Single iron redox sites boost Methanol-SCR at low temperature.

Abstract

Selective catalytic reduction of NO_x to N₂ by methanol as a reducing agent presents a prospective solution for the removal of NO_x from the exhaust of methanol engines and the coal-fired power plant, but it confronts the problem of insufficient deNO_x activity at low temperatures (<350 °C). Here, we discover a strategy for boosting the activity of low-temperature Methanol-SCR by the collaboration of zeolitic acid sites with single iron redox sites. The further pilot-scale bench test using the coated monolithic catalyst also exhibits a remarkable NO_x conversion and a high stability at low temperature. The location of different Fe sites in FER zeolite is identified by X-ray absorption spectroscopy, Mössbauer spectroscopy, as well as 2D ¹H-¹H DQ MAS NMR technology. While the dynamic evolution of [FeO]⁺ as the critical redox site for NO oxidation is successfully captured by in situ Mössbauer spectroscopy, which unravels the mechanism for the generation of key intermediate HONO on [FeO]⁺ sites contributing the low-temperature Methanol-SCR activity. These results indicate the great potential application of Fe-FER zeolite catalyst in industrial Methanol-SCR and provide an atomic-level comprehension of how the dual-active-sites contribute to low-temperature Methanol-SCR activity.