Characterizing Zeolite Surface Growth At the Microscopic Level Using in Situ Atomic Force Microscopy

Characterizing Zeolite Surface Growth at the Microscopic Level using In Situ Atomic Force Microscopy

Alexandra I. Lupulescu, Jeffrey D. Rimer

University of Houston, Department of Chemical and Biomolecular Engineering,

4800 Calhoun Rd., Houston, TX 77004

The exceptional thermal stability, unique shape-selectivity, and high acidity of zeolites contribute to their frequent use as industrial catalysts. The inability to a priori control single crystal growth, however, often yields materials with limited catalytic performance due to long, tortuous internal diffusion pathlengths, as well as restricted access to surface active sites. Rational design approaches capable of selectively tailoring zeolite morphology and structure can dramatically improve catalyst activity and lifetime ^1,2, and given the potential application of zeolite catalysts for alternative fuels production and vehicle emission technologies, there exists a critical need to expand the fundamental understanding of zeolite growth as well as design more robust synthetic schemes to optimize zeolite catalysts ³. We will discuss a new advancement in atomic force microscopy (AFM) to image zeolite surface growth in situ, which allows zeolite catalysts to be characterized under realistic synthesis conditions. AFM offers unparalleled insight into the surface mechanism of zeolite growth at near-molecular resolution ^4,5. Here, we will present the first application of AFM to continuously image zeolite surface step growth at elevated temperatures and long periods of time (i.e. greater than 10 hours). We will discuss the distinctive set of challenges that zeolite in situ growth presents and a comprehensive study of silicalite-1 growth under various conditions, including the effect of zeolite growth modifiers (ZGMs), which are molecular additives used to mediate anisotropic growth rates of zeolites and tailor their bulk crystal habit ^6,7.

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

 330 (2010) 337-341

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