WorldWideScience
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Exposition by inhalation to the benzene, toluene, ethyl-benzene and xylenes (BTEX) in the air. Sources, measures and concentrations  

International Nuclear Information System (INIS)

This document presents the main techniques today available to characterize the benzene, toluene, ethyl-benzene and xylene (BTEX) concentrations in the air for different contexts: urban and rural areas or around industrial installations but also indoor and occupational area. It provides information to guide laboratories and research departments. A synthesis gives also the main emissions sources of these compounds as reference concentrations measured in different environments. (A.L.B.)

2

Biodegradation characteristics of naphthalene and benzene, toluene, ethyl benzene, and xylene (BTEX) by bacteria enriched from activated sludge.  

Science.gov (United States)

Naphthalene and BTEX (benzene, toluene, ethyl benzene, and xylene) are frequently detected toxic hydrocarbons in contaminated sites, which can easily enter the soil or groundwater system. To test the potential of treating these hydrocarbons in a conventional water resource recovery facility, municipal activated sludge was used as the seed and the bacteria successfully enriched using naphthalene or BTEX as the sole carbon source under aerobic conditions. The pseudo first order kinetic constant for naphthalene degradation by enriched bacteria was 14.053 L h(-1) g(-1). For BTEX degradation, kinetic constants of 0.234, 0.958, 1.212, and 0.455 L h(-1) g(-1)1' were obtained for benzene, toluene, ethyl benzene, and xylene, respectively, which collectively accounted for a total BTEX removal rate constant of 0.550 L h(-1) g(-1) . Through cloning and sequencing, Pseudomonas and Burkholderia were identified as the primary bacteria communities in the naphthalene degradation reactor, whereas for BTEX degradation, Pseudomonas and Acidovorax dominated in the reactor. PMID:24734475

Huang, Yuanxing; Li, Liang

2014-03-01

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Exposition by inhalation to the benzene, toluene, ethyl-benzene and xylenes (BTEX) in the air. Sources, measures and concentrations; Exposition par inhalation au benzene, toluene, ethylbenzene et xylenes (BTEX) dans l'air. Source, mesures et concentrations  

Energy Technology Data Exchange (ETDEWEB)

This document presents the main techniques today available to characterize the benzene, toluene, ethyl-benzene and xylene (BTEX) concentrations in the air for different contexts: urban and rural areas or around industrial installations but also indoor and occupational area. It provides information to guide laboratories and research departments. A synthesis gives also the main emissions sources of these compounds as reference concentrations measured in different environments. (A.L.B.)

Del Gratta, F.; Durif, M.; Fagault, Y.; Zdanevitch, I

2004-12-15

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Enthalpy of mixing and heat of vaporization of ethyl acetate with benzene and toluene at 298.15 k and 308.15 k  

Directory of Open Access Journals (Sweden)

Full Text Available The present work was carried out in two phases. First, enthalpy of mixing was measured and then the heat of vaporization for the same mixtures was obtained. The data are useful in the design of separation equipments. From the various designs available for the experimental determination of enthalpy of mixing, and heat of vaporization, the apparatus was selected, modified and constructed. The apparatus of enthalpy of mixing was tested with a known system Benzene - i-Butyl Alcohol and the data obtained was in very good agreement with literature values. Experiments were then conducted for mixtures of Ethyl Acetate with Benzene and Toluene. The experimental data was fitted to the standard correlations and the constants were evaluated. Heat of vaporization data were obtained from a static apparatus and tested for accuracy by conducting experiments with a known system Benzene - n-Hexane and the data obtained were found to be in agreement with literature values. Experiments were then conducted to measure heat of vaporization for the mixtures of Ethyl Acetate with Benzene and Toluene. Using experimental data of enthalpy of mixing from the first phase, and heat capacity data, the heat of vaporization were calculated.

K. L. Shivabasappa

2008-03-01

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Optimization of an automated FI-FT-IR procedure for the determination of o-xylene, toluene and ethyl benzene in n-hexane  

OpenAIRE

The development and optimization of an automated flow injection (FI) manifold coupled with a Fourier transform infrared (FT-IR) detector for the determination of toluene, ethyl benzene and o-xylene in an n-hexane matrix is described. FT-IR parameters optimized were resolution and number of co-added scans; FI parameters optimized were type of pump tubing, carrier flow rate and sample volume. ATR and transmission flow cells were compared for the determination of o-xylene, the ATR cell was ea...

Ian Wells; Worsfold, Paul J.

1999-01-01

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Diaquabis(L-phenylalaninato)nickel(II) encapsulated in zeolite: an efficient heterogeneous catalyst system for the oxidation of cyclohexene, toluene and ethyl benzene  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese L-Fenilalanina reage com zeólita Y submetida a uma troca iônica com níquel(II) para formar diaquabis(L-fenilalaninato)níquel(II), o qual é encapsulado nos poros da zeólita. Nesta forma encapsulada, o complexo de níquel funciona como um catalisador eficiente quando ciclo-hexeno, tolueno e etilbenzeno [...] são oxidados por peróxido de hidrogênio na presença de bicarbonato de sódio como cocatalisador. O catalisador foi facilmente recuperado da mistura de reação e foi reutilizado por três vezes sem perda observável de atividade. O catalisador heterogêneo apresentou atividade e seletividade significativamente mais altas quando comparado com o complexo diaquabis(L-fenilalaninato)níquel(II). Abstract in english L-Phenylalanine reacts with nickel-exchanged zeolite Y to form diaquabis(L-phenylalaninato)nickel(II), which is encapsulated in the pores of the zeolite. In this zeolite-encapsulated form, the nickel derivative functions as an efficient catalyst when cyclohexene, toluene and ethyl benzene are oxidiz [...] ed by hydrogen peroxide in the presence of sodium bicarbonate (as co-catalyst). The catalyst was readily recovered from the reaction mixture, and it could be re-used for other three runs without noticeable loss of activity. The heterogeneous catalyst exhibited significantly higher activity and selectivity compared with diaquabis(L-phenylalaninato)nickel(II) itself.

Massomeh, Ghorbanloo; Somayeh, Ghamari; Nahid, Shahbakhsh; Seik Weng, Ng.

2073-20-01

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Enthalpy of mixing and heat of vaporization of ethyl acetate with benzene and toluene at 298.15 k and 308.15 k  

OpenAIRE

The present work was carried out in two phases. First, enthalpy of mixing was measured and then the heat of vaporization for the same mixtures was obtained. The data are useful in the design of separation equipments. From the various designs available for the experimental determination of enthalpy of mixing, and heat of vaporization, the apparatus was selected, modified and constructed. The apparatus of enthalpy of mixing was tested with a known system Benzene - i-Butyl Alcohol and the data o...

Shivabasappa, K. L.; Nirguna Babu, P.; Jagannadha Rao, Y.

2008-01-01

8

Treatment of co-mingled benzene, toluene and TCE in groundwater.  

Science.gov (United States)

This work addressed a hypothetical but practical scenario that includes biological oxidation and reductive dechlorination in treating groundwater containing co-mingled plume of trichloroethene (TCE), benzene and toluene. Groundwater immediately downgradient from the commonly used zero-valent iron (ZVI) has shown alkaline pH (up to 10.7). The elevated pH may influence BTEX compounds (i.e., benzene, toluene, ethyl benzene, and xylenes) biodegradation, which could also be inhibited by elevated concentrations of TCE. Data from this work suggests that the inhibition coefficients (IC) value for 100 ?g/L and 500 ?g/L of TCE on benzene and toluene degradation are 2.1-2.8 at pH 7.9, and 3.5-6.1 at pH 10.5. For a co-mingled plume, it appears to be more effective to reduce TCE by ZVI before addressing benzene and toluene biodegradation. The ample buffering capacity of most groundwater and the adaptation of benzene and toluene-degrading microbes are likely able to eliminate the adverse influence of pH shifts downgradient from a ZVI-PRB. PMID:24857895

Chen, Liang; Liu, Yulong; Liu, Fei; Jin, Song

2014-06-30

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Densities and Kinematic Viscosities for the Systems Benzene + Methyl Formate, Benzene + Ethyl Formate, Benzene + Propyl Formate, and Benzene + Butyl Formate  

DEFF Research Database (Denmark)

Densities and kinematic viscosities have been measured for the system benzene + methyl formate at 20°C and for the systems benzene + ethyl formate, benzene + propyl formate, and benzene + butyl formate from 20°C to 50°C. The results for the system benzene + methyl formate have been correlated using a Redlich-Kister type of expression with temperature-independent parameters and the data for the systems benzene + ethyl formate, benzene + propyl formate, and benzene + butyl formate with temperature-dependent parameters. The viscosities have furthermore been compared to values predicted by means of the GC-UNIMOD model.

Emmerling, Uwe; Rasmussen, Peter

1998-01-01

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Metabolism of Benzene, Toluene, and Xylene Hydrocarbons in Soil†  

OpenAIRE

Enrichment cultures obtained from soil exposed to benzene, toluene, and xylene (BTX) mineralized benzene and toluene but cometabolized only xylene isomers, forming polymeric residues. This observation prompted us to investigate the metabolism of 14C-labeled BTX hydrocarbons in soil, either individually or as mixtures. BTX-supplemented soil was incubated aerobically for up to 4 weeks in a sealed system that automatically replenished any O2 consumed. The decrease in solvent vapors and the produ...

Tsao, C. -w; Song, H. -g; Bartha, R.

1998-01-01

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Subtle Difference between Benzene and Toluene Dioxygenases of Pseudomonas putida  

OpenAIRE

Benzene dioxygenase and toluene dioxygenase from Pseudomonas putida have similar catalytic properties, structures, and gene organizations, but they differ in substrate specificity, with toluene dioxygenase having higher activity toward alkylbenzenes. The catalytic iron-sulfur proteins of these enzymes consist of two dissimilar subunits, ? and ?; the ? subunit contains a [2Fe-2S] cluster involved in electron transfer, the catalytic nonheme iron center, and is also responsible for substrate ...

Bagne?ris, Claire; Cammack, Richard; Mason, Jeremy R.

2005-01-01

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Instrument for benzene and toluene emission measurements of glycol regenerators  

International Nuclear Information System (INIS)

We introduce an in-field and in-explosive atmosphere useable instrument, which can measure the benzene and toluene concentration in two gas and two glycol samples produced by natural gas dehydration units. It is a two-phase, on-line gas chromatograph with a photoacoustic spectroscopy based detector. The time resolution is 10 min per cycle and the minimum detectable concentrations are 2 mg m?3 for benzene, 3 mg m?3 for toluene in natural gas, and 5 g m?3 for benzene and 6 g m?3 for toluene in glycol. Test measurements were carried out at a dehydration plant belonging to MOL Hungarian Oil and Gas Company. Benzene and toluene emissions of gas dehydration unit are calculated from the measured values based on mass balance of a glycol regenerator. The relationship between the outdoor temperature and the measured concentration was observed which is caused by temperature-dependent operation of the whole dehydration unit. Emission decreases with increase of outdoor temperature. (paper)

13

Toluene-degrading bacteria are chemotactic towards the environmental pollutants benzene, toluene, and trichloroethylene.  

Science.gov (United States)

The bioremediation of polluted groundwater and toxic waste sites requires that bacteria come into close physical contact with pollutants. This can be accomplished by chemotaxis. Five motile strains of bacteria that use five different pathways to degrade toluene were tested for their ability to detect and swim towards this pollutant. Three of the five strains (Pseudomonas putida F1, Ralstonia pickettii PKO1, and Burkholderia cepacia G4) were attracted to toluene. In each case, the response was dependent on induction by growth with toluene. Pseudomonas mendocina KR1 and P. putida PaW15 did not show a convincing response. The chemotactic responses of P. putida F1 to a variety of toxic aromatic hydrocarbons and chlorinated aliphatic compounds were examined. Compounds that are growth substrates for P. putida F1, including benzene and ethylbenzene, were chemoattractants. P. putida F1 was also attracted to trichloroethylene (TCE), which is not a growth substrate but is dechlorinated and detoxified by P. putida F1. Mutant strains of P. putida F1 that do not oxidize toluene were attracted to toluene, indicating that toluene itself and not a metabolite was the compound detected. The two-component response regulator pair TodS and TodT, which control expression of the toluene degradation genes in P. putida F1, were required for the response. This demonstration that soil bacteria can sense and swim towards the toxic compounds toluene, benzene, TCE, and related chemicals suggests that the introduction of chemotactic bacteria into selected polluted sites may accelerate bioremediation processes. PMID:10966434

Parales, R E; Ditty, J L; Harwood, C S

2000-09-01

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Comparison of measurement methods for benzene and toluene  

Science.gov (United States)

Diffusive sampling and active (pumped) sampling (tubes filled with Tenax TA or Carbopack B) were compared with an automatic BTX instrument (Chrompack, GC/FID) for measurements of benzene and toluene. The measurements were made during differing pollution levels and different weather conditions at a roof-top site and in a densely trafficked street canyon in Stockholm, Sweden. The BTX instrument was used as the reference method for comparison with the other methods. Considering all data the Perkin-Elmer diffusive samplers, containing Tenax TA and assuming a constant uptake rate of 0.406 cm3 min-1, showed about 30% higher benzene values compared to the BTX instrument. This discrepancy may be explained by a dose-dependent uptake rate with higher uptake rates at lower dose as suggested by laboratory experiments presented in the literature. After correction by applying the relationship between uptake rate and dose as suggested by Roche et al. (Atmos. Environ. 33 (1999) 1905), the two methods agreed almost perfectly. For toluene there was much better agreement between the two methods. No sign of a dose-dependent uptake could be seen. The mean concentrations and 95% confidence intervals of all toluene measurements (67 values) were (10.80±1.6) ?g m -3 for diffusive sampling and (11.3±1.6) ?g m -3 for the BTX instrument, respectively. The overall ratio between the concentrations obtained using diffusive sampling and the BTX instrument was 0.91±0.07 (95% confidence interval). Tenax TA was found to be equal to Carbopack B for measuring benzene and toluene in this concentration range, although it has been proposed not to be optimal for benzene. There was also good agreement between the active samplers and the BTX instrument.

Wideqvist, U.; Vesely, V.; Johansson, C.; Potter, A.; Brorström-Lundén, E.; Sjöberg, K.; Jonsson, T.

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Enhanced Anaerobic Biodegradation of Benzene-Toluene-Ethylbenzene-Xylene-Ethanol Mixtures in Bioaugmented Aquifer Columns  

OpenAIRE

Methanogenic flowthrough aquifer columns were used to investigate the potential of bioaugmentation to enhance anaerobic benzene-toluene-ethylbenzene-xylene (BTEX) degradation in groundwater contaminated with ethanol-blended gasoline. Two different methanogenic consortia (enriched with benzene or toluene and o-xylene) were used as inocula. Toluene was the only hydrocarbon degraded within 3 years in columns that were not bioaugmented, although anaerobic toluene degradation was observed after on...

Da Silva, Marcio L. B.; Alvarez, Pedro J. J.

2004-01-01

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A comparison of benzene, toluene and C 2-benzenes mixing ratios in automotive exhaust and in the suburban atmosphere during the introduction of catalytic converter technology to the Swiss Car Fleet  

Science.gov (United States)

Time-resolved chemical ionization mass spectrometry (CIMS) has been used to investigate the variations of the mixing ratios of benzene, toluene and the C 2-benzenes (xylenes and ethyl benzene) in automotive exhaust during transient engine operation. A significant increase of the benzene/toluene ratios from 0.35 to 1.31 (median) was found upon introduction of a catalytic converter system. A preliminary emission model was developed from these test stand measurements to simulate benzene/toluene ratios of passenger car fleets with variable proportions of three-way catalyst vehicles. Although only the emissions of gasoline-driven passenger cars have been considered so far, the predicted increase of the benzene/toluene ratios during the introduction period of the three-way catalyst from 1980 to 2000 is in good agreement with the observed increase of the atmospheric benzene/toluene ratio measured at a suburban monitoring site (Dübendorf, Switzerland) which is strongly influenced by road traffic emissions. At this site, the atmospheric concentrations of benzene and alkyl benzenes have been detected at hourly intervals since 1993. A steady decrease of the yearly mean from 3.54 to 2.00 ppb for toluene and from 2.87 to 1.33 ppb for the sum of C 2-benzenes was found from 1994 to 1998, respectively, when the proportion of three-way catalyst passenger cars increased from 60 to 82%. Nevertheless, the mean benzene concentration was only affected to a small degree (from 1.10 to 0.97 ppb) within the same period of time. Thus, the observed increase of the atmospheric benzene/toluene-mixing ratios from 0.32 to 0.58 (mean) is in good agreement with the predicted values from the presented emission model. Reduced catalyst conversion efficiency for benzene with respect to alkylated benzenes can explain most of the observed increase of the benzene/toluene and benzene/C 2-benzenes mixing rations. In addition, benzene emissions e.g. from the class of light duty vehicles, which are operated more frequently at sub-optimal combustion conditions, may also contribute to the unexpectedly stable atmospheric benzene concentration at the investigated suburban monitoring site.

Heeb, Norbert V.; Forss, Anna-Maria; Bach, Christian; Reimann, Stefan; Herzog, Alex; Jäckle, Hans W.

17

Gas yields in the radiolysis of benzene, toluene styrene and their mixtures  

International Nuclear Information System (INIS)

The G-values of H2, CH4 and C2H2 are determined in toluene-benzene and toluene-styrene mixtures. From the results it is concluded that CH3 radicals generated from toluene are captured both by benzene and styrene but, as expected, the reaction is much more efficient with styrene. A radical precursor of C2H2 which could be hexatrienyl is efficiently scavenged by toluene, presumably by H atom transfer. This reaction also accounts for the very low yield of C2H2 in pure toluene. (author)

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Competitive Nitration of Benzene-Fluorobenzene and Benzene-Toluene Mixtures: Orientation and Reactivity Studies Using HPLC  

Science.gov (United States)

The reactivity and orientation effects of a substituent are analyzed by using HPLC to determine the competitive nitration of the benzene-toluene and benzene-fluorobenzene mixtures. The results have shown that HPLC is an excellent instrumental method to use in analyzing these mixtures.

Blankespoor, Ronald L.; Hogendoorn, Stephanie; Pearson, Andrea

2007-01-01

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Study of thermodesorption of ethyl benzene from zeolite catalysts  

International Nuclear Information System (INIS)

Thermodesorption of ethyl benzene from different cation and decationized zeolite forms of NaX and NaY types including BeY, NdY, CeY has been investigated by the chromatography method. The thermodesorption spectrum of all the specimens investigated consists of a single peak. Na cation exchange for polyvalent cations results in shifting temperature of thermodesorption type maximum to the low-temperature region. Calculated are diffusion activation energy, pre-exponential factors, effective diffusion coefficients. Dependences of the reaction rate of oxidizing dehydrogenation of ethyl benzene, effective diffusion coefficient on the value of electrostatic cation potential in the Y zeolite go through the NdY maximum

20

In vitro metabolism of benzene, toluene, and xylene in rat liver  

International Nuclear Information System (INIS)

A headspace gas chromatographic method was used to study the metabolism of benzene, toluene, and m-xylene in rat liver. Metabolism of benzene was lower than that of toluene, or m-xylene. Investigating metabolic rates of subcellular fractions, it was found that glutathione and glutathione S-transferase in the cytosol are involved in metabolism of benzene and toluene by microsomes. When both benzene and toluene are present in the incubation medium, they act as inhibitors of each others metabolism. Toluene and m-xylene metabolism were induced by the pretreatment of rats with phenobarbital (75 mg/kg), or 3-methylcholanthrene (25 mg/kg), or Aroclor 1254 (75 mg/kg) for 3 days, whereas benzene metabolism was not induced by all pretreatments. Another series of experiments was conducted to compare the effects of benzene, toluene, and xylene pretreatment on liver metabolism. In vivo metabolism of 14C-toluene and possible covalent binding of 14C-toluene to microsomes were also investigated. 14C-toluene when incubated with liver microsomes in the presence of a NADPH generating system formed benzylalcohol and cresols. Some of the radioactivity was covalently bound preferentially to microsomal proteins. The binding process required cytochrome P-450 dependent mixed function oxidases. This study suggests that toluene is metabolized to several reactive intermediates by liver microsomal enzymes and these metabolites are responsible for the covalent bindites are responsible for the covalent binding to macromolecules which represents a subcellular mechanism by which toluene may express its own in vivo toxicity

21

Ignition delay times of benzene and toluene with oxygen in argon mixtures  

Science.gov (United States)

The ignition delay times of benzene and toluene with oxygen diluted in argon were investigated over a wide range of conditions. For benzene the concentration ranges were 0.42 to 1.69 percent fuel and 3.78 to 20.3 percent oxygen. The temperature range was 1212 to 1748 K and the reflected shock pressures were 1.7 to 7.89 atm. Statistical evaluation of the benzene experiments provided an overall equation which is given. For toluene the concentration ranges were 0.5 to 1.5 percent fuel and 4.48 to 13.45 percent oxygen. The temperature range was 1339 to 1797 K and the reflected shock pressures were 1.95 to 8.85 atm. The overall ignition delay equation for toluene after a statistical evaluation is also given. Detailed experimental information is provided.

Burcat, A.; Snyder, C.; Brabbs, T.

1985-01-01

22

Dynamics of Ethyl Benzene Synthesis Using Aspen Dynamics  

Directory of Open Access Journals (Sweden)

Full Text Available The objective of the study is to generate a plant wide control strategy using Aspen Dynamics for synthesis of Ethyl Benzene process which consists of two CSTRs in series followed by two distillation columns. Steady state simulation has been carried out prior to dynamic simulation using Aspen Plus and exported to Aspen dynamics after providing the required sizing details under flow driven mode. In addition to default controllers, five more controllers are added and the necessary specifications regarding process variable, output variable and set point are specified for each controller. One cascade controller, two ratio controllers, two pressure controllers, four temperature controllers and six level controllers are used in the present study. Controllers are tuned by using Tyreus-Luyben and Ziegler-Nichols controller settings. The response of the whole process is studied for various step disturbances to find the optimal controller parameters and control structure.

A. Sarath Babu, Babasheb Londhe

2014-07-01

23

Kinetics of the reactions of hydroxyl radical with benzene and toluene  

International Nuclear Information System (INIS)

Absolute rate constants for the reactions of the hydroxyl radical with benzene and toluene were measured within the temperature and pressure ranges 213 less than or equal to T less than or equal to 1150 K and 20 less than or equal to P less than or equal to 200 torr by using He, Ar, and SF6 as diluent gases. To help elucidate the variations in reaction mechanism with temperature, we also studied OH reactions with deuterated benzene (C6D6) and with selectively deuterated toluenes (C6H5CD3, C6D5CD3, and C6D5CH3). Three major reaction channels were characterized kinetically. At T less than or equal to 298 K, electrophilic addition of the OH radical to the aromatic ring is the dominant reactive pathway in all systems studied. At temperatures above 500 K, rapid decomposition of the thermalized adduct back to reactants diminishes the importance of the addition channel and leads to bimolecular reaction rate-constant values significantly lower than those measured near room temperature. At elevated temperatures, the ring hydrogen abstraction (for benzene) and side-chain hydrogen abstraction (for toluene) pathways are shown to be predominant. The measured bimolecular rate constants increase monotonically with increases in temperature above 500 K, and kinetic separation of the two hydrogen abstraction modes for toluene is achievedfor toluene is achieved

24

Photoacoustic spectroscopy-based detector for measuring benzene and toluene concentration in gas and liquid samples  

International Nuclear Information System (INIS)

Here we present a novel instrument for on-line, automatic measurement of benzene and toluene concentration in gas and liquid samples produced in the natural gas industry. Operation of the instrument is based on the collection of analytes on an adsorbent, separation using a chromatographic column and detection by near-infrared diode laser-based photoacoustic spectroscopy. Sample handling, measurement and data evaluation are carried out fully automatically, using an integrated, programmable electronic unit. The instrument was calibrated in the laboratory for natural gas, nitrogen and liquid glycol samples, and tested under field conditions at a natural gas dehydration unit of the MOL Hungarian Oil and Gas Company. Minimum detectable concentrations (3?m?1) were found to be 2.5 µg l?1 for benzene and 4 µg l?1 for toluene in gas samples, while 1.5 mg l?1 for benzene and 3 mg l?1 for toluene in liquid samples, which is suitable for measuring benzene and toluene concentration in natural gas and glycol samples occurring at natural gas dehydration plants

25

Low temperature oxidation of benzene and toluene in mixture with n-decane.  

Science.gov (United States)

The oxidation of two blends, benzene/n-decane and toluene/n-decane, was studied in a jet-stirred reactor with gas chromatography analysis (temperatures from 500 to 1100 K, atmospheric pressure, stoichiometric mixtures). The studied hydrocarbon mixtures contained 75% of aromatics in order to highlight the chemistry of the low-temperature oxidation of these two aromatic compounds which have a very low reactivity compared to large alkanes. The difference of behavior between the two aromatic reactants is highly pronounced concerning the formation of derived aromatic products below 800 K. In the case of benzene, only phenol could be quantified. In the case of toluene, significant amounts of benzaldehyde, benzene, and cresols were also formed, as well as several heavy aromatic products such as bibenzyl, phenylbenzylether, methylphenylbenzylether, and ethylphenylphenol. A comparison with results obtained with neat n-decane showed that the reactivity of the alkane is inhibited by the presence of benzene and, to a larger extent, toluene. An improved model for the oxidation of toluene was developed based on recent theoretical studies of the elementary steps involved in the low-temperature chemistry of this molecule. Simulations using this model were successfully compared with the obtained experimental results. PMID:23762017

Herbinet, Olivier; Husson, Benoit; Ferrari, Maude; Glaude, Pierre-Alexandre; Battin-Leclerc, Frédérique

2013-01-01

26

Monitoring in situ biodegradation of benzene and toluene by stable carbon isotope fractionation.  

Science.gov (United States)

Intrinsic biodegradation of benzene and toluene in a heavily contaminated aquifer at the site of a former hydrogenation plant was investigated by means of isotope fractionation processes. The carbon isotope compositions of benzene and toluene were monitored in two campaigns within a time period of 12 months to assess the extent of the in situ biodegradation and the stability of the plume over time. The Rayleigh model, applied to calculate the extent of biodegradation and residual theoretical concentrations of toluene, showed that in situ biodegradation was a relevant attenuation process. The biodegradation rate constant for toluene was estimated to be k = 5.7+/-0.5 microM/d in the groundwater flow path downstream of the source area. The spatial distribution of the carbon isotope composition of benzene indicated that in situ biodegradation occurred at marginal zones of the plume where concentrations were lower than 30 mg/L. The vertical structure of the benzene plume provided evidence for in situ degradation processes at the upper and lower fringes of the plume. The results show that isotope fractionation can be used to quantify the extent of microbial in situ degradation in contaminated aquifers and to develop conceptual models for natural attenuation approaches. PMID:15683167

Vieth, Andrea; Kästner, Matthias; Schirmer, Mario; Weiss, Holger; Gödeke, Stefan; Meckenstock, Rainer U; Richnow, Hans H

2005-01-01

27

Toluene-Degrading Bacteria Are Chemotactic towards the Environmental Pollutants Benzene, Toluene, and Trichloroethylene  

OpenAIRE

The bioremediation of polluted groundwater and toxic waste sites requires that bacteria come into close physical contact with pollutants. This can be accomplished by chemotaxis. Five motile strains of bacteria that use five different pathways to degrade toluene were tested for their ability to detect and swim towards this pollutant. Three of the five strains (Pseudomonas putida F1, Ralstonia pickettii PKO1, and Burkholderia cepacia G4) were attracted to toluene. In each case, the response was...

Parales, Rebecca E.; Ditty, Jayna L.; Harwood, Caroline S.

2000-01-01

28

Nucleotide sequence analysis of genes encoding a toluene/benzene-2-monooxygenase from Pseudomonas sp. strain JS150.  

OpenAIRE

It was previously shown by others that Pseudomonas sp. strain JS150 metabolizes benzene and alkyl- and chloro-substituted benzenes by using dioxygenase-initiated pathways coupled with multiple downstream metabolic pathways to accommodate catechol metabolism. By cloning genes encoding benzene-degradative enzymes, we found that strain JS150 also carries genes for a toluene/benzene-2-monooxygenase. The gene cluster encoding a 2-monooxygenase and its cognate regulator was cloned from a plasmid ca...

Johnson, G. R.; Olsen, R. H.

1995-01-01

29

Removal of benzene and toluene by carbonized bamboo materials modified with TiO2.  

Science.gov (United States)

Carbonized moso bamboo (Phyllostachys pubescens) was coated with TiO(2) nanoparticles to enhance its removal efficiency of harmful gases. Carbonized bamboo-TiO(2) composite (CBC) was prepared by heating mixtures of carbonized bamboo powder (CB) and TiO(2) nanoparticles, denoted as CBM, under nitrogen condition. TiO(2) nanoparticle and carbonized bamboo powder were mixed with the mass ratios of 1/1 and 2/1, respectively. At the same mass ratio of TiO(2) to CB, the benzene and toluene removal efficiencies follow the trend: CBC>CBM>CB, which is consistent with the amount of TiO(2) validated by elemental analysis. Sorption mechanism of benzene and toluene by CB, CBM and CBC might belong to hydrophobic-hydrophobic interaction, observed by depletion of untreated bamboo (UB) carbohydrates during carbonization. Sorption kinetics was further analyzed, and optimal correlation was found by fitting with the Elovich kinetic equation. PMID:17459699

Chuang, Chih Shen; Wang, Ming-Kuang; Ko, Chun-Han; Ou, Chia-Chih; Wu, Chien-Hou

2008-03-01

30

Irradiation with benzene, toluene and phenol electron beams in aqueous solution  

International Nuclear Information System (INIS)

It is described a methodology for waste water treatment which is simulated doing a benzene-toluene-phenol mixture in aqueous solution. Three different concentrations of them ones were used which were irradiated with electron beams coming from a Pelletron Accelerator carrying out the degradation effect of these compounds in CO2 and H2O. By mean of gas chromatography the analytical determinations were realized finding that in lower concentration of benzene and toluene performances of degradation higher than 95 % were obtained, but higher concentrations (100 ppm) the performance diminishes at 89 %, while for phenol in higher concentrations its degradation is over 60 % and in lower concentrations the degradation is under 80 %. The results are obtained with a constant irradiation time of 12 seconds and neutral pH. (Author

31

Radiolysis ob benzene, toluene and phenol aqueous solutions utilizing high energy electron beam  

International Nuclear Information System (INIS)

In a search for solutions to environmental pollution problems, radiolysis has proved to be an innovative technique for the removal of organic chemical pollutants in aqueous solution. Radiolysis has shown many advantages over many other techniques, as highly reactive species formed in water by ionizing radiation oxidize organic pollutants breaking down organic molecules to final simple products by oxidation to carbon dioxide and water in a complete oxidation. Our work consisted in doing some experiments in radiolysis with simulated polluted water to help us understand this technique and also develop, in a near future, a project for large scale water treatment. Our project includes the application of a Pelletron type Mexican made Electron Accelerator, which will affirm its capability and usefulness in performing investigation in this field of study. Experiments consisted in treating benzene, toluene and phenol aqueous solutions with an Electron Beam (0.48-0.55 MeV; 24 ?A). Two concentrations were used for each compound: 5 and 20 ppm (mg/l) for benzene and toluene; 10 and 50 ppm for phenol. Solutions were prepared with pure, mineral free water and two different p H (5.9), in order to study the effect of concentration and p H on removal efficiency, but avoiding the interference of radical scavengers. Results obtained coincide with the ones reported by Cooper, Nickelsen and Kurucz; highly efficient removal was achieved for benzene (>99.8%), toluene (>98.0%) and phenol (>88%). There was no visible important effect of p H on radiolysis efficiency for benzene nor toluene, phenol however, showed lower removal efficiency in acidic conditions. Concentration of aqueous solutions, nevertheless, did show an important effect at low doses for phenol. Results obtained reveal the importance of this technique in water pollution control and water remedial as expressed by Cooper, Nickelsen and Kurucz, who have studied radiolysis of organic compounds and apply this technique in water site remedial with a mobile Electron Beam facility. (Author)

32

Hydrogen isotope analysis of benzene and toluene emitted from vehicles  

Science.gov (United States)

The isotopic analysis of atmospheric volatile organic compounds (VOCs), and in particular their hydrogen isotope ratio (?2H), has the potential to be an effective tool for clearly identifying sources of VOCs. However, to date there have been very few such analyzes. Here, we have analyzed the ?2H values of VOCs using thermal desorption and chromatography, thermal conversion, and isotope ratio mass spectrometry (TD-GC/TC/IRMS). After determining the analytical conditions needed for high precision and accurate analysis, we adopted minimum peak area thresholds of 10 Vs for the low concentration samples and 15 Vs for other samples. We also confirmed that breakthrough during adsorption of samples would have only minimal effect. We found that the collected samples could be stored for at least 7 days. Precisions of 1.1‰-5.3‰ (n = 7) were obtained for 28 standard compounds in a standard gas containing 58 VOCs (C6-C11). Next, we collected the exhaust gas produced in cold mode and hot mode from five vehicles, and measured the ?2H values. For benzene, we found that the ?2H value for the hot mode vehicle emissions was 19.3-104.7‰ lighter than that for the cold mode, while the ?2H value of the vaporized gasoline was 0.7-25.2‰ close to that in the cold mode. It should, therefore, be possible to distinguish cold mode vehicle emissions from those of the hot mode by analyzing the hydrogen isotope ratio. For benzene, particularly, the difference in ?2H values between 2 modes is important since emitted in large quantity from vehicles generally. Additionally, we measured VOCs in vaporized gasoline and roadside air, and compared the results with those for vehicle emissions. The roadside samples were characterized mainly by the hot mode. It has been shown that the hot mode has a significant impact on roadside VOCs, if no isotopic fractionation in the atmosphere is assumed. The results suggest that our approach could improve our understanding of the origin and fate of atmospheric VOCs, by allowing measurement of the ?2H values of further target compounds and sources.

Kikuchi, Nami; Kawashima, Hiroto

2013-06-01

33

Carcinogenic potential of benzene and toluene when evaluated using cyclin-dependent kinase activation and p53-DNA binding  

Energy Technology Data Exchange (ETDEWEB)

Benzene is carcinogenic, whereas toluene is thought to have little carcinogenic potential. Benzene and toluene were found to activate cyclin-dependent kinase 2 in rat liver epithelial (RLE) and HL60 cells. pRb105 was hyperphosphorylated in RLE cells treated with either solvent. Kinase activation and subsequent hyperphosphorylation of pRb105 and p53 by benzene or toluene may be responsible for their growth promotional effects, but it does not account for increased potential of benzene to induce cancer. Therefore, we examined the ability of these solvents to increase p53-DNA site-specific binding in RLE cells. Benzene increased p53-DNA site-specific DNA binding in RLE cells compared to control levels or the effects of toluene. Increased p53-DNA site-specific binding by benzene may be caused by damage to cellular DNA. If so, although both solvents appear to have promotional activity, the increased potential of benzene to damage DNA may be responsible to the difference in the ability of benzene to cause cancer. 14 refs., 4 figs.

Dees, C. [Oak Ridge National Lab., TN (United States); Askari, M.; Henley, D. [Univ. of Tennessee, TN (United States)

1996-12-01

34

Coordination chemistry of metal surfaces. 3. Benzene and toluene interactions with nickel surfaces  

International Nuclear Information System (INIS)

Ni surfaces were the low Miller index planes (111), (110), and (100) and the stepped and stepped-kinked surfaces 9(111) x (111) and 7(111) x (310). Effects of surface C and O were established for low surface coverages. Benzene chemisorption was fully associative (molecular) on Ni(111) up to 1000C; no H-D exchange occurred between C6H6 and C6D6 up to 1000C. Up to 1000C, benzene was displaced as C6H6(g) by P(CH3)3. Benzene reversible thermal desorption occurred at 115 to 1250C, accompanied by extensive irreversible decomposition to H2(g) + Ni(111)-C. Analogous behavior was observed for benzene chemisorbed on the stepped and stepped-kinked surface. On the (110) surface, the benzene thermal desorption and benzene chemical displacement by P(CH3)3 was comparable to the stepped-kinked surface. Chemisorption of benzene on Ni(100) was differentiated from the other surfaces: the degree of thermal reversibility was higher than and the temperature for the thermal desorption maximum was 1000C higher than that for Ni(111). H-D exchange did not occur with D2 + C6H6 and with C6H6 + C6D6 on Ni(100). Toluene chemisorption on all the nickel surfaces was thermally irreversible and toluene was not displaced from these surfaces by strong fieisplaced from these surfaces by strong field ligands like P(CH3)3 and CH3NC. Heating the Ni-toluene surfaces led to hydrogen evolution. For the decomposition of C6D5CD3 on Ni(111) there were two D2 thermal desorption maxima, 130 and 1900C. For the analogous decomposition of C6H5CD3 and C6D5CH3 respectively, there were single D2 desorption curves with maxima at 130 and 1850C, respectively. Thus, aliphatic C-H bonds are broken first and no aromatic C-H bond is broken until near 1600C. Identical behavior was observed for the stepped and stepped-kinked surfaces, and an analogous behavior was observed for the (100) surface

35

UV Fourier transform measurements of tropospheric O3, NO2, SO2, benzene, and toluene  

International Nuclear Information System (INIS)

Using the differential optical absorption spectroscopy (DOAS) technique and a Fourier transform spectrometer, NO2, SO2, O3, benzene, and toluene were measured during three measurement campaigns held in Brussels in 1995, 1996, and 1997. The O3 concentrations could be explained as the results of the local photochemistry and the dynamical properties of the mixing layer. NO2 concentrations were anti-correlated to the O3 concentrations, is expected. SO2 also showed a pronounced dependence on car traffic. Average benzene and toluene concentrations were, respectively 1.7 ppb and between 4.4 and 6.6 pbb, but high values of toluene up to 98.8 ppb were observed. SO2 concentrations and to a lesser extent, those of NO2 and O3, were dependent on the wind direction. Ozone in Brussels has been found to be influenced by the meteorological conditions prevailing in central Europe. Comparisons with other measurements have shown that O3 and SO2 data are in general in good agreement, but our NO2 concentrations seem to be generally higher. (author)

36

Carbon and hydrogen isotope fractionation of benzene and toluene during hydrophobic sorption in multistep batch experiments.  

Science.gov (United States)

The application of compound-specific stable isotope analysis (CSIA) for evaluating degradation of organic pollutants in the field implies that other processes affecting pollutant concentration are minor with respect to isotope fractionation. Sorption is associated with minor isotope fractionation and pollutants may undergo successive sorption-desorption steps during their migration in aquifers. However, little is known about isotope fractionation of BTEX compounds after consecutive sorption steps. Here, we show that partitioning of benzene and toluene between water and organic sorbents (i.e. 1-octanol, dichloromethane, cyclohexane, hexanoic acid and Amberlite XAD-2) generally exhibits very small carbon and hydrogen isotope effects in multistep batch experiments. However, carbon and hydrogen isotope fractionation was observed for the benzene-octanol pair after several sorption steps (??(13)C=1.6 ± 0.3‰ and ??(2)H=88 ± 3‰), yielding isotope fractionation factors of ?C=1.0030 ± 0.0005 and ?H=1.195 ± 0.026. Our results indicate that the cumulative effect of successive hydrophobic partitioning steps in an aquifer generally results in insignificant isotope fractionation for benzene and toluene. However, significant carbon and hydrogen isotope fractionation cannot be excluded for specific sorbate-sorbent pairs, such as sorbates with ?-electrons and sorbents with OH-groups. Consequently, functional groups of sedimentary organic matter (SOM) may specifically interact with BTEX compounds migrating in an aquifer, thereby resulting in potentially relevant isotope fractionation. PMID:24726480

Imfeld, G; Kopinke, F-D; Fischer, A; Richnow, H-H

2014-07-01

37

H atom formation from benzene and toluene photoexcitation at 248 nm  

Science.gov (United States)

The technique of excimer laser excitation/Lyman alpha H atom laser induced fluorescence was used to investigate the formation of H atoms from the 248 nm photoexcitation of benzene and toluene. The H atom signal dependence on laser excitation energy demonstrated that it is produced from two photon photolysis of the aromatics; absorption of the first photon populates the bound B12u level followed by absorption from this level to a dissociative level, which produces H atoms, among other potential channels. Analysis of the data yields the second photon absorption cross section to produce H and is equal to 1.0 and 5.2×10-19 cm2 for benzene and toluene, respectively. In addition, the yield of H atoms was observed to be pressure dependent. This is because at sufficiently high pressures the nanosecond lifetime of the B12u state can be pressure quenched and hence may compete with the absorption of the second photon. The yields of H atoms were determined as a function of pressure for a range of the laser energies and with various collider gases. The analysis of these data allowed the total absorption cross section for the second photon to be determined and is equal to 2.8 and 1.7×10-17 cm2 for benzene and toluene, respectively. In addition, the rate constants for quenching B12u with various gases (He, Ar, N2, and O2) were determined. This large absorption coefficient for the second photon implies that with a pulsed laser source of 248 nm it is difficult to avoid aromatic photodissociation. We highlight a few previous studies that may need to be reevaluated in the light of the results from this study.

Kovács, Tamás; Blitz, Mark A.; Seakins, Paul W.; Pilling, Michael J.

2009-11-01

38

Reactions of the CN radical with benzene and toluene: product detection and low-temperature kinetics.  

Science.gov (United States)

Low-temperature rate coefficients are measured for the CN + benzene and CN + toluene reactions using the pulsed Laval nozzle expansion technique coupled with laser-induced fluorescence detection. The CN + benzene reaction rate coefficient at 105, 165, and 295 K is found to be relatively constant over this temperature range, (3.9-4.9) x 10(-10) cm(3) molecule(-1) s(-1). These rapid kinetics, along with the observed negligible temperature dependence, are consistent with a barrierless reaction entrance channel and reaction efficiencies approaching unity. The CN + toluene reaction is measured to have a rate coefficient of 1.3 x 10(-10) cm(3) molecule(-1) s(-1) at 105 K. At room temperature, nonexponential decay profiles are observed for this reaction that may suggest significant back-dissociation of intermediate complexes. In separate experiments, the products of these reactions are probed at room temperature using synchrotron VUV photoionization mass spectrometry. For CN + benzene, cyanobenzene (C(6)H(5)CN) is the only product recorded with no detectable evidence for a C(6)H(5) + HCN product channel. In the case of CN + toluene, cyanotoluene (NCC(6)H(4)CH(3)) constitutes the only detected product. It is not possible to differentiate among the ortho, meta, and para isomers of cyanotoluene because of their similar ionization energies and the approximately 40 meV photon energy resolution of the experiment. There is no significant detection of benzyl radicals (C(6)H(5)CH(2)) that would suggest a H-abstraction or a HCN elimination channel is prominent at these conditions. As both reactions are measured to be rapid at 105 K, appearing to have barrierless entrance channels, it follows that they will proceed efficiently at the temperatures of Saturn's moon Titan ( approximately 100 K) and are also likely to proceed at the temperature of interstellar clouds (10-20 K). PMID:20043665

Trevitt, Adam J; Goulay, Fabien; Taatjes, Craig A; Osborn, David L; Leone, Stephen R

2010-02-01

39

Reactions of the CN Radical with Benzene and Toluene: Product Detection and Low-Temperature Kinetics  

Energy Technology Data Exchange (ETDEWEB)

Low temperature rate coefficients are measured for the CN + benzene and CN + toluene reactions using the pulsed Laval nozzle expansion technique coupled with laser-induced fluorescence detection. The CN + benzene reaction rate coefficient at 105, 165 and 295 K is found to be relatively constant over this temperature range, 3.9 - 4.9 x 10-10 cm3 molecule-1 s-1. These rapid kinetics, along with the observed negligible temperature dependence, are consistent with a barrierless reaction entrance channel and reaction efficiencies approaching unity. The CN + toluene reaction is measured to have a slower rate coefficient of 1.3 x 10-10 cm3 molecule-1 s-1 at 105 K. At room temperature, non-exponential decay profiles are observed for this reaction that may suggest significant back-dissociation of intermediate complexes. In separate experiments, the products of these reactions are probed at room temperature using synchrotron VUV photoionization mass spectrometry. For CN + benzene, cyanobenzene (C6H5CN) is the only product recorded with no detectable evidence for a C6H5 + HCN product channel. In the case of CN + toluene, cyanotoluene (NCC6H4CH3) constitutes the only detected product. It is not possible to differentiate among the ortho, meta and para isomers of cyanotoluene because of their similar ionization energies and the ~;; 40 meV photon energy resolution of the experiment. There is no significant detection of benzyl radicals (C6H5CH2) that would suggest a H-abstraction or a HCN elimination channel is prominent at these conditions. As both reactions are measured to be rapid at 105 K, appearing to have barrierless entrance channels, it follows that they will proceed efficiently at the temperatures of Saturn?s moon Titan (~;;100 K) and are also likely to proceed at the temperature of interstellar clouds (10-20 K).

Trevitt, Adam J.; Goulay, Fabien; Taatjes, Craig A.; Osborn, David L.; Leone, Stephen R.

2009-12-23

40

Oxidation of Benzene to Phenol, Catechol, and 1,2,3-Trihydroxybenzene by Toluene 4-Monooxygenase of Pseudomonas mendocina KR1 and Toluene 3-Monooxygenase of Ralstonia pickettii PKO1  

OpenAIRE

Aromatic hydroxylations are important bacterial metabolic processes but are difficult to perform using traditional chemical synthesis, so to use a biological catalyst to convert the priority pollutant benzene into industrially relevant intermediates, benzene oxidation was investigated. It was discovered that toluene 4-monooxygenase (T4MO) of Pseudomonas mendocina KR1, toluene 3-monooxygenase (T3MO) of Ralstonia pickettii PKO1, and toluene ortho-monooxygenase (TOM) of Burkholderia cepacia G4 c...

Tao, Ying; Fishman, Ayelet; Bentley, William E.; Wood, Thomas K.

2004-01-01

41

Conversion of toluene to benzene and mixed xylenes on old Thermofor Catalytic Cracking Units (TCC) in Russia  

Energy Technology Data Exchange (ETDEWEB)

World demand on toluene was in regression during the last years due to environmental and economical reasons, and there is a surplus of this compound from the processing to the petrochemical products. Disproportionation and transalkylation for the production of benzene and xylenes from toluene are now important industrial processes (Ikai Wang, 1999.). We analyze here the possibility of processing toluene on the Russian 43-102 'Houdry' type continuous Catalytic Cracking units (TCC), by studying the behaviour of EMCAT-100 catalyst on the disproportionation of toluene under the VHSV, temperature and catalyst/feed mass ratio characteristic for 43-102 facilities. Our previous results show that toluene disproportionation could be carried out on the Russian TCC units. (author)

Romero, Alfonso; Usachev, Nikolai Y.; Kalinin, Valera P. [Russian Academy of Sciences, Moscow (Russian Federation). Zelinsky Institute of Organic Chemistry]. E-mails: romero@orc.ru; ny@ioc.ac.ru

2004-07-01

42

Experimental study and kinetic modeling of the thermal degradation of aromatic volatile organic compounds (benzene, toluene and xylene-para) in methane flames; Etude experimentale et modelisation cinetique de la degradation thermique des composes organiques volatils aromatiques benzenes, toluene et para-xylene dans des flammes de methane  

Energy Technology Data Exchange (ETDEWEB)

This study treats of the thermal degradation of a family of aromatic volatile organic compounds (VOCs) in laminar premixed methane flames at low pressure. The experimental influence of benzene, toluene and xylene-para on the structure of a reference methane flame has been studied. The molar fraction profiles of the stable and reactive, aliphatic, aromatic and cyclic species have been established by the coupling of the molecular beam sampling/mass spectroscopy technique with the gas chromatography/mass spectroscopy technique. Temperature profiles have been measured using a covered thermocouple. A detailed kinetic mechanism of oxidation of these compounds in flame conditions has been developed. Different available sub-mechanisms have been used as references: the GDF-Kin 1.0 model for the oxidation of methane and the models of Tan and Franck (1996) and of Lindstedt and Maurice (1996) in the case of benzene and toluene. In the case of para-xylene, a model has been developed because no mechanisms was available in the literature. These different mechanisms have been refined, completed or adjusted by comparing the experimental results with those obtained by kinetic modeling. The complete kinetic mechanism, comprising 156 chemical species involved in 1072 reactions allows to reproduce all the experimental observations in a satisfactory manner. The kinetic analysis of reactions velocity has permitted to determine oxidation kinetic schemes for benzene, toluene, xylene-para and for the cyclopentadienyl radical, main species at the origin of the rupture of the aromatic cycle. Reactions of recombination with the methyl radicals formed during methane oxidation, of the different aromatic or aliphatic radicals created during the oxidation of aromatics, play an important role and lead to the formation of several aromatic pollutants (ethyl-benzene for instance) or aliphatic pollutants (butadiene or penta-diene for instance) in flames. (J.S.)

Dupont, L.

2001-02-01

43

Genotoxicity and apoptosis in Drosophila melanogaster exposed to benzene, toluene and xylene: attenuation by quercetin and curcumin.  

Science.gov (United States)

Monocyclic aromatic hydrocarbons (MAHs) such as benzene, toluene and xylene are being extensively used for various industrial and household purposes. Exposure to these hydrocarbons, occupationally or non-occupationally, is harmful to organisms including human. Several studies tested for toxicity of benzene, toluene and xylene, and interestingly, only a few studies looked into the attenuation. We used Drosophila model to test the genotoxic and apoptotic potential of these compounds and subsequently evaluated the efficiency of two phytochemicals, namely, quercetin and curcumin in attenuating test chemical induced toxicity. We exposed third instar larvae of wild type Drosophila melanogaster (Oregon R+) to 1.0-100.0 mM benzene, toluene or xylene, individually, for 12, 24 and 48 h and examined their apoptotic and genotoxic potential. We observed significantly (Phydrocarbon receptor (AhR) blocker. Interestingly, we observed a significant reduction in cytochrome P450 activity, GST levels, oxidative stress parameters, genotoxic and apoptotic endpoints when organisms were exposed simultaneously to test chemical along with quercetin or curcumin. The study further suggests the suitability of D. melanogaster as an alternate animal model for toxicological studies involving benzene, toluene and xylene and its potential in studying the protective role(s) of phytochemicals. PMID:21420423

Singh, Mahendra P; Mishra, M; Sharma, A; Shukla, A K; Mudiam, M K R; Patel, D K; Ram, K Ravi; Chowdhuri, D Kar

2011-05-15

44

Substrate interactions of benzene, toluene, and para-xylene during microbial degradation by pure cultures and mixed culture aquifer slurries  

International Nuclear Information System (INIS)

Release of petroleum hydrocarbons in the environment is a widespread occurrence. One particular concern is the contamination of drinking water sources by the toxic, water-soluble, and mobile petroleum components benzene, toluene, and xylene (BTX). Benzene, toluene, and p-xylene (BTX) were degraded by indigenous mixed cultures in sandy aquifer material and by two pure cultures isolated from the same site. Although BTX compounds have a similar chemical structure, the fate of individual BTX compounds differed when the compounds were fed to each pure culture and mixed culture aquifer slurries. The identification of substrate interactions aided the understanding of this behavior. Beneficial substrate interactions included enhanced degradation of benzene-dependent degradation of toluene and p-xylene by Arthrobacter sp. strain HCB. Detrimental substrate interactions included retardation in benzene and toluene degradation by the presence of p-xylene in both aquifer slurries and Pseudomonas incubations. The catabolic diversity of microbes in the environment precludes generalizations about the capacity of individual BTX compounds to enhance or inhibit the degradation of other BTX compounds

45

Genetic effects of thinner, benzene and toluene in Drosophila melanogaster. 2. Sex linked recessive lethal, mutations and translocations II-III  

Directory of Open Access Journals (Sweden)

Full Text Available The effects of thinner, benzene and toluene on the;induction of sex-linked recessive lethal mutations and translocations 11-111 in D~osophila melanogaster were investigated by means of a genetic scheme designed. by Oster and a modified z for statistical analysis. Thinner induced sex-linked recessive lethals while benzene and toluene did not. Translocations 11-111 were produced only by benzene.

Rosario Rodr\\u00EDguez Arnaiz

1985-01-01

46

Heats of adsorption of benzene and toluene vapors on polyhydroxyaluminum montmorillonite  

Science.gov (United States)

Changes that occur in the surface properties and porous structure of montmorillonite when sodium ions are replaced with polyhydroxyaluminum ions are studied. It is established that thermal evacuation significantly affects the adsorption and energy properties of polyhydroxyaluminum montmorillonite (PHAM). The dependences of the differential isosteric heats of adsorption and desorption on the amount of adsorbed substance are determined from data on a series of isosteres for the sorption of benzene and toluene on dehydrated PHAMs, where the curves of the heats of sorption of C6H6 and C7H8 are of an extreme character. It is concluded that the occurrence of maxima is determined by the interaction between molecules of adsorbates and active centers (and with one another) due to packing upon the filling of the volumes of slittype micropores.

Muminov, S. Z.; Khandamov, D. A.; Agzamkhodzhaev, A. A.

2014-09-01

47

Directed evolution of biphenyl dioxygenase: emergence of enhanced degradation capacity for benzene, toluene, and alkylbenzenes.  

Science.gov (United States)

Biphenyl dioxygenase (Bph Dox) catalyzes the initial oxygenation of biphenyl and related compounds. Bph Dox is a multicomponent enzyme in which a large subunit (encoded by the bphA1 gene) is significantly responsible for substrate specificity. By using the process of DNA shuffling of bphA1 of Pseudomonas pseudoalcaligenes KF707 and Burkholderia cepacia LB400, a number of evolved Bph Dox enzymes were created. Among them, an Escherichia coli clone expressing chimeric Bph Dox exhibited extremely enhanced benzene-, toluene-, and alkylbenzene-degrading abilities. In this evolved BphA1, four amino acids (H255Q, V258I, G268A, and F277Y) were changed from the KF707 enzyme to those of the LB400 enzyme. Subsequent site-directed mutagenesis allowed us to determine the amino acids responsible for the degradation of monocyclic aromatic hydrocarbons. PMID:11514531

Suenaga, H; Mitsuoka, M; Ura, Y; Watanabe, T; Furukawa, K

2001-09-01

48

Mobility of Supercooled liquid Toluene, Ethylbenzene, and Benzene near their Glass Transition Temperatures Investigated using Inert Gas Permeation  

Energy Technology Data Exchange (ETDEWEB)

We investigate the mobility of supercooled liquid toluene, ethylbenzene, and benzene near their respective glass transition temperatures (Tg). The permeation rate of Ar, Kr, and Xe through the supercooled liquid created when initially amorphous overlayers heated above their glass transition temperature is used to determine the diffusivity. Amorphous benzene crystallizes at temperatures well below its Tg and as a result the inert gas underlayer remains trapped until the onset of benzene desorption. In contrast, for toluene and ethylbenzene the onset of inert gas permeation is observed at temperatues near Tg. The inert gas desorption peak temperature as a function of the heating rate and overlayer thickness is used to quantify the diffusivity of supercooled liquid toluene and ethylbenzene from 115 K to 135 K. In this temperature range, diffusivities are found to vary across five orders of magnitude (~10-14 to 10-9 cm2/s). These data are compared to viscosity measurements and used to determine the low temperature fractional Stokes-Einstein exponent. Efforts to determine the diffusivity of a mixture of benzene and ethylbenzene are detailed, and the effect of mixing these materials on benzene crystallization is explored using infrared spectroscopy.

May, Robert A.; Smith, R. Scott; Kay, Bruce D.

2013-11-21

49

Genotoxicity and apoptosis in Drosophila melanogaster exposed to benzene, toluene and xylene: Attenuation by quercetin and curcumin  

International Nuclear Information System (INIS)

Monocyclic aromatic hydrocarbons (MAHs) such as benzene, toluene and xylene are being extensively used for various industrial and household purposes. Exposure to these hydrocarbons, occupationally or non-occupationally, is harmful to organisms including human. Several studies tested for toxicity of benzene, toluene and xylene, and interestingly, only a few studies looked into the attenuation. We used Drosophila model to test the genotoxic and apoptotic potential of these compounds and subsequently evaluated the efficiency of two phytochemicals, namely, quercetin and curcumin in attenuating test chemical induced toxicity. We exposed third instar larvae of wild type Drosophila melanogaster (Oregon R+) to 1.0-100.0 mM benzene, toluene or xylene, individually, for 12, 24 and 48 h and examined their apoptotic and genotoxic potential. We observed significantly (P < 0.001) increased apoptotic markers and genotoxicity in a concentration- and time-dependent manner in organisms exposed to benzene, toluene or xylene. We also observed significantly (P < 0.001) increased cytochrome P450 activity in larvae exposed to test chemicals and this was significantly reduced in the presence of 3',4'-dimethoxyflavone, a known Aryl hydrocarbon receptor (AhR) blocker. Interestingly, we observed a significant reduction in cytochrome P450 activity, GST levels, oxidative stress parameters, genotoxic and apoptotic endpoints when organisms were exposed simultaneously to test chemical aloxposed simultaneously to test chemical along with quercetin or curcumin. The study further suggests the suitability of D. melanogaster as an alternate animal model for toxicological studies involving benzene, toluene and xylene and its potential in studying the protective role(s) of phytochemicals.

50

Wetlands for the remediation of BTEX [benzene, toluene, ethylbenzene, xylenes] contamination: Amalgamation of policy and technology  

International Nuclear Information System (INIS)

The fate and transport of benzene, toluene, ethylbenzene, and xylenes (BTEX) as they pass from a groundwater to a surface water environment was studied in three separate field experiments. The first examined the fate of BTEX from a spilled gasoline plume as it travelled vertically in the groundwater flow regime from a mineral soil unit through an organic soil unit to a surface wetland. The second considered surface water processes in the swamp that result in losses of BTEX concentrations. The final experiment evaluated the effects of seasonal and temporal changes on the processes occurring in the swamp that affect the fate and transport of BTEX under natural flow conditions. Significant reductions in BTEX were observed as the plume travelled vertically to reach the surface water. Reductions in contaminant levels were primarily due to sorption and biodegradation. On reaching the surface, overall reduction of compound concentration over 6 m of horizontal flow ranged from 92% for benzene to 85% for m-xylene. BTEX losses were mainly due to dilution, volatilization, and sorption. Limitations existing in the approach taken by present legislation and guidelines for wetland protection are discussed. Reactive legislation and guidelines should allow natural remediation of contamination in wetlands to be considered, especially when contaminant remediation requires alteration of the hydrologic flow regime or removal of contaminated material that may result in elimination of the wal that may result in elimination of the wetland. 70 refs., 20 figs., 14 tabs

51

Thermodynamics of mixtures containing oxaalkanes. 6. Random mixing in ether + benzene, or + toluene systems  

Energy Technology Data Exchange (ETDEWEB)

The Flory model has been applied to linear or cyclic ether + benzene, or +toluene mixtures. In addition, the relative variation of the molar excess enthalpy, H{sub m}{sup E}, along homologous series of the considered systems, has been discussed taking into account the contributions to H{sub m}{sup E} from the ether-ether, aromatic-aromatic and ether-aromatic interactions. It has been shown that in CH{sub 3}(CH{sub 2}){sub u-1}O(CH{sub 2}CH{sub 2}O){sub v}(CH{sub 2}){sub u-1}CH{sub 3} + benzene mixtures, the u increase (v fixed) leads to a weakening of interactions between unlike molecules, and that proximity effects also weaken this type of interactions. In contrast, the v increase (u fixed) or cyclization lead to stronger interactions between unlike molecules. From the application of the model, it is concluded that the random mixing hypothesis may be considered to be valid to a large extent for many of the investigated solutions. Erroneously, strong orientational effects are predicted for 1,3-dioxolane, or 1,4-dioxane + benzene systems, but this has been attributed to the model can not describe asymmetric H{sub m}{sup E} curves when the mixture compounds show close values for V{sub i} (molar volume) and for V{sub i}{sup *} (reduction parameter for volume). Previous calculations on the basis of the Kirkwood-Buff integrals formalism confirm that the mixture structure is close to random mixing. Flory results on the excess molar volumes have been discussed taking into account the so-called curvature and P* contributions to this excess function.

Gonzalez, Juan Antonio, E-mail: jagl@termo.uva.es [G.E.T.E.F., Departamento de Fisica Aplicada, Facultad de Ciencias, Universidad de Valladolid, 47071 Valladolid (Spain); Garcia De La Fuente, Isaias; Cobos, Jose Carlos; Mozo, Ismael; Alonso, Ivan [G.E.T.E.F., Departamento de Fisica Aplicada, Facultad de Ciencias, Universidad de Valladolid, 47071 Valladolid (Spain)

2011-02-20

52

Quantitative detection of benzene in toluene- and xylene-rich atmospheres using high-kinetic-energy ion mobility spectrometry (IMS).  

Science.gov (United States)

One major drawback of ion mobility spectrometry (IMS) is the dependence of the response to a certain analyte on the concentration of water or the presence of other compounds in the sample gas. Especially for low proton affine analytes, e.g., benzene, which often exists in mixtures with other volatile organic compounds, such as toluene and xylene (BTX), a time-consuming preseparation is necessary. In this work, we investigate BTX mixtures using a compact IMS operated at decreased pressure (20 mbar) and high kinetic ion energies (HiKE-IMS). The reduced electric field in both the reaction tube and the drift tube can be independently increased up to 120 Td. Under these conditions, the water cluster distribution of reactant ions is shifted toward smaller clusters independent of the water content in the sample gas. Thus, benzene can be ionized via proton transfer from H3O(+) reactant ions. Also, a formation of benzene ions via charge transfer from NO(+) is possible. Furthermore, the time for interaction between ions and neutrals of different analytes is limited to such an extent that a simultaneous quantification of benzene, toluene, and xylene is possible from low ppbv up to several ppmv concentrations. The mobility resolution of the presented HiKE-IMS varies from R = 65 at high field (90 Td) to R = 73 at lower field (40 Td) in the drift tube, which is sufficient to separate the analyzed compounds. The detection limit for benzene is 29 ppbv (2 s of averaging) with 3700 ppmv water, 12.4 ppmv toluene, and 9 ppmv xylene present in the sample gas. Furthermore, a less-moisture-dependent benzene measurement with a detection limit of 32 ppbv with ca. 21?000 ppmv (90% relative humidity (RH) at 20 °C) water present in the sample gas is possible evaluating the signal from benzene ions formed via charge transfer. PMID:25360539

Langejuergen, Jens; Allers, Maria; Oermann, Jens; Kirk, Ansgar; Zimmermann, Stefan

2014-12-01

53

The Role of Acid Strength of Modified NaX Zeoliteson Gas Phase Ethylation of Benzene  

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Full Text Available The role of acid strength of modified NaX zeolites in gas phase ethylation of benzene were studied over Ce exchanged NaX zeolite of different types. Acidity of the modified zeolite was investigated by means of adsorbing ammonia at different temperature. The conversion of reactantsvaries with the acid strength as well as the different types of the zeolites. The strong acid sites are active centers while the weak acid sites are inactive. The influences of various process parameters such as temperature, space-time and the feed ratio of benzene to ethanol on benzene conversion over most acidic zeolite were studied. The kinetic and adsorption constants of the rate equations were estimated by the best fit. From the estimated kinetic constants, the activation energies and frequency factors for various reactions were determined. The activation energy values compared well with those reported by other investigators for same reactions over similar catalysts.

Sanghamitra Barman

2010-01-01

54

Risk assessment of volatile organic compounds benzene, toluene, ethylbenzene, and xylene (BTEX) in consumer products.  

Science.gov (United States)

Exposure and risk assessment was performed by evaluating levels of volatile organic compounds (VOC) benzene, toluene, ethylbenzene, and xylene (BTEX) in 207 consumer products. The products were categorized into 30 different items, consisting of products of different brands. Samples were analyzed for BTEX by headspace-gas chromatography/mass spectrometry (headspace-GC/MS) with limit of detection (LOD) of 1 ppm. BTEX were detected in 59 consumer products from 18 item types. Benzene was detected in whiteout (ranging from not detected [ND] to 3170 ppm), glue (1486 ppm), oil-based ballpoint pens (47 ppm), and permanent (marking) pens (2 ppm). Toluene was detected in a leather cleaning product (6071 ppm), glue (5078 ppm), whiteout (1130 ppm), self-adhesive wallpaper (15-1012 ppm), shoe polish (806 ppm), permanent pen (609 ppm), wig adhesive (372 ppm), tapes (2-360 ppm), oil-based ballpoint pen (201 ppm), duplex wallpaper (12-52 ppm), shoes (27 ppm), and air freshener (13 ppm). High levels of ethylbenzene were detected in permanent pen (ND-345,065 ppm), shoe polish (ND-277,928 ppm), leather cleaner (42,223 ppm), whiteout (ND-2,770 ppm), and glue (ND-792 ppm). Xylene was detected in permanent pen (ND-285,132 ppm), shoe polish (ND-87,298 ppm), leather cleaner (12,266 ppm), glue (ND-3,124 ppm), and whiteout (ND-1,400 ppm). Exposure assessment showed that the exposure to ethylbenzene from permanent pens ranged from 0 to 3.11 mg/kg/d (men) and 0 to 3.75 mg/kg/d (women), while for xylene, the exposure ranges were 0-2.57 mg/kg/d and 0-3.1 mg/kg/d in men and women, respectively. The exposure of women to benzene from whiteout ranged from 0 to 0.00059 mg/kg/d. Hazard index (HI), defined as a ratio of exposure to reference dose (RfD), for ethylbenzene was 31.1 (3.11 mg/kg/d/0.1 mg/kg/d) and for xylene (2.57 mg/kg/d/0.2 mg/kg/d) was 12.85, exceeding 1 for both compounds. Cancer risk for benzene was calculated to be 3.2 × 10(-5) based on (0.00059 mg/kg/d × 0.055 mg/kg-d(-1), cancer potency factor), assuming that 100% of detected levels in some products such as permanent pens and whiteouts were exposed in a worst-case scenario. These data suggest that exposure to VOC via some consumer products exceeded the safe limits and needs to be reduced. PMID:25343298

Lim, Seong Kwang; Shin, Han Seung; Yoon, Kyung Sil; Kwack, Seung Jun; Um, Yoon Mi; Hyeon, Ji Hyeon; Kwak, Hyo Min; Kim, Ji Yun; Kim, Tae Young; Kim, Yeon Joo; Roh, Tae Hyun; Lim, Duck Soo; Shin, Min Kyung; Choi, Seul Min; Kim, Hyung Sik; Lee, Byung-Mu

2014-01-01

55

Analysis of benzene, toluene, ethylbenzene and xylenes in soils by headspace and gas chromatography/flame ionization detector  

Directory of Open Access Journals (Sweden)

Full Text Available The constituents of gasoline: benzene, toluene, ethylbenzene and xylenes (BTEX are frequently found in soils due to leaks in fuel storage tanks and they present chronic toxicity. In this work it was developed and validated a methodology of BTEX analysis in soil by gas chromatography/ flame ionization detector and static headspace. The recovery of BTEX in soil samples was evaluated using soils with different textures (sandy and loamy. The analysis method showed good resolution, in a low time of analysis (less than 30 minutes. Limits of quantification of 0.05 mg Kg¯¹ soil for benzene, toluene, ethylbenzene and xylenes are below the guiding values that range from 0.15 to 95 mg Kg¯¹ soil, established to determine soil quality. It was verified that the methodology enables the use of this method for BTEX analysis of soil samples for passive environmental identification of gas stations.

Jurandir Pereira Pinto

2006-02-01

56

Nucleotide sequence analysis of genes encoding a toluene/benzene-2-monooxygenase from Pseudomonas sp. strain JS150.  

Science.gov (United States)

It was previously shown by others that Pseudomonas sp. strain JS150 metabolizes benzene and alkyl- and chloro-substituted benzenes by using dioxygenase-initiated pathways coupled with multiple downstream metabolic pathways to accommodate catechol metabolism. By cloning genes encoding benzene-degradative enzymes, we found that strain JS150 also carries genes for a toluene/benzene-2-monooxygenase. The gene cluster encoding a 2-monooxygenase and its cognate regulator was cloned from a plasmid carried by strain JS150. Oxygen (18O2) incorporation experiments using Pseudomonas aeruginosa strains that carried the cloned genes confirmed that toluene hydroxylation was catalyzed through an authentic monooxygenase reaction to yield ortho-cresol. Regions encoding the toluene-2-monooxygenase and regulatory gene product were localized in two regions of the cloned fragment. The nucleotide sequence of the toluene/benzene-2-monooxygenase locus was determined. Analysis of this sequence revealed six open reading frames that were then designated tbmA, tbmB, tbmC, tbmD, tbmE, and tbmF. The deduced amino acid sequences for these genes showed the presence of motifs similar to well-conserved functional domains of multicomponent oxygenases. This analysis allowed the tentative identification of two terminal oxygenase subunits (TbmB and TbmD) and an electron transport protein (TbmF) for the monooxygenase enzyme. In addition to these gene products, all the tbm polypeptides shared significant homology with protein components from other bacterial multicomponent monooxygenases. Overall, the tbm gene products shared greater similarity with polypeptides from the phenol hydroxylases of Pseudomonas putida CF600, P35X, and BH than with those from the toluene monooxygenases of Pseudomonas mendocina KR1 and Burkholderia (Pseudomonas) pickettii PKO1. The relationship found between the phenol hydroxylases and a toluene-2-monooxygenase, characterized in this study for the first time at the nucleotide sequence level, suggested that DNA probes used for surveys of environmental populations should be carefully selected to reflect DNA sequences corresponding to the metabolic pathway of interest. PMID:7574644

Johnson, G R; Olsen, R H

1995-09-01

57

Substrate interactions of benzene, toluene, and para-xylene during microbial degradation by pure cultures and mixed culture aquifer slurries.  

OpenAIRE

Benzene, toluene, and p-xylene (BTX) were degraded by indigenous mixed cultures in sandy aquifer material and by two pure cultures isolated from the same site. Although BTX compounds have a similar chemical structure, the fate of individual BTX compounds differed when the compounds were fed to each pure culture and mixed culture aquifer slurries. The identification of substrate interactions aided the understanding of this behavior. Beneficial substrate interactions included enhanced degradati...

Alvarez, P. J.; Vogel, T. M.

1991-01-01

58

Observation of AlCl sub 3 -catalyzed trialkylsilylation of benzene and toluene with chlorotrialkylsilanes in the presence of Huenig bases  

Energy Technology Data Exchange (ETDEWEB)

The authors now report observation of the direct silylation of benzene and toluene with a series of chlorotrialkylsilanes under Friedel-Crafts conditions in the presence of Huenig bases (hindered tertiary amines) as proton acceptors. When excess benzene or toluene was heated with chlorotrialkylsilane and aluminum trichloride in the presence of diisopropylethylamine at 150{degree}C in a sealed heavy walled glass tube for 24 h, the corresponding aryltrialkylsilanes were obtained in low, but detactable amounts.

Olah, G.A.; Bach, T.; Prakash, G.K.S. (Univ. of Southern California, Los Angeles (USA))

1989-08-04

59

An improved approach for accurate quantitation of benzene, toluene, ethylbenzene, xylene, and styrene in blood.  

Science.gov (United States)

Widespread exposure to benzene, toluene, ethylbenzene, xylene, and styrene (BTEXS) and the potential for this exposure to cause health effects drives the need to develop improved methods for measuring exposure. In this work, we demonstrate our latest assay for quantifying BTEXS in blood and characterize sources of both positive and negative biases. This method involves blood sample collection using common techniques followed by static headspace sampling using solid-phase microextraction and gas chromatography/mass spectrometry analysis. We found that the greatest and unexpected source of positive bias was from contamination of butyl rubber materials used in sample preparation consumables such as Vacutainer stoppers, syringe plungers, and sample vial septa. Conversely, the primary cause of negative bias observed was from the diffusion loss of BTEXS from blood during transfer into sample vials. By minimizing or eliminating these and other sources of bias, we improved method accuracy and precision to within 10% while maintaining low-picogram per milliliter detection. Furthermore, upon comparison of these results with those from other laboratories, we observe substantially lower blood BTEXS levels reported to date for nonoccupationally exposed nonsmokers. A relatively unbiased method, as such, will help elucidate any potential associations between adverse health effects and human exposure to low levels of BTEXS. PMID:16878872

Chambers, David M; McElprang, David O; Waterhouse, Michael G; Blount, Benjamin C

2006-08-01

60

Coherence in UV resonance Raman spectroscopy of liquid benzene and toluene, but not ice  

Science.gov (United States)

We have measured UV resonance Raman scattering at and near the resonance absorption lines of liquid benzene and toluene. Resonance occurs for excitation on the symmetry-forbidden but strongly phonon coupled states in the 1B2u band, ~230-270 nm, resulting in enhancements corresponding to the vapor phase absorptions rather than those of the liquid phase. This effect is related to the coherence forced by the internal molecular resonance required to absorb light at this energy. The resonance gains (~1000x) are larger than expected due to the narrower vapor phase lines. Several multiplet and overtone modes are enhanced along with the strongly coupled ring-breathing mode. A contrasting case of resonance Raman of ice is also discussed; in this case resonance is observed for excitation energy corresponding to absorptions that depend upon the final state shielding by the neighbors, and corresponds with the solid phase absorption. This typifies the more common, slow, time dependence of the resonance Raman process.

Hallen, Hans D.; Neely, Ryan R.; Willitsford, Adam H.; Chadwick, C. T.; Philbrick, C. R.

2013-09-01

61

Mixture effects of benzene, toluene, ethylbenzene, and xylenes (BTEX) on lung carcinoma cells via a hanging drop air exposure system.  

Science.gov (United States)

A recently developed hanging drop air exposure system for toxicity studies of volatile chemicals was applied to evaluate the cell viability of lung carcinoma A549 cells after 1 and 24 h of exposure to benzene, toluene, ethylbenzene, and xylenes (BTEX) as individual compounds and as mixtures of four or six components. The cellular chemical concentrations causing 50% reduction of cell viability (EC50) were calculated using a mass balance model and came to 17, 12, 11, 9, 4, and 4 mmol/kg cell dry weight for benzene, toluene, ethylbenzene, m-xylene, o-xylene, and p-xylene, respectively, after 1 h of exposure. The EC50 decreased by a factor of 4 after 24 h of exposure. All mixture effects were best described by the mixture toxicity model of concentration addition, which is valid for chemicals with the same mode of action. Good agreement with the model predictions was found for benzene, toluene, ethylbenzene, and m-xylene at four different representative fixed concentration ratios after 1 h of exposure, but lower agreement with mixture prediction was obtained after 24 h of exposure. A recreated car exhaust mixture, which involved the contribution of the more toxic p-xylene and o-xylene, yielded an acceptable, but lower quality, prediction as well. PMID:24836216

Liu, Faye F; Escher, Beate I; Were, Stephen; Duffy, Lesley; Ng, Jack C

2014-06-16

62

Evaluation of the occupational risk for exposition to Benzene, Toluene and Xylene in a paintings industry in Bogota  

International Nuclear Information System (INIS)

It was determined Benzene, Toluene and Xylene (BTX) levels in air from paint manufacture assigned to Instituto Colombiano de Seguro Social with the purpose to evaluate the occupational hazard caused by the use of these solvents. These results were compared with the threshold limit value (TLV). It was selected as sampling strategy, the methodology of partial period with consecutive samples and charcoal tubes as adsorbent of solvents. The extraction was realized with carbon disulfide and it was used gas chromatography with FID as analysis method. It was found that the method is highly selective because in presence of the others ten solvents, utilized in paint manufacture, were obtained a good separation for BTX. The precision, expressed a variance coefficient, was lower than 10%, the accuracy varied between 85 and 99 % for the three solvents. The airborne concentration found was between no detectable and 55,1 mg/m3 for benzene, 18,3 and 253 mg/m3 for toluene and 11,8 and 122,2 mg/m3 for xylene. The corrected TLV values for benzene, toluene and xylenes according to the brief and scale model for the ten hours shift were 1,1, 132 and 304 mg/m3 respectively. It was found occupational risk for benzene in some workplaces; this one is worried because benzene is not used as raw material for the paint manufacture. It was determinate that exist occupational risk in almost every workplace of the industry when it is considered the mixtureindustry when it is considered the mixture of the three solvents

63

Optimization of Solid Phase Micro-Extraction (SPME for Monitoring Occupational Exposure to Ethyl Benzene  

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Full Text Available

Background and Objectives: Analytical methods for volatile organic compounds (VOCs in different samples need extraction of compounds, by applying hazardous solvents. Solid phase micro-extraction (SPME is a solvent-free equilibrium extraction method, in which proper calibration can allow quantitative determinations of VOCs at a very good sensitivity without the use of any organic solvent. VOCs are generally present in urine only at trace levels, therefore, a sensitive procedure is needed for their trace determinations. Throughout this study, headspace solid phase micro-extraction (HS-SPME was followed by GC-FID for ethyl benzene in spiked urine was optimized.

Methods: In this study, the parameters influencing SPME and gas chromatography of ethyl benzene, including extraction time, temperature, desorption temperature, desorption time, salt addition, sample pH, sample volume and sample agitation were investigated.

Results: Extraction procedure was performed at 30°C for 6 min, using 0.2 gml-1 of NaCl in the sample solution. The sample volume and sample pH were optimized at 5 ml and 7 (neutral pH, respectively. Desorption of the ethyl benzene was carried out for 60 sec. at 250°C. The method was also validated with three different spiked urine samples and illustrated an appropriate reproducibility over six consecutive days as well as six within-day experiments. During this investigation, parameters of accuracy, linearity, and detection limits of the procedure were also evaluated.

Conclusion: The developed method of HS- SPME-GC-FID proved to be a simple, convenient, and practical procedure, and was successfully used for measuring of ethyl benzene in spiked urine.

H Heidari

2012-05-01

64

Concentrations of benzene and toluene in the atmosphere of the southwestern area at the Mexico City Metropolitan Zone  

Energy Technology Data Exchange (ETDEWEB)

The Mexico City Metropolitan Zone (MCMZ) presents important emissions of hazardous air pollutants. It is well documented that the MCMZ suffers a critical air pollution problem due to high ozone and particulate matter concentrations. However, toxic air pollutants such as benzene and toluene have not been considered. Benzene has accumulated sufficient evidence as a human carcinogen, and the ratio benzene/toluene is an excellent indicator to evaluate control strategies efficiency. In order to evaluate the levels of these two air toxic pollutants in the MCMZ, ambient air samples were collected in canisters and analyzed with a gas chromatograph with a flame ionization detector, according to procedures described in the United States Environmental Protection Agency (USEPA) method TO-15. Quality assurance was performed collecting duplicate samples which were analyzed in replicate to quantify the precision of air-quality measurements. Three different sites located in the Southwestern area in the MCMZ were selected for the sampling: the University campus, a gas station, and a vertical condominium area, in the same neighborhood, which presents different activities. At these sites, grab air samples were collected during the morning hours (7-8 a.m.), while for the University area, 24 h integrated air samples were collected simultaneously, with grab samples. Benzene concentrations (24 h sampling) in the atmosphere around the University campus have similar present levels as in other cities of North America. Mean values in this site were about 1.7 ppb. A significant variation exists between the benzene and toluene concentrations in the studied sites, being the more critical values than those registered at the gas station (an average of 25.8 ppb and a maximum of 141 ppb of benzene). There is a fuel regulation for gasoline in Mexico, which allows a maximum of 1 percent of benzene. However, since more than 60 percent of vehicles do not have catalytic converters (models before 1991) it is expected that most of this benzene be emitted through exhaust pipe. Another strategy being implemented is the use of vapor recovery systems at the gas stations. Vehicles emission control technology must be matched with adequate fuel characteristics in the problem area where it will be implemented, to achieve maximum emission reductions. (author)

Bravo, H.; Sosa, R.; Sanchez, P. [Universidad Autonoma de Mexico, Ciudad Universitaria (Mexico). Centro de Ciencias de la Atmosfera; Bueno, E.; Gonzalez, L. [Centro Nacional de Investigacion y Capacitacion Ambiental, Instituto Nacional de Ecologia, SEMARNAP, Mexico (Mexico)

2002-08-01

65

Emissions of benzene, toluene, xylenes and 1,3-butadiene from a representative portion of the Australian car fleet  

Science.gov (United States)

The exhaust emissions of the air toxics benzene, toluene, total xylenes and 1,3-butadiene have been measured in the cold transient (CT), cold stabilised (CS) and hot transient (HT) phases of the Australian Design Rule (ADR) 37/00 Drive cycle for 19 pre-1986 non-catalyst-equipped vehicles fuelled with leaded petrol, and 56 post-1985 catalyst-equipped vehicles fuelled with unleaded petrol. Per vehicle exhaust emissions, averaged over the 3 phases of the ADR 37/00 test, of 1,3-butadiene, benzene, toluene, and total xylenes for the older vehicles were about 19, 139, 240 and 164 mg km -1 respectively. The corresponding emissions for the better 46 of the 56 post-1985 vehicles tested were 1.7, 28.1, 36.4, and 27.0 mg km- 1 respectively. The remaining 10 high polluting post-1985 vehicles had emission rates comparable to those vehicles not equipped with catalytic converters, suggesting that about 20% of post-1985 vehicles have malfunctioning or poorly operating catalysts. For the non-catalyst-equipped, pre-1986 vehicles, CS and HT emissions were about 60% of the CT emissions. For the better 46 post-1985 vehicles, average emissions during the CS and HT phases were about 20-25%, 12-16%, 11-14%, and 7-13% of the CT emissions for benzene, toluene, the xylenes, and 1,3-butadiene, respectively. The emissions from a small number (9) of non-catalyst-equipped, pre-1986 vehicles were determined using unleaded and leaded petrol. The emissions of all four target compounds were found to be significantly lower when unleaded petrol was substituted for leaded petrol. The greatest percentage emission reductions were observed for the CT phase, ranging from 25% for 1,3-butadiene to 35% for toluene. Emissions averaged over the 3 phases were reduced by 10% for 1,3-butadiene and by 16-18% for the aromatic compounds. Per vehicle total (heat build and hot soak) evaporative emissions of 1,3-butadiene, benzene, toluene and xylenes from pre-1985 vehicles during the Sealed Housing Evaporative Determination tests were 36, 646, 679 and 260 mg per test, respectively. Corresponding values for the post-1985 vehicles were much lower at 14, 76, 131 and 65 mg per test, respectively. Heat build evaporative emissions of the four air toxics from pre-1986 vehicles were greater than those from the newer vehicles by factors ranging from 2.8 for 1,3-butadiene to 16 for benzene. The corresponding values for hot soak emissions were 1.8 and 5.2 respectively.

Duffy, B. L.; Nelson, P. F.; Ye, Y.; Weeks, I. A.; Galbally, I. E.

66

Hydrogeochemical modeling of enhanced benzene, toluene, ethylbenzene, xylene (BTEX) remediation with nitrate  

Science.gov (United States)

During a 5-month field test, active remediation of a benzene, toluene, ethylbenzene, xylene (BTEX)-contaminated aquifer was initiated by injecting water with varying amounts of KNO3. The experiment was performed prior to selecting bioremediation for full-scale cleanup, particularly to evaluate the competing reaction of nitrate with hydrocarbons and reduced sulfur components. The nitrate oxidized sulfides that had precipitated earlier as a result of the natural degradation of BTEX with SO42- from groundwater. When the sulfides were exhausted, BTEX degradation was enhanced by nitrate. A hydrogeochemical model with kinetic oxidation reactions for Fe(II), FeS and BTEX by nitrate was developed to calculate the observed concentration patterns along a flow line in the aquifer. The rates for the kinetic model were based on published kinetic reaction equations for oxidation with oxygen. Nitrate was introduced in the equations in the same form as oxygen, with a premultiplier added to fit the observed concentration changes in the aquifer. The oxidation of Fe(II) with nitrate in the aquifer was 4 times slower than the abiological oxidation reaction with oxygen in water. Similar rates were found for oxidation of FeS with nitrate as for FeS2 with oxygen, but the specific surface area of FeS in the aquifer was larger. The reaction rate for degradation of BTEX compounds was about 107 times faster than for natural organic matter. BTEX release from pools in the aquifer was modeled with a linear driving force equation in which the pollutant/water interfacial area was linked to the mass of BTEX. The release rate and the denitrification rate were used to calculate the initial amounts of BTEX at the start of the KNO3 injection. This study shows that an assessment of the efficiency of nitrate addition for stimulating bioremediation has to consider possible reactions of nitrate with reduced sulfur components and ferrous iron.

Eckert, Paul; Appelo, C. A. J.

2002-08-01

67

Development of portable preconcentration-gas chromatography system for fast analysis of trace benzene, toluene and xylene in air  

International Nuclear Information System (INIS)

An automated on-line portable preconcentration-short column gas chromatography was developed, which used preconcentrator using adsorption tube with Tenax-GR and Curie-point heating. The developed system operated with 3 steps of processing, preconcentration, thermal desorption, and analysis and cleaning, and could continued operating within 1 ? 2 min cycle. The recoveries of preconcentrator for toluene was ranged between 94.7±6.6% and 103.8±3.1% with less than 7% of RSD. For benzene, toluene and xylene(BTX) standard gas test, IDL was 41, 49, 472 ng/m3 benzene, toluene and ?-xylene, respectively. The BTX mixture was analyzed within 30 sec with baseline separation by the system equipped with 4 m long capillary column. The deficiency of separation power caused by short column was solved by the control of sample injection volume and inlet/outlet pressure ratio. The automated portable preconcentration-short column gas chromatograph system was found to be useful for the continuous air monitoring of BTX at ppb levels ambient air

68

Airborne determination of the temporo-spatial distribution of benzene, toluene, nitrogen oxides and ozone in the boundary layer across Greater London, UK  

Science.gov (United States)

Highly spatially resolved mixing ratios of benzene and toluene, nitrogen oxides (NOx) and ozone (O3) were measured in the atmospheric boundary layer above Greater London during the period 24 June to 9 July 2013 using a Dornier 228 aircraft. Toluene and benzene were determined in-situ using a proton transfer reaction mass spectrometer (PTR-MS), NOx by dual channel NOx chemiluminescence and O3 mixing ratios by UV absorption. Average mixing ratios observed over inner London at 360 ± 10 m a.g.l. were 0.20 ± 0.05, 0.28 ± 0.07, 13.2 ± 8.6, 21.0 ± 7.3 and 34.3 ± 15.2 ppbv for benzene, toluene, NO, NO2 and NOx respectively. Linear regression analysis between NO2, benzene and toluene mixing ratios yielded a trimodal distribution indicating that these compounds predominantly share the same or co-located sources within the city and that a significant fraction of NOx is directly emitted as NO2. Average mixing ratios measured at 360 ± 10 m a.g.l. over outer London were always lower than over inner London. Where traffic densities were highest, the toluene / benzene (T / B) concentration ratios were highest (average of 1.8 ± 0.3 ppbv ppbv-1) indicative of strong local sources. Daytime maxima in NOx, benzene and toluene mixing ratios were observed in the morning (~40 ppbv NOx, ~350 pptv toluene and ~200 pptv benzene) and for ozone in the mid-afternoon (~40 ppbv O3) all at 360 ± 10 m a.g.l.

Shaw, M. D.; Lee, J. D.; Davison, B.; Vaughan, A.; Purvis, R. M.; Lewis, A. C.; Hewitt, C. N.

2014-10-01

69

Vapor-phase testing of the memory-effects in benzene- and toluene-imprinted polymers conditioned at elevated temperature.  

Science.gov (United States)

The preparation of polymers imprinted with common aromatic solvents such as benzene and toluene is an under-exploited subject of research. The present study was aimed at the understanding of whether true solvent memory effects can be achieved by molecular imprinting, as well as if they are stable at elevated temperature. A set of copolymers, comprising low and high cross-linking levels, was prepared from four different combinations of functional monomer and cross-linker, namely methacrylic acid (MAA)/ethylene glycol dimethacrylate (EGDMA), methyl methacrylate (MMA)/EGDMA, MAA/divinyl benzene (DVB) and MMA/DVB. Each possible combination was prepared separately in benzene, toluene and acetonitrile. The obtained materials were applied as coatings onto nickel-titanium (Ni-Ti) alloy wires which were incorporated into solid-phase microextraction devices and finally tested for their ability to competitively adsorb vapors from the headspace of an aqueous solution containing a few volatile organic compounds. Porosity analysis showed that, regardless of the solvent used, only a high cross-linking level permitted the preparation of mesoporous copolymers (BJH radius typically in the range 13-15 nm), a requirement for providing accessibility to the targeted nanoscale-imprinted cavities. A noticeable exception was, however, observed for the MMA/DVB copolymers which exhibited much diminished BJH radius. The porosity data correlated well with the extraction profiles found, which suggested the presence of benzene-imprinted sites in all the highly cross-linked copolymers prepared in benzene, except for the MMA/DVB copolymers. Concerning the effect of an elevated conditioning temperature on the memory-effects created by the imprinting process, the results were clearly indicative that the tested copolymers, including the more robust highly cross-linked ones, are not suitable for high temperature applications such as solid-phase microextraction coupled to gas chromatography. PMID:24176503

Azenha, Manuel; Schillinger, Eric; Sanmartin, Esther; Regueiras, M Teresa; Silva, Fernando; Sellergren, Börje

2013-11-13

70

Determination of Benzene, Toluene and Xylene (BTX) Concentrations in Air Using HPLC Developed Method Compared to Gas Chromatography  

OpenAIRE

A new method for analysis of benzene, toluene, and xylene (BTX) using High Performance Liquid Chromatography-UV detection (HPLC-UV) is described and compared to the gas chromatography (GC) method. A charcoal adsorption tube connected to a small pump was used to obtain samples from an atmosphere chamber standard. Samples were extracted with methanol and analyzed by HPLC-UV. Chromatography was isocratic in a mobile phase consisting of water-methanol (30-70). The flow rate was set at 1 ml/min. T...

Abdulrahman Bahrami; Hosien Mahjub; Marzieh Sadeghian; Farideh Golbabaei

2011-01-01

71

Comparative study of the effects of toluene, benzene, 1,1,1-trichloroethane, diethyl ether, and flurothyl on anxiety and nociception in mice  

International Nuclear Information System (INIS)

The main purpose of this study was to compare the effects of solvents from different chemical classes on anxiety and nociception. Independent groups of mice were exposed to air (control group), toluene (1000-4000 ppm), benzene (1000-4000 ppm), 1,1,1-trichloroethane (TCE, 2000-12000 ppm), diethyl ether (10,000-30,000) or flurothyl (200-600 ppm). After a 30-min exposure, animals were tested either in the anxiety paradigm conditioned defensive burying (CDB) test or in the hot plate test. All solvents but flurothyl produced anxiolytic-like actions being the order of potency toluene > benzene > TCE > diethyl ether. When tested in the hot plate paradigm, toluene and TCE increased nociception, benzene and diethyl ether had no effects, and flurothyl decreased nociception Additional groups of mice were conditioned to recognize the aversive stimulus (electrified prod) prior to toluene exposure and then tested in the CDB test. In unconditioned animals, toluene increased the number of shocks that mice received; however, when mice had previous experience in the CDB test, toluene lacked this effect. Taken together, these results show that inhalants have different effects with different potencies both in the CDB and in the hot plate tests. Additionally, data suggest that acute administration of toluene could impair learning

72

Health Risk Assessment of Ambient Air Concentrations of Benzene, Toluene and Xylene (BTX in Service Station Environments  

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Full Text Available A comprehensive evaluation of the adverse health effects of human exposures to BTX from service station emissions was carried out using BTX exposure data from the scientific literature. The data was grouped into different scenarios based on activity, location and occupation and plotted as Cumulative Probability Distributions (CPD plots. Health risk was evaluated for each scenario using the Hazard Quotient (HQ at 50% (CEXP50 and 95% (CEXP95 exposure levels. HQ50 and HQ95 > 1 were obtained with benzene in the scenario for service station attendants and mechanics repairing petrol dispensing pumps indicating a possible health risk. The risk was minimized for service stations using vapour recovery systems which greatly reduced the benzene exposure levels. HQ50 and HQ95 < 1 were obtained for all other scenarios with benzene suggesting minimal risk for most of the exposed population. However, HQ50 and HQ95 < 1 was also found with toluene and xylene for all scenarios, suggesting minimal health risk. The lifetime excess Cancer Risk (CR and Overall Risk Probability for cancer on exposure to benzene was calculated for all Scenarios and this was higher amongst service station attendants than any other scenario.

Benjamin Edokpolo

2014-06-01

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Health risk assessment of ambient air concentrations of benzene, toluene and xylene (BTX) in service station environments.  

Science.gov (United States)

A comprehensive evaluation of the adverse health effects of human exposures to BTX from service station emissions was carried out using BTX exposure data from the scientific literature. The data was grouped into different scenarios based on activity, location and occupation and plotted as Cumulative Probability Distributions (CPD) plots. Health risk was evaluated for each scenario using the Hazard Quotient (HQ) at 50% (CEXP50) and 95% (CEXP95) exposure levels. HQ50 and HQ95 > 1 were obtained with benzene in the scenario for service station attendants and mechanics repairing petrol dispensing pumps indicating a possible health risk. The risk was minimized for service stations using vapour recovery systems which greatly reduced the benzene exposure levels. HQ50 and HQ95 < 1 were obtained for all other scenarios with benzene suggesting minimal risk for most of the exposed population. However, HQ50 and HQ95 < 1 was also found with toluene and xylene for all scenarios, suggesting minimal health risk. The lifetime excess Cancer Risk (CR) and Overall Risk Probability for cancer on exposure to benzene was calculated for all Scenarios and this was higher amongst service station attendants than any other scenario. PMID:24945191

Edokpolo, Benjamin; Yu, Qiming Jimmy; Connell, Des

2014-06-01

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Tar removal from biosyngas in the biomass gasification process. (Liquid + liquid) equilibrium {water + solvent (paraxylene and methyl hexadecanoate) + model molecules of tar (benzene, toluene, phenol)}  

International Nuclear Information System (INIS)

Highlights: ? (Liquid + liquid) equilibria at atmospheric pressure. ? Solubility of benzene (or toluene or phenol) in paraxylene at (303 to 343) K. ? Solubility of benzene (or toluene or phenol) in methyl palmitate or methyl hexadecanoate at (303 to 343) K. ? Correlation of LLE using NRTL model. - Abstract: Tar is generated in the process by the condensation of the gas resulting from biomass gasification. The objective of this work is a contribution to the database on thermodynamic quantity which will be useful at the operation of tar removal from aqueous medium. With this aim, (liquid + liquid) equilibrium of {water + solvent (paraxylene and methyl hexadecanoate) + model molecules of tar (benzene, toluene, phenol)} was studied at temperatures (303.2, 323.2, and 343.2) K. The data obtained were correlated with the non-random two-liquid (NRTL) model.

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A chromosomally based tod-luxCDABE whole-cell reporter for benzene, toluene, ethybenzene, and xylene (BTEX) sensing  

International Nuclear Information System (INIS)

A tod-luxCDABE fusion was constructed and introduced into the chromosome of Pseudomonas putida F1, yielding the strain TVA8. This strain was used to examine the induction of the tod operon when exposed to benzene, toluene, ethylbenzene, and xylene (BTEX) compounds and aqueous solutions of JP-4 jet fuel constituents. Since this system contained the complete lux cassette (luxCDABE), bacterial bioluminescence in response to putative chemical inducers of the tod operon was measured on-line in whole cells without added aldehyde substrate. There was an increasing response to toluene concentrations from 30 microg/liter to 50 mg/liter, which began to saturate at higher concentrations. The detection limit was 30 microg/liter. There was a significant light response to benzene, m- and p-xylenes, phenol, and water-soluble JP-4 jet fuel components, but there was no bioluminescence response upon exposure to o-xylene. The transposon insertion was stable and had no negative effect on cell growth

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Electrodeposited ZnO/ Zn Photo catalysts for the Degradation of Benzene-Toluene-Xylene Mixture in Aqueous Phase  

International Nuclear Information System (INIS)

The recognition of the ability of volatile organic compounds, (VOCs) to pollute the ground water is now well documented. VOCs such as benzene, toluene and xylene from the petroleum industries processed water leaked through the underground old piping system into the soils and groundwater during its transportation to the wastewater plant. Photo catalysis have been used as a potential system in the degradation of VOCs in the wastewater. However, the powdered form photo catalysts that were used in various studies are difficult to be separated from the aqueous solution at the end of the treatment. Therefore, the main objective of this research is to prepare the electrodeposited photo catalysts for the degradation of aromatic hydrocarbon mixture, benzene-toluene-xylene (BTX) solution under UV light (354 nm). The concentrations of electrolyte and electrodeposition voltages used to prepare the photo catalysts were studied for their efficiency in the degradation. From the research, ZnO/ Zn prepared in 0.8 M NaOH and under 12 V possessed the best catalytic degradation performance by degrading 32.37 % of BTX in the solution. The ZnO/ Zn photo catalyst was characterized using X-ray Diffraction Techniques (XRD) which illustrated high crystallinity of Zn species and reasonably high amorphous phase of ZnO species. (author)

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Evaluation of seawater contamination with benzene, toluene and xylene in EHE Ubatuba Region and study of their degradation by ionizing radiation  

International Nuclear Information System (INIS)

A major concern with leaking petroleum is the environmental contamination by toxic and low water-soluble components such as benzene, toluene, and xylenes (BTX). These hydrocarbons have relatively high pollution potential because of their significant toxicity. The objective of this study was to evaluate the contamination of seawater by the main pollutants of the output and transport of petroleum, such as benzene, toluene, and xylenes, and their removal by exposure to ionizing radiation. The studied region was Ubatuba region, SP, between 23 deg 26'S and 23 deg 46' S of latitude and 45 deg 02' W and 45 deg 11' W of longitude, area of carry and output of petroleum, and samples were collected from November, 2003 to July, 2005. For BTX in seawater analysis, the Purge and Trap concentrator with FIDGC detector showed significantly higher sensibility than headspace concentrator with MSGC detector. The minimal detected limits (MDL) obtained at FIDGC were of 0.50 ?g/L for benzene, 0.70 /L for toluene, and 1.54 /L for xylenes, and the obtained experimental variability was 15%. While the concentrator type Headspace system with MS detector showed higher MDL, about of 9.30 mg/L for benzene, 8.50 mg/L for toluene, and 9.80 mg/L for xylenes, and 10% of experimental variability. In the studied area the benzene concentration varied from 1.0 ?g/L to 2.0 ?g/L, the concentration of toluene varied from 60Co. The results showed a removal from 10% to 40% of benzene at 20 kGy absorbed doses and concentration of 35.1 mg/L and 70.2 mg/L, respectively. For toluene the removal were from 20% to 60% with 15 kGy and xylenes were removed from 20% to 80% with 15 kGy and similar concentrations. (author)

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Effective ligand functionalization of zirconium-based metal-organic frameworks for the adsorption and separation of benzene and toluene: a multiscale computational study.  

Science.gov (United States)

The adsorption and separation properties of benzene and toluene on the zirconium-based frameworks UiO-66, -67, -68, and their functional analogues UiO-Phe and UiO-Me2 were studied using grand canonical Monte Carlo simulations, density functional theory, and ideal adsorbed solution theory. Remarkable higher adsorption uptakes of benzene and toluene at low pressures on UiO-Phe and -Me2 were found compared to their parent framework UiO-67. It can be ascribed to the presence of functional groups (aromatic rings and methyl groups) that significantly intensified the adsorption, majorly by reducing the effective pore size and increasing the interaction strength with the adsorbates. At high pressures, the pore volumes and accessible surfaces of the frameworks turned out to be the dominant factors governing the adsorption. In the case of toluene/benzene separation, toluene selectivities of UiOs showed a two-stage separation behavior at the measured pressure range, resulting from the greater interaction affinities of toluene at low pressures and steric hindrance effects at high pressures. Additionally, the counterbalancing factors of enhanced ? delocalization and suitable pore size of UiO-Phe gave rise to the highest toluene selectivity, suggesting the ligand functionalization strategy could reach both high adsorption capacity and separation selectivity from aromatic mixtures at low concentrations. PMID:25700143

Wu, Ying; Chen, Huiyong; Liu, Defei; Xiao, Jing; Qian, Yu; Xi, Hongxia

2015-03-18

79

Assessment of genotoxicity of methyl-tert-butyl ether, benzene, toluene, ethylbenzene, and xylene to human lymphocytes using comet assay  

International Nuclear Information System (INIS)

Methyl-tert-butyl ether (MTBE) is a gasoline oxygenate and antiknock additive substituting for lead alkyls currently in use worldwide. Benzene, toluene, ethylbenzene, and xylene (BTEX) are volatile monoaromatic hydrocarbons which are commonly found together in crude petroleum and petroleum products such as gasoline. The aim of this study is to evaluate the genotoxic effects of these tested chemicals in human lymphocytes. Using the alkaline comet assay, we showed that all of the tested chemicals induce DNA damage in isolated human lymphocytes. This effect could follow from the induction of DNA strands breaks. The neutral version of the test revealed that MTBE, benzene, and xylenes induce DNA double-strand breaks at 200 ?M. Apart from MTBE, the spin traps, 5,5-dimethyl-pyrroline-N-oxide (DMPO) and N-tert-butyl-?-phenylnitrone (PBN) can decrease the level of DNA damage in BTEX at 200 ?M. This indicated that DNA damage could result from the participation of free radicals in DNA-damaging effect, which was further supported by the fact that post-treatment of formamidopyrimidine-DNA glycosylase (Fpg), enzyme recognizing oxidized DNA purines, gave rise to a significant increase in the extent of DNA damage in cells treated with benzene, and xylene at 200 ?M. The results obtained suggested that MTBE and BTEX could induce a variety type of DNA damage such as single-strand breaks (SSBs), double-strand breaks (DSBs), and oxidative base modificationification

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Spatial variability in levels of benzene, formaldehyde, and total benzene, toluene, ethylbenzene and xylenes in New York City: a land-use regression study  

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Full Text Available Abstract Background Hazardous air pollutant exposures are common in urban areas contributing to increased risk of cancer and other adverse health outcomes. While recent analyses indicate that New York City residents experience significantly higher cancer risks attributable to hazardous air pollutant exposures than the United States as a whole, limited data exist to assess intra-urban variability in air toxics exposures. Methods To assess intra-urban spatial variability in exposures to common hazardous air pollutants, street-level air sampling for volatile organic compounds and aldehydes was conducted at 70 sites throughout New York City during the spring of 2011. Land-use regression models were developed using a subset of 59 sites and validated against the remaining 11 sites to describe the relationship between concentrations of benzene, total BTEX (benzene, toluene, ethylbenzene, xylenes and formaldehyde to indicators of local sources, adjusting for temporal variation. Results Total BTEX levels exhibited the most spatial variability, followed by benzene and formaldehyde (coefficient of variation of temporally adjusted measurements of 0.57, 0.35, 0.22, respectively. Total roadway length within 100?m, traffic signal density within 400?m of monitoring sites, and an indicator of temporal variation explained 65% of the total variability in benzene while 70% of the total variability in BTEX was accounted for by traffic signal density within 450?m, density of permitted solvent-use industries within 500?m, and an indicator of temporal variation. Measures of temporal variation, traffic signal density within 400?m, road length within 100?m, and interior building area within 100?m (indicator of heating fuel combustion predicted 83% of the total variability of formaldehyde. The models built with the modeling subset were found to predict concentrations well, predicting 62% to 68% of monitored values at validation sites. Conclusions Traffic and point source emissions cause substantial variation in street-level exposures to common toxic volatile organic compounds in New York City. Land-use regression models were successfully developed for benzene, formaldehyde, and total BTEX using spatial indicators of on-road vehicle emissions and emissions from stationary sources. These estimates will improve the understanding of health effects of individual pollutants in complex urban pollutant mixtures and inform local air quality improvement efforts that reduce disparities in exposure.

Kheirbek Iyad

2012-07-01

81

Human urine certified reference material CZ 6010: creatinine and toluene metabolites (hippuric acid and o-cresol) and a benzene metabolite (phenol).  

Czech Academy of Sciences Publication Activity Database

Ro?. 387, ?. 7 (2007), s. 2419-2424. ISSN 1618-2642 Institutional research plan: CEZ:AV0Z10480505 Keywords : toluene metabolites * benzene metabolite * human urine Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 2.867, year: 2007

Šperlingová, I.; Dabrowská, L.; Stránský, V.; Ku?era, Jan; Tichý, M.

2007-01-01

82

Dynamics of an Oligotrophic Bacterial Aquifer Community during Contact with a Groundwater Plume Contaminated with Benzene, Toluene, Ethylbenzene, and Xylenes: an In Situ Mesocosm Study.  

Czech Academy of Sciences Publication Activity Database

Ro?. 71, ?. 7 (2005), s. 3815-3825. ISSN 0099-2240 Grant ostatní: European Commission(XE) QLK3-CT2000-0031 Institutional research plan: CEZ:AV0Z50200510 Keywords : oligotrophic bacterial * benzene * toluene Subject RIV: EE - Microbiology, Virology Impact factor: 3.818, year: 2005

Hendrickx, B.; Dejonghe, W.; Boenne, W.; Brennerová, Mária; ?erník, M.; Lederer, T.; Bucheli-Vitschel, M.; Bastiaens, L.; Verstraete, W.; Top, E.M.; Diels, L.; Springael, D.

2005-01-01

83

Experimental and theoretical study of surface tension of binary mixtures of (n-alkyl acetates + heptane, benzene, and toluene)  

International Nuclear Information System (INIS)

Surface properties of binary mixtures of (n-alkyl acetates + heptane, benzene, and toluene) have been measured by surface tension method at T = 298.15 K and atmospheric pressure. Also, the surface tension has been predicted based on the Suarez method. This method combines a model for the description of surface tension of liquid mixtures with a group contribution method for the calculation of activity coefficient. The mean relative standard deviations obtained from the comparison of experimental (measured) and calculated surface tension values for the eight binary systems are less than 1.5%, which leads to concluding that the model shows a good accuracy in different situations in comparison with other predicted equations. In addition, the relative Gibbs adsorption and the surface mole fraction have been evaluated using this model. The surface tension deviations were calculated from experimental results and have been fitted to the Redlich-Kister type polynomial relation

84

Ceria Zirconia Mixed Oxides Prepared by Hydrothermal Templating Method for the Oxidation of Ethyl Benzene  

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Full Text Available CeO2–ZrO2 oxides were prepared by the surfactant-templated method using cetyl trimethyl ammonium bromide (CTAB as template. These were characterized by XRD, FT-IR, TEM, SEM, BET and TPD-CO2. The XRD data showed that as prepared CeO2-ZrO2 powder particles have single phase cubic fluorite structure. HRTEM shows mesoscopic ordering. Average particle size is 12-13 nm as calculated from particle histogram. The nitrogen adsorption/desorption isotherm were classified to be type IV isotherm, typical of mesoporous material. The presence of uni-modal mesopores are confirmed by the pore size distribution which shows pore distribution at around 60 A°. The catalytic activities of the prepared material were tested in liquid phase oxidation of ethylbenzene with tert-butyl hydroperoxide (TBHP as an oxidant. Ceria zirconia catalyst modified with chromium was active for ethylbenzene conversion (65.3% with 77% selectivity towards acetophenone.  © 2013 BCREC UNDIP. All rights reservedReceived: 4th June 2013; Revised: 20th July 2013; Accepted: 18th August 2013[How to Cite: Daniel, C.A., Sugunan, S. (2013. Ceria Zirconia Mixed Oxides Prepared by Hydrothermal Templating Method for the Oxidation of Ethyl Benzene. Bulletin of Chemical Reaction Engineering & Catalysis, 8 (2: 97-104. (doi:10.9767/bcrec.8.2.5053.97-104][Permalink/DOI: http://dx.doi.org/10.9767/bcrec.8.2.5053.97-104

Cimi A Daniel

2013-12-01

85

Effects of co-exposure of benzene, toluene and xylene to Drosophila melanogaster: alteration in hsp70, hsp60, hsp83, hsp26, ROS generation and oxidative stress markers.  

Science.gov (United States)

Benzene, toluene and xylene are monocyclic aromatic hydrocarbon compounds, used both as individual compound and as mixtures, in industry as well as household. Previous studies involving exposures to these compounds, individually, have shown that benzene was more toxic compared to toluene or xylene. Here, we tested a working hypothesis that toluene and/or xylene in a mixture containing benzene affect benzene induced toxicity in a non-target organism, Drosophila melanogaster. We exposed D. melanogaster larvae transgenic for hsp70, hsp83 or hsp26 and wild type (Oregon R strain) larvae to 25.0-100.0mM benzene, 25.0-100.0mM toluene and 25.0-100mM xylene, individually or in mixtures. Subsequently, we examined the expression of stress genes (encoding heat shock proteins, hsps), generation of reactive oxygen species (ROS), induction of anti-oxidant stress markers and emergence of flies under treatment as well as control conditions. We observed that all these endpoints were significantly altered in all the treatment groups compared to their respective controls. However, the magnitude of toxicity of a benzene-toluene (BT) or benzene-xylene (BX) or benzene-toluene-xylene (BTX) mixture was significantly lower in the organism than that of individual chemical. Our results also show the modulation of toluene toxicity by xylene. Present study suggests antagonistic effect of xylene and toluene on benzene toxicity and additive/synergistic effect of xylene on toluene induced toxicity. Thus, expression of stress genes may be used as an assay for detection of early cellular toxicity. Further, our study supports the use of Drosophila as an alternative animal model for first tier screening of adverse effects of chemical mixtures. PMID:20188393

Singh, Mahendra Pratap; Ram, K Ravi; Mishra, M; Shrivastava, M; Saxena, D K; Chowdhuri, D Kar

2010-04-01

86

Optimization of SPE for Analysis of Mandelic Acid as a Biomarker of Exposure to Ethyl Benzene  

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Full Text Available Ethyl benzene is an important constituent of widely used solvents in industries and laboratories, causing widespread environmental and industrial pollutions. For evaluation of occupational exposure to such pollutants, biological monitoring is an essential process, in which, preparation of environmental and biological samples is one of the most time-consuming and error-prone aspects prior to chromatographic techniques. The use of solid-phase extraction (SPE has been grown and is a fertile technique of sample preparation as it provides better results than those of liquid-liquid extraction (LLE. In this study, SPE using bonded silica has been optimized with regard to sample pH, sample concentration, elution solvent, elution volume, sorbent type, and sorbent mass. Through experimental evaluation, a strong anion exchange silica cartridge (SAX has been found successful in simplifying sample preparation. The present approach proved that, mandelic acid could be retained on SAX sorbent based on specific interaction. Further study was employed using 10% acetic acid to extract the analyte from spiked urine and gave a clean sample for HPLC-UV system. In this study, a high performance liquid chromatography, using reverse-phase column was used. The isocratic run was done at a constant flow rate of 0.85 ml/min, the mobile phase was water/methanol/acetic acid and a UV detector was used, setting at 225 nm. At the developed conditions the extraction recovery was exceeded 98%. The factors were evaluated statically and also validated with three different pools of spiked urine samples and showed a good reproducibility over six consecutive days as well as six within-day experiments.

SJ Shahtaheri, M Abdollahi, F Golbabaei, A Rahimi-Froushani, F Ghamari

2004-10-01

87

Modeling annual benzene, toluene, NO2, and soot concentrations on the basis of road traffic characteristics  

International Nuclear Information System (INIS)

The investigation of potential adverse health effects of urban traffic-related air pollution is hampered by difficulties encountered with exposure assessment. Usually public measuring sites are few and thereby do not adequately describe spatial variation of pollutant levels over an urban area. In turn, individual monitoring of pollution exposure among study subjects is laborious and expensive. We therefore investigated whether traffic characteristics can be used to adequately predict benzene, NO2, and soot concentrations at individual addresses of study subjects in the city area of Munich, Germany. For all road segments with expected traffic volumes of at least 4000 vehicles a day (n=1840), all vehicles were counted manually or a single weekday in 1995. The proportion of vehicles in 'stop-go' mode, n estimate of traffic jam, was determined. Furthermore, annual concentrations of benzene, NO2, and soot from 18 high-concentration sites means: 8.7, 65.8, and 12.9 ?g/m3, respectively) and from 16 school sites with moderate concentrations (means: 2.6, 32.2, and 5.7 ?g/m3, respectively) were measured from 1996 to 1998. Statistical analysis of the data was performed using components of two different statistical models recently used to predict air pollution levels in comparable settings. Two traffic characteristics, traffic volume and traffic jam percentage, adequately described air pollutant concentrations (R2: 0.76-0.8 concentrations (R2: 0.76-0.80, P=0.0001). This study shows that air pollutant concentrations can be accurately predicted by two traffic characteristics and that these models compare favorably with other more complex models in the literature

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The effect of the potential fuel additive isobutanol on benzene, toluene, ethylbenzene, and p-xylene degradation in aerobic soil microcosms.  

Science.gov (United States)

Isobutanol is being considered as a fuel additive; however, the effect of this chemical on gasoline degradation (following a spill) has yet to be fully explored. To address this, the current study investigated the effect of isobutanol on benzene, toluene, ethylbenzene and p-xylene (BTEX) degradation in 14 sets of experiments in saturated soils. This involved four hydrocarbons for three soils (12 experiments) and two extra experiments with a lower level of isobutanol (for toluene only). Each soil and hydrocarbon combination involved four abiotic control microcosms and 12 sample microcosms (six with and six without isobutanol). The time for complete degradation of each hydrocarbon varied between treatments. Both toluene and ethylbenzene were rapidly degraded (5-13 days for toluene and 3-13 days for ethylbenzene). In contrast, the time for complete degradation for benzene ranged from 5 to 47 days. The hydrocarbon p-xylene was the most recalcitrant chemical (time for removal ranged from 14 to 86 days) and, in several microcosms, no p-xylene degradation was observed. The effect of isobutanol on hydrocarbon degradation was determined by comparing degradation lag times with and without isobutanol addition. From the 14 treatments, isobutanol only affected degradation lag times in three cases. In two cases (benzene and p-xylene), an enhancement of degradation (reduced lag times) was observed in the presence of isobutanol. In contrast, toluene degradation in one soil was inhibited (increased lag time). These results indicate that co-contamination with isobutanol should not inhibit aerobic BTEX degradation rates. PMID:25413118

Ding, Liang; Cupples, Alison M

2015-01-01

89

Complete Genome Sequences of Pseudomonas monteilii SB3078 and SB3101, Two Benzene-, Toluene-, and Ethylbenzene-Degrading Bacteria Used for Bioaugmentation  

Science.gov (United States)

Pseudomonas monteilii SB3078 and SB3101 are benzene-, toluene-, and ethylbenzene-degrading strains used for bioaugmentation in relation to treatment of wastewater contaminated with petrochemical hydrocarbons. Complete genome sequencing of the bioaugmentation strains confirms that they are very closely related (100.0% average nucleotide identity). Both strains contain extensive integration of phage elements, with the main difference being insertion of additional phage elements in the SB3078 genome. PMID:24874689

Albertsen, Mads; D’Imperio, Seth; Tale, Vaibhav P.; Lewis, Derrick; Nielsen, Per Halkjær; Nielsen, Jeppe Lund

2014-01-01

90

Biodegradation Kinetics of Tetrahydrofuran, Benzene, Toluene, and Ethylbenzene as Multi-substrate by Pseudomonas oleovorans DT4  

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Full Text Available The biodegradation kinetics of tetrahydrofuran, benzene (B, toluene (T, and ethylbenzene (E were systematically investigated individually and as mixtures by a series of aerobic batch degradation experiments initiated by Pseudomonas oleovorans DT4. The Andrews model parameters, e.g., maximum specific growth rates (?max, half saturation, and substrate inhibition constant, were obtained from single-substrate experiments. The interaction parameters in the sum kinetics model (SKIP were obtained from the dual substrates. The ?max value of 1.01 for tetrahydrofuran indicated that cell growth using tetrahydrofuran as carbon source was faster than the growth on B (?max, B = 0.39 or T (?max, T = 0.39. The interactions in the dual-substrate experiments, including genhancement, inhibition, and co-metabolism, in the mixtures of tetrahydrofuran with B or T or E were identified. The degradation of the four compounds existing simultaneously could be predicted by the combination of SKIP and co-metabolism models. This study is the first to quantify the interactions between tetrahydrofuran and BTE.

Dong-Zhi Chen

2014-12-01

91

Rapid intrinsic biodegradation of benzene, toluene, and xylenes at the boundary of a gasoline-contaminated plume under natural attenuation.  

Science.gov (United States)

A groundwater plume contaminated with gasoline constituents [mainly benzene, toluene, and xylenes (BTX)] had been treated by pumping and aeration for approximately 10 years, and the treatment strategy was recently changed to monitored natural attenuation (MNA). To gain information on the feasibility of using MNA to control the spread of BTX, chemical and microbiological parameters in groundwater samples obtained inside and outside the contaminated plume were measured over the course of 73 weeks. The depletion of electron acceptors (i.e., dissolved oxygen, nitrate, and sulfate) and increase of soluble iron were observed in the contaminated zone. Laboratory incubation tests revealed that groundwater obtained immediately outside the contaminated zone (the boundary zone) exhibited much higher potential for BTX degradation than those in the contaminated zone and in uncontaminated background zones. The boundary zone was a former contaminated area where BTX were no longer detected. Denaturing gradient gel electrophoresis (DGGE) analysis of polymerase chain reaction (PCR)-amplified bacterial 16S rRNA gene fragments revealed that DGGE profiles for groundwater samples obtained from the contaminated zone were clustered together and distinct from those from uncontaminated zones. In addition, unique bacterial rRNA types were observed in the boundary zone. These results indicate that the boundary zone in the contaminant plumes served as a natural barrier for preventing the BTX contamination from spreading out. PMID:16957896

Takahata, Yoh; Kasai, Yuki; Hoaki, Toshihiro; Watanabe, Kazuya

2006-12-01

92

Biodegradation kinetics of benzene and toluene as single and mixed substrate: estimation of biokinetics parameters by applying particle swarm optimization  

Scientific Electronic Library Online (English)

Full Text Available This paper aims to describe the microbial biodegradation kinetics of benzene and toluene as single and mixed substrates. Particle Swarm Optimization (PSO) is used as the parameter identification procedure. Initially, the Monod and Andrews models were used. To predict the interactions between the sub [...] strates, more sophisticated models of inhibition and the SKIP model were applied. The development of the changes on the competitive inhibition model was also described. The models were evaluated using experimental data on Pseudomonas putida F1 activity found in the literature. Simulation results showed that the best description of the biodegradation process of a pure substrate can be achieved by the Andrews model and in the case of a mixture by the modified competitive inhibition model. These results were expected because both substrates are catabolized by the same metabolic pathway through Pseudomonas putida F1. The SKIP model also captured the substrate interactions well. The performance of PSO was excellent and the methodology developed in this work can be considered as very efficient.

D.E.G., Trigueros; A.N., Módenes; M.A.S.S., Ravagnani.

2010-07-01

93

Determination of Benzene, Toluene and Xylene (BTX Concentrations in Air Using HPLC Developed Method Compared to Gas Chromatography  

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Full Text Available A new method for analysis of benzene, toluene, and xylene (BTX using High Performance Liquid Chromatography-UV detection (HPLC-UV is described and compared to the gas chromatography (GC method. A charcoal adsorption tube connected to a small pump was used to obtain samples from an atmosphere chamber standard. Samples were extracted with methanol and analyzed by HPLC-UV. Chromatography was isocratic in a mobile phase consisting of water-methanol (30-70. The flow rate was set at 1 ml/min. The analyses were completely separated and were quantified using both methods. The results demonstrated no statistically significant differences between BTX concentrations between the two analytical methods with a correlation coefficient of 0.98-0.99. The GC method provided higher sensitivity than HPLC, but the HPLC determination of BTX were applicable to real samples because its sensivity was lower than the thershold limit recommended by the American Conference of Governmental Industrial Hygienist (ACGIH for an 8-hour workday.

Abdulrahman Bahrami

2011-01-01

94

Biodegradation and transport of benzene, toluene, and xylenes in a simulated aquifer: comparison of modelled and experimental results  

Science.gov (United States)

Both laboratory experiments and numerical modelling were conducted to study the biodegradation and transport of benzene-toluene-xylenes (BTX) in a simulated semi-confined aquifer. The factors incorporated into the numerical model include advection, hydrodynamic dispersion, adsorption, and biodegradation. The various physico-chemical parameters required by the numerical model were measured experimentally.In the experimental portion of the study, BTX compounds were introduced into the aquifer sand. After the contaminants had been transported through the system, BTX concentrations were measured at 12 equally spaced wells. Subsequently, microorganisms obtained from the activated sludge of a sewage treatment plant and cultured in BTX mixtures were introduced into the aquifer through the 12 sampling wells. The distribution data for BTX adsorption by the aquifer sand form a nonlinear isotherm. The degree of adsorption by the sand varies, depending on the composition of the solute. The degradation time, measured from the time since the bacteria were added to the aquifer until a specific contaminant was no longer detectable, was 35-42 h for BTX. The dissolved oxygen, after degradation by BTX compounds and bacteria, was consumed by about 40-60% in the entire simulated aquifer; thus the aerobic conditions were maintained. This study provides insights for the biodegradation and transport of BTX in aquifers by numerical modelling and laboratory experiments. Experimental and numerical comparisons indicate that the results by Monod degradation kinetics are more accurate than those by the first-order degradation kinetics.

Jean, Jiin-Shuh; Tsai, Ching-Lang; Ju, Shen-Haw; Tsao, Chun-Wen; Wang, Shih-Ming

2002-11-01

95

Transgenic plants of Petunia hybrida harboring the CYP2E1 gene efficiently remove benzene and toluene pollutants and improve resistance to formaldehyde  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english The CYP2E1 protein belongs to the P450 enzymes family and plays an important role in the metabolism of small molecular and organic pollutants. In this study we generated CYP2E1 transgenic plants of Petunia using Agrobacterium rhizogenes K599. PCR analysis confirmed that the regenerated plants contai [...] ned the CYP2E1 transgene and the rolB gene of the Ri plasmid. Southern blotting revealed the presence of multiple copies of CYP2E1 in the genome of transgenic plants. Fluorescent quantitative PCR revealed exogenous CYP2E1 gene expression in CYP2E1 transgenic plants at various levels, whereas no like expression was detected in either GUS transgenic plants or wild-types. The absorption of benzene and toluene by transgenic plants was analyzed through quantitative gas chromatography. Transgenic plants with high CYP2E1 expression showed a significant increase in absorption capacity of environmental benzene and toluene, compared to control GUS transgenic and wild type plants. Furthermore, these plants also presented obvious improved resistance to formaldehyde. This study, besides being the first to reveal that the CYP2E1 gene enhances plant resistance to formaldehyde, also furnishes a new method for reducing pollutants, such as benzene, toluene and formaldehyde, by using transgenic flowering horticultural plants.

Daoxiang, Zhang; Taihe, Xiang; Li, Peihan; Lumin, Bao.

96

Hollow fiber supported liquid-phase microextraction using ionic liquid as extractant for preconcentration of benzene, toluene, ethylbenzene and xylenes from water sample with gas chromatography-hydrogen flame ionization detection.  

Science.gov (United States)

A novel method has been developed for the analysis of benzene, toluene, ethyl-benzene, and o-, m- and p-xylenes (BTEXs) in water using hollow fiber supported liquid-phase microextraction (HF-LPME) followed by gas chromatography-hydrogen flame ionization detection. Ionic liquid 1-butyl-3-methy-limidazolium hexafluorophosphate ([BMIM][PF(6)]) was acted as the extractant for extraction and preconcentration of BTEXs from aqueous samples, and a porous-walled polypropylene hollow fiber was utilized to stabilize and protect [BMIM][PF(6)] during the extraction process. Various parameters that affect extraction efficiency were investigated in detail, and the optimized experimental conditions were as follows: 8 ?L of [BMIM][PF(6)] as extraction solvent for the target analytes in 20 mL of sample solution, 30 min of extraction time, a stirring rate of 1400 rpm and 15% NaCl (w/v) in aqueous sample at 25°C (ambient temperature). The recovery was found to be 90.0-111.5% with RSD (n=5) of 1.3-5.4%, and the detection limits (S/N=3) were in the range of 2.7-4.0 ?g/L. The proposed method was simple, cheap, rapid, sensitive and environmentally benign, and could act as an alternative to techniques for BTEXs analysis with expensive instrumentations. PMID:21871732

Ma, Xiaoguo; Huang, Minghua; Li, Zhihua; Wu, Jianmei

2011-10-30

97

Oxidation of benzene to phenol, catechol, and 1,2,3-trihydroxybenzene by toluene 4-monooxygenase of Pseudomonas mendocina KR1 and toluene 3-monooxygenase of Ralstonia pickettii PKO1.  

Science.gov (United States)

Aromatic hydroxylations are important bacterial metabolic processes but are difficult to perform using traditional chemical synthesis, so to use a biological catalyst to convert the priority pollutant benzene into industrially relevant intermediates, benzene oxidation was investigated. It was discovered that toluene 4-monooxygenase (T4MO) of Pseudomonas mendocina KR1, toluene 3-monooxygenase (T3MO) of Ralstonia pickettii PKO1, and toluene ortho-monooxygenase (TOM) of Burkholderia cepacia G4 convert benzene to phenol, catechol, and 1,2,3-trihydroxybenzene by successive hydroxylations. At a concentration of 165 microM and under the control of a constitutive lac promoter, Escherichia coli TG1/pBS(Kan)T4MO expressing T4MO formed phenol from benzene at 19 +/- 1.6 nmol/min/mg of protein, catechol from phenol at 13.6 +/- 0.3 nmol/min/mg of protein, and 1,2,3-trihydroxybenzene from catechol at 2.5 +/- 0.5nmol/min/mg of protein. The catechol and 1,2,3-trihydroxybenzene products were identified by both high-pressure liquid chromatography and mass spectrometry. When analogous plasmid constructs were used, E. coli TG1/pBS(Kan)T3MO expressing T3MO formed phenol, catechol, and 1,2,3-trihydroxybenzene at rates of 3 +/- 1, 3.1 +/- 0.3, and 0.26 +/- 0.09 nmol/min/mg of protein, respectively, and E. coli TG1/pBS(Kan)TOM expressing TOM formed 1,2,3-trihydroxybenzene at a rate of 1.7 +/- 0.3 nmol/min/mg of protein (phenol and catechol formation rates were 0.89 +/- 0.07 and 1.5 +/- 0.3 nmol/min/mg of protein, respectively). Hence, the rates of synthesis of catechol by both T3MO and T4MO and the 1,2,3-trihydroxybenzene formation rate by TOM were found to be comparable to the rates of oxidation of the natural substrate toluene for these enzymes (10.0 +/- 0.8, 4.0 +/- 0.6, and 2.4 +/- 0.3 nmol/min/mg of protein for T4MO, T3MO, and TOM, respectively, at a toluene concentration of 165 microM). PMID:15240250

Tao, Ying; Fishman, Ayelet; Bentley, William E; Wood, Thomas K

2004-07-01

98

Biomass fuels and coke plants are important sources of human exposure to polycyclic aromatic hydrocarbons, benzene and toluene.  

Science.gov (United States)

Large amounts of carcinogenic polycyclic aromatic hydrocarbons (PAHs), benzene and toluene (BT) might be emitted from incomplete combustion reactions in both coal tar factories and biomass fuels in rural China. The health effects arising from exposure to PAHs and BT are a concern for residents of rural areas close to coal tar plants. To assess the environmental risk and major exposure sources, 100 coke plant workers and 25 farmers in Qujing, China were recruited. The levels of 10 mono-hydroxylated PAHs (OH-PAHs), four BT metabolites and 8-hydroxy-2'-deoxyguanosine (8-OHdG) in the urine collected from the subjects were measured. The 8-OHdG levels in the urine were determined to evaluate the oxidative DNA damage induced by the PAHs and BT. The results showed that the levels of the OH-PAHs, particularly those of 1-hydroxynathalene and 1-hydroxypyrene, in the farmers were 1-7 times higher than those in the workers. The concentrations of the BT metabolites were comparable between the workers and farmers. Although the exact work location within a coke oven plant might affect the levels of the OH-PAHs, one-way ANOVA revealed no significant differences for either the OH-PAHs levels or the BT concentrations among the three groups working at different work sites. The geometric mean concentration (9.17 µg/g creatinine) of 8-OHdG was significantly higher in the farmers than in the plant workers (6.27 µg/g creatinine). The levels of 8-OHdG did not correlate with the total concentrations of OH-PAHs and the total levels of BT metabolites. Incompletely combusted biomass fuels might be the major exposure source, contributing more PAHs and BT to the local residents of Qujing. The estimated daily intakes (EDIs) of naphthalene and fluorene for all of the workers and most of the farmers were below the reference doses (RfDs) recommended by the U.S. Environmental Protection Agency (EPA), except for the pyrene levels in two farmers. However, the EDIs of benzene in the workers and local farmers ranged from 590 to 7239 µg/day, and these levels were 2- to 30-fold higher than the RfDs recommended by the EPA. Biomass fuel combustion and industrial activities related to coal tar were the major sources of the PAH and BT exposure in the local residents. Using biomass fuels for household cooking and heating explains the higher exposure levels observed in the farmers relative to the workers at the nearby coal tar-related industrial facility. PMID:25261857

Fan, Ruifang; Li, Junnan; Chen, Laiguo; Xu, Zhencheng; He, Dechun; Zhou, Yuanxiu; Zhu, Yuanyuan; Wei, Fusheng; Li, Jihua

2014-11-01

99

Quantitation of urinary metabolites of toluene, xylene, styrene, ethylbenzene, benzene and phenol by automated high performance liquid chromatography.  

Science.gov (United States)

An automated high performance liquid chromatographic method (HPLC) for the direct determination of urinary concentrations of hippuric acid (HA), and o-, m- and p-methyl hippuric acids (MHAs), metabolites of toluene and o-, m-, and p-xylenes, and of urinary phenyl glyoxylic acid (PGA) and mandelic acid (MA), metabolites of styrene or ethylbenzene, is described. Methanol was added to urine, the mixture was centrifuged and the supernatant was injected into HPLC. A stainless-steel column packed with octadecyl silanized silicate was used and the mobile phase was a mixed solution of 5 mM potassium phosphate monobasic/acetonitrile (90/10). The method is simple and specific. Urine can be analyzed without solvent extraction. Analysis can be performed satisfactorily within 45 min for samples containing HA, MHAs, PGA and MA, and within 15 min for those containing HA, PGA and MA. Another automated HPLC method for the determination of urinary concentrations of phenylsulfate (PhS) and phenylglucuronide (PhG), metabolites of benzene and phenol, is also described. Urine was centrifuged and the supernatant was injected into HPLC. A column packed with octadecyl silicate and a mobile phase of 50 mM of potassium phosphate monobasic/acetonitrile (85/15) were used. The whole analyses and quantitative determination can be performed within 15 min for samples containing PhS and PhG in the worker's urine with a simple mobile phase. The accuracy and precision in the present methods by the use of automated HPLC were satisfactory. PMID:3570490

Ogata, M; Taguchi, T

1987-01-01

100

Evaluation of indoor exposition to benzene, toluene, ethylbenzene, xylene, and styrene by passive sampling with a solid-phase microextraction device.  

Science.gov (United States)

A solid-phase microextraction (SPME) sampling method is developed to evaluate indoor exposure to benzene, toluene, ethylbenzene, xylene, and styrene with gas chromatography and flame ionization detection for quantitative analysis. An SPME holder with a 100-pm polydimethylsiloxane (PDMS) and 65-pm PDMS-divinylbenzene fiber coating is tested in different air relative humidity conditions. The method gives good resolution, shows a linear response, is repeatable, and presents high sensitivity. This method is compared with National Institute of Occupational Safety and Health (NIOSH) active sampling. PMID:11954648

Parreira, Fabrício V; de, Carvalho Ciomara R; de, Cardeal Zenilda L

2002-03-01

101

Experimental density, viscosity, interfacial tension and water solubility of ethyl benzene-?-methyl benzyl alcohol–water system  

International Nuclear Information System (INIS)

Highlights: • Properties were measured for MBA (methyl benzyl alcohol)-EB (ethyl benzene)-water. • MBA concentration was found to influence all the properties strongly. • The water solubility, density, and viscosity increased at high MBA concentration. • The interfacial tension decreased sharply at high MBA concentration. • MBA dictates the phase separation and mass transfer of the ternary system. -- Abstract: Density, viscosity, interfacial tension, and water solubility were measured for the (?-methyl benzyl alcohol (MBA) + Ethyl benzene (EB)) system at different concentrations of MBA in contact with water and sodium hydroxide solution (0.01 mol · kg?1) as aqueous phases. The properties were measured to identify the component which plays a governing role in changing the physical properties relevant to mass transfer and phase separation of the ternary system. The concentration of MBA was found to be the major factor influencing all the properties. The water solubility, the density, and the viscosity increased notably at higher concentrations of MBA; while, the interfacial tension decreased strongly. The use of 0.01 mol · kg?1 NaOH as an aqueous phase resulted in a decrease of the interfacial tension and a minor decrease in the water solubility. The density data were correlated using a quadratic mixing rule to describe the influence of concentration at any temperature. The viscosity data are correlated using the Nissan and Grunberg and Katti-Chaudhri equations. The Szyzkowski’s equation was used to correlate the interfacial tension data. The water solubility data were described using an exponential relationship. All the correlations described the experimental physical property data adequately

102

Determination of exposure to benzene, toluene and xylenes in Turkish primary school children by analysis of breath and by environmental passive sampling.  

Science.gov (United States)

Benzene, toluene, m/p-xylene and o-xylene (BTX) are toxic volatile organic compounds and ubiquitous air pollutants. Smoking and consumer products are indoor sources of BTX, whereas traffic and industrial activities are primary sources contributing to outdoor levels of BTX. The aim of this study was to characterize exposure of children to BTX by personal air sampling using diffusive samplers and by analysis of end-exhaled air. For this study, 101 children of 10-11 years of age were recruited from four primary schools in Southern Turkey during the warm season (May 2008). Two schools were situated in a residential area near primary and secondary iron and steel works (Payas) and two schools were located in a non-industrialized city (Iskenderun). The children and their parents were visited at home for an interview and to identify possible sources of BTX in the residence. Median concentrations of benzene determined by diffusive samplers were higher in Payas (4.1 microg/m(3)) than in Iskenderun (2.7 microg/m(3), pIskenderun). Concentrations of toluene in end-exhaled air were 50% higher in children living with household members who smoked indoors (p<0.05) and benzene in end-exhaled air was more than 3-fold higher for those children who were exposed to tobacco smoke inside a vehicle (p<0.001). End-exhaled concentrations of benzene were also higher in children living in a residence with an attached garage (p<0.05). These exposure modifying factors were not identified when using the results obtained with diffusive samplers. PMID:20619876

Scheepers, Paul T J; Konings, Joke; Demirel, Gülcin; Gaga, Eftade O; Anzion, Rob; Peer, Petronella G M; Dogeroglu, Tuncay; Ornektekin, Sermin; van Doorn, Wim

2010-09-15

103

The pyrolytic formation of polycyclic aromatic hydrocarbons from benzene, toluene, ethylbenzene, styrene, phenylacetylene and n-decane in relation to fossil fuels utilization  

Energy Technology Data Exchange (ETDEWEB)

The yields of groups of Polycyclic Aromatic Hydrocarbons from the pyrolysis of benzene, toluene, ethylbenzene, styrene, phenylacetylene and n-decane in the temperature range of 900-1250 K are reported. At temperatures between 900 and 1100 K the aromatic precursors are converted mainly into non-condensed dimeric compounds, viz. biphenyl in benzene pyrolysis, 1,2-diphenylethane, 1,2-diphenylethylene and 1,2-diphenylacetylene in toluene and ethylbenzene pyrolysis. From n-decane these products are hardly observed. At 1250 K the non-condensed and hydrogenated condensed compounds are thermally unstable. Of the condensed compounds phenanthrene, anthracene and fluorene yields still depend on the type of precursor but acenaphthylene, fluoranthene and pyrene yields are merely a function of temperature. A general mechanism of condensed PAH-formation is derived from the product distribution as a function of temperature. At relatively low temperatures (<1100 K) radical dimerization is the most important reaction followed by dehydrogenation and dealkylation. A second route is condensation possibly via benzyn intermediates. The anthracene/phenanthrene ratio is discussed in view of the PMO-theory; it is concluded that this ratio is determined both by the stable intermediate precursors of phenanthrene and the instability of anthracene itself. 16 refs., 10 figs., 2 tabs.

Bruinsma, O.S.L.; Moulijn, J.A.

1988-05-01

104

Combined application of conservative transport modelling and compound-specific carbon isotope analyses to assess in situ attenuation of benzene, toluene, and o-xylene  

Science.gov (United States)

In recent years, compound specific isotope analyses (CSIA) have developed into one of the most powerful tools for the quantification of in situ biodegradation of organic contaminants. In this approach, the calculation of the extent of biodegradation of organic contaminants in aquifers is usually based on the Rayleigh equation, and thus neglects physical transport processes such as dispersion that contribute to contaminant dilution in aquifers. Here we combine compound specific isotope analyses with a conservative transport model to study the attenuation of aromatic hydrocarbons at a former gasworks site. The conservative transport model was first used to simulate concentration reductions caused by dilution at wells downgradient of a BTEX source. In a second step, the diluted concentrations, together with the available stable carbon isotope ratios and carbon fractionation factors for benzene, toluene and o-xylene were applied in the Rayleigh equation to quantify the degree of biodegradation at each of those wells. At the investigated site, where other attenuation processes such as sorption and volatilisation were proven to be negligible, the combined approach is recommended for benzene, which represents a compound for which the effect of biodegradation is comparable to or less than the effect of dilution. As demonstrated for toluene and o-xylene, the application of the Rayleigh equation alone is sufficient if dilution can be proved to be insignificant in comparison to biodegradation. The analysis also suggests that the source width and the position of the observation wells relative to the plume center line are significantly related to the degree of dilution.

Mak, K. S.; Griebler, C.; Meckenstock, R. U.; Liedl, R.; Peter, A.

2006-12-01

105

Heterogeneous adsorption and catalytic oxidation of benzene, toluene and xylene over spent and chemically regenerated platinum catalyst supported on activated carbon  

Science.gov (United States)

The heterogeneous adsorption and catalytic oxidation of benzene, toluene and o-xylene (BTX) over the spent platinum catalyst supported on activated carbon (Pt/AC) as well as the chemically treated spent catalysts were studied to understand their catalytic and adsorption activities. Sulfuric aqueous acid solution (0.1N, H 2SO 4) was used to regenerate the spent Pt/AC catalyst. The physico-chemical properties of the catalysts in the spent and chemically treated states were analyzed by using nitrogen adsorption-desorption isotherm and elemental analysis (EDX). The gravimetric adsorption and the light-off curve analysis were employed to study the BTX adsorption and oxidation on the spent catalyst and its modified Pt/AC catalysts. The experimental results indicate that the spent Pt/AC catalyst treated with the H 2SO 4 aqueous solution has a higher toluene adsorption and conversion ability than that of the spent Pt/AC catalyst. A further studies of H 2SO 4 treated Pt/AC catalyst on their catalytic and heterogeneous adsorption behaviours for BTX revealed that the activity of the H 2SO 4 treated Pt/AC catalyst follows the sequence of benzene > toluene > o-xylene. The adsorption equilibrium isotherms of BTX on the H 2SO 4 treated Pt/AC were measured at different temperatures ranging from 120 to 180 °C. To correlate the equilibrium data and evaluate their adsorption affinity for BTX, the two sites localized Langmuir (L2m) isotherm model was employed. The heterogeneous surface feature of the H 2SO 4 treated Pt/AC was described in detail with the information obtained from the results of isosteric enthalpy of adsorption and adsorption energy distributions. Furthermore, the activity of H 2SO 4 treated Pt/AC about BTX was found to be directly related to the Henry's constant, isosteric enthalpy of adsorption and adsorption energy distribution functions.

Shim, Wang Geun; Kim, Sang Chai

2010-06-01

106

Preliminary study to prepare a reference material of toluene metabolite - o-cresol and benzene metabolite-phenol - in human.  

Czech Academy of Sciences Publication Activity Database

Ro?. 11, ?. 5 (2006), s. 231-235. ISSN 0949-1775 R&D Projects: GA MZd NR7831 Institutional research plan: CEZ:AV0Z10480505 Keywords : reference material * toluene metabolites * o-cresol Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 0.640, year: 2006

Šperlingová, I.; Dabrowská, L.; Stránský, V.; Ku?era, Jan; Tichý, M.

2006-01-01

107

Substoichiometric isotope dilution analysis of arsenic in biological and environmental standard reference materials by solvent extraction using toluene-3,4-dithiol in benzene  

International Nuclear Information System (INIS)

A radiochemical solvent extraction procedure has been developed for the determination of As(III) using 76As tracer. It is based on the complexation of As(III) with toluene-3,4-dithiol (TDT) at pH 2 and subsequent extraction in benzene. The effect of various parameters such as pH, time of equilibration, nature of solvent, quantitative character and interferences have been studied. The method has been further developed into substoichiometric isotope dilution analysis for the determination of As at < 1?g level and employed for the analysis of several environmental and biological standard Reference Materials from NIST (USA), IAEA (Vienna) and NIES (Japan). (author) 39 refs.; 4 figs.; 4 tabs

108

Thermodynamic properties of (tetradecane + benzene, + toluene, + chlorobenzene, + bromobenzene, + anisole) binary mixtures at T = (298.15, 303.15, and 308.15) K  

International Nuclear Information System (INIS)

Density ?, viscosity ?, and refractive index n D, values for (tetradecane + benzene, + toluene, + chlorobenzene, + bromobenzene, + anisole) binary mixtures over the entire range of mole fraction have been measured at temperatures (298.15, 303.15, and 308.15) K at atmospheric pressure. The speed of sound u has been measured at T = 298.15 K only. Using these data, excess molar volume V E, deviations in viscosity ??, Lorentz-Lorenz molar refraction ?R, speed of sound ?u, and isentropic compressibility ?k s have been calculated. These results have been fitted to the Redlich and Kister polynomial equation to estimate the binary interaction parameters and standard deviations. Excess molar volumes have exhibited both positive and negative trends in many mixtures, depending upon the nature of the second component of the mixture. For the (tetradecane + chlorobenzene) binary mixture, an incipient inversion has been observed. Calculated thermodynamic quantities have been discussed in terms of intermolecular interactions between mixing components

109

Modified dispersive liquid-liquid microextraction for pre-concentration of benzene, toluene, ethylbenzene and xylenes prior to their determination by GC  

International Nuclear Information System (INIS)

We have developed a modified method for the extraction and preconcentration of benzene, toluene, ethylbenzene and xylenes (BTEX) in aqueous samples. It based on dispersive liquid-liquid microextraction along with solidification of floating organic microdrops. The dispersion of microvolumes of an extracting solvent into the aqueous occurs without dispersive solvent. Various parameters have been optimized. BTEX were quantified via GC with FID detection. Under optimized conditions, the preconcentration factors range from 301 to 514, extraction efficiencies from 60 to 103 %, repeatabilities from 2.2 to 4.1 %, and intermediate precisions from 3.5 to 7.0 %. The relative recovery for each analyte in water samples at three spiking levels is >85.6 %, with a relative standard deviation of <7.4 %. (author)

110

Combined application of conservative transport modelling and compound-specific carbon isotope analyses to assess in situ attenuation of benzene, toluene, and o-xylene.  

Science.gov (United States)

In recent years, compound specific isotope analyses (CSIA) have developed into one of the most powerful tools for the quantification of in situ biodegradation of organic contaminants. In this approach, the calculation of the extent of biodegradation of organic contaminants in aquifers is usually based on the Rayleigh equation, and thus neglects physical transport processes such as dispersion that contribute to contaminant dilution in aquifers. Here we combine compound specific isotope analyses with a conservative transport model to study the attenuation of aromatic hydrocarbons at a former gasworks site. The conservative transport model was first used to simulate concentration reductions caused by dilution at wells downgradient of a BTEX source. In a second step, the diluted concentrations, together with the available stable carbon isotope ratios and carbon fractionation factors for benzene, toluene and o-xylene were applied in the Rayleigh equation to quantify the degree of biodegradation at each of those wells. At the investigated site, where other attenuation processes such as sorption and volatilisation were proven to be negligible, the combined approach is recommended for benzene, which represents a compound for which the effect of biodegradation is comparable to or less than the effect of dilution. As demonstrated for toluene and o-xylene, the application of the Rayleigh equation alone is sufficient if dilution can be proved to be insignificant in comparison to biodegradation. The analysis also suggests that the source width and the position of the observation wells relative to the plume center line are significantly related to the degree of dilution. PMID:17011071

Mak, K S; Griebler, C; Meckenstock, R U; Liedl, R; Peter, A

2006-12-15

111

Isotope effects in aqueous systems. 13. The hydrophobic interaction. Some thermodynamic properties of benzene/water and toluene/water solutions and their isotope effects  

International Nuclear Information System (INIS)

Henry's law constants, K/sub H/ = K0 + K1X, have been measured as a function of concentration for the water-rich and benzene-rich solutions C6H6/H2O and C6H6/D2O and for the water-rich solutions C6D6/H2O and C6D6/D2O at several temperatures The constants K0 and K1 are sensitive to temperature and to isotopic label. The vapor pressure results have been supplemented with measurements of the apparent molar volumes of the solutions listed above, as well as for H2O- and D2O-rich solutions of toluene and deuteriotoluene, and with determinations of the solubilities and solubility isotope effects of the toluene solutions. The data have been interpreted in the context of the theory of isotope effects in condensed-phase systems. That analysis indicates that a significant dynamical vibrational coupling between solute and solvent normal modes occurs in these solutions. The result is of interest particularly as it pertains to models of the hydrophobic interaction

112

The dissolution of benzene, toluene, m-xylene and naphthalene from a residually trapped non-aqueous phase liquid under mass transfer limited conditions  

Science.gov (United States)

The results of dissolution experiments for benzene, toluene, m-xylene and naphthalene (BTXN) from a relatively insoluble oil phase (tridecane), residually trapped in a non-sorbing porous medium, are described. This mixture was chosen to simulate dissolution of soluble aromatic compounds from a petroleum hydrocarbon mixture, e.g., crude oil, for which a large fraction of the mixture is relatively insoluble. The experiments were carried out at a small source length to interstitial velocity ratio, L/ v, so that dissolution would be mass transfer limited (MTL). When fitted to data for toluene, a multiregion mass transfer model was found to predict the experimental data satisfactorily for the other components without adjustment of the mass transfer rate parameters. These results indicate that the dissolution process can be generalized for various hydrophobic organic compounds present in a multicomponent non-aqueous phase liquid (NAPL) when mass transfer limitations are present. This also suggests that dissolution data obtained for one compound can be useful for predicting the dissolution histories for other compounds from petroleum hydrocarbon mixtures.

Garg, Sanjay; Rixey, William G.

1999-03-01

113

Determinação de benzeno, tolueno, etilbenzeno e xilenos em gasolina comercializada nos postos do estado do Piauí Determination of benzene, toluene, ethylbenzene and xylenes in commercial gasoline from Piaui state  

OpenAIRE

Automotive gasoline consists of a complex mixture of flammable and volatile hydrocarbons derived from crude oil with carbon numbers within the range of 4-12 and boiling points range of 30-225 ºC. Its composition varies with the kind of crude oil and the type of refinery process that they undergone. Aromatics hydrocarbons, in particular benzene, toluene, ethylbenzene and isomeric xylenes (BTEX) are the toxic group constituents presents. GC-FID was employed to quantify these hydrocarbons in 50...

Silva, Flamys Lena Do N.; José Ribeiro dos Santos Jr.; José Machado Moita Neto; Da Silva, Rosa Lina G. Do N. P.; Danilo Luiz Flumignan; José Eduardo de Oliveira

2009-01-01

114

Gamma radiolysis of toluene and deuterated toluenes: Pt. 1  

International Nuclear Information System (INIS)

The ? radiolysis of liquid toluene and toluene-d8 was studied at 50degC. For toluene, product yields were 0.14 molecules of hydrogen, 0.006 of methane, 0.090 of biphenyl and 0.9 of ''polymer'' for each 100 eV absorbed. For toluene-d8, these yields are lower by a factor of two to three. Radiolysis of mixtures of toluene and toluene-d8 shows a disproportionately high decomposition of the light toluene, suggesting that energy initially absorbed in toluene-d8 transfers to toluene before decomposition occurs. Deuterium tracer studies indicate that about 14% of the hydrogen arises from unimolecular processes, whereas none of the methane or bibenzyl arises in this way. Studies using an electron scavenger, ethyl bromide, and a proton scavenger, ethanol, showed that the hydrogen yield did not likely have long-lived electrons or ions as precursors. Thus the energy transfer from toluene-d8 to toluene is probably by direct excitation transfer, and not by charge transfer. (author)

115

Gas-phase reaction of daughter ions from the decay of multitritiated propane with benzene and toluene. Solution of a longstanding anomaly  

International Nuclear Information System (INIS)

The population of the daughter ions from the decay of multitritiated propane has been sampled by using as a probe their gas-phase reactions with benzene and toluene at pressures up to 400 torr. Tritiated n- and isopropylated arenes account together for 70 to 75% of the total activity of the decay ions. This observation - and the failure to detect aromatic allylation - removes an early radiochemical anomaly, by showing that decay of tritiated propane yields propyl ions as the most abundant daughter species, following a trend established for all other tritiated hydrocarbons. The abnormally high abundance of allyl ions measured by mass spectrometry is traced to the decomposition C3H7+ ? C3H5 + H2 allowed by its low activation energy, the lack of collisional stabilization, and the long residence time which characterizes operation of a charge mass spectrometer. The excitation energy required for the decomposition is likely to arise from the deformation energy of the propyl cations, born from the sudden nuclear transition in a shape reminiscent of the parent hydrocarbon molecule

116

Thermodynamic properties of (tetradecane + benzene, + toluene, + chlorobenzene, + bromobenzene, + anisole) binary mixtures at T = (298.15, 303.15, and 308.15) K  

Energy Technology Data Exchange (ETDEWEB)

Density {rho}, viscosity {eta}, and refractive index n {sub D}, values for (tetradecane + benzene, + toluene, + chlorobenzene, + bromobenzene, + anisole) binary mixtures over the entire range of mole fraction have been measured at temperatures (298.15, 303.15, and 308.15) K at atmospheric pressure. The speed of sound u has been measured at T = 298.15 K only. Using these data, excess molar volume V {sup E}, deviations in viscosity {delta}{eta}, Lorentz-Lorenz molar refraction {delta}R, speed of sound {delta}u, and isentropic compressibility {delta}k {sub s} have been calculated. These results have been fitted to the Redlich and Kister polynomial equation to estimate the binary interaction parameters and standard deviations. Excess molar volumes have exhibited both positive and negative trends in many mixtures, depending upon the nature of the second component of the mixture. For the (tetradecane + chlorobenzene) binary mixture, an incipient inversion has been observed. Calculated thermodynamic quantities have been discussed in terms of intermolecular interactions between mixing components.

Mutalik, Venkatesh [Department of Chemistry, Karnatak University, Dharwad 580 003 (India); Manjeshwar, Lata S. [Department of Chemistry, Karnatak University, Dharwad 580 003 (India)]. E-mail: latamanjeshwar@yahoo.com; Sairam, Malladi [Center of Excellence in Polymer Science, Karnatak University, Dharwad 580 003 (India); Aminabhavi, Tejraj M. [Center of Excellence in Polymer Science, Karnatak University, Dharwad 580 003 (India)]. E-mail: aminabhavi@yahoo.com

2006-08-15

117

Cobalt oxide nanoparticles as a novel high-efficiency fiber coating for solid phase microextraction of benzene, toluene, ethylbenzene and xylene from aqueous solutions  

International Nuclear Information System (INIS)

Highlights: • Co3O4 nanoparticles were introduced as a novel SPME fiber coating. • The fiber was evaluated for the extraction of BTEX in combination with GC–MS. • The fiber showed extraction efficiencies better than a PDMS fiber toward BTEX. • The fiber was successfully applied to the determination of BTEX in real samples. - Abstract: In this work cobalt oxide nanoparticles were introduced for preparation of a novel solid phase microextraction (SPME) fiber coating. Chemical bath deposition (CBD) technique was used in order for synthesis and immobilization of the Co3O4 nanomaterials on a Pt wire for fabrication of SPME fiber. The prepared cobalt oxide coating was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The fiber was evaluated for the extraction of benzene, toluene, ethylbenzene and xylene (BTEX) in combination with GC–MS. A simplex optimization method was used to optimize the factors affecting the extraction efficiency. Under optimized conditions, the proposed fiber showed extraction efficiencies comparable to those of a commercial polydimethylsiloxane (PDMS) fiber toward the BTEX compounds. The repeatability of the fiber and its reproducibility, expressed as relative standard deviation (RSD), were lower than about 11%. No significant change was observed in the extraction efficiency of the new SPME fiber after over 50 extractions. The fiber was successfully applied to the determination of BTEX compounds in real samples. The proposed nanostructure cobalt oxide fiber is a promising alternative to the commercial fibers as it is robust, inexpensive and easily prepared

118

Simultaneous determination of the urinary metabolites of benzene, toluene, xylene and styrene using high-performance liquid chromatography/hybrid quadrupole time-of-flight mass spectrometry.  

Science.gov (United States)

A simple and rapid method using reversed-phase liquid chromatography/tandem mass spectrometry (LC/MS/MS) for the simultaneous determination of the urinary metabolites of benzene, toluene, xylene and styrene in human urine specimens and standard solutions is described. A hybrid quadrupole/time-of-flight (QqTOF) mass spectrometer was compared for the determination of metabolite of aromatic solvents in urine samples. The metabolites selected were: trans,trans-muconic acid, hippuric acid, o-, m- and p-methylhippuric acid and phenylglyoxylic acid. The compounds were well separated from each other on narrow-bore 1-mm i.d. reversed-phase LC C-18 columns. Average recoveries for loading 100 microL of urine samples varied from 88-110% and the quantification limits were less than 30 ng/mL for each analyte (3 ng/mL for trans,trans-muconic acid). The qualitative information obtained (mass accuracy, resolution and full-scan spectra) with the QqTOF mass spectrometer allows a secure identification of analytes in biological matrices. PMID:14755610

Marchese, Stefano; Curini, Roberta; Gentili, Alessandra; Perret, Daniela; Rocca, Lucia Mainero

2004-01-01

119

Cobalt oxide nanoparticles as a novel high-efficiency fiber coating for solid phase microextraction of benzene, toluene, ethylbenzene and xylene from aqueous solutions.  

Science.gov (United States)

In this work cobalt oxide nanoparticles were introduced for preparation of a novel solid phase microextraction (SPME) fiber coating. Chemical bath deposition (CBD) technique was used in order for synthesis and immobilization of the Co3O4 nanomaterials on a Pt wire for fabrication of SPME fiber. The prepared cobalt oxide coating was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The fiber was evaluated for the extraction of benzene, toluene, ethylbenzene and xylene (BTEX) in combination with GC-MS. A simplex optimization method was used to optimize the factors affecting the extraction efficiency. Under optimized conditions, the proposed fiber showed extraction efficiencies comparable to those of a commercial polydimethylsiloxane (PDMS) fiber toward the BTEX compounds. The repeatability of the fiber and its reproducibility, expressed as relative standard deviation (RSD), were lower than about 11%. No significant change was observed in the extraction efficiency of the new SPME fiber after over 50 extractions. The fiber was successfully applied to the determination of BTEX compounds in real samples. The proposed nanostructure cobalt oxide fiber is a promising alternative to the commercial fibers as it is robust, inexpensive and easily prepared. PMID:24725745

Gholivand, Mohammad Bagher; Shamsipur, Mojtaba; Shamizadeh, Mohammad; Moradian, Rostam; Astinchap, Bandar

2014-04-25

120

Effect of ethanol on microbial community structure and function during natural attenuation of benzene, toluene, and o-xylene in a sulfate-reducing aquifer.  

Science.gov (United States)

Ethanol (EtOH) is a commonly used fuel oxygenate in reformulated gasoline and is an alternative fuel and fuel supplement. Effects of EtOH release on aquifer microbial ecology and geochemistry have not been well characterized in situ. We performed a controlled field release of petroleum constituents (benzene (B), toluene (T), o-xylene (o-X) at approximately 1-3 mg/L each) with and without EtOH (approximately 500 mg/L). Mixed linear modeling (MLM) assessed effects on the microbial ecology of a naturally sulfidic aquifer and how the microbial community affected B, T, and o-X plume lengths and aquifer geochemistry. Changes in microbial community structure were determined by quantitative polymerase chain reaction (qPCR) targeting Bacteria, Archaea, and sulfate reducing bacteria (SRB); SRB were enumerated using a novel qPCR method targeting the adenosine-5'-phosphosulfate reductase gene. Bacterial and SRB densities increased with and without EtOH-amendment (1-8 orders of magnitude). Significant increases in Archaeal species richness; Archaeal cell densities (3-6 orders of magnitude); B, T, and o-X plume lengths; depletion of sulfate; and induction of methanogenic conditions were only observed with EtOH-amendment MLM supported the conclusion that EtOH-amendment altered microbial community structure and function, which in turn lowered the aquifer redox state and led to a reduction in bioattenuation rates of B, T, and o-X. PMID:18504955

Feris, Kevin; Mackay, Doug; de Sieyes, Nick; Chakraborty, Irina; Einarson, Murray; Hristova, Krassimira; Scow, Kate

2008-04-01

121

Response surface modeling of ultrasound-assisted dispersive liquid-liquid microextraction for determination of benzene, toluene and xylenes in water samples: Box-Behnken design.  

Science.gov (United States)

A simple, fast and effective pre-concentration procedure for the extraction of benzene, toluene and xylenes isomers (BTX) was developed using an ultrasound-assisted dispersive liquid-liquid microextraction coupled with gas chromatography-flame ionization detector in water samples. The effects of different experimental parameters in the extraction step including type and volume of extraction and dispersive solvents, ionic strength, extraction time and sample volume were studied using two techniques, namely one-variable-at-a-time and response surface methodology. The results of "one-variable-at-a-time" showed that the ionic strength and extraction time were not significant on the extraction efficiency. Therefore, a three-factor, three-level Box-Behnken experimental design was employed to optimize the BTX extraction. The optimal conditions were determined to be a volume of extraction solvent (chloroform) of 51 ?L, volume of dispersive solvent (methanol) of 514 ?L and volume of sample of 12 mL. The enrichment factors of 241.2-305.1, the limit of detections of 205-382 ng L(-1) were obtained for the BTX at the optimum conditions. In addition, the relative standard deviations for 50 ?g L(-1) of the BTX in the water samples were found to be in the range of 1.9 %-5.7 % (n = 5). The developed procedure was then applied for the extraction and determination of BTX in the water samples. PMID:22555540

Khajeh, Mostafa; Zadeh, Fatemeh Musavi

2012-07-01

122

Preparation and application of carbon nanotubes/poly(o-toluidine) composite fibers for the headspace solid-phase microextraction of benzene, toluene, ethylbenzene, and xylenes.  

Science.gov (United States)

A novel nanocomposite coating of poly(o-toluidine) and oxidized multiwalled CNTs (MWCNTs, where CNTs is carbon nanotubes) was electrochemically prepared on a stainless-steel wire. The applicability of the fiber was assessed for the headspace solid-phase microextraction of benzene, toluene, ethylbenzene, and xylenes in aqueous samples followed by GC with flame ionization detection. In order to obtain an adherent and stable composite coating, several experimental parameters related to the coating process, such as polymerization potential and time, and the concentration of o-toluidine and oxidized MWCNTs were optimized. The combination of MWCNTs and polymer in a nanocomposite form presents desirable opportunities to produce materials for new applications. The effects of various parameters on the efficiency of the headspace solid-phase microextraction process, such as desorption temperature and time, extraction temperature and time, and ionic strength were also investigated. At the optimum conditions, LODs were 0.03-0.06 ?g/L. The method showed linearity in the range of 0.5-300 ?g/L with coefficients of determination >0.99. The intraday and interday RSDs obtained at a 5 ?g/L concentration level (n = 5) using a single fiber were 1.2-5.2 and 3.2-7.5%, respectively. The fiber-to-fiber RSD (%; n = 3) at 5 ?g/L was 6.1-9.2%. PMID:24106154

Behzadi, Mansoureh; Noroozian, Ebrahim; Mirzaei, Mohammad

2013-11-01

123

Biodegradation of BTEX (Benzene, Toluene, Ethylbenzene and Xylenes) composites present in the petrochemical effluents industries; Biodegradacao dos compostos BTX (Benzeno, Tolueno e Xilenos) presentes em efluentes petroquimicos  

Energy Technology Data Exchange (ETDEWEB)

The compounds BTX inside of the petrochemical effluent have presented a high potential of pollution, representing a serious risk to the environment and to the human. The great improvements in the field of biological treatment of liquid effluent were reached through the process using biofilm capable of degrading toxic compounds. The objective of this paper is to determine the degradation kinetics of BTX using biofilm. The experimental data were compared with two kinetic models, kinetic of first order and model of Michaelis-Menten. The kinetic parameters of BTX compounds were experimentally obtained in a bioreactor in batch with biomass immobilized in activated-carbon, being fed daily with solution of nutrients and BTX. For the kinetic models studied in this paper, the best performance was achieved with the model of Michaelis-Menten showing a good correlation coefficient for the three compounds. The biomass amount in these bioreactors was 49.18, 28.35 and 5.15 mg of SSV per gram of support for the toluene, benzene and o-xylene, respectively. The experimental tests showed that the biomass inside of bioreactor is capable to degrade all compounds in a time of approximately 300 minutes. (author)

Minatti, Gheise; Mello, Josiane M.M. de; Souza, Selene M.A. Guelli Ulson de; Antonio Augusto Ulson de [Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil)

2008-07-01

124

Automated dynamic headspace organic solvent film microextraction for benzene, toluene, ethylbenzene and xylene. Renewable liquid film as a sampler by a programmable motor.  

Science.gov (United States)

A simple, fast and efficient dynamic headspace-organic solvent film microextraction (DHS-OSFME) method using a new automatic device was developed. The renewable organic films were formed inside a microsyringe barrel using the uniform and repeated movement of the syringe plunger enabled by programmable stirring motor. The plunger speed, number of extraction cycles, and dwell time (stop time after each half round) were controlled by a computer software, which was written by C++ Builder. A theoretical treatment of the DHS-OSFME based on the consecutive first-order process is proposed in this report. A mathematical solution for the dynamic process of the mass transfer was obtained by correlating the variation of analyte concentration in the syringe volume with the plunger speed and the amount of analyte extracted to the OSF. Benzene, toluene, ethylbenzene, and o-xylene (BTEX) were employed as model compounds to assess the extraction procedure and were determined by gas chromatography-flame ionization detection. Of the three organic solvents (1-octanol, benzyl alcohol and n-dodecane) studied as extractants, n-dodecane proved to be the most sensitive solvent for the extraction of these analytes. Several parameters, including the syringe withdrawal rate, dwelling time, number of extraction cycles, sampling volume, sample temperature, and ionic strength of the solution, were investigated for their effects on the extraction performance. The calibration graphs were linear in the range of 0.5-200 ng ml(-1), with the detection limits between 0.18 and 0.35 ng ml(-1). Wastewater samples were extracted by the optimized method, and determined using the standard addition method. PMID:16427647

Mohammadi, Abdorreza; Alizadeh, Naader

2006-02-24

125

Cobalt oxide nanoparticles as a novel high-efficiency fiber coating for solid phase microextraction of benzene, toluene, ethylbenzene and xylene from aqueous solutions  

Energy Technology Data Exchange (ETDEWEB)

Highlights: • Co{sub 3}O{sub 4} nanoparticles were introduced as a novel SPME fiber coating. • The fiber was evaluated for the extraction of BTEX in combination with GC–MS. • The fiber showed extraction efficiencies better than a PDMS fiber toward BTEX. • The fiber was successfully applied to the determination of BTEX in real samples. - Abstract: In this work cobalt oxide nanoparticles were introduced for preparation of a novel solid phase microextraction (SPME) fiber coating. Chemical bath deposition (CBD) technique was used in order for synthesis and immobilization of the Co{sub 3}O{sub 4} nanomaterials on a Pt wire for fabrication of SPME fiber. The prepared cobalt oxide coating was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The fiber was evaluated for the extraction of benzene, toluene, ethylbenzene and xylene (BTEX) in combination with GC–MS. A simplex optimization method was used to optimize the factors affecting the extraction efficiency. Under optimized conditions, the proposed fiber showed extraction efficiencies comparable to those of a commercial polydimethylsiloxane (PDMS) fiber toward the BTEX compounds. The repeatability of the fiber and its reproducibility, expressed as relative standard deviation (RSD), were lower than about 11%. No significant change was observed in the extraction efficiency of the new SPME fiber after over 50 extractions. The fiber was successfully applied to the determination of BTEX compounds in real samples. The proposed nanostructure cobalt oxide fiber is a promising alternative to the commercial fibers as it is robust, inexpensive and easily prepared.

Gholivand, Mohammad Bagher, E-mail: MB.Gholivand@yahoo.com [Department of Analytical Chemistry, Faculty of Chemistry, Razi University, Kermanshah (Iran, Islamic Republic of); Shamsipur, Mojtaba; Shamizadeh, Mohammad [Department of Analytical Chemistry, Faculty of Chemistry, Razi University, Kermanshah (Iran, Islamic Republic of); Moradian, Rostam; Astinchap, Bandar [Physics Department, Faculty of Science, Razi University, Kermanshah (Iran, Islamic Republic of); Nano Technology Research Laboratory, Razi University, Kermanshah (Iran, Islamic Republic of)

2014-04-01

126

Benzene, toluene and xylene biodegradation by Pseudomonas putida CCMI 852 / Biodegradação de benzeno, tolueno e xileno pela Pseudomonas putida CCMI 852  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese Meio mineral líquido contendo benzeno (B) ou tolueno (T) ou xileno (X) a 100 mg L-1 e suas misturas de BT, BX e TX (50 + 50 mg L-1 cada mistura) e BTX (33,3 + 33,3 + 33,3 mg L-1 cada mistura) foram utilizados para avaliar a atividade de degradação de B, T e X por Pseudomonas putida CCMI 852 contendo [...] um plasmídeo TOL. Após 18 a 24 horas de homogenização da mistura, o inoculo foi adicionado e o decréscimo da concentração dos solventes foi determinado entre 24 e 25 horas por GC. Pseudomonas putida CCMI 852 foi capaz de metabolizar T e X, mas não B. Na mistura BTX, B não foi metabolizado também e a velocidade de degradação de T e X decresceu cerca de 50% comparado com soluções contendo apenas T ou X. Abstract in english A minimal liquid medium containing benzene (B), toluene (T) and xylene (X) and mixtures thereof, was used to evaluate degradation activity of Pseudomonas putida CCMI 852 containing a TOL plasmid. Experiments were developed with B, T and X (100 mg L-1), with mixtures of BT, BX, and TX (50 + 50 mg L-1 [...] each) and BTX (33.3 + 33.3 + 33.3 mg L-1 each), added to 500 mL of medium. After 18 to 24 hours, the inoculum was added and solvent disappearance was determined after 24 to 25 hours by GC. Results showed that P. putida CCMI 852 was able to metabolize T and X, but B was not metabolized. In a BTX mixture, B was not metabolized and T and X degradation rate decreased 50%.

Marcelo Henrique, Otenio; Maria Teresa Lopes da, Silva; Maria Luiza Oliveira, Marques; José Carlos, Roseiro; Ederio Dino, Bidoia.

2005-09-01

127

Benzene, toluene and xylene biodegradation by Pseudomonas putida CCMI 852 Biodegradação de benzeno, tolueno e xileno pela Pseudomonas putida CCMI 852  

Directory of Open Access Journals (Sweden)

Full Text Available A minimal liquid medium containing benzene (B, toluene (T and xylene (X and mixtures thereof, was used to evaluate degradation activity of Pseudomonas putida CCMI 852 containing a TOL plasmid. Experiments were developed with B, T and X (100 mg L-1, with mixtures of BT, BX, and TX (50 + 50 mg L-1 each and BTX (33.3 + 33.3 + 33.3 mg L-1 each, added to 500 mL of medium. After 18 to 24 hours, the inoculum was added and solvent disappearance was determined after 24 to 25 hours by GC. Results showed that P. putida CCMI 852 was able to metabolize T and X, but B was not metabolized. In a BTX mixture, B was not metabolized and T and X degradation rate decreased 50%.Meio mineral líquido contendo benzeno (B ou tolueno (T ou xileno (X a 100 mg L-1 e suas misturas de BT, BX e TX (50 + 50 mg L-1 cada mistura e BTX (33,3 + 33,3 + 33,3 mg L-1 cada mistura foram utilizados para avaliar a atividade de degradação de B, T e X por Pseudomonas putida CCMI 852 contendo um plasmídeo TOL. Após 18 a 24 horas de homogenização da mistura, o inoculo foi adicionado e o decréscimo da concentração dos solventes foi determinado entre 24 e 25 horas por GC. Pseudomonas putida CCMI 852 foi capaz de metabolizar T e X, mas não B. Na mistura BTX, B não foi metabolizado também e a velocidade de degradação de T e X decresceu cerca de 50% comparado com soluções contendo apenas T ou X.

Marcelo Henrique Otenio

2005-09-01

128

Ultrasonic-assisted drop-to-drop solvent microextraction in a capillary tube for analyzing trace benzene, toluene, xylene in one drop of a water sample  

Energy Technology Data Exchange (ETDEWEB)

A novel analytical technique termed ultrasonic-assisted drop-to-drop solvent microextraction (USA-DDSME) in a capillary tube was developed to determine trace benzene, toluene, xylene in one drop of a water sample, which was combined with gas chromatography-flame ionization detection (GC-FID). The advantages of this method are rapidity, convenience, ease of operation, simplicity of the device, and extremely little solvent and sample consumption. Extraction conditions including the type of extraction solvent, the volume of extraction solvent, the volume of sample, extraction time and effect of salt concentration were optimized. The best optimum parameters for extraction were achieved with 3 {mu}L of extraction solvent. Chloroform was divided into four equal divisions in 20 {mu}L water sample (without salt addition) in a capillary tube and ultrasonicated for 10 min, centrifugalized at 2,500 rpm for 5 min to let the extraction solvent settle at the bottom of the capillary tube, then 1 {mu}L of the separated extraction solvent was injected into the GC-FID for analysis. Linearity of the method was determined by analyzing spiked water samples over a concentration range of 0.1-50 {mu}g mL{sup -1}. Correspondingly, the LOD values were 0.01 {mu}g mL{sup -1}. All calibration curves were found to have good linearity with correlation coefficients (r{sup 2}) > 0.995. The precision (RSD) of the system, measured by six repeated determinations of the analytes at 1 {mu}g mL{sup -1} were in the range of 1.6-3.5%. (orig.)

Zhang, Maosheng; Wu, Lijuan [Zhangzhou Normal Univ. (China). Dept. of Chemistry and Environmental Science; Fujian Province Univ. (China). Key Lab. of Analytical Science; Huang, Jiarong [Zhangzhou Entry-Exit Inspection and Quarantine Bureau (China); Zheng, Xianghua [Xiamen Entry-Exit Inspection and Quarantine Bureau (China). Inspection and Quarantine Technical Center

2010-12-15

129

Excess molar volumes and refractive indices of (methoxybenzene+benzene, or toluene, or o-xylene, or m-xylene, or p-xylene, or mesitylene) binary mixtures between T=(288.15 to 303.15)K  

Energy Technology Data Exchange (ETDEWEB)

Densities {rho} and refractive indices n{sub D} for (anisole+benzene, or toluene, or o-xylene, or m-xylene or p-xylene or mesitylene) binary mixtures over the entire range of mole fraction, at temperatures (288.15, 293.15, 298.15, and 303.15)K and atmospheric pressure, have been measured. The excess molar volume V{sup E} and molar refraction deviation {delta}R{sub m}, have been calculated and fitted to the Redlich-Kister polynomial relation to estimate the binary coefficients and standard errors. The excess molar volumes are positive for (anisole+mesitylene) binary mixtures and negative for (anisole+benzene, or toluene, or xylene isomers) binary mixtures at various temperatures. Partial molar volumes V-bar {sub i} and partial excess molar volumes V-bar {sub i}{sup E} have been also derived from the experimental data. The calculated values have been used to explain the dependency of intermolecular interaction between the mixing components on the alkyl substitution on benzene ring.

Al-Kandary, Jasem A. [Department of Chemical Engineering, College of Technological Studies, P.O. Box 42325, Shuwaikh 70654 (Kuwait)]. E-mail: jalkandary@yahoo.com; Al-Jimaz, Adel S. [Department of Chemical Engineering, College of Technological Studies, P.O. Box 42325, Shuwaikh 70654 (Kuwait); Abdul-Latif, Abdul-Haq M. [Department of Chemical Engineering, College of Technological Studies, P.O. Box 42325, Shuwaikh 70654 (Kuwait)

2006-11-15

130

Excess molar volumes and refractive indices of (methoxybenzene+benzene, or toluene, or o-xylene, or m-xylene, or p-xylene, or mesitylene) binary mixtures between T=(288.15 to 303.15)K  

International Nuclear Information System (INIS)

Densities ? and refractive indices nD for (anisole+benzene, or toluene, or o-xylene, or m-xylene or p-xylene or mesitylene) binary mixtures over the entire range of mole fraction, at temperatures (288.15, 293.15, 298.15, and 303.15)K and atmospheric pressure, have been measured. The excess molar volume VE and molar refraction deviation ?Rm, have been calculated and fitted to the Redlich-Kister polynomial relation to estimate the binary coefficients and standard errors. The excess molar volumes are positive for (anisole+mesitylene) binary mixtures and negative for (anisole+benzene, or toluene, or xylene isomers) binary mixtures at various temperatures. Partial molar volumes V-bar i and partial excess molar volumes V-bar iE have been also derived from the experimental data. The calculated values have been used to explain the dependency of intermolecular interaction between the mixing components on the alkyl substitution on benzene ring

131

2-{(E-1-[2-(2-Nitrophenylhydrazin-1-ylidene]ethyl}benzene-1,3-diol monohydrate  

Directory of Open Access Journals (Sweden)

Full Text Available The hydrazone molecule in title monohydrate, C14H13N3O4·H2O, is almost coplanar, the dihedral angle between the terminal benzene rings being 3.22?(15°; the nitro group is coplanar with the benzene ring to which it is bonded [O—N—C—C = ?2.8?(4°]. The hydroxy group forms an intramolecular hydrogen bond with the imine N atom, and the conformation about the imine bond [1.305?(3?Å] is E. In the crystal, supramolecular layers in the (203 plane are connected into a double layer via water–nitro O—H...O hydrogen bonds, along with ?–? interactions [ring centroid–centroid distance = 3.7859?(19?Å].

Edward R. T. Tiekink

2012-03-01

132

The volumetric properties of (1,2-propanediol carbonate+benzene, or toluene, or styrene) binary mixtures at temperatures from T=293.15 K to T=353.15 K  

International Nuclear Information System (INIS)

The densities and excess molar volumes VmE for binary liquid mixtures of (1,2-propanediol carbonate+benzene, or toluene, or ethylbenzene, or styrene) have been measured as a function of compositions using a vibrating-tube densimeter in the temperature range of (293.15 to 353.15) K and at atmospheric pressure. The VmE results were correlated using the fourth-order Redlich-Kister equation. It was found that the VmE in these systems studied increases with rising temperature

133

Excess and deviation properties for the binary mixtures of methylcyclohexane with benzene, toluene, p-xylene, mesitylene, and anisole at T = (298.15, 303.15, and 308.15) K  

Energy Technology Data Exchange (ETDEWEB)

Experimental data on density, viscosity, and refractive index at T = (298.15, 303.15, and 308.15) K, while speed of sound values at T = 298.15 K are presented for the binary mixtures of (methylcyclohexane + benzene), methylbenzene (toluene), 1,4-dimethylbenzene (p-xylene), 1,3,5-trimethylbenzene (mesitylene), and methoxybenzene (anisole). From these data of density, viscosity, and refractive index, the excess molar volume, the deviations in viscosity, molar refraction, speed of sound, and isentropic compressibility have been calculated. The computed values have been fitted to Redlich-Kister polynomial equation to derive the coefficients and estimate the standard errors. Variations in the calculated excess quantities for these mixtures have been studied in terms of molecular interactions between the component liquids and the effects of methyl and methoxy group substitution on benzene ring.

Baragi, Jagadish G. [Department of Chemistry, Karnatak University, Dharwad 580 003 (India); Aralaguppi, Mrityunjaya I. [Department of Chemistry, Karnatak University, Dharwad 580 003 (India)]. E-mail: Aralaguppi@yahoo.com

2006-12-15

134

Excess and deviation properties for the binary mixtures of methylcyclohexane with benzene, toluene, p-xylene, mesitylene, and anisole at T = (298.15, 303.15, and 308.15) K  

International Nuclear Information System (INIS)

Experimental data on density, viscosity, and refractive index at T = (298.15, 303.15, and 308.15) K, while speed of sound values at T = 298.15 K are presented for the binary mixtures of (methylcyclohexane + benzene), methylbenzene (toluene), 1,4-dimethylbenzene (p-xylene), 1,3,5-trimethylbenzene (mesitylene), and methoxybenzene (anisole). From these data of density, viscosity, and refractive index, the excess molar volume, the deviations in viscosity, molar refraction, speed of sound, and isentropic compressibility have been calculated. The computed values have been fitted to Redlich-Kister polynomial equation to derive the coefficients and estimate the standard errors. Variations in the calculated excess quantities for these mixtures have been studied in terms of molecular interactions between the component liquids and the effects of methyl and methoxy group substitution on benzene ring

135

Studies on the behavior of diluents on extraction of uranium from phosphoric acid medium using di-2 ethyl hexyl phosphoric acid as extraction  

International Nuclear Information System (INIS)

Extraction studies of uranium from phosphoric acid medium have been carried out by di-2-ethyl hexyl phosphoric acid (D2EHPA) using different diluents viz. xylene, benzene, toluene, carbon tetra chloride, chloroform, hexane and kerosene. Higher extraction of uranium is observed from lower acidities of phosphoric acid (0.5 M) when kerosene, xylene, benzene, hexane and toluene are used as diluents kerosene being the best among these. In the acid range of 0.75-2 M xylene, hexane and toluene are better diluents. Extraction of uranium decreases as the acidity of phosphoric acid increases. Benzene and hexane are least preferred diluents with lower percentage extraction. When carbon tetrachloride and chloroform are used as diluents, it is observed that below 2 M of phosphoric acid a third phase is formed due to which mass distribution is not uniform in organic and aqueous phase and an error is observed in mass balance. (author)

136

Determinação de benzeno, tolueno, etilbenzeno e xilenos em gasolina comercializada nos postos do estado do Piauí / Determination of benzene, toluene, ethylbenzene and xylenes in commercial gasoline from Piaui state  

Scientific Electronic Library Online (English)

Full Text Available [...] Abstract in english Automotive gasoline consists of a complex mixture of flammable and volatile hydrocarbons derived from crude oil with carbon numbers within the range of 4-12 and boiling points range of 30-225 ºC. Its composition varies with the kind of crude oil and the type of refinery process that they undergone. [...] Aromatics hydrocarbons, in particular benzene, toluene, ethylbenzene and isomeric xylenes (BTEX) are the toxic group constituents presents. GC-FID was employed to quantify these hydrocarbons in 50 commercial gasoline samples from Piauí state. Statistical analysis techniques, such as PCA and HCA were used to analyze the data. Moreover, several validation parameters were evaluated.

Flamys Lena do N., Silva; José Ribeiro dos, Santos Jr.; José Machado, Moita Neto; Rosa Lina G. do N. P. da, Silva; Danilo Luiz, Flumignan; José Eduardo de, Oliveira.

137

Correlation and prediction of the phase behavior and thermal properties of binary and ternary systems of 2,2?-oxybis[propane] + benzene, toluene, cyclohexane or n-heptane  

Energy Technology Data Exchange (ETDEWEB)

Highlights: ? To provide original data of excess enthalpies of systems containing additive gasoline. ? To predict excess functions using statistical model. ? To examine the thermal behavior of ethers with hydrocarbons using theoretical models. ? Increasing information of thermodynamic behavior will increase quality of the fuel and economy. - Abstract: The experimental excess molar enthalpies data of liquid binary and ternary mixtures of DIPE with benzene, toluene, cyclohexane and n-heptane have been measured at 303.15 K and constant pressure using a Calvet type microcalorimeter, C80 (Setaram, France). A Redlich–Kister type equation was used to correlate experimental values. The theoretical results obtained by the DISQUAC model are significantly closer to the experimental values.

Didaoui, Saéda, E-mail: sdidaoui@hotmail.com [Laboratoire de thermodynamique et de modélisation moléculaire, Faculté de chimie, Université des Sciences et de la Technologie Houari Boumediene B.P.32, El-Alia Bab-Ezzouar 16111 Alger (Algeria); Ait-Kaci, Ahmed [Laboratoire de thermodynamique et de modélisation moléculaire, Faculté de chimie, Université des Sciences et de la Technologie Houari Boumediene B.P.32, El-Alia Bab-Ezzouar 16111 Alger (Algeria)

2013-09-10

138

Gamma radiolysis of toluene and deuterated toluenes—I. Isotopic exchange  

Science.gov (United States)

The ? radiolysis of liquid toluene and toluene-d 8 was studied at 50°C. For toluene, product yields were 0.14 molecules of hydrogen, 0.006 of methane, 0.090 of biphenyl and 0.9 of "polymer" for each 100 eV absorbed. For toluene-d 8, these yields are lower by a factor of two to three. Radiolysis of mixtures of toluene and toluene-d 8 shows a disproportionately high decomposition of the light toluene, suggesting that energy initially absorbed in toluene-d 8 transfers to toluene before decomposition occurs. Deuterium tracer studies indicate that about 14% of the hydrogen arises from unimolecular processes, whereas none of the methane or bibenzyl arises in this way. Studies using an electron scavenger, ethyl bromide, and a proton scavenger, ethanol, showed that the hydrogen yield did not likely have long-lived electrons or ions as precursors. Thus the energy transfer from toluene-d 8 to toluene is probably by direct excitation transfer, and not by charge transfer.

Sagert, Norman H.; MacFarlane, Roy; Kremers, Walter

139

Poly[[[[1-ethyl-6,8-difluoro-7-(3-methylpiperazin-1-yl)-4-oxo-1,4-dihydroquinoline-3-carboxylato]cadmium]-μ-benzene-1,4-dicarboxylato] trihydrate  

OpenAIRE

In the title layered coordination polymer, {[Cd(C17H18F2N3O3)(C8H4O4)]·3H2O}n, the CdII atom exhibits a very distorted CdO6 octahedral geometry defined by one O3,O4-bidentate 1-ethyl-6,8-difluoro-7-(3-methylpiperazin-1-yl)-4-oxo-1,4-dihydroquinoline-3-carboxylate (lome) ligand, one O,O?-bidentate benzene-1,4-dicarboxylate (bdc) dianion and two O-monodentate bdc dianions. Both the bdc species in the asymmetric unit are completed by crystallographic inversion symmetry. The br...

Xin-Ping Kang; Zhe An; Rena Kasimu

2010-01-01

140

Knoevenagel condensation of aromatic aldehydes with ethyl 4-chloro-3-oxobutanoate in ionic liquids  

Energy Technology Data Exchange (ETDEWEB)

Knoevenagel condensations of aromatic aldehydes with ethyl 4-chloro-3-oxobutanoate catalyzed by morpholine/acetic acid were carried out in ionic liquids to give ethyl 2-chloroacetyl-3-arylpropenoates in 44-84% yield after 0.5 to 2 h at room temperature (25-28 deg C). These conditions represent a greener protocol for the Knoevenagel condensation than those using refluxing benzene or toluene as solvent. Aromatic aldehydes having aryl groups 4-chlorophenyl, 4-methoxyphenyl, 2-thiofuranyl, 2-furanyl, phenyl and 3,4-methylenedioxyphenyl gave (E)/(Z) diastereomeric ratios of products from 56/44 to 85/15. The two isomers of each compound were separately isolated and characterized. The structure of the (E)-isomer of ethyl 2-chloroacetyl-3-(3',4'methylenedioxyphenyl) propenoate was determined by X-ray crystallography and an unequivocal methodology of (E)/(Z)-structural analysis by {sup 13}C NMR (nuclear magnetic resonance) is presented. (author)

Paula, Bruno R.S. de; Zampieri, Davila S.; Rodrigues, Jose Augusto R.; Moran, Paulo J.S., E-mail: moran@iqm.unicamp.br [Institute of Chemistry, University of Campinas, Campinas-SP (Brazil); Zukerman-Schpector, Julio [Department of Chemistry, Federal University of Sao Carlos, SP (Brazil); Tiekink, Edward R.T. [Department of Chemistry, University of Malaya, Kuala Lampur (Malaysia)

2012-05-15

141

Comparação entre injeção na coluna ("on-column") e headspace dinâmico na determinação de benzeno, tolueno e xilenos (BTX) em amostras de água Comparison between on-column injection and dynamic headspace in the determination of Benzene, Toluene and Xylene (BTX) in water  

OpenAIRE

The analysis of water samples containing volatile organic compounds has become an important task in analytical chemistry. Gas chromatography has been widely used for the analysis of volatile organic compounds in water. The headspace analysis shows as a principal characteristic the possibility of determination of the volatile components in drinking water. Benzene, Toluene and Xylene (BTX) are important compounds usually present in drinking water, from contamination by petroleum derivatives. Si...

Gobato, Elaine A. A. F.; Lanc?as, Fernando M.

2001-01-01

142

New polypyrrole-carbon nanotubes-silicon dioxide solid-phase microextraction fiber for the preconcentration and determination of benzene, toluene, ethylbenzene, and o-xylene using gas liquid chromatography.  

Science.gov (United States)

For the first time, a polypyrrole-carbon nanotubes-silicon dioxide composite film coated on a steel wire was prepared by an electrochemical method. Scanning electron microscopy images showed that this composite film was even and porous. The prepared fiber was used as an absorbent for the headspace solid-phase microextraction of benzene, toluene, ethylbenzene, and o-xylene, followed by gas chromatographic analysis. This method presented an excellent performance, which was much better than that of a polypyrrole-carbon nanotube fiber. It was found that under the optimized conditions, the linear ranges were 0.01-200 ng/mL with correlation coefficients >0.9953, the detection limits were 0.005-0.020 ng/mL, the relative standard deviations were 3.9-6.4% for five successive measurements with a single fiber, and the reproducibility was 5.5-8.5% (n = 3). Finally, the developed method was successfully applied to real water samples, and the relative recoveries obtained for the spiked water samples were from 91.0 to 106.7%. PMID:24995551

Sarafraz-Yazdi, Ali; Rounaghi, Gholamhossein; Razavipanah, Iman; Vatani, Hossein; Amiri, Amirhassan

2014-09-01

143

Simultaneous determination of benzene and total aromatic fraction of gasoline by HPLC-DAD  

Energy Technology Data Exchange (ETDEWEB)

A new method is described for the simultaneous determination of benzene and the total aromatic fraction in gasoline by HPLC coupled with a diode array detector (DAD). The detection wavelength of 205 nm was selected on the basis of the UV spectra of benzene, its homologues and interfering compounds, obtained by diode array detector. The use of this wavelength plays an important role in minimizing positive interference from trace compounds, which have a strong absorbance at 254 nm, the typical wavelength at which aromatics are detected. To develop the method a standard solution of seven aromatics compounds was used (benzene, toluene, ortho-, meta- and para-xylenes, ethyl-benzene and 1,3,5-trimethyl-benzene), each at 5% v/v in hexane to simulate the behavior of a gasoline with 35% v/v of total aromatics. The sensitivity of this method to benzene is in the range of 2 x 10{sup -3}% v/v. This method was also applied to a gasoline with a known percentage of benzene and total aromatics and proved quite accurate. (orig.)

Zoccolillo, L.; Alessandrelli, M.; Felli, M. [Rome Univ. (Italy). Dipartimento di Chimica

2001-11-01

144

Noncatalytic and catalytic pyrolysis of toluene  

Energy Technology Data Exchange (ETDEWEB)

Investigation of the effects of process variables on conversion and product yields during catalytic and noncatalytic pyrolysis of toluene was described. The catalyst used was potassium carbonate-impregnated calcium aluminate. Kinetics of the pyrolysis of toluene was also studied. Compared to noncatalytic pyrolysis, the conversions were significantly higher in the presence of the catalyst, although product sensitivities were not affected. With nitrogen as a diluent the main products were hydrogen, methane, benzene, bibenzyl and higher hydrocarbons. Using steam as the diluent, significant amounts of carbon monoxide and carbon dioxide were also produced. Based on the result, it was concluded that the overall consumption of toluene can be represented by two parallel reactions. one for the toluene decomposition, the other for the toluene-steam reaction. The activation energy for toluene decomposition was significantly reduced in the presence of the catalyst; only marginal reduction in the activation energy was observed when steam was used as the diluent. 11 refs., 2 tabs., 5 figs.

Pant, K. K.; Kunzru, D. [Indian Institute of Technology, Dept. of Chemical Engineering, Kanpur (India)

1999-02-01

145

Poly[[[[1-ethyl-6,8-difluoro-7-(3-methylpiperazin-1-yl-4-oxo-1,4-dihydroquinoline-3-carboxylato]cadmium]-?-benzene-1,4-dicarboxylato] trihydrate  

Directory of Open Access Journals (Sweden)

Full Text Available In the title layered coordination polymer, {[Cd(C17H18F2N3O3(C8H4O4]·3H2O}n, the CdII atom exhibits a very distorted CdO6 octahedral geometry defined by one O3,O4-bidentate 1-ethyl-6,8-difluoro-7-(3-methylpiperazin-1-yl-4-oxo-1,4-dihydroquinoline-3-carboxylate (lome ligand, one O,O?-bidentate benzene-1,4-dicarboxylate (bdc dianion and two O-monodentate bdc dianions. Both the bdc species in the asymmetric unit are completed by crystallographic inversion symmetry. The bridging bdc dianions link the cadmium nodes into a rectangular grid lying parallel to (01overline{1}. A network of N—H...O and O—H...O hydrogen bonds helps to establish the packing.

Xin-Ping Kang

2010-11-01

146

Development and characterization of an enzyme-immunoassay with polyclonal antisera for benzene, toluene, and xylenes (BTX); Entwicklung und Charakterisierung eines Enzym-Immunoassays mit polyklonalen Antikoerpern fuer Benzol, Toluol und Xylole (BTX)  

Energy Technology Data Exchange (ETDEWEB)

An indirect competitive enzyme immunoassay for the detection of the volatile organic compounds benzene, toluene, and xylenes has been developed with polyclonal antibodies. The limit of determination for the equal amount of the five analytes in water was 210 {mu}g/l with a center point value of 1.7 mg/l. The addition of 10% of dimethyl sulfoxide (DMSO) to the sample decreased the limit of determination of 80 {mu}g/l and the center point value to 540 {mu}g/l. The specificity of the polyclonal antibodies was investigated based on its cross-reactivity. The influence of increasing concentrations of organic solvents and humic acid on the sensitivity of the antibodies was studied. Water samples were analysed both with GC-FID and by an immunochemical method in order to evaluate the suitability of the assay for environmental analysis. (orig.) [Deutsch] Zur Bestimmung von Benzol, Toluol und den drei Xylol-Isomeren (BTX) wird ein indirekter kompetitiver Enzym-Immunoassay auf der Basis von polyklonalen Antikoerpern beschrieben. Die Bestimmungsgrenze in Wasser liegt bei 210 {mu}g/l und der Testmittelpunkt der sigmoiden Kalibrierkurve bei 1,7 mg/l fuer ein aequivalentes Volumengemisch der fuenf Einzelverbindungen. Durch Loesemittelzusatz, zum Beispiel 10% Dimethylsulfoxid (DMSO), laesst sich die Bestimmungsgrenze auf 80 {mu}g/l und der Testmittelpunkt auf 540 {mu}g/l verringern. Die Spezifitaet der Antikoerper wurde durch Bestimmung von Kreuzreaktionen ermittelt. Weiterhin wurde der Einfluss unterschiedlicher Loesemittelgehalte und von Huminsaeure auf die Affinitaet der Antikoerper im Hinblick auf die Anwendung fuer Realproben untersucht. Um die Eignung des Tests fuer die Routineanalytik zu pruefen, wurde parallel zur immunochemischen Methode eine gaschromatographische Bestimmung BTX in Wasserproben durchgefuehrt. (orig.)

Beyer, K.; Knopp, D.; Niessner, R. [Technische Univ. Muenchen (Germany). Lehrstuhl fuer Hydrogeologie, Hydrochemie und Umweltanalytik

1997-11-01

147

(Liquid + liquid) equilibria in the binary systems (aliphatic, or aromatic hydrocarbons + 1-ethyl-3-methylimidazolium ethylsulfate, or 1-butyl-3-methylimidazolium methylsulfate ionic liquids)  

Energy Technology Data Exchange (ETDEWEB)

(Liquid + liquid) equilibria of 14 binary systems composed of n-hexane, n-heptane, benzene, toluene, o-xylene, m-xylene, or p-xylene and 1-ethyl-3-methylimidazolium ethylsulfate, [emim]EtSO{sub 4}, or 1-butyl-3-methylimidazolium methylsulfate, [bmim]MeSO{sub 4}, ionic liquids have been done in the temperature range from (293.2 to 333.2) K. The solubility of aliphatic is less than those of the aromatic hydrocarbons. In particular, the solubility of hydrocarbons in both ionic liquids increases with the temperature in the order n-heptane < n-hexane < m-xylene < p-xylene < o-xylene < toluene < benzene. Considering the high solubility of aromatics and the low solubility of aliphatic hydrocarbons as well as totally immiscibility of the ionic liquids in all hydrocarbons, these new green solvents may be used as potentials extracting solvents for the separation of aromatic and aliphatic hydrocarbons.

Garcia, Julian, E-mail: jgarcia@quim.ucm.e [Department of Chemical Engineering, Complutense University of Madrid, E-28040 Madrid (Spain); Torrecilla, Jose S.; Fernandez, Adela; Oliet, Mercedes; Rodriguez, Francisco [Department of Chemical Engineering, Complutense University of Madrid, E-28040 Madrid (Spain)

2010-01-15

148

Rapid determination of benzene derivatives in water samples by trace volume solvent DLLME prior to GC-FID  

Energy Technology Data Exchange (ETDEWEB)

An inexpensive, simple and environmentally friendly method based on dispersive liquid liquid microextraction (DLLME) for rapid determination of benzene derivatives in water samples was proposed. A significant improvement of DLLME procedure was achieved. Trace volume ethyl acetate (60 {mu}L) was exploited as dispersion solvent instead of common ones such as methanol and acetone, the volume of which was more than 0.5 mL, and the organic solvent required in DLLME was reduced to a great extent. Only 83-{mu}L organic solvent was consumed in the whole analytic process and the preconcentration procedure was less than 10 min. The advantageous approach coupled with gas chromatograph-flame ionization detector was proposed for the rapid determination of benzene, toluene, ethylbenzene and xylene isomers in water samples. Results showed that the proposed approach was an efficient method for rapid determination of benzene derivatives in aqueous samples. (orig.)

Diao, Chun Peng; Wei, Chao Hai; Feng, Chun Hua [South China Univ. of Technology, Guangzhou Higher Education Mega Center (China). College of Environmental Science and Engineering; Guangdong Regular Higher Education Institutions, Guangzhou (China). Key Lab. of Environmental Protection and Eco-Remediation

2012-05-15

149

A solid phase microextraction coating based on ionic liquid sol-gel technique for determination of benzene, toluene, ethylbenzene and o-xylene in water samples using gas chromatography flame ionization detector.  

Science.gov (United States)

Ionic liquid mediated sol-gel sorbents for head-space solid phase microextraction (HS-SPME) were developed for the extraction of benzene, toluene, ethylbenzene and o-xylene (BTEX) compounds from water samples in ultra-trace levels. The analytes were subsequently analyzed with gas chromatography coupled to flame ionization detector (GC-FID). Three different coating fibers were prepared including: poly(dimethylsiloxane) (PDMS), coating prepared from poly(dimethylsiloxane) in the presence of ionic liquid as co-solvent and conditioned at a higher temperature than decomposition temperature of ionic liquid (PDMS-IL-HT) and coating prepared from poly(dimethylsiloxane) in the presence of ionic liquid as co-solvent and conditioned at a lower temperature than decomposition temperature of ionic liquid (PDMS-IL-LT). Prepared fibers demonstrate many advantages such as high thermal and chemical stabilities due to the chemical bonding of the coatings with the silanol groups on the fused-silica surface fiber. These fibers have shown long life time up to 180 extractions. The scanning electron micrographs of the fibers surfaces revealed that addition of ionic liquid into the sol solution during the sol-gel process increases the fiber coating thickness, affects the form of fiber structure and also leaves high pores in the fiber surface that cause high surface area and therefore increases sample capacity of the fibers. The important parameters that affect the extraction efficiency are desorption temperature and time, sample volume, extraction temperature, extraction time, stirring speed and salt effect. Therefore these factors were investigated and optimized. Under optimal conditions, the dynamic linear range with PDMS-IL-HT, PDMS and PDMS-IL-LT fibers were 0.3-200,000; 50-200,000 and 170-150,000pgmL(-1) and the detection limits (S/N=3) were 0.1-2 and 15-200 and 50-500pgmL(-1), and limit of quantifications (S/N=10) were 0.3-8 and 50-700 and 170-1800, respectively. The relative standard deviations (RSD) for one fiber (repeatability) (n=5), were obtained from 3.1 up to 5.4% and between fibers or batch to batch (reproducibility) (n=3) in the range of 3.8-8.5% for three fibers. The developed method was successfully applied to the real water samples while the relative recovery percentages obtained for the spiked water samples at 20pgmL(-1) were from 91.2 to 103.3%. PMID:23582769

Sarafraz-Yazdi, Ali; Vatani, Hossein

2013-07-26

150

Alteraciones hematológicas en trabajadores expuestos ocupacionalmente a mezcla de benceno- tolueno-xileno (BTX en una fábrica de pinturas Blood disorders among workers exposed to a mixture of benzene-toluene-xylene (BTX in a paint factory  

Directory of Open Access Journals (Sweden)

Full Text Available Objetivos. Evaluar las tres series celulares sanguíneas e identificar la presencia de hipocromía, macrocitosis, leucopenia, linfocitopenia y trombocitopenia en un grupo de trabajadores expuestos a la mezcla de benceno-tolueno-xileno (BTX. Materiales y métodos. Estudio transversal donde se incluyó a 97 trabajadores de una empresa de pinturas de México a los que se les realizó una biometría hemática convencional y les fue estimada la exposición a través de la dosis diaria potencial acumulada para vapores de BTX. Resultados. Del total de trabajadores, 19,6%, mostró macrocitosis, 18,6%, linfocitopenia, 10,3% hipocromía, 7,2% trombocitopenia y 5,2% leucopenia. La asociación cruda de macrocitosis con exposición a dosis alta de mezcla de BTX fue la única significativa (OR:3,6; IC95%: 1,08 - 13,9; p=0,02 y en la que se estructuró un modelo de regresión logística (OR:6,7; IC95%: 1,33 - 13,55; p:0,02 ajustada por edad, consumo de alcohol y tabaquismo. Conclusiones. Todos los componentes citohemáticos analizados mostraron cambios leves; que podrían estar asociados con la exposición a la mezcla de BTX. De ellos, la macrocitosis podría constituirse en una manifestación precoz que merece ser vigilada.Objectives. Evaluate the three blood cell series and identify the presence of hypochromia, macrocytosis, leucopenia, lymphopenia, and thrombocytopenia in a group of workers exposed to the mixture of benzene-toluene-xylene (BTX. Materials and methods. A cross-sectional study which included 97 workers from a paint factory in Mexico. The participants underwent conventional blood count and tests for potential cumulative daily dose of BTX fumes, to estimate exposure. Results. From the total of workers, 19.6% showed macrocytosis, 18.6%, lymphopenia, hypochromia 10.3%, 7.2% and 5.2% thrombocytopenia leukopenia. The crude association of macrocytosis with exposure to high doses of BTX mixture was the only with statistical significance (OR: 3.6, 95% CI 1.08 to 13.9, P = 0.02, and the base for a logistic regression model (OR: 6.7, 95% CI 1.33 to 13.55, P = 0.02 adjusted for age, alcohol consumption, and smoking. Conclusions. All blood cytological components analyzed demonstrated mild changes, potentially associated with exposure to the mixture of BTX. Macrocytosis could constitute an early manifestation worthy for surveillance.

Luis Haro-García

2012-06-01

151

Molecular orbital studies (hardness, chemical potential, electronegativity and electrophilicity), vibrational spectroscopic investigation and normal coordinate analysis of 5-{1-hydroxy-2-[(propan-2-yl)amino]ethyl}benzene-1,3-diol  

Science.gov (United States)

FT-IR and FT-Raman spectra of 5-{1-hydroxy-2-[(propan-2-yl) amino] ethyl} benzene-1,3-diol (abbrevi- 54 ated as HPAEBD) were recorded in the region 4000-450 cm-1 and 4000-100 cm-1 respectively. The structure of the molecule was optimized and the structural characteristics were determined by density functional theory (B3LYP) and HF method with 6-31 G(d,p) as basis set. The theoretical wave numbers were scaled and compared with experimental FT-IR and FT-Raman spectra. A detailed interpretation of the vibrational spectra of this compound has been made on the basis of the calculated Potential energy distribution (PED). Stability of the molecule arising from hyperconjugation and charge delocalization is confirmed by the natural bond orbital analysis (NBO). The results show that electron density (ED) in the ? antibonding orbitals and E (2) energies confirm the occurrence of intra molecular charge transfer (ICT) within the molecule. The molecule orbital contributions were studied by using the total (TDOS), sum of ? and ? electron (??DOS) density of States. Mulliken population analysis of atomic charges is also calculated. The calculated HOMO and LUMO energy gap shows that charge transfer occurs within the molecule. The electron density-based local reactivity descriptors such as Fukui functions were calculated to explain the chemical selectivity or reactivity site in this compound. On the basis of vibrational analyses, the thermodynamic properties of title compound at different temperatures have been calculated.

Muthu, S.; Renuga, S.

2014-01-01

152

Toluene 3-Monooxygenase of Ralstonia pickettii PKO1 Is a para-Hydroxylating Enzyme  

OpenAIRE

Oxygenases are promising biocatalysts for performing selective hydroxylations not accessible by chemical methods. Whereas toluene 4-monooxygenase (T4MO) of Pseudomonas mendocina KR1 hydroxylates monosubstituted benzenes at the para position and toluene ortho-monooxygenase (TOM) of Burkholderia cepacia G4 hydroxylates at the ortho position, toluene 3-monooxygenase (T3MO) of Ralstonia pickettii PKO1 was reported previously to hydroxylate toluene at the meta position, producing primarily m-creso...

Fishman, Ayelet; Tao, Ying; Wood, Thomas K.

2004-01-01

153

Thermally enhanced bioremediation of a gasoline-contaminated aquifer using toluene oxidizing bacteria  

International Nuclear Information System (INIS)

The combined application of steam injection and vacuum extraction has proved to be very effective for the in situ remediation of a gasoline contaminated aquifer. It is expected that the steam treated zone with its near-sterile nature, increased temperature, and decreased level of contaminant concentration will provide a superior environment for enhanced bioremediation, and will favor the survival of an introduced microbial culture for the destruction of residual gasoline hydrocarbons and especially BTEX compounds (Benzene, Toluene, Ethyl benzene, and Xylene). A mixed microbial culture seeded from the pre-steamed aquifer material was enriched in a laboratory chemostat on toluene, a major gasoline aromatic. Studies were conducted to determine the optimal conditions for microbial growth and activity. Growth rate studies conducted at different temperatures revealed that cell growth was optimal at 35 C, a temperature at which the aquifer can be maintained using the existing steam injection wells. The enriched culture was shown to degrade all BTEX compounds successfully both individually and in mixtures. Substrate toxicity was observed for some of the gasoline aromatics but at concentration levels well above those found in groundwater. When cells were exposed to mixtures of BTEX compounds, the biodegradation of xylene, the most recalcitrant aromatic among BTEX compounds, was stimulated. When cells were exposed to gasoline, BTEX degradation proceeded with no apparent inhibitadation proceeded with no apparent inhibition by gasoline aliphatics; little aliphatic degradation took place, however, suggesting the absence of monooxygenase enzymes in the mixed culture. In mixtures of both toluene and propane enriched cultures, only dioxygenase activity was observed

154

Comparação entre injeção na coluna ("on-column") e headspace dinâmico na determinação de benzeno, tolueno e xilenos (BTX) em amostras de água / Comparison between on-column injection and dynamic headspace in the determination of Benzene, Toluene and Xylene (BTX) in water  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese [...] Abstract in english The analysis of water samples containing volatile organic compounds has become an important task in analytical chemistry. Gas chromatography has been widely used for the analysis of volatile organic compounds in water. The headspace analysis shows as a principal characteristic the possibility of det [...] ermination of the volatile components in drinking water. Benzene, Toluene and Xylene (BTX) are important compounds usually present in drinking water, from contamination by petroleum derivatives. Since they are toxic compounds even when present in low concentration levels, their determination is important in order to define the quality of the water. The sampling technique using headspace, coupled with gas chromatography as the separation method, showed to be suitable for BTX analysis in several samples at the mug/L (ppb) level.

Elaine A. A. F., Gobato; Fernando M., Lanças.

2001-04-01

155

Cerebellar dysfunction caused by sniffing of toluene-containing thinner  

Energy Technology Data Exchange (ETDEWEB)

A 19-year-old man who had sniffed lacquer thinner for 8 months was found to suffer from cerebellar dysfunction and visual disorders. He had blurred vision, dysarthria, nystagmus, slight intention tremor, staggering gait and an abnormal EEG. The thinner contained 68% toluene, 18% ethyl acetate, 9% methyl isobutyl ketone (MIBK), 3% isopropyl alcohol (IPA) and 3% butyl acetate. The concentration of each solvent in the plastic bag used for sniffing was 12,000 ppm toluene, 11,500 ppm ethyl acetate, 6,000 ppm IPA and 2,000 ppm MIBK. Previously reported cerebellar dysfunction due to toluene or toluene-containing solvents are summarized and discussed. Based on these reports and the present case, toluene is presumed to impair function in the order of the vermis,cerebellar hemispheres, and cerebrum, when a relatively high concentration of toluene is inhaled. The effects of organic solvents, especially toluene, on the cerebellum are considered to be very important from the viewpoint of occupational health, since toluene is widely used in industry and many workers are exposed to it.

Takeuchi, Y. (Nagoya Univ. School of Medicine, Japan); Hisanaga, N.; Ono, Y.; Ogawa, T.; Hamaguchi, Y.; Okamoto, S.

1982-01-01

156

{μ-1,3-Bis[(3,5-dimethylpyrazol-1-yl)methyl]benzene-κ2N2:N2′}di-μ-chlorido-bis[chloridopalladium(II)] toluene solvate  

OpenAIRE

In the title complex, [Pd2Cl4(C18H22N4)]·C7H8, each of the two four-coordinated PdII atoms is in a slightly distorted square-planar geometry, defined by one N atom from the ligand, two bridging Cl atoms and one terminal Cl atom. Intermolecular C—H...? interactions between the pyrazole ring H atom and the toluene ring stabilize the crystal structure.

Bernard Omondi; Asheena Budhai; James Darkwa

2009-01-01

157

Excess Molar Volumes of (Octane + Benzene, or + Toluene, or + 1,3-Xylene, or 1,3,5-Trimethylbenzene) at Temperatures between (298.15 K and 328.15) K.  

Czech Academy of Sciences Publication Activity Database

Ro?. 40, ?. 4 (2008), s. 671-676. ISSN 0021-9614 R&D Projects: GA ?R(CZ) GA104/06/0656 Institutional research plan: CEZ:AV0Z40720504 Keywords : octane * benzene * excess volume Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.876, year: 2008

Morávková, Lenka; Linek, Jan

2008-01-01

158

Electron beam degradation of simulated toluene-containing exhaust gas  

International Nuclear Information System (INIS)

With toluene as an example, experimental investigation on VOCs treatment by electron beam irradiation was carried out. The system uses 0.8 MeV electron beams to irradiate simulated toluene-containing gases to 5kGy-40kGy for investigatiing effects of initial concentration, absorbed dose, humidity on toluene removal rate. The toluene removal rate increased with absorbed dose. With 0.5-l.2Nm3/h of the gas flow at an initial toluene concentration of 1600mg/Nm3, the toluene removal rate was 46.5% at 10kGy and 72.2% at 40kGy. And increasing humidity increased the toluene removal rate, too. Qualitative analysis on by-products of the toluene degradation was made by means of Gas Chromatogram-Mass Spectrometer (GC/MS) and Chromatography of Ions (IC). It was found that the by-products consist of mainly benzaldehyde and formic acid, plus a little benzoic acid, benzyl alcohol, methyl pyridine, nitrotoluene, o-cresol, phenol and benzoin ethyl etherl. Mechanisms of the E-beam toluene removal, i.e. the contributions of OH free radicals and O2 to the oxidation of toluene, were discussed. (authors)

159

Protein Engineering of Toluene Monooxygenases for Synthesis of Chiral Sulfoxides?  

OpenAIRE

Enantiopure sulfoxides are valuable asymmetric starting materials and are important chiral auxiliaries in organic synthesis. Toluene monooxygenases (TMOs) have been shown previously to catalyze regioselective hydroxylation of substituted benzenes and phenols. Here we show that TMOs are also capable of performing enantioselective oxidation reactions of aromatic sulfides. Mutagenesis of position V106 in the ?-hydroxylase subunit of toluene ortho-monooxygenase (TOM) of Burkholderia cepacia G4 a...

Feingersch, Roi; Shainsky, Janna; Wood, Thomas K.; Fishman, Ayelet

2008-01-01

160

Exposure Evaluation for Benzene, Lead and Noise in Vehicle and Equipment Repair Shops  

Energy Technology Data Exchange (ETDEWEB)

An exposure assessment was performed at the equipment and vehicle maintenance repair shops operating at the U. S. Department of Energy Hanford site, in Richland, Washington. The maintenance shops repair and maintain vehicles and equipment used in support of the Hanford cleanup mission. There are three general mechanic shops and one auto body repair shop. The mechanics work on heavy equipment used in construction, cranes, commercial motor vehicles, passenger-type vehicles in addition to air compressors, generators, and farm equipment. Services include part fabrication, installation of equipment, repair and maintenance work in the engine compartment, and tire and brake services. Work performed at the auto body shop includes painting and surface preparation which involves applying body filler and sanding. 8-hour time-weighted-average samples were collected for benzene and noise exposure and task-based samples were collected for lead dust work activities involving painted metal surfaces. Benzene samples were obtained using 3M™ 3520 sampling badges and were analyzed for additional volatile organic compounds. These compounds were selected based on material safety data sheet information for the aerosol products used by the mechanics for each day of sampling. The compounds included acetone, ethyl ether, toluene, xylene, VM&P naphtha, methyl ethyl ketone, and trichloroethylene. Laboratory data for benzene, VM&P naphtha, methyl ethyl ketone and trichloroethylene were all below the reporting detection limit. Airborne concentrations for acetone, ethyl ether, toluene and xylene were all less than 10% of their occupational exposure limit. The task-based samples obtained for lead dusts were submitted for a metal scan analysis to identify other metals that might be present. Laboratory results for lead dusts were all below the reporting detection limit and airborne concentration for the other metals observed in the samples were less than 10% of the occupational exposure limit. Noise dosimetry sampling was performed on a random basis and was representative of the different work activities within the four shops. Twenty three percent of the noise samples exceeded the occupational exposure limit of 85 decibels for an 8-hour time-weightedaverage. Work activities where noise levels were higher included use of impact wrenches and grinding wheels.

Sweeney, Lynn C.

2013-04-10

161

Studies on the mechanism of benzene toxicity.  

OpenAIRE

Using the 59Fe uptake method of Lee et al. it was shown that erythropoiesis in female mice was inhibited following IP administration of benzene, hydroquinone, p-benzoquinone, and muconaldehyde. Toluene protected against the effects of benzene. Coadministration of phenol plus either hydroquinone or catechol resulted in greatly increased toxicity. The combination of metabolites most effective in reducing iron uptake was hydroquinone plus muconaldehyde. We have also shown that treating animals w...

Snyder, R.; Dimitriadis, E.; Guy, R.; Hu, P.; Cooper, K.; Bauer, H.; Witz, G.; Goldstein, B. D.

1989-01-01

162

Optimización de iones de fierro para la eliminación de piocianina en la reacción de degradación de Tolueno, Benceno y Fenol por Pseudomonas aeruginosa / Optimization of iron ions to eliminate pyocyanine in the degradation reaction of Toluene, Benzene and Phenol by Pseudomonas aeruginosa  

Scientific Electronic Library Online (English)

Full Text Available Una amplia gama de substancias xenobióticas representan un serio problema como contaminantes ambientales por su toxicidad; entre ellos los compuestos aromáticos pueden ser biodegradados por microorganismos que los usan como fuente de carbono y energía. El género Pseudomonas destaca por sus múltiples [...] aplicaciones biotecnológicas debido a su gran versatilidad metabólica; puede producir metabolitos útiles, transformaciones enzimáticas, biodegradación y biorremediación de suelos, y en aguas contaminadas con petróleo y plaguicidas. En esta investigación se usaron células de P. aeruginosa para degradar tolueno, benceno y fenol. La cepa fue cultivada en medio mineral sólido y se establecieron las concentraciones óptimas para el desarrollo de células viables: 0.31, 0.19 y 0.13 M para tolueno, benceno y fenol. Los ambientes con concentraciones limitadas de Fe(III) favorecen la producción de piocianina, pigmento que puede interferir en el método analítico de biodegradación de compuestos aromáticos. Este efecto fue eliminado aumentando la concentración de iones de fierro en el medio. Con base en lo anterior, se optimizó y estableció el medio de cultivo mineral con 0.04 g L-1 de FeSO4 en presencia de tolueno (0.03 M) y con esta concentración inicial la tasa de biodegradación fue 75 %. Las pruebas de degradación específicas para los compuestos aromáticos mostraron que la cepa de P. aeruginosa usada puede degradar tolueno, benceno y fenol. Las tasas de degradación fueron mayores para tolueno (58.4 %) y benceno (70.11 %) con concentraciones iniciales de 0.14 M y 0.16 M, y la degradación fue menor para fenol (24.65 %) con una concentración inicial 0.10 M. La capacidad degradadora de P. aeruginosa tuvo proporción directa con su crecimiento en presencia de los xenobióticos estudiados, mostrando una mayor cantidad de proteína celular en los cultivos con benceno (1.4982 mg mL-1), tolueno (0.8629 mg mL-1) y menor en los cultivos desarrollados en presencia de fenol (0.4431 mg mL-1); lo cual muestra que un deficiente desarrollo bacteriano (biomasa) influye en una subóptima biodegradación. Abstract in english A wide range of xenobiotic substances represent a serious problem as environmental pollutants because of their toxicity, among them are found aromatic compounds that can be biodegraded by microorganisms, which use them as their source of carbon and energy. The genus Pseudomonas is outstanding for it [...] s multiple biotechnological applications due to its remarkable metabolic versatility. It is capable of producing useful metabolites, enzymatic transformations, biodegradation and bioremediation in soil, as well as in water polluted with oil and pesticides. In this study, cells of P. aeruginosa were used to degrade toluene, benzene and phenol. The strain was cultivated in a solid mineral medium, and the following optimal concentrations were established for the development of viable cells: 0.31, 0.19, and 0.13 M for toluene, benzene and phenol. The environments with limited concentrations of Fe(III) favored the production of pyocyanine, a pigment that can interfere in the analytical method of aromatic compound biodegradation. This effect was eliminated by increasing the concentration of iron ions in the medium. On this basis, the mineral culture medium was optimized and established at 0.04 g L-1 FeSO4 in presence of toluene (0.03 M). With this initial concentration, a rate of biodegradation of 75 % was obtained. The specific degradation tests for the aromatic compounds showed that the P. aeruginosa strain used can degrade toluene, benzene and phenol. The rates of degradation were higher for toluene (58.4 °/o) and benzene (70.11 °/o) with the initial concentrations of 0.14 M and 0.16 M. Degradation was less for phenol (24.65 %) with an initial concentration of 0.10 M. The degrading capacity of P. aeruginosa was directly proportional to its growth in the presence of the xenobiotic substances studied. A larger amount of cell protein was exhibited in cultures with benzene (1.4982

María de L., Rangel-García; Jesús, Rodríguez-Martínez; Yolanda, Garza-García; José L., Martínez-Hernández.

2010-03-01

163

Quantitative trace analysis of benzene using an array of plasma-treated metal-decorated carbon nanotubes and fuzzy adaptive resonant theory techniques.  

Science.gov (United States)

The functionalization of carbon nanotube sidewalls with metal nanoparticles is exploited here to improve the sensitivity and selectivity of gas sensors operated at room temperature. An array of sensors using oxygen plasma treated multiwalled carbon nanotubes (bare and decorated with Pt, Pd or Rh nanoparticles) is shown to selectively detect traces of benzene (i.e., 100 ppb) in the presence of carbon monoxide, hydrogen sulfide or nitrogen dioxide at different humidity levels. Employing a quantitative fuzzy adaptive resonant theory (ART) network whose inputs are the responses of the sensor array, it is possible to accurately estimate benzene concentration in a changing background. The quantitative fuzzy ART is especially suited for compensating the nonlinear effects in sensor response caused by changes in ambient humidity, which explains why this method clearly outperforms partial least squares calibration models at estimating benzene concentration. These results open the way to design new affordable, wearable, sensitive and selective detectors aimed at the personal protection of workers subject to occupational exposure to benzene, toluene, ethyl benzene and xylenes. PMID:22093340

Leghrib, Radouane; Llobet, Eduard

2011-12-01

164

Icosapent Ethyl  

Science.gov (United States)

... to icosapent ethyl; fish, including shellfish (clams, scallops, shrimp, lobster, crayfish, crab, oyster, mussels, others); any other ... ever had diabetes or liver, thyroid, or pancreatic disease.tell your doctor if you are pregnant, plan ...

165

Studies on the mechanism of benzene toxicity  

Energy Technology Data Exchange (ETDEWEB)

Using the 59Fe uptake method of Lee et al. it was shown that erythropoiesis in female mice was inhibited following IP administration of benzene, hydroquinone, p-benzoquinone, and muconaldehyde. Toluene protected against the effects of benzene. Coadministration of phenol plus either hydroquinone or catechol resulted in greatly increased toxicity. The combination of metabolites most effective in reducing iron uptake was hydroquinone plus muconaldehyde. We have also shown that treating animals with benzene leads to the formation of adducts of bone marrow DNA as measured by the 32P-postlabeling technique.

Snyder, R.; Dimitriadis, E.; Guy, R.; Hu, P.; Cooper, K.; Bauer, H.; Witz, G.; Goldstein, B.D. (Rutgers, State Univ. of New Jersey, Piscataway (USA))

1989-07-01

166

Studies on the mechanism of benzene toxicity  

International Nuclear Information System (INIS)

Using the 59Fe uptake method of Lee et al. it was shown that erythropoiesis in female mice was inhibited following IP administration of benzene, hydroquinone, p-benzoquinone, and muconaldehyde. Toluene protected against the effects of benzene. Coadministration of phenol plus either hydroquinone or catechol resulted in greatly increased toxicity. The combination of metabolites most effective in reducing iron uptake was hydroquinone plus muconaldehyde. We have also shown that treating animals with benzene leads to the formation of adducts of bone marrow DNA as measured by the 32P-postlabeling technique

167

Radiolysis of Aqueous Toluene Solutions  

International Nuclear Information System (INIS)

Aqueous toluene solutions have been irradiated with Co ?-rays. In unbuffered solutions the various cresol isomers are formed in a total yield of 0.45, 0.87 and 0.94 molecules/100 eV absorbed energy in argon-, N2O- and air - saturated solutions, respectively. The yields are reduced in acid (pH 3) solutions (G 0.14, 0.14 and 0.52, respectively) but the reduction is compensated by the formation of 1,2-di-phenylethane in yields of 0.49 and 1.60 in argon- and N2O-saturated solutions, respectively. Benzyl radicals are formed through an acid catalysed water elimination reaction from the initially formed hydroxymethylcyclohexadienyl radical. Phenyltolylmethanes, dimethylbiphenyls and partly reduced dimers are also formed during the radiolysis. Hydrogen is formed in the same yield as the molecular yield, g(H2). Xylene isomers and benzene are formed in trace quantities. The most remarkable effects of the addition of Fe(III) ions to deaerated acid toluene solutions are the formation of benzyl alcohol and benzaldehyde and an increase in the yield of 1,2-diphenylethane

168

Liquid-liquid extraction/headspace/gas chromatographic/mass spectrometric determination of benzene, toluene, ethylbenzene, (o-, m- and p-)xylene and styrene in olive oil using surfactant-coated carbon nanotubes as extractant.  

Science.gov (United States)

BTEX-S compounds are widely distributed in the environment and can be present in different foodstuffs, including olive oil. Taking into account the risks of the exposure to these compounds, analytical methods for their determination in different matrices are mandatory. In this paper, the use of surfactant-coated multiwalled carbon nanotubes as additive in liquid-liquid extraction is applied for the determination of single-ring aromatic compounds in olive oil samples. After sample treatment, the aqueous extracts are subsequently analyzed by headspace/gas chromatography/mass spectrometry allowing the determination of BTEX-S within ca. 15 min. Each stage of the proposed LLE/HS/GC/MS configuration involves a selectivity enhancement avoiding the interference of other compounds of the sample matrix. Limits of detection were in the range 0.25 ng mL(-1) (obtained for ethylbenzene) and 0.43 ng mL(-1) (for benzene). The repeatability of the proposed method expressed as RSD varied between 1.9% (styrene) and 3.3% (benzene) (n=11). PMID:17919647

Carrillo-Carrión, Carolina; Lucena, Rafael; Cárdenas, Soledad; Valcárcel, Miguel

2007-11-01

169

Preparation of methylbenzene-ring-14C from benzene-14C on the basis of a microcatalytic process  

International Nuclear Information System (INIS)

The known processes of benzene alkylation are relatively non-selective and give low yields. Therefore, they are not very suitable for the preparation of toluene- and xylene-ring-14C. Since the catalytic disproportionation of toluene into benzene and xylene is already used it was attempted to develop a procedure for the preparation of the above-mentioned 14C-compounds by reversing this reaction and using benzene-14C. The obtained results are presented and the developed synthesis is explained, using the preparation of toluene-ring-14C as an example. The average activity yield is 58%. (author)

170

Substrate interactions during aerobic biodegradation of benzene.  

Science.gov (United States)

This study dealt with the interactions with benzene degradation of the following aromatic compounds in a mixed substrate: toluene, o-xylene, naphthalene, 1,4-dimethylnaphthalene, phenanthrene, and pyrrole. The experiment was performed as a factorial experiment with simple batch cultures. The effect of two different types of inocula was tested. One type of inoculum was grown on a mixture of aromatic hydrocarbons; the other was grown on a mixture of aromatic hydrocarbons and nitrogen-, sulfur-, and oxygen-containing aromatic compounds (NSO compounds), similar to some of the compounds identified in creosote waste. The culture grown on the aromatic hydrocarbons and NSO compounds was much less efficient in degrading benzene than the culture grown on only aromatic hydrocarbons. The experiments indicated that toluene- and o-xylene-degrading bacteria are also able to degrade benzene, whereas naphthalene-, 1,,4-dimethylnaphthalene-, and phenanthrene-degrading bacteria have no or very little benzene-degrading ability. Surprisingly, the stimulating effect of toluene and o-xylene was true only if the two compounds were present alone. In combination an antagonistic effect was observed, i.e., the combined effect was smaller than the sum from each of the compounds. The reason for this behavior has not been identified. Pyrrole strongly inhibited benzene degradation even at concentrations of about 100 to 200 micrograms/liter. Future studies will investigate the generality of these findings. PMID:2619308

Arvin, E; Jensen, B K; Gundersen, A T

1989-12-01

171

Anaerobic benzene oxidation via phenol in Geobacter metallireducens.  

Science.gov (United States)

Anaerobic activation of benzene is expected to represent a novel biochemistry of environmental significance. Therefore, benzene metabolism was investigated in Geobacter metallireducens, the only genetically tractable organism known to anaerobically degrade benzene. Trace amounts (Geobacter metallireducens anaerobically oxidizing benzene to carbon dioxide with the reduction of Fe(III). Phenol was not detected in cell-free controls or in Fe(II)- and benzene-containing cultures of Geobacter sulfurreducens, a Geobacter species that cannot metabolize benzene. The phenol produced in G. metallireducens cultures was labeled with (18)O during growth in H2(18)O, as expected for anaerobic conversion of benzene to phenol. Analysis of whole-genome gene expression patterns indicated that genes for phenol metabolism were upregulated during growth on benzene but that genes for benzoate or toluene metabolism were not, further suggesting that phenol was an intermediate in benzene metabolism. Deletion of the genes for PpsA or PpcB, subunits of two enzymes specifically required for the metabolism of phenol, removed the capacity for benzene metabolism. These results demonstrate that benzene hydroxylation to phenol is an alternative to carboxylation for anaerobic benzene activation and suggest that this may be an important metabolic route for benzene removal in petroleum-contaminated groundwaters, in which Geobacter species are considered to play an important role in anaerobic benzene degradation. PMID:24096430

Zhang, Tian; Tremblay, Pier-Luc; Chaurasia, Akhilesh Kumar; Smith, Jessica A; Bain, Timothy S; Lovley, Derek R

2013-12-01

172

Development and Characterization of a Green Fluorescent Protein-Based Bacterial Biosensor for Bioavailable Toluene and Related Compounds†  

OpenAIRE

A green fluorescent protein-based Pseudomonas fluorescens strain A506 biosensor was constructed and characterized for its potential to measure benzene, toluene, ethylbenzene, and related compounds in aqueous solutions. The biosensor is based on a plasmid carrying the toluene-benzene utilization (tbu) pathway transcriptional activator TbuT from Ralstonia pickettii PKO1 and a transcriptional fusion of its promoter PtbuA1 with a promoterless gfp gene on a broad-host-range promoter probe vector. ...

Stiner, Lawrence; Halverson, Larry J.

2002-01-01

173

Diaqua­(5-carb­oxy­benzene-1,3-dicarboxyl­ato-?O 1)[8-ethyl-5-oxo-2-(piperazin-4-ium-1-yl)-5,8-dihydro­pyrido[2,3-d]pyrimidine-6-carboxyl­ato-?2 O 5,O 6]zinc monohydrate  

OpenAIRE

In the title compound, [Zn(C14H17N5O3)(C9H4O6)(H2O)2]·H2O, the complex mol­ecule exists in a zwitterionic form. The ZnII ion exhibits a distorted tetra­gonal-pyramidal geometry, being coordinated by two O atoms from the zwitterionic 8-ethyl-5-oxo-2-(piperazin-4-ium-1-yl)-5,8-dihydro­pyrido[2,3-d]pyrimidine-6-carboxyl­ate (L) ligand, one O atom from the 5-carb­oxy­benzene-1,3-dicarboxyl­ate dianion, [Hbtc]2?, and two O atoms from two aqua ligands. In the crystal, N—H?O and O—H?...

Ye, Zhong-li; Xin, Guang-hua; Zhang, Fu-tian; Xiao, Dong-rong

2013-01-01

174

Pallidol hexaacetate ethyl acetate monosolvate  

Directory of Open Access Journals (Sweden)

Full Text Available The entire molecule of pallidol hexaacetate {systematic name: (±-(4bR,5R,9bR,10R-5,10-bis[4-(acetyloxyphenyl]-4b,5,9b,10-tetrahydroindeno[2,1-a]indene-1,3,6,8-tetrayl tetraacetate} is completed by the application of twofold rotational symmetry in the title ethyl acetate solvate, C40H34O12·C4H8O2. The ethyl acetate molecule was highly disordered and was treated with the SQUEEZE routine [Spek (2009. Acta Cryst. D65, 148–155]; the crystallographic data take into account the presence of the solvent. In pallidol hexaacetate, the dihedral angle between the fused five-membered rings (r.m.s. deviation = 0.100?Å is 54.73?(6°, indicating a significant fold in the molecule. Significant twists between residues are also evident as seen in the dihedral angle of 80.70?(5° between the five-membered ring and the pendent benzene ring to which it is attached. Similarly, the acetate residues are twisted with respect to the benzene ring to which they are attached [C—O(carboxy—C—C torsion angles = ?70.24?(14, ?114.43?(10 and ?72.54?(13°]. In the crystal, a three-dimensional architecture is sustained by C—H...O interactions which encompass channels in which the disordered ethyl acetate molecules reside.

Qinyong Mao

2013-07-01

175

Investigation of the near-degeneracy effects of the mono-alkyl substituted benzenes by ESR and ENDOR  

International Nuclear Information System (INIS)

Author.In the first chapter, we introduce the theory of ESR and ENDOR spectroscopy. In the second chapter, a description is given of the ESR and ENDOR spectrometers used in our measurements, also included is the sample preparation technique. Chapter three gives an outline of the Huckel and Mclachlan molecular orbital theory used in this thesis. We also discuss the mechanism of proton hyperfine coupling. The effect of alkyl substitution in the lifting of the degeneracy of benzene and the possible explanation of the resulting spin densities, such as the thermal mixing, Jahn-Teller and vibronic effects. In chapter four, we present the results of our ESR and ENDOR measurements on a number of mono-alkyl substituted benzenes. Proton hyperfine splitting constants of toluene, ethyl, n-propyl, n-butyl, n-amyl, iso-propyl, sec-butyl, t-butyl benzenes, 1-phenyl hexane and 1-phenyl heptane are reported. The results are discussed in the light of spin density calculations using the HMO and Mclachlan methods and compared with other calculations found in the literature. Estimations of the mining between the two lowest antibonding states have been made. Finally, temperature dependence of some of the splittings were measured in an attempt to determine the importance of the thermal contribution of the mixing

176

Preparation of toluenes specifically labelled with C-14  

International Nuclear Information System (INIS)

The attempt to prepare toluene-2 C-14 starting from ethyl acetoacetate failed because the reaction of sodium ethyl acetoacetate with dibromopropane could not be performed. This labelling was also attempted starting from methyl tetrahydropyran. This synthesis was not successful because the preparationof 2-methyl pimelic acid was impossible. Labellimg of carbon-3 of toluene starting from succinic acid could not be carried out because the Grignard reaction of a-ketoglutaric acid as unsuccessful. The radioactive syntheses started from propanediol resp. from c-butyrolactone. (The labelling of carbon-3 of toluene was not possible in this case because the reduction of malonic acid to propanediol could not be carried out). The synthesis course was identical for all labellings. The synthesis differed only in the introduction of the activiy from potassium cyanide C-14. The starting compounds were reacted to propanedinitril, which was saponified to glutaric acid. The acid was reduced to pentanediol. From the diol, dibromopentane was produced. Reaction with potassium cyanide yielded, after saponification, pimelic acid. The acid was cyclizated to cyclohexanone, which was reduced to cyclohexanol. The OH group was replaced by bromine and subsequently by a methyl group. Dehydration yielded toluene. The following labellings were carried out: Toluene-2, -2.6, -1.2.6, -1.2 C-14. (G.G.)

177

21 CFR 584.200 - Ethyl alcohol containing ethyl acetate.  

Science.gov (United States)

...false Ethyl alcohol containing ethyl acetate. 584.200 Section 584...200 Ethyl alcohol containing ethyl acetate. The feed additive ethyl alcohol containing ethyl acetate meets the requirement of 27...

2010-04-01

178

Mesophilic and thermophilic BTEX substrate interactions for a toluene-acclimatized biofilter.  

Science.gov (United States)

Benzene, toluene, ethylbenzene and xylene (BTEX) substrate interactions for a mesophilic (25 degrees C) and thermophilic (50 degrees C) toluene-acclimatized composted pine bark biofilter were investigated. Toluene, benzene, ethylbenzene, o-xylene, m-xylene and p-xylene removal efficiencies, both individually and in paired mixtures with toluene (1:1 ratio), were determined at a total loading rate of 18.1 g m(-3) h(-1) and retention time ranges of 0.5-3.0 min and 0.6-3.8 min for mesophilic and thermophilic biofilters, respectively. Overall, toluene degradation rates under mesophilic conditions were superior to degradation rates of individual BEX compounds. With the exception of p-xylene, higher removal efficiencies were achieved for individual BEX compounds compared to toluene under thermophilic conditions. Overall BEX compound degradation under mesophilic conditions was ranked as ethylbenzene >benzene > o-xylene > m-xylene > p-xylene. Under thermophilic conditions overall BEX compound degradation was ranked as benzene > o-xylene >ethylbenzene > m-xylene > p-xylene. With the exception of o-xylene, the presence of toluene in paired mixtures with BEX compounds resulted in enhanced removal efficiencies of BEX compounds, under both mesophilic and thermophilic conditions. A substrate interaction index was calculated to compare removal efficiencies at a retention time of 0.8 min (50 s). A reduction in toluene removal efficiencies (negative interaction) in the presence of individual BEX compounds was observed under mesophilic conditions, while enhanced toluene removal efficiency was achieved in the presence of other BEX compounds, with the exception of p-xylene under thermophilic conditions. PMID:14666388

Strauss, J M; Riedel, K J; Du Plessis, C A

2004-06-01

179

Simultaneous determination of polycyclic aromatic hydrocarbons and benzene, toluene, ethylbenzene and xylene in water samples using a new sampling strategy combining different extraction modes and temperatures in a single extraction solid-phase microextraction-gas chromatography-mass spectrometry procedure.  

Science.gov (United States)

This study proposes a new optimization approach for the simultaneous determination of polycyclic aromatic hydrocarbons (PAHs) and benzene, toluene, ethylbenzene and xylene isomers (BTEX) from water samples using the solid-phase microextraction technique followed by gas chromatography-mass spectrometry (GC-MS) separation and detection. The objective of the study was to achieve compromise extraction conditions, suitable for all semi-volatile and volatile compounds, under which the amount extracted is maximized for all analytes. This was achieved by careful optimization of the fiber coating, salting-out effect, extraction time and temperature and extraction mode (headspace or direct immersion). With the optimized fiber coating - PDMS/DVB 65 ?m - the other selected factors were optimized using a response surface methodology through central composite designs. As expected, the optimized results for each class of analytes varied significantly, probably due to the differences in their volatility and the equilibrium constants for the analyte/fiber coating. In order to overcome this issue, a new optimization approach was proposed based on a combination of extraction modes and extraction temperatures in a single extraction procedure. The final optimized procedure was: 48 min of extraction in direct immersion mode with the sample maintained at 80 °C followed by a further 32 min of headspace extraction with the sample temperature kept at 10 °C. The proposed procedure was compared with conventional methods based on the use of a single extraction mode and temperature (80 min of headspace extraction at 60 °C or 80 min of direct immersion extraction at 50 °C). The newly proposed method was shown to be more attractive as it extracted higher amounts of both semi-volatile and volatile compounds in a single extraction procedure compared to the conventional approaches. The optimized method was validated and excellent results were obtained. PMID:22386255

Bianchin, Joyce Nunes; Nardini, Giuliana; Merib, Josias; Dias, Adriana Neves; Martendal, Edmar; Carasek, Eduardo

2012-04-13

180

Determination of benzene in exhaust gas from biofuels. Final report; Bestimmung von Benzol im Abgas von Biokraftstoffen. Abschlussbericht  

Energy Technology Data Exchange (ETDEWEB)

With the advance of environmental legislation and practices oriented towards sustainability renewable energy resources are becoming increasingly important. Use of replenishable raw materials helps preserve fossil resources. In the fuel sector the most widely used replenishable materials are rape methyl ester (RME) and ethyl tertiary butyl ether (ETBE). The purpose of the present project on the ''Determination of benzene in exhaust gas from biofuels'' was to generate orienting data on the potential health relevance of mixtures of fossil and renewable fuel intended for use in spark ignition and diesel engines. This included a determination of benzene emissions and the mutagenicity of particles. Beyond the applied-for scope of research measurements were also performed on the test engine's toluene, ethyl benzene and xylene emissions as well as on the smoke spot number and nitrogen oxide (NO{sub x}) and hydrocarbon (HC) emissions of the diesel engine. [German] Regenerative Energien gewinnen durch die Umweltgesetzgebungen und das Streben nach einer nachhaltigen Entwicklung zunehmend an Bedeutung. Durch die Verwendung nachwachsender Rohstoffe koennen die fossilen Ressourcen geschont werden. Im Kraftstoffsektor sind hier hauptsaechlich Rapsoelmethylester (RME) und optional Ethyltertiaerbutylether (ETBE) zu nennen. Um fuer Diesel- und Ottomotoren insbesondere mit Blick auf Kraftstoffgemische aus fossilen und regenerativen Komponenten orientierende Daten ueber eine potenzielle Gesundheitsrelevanz zu generieren, wurde das Projekt 'Bestimmung von Benzol im Abgas von Biokraftstoffen' durchgefuehrt. Neben der Benzolemission wurde die Mutagenitaet der Partikeln ermittelt. Ueber den beantragten Untersuchungsrahmen hinaus wurden die Tuluol-, Ethylbenzol-, und Xylolemissionen der eingesetzten Motoren, sowie die Russzahl (RZ) und die Stickoxid- (NO{sub x}) und Kohlenwasserstoffemissionen (HC) des Dieselmotors bestimmt. (orig.)

Dutz, M.; Buenger, J.; Gnuschke, H.; Halboth, H.; Gruedl, P.; Krahl, J.

2001-10-01

181

Substrate interactions during aerobic biodegradation of benzene.  

OpenAIRE

This study dealt with the interactions with benzene degradation of the following aromatic compounds in a mixed substrate: toluene, o-xylene, naphthalene, 1,4-dimethylnaphthalene, phenanthrene, and pyrrole. The experiment was performed as a factorial experiment with simple batch cultures. The effect of two different types of inocula was tested. One type of inoculum was grown on a mixture of aromatic hydrocarbons; the other was grown on a mixture of aromatic hydrocarbons and nitrogen-, sulfur-,...

Arvin, E.; Jensen, B. K.; Gundersen, A. T.

1989-01-01

182

Knoevenagel condensation of aromatic aldehydes with ethyl 4-chloro-3-oxobutanoate in ionic liquids  

Scientific Electronic Library Online (English)

Full Text Available Condensações de Knoevenagel de aldeídos aromáticos com 4-cloro-3-oxobutanoato de etila catalisadas por morfolina/ácido acético foram conduzidas em líquidos iônicos para fornecerem 2-cloroacetil-3-arilpropenoatos de etila em 44 a 84% de rendimentos após 0,5 a 2 h à temperatura ambiente (25-28 ºC). Es [...] tas condições representam um protocolo mais verde para a condensação de Knoevenagel do que aquelas realizadas com refluxo de benzeno e tolueno, utilizados como solventes. Aldeídos aromáticos contendo grupos arila, 4-clorofenila, 4-metoxifenila, 2-tiofuranila, 2-furanila, fenila e 3,4-metilenodioxifenila apresentaram razões diastereoméricas (E)/(Z) de 56/44 a 85/15. A estrutura do isômero-(E) do 2-cloroacetil-3-(3',4'-metilenodioxifenil)propenoato de etila foi determinada por difração de raio X, e uma metodologia inequívoca da análise estrutural-(E)/(Z) por RMN de 13C (ressonância magnética nuclear) é apresentada. Abstract in english Knoevenagel condensations of aromatic aldehydes with ethyl 4-chloro-3-oxobutanoate catalyzed by morpholine/acetic acid were carried out in ionic liquids to give ethyl 2-chloroacetyl-3-arylpropenoates in 44-84% yield after 0.5 to 2 h at room temperature (25-28 ºC). These conditions represent a greene [...] r protocol for the Knoevenagel condensation than those using refluxing benzene or toluene as solvent. Aromatic aldehydes having aryl groups 4-chlorophenyl, 4-methoxyphenyl, 2-thiofuranyl, 2-furanyl, phenyl and 3,4-methylenedioxyphenyl gave (E)/(Z) diastereomeric ratios of products from 56/44 to 85/15. The two isomers of each compound were separately isolated and characterized. The structure of the (E)-isomer of ethyl 2-chloroacetyl-3-(3',4' methylenedioxyphenyl)propenoate was determined by X-ray crystallography and an unequivocal methodology of (E)/(Z)-structural analysis by 13C NMR (nuclear magnetic resonance) is presented.

Bruno R. S. de, Paula; Dávila S., Zampieri; Julio, Zukerman-Schpector; Edward R. T., Tiekink; José Augusto R., Rodrigues; Paulo J. S., Moran.

2012-05-01

183

Benzene complexes in cyclopentadienylcobalt(I) reaction systems  

OpenAIRE

Photolysis of (C5H5)Co(CO)2 in an aromatic solvent, such as benzene, toluene or s-mesitylene generates the corresponding (C5H5)Co(arene) and (C5H5)Co(arene)2 complexes. The benzene complex (C5H5)Co(C6H6) reacts with 2-butyne to form the hexamethyl benzene derivative (C5H5)Co(C6(CH3)6) but does not catalyze the formation of free hexamethylbenzene from excess 2-butyne.

Lee, Wai-sun; Koola, Johnson D.; Brintzinger, Hans-herbert

1981-01-01

184

CFD SIMULATIONS OF BENZENETOLUENE SYSTEM OVER SIEVE TRAY  

Directory of Open Access Journals (Sweden)

Full Text Available High degree of competitiveness associated with petroleum leads to the exhaustive search for new technologies that enable greater efficiency in the related processes. A three-dimensional mathematical homogeneous biphasic model was implemented in the commercial code of computational fluid dynamics (CFD, FLUENT package to predict concentration and temperature distributions on sieve trays of distillation columns and good simulation results are obtained. The tray geometries and operating conditions are based on the experimental works of Indian oil corporation limited(R & D. The dispersed gas phase and continuous liquid phase are modelled in the Mixture model for two interpenetrating phases with inter phase momentum, heat and mass transfer. The main objective of this study has been to find the extent to which CFD can be used as a prediction tool for real behaviour, and concentration and temperature distributions of sieve trays. The simulation results are shown that CFD is a powerful tool in tray design, analysis and trouble shooting, and can be considered as a new approach for efficiency calculations.

Sumit Singh

2012-08-01

185

Solubilities of some organic solutes in 1-ethyl-3-methylimidazolium acetate. Chromatographic measurements and predictions from COSMO-RS  

International Nuclear Information System (INIS)

Highlights: ? New solubility data are reported. ? Two experimental procedures for measuring solubilities are used. ? The experimental results from both procedures are compared. ? Experiments are compared with the theoretical calculations. - Abstract: Infinite-dilution activity coefficients and Henry’s constants for several organic solutes in 1-ethyl-3-methylimidazolium acetate [EMIM][Ac] were measured from T = 313 K to T = 413 K using two types of gas–liquid chromatography columns: packed columns and an open tubular wall-coated (OTWC) column. The organic solutes include n-hexane, 1-hexene, cyclohexane, heptane, benzene, toluene, ethyl acetate, tetrahydrofuran, 1,4-dioxane, acetonitrile, nitromethane, 1,2-methoxyethane, 1-propanol, 2-propanol, t-butanol and t-amyl alcohol. Results using packed columns are in good agreement with those using the OTWC column. However, there is a useful advantage associated with an OTWC column: for solutes such as alcohols, that have strong interactions with the stationary phase, measurements are faster due to their shorter retention time compared to those in packed columns.

186

Demand boom boosts ethyl, butyl acetate  

International Nuclear Information System (INIS)

US ethyl and butyl acetate markets are being described as 'extremely tight.' One major domestic producer is 'in a sold-out position' and has 'gone on sales control' with respect to these two products. Producers say that sales of both ethyl and butyl acetate have increased during the past year, and industry observers say they expect to see an April 1 price initiative of 2 cts to 3 cts/lb, and possibly a second increase in October. While one producer suggests that this market strength could be 'a sign that the coatings industry is turning around,' most agree that reformulation is the principal driver of growth. Ethyl acetate is said to be replacing methyl ethyl ketone in many formulations, while butyl acetate and butyl acetate blends are substituting for methyl isobutyl ketone. In addition, both ethyl and butyl acetate work as substitutes for xylene and toluene in certain applications. In an effort to conform to the requirements of the Clean Air Act of 1990 and to cooperate with the Environmental Protection Agency's 33/50 voluntary emissions reduction program, coatings manufacturers are moving as quickly as possible to eliminate solvents from their products. And although solvents as a whole will eventually see a dramatic decline in consumption, the temporary beneficiaries of reformulation will be certain of the oxygenated solvents, says Jeff Back, business manager at Kline ampersand Co

187

1-Ethyl-3-(2,4,6-trimethylphenylimidazolium tetrafluoroborate  

Directory of Open Access Journals (Sweden)

Full Text Available The title compound, C14H19N2+·BF4?, was obtained by reaction of 1-ethyl-3-(2,4,6-trimethylphenylimidazolium tetrafluoroborate with sodium tetrafluoroborate. The imidazole ring makes a dihedral angle of 78.92?(13° with the benzene ring.

Jin-Tao Guan

2010-08-01

188

Ethyl 2-(5-bromo-3-ethyl­sulfinyl-1-benzofuran-2-yl)acetate  

OpenAIRE

The title compound, C14H15BrO4S, was prepared by the oxidation of ethyl 2-(5-bromo-3-ethylsulfanyl-1-benzofuran-2-yl)acetate with 3-chloroperoxybenzoic acid. The crystal structure is stabilized by aromatic ?–? interactions between the benzene rings of neighbouring molecules [centroid–centroid distance = 3.814?(9)?Å], and possibly by weak C—H...? interactions. In addition, the crystal structure exhibits three...

Hong Dae Choi; Pil Ja Seo; Byeng Wha Son; Uk Lee

2009-01-01

189

Calorimetric study of methyl and ethyl 2-thiophenecarboxylates and ethyl 2- and 3-thiopheneacetates  

International Nuclear Information System (INIS)

The standard (p0=0.1MPa) molar enthalpies of formation, in the condensed phase, of the liquids methyl 2-thiophenecarboxylate, ethyl 2-thiophenecarboxylate, ethyl 2-thiopheneacetate, and ethyl 3-thiopheneacetate, at T = 298.15 K, were derived from the standard massic energies of combustion, in oxygen, to yield CO2 (g) and H2SO4 . 115H2O (aq), measured by rotating bomb combustion calorimetry. For these four compounds, the standard molar enthalpies of vaporization, ?lgHm0, at T = 298.15 K, were obtained by high temperature Calvet microcalorimetry. The standard (p0=0.1MPa) molar enthalpies of formation, in the gaseous phase, were derived from the experimental results and they are interpreted in terms of enthalpic increments of the introduction of a methylene group to the substituent chain. Moreover, the results are compared with the analogue benzene derivative.

190

Critical issues in benzene toxicity and metabolism: The effect of interactions with other organic chemicals on risk assessment  

Energy Technology Data Exchange (ETDEWEB)

Benzene, an important industrial solvent, is also present in unleaded gasoline and cigarette smoke. The hematotoxic effects of benzene are well documented and include aplastic anemia and pancytopenia. Some individuals exposed repeatedly to cytotoxic concentrations of benzene develop acute myeloblastic anemia. It has been hypothesized that metabolism of benzene is required for its toxicity, although administration of no single benzene metabolite duplicates the toxicity of benzene. Several investigators have demonstrated that a combination of metabolites (hydroquinone and phenol, for example) is necessary to duplicate the hematotoxic effect of benzene. Enzymes implicated in the metabolic activation of benzene and its metabolites include the cytochrome P450 monooxygenases and myeloperoxidase. Since benzene and its hydroxylated metabolites (phenol, hydroquinone, and catechol) are substrates for the same cytochrome P450 enzymes, competitive interactions among the metabolites are possible. In vivo data on metabolite formation by mice exposed to various benzene concentrations are consistent with competitive inhibition of phenol oxidation by benzene. Other organic molecules that are substrates for cytochrome P450 can inhibit the metabolism of benzene. For example, toluene has been shown to inhibit the oxidation of benzene in a noncompetitive manner. Enzyme inducers, such as ethanol, can alter the target tissue dosimetry of benzene metabolites by inducing enzymes responsible for oxidation reactions involved in benzene metabolism. 24 refs., 6 figs., 2 tabs.

Medinsky, M.A.; Schlosser, P.M.; Bond, J.A. [Chemical Industry Institute of Toxicology, Research Triangle Park, NC (United States)

1994-11-01

191

N-(2,6-Diisopropylphenylformamide toluene 0.33-solvate  

Directory of Open Access Journals (Sweden)

Full Text Available The crystal packing of the title compound, C13H19NO·0.33C7H8, shows a channel at [001], which contains grossly disordered toluene solvent molecules. The angle between the benzene ring and the mean plane of the formamide group is 71.1?(1°. The amide groups of neighbouring molecules are connected by N—H...O hydrogen bonds, forming 21 helical chains propagating along [001]. Molecules are also connected by weak intermolecular C—H...O hydrogen bonds, forming 61 helices.

Norbert Auner

2012-05-01

192

Acclimation of aerobic-activated sludge degrading benzene derivatives and co-metabolic degradation activities of trichloroethylene by benzene derivative-grown aerobic sludge.  

Science.gov (United States)

The acclimation of aerobic-activated sludge for degradation of benzene derivatives was investigated in batch experiments. Phenol, benzoic acid, toluene, aniline and chlorobenzene were concurrently added to five different bioreactors which contained the aerobic-activated sludge. After the acclimation process ended, the acclimated phenol-, benzoic acid-, toluene-, aniline- and chlorobenzene-grown aerobic-activated sludge were used to explore the co-metabolic degradation activities of trichloroethylene (TCE). Monod equation was employed to simulate the kinetics of co-metabolic degradation of TCE by benzene derivative-grown sludge. At the end of experiments, the mixed microbial communities grown under different conditions were identified. The results showed that the acclimation periods of microorganisms for different benzene derivatives varied. The maximum degradation rates of TCE for phenol-, benzoic acid-, toluene-, aniline- and chlorobenzene-grown aerobic sludge were 0.020, 0.017, 0.016, 0.0089 and 0.0047 mg g SS(-1) h(-1), respectively. The kinetic of TCE degradation in the absence of benzene derivative followed Monod equation well. Also, eight phyla were observed in the acclimated benzene derivative-grown aerobic sludge. Each of benzene derivative-grown aerobic sludge had different microbial community composition. This study can hopefully add new knowledge to the area of TCE co-metabolic by mixed microbial communities, and further the understanding on the function and applicability of aerobic-activated sludge. PMID:25409590

Wang, Shizong; Yang, Qi; Bai, Zhiyong; Wang, Shidong; Wang, Yeyao; Nowak, Karolina M

2015-01-01

193

Quantification of urinary metabolites of principle superior counterpart of benzene; Dosage des metabolites urinaires des principaux homologues superieurs du benzene  

Energy Technology Data Exchange (ETDEWEB)

In the aim of a medical surveillance of personnel exposed to superior counterpart of benzene, it is advisable to measure in urines, the hippuric, methyl hippuric and mandelic acids, as respective biological indicators of exposure to toluene, to xylenes and styrene (chapter 1). In a first time, we give some generalities on principal superior counterparts of benzene and about the biological surveillance of workers exposed to these products. Then, we present the quantification of their urinary metabolites, as it has be done in the stage. (N.C.)

Ruetsch, O. [CEA Centre d`Etudes de Fontenay-aux-Roses, 92 (France). Dept. de Protection de la Sante de l`Homme et de Dosimetrie]|[Lille-2 Univ., 59 (France)

1997-12-31

194

Anaerobic degradation of benzene by marine sulfate-reducing bacteria  

Science.gov (United States)

Benzene, the archetypal aromatic hydrocarbon is a common constituent of crude oil and oil-refined products. As such, it can enter the biosphere through natural oil seeps or as a consequence of exploitation of fossil fuel reservoirs. Benzene is chemically very stable, due to the stabilizing aromatic electron system and to the lack of functional groups. Although the anaerobic degradation of benzene has been reported under denitrifying, sulfate-reducing and methanogenic conditions, the microorganisms involved and the initial biochemical steps of degradation remain insufficiently understood. Using marine sediment from a Mediterranean lagoon a sulfate-reducing enrichment culture with benzene as the sole organic substrate was obtained. Application of 16S rRNA gene-based methods showed that the enrichment was dominated (more than 85% of total cells) by a distinct phylotype affiliated with a clade of Deltaproteobacteria that include degraders of other aromatic hydrocarbons, such as naphthalene, ethylbenzene and m-xylene. Using benzoate as a soluble substrate in agar dilution series, several pure cultures closely related to Desulfotignum spp. and Desulfosarcina spp. were isolated. None of these strains was able to utilize benzene as a substrate and hybridizations with specific oligonucleotide probes showed that they accounted for as much as 6% of the total cells. Incubations with 13C-labeled benzene followed by Halogen in situ Hybridization - Secondary Ion Mass Spectroscopy (HISH-SIMS) analysis showed that cells of the dominant phylotype were highly enriched in 13C, while the accompanying bacteria had little or no 13C incorporation. These results demonstrate that the dominant phylotype was indeed the apparent benzene degrader. Dense-cell suspensions of the enrichment culture did not show metabolic activity toward added phenol or toluene, suggesting that benzene degradation did not proceed through anaerobic hydroxylation or methylation. Instead, benzoate was identified in analyses of metabolites with benzene-grown cultures, suggesting an activation of benzene via carboxylation.

Musat, Florin; Wilkes, Heinz; Musat, Niculina; Kuypers, Marcel; Widdel, Friedrich

2010-05-01

195

N-Benzyl-N-ethyl-4-methyl­benzene­sulfonamide  

Science.gov (United States)

In the title compound, C16H19NO2S, the dihedral angle between the two aromatic rings is 84.78?(7)°. Weak inter­molecular C—H?O inter­actions stabilize the crystal structure by the formation of a 16-membered R 2 2(16) ring motif. PMID:21587503

Khan, Islam Ullah; Ahmad, Waqar; Arshad, Muhammad Nadeem; Sharif, Shahzad; Ahmed, Jamil

2010-01-01

196

N-Benzyl-N-ethyl-4-methyl-benzene-sulfonamide.  

Science.gov (United States)

In the title compound, C(16)H(19)NO(2)S, the dihedral angle between the two aromatic rings is 84.78?(7)°. Weak inter-molecular C-H?O inter-actions stabilize the crystal structure by the formation of a 16-membered R(2) (2)(16) ring motif. PMID:21587503

Khan, Islam Ullah; Ahmad, Waqar; Arshad, Muhammad Nadeem; Sharif, Shahzad; Ahmed, Jamil

2010-01-01

197

N-Benzyl-N-ethyl-4-methyl­benzene­sulfonamide  

OpenAIRE

In the title compound, C16H19NO2S, the dihedral angle between the two aromatic rings is 84.78?(7)°. Weak inter­molecular C—H?O inter­actions stabilize the crystal structure by the formation of a 16-membered R 2 2(16) ring motif.

Shahzad Sharif; Muhammad Nadeem Arshad; Waqar Ahmad; Islam Ullah Khan; Jamil Ahmed

2010-01-01

198

Transformation of microflora during degradation of gaseous toluene in a biofilter detected using PCR-DGGE.  

Science.gov (United States)

A laboratory-scale biofiltration system, the rotatory-switching biofilter (RSB), was operated for 199 days using toluene as a model pollutant. The target gaseous pollutant for the biofiltration experiment was approximately 300 ppmv of toluene. Toluene removal efficiency (RE, %) was initially approximately 20% with a 247-ppmv concentration (0.9 g m(-3)) of toluene during the first 10 days. Although the RE decreased several times whenever nitrogen was consumed, it again reached almost 100% when the nitrogen source was in sufficient supply. Denaturing gradient gel electrophoresis (DGGE) analysis was employed to assess the transformation ofmicroflora during operation of the biofilter The results based on a 16S rRNA gene profile showed that the microbial community structure changed with operation time. Although the microflora changed during the initial period (before day 40), transformation of the bacterial component was hardly observed after day 51. Statistical analyses of the DGGE profiles indicated that the bacterial community was almost unaffected by the environmental factors, such as adding ozone, high-level nitrogen supply, increase of loading toluene, and the shutdown of the RSB. The DGGE profile using tmoA-like genes, which encode proteins belonging to the hydroxylase component mono-oxygenases involved in the initial attack of aerobic benzene, toluene, ethylbenzene, and xylene degradation, confirmed the existence of toluene-degrading bacteria. There were at least four kinds of toluene-degradable bacteria having tmoA-like genes up to day 36, which decreased to two species after day 40. Sequence analysis after DGGE profiling revealed that Burkholderia cepacia, Sphingobacterium multivorum, and Pseudomonas putida were present in the biofilter. Only Alicycliphilus denitrificans was present throughout the whole operation period. In the initial stage of operating the RSB, many types of bacteria may have tried to adapt to the conditions, and subsequently, only selected bacteria were able to grow and to degrade toluene. PMID:22866576

Okunishi, Suguru; Morita, Yasutaka; Higuchi, Takashi; Maeda, Hiroto; Nishi, Katsuji

2012-07-01

199

The toxicology of benzene.  

OpenAIRE

Benzene is metabolized, primarily in the liver, to a series of phenolic and ring-opened products and their conjugates. The mechanism of benzene-induced aplastic anemia appears to involve the concerted action of several metabolites acting together on early stem and progenitor cells, as well as on early blast cells, such as pronormoblasts and normoblasts to inhibit maturation and amplification. Benzene metabolites also inhibit the function of microenvironmental stromal cells necessary to suppor...

Snyder, R.; Witz, G.; Goldstein, B. D.

1993-01-01

200

Catalytic oxidation of toluene in contaminant emission control systems using Mn-Ce/gamma-Al2O3.  

Science.gov (United States)

Toluene, the alkyl benzene, is a common constituent of contaminant streams emitted by hydrocarbon fuel combustion systems. The oxidation of toluene to less toxic compounds can be enhanced through catalysis. The capacity of Mn-Ce/gamma-Al2O3 to catalyze toluene oxidation was investigated using a fixed bed flow reactor, operating within a temperature range of 160-400 degrees C. Mono-metallic catalysts were prepared with the manganese and cerium contents of 1-21 wt% on gamma-Al2O3, support and bi-metallic catalysts were prepared with cerium (0.5-21 wt%/) on 18.2 wt% manganese. The results indicate that the 18.2 wt% Mn-10.0 wt% Ce catalyst combination had the best catalytic efficiency for toluene oxidation. Increase in cerium loading reduces the surface area of catalytic materials measured by BET, but increases catalytic activity. Data obtained through TGA (Thermogravimetric analysis), XRD (X-ray diffraction) and toluene-TPR (Temperature Programmed Reduction) measurements show that the reduction of the catalysts in the process of toluene oxidation is directly proportional to observed weight loss under hydrogen flow. From these results, it is concluded that cerium improves the catalytic role of manganese in toluene oxidation. Oxygen mobility is also promoted in a redox mechanism in which MnO2 serves as the active sites. These results are useful in the development of toluene emission control systems for hydrocarbon fuel combustion systems. PMID:18661740

Kim, H-J; Choi, S-W; Inyang, H I

2008-05-01

201

Which Hydrogen Atom of Toluene Protonates PAH molecules in (+)-Mode APPI MS Analysis?  

Science.gov (United States)

A previous study (Ahmed, A. et al., Anal. Chem. 84, 1146-1151( 2012) reported that toluene used as a solvent was the proton source for polyaromatic hydrocarbon compounds (PAHs) that were subjected to (+)-mode atmospheric-pressure photoionization. In the current study, the exact position of the hydrogen atom in the toluene molecule (either a methyl hydrogen or an aromatic ring hydrogen) involved in the formation of protonated PAH ions was investigated. Experimental analyses of benzene and anisole demonstrated that although the aromatic hydrogen atom of toluene did not contribute to the formation of protonated anthracene, it did contribute to the formation of protonated acridine. Thermochemical data and quantum mechanical calculations showed that the protonation of anthracene by an aromatic ring hydrogen atom of toluene is endothermic, while protonation by a methyl hydrogen atom is exothermic. However, protonation of acridine by either an aromatic ring hydrogen or a methyl hydrogen atom of toluene is exothermic. The different behavior of acridine and anthracene was attributed to differences in gas-phase basicity. It was concluded that both types of hydrogen in toluene can be used for protonation of PAH compounds, but a methyl hydrogen atom is preferred, especially for non-basic compounds.

Ahmed, Arif; Ghosh, Manik Kumer; Choi, Myung Chul; Choi, Cheol Ho; Kim, Sunghwan

2013-03-01

202

Excretion of 1,2,4-benzenetriol in the urine of workers exposed to benzene.  

OpenAIRE

Urine samples were collected from 152 workers (64 men, 88 women) who had been exposed to benzene, 53 workers (men only) exposed to a mixture of benzene and toluene, and 213 non-exposed controls (113 men, 100 women). The samples were analysed for 1,2,4-benzentriol (a minor metabolite of benzene) by high performance liquid chromatography. The time weighted average solvent exposure of each worker was monitored by diffusive sampling technique. The urinary concentration of 1,2,4-benzentriol relate...

Inoue, O.; Seiji, K.; Nakatsuka, H.; Watanabe, T.; Yin, S.; Li, G. L.; Cai, S. X.; Jin, C.; Ikeda, M.

1989-01-01

203

Investigation of radical formation at ?-radiolysis of alkyl benzenes with help of spin traps  

International Nuclear Information System (INIS)

Investigated is radical formation in ?-irradiated benzene, toluene and o-xylene with the help of nitroso dure e (ND) and 2,4,6-tri-tret-butyl nitrobenzene (BNB). The samples were vacuumized till 5x10-5 Torr and irradiated by Co60 ?-rays at 20 and 20deg C. It is shown that at ?-radiolysis of liquid alkyl benzenes in the presence of BNB adducts are formed with aryl (phenyl) radicals, ciclohexadienyl and benzene radicals. Free radicals formed at radiolysis of aromatic carbon hydrides in the liquid phase may be identified with the help of two spin traps; ND and BNB supplementing each other

204

Benzene from Traffic : Fuel Content and Ambient Air Concentrations  

DEFF Research Database (Denmark)

The measurements of benzene showed very clear decreasing trends in the air concentrations and the emissions since 1994. At the same time the measurements of CO and NOx also showed a decreasing trend, but not so strong as for benzene. The general decreasing trend is explained by the increasing number of petrol vehicles with three way catalysts, 60-70% in 1999. The very steep decreasing trend for benzene at the beginning of the period from 1994 was explained by the combination of more catalyst vehicles and reduced benzene content in Danish petrol. The total amount of aromatics in petrol, including toluene, increased only weakly. The analyses of air concentrations were confirmed by analyses of petrol sold in Denmark. The concentration of benzene at Jagtvej in Copenhagen is still in 1998 above the expected new EU limit value, 5 µg/m3 as annual average. However, the reduced content of benzene in petrol from 1998 and the increasing number of vehicles with catalysts will probably lead to compliance with this limit value

Palmgren, F.; Berkowicz, R.

2000-01-01

205

Benzene from catalytic hydrocracking  

Energy Technology Data Exchange (ETDEWEB)

The physiochemical and explosion properties of benzene, produced in the catalytic hydrocracking process at the Bosanski Brod petroleum refineries, were studied. The fractionation and group chemical composition of light (specific weight 0.6487) and heavy fractions (specific weight 0.7024) are given. The explosion characteristics are investigated together with the sensitivity to an injection of 6 grams explosion additives per one liter benzene. A heavy benzene fraction should be subjected to additional treatment in a catalytic reforming assembly. A variation in benzene's octane characteristics when compounded in a reformate of 10-40 percent light or heavy hydrocracking benzene fractions is studied. Graphs are designed which reflect an increase in the octane number of light (from 83 to 94) and heavy (from 63 to 80) benzene fractions when tetraethyllead (0.1-0.7 grams of lead to one liter of benzene) is injected. It is demonstrated that the hydrocracking catalytic process makes is possible to produce high quality benzene for carburator motors and a heavy fraction, which is a valuable raw material for hydrocracking catalytic assemblies.

Cindric, M.

1982-01-01

206

The impact of candle burning during All Saints' Day ceremonies on ambient alkyl-substituted benzene concentrations.  

Science.gov (United States)

Research findings concerning benzene, toluene, ethylobenzene, meta-, para- and ortho-xylene as well as styrene (BTEXS) emission at public cemeteries during All Saints' Day are presented here. Tests were carried out at town-located cemeteries in Opole and Grodków (southern Poland) and, as a benchmark, at the centres of those same towns. The purpose of the study was to estimate BTEXS emissions caused by the candle burning and, equally important to examine, whether emissions generated by the tested sources were similar to the BTEXS emissions generated by road transport. During the festive period, significant increases in benzene concentrations, by 200 % and 144 %, were noted at the cemeteries in Opole and Grodków, as well as in toluene, by 366 % and 342 %, respectively. Styrene concentrations also increased. It was demonstrated that the ratio of toluene to benzene concentrations from emissions caused by the burning candles are comparable to the ratio established for transportation emissions. PMID:24052143

Olszowski, Tomasz; K?os, Andrzej

2013-11-01

207

Ethyl 2-(2,3,4,5,6-Pentabromophenylacetate  

Directory of Open Access Journals (Sweden)

Full Text Available The title compound PBPEA, C10H7Br5O2, has its ethyl acetate portion nearly orthogonal to the benzene ring, with a C—C—C—C torsion angle of 88.3?(5°. The packing involves an intermolecular contact with a Br...Br distance of 3.491?(1?Å, having C—Br...Br angles of 173.4?(2 and 106.0?(2°. The crystal studied was an inversion twin.

Anne M. Sauer

2010-08-01

208

Steam reforming of toluene as model compound of biomass pyrolysis tar for hydrogen  

International Nuclear Information System (INIS)

Steam reforming of tar during biomass pyrolysis for hydrogen will not only avoid frequent equipment shutdown for maintenance and repair but also increase hydrogen yield. In this paper, the effects of temperature and steam/carbon molar ration on steam reforming of toluene as model compound of tar was studied by simulation of thermodynamic equilibrium and experiments using Ni/cordierite catalyst in a fixed bed reactor. The results of thermodynamic simulations indicate that the S/C molar ratio of 2 and the temperature range from 1023 K to 1173 K provide favorable operating conditions for steam reforming of toluene in order to get high hydrogen productivity. These operating parameters were adopted in the experiments using Ni/cordierite catalyst in a fixed bed reactor. H2 content remains about 66 mol% and slightly varies with the increasing temperature. Conversion efficiency of toluene increases with temperature, reaching 94.1% at 1173 K. The simulation was improved in order to be closer to experimental results. It is found that only a very small amount of toluene did not participate in the reaction. In the aromatic hydrocarbons of reactive system, benzene and naphthalene were the main products and the proportion of naphthalene decreases with increasing temperature while that of benzene increases.

209

A detailed kinetic modeling study of toluene oxidation in a premixed laminar flame  

Energy Technology Data Exchange (ETDEWEB)

An improved chemical kinetic model for the toluene oxidation based on experimental data obtained in a premixed laminar low-pressure flame with vacuum ultraviolet (VUV) photoionization and molecular beam mass spectrometry (MBMS) techniques has been proposed. The present mechanism consists of 273 species up to chrysene and 1740 reactions. The rate constants of reactions of toluene, decomposition, reaction with oxygen, ipso-additions and metatheses with abstraction of phenylic H-atom are updated; new pathways of C{sub 4} + C{sub 2} species giving benzene and fulvene are added. Based on the experimental observations, combustion intermediates such as fulvenallene, naphtol, methylnaphthalene, acenaphthylene, 2-ethynylnaphthalene, phenanthrene, anthracene, 1-methylphenanthrene, pyrene and chrysene are involved in the present mechanism. The final toluene model leads to an overall satisfactory agreement between the experimentally observed and predicted mole fraction profiles for the major products and most combustion intermediates. The toluene depletion is governed by metathese giving benzyl radicals, ipso-addition forming benzene and metatheses leading to C{sub 6}H{sub 4}CH{sub 3} radicals. A sensitivity analysis indicates that the unimolecular decomposition via the cleavage of a C-H bond has a strong inhibiting effect, while decomposition via C-C bond breaking, ipso-addition of H-atom to toluene, decomposition of benzyl radicals and reactions related to C{sub 6}H{sub 4}CH{sub 3} radicals have promoting effect for the consumption of toluene. Moreover, flow rate analysis is performed to illustrate the formation pathways of mono- and polycyclic aromatics.

Tian, Z; Pitz, W J; Fournet, R; Glaude, P; Battin-Leclerc, F

2009-12-18

210

Determination of Bioactive Components of Ethyl Acetate Fraction of Punica granatum Rind Extract  

OpenAIRE

Punica granatum belongs to a Punicaceae family. The Punica granatum is valued as a powerful medicinal plant and used in folk medicines. Hence the present investigation was carried out to determine the possible chemical components from ethyl acetate fraction of Punica granatum rind extract by GC-MS Technique. This analysis revealed that ethyl acetate fraction of Punica granatum rind extract contain Pyrogallol (41.88%), 5-Hydroxymethylfurfural (14.10%), D-Allose (9.17%), 2-Methoxy-1, 4-Benzened...

Sangeetha, J.; Vijayalakshmi, K.

2011-01-01

211

Reverse isotope dilution method for determining benzene and metabolites in tissues  

International Nuclear Information System (INIS)

A method utilizing reverse isotope dilution for the analysis of benzene and its organic soluble metabolites in tissues of rats and mice is presented. Tissues from rats and mice that had been exposed to radiolabeled benzene were extracted with ethyl acetate containing known, excess quantities of unlabeled benzene and metabolites. Butylated hydroxytoluene was added as an antioxidant. The ethyl acetate extracts were analyzed with semipreparative reversed-phase HPLC. Isolated peaks were collected and analyzed for radioactivity (by liquid scintillation spectrometry) and for mass (by UV absorption). The total amount of each compound present was calculated from the mass dilution of the radiolabeled isotope. This method has the advantages of high sensitivity, because of the high specific activity of benzene, and relative stability of the analyses, because of the addition of large amounts of unlabeled carrier analogue

212

Benzene release. Status report  

International Nuclear Information System (INIS)

Scoping benzene release measurements were conducted on 4 wt percent KTPB 'DEMO' formulation slurry using a round, flat bottomed 100-mL flask containing 75 mL slurry. The slurry was agitated with a magnetic stirrer bar to keep the surface refreshed without creating a vortex. Benzene release measurements were made by purging the vapor space at a constant rate and analyzing for benzene by gas chromatography with automatic data acquisition. Some of the data have been rounded or simplified in view of the scoping nature of this study

213

Drying up the benzene  

Energy Technology Data Exchange (ETDEWEB)

In 2007, a directive from the Alberta Energy Resources Conservation Board asked companies running glycol dehydrators to report their benzene emissions. In order to help companies to do so, Process Ecology Inc. developed an online system that calculates, reports and manages dehydrators benzene emissions. This Benzene Emissions Advisor collects data, runs simulation models and stores the results in a database accessible to clients through its website. This software, used by 25 per cent of the market, can now be used for energy optimization purposes. It can inform operators of many saving opportunities, for example turning down the glycol pump.

Harrison, Lynda

2011-03-15

214

Benzene release. status report  

Energy Technology Data Exchange (ETDEWEB)

Scoping benzene release measurements were conducted on 4 wt percent KTPB `DEMO` formulation slurry using a round, flat bottomed 100-mL flask containing 75 mL slurry. The slurry was agitated with a magnetic stirrer bar to keep the surface refreshed without creating a vortex. Benzene release measurements were made by purging the vapor space at a constant rate and analyzing for benzene by gas chromatography with automatic data acquisition. Some of the data have been rounded or simplified in view of the scoping nature of this study.

Dworjanyn, L.O. [Westinghouse Savannah River Company, AIKEN, SC (United States); Rappe, K.G.; Gauglitz, P.A. [Pacific Northwest National Lab., Richland, WA (United States)

1997-11-04

215

Hydrogen bonding and charge transfer interactions in exciplexes formed by excited indole and monosubstituted benzenes in cyclohexane  

Science.gov (United States)

The interaction between the excited singlet state of indole derivatives with simple monosubstituted benzenes has been investigated in cyclohexane by steady state and time resolved fluorescence spectroscopy. The fluorescence quenching efficiency of indole increases in the order benzene, toluene, chlorobenzene and benzonitrile. For indole derivatives substituted on the N atom of the heterocyclic ring the quenching efficiency is much lower. At high concentrations of the benzenes derivatives the emission spectrum is broader and red shifted and the decay of the emission becomes biexponential. The results are analysed in terms of an exciplex forming mechanism. The binding forces in the exciplex are predominantly of hydrogen bonding for the case of benzene and toluene, while a charge transfer interaction is more likely in the case of chlorobenzene and benzonitrile.

Rivarola, Claudia; Bertolotti, Sonia G.; Borsarelli, Claudio D.; Cosa, Juan J.; Previtali, Carlos M.; Neumann, Miguel G.

1996-11-01

216

Analysis of the gene cluster encoding toluene/o-xylene monooxygenase from Pseudomonas stutzeri OX1  

Energy Technology Data Exchange (ETDEWEB)

The toluene/o-xylene monooxygenase cloned from Pseudomonas stutzeri OX1 displays a very broad range of substrates and a very peculiar regioselectivity, because it is able to hydroxylate more than one position on the aromatic ring of several hydrocarbons and phenols. The nucleotide sequence of the gene cluster coding for this enzymatic system has been determined. The sequence analysis revealed the presence of six open reading frames (ORFs) homologous to other genes clustered in operons coding for multicomponent monooxygenases found in benzene- and toluene-degradative pathways cloned from Pseudomonas strains. Significant similarities were also found with multicomponent monooxygenase systems for phenol, methane, alkene, and dimethyl sulfide cloned from different bacterial strains. The knockout of each ORF and complementation with the wild-type allele indicated that all six ORFs are essential for the full activity of the toluene/o-xylene monooxygenase in Escherichia coli. This analysis also shows that despite its activity on both hydrocarbons and phenols, toluene/o-xylene monooxygenase belongs to a toluene multicomponent monooxygenase subfamily rather than to the monooxygenases active on phenols.

Bertoni, G.; Martino, M.; Galli, E.; Barbieri, P. [Univ. degli Studi di Milano, Milan (Italy). Dept. di Genetica e di Biologia dei Microorganismi

1998-10-01

217

Leukemia and Benzene  

OpenAIRE

Excessive exposure to benzene has been known for more than a century to damage the bone marrow resulting in decreases in the numbers of circulating blood cells, and ultimately, aplastic anemia. Of more recent vintage has been the appreciation that an alternative outcome of benzene exposure has been the development of one or more types of leukemia. While many investigators agree that the array of toxic metabolites, generated in the liver or in the bone marrow, can lead to traumatic bone marrow...

Robert Snyder

2012-01-01

218

Benzene Monitor System report  

International Nuclear Information System (INIS)

Two systems for monitoring benzene in aqueous streams have been designed and assembled by the Savannah River Technology Center, Analytical Development Section (ADS). These systems were used at TNX to support sampling studies of the full-scale open-quotes SRAT/SME/PRclose quotes and to provide real-time measurements of benzene in Precipitate Hydrolysis Aqueous (PHA) simulant. This report describes the two ADS Benzene Monitor System (BMS) configurations, provides data on system operation, and reviews the results of scoping tests conducted at TNX. These scoping tests will allow comparison with other benzene measurement options being considered for use in the Defense Waste Processing Facility (DWPF) laboratory. A report detailing the preferred BMS configuration statistical performance during recent tests has been issued under separate title: Statistical Analyses of the At-line Benzene Monitor Study, SCS-ASG-92-066. The current BMS design, called the At-line Benzene Monitor (ALBM), allows remote measurement of benzene in PHA solutions. The authors have demonstrated the ability to calibrate and operate this system using peanut vials from a standard Hydragard trademark sampler. The equipment and materials used to construct the ALBM are similar to those already used in other applications by the DWPF lab. The precision of this system (±0.5% Relative Standard Deviation (RSD) at 1 sigma) is better than the purge ampersand trap-gas chromatograpy reference method currently in use. Both BMSs provide a direct measurement of the benzene that can be purged from a solution with no sample pretreatment. Each analysis requires about five minutes per sample, and the system operation requires no special skills or training. The analyzer's computer software can be tailored to provide desired outputs. Use of this system produces no waste stream other than the samples themselves (i.e. no organic extractants)

219

Anaerobic benzene degradation by bacteria  

OpenAIRE

Benzene is a widespread and toxic contaminant. The fate of benzene in contaminated aquifers seems to be primarily controlled by the abundance of oxygen: benzene is aerobically degraded at high rates by ubiquitous microorganisms, and the oxygen?dependent pathways for its breakdown were elucidated more than 50 years ago. In contrast, benzene was thought to be persistent under anoxic conditions until 25 years ago. Nevertheless, within the last 15 years, several benzene?degrading cultures hav...

Vogt, Carsten; Kleinsteuber, Sabine; Richnow, Hans?hermann

2011-01-01

220

An overview of benzene metabolism.  

OpenAIRE

Benzene toxicity involves both bone marrow depression and leukemogenesis caused by damage to multiple classes of hematopoietic cells and a variety of hematopoietic cell functions. Study of the relationship between the metabolism and toxicity of benzene indicates that several metabolites of benzene play significant roles in generating benzene toxicity. Benzene is metabolized, primarily in the liver, to a variety of hydroxylated and ring-opened products that are transported to the bone marrow w...

Snyder, R.; Hedli, C. C.

1996-01-01

221

Altering Toluene 4-Monooxygenase by Active-Site Engineering for the Synthesis of 3-Methoxycatechol, Methoxyhydroquinone, and Methylhydroquinone  

OpenAIRE

Wild-type toluene 4-monooxygenase (T4MO) of Pseudomonas mendocina KR1 oxidizes toluene to p-cresol (96%) and oxidizes benzene sequentially to phenol, to catechol, and to 1,2,3-trihydroxybenzene. In this study T4MO was found to oxidize o-cresol to 3-methylcatechol (91%) and methylhydroquinone (9%), to oxidize m-cresol and p-cresol to 4-methylcatechol (100%), and to oxidize o-methoxyphenol to 4-methoxyresorcinol (87%), 3-methoxycatechol (11%), and methoxyhydroquinone (2%). Apparent Vmax values ...

Tao, Ying; Fishman, Ayelet; Bentley, William E.; Wood, Thomas K.

2004-01-01

222

Dealkylation of Alkylbenzenes: A Significant Pathway in the Toluene, o-, m-, p-Xylene + OH Reaction  

Science.gov (United States)

The OH-radical initiated oxidation of a series of monocyclic aromatic hydrocarbons (benzene, toluene, o-, m-, and p-xylene) in the presence of oxygen and NOx was investigated in a flowtube coupled with a chemical ionization mass spectrometer (CIMS). OH-radical addition to the aromatic ring - the major reaction pathway - has previously been shown to have a particular sensitivity to experimental conditions. This is the first flowtube study that demonstrates the atmospheric relevance of product yields from the OH-addition channel on the millisecond time scale (35-75 ms); the phenol yield from benzene and cresol yields from toluene are found to be 51.0 ± 4.3% and 17.7 ± 2.1%, in excellent agreement with previous studies under close to atmospheric conditions. We further report unambiguous experimental evidence that dealkylation is a novel and significant pathway for toluene and o-, m-, and p-xylene oxidation. At 150 Torr of O2 partial pressure, toluene is found to dealkylate with a yield of 5.4 ± 1.2% phenol; similarly, m-, o-, and p-xylene dealkylate with yields of 11.2 ± 3.8%, 4.5 ± 3.2%, and 4.3 ± 3.1% cresol, respectively. A dealkylation mechanism via OH-addition in the ipso position is feasible (?H = -9 kcal/mol for phenol formation from toluene) but does not lend itself easily to explain the significant isomer effect observed among xylenes; instead an alternative mechanism is presented that can explain this isomer effect and forms phenol and likely epoxide type products with identical m/z (indistinguishable in our CIMS analysis) via a carbene-type intermediate. Dealkylation adds to the atmospheric production of phenol- and likely epoxide-type products, with aldehydes as expected co-products, and helps improve the carbon balance in the initial stages of aromatic oxidation.

Noda, Jun; Volkamer, Rainer; Molina, Mario J.

2009-08-01

223

(2E-2-Benzylidene-4-ethyl-3,4-dihydronaphthalen-1(2H-one  

Directory of Open Access Journals (Sweden)

Full Text Available In the title compound, C19H18O, the exocyclic C=C double bond has an E configuration. The ethyl substituent on the cyclohexanone ring is in an axial position. The cyclohexanone ring adopts a half-chair conformation, presumably due to conjugation in the benzene ring.

Mohamed Akhazzane

2011-07-01

224

Determination of conformational and spectroscopic features of ethyl trans-alfa-cyano-3-indole-acrylate compound: An experimental and quantum chemical study  

Science.gov (United States)

The optimized geometrical structure, vibrational and electronic transitions, chemical shifts and non-linear optical properties of ethyl trans-alfa-cyano-3-indole-acrylate (C14H12N2O2) compound were presented in this study. The ground state geometrical structure and vibrational wavenumbers were carried out by using density functional (DFT/B3LYP) method with 6-311++G(d,p) as basis set. The vibrational spectra of title compound were recorded in solid state with FT-IR and FT-Raman in the range of 4000-400 cm-1 and 4000-10 cm-1, respectively. The fundamental assignments were done on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanical (SQM) method. The 1H, 13C and DEPT NMR spectra were recorded in DMSO solution, and gauge-invariant atomic orbitals (GIAO) method was used to predict the isotropic chemical shifts. The UV-Vis absorption spectra of the compound were recorded in the range of 200-800 nm in various solvents of different polarity (acetone, benzene, chlorobenzene, chloroform, DMSO, ethanol, methanol and toluene). Solvent effects were calculated using TD-DFT and CIS method. To investigate the non-linear optical properties, the polarizability, anisotropy of polarizability and molecular first hyperpolarizability were computed. A detailed description of spectroscopic behaviors of compound was given based on the comparison of experimental measurements and theoretical computations.

Cinar, Mehmet; Karabacak, Mehmet

2013-03-01

225

Índicesde refracción y densidad de mezclas binarias de heptano con ciclohexano, benceno y tolueno a 293.15, 298.15, 303.15 y 308.15 K / Refraction indexes and density for binary mixtures of heptane with cyclohexane, benzene and toluene at 293.15, 298.15, 303.15 K / Índices derefração e densidade de misturas binárias de heptano com ciclo-hexano, benzenoe tolueno a 293.15, 298.15, 303.15 e 308.15 K  

Scientific Electronic Library Online (English)

Full Text Available Determinam-sedensidades e índices de refração de misturas binárias de ciclo-hexano, benzenoe tolueno com heptano a (293.15, 298.15, 303.15 e 308.15) K. Se calcularem osvolumes de excesso molar e o cambio do índice de refração (??D) a partir dosdados experimentais e ajustados à uma equação polinomial [...] de Redlich-Kister deordem quatro. Abstract in spanish Semidieron densidades e índices de refracción de mezclas binarias de ciclohexano,benceno y tolueno con heptano a (293.15, 298.15, 303.15 y 308.15) K. El volumende exceso molar y el cambio de índice de refracción (??D) son calculados desdelos datos experimentales y ajustados con una ecuación polinomi [...] al deRedlich-Kister de orden cuatro. Abstract in english Density and refraction indexes forbinary mixtures of cyclohexane, benzene and toluene with heptane (293.15, 298.15,303.15 and 308.15 K) were measured. Excess molar volume and refraction indexchange (??D) werecalculated from experimental data and adjusted with a fourth-orderRedlich-Kister polynomial [...] equation.

Marlon D., Martínez-Reina; Eliseo, Amado-González.

2012-06-01

226

Hydrotreating of wheat straw in toluene and ethanol.  

Science.gov (United States)

In the present work, wheat straw was hydroliquefied at a temperature of 300°C for 4h in ethanol or toluene in order to obtain bio-components which are useful for fuel purposes. The experiments were performed in a 100mL batch reactor under hydrogen pressure of 70 bar. Typically, 2g of straw and 0.1g of catalyst (66%Ni/SiO2-Al2O3) were dispersed in 15 g of solvent. The main compounds of the oil produced during the liquefaction of hemicellulose, cellulose and lignin of wheat straw in both solvents are: tetrahydrofuran-2-methanol, 1,2-butanediol and butyrolactone. Besides the mentioned compounds, ethanol favoured the decomposition of bigger molecules to short-chain alcohols such as 1-butanol, 1,2-propanediol and 1,2-ethanediol. Toluene contributes to the production of furans and other cyclic compounds. The light fractions distilled together with the solvent also contain the following: 1-propanol, 2-methyl-cyclopentanone, acetic acid and ethyl acetate. PMID:24787323

Murnieks, Raimonds; Kampars, Valdis; Malins, Kristaps; Apseniece, Lauma

2014-07-01

227

Chemical kinetic study of the oxidation of toluene and related cyclic compounds  

Energy Technology Data Exchange (ETDEWEB)

Chemical kinetic models of hydrocarbons found in transportation fuels are needed to simulate combustion in engines and to improve engine performance. The study of the combustion of practical fuels, however, has to deal with their complex compositions, which generally involve hundreds of compounds. To provide a simplified approach for practical fuels, surrogate fuels including few relevant components are used instead of including all components. Among those components, toluene, the simplest of the alkyl benzenes, is one of the most prevalent aromatic compounds in gasoline in the U.S. (up to 30%) and is a promising candidate for formulating gasoline surrogates. Unfortunately, even though the combustion of aromatics been studied for a long time, the oxidation processes relevant to this class of compounds are still matter of discussion. In this work, the combustion of toluene is systematically approached through the analysis of the kinetics of some important intermediates contained in its kinetic submechanism. After discussing the combustion chemistry of cyclopentadiene, benzene, phenol and, finally, of toluene, the model is validated against literature experimental data over a wide range of operating conditions.

Mehl, M; Frassoldati, A; Fietzek, R; Faravelli, T; Pitz, W; Ranzi, E

2009-10-01

228

Radiation chemical oxidation of substituted benzenes by Cl2.-  

International Nuclear Information System (INIS)

Reaction of Cl2.- radical with chloro, methyl and methoxylated benzenes was studied by pulse radiolysis in acidic condition. The rate of Cl2.- reaction with chlorobenzene, toluene and chlorotoluene was lower (0.8 - 15 x 106 dm3 mol-1 s-1), however, formation of radical cations was observed only with anisole and 3-chloroanisole where Cl2.- radical reacts with the higher rates of 3.4 and 2.1 x 108 dm3 mol-1 s-1 respectively. (author). 5 refs., 1 fig

229

Electronic absorption spectra of alkyl derivatives of bis-benzene chromium(O) in the gas phase  

International Nuclear Information System (INIS)

The authors analyze the electronic absorption and photoelectron spectra of the alkylated chromium complexes of bis-benzene and bis-toluene construct a quantum-chemical atomic model to determine ionization potentials, oscillator strengths, Rydberg constants and corrections, and various spin, dipole, and forbidden transitions allowed by the symmetry groups used for the complexes. Line widths are analyzed and tabulated

230

Sorption of toluene by humic acids derived from lake sediment and mountain soil at different pH.  

Science.gov (United States)

Contamination of soil and groundwater with BTEX compounds (benzene, toluene, ethylbenzene, and xylene) depends on the sorption behavior of these compounds by soil organic matter (SOM) and humic acids (HAs). In this study sorption of toluene by HAs extracted from lake sediment and mountain soil was investigated. HA suspensions were adjusted to pH 4.00, 6.00, or 8.00 and made to the concentration of 200 mg L(-1). Each HA suspension or solution was subjected to particle size analysis using high performance particle sizer (HPPS). The particle size of HA from lake sediment was around 1000-1200 nm while that from mountain soil was 220-320 nm at suspension pH 4.00. Kinetic studies showed that sorption of toluene by the two HAs followed pseudo-first-order and mainly pseudo-zero-order kinetics. At suspension pH 4.00, the sorption of toluene by the two HAs was best described by Langmuir and Temkin adsorption isotherm models. Further, sorption of toluene by the lake sediment HA was significantly greater than that by mountain soil HA. It was thus suggested that the lake sediment HA with larger particle size may develop beneficially chemical conformation for sorption of toluene and related compounds in soil and associated environments. PMID:20106594

Chang Chien, S W; Chen, C Y; Chang, J H; Chen, S H; Wang, M C; Mannepalli, Madhava Rao

2010-05-15

231

Thermodynamics of mixtures involving some (benzene derivatives+benzonitrile)  

Energy Technology Data Exchange (ETDEWEB)

Interactions of binary mixtures involving some benzene derivatives (ethylbenzene, o-, m-, p-xylene, isopropylbenzene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, and methoxybenzene) with benzonitrile were investigated in continuation of our previous studies on binary systems (benzene or toluene+benzonitrile). Heat capacities by volume unit, determined with a Picker flow calorimeter at T=298.15K, and densities, measured by using Picker vibrating densimeters at the temperatures (298.15 and 308.15)K, are reported. Measurements were made over the entire range of mole fraction. From the primary measurements, the corresponding excess quantities V{sup E} and C{sub p,m}{sup E} are obtained. The magnitude of these experimental quantities together with H{sup E} literature data is discussed in terms of the nature and type of intermolecular interactions in binary mixtures.

Calvo-Iglesias, E. [Departamento de Fisica Aplicada, Facultad de Fisica, Universidad de Santiago de Compostela, E-15782 Santiago de Compostela (Spain)]. E-mail: faencina@usc.es; Bravo, R. [Departamento de Fisica Aplicada, Facultad de Fisica, Universidad de Santiago de Compostela, E-15782 Santiago de Compostela (Spain); Pintos, M. [Departamento de Fisica Aplicada, Facultad de Fisica, Universidad de Santiago de Compostela, E-15782 Santiago de Compostela (Spain); Amigo, A. [Departamento de Fisica Aplicada, Facultad de Fisica, Universidad de Santiago de Compostela, E-15782 Santiago de Compostela (Spain); Roux, A.H. [Thermodynamique des Solutions et des Polymeres, UMR CNRS 6003, Universite Blaise Pascal, 63177 Aubiere cedex (France); Roux-Desgranges, G. [Thermodynamique des Solutions et des Polymeres, UMR CNRS 6003, Universite Blaise Pascal, 63177 Aubiere cedex (France)

2007-04-15

232

Thermodynamics of mixtures involving some (benzene derivatives+benzonitrile)  

International Nuclear Information System (INIS)

Interactions of binary mixtures involving some benzene derivatives (ethylbenzene, o-, m-, p-xylene, isopropylbenzene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, and methoxybenzene) with benzonitrile were investigated in continuation of our previous studies on binary systems (benzene or toluene+benzonitrile). Heat capacities by volume unit, determined with a Picker flow calorimeter at T=298.15K, and densities, measured by using Picker vibrating densimeters at the temperatures (298.15 and 308.15)K, are reported. Measurements were made over the entire range of mole fraction. From the primary measurements, the corresponding excess quantities VE and Cp,mE are obtained. The magnitude of these experimental quantities together with HE literature data is discussed in terms of the nature and type of intermolecular interactions in binary mixtures

233

Phase II metabolism of benzene.  

OpenAIRE

The hepatic metabolism of benzene is thought to be a prerequisite for its bony marrow toxicity. However, the complete pattern of benzene metabolites formed in the liver and their role in bone marrow toxicity are not fully understood. Therefore, benzene metabolism was studied in isolated rodent hepatocytes. Rat hepatocytes released benzene-1,2-dihydrodiol, hydroquinone (HQ), catechol (CT), phenol (PH), trans-trans-muconic acid, and a number of phase II metabolites such as PH sulfate and PH glu...

Schrenk, D.; Orzechowski, A.; Schwarz, L. R.; Snyder, R.; Burchell, B; Ingelman-sundberg, M.; Bock, K. W.

1996-01-01

234

Quaternary (liquid + liquid) equilibrium data for the extraction of toluene from alkanes using the ionic liquid [EMim][MSO4  

International Nuclear Information System (INIS)

Highlights: • EMim[MSO4] was proposed as solvent for the extraction of toluene from alkanes. • The quaternary system {heptane + cyclohexane + toluene + [EMim][MSO4]} was evaluated. • The extraction of toluene would be facilitated in the presence of one alkane. • Experimental LLE data were successfully correlated with the NRTL model. - Abstract: (Liquid + liquid) equilibrium (LLE) studies for the extraction of aromatics from alkanes present in the petroleum fractions are important to develop theoretical/semiempirical (liquid + liquid) equilibrium models, which are used in the design of extraction processes. In this work, the ionic liquid 1-ethyl-3-methylimidazolium methylsulfate, [EMim][MSO4], was evaluated as potential solvent for the separation of toluene from heptane and cyclohexane. The LLE data for the quaternary system {heptane (1) + cyclohexane (2) + toluene (3) + [EMim][MSO4] (4)} were experimentally determined at T = 298.15 K and atmospheric pressure. Moreover, the LLE data for the ternary systems {heptane or cyclohexane (1) + toluene (2) + [EMim][MSO4] (3)} were also determined. Solute distribution ratios and selectivities were calculated and analysed in order to evaluate the capability of the ionic liquid to accomplish the separation target. A comparison between the solute distribution ratios and selectivities for the quaternary and the ternary systems was also made. Finally, the experimental tie-line data were correlated with the NRTL model

235

Hematotoxicity and carcinogenicity of benzene.  

OpenAIRE

The hematotoxicity of benzene exposure has been well known for a century. Benzene causes leukocytopenia, thrombocytopenia, pancytopenia, etc. The clinical and hematologic picture of aplastic anemia resulting from benzene exposure is not different from classical aplastic anemia; in some cases, mild bilirubinemia, changes in osmotic fragility, increase in lactic dehydrogenase and fecal urobilinogen, and occasionally some neurological abnormalities are found. Electromicroscopic findings in some ...

Aksoy, M.

1989-01-01

236

Quantum chromodynamics quark benzene  

OpenAIRE

A six-quark state with the benzene-like structure is proposed and studied based on color string model. The calculation with the quadratic confinement show that such structure has the lowest energy among the various hidden color six-quark structures proposed so far. Its possible effect on $NN$ scattering is discussed.

Ping, Jialun; Deng, Chengrong; Wang, Fan; Goldman, T.

2006-01-01

237

Consistent Assignment of the Vibrations of Monohalosubstituted Benzenes  

Science.gov (United States)

When substituted benzenes become a focus of a spectroscopic study there are various well known vibrational labelling schemes present, however it was shown in recent works the description of monohalobenzene vibrations in terms of benzene modes (ie. Wilson notation) is questionable in some cases. A new scheme is presented which uses the motions of monofluorobenzene vibrations as a basis for labelling vibrational assignments of monosubstituted benzenes.d The scheme has been successfully applied to the ground and excited states of toluene and its deuterated-methyl group isotopologue. Here we present the application of the scheme to fluorobenzene and its fully deuterated analogue. One-colour resonance-enhanced multiphoton ionization (REMPI) spectroscopy was employed in order to characterise the fluorobenzene and fluorobenzene-d5 excited state. E. B. Wilson Jr., Phys. Rev., 45, 706 (1934) G .Varsanyi, Assignments of the Vibrational Spectra of Seven Hundred Benzene Derivatives,Wiley, New York, 1974, Vol. I and II I. Pugliesi, N. C. Tonge and M. C. R. Cockett, J. Chem. Phys., 129, 104303 (2008) A. M. Gardner and T. G. Wright, J. Chem. Phys., 135,114305 (2011) A. M. Gardner, A. M. Green, V. M. Tame-Reyes, V. H. K. Wilton and T. G. Wright, 138, 134303 (2013) A. M. Gardner, A. M. Green, V. M. Tame-Reyes, K. L. Reid, J. A. Davies, V. H. K. Wilton and T. G. Wright, manuscript accepted

Harris, Joe; Andrejeva, Anna; Tuttle, William Duncan; Pugliesi, Igor; Schriever, Christian; Wright, Tim

2014-06-01

238

Photocatalytic Degradation of Benzene Derivatives on TiO2 Catalyst  

Science.gov (United States)

The photocatalytic degradation of some benzene derivatives over TiO2 (Phenol, Chlorobenzene and Toluene) in aqueous medium is compared to the reaction of the benzene. The rates of disappearence fit Langmuir-Hinshelwood kinetics and the parameter k has been determined. The electronic effect of the substituent is responsible of the kinetic of photodegradation of the aromatic compound and can lead to particular modes of adsorption on catalyst: more reactivity is observed with an electron-donating substituent. New concepts for new photocatalysts can then be defined by doping foreign materials into TiO2 photocatalyst.

Bougheloum, Ch.; Messalhi, A.

2009-11-01

239

Ethyl anion preferred conformation  

Science.gov (United States)

Ab initio architecture and torsional barrier for ethyl anion, C2H -5 are analyzed using natural bond orbital methodology. The B3LYP/6-311++G(3df,2p) 2-kcal/mol torsional barrier between the preferred staggered and higher-energy eclipsed conformer is calculated to be one-third lower than for ethane. This decrease is largely attributed to reduced hyperconjugative stabilization of the equilibrium anion conformer compared to that for ethane. Proton removal is also predicted to cause opening of the ethane central CCH angle by 7°, attributed to decreased steric repulsion and to increased hyperconjugative stabilization accompanying angle widening in the ion.

Goodman, Lionel; Sauers, Ronald R.

240

9-Ethyl-9H-carbazole-3-carbaldehyde  

Directory of Open Access Journals (Sweden)

Full Text Available The title molecule, C15H13NO, approximates a planar conformation except for the alkyl chain (ethyl group bonded to the N atom with a maximum deviation from the least-squares plane through the 15 planar atoms of 0.120?(2?Å for the O atom. The distance of the formyl O atom from the plane of the carbazole ring is 0.227?(2?Å. The N—C bond lengths in the central ring are significantly different, reflecting the electron-withdrawing properties of the aldehyde group. As a consequence, charge transfer may occur from the carbazole N atom to the substituted benzene ring.

Mao-Sen Yuan

2010-08-01

241

Composition of toluene-degrading microbial communities from soil at different concentrations of toluene  

Energy Technology Data Exchange (ETDEWEB)

Toluene-degrading bacteria were isolated from hydrocarbon-contaminated soil by incubating liquid enrichment cultures and agar plate cultures in desiccators in which the vapor pressure of toluene was controlled by dilution with vacuum pump oil. Incubation in desiccators equilibrated with either 100, 10, or 1% (wt/wt) toluene in vacuum pump oil and testing for genomic cross-hybridization resulted in four genomically distinct strains (standards) capable of growth on toluene (strains Cstd1, Cstd2, and Cstd5, and Cstd7). The optimal toluene concentrations for growth of these standards on plating media differed considerably. Cstd1 grew best in an atmosphere equilibrated with 0.1% (wt/wt) toluene, but Cstd5 failed to grow in this atmosphere. Conversely, Cstd5 grew well in the presence of 10% (wt/wt) toluene, which inhibited growth of Cstd1. 16S ribosomal DNA sequencing and cross-hybridization analysis indicated that both Cstd1 and Cstd5 are members of the genus Pseudomonas. An analysis of the microbial communities in soil samples that were incubated with 10% (wt/wt) toluene with reverse sample genome probing indicated that Pseudomonas strain Cstd5 was the dominant community member. However, incubation of soil samples with 0.1% (wt/wt) toluene resulted in a community that was dominated by Pseudomonas strain Q7, a toluene degrader that has been described previously. Q7 was not able to grow by itself in an atmosphere equilibrated with 0.1% (wt/wt) toluene but grew efficiently in coculture with Cstd1, suggesting that toluene or metabolic derivatives of toluene were transferred from Cstd1 to Q7.

Hubert, C.; Shen, Y.; Voordouw, G. (Univ. of Calgary, Alberta (Canada). Dept. of Biological Sciences)

1999-07-01

242

N-(2,6-Diisopropyl­phen­yl)formamide toluene 0.33-solvate  

Science.gov (United States)

The crystal packing of the title compound, C13H19NO·0.33C7H8, shows a channel at [001], which contains grossly disordered toluene solvent mol­ecules. The angle between the benzene ring and the mean plane of the formamide group is 71.1?(1)°. The amide groups of neighbouring mol­ecules are connected by N—H?O hydrogen bonds, forming 21 helical chains propagating along [001]. Mol­ecules are also connected by weak inter­molecular C—H?O hydrogen bonds, forming 61 helices. PMID:22590423

Berger, Matthias; Bats, Jan W.; Auner, Norbert

2012-01-01

243

N-(2,6-Diisopropyl-phen-yl)formamide toluene 0.33-solvate.  

Science.gov (United States)

The crystal packing of the title compound, C(13)H(19)NO·0.33C(7)H(8), shows a channel at [001], which contains grossly disordered toluene solvent mol-ecules. The angle between the benzene ring and the mean plane of the formamide group is 71.1?(1)°. The amide groups of neighbouring mol-ecules are connected by N-H?O hydrogen bonds, forming 2(1) helical chains propagating along [001]. Mol-ecules are also connected by weak inter-molecular C-H?O hydrogen bonds, forming 6(1) helices. PMID:22590423

Berger, Matthias; Bats, Jan W; Auner, Norbert

2012-05-01

244

N-(2,6-Diisopropylphenyl)formamide toluene 0.33-solvate  

OpenAIRE

The crystal packing of the title compound, C13H19NO·0.33C7H8, shows a channel at [001], which contains grossly disordered toluene solvent molecules. The angle between the benzene ring and the mean plane of the formamide group is 71.1?(1)°. The amide groups of neighbouring molecules are connected by N—H...O hydrogen bonds, forming 21 helical chains propagating along [001]. Molecules are also connected by weak intermolecular C—H...O hydrogen bonds...

Norbert Auner; Bats, Jan W.; Matthias Berger

2012-01-01

245

N-(2,6-Diisopropyl­phen­yl)formamide toluene 0.33-solvate  

OpenAIRE

The crystal packing of the title compound, C13H19NO·0.33C7H8, shows a channel at [001], which contains grossly disordered toluene solvent mol­ecules. The angle between the benzene ring and the mean plane of the formamide group is 71.1?(1)°. The amide groups of neighbouring mol­ecules are connected by N—H(...)O hydrogen bonds, forming 21 helical chains propagating along [001]. Mol­ecules are also connected by weak inter­molecular C—H(...)O hydrogen bonds, forming 61 helices.

Berger, Matthias; Bats, Jan W.; Auner, Norbert

2012-01-01

246

Measurements of activity coefficients at infinite dilution for organic solutes and water in the ionic liquid 1-ethyl-3-methylimidazolium methanesulfonate  

International Nuclear Information System (INIS)

Highlights: ? Measurements of activity coefficients at infinite dilution using GLC. ? Forty-two organic solvents and water in the ionic liquid 1-ethyl-3-methylimidazolium methanesulfonate. ? High selectivity for heptane/thiophene. ? Possible entrainer for different separation processes with water. ? The excess thermodynamic functions and the gas–liquid partition coefficients were calculated. - Abstract: The activity coefficients at infinite dilution, ?13?, for 43 solutes, including alkanes, cycloalkanes, alkenes, alkynes, aromatic hydrocarbons, alcohols, water, thiophene, ethers, ketones, acetonitrile, pyridine, and 1-nitropropane in the ionic liquid 1-ethyl-3-methylimidazolium methanesulfonate [EMIM][MeSO3] were determined by gas–liquid chromatography at six temperatures within the range (308.15 to 358.15) K. The interaction of these 42 organic compounds and water with the ionic liquid were described with the partial molar excess Gibbs free energy, ?G1E,?, enthalpy ?H1E,?, and entropy Tref?S1E,? at infinite dilution, calculated from the experimental ?13? values obtained over the temperature range. The gas–liquid partition coefficients, KL were calculated for all solutes. The values of the selectivity for few separation problems as heptane/toluene, cyclohexane/benzene, heptane/xylenes and heptane/nd heptane/thiophene were calculated from ?13? and compared to literature values for N-methyl-2-pyrrolidinone (NMP), sulfolane, and other ionic liquids based on [EMIM]+ cation. Comparison with the results published earlier for [EMIM][MeSO3] show much lower selectivities in the discussed separation problems. By contrast with the former measured ILs [EMIM][MeSO3] reveals the average selectivity for the separation of aromatics/aliphatics and low capacity for benzene. An interesting high value of selectivity was observed in the separation of thiophene/aliphatics. Very high values of selectivity may be expected in the separation of the azeotropic systems including water. The density of [EMIM][MeSO3] within temperature range from (298.15 to 358.15) K was measured and compared to the literature values.

247

Proteogenomic Elucidation of the Initial Steps in the Benzene Degradation Pathway of a Novel Halophile, Arhodomonas sp. Strain Rozel, Isolated from a Hypersaline Environment  

OpenAIRE

Lately, there has been a special interest in understanding the role of halophilic and halotolerant organisms for their ability to degrade hydrocarbons. The focus of this study was to investigate the genes and enzymes involved in the initial steps of the benzene degradation pathway in halophiles. The extremely halophilic bacteria Arhodomonas sp. strain Seminole and Arhodomonas sp. strain Rozel, which degrade benzene and toluene as the sole carbon source at high salinity (0.5 to 4 M NaCl), were...

Dalvi, Sonal; Azetsu, Sei; Patrauchan, Marianna A.; Aktas, Deniz F.; Fathepure, Babu Z.

2012-01-01

248

ASPEN HYSYS SIMULATION AND COMPARISON BETWEEN ORGANIC SOLVENTS (SULFOLANE AND DMSO) USED FOR BENZENE EXTRACTION  

OpenAIRE

Due to the high increase of the production of aromatic hydrocarbons: benzene, toluene and xylenes BTX from oil because of the large activity of their big markets especially with the availability of great quantities of these aromatic fractions in the oil. This study has two main parts the first presents a general vision of the aromatic hydrocarbons, the second is going to focus on the liquid-liquid extraction with the selected solvents as a separation method. The solvent selection depends on m...

Zaiz, T.; Lanez, H.; Kechida, B.

2013-01-01

249

[Hydroxy(tosyloxyiodo]benzene Mediated α-Azidation of Ketones  

Directory of Open Access Journals (Sweden)

Full Text Available Reaction of various ketones with [hydroxy(tosyloxyiodo]benzene (HTIB followed by treatment of the α-tosyloxy ketones thus generated in situ with NaN3 offers a one-pot procedure for the synthesis of α-azido ketones. The HTIB used in this conversion may also be generated in situ by using iodosobenzene in combination with p-toluene- sulphonic acid.

Anita Batra

2006-07-01

250

Volatilization of benzene and eight alkyl-substituted benzene compounds from water  

Science.gov (United States)

Predicting the fate of organic compounds in streams and rivers often requires knowledge of the volatilization characteristics of the compounds. The reference-substance concept, involving laboratory-determined ratios of the liquid-film coefficients for volatilization of the organic compounds to the liquid-film coefficient for oxygen absorption, is used to predict liquid-film coefficients for streams and rivers. In the absence of experimental data, two procedures have been used for estimating these liquid-film coefficient ratios. These procedures, based on the molecular-diffusion coefficient and on the molecular weight, have been widely used but never extensively evaluated. Liquid-film coefficients for the volatilization of benzene and eight alkyl-substituted benzene compounds (toluene through n-octylbenzene) from water were measured in a constant-temperature, stirred water bath. Liquid-film coefficients for oxygen absorption were measured simultaneously. A range of water mixing conditions was used with a water temperature of 298.2 K. The ratios of the liquid-film coefficients for volatilization to the liquid-film coefficient for oxygen absorption for all of the organic compounds were independent of mixing conditions in the water. Experimental ratios ranged from 0.606 for benzene to 0.357 for n-octylbenzene. The molecular-diffusion-coefficient procedure accurately predicted the ratios for ethylbenzene through n-pentylbenzene with a power dependence of 0.566 on the molecular-diffusion coefficient, in agreement with published values. Predicted ratios for benzene and toluene were slightly larger than the experimental ratios. These differences were attributed to possible interactions between the molecules of these compounds and the water molecules and to benzene-benzene interactions that form dimers. Because these interactions also are likely to occur in natural waters, it was concluded that the experimental ratios are more correct than the predicted ratios for application purposes in the reference-substance concept. Predicted ratios for n-hexylbenzene, n-heptylbenzene, and n-octylbenzene were larger than the experimental ratios. These differences were attributed to a sorption-desorption process between these compounds and the surfaces of the constant-temperature water bath. Other experimental problems associated with preparing water solutions of these slightly soluble compounds also may have contributed to the differences. Because these processes are not part of the true volatilization process, it was concluded that the predicted ratios for these three compounds are probably more correct than the experimental ratios for application purposes in the reference-substance concept. Any model of the fate of these compounds in streams and rivers would have to include terms accounting for sorption processes, however. The molecular-weight procedure accurately predicted the ratios for ethylbenzene through n-pentylbenzene, but only if the power dependence on the molecular weight was decreased from the commonly used -0.500 to -0.427. Deviations for the low- and high-molecular-weight compounds were similar to those observed for the molecular-diffusion-coefficient procedure.

Rathbun, R.E.; Tai, D.Y.

1988-01-01

251

Atmospheric oxidation mechanism of toluene.  

Science.gov (United States)

The atmospheric oxidation mechanism of toluene initiated by OH radical addition is investigated by quantum chemistry calculations at M06-2X, G3MP2-RAD, and ROCBS-QB3 levels and by kinetics calculation by using transition state theory and unimolecular reaction theory coupled with master equation (RRKM-ME). The predicted branching ratios are 0.15, 0.59, 0.05, and 0.14 for OH additions to ipso, ortho, meta, and para positions (forming R1-R4 adducts), respectively. The fate of R2, R4, and R1 is investigated in detail. In the atmosphere, R2 reacts with O2 either by irreversible H-abstraction to form o-cresol (36%), or by reversible recombination to R2-1OO-syn and R2-3OO-syn, which subsequently cyclize to bicyclic radical R2-13OO-syn (64%). Similarly, R4 reacts with O2 with branching ratios of 61% for p-cresol and 39% for R4-35OO-syn, while reaction of R1 and O2 leads to R1-26OO-syn. RRKM-ME calculations show that the reactions of R2/R4 with O2 have reached their high-pressure limits at 760 Torr and the formation of R2-16O-3O-s is only important at low pressure, i.e., 5.4% at 100 Torr. The bicyclic radicals (R2-13OO-syn, R4-35OO-syn, and R1-26OO-syn) will recombine with O2 to produce bicyclic alkoxy radicals after reacting with NO. The bicyclic alkoxy radicals would break the ring to form products methylglyoxal/glyoxal (MGLY/GLY) and their corresponding coproducts butenedial/methyl-substituted butenedial as proposed in earlier studies. However, a new reaction pathway is found for the bicyclic alkoxy radicals, leading to products MGLY/GLY and 2,3-epoxybutandial/2-methyl-2,3-epoxybutandial. A new mechanism is proposed for the atmospheric oxidation mechanism of toluene based on current theoretical and previous theoretical and experimental results. The new mechanism predicts much lower yield of GLY and much higher yield of butenedial than other atmospheric models and recent experimental measurements. The new mechanism calls for detection of proposed products 2,3-epoxybutandial and 2-methyl-2,3-epoxybutandial. PMID:24901213

Wu, Runrun; Pan, Shanshan; Li, Yun; Wang, Liming

2014-06-26

252

Determination of (BTEX) of the gasoline's combustion in Ecuador  

International Nuclear Information System (INIS)

The contents of benzene, toluene, ethyl benzene and xylenes (BTEX) were determined and quantified in the gasoline's combustion on an internal combustion engine. Gas chromatography with flame ionization detector were used for chemical determinations

253

Reactions of 9-Alkyl-3-aminocarbazoles with Ethyl-3-oxo-butanoate and Identification of the Products Obtained  

Directory of Open Access Journals (Sweden)

Full Text Available The reactions in benzene of 9-alkyl-3-aminocarbazoles with ethyl-3-oxobutanoateyielded ethyl-3-[(9-alkyl-9H-carbazol-3-ylamino]but-2-enoate condensation products or N-(9-ethyl-9H-carbazol-3-yl-3-oxobutanamide acylation products. The condensation productswere cyclized to the corresponding 4,7-dihydro-pyrido[2,3-c]-carbazol-1-ones upon heatingin mineral oil at 240-250 °C. The structures of the synthesized compounds were investigatedby IR, mass spectrometry, 1H- and 13C-NMR spectroscopy and MM2 molecular mechanicsand AM1 semi-empirical quantum mechanical methods.

Gema Mikulskiene

2006-01-01

254

Toluene 3-monooxygenase of Ralstonia pickettii PKO1 is a para-hydroxylating enzyme.  

Science.gov (United States)

Oxygenases are promising biocatalysts for performing selective hydroxylations not accessible by chemical methods. Whereas toluene 4-monooxygenase (T4MO) of Pseudomonas mendocina KR1 hydroxylates monosubstituted benzenes at the para position and toluene ortho-monooxygenase (TOM) of Burkholderia cepacia G4 hydroxylates at the ortho position, toluene 3-monooxygenase (T3MO) of Ralstonia pickettii PKO1 was reported previously to hydroxylate toluene at the meta position, producing primarily m-cresol (R. H. Olsen, J. J. Kukor, and B. Kaphammer, J. Bacteriol. 176:3749-3756, 1994). Using gas chromatography, we have discovered that T3MO hydroxylates monosubstituted benzenes predominantly at the para position. TG1/pBS(Kan)T3MO cells expressing T3MO oxidized toluene at a maximal rate of 11.5 +/- 0.33 nmol/min/mg of protein with an apparent Km value of 250 microM and produced 90% p-cresol and 10% m-cresol. This product mixture was successively transformed to 4-methylcatechol. T4MO, in comparison, produces 97% p-cresol and 3% m-cresol. Pseudomonas aeruginosa PAO1 harboring pRO1966 (the original T3MO-bearing plasmid) also exhibited the same product distribution as that of TG1/pBS(Kan)T3MO. TG1/pBS(Kan)T3MO produced 66% p-nitrophenol and 34% m-nitrophenol from nitrobenzene and 100% p-methoxyphenol from methoxybenzene, as well as 62% 1-naphthol and 38% 2-naphthol from naphthalene; similar results were found with TG1/pBS(Kan)T4MO. Sequencing of the tbu locus from pBS(Kan)T3MO and pRO1966 revealed complete identity between the two, thus eliminating any possible cloning errors. 1H nuclear magnetic resonance analysis confirmed the structural identity of p-cresol in samples containing the product of hydroxylation of toluene by pBS(Kan)T3MO. PMID:15126473

Fishman, Ayelet; Tao, Ying; Wood, Thomas K

2004-05-01

255

Studies of the exchange reaction between deuterium oxide and substituted benzenes and of the clustering reaction between water and substituted phenols in chemical ionization mass spectrometry  

International Nuclear Information System (INIS)

Evidence is presented for the protonation site in substituted benzenes. Benzene itself was found to undergo an exchange of ring hydrogens only when protonated. In addition, benzene did not undergo a clustering reaction with water. Based on similar behavior, benzene, toluene, bromobenzene, iodobenzene, fluorobenzene, the xylenes, mesitylene, and the di- and tri-fluorobenzenes were found to protonate on the ring. Nitrobenzene, anisole, phenol, benzaldehyde, and aniline were found to protonate on the substituent. These results are consistent with theoretical predictions for benzene, toluene, and the xylenes. However, discrepancies exist for anisole and phenol (in coomparison to calculations done on the cresols and methylanisoles). The result for anisole also disagrees with a determination by an ICR technique. Kinetics of the exchange reaction for benzene, toluene, the xylenes, and mesitylene were observed. Based on a simple model of consecutive pseudo-first order reactions, rate constants for each step in the reaction sequence were determined. The possibility of a more complicated mechanism is also discussed. The clustering reaction between water molecules and a chemical ionization sample has been studied for a series of substituted phenols. In the nitrophenols, protonation at the nitro group is favored whereas in the methylphenols, ethylphenols, chlorophenols, hydroxphenols, and aminophenols, protonation at the hydroxy group is favored. In the pulsed ionization mode equfavored. In the pulsed ionization mode equilibrium effects dominated the spectra obtained in the continuous ionization mode

256

Primary atmospheric oxidation mechanism for toluene.  

Science.gov (United States)

The products of the primary OH-initiated oxidation of toluene were investigated using the turbulent flow chemical ionization mass spectrometry technique at temperatures ranging from 228 to 298 K. A major dienedial-producing pathway was detected for the first time for toluene oxidation, and glyoxal and methylglyoxal were found to be minor primary oxidation products. The results suggest that secondary oxidation processes involving dienedial and epoxide primary products are likely responsible for previous observations of glyoxal and methylglyoxal products from toluene oxidation. Because the dienedial-producing pathway is a null cycle for tropospheric ozone production and glyoxal and methylglyoxal are important secondary organic aerosol precursors, these new findings have important implications for the modeling of toluene oxidation in the atmosphere. PMID:19118482

Baltaretu, Cristian O; Lichtman, Eben I; Hadler, Amelia B; Elrod, Matthew J

2009-01-01

257

Construction and comparison of fluorescence and bioluminescence bacterial biosensors for the detection of bioavailable toluene and related compounds  

International Nuclear Information System (INIS)

Environmental pollution with petroleum products such as benzene, toluene, ethylbenzene, and xylenes (BTEX) has garnered increasing awareness because of its serious consequences for human health and the environment. We have constructed toluene bacterial biosensors comprised of two reporter genes, gfp and luxCDABE, characterized by green fluorescence and luminescence, respectively, and compared their abilities to detect bioavailable toluene and related compounds. The bacterial luminescence biosensor allowed faster and more-sensitive detection of toluene; the fluorescence biosensor strain was much more stable and thus more applicable for long-term exposure. Both luminescence and fluorescence biosensors were field-tested to measure the relative bioavailability of BTEX in contaminated groundwater and soil samples. The estimated BTEX concentrations determined by the luminescence and fluorescence bacterial biosensors were closely comparable to each other. Our results demonstrate that both bacterial luminescence and fluorescence biosensors are useful in determining the presence and the bioavailable fractions of BTEX in the environment. - The choice of reporter genes for toluene bacterial biosensors to determine BTEX bioavailability is case-specific

258

Phylogenetic and functional diversity within toluene-degrading, sulphate-reducing consortia enriched from a contaminated aquifer.  

Science.gov (United States)

Three toluene-degrading microbial consortia were enriched under sulphate-reducing conditions from different zones of a benzene, toluene, ethylbenzene and xylenes (BTEX) plume of two connected contaminated aquifers. Two cultures were obtained from a weakly contaminated zone of the lower aquifer, while one culture originated from the highly contaminated upper aquifer. We hypothesised that the different habitat characteristics are reflected by distinct degrader populations. Degradation of toluene with concomitant production of sulphide was demonstrated in laboratory microcosms and the enrichment cultures were phylogenetically characterised. The benzylsuccinate synthase alpha-subunit (bssA) marker gene, encoding the enzyme initiating anaerobic toluene degradation, was targeted to characterise the catabolic diversity within the enrichment cultures. It was shown that the hydrogeochemical parameters in the different zones of the plume determined the microbial composition of the enrichment cultures. Both enrichment cultures from the weakly contaminated zone were of a very similar composition, dominated by Deltaproteobacteria with the Desulfobulbaceae (a Desulfopila-related phylotype) as key players. Two different bssA sequence types were found, which were both affiliated to genes from sulphate-reducing Deltaproteobacteria. In contrast, the enrichment culture from the highly contaminated zone was dominated by Clostridia with a Desulfosporosinus-related phylotype as presumed key player. A distinct bssA sequence type with high similarity to other recently detected sequences from clostridial toluene degraders was dominant in this culture. This work contributes to our understanding of the niche partitioning between degrader populations in distinct compartments of BTEX-contaminated aquifers. PMID:24623528

Kuppardt, Anke; Kleinsteuber, Sabine; Vogt, Carsten; Lüders, Tillmann; Harms, Hauke; Chatzinotas, Antonis

2014-08-01

259

Ab initio calculations of structures and interaction energies of toluene dimers including CCSD(T) level electron correlation correction  

Science.gov (United States)

The intermolecular interaction energy of the toluene dimer has been calculated with the ARS-F model (a model chemistry for the evaluation of intermolecular interaction energy between ARomatic Systems using Feller's method), which was formerly called as the AIMI model III. The CCSD(T) (coupled cluster calculations with single and double substitutions with noniterative triple excitations) interaction energy at the basis set limit has been estimated from the second-order Møller-Plesset perturbation interaction energy at the basis set limit obtained by Feller's method and the CCSD(T) correction term obtained using a medium-size basis set. The cross (C2) dimer has the largest (most negative) interaction energy (-4.08kcal/mol). The antiparallel (C2h) and parallel (CS) dimers (-3.77 and -3.41kcal/mol, respectively) are slightly less stable. The dispersion interaction is found to be the major source of attraction in the toluene dimer. The dispersion interaction mainly determines the relative stability of the stacked three dimers. The electrostatic interaction of the stacked three dimers is repulsive. Although the T-shaped and slipped-parallel benzene dimers are nearly isoenergetic, the stacked toluene dimers are substantially more stable than the T-shaped toluene dimer (-2.62kcal/mol). The large dispersion interaction in the stacked toluene dimers is the cause of their enhanced stability.

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

2005-04-01

260

Toluene Monooxygenase-Catalyzed Epoxidation of Alkenes  

OpenAIRE

Several toluene monooxygenase-producing organisms were tested for their ability to oxidize linear alkenes and chloroalkenes three to eight carbons long. Each of the wild-type organisms degraded all of the alkenes that were tested. Epoxides were produced during the oxidation of butene, butadiene, and pentene but not hexene or octadiene. A strain of Escherichia coli expressing the cloned toluene-4-monooxygenase (T4MO) of Pseudomonas mendocina KR1 was able to oxidize butene, butadiene, pentene, ...

Mcclay, Kevin; Fox, Brian G.; Steffan, Robert J.

2000-01-01

261

Stemofoline ethyl acetate solvate  

OpenAIRE

Crystals of the title compound, C22H29NO5·C4H8O2, {[systematic name: (2R,3R,5R,5aS,6R,8aR,9S)-(5Z)-5-[3-butyl­tetra­hydro-6-methyl-2,5-methano-4,3,8a-[1]propan­yl[3]yl­idene­furo[3,2-f][1,4]oxazepin-7(5H)-yl­idene]-4-meth­oxy-3-methyl­furan-2(5H)-one ethyl acetate solvate} were isolated from the root extracts of Stemona aphylla (Stemonaceae). The structure closely resembles those of stemofoline derivatives which have previously been reported. Inter­molecular contacts are observed be...

Pitchaya Mungkornasawakul; Pyne, Stephen G.; Ung, Alison T.; Araya Jatisatienr; Willis, Anthony C.

2009-01-01

262

Ambient air benzene at background sites in China's most developed coastal regions: Exposure levels, source implications and health risks.  

Science.gov (United States)

Benzene is a known human carcinogen causing leukemia, yet ambient air quality objectives for benzene are not available in China. The ambient benzene levels at four background sites in China's most developed coastal regions were measured from March 2012 to February 2013. The sites are: SYNECP, in the Northeast China Plain (NECP); YCNCP, in the North China Plain (NCP); THYRD, in the Yangtze River Delta (YRD) and DHPRD, in the Pearl River Delta (PRD). It was found that the mean annual benzene levels (578-1297ppt) at the background sites were alarmingly higher, especially when compared to those of 60-480pptv monitored in 28 cities in the United States. Wintertime benzene levels were significantly elevated at both sites (SYNECP and YCNCP) in northern China due to heating with coal/biofuels. Even at these background sites, the lifetime cancer risks of benzene (1.7-3.7E-05) all exceeded 1E-06 set by USEPA as acceptable for adults. At both sites in northern China, good correlations between benzene and CO or chloromethane, together with much lower toluene/benzene (T/B) ratios, suggested that benzene was largely related to coal combustion and biomass/biofuel burning. At the DHPRD site in the PRD, benzene revealed a highly significant correlation with methyl tert-butyl ether (MTBE), indicating that its source was predominantly from vehicle emissions. At the THYRD site in the YRD, higher T/B ratios and correlations between benzene and tetrachloroethylene, or MTBE, implied that benzene levels were probably affected by both traffic-related and industrial emissions. PMID:25618820

Zhang, Zhou; Wang, Xinming; Zhang, Yanli; Lü, Sujun; Huang, Zhonghui; Huang, Xinyu; Wang, Yuesi

2015-04-01

263

Biomarkers of environmental benzene exposure.  

OpenAIRE

Environmental exposures to benzene result in increases in body burden that are reflected in various biomarkers of exposure, including benzene in exhaled breath, benzene in blood and urinary trans-trans-muconic acid and S-phenylmercapturic acid. A review of the literature indicates that these biomarkers can be used to distinguish populations with different levels of exposure (such as smokers from nonsmokers and occupationally exposed from environmentally exposed populations) and to determine d...

Weisel, C.; Yu, R.; Roy, A.; Georgopoulos, P.

1996-01-01

264

Crystal structure of ethyl 4-[(1H-pyrazol-1-yl)meth-yl]benzoate.  

Science.gov (United States)

In the title mol-ecule, C13H14N2O2, the dihedral angle between the pyrazole and benzene ring mean planes is 76.06?(11)°, and the conformation of the ethyl side chain is anti [C-O-C-C = -175.4?(3)°]. In the crystal, the only directional inter-actions are very weak C-H ?? inter-actions involving both the pyrazole and benzene rings, leading to the formation of a three-dimensional network. PMID:25553050

Wang, Ju-Xian; Feng, Chao

2014-12-01

265

Crystal structure of ethyl 4-[(1H-pyrazol-1-yl)meth­yl]benzoate  

Science.gov (United States)

In the title mol­ecule, C13H14N2O2, the dihedral angle between the pyrazole and benzene ring mean planes is 76.06?(11)°, and the conformation of the ethyl side chain is anti [C—O—C—C = ?175.4?(3)°]. In the crystal, the only directional inter­actions are very weak C—H ?? inter­actions involving both the pyrazole and benzene rings, leading to the formation of a three-dimensional network. PMID:25553050

Wang, Ju-Xian; Feng, Chao

2014-01-01

266

Protein engineering of toluene monooxygenases for synthesis of chiral sulfoxides.  

Science.gov (United States)

Enantiopure sulfoxides are valuable asymmetric starting materials and are important chiral auxiliaries in organic synthesis. Toluene monooxygenases (TMOs) have been shown previously to catalyze regioselective hydroxylation of substituted benzenes and phenols. Here we show that TMOs are also capable of performing enantioselective oxidation reactions of aromatic sulfides. Mutagenesis of position V106 in the alpha-hydroxylase subunit of toluene ortho-monooxygenase (TOM) of Burkholderia cepacia G4 and the analogous position I100 in toluene 4-monooxygenase (T4MO) of Pseudomonas mendocina KR1 improved both rate and enantioselectivity. Variant TomA3 V106M of TOM oxidized methyl phenyl sulfide to the corresponding sulfoxide at a rate of 3.0 nmol/min/mg protein compared with 1.6 for the wild-type enzyme, and the enantiomeric excess (pro-S) increased from 51% for the wild type to 88% for this mutant. Similarly, T4MO variant TmoA I100G increased the wild-type oxidation rate by 1.7-fold, and the enantiomeric excess rose from 86% to 98% (pro-S). Both wild-type enzymes showed lower activity with methyl para-tolyl sulfide as a substrate, but the improvement in the activity and enantioselectivity of the mutants was more dramatic. For example, T4MO variant TmoA I100G oxidized methyl para-tolyl sulfide 11 times faster than the wild type did and changed the selectivity from 41% pro-R to 77% pro-S. A correlation between regioselectivity and enantioselectivity was shown for TMOs studied in this work. Using in silico homology modeling, it is shown that residue I100 in T4MO aids in steering the substrate into the active site at the end of the long entrance channel. It is further hypothesized that the main function of V106 in TOM is the proper positioning or docking of the substrate with respect to the diiron atoms. The results from this work suggest that when the substrate is not aligned correctly in the active site, the oxidation rate is decreased and enantioselectivity is impaired, resulting in products with both chiral configurations. PMID:18192418

Feingersch, Roi; Shainsky, Janna; Wood, Thomas K; Fishman, Ayelet

2008-03-01

267

(2E)-2-Benzyl­idene-4-ethyl-3,4-dihydro­naphthalen-1(2H)-one  

OpenAIRE

In the title compound, C19H18O, the exocyclic C=C double bond has an E configuration. The ethyl substituent on the cyclo­hexa­none ring is in an axial position. The cyclo­hexa­none ring adopts a half-chair conformation, presumably due to conjugation in the benzene ring.

Akhazzane, Mohamed; Zouihri, Hafid; Bennani, A. Kella; Kerbal, Abdelali; Al Houari, Ghali

2011-01-01

268

Ethyl 4,4''-Dibromo-5'-(butylamino-2',6'-dinitro-[1,1':3',1''-terphenyl]-4'-carboxylate  

Directory of Open Access Journals (Sweden)

Full Text Available Ethyl 4,4''-Dibromo-5'-(butylamino-2',6'-dinitro-[1,1':3',1''-terphenyl]-4'-carboxylate (2 which is a m-terphenyl derivative containing an hexasubstituted, highly functionalized substituted benzene core, has been synthesized.

Damiano Rocchi

2015-03-01

269

BENZENE OXIDE PROTEIN ADDUCTS AS BIOMARKERS OF BENZENE EXPOSURE  

Science.gov (United States)

Benzene is known to be hematotoxic and carcinogenic in animals and humans. While metabolism is required for toxicity, the identity of the ultimate carcinogen(s) remains unknown. Benzene oxide (BO) is the first and most abundant of the metabolites, but very little is known about...

270

Hematotoxicity and carcinogenicity of benzene  

Energy Technology Data Exchange (ETDEWEB)

The hematotoxicity of benzene exposure has been well known for a century. Benzene causes leukocytopenia, thrombocytopenia, pancytopenia, etc. The clinical and hematologic picture of aplastic anemia resulting from benzene exposure is not different from classical aplastic anemia; in some cases, mild bilirubinemia, changes in osmotic fragility, increase in lactic dehydrogenase and fecal urobilinogen, and occasionally some neurological abnormalities are found. Electromicroscopic findings in some cases of aplastic anemia with benzene exposure were similar to those observed by light microscopy. Benzene hepatitis-aplastic anemia syndrome was observed in a technician with benzene exposure. Ten months after occurrence of hepatitis B, a severe aplastic anemia developed. The first epidemiologic study proving the leukemogenicity of benzene was performed between 1967 and 1973 to 1974 among shoe workers in Istanbul. The incidence of leukemia was 13.59 per 100,000, which is a significant increase over that of leukemia in the general population. Following the prohibition and discontinuation of the use of benzene in Istanbul, there was a striking decrease in the number of leukemic shoe workers in Istanbul. In 23.7% of the series, consisting of 59 leukemic patients with benzene exposure, there was a preceding pancytopenic period. Furthermore, a familial connection was found in 10.2% of them. The 89.8% of the series showed the findings of acute leukemia. The possible factors that may determine the types of leukemia in benzene toxicity are discussed. The possible role of benzene exposure is presented in the development of malignant lymphoma, multiple myeloma, and lung cancer.

Aksoy, M. (Scientific and Technical Research Council of Turkey, Kocaeli (Turkey))

1989-07-01

271

Measurements of photo-oxidation products from the reaction of a series of alkyl-benzenes with hydroxyl radicals during EXACT using comprehensive gas chromatography  

OpenAIRE

Photo-oxidation products from the reaction of a series of alkyl-benzenes, (benzene, toluene, p-xylene and 1,3,5-trimethyl-benzene) with hydroxyl radicals in the presence of NOx have been investigated using comprehensive gas chromatography (GCxGC). A GCxGC system has been developed which utilises valve modulation and independent separations as a function of both volatility and polarity. A number of carbonyl-type compounds were identified during a series of reactions carried out at the Eu...

Hamilton, J. F.; Lewis, A. C.; Bloss, C.; Wagner, V.; Henderson, A. P.; Golding, B. T.; Wirtz, K.; Martin-reviejo, M.; Pilling, M. J.

2003-01-01

272

Methane from benzene in argon dielectric barrier discharge  

Energy Technology Data Exchange (ETDEWEB)

Highlights: ? Efficient on-line conversion of benzene to methane at room temperature. ? Absence of other H-atom donor suggests new type of chemistry. ? For parent loss > 90%, methane yield was ?40% of limit due to H-atom availability. ? Surface moisture contributed ·OH radical for trace phenolic products’ formation. ? This method may emerge as an exploitable tactic for pollutants’ usable alterations. -- Abstract: A first-time account of direct, on-line, instantaneous and efficient chemical conversion of gas phase benzene to methane in argon Dielectric Barrier Discharge (DBD) is presented. In the absence of another overt hydrogen-donating source, potency of analogous parents toward methane generation is found to follow the order: benzene > toluene > p-xylene. Simultaneous production of trace amounts of phenolic surface deposits suggest (a) prompt decomposition of the parent molecules, including a large fraction yielding atomic transients (H-atom), (b) continuous and appropriate recombination of such parts, and (c) trace moisture in parent contributing ·OH radicals and additional H-atoms, which suitably react with the unreacted fraction of the parent, and also other intermediates. Results highlight Ar DBD to be a simple and exploitable technology for transforming undesirable hazardous aromatics to usable/useful low molecular weight open-chain products following the principles of green chemistry and engineering.

Das, Tomi Nath, E-mail: tndas@barc.gov.in [Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Dey, G.R., E-mail: grdey@barc.gov.in [Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India)

2013-03-15

273

Methane from benzene in argon dielectric barrier discharge  

International Nuclear Information System (INIS)

Highlights: ? Efficient on-line conversion of benzene to methane at room temperature. ? Absence of other H-atom donor suggests new type of chemistry. ? For parent loss > 90%, methane yield was ?40% of limit due to H-atom availability. ? Surface moisture contributed ·OH radical for trace phenolic products’ formation. ? This method may emerge as an exploitable tactic for pollutants’ usable alterations. -- Abstract: A first-time account of direct, on-line, instantaneous and efficient chemical conversion of gas phase benzene to methane in argon Dielectric Barrier Discharge (DBD) is presented. In the absence of another overt hydrogen-donating source, potency of analogous parents toward methane generation is found to follow the order: benzene > toluene > p-xylene. Simultaneous production of trace amounts of phenolic surface deposits suggest (a) prompt decomposition of the parent molecules, including a large fraction yielding atomic transients (H-atom), (b) continuous and appropriate recombination of such parts, and (c) trace moisture in parent contributing ·OH radicals and additional H-atoms, which suitably react with the unreacted fraction of the parent, and also other intermediates. Results highlight Ar DBD to be a simple and exploitable technology for transforming undesirable hazardous aromatics to usable/useful low molecular weight open-chain products following the principles of green chemistry and engineering

274

DEVELOPMENT OF A MODEL OF TOLUENE BLOOD LEVEL FOLLOWING SUBCUTANEOUS INJECTION OF TOLUENE IN THE RAT  

Science.gov (United States)

A model of toluene level in blood following subcutaneous injection of toluene mixed with polyoxyethylated vegetable oil vehicle was developed. The purpose was to provide a means of predicting dose received, for subsequent toxicologic studies for any time and dose comuination. The...

275

Benzene Oxidation Coupled to Sulfate Reduction  

OpenAIRE

Highly reduced sediments from San Diego Bay, Calif., that were incubated under strictly anaerobic conditions metabolized benzene within 55 days when they were exposed initially to 1 (mu)M benzene. The rate of benzene metabolism increased as benzene was added back to the benzene-adapted sediments. When a [(sup14)C]benzene tracer was included with the benzene added to benzene-adapted sediments, 92% of the added radioactivity was recovered as (sup14)CO(inf2). Molybdate, an inhibitor of sulfate r...

Lovley, D. R.; Coates, J. D.; Woodward, J. C.; Phillips, E.

1995-01-01

276

Fuel Dependence of Benzene Pathways  

Energy Technology Data Exchange (ETDEWEB)

The relative importance of formation pathways for benzene, an important precursor to soot formation, was determined from the simulation of 22 premixed flames for a wide range of equivalence ratios (1.0 to 3.06), fuels (C{sub 1}-C{sub 12}), and pressures (20 to 760 torr). The maximum benzene concentrations in 15 out of these flames were well reproduced within 30% of the experimental data. Fuel structural properties were found to be critical for benzene production. Cyclohexanes and C{sub 3} and C{sub 4} fuels were found to be among the most productive in benzene formation; and long-chain normal paraffins produce the least amount of benzene. Other properties, such as equivalence ratio and combustion temperatures, were also found to be important in determining the amount of benzene produced in flames. Reaction pathways for benzene formation were examined critically in four premixed flames of structurally different fuels of acetylene, n-decane, butadiene, and cyclohexane. Reactions involving precursors, such as C{sub 3} and C{sub 4} species, were examined. Combination reactions of C{sub 3} species were identified to be the major benzene formation routes with the exception of the cyclohexane flame, in which benzene is formed exclusively from cascading fuel dehydrogenation via cyclohexene and cyclohexadiene intermediates. Acetylene addition makes a minor contribution to benzene formation, except in the butadiene flame where C{sub 4}H{sub 5} radicals are produced directly from the fuel, and in the n-decane flame where C{sub 4}H{sub 5} radicals are produced from large alkyl radical decomposition and H atom abstraction from the resulting large olefins.

Zhang, H; Eddings, E; Sarofim, A; Westbrook, C

2008-07-14

277

Toluene combustion: reaction paths, thermochemical properties, and kinetic analysis for the methylphenyl radical + O2 reaction.  

Science.gov (United States)

Aromatic compounds such as toluene and xylene are major components of many fuels. Accurate kinetic mechanisms for the combustion of toluene are, however, incomplete, as they do not accurately model experimental results such as strain rates and ignition times and consistently underpredict conversion. Current kinetic mechanisms for toluene combustion neglect the reactions of the methylphenyl radicals, and we believe that this is responsible, in part, for the shortcomings of these models. We also demonstrate how methylphenyl radical formation is important in the combustion and pyrolysis of other alkyl-substituted aromatic compounds such as xylene and trimethylbenzene. We have studied the oxidation reactions of the methylphenyl radicals with O2 using computational ab initio and density functional theory methods. A detailed reaction submechanism is presented for the 2-methylphenyl radical + O2 system, with 16 intermediates and products. For each species, enthalpies of formation are calculated using the computational methods G3 and G3B3, with isodesmic work reactions used to minimize computational errors. Transition states are calculated at the G3B3 level, yielding high-pressure limit elementary rate constants as a function of temperature. For the barrierless methylphenyl + O2 and methylphenoxy + O association reactions, rate constants are determined from variational transition state theory. Multichannel, multifrequency quantum Rice-Ramsperger-Kassel (qRRK) theory, with master equation analysis for falloff, provides rate constants as a function of temperature and pressure from 800 to 2400 K and 1 x 10(-4) to 1 x 10(3) atm. Analysis of our results shows that the dominant pathways for reaction of the three isomeric methylphenyl radicals is formation of methyloxepinoxy radicals and subsequent ring opening to methyl-dioxo-hexadienyl radicals. The next most important reaction pathway involves formation of methylphenoxy radicals + O in a chain branching process. At lower temperatures, the formation of stabilized methylphenylperoxy radicals becomes significant. A further important reaction channel is available only to the 2-methylphenyl isomer, where 6-methylene-2,4-cyclohexadiene-1-one (ortho-quinone methide, o-QM) is produced via an intramolecular hydrogen transfer from the methyl group to the peroxy radical in 2-methylphenylperoxy, with subsequent loss of OH. The decomposition of o-QM to benzene + CO reveals a potentially important new pathway for the conversion of toluene to benzene during combustion. A number of the important products of toluene combustion proposed in this study are known to be precursors of polyaromatic hydrocarbons that are involved in soot formation. Reactions leading to the important unsaturated oxygenated intermediates identified in this study, and the further reactions of these intermediates, are not included in current aromatic oxidation mechanisms. PMID:17696501

da Silva, Gabriel; Chen, Chiung-Chu; Bozzelli, Joseph W

2007-09-01

278

Ethyl 2,4-dimethylpyrido[1,2-a]benzimidazole-3-carboxylate  

Directory of Open Access Journals (Sweden)

Full Text Available The title compound, C16H16N2O2, was synthesized using a novel tandem annulation reaction between 1-(1H-benzo[d]imidazol-2-ylethanone and ethyl (E-4-bromobut-2-enoate under mild conditions. The dihedral angles formed by the mean plane of the five-membered imidazole ring with the dihydropyridin and benzene rings are 1.54?(9 and 1.85?(9°, respectively.

Ai Guo Zhu

2012-10-01

279

Ethyl 2-(3-ethylsulfinyl-5-methyl-1-benzofuran-2-yl)acetate  

OpenAIRE

The title compound, C15H18O4S, was prepared by the oxidation of ethyl 2-(3-ethylsulfanyl-5-methyl-1-benzofuran-2-yl)acetate with 3-chloroperoxybenzoic acid. The crystal structure is stabilized by aromatic ?–? interactions between the benzene rings of neighbouring molecules [centroid–centroid distance = 3.655?(3)?Å] and by three intermolecular C—H...O non-classical hydrogen bonds.

Hong Dae Choi; Pil Ja Seo; Byeng Wha Son; Uk Lee

2009-01-01

280

Molecular Structure of Ethyl maltol  

Science.gov (United States)

Ethyl maltol was discovered in the 1970s. It was originally isolated from larch tree bark and is produced through fermentation-organic synthesis. Ethyl maltol occurs naturally in cereal, bread crust, coffee, and cocoa. This substance is also used as a flavor enhancer because it tends to mask bad tasting chemicals, and heightens richness and creaminess. The compound has been employed as a flavor enhancer in wine, chocolate, vanilla, fruit flavored drinks, pastries, candy, tobacco, cosmetics, and medicines.

2002-10-11

281

Radioluminescence of solid ethyl acetate  

International Nuclear Information System (INIS)

In the crystalline environment the reaction of thermalized electrons with ethyl acetate molecules is less effective than in glassy environment. Therefore more excess electrons are observed in crystalline ethyl acetate by isothermal luminescence and radiothermoluminescence. In the glassy environment other trapped species, like radical-anions CH3COOC2H5- or radicals CH3COOCHCH3, become reactive at lower temperatures than in the crystalline environment because of glass transition. (author)

282

Menstrual function in workers exposed to toluene.  

OpenAIRE

Rates of menstrual disorders were studied in 231 female production workers with high exposure to toluene (mean 88 (range 50-150 ppm) in a factory manufacturing audio speakers and compared with a control group of 58 female production workers in other departments in the same factory who had little or no exposure to toluene (0-25 ppm). An external community control group of 187 working class women under routine care at public maternal and child health centres were also studied. Detailed menstrua...

Ng, T. P.; Foo, S. C.; Yoong, T.

1992-01-01

283

Collision lifetimes of polyatomic molecules at low temperatures: Benzene-benzene vs benzene-rare gas atom collisions  

Science.gov (United States)

We use classical trajectory calculations to study the effects of the interaction strength and the geometry of rigid polyatomic molecules on the formation of long-lived collision complexes at low collision energies. We first compare the results of the calculations for collisions of benzene molecules with rare gas atoms He, Ne, Ar, Kr, and Xe. The comparison illustrates that the mean lifetimes of the collision complexes increase monotonically with the strength of the atom-molecule interaction. We then compare the results of the atom-benzene calculations with those for benzene-benzene collisions. The comparison illustrates that the mean lifetimes of the benzene-benzene collision complexes are significantly reduced due to non-ergodic effects prohibiting the molecules from sampling the entire configuration space. We find that the thermally averaged lifetimes of the benzene-benzene collisions are much shorter than those for Xe with benzene and similar to those for Ne with benzene.

Cui, Jie; Li, Zhiying; Krems, Roman V.

2014-10-01

284

Collision lifetimes of polyatomic molecules at low temperatures: Benzene–benzene vs benzene–rare gas atom collisions  

International Nuclear Information System (INIS)

We use classical trajectory calculations to study the effects of the interaction strength and the geometry of rigid polyatomic molecules on the formation of long-lived collision complexes at low collision energies. We first compare the results of the calculations for collisions of benzene molecules with rare gas atoms He, Ne, Ar, Kr, and Xe. The comparison illustrates that the mean lifetimes of the collision complexes increase monotonically with the strength of the atom–molecule interaction. We then compare the results of the atom–benzene calculations with those for benzene–benzene collisions. The comparison illustrates that the mean lifetimes of the benzene–benzene collision complexes are significantly reduced due to non-ergodic effects prohibiting the molecules from sampling the entire configuration space. We find that the thermally averaged lifetimes of the benzene–benzene collisions are much shorter than those for Xe with benzene and similar to those for Ne with benzene

285

Collision lifetimes of polyatomic molecules at low temperatures: Benzene–benzene vs benzene–rare gas atom collisions  

Energy Technology Data Exchange (ETDEWEB)

We use classical trajectory calculations to study the effects of the interaction strength and the geometry of rigid polyatomic molecules on the formation of long-lived collision complexes at low collision energies. We first compare the results of the calculations for collisions of benzene molecules with rare gas atoms He, Ne, Ar, Kr, and Xe. The comparison illustrates that the mean lifetimes of the collision complexes increase monotonically with the strength of the atom–molecule interaction. We then compare the results of the atom–benzene calculations with those for benzene–benzene collisions. The comparison illustrates that the mean lifetimes of the benzene–benzene collision complexes are significantly reduced due to non-ergodic effects prohibiting the molecules from sampling the entire configuration space. We find that the thermally averaged lifetimes of the benzene–benzene collisions are much shorter than those for Xe with benzene and similar to those for Ne with benzene.

Cui, Jie; Krems, Roman V. [Department of Chemistry, University of British Columbia, Vancouver, British Columbia V6T 1Z1 (Canada); Li, Zhiying [Department of Physics, Harvard University, Cambridge, Massachusetts 02138 (United States)

2014-10-28

286

Activation volumes for the quenching of the first electronically excited singlet state of oxygen by toluene molecules in pure toluene and four different solvents  

Science.gov (United States)

Second-order rate constants kD, of the quenching of singlet oxygen in its a 1? g state by toluene molecules in bulk solvent and four different solvent environments have been determined with the pressure dependence up to 1200 bar, using time-resolved phosphorescence. Experimental activation volumes ?V ‡exp were analysed taking into account contact complex formation as the initial step. The reaction volume of the formation of the contact complex ? VC was evaluated using the hard-sphere model of Yoshimura and Nakahara. The data indicate that ? VC is the main part of ?V ‡exp. A correlation was found between the kD values at 1 bar and the radial distribution function, as expected of the theory of Einwohner and Alder. The quenching rate constants for benzene and cyclohexane at normal pressure are in agreement with this correlation.

Hild, Markus; Brauer, Hans-Dieter

1998-01-01

287

Toluene exposure increases aminophylline-induced seizure susceptibility in mice  

International Nuclear Information System (INIS)

The effects of toluene on the sensitivity to seizures induced by aminophylline were investigated. Mice were pretreated with an ip injection of corn oil or toluene (100-500 mg/kg) followed by a timed intravenous infusion of aminophylline at various time intervals to assess the seizure thresholds and lethal doses. Toluene increased seizure susceptibility to aminophylline in a dose- and time-dependent manner. Toluene-induced enhancement of seizure susceptibility to aminophylline occurred as early as 30 min and persisted for at least 3 days after a single administration of toluene (500 mg/kg). Treatment of benzaldehyde, one of toluene's metabolites, also showed an increase in the susceptibility to aminophylline. The enhancing effect was also observed in caffeine-induced seizures 1 h, but not 1 day after toluene treatment. These results suggest that individuals with toluene exposure may increase the risk for convulsive and even lethal complications associated with the therapeutic use of aminophylline

288

Performance of rare earth modified faujasites in the process of toluene disproportionation  

International Nuclear Information System (INIS)

The purpose of the present paper is the study of the performances of some catalysts based on y-type faujasite exchanged with La (3+) and Ce (3+) cations in the process of toluene disproportionation to benzene and xylenes. In the first stage the crystallographic study by the X-rays diffraction method shows that the cation exchange causes 311 plane displacements in the zeolite structure, accompanied by a decrease of diffraction limit intensity. Further the faujasite pretreatment with NH4 (4+) ions plays some role in the protection of the crystallinity. Moreover the cation exchange seems to take an optimum value around 73% for which the toluene conversion is maximum. This phenomenon is probably due to a decrease of the internal free volume for a pronounced cation exchange. The best performances are obtained by the zeolite that has undergone a slow and programmed thermal activation after cation exchange. This is probably due to the slowness of ion rearrangement phenomena, and of the catalytic surface restructuration. In the second stage the realization of toluene disproportionation process shows that the cation exchange with such elements confers to the faujasite an appreciable catalytic activity in the temperature range of 350-500 degC. The catalysts obtained permit about 20-60% toluene conversions. The catalytic activity is slightly higher in La-modified samples, whereas those containing Ce (3+) present relatively a better selectivity to the main process. Nevertheless, both types of catalysts show approximately a similar behaviour, favourizing the p-xylene formation. The proportion of the latter exceeds that of thermodynamic equilibrium at temperatures less than 430 degC. The temperature increase affects this selectivity. This is probably due to dehydration phenomenon which are frequent around this value

289

Intrinsic bioremediability of an aromatic hydrocarbon-polluted groundwater: diversity of bacterial population and toluene monoxygenase genes  

Energy Technology Data Exchange (ETDEWEB)

The functional and phylogenetic biodiversity of bacterial communities in a benzene, toluene, ethylbenzene and xylene (BTEX)-polluted groundwater was analysed. To evaluate the feasibility of using an air sparging treatment to enhance bacterial degradative capabilities, the presence of degrading microorganisms was monitored. The amplification of gene fragments corresponding to toluene monooxygenase (tmo), catechol 1,2-dioxygenase, catechol 2,3-dioxygenase and toluene dioxygenase genes in DNA extracted directly from the groundwater samples was associated with the presence of indigenous degrading bacteria. Five months of air injection reduced species diversity in the cultivable community (as calculated by the Shannon-Weaver index), while little change was noted in the degree of biodiversity in the total bacterial community, as characterised by denaturing gradient gel electrophoresis (DGGE) analysis. BTEX-degrading strains belonged to the genera Pseudomonas, Microbacterium, Azoarcus, Mycobacterium and Bradyrhizobium. The degrading capacities of three strains in batch liquid cultures were also studied. In some of these microorganisms different pathways for toluene degradation seemed to operate simultaneously. Pseudomonas strains of the P24 operational taxonomic unit, able to grow only on catechol and not on BTEX, were the most abundant, and were present in the groundwater community at all stages of treatment, as evidenced both by cultivation approaches and by DGGE profiles. The presence of different tmo-like genes in phylogenetically distant strains of Pseudomonas, Mycobacterium and Bradyrhizobium suggested recent horizontal gene transfer in the groundwater. (orig.)

Cavalca, L.; Dell' Amico, E.; Andreoni, V. [Dipt. di Scienze e Tecnologie Alimentari e Microbiologiche, Univ. degli Studi di Milano, Milan (Italy)

2004-07-01

290

Benzodiazepine-like discriminative stimulus effects of toluene vapor  

OpenAIRE

In vitro studies show that the abused inhalant toluene affects a number of ligand-gated ion channels. The two most consistently implicated of these are ?-aminobutyric acid type A (GABAA) receptors which are positively modulated by toluene and N-methyl-D-aspartate (NMDA) receptors which are negatively modulated by toluene. Behavioral studies also suggest an interaction of toluene with GABAA and/or NMDA receptors but it is unclear if these receptors underlie the abuse-related intoxicating effe...

Shelton, Keith L.; Nicholson, Katherine L.

2013-01-01

291

Toluene monooxygenase-catalyzed epoxidation of alkenes.  

Science.gov (United States)

Several toluene monooxygenase-producing organisms were tested for their ability to oxidize linear alkenes and chloroalkenes three to eight carbons long. Each of the wild-type organisms degraded all of the alkenes that were tested. Epoxides were produced during the oxidation of butene, butadiene, and pentene but not hexene or octadiene. A strain of Escherichia coli expressing the cloned toluene-4-monooxygenase (T4MO) of Pseudomonas mendocina KR1 was able to oxidize butene, butadiene, pentene, and hexene but not octadiene, producing epoxides from all of the substrates that were oxidized. A T4MO-deficient variant of P. mendocina KR1 oxidized alkenes that were five to eight carbons long, but no epoxides were detected, suggesting the presence of multiple alkene-degrading enzymes in this organism. The alkene oxidation rates varied widely (ranging from 0. 01 to 0.33 micromol of substrate/min/mg of cell protein) and were specific for each organism-substrate pair. The enantiomeric purity of the epoxide products also varied widely, ranging from 54 to >90% of a single epoxide enantiomer. In the absence of more preferred substrates, such as toluene or alkenes, the epoxides underwent further toluene monooxygenase-catalyzed transformations, forming products that were not identified. PMID:10788354

McClay, K; Fox, B G; Steffan, R J

2000-05-01

292

The Impact of Candle Burning During All Saints’ Day Ceremonies on Ambient Alkyl-Substituted Benzene Concentrations  

OpenAIRE

Research findings concerning benzene, toluene, ethylobenzene, meta-, para- and ortho-xylene as well as styrene (BTEXS) emission at public cemeteries during All Saints’ Day are presented here. Tests were carried out at town-located cemeteries in Opole and Grodków (southern Poland) and, as a benchmark, at the centres of those same towns. The purpose of the study was to estimate BTEXS emissions caused by the candle burning and, equally important to examine, whether emissions generated by the ...

Olszowski, Tomasz; K?os, Andrzej

2013-01-01

293

Substituent effect in benzene dication  

OpenAIRE

2 Abstract It was r ecently postulated that the benzene ring and its 4n+2 ? - electron analogues are resistant to the substituent effect due to the fact that such systems tend to keep its delocalized character. Therefore, the 4n ? - electron dicationic form of benzene should appear to be less resistant to the substituent effect, as compar ed with its parent neutral molecule. For this reason the effect of substi...

Palusiak, Marcin; Domaga?a, Ma?gorzata; Dominikowska, Justyna; Bickelhaupt, F. Matthias

2014-01-01

294

Law and regulation of benzene.  

OpenAIRE

OSHA has created final benzene regulations after extensive rulemakings on two occasions, 1978 and 1987. These standards have been the subject of extensive litigation for nearly 20 years. This article examines in detail the conceptual underpinnings of the Benzene Case, (which was decided by the U.S. Supreme Court in 1980) in light of U.S. administrative law precedents that have set limits upon administrative discretion under the test for "substantial evidence" and the "hard look doctrine." Thi...

Feitshans, I. L.

1989-01-01

295

Major sources of benzene exposure.  

OpenAIRE

Data from EPA's TEAM Study allow us to identify the major sources of exposure to benzene for much of the U.S. population. These sources turn out to be quite different from what had previously been considered the important sources. The most important source of exposure for 50 million smokers is the mainstream smoke from their cigarettes, which accounts for about half of the total population burden of exposure to benzene. Another 20% of nationwide exposure is contributed by various personal act...

Wallace, L. A.

1989-01-01

296

Effects of Benzene on human hematopoiesis  

OpenAIRE

Benzene, an aromatic hydrocarbon that is a natural component of crude oil and natural gas, is toxic to the blood and blood-forming organs. Epidemiological studies have established an association between benzene exposure and acute myeloid leukemia, and increasing evidence also indicates a possible association between benzene and multiple myeloma. A specific benzene-associated myelodysplastic syndrome has also been suggested. Chronic hematotoxic effects of benzene exposure, includin...

Kirkeleit, Jorunn; Riise, Trond; Gjertsen, Bjørn Tore; Moen, Bente E.; Bra?tveit, Magne; Bruserud, Øystein

2008-01-01

297

Mixed aggregates of an alkyl lithium reagent and a chiral lithium amide derived from N-ethyl-O-triisopropylsilyl valinol.  

Science.gov (United States)

The crystal structure of a mixed aggregate containing lithiated (S)-N-ethyl-3-methyl-1-(triisopropylsilyloxy)butan-2-amine derived from (S)-valinol and cyclopentyllithium is determined by X-ray diffraction. The mixed aggregate adopts a ladder structure in the solid state. The ladder-type mixed aggregate is also the major species in a toluene-d8 solution containing an approximately 1:1 molar ratio of the lithiated chiral amide to cyclopentyllithium. A variety of NMR experiments including diffusion-ordered NMR spectroscopy (DOSY) with diffusion coefficient-formula (D-FW) weight correlation analyses and other one- and two-dimensional NMR techniques allowed us to characterize the complex in solution. Solution state structures of the mixed aggregates of n-butyl, sec-butyllithium, isopropyllithium with lithiated (S)-N-ethyl-3-methyl-1-(triisopropylsilyloxy)butan-2-amine are also reported. Identical dimeric, ladder-type, mixed aggregates are the major species at a stoichiometric ratio of 1:1 lithium chiral amide to alkyllithium in toluene-d8 solution for all of the different alkyllithium reagents. PMID:23980610

Su, Chicheung; Hopson, Russell; Williard, Paul G

2013-09-25

298

Benzene emitted from glowing charcoal  

Energy Technology Data Exchange (ETDEWEB)

Benzene was assessed as the predominant aromatic compound emitted from glowing charcoal and firewood embers. Concentrations measured above charcoal used for grilling exceeded 10 mg m{sup -3} at a 5% carbon dioxide level. Charcoal with a high carbon content released less benzene. Glowing wood pellets emitted less benzene than glowing firewood remainders. The emissions of ethene and propene relative to benzene were low for commercial charcoal and wood-pellet embers, but high for firewood ember. The proportions of methylbenzene and naphthalene from charcoal were typically only 10% relative to benzene, and those of benzofuran, dibenzofuran and benzonitrile were typically below 5%. The polycyclic aromatic hydrocarbon (PAH) indicator phenanthrene was below the 1% level. Adsorbent sampling and GC-MS were used for assessing all the aromatic compounds. Earlier studies of charcoal emissions have focused on carbon monoxide, PAH and dioxins. It is concluded that the carcinogenic benzene may be an even more severe health hazard to be addressed by exposure-decreasing measures.

Olsson, Maria; Petersson, Goran [Department of Chemical Environmental Science, Chalmers University of Technology, SE-412 96 Goteborg (Sweden)

2003-03-01

299

Benzene emitted from glowing charcoal.  

Science.gov (United States)

Benzene was assessed as the predominant aromatic compound emitted from glowing charcoal and firewood embers. Concentrations measured above charcoal used for grilling exceeded 10 mg m(-3) at a 5% carbon dioxide level. Charcoal with a high carbon content released less benzene. Glowing wood pellets emitted less benzene than glowing firewood remainders. The emissions of ethene and propene relative to benzene were low for commercial charcoal and wood-pellet embers, but high for firewood ember. The proportions of methylbenzene and naphthalene from charcoal were typically only 10% relative to benzene, and those of benzofuran, dibenzofuran and benzonitrile were typically below 5%. The polycyclic aromatic hydrocarbon (PAH) indicator phenanthrene was below the 1% level. Adsorbent sampling and GC-MS were used for assessing all the aromatic compounds. Earlier studies of charcoal emissions have focused on carbon monoxide, PAH and dioxins. It is concluded that the carcinogenic benzene may be an even more severe health hazard to be addressed by exposure-decreasing measures. PMID:12606161

Olsson, Maria; Petersson, Göran

2003-03-01

300

Vibrational energy flow in substituted benzenes  

Science.gov (United States)

Using ultrafast infrared (IR) Raman spectroscopy, vibrational energy flow was monitored in several liquid-state substituted benzenes at ambient temperature. In a series of mono-halogenated benzenes, X-C6H 5 (X = F, Cl, Br, I), a similar CH-stretch at 3068 cm-1 was excited using picosecond IR pulses and the resulting vibrational relaxation and overall vibrational cooling processes were monitored with anti-Stokes spectroscopy. In the molecules with a heavier halide substituent the CH-stretch decayed slower while midrange vibrations decayed faster. This result was logical if the density of states (DOS) in the first few tiers, which is the DOS composed of vibrations with smaller quantum number, is what primarily determines energy flow. For tiers 1-4, the DOS was nearly identical in the CH-stretch region while it increased in the midrange region for heavier halide mass. Excitation spectroscopy, an extension of 3D IR-Raman spectroscopy, was developed and used to selectively pump vibrations localized to the substituent or the phenyl group in nitrobenzene (NB), o-fluoronitrobenzene (OFNB) and o-nitrotoluene (ONT) and in the alkylbenzene series toluene, isopropylbenzene (IPB), and t-butylbenzene (TBB). Using quantum chemical calculations, each Raman active vibration was sorted, according to their atomic displacements, into three classifications: substituent, phenyl, or global. Using IR pump wavenumbers that initially excited substituent or phenyl vibrations, IR-Raman spectroscopy was used to monitor energy flowing from the substituent to phenyl vibrations and vice versa. In NB nitro-to-phenyl and nitro-to-global energy flow was almost nonexistent while phenyl-to-nitro and phenyl-to-global was weak. When ortho substituents (-CH3, -F) were introduced, energy flow from nitro-to-phenyl and nitro-to-global was activated. In ONT, phenyl-to-nitro energy flow ceased possibly due to the added methyl group diverting energy from entering the nitro vibrations. Energy flow is therefore unidirectional in the phenyl-to-nitro direction in NB while in ONT it is unidirectional in the nitro-to-phenyl direction. In the alkylbenzenes phenyl-to-substituent energy flow was about the same in each while substituent-to-phenyl energy was accelerated for larger alkyl substituents. If the DOS controls energy flow this is opposite of what would be expected and gives a possible route to control energy flow from an attached alkyl substituent to a phenyl group.

Pein, Brandt C.

301

Modelling and Simulation Of Benzene Alkylation Process Reactors For Production Of Ethylbenzene  

Directory of Open Access Journals (Sweden)

Full Text Available The goal of this paper is to develop a simulation software for the ethyl benzene production unit in aPetrochemical Complex of Iran. Ethyl benzene whose consumption has rapidly increased in recent years, isthe feed for production of styrene monomer. This material is produced from alkylation of benzene withethylene. A process simulator can play a very important role in the development of this process. In thisresearch, alkylation of benzene for production of ethylbenzene has been simulated. First the mass, energyand momentum balance equations have been developed for the axial flow reactor. Optimization techniqueshave then been applied to modify the kinetic equations presented in literature to somehow satisfy the unitconditions. Finally the model predicted values such as pressure, reactor temperature, reactant conversionand products compositions have been compared with those of experimental ones adopted from theindustrial unit. The comparison reveals that the model predicted values are adequately in compliance withthe experimental data and hence can be used, with sufficient accuracy, to design pilot plants and other newunits.

Majid Kakavand

2004-10-01

302

Pallidol hexaacetate ethyl acetate monosolvate  

OpenAIRE

The entire molecule of pallidol hexaacetate {systematic name: (±)-(4bR,5R,9bR,10R)-5,10-bis[4-(acetyloxy)phenyl]-4b,5,9b,10-tetrahydroindeno[2,1-a]indene-1,3,6,8-tetrayl tetraacetate} is completed by the application of twofold rotational symmetry in the title ethyl acetate solvate, C40H34O12·C4H8O2. The ethyl acetate molecule was highly disordered and was treated with the SQUEEZE routine [Spek (2009). Acta Cryst. D65, 148–155]; the crystallographic data take into account the p...

Qinyong Mao; Taylor, Dennis K.; Seik Weng Ng; Tiekink, Edward R. T.

2013-01-01

303

FIELD COMPARISON OF TWO KINDS OF CHARCOAL TUBES FOR SAMPLING AROMATIC HYDROCARBONS (TOLUENE & XYLENE IN A PAINT FACTORY  

Directory of Open Access Journals (Sweden)

Full Text Available In order to evaluate the effectiveness of the Iranian made charcoal tubes in the field , 60 local made and 60 imported ones (SKC type were randomly selected and placed side by side for sampling aromatic hydrocarbons (including Benzene, Toluene, Xylene in workers breathing zone in a paint factory. The results indicated that there were no statistically significant differences between the mean concentrations of aromatic hydrocarbons measured in studied groups. The ratios of pressure drop to flow rate of Iranian made tubes were statistically higher than the SKC ones (P<0.0l.

P .Nassiri; F. Golbabai; A. Barzegar

1996-08-01

304

Session 4: Study of alkyl-aromatics hydrodealkylation reaction to orient the production of benzene from the catalytic reforming process  

Energy Technology Data Exchange (ETDEWEB)

Due to more stringent environmental constraints, the benzene content in the gasoline decreases regularly and has been fixed to 1% since January 2001. In the same time, the demand in aromatics, benzene, toluene, and xylenes, for the petrochemistry continuously increases. The aim of this work is to study the hydrodealkylation reactions and particularly the benzene formation under reforming operating conditions, with the bifunctional industrial catalyst. It is, therefore, of great importance to determine the role of each function of the catalyst involved in the benzene production in order to orient the reaction by modification of the catalyst. n-propylbenzene transformation was investigated on each family of model catalysts and allowed us to propose a detailed scheme for the reaction on acidic and metallic sites. The identified reactions are: - on metallic sites: dehydrogenation, cyclisation and hydrogenolysis A detailed reaction scheme for this transformation has already been proposed involving the formation of cyclisation products and the existence of a common reactive adsorbate for the indene compounds and ethylbenzene; - on acidic sites: dehydrogenation, isomerization and cracking. The study of the cracking reactions coupled with measurements of the acidity of the catalyst, shows that benzene is the preferentially formed cracking product, on the Broensted sites of the catalyst, through a carbo-cationic mechanism. Conversely, ethylbenzene and toluene are formed through a 'radical' mechanism over the Lewis acid sites of alumina. As far as the cracking reaction leading to benzene is concerned, two compulsory steps were pointed out: the first one is the isomerization of n-propylbenzene to iso-propylbenzene, and the second one is the cracking of iso-propylbenzene into benzene. The increase of strong Broensted acidity over model acidic catalysts, has been correlated with a strong increase of the benzene formation rate, emphasizing the role of strong Broensted sites in the formation of benzene. With the bifunctional Pt-Al{sub 2}O{sub 3}-Cl catalysts, an increase of the acidity is also correlated to a strong increase of the benzene formation rate, while ethylbenzene and toluene formation rates are not affected. The introduction of Sn in this previous catalyst leads from one hand, to a decrease of the global activity and, to the other hand, when Sn content is higher than 0,1 wt% to a decrease of the formation of benzene. This latter decrease could be attributed to a modification of the Broensted acid sites through the Sn atoms interacting with the support. The studies performed on model monofunctional and bifunctional catalysts allowed us to conclude that on bifunctional catalysts, toluene and ethylbenzene are formed on metallic sites by hydrogenolysis while benzene comes from the cracking of n-propylbenzene through isopropylbenzene formation on strong Broensted acid sites. From these studies new ways for reforming catalysts preparation could be considered to limit the benzene content in the reformate and particularly, the limitation as far as possible, of the chlorine content, and may be the use of more adequate tin precursor. (authors)

Toppi, S.; Thomas, C.; Sayag, C.; Brodzki, D.; Djega-Mariadassou, G. [Universite Pierre et Marie Curie, Lab. de Reactivite de Surface, UMR CNRS 7609, 75 - Paris (France); Toppi, S.; Travers, C.; Le Peltier, F. [Institut Francais du Petrole (IFP), 92 - Rueil-Malmaison (France)

2004-07-01

305

27 CFR 21.108 - Ethyl ether.  

Science.gov (United States)

...Firearms 1 2010-04-01 2010-04-01 false Ethyl ether. 21.108 Section 21.108 Alcohol, Tobacco Products...AND RUM Specifications for Denaturants § 21.108 Ethyl ether. (a) Odor. Characteristic odor. (b) Specific...

2010-04-01

306

Role of toluene in hydrogen sulfide combustion under Claus condition  

International Nuclear Information System (INIS)

Highlights: • Examined the role of toluene addition in hydrogen sulfide combustion. • Effect of 0%, 0.5%, 1% and 5% of toluene in H2S gas stream was examined. • Toluene addition triggers production of H2 which provides oxidation competition to H2S. • Increased amount of toluene in H2S gas reduced SO2 and increased asymptotic value of H2S. • Toluene addition enhanced the formation of CO and COS. - Abstract: Experimental investigations on the effect of different amounts of toluene addition to H2S combustion in oxygen under Claus condition (? = 3) are presented. Three toluene concentrations of 0.5%, 1% and 5% in H2S are presented and compared with the baseline case of 100% H2S oxygen combustion. Temperature data showed that addition of toluene to H2S gas stream increases the flame temperature because of large heating value associated with toluene. Addition of toluene resulted in the production of H2, which increased with increase in the amounts of toluene addition. Furthermore, increased addition of toluene concentration increased the asymptotic minimum value of hydrogen sulfide due to oxidation competition between the formed H2 and H2S. The results also showed that the presence of CO triggers the formation of COS with toluene addition due to reaction of CO with SO2. The results showed that SO2 mole fraction increased to a maximum value then decayed with distance along the reactor. Addition of toluene increased the rate of SO2 decay. These results have direct impact on sulfur capture in the Claus reactor and its performance

307

Radiolysis of ferric hexafluoroacetoacetylacetonate-toluene solutions  

International Nuclear Information System (INIS)

Ferric hexafluoroacetylacetonate was used to determine the yield of radicals captured in the gamma radiolysis of air-free toluene at 27 deg C. The G value for disappearance of the ferric chelate by radical capture and for the resulting formation of inert ferrous hexafluoroacetylacetonate is 1.05 molecules/eV. The chelates were determined spectrophotimetrically. No hexafluoroacetylacetone was formed. Radicals that are scavenged are the methyl radical and an unknown radical which is capable of combining with the benzyl radical. The effect of ferric chelate is therefore actually to increase the yield of bibenzyl. Activation energies are calculated. Experiments on flash photolysis indicated that the ferric chelate does not react with excited toluene molecules. (N.D.H.)

308

Developmental toxicity of prenatal exposure to toluene  

OpenAIRE

Organic solvents have become ubiquitous in our environment and are essential for industry. Many women of reproductive age are incresingly exposed to solvents such as toluene in occupational settings (ie, long-term, lowconcentration exposures) or through inhalant abuse (eg, episodic, binge exposures to high concentrations). The risk for teratogenic outcome is much less with low to moderate occupational solvent exposure compared with the greater potential for adverse pregnancy outcomes, develop...

Bowen, Scott E.; Hannigan, John H.

2006-01-01

309

ASSESSMENT OF HUMAN EXPOSURE TO TOLUENE DIISOCYANATE  

Directory of Open Access Journals (Sweden)

Full Text Available Assessment of human exposure to toluene diisocyanate. Toluene diisocyanate (TDI, an aromatic compound, may be dangerous for human health. Diisocyanates have wide industrial use in the fabrication of flexible and rigid foams, fibers, elastomers, and coatings such as paints and varnishes. Isocyanates are known skin and respiratory sensitizers, and proper engineering controls should be in place to prevent exposure to isocyanate liquid and vapor; exposure to TDI vapors is well documented to increase asthma risk. The study focused on the exposure of workers and nearby populations to toluene diisocyanate in a Polyurethane Foam Factory located in Baia Mare, Romania. Workplace air measurements were performed in different departments of the plant, after sampling either in fixed points or as personal monitoring. Sampling in four different locations of Baia Mare town was carried out, - during and after the foaming process. TDI sampling was performed on silica cartridge followed by GC-MS analysis. TDI concentration at workplace was lower than 0,035 mg/m³, which represents the permissible exposure limit, while in the city the TDI concentration had shown values below 0,20 ?g/m³. Health assessment of a group of 49 workers was based on questionnaire interview, determination of TDI antibodies and lung function tests. Data collected until this stage do not show any negative effects of TDI on the employees health. Since this plant had only recently begun operating, continuous workplace and ambient air TDI monitoring, along with workers health surveillance, is deemed necessary.

OLIVIA ANCA RUSU

2011-03-01

310

In vitro antiperoxidative, free radical scavenging and xanthine oxidase inhibitory potentials of ethyl acetate fraction of Saraca ashoka flowers.  

Science.gov (United States)

Saraca ashoka is a widely used medicinal herb claimed to cure many diseases. This study investigated the antiperoxidative, free radical scavenging and xanthine oxidase (XO) inhibitory potential of the ethyl acetate fraction of S. ashoka flowers (SAF) and compared it with standard compounds like gallic acid, ascorbic acid, butylated hydroxyl toluene and allopurinol. The ethyl acetate fraction of SAF exhibited free radical scavenging activity against the 1,1-diphenyl-2-picrylhydrazyl radical and superoxide radical, along with hydroxyl radical scavenging activity. Lipid peroxidation inhibitory potential of SAF was studied using a linoleic acid emulsion system, which shows significant antioxidant potential. SAF also demonstrated significant XO (key enzyme linked to inflammation) inhibitory activity, which revealed its therapeutic potential as an antioxidant and XO inhibitor. HPLC profiling of the ethyl acetate fraction of SAF revealed that it contains ellagic acid as a major compound and thus the beneficial effects of this fraction may be due to the presence of this compound. PMID:21294042

Prathapan, A; Lijo Cherian, O; Nampoothiri, Suresh V; Mini, S; Raghu, K G

2011-02-01

311

Trends in electron-ion dissociative recombination of benzene analogs with functional group substitutions: Negative Hammett ?para values  

Science.gov (United States)

An in-depth study of the effects of functional group substitution on benzene's electron-ion dissociative recombination (e-IDR) rate constant has been conducted. The e-IDR rate constants for benzene, biphenyl, toluene, ethylbenzene, anisole, phenol, and aniline have been measured using a Flowing Afterglow equipped with an electrostatic Langmuir probe (FALP). These measurements have been made over a series of temperatures from 300 to 550 K. A relationship between the Hammett ?para values for each compound and rate constant has indicated a trend in the e-IDR rate constants and possibly in their temperature dependence data. The Hammett ?para value is a method to describe the effect a functional group substituted to a benzene ring has upon the reaction rate constant.

Osborne, David; Lawson, Patrick Andrew; Adams, Nigel; Dotan, Itzhak

2014-06-01

312

ESTUDIO DEL EQUILIBRIO LÍQUIDO-LÍQUIDO DE BENCENO + (HEXANO, HEPTANO Y CICLOHEXANO) CON EL LÍQUIDO IÓNICO 1-ETIL-3-METILIMIDAZOLIO ETILSULFATO A 308,15 K / STUDY 0F LIQUID-LIQUID EQUILIBRIIM 0F BENZENE + (HEXAXE, HEPTME A\\D CYCLOHEXAXE) WITH THE IOMC LIQUID 1-ETHYL-3-METHYLIMIDAZ0LIIM ETHYLSULFATE AT 308.15 K / ESTUDO DO EQUILÍBRIO LÍQUIDO-LÍQUIDO DE BENZENO + (HEXANO, HEPTANO E CICLO-HEXANO) COM O LÍQUIDO IÔNICO 1-ETIL-3-METILIMIDAZOLIO ETILSULFATO A 308,15 K  

Scientific Electronic Library Online (English)

Full Text Available O equilíbrio líquido-líquido (ELL) de los sistemas ternários benzeno + (hexa-no, heptano e ciclo-hexano) com o líquido iônico 1-etil-3-metilimidazólio etilsulfato (EMIM-EtS0(4)) com 308,15 K, seletividade (S) e o coeficiente de distribuição (?) são calculados a partir dos dados experimentais. Ela de [...] termina a capacidade de líquido iônico como solvente para a separação de aromático a partir de suas misturas com hidrocar-bonetos alifáticos. A região de imiscibilidade aumentou na seguinte ordem: ciclo-hexano Abstract in spanish Se determinó el equilibrio líquido-líquido (ELL) de los sistemas ternarios benceno + (hexano, heptano y ciclohexano) con el líquido iónico 1-etil-3-metilimidazolio etilsulfato (EMIM-EtSO4) a 308,15 K; la selectividad (S) y el coeficiente de distribución (?) se calcularon desde los datos experimental [...] es que se utilizaron para determinar la capacidad del líquido iónico como solvente para la separación del aromático desde sus mezclas con hidrocarburos alifáticos. La región de inmiscibilidad aumentó en el siguiente orden: ciclohexano Abstract in english The equilibrium liquid-liquid (ELL) of ternary systems benzene + (hexane, heptane and cyclohexane) with the ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate (EMIM-EtS0(4)) at 308.15 K, selectivity (S) and the distribution coefficient (?) are calculated from experimental data. The ability of ion [...] ic liquid as solvent for separation of the aromatic from their mixtures with ali-phatic hydrocarbons is analyzed. The region of immiscibility increased in the following order: cyclohexane

Marlon, Martínez Reina; Eliseo, Amado González; Yonny Mauricio, Muñoz Muñoz.

2012-01-01

313

Decomposition of toluene in air mixtures under electron beam irradiation  

International Nuclear Information System (INIS)

The model gases of toluene-air mixtures were prepared by blowing technical air into liquid toluene and then irradiated with an ILU-6 accelerator located at the Institute of Nuclear Chemistry and Technology (INCT), Poland. It was found that the decomposition efficiency of toluene increases with absorbed dose and decreases with initial concentration of toluene. At 14.5 kGy dose, the decomposition efficiencies of toluene were 50, 37 and 34.5% for the initial concentrations of toluene 32.0, 63.4 and 78.0 ppm, respectively. At 58.0 kGy dose, the decomposition efficiencies of toluene were 93.8 and 78.1%, the initial concentrations of toluene being 32.0 and 63.4 ppm, respectively. Benzaldehyde was identified as one of the by-products of toluene decomposition in an air mixture. The decomposition efficiency and by-product formation under EB irradiation were compared between toluene and 4-chlorotoluene. (authors)

314

Benzodiazepine-like discriminative stimulus effects of toluene vapor.  

Science.gov (United States)

In vitro studies show that the abused inhalant toluene affects a number of ligand-gated ion channels.The two most consistently implicated of these are ?-aminobutyric acid type A(GABAA) receptors which are positively modulated by toluene and N-methyl-D-aspartate(NMDA) receptors which are negatively modulated by toluene. Behavioral studies also suggest an interaction of toluene with GABAA and/or NMDA receptors but it is unclear if these receptors underlie the abuse-related intoxicating effects of toluene. Seventeen B6SJLF1/J mice were trained using a two-choice operant drug discrimination procedure to discriminate 10 min of exposure to 2000 ppm toluene vapor from 10 min of exposure to air. The discrimination was acquired in a mean of 65 training sessions. The stimulus effects of 2000 ppm toluene vapor were exposure concentration-dependent but rapidly diminished following the cessation of vapor exposure. The stimulus effects of toluene generalized to the chlorinated hydrocarbon vapor perchloroethylene but not 1,1,2-trichloroethane nor the volatile anesthetic isoflurane. The competitive NMDA antagonist CGS-19755, the uncompetitive antagonist dizocilpine and the glycine-site antagonist L701,324 all failed to substitute for toluene. The classical nonselective benzodiazepines midazolam and chlordiazepoxide produced toluene-like stimulus effects but the alpha 1 subunit preferring positive GABAA modulator zaleplon failed to substitute for toluene. The barbiturates pentobarbital and methohexital and the GABAA positive modulator neurosteroid allopregnanolone did not substitute for toluene. These data suggest that the stimulus effects of toluene may be at least partially mediated by benzodiazepine-like positive allosteric modulation of GABAA receptors containing alpha 2, 3 or 5 subunits. PMID:24436974

Shelton, Keith L; Nicholson, Katherine L

2013-11-15

315

The Solubility of Phenylborate Compounds in Benzene  

International Nuclear Information System (INIS)

The original goal of this scoping study was to determine if the solubility of sodium and potassium tetraphenylborates in benzene was sufficiently large to justify designing and performing kinetic studies on a benzene-phase catalytic reaction

316

Uptake of benzene and alkylbenzenes by cation- and anion-exchange resins from aqueous solutions.  

Science.gov (United States)

Uptakes of benzene and 12 alkylbenzenes (from toluene to n-pentylbenzene including xylene and trimethylbenzene isomers) by both strong acid cation (Dowex 50W-X4 and X8) and strong base anion (Dowex 1-X4 and X8) exchange resins have been studied in aqueous solutions at 25 degrees C; their distribution constants (K) have been determined. The relationship between the octanol-water partition coefficient (K(ow)) and the resin affinity for solutes has been analyzed. The K values of benzene and alkylbenzenes were larger than the K values of aliphatic hydrocarbons expected from the K(ow) values. While the K value was increased with the alkyl chain length, no further increase in the K value was observed for n-butylbenzene and n-pentylbenzene. PMID:16772693

Sanemasa, Isao

2006-06-01

317

The preparation of alkyl benzene sulphonate, 14C-labelled in the benzene ring  

International Nuclear Information System (INIS)

The paper describes the preparation of sodium alkyl sulphonate 14C-labelled in the benzene ring. The composition of the resultant product largely corresponded to that of a technical alkyl benzene sulphonate. It was obtained by sulphonation of alkyl benzene which, in turn, had been made by reacting 14C-labelled benzene with a technical olefin fraction. (orig.)

318

Anaerobic Benzene Oxidation by Geobacter Species  

OpenAIRE

The abundance of Geobacter species in contaminated aquifers in which benzene is anaerobically degraded has led to the suggestion that some Geobacter species might be capable of anaerobic benzene degradation, but this has never been documented. A strain of Geobacter, designated strain Ben, was isolated from sediments from the Fe(III)-reducing zone of a petroleum-contaminated aquifer in which there was significant capacity for anaerobic benzene oxidation. Strain Ben grew in a medium with benzen...

Zhang, Tian; Bain, Timothy S.; Nevin, Kelly P.; Barlett, Melissa A.; Lovley, Derek R.

2012-01-01

319

Species differences in the metabolism of benzene.  

OpenAIRE

The pathways of metabolism of benzene appear to be qualitatively similar in all species studied thus far. However, there are quantitative differences in the fraction of benzene metabolized by the different pathways. These species differences become important for risk assessments based on animal data. Mice have a greater overall capacity to metabolize benzene than rats or primates, based on mass balance studies conducted in vivo using radiolabled benzene. Mice and monkeys metabolize more of th...

Henderson, R. F.

1996-01-01

320

ATMOSPHERIC BENZENE DEPLETION BY SOIL MICROORGANISMS  

Science.gov (United States)

Gaseous benzene was rapidly depleted in exposure chambers containing viable soils and plants. When separate components of the system were analyzed, no benzene was detected in soils, plants, or water. Soil microorganisms were shown to be responsible for metabolizing benzene, yield...

321

Role of delocalization in benzene  

Energy Technology Data Exchange (ETDEWEB)

The influence of [pi] delocalization on the geometry of benzene is examined at the ab initio SCF level of theory. We find that benzene favors a bond alternating geometry when its canonical [pi] MOs are replaced by three localized ethylenic orbitals, revealing that delocalization is in part responsible for the equilibrium symmetric structure. In apparent contrast, a [sigma]-[pi] energy partitioning analysis suggests that the benzene [sigma] framework is responsible for the symmetric structure, the [pi] system preferring a distorted geometry. Shaik et al. have therefore concluded that delocalization in not an important symmetrizing force in this molecule. We show, however, that the [pi] energy component contains a sizable and strongly geometry dependent contribution from the localized (Kekule) wave function. Thus, it appears to be misleading to judge the nature of delocalization based on a [sigma]-[pi] partition. We conclude that delocalization effects act to strongly stabilize symmetric benzene in essential accord with the concepts of classical resonance theory. 27 refs., 6 figs., 2 tabs.

Glendening, E.D.; Faust, R.; Streitwieser, A.; Vollhardt, K.P.C. (Univ. of California, Berkeley, CA (United States) Lawrence Berkeley Lab., CA (United States)); Weinbold, F. (Univ. of Wisconsin, Madison, WI (United States))

1993-11-17

322

Somatosensory evoked potentials in workers exposed to toluene and styrene.  

OpenAIRE

Somatosensory evoked potentials (SEPs) were used to evaluate possible subclinical impairment of the nervous system due to occupational exposure to toluene and styrene. A group of 36 rotogravure printers with severe exposure to toluene, 20 workers with severe exposure to styrene in a glass laminate manufacturing plant, and a comparison group of healthy subjects were studied. The severity of exposure was documented by measurements of toluene and styrene concentrations in breathing zone air, by ...

Ste?tka?rova?, I.; Urban, P.; Procha?zka, B.; Luka?s, E.

1993-01-01

323

Resonance enhanced Raman scatter in liquid benzene at vapor-phase absorption peaks.  

Science.gov (United States)

The resonance enhanced Raman spectra in the 1B2u mode of the forbidden benzene electronic transition band, ~230-270 nm, has been investigated. Resonance enhanced Raman scattering in both liquid benzene and liquid toluene exhibit the greatest enhancement when the wavelength of excitation is tuned to the vapor-phase absorption peaks; even though the sample volume is in a liquid state. Raman signals for the symmetric breathing mode of the carbon ring are found to be resonantly enhanced by several orders of magnitude (>500X) with deep UV excitation compared to non-resonant visible excitation. Since the benzene absorbs near this resonant wavelength, its effect on the sampled volume cannot be neglected in determining the resonance gain, as we discuss in detail. Large resonant gains correspond with excitation at the 247, 253, and 259 nm absorption peaks in the benzene vapor spectrum. The narrow region of resonance gain is investigated in detail around the absorption peak located at 259 nm using 0.25 nm steps in the excitation wavelength. We observe the resonance gain tracking the vapor phase absorption peaks and valleys within this narrow range. Results are interpreted in terms of the coherence forced by the use of a forbidden transition for resonance excitation. PMID:24216839

Willitsford, Adam; Chadwick, C Todd; Hallen, Hans; Kurtz, Stewart; Philbrick, C Russell

2013-11-01

324

Chloroform mineralization by toluene-oxidizing bacteria.  

OpenAIRE

Seven toluene-oxidizing bacterial strains (Pseudomonas mendocina KR1, Burkholderia cepacia G4, Pseudomonas putida F1, Pseudomonas pickettii PKO1, and Pseudomonas sp. strains ENVPC5, ENVBF1, and ENV113) were tested for their ability to degrade chloroform (CF). The greatest rate of CF oxidation was achieved with strain ENVBF1 (1.9 nmol/min/mg of cell protein). CF also was oxidized by P. mendocina KR1 (0.48 nmol/min/mg of cell protein), strain ENVPC5 (0.49 nmol/min/mg of cell protein), and Esche...

Mcclay, K.; Fox, B. G.; Steffan, R. J.

1996-01-01

325

Tricarbonylbis(tricyclohexylphosphine-?Pruthenium(0 toluene solvate  

Directory of Open Access Journals (Sweden)

Full Text Available The title compound, [Ru(C18H33P2(CO3]·C7H8, shows a distorted trigonal-bipyramdial coordination around the central Ru atom, with the two phosphine ligands occupying the axial positions. Two toluene molecules per asymmetric unit with site-occupation factors of 0.5 are observed. One of them forces two of the CO ligands to enclose a wider C—Ru—C bond angle [127.5?(3°] than in the solvent-free crystal structure of [Ru(PCy32(CO3] (Cy is cyclohexyl.

Andreas Nader

2008-11-01

326

Occupational exposure to benzene in China.  

OpenAIRE

Of a total of 528,729 workers exposed to benzene or benzene mixtures in China, 508,818 (96.23%) were examined. Altogether 2,676 cases of benzene poisoning were found, a prevalence of 0.15%. A higher prevalence of benzene poisoning was found in the cities of Hangjou, Hefei, Nanjing, Shenyang, and Xian. The geometric mean concentration of benzene in 50,255 workplaces was 18.1 mg/m3 but 64.6% of the workplaces had less than 40 mg/m3. There was a positive correlation between the prevalence of ben...

Yin, S. N.; Li, Q.; Liu, Y.; Tian, F.; Du, C.; Jin, C.

1987-01-01

327

Phenol and 2-naphthol production by toluene 4-monooxygenases using an aqueous/dioctyl phthalate system.  

Science.gov (United States)

A two-phase system is developed here for converting: (1) benzene to phenol and (2) naphthalene to 2-naphthol, using whole cells expressing wild-type toluene 4-monooxygenase (T4MO) and the alpha subunit variant TmoA I100A from Pseudomonas mendocina KR1. Using the T4MO TmoA I100A variant, the solubility of naphthalene was enhanced and the toxicity of the naphthols was prevented by the use of a water/dioctyl phthalate (80:20, vol%) system which yielded 21-fold more 2-naphthol. More than 99% 2-naphthol was extracted to the dioctyl phthalate phase, dihydroxynaphthalene formation was prevented, 92% 2-naphthol was formed, and 12% naphthalene was converted. Similarly, using 50 vol% dioctyl phthalate, an initial concentration of 3.0 g l(-1) (39 mM), and wild-type T4MO, a 51+/-9% conversion of benzene was obtained and phenol was produced at a purity of 97%. Relative to the one-phase system, there was a 12-fold reduction in the formation of the byproduct catechol. PMID:15742167

Tao, Ying; Bentley, William E; Wood, Thomas K

2005-09-01

328

Chemical Kinetic Characterization of Combustion Toluene  

Energy Technology Data Exchange (ETDEWEB)

A study is performed to elucidate the chemical kinetic mechanism of combustion of toluene. A detailed chemical kinetic mechanism for toluene was improved by adding a more accurate description of the phenyl + O{sub 2} reaction channels. Results of the chemical kinetic mechanism are compared with experimental data obtained from premixed and nonpremixed systems. Under premixed conditions, predicted ignition delay times are compared with new experimental data obtained in shock tube. Also, calculated species concentration histories are compared to experimental flow reactor data from the literature. Critical conditions of extinction and ignition were measured in strained laminar flows under nonpremixed conditions in the counterflow configuration. Numerical calculations are performed using the chemical kinetic mechanism at conditions corresponding to those in the experiments. Critical conditions of extinction and ignition are predicted and compared with the experimental data. For both premixed and nonpremixed systems, sensitivity analysis was used to identify the reaction rate constants that control the overall rate of oxidation in each of the systems considered.

Pitz, W J; Seiser, R; Bozzelli, J W; Da Costa, I; Fournet, R; Billaud, F; Battin-Leclerc, F; Seshadri, K; Westbrook, C K

2001-03-20

329

Chloroform mineralization by toluene-oxidizing bacteria.  

Science.gov (United States)

Seven toluene-oxidizing bacterial strains (Pseudomonas mendocina KR1, Burkholderia cepacia G4, Pseudomonas putida F1, Pseudomonas pickettii PKO1, and Pseudomonas sp. strains ENVPC5, ENVBF1, and ENV113) were tested for their ability to degrade chloroform (CF). The greatest rate of CF oxidation was achieved with strain ENVBF1 (1.9 nmol/min/mg of cell protein). CF also was oxidized by P. mendocina KR1 (0.48 nmol/min/mg of cell protein), strain ENVPC5 (0.49 nmol/min/mg of cell protein), and Escherichia coli DH510B(pRS202), which contained cloned toluene 4-monooxygenase genes from P. mendocina KR1 (0.16 nmol/min/mg of cell protein). Degradation of [14C]CF and ion analysis of culture extracts revealed that CF was mineralized to CO2 (approximately 30 to 57% of the total products), soluble metabolites (approximately 15%), a total carbon fraction irreversibly bound to particulate cellular constituents (approximately 30%), and chloride ions (approximately 75% of the expected yield). CF oxidation by each strain was inhibited in the presence of trichloroethylene, and acetylene significantly inhibited trichloroethylene oxidation by P. mendocina KR1. Differences in the abilities of the CF-oxidizing strains to degrade other halogenated compounds were also identified. CF was not degraded by B. cepacia G4, P. putida F1, P. pickettii PKO1, Pseudomonas sp. strain ENV113, or P. mendocina KRMT, which contains a tmo mutation. PMID:8702263

McClay, K; Fox, B G; Steffan, R J

1996-08-01

330

Molecular Structure of Ethyl acetate  

Science.gov (United States)

Ethyl acetate is a colorless, volatile liquid with a mild and fragrant odor. It is used as solvent in chemistry laboratories but can also be found in many household products such as paints, coatings, and adhesives. The compound is also used in some extraction processes such as decaffeination or purification of antibiotics. It is present in both nail polish and removers. Some synthetic fruit essences may contain this and other esters. Etymologists like to use this solvent for insect collecting as the vapor kill the insect quickly and keep it soft for mounting.

2006-03-08

331

Preparation of a new viscosity index improver based on a copolymer of vinyl 2-ethyl hexanoate  

Energy Technology Data Exchange (ETDEWEB)

Copolymers of different ratios of 2-ethyl hexyl acrylate with vinyl 2-ethyl hexanoate were prepared in benzene solution. The presence of the copolymers was confirmed by solubility, IR and NMR tests as well as by the analysis of the residues obtained by transesterification with sodium methoxide. The molecular weight and the polydispersity of the polymers were estimated by GPC. The polymers were evaluated and compared with currently used products as viscosity improvers in two ISO 20 base oils with different viscosity indices (VIs). Copolymers were fractioned in order to study the effect of the poly-dispersity. From viscosity, viscosity index, the ratio of the specific viscosity at 40{degrees}C and 100{degrees}C (Q value) and shear stability values, the polymers obtained could be used as a VI additive in ISO 20 base oils. 30 refs., 9 figs., 9 tabs.

Bataille, P. [Ecole Polytechnique, Montreal (Canada); Sharifi-Sanjani, N. [Univ. of Tehran (Iran, Islamic Republic of)

1995-12-01

332

Ethyl 1-(butan-2-yl-2-(2-methoxyphenyl-1H-benzimidazole-5-carboxylate  

Directory of Open Access Journals (Sweden)

Full Text Available In the title compound, C21H24N2O3, the mean planes of the benzene ring and the benzimidazole ring system form a dihedral angle of 69.94?(7°. The ethyl group atoms of the ethanoate fragment are disordered over two sets of sites, with refined occupancies of 0.742?(6 and 0.258?(6. In the crystal, there are weak C—H...N hydrogen bonds which connect molecules into chains along the b axis. A weak intermolecular C—H...? interaction is also observed.

Natarajan Arumugam

2011-12-01

333

N,N,N?,N?-Tetra­ethyl-N??-(2-fluoro­benzo­yl)phospho­ric triamide  

OpenAIRE

In the title compound, C15H25FN3O2P, the phosphoryl group is in an anti and syn orientation to the C=O and N—H groups, respectively. The P atom is in a distorted tetra­hedral environment. One of the ethyl groups is disordered over two sets of sites with refined occupancies of 0.755?(6) and 0.245?(6). In addition, the F atom was refined as disordered with occupancies fixed at 0.9 and 0.1. This disorder corresponds to a rotation of approximately 180° of the fluoro­benzene ring about it...

Tarahhomi, Atekeh; Pourayoubi, Mehrdad; Rheingold, Arnold L.; Golen, James A.

2011-01-01

334

Evaluation of the performance of a passive sampler in the monitoring of benzene and other volatile aromatic compounds in urban and indoor sites  

International Nuclear Information System (INIS)

Laboratory and field tests have been performed on a new passive device, properly designed for the collection of volatile organic compounds from ambient air on an active charcoal layer. Tests performed in order to determine accuracy and precision, response linearity and employment limits show that this device may be helpful in long and medium-time determinations of BTX (benzene, toluene and xylenes) in the atmosphere. The sampler is optimised for a four weeks sampling in open air

335

CARDIOVASCULAR AND THERMOREGULATORY RESPONSE TO ORAL TOLUENE IN THE RAT.  

Science.gov (United States)

Toluene and other volatile organic compounds have often been shown to affect behavior in animals when given by inhalation, and less effective when given orally. Previous work showed that toluene increased heart rate (HR) and motor activity (MA), and reduced core temperature (Tc) ...

336

Comparison of blood toluene levels after inhalation and oral administration  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this investigation was to compare blood toluene levels in Sprague-Dawley rats after oral and inhalation administration. Groups of 30 rats were dosed by gavage with 86.7, 217, 433, or 867 mg toluene/kg body wt or exposed for up to 6 hr, 5 rats per exposure, to an atmosphere of either 200 or 1000 ppm toluene. Blood was sampled by cardiac puncture from 5 rats in each of the six dose groups at 0.5, 1.0, 2.0, 4.0, 6.0, and 24.0 hr after gavage dosing or the beginning of the inhalation exposure. Blood toluene levels were analyzed. A four-parameter model was fitted to the blood toluene levels of the orally dosed rats. The area under the curve generated by this model, representing total blood toluene concentration over 6 hr, was calculated and compared to the area under the blood toluene curve for the 6-hr inhalation exposure. Integrated areas from the two routes of exposure were used for direct comparison of oral and inhalation exposures. The data demonstrate that gavage dosing can be used to approximate inhalation exposure to toluene.

Sullivan, M.J.; Conolly, R.B.

1988-02-01

337

Intermolecular interactions in solid benzene  

Science.gov (United States)

The lattice dynamics and molecular vibrations of benzene and deuterated benzene crystals are calculated from force constants derived from density-functional theory (DFT) calculations and compared with measured inelastic neutron-scattering spectra. A very small change (0.5%) in lattice parameter is required to obtain real lattice-mode frequencies across the Brillouin zone. There is a strong coupling between wagging and breathing modes away from the zone center. This coupling and sensitivity to cell size arises from two basic interactions. Firstly, comparatively strong interactions that hold the benzene molecules together in layers. These include an intermolecular interaction in which H atoms of one molecule link to the center of the aromatic ring of a neighboring molecule. The layers are held to each other by weaker interactions, which also have components that hold molecules together within a layer. Small changes in the lattice parameters change this second type of interaction and account for the changes to the lattice dynamics. The calculations also reveal a small auxetic effect in that elongation of the crystal along the b axis leads to an increase in internal pressure in the ac plane, that is, elongation in the b direction induces expansion in the a and c directions.

Kearley, G. J.; Johnson, M. R.; Tomkinson, J.

2006-01-01

338

Optical emission study of radio-frequency excited toluene plasma.  

Science.gov (United States)

UV-visible emission spectra of radio-frequency (rf) excited toluene plasma were studied. Benzyl radicals as well as toluene monomer and excimer were observed in toluene plasma. It was found that the intensities, peak positions, and linewidths of monomer and excimer emission bands exhibit strong dependence on rf power and plasma processing time. This can be ascribed to photochemical reactions in plasma. Gas-chromatographic analysis of the deposition products from toluene plasma indicated that the main component was bibenzyl. Spectroscopic evidence has shown that the bibenzyl molecule was formed by the coupling reaction between two benzyl radicals in plasma. The spectroscopic characteristics of toluene monomer and excimer are correlated with a kinetic model in plasma. PMID:19049320

Lee, Szetsen; Liu, Shiao-Jun; Liang, Rui-Ji

2008-12-25

339

AGONISTIC SENSORY EFFECTS OF AIRBORNE CHEMICALS IN MIXTURES: ODOR, NASAL PUNGENCY, AND EYE IRRITATION  

Science.gov (United States)

Threshold responses of odor, nasal pungency (irritation), and eye irritation were measured for single chemicals (1-propanol, 1-hexanol, ethyl acetate, heptyl acetate, 2-pentanone, 2-heptanone, toluene, ethyl benzene, and propyl benzene) and mixtures of them (two three-component m...

340

Epoxidation of cyclohexene by ethyl-benzene hydroperoxide in the presence of molybdenum catalyst  

International Nuclear Information System (INIS)

A study has been made of the kinetic experimental pattern and mechanism of epoxidation of cyclohexene by ethylbenzene hydroperoxide during catalysis by Mo(CO)6 in various solvents. A first order of reaction with respect to the catalyst and complex order of reaction with respect to the hydroperoxide and olefine have been established. Simple (square and cross) inhibition by reaction products, cyclohexene oxide and methylphenylcarbinol, have been found. An increase in the dielectric constant of the solvent diminishes the epoxidation rate. The mechanism scheme of the process is proposed and main kinetic parameters calculated

341

Epoxidation of cyclohexene by ethyl-benzene hydroperoxide in the presence of molybdenum catalyst  

International Nuclear Information System (INIS)

A study has been made of catalytic activity of molybdenum hexacarbonyl derivatives in the process of epoxidation of cyclohexene by ethylbenzene peroxide in an ethylbenzene solution. The effect of the degree of substitution of the CO group and nature of a non-carbonyl ligand has been investigated. The reaction has been found to have the first order with respect to the catalyst for all the carbonyl complexes studied. A new method has been proposed for preparation of the catalytic system active in epoxidation using ultraviolet irradiation of Mo(CO)6 solutions

342

Adsorption of toluene and toluene–water vapor mixture on almond shell based activated carbons  

OpenAIRE

The aim of work is to study the adsorption of a common volatile organic compound such as toluene using activated carbons prepared by chemical activation with phosphoric acid of a lignocellulosic precursor, almond shell, under different conditions. The Impregnation ratio, temperature and time of activation were modified to obtain activated carbons with different characteristics. Regarding the characteristics of the activated carbons, the effects of porous structure and surface chemistry on the...

Marti?nez Yuso, A.; Izquierdo Pantoja, Mari?a Teresa; Rubio Villa, Begon?a; Carrot, P. J. M.

2013-01-01

343

Unimolecular dissociation of doubly ionized toluene and electron transfer between neutral toluene and its dication.  

Czech Academy of Sciences Publication Activity Database

Ro?. 534, 1 May (2012), s. 8-12. ISSN 0009-2614 R&D Projects: GA ?R GA203/09/1223; GA ?R GAP208/11/0446 Institutional research plan: CEZ:AV0Z40550506; CEZ:AV0Z40400503 Keywords : dications * electron transfer * photoionization * toluene * synchrotron radiation Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.145, year: 2012

Shaffer, Christopher; Schröder, Detlef; Zins, E. L.; Alcaraz, Ch.; Žabka, Ján; Roithová, J.

2012-01-01

344

[Effect of thermal enhanced soil vapor extraction on benzene removal in different soil textures].  

Science.gov (United States)

Experiments were carried out to investigate the effect of thermal enhanced soil vapor extraction (SVE) on benzene removal from sand, loam and clay and the mechanism. Compared to the routine control treatment, the benzene removal rates were improved by 13. 1% and 12. 3% and the remediation periods were reduced by 75% and 14%, from sand and loam respectively using thermal enhanced SVE. Thermal enhancement decreased the moisture content and increased the soil permeability of clay. On the surface of clay particles, absorption peaks of carboxyl and ethyl disappeared and the content of soil organic substances decreased significantly. Compared to the conventional SVE, the benzene removal rate was improved by 34% in clay soil treated by thermal enhanced SVE. For sand and loam, thermal enhancement could increase the removal rate by promoting the diffusion of benzene in the soil and achieve substantial removal of pollutants in a relatively short period of time. For clay, it could enhance the effect of SVE by reducing the absorption capacity between soil particle surface and contaminant and improving the performance of the gas diffusion in soil by decreasing the moisture content and increasing the soil permeability. PMID:25693398

Li, Peng; Liao, Xiao-Yong; Yan, Xiu-Lan; Cui, Xiao-Yong; Ma, Dong

2014-10-01

345

Benzene and leukemia: an epidemiologic risk assessment.  

OpenAIRE

To assess quantitatively the association between benzene and leukemia, we evaluated the rate of mortality experienced by a cohort occupationally exposed to benzene. Using data from historical air sampling surveys, we estimated the daily benzene exposure for each member of the cohort. The expected number of leukemia deaths was calculated and compared to the actual number of leukemia deaths that occurred. The overall standardized mortality ratio (SMR) for leukemia was 337. Person-years at risk ...

Rinsky, R. A.

1989-01-01

346

Genetic susceptibility to benzene toxicity in humans.  

OpenAIRE

Human metabolism of benzene involves pathways coded for by polymorphic genes. To determine whether the genotype at these loci might influence susceptibility to the adverse effects of benzene exposure, 208 Bulgarian petrochemical workers and controls, whose exposure to benzene was determined by active personal sampling, were studied. The frequency of DNA single-strand breaks (DNA-SSB) was determined by alkaline elution, and genotype analysis was performed for five metabolic loci. Individuals c...

Garte, Seymour; Taioli, Emanuela; Popov, Todor; Bolognesi, Claudia; Farmer, Peter; Merlo, Franco

2008-01-01

347

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

Science.gov (United States)

...Carbonyl sulfide 100414 Ethyl benzene 107211 Ethylene glycol 75050 Acetaldehyde 50000 Formaldehyde 110543 n-Hexane 91203 Naphthalene 108883 Toluene 540841 2,2,4-Trimethylpentane 1330207 Xylenes (isomers and...

2010-07-01

348

40 CFR Appendix to Subpart Hh of... - Tables  

Science.gov (United States)

...disulfide 463581 Carbonyl sulfide 100414 Ethyl benzene 107211 Ethylene glycol 50000 Formaldehyde 110543 n-Hexane 91203 Naphthalene 108883 Toluene 540841 2,2,4-Trimethylpentane 1330207 Xylenes (isomers and...

2010-07-01

349

Acute cardiotoxic effects of high dose toluene: an experimental study  

Directory of Open Access Journals (Sweden)

Full Text Available Objective: This study aimed to investigate the acute cardiotoxic effects of high dose toluene and its damage mechanisms on heart tissue in the acute period.Methods: Twenty adult male Wistar Albino rats (200-220 g were used in this controlled experimental animal study. Animals were divided into two equal groups: a control group (Group 1 and a high dose (6 mL/kg/gavage toluene-administered group (Group 2. Arterial blood pressure (BP and heart rate (HR values were measured at 30th, 60th and 90th minutes after toluene was administered. At the end of the experimental period, blood samples and heart tissues were taken from the rats. Serum troponin T levels were assayed. Heart tissue sections were stained using routine histological methods and examined under a light microscope. In addition, the sections were immunohistochemically stained using the avidin-biotin-peroxidase method to determine caspase-3 immunoreactivity and TUNEL to detect apoptosis. To compare the apoptotic index, the Mann-Whitney U test was used. For comparisons between the two groups, the independent t- test was used. In addition, time-based changes of intra-group parameters were evaluated using paired t tests. Results: BP and HR values were low in toluene-treated rats compared to the control group. Troponin T levels were increased in toluene-administered animals as compared with controls [Toluene group: 0.140 (0.010-2.000 ng/mL vs control group: 0.010 (0.010-0.010 ng/mL, p=0.01]. Histopathologic examination of heart tissue sections showed congestion and edema in toluene administrated rats. Higher TUNEL positivity and (+++ immunoreactivity for caspase-3 protein were observed in the toluene group compared to the control group. Conclusion: The present study demonstrated that high doses of toluene cause apoptosis and may lead to impairment of cardiac function in the acute period.

Ufuk Ta?

2013-03-01

350

Neutron scattering model for benzene  

International Nuclear Information System (INIS)

A theoretical model analogous to the Nelkin model for water for neutron scattering by protons bound in benzene is proposed. The physical model comprises a free translator of mass 78, a hindered ratational oscillator of effective mass 21.3 at an energy of 0.02 eV and two vibrational oscillators at energies 0.146 and 0.38 eV with masses of 1.62 and 3.09 respectively. The diffusion constant of 51 000 cm2/sec calculated by the model agrees well with the experimental value of (50 360 +- 200) cm2/sec. (orig.)

351

Linking Toluene Degradation with Specific Microbial Populations in Soil  

OpenAIRE

Phospholipid fatty acid (PLFA) analysis of a soil microbial community was coupled with 13C isotope tracer analysis to measure the community’s response to addition of 35 ?g of [13C]toluene ml of soil solution?1. After 119 h of incubation with toluene, 96% of the incorporated 13C was detected in only 16 of the total 59 PLFAs (27%) extracted from the soil. Of the total 13C-enriched PLFAs, 85% were identical to the PLFAs contained in a toluene-metabolizing bacterium isolated from the same so...

Hanson, Jessica R.; Macalady, Jennifer L.; Harris, David; Scow, Kate M.

1999-01-01

352

Toluene alters p75NTR expression in the rat brainstem.  

Science.gov (United States)

Toluene is a neurotoxic organic solvent widely used in industry. Acute toluene administration in rats induced a significant increase in the numbers of neural cells immunostained for p75NTR in several brainstem regions, such as the raphe magnus and the nucleus of the solitary tract, as well as in the lateral reticular, gigantocellular, vestibular and ventral cochlear nuclei, without any in the facial and spinal trigeminal nuclei and the dorsal horn of the spinal cord. These data suggest that p75NTR could be involved in toluene-induced neurotoxic efffects in the rat brainstem. PMID:14964621

Pascual, Jesús; Morón, Lena; Zárate, Jon; Gutiérrez, Arantza; Churruca, Itziar; Echevarría, Enrique

2004-01-01

353

Occupational exposure to benzene in South Korea.  

Science.gov (United States)

Benzene has been used in various industries as glues or solvents in Korea. Since 1981, a preparation containing more than 1% benzene is not allowed to be manufactured, used or dealt with in the workplace, except in laboratories and in those situations benzene must be used in a completely sealed process as specified in Industrial Safety and Health Act (ISHA). Claims for compensation of hematopoietic diseases related to benzene have been rising even though the work environment has been improved. This study was conducted to assess the status of benzene exposure in different industries in Korea. We reviewed the claimed cases investigated by the Korea Occupational Safety and Health Agency (KOSHA) between 1992 and 2000. The Survey of National Work Environment Status in 1998 was analyzed to assume the number of workers and factories exposed to benzene. In 2000, six factories were investigated to evaluate benzene exposure. Personal air monitoring was performed in 61 workers and urine samples were collected from 57 workers to measure trans,trans-muconic acid (t,t-MA). Hematologic examination has performed. Thirty-four cases of hematopoietic diseases were investigated by KOSHA including eight cases of myelodysplastic syndrome and eight cases of acute myelocytic leukemia. Eight cases were accepted as related to benzene exposure. The number of workers possibly exposed to benzene can be estimated to be 196,182 workers from 6219 factories based on the database. The geometric mean of benzene in air was 0.094 (0.005-5.311) ppm. Seven samples were higher than 1 ppm but they did not go over the 10 ppm occupational exposure limit (OEL) value in Korea. The geometric mean of trans,trans-muconic acid in urine was 0.966 (0.24-2.74) mg/g creatinine. The benzene exposure level was low except in a factory where benzene was used to polymerize other chemicals. The ambient benzene from 0.1 to 1 ppm was significantly correlated with urine t,t-MA concentration (r=0.733, p<0.01). Hematologic parameters did not show significant difference among groups divided into the level of exposure. Korean workers were not highly exposed to benzene and the level of exposure was mostly less than 1 ppm. However, there might be an excessive risk of hematopoietic disorders due to relatively high past exposure. The OEL value of benzene was amended to 1 ppm from 10 ppm in 2002 and was effective since July 2003. PMID:15935801

Kang, Seong-Kyu; Lee, Mi-Young; Kim, Tae-Kyun; Lee, Jeong-Oh; Ahn, Yeon Soon

2005-05-30

354

Mechanistic considerations in benzene physiological model development  

Energy Technology Data Exchange (ETDEWEB)

Benzene, an important industrial solvent, is also present in unleaded gasoline and cigarette smoke. The hematotoxic effects of benzene in humans are well documented and include aplastic anemia, pancytopenia, and acute myelogenous leukemia. However, the risks of leukemia at low exposure concentrations have not been established. A combination of metabolites (hydroquinone and phenol, for example) may be necessary to duplicate the hematotoxic effect of benzene, perhaps due in part to the synergistic effect of phenol on myeloperoxidase-mediated oxidation of hydroquinone to the reactive metabolite benzoquinone. Because benzene and its hydroxylated metabolites (phenol, hydroquinone, and catechol) are substrates for the same cytochrome P450 enzymes, competitive interactions among the metabolites are possible. In vivo data on metabolite formation by mice exposed to various benzene concentrations are consistent with competitive inhibition of phenol oxidation by benzene. In vitro studies of the metabolic oxidation of benzene, phenol, and hydroquinone are consistent with the mechanism of competitive interaction among the metabolites. The dosimetry of benzene and its metabolites in the target tissue, bone marrow, depends on the balance of activation processes such as enzymatic oxidation and deactivation processes such as conjugation and excretion. Phenol, the primary benzene metabolite, can undergo both oxidation and conjugation. Thus the potential exists for competition among various enzymes for phenol. Zonal localization of phase I and phase 11 enzymes in various regions of the liver acinus also impacts this competition. Biologically based dosimetry models that incorporate the important determinants of benzene flux, including interactions with other chemicals, will enable prediction of target tissue doses of benzene and metabolites at low exposure concentrations relevant for humans. 39 refs., 4 figs., 2 tabs.

Medinsky, M.A.; Kenyon, E.M.; Seaton, M.J.; Schlosser, P.M. [Chemical Industry Institute of Toxicology, Research Triangle Park, NC (United States)

1996-12-01

355

Anaerobic benzene oxidation by Geobacter species.  

Science.gov (United States)

The abundance of Geobacter species in contaminated aquifers in which benzene is anaerobically degraded has led to the suggestion that some Geobacter species might be capable of anaerobic benzene degradation, but this has never been documented. A strain of Geobacter, designated strain Ben, was isolated from sediments from the Fe(III)-reducing zone of a petroleum-contaminated aquifer in which there was significant capacity for anaerobic benzene oxidation. Strain Ben grew in a medium with benzene as the sole electron donor and Fe(III) oxide as the sole electron acceptor. Furthermore, additional evaluation of Geobacter metallireducens demonstrated that it could also grow in benzene-Fe(III) medium. In both strain Ben and G. metallireducens the stoichiometry of benzene metabolism and Fe(III) reduction was consistent with the oxidation of benzene to carbon dioxide with Fe(III) serving as the sole electron acceptor. With benzene as the electron donor, and Fe(III) oxide (strain Ben) or Fe(III) citrate (G. metallireducens) as the electron acceptor, the cell yields of strain Ben and G. metallireducens were 3.2 × 10(9) and 8.4 × 10(9) cells/mmol of Fe(III) reduced, respectively. Strain Ben also oxidized benzene with anthraquinone-2,6-disulfonate (AQDS) as the sole electron acceptor with cell yields of 5.9 × 10(9) cells/mmol of AQDS reduced. Strain Ben serves as model organism for the study of anaerobic benzene metabolism in petroleum-contaminated aquifers, and G. metallireducens is the first anaerobic benzene-degrading organism that can be genetically manipulated. PMID:23001648

Zhang, Tian; Bain, Timothy S; Nevin, Kelly P; Barlett, Melissa A; Lovley, Derek R

2012-12-01

356

Anaerobic Benzene Oxidation via Phenol in Geobacter metallireducens  

OpenAIRE

Anaerobic activation of benzene is expected to represent a novel biochemistry of environmental significance. Therefore, benzene metabolism was investigated in Geobacter metallireducens, the only genetically tractable organism known to anaerobically degrade benzene. Trace amounts (

Zhang, Tian; Tremblay, Pier-luc; Chaurasia, Akhilesh Kumar; Smith, Jessica A.; Bain, Timothy S.; Lovley, Derek R.

2013-01-01

357

40 CFR 721.1210 - Benzene, (2-chloroethoxy)-.  

Science.gov (United States)

...2010-07-01 2010-07-01 false Benzene, (2-chloroethoxy)-. 721.1210...Specific Chemical Substances § 721.1210 Benzene, (2-chloroethoxy)-. (a) Chemical...The chemical substance identified as benzene, (2-chloroethoxy)- (PMN...

2010-07-01

358

[Benzene pollution in the city of Bari].  

Science.gov (United States)

The Authors reported data of benzene concentrations obtained in Bari during period of time between 1990 and 1995; the measured levels of benzene concentrations are not in accord with referent values prescribed by the law, mostly always they are exceeded. Present study also discuss problems related to gasoline consumption and the number of cars in circulation. PMID:9658241

Cassano, F; Bavaro, P; De Marinis, G; Bukvic, N; Giacomantonio, A

1998-01-01

359

46 CFR 30.25-3 - Benzene.  

Science.gov (United States)

46 ? Shipping ? 1 ? 2010-10-01 ? 2010-10-01 ? false ? Benzene. ? 30.25-3 ? Section 30.25-3 ? Shipping ? COAST GUARD, DEPARTMENT OF HOMELAND SECURITY ? TANK VESSELS ? GENERAL PROVISIONS ? Commodities Regulated ? § 30.25-3 ? Benzene. ? The provisions contained in 46 CFR part 197, subpart C, apply...

2010-10-01

360

Enhanced visible-light induced degradation of benzene on Mg-ferrite/hematite/PANI nanospheres: In situ FTIR investigation  

Energy Technology Data Exchange (ETDEWEB)

Graphical abstract: The dramatic enhanced visible-light photocatalytic activity of Mg-ferrite/hematite nanospheres photocatalyst on benzene were obtained after hybridized by polyaniline (PANI) using the chemisorption method. The enhancement of photocatalytic degradation of benzene under visible-light irradiation was mainly ascribed to the high efficiency of charge separation induced by the hybrid effect of PANI and Mg-ferrite/hematite. By using the in situ FTIR technique, ethyl acetate, carboxylic acid and aldehyde could be regarded as the intermediate products, and CO{sub 2} is produced as the final product during the reaction process. Highlights: Black-Right-Pointing-Pointer Mg-ferrite/hematite/PANI photocatalysts showed enhanced photocatalytic activity. Black-Right-Pointing-Pointer Ethyl acetate, carboxylic acid and aldehyde were the intermediate products. Black-Right-Pointing-Pointer CO{sub 2} was produced as the final product during the reaction process. Black-Right-Pointing-Pointer The high efficiency of charge separation was mainly ascribed to the hybrid effect. - Abstract: The dramatic enhanced visible-light photocatalytic activity of Mg-ferrite/hematite nanospheres photocatalysts on benzene were obtained after hybridized by polyaniline (PANI) using the chemisorption method. The samples were characterized by scanning electron microscope, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectra and UV-Vis diffuse reflectance spectroscopy. The enhancement of photocatalytic degradation of benzene under visible-light irradiation was mainly ascribed to the high efficiency of charge separation induced by the hybrid effect of PANI and Mg-ferrite/hematite. By using the in situ FTIR technique, ethyl acetate, carboxylic acid and aldehyde could be regarded as the intermediate products, and CO{sub 2} is determined as the final product during the reaction process.

Shen, Yu [Key Laboratory of Industrial Ecology and Environmental Engineering and State Key Laboratory of Fine Chemical, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024 (China); School of Environmental and Chemical Engineering, Dalian Jiaotong University, Dalian 116028 (China); Zhao, Qidong [Key Laboratory of Industrial Ecology and Environmental Engineering and State Key Laboratory of Fine Chemical, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024 (China); Li, Xinyong, E-mail: xyli@dlut.edu.cn [Key Laboratory of Industrial Ecology and Environmental Engineering and State Key Laboratory of Fine Chemical, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024 (China); Department of Chemical Engineering, Curtin University, Perth, WA 6845 (Australia); Yuan, Deling; Hou, Yang [Key Laboratory of Industrial Ecology and Environmental Engineering and State Key Laboratory of Fine Chemical, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024 (China); Liu, Shaomin, E-mail: shaomin.liu@curtin.edu.au [Department of Chemical Engineering, Curtin University, Perth, WA 6845 (Australia)

2012-11-30

361

[The sonochemical-degradation mechanism of toluene in aqueous solution].  

Science.gov (United States)

The sonochemical degradation of toluene in the airproof aqueous solution was studied, and the mechanism and course of degradation was explored. It was found that the sonication time had great effect on the removal rate of toluene, and the degradation followed a pseudo-first-order kinetic law, and 90%-95% of toluene was removed only after being irradiated for 40 min, types of dissolved gas and pH also had some effects. After aqueous solution was analyzed pH and scanned UV-wavelength and identified components with SMPE-GC-MS, results confirmed that radical-oxidation controlled the sonochemical-oxidation of toluene, and main middle-products included benzaldehyde, bibenzyl, dibutyl phthalate, et al., final products were carbon dioxide and water. PMID:11507914

Bian, H; Zhang, D; Zhao, Y; Jin, Z; Hua, B

2001-05-01

362

Rheology of asphaltene-toluene/water interfaces.  

Science.gov (United States)

The stability of water-in-crude oil emulsions is frequently attributed to a rigid asphaltene film at the water/oil interface. The rheological properties of these films and their relationship to emulsion stability are ill defined. In this study, the interfacial tension, elastic modulus, and viscous modulus were measured using a drop shape analyzer for model oils consisting of asphaltenes dissolved in toluene for concentrations varying from 0.002 to 20 kg/m(3). The effects of oscillation frequency, asphaltene concentration, and interface aging time were examined. The films exhibited viscoelastic behavior. The total modulus increased as the interface aged at all asphaltene concentrations. An attempt was made to model the rheology for the full range of asphaltene concentration. The instantaneous elasticity was modeled with a surface equation of state (SEOS), and the elastic and viscous moduli, with the Lucassen-van den Tempel (LVDT) model. It was found that only the early-time data could be modeled using the SEOS-LVDT approach; that is, the instantaneous, elastic, and viscous moduli of interfaces aged for at most 10 minutes. At longer interface aging times, the SEOS-LVDT approach was invalid, likely because of irreversible adsorption of asphaltenes on the interface and the formation of a network structure. PMID:16316096

Sztukowski, Danuta M; Yarranton, Harvey W

2005-12-01

363

Consequences of limiting benzene content of motor gasoline  

Energy Technology Data Exchange (ETDEWEB)

Current motor gasoline benzene levels, related legislation in Western Europe and the consequences of limiting the benzene content of gasoline are considered. The sources of benzene in gasoline are reviewed and the existing legislation on allowable levels is summarized. The benzene levels in current motor gasolines are surveyed and the causes of variations are analyzed. Means of reducing benzene contents, either by adjusting existing processing routes or by extracting benzene from gasoline blending components, are considered. The impact of benzene limitations on the production of motor gasolines are assessed in terms of the costs involved and the energy penalties incurred. Finally, the potential problem of the disposal of extracted benzene is discussed.

Spencer, E.H.; Conrard, M.C.; Cremer, G.; Hancke, J.; De Roocker, A.; Roshier, M.J.S.; Sibra, P.; De Valois, A.A.; Wake, R.H.

1983-12-01

364

Current collapse in tunneling transport through benzene  

CERN Document Server

We investigate the electrical transport through a system of benzene coupled to metal electrodes by electron tunneling. Using electronic structure calculations, a semi--quantitative model for the pi-electrons of the benzene is derived that includes general two-body interactions. After exact diagonalization of the benzene model the transport is computed using perturbation theory for weak electrode-benzene coupling (golden rule approximation). We include the effect of an applied electric field on the molecular states, as well as radiative relaxation. We predict a current collapse and strong negative differential conductance due to a ``blocking'' state when the electrode is coupled to the para-position of benzene. In contrast, for coupling to the meta-position, a series of steps in the I-V curve is found.

Hettler, M H; Wegewijs, M R; Schoeller, H

2002-01-01

365

Solubility data for toluene in various aqueous alkanolamine solutions  

International Nuclear Information System (INIS)

This paper is the second part concerning the study of the solubility of aromatics in aqueous alkanolamine solutions. Vapor pressures over (liquid + liquid) mixtures and toluene solubility data are reported herein for toluene with pure water and aqueous alkanolamine solutions: monoethanolamine (MEA), diethanolamine (DEA), methyldiethanolamine (MDEA), and diglycolamine[reg] (DGA). Modelling of solubility data are achieved using a simple model based on activity coefficients

366

Risk of spontaneous abortion in workers exposed to toluene.  

OpenAIRE

Rates of spontaneous abortions were determined using a reproductive questionnaire administered by personal interview to 55 married women with 105 pregnancies. They were employed in an audio speaker factory and were exposed to high concentrations of toluene (mean 88, range 50-150 ppm). These rates of spontaneous abortion were compared with those among 31 women (68 pregnancies) who worked in other departments in the same factory and had little or no exposure to toluene (0-25 ppm), as well as wi...

Ng, T. P.; Foo, S. C.; Yoong, T.

1992-01-01

367

Biotransformation of nitrobenzene by bacteria containing toluene degradative pathways.  

OpenAIRE

Nonpolar nitroaromatic compounds have been considered resistant to attack by oxygenases because of the electron withdrawing properties of the nitro group. We have investigated the ability of seven bacterial strains containing toluene degradative pathways to oxidize nitrobenzene. Cultures were induced with toluene vapor prior to incubation with nitrobenzene, and products were identified by high-performance liquid chromatography and gas chromatography-mass spectrometry. Pseudomonas cepacia G4 a...

Haigler, B. E.; Spain, J. C.

1991-01-01

368

Anaerobic Benzene Degradation in Petroleum-Contaminated Aquifer Sediments after Inoculation with a Benzene-Oxidizing Enrichment  

OpenAIRE

Sediments from the sulfate-reduction zone of a petroleum-contaminated aquifer, in which benzene persisted, were inoculated with a benzene-oxidizing, sulfate-reducing enrichment from aquatic sediments. Benzene was degraded, with apparent growth of the benzene-degrading population over time. These results suggest that the lack of benzene degradation in the sulfate-reduction zones of some aquifers may result from the failure of the appropriate benzene-degrading sulfate reducers to colonize the a...

Weiner, Jonathan M.; Lovley, Derek R.

1998-01-01

369

Hepatic metabolism of toluene after gastrointestinal uptake in humans  

DEFF Research Database (Denmark)

The metabolism of toluene and the influence of small doses of ethanol were measured in eight male volunteers after gastrointestinal uptake, the toluene concentration in alveolar air and the urinary excretion of hippuric acid and ortho-cresol being used as the measures of metabolism. During toluene exposure to 2 mg.min-1 for 3 h the alveolar toluene concentration was 0.07 (range 0-0.11) mg.m-3; exposure to 6 mg.min-1 for 30 min increased the alveolar concentration to 0.9 (range 0.03-2.6) mg.m-3. Ingestion of 0.08, 0.16, and 0.32 g of ethanol per kilogram of body weight during toluene exposure of 2 mg.min-1 increased the alveolar concentration within 10 min, and maximal alveolar concentrations of 5 (SD 3), 24 (SD 11), and 39 (SD 28) mg.m-3 were reached after 30, 60, and 90 min for the three doses, respectively. Hippuric acid excretion was only decreased by an ethanol dose of 0.32 g.kg-1. Very low doses of ethanol inhibit toluene metabolism, and the procedure is sensitive enough to measure metabolic interactionsbetween solvents and other xenobiotics in humans.

Bælum, Jesper; MØlhave, Lars

1993-01-01

370

The cyanogen-ethyl ethers of glycerin  

International Nuclear Information System (INIS)

The cyanogen-ethylation is one of the characteristic reaction of hydroxyl comprising compounds and run with addition them to acryl nitride. The catalysis of process are substances, which have basic character

371

Hemo-De as substitute for ethyl acetate in formalin-ethyl acetate concentration technique.  

OpenAIRE

In comparative studies, Hemo-De (PMP Medical Industries, Inc., Irving, Tex.) was found to be a suitable replacement for ethyl acetate in the Formalin-ethyl acetate concentration technique. With essentially equivalent recovery rates for both procedures, the Formalin-Hemo-De concentration technique is considered to be the preferred technique because Hemo-De is less toxic and less flammable and does not present disposal problems, and its cost is approximately one-fourth that of ethyl acetate.

Neimeister, R.; Logan, A. L.; Gerber, B.; Egleton, J. H.; Kleger, B.

1987-01-01

372

Benzene and ethylene in Bio-SNG production. Nuisance, fuel or valuable products?  

Energy Technology Data Exchange (ETDEWEB)

Gasification of biomass with the aim to produce Substitute Natural Gas (SNG) is best performed at temperatures around 850C, where 50% of the combustion value of the producer gas is concentrated in hydrocarbons. After removal of the heavy hydrocarbons (i.e. tar) and sulphur components, the producer gas can be converted catalytically to a mixture of mainly methane, carbon dioxide and water. Using producer gas as intermediate instead of syngas can lead to 10% higher efficiency, as producer gas does contain a significant amount of methane already and because less heat is evolved in the conversion of the remainder than for a mixture of carbon monoxide and hydrogen. Some of the hydrocarbons in producer gas, notably benzene, toluene, acetylene and ethylene, together with some of the more volatile tar compounds, can be a nuisance in the conversion step, as they easily form carbon deposits on the methanation catalysts involved. Several strategies can be followed to make these annoying components useful. Here, we will focus on benzene and ethylene, as each represents nearly 90% of the total amount of aromatic and unsaturated hydrocarbons respectively in biomass producer gas. One approach, followed in the SNG demonstration plant in Guessing, is to remove benzene nearly completely from producer gas in a low-temperature scrubber. Recovered benzene with some of the scrubbing liquid is used as fuel to provide heat for the gasifier. Any benzene remaining in the producer gas and ethylene are converted in the fluidized bed methanation reactor. The fluidized bed creates conditions in which carbon deposits are gasified before they can harm the catalyst performance. The use of benzene as heat source in the gasifier reduces the need to burn part of the producer gas for that purpose. Effectively, more 'clean' producer gas becomes available for the methanation step. The MILENA type gasifier developed by ECN has a lower heat demand than the Guessing FICFB gasifier. Consequently, it has no use for benzene as an additional heat source. That is why ECN research focuses on solving problems associated with the conversion of benzene and ethylene to methane. One of the problems is removal of organic sulphur compounds, especially thiophene and its derivatives like benzo-thiophene. The main route pursued by ECN is conversion of thiophenes by a hydrodesulphurization (HDS) catalyst, followed by adsorption of the hydrogensulphide produced. Benzene removed from producer gas by liquid scrubbing or adsorption to a solid sorbent can also be recovered for use as fuel in a separate boiler. An advantage of that approach would be that benzene can be stored more easily than producer gas to match heat production with demand by e.g. a district heat system or to provide heat during gasifier maintenance. In fact, that would copy the approach followed in Harbooere with tar. Another promising option is cryogenic separation of producer gas. In principle, that would make it possible to separate and recover not only benzene but also ethylene. Even without purification, these may have more value as chemical base materials than when used as fuel. The cryogenic treatment would probably also capture sulphur compounds, thus considerably simplifying the gas cleaning needed for protection of the methanation catalyst. Advantages and disadvantages of the above options will be discussed. Experimental results of ECN research on hydrodesulphurization and adsorbents will be presented. Further research questions will be addressed.

Rabou, L.P.L.M. Rabou; Van der Drift, A. [ECN Biomass and Energy Efficiency, Petten (Netherlands)

2011-11-15

373

Methyl rotor dependent vibrational interactions in toluene  

Science.gov (United States)

The methyl rotor dependence of a three state Fermi resonance in S1 toluene at ˜460 cm-1 has been investigated using two-dimensional laser induced fluorescence. An earlier time-resolved study has shown the Fermi resonance levels to have different energy spacings at the two lowest methyl rotor states, m = 0 and 1 [J. A. Davies, A. M. Green, and K. L. Reid, Phys. Chem. Chem. Phys. 12, 9872 (2010)]. The overlapped m = 0 and 1 spectral features have been separated to provide direct spectral evidence for the m dependence of the resonance. The resonance has been probed at m = 3a?1 for the first time and found to be absent, providing further evidence for a large change in the interaction with m. Deperturbing the resonance at m = 0 and 1 reveals that the m dependence arises through differences in the separations of the "zero-order," locally coupled states. It is shown that this is the result of the local "zero-order" states being perturbed by long-range torsion-vibration coupling that shifts their energy by small amounts. The m dependence of the shifts arises from the ?m = ±3n (n = 1, 2, …) coupling selection rule associated with torsion-rotation coupling in combination with the m2 scaling of the rotor energies, which changes the ?E for the interaction for each m. There is also an increase in the number of states that can couple to m = 1 compared with m = 0. Consideration of the magnitude of reported torsion-rotation coupling constants suggests that this effect is likely to be pervasive in molecules with methyl rotors.

Gascooke, Jason R.; Lawrance, Warren D.

2013-04-01

374

Toluene-4-monooxygenase, a three-component enzyme system that catalyzes the oxidation of toluene to p-cresol in Pseudomonas mendocina KR1.  

OpenAIRE

Pseudomonas mendocina KR1 grows on toluene as a sole carbon and energy source. A multicomponent oxygenase was partially purified from toluene-grown cells and separated into three protein components. The reconstituted enzyme system, in the presence of NADH and Fe2+, oxidized toluene to p-cresol as the first detectable product. Experiments with p-deutero-toluene led to the isolation of p-cresol which retained 68% of the deuterium initially present in the parent molecule. When the reconstituted ...

Whited, G. M.; Gibson, D. T.

1991-01-01

375

Apparent Benzene Solubility in Tetraphenylborate Slurries  

International Nuclear Information System (INIS)

Personnel conducted testing to determine the apparent solubility of benzene in potassium tetraphenylborate (KTPB) slurries. The lack of benzene vapor pressure suppression in these tests indicate that for a 6.5 wt percent solids KTPB slurry in 4.65 M Na+ salt solution at approximately 25 degrees Celsius, no significant difference exists between the solubility of benzene in the slurry and the solubility of benzene in salt solution without KTPB solids. The work showed similar results in slurry with 6,000 mg/L sludge and 2,000 mg/L monosodium titanate added. Slurries containing tetraphenylborate decomposition intermediates (i.e., 4,200 mg/L triphenylboron (3PB), 510 mg/L diphenylborinic acid (2PB) and 1,500 mg/L phenylboric acid (1PB) or 100 mg/L tri-n-butylphosphate (TBP)) also showed no significant difference in benzene solubility form filtrate containing no KTPB solids. Slurry containing 2,000 mg/L Surfynol 420 did exhibit significant additional benzene solubility, as did irradiated slurries. The vapor pressure depression in the irradiated slurries presumably results from dissolution of biphenyl and other tetraphenylborate irradiation products in the benzene

376

Spatial variability in levels of benzene, formaldehyde, and total benzene, toluene, ethylbenzene and xylenes in New York City: a land-use regression study  

OpenAIRE

Abstract Background Hazardous air pollutant exposures are common in urban areas contributing to increased risk of cancer and other adverse health outcomes. While recent analyses indicate that New York City residents experience significantly higher cancer risks attributable to hazardous air pollutant exposures than the United States as a whole, limited data exist to assess intra-urban variability in air toxics exposures. Methods To assess intra-urban spatial variability in exposures to common ...

Kheirbek Iyad; Johnson Sarah; Ross Zev; Pezeshki Grant; Ito Kazuhiko; Eisl Holger; Matte Thomas

2012-01-01

377

Synthesis, spectroscopic, thermal and antimicrobial studies of toluene-3,4-dithiolatoarsenic(III) derivatives with some oxygen and sulphur donor ligands  

Science.gov (United States)

Replacement reactions of toluene-3,4-dithiolatoarsenic(III) chloride with oxygen and sulphur donor ligands like benzoic acid, thiobenzoic acid, anhydrous sodium acetate, thioacetic acid, phenol, thiophenol, sodium salicylate and thio glycolic acid in 1:1 molar ratio as well as disodium oxalate in 2:1 molar ratio in refluxing anhydrous benzene yielded toluene-3,4-dithiolatoarsenic(III) mono oxo or thio carboxylic or phenolic derivatives of the general formula SC6H3(CH3)SAsR {where R = OOCC6H5, SOCC6H5, OOCCH3, SOCCH3, OC6H5, SC6H5, OOCC6H4(OH), SCH2COOH} and SC6H3(CH3)SAsOOC-COOAsS(CH3)C6H3S. These synthesized derivatives are yellow, yellow-brown solids/ liquids and are soluble in common organic solvents like benzene, chloroform, dichloromethane, dimethyl formamide, dimethyl sulphoxide etc. These derivatives have been characterized by melting point determination, molecular weight determination, elemental analysis (C, H, S and As), spectral {UV, IR, NMR (1H and 13C), ESI-Mass, SEM and powder X-ray diffraction} and thermal (TGA, DTA and DSC) studies. Some of these compounds have been screened for their antimicrobial activities using the disc diffusion method. These derivatives have shown good activity as antibacterial and antifungal agents on some selected bacterial and fungal strains, which increased on increasing the concentration. Chloroamphenicol and terbinafin were used as standards for the comparison.

Chauhan, H. P. S.; Bhatiya, Sumit

2012-11-01

378

S-p -Toluylmercapturic acid in the urine of workers exposed to toluene: a new biomarker for toluene exposure  

Energy Technology Data Exchange (ETDEWEB)

A mercapturic acid attached to the aromatic ring of toluene was for the first time detected in human urine as a metabolite of toluene. Since the metabolism of toluene is usually considered to take place at the side-chain, this gives, besides the biosynthesis of cresols, a further hint of a metabolic conversion of the aromatic system. We examined a group of 33 workers occupationally exposed to toluene, determining the concentrations of toluene in ambient air and in whole blood, o-cresol and hippuric acid in urine and p-toluylmercapturic acid (p-TMA) in urine. All blood and urine samples were collected post-shift. The renal excretion of S-p-toluylmercapturic acid showed highly significant correlations with established parameters of a biological monitoring of toluene. The median ambient air concentration was 63 ppm, ranging from 13 to 151 ppm, the median concentration of toluene in whole blood was 804 {mu}g/l, corresponding to median urinary concentrations for o-cresol of 2.3 mg/l, hippuric acid of 2.3 g/l and p-TMA of 20.4 {mu}g/l. p-TMA was not detectable in urine samples of a control group of 10 non-exposed persons. Both the German Biological Tolerance Values (BAT-values) for toluene in blood (1000 {mu}g/l) and o-cresol in urine (3 mg/l) correspond to a mean p-TMA elimination of {proportional_to}50 g/l, and thus are in agreement with each other. According to our results p-TMA reflects internal toluene exposure diagnostically sensitive and specifical. With the developed analytical procedure we determined a median benzylmercapturic acid (BMA) concentration of 190 {mu}g/l in the urine samples of the toluene exposed persons. We also determined a median BMA concentration of 30 {mu}g/l in the control samples of non-exposed persons. However, these results are preliminary and require further confirmation as the reliability of the method was determined only for p-TMA. (orig.) With 3 figs., 1 tab., 24 refs.

Angerer, J.; Schildbach, M.; Kraemer, A. [Friedrich-Alexander-University of Erlangen-Nuernberg, Institute and Clinic of Occupational-, Social- and Environmental Medicine, Erlangen (Germany)

1998-01-01

379

Deuterium isotope effect in 1H chemical shift of benzene-d1  

International Nuclear Information System (INIS)

90 MHz 1H-NMR spectrum of liquid benzene-d1 has been measured and completely analysed as an AB2C2X (X = D, I = 1) system. The deuterium isotopic shifts relative to internal benzene, ?sub(A) = -1.4 ppb, ?sub(B) = -1.3 ppb and ?sub(C) = +0.3 ppb, have been determined. (author)

380

Aromaticity of benzene in condensed phases. A case of a benzene-water system  

Science.gov (United States)

A theoretical Density Functional Theory study was performed for a benzene molecule in water cages. Two DFT functionals (B3LYP and BLYP) were employed. The optimized geometries of the studied clusters were used to calculate the aromaticity of benzene in a condensed phase using the aromaticity indices: HOMA, NICS, PDI, and H. The results were compared with aromaticity of a single benzene molecule in the gas phase and in the solvent environment provided by the PCM continuum model. It is argued that high aromaticity of benzene in the gas phase is retained in the water environment.

Zborowski, Krzysztof K.

2014-05-01

381

The inorganic analogues of carbo-benzene  

Science.gov (United States)

Inspired by carbo-benzene, we have analyzed in silico the stability of carbo-borazine (C12B3N3H6) and the iminobora-mer of borazine (B9N9H6). Both systems may be regarded as the inorganic analogues of carbo-benzene, being B9N9H6 the perfect case. Unlike aromatic carbo-benzene, C12B3N3H6 and B9N9H6 can be classified as almost nonaromatic systems as indicated by the computed induced magnetic field. All these systems undergo dimerization very readily; therefore, they cannot be synthesized as such. However, akin to substituted carbo-benzene, the substitution of the hydrogen atom of C12B3N3H6 and B9N9H6 by other groups could stabilize them.

Jalife, Said; Audiffred, Martha; Islas, Rafael; Escalante, Sigfrido; Pan, Sudip; Chattaraj, Pratim K.; Merino, Gabriel

2014-08-01

382

Electromers of the benzene dimer radical cation.  

Science.gov (United States)

The well-studied benzene dimer radical cation, which is prototypical for this class of species, has been reinvestigated computationally. Thereby it turned out that both the ?-hemibonded and the half-shifted sandwich structures of the benzene dimer cation, which had been independently proposed, represent stationary points on the B2PLYP-D potential energy surfaces. However, these structures belong to distinct electronic states, both of which are associated with potential surfaces that are very flat with regard to rotation of the two benzene rings in an opposite sense relative to each other. The surfaces of these two "electromers" of the benzene dimer cation are separated by only 3-4 kcal mol(-1) and do not intersect along the rotation coordinate, which represents a rather unique electronic structure situation. When moving on either of the two surfaces the title complex is an extremely fluxional species, in spite of its being bound by over 20 kcal mol(-1). PMID:25804703

B?och-Mechkour, Anna; Bally, Thomas

2015-04-01

383

Potassium 2-iodo-benzene-sulfonate monohydrate.  

Science.gov (United States)

In the crystal structure of the title compound, K(+)·C(6)H(4)IO(3)S(-)·H(2)O, the potasium cation is 2.693?(3)-2.933?(3)?Å from the sulfonate and water O atoms (including symmetry-related atoms) and forms a two-dimensional sheet-like structure in the bc plane, with the iodo-benzene rings protruding above and below. The water mol-ecule of crystallization is hydrogen-bonded to sulfonate O atoms within this two-dimensional arrangement. Symmetry-related iodo-benzene rings are arranged perpendicular to one another with the I atom ca 4.1?Å from the centroid of the neighbouring benzene ring. In the crystal structure, these two-dimensional sheet-like supramolecular structures are arranged parallel to one another, stacked along the a-axis direction, with the benzene rings inter-digitated. PMID:21203089

Arshad, Muhammad Nadeem; Khan, Islam Ullah; Ahmad, Saeed; Shafiq, Muhammad; Stoeckli-Evans, Helen

2008-01-01

384

Recommended sublimation pressure and enthalpy of benzene  

International Nuclear Information System (INIS)

Highlights: • Sublimation pressures of benzene were measured. • Benzene thermodynamic properties in the state of ideal gas were calculated. • Recommended sublimation pressure and enthalpy of benzene were developed. -- Abstract: Recommended vapor pressures of solid benzene (CAS Registry Number: 71-43-2) which are consistent with thermodynamically related crystalline and ideal-gas heat capacities as well as with properties of the liquid phase at the triple point temperature (vapor pressure, enthalpy of vaporization) were established. The recommended data were developed by a multi-property simultaneous correlation of vapor pressures and related thermal data. Vapor pressures measured in this work using the static method in the temperature range from 233 K to 260 K, covering pressure range from 99 Pa to 1230 Pa, were included in the simultaneous correlation. The enthalpy of sublimation was established with uncertainty significantly lower than the previously recommended values

385

Multiphoton ionization of benzene in solution  

International Nuclear Information System (INIS)

The multiphoton ionization spectrum of benzene in a dilute solution in n-pentane has been measured for laser excitation wavelengths from 360-560 nm. The observed spectrum, from 460-560 nm, has been measured using linearly and circularly polarized light and has been ascribed to multiphoton ionization via the two-photon resonant 1B2/sub u/-1A1/sub q/ transitions of benzene. The order of the multiphoton ionization process has been determined, and the observed resonances in the spectral region from 360-445 nm are discussed. Power measurements at 337.1 nm indicate that two photons can ionize benzene in this energy region, giving an upper limit to the ionization threshold of benzene in n-pentane of approx.7.36 eV

386

Dual responsive pickering emulsion stabilized by poly[2-(dimethylamino)ethyl methacrylate] grafted cellulose nanocrystals.  

Science.gov (United States)

A weak polyelectrolyte, poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA), was grafted onto the surface of cellulose nanocrystals via free radical polymerization. The resultant suspension of PDMAEMA-grafted-cellulose nanocrystals (PDMAEMA-g-CNC) possessed pH-responsive properties. The grafting was confirmed by FTIR, potentiometric titration, elementary analysis, and thermogravimetric analysis (TGA); the surface and interfacial properties of the modified particles were characterized by surface tensiometer. Compared to pristine cellulose nanocrystals, modified CNC significantly reduced the surface and interfacial tensions. Stable heptane-in-water and toluene-in-water emulsions were prepared with PDMAEMA-g-CNC. Various factors, such as polarity of solvents, concentration of particles, electrolytes, and pH, on the properties of the emulsions were investigated. Using Nile Red as a florescence probe, the stability of the emulsions as a function of pH and temperature was elucidated. It was deduced that PDMAEMA chains promoted the stability of emulsion droplets and their chain conformation varied with pH and temperature to trigger the emulsification and demulsification of oil droplets. Interestingly, for heptane system, the macroscopic colors varied depending on the pH condition, while the color of the toluene system remained the same. Reversible emulsion systems that responded to pH were observed and a thermoresponsive Pickering emulsion system was demonstrated. PMID:24983405

Tang, Juntao; Lee, Micky Fu Xiang; Zhang, Wei; Zhao, Boxin; Berry, Richard M; Tam, Kam C

2014-08-11

387

1-Ethyl-1H-2,1-benzothiazin-4(3H-one 2,2-dioxide  

Directory of Open Access Journals (Sweden)

Full Text Available In the title compound, C10H11NO3S, there is distorted tetrahedral geometry around the S atom. The heterocyclic thiazine ring adopts a half-chair conformation. The ethyl and sulfonyl groups form dihedral angles of 82.53?(13 and 88.91?(9°, respectively, with the plane formed by the benzothiazine ring, excluding the S atom; the S atom and the ethyl group lie on opposite sides of the ring. The molecules are linked into dimers by intermolecular C—H...O hydrogen bonds involving benzene C—H and carbonyl O atoms, thus forming eight-membered rings. The dimers are linked into chains via interactions of a similar type. There is an intramolecular C—H...O hydrogen bond.

Waseeq Ahmad Siddiqui

2008-03-01

388

Positron and positronium annihilation in benzene solutions  

International Nuclear Information System (INIS)

Positron annihilation in nitrobenzene and manganese oleate solutions in benzene was studied in the liquid and solid states using both lifetime and angular correlation methods. It was found that a long lifetime component (tau2 approximately 1.3 ns) appeared in the lifetime spectrum for the solid state of a nitrobenzene solution in benzene but not in the liquid state. The results are briefly discussed. (orig.)

389

Evaluation of biomarkers for occupational exposure to benzene.  

OpenAIRE

OBJECTIVE--To evaluate the relations between environmental benzene concentrations and various biomarkers of exposure to benzene. METHODS--Analyses were carried out on environmental air, unmetabolised benzene in urine, trans, trans-muconic acid (ttMA), and three major phenolic metabolites of benzene; catechol, hydroquinone, and phenol, in two field studies on 64 workers exposed to benzene concentrations from 0.12 to 68 ppm, the time weighted average (TWA). Forty nonexposed subjects were also i...

Ong, C. N.; Kok, P. W.; Lee, B. L.; Shi, C. Y.; Ong, H. Y.; Chia, K. S.; Lee, C. S.; Luo, X. W.

1995-01-01

390

Benzene, cytochrome, carcinogenesis: A topic in preventive toxicology  

OpenAIRE

Benzene is a common chemical substance with confirmed toxicity to human beings. The benzene toxicity can be in either acute or chronic. Also, the carcinogenicity of benzene is confirmed. Hence, the control of benzene usage is a topic in preventive toxicology; however, this substance is still problematic in many industrialized settings. In this article, the author discusses benzene and cytochrome focusing on the carcinogenesis process. A further extrapolation on the aspects on preventive toxic...

Wiwanitkit, Viroj

2014-01-01

391

Toluene-4-monooxygenase, a three-component enzyme system that catalyzes the oxidation of toluene to p-cresol in Pseudomonas mendocina KR1.  

Science.gov (United States)

Pseudomonas mendocina KR1 grows on toluene as a sole carbon and energy source. A multicomponent oxygenase was partially purified from toluene-grown cells and separated into three protein components. The reconstituted enzyme system, in the presence of NADH and Fe2+, oxidized toluene to p-cresol as the first detectable product. Experiments with p-deutero-toluene led to the isolation of p-cresol which retained 68% of the deuterium initially present in the parent molecule. When the reconstituted enzyme system was incubated with toluene in the presence of 18O2, the oxygen in p-cresol was shown to be derived from molecular oxygen. The results demonstrate that P. mendocina KR1 initiates degradation of toluene by a multicomponent enzyme system which has been designated toluene-4-monooxygenase. PMID:2019563

Whited, G M; Gibson, D T

1991-05-01

392

Benzene-derived carbon nanothreads  

Science.gov (United States)

Low-dimensional carbon nanomaterials such as fullerenes, nanotubes, graphene and diamondoids have extraordinary physical and chemical properties. Compression-induced polymerization of aromatic molecules could provide a viable synthetic route to ordered carbon nanomaterials, but despite almost a century of study this approach has produced only amorphous products. Here we report recovery to ambient pressure of macroscopic quantities of a crystalline one- dimensional sp3 carbon nanomaterial formed by high-pressure solid-state reaction of benzene. X-ray and neutron diffraction, Raman spectroscopy, solid-state NMR, transmission electron microscopy and first-principles calculations reveal close- packed bundles of subnanometre-diameter sp3-bonded carbon threads capped with hydrogen, crystalline in two dimensions and short-range ordered in the third. These nanothreads promise extraordinary properties such as strength and stiffness higher than that of sp2 carbon nanotubes or conven tional high-strength polymers. They may be the first member of a new class of ordered sp3 nanomaterials synthesized by kinetic control of high-pressure solid-state reactions.

Fitzgibbons, Thomas C.; Guthrie, Malcolm; Xu, En-Shi; Crespi, Vincent H.; Davidowski, Stephen K.; Cody, George D.; Alem, Nasim; Badding, John V.

2015-01-01

393

Experimental and kinetic modeling study of benzene and toluene combustion in premixed, laminar and one-dimensional flames  

OpenAIRE

Flames that have an excess of fuel, compared to the stoichiometry, or where the mixing between fuel and oxidizer is imperfect, result in an incomplete combustion. The excess of fuel is principally converted into Polycyclic Aromatic Hydrocarbons (PAH), which are molecular precursors of soot. In addition to the carcinogenic hazard of PAH, soot promotes the atmospheric solar heating or causes the coating of combustion chambers in the industry. It is therefore very important to understand mechani...

Detilleux, Vale?ry

2011-01-01

394

Health Risk Assessment of Ambient Air Concentrations of Benzene, Toluene and Xylene (BTX) in Service Station Environments  

OpenAIRE

A comprehensive evaluation of the adverse health effects of human exposures to BTX from service station emissions was carried out using BTX exposure data from the scientific literature. The data was grouped into different scenarios based on activity, location and occupation and plotted as Cumulative Probability Distributions (CPD) plots. Health risk was evaluated for each scenario using the Hazard Quotient (HQ) at 50% (CEXP50) and 95% (CEXP95) exposure levels. HQ50 and HQ95 > 1 were obtain...

Benjamin Edokpolo; Qiming Jimmy Yu; Des Connell

2014-01-01

395

SYNCHROTRON X-RAY MICROTOMOGRAPHY, ELECTRON PROBE MICROANALYSIS, AND NMR OF TOLUENE WASTE IN CEMENT.  

Energy Technology Data Exchange (ETDEWEB)

Synchrotron X-ray microtomography shows vesicular structures for toluene/cement mixtures, prepared with 1.22 to 3.58 wt% toluene. Three-dimensional imaging of the cured samples shows spherical vesicles, with diameters ranging from 20 to 250 {micro}m; a search with EPMA for vesicles in the range of 1-20 {micro}m proved negative. However, the total vesicle volume, as computed from the microtomography images, accounts for less than 10% of initial toluene. Since the cements were cured in sealed bottles, the larger portion of toluene must be dispersed within the cement matrix. Evidence for toluene in the cement matrix comes from {sup 29}Si MAS NMR spectroscopy, which shows a reduction in chain silicates with added toluene. Also, {sup 2}H NMR of d{sub 8}-toluene/cement samples shows high mobility for all, toluene and thus no toluene/cement binding. A model that accounts for all observations follows: For loadings below about 3 wt%, most toluene is dispersed in the cement matrix, with a small fraction of the initial toluene phase separating from the cement paste and forming vesicular structures that are preserved in the cured cement. Furthermore, at loadings above 3 wt%, the abundance of vesicles formed during toluene/cement paste mixing leads to macroscopic phase separation (most toluene floats to the surface of the cement paste).

BUTLER,L.G.

1999-07-22

396

SYNCHROTRON X-RAY MICROTOMOGRAPHY, ELECTRON PROBE MICROANALYSIS, AND NMR OF TOLUENE WASTE IN CEMENT  

International Nuclear Information System (INIS)

Synchrotron X-ray microtomography shows vesicular structures for toluene/cement mixtures, prepared with 1.22 to 3.58 wt% toluene. Three-dimensional imaging of the cured samples shows spherical vesicles, with diameters ranging from 20 to 250 microm; a search with EPMA for vesicles in the range of 1-20 microm proved negative. However, the total vesicle volume, as computed from the microtomography images, accounts for less than 10% of initial toluene. Since the cements were cured in sealed bottles, the larger portion of toluene must be dispersed within the cement matrix. Evidence for toluene in the cement matrix comes from 29Si MAS NMR spectroscopy, which shows a reduction in chain silicates with added toluene. Also, 2H NMR of d8-toluene/cement samples shows high mobility for all, toluene and thus no toluene/cement binding. A model that accounts for all observations follows: For loadings below about 3 wt%, most toluene is dispersed in the cement matrix, with a small fraction of the initial toluene phase separating from the cement paste and forming vesicular structures that are preserved in the cured cement. Furthermore, at loadings above 3 wt%, the abundance of vesicles formed during toluene/cement paste mixing leads to macroscopic phase separation (most toluene floats to the surface of the cement paste)

397

Radiolysis of Aqueous Benzene Solutions  

International Nuclear Information System (INIS)

Aerated and deaerated aqueous solutions of benzene have been irradiated with 60Co ?-rays. The products of radiolysis in deaerated, unbuffered or acid, solutions were phenol, biphenyl, hydrogen and in acid solutions also hydrogen peroxide with the following yields: G(phenol) = 0. 37 (0. 37), G(biphenyl) = 1.3 (1.7), G(H2) = 0.44 (0. 43) and G(H2O2) = 0 (0.60), the figures in brackets giving the results for acid solutions. The results are shown to agree with the conclusion that k(e-aq + H2O2) >> k(H + H2O2). Furthermore, the results indicate that a competition takes place between the reactions: 2 C6H6OH · -> dimer -> biphenyl. C6H7 · + C6H6OH · -> dimer -> biphenyl. The yields in aerated, unbuffered or acid, solutions were: G(phenol) = 2.1 (2.3), G(biphenyl) = 0 (0), and G(H2O2) = 2.2 (3.1), the figures in brackets being valid for acid solutions. The ratio k(H + C6H6)/k(H + O2) was 1.4x10-2. The results indicate that peroxides, or more probably hydroperoxides, take part in the reactions. After the addition of Fe2+ or Fe3+ to aerated acid solutions G(phenol) was increased to 6.6 and 3.4 respectively. Oxygen was consumed more rapidly in the presence of Fe. Reaction mechanisms are discussed

398

Hydrogen bonding in (substituted benzene)·(water)n clusters with n?4  

International Nuclear Information System (INIS)

Infrared ion-depletion spectroscopy, a double resonance method combining vibrational predissociation with resonant two-photon ionization (R2PI) spectroscopy, has been applied to study mixed clusters of the type (substituted benzene)·(H2O)n with n?4. The UV chromophores were p-difluorobenzene, fluorobenzene, benzene, toluene, p-xylene and anisole. From the IR depletion spectra in the region of the OH stretching vibrations it could be shown that the water molecules are attached as subclusters to the chromophores. Size and configuration of the subclusters could be deduced from the IR depletion spectra. In the anisole·(H2O)1and2 complexes the water clusters form an ordinary hydrogen bond to the oxygen atom of the methoxy group. In all other mixed complexes a ?-hydrogen bond is formed between one of the free OH groups of a water subcluster and the ?-system of the chromophore. According to the strength of this interaction the frequency of the respective absorption band exhibits a characteristic red-shift which could be related to the total atomic charges in the aromatic ring. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

399

PHOSPHOLIPIDS OF FIVE PSEUDOMONAD ARCHETYPES FOR DIFFERENT TOLUENE DEGRADATION PATHWAYS  

Science.gov (United States)

Liquid chromatography/electrospray ionization/mass spectrometry (LC/ESI/MS) was used to determine phospholipid profiles for five reference pseudomonad strains harboring distinct toluene catabolic pathways: Pseudomonas putida mt-2, Pseudomonas putida F1, Burkholderia cepacia G4, B...

400

Antipyrine clearance during experimental and occupational exposure to toluene  

DEFF Research Database (Denmark)

Exposure to toluene vapour enhances hepatic microsomal enzyme function in animals as assessed by the metabolism of the test drug antipyrine. Thirty six printing trade workers with long term occupational exposure to a mixture of organic solvents and 39 matched controls were randomly allocated into four groups. Eighteen printers and 21 controls were exposed to 100 ppm of toluene during 6.5 hours in an exposure chamber. The remaining 18 printers and 18 controls were exposed to 0 ppm of toluene under similar conditions. The salivary clearance of antipyrine was measured immediately after the stay in the exposure chamber to investigate a possible acute change in liver function and was repeated two weeks later, shortly before the summer vacation. Antipyrine clearance was measured again at the end of the summer vacation-four weeks after exposure. To study a possible effect of chronic exposure on antipyrine clearance 12 printing trade workers with 17 years (median) of occupational exposure to toluene vapour at concentrations of about 100 ppm were investigated before and four weeks after cessation of exposure. No difference in antipyrine clearance was found either within the groups or between the groups at any of the measurements.

DØssing, M; Bælum, Jesper

1983-01-01

401

Benzene monitoring at CPPI service stations  

International Nuclear Information System (INIS)

A study was conducted in which ambient airborne concentration levels of benzene were measured at a representative set of gasoline service stations in Toronto and Vancouver. Benzene is considered to be toxic under the Canadian Environmental Protection Act (CEPA). It is a component in gasoline (0.1 to 4.7 per cent by volume) and is present in vehicle evaporative and exhaust emissions. Measurements were made every 18 days at each station for one year. The objective of the study was to assess the ambient and employee exposure levels of benzene at service stations and to determine whether the levels were typical of those published in the literature. In a 1986 PACE (Petroleum Association for Conservation of the Canadian Environment) survey of exposure to gasoline hydrocarbon vapours at Canadian service stations, airborne benzene concentration data was inconsistent with similar ambient and personal exposure data in the international literature. It was concluded that both the mean ambient benzene concentration and the personal exposure level measurements in this study were generally lower than similar measurements made in other countries. The same observation was made with respect to ambient and personal exposure levels measured in this study vis-a-vis those measured during the PACE study conducted in 1985/86. . 31 refs., 24 tabs., 5 figs

402

Ethyl 1-sec-butyl-2-(4-chlorophenyl-1H-benzimidazole-5-carboxylate  

Directory of Open Access Journals (Sweden)

Full Text Available In the title compound, C20H21ClN2O2, the ethyl 1H-benzimidazole-5-carboxylate ring system, excluding the methylene and methyl H atoms, is almost planar, with a maximum deviation of 0.055?(1?Å, and makes a dihedral angle of 40.63?(4° with the benzene ring. The sec-butyl group is disordered over two positions, with refined site occupancies of 0.855?(4 and 0.145?(4. In the crystal, molecules are linked into chains along [010] via intermolecular C—H...O hydrogen bonds and are further interconnected by C—H...Cl interactions into two-dimensional networks parallel to (001. The crystal structure is further consolidated by C—H...? interactions.

Natarajan Arumugam

2010-09-01

403

N,N,N?,N?-Tetra­ethyl-N??-(2-fluoro­benzo­yl)phospho­ric triamide  

Science.gov (United States)

In the title compound, C15H25FN3O2P, the phosphoryl group is in an anti and syn orientation to the C=O and N—H groups, respectively. The P atom is in a distorted tetra­hedral environment. One of the ethyl groups is disordered over two sets of sites with refined occupancies of 0.755?(6) and 0.245?(6). In addition, the F atom was refined as disordered with occupancies fixed at 0.9 and 0.1. This disorder corresponds to a rotation of approximately 180° of the fluoro­benzene ring about its connecting C—C bond. In the crystal, pairs of inter­molecular N—H?O(=P) hydrogen bonds form centrosymmetric dimers. PMID:22058773

Tarahhomi, Atekeh; Pourayoubi, Mehrdad; Rheingold, Arnold L.; Golen, James A.

2011-01-01

404

N,N,N',N'-Tetra-ethyl-N''-(2-fluoro-benzo-yl)phospho-ric triamide.  

Science.gov (United States)

In the title compound, C(15)H(25)FN(3)O(2)P, the phosphoryl group is in an anti and syn orientation to the C=O and N-H groups, respectively. The P atom is in a distorted tetra-hedral environment. One of the ethyl groups is disordered over two sets of sites with refined occupancies of 0.755?(6) and 0.245?(6). In addition, the F atom was refined as disordered with occupancies fixed at 0.9 and 0.1. This disorder corresponds to a rotation of approximately 180° of the fluoro-benzene ring about its connecting C-C bond. In the crystal, pairs of inter-molecular N-H?O(=P) hydrogen bonds form centrosymmetric dimers. PMID:22058773

Tarahhomi, Atekeh; Pourayoubi, Mehrdad; Rheingold, Arnold L; Golen, James A

2011-10-01

405

2-Ethyl-6-methylanilinium 4-methylbenzenesulfonate  

Directory of Open Access Journals (Sweden)

Full Text Available The title compound, C9H14N+·C7H7SO3?, contains a 2-ethyl-6-methylanilinium cation and a 4-methylbenzenesulfonic anion. The cations are anchored between the anions through N—H...O hydrogen bonds. Electrostatic and van der Waals interactions, as well as hydrogen bonds, maintain the structural cohesion.

Jiao Ye

2009-02-01

406

N-Ethyl-N-phenyl-p-toluenesulfonamide  

Directory of Open Access Journals (Sweden)

Full Text Available In the title compound, C15H17NO2S, the aromatic rings are oriented at a dihedral angle of 32.8?(1°. The ethyl group and phenyl ring on the N atom adopt a staggered conformation with respect to the O atoms.

Islam Ullah Khan

2010-04-01

407

Microwave Spectrum of gauche-Ethyl Selenocyanate  

Science.gov (United States)

The microwave spectra of ethyl selenocyanate, CH 3CH 2SeCN ( 80Se and 78Se species), have been observed in the frequency range from 8000 to 27 000 MHz. The rotational constants are determined to be A = 3922.92(18), B = 2898.00(8), and C = 1789.82(2) MHz for 80Se species and A = 3960.25(28), B = 2898.17(13), and C = 1796.27(2) MHz for 78Se species. Only one rotational isomer was identified as having the synclinal ( gauche) form. The dihedral angle is found to be about 590 from the synperiplanar ( cis) position. The dipole moments of this rotamer are determined to be ? a = 4.37(10), ? b = 0.80(5), ? c = 0.50(5). and ? total = 4.47(10) D for the 80Se species. The rotational conformer of ethyl selenocyanate was similar to that of ethyl thiocyanate hut was different from that of ethyl cyanate.

Sakaizumi, T.; Itakura, T.

1994-01-01

408

Manufacturing Ethyl Acetate From Fermentation Ethanol  

Science.gov (United States)

Conceptual process uses dilute product of fermentation instead of concentrated ethanol. Low-concentration ethanol, extracted by vacuum from fermentation tank, and acetic acid constitutes feedstock for catalytic reaction. Product of reaction goes through steps that increases ethyl acetate content to 93 percent by weight. To conserve energy, heat exchangers recycle waste heat to preheat process streams at various points.

Rohatgi, Naresh K.; Ingham, John D.

1991-01-01

409

Toluene metabolism during exposure to varying concentrations combined with exercise  

DEFF Research Database (Denmark)

The urinary excretion of hippuric acid (HA) and ortho-cresol (O-cr) in man was measured in two studies of 7-h exposure to toluene in a climate chamber, either constant concentration of 100 ppm or varying concentrations containing peaks of 300 ppm but with a time-weighted average of 100 ppm. In Study A, four males were exposed to clean air and to constant and varying concentrations of toluene in combination with rest and with 100 W exercise in 140 min. Exercise increased end exposure excretion rate of HA and O-cr by 47 and 114%, respectively. After exposure, all excess HA was excreted within 4 h, while O-cr was eliminated with a half life of about 3 h. Alveolar air concentration of toluene varied between 21 and 31 ppm during constant exposure and between 13 and 57 ppm during varying exposure, but no difference in mean alveolar toluene concentration or in metabolite excretion was seen between the exposure schedules. In Study B, 32 males and 39 females aged between 31 and 50 years were exposed once to either clean air, constant or varying concentrations of toluene. Background excretion rate of HA was 0.97 +/- 0.75 mg/min (1.25 +/- 1.05 g/g creatinine) and rose to 3.74 +/- 1.40 mg/min (3.90 +/- 1.85 g/g cr) during the last 3 h of exposure to 100 ppm toluene. The corresponding figures for O-cr were 0.05 +/- 0.05 micrograms/min (0.08 +/- 0.14 mg/g cr), and 2.04 +/- 0.84 micrograms/min (2.05 +/- 1.18 mg/g cr). The individual creatinine excretion rate was considerably influenced by sex, body weight and smoking habits, thus influencing the metabolite concentration standardised in relation to creatinine. It is concluded that both metabolites are estimates of toluene exposure. O-cr is more specific than HA, but the individual variation in excretion of both metabolites is large, and when implementing either of them as biological exposure indices, the influence of sex, body size, age as well as consumption of tobacco and alcohol has to be considered.

Bælum, Jesper; DØssing, M

1987-01-01

410

Effect of ethanol, cimetidine and propranolol on toluene metabolism in man  

DEFF Research Database (Denmark)

In a climatic exposure chamber four healthy volunteers were exposed to 100ppm toluene, 100ppm toluene + ethanol, 100ppm toluene + cimetidine, and 100ppm toluene + propranolol for 7h each at random over four consecutive days. A control experiment and 3.5h of exposure to 200ppm toluene were also performed. Ethanol inhibited toluene metabolism by 0.5 as expressed by the urinary excretion of two of the metabolites of toluene, namely o-cresol and hippuric acid. In agreement with this, the mean alveolar concentration of toluene was greater by 1.7 during ethanol exposure; 45 min after discontinuation of exposure the increase was by 3.3. Neither cimetidine nor propranolol changed toluene metabolism significantly. The results indicate that ethanol may prolong the time interval in which toluene is retained in the human body in persons simultaneously exposed to ethanol and toluene. When using o-cresol or hippuric acid in biological monitoring of persons occupationally exposed to toluene, the consumption of ethanol should be considered.

DØssing, M; Bælum, Jesper

1984-01-01

411

Water and polymer dynamics in poly(hydroxyl ethyl acrylate-co-ethyl acrylate) copolymer hydrogels  

OpenAIRE

Water and polymer dynamics in hydrogels based on random copolymers of hydrophilic poly( hydroxyl ethyl acrylate) (PHEA) and hydrophobic poly(ethyl acrylate) (PEA), in wide ranges of composition, were investigated by means of two dielectric techniques, thermally stimulated depolarization currents (TSDC) and, mainly, broadband dielectric relaxation spectroscopy (DRS) at several levels of relative humidity/water content. Water sorption of the hydrogels was studied by equilibrium sorption isother...

Rodri?guez Herna?ndez, Jose? Carlos; Go?mez Ribelles, Jose? Lui?s; Monleo?n Pradas, Manuel; Pissis, P.; Kyritsis, A.; Spanoudaki, A.; Pandis, C.; Hartmann, L.; Pelster, R.; Shinyashiki, N.; Pissis, Polykarpos

2011-01-01

412

Altering toluene 4-monooxygenase by active-site engineering for the synthesis of 3-methoxycatechol, methoxyhydroquinone, and methylhydroquinone.  

Science.gov (United States)

Wild-type toluene 4-monooxygenase (T4MO) of Pseudomonas mendocina KR1 oxidizes toluene to p-cresol (96%) and oxidizes benzene sequentially to phenol, to catechol, and to 1,2,3-trihydroxybenzene. In this study T4MO was found to oxidize o-cresol to 3-methylcatechol (91%) and methylhydroquinone (9%), to oxidize m-cresol and p-cresol to 4-methylcatechol (100%), and to oxidize o-methoxyphenol to 4-methoxyresorcinol (87%), 3-methoxycatechol (11%), and methoxyhydroquinone (2%). Apparent Vmax values of 6.6 +/- 0.9 to 10.7 +/- 0.1 nmol/min/ mg of protein were obtained for o-, m-, and p-cresol oxidation by wild-type T4MO, which are comparable to the toluene oxidation rate (15.1 +/- 0.8 nmol/min/mg of protein). After these new reactions were discovered, saturation mutagenesis was performed near the diiron catalytic center at positions I100, G103, and A107 of the alpha subunit of the hydroxylase (TmoA) based on directed evolution of the related toluene o-monooxygenase of Burkholderia cepacia G4 (K. A. Canada, S. Iwashita, H. Shim, and T. K. Wood, J. Bacteriol. 184:344-349, 2002) and a previously reported T4MO G103L regiospecific mutant (K. H. Mitchell, J. M. Studts, and B. G. Fox, Biochemistry 41:3176-3188, 2002). By using o-cresol and o-methoxyphenol as model substrates, regiospecific mutants of T4MO were created; for example, TmoA variant G103A/A107S produced 3-methylcatechol (98%) from o-cresol twofold faster and produced 3-methoxycatechol (82%) from 1 mM o-methoxyphenol seven times faster than the wild-type T4MO (1.5 +/- 0.2 versus 0.21 +/- 0.01 nmol/min/mg of protein). Variant I100L produced 3-methoxycatechol from o-methoxyphenol four times faster than wild-type T4MO, and G103S/A107T produced methylhydroquinone (92%) from o-cresol fourfold faster than wild-type T4MO and there was 10 times more in terms of the percentage of the product. Variant G103S produced 40-fold more methoxyhydroquinone from o-methoxyphenol than the wild-type enzyme produced (80 versus 2%) and produced methylhydroquinone (80%) from o-cresol. Hence, the regiospecific oxidation of o-methoxyphenol and o-cresol was changed for significant synthesis of 3-methoxycatechol, methoxyhydroquinone, 3-methylcatechol, and methylhydroquinone. The enzyme variants also demonstrated altered monohydroxylation regiospecificity for toluene; for example, G103S/A107G formed 82% o-cresol, so saturation mutagenesis converted T4MO into an ortho-hydroxylating enzyme. Furthermore, G103S/A107T formed 100% p-cresol from toluene; hence, a better para-hydroxylating enzyme than wild-type T4MO was formed. Structure homology modeling suggested that hydrogen bonding interactions of the hydroxyl groups of altered residues S103, S107, and T107 influence the regiospecificity of the oxygenase reaction. PMID:15231803

Tao, Ying; Fishman, Ayelet; Bentley, William E; Wood, Thomas K

2004-07-01

413

Metabolites formed during anaerobic transformation of toluene and o-xylene and their proposed relationship to the initial steps of toluene mineralization.  

OpenAIRE

Strain T1 is a facultative bacterium that is capable of anaerobic toluene degradation under denitrifying conditions. While 80% of the carbon from toluene is either oxidized to carbon dioxide or assimilated into cellular carbon, a significant portion of the remainder is transformed into two dead-end metabolites. These metabolites were produced simultaneous to the mineralization of toluene and were identified as benzylsuccinic acid and benzylfumaric acid. Identification was based on comparison ...

Evans, P. J.; Ling, W.; Goldschmidt, B.; Ritter, E. R.; Young, L. Y.

1992-01-01

414

Benzene partial hydrogenation: advances and perspectives.  

Science.gov (United States)

The partial hydrogenation of benzene to cyclohexene is an economically interesting and technically challenging reaction. Over the last four decades, a lot of work has been dedicated to the development of an exploitable process and several approaches have been investigated. However, environmental constraints often represent a limit to their industrial application, making further research in this field necessary. The goal of this review is to highlight the main findings of the different disciplines involved in understanding the governing principles of this reaction from a sustainable chemistry standpoint. Special emphasis is given to ruthenium-catalyzed liquid phase batch hydrogenation of benzene. PMID:25588547

Foppa, Lucas; Dupont, Jairton

2015-04-01

415

40 CFR 80.1220 - What are the implementation dates for the gasoline benzene program?  

Science.gov (United States)

...the implementation dates for the gasoline benzene program? 80.1220 Section 80.1220...OF FUELS AND FUEL ADDITIVES Gasoline Benzene General Information § 80.1220 ...the implementation dates for the gasoline benzene program? (a) Benzene...

2010-07-01

416

4-(3-Methyl­benzene­sulfonamido)­phenyl 3-methyl­benzene­sulfonate  

OpenAIRE

The complete mol­ecule of the title compound, C20H19NO5S2, is generated by a crystallographic twofold axis and the O atom and N—H group attached to the central benzene ring are statistically disordered. The dihedral angle between the central and terminal benzene rings is 56.91?(5)° and that between the terminal benzene rings is 29.80?(5)°. In the crystal, N—H?O hydrogen bonding links the mol­ecules into sheets lying parallel to the ab plane.

Al-najjar, Belal O.; Tengku Muhammad, Tengku Sifzizul; Wahab, Habibah A.; Rosli, Mohd Mustaqim; Fun, Hoong-kun

2012-01-01

417

4-(3-Methyl-benzene-sulfonamido)-phenyl 3-methyl-benzene-sulfonate.  

Science.gov (United States)

The complete mol-ecule of the title compound, C(20)H(19)NO(5)S(2), is generated by a crystallographic twofold axis and the O atom and N-H group attached to the central benzene ring are statistically disordered. The dihedral angle between the central and terminal benzene rings is 56.91?(5)° and that between the terminal benzene rings is 29.80?(5)°. In the crystal, N-H?O hydrogen bonding links the mol-ecules into sheets lying parallel to the ab plane. PMID:22346904

Al-Najjar, Belal O; Tengku Muhammad, Tengku Sifzizul; Wahab, Habibah A; Rosli, Mohd Mustaqim; Fun, Hoong-Kun

2012-02-01

418

Catalytic performance of the exchanged Y faujasites by Ce3+, La3+, UO22+, Co2+, Sr2+, Pb2+, Tl+ and NH4+ cations in the disproportionation reaction of toluene  

International Nuclear Information System (INIS)

The catalytic performance of exchanged Y faujasites by Ce3+, La3+, UO22+, Co2+, Sr2+, Pb2+, Tl+ and NH4+ ions were studied in a disproportionation reaction in the gaseous phase. It was shown that total acidity generated by exchanged ions is responsible of the catalytic activity. Rare earths (cerium, lanthanum and uranium) catalysts have appreciable performance and allowed one to obtain an important xylenes proportion at 400 to 450 C. The decrease of xylenes and trimethyl-benzenes proportion in studied catalysts shows the implication of xylenes in toluene disproportionation reaction. (authors)

419

2-{2,4,6-Tris(bromo­meth­yl)-3,5-bis­[(1,3-dioxoisoindolin-2-yl)meth­yl]benz­yl}iso­indoline-1,3-dione toluene monosolvate  

OpenAIRE

In the title compound, C36H24Br3N3O6·C7H8, the toluene solvent molecule is associated with the receptor molecule via C—H...? bonding. The planes of the phthalimido groups are inclined at 77.0?(1), 63.0?(1) and 77.8?(1)° with respect to the benzene ring. The molecular conformation is stabilized by C—H...O and C—H...Br hydrogen bonds. The crystal structure features non-classical hydrogen bonds of the C—H...N, C—H...O and C—H...Br type, leading to a three-dimensional cross-l...

Niklas Koch; Wilhelm Seichter; Monika Mazik

2014-01-01

420

Consequences of limiting benzene content of motor gasoline  

Energy Technology Data Exchange (ETDEWEB)

This report considers current motor gasoline benzene levels, related legislation in Western Europe and the consequences of limiting the benzene content of gasoline. The report first reviews the sources of benzene in gasoline and summarises the existing legislation on allowable levels. It then surveys the benzene levels in current motor gasolines and analyses the causes of variations. Means of reducing benzene contents, either by adjusting existing processing routes or by extracting benzene from gasoline blending components, are considered. The impact of benzene limitations on the production of motor gasolines are assessed in terms of the costs involved and the energy penalties incurred. Finally, the report looks at the potential problem of the disposal of extracted benzene. (Copyright (c) CONCAWE Den Haag December 1983.)

Spencer, E.H.; Conrard, M.C.; Cremer, G.; Hancke, J.; De Roocker, A.

1983-01-01