Nano-sulfonated sepiolite for efficient biodiesel yield from waste oil: A versatile solid acid catalyst

The present study investigates the applicability of inexpensive natural clay sepiolite as a solid support for preparing sulfonic acid functionalized nanocatalysts producing biodiesel as an alternative fuel. The nanocatalyst is characterized by standard analyses such as XRD, FT-IR, BET, and FE-SEM to evaluate its physical and chemical properties. To avoid soap formation in the transesterification process and to modify the functionality of a mineral-grade sepiolite, sulfonic acid (Sep-SO₃H) has been used to enhance its activity and stability. The resulting heterogeneous catalyst is a nanosized solid acid that can handle edible waste oil as a low-value feedstock with high levels of impurities and acidity in the feedstock. The biodiesel production efficiency is determined by GC-mass spectrometry. Using 2 wt.% of the nanocatalyst resulted in a conversion of 94.7% of the waste cooking oil, demonstrating the high efficiency and promising potential of the materials and method, considering the nature of the feedstock and excellent recycling performance.