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