The mechanistic study of simultaneous removal of NO and Hg0 from flue gas using coal fly ash-derived Cu-Ce-SSZ-13 catalysts

The coexistence of NO x and elemental mercury (Hg 0 ) in flue gas presents a significant challenge for pollution control, underscoring the need for the development of cost-effective and integrated removal technologies. In this study, we synthesized a Cu-Ce-SSZ-13 zeolite catalyst derived from coal fly ash, which achieved simultaneous and efficient removal of both NO and Hg 0 at a temperature of 250 °C, with conversion rates reaching 100% for both pollutants. To understand the synergistic reaction mechanism, we systematically investigated the interactions among NO, ammonia (NH 3 ), and Hg 0 during the reaction process. The findings indicate that Hg 0 has minimal impact on the removal of NO within the mid-temperature range, while NO actively promotes the oxidation of Hg 0 . Conversely, NH 3 appears to inhibit Hg 0 removal by consuming surface-active oxygen species and competing for adsorption sites. Additionally, the presence of both NO and NH 3 can reduce already formed mercury oxide (HgO), further exacerbating the inhibition effect. The synergistic relationship between the NO-selective catalytic reduction (SCR) cycle and the Hg 0 oxidation pathway was further elucidated through X-ray Photoelectron Spectroscopy (XPS) and in situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) analyses. This study clarifies the critical role of gas-phase components in the simultaneous removal process and offers theoretical guidance for designing efficient and low-cost integrated catalysts aimed at multi-pollutant purification. Furthermore, it demonstrates a feasible approach that combines the resource utilization of fly ash with green catalysis.