Summary of the technology for the manufacture of higher alpha-sulfo fatty acid esters

Interest in α-sulfonated higher molecular weight (up to C₂₀) fatty esters has increased in recent years in the surfactant industry due to the advent of economical sulfonation processes and methyl esters of fatty acids. In this paper, the authors present a review of the chemistry of the sulfonation of fatty esters and the two-step mechanism leading to α-sulfonation. Laboratory and pilot plant scale preparation of long chain fatty acid α-sulfoesters with vaporized SO₃ without the use of solvents are also summarized. Work on the falling film equipment with hydrogenated methyl tallowate with vaporized SO₃ is described along with procedures for neutralization and bleaching. Analytical methods for defining the α-sulfonates are discussed. A larger scale unit to continuously manufacture α-sulfo fatty esters from long chain fatty acid is described. A review of the commercially available continuous processes for sulfonation of the fatty acid esters with vaporized sulfur-trioxide have also been included. The properties of the salts of α-sulfo fatty esters including the hydrolytic stability, aqueous solubility, lime soap dispersing ability, and biological properties have been tabulated. Uses of these surfactant range α-sulfo esters are included in this discussion. Presented at the AOCS Meeting, New Orleans, April 1976.