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Interaction between Anionic Surfactants and Inorganic Salts

Author: ZhaoTaoTao
Tutor: XuGuiYing
School: Shandong University
Course: Colloid and Interface Chemistry
Keywords: Anionic surfactant Molecular dynamics simulations Inorganic salts Interaction
CLC: TQ423
Type: Master's thesis
Year: 2010
Downloads: 353
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Abstract

Surfactant plays an important role in chemical flooding process, in order to adapt to the reservoir high-temperature, high-salinity conditions, the surfactant temperature and salt resistance has been a subject of much attention. Existing research focuses on inorganic salts affect the macroscopic properties of the surfactant solution, such as the critical micelle concentration, surfactant aggregates, rheological properties, mainly through changes in the system of physical and chemical properties of these studies to infer mutual role in the mechanism, in the microscopic point of the lack of a precise description. Molecular dynamics simulations have been proven to be a research surfactant system effective means to explore the surface active agent and the interaction of the inorganic salt can be in the level of molecules, atoms. In view of this, the thesis application of molecular dynamics simulations to study the interaction of inorganic salts with anionic surfactants, and compare the impact of different inorganic salts on the nature of the anionic surfactant. The thesis consists of the following five parts: the first part of the paper illustrates the study of anionic surfactants and inorganic salts important theoretical significance of the interaction, and of salts on the physical and chemical properties of the surfactant and its research progress. The second part describes the calculation method of molecular dynamics simulations, mainly from molecular dynamics simulations of basic principles and calculation elaborate. A third portion of the paper to the heavy alkylbenzene sulfonate 4 - (1'-hexadecyl) benzene sulfonate (1-16) and 4 - (5'-16 alkyl) benzene sulfonate (5C16 ) interaction with NaCl, CaCl2 and MgCl2. Heavy alkyl benzene sulfonate in oil production occupies an important position in the surfactant flooding alkylbenzene sulfonate is a mixture of different relative molecular mass alkyl benzene sulfonate composition, due to the complexity of its composition, molecular equivalent distribution width, purification difficulties, experimental studies variability factors many macroeconomic performance measurement is difficult in the mechanism of action to make a satisfactory explanation, so we apply the method of molecular dynamics simulations to overcome this difficulty, in the microscopic study single alkylphenyl sulfonate nature. The results showed that 1-16 are arranged at the interface than in the two surfactants 5C16 more rough, this is because the 1-16 single molecules at the interface area is less than 5C16 1-16 repulsion between the polar head groups are more apparent. . The added inorganic counter ions (Na, Mg2, Ca2) are distributed in the surrounding of the monomolecular layer of the negatively charged, and be able to shield the electrostatic repulsion between the polar head, the size of its role in the order of: Ca2 GT; of Mg2 GT; Na. The smaller radius of hydration of C2 to more easily enter into the hydration layer of the polar head group of the surfactant, thus bound in this part of the movement of water molecules. In addition, the salt resistance of the branched-chain 5C16 better than the straight-chain from 1-16. The fourth part of the thesis anionic surfactant sodium dodecyl sodium sulfate (SDS), a combination of methods of application experiments and molecular dynamics simulations to study its interaction mechanism with CaCl2, MgCl2 to anionic surfactants for research salt tolerance mechanism of the agent in the aqueous solution to provide microscopic information useful. The experimental results show that, evident SDS/CaCl2, SDS/MgCl2 System with a precipitation - redissolved area, wherein the role of Ca2 and SDS more apparent, this is because of the smaller radius of Ca2 of hydration, which go to hydration than water of a larger radius, smaller Mg2 Ca2 easier with SDS hydrophilic head group. NaCl and TX-100 can significantly improve the ability of SDS anti-calcium and magnesium. The fifth section discusses the impact of the gas / liquid interface aggregation behavior of LiCl, NaCl, KCl, MgCl2 and CaCl2 on two - ethyl - hexyl succinate sulfonate (AOT). The study found that the arrangement of AOT in the gas / liquid interface is rough, the hydrocarbon chain tail bent toward the gas phase, most of the counter ion is located near the AOT polar head. In near AOT polarity head there is an obvious hydration layer, This is because the water molecules through the hydrophilic head group of the strong hydrogen bonding interactions with the AOT \When the inorganic salt was added to the system, AOT, adding the counter-ion (Li, Na, K, Mg2, Ca2) is able to compress the AOT diffuse double layer, reduce the electrostatic repulsion between the AOT polar head, so that the AOT ions at the interface more closely arranged. Smallest K in the three kinds of monovalent counter ions, the hydration volume can be more easily compression AOT the hydration layer of the polar head, go to the hydration capacity strongest in three kinds monovalent counter ion, so K AOT single The molecular layer of the greatest impact on the role of Na, followed by Li. Also, K may also be embedded into the gap between the AOT molecule which caused AOT polar head of water molecules interacting weakened. In the two kinds of divalent counter ion, the hydration of a small radius of Ca2 AOT monolayer impact than the hydration of a large radius of Mg2 strongly.

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