(735b) Tailored Catalytic Properties of MFI-Type Zeolite Through Controlled Surface Modifications: Theory, Synthesis and Catalytic Testing

Tailored
Catalytic Properties of MFI-Type Zeolite through Controlled Surface
Modifications: Theory, Synthesis and Catalytic Testing

Arian
Ghorbanpour, Lars C. Grabow, and
Jeffrey D. Rimer

University of Houston, Department of
Chemical and Biomolecular Engineering,

4800 Calhoun Rd., Houston,
TX 77004

Nanoporous zeolites are
utilized in many industrial processes because of their superior thermal
stability, tunable acidity, and shape-selectivity. Notably, the aluminosilicate MFI-type zeolite (termed ZSM-5) is active
for various reactions. Much attention has been given to the activity and
identity of catalytic sites within the interior pores; however, active sites
located on the external surfaces of zeolite catalysts may be equally, if not
more, important. Although the shape-selectivity effect in zeolite catalysis has
been investigated ^1,2, differences between the inner and outer
surface activity of zeolite catalysts are not well understood, which
necessitates increased research thrusts to develop an improved fundamental
knowledge of the active site(s). To this end, we have synthesized core-shell
MFI-type zeolites composed of an active (ZSM-5) core and a non-active shell of
silicalite-1 (siliceous analogue of ZSM-5) with 5 – 10 nm thickness. The "passivation"
of external active sites with this thin silica layer helps to distinguish
differences in the intrinsic activity of internal and external sites. Here, we
will discuss results from catalyst synthesis, testing, and computational
modeling using density functional theory (DFT) to calculate the stability of
bulk and surface acidic sites and to model reaction kinetics. Proper catalytic
tests are carried out to compare the performance of our core-shell materials
with that of ZSM-5. This unique combination of synthesis, testing and modeling
represents a synergistic approach in rational catalyst design that allows us to
develop structure-function relationships in zeolite catalysis.

References:

¹ D.V.
Vu, M. Miyamoto, N. Nishiyama, Y. Egashira,
K. Ueyama, J. Catal. 243
(2006) 389-394.

²
Y-J. Ji, B. Zhang, L. Xu,
H. Wu, H. Peng, L. Chen, Y. Liu, P. Wu, J. Catal. 283 (2011) 168-177.