Heptane In Presence Research Articles

Stability of an aqueous foam lamella at simulated fire conditions containing surfactants relevant to firefighting foams

To better understand interactions between firefighting foams and a fire environment, we isolated interactions to a single surfactant containing bubble lamellae. A horizontal thin liquid film experiment was designed to study film rupture in the presence of heated air and heptane vapors. Thin films were formed from aqueous solutions of alkylpolyglycosides (APGs, G215 and G225), trisiloxane (502W and L77), and fluorinated (Cap) surfactants and their mixtures. The Cap surfactant film was the most stable to heat but in the presence of heptane, the surfactant film had a comparable (and the Cap:G215 mixture had a shorter) rupture time to the fluorine-free surfactant films. APG films showed the least destabilization with heptane followed by the trisiloxane films and the Cap film which was the most destabilized by heptane. L77, Cap, and their respective mixtures formed possible emulsions with the fuel vapors, turning cloudy with vapor introduction. The correlation between film rupture behavior and fuel induced foam lifetime may be better defined by minimizing error in lifetime and producing longer film lifetimes. This thin film experiment represents a new way of observing surfactant/fuel interactions that may elucidate important surfactant properties for firefighting foams.

ЭКСТРАКЦИОННАЯ ОЧИСТКА ТЯЖЕЛОГО ГАЗОЙЛЯ ЗАМЕДЛЕННОГО КОКСОВАНИЯ С ИСПОЛЬЗОВАНИЕМ ЭКСТРАКЦИОННОЙ СИСТЕМЫ N-МЕТИЛПИРРОЛИДОН – ГЕПТАН

The article presents the results of the extraction purification of heavy delayed coking gas oil with mass ratios of N-methylpyrrolidone with 2 % mas water to raw materials as 0.5 : 1, 0.75 : 1, 1 : 1, and in the presence of heptane at mass ratio to raw materials as 0.3 : 1 and temperature of 40 оC. It was found that the introduction of heptane into the extraction system with N-methylpyrrolidone leads to an increase in the yield of raffinate due to an increase in the selectivity of the release of polyaromatic hydrocarbons. However, due to the presence in the gas oil of delayed coking of sulfur compounds of not only aromatic nature, but also saturated thiacyclanes and dialkylsulfides forming systems close to ideal with heptane, the efficiency of gas oil desulfurization decreases.

Probing the Interaction Forces between Bitumen-Coated Mineral Surfaces with Implications for the Removal of Fine Solids from Oil Product: Effect of Solvent

Summary Considerable amounts of fine solids retained in the bitumen product have been a significant challenge hindering the commercialization of nonaqueous extraction (NAE) of bitumen from oil sands. Understanding the surface interaction between bitumen-coated fine particles and the suspension stability in NAE bitumen products is essential for developing suitable solutions to remove these undesired particles. In this work, the adsorption behaviors of bitumen on a model clay surface (i.e., molecularly smooth mica surface) in organic solvents (i.e., cyclohexane and cyclohexane-heptane mixtures) were systematically investigated using a surface force apparatus (SFA). Furthermore, the interaction forces between bitumen-coated mica surfaces were directly measured in different organic solvents to reveal the stabilization mechanism of fine solids during the NAE process. It was found that the solvent type and adsorption time significantly affect the adsorption behavior of bitumen on mica surface and regulate the interaction forces between bitumen-coated mica surfaces, which in turn have an impact on the stability of suspended fine solids in solvents. In cyclohexane or cyclohexane-rich solution, a thin layer of bitumen (~5 nm) was quickly deposited on fresh mica surface within 5 minutes and gradually equilibrated to form a soft layer after a long process (>40 minutes). Only pure repulsive force due to steric repulsion was measured between the adsorbed layers, which led to a stable suspension of fine solids in solvents. In contrast, the presence of heptane caused the bitumen to rapidly (<20 minutes) form a compact packing adsorption layer, and a weak adhesive force (<5 mN/m) was measured between the bitumen-coated surface during the separation process. The adhesive force could be mainly brought by the interpenetration of long hydrocarbon chains or the conformation change of the organic network in both solution and substrate surface, which could lead to aggregation and settling of fine solids. Our SFA results provide valuable insights into the adsorption behavior of bitumen onto mineral surfaces and the interaction mechanism of bitumen-coated mineral surfaces in organic media, with important implications for the removal of fine solids from oil products.

Factorial design to obtain magnetized poly(ethyl acrylate-co-divinylbenzene)

Abstract Magnetized polymers are produced by incorporating magnetic particles in a polymeric matrix. This article describes the use of the suspension polymerization technique using ethyl acrylate and divinylbenzene as monomers, in the presence of heptane and/or toluene as diluent, initiated by free radicals. To produce the polymer, we first performed fractional factorial planning to help visualize the factors that could influence the results, to verify the action of different responses simultaneously. Five factors were evaluated that influence the production of the polymer and incorporation of iron in the matrix. Infrared spectroscopy, X-ray fluorescence, magnetic force testing and scanning electron microscopy were used to characterize the samples. The results indicated the positive influence of the quantity of the polymerization initiator on the yield of the process and the negative effect of the content of divinylbenzene on the incorporation of iron in the matrix and on the magnetic force.

Highly clean and efficient enzymatic dehairing in green solvents

Enzymatic dehairing in aqueous medium is in demand over lime-sulphide based conventional method of leather making due to the environmental concerns. However, the use of water not only depletes precious natural resource but also leads to incomplete hair removal. Here, we report the enzyme-only dehairing of sheepskins in chosen green solvents. The enzyme showed better activity in the presence of heptane and propylene glycol than in aqueous medium. This was substantiated with a limited computational study involving protease-solvent interface. Further, it is demonstrated that the solvent-enzyme mixture removed hair more efficiently without any sulphide and lime than aqueous enzyme-lime-sulphide system and produced leathers with properties similar to conventional method. Also, a complete elimination of sulphide emission and reduction in the pollution loads such as lime and total dissolved solids is observed. Recycling studies demonstrate that it is industrially feasible to replace water with green solvents for enzymatic dehairing process. The findings have great implications for not only leather industry but also other industries where usage of enzyme is contemplated.

Properties of novel spherical carbon adsorbents synthesized from phosphorylated polymeric precursors

Phosphorus-containing carbon adsorbents have been prepared by the carbonization and CO2 activation of two sets of submicroporous phosphorylated styrene/divinylbenzene copolymers in various (H+, Cs+, Cu2+, Co2+ and Fe3+) ionic forms. These copolymers have been synthesized in the form of beads, using the suspension polymerization technique. The polymerization was carried out in the presence of heptane and toluene in order to obtain porous material and polymers were subsequently subjected to phosphorylation. The content of the phosphinic groups in the modified polymers is ca. 4mmol/g. Thermal degradation of the polymer precursors was monitored using thermogravimetric analysis. It was found that the carbonization yield is ca. 20% for the phosphinic acid forms and reaches ca. 60% for the various phosphinic acid salts. Scanning electron microscopy (SEM) was used to investigate the structure of the obtained carbon adsorbents. The metal ion in the phosphinic acid salt and porous structure of polymeric precursor determine the morphology and mechanical strength of the obtained carbon grains. Chemical composition were investigated using XPS, XRD and pH titrations methods. The characteristics of the porous structure of the polymer precursors and carbon materials were obtained by benzene and CO2 adsorption. The resultant carbon adsorbents are predominantly microporous and their specific surface area is in the range of 300–1500m2/g depending on the ionic form and the porosity of polymeric precursors.

Insights into chromatographic enantiomeric separation of allenes on cellulose carbamate stationary phase

Allenes are cumulenes with three contiguous carbons linked together through double bonds. 1,3-disubstituted allenes are not superimposable on their mirror image; as a consequence they are chiral. Chiral allenes are increasingly important in organic synthesis due to their interesting reactivity. Because of their applications in the field of asymmetric catalysis and in the pharmaceutical industry their optical purity is always a parameter which needs to be determined. In this article, we report the enantiomeric separation of hexa-3,4-diene-3-ylbenzene, an aromatic allene, on a cellulose carbamate (Chiralcel OD-3) stationary phase, using heptane as the mobile phase. Spectroscopic studies using infrared (IR) and vibrational circular dichroism revealed that, in the presence of heptane, the stationary phase undergoes a conformational change due to intermolecular H-bonding between the CO and NH of the neighboring polymer chains. Van’t Hoff plots for the retention factor, k, showed that the retention of the two enantiomers is dominated by the enthalpy, while the plot for the selectivity, α, is entropy driven. This suggests that the enantioselectivity is a result of inclusion of the enantiomers in the cavities of the chrial stationary phase. VCD spectra, along with density functional theory calculation (DFT) of the interaction between each enantiomer and the chiral stationary phase, supported the chromatographic elution order findings.

Anisotropic Sm2Co17 nano-flakes produced by surfactant and magnetic field assisted high energy ball milling

Anisotropic Sm2Co17 flakes with high aspect ratio were prepared by magnetic field assisted high energy ball milling in the presence of heptane and oleic acid (OA). The thickness of flakes was only tens of nanometers. Coercivity of 3 kOe was achieved in the nano-flakes. Most interestingly, the magnetic crystalline anisotropy of Sm2Co17 flakes was improved compared to that of particles made by traditional ball milling. These anisotropic Sm2Co17 nano-flakes could be the building blocks for the future high-performance nano-composite permanent magnets with an enhanced energy product.

Rapid Synthesis of SBA-15 Rods with Variable Lengths, Widths, and Tunable Large Pores

Dispersed SBA-15 rods have been synthesized with varying lengths, widths, and pore sizes in a low-temperature synthesis in the presence of heptane and NH(4)F. The pore size of the material can systematically be varied between 11 and 17 nm using different hydrothermal treatment times and/or temperatures. The particle length (400-600 nm) and width (100-400 nm) were tuned by varying the HCl concentration. All the synthesized materials possess a large surface area of 400-600 m(2)/g and a pore volume of 1.05-1.30 cm(3). A mechanism for the effect of the HCl concentration on the particle morphology is suggested. Furthermore, it is shown that the reaction time can be decreased to 1 h, with well-retained pore size and morphology. This work has resulted in SBA-15 rods with the largest pore size reported for this morphology.

Extracellular terpenoid hydrocarbon extraction and quantitation from the green microalgae Botryococcus braunii var. Showa

Mechanical fractionation and aqueous or aqueous/organic two-phase partition approaches were applied for extraction and separation of extracellular terpenoid hydrocarbons from Botryococcus braunii var. Showa. A direct spectrophotometric method was devised for the quantitation of botryococcene and associated carotenoid hydrocarbons extracted by this method. Separation of extracellular botryococcene hydrocarbons from the Botryococcus was achieved upon vortexing of the micro-colonies with glass beads, either in water followed by buoyant density equilibrium to separate hydrocarbons from biomass, or in the presence of heptane as a solvent, followed by aqueous/organic two-phase separation of the heptane-solubilized hydrocarbons (upper phase) from the biomass (lower aqueous phase). Spectral analysis of the upper heptane phase revealed the presence of two distinct compounds, one absorbing in the UV-C, attributed to botryococcene(s), the other in the blue region of the spectrum, attributed to a carotenoid. Specific extinction coefficients were developed for the absorbance of triterpenes at 190 nm (ε = 90 ± 5 mM −1 cm −1) and carotenoids at 450 nm (ε = 165 ± 5 mM −1 cm −1) in heptane. This enabled application of a direct spectrophotometric method for the quantitation of water- or heptane-extractable botryococcenes and carotenoids. B. braunii var. Showa constitutively accumulates ∼30% of the dry biomass as extractable (extracellular) botryococcenes, and ∼0.2% of the dry biomass in the form of a carotenoid. It was further demonstrated that heat-treatment of the Botryococcus biomass substantially accelerates the rate and yield of the extraction process. Advances in this work serve as foundation for a cyclic Botryococcus growth, non-toxic extraction of extracellular hydrocarbons, and return of the hydrocarbon-depleted biomass to growth conditions for further product generation.

Kinetic inhibitor effects on methane/propane clathrate hydrate-crystal growth at the gas/water and water/ n-heptane interfaces

The influence of the kinetic inhibitor poly( N-vinylpyrrolidone) or PVP on hydrate methane/propane hydrate formation was studied in pre-saturated liquid water with and without the presence of heptane under different undercooling conditions. It was found that when the inhibitor concentration was 0.1 wt%, hydrate formation started as a film at the gas/water interface similar to the crystal behavior without inhibitor. When the inhibitor concentration was 0.5 wt% hydrate formation started at the wall above the gas/water interface and the hydrate film at the gas/water interface was observed as well. However, for inhibitor concentration 1.0 wt%, the hydrate started forming from water droplets attached to the wall above the gas/liquid interface and grew catastrophically. When the inhibitor concentration was 0.1 wt% and undercooling was 13.7 or 8.1 K whiskery or fiber-type hydrate crystals, respectively, were seen within the liquid pool. This morphology was not observed in the absence of PVP. When inhibitor concentration was 0.5 or 1.0 wt% or undercooling was 3.2 K, there was no crystal growth within the liquid pool. Floating crystals were also observed, but were needle-type and thus different from the equiaxed floating crystals found in the system without the inhibitor.

Quaternization reaction of 2-vinylpyridine and 4-vinylpyridine network copolymers for 4-nitrophenol adsorption

This article aims to evaluate porous copolymers (based on styrene-STY and vinylpyridine-VP, cross-linked with divinylbenzene-DVB) as adsorbents for 4-nitrophenol from aqueous solution. These copolymers were synthesized by suspension polymerizations in the presence of heptane (HEP) and toluene (TOL) in different proportions as porogenic agents. The VP units of the copolymers were chemically modified by the addition of the electrophilic ethylenic compound (acrylonitrile). The quaternized copolymers were characterized by infrared spectrometry (FTIR), elemental analysis (CHN), optical microscopy (OM) and scanning electron microscopy (SEM).

Production of butyl acetate ester by lipase from novel strain of Rhizopus oryzae

A new lipase preparation from Rhizopus oryzae was used to catalyze the esterification reaction between acetic acid and butanol to produce butyl acetate ester (pineapple flavor). This flavor compound can be used in food, cosmetic and pharmaceutical industries. Only 3% of butyl acetate was obtained when free lipase was used in the synthesis containing only the substrates. In contrast, the conversion yield reached 25% when immobilized lipase was used under the same conditions. The synthesis of butyl acetate catalyzed by immobilized lipase in nonconventional media was optimized. A maximum conversion yield of 60% in a solvent-free system was obtained under the following conditions: amount of immobilized lipase, 500 IU; amount of initially added water, 45%; acetic acid/butanol molar ratio, 1:1; and in incubation temperature, 37 degrees C. Immobilized lipase could be repeatedly used for three cycles without a decrease in synthesis activity. The production of butyl acetate esters by immobilized R. oryzae lipase was also studied in the presence of organic solvents. Compared with a solvent-free system, the synthesis activity was improved in the presence of heptane and hexane with conversion yields of 80% and 76%, respectively. However, solvent-free systems tend to purify more easily the products without any toxicity and inflammability problems.

Efficient Methods for Calculations of Compressibility, Density, and Viscosity of Natural Gases

Abstract This study presents two new methods for calculating the properties of natural gases. The first is an efficient empirical model to calculate compressibility and density of natural gases containing high amounts of heptane plus and non-hydrocarbon components. The model is derived from 2,400 measurements of compressibility and density of various gases presented in this study. Accuracy of the model is compared to various equations of state (EOS), corresponding state, and empirical methods. The study shows that the new model is simpler and more efficient than EOS. It eliminates the numerous computations involved in EOS calculations. The new method also eliminates the characterization of the heptane plus fraction and estimation of binary interaction parameters needed for EOS calculations. Experimentally measured densities of several gases have been used to study the validity of the proposed method. These measurements indicate that the new method successfully captures the physical trend of changing gas density as a function of pressure, temperature, and composition. The second method is a modification of the Lee-Gonzalez- Eakin gas viscosity correlation. The new method accounts for the presence of heptane plus, hydrogen sulfide, and carbon dioxide in natural gases. The proposed method is compared to other EOS-based viscosity models, corresponding state methods, and correlations. The comparison indicates the superiority of the new method over other methods used to calculate the viscosity of natural gases. Introduction The compressibility, density, and viscosity of natural gas are necessary in most petroleum and natural gas engineering calculations. Some of these calculations are used for gas metering, gas compression, design of processing units, and design of pipeline and surface facilities. Properties of natural gas are also important in the calculation of gas flow rate through reservoir rock, material balance calculations, evaluation of gas reserves, and reservoir simulations. Usually, the gas properties are measured in the laboratory. Occasionally, experimental data is unavailable and estimations from EOS or empirical correlations becomes a necessity. In the past three decades, a number of sour natural gas and gas condensates fields have been discovered around the world. Some of these fields have been classified as heavy natural gas. For these gases, the methods available in the literature for the calculation of the properties of heavy gases such as condensates and sour gases produce unsatisfactory results. These methods can be classified into three groups(1). The first group uses gas composition or gas gravity to calculate pseudo-critical properties of gases and predicts gas properties from empirical correlations. In this group, gas density is often used to predict viscosity. Hence, the prediction of viscosity is dependent on the choice of the method that is used to estimate the gas density. The second group uses gas composition to estimate gas properties via the method of corresponding states. The third group, and the most recent one, is based on an equations of state (EOS) approach. The last group has the advantage of using a single equation to calculate k-values, compressibility, density, and viscosity(2–4).

Immobilization of Lipase on Macroporous Resin and Its Application in Synthesis of Biodiesel in Low Aqueous Media

Lipase from Candida sp. 99-125 was immobilized by physical adsorption onto macroporous resins. The results showed that the nonpolar resin NKA was the best carrier used in low aqueous media. 98.98 % of degree of immobilization could be achieved when the adsorption procedure was performed in the presence of heptane. The lipolytic activity and the apparent activity recovery of lipase adsorbed on resin in heptane were 4.07 and 3.43 times higher than that of lipase adsorbed in sodium phosphate buffer, respectively. The catalytic properties of immobilized lipase for production of biodiesel in low aqueous media were studied. Immobilized lipase displayed the highest activity when the crude enzyme/resin weight ratio was 1.92:1 and the water content (water/ oil weight ratio) was 15 % at 40 °C under pH 7.4. As lipase was adsorbed on NKA in heptane to produce biodiesel, the batch conversion rate reached 97.3 % when a three-step methanolysis protocol was used. After 19 consecutive batches, the conversion rate remained 70.2 %.

Dispersant Adsorption during Asphaltene Aggregation Studied by Fluorescence Resonance Energy Transfer (FRET)

Fluorescence resonance energy transfer (FRET) is used to study the adsorption of a commercial dispersant on asphaltenes in a toluene−heptane solution. We induce the asphaltene aggregation process by changing the heptane volumetric fraction, where heptane plays the role of a precipitant agent. The dispersant and asphaltenes are naturally fluorescent, and no special labeling was performed to use this fluorescent technique. Low concentrations of asphaltene and dispersant were used in this work0.007 and 0.055 g/L, respectivelyto avoid self-association of the dispersant and to induce asphaltene aggregation only by the presence of heptane in the solution. The results show different behavior of the energy transfer below and above the precipitation onset of the asphaltenes, corresponding to a heptane volumetric fraction of 0.6. The dispersant adsorption was followed during the induced aggregation by measuring the resonance energy transfer from the dispersant (energy donor) to the asphaltenes (energy acceptor) above a heptane volumetric fraction of 0.7, where aggregates are formed and stabilized by the dispersant. The fluorescent experiments presented here also give information about the asphaltene stability in the solvent below the asphaltene precipitation onset.

Silica gel supported [1,4-bis(salicylidene amino)-phenylene] vanadium oxo complex catalyst for the oxidation of n-heptane using molecular oxygen

A complex of vanadium with nitrogen containing ligand, vanadium(II) [1,4-bis(salicylidene amino)-phenylene] vanadium oxo, has been covalently bonded on chemically modified silica gel, which serves as a catalyst for the oxidation of n-heptane in presence of molecular oxygen. The reaction occurs at low temperature (at 150 °C, 200 psi and reaction time of 480 min) and the nine major reaction products formed have been identified by the GC–MS analysis. Most of the products are substitution products of n-heptane and 2-heptanol (∼38.1%) is formed with high specificity with very little acid (∼8.0%). The product distribution is completely different from those reported in literature and suggests that heptane in presence of this catalyst undergoes negligible cracking or isomerization reactions at this temperature.

Size, Hydration, and Shape of SDS/Heptane Micelles Investigated by Time-Resolved Fluorescence Quenching and Electron Spin Resonance

Time-resolved fluorescence quenching (TRFQ) and electron spin resonance (ESR) are used to investigate sodium dodecyl sulfate/heptane micelles in water in the presence of varying amounts of sodium chloride (NaCl). Aggregation numbers are obtained from TRFQ and the micelle hydration from ESR. At any zero or any fixed sodium chloride concentration ≤375 mM, micelles grow with heptane while maintaining the volume fraction of water in the polar shell of the micelle, referred to as hydration index, constant. Core−shell model calculations, using simple geometry, show that some hydrocarbon density extends into the polar shell. The shell comprises about 15−17% of the core hydrocarbon in addition to the headgroups and hydration water. The rate of micelle growth with sodium chloride is smaller in the presence of heptane, and at higher salt concentrations (>375 mM), the micelles decrease in size with heptane. The rate of variation of hydration index with [NaCl] or aggregation number is indicative of micelle shape and shows that the sphere-to-rod transformation occurs at higher aggregation numbers and higher salt concentrations when heptane is present.

Extraction Refining of Heavy Vacuum Gas Oil

Selective refining of heavy vacuum gas oil and a combined fraction of light and heavy vacuum gas oils to remove aromatic and organoelement compounds and heavy metals by five-step countercurrent extraction with N-methylpyrrolidone or dimethylacetamide in the presence of heptane containing 1 wt % toluene was studied.

Immobilisation studies and catalytic properties of microbial lipase onto styrene–divinylbenzene copolymer

Microbial lipase from Candida rugosa was immobilised by physical adsorption onto styrene–divinylbenzene (STYDVB) copolymer. Two different coupling media were evaluated: aqueous solution (sodium phosphate buffer) and organic solvent (heptane). The choice of the immobilisation medium had a large effect on the hydrolytic and synthetic lipase activities. Better results were found when the coupling procedure was performed in the presence of heptane. The effects of enzyme loading and support capacity regeneration were also studied. Both, free and immobilised lipases were characterised by determining the activity profile as a function of pH, temperature and thermal stability. For the immobilised lipase, operational and storage stabilities were also determined. Operational stability tests indicated that a small enzyme deactivation occurs after 12 consecutive batches of 24 h each. Such results revealed good potential for recycling under non-aqueous system.