Preferential Siting of Aluminum Heteroatoms in the Zeolite Catalyst Al‐SSZ‐70

Abstract

The adsorption and reaction properties of heterogeneous zeolite catalysts (e.g.for catalytic cracking of petroleum, partial oxidation of natural gas) depend strongly on the types and distributions of Al heteroatoms in the aluminosilicate frameworks.T he origins of these properties have been challenging to discern, owinginpart to the structural complexity of aluminosilicate zeolites.H erein, combined solid-state NMR and synchrotron X-rayp owder diffraction analyses show the Al atoms locate preferentially in certain framework sites in the zeolite catalyst Al-SSZ-70. Through-covalent-bond 2D 27 Al{ 29 Si}J -correlation NMR spectra allow distinct framework Al sites to be identified and their relative occupancies quantified. The analyses show that 94 %o ft he Al atoms are located at the surfaces of the large-pore interlayer channelso f Al-SSZ-70, while only 6% are in the sub-nm intralayer channels.T he selective siting of Al atoms accounts for the reaction properties of catalysts derived from SSZ-70. Supportinginformation (experimentald etails, 2D 27 Al MQMAS analyses, 1D 27 Al and 29 Si NMR spectra, NMR sensitivity enhancement under low-temperature conditions, additionaldiscussion) and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

Increasing the Number of Aluminum Atoms in T3 Sites of a Mordenite Zeolite by Low‐Pressure SiCl4 Treatment to Catalyze Dimethyl Ether Carbonylation

“…However, it is difficult to give more detailed T-site occupancy due to that the Q 4 resonance signals corresponding to Si in T 2 and T 4 sites are roughly overlapped. So that we try to use 27 Al MAS NMR and 2D 27 Al multiple-quantum magic-angle spinning (MQMAS) NMR techniques to solve the problem, [25] although the technique hardly distinguishes the framework Al occupancy at different T-sites of MOR zeolites due to its singlet signal in 27 Al NMR spectra. [4b, 26] Figure 3 shows the 27 Al MAS NMR spectra acquired at 18.8 T of the MOR samples before and after the LPST.…”

“…The location of framework Al of zeolites determines the distribution of BASs [25a, 31] . The BASs in 8‐MR channels of MOR zeolite are mainly originated by framework Al in T 3 sites, and the Brønsted H + corresponding to framework Al in T 4 sites are in 12‐MR channels [5b] .…”

Rational Manipulation of Stacking Arrangements in Three‐Dimensional Zeolites Built from Two‐Dimensional Zeolitic Nanosheets

“…We postulated that the different dealumination degrees might be, at least partially, related to the MWW‐layer stacking. Previous NMR investigation has shown that C 4 ‐IM directed 94 % of framework Al atoms sited near the MWW‐layer surface [16] . According to the MWW‐layer structure, T1 site was one possible position to hold the surface Al atoms (Figure S11).…”

Olefin-surface interactions modulate the activity of silica-supported Mo-based olefin metathesis catalysts

“…observed under DNP-NMR conditions for silicate and aluminosilicate zeolites 54,55 and other silica based materials, 56 though such species are expected to be dilute in the dehydroxylated supported catalyst (≡SiO)2Mo(=O)2-red.…”