Model Oil Systems Research Articles

Indirect Method: A Novel Technique for Experimental Determination of Asphaltene Precipitation

Asphaltenes represent one of the major potential flow assurance problems in the upstream oil industry. Asphaltene precipitation determination is a key step in studying the asphaltene deposition problems because precipitation is a necessary condition for the asphaltenes to deposit. In this work, a novel experimental technique called the “indirect method” is used for studying asphaltene precipitation on both model oil and real crude oil systems. This method, which is a combination of gravimetric and spectroscopic techniques, is proposed for the detection and quantification of asphaltene precipitation in dead oil samples. The term “indirect” refers to an indirect detection of the precipitation of asphaltenes, by measuring the absorbance of the supernatant fluid after centrifugation of oil/n-alkane mixtures. The results obtained in this study show that the indirect method has three main advantages over direct methods. First, it can be applied to detect asphaltene precipitation and also to quantify the amount ...

Effect of Natural Antioxidants and Lipid Model System on Lipid Oxidation

Antioxidant effects of natural antioxidants were evaluated by direct analysis and three high-lipid model systems. The direct analysis assays compared three antioxidant extracts (pomegranate, grape seed and selenium), a synthetic antioxidant (butylated hydroxyanisole) and three natural antioxidant controls (d,l-α-tocopherol, ascorbic acid and gallic acid). Evaluation compared reducing power determined by Folin–Ciocalteu reagent and ferricyanide method, free radical scavenging of 2,2-diphenyl-1-picrylhydrazyl and oxygen radical absorbance capacity. Results indicated that pomegranate and grape seed extracts had better antioxidant efficacy than the synthetic antioxidant. Model systems were constructed in triplicate of three commercial lipid (canola oil, lard and ground beef); samples were subject to an antioxidant treatment (pomegranate extract, grape seed extract, dietary selenium from yeast, butylated hydroxyanisole or no treatment) and chemically evaluated (thiobarbituric acid-reactive substances and diene conjugation) over 9 days. Butylated hydroxyanisole was the most potent antioxidant. The canola oil matrix found no difference in antioxidant treatment under descriptive analysis by a trained panel. Practical Applications Antioxidant food additives are of great importance to the food industry, with many consumers showing a preference for “natural” food additives in the ingredient line. Phenolic compounds, such as those found in pomegranates and grapes, may be particularly useful in the food industry through retarding lipid oxidation. The use of ground beef, lard and oil model systems to study lipid oxidation (or antioxidant capacity by retarding lipid oxidation) is common, but time consuming. Direct analysis and chemical assays that measure oxidative end products can be fast, reliable and less costly that descriptive analysis panels. However, Qualitative Descriptive Analysis (QDA) is commonly used to denote the complete experience that consumer may undergo. Furthermore, evaluating antioxidant efficacy on sight and smell is integral when dealing with products that contain a large amount of polyunsaturated fatty acids, as consumers interact with both aspects during point of purchase.

Dynamic interfacial tensions of p -( n -lauryl)-benzyl polyoxyethylene ether carboxybetaine solutions

Abstract The dynamic interfacial tensions (IFT) of four p -( n -lauryl)-benzyl polyoxyethylene ether carboxybetaine C 12 BE x CB ( x =0, 1, 2, 3) have been investigated by a spinning drop interfacial tensiometer. The influence factors such as ethylene oxide group, surfactant concentration, organic base, electrolyte concentration and type are explored between C 12 BE x CB solutions and two oils including n -alkane model oil and Shengli crude oil. It is found that the n min (the minimum alkane carbon number) and IFT min increase with increase in the ethylene oxide group for n -alkane model oil systems. For Shengli crude oil, the C 12 BE x CB surfactants used alone cannot reduce the IFT to ultralow value. In order to meet the demand, the organic base, monoethanolamine (MEA), is applied together with C 12 BE x CB to form organic base/surfactant system. The results show that there exists a synergistic effect between organic alkaline MEA and C 12 BE x CB surfactant. At optimum MEA concentration (0.10 wt%) and optimum ethylene oxide group number ( x =0, 1), the IFT value becomes lower than 10 −2 mN/m. All these results show that the interfacial surfactant concentration and the surfactant molecular size are two most important factors in dominating ultralow IFT. Moreover, it is found that electrolyte concentration and type have little effects on IFT and the C 12 BE x CB surfactants exhibit good salinity resistance.

Estimating the time of frying oils have been used for French fries based on profile changes of fatty acids derived from heated oil model systems

Time of use for frying oils recovered from French fries was estimated based on ratios of fatty acids and values of conjugated dienoic acid (CDA) and/or p-anisidine (p-AV) derived from oxidation data of oils heated to 180°C in model systems. Changes in CDA and p-AV values in oils occurred faster than changes in ratios of fatty acids (oleic to linoleic acids, O/L) and saturated to unsaturated fatty acids (SFAs/UFAs). Oil use times estimated by O/L SFAs/UFAs ratios, and on CDA and p-AV values in oil recovered from French fries were 1.38, 1.42, 0.36, and 0.22 h, respectively. The actual oil use time was 1.5 h. Although oxidation parameters from heated oil models may not accurately reflect changes in oils during deep-fat frying of French fries, ratios of fatty acids in oils may be more useful for predicting the use time of frying oils than CDA and p-AV values.

PT434 Establishing Rheumatic Heart Disease Control Program in Sudan: achievements and challenges

Nontraditional oilseeds have attracted great interest because their components have unique properties and may augment the supply of functional products. Black cumin (Nigella sativa L.) seeds and their essential oil have been widely used in functional foods, nutraceutical, and pharmaceutical products. Analysis of N. sativa essential oil using gas chromatography and gas chromatography–mass spectrometry resulted in the identification of many bioactive compounds representing around 85% of the total content. The main identified compounds include p-cymene, thymoquinone, α-thujene, longifolene, β-pinene, α-pinene, and carvacrol. Nigella sativa essential oil exhibited different biological activities including antifungal, antibacterial, and antioxidant potentials. Nigella sativa essential oil showed complete inhibition zones against different Gram-negative and Gram-positive bacteria including Penicillium citrinum, Bacillus cereus, Bacillus subtilis, Staphylococcus aureus, and Pseudomonas aeruginosa. The essential oil showed stronger antioxidant potential compared with synthetic antioxidants (e.g., butylated hydroxyanisole and butylated hydroxytoluene) in a rapeseed oil model system. The oil also exhibited stronger radical scavenging activity against 2,2-diphenyl-1-picrylhydrazyl radical compared with synthetic antioxidants. The diversity of food applications to which N. sativa essential oil can be put gives this oil industrial importance.

Antioxygenic Activity of <i>Solanum nigrum L.</i> Leaves in Sunflower Oil Model System and Its Thermal Stability

The antioxygenic activity of Solanum nigrum L. leaves and its various solvent extracts were evaluated using sunflower oil model system. Leaf powder and its methanol/water (80:20) soluble fraction showed strong antioxygenic activity in refined sunflower oil. On the other hand, ethyl acetate fraction exhibited marginal antioxygenic activity, whereas the water soluble fraction was practically devoid of any activity in refined sunflower oil. Thermal stability of different extracts of Solanum nigrum L. leaves heated at 80?C in refined sunflower oil also indicated the strong efficacy of methanol/water (80:20) extract to inhibit thermal oxidation. Solanum nigrum L. contain high levels of magnesium (239.0 mg/100g) and phosphorous (80.3 mg/100g). Fatty acid analysis of the lipid extracted from Solanum nigrum L. leaves indicated the presence of linoleic (59.1%) as a major fatty acid. The result of this study confirmed the presence of antioxygenic compounds in leaves, in particular its methanol/water (80:20) extracts showed great potential as a natural antioxidant to inhibit lipid peroxidation in foods.

Asphaltene Deposition in Different Depositing Environments: Part 1. Model Oil

Among the asphaltene flow assurance issues, the most major concern because of asphaltene is its potential to deposit in reservoir, well tubing, flow lines, separators, and other systems along production lines causing significant production losses. Hence, the focus of this study is to understand the depositional tendency of asphaltene using quartz crystal microbalance with dissipation (QCM–D) measurements. The results are presented in two consecutive papers, with this paper (part 1) dealing with model oil systems. The depositing environment is varied by changing the system temperature, asphaltene polydispersity, solvent (asphaltene stability), depositing surface, and flow rate. This paper also discusses the roles of convective, diffusive, and adsorption kinetics on asphaltene deposition by modeling the adsorbed mass before asphaltene precipitation onset. The successive paper (part 2; 10.1021/ef401868d) will deal with real crude oil systems and modeling of the deposited mass after asphaltene precipitation o...

Rate‐limiting step analysis of the microbial desulfurization of dibenzothiophene in a model oil system

A mechanistic analysis of the various mass transport and kinetic steps in the microbial desulfurization of dibenzothiophene (DBT) by Rhodococcus erythropolis IGTS8 in a model biphasic (oil-water), small-scale system was performed. The biocatalyst was distributed into three populations, free cells in the aqueous phase, cell aggregates and oil-adhered cells, and the fraction of cells in each population was measured. The power input per volume (P/V) and the impeller tip speed (vtip ) were identified as key operating parameters in determining whether the system is mass transport controlled or kinetically controlled. Oil-water DBT mass transport was found to not be limiting under the conditions tested. Experimental results at both the 100 mL and 4 L (bioreactor) scales suggest that agitation leading to P/V greater than 10,000 W/ m(3) and/or vtip greater than 0.67 m/s is sufficient to overcome the major mass transport limitation in the system, which was the diffusion of DBT within the biocatalyst aggregates.

Controlled Shear Stress and Controlled Shear Rate Nonoscillatory Rheological Methodologies for Gelation Point Determination

An experimental rheometric investigation is performed to assess the utility of various gelation point determination methodologies. Controlled shear stress and controlled shear rate methods are developed to investigate gelation processes in waxy oils. The nonoscillatory rheological method exhibits high reproducibility for model wax oils as well as for real crude oils. In addition, the nonoscillatory methods are in good agreement with standard oscillatory gel point determination methods. The effect of imposed shear stress, imposed shear rate, and cooling rate on gelation point is investigated with two types of model oils: 5 wt % macrocrystalline wax in Primol 352 and 5 wt % macrocrystalline wax in dodecane. In addition, the effect of wax content on gel temperature of macrocrystalline wax in dodecane is investigated. Moreover, the effect of additives (A3 and A4) on gelation point of a real crude oil UL-YS1 is investigated. Finally, the gelation temperatures of 5 wt % macrocrystalline wax in Primol 352, crude oil UL-YS1, and Se-7-E06 are investigated by three methods: constant imposed shear stress, constant imposed shear rate, and oscillatory G′–G″. Gel point results are obtained with the various protocols for real and model oil systems. The nonoscillatory rheological method is applicable for gel point determination of model wax oils as well as real crude oils. Hence, due to its high repeatability and instrumental accuracy, the nonoscillatory rheological method is a promising method for gel point determination.

Tribological performance and tribochemical processes in a DLC/steel system when lubricated in a fully formulated oil and base oil

Diamond-like carbon (DLC) coatings show extremely good promise for a number of applications in automotive components as they exhibit excellent tribological properties such as low friction and good wear resistance. This can impact on improved fuel economy and durability of the engine components. Much work has been reported on the dry sliding of DLC coatings with less so in lubricated contacts and, as such, there is a need to further understand the tribochemistry of lubricated DLC contacts. Commercially-available oils are normally optimised to work on ferrous surfaces. Previous studies on DLC lubricated contacts have tended to use model oil systems rather than fully formulated lubricants and from this an interesting picture of lubrication mechanisms is emerging. Optimising compatibility between a surface and a set of lubricant additives may lead to excellent durability (wear) as well as increased fuel economy (low friction). In this work, the friction and wear properties of a DLC coating under boundary lubrication conditions have been investigated and the tribological performance compared with that of an uncoated steel system.A pin-on-plate tribotester was used to run the experiments using High speed steel (HSS) M2 grade plates coated with 15at.% hydrogenated DLC (a-C:15H) sliding against cast iron pins. A Group III mineral base oil, fully synthetic Group IV PAO and four different fully formulated oils were used in this study. Furthermore optical and scanning electron microscopes (SEM) were used to observe the wear scar and to assess the durability of the coatings. Energy-Dispersive X-ray analysis (EDX), X-ray Photoelectron Spectroscopy (XPS) and Raman spectroscopy analyses were performed on the tribofilms to understand the tribochemical interactions between oil additives and the a-C:15H coating.This study show that the durability of the a-C:15H coating strongly depends on the selected additive package in the oils. In addition the effect of detergent, dispersant and antioxidants on the performance of the molybdenum-based friction modifier (Mo-FM) and ZDDP anti-wear additive was investigated and results are reported in this paper.

Antioxidant activity of phytosteryl phenolates in different model systems

As part of a comprehensive study of the physiochemical and biological properties of phytosteryl phenolates, successfully synthesized chemoenzymatically in our lab, their antioxidant activity was evaluated using three different in vitro model systems, namely bulk oil model system, β-carotene–linoleate model system and low-density lipoprotein cholesterol (LDL-C) oxidation assay. In the bulk oil system, phytosteryl phenolates showed similar or lower antioxidant activity compared with those of phenolic acids. However, in β-carotene–linoleate assay, an emulsion model system, phytosteryl phenolates showed enhanced antioxidant activity except phytosteryl ferulates. Moderate inhibitory effect of LDL-C oxidation by phytosteryl phenolates was observed. These findings demonstrate that use of multidimensional antioxidant activity determinations with differing reaction mechanisms is necessary to provide an overall understanding of the mechanisms of antioxidant action of phytosteryl phenolates.

Reducing Oil Losses in Alkali Refining

AbstractNeutralization is an important step in the chemical refining of edible oils. Free fatty acids (FFA) are generally removed in neutralization as sodium soaps but neutral oil is also entrapped in the emulsion and removed with the soap during centrifugation. Thus, alkali neutralization causes a major loss of neutral oil in the chemical refining of edible oils. The effects of demulsifiers (NaCl, KCl, Na2SO4 and tannic acid) on reducing alkali refining losses of refined palm, soybean, and sunflower oils (used as model oils) incorporated with FFA from rice bran oil were investigated. Adding small amounts of demulsifiers to the alkali neutralization step significantly reduced neutral oil loss of these model oils. All demulsifiers except for tannic acid had similar effects on refining losses in all oil model systems. The optimum demulsifier content was 1.0 % (w/w of oil).

Oxidative behaviour of four Malaysian edible plant extracts in model and food oil systems

The present study was conducted to investigate the antioxidative behaviour of four local plant extracts in Malaysia-- red spinatch (Amarantus gangeticus), “kucai” (Allium odorum), Chinese cabbage (Brassica chinensis), and “kesom” (Polygonum minus)-- in palm olein system and in a linoleic acid model system. The antioxidative capacities of these local plants were then compared to the activity of rosemary and sage, two types of antioxidant commonly found in the market. From the analysis using Oxigen Consumption Method, it was found that among the samples evaluated, red spinatch had the longest time to reach the 50% oxygen in the chamber, with 110 min, meaning that this sample had the highest level of antioxidative activity. This was followed by the extracts of Chinese cabbage (80 min), “kucai” (60 min), and “kesom” (40 min). The antioxidative activities of these plants, however, were lower than those of rosemary and sage. These commercial antioxidants were found to have 150 and 130 min time, respectively, to reach the 50% oxygen in the chamber. Results from differential scanning calorimetry (DSC) analysis showed that addition of red spinatch and Chinese cabbage extract samples to the oil in the system reduced the oxidation as evidenced by longer To of antioxidants-treated samples. The onset time (To) of the oxidation reaction corresponded closely to the intersection of the extrapolated baseline and the tangent line (leading edge) of the exotherm, meaning that the longer To, the greater the antioxidative activity of a sample. Statistical analysis from this study showed that there was no significant difference between To of red spinatch and those of rosemary and sage. This meant that the antioxidative activity of red spinacth samples was comparable to the activities of rosemary and sage. The antioxidative activities of Chinese cabbage, “kucai” and “kesom” were also much higher than that of control. The finding from this study indicated that all samples used in this study had very good potential to be explored as sources of natural antioxidants. Key word: Oxidative behavior, edible plants, model system, red spinatch.

Deep Desulfurization of Light Oil through Extraction and Oxidation Processes using H2O2/Tungstophosphoric Acid in Room‐temperature Ionic Liquids

AbstractIn this research, using room‐temperature ionic liquids (RTILs) as the solvents to combine solvent extraction and chemical oxidation processes in one‐pot operation for the desulfurization of fuel oil was pursued. In this solvent extraction and chemical oxidation desulfurization (SECOD), RTILs as media are immiscible with oil; sulfur compounds in oil are extracted into RTILs and oxidized thereafter to the corresponding sulfones by H2O2/TPA (tungstophosphoric acid). During SECOD, these high polar sulfones partition mainly in the ionic liquid phase. Hence, it results in their continuous removal from oil, which leads to deep desulfurization. To study the SECOD, we employed dibenzothiophene (DBT) and 4,6‐dimethyldibenzothiophene (4,6‐DMDBT) in hexadecane as model oil systems and compared the effects of RTILs on the removal of DBT and 4,6‐DMDBT. The desulfurization rates followed the order OMIM+PF6− > BMIM+PF6− > BMIM+BF4−. Both OMIM+PF6− and BMIM+PF6− are water‐immiscible and form three‐phase (oil–water–ionic liquid) reaction systems; these three‐phase systems offer higher removal efficiencies of sulfur compounds from oil. Under the optimized conditions, SECOD process reduced the sulfur content of diesel light oil from 897 to 42 ppm (i.e., 95% desulfurization efficiency) in a one‐batch operation.

Interfacial Dilational Properties of Acidic Model Oil and Chemical Flooding Systems

The interfacial dilational properties of lauric acid model oil and chemical flooding systems have been investigated by means of longitudinal method. The influences of acid on the dilational viscoelasticity of partly hydrolyzed polyacrylamide (HPAM) and anionic surfactants (4,5-diheptyl-2-propylbenzene sulfonate 377 and Gemini surfactant C12COONa-p-C9SO3Na) have been expounded. The results show that lauric acid concentration is an important factor in controlling the dilational properties of mixed-adsorption layer. The addition of small amounts of lauric acid to solutions of anionic surfactant appears to increase the dilational modulus, while the superfluous addition could decrease the dilational modulus mainly due to the weakening of strong interaction among long alkyl chains of surfactant molecules. The polymer plays different roles in influencing the nature of adsorbed layers at different lauric acid concentrations: at low concentration, the addition of polymer perhaps weakens the hydrophobic interactions of lauric acid molecules, which results in decreasing the dilational modulus of adsorbed layer. At high concentration, the addition of the polymer increases the dilational modulus due to hydrophobic interactions between polymer and lauric acid molecules. At the same time, the mixed adsorbed layer shows low frequency due to the slow diffusivity of polymer molecules. The addition of lauric acid to polymer-surfactant system will further increases diffusion-exchange process between the interface and the bulk, which consequently leads to the decrease in dilational modulus.

Interfacial dilational properties of model oil and chemical flooding systems by relaxation measurements

In the present work, the influences of a model organic acid (oleic acid) on the interfacial dilational properties of different types of surfactants (anionic surfactant sodium 4,5-diheptyl-2-propylbenzene sulfonate 377 and asymmetrical anionic Gemini surfactant C 12COONa-p-C 9SO 3Na) and polymers (HPAM and HMPAM) systems were studied at decane–water interface, respectively, by means of interfacial tension relaxation measurements. The decay curves of interfacial tension were fitted by the summation of a number of exponential functions. The dilational elasticity and dilational viscosity component were calculated by Fourier transform and displayed as Cole–Cole plots (plotting ɛ i or ɛ i / ɛ 0 as a function of ɛ r or ɛ r / ɛ 0, respectively). The experimental results show that the interfacial behaviors of both surfactants are part conformance with a diffusion-controlled process and part conformance with a reorientation controlled process. In the case of partly hydrolyzed polyacrylamide Mo-4000, the nature of mixed film is controlled mainly by interaction between polymer chains and surfactant molecules in the interface. As for hydrophobically modified polyacrylamide, the film properties are controlled by the formation of mixed surfactant-hydrophobic block associations in the interface and the reorientation process resulted from exchange of associations between different regions of interface. Under our experimental conditions, the mixed adsorption films formed by oleic acid and surfactant molecules are more compact than pure surfactant films.

Application of DPPH absorbance method to monitor the degree of oxidation in thermally-oxidized oil model system with antioxidants

Changes of 2,2-diphenyl-1-picrylhydrazyl (DPPH) absorbance were monitored in thermally-oxidized lard containing free radical scavengers (FRSs). Hydrogen donating abilities of α-tocopherol to DPPH were higher than those of sesamol and butylated hydroxyanisole (BHA), indicating reactivity of DPPH and FRSs in lard depends on the types of FRSs. For the first 20 min oxidation, DPPH absorbance from lard with 3.38 μmol/g α-tocopherol, sesamol, and BHA increased by 0.324, 0.240, and 0.313, respectively while those from lard without FRS decreased by 0.350. Results of conjugated dienoic acid (CDA), and p-anisidine value (p-AV) showed that antioxidative activity were high in the order of sesamol, BHA, and α-tocopherol, which implies that hydrogen donating abilites of FRSs may not be the most critical factor to determine antioxidant effectiveness. Monitoring DPPH absorbance in oxidized lard with FRS could be useful indicators for comparing antioxidative ability of FRSs.

Comparison of tea and sesame seed oils as two natural antioxidants in a fish oil model system by radical scavenging activity

Tea and sesame seed oils, two natural antioxidants at 5% and 10% levels, were added to carp (Cyprinus caprio) and common kilka (Clupeonella cultiventris caspia) oils, and the peroxide value and thiobarbituric acid were evaluated after 13 days at 60°C (oven test). The results showed that the antioxidant effects of tea and sesame seed oils in the two aforementioned fish oils were statistically similar. In addition, the radical scavenging activity (RSA) of tea and sesame seed oils (extracted with two solvents:n-hexane and benzene) and their methanolic extract (methanol-soluble phase), ethanolic extract (ethanol-soluble phase) and lipid fraction (non-soluble in methanol or ethanol) were evaluated by the 2,2-diphenyl-1-picrylhydrazyl radical method. The results revealed that the RSA of sesame seed oil was higher than that of tea seed oil (IC50 = 52 mg and 45 mg, respectively). In addition, among ethanolic and methanolic extracts, the RSA of the ethanolic extract of sesame seed oil (IC50 = 65 ml and 68 ml in n-hexane and benzene solvents, respectively) and of the ethanolic extract of tea seed oil in benzene solvent (IC50 = 73 ml) were the highest. Also, the RSA in the lipid fraction, non-soluble phase of sesame seed oil was the highest (IC50 = 74 mg and 81 mg in n-hexane and benzene solvents, respectively). Furthermore, after 6 days at 60°C the RSA values of tea and sesame seed oils were the same.

Comparison of tea and sesame seed oils as two natural antioxidants in a fish oil model system by radical scavenging activity

Comparison of tea and sesame seed oils as two natural antioxidants in a fish oil model system by radical scavenging activity

Efficacy of He-Ne Laser Irradiation on the Improvement of Biodesulfurizing Activity of Gordonia sp. WQ-01

Low-energy laser has been widely applied in breeding of microorganisms, treatment of wound healing, and cancer therapy for many years, but the molecular mechanisms of the laser irradiation are still unclear. In this study, the biological effects of the He-Ne laser irradiation on the dibenzothiophene monooxygenase (DszC) were analyzed, comparing the wild-type bacteria strain of Gordonia sp. WQ-01 and its He-Ne laser irradiated strain WQ-01A. First, the gene and protein sequences of the DszC were analyzed. The results indicated that there were ten point mutations on the dszC gene sequences, and four of them further caused alteration of four amino acid residues in DszC protein. Then, the enzymatic activities of the DszC were analyzed. It was indicated that the enzymatic activity of the mutant protein DszC was higher than wild-type protein DszC. Finally, the biodesulfurization (BDS) capacities of both the wild-type strain and the mutant strain in aqueous model oil and light gas oil systems were analyzed. The results indicated that biodesulfurization capacities of the mutant strain WQ-01A were enhanced in all the above systems. Therefore, the He-Ne laser irradiation caused the point mutation in the dszC and alteration of amino acid residues of DszC, and further enhanced the BDS capacities of the mutant strain WQ-01A.