Preparation method of polyethylene glycol fatty acid ester

The invention provides a preparation method of polyethylene glycol fatty acid ester. The preparation method comprises the following steps: (1) putting polyethylene glycol, fatty acid and activated carbon into a reactor and mixing; (2) carrying out air replacement operation in the reactor, and then carrying out esterification reaction at the reaction temperature of 160-250 DEG C to obtain a reaction product; and (3) after the reaction is finished, carrying out degassing treatment on a reaction product, then carrying out dehydration treatment at the dehydration pressure of -0.09 to-0.1 MPa and the dehydration temperature of 100-140 DEG C, and then carrying out filter pressing treatment to obtain the polyethylene glycol fatty acid ester. According to the method, no catalyst is used, so that the cost is reduced, the generation of solid wastes is reduced, and the requirement of green production is met. The reaction conditions are mild, the operation is simple, small molecules in the product are removed, and the us