The activity of Rh/Al2O3 and Rh–Na/Al2O3 catalysts for PAHs removal in the waste incineration processes: Effects of particulates, heavy metals, and acid gases

This study investigated the activity of Rh/Al2O3 and Rh–Na/Al2O3 catalysts for polycyclic aromatic hydrocarbons (PAHs) removal and the influence of particulates, heavy metals, and acid gases (SO2 and HCl) on the performance of catalysts. The experiments were carried out in a laboratory-scale waste incineration system. Experimental results show that the destruction removal efficiency (DRE) of PAHs by Rh/Al2O3 and Rh–Na/Al2O3 catalysts were 80% and 59%, respectively when the flue gas did not contain any pollutants. The concentrations of PAHs increased by using a Rh/Al2O3 catalyst when the flue gas contained Cd, Pb, and SO2 and also increased by using a Rh–Na/Al2O3 catalyst when the flue gas contained particulates, Cd, and HCl. Adding Na to the Rh/Al2O3 catalyst can inhibit the increases of 3–4 ring PAHs when the flue gas contained Pb. The influence of acid gases on the performance of the Rh/Al2O3 and Rh–Na/Al2O3 catalysts followed the sequence SO2 > HCl > SO2 + HCl. The activity of the catalysts for PAHs removal was significantly suppressed by increased concentrations in particulates and Cd, yet promoted by a high Pb concentration. The results of ESCA analysis indicated that the presence of Cd and Pb did not change the chemical states of Rh and Na, but the presence of SO2 and HCl did.