The characterization of CrCe-doped on TiO2-pillared clay nanocomposites for NO oxidation and the promotion effect of CeOx

A series of chromium-ceria doped on TiO2-pillared clay nanocomposites catalysts with various Cr/Ce ratios were investigated in the oxidation of NO. This study aimed to not only synthesize the CrCe/TiO2-PILC nanocomposites, but also figure out the promotion effect of Ce in the oxidation process and the interaction between chromium and ceria on the surface of TiO2-PILC. The samples were characterized by XRD, SEM, TEM, XPS and H2-TPR methods. The best catalyst Cr(1)Ce(0.25)/TiO2-pillared clay yielded 69% NO to NO2 conversion at 350 °C (in the condition of GHSV = 35,400 h−1). With the content of ceria increasing, the NO conversion increased significantly while when the Cr/Ce equaled 1:1, the activity decreased. The chromium oxides were well dispersed on the surface of the support. Analysis of XPS indicated that the addition of ceria oxides could promote the formation of chemisorbed oxygen and raise the quantivalency of Cr. The powerful electron withdrawing ability of Ce made the electron density around Ti atoms decrease. The result showed that CeOx enhanced the metal–support interaction. H2-TPR indicated that the proper addition of CeOx increased the reducible phase that was beneficial to the reaction. Moreover, the catalysts showed a good resistance to SO2 and H2O. When SO2 and H2O were added in the feed gas, the catalytic activity decreased but when removed, the activity recovered. The deactivation was not totally irreversible.