Synthesis of Alkylbenzene from Medium-Chain Olefins Catalyzed by an Acidic Ionic Liquid and the Surface Properties of Their Sulfonate

The Fischer-Tropsch synthesis can be used to achieve a high content of α-olefin (C5–C11) products using Fe-based catalysts. Herein, C6 and C8 α-olefins have been selected as examples for the alkylation of benzene catalyzed by using an acidic ionic liquid (Et3NHCl-AlCl3) to obtain a variety of intermediates used to prepare surfactants. A series of alkylbenzenes were synthesized by controlling the reaction conditions and their corresponding alkylbenzene sulfonates were successfully obtained by sulfonation and neutralization. It was found that the single chain alkylbenzene sulfonate derivatives did not display typical surfactant properties due to their short hydrophobic chain length. However, double chain alkylbenzene sulfonates exhibit excellent surfactant properties, and decrease the water surface tension compared to commercially available sodium dodecylbenzene sulfonates. A γ cmc (mN m−1) value of 32.70 was observed for sodium di-hexylbenzene sulfonates, 29.98 for sodium di-octylbenzene sulfonates, and 36.0 for sodium dodecylbenzene sulfonates. In addition, double chain alkylbenzene sulfonates show an improved emulsifying and wettability performance compared to sodium dodecylbenzene sulfonate. This demonstrates that the capability of alkylbenzene sulfonate to decrease the surface tension are closely related to the total carbon number of side chain-alkyl groups connected to the benzene ring.