Fine Synthesis And Properties Of Long-chain Alkyl Ethylbenzene Sulfonates

By means of molecular designing, p-ethylbenzene alkyl ketones, prepared by Frieded-Crafts acylation of ethyl benzene and fatty acids of diverse carbon chain, reacted with Grignard reagents to give tertiary alcohols (aryl and hydroxyl were attached to the same carbon) which were reduced to be alkyl p-ethylbenzenes by Pd/C,alkyl p-ethylbenzenes were then sulfonated and neutralized to be line alkylbenzene sulfonates with unique structure, codenamed respectively C12-1S, C12-3S, C12-5S, C14-3S,C14-5S, C14-7S, C16-3S, C16-5S and C16-7S. All the products were purified by recrystallization, the content of surfactant in the products were all over 95% determined by two-phase titration.PPA was chosen as a catalyst in the synthesis of p-ethylbenzene alkyl ketones with the advantages of moderate reaction and few side reactions. By orthogonal experiments, the effect of the ratio of raw materials and reaction time on the yield of p-ethylbenzene decanone was examined. In the optimum conditions: n (p-ethylbenzene): n (PPA): n (fatty acid) = 5:2:1, and the reaction time was 20h, under which the yield of p-ethylbenzene decanone was between 45% and 50%.The structures of the intermediates and final products were proved by FT-IR, 1H NMR, 13C NMR and ESI-MS to be right as expected.By measuring the surface tension, the surface properties of several products were investigated. The results showed that, among the isomers, as the aromatic ring shifting to the middle of the long carbonic chain, the degree of branching increasing, it was difficult to form micelles, and the cmc increased. Among the homologues, as the hydrophobic of the surfactant enhanced, it was easy to form micelles, and the cmc reduced. Theγcmc were directly related to the adsorption quantity, the arrangement state and compactness of the hydrophobic chain in the surface layer. As the increasing of the hydrophobic of the surfactant, the efficiency of reducing surface tension increased, moreover, as the increasing of the degree of molecule branching, the efficiency of reducing surface tension reduced.The interfacial performance of the surfactants was also investigated. Through scanning interfacial tension measurement, nmin values of these six types of surfactants were given, which will offer data for screening and complex in practice. The scanning pattern showed that, among the isomers, as the aromatic ring shifting to the middle of the long carbonic chain, the nmin value increased gradually, and the selectivity for alkanes also increased. Between the C14 and C16 homologues, as the hydrophobic chain increasing, the interfacial tension (IFT) between sulfonate and its equivalent alkane reduced gradually, and the IFT between C16-7S and nonane could be reduced to 3.9×10-4mN/m. Dynamic oil-water interfacial tension reduced gradually on the whole. As the time increasing,IFT decreased gradually and finally tended to remaining unchanged. For most curves, IFT decreased quickly in about 15 mins, then decreased slowly between 15 and 45 mins, finally can reach steady-state value after 45 mins. Then the effect of different types of sulfonates, sodium chloride, sodium hydroxide on the interfacial tension between p-cetyl ethylbenzene sulfonate solution and alkane were studied at certain concentration and finally a suitable explanation was made.