Mixture Of Aliphatic Hydrocarbons Research Articles

Selection of ionic liquids for the extraction of aromatic hydrocarbons from aromatic/aliphatic mixtures

The separation of aromatic hydrocarbons (benzene, toluene, ethyl benzene and xylenes) from C 4 to C 10 aliphatic hydrocarbon mixtures is challenging since these hydrocarbons have boiling points in a close range and several combinations form azeotropes. In this work, we investigated the separation of toluene from heptane by extraction with ionic liquids. Several ionic liquids are suitable for extraction of toluene from toluene/heptane mixtures. The toluene/heptane selectivities at 40 °C and 75 °C with several ionic liquids, [mebupy]BF 4, [mebupy]CH 3SO 4, [bmim]BF 4 (40 °C) and [emim] tosylate (75 °C), are a factor of 1.5–2.5 higher compared to those obtained with sulfolane ( S tol/hept = 30.9, D tol = 0.31 at 40 °C), which is the most industrially used solvent for the extraction of aromatic hydrocarbons from a mixed aromatic/aliphatic hydrocarbon stream. From these five ionic liquids, [mebupy]BF 4 appeared to be the most suitable, because of a combination of a high toluene distribution coefficient ( D tol = 0.44) and a high toluene/heptane selectivity ( S tol/hept = 53.6). Therefore, with [mebupy]BF 4 also extraction experiments with other aromatic/aliphatic combinations (benzene/ n-hexane, ethylbenzene/ n-octane and m-xylene/ n-octane) were carried out. The aromatic/aliphatic selectivities were all in the same range, from which it can be concluded that the toluene/heptane mixture is a representative model system for the aromatic/aliphatic separation.

Determination of the Elemental Composition of Hydrocarbon Mixtures by Gas Chromatography with Atomic Emission Detection: Increasing the Accuracy

In this work, the accuracy of the ratio of the numbers of carbon and hydrogen atoms (nC/nH) determined in the molecules of the components of aliphatic hydrocarbon mixtures by gas chromatography with atomic emission detection (GC-AED) is studied as a function of the oxygen concentration in helium. It is shown that the highest accuracy is achieved at about 9% of oxygen, which is the highest oxygen concentration possible for the Agilent model G2350A GC-AED device. At the standard oxygen concentration (about 1.5%) recommended by the manufacturer, the accuracy of the nC/nH ratios was five to ten times lower. It is shown that improving the accuracy of the nC/nH ratios at the maximum oxygen concentration in plasma is followed by an increase in the detection limit approximately by an order of magnitude.

Increasing the accuracy of determination of nC/ nH ratios by gas chromatography–atomic emission detection

The influence of oxygen content in helium on the accuracy of n C/ n H ratio determination for model mixtures of aliphatic and polyaromatic hydrocarbons and polychlorinated biphenyls was studied. The best accuracy was achieved at the oxygen content ca. 9%, which was the maximal possible oxygen content in helium for this GC–atomic emission detection (helium flow rate was 25 ml min −1). Using the maximal oxygen flow in plasma the n C/ n H ratio determination accuracy improvement was accompanied by 10-fold increase in detection limit.

Polyelectrolyte membranes for aromatic–aliphatic hydrocarbon separation by pervaporation

Different types of membranes based on polyelectrolytes were developed for the separation of aromatic–aliphatic hydrocarbon mixtures by pervaporation (PV). For that purpose, composite membranes with different polyelectrolytes, soluble either in water (sulfoethylcellulose) or in ethanol (custom-made copolymers of methyl methacrylate (MMA) and methacrylic acid [3-sulfo-propyl ester] potassium salt) were prepared by an interfacial reaction with oppositely charged ionic surfactants. The latter copolymer could also be cross-linked with Co 2+ ions. Both membrane types show a clear enrichment of aromatic components (toluene or benzene) in the course of the PV process (from 20 wt.% in the feed to about 55 wt.% in the permeate). The fluxes are in the range of 1 kg/hm 2 at a feed temperature of 80 °C. The separation of a benzene/cyclohexane mixture was also successful at 50 °C. In all cases, higher fluxes were obtained with benzene/cyclohexane feed mixtures than with toluene/heptane mixtures. Also, in multi-component feed mixtures, benzene exhibit the better permeate rates.

Corresponding-states correlation for compressed liquid density of mixtures

Our previous corresponding-states correlation for the prediction of the compressed liquid density of pure substances has been extended to mixtures. The correlation requires the values of critical constants, acentric factor, freezing temperature, liquid density at the freezing point, and an adjustable parameter to determine the saturated liquid densities. The mixtures applied with this correlation are liquefied noble gas and inorganic gas mixtures, mixtures of saturated, aromatic, and aliphatic hydrocarbons, refrigerant mixtures, and mixtures of strongly hydrogen-bonded and polar fluids. The predicted results are compared with the well-known corresponding-states liquid densities by Hankinson et al. and with the correlation recently proposed by Nasrifar et al. It is shown that the present correlation works better than both of them.

Characterization of a new solvent-responsive gene locus in Pseudomonas putida F1 and its functionalization as a versatile biosensor.

A new gene cluster, designated sepABC and a divergently transcribed sepR, was found downstream of the two-component todST phosphorelay system that regulates toluene degradation (the tod pathway) in Pseudomonas putida F1 (PpF1). The deduced amino acid sequences encoded by sepABC show a high homology to bacterial proteins known to be involved in solvent efflux or multidrug pumps. SepA, SepB and SepC are referred to be periplasmic, inner membrane and outer membrane efflux proteins respectively. Effects on growth of various PpF1 mutants compared to that of the wild type in the presence of toluene indicated a possible protective role of the solvent efflux system in a solvent-stressed environment. Growth tests with the complemented mutants confirmed the involvement of the Sep proteins in conferring solvent tolerance. The sepR gene encodes a 260-residue polypeptide that is a member of the E. coli IclR repressor protein family. The repressor role of SepR was established by conducting tests with a sep-lacZ transcriptional fusion in Escherichia coli and PpF1, expression of SepR as a maltose-binding fusion protein in a DNA binding assay, and mRNA analysis. Southern hybridization experiments and analysis of the P. putida KT2440 genome sequence indicated that sepR is a relatively rare commodity compared to homologues of the sepABC genes. We developed a whole-cell bioluminescent biosensor, PpF1G4, which contains a chromosomally based sep-lux transcriptional fusion. The biosensor showed significant induction of the sepABC genes by a wide variety of aromatic molecules, including benzene, toluene, ethylbenzene, and all three isomers of xylene (BTEX), naphthalene, and complex mixtures of aliphatic and aromatic hydrocarbons. PpF1G4 represents a second-generation biosensor that is not based on a catabolic promoter but is nonetheless inducible by aromatic pollutants and moreover functional under nutrient-rich conditions.

Degradation of straight-chain aliphatic and high-molecular-weight polycyclic aromatic hydrocarbons by a strain of Mycobacterium austroafricanum.

Our goal was to characterize a newly isolated strain of Mycobacterium austroafricanum, obtained from manufactured gas plant (MGP) site soil and designated GTI-23, with respect to its ability to degrade polycyclic aromatic hydrocarbons (PAHs). GTI-23 is capable of growth on phenanthrene, fluoranthene, or pyrene as a sole source of carbon and energy; it also extensively mineralizes the latter two in liquid culture and is capable of extensive degradation of fluorene and benzo[a]pyrene, although this does not lead in either of these cases to mineralization. Supplementation of benzo[a]pyrene-containing cultures with phenanthrene had no significant effect on benzo[a]pyrene degradation; however, this process was substantially inhibited by the addition of pyrene. Extensive and rapid mineralization of pyrene by GTI-23 was also observed in pyrene-amended soil. Strain GTI-23 shows considerable ability to mineralize a range of polycyclic aromatic hydrocarbons, both in liquid and soil environments. In this regard, GTI-23 differs markedly from the type strain of Myco. austroafricanum (ATCC 33464); the latter isolate displayed no (or very limited) mineralization of any tested PAH (phenanthrene, fluoranthene or pyrene). When grown in liquid culture, GTI-23 was also found to be capable of growing on and mineralizing two aliphatic hydrocarbons (dodecane and hexadecane). These findings indicate that this isolate of Myco. austroafricanum may be useful for bioremediation of soils contaminated with complex mixtures of aromatic and aliphatic hydrocarbons.

Interfacial tension of chlorinated aliphatic DNAPL mixtures as a function of organic phase composition.

This research evaluates the ability of three models to predict the organic liquid-water interfacial tension (IFT) of chlorinated aliphatic hydrocarbon mixtures that are dense nonaqueous-phase liquids (DNAPLs). Prediction of the IFT is relevantto quantify processes such as DNAPL trapping in soil pores and kinetic interphase mass transfer. Three models are evaluated: the Fu et al. method (FU) [Fu, J.; Buqiang, L.; Zihao, W. Chem. Eng. Sci. 1986,41 (10), 2673-2679]; a modified version of the Apostoluk and Szymanowski method (AS) [Apostoluk, W.; Szymanowski, J. Solvent Extr. Ion Exch. 1996, 14 (4), 635-651], and a simple linear ideal mixing theory (LIMT). The FU and AS methods require knowledge of NAPL-phase mole fractions and mutual solubilities. The LIMT method requires the pure organic liquid IFT and DNAPL-phase mole fraction as model input. Forty chlorinated DNAPL mixtures were used. The mixtures include two-, three-, and four-component DNAPL mixtures of tetrachloroethylene, trichloroethylene, 1,2-cis-dichloroethylene, 1,2-trans-dichloroethylene, and carbon tetrachloride. Measured IFTvaries nearlylinearlywith DNAPL-phase mole fraction for the all the DNAPL mixtures except those that include 1,2-DCE. The FU and LIMT models generally provided acceptable results for all mixtures. The FU model yielded an average relative error in the predicted IFT of 6.4%, while the LIMT model exhibited an average error of 9.3%. The AS method exhibited an average error of 16.4%.

Adsorption of hydrocarbons from gas-air mixture on polypropylene stereoisomers

Kinetics of absorption of a mixture of aliphatic, aromatic, and unsaturated hydrocarbons from the gas phase onto polypropylene containing 5, 18, and 40% atactic polymer in its molecular lattice was studied. The kinetic parameters, equilibrium constant, and Gibbs energy of adsorption-desorption of the hydrocarbons were determined by zero-, first-, and second-order optimization of the solution of the multiparameter equation. These parameters were correlated with the adsorbent composition and the number of sorption-desorption cycles.

Effects of white spirits on rat brain 5-HT receptor functions and synaptic remodeling

Previously, inhalation exposure to different types of white spirit (i.e. complex mixtures of aliphatic, aromatic, alkyl aromatic, and naphthenic hydrocarbons) has been shown to induce neurochemical effects in rat brains. Especially, the serotonergic system was involved at the global, regional, and subcellular levels. This study investigates the effects of two types of white spirit on 5-hydroxytryptamine (5-HT) transporters (5-HTT), 5-HT 2A and 5-HT 4 receptor expression in forebrain, and on neural cell adhesion molecule (NCAM) and 25-kDa synaptosomal associated protein (SNAP-25) concentrations when applied as indices for synaptic remodeling in forebrain, hippocampus, and entorhinal cortex. Male Wistar rats were exposed to 0, 400, or 800 ppm of aromatic (20 vol.% aromatic hydrocarbons) or dearomatized white spirit (catalytically hydrogenated white spirit) in the inhaled air for 6 h/day, 7 days/week for 3 weeks. The 5-HTT B max and K d were not affected. Both types of white spirit at 800 ppm decreased B max for the 5-HT 2A receptor. The aromatic type decreased the K d of the 5-HT 2A and 5-HT 4 receptors at 800 ppm. Aromatic white spirit did not affect NCAM or SNAP-25 concentrations or NCAM/SNAP-25 ratio in forebrain, whereas NCAM increased in hippocampus and the NCAM/SNAP-25 ratio decreased in entorhinal cortex. Dearomatized white spirit did not affect NCAM, SNAP-25, or NCAM/SNAP-25 ratio in any brain region. The affected 5-HT receptor expression and synaptic plasticity marker proteins indicate that inhalation exposure to high concentrations of white spirit may be neurotoxic to rats, especially the aromatic white spirit type.

Ubiquitous occurrence of high molecular weight hydrocarbons in crude oils

For many years the presence of waxes in crude oils has been associated with organic matter derived from terrigenous sources. High temperature gas chromatography (HTGC) has been used to establish the ubiquitous presence of high molecular weight (HMW) hydrocarbons, extending as high as C120, in crude oils. HMW hydrocarbons (>C40+) have been observed in crude oils derived from terrigenous, lacustrine, and marine source materials. Modified extraction techniques have also led to the detection of HMW hydrocarbons in source rock extracts. The fractions of HMW hydrocarbons are complex mixtures of long-chain aliphatic and alkyl-aromatic hydrocarbons, and can represent up to 8% of a whole oil. The carbon preference index (CPI) of HMW alkylcyclopentanes in the C42–C46 range provides useful information on the characteristics of the original depositional environment. Age, maturity, and degree of biodegradation do not appear to affect the CPI of alkylcyclopentanes used for evaluating depositional environments. Differences in the distributions of the HMW hydrocarbons between the source rock extracts and the crude oils in the reservoirs may reflect changes occurring due to migration.

Correlation, verification and prediction of vapour–liquid equilibria using equation of state with association term: I. Alcohols+aliphatic hydrocarbons

The equation of state with association term (EoSC) developed by Góral, was used to correlate all available binary VLE data sets for mixtures of alcohols with aliphatic hydrocarbons. The self-association of alcohol has been described with the model of Mecke and Kempter. The same mixture independent association constant was used for all alcohols except of methanol and its deuterium substituted derivatives. The temperature dependence of the association constant was approximated with van’t Hoff equation using the same enthalpy of association for all alcohols. The correlation of the VLE data with one binary interaction parameter was compared with the accuracy of the Wilson equation for G E. The method of the Hilbert space was used to develop formulae to predict the binary interaction parameter in EoSC. Using this parameter, VLE can be calculated for the systems for which no experimental data are available. The verification of the VLE data for mixtures of alcohols and aliphatic hydrocarbons is described and recommended data are given.

Alteration and release of aliphatic compounds by the polychaete Nereis virens (Sars) experimentally fed with hydrocarbons.

In the laboratory, marine worms were fed with a mixture of algae and several aliphatic hydrocarbons for 15 days. After ingestion by the worms, 34.9% of hydrocarbons are found in the faeces and only 3.1% accumulated in the gut. The comparison between the initial mixture and the faeces shows that the worm's digestive process lead to changes in the distribution of the n-alkane mixture. These changes are different from those only due to physical processes in the experimental conditions. In our experiment, no variation in the distribution of hydrocarbons in faeces with time and no microbial hydrocarbon biodegradation were evidenced. Our results suggest that marine worm feeding can substantially affect the fate of hydrocarbons in the sedimentary marine ecosystem by predominantly stimulating dissolution processes.

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Degradation of coals and chars from poly(vinyl chloride) (PVC) and mixtures of PVC with other polymers such as polyethylene glycol, poly(vinyl alcohol), polystyrene, and polyethylene using a mixture of copper(II) oxide (CuO) and aqueous potassium carbonate solution at 500 °C to give a mixture of aliphatic and aromatic hydrocarbons, carbon dioxide, potassium hydrogencarbonate, and water soluble and easily decomposable materials with dilute hydrochloric acid. It was revealed that CuO promoted the decomposition of highly aromatized materials such as chars from PVC or coals and the preferential formation of benzene in the decomposition of those materials.

Sources, Distribution, and Water Column Processes of Aliphatic and Polycyclic Aromatic Hydrocarbons in the Northwestern Black Sea Water

Aliphatic and aromatic hydrocarbons have been determined in (28 samples) suspended particulate matter (>0.7 μm) collected at subsurficial seawater and three vertical profiles in a transect from the continental shelf, slope, and deep basin (15 samples) of the western Black Sea. The dissolved phase (<0.7 μm) was collected at subsurficial and in the redoxcline (6 subsurficial and 5 deeper). The highest concentrations of hydrocarbons were detected in the Danube, Dnieper, and Dniester River Estuaries and other point sources of pollution located offshore Romania and Bulgaria where oil production and refining is carried out (i.e., Constantza, Varna). Concentrations of hydrocarbons decreased with increasing distance from the coast, but relatively high concentrations were found at the open stations where the particulate organic carbon (POC) is higher. Fossil PAHs are predominant in the coastal stations, and the unresolved complex mixture (UCM) of aliphatic hydrocarbons is predominantly of a fossil common origin ac...

Field test of high molecular weight alcohol flushing for subsurface nonaqueous phase liquid remediation

A pilot scale field test of non‐aqueous phase liquid (NAPL) removal using high molecular weight alcohols was conducted at Operable Unit 1, Hill Air Force Base, Utah. Petroleum hydrocarbons and spent solvents were disposed of in chemical disposal pits at this site, and these materials are now present in the subsurface in the form of a light non‐aqueous phase liquid (LNAPL). This LNAPL is a complex mixture of aromatic and aliphatic hydrocarbons, chlorinated solvents, and other compounds. The field experiment was performed in a 5 m by 3 m confined test cell, formed by driving interlocking sheet pile walls through the contaminated zone into an underlying clay. The test involved the injection and extraction of about four pore volumes (1 pore volume=7000 L) of a mixture of 80% tert‐butanol and 15% n‐hexanol. The contaminants were removed by a combination of NAPL mobilization and enhanced dissolution, and the results of postflood soil coring indicate better than 90% removal of the more soluble contaminants (trichloroethane, toluene, ethylbenzene, xylenes, trimethylbenzene, naphthalene) and 70–80% removal of less soluble compounds (decane and undecane). The results of preflood and postflood NAPL partitioning tracer tests show nearly 80% removal of the total NAPL content from the test cell. The field data suggest that a somewhat higher level of removal could be achieved with a longer alcohol injection.

Detoxification of a mixture of aliphatic chlorinated hydrocarbons in a fixed-bed bioreactor: Continuous on-line monitoring via an attenuated total reflection-fourier transform infrared sensor

A methanogenic microbial community immobilised on an inert carrier was acclimated to a mixture of chlorinated aliphatic hydrocarbons in a bioreactor used for their detoxification. The mixture contained trichloroethylene (TCE), tetrachloroethylene (PCE), carbon tetrachloride (CT) and hexachlorobutadiene (HCB). An attenuated total reflection-Fourier transform infrared (ATR-FTIR) optical sensor was developed for continuous on-line measurements of the toxic compounds in the dechlorinating bioreactor. The sensor consisted of an ATR internal reflection element (IRE) coated with an extracting polymer which was continuously enriched with the toxic compounds. The bioprocess was monitored through the sensor, which was coupled permanently to the bioreactor, over a period of three days of continuous operation. The sensor tracked the progression of absorbance spectra over time in a non-invasive manner. The concentration of organochlorine compounds in the bioreactor was predicted from the absorbance spectra using a partial least squares (PLS) calibration model which was developed for all components simultaneously. The accuracy and reproducibility of this ATR-FTIR sensor was tested by checking the spectra-based concentration values of the toxic analytes in the bioreactor effluents against off-line gas chromatography (GC) measurements. This novel sensor is useful for routine continuous on-line monitoring of the dechlorinating bioreactor.

Characterization of organic compounds in compost-amended soil

Samples of compost-amended soil from waste dumping sites in Lagos Metropolis were extracted with dichloromethane (3 × 20 cm3) and the extract was evaporated at 35 °>C. The residue was extracted with 2,2,4-trimethylpentane, and portions of the solution were applied to a column containing silica gel from which aliphatic and aromatic hydrocarbons were eluted with n-hexane and toluene respectively. Analysis of the n-hexane fraction using gas chromatography showed the presence of a mixture of aliphatic hydrocarbons, ranging from C9 to C25, while ultraviolet analysis of the toluene fraction suggested 1,2-benzanthracene; 2,3-benzphenanthrene, chrysene and pyrene as polyaromatic compounds present in samples analyzed. The crude extracts were highly coloured and viscous. Total extractable organic residues in the 2,2,4-trimethylpentane extracts ranged from 36 to 89 mg g-1 of soil.

Comparison of TCE Transformation Abilities of Methane- and Propane-Utilizing Microorganisms

Subsurface microorganisms from McClellan Air Force Base (AFB) were grown in batch aquifer microcosms on methane, propane, and butane to evaluate the potential for aerobic trichloroethylene (TCE) cometabolism. Microorganisms stimulated on all three substrates indicated the existence of a subsurface microbial community capable of utilizing alkanes as growth substrates. Initial growth substrate utilization lag periods of 2 weeks for methane and 3 weeks for propane and butane were observed. Methane- and propane-utilizers were active toward TCE cometabolism, whereas butane-utilizers showed no ability to transform TCE. Gradually increasing TCE concentrations were effectively transformed with uniform additions of methane and propane for up to 1 year. TCE was transformed most rapidly during active methane utilization, and continued at a slower rate for approximately 1 week after methane was consumed. Propane microcosms maintained first-order TCE transformation for up to 4 weeks after propane was consumed. The microbial communities remained active toward primary substrate utilization as the TCE concentration was gradually increased. Both methane- and propane-utilizers showed positive correlations between TCE transformation rates and primary substrate utilization rates. Observed maximum TCE transformation yields were 0.068 g TCE/g methane and 0.048 g TCE/g propane. The methane-utilizers also transformed chloroform (CF) but not 1,1,1-trichloroethane (1,1,1-TCA). Propane-utilizers transformed both CF and 1,1,1-TCA, indicating they were better suited for cometabolizing chlorinated aliphatic hydrocarbon mixtures in the McClellan AFB subsurface.

Performance studies of various cracking catalysts in the conversion of canola oil to fuels and chemicals in a fluidized‐bed reactor

AbstractStudies were conducted at atmospheric pressure at temperatures in the range of 400–500°C and fluidizing gas velocities in the range of 0.37–0.58 m/min (at standard temperature and pressure) to evaluate the performance of various cracking catalysts for canola oil conversion in a fluidized‐bed reactor. Results show that canola oil conversions were high (in the range of 78–98 wt%) and increased with an increase in both temperature and catalyst acid site density and with a decrease in fluidizing gas velocity. The product distribution mostly consisted of hydrocarbon gases in the C1–C5 range, a mixture of aromatic and aliphatic hydrocarbons in the organic liquid product (OLP) and coke. The yields of C4 hydrocarbons, aromatic hydrocarbons and C2–C4 olefins increased with both temperature and catalyst acid site density but decreased with an increase in fluidizing gas velocity. In contrast, the yields of aliphatic and C5 hydrocarbons followed trends completely opposite to those of C2–C4 olefins and aromatic hydrocarbons. A comparison of performance of the catalysts in a fluidized‐bed reactor with earlier work in a fixed‐bed reactor showed that selectivities for formation of both C5 and iso‐C4 hydrocarbons in a fluidized‐bed reactor were extremely high (maximum of 68.7 and 18 wt% of the gas product) as compared to maximum selectivities of 18 and 16 wt% of the gas product, respectively, in the fixed‐bed reactor. Also, selectivity for formation of gas products was higher for runs with the fluidized‐bed reactor than for those with the fixed‐bed reactor, whereas the selectivity for OLP was higher with the fixed‐bed reactor. Furthermore, both temperature and catalyst determined whether the fractions of aromatic hydrocarbons in the OLP were higher in the fluidized‐bed or fixed‐bed reactor.