Method for preparing high-content conjugated linoleic acid with vegetable oil

A method for preparing high-content conjugated linoleic acid (CLA) through purification of vegetable oil comprising the following steps:

• step 1) stirring vegetable oil, catalyst and alcohol solution in a container at 50-75° C. for 0.5-2 h to get a mixture of solution, and wash the mixture of solution layer by layer to obtain a alcoholysis product;
• step 2) conducting primary purification for the alcoholysis product by rectification or crystallization to remove low-boiling and high-melting impurities and obtain primary purified alcoholysis product;
• step 3) weigh out an appropriate amount of primary purified alcoholysis product, add it into silver-based silicagel column after moderate dilution, adsorb it in static state for 5-30 min in a dark place, conduct gradient elution with eluent, collect it section by section, remove the eluent, and measure a content of linoleate in each component gotten from each section;
• step 4) mixing the linoleate, base catalyst and alcohol solvent together, inject nitrogen in to the mixture thereof, stir the mixture at 100-190° C. for 1-8 h, add water to terminate the reaction and cool to room temperature, dropwise add acid into the mixture until pH reaches 1-3, layer, and wash a upper-layer of free fatty acid with 1-5% NaCl solution, 10-50% methanol aqueous solution and pure water in succession until it is clear and neutral to obtain high-content CLA.