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 (NO₃⁻) reduction in batch and continuous mode. Complete NO₃⁻ removal with fast reduction kinetics (k = 18.16 × 10⁻² min⁻¹) and 71% selectivity toward N₂ were achieved by the Sn–Pd-kaolinite catalyst during batch reactions. During continuous tests, 100% NO₃⁻ removal and 80% N₂ was achieved for 60 h. However, NO₃⁻ removal efficiency gradually decreased to 80% in170 h. The catalyst was then successfully regenerated in the system by increasing H₂ flow which achieved a complete NO₃⁻ 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.