Synthesis of Natural Tea-Saponin-Based Succinic Acid Sulfonate as Anionic Foaming Agent

Tea saponin (TS) is a relatively inexpensive natural nonionic surfactant extracted from parts of tea plants, which can be modified into an anionic surfactant to achieve better surface activity. In this paper, the synthesis of TS-based succinic acid sulfonate as an anionic foaming agent is described. TS used as the hydrophobic source was modified by maleic anhydride (MAH) and then reacted with sodium bisulfite. Orthogonal experiment of a 2-step reaction was designed and performed, resulting in 9 kinds of succinic acid tea-saponin sulfonate (STS). 4-Dimethylaminopyridine and tetrabutylammonium bromide were, respectively, used as catalyst for the esterification with MAH and the sulfonation with sodium bisulfite. During the synthesis process, N,N-dimethylformamide was employed as the solvent and ethyl acetate as the extractant. The molecular structure of STS was confirmed by infrared spectroscopy and mass spectrometry. The foaming property of STS was investigated through comparison with different kinds of common surfactants. The results show great prospects of these environmentally friendly anionic surfactants.