Active Learning in the Undergraduate Chemistry Laboratory: Synthesis of Biodiesel from an Amazon Region Oil (Babassu): Keep It Simple!

An active-learning approach was employed in a project for our chemistry major students on the synthesis of biodiesel (BD) from an Amazon region oil. The project, involving activities in class and in the laboratory, was given during 8 weeks of the spring semester of 2022. The students were asked about their previous contact with the synthesis and analysis of BD, ionic liquids as solvents and catalysts, and the use of chemometrics for yield optimization. The students were asked to do a literature survey, suggesting renewable starting materials (oil and alcohol) and a homogeneous catalyst for BD synthesis. The students selected babassu oil, bioethanol, and a Brønsted acid as a task-specific ionic liquid catalyst. As "independent" experimental variables, the students suggested studying the effects of reaction mixture composition (oil, alcohol, catalyst) and reaction time and temperature. Based on a second questionnaire, the students chose viscosity for the determination of the BD yield. By using design of experiment and varying the molar ratios of bioethanol/babassu oil (6-12) and catalyst/babassu oil (0.1-0.2) and reaction time (1-2 h), the students calculated the effect of these variables on BD yield. The resulting mathematical correlations were validated by using additional experiments. Measuring product viscosity, after its appropriate purification, is a simple and attractive alternative to gas chromatography, being less time- and energy-consuming. The students positively evaluated the project because of the socioeconomic importance of BD, the use of renewable starting materials, application of chemometrics for yield optimization, and they were involved in decision making.