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In this work the physical-chemical properties of asphaltene-resin-paraffin deposits are studied. Their component composition was determined. The results obtained are the basis for the selection of effective solvents and the choice of the method of removing deposits from oil reservoirs. Two hydrocarbon solvents with the brands "TSK A" and "TSK B" were tested. The solvent ability of solvents was tested. [ABSTRACT FROM AUTHOR]

A study was carried out on the effect of surfactant-depressants such as Paraflow, Santopur, poly(alkyl methacrylate), and oxidized petrolatum on the temperatures of dissolution, crystallization, and solidification of solutions of natural and synthetic paraffins in various types of hydrocarbon solvents differing in composition and viscosity. The activity of the depressant should be evaluated relative to paraffin content and development of dispersed structure, which it prevents in the given solvent. Hysteresis was found for the temperatures of the onset of crystallization and dissolution of the paraffin in solvents with added depressant. Paraflow is not considered a micellar surfactant but forms molecular complexes with n-paraffins. [ABSTRACT FROM AUTHOR]

The temperatures of the beginning of crystallization and solidification of solutions of petroleum and synthetic paraffins of different concentrations in nonpolar and weakly polar hydrocarbon solvents of different composition and viscosity are studied. Paraffins of different origin and hydrocarbon composition and with similar melting points are shown to have slightly different crystallization and solidification temperatures in a given solvent. The range between the temperatures of the beginning of crystallization and solidification of the studied paraffin solutions is established. [ABSTRACT FROM AUTHOR]

The results of a study of melting the commercial waxes in the composition of asphaltene-resin-paraffin deposits and for comparison of petroleum waxes in multicomponent solvents of various nature are presented. It was found that with an increase in the amount of the aliphatic component in the solvent, the content of the crystalline phase in paraffin wax rises. Patterns in the variation of paraffin melting temperatures depending on the content of the crystalline phase were revealed. Recommendations for choosing an effective solvent for removing deposits under conditions of permafrost influence are suggested. [ABSTRACT FROM AUTHOR]

This paper studies the effect of solvent chemical nature on the kinetic parameters of dissolution and the morphology of the petroleum waxes. The kinetics of the petroleum wax dissolution in gas condensate and the hexane-cyclohexane-benzene mixture was examined on the torsion balance within the temperature range from 10 to 40°C. The process was described using the Erofeev-Kolmogorov equation. The following kinetic parameters were calculated: reaction rate, the order of reactions and effective energy for activation the wax dissolution in the studied solvents. It was found that the wax dissolution rate in the ternary composite is an order of magnitude greater and the activation energy is three times less in comparison with the process of wax dissolution in the gas condensate. The morphological features of the wax samples, treated by these solvents, were examined by means of scanning electron microscopy. It was found that in the ternary composite, wax has a porous structure and in the gas condensate, it is compressed. Thus, the identified kinetic and morphological behavior of petroleum waxes indicates the influence of the chemical nature of the solvent. The findings of this study can be useful when choosing a solvent for the paraffin deposits removal. [ABSTRACT FROM AUTHOR]

The European chemical control regulation (REACH) requires that data on physical/chemical, toxicological and environmental hazards be compiled. Additionally, REACH requires formal assessments to ensure that substances can be safely used for their intended purposes. For health hazard assessments, reference values (Derived No Effect levels, DNELs) are calculated from toxicology data and compared to estimated exposure levels. If the ratio of the predicted exposure level to the DNEL, i.e. the Risk Characterization Ratio (RCR), is less than 1, the risk is considered controlled; otherwise, additional Risk Management Measures (RMM) must be applied. These requirements pose particular challenges for complex substances. Herein, “white spirit”, a complex hydrocarbon solvent, is used as an example to illustrate how these procedures were applied. Hydrocarbon solvents were divided into categories of similar substances. Representative substances were identified for DNEL determinations. Adjustment factors were applied to the no effect levels to calculate the DNELs. Exposure assessments utilized a standardized set of generic exposure scenarios (GES) which incorporated exposure predictions for solvent handling activities. Computer-based tools were developed to automate RCR calculations and identify appropriate RMMs, allowing consistent communications to users via safety data sheets. [ABSTRACT FROM AUTHOR]

Hydrocarbon solvents are liquid hydrocarbon fractions, often with complex compositions. Due to the potential for human exposure, primarily to the more volatile solvents, substantial effort has been directed toward the development of occupational exposure recommendations. Because of the complex and variable nature of these substances, a proposed approach is to calculate occupational exposure levels (OELs) using an adaptation of the mixture formula developed by the ACGIH® in which “group guidance values” are assigned to similar constituents. This approach is supported by the results of toxicological studies of hydrocarbon solvents and their constituents which have shown that, with a few well-characterized exceptions, these substances have similar toxicological properties and produce additive effects. The objective of the present document is to summarize recommended revisions to the earlier proposals; these recommendations take into account recent toxicological information and changes in regulatory advice. Practical demonstrations on how to use these recommendations to develop occupational exposure advice in different situations (from simple complex solvents to blends of complex solvents) are also provided. Finally, a quantitative ideal gas method is proposed as a means of calculating occupational exposure limits for solvent blends in which, because the blended components have differing vapor pressures, there may be substantial differences between the liquid and vapor phase compositions. [ABSTRACT FROM PUBLISHER]

• Diffusion coefficients of C 2 H 6 and CO 2 in some hydrocarbon solvents were predicted by molecular dynamics simulation. • COMPASS force field showed better predictions in comparison with other force fields (Universal, Dreiding, Cvff, and Pcff). • Effect of temperature on the diffusivities and the activation energies and pre-exponential constants were determined. In this paper, the diffusion coefficients of C 2 H 6 and CO 2 in various hydrocarbon solvents have been determined using molecular dynamics simulation at different temperatures and atmospheric pressure. Effect of force field type and number of cell molecules on MD simulation results were investigated. The optimum number of molecules in amorphous cell was obtained and it was found that COMPASS force field showed the best result in comparison with the other investigated force fields forces (Universal, Dreiding, Cvff, and Pcff). In addition, the diffusion coefficients of ethane and CO 2 were found to comply with the Stokes–Einstein equation. These coefficients were calculated from the slope of mean square displacement (MSD) curves. Temperature changes also showed an increasing effect on the diffusion coefficients and the activation energies (Ea) and pre-exponential constants (D 0) for C 2 H 6 diffusion in heptane and hexane solvents were obtained using Arrhenius theory. The simulated results indicated a good agreement with the experimental data for C 2 H 6 in heptane, hexane, octane, dodecane, and hexadecane solvents and CO 2 in hexadecane solvent. [ABSTRACT FROM AUTHOR]

For a supercritical gas such as hydrogen, thermodynamic models for Henry's constant, partial molar volume, and partial molar enthalpy are sufficient in representing the thermodynamics of hydrogen-containing systems at infinite dilution. This work presents a generalized method and correlations for Henry's constant in binary systems containing hydrogen as a function of temperature. Experimental vapor–liquid equilibrium data were used to obtain this Henry's constant correlation with (i) three specific parameters, (ii) one specific parameter, and (iii) no specific parameter. These three Henry's constant correlations for hydrogen vary in the degrees of generalization and accuracy. A generalized corresponding states correlation for partial molar enthalpy of hydrogen in hydrocarbon systems at infinite dilution was derived from the newly developed Henry's constant correlation and from a correlation for infinite-dilution partial molar volumes of hydrogen available in the literature. Overall, this work provides the most extensive method for infinite-dilution thermodynamic properties of hydrogen-containing systems. [ABSTRACT FROM AUTHOR]

Saturated and unsaturated, linear, branched, and cyclic hydrocarbons, as well as polyaromatic and heteroaromatic hydrocarbons, were successfully ionized by atmospheric pressure chemical ionization (APCI) using small hydrocarbons as reagents in a linear quadrupole ion trap (LQIT) mass spectrometer. Pentane was proved to be the best reagent among the hydrocarbon reagents studied. This ionization method generated different types of abundant ions (i.e., [M + H], M, [M - H] and [M - 2H]), with little or no fragmentation. The radical cations can be differentiated from the even-electron ions by using dimethyl disulfide, thus facilitating molecular weight (MW) determination. While some steroids and lignin monomer model compounds, such as androsterone and 4-hydroxy-3-methoxybenzaldehyde, also formed abundant M and [M + H] ions, this was not true for all of them. Analysis of two known mixtures as well as a base oil sample demonstrated that each component of the known mixtures could be observed and that a correct MW distribution was obtained for the base oil. The feasibility of using this ionization method on the chromatographic time scale was demonstrated by using high-performance liquid chromatography (HPLC) with hexane as the mobile phase (and APCI reagent) to separate an artificial mixture prior to mass spectrometric analysis. [ABSTRACT FROM AUTHOR]

This article reports neurobehavioral tests in rats with C5-C11 isoparaffinic and cycloparaffinic hydrocarbons. Testing, conducted shortly after exposure, evaluated the effects in several domains including clinical effects, motor activity, functional observations, and visual discrimination performance. Isopentane and cyclopentane did not produce any evidence of acute central nervous system (CNS) effects at levels up to 20 000 mg/m3. A C6/C7 mixed cycloparaffinic solvent produced minor, reversible changes in latency to response in visual discrimination testing at 14 000 mg/m3; the no-effect level was 4200 mg/m3. A C8 isoparaffin produced no effects at 14 000 mg/m3, the highest level tested. A C9/C11 isoparaffinic solvent produced minor acute CNS effects at 5000 mg/m3, with 1500 mg/m3 as the no-effect level. A C10 cycloparaffinic solvent did not produce any statistically significant CNS effects at 5000 mg/m3. These studies were designed to provide data that may be useful in setting occupational exposure limits for C5-C11 isoparaffinic and cycloparaffinic hydrocarbons. [ABSTRACT FROM PUBLISHER]

This article reports the results of neurobehavioral tests on C5-C10 normal paraffinic constituents (n-paraffins). Shortly after exposure, effects were evaluated in several domains including clinical effects, motor activity, functional observations, and visual discrimination performance. The representative C 5 n-paraffin, n-pentane, did not produce any evidence of acute central nervous system (CNS) effects at levels up to 20 000 mg/m3. Similarly, there was no compelling evidence that n-octane (C8) produced CNS effects at 14 000 mg/m3, the highest concentration tested. n-decane (C10) produced minor, reversible acute CNS effects at 5000 mg/m 3, with 1500 mg/m3 as the no-effect level. Consistent with literature data, there seemed to be a relationship between increasing molecular weight up to C10 and acute CNS effects. However, the CNS effects were reversible. Repeated exposures did not provide evidence of metabolic induction. [ABSTRACT FROM PUBLISHER]

Bitumen miscibility in low-molecular-weight hydrocarbon liquids was evaluated. The presence of toluene in bitumen-solvent blends improved bitumen miscibility and led to the delay in onset of asphaltenes precipitation due to the dipole-dipole and heteromolecular interactions. For heavy naphtha, the results showed reduced asphaltenes precipitation and enthalpy of mixing due to strong hydrogen bonding and moderate homomolecular interactions. Hexane and light naphtha systems showed higher heats of mixing and higher asphaltenes precipitation due to homomolecular interactions. The best miscibility characteristics of heavy petroleum were obtained with aromatic solvents and solvent mixtures that contained increasing composition of toluene. [ABSTRACT FROM AUTHOR]

Abstract: The growth kinetics for AgI nanoparticles formed in the solutions of water/AOT reverse micelles in n-hexane, n-octane, n-decane, and n-dodecane were investigated. In small micelles, the rate of nanoparticles growth was found to be independent of the type of solvent, while in large micelles the growth rate grew with increasing length of solvent molecules. The effect was explained by a different amount of free water in the micelle pools of the same size. [Copyright &y& Elsevier]

This review of the toxicology of mineral spirits covers studies of the major classes of mineral spirits and several toxicologically important mineral spirit constituents. This review cites data from numerous previously unpublished animal toxicology studies conducted on mineral spirits during the past 30 years, expanding the existing database on the toxicology of this group of hydrocarbon solvents. The data can be used to better evaluate the potential effects associated with exposure to these materials, including health and environmental reviews such as the U.S. Environmental Protection Agency High Production Volume (HPV) chemical program and the Organization for Economic Cooperation and Development (OECD) HPV Screening Information Data Set (SIDS) program. The majority of animal toxicology studies in the available literature were conducted on mineral spirits categorized as ASTM D235 Type I Class A (149°C to 213°C boiling range; 8% to 22% aromatics) and demonstrate that Type I Class A mineral spirits have a low order of acute toxicity and do not produce significant systemic effects. Some additional studies conducted with ASTM D235 Type II Class C mineral spirits (177°C to 213°C boiling range; < 2% aromatics) suggest that Type II Class C mineral spirits have similar toxicity to Type I Class A mineral spirits, though there is some evidence that Type II, Class C mineral spirits have a lesser degree of central nervous system (CNS) effects than the higher aromatic containing Type I Class A materials. In addition, toxicity data on selected chemical constituents of mineral spirits (e.g., n-nonane, n-decane, n-undecane) indicate that these chemicals have similar toxicological properties to mineral spirits. Overall, the data showed that mineral spirits have a low order of acute toxicity and do not appear to produce toxicologically relevant systemic effects. Ongoing studies are evaluating the concerns associated with chronic low-level exposure and central nervous system effects. [ABSTRACT FROM AUTHOR]

Abstract: In order to form nanocarbon materials, an arc discharge plasma method in hydrocarbon solvent is developed. In the case that the arc discharge is performed in toluene with nickel electrodes, tube-like nanocarbons were formed from toluene. The catalysis of the metal electrodes is found to be an important factor for the formation of the nanocarbons by the arc discharge in toluene. This method has a possibility of forming carbon nanotubes from liquid state solvents as a new carbon source by using catalyst ingredient as discharge electrodes. [Copyright &y& Elsevier]

Viscosity-temperature correlation has been developed for light hydrocarbon solvents. The correlation is based on one-parameter viscosity model developed by Puttagunta et al. (Chem. Eng. Res. Des., Vol 70, 1992, p 627-631) for conventional crude oils, which has been modified by incorporating a solvent viscosity reduction factor, Φ. The correlation was compared with the model of Puttagunta et al. on 22 light hydrocarbon solvents for a total of 318 data points. The average absolute deviation improves to 1.9%, compared with 2.2% obtained with the model over a temperature range from -54.41 to 160 °C. The correlation can accurately predict the viscosity of any light hydrocarbon solvent without the need to determine multiple characteristic parameters. This eliminates the consumption of time, energy, and money by costly and cumbersome calculations. [ABSTRACT FROM AUTHOR]

Objectives: To determine which exposure metrics are sufficient to characterize ‘peak’ inhalation exposure to organic solvents (OS) during spraying operations.Methods: Personal exposure measurements (n = 27; duration 5–159 min) were collected during application of paints, primers, resins and glues in 15 companies. A MiniRAE Photo-Ionization Detector measured OS concentrations every second. These readings were adjusted for OS composition, which was determined by charcoal tubes. A peak was defined as a period during which exposure exceeded the time-weighted average (TWA) exposure. Five second and 1 and 15 min moving average times were considered in defining a peak. The number of peaks per hour, the duration of a peak, the maximum concentration within a peak, the average concentration within a peak, the ratio between maximum and average concentration within a peak and the average time between two peaks were recorded for each sample. Data were analyzed using factor analysis on 13 variables for the 27 samples: TWA concentration of the task and the six peak characteristics based on the 5 s and 1 min moving averaging time.Results: There were three statistically independent sources of correlation among metrics of peak exposure, explaining 87% of the multiple correlation. The first factor reflected the intensity of peak exposure; it was also associated with the TWA. The second and third factors were related to measures of variability (in frequency and intensity) and duration of peaks, respectively.Conclusions: We present a method for describing peak profiles for inhalation exposure in terms of various distinguishable and independent parameters. Pending development of toxicologically justified peak exposure metrics, such investigations can be of value in identifying exposure metrics for which non-confounded risk estimates can be obtained in epidemiological studies. [ABSTRACT FROM AUTHOR]

In the present work, the effects of aliphatic (n-nonane and n-decane), alicyclic (1,2,4-trimethylcyclohexane and tert-butylcyclohexane, t-BCH) and aromatic (trimethylbenzene and tert-butylbenzene) hydrocarbon solvents on formation of reactive oxygen species (ROS) and the proinflammatory cytokine TNF-α in rat alveolar macrophages (AM) have been investigated. Formation of ROS was assessed by monitoring oxidation of 2′,7′-dichlorofluorescin to 2′,7′-dichlorofluorescein (DCF), and the proinflammatory cytokine tumour necrosis factor α (TNF-α) was detected using an enzyme-linked immunosorbent assay. DCF fluorescence was elevated in a concentration-dependent manner by the alicyclic hydrocarbons. The involvement of transcellular signalling pathways in the production of ROS by t-BCH, the most active compound, was elucidated by use of specific inhibitors. Preincubation of the AM with the mitogen-activated protein kinase (ERK 1/2) inhibitor U0126, the protein kinase C inhibitor bisindolylmaleimide, the superoxide dismutase inhibitor diethyldithiocarbamate, and the iron ion chelating agent deferoxamine reduced the DCF fluorescence significantly. t-BCH gave an increase in TNF-α release. Further, nitric oxide production measured by a modified Griess method, and intracellular calcium concentration measured by fura-2, were increased in the rat AM after exposure to t-BCH. [ABSTRACT FROM AUTHOR]

The methoxy-substituted aromatic reagents 1,2- and 1,3-dimethoxybenzene (1,2-DMB and 1,3-DMB) and 1,2,4-trimethoxybenzene (1,2,4-TMB) each undergo directed ortho-metalation in high yield in n-BuLi/hydrocarbon media without the aid of a catalyst. These reactions, coined ‘substrate-promoted ortho-metalations’, proceed with the methoxy aromatic substrate functioning as both the directing metalation group (DMG) and as the deoligomerization agent. Evidence that the substrates themselves serve to deoligomerize n-BuLi comes from 13C NMR. The relative extent of metalated product formed as a function of time for each of the three aromatics directly correlates with the substrate''s time-dependent ability to coordinate to n-BuLi as measured by 13C NMR. The interpretation of NMR results from experiments involving 1,2,4-TMB is consistent with the metalation proceeding via the activated complex [(1,2,4-TMB)2·(n-BuLi)2]. Finally, conclusions from solubility experiments are that for every substrate-promoted metalation investigated, a precipitate forms in the hydrocarbon solvent, and this precipitate mostly contains the ortho-lithiated aryl intermediate. [Copyright &y& Elsevier]

Studies of workers exposed to hydrocarbon solvents are reviewed in order to address the question, ‘Does long-term human exposure to hydrocarbon solvents at concentrations around occupational exposure limits result in clinically important neurobehavioural effects?’ Studies selected evaluated exposure-response (E-R) trends with some control of potential confounders. Tests of neurobehavioural performance were classified into specific functional categories, within those of cognitive, psychomotor and sensory functions to increase specificity and power to detect patterns of effect. The weight-of-evidence was evaluated with respect to criteria for determining causality. The temporality criterion was met as latency was adequate for the occurrence of chronic effects. There were few significant associations, and when present, were consistently weak even in the most-exposed workers. Exposure response showed no consistent or significant pattern for any tests of functional mortality. The weight of evidence suggests that exposure to hydrocarbon solvents at current limits does not appear to cause adverse neurobehavioural effects. [ABSTRACT FROM PUBLISHER]

The possibility of increase of microsomal enzyme activities in the liver by inhaled hydrocarbon solvents has been tested in preliminary investigations with male Wistar rats. The animals were exposed 5 hrs per day to an atmosphere containing various solvents, in a test period of 10 or 28 days. Dichloromethane, carbon tetrachloride, trichloroethylene, and benzene in a concentration of 450-500 ppm caused slight increases of cytochrome P and/or of aminopyrine demethylase activity after 10 days ( P>0.02). At a test period of 28 days already 50 ppm of carbon tetrachloride led to an increase of cytochrome P in the liver cell ( P>0.02). It is reasonable to assume that with prolonged exposure even small solvent concentrations in the respiratory air may lead to undesirable alterations in biotransformation of foreign substances and endogenous compounds in the liver. [ABSTRACT FROM AUTHOR]

Hexane has been used for decades to extract edible oil from cottonseed. However, due to increased regulations affecting hexane because of the 1990 Clean Air Act and potential health risks, the oil-extraction industry urgently needs alternative hydrocarbon solvents to replace hexane. Five solvents, n-heptane, isohexane, neohexane, cyclohexane, and cylopentane, were compared with commercial hexane using a benchscale extractor. The extractions were done with a solvent to cottonseed flake ratio of 5.5 to 1 (w/w) and a miscella recycle flow rate of 36 mL/min/sq cm (9 gal/min/sq ft) at a temperature of 10 to 45°C below the boiling point of the solvent. After a 10-min single-stage extraction, commercial hexane removed 100% of the oil from the flakes at 55°C; heptane extracted 100% at 75°C and 95.9% at 55°C; isohexane extracted 93.1% at 45°C; while cyclopentane, cyclohexane, and neohexane removed 93.3, 89.4, and 89.6% at 35, 55, and 35°C, respectively. Each solvent removed gossypol from cottonseed flakes at a different rate, with cyclopentane being most and neohexane least effective. Based on the bench-scale extraction results and the availability of these candidate solvents, heptane and isohexane are the alternative hydrocarbon solvents most likely to replace hexane. [ABSTRACT FROM AUTHOR]