Amorphous Ce-Ti composite as an efficient bifunctional catalyst for deep oxidation of volatile organic compounds and selective catalytic reduction of NO

Abstract

Listen

Translate article

In this work, a series of Ce-Ti composite oxides with different Ti/Ce molar ratios was prepared by co-precipitation method, and investigated for the catalytic degradation of toluene and selective catalytic reduction of NO. The phase transition process between Ce species and Ti species is limited by modulating the interaction between Ce4+ and Ti4+, while a completely amorphous composite is generated with an appropriate molar ratio of Ti/Ce (1.5/1). The catalyst CeTi1.5Ox exhibits the best catalytic performance, where the values of T90 and T50 for deep degradation of toluene are 297 and 330 °C respectively at high weight hours space velocity (WHSV=120000 mL/(g⋅h)). Compared with CeO2, T90 and T50 decrease by 48 and 34 °C respectively while declining by 67 and 70 °C compared to TiO2. For the SCR reaction, CeTi1.5Ox reaches 100% NO conversion at 250 °C with WHSV=60000 mL/(g⋅h), reduced by 50 °C compared to pure CeO2. The amorphous nanostructure with highly dispersed Ce and Ti species was confirmed by transmission electron microscopy (TEM) and X-ray diffraction (XRD) characterizations. The X-ray photoelectron spectroscopy (XPS) and Raman analyses show that a large number of active Ce-O-Ti species and surface oxygen vacancies are generated due to the strong interaction between Ti4+ and Ce4+ in CeTi1.5Ox. Additionally, H2-TPR and O2-TPD further confirm that the interaction promotes the low-temperature reducibility and mobility of surface-active oxygen species. Meanwhile, in-situ DRIFTS study reveals that CeTi1.5Ox with amorphous nanostructure can dramatically enhance the dissociative and complete oxidation capacity for toluene.