Preparation method for producing biodiesel from cottonseed oil

The invention discloses a method for preparing biodiesel from cottonseed oil. The method comprises the following steps: by taking an organic alkali as a catalyst, carrying out one-step ester exchangeto produce biodiesel, and connecting cavitation equipment, an ultrasonic reactor, or cavitation equipment with more than two stages and the ultrasonic reactor in series to reinforce the reaction process. The method comprises the following specific steps: by taking cottonseed oil as a raw material, adding methanol, wherein controlling the oil-alcohol ratio (W/W) of cottonseed oil to methanol to be(5-8): 1, controlling the mass dosage of the organic alkali to be 0.3-0.8% of the mass of cottonseed oil, controlling the ester exchange reaction temperature to be 40-64 DEG C, and the reaction timeto be 10-60 minutes; applying ultrasonic waves generated by the cavitation equipment or the ultrasonic reactor to reactants in the ester exchange process. The adopted catalyst comprises potassium methoxide, sodium methoxide or c