Application of ReOx/TiO2 catalysts with excellent SO2 tolerance for the selective catalytic reduction of NOx by NH3

Abstract

Non-vanadium-based catalysts with high SO₂ tolerance are still interesting in selective catalytic reduction of NO by NH₃ (NH₃-SCR) and SO₂ adsorption is the foremost step for the deactivation of catalysts. In order to alleviate the adsorption of SO₂, we fabricated a series of rhenium (Re; without stable sulfate) supported TiO₂ catalysts and studied their SO₂ tolerance for the first time. Owing to suitable surface acidity and reducibility, ReO_x/TiO₂ catalysts exhibited satisfactory activity in a wide temperature range of 250–350 °C. As expected, experimental results and DFT calculations indicated that SO₂ adsorption on ReO_x/TiO₂ catalysts was rather weak, thus the catalysts performed excellent SO₂ tolerance in the NH₃-SCR reaction. Moreover, in situ DRIFTS indicated that the NH₃-SCR reaction on ReO_x/TiO₂ catalysts followed the Eley–Rideal mechanism and SO₂ had little effect on the reaction mechanism. Our findings should provide new insights into the development of SCR catalysts with high SO₂ tolerance.