| With bleached waste frying oil (acid value 4.20 mgKOH/g, moisture and volatile matter content 0.072%, saponification value 197.24 mgKOH/g, average molar mass 871.82 g/mol) as raw material and KOH as catalyst, biodiesel was produced by ultrasound-assisted transesterification and analyzed by gas chromatography.Based on previous research on the reaction conditions (molar ratio of methanol to oil 6∶1 and catalyst dosage 1% (based on the mass of bleached waste frying oil)), the reinforcement effect of ultrasound on transesterification was studied. It was determined that the reinforcement effect of ultrasound originated from physical change caused by cavitation via catalyst-free experiment,then the impacts of reaction temperature, ultrasonic power and position of ultrasound field on transesterification were researched. The optimal reaction temperature was determined as 45℃ through comprehensive consideration of system activity and cavitation intensity, and the optimal ultrasonic power was determined as 100 W through comprehensive consideration of intensity and concentration of sound field; when the phase interface of reactants was nearby the position of standing wave in the sound field (30 mm distance from the bottom of ultrasound tank), the transesterification was effectively promoted,and the conversion rate of biodiesel could reach 99.64% in 5 min under the optimal conditions. |
