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1

A comparative study on the neurotoxicity of n-pentane, n-hexane, and n-heptane in the rat.  

PubMed Central

The neurotoxicity of n-pentane, n-hexane, and n-heptane have been studied in Wistar strain male rats after exposure to 3000 ppm of n-pentane, n-hexane, or n-heptane for 12 hours a day for 16 weeks. The nerve conduction velocity and the distal latency were measured before the beginning of the exposure and after exposure for four, eight, 12, and 16 weeks. The experiment showed that n-hexane disturbed the conduction velocity of the motor nerve and the mixed nerve and prolonged the distal latency in the rat's tail, but that n-pentane and n-heptane did not. The light and electron microscopic examination showed that the peripheral nerve, the neuromuscular junction, and the muscle fibre of the rats exposed to n-hexane were severely impaired, but those of the rats exposed to n-pentane or n-heptane showed no particular changes even after 16 weeks of exposure. These results show that n-hexane is far more toxic to the peripheral nerve of the rat than n-pentane or n-heptane. It is necessary to study the neurotoxicity of other petroleum hydrocarbons, since some reports suggest that petroleum solvents might possibly contain neurotoxic hydrocarbons other than n-hexane. Images PMID:7426474

Takeuchi, Y; Ono, Y; Hisanaga, N; Kitoh, J; Sugiura, Y

1980-01-01

2

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

SciTech Connect

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

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

1987-11-01

3

Spark breakdown of liquid hydrocarbons. II. Temporal development of the electric spark resistance in n-pentane, n-hexane, 2,2 dimethylbutane, and n-decane  

NASA Astrophysics Data System (ADS)

The temporal variation of the spark resistance RFS of a tip-plane and a rod-plane electrode gap immersed in n-hexane, n-pentane, n-decane, and 2,2 dimethylbutane (neohexane) was measured by employing fast high-voltage and current measurement techniques. Three distinct regions were found: (1) rapid decrease of the resistance to 103 ?, (2) development of the spark channel with RFS decreasing to 102 ?, and (3) an exponential variation of RFS in time.

Fuhr, Jitka; Schmidt, Werner F.

1986-06-01

4

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

5

Equilibrated thermodesorption studies of adsorption of n-hexane and n-heptane on zeolites Y, ZSM-5 and ZSM-11  

NASA Astrophysics Data System (ADS)

Gravimetric measurements of thermodesorption of n-hexane and n-heptane were performed under quasi-equilibrium conditions. Differential thermodesorption profiles for ZSM-5 and ZSM-11 showed two peaks, but for Y zeolites, only one thermodesorption peak was observed. A model function, derived from the Langmiur adsorption model, was fitted to the experimental data, and the model parameters (the adsorption entropy and enthalpy) were estimated. The two-step desorption profiles observed for ZSM-5 and ZSM-11 were attributed to the commensurate freezing effect, i.e. a transition in the adsorbed phase resulting in ordering of the adsorbed molecules in the zeolite channels. The results observed for ZSM-11 indicate that the zigzag channels typical for ZSM-5 micropore system are not necessary for this transition to occur.

Makowski, Wac?aw; Majda, Dorota

2005-10-01

6

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

7

[Metabolism and toxicity of n-pentane and isopentane].  

PubMed

n-Pentane and isopentane have a wide range of use, for example, for cleaning precision machinery, extracting essence and oil, and as liquid fuel for now very popular disposable lighters. They are contained in liquefied petroleum gas and natural gas as trace constituents. In our present experiments, we studied the metabolism and toxicity of these n-pentane and isopentane metabolites. Male mice of ICR strain were exposed to about 5% n-pentane for one hour while the oxygen in the environmental air was maintained at about 20%. Then their blood and liver tissue were collected and analyzed by means of GC and GC-MS. The metabolites thus obtained were 2-pentanol, 3-pentanol and 2-pentanone. The same procedure was repeated with isopentane; 3-methyl-2-butanol, 2-methyl-2-butanol and 3-methyl-2-butanone were detected as the resultant metabolites. In the presence of the NADPH-generating system liver microsomes were made to react to the substrate of saturated n-pentane or isopentane aqueous solution at 37 degrees C for one hour. As a result, the same metabolites were produced as obtained in the exposure experiment. It was therefore suggested that n-pentane and isopentane were metabolized chiefly by liver microsomes. Male mice of ICR strain were fed with 80 mg/kg b.w. of phenobarbital for consecutive four days and exposed to n-pentane or isopentane for one hour. This resulted in an increase in the amount of 2-pentanol and 2-pentanone in the n-pentane inhalation and 2-methyl-2-butanol in the isopentane inhalation experiment. The toxicity of each metabolite was studied on cultured cells. The metabolites were individually mixed with HeLa S3 cell suspension, incubated for three days, and their concentration which inhibited the growth of cells by 50% (IGC 50) were compared. It was demonstrated as a result that the IGC 50 for any of the metabolites was lower than that for methanol, ethanol or acetone used as control. PMID:1920919

Chiba, S; Oshida, S

1991-04-01

8

Microporous Materials DOI: 10.1002/anie.200502553  

E-print Network

,11] and of other gases (H2, N2, CO2) and alkanes (methane, n-pentane, n-hexane, cyclohexane, n- heptane) in MOF-5, ethane, n- hexane, and benzene by pulsed field gradient (PFG) NMR,[13,14] which is a well five (benzene, n-hexane) and six (methane, ethane) carbon atoms of the adsorbate mole- cule per cavity

Yaghi, Omar M.

9

N-hexane maculopathy in industrial workers  

Microsoft Academic Search

A neuro-ophthalmologic examination, including fluorescein angiography and colour discrimination tests, was made of 15 workers (age range 30–65 years, mean 45.8 years) exposed to n-hexane (range of exposure 5–21 years) during vegetable oil extracting and adhesive bandage manufacturing. Visual acuity, visual fields, intraocular pressure, and biomicroscopical findings were normal. Ophthalmocopy revealed delicate macular changes in 11 of the 15 subjects.

Christina Raitta; Anna-Maria Seppäläinen; Matti S. Huuskonen

1978-01-01

10

Neurotoxicity of petroleum benzine compared with n-hexane.  

PubMed

Petroleum benzine is one of the mixtures of organic solvents containing n-hexane. The occurrence of polyneuropathy in the workers using petroleum benzines is attributed mainly to n-hexane, though other hydrocarbons present are also suspected of having some neurotoxicity or some potential which could modify the neurotoxicity of n-hexane. The present experiment was performed in order to clarify the toxicity of petroleum benzine to the peripheral nerve and compare it with that of n-hexane. Forty rats were randomly divided into five groups. The groups were exposed to 200 ppm n-hexane, 500 ppm n-hexane, and petroleum benzine vapor containing 200 ppm n-hexane or 500 ppm n-hexane, together with aliphatic and aromatic hydrocarbons for 12 h a day for 24 weeks. The body weight, motor nerve conduction velocity, motor distal latency, and mixed nerve conduction velocities were measured before exposure and every 4 weeks of exposure. A rat from each exposed group was histopathologically examined after 24 weeks' exposure. The function of the peripheral nerve was conspicuously impaired by 500 ppm n-hexane, slightly impaired by 200 ppm n-hexane and petroleum benzine containing 500 ppm n-hexane, and even less impaired by petroleum benzine containing 200 ppm n-hexane. Degenerations of the myelin sheaths and axons were demonstrated in all exposed groups upon examination of the revealed tail nerves. Thus, the experiment revealed that petroleum benzine could impair the peripheral nerves, while some components of petroleum benzine were considered to inhibit the neurotoxicity of n-hexane. PMID:7129648

Ono, Y; Takeuchi, Y; Hisanaga, N; Iwata, M; Kitoh, J; Sugiura, Y

1982-01-01

11

Atmos. Chem. Phys., 5, 34333440, 2005 www.atmos-chem-phys.org/acp/5/3433/  

E-print Network

.31±0.19)�10-10; trans-2-hexenal (1.92±0.22)�10-10; trans-2-heptenal (2.40±0.29)�10-10; n-pentanal (2.56±0.27)�10-10; n-hexanal which have not been studied previously, excepting n-pentanal, n-hexanal and n-heptanal. The ob- tained

Paris-Sud XI, Université de

12

Polyneuropathy induced by n-hexane intoxication in Taiwan.  

PubMed

n-Hexane and methyl n-butyl ketone share a common metabolite, 2,5-hexanedione, a potent neurotoxin. Neurotoxic effects to both peripheral and central nervous systems may occur after occupational exposure or recreational abuse of n-hexane. Initial clinical manifestations include numbness and tingling sensation in the toes and fingers, followed by progressive weakness and areflexia, particularly in the distal limbs. Chronic low-dose n-hexane exposure, often observed in industrial workers, apparently causes axonal loss with sensory impairment. Subacute high-dose n-hexane exposure, often observed in glue-sniffers, can cause axonal swelling and secondary demyelination with muscle wasting and weakness. Electrophysiological studies demonstrate prominent prolongation of distal latencies, slowing of nerve conduction velocities, and conduction block with temporal dispersion particularly in severely intoxicated patients. Pathological hallmarks include giant axonal swelling with secondary demyelination and relative loss of large myelinated fibers. Giant axons are accumulated by 10 nm neurofilaments. The clinical course tends to be biphasic with "coasting" for 2-3 months, followed by a slow recovery for about 1-2 years after cessation of exposure to n-hexane. Prognosis is usually favorable. Severely affected patients may develop sequelae of muscle wasting, foot drop, and spasticity. Increased awareness of the n-hexane neurotoxicity in industrial workers and glue sniffers as well as use of safe solvents and adequate ventilation systems are important for preventing n-hexane toxicity. PMID:18564821

Huang, Chin-Chang

2008-03-01

13

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

14

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

15

The Burning of Large N-Heptane Droplets in Microgravity  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

16

Changes of n-hexane metabolites in urine of rats exposed to various concentrations of n-hexane and to its mixture with toluene or MEK  

Microsoft Academic Search

It is well known that n-hexane produces peripheral neuropathy, and 2,5-hexanedione, one of the metabolites of n-hexane, is thought to be the main causative agent. Recently, the metabolites of n-hexane in urine have been measured by gas chromatography, and 2,5-hexanedione was proved to be useful for the biological monitoring of n-hexane exposure. In the present experiment, we intended to clarify

Masamitsu Iwata; Yasuhiro Takeuchi; Naomi Hisanaga; Yuichiro Ono

1983-01-01

17

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

18

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

19

Operation of limited streamer tubes with the gas mixture Ar + CO2 + n-pentane  

Microsoft Academic Search

The active detectors of the ALEPH hadron calorimeter at LEP consist of plastic streamer tubes developed in Frascati. The standard gas mixture for the operation of such devices is argon-isobutane (30\\/70). However, in underground experiments, for safety reasons, one has to reduce the hydrocarbon content. Therefore a study of the behaviour of streamer tubes operated with a Ar\\/CO2\\/n-pentane mixture has

G. Bagliesi; R. Baldini-Celio; G. Batignani; G. Bencivenni; G. G. Bologna; F. Bossi; U. Bottigli; C. Bradaschia; P. Campana; G. Capon; M. G. Catanesi; V. Chiarella; G. de Ninno; M. de Palma; B. D'Ettorre Piazzoli; M. Dreucci; G. Felici; L. Foà; A. Giassi; G. Iaselli; P. Laurelli; G. Maggi; G. Mannocchi; G. P. Murtas; G. Nicoletti; S. Nuzzo; P. Picchi; A. Ranieri; G. Raso; H. Rigoni; F. Romano; F. Ruggieri; S. Scapellato; G. Selvaggi; R. Tenchini; G. Zito

1988-01-01

20

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.

21

The Spontaneous Ignition of Mixture of n-Heptane and 1Heptene in Oxygen  

Microsoft Academic Search

Studies of the ignition in oxygen of binary mixtures of n-heptane and 1-heptene at temperatures below 400 ^circC show that under all conditions investigated both hydrocarbons are consumed during ignition. However, below ca. 300 ^circC, where 1-heptene is considerably less reactive than n-heptane, the alkene is not involved in the process leading to ignition and the ignitability of mixtures is

C. F. Cullis; A. Fish; J. F. Gibson

1969-01-01

22

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

23

Probing molecular conformations in momentum space: The case of n-pentane  

NASA Astrophysics Data System (ADS)

A comprehensive study, throughout the valence region, of the electronic structure and electron momentum density distributions of the four conformational isomers of n-pentane is presented. Theoretical (e,2e) valence ionization spectra at high electron impact energies (1200eV+electron binding energy) and at azimuthal angles ranging from 0° to 10° in a noncoplanar symmetric kinematical setup are generated according to the results of large scale one-particle Green's function calculations of Dyson orbitals and related electron binding energies, using the third-order algebraic-diagrammatic construction [ADC(3)] scheme. The results of a focal point analysis (FPA) of relative conformer energies [A. Salam and M. S. Deleuze, J. Chem. Phys. 116, 1296 (2002)] and improved thermodynamical calculations accounting for hindered rotations are also employed in order to quantitatively evaluate the abundance of each conformer in the gas phase at room temperature and reliably predict the outcome of experiments on n-pentane employing high resolution electron momentum spectroscopy. Comparison with available photoelectron measurements confirms the suggestion that, due to entropy effects, the trans-gauche (tg) conformer strongly dominates the conformational mixture characterizing n-pentane at room temperature. Our simulations demonstrate therefore that experimental measurements of (e,2e) valence ionization spectra and electron momentum distributions would very consistently and straightforwardly image the topological changes and energy variations that molecular orbitals undergo due to torsion of the carbon backbone. The strongest fingerprints for the most stable conformer (tt) are found for the electron momentum distributions associated with ionization channels at the top of the inner-valence region, which sensitively image the development of methylenic hyperconjugation in all-staggered n-alkane chains.

Knippenberg, S.; Huang, Y. R.; Hajgató, B.; François, J.-P.; Deng, J. K.; Deleuze, M. S.

2007-11-01

24

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

Microsoft Academic Search

Partition coefficients for a number of varied compounds were determined for n-heptane-2,2,2-trifluoroethanol and n-heptane-1,1,1,3,3,3-hexafluoro-2-propanol and used to derive a general model for the distribution of neutral compounds in the biphasic systems. The partition coefficient, logKp, was correlated through the solvation parameter model giving logKp=0.160+1.190V+0.856E?1.538S?1.325A?2.965B for the n-heptane-2,2,2-trifluoroethanol system with a multiple correlation coefficient of 0.988, standard error of the estimate

Jing Qian; Colin F. Poole

2007-01-01

25

Molecular Dynamics Simulations of n-Hexane at [bmim][Tf2N] Interface  

E-print Network

Molecular Dynamics Simulations of n-Hexane at [bmim][Tf2N] Interface Martin L´isal1,2, and Pavel Iz, respectively, the neat interface and interfaces with the n-hexane surface density s = 0.743 µmol/m2 , 1-interfacial layers for the [bmim][Tf2N]/n-hexane systems at a temperature of 300 K, expressed in terms of the average

Lisal, Martin

26

An experimental study of the combined effects of n-hexane and methyl ethyl ketone  

Microsoft Academic Search

This study was intended to determine whether or not methyl ethyl ketone (MEK) enhances the neurotoxicity of n-hexane at low concentration and after long term exposure. Separate groups of eight rats were exposed to 100 ppm n-hexane, 200 ppm MEK, 100 ppm n-hexane plus 200 ppm MEK, or fresh air in an exposure chamber for 12 hours a day for

Y Takeuchi; Y Ono; N Hisanaga; M Iwata; M Aoyama; J Kitoh; Y Sugiura

1983-01-01

27

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

E-print Network

Modelling of heating and evaporation of n-Heptane droplets: Towards a generic model for fuel East, Denmark h i g h l i g h t s A model for droplet heating and evaporation is developed 2014 Keywords: Evaporation n-Heptane droplet Generic model Pyrolysis Bio-oil a b s t r a c t This study

Yin, Chungen

28

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

E-print Network

of n-heptane consumed at the first stage of ignition compared to the experimental data. Consequently% n-heptane ignition results, the experimental data show that n-butanol slows the reactivity of n, many of the species concentration predictions show a sharp rise at the first stage of ignition, a trend

Wooldridge, Margaret S.

29

A reactive molecular dynamics study of n-heptane pyrolysis at high temperature.  

PubMed

n-Heptane is the most important straight chain paraffin in the fossil-fuel industry. In this work, pyrolysis of n-heptane at high temperature is investigated by a series of ReaxFF based reactive molecular dynamic simulations. The pyrolysis correlated intermediate reactions, important product/intermediate distributions, and corresponding kinetics behaviors are systematically analyzed at atomistic level. The results indicate that the entire pyrolysis process is radical-dominated. The unimolecular dissociation is the main pathway of n-heptane decomposition. Initiation of the decomposition is mainly through C-C bond fission. Central C-C bonds would dissociate prior to the terminal ones. Besides, the Rice-Kossiakoff theory is proved for the pyrolysis of n-heptane at the atomistic level. To give a better description of the pyrolysis behavior, some alkane related intermolecular reactions should be considered in the mechanism. The apparent activation energy extracted from the present simulations is 43.02-54.49 kcal/mol in the temperature range 2400-3000 K, which is reasonably consistent with the experimental results. PMID:23544797

Ding, Junxia; Zhang, Liang; Zhang, Yan; Han, Ke-Li

2013-04-25

30

Ignition of n-heptane pool by heated stagnating oxidizing flow  

SciTech Connect

The ignition temperature of a liquid pool of n-heptane by heated oxidizer in a stagnation flow was experimentally determined for system pressures of 0.61-3 atm and pressure-weighted strain rates of 60-350 s{sup -1}. The surface of the liquid pool was maintained at a fixed location through continuous replenishment. The state of ignition was brought about, and monitored, by gradually increasing the oxidizer temperature. The strain rate was determined by seeding and measuring the oxidizer flow velocity using laser Doppler velocimetry (LDV). Computational simulation of the ignition event with detailed chemistry and transport was conducted by using a stagnation-flow code. The kinetic mechanisms utilized are a high-temperature n-heptane oxidation model, with 130 species and 955 reactions, and a reduced one of 58 species derived from a detailed mechanism of 561 species and 2539 reactions. The former mechanism yielded better agreement with the experimental measurements in general over the conditions examined. It was also found that the mole fraction of n-heptane at the interface changed only slightly with pressure and strain rate, and can be considered to have minimal effect on the ignition responses studies herein. A recently developed explosive mode analysis (EMA) was conducted to identify the controlling radicals and reactions in the non-premixed ignition of n-heptane. (author)

Liu, Wei; Zhu, Delin; Wu, Ning; Law, Chung K. [Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544 (United States)

2010-02-15

31

Effect of Methanol on Exhaust Composition of a Fuel Containing Toluene, n-Heptane, and Isooctane  

Microsoft Academic Search

This study describes the variations in the chemical composition of the exhaust from a single cylinder engine when up to 25% methanol is added to a fuel blend of toluene, isooctane, and n-heptane. Under fuel-rich conditions, and with increasing methanol concentration, it is observed that unburned fuel and benzene emissions increase, exhaust acetylene remains constant, and propylene, isobutylene, methane, ethylbenzene,

J. S. Ninomiya; A. Golovoy; S. S. Labana

1970-01-01

32

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

33

Urinary 2,5 hexanedione as a biomarker of n-hexane exposure.  

PubMed

n-Hexane is a saturated aliphatic hydrocarbon widely used in industry. In most cases it is used as a mixture with hexane isomers and various others solvents in the form of commercial hexane. n-Hexane is metabolized oxidatively to a number of compounds, including 2,5-hexanedione (2,5-HD), which is eliminated through the urine and is implicated in the neurotoxic effect of this solvent. The main objective of this study was to evaluate urinary 2,5-HD as a biomarker of n-hexane exposure. The study was carried out in seven industrial units. Post-shift urine samples from 111 workers who handled commercial hexane were collected and analysed for 2,5-HD by capillary gas chromatography. Air sampling was performed in the breathing zones of the workers, and the air samples were analysed using validated methods. Monitoring individual exposures showed that n-hexane exposure varied from 5 to 70 p.p.m. (mean +/- SD = 15.24 +/- 2.98 p.p.m.). Significant correlation was observed between exposure to n-hexane and urinary 2,5-HD levels, with high correlation coefficients (rho = 0.81, p = 0.000), suggesting that urinary 2,5-HD is a good biomarker of occupational exposure to n-hexane. Urinary 2,5-HD is recommended as a better tool than air monitoring in the assessment of health risk, namely the early detection of n-hexane neurotoxicity. PMID:12171757

Mayan, Olga; Teixeira, Joao Paulo; Alves, Sandra; Azevedo, Conceição

2002-01-01

34

THE JOURNAL OF CHEMICAL PHYSICS 139, 014704 (2013) Molecular dynamics simulations of n-hexane at 1-butyl-3-  

E-print Network

THE JOURNAL OF CHEMICAL PHYSICS 139, 014704 (2013) Molecular dynamics simulations of n-hexane at 1) Molecular dynamics simulations of n-hexane adsorbed onto the interface of 1-butyl-3- methylimidazolium bis(trifluoromethylsulfonyl) imide ([bmim][Tf2N]) are performed at three n- hexane surface densities, ranged from 0.7 to 2.3 mol/m2

Lisal, Martin

35

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

36

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

37

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

Microsoft Academic Search

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

ZHIJUN PENG; HUA ZHAO; TOM MA; NICOS LADOMMATOS

2005-01-01

38

A SemiEmpirical Reaction Mechanism for n-Heptane Oxidation and Pyrolysis  

Microsoft Academic Search

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

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

1997-01-01

39

Combined CO 2 reforming and partial oxidation of n-heptane on noble metal zirconia catalysts  

Microsoft Academic Search

The combined CO2 reforming and partial oxidation (POX) of n-heptane was studied on various noble metal zirconia catalysts between 700 and 900°C. The activity order of the metals was Rh>Pd>Ir>Pt. Selectivity to syngas increased with the activity of the catalysts but the H2 to CO molar ratio decreased. The activity and selectivity of the 0.25wt% Rh\\/ZrO2 catalyst were close to

K. J. Puolakka; S. Juutilainen; A. O. I. Krause

2006-01-01

40

[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

41

Characterization of the Acid Properties of Tungsten\\/Zirconia Catalysts Using Adsorption Microcalorimetry and n-Pentane Isomerization Activity  

Microsoft Academic Search

Ammonia adsorption microcalorimetry was conducted on various solid acid tungsten\\/zirconia catalysts prepared by different techniques. The calorimetric data were compared to catalytic test results using n-pentane isomerization as a measure of acid activity. The results show that (1) the co-precipitation method of making the tungsten\\/zirconia catalyst produces a greater number of acidic sites than impregnating tungsten on hydrous zirconia, resulting

J. C. Vartuli; J. G. Santiesteban; P. Traverso; N. Cardona-Martinéz; C. D. Chang; S. A. Stevenson

1999-01-01

42

Hydrogen spillover effect on cumene cracking and n-pentane hydroisomerization over Pt\\/SiO 2 + H-Beta  

Microsoft Academic Search

The effects of catalytic component, hydrogen partial pressure, metal amount and dose amount on cumene cracking and n-pentane hydroisomerization over Pt\\/SiO2+H-Beta physically mixed catalyst were studied with a pulse reactor system to examine the function of spilt-over hydrogen species. In cumene cracking, high catalytic activity was observed on H-Beta containing catalysts. On the contrary, platinum, hydrogen and H-Beta were indispensable

Toshiaki Kusakari; Keiichi Tomishige; Kaoru Fujimoto

2002-01-01

43

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

44

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

PubMed

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

2001-11-16

45

Production and in situ separation of mono- or diacylglycerol catalyzed by lipases in n-hexane  

Microsoft Academic Search

For the lipase-catalyzed production of mono- or dipalmitoylglycerol in n-hexane, various inert solid supports were directly added to the reaction system, resulting in an increase in the equilibrium conversion and the interfacial area between glycerol and palmitate in n-hexane. Among the solid supports tested, silica gel was found to be most suitable. However, high yields of mono- or dipalmitoylglycerol were

Seok Joon Kwon; Jeong Jun Han; Joon Shick Rhee

1995-01-01

46

Thermodynamics of solvation of calix[4]arenes in n-hexane  

NASA Astrophysics Data System (ADS)

The solubility of eight calix[4]arenes and crown-calix[4]arenes in n-hexane at five different temperatures was determined by isothermal saturation. The thermodynamic dissolution parameters were calculated. Thermodynamics of solvation in n-hexane was calculated using thermodynamic parameters of sublimation obtained earlier. Thermogravimetric analysis of the bottom phase was carried out to detect crystallosolvates. The stoichiometry of the crystallosolvates formed was ascertained.

Surov, O. V.; Voronova, M. I.; Mamardashvili, N. Zh.; Zakharov, A. G.

2010-11-01

47

Role of surface properties of the vanadyl pyrophosphate in the formation of maleic and phthalic anhydrides by n-pentane oxidation  

Microsoft Academic Search

The mechanism of synthesis of maleic and phthalic anhydrides by the gas phase oxidation of n-pentane over VPO-based catalysts was studied. The oxidation of the paraffin was carried out under conditions which may lead to the isolation of possible reaction intermediates: very low residence time and high n-pentane\\/oxygen ratio. Under these conditions a number of by-products were identified, which were

F. Cavani; A. Colombo; F. Giuntoli; E. Gobbi; F. Trifirò; P. Vazquez

1996-01-01

48

Microstructures of capped ethylene oxide oligomers in water and $n$-hexane  

E-print Network

This report documents microstructural features of CH3(CH2-O-CH2)mCH3 dissolved in water and n-hexane for m = 11, 21, and 31. Probability densities for end-to-end distance, and the associated potential-of-mean-force (pmf), are more revealing of chain microstructures than are the corresponding results for the radii of gyration. For water, the pmf identifies three distinct regions: loop-closure, globule, and high-extension regions. The globule region affirms a water-swollen chain, and is not evident in the n-hexane results. Chain C-atom density profiles from the chain centroid are also different in the water and n-hexane cases. For n-hexane (but not water), the density profiles are similar for the different chain lengths when the distances are scaled by the observed ^{1/2}. For water (but not n-hexane) and the smaller chains considered, the carbon material exhibits a distinctive enhanced concentration, or internal condensation, at the centroid core of the structure.

Chaudhari, Mangesh I

2012-01-01

49

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

50

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

Microsoft Academic Search

An electrophysiological study was undertaken to determine whether toluene affected the neurotoxicity of n-hexane. Separate groups of eight rats were exposed to 1000 ppm n-hexane, 1000 ppm toulene, 1000 ppm n-hexane plus 1000 ppm toluene, of fresh air in an exposure chamber for 12 hours a day for 16 weeks. The body weight, MCV, DL, MNCVs were measured before exposure,

Y Takeuchi; Y Ono; N Hisanaga

1981-01-01

51

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

SciTech Connect

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

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

2011-12-31

52

Solubility and diffusion of organic vapors in silicone polymers  

Microsoft Academic Search

Study of solubility and diffusion of organic vapors in polymer membranes is important for the development of membrane processes for the removal of organic vapors from air for environmental applications. The solubility and absorption\\/desorption kinetics of seven organic vapors, namely, n-pentane, n-hexane, n-heptane, benzene, cyclohexane, methanol, and 1-propanol in two polymer membranes, i.e. poly(dimethyl siloxane), PDMS, and poly(trifluoropropyl methyl siloxane),

Jindarat Pimsamarn

1998-01-01

53

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

Microsoft Academic Search

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

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

1990-01-01

54

n-Hexane Neuropathy Caused by Addictive Inhalation: Clinical and Electrophysiological Features  

Microsoft Academic Search

To assess the clinical and electrophysiological features of n-hexane neuropathy caused by addictive inhalation, 4 patients were studied in the progressive phase. The neurological manifestations were characterized by subacute predominantly motor polyneuropathy and disease progression despite discontinuance of the chemicals, which were similar to those reported in industrial exposure, although with a severer degree associated with anorexia and body weight

Satoshi Kuwabara; Margareth Reiko Kai; Hitoshi Nagase; Takamichi Hattori

1999-01-01

55

Effect of saponins on n-hexane removal in biotrickling filters.  

PubMed

Saponins was applied to enhance the removal of n-hexane in a biotrickling filter (BTF) in this study. Comparison experiments were carried out to examine the effect of saponins on n-hexane removal in two BTFs at various saponins concentrations, n-hexane loading rates (LRs) and gas empty bed contact times (EBCTs). Results show that the optimum concentration of saponins in nutrient feed was 50.0mgL(-1). When organic LR of n-hexane increased from 47.8 to 120.0gm(-3)h(-1), the removal efficiency (RE) for BTF1 (with saponins) and BTF2 (without saponins) decreased from 91.3% to 83.3% and from 62.8% to 56.8%, respectively. As gas EBCT decreased from 30.0 to 7.5s, the RE declined from 88.4% to 64.5% for BTF1 and from 61.4% to 38.3% for BTF2. Saponins could also decrease the biomass accumulation rate within the medium bed. These results could be referred in the design and operation of BTFs for hydrophobic VOC removal. PMID:25459827

Tu, Yanhong; Yang, Chunping; Cheng, Yan; Zeng, Guangming; Lu, Li; Wang, Lu

2014-10-22

56

Antipyretic and anticonvulsant activity of n-hexane fraction of Viola betonicifolia  

PubMed Central

Objective To investigate the antipyretic and anticonvulsant activities of n-hexane fraction of Viola betonicifolia (V. betonicifolia). Methods The antipyretic effect was scrutinized using brewer's yeast induced pyrexia and anticonvlsion effect was tested using pentylenetetrazol and strychnine induced convulsion in mice. Results N-hexane fraction of V. betonicifolia demonstrated highly significant antipyretic activity during various assessment times (1-5 h) when challenged in yeast induced pyrexia test. The effect was in a dose dependent manner with maximum attenuation (82.50%) observed at 300 mg/kg i.p. When tested in pentylenetetrazol induced convulsion test, the 1st stage (Ear and facial twitching) and 2nd stage (Convulsive wave through the body) was 100% protected during 24 h at all the test doses (300, 400 and 500 mg/kg i.p.), while the latency time of remaining stages was significantly increased. The maximum effect was observed by n-hexane fraction of V. betonicifolia at 400 and 500 mg/kg i.p., as the latency time for generalized clonic-tonic seizure (5th stage) was increased up to 25.34 min. However, n-hexane fraction of V. betonicifolia had no protection in strychnine induced convulsion test. Conclusions In conclusion, phytopharmacological studies provide scientific foundation to the folk uses of the plant in the treatment of pyrexia and neurological disorders. PMID:23620851

Muhammad, Naveed; Saeed, Muhammad; Khan, Haroon; Raziq, Naila; Halimi, Syed Muhammad Ashhad

2013-01-01

57

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....

58

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

59

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

60

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

61

A comprehensive and compact n-heptane oxidation model derived using chemical lumping.  

PubMed

A detailed reaction mechanism for n-heptane oxidation has been compiled and subsequently simplified. The model is based on a kinetic model for C1-C4 fuel oxidation of Hoyermann et al. [Phys. Chem. Chem. Phys., 2004, 6, 3824] and a detailed mechanism for n-heptane oxidation developed by Curran et al. [Combust. Flame, 1998, 114, 149]. The generated mechanism is kept compact by limiting the application of the low temperature oxidation pathways to the fuel molecule. The first reaction steps and the complex low temperature paths in the oxidation process have been simplified and reorganized by linear chemical lumping. The reported procedure allows a decrease in number of species and reactions with only a minor loss of model accuracy. The simplified model is of very compact size and gives an advantageous starting point for further model reduction. By this chemically lumped general mechanism without further adjustments the large set of experimental data for the high and low temperature oxidation (ignition delay times, species concentration profiles, heat release and engine pressure profiles, flame speeds and flame structure data) for conditions ranging from very low to high temperatures (550-2300 K), very lean to extremely fuel rich (0.22 < phi < 3) mixtures and pressures between 1 and 42 bar is consistently described providing a basis for reliable predictions for future applications, (i) building reaction mechanisms for similar but chemically more complex fuels (e.g. iso-octane, n-decane,...) and (ii) calculating complex flow fields ("fluid dynamics") after further simplification with advanced reduction tools. PMID:17311154

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

2007-03-01

62

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...

63

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

64

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

65

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

NASA Astrophysics Data System (ADS)

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

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

2010-01-01

66

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

Microsoft Academic Search

The absorption spectra of lycopene in n-hexane and CS2 are measured under high pressure and the results are compared with beta-carotene. In the lower pressure range, the deviation from the linear dependence on the Bayliss parameter (BP) for beta-carotene is more visible than that for lycopene. With the further increase of the solvent BP, the 0-0 bands of lycopene and

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

2010-01-01

67

Reactive Extraction of Lactic Acid with Trioctylamine\\/Methylene Chloride\\/n-Hexane  

Microsoft Academic Search

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

Dong Hoon Han; Won Hi Hong

1996-01-01

68

Conversion of n-hexane over monofunctional supported and unsupported PtSn catalysts  

Microsoft Academic Search

Alumina- and silica-supported platinum and platinum\\/tin and the unsupported alloys PtâSn, PtSn, PtâSnâ, and PtSnâ were prepared by various methods. Oxygen-hydrogen titration and temperature-programed reduction confirmed that all tin reduced to the zero-valent state (except for a small amount that interacted with the alumina supports) and that it was present in bimetallic clusters or alloys. In tests on n-hexane conversion

F. M. Dautzenberg; J. N. Helle; P. Biloen; W. M. H. Sachtler

1980-01-01

69

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

70

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

71

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

E-print Network

Molecular dynamics of n-hexane: A quasi-elastic neutron scattering study on the bulk and spatially OF CHEMICAL PHYSICS 136, 124505 (2012) Molecular dynamics of n-hexane: A quasi-elastic neutron scattering transfer range from 0.4 Ã?-1 to 1.6Ã? -1 on liquid n-hexane confined in cylindrical, parallel

72

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

PubMed

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

Lin, Ligang; Zhang, Yuzhong; Kong, Ying

2009-11-01

73

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

74

Observations on a Slow Burning Regime for Hydrocarbon Droplets - N-Heptane/Air Results  

NASA Technical Reports Server (NTRS)

Experiments on n-heptane/airdroplet combustion under reduced gravity have served as a benchmark for much of the existing theoretical efforts on the modeling of sphero-synmmetric droplet burning. New experiments conducted in the NASA-Lewis Research Center 2.2 second droptower (at less than 10 exp -5 g) which emphasize the production of sphero-symmetry and low relative droplet/gas convection produce burning rates in air (for about 1 mm droplets) as much as 40-percent lower than the classical result (0.78 sq mm/s). The burning rate is proportional to the measured droplet/gas relative velocity, and the observed functional dependence is much larger than predicted by published convective correlations. New results clearly indicate that the droplet/laboratory velocity does not correspond to the relative droplet/gas velocity. Thus, the convective effects on droplet combustion is not properly characterized by droplet motion alone. Differences in the burning rates are speculated to result from the effects of the accumulated soot as well as the asymmetry (caused by convection) in the temperature and species distributions surrounding the droplet.

Choi, Mun Y.; Dryer, Frederick L.; Haggard, John B., Jr.

1991-01-01

75

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

76

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

77

Phosphorus-Doped Tungsten Oxynitrides: Synthesis, Characterization, and Catalytic Behavior in Propene Hydrogenation and n-Heptane Isomerization  

Microsoft Academic Search

The effect of phosphorus on tungsten oxynitrides has been studied. Phosphorus was introduced via tungsten heteropolyanions. Propene hydrogenation and n-heptane isomerization were used to probe the activity and selectivity of the doped materials. Catalysts were characterized using elemental analysis, X-ray diffraction, N2 BET surface area, CO chemisorption, and X-ray photoelectron spectroscopy (XPS). Reactivity experiments over P-containing oxynitrides show enhanced hydrogenating

P. Pérez-Romo; C. Potvin; J.-M. Manoli; G. Djéga-Mariadassou

2002-01-01

78

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

79

Combustion characteristics and influential factors of isooctane active-thermal atmosphere combustion assisted by two-stage reaction of n-heptane  

SciTech Connect

This paper presents an experimental study on the isooctane active-thermal atmosphere combustion (ATAC) which is assisted by two-stage reaction of n-heptane. The active-thermal atmosphere is created by low- and high-temperature reactions of n-heptane which is injected at intake port, and isooctane is directly injected into combustion chamber near the top dead center. The effects of isooctane injection timing, active-thermal atmosphere intensity, overall equivalence ratio, and premixed ratio on combustion characteristics and emissions are investigated. The experimental results reveal that, the isooctane ignition and combustion can be classified to thermal atmosphere combustion, active atmosphere combustion, and active-thermal atmosphere combustion respectively according to the extent of n-heptane oxidation as well as effects of isooctane quenching and charge cooling. n-Heptane equivalence ratio, isooctane equivalence ratio and isooctane delivery advance angle are major control parameters. In one combustion cycle, the isooctane ignited and burned after those of n-heptane, and then this combustion phenomenon can also be named as dual-fuel sequential combustion (DFSC). The ignition timing of the overall combustion event is mainly determined by n-heptane equivalence ratio and can be controlled in flexibility by simultaneously adjusting isooctane equivalence ratio. The isooctane ignition regime, overall thermal efficiency, and NO{sub x} emissions show strong sensitivity to the fuel delivery advance angle between 20 CA BTDC and 25 CA BTDC. (author)

Lu, Xingcai; Ji, Libin; Ma, Junjun; Zhou, Xiaoxin; Huang, Zhen [Key Lab. for Power Machinery and Engineering of MOE, Shanghai Jiao Tong University, 200240 Shanghai (China)

2011-02-15

80

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

81

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

82

Aircraft experiments on microgravity pool boiling - Vapor-liquid behaviour and heat transfer characteristics in boiling of n-pentane, CFC113 and water  

Microsoft Academic Search

Boiling of n-pentane, CFC-113 and water under microgravity were studied, utilizing parabolic flight maneuvers with a Caravelle aircraft. The experimental apparatus was constructed so as to permit simultaneous video recording of the side view of vapor bubbles, generated on a Joule-heated, transparent indium-oxide film plated on a glass substrate, and the backside view through the substrate. The heat transfer to

Toshiharu Oka; Yoshiyuki Abe; Yasuhiko H. Mori; Akira Nagashima

1992-01-01

83

Electron attachment to toluene in n-hexane and 2,2-dimethylbutane at high pressure  

SciTech Connect

The effect of dilute concentration of toluene on the electron mobility in two isometric hexanes was studied as a function of pressure from 1 bar to 3 kbar and at selected temperatures between 9 and 60[degrees]C. The effect of toluene on the mobility is small at 1 bar but quite large at the higher pressures. The results are interpreted in terms of reversible electron attachment to a toluene species which is the monomer in n-hexane. For this reaction [triangle]H[sub r] is - 12.0 kcal /mol in n-hexane at 2.5 kbar. In 2,2-dimethylbutane attachment to a dimeric species is indicated. The volume changes for these attachment reactions are large, between [minus]80 and [minus]100 cm[sup 3]/mol. In hexane the volume changes are attributed in part to the electrostriction of the solvent by the toluene anion and in part to a positive molar volume of the electron. 19 refs., 8 figs., 3 tabs.

Itoh, Kengo; Nishikawa, Masaru (Univ. of Tokyo (Japan)); Holroyd, R. (Brookhaven National Lab., Upton, NY (United States))

1993-01-14

84

Performance and bacterial population composition of an n-hexane degrading biofilter working under fluctuating conditions.  

PubMed

In this work, several conditions of pH and inlet load (IL) were applied to a scale laboratory biofilter treating n-hexane vapors during 143 days. During the first 79 days of operation (period 1, P1), the system was fed with neutral pH mineral medium (MM) and the IL was progressively decreased from 177 to 16 g m(-3) h(-1). A maximum elimination capacity (EC) of 30 g m(-3) h(-1) was obtained at an IL of 176.9?±?9.8 g m(-3) h(-1). During the following 64 days (period 2, P2), acidic conditions were induced by feeding the biofilter with acidic buffer solution and pH 4 MM in order to evaluate the effect of bacterial community changes on EC. Within the acidic period, a maximum EC of 54 g m(-3) h(-1) (IL 132.3?±?13 g m(-3) h(-1)) was achieved. Sequence analysis of 16S rDNA genes amplified from the consortium revealed the presence of Sphingobacteria, Actinobacteria, and ?-, ?- and ?-Proteobacteria. An Actinobacteria of the Mycobacterium genus had presence throughout the whole experiment of biofiltration showing resistance to fluctuating pH and IL conditions. Batch tests confirm the bacterial predominance and a negligible contribution of fungi in the degradation of n-hexane. PMID:25099371

Valenzuela-Reyes, Edgardo; Casas-Flores, Sergio; Isordia-Jasso, Isabel; Arriaga, Sonia

2014-09-01

85

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

86

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

87

n-hexane-induced synthesis of hepatic metallothionein is mediated by IL-6 in mouse.  

PubMed

The mechanism of metallothionein (MT) synthesis in the liver by n-hexane (HX) was examined. The increased synthesis of MT in the liver by HX was inhibited by dexamethasone pretreatment. Serum IL-6 was increased soon after HX injection, reaching a maximum at 8-16 hr, and then decreased, but neither IL-1 nor TNF was increased. The hepatic MT concentration reached a maximum later than did the serum IL-6 concentration, at 2 days after administration. When the MT synthesis induced by HX was inhibited by dexamethasone pretreatment, the concentration of IL-6 in the serum was suppressed to a very low level. Furthermore, the increase in concentration of hepatic MT and plasma fibrinogen was significantly decreased by the anti-mouse IL-6 monoclonal antibody. The concentration of hepatic MT was higher when the concentration of HX in the olive oil of the solution for injection was higher, even when the amount of HX administered was the same. It is suggested that the cytokine(s) is produced by the macrophage and fibroblast through injury and inflammation at the site of administration. These findings suggest that MT synthesis resulting from HX is induced indirectly through cytokine(s) production, especially IL-6. PMID:8122271

Itoh, N; Okamoto, H; Ohta, M; Hori, T; Min, K S; Onosaka, S; Nakanishi, H; Okabe, M; Muto, N; Tanaka, K

1994-02-01

88

H{sub 2}O{sub 2} enhanced thermal oxidation of n-heptane and chlorobenzene  

SciTech Connect

The destruction of certain volatile organic compounds (VOCs) by incineration requires high temperatures and long residence times. The oxidation process occurs by a complex series of reactions initiated and propagated by free radicals. It was postulated that the addition of hydrogen peroxide to a heated stream of VOCs in air would enhance the kinetics of thermal oxidation. In this work, the VOCs studied include n-heptane and chlorobenzene. Results show that H{sub 2}O, is effective in enhancing the thermal destruction of both compounds. Computer kinetic modeling was done using the Chemkin II program package and the predicted products of incomplete combustion (PICs) were compared with those found experimentally using GC and GC-MS analysis. Although the model does not accurately predict PICs for both parent compounds, the experimental data for further adjustments of the model and a better understanding of what reactions may be of importance in the proposed mechanisms.

Geiger, C.L.; Clausen, C.A.; Martinez, A.; Cooper, C.D. [Univ. of Central Florida, Orlando, FL (United States)

1995-12-01

89

Preferred orientation of n-hexane crystallized in silicon nanochannels: A combined x-ray diffraction and sorption isotherm study  

E-print Network

We present an x-ray diffraction study on n-hexane in tubular silicon channels of approximately 10 nm diameter both as a function of the filling fraction f of the channels and as a function of temperature. Upon cooling, confined n-hexane crystallizes in a triclinic phase typical of the bulk crystalline state. However, the anisotropic spatial confinement leads to a preferred orientation of the confined crystallites, where the crystallographic direction coincides with the long axis of the channels. The magnitude of this preferred orientation increases with the filling fraction, which corroborates the assumption of a Bridgman-type crystallization process being responsible for the peculiar crystalline texture. This growth process predicts for a channel-like confinement an alignment of the fastest crystallization direction parallel to the long channel axis. It is expected to be increasingly effective with the length of solidifying liquid parcels and thus with increasing f. In fact, the fastest solidification front...

Henschel, Anke; Hofmann, Tommy; Knorr, Klaus; Huber, Patrick; 10.1103/PhysRevE.79.032601

2009-01-01

90

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

91

Esterification of fatty acids using nylon-immobilized lipase in n-hexane: kinetic parameters and chain-length effects  

Microsoft Academic Search

The esterification of long-chain fatty acids in n-hexane catalyzed by nylon-immobilized lipase from Candida rugosa has been investigated. Butyl oleate (22 carbon atoms), oleyl butyrate (22 carbon atoms) and oleyl oleate (36 carbon atoms) were produced at maximum reaction rates of ?60 mmol h?1 g?1 immobilized enzyme when the substrates were present in equimolar proportions at an initial concentration of

A Zaidi; J. L Gainer; G Carta; A Mrani; T Kadiri; Y Belarbi; A Mir

2002-01-01

92

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

PubMed Central

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

Penduka, Dambudzo; Okoh, Anthony I.

2011-01-01

93

Spark breakdown of liquid hydrocarbons. I. Fast current and voltage measurements of the spark breakdown in liquid n-hexane  

NASA Astrophysics Data System (ADS)

A fast coaxial discharge line for the study of the electric breakdown of liquid hydrocarbons is described. It allows the simultaneous measurement of discharge current (up to 5 kA) and voltage (up to 50 kV) with nanosecond time resolution. The spark gap is of tip-plane geometry. A detailed frequency analysis of the discharge and measurement circuits has been performed. Examples for the spark breakdown of n-hexane under a variety of conditions are presented.

Fuhr, Jitka; Schmidt, Werner F.; Sato, Shuji

1986-06-01

94

Biological Exposure Indices of Pyrrole Adducts in Serum and Urine for Hazard Assessment of n-Hexane Exposure  

PubMed Central

Background Pyrrole adducts might be used as a biomarker for monitoring occupational exposure to n-hexane, but the Biological Exposure Indices of pyrrole adducts in serum and urine are still unknown. The current study was designed to investigate the biological exposure limit of pyrrole adducts for hazard assessment of n-hexane. Methods Male Wistar rats were given daily dose of 500, 1000, 1500, 2000, 4000 mg/kg bw n-hexane by gavage for 24 weeks. The levels of pyrrole adducts in serum and urine were determined at 8, 24 hours postdose once a week. The Biological Exposure Indices was evaluated by neurological evaluation and the levels of pyrrole adducts. The difference in pyrrole adducts formation between humans and rats were estimated by using in vitro test. Results Dose-dependent effects were observed between the doses of n-hexane and pyrrole adducts in serum and urine, and the levels of pyrrole adduct in serum and urine approached a plateau at week 4. There was a significantly negative correlation between the time to paralysis and the level of pyrrole adducts in serum and urine, while a positive correlation between gait score and levels of pyrrole adducts in serum and urine was observed. In vitro, pyrrole adducts formed in human serum was about two times more than those in rat serum at the same level of 2,5-HD. Conclusion It was concluded that the BEIs of pyrrole adducts in humans were 23.1±5.91 nmol/ml in serum 8 h postdose, 11.7±2.64 nmol/ml in serum 24 h postdose, 253.8±36.3 nmol/ml in urine 8 h postdose and 54.6±15.42 nmol/ml in urine 24 h postdose. PMID:24465904

Yin, Hongyin; Zhang, Chunling; Guo, Ying; Shao, Xiaoying; Zeng, Tao; Zhao, Xiulan; Xie, Keqin

2014-01-01

95

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

96

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

97

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

98

Partition coefficients of some industrial aliphatic hydrocarbons (C5-C7) in blood and human tissues.  

PubMed

Saline/air, blood/air, olive oil/air, and tissue/air (lung, kidney, liver, brain, muscle, heart, and fat) partition coefficients were determined for nine aliphatic hydrocarbons: n-pentane, 2,2-dimethylbutane, 3-methylpentane, 2-methylpentane, methylcyclopentane, n-hexane, cyclohexane, 3-methylhexane, and n-heptane. Blood/air partition coefficients were found to range between 0.38 (n-pentane) and 1.9 (n-heptane) and the value of the tissue/air partition coefficients rose from n-pentane to n-heptane. The tissue/air partition coefficients were significantly correlated with the blood/air partition coefficients (r = 0.92-0.98). According to the slope of the regression lines, the mean solubility of the nine aliphatic hydrocarbons in the different tissues was higher than in blood by the factors: lung 1.4 (range 1.2-2.1) heart 3.9 (range 0.5-4.5), liver 5.6 (range 5.5-13.5), kidney 5.2 (range 1.6-5.8), brain 6.5 (range 5.8-10.7), muscle 7.6 (range 1.8-8.8), and fat 205 (range 104-254). The blood/air and olive oil/air partition coefficients were significantly correlated with the boiling points and the molecular weights of the aliphatic hydrocarbons studied. PMID:3970880

Perbellini, L; Brugnone, F; Caretta, D; Maranelli, G

1985-03-01

99

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

100

Anaerobic degradation of n -hexane in a denitrifying bacterium: Further degradation of the initial intermediate (1-methylpentyl)succinate via C-skeleton rearrangement  

Microsoft Academic Search

The anaerobic degradation pathway of the saturated hydrocarbon n-hexane in a denitrifying strain (HxN1) was examined by gas chromatography-mass spectrometry of derivatized extracts from cultures grown with unlabeled and deuterated substrate; several authentic standard compounds were included for comparison. The study was focused on possible reaction steps that follow the initial formation of (1-methylpentyl)succinate from n-hexane and fumarate. 4-Methyloctanoic, 4-methyloct-2-enoic,

Heinz Wilkes; Ralf Rabus; Thomas Fischer; Antje Armstroff; Astrid Behrends; Friedrich Widdel

2002-01-01

101

The Role of Metabolism in Establishing Chemical-Specific Adjustment Factors for n-Hexane and Methyl n-Butyl Ketone  

Microsoft Academic Search

This paper focuses on the derivation of chemical-specific adjustment factors (CSAFs) for two neurotoxic solvents, n-hexane and methyl n-butyl ketone (MBK). Workers are exposed to the chemicals mainly via inhalation when they are used, for example, as solvents in adhesives. In order to derive CSAFs for n-hexane and MBK, research data were used from animal studies conducted in our laboratory.

Gloria A. Skowronski; Mohamed S. Abdel-Rahman

2004-01-01

102

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

103

Influence of Gravity and Ambient Pressure on Combustion and Flammability of n-Heptane and 1Propanol Droplets in Air-Diluent Environments  

Microsoft Academic Search

Reduced gravity and normal gravity combustion experiments were performed with individual fiber-supported n-heptane and 1-propanol droplets with initial diameters in the 1-mm size range. Experiments were performed with air-inert mixtures at 0.1 MPa or 0.3 MPa and about 298 K, where helium, carbon dioxide, or xenon were separately used as inerts. The amount of inert gas required to suppress combustion was generally higher

B. D. Shaw; J. B. Wei

2011-01-01

104

Second-Order Conditional Moment Closure Simulations of Autoignition of an n-heptane Plume in a Turbulent Coflow of Heated Air  

Microsoft Academic Search

Autoignition of an n-heptane plume in a turbulent coflow of heated air has been studied using the conditional moment closure\\u000a (CMC) method with a second-order closure for the conditional chemical source term. Two different methodologies have been considered:\\u000a (i) the Taylor expansion method, in which the second order correction was based on the solution of the full covariance matrix\\u000a for

G. De Paola; I. S. Kim; E. Mastorakos

2009-01-01

105

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

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

106

Fluxes and rejections for nanofiltration with solvent stable polymeric membranes in water, ethanol and n-hexane  

Microsoft Academic Search

The solvent flux and rejection of 2,2?-methylenebis-(6-tert-butyl-4-methyl phenol) was studied in water, ethanol and n-hexane for four solvent-stable polymeric nanofiltration membranes (N30F, NF-PES-10, MPF-44 and MPF-50). Solvent fluxes were analysed with the Machado model to determine hydrophobicity\\/hydrophilicity of the membranes. The results are consistent with N30F, NF-PES-10 and MPF-44 being hydrophilic membranes, and MPF-50 being a hydrophobic membrane. The solvent

B. Van der Bruggen; J. Geens; C. Vandecasteele

2002-01-01

107

Aliphatic hydrocarbon solvents in chemically sensitive patients.  

PubMed

The purpose of the present study was to see if chemically sensitive individuals had aliphatic hydrocarbon solvents as part of their total body load. This was done by measuring blood levels from 85 chemically sensitive patients. These were measured by a purging trap method with gas chromatography/mass spectrometry (GCC/MS) by the methods of Laseter. Thirteen patients had blood levels below the detection limit of less than 1 ppb and 72 were above the detection limit. An average of three solvents, out of seven measured, including n-pentane, 2,2-dimethylbutane, cyclopentane, 2-methylpentane, 3-methylpentane, n-hexane, n-heptane, was found in 85% of the patients' blood on the 1 to 299 ppb range. The means were as follows: n-pentane 14.7 ppb, 2,2-dimethylbutane 2.5 ppb, cyclopentane 9.0 ppb, 2-methylpentane 16.7 ppb, 3-methylpentane 28.0 ppb, n-heptane 5.5 ppb. The most frequently found of the above solvents was 2-methylpentane (found in 68.1% of the patients), 3-methylpentane (62.5%), n-hexane (61.1%), and pentane (40.3%). PMID:1817510

Pan, Y; Johnson, A R; Rea, W J

1991-07-01

108

Benchmark thermochemistry of the C_nH_{2n+2} alkane isomers (n=2--8) and performance of DFT and composite ab initio methods for dispersion-driven isomeric equilibria  

E-print Network

The thermochemistry of linear and branched alkanes with up to eight carbons has been reexamined by means of W4, W3.2lite and W1h theories. `Quasi-W4' atomization energies have been obtained via isodesmic and hypohomodesmotic reactions. Our best atomization energies at 0 K (in kcal/mol) are: 1220.04 n-butane, 1497.01 n-pentane, 1774.15 n-hexane, 2051.17 n-heptane, 2328.30 n-octane, 1221.73 isobutane, 1498.27 isopentane, 1501.01 neopentane, 1775.22 isohexane, 1774.61 3-methylpentane, 1775.67 diisopropyl, 1777.27 neohexane, 2052.43 isoheptane, 2054.41 neoheptane, 2330.67 isooctane, and 2330.81 hexamethylethane. Our best estimates for $\\Delta H^\\circ_{f,298K}$ are: -30.00 n-butane, -34.84 n-pentane, -39.84 n-hexane, -44.74 n-heptane, -49.71 n-octane, -32.01 isobutane, -36.49 isopentane, -39.69 neopentane, -41.42 isohexane, -40.72 3-methylpentane, -42.08 diisopropyl, -43.77 neohexane, -46.43 isoheptane, -48.84 neoheptane, -53.29 isooctane, and -53.68 hexamethylethane. These are in excellent agreement (typically be...

Karton, Amir; Martin, Jan M L

2009-01-01

109

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

SciTech Connect

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

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

2009-04-06

110

Correlation between Levels of 2, 5-Hexanedione and Pyrrole Adducts in Tissues of Rats Exposure to n-Hexane for 5-Days  

PubMed Central

Background The formation of pyrrole adducts might be responsible for peripheral nerve injury caused by n-hexane. The internal dose of pyrrole adducts would supply more information for the neurotoxicity of n-hexane. The current study was designed to investigate the tissue distributions of 2, 5-hexanedione (2,5-HD) and pyrrole adducts in rats exposed to n-hexane, and analyze the correlation between pyrrole adducts and 2,5-HD in tissues. Methods Male Wistar rats were given daily dose of 500,1000, 2000, 4000 mg/kg bw n-hexane by gavage for 5 days. The rats were sacrificed 24 hours after the last administration. The levels of 2, 5-hexanedione and pyrrole adducts in tissues were measured by gas chromatography and Ehrlich’s reagent, respectively. The correlations between 2, 5-hexanedione and pyrrole adducts were analyzed by linear regression Results Dose-dependent effects were observed between the dosage of n-hexane and 2, 5-hexanedione, and pyrrole adducts in tissues. The highest level of 2, 5-hexanedione was found in urine and the lowest in sciatic nerve, while the highest level of pyrrole adducts was seen in liver and the lowest in serum. There were significant correlations among the free 2, 5-hexanedione, total 2, 5-hexanedione and pyrrole adducts within the same tissues. Pyrrole adducts in serum showed the most significant correlation with free 2, 5-hexanedione or pyrrole adducts in tissues. Conclusion The findings suggested that pyrrole adducts in serum might be a better indicator for the internal dose of free 2, 5-hexanedione and pyrrole adducts in tissues. PMID:24098756

Yin, Hongyin; Guo, Ying; Zeng, Tao; Zhao, Xiulan; Xie, Keqin

2013-01-01

111

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

112

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

113

Ultrasonic and spectroscopic studies on hydrogen bonded complexes of aromatic amine and aryl ketones in n-hexane at 303.15 K  

Microsoft Academic Search

Viscometric and ultrasonic studies have been carried out in n-hexane solutions, containing equimolar concentration from 0.02 to 0.2M of aromatic ketones and N-methylaniline (NMANI), at 303.15K and at atmospheric pressure. The ketones studied in the present investigation are acetophenone (ACP), 4-chloroacetophenone (ClACP) and 4-methylacetophenone (MACP). The behaviour of measured ultrasonic velocity (u), density (?) and viscosity (?) and also the

R. Kumar; N. Swarnalatha; R. Mahesh; B. Shanmugapriyan; V. Kannappan

2011-01-01

114

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

PubMed

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

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

2012-01-01

115

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

116

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  

SciTech Connect

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 isomerized alkylperoxy radicals, internal H atom abstractions, and reactions involving O-heterocyclic species. The mechanism is then used to study the influence of fuel composition on knocking in internal combustion engines. Autoignition of mixtures of iso-octane and n-heptane is examined. The computations reproduce the variations of autoignition delay time with octane number and these variations are interpreted in terms of detailed differences in the structure of the two primary reference fuels. Sensitivity analyses of the computations are also presented. 30 refs., 2 figs.

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

1988-01-11

117

Association and transport properties in solvents of medium and low relative permittivity: Quaternary ammonium picrates in acetone– n-hexane mixed solvents  

Microsoft Academic Search

The behavior of tetra-n-butylammonium picrate, TBAPic, in acetone–n-hexane mixed solvent, with the relative permittivity changing gradually from ?r=20.53 to 4.99 and only slightly changing viscosity, was studied at 25.0°C using conductometry. The association constants (TBA++Pic–?TBA+Pic–,KA) and the limiting molar conductivities were determined using the Lee–Wheaton equation. At acetone content 50 mass % (?r=8.76) and higher, the 1:1 association model is

Irina N. Palval; Alexander V. Lebed; Nikolay O. Mchedlov-Petrossyan

2011-01-01

118

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

119

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

120

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

121

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

PubMed

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

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

2008-07-15

122

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

PubMed

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

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

2008-07-17

123

Separation of n-hexane/acetone mixtures by pervaporation using high density polyethylene/ethylene propylene diene terpolymer rubber blend membranes.  

PubMed

Polymer membranes were prepared by blending high density polyethylene (HDPE) with ethylene propylene diene terpolymer rubber (EPDM). These blend membranes were evaluated for the selective separation of n-hexane from acetone. The flux and selectivity of the membranes were determined both as a function of the blend composition and feed mixture composition. Results showed that polymer blending method could be very useful to develop new membranes with improved selectivity. Pervaporation properties could be optimized by adjusting the blend composition. The effects of blend ratio, feed composition, and penetrant size on the pervaporation process were analyzed. The permeation properties have been explained on the basis of interaction between the membrane and solvents and blend morphology. Flux increases with increasing alkane content in the feed composition. PMID:22118848

Kumar, P V Anil; Anilkumar, S; Varughese, K T; Thomas, Sabu

2012-01-15

124

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

125

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

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 (1)H 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; Ritter, Helmut

2013-01-01

126

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

127

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

E-print Network

We present incoherent quasi-elastic neutron scattering measurements in a wavevector transfer range from 0.4 AA^{-1} to 1.6AA^{-1} on liquid n-hexane confined in cylindrical, parallel-aligned nanochannels of 6 nm mean diameter and 260 micrometer length in monolithic, mesoporous silicon. They are complemented with, and compared to, measurements on the bulk system in a temperature range from 50K to 250K. The time-of-flight spectra of the bulk liquid can be modeled by microscopic translational as well as fast localized rotational, thermally-excited, stochastic motions of the molecules. In the nano-confined state of the liquid, which was prepared by vapor condensation, we find two molecular populations with distinct dynamics, a fraction which is immobile on the time scale of 1ps to 100ps probed in our experiments and a second component with a self-diffusion dynamics slightly slower than observed for the bulk liquid. No hints of an anisotropy of the translational diffusion with regard to the orientation of the chan...

Hofmann, Tommy; Mayorova, Maria; Zorn, Reiner; Frick, Bernhard; Huber, Patrick; 10.1063/1.3696684

2012-01-01

128

Probing mechanisms of axonopathy. Part II: Protein targets of 2,5-hexanedione, the neurotoxic metabolite of the aliphatic solvent n-hexane.  

PubMed

Neuroprotein changes in the spinal cord of rodents with aliphatic gamma-diketone axonopathy induced by 2,5-hexanedione (2,5-HD) are compared with those reported previously in aromatic gamma-diketone-like axonopathy induced by 1,2-diacetylbenzene (1,2-DAB). Sprague-Dawley rats were treated intraperitoneally with 500 mg/kg/day 2,5-HD, equimolar doses of 2,3-hexanedione (negative control), or an equivalent amount of saline containing 50% dimethyl sulfoxide (vehicle), 5 days a week, for 3 weeks. Analysis of the lumbosacral proteome by 2-dimensional differential in-gel electrophoresis and matrix-assisted laser desorption ionization time-of-flight/tandem mass spectrometry revealed 34 proteins markedly modified by 2,5-HD of which neurofilament triplet L, gelsolin, protein disulfide isomerase, glutathione S-transferase, nicotinamide adenine dinucleotide (reduced) dehydrogenase 1 alpha, pyruvate kinase, and fatty acid synthase were also modified by 1,2-DAB. The expression of proteins involved in maintaining the physical integrity of the cytoskeleton or controlling the redox and protein-folding mechanisms was reduced, whereas that of proteins supporting energy metabolism was mainly increased. The similarity of the neuroproteomic patterns of 2,5-HD and 1,2-DAB axonopathy suggests common biomarkers and/or mechanisms of neurotoxicity associated with exposure to their parent chemicals, namely the industrial solvents n-hexane and 1,2-diethylbenzene, respectively. PMID:19033394

Tshala-Katumbay, Desire; Monterroso, Victor; Kayton, Robert; Lasarev, Michael; Sabri, Mohammad; Spencer, Peter

2009-02-01

129

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

130

Experimental neurotoxicity and urinary metabolites of the C5-C7 aliphatic hydrocarbons used as glue solvents in shoe manufacture.  

PubMed

Rats were intermittently exposed (9 to 10 h/d, 5 to 6 d/week) to controlled concentrations of single analytical grad solvents in ambient air. After periods ranging from 7 to 30 weeks the animals were perfused with glutaraldehyde and samples of nerves were processed for light microscopy of sections and of teased fibers. Animals treated with n-hexane at 5000 ppm (14 weeks) or 2500 ppm (30 weeks) developed the typical giant axonal degeneration already described in rats treated continuously with 400 to 600 ppm of the same solvent for 7 weeks or more. No such alterations were found in rats subjected to the following intermittent respiratory treatments: n-hexane 500 ppm (30 weeks) or 1500 ppm (14 weeks), cyclohexane 1500 or 2500 (30 weeks), n-pentane 3000 ppm (30 weeks), n-heptane 1500 ppm (30 weeks), 2-methylpentane 1500 ppm (14 weeks), and 3-methylpentane 1500 ppm (14 weeks). The following metabolites were found in the urine of rats according to treatment (in parenthesis): 2-methyl-2-pentanol (2-methylpentane); 3-methyl-2-pentanol and 3-methyl-3-pentanol (3-methylpentane), 2-hexanol, 3-hexanol, gamma-valerolactone, 2,5-dimethylfuran, and 2,5-hexanedione (n-hexane). 2-Hexanol was found to be the main urinary metabolite of n-hexane, while 2,5-hexanedione was present only in a lesser proportion. This feature of rat metabolism suggests that in this species 2,5-hexanedione reaches an effective level at its site of action during intermittent respiratory treatment with n-hexane with difficulty and explains the high concentrations necessary to cause polyneuropathy in rats subjected to this treatment. PMID:6277548

Frontali, N; Amantini, M C; Spagnolo, A; Guarcini, A M; Saltari, M C; Brugnone, F; Perbellini, L

1981-12-01

131

High-temperature catalytic reforming of n-hexane over supported and core-shell Pt nanoparticle catalysts: role of oxide-metal interface and thermal stability.  

PubMed

Designing catalysts with high thermal stability and resistance to deactivation while simultaneously maintaining their catalytic activity and selectivity is of key importance in high-temperature reforming reactions. We prepared Pt nanoparticle catalysts supported on either mesoporous SiO2 or TiO2. Sandwich-type Pt core@shell catalysts (SiO2@Pt@SiO2 and SiO2@Pt@TiO2) were also synthesized from Pt nanoparticles deposited on SiO2 spheres, which were encapsulated by either mesoporous SiO2 or TiO2 shells. n-Hexane reforming was carried out over these four catalysts at 240-500 °C with a hexane/H2 ratio of 1:5 to investigate thermal stability and the role of the support. For the production of high-octane gasoline, branched C6 isomers are more highly desired than other cyclic, aromatic, and cracking products. Over Pt/TiO2 catalyst, production of 2-methylpentane and 3-methylpentane via isomerization was increased selectively up to 420 °C by charge transfer at Pt-TiO2 interfaces, as compared to Pt/SiO2. When thermal stability was compared between supported catalysts and sandwich-type core@shell catalysts, the Pt/SiO2 catalyst suffered sintering above 400 °C, whereas the SiO2@Pt@SiO2 catalyst preserved the Pt nanoparticle size and shape up to 500 °C. The SiO2@Pt@TiO2 catalyst led to Pt nanoparticle sintering due to incomplete protection of the TiO2 shells during the reaction at 500 °C. Interestingly, over the Pt/TiO2 catalyst, the average size of Pt nanoparticles was maintained even after 500 °C without sintering. In situ ambient pressure X-ray photoelectron spectroscopy demonstrated that the Pt/TiO2 catalyst did not exhibit TiO2 overgrowth on the Pt surface or deactivation by Pt sintering up to 600 °C. The extraordinarily high stability of the Pt/TiO2 catalyst promoted high reaction rates (2.0 ?mol · g(-1) · s(-1)), which was 8 times greater than other catalysts and high isomer selectivity (53.0% of C6 isomers at 440 °C). By the strong metal-support interaction, the Pt/TiO2 was turned out as the best catalyst with great thermal stability as well as high reaction rate and product selectivity in high-temperature reforming reaction. PMID:25078630

An, Kwangjin; Zhang, Qiao; Alayoglu, Selim; Musselwhite, Nathan; Shin, Jae-Youn; Somorjai, Gabor A

2014-08-13

132

Excess molar volumes and excess molar enthalpies of binary and ternary mixtures of 1-butanol, a tertiary amine (tri- n-butylamine or tri- n-octylamine) and n-hexane: Experimental results and ERAS-model calculations  

Microsoft Academic Search

Experimental data at T=298.15K and ambient pressure of excess molar volumes VmE and excess molar enthalpies HmE are reported for two ternary and the corresponding binary mixtures of {1-butanol, tri-n-butylamine (TBA), or tri-n-octylamine (TOA), and n-hexane}. A vibrating-tube densitometer was used to determine VmE. HmE was measured using a quasi-isothermal flow calorimeter. The experimental results are used to test the

Matthias Kwaterski; Elena N. Rezanova; Rüdiger N. Lichtenthaler

2006-01-01

133

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

134

40 CFR Appendix A to Part 439 - Tables  

Code of Federal Regulations, 2014 CFR

...Phenol Isobutyraldehyde 1 Aldehydes. n-Heptane 1 Alkanes. n-Hexane 1 Diethylamine 1 Amines. Triethylamine...Chlorobenzene o-Dichlorobenzene Chloroform 1 Chlorinated Alkanes. Methylene chloride 1 1,2-Dichloroethane 1...

2014-07-01

135

40 CFR Appendix A to Part 439 - Tables  

Code of Federal Regulations, 2013 CFR

...Phenol Isobutyraldehyde 1 Aldehydes. n-Heptane 1 Alkanes. n-Hexane 1 Diethylamine 1 Amines. Triethylamine...Chlorobenzene o-Dichlorobenzene Chloroform 1 Chlorinated Alkanes. Methylene chloride 1 1,2-Dichloroethane 1...

2013-07-01

136

40 CFR Appendix A to Part 439 - Tables  

Code of Federal Regulations, 2010 CFR

...Phenol Isobutyraldehyde 1 Aldehydes. n-Heptane 1 Alkanes. n-Hexane 1 Diethylamine 1 Amines. Triethylamine...Chlorobenzene o-Dichlorobenzene Chloroform 1 Chlorinated Alkanes. Methylene chloride 1 1,2-Dichloroethane 1...

2010-07-01

137

40 CFR Appendix A to Part 439 - Tables  

Code of Federal Regulations, 2012 CFR

...Phenol Isobutyraldehyde 1 Aldehydes. n-Heptane 1 Alkanes. n-Hexane 1 Diethylamine 1 Amines. Triethylamine...Chlorobenzene o-Dichlorobenzene Chloroform 1 Chlorinated Alkanes. Methylene chloride 1 1,2-Dichloroethane 1...

2012-07-01

138

40 CFR Appendix A to Part 439 - Tables  

Code of Federal Regulations, 2011 CFR

...Phenol Isobutyraldehyde 1 Aldehydes. n-Heptane 1 Alkanes. n-Hexane 1 Diethylamine 1 Amines. Triethylamine...Chlorobenzene o-Dichlorobenzene Chloroform 1 Chlorinated Alkanes. Methylene chloride 1 1,2-Dichloroethane 1...

2011-07-01

139

n—? electron-donor—acceptor complexes—IV. The interaction of aliphatic amines with 1,3-dicyanobenzene in n-hexane. The importance of preferred orientation in the stability of the complexes  

NASA Astrophysics Data System (ADS)

The stability constants ( K) for the electron-donor—acceptor (EDA) complexes formed between aliphatic amines as n-donors and 1,3-dicyanobenzene (1,3-DCB) have been determined in n-hexane as solvent. By means of free energy substitutent parameters and regression analysis, the electronic and steric effects of the N-amine substituents were quantitatively separated. Thus, values of log K were correlated with Taft's polar substituents, ?*, and Hancock's corrected steric substituent constants, ECs. Large steric effects are inferred which lead us to propose a preferential site of interaction. This preferential orientation may also explain the greater stability of the 1,3-DCB—amine complexes with respect to the corresponding 1,4-DCB—amine complexes. The proposal is supported by the excess of atomic charge predicted by the Mulliken population analysis, obtained by MNDO calculations for the acceptors and by considering that for weak n—? complexes, the electrostatic energy may be of major importance in the energy of interaction.

Biasutti, M. A.; Anunziata, J. D.; Silber, J. J.

1992-02-01

140

(Z)-3-Dodecenoic acid is the main component of full-body n-hexane extracts from two Acacia gall-inducing thrips (Thysanoptera) and may function as an alarm pheromone.  

PubMed

A major interest in the gall-inducing thrips of Australia began with the discovery that some species have eusocial colonies. The origin of social castes remains one of the outstanding questions in evolutionary biology. The inference of the ancestral stage from study of solitary species is important to understanding the evolutionary history of semiochemicals in social species. Here we investigated two solitary species, Kladothrips nicolsoni and K. rugosus. Whole body extracts revealed that (Z)-3-dodecenoic acid, here reported for the first time in a thrips species, is the main component. (Z)-3-Dodecenoic acid and (E)-3-dodecenoic acid were synthesized in high stereoisomeric purity (> 99.8%) and exposed to K. nicolsoni 2nd-instar larvae in a contact chemoreception bioassay to test for potential bioactivity. Both isomers decreased the average time spent in the treated area per entry suggesting repellence at the tested dose. (Z)-3-Dodecenoic acid may function as alarm pheromone. (E)-3-Dodecenoic acid increased also the absolute change in direction of larvae compared to an n-hexane control and could potentially function as a repellent. PMID:25265854

Wallin, Erika A; De Facci, Monica; Anderbrant, Olle; Hedenström, Erik

2014-01-01

141

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...

142

A PLP-LIF kinetic study of the atmospheric reactivity of a series of C 4-C 7 saturated and unsaturated aliphatic aldehydes with OH  

NASA Astrophysics Data System (ADS)

Absolute rate coefficients for the reaction of OH radical with a series of saturated and unsaturated aliphatic aldehydes were measured with the pulsed laser photolysis/laser-induced fluorescence technique at room temperature and as a function of total pressure ( pT=100-400 Torr). No pressure dependence of the rate coefficients was observed. The weighted average values obtained, kOH±2 ?, in units of 10 -11 cm 3 molecule -1 s -1, were 2.88±0.26 for n-butanal, 2.48±0.24 for n-pentanal, 2.60±0.21 for n-hexanal, 2.96±0.23 for n-heptanal, 3.51±0.71 for crotonaldehyde, 2.35±0.32 for trans-2-pentenal, 2.95±0.45 for trans-2-hexenal and 2.45±0.30 for trans-2-heptenal, respectively. The results are compared with previous data when available and with the corresponding coefficients for the reactions with NO 3 and O 3. The dominant tropospheric chemical loss process for these aliphatic aldehydes is the daytime reaction with OH, except in the case of trans-2-heptenal where the estimated lifetime for the reaction with NO 3 radical is smaller than the corresponding value for the OH reaction.

Albaladejo, José; Ballesteros, Bernabé; Jiménez, Elena; Martín, Pilar; Martínez, Ernesto

143

Kinetic study of the gas-phase reaction of atomic chlorine with a series of aldehydes  

NASA Astrophysics Data System (ADS)

The reactions of Cl atoms with a series of unsaturated aldehydes have been investigated for the first time using a relative method. In order to obtain additional information for a qualitative structure versus reactivity discussion, we have also determined, for the first time, the rate coefficients for the reactions of atomic chlorine with their respective saturated aldehydes. These relative measurements were performed at room temperature and atmospheric pressure of air and N2, by using ethane, propene and 1-butene as reference compounds. The weighted average relative rate constants obtained, kCl±2? (in units of cm3 molecule-1 s-1) were: trans-2-pentenal (1.31±0.19)×10-10; trans-2-hexenal (1.92±0.22)×10-10; trans-2-heptenal (2.40±0.29)×10-10; n-pentanal (2.56±0.27)×10-10; n-hexanal (2.88±0.37)×10-10; n-heptanal (3.00±0.34)×10-10. Finally, results and atmospheric implications are discussed and compared with the reactivity with OH and NO3 radicals.

Rodríguez, D.; Rodríguez, A.; Notario, A.; Aranda, A.; Díaz-de-Mera, Y.; Marínez, E.

2005-07-01

144

Kinetic study of the gas-phase reaction of atomic chlorine with a series of aldehydes  

NASA Astrophysics Data System (ADS)

The reactions of Cl atoms with a series of unsaturated aldehydes have been investigated for the first time using a relative method. In order to obtain additional information for a qualitative structure versus reactivity discussion, we have also determined the rate coefficients for the reactions of atomic chlorine with their respective saturated aldehydes. These relative measurements were performed at room temperature and atmospheric pressure of air and N2, by using ethane, propene and 1-butene as reference compounds. The weighted average relative rate constants obtained, kCl±2? (in units of cm3 molecule-1 s-1) were: trans-2-pentenal (1.31±0.19)×10-10; trans-2-hexenal (1.92±0.22)×10-10; trans-2-heptenal (2.40±0.29)×10-10; n-pentanal (2.56±0.27)×10-10; n-hexanal (2.88±0.37)×10-10; n-heptanal (3.00±0.34)×10-10.

Finally, results and atmospheric implications are discussed and compared with the reactivity with OH and NO3 radicals.

Rodríguez, D.; Rodríguez, A.; Notario, A.; Aranda, A.; Díaz-de-Mera, Y.; Martínez, E.

2005-12-01

145

Electron mobility, free ion yields, and electron thermalization distances in n-alkane liquids: Effect of chain length  

NASA Astrophysics Data System (ADS)

The electron mobility ?o was measured as a function of temperature in liquid n-hexane, n-heptane, n-octane, n-nonane, and n-undecane, and at 295 K in n-pentane. Combination of these with earlier measurements of ours showed that ?0 at 295 K decreased monotonically with increasing carbon chain length in n-alkane liquids from ethane to n-tetradecane. There was no significant difference between odd and even carbon number compounds. The results were in accord with two-state interpretations of electron transport. Free ion yields were measured in liquid n-Cx H2x+2 (4?x?14, except 13) and electron thermalization ranges bGP were estimated using the extended Onsager model. The zero field free ion yield G0fi at 295 K decreased with increasing chain length. The density-normalized thermalization range of electrons was bGPd=(41±1)×10-7 kg/m2 in all n-alkanes from C4 to C14 under the conditions of this study.

Gee, Norman; Senanayake, P. Chandani; Freeman, Gordon R.

1988-09-01

146

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

147

Temperature-dependence study of the gas-phase reactions of atmospheric Cl atoms with a series of aliphatic aldehydes  

NASA Astrophysics Data System (ADS)

The reactions of Cl with a series of linear aldehydes: propanal ( k1), n-butanal ( k2), n-pentanal ( k3), n-hexanal ( k4) and n-heptanal ( k5), were investigated for the first time as a function of temperature in the range 265-381 K, by laser photolysis-resonance fluorescence. The obtained kinetic data were used to derive the Arrhenius expressions: k1=(2.41±0.23) × 10 -11 exp[(453 ± 54)/ T], k2=(3.09 ± 0.40) × 10 -11 exp[(446 ± 77)/ T], k3=(4.17 ± 0.54) × 10 -11 exp[(450 ± 80)/ T], k4=(7.91 ± 0.66) × 10 -11 exp[(349 ± 51)/ T] and k5=(1.06 ± 0.20) × 10 -10 exp[(306 ± 115)/ T] (in units of cm 3 molecule -1 s -1). To our knowledge, these are also the first absolute kinetic data reported for each of the reactions studied. The obtained rate coefficients are compared with previous studies carried out by relative techniques at room temperature, and also with the reactivity towards the OH radicals. The results are also discussed in terms of the structure-reactivity relationship. In addition, the atmospheric implications are discussed.

Cuevas, Carlos A.; Notario, Alberto; Martínez, Ernesto; Albaladejo, José

148

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

149

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

150

[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

151

Reaction zone visualisation in swirling spray n-heptane flames  

E-print Network

. Thirdly, a transformation matrix relating the two sets of coordinates was computed and then used to map the OH images onto the coordinates system of the CH2O images. The images were further processed via Matlab with background subtraction, laser profile... -Douwel, N.J. Dam, W.L. Meerts, J.J. ter Meulen, Combust. Flame, 157 (2010) 155–166. [12] M. R. Schrewe, J. B. Ghandhi, Proc. Combust. Inst. 31 (2007) 2871-2878. [13] H. N. Najm, P. H. Paul, C. J. Mueller, P. S. Wyckoff, Combust. Flame, 113 (1998) 312- 332...

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

2014-06-26

152

[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

153

stav chemickch proces Akademie vd  

E-print Network

[%]Solvent Druh záení OHOH ortho-ortho OH OH ortho-para OH OH para-para Stupe pemny [%] n-Hexan MW-UV 45 55 0 [%] n-Hexan Acetofenon MW-UV 44 56 0 36 UV 57 43 0 47 Benzofenon MW-UV 40 60 0 46 UV 47 53 0 34 Akridin-ortho OH 2TBP Stupe pemny [%] n-Hexan MW-UV 22 62 16 20 UV 27 46 27 18 n-Heptan MW-UV 58 30 12 36 UV 58 28

Cirkva, Vladimir

154

Carbonyls in urban fog, ice fog, cloudwater and rainwater  

NASA Astrophysics Data System (ADS)

Formaldehyde, acetaldehyde, propanal, acetone + acrolein, n-butanal, 2-butanone, n- pentanal, n-hexanal and benzaldehyde have been identified in fog, ice fog, mist, cloudwater and rainwater samples collected at urban locations in California (Los Angeles) and Alaska (Fairbanks). Formaldehyde concentrations, up to ~ 2 mg ? -1, were highest in urban fog and ice fog samples. Concentrations of other carbonyls occasionally approached or exceeded that of formaldehyde. The results are briefly discussed in terms of scavenging of gas-phase atmospheric carbonyls.

Grosjean, Daniel; Wright, Barbara

155

Solubility and diffusion of organic vapors in silicone polymers  

NASA Astrophysics Data System (ADS)

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

Pimsamarn, Jindarat

156

Corona discharge of Titan's troposphere.  

PubMed

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

Navarro-Gonzalez, R; Ramirez, S I

1997-01-01

157

Corona chemistry in Titan.  

PubMed

The atmosphere of Titan is constantly bombarded by galactic cosmic rays and Saturnian magnetospheric electrons causing the formation of free electrons and primary ions, which are then stabilized by ion cluster formation and charging of aerosols. These charged particles accumulate in drops in cloud regions of the troposphere. Their abundance can substantially increase by friction, fragmentation or collisions during convective activity. Charge separation occurs with help of convection and gravitational settling leading to development of electric fields within the cloud and between the cloud and the ground. Neutralization of these charged particles leads to corona discharges which are characterized by low current densities. We have therefore, experimentally studied the corona discharge of a simulated Titan's atmosphere (10% methane and 2% argon in nitrogen) at 500 Torr and 298 K by GC-FTIR-MS techniques. The main products have been identified as hydrocarbons (ethane, ethyne, ethene, propane, propene+propyne, cyclopropane, butane, 2-methylpropane, 2-methylpropene, n-butane, 2-butene, 2,2-dimethylpropane, 2-methylbutane, 2-methylbutene, n-pentane, 2,2-dimethylbutane, 2-methylpentane, 3-methylpentane, n-hexane, 2,2-dimethylhexane, 2,2-dimethylpentane, 2,2,3-trimethylbutane, 2,3-dimethylpentane and n-heptane), nitriles (hydrogen cyanide, cyanogen, ethanenitrile, propanenitrile, 2-methylpropanenitrile and butanenitrile) and a highly branched hydrocarbon deposit. We present the trends of hydrocarbons and nitriles formation as a function of discharge time in an ample interval and have derived their initial yields of formation. The results clearly demonstrate that a complex organic chemistry can be initiated by corona processes in the lower atmosphere. Although photochemistry and charged particle chemistry occurring in the stratosphere can account for many of the observed hydrocarbon species in Titan, the predicted abundance of ethene is too low by a factor of 10 to 40. While some ethene will be produced by charged-particle chemistry, the production of ethene by corona processes and its subsequent diffusion into the stratosphere appears to be an adequate source. Because little UV penetrates to the lower atmosphere to destroy the molecules formed there, the corona-produced species may be long-lived and contribute significantly to the composition of the lower atmosphere and surface. PMID:11541887

Navarro-Gonzalez, R; Ramirez, S I; Matrajt, G; Basiuk, V; Basiuk, E

1998-06-01

158

Viscosity of Selected Liquid n-Alkanes  

NASA Astrophysics Data System (ADS)

A critical assessment has been made of the available experimental viscosity data for liquid n-hexane, n-heptane, n-octane, n-decane, n-dodecane, and n-tetradecane, with the aim of establishing standard reference values along the saturation line. Recommended viscosities are given at 298.15 K with an uncertainty conservatively estimated to be ±0.3%, except for n-hexane and n-heptane where it is 0.4%. Selected data which cover most of the normal liquid range are satisfactorily correlated using a modified form of Arrhenius equation. The estimated uncertainty in this correlation is ±0.5% for viscosities above 0.25 mPa s and ±1% for lower viscosities.

Dymond, J. H.; Øye, H. A.

1994-01-01

159

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.

160

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

E-print Network

. . . . APPENDIX B: SAMPLE SIZE CALCULATION FOR THE HYDROCARBON - CARBON DIOXIDE EXPERIMENT APPENDIX C: GAS BOOSTING CALCULATION . . . . VITA . page 106 121 143 147 LIST OF FIGURES Figure Page 3. 1 3. 2 3. 3 3. 4 3. 8 3. 5. 3. 6. 3. 7. 3. 9. 3... mixtures LP pRasL ID 100M HC LP. PPKSC 416 LP. IOKSS I I 4 OOLHC 40LCC2 LP. PIKM 416 LP, PI%86 414 20HHC 8W CC2 0. 00 3. 21 8. 4 e e. to 28 at 28 00 Oe. at 51. 24 72 73 75 85 88 25 102. 5D 128AO 'I 31. DO I 80. 20 164 00 1...

Wirawan, Januar Fitri Santo

2012-06-07

161

Picosecond pulse radiolysis studies of the primary processes in hydrocarbon radiation chemistry  

NASA Astrophysics Data System (ADS)

Picosecond pulse radiolysis studies have been performed on n-pentane, n-hexane and cyclohexane to learn about the primary radiolytic processes occurring in these alkanes. The transient absorption profiles obtained result from the superimposition of several processes: the geminate recombination between positive ions and electrons; the disappearance of highly excited alkali radical-cations (by spontaneous fragmentation of C-H bonds or dimolecular reaction with the solvent); and the exponential decay of the singlet solvent excited states. Fragmentation of excited alkane positive ions appears to be faster when the number of carbon atoms decreases in the aliphatic chain: it becomes so fast in n-pentane that only pentene positive ions are detected after 25 ps pulses. The recombination kinetics between pentene holes and the electrons is similar to that predicted for a geminate ion decay in which the spatial distribution function of ions is exponential. Contrary to linear alkane cations, cyclohexane holes do not exhibit a pronounced tendency to dissociate. The short lifetimes of the n-pentane and n-hexane S 1 states mean that the absorption of the S 1 state is not important; in contrast, the S 1 state of cyclohexane decays more slowly and thus contributes much more to the optical absorption. A non-negligible fraction of cyclohexane S 1 states are generated by geminate recombination.

Le Motais, B. C.; Jonah, C. D.

162

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

163

Lipase-catalyzed synthesis of terpene esters by transesterification in n-hexane  

Microsoft Academic Search

Short chain fatty acid esters of geraniol and citronellol were synthesized by lipase-catalyzèd transesterification with yields as high as 98% molar conversion. Triacylglycerols were the best substrates and immobilized Candida antarctica lipase, SP435 gave the highest overall yields. The lipases tested successfully accommodated novel acyl donors such as isopropenyl acetate and glycidyl butyrate.

Paul A. Claon; Casimir C. Akoh

1994-01-01

164

Enzymatic alcoholysis of palm kernel oil in n-hexane and SCCO 2  

Microsoft Academic Search

The use of biocatalysts in supercritical CO2 (SCCO2) has received widespread attention in recent years. Biocatalysts have the advantage of substrate specificity under mild reaction conditions and SCCO2 has several advantages over liquid solvents such as high solute diffusivities and low viscosity, which can accelerate mass transfer-limited enzymatic reactions. Concerning the enzymatic alcoholysis of vegetable oils, very little experimental data

D Oliveira; J. Vladimir Oliveira

2001-01-01

165

Enzymatic synthesis of geraniol and citronellol esters by direct esterification in n-hexane  

Microsoft Academic Search

Short chain fatty acid esters of geraniol and citronellol were synthesized by lipase-catalyzed direct esterification with yields ranging from 90 to 100% molar conversion. The effect of the order of addition of substrates, solvent and enzyme was investigated. Yields were highest when the solvent was added first followed by the substrates and then the lipase.

Paul A. Claon; Casimir C. Akoh

1993-01-01

166

Enzymatic synthesis of geranyl acetate in n -hexane with Candida antarctica lipases  

Microsoft Academic Search

Geranyl acetate is an important flavor and fragrance compound. Two immobilizedCandida antarctica lipases, SP382 and SP435, were investigated for their use in the synthesis of geranyl acetate by direct esterification. Yields\\u000a between 95 and 99% molar conversion were obtained with 2 and 15% (w\\/w reactants) of SP435 and SP382 lipases, respectively.\\u000a Optimum yields were obtained at 0.1M acetic acid and

Paul A. Claon; Casimir C. Akoh

1994-01-01

167

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

E-print Network

) By following the procedure set forth by Liu and Admundson (1962) and by Edgar et al. (1970), one obtains the follow- ing set of integral equations. G (s, T) = R ' (s) exp (s ? I) adT dT I 2 1 0 T 1 (52) ! 3G] = R 'dT + R ' ndT dT = M ? M (53) 9sJ 1 I... 0 s=l 0 0 1 T T 2 R ' ndT 0 1 T T 2 dT + R ' ndT dT (54) 1 I 2 1 0 1 The solution of these differential and integral equations by the procedures listed by Edgar et al. (1970) lead to the calculation of the initiator and monomer...

Porter, Raymond Eugene

2012-06-07

168

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

PubMed

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

Arriaga, Sonia; Revah, Sergio

2005-12-01

169

Dehydrocyclization of n-hexane and the possible role of Pt-ions  

SciTech Connect

It is obvious that it is virtually impossible to vary the Pt{sup n{plus}}/Pt ratio and to keep all factors mentioned constant. Nevertheless, we have made an attempt to solve the title problem and, in view of the complexities it is not very surprising that only a limited success was achieved. The strategy was to study the skeletal reactions under such conditions that only (or mainly) Pt (or Pt{sup n{plus}} ) sites are important. This is expected to be the case in the {und L}ow {und T}emperature {und R}eactions (LTR) in the region 480-590{degree}K. After studying this region, we also studied hexane reactions at higher temperatures (HTR): 650-700{degree}D. In this temperature region, the consecutive reactions must be checked and it was decided to keep the ratio S(Pt)/F constant and to compare the catalysts at the same temperature and at conversions as low as possible. The results have to be analyzed then with regard to a possible role of acid sites.

Botman, M.J.P.; Ponec, V. (Leiden Univ. (The Netherlands))

1987-08-01

170

Estimation of Absolute Free Energies of Hydration using Continuum Methods: Accuracy of Partial Charge Models and Optimization of Nonpolar Contributions  

E-print Network

-methylpropane 2.32 6 n-pentane 2.32 7 2-methylbutane 2.38 8 2,2-dimethylpropane 2.51 9 n-hexane 2.48 10 2.50 132 propionaldehyde -3.43 133 butyraldehyde -3.18 134 pentanal -3.03 135 hexanal -2.81 136 heptanal -2-methylbutan-2-one -3.24 147 hexan-2-one -3.28 148 4-methylpentan-2-one -3.05 #12;149 heptan-2-one -3.04 150

Rizzo, Robert C.

171

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

172

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

173

Figure S1. The 17-monitor-average daily maximal 8-hour O3 in the Houston metropolitan area during July-October in both 2000 and 2006; the time periods of the two TexAQS are marked by  

E-print Network

_all n_butane_all 1_butene_all t_2_butene_all c_2_butene_all 1_3_butandiene_all cyclopentane_all cyclopentene_all isopentane_all n_pentane_all 1_pentene_all t_2_pentene_all c_2_pentene_all 3_methyl_1_butene_all 2_methyl_2_butene_all 2_methyl_1_butene_all isoprene_all n_hexane_all 2_methyl_pentane_all 3_methyl

Meskhidze, Nicholas

174

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

175

Comparison between exhaled and sputum oxidative stress biomarkers in chronic airway inflammation  

Microsoft Academic Search

ABSTRACT: The aim of the present study was to compare,aldehyde,levels resulting from lipid peroxidation in exhaled breath condensate,(EBC) and induced sputum,(IS) supernatant,of subjects with,asthma,and,chronic,obstructive,pulmonary,disease (COPD). Aldehydes (malondialdehyde (MDA), acrolein, n-hexanal (C6), n-heptanal (C7), n- nonanal (C9), 4-hydroxynonenal (HNE) and 4-hydroxyhexenal (HHE)) in both biological fluids were measured,by liquid chromatography-tandem,mass spectrometry. MDA concentrations in sputum,were 132.5 nM (82.5?268.8) and 23.7 nM

M. Corradi; P. Pignatti; P. Manini; R. Andreoli; M. Goldoni; M. Poppa; G. Moscato; B. Balbiz; A. Mutti

2004-01-01

176

Solubility and Excess Molar Properties of 1,3-Dimethylimidazolium Methylsulfate, or 1Butyl3-Methylimidazolium Methylsulfate, or 1Butyl3-Methylimidazolium Octylsulfate Ionic Liquids with n Alkanes and Alcohols: Analysis in Terms of the PFP and FBT Models 1  

Microsoft Academic Search

The solubility of 1-butyl-3-methylimidazolium octylsulfate, [BMIM][OcSO4], has been determined in hydrocarbon (n-hexane, n-heptane, n-octane or n-decane) solutions and alcohol (methanol, 1-butanol, 1-hexanol, 1-octanol or 1-decanol) solutions. Densities and excess molar\\u000a volumes, V\\u000a E\\u000a m, have been determined for 1-methyl-3-methylimidazolium methylsulfate, [MMIM][CH3SO4], solutions with an alcohol (methanol, ethanol or 1-butanol) and with water; for 1-butyl-3-methylimidazolium methylsulfate,\\u000a [BMIM][CH3SO4], with an alcohol (methanol,

U. Doma?ska; A. Pobudkowska; A. Wi?niewska

2006-01-01

177

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

178

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

E-print Network

radicals and H/CH3 radicals. Olefins are consumed by direct decomposition, radical-addition, and hydrogen using mass spectrometry,2 and to provide added insights in how olefins are formed and consumed. Normal-workers, validated with experimental data of counter-flow diffusion flames, pre- mixed flames, ignition behind

Utah, University of

179

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

Microsoft Academic Search

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

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

2010-01-01

180

Improving the n -pentane hydroisomerization of Pt\\/SO 4 2? SiO 2 ) catalysts through mixing with ZrO 2  

Microsoft Academic Search

The performance of Pt catalysts supported on sulfated zirconia-silica with different stoichiometries is investigated in then-pentane hydroisomerization reaction. Comparatively, with respect to the Pt\\/SO42--SiO2 or Pt\\/SO42--ZrO2 catalysts, the sulfated mixed oxides show an enhancement of the catalytic activity that increases with the content of ZrO2, reaching its maximum at values between 10 and 15 wt% zirconia. The characterization of the

J. Salmones; R. Licona; J. Navarrete; P. Salas; J. Morales

1996-01-01

181

Hydroperoxy-arachidonic acid mediated n-hexanal and ( Z)-3- and ( E)-2-nonenal formation in Laminaria angustata  

Microsoft Academic Search

In higher plants, C6 and C9 aldehydes are formed from C18 fatty acids, such as linoleic or linolenic acid, through formation of 13- and 9-hydroperoxides, followed by their stereospecific cleavage by fatty acid hydroperoxide lyases (HPL). Some marine algae can also form C6 and C9 aldehydes, but their precise biosynthetic pathway has not been elucidated fully. In this study, we

Kangsadan Boonprab; Kenji Matsui; Yoshihiko Akakabe; Norishige Yotsukura; Tadahiko Kajiwara

2003-01-01

182

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

PubMed Central

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

2014-01-01

183

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

NASA Astrophysics Data System (ADS)

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

Notesco, G.; Bar-Nun, A.

1997-04-01

184

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

185

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

186

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

187

Application of multispectral techniques to the precise identification of aldehydes in the environment  

SciTech Connect

By using gas chromatography coupled with low- and high-resolution electron-impact mass spectrometry, low- and high-resolution chemical ionization mass spectrometry, and Fourier transform infrared spectroscopy, eight straight-chain aldehydes were identified in a water sample taken from the overflow pipe of a municipal sewer line that contained a combination of industrial and domestic sewage. This combination of infrared and mass spectral techniques yielded precise identifications of n-hexanal, n-heptanal, 2-heptenal, n-octanal, 2-octenal, n-nonanal, 2-decenal, and 2-undecenal. These findings were significant because few straight-chain aldehydes have been identified in the environment, and all those previously found were saturated.

Richardson, S.D.; Thruston, A.D.; Collette, T.W.; McGuire, J.M.

1991-01-01

188

Empirical and Semi-theoretical Methods for Predicting the Viscosity of Binary n-Alkane Mixtures  

NASA Astrophysics Data System (ADS)

In this study, empirical and semi-theoretical methods for predicting the viscosity of binary mixtures of n-alkanes are presented at atmospheric pressure and in the temperature range from 288 to 333 K. In the empirical viscosity calculation method, a modified version of the Andrade equation and a simple mixture rule are used. The proposed semi-theoretical method employs both the Enskog’s hard-sphere theory for dense fluids and the principle of corresponding states. The viscosities of binary mixtures of n-heptane with n-hexane and n-nonane covering different compositions were calculated using these methods which require only critical properties and the normal boiling point as input data. The predictions were compared with accurate experimental data in the literature. Highly satisfactory results were obtained. The percent average absolute deviations amount to 1.2 and 0.9% utilizing the empirical and semi-theoretical viscosity methods, respectively, for 27 data points.

Yucel, H. G.

2005-11-01

189

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

190

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

191

Some aspects of TLC in homogenous magnetic fields.  

PubMed

This article consists of two parts. First part is a short review about the role of magnetic phenomena in natural environment, human surroundings, and his activities such as science, engineering, and medicine. The second part of the article presents a set of experiments, their results, and data obtained in a static homogenous magnetic field, generated by a pair of permanent magnets and outside it. Adsorption chromatographic systems were investigated: as chromatographed substances - polyaromatic hydrocarbon (PAH), as stationary phase - silica gel 60, as monocomponent mobile phases - n-hexane, n-heptane, n-octane, and benzene were used and binary mobile phases n-hydrocarbons - benzene. Magnetic field influences retention and efficiency of investigated chromatographic systems. Experimental data analysis (RF, N) allows us to propose some explanations of the differences between experiment results performed in induced magnetic field and outside it, and in consequence on the changes in the interfacial phenomena induced by field presence. PMID:25363353

Malinowska, Irena; Studzi?ski, Marek; Malinowski, Henryk

2011-08-01

192

The relevance of 4,5-dihydroxy-2-hexanone in the excretion kinetics of n -hexane metabolites in rat and man  

Microsoft Academic Search

Male Wistar rats were exposed ton-hexane concentrations between 50 and 3000 ppm for 8 h, and urinary excretion kinetics of then-hexane metabolites 1-hexanol, 2-hexanol, 3-hexanol, 2-hexanone, 2,5-hexanedione, and 4,5-dihydroxy-2-hexanone were assessed. The amounts of metabolites excreted were linearly dependent on then-hexane exposure concentration, up to an exposure of about 300 ppm. Above 300 ppm exposure the metabolite excretion indicated saturation

N. Fedtke; H. M. Bolt

1987-01-01

193

Catalytic properties and deactivation behavior of crystalline microporous MAPO-36  

SciTech Connect

MAPO-36 showed high catalytic activity in conversion reactions of alcohols, linear, branched, and cycloalkanes, and aromatics. In ethanol, n-hexane, cyclohexane, and isooctane conversion reactions, MAPO-36 showed significantly higher conversion and concentration of aromatics than MAPO-5, SAPO-5, and AIPO[sub 4]-5. The distribution of aliphatics and aromatics is different in these reactions over MAPO-36, MAPO-5, SAPO-5, AIPO[sub 4]-5, and H-ZSM-5. MAPO-36 exhibited lower n-hexane conversion than H-ZSM-5; however, the aromatics yield was higher. The trend was reversed in the cyclohexane conversion reaction. The toluene disproportionation and o-xylene conversion activity of MAPO-36 is very high as compare to MAPO-5, SAPO-5, AIPO[sub 4]-5, and H-ZSM-5. In the o-xylene conversion reaction, MAPO-36 exhibited higher xylene loss, indicating poisoned strong acid sites on the catalytic properties of the catalysts was studied. The influence of pulse number on the catalytic activity of MAPO-36 in n-pentane, n-hexane, 3-methylpentane, cyclohexane, methanol, and toluene reactions was investigated. The deactivation of MAPO-36 is lowest as compared to MAPO-5, SAPO-5, and AIPO[sub 4]-5 in the ethylbenzene conversion reaction. The results on the dependence of cumene cracking activity of MAPO-36, SAPO-5, and AIPO[sub 4]-5 or time-on-stream show that the initial activity of MAPO-36 is high, though it decreases faster than that of SAPO-5 an AIPO[sub 4]-5. In situ IR techniques were used to investigate coke formation and temperature programmed oxidation of coke deposited during the cumene cracking reaction over MAPO-36. 23 refs., 8 figs., 8 tabs.

Akolekar, D.B. (Univ. of Laval, Quebec (Canada))

1993-11-01

194

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

195

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

Microsoft Academic Search

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

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

1998-01-01

196

A field-space conformal-solution method: Binary vapor-liquid phase behavior  

NASA Astrophysics Data System (ADS)

The field-space conformal solution method provides an entirely new thermodynamic framework for the description of fluid mixtures in terms of the properties of a pure reference fluid. The utility and performance of the method are examined in the special case of vapor-liquid equilibrium correlation for simple mixtures. This is one of several cases in which field-space methods have numerical or theoretical advantages over methods presently used in mixture property correlation; only properties along the vapor pressure curve of the purefluid reference system are required for a complete description of the mixture phase behavior. Vapor-liquid equilibrium data for three binary hydrocarbon mixtures, n-butane + n-pentane, n-butane + n-hexane, and n-butane + n-octane, are correlated with a simple implementation of the method having two independent mixture parameters. Two pure-fluid equations of state, a Peng-Robinson equation and a 32-constant modified Benedict-Webb-Rubin equation, are tested as reference systems. The effects of differences in the quality of the reference system and of a range of mixture component size ratios are examined.

Storvick, T. S.; Fox, J. R.

1990-01-01

197

Separation of tricyclic psychosedative drugs by high-speed ion-pair partition and liquid-solid adsorption chromatography.  

PubMed

The application of high-speed ion-pair partition and liquid-solid adsorption chromatography to the separation of twenty common tricyclic tranquilizers and antidepressant drugs is described. In the ion-pair system, amine-perchlorate ion-pairs were extracted from an aqueous stationary phase supported on 10-mum silica gel by organic eluents containing a chloromethane and a higher aliphatic alcohol, and chromatographic parameters for elution by eight eluent mixtures are presented. Using 5 mm times 120 mm columns good separations, according to chemical class, were achieved. For adsorption chromatography, the components were eluted from 20-mum spherical alumina using eluents containing methylene chloride, n-hexane or n-pentane, and acetic acid. Chromatographic parameters are given for eight eluent compositions. Components differing little in structure are well separated by liquid-solid adsorption chromatography. Compared with ion-pair partition chromatography, adsorption chromatography is much more selective for compounds of the same chemical type. The two methods are therefore complementary. Both methods gave plate heights in the range of 0.1 to 0.3 mm. PMID:234973

Knox, J H; Jurand, J

1975-01-22

198

Performance of ab initio and density functional methods for conformational equilibria of CnH2n+2 alkane isomers (n=2-8)  

E-print Network

Conformational energies of n-butane, n-pentane, and n-hexane have been calculated at the CCSD(T) level and at or near the basis set limit. Post-CCSD(T) contribution were considered and found to be unimportant. The data thus obtained were used to assess the performance of a variety of density functional methods. Double-hybrid functionals like B2GP-PLYP and B2K-PLYP, especially with a small Grimme-type empirical dispersion correction, are capable of rendering conformational energies of CCSD(T) quality. These were then used as a `secondary standard' for a larger sample of alkanes, including isopentane and the branched hexanes as well as key isomers of heptane and octane. Popular DFT functionals like B3LYP, B3PW91, BLYP, PBE, and PBE0 tend to overestimate conformer energies without dispersion correction, while the M06 family severely underestimates GG interaction energies. Grimme-type dispersion corrections for these overcorrect and lead to qualitatively wrong conformer orderings. All of these functionals also ex...

Gruzman, David; Martin, Jan M L

2009-01-01

199

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

200

A fishy odor episode in a north China reservoir: occurrence, origin, and possible odor causing compounds.  

PubMed

A significant outbreak of fishy odor occurred in a reservoir located in Inner Mongolia, China, in the winter of 2011, and the odor rating, algal density and concentrations of some potential odorous compounds were monitored over a period of two months. The peak odor rating of the fishy odor was 7 according to flavor profile analysis. Among the dominant algal species (two diatom and one chrysophyte species) observed during the survey, the chrysophyte Dinobryon sp. was the most abundant species, with the peak density recorded at 88,520 cells/mL. Seven potential algal metabolites including heptanal, 2,4-heptadienal, 2,4-decadienal, nonanal, 2-octenal, 2,6-nonadienal and hexanal were detected. The principal component analysis result showed that n-hexanal, n-heptanal and 2,4-decadienal, possibly the metabolites of diatoms, and 2,4-heptadienal, possibly the metabolite of Dinobryon sp., might have contributed to the fishy odor episode. This study demonstrated that the fishy odor episode in this reservoir might be caused by the abnormal growth of chrysophytes and diatoms under the ice-cover. PMID:24649665

Zhao, Yunyun; Yu, Jianwei; Su, Ming; An, Wei; Yang, Min

2013-12-01

201

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

PubMed

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

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

2014-04-15

202

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

NASA Astrophysics Data System (ADS)

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

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

2009-03-01

203

Effects of organic solvents on immobilized lipase in pectin microspheres.  

PubMed

Lipase from Brevibacillus agri 52 was found stable up to 90% diethylenglycol (DEG), glycerol (GLY), and 1,2 propanediol (1,2 PRO) at 37 degrees C for 1 h and the stability was reduced only approximately 20% after 12 h incubation, but in 40% dimethylsulfoxide (DMSO), lipase activity was stable only for 1 h. Inhibition of the biocatalysts with dimethylformamide (DMF) was detected at 20% solvent concentration. In water immiscible systems, the stability of lipase in n-hexane, n-tetradecane and n-heptane resembles the water activity, but in the presence of isobutanol, 1-hexanol, and butylbutirate, the stability was significantly reduced. Lipase 52 precipitates in the presence of 50% acetone or ethanol/water mixtures, but enzymatic activity was partially recovered by adding 20% GLY, DEG, 1,2 PRO, or DMSO to the reaction mixture. Furthermore, by increasing DEG in 70% DMF/DEG mixtures, the lipase activity was protected. Encapsulation of lipase in pectin gels cross-linked with calcium ions brings three to four times more enzymatic activity in 70% water miscible organic solvents compared to aqueous systems. PMID:18543116

Costas, L; Bosio, V E; Pandey, A; Castro, G R

2008-12-01

204

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

NASA Astrophysics Data System (ADS)

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

Wakefield, D. L.

1988-05-01

205

Hot Surface Ignition and Flame Propagation of Hydrocarbon Air Mixtures  

NASA Astrophysics Data System (ADS)

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

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

2010-11-01

206

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

207

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

PubMed Central

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

2014-01-01

208

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

SciTech Connect

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 10(-13) cm3/sec is given for the sum penta- and hexa-chlorobiphenyls (PCB). Rate coefficients for the ozone reaction are given for beta-pinene, limonene, delta 3-carene, cineol, vinyl chloride and 1,3-butadiene. In cases where the literature data are available for comparison, the rate coefficients (kappa OH and kappa O3) reported here compare favorably with the best data reported. The direct photochemical reactivity has been shown to be measurable if the chamber is cleaned carefully. Preliminary results on benzophenone are reported. The methods described here, except that of direct photochemical reactivity, are in agreement with those proposed to OECD. Moreover, part of the Draft OECD Test Guideline (Berlin, 1987) on Photochemical-Oxidative Degradation in the Atmosphere is based on work described here and on closely related work in other laboratories.

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

1988-06-01

209

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

210

[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

211

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

PubMed

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

Doma?ska, Urszula; Królikowski, Marek; Ramjugernath, Deresh; Letcher, Trevor M; Tumba, Kaniki

2010-11-25

212

Chloroform degradation by butane-grown cells of Rhodococcus aetherovorans BCP1.  

PubMed

The ability of a Rhodococcus aetherovorans strain, BCP1, to grow on butane and to degrade chloroform in the 0-633 microM range (0-75.5 mg l(-1)) via aerobic cometabolism was investigated by means of resting-cell assays. BCP1 degraded chloroform with a complete mineralization of the organic Cl. The resulting butane and chloroform maximum specific degradation rates were equal to 118 and 22 micromol mg(protein)(-1)day(-1), respectively. Butane inhibition on chloroform degradation was satisfactorily interpreted by means of a model of competitive inhibition, with an inhibition constant equal to 38 % of the estimated butane half-saturation constant, whereas chloroform (at 11 microM) did not inhibit butane utilization. Acetylene (1,720 microM) induced an almost complete inactivation of the degradation of both butane and chloroform, indicating that the studied cometabolic process is mediated by a monooxygenase enzyme. BCP1 proved capable of degrading vinyl chloride and 1,1,2-trichloroethane, but not 1,2-trans-dichloroethylene. BCP1 could grow on the intermediates of the most common butane metabolic pathways and on the aliphatic hydrocarbons from ethane to n-heptane. After growth on n-hexane, it was able to deplete chloroform (13 microM) with a degradation rate higher than that obtained, at the same chloroform concentration, after growth on butane. PMID:17058077

Frascari, Dario; Pinelli, Davide; Nocentini, Massimo; Fedi, Stefano; Pii, Youri; Zannoni, Davide

2006-11-01

213

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

214

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

215

Oil & Chemical Pollution 6 (19'X)} 81-  

E-print Network

by dissolving thesecompounds in n-hexane. Aliquots of thesesolutions were diluted when required with n-hexane were rinsed with n-hexane and allowed to air dry. Used items were soaked in ethanol before washing

Canberra, University of

216

KEY COMPARISON: International Comparison CCQM-K16: Composition of natural gas types IV and V  

NASA Astrophysics Data System (ADS)

Natural gas is an important energy vector. The determination of its composition is often used as the basis for the calculation of the calorific value. The calorific value in turn is one of the two key parameters used in natural gas trade. In the first series of key comparisons (CCQM-K1e-g), natural gas was already included with three different compositions. These mixtures contained carbon dioxide, nitrogen, ethane, propane and n-butane in methane (matrix) and were only to a limited extent representative of real natural gas. In the past years, national metrology institutes have broadened the range of components by including, e.g., i-butane, neo-pentane, n-pentane, i-pentane and n-hexane. Based on this extended components list, two new mixtures have been defined, one characteristic for a low calorific mixture (type IV) and the other for a high calorific mixture (type V). In the low calorific mixture, helium was also present. Due to presence of the butane and pentane isomers, the mixtures of type IV and V are more demanding with respect to the separation technique than the mixtures used in CCQM-K1e-g. The measurements in this key comparison took place in 2001. There were eight participants and two coordinating laboratories. The key comparison reference value (KCRV) was based on the gravimetric preparation for all components. Even for the heavier hydrocarbons (pentanes and n-hexane) the effects of, e.g., adsorption can be controlled to such an extent that this approach is still valid. The uncertainty evaluation of the KCRVs reflected also the extent to which the preparation data could be demonstrated to be valid. The validity of the preparation data was demonstrated by comparing the composition of the mixtures prepared for this comparison with measurement standards maintained by the coordinating laboratories. The key comparisons demonstrated that the results of the laboratories agreed within 1% relative to the reference value for most components. Even better agreement was obtained for nitrogen in the low calorific mixture (0.5%), carbon dioxide (0.5%), ethane (0,5%), propane (0.5%) and methane (0.1%). In some cases, larger differences were observed, which then also exceeded the associated expanded uncertainty 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 Mutual Recognition Arrangement (MRA).

van der Veen, Adriaan M. H.; Heine, Hans-Joachim; Brinkmann, Freek N. C.; Ziel, Paul R.; de Leer, Ed W. B.; Zhen, Wang Lin; Kato, Kenji; Konopelko, Leonid A.; Popova, Tatjana A.; Alexandrov, Yuri I.; Kortchagina, Elena N.; Kustikov, Yuri A.; Musil, Stanislav; Milton, Martin J. T.; Guenther, Franklin; Rhoderick, George

2005-01-01

217

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

NASA Astrophysics Data System (ADS)

C6-C10 n-aldehydes were analyzed in samples of freshly fallen snow collected at the high alpine research station Jungfraujoch, Switzerland, during the Cloud and Aerosol Characterization Experiments (CLACE) 5 in February and March 2006. Sampling was carried out on the Sphinx platform. Headspace - solid phase dynamic extraction (HS-SPDE) combined with gas chromatography/mass spectrometry (GC/MS) was used to quantify n-aldehydes in melted snow samples. n-Hexanal was identified as the most abundant n-aldehyde (median concentration 1.324 µg L-1) followed by n-nonanal, n-decanal, n-octanal and n-heptanal (median concentrations 1.239, 0.863, 0.460 and 0.304 µg L-1, respectively). A wide range of concentrations of n-aldehydes was found in snow samples from Jungfraujoch, even for samples collected at the same time during the same snowfall event. According to their physical and chemical characteristics, n-aldehydes are expected to be primarily linked to aerosol particles in the atmosphere suggesting the uptake of n-aldehydes into snow via the particle phase. Particle scavenging can occur during snow formation in clouds. The high concentration variations of the n-aldehydes among the snow samples can be explained assuming that aerosol particles, which are loaded with n-aldehydes, are heterogeneously distributed throughout the snow samples. Higher median concentrations of all n-aldehydes were observed when air masses reached Jungfraujoch from the north-northwest in comparison to air masses arriving from the southeast-southwest. The sources of atmospheric n-aldehydes present at Jungfraujoch are most likely to be related to direct and indirect biogenic emissions. The presence of n-aldehydes as semivolatile constituents of direct biogenic emissions from vegetation has been reported previously in studies of Ciccioli et al. [1], Yokouchi et al. [2] and Kesselmeier and Staudt [3]. The distribution pattern of the n-aldehydes in emissions from vegetation largely matches with the n-aldehyde pattern found in snow collected at Jungfraujoch. One exception is the significantly higher proportion of n-hexanal in the Jungfraujoch samples compared to vegetation emission. Additionally, indirect biogenic emissions can contribute to the atmospheric concentrations of n-aldehydes through oxidation of precursor compounds of biogenic origin. In this context, Moise and Rudich [4] and Thornberry and Abbatt [5] proposed the preferential formation of n-nonanal and n-hexanal from the cleavage by ozonolysis of double bonds in unsaturated fatty acids (namely oleic acid and linoleic acids). The predominance of n-hexanal and n-nonanal among the C6-C10 n-aldehydes in the snow samples collected at Jungfraujoch during CLACE 5 is therefore an argument for the formation of the aldehydes through oxidation of unsaturated fatty acids in the atmosphere. Anthropogenic emissions of n-aldehydes i.e. from fossil fuel burning are thought to be negligible in the air masses reaching Jungfraujoch. References: [1] P. Ciccioli, E. Brancaleoni, M. Frattoni, A. Cecinato, A. Brachetti, Atmos. Environ., Part A 27 (1993) 1891. [2] Y. Yokouchi, H. Mukai, K. Nakajima, Y. Ambe, Atmos. Environ., Part A 24 (1990) 439. [3] J. Kesselmeier, M. Staudt, J. Atmos. Chem. 33 (1999) 23. [4] T. Moise, Y. Rudich, J. Phys. Chem. 106 (2002) 6469. [5] T. Thornberry, J.P.D. Abbatt, Phys. Chem. Chem. Phys. 6 (2004) 84.

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

2009-04-01

218

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

219

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

220

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

221

METHYL KETONE METABOLISM IN HYDROCARBON-UTILIZING MYCOBACTERIA.  

PubMed

Lukins, H. B. (University of Texas, Austin) and J. W. Foster. Methyl ketone metabolism in hydrocarbon-utilizing mycobacteria. J. Bacteriol. 85: 1074-1087. 1963.-Species of Mycobacterium especially M. smegmatis 422, produced the homologous methyl ketones during the oxidation of propane, n-butane, n-pentane, or n-hexane. A carrier-trapping experiment demonstrated the formation of 2-undecanone, as well as 1,11-undecanedioic acid, during the oxidation of undecane-1-C(14). Aliphatic alkane-utilizing mycobacteria were able to grow at the expense of several aliphatic methyl ketones as sole sources of carbon. Other ketones which did not support growth were oxidized by resting bacterial suspensions. M. smegmatis 422 cells grown on propane or acetone were simultaneously adapted to oxidize both substrates, as well as n-propanol. n-Propanol cells were unadapted to propane or acetone. Acetone produced from propane in a medium enriched in D(2)O contained a negligible quantity of D, presumably eliminating propylene as an intermediate in the oxidation. Cells grown at the expense of alkanes or methyl ketones in the presence of O(2) (18) had a higher content of O(18) than did cells grown on terminally oxidized compounds, e.g., primary alcohols or fatty acids. An oxygenase reaction is postulated for the attack on methyl ketones. Acetol was isolated and characterized as an oxidation product of acetone by M. smegmatis 422. Acetol-grown cells had a higher O(18) content than did n-propanol cells, and its utilization appears to involve at least one oxygenase reaction. Acetol produced from acetone in the presence of O(2) (18) was not enriched in the isotope, indicating the occurrence of exchange reactions or of oxygenation reactions at a later stage in the assimilation of acetone and acetol. PMID:14043998

LUKINS, H B; FOSTER, J W

1963-05-01

222

Phase equilibria study of the binary systems (1-butyl-3-methylimidazolium thiocyanate ionic liquid + organic solvent or water).  

PubMed

(Solid + liquid) phase equilibria (SLE) for the binary systems, ionic liquid (IL) 1-butyl-3-methylimidazolium thiocyanate [BMIM][SCN] with an alcohol (1-octanol, 1-nonanol, 1-decanol, 1-undecanol, or 1-dodecanol) or water, and (liquid + liquid) phase equilibria (LLE) for the binary systems of [BMIM][SCN] with an alkane (n-hexane, n-heptane, n-octane, n-nonane, or n-decane), benzene, an alkylbenzenes (toluene or ethylbenzene), tetrahydrofuran (THF), cycloalkanes (cyclohexane or cycloheptane), or ethers (di-n-propyl ether, di-n-butyl ether, di-n-pentyl ether, n-butylmethyl ether, tert-butylmethyl ether (MTBE), or tert-butylethyl ether (ETBE)) have been determined at ambient pressure. A dynamic method was used over a broad range of mole fractions and temperatures from 250 to 430 K. In the case of systems IL + alkane, cycloalkane, or ether, the mutual immiscibility with an upper critical solution temperature (UCST) was detected, and in the systems of IL + benzene, alkylbenzene, or THF, the mutual immiscibility with a lower critical solution temperature (LCST) was observed. UV-vis spectroscopy was used to determine the very small compositions of the IL in the n-hexane (about 2 x 10(-5) IL mole fraction), benzene (about 2 x 10(-3) IL mole fraction), cyclohexane (about 2 x 10(-5) IL mole fraction), and THF (about 1.2 x 10(-2) IL mole fraction). For the binary systems containing alcohol, it was noticed that with increasing chain length of an alcohol, the solubility decreases. The basic thermal properties of the pure IL, that is, the glass-transition temperature as well as the heat capacity at the glass-transition temperature, have been measured using a differential scanning microcalorimetry technique (DSC). Decomposition of the IL was detected by the simultaneous TG/DTA experiments. Well-known UNIQUAC, Wilson, and NRTL equations have been used to correlate the experimental SLE data sets for alcohols and water. For the systems containing immiscibility gaps {IL + alkane, benzene, alkylbenzene, cycloalkane, tetrahydrofuran, or ether}, the parameters of the LLE correlation have been derived using the NRTL equation. PMID:19402727

Doma?ska, Urszula; Laskowska, M; Pobudkowska, Aneta

2009-05-01

223

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

PubMed

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

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

2012-04-12

224

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

225

Application of high-performance liquid chromatography with ultraviolet diode array detection and refractive index detection to the determination of class composition and to the analysis of gasoline.  

PubMed

A method of effective application of normal-phase high-performance liquid chromatography (NP-HPLC) with ultraviolet diode array detection (DAD) and refractive index detection (RID) for the determination of class composition of gasoline and its components, i.e. for the determination of content of alkenes, aromatic and saturated hydrocarbons in gasoline meeting modern quality standards, has been developed. An aminopropyl-bonded silica stationary phase was used along with n-hexane or n-heptane as the mobile phase. A DAD signal integrated over the 207-240 nm range was used to determine alkenes. This eliminates the necessity of separating alkenes from saturates, because the latter do not absorb UV radiation above 200 nm. The content of aromatic hydrocarbons is determined by means of a refractive index detector. Calibration was based on hydrocarbon type composition determined by the fluorescent indicator adsorption method, ASTM D1319. The results obtained by the developed method were found to be consistent with those obtained by fluorescent indicator adsorption or by a multidimensional GC method (PIONA) (ASTM D5443). The method can be applied to gasoline meeting recent quality standards, irrespective of refining technology used in the production of gasoline components, including gasoline with various contents of oxygenates. The developed method cannot be used to determine the hydrocarbon type composition of gasoline that contains as a component the so-called pyrocondensate, i.e. the fraction with a boiling point up to 220 degrees C, obtained through thermal pyrolysis of distillation residues of crude oil or coal and, consequently, does not meet the quality standards. The paper includes the procedure for identification of this type of gasoline. PMID:15032352

Kami?ski, Marian; Kartanowicz, Rafa?; Przyjazny, Andrzej

2004-03-12

226

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

PubMed

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

Gillet, Jean-Numa

2015-04-01

227

[Comparative thin-layer chromatographic studies for determining phorate and fenthion].  

PubMed

Experiments were carried out to use thin-layer chromatography to determine pure substances of the organic phosphorous insecticides forat and phenothion. Three sorbents were employed to establish the most appropriate conditions for the application of a fast, readily applicably and highly sensitive method--silica gel G, DG and Kiselgur "Merk", as well as 14 mobile phases--monocompound (n-hexane, n-heptane, acetone benzol and toluol), double combinations (hexane-acetone 4:1, hexane-acetone 9:1, hexane-benzol 1:1, hexane-benzol 4:1, heptane-acetone 7:1, benzol-hexane 4:1, benzol-acetone 9:1, and petrolium ether-tetrachlormethane) and triple combinations (acetone-toluol-hexane 1:15 and 5 developers (a diazosalt, bromine vapours + diazosalt, palladium bichloride, bromphenol blue, and silver nitrate, sodium hydroxide, ammonia gas). Established was the fact that the best results are obtained with the use of silica gel G, the mobile phase heptan-acetone 7:1, and the developer of 0.2% solution of palladium bichloride in 0.5 per cent solution of hydrochloric acid. In chromatogrammes the forat compound appears as a tile red portion with a darker peripheral part and Rf = 0.61, and phenothion--in yellow, with a brownish halo and Rf = 0.41. The method is highly sensitive--for forat 0.5 microgram, and for phenothion 0.5 microgram. In determining these insecticides it is possible to use as a sorbent silica gel "Merk" 1:1 with the same degree of sensitivity, but with higher Rf values. PMID:906307

Ignatov, M

1977-01-01

228

Dielectric relaxation phenomena of rigid polar liquid molecules under giga hertz electric field  

NASA Astrophysics Data System (ADS)

The dielectric relaxation phenomena of rigid polar liquid molecules chloral and ethyltrichloroacetate (j) in benzene, n-hexane and n-heptane (i) under 4.2, 9.8 and 24.6 GHz electric fields at 30oC are studied to show the possible existence of double relaxation times t2 and t1 for rotations of the whole and the flexible parts of molecules. The probability of showing double relaxation is more in aliphatic solvents indicating their nonrigidity. The symmetric and asymmetric distribution parameters g and d are obtained from c 'ij /c 0ij and c''ij/c0ij at wj --> 0 where c'ij and c'ij are real and imaginary parts of the complex orientational susceptibility c*ij and c0ij is the low frequency susceptibility which is real. cij's are involved with the measured dielectric relative permittivities e'ij, e''ij, e 0ij and eij of solutions. The theoretical weighted contributions c1 and c2 towards dielectric dispersions by Fröhlich's method are compared with the experimental ones obtained from the graphical variation of c'ij /c0ij and c''ij/c0ij with weight fractions wj's at wj --> 0. The measured dipole moments m2 and m 1 of the whole and the flexible part of a polar molecule in terms of the linear coefficients b's of c'ij's with wj's and the estimated t2 and t1 reveal their associations with aliphatic solvents. The theoretical dipole moments mtheo's from the available bond angles and bond moments of the substituent polar groups of the molecules with the estimated m's suggest the mesomeric, inductive and electromeric effects in them under GHz electric field.

Dutta, K.; Sit, S. K.; Acharyya, S.

2001-10-01

229

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

230

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

6upsaaussu3 Ieapeaqg:ioaLqnS so(eg s86T &aqea&aQ 3DN3IDS d0 33ZSVH go aazsaQ aqS soy sSuaurazsnbae aqq Zo OuamI[IIInd Ie~lzed us Aisssansun H g V sexaZ Zo aiaIIog a1enpe~0 aqq oi pai&qeqnS NOIHdd00 3NV'l KVHV'I sssayg v FHdVEOOZ'A1CKH'J SVO... NOI ~ VEEQZH3 d GNISA 0o58 ZV 33/lZXIH 3N3'IFdOHdAQOd-DIZDVZV / 'IONVdOHd-OSI IHVNIB 3HZ GNV OoOS. QNV OoSOY ZV 33flZXIH 3NVZd3H-N / 3N3'IkdOHdk'IOd-DIZDVZV / 'IONVdOHd-OSI IEVNHHZ 3HZ Nod HQIHHIaIn03 QIQGIa ZodVn do NOIZVNIH33XHQ ( Iaqrrra...

Joffrion, Lamar Lane

1984-01-01

231

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

NASA Astrophysics Data System (ADS)

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

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

1998-09-01

232

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

233

J. Chem. Sci. Vol. 124, No. 2, March 2012, pp. 355373. c Indian Academy of Sciences. Excited state intramolecular charge transfer reaction  

E-print Network

-(1-morpholenyl) benzonitrile (M6C) in AOT/n-heptane/acetonitrile and AOT/n-heptane/methanol reverse micelles methanol and acetonitrile show a decrease from the respective bulk values by a factor of 3 micelles in presence of a nonpolar solvent (usually isooctane or heptane). The polar solvents trapped

Biswas, Ranjit

234

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

SciTech Connect

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

Subramaniam, B.

1993-10-01

235

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

236

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

237

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

238

Pollutant Emissions from Gasoline Combustion. 1. Dependence on Fuel  

E-print Network

-paraffins number: n for paraffins. A number of studies have been published concerning the combustion chemistry of paraffinic gasoline mechanism based on the chemistry of n-heptane and isooctanesthe two indicator fuels for octane

Utah, University of

239

AIAA JOURNAL Vol. 40, No. 11, November 2002  

E-print Network

characterize the n-heptane/air chemistry in these two reaction zones. The fuel is completely consumed, the combustion processin both the spark-ignition6 and diesel7 enginesis dominated by partially premixed or two

Aggarwal, Suresh K.

240

Experimental Investigation of the Effects of Turbulence and Mixing on Autoignition Chemistry  

Microsoft Academic Search

The autoignition of acetylene, released from a finite-sized circular nozzle into a turbulent coflow of hot air confined in\\u000a a pipe, has been the subject of a recent experimental study to supplement previous work for hydrogen and n-heptane. As with hydrogen and n-heptane, autoignition appears in the form of well-defined localized spots. Quantitative information is presented concerning\\u000a the effects of

Christos N. Markides; Epaminondas Mastorakos

2011-01-01

241

Diffusion Combustion of Liquid Heptane in a Small Tube with and Without Heat Recirculating  

Microsoft Academic Search

To understand diffusion flame characteristics in a small tube, combustion of liquid n-heptane and air was experimentally and numerically studied. A tube of ID 4 mm and OD 6 mm made of quartz was used as the burner. Liquid n-heptane was delivered into a capillary from a syringe pump. Stable flames were established inside the burner with and without heat recirculating. Additionally,

Li Junwei; Huang Jinghuai; Zhao Dan; Zhao Junying; Yan Mi; Wang Ningfei

2012-01-01

242

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

NASA Astrophysics Data System (ADS)

Because of the importance of information on the concentration and speciation of Volatile Organic Compounds (VOC) in the atmosphere for the development of regulatory programs or emission control, is necessary to determine the type and the concentrations of reactive and toxic VOC in atmospheric air. The aim of this study is to determine the speciation and quantification of VOC in the atmospheric air of the Mexico City Metropolitan Area (MCMA), from samples obtained in November-December 2011 (cold-dry) and March-April (warm-dry). This study presents the results of characterization of VOC in ambient air in the MCMA conducted during 2011-2012. Sampling of VOC was done in two sampling campaigns: from November 17th to December 11th, 2011, and March 1st to April 6th, 2012 through collection of ambient air each six days in six liters stainless steel SUMMA canisters of 24 hours integrated samples, in three sites (Merced: commercial area with vehicular sources, Pedregal: residential area with vehicular sources and San Agustin: industrial sources with heavy traffic), in the MCMA. The analysis of samples was carried out with two chromatographic systems: 1) method equivalent to the EPA's Method TO-14, and 2) GC/MSD coupled to a preconcentrator ENTECH, for the analysis of the compounds listed in EPA method TO15. It was investigated the concentration of 111 volatile organic compounds, (ozone precursors and toxic compounds). It was found that concentrations of 23 species, constitute 80% of the total VOC concentration tested: ethane, propane, isobutane, n-butane, n-pentane, n-hexane, isopentane, methylcyclopentane, ethylene, propylene, acetylene, benzene, toluene, ethylbenzene, m/p-xylene, o-xylene, 1,2,4-trimethylbenzene, ethyl and isopropyl alcohols, acetone, 2-butanone, MTBE and ethyl acetate. Both in 2011 and 2012, the highest concentrations measured in the three sites were for compounds associated with the combustion of LPG gas: propane, n-butane. The highest concentrations of 25.2±14.5 ppbV and 16.6±9 ppbV for butane and propane respectively, was achieved in Merced in 2011 and 14.7±3.5 ppbV and 28.4±6.7 ppbV for the same compounds, in San Agustin in 2012). In the case of vehicular emissions, in both campaigns, 2011 and 2012, Merced showed the highest levels: 12.3±4.8 ppbV, 2.7±1.1 ppbV and 4.3±3.3 ppbV for toluene, benzene and MTBE respectively in 2011 and 9.48±6.5 ppbV, 1.5±0.9 ppbV and 2.4±1.0 ppbV for the same compounds in 2012. The compounds which comes from industrial emissions, have the lowest average concentrations in all stations. The VOCs measurement in atmospheric air, allowed determinate that the main source of VOC in the three studied sites of the MCMA are emissions of LPG gas and vehicular emissions. The highest concentrations were found during the cold-dry period in 2011. These data are consistent with continuous measurements determined in the southeastern MCMA during 2000-2007.

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

2013-05-01

243

Experimental Investigation of the Low Temperature Oxidation of the Five Isomers of Hexane  

E-print Network

1 Experimental Investigation of the Low Temperature Oxidation of the Five Isomers of Hexane of the five hexane isomers (n-hexane, 2-methyl-pentane, 3-methyl-pentane, 2,2-dimethyl-butane, and 2 of the reaction products and their distribution. At low temperature (below 800 K), n-hexane was the most reactive

Boyer, Edmond

244

Journal of Catalysis 245 (2007) 316325 www.elsevier.com/locate/jcat  

E-print Network

Journal of Catalysis 245 (2007) 316­325 www.elsevier.com/locate/jcat Catalytic oxidation of n-hexane Abstract The effects of channel structure and spatial constraints on n-hexane oxidation rates (MOR) channels by sublimation of MnI2. Synthesis rates for hexanols (ROH), hexanal/hexanones (R

Iglesia, Enrique

245

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

246

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

PubMed

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

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

2013-03-01

247

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

248

Understanding nanofluid stability through molecular simulation  

SciTech Connect

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

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

2012-11-01

249

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

250

UNIVERSITE DE BOURGOGNE Equipe EMMA EA 581-IUVV Institut Jules Guyot  

E-print Network

thermiques et mécaniques des films ont été étudiées en présence ou non de n-hexanal. Les propriétés de'eau et à l'eau liquide, au n-hexanal et au D limonène à l'état vapeur et liquide et à 6 autres composés d'aromes (esters d'éthyle, cétone et alcools). L'ajout de n-hexanal dans la matrice d'iota-carraghènane modifie le

Paris-Sud XI, Université de

251

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

252

Stat 511 Exam 2 April 7, 2009  

E-print Network

vapor pressure of the sample 10 ASTM 10% point volatility of the crude oil sample end point volatility-pentane to iso-pentane upon some partial pressures. For 1 2 3 gm of iso-pentance produced per hour per gm of catalyst hydrogen partial pressure n-pentane partial pressure iso-pentane partial pressure y rate x H x n

Vardeman, Stephen B.

253

Multiphoton ionization and excitation spectroscopy of molecules in liquids. [Fluoranthene  

SciTech Connect

The two-photon ionization and excitation spectra of fluoranthene in liquid n-pentane have been measured and together with laser power versus signal intensity measurements have been utilized to elucidate the multiphoton ionization mechanism for this and other molecules in liquids.

Siomos, K.; Faidas, H.; Christophorou, L.G.

1984-01-01

254

Mineralization of methyl tert-butyl ether and other gasoline oxygenates by Pseudomonads using short n-alkanes as growth source.  

PubMed

Biodegradation of methyl tert-butyl ether (MTBE) by cometabolism has shown to produce recalcitrant metabolic intermediates that often accumulate. In this work, a consortium containing Pseudomonads was studied for its ability to fully degrade oxygenates by cometabolism. This consortium mineralized MTBE and TBA with C3-C7 n-alkanes. The highest degradation rates for MTBE (75 +/- 5 mg g(protein) (-1) h(-1)) and TBA (86.9 +/- 7.3 mg g(protein) (-1) h(-1)) were obtained with n-pentane and n-propane, respectively. When incubated with radiolabeled MTBE and n-pentane, it converted more than 96% of the added MTBE to (14)C-CO(2). Furthermore, the consortium degraded tert-amyl methyl ether, tert-butyl alcohol (TBA), tert-amyl alcohol, ethyl tert-butyl ether (ETBE) when n-pentane was used as growth source. Three Pseudomonads were isolated but only two showed independent MTBE degradation activity. The maximum degradation rates were 101 and 182 mg g(protein) (-1) h(-1) for Pseudomonas aeruginosa and Pseudomonas citronellolis, respectively. The highest specific affinity (a degrees (MTBE)) value of 4.39 l g(protein) (-1) h(-1) was obtained for Pseudomonas aeruginosa and complete mineralization was attained with a MTBE: n-pentane ratio (w/w) of 0.7. This is the first time that Pseudomonads have been reported to fully mineralize MTBE by cometabolic degradation. PMID:18814038

Morales, Marcia; Nava, Verónica; Velásquez, Elia; Razo-Flores, Elías; Revah, Sergio

2009-04-01

255

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

256

F-g#a (50% ; ; #$$$hCA$$$++$& ; g!&&t~@) 1. The structural formulas indicate that one should predict that which of the  

E-print Network

;15. Consider the compounds: butanone, pentanoic acid, hexanal, n-hexane, and n-heptanol. The boiling points is the correct sequence of the boiling points fiom low to high? . I 1 (A) butanone hexanal hexane hexane hexanal hexane

Huang, Haimei

257

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

SciTech Connect

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

Keyworth, D.A.

1989-03-28

258

40 CFR 795.232 - Inhalation and dermal pharmacokinetics of commercial hexane.  

Code of Federal Regulations, 2010 CFR

...the unlabeled test substance, information on lot number and the percentage of MCP and n -hexane. (C) Results of chromatography. (iii) A full description of the sensitivity, precision, and accuracy of all procedures used to obtain the...

2010-07-01

259

Spectroscopic studies on the formation of coke on individual Fluid Catalytic Cracking particles: the effect of poisoning metal compounds.  

E-print Network

??The formation of coke on individual Fluid Catalytic Cracking (FCC) catalyst particles was studied using UV/Vis microspectroscopy and confocal fluorescence microscopy, with n-hexane cracking as… (more)

Goetze, J.G.

2013-01-01

260

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

261

Temperature effects in positronium formation and lifetime in solutions of nonpolar organic solvents  

NASA Astrophysics Data System (ADS)

The temperature dependence of the positron annihilation lifetime (PAL) spectra of several solutions are examined. Four solvents are investigated: n-hexane, cyclohexane, squalane, and an equivolume mixture of n-hexane and squalane. Solutes in the study are nitrobenzene, nitrocyclohexane, and hexafluorobenzene. Arrhenius plots of lifetimes are made from 10 °C to 50 °C. The temperature dependence of the PAL spectra of nitrobenzene solutions in a magnetic field varying up to 15 kG are also presented. Anomalous behavior is observed for the solvents n-hexane and squalane, both neat and with nitrobenzene as a solute. In addition, it is found that the behavior of neat and nitrobenzene solutions of the n-hexane-squalane mixture is not intermediate between those involving n-hexane and squalane separately. We conclude that there is a change in the mechanism for positronium formation from n-hexane to squalane which is not accounted for by changes in free volume. Nitrocyclohexane is found to enhance positronium formation in squalane. This is the first example of antiinhibition by an aliphatic solute known to the authors.

Diehl, D. A.; Schrader, D. M.

1991-06-01

262

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

263

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

264

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

265

Data reconciliation and optimal operation of a catalytic naphtha reformer  

E-print Network

Data reconciliation and optimal operation of a catalytic naphtha reformer Tore Lid Statoil Mongstad in an engine when the fuel self detonates due to high pressure and temperature before it is ignited to a mixture of 95% of iso-octane and 5% n-heptane. A simplified process model of a semiregenerative catalytic

Skogestad, Sigurd

266

LOW OZONE-DEPLETING HALOCARBONS AS TOTAL-FLOOD AGENTS: VOLUME 2. LABORATORY-SCALE FIRE SUPPRESSION AND EXPLOSION PREVENTION TESTING  

EPA Science Inventory

The report gives results from (1) flame suppression testing of potential Halon-1301 (CF3Br) replacement chemicals in a laboratory cup burner using n-heptane fuel and (2) explosion prevention (inertion) testing in a small-scale explosion sphere using propane and methane as fuels. ...

267

The Effects of Fuel Composition and Compression Ratio on Thermal Efficiency in an HCCI Engine  

Microsoft Academic Search

The effects of variable compression ratio (CR) and fuel composition on thermal efficiency were investigated in a homogeneous charge compression ignition (HCCI) engine using blends of n-heptane and toluene with research octane numbers (RON) of 0 to 88. Experiments were conducted by performing CR sweeps at multiple intake temperatures using both unthrottled operation, and constant equivalence ratio conditions by throttling

James P Szybist; Bruce G Bunting

2007-01-01

268

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

269

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

270

Nanoparticles in Flow Assurance in Hydrocarbon Energy Production Abbas Firoozabadi  

E-print Network

and Firoozabadi, AIChE Journal, 2000. Crude oils are made of many components, the heaviest being asphaltenes, defined as the crude fraction insoluble in n-heptane, and soluble in toluene. Asphaltenes in crude oil of crude oil include resins and waxes, which complex with asphaltene molecules in solution producing

Firoozabadi, Abbas

271

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

272

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

273

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

274

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

275

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

276

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

277

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

278

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

279

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

PubMed

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

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

2011-04-01

280

Use of sequential ASE extraction to evaluate the bioavailability of DDT and its metabolites to wheat roots in soils with various organic carbon contents.  

PubMed

An accelerated solvent extraction (ASE) procedure using water, n-hexane and a mixture of n-hexane and acetone as solvents in sequence was developed and tested to evaluate the bioavailability of DDT and its metabolites including p,p'-DDT, o,p'-DDT, p,p'-DDE, and p,p'-DDD (SigmaDDTs) to wheat uptake from soils characterized by varied organic carbon contents. Results indicated that the extractability of SigmaDDTs with water was enhanced considerably in the presence of water soluble organic carbon (WSOC), while the amount of SigmaDDTs extracted with n-hexane was negatively correlated to the content of water insoluble organic carbon (WIOC). The interaction between SigmaDDTs and WIOC also reduced the bioavailability of the pesticides to wheat roots during uptake. There was a good positive correlation between the amount of SigmaDDTs extracted by n-hexane and the amount of SigmaDDTs accumulated in wheat roots, suggesting some potential for the use of the n-hexane ASE-extracted fraction as an indicator of SigmaDDTs' bioavailability to plant uptake. As such, the three sequentially extracted fractions may be viewed as representing the mobile, bioavailable, and fixed pools of SigmaDDTs in the soil. PMID:14987922

Tao, S; Guo, L Q; Wang, X J; Liu, W X; Ju, T Z; Dawson, R; Cao, J; Xu, F L; Li, B G

2004-03-01

281

Thermo-economic optimization of waste heat recovery Organic Rankine Cycles  

Microsoft Academic Search

The present paper focuses both on the thermodynamic and on the economic optimization of a small scale ORC in waste heat recovery application. A sizing model of the ORC is proposed, capable of predicting the cycle performance with different working fluids and different components sizes. The working fluids considered are R245fa, R123, n-butane, n-pentane and R1234yf and Solkatherm. Results indicate

Sylvain Quoilin; Sébastien Declaye; Bertrand F. Tchanche; Vincent Lemort

2011-01-01

282

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

PubMed Central

Pseudomonas mendocina KR-1 grew well on toluene, n-alkanes (C5 to C8), and 1° alcohols (C2 to C8) but not on other aromatics, gaseous n-alkanes (C1 to C4), isoalkanes (C4 to C6), 2° alcohols (C3 to C8), methyl tertiary butyl ether (MTBE), or tertiary butyl alcohol (TBA). Cells grown under carbon-limited conditions on n-alkanes in the presence of MTBE (42 ?mol) oxidized up to 94% of the added MTBE to TBA. Less than 3% of the added MTBE was oxidized to TBA when cells were grown on either 1° alcohols, toluene, or dextrose in the presence of MTBE. Concentrated n-pentane-grown cells oxidized MTBE to TBA without a lag phase and without generating tertiary butyl formate (TBF) as an intermediate. Neither TBF nor TBA was consumed by n-pentane-grown cells, while formaldehyde, the expected C1 product of MTBE dealkylation, was rapidly consumed. Similar Ks values for MTBE were observed for cells grown on C5 to C8 n-alkanes (12.95 ± 2.04 mM), suggesting that the same enzyme oxidizes MTBE in cells grown on each n-alkane. All growth-supporting n-alkanes (C5 to C8) inhibited MTBE oxidation by resting n-pentane-grown cells. Propane (Ki = 53 ?M) and n-butane (Ki = 16 ?M) also inhibited MTBE oxidation, and both gases were also consumed by cells during growth on n-pentane. Cultures grown on C5 to C8 n-alkanes also exhibited up to twofold-higher levels of growth in the presence of propane or n-butane, whereas no growth stimulation was observed with methane, ethane, MTBE, TBA, or formaldehyde. The results are discussed in terms of their impacts on our understanding of MTBE biodegradation and cometabolism. PMID:14660389

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

2003-01-01

283

Cometabolism of methyl tertiary butyl ether and gaseous n-alkanes by Pseudomonas mendocina KR-1 grown on C5 to C8 n-alkanes.  

PubMed

Pseudomonas mendocina KR-1 grew well on toluene, n-alkanes (C5 to C8), and 1 degrees alcohols (C2 to C8) but not on other aromatics, gaseous n-alkanes (C1 to C4), isoalkanes (C4 to C6), 2 degrees alcohols (C3 to C8), methyl tertiary butyl ether (MTBE), or tertiary butyl alcohol (TBA). Cells grown under carbon-limited conditions on n-alkanes in the presence of MTBE (42 micromoles) oxidized up to 94% of the added MTBE to TBA. Less than 3% of the added MTBE was oxidized to TBA when cells were grown on either 1 degrees alcohols, toluene, or dextrose in the presence of MTBE. Concentrated n-pentane-grown cells oxidized MTBE to TBA without a lag phase and without generating tertiary butyl formate (TBF) as an intermediate. Neither TBF nor TBA was consumed by n-pentane-grown cells, while formaldehyde, the expected C1 product of MTBE dealkylation, was rapidly consumed. Similar Ks values for MTBE were observed for cells grown on C5 to C8 n-alkanes (12.95 +/- 2.04 mM), suggesting that the same enzyme oxidizes MTBE in cells grown on each n-alkane. All growth-supporting n-alkanes (C5 to C8) inhibited MTBE oxidation by resting n-pentane-grown cells. Propane (Ki = 53 micromoles) and n-butane (Ki = 16 micromoles) also inhibited MTBE oxidation, and both gases were also consumed by cells during growth on n-pentane. Cultures grown on C5 to C8 n-alkanes also exhibited up to twofold-higher levels of growth in the presence of propane or n-butane, whereas no growth stimulation was observed with methane, ethane, MTBE, TBA, or formaldehyde. The results are discussed in terms of their impacts on our understanding of MTBE biodegradation and cometabolism. PMID:14660389

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

2003-12-01

284

COI Name COI Synonym CAS 1-Pentene 109-67-1  

E-print Network

,4-Bis(2-chloroethylthio)-n-butane 142868-93-7 1,5-Bis(2-chloroethylthio)-n-pentane 142868-94-8 1-Butene [Propane, 2,2-dimethyl-] 463-82-1 2-Butene 107-01-7 2-Butene-cis 590-18-1 2-Butene-trans [2-Butene, (E-98-2 2-Methyl-1-butene 563-46-2 2-Methylpropene [1-Propene, 2-methyl-] 115-11-7 2-Pentene, (E)- 646

Movileanu, Liviu

285

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

286

Effects of pressure, temperature, adsorbent surface, and mobile phase composition on the supercritical fluid chromatographic fractionation of monodisperse polystyrenes  

Microsoft Academic Search

No significant differences have been found in the separation behavior of oligomers of monodisperse polystyrene samples when using n-pentane as the mobile phase and a phenyl or an n-octadecyl bonded stationary phase. For low-molecular weight polystyrenes used in this study, there was no evidence of steric exclusion effects when using non-derivatized silica. In all cases, the addition of either isopropanol

J. E. Conaway; J. A. Graham; L. B. Rogers

1978-01-01

287

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

Microsoft Academic Search

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

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

1998-01-01

288

Aircraft experiments of microgravity pool boiling - Evaluation of the effects of residual acceleration  

Microsoft Academic Search

The paper describes analyses of the data obtained in our aircraft pool-boiling experiments performed at Bretigny, France, in December 1989, placing the focus on possible effects of residual acceleration on the vapor-bubble behavior as well as the heat transfer characteristics. In the experiments, the apparatus including a boiling cell filled with subcooled n-pentane was fixed onto the cabin floor of

Toshiharu Oka; Yoshiyuki Abe; Kotaro Tanaka; Yasuhiko H. Mori; Akira Nagashima

1991-01-01

289

Observational study of pool boiling under microgravity  

Microsoft Academic Search

Pool boiling experiments under microgravity were conducted, utilizing parabolic flight maneuvers with a CNES Caravelle 6R aircraft. The experimental apparatus taken aboard the aircraft was constructed to enable simultaneous recording, by a video camera, of the side view of vapor bubbles generated on Joule-heated titanium foil immersed in a pool of n-pentane liquid, and the color pattern exhibited by a

Toshiharu Oka; Yoshiyuki Abe; Kotaro Tanaka; Yasuhiko H. Mori; Akira Nagashima

1992-01-01

290

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

291

Isolation of aurantiamides from gomphrena celosioides C. Mart.  

PubMed

In West Africa and Nigeria in particular, many virgin plants are still waiting to be evaluated for their medicinal importance. Claims of plants with folk medicinal applications need to be evaluated and verified. Gomphrena celosioides (family - Amaranthaceae) is a weed grown in lawns and the biological activity of the extract had earlier been established. In the present study, the plant was collected, air dried, ground and soxhlet extracted with n-hexane and two compounds were isolated from the flakes that were recovered from the n-hexane extract on cooling. Column chromatography using 5% chloroform in n-hexane effected the separation. The structures of the isolated compounds were elucidated by spectroscopic analysis using IR, NMR ((1)H and (13)C) and EI-MS. The compounds were found to be aurantiamide and aurantiamide acetate. This is the first report of isolation of these compounds in Gomphrena celosioides. PMID:24734065

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

2014-01-01

292

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

PubMed

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

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

2013-01-01

293

Separation of neutral lipids by high-performance liquid chromatography: quantification by ultraviolet, light scattering and fluorescence detection.  

PubMed

The recent increased use of cell cultures to model physiological events, in particular signal transduction and traumatic injury, has produced a need for a quantitative, high-performance liquid chromatographic separation of neutral lipid classes with a high degree of resolution and reproducibility. We report an isocratic separation using a Phenomenex Selectosil silica column (5 microns). Two solvents were used, 1.2% 2-propanol in n-hexane containing 0.1% acetic acid (90%) and n-hexane (10%) at a flow-rate of 0.6 ml/min. Column temperature was maintained at 55 degrees C and this temperature was critical for baseline resolution of 1,3-diacylglycerol and cholesterol. The use of 10% n-hexane permitted the resolution of low polarity compounds such as butylated hydroxytoluene, triacylglycerols and cholesteryl esters. All of the detectors used produced standard curves with linearity over a wide concentration range. PMID:8930747

Murphy, E J; Rosenberger, T A; Horrocks, L A

1996-10-11

294

Astrocytic regulatory functions: A possible target for CNS effects of organic solvents.  

PubMed

Primary astrocyte cultures from newborn rats were exposed to two model solvents, one chlorinated hydrocarbon (carbon tetrachloride) and one aliphatic hydrocarbon (n-hexane), for 1 hr in a closed chamber system. Both solvents caused a reduction in basal oxygen consumption by approximately 40%. Glutamate-stimulated respiration was reduced to a similar extent. Carbon tetrachloride caused a 100% increase and a 50% decrease, respectively, in the potassium- and A2 receptor-mediated elevation in cAMP levels. On the other hand, n-hexane affected only the basal level of cAMP, causing an eight-fold increase. These results indicate that carbon tetrachloride and n-hexane may interfere with essential astrocyte functions. PMID:20732065

Ekblad-Sekund, G; Walum, E

1991-01-01

295

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

296

Upgrading light hydrocarbons via tandem catalysis: a dual homogeneous Ta/Ir system for alkane/alkene coupling.  

PubMed

Light alkanes and alkenes are abundant but are underutilized as energy carriers because of their high volatility and low energy density. A tandem catalytic approach for the coupling of alkanes and alkenes has been developed in order to upgrade these light hydrocarbons into heavier fuel molecules. This process involves alkane dehydrogenation by a pincer-ligated iridium complex and alkene dimerization by a Cp*TaCl2(alkene) catalyst. These two homogeneous catalysts operate with up to 60/30 cooperative turnovers (Ir/Ta) in the dimerization of 1-hexene/n-heptane, giving C13/C14 products in 40% yield. This dual system can also effect the catalytic dimerization of n-heptane (neohexene as the H2 acceptor) with cooperative turnover numbers of 22/3 (Ir/Ta). PMID:23799786

Leitch, David C; Lam, Yan Choi; Labinger, Jay A; Bercaw, John E

2013-07-17

297

Removal of petroleum hydrocarbons from aqueous solution using sugarcane bagasse as adsorbent.  

PubMed

In the present work, the adsorption ability of sugarcane bagasse to remove oil by-products from aqueous solution was evaluated. The objective was treating the contaminated wastewater while enriching the bagasse for its later use as fuel in boilers. Adsorption experiments were carried out in an agitated reactor at room temperature to obtain kinetic curves and adsorption isotherms of gasoline and n-heptane on sugarcane bagasse. The results showed the great potential of bagasse as an adsorbent, since it was able to adsorb up to 99% of gasoline and 90% of n-heptane in solutions containing about 5% of these contaminants. In the adsorption kinetics of gasoline, the equilibrium was reached after just 5 min. This result shows that the adsorption is very favorable. Langmuir, Freundlich, Temkin and D-R models did not describe well the adsorption behavior obtained for these systems. PMID:19932555

Brandão, Poliana C; Souza, Túlio C; Ferreira, Cíntia A; Hori, Carla E; Romanielo, Lucienne L

2010-03-15

298

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

299

Gas chromatographic method using photoionization detection for the determination of breath pentane.  

PubMed

Lipid peroxidation is thought to be an important event in the pathogenesis of atherosclerosis. It has been suggested that pentane, which can be formed during the oxidation of omega-6 fatty acids, is a marker of lipid peroxidation. Previous studies have reported elevated breath pentane and serum markers of lipid peroxidation in smokers. However, chromatographic separation of pentane from isoprene in virtually all of these studies was incomplete and the methods used did not resolve pentane into its isomers, n-pentane and isopentane. Additionally, most current methods are complicated, requiring trapping and concentrating steps to obtain adequate sensitivity prior to hydrocarbon analysis. The purpose of the current study was to develop a gas chromatographic system to analyze breath pentane, that addresses the above technical problems and that would provide a simple in vivo method for measuring lipid. n-Pentane and isopentane standards were easily separated from isoprene with a Al2O3/KCI capillary column contained in a portable gas chromatograph equipped with a photoionization detector. The analysis of repeated measures showed a low coefficient of variation for measurements of n-pentane (10%) and isopentane (9%). We measured breath pentane in 27 subjects (15 smokers, 12 non-smokers). There were no significant difference between the baseline and 4 week interval measurements of n-pentane for smokers both before and after cigarette smoking. The within-subject variability data showed that the assay is highly reproducible for both low and high pentane levels in smokers. Smokers were found to have higher levels of both n-pentane and isopentane than non-smokers (P < 0.001). In addition, smokers had further significant elevation of pentane levels 10 min after smoking (P < 0.001), which returned to baseline by 1 h. These studies demonstrate that measurement of breath pentane, using a gas chromatograph with a photoionization detector, is simple and reproducible. Additionally, these results suggest that pentane elevation associated with smoking is secondary to the oxidant effects of cigarette smoke and an important temporal relationship exists between cigarette smoking and breath sample analysis. PMID:8953161

Mohler, E R; Reaven, P; Stegner, J E; Fineberg, N S; Hathaway, D R

1996-10-25

300

The thermal conductivity of liquid mixtures at elevated pressures  

Microsoft Academic Search

This paper reports new, absolute measurements of the thermal conductivity of liquid mixtures of n-heptane and isooctane in the pressure range 0.1 to 430 MPa for temperatures of 307.85 and 337.15 K. The results represent a preliminary investigation of the advantages of attempting to describe the isothermal composition dependence of the thermal conductivity of liquid mixtures along isochores, rather than

J. M. N. A. Fareleira; S. F. Y. Li; W. A. Wakeham

1989-01-01

301

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

302

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

303

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

304

Interrelation between the structural and transport properties of pervaporation membranes with diffusion layers based on poly-?-benzyl-L-glutamate  

NASA Astrophysics Data System (ADS)

The interrelation between the transport properties of pervaporation membranes (used to separate toluene-n-heptane mixtures) and the structure of poly-?-benzyl- L-glutamate diffusion layers has been studied. The decrease in the membrane selectivity while increasing the flux at the transition from 3 to 50 wt % toluene in the mixture under separation is accompanied by a change in the ordered structure of poly-?-benzyl- L-glutamate structure without variation in the ?-helical conformation of the polypeptide chain.

Kononova, S. V.; Kremnev, R. V.; Baklagina, Yu. G.; Volchek, B. Z.; Vlasova, E. N.; Shabsels, B. M.; Romashkova, K. A.; Romanov, D. P.; Arkhipov, S. N.; Bogomazov, A. V.; Uchytil, P.

2011-05-01

305

Swelling of medical grade silicones in liquids and calculation of their cross-link densities  

Microsoft Academic Search

Four medical grade silicones were swollen, until they reached equilibrium (i.e. constant mass) in eight liquids at 25°C. The greatest swelling was obtained with n-heptane but the volume fraction, ?, of the silicones in their swollen state was not significantly different (p<0.05) in this liquid than in cyclohexane. For each grade of silicone, ? was plotted against ?l, the liquid

Aziza Mahomed; David W. L. Hukins; Stephen N. Kukureka

2010-01-01

306

The effect of aliphatic, naphthenic, and aromatic hydrocarbons on production of reactive oxygen species and reactive nitrogen species in rat brain synaptosome fraction: the involvement of calcium, nitric oxide synthase, mitochondria, and phospholipase A 1 1 Abbreviations: BIM, bisindolylmaleimide; [Ca 2+] i, concentration of intracellular calcium; ChAT, cholin acetyltransferase; CSA, cyclosporin A; DCF, 2?,7?-dichlorofluorescein; H 2DCF-DA, 2?,7?-dichlorodihydrofluorescin diacetate; DEDA, dimethyleicosadienoic acid; ERK, extracellular signal-regulated kinases; Fura-2 AM, 5-oxazolecarboxylic acid, 2-(6-(bis(2-((acetyloxy)methoxy)-2-oxoethyl)amino)-5-(2-(bis(2-((acetyloxy)methoxy)-2oxoethyl)amino)-5-methylphenoxy)ethoxy)-2-benzofuranyl)-, (acetyloxy) methyl ester; GABA-T, gamma-aminobutyric acid transaminase; HBSS, Hanks’ balanced salt solution; La 3+, lanthanum; MAPK, mitogen-activated protein kinase; MeHg, methyl mercury; MEK, extracellular signal-regulated protein kinase; MeOH, methan  

Microsoft Academic Search

This study investigated the effects of C7 and C9 aliphatic (n-heptane, n-nonane), naphthenic (methylcyclohexane, 1,2,4-trimethylcyclohexane (TMCH)) and aromatic (toluene, 1,2,4-trimethylbenzene (TMB)) hydrocarbons on the production of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in rat brain synaptosome fraction. Methyl mercury (MeHg) was included as a positive control. Exposure of the synaptosomes to the hydrocarbons produced a concentration-dependent linear

Oddvar Myhre; Frode Fonnum

2001-01-01

307

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

308

Modeling evaporation effects in conditional moment closure for spray autoignition  

Microsoft Academic Search

Simulations of an n-heptane spray autoigniting under conditions relevant to a diesel engine are performed using two-dimensional, first-order conditional moment closure (CMC) with full treatment of spray terms in the mixture fraction variance and CMC equations. The conditional evaporation term in the CMC equations is closed assuming interphase exchange to occur at the droplet saturation mixture fraction values only. Modeling

Giulio Borghesi; Epaminondas Mastorakos; Cécile B. Devaud; Robert W. Bilger

2011-01-01

309

On the Collision of a Droplet with a Solid Surface  

Microsoft Academic Search

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

S. Chandra; C. T. Avedisian

1991-01-01

310

Sensitized extraction spectrophotometric determination of Hg(II) with dithizone after its flotation as ion-associate using iodide and ferroin  

Microsoft Academic Search

This paper describes a simple and highly selective method for the separation, preconcentration and spectrophotometric determination of extremely low concentration of mercury. The method is based on the flotation of an ion-associate of HgI42? and ferroin between aqueous and n-heptane interface at pH 5. The ion-associate was then separated and treated with ammonia and dithizone solutions to extract only the

Mohammad Saeid Hosseini; Hamid Hashemi-Moghaddam

2005-01-01

311

Lateral motion and interaction of gas bubbles growing over spherical and plate heaters  

Microsoft Academic Search

This work investigates the motion of CO2 bubbles emerging in n-heptane when a heat pulse given to a submerged heater creates local supersaturation. The ensuing slow\\u000a diffusion-induced bubble expansion makes bubble motion easy to observe. The low gravity environment of a parabolic flight\\u000a allows bubbles to reach large sizes without departing from the heater while retaining their spherical shape. A

Nikolaos Divinis; Thodoris D. Karapantsios; Margaritis Kostoglou; Vasilis Bontozoglou; Robert de Bruijn; J. C. Legros

2006-01-01

312

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

313

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

314

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

315

Autothermal reforming of simulated gasoline and diesel fuels  

Microsoft Academic Search

Autothermal reforming (ATR) of simulated fuels was studied with n-heptane, n-dodecane, toluene, and methylcyclohexane as model compounds for different fractions of gasoline and diesel on zirconia-supported Rh and Pt. A performance comparison was made on commercial nickel catalyst. No inhibiting effect was observed between the hydrocarbons on any catalyst, even though aliphatic hydrocarbons are more reactive than aromatics. The product

R. K. Kaila; A. O. I. Krause

2006-01-01

316

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

317

New anti-inflammatory triterpene from the root of Ricinus communis.  

PubMed

Liquid-liquid partitioning of Ricinus communis root methanol extract resulted in enrichment of compounds. Purification of the n-hexane fraction led to the isolation and characterisation of two triterpenes: one known compound lupeol (1) and a new diketone pentacyclic triterpene named as erandone (urs-6-ene-3,16-dione) (2), from the plant. Their structures were determined by various spectroscopic techniques. Crude methanolic, enriched n-hexane fraction and isolates at doses 100 mg/kg p.o. exhibited significant (P < 0.001) anti-inflammatory activity in carrageenan-induced hind paw oedema model. PMID:24279342

Srivastava, Pooja; Jyotshna; Gupta, Namita; Maurya, Anil Kumar; Shanker, Karuna

2014-01-01

318

Cyclohexane transformations over metal oxide catalysts. 1. Effect of the nature of metal and support on the catalytic activity in cyclohexane ring opening  

Microsoft Academic Search

The activities of monometallic Pt-, Ru-, and Rh-containing catalysts supported on Al2O3, Al2O3—F, SiO2, WO3\\/ZrO2, and La2Î3\\/ZrO2, in cyclohexane ring opening to form n-hexane were studied. The most active catalyst is Rh\\/Al2O3. Cyclohexane hydrogenolysis to n-hexane also occurs over the Pt\\/Al;>2O3 and Pt\\/La2Î3\\/ZrO2 catalysts. Ring opening over the Ru catalysts proceeds at significantly lower temperatures (210—230 °C) than over the

O. V. Masloboishchikova; T. V. Vasina; E. G. Khelkovskaya-Sergeeva; L. M. Kustov; P. Zeuthen

2002-01-01

319

A reduced chemical kinetic model for IC engine combustion simulations with primary reference fuels  

SciTech Connect

A reduced chemical kinetic mechanism for the oxidation of primary reference fuel (PRF) has been developed and applied to model internal combustion engines. Starting from an existing reduced reaction mechanism for n-heptane oxidation, a new reduced n-heptane mechanism was generated by including an additional five species and their relevant reactions, by updating the reaction rate constants of several reactions pertaining to oxidation of carbon monoxide and hydrogen, and by optimizing reaction rate constants of selected reactions. Using a similar approach, a reduced mechanism for iso-octane oxidation was built and combined with the n-heptane mechanism to form a PRF mechanism. The final version of the PRF mechanism consists of 41 species and 130 reactions. Validation of the present PRF mechanism was performed with measurements from shock tube tests, and HCCI and direct injection engine experiments available in the literature. The results show that the present PRF mechanism gives reliable performance for combustion predictions, as well as computational efficiency improvements for multidimensional CFD simulations. (author)

Ra, Youngchul; Reitz, Rolf D. [Engine Research Center, University of Wisconsin-Madison, 1500 Engineering Drive, ERB 1016B, Madison, WI 53706 (United States)

2008-12-15

320

Stability and aerosolization of pressurized metered dose inhalers containing thymopentin nanoparticles produced using a bottom-up process.  

PubMed

The objective of this study was to investigate the stability and aerosolization of pressurized metered dose inhalers (pMDIs) containing thymopentin nanoparticles. Thymopentin nanoparticles, fabricated by a bottom-up process, were suspended in hydrofluoroalkane (HFA) 134a together with cineole and/or n-heptane to produce pMDI formulations. The stability study of the pMDIs obtained was carried out at ambient temperature for 6 months. The amount of thymopentin and the aerosolization properties of pMDIs were determined using high-performance liquid chromatography (HPLC) and a twin-stage impinger (TSI), respectively. Based on the results, thymopentin nanoparticles were readily suspended in HFA 134a with the aid of cineole and/or n-heptane to form physically stable pMDI formulations, and more than 98% of the labeled amount of thymopentin and over 50% of the fine particle fraction (FPF) of the pMDIs were achieved. During storage, it was found that for all pMDIs more than 97% of the labeled amount of thymopentin and FPF greater than 47% were achieved. Moreover, the size of thymopentin nanoparticles in propellant containing cineole and n-heptane showed little change. It is, therefore, concluded that the pMDIs comprising thymopentin nanoparticles developed in this study were stable and suitable for inhalation therapy for systemic action. PMID:22343132

Tan, Yinhe; Yang, Zhiwen; Pan, Xin; Chen, Meiwan; Feng, Min; Wang, Lili; Liu, Hu; Shan, Ziyun; Wu, Chuanbin

2012-05-10

321

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

322

Purification of antibiotics from the biocontrol agent Streptomyces anulatus S37 by centrifugal partition chromatography.  

PubMed

A novel actinomycete strain, Streptomyces anulatus S37, has been isolated from the rhizosphere of healthy Moroccan Vitis vinifera on the basis on its ability to promote grapevine growth and to induce natural defences against various phytopathogens. In the present work, the main bioactive metabolites produced by S. anulatus S37 were isolated. A crude n-BuOH extract of the S37 fermentation broth was firstly partitioned in a biphasic solvent system composed of n-heptane, methanol, and water (5:1.5:3.5, v/v). The most active organic fraction (1.1g) as revealed by TLC-bioautography was subsequently separated by a two-step centrifugal partition chromatography procedure. The first separation was performed in the ascending mode at 6mL/min with the biphasic solvent system n-heptane, ethyl acetate, methanol and water (2:1:2:1, v/v), to finally recover 40mg of a pure compound identified as streptochlorin by NMR spectroscopy. In a second separation, the solvent system n-heptane, acetonitrile, and water (5:5:4, v/v) was used in the ascending mode at 3mL/min to purify 135mg of nigericin and 53mg of piericidin A1. Assays performed with the three compounds have confirmed their inhibitory impact on the growth of Botryris cinerea in dual confrontation and also on V. vinifera L. plantlets. PMID:24291716

Couillerot, Olivier; Loqman, Souad; Toribio, Alix; Hubert, Jane; Gandner, Léa; Nuzillard, Jean-Marc; Ouhdouch, Yedir; Clément, Christophe; Barka, Essaid Ait; Renault, Jean-Hugues

2014-01-01

323

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

324

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...

325

RATE CONSTANTS FOR THE REACTION OF OH RADICALS WITH A SERIES OF ALKENES AND DIALKENES AT 295 + OR - 1 K  

EPA Science Inventory

Using a relative rate technique, rate constants for the gas phase reactions of the OH radical with n-butane, n-hexane and a series of alkenes and dialkenes, relative to that for propene, have been determined in one atmosphere of air at 295 + or - 1K. The resulting rate constant d...

326

Comparison of the concepts used to develop and apply occupational exposure limits for ionizing radiation and hazardous chemical substances  

Microsoft Academic Search

The rationales used by the American Conference of Governmental Industrial Hygienists (AC-GIH) to recommend exposure limits for 10 chemicals were reviewed. The 10 chemicals chosen were known to produce chronic disease after prolonged overexposure in the workplace. The chemicals were toluene diisocyanate, hydrogen fluoride, n-hexane, carbon disulfide, cadmium, inorganic mercury, cobalt, nitroglycerol, silica, and vinyl chloride. The rationales used by

D HALTON

1988-01-01

327

Hexane Air Combustion  

E-print Network

Hot surface ignition and subsequent flame propagation of premixed n-hexane air mixtures are shown in this fluid dynamics video. High speed schlieren photography revealed 3 distinct behaviors of ignition and propagation as a function of mixture composition and initial pressure.

Boettcher, Philipp A; Shepherd, Joseph E

2010-01-01

328

Conductivity of solvated electrons in hexane investigated with terahertz time-domain spectroscopy  

E-print Network

Conductivity of solvated electrons in hexane investigated with terahertz time-domain spectroscopy and recombination dynamics of quasifree electrons in liquid n-hexane and cyclohexane performed using terahertz time- uids of hexane and cyclohexane. The nature of solvated electrons in nonpolar liquids such as hexane has

Heinz, Tony F.

329

Mixed-Ligand MetalOrganic Frameworks with Large Pores: Gas Sorption Properties and Single-Crystal-to-Single-Crystal Transformation on Guest  

E-print Network

-crystal-to-single-crystal transformation on exchange of the DMF guest molecules with hexane to form {[Zn2ACHTUNGTRENNUNG(BPnDC)2ACHTUNGTRENNUNG(dabco)]·6ACHTUNGTRENNUNG(n-hexane)·3H2O}n (2hexane). The X-ray structure of 2hexane reveals

Paik Suh, Myunghyun

330

Class separation of aromatic compounds in rock extracts and fossil fuels by liquid chromatography  

Microsoft Academic Search

A method for semipreparative liquid chromatographic separation of aromatic ring classes in crude oils and the organic extracts of rock and coal samples was developed. Partially deactivated microparticulate alumina was used as the stationary phase. Reproducible retentions could be achieved with a moisture-control system. Application of a stepwise gradient of dichloromethane in n-hexane resulted in four aromatic subfractions, which were

Matthias. Radke; Helmut. Willsch; Dietrich. Welte

1984-01-01

331

Stability During Frying of Moringa oleifera Seed Oil Variety “Periyakulam 1”  

Microsoft Academic Search

The frying performance of the Moringa oleifera seed oil variety Periyakulam 1 (PKM 1) from India, extracted using cold press (CP) and n -hexane (H), during frying of potatoes and cod was studied especially as regards repeated frying operations. The oils were used for intermittent frying of potato slices and cod filets at a temperature of 175±5°C for 5 consecutive

John Tsaknis; Stavros Lalas

2002-01-01

332

Coumarins from Zosima absinthifolia seeds, with allelopatic effects  

Microsoft Academic Search

Zosima absinthifolia belongs to the Apiaceae family and is found in Iran, Turkey, Iraq and different countries of the Caucasus, Middle East and Central Asia. The fruits are used as food flavoring and as a food spice in Iran. In the present work, an n-hexane extract of the plant seeds was purified by vacuum liquid chromatography and preparative TLC for

Seyed Mehdi RAZAVI; Gholamhassan IMANZADEH; Mahdi DAVARI

2010-01-01

333

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

334

J. Phys. I France 2 (1992) 1541-1548 AUGUST 1992, PAGE 1541 Classification  

E-print Network

by liquid chromatography (n-hexane + 5 9l toluene) on neutral A1203. As a final step C70 was heated to 250 °C for 16 h under vacuum to drive off residual solvents. Crystals of the new phase were grown from

Paris-Sud XI, Université de

335

Epoxidation of Fatty Acid Methyl Esters derived from Jatropha oil  

Microsoft Academic Search

Fatty Acid Methyl Esters (FAMEs) from transesterification of Jatropha oil were obtained by both acid and base catalyzed transesterification reactions. These FAMEs were epoxidized in or without solvent by either peroxyformic acid or peroxyacetic acid, formed in situ by 30% hydrogen peroxide. n-hexane was used as solvent. Detailed study regarding effects of type and concentration of organic acid used in

Muhammad Mushtaq; Isa B. Tan; Cecilia Devi; Saeed Majidaie; Muhammad Nadeem; Susan Lee

2011-01-01

336

VANADIUM PHOSPHORUS OXIDE AS AN EFFICIENT CATALYST FOR HYDROCARBON OXIDATIONS USING HYDROGEN PEROXIDE  

EPA Science Inventory

Calcined vanadium phosphorus oxide (VPO) prepared by an organic route is found to be an efficient catalyst for the oxidation of various alkanes such as cyclopentane, cyclohexane, n-hexane, cycloheptane, cyclooctane, cyclodecane and adamantane in acetonitrile solvent using the env...

337

Solution scattering studies of the hierarchical assembly of porphyrin trimers based on benzene triscarboxamide.  

PubMed

The self-assembly of achiral and chiral porphyrin trimers based on benzene triscarboxamide in solution is studied with the help of NMR, FT-IR, UV-vis, and CD spectroscopy. These studies revealed that in apolar solvents the porphyrin trimers self-assembled in columnar stacks via a combination of hydrogen bonding and ?-? stacking interactions. While the critical aggregation constant is about 0.2 mM in chloroform, aggregation already occurs at micromolar concentrations in n-hexane. Small angle neutron scattering (SANS) studies in chloroform, toluene, and n-hexane confirmed aggregation of the trimers into columnar stacks. In chloroform and n-hexane, but not in toluene, the trimers gelated the solvent. In chloroform the stacks of the achiral trimer were found to contain on average about 70 molecules, while in toluene the stacks were much smaller and contained on average 7-9 molecules. In n-hexane the SANS studies revealed that the chiral trimer formed a gel with an average mesh size of the transient network of chains of approximately 90 nm, with chains being built up from effective cylindrical aggregates with an average length of 20 nm. PMID:25363515

van Hameren, Richard; van Buul, Arend M; Visser, Dirk; Heenan, Richard K; King, Stephen M; Rowan, Alan E; Nolte, Roeland J M; Pyckhout-Hintzen, Wim; Elemans, Johannes A A W; Feiters, Martin C

2014-12-28

338

Molecular mechanics and quantum mechanical modeling of hexane soot structure and interactions with pyrene  

Microsoft Academic Search

: Molecular simulations (energy minimizations and molecular dynamics) of an n-hexane soot model developed by Smith and co-workers (M. S. Akhter, A. R. Chughtai and D. M. Smith, Appl. Spectrosc., 1985, 39, 143; ref. 1) were performed. The MM+ (N. L. Allinger, J. Am. Chem. Soc., 1977, 395, 157; ref. 2) and COMPASS (H. Sun, J. Phys. Chem., 1998, 102,

J. D. Kubicki

2000-01-01

339

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

340

Discrepancy Between the Theoretical Plate Number (N) and Peak Resolution (Rs) for Optimizing the Flow Rate in Countercurrent Chromatography  

Microsoft Academic Search

This paper deals with a problem in optimizing the flow rate of the mobile phase in countercurrent chromatography (CCC), A set of data including theoretical plate number (N), resolution factor (Rs), % retention, etc. are obtained from the separation of three indole auxins in a two-phase solvent system of n-hexane \\/ ethyl acetate \\/ methanol \\/ water (1:1:1:1) by applying

Hisao Oka; Yoshitomo Ikai; Junko Hayakawa; Ken-Ichi Harada; Kazuko Nagase; Makoto Suzuki; Hiroyuki Nakazawa; Yoichiro Ito

1992-01-01

341

Implications of Transition State Confinement within Small Voids for Acid Catalysis  

E-print Network

Implications of Transition State Confinement within Small Voids for Acid Catalysis Andrew J. Jones aluminosili- cates reflects their unique ability to confine transition states within intracrystalline voids exponentially on n-hexane physisorption energies for different void size and shape and proton location

Iglesia, Enrique

342

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

343

Solubility and Flory Huggins parameters of SBES, poly(styrene-b-butene\\/ethylene-b-styrene) triblock copolymer, determined by intrinsic viscosity  

Microsoft Academic Search

Solubility parameter and Flory Huggins interaction parameter of a triblock SBES have been obtained from intrinsic viscosity measurements. The solubility of the block copolymer in all solvents (methyl-cyclohexane, cyclohexane, cyclopentane, toluene and benzene) was found good except in the case of n-hexane. The results obtained are similar to other found in literature for SBR and SBS rubbers, and indicate that

G. Ovejero; P. Pérez; M. D. Romero; I. Guzmán; E. D?´ez

2007-01-01

344

Effects of lemon balm ( Melissa officinalis L.) extract on germination and seedling growth of six plants  

Microsoft Academic Search

The n-hexane-, acetone- and water-soluble fractions obtained from an aqueous acetone extract of lemon balm (Melissa officinalis L.) shoots inhibited the germination and the growth of roots and shoots of cockscomb (Amaranthus caudatus L.), cress (Lepidium sativum L.), crabgrass (Digitaria sanguinalis L.), timothy (Phleum pratense L.), lettuce (Lactuca sativa L.) and ryegrass (Lolium multiflorum Lam.). The inhibitory activity of the

Hisashi Kato-Noguchi

2001-01-01

345

One-dimensional channels constructed from per-hydroxylated pillar[6]arene molecules for gas and vapour adsorption.  

PubMed

Per-hydroxylated pillar[6]arene molecules formed highly ordered one-dimensional channels with a diameter of 6.7 Å. The channels can capture various gases, such as CO2, N2 and n-butane, and vapours of saturated hydrocarbons such as n-hexane and cyclohexane. PMID:25339195

Ogoshi, Tomoki; Sueto, Ryuta; Yoshikoshi, Kumiko; Yamagishi, Tada-aki

2014-12-14

346

Cancer-suppressive potential of extracts of endemic plant Helichrysum zivojinii: effects on cell migration, invasion and angiogenesis.  

PubMed

Helichrysum zivojinii Cernjavski & Soska is an endemic plant species that grows in the National Park Galicica in Macedonia. Five extracts were isolated as fractions from the aerial parts of the plant: a n-hexane extract (1), a dichloromethane extract (2), an ethyl-acetate extract (3), a n-butanol extract (4) and a methanol extract (5). A dose-dependent cytotoxic activity of the extracts on MDA-MB-231 and EA.hy926 cells was observed. Extracts exhibited more pronounced cytotoxic actions on MDA-MB-231 cells than on EA.hy926 cells. The n-hexane extract (1), at a non-toxic concentration, exhibited an inhibitory effect on the migration as well the invasiveness of MDA-MB-231 cells. The dichloromethane extract (2), at a non-toxic concentration, demonstrated inhibition of MDA-MB-231 cells invasion. Each of the five extracts applied at non-toxic concentrations inhibited migration of EA.hy926 cells. The prominent inhibitory effect of the n-hexane extract on EA.hy926 cells migration was associated with a notable anti-angiogenic action of this extract. The other four tested extracts demonstrated mild anti-angiogenic activity. Our data highlight the prominent anticancer potential of n-hexane (1) and dichloromethane (2) extracts, which could be attributed to their very pronounced and selective cytotoxic activities as well as their anti-invasive and anti-angiogenic properties. PMID:24273869

Mati?, Ivana Z; Aljanci?, Ivana; Vajs, Vlatka; Jadranin, Milka; Gligorijevi?, Nevenka; Milosavljevi?, Slobodan; Jurani?, Zorica D

2013-09-01

347

40 CFR 795.232 - Inhalation and dermal pharmacokinetics of commercial hexane.  

Code of Federal Regulations, 2013 CFR

...be demonstrated that the analytical sensitivity of the method used with the unlabeled...substance is equal to or greater than the sensitivity which could be obtained with the radiolabeled...C-n -hexane or, if the analytical sensitivity is equal or greater, unlabeled...

2013-07-01

348

40 CFR 795.232 - Inhalation and dermal pharmacokinetics of commercial hexane.  

Code of Federal Regulations, 2011 CFR

...be demonstrated that the analytical sensitivity of the method used with the unlabeled...substance is equal to or greater than the sensitivity which could be obtained with the radiolabeled...C-n -hexane or, if the analytical sensitivity is equal or greater, unlabeled...

2011-07-01

349

40 CFR 795.232 - Inhalation and dermal pharmacokinetics of commercial hexane.  

Code of Federal Regulations, 2012 CFR

...be demonstrated that the analytical sensitivity of the method used with the unlabeled...substance is equal to or greater than the sensitivity which could be obtained with the radiolabeled...C-n -hexane or, if the analytical sensitivity is equal or greater, unlabeled...

2012-07-01

350

40 CFR 795.232 - Inhalation and dermal pharmacokinetics of commercial hexane.  

Code of Federal Regulations, 2014 CFR

...be demonstrated that the analytical sensitivity of the method used with the unlabeled...substance is equal to or greater than the sensitivity which could be obtained with the radiolabeled...C-n -hexane or, if the analytical sensitivity is equal or greater, unlabeled...

2014-07-01

351

Assessment of dermal wound healing and in vitro antioxidant properties of Avena sativa L  

Microsoft Academic Search

Avena sativa L. (Poaceae) has been reported to have traditional utilization against skin diseases and inflammation. Therefore, in this study, the n-hexane, ethyl acetate, ethanol, and water extracts of A. sativa were investigated for their wound healing and antioxidant activities. Total phenol and flavonoid contents of the extracts were established spectrophotometrically. For the wound healing activity, linear incision and circular

E. Küpeli Akkol; I. Süntar; I. Erdogan Orhan; H. Keles; G. Çoksari; A. Kan

2011-01-01

352

Wound Healing Activity of Rubus sanctus Schreber (Rosaceae): Preclinical Study in Animal Models  

Microsoft Academic Search

Young shoots of Rubus species have been used for healing of wounds, infected insect bites and pimples in folk medicine for ages. In order to evaluate the wound healing activity of Rubus sanctus, four different extracts were prepared from the whole aerial parts of the plant by using n-hexane, chloroform, ethyl acetate and methanol, respectively. Incision wound healing model by

Ipek Pesin; Ufuk Koca; Hikmet Keles; Esra Kupeli Akkol

2009-01-01

353

Dichroism and birefringence induced by shear in a critical binary fluid  

NASA Astrophysics Data System (ADS)

A large anisotropy in the absorption of light has been detected in a sheared mixture of nitrobenzene and n-hexane at critical concentration. This dichroism is well supported by the Onuki and Kawasaki theory. The corresponding birefringence amplitude exhibits some discrepancy when compared with the above theory, but this vanishes if the same scaling function as for dichroism is used.

Beysens, D.; Gastaud, R.; Decruppe, F.

1984-08-01

354

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...

355

40 CFR 799.2155 - Commercial hexane.  

Code of Federal Regulations, 2011 CFR

...with the American Society for Testing and Materials Designation D 1836-83 (ASTM D 1836), consists primarily of six-carbon alkanes or cycloalkanes, and contains at least 40 liquid volume percent n -hexane (CAS No. 110-54-3) and at least 5...

2011-07-01

356

Molecular mechanism of hydrocarbons binding to the metal–organic framework  

SciTech Connect

The adsorption and diffusivity of methane, ethane, n-butane, n-hexane and cyclohexane in a metal organic framework (MOF) with the organic linker tetrakis[4-(carboxyphenyl)oxamethyl]methane, the metal salt, Zn2+, and organic pillar, 4,4’-bipyridin was studied using molecular dynamics simulations. For the n-alkanes, the longer the chain, the lower the free energy of adsorption, which was attributed to a greater number of contacts between the alkane and MOF. Cyclohexane had a slightly higher adsorption free energy than n-hexane. Furthermore, for cyclo- and n-hexane, there were no significant differences in adsorption free energies between systems with low to moderate loadings. The diffusivity of the n-alkanes was found to strongly depend on chain length with slower diffusion for longer chains. Cyclohexane had no effective diffusion, suggesting that the selectivity the MOF has towards n-hexane over cyclohexane is the result of kinetics instead of energetics. This work was supported by the U.S. Department of Energy's (DOE) Office of Basic Energy Sciences, Chemical Sciences program. The Pacific Northwest National Laboratory is operated by Battelle for DOE.

Sun, Xiuquan; Wick, Collin D.; Thallapally, Praveen K.; McGrail, B. Peter; Dang, Liem X.

2011-01-07

357

40 CFR 799.2155 - Commercial hexane.  

Code of Federal Regulations, 2012 CFR

...with the American Society for Testing and Materials Designation D 1836-83 (ASTM D 1836), consists primarily of six-carbon alkanes or cycloalkanes, and contains at least 40 liquid volume percent n -hexane (CAS No. 110-54-3) and at least 5...

2012-07-01

358

40 CFR 799.2155 - Commercial hexane.  

Code of Federal Regulations, 2013 CFR

...with the American Society for Testing and Materials Designation D 1836-83 (ASTM D 1836), consists primarily of six-carbon alkanes or cycloalkanes, and contains at least 40 liquid volume percent n -hexane (CAS No. 110-54-3) and at least 5...

2013-07-01

359

40 CFR 799.2155 - Commercial hexane.  

Code of Federal Regulations, 2014 CFR

...with the American Society for Testing and Materials Designation D 1836-83 (ASTM D 1836), consists primarily of six-carbon alkanes or cycloalkanes, and contains at least 40 liquid volume percent n -hexane (CAS No. 110-54-3) and at least 5...

2014-07-01

360

Self-Assembly of Luminescent Molecular Squares Featuring Octahedral Rhenium Corners Robert V. Slone, Joseph T. Hupp,* Charlotte L. Stern, and Thomas E. Albrecht-Schmitt  

E-print Network

1 and 2 were grown by first solubilizing the samples in acetone and then layering with n-hexanes.10 of the nominally equivalent pyrazine protons is attributed to a subtle difference in the environment surrounding the neighboring pyrazine rings, where they are expected to experience a ring current effect and, therefore

361

Selective enzymatic synthesis of amide surfactants from diethanolamine  

Microsoft Academic Search

Kinetic strategies for selective preparation of amides from diethanolamine have been designed using Novozym 435 lipase as a biocatalyst. Two different routes, direct acylation and transacylation, have been optimized. In n-hexane, the reaction is more selective for formation of the amide by direct acylation, while in dioxane, the O-acylation reaction is highly favored. However, the initial rates of direct acylation

Mónica Fernández-Pérez; Cristina Otero

2003-01-01

362

This is an author-deposited version published in: http://oatao.univ-toulouse.fr/ Eprints ID: 8587  

E-print Network

, Luc Biodiesel production from jatropha seeds: Solvent extraction and in situ transesterification production from jatropha seeds: Solvent extraction and in situ transesterification in a single step I. Amalia conducted using milled jatropha seeds, and n-hexane as extracting solvent. The influence of methanol to seed

Boyer, Edmond

363

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

364

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

365

Hydrostaticity and hidden order: effects of experimental conditions on the temperature-pressure phase diagram of URu2Si2  

NASA Astrophysics Data System (ADS)

The pressure-dependence of the hidden order phase transition of URu2Si2 is shown to depend sensitively upon the quality of hydrostatic pressure conditions during electrical resistivity measurements. Hysteresis in pressure is demonstrated for two choices of pressure medium: the commonly-used mixture of 1:1 Fluorinert FC70/FC77 and pure FC75. In contrast, no hysteresis is observed when the pressure medium is a 1:1 mixture of n-pentane/isoamyl alcohol, as it remains hydrostatic over the entire studied pressure range. Possible ramifications for the interpretation of the temperature-pressure phase diagram of URu2Si2 are discussed.

Butch, N. P.; Jeffries, J. R.; Zocco, D. A.; Maple, M. B.

2009-06-01

366

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

367

Oxidative transformations of cyclohexane, methylcyclopentane, and pentane on treatment with superelectrophiles based on polyhalomethane and aluminum halides  

Microsoft Academic Search

Cyclohexane and methylcyclopentane dimerize into dimethyldecalins on treatment with superelectrophilic systems containing polyhalomethanes (CBr4, CCl4, CHCl3) and aluminum halides (AlBr3, AlCl3). At 20 °C, the yields of C12H22 hydrocarbons reach 140 mol.% based on the superelectrophile. Under the action of CBr4·2AlBr3 at 20 °C in CH2Br2 or without a solvent, n-pentane is converted predominantly into lower alkanes (mainly, isopentane). In

I. S. Akhrem; I. M. Churilova; S. V. Vitt

2001-01-01

368

Investigation of Molecular Exchange Using DEXSY with Ultra-High Pulsed Field Gradients  

SciTech Connect

Diffusion exchange spectroscopy has been employed for the investigation of water exchange between different regions of a cosmetic lotion as well as for the exchange of n-pentane between the inter- and intra-crystalline space in zeolite NaX. We successfully combined this two-dimensional (2D) NMR experiment with methods for the application of ultra-high pulsed field gradients of up to 35 T/m, resulting in observation times and mixing times as short as 2 ms and 2.8 ms, respectively.

Gratz, Marcel; Galvosas, Petrik [Faculty of Physics and Earth Sciences, University of Leipzig (Germany)

2008-12-05

369

Searching for voids in liquids with optical Kerr effect spectroscopy.  

PubMed

It has recently been shown [J. Chem. Phys. 2005, 122, 134506; J. Am. Chem. Soc. 2006, 128, 5119] that liquid tetrahydrofuran has an unusual structure that features voids of significant dimension. Such voids should affect other observable properties of this liquid. Here we present temperature-dependent, optical Kerr effect data for tetrahydrofuran and a number of related liquids (furan, cyclopentane, tetrahydropyran, cyclohexane, diethyl ether, and n-pentane) as well as hexamethylphosphoramide to test whether this technique can be used to reveal the presence of sizable voids in liquids. PMID:18590321

Zhong, Qin; Fourkas, John T

2008-07-24

370

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

371

Molecular dynamics simulation study of solvent effects on conformation and dynamics of polyethylene oxide and polypropylene oxide chains in water and in common organic solvents  

NASA Astrophysics Data System (ADS)

In this paper, the conformation and dynamics properties of polyethylene oxide (PEO) and polypropylene oxide (PPO) polymer chains at 298 K have been studied in the melt and at infinite dilution condition in water, methanol, chloroform, carbon tetrachloride, and n-heptane using molecular dynamics simulations. The calculated density of PEO melt with chain lengths of n = 2, 3, 4, 5 and, for PPO, n = 7 are in good agreement with the available experimental data. The conformational properties of PEO and PPO show an increasing gauche preference for the O-C-C-O dihedral in the following order water>methanol>chloroform>carbon tetrachloride = n-heptane. On the contrary, the preference for trans conformation has a maximum in carbon tetrachloride and n-heptane followed in the order by chloroform, methanol, and water. The PEO conformational preferences are in qualitative agreement with results of NMR studies. PEO chains formed different types of hydrogen bonds with polar solvent molecules. In particular, the occurrence of bifurcated hydrogen bonding in chloroform was also observed. Radii of gyration of PEO chains of length larger than n = 9 monomers showed a good agreement with light scattering data in water and in methanol. For the shorter chains the observed deviations are probably due to the enhanced hydrophobic effects caused by the terminal methyl groups. For PEO the fitting of end-to-end distance distributions with the semi-flexible chain model at 298 K provided persistence lengths of 0.375 and 0.387 nm in water and methanol, respectively. Finally, the radius of gyration of Pluronic P85 turned out to be 2.25 ± 0.4 nm at 293 K in water in agreement with experimental data.

Hezaveh, Samira; Samanta, Susruta; Milano, Giuseppe; Roccatano, Danilo

2012-03-01

372

The Effects of Fuel Composition and Compression Ratio on Thermal Efficiency in an HCCI Engine  

SciTech Connect

The effects of variable compression ratio (CR) and fuel composition on thermal efficiency were investigated in a homogeneous charge compression ignition (HCCI) engine using blends of n-heptane and toluene with research octane numbers (RON) of 0 to 88. Experiments were conducted by performing CR sweeps at multiple intake temperatures using both unthrottled operation, and constant equivalence ratio conditions by throttling to compensate for varying air density. It was found that CR is effective at changing and controlling HCCI combustion phasing midpoint, denoted here as CA 50. Thermal efficiency was a strong function of CA 50, with overly advanced CA 50 leading to efficiency decreases. Increases in CR at a constant CA 50 for a given fuel composition did, in most cases, increase efficiency, but the relationship was weaker than the dependence of efficiency on CA 50. The increase in efficiency with higher CR was fuel-dependent, so that the fuels requiring a higher CR to achieve ignition did not gain a proportionate efficiency increase. For example, n-heptane achieved an indicated thermal efficiency (ITE) of 38% at a CR of 9:1, whereas a 50 wt% blend of toluene with n-heptane required a CR of 12:1 to achieve the same ITE. A simple heat balance around the engine showed that higher toluene content fuels had higher cooling losses. The high toluene fuels exhibited higher rates of maximum pressure rise than the lower octane fuels. The increased cooling losses can be attributed to the higher pressure rise rates, which are a driving force for heat transfer.

Szybist, James P [ORNL; Bunting, Bruce G [ORNL

2007-01-01

373

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

374

Standard test method for existent gum in fuels by jet evaporation  

SciTech Connect

This method covers determination of the existent gum in motor gasoline and aircraft fuels at the time of test. Provisions are made for the determination of the unwashed gum content of motor gasoline. Summary of method: a measured quantity of fuel is evaporated under controlled conditions of temperature and flow of air or steam. For aviation gasoline and aircraft turbine fuel, the resulting residue is weighed and reported as milligrams per 100 mL. For motor gasoline, the residue is weighed before and after extracting with n-heptane and the results reported as milligrams per 100 mL.

Not Available

1980-01-01

375

Syngas production from heavy liquid fuel reforming in inert porous media  

E-print Network

hydrogen produced) and coal gasification (18% of the total hydrogen produced) without CCS, and it is used primarily in the chemical and refinery industries [16; 17; 18]. Since hydrogen production from renewable 3 1.2 Fuel reforming and nuclear energy needs... . Pastore and E. Mastorakos. “Rich n-heptane and Diesel Com- bustion in Porous Media”, Experimental Thermal and Fluid Sci- ence, 34:359-365, 2010. • A. Pastore and E. Mastorakos. “Syngas Production from Liquid Fuels in a Non-Catalytic Porous Burner”, Fuel...

Pastore, Andrea

2010-11-16

376

Two-dimensional thin-layer chromatography of Dns-amino acids on reversed-phase silica gel.  

PubMed

Ready-for-use reversed-phase high-performance thin-layer chromatographic plates were used for the separation of Dns-amino acids. The development was performed by using methanol-2% acetic acid (75.25) or methanol-0.01 M Na2HPO4 (75:25). Reversed-phase plates were used also for adsorption chromatography using a non-aqueous solvent system such as benzene-chloroform-acetic acid (50:48:2) or n-heptane-ethyl acetate-acetic acid (65:33:2). Good separations were achieved by using both principles in the two-dimensional arrangement. PMID:6247357

Macek, K; Deyl, Z; Smrz, M

1980-05-30

377

Monodispersed Pd-nanoparticles on carbon fiber fabrics as structured catalyst for selective hydrogenation  

Microsoft Academic Search

Monodispersed Pd-nanoparticles (?8nm) prepared via a modified microemulsion method were deposited on active carbon fibers (ACF) fabrics and studied in a semi-batch 1-hexyne liquid-phase hydrogenation. The catalyst Pd(0.45wt%)\\/ACF demonstrated >96% selectivity to 1-hexene up to 90% of conversion. Initial activity at 303K, 1.3MPa pressure, in n-heptane as a solvent was 0.14kmolH2kgPd-1s-1. Assuming a Langmuir–Hinshelwood kinetics with a weak hydrogen adsorption

N. Semagina; A. Renken; L. Kiwi-Minsker

2007-01-01

378

Superbenzene-porphyrin conjugates.  

PubMed

A free-base porphyrin carrying two hexabenzocoronene (HBC) substituents in a trans arrangement and its zinc complex have been prepared. The compounds were characterized extensively and found to form tricationic dimers in the gas phase. X-ray crystallography confirms for the zinc complex a profound ?-stacking of the HBC moieties. In contrast, the free-base porphyrin incarcerates n-heptane which essentially prevents ?-stacking. Upon excitation of the HBC substituents, efficient energy transfer to the central porphyrin is observed. PMID:25244699

Lungerich, Dominik; Hitzenberger, Jakob F; Marcia, Mario; Hampel, Frank; Drewello, Thomas; Jux, Norbert

2014-11-01

379

Hydrogen bond fluctuations and dispersive interactions of alcohol/alkane mixtures. An ultrasonic relaxation study  

NASA Astrophysics Data System (ADS)

The relaxation behaviour of 1-hexanol/n-heptane and 1-dodecanol/n-tetradecane mixtures has been studied at some compositions using ultrasonic attenuation spectrometry in the frequency range 0.4-3000 MHz. All mixtures reveal a relaxation term due to hydrogen network fluctuations. It is discussed in conjunction with the principle dielectric relaxation of alcohol/alkane mixtures, indicating a dynamically micro-heterogeneous liquid structure. The spectra of the long-chain alcohol system display an additional relaxation due to the structural isomerisation of the hydrocarbon chains. In terms of a torsional oscillator model this relaxation reveals the effect of molecular ordering on the enthalpy of activation.

Kaatze, Udo; Behrends, Ralph

2011-06-01

380

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

381

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

382

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

383

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

384

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

385

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

386

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

387

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

388

Coupled-cluster, Möller Plesset (MP2), Density Fitted Local MP2, and Density Functional Theory Examination of the Energetic and Structural Features of Hydrophobic Solvation: Water and Pentane  

SciTech Connect

The interaction potentials between immiscible polar and non-polar solvents are a major driving force behind the formation of liquid:liquid interfaces. In this work, the interaction energy of water–pentane dimer has been determined using coupled-cluster theory with single double (triple) excitations [CCSD(T)], 2nd order Möller Plesset perturbation theory (MP2), density fitted local MP2 (DF-LMP2), as well as density functional theory using a wide variety of density functionals and several different basis sets. The M05-2X exchange correlation functionals exhibit excellent agreement with CCSD(T) and DF-LMP2 after taking into account basis set superposition error. The gas phase water–pentane interaction energy is found to be quite sensitive to the specific pentane isomer (2,2- dimethylpropane vs. n-pentane) and relative orientation of the monomeric constituents. Subsequent solution phase cluster calculations of 2,2-dimethylpropane and n-pentane solvated by water indicate a positive free energy of solvation that is in good agreement with available experimental data. Structural parameters are quite sensitive to the density functional employed and reflect differences in the two-body interaction energy calculated by each method. In contrast, cluster calculations of pentane solvation of H2O solute are found to be inadequate for describing the organic solvent, likely due to limitations associated with the functionals employed (B3LYP, BHandH, and M05-2X).

Ghadar, Yasaman; Clark, Aurora E.

2012-02-02

389

Preliminary antioxidant profile of Pistacia integerrima Stewart.  

PubMed

To explore the free radical scavenging properties of crude ethanolic extract of galls, bark, leaves, roots of Pistacia integerrima and its subsequent solvent fractions viz., n-hexane, chloroform, ethyl acetate and methanol against 1, 1-diphenyl-2-picrylhydrazyl (DPPH) stable. In vitro DPPH based free radical was employed using querceitin as standard antioxidant while methanol as negative control. Different parts of P. integerrima showed marked scavenging on DPPH in a concentration dependent manner. The ethanolic extract exhibited 60.51 88.51% scavenging effect on DPPH which differentiated upon fractionation. of the part used, leaves of the plant were the least effective while n-hexane was the least dominant fraction. However, the rest of the parts and fractions demonstrated profound scavenging potential. This in-vitro study revealed an outstanding free radical scavenging potential of various solvent fractions of different parts of whole plant P. integerrima. PMID:25015451

Rauf, Abdur; Uddin, Ghias; Khan, Haroon; Roohullah

2014-07-01

390

[Determination of buprofezin, methamidophos, acephate, and triazophos residues in Chinese tea samples by gas chromatography].  

PubMed

A method has been developed for the simultaneous determination of buprofezin, methamidophos, acephate and triazophos residues in Chinese tea samples. The pesticide residues were extracted from tea samples with a mixture of ethyl acetate and n-hexane (50:50, v/v) at 45 degrees C. The extracts were subsequently treated with a column packed with 40 mg of active carbon by gradient elution with ethyl acetate and n-hexane. Buprofenzin and the three organophosphorus pesticides were analyzed by gas chromatography using a DB-210 capillary column and a nitrogen-phosphorus detector. The recoveries for spiked standards were 73.4%-96.9%. The relative standard deviations were all within 4.63%. The limits of quantitation (3sigma) in the tea samples were about 7.0-12.0 microg/kg. PMID:15712876

Zhang, Shuiba; Yi, Jun; Ye, Jianglei; Zheng, Wenhui; Cai, Xueqin; Gong, Zhenbin

2004-03-01

391

Phytochemical investigation and biological studies of Bombax malabaricum flowers.  

PubMed

In this study, extracts of the flowers of the folk medicinal plant Bombax malabaricum DC were biologically and chemically screened. Chemical constituents in the n-hexane fraction from the flowers of B. malabaricum DC were investigated using gas-liquid chromatography (GLC) analysis, affording 14 compounds, including cholesterol, stigmasterol, campesterol and ?-amyrin, while the residual 10 compounds are hydrocarbons. GLC analysis of the fatty acid (FA) esters established the majority abundance of the saturated FA over their unsaturated analogues. The polar methanol fraction afforded seven flavones: vicenin 2 (1), linarin (2), saponarin (3), cosmetin (4), isovitexin (5), xanthomicrol (6) and apigenin (7). Structures 1-7 were established by intensive studies of various spectral data (H-NMR, mass spectroscopy and UV) and comparison with authentic samples. Compounds 1-7 are described here for the first time from this plant. Extracts of n-hexane and methanol exhibited significant antioxidant and antimicrobial activities. PMID:21246441

El-Hagrassi, Ali M; Ali, Mamdouh M; Osman, Abeer F; Shaaban, Mohamed

2011-01-01

392

Immobilization of lipase B within micron-sized poly-N-isopropylacrylamide hydrogel particles by solvent exchange.  

PubMed

The aim of the present work is the use of a water soluble enzyme in an organic solvent, still with a pronounced catalytic activity. Therefore, lipase B from Candida antarctica (CalB) is immobilized within micron-sized thermosensitive p-NIPAM hydrogel particles using a solvent exchange from polar to organic solvents. The absorbed amount of CalB is investigated at different immobilization temperatures. Confocal laser scanning microscopy (CLSM) shows that CalB is homogeneously distributed within the polymer network. An enhanced specific activity of CalB in n-hexane is achieved after immobilization within the p-NIPAM microgels. In order to get information on the supply of the substrate depending on the temperature, the activity is determined at different reaction temperatures. Additionally, the system is stable in the organic solvent, namely n-hexane, and shows a good reusability. PMID:22684227

Gawlitza, Kornelia; Wu, Changzhu; Georgieva, Radostina; Wang, Dayang; Ansorge-Schumacher, Marion B; von Klitzing, Regine

2012-07-21

393

PTP1B inhibitory effect of alkyl p-coumarates from Calystegia soldanella.  

PubMed

In this report, the PTP1B inhibitory effect of Calystegia soldanella was investigated. Bioassay-guided fractionation of the crude extracts revealed that the n-hexane fraction had the strongest PTP1B inhibitory effect. Nine known alkyl p-coumarates were isolated from the n-hexane fraction, and each compound was evaluated for its effect on PTP1B. All compounds effectively inhibited PTP1B activity. The IC50 values of the compounds were 3 (10.8 ?g/mL) > 2 (15.5 ?g/mL) > 7 (26.6 ?g/mL) > 1 (37.0 ?g/mL) > 8 (41.2 ?g/mL) > 9 (43.4 ?g/mL) > 5 (44.7 ?g/mL) > 4 (> 50 ?g/mL) > 6 (> 50 ?g/mL). PMID:25532287

Lee, Jung Im; Kim, In-Hye; Choi, Youn Hee; Kim, Eun-Young; Nam, Taek-Jeong

2014-11-01

394

Near critical phase behaviour of dilute mixtures  

NASA Astrophysics Data System (ADS)

Predictions of the limiting phase behaviour of dilute mixtures of n-decane, n-tetradecane, n-octadecane, and n-docosane with n-hexane in the highly compressible region close to the critical point of n-hexane are presented. The predictions are based on a classical Taylor expansion of the Helmholtz energy about the critical point of the solvent [1, 2] and make use of the measured critical properties of the dilute mixtures. The importance of the Krichevskii parameter as a key factor influencing the limiting phase behaviour of dilute mixtures is demonstrated in the case of infinite dilution partition coefficients as well as solute partial molar volumes, and the link to a statistical mechanical description is made.

Gude, Michael T.; Teja, Amyn S.

395

Phenomenological model of fungal biofilters for the abatement of hydrophobic VOCs.  

PubMed

This work describes the growth of filamentous fungi in biofilters for the degradation of hydrophobic VOCs. The study system was n-hexane and Fusarium solani B1. The system is mathematically described and the main physical, kinetic data and morphological parameters were obtained by independent experiments and validated with data from laboratory experiments. The model describes the increase in the transport area by the growth of the filamentous cylindrical mycelia and its relation with n-hexane elimination in quasi-stationary state in a biofilter. The model describing fungal growth includes Monod-Haldane kinetic and hyphal elongation and ramification. A specific surface area of transport (SSAT) of 1.91 x 10(5) m(2) m(-3) and a maximum elimination capacity (EC) of 248 g m(-3) h(-1) were obtained by the mathematical model simulation, with a 10% of error with respect to the experimental EC. PMID:18781682

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

2008-12-15

396

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

397

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

398

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

399

Antioxidant activity of fractionated extracts of rhizomes of high-altitude Podophyllum hexandrum : Role in radiation protection  

Microsoft Academic Search

Whole extract of rhizomes of Podophyllum hexandrum has been reported earlier by our group to render whole-body radioprotection. High-altitude P. hexandrum (HAPH) was therefore fractionated using solvents of varying polarity (non-polar to polar) and the different fractions were designated as, n-hexane (HE), chloroform (CE), alcohol (AE), hydro-alcohol (HA) and water (WE). The total polyphenolic content (mg% of quercetin) was determined

Raman Chawla; Rajesh Arora; Raj Kumar; Ashok Sharma; Jagdish Prasad; Surendar Singh; Ravinder Sagar; Pankaj Chaudhary; Sandeep Shukla; Gurpreet Kaur; Rakesh Kumar Sharma; Satish Chander Puri; Kanaya Lal Dhar; Geeta Handa; Vinay Kumar Gupta; Ghulam Nabi Qazi

2005-01-01

400

Occurrence of Astaxanthin in the Flower Petals of Adonis annua L  

Microsoft Academic Search

WHEN the dried petals of Adonis annua L. (Ranunculaceæ) (pheasant's eye) are extracted with light petroleum or methanol comparatively large quantities of a deep orange-red carotenoid are obtained. This pigment had an absorption spectrum (in light petroleum, n-hexane, carbon disulphate and pyridine) very similar to that of astaxanthin1; as the pigment is epiphasic in the 90 per cent aqueous methanol\\/light

A. Seybold; T. W. GOODWIN

1959-01-01

401

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

402

Enhanced enantioselectivity of lipase from Pseudomonas sp. at high temperatures and fixed water activity in the ionic liquid, 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]amide  

Microsoft Academic Search

The water activity equilibration over saturated salt solutions was monitored in the ionic liquid 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]amide and in two organic solvents (methyl tert-butylether and n-hexane). Water uptake by the ionic liquid was comparable to that in polar organic solvents. Furthermore, the kinetic resolution of (R,S)-1-phenylethanol catalysed by a lipase from Pseudomonas sp. had a higher selectivity in the ionic liquid

Marrit Eckstein; Peter Wasserscheid; Udo Kragl

2002-01-01

403

Hexanal as a measure of rancidity in low fat foods  

Microsoft Academic Search

and Summary  The concentration of n-hexanal in low fat, dehydrated foods can be determined in 10 min by the gas chromatographic analysis\\u000a of the vapors from a 15 g sample suspended in boiling water. With 4-heptanone as an internal standard good day-to-day reproducibility\\u000a was obtained and the results could be expressed as ppm hexanal in the sample. The onset of rancid

C. W. Fritsch; J. A. Gale

1977-01-01

404

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

405

Trypanocidal, leishmanicidal and antifungal potential from marine red alga Bostrychia tenella J. Agardh (Rhodomelaceae, Ceramiales)  

Microsoft Academic Search

Specimens of the red alga Bostrychia tenella J. Agardh (Rhodomelaceae, Ceramiales) were collected from the São Paulo coast and submitted to room temperature solvent extraction. The resulting extract was fractionated by partitioning with organic solvent. The n-hexane (BT-H) and dichloromethane (BT-D) fractions showed antiprotozoal potential in biological tests with Trypanosoma cruzi and Leishmania amazonensis and presented high activity in an

Rafael de Felício; Sérgio de Albuquerque; Maria Cláudia Marx Young; Nair Sumie Yokoya; Hosana Maria Debonsi

2010-01-01

406

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

407

Stability-Indicating HPTLC Method for Simultaneous Determination of Ezetimibe and Simvastatin  

Microsoft Academic Search

Simvastatin and ezetimibe are used to treat hyperlipidemia. A simple, selective and stability-indicating HPTLC method has\\u000a been established for analysis of simvastatin and ezetimibe. The method has been validated so that both drugs can routinely\\u000a be analyzed simultaneously. The method uses aluminum-backed silica gel 60F254 TLC plates as stationary phase with n-hexane–acetone 6:4 (v\\/v) as mobile phase. Densitometric analysis of

Rahul P. Dixit; Chandrashekhar R. Barhate; Mangal S. Nagarsenker

2008-01-01

408

Characterization of Moringa oleifera Variety Mbololo Seed Oil of Kenya  

Microsoft Academic Search

The oil from Moringa oleifera variety Mbololo seeds from Kenya was extracted using three different procedures including cold press (CP), extraction with n-hexane (H), and extraction with a mixture of chloroform\\/methanol (50:50) (CM). The oil concentration ranged from 25.8% (CP) to 31.2% (CM). The density, refractive index, color, smoke point, viscosity, acidity, saponification value, iodine value, fatty acid methyl esters,

J. Tsaknis; S. Lalas; V. Gergis; V. Dourtoglou; V. Spiliotis

1999-01-01

409

Characterization of Moringa oleifera Seed Oil Variety “Periyakulam 1”  

Microsoft Academic Search

The oil from Moringa oleifera seeds variety Periyakulam 1 (PKM 1) from India was extracted using three different procedures including cold press (CP), extraction with n-hexane (H) and extraction with a mixture of chloroform:methanol (1:1) (CM). The oils were compared with those of a commercial virgin olive oil and Moringa oleifera var. Mbololo seed oil. The oil concentration ranged from

Stavros Lalas; John Tsaknis

2002-01-01

410

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

411

Preparative isolation of four new and two known flavonoids from the leaf of Patrinia villosa Juss. by counter-current chromatography and evaluation of their anticancer activities in vitro  

Microsoft Academic Search

A preparative counter-current chromatography (CCC) was used to isolate and separate chemical constituents from the leaf of Patrinia villosa, a famous traditional Chinese medicinal herb. Six flavonoids including two known and four novel compounds were successfully simultaneous purified by CCC with a two-phase solvent system composed of n-hexane–ethyl acetate–methanol–water (10: 13: 13: 10, v\\/v) by increasing the flow rate of

Jinyong Peng; Guorong Fan; Yutian Wu

2006-01-01

412

C 6-alkane conversion over ?-alumina supported palladium and platinum catalysts  

Microsoft Academic Search

A comparable study of n-hexane and 2,2-dimethylbutane reactions in excess hydrogen carried out on differently loaded Pd\\/Al2O3 and Pt\\/Al2O3 catalysts at ?290°C furnished information which is useful in assessing the role of activated alumina in catalyzing C6-alkane conversion. In particular, it was confirmed that in effect of high temperature reduction (at 600°C) Al2O3 gains a considerable acidity which must play

Maciej Skotak; Zbigniew Karpi?ski

2002-01-01

413

LC determination of citral in Cymbopogon citratus volatile oil  

Microsoft Academic Search

It was the aim of this study to develop and validate a HPLC method for the quantitative determination of citral in Cymbopogon citratus volatile oil. The HPLC assay was performed using a Spherisorb® CN column (250mm×4.6mm, 5?m), a n-hexane:ethanol (85:15) mobile phase and an UV detector (set at 233nm). The following parameters were evaluated: linearity, precision, accuracy, specificity, quantification and

Cristiane da S. Rauber; Sílvia S. Guterres; Elfrides E. S. Schapoval

2005-01-01

414

Insect Sex Pheromone Type Alkenes from the Seeds of Quercus robur  

Microsoft Academic Search

A combination of vacuum liquid chromatography and preparative thin layer chromatography of the combined n-hexane and dichloromethane extracts of the seeds of Quercus robur afforded two insect sex pheromone type alkenes, 5E-tetradecen-1-ol (1) and 6E-tetradecen-1-ol (2), none of which has ever been isolated from any plant sources. The structures of these alkenes were determined by spectroscopic techniques.

S. D. Sarker; Y. Kumarasamy; L. Nahar

2004-01-01

415

Natural wax constituents of a supercritical fluid CO 2 extract from quince ( Cydonia oblonga Mill.) pomace  

Microsoft Academic Search

The chemical constituents of a lipophilic extract from quince (Cydonia oblonga Mill.), obtained by supercritical fluid CO2 extraction of the dried fruit pomace were investigated. Solvent partition of quince wax with n-hexane or acetone yielded an insoluble (crystalline) and a soluble (oily) fraction. Both fractions were analyzed separately\\u000a using gas chromatography\\/mass spectrometry (GC\\/MS). The insoluble fraction consisted of saturated n-aldehydes,

Peter Lorenz; Melanie Berger; Julia Bertrams; Kristian Wende; Kristin Wenzel; Ulrike Lindequist; Ulrich Meyer; Florian C. Stintzing

2008-01-01

416

Determination of Coumarin, 7HydroxyCoumarin, 7Hydroxycoumarin-Glucuronide, and 3Hydroxycoumarin by High-Performance Liquid Chromatography  

Microsoft Academic Search

A selective and sensitive method for the determination of coumarin and its main metabolites 7-hydroxycoumarin, 7-hydroxycoumarin-glucuronide and 3-hydroxycoumarin in human plasma and\\/or urine is described. Coumarin and 7-hydroxycoumarin were extracted from plasma with n-hexane\\/chloroform and with chloroform. After evaporation under vacuum, the residue was redissolved in methanol\\/water and injected onto the HPLC column (LiChroCART 250-4, RP 8e 5 ?m; Merck,

Sheida Sharifi; Hans Christoph Michaelis; Erich Lotterer; Johannes Bircher

1993-01-01

417

Evaluation of antidiarrhoeal activity Rumex maritimus root.  

PubMed

The partitioned n-hexane, ethylacetate and residual methanol extracts of the root of Rumex maritimus were evaluated for antidiarrhoeal activity in mice using castor oil and serotonin induced diarrhoea and also charcoal motility test at 50, 100 and 200 mg/kg body weight dose. Among these, the methanol extract most significantly prolonged the time for induction of diarrhoea, reduced the frequency of diarrhoeal episodes and also decreased the propulsion of charcoal meal through the gastrointestinal tract. PMID:12648830

Rouf, A S S; Islam, M S; Rahman, M T

2003-02-01

418

Preparation of biodiesel from Jatropha curcas L. oil produced by two-phase solvent extraction  

Microsoft Academic Search

In the present work the preparation of biodiesel from Jatropha curcas L. oil produced by two-phase solvent extraction (TSE) was studied. The experimental results of TSE process showed that the optimal extraction conditions were 30g samples, 240mL of extraction solvent mixture and methanol\\/n-hexane volume ratio 60:40, extraction temperature 35°C, extraction time 30min. Further, the effect of methanol recycling on the

Junfeng Qian; Haixian Shi; Zhi Yun

2010-01-01

419

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

420

Formulation and Evaluation of 5FU Loaded Eudragit Microspheres: Effect of Various Eudragit on Micromeretic Properties of Microspheres  

Microsoft Academic Search

The aim of the present study was to prepare and evaluate microspheres of Eudragit (RS, RL and RSPO) containing an anticancer drug 5-FU. Microspheres were prepared by O\\/O solvent evaporation method using a acetone\\/liquid paraffin system. Magnesium stearate was used as the droplet stabilizer and n-hexane was added to harden the microspheres. The prepared microspheres were characterized for their micromeretic

Subhash Vaghani; S. Vasanti; Kiran Chaturvedi; C. S. Satish; S. J. Shankar

2008-01-01

421

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

422

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

423

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

424

Extraction of Tb(III) with N, N, N', N'- tetrabutylmalonamide  

Microsoft Academic Search

The study on the extraction and separation of rare earths with new extractants is important in rare earth hydrometallurgy and nuclear fuel reprocessing. In this work, a new synthesis method of N,N,N',N'-tetrabutylmalonamide (TBMA) is described with a yield higher than 80 %. The extraction behavior of TBMA employing n-hexane-20 % n-octanol, benzene and toluene as diluents toward Tb(III) was investigated.

Sun Guoxin; Cui Yu; Jiang Runtian; Xu Rongqi; Sun Sixiu

2002-01-01

425

Submerged electric arc between graphite electrodes: a one-pot tool for the synthesis of long-chain polyynes in solution  

Microsoft Academic Search

Polyynes, a class of molecules described by the general formula H–(C?C)mH (where m is an integer) can be synthesized using an electric arc between graphite electrodes submerged in an organic solvent such as methanol, n-hexane, n-dodecane, decahydronaphthalene or acetonitrile. When the electric arc is used in acetonitrile at ?40°C, polyyne chains of up to 18 carbon atoms (m=9) have been

Franco Cataldo

2004-01-01

426

Synthesis of polyynes in a submerged electric arc in organic solvents  

Microsoft Academic Search

The products formed by the electric arc between graphite electrodes submerged in organic solvents like acetonitrile, n-hexane and methanol consist of a series of polyynes having the general chemical structure: H?(C?C)m?H (with m an integer 1,2,3,…m). The polyynes were separated through liquid chromatography (HPLC) and identified through their characteristic electronic absorption spectra recorded by a diode-array detector. When acetonitrile was

Franco Cataldo

2004-01-01

427

Polyynes and cyanopolyynes synthesis from the submerged electric arc: about the role played by the electrodes and solvents in polyynes formation  

Microsoft Academic Search

The products of the electric arc between graphite electrodes have been investigated by high performance liquid chromatography-diode-array detector (HPLC-DAD) analysis in various media: distilled water, liquid nitrogen, methanol, ethanol, n-hexane and benzene. In distilled water, hydrogen capped polyynes H–(C?C)n–H were the unique products demonstrating that carbon is supplied by the graphite electrodes while hydrogen is supplied by the solvent plasmalysis

Franco Cataldo

2004-01-01

428

Gas chromatographic method for the determination of hexaconazole residues in black tea  

Microsoft Academic Search

A highly reliable, quantitative and sensitive analytical method for determining the residues of the fungicide, hexaconazole\\u000a in black tea is described. The proposed method is based on liquid-liquid extraction followed by gas chromatographic determination,\\u000a using nitrogen phosphorus detector (GC-NPD) for the identification and quantitation of hexaconazole. The most appropriate\\u000a solvent mixture for extracting hexaconazole residues from black tea was n-hexane:acetone

Chinnachamy Karthika; Paul James Sachin

2008-01-01

429

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

E-print Network

.4.2012 Obs: matrikelnummer = a b c d e och z = max(c,d,e) Note: input data depends on matriculation number = a b c d e and z = max(c,d,e). 1205. Pentan (C5) ska separeras från hexan (C6) i en vätskefas vid kokpunkts-temperaturen (dvs. q = 1). Trycket är p = 1.05+(d/40) bar. �terflödesförhållandet R

Zevenhoven, Ron

430

Influence of Crystal Expansion/Contraction on Zeolite Membrane Permeation  

SciTech Connect

X-ray diffraction was used to measure the unit cell parameters of B-ZSM-5, SAPO-34, and NaA zeolite powders as a function of adsorbate loading at 303 K, and in one case, at elevated temperatures. Most adsorbates expanded the zeolite crystals below saturation loading at 303 K: n-hexane and SF6 in B-ZSM-5, methanol and CO2 in SAPO-34, and methanol in NaA zeolite. As the loadings increased, the crystals expanded more. Changes in the unit cell volumes of B-ZSM-5 and SAPO-34 zeolite powders correlated with changes in permeation through zeolite membranes defects. When the zeolite crystals expanded or contracted upon adsorption, the defect sizes decreased or increased. In B-ZSM-5 membranes, the fluxes through defects decreased dramatically when n-hexane or SF6 adsorbed. In contrast, i-butane adsorption at 303 K contracted B-ZSM-5 crystals at low loadings and expanded them at higher loadings. Correspondingly, the flux through B-ZSM-5 membrane defects increased at low i-butane loadings and decreased at high loading because the defects increased in size at low loading and decreased at high loadings. At 398 K and 473 K, n-hexane expanded the B-ZSM-5 unit cell more as the temperature increased from 303 to 473 K. The silicalite-1 and B-ZSM-5 unit cell volumes expanded similarly upon n-hexane adsorption at 303 K; boron substitution had little effect on volume expansion.

Sorenson, Stephanie G [University of Colorado, Boulder; Payzant, E Andrew [ORNL; Noble, Richard D [University of Colorado, Boulder; Falconer, John L. [University of Colorado, Boulder

2010-01-01

431

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

432

Quantification of rabeprazole in human plasma by liquid chromatography–tandem mass spectrometry  

Microsoft Academic Search

An analytical method based on liquid chromatography coupled with tandem mass spectrometry detection has been developed and validated for the determination of rabeprazole in human plasma using omeprazole as the internal standard. The analyte and internal standard was extracted with n-hexane–dichloromethane–isopropanol (20:10:1, v\\/v) and chromatographed isocratically on a Diamonsil C18 analytical column. Methanol was used as the mobile phase to

Yong Zhang; Xiaoyan Chen; Qi Gu; Dafang Zhong

2004-01-01

433

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

434

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

435

An assessment of heavy metal contamination in surface sediment using statistical analysis  

Microsoft Academic Search

The distribution and accumulation of heavy metals in the sediments, especially those nearest of wastewater discharges of south\\u000a of Spain, were investigated. Sediment samples from 14 locations were collected and characterised for metal content (e.g. Ni,\\u000a Cu, Zn, Cr, Pb, Mn, Cd and Hg), organic carbon, total nitrogen, total phosphorous, n-hexane-extractable material, carbonates and grain size. Concentration data were processed

M. R. Rodríguez-Barroso; J. L. García-Morales; M. D. Coello Oviedo; J. M. Quiroga Alonso

2010-01-01

436

Fatal intoxication with tianeptine ( Stablon ®)  

Microsoft Academic Search

Tianeptine (Stablon®), although structurally similar to tricyclic antidepressants, acts by enhancing the reuptake of serotonin. A fatal case is presented involving a 26-year-old man, found lying in bed with a “mushroom of foam” around his mouth. Empty blister packs of Stablon® and a suicide note were found next to the body. A liquid–liquid extraction procedure with n-hexane: ethyl acetate and

Paula Proença; Helena Teixeira; João Pinheiro; Paula V. Monsanto; Duarte Nuno Vieira

2007-01-01

437

The thermodynamic properties of mixtures of normal hexane and branched paraffin hydrocarbons  

E-print Network

Committee: Dr. Richard R. Davison The vapor-liquid equilibrium of hydracarbon binary systems of n-hexane with 2-methylpentane, 3-methylpentane, and 2, 4-dimethylpentane are studied at 10'C, 20'C, 30'C, and 40'C. Isothermal values of the total vapor... pressures of pure components and mixtures were obtained by using a modified static vapor pressure apparatus. Barker's least squares method was employed to calcu- late equilibrium vapor compositions, activity coeffi- cients, and excess thermodynamic...

Ho, Chun Leung

2012-06-07

438

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

439

Evidence for magnetic interactions among magnetite nanoparticles dispersed in photoreticulated PEGDA-600 matrix  

Microsoft Academic Search

Magnetite nanoparticles having mean diameter of about 8 nm have been prepared by a thermo-chemical route. Different amounts\\u000a (5 and 10% wt) of a stable dispersion of magnetite nanoparticles in n-hexane were added to polyethylene glycol diacrylate (PEGDA-600) oligomer containing 2% wt of radicalic photoinitiator. The\\u000a homogenized mixture was poured on a silica glass substrate and the resulting film was photoreticulated in N2

P. Allia; P. Tiberto; M. Coisson; A. Chiolerio; F. Celegato; F. Vinai; M. Sangermano; L. Suber; G. Marchegiani

440

Anti-proliferative effects of estrogen receptor-modulating compounds isolated from Rheum palmatum  

Microsoft Academic Search

The Rheum palmatum L., a traditional medicine in Korea, was screened for their estrogenic activity in a recombinant yeast system with a human\\u000a estrogen receptor (ER) expression plasmid and a reporter plasmid used in a previous study. The EC50 values of the n-hexane, dichloromethane, ethyl acetate, n-butanol, and water fractions of the methanolic extract of R. palmatum in the yeast-based

Se Chan Kang; Chang Min Lee; Eui Su Choung; Jong Phil Bak; Jong Jin Bae; Hyun Sook Yoo; Jong Hwan Kwak; Ok Pyo Zee

2008-01-01

441

Catalytic properties and deactivation behavior of crystalline microporous MAPO-36  

Microsoft Academic Search

MAPO-36 showed high catalytic activity in conversion reactions of alcohols, linear, branched, and cycloalkanes, and aromatics. In ethanol, n-hexane, cyclohexane, and isooctane conversion reactions, MAPO-36 showed significantly higher conversion and concentration of aromatics than MAPO-5, SAPO-5, and AIPO[sub 4]-5. The distribution of aliphatics and aromatics is different in these reactions over MAPO-36, MAPO-5, SAPO-5, AIPO[sub 4]-5, and H-ZSM-5. MAPO-36 exhibited

D Akolekar

1993-01-01

442

Separation of Styrene-Butyl Methacrylate Copolymers by High Performance Liquid Chromatography  

Microsoft Academic Search

Styrene\\/n-butyl methacrylate (S\\/nBMA) and styrene\\/t-butyl methacrylate (S\\/tBMA) copolymers were separated by chemical composition using HPLC. In the case of normal phase HPLC using acrylamide gel or acrylonitrile gel as a stationary phase, S\\/nBMA and S\\/tBMA copolymers were separated by chemical composition. S\\/BMA copolymers were eluted from higher styrene content using dichloromethane\\/n-hexane as an eluent, while with the opposite elution order

Kenji Ogino; Tooru Maruo; Hisaya Sato

1994-01-01

443

Process optimization studies on solvent extraction with naphthalene-2-boronic acid ion-pairing with trioctylmethylammonium chloride in sugar purification using design of experiments  

Microsoft Academic Search

The extraction of xylose and glucose from aqueous solution with naphthalene-2-boronic acid (N2B) in diluents of n-hexane:1-octanol (85:15 v\\/v) was investigated. The influence of pH, N2B concentration and phase ratio (O\\/W) (organic phase volume to aqueous phase volume) were investigated for an optimized condition of xylose and glucose extraction from the aqueous solution. The optimization process was analyzed using Central

H. Abdul Aziz; A. H. Kamaruddin; M. Z. Abu Bakar

2008-01-01

444

[Screening method for 29 forbidden or limited synthetic pigments in cheese by liquid chromatography/quadrupole time-of-flight mass spectrometry].  

PubMed

A screening method for 29 forbidden or limited synthetic pigments in cheese samples was established by liquid chromatography/quadrupole time-of-flight mass spectrometry (LC/Q-TOF MS). The pigments were extracted by n-hexane/water (3:1, v/v). After extraction, the n-hexane extract, water extract and residue, were obtained. The n-hexane extract was then cleaned-up by gel permeation chromatography (GPC). The water extract was extracted by acetonitrile, and the residue by ammonia water/methanol (1:99, v/v). The results showed that the 29 synthetic pigments with a wide range of polarities were extracted effectively with the recoveries between 70% and 95%, and matched well by Q-TOF MS precision mass searching to the mass spectral library with matching scores between 59. 66 and 99. 47. The quantitative analysis of the 29 pigments was carried out by Target MS/MS. The limits of detection (LODs) for 8 Sudan dyes were 0.4-2.5 micro/kg while for 21 water-soluble synthetic pigments were 20-80 microg/kg. The screening method is suitable for a wide range of synthetic pigments, and can be applied to food samples with proteins and fat in matrix. PMID:22097789

Zhao, Yansheng; Yang, Minli; Zhang, Feng; Feng, Feng; Chu, Xiaogang; Dong, Ying

2011-07-01

445

Analysis of Dns-amino acids by liquid chromatography. I. Selection of optimum mobile phase composition for separation of Dns-amino acids on polyvinyl acetate gel.  

PubMed

The separation of a mixture of ten Dns-amino acids (Gns-Gly, -Ala, -Val, -Leu, -Pro, -Hypro, -Met, -Ser, -Asn and -Gln) was carried out by liquid chromatography by using macroreticular polyvinyl acetate gel as a packing material. Different mobile phase systems were investigated, based mainly on mixtures of n-hexane with ethanol, methanol, chloroform, acetone, methyl ethyl ketone, ethyl acetate, dioxane and tetrahydrofuran. The solvent composition was fixed so as to elute all of the components of the sample mixture in a practical period of 2 h. Satisfactory separation of the ten components was obtained with the n-hexane-ethanol (90:10) system. The presence of methanol as a modifier in the n-hexane was effective in reducing the elution time, but the separation was not as satisfactory. Chloroform or dioxane was useful only for the separation of Ser, Asn and Gln. Acetone, methyl ethyl ketone, ethyl acetate and tetrahydrofuran were not suitable for practical separations of Dns-amino acids. PMID:1150766

Yamabe, T; Takai, N; Nakamura, H

1975-02-12

446

Preparation of biodiesel from Jatropha curcas L. oil produced by two-phase solvent extraction.  

PubMed

In the present work the preparation of biodiesel from Jatropha curcas L. oil produced by two-phase solvent extraction (TSE) was studied. The experimental results of TSE process showed that the optimal extraction conditions were 30 g samples, 240 mL of extraction solvent mixture and methanol/n-hexane volume ratio 60:40, extraction temperature 35 degrees C, extraction time 30 min. Further, the effect of methanol recycling on the TSE process was also investigated. After TSE process, the investigations were carried out on transesterification of methanol with oil-n-hexane solution coming from TSE process in the presence of sodium hydroxide as the catalyst. The conversion could achieve 98% with 3:1 n-hexane/oil weight ratio, 60 degrees C reaction temperature, 7:1 methanol/oil mole ratio, 1.1% alkali catalyst concentration and 120 min reaction time. The properties of fatty acid methyl ester (FAME) product prepared from Jatropha curcas L. oil produced by two-phase solvent extraction met the ASTM specifications for biodiesel. PMID:20434330

Qian, Junfeng; Shi, Haixian; Yun, Zhi

2010-09-01

447

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

448

Chemical composition of desert willow (Salix psammophila) grown in the Kubuqi Desert, Inner Mongolia, China: bark extracts associated with environmental adaptability.  

PubMed

Bark of desert willow (Salix psammophila, Spsa) grown in Inner Mongolia was successively extracted with n-hexane, diethyl ether, acetone, methanol, and hot water to examine chemical components associated with its environmental adaptability to desert conditions. The yield of n-hexane extract (5.0% based on dry bark), mainly composed of wax, was higher than those of acetone and methanol extracts (3.7% and 4.2%, respectively), whereas the yields of n-hexane extract (1.4%) from willow bark grown in humid areas were much lower than those of acetone (17.4% and 19.9%) and methanol (12.5% and 14.0%) extracts. Unlike other willow bark samples, Spsa bark contained a certain amount of sugar alcohols. In particular, we identified arabinitol (0.21%), which has not previously been reported as a major component of extracts of willow bark. The high content of wax and sugar alcohol would be associated with the ability of Spsa to survive in desert conditions. Accumulation of wax on the outer bark surface would reduce water loss, while sugar alcohols might improve freezing tolerance. PMID:24274758

Kubo, Satoshi; Hashida, Koh; Makino, Rei; Magara, Kengo; Kenzo, Tanaka; Kato, Atsushi; Aorigele

2013-12-18

449

Stereoselective determination of allethrin by two-dimensional achiral/chiral liquid chromatography with ultraviolet/circular dichroism detection.  

PubMed

A two-dimensional achiral/chiral HPLC method with circular dichroism (CD) detection was optimized for the stereochemical resolution and determination of the elution order of the eight stereoisomers of synthetic allethrin. A monolithic silica HPLC column (Chromolith, Merck, 100 mm x 4.6 mm i.d.) was put orthogonally to an enantioselective OJ Daicel column (250 mm x 4.6 mm i.d.) by means of a switching valve. The resolution of cis and trans diastereoisomers on the silica column was obtained by using a mobile phase consisting of n-hexane:tert-butyl methyl ether (96:4) (v/v) at a flow rate of 1 ml min(-1). The cis and trans peaks were then switched to the enantioselective OJ column separately in two subsequent injections. The resolution of the four trans stereoisomers was accomplished by using n-hexane:tert-butyl methyl ether (90:10) (v/v), while the mobile phase composition for the four cis stereoisomers consisted of n-hexane:isopropanol (99.3:0.7) (v/v). The CD based detection system allowed the determination of the elution order on the basis of the CD signals of the single stereoisomers, together with the injection of pure stereoisomers. Under the final conditions, the validated method was applied to the determination of stereoisomeric composition and absolute configuration of the prevailing stereoisomers of real samples, i.e. commercial batches of different sources of d-allethrin. PMID:15387172

Mancini, F; Fiori, J; Bertucci, C; Cavrini, V; Bragieri, M; Zanotti, M C; Liverani, A; Borzatta, V; Andrisano, V

2004-08-13

450

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

451

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

452

Diterpenoids and flavonoids from the fruits of Vitex agnus-castus and antioxidant activity of the fruit extracts and their constituents.  

PubMed

From the n-hexane fraction of the fruits of Vitex agnus-castus, two labdane-type diterpenes, vitetrifolin B and C, were isolated by means of multiple chromatographic separations, together with the previously identified rotundifuran, vitexilactone and the sesquiterpene spathulenol. From the EtOAc fraction, eupatorin was identified for the first time, besides the known casticin, penduletin, vitexin and orientin. The n-hexane, EtOAc and MeOH-H(2)O fractions of the MeOH extract of Agni-casti fructus were subjected to in vitro antioxidant assays. The EtOAc extract displayed a significant concentration-dependent effect when tested by 1,1-diphenyl-2-picrylhydrasyl (DPPH) free radical assay (IC(50) = 68 microg/mL) and against the autooxidation of a standard rat brain homogenate (IC(50) = 14 microg/mL). The MeOH-H(2)O fraction was less active with 3643 microg/mL (DPPH test) and IC(50) = 125 microg/mL (rat brain homogenate), while the n-hexane phase proved to be inactive. The main flavonoid constituents of the EtOAc extract, casticin, vitexin and orientin were assayed for antioxidant activity and found that only casticin possesses a marked lipid peroxidation inhibitory effect (IC(50) = 0.049 mm) compared with that of the positive control ascorbic acid (IC(50) = 0.703 mm). PMID:17262892

Hajdú, Zsuzsanna; Hohmann, Judit; Forgo, Peter; Martinek, Tamás; Dervarics, Máté; Zupkó, István; Falkay, György; Cossuta, Daniel; Máthé, Imre

2007-04-01

453

Dielectric constant of liquid alkanes and hydrocarbon mixtures.  

PubMed

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. PMID:11538383

Sen, A D; Anicich, V G; Arakelian, T

1992-01-01

454

[Analysis of pesticides including chlorine in welsh onions and mushrooms using gas chromatograph with an atomic emission detector (GC-AED)].  

PubMed

An analytical method for the determination of 32 kinds of pesticide residues in onions, Welsh onions and mushrooms using gas chromatograph with an atomic emission detector (GC-AED) was developed. The pesticides were extracted with acetone-n-hexane (2:3) mixture. The crude extract was partitioned between 5% sodium chloride and ethyl acetate-n-hexane (1:4) mixture. The extract was passed through a Florisil mini-column for cleanup with 10 mL of acetone-n-hexane (1:9) mixture. Although the sensitivity of GC-AED was inferior to that of GC-ECD, GC-AED has a superior element-selectivity. Therefore pesticide residues in foods could be analyzed more exactly by using GC-AED. Thirty-two pesticides including chlorine in onion, Welsh onion and shiitake mushroom were detected without interference. Recoveries of these pesticides from samples determined by GC-AED were 64-114%, except for a few pesticides. PMID:15794090

Tateishi, Yukinari; Takano, Ichiro; Kobayashi, Maki; Tamura, Yasuhiro; Tomizawa, Sanae; Sakai, Naoko; Kamijo, Kyoko; Nagayama, Toshihiro; Kamata, Kunihiro

2004-12-01

455

Computational study of hydrocarbon adsorption in metal-organic framework Ni2(dhtp)  

SciTech Connect

Molecular dynamic simulations were carried out to study the sorption, structural properties, and diffusivities of n-hexane and cyclohexane adsorbed in Ni2(dhtp). The results indicated strong interactions between the alkanes and the host material. The free energy perturbation method was employed to investigate the adsorption free energies of methane, ethane, n-butane, n-hexane and cyclohexane. For linear alkanes, the free energy lowered as the length of the carbon chain increased. Also, the adsorption of n-hexane was preferred over cyclohexane, due to its ability to rearrange its structure to maximize contacts with the host. Furthermore, due to the large pore size of Ni2(dhtp), higher loadings of alkanes did not significantly affect the alkane structure, and enhanced the free energy of adsorption for subsequent alkanes being loaded. According to our studies, Ni2(dhtp) has a very promising potential for adsorption and storage of alkanes. This work was supported by the US Department of Energy Basic Energy Sciences' Chemical Sciences, Geosciences & Biosciences Division. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

Sun, Xiuquan; Wick, Collin D.; Thallapally, Praveen K.; McGrail, B. Peter; Dang, Liem X.

2011-03-31

456

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

457

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

458

[Identification of migrants from nitrile-butadiene rubber gloves].  

PubMed

Polyvinyl chloride gloves containing di(2-ethylhexyl) phthalate are restricted for food contact use. In their place, disposable gloves made from nitrile-butadiene rubber (NBR) are used in contact with foodstuffs. Some unknown substances were found to migrate into n-heptane from NBR gloves. By GC/MS, HR-MS and NMR, their chemical structures were confirmed to be 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (used as a plasticizer), 4,4'-butylidenedi(6-tert-butyl-m-cresol), a mixture of styrenated phenols consisting of 2-(alpha-methylbenzyl)phenol, 4-(alpha-methylbenzyl)phenol, 2,6-di(alpha-methylbenzyl)phenol, 2,4-di(alpha-methylbenzyl)phenol and 2,4,6-tri(alpha-methylbenzyl)phenol (used as antioxidants), and 2,4-di-tert-butylphenol, which seems to a degradation product of antioxidant. Migration levels of these compounds were 1.68 micrograms/cm2 of 2,4-di-tert-butylphenol, 2.80 micrograms/cm2 of 2,2,4-trimethyl-1,3-pentanediol diisobutyrate, 46.08 micrograms/cm2 of styrenated phenols and 4.22 micrograms/cm2 of 4,4'-butylidenedi(6-tert-butyl-m-cresol) into n-heptane, respectively. The content of total styrenated phenols was 6,900 micrograms/g in NBR gloves. PMID:12846157

Mutsuga, Motoh; Kawamura, Yoko; Wakui, Chiseko; Maitani, Tamio

2003-04-01

459

Pervaporation separation of thiophene-heptane mixtures with polydimethylsiloxane (PDMS) membrane for desulfurization.  

PubMed

Cross-linked polydimethylsiloxane (PDMS)-polyetherimide (PEI) composite membranes were prepared, in which asymmetric microporous PEI membrane prepared with phase inversion method was acted as the microporous supporting layer in the flat-plate composite membrane. Membrane characterization was conducted by Fourier transform infrared and scanning electronic microscopy analysis. The composite membranes were employed in pervaporation separation of n-heptane-thiophene mixtures. Effect of amount of PDMS, cross-linking temperature, amount of cross-linking agent, and cross-linking time on the separation efficiency of n-heptane-thiophene mixtures was investigated experimentally. Experiment results demonstrated that 80-100 degrees degrees C of cross-linking temperature was more preferable for practical application, as the amount of cross-linking agent was up to 20 wt.%, and 25 wt.% of PDMS amount was more optimal as far as flux and sulfur enrichment factor were concerned. In addition, the swelling degree of and stableness of composite membrane during long-time operation were studied, which should be significant for practical application. PMID:18830823

Chen, Jian; Li, Jiding; Qi, Rongbin; Ye, Hong; Chen, Cuixian

2010-01-01

460

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

461

Oxides of Nitrogen Emissions from the Combustion of Monodisperse Liquid Fuel Sprays. Ph.D. Thesis  

NASA Technical Reports Server (NTRS)

A study of NO sub x formation in a one dimensional monodisperse spray combustion system, which allowed independent droplet size variation, was conducted. Temperature, NO and NO sub x concentrations were measured in the transition region, encompassing a 26 to 74 micron droplet size range. Emission measurements of hydrocarbons, carbon monoxide, carbon dioxide and oxygen were also made. The equivalence ratio was varied between 0.8 and 1.2 for the fuels used, including methanol, isopropanaol, n-heptane and n-octane. Pyridine and pyrrole were added to n-heptane as nitrogen-containing additives in order to simulate synthetic fuels. Results obtained from the postflame regions using the pure fuels indicate an optimum droplet size in the range of 43 to 58 microns for minimizing NO sub x production. For the fuels examined, the maximum NO sub x reductions relative to the small droplet size limit were about 10 to 20% for lean and 20 to 30% for stoichiometric and rich mixtures. This behavior is attributed to droplet interactions and the transition from diffusive to premixed type of burning. Preflame vaporization controls the gas phase stoichiometry which has a significant effect on the volume of the hot gases surrounding a fuel droplet, where NO sub x is formed.

Sarv, H.

1985-01-01

462

Group type analysis of asphalt by column liquid chromatography  

SciTech Connect

An improved analysis method for characterization of asphalt was established. The method is based on column chromatography technique. The asphalts were separated into four groups: saturates, aromatics, resins, and asphaltenes, quantitatively. About 0.1 g of sample was required in each analysis. About 20 mL of n-heptanes was used to separate out saturates first. Then about 35 mL of n-heptanes/dichloromethane (.5, v/v) mixture was used to separate out aromatics. About 30 mL of dichloromethane/tetrahydrofuran (1/3, v/v) mixture was used to separate out resin. The quality of the separation was confirmed by infrared spectra (IR) and {sup 1}H NMR analysis. The model compounds, tetracosan for saturates, dibenz(o)anthracen for aromatics, and acetanilide for resins were used for verification. The IR and {sup 1}H NMR analysis of the prepared fractions from the column liquid chromatography were in good agreement that of pure reagents.

Zhang, C.; Yang, J.; Xue, Y.; Li, Y. [Chinese Academy of Science, Taiyuan (China)

2008-07-01

463

Screening of crude oils for asphalt precipitation: Theory, practice, and the selection of inhibitors  

SciTech Connect

This paper describes a simple method to screen crude oils for their tendency to precipitate asphalt, which may cause problems during production. The method is based on a thermodynamic model of asphalt solubility, derived earlier by Flory and Huggins. The most important parameters in this model are the Hildebrand solubility parameters for oil and asphaltene, and their molar volumes. The oil parameters can all be correlated with the in-situ density of the crude. It is shown that heavy crudes usually will give fewer problems with asphalt precipitation, despite their higher asphaltene content, certainly if the reservoir pressure is close to bubblepoint pressure. Consequently, the tendency for asphalt precipitation is mainly determined by three parameters: the extent to which the crude is undersaturated with gas, the density of the crude at reservoir conditions, and its saturation with asphalt at downhole conditions. Apart from the simple screening method, more elaborate methods are described to assess the potential for asphalt precipitation more accurately; asphaltene analysis on produced reservoir fluid and tank oil; n-heptane titration of the tank oil; visual inspection of a bottom-hole sample in a high-pressure cell during pressure reduction; and dynamic flow tests on tank oil after n-heptane addition.

Boer, R.B. de; Leerlooyer, K.; Bergen, A.R.D. van (Koninklijke Shell E and P Lab., Rijswijk (Netherlands)); Eigner, M.R.P.

1995-02-01

464

Perinaphthenone phototransformation in a model of leaf epicuticular waxes.  

PubMed

Perinaphthenone (1H-phenalen-1-one, PN) is a reference photosensitizer producing singlet oxygen with a quantum yield close to one in a large variety of solvents. It is also the basic structure of a class of phototoxic phytoalexins. In this work, the PN photoreactivity was studied for the first time in a paraffinic wax, used as model of leaf epicuticular waxes. The PN photodegradation was monitored by UV-Vis spectroscopy. The triplet excited state, singlet oxygen and the hydroxyperinaphthenyl radical were detected by diffuse reflectance laser flash photolysis, near infrared phosphorescence and by EPR spectroscopy, respectively. The PN phototransformation was found to be fivefold faster in the wax than in n-heptane under steady-state irradiation. The hydroxyperinaphthenyl radical formation was observed in aerated irradiated paraffin wax while in n-heptane solution the radical was observed only in the absence of oxygen. These results show that under continuous irradiation, PN is much more easily phototransformed in a solid environment than in solution. Several photoproducts were identified, in particular phenalanone, PN dimers, and oxidized PN-alkanes adducts. Finally, when pyrethrum extract is added into the wax along with PN, the hydroxyperinaphthenyl radical concentration was increased by a factor of 2.4. Such photochemical reactions may occur when systemic pesticides enter the plant cuticle. PMID:24300996

Trivella, Aurélien S; Monadjemi, Shirin; Worrall, David R; Kirkpatrick, Iain; Arzoumanian, Emmanuel; Richard, Claire

2014-01-01

465

Laminar burning velocities at high pressure for primary reference fuels and gasoline: Experimental and numerical investigation  

SciTech Connect

Spherical flames of n-heptane, iso-octane, PRF 87 and gasoline/air mixtures are experimentally investigated to determine laminar burning velocities and Markstein lengths under engine-relevant conditions by using the constant volume bomb method. Data are obtained for an initial temperature of 373 K, equivalence ratios varying from {phi}=0.7 to {phi}=1.2, and initial pressures from 10 to 25 bar. To track the flame front in the vessel a dark field He-Ne laser Schlieren measurement technique and digital image processing were used. The propagating speed with respect to the burned gases and the stretch rate are determined from the rate of change of the flame radius. The laminar burning velocities are obtained through a linear extrapolation to zero stretch. The experimentally determined Markstein numbers are compared to theoretical predictions. A reduced chemical kinetic mechanism for n-heptane and iso-octane was derived from the Lawrence Livermore comprehensive mechanisms. This mechanism was validated for ignition delay times and flame propagation at low and high pressures. In summary an overall good agreement with the various experimental data sets used in the validation was obtained. (author)

Jerzembeck, S.; Peters, N. [RWTH, Aachen (Germany); Pepiot-Desjardins, P.; Pitsch, H. [Department of Mechanical Engineering, Stanford University, CA (United States)

2009-02-15

466

A reduced thermokinetic model for the autoignition of fuels with variable octane ratings  

SciTech Connect

The autoignition characteristics of the reference fuels i-octane, n-heptane, and their mixtures at temperatures 600--1,500 K and pressures ranging 0.3--4.2 MPa are studied by means of a reduced kinetic mechanism comprising five species in six reactions altogether. The scheme is readily adaptable to mixtures of the primary reference fuels via input of an octane number between 0 (= n-heptane) and 100 (= i-octane). Emphasis is placed on the dependence of ignition delay on gas temperature, on the evolution of reaction as portrayed in the temperature-time records, and on the multitude of dynamic features, e.g., two-stage (or multistage) ignition and negative temperature coefficient characteristics inherent to alkane combustion. The reduced model was fitted to numerical results derived from quantitative kinetic modelling and validated against currently available data from experimental systems. It was originally designed for application in a computational fluid dynamics code based on a transport equation for the joint probability density function (PDF) of the reacting species. Flame propagation and engine ``knock`` may thus be described by one consistent model.

Schreiber, M.; Sakak, A.S.; Lingens, A. [RWTH Aachen (Germany). Lehrstuhl fuer Technische Thermodynamik; Griffiths, J.F. [Univ. of Leeds (United Kingdom). School of Chemistry

1994-12-31

467

Fischer Tropsch synthesis in supercritical fluids. Quarterly technical progress report, April 1, 1995--June 30, 1995  

SciTech Connect

Our objective for this quarter was to study the effect of co-feeding a 1-olefin on the Ruhrchemie catalyst activity and selectivity, during-both conventional Fisher-Tropsch synthesis (FTS) and FTS under supercritical conditions. We used propane as the supercritical fluid and 1-dodecene (1-C{sub 12}H{sub 24}) in this test. Motivation for this study was the work of Fujimoto and co-workers who reported that suppression of methane and enhancement of high molecular weight hydrocarbons selectivities occurs with co-feeding of 1-olefins (1-heptene, 1-tetradecene, or 1-hexadecene) during FTS under supercritical conditions, but not during the conventional FTS (Co-La catalyst supported on silica in supercritical n-pentane).The diffusion coefficients of products in supercritical fluids is discussed.

Akgerman, A.; Bukur, D.B.

1996-05-01

468

A time-accurate algorithm for chemical non-equilibrium viscous flows at all speeds  

NASA Technical Reports Server (NTRS)

A time-accurate, coupled solution procedure is described for the chemical nonequilibrium Navier-Stokes equations over a wide range of Mach numbers. This method employs the strong conservation form of the governing equations, but uses primitive variables as unknowns. Real gas properties and equilibrium chemistry are considered. Numerical tests include steady convergent-divergent nozzle flows with air dissociation/recombination chemistry, dump combustor flows with n-pentane-air chemistry, nonreacting flow in a model double annular combustor, and nonreacting unsteady driven cavity flows. Numerical results for both the steady and unsteady flows demonstrate the efficiency and robustness of the present algorithm for Mach numbers ranging from the incompressible limit to supersonic speeds.

Shuen, J.-S.; Chen, K.-H.; Choi, Y.

1992-01-01

469

Sub-ppm detection of vapors using piezoresistive microcantilever array sensors  

NASA Astrophysics Data System (ADS)

The performance of microfabricated piezoresistive cantilever array sensors has been evaluated using various vapors of volatile organic compounds including alkanes with different chain length from 5 (n-pentane) to 14 (n-tetradecane). We demonstrate that piezoresistive microcantilever array sensors have the selectivity of discriminating individual alkanes in a homologous series as well as common volatile organic compounds according to principal component analysis. We developed a new method to evaluate the sensitivity, taking advantage of the low vapor pressures of alkanes with longer chains, such as n-dodecane, n-tridecane and n-tetradecane, under saturated vapor conditions. This method reveals sub-ppm sensitivity and the cantilever response is found to follow the mass of evaporated analytes as calculated using a quantitative model based on the Langmuir evaporation model.

Yoshikawa, Genki; Lang, Hans-Peter; Akiyama, Terunobu; Aeschimann, Laure; Staufer, Urs; Vettiger, Peter; Aono, Masakazu; Sakurai, Toshio; Gerber, Christoph

2009-01-01

470

Sub-ppm detection of vapors using piezoresistive microcantilever array sensors.  

PubMed

The performance of microfabricated piezoresistive cantilever array sensors has been evaluated using various vapors of volatile organic compounds including alkanes with different chain length from 5 (n-pentane) to 14 (n-tetradecane). We demonstrate that piezoresistive microcantilever array sensors have the selectivity of discriminating individual alkanes in a homologous series as well as common volatile organic compounds according to principal component analysis. We developed a new method to evaluate the sensitivity, taking advantage of the low vapor pressures of alkanes with longer chains, such as n-dodecane, n-tridecane and n-tetradecane, under saturated vapor conditions. This method reveals sub-ppm sensitivity and the cantilever response is found to follow the mass of evaporated analytes as calculated using a quantitative model based on the Langmuir evaporation model. PMID:19417252

Yoshikawa, Genki; Lang, Hans-Peter; Akiyama, Terunobu; Aeschimann, Laure; Staufer, Urs; Vettiger, Peter; Aono, Masakazu; Sakurai, Toshio; Gerber, Christoph

2009-01-01

471

Combustion of liquid sprays at high pressures  

NASA Technical Reports Server (NTRS)

The combustion of pressure atomized fuel sprays in high pressure stagnant air was studied. Measurements were made of flame and spray boundaries at pressures in the range 0.1-9 MPa for methanol and n-pentane. At the higher test pressure levels, critical phenomena are important. The experiments are compared with theoretical predictions based on a locally homogeneous two-phase flow model. The theory correctly predicted the trends of the data, but underestimates flame and spray boundaries by 30-50 percent, indicating that slip is still important for the present experiments (Sauter mean diameters of 30 microns at atmospheric pressure under cold flow conditions). Since the sprays are shorter at high pressures, slip effects are still important even though the density ratio of the phases approach one another as the droplets heat up. The model indicates the presence of a region where condensed water is present within the spray and provides a convenient means of treating supercritical phenomena.

Shearer, A. J.; Faeth, G. M.

1977-01-01

472

Two-fluid model for reacting turbulent two-phase flows  

NASA Astrophysics Data System (ADS)

A reacting two-fluid model, based on the solution of separate transport equations for reacting gas-liquid two-phase flow, is presented. New time-mean transport equations for two-phase mixture fraction bar-f and its variance g are derived. The new two-fluid transport equations for bar-f and g are useful for two-phase reacting flows in which phases strongly interact. They are applicable to both submerged and nonsubmerged combustion. A pdf approach to the reaction process is adopted. The mixture fraction pdf assumes the shape of a beta function while the instantaneous thermochemical properties are computed from an equilibrium model. The proposed two-fluid model is verified by predicting turbulent flow structures of an n-pentane spray flame and a nonreacting bubbly jet flow for which experimental data exist. Good agreement is found between the predictions and the corresponding experimental data.

Chan, S. H.; Abou-Ellail, M. M. M.

1994-05-01

473

Temperature and moisture effect on spore emission in the fungal biofiltration of hydrophobic VOCs.  

PubMed

The effect of temperature and moisture on the elimination capacity (EC), CO(2) production and spore emission by Fusarium solani was studied in biofilters packed with vermiculite and fed with n- pentane. Three temperatures (15, 25 and 35°C) were tested and the highest average EC (64 g m(-3) h(-1)) and lower emission of spores (2.0 × 10(3) CFU m(-3) air) were obtained at 25°C. The effect of moisture content of the packing material indicates that the highest EC (65 g m(-3) h(-1)) was obtained at 50 % moisture. However, lowest emission (1.3 × 10(3) CFU m(-3) air) was obtained at 80 % moisture. Furthermore, the results show that a slight decrease in spore emission was found with increasing moisture content. In all cases, the depletion of the nitrogen source in the biofilter induced the sporulation, a decay of the EC and increased spore emission. PMID:22375544

Vergara-Fernández, Alberto; Salgado-Ísmodes, Vanida; Pino, Miguel; Hernández, Sergio; Revah, Sergio

2012-01-01

474

Dithioether ligands containing a 2,6-disubstituted pyridine linker with two thioether-heterocycle arms.  

PubMed

The structure of 2,6-bis(2-pyridyltsulfanylmethyl)pyridine (pytmp), (I), C(17)H(15)N(3)S(2), presents a twisted conformation, with the three planar moieties almost perpendicular to each other. The structures of two related derivatives, namely 2,6-bis(6-methyl-2-pyridylsulfanylmethyl)pyridine (mpytmp), (II), C(19)H(19)N(3)S(2), and 2,6-bis(4-methyl-2-pyrimidylsulfanylmethyl)pyridine (mprtmp) n-pentane hemisolvate, (III), C(17)H(17)N(5)S(2).0.5C(5)H(12), present extended planar fragments with just one quasi-perpendicular arylsulfanylmethyl side arm, such that the molecules are folded in an L-shaped conformation. All three conformations appear different from those adopted by similar compounds, demonstrating the great flexibility of such species, although such differences in conformational behaviour might drive specific coordination modes. PMID:20048417

Rotondo, Archimede; Bruno, Giuseppe; Nicoló, Francesco; Tresoldi, Giuseppe; Di Pietro, Santo

2010-01-01

475

Minutes of the tenth meeting of the centers for the analysis of thermal/mechanical energy conversion concepts  

SciTech Connect

The agenda, list of participants, and minutes of the meeting are presented. Included in the appendices are figures, data, outlines, etc. from the following presentations: 500 kW Direct-Contact Heat Exchanger Pilot Plant; LBL/EPRI Heat Exchanger Field Test, Critical Temperature and Pressure Comparisons for n-Butane/n-Pentane Mixtures; Second Law Techniques in the Correlation of Cost-Optimized Binary Power Plants; Outline of Chapter on Geothermal Well Logging; Outline and Highlights from Geothermal Drilling and Completion Technology Development Program Annual Progress: October 1979-September 1980; Geothermal Well Stimulation; World Update on Installed Geothermal Power Pl