Process intensification of thumba methyl ester (Biodiesel) production using hydrodynamic cavitation

Abstract

The development of clean and sustainable biofuel generation from sustainable feedstock using an integrated process intensification approach like hydrodynamic cavitation (HC) is essential now. The current research is a 'first of its kind' where hydrodynamic cavitation is integrated with heterogeneous catalyst, i.e. TiO2, to prepare thumba methyl esters (TME). So far, no studies on biodiesel production using heterogeneous catalysts using HC are reported in the literature. Experiments were performed with an optimized orifice plate to investigate the effects of operating parameters viz., Thumba oil to methanol molar ratio (1:4–1:8), TiO2 concentration (1–1.4% by weight of oil), and operating temperature (50 °C to 70 °C). Maximum triglyceride conversion (71.8%) was obtained at thumba oil to methanol ratio of 1:6, TiO2 concentration of 1.2% weight percentage and operating temperature of 60 °C in hydrodynamic cavitation reactor within 1 h at 5 bar. The cavitational yield for HC was found to be 9.3 × 10−6 moles L/J, which was almost 27% higher than the value for the conventional approach (3.37 × 10−7 moles L/J). The experimental data fitted second-order reaction kinetics w.r.t limiting reactant, i.e., thumba oil and first-order w.r.t excess reactant, i.e., methanol. The pre-exponential factor (k0) and activation energy (E) of the alcoholysis reaction was found to be 82.26 L2 mol−2 min−1 and 15.44 kJ/mol, respectively. The thermodynamic analysis suggested that the alcoholysis of the thumba oil followed the endergonic reaction pathway. Thumba methyl ester (TME) synthesized via this intensified approach is a novel and energy-efficient method compared to the conventional method.