Synthesis and characterization of epitaxial FAU-on-EMT zeolite overgrowth materials

Epitaxial FAU zeolite films were achieved on micrometersized EMT support cr ystals using a two-step synthetic procedure, in which EMT support crystals with hexagonal-platelet morphology were added to a synthesis gel for the cr ystallization of an FAU phase. Identification of the appropriate synthesis parameters made it possible to suppress homogeneous nucleation and initial breeding, and to promote the secondary nucleation of the FAU crystallites o n the surface of the EMT support crystals. The presence of both an FAU and an EMT phase was verified with powder X-ray diffraction (XRD). Scanning ele ctron microscopy (SEM) was used to confirm the formation of a layer of FAU crystallites on the EMT support crystals. The growth of the FAU phase was f ound to start at the corners and edges of the EMT support. An FAU crystalli zation front progressed from the edges towards the center of the hexagon un til the EMT support crystals became completely covered by an FAU zeolite fi lm with a thickness of ca. 300nm. The compositional difference between the EMT support: and the FAU film was investigated with Si-29 magic angle spinn ing (MAS) nuclear magnetic resonance (NMR) spectroscopy, X-ray photoelectro n spectroscopy (XPS) and energy-dispersive analysis of X-rays (nano-EDAX). The continuous nature of the film was confirmed by the absence of intracrys talline mesopores, which was evidenced by nitrogen physisorption.