Kinetics for the biodiesel production from lauric acid over Keggin heteropolyacid

What is it about?

Kinetic models were developed to describe the esterification reaction of lauric acid and ethanol over heterogeneous catalysts, which is a reaction of special interest in the biodiesel production. Vanadium Keggin heteropolyacid was included on a silica framework by sol–gel procedure, using different loadings. The synthesized materials were characterized by FT-IR, XRD, SEM, nitrogen adsorption/desorption isotherms, and potentiometric titration, and tested as solid catalysts in the esterification of lauric acid. Best performance was achieved with SiO2@20PMoV, which was used in the esterification of others fatty acid and alcohols. The reuse was successfully tested in five consecutive runs. Kinetic data using SiO2@20PMoV were obtained at different temperatures (48–78 °C), fatty acid:alcohol molar ratios (4 mmol of lauric acid and 2.5, 5, 10 and 15 mL of ethanol), and catalyst amounts (12.5, 25 and 50 mg). The best heterogeneous models were LH3 (surface reaction as rate-limiting step) and ER3 (desorption of ethyl laurate as rate-limiting step when the adsorbed reactant is lauric acid). The activation energies were 56.1 kJ mol−1 and 64.8 kJ mol−1, and the reaction rate constants at 78 °C were 0.2791 mol g−1 h−1 and 0.0768 mol g−1 h−1 for LH3 and ER3, respectively.

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Why is it important?

Biomass is a potential alternative to non-renewable fossil fuels for the future, due to aggravation of the energy crisis and to that its use as feedstock reduces the CO2 content in the atmosphere. Biodiesel is a renewable fuel consist of long-chain esters formed from fatty acids and methanol or ethanol that can be obtained either by transesterification reaction of vegetable oils and fats or esterification reaction of fatty acids present in animal fats (e.g. lard or tallow); contrary to fossil-based diesel, biodiesel also offers biodegradability and non-toxicity. The key factor of the globalization of biodiesel is its sustainability with available diesel engines without the need of mechanical modifications.