Selective catalytic reduction of NOx by NH3 over CeO2 supported on TiO2: Comparison of anatase, brookite, and rutile

Abstract

Anatase (A) TiO2 is widely used as a support of the supported vanadium-based and non-vanadium-based catalysts for NH3-SCR reaction. However, there is lack of enough attention for brookite (B) and rutile (R) TiO2. Therefore, in the present work, we synthesize a series of TiO2-A, TiO2-B, and TiO2-R, and then used as supports to prepare CeO2/TiO2-A, CeO2/TiO2-B, and CeO2/TiO2-R catalysts with the purpose of clarifying the crystal form effect of TiO2 supports on the physicochemical properties and catalytic performance of these supported ceria-based catalysts for NH3-SCR reaction. Characterization results exhibit that H2 consumption (responding to reduction property), acid amounts, surface Ce3+ content, surface adsorbed oxygen species, and catalytic performance of these supported ceria-based catalysts give the order of CeO2/TiO2-R>CeO2/TiO2-B>CeO2/TiO2-A, which is related to the interaction (i.e., Ce3++Ti4+↔Ce4++Ti3+) between CeO2 and TiO2 (anatase, brookite, and rutile). Especially, CeO2/TiO2-R catalyst exhibits the optimal catalytic performance for NH3-SCR reaction among these supported ceria-based catalysts owing to the most excellent reduction property as well as the largest amounts of acid sites, surface Ce3+ content, and surface adsorbed oxygen species.