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Title: Theoretical Determination of Size Effects in Zeolite-Catalyzed Alcohol Dehydration

Abstract

In the upgrading of biomass pyrolysis vapors to hydrocarbons, dehydration accomplishes a primary objective of removing oxygen, and acidic zeolites represent promising catalysts for the dehydration reaction. Here, we utilized density functional theory calculations to estimate adsorption energetics and intrinsic kinetics of alcohol dehydration over H-ZSM-5, H-BEA, and H-AEL zeolites. The ONIOM (our Own N-layered Integrated molecular Orbital and molecular Mechanics) calculations of adsorption energies were observed to be inconsistent when benchmarked against QM (Quantum Mechanical)/Hartree–Fock and periodic boundary condition calculations. However, reaction coordinate calculations of adsorbed species and transition states were consistent across all levels considered. Comparison of ethanol, isopropanol (IPA), and tert-amyl alcohol (TAA) over these three zeolites allowed for a detailed examination of how confinement impacts on reaction mechanisms and kinetics. The TAA, seen to proceed via a carbocationic mechanism, was found to have the lowest activation barrier, followed by IPA and then ethanol, both of which dehydrate via a concerted mechanism. Barriers in H-BEA were consistently found to be lower than in H-ZSM-5 and H-AEL, attributed to late transition states and either elevated strain or inaccurately estimating long-range electrostatic interactions in H-AEL, respectively. Molecular dynamics simulations revealed that the diffusivity of these three alcohols in H-ZSM-5more » were significantly overestimated by Knudsen diffusion, which will complicate experimental efforts to develop a kinetic model for catalytic fast pyrolysis.« less

Authors:
 [1];  [1];  [1];  [2]; ORCiD logo [1];  [2];  [2]; ORCiD logo [1]; ORCiD logo [1]
  1. National Renewable Energy Lab. (NREL), Golden, CO (United States)
  2. Argonne National Lab. (ANL), Lemont, IL (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:
1567023
Report Number(s):
NREL/JA-2700-74616
Journal ID: ISSN 2073-4344; CATACJ
Grant/Contract Number:  
AC36-08GO28308
Resource Type:
Accepted Manuscript
Journal Name:
Catalysts
Additional Journal Information:
Journal Volume: 9; Journal Issue: 9; Journal ID: ISSN 2073-4344
Publisher:
MDPI
Country of Publication:
United States
Language:
English
Subject:
09 BIOMASS FUELS; biomass pyrolysis; alcohol dehydration; zeolite; DFT; ONIOM

Citation Formats

Kunz, Larissa Y., Bu, Lintao, Knott, Brandon C., Liu, Cong, Nimlos, Mark R., Assary, Rajeev S., Curtiss, Larry A., Robichaud, David J., and Kim, Seonah. Theoretical Determination of Size Effects in Zeolite-Catalyzed Alcohol Dehydration. United States: N. p., 2019. Web. doi:10.3390/catal9090700.
Kunz, Larissa Y., Bu, Lintao, Knott, Brandon C., Liu, Cong, Nimlos, Mark R., Assary, Rajeev S., Curtiss, Larry A., Robichaud, David J., & Kim, Seonah. Theoretical Determination of Size Effects in Zeolite-Catalyzed Alcohol Dehydration. United States. doi:10.3390/catal9090700.
Kunz, Larissa Y., Bu, Lintao, Knott, Brandon C., Liu, Cong, Nimlos, Mark R., Assary, Rajeev S., Curtiss, Larry A., Robichaud, David J., and Kim, Seonah. Wed . "Theoretical Determination of Size Effects in Zeolite-Catalyzed Alcohol Dehydration". United States. doi:10.3390/catal9090700. https://www.osti.gov/servlets/purl/1567023.
@article{osti_1567023,
title = {Theoretical Determination of Size Effects in Zeolite-Catalyzed Alcohol Dehydration},
author = {Kunz, Larissa Y. and Bu, Lintao and Knott, Brandon C. and Liu, Cong and Nimlos, Mark R. and Assary, Rajeev S. and Curtiss, Larry A. and Robichaud, David J. and Kim, Seonah},
abstractNote = {In the upgrading of biomass pyrolysis vapors to hydrocarbons, dehydration accomplishes a primary objective of removing oxygen, and acidic zeolites represent promising catalysts for the dehydration reaction. Here, we utilized density functional theory calculations to estimate adsorption energetics and intrinsic kinetics of alcohol dehydration over H-ZSM-5, H-BEA, and H-AEL zeolites. The ONIOM (our Own N-layered Integrated molecular Orbital and molecular Mechanics) calculations of adsorption energies were observed to be inconsistent when benchmarked against QM (Quantum Mechanical)/Hartree–Fock and periodic boundary condition calculations. However, reaction coordinate calculations of adsorbed species and transition states were consistent across all levels considered. Comparison of ethanol, isopropanol (IPA), and tert-amyl alcohol (TAA) over these three zeolites allowed for a detailed examination of how confinement impacts on reaction mechanisms and kinetics. The TAA, seen to proceed via a carbocationic mechanism, was found to have the lowest activation barrier, followed by IPA and then ethanol, both of which dehydrate via a concerted mechanism. Barriers in H-BEA were consistently found to be lower than in H-ZSM-5 and H-AEL, attributed to late transition states and either elevated strain or inaccurately estimating long-range electrostatic interactions in H-AEL, respectively. Molecular dynamics simulations revealed that the diffusivity of these three alcohols in H-ZSM-5 were significantly overestimated by Knudsen diffusion, which will complicate experimental efforts to develop a kinetic model for catalytic fast pyrolysis.},
doi = {10.3390/catal9090700},
journal = {Catalysts},
number = 9,
volume = 9,
place = {United States},
year = {2019},
month = {8}
}

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