Cerium manganese oxides coupled with ZSM-5: A novel SCR catalyst with superior K resistance

The application of cerium-manganese oxides (CeMn) in controlling exhaust gas from biomass combustion is greatly inhibited due to poor resistance to alkali metals. Herein, we report a smart strategy to circumvent the K poisoning problem of CeMn by physically coupling with ZSM-5, which exhibited almost no activity loss even under a high loading of 2 wt% K2O. Results showed that in contrast to the conventionally believed disturbance of redox property and reduction of acid sites, the dominant effect from K loading on the deactivation of CeMn catalysts lies on the formation of chemically inert nitrates, which significantly restrains the reaction cycle via Langmuir-Hinshelwood route. With ZSM-5 hybridization, the stable nitrates over CeMn can be facilely activated and consumed by NH4+ species introduced by ZSM-5, thus transforming poisoning sites into active sites and ensuring superior catalytic performance. The study presenting here not only provides an efficient strategy for fabricating NH3-SCR catalysts with superior K resistance but also sheds new light on the deactivation mechanism of K over CeMn catalysts.