Method for producing biodiesel by catalyzing microalgae oil by ultrasonic-assisted ionic liquid

The invention relates to a method for producing biodiesel from microalgae oil, particularly a method for producing biodiesel by catalyzing microalgae oil by an ultrasonic-assisted ionic liquid. The invention aims to solve the severe problems of low extraction efficiency, high cost and environmental pollution of reagents in the existing biodiesel preparation method. The method provided by the invention comprises the following steps: 1. preparing [BMIM]Cl, mixing the [BMIM]Cl and NaBF4 in a mol ratio of 1:1, adding acetone to react for 18-24 hours, filtering, and carrying out vacuum distillation to obtain an ionic liquid [BMIM]BF4; and 2. mixing the microalgae oil with methanol or ethanol, adding the mixture into the ionic liquid [BMIM]BF4, carrying out ultrasonic treatment for 20-50 minutes, extracting, collecting the supernatant solution, and carrying out vacuum distillation to obtain the biodiesel. The biodiesel yield of the invention is greater than 90%. The invention is applicable to the field of biodiesel preparation.