Morphology-controlled synthesis of 3D flower-like TiO2 and the superior performance for selective catalytic reduction of NOx with NH3

Abstract

Morphology of 3D TiO2 support was regulated by modulating the hydrothermal time. Notably, the increase of hydrothermal time could greatly promote the transformation of rod-like TiO2 to flower-like TiO2, while the continuous increase of hydrothermal time damaged the integrity of flower-like TiO2 and led to the appearance of large TiO2 particles. After that, a series of CeO2-WO3/TiO2 catalysts were prepared by a typical impregnation method. The catalytic performance of these CeO2-WO3/TiO2 catalysts for the selective catalytic reduction of nitrogen oxides (NH3-SCR) verified that NOx conversion was greatly related to morphological integrity of flower-like TiO2. Prominently, activity of CeO2-WO3/TiO2-8 catalyst was still excellent after introducing H2O and SO2, and thus the combined CeO2-WO3/TiO2-8 catalyst showed high catalytic activity and good resistance to H2O and SO2. Various characterizations indicated that the integrity of flower-like structure could evidently alter the surface atomic ratio of Ce3+/(Ce3+ + Ce4+) as well as acid sites. With the increase of surface atomic ratio of Ce3+/(Ce3+ + Ce4+), the SCR performance of the catalysts was obviously improved. In short, the superior catalytic performance of CeO2-WO3/TiO2 for the SCR of NOx was related to the morphology of TiO2 support, the highly dispersed active species, the valence of Ce, acid sites and lots of surface adsorbed oxygen.