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Complete conformational analyses of perfluoro- n-pentane, perfluoro- n-hexane, and perfluoro- n-heptane  

Microsoft Academic Search

Complete conformational analyses of perfluoro-n-pentane, perfluoro-n-hexane, and perfluoro-n-heptane were carried out at both the semiempirical PM3 and the ab initio Hartree–Fock RHF\\/3-21G(*) levels of theory, and confirmed at the RHF\\/6-31G* level of theory, using the PC Spartan Pro computational package. These analyses indicated that the lowest-energy conformation of each of the perfluoroalkanes is helical. The conformational analyses also demonstrated that

William G. Golden; Erin M. Brown; Sadie E. Solem; Robert W. Zoellner



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

Microsoft Academic Search

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

Kenneth Harstad; Josette Bellan



Isomerization of n-hexane and n-pentane mixture on Pt-alumina catalyst  

SciTech Connect

A mixture of n-hexane and n-penane (1:1) by volume was isomerized on commercial Pt-alumina catalyst in a continuously fixed-bed reactor at atmospheric pressure. The effect of temperature, LHSV, hydrogen/hyrocarbon molar ratio and chlorine concentration were studied. It was found that the yield of isohexanes and isopentane increases with increasing the chloride added up to 0.1 and 0.2 mole % CCl/sub 4/ respectively. The rate of isomerization became slower at higher concentrations. Isomerization activity of the catalyst increases with increasing temperature ranging between 350-400/sup 0/C. The yield of isomers decrease with increasing temperature above 400/sup 0/C. The relative conversion of n-hexane in the mixture was found to be more than the conversion of pure n-hexane at the same conditions.

Radhi, M.A.; Al-Mutawalli, F.S.; Al-Sammarie, E.A.



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)



Catalytic reactions of hydrocarbons over Pt-Pd alloys--3. Skeletal reactions of n-pentane and n-hexane over Pt-Pd/Sio/sub 2/ catalysts  

SciTech Connect

The isomerization, cyclization, and hydrogenolysis kinetics of n-pentane and n-hexane were studied on dispersed silica-supported 1% alloy consisting of 0-100% palladium/platinum. The catalysts were calcined for 25 hr at 600/sup 0/C prior to reduction or only reduced in hydrogen at 400/sup 0/C. The surface composition was probably similar to bulk composition. The catalytic activity vs. composition curves were similar for precalcined and uncalcined catalysts and for various reaction temperatures (300/sup 0/-360/sup 0/C). For n-pentane, hydrogenolysis was higher on palladium than on platinum or low-palladium alloys but more selective towards butane on platinum; isomerization decreased with increasing palladium content; and cyclization went through a maximum on alloy catalysts. The reaction patterns were similar with n-hexane, except that precalcination of the catalyst suppressed cyclization to methylcyclopentane and benzene. The catalysts underwent a poisoning process which was generally highest at the higher temperatures and higher palladium contents. The results were compared with results obtained on Pt-Pd foil and mechanisms were discussed.

Karpinski, Z.; Koscielski, T.



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



Mechanism of pyrolysis of n-alkanes. 3. n-Hexane  

SciTech Connect

The distribution of products from the pyrolysis of n-pentane and n-hexane, including comparisons between calculated and experimental data, was examined. Purity of the original n-hexane was 99.97% by weight. Reactor temperature was 660/sup 0/C. The feed was supplied by a micropump or was fed from an argon-pressurized metal cylinder. The number of primary and secondary radicals formed in the pyrolysis of n-hexane were determined by examining their decomposition paths in the state of chain propagation in a radical chain scheme. Calculated values for the isomerization of primary n-pentyl and n-hexyl radicals into secondary radicals, using the Arrhenius equation, are presented.

Rumyantsev, A.N.; Oganesova, E.Yu.



Urinary excretion of n -hexane metabolites  

Microsoft Academic Search

Exposure to n-hexane, a component of many industrial solvent mixtures, is known to cause polyneuropathy in man. The concentration of metabolites in urine following exposure may be useful in biological monitoring. In a comparative study experimental animals (rat, rabbit and monkey) were subjected to single inhalatory treatments of 6, 12 and 24 h with 5,000 ppm of pure n-hexane. At

L. Perbellini; M. C. Amantini; F. Brugnone; N. Frontali



Slow-Combustion of n-Heptane, iso-Octane and a Toluene\\/n-Heptane Mixture  

Microsoft Academic Search

The oxidation of n-heptane, iso-octane and a toluene\\/n-heptane mixture was studied in a jet-stirred flow reactor operating under pressure at stoichiometric feed ratio in the low-temperature range. In particular, the transition from slow-combustion to a higher reactivity condition was examined by analyzing the composition of the reaction products as the residence time was increased.It was found that high-octane-number fuels, such




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

NASA Astrophysics Data System (ADS)

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

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



Dielectric constant measurements on n-heptane and 2-heptanone  

SciTech Connect

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

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



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)



The Oxidation of N-Heptane in the Presence of Oxygenated Octane Improvers: MTBE and ETBE  

Microsoft Academic Search

The oxidation of n-heptane and mixtures n-heptane-MTBE (50:50) and n-heptane-ETBE (50:50) has been studied experimentally in a high-pressure jet-stirred reactor in a wide range of conditions covering the low and high temperature oxidation regimes (570-1150 K, 10 atm, 0=1, 0.1% of fuel). The mole fractions of reactants, intermediates and final products have been measured. The influence of the additives on

Philippe Dagaur; Ralf Koch; Michel Cathonnet



Reactions of methylcyclohexane and n-heptane over supported Pt and Pt-Re catalysts  

Microsoft Academic Search

Reactions of methylcyclohexane (MCH) and n-heptane were compared, using industrial Pt\\/AlâOâ or Pt-Re\\/AlâOâ catalysts. Although the same products were generally observed, product selectivity and rate of catalyst deactivation differed substantially for the two reactants. With n-heptane, greater amounts of light cracked products (Câ-Câ), heavy alkylated aromatics, and coke were produced. With n-heptane the total aromatic yield (benzene + toluene yields)

W. J. Doolittle; N. D. Skoularikis; R. W. Coughlin



Vapor-liquid equilibrium of methane-n-pentane system at low temperatures and high pressures  

Microsoft Academic Search

Rice University reports vapor-liquid equilibrium data for a methane-n-pentane system at temperatures applied in natural gas processing: 0, -25, -50, -75, -80.95, and -100°C. Measurements of the bubble-point compositions are combined with earlier dew-point data to give K-values for the system at pressures ranging from the vapor pressure of n-pentane to the critical pressure or vapor pressure of methane. The

Teh-Cheng Chu; Roger J. J. Chen; Patsy S. Chappelear; Riki Kobayashi



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)



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

NASA Astrophysics Data System (ADS)

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

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



Strategies for mechanism reduction for large hydrocarbons: n-heptane  

SciTech Connect

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

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



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

NASA Astrophysics Data System (ADS)

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

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



Statistical study of nanosecond electric breakdowns in n -hexane  

Microsoft Academic Search

Methods for analyzing statistical distributions of the breakdown delay time are generalized. A statistical approach is used\\u000a to study electric breakdown in n-hexane in a 2.1-MV\\/cm quasi-uniform electric field at a pulse duration of ?510?8 s. Two different mechanisms for the anode breakdown are shown to coexist and compete with each other. One of them incorporates\\u000a the “bubble” stage, whereas

V. F. Klimkin



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

ERIC Educational Resources Information Center

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

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



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

ERIC Educational Resources Information Center

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

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



Investigations of the adsorption of n-pentane in several representative zeolites.  


We have examined the adsorption of n-pentane in several representative zeolites such as silicalite (MFI), ferrierite (FER), zeolite L (LTL), and faujasite zeolites with FAU structure including siliceous Y (Si-Y) and Na-Y by using FT-Raman spectroscopy in combination with thermogravimetric analysis (TGA) with particular attention being paid to the conformational and dynamic behavior of the guest molecule. The results indicate that the framework topology mainly dictates the conformation of n-pentane in a zeolite. For the zeolites with channel systems such as silicalite, ferrierite, and zeolite L, the population of the all-trans conformer increases upon loading, given that the geometry of the isomer fits better in the channel. When n-pentane is adsorbed in zeolites with a large cavity, such as Si-Y and Na-Y, the distribution of the all-trans (TT) and trans-gauche (TG) conformers is similar to that of pure liquid, suggesting that the large supercage in the framework imposes minimal effect on the conformational equilibrium. The dynamics of the guest molecule is, however, influenced significantly by the existence of cations. Adsorption of n-pentane in a siliceous framework such as silicalite and Si-Y results in extensive molecular motion at room temperature, the degree of which decreases with decreasing temperature. In zeolites ferrierite, L, and Na-Y, the presence of cations in the framework markedly hinders the overall molecular motion. The cations clearly play a role in the observed static disorder of the guest molecule in zeolite L. Important information regarding the location of the n-pentane molecules within silicalite and ferrierite is also obtained. PMID:16623502

Wang, Haiyan; Turner, Elizabeth A; Huang, Yining



Reactions of methylcyclohexane and n-heptane over supported Pt and Pt-Re catalysts  

SciTech Connect

Reactions of methylcyclohexane (MCH) and n-heptane were compared, using industrial Pt/Al/sub 2/O/sub 3/ or Pt-Re/Al/sub 2/O/sub 3/ catalysts. Although the same products were generally observed, product selectivity and rate of catalyst deactivation differed substantially for the two reactants. With n-heptane, greater amounts of light cracked products (C/sub 1/-C/sub 5/), heavy alkylated aromatics, and coke were produced. With n-heptane the total aromatic yield (benzene + toluene yields) was substantially less and the decline in the total aromatic yield during the first feed cycle was in general much greater. Selectivity for aromatic products immediately following hydrogen treatment of the coked Pt-Re catalysts was less with MCH than with n-heptane. Presulfiding the Pt catalyst slightly poisoned the dehydrogenation and dehydrocyclization activities. However, the presulfided Pt-Re/Al/sub 2/O/sub 3/ catalyst was very selective for these reactions and a high total aromatic yield was observed with either MCH or n-heptane. Sulfur quenched hydrogenolysis, demethylation, and reactions which form alkylated aromatics of higher molecular weight than toluene.

Doolittle, W.J.; Skoularikis, N.D.; Coughlin, R.W.



Method for the simultaneous quantification of n-hexane metabolites: application to n-hexane metabolism determination.  


1. The described analytical procedure permits the simultaneous determination of the main n-hexane metabolites in urine. 2-Hexanone, 2-hexanol, 2, 5-hexanediol and 2, 5-hexanedione, were chosen to dose the rats used in this study. All urine samples were collected and analysed on a daily basis, before and after acidic hydrolysis (pH 0.1) by GC/MS. 2-Hexanone, 2, 5-dimethylfurane, gamma-valerolactone and 2, 5-hexanedione were determined before hydrolysis: 2-hexanol and 2, 5-hexanediol, after hydrolysis; and 5-hydroxy-2-hexanone and 4, 5-dihydroxy-2-hexanone were calculated by the difference between gamma-valerolactone and 2, 5-hexanedione with and without hydrolysis, respectively. 2. A metabolic scheme was proposed reflecting the biotransformations undergone by the four compounds assayed. We consider 2, 5-dimethylfurane as a "true metabolite' because the quantities detected were always greater before hydrolysis. 3. It has been reported that human and rat n-hexane metabolism follow a similar pattern. Therefore, as a practical application and without increasing either sample or time requirements, the simultaneous quantification of the different metabolites and their excretion profile could provide better information about the metabolic situation of exposed workers than the determination of 2, 5-hexanedione alone. According to our experimental results, 4, 5-dihydroxy-2-hexanone itself would be a good toxicity indicator. PMID:8793533

Soriano, T; Menéndez, M; Sanz, P; Repetto, M



n-Pentane\\/ i-pentane separation by using zeolite–PDMS mixed matrix membranes  

Microsoft Academic Search

The performances of various zeolite filled polymeric membranes in the separation of n-pentane from i-pentane were investigated as a function of zeolite loading and various experimental conditions. Polydimethylsiloxane (PDMS) was chosen as the polymer phase and HZSM-5, NaZSM-5, 4A and 5A were used as zeolite fillers. Different Si\\/Al ratios and different activation temperatures were tested for ZSM-5 and A type

?. Birgül Tantekin-Ersolmaz; Lara ?enorkyan; Niso Kalaonra; Melkon Tatl?er; Ay?e Erdem-?enatalar



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

NASA Astrophysics Data System (ADS)

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

Pekárek, S.



Kinetic model of alkane oxidation at high pressure from methane to n-heptane  

Microsoft Academic Search

This work describes the kinetic model of alkane oxidation which is the result of creating a united kinetic mechanism for a whole homologous series of hydrocarbons, in this case from methane to n-heptane. The detail kinetic model consists of 549 species and 2518 reactions. The developed mechanism was validated against experimental data from a shock tube. The kinetic model agrees

Victor P. Zhukov



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


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



Combustion characteristics of n-heptane and wood crib fires at different altitudes  

Microsoft Academic Search

This paper contains descriptions of a preliminary experimental investigation of the fire combustion characteristics at different altitudes. Fire experiments were conducted in two laboratories located at different altitudes. Two n-heptane tanks and two wood cribs were used in the fire experiments conducted in two combustion chambers of the same size. Several parameters, including flame temperature, thermal radiation flux and fuel

Zhen-hua Li; Yaping He; Hui Zhang; Jian Wang



Excess enthalpies of the ternary mixtures: tetrahydrofuran + (diisopropyl ether or 2-methyltetrahydrofuran) + n-heptane at 298.15 K  

Microsoft Academic Search

Excess molar enthalpies, measured at 298.15K in a flow microcalorimeter, are reported for the ternary mixtures (tetrahydrofuran + diisopropyl ether + n-heptane) and (tetrahydrofuran + 2-methyltetrahydrofuran + n-heptane). Smooth representations of the results are described and used to construct constant excess molar enthalpy contours on Roozeboom diagrams. The latter are compared with diagrams obtained when the model of Liebermann and

Zhaohui Wang; Daisuke Kodama; George C Benson; Benjamin C.-Y Lu



Effect of benzene on the isomerization of n-pentane on palladium-zeolite catalysts  

SciTech Connect

An investigation has been made of the effect of benzene on the isomerization of n-pentane on palladium catalysts based on Y, mordenite and TsVM zeolites. The palladium content of the catalysts was varied form 0.001 to 0.5 wt.%. It was shown that, in the presence of benzene, there is a reduction in the isopentane yield, and isomerization is less selective. The activity of catalysts in isomerization and cracking increases with their palladium content. The hydrogenation of benzene begins with palladium contents of 0.05-0.1 wt.%. It was established that hydrocarbon cracking and isomerization occurs on acid centres of the catalyst. Here, in the case of catalysts based on HTsVM, the state of the acid centres is such that the intermediate carbonium ions on them act like radicals. This is indicated by the magnitude of the isobutane/n-butane ratio in the cracking products. The results obtained are explained on the basis of the bifunctional mechanism of action of the catalyst and by movement of the isomerization of n-pentane in the presence of benzene to acid centres of lower strength. 11 refs., 7 figs., 2 tabs.

Minachev, Kh.M.; Kharlamov, V.V.; Fomin, A.S.; Shkitov, A.M. [N.D. Zelinskii Institute of Organic Chemistry, Moscow (Russian Federation)



Process for the solvent deasphalting of asphaltene-containing hydrocarbons  

SciTech Connect

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

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



Process for the solvent deasphalting of asphaltene containing hydrocarbons  

SciTech Connect

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

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



Isothermal v.l.e. and excess molar Gibbs energy of binary and ternary mixtures containing diisopropyl ether, n -heptane and isopropanol at T = 313.15 K  

Microsoft Academic Search

(Vapour + liquid) equilibrium of {diisopropyl ether(DIPE)+n - heptane + isopropanol }, {diisopropyl ether (DIPE)+n -heptane}, {diisopropyl ether (DIPE) + isopropanol } and ( n - heptane + isopropanol) were measured at T= 313.15 K. Data reduction by Barker’s method provides correlations for the excess molar Gibbs energy GmEusing the Margules equation for the binary systems and the Wohl expansion

Mar??a C. Mart??n; Miguel A. Villamañán



Structure of n-heptane\\/air triple flames in partially-premixed mixing layers  

Microsoft Academic Search

Results of a detailed numerical analysis of an n-heptane\\/air edge flame are presented. The equations of a low-Mach number reacting flow are solved in a two-dimensional domain using detailed models for species transport and chemical reactions. The reaction mechanism involves 560 species and 2538 reversible reactions. We consider an edge flame that is established in a mixing layer with a

J. Prager; H. N. Najm; M. Valorani; D. A. Goussis



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

Microsoft Academic Search

Direct numerical simulation was used for fundamental studies of the ignition of turbulent n-heptane liquid-fuel spray jets. A chemistry mechanism with 33 species and 64 reactions was adopted to describe the chemical reactions. The Eulerian method is employed to solve the carrier-gas flow field and the Lagrangian method is used to track the liquid-fuel droplets. Two-way coupling interaction is considered

Y. Wang; C. J. Rutland



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

Microsoft Academic Search

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

Mouldi Chrigui; Ali Zghal; Amsini Sadiki; Johannes Janicka



The auto-ignition of single n-heptane\\/ iso-octane droplets  

Microsoft Academic Search

Numerical simulations including detailed chemical and physical models are performed to investigate the influence of different physical parameters on the auto-ignition of n-heptane\\/iso-octane droplets in air. Simulations are performed for isobaric conditions with an ambient pressure of 8bar and a droplet radius of 200?m. The ambient gas temperature ranges from 800K to 2000K and the droplet temperature was varied from

R. Stauch; U. Maas



Experimental Study of 1 Atmosphere, Rich, Premixed n-heptane and iso-octane Flames  

Microsoft Academic Search

Temperature and species mole fraction profiles have been measured in laminar premixed n-heptane\\/O2\\/N2 and iso-octane\\/O2\\/N2 flames. Both flames have been stabilized on a flat-flame burner, at atmospheric pressure. Species identification and concentration measurements have been performed by gas chromatography and GC-MS analysis of samples withdrawn locally by a quartz microprobe. Temperature profiles were measured by Pt-Pt 10%Rh thermocouples with radiative




A numerical study of the unsteady burning behaviour of n-heptane droplets  

Microsoft Academic Search

Unsteady, sphero-symmetric n-heptane droplet burning behaviour is investigated by performing a numerical model simulation from deployment of the droplet to quasi-steady burning. The numerical model used in the present study incorporates complex chemistry consisting of 96 forward and backward reaction steps and a detailed molecular transport mechanism such that droplet burning behaviour can be simulated with almost no simplification. Unsteady

Seog Yeon Cho; Frederick L Dryer



Alkaline earth metal ion-exchanged ? zeolite supported Pt catalysts for hydroisomerization of n -heptane  

Microsoft Academic Search

Alkaline earth metal (Mg, Ca, Sr and Ba) ions were exchanged into H? zeolite, which were used as the supports to load the\\u000a noble metal Pt to prepare bifunctional catalysts for hydroisomerization of n-heptane. The catalysts were characterized by ICP, XRD, BET, NH3-TPD, H2-TPR and H2-chemisorption techniques, and evaluated in an atmospheric fixed bed reactor. The catalysts promoted by the

Ping Liu; Xingguang Zhang; Yue Yao; Jun Wang



Toluene and n-heptane sorption in Matrimid ® asymmetric hollow fiber membranes  

Microsoft Academic Search

Equilibrium and transient sorption isotherms were obtained for toluene and n-heptane in both annealed and non-annealed Matrimid® asymmetric hollow fiber membranes at 35°C. Equilibrium sorption follows the dual mode model except for toluene sorption into annealed fibers above a pressure of 0.5psia. Except at the highest toluene exposure pressure, the equilibrium uptake of penetrant in annealed fibers was signigicantly less

Jong Suk Lee; Ryan T. Adams; William Madden; William J. Koros



Comparative Study on the Structure of Water in Reverse Micelles Stabilized with Sodium Bis(2-ethylhexyl) Sulfosuccinate or Sodium Bis(2-ethylhexyl) Phosphate in n-Heptane  

Microsoft Academic Search

The microstructure of water solubilized in H2O\\/surfactant\\/n-heptane ternary systems has been investigated by employing 1H-NMR and FT-IR spectroscopic techniques. Two reverse micellar systems were prepared and studied, i.e., sodium bis(2-ethylhexyl) sulfosuccinate in n-heptane (H2O\\/AOT\\/n-heptane) and sodium bis(2-ethylhexyl) phosphate in n-heptane (H2O\\/NaDEHP\\/n-heptane). 1H-NMR data showed that the chemical shift of water protons for the AOT and NaDEHP reverse micelles varied downfield

Quan Li; Tao Li; Jinguang Wu; Naifu Zhou



Effects of n-hexane and its metabolites on cloned voltage-operated neuronal potassium channels  

Microsoft Academic Search

In order to study the mechanisms of acute n-hexane?intoxication, the effects of n-hexane and its metabolites 2-hexanol, methyl-n-butyl\\u000a ketone, 2,5-hexanediol and 2,5-hexanedione on the cloned voltage-operated potassium channels Kv1.1, Kv1.4, Kv2.1 and Kv3.4\\u000a were investigated with electrophysiological techniques in the expression system of Xenopus oocytes. n-Hexane had no effect at any channel, whereas some of its metabolites led to reductions

Michael Madeja; Norbert Binding; Ulrich Mußhoff; Ute Witting; Erwin-Josef Speckmann



Pt catalysts supported on ? zeolite ion-exchanged with Cr(III) for hydroisomerization of n-heptane  

Microsoft Academic Search

A series of Pt catalysts supported on H? zeolite ion-exchanged with Cr(III) were prepared, characterized by ICP, XRD, BET, NH3-TPD, H2-TPR and H2-chemisorption techniques, and evaluated in hydroisomerization of n-heptane with an atmospheric fixed-bed flow reactor. Pt catalyst supported on H? zeolite exhibits both lower selectivity to isomerized products and lower conversion of n-heptane than the counterparts supported on Cr(III)-exchanged

Ping Liu; Xingguang Zhang; Yue Yao; Jun Wang



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

SciTech Connect

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

Owston, Rebecca; Magi, Vinicio; Abraham, John [School of Mechanical Engineering, Purdue University, Chaffee Hall, 500 Allision Road, West Lafayette, IN 47907 (United States)



N-pentane isomerization with catalysts formed from brominated intermetallic compounds  

SciTech Connect

The intermetallic compounds of aluminum with lanthanum (LaAl/sub 2/), cerium (CeAl/sub 2/), praseodymium (PrAl/sub 2/), erbium (ErAl/sub 2/), samarium (SmAl), and thorium (ThAl/sub 2/) were finely ground and suspended in dichloromethane (1 mmole/8 ml); 2 ml of n-pentane were then injected. Isopentane was the only primary product, but isobutane and C/sub 6/ hydrocarbons formed as secondary products. The conversions and isomerization selectivities after 0.5 hr at 0/sup 0/C were 6.0 and 90% for LaAl/sub 2/, 27.2 and 94.8% for CeAl/sub 2/, 8.9 and 85.3% for PrAl/sub 2/, 16.2 and 92.6% for ErAl/sub 2/, 3.6 and 91.3% for SmAl, and 16.7 and 97Vertical Bar3< for ThAl/sub 2/. With increasing extent of bromination beyond a 1:3 intermetallic compound/bromine ratio, the conversion increased and the isopentane yield decreased.

Imamura, H.; Wallace, W.E.



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


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



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

PubMed Central

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

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



Role of Lewis acidity in the isomerization of n-pentane and o-xylene on dealuminated H-mordenites  

SciTech Connect

n-Pentane and o-xylene isomerizations have been studied at 285 and 150{degrees}C, respectively, on seven dealuminated H-mordenites containing different amounts of framework and nonframework aluminum which were prepared by steaming or calcining NH{sub 4}-mordenite. The number of Bronsted and Lewis sites were known beforehand from {sup 29}Si high-resolution magnetic resonance and infrared study of low-temperature CO adsorption. In addition, the availability of the acid sites to the reactants was estimated from the ratios of the liquid monolayer volume of the reactant (n-pentane or o-xylene) to that of N{sub 2}, the availability of the active sites to N{sub 2} and CO being the same. A synergistic enhancement of the acidity by the interaction between Bronsted and Lewis acid centers is suggested. Other aspects related with the product distribution are also discussed. 32 refs., 9 figs., 5 tabs.

Hong, Y.; Gruver, V.; Fripiat, J.J. [Univ. of Wisconsin, Milwaukee, WI (United States)



Isothermal vapor–liquid equilibria for ethanol and n-pentane system at the near critical region  

Microsoft Academic Search

Isothermal VLE data of n-pentane and ethanol system were obtained at near critical temperatures. A circulating type equipment with the view cell has been built and tested with the data reported by Campbell et al. [S.W. Campbell, R.A. Wilisak, J. Thodos, J. Chem. Thermodyn. 19 (1987) 449–460] for the same system at 422.6K. Critical pressure was also determined from the

Jungha Seo; Jongcheon Lee; Hwayong Kim



Adsorption of n-pentane and iso-octane for the evaluation of the porosity of dealuminated BEA zeolites  

Microsoft Academic Search

Adsorption of n-pentane and 2,2,4-trimethylpentane at 298K was carried out in order to characterize the porosity of a series of HBEA dealuminated zeolites. The HBEA samples were prepared from a calcined parent sample by steaming, by treatment with hydrochloric acid and by treatment with ammonium hexafluorosilicate (HFS) solutions. The comparison of the adsorption results with those previously obtained by nitrogen

M. M. L. Ribeiro Carrott; P. A. Russo; C. Carvalhal; P. J. M. Carrott; J. P. Marques; J. M. Lopes; I. Gener; M. Guisnet; F. Ramôa Ribeiro



The influence of intermolecular interactions in n-pentane-alkane-1-ol systems on their physicochemical properties  

Microsoft Academic Search

The Helmholtz energy of dipole-dipole interaction (SigmaDeltad F) and its long-range (Deltad F°) and short-range (Deltad F*) components were calculated for n-pentane-alkane-1-ol (from methanol to dodecane-1-ol) systems at 298.15 K using the Winkelmann statistical model theory of liquid dielectrics. It was shown that the longer the alkane-1-ol hydrocarbon radical, the greater the extent to which the properties of the systems

E. D. Totchasov; G. A. Al'Per



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


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

Martin, Jan M L



Measurements of the viscosity of n-heptane + n-undecane mixtures at pressures up to 75 MPa  

NASA Astrophysics Data System (ADS)

New absolute measurements of the viscosity of binary mixtures of n-heptane and n-undecane are presented. The measurements, performed in a vibrating-wire instrument, cover the temperature range 295 335 K and pressures up to 75 MPa. The concentrations studied were 40 and 70%, by weight, of n-heptane. The overall uncertainty in the reported viscosity data is estimated to be ±0.5%. A recently extended semiempirical scheme for the prediction of the thermal conductivity of mixtures from the pure components is used to predict successfully both the thermal conductivity and the viscosity of these mixtures, as a function of composition, temperature, and pressure.

Assael, M. J.; Karagiannidis, L.; Papadaki, M.



Crosslinking of elastomers resulting from ageing: use of thermoporosimetry to characterise the polymeric network with n-heptane as condensate  

Microsoft Academic Search

Thermoporosimetry has been used to characterise the network generated by UV-irradiation of Ethylene-Propylene-Diene-Monomer (EPDM) samples. The technique was calibrated by using well characterised monodisperse silica gel samples. In the case of n-heptane, the following relationship between the freezing point depression (?T) of the solvent and the radius of the pore in which it crystallizes is found:RpA°=?587.4?T+2.4with?40n-heptane as

M. Baba; J. M. Nedelec; J. Lacoste; J. L. Gardette; M. Morel



Experimental and modeling study of laminar flame speed and non-premixed counterflow ignition of n-heptane  

Microsoft Academic Search

Laminar flame speeds were determined for n-heptane–oxygen–nitrogen mixtures over the pressure range of 0.5–2atm and equivalence ratio range of 0.7–1.4, using the counterflow twin-flame technique. For pressure at or below 1.5atm, the laminar flame speeds were collected for n-heptane–air mixtures, whereas the data at 2atm are reported for diluted air of 18% O2–82% N2. These experimental data, together with those

A. J. Smallbone; W. Liu; C. K. Law; X. Q. You; H. Wang



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

SciTech Connect

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

Ferworn, K.A.; Svrcek, W.Y.; Mehrotra, A.K. (Univ. of Calgary, Alberta (Canada))



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


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



Evaluation of 2,5-hexanedione in urine of workers exposed to n-hexane in Brazilian shoe factories  

Microsoft Academic Search

Urinary 2,5-hexanedione (2,5-HD) is used as a biomarker for biological monitoring of workers exposed to n-hexane. The purpose of this study was to compare two types of treatment of urine samples during clean-up (with and without acidic hydrolysis) and to study the exposure situation of workers exposed to n-hexane during shoe manufacturing. There, various glues containing n-hexane are used. Quantification

Claudia Regina dos Santos; Miriam Meyer Passarelli; Elizabeth de Souza Nascimento



Urinary 2,5-hexanedione increases with potentiation of neurotoxicity in chronic coexposure to n -hexane and methyl ethyl ketone  

Microsoft Academic Search

Objective: MEK (methyl ethyl ketone) is widely and frequently used as an ingredient of mixed solvents together with n-hexane. MEK is known to decrease urinary levels of 2,5-hexanedione dose-dependently in an acute or chronic coexposure with\\u000a a constant level of n-hexane. This change in urinary 2,5-hexanedione appears to contradict the potentiation effect of MEK on n-hexane-induced neurotoxicity because it is

Gaku Ichihara; Isao Saito; Michihiro Kamijima; Xiaozhong Yu; Eiji Shibata; Machiko Toida; Yasuhiro Takeuchi



Molecular dynamic simulation of electron bubble transport in n-hexane liquid  

Microsoft Academic Search

Mobility and diffusion coefficient of an electron in hydrocarbon liquid is calculated by molecular dynamics (MD) simulation. Electron bubble model is used as an electron status in the liquid, which consists of n-hexane molecule of flexible chain model. Rattle algorithm is used for the time evaluation of molecular motion, and temperature and simulation volume are kept constant. The electric field,

T. Funakawa; W. Balachandran



Solubilities of solanesol in acetonitrile, ethanol and n-hexane from 285 to 310K  

Microsoft Academic Search

Using a laser monitoring observation technique, we measured the solubilities of solanesol in acetonitrile, ethyl alcohol and\\u000a n-hexane by a synthetic method at temperatures ranging from 285 to 310 K at atmospheric pressure. Empirical equations were\\u000a proposed and the calculated results show good agreement with the experimental solubilities.

Jiang-Chu Liu; Dian-Qing Li; Rong-Qi Zhou; Fei Hao




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....


A rapid compression machine investigation of oxidation and auto-ignition of n-Heptane: Measurements and modeling  

Microsoft Academic Search

n-Heptane oxidation and auto-ignition in a rapid compression machine is studied in the low and intermediate temperature regimes at high pressures. Experimental ignition delay times and some phenomenological aspects related to knock in engines are presented, providing additional information at lower temperatures on previously published delays from shock tube experiments. The products of oxidation are identified and time profiles are

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




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...


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

Microsoft Academic Search

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

Kenneth Harstad; Josette Bellan



Cracking of n-heptane on a CrHNaY zeolite catalyst. The network of the reaction  

SciTech Connect

The cracking of n-heptane has been studied at 400, 450, and 470/sup 0/C over a CrHNaY zeolite catalyst using a tubular packed-bed reactor. The concept of Optimum Performance Envelope was used in order to identify which of the observed reaction products are primary and which are secondary. In this way the initial selectivity values for all primary products have been calculated and from such values we have seen that primary reactions other than cracking occur in this process. These reactions include isomerization and disproportionation of n-heptane. All the primary reactions which appear in the cracking of n-heptane can be explained as occurring on acid centers and consequently no direct catalysis by chromium ions in the first steps needs to be invoked to rationalize our results. Finally, a network for the cracking of n-heptane on the CrHNaY zeolite catalyst has been constructed on the basis of the observed behaviour of the selectivity curves.

Lopez Agudo, A.; Asensio, A.; Corma, A.



Oxidation of 1-butanol and a mixture of n-heptane/1-butanol in a motored engine  

SciTech Connect

The oxidation of neat 1-butanol and a mixture of n-heptane and 1-butanol was studied in a modified CFR engine at an equivalence ratio of 0.25 and an intake temperature of 120 C. The engine compression ratio was gradually increased from the lowest point to the point where significant high temperature heat release was observed. Heat release analyses showed that no noticeable low temperature heat release behavior was observed from the oxidation of neat 1-butanol while the n-heptane/1-butanol mixture exhibited pronounced cool flame behavior. Species concentration profiles were obtained via GC-MS and GC-FID/TCD. Quantitative analyses of the reaction products from the oxidation of neat 1-butanol indicate that 1-butanol is consumed mainly through H-atom abstraction. Among the H-atom abstraction reactions, it is observed that the H-atom abstraction from the {alpha}-carbon of 1-butanol is particularly favored. The investigation on the oxidation of the mixture of n-heptane/1-butanol showed that the oxidation of 1-butanol is facilitated at low temperatures through the radical pool generated from the oxidation of n-heptane. (author)

Zhang, Yu.; Boehman, Andre L. [EMS Energy Institute, The Pennsylvania State University, University Park, PA 16802 (United States)



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

PubMed Central

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

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



The influence of intermolecular interactions in n -pentane-alkane-1-ol systems on their physicochemical properties  

Microsoft Academic Search

The Helmholtz energy of dipole-dipole interaction (??d\\u000a F) and its long-range (?d\\u000a F°) and short-range (?d\\u000a F*) components were calculated for n-pentane-alkane-1-ol (from methanol to dodecane-1-ol) systems at 298.15 K using the Winkelmann statistical model theory of\\u000a liquid dielectrics. It was shown that the longer the alkane-1-ol hydrocarbon radical, the greater the extent to which the\\u000a properties of the systems

E. D. Totchasov; G. A. Al’per



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

SciTech Connect

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

Wang, Y.; Rutland, C.J. [Department of Mechanical Engineering, University of Wisconsin-Madison, WI 53706 (United States)



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


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



Solid-state NMR investigation of n-heptane cracking over zeolite beta  

SciTech Connect

n-Heptane cracking over zeolite H-Beta has been studied by solid-state NMR spectroscopy. It is shown that isomerisation and cracking are two related processes at the early stages of the reaction. Isomerisation is proposed to proceed faster than cracking via the intermediacy of protonated cyclopropane wheras cracking is suggested to progress through the classical {beta}-scission route. Catalyst loading in the NMR experiments seems to be a very important factor for both initiation of the reaction and final product distribution. The initial source of i-butane, which is observed as primary product, is the isomer 2,2-dimethylpentane, which cracks to i-butane and propene. Propene, which has never been observed, is suggested to be involved in polymerisation reactions producing long hydrocarbon chains which can rearrange and finally crack to a number of C{sub 5}-C{sub 7} isomers. At later stages, the reaction becomes very complex. More of the heptane isomers crack by {beta}-scission to a number of C{sub 4} and C{sub 3} fractions. The carbenium ions desorb as paraffins by H-transfer while the olefinic fraction is involved in polymerisation reactions. At the final stages of the reaction, protolytic cracking starts contributing to this process, producing methane, ethane, and propane. Of great interest is the catalyst loading effect on this monomolecular reaction process which defines the final product distribution. 30 refs., 6 figs., 1 tab.

Philippou, A.; Anderson, M.W. [UMIST, Manchester (United Kingdom)



Structural characterization of frozen n-heptane solutions of metal-containing reverse micelles.  


The microstructure of temperature-quenched solutions of reverse micelles formed by sodium, cobalt, ytterbium, and cobalt/ytterbium bis(2-ethylhexyl)sulfosuccinate in n-heptane has been investigated by SAXS and EXAFS. Some changes in the X-ray absorption spectra with respect to the same systems at room temperature have been observed. The analysis of the SAXS spectra leads to the hypothesis that at 77 K the closed spherical structure of reverse micelles is retained and that during the temperature quench they undergo a clustering process involving the transition from a quite random dispersion to the formation of more or less large clusters of strongly packed reverse micelles. This behavior is attributed to competitive effects caused by the temperature decrease. The prevalence of intermicellar attractive interactions with respect to Brownian motions leading to a collapse to more compact structure is in competition with the rapid decrease of reverse micelle diffusion rate involving a freezing of the local structures. In the case of cobalt, ytterbium, and cobalt/ytterbium bis(2-ethylhexyl)sulfosuccinate reverse micelles, further information from EXAFS measurements indicates that within the reverse micelle core exists a quite ordered nanosized domain composed of water, surfactant counterions, and oxygen atoms of the SO3- head groups. The conservation of local order and inverse structure during the clustering phenomenon that results from the fast freezing with liquid nitrogen of solutions of reverse micelles could have biological implications, i.e., the preservation of tissue samples at cryogenic temperatures. PMID:17915898

Longo, Alessandro; Portale, Giuseppe; Bras, Wim; Giannici, Francesco; Ruggirello, Angela M; Liveri, Vincenzo Turco



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

SciTech Connect

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

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



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



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

NASA Astrophysics Data System (ADS)

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

Hwang, In-Wook; Kim, Yong-Rok



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.



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.



Extraction of technetium(VII) from uranium(VI) in nitric acid system by primary amine — n-heptane solution  

Microsoft Academic Search

Separation of technetium(VII) from uranium(VI) has been studied through experiments on the coprecipitation of technetium(VII) with precipitation of ammonium diuranate, and on the extraction of technetium(VII) from a 3M aqueous nitric acid solution using, as extractant, a primary amine (Primene JMT) dissolved in either chloroform or n-heptane solution. Ammonium diuranate precipitation proved to provide the most satisfactory means of separating

K. Ito



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

Microsoft Academic Search

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

Philippe Dagaut; Marcelline Reuillon; Michel Cathonnet



Soot formation in shock-tube pyrolysis of toluene- n-heptane and toluene-iso-octane mixtures  

Microsoft Academic Search

Soot formation during the pyrolysis of argon-diluted mixtures of toluene and n-heptane and of toluene and iso-octane in a reflected-shock tube was studied. Soot induction times and rates of formation measured at 632.8 nm by laser beam attenuation showed an Arrhenius dependence on reflected-shock temperature. The maximum in bell-shaped distribution of soot yield and concentration as a function of temperature

A. Alexiou; A. Williams



Computational modeling of n-heptane droplet combustion in air–diluent environments under reduced-gravity  

Microsoft Academic Search

The combustion and extinguishment of n-heptane droplets in air–diluent environments under reduced-gravity are studied, where carbon dioxide, helium and xenon are used as diluents. A gasification model employing the volume of fluid (VOF) method was developed and implemented into the CFD package FLUENT. The droplet evaporation, combustion and parasitic current were validated by comparing with the previous study. The numerical

Y. Jin; B. D. Shaw



Catalytic performances of dealuminated H? zeolite supported Pt catalysts doped with Cr in hydroisomerization of n-heptane  

Microsoft Academic Search

A series of dealuminated H? zeolite supported Pt catalysts doped with Cr, Ce, La or Zn were prepared via co-impregnation and characterized by X-ray diffraction (XRD), BET, NH3-TPD, H2-TPR, ICP, and H2-chemisorption techniques. The catalytic performance was evaluated in hydroisomerization of n-heptane with an atmospheric fixed bed flow reactor. At the reaction temperature 250°C, H? zeolite supported Pt catalyst showed

Ping Liu; Jun Wang; Xingguang Zhang; Ruiping Wei; Xiaoqian Ren



A Highly Efficient H? Zeolite Supported Pt Catalyst Promoted by Chromium for the Hydroisomerization of n Heptane  

Microsoft Academic Search

H? zeolite supported Pt catalysts promoted by Cr, La, Ce, Al or Zn were prepared by the co-impregnation method, and characterized\\u000a by XRD, BET, NH3-TPD and H2-TPR. Their catalytic activities were evaluated in the hydroisomerization of n-heptane with an atmospheric fixed-bed reactor. The Pt-bearing catalyst doped with Cr, La or Ce, especially Cr, is found to\\u000a exhibit a much higher

Ping Liu; Jun Wang; Ruiping Wei; Xiaoqian Ren; Xingguang Zhang



Experiments and Simulations of n Heptane Spray Auto-Ignition in a Closed Combustion Chamber at Diesel Engine Conditions  

Microsoft Academic Search

Auto-igniting n-heptane sprays have been studied experimentally in a high pressure, high temperature constant volume combustion chamber with\\u000a optical access. Ignition delay and the total pressure increase due to combustion are highly repeatable whereas the ignition\\u000a location shows substantial fluctuations. Simulations have subsequently been performed by means of a first-order fully elliptic\\u000a Conditional Moment Closure (CMC) code. Overall, the simulations

Yuri M. Wright; Ourania-Nektaria Margari; Konstantinos Boulouchos; Giorgio De Paola; Epaminondas Mastorakos



Factors affecting isomer yield for n-heptane hydroisomerization over as-synthesized and dealuminated zeolite catalysts loaded with platinum  

Microsoft Academic Search

Pt loaded Y, USY, beta, mordenite, ZSM-12, and ZSM-5 zeolites with different Si\\/Al ratios and a USY and ZSM-12 sample having enhanced activity were studied for the hydroisomerization of n-heptane. All the possible heptane isomers were obtained over Pt\\/H-ZSM-12 and the product distribution was closer to that over Y and beta catalysts, but very different from that over Pt\\/H-ZSM-5. Shape-selective

Srikant Gopal; Panagiotis G. Smirniotis



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.



Formulation reproducing the ignition delays simulated by a detailed mechanism: Application to n-heptane combustion  

SciTech Connect

This article is part of the project to model the kinetics of high-temperature combustions, occurring behind shock waves and in detonation waves. The ''conventional'' semi-empirical correlations of ignition delays have been reformulated, by keeping the Arrhenius equation form. It is shown how a polynomial with 3{sup N} coefficients (where N element of is the number of adjustable kinetic parameters, likely to be simultaneously chosen among the temperature T, the pressure P, the inert fraction X{sub Ar}, and the equivalence ratio {phi}) can reproduce the delays predicted by the Curran et al. [H.J. Curran, P. Gaffuri, W.J. Pitz, C.K. Westbrook, Combust. Flame 129 (2002) 253-280] detailed mechanism (565 species and 2538 reactions), over a wide range of conditions (comparable with the validity domain). The deviations between the simulated times and their fits (typically 1%) are definitely lower than the uncertainties related to the mechanism (at least 25%). In addition, using this new formalism to evaluate these durations is about 10{sup 6} times faster than simulating them with SENKIN (CHEMKIN III package) and only 10 times slower than using the classical correlations. The adaptation of the traditional method for predicting delays is interesting for modeling, because those performances are difficult to obtain simultaneously with other reduction methods (either purely mathematical, chemical, or even mixed). After a physical and mathematical justification of the proposed formalism, some of its potentialities for n-heptane combustion are presented. In particular, the trends of simulated delays and activation energies are shown for {sub T} {sub element} {sub of} {sub [1500} {sub K,1900} {sub K},} {sub P} {sub element} {sub of} {sub [10kPa,1MPa]}, X{sub Ar} element of [0,0.7], and {phi} element of {sub [0.25,4.0]}. (author)

Imbert, Bruno [LENI, IGM, STI, EPFL, Station 9, CH-1015 Lausanne (Switzerland); Lafosse, Fabien; Catoire, Laurent; Paillard, Claude-Etienne [ICARE, CNRS, and University of Orleans, 1C Av. de la Recherche Scientifique, F-45067 Orleans (France); Khasainov, Boris [LCD, CNRS, ENSMA, 1 Av. Clement Ader, F-86961 Futuroscope (France)




Microsoft Academic Search

A certain possible approach for the control of HCCI chemistry is to use kinetic chemistry mechanisms. This opens a field of interest that lead to the composition of a validated reduced PRF chemistry mechanism. For this purpose a skeletal chemical reaction mechanism for n-heptane and for iso-octane are constructed from a detailed n-heptane and iso-octane mechanism of the Chalmers University




Effects of oil concentration and particle size on the cleaning of Spanish high-rank coals by agglomeration with n-heptane  

Microsoft Academic Search

The response of three high-ash Spanish anthracites to agglomeration with n-heptane was evaluated by measuring the organic matter recovery, ash rejection and pyritic sulfur rejection. The influence of oil concentration and coal particle size on the agglomeration results was investigated. The combustible recoveries of these coals increased to a maximum as the n-heptane concentration is raised, and then decreased. Ash

Ana B. Garcia; José M. G. Vega; M. Rosa Martinez-Tarazona



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

SciTech Connect

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

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



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)



Mutual diffusivity of a mixture of n-hexane and nitrobenzene near its consolute point  

SciTech Connect

It is demonstrated that the Taylor dispersion method can be used to measure the mutual diffusivity of liquid mixtures near a critical mixing point. For this purpose the authors have measured the mutual diffusivity of a liquid mixture of n-hexane and nitrobenzene at the critical composition at temperatures from 16 K down to 1 K above the critical temperature. The results are in agreement with the theoretically predicted behavior of the diffusivity near a critical point of mixing. 35 refs., 3 figs., 2 tabs.

Matos Lopes, M.L.S.; Castro, C.A.N. de (Universidade de Lisboa, Campo Grande (Portugal) Instituto Superior Tecnico, Lisboa Codex (Portugal)); Sengers, J.V. (Univ. of Maryland, College Park (United States))



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


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/m(2) at 300 K. For [bmim][Tf2N] room-temperature ionic liquid, we use a non-polarizable all-atom force field with the partial atomic charges based on ab initio calculations for the isolated ion pair. The net charges of the ions are ±0.89e, which mimics the anion to cation charge transfer and polarization effects. The OPLS-AA force field is employed for modeling of n-hexane. The surface tension is computed using the mechanical route and its value decreases with increase of the n-hexane surface density. The [bmim][Tf2N]/n-hexane interface is analyzed using the intrinsic method, and the structural and dynamic properties of the interfacial, sub-interfacial, and central layers are computed. We determine the surface roughness, global and intrinsic density profiles, and orientation ordering of the molecules to describe the structure of the interface. We further compute the survival probability, normal and lateral self-diffusion coefficients, and re-orientation correlation functions to elucidate the effects of n-hexane on dynamics of the cations and anions in the layers. PMID:23822317

Lísal, Martin; Izák, Pavel



Cyclohexane as an Alternative Vapor of Carbon Tetrachloride for the Assessment of Gas Removing Capacities of Gas Masks  

Microsoft Academic Search

An alternative vapor was explored to replace carbon tetrachloride (CCl 4) for testing breakthrough times of cartridges and canisters of gas masks in the National Approval Test of Respirators. Cyclohexane was single out as a candidate for the alternative vapor out of six vapors: trichloroethylene, n-pentane, n-hexane, n-heptane, toluene and cyclohexane from the viewpoints of similarity of vapor pressure and

Mitsuya FURUSE; Seiichiro KANNO; Tsuguo TAKANO; Yoshimi MATSUMURA



Acute Inhalation Toxicology of Volatile Hydrocarbons  

Microsoft Academic Search

Mice were exposed to various concentrations of volatile hydrocarbons and measurements made of respiratory rate, depth and configuration while the animals were inhaling the agent. Mice were exposed to the volatile hydrocarbons n-pentane, n-hexane, n-heptane or iso-octane. Additional mice were also exposed to the anesthetics diethyl ether or methoxyflurane for comparative purposes. The concentrations used were 1,000; 2,000; 4,000; 8,000;




Comparisons of Completeness of Combustion for Alcohol and Alkane Laminar Wall Fires  

Microsoft Academic Search

Steady, fully burning wall fires were studied using alkanes (n-pentane, n-hexane, and n-heptane) burning in air. Completeness of combustion was characterized and evaluated for the three alkanes studied and was compared with results previously obtained for alcohols (methanol, I-propanol, and I-butanol) burning in air. When the alkanes were burred, with CO and CO2 the principal carbon-containing products, less than 15%




Adsorption potential of hydrocarbons at the gas-liquid interface of water  

Microsoft Academic Search

In this work, the adsorption potential of 5 hydrocarbons is calculated at the gas-liquid interface of water and compared to the minimum value with the experimental adsorption energy obtained at zero surface coverage by gas chromatography. For 3 of the molecules (n-pentane, n-hexane, and n-heptane), the calculation consisted of dispersion and induction interactions between solute and liquid adsorbent. For 2

Claire Vidal-Madjar; Georges Guiochon; Barry L. Karger



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

SciTech Connect

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

Lue, Xingcai; Ji, Libin; Zu, Linlin; Hou, Yuchun; Huang, Cheng; Huang, Zhen [School of Mechanical and Power Engineering, Shanghai Jiaotong University, Shanghai (China)



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

NASA Astrophysics Data System (ADS)

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

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



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



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

SciTech Connect

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

Sahetchian, K.A.; Blin, N.; Rigny, R.; Seydi, A. (Paris-6 Univ., 75 (France)); Murat, M. (Laboratoire de Thermdynamique Appliquee aux Machines, Universite P. et M. Curie, CNRS UA 40879, 78210 St Cyr l'Ecole (FR))



Rare Earth Metals Ion-exchanged ?-Zeolites as Supports of Platinum Catalysts for Hydroisomerization of n-Heptane  

Microsoft Academic Search

A series of Pt catalysts supported on the H?-zeolite that is ion-exchanged with the rare earth metal ions of Ce(III) and La(III), are prepared by impregnation, characterized by inductively coupled plasma (ICP), X-ray diffraction (XRD), BET, temperature-programmed desorption of ammonia (NH3-TPD), temperature-programmed reduction of hydrogen (H2-TPR) and H2-chemisorption techniques, and evaluated in the hydroisomerization of n-heptane with an atmospheric fixed-bed

Ping LIU; Yue YAO; Xingguang ZHANG; Jun WANG



Process for the solvent deasphalting of asphaltene-containing hydrocarbons  

SciTech Connect

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

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



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

SciTech Connect

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

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



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


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

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



Exciplex type emission from anthracene doped aggregates of phenanthrene formed in n-hexane frozen solutions  

NASA Astrophysics Data System (ADS)

Fluorescence, absorption and fluorescence excitation spectra of concentrated (3 × 10 -4 M) solutions of phenanthrene in frozen n-hexane in the presence of anthracene have been investigated at 77 and 4 K. Decay time analysis of the anthracene sensitized emission reveals the existence of at least two types of superposed emissions. One emission (? M ? 9 ns) is similar to that from solid solutions of anthracene in phenanthrene crystal while the other is structureless and anthracene-concentration dependent (? M ? 30-65 ns). The latter has been assigned to an exciplex type emission from particular anthracene-phenanthrene configurations which occur in very small size phenanthrene pseudocrystallites, imbedded in an n-alkane matrix.

Rima, J.; Lamotte, M.; Joussot-Dubien, J.



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

SciTech Connect

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

Not Available



Characterization of the acid properties of tungsten/zirconia catalysts using adsorption microcalorimetry and n-pentane isomerization activity  

SciTech Connect

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 in a more active catalyst, and (2) the addition of small amounts of iron to the tungsten/zirconia catalyst increases the acid site strength as determined by ammonia adsorption and improves the paraffin isomerization activity. The calorimetry data indicate that the acid site strength of the tungsten/zirconia materials is similar to or slightly higher than that found in zeolites or sulfated zirconia and is comparable to sulfuric acid. However, the paraffin isomerization activity results suggest that the acid sites of the tungsten/zirconia catalyst should be about four orders of magnitude more active than that of zeolite {beta} on the basis of turnover frequency. Their experimental results indicate a lack of correlation between the heat of ammonia adsorption with catalytic activity. Comparisons of catalytic activity between materials based entirely on acid strength may not be valid, and kinetic probes would be more appropriate.

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



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

NASA Astrophysics Data System (ADS)

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

Jacobs, Gary


Deactivation of ruthenium catalysts prepared by the sol-gel method in reactions of benzene hydrogenation and n-pentane hydrogenolysis  

Microsoft Academic Search

The self-poisoning of ruthenium silica catalyst has been studied for benzene hydrogenation and n-pentane hydrogeolysis. The catalysts were synthesized by the sol-gel method, which consists of adding the active metal to a sol followed by transformation to a gel. As a reference, a catalyst has been prepared by the classical impregnation method using commercial silica. In the hydrogenation of benzene,

T. Lopez; A. Lopez-Gaona; R. Gomez



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

SciTech Connect

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

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



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

NASA Astrophysics Data System (ADS)

n-Heptane/urea is an aperiodic inclusion compound in which the ratio of host and guest repeats along the channel axis is very close to unity and is found to have a constant value (0.981) from 280 K to 90 K. Below 280 K, two phase transitions are observed. The first (Tc1 = 145 K) is a ferroelastic phase transition that generates superstructure reflections for the host while leaving the guest with 1D order. The second (Tc2 = 130 K) is a ``phase ordering'' transition to a four-dimensional structure (P2111(0??)) with pronounced host-guest intermodulation and a temperature dependent phase shift between guests in adjacent channels.

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



The substrate binding cavity of particulate methane monooxygenase from Methylosinus trichosporium OB3b expresses high enantioselectivity for n-butane and n-pentane oxidation to 2-alcohol.  


The particulate methane monooxygenase (pMMO) of Methylosinus trichosporium OB3b oxidized n-butane and n-pentane and mainly produced (R)-2-butanol and (R)-2-pentanol that comprised 78 and 89% of the product, respectively, indicating that the pro-R hydrogen of the 2-position carbon of n-butane and n-pentane is oriented toward a catalytic site within the substrate binding site of pMMO. The protein cavity adjacent to the catalytic center for pMMO has optimum volume for recognizing n-butane and n-pentane for enantioselective hydroxylation. PMID:21744144

Miyaji, Akimitsu; Miyoshi, Teppei; Motokura, Ken; Baba, Toshihide



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

SciTech Connect

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

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



Calculation of the density of solutions (sunflower oil + n-hexane) over a wide range of temperatures and pressure  

NASA Astrophysics Data System (ADS)

We present the results from an experimental investigation of the density of the sunflower oil system as a function of the mass concentration of n-hexane in the ranges of temperatures T=290 520 K and pressures P=0.101 98.1 MPa. A method of hydrostatic weighing was used to measure the density of the solutions under study.

Safarov, M. M.; Abdukhamidova, Z.



One and two component adsorption layers of n-hexane and benzene on graphite studied by 2H NMR spectroscopy  

NASA Astrophysics Data System (ADS)

Deuteron (2H) nuclear magnetic resonance (NMR) spectra were measured at temperatures between 300 and 90 K for n-hexane (C6D14), benzene (C6D6), and a mixture of n-hexane and benzene (C6D14/C6H6 and C6H14/C6D6) adsorbed on the graphitized carbon black Carbopack B. The amounts adsorbed correspond to one monolayer coverage of each substance for both the single and the two-component adsorption. The single component layers each undergo a two-dimensional (2D) fluid/solid phase transition spread over a 30-40 K interval centred at about the transition temperatures reported from diffraction studies. The surface diffusion coefficients in the 2D fluid regime are reported. On cooling to temperatures of about 200 to 160 K, three-dimensional benzene crystallites are formed leaving the n-hexane component in the one monolayer 2D fluid state. On further cooling, the n-hexane layer undergoes a 2D fluid/solid phase transition analogous to the corresponding one-component case.

Grundke, V.; Boddenberg, B.


Kinetic modeling of n-hexane oxyfunctionalization by hydrogen peroxide on titanium silicalites of MEL structure (TS-2)  

SciTech Connect

The authors present mathematical models of catalytic oxyfunctionalization of n-hexane over titanium silicalites. The model showed second-order reaction rates with respect to H{sub 2}O{sub 2} concentration in the aqueous phase. 56 refs., 7 figs., 3 tabs.

Gallot, J.E.; Fu, H.; Kapoor, M.P. [Universite Laval, Ste-Foy, Quebec (Canada)] [and others



Antidepressant-like activity of n-hexane extract of nutmeg (Myristica fragrans) seeds in mice.  


The present study was undertaken to investigate the effect of an n-hexane extract of Myristica fragrans seeds on depression in mice by using the forced swim test (FST) and the tail suspension test (TST). M. fragrans extract (5, 10, and 20 mg/kg) was administered orally for 3 successive days to different groups of Swiss male young albino mice. M. fragrans extract significantly decreased immobility periods of mice in both the FST and the TST. The 10 mg/kg dose was found to be most potent, as indicated by the greatest decrease in the immobility period compared with the control. Furthermore, this dose of the extract was found to have comparable potency to imipramine (15 mg/kg i.p.) and fluoxetine (20 mg/kg i.p.). The extract did not have a significant effect on locomotor activity of mice. Prazosin (62.5 microg/kg i.p.; an alpha (1)-adrenoceptor antagonist), sulpiride (50 mg/kg i.p.; a selective D(2) receptor antagonist), and p-chlorophenylalanine (100 mg/kg i.p.; an inhibitor of serotonin synthesis) significantly attenuated the M. fragrans extract-induced antidepressant-like effect in the TST. Thus, extract of M. fragrans elicited a significant antidepressant-like effect in mice, when assessed in both the TST and the FST. The antidepressant-like effect of the extract seems to be mediated by interaction with the adrenergic, dopaminergic, and serotonergic systems. PMID:16579733

Dhingra, Dinesh; Sharma, Amandeep



Reflectionless absorption of superhigh-frequency radiation in solutions of methyl ethyl ketone and methyl isobutyl ketone in n-heptane  

NASA Astrophysics Data System (ADS)

Investigations of dielectric properties of solutions of methyl ethyl ketone and methyl isobutyl ketone in n-heptane in a microwave range established the existence, in these solutions, of a spectrum of concentrations and thicknesses of the solution layer at which resonant reflectionless radiation absorption originates.

Veliev, M. I.; Kasimov, R. M.; Kadzhar, Ch. O.



Evaluation of n-hexane extract of Viola betonicifolia for its neuropharmacological properties.  


Viola betonicifolia (whole plant) has been used as a sedative and in various nervous disorders in Pakistani traditional medicines. The n-hexane extract of the whole plant of V. betonicifolia (HEVB) was investigated for neuropharmacological properties such as anxiolytic, muscle relaxant, sleep induction, antidepressant and sedative to ascertain its folk use. Anxiolytic activity was tested using the staircase test, while the muscle relaxing property of the extract was tested in various muscle relaxant paradigms, i.e. chimney test, traction test, rota rod and inclined plane. In anxiolytic and muscle relaxant tests, HEVB (0.3, 0.4 and 0.5 g/kg, i.p.), diazepam (1 mg/kg, i.p.) or distilled water (10 ml/kg i.p.) were administered 30, 60 and 90 min before performing the tests in mice. HEVB was also screened for a sleep-inducing effect. The antidepressant activity was determined by using the forced swimming test (FST), while line crossing in a special box was used for locomotor activity. HEVB showed a significant (P < 0.05) dose-dependent anxiolytic action in the staircase test. In muscle relaxant paradigms, a dose-dependent muscle relaxation was observed. For the phenobarbitone sleep induction test, HEVB notably (P < 0.05) reduced the latency time and increased the total sleeping duration. However, HEVB was devoid of any antidepressant activity, while the movements of mice were reduced significantly (P < 0.05) in locomotor activity. The results suggest that HEVB has anxiolytic, muscle relaxant, sleep-inducing (sedative) activity and, thus, provides pharmacological justification for the use of this plant as a sedative and for the relief of various nervous disorders. PMID:22359189

Muhammad, Naveed; Saeed, Muhammad; Khan, Haroon; Haq, Ikramul



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

Microsoft Academic Search

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

Jungha Seo; Jongcheon Lee; Hwayong Kim



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

SciTech Connect

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

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



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

SciTech Connect

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

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



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

SciTech Connect

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

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



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


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

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



A modelling study of the combustion of n-heptane and iso-octane in a high pressure turbulent flow reactor  

SciTech Connect

The primary reference fuels n-heptane and iso-octane and their mixtures are used as a measure of the tendency of a given automotive fuel to cause knocking or pre-ignition in an internal combustion engine. Consequently, many experimental studies have been performed on these hydrocarbons in an attempt to better understand their oxidation. Shock tube studies at high temperature and pressure have been performed. Low temperature studies, in which species concentration profiles of primary, intermediate and final products, have been carried out using jet stirred flow reactors. In addition, experiments have been performed in CFR engines and fundamental features of n-heptane autoignition have been observed using a rapid compression machine. A detailed chemical kinetic reaction mechanism is employed here to study the oxidation of both fuels. Computed results are compared with experimental data obtained in the High Pressure Turbulent Flow Reactor at Princeton University.

Curran, H.J.; Gaffuri, P.; Pitz, W.J.; Westbrook, C.K. [Lawrence Livermore National Lab., CA (United States); Callahan, C.; Dryer, F.L.; Held, T. [Princeton Univ., NJ (United States)



Excess enthalpies of the ternary mixtures: diisopropyl ether + (2,2,4-trimethylpentane or n-heptane) + methylcyclohexane at 298.15 K  

Microsoft Academic Search

Excess molar enthalpies, measured at 298.15 K in a flow microcalorimeter, are reported for the ternary mixtures (diisopropyl ether (DIPE) + 2,2,4-trimethylpentane (TMP) + methylcyclohexane (MCH)) and (diisopropyl ether + n-heptane (nC7) + methylcyclohexane). Smooth representations of the results are described and used to construct constant excess molar enthalpy contours on Roozeboom diagrams. The latter are compared with diagrams obtained

Zhaohui Wang; George C. Benson; Benjamin C.-Y. Lu



Excess molar enthalpies of the ternary mixtures: (diisopropyl ether or 2-methyltetrahydrofuran) + cyclohexane + n-heptane at 298.15 K  

Microsoft Academic Search

Microcalorimetric measurements of excess molar enthalpies, at 298.15K, are reported for the two ternary systems formed by mixing either diisopropyl ether or 2-methyltetrahydrofuran with binary mixtures of cyclohexane and n-heptane. Smooth representations of the results are presented and used to construct constant excess molar enthalpy contours on Roozeboom diagrams. It is shown that useful estimates of the ternary enthalpies can

Zhaohui Wang; George C Benson; Benjamin C.-Y Lu



Calorimetric, Viscosimetric, and Light Scattering Studies of the Aggregation of, and the Solubilization of Water by, Triton X-35 in n-Heptane.  


The behavior of a nonionic surfactant TX-35 in solution in n-heptane in the presence and absence of added water has been examined using the microcalorimetric, viscosimetric, and quasielastic light scattering experimental methods. In this paper, we were interested in the aggregation process of the poly(oxyethylene) glycol alkylphenyl ether in n-heptane and in the solubilization of water in the reverse micelle of the surfactant (micellar solubilization). The analysis of the differential molar enthalpies of dilution of TX-35 in dried n-heptane has shown the occurrence of a gradual exothermic aggregation process on a very wide range of concentration which takes place at particular concentration so-called "operational CMC". This operational CMC value has been confirmed by viscosities measurements. The differential molar enthalpies of hydration of TX-35 were also measured and found to be exothermic. The maximal hydration ratio (w0) was found to be equal to 3.2 mol H2O per mole of TX-35 before the point of phase separation. The measurements of the variation of the amount of water contained in TX-35 solutions at different concentrations in n-heptane also show the occurence of a gradual aggregation process and confirm the value of the maximal hydration ratio already determined by microcalorimetry. In the absence of added water, from the quasielastic light scattering experiments, a mean diameter of the aggregates close to 45 Å has been determine, while in the presence of water, a mean diameter of 61 Å was detected and remained unchanged with increasing the hydration ratio indicating that the size of the aggregate is more influenced by the presence of water than by the amount. In the presence of water, it is relevant to discuss aggregates of lamellar or filament shape. Copyright 1999 Academic Press. PMID:9885255

Lagerge; Grimberg-Michaud; Guerfi; Partyka



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

Microsoft Academic Search

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

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



High Pressure Oxidation of Liquid Fuels from Low to High Temperature. 2. Mixtures of n-Heptane and iso-Octane  

Microsoft Academic Search

The oxidation of mixtures of n-heptane and iso-octane in a high-pressure jet-stirred reactor has been investigated experimentally in a wide range of conditions covering the low and high temperature oxidation regimes (550-1150K, 10 atm, ø=1). The cool flame and negative temperature coefficient regimes were observed below 750K, Above 750 K, the normal high temperature oxidation of both fuels was observed. Reactants, intermediates




Vapor–liquid equilibria for the ternary system benzene+ n-heptane+ N, N-dimethylformamide at 101.33 kPa  

Microsoft Academic Search

Isobaric vapor–liquid-equilibrium (VLE) data at 101.33kPa for the system formed by benzene, n-heptane and N,N-dimethylformamide (DMF) are reported. Data reduction has been carried out through Wilson, NRTL, and UNIQUAC thermodynamic models for correlating the liquid-phase activity coefficients. Activity coefficients of the components in the mixture indicate positive deviations from Raoult’s law. Experimental results show that DMF is a good extractive

Beatriz Blanco; Maria Teresa Sanz; Sagrario Beltrán; José Luis Cabezas; José Coca



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



Vapor–liquid equilibria of the binary mixtures of tetrahydrofuran with 2,2,4-trimethylpentane, methylcyclohexane and n-heptane at 101.3 kPa  

Microsoft Academic Search

Vapor–liquid equilibrium (VLE) data have been measured at 101.3kPa for three binary mixtures of tetrahydrofuran with 2,2,4-trimethylpentane, methylcyclohexane and n-heptane. The isobaric T–x–y data have been reported and the thermodynamic consistency has been examined. The non-ideal behavior of the vapor phase has been considered by using the Soave–Redlich–Kwong (SRK) equation of state in calculating the fugacity coefficient. The Wilson, NRTL

Tz-Bang Du; Muoi Tang; Yan-Ping Chen



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.



Method 1664: N-hexane extractable material (hem) and silica gel treated n-hexane extractable material (SGT-HEM) by extraction and gravimetry (oil and grease and total petroleum hydrocarbons), April 1995  

SciTech Connect

Method 1664 was developed by the United States Environmental Protection Agency Office of Science and Technology to replace previously used gravimetric procedures that employed Freon-113, a Class I CFC, as the extraction solvent for the determination of oil and grease and petroleum hydrocarbons. Method 1664 is a performance-based method applicable to aqueous matrices that requires the use of n-hexane as the extraction solvent and gravimetry as the determinative technique. In addition, QC procedures designed to monitor precision and accuracy have been incorporated into Method 1664.




On-line monitoring of methanol in n-hexane by an organic-phase alcohol biosensor.  


An organic-phase alcohol biosensor has been developed by co-entrapping alcohol oxidase and horseradish peroxidase within an ionotropy polymer hydrogel matrix fabricated from silica gel particles, hydroxyethyl carboxymethylcellulose, an adduct of 3-methoxy-4-ethoxybenzaldehyde and 4-tert-butylpyridinium acetohydrazone, and octadecylsilica particles. The viability of the immobilised enzymes for the biocatalytic reaction of methanol in n-hexane was comparatively studied by using a bulk cell or a volume-changeable flow-through cell coupled with an oxygen optical transducer. It was found that the microenvironment around the enzyme, the deterioration property of the enzyme, the substrate throughput and the mass transfer process of the reactant in the bioreactor were the crucial parameters affecting the performance of the alcohol organic-phase biosensor. Our optimal biosensor was constructed from a flow-through cell packed with small particles of immobilised enzymes and it could maintain the biocatalytic reaction at high and stable rate for on-line detection of methanol in n-hexane under flow operation mode. The biosensor had an analytical working range of 2.3-90 mM methanol in n-hexane. The response times (t95) were 4.5 and 7.5 min for 60 and 10 mM methanol, respectively. The operational lifetime of the biosensor was more than 45 assays and the shelf lifetime was longer than 2 weeks. The biosensor has been successfully applied to determine the methanol content in a commercial gasoline-methanol blend sample with good recovery. PMID:16829067

Wu, Xiao Jun; Choi, Martin M F; Chen, Chang Shun; Wu, Xiao Min



Anthelmintic effects of Prosopis laevigata n-hexanic extract against Haemonchus contortus in artificially infected gerbils ( Meriones unguiculatus).  


The anthelmintic effect of Prosopis laevigata (mezquite) n-hexanic extract was evaluated against Haemonchus contortus endoparasitic stages in artificially infected gerbils (Meriones unguiculatus). Prosopis laevigata leaves were collected from the Sierra de Huautla, Ecological Reserve of the Biosphere, in Morelos State, Mexico; dehydrated under shade and macerated with n-hexane for 3 days, followed by distillation for 8 h. This procedure was repeated three times and the final extract was kept at 4 degrees C. The in vivo effect of the plant extract was evaluated in gerbils artificially infected with H. contortus. Plant extract concentration was 40 mg/ml. Three groups of gerbils were as follows: group 1 (n = 7), P. laevigata extract at 100 microl intraperitoneally (IP); group 2 (n = 6), control--Tween 20 in water at a single dose of 100 microl IP; group 3 (n = 8) also served as a control, receiving water only, to determine the mortality due to causes other than the plant extract. An additional group of seven gerbils (group 4) was administered fenbendazole, as a positive control. Five days later the animals were euthanized and stomach and mucosa removed to quantify the nematodes. Data were analysed using the Student's t-test to compare the mean of nematodes obtained in groups 1, 2 and 3. The parasite population in the plant extract treated group 1 was reduced by 42.5% (P < 0.05) with respect to the control group 2; and when control group 3 was used for comparison the parasitic reduction was estimated as 53.11%. This study shows the in vivo anthelmintic effect of P. laevigata n-hexane extract for the first time, using gerbils as an in vivo model, with potential use in sheep. PMID:19619382

De Jesús-Gabino, A F; Mendoza-de Gives, P; Salinas-Sánchez, D O; López-Arellano, M E; Liébano-Hernández, E; Hernández-Velázquez, V M; Valladares-Cisneros, G



Effects of occupational chronic co-exposure to n-hexane, toluen, and methyl ethyl ketone on NK cell activity and some immunoregulatory cytokine levels in shoe workers  

Microsoft Academic Search

1 To evaluate the effects of occupational long-term coexposure to n-hexane, toluen, and methyl ethyl ketone (MEK) on NK cell activity and serum IL-2, g-IFN levels, we studied a group of workers employed in a shoe factory where the jobs include use of glues and adhesives containing mainly n-hexane, and at low concentrations, toluen and MEK.2 No differences were found

B. Yücesoy; A. Yücel; O. Erdem; S. Burgaz; A. E. Karakaya



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



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

PubMed Central

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

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



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.



Volume ratios for n-pentane in the temperature range 278-338 K and at pressures up to 280 MPa  

SciTech Connect

Volume ratios (V/sub p//V/sub 0.1/), and isothermal compressibilities calculated from them, are reported for n-pentane for seven temperatures in the range 278 to 338 K for pressures up to 280 MPa. The isobaric measurements were made with a bellows volumometer for which a novel technique had to be devised to enable measurements to be made above the normal boiling point (309.3 K). The accuracy of the volume ratios is estimated to be +/- 0.05 to 0.1% up to 303.15 K and +/- 0.1 to 0.2% from 313.15 to 338.15 K. The volume ratios are in good agreement with those calculated from recent literature data up to the maximum pressure of the latter, viz., 60 MPa.

Easteal, A.J.; Woolf, L.A.



Aggregation behavior of cobalt(II), nickel(II), and copper(II) bis(2-ethylhexyl)phosphate complexes in n-heptane  

SciTech Connect

The solution behavior of divalent transition metal-bis(2-ethylhexyl) phosphate (M(DEHP){sub 2}, M = cobalt, nickel or copper) complexes in n-heptane have been investigated by vapor pressure osmometry, viscometry and dynamic light scattering. The present study provides evidence that divalent transition metal-HDEHP complexes of Ni, Co or Cu can form reversed micelles and shows that molecular modeling can provide new information on the molecular structure of these reversed micellar systems. Improved knowledge of the association microstructure type, structure and composition and of the effect of phase additives on reversed micellar behavior is essential to advance the fundamental understanding of solvent extraction mechanisms.

Yu, Z.J.; Ibrahim, T.H.; Neuman, R.D. [Auburn Univ., AL (United States). Dept. of Chemical Engineering



On the influence of sulfur on the platinum/iridium bimetallic catalysts in n-hexane/hydrogen reactions  

SciTech Connect

The reaction of n-hexane and hydrogen have been studied over silica- and {gamma}-alumina-supported monometallic and bimetallic Pt/Ir catalysts. Temperature-programmed reduction and X-ray diffraction clearly indicated alloy formation in the silica-supported catalysts. Changing the Ir content in the bulk of the catalyst resulted in a dramatic shift in selectivity due to the hydrogenolytic activity of Ir. However, after sulfurization all catalysts containing Ir showed a Pt-like behavior with respect to the selectivity. The increased yields of the sulfided Ir and pt/Ir catalysts, when compared with the sulfided Pt catalysts, might be due to the relatively high dehydrogenating activity of Ir.

Dees, M.J.; Ponec, V. (Leiden Univ. (Netherlands))



Critical phenomena in a binary mixture of n-hexane and nitrobenzene. Analysis of viscosity and light-scattering data  

NASA Astrophysics Data System (ADS)

Extensive measurements were made of light scattering intensity, quasielastic spectral width, and shear viscosity of the binary-liquid system n-hexane and nitrobenzene in the critical region. The measurements cover both the critical isochore and some other isochores in the temperature range T=1 mK to 30 K around the consolute temperature. The scattering experiments were made at five different angles covering a range of wave-vector transfer q from 3.5×104 to 28.2×104 cm-1 with values of the scaling variable q? (? is the correlation length) spanning from 0.006 to 51. The data on viscosity and linewidth are analyzed in the light of recent theoretical predictions taking into account the background effects on the transport coefficients. The agreement between theory and the experiments is very good in the whole range of q? when the background effect is included.

Chen, Sow-Hsin; Lai, Ching-Chung; Rouch, Jaques; Tartaglia, Piero



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


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

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



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

SciTech Connect

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

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



Effect of Na+, Mg2+, and Zn2+ chlorides on the structural and thermodynamic properties of water/n-heptane interfaces.  


The effect on the structural and thermodynamic properties in water/n-heptane interfaces on addition of NaCl, MgCl(2), and ZnCl(2) has been examined through five independent 100-ns molecular dynamics simulations. Results indicate that the interfacial thickness within the framework of the capillary-wave model decreases on addition of electrolytes in the order Na(+) < Mg(2+) < Zn(2+), whereas the interfacial tension increases in the same order. Ionic density profiles and self-diffusion coefficients are strongly influenced by the strength of the first hydration shell, which varies in the order Na(+) < Mg(2+) < Zn(2+). On the other hand, the Cl(-) behavior, that is, diffusion and solvation sphere, is influenced by its counterion. Accordingly, cations are strongly expelled from the interface, which is especially remarkable for the small divalent cations. This fact alters the water geometry near the interface and in a lesser extent n-heptane order and number of hydrogen bonds per water molecule close to the interface. PMID:21462228

Rodríguez-Ropero, Francisco; Fioroni, Marco



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

NASA Astrophysics Data System (ADS)

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

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



Transport Properties of Gaseous Hydrocarbons  

Microsoft Academic Search

Measurements have been made, at temperatures between 35 and 100 degrees C, of the viscosities and thermal conductivities of gaseous methane, ethane, ethylene, propane, propylene, cyclo-propane, n-butane, cis-2-butene, trans-2-butene, 1:3-butadiene, iso-butane, n-pentane, iso-pentane, neo-pentane, cyclo-pentane, n-hexane, neo-hexane, cyclo-hexane, benzene, n-heptane, 2:4-dimethyl-pentane, n-octane, 2:3:4-trimethyl-pentane and of carbon tetrafluoride. Viscosities were measured by observing the damping of a pendulum swinging in the

J. D. Lambert; K. J. Cotton; M. W. Pailthorpe; A. M. Robinson; J. Scrivins; W. R. F. Vale; R. M. Young



Solvatochromic behavior of phenol blue in CO2+ethanol and CO2+n-pentane mixtures in the critical region and local composition enhancement  

NASA Astrophysics Data System (ADS)

The UV-Vis spectra of probe phenol blue in CO2+ethanol and CO2+n-pentane binary mixtures were studied at 308.15 K and different pressures. The experiments were conducted in both supercritical region and subcritical region of the mixtures by changing the compositions of the mixed solvents. On the basis of the experimental results the local compositions of the solvents about phenol blue were estimated by neglecting the size difference of CO2 and the cosolvents. Then the local composition data were corrected by a method proposed in this work, which is mainly based on Lennard-Jones sphere model. It was demonstrated that the local mole fraction of the cosolvents is higher than that in the bulk solution at all the experimental conditions. In the near critical region of the mixed solvents the local composition enhancement, defined as the ratio of cosolvent mole fraction about the solute to that in the bulk solution, increased significantly as pressure approached the phase boundary from high pressure. The local composition enhancement was not considerable as pressure was much higher than the critical pressure. In addition, in subcritical region the degree of composition enhancement was much smaller and was not sensitive to pressure in the entire pressure range as the concentration of the cosolvents in the mixed solvents was much higher than the concentration at the critical point of the mixtures.

Chen, Jiawei; Shen, Dong; Wu, Weize; Han, Buxing; Wang, Bo; Sun, Donghai



Human polymorphonuclear leukocyte chemotaxis as a tool in detecting biological early effects in workers occupationally exposed to low levels of n-hexane.  


Human polymorphonuclear leukocytes (PMN) were chosen to measure two cellular end points--chemotaxis and respiratory burst--and to verify whether they could function as biomarkers of early effect in detecting occupational exposure to n-hexane of apparently healthy shoe workers, without any electroneuromyographic (ENMG) abnormality. Chemotaxis, but not respiratory burst, was found to be impaired. A negative linear correlation between chemotaxis of PMN of those workers that had been exposed to n-hexane versus 2,5-hexanedione (2,5-HD) urinary concentrations were found. This negative trend is consistent with our previous in vitro experimental findings: it was observed that the progressive addition of 2,5-HD to PMN suspensions inhibited chemotaxis in a dose-dependent mode, while chemiluminescence was not modified. Now we have confirmed in vivo that chemotaxis is more sensitive than the respiratory burst response to 2,5-HD. Such results justify the interest in the behaviour of PMN harvested from workers exposed to n-hexane. Since significant inhibition of chemotactic activity was observed in some workers whose urinary 2,5-HD levels were lower than 5 mg l-1, which is the biological exposure index suggested by ACGIH, this study suggests that PMN chemotaxis may be proposed as a useful biomarker in detecting occupational exposure to low level of n-hexane. PMID:7826683

Governa, M; Valentino, M; Visonà, I; Monaco, F



Proliferative response of peripheral blood lymphocytes and lymphocyte subpopulations in n-Hexane, toluen, and methyl ethyl ketone co-exposed workers  

Microsoft Academic Search

To estimate the quantitative relation between chronic co-exposure to airborne n-hexane, toluen, methyl ethyl ketone (MEK) and various markers of immune function such as proliferative response of peripheral blood lymphocytes and lymphocyte subpopulations, a group of workers employed in a shoe factory were examined and compared with the unexposed controls. A significant increase was observed in the proliferative response of

Asuman Karakaya; Berran Yücesoy; Ay?egül Yücel; Nurten Erdem; ?lker Ate?; Handan U Sabir; Turgut ?mir



Physiologicomathematical model for studying human exposure to organic solvents: kinetics of blood/tissue n-hexane concentrations and of 2,5-hexanedione in urine.  

PubMed Central

The physiologicomathematical model with eight compartments described allows the simulation of the absorbtion, distribution, biotransformation, excretion of an organic solvent, and the kinetics of its metabolites. The usual compartments of the human organism (vessel rich group, muscle group, and fat group) are integrated with the lungs, the metabolising tissues, and three other compartments dealing with the metabolic kinetics (biotransformation, water, and urinary compartments). The findings obtained by mathematical simulation of exposure to n-hexane were compared with data previously reported. The concentrations of n-hexane in alveolar air and in venous blood described both in experimental and occupational exposures provided a substantial validation for the data obtained by mathematical simulation. The results of the urinary excretion of 2,5-hexanedione given by the model were in good agreement with data already reported. The simulation of an exposure to n-hexane repeated five days a week suggested that the solvent accumulates in the fat tissue. The half life of n-hexane in fat tissue equalled 64 hours. The kinetics of 2,5-hexanedione resulting from the model suggest that occupational exposure results in the presence of large amounts of 2,5-hexanedione in the body for the whole working week.

Perbellini, L; Mozzo, P; Brugnone, F; Zedde, A



Localized Raman scattering probes of molecular-scale motions in case II swelling of polystyrene in n-hexane  

SciTech Connect

Surface-enhanced Raman scattering (SERS) active metal island films placed within micrometer-sized polymer sandwich thin film structures were explored as molecular-level probes of case II diffusion events for n-hexane swelling of polystyrene. The fabrication and use of these structures in an internal reflection geometry is detailed. A comparison of Ag and Au films indicates that strong SERS signals are obtained from Au island structures interspersed to various depths within polystyrene, while simultaneously avoiding photooxidation problems typically encountered with Ag-enhancing structures. The physical spread of the Au island structure in the depth direction was determined to be [le]200 A by Auger depth profiling and physical profilometry. Combining this physical spread and the SERS-distance dependence d(1/e) [approx] 50 [angstrom] yields a spatial resolution for this technique of [le]300 [angstrom]. Although the SERS features of the solvent within the swollen polymer film were generally substantially lower than those of the polystyrene, in situ observation of permeant progression was possible for unannealed samples. Large changes in the vibrational spectrum with solvent influx were noted for the polystyrene features at 1070 and 1371 cm[sup [minus]1]. In particular, changes in the latter band are interpreted in terms of an increase in chain mobility, with solvent passage, which allows the pendant phenyl moieties to align parallel to the semimajor axes of the oblate spheroidal particles, thus increasing their effective scattering cross section. 39 refs., 7 figs.

Drake, P.A.; Bohn, P.W. (Univ. of Illinois, Urbana-Champaign, IL (United States))



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.

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



Supercritical SC-CO(2) and Soxhlet n-Hexane Extract of Tunisian Opuntia ficus indica Seeds and Fatty Acids Analysis.  


The fatty acids profiles of Tunisian Opuntia ficus indica seeds (spiny and thornless form) were investigated. Results of supercritical carbon dioxide (SC-CO(2)) and soxhlet n-hexane extract were compared. Quantitatively, the better yield was obtained through soxhlet n-hexane: 10.32% (spiny) and 8.91% (thornless) against 3.4% (spiny) and 1.94% (thornless) by SC-CO(2) extract (T?=?40°C, P = 180 bar, time?=?135?mn, CO(2) flow rate?=?15?mL·s(-1)). Qualitatively, the main fatty acids components were the same for the two types of extraction. Linoleic acid was the major compound, SC-CO(2):?57.60% (spiny), 59.98% (thornless), soxhlet n-hexane: 57.54% (spiny), 60.66% (thornless), followed by oleic acid, SC-CO(2):?22.31% (spiny), 22.40% (thornless), soxhlet n-hexane: 25.28% (spiny), 20.58% (thornless) and palmitic acid, SC-CO(2):?14.3% (spiny), 12.92% (thornless), soxhlet n-hexane: 11.33% (spiny), 13.08% (thornless). The SC-CO(2) profiles fatty acids showed a richness with other minority compounds such as C(20:1), C(20:2), and C(22).The seeds oil was highly unsaturated (US?=?4.44-5.25), and the rising temperatures donot affect the selectivity of fatty acids extract by SC-CO2: US?=?4.44 (T?=?40°C) and 4.13 (T?=?70°C). PMID:22754699

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



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

PubMed Central

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

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



Reference Correlation of the Thermal Conductivity of n-Heptane from the Triple Point to 600 K and up to 250 MPa  

NASA Astrophysics Data System (ADS)

This paper contains new, representative reference equations for the thermal conductivity of n-heptane. The equations are based in part upon a body of experimental data that have been critically assessed for internal consistency and for agreement with theory whenever possible. In the case of the dilute-gas thermal conductivity, a theoretically based correlation was adopted in order to extend the temperature range of the experimental data. Moreover, in the critical region, the experimentally observed enhancement of the thermal conductivity is well represented by theoretically based equations containing just one adjustable parameter. The correlations are applicable for the temperature range from the triple point to 600 K and pressures up to 250 MPa. The overall uncertainty (considered to be estimates of a combined expanded uncertainty with a coverage factor of 2) of the proposed correlation is estimated, for pressures less than 250 MPa and temperatures less than 600 K, to be less than 4%.

Assael, M. J.; Bogdanou, I.; Mylona, S. K.; Huber, M. L.; Perkins, R. A.; Vesovic, V.



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

Microsoft Academic Search

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

G. Gu; W. Wang; H. Yan



Comparative study on the antioxidant activities of the different extracts and the composition of the oil extracted by n-hexane from Iranian Vitex pseudo-negundo  

Microsoft Academic Search

Antioxidant activities of different extracts obtained from the aerial parts of Vitex pseudo-negundo from Kashan, central Iran, were evaluated for the first time in this study using ?-carotene\\/linoleic acid and scavenging of free-radical (DPPH) assays. Water extract showed the highest activity in both assays. GC–MS analysis of the oil extracted by n-hexane revealed 46 compounds with trans-?-farnesene being the main

Mohammadreza Mozdianfard; Maryam Akhbari; Hossein Batooli



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.



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

Microsoft Academic Search

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

Robert Tardif; Véronique Nadeau; Ginette Truchon; Martin Brochu



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

SciTech Connect

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

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



Anaerobic Initial Reaction of n-Alkanes in a Denitrifying Bacterium: Evidence for (1-Methylpentyl)succinate as Initial Product and for Involvement of an Organic Radical in n-Hexane Metabolism†  

PubMed Central

A novel type of denitrifying bacterium (strain HxN1) with the capacity to oxidize n-alkanes anaerobically with nitrate as the electron acceptor to CO2 formed (1-methylpentyl)succinate (MPS) during growth on n-hexane as the only organic substrate under strict exclusion of air. Identification of MPS by gas chromatography-mass spectrometry was based on comparison with a synthetic standard. MPS was not formed during anaerobic growth on n-hexanoate. Anaerobic growth with [1-13C]n-hexane or d14-n-hexane led to a 1-methylpentyl side chain in MPS with one 13C atom or 13 deuterium atoms, respectively. This indicates that the 1-methylpentyl side chain originates directly from n-hexane. Electron paramagnetic resonance spectroscopy revealed the presence of an organic radical in n-hexane-grown cells but not in n-hexanoate-grown cells. Results point at a mechanistic similarity between the anaerobic initial reaction of n-hexane and that of toluene, even though n-hexane is much less reactive; the described initial reaction of toluene in anaerobic bacteria is an addition to fumarate via a radical mechanism yielding benzylsuccinate. We conclude that n-hexane is activated at its second carbon atom by a radical reaction and presumably added to fumarate as a cosubstrate, yielding MPS as the first stable product. When 2,3-d2-fumarate was added to cultures growing on unlabeled n-hexane, 3-d1-MPS rather than 2,3-d2-MPS was detected, indicating loss of one deuterium atom by an as yet unknown mechanism.

Rabus, Ralf; Wilkes, Heinz; Behrends, Astrid; Armstroff, Antje; Fischer, Thomas; Pierik, Antonio J.; Widdel, Friedrich



Reactions of n-heptane and methylcyclopentane over an oxygen-modified molybdenum carbide catalyst. Study of coke formation, catalyst deactivation, and regeneration  

SciTech Connect

After an oxidative treatment, molybdenum carbide is an active and very selective catalyst for the isomerization of n-heptane. An important parameter in the choice of a catalyst for application in industry is its resistance to deactivation by coke formation, which can be caused by the presence of cyclic molecules. In this work, a study of the effect of methylcyclopentane (MCP) on the deactivation of the oxygen-modified molybdenum carbide catalyst has been performed. It has been found that the catalyst deactivates in the presence of pure MCP and that a lower activity for heptane isomerization is obtained after the reaction under MCP. TEM showed that coke formation is the cause of the deactivation. It has also been shown that increasing the total pressure when the MCP is reacted leads to a large decrease in the catalyst deactivation and that heptane isomerization can be carried out over this deactivated sample with only a small loss in activity. Further, the catalyst can be totally regenerated in air.

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



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.



The effect of workload on biological monitoring of occupational exposure to toluene and n-Hexane: contribution of physiologically based toxicokinetic modeling.  


A physiologically based toxicokinetic model was used to examine the impact of work load on the relationship between the airborne concentrations and exposure indicator levels of two industrial solvents, toluene and n-Hexane. The authors simulated occupational exposure (8 hr/day, 5 days/week) at different concentrations, notably 20 ppm and 50 ppm, which are the current threshold limit values recommended by ACGIH for toluene and n-hexane, respectively. Different levels of physical activity, namely, rest, 25 W, and 50 W (for 12 hr followed by 12 hr at rest) were simulated to assess the impact of work load on the recommended biological exposure indices: toluene in blood prior to the last shift of the workweek, urinary o-cresol (a metabolite of toluene) at the end of the shift, and free (nonhydrolyzed) 2,5-hexanedione (a metabolite of n-hexane) at the end of the shift at the end of the workweek. In addition, urinary excretion of unchanged toluene was simulated. The predicted biological concentrations were compared with the results of both experimental studies among human volunteers and field studies among workers. The highest predicted increase with physical exercise was noted for toluene in blood (39 microg/L at 50 W vs. 14 microg/L at rest for 20 ppm, i.e., a 2.8-fold increase). The end-of-shift urinary concentrations of o-cresol and toluene were two times higher at 50 W than at rest (for 20 ppm, 0.65 vs. 0.33 mg/L for o-cresol and 43 vs. 21 microg/L for toluene). Urinary 2,5-hexanedione predicted for 50 ppm was 1.07 mg/L at 50 W and 0.92 mg/L at rest (+16%). The simulations that best describe the concentrations among workers exposed to toluene are those corresponding to 25 W or less. In conclusion, toxicokinetic modeling confirms the significant impact of work load on toluene exposure indicators, whereas only a very slight effect is noted on n-hexane kinetics. These results highlight the necessity of taking work load into account in risk assessment relative to toluene exposure. PMID:19384711

Sari-Minodier, Irène; Truchon, Ginette; Charest-Tardif, Ginette; Bérubé, Anick; Tardif, Robert



Determination of methylmercury in fish using focused microwave digestion following by Cu2+ addition, sodium tetrapropylborate derivatization, n-heptane extraction, and gas chromatography-mass spectrometry.  


The analytical procedure for analysis of methylmercury in fish was developed. It involves microwave-assisted digestion with alkaline solution (tetramethylammonium hydroxide), addition of Cu2+, aqueous-phase derivatization of methylmercury with sodium tetrapropylborate, and subsequent extraction with n-heptane. The methylmercury derivative was desorbed in the splitless injection port of a gas chromatograph and subsequently analyzed by electron impact mass spectrometry. Optimum conditions allowed sample throughout to be controlled by the instrumental analysis time (near 7 min per sample) but not by the sample preparation step. At the power of 15-30, 45, and 60-75 W, sample preparation time is only 3.5, 2.5, and 1.5 min, respectively. The proposed method was finally validated by the analysis of three biological certified reference materials, BCR CRM 464 tuna fish, NRC DORM-2 dogfish muscle, and NRC DOLT-2 dogfish liver. The detection limit of the overall procedure was found to be 40 ng/g of biological tissue for methylmercury. The recovery of methylmercury was 91.2-95.3% for tuna, 89.3-94.7% for marlin, and 91.7-94.8% for shark, respectively. The detected and certified values of methylmercury of three biological certified reference materials were as follows: 5.34 +/- 0.30 microg/g (mean +/- S.D.) and 5.50 +/- 0.17 microg/g for CRM 464 tuna fish, 4.34 +/- 0.24 and 4.47 +/- 0.32 microg/g for NRC DORM-2 dogfish muscle, and 0.652 +/- 0.053 and 0.693 +/- 0.055 microg/g for NRC DOLT-2 dogfish liver, respectively. It indicated that the method was well available to quantify the methylmercury in fish. PMID:14753723

Chen, Syr-Song; Chou, Shin-Shou; Hwang, Deng-Fwu



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


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



Reference Correlation of the Viscosity of n-Hexane from the Triple Point to 600 K and up to 100 MPa  

NASA Astrophysics Data System (ADS)

This paper contains new, representative reference equations for the viscosity of n-hexane. The equations are based in part upon a body of experimental data that has been critically assessed for internal consistency and for agreement with theory whenever possible. The correlations are valid from the triple point to 600 K, and at pressures up to 100 MPa. We estimate the expanded uncertainty at a 95% confidence level to be 2% for the liquid phase at temperatures from the triple point to 450 K and pressures to 100 MPa. For the liquid at 450-600 K at pressures to 100 MPa, the expanded uncertainty at the 95% confidence level is 6%, and is 0.3% for the low-density gas at pressures to 0.3 MPa.

Michailidou, E. K.; Assael, M. J.; Huber, M. L.; Perkins, R. A.



PhysicoChemical Studies on Microemulsion: Effect of Cosurfactant Chain Length on the Phase Behavior, Formation Dynamics, Structural Parameters and Viscosity of Water\\/(Polysorbate-20 +  n Alkanol)\\/ n Heptane Water-in-Oil Microemulsion  

Microsoft Academic Search

The pseudo-ternary water-in-oil microemulsion system, comprising water\\/polyoxyethylene sorbitan monolaurate (Polysorbate-20) + n-alkanol\\/n-heptane, have been studied by phase manifestation, method of dilution, viscosity and dynamic light scattering measurements.\\u000a Polysorbate-20, in combination with equal mass of cosurfactants (of varying chain length, from n-butanol to n-octanol) were used in studying the systems in the temperature range 303–323 K. Appearance of turbidity was noted visually,\\u000a which indicated

Sujoy Paul; Amiya Kumar Panda


Speed of sound, viscosity and refractive index of multicomponent systems: theoretical predictions from the properties of pure components  

Microsoft Academic Search

Theoretical prediction of speed of sound, viscosity and refractive index of three ternary systems: toluene + n-heptane + n-hexane (I), cyclohexane + n-heptane + n-hexane(II) and n-hexane + n-heptane + n-decane (III) have been made on the basis of empirical, semi-empirical and statistical mechanical theories using the properties of pure components. Theoretical results are compared with the experimentally measured values

J. D. Pandey; V. Vyas; P. Jain; G. P. Dubey; N. Tripathi; R. Dey



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


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



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

NASA Astrophysics Data System (ADS)

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

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



Viscosity correlations for binary supercritical fluids  

SciTech Connect

The viscosities and densities of supercritical mixtures of methanol, ethanol, n-propanol, isopropanol, n-pentane, n-hexane, n-heptane, and acetone in carbon dioxide, at concentrations between 1 and 5 mol %, were determined using a falling weight viscometer at pressures up to 240 bar and at temperatures between 313 and 328 K. The effects of pressure, temperature, cosolvent concentration, and the physical properties of the cosolvents on the mixture viscosity and density were examined. The viscosities and the densities of the mixtures were found to increase with the size, polarity, and concentration of the cosolvent molecule. The mixture viscosity was correlated with several empirical dense gas viscosity correlations. The best correlation was the Ely and Hanley technique modified with a density-dependent noncorrespondence factor. The Peng-Robinson equation of state was used to correlate the mixture densities.

Tilly, K.D.; Foster, N.R.; Macnaughton, S.J.; Tomasko, D.L. (Univ. of New South Wales, Kensington (Australia). School of Chemical Engineering and Industrial Chemistry)




EPA Science Inventory

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


Measurement and correlation of the ( p, ?, T) relation of liquid n-heptane, n-nonane, 2,4-dichlorotoluene, and bromobenzene in the temperature range from (233.15 to 473.15) K at pressures up to 30 MPa for use as density reference liquids  

Microsoft Academic Search

Comprehensive (p,?,T) measurements on n-heptane, n-nonane, 2,4-dichlorotoluene, and bromobenzene were carried out in the homogeneous liquid phase for temperatures from (233.15 to 473.15)K at pressures up to 30MPa. The measurements were performed by using an accurate single-sinker densimeter based on the Archimedes’ buoyancy principle. The total uncertainty of the measurements in density was estimated to be 0.02% (level of confidence

G. Schilling; R. Kleinrahm; W. Wagner



Aggregation of Alcohols Ethoxylates in n Heptane  

Microsoft Academic Search

The solubility and aggregation process of polyethoxylated non-ionic surfactants, of general formula C\\u000a i\\u000a H2i+1–(O–CH2–CH2)\\u000a j\\u000a –OH with i = 6, 8, 10 and j = 3–6 (C\\u000a i\\u000a EO\\u000a j\\u000a ), in heptane were studied. The aggregation of C\\u000a i\\u000a EO\\u000a j\\u000a surfactants in heptane was investigated by using methylene blue (MB) as an absorption probe. In solutions of MB in the presence

José Antonio Gárate; María Pilar Gárate; Andrés F. Olea



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

SciTech Connect

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

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



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

NASA Astrophysics Data System (ADS)

Stable carbon isotope ratios for 37 hydrocarbon, CFC and halocarbon compounds were determined over the course of 1 year (86 samples) from the urban Belfast environment, Northern Ireland (NI). A smaller number of samples were collected from rural locations at Crossgar and Hillsborough, NI, and one marine location at Mace Head, Republic of Ireland. Source ?13C "signatures" suggest that C5 alkanes and ?C4 alkenes are most likely derived from vehicle emissions. C3-C5 hydrocarbons show significant enrichment of ?13C with iso-alkanes < n-alkanes < alkenes < alkynes. There is also significant enrichment of ?13C from propane to n-butane to n-pentane. There is no significant separation between n-pentane, n-hexane, n-heptane or methyl-butane, methyl pentane and methyl hexanes. Calculated hydroxyl reaction kinetic isotope effects and subsequent ?13C enrichment are insufficient to explain shifts in isotopic ratio relative to concentration for all compounds as is differences in origin of air mass. Very few compounds show significant diurnal shifts; however, alkanes and ?C4 alkenes demonstrate consistent enrichment of isotopic ratios when summer samples are compared to winter samples. Benzene is the sole compound measured that appears to become more depleted in ?13C when summer samples are compared against winter samples. Urban air, sampled at Belfast, which has originated in Europe shows enriched values for hydrocarbons while air which has originated in the Arctic Ocean is most similar to marine air off the Atlantic, sampled at Mace Head, Ireland.

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



Generalized Flory theory for hard alkane fluids  

NASA Astrophysics Data System (ADS)

Generalized Flory-dimer (GF-D) theory is extended to hard n-alkane fluids modelled as fused hard spheres constrained according to the rotational isomeric state approximation. Theoretical predictions for the second to the fifth virial coefficients for each conformer from n-butane to n-octane are compared with numerical results. Predictions for the second viral coefficient are in excellent agreement with recent simulation results; however, GF-D theory systematically overpredicts the third virial coefficient and underpredicts the fourth and the fifth virial coefficients. GF-D predictions for the compressibility factor for n-alkanes from n-butane to n-octane are compared with molecular dynamic simulation results for a closely related model. Despite the over- and underprediction of the individual virial coefficients, excellent agreement is observed between theory and simulation for the compressibility factors of n-butane and n-pentane using no adjustable parameters. However, in the cases of n-hexane, n-heptane and n-octane, GF-D theory slightly underpredicts the pressure at high volume fractions. Theoretical considerations suggest that probably the predictions of GF-D theory will deteriorate with increasing chain length.

Mehta, Sameer D.; Honnell, Kevin G.


DFT derived solvation models for organic compounds in alkane solvents  

NASA Astrophysics Data System (ADS)

From a density functional theory (DFT) analysis of solvation and the different components which comprise the free energy of solvation we propose quantitative structure property relationship (QSPR) models to predict free energy of solvation, ?GS0, of organic compounds in seven alkane solvents (n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, and n-hexadecane). The data contains 151 structurally different compounds containing diverse organic functions: unbranched and branched alkanes, cycloalkanes, aromatics, alcohols, aldehydes, ketones, esters, ethers, amines, nitriles, pyridines, fluorinated hydrocarbons, thiols, sulfides, carboxylic acids and nitro hydrocarbons; covering a ?GS0 range from about -50 to 0 kJ/mol. The models for the seven n-alkane solvents contain the same two molecular descriptors, one DFT descriptor (softness) and one geometric (molecular surface area). This fact suggests that the physical mechanisms behind the solvation of organic compounds in n-alkane solvents are of the same nature, as expected from the similar physical and chemical properties of alkanes. The models proposed have the merit of predicting free energy of solvation in alkane solvents with fewer descriptors than other QSPR models reported in the literature having similar statistics, allowing in this way a well-defined physical interpretation. The two descriptors have definite physical meaning corresponding to the different components which comprise free energy of solvation. Thus, the models proposed reach the desired compromise among simpleness, physical interpretation and computation time.

Delgado, Eduardo J.; Alderete, Joel B.; Jaña, Gonzalo A.



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



Deciphering biodegradation effects on light hydrocarbons in crude oils using their stable carbon isotopic composition: A case study from the Gullfaks oil field, offshore Norway  

NASA Astrophysics Data System (ADS)

Compound-specific isotope analysis has become an important tool in environmental studies and is an especially powerful way to evaluate biodegradation of hydrocarbons. Here, carbon isotope ratios of light hydrocarbons were used to characterise in-reservoir biodegradation in the Gullfaks oil field, offshore Norway. Increasing biodegradation, as characterised, for example, by increasing concentration ratios of Pr/ n-C 17 and Ph/ n-C 18, and decreasing concentrations of individual light hydrocarbons were correlated to 13C-enrichment of the light hydrocarbons. The ?13C values of C 4 to C 9n-alkanes increase by 7-3‰ within the six oil samples from the Brent Group of the Gullfaks oil field, slight changes (1-3‰) being observed for several branched alkanes and benzene, whereas no change (<1‰) in ?13C occurs for cyclohexane, methylcyclohexane, and toluene. Application of the Rayleigh equation demonstrated high to fair correlation of concentration and isotope data of i- and n-pentane, n-hexane, and n-heptane, documenting that biodegradation in reservoirs can be described by the Rayleigh model. Using the appropriate isotope fractionation factor of n-hexane, derived from laboratory experiments, quantification of the loss of this petroleum constituent due to biodegradation is possible. Toluene, which is known to be highly susceptible to biodegradation, is not degraded within the Gullfaks oil field, implying that the local microbial community exhibits rather pronounced substrate specificities. The evaluation of combined molecular and isotopic data expands our understanding of the anaerobic degradation processes within this oil field and provides insight into the degradative capabilities of the microorganisms. Additionally, isotope analysis of unbiodegraded to slightly biodegraded crude oils from several oil fields surrounding Gullfaks illustrates the heterogeneity in isotopic composition of the light hydrocarbons due to source effects. This indicates that both source and also maturity effects have to be well constrained when using compound-specific isotope analysis for the assessment of biodegradation.

Vieth, Andrea; Wilkes, Heinz



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

SciTech Connect

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

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



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

Microsoft Academic Search

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

Ana Maria Blanco; Juan Ortega



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


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



Effectiveness factors for hydroprocessing of coal and coal liquids. Progress report No. 9, September 15, 1989-December 15, 1989.  

National Technical Information Service (NTIS)

During this quarterly report period, experimental studies were completed on the effect of solvent on ambient, non-reactive effective diffusivities for coronene in the pores of NiMo-325 catalyst. Solvents employed included cyclohexane, n-hexane, n-heptane,...

F. E. Massoth J. D. Seader



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

SciTech Connect

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

Escobedo, J.; Mansoori, G.A. [Univ. of Illinois, Chicago, IL (United States)



Flame Propagation: The Measurement of Burning Velocities of Slow Flames and the Determination of Limits of Combustion  

Microsoft Academic Search

A method of measuring burning velocities of combustible gas\\/air mixtures near the limits of combustion is developed, using a burner providing a flat disk-shaped flame. The method is applied to methane, propane, n-pentane, n-heptane, ethylene, acetylene and benzene flames of velocities 5 to 10 cm\\/s. The characteristics of the burner and the flames are discussed; the time during which unburnt

Alfred Egerton; S. K. Thabet



Viscometric Determination of the Onset of Asphaltene Flocculation: A Novel Method  

Microsoft Academic Search

A new technique for the determination of the onset of asphaltene flocculation has been developed through accurate viscosity measurements of a crude oil being diluted with a precipitating agent (n-pentane, n-heptane, n-nonane). This detection method is based on experimental observations of an increase in the viscosity of a crude oil-asphaltene-precipitating agent suspension in which asphaltene particle aggregation occurs. The key

Escobedo Joel; G. A. Mansoori



Exceptional Performance of a Nuclear Ignition Otto-cycle Engine using n-Pentane as Fuel  

Microsoft Academic Search

KNOCKING combustion (detonation) in Otto-cycle engines using hydrocarbon fuel is attributed by King1 to the effect of finely divided carbon in igniting the unburned combustible mixture ahead of the flame front (the end gas). The carbon particles can, according to this view, be provided (a) by pyrolysis of the hydrocarbon at the high pressure and temperature attained by the end

R. O. King



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

Microsoft Academic Search

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

Lihua Wang; Zhiping Zhao; Jiding Li; Cuixian Chen




Microsoft Academic Search

One of the most important properties of premixed flames is burning velocity. Laminar burning velocities play essential roles in determining several important aspects of the combustion process in spark ignition engines; among these are the ignition delay, the thickness of the wall quench layers, and the minimum ignition energy. It is found that a detailed knowledge of laminar premixed flames

HARA Takashi; TANOUE Kimitoshi


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

Microsoft Academic Search

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

Ligang Lin; Yuzhong Zhang; Ying Kong



Aromatisation of n -heptane over ZSM-5 prepared without the aid of a template  

Microsoft Academic Search

ZSM-5 was prepared without the aid of an organic template. Effect of synthesis parameters on its catalytic activity in aromatisation ofn-heptane are discussed. Addition of seed material increased the crystallinity of the ZSM-5 phase. The catalytic activity was comparable with a sample prepared using an organic template. Formation of higher amount of C9– aromatics was observed over the non-templated zeolite.

A. R. Pradhan; N. Viswanadham; S. Suresh; O. P. Gupta; N. Ray; G. Muralidhar; Uma Shanker; T. S. R. Prasada Rao



A thermodynamic study of ketoreductase-catalyzed reactions 3. Reduction of 1-phenyl-1-alkanones in non-aqueous solvents  

Microsoft Academic Search

The equilibrium constants K for the reactions (1-phenyl-1-alkanone+2-propanol=1-phenyl-1-alkanol+acetone) in the solvents n-pentane and n-hexane have been determined by using gas chromatography at the temperature 298.15K. The 1-phenyl-1-alkaones included in this study were: 1-phenyl-1-ethanone, 1-phenyl-1-propanone, 1-phenyl-1-butanone, 1-phenyl-1-pentanone, 1-phenyl-1-hexanone, and 1-phenyl-1-heptanone. The equilibrium constants for the reaction involving 1-phenyl-1-ethanone were measured in the solvent n-hexane as a function of temperature (288 K

Yadu B. Tewari; Nand Kishore; J. David Rozzell; David J. Vanderah; Michele M. Schantz



One-pot conversion of sugar and sugar polyols to n-alkanes without C-C Dissociation over the Ir-ReOx /SiO2 catalyst combined with H-ZSM-5.  


High (?95 % C) yields of n-hexane and n-pentane were obtained by hydrogenolysis of aqueous sorbitol and xylitol, respectively, at 413-443 K by using the Ir-ReOx /SiO2 catalyst combined with H-ZSM-5 as a cocatalyst and n-dodecane as a cosolvent. The direct production of n-hexane from glucose or cellobiose can be achieved by using the same system. The catalyst can be reused simply by the removal of the n-dodecane phase, which contains the product alkane, and the addition of fresh n-dodecane and substrate. PMID:23463694

Chen, Kaiyou; Tamura, Masazumi; Yuan, Zhenle; Nakagawa, Yoshinao; Tomishige, Keiichi



Spin-lattice relaxation of the quinoxaline triplet state in n-alkane matrices measured in zero magnetic field  

Microsoft Academic Search

The individual spin-lattice relaxation (SLR) rate constants (Wij) between the sublevels of the lowest triplet state of quinoxaline in n-pentane and in n-hexane Sphol’skii hosts over the temperature range of 1.2 to 4.2 K have been measured in zero applied magnetic field. The anisotropy pattern for the Wij for quinoxaline in these n-alkane hosts differs from that observed in a

Sanjib Ghosh; Michael Petrin; August H. Maki



Tropospheric OH and Cl levels deduced from non-methane hydrocarbon measurements in a marine site  

Microsoft Academic Search

In situ continuous hourly measurements of C2-C8 non-methane hydrocarbons (NMHCS) have been performed from March to October 2006 at two coastal locations on the island of Crete, in the Eastern Mediterranean. Well defined diurnal variations were observed for several short lived NMHCS (including ethene, propene, n-butane, n-pentane, n-hexane, 2-methyl-pentane). The daytime concentration of hydroxyl (OH) radicals estimated from these experimental

C. Arsene; A. Bougiatioti; M. Kanakidou; B. Bonsang; N. Mihalopoulos



Excess Electrons in Liquid Hydrocarbons  

Microsoft Academic Search

Stable electronic charge carriers have been observed in n-hexane, n-pentane, benzene, and methylbutene with room temperature mobilities of 0.07, 0.07, 0.6, and 3.6 cm2 V?1·sec?1, respectively. The charge carriers were injected into the highly purified hydrocarbon liquids by photoemission of electrons from a low work function surface. Mobilities increase rapidly with temperature and obey an Arhennius expression with activation energies

R. M. Minday; L. D. Schmidt; H. T. Davis



Effect of temperature on conduction band energies of electrons in nonpolar liquids  

Microsoft Academic Search

The energy of injection of an electron from vacuum into various nonpolar liquids was studied as a function of temperature. The method used was based on the difference in the photoelectric work function of zinc under vacuum and in the liquid; the difference: phi\\/sub liq\\/ -- phi\\/sub vac\\/, is denoted Vâ. Measurements are reported for n-pentane, n-hexane, 2,2-dimethylbutane, 2,2,4-trimethylpentane, 2,2,5-trimethylhexane,

Richard A. Holroyd; Steven Tames; Alvin Kennedy



Measurements of the 12C/13C kinetic isotope effects in the gas-phase reactions of light alkanes with chlorine atoms.  


The carbon kinetic isotope effects (KIEs) of the reactions of several light non-methane hydrocarbons (NMHC) with Cl atoms were determined at room temperature and ambient pressure. All measured KIEs, defined as the ratio of the Cl reaction rate constants of the light isotopologue over that of the heavy isotopologue (Clk12/Clk13) are greater than unity or normal KIEs. For simplicity, measured KIEs are reported in per mil according to Clepsilon=(Clk12/Clk13 -1)x1000 per thousand unless noted otherwise. The following average KIEs were obtained (all in per thousand): 10.73+/-0.20 (ethane), 6.44+/-0.14 (propane), 6.18+/-0.18 (methylpropane), 3.94+/-0.01 (n-butane), 1.79+/-0.42 (methylbutane), 3.22+/-0.17 (n-pentane), 2.02+/-0.40 (n-hexane), 2.06+/-0.19 (n-heptane), 1.54+/-0.15 (n-octane), 3.04+/-0.09 (cyclopentane), 2.30+/-0.09 (cyclohexane), and 2.56+/-0.25 (methylcyclopentane). Measurements of the 12C/13C KIEs for the Cl atom reactions of the C2-C8 n-alkanes were also made at 348 K, and no significant temperature dependence was observed. To our knowledge, these 12C/13C KIE measurements for alkanes+Cl reactions are the first of their kind. Simultaneous to the KIE measurement, the rate constant for the reaction of each alkane with Cl atoms was measured using a relative rate method. Our measurements agree with published values within+/-20%. The measured rate constant for methylcyclopentane, for which no literature value is available, is (2.83+/-0.11)x10-10 cm3 molecule-1 s-1, 1sigma standard error. The Clepsilon values presented here for the C2-C8 alkanes are an order of magnitude smaller than reported methane Clepsilon values (Geophys. Res. Lett., 2000, 27, 1715), in contrast to reported OHepsilon values for methane (J. Geophys. Res. (Atmos.), 2001, 106, 23, 127) and C2-C8 alkanes (J. Phys. Chem. A, 2004, 108, 11537), which are all smaller than 10 per thousand. This has important implications for atmospheric modeling of saturated NMHC stable carbon isotope ratios. 13C-structure reactivity relationship values (13C-SRR) for alkane-Cl reactions have been determined and are similar to previously reported values for alkane-OH reactions. PMID:17228898

Anderson, Rebecca S; Huang, Lin; Iannone, Richard; Rudolph, Jochen



Corona chemistry in Titan.  


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




Microsoft Academic Search

The effect of various diluents such as n-hexane, n-heptane n-octane, isooctane, n-decane, n-undecane, n-dodecane, n-tetradecane, n-hexadecane, cyclohexane, benzene, toluene, p-xylene, mesitylene and o-dichlorobenzene on the enthalpy of extraction of uranyl nitrate by tri-n-amyl phosphate (TAP) over the temperature range 283 K - 333 K has been studied. The results indicate that the enthalpy of extraction does not vary significantly with

T. G. Srinivasan; P. R. Vasudeva Rao; D. D. Sood




Microsoft Academic Search

The UV-Visible spectroscopic features of tarry and solid carbon species produced in premixed flames burning aliphatic (ethylene, n-hexane, cyclohexane, n-heptane) and aromatic fuels (benzene) were investigated in terms of spectral shape and mass specific absorption coefficients. The spectral properties of dry soot showed significant changes as a function of the flame position and of C\\/O ratio. Moreover, some peculiarities of




Retention Phenomena Induced by Large Volume Injection of Solvents Non?Miscible with the Mobile Phase in Reversed?Phase Liquid Chromatography  

Microsoft Academic Search

Enhancement of sensitivity for spectrometric detection in liquid chromatography is obtained when increased sample volumes are loaded into the chromatographic column. A new approach of injecting large volumes of solvents non?miscible with the mobile phase is proposed. The paper focuses on the retention study of butylated hydroxyanisole (BHA) loaded into the chromatographic column dissolved in liquid alkanes (n?hexane, n?heptane, and

Andrei Medvedovici; Vasile David; Victor David; Cristina Georgita




Microsoft Academic Search

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




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

Microsoft Academic Search

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 30°C are studied to show the possible existence of double relaxation times\\u000a ?\\u000a 2 and ?\\u000a 1 for rotations of the whole and the flexible parts of molecules. The probability of showing

K. Dutta; SK Sit; S. Acharyya



Dielectric relaxation phenomena and high frequency conductivity of rigid polar liquids in different solvents  

Microsoft Academic Search

The double relaxation phenomena in apparently rigid aliphatic polar liquids (j) like chloral and ethyltrichloroacetate in nonpolar solvents (i) benzene, n-hexane and n-heptane under 4.2, 9.8 and 24.6 GHz electric fields at 30°C have been studied. Only five systems of polar-nonpolar liquid mixtures show the double relaxation times ?1 and ?2 due to rotation of their flexible parts and the

K Dutta; RC Basak; S. K Sit; S Acharyya



Effect of Coexposure to Methyl Ethyl Ketone (MEK) on n-Hexane Toxicokinetics in Human Volunteers  

Microsoft Academic Search

In order to study the effects of methyl ethyl ketone (MEK) on the toxicokinetics ofn-hexane and, in particular, the formation of 2,5-hexanedione fromn-hexane in humans, volunteers were exposed ton-hexane (approx. 60 ppm, 2.4 ?min the inhaled air) with or without simultaneous inhalatory coexposure to MEK for 15.5 min. The concentration–time course ofn-hexane (in exhaled alveolar air) and its neurotoxic metabolite,

Jacqueline G. M. van Engelen; Wilhelmina Rebel-de Haan; Joannes J. G. Opdam; Gerard J. Mulder



Kinetic Modeling of Autoignition of Higher Hydrocarbons: N-Heptane, n-Octane and ISO-Octane.  

National Technical Information Service (NTIS)

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 ...

C. K. Westbrook W. J. Pitz



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

Microsoft Academic Search

The algorithm of directed relation graph recently developed for skeletal mechanism reduction was extended to overall linear time operation, thereby greatly facilitating the computational effort in mechanism reduction, particularly for those involving large mechanisms. Together with a two-stage reduction strategy and using the kinetic responses of autoignition and perfectly stirred reactor (PSR) with extensive parametric variations as the criteria in

Tianfeng Lu; Chung K. Law



Laser-induced-fluorescence imaging of NO in an n -heptane- and diesel-fuel-driven diesel engine  

Microsoft Academic Search

Continuous on-line imaging by 2D-LIF techniques of in-cylinder NO distributions in a running Diesel engine is explored using an ArF-excimer laser at 193 nm operating at low power. For the first time NO excitation spectra could be measured as a result of high optical transparencies during measurements over longer periods of time. The averaged distributions show different combustion behaviour of

Th. M. Brugman; RJH Klein-Douwel; G. Huigen; Walwijk van E; J. J. ter Meulen



Laser-induced-fluorescence imaging of NO in an n-heptane- and diesel-fuel-driven diesel engine  

NASA Astrophysics Data System (ADS)

Continuous on-line imaging by 2D-LIF techniques of in-cylinder NO distributions in a running Diesel engine is explored using an ArF-excimer laser at 193 nm operating at low power. For the first time NO excitation spectra could be measured as a result of high optical transparencies during measurements over longer periods of time. The averaged distributions show different combustion behaviour of both fuels proving the potential of the 2D-LIF technique in application to non-intrusive combustion diagnostics in a steady running Diesel engine.

Brugman, Th. M.; Klein-Douwel, R.; Huigen, G.; van Walwijk, E.; Ter Meulen, J. J.



Laser-induced-fluorescence imaging of NO in an n-heptane- and diesel-fuel-driven diesel engine  

Microsoft Academic Search

Continuous on-line imaging by 2D-LIF techniques of in-cylinder NO distributions in a running Diesel engine is explored using an ArF-excimer laser at 193 nm operating at low power. For the first time NO excitation spectra could be measured as a result of high optical transparencies during measurements over longer periods of time. The averaged distributions show different combustion behaviour of

Th. M. Brugman; R. Klein-Douwel; G. Huigen; E. van Walwijk; J. J. Ter Meulen



Modeling of Spherically Symmetric Droplet Flames Including Complex Chemistry: Effect of Water Addition on n-Heptane Droplet Combustion  

Microsoft Academic Search

A spherically symmetric quasi-steady model has been formulated for droplet combustion which includes complex chemistry and variable properties. The model is applied to mixtures of heptane and water.Calculations from the model show that the acetylene concentration inside a heptane flame increases with increasing droplet diameter. This trend suggests an increased propensity for soot formation with increasing droplet diameter which is




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

PubMed Central

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

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



Evaluation of low-temperature diesel combustion regimes with n-Heptane fuel in a constant-volume chamber  

Microsoft Academic Search

The concept of Low Temperature Combustion (LTC) has been advancing rapidly because it may reduce emissions of NOx and soot\\u000a simultaneously. Various LTC regimes that yield specific emissions have been investigated by a great number of experiments.\\u000a To accelerate the evaluation of the spray combustion characteristics of LTC, to identify the soot formation threshold in LTC,\\u000a and to implement the

U. B. Azimov; K. S. Kim; D. S. Jeong; Y. G. Lee



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


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

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



Catalytic properties of superhigh-silica zeolites in conversions of certain hydrocarbons  

SciTech Connect

The catalytic activity of type TsVK zeolites with various SiO/sub 2//Al/sub 2/O/sub 3/ ratios in reactions of isomerization of C/sub 4/-C/sub 6/ n-paraffins, hydrogenation and hydroisomerization of benzene, and the side reactions of hydrocracking and disproportionation was studied in this report. Results determined on the basis of decationized forms of superhigh-silica zeolites with a mole ratio SiO/sub 2//Al/sub 2/O/sub 3/ from 33 to 83, indicated that new and effective Pd catalysts have been synthesized for n-pentane isomerization, n-butane disproportionation, n-hexane isomerization and hydrocracking, and benzene hydrogenation.Also, a correlation has been established between the hydrocracking (or cracking) activity of the decationized forms of the zeolites and the isomerizing activity of the Pd/HTsVK catalysts in n-pentane conversions.

Minachev, K.M.; Garanin, V.I.; Isakova, T.A.; Mironova, I.L.; Fomin, A.S.; Lipkind, B.A.



Hazardous organic compounds in groundwater near Tehran automobile industry.  


Potential of groundwater contamination by trichloroethylene (TCE) and other volatile organic compounds VOCs near car industry was conducted in this study. TCE, PCE, toluene, xylene, dichloromethane, cyclohexane, n-hexane and n-pentane were detected in all groundwaters. Mean TCE levels in groundwater ranged from 124.37 to 1,035.9 ?g L?¹ with maximum level of 1,345.7 ?g L?¹. Due to the data obtained from conventional wastewater treatment in car factory the TCE removal efficiency was only 24 percent which necessitates the TCE removal by advanced treatment processes before the use of well water. PMID:21069286

Dobaradaran, Sina; Mahvi, Amir Hossein; Nabizadeh, Ramin; Mesdaghinia, Alireza; Naddafi, Kazem; Yunesian, Masoud; Rastkari, Noushin; Nazmara, Shahrokh



Two sources of synergism in the reforming of n -hexane, methylcyclopentane, methylcyclohexane mixtures over composites of basic and acidic zeolites  

Microsoft Academic Search

Pt supported on composites of the basic L zeolite with either H\\/ß or H\\/USY acidic zeolite are employed in the reforming ofn-hexane, methylcyclopentane, methylcyclohexane and their mixtures. It was found that when mixtures of the above three compounds are used as feeds, the composites provide decreased benzene selectivity and increased conversion and aromatic selectivity in comparison with the conversion and

Eli Ruckenstein; Panagiotis G. Smirniotis



Thermogravitational measurement of the Soret coefficient of liquid mixtures  

NASA Astrophysics Data System (ADS)

We have designed and constructed a thermogravitational column for determining the Soret coefficient of liquid mixtures. The excellent agreement of the results obtained for toluene and n-hexane mixtures with recent accurate measurements performed by optical methods shows the validity of the thermogravitational method when a column with the correct geometry is used. We have applied this technique to determine the Soret coefficient of the binary systems benzene-n-heptane and carbon tetrachloride with cyclohexane, methanol and ethanol. Comparison with the literature data allows us to determine the reliability of the existing measurements of thermal diffusion for these mixtures.

Bou-Ali, M. M.; Ecenarro, O.; Madariaga, J. A.; Santamaría, C. M.; Valencia, J. J.



Phase behaviour of 1-methyl-3-octylimidazolium bis[trifluoromethylsulfonyl]imide with thiophene and aliphatic hydrocarbons: The influence of n-alkane chain length  

Microsoft Academic Search

This paper reports the results of a new experimental study on the capacity of an ionic liquid to extract a sulfur compound from its mixtures with aliphatic hydrocarbons. With this aim, liquid+liquid equilibrium data of ternary systems containing 1-methyl-3-octyl-imidazolium bis(trifluoromethylsulfonyl)-imide ([C8mim][NTf2]), thiophene and n-hexane, n-heptane or n-hexadecane have been determined at T=298.15K. All systems showed high solubility of thiophene in

Luisa Alonso; Alberto Arce; María Francisco; Ana Soto



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

Microsoft Academic Search

The partial molar volumes, V1M, and the molar volume of isotactic crystalline low-molecular-weight poly(1-butene), iPBu-1, V1, have been calculated from the measured density of {iPBu-1+solvent (n-hexane, n-heptane, n-nonane, n-decane, p-xylene, cyclohexane and chloroform)} systems. Some of the thermodynamic quantities were also obtained for the iPBu-1 with eight hydrocarbons (n-octane, n-decane, n-undecane, n-dodecane, n-tridecane, o-xylene, m-xylene, p-xylene) by the method of

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



Excess properties of the binary mixtures of methylcyclohexane + alkanes (C 6 to C 12) at T = 298.15 K to T = 308.15 K  

Microsoft Academic Search

Experimental values of density, viscosity, and refractive index at T=(298.15, 303.15, and 308.15)K while the speed of sound at T=298.15K in the binary mixtures of methylcyclohexane with n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-dodecane, and iso-octane are presented over the entire mole fraction range of the binary mixtures. Using these data, excess molar volume, deviations in viscosity, molar refraction, speed of

J. G. Baragi; M. I. Aralaguppi; M. Y. Kariduraganavar; S. S. Kulkarni; A. S. Kittur; T. M. Aminabhavi



A Comparative Study of n-Pentane and n-Butane Isomerization over Zirconia-Supported Tungsten Oxide: Pulse and Flow Studies and DRIFTS Catalyst Characterization  

Microsoft Academic Search

The reactions ofn-pentane andn-butane over both tungstated zirconia (WZ) and platinum supported on tungstated zirconia (PtWZ) in the presence of hydrogen were studied in the pulse mode. Influence of contact time at 666 kPa, andn-pentane flow mode results in an atmospheric pressure packed-bed reactor are reported. The diffuse reflectance infrared (DRIFTS) spectra of adsorbed CO on PtWZ and the tungsten

Luc??a M. Petkovic; James R. Bielenberg; Gustavo Larsen



Development of an alternative eluent system for Ag+-HPLC analysis of conjugated linoleic acid isomers.  


In this study, 13 different eluent systems containing n-hexane, n-heptane and iso-octane as main solvents and ACN, propionitrile (PCN) and butyronitrile (BCN) in concentrations between 0.1 and 0.2% as modifiers were tested for their influence on retention time shifts (RTS) and resolution of conjugated linoleic acid (CLA) methyl esters using two ChromSpher 5 Lipids columns (250 mm x 4.6 mm, 5 microm) in series. The eluent system n-hexane/PCN 0.2% showed the highest stability with an obtained RTS of 0.26 min for the cis/trans-group after 14 consecutive injections of a CLA isomer mix compared to the reference system of n-hexane/ACN 0.15% (RTS of 2.35 min). This enhanced stability is due to better solubility of PCN in n-hexane compared to ACN. The enhanced stability coincided with a negligible loss in resolution for the cis,trans/trans,cis- and the cis,cis-groups. As shown for the analysis of human aortic endothelial cells spiked with t10c12-CLA, data from CLA-analysis by Ag+-HPLC-DAD must be judged very carefully, especially at low concentrations, as coeluting matrix compounds may give false-positive results. Therefore, results should be confirmed by GC-FID and GC-MS. PMID:16544876

Müller, André; Düsterloh, Kaja; Ringseis, Robert; Eder, Klaus; Steinhart, Hans



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

SciTech Connect

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

Jiang, J.C.; Patil, S.L.; Kamath, V.A. (Univ. of Alaska, Fairbanks (United States))



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.



The entropies of n-heptane, n-octane, n-nonane, and n-undecane over a wide range of the liquid and gaseous states  

NASA Astrophysics Data System (ADS)

The entropies S of C7 C11 normal alkanes over the temperature and pressure ranges 300 620 K and 0.5 60 MPa were obtained by the integration of the experimental isobars of isobaric heat capacity C p . The C p data were obtained using a flow adiabatic calorimeter with calorimetric flow rate measurements. The entropy values were determined up to critical temperatures by extrapolation from the sides of liquid S' and gas S? phases. The p-T-S thermodynamic surfaces of the alkanes under consideration in the liquid and gas phases were constructed. A generalized temperature dependence of S' and S? was determined for the homologous series over the temperature range from the triple to critical point within the framework of similarity theory.

Kuznetsov, M. A.



Numerical investigations on methods to control the rate of heat release of HCCI combustion using reduced mechanism of n-heptane with a multidimensional CFD code  

Microsoft Academic Search

In this study a semi-reduced reaction scheme developed previously was used to derive a 26 step reduced mechanism, using the sensitivity approach and the steady state approximation (QSS) with Chemkin code. This 26 step model has been implemented in a CFD combustion code (Star-CD\\/Kinetics) to study combustion process in homogeneous charge compression ignition (HCCI) engines. The first results obtained have

F. Maroteaux; L. Noel; A. Ahmed



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

Microsoft Academic Search

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

M Shahbakhti; C R Koch



Hydrogenolysis of cyclohexane over Ir/SiO(2) catalyst: a mechanistic study of carbon--carbon bond cleavage on metallic surfaces.  


The hydrogenolysis of cyclohexane catalyzed by supported Ir/SiO(2) has been studied to get mechanistic information on the elementary steps of C--C bond cleavage for cyclic saturated hydrocarbons. The reaction was studied under conditions in which no dehydrogenation to benzene occurs. When a mixture of cyclohexane and H(2) flows over a Ir/SiO(2) catalyst at 200 degrees C and for a H(2)/cyclohexane ratio superior to 40, methane, ethane, propane, n-butane, n-pentane, and n-hexane are identified to be primary products. The hydrogenolysis of ethane and n-hexane has also been studied to clarify several mechanistic questions. To account for the primary products in the above reactions, a mechanism is proposed in which the key step of the carbon--carbon bond cleavage occurs via concerted electronic transfer in dimetallacyclopentane intermediate. The comparison of product distributions in the hydrogenolysis of cyclohexane and that observed for n-hexane led to conclusions about the relative ease of carbon--carbon bond cleavage with respect to surface alkyl isomerization. PMID:11456765

Locatelli, F; Candy, J P; Didillon, B; Niccolai, G P; Uzio, D; Basset, J M



Relative permittivities and refractive indices on mixing for ( n -hexane + 1-pentanol, or 1-hexanol, or 1-heptanol ) at T = 298.15 K  

Microsoft Academic Search

A previous study on the physical properties of (1-alcohol +n -alkane) has established a correlation between dielectric permittivity at 1 GHz and excess molar volumesVE for all binary systems that were studied. In order to determine whether this behaviour is similar at lower frequencies, relative permittivity ??was measured at 100 kHz. The refractive indexnD was measured to explore the effects

M. I. Paz Andrade



The n-octanol and n-hexane\\/water partition coefficient of environmentally relevant chemicals predicted from the mobile order and disorder (MOD) thermodynamics  

Microsoft Academic Search

The quantitative thermodynamic development of the mobile order and disorder theory in H-bonded liquids is extended in order to predict the partition coefficient. With respect to the classical predictive methods, the great advantage of the present approach resides in the possibility of predicting partition coefficient not only in the reference n-octanol\\/water partitioning system, but also in any mutually saturated two-phase

Paul Ruelle



Vacuum ultraviolet absorption spectra of aromatic molecules in solution  

SciTech Connect

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

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



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

NASA Astrophysics Data System (ADS)

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

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



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

NASA Astrophysics Data System (ADS)

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

Sun, Lanyi; Zhai, Cheng; Zhang, Hui


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.



Development and application of analytical techniques to chemistry of donor solvent liquefaction. Quarterly progress report, January-March 1981  

SciTech Connect

The operation of modern superconducting magnet based spectrometers in the liquid chromatography-proton nuclear magnetic resonance spectroscopy (LC-/sup 1/H) NMR mode is fairly simple. In light of the considerable improvements made in this technique, LC-/sup 1/H NMR has shown itself to be quite useful in fuel analysis. The limits of detection are now sufficiently low to be near that of the refractive index detector. Improvements in resolution (both chromatographic and spectroscopic) have made speciation within a class possible. The LC-/sup 1/H NMR technique increases the convenience and reliability of determining the average degree of substitution. Results are reported of runs made on a jet fuel and a model mixture which was prepared by mixing n-butylbenzene, m-xylene, tetralin, naphthalene, dodecane, isooctane, n-hexane, nonane, hexadecane and n-pentane.

Dorn, H.C.; Taylor, L.T.



Experimental determination of superheated liquids boiling-up expectancy time probabilities distribution  

NASA Astrophysics Data System (ADS)

Results of statistical measurement of n-pentane and n-hexane boiling-up expectancy time near the boundary of attainable superheating are presented. Experiments were carried out in glass capillaries with various volumes of superheated liquid. Several samples with the volume from 100 to 200 measurements of life time for preset metastable state have been obtained ( p, T = const). Their histograms contain small empty initial section, maximum and long “tail” in the area of large times. Non-monotonous dependence of probability distribution density on time proves non-stationary character of the random process resulting in the production of supercritical embryo. Two simple approximations of non-stationary nucleation flow well describing experimental data have been considered. For exponential distribution, the probabilities of experimentally found peculiarities of boiling-up expectancy time distribution density have been evaluated; they prove incompatibility of this distribution with the experimental one.

Lipnyagov, E. V.; Perminov, S. A.; Ermakov, G. V.; Smolyak, B. M.



Studies of reaction parameters on synthesis of Citronellyl laurate ester via immobilized Candida rugosa lipase in organic media.  


Immobilized Candida rugosa lipase was used for the synthesis of citronellyl laurate from citronellol and lauric acid. Screening of different types of support (Amberlite MB-1 and Celite) for immobilization of lipase and solvent (n-hexane, n-heptane, and iso-octane) and optimization of reaction conditions, such as catalyst loading, effect of substrates molar ratio and temperature, have been studied. The maximum enzyme activity was obtained at 310 K. The immobilized C. rugosa lipase onto Amberlite MB-1 support was found to be the best support with a conversion of 89% of citronellyl laurate ester in iso-octane compared to Celite 545. Deactivation of C. rugosa lipase at 313, 318 and 323 K were observed. Ordered bi bi mechanism with dead end complex of lauric acid was found to fit the initial rate data and the kinetic parameters were obtained by non-linear regression analysis. PMID:16868763

Serri, N Aziah; Kamaruddin, A H; Long, W S



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



The utility of volatile hydrocarbon analysis in cases of carbon monoxide poisoning.  


A new approach to investigate the circumstances relating to carbon monoxide intoxication by analysing volatile hydrocarbons in the blood of cadavers is reported. Headspace gas chromatography/mass spectrometry was used to demonstrate the hydrocarbons. The results can be characterized into four categories depending on the compounds detected. In construction fire cases where no accelerants were found at the scene benzene, toluene and styrene were detected in the blood. In cases where gasoline was found in the fire debris surrounding the victim, high levels of benzene, toluene, ethylbenzene, xylene isomers, n-hexane and n-heptane were detected in the blood. In cases where kerosene was found in the fire debris around the victim, benzene, toluene, ethylbenzene, xylene isomers, C9-aromatics(n-propylbenzene, trimethyl-benzene isomers), n-octane, n-nonane and n-decane were detected in the blood. In cases where the victim was found inside a gasoline-fuelled automobile filled with exhaust gas, benzene, toluene, ethylbenzene, xylene isomers, C9-aromatics were found, but no aliphatic hydrocarbons such as components of petroleum. The analyses of the combustion gases of inflammable materials, exhaust gas, gasoline vapours and kerosene vapours were also performed to evaluate the results of the blood analyses. Consequently, some compounds are proposed as indicators to discriminate between inhaled gases i.e. styrene in common combustion gas, n-hexane and n-heptane as well as benzene, toluene and C9-aromatics in gasoline cases, n-nonane and n-octane as well as benzene, toluene and C9-aromatics in kerosene cases, and benzene, toluene, C9-aromatics but no aliphatic hydrocarbons in exhaust gas cases. PMID:8912051

Morinaga, M; Kashimura, S; Hara, K; Hieda, Y; Kageura, M



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


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

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



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))



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



Experimental validation of a kinetic multi-component mechanism in a wide HCCI engine operating range for mixtures of n-heptane, iso-octane and toluene: Influence of EGR parameters  

Microsoft Academic Search

The parameters that are present in exhaust gas recirculation (EGR) are believed to provide an important contribution to control the auto-ignition process of the homogeneous charge compression ignition (HCCI) in an engine. For the investigation of the behaviour of the auto-ignition process, a kinetic multi-component mechanism has been developed in former work, containing 62 reactions and 49 species for mixtures

Hatim Machrafi



Electrochemical trifluoromethylation of acrylonitrile and crotonitrile. Preparation of 2,3-bis(2,2,2-trifluoroethyl)succinonitrile and 3,4-dicyano-2,5-bis(trifluoromethyl)-n-hexane  

Microsoft Academic Search

Electrooxidation of trifluoroacetic acid in the presence of acrylonitrile in an acetonitrile-water solution, followed by simple steam distillation of the reaction mixture, provided almost pure 2,3-bis(2,2,2-trifluoroethyl)succinonitrile in a 20 – 25% yield and in a 1 : 1 diastereoisomers ratio. The meso isomer has been isolated and its structure confirmed by X-ray analysis. Similarly, the reaction in the presence of

Wojciech Dmowski; Albert Biernacki; Tomasz Kozlowski; Przemyslaw Gluzi?ski; Zofia Urba?czyk-Lipkowska



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

SciTech Connect

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

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



Extraction mechanism of Sc(III) and separation from Th(IV), Fe(III) and Lu(III) with bis(2,4,4-trimethylpentyl)phosphinic acid in n-hexane from sulphuric acid solutions  

SciTech Connect

The extraction equilibrium data of sulphuric acid and scandium(III) with bis(2,4,4-trimethylpentyl)phosphinic acid (H[BTMPP]) from sulphuric acid solutions have been obtained. There are two extraction mechanisms of scandium(III) with H[BTMPP] at different ranges of aqueous acidity. The extraction of Sc(III) proceeds according to a cation exchange reaction at lower aqueous acidity and to a solvating reaction at higher acidity. The practicability of separating Sc(III) from Th(IV),Fe(III) and Lu(III) by controlling the aqueous acidity was discussed. The effect of temperature on extraction of Sc(III) was observed and thermodynamic functions were calculated. IR and NMR spectra were made for organic extracts. The extraction characteristics of H[BTMPP] and di(2-ethylhexyl)phosphinic acid (H[DEHP]) were contrasted to obtain more information about extraction with H[BTMPP]. 12 refs., 6 figs., 1 tab.

Wang, Chun; Li, Deqian (Changchun Inst. of Applied Chemistry and Physics (China))



The n-hexane and chloroform fractions of Piper betle L. trigger different arms of immune responses in BALB\\/c mice and exhibit antifilarial activity against human lymphatic filarid Brugia malayi  

Microsoft Academic Search

Modulation of immune functions by using herbal plants and their products has become fundamental regime of therapeutic approach. Piper betle Linn. (Piperaceae) is a widely distributed plant in the tropical and subtropical regions of the world and has been attributed as traditional herbal remedy for many diseases. We have recently reported the antifilarial and antileishmanial efficacy in the leaf extract

Meghna Singh; Shilpy Shakya; Vishal Kumar Soni; Anil Dangi; Nikhil Kumar; Shailja-Misra Bhattacharya



The actions of some general anaesthetics on the potassium current of the squid giant axon.  

PubMed Central

A number of small organic molecules with general anaesthetic action have been examined for their effects on the voltage-dependent potassium current of the squid giant axon. They include representatives of the three classes of anaesthetics examined in previous studies on the sodium current (Haydon & Urban, 1983a, b, c), i.e. the non-polar molecules n-pentane, cyclopentane and CCl4, several n-alkanols and the inhalation anaesthetics chloroform, halothane, diethyl ether and methoxyflurane. Potassium currents under voltage clamp were recorded in intact and in intracellularly perfused axons before, during and after exposure to the test substances, and the records were fitted with equations similar to those proposed by Hodgkin & Huxley (1952). Shifts in the curves of the steady-state activation against membrane potential and reductions in the potassium conductance at 60 or 70 mV membrane potential have been tabulated. On the same intact axons, all the anaesthetics with the exception of methoxyflurane reduced potassium currents less than sodium currents by about a factor of two or more. For the n-alkanols, butanol to decanol, the concentrations required to reduce the potassium current at 60 mV membrane potential by 50% were determined. For n-butanol to n-heptanol, the standard free energy per CH2 for adsorption to the site of action was estimated to be -2.91 kJ mol-1 as compared with -3.04 kJ mol-1 for reduction of the sodium current. The magnitude of the free energy decreased for alkanols with longer chain lengths. At anaesthetic concentrations that reduce the sodium current by 50%, the hydrophobic substances n-pentane and cyclopentane reduced the maximal sodium conductance, gNa, and the potassium conductance at 70 mV, gK70, equally by about a third, while the n-alkanols reduced both parameters by less than 10%. By contrast, diethyl ether and methoxyflurane were more effective in reducing the maximal potassium conductance. All of the test substances examined, except n-pentane and n-hexane, shifted the voltage dependence of the potassium steady-state activation in the depolarizing direction. A broad qualitative correlation was found between the shifts in the activation curves for sodium and potassium currents but, quantitatively, the agreement between the two shifts was poor. In n-decanol and methoxyflurane solutions, the voltage-clamped potassium currents exhibited pronounced inactivation-like behaviour. These currents can be fitted by the Hodgkin-Huxley formalism if an inactivation term analogous to the sodium current inactivation is added.(ABSTRACT TRUNCATED AT 400 WORDS)

Haydon, D A; Urban, B W



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

SciTech Connect

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

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



Activated aluminum oxide selectively retaining long chain n-alkanes. Part I, description of the retention properties.  


Aluminum oxide activated by heating to 350-400 degrees C retains n-alkanes with more than about 20 carbon atoms, whereas iso-alkanes largely pass the column non-retained. Retention of n-alkanes is strong with n-pentane or n-hexane as mobile phase, but weak or negligible with cyclohexane or iso-octane. It is strongly reduced with increasing column temperature. Even small amounts of polar components, such as modifiers or impurities in the mobile phase, cause the retention of n-alkanes to irreversibly collapse. Since n-alkanes are not more polar than iso-alkanes and long chain n-alkanes not more polar than those of shorter chains, retention by a mechanism based on steric properties is assumed. The sensitivity to deactivation by polar components indicates that polar components and n-alkanes are retained by the same sites. The capacity for retaining n-alkanes is low, with the effect that the retention of n-alkanes depends on the load with retained paraffins. These retention properties are useful for the pre-separation of hydrocarbons in the context of the analysis of mineral oil paraffins in foodstuffs and tissue, where plant n-alkanes, typically ranging from C(23) to C(33), may severely disturb the analysis (subject of Part II). PMID:19154816

Fiselier, Katell; Fiorini, Dennis; Grob, Koni



Correlations of Henry's Law Gas-Solid Virial Coefficients and Chromatographic Retention Times for Hydrocarbons and Halocarbons Adsorbed on Carbopack C Carbon.  


Second gas-solid virial coefficients were determined at 403.5 +/- 0.5 K for 6 adsorbates, including butane, chloroform, trichlorofluoromethane (Freon 11), bromochloromethane, 1-chloro-2-methylpropane, and dibromodifluoromethane. For another 11 adsorbates, including dichlorodifluoromethane (Freon 12), chlorodifluoromethane (Freon 22), methyl chloride, methylene chloride, propane, n-pentane, n-hexane, carbon tetrachloride, 1,2-dichloropropane, butyl chloride, and cyclohexane, B(2s) was measured over a range of temperatures between 308 and 494 K. These values were found using gas-solid chromatography with Carbopack C (Supelco Inc.), a graphitized carbon black powder, as the adsorbent. We find that both the ln B(2s) values and the gas-solid interaction energies are effectively correlated with adsorbate-calculated molar refractivity, r(2) = 0.947 and r(2) = 0.964, respectively. Dipole moment alone provides a nearly random correlation of ln B(2s) and, if used with molar refractivity, gives r(2) = 0.970 for the 17 hydrocarbon and alkyl halide (halocarbon) adsorbates. A theoretical equation was developed that predicts a quantitative structure retention relationship (QSRR) used to correlate ln B(2s) values with molar refractivity. B(2s) values are directly proportional to the retention times of the adsorbates. Using one-surface and two-surface models, a calculation of the surface area of the Carbopack C for each of the 17 adsorbates provided a check on the consistency of the analysis as the adsorbate was varied. Copyright 1999 Academic Press. PMID:10550252

Rybolt; Logan; Milburn; Thomas; Waters



Tropospheric OH and Cl levels deduced from non-methane hydrocarbon measurements in a marine site  

NASA Astrophysics Data System (ADS)

In situ continuous hourly measurements of C2-C8 non-methane hydrocarbons (NMHCS) have been performed from March to October 2006 at two coastal locations on the island of Crete, in the Eastern Mediterranean. Well defined diurnal variations were observed for several short lived NMHCS (including ethene, propene, n-butane, n-pentane, n-hexane, 2-methyl-pentane). The daytime concentration of hydroxyl (OH) radicals estimated from these experimental data varied from 1.3×106 to ~4.0×106 radical cm-3, in good agreement with box-model simulations. In addition the relative variability of various hydrocarbon pairs (at least 7) was used to derive the tropospheric levels of Cl atoms. The Cl atom concentration has been estimated to range between 0.6×104 and 4.7×104 atom cm-3, in good agreement with gaseous hydrochloric acid (HCl) observations in the area. Such levels of Cl atoms can be of considerable importance for the oxidation capacity of the troposphere on a regional scale.

Arsene, C.; Bougiatioti, A.; Kanakidou, M.; Bonsang, B.; Mihalopoulos, N.



Tropospheric OH and Cl levels deduced from non-methane hydrocarbon measurements in a marine site  

NASA Astrophysics Data System (ADS)

In situ continuous hourly measurements of C2-C8 non-methane hydrocarbons (NMHCS) have been performed from March to October 2006 at two coastal locations (natural and rural) on the island of Crete, in the Eastern Mediterranean. Well defined diel variations were observed for several short lived NMHCS (including ethene, propene, n-butane, n-pentane, n-hexane, 2-methyl-pentane). The daytime concentration of hydroxyl (OH) radicals estimated from these experimental data varied from 1.3×106 to ~4.0×106 radical cm-3, in good agreement with box-model simulations. In addition the relative variability of various hydrocarbon pairs (at least 7) was used to derive the tropospheric levels of Cl atoms. The Cl atom concentration has been estimated to range between 0.6×104 and 4.7×104 atom cm-3, in good agreement with gaseous hydrochloric acid (HCl) observations in the area. Such levels of Cl atoms can be of considerable importance for the oxidation capacity of the troposphere on a regional scale.

Arsene, C.; Bougiatioti, A.; Kanakidou, M.; Bonsang, B.; Mihalopoulos, N.



Isomerization of C/sub 4/-C/sub 6/ alkanes in the presence of hydrogen on catalysts promoted with fluorine and chlorine  

SciTech Connect

We investigated the effect of hydrogen (molar ratio H/sub 2/:C/sub n/H/sub 2n+2/ and working pres-pressure) on the isomerization of C/sub 4/-C/sub 6/ alkanes on platinized and unplatinized chlorinated eta-Al/sub 2/O/sub 3/. The efficient isomerization of C/sub 4/-C/sub 5/ alkanes on a chlorinated alumina-platinum catalysts requires the presence of hydrogen. In the isomerization of alkanes in the gas phase (butane on a chlorinated catalyst of C/sub 5/-C/sub 6/ alkanes on a fluorinated catalyst) the changes in the degree of isomerization with the working pressure or the hydrogen:starting material ratio show common characteristics. The possible formation by C/sub 5/-C/sub 6/ alkanes of a liquid phase containing dissolved hydrogen in the pores of a chlorinated alumina-platinum catalysts determines the special character of the variation in the degree of isomerization of n-pentane and n-hexane with the working pressure and hydrogen:alkane ratio.

Borutskii, P.N.; Bursian, N.R.; Volkov, I.A.; Stavrova, G.V.



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.



Adsorption of aliphatic, alicyclic, and aromatic hydrocarbons on poly(ethylvinylbenzene-divinylbenzene) adsorbent at from effective zero to finite adsorbate surface coverage  

SciTech Connect

The solid/gas partition coefficients, K/sub s/, and related thermodynamic properties of a number of hydrocarbon adsorbates at effective zero surface coverage on commercial samples of the title adsorbent, Porapak Q, were measured over the temperature range 293-443 K. The enthalpies of adsorption derived from the averaged absolute K/sub s/ gave incremental s//sup 0/ of -7.5 kJ mol/sup -1/ for aliphatic and alicyclic -CH/sub 2/-, as well as aromatic -CH=, and -12 kJ mol/sup -1/ for -CH/sub 3/, while the differential entropies calculated in terms of translational motions were found to predict correctly the trends observed in the experimental s//sup 0/. The technique of elution by characteristic point (ECP) was then used to derive the finite concentration adsorption isotherms and isosteric heats of adsorption of n-hexane, n-heptane, cyclohexane, benzene, carbon tetrachloride, and acetone at fractional adsorbate pressures, p/p/sup 0/, of no greater than 10/sup -2/ on a particular sample of the title absorbent at 20/sup 0/ intervals over the temperature range 413-493 K.

Djordjevic, N.M.; Laub, R.J.; Kopecni, M.M.; Milonjic, S.K.



Classification performance of carbon black-polymer composite vapor detector arrays as a function of array size and detector composition  

NASA Astrophysics Data System (ADS)

The vapor classification performance of arrays of conducting polymer composite vapor detectors has been evaluated as a function of the number and type of detectors in an array. Quantitative performance comparisons were facilitated by challenging a collection of detector arrays with vapor discrimination tasks that were sufficiently difficult that at least some of the arrays did not exhibit perfect classification ability for all of the tasks of interest. For nearly all of the discrimination tasks investigated in this work, classification performance either increased or did not significantly decrease as the number of chemically different detectors in the array increased. Any given subset of the full array of detectors, selected because it yielded the best classification performance at a given array size for one particular task, was invariably outperformed by a different subset of detectors, and by the entire array, when used in at least one other vapor discrimination task. Arrays of detectors were nevertheless identified that yielded robust discrimination performance between compositionally close mixtures of 1-propanol and 2-propanol, n-hexane and n-heptane, and meta-xylene and para-xylene, attesting to the excellent analyte classification performance that can be obtained through the use of such semi-selective vapor detector arrays.

Burl, Michael C.; Sisk, Brian C.; Vaid, Thomas P.; Lewis, Nathan S.



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

SciTech Connect

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

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



Investigation of thermodynamic properties of poly(methyl methacrylate-co-n-butylacrylate-co-cyclopentyl styryl-polyhedral oligomeric silsesquioxane) by inverse gas chromatography.  


The thermodynamic properties of poly(methyl methacrylate-co-butyl acrylate-co-cyclo -pentylstyryl polyhedral oligomeric silsesquioxane) (poly(MMA-co-BA-co-styryl-POSS)) were investigated by means of inverse gas chromatography (IGC) using 20 different kinds of solvents as the probes. Some thermodynamic parameters, such as molar heats of sorption, weight fraction activity coefficient, Flory-Huggins interaction parameter, partial molar heats of mixing and solubility parameter were obtained to judge the interactions between POSS-contained polymers and solvents and the solubility of the polymers in these solvents. It was found that acetates, aromatic hydrocarbons and hydrocarbon halides were good solvents, n-hexane, ethanol, n-propanol, n-butanol and n-pentanol were moderate solvents, while n-heptane, n-octane, n-nonane, n-decane and methanol were poor solvents for all POSS-contained polymers within the experimental temperature range. Incorporation of POSS in polymer increased the solubility of polymers in solvents, and the more the POSS in polymer was, the better the solubility was and stronger the hydrogen bonding interaction was, but the POSS content in polymers seemed to have no obvious influence on the solubility parameter of polymers. PMID:16846607

Zou, Qi-Chao; Zhang, Shi-Ling; Wang, Shi-Min; Wu, Li-Min



Interpolation between State Points in the Simulated Perturbation Contributions of Polymer Solutions  

NASA Astrophysics Data System (ADS)

Polymeric mixtures of hydrocarbons, alcohols have been simulated with discontinuous potential models to characterize the Helmholtz energy of the repulsive reference fluids (A0) along with the first and second order perturbation contributions (A1, A2) as functions of density and composition. Taken together, these terms generate a complete equation of state for the mixture, including temperature effects as well as density and composition. The specific hydrocarbons studied were methane, ethane, propane, n-butane, n-hexane, n-heptane, n-decane, and benzene. The specific alcohols were water, methanol, ethanol, n-propanol, and n-octanol. Unfortunately, a slight inconsistency was encountered when the trend observed for these small molecules was extrapolated to the long chain limit. Therefore, we extend the analysis to mixtures of n-alkanes, branched hydrocarbons, and aromatics with polymeric molecules of: n-alkanes, ethyl-styrenes, ethyl-propylenes, and isoprenes. The perturbation contributions can be accurately characterized by van der Waals mixing rules and compared with the MCSL SAFT and Guggenheim-Staverman theories.

Vahid, Amir; Gray, Neil H.; Elliott, J. Richard



Effectiveness factors for hydroprocessing of coal and coal liquids  

SciTech Connect

During this quarterly report period, experimental studies were completed on the effect of solvent on ambient, non-reactive effective diffusivities for coronene in the pores of NiMo-325 catalyst. Solvents employed included cyclohexane, n-hexane, n-heptane, n-decane, and iso-octane. In addition, data were obtained for TPP in iso-octane. In addition, ambient diffusion tests with NiMo-325 for coronene in iso-octane in the presence of water were performed. Effort continued on the development of an explanation for the large value of the exponent, z (7.2 compared to the theoretical value of 4), obtained under reactive, hydroprocessing conditions, in the equation for the restrictive factor, K{sub r} = (1-{lambda})z. In addition, work was begun on the effect of solvent and temperature at reactive conditions on the restrictive factor by obtaining experimental data for the hydrogenation of Ni-TPP and Ni-TBP in decalin and mesitylene solvents with NiMo catalysts of varying particle sizes at two temperatures. 2 refs., 2 figs., 5 tabs.

Massoth, F.E.; Seader, J.D.



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



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


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



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.



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

NASA Astrophysics Data System (ADS)

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

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


QCM gas phase detection with ceramic materials--VOCs and oil vapors.  


Titanate sol-gel layers imprinted with carbonic acids were used as sensitive layers on quartz crystal microbalance. These functionalized ceramics enable us detection of volatile organic compounds such as ethanol, n-propanol, n-butanol, n-hexane, n-heptane, n-/iso-octane, and n-decane. Variation of the precursors (i.e., tetrabutoxy titanium, tetrapropoxy titanium, tetraethoxy titanium) allows us to tune the sensitivity of the material by a factor of 7. Sensitivity as a function of precursors leads to selective inclusion of n-butanol vapors down to 1 ppm. The selectivity of materials is optimized to differentiate between isomers, e.g., n- and iso-octane. The results can be rationalized by correlating the sensor effects of hydrocarbons with the Wiener index. A mass-sensitive sensor based on titanate layer was also developed for monitoring emanation of degraded engine oil. Heating the sensor by a meander avoids vapor condensation. Thus, a continuously working oil quality sensor was designed. PMID:21301823

Latif, Usman; Rohrer, Andreas; Lieberzeit, Peter A; Dickert, Franz L



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: [Chemical Engineering Department, Institute of Chemical Technology, Matunga, Mumbai 400 019 (India)



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


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

Hwang, Jinyoung; Chung, Hoeil



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


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

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



Temperature-dependent mid-IR absorption spectra of gaseous hydrocarbons  

NASA Astrophysics Data System (ADS)

Quantitative mid-IR absorption spectra (2500 3400 cm-1) for 12 pure hydrocarbon compounds are measured at temperatures ranging from 25 to 500 °C using an FTIR spectrometer. The hydrocarbons studied are n-pentane, n-heptane, n-dodecane, 2,2,4-trimethyl-pentane (iso-octane), 2-methyl-butane, 2-methyl-pentane, 2,4,4-trimethyl-1-pentene, 2-methyl-2-butene, propene, toluene, m-xylene, and ethylbenzene. Room-temperature measurements of neat hydrocarbon vapor were made with an instrument resolution of both 0.1 and 1 cm-1 (FWHM) to confirm that the high-resolution setting was required only to resolve the propene absorption spectrum while the spectra of the other hydrocarbons could be resolved with 1 cm-1 resolution. High-resolution (0.1 cm-1), room-temperature measurements of neat hydrocarbons were made at low pressure (˜1 Torr, 133 Pa) and compared to measurements of hydrocarbon/N2 mixtures at atmospheric pressure to verify that no pressure broadening could be observed over this pressure range. The temperature was varied between 25 and 500 °C for atmospheric-pressure measurements of hydrocarbon/N2 mixtures (Xhydrocarbon˜0.06 1.5%) and it was found that the absorption cross section shows simple temperature-dependent behavior for a fixed wavelength over this temperature range. Comparisons with previous FTIR data over a limited temperature range and with high-resolution laser absorption data over a wide temperature range show good agreement.

Klingbeil, Adam E.; Jeffries, Jay B.; Hanson, Ronald K.



Hydroconversion of heavier n-paraffins with Pt/ZrO sub 2 /SO sub 4 sup 2 minus  

SciTech Connect

The development of effective solid acid catalysts has gained great interest in the refining and petrochemical industries for the last two decades, mainly due to the advantages of less corrosivity, fewer environmental problems, and easy separation from reaction mixtures of these solid acids. Recently, Pt/ZrO{sub 2}/SO{sub 4}{sup 2{minus}}, a solid superacid, was reported to be active for the hydroisomerization of n-pentane and desulfurized light naphtha at low temperatures. In a previous study, the same catalyst was also found effective for hydroisomerization and hydrocracking of n-heptane and n-hexadecane under mild reaction conditions, i.e., 130-170 C and 300 psig hydrogen pressure. Results indicated that the conversion to isobutane and n-butane was greater than expected, with more than 90% selectivity to isobutane. In addition, the multibranched-to-monobranched ratio of isohexadecanes was found to be greater than two. The preparation of a zirconium superacid from zirconium salts containing noncomplexing species, such as Cl{sup {minus}} and NO{sub 3}{sup {minus}}, has been established. However, the preparation of a similar catalyst from a zirconium salt containing SO{sub 4}{sup 2{minus}} has not been reported. The Pt/ZrO{sub 2}/SO{sub 4}{sup 2{minus}} showed high activity for hydroconversion of long chain n-paraffins; even the zirconium sulfate oxide heated to 650 C showed activity. In addition, catalyst activity was enhanced by further treatment with 1N-H{sub 2}SO{sub 4}. Isomerization of high molecular weight n-paraffins (waxes) for the production of premium engine oil (VI > 145) has been a constant interest in refining industries. Use of a solid superacid, such as Pt/ZrO{sub 2}SO{sub 4}{sup 2{minus}}, with hydride donor solvents may provide a new route for possible cheaper premium lubricant oils from waxes.

Wen, M.Y.; Kundurmutt, J.; Tierney, J.W.; Wender, I. (Univ. of Pittsburgh, PA (United States))



Exciplex luminescence in D 2O solubilized AOT reverse micelle: A magnetic field effect study  

NASA Astrophysics Data System (ADS)

Magnetic field modulated pyrene- N, N-dimethylanilne exciplex fluorescence has been studied in reverse micelle of D 2O/AOT/ n-heptane. Results have been compared with those in H 2O/AOT/ n-heptane to understand the effect of deuterium on exciplex luminescence. Strikingly the extent of magnetic field effect (MFE) has been found to be much larger in D 2O/AOT/ n-heptane. The fluorescence lifetime of the exciplexes have been found to be larger in D 2O/AOT/ n-heptane than that in H 2O/AOT/ n-heptane. The stronger hydrogen bond strength in D 2O compared to that of H 2O has been identified to be the prime factor for the effect. Variation of the MFE with temperature in D 2O/AOT/ n-heptane and H 2O/AOT/ n-heptane has also been studied.

Das, Doyel; Nath, Deb Narayan



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 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



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



Performance of Ab Initio and Density Functional Methods for Conformational Equilibria of CnH2n+2 Alkane Isomers (n = 4-8)  

NASA Astrophysics Data System (ADS)

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) contributions 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 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 exhibit deficiencies in the conformer geometries, particularly the backbone torsion angles. The PW6B95 and, to a lesser extent, BMK functionals are relatively free of these deficiencies. Performance of these methods is further investigated to derive conformer ensemble corrections to the enthalpy function, H298 - H0, and the Gibbs energy function, gef(T) ? -[G(T) - H0]/T, of these alkanes. These are essential for accurate computed heats of formation of especially the larger species as the corrections for these are several times the expected uncertainty in modern computational thermochemistry methods such as W4 theory. While H298 - H0 is only moderately sensitive to the level of theory, gef(T) exhibits more pronounced sensitivity. Once again, double hybrids acquit themselves very well. The effects of zero-point energy and nonfactorizable rovibrational partition functions have been considered.

Gruzman, David; Karton, Amir; Martin, Jan M. L.



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


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

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



Ambient levels of gas phase pollutants in Porto Alegre, Brazil  

NASA Astrophysics Data System (ADS)

Air samples have been collected using electropolished canisters in downtown Porto Alegre, Brazil, where ethanol is used as a vehicle fuel and methyl-tert-butyl ether (MTBE) is used as a vehicle fuel additive. The 150 volatile organic compounds (VOC) identified by GC-FID and GC-MS included 46 alkanes, 30 alkenes, 22 aromatics, 17 carbonyls, 3 alcohols, 8 bicyclic aromatics, 11 halogenated hydrocarbons and 13 other compounds. The most abundant VOC on a mass concentration basis (after CO 2, CH 4 and CO) included acetylene, MTBE, ethanol, the alkanes propane, n-butane, n-pentane, isopentane, n-hexane, 2-methylpentane and indane, the alkenes ethylene and propene, and the aromatics benzene, toluene, ethylbenzene and ( m+ p) xylene. During the ca. one-year period studied, 20 March, 1996-16 April, 1997, ambient concentrations of VOC correlated well with those of carbon monoxide, for which vehicle exhaust emissions account for ca. 99% of total emissions in Porto Alegre. Two VOC photochemical reactivity rankings are presented: one involves reaction with OH (product of VOC concentration and VOC-OH reaction rate constant) and the other involves production of ozone (product of VOC concentration and VOC maximum incremental reactivity coefficient). Reaction with OH is dominated by CO followed by 2-methyl-2-butene and by several other alkenes. Ozone production is dominated by ethylene and CO (about equal contribution) followed by several alkenes, alkylbenzenes and aldehydes. The two fuel oxygenates, ethanol and MTBE, play only a minor role as photochemical precursors (reaction with OH and production of ozone) in the atmosphere of Porto Alegre.

Grosjean, Eric; Rasmussen, Reinhold A.; Grosjean, Daniel


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


(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



Selective hydroxylation of alkanes by an extracellular fungal peroxygenase  

PubMed Central

Fungal peroxygenases are novel extracellular heme-thiolate biocatalysts that are capable of catalyzing the selective monooxygenation of diverse organic compounds, using only H2O2 as a cosubstrate. Little is known about the physiological role or the catalytic mechanism of these enzymes. We have found that the peroxygenase secreted by Agrocybe aegerita catalyzes the H2O2-dependent hydroxylation of linear alkanes at the 2-position and 3-position with high efficiency, as well as the regioselective monooxygenation of branched and cyclic alkanes. Experiments with n-heptane and n-octane showed that the hydroxylation proceeded with complete stereoselectivity for the (R)-enantiomer of the corresponding 3-alcohol. Investigations with a number of model substrates provided information about the route of alkane hydroxylation: (a) the hydroxylation of cyclohexane mediated by H218O2 resulted in complete incorporation of 18O into the hydroxyl group of the product cyclohexanol; (b) the hydroxylation of n-hexane-1,1,1,2,2,3,3-D7 showed a large intramolecular deuterium isotope effect [(kH/kD)obs] of 16.0 ± 1.0 for 2-hexanol and 8.9 ± 0.9 for 3-hexanol; and (c) the hydroxylation of the radical clock norcarane led to an estimated radical lifetime of 9.4 ps and an oxygen rebound rate of 1.06 × 1011 s?1. These results point to a hydrogen abstraction and oxygen rebound mechanism for alkane hydroxylation. The peroxygenase appeared to lack activity on long-chain alkanes (> C16) and highly branched alkanes (e.g. tetramethylpentane), but otherwise exhibited a broad substrate range. It may accordingly have a role in the bioconversion of natural and anthropogenic alkane-containing structures (including alkyl chains of complex biomaterials) in soils, plant litter, and wood.

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



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


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

Stancu, Mihaela Marilena; Grifoll, Magdalena



Simultaneous indoor and outdoor on-line hourly monitoring of atmospheric volatile organic compounds in an urban building. The role of inside and outside sources.  


Indoor air quality (IAQ) has become a very important issue in recent years. As in developed countries people spend more than 90% of their time indoors, besides outdoor pollution assessment, the indoor one is also required. IAQ is not only affected by indoor sources linked to indoor activities, outdoor sources such as road or street traffic and industrial and commercial activities have their role too. Volatile organic compounds (VOCs) frequently show higher indoor mixing ratios with respect to the outdoor ones, and monitoring is required to report their indoor mixing ratios. Many studies have reported average indoor VOCs' mixing ratios in different environments, but their temporal variability has not been well documented. The main objective of this work was to simultaneously measure VOCs' indoor and outdoor mixing ratios with high time-resolution in order to assess the effect of sources inside and outside the building upon indoor mixing ratios of individual VOCs. Simultaneous hourly, continuous, and on-line measurements of C(2)-C(11) VOCs were performed inside and outside the School of Engineering of Bilbao (ETSI) building, located in the city center of Bilbao, an urban area in Northern Spain. The analysis of simultaneous data allowed the classification of VOCs based on their main sources. Some VOCs were mainly emitted by indoor sources (1-pentene, 2-methylpentane, n-hexane, methylcyclopentane, benzene, 1-heptene+2,2,4-trimethylbenzene, and tetrachloroethylene) or by outdoor sources (n-heptane, C(8) alkanes except trimethylpentanes and C(9) aromatics). Other VOCs, such as toluene, were emitted by both indoor and outdoor sources. The isoprene indoor pattern indicated that its main indoor source could be the air exhaled by people occupying the building. Some halocarbons, such as trichloroethylene, tetrachloroethylene, and carbon tetrachloride may be generated from the use inside the building of chlorine bleach containing products. PMID:22542255

de Blas, Maite; Navazo, Marino; Alonso, Lucio; Durana, Nieves; Gomez, Maria Carmen; Iza, Jon



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


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



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.



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


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

Shin, Seung H; Jo, Wan K



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

PubMed Central

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 (9–53.7) in EBC. Similarly, C6, C7 and C9 concentrations in IS were 1.5–4.7-fold higher than in EBC. Acrolein levels were 131.1 nM (55.6–264.6) in IS and 45.3 nM (14.4–127.1) in EBC. The concentrations of HNE and HHE in IS were not significantly different from the levels in EBC. Aldehyde levels in EBC did not show any correlation with aldehyde levels in IS or with differential sputum cellular count. In COPD, MDA in EBC, but not its IS counterpart, was negatively correlated with the severity of disease. In conclusion, the data presented here show that aldehydes can be detected in both exhaled breath condensate and supernatant of induced sputum, but that their relative concentrations are different and not correlated with each other. Therefore, with regard to lipid peroxidation products, exhaled breath condensate and induced sputum must be considered as independent techniques.

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



Adsorption Selectivity of FSM-16 for Several Organic Compounds  

Microsoft Academic Search

A folded-sheet mesoporous material (FSM-16) was prepared, and its adsorption selectivity for several organic compounds (p-nitrophenol, toluene, n-heptane, benzene, cyclohexane, and o-dichlorobenzene) was studied. The adsorbed amounts of these compounds were measured by batch operation in liquid phase. The p-nitrophenol in aqueous solution was hardly adsorbed into FSM-16, but toluene (in n-heptane solvent) and benzene (in n-heptane solvent or cyclohexane

Masahiro Katoh; Hitoshi Takao; Naoto Abe; Tahei Tomida



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

National Technical Information Service (NTIS)

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

W. H. McCarty G. Parravano



Analysis of natural gas: the necessity of multiple standards for calibration.  


The importance of natural gas as an international trading commodity and the cost to consumers has made the accuracy of determinations for the components of natural gas very important. Pricing of natural gas is based on the heating value of the gas determined from either calorimetry measurements or calculations based on individual component concentrations determined by gas chromatography (GC). Due to the expense of accurate calibration standards, many analysts and laboratories will use a single calibration standard to perform natural gas determinations. Therefore, the purpose of this study was to determine whether an analyst could accurately measure the components of natural gas, in particular methane, using a single standard, or whether a suite of standards is necessary to calibrate the analytical instrument. A suite of eight gravimetric primary standards was prepared covering a concentration range for methane of 64-94 mol%, with uncertainties of +/-0.05% relative (95% confidence interval). These natural gas primary standards also contained nitrogen, carbon dioxide, ethane, propane, iso-butane, n-butane, iso-pentane, n-pentane, and n-hexane with varying concentrations from 0.02 to 14%. A single analytical method was used in which only the amount of sample injected onto the column was altered. The results show that when injecting a 0.5 ml sample volume a second-order regression through the standards is necessary for the determination of methane. The results for nitrogen, ethane and propane also show the same trend. Only those individual standards whose methane concentration is within 1% of the test mixture predicted a concentration within 0.05% of the regression value. Those individual primary standards whose methane concentration is different by more than +/-1% of the test mixture predicted values differing by +/-0.5 to +/-2.0% from the regression value. These differences lie well outside the predicted concentration uncertainty interval of +/-0.20%. A smaller sample volume, 0.1 ml, resulted in a set of data that could be fit using linear regression. Each of the eight primary standards individually predicted the methane in the test mixture to be within +/-0.11% of the predicted value from linear regression. The data confirm that it is imperative to fully characterize the analytical system before proceeding with an analysis. PMID:14584698

Rhoderick, George C



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.



Trace gas variations at Cape Point, South Africa, during May 1997 following a regional biomass burning episode  

NASA Astrophysics Data System (ADS)

During the continuous monitoring of atmospheric parameters at the station Cape Point (34°S, 18°E), a smoke plume originating from a controlled fire of 30-yr-old fynbos was observed on 6 May 1997. For this episode, which was associated with a nocturnal inversion and offshore airflow, atmospheric parameters (solar radiation and meteorological data) were considered and the levels of various trace gases compared with those measured at Cape Point in maritime air. Concentration maxima in the morning of 6 May for CO 2, CO, CH 4 and O 3 amounted to 370.3 ppm, 491 ppb, 1730 ppb and 47 ppb, respectively, whilst the mixing ratios of several halocarbons (F-11, F-12, F-113, CCl 4 and CH 3CCl 3) remained at background levels. In the case of CO, the maritime background level for this period was exceeded by a factor of 9.8. Differences in ozone levels of up to 5 ppb between air intakes at 4 and 30 m above the station (located at 230 m above sea level) indicated stratification of the air advected to Cape Point during the plume event. Aerosols within the smoke plume caused the signal of global solar radiation and UV-A to be attenuated from 52.4 to 13.0 mW cm -2 and from 2.3 to 1.3 mW cm -2, respectively, 5 h after the trace gases had reached their maxima. Emission ratios (ERs) calculated for CO and CH 4 relative to CO 2 mixing ratios amounted to 0.042 and 0.0040, respectively, representing one of the first results for fires involving fynbos. The CO ER is somewhat lower than those given in the literature for African savanna fires (average ER=0.048), whilst for CH 4 the ER falls within the range of ERs reported for the flaming (0.0030) and smouldering phases (0.0055) of savanna fires. Non-methane hydrocarbon (NMHC) data obtained from a grab sample collected during the plume event were compared to background levels. The highest ERs (?NMHC/?CH 4) have been obtained for the C 2-C 3 hydrocarbons (e.g. ethene at 229.3 ppt ppb -1), whilst the C 4-C 7 hydrocarbons were characterised by the lowest ERs (e.g. n-hexane at 1.0 and n-pentane at 0.8 ppt ppb -1).

Brunke, E.-G.; Labuschagne, C.; Scheel, H. E.


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.



Influence of the texture of chromia catalysts on their activity in synthesis of 2-methylthiophene  

Microsoft Academic Search

The texture of Cr2O3-K2O\\/Al2O3catalysts containing oxides of rare earth elements (REE) was studied. The catalysts are used for the synthesis of 2-methylthiophene by the reaction of H2S with n-pentane or piperilene. The heterocyclization of n-pentane is a consecutive reaction involving a step of dehydrogenation of initial hydrocarbon. At this step the texture of the catalyst affects the yield of 2-methylthiophene.

M. A. Ryashentseva; T. R. Brueva



Evaporation of a volatile-liquid lens floating on the surface of a stagnant immiscible liquid  

Microsoft Academic Search

This paper presents experimental results of evaporation of isolated lenses of n-pentane or R 113 (CâClâFâ) at a horizontal interface between a hot water and the common vapors of the two fluid substances. n-Pentane lenses often became unstable and even split into smaller lenses during evaporation process, while R 113 lenses were always stable. Corresponding to this fact, the evaporation

M. Kaneko; Y. H. Mori



Pentane and butane isomerization over platinum promoted sulfated zirconia catalysts  

Microsoft Academic Search

Skeletal isomerizations of n-pentane and n-butane have been studied at 11 bar in a microflow reactor over platinum containing sulfated zirconia (PtSZ) catalysts. The isomerization rate of n-pentane is about seven times higher than that of n-butane; selectivity to i-pentane is 91.6% at p(H2)= 2.2 bar. Hexanes and butanes are the main byproducts of pentane isomerization; the C6\\/C4 ratio is

H. Liu; G. D. Lei; W. M. H. Sachtler



Pressure dependence of the conduction-band energy of nonpolar liquids  

Microsoft Academic Search

The energy V0 of the conduction state of the quasifree electron is reported as a function of pressure up to 2.5 kbar for n-pentane, 2,2-dimethylbutane, 2,2,4-trimethylpentane, 2,2,4,4-tetramethylpentane, and tetramethylsilane (TMS). For each liquid, V0 increases with increasing pressure. The largest change with pressure is observed for n-pentane, the smallest change for TMS. The results are used together with a density-fluctuation

Richard Holroyd; Masaru Nishikawa; Kazumichi Nakagawa; Noriyuki Kato



Critical Opalescence of Binary Liquid Mixtures. The Debye Molecular Interaction Range.  

National Technical Information Service (NTIS)

Critical opalescence of two binary liquid mixtures, n-heptane-perfluorocyclic oxide and carbon tetrachloride-perfluorocyclic oxide, is investigated. The results indicate that the molecular interaction range of Debye, discussed in terms of the solubility p...

B. Chu



21 CFR 175.350 - Vinyl acetate/crotonic acid copolymer.  

Code of Federal Regulations, 2013 CFR

...2) of this section. (1) Specifications. (i) The chloroform-soluble portion of the water extractives of the coated film...milligram per square inch of coated surface. (ii) The chloroform-soluble portion of the n- heptane extractives of...



Measurement of Leachables from Tampons.  

National Technical Information Service (NTIS)

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

N. Lao



Monitoring of alkane vapor concentrations with polyimide lightguides  

NASA Astrophysics Data System (ADS)

Planar polyimide light guides can be used for the optical detection of various vapor concentrations. Therefore the birefringence of the light guide is monitored as a function of the actual vapor pressure. Using this principal several vapor concentrations of n-heptane and n- octane have been determined. Similar dynamic behavior can be observed for both components only differing in time constants. Furthermore the detection of n-heptane in a mixture with iso- octane can be realized. The waveguide sensor shows a sensitivity only to n-heptane and not so iso-octane vapors. The determination of the n-heptane concentration is not affected by the presence of iso-octane.

Podgorsek, R. P.; Franke, Hilmar



Excess volumes and isobaric heat capacities of diisopropyl ether with several alkanols at 298.15 K  

Microsoft Academic Search

Excess molar volumes vE and isobaric heat capacities CpE at 298.15K were measured for 11 mixtures of diisopropyl ether (DIPE)+alcohol (from methanol to 1-undecanol), DIPE with n-heptane and 2,4-dimethylpentane with 1-octanol. Moreover the excess molar enthalpy hE of DIPE with n-heptane at the same temperature was also measured in order to obtain the self-association parameters of the symmetrical extended real

Ángel Piñeiro



Liquid–Liquid Equilibria of Oxygenate Fuel Additives with Water at 298.15 K: Ternary and Quaternary Aqueous Systems of Diisopropyl Ether and Hydrocarbons with 2Propanol  

Microsoft Academic Search

Experimental tie-line data were determined for one ternary system, water + diisopropyl ether + n-heptane and two quaternary systems, water + diisopropyl ether + 2-propanol + n-heptane or toluene at 298.15 K and ambient pressure. The experimental liquid–liquid equilibrium data were successfully correlated\\u000a using a modified UNIQUAC model with ternary and quaternary mixture parameters, in addition to the binary ones.

Yao Chen; Yanhui Dong



Experimental and Numerical Investigations on HCCI- Combustion  

Microsoft Academic Search

Numerical and experimental investigations are presented with regard to homogeneous-charge- compression-ignition for two different fuels. N-heptane and n-butane are considered for covering an appropriate range of ignition behaviour typical for higher hydrocarbons. One fuel is closer to diesel (n-heptane), the other closer to gasoline ignition properties (n- butane). Butane in particular, being gaseous under atmospheric conditions, is used to also

G. Barroso; A. Escher; K. Boulouchos


Antiplasticization and plasticization of Matrimid ® asymmetric hollow fiber membranes—Part A. Experimental  

Microsoft Academic Search

The complex effects of highly sorbing feed gas contaminants such as toluene and n-heptane on performance of both annealed and non-annealed Matrimid® asymmetric fibers relevant to CO2\\/CH4 separation are reported. Membrane performance was quantified both during contaminant exposure and after removal of the contaminant from the feed stream. Exposure to either toluene or n-heptane during permeation reduces carbon dioxide permeance

Jong Suk Lee; William Madden; William J. Koros



Experimental studies on hydrocarbon neuropathies induced by methyl-ethyl-ketone (MEK)  

Microsoft Academic Search

An outbreak of neuropathies among Berlin solvent sniffers was closely related to the denaturation by methyl-ethyl-ketone (MEK) of the mixture used. The solvent was composed of n-hexane, toluene and ethyl-acetate. Nervous system responses to chronic repeated exposure to 10,000 ppm pure n-hexane, 10,000 ppm MEK\\/n-hexane (ratio 1:9) and 6000 ppm pure MEK were investigated in rats. Motor neuropathy of the

H. Altenkirch; G. Stoltenburg; H. M. Wagner



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


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



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

NASA Astrophysics Data System (ADS)

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

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



Preparation of HfO2 Thin Films Using Flashing Spray CVD Method  

NASA Astrophysics Data System (ADS)

The authors proposed the novel evaporation supply method, flashing spray chemical vapor deposition (FS-CVD). In the experiment, tetrakisethylmethylamidohafnium (TEMAH) was used as the precursor and n-pentane was used as the low boiling point organic solvent. The critical consolute temperature of TEMAH and n-pentane mixed material solution was 276K. The vapor pressure of the mixed material solution was ten times higher than that of TEMAH by formation of two-phase region. HfO2 film was deposited on Si wafer by using TEMAH and n-pentane with FS-CVD. As the result, the uniformity of HfO2 film was +/-5% and film thickness was 133.6nm. The uniformity of HfO2 film of refractive index was +/-5% and refractive index was 1.63. It is found that the precursor was evaporated by flash boiling and HfO2 film was deposited by decomposition.

Ohshima, Motohiro; Kimura, Daiichiro; Tsuchida, Tomoya; Senda, Jiro


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

SciTech Connect

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

Tierney, J.W.; Wender, I.



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

SciTech Connect

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

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



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


The optical anisotropy of planar polyimide lightguides in an atmosphere of n-heptaney/iso-octane is investigated in a transient experiment for pure and several mixed-vapor concentrations. The polymer sensor responds only to n-heptane and not to iso-octane vapors. However, the presence of the latter affects the dynamic behavior of the waveguide anisotropy, which can be fitted by a stretched exponential time dependence. The saturation values of the birefringence are an absolute measure for the n-heptane concentration and are not affected by the presence of the iso-octane vapors. PMID:19859234

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



Synthesis and Characterization of (Zn(SEt)Et)10, Formed via Insertion of Sulfur into Zn-C Bonds: A New Class of Wurtzite-like Cluster Framework.  

National Technical Information Service (NTIS)

The reaction of a toluene solution of ZnEt2 with one equivalent of sulfur (1/8 S8) results in dissolution of the sulfur to form a colorless solution. After addition of n-pentane and cooling, colorless crystals of Zn10(SEt)10Et10 were isolated and characte...

M. J. Hampden-Smith D. Zeng E. Duesler



Production of nanotubes by the catalytic decomposition of different carbon-containing compounds  

Microsoft Academic Search

Carbon nanotubes were prepared in the catalytic decomposition of different carbon containing compounds over supported transition metal catalysts. Besides acetylene, ethylene, propylene, acetone, n-pentane, methanol, toluene, and methane were tested and each resulted in carbon nanotube formation. The quality of as-made nanotubes was investigated by TEM and was found to be at least as good as obtained in acetylene decomposition.

Klara Hernadi; Antonio Fonseca; Janos B Nagy; Andrea Siska; Imre Kiricsi



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


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



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



The removal of alkanes in a liquid-continuous gas-phase bioreactor: Preliminary considerations  

Microsoft Academic Search

Columnar bioreactors are being tested for the treatment of volatile organics. The bioreactors contain microorganisms that are able to remove and degrade the dilute gaseous hydrocarbons (n-pentane and isobutane) from effluent air streams by biological action. Columnar bioreactors, including a liquid continuous packed column, were continuously operated for over 18 mo with sustained degradation of the gaseous hydrocarbons. In these

B. H. Davison; J. E. Thompson



Electron Transport in Paracoccus Halodenitrificans and the Role of Ubiquinone.  

National Technical Information Service (NTIS)

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 activi...

L. I. Hochstein S. E. Cronin



Complex Formation between Dimethyl Methylphosphonate and Hexafluoroisopropanol.  

National Technical Information Service (NTIS)

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

D. C. Leggett



Glycerolysis of olive oil: batch operational stability of Candida rugosa lipase immobilized in hydrophilic polyurethane foams  

Microsoft Academic Search

The operational stability of the Candida rugosa lipase immobilized in a hydrophilic polyurethane foam was evaluated in consecutive batches for the glycerolysis of olive oil in n-hexane, aimed at the production of monoglycerides.

S. Ferreira-Dias; M. M. R. Fonseca



21 CFR 177.1620 - Polyethylene, oxidized.  

Code of Federal Regulations, 2013 CFR

...DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) INDIRECT FOOD ADDITIVES...air oxidation of polyethylene conforming to the density, maximum n- hexane extractable...



21 CFR 177.1610 - Polyethylene, chlorinated.  

Code of Federal Regulations, 2013 CFR

...DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) INDIRECT FOOD ADDITIVES...chlorination of polyethylene conforming to the density, maximum n- hexane extractable...



Compatibility of Organic Solvents with the Microscreen Prophage-Induction Assay: Solvent - Mutagen Interactions.  

National Technical Information Service (NTIS)

The following solvents did not induce prophage lambda in the Escherichia coli WP2 lambda Microscreen assay: acetone, benzene, chloroform, ethanol, n-hexane, isopropanol, methanol, toluene, and a mixture of the three isomers of xylene. Dimethyl sulfoxide w...

D. M. DeMarini B. K. Lawrence H. G. Brooks V. S. Houk



Extraction Behavior of Technetium(VII) From Chromate Solutions of Sulfuric, Perchloric and Phosphoric Acids into Bis (2-Ethylhexyl) Hydrogen Phosphate (HDEHP).  

National Technical Information Service (NTIS)

The partitioning of technetium (VII) between CrO sub 4 /sup 2-/ solutions of H sub 2 SO sub 4 , HClO sub 4 and H sub 3 PO sub 4 and n-heptane solutions of HDEHP was measured radiometrically. In moderately acidic media, Tc(VII) partitioned in the organic p...

R. A. Wood S. T. Wakakuwa N. S. MacDonald



Spectroscopic Determination of Ternary Phase Diagrams  

NASA Astrophysics Data System (ADS)

Ternary phase diagrams describe phase equilibria among three components as a function of composition at constant temperature and pressure. The system of n-propanol, n-heptane, and water exhibits a simple ternary diagram with two well-demarcated regions. One region represents complete liquid miscibility at high proportions of n-propanol. The second region delineates the compositions where two immiscible liquid phases coexist--a water-rich layer and a heptane-rich layer with distinct amounts of solubilized n-propanol. The ternary phase diagram for such partially miscible liquid systems is generally determined in an undergraduate laboratory experiment by both visual methods and classical techniques. Indeed, the demarcation between the one- and two-phase liquid regions is visually discernible through titrations of n-propanol-n-heptane mixtures with water until a second liquid phase appears. However, the compositions of the immiscible liquid phases within the two-phase region can not be determined using classical pH titrations or refractive index measurements. Acidic or basic species are absent, and n-heptane and n-propanol exhibit refractive indices that differ by only 0.002 at room temperature. We have designed a modern experiment using conventional absorbance or fluorescence spectroscopy to rapidly, accurately, ad conveniently construct the n-propanol-n-heptane-water ternary phase diagram.

Karukstis, Kerry K.; Avrantinis, Sara K.; Boegeman, Stephanie L.; Conner, Jeanie N.; Hackman, Blaine M.; Lindsay, Jennifer M.; Mandel, Alexander L.; Miller, Elizabeth J.



Low Ozone-Depleting Halocarbons as Total-Flood Agents. Volume 2. Laboratory-Scale Fire Suppression and Explosion Prevention Testing.  

National Technical Information Service (NTIS)

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 (3) explosion prevention (inertion) testing in a small-scale explosion sphere using propa...

S. R. Skaggs E. W. Heinonen T. A. Moore J. A. Kirst




Microsoft Academic Search

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





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. ...


Investigation of Droplet Combustion with Nongray Gas Radiation Effects  

Microsoft Academic Search

Single droplet combustion processes including heating, evaporation, burning, soot formation and flame radiation were theoretically investigated by adopting nongray gas radiation model for the radiative transfer equation (RTE). n-Heptane was chosen as a fuel in the numerical calculation and the results were compared with the experimental data available in the literature. The discrete ordinate method (DOM) was employed to solve




Numerical analysis of droplet combustion process: Heating, evaporation, ignition and burning  

Microsoft Academic Search

Droplet combustion processes of benzene and n?heptane liquid fuels, including heating, evaporation, ignition and burning, are numerically investigated and compared with the available measured results found in the literature. Investigation shows that the consideration of thermal radiation effect does not introduce too many differences of ignition?time predictions in the modeling compared to that obtained without thermal radiation effect. However, the



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.



Nonlinear model predictive control of a packed distillation column  

Microsoft Academic Search

A rigorous dynamic model based on fundamental chemical engineering principles was formulated for a packed distillation column separating a mixture of cyclohexane and n-heptane. This model was simplified to a form suitable for use in on-line model predictive control calculations. A packed distillation column was operated at several operating conditions to estimate two unknown model parameters in the rigorous and

Ashutosh A. Patwardhan; Thomas F. Edgar



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


An improved GROMOS96 force field for aliphatic hydrocarbons in the condensed phase  

Microsoft Academic Search

Over the past 4 years the GROMOS96 force field has been successfully used in biomolecular simulations, for example in peptide folding studies and detailed protein investigations, but no applications to lipid systems have been published yet. Here we provide a detailed investigation of aliphatic liquid systems. For liquids of larger aliphatic chains, n-heptane and longer, the standard GROMOS96 parameter sets

Lukas D. Schuler; Xavier Daura; Wilfred F. Van Gunsteren



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.



Fatty acid ethyl ester concentrations in hair and self-reported alcohol consumption in 644 cases from different origin  

Microsoft Academic Search

For diagnosis of chronic alcohol abuse, fatty acid ethyl esters (FAEE) were determined in hair samples from 644 individuals, mainly parents from child protection cases. The analysis for ethyl myristate, ethyl palmitate, ethyl oleate and ethyl stearate was performed according to a validated procedure consisting of external degreasing by two times washing with n-heptane, extraction with a mixture of dimethylsulfoxide

Silke Süße; Carl M. Selavka; Tom Mieczkowski; Fritz Pragst



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



Uptake of Nitric Acid by Soot: Evidence for Reversible, Dissociative Adsorption  

Microsoft Academic Search

The uptake of nitric acid on n-hexane soot was measured in a coated-wall flow tube coupled to an electron-impact mass spectrometer. The soot films were prepared by combusting n-hexane in a burner and collecting the soot onto a pyrex tube with a total sample mass ranging from 0.0076 g to 0.5610 g. The surface area of the soot film was

D. G. Aubin; J. P. Abbatt



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

Microsoft Academic Search

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

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



Direct-acting mutagenicity of extracts of coal burning-derived particulates and contribution of nitropolycyclic aromatic hydrocarbons  

Microsoft Academic Search

Benzene–ethanol extracts from particulates produced by coal burning were separated into four fractions by silica-gel column chromatography using n-hexane (240ml), n-hexane–dichloromethane (3:1, v\\/v) (200ml), dichloromethane (200ml) and methanol (450ml), as the corresponding eluents. The mutagenicity of each fraction was assayed by the Ames test using the Salmonellatyphimurium YG1024 strain. The nitropolycyclic aromatic hydrocarbons (NPAHs) of each fraction were assayed by

Rina Taga; Ning Tang; Tetsuyuki Hattori; Kenji Tamura; Shigekatsu Sakai; Akira Toriba; Ryoichi Kizu; Kazuichi Hayakawa



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

Microsoft Academic Search

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

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



Anxiogenic activity of Myristica fragrans seeds  

Microsoft Academic Search

In the present study, the n-hexane extract of Myristica fragrans (MF) seeds, acetone-insoluble part of the n-hexane extract (AIMF) and trimyristin (TM) were assessed for their anxiogenic activity. The MF (10 and 30 mg\\/kg), AIMF (30, 100, and 300 mg\\/kg), and TM (10, 30, and 100 mg\\/kg) administered intraperitoneally exhibited anxiogenic activity in elevated plus-maze (EPM) paradigm. The open-field test

G. S Sonavane; V. P Sarveiya; V. S Kasture; S. B Kasture



Optimisation of enzymatic synthesis of diacylglycerols in binary medium systems containing ionic liquids  

Microsoft Academic Search

Two different approaches, namely the n-hexane\\/ionic liquid (IL) system and the binary IL system, were optimised as a reaction medium for selective production of diacylglycerols (DGs) by lipase-catalysed glycerolysis of triolein. ILs used are [BMIM]·[BF4], [BMIM].[PF6], [OMIM]·[PF6], [TOMA]·[TFA], [TOMA]·[Tf2N], and Ammoeng 120. The effect of mixing n-hexane with IL in different ratios and at different temperatures was found to depend

Derya Kahveci; Zheng Guo; Beraat Özçelik; Xuebing Xu



Boundary effects of molecular diffusion in nanoporous materials: A pulsed field gradient nuclear magnetic resonance study  

Microsoft Academic Search

The boundary conditions of intraparticle diffusion in nanoporous materials may be chosen to approach the limiting cases of either absorbing or reflecting boundaries, depending on the host-guest system under study and the temperature of measurement. Pulsed field gradient nuclear magnetic resonance is applied to monitor molecular diffusion of n-hexane and of an n-hexane-tetrafluoromethane mixture adsorbed in zeolite crystallites of type

Oliver Geier; Randall Q. Snurr; Frank Stallmach; Jörg Kärger



Investigation of energy and feedstock saving production of gasoline blending components free of benzene  

Microsoft Academic Search

In the production of environmentally friendly and human biologically favorable blending components of engine gasolines isoparaffin fractions having low carbon number (C5–C6) are indispensable. The objective of the research work was to select a catalyst that is applicable for the isomerization of benzene-containing n-hexane fractions at low temperature (<200 °C). n-Hexane isomerizing and benzene saturating ability of a commercial Pt\\/Al2O3 catalyst

Jen? Hancsók; Szabolcs Magyar; Zsolt Szoboszlai; Dénes Kalló



Antioxidant activity of Vitex agnus-castus L. extracts.  


The ethanol, n-hexane and water extracts of Vitex agnus-castus L. leaves and fruits were screened for antioxidant activity. The antioxidant activity of plant extracts was determined by an improved assay based on the decolorization of the radical monocation of 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS.+). The water and ethanol extracts showed stronger antioxidant activity than the n-hexane extracts. PMID:17600861

Sa?lam, Hüsniye; Pabuçcuo?lu, Aysun; Kivçak, Bijen



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


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



Zero ODP, Zero GWP, Halogen-Free, and Low K-factor Azeotropes as Blowing Agents for Isocyanate-Based Foams  

Microsoft Academic Search

Due to the ozone depletion potential (ODP) problem of CFCs and HCFCs, a number of alternative physical blowing agents for isocyanate-based foams are being investigated. Among them, two representative candidates are HFCs (hydrofluorocarbons) and halogen-free, aliphatic hydrocarbons in which the major hydrocarbons are n-pentane and cyclopentane. Another accompanying problem of CFCs and HCFCs is global warming potential (GWP).This paper describes

K. Ashida; K. Morimoto; A. Yufu



Quantitative Aspects of Alkylperoxy Radical Isomerization During Hydrocarbon Combustion  

Microsoft Academic Search

Detailed studies of the distribution of the products formed in the different regimes of combustion of n-pentane indicate the importance in the overall oxidation mechanism of the isomerization of amylperoxy radicals. It has been shown that C_5 O-heterocycles and C_5 alkenes are formed as a result of the intramolecular rearrangement of such radicals but that O-heterocycles, carbonyl compounds and alkenes

C. F. Cullis; M. Saeed; D. L. Trimm



A biomass-fired micro-scale CHP system with organic Rankine cycle (ORC) – Thermodynamic modelling studies  

Microsoft Academic Search

This paper presents the results of thermodynamics modelling studies of a 2 kW (e) biomass-fired CHP system with organic Rankine cycle (ORC). Three environmentally friendly refrigerants, namely HFE7000, HFE7100 and n-pentane, have been selected as the ORC fluids. The thermodynamic properties of the selected ORC fluids which have been predicted by commercial software (EES) are used to predict the thermal efficiency

Hao Liu; Yingjuan Shao; Jinxing Li



Isotope dilution determination of polycyclic aromatic hydrocarbons in olive pomace oil by gas chromatography–mass spectrometry  

Microsoft Academic Search

A gas chromatographic (GC) method with mass spectrometry detection (MS) for the determination of eight polycyclic aromatic hydrocarbons (PAHs) in olive pomace oil has been developed. The oil was diluted with n-pentane and extracted by liquid–liquid partition with dimethyl sulphoxide (DMSO). After water addition and back-extraction with cyclohexane, a thin-layer chromatography on silica gel was performed as a further purification

Gianfranco Diletti; Giampiero Scortichini; Rossana Scarpone; Giuseppe Gatti; Luigi Torreti; Giacomo Migliorati



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

Microsoft Academic Search

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

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



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

Microsoft Academic Search

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

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



Synthesis and characterization of (Zn(SEt)Et)10, formed via insertion of sulfur into Zn-C bonds: A new class of Wurtzite-like cluster framework  

Microsoft Academic Search

The reaction of a toluene solution of ZnEt2 with one equivalent of sulfur (1\\/8 S8) results in dissolution of the sulfur to form a colorless solution. After addition of n-pentane and cooling, colorless crystals of Zn10(SEt)10Et10 were isolated and characterized by a variety of spectroscopic characterization techniques and by single-crystal X-ray diffraction. Crystallographic data for Zn10(SEt)10Et10 at 293K: space group

Mark J. Hampden-Smith; D. Zeng; Eileen N. Duesler



Preparation and Characterization of Expandable St\\/MMA Copolymers Produced by Suspension Polymerization  

Microsoft Academic Search

Free radical suspension copolymerization of styrene (St) with methyl methacrylate (MMA) in the presence of n-pentane was investigated. The batch polymerization was performed in a stirred reactor via a two-stage process. First, free radical suspension polymerization of St and MMA in aqueous media was carried out at about 80—90°C with the aid of a monofunctional initiator to the monomer conversions

K. Jalili; F. Abbasi; M. Nasiri; M. Ghasemi; E. Haddadi



Elementary reconstitution of the water splitting light reaction in photosynthesis. 3. Photooxidative properties of chlorophyll dihydrate on metal as catalyst for water photolysis  

Microsoft Academic Search

The photooxidative properties of chlorophyll a dihydrate as photocatalyst for the water splitting reaction are examined using Pt and other metals as nonbiological catalysts for reaction product formation. The photoelectrodeposition of (Chl a 2HâO)\\/sub n\\/ microcrystals from n-pentane suspensions on Pt electrodes is described. The formation of a contiguous multilayer of (Chl a 2HâO)\\/sub n\\/ on Pt is examined by

Michael S. Showell; Francis K. Fong



Flavour substances of Chinese traditional smoke-cured bacon  

Microsoft Academic Search

Flavour components from Chinese traditional smoke-cured bacon were trapped by condensing and dissolving in organic solvent (ether and n-pentane), using the nitrogen purge-and-steam distillation (NPSD) method. Qualitative and quantitative characterizations of the extract were performed by means of gas chromatography-mass spectrometry and gas chromatography with a flame ionization detector, respectively. Using Chinese traditional smoke-cured bacon, under the condition of stewing,

Yu Ai-Nong; Sun Bao-Guo



Adsorption and Desorption of Hydrocarbons on a Supported Nickel Cracking Catalyst  

Microsoft Academic Search

A study has been made of the properties of the radicals formed by the dissociative adsorption of small volumes of methane, n-pentane, 2,2-dimethylbutane, cyclohexane, cyclohexene and benzene on a high area supported nickel cracking catalyst. Measurements have been made of (i) the change in volume of hydrogen adsorbed, after standard preparation of the catalyst, when a known volume of each

A. K. Galwey



Hydrostatic limits of 11 pressure transmitting media  

Microsoft Academic Search

We present a systematic and comparative study of the pressure-induced solidification of 11 frequently used pressure transmitting fluids using the ruby fluorescence technique in a diamond anvil cell. These fluids are 1 : 1 and 5 : 1 iso-n pentane, 4 : 1 deuterated methanol–ethanol, 16 : 3 : 1 deuterated methanol–ethanol-water, 1 : 1 FC84-FC87 Fluorinert, Daphne 7474, silicone

S Klotz; J-C Chervin; P Munsch; G Le Marchand



The removal of alkanes in a liquid-continuous gas-phase bioreactor: Preliminary considerations  

Microsoft Academic Search

Columnar bioreactors are being tested for the treatment of volatile organics. The bioreactors contain microorganisms that\\u000a are able to remove and degrade the dilute gaseous hydrocarbons (n-pentane and isobutane) from effluent air streams by biological action. Columnar bioreactors, including a liquid continuous\\u000a packed column, were continuously operated for over 18 mo with sustained degradation of the gaseous hydrocarbons. In these

Brian H. Davison; James E. Thompson



Halogen-free flame retardants for polymeric foams  

Microsoft Academic Search

The effectiveness of some mixtures of halogen-free flame retardants (i.e. expandable graphite, triethylphosphate and red phosphorus) in flame retardancy of polyisocyanurate-polyurethane (PIR-PUR) foams, blown with n-pentane, has been investigated by means of DIN 4102-B2 and oxygen index tests. The thermal stability and mechanical properties of PIR-PUR filled foams have also been considered. The results showed that the introduction of increasing

M. Modesti; A. Lorenzetti



Working fluids for low-temperature heat source  

Microsoft Academic Search

The performance of different working fluids to recover low-temperature heat source is studied. A simple Rankine cycle with subcritical configuration is considered. This work is to screen working fluids based on power production capability and component (heat exchanger and turbine) size requirements. Working fluids considered are R134a, R123, R227ea, R245fa, R290, and n-pentane. Energy balance is carried out to predict

Amlaku Abie Lakew; Olav Bolland



Multicomponent vapor-liquid equilibria measurements for the development of an extractive distillation process for the processing of gas issuing from a COâ\\/EOR project. [Associated gas from COâ injection  

Microsoft Academic Search

This paper presents V-L-E data for a multicomponent COâ-rich gas added to n-pentane at a series of fixed temperatures to produce an equilibrium mixture of various fixed total pressures to form a quasi-binary system containing compounds such as COâ, CâHâ, CâHâ, HâS, n-CâHââ, and n-CâHââ. The experimental results provide data useable to adjust parameters and test for ''proof of correlations.''

J. H. Hong; R. Kobayashi



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

Microsoft Academic Search

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




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

Microsoft Academic Search

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

M Modesti; A Lorenzetti; F Simioni; G Camino



Efficient Extraction of Fuel Oil Hydrocarbons from Wood  

Microsoft Academic Search

Sequential cold (room temperature) extraction from aged contaminated wood samples (southern yellow pine) with acetone followed by n?pentane (upon a 3–4 days of sample incubation with each solvent) yielded more than 90% analyte recovery for both ambient (natural moisture content) and water?submerged wood, significantly exceeding the recoveries obtained with one?step extraction using single solvents and\\/or their mixtures. By contrast, a

Inna E. Popova; Evguenii I. Kozliak



Hydrocarbon Cool Flames and the Influence of Hydrogen Bromide  

Microsoft Academic Search

Small amounts of hydrogen bromide added to n-pentane + 1.33 O2 mixtures lower both the limiting pressure for the onset of two-stage ignition and also, to a smaller extent, that for the appearance of cool flames. The induction period preceding the first cool flame, tau 1, is shown to be related to the initial pressure, P0, by a relation of

A. W. Bastow; C. F. Cullis



Carbon Isotope Fractionation Associated with Aerobic Microbial Oxidation of Natural Gas  

Microsoft Academic Search

Carbon stable isotope fractionation associated with the aerobic microbial consumption of propane (C3), n-butane (n-C4) and n-pentane (n-C5) of natural gas were analyzed from the gas seepages of Chianan (Chiayi-Tainan) foothill zone and Hualine hot spring field of Taiwan. The aerobic biologic effect on natural gas is related to subsurface structure, the aerobic and anoxic environment of shallow depth and

Yane-Shih Wang; Chun-Yin Hwang; Jong-chang Wu; Cheng-Lung Kuo


Supercritical extraction of coal  

Microsoft Academic Search

Supercritical extraction of Wyodak coal was studied by passing various solvents upwards through a 15 gram sample of 12-20 mesh coal. For the high temperature experiments, the coal was heated to 375°C and 425°C in a hot fluidized sand bath. The main solvent used was toluene, while extractions with n-pentane, xylene, methanol, and water were also done. The extract was




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

PubMed Central

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

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



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



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


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



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


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

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



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.



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

SciTech Connect

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

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



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


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



Influence of tray geometry on scaling up distillation efficiency from laboratory data  

SciTech Connect

This paper studies the effect of tray geometry (especially hole diameter) and liquid tray composition on tray efficiency in a bench-scale distillation column. The results of this study are used for scaling up tray efficiency. Two binary systems, ethanol/water and cyclohexane/n-heptane, were considered. The operating conditions were atmospheric pressure and total reflux. For each one, two different hole diameters (small and large) were also tested. Kirschbaum`s industrial data (1962) for the ethanol/water system and of Yanagi and Sakata`s (1982) for the cyclohexane/n-heptane system were considered as reference values. The results show the importance of reproducing the hole diameter and liquid tray composition in small trays for using laboratory data to predict large tray efficiency.

Lopez, F.; Castells, F. [Univ. Rovira i Virgili, Catalunya (Spain). Dept. of Chemical Engineering



Boiling of droplets on a hot surface in low gravity  

Microsoft Academic Search

The boiling of single droplets of water and n-heptane on a hot stainless steel surface was observed in a low gravity environment, obtained on board a platform in free fall. Droplet impact was photographed using a single-shot flash-photographic method. Surface temperature variation during droplet impact was recorded using a fast-response thermocouple. Droplets could not be maintained in stable film boiling

Y. M. Qiao; S. Chandra



Determination of propranolol in dog plasma by HPLC method  

Microsoft Academic Search

A rapid, sensitive and accurate high performance liquid chromatographic (HPLC) method for determination of propranolol in dog plasma is described. Propranolol was extracted from dog plasma using a mixture of n-heptane and isoamyl alcohol (98.5:1.5, v\\/v) and separated on a C18 column. The mobile phase consisting of a mixture of acetonitrile- water (containing of 1% acetic acid and 0.2 %

Shuhua Xiao; Guangli Wei; Hong Guo; Heng Liu; Changxiao Liu


Use of modified membrane carrier system for recovery of gold cyanide from alkaline cyanide media using hollow fiber supported liquid membranes: feasibility studies and mass transfer modeling  

Microsoft Academic Search

This investigation is concerned with the applications of hollow fiber supported liquid membranes for the recovery of gold(I) (Au(CN)2?) from alkaline cyanide media using microporous hydrophobic hollow fiber with modified membrane extractant (carrier). The organic extractant used for gold(I) permeation was LIX79 alone and mixture of TOPO+LIX79 diluted with n-heptane. The mixture of LIX79+TOPO affords better performance than LIX79 alone.

Anil Kumar; R. Haddad; G. Benzal; R. Ninou; A. M. Sastre



Liquid-fuel combustion in a narrow tube using an electrospray technique  

Microsoft Academic Search

This study experimentally investigated the possibility of stable burning conditions of liquid fuel inside a narrow tube using an electrospray technique without external heating or a catalyst. The mixture of 30% volume ethanol and 70% volume n-heptane was used as a liquid fuel atomized by the electrospray method with single capillary-ring extractor-mesh collector electrode configuration placed inside a quartz glass

Lilis Yuliati; Takehiko Seo; Masato Mikami


Diffusive characterization of large pore mesoporous materials with semi- crystalline zeolitic framework  

Microsoft Academic Search

Diffusion (kinetics) characterization of composite mesoporous materials that contain nano- zeolite particles in the mesoporous walls (UL-zeolite) is considered very important to further assess their potential as unique materials for separation and catalysis. Two different bimodal materials were investigated using two probe molecules, i.e., n-heptane and toluene of different kinetic diameter. Results showed varied behavior with respect to diffusion rates,

H. V. Thang; A. Malekian; M. Ei?; D. Trong On; S. Kaliaguine



Influence of low air pressure on combustion characteristics and flame pulsation frequency of pool fires  

Microsoft Academic Search

To investigate the effect of low air pressure on the combustion characteristics and puffing flame frequency of pool fires, ethanol and n-heptane pool fires were performed using 15 square burners of various size in both Lhasa (altitude: 3650m; air pressure: 65kPa) and Hefei (altitude: 24m, air pressure: 100.8kPa) fire laboratories. Comparison of the experimental results for pool fires of the

Jun Fang; Ran Tu; Jin-fu Guan; Jin-jun Wang; Yong-ming Zhang



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

Microsoft Academic Search

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




Transition from cool flame to thermal flame in compression ignition process  

SciTech Connect

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

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



Characterization of molecular change of heavy oil under mild thermal processing using FT-IR spectroscopy  

Microsoft Academic Search

In order to quickly and economically obtain the information of molecular changes occurring in heavy oils during thermal processing, simulated mixtures of heavy oils and their pyrolyzed products were prepared from four model compounds, i.e., naphthalene, tetralin, decalin, and n-heptane. FT-IR absorption characteristics and average molecular parameters of the mixtures were correlated; the molecular parameters included the number ratio of

Ai-jun GUO; Zhi-hui REN; Ling-yan TIAN; Zong-xian WANG



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.



High-Current Brushes, Part II: Effects of Gases and Hydrocarbon Vapors  

Microsoft Academic Search

The performance of metal-graphite brushes sliding against a copper ring while carrying high current loads (to 80 A\\/cm2current density) has been evaluated under five nonoxidizing gas atmospheres (CO2, SF6, N2, He, and A) in the presence of constant water partial pressure (600 Pa) and under a dry CO2atmosphere in the presence of n-paraffinic hydrocarbon vapors (n-heptane to n-hexadecane, 0.2-1300 Pa)




Asphaltene adsorption on clays and crude oil reservoir rocks  

Microsoft Academic Search

The adsorption of asphaltene on different clay minerals (kaolinite, illite, montmorillonite) and mineral oil reservoir rocks was studied. In toluene solution, specific adsorption was observed on kaolinite and a decrease in adsorption was found in the order illite-montmorillonite. In toluene\\/n-heptane mixtures a two-stage isotherm was recorded on the surface of the adsorbents. Surface modification by the adsorption of asphaltenes was

Tímea Pernyeszi; Ágnes Patzkó; Ottó Berkesi; Imre Dékány



Synthesis of window glazing coated with silica aerogel films via ambient drying  

Microsoft Academic Search

An ambient drying process (1 atm, 270 °C) has been developed in order to synthesize window glazing coated with silica aerogel films. The aerogel film could be manufactured by this process of wet gel films obtained via a dip-\\/spin-coating of the silica sol on a glass slide. Before drying, the isoproponol solvent in wet gels was exchanged with n-heptane to

Gun-Soo Kim; Sang-Hoon Hyun



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

Microsoft Academic Search

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

Szybist; James P



UV-Vis Investigation on the Hydrocarbon Length Effect on the ? Tocopherol Solubility in an AOT\\/ n Alkane\\/Water System  

Microsoft Academic Search

The influence of n-alkane hydrocarbon chain length on both binding and distribution constants of ?-tocopherol and Aerosol-OT [sodium bis(2-ethylhexyl) sulfosuccinate] reversed micelles were studied with the UV-vis method\\u000a using n-heptane and n-decane as solvents. The amount of water in the system was determined by R defined as the ratio of water to surfactant molalities (). No significant water influence on

Hanna Wilczura-Wachnik; Izabela Gregorczyk; Adam Myslinski



Numerical and experimental study of water\\/oil emulsified fuel combustion in a diesel engine  

Microsoft Academic Search

Numerical and experimental studies were made on some of the chemical and physical properties of water\\/oil emulsified fuel (W\\/OEF) combustion characteristics. Numerical investigations of W\\/OEF combustion's chemical kinetic aspects have been performed by simulation of water\\/n-heptane mixture combustion, assuming a model of a homogenous reactor's concentric shells. The injection and fuel spray characteristics are analyzed numerically also in order to

Niko Samec; Breda Kegl; Robert W. Dibble



Catalytic activity of synthetic saponite clays: effects of tetrahedral and octahedral composition  

Microsoft Academic Search

This paper describes the catalytic characteristics of synthetic saponites with well-known chemical composition, thermal stability, and acidity in three catalytic reactions: (1) catalytic cracking of n-dodecane, (2) hydro-isomerisation of n-heptane, and (3) Friedel–Crafts alkylation of benzene. Saponites with Mg in the octahedral position were by far the best catalysts for the catalytic cracking of n-dodecane, which can be explained by

R. J. M. J. Vogels; J. T. Kloprogge; J. W. Geus



Study of Fischer-Tropsch model compounds reacting over ZSM-5. [MS Thesis  

SciTech Connect

The decomposition of three Fischer-Tropsch model compounds (1-decanol, decanal, and n-heptane) over ZSM-5 catalysts ion exchanged with nickel, zinc, and hydrogen was studied. The mechanisms of decomposition and the reaction kinetics of the model compounds were investigated as well as how exchanging the ZSM-5 with different cations affected the mechanisms, kinetics, and product distribution. The mechanism for 1-decanol decomposition was found to be formation of di-n-decyl ether, which then dehydrated to form 1-decene. Decanal was seen to decompose by three different mecanisms: Aldol condensation, cleavage of CO to form n-nonane, and reduction to 1-decanol. Heptane was seen to follow classical carbonium ion chemistry. First order rate constants and activation energies were calculated for n-heptane/Ni-ZSM-5, 1-decanol/Ni-ZSM-5, 1-decanol/H-ZSM-5, decanal/Ni-ZSM-5, and decanal/H-ZSM-5. The activation energies for decomposition were found to be 21 +- 4 Kcal/gmole for 1-decanol to 1-decene; 32 +- 3 Kcal/gmole for n-heptane; and 15 +- 3 Kcal/gmole on Ni-ZSM-5 and 21 +- 1 Kcal/gmole on H-ZSM-5 for decanal decomposing to n-nonane and CO. H-ZSM-5 was determined to be the most active catalyst of the three tested for decomposition of oxygenates. N-ZSM-5 was the most effective catalyst in the cracking of n-heptane. Due to its superior ability to decompose oxygenates, H-ZSM-5 appears to be the best choice for a Fischer-Tropsch liquid up-grading catalyst. For Fischer-Tropsch liquids with high linear alkane contents a small amount of nickel or other dehydrogenation catalyst added to the H-ZSM-5 would probably prove beneficial. 26 references, 12 figures, 8 tables.

Riley, M.G.



A kinetic modeling study on the oxidation of primary reference fuel–toluene mixtures including cross reactions between aromatics and aliphatics  

Microsoft Academic Search

A detailed chemical kinetic model for the mixtures of primary reference fuel (PRF: n-heptane and iso-octane) and toluene has been proposed. This model is divided into three parts; a PRF mechanism [T. Ogura, Y. Sakai, A. Miyoshi, M. Koshi, P. Dagaut, Energy Fuels 21 (2007) 3233–3239], toluene sub-mechanism and cross reactions between PRF and toluene. Toluene sub-mechanism includes the low

Yasuyuki Sakai; Akira Miyoshi; Mitsuo Koshi; William J. Pitz



Comparing late-cycle autoignition stability for single- and two-stage ignition fuels in HCCI engines  

Microsoft Academic Search

The characteristics of autoignition after top-dead-center (TDC) for both single- and two-stage ignition fuels have been investigated in a homogeneous charge compression ignition (HCCI) engine. The single-stage ignition fuel was iso-octane and the two-stage ignition fuel was PRF80 (80% iso-octane and 20% n-heptane). The results show that the heat-release rate and pressure-rise rate both decrease as the combustion is retarded

Magnus Sjöberg; John E. Dec



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.



Autoignition of gasoline surrogate mixtures at intermediate temperatures and high pressures: Experimental and numerical approaches  

Microsoft Academic Search

Ignition-delay times were measured in shock-heated gases for a surrogate gasoline fuel comprised of ethanol\\/iso-octane\\/n-heptane\\/toluene at a composition of 40%\\/37.8%\\/10.2%\\/12% by liquid volume with a calculated octane number of 98.8. The experiments were carried out in stoichiometric mixtures in air behind reflected shock waves in a heated high-pressure shock tube. Initial reflected shock conditions were as follows: Temperatures of 690–1200K,

L. R. Cancino; M. Fikri; A. A. M. Oliveira; C. Schulz



Laminar flame speeds of primary reference fuels and reformer gas mixtures  

Microsoft Academic Search

The laminar flame speeds of neat primary reference fuels (PRFs), n-heptane and iso-octane, PRF blends, reformer gas, and reformer gas\\/iso-octane\\/air mixtures are measured over a range of equivalence ratios at atmospheric pressure, using counterflow configuration and digital particle image velocimetry (DPIV). PRF blends with various octane numbers are studied. The synthetic reformer gas mixture employed herein has a composition that

Y. Huang; C. J. Sung; J. A. Eng



Experiments on the ignition of monocomponent and bicomponent fuel droplets in convective flow  

Microsoft Academic Search

The ignition of free and suspended monocomponent (iso-octane) and bicomponent (mixtures of n-hexadecane with n-heptane, n-dodecane, or iso-octane) droplets was experimentally investigated in the postflame gases (gas temperature, T?, between 1080 and 1300 K; flow velocity U? of 2.0–2.5 m\\/s) of a flat-flame burner. Initial droplet diameters, d0, ranged from 300 to 1500 ?m and droplet Reynolds numbers from 3.5

Jeng-Renn Yang; Chung-Yu Yukao; Ju-Jeng Whang; Shwin-Chung Wong



A wide-range modeling study of iso-octane oxidation  

Microsoft Academic Search

This paper presents a semidetailed kinetic scheme for the oxidation of iso-octane (2,2,4-trimethyl-pentane). Both the low- and high-temperature primary mechanisms are reduced to a lumped kinetic model involving only a limited number of intermediate steps. This primary reaction scheme, similar to the one already presented for n-heptane [1], is flexible enough to maintain accurate prediction of intermediate components, heat release,

Andrea D'Anna; Anna Ciajolo



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



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

Microsoft Academic Search

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




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

Microsoft Academic Search

The self-ignition of several spark-ignition (SI) engine fuels (iso-octane, methanol, methyl tert-butyl ether and three different mixtures of iso-octane and n-heptane), mixed with air, was investigated experimentally under relevant engine conditions by the shock tube technique. Typical modes of the self-ignition process were registered cinematographically. For temperatures relevant to piston engine combustion, the self-ignition process always starts as an inhomogeneous,

K. Fieweger; R. Blumenthal; G. Adomeit



Partial Wetting in Capillary Liquid Absorption by Limestones  

Microsoft Academic Search

We report measurements of the capillary absorption (imbibition) of water, n-heptane, n-decane, n-dodecane, methanol, ethanol, propan-2-ol, and ethanol–water mixtures into a number of dry calcitic limestones. The data are analyzed on the basis of unsaturated flow theory to give values of sorptivity S for water and for each organic liquid at different temperatures. The results show that for the organic

Sarah C. Taylor; Christopher Hall; William D. Hoff; Moira A. Wilson



Modelling on isoamyl isovalerate synthesis from Rhizomucor miehei lipasein organic media: optimization studies  

Microsoft Academic Search

Immobilized lipase from Rhizomucor miehei (Lipozyme IM-20) was employed in the esterification of isovaleric acid and isoamyl alcohol to synthesize isoamyl isovalerate in n-heptane. Response surface methodology (RSM) based on a five-level, five-variable central composite rotatable design (CCRD) was used to evaluate the effects of important variables: enzyme concentration (20–40% w\\/w of acid), acid concentration (0.2–1.0 M), incubation period (24–120

G. V. Chowdary; S. Divakar; S. G. Prapulla



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




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



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

Microsoft Academic Search

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

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



A study on the surface free energy of modified silica fillers and poly(ethylene terephthalate) fibers by inverse gas chromatography  

Microsoft Academic Search

The surface free energy of modified silica fillers and poly(ethylene terephthalate) (PET) fibers was analyzed by inverse\\u000a gas chromatography in order to investigate the relationship between their surface characteristics and the performance of the\\u000a composite formed from these materials. The adsorption isotherms of n-heptane and 1-propanol were determined by the elution-peak-maximum method. The dispersive and polar components of the surface

M. Kimura; S. Kataoka; K. Tsutsumi



A New Multicomponent Diffusion Formulation for the Finite-Volume Method: Application to Convective Droplet Combustion  

Microsoft Academic Search

A new multicomponent formulation, appropriate for use with the finite-volume method, has been developed to describe mass diffusion velocities accurately. The new formulation is applied in a quasi-steady numerical model for n-heptane fuel droplet combustion in a forced-convection environment. Results obtained using the complete formulation are compared to the results obtained under various assumptions. Using a single binary diffusion coefficient

Daniel N. Pope; George Gogos



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

Microsoft Academic Search

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

Karin Wiberg; Sune Sporring; Peter Haglund; Erland Björklund



Low temperature solubilities of fatty acids in selected organic solvents  

Microsoft Academic Search

Summary  A number of highly purified fatty acids have been prepared and their solubilities determined in six common organic solvents\\u000a within the temperature range from 10? to ?70?. The acids studied were palmitic, stearic, oleic, elaidic, petroselinic, petroselaidic,\\u000a linoleic, stearolic, arachidic, eicosenoic, behenic, erucic, and brassidic. The solvents used were methanol, ethyl acetate,\\u000a diethyl ether, acetone, toluene, and n-heptane, representing six

Doris K. Kolb; J. B. Brown



Monitoring of the particle size of MoS x nanoparticles by a new microemulsion-based synthesis  

Microsoft Academic Search

Molybdenum sulfide nanoparticles in the size-range 3-10 nm have been synthesized in mild conditions using a microemulsion-based route. The reverse microemulsion phase, AOT\\/ n-heptane\\/ water, was first characterized by Transmission Electron Microscopy (TEM) of Freeze Fractures (FF) obtained via High Pressure Freezing (HPF) as well as Dynamic Light Scattering (DLS). The impacts of various parameters such as water-to- surfactant molar

Karin Marchand; Maud Tarret; Laurent Normand; Slavik Kasztelan; Tivadar Cseri



Investigation of AOT-based microemulsions for the controlled synthesis of MoS x nanoparticles : an electron microscopy study  

Microsoft Academic Search

Molybdenum sulfide nanoparticles have been synthesized using microreactors made of Bis(2-ethylhexyl)sulfosuccinate (AOT)\\/water\\/n-heptane microemulsions. The reverse microemulsion phase was characterized by transmission electron microscopy (TEM) after freeze fracture (FF) and replication. Freezing was achieved using a high pressure cooling device. It was found to be very respectful of the sample structure, and allowed the study of various parameters such as the

K. E Marchand; M Tarret; J. P Lechaire; L Normand; S Kasztelan; T Cseri



Production of metal oxide nanoparticles by supercritical emulsion reaction  

Microsoft Academic Search

A technique derived from SAS is proposed for the production of silicon, tungsten and molybdenum oxides nanoparticles in which supercritical CO2 plays a double role, acting as antisolvent and as reactant. A liquid mixture, that will be used as the continuous phase, containing i-octane, n-heptane, cyclohexane or ethyl acetate and sodium bis (2-ethylhexyl) sulfosuccinate (AOT) or Tween80 as surfactant is

E. Reverchon; G. Della Porta; E. Torino



Synthesis and Emulsification Properties of an Amphiphilic Polymer for Enhanced Oil Recovery  

Microsoft Academic Search

A novel amphiphilic polymer, APAM, for enhanced oil recovery (EOR), was synthesized by radical copolymerization of acrylamide, dodecyl polyoxyethylene acrylate (DPEA), and N-(1,1,3,3-tetramethyl butyl) acrylamide (TBA), using potassium persulfate-sodium bisulfite as initiator–activator. The aggregation morphological observation of APAM in aqueous and NaCl solutions was performed using scanning electron microscope. The ability of APAM to solubilize and emulsify n-heptane and crude

Jinhong Sun; Xiaohui Xu; Jinben Wang; Wei Zhang; Hui Yang; Xiaoyan Jing; Xuefeng Shi



Degradation of jet fuel hydrocarbons by aquatic microbial communities. Interim report 23 October 1981-30 September 1983  

Microsoft Academic Search

A model fuel mixture of fifteen hydrocarbons representative of those in distillate jet fuels was used to determine whether degradation by natural microbial communities could affect the persistence of such fuels released into aquatic environments. The mixture included hexane, cyclohexane, n-heptane, methylcyclohexane, toluene, n-octane, ethylcyclohexane, p-xylene, cumene, 1,3,5-trimethylbenzene, indan, naphthalene, 2-methylnaphthalene, n-tetradecane, and 2,3-dimethylnaphthalene. The water-soluble fraction of the model

J. C. Spain; C. C. Somerville; L. C. Butler; T. J. Lee; A. W. Bourquin



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

Microsoft Academic Search

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

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



Dynamics of water-containing sodium bis(2-ethylhexyl)sulfosuccinate (AOT) reverse micelles: A high-frequency dielectric study  

Microsoft Academic Search

The high-frequency dielectric response of AOT reverse micelles in n-heptane and CCl4 has been measured in the range 0.01-20 GHz as a function of the water-surfactant ratio (W). A relaxation phenomenon has been observed which is connected to the single particle dynamics. This dielectric relaxation depends on surfactant hydration and is markedly affected by interparticle interactions. At low values of

M. D'angelo; D. Fioretto; G. Onori; L. Palmieri; A. Santucci



Pervaporation Separation of Thiophene–Heptane Mixtures with Polydimethylsiloxane (PDMS) Membrane for Desulfurization  

Microsoft Academic Search

Cross-linked polydimethylsiloxane (PDMS)–polyetherimide (PEI) composite membranes were prepared, in which asymmetric microporous\\u000a PEI membrane prepared with phase inversion method was acted as the microporous supporting layer in the flat-plate composite\\u000a membrane. Membrane characterization was conducted by Fourier transform infrared and scanning electronic microscopy analysis.\\u000a The composite membranes were employed in pervaporation separation of n-heptane–thiophene mixtures. Effect of amount of PDMS,

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



Noble metal-doped perovskites for the oxidation of organic air pollutants  

Microsoft Academic Search

Ag-Pt- and Pd-doped LaMnO3-based perovskite catalysts were prepared and their activity in the oxidation of toluene, n-heptane and ethanol was investigated. The activity of LaMnO3-based catalyst was very high in the oxidation of each compound tested. The Ag-doped catalyst was the most active in the oxidation of each compound and it displayed the highest BET specific surface area (SSA) also.

Anna Musialik-Piotrowska; Holger Landmesser



“Coulomb Staircase” at Room Temperature in a Self-Assembled Monolayer of Hydrophobic Fe\\/Pt@Au Core-Shell Nanoparticle  

Microsoft Academic Search

Hydrophobic Fe\\/Pt@Au core-shell nanoparticles (NPs) were synthesized in a quaternary CTAB\\/n-butanol\\/n-heptane\\/water reverse micelle. Dodecylthiol coated around the NPs as functional agent could be help the NPs to form a self-assembled monolayer of which can be viewed clearly by transmission electron microscopy (TEM). A scanning tunneling microscope (STM) was used to find the subtle self-assembled monolayer of the NPs and to

Yun Zhi Fu; Jin Ru Li



Quenched nonisothermal pyrolysis of Asphalt Ridge tar sand and Boscan heavy oil mixtures  

Microsoft Academic Search

Quenched nonisothermal experiments were performed on Asphalt Ridge tar sand and on mixtures of tar sand and Boscan oil at two heating rates. Reactions were quenched at temperatures in the range of 200-- 600°C (392--1112°F) and the nonvolatile organic products were sequentially extracted with n-heptane, toluene, and pyridine. Coke contents were determined by combustion. Kinetic analyses of the coversion of

T. F. Turner; R. R. Glaser; B. E. Thomas



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

Microsoft Academic Search

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

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



Glass still for the evaluation of column packing with uranium hexafluoride  

Microsoft Academic Search

The operating holdup and flooding rates of uranium hexafluoride, n-heptane, and perfluorodimethylcyclohexane have been studied in a glass still filled with 1\\/8 inch nickel Heli-Pak. The flooding rates of the latter two substances are 46.0 and 48.0 cc.\\/min. respectively and the flooding rate for uranium hexafluoride, calculated from the Bertetti equation, is 42.9 cc.\\/min. The operating holdups for these three




Isothermal vapour-liquid equilibria for ternary and quaternary systems of butyl chlorides with nheptane, toluene and methylcyclohexane at 323.15 K  

Microsoft Academic Search

Isothermal P, x and y data were measured in ternary and quaternary systems containing one of butyl chlorides (1-chlorobutane, 2-chlorobutane, 2-chloro-2-methylpropane) with n-heptane, toluene and methylcyclohexane. The data were smoothed by means of the maximum likelihood method using 3-suffix Margules, Van Laar, Wilson, NRTL (? = 1) and UNIQUAC equations. The DISQUAC model was applied to the prediction of data

Omar Dahmani; Ivan Wichterle; Ahmed Ait-Kaci



Isothermal vapour-liquid equilibria for binary systems of chloroalkanes with heptane, toluene and methylcyclohexane at 323.15 and 333.15 K  

Microsoft Academic Search

Isothermal P, x, and y data were measured for twelve systems. Nine were binary chloroalkane + hydrocarbon systems, namely: 1-chlorobutane, 2-chlorobutane and 2-chloro-2-methylpropane with n-heptane, toluene and methylcyclohexane. Similar data were also measured for the binary systems 1-chlorobutane + 2-chlorobutane, 1-chlorobutane + 2-chloro-2-methylpropane and 2-chlorobutane + 2-chloro-2-methylpropane. The experimental data were correlated using the following five two-parameter models by means

Omar Dahmani; Ivan Wichterle; Ahmed Ait-Kaci



Influence of external surface area of rare-earth containing Y zeolites on the cracking of 1,3,5-triisopropylbenzene  

Microsoft Academic Search

NaY zeolites measuring 63 and 193 nm (average crystallite size) have been synthesized by dosing different amounts of seeds in the crystallization step. Evaluation of catalytic activity of both zeolites after ion exchange with rare-earth ions and calcination has been carried out with two reactants of different molecular size: n-heptane and 1,3,5-triisopropylbenzene. No influence of the crystallite size (and therefore

Eduardo Falabella S. Aguiar; Marcos P. Silva; Débora F. Silva



Antiplasticization and plasticization of Matrimid ® asymmetric hollow fiber membranes. Part B. Modeling  

Microsoft Academic Search

A previous paper characterized effects of exposure of Matrimid® asymmetric fibers to either toluene or n-heptane or a combination of both contaminants during permeation. In all cases, reductions in the carbon dioxide permeance and the carbon dioxide\\/methane selectivity were observed for both annealed and non-annealed samples. In this paper, the respective potential impacts of competitive sorption, fiber compaction, and antiplasticization\\/plasticization

Jong Suk Lee; William Madden; William J. Koros



Separation of solvent-refined coal into solvent-derived fractions  

SciTech Connect

A method for the separation of solvent-refined coal (SRC) and hydrotreated SRC into n-hexane soluble 'oils', toluene soluble n-hexane insoluble 'asphaltenes', and pyridine soluble toluene insoluble 'preasphaltenes' was developed. The separation into solvent-derived fractions was achieved by eluting a SRC sample which was coated on an inert support material (Fluoropak) from a liquid chromatographic column. A sequence of n-hexane, toluene, and pyridine solvents were used to elute the SRC fractions. The unique feature of the method allows for further separation of the solvent-derived fractions into major compound classes without the need to evaporate solvents and redissolve fractions. This can be achieved by integrating the SRC-coated Fluoropak column with liquid chromatographic columns. Various SRC samples were investigated by using the procedure.

Boduszynski, M.M.; Hurtubise, R.J.; Silver, H.F.



Chemical composition of some traditional herbal drug preparations: essential oil and aromatic water of costmary (Balsamita suaveolens Pers.).  


The compositions of the essential oil and the aromatic water of costmary (Balsamita suaveolens Pers.) cultivated in Tuscany were investigated. They represent the main ingredients of some traditional preparations sold commercially. The essential oil as such and the n-hexane extract of the aromatic water were analyzed by GC and GC-MS. Both samples were found to be rich in monoterpenes. Eighty-five compounds were identified, accounting for 95.1 and 95.4% of the essential oil and n-hexane extract of aromatic water, respectively. Carvone was the main compound (43.5% in the essential oil and 74.9% in the n-hexane extract of aromatic water). In addition, solid phase microextraction was used to sample the volatile organic compounds emitted from the fresh plant and from the aromatic water, and carvone was again the main component, amounting to 46.2 and 41.3%, respectively. PMID:11743783

Gallori, S; Flamini, G; Bilia, A R; Morelli, I; Landini, A; Vincieri, F F



Hydrophobic response of the fungus Rhinocladiella similis in the biofiltration with volatile organic compounds with different polarity.  


Rhinocladiella similis biodegraded volatile organic compounds (VOCs) of different polarity in gas-phase biofilters. Elimination capacities, (EC) of 74 g(hexane) m(-3) h(-1), 230 g(ethanol) m(-3) h(-1), 85 g(toluene) m(-3) h(-1) and 30 g(phenol) m(-3) h(-1) were obtained. EC values correlated with the solubility of the VOCs. R. similis grown with n-hexane or ethanol in biofilters packed with Perlite showed that the surface hydrophobicity was higher with n-hexane than ethanol. The hydrophobin-like proteins extracted from the mycelium produced with n-hexane (15 kDa) were different from those in the ethanol biofilter (8.5 kDa and 7 kDa). PMID:19343504

Vigueras, Gabriel; Arriaga, Sonia; Shirai, Keiko; Morales, Marcia; Revah, Sergio



Transition metal catalysis in the generation of petroleum: A genetic anomaly in Ordovician oils  

SciTech Connect

The transition metals, captured from sedimentary waters by chlorophyll, have been proposed as the catalytic agents that convert n-alkane biolipids into the rearranged light hydrocarbons in petroleum. Certain ancient oils (Ordovician) display a depletion in chlorophyll, suggesting that they may have been derived from sedimentary rocks also depleted in transition metals. These oils show anomalously high concentrations of n-heptane relative to their respective rearranged isoalkane and cycloalkane products. This extraordinary enrichment in light n-alkanes appears unique to the chlorophyll-deficient Ordovician oils. The high concentrations of n-heptane may have resulted from the thermal cracking of higher n-alkanes, which are known to be dominant components of the kerogenous precursors to the Ordovician oils. However, the methylhexanes, which have no thermolytic precursors enriched in the kerogenous source, show a proportionate increase in concentration. The contention, therefore, that thermal cracking might explain the n-heptane anomaly is untenable since a kerogenous starting material enriched in n-alkanes and depleted in isoalkanes cannot reasonably crack to a light hydrocarbon product enriched in both n-alkanes and isoalkanes. According to a postulated catalytic cycle, n-alkane and isoalkane concentrations are controlled by the relative rates of two divergent pathways. If the various transition metals that may catalyze these reactions differ in activity, then a unique distribution of metals created by a chlorophyll deficiency could explain the Ordovician anomaly.

Mango, F.D. (Rice Univ., Houston, TX (United States))



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

SciTech Connect

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

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



Reverse shape selectivity in the liquid-phase adsorption of xylene isomers in zirconium terephthalate MOF UiO-66.  


Powder, agglomerates, and tablets of the microporous zirconium(IV) terephthalate metal-organic framework UiO-66 were evaluated for the selective adsorption and separation of xylene isomers in the liquid phase using n-heptane as the eluent. Pulse experiments, performed at 313 K in the presence of n-heptane, revealed the o-xylene preference of this material, which was further confirmed by binary and multicomponent breakthrough experiments in the presence of m- and p-xylene, resulting in selectivities at 313 K of 1.8 and 2.4 with regards to m-xylene and p-xylene, respectively. Additionally, because p-xylene is the less retained isomer, UiO-66 presents a selectivity pattern that is reverse of that of the xylenes' molecular dimension with respect to shape selectivity. The shaping of the material as tablets did not significantly change its selectivity toward the o-xylene isomer or toward p-xylene, which was the less retained isomer, despite a loss in capacity. Finally, the selectivity behavior of UiO-66 in the liquid n-heptane phase makes it a suitable material for o-xylene separation in the extract (heavy product) or p-xylene separation in the raffinate (light product) by simulated moving bed technology. PMID:22404208

Moreira, Mariana A; Santos, João C; Ferreira, Alexandre F P; Loureiro, José M; Ragon, Florence; Horcajada, Patricia; Shim, Kyu-E; Hwang, Young-K; Lee, U-Hwang; Chang, Jong-S; Serre, Christian; Rodrigues, Alírio E



Charge-transfer photodissociation of adsorbed molecules via electron image states  

SciTech Connect

The 248 and 193 nm photodissociations of submonolayer quantities of CH{sub 3}Br and CH{sub 3}I adsorbed on thin layers of n-hexane indicate that the dissociation is caused by dissociative electron attachment from subvacuum level photoelectrons created in the copper substrate. The characteristics of this photodissociation-translation energy distributions and coverage dependences show that the dissociation is mediated by an image potential state which temporarily traps the photoelectrons near the n-hexane-vacuum interface, and then the charge transfers from this image state to the affinity level of a coadsorbed halomethane which then dissociates.

Jensen, E. T. [Physics Department, University of Northern British Columbia, 3333 University Way, Prince George, British Columbia V2N 4Z9 (Canada)



High-efficiency cis-trans isomerization of phenylnaphthylethylene, photosensitized by iodine  

SciTech Connect

Measurements were made of the quantum yields in the iodine-sensitized cis-trans isomerization of 1-phenyl-2-(1-naphthyl)-ethylene (PNE) and stilbene (STB) in n-hexane at room temperature over a wide range of variation of the exposure time, the concentrations of arylethylene and iodine, and the light intensity. The quantum yield in the iodine-photosensitized isomerization in a PNE melt was measured at 40/degree/C in a layer 15 /mu/m thick, and the analysis of the isomer composition was performed by subsequently dissolving the samples in n-hexane and measuring the absorption spectra of the respective solutions.

Lednev, I.K.; Khenkina, T.V.; Razumov, V.F.; Alfimov, M.V.



Isolation and identification of fatty acid amides from Shengli coal  

SciTech Connect

Shengli coal, a Chinese brown coal, was extracted with carbon disulfide and the extract was gradiently eluted with n-hexane and ethyl acetate (EA)/n-hexane mixed solvents with different concentrations of EA in a silica gel-filled column. A series of fatty acid amides, including fourteen alkanamides (C{sub 15}-C{sub 28}) and three alkenamides (C{sub 18} and C{sub 22}), were isolated from the coal by this method and analyzed with a gas chromatography/mass spectrometry. 26 refs., 2 figs., 2 tabs.

Ming-Jie Ding; Zhi-Min Zong; Ying Zong; Xiao-Dong Ou-Yang; Yao-Guo Huang; Lei Zhou; Feng Wang; Jiang-Pei Cao; Xian-Yong Wei [China University of Mining and Technology, Xuzhou (China). School of Chemical Engineering



Chemical changes in terpenes of sugi ( Cryptomeria japonica ) wood during steam drying in kiln at high temperature  

Microsoft Academic Search

Sawdusts of sugi (Cryptomeria japonica) wood prepared before and after steam drying at 120°C in a kiln were extracted with n-hexane and ethyl acetate to give n-hexane extracts and ethyl acetate extracts. From gas chromatography-mass spectrometry analysis of the ethyl acetate extracts\\u000a from woods before and after steam drying, the components of 4-epi-cubebol, cubebol, and 2,7(14),10-bis-abolatrien-1-ol-4-one, which existed in the

Yoh-ichi Matsushita; Kazuhiro Sugamoto; Kenji Miyakubo; Chiaki Kurogi; Takanao Matsui; Hisato Oda; Hideto Fujimoto



Influence of solvent and storage conditions on the stability of acaricide standard stock solutions  

Microsoft Academic Search

The stability of bromopropylate, coumaphos, amitraz and chlordimeform stock solutions in methanol and in n-hexane and the incidence of storage conditions have been studied using GC-MS. It has been found that the initial concentrations have a progressive depletion from the starting time, this fact is more important when methanolic solutions are stored at room temperature. Several degradation products have been

J. L. Bernal; M. del Nozal; J. J. Jiménez



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.



Water activity dependence of performance of surface-displayed lipase in yeast cells: A unique water requirement for enzymatic synthetic reaction in organic media  

Microsoft Academic Search

Water activity (aw) is a crucial parameter affecting enzymatic synthetic reactions in organic media. In this paper, we report on the aw dependence of surface-displayed lipases, genetically immobilized on yeast cells via fusion with cell wall proteins. When Saccharomyces cerevisiae displaying Rhizopus oryzae lipase was used for esterification in n-hexane, equilibrating the dried cells with water prior to the reaction

Ayumi Yoshida; Shinji Hama; Kazunori Nakashima; Akihiko Kondo



Adsorption and microcalorimetric measurements on activated carbons prepared from polyethylene terephtalate  

Microsoft Academic Search

This paper deals with the characterization of activated carbons obtained from Polyethylene Terphtalate (PET). This has been carried out by using several techniques. Among them immersion calorimetry of several organic vapours (n-hexane, benzene, cyclohexane and 2,2-DMB) and adsorption of the same vapours. Nice agreement is found between the textural characteristics determined by both techniques.

M. C. Almazán-Almazán; M. Domingo-Carcía; I. Fernández-Morales; F. J. López-Garzon; I. Rodríguez-Ramos; A. Guerrero-Ruiz; A. Martínez-Alonso



Pressure Dependence of the Ultrasonic Absorption in Toluene and Hexane.  

National Technical Information Service (NTIS)

Ultrasonic absorption and sound speed have been measured in toluene and n-hexane in the pressure range 1-10,000 kg/sq cm at 30C. In these Kneser-type liquids, for which the absorption may be attributed to thermal relaxational processes as well as to the d...

J. Allegra S. Hawley G. Holton



Bioactivity-directed isolation, identification of diuretic compounds from Polyporus umbellatus  

Microsoft Academic Search

Aim of the studyPolyporus umbellatus is a fungus used as a diuretic medicine. The objective of this study was to isolate and elucidate the diuretic constituents of n-hexane, ethyl acetate, n-butanol and water extracts of Polyporus umbellatus and to evaluate their diuretic activity.

Ying-yong Zhao; Ren-ming Xie; Xu Chao; Yongmin Zhang; Rui-chao Lin; Wen-ji Sun



Isothermal vapor-liquid equilibrium data for binary systems containing ethane at high pressures  

Microsoft Academic Search

Isothermal vapor-liquid equilibrium data for binary systems containing carbon dioxide at high pressure have been reported previously. In those studies, methanol, acetone, methyl acetate, ethyl ether, n-hexane, and benzene were chosen as the solvent components. In this study, the same solvent components were used and carbon dioxide was replaced with ethane having similar critical temperature to that of carbon dioxide.

F. Sano; K. Ohgaki; Takashi Katayama



Evaluation of the leachability of polychlorinated dibenzo-p-dioxins and dibenzofurans in raw and solidified air pollution control residues from municipal waste incinerators.  


Leachability of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from raw and solidified air pollution control (APC) residues with selected solvents, including acetic acid, simulated acid rain, humic acid, linear alkylbenzene sulfonate (LAS) and n-hexane was investigated. High-chlorinated PCDD/F congeners were observed in all leachates of raw APC residue samples, with the largest total leaching concentration (61.60 ngm(-3); 0.30 ngI-TEQm(-3)) from treatment with humic acid. Low-chlorinated congeners were mainly leached with LAS and n-hexane. Solidification and stabilization (S/S) processes with cement and sulfur-containing chelating agent decreased the leachability of PCDD/Fs by up to 98% with humic acid and LAS as solvents. However, S/S processes enhanced the leachability of both high- and low-chlorinated PCDD/F congeners with n-hexane as the solvent, which largely increased the toxic equivalent quantity of leachates. These results suggest that conventional S/S processes may effectively restrain the release of PCDD/Fs when APC residues are leached with rain water or natural organic compounds (e.g., humic acid), but may have a deteriorated effect when APC residues are leached with nonpolar organic solvents (e.g., n-hexane) coexisting in the landfill sites. PMID:17109922

Hsi, Hsing-Cheng; Yu, Tsung-Hsien



40 CFR 60.485 - Test methods and procedures.  

Code of Federal Regulations, 2013 CFR

...air (less than 10 ppm of hydrocarbon in air); and (ii) A mixture of methane or n-hexane and air at a concentration of about, but less...3) The maximum permitted velocity for air assisted flares shall be computed using the...



40 CFR 61.245 - Test methods and procedures.  

Code of Federal Regulations, 2013 CFR

...air (less than 10 ppm of hydrocarbon in air); and (ii) A mixture of methane or n-hexane and air at a concentration of approximately...maximum permitted velocity, Vmax , for air-assisted flares shall be determined by the...



40 CFR 60.485a - Test methods and procedures.  

Code of Federal Regulations, 2013 CFR

...air (less than 10 ppm of hydrocarbon in air); and (ii) A mixture of methane or n-hexane and air at a concentration no more than...3) The maximum permitted velocity for air assisted flares shall be computed using the...



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

Technology Transfer Automated Retrieval System (TEKTRAN)

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


Antimicrobial Screening of Medicinal Plant - Artemisia pallens  

Microsoft Academic Search

Artemisia pallens Wall, a medicinally important plant, belongs to family Asteraceae. It is This plant is used in Ayurvedic system of medicines. In order to search for antimicrobial activity of secondary metabolites, screening of aerial parts of A. pallens was carried out. Air shade dried powdered plant material was extracted using solvents of increasing polarity from non polar ( n-hexane

Anjali D. Ruikar; Gayatri S. Kamble; Vedavati G. Puranik; Nirmala R. Deshpande



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...


Antimicrobial activity of crude extracts and pure compounds of Hypericum hircinum  

Microsoft Academic Search

The antimicrobial activity of the n-hexane (H) and chloroform (C) extracts, the methanol extract (M) and its ethyl acetate (E) and n-butanol (B) fractions, and six isolated constituents of the aerial parts of Hypericum hircinum was investigated using an agar diffusion method. The maximum activity was exhibited by the methanolic extract against Staphylococcus aureus, while all pure constituents showed no

L Pistelli; A Bertoli; S Zucconelli; I Morelli; L Panizzi; F Menichini



The influence on enzyme activity of storage of tissue blocks at ?70° C  

Microsoft Academic Search

Blocks of tissue from various organs of the rat have been chilled by precipitate immersion in n-hexane cooled to -70° C, and then stored at -70° C. At various intervals (up to 14 days) after chilling, cryostat sections were prepared from these blocks and assayed for the activity of a variety of enzymes. Enzyme activity was measured by scanning and

B. Henderson; N. Loveridge; W. R. Robertson; M. T. Smith



Enzymatic glycerolysis of olive oil: A reactional system with major analytical problems  

Microsoft Academic Search

Major analytical problems were encountered while carrying out the lipase catalyzed glycerolysis of olive oil in n-hexane. Since direct quantification of monoglycerides could not be achieved, an alternative methodology is proposed: the estimation of monoglyceride production from a mass balance after having assayed for the unconverted triolein, as well as for the diolein and free fatty acids formed.

S. Ferreira-Dias; M. M. R. Fonseca



Heterogeneous Adsorption Characteristics of Volatile Organic Compounds (VOCs) on MCM?48  

Microsoft Academic Search

This work focuses on the fundamental studies of heterogeneous adsorption characteristics of mesoporous adsorbent. MCM?48 was synthesized to investigate the adsorption properties of eight different volatile organic compounds (benzene, cyclohexane, n?hexane, toluene, methanol, acetone, methyl ethyl ketone (MEK), and trichloroethylene (TCE)). The gravimetric method was used to measure the adsorption equilibrium amount. Several simple and reliable methods such as isosteric

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



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



Vapor Adsorption and Displacement on Porous Glass by Surface Conductivity  

Microsoft Academic Search

There is a marked increase in surface conductivity on adsorption of water vapor on porous glass. The relationship between the amount of adsorbed water vapor, the characteristic adsorption states of water molecules, and the surface conductivity for high surface area samples were obtained for nonmethylated and methylated conditions. Also the changes in conductivity with preadsorbed n-hexane on adsorption of water,

Koji Kawasaki; Norman Hackerman



Leishmanicidal compounds from the fruits of Piper longum.  


One new alkaloid amide, piperlongumide (1) [N-isobutyl-19-(3',4'-methylenedioxyphenyl)-2E,4E nonadecadienamide], and six known compounds with leishmanicidal activity against promastigotes and axenic amastigotes of Leishmania donovani were isolated from the n-hexane fraction of the fruits of Piper longum. The structure of 1 was elucidated by spectroscopic evidences. PMID:22576441

Ghosal, Sabari; Deb, Anindita; Mishra, Priyanka; Vishwakarma, Ram



Contribution of response surface design to the development of glycerolysis systems catalyzed by commercial immobilized lipases  

Microsoft Academic Search

Two commercial immobilized lipases (“Lipozyme® IM” and “Novozym® 435”) were tested as biocatalysts for the glycerolysis of olive residue oil in n-hexane aimed at the production of monoglycerides (MG) and diglycerides (DG). A central composite rotatable design (CCRD) was followed to model and optimize glycerolysis as a function of both the amount of biocatalyst (L) and of the molar ratio

S Ferreira-Dias; A. C Correia; F. O Baptista; M. M. R da Fonseca



Effects of Covered Solid Sorbent Tube Sample Holders on Organic Vapor Measurements  

Microsoft Academic Search

A study was conducted to examine whether there are significant differences between organic vapor concentrations measured using charcoal tubes with three different configurations: uncovered sample holder (open tube), SKC and Buck brand covered sample holders. A fractional factorial experimental design was used with the following factors and levels: vapor (n-hexane vs. m-xylene), pump type (pulsating vs. continuous), exposure profile (variable

B. S. Marpoe; W. A. Groves; E. G. Lee; J. E. Slaven; M. Harper