Synthesis and structure–property relationship of coal-based isomeric alkylbenzene sulfonate surfactants

Abstract

Using coal resources to synthesize high-value surfactants is effective for clean coal utilization and low-carbon conversion, attracting more attention from academia and industry. Herein, three coal-based isomeric alkylbenzene sulfonate surfactants were successfully synthesized via sulfonation with gas phase SO3 utilizing isomeric alkylbenzenes, derived from the alkylation of benzene and Fischer–Tropsch synthesized α-olefins, as raw materials in a microchannel reactor. Moreover, their surfactant properties were systematically investigated to reveal the structure–property relationship. The results indicated that the equilibrium surface tension (γCMC) for the synthesized surfactants was reduced with the increase of the degree of hydrophobic tails branching, and the order of γCMC was: sodium dodecylbenzene sulfonate (35.67 mN·m−1) > sodium C6 olefin dimer alkylbenzene sulfonate (34.18 mN·m−1) > sodium dihexylalkylbenzene sulfonate (29.94 mN·m−1). Sodium dihexylalkylbenzene sulfonate with the lower γCMC exhibited superior wettability (the contact angle of 50.2 ° at 30 s) and excellent emulsifying capacity (emulsification time of 1337 s) at the corresponding critical micelle concentration. This study provides new insights into rational design of hydrophobic tail architectures of surfactant molecules to meet specific needs in various fields.