The impact of Fe speciation on low-temperature NH3-SCR activity of Fe-CHA and Fe-BEA catalysts probed by operando HERFD-XANES

The development of after-treatment catalysts for internal combustion engines remains of great importance. This is because, despite the shifting focus to more carbon-neutral technologies, there is a growing demand for diesel cars in developing countries as well as a high demand for heavy-duty trucks. Over the last 20 yeasr, Cu-CHA catalysts have dominated the aftertreatment technology market for diesel exhaust systems. With upcoming legislation putting restriction on levels of N2O - a greenhouse gas - for the first time, the low N2O formation on Fe-modified zeolites make them particularly desirable for new technologies. There is, however, some way to go before Fe-modified zeolites can measure up to Cu-CHA, particularly in the low temperature window. Understanding the active Fe species required for low temperature SCR reactivity is paramount to developing the new technologies. The speciation information obtained by HERFD-XANES measurements will provide this much needed insight.