Innovative valorization of ceramic waste by transforming it into high-performance heterogeneous catalysts for green and efficient benzothiazole derivatives synthesis

This work introduces a sustainable strategy for catalyst development by repurposing ceramic waste—specifically kaolin–quartz residues—into efficient heterogeneous catalysts for the synthesis of benzothiazole derivatives, a class of compounds with significant pharmaceutical and agrochemical value. The two waste-derived catalysts were characterized using XRD, FT-IR, XRF, BET, SEM, and EDX techniques. Their catalytic activity was assessed in the condensation of 2-aminothiophenol with a variety of aldehydes, affording the target benzothiazole compounds in excellent yields (85–95 %) within 60 min. High turnover frequencies (TOF) confirmed the strong efficiency of the catalytic system.

The process exhibits multiple green chemistry advantages, including low catalyst loading, mild reaction conditions, straightforward work-up, and easy product separation. Both catalysts also showed remarkable recyclability, retaining their activity over at least five consecutive cycles with no significant structural degradation. Catalyst heterogeneity was confirmed via a hot filtration test, further supporting their applicability in sustainable heterogeneous catalysis.

To quantitatively assess environmental performance, several green chemistry metrics were calculated—including the Environmental Factor (E-factor), Atom Economy (AE), Reaction Mass Efficiency (RME), Carbon Efficiency (CE), and Optimum Efficiency (OE)—all of which indicated favorable ecological and material efficiency.

Overall, this study not only advances environmentally responsible synthetic methodologies but also promotes the circular use of industrial waste. The findings position ceramic waste-based catalysts as cost-effective, recyclable, and eco-friendly alternatives to conventional systems, aligning with current goals for sustainable and greener chemical practices.