Preparation of Methyl Hydroxystearate from Oleic Acid by a Reusable Solid Acid and Its Evaluation as Raw Material for Branched Biobased Surfactant

An efficient method has been developed to synthesize 9/10-methyl hydroxystearate (9/10-HSM) from oleic acid in a one-pot/two-step approach, which is an important hydrophobic raw material for branched polyoxyethylene biobased surfactants. The solid superacid, Aquivion PFSA, has been demonstrated to exhibit exceptional catalytic and stability characteristics in both the indirect hydration and hydrolysis process. A novel branched nonionic biobased surfactant, ethoxylated methyl monohydroxystearate (9/10-HMEEn) with a Y-shaped structure, was synthesized and characterized by introducing a polyoxyethylene group in the hydroxyl position inside the 9/10-HSM. The distinctive molecular configuration endows 9/10-HMEEn with distinctive aggregation and adsorption behavior in aqueous solution, diverging from those observed in traditional straight-chain biobased surfactants, resulting in good surface tension, wettability, low foaming, and fast defoaming. Furthermore, the product demonstrated a significantly enhanced compatibility with commercially available anionic surfactants, was considered suitable for anionic/nonionic formulation applications, and exhibited effective cleaning performance on hard surfaces of various materials, suggesting that it has the potential to be utilized in industrial cleaners.