Synthesis and crystal growth mechanism of ZSM-22 zeolite nanosheets

Abstract

† Electronic supplementary information (ESI) available: XRD, ICP and N 2 adsorption characterization results of samples synthesized with different SiO 2 /Al 2 O 3 ratios. See

Correlated super-resolution fluorescence and electron microscopy reveals the catalytically active nanorods within individual H-ZSM-22 zeolite particles

“…As a result, elementary nanorod particles are obtained with an Al enriched outer surface. This is indirectly confirmed by combined inductively coupled plasma atomic emission spectroscopy (ICP-AES) and X-ray photoelectron spectroscopy (XPS), [13,24] while the possibility of direct Al concentration mapping by energy-dispersive X-ray spectrometry high-angle annular dark field scanning transmission electron microscopy (EDX-HAADF-STEM) is limited due to low Al content (Figure S1). Ex-situ scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) show that in the final stages of H-ZSM-22 synthesis these nanorods fuse together laterally and give rise to the larger needle-shaped aggregates.…”

“…The growth mechanism of needle-shaped H-ZSM-22 particles has been described in literature by several groups independently. [13,24,25] Initially, amorphous particles are formed by the coalescence of silica sol grains around which a template (diethanolamine)-rich secondary gel precipitates. During synthesis, the silica rich core slowly dissolves while heterogeneous zeolite nucleation takes place at the organophilic surface of the secondary gel.…”

Two-Dimensional Zeolite Materials: Structural and Acidity Properties

“…For example, MIT (Massachusetts Institute of Technology)-1 [67] and self-pillared pentasil (SPP) [40,68] have been prepared using the templating method in a one-step crystallization processes. Other aluminosilicate zeolites, such as MEL (ZSM-11 (eleven)) [69], FAU (faujasite) [70][71][72], TON (Theta-1) [73], MOR (mordenite) [74] and MRE (ZSM-48 (forty-eight)) [75], with 2D lamellar structures have also been explored, although the obtained layer structures have not been downsized into the unit-cell thickness level.…”

“…The successful synthesis of lamellar MFI zeolite inspired the exploration of other 2D zeolite frameworks containing heteroatoms and medium/large micropores. In the past decade, 2D lamellar zeolites with MEL [69], MOR [74], MRE [75], TON [73], and FAU [70,71] topologies have been prepared. It should be noted that these zeolites do not yet have unilamellar, multilamellar, or 2D derivative structures, unlike the 2D layered zeolites discussed in Sections 3.1-3.4 above.…”

“…The 2D TON (i.e., ZSM-22) zeolite nanoplates, with a thickness of about 100 Å, were synthesized through hydrothermal crystallization using a 1-ethylpyridinium bromide template. The mechanism was assumed to be a multi-step crystallization process involving the aggregation and fusion of elementary nanorods, and inhomogeneous Al distribution was considered to be a key factor [73]. TON is known as a 1D channel system with 10-MR pore openings of 4.5 Å × 5.5 Å.…”