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AbstractThe widespread use of polymer flooding has resulted in a large number of produced liquids consisting of crude oil emulsions and oily wastewater. Efficient flocculants are required to treat these produced liquids till the oily wastewater satisfies the requirements for reinjection formation in order to maintain the regular manufacturing process. In this work, an unsaturated polyether macromonomer (PEP-30) was prepared by ring-opening polymerization using isobutenol as a starting material. Subsequently, a novel flocculant (PMAP) was obtained by copolymerization of dimethylamino propylmethacrylamide (DMAPMA) and PEP-30. For the produced liquids with different crude oil emulsion content, the oil removal rate of PMAP at a dosage of 150 mg/L was more than 75%, and the oil removal rate and versatility were better than those of conventional cationic flocculants. Furthermore, the findings of the flocculation mechanism investigation demonstrated that PMAP had a low interfacial elastic modulus and a large interfacial adsorption mass. Specifically, the optical tweezers were used to detect the interaction force between oil droplets. PMAP effectively strengthened the attraction between oil droplets, extending their duration in contact during flocculation and promoting their coalescence. [ABSTRACT FROM AUTHOR]

AbstractThe study of emulsion stabilization mechanisms is of great importance in the field of crude oil extraction, transportation and processing. In order to further investigate the roles of asphaltenes and surfactants in the emulsion stabilization process, the adsorption mechanisms of asphaltenes and surfactants at the oil-water interface were investigated using dissipative particle dynamics. The results show that: the asphaltene interfacial film gradually becomes thicker before the saturation adsorption of asphaltene molecules at the oil-water interface, and the interfacial tension decreases with the increase of the number of molecules until it reaches the equilibrium state; different surfactant molecules have different influences on the interface, and the calculations of the radial distribution function and the interfacial tension show that H2T4 molecules have a stronger effect than H4T4 at the oil-water interface and have stronger surface activity. H2T4 reaches saturation adsorption capacity faster than H4T4 and has higher interfacial efficiency. The asphaltene-surfactant composite system can stabilize the oil-water interface more effectively. Competitive and synergistic effects of asphaltene and surfactant in the process of interfacial adsorption. When the concentration of surfactant in the composite system is low, there is a synergistic effect between the two in the interfacial adsorption process; when the concentration of surfactant is high, there is a competitive effect between the two in the synergistic adsorption process. The surfactant H4T4 has both interfacial adsorption and self-aggregation in the competitive adsorption process. This paper provides ideas for exploring the kinematic laws of molecular behavior in the stabilization mechanism of crude oil emulsions. [ABSTRACT FROM AUTHOR]

The gas-liquid interface properties and molecular adsorption of the binary mixtures of anionic surfactant sodium dodecyl sulfate (SDS) and cationic surfactant dodecyl trimethyl ammonium chloride (DTAC) with different molar ratios were described through molecular dynamics (MD) method with the aim of providing supplements to the experiments at the molecular level. The simulation results showed that the anionic/cationic surfactant mixtures can form a denser interfacial monomolecular layer than single surfactants, and the interface will tend to form equimolar adsorption eventually. The entry barrier of the interface under different molar ratios was investigated, the system with a high SDS ratio has higher the entry barrier, which means that the initial non-equal molar ratio of the interface composition may be more conducive to prolonging the existence time of the interface. The rupture process of the microscopic liquid film was simulated, and it was found that the site not covered by surfactant molecules was the point where the liquid film was prone to rupture. The critical rupture thickness of each models was about 0.8 ∼ 1.2 nm. [ABSTRACT FROM AUTHOR]

The proteins and polysaccharides complexes could play the important role on the delivery systems in the food and pharmaceutical industries, it's necessary to investigate the interaction between them and the interfacial behavior during their application. In this research, complex of xanthan gum (XG) and lactoferrin (LF) were prepared and the phase behavior and the interfacial properties were investigated with turbidity, size and Zeta-potential. Also the interfacial adsorption kinetics was analyzed. The results showed that the state of LF-XG solution with pH above 5 showed uniform gel-like, with the rise of XG concentration, the interfacial tension at endpoint decreased from 17.48 to 15.52 mN/m, the rate of penetration and rearrangement of LF-XG system lower than the LF solution, which indicated that XG could promote the stabilization of LF-XG complex and the interactions between LF and XG influenced the interfacial behavior of LF. [ABSTRACT FROM AUTHOR]

The interfacial behavior and the process of micellization of octadecyltrimethylammonium bromide (OTAB) in aqueous solution without or with 70 g/L short chain alcohol including methanol, ethanol, 1-propanol and 1-butanol were investigated by both the tensiometry and the conductometry at 313.15 K. Based on the data of tension and conductivity, the maximum adsorption (Γmax) at the air-liquid interface, the minimum area per molecule (ASmin) at the saturated interface, the critical micelle concentration (cmc), the degree of ionization (α) at the surface of micelle, the packing parameter (P) and the standard free energy change of micellization (ΔG0mic) were obtained. The presence of alcohol and the change of the chain length of alcohol alter the hydrophobic effect, the electrostatic interaction and the presence of alcohol molecule at the air-liquid interface or in the micelle, causing the variation in the interfacial or micellization behavior. The data of ΔG0mic also confirm the process of micellization. These findings help with understanding the molecular interaction between surfactant and alcohol and further obtain some information about the contribution of cosolvent on the surfactant formulation. [ABSTRACT FROM AUTHOR]

An acrylic emulsion-type inverse demulsifier (named as PMEMA latex) was prepared by using methyl methacrylate (MMA), ethyl acrylate (EA), methacrylic acid (MAA), and acrylamide (AM) as monomers. The effects of reaction conditions toward the copolymerization results were investigated by evaluating various evaluation parameters, including conversion, molecular weight, and diameter. In addition, the interfacial properties of PMEMA latex were investigated to study its demulsification mechanism about treating the O/W emulsion. [ABSTRACT FROM AUTHOR]

High-quality graphene quantum dots (GQDs) were prepared through a facile route of microwave-assisted one-step mild oxidation of cheap deoiled asphalt (DOA). The as-prepared DOA-derived GQDs dissolved in water with a much smaller and thinner size than most of the reported GQDs, and luminesced bright green light by excitation of 365 nm. Furthermore, the GQDs possessed excellent properties of excitation-tuned fluorescence behavior with a high quantum yield up to 16.4%. In addition, the GQDs showed amphipathic properties and could significantly reduce the interfacial tension, which give them great potential as surfactants for asphalt emulsion. [ABSTRACT FROM PUBLISHER]

This article describes interfacial properties of acidic asphaltenes and their ability to stabilize emulsions. Asphaltenes extracted from crude oil were esterified with methanol to prevent ionization of carboxylic acid at high pH. Interfacial tension (IFT) between water and asphaltenes in xylene was significantly lower in basic than in acidic and neutral media, while the elasticity of the corresponding films was higher. These results are consistent with much more stable asphaltene-based emulsions in basic medium. For ester-asphaltenes, the IFT only showed a slight decrease under basic conditions and the interfacial elasticity was close to that in acidic solutions and only slightly higher than for neutral medium. While the asphaltene-stabilized emulsions showed a strong increase in stability in basic medium, this increase was much less for esterasphaltene emulsions. Salt influenced the interfacial properties and generally reduced emulsion stability. [ABSTRACT FROM AUTHOR]

Oil-in-water emulsion is an innovate manner by which heavy crude oil can be transported from producing sites to transforming sites through pipelines. The effect of emulsifier on the interfacial properties and demulsification performance of demulsifier for heavy crude oil–in-water emulsion has been studied by many researchers. However, the influence of asphaltene in heavy crude oil on the interfacial properties of demulsifier has not been investigated yet. In this article, the influence of asphaltene concentration of two typical demulsifiers (straight-chained SP-1 and branch-chained AE-1) was systematically studied in terms of absorption thermodynamics, absorption kinetics, and coalescence kinetics. The results revealed that the demulsifier adsorption was aΔScontrolled spontaneous process. The absolute value ofΔGof SP-1 adsorption was found to decrease with asphaltene concentration, whilst the asphaltene concentration had no significant influence on that of AE-1. With the increase of asphaltene concentration, the demulsifiers’ adsorption rates increased, but the reorganization rates on the interface decreased. Coalescence speed of asphaltene droplet decreased with asphaltene concentration in spite of demulsifier type. Additionally, AE-1 had higher absolute value ofΔG, adsorption speed, and coalescence speed than that of SP-1 at the same condition. [ABSTRACT FROM PUBLISHER]

Six oil soluble nonionic surfactants with different HLBs have been prepared. Their HLBs situate between 3.9 and 6.7. Transesterification was carried out for glycerol and triethanol amine with oleic acid at different moles to obtain six emusilifiers. They named glycerol momooleate (I), glycerol diooleate (II), glycerol trioleate (III), triethanol amine mono-, di- and tri-oleate (IV), (V,) and (VI). The chemical structure was confirmed using; the elemental analysis, FTIR and 1HNMR. They were evaluated as a primary emulsifiers (PE) for thdrilling fluids (oil base mud) comparing with a currently used primary emulsifier (Fc). The water in oil base mud (w/o emulsions) was prepared. The concentration of emulsifiers and their HLB exhibited interesting rheology properties including shear-thinning behavior, yield value, viscoelastic effects, thixtropy, gel strength, and filtration loss. The rheology properties of such emulsions strongly depended on the average size distribution of the dispersed droplets that could be varied both with the bulk concentration and HLB value of the emulsifiers. The interfacial and surface properties of these emulsifiers suggest that the droplet size of the dispersed phase and bulk concentration are strongly related to the HLB value of emulsifiers. The w/o emulsion (mud formulation) stability is sensitive to the droplet size of the dispersed phase and HLB value of the used emulsifier. The results were discussed on the light the chemical structure of the primary emulsifiers and the emulsion ingredients. [ABSTRACT FROM AUTHOR]

Quaternary ammonium salts of 2-undecyl (heptadecyl)-1-dithioureido-ethyl-imidazoline (SUDEI/SHDEI) have been synthesized, and their interfacial properties are investigated. The effects of temperature, alkyl chain R length, and polarity of solvents on the surface tension are discussed. The results show that surface tension of SUDEI and SHDEI in water solutions decreases with increasing of temperature, and SHDEI shows lower cmc value than SUDEI at constant temperature, indicating that it is easier for SHDEI to form micelles in water. SUDEI and SHDEI show much higher cmc in ethanol-water (1:4, v/v) than that in pure water. The molecular structure of SUDEI/SHDEI is composed of lipophilic group R and hydrophilic group comprising active elements S, N and imidazoline ring and the two groups are of similar length, which is similar to that of bi-block copolymer. Thus, interesting results have been found in the preparation of nanomaterials in the presence of imidazoline surfactants. The corresponding mechanisms are still under investigation. [ABSTRACT FROM AUTHOR]