Synthesis And Properties Study Of Anionic Gemini Surfactants

In the dissertation,novel six di-n-alkyl diol intermediates were synthesized from 1, 2-epoxytetradecane and short-chain diols through ring-opening, sulfation and neutralization. The chemical structures were characterized by FT-IR, 1H-NMR and ESI-MS methods. As model compounds, the relations of structure and properties of the highly purified anionic gemini surfactants were studied. The main work and conclusions are as following:The surface tensions of anionic Geminis were investigated in aqueous solutions by Wilhelmy plate method, to study the adsorption behavior at the water/air interface, and the effect of temperature and ionic strength to adsorption properties. The values of cmc,γcmc, pC20,Γmax, ? Ga0d were obtained by theγ-lgC curves. It is indicated that the anionic Geminis are three orders of magnitude more surface active than that of their single-chained counterparts, cmc values are lowered by two to three orders of magnitude, and easier adsorbed at the interface. The smallestγcmc values are Geminis with spacer groups of short, slightly hydrophilic (just capable of hydrogen bonding with water) hydrophobic and flexible. The properties of spacer groups are remarkably important to the surface adsorption. Partial charge of the hydrophilic group was neutralized, the repulsive force was weakened, and the intermolecular ordered structure was strengthened because of the addition of sodium chloride. The factor of temperature will influence the formation of micelles, thus the behavior in aqueous solution will be changed.Dynamic surface tensions of anionic Geminis with spacer group of EO units were investigated in aqueous solution. Dynamic surface parameters were obtained by use of Rosen equation. The results show that, the more length of spacer chain, the slower diffusion rate of molecular from bulk phase to surface, the stronger adsorption at aqueous surface, and the lower dynamic surface activity.The foam properties of anionic Geminis in aqueous solutions at different conditions, such as the molecular structure, concentration of Geminis, temperature and different additives (sodium chloride, polymer and aliphatic alcohol, etc.) were measured by the Foamscan. It is found that the anionic Geminis display good foaming performance at room temperature. Essentially, the foam performance is influenced by the molecular arrangement at air/water interface.The interfacial tension between anionic Geminis and n-alkanes, crud oil had been investigated at different conditions, such as the concentration of anionic Geminis, spacer group structure and inorganic salt. The minimum alkyl carbon number (nmin) of anionic Geminis is dodecane by interfacial tension scanning. The structure of spacer group makes no influence to nmin. Anionic Geminis display outstanding salt resistance. The interfacial tensions reduce as the salt concentration and the number of EO units in spacer group increasing. Ultra low interfacial tension could be achieved in water/crude oil system of T2E1 and T2H1. T2E1 was selected as EOR surfactant to study the static adsorption consumption by oil sand and thermal stability. Core flooding experiment shows that enhanced oil recovery is 16.3% (OOIP).