Effects of synthesis methods on catalytic activities of CoOx-TiO2 for low-temperature NH3-SCR of NO

Abstract

A series of cobalt doped TiO₂ (Co-TiO₂) and CoO_x loaded TiO₂ (Co/TiO₂) catalysts prepared by sol-gel and impregnation methods respectively were investigated on selective catalytic reduction with NH₃ (NH₃-SCR) of NO. It was found that Co-TiO₂ catalyst showed more preferable catalytic activity at low temperature range. From characterization results of XRD, TEM, Raman and FT-IR, Co species were proved to be doped into TiO₂ lattice by replaced Ti atoms. After being characterized and analyzed by NH₃-TPD, PL, XPS, EPR and DRIFTS, it was found that the better NH₃-SCR activities of Co-TiO₂ catalysts, compared with Co/TiO₂ catalyst, were ascribed to the formation of more oxygen vacancies which further promoted the production of more superoxide ions (O₂^-). The superoxide ions were crucial for the formation of low temperature SCR reaction intermediates (NO₃^-) by reacting with adsorbed NO molecule. Therefore, these aspects were responsible for the higher low temperature NH₃-SCR activity of Co-TiO₂ catalysts.

Keywords: CoO(x)–TiO(2) catalysts; NH(3)-SCR; Oxygen vacancies; Superoxide ions.