Exploring the effect of calcination temperature and sulphuric acid impregnation treatment on the NH3-SCR activity of cold-rolled sludge

Abstract

In recent years, sulphate materials have received more and more attention because of high activity in the selective catalytic reduction of nitrogen oxides with ammonia (NH3-SCR). In this paper, a series of catalysts for NH3-SCR were prepared by sulphuric acid impregnation and calcination at different temperatures of cold-rolled sludge which main component is iron oxide. The performance of cold-rolled sludge catalyst was measured by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), temperature programmed-reduction of hydrogen (H2-TPR), temperature programmed desorption of ammonia (NH3-TPD) and X-ray photoelectron spectroscopy (XPS). It was demonstrated that the increase of iron sulphate and Fe3+ content can be observed in the cold-rolled sludge after sulfuric acid impregnation and low temperature calcination (300 ℃), which leads to the improvement of SCR denitration performance. The results show that 100% denitration conversion can be achieved at 280 °C via the modified cold-rolled sludge, with 94% of the performance was retained after the introduction of SO2 and H2O for 5 h. There are minor morphological structural changes in the catalyst, while the redox properties and acidity of the catalyst changed significantly after the treatment process of sulfuric acid impregnation and calcination. This means that the enhanced redox properties and acidity of the catalyst play a key role in improving the activity of NH3-SCR.