(600ar) Employing Molecular Modifiers to Tailor the Crystal Morphology of Zeolite Catalysts

 Employing Molecular Modifiers to Tailor the Crystal
Morphology of Zeolite Catalysts

Alexandra I. Lupulescu, Jeffrey D.
Rimer

University of Houston, Department
of Chemical and Biomolecular Engineering,

4800 Calhoun Rd., Houston, TX 77004

Zeolite catalysts are ubiquitous in the
petrochemical and fine chemical industries due to their exceptional thermal
stability, unique shape-selectivity, and high acidity; however, the inability
to a priori control crystal growth often
yields suboptimal materials with limited catalytic performance due to mass
transfer limitations. Rational design approaches capable of selectively
tailoring zeolite morphology and structure can
address these challenges by eliminating long, tortuous internal diffusion pathlengths to dramatically improve catalyst activity and
lifetime ^1,2. We will present a novel
synthesis technique that draws inspiration from natural processes, wherein
molecular modifiers are employed to mediate anisotropic growth rates of zeolite crystals ³. This versatile, facile approach
was used to synthesize several zeolite framework
types, with silicalite-1 (MFI type) serving as the primary case study ⁴.
The judicious selection of high efficacy zeolite
growth modifiers (ZGMs) resulted in more than an order of magnitude decrease in
silicalite-1 platelet thickness, as well as selectively-tailored crystal aspect
ratios and surface architecture. Interfacial studies were performed to validate
growth inhibition at the microscale; and force
spectroscopy was used to probe interactions between ZGM functional groups and zeolite surfaces. Collectively, these studies have shown
that ZGMs are a cost-effective and robust design scheme for achieving
unparalleled 3-dimensional control of zeolite crystal
morphology.

[1] Choi, M., Na, K., Kim, J., Sakamoto, Y., Terasaki O., Ryoo, R.,
Nature 461 (2009)
246-249

[2] Corma, A., J. Catalysis
216 (2003) 298-312

[3] Rimer, J.D., An, Z., Zhu, Z., Lee,
M.H., Goldfarb, D.S., Wesson, J.A., Ward, M.D., Science

 330 (2010)
337-341

[4] Lupulescu, A.I.
and Rimer, J.D., Angew. Chem. Int. Ed. 51 (2012) 3345-3349