Nowadays, there are many intensification technologies for biodiesel production that have been devised to solve the problems of
reaction reversibility and the immiscibility of the two reactants[1].
Many types of reactor, such as a membrane reactor[2–4], reactive
distillation[5]and reactive absorption[6]have been developed to
improve transesterification rate by removing the products during
the reaction, thus shifting the reaction equilibrium and facilitating
increased biodiesel yield. Rotating packed bed reactors[7], bubble
column reactors[8], jet flow stirred reactors [9], etc. have all been
applied to create a sufficient contact surface area between two
immiscible phases and assist the mixing of the two reactants.
Efficient multi-transducer sonochemical reactors (US) can
strongly promote the biodiesel production thanks to cavitational
phenomena which generate nucleation, growth, and consequent
collapse of microbubbles in the liquid medium, affecting positively
both heat and mass transfer. High power ultrasound waves cause a
series of compression and rarefaction determining intense cavitation. The rarefaction cycle may exceed the attractive forces of liquid molecules and some microbubbles form. At this point, small
amount of vapor of the medium enters the bubbles during its
expansion phase and is not fully discharged during compression