Study On The Synthesis And Physicochemical Properties Of Anionic Surfactants With Aromatic Nucleus In The Branches

It is valuable in theory and practice to design surfactants for special application fields. Many researches had shown that surfactants with branches can reduce surface tension obviously, which may break a new path to design surfactants for Enhanced Oil Recovery (EOR). The studies on bulk and surface (interface) properties of anionic surfactants with aromatic nucleus in the branches are rarely reported, which leads to lacking systematical knowledge in the relationship of the molecular structure and performance of this kind of surfactants. The few researches have indicated that the arylalkyl sulfonates, containing aromatic nucleus in the branches, performed better interfacial properties, which made them potential candidates for a wide variety of surfactant applications in EOR. In the dissertation, two types of anionic surfactants with aromatic nucleus in the branches have been synthesized and their properties have been studied. The experiments and results are as following:The arylalkyl sulfonates were prepared through a novel route, including Friedel-Crafts alkylation, photo-sulfochlorination and saponification reaction, using benzene (or alkylbenzene) andα-olefin as starting materials. The interfacial activities were explored by measuring the interfacial tensions between arylalkyl sulfonate aqueous solution and Shengli crude oil. It's shown the arylalkyl sulfonates were very salt tolerant, and can be used at low concentrations to produce ultra-low interfacial tensions without alkaline, which indicated the potential applications of arylalkyl sulfonates in Enhanced Oil Recovery. Novel sodium 2-(2-(alkylaryloxy)-alkylamido)ethanesulfonates (m+nAr-T, m, n: carbon numbers; Ar: aromatic nucleus; T: taurine) with high purity were synthesized through bromization, esterification, Fries rearrangement, Pd-catalyzed hydrogenation, Williamson reaction, and acylation, et al, using carboxylic acid, phenol (alkylphenol or naphthol) and taurine as starting materials. The structures and purities were characterized. The optimum conditions on etherification were explored, and the esterification could undergo in high yield when K2CO3 was used as acid accepter and water was separated from the system. The 2-(alkylaryloxy)carboxylic acid reacted with taurine mildly when catalyzed by dicyclohexylcarbodiimide and N-hydroxysuccinimide, and the conversions were higher than 90%.The surface tensions of m+nAr-T aqueous solutions have been investigated by Wilhelmy plate method. The values of critical micelle concentration (cmc), surface tension at cmc (γcmc), efficiency in surface tension reduction (pC20), saturation adsorption amount (Γm ax), standard free energy of adsorption (ΔG m0ic), and of micellization (ΔGa0d) were obtained by thermodynamic calculation fromγ?lgc curves. It was discovered that the inclusion of aromatic nucleus in branches enhanced the surface activities. In aqueous solution, theΓm ax decreased with the branch getting larger or longer, while the effectiveness and efficiency of surface tension reduction showed opposite tendency. These phenomena were reasonably explained on the basis of the two-dimensional gas model of Blankschtein.The dilational viscoelastic properties of m+nAr-T at air-water and oil-water interfaces were investigated by means of two methods: the interfacial tension response to sinusoidal area variations and interfacial tension relaxation method respectively. The dependencies of dilational modulus and phase angle on the concentration, time, and frequency were explored. The dilational modulus and phase angle changed regularly with changing of concentration, time, and frequency. The dilational modulus values of sodium 2-(2-(2-naphthoxy-tetradecanamido)ethanesulfonate (12+N-T) higher than sodium 2-(2-phenoxy-tetradecanamido)ethanesulfonate (12+B-T) indicated stronger intermolecular interaction of the former. The dilational modulus increased with increment of the side chain.The foam properties of m+nAr-T in the aqueous solution at different physicochemical condition were measured by air flowing method. The surfactants with m+n≤16 showed good foaming ability and foaming stability. The foaming ability increased with the temperature increasing, while the foaming stability showed opposite tendency. The foaming stability was increased when NaCl was added, while the foaming ability was influenced little by NaCl in our study.The micellezation and aggregation properties of m+nAr-T surfactants in aqueous solutions were investigated by fluorescence spectra of extrinsic probe (pyrene) and intrinsic probe. It's shown the inclusion of aromatic nucleus in the branch influenced the micelle formation and aggregation properties. The fluorescent intensity ratio of the first vibronic peak (λ=373 nm) to the third vibronic peak (λ=383 nm) of pyrene solubilized in micelle decreased gradually, which was different from the conventional surfactant, such as SDS. The aberrant property indicated a broad micelle size for the m+nAr-T surfactants. That is, the aggregates of the studied surfactants gradually grew in size with increasing concentration over wide concentration range. That the aggregation number N, characterized by quenching the aryloxyl residue of m+nAr-T with methyl viologen (MV2+) as the extrinsic quencher, gradually increased with increasing surfactant concentration also confirmed it.