Justin T. Fermann and Scott M. Auerbach,
``Reaction Dynamics in Acidic Zeolites: Room Temperature
Tunneling Effects,'' in Zeolites and Mesoporous Materials at the
Dawn of the 21st Century:
Proceedings of the 13th International
Zeolite Conference}, A. Galarneau, F. Di Renzo, F. Fajula and J. Vedrine
(editors), Stud. Surf. Sci. Catal. 135, Elsevier, Amsterdam, 2001.
Abstract
The potentially quantum mechanical nature of proton transfer reactions in acid
zeolite catalysis leads us to consider tunneling as an additional reaction
mechanism. We have developed a uniformly stable semiclassical harmonic
transition state theory that is compared to more rigorous rate theories, and
we present the application of our theory to the problem of acid site dynamics
in zeolites. Using a variety of computational models, we have obtained
dynamical parameters for simple proton transfer reactions in H-Y and other
zeolites. We outline the minimum treatment needed to obtain those parameters
to ``chemical accuracy.'' We find that tunneling can be the dominant mechanism
for proton transfer up to and slightly above room temperature, and indicate
that this leads to a significant underestimation of activation energies when
tunneling is neglected in interpreting experimental rate data.
Prof SM Auerbach
16 October 2001