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Mechanistic insights into the formation of butene isomers from 1-butanol in H-ZSM-5 : DFT based microkinetic modelling

Mathew John, Konstantinos Alexopoulos, Marie-Françoise Reyniers UGent and Guy Marin UGent (2017) CATALYSIS SCIENCE & TECHNOLOGY. 7(5). p.1055-1072
abstract
Besides being a renewable energy source, the catalytic conversion of bio-alcohols can serve as a sustainable means of producing high-value chemicals. Butenes produced by dehydration of 1-butanol could serve as building blocks for several essential compounds such as fuels and polymers. This study provides theoretical insights into the competing pathways for the formation of butene isomers (1-butene, cis/trans 2-butenes and iso-butene) during catalytic dehydration of 1-butanol in H-ZSM-5. As di-1-butyl ether (DBE) is one of the key products during low temperature dehydration of 1-butanol, a new mechanism for direct formation of trans-2-butene from DBE via E1 elimination is also envisaged along with the direct dehydration of 1-butanol to trans-2-butene. A 2-butoxide mediated stepwise mechanism and a concerted mechanism involving simultaneous protonation of the double bond by the Brønsted acid site and abstraction of the Hγ by the zeolite oxygen are considered for the double bond isomerization in H-ZSM-5. A monomolecular 2-butoxide and iso-butoxide mediated mechanism is considered for the skeletal isomerization. The transformation of 2-butoxide to iso-butoxide occurs via a π-bonded propene–methyl carbocationic transition state. DFT based microkinetic simulations show that, except for very low conversion levels where 2-butenes are produced via E1 elimination of 1-butanol from the protonated di-1-butyl ether (DBE*), the formation of 2-butenes occurs essentially via double bond isomerization mechanisms with comparable contributions of both concerted and 2-butoxide mediated stepwise mechanisms. Owing to the higher activation barrier for the skeletal isomerization, isobutene is not observed in the simulated temperature range of 450–500 K. Simulation results indicate that low reaction temperature, low site time and high butanol pressure favor production of 1-butene and DBE, while high temperature and site time and low butanol pressure favor the consecutive reactions leading to production of butene isomers.
Please use this url to cite or link to this publication:
author
organization
year
type
journalArticle (original)
publication status
published
keyword
DENSITY-FUNCTIONAL THEORY, H-FERRIERITE CATALYST, DOUBLE-BOND MIGRATION, SKELETAL ISOMERIZATION, AB-INITIO, N-BUTANOL, ADSORPTION THERMODYNAMICS, DEHYDRATION PATHWAYS, ZEOLITE H-ZSM-5, LINEAR BUTENES
journal title
CATALYSIS SCIENCE & TECHNOLOGY
volume
7
issue
5
pages
1055 - 1072
Web of Science type
Article
Web of Science id
000396137800005
ISSN
2044-4753
DOI
10.1039/c6cy02474b
language
English
UGent publication?
yes
classification
A1
id
8536588
handle
http://hdl.handle.net/1854/LU-8536588
date created
2017-11-08 13:40:10
date last changed
2017-11-13 10:49:00
@article{8536588,
  abstract     = {Besides being a renewable energy source, the catalytic conversion of bio-alcohols can serve as a sustainable means of producing high-value chemicals. Butenes produced by dehydration of 1-butanol could serve as building blocks for several essential compounds such as fuels and polymers. This study provides theoretical insights into the competing pathways for the formation of butene isomers (1-butene, cis/trans 2-butenes and iso-butene) during catalytic dehydration of 1-butanol in H-ZSM-5. As di-1-butyl ether (DBE) is one of the key products during low temperature dehydration of 1-butanol, a new mechanism for direct formation of trans-2-butene from DBE via E1 elimination is also envisaged along with the direct dehydration of 1-butanol to trans-2-butene. A 2-butoxide mediated stepwise mechanism and a concerted mechanism involving simultaneous protonation of the double bond by the Br{\o}nsted acid site and abstraction of the H\ensuremath{\gamma} by the zeolite oxygen are considered for the double bond isomerization in H-ZSM-5. A monomolecular 2-butoxide and iso-butoxide mediated mechanism is considered for the skeletal isomerization. The
transformation of 2-butoxide to iso-butoxide occurs via a \ensuremath{\pi}-bonded propene--methyl carbocationic transition
state. DFT based microkinetic simulations show that, except for very low conversion levels where 2-butenes are produced via E1 elimination of 1-butanol from the protonated di-1-butyl ether (DBE*), the formation of 2-butenes occurs essentially via double bond isomerization mechanisms with comparable contributions of both concerted and 2-butoxide mediated stepwise mechanisms. Owing to the higher activation barrier for the skeletal isomerization, isobutene is not observed in the simulated temperature range of 450--500 K. Simulation results indicate that low reaction temperature, low site time and high butanol pressure favor production of 1-butene and DBE, while high temperature and site time and low butanol pressure favor the consecutive reactions leading to production of butene isomers.},
  author       = {John, Mathew and Alexopoulos, Konstantinos and Reyniers, Marie-Fran\c{c}oise and Marin, Guy},
  issn         = {2044-4753 },
  journal      = {CATALYSIS SCIENCE \& TECHNOLOGY},
  keyword      = {DENSITY-FUNCTIONAL THEORY,H-FERRIERITE CATALYST,DOUBLE-BOND MIGRATION,SKELETAL ISOMERIZATION,AB-INITIO,N-BUTANOL,ADSORPTION THERMODYNAMICS,DEHYDRATION PATHWAYS,ZEOLITE H-ZSM-5,LINEAR BUTENES},
  language     = {eng},
  number       = {5},
  pages        = {1055--1072},
  title        = {Mechanistic insights into the formation of butene isomers from 1-butanol in H-ZSM-5 : DFT based microkinetic modelling},
  url          = {http://dx.doi.org/10.1039/c6cy02474b},
  volume       = {7},
  year         = {2017},
}

Chicago
John, Mathew, Konstantinos Alexopoulos, Marie-Françoise Reyniers, and Guy Marin. 2017. “Mechanistic Insights into the Formation of Butene Isomers from 1-butanol in H-ZSM-5 : DFT Based Microkinetic Modelling.” Catalysis Science & Technology 7 (5): 1055–1072.
APA
John, M., Alexopoulos, K., Reyniers, M.-F., & Marin, G. (2017). Mechanistic insights into the formation of butene isomers from 1-butanol in H-ZSM-5 : DFT based microkinetic modelling. CATALYSIS SCIENCE & TECHNOLOGY, 7(5), 1055–1072.
Vancouver
1.
John M, Alexopoulos K, Reyniers M-F, Marin G. Mechanistic insights into the formation of butene isomers from 1-butanol in H-ZSM-5 : DFT based microkinetic modelling. CATALYSIS SCIENCE & TECHNOLOGY. 2017;7(5):1055–72.
MLA
John, Mathew, Konstantinos Alexopoulos, Marie-Françoise Reyniers, et al. “Mechanistic Insights into the Formation of Butene Isomers from 1-butanol in H-ZSM-5 : DFT Based Microkinetic Modelling.” CATALYSIS SCIENCE & TECHNOLOGY 7.5 (2017): 1055–1072. Print.