Catalytic performance over Mn-Ce catalysts for NH3-SCR of NO at low temperature: Different zeolite supports

To clarify the low-temperature NH3-SCR performance of Mn-Ce/zeolite catalysts and the specific promotion influence between Mn-Ce active components and zeolite supports, Mn-Ce/zeolite catalysts were synthesized using Mn-Ce mix oxides loading on several kinds of zeolites (ZSM-5 zeolite, Beta zeolite, X zeolite and Y zeolite) by impregnation method. The results indicated that Mn-Ce/X catalyst had high NO conversion of nearly 100% at 150 °C and the excellent SO2 resistance at different temperature. The Mn-Ce/ZSM-5 and Mn-Ce/Beta catalysts had NO conversion of about 100% at 275 °C while the Mn-Ce/Y catalyst had the lowest NO conversion. Additionally, Mn-Ce/X catalyst had higher relative ratio of Mn4+ and Ce3+ species, more Brønsted acid sites and better reducibility than that of other three catalysts, which could promote NH3-SCR activity. Moreover, the Brønsted acid sites and the Lewis acid sites on Mn-Ce/X catalyst were more stable at low-temperature. Besides, the SCR reaction of Mn-Ce/ZSM-5, Mn-Ce/Beta and Mn-Ce/X catalysts mainly followed Langmuir-Hinshelwood (L-H) mechanism at lower temperature and Eley-Rideal (E-R) mechanism at higher temperature. Furthermore, Mn-Ce/X catalyst had better adsorption ability of nitrate and nitrite species as well, which could enhance NH3-SCR reaction process