Synthesis Of A Series Of Mono-isomeric Alkylbenzenesulfonates And Studies On Their Interfacial Tension Behavior And The Relationship Between Molecular Structure And Performance

The primary object of this dissertation is to synthesize a series of mono-isomeric alkylbenzene sulfonates, find out the molecular structure having the best ability in lowering the interfacial tension between oil and water by investigating the relationship between molecular structure and performance of this kind of surfactants and interpret the mechanism on producing ultra-low interfacial tension from microcosmic point of view, thus provide theoretical fundamentals for designing surfactant molecules in enhanced oil recovery.A series of mono-isomeric alkylbenzene sulfonates of various lengths of alkyl chains with benzene rings located at different positions along the alkyl chains are synthesized. The purities of three kinds of intermediates, alkyl phenyl ketones, tertiary carbinols and phenyl alkanes, are analyzed by GC and structures are characterized by GC-MS. HPLC indicates the purities of final product alkylbenzene sulfonates are all above 95% and their structures are confirmed to be correct by EI-MS, 1H NMR and 13C NMR investigations.The interfacial tension behavior of this series of alkylbenzene sulfonates is investigated in alkane/aqueous system and crude oil/alkali system respectively. Studies on the dynamic interfacial tension behavior show that interfacial tension decreases monotonically against alkane but goes through a minimum against crude oil. The transient low interfacial tension in crude oil/alkali system is caused by the synergistic effects between surfactant and the active species generated by the in situ reaction of acid in crude oil and alkali in water at the interface. After active species desorb from interface and diffuse into the bulk phase, the added surfactant molecules play the dominant role at equilibrium. From the studies on alkane preference and alkalinity dependence of interfacial tension, it is found that alkylbenzene sulfonate of 16 total alkyl carbon number with benzene ring located near the center of the alkyl chain is the most ideal structure for enhanced oil recovery because it can reduce the interfacial tension to ultra-low at low alkalinity and be applicable to a wide range of oils.The relationships between surfactant molecular structure and micelle structure, ability in lowering surface tension and configuration of adsorption layer are clarified by investigating the surface tension behavior and proton NMR relaxation time of this series of mono-isomeric alkylbenzene sulfonates. The configurations of organized assemblies of these compounds in aqueous solution are characterized by transmission electron microscopy and polarizing microscopy and it is found that the 5-isomers can form monolamellar vesicles spontaneously, whereas the 7-isomers form lamellar liquid...