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Title: Diffusion of aromatic hydrocarbons in hierarchical mesoporous H-ZSM-5 zeolite

Journal Article · · Catalysis Today
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  1. National Renewable Energy Lab. (NREL), Golden, CO (United States)

Hierarchical mesoporous zeolites exhibit higher catalytic activities and longer lifetime compared to the traditional microporous zeolites due to improved diffusivity of substrate molecules and their enhanced access to the zeolite active sites. Understanding diffusion of biomass pyrolysis vapors and their upgraded products in such materials is fundamentally important during catalytic fast pyrolysis (CFP) of lignocellulosic biomass, since diffusion makes major contribution to determine shape selectivity and product distribution. However, diffusivities of biomass relevant species in hierarchical mesoporous zeolites are poorly characterized, primarily due to the limitations of the available experimental technology. In this work, molecular dynamics (MD) simulations are utilized to investigate the diffusivities of several selected coke precursor molecules, benzene, naphthalene, and anthracene, in hierarchical mesoporous H-ZSM-5 zeolite. The effects of temperature and size of mesopores on the diffusivity of the chosen model compounds are examined. The simulation results demonstrate that diffusion within the microspores as well as on the external surface of mesoporous H-ZSM-5 dominates only at low temperature. At pyrolysis relevant temperatures, mass transfer is essentially conducted via diffusion along the mesopores. Furthermore, the results illustrate the heuristic diffusion model, such as the extensively used Knudsen diffusion, overestimates the diffusion of bulky molecules in the mesopores, thus making MD simulation a powerful and compulsory approach to explore diffusion in zeolites.

Research Organization:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Organization:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Sustainable Transportation Office. Bioenergy Technologies Office
Grant/Contract Number:
AC36-08GO28308
OSTI ID:
1424576
Alternate ID(s):
OSTI ID: 1591656
Report Number(s):
NREL/JA-2700-71045; TRN: US1801924
Journal Information:
Catalysis Today, Vol. 312, Issue C; ISSN 0920-5861
Publisher:
ElsevierCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 36 works
Citation information provided by
Web of Science

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