Remarkably enhanced density and specific activity of active sites in Al-rich Cu-, Fe- and Co-beta zeolites for selective catalytic reduction of NOx

Abstract The efficiency of catalysts for abatement of emissions of nitrogen oxides (NO x ) from stationary and especially mobile sources using selective catalytic reduction (SCR) is obviously still not sufficient to meet increasingly more stringent environmental limits. We demonstrate that the conversion of NO x to nitrogen under the relevant conditions of the SCR-NO x can be dramatically increased using Al-rich beta zeolite catalysts with a high concentration of transition metal counter-ions, bearing extra-framework oxygen ligand (M/M-oxo, where M = Cu, Co, Fe), particularly in the low-temperature region as well as at high space velocities. The high concentration of framework Al and corresponding high population of AlSiAl sequences in template-free synthesized Al-rich beta zeolite does not result in relative increased binding of bare non-reducible and non-active M(II) ions. To the contrary, the unparalleled high concentration of the atomically dispersed M/M-oxo counter-ions with appropriate redox properties and enhanced specific activities provides 3–12 times higher reaction rates for the SCR-NO x using ammonia, methane and propane as reducing agents compared to state-of-the-art Si-rich zeolite catalysts.