(521dp) New Synthesis Approaches for Hierarchical Zeolites with Intergrowth Structures

Zhiyin Niu and Jeffrey D. Rimer*

Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204

*jrimer@central.uh.edu

Hierarchical zeolites contain highly interconnected networks of zeolite micropores combined with mesopores and/or macropores. Interest in these materials stems from the higher reaction rates, improved selectivity, resistance to deactivation, and novel adsorption behavior they exhibit in comparison to conventional zeolites containing only micropores. Among the synthesis approaches used to achieve hierarchical zeolites, the introduction of repetitive branching by rotational intergrowths holds significant promise for developing a new class of industrial catalysts. Advancements in this area of research are becoming even more commercially viable owing to the design of facile, economic synthesis approaches that require a single step and in many instances the use of simple organic structure-directing agents or additives.

Among zeolite intergrowths reported in literature, faujasite-based materials have attracted considerable attention due to their superior catalytic properties for a wide variety of (petro)chemical processes. Here, we will discuss recent progress in the preparation of faujasite-based hierarchical materials using one-step synthesis protocols where unique morphologies are achieved through the judicious selection of structure-directing agents. Examples include FAU-EMT and FAU-AEI intergrowths where combinations of inorganics and organics can lead to house-of-cards nanosheet architecture. These atypical morphologies improve diffusion properties, which improves their performance in catalytic reactions. We will also discuss unique organics used to direct zeolites with unusual physicochemical properties, such as nanosheets (< 50 nm thickness) of 3-dimensional pore zeolites. Our findings reveal that these materials exhibit improved mass transport properties compared to materials obtained by more conventional synthesis protocols.