Stability of Sn-Pd-Kaolinite catalyst during heat treatment and nitrate reduction in continuous flow Reaction

In this study, a novel and highly reactive Sn–Pd catalyst supported by environmentally benign kaolinite (Sn–Pd-kaolinite) was developed and evaluated for stability for effective nitrate (NO ₃ ⁻) reduction in batch and continuous mode. Complete NO ₃ ⁻ removal with fast reduction kinetics (k = 18.16 × 10 ⁻² min ⁻¹) and 71% selectivity toward N ₂ were achieved by the Sn–Pd-kaolinite catalyst during batch reactions. During continuous tests, 100% NO ₃ ⁻ removal and 80% N ₂ was achieved for 60 h. However, NO ₃ ⁻ removal efficiency gradually decreased to 80% in170 h. The catalyst was then successfully regenerated in the system by increasing H ₂ flow which achieved a complete NO ₃ ⁻ removal again. The metal leaching from catalyst surface was negligible (Sn 0.01% and Pd 0.006%) and the structure was stable during the continuous test, confirming that the Sn–Pd-Kaolinite catalyst had a superior reaction kinetics and operational durability.