Structure and performance of a V2O5–WO3/TiO2–SiO2 catalyst derived from blast furnace slag (BFS) for DeNOx

Abstract

The titanium-bearing blast furnace slag (BFS), a solid waste with high TiO₂ content (around 20%) and huge production (3.6 million tons per year), has caused serious environmental problems in China. The reuse of BFS in making DeNO_x catalysts has been confirmed to be promising because of its low cost and high effectiveness for DeNO_x. In this work, four V₂O₅–WO₃/TiO₂–SiO₂ samples from BFS and commercial Ti/Si were made with different amounts of Al₂O₃/Fe₂O₃/SO₄²⁻ dopants to reveal the unique structure effect of a slag-based catalyst on the catalytic behavior for DeNO_x. Catalyst characterization clarified that the Al₂O₃/Fe₂O₃/SO₄²⁻ dopants from BFS may facilitate the formation of Ti–O–Si linkages with abundant structure defects. The structure possibly played a key role in acquiring a high surface area, well-dispersed active VO_x species, sufficient weak acid sites and a high amount of O_ads and V⁴⁺ species for the slag-based catalyst. These advantages in structure were confirmed by catalytic tests showing superior DeNO_x performances. Nonetheless, too many SO₄²⁻ dopants caused agglomeration of TiO₂–SiO₂ particles, formation of strong acid sites and a high amount of O_ads species to negatively impact the DeNO_x activity, selectivity and catalyst lifetime.