Heteroatoms doped iron oxide-based catalyst prepared from zinc slag for efficient selective catalytic reduction of NOx with NH3

Abstract

Excessive emissions of nitrogen oxides from flue gas have imposed various detrimental impacts on environment, and the development of deNO_x catalysts with low-cost and high performance is an urgent requirement. Iron oxide-based material has been explored for promising deNO_x catalysts. However, the unsatisfactory low-temperature activity limits their practical applications. In this study, a series of excellent low-temperature denitrification catalysts (Ha-FeO_x/yZS) were prepared by acid treatment of zinc slag, and the mass ratios of Fe to impure ions was regulated by adjusting the acid concentrations. Ha-FeO_x/yZS showed high denitrification performance (> 90%) in the range of 180–300 °C, and the optimal NO conversion and N₂ selectivity were higher than 95% at 250 °C. Among them, the Ha-FeO_x/2ZS synthesized with 2 mol/L HNO₃ exhibited the widest temperature window (175–350 °C). The excellent denitrification performance of Ha-FeO_x/yZS was mainly attributed to the strong interaction between Fe and impurity ions to inhibit the growth of crystals, making Ha-FeO_x/yZS with amorphous structure, nice fine particles, large specific surface area, more surface acid sites and high chemisorbed oxygen. The in-situ DRIFT experiments confirmed that the SCR reaction on the Ha-FeO_x/yZS followed both Langmuir-Hinshelwood (L-H) mechanism and Eley-Rideal (E-R) mechanism. The present work proposed a high value-added method for the preparation of cost-effective catalysts from zinc slag, which showed a promising application prospect in NO_x removal by selective catalytic reduction with ammonia.