Economically viable production of biodiesel using a novel heterogeneous catalyst: Kinetic and thermodynamic investigations

Highlights: • Usage of Madhuca Indica oil as a potential feedstock. • Synthesis of novel Barium Lanthanum Oxide as a catalyst. • Study on the effect of catalyst synthesis routes for its activity in transesterification reaction. • Reusability extended up to fifth runs with 83% FAME conversion at 1.5 wt% of catalyst concentration. - Abstract: Biodiesel was produced in laboratory in two consecutive steps i.e. esterification followed by transesterification using a novel heterogeneous base catalyst and Madhuca indica (Mahua) oil as a feedstock. Barium lanthanum oxide, a novel catalyst was synthesized by four different methods i.e., co-precipitation (BLOC), solid state (BLOS) and the citrate route or auto-combustion method (BLOA1 and BLOA2). The catalyst was characterized and the catalytic activity was measured by quantifying the FAME content of the biodiesel. It has been observed that BLOA1, BLOA2, and BLOC resemble with each other as they have the same phase with an identical structural formula of Ba₂La₂O₅. This observed structural formula constituted the mixture of the perovskite and metal oxides. The BLOS sample had the structural formula of Ba₁₀La₂O₁₃ which proved the extensive formation of individual metal oxides. Out of the samples, BLOA2 synthesized by citrate route was efficient in biodiesel production. The citrate route synthesis performed at pH 2.31 enriched the catalyst mixed metal oxide surface with free OH⁻ groups, which ultimately avoided the formation of the carbonate species, produced biodiesel with 97.5% FAME conversion. Hence, Barium Lanthanum Mixed metal oxide prepared by citrate route in acidic medium is a potential catalyst for biodiesel production. The reaction mechanism followed first-order kinetics. The activation energy (E_A) was 34.44 kJ mol⁻¹ and the frequency factor (A) was 7.94 min⁻¹. The physicochemical properties of the synthesized Mahua oil methyl ester (MOME) were measured according to ASTM D 6751 and were found to be within the permissible range.