This paper investigates the transesterification of waste cooking oil using TiO2, CuO, and GO as catalysts in solar plain and helical glass microreactors. Catalyst properties were determined through XRD, SEM, and FT-IR analyses. Response surface methodology was employed to optimize biodiesel production, with GO catalyst and helical microreactor proving most effective due to their unique geometry. The highest biodiesel purity was achieved with GO at 99.98%, followed by TiO2 at 95.78% and CuO at 93.55%, all with a 3% catalyst dose, 200 s residence time, and oil-to-methanol volume ratio of 2. The study utilized solar energy and glass microreactors, resulting in a 94% reduction in energy consumption.
