(600bk) Mesopore Formation During Zeolite Dry Gel Syntheses: A FIB/SEM Study

Mesopore Formation during Zeolite Dry Gel
Syntheses: A FIB/SEM Study

Gregory T. Neumann, and Jason C. Hicks^*
Department of Chemical and
Biomolecular Engineering, University of Notre Dame, IN

As a method to upgrade large molecular weight
feedstocks, such as heavy oil, biomass and pyrolysis oil, zeolite materials
have been synthesized to contain both mesopores and micropores within the crystalline
particles.  These hierarchical
materials have been reported to enhance the diffusion of many larger molecular
weight molecules while maintaining catalytic activity and selectivity.  Several synthesis methods exist that
introduce mesopores within the catalyst particles: 1) destructive, post
synthesis silicon etching, 2) constructive, dual templating methods using
either hard or soft mesoporous templates, and 3) constructive, assembly of
zeolite nanocrystals around mesopore
templates.  Here we report the
results of mesopore formation in HZSM-5 using a dual
templating dry gel synthesis method followed by steam assisted crystallization.  Using the combination of focused ion
beam (FIB) coupled with scanning electron microscopy (SEM), mesopore
formation was investigated for materials steamed at various times using different
soft mesopore templates and additives.  Additionally, these materials were
characterized by X-ray diffraction (XRD), N₂ physisorption, and NH₃
temperature-programmed desorption (NH­­₃-TPD).