Molecular Simulation Of The Influence Of Fatty Alcohol Polyether Sulfonate On Oil-water Interface

Fatty alcohol polyoxyethylene ether sulfonate surfactants are typical anionic nonionic surfactants,which can combine the advantages of nonionic and anionic surfactants.They have good salt tolerance,good stability and environmental friendliness,and are gradually applied to the petroleum industry.This thesis chooses sodium dodecyl alcohol polyoxyethylene ether sulfonate(AESO)as the basic research object,and designs a series of simulation experiments by changing the partial structure of the hydrophilic group of AESO and the components of the oil phase and the water phase.In this thesis,the molecular dynamics simulation method is used to study the interfacial properties of oil/surfactant/water ternary system and its microscopic mechanism at room temperature and atmospheric pressure.First,the thesis investigates the effect of polymerization degree on the properties of surfactants by studying the interfacial regularity of sodium dodecyl alcohol polyoxyethylene ether sulfonate including different quantities of polyethylene at n-dodecane/water interface;secondly,the thesis investigates the effects of oil phase and polymerization degree on the interfacial properties of the system by simulating oil/surfactant/water ternary system with different oil phase components;finally,the salt resistance of fatty alcohol polyoxyethylene ether sulfonate surfactants is investigated by simulating sodium dodecyl alcohol polyoxyethylene ether sulfonate at the interface between electrolyte solution and n-dodecane group by group,which has different counterions.The simulation results show that fatty alcohol polyoxyethylene ether sulfonate surfactants form a stable monolayer at the oil-water interface,which is curved and has a certain thickness.In this paper,the influence factors and changes of fatty alcohol polyoxyethylene ether sulfonate surfactants with different polymerization degree on the interfacial tension of oil and water were evaluated theoretically by calculating parameters such as generation energy,density distribution and thickness of interface layer.When the range of polymerization degree is 3-9,AESO with a degree of polymerization of 6 are more active at the n-dodecane/water interface and the n-cetyl/water interface.The AESO has excellent salt resistance,the longer the EO chain,the better the salt resistance.When the degree of polymerization is 3,the order of salt resistance of the AESO is Na⁺>Ca²⁺>Mg²⁺.The thesis provides theoretical guidance for the optimization and design of surfactants through simulation.