(337h) The Role of Surface Barriers As Dominant Transport Mechanism in Hierarchically Structured Zeolites-- Application to the Alkylation of Benzene with Ethylene

Authors: 
Rao, S. M., Rensselaer Polytechnic Institute
Saraçi, E., University of Leipzig
Glaeser, R., University of Leipzig
Coppens, M. O., University College London
The meso-macropore network of a hierarchically structured zeolite catalyst is numerically optimized to
maximize the volume-integrated reaction yield in the ethylation of benzene to produce ethylbenzene
over zeolite H-ZSM-5. A hierarchical approach is used at multiple length scales to determine the optimal
pore network properties. The maximum volume-integrated reaction yield of the hierarchically structured
zeolite catalyst containing meso- and macropores is nearly twice the yield of a zeolite pellet containing
only macropores, at the same macroporosity. To bridge the gap between modeling and experiments, a
series of physical mixtures of ZSM-5 crystals and mesoporous silica, containing different weight fractions
of zeolite is synthesized and used in fixed bed reactor experiments to determine the optimal pellet structure
to maximize the conversion of ethylene. Comparison with reactor simulations of the zeolite composites
shows that the performance of the zeolite composites might be limited by surface barriers at the
external surface of the zeolite crystals, rather than by diffusion limitations within the meso-macropore
network of the pellets.

References:

Rao, S. M.; Saraci, E.; Glaeser, R.; Coppens, M.-O. Chem. Eng. J. 2017 (http://doi.org/10.1016/j.cej.2017.04.015)

Topics: