Synthesis of alkylbenzenes via the alkylation of benzene using α-olefin dimers and the surfactant properties of their sulfonates

Abstract

Abstract Fischer-Tropsch syncrude prepared via the Fischer-Tropsch synthesis (FTS) using a Fe-based catalyst is featured by its high content of linear α-olefins (C5–C13). The utilization of C6–C8 α-olefins for the synthesis of alkyl benzene sulfonate surfactants was performed in the present work via dimerization, benzene alkylation, and sulfonation. The effects of the reaction conditions on benzene alkylation over a trimethyl amine hydrochloride-acidic anhydrous aluminum chloride ionic liquid catalyst (Et3NHCl-AlCl3) have been studied in detail using C6 α-olefin dimers as a model alkylation agent. Under the optimal reaction conditions (molar ratio of AlCl3 to Et3NHCl = 2, catalyst loading = 0.29 mol %, reaction temperature = 30 °C, and molar ratio of benzene to C6 α-olefin dimer = 10) the conversion of the C6 α-olefin dimer was 100% and the selectivity toward the mono alkylbenzene product was 91.0%. C6–C8 α-olefin dimer alkylbenzene sulfonates (C6–C8 DBS) were synthesized via sulfonation using chlorosulfonic acid and characterized using Fourier Transform Infrared (FT-IR) spectroscopy and Liquid Chromatography–Mass Spectrometry (LC–MS). The surfactant properties of the C6–C8 DBS, including their equilibrium and dynamic surface tension, foaming, wetting and emulsifying capabilities, were closely explored and compared with a commercial linear alkylbenzene sulfonate (LAS). The limiting surface tension (γ CMC = 34.62 mN m−1) and critical micelle concentration (CMC = 2.15 mmol L−1) of C6 α-olefin dimer alkylbenzene sulfonate (C6-DBS) were similar to those of LAS. Upon increasing the hydrocarbon chain length, the γ CMC of C6-DBS, C7-DBS, and C8-DBS remained unchanged, while the CMC decreased. C6–C8-DBS exhibited foaming, emulsifying, and wetting properties comparable to LAS.