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Title: Diffusion of biomass pyrolysis products in H-ZSM-5 by molecular dynamics simulations

Abstract

Diffusion of biomass pyrolysis vapors and their upgraded products is an essential catalytic property of zeolites during catalytic fast pyrolysis and likely plays a critical role in the selectivity of these catalysts. Characterizing the diffusivities of representative biofuel molecules is critical to understand shape selectivity and interpret product distribution. Yet, experimental measurements on the diffusivities of oxygenated biofuel molecules at pyrolysis temperatures are very limited in the literature. As an alternative approach, we conducted MD simulations to measure the diffusion coefficients of several selected molecules that are representative of biomass pyrolysis vapors, namely water, methanol, glycolaldehyde, and toluene in H-ZSM-5 zeolite. The results show the diffusion coefficients calculated via MD simulations are consistent with available NMR measurements at room temperature. The effect of molecular weight and molecular critical diameter on the diffusivity among the chosen model compounds is also examined. Furthermore, we have characterized the diffusivities of representative biofuel molecules, namely xylene isomers, in H-ZSM-5. Our calculations determined that the ratio of the diffusion coefficients for xylene isomers is p-xylene: o-xylene: m-xylene ≈ 83:3:1 at 700 K. Furthermore, our results also demonstrate the different diffusivity between p-xylene and toluene is due to the molecular orientations when the molecules diffuse alongmore » the channels in H-ZSM-5 and provide deep insight into the effect of molecular orientation on its diffusivity.« less

Authors:
 [1];  [1];  [1]; ORCiD logo [1]
  1. National Renewable Energy Lab. (NREL), Golden, CO (United States)
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Bioenergy Technologies Office (EE-3B)
OSTI Identifier:
1339609
Report Number(s):
NREL/JA-5100-67506
Journal ID: ISSN 1932-7447
Grant/Contract Number:  
AC36-08GO28308
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. C
Additional Journal Information:
Journal Volume: 121; Journal Issue: 1; Journal ID: ISSN 1932-7447
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
09 BIOMASS FUELS; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; molecular dynamics; biomass pyrolysis; diffusion coefficient; zeolite; xylene

Citation Formats

Bu, Lintao, Nimlos, Mark R., Robichaud, David J., and Kim, Seonah. Diffusion of biomass pyrolysis products in H-ZSM-5 by molecular dynamics simulations. United States: N. p., 2016. Web. doi:10.1021/acs.jpcc.6b10871.
Bu, Lintao, Nimlos, Mark R., Robichaud, David J., & Kim, Seonah. Diffusion of biomass pyrolysis products in H-ZSM-5 by molecular dynamics simulations. United States. doi:10.1021/acs.jpcc.6b10871.
Bu, Lintao, Nimlos, Mark R., Robichaud, David J., and Kim, Seonah. Tue . "Diffusion of biomass pyrolysis products in H-ZSM-5 by molecular dynamics simulations". United States. doi:10.1021/acs.jpcc.6b10871. https://www.osti.gov/servlets/purl/1339609.
@article{osti_1339609,
title = {Diffusion of biomass pyrolysis products in H-ZSM-5 by molecular dynamics simulations},
author = {Bu, Lintao and Nimlos, Mark R. and Robichaud, David J. and Kim, Seonah},
abstractNote = {Diffusion of biomass pyrolysis vapors and their upgraded products is an essential catalytic property of zeolites during catalytic fast pyrolysis and likely plays a critical role in the selectivity of these catalysts. Characterizing the diffusivities of representative biofuel molecules is critical to understand shape selectivity and interpret product distribution. Yet, experimental measurements on the diffusivities of oxygenated biofuel molecules at pyrolysis temperatures are very limited in the literature. As an alternative approach, we conducted MD simulations to measure the diffusion coefficients of several selected molecules that are representative of biomass pyrolysis vapors, namely water, methanol, glycolaldehyde, and toluene in H-ZSM-5 zeolite. The results show the diffusion coefficients calculated via MD simulations are consistent with available NMR measurements at room temperature. The effect of molecular weight and molecular critical diameter on the diffusivity among the chosen model compounds is also examined. Furthermore, we have characterized the diffusivities of representative biofuel molecules, namely xylene isomers, in H-ZSM-5. Our calculations determined that the ratio of the diffusion coefficients for xylene isomers is p-xylene:o-xylene:m-xylene ≈ 83:3:1 at 700 K. Furthermore, our results also demonstrate the different diffusivity between p-xylene and toluene is due to the molecular orientations when the molecules diffuse along the channels in H-ZSM-5 and provide deep insight into the effect of molecular orientation on its diffusivity.},
doi = {10.1021/acs.jpcc.6b10871},
journal = {Journal of Physical Chemistry. C},
issn = {1932-7447},
number = 1,
volume = 121,
place = {United States},
year = {2016},
month = {12}
}

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