Soo-Hyun Kim; Nalin Siriwardhana; Jin-Hwan Ha; Ki-Wan Lee; You-Jin Jeon

2006-01-01

458

Efficacy of Piper guineense (Schum & Thonn) seed extract against maize weevil, Sitophilus zeamais (Motschulsky) as influenced by different extraction solvents  

Microsoft Academic Search

The seed extract of black pepper Piper guineense Schum & Thonn was evaluated for its biological activity against the maize weevil Sitophilus zeamais Motschulsky at 30°C, 65 ± 2% R.H and 12:12-h light:dark regimes in the laboratory. The different solvents used for the extraction were acetone, ethanol, n-hexane, petroleum ether (60:80) and distilled water at 0.3% dosage level. The acetone extract had

Elechi F. Asawalam; Steve O. Emosairue; Friday Ekeleme; Roland Wokocha

2007-01-01

459

A chemical extraction method for mimicking bioavailability of polycyclic aromatic hydrocarbons to wheat grown in soils containing various amounts of organic matter  

SciTech Connect

Severe contamination of agricultural soils by polycyclic aromatic hydrocarbons (PAHs) occurs in many places in China mainly as a result of coal and biomass combustion. Because ingestion is the main source of human exposure to PAHs and vegetables are basic ingredients for the Chinese diet, it is important to know how and to what extent PAHs are accumulated in vegetables produced in contaminated soils. This study, evaluated the extent to which organic matter contents in soils influence the accumulation of PAHs by the roots of wheat plants and have developed a rapid chemical method for determining the bioavailability of PAH. Four PAHs, naphthalene, acenaphthylene, fluorene, and phenanthrene, were added to natural soil samples with different amounts of organic matter for pot experiments to evaluate apparent bioavailability of PAHs to wheat roots (Triticum aestivum L.). The extractabilities of PAHs in the soil were tested by a sequential extraction scheme using accelerated solvent extraction with water, n-hexane, and a mixture of dichloromethane and acetone as solvents. The water or n-hexane-extractable PAHs were positively correlated to dissolved organic matter (DOM) and negatively correlated to total organic matter (TOM), indicating mobilization and immobilization effects of DOM and TOM on soil PAHs, respectively. The apparent accumulation of PAHs by wheat roots was also positively and negatively correlated to DOM and TOM, respectively. As a result, there are positive correlations between the amounts of PAHs extracted by water or n-hexane and the quantities accumulated in plant roots, suggesting the feasibility of using water- or n-hexanes-extractable fractions as indicators of PAH availability to plants. 19 refs., 8 figs., 1 tab.

Shu Tao; Fuliu Xu; Wenxin Liu; Yanhong Cui; Raymond M. Coveney, Jr. [Peking University, Beijing (China). Laboratory for Earth Surface Processes, College of Environmental Sciences

2006-04-01

460

Study of electric breakdown of liquid dielectrics using Schlieren optical techniques  

Microsoft Academic Search

The work is a contribution to the understanding of the mechanism of electric breakdown in liquid dielectrics. The liquid dielectric chosen throughout the experiments was n-hexane, because an extensive literature exists on the breakdown of this material. The applied voltage was a rectangular pulse of different durations supplied from a 125 kv, five-stage Marx-Goodlet impulse generator. A novel rotary multiple

B. Farazmand

1961-01-01

461

Pyrene-POSS nanohybrid as a dispersant for carbon nanotubes in solvents of various polarities: its synthesis and application in the preparation of a composite membrane.  

PubMed

In this study we report the preparation of nanohybrid dispersant molecules based on pyrene and polyhedral oligomeric silsesquioxanes for non-covalent functionalization of multi-walled carbon nanotubes (MWCNTs). The prepared dispersant improves the dispersion of MWCNTs in organic solvents with very different polarities such as tetrahydrofuran, toluene, and n-hexane. The functionalized MWCNTs were used to introduce conductivity into polydimethylsiloxane membranes which can be used for electrostatic discharge applications. PMID:22676373

Majeed, Shahid; Filiz, Volkan; Shishatskiy, Sergey; Wind, Jan; Abetz, Clarissa; Abetz, Volker

2012-01-01

462

A sensitive colorimetric high-throughput screening method for lipase synthetic activity assay.  

PubMed

A sensitive and practical high-throughput screening method for assaying lipase synthetic activity is described. Lipase-catalyzed transesterification between vinyl acetate and n-butanol in n-hexane was chosen as a model reaction. The released acetaldehyde was determined by the colorimetric method using 3-methyl-2-benzothialinone (MBTH) derivatization. In comparison with other methods, the major advantages of this process include high sensitivity, simple detection, inexpensive reagents, and low requirements for instruments. PMID:24525041

Zheng, Jianyong; Fu, Xianfeng; Ying, Xiangxian; Zhang, Yinjun; Wang, Zhao

2014-05-01

463

Isoprenylated xanthone and benzophenone constituents of the pericarp of Garcinia planchonii.  

PubMed

A new xanthone, planchoxanthone (1), together with six known compounds, garcinianone A (2), cowanin (3), rubraxanthone (4), f-mangostin (5), dulcisxanthone B (6), and guttiferone Q (7), were isolated from an n-hexane extract of the pericap of Garcinia planchonii. Their structures were elucidated using spectroscopic methods. Antioxidant activity of the isolated compounds was tested using the DPPH free radical scavenging assay. PMID:25632472

Trinh, Duong Hoang; Ha, Ly Dieu; Tran, Phuong Thu; Nguyen, Lien-Hoa Dieu

2014-12-01

464

Characteristic study of polycyclic aromatic hydrocarbons for fine and coarse particulates at Pastureland near Industrial Park sampling site of central Taiwan  

Microsoft Academic Search

The concentrations of ambient air polycyclic aromatic hydrocarbons were measured in a farm area (Tunghai University Pastureland) between August 2001 and April 2002 in central Taiwan, Taichung. Particle-bound polycyclic aromatic hydrocarbons (PAHs) were collected on quartz filters, the collected sample was extracted with a dichloromethane (DCM)\\/n-hexane mixture (50\\/50, v\\/v) for 24h, and then the extracts were subjected to gas chromatography–mass

Guor-Cheng Fang; Yuh-Shen Wu; Jyh-Cherng Chen; Peter Pi-Cheng Fu; Cheng-Nan Chang; Tse-Tsung Ho; Ming-Hsiang Chen

2005-01-01

465

Analysis of Benzo[a]pyrene in Vegetable Oils Using Molecularly Imprinted Solid Phase Extraction (MISPE) Coupled with Enzyme-Linked Immunosorbent Assay (ELISA)  

PubMed Central

This paper describes the development of a molecularly imprinted polymer-based solid phase extraction (MISPE) method coupled with enzyme-linked immunosorbent assay (ELISA) for determination of the PAH benzo[a]pyrene (B[a]P) in vegetable oils. Different molecularly imprinted polymers (MIPs) were prepared using non-covalent 4-vinylpyridine/divinylbenzene co-polymerization at different ratios and dichloromethane as porogen. Imprinting was done with a template mixture of phenanthrene and pyrene yielding a broad-specific polymer for PAHs with a maximum binding capacity (Q) of ?32 ?g B[a]P per 50 mg of polymer. The vegetable oil/n-hexane mixture (1:1, (v/v)) was pre-extracted with acetonitrile, the solvent evaporated, the residue reconstituted in n-hexane and subjected to MISPE. The successive washing with n-hexane and isopropanol revealed most suitable to remove lipid matrix constituents. After elution of bound PAHs from MISPE column with dichloromethane, the solvent was evaporated, the residue reconstituted with dimethyl sulfoxide and diluted 100-fold with methanol/water (10:90, (v/v)) for analysis of B[a]P equivalents with an ELISA. The B[a]P recovery rates in spiked vegetable oil samples of different fatty acid composition were determined between 63% and 114%. The presence of multiple PAHs in the oil sample, because of MIP selectivity and cross-reactivity of the ELISA, could yield overestimated B[a]P values. PMID:24887045

Pschenitza, Michael; Hackenberg, Rudolf; Niessner, Reinhard; Knopp, Dietmar

2014-01-01

466

In vitro antiprotozoal activity of extracts of five Turkish Lamiaceae species.  

PubMed

The in vitro antiprotozoal activities of crude methanolic extracts from the aerial parts of five Lamiaceae plants (Salvia tomentosa, S. sclarea, S. dichroantha, Nepeta nuda subsp. nuda and Marrubium astracanicum subsp. macrodon) were evaluated against four parasitic protozoa, i.e. Trypanosoma brucei rhodesiense, T. cruzi, Leishmania donovani and Plasmodium falciparum. The cytotoxic potentials of the extracts on L6 cells were also evaluated. Melarsoprol, benznidazole, miltefosine, chloroquine and podophyllotoxin were used as reference drugs. All crude MeOH extracts showed antiprotozoal potential against at least three parasites, so they were dispersed in water and partitioned against n-hexane and chloroform to yield three subextracts that were screened in the same test systems. The n-hexane extract of N. nuda was the most active against T. brucei rhodesiense while the CHCl3 extracts of S. tomentosa and S. dichroantha showed significant activity against L. donovani. All organic extracts displayed in vitro antimalarial and moderate trypanocidal activities against T. cruzi with the n-hexane extract of S. sclarea being the most active against the latter. The extracts displayed low or no cytotoxicity towards mammalian L6 cells. PMID:22224291

Kirmizibekmez, Hasan; Atay, Irem; Kaiser, Marcel; Yesilada, Erdem; Tasdemir, Deniz

2011-11-01

467

Effects of ammonium sulfate aerosols on the gas-phase reactions of the hydroxyl radical with organic compounds  

NASA Astrophysics Data System (ADS)

Air quality modeling is of seminal importance to the assessment of air pollution control strategies. Traditionally, these models include four basic components: meteorology data, emissions data, transport mechanisms, and chemistry. The gas-phase chemistry portions have been based on kinetic and product laboratory studies in relatively pristine gas-phase environments. However, given the abundance of particles in the atmosphere, it is possible that aerosols can have catalytic effects on gas-phase reaction kinetics. These studies focus on elucidating those effects. Ultimately, the data gained can be used to improve regional air quality models. Relative rate studies of the OH radical initiated reactions of n-hexane, p-xylene, and 1-propanol were conducted in a Tedlar bag in the presence of ammonium sulfate aerosols. Results show that ammonium sulfate aerosols promote the reaction of 1-propanol with OH radicals compared to the reactions of n-hexane with OH radicals and p-xylene with OH radicals. The relative rate of the 1-propanol/·OH reaction versus the n-hexane/·OH reaction increased from 0.85±0.05 in the absence of (NH 4) 2SO 4 aerosols to 1.07±0.05 in the presence of aerosols. Also, the relative rate of the 1-propanol/·OH reaction versus the p-xylene/·OH reaction increased from 0.45±0.03 in the absence of (NH 4) 2SO 4 aerosols to 0.56±0.02 in the presence of aerosols.

Oh, Sewon; Andino, Jean M.

468

P-Glycoprotein inhibitory activity of lipophilic constituents of Echinacea pallida roots in a human proximal tubular cell line.  

PubMed

The N-hexane root extracts from Echinacea pallida, Echinacea angustifolia and Echinacea purpurea were evaluated for inhibition of the multidrug transporter P-glycoprotein (Pgp) activity, the product of the ABCB1 gene, involved in cancer multidrug resistance (MDR) and in herb-drug or drug-drug interactions. The biological assay was performed using the human proximal tubule HK-2 cell line that constitutively expresses ABCB1. The N-hexane extracts of all three species reduced the efflux of the Pgp probe calcein-AM from HK-2 cells two-fold in a concentration-dependent manner, and E. pallida was found to be the most active species. For the first time, two polyacetylenes and three polyenes, isolated from the N-hexane extract of E. pallida roots by a bioassay-guided fractionation, were found to be able to reduce Pgp activity. Pentadeca-(8 Z,13 Z)-dien-11-yn-2-one was the most efficient compound, being able to decrease the calcein-AM efflux about three-fold with respect to the control at 30 microg/mL. PMID:18425719

Romiti, Nadia; Pellati, Federica; Nieri, Paola; Benvenuti, Stefania; Adinolfi, Barbara; Chieli, Elisabetta

2008-02-01

469

Asparagopsis armata and Sphaerococcus coronopifolius as a natural source of antimicrobial compounds.  

PubMed

Methanol, n-hexane and dichloromethane extracts of twelve marine macro-algae (Rhodophyta, Chlorophyta and Heterokontophyta divisions) from Peniche coast (Portugal) were evaluated for their antibacterial and antifungal activity. The antibacterial activity was evaluated by disc diffusion method against Bacillus subtilis (gram positive bacteria) and Escherichia coli (gram negative bacteria). Saccharomyces cerevisiae was used as a model for the antifungal activity by evaluating the growth inhibitory activity of the extracts. The high antibacterial activity was obtained by the Asparagopsis armata methanolic extract (10 mm-0.1 mg/disc), followed by the Sphaerococcus coronopifolius n-hexane extract (8 mm-0.1 mg/disc), and the Asparagopsis armata dichloromethane extract (12 mm-0.3 mg/disc) against Bacillus subtilis. There were no positive results against Escherichia coli. Sphaerococcus coronopifolius revealed high antifungal potential for n-hexane (IC50 = 40.2 µg/ml), dichloromethane (IC50 = 78.9 µg/ml) and methanolic (IC50 = 55.18 µg/ml) extracts against Saccharomyces cerevisiae growth. The antifungal potency of the Sphaerococcus coronopifolius extracts was similar with the standard amphotericin B. Asparagopsis armata and Sphaerococcus coronopifolius reveal to be interesting sources of natural compounds with antimicrobial properties. PMID:25588525

Pinteus, Susete; Alves, Celso; Monteiro, Hugo; Araújo, Ernesto; Horta, André; Pedrosa, Rui

2015-03-01

470

Antimicrobial Activity and Brine Shrimp Lethality Bioassay of the Leaves Extract of Dillenia indica Linn  

PubMed Central

The crude methanolic extract of Dillenia indica Linn. (Dilleniaceae) leaves has been investigated for the evaluation of antimicrobial and cytotoxic activities. Organic solvent (n-hexane, carbon tetrachloride and chloroform) fractions of methanolic extract and methanolic fraction (aqueous) were screened for their antimicrobial activity by disc diffusion method. Besides, the fractions were screened for cytotoxic activity using brine shrimp (Artemia salina) lethality bioassay. Among the four fractions tested, n-hexane, carbon tetrachloride, and chloroform fractions showed moderate antibacterial and antifungal activity compared to standard antibiotic, kanamycin. The average zone of inhibition was ranged from 6 to 8 mm at a concentration of 400 µg/disc. But the aqueous fraction was found to be insensitive to microbial growth. Compared to vincristine sulfate (with LC50 of 0.52 µg/ ml), n-hexane and chloroform fractions demonstrated a significant cytotoxic activity (having LC50 of 1.94 µg/ml and 2.13 µg/ml, respectively). The LC50 values of the carbon tetrachloride and aqueous fraction were 4.46 µg/ml and 5.13 µg/ ml, respectively. The study confirms the moderate antimicrobial and potent cytotoxic activities of Dillenia indica leaves extract and therefore demands the isolation of active principles and thorough bioassay. PMID:21331191

Apu, AS; Muhit, MA; Tareq, SM; Pathan, AH; Jamaluddin, ATM; Ahmed, M

2010-01-01

471

Ultrasound-assisted extraction and solid-phase extraction as a cleanup procedure for organochlorinated pesticides and polychlorinated biphenyls determination in aquatic samples by gas chromatography with electron capture detection.  

PubMed

The feasibility of developing a quick, easy, efficient procedure for the simultaneous determination of organochlorinated pesticides and polychlorinated biphenyls in aquatic samples using gas chromatography with electron capture detection based on solid-phase extraction was investigated. The extraction solvent (n-hexane/acetone, cyclohexane/ethyl acetate, n-hexane/dichloromethane, n-hexane) for ultrasound-assisted solid-liquid extraction and solid-phase extraction columns (florisil, neutral alumina, acidic alumina, aminopropyl trimethoxy silane, propyl ethylenediamine, aminopropyl trimethoxy silane/propyl ethylenediamine, graphitized carbon black and silica) for cleanup procedure were optimized. The gas chromatography with electron capture detection method was validated in terms of linearity, sensitivity, reproducibility, and recovery. Mean recoveries ranged from 75 to 115% with relative standard deviations <13%. Quantification limits were 0.20-0.40 ng/g for organochlorinated pesticides and polychlorinated biphenyls. The satisfactory data demonstrated the good reproducibility of the method with relative standard deviations lower than 13%. In comparison to other related methods, this method requires less time and solvent and allows for rapid isolation of the target analytes with high selectivity. This method therefore allows for the screening of numerous samples and can also be used for routine analyses. PMID:25529797

Sun, Xiumei; Hu, Hongmei; Zhong, Zhi; Jin, Yanjian; Zhang, Xiaojun; Guo, Yuanming

2015-02-01

472

Excess molar volumes of ternary mixtures of [x{sub 1}CH{sub 3}CH{sub 2}COOCH{sub 2}CH{sub 3} + x{sub 2}CH{sub 3}(CH{sub 2}){sub 4}CH{sub 3} + (1 {minus} x{sub 1} {minus} x{sub 2})CH{sub 3}(CH{sub 2}){sub 6}OH or CH{sub 3}(CH{sub 2}){sub 7}OH] at the temperature of 298.15 K  

SciTech Connect

Excess molar volumes at the temperature 298.15 K were measured for the ternary systems [x{sub 1}ethyl propanoate + x{sub 2}hexane + (1 {minus} x{sub 1} {minus} x{sub 2})heptan-1-ol or (1 {minus} x{sub 1} {minus} x{sub 2})octan-1-ol] and for binary mixtures [x{sub 1}ethyl propanoate + (1 {minus} x{sub 1})n-hexane], [x{sub 1}ethyl propanoate + (1 {minus} x{sub 1})heptan-1-ol], [x{sub 1}n-hexane + (1 {minus} x{sub 1})heptan-1-ol], [x{sub 1}ethyl propanoate + (1 {minus} x{sub 1})octan-1-ol], and [x{sub 1}n-hexane + (1 {minus} x{sub 1})octan-1-ol]. Excess molar volumes were determined using a densimeter Anton Paar DMA 60/602. The experimental values were compared with the results obtained with some empirical methods for the estimation of ternary properties from binary results.

Jimenez, E.; Franjo, C.; Segade, L. [Univ. da Coruna (Spain)] [Univ. da Coruna (Spain); Legido, J.L. [Univ. de Vigo (Spain)] [Univ. de Vigo (Spain); Paz Andrade, M.I. [Univ. de Santiago (Spain)] [Univ. de Santiago (Spain)

1997-03-01

473

KEY COMPARISON: International comparison CCQM-K54: Primary standard gas mixtures of hexane in methane  

NASA Astrophysics Data System (ADS)

The aim of this comparison is to evaluate the gravimetry and purity verification of gas mixtures prepared by introducing a liquid into a gas cylinder. This type of preparation is well known from, e.g., ethanol in nitrogen/air (CCQM-K4), and n-hexane in synthetic natural gas (CCQM-K16). The choice for n-hexane in methane is based on the relevance of natural gas primary standard mixtures and higher hydrocarbons in synthetic natural gas (for, e.g., dew point calibrations). Furthermore, n-hexane is relatively straightforward to analyse using a GC/FID (gas chromatograph equipped with a flame ionisation detector) with good repeatability. Eight laboratories participated. After the data evaluation, the result of one laboratory was eliminated to arrive at a consistent subset. The quality of the fitted line was not overly good, leading to small discrepancies in the degrees-of-equivalence calculated for three other laboratories. Only four laboratories are consistent with the KCRV. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

van der Veen, Adriaan M. H.; Chander, Hima; Ziel, Paul R.; Wessel, Rob M.; de Leer, Ed W. B.; Smeulders, Damian; Besley, Laurie; Kato, Kenji; Watanabe, Takuro; Seog Kim, Jin; Woo, Jin-Chun; Bae, Hyun Kil; Doo Kim, Yong; Pérez Castorena, Alejandro; Rangel Murillo, Francisco; Serrano Caballero, Victor M.; Ramírez Nambo, Carlos; de Jesús Avila Salas, Manuel; Konopelko, Leonid A.; Popova, Tatjana A.; Pankratov, V. V.; Kovrizhnih, M. A.; Kuzmina, T. A.; Efremova, O. V.; Kustikov, Yury A.; Milton, Martin J. T.; Vargha, Gergely; Guenther, Frank R.; Rhoderick, George C.

2010-01-01

474

[Simultaneous determinations of carbamate pesticides in cereal by high performance liquid chromatography with post-column fluorescence derivatization].  

PubMed

A liquid chromatographic method for the simultaneous determination of carbamate pesticides in cereal by Waters Carbamate Analysis System with post-column fluorescence derivatization is described. The cereal sample homogenate was extracted with acetone and water. The extract was partitioned between 5% sodium chloride solution and dichloromethane. The dichloromethane layer was concentrated to dryness. The residue was dissolved in n-hexane and extracted with acetonitrile (saturated with n-hexane). The acetonitrile layer was decreased with n-hexane (saturated with acetonitrile), then the acetonitrile layer was concentrated to dryness. The residue was dissolved in methanol. It's the test solution for HPLC. Nine carbamate pesticides and their three metabolites were separated by Waters Carbamate Column with gradient elution. Two steps underwent in the post-column system: hydrolysis by NaOH solution and the reaction of the product with o-phthalaldehyde and 2-mercaptoethanol. The resulting fluorescence derivative was detected at 445 nm (excitation at 339 nm). The selectivity, reproducibility and sensitivity of proposed method are better than those reported with other methods. The detection limits was 5 micrograms/kg of samples. PMID:11498925

Yu, W; Wang, C; Chu, X

1998-09-01

475

Antidiabetic effect of Equisetum arvense L. (Equisetaceae) in streptozotocin-induced diabetes in male rats.  

PubMed

In view of alleged antidiabetic potential effect of the methanol, n-hexan and dichloromethane extracts of Equisetum arvense of blood sugar and body weight in streptozotocin-induced (50 mg kg(-1), i.p. dissolved in normal saline) diabetic rats were investigated. The blood glucose lowering activity of the methanol, n-hexan and dichloromethane extracts was determined in steptozotocin-induced diabetic rats; after oral administration in doses of 50, 100, 250 and 500 mg kg(-1) daily for 5 weeks. The data was compare statistically using one-way ANOVA tukey test. The results showed that in different doses of methanolic extract, dichloromethane extract at doses of 50 and 250 mg kg(-1) and n-hexan extract (50 mg kg(-1)), blood sugar decreased significantly in comparison with the treatment and control groups of diabetic rats. Also the weights of methanolic-extract treatment group were higher than the other treatment groups. The present studies clearly indicate a significant antidiabetic effect with the methanolic extract of Equisetum arvense and lend support for its traditional usage. Further investigation on identification of the active principles and their mode of action are needed to unravel the molecular mechanisms involved in the observed effects. PMID:19086514

Safiyeh, Soleimani; Fathallah, Fathiazar Baijani; Vahid, Nejati; Hossine, Nazemiyeh; Habib, Shojaei Sadee

2007-05-15

476

Dielectric constant of liquid alkanes and hydrocarbon mixtures  

NASA Technical Reports Server (NTRS)

The complex dielectric constants of n-alkanes with two to seven carbon atoms have been measured. The measurements were conducted using a slotted-line technique at 1.2 GHz and at atmospheric pressure. The temperature was varied from the melting point to the boiling point of the respective alkanes. The real part of the dielectric constant was found to decrease with increasing temperature and correlate with the change in the molar volume. An upper limit to all the loss tangents was established at 0.001. The complex dielectric constants of a few mixtures of liquid alkanes were also measured at room temperature. For a pentane-octane mixture the real part of the dielectric constant could be explained by the Clausius-Mosotti theory. For the mixtures of n-hexane-ethylacetate and n-hexane-acetone the real part of the dielectric constants could be explained by the Onsager theory extended to mixtures. The dielectric constant of the n-hexane-acetone mixture displayed deviations from the Onsager theory at the highest fractions of acetone. The dipole moments of ethylacetate and acetone were determined for dilute mixtures using the Onsager theory and were found to be in agreement with their accepted gas-phase values. The loss tangents of the mixtures exhibited a linear relationship with the volume fraction for low concentrations of the polar liquids.

Sen, A. D.; Anicich, V. G.; Arakelian, T.

1992-01-01

477

Analysis of benzo[a]pyrene in vegetable oils using molecularly imprinted solid phase extraction (MISPE) coupled with enzyme-linked immunosorbent assay (ELISA).  

PubMed

This paper describes the development of a molecularly imprinted polymer-based solid phase extraction (MISPE) method coupled with enzyme-linked immunosorbent assay (ELISA) for determination of the PAH benzo[a]pyrene (B[a]P) in vegetable oils. Different molecularly imprinted polymers (MIPs) were prepared using non-covalent 4-vinylpyridine/divinylbenzene co-polymerization at different ratios and dichloromethane as porogen. Imprinting was done with a template mixture of phenanthrene and pyrene yielding a broad-specific polymer for PAHs with a maximum binding capacity (Q) of ~32 ?g B[a]P per 50 mg of polymer. The vegetable oil/n-hexane mixture (1:1, (v/v)) was pre-extracted with acetonitrile, the solvent evaporated, the residue reconstituted in n-hexane and subjected to MISPE. The successive washing with n-hexane and isopropanol revealed most suitable to remove lipid matrix constituents. After elution of bound PAHs from MISPE column with dichloromethane, the solvent was evaporated, the residue reconstituted with dimethyl sulfoxide and diluted 100-fold with methanol/water (10:90, (v/v)) for analysis of B[a]P equivalents with an ELISA. The B[a]P recovery rates in spiked vegetable oil samples of different fatty acid composition were determined between 63% and 114%. The presence of multiple PAHs in the oil sample, because of MIP selectivity and cross-reactivity of the ELISA, could yield overestimated B[a]P values. PMID:24887045

Pschenitza, Michael; Hackenberg, Rudolf; Niessner, Reinhard; Knopp, Dietmar

2014-01-01

478

In vitro antimicrobial activity on clinical microbial strains and antioxidant properties of Artemisia parviflora  

PubMed Central

Background Artemisia parviflora leaf extracts were evaluated for potential antimicrobial and antioxidant properties. Antimicrobial susceptibility assay was performed against ten standard reference bacterial strains. Antioxidant activity was analyzed using the ferric thiocyanate and 2, 2-Diphenyl-1-Picrylhydrazyl (DPPH) assays. Radical scavenging activity and total phenolic content were compared. Phytochemical analyses were performed to identify the major bioactive constitution of the plant extract. Results Hexane, methanol and ethyl acetate extracts of A. parviflora leaves exhibited good activity against the microorganisms tested. The n-hexane extract of A. parviflora showed high inhibition of the growth of Pseudomonas aeruginosa, Escherichia coli and Shigella flexneri. Methanol extract showed strong radical scavenging and antioxidant activity, other extracts showed moderate antioxidant activity. The major derivatives present in the extracts are of terpenes, steroids, phenols, flavonoids, tannins and volatile oil. Conclusions The results obtained with n-hexane extract were particularly significant as it strongly inhibited the growth of P. aeruginosa, E. coli and S. flexneri. The major constituent of the n-hexane extract was identified as terpenes. Strong antioxidant activity could be observed with all the individual extracts. The antimicrobial and antioxidant property of the extracts were attributed to the secondary metabolites, terpenes and phenolic compounds present in A. parviflora and could be of considerable interest in the development of new drugs. PMID:23171441

2012-01-01

479

Profile of volatile components of hydrodistilled and extracted leaves of Jacaranda acutifolia and their antimicrobial activity against foodborne pathogens.  

PubMed

Volatile constituents of the essential oil and n-hexane extract of Jacaranda acutifolia Humb. and Bonpl. (Bignoniaceae) leaves were determined, and their antimicrobial activities were investigated using an agar diffusion method. The minimum inhibitory concentrations (MIC) were determined and compared with those of standard antibiotics (penicillin, gentamicin and nystatin). The chemical composition of the oils was analyzed by capillary gas chromatography (GLC-FID) and gas chromatography-mass spectrometry (GLC-MS). Thirty-four components, comprising almost 93.8% of the total peak area, were identified in the leaf essential oil. The main components were methyl linolenate (26.7%), 1-octen-3-ol (10.8%), methyl phenyl acetate (9.9%), beta-linalool (5.5%) and palmitic acid (4.7%). The n-hexane extract revealed similar oil constituents, but also p-benzoquinone, phenyl acetic acid, resorcinol and homogentisic acid. The oil showed some activity against Staphylococcus aureus and Escherichia coli with MIC values of 2.2 and 2.9 mg/mL, respectively, and moderate activity against Candida albicans, Salmonella typhimurium and Shigella flexneri. The n-hexane extract showed moderate activities against all tested microorganisms, with MIC values ranging from 3.5 to 10.2 mg/mL. The antimicrobial activities of the hydrodistilled and extracted leaves make their local traditional uses rational. PMID:25230515

Singab, Abdel Nasser B; Mostafa, Nada M; Eldahshan, Omayma A; Ashour, Mohamed L; Wink, Michael

2014-07-01

480

Lysophosphatidylcholine Synthesis by Lipase-catalyzed Ethanolysis.  

PubMed

Lysophosphatidylcholine (LPC) is amphiphilic substance, and possesses excellent physiological functions. In this study, LPC was prepared through ethanolysis of phosphatidylcholine (PC) in n-hexane or solvent free media catalyzed by Novozym 435 (from Candida antarctica), Lipozyme TLIM (from Thermomcyces lanuginosus) and Lipozyme RMIM (from Rhizomucor miehei). The results showed that three immobilized lipases from Candida Antarctica, Thermomcyces lanuginosus and Rhizomucor miehei could catalyze ethanolysis of PC efficiently. In n-hexane, the LPC conversions of ethanolysis of PC catalyzed by Novozyme 435, Lipozyme TLIM and Lipozyme RMIM could reach to 98.5 ± 1.6%, 94.6 ± 1.4% and 93.7 ± 1.8%, respectively. In solvent free media, the highest LPC conversions of ethanolysis of PC catalyzed by Novozyme 435, Lipozyme TL IM and Lipozyme RM IM were 97.7 ± 1.7%, 93.5 ± 1.2% and 93.8 ± 1.9%, respectively. The catalytic efficiencies of the three lipases were in the order of Novozyme 435 > Lipozyme TLIM > Lipozyme RMIM. Furthermore, their catalytic efficiencies in n-hexane were better than those in solvent free media. PMID:25766935

Yang, Guolong; Yang, Ruoxi; Hu, Jingbo

2015-04-01

481

Functionalized hollow siliceous spheres for VOCs removal with high efficiency and stability.  

PubMed

Functionalized hollow siliceous spheres (HSSs) have been prepared by surface modification with trimethylchlorosilane (TMCS) for the removal of volatile organic compounds (VOCs). The resultant HSSs-TMCS possesses a uniform and well-dispersed hollow spherical structure, high surface area, large total pore volume, high VOCs adsorption capacity, and small water vapor adsorption capacity. The adsorption and desorption performance of HSSs-TMCS under static (n-hexane and 93# gasoline) and dynamic (n-hexane) conditions was investigated. Compared with commercial silica gel (SG) and activated carbon (AC), HSSs-TMCS show higher capacity of adsorbing n-hexane and 93# gasoline with good stability and low water vapor adsorption capacity under static adsorption conditions, higher dynamic adsorption capacity and stable breakthrough time under dynamic adsorption conditions. The high efficiency and stability of functionalized HSSs are associated with their unique hollow morphology and structure parameters. The designed HSSs-TMCS with high VOCs removal capacity and recyclability are promising candidates for the treatment of air pollution. PMID:24486614

Wang, Hongning; Tang, Mei; Zhang, Ke; Cai, Daofei; Huang, Weiqiu; Chen, Ruoyu; Yu, Chengzhong

2014-03-15

482

Microgravity Droplet Combustion in CO2 Enriched Environments at Elevated Pressures  

NASA Technical Reports Server (NTRS)

Microgravity droplet combustion experiments were performed in elevated concentrations of CO2 at pressures of 1.0 atm, 3.0 atm, and 5.0 atm to examine the effects of a radiatively participating suppression agent in space applications. Methanol and n-heptane droplets, with an initial diameter of 2.0 mm supported on a quartz fiber, were used in these experiments. The ambient O2 concentration was held constant at 21% and the CO2 concentrations ranged from 0% to a maximum of 70%, by volume with the balance consisting of N2 . Results from the methanol tests showed slight decreases in burning rates with increased CO2 concentrations at all ambient pressures. The n-heptane tests show slight increases in burning rates with increasing CO2 concentrations at each pressure level. Instantaneous radiative heat flux was also measured using both a broadband radiometer (i.e., wavelengths from 0.6 microns to 40.0 microns) and a narrowband radiometer (i.e., centered at 5.6 microns with a filter width at half maximum of 1.5 microns). Radiative exchanges between the droplet and surrounding gases as well as the soot field produce departures from the classical quasisteady theory which would predict a decrease in burning rates with increasing CO2 concentrations in microgravity.

Hicks, Michael C.; Nayagam, V.; Williams, F. A.

2007-01-01

483

Interference-free mid-IR laser absorption detection of methane  

NASA Astrophysics Data System (ADS)

A novel, mid-IR scanned-wavelength laser absorption diagnostic was developed for time-resolved, interference-free, absorption measurement of methane concentration. A differential absorption (peak minus valley) scheme was used that takes advantage of the structural differences of the absorption spectrum of methane and other hydrocarbons. A peak and valley wavelength pair was selected to maximize the differential cross-section (?peak minus valley) of methane for the maximum signal-to-noise ratio, and to minimize that of the interfering absorbers. Methane cross-sections at the peak and valley wavelengths were measured over a range of temperatures, 1000 to 2000 K, and pressures 1.3 to 5.4 atm. The cross-sections of the interfering absorbers were assumed constant over the small wavelength interval between the methane peak and valley features. Using this diagnostic, methane concentration time histories during n-heptane pyrolysis were measured behind reflected shock waves in a shock tube. The differential absorption scheme efficiently rejected the absorption interference and successfully recovered the vapor-phase methane concentration. These measurements allowed the comparison with methane concentration time-history simulations derived from a current n-heptane reaction mechanism (Sirjean et al 2009 A high-temperature chemical kinetic model of n-alkane oxidation JetSurF version 1.0).

Pyun, Sung Hyun; Cho, Jungwan; Davidson, David F.; Hanson, Ronald K.

2011-02-01

484

The effect of azeotropism on combustion characteristics of blended fuel pool fire.  

PubMed

The effect of azeotropism on combustion characteristics of blended fuel pool fire was experimentally studied in an open fire test space of State Key Laboratory of Fire Science. A 30 cm × 30 cm square pool filled with n-heptane and ethanol blended fuel was employed. Flame images, burning rate and temperature distribution were collected and recorded in the whole combustion process. Results show that azeotropism obviously dominates the combustion behavior of n-heptane/ethanol blended fuel pool fire. The combustion process after ignition exhibits four typical stages: initial development, azeotropic burning, single-component burning and decay stage. Azeotropism appears when temperature of fuel surface reaches azeotropic point and blended fuel burns at azeotropic ratio. Compared with individual pure fuel, the effect of azeotropism on main fire parameters, such as flame height, burning rate, flame puffing frequency and centerline temperature were analyzed. Burning rate and centerline temperature of blended fuel are higher than that of individual pure fuel respectively at azeotropic burning stage, and flame puffing frequency follows the empirical formula between Strouhal and Froude number for pure fuel. PMID:24632362

Ding, Yanming; Wang, Changjian; Lu, Shouxiang

2014-04-30

485

Glycerol monooleate reverse micelles in nonpolar solvents: computer simulations and small-angle neutron scattering.  

PubMed

The formation of glycerol monooleate reverse micelles in n-heptane and toluene at room temperature is studied using molecular-dynamics simulations and small-angle neutron scattering. The glycerol monooleate concentrations under consideration are in the range of 5-20 wt %. Under these conditions, spontaneous reverse-micelle formation is observed on the simulation timescale (up to 30 ns). From simulations, the typical dimensions (semiaxes) of the equivalent ellipsoids with the same masses and moments of inertia are in the range of 15-23 Å, with instantaneous shapes that are slightly nonspherical. By analyzing the scattering form factors from simulation and experiment, the radii of gyration of the reverse micelles are determined to be approximately 15 Å. The number of glycerol monooleate molecules in a reverse micelle is smaller in toluene (?20) than in n-heptane (?30), but the overall dimensions are similar due to greater penetration of the toluene in to the reverse micelle. The effects of low concentrations (1 wt %) of water, acetic acid, and ethanol on the reverse-micelle dimensions are determined. The overall structural effects are small, but the distributions of the molecules within the reverse micelles are shown to be sensitive to the molecular polarity. PMID:25721707

Bradley-Shaw, Joshua L; Camp, Philip J; Dowding, Peter J; Lewtas, Ken

2015-03-19

486

Isolation and purification of series bioactive components from Hypericum Perforatum L. by high-speed counter-current chromatography  

PubMed Central

High-speed counter-current chromatography (HSCCC) combined with pre-separation by ultrasonic solvent extraction was successively used for the separation of series bioactive compounds from the crude extract of Hypericum perforatum L. The petroleum ether extract was separated by the solvent system of n-heptane-methanol-acetonitrile (1.5:0.5:0.5, v/v) and n-heptane-methanol (1.5:1, v/v) in gradient elution, yielding a phloroglucinol compound, hyperforin with HPLC purity over 98%. The ethyl acetate extract was separated by using the solvent system composed of hexane-ethyl acetate-methanol-water (1:1:1:1 and 1:3:1:3, v/v) in gradient through both reverse phase and normal phase elution mode, yielding a naphthodianthrone compound, hypericin with HPLC purity about 95%. The n-butanol extract was separated with the solvent system composed of n-butanol-ethyl acetate–water (1:4:5 and 1.5:3.5:5, v/v) in elution and back-extrusion mode, yielding two of flavones, rutin and hyperoside, with HPLC purity over 95%. HPLC-MS, reference sample and UV spectrum were selectively used in separation to search for target compounds from HPLC-DAD profiles of different sub-extracts. The structures of isolated compounds were further identified by ESI-MS, 1HNMR and 13CNMR. PMID:21306961

Cao, Xueli; Wang, Qiaoe; Li, Yan; Bai, Ge; Ren, Hong; Ito, Yiochiro

2011-01-01

487<