Abstract: Based on the homogeneous esterification, the conversions of biodiesel products from rapeseed oil were performed using NaOH as catalyst under different heating methods, i.e. water bathing, ultrasonic and microwave , respectively. A single factors and orthogonal test experimental design were used for optimization of process conditions. The optimal conversion conditions could be proposed as follows: MeOH to oil ratio of 10:1(w/w), catalyst dosage of 0.5%, reaction temperature of 55 ℃, reaction time of 60 min. Kinematic viscosities and acid values were investigated under different heating methods for different reaction time intervals The energy-saving effects on producing biodiesel under three different heating conditions can be listed in an ascent order as:microwave>ultrasonic>water bath and under microwave heating method is a perfectible measure, after 5 min, with acid value 1.31 mg/g and viscosity 5.31 mm²/s, which confirming to the national standards.

Key words: biodiesel, homogeneous esterification, ultrasonic, microwave, acid value, kinematic viscosity