Accelerated esterification of free fatty acid using pulsed microwaves

► Pulsed microwave accelerates the FFA esterification more than continuous microwave. ► 400Hz square-pulsed microwave with the same energy as continuous microwave is used. ► Pulsed microwaves improve conversion from 39.9% to 66.1% after 15min. ► Repetitive instantaneous strong power is more effective than continuous mild power. It was demonstrated that pulsed microwave irradiation is a more effective method to accelerate the esterification of free fatty acid with a heterogeneous catalyst than continuous microwave irradiation. A square-pulsed microwave with a 400Hz repetition rate and a 10–20% duty cycle with the same energy as the continuous microwave were used in this study. The pulsed microwaves improved the esterification conversion from 39.9% to 66.1% after 15min in comparison with the continuous microwave under the same reaction conditions. These results indicated that pulsed microwaves with repetitive strong power could enhance the efficiency of biodiesel production relative to the use of continuous microwave with mild power.