Effect of Inorganic Solids,Wax to Asphaltene Ratio,and Water Cut on the Stability of Water-in-Crude Oil Emulsions

The formation of stable water-in-crude oil emulsions during petroleum production and refinery may create sever and costly separation problems. It is very important to understand the mechanism and factors contributing to the formation and stabilization of such emulsions for both great economic and environmental development. This article investigates some of the factors controlling the stability of water-in-crude oil emulsions formed in Burgan oil field in Kuwait. Water-in-crude oil emulsion samples collected from Burgan oil filed have been used to separate asphaltenes, resins, waxes, and crude oil fractions. These fractions were used to prepare emulsion samples to study the effect of solid particles (Fe₃O₄) on the stability of emulsions samples. Results indicate that high solid content lead to higher degree of emulsion stability. Stability of emulsion samples under various waxes to asphaltenes (W/A) ratios have also been tested. These tests showed that at low W/A content, the emulsions were very stable. While at a wax to asphaltene ratio above 1 to 1, the addition of wax reduced emulsion stability. Stability of emulsion samples with varying amount of water cut has also been investigated. Results indicated that stability and hence viscosity of emulsion increases as a function of increasing the water cut until it reaches the inversion point where a sharp decline in viscosity takes place. This inversion point was found to be approximately at 50% water cut for the crude oils considered in this study.     

FRAGRANCE EMULSIONS STABILIZED BY A TRIBLOCK COPOLYMER

The phase diagram was determined of the system a fragrance oil, phenethyl alcohol, a commercial triblock copolymer, PE/L101, and water. The stability of emulsions containing 95 wt% water and various amounts of the fragrance and polymer was investigated both visually and with the aid of an optical microscope. The stability of the two-phase emulsions was explained through the interfacial behavior of the polymer and the density change of the oil phase. Double emulsions were found to form when the oil phase composition is close to that of the L₂ phase with maximum water solubilization.     

Effect of Interfacially Active Fractions of Some Egyptian Crude Oils on Their Emulsion Stability

Four samples from different crude oils were used for this study: light and heavy crude oils from Iran and two crude oils from Egypt, namely, Ras Gharb and Suez mix. The asphaltenes were separated from these crude oils and then the maltene (non‐asphaltenic fraction) was fractionated into waxes, aromatics, and resins. All fractions were characterized using FTIR and UV spectroscopic analyses in addition to gel permeation chromatograph (GPC). These fractions were tested for their emulsion stability. For chemometric analysis different parameters (variables) have been used to study the effect of different fractions (objects) on the emulsion stability. Such variables included the integrated areas under the stretching absorption peaks of CH in the range of 3000–2800 cm^?1, C?O in the range of 1750–1650 cm^?1, and the aromatic C?C in the range of 1650–1550 cm^?1, as well as UV absorption value at 235 nm and average molecular weight (MW). Principal component analysis (PCA) and multiple linear regression (MLR) were conducted for examining the relationship between multiple variables and the stability of water‐in‐crude oil emulsions. The results of PCA explain the interrelationships between the observations and variables in multivariate data. The correlation coefficients between different parameters derived from PCA reveals that the UV absorption value and MW are strongly correlated with emulsion stability. It also reveals that the resins, asphaltenes, and maltene have better emulsion stability than waxes and lower molecular weight aromatics. The linear relationship between the parameters and the stability of water‐in‐crude oil emulsions using MLR was modeled according to the better statistical results. The obtained mathematical model can be used to predict the stability of water‐in‐crude oil emulsions from the chemical groups and functionalities in each crude oil fraction.     

EFFECTS OF INTERFACIAL POLYUREA FILM ON THE STABILITY OF OIL IN WATER EMULSIONS

The stability of oil in water emulsions containing a triisocyanate soluble in the oil phase was investigated. The oil component was either di-n-butyl phthalate (DBP) or a mixture of DBP with liquid paraffin. The time required for the average size parameter to reach a constant value was studied. It was found that the polyurea film produced by an interfacial polymerization reaction between water and a triisocyanate contributed to make the stable emulsions. The effects of drop size, temperature, polarity of oil phase, triisocyanate concentration, and mechanical stirring on the stability of the emulsions were established in this study. The film thickness at the point where the average size parameter reached a constant value was found to be of the order of 0. 002 ～ 0. 004μ.     

SEMICONTINUOUS EMULSION POLYMERIZATION OF VINYL ACETATE X. KINETICS OF HOMOPOLYMERIZATION,CO POLYMERIZATION,AND INITIATOR DECOMPOSITION IN THE PRESENCE OF SULFOSUCCINATE-TYPE SURFACTANTS

ABSTRACT

Miorocrystalline cellulose stabilized emulsions (o/w) were evaluated by means of brightfield and polarized light microscopy, freeze-etch electron microscopy, droplet size analyses and rheologic measurements. These studies indicated that miorocrystalline cellulose (Avicel RC591 ) forms a network around emulsified oil droplets. This structure provides a mechanical barrier at the o/w interface which stabilizes the emulsion without the necessity for decreasing interfacial tension, as in conventional surfactant-stabilized emulsions. Rheologic studies indicated that emulsions containing Avicel RC591 had a considerable degree of thlxotropy which contributed to their stability. When Tween 80 was incorporated in this system, oil droplets coalesced indicating that the stability of the emulsion was affected adversely.     

Long-term stability of emulsion based on rose oil

This paper was aimed at determining the parameters responsible for the long-term stability of emulsions. Compositions of six emulsions with different amounts of emulsifier and thickener were developed according to the authors’ own specifications and requirements of KT-Skor software (based on Kleeman’s method). Physical properties of the emulsions were evaluated (determination of emulsion type, structure of emulsion, stability tests, viscosity, average particle size, and dispersity index). The results obtained indicate that the emulsion containing 10?g of rose oil and 0.2?g of thickener exhibited the highest stability.     

Stability of W/O Emulsions Encapsulating Polysaccharides

In the frame of formulation of W/O emulsions entrapping polysaccharides devoted to agricultural applications, the aim of this work was to study the stability over time of these emulsions, stabilized with either soybean lecithin or polyglycerol polyricinoleate (PGPR) as emulsifiers. Emulsifiers were dissolved in oil phase, and polysaccharides (carboxymethycellulose (CMC), guar, xanthan) in ultrapure water. Emulsions stability was studied through natural aging tests and accelerated aging tests, using bottle tests, microscopy and calorimetry. Experiments showed that PGPR was more efficient than lecithin to stabilize emulsions containing the polysaccharides studied, and that emulsions prepared with CMC showed the best stability.     

EFFECT OF PREMIX CONDITION,SURFACTANT CONCENTRATION,AND OIL LEVEL ON THE FORMATION OF OIL-IN-WATER EMULSIONS BY HOMOGENIZATION

Oil-in-water emulsions were prepared on a homogenizer from good premixes and poor premixes. The quality of the emulsions was determined by measuring the droplet size distribution using spectroturbidimetry. A good premix to the homogenizer produces a better emulsion than a poor premix. Premix conditions become less important when the concentration of emulsifier is increased in relation to the amount of oil. Increasing oil concentration results in a poorer final emulsion. Large amounts of emulsifier negate the advantage of using the homogenizer, but greater mechanical energy input can compensate for reduced emulsifier concentration, a cost saving when formulating an emulsion.     

Impact of Adding Polysaccharides on the Stability of Egg Yolk/Fish Oil Emulsions under Accelerated Shelf-Life Conditions

Polysaccharides can form interfacial complexes with proteins to form emulsions with enhanced stability. We assessed the effect of adding gum guar or gum arabic to egg yolk/fish oil emulsions. The emulsions were produced using simple or high-pressure homogenization, stored for up to 10 days at 45 °C, and characterized for their particle size and distribution, viscosity, encapsulation efficiency, oxidative stability, and cytotoxicity. Emulsions containing gum guar and/or triglycerides had the highest viscosity. There was no significant difference in the encapsulation efficiency of emulsions regardless of the polysaccharide used. However, emulsions containing gum arabic displayed a bridging flocculation effect, resulting in less stability over time compared to those using gum guar. Emulsions produced using high-pressure homogenization displayed a narrower size distribution and higher stability. The formation of peroxides and propanal was lower in emulsions containing gum guar and was attributed to the surface oil. No significant toxicity toward Caco-2 cells was found from the emulsions over time. On the other hand, after 10 days of storage, nonencapsulated fish oil reduced the cell viability to about 80%. The results showed that gum guar can increase the particle stability of egg yolk/fish oil emulsions and decrease the oxidation rate of omega-3 fatty acids.     

应用分子电距矢量对地笋中挥发油化学成分色谱保留值分析

采用分子电性距离矢量(MEDV)表征地笋中挥发油化学成分的分子结构,并对其气相色谱保留时间进行了系统的定量结构-色谱保留关系(QSRR)研究。在变量筛选的基础上建立了多个挥发油化学成分QSRR模型,相关系数均在0.90以上。通过严格的统计检验表明所建模型具有良好的稳定性与预测能力。     

FLOW PROPERTIES OF WEATHERED CRUDE OILS AND THEIR EMULSIONS

The present paper proposes the emulsification of weathered crude oils in water as a competitive and cost effective method for reducing their viscosities. Weathered crude oil samples were collected from major Kuwaiti oil lakes. Emulsion preparation involved using, either a nonionic surfactant or alkali, as well as both alkali and fatty acid. The obtained emulsions were characterized by measuring the droplet size distribution of the dispersed phase using optical microscopy. Emulsion stability was also examined in terms of the system breakdown. The rheological properties were measured using a concentric cylinder rotary rheometer. The emulsion rheological behavior has been studied as a function of composition, temperature, and shear rate. A constitutive model was developed to characterize the pseudoplastic behavior of the crude oil and the emulsion systems. The model fitted well the experimental results with a correlation coefficient higher than 95%. Associated with the pseudoplastic behavior, viscoelastic behavior has been observed with emulsions and some oils at high shear rates.

The results of this investigation indicated that the examined weathered crude oils can be transported through pipelines as emulsions of up to 80 vol.% oil concentrations. The proposed method of treatment with NaOH and oleic acid offers several advantages over the surfactant treatment. It exhibited comparable rheological behavior at lower cost and less mixing energy. It also provided higher emulsion stability, which favors oil transportation for longer distances.     

Emulsion Inversion in an Oil‐Surfactant‐Water System Based on Model Naphthenic Acids under Alkaline Conditions

Emulsion inversion has been studied in a system based on oil (toluene/heptane), 5β‐cholanic acid, and an alkaline brine solution by varying the concentration of sodium hydroxide. At an intermediate pH w/o emulsions were formed, and in the high pH region o/w emulsions were formed. Emulsion inversion occurred in the pH range 8.5–10. The w/o emulsions were consistently more stable compared to the o/w emulsions. Increasing the amount of acid enhanced the stability of the emulsions. Maximum stability was observed close to pH 8, where the ratio between the undissociated and dissociated acid was approximately 1.5. From light microscopy, it can be seen that the emulsions are stabilized by a liquid gel phase. At equilibrium the system consists of an oil phase, a liquid gel phase, and an aqueous phase. Increasing the oil fraction eventually gave only w/o emulsions in the pH range between 7 and 14. For these emulsions, no obvious difference in stability was observed at pH 8, while the stability of the emulsions in the high pH region was significantly enhanced. An increase of the ratio between toluene and heptane gave no obvious difference in either stability or type of emulsion while varying the pH. Use of a less lipophilic acid, such as 4‐octylbenzoic acid, gave very unstable w/o emulsions in the intermediate pH region, while stable o/w emulsions were found in the high pH region.     

Effect of emulsifier HLB and stabilizer addition on the physical stability of thyme essential oil emulsions

The objective of this work was to formulate and to further improve the stability of emulsions based on thyme essential oil. Several nonionic surfactants of different nature and with different hydrophilic?lipophilic balance (HLB) values were investigated. The surfactant with optimal HLB found for the thyme essential oil was Appyclean 6548 (HLB: 9-9.5). Afterwards, stabilizing biopolymers were added in order to improve emulsion stability. Properties of emulsions were evaluated in terms of droplet size and physical stability. Thyme essential oil/W emulsions formulated with a new biodegradable emulsifier (alkyl polypentoside) and welan gum as stabilizer were obtained with high shelf-life.     

碳酸钙微粒稳定的橄榄油/水乳液及其缓释性能

1907年,Pickering发现超细固体颗粒对乳液具有一定的稳定作用~([1]).此后,由固体颗粒单独稳定的乳状液也被称为Pickering乳液.Pickering乳液在新材料合成、生物活性分子保护、食品和医药等领域具有重要的应用价值~([2-7]).     

Formulating Neem Oil Emulsion as Potent Agrochemicals Using a Binary Emulsifier System

Neem oil is a natural pesticide and has excellent insecticidal properties. Hence, in this study the efforts have been made to formulate the Neem oil emulsions which would be used as agrochemicals. In order to formulate stable Neem oil emulsions, a binary emulsifier system of Hydol-6 (Polyoxyethylene Alkyl Ether-6 moles of ethylene oxids) and Hydol-10 (Polyoxyethylene Alkyl Ether-10 moles of ethylene oxids) were employed. Stability of Neem oil emulsions as a function of concentration of Neem oil, Hydol-6, Hydol-10, the amount of water, homogenization speed, and homogenization time was studied in depth. Apart from this, it was observed that the nature of water also affects the stability of the emulsions. The concentration of Neem oil in the stable emulsions was also found to exhibit the varying effects on the properties like dispersibility, spreading power, and droplet size of the emulsions. Larvasidal effects of stable Neem oil emulsions were examined.     

DYNAMICS OF EMULSION FORMATION

Stochastic model for oil emulsification in water has been deduced. The model in the form of differential equation was starting point to get various mathematical expressions and relations connecting different factors and parameters of the emulsification process and dispersion and Theological properties of the emulsion. Experimental investigations of particle size distribution, Theological behaviour and stability of great number of oil-in-water emulsions have been performed. The aim of the experimental investigations was to verify validity of the expressions derived. The validity of the derived expressions was checked not only for emulsions of different compositions, but also for the changes and phenomena at different stages of the emulsification process.     

FORMATION AND APPLICATIONS OF MULTIPLE EMULSIONS

Multiple emulsions, especially water-in-oil-in-water (W/O/W) type systems, have potential applications for the formulation and processing of foods, drugs, cosmetics, etc, as each dispersed globule in this type of emulsions consists of liquid compartments separated from the same liquid suspending medium by a thin layer of another immiscible liquid components. This article reviews a series of fundamental works on the formation and dispersion state of multiple emulsion systems and integrates advances made in the area of colloid science so as to obtain further insights into the formulation of W/O/W emulsions. The contents are divided into three sections: methods for preparing multiple emulsions in view of the phase diagram of mixed components, dynamic aspects of oil layer in W/O/W emulsions, and stability of this type of emulsions.     

Multiple emulsion stability: pressure balance and interfacial film strength

The objective of this study was to investigate the significance of inner and outer phase pressure, as well as interfacial film strength on W/O/W multiple emulsion stability using microscopy and long-term stability tests. It was observed that immediately upon applying a coverslip to samples the multiple droplets deformed and there was coalescence of the inner aqueous droplets. Under certain conditions (such as lipophilic surfactant concentration and internal phase osmotic pressure) the destabilized multiple emulsions formed unique metastable structures that had a "dimpled" appearance. The formation of these metastable structures correlated with the real-time instability of the W/O/W multiple emulsions investigated. Multiple emulsion stability also correlated with the interfacial film strength (measured by interfacial elasticity) of the hydrophobic surfactant at the mineral oil/external continuous aqueous phase interface. The formation of the metastable dimpled structures and the long-term stability of the multiple emulsions were dependent on the osmotic pressure of the inner droplets and the Laplace curvature pressure as described by the Walstra Equation (P. Walstra, "Encyclopedia of Emulsion Technology" (P. Becher, Ed.), Vol. 4. Dekker, New York, 1996). It appears that the effect of coverslip pressure on multiple emulsions may be useful as an accelerated stability testing method or for initial formulation screening.     

Influence of pH on the stability of oil-in-water emulsions stabilized by a splittable surfactant

A laboratory study was conducted to evaluate the effect of pH on the stability of oil-in-water emulsions stabilized by a commercial splittable surfactant Triton SP-190 by comparison with the results obtained by a common surfactant Triton X-100. The emulsion stability was explored by measuring the volume of oil phase separated and the size of the dispersed droplets. It was found that the addition of inorganic acids did not significantly affect the stability of emulsions stabilized by Triton X-100, but had a profound influence on the stability of emulsions stabilized by Triton SP-190. Moreover, the droplet size of a Triton X-100-stabilized emulsion and its dynamic interfacial activity were insensitive to acids. However, at lower pH the droplet size of the emulsions stabilized by Triton SP-190 was considerably increased. From the dynamic interfacial tension measurements the dynamic interfacial activity of Triton SP-190 at the oil/water interface was found to be strongly inhibited by the addition of acids, resulting in a slower decreasing rate of dynamic interfacial tension. The results demonstrate that the dramatic destabilization of Triton SP-190-stabilized emulsions could be realized by the use of acids, which evidently changed the interfacial properties of the surfactant and resulted in a higher coalescence rate of oil droplets.     

无皂乳液聚合制备含铕荧光共聚物乳液的研究及其表征

以丙烯酸(AA)为第一配体、邻菲罗啉(Phen)为第二配体、Eu3+为中心离子,合成了一种可聚合的稀土铕配合物.以配合物单体、甲基丙烯酸甲酯、丙烯酰胺和对苯乙烯磺酸钠为共聚单体,通过无皂乳液聚合的方法,制备了含铕荧光共聚物乳液.采用红外光谱对共聚物的结构进行了表征,并探讨了配合物单体含量对共聚物乳液性能的影响.透射电子显微镜(TEM)和激光光散射粒度仪(PCS)测试结果表明,共聚物乳液形成了相对均一的球状结构,但随着配合物单体含量增加,共聚物微球粒径逐渐增大、分散性变差.采用荧光分光光度计测试了共聚物乳液的荧光性能,在594和619 nm处出现Eu3+的特征发射光谱,且荧光强度随着配合物单体含量增加而增强.