Improved rate of transesterification reaction in biodiesel synthesis using hydrodynamic cavitating devices of high throat perimeter to flow area ratios

The present study reports the process intensification of biodiesel synthesis from waste cooking oil using hydrodynamic cavitation (HC) which was achieved by increasing the ratio of the throat/hole perimeter to flow cross section area (alpha) (alpha: 1.33 to 13.33 mm(-1)) of the cavitating device. Initially, the optimization of process reaction parameters such as oil to alcohol molar ratio (1:6.8) and catalyst concentration (NaOH; 1 wt. % of oil) was carried out by response surface methodology (RSM). Thereafter, biodiesel synthesis was carried out in the HC reactor for optimization of cavitating devices (circular Venturi and three orifice plates). Maximum of 99% yield was obtained in 5 min of treatment time by using an orifice plate having 100 circular holes of 0.3 mm diameter each (alpha: 13.33 mm(-1)) at the optimum operating inlet pressure of 7 bar. LC-MS and FT-IR analysis of the biodiesel product confirmed the formation of fatty acid methyl esters (FAME). The energy efficiency evaluation of HC revealed that the intensification of HC using alpha cavitating device of higher a value significantly reduced the energy requirement for the synthesis of biodiesel as compared to the other conventional approaches of cavitation as well as increased the overall reaction rate.