Dual Templating for AFX/LEV Intergrowth Zeolite

Abstract

Zeolite composed of an intergrowth structure based on AFX and LEV framework types was successfully synthesized by dual-templating strategy using 1,1′-(1,4-butanediyl)bis(1-azonia-4-azabicyclo[2,2,2]octane) and dimethylpiperidinium hydroxides. DIFFaX simulation and 13C NMR results indicated that the AFX framework-type is the main component of the intergrowth structure. The intergrowth material obtained was characterized using XRD, SEM, 27Al and 29Si NMR, and N2 adsorption measurements.

Intergrowth Zeolites, Synthesis, Characterization, and Catalysis

“…As in Figure , we employ tile alignment animation diagrams to reveal five examples of fault frameworks (CHA/AFX, CHA/GME, AFX/LEV, ERI/LEV, ERI/OFF) of the promising ABC-6 series zeolites, in order to facilitate a better understanding of the exact location and structure of the phase boundaries from a three-dimensional point of view. It is noteworthy that all these intergrowth frameworks exhibit well-matched “tiles” at the phase boundaries, which implies that these intergrowths with a high degree of crystallinity can be obtained by synthesis, which is consistent with the literatures. ,,,, A variety of intergrowth phase-boundary structures can be formed by using different “tiles” and arrangements, and it is clear that the openness of the channels at these phase boundaries is strictly controlled by the alignment of the “tiles” sizes and opening pore widths. Among them, the placement of double hexagonal ring tiles in the [001] direction determines the intergrowth phase-boundary structure, because there are always other “tiles” that happen to occupy these three-dimensional spaces between these double hexagonal rings, such as cages of different sizes like can, gme, lev, cha, afx, and so on.…”

“…Therefore, further understanding the structural characteristics of each intergrowth zeolite is crucial. For example, the kinetic diameters of reacting molecules are relatively small (>3.8 Å) for both NH 3 -SCR and MTO reactions, so small pore zeolites with 8 MR are chosen to hinder the entry of macromolecules allowing for a slower catalyst deactivation, such as AEI/CHA, AFX/CHA, and AFX/LEV . Importantly, none of these intergrowth phase boundaries create a barrier to mass transfer and they allow the molecules to complete their catalytic reactions in respective channel systems, with only concomitant differences in catalytic properties at the phase boundaries.…”