Novel SCR catalyst with superior alkaline resistance performance: enhanced self-protection originated from modifying protonated titanate nanotubes

Abstract

In this paper, ion-exchangeable titanate nanotubes were synthesized with a treatment of ethanol washing (referred to as TNTs-eth), which were utilized as supports for ceria (CeO₂) catalysts. The resulting catalysts showed excellent resistance to alkali metal and alkaline earth metal poisoning in NH₃-SCR applications, where the NO conversions could be maintained at 97%, 88% and 95% (at 350 °C) when Na⁺, K⁺ and Ca²⁺ were added, respectively. After the catalysts were subjected to a range of analyses, it was found that the resistance was mainly attributed to the significant increase in structural ion-exchangeable OH groups in the TNTs-eth catalyst, which led to a remarkable surface acid strength and abundant acid content, effectively neutralizing the basicity induced by the alkali metals and alkaline earth metals and retaining the SCR performance. Moreover, the repeatable Ce⁴⁺/Ce³⁺ redox cycles and the well-maintained nano-tubular structure also accounted for the excellent resistance performance of the Ce/TNTs-eth catalyst. We expect that the self-protection effect of the Ce/TNTs-eth catalyst (that was induced by its ion exchange ability) might provide a novel approach for the design and synthesis of SCR catalysts to relieve their alkali metal and alkaline earth metal poisoning.