Effect of hydrothermal aging on NOx reduction performance for Sb–V–CeO2/TiO2 catalyst

Abstract

Herein, we investigated the NOx reduction performance of Sb–V–CeO2/TiO2 (SbVCT) catalyst subjected to hydrothermal aging, where 6 vol% of H2O was fed to the SbVCT for 16 h with variable temperatures of 550–750 °C. The structural, morphological, redox, and acid properties of fresh and aged catalysts were comprehensively characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman, N2-physisorption, temperature programmed reduction/desorption (H2–TPR/NH3/NO–TPD) and in situ DRIFTS. The XRD, Raman and TEM results of the fresh and the one hydrothermally aged at 550, 600 °C catalysts indicated the presence of finely dispersed polymeric vanadia, antimony, and nano-crystalline ceria species on TiO2 support. The SbVCT catalysts hydrothermally aged at the temperatures ≤ 600 °C showed better NOx conversions than the others aged > 600 °C. This was because aging at the temperatures ≤ 600 °C could help to minimize the loss of surface redox/acid properties that were originally inherent to surface vanadyl and CeO2 species that went into CeVO4 and large CeO2 aggregates. This in turn led to the loss of surface redox and acidic characters indigenous to the SbVCT and reduced its NOx reduction performance. Moreover, the NOx reduction performance of hydrothermally aged V–WO3–TiO2 catalyst, when compared with that of SbVCT catalyst, showed relatively low NOx conversions at the temperatures below 300 °C.