Eco-friendly biodiesel production using passion fruit peels and cupua?u seeds: Catalyst development and process optimization

Yellow passion fruit peel and cupuacu seeds are common wastes. Usually, they have few or no applications and are discarded, causing environmental pollution. To use them in a new way and reduce ecological pollution, we obtained the ash of yellow passion fruit peels by calcination. We characterized it using Fourier-transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR), X-ray fluorescence (XRF), X-ray diffractometry (XRD), adsorption-desorption of N2, scanning electron microscopy (SEM), basicity, and soluble alkalinity. It was observed that the ash was mainly composed of potassium (69%) in the form of carbonate, chloride, and sulfate, with a good surface area (11.23 m2 g-1). The cupuacu butter was also extracted from the cupuacu seeds and characterized, showing low acidity, peroxide, saponification, and iodine indexes, in addition to presenting a lipid profile with 57% saturated fatty acid and 43% unsaturated fatty acid. Oleic and stearic acids were present in higher proportions. These results demonstrate that this butter can be a sustainable input in biodiesel production. Thus, the ash was used as a heterogeneous catalyst in the butter transesterification. The biodiesel synthesis was optimized, resulting in 97.8% butter conversion into biodiesel under the following conditions: reaction time of 2 h, 5 wt% of catalyst, 80 degrees C, and a methanol-to-oil molar ratio of 30. This work, therefore, shows that it is possible to obtain and utilize bioinputs, such as cupuacu butter and passion fruit peel ash, to produce biodiesel through transesterification, and the use of waste materials (precisely passion fruit peels and cupuacu seeds) makes this method a cost-effective and environmentally friendly approach to biofuel production.