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The TNU-9 zeolite (TUN framework) is one of the most complex zeolites known. It represents a highly promising matrix for both acid and redox catalytic reactions. We present here a newly developed approach involving the use of 29Si and 27Al (3Q) MAS NMR spectroscopy, CoII as probes monitored by UV/Vis and FTIR spectroscopy, and extensive periodic DFT calculations, including molecular dynamics, to investigating the aluminum distribution in the TUN framework and the location of aluminum pairs and divalent cations in extra-framework cationic positions. Our study reveals that 40 and 60 % of aluminum atoms in the TNU-9 zeolite are isolated single aluminum atoms and aluminum pairs, respectively. The aluminum pairs are present in two types of six-membered rings forming the corresponding α and β (15 and 85 %, respectively, of aluminum pairs) sites of bare divalent cations. The α site is located on the TUN straight channel wall and it connects two channel intersections. The suggested near-planar β site is present at the channel intersection. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

An Al-rich Co-BEA ∗ zeolite (Si/Al 4.2, Co/Al 0.5) was prepared by organotemplate-free hydrothermal synthesis and [Co(II)(H 2 O) 6 ] 2+ ion exchange. The structure of the Co species and their activity in C 3 H 8 –SCR-NO x were compared to that of Si-rich Co-BEA ∗ (Si/Al 11.3). The high population of AlSiAl sequences in Al-rich BEA ∗ with AlO 4 − facing different channels, contrary to their absence in Si-rich BEA ∗ , results in dehydrated Co-BEA ∗ in easily reducible counter-ion [Co(III)O] + species attached to one AlO 4 − . The high concentration and density of these Co-oxo species in Al-rich Co-BEA ∗ facilitates extra-ordinarily high SCR-NO x rate even under water vapor up to 10 vol.%, twelve-times outperforming Si-rich Co-BEA ∗ . The five-to-six times increased TOF and easier reducibility suggest a synergetic redox effect of water-resistant Co-oxo species. The Al-rich Co-BEA ∗ provides the highest reaction rate at conditions of wet NO x streams, exceeding that previously reported for metal ion/oxo zeolite catalysts, with a high selectivity to molecular nitrogen and efficient utilization of propane. [ABSTRACT FROM AUTHOR]

The TNU‐9 zeolite of the TUN framework is one of the most complex zeolites known. Here, a newly developed approach, which includes 29Si and 27Al (3Q) MAS NMR spectroscopy, CoII cations as probes monitored by UV/Vis and FTIR spectroscopies, and extensive periodic DFT calculations including molecular dynamics, is presented for the investigation of the Al distribution and the location of Al pairs and divalent cations in extra‐framework cationic positions in TNU‐9. The α (blue) and β (red) cationic sites for bare divalent cations are suggested. More information can be found in the Full Paper by S. Sklenak et al. on page 8857. [ABSTRACT FROM AUTHOR]