Surfactant type catalytic system and one-step process for methyl esterification of high-free-acid grease

The invention relates to a novel technology for preparing fatty acid methyl ester from waste grease having high free fatty acid content and produced in catering, grease refining and other industries. Under the synergistic catalysis of an alkyl aromatic sulfonic acid surfactant type catalyst and a small amount of concentrated sulfuric acid and through a hydrolysis-esterification coupling reaction mechanism, two-step reaction is carried out at a temperature of lower than 100 DEG C under a normal pressure or low pressure condition, and the quality yield of a fatty acid methyl ester product reaches 96% or above; a mixture of water and glycerol generated by the reaction is easily separated from the fatty acid methyl ester product, and a reaction separation coupling process improves the equilibrium conversion rate of the whole esterification process; and the utilization rate of fatty acid and glyceride in raw materials can reach 98% or above. The process of the invention has the technical characteristics of simple