Method for synthesizing bio-plasticizers using acidic ionic liquids as catalysts

A method for synthesizing bio-plasticizers using acidic ionic liquids as catalysts, comprising the following steps:

• synthesizing Bronsted acidic ionic liquids with a strong Bronsted acid and an alkyl sulfonic acid, which replaces amphoteric compounds of pyridinium, wherein a molar ratio of the alkyl sulfonic acid to the strong Bronsted acid is between 1.0 and 1.5;
• heating fatty acid alkyl esters, organic acids and Bronsted acidic ionic liquids, all of which have been mixed pro rata, to 50° C. and further mixing in hydrogen peroxide solutions instilled within 1 hour, for development of reaction solutions, then further heating the resulting mixture to a temperature of 50-100° C. for epoxidation and maintaining the epoxidation temperature for 0.5-5 hours, wherein a molar ratio of fatty acid alkyl esters to organic acids to hydrogen peroxide is 1:0.2-1:0.2-5, and a weight of Bronsted acidic ionic liquids is 1-15% of the total weight of organic acids and hydrogen peroxide solutions;
• and
• separating oil-phase solutions of the reaction solutions from aqueous-phase solutions and rinsing the oil-phase solutions with lye and deionized water for preparation of epoxidized fatty acid esters after removal of water,
• wherein the Bronsted acidic ionic liquids are reused at least 10 cycles and the catalytic efficiency is more than 95% in each cycle, and
• wherein the productivity of the oleates based on the method is up to 85%.