Smart Modification of HZSM-5 with Manganese Species for the Removal of Mercury

Abstract

In this study, a series of Mn-modified HZSM-5 samples were synthesized using the solid-state ion-exchange method, and the effects of the manganese loading amount, calcination temperature, reaction temperature, and gas components on mercury removal efficiency were systematically explored. Given that the mass ratio of HZSM-5 to KMnO4 and the calcination and reaction temperatures were set to 10:2.6 and 400 and 150 °C, Hg removal efficiency could reach a peak value of 96.4% when exposed to the flue gas containing 5% O2 and N2 as the balance. Among the various gas components, O2 and NO showed a positive impact on Hg removal; Hg removal efficiency could even reach ca. 100% when O2 and NO were simultaneously introduced. In contrast, the introduction of SO2 led to a decline of Hg removal efficiency by ca. 16%. In addition, Hg removal efficiency could still retain ca. 92% of that for the fresh sample after six regeneration and reuse cycles, which is indicative of a satisfactory stability and renewability. Finally, Mars-Maessen mechanisms dominated in the mercury chemical adsorption process.