Details
| Original language | English |
|---|---|
| Pages (from-to) | 7188-7199 |
| Number of pages | 12 |
| Journal | Chemistry - A European Journal |
| Volume | 24 |
| Issue number | 28 |
| Early online date | 21 Feb 2018 |
| Publication status | Published - 17 May 2018 |
Abstract
Among noble metal catalysts, rhodium (Rh) is unique in its ability to perform a one-step synthesis of ethanol from syngas. The first steps following the adsorption of syngas on Rh surfaces are assumed to be responsible for the conversion of CO and the selectivity effects between C1, C2, and oxygenated species. In the current work, constrained ab initio molecular dynamics are applied to investigate the kinetics of CO dissociation and hydrogenation over flat and stepped Rh surfaces. The obtained barriers for the Rh(111) surface are in good agreement with the literature data. On the stepped Rh(211) surface, a large site-dependent variation in barrier height is shown, with the upper terrace exhibiting behavior comparable to the Rh(111) surface, whereas the barriers over the lower terrace site are generally significantly lower. The rate constants are calculated using transition state theory for both surfaces, and are applied successfully in a microkinetic model, confirming the predicted impact on CO conversion and CH4/C1-oxygenate/C2Hn selectivity. In addition to the high-accuracy energetics and rate constants reported for CO dissociation/hydrogenation and the presentation of an updated microkinetic mechanism for Rh catalysts, the applicability of constrained molecular dynamics for reaction barrier calculation is confirmed, and sensitive pathways affecting the selectivity between formaldehyde/methanol over Rh catalysts are highlighted.
Keywords
- ab initio calculations, density functional calculations, microkinetic modeling, molecular dynamics, rhodium, syngas
ASJC Scopus subject areas
- Chemical Engineering(all)
- Catalysis
- Chemistry(all)
- Organic Chemistry
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In: Chemistry - A European Journal, Vol. 24, No. 28, 17.05.2018, p. 7188-7199.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Constrained Chemical Dynamics of CO Dissociation/Hydrogenation on Rh Surfaces
AU - Kraus, Peter
AU - Frank, Irmgard
N1 - Publisher Copyright:© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Copyright:Copyright 2018 Elsevier B.V., All rights reserved.
PY - 2018/5/17
Y1 - 2018/5/17
N2 - Among noble metal catalysts, rhodium (Rh) is unique in its ability to perform a one-step synthesis of ethanol from syngas. The first steps following the adsorption of syngas on Rh surfaces are assumed to be responsible for the conversion of CO and the selectivity effects between C1, C2, and oxygenated species. In the current work, constrained ab initio molecular dynamics are applied to investigate the kinetics of CO dissociation and hydrogenation over flat and stepped Rh surfaces. The obtained barriers for the Rh(111) surface are in good agreement with the literature data. On the stepped Rh(211) surface, a large site-dependent variation in barrier height is shown, with the upper terrace exhibiting behavior comparable to the Rh(111) surface, whereas the barriers over the lower terrace site are generally significantly lower. The rate constants are calculated using transition state theory for both surfaces, and are applied successfully in a microkinetic model, confirming the predicted impact on CO conversion and CH4/C1-oxygenate/C2Hn selectivity. In addition to the high-accuracy energetics and rate constants reported for CO dissociation/hydrogenation and the presentation of an updated microkinetic mechanism for Rh catalysts, the applicability of constrained molecular dynamics for reaction barrier calculation is confirmed, and sensitive pathways affecting the selectivity between formaldehyde/methanol over Rh catalysts are highlighted.
AB - Among noble metal catalysts, rhodium (Rh) is unique in its ability to perform a one-step synthesis of ethanol from syngas. The first steps following the adsorption of syngas on Rh surfaces are assumed to be responsible for the conversion of CO and the selectivity effects between C1, C2, and oxygenated species. In the current work, constrained ab initio molecular dynamics are applied to investigate the kinetics of CO dissociation and hydrogenation over flat and stepped Rh surfaces. The obtained barriers for the Rh(111) surface are in good agreement with the literature data. On the stepped Rh(211) surface, a large site-dependent variation in barrier height is shown, with the upper terrace exhibiting behavior comparable to the Rh(111) surface, whereas the barriers over the lower terrace site are generally significantly lower. The rate constants are calculated using transition state theory for both surfaces, and are applied successfully in a microkinetic model, confirming the predicted impact on CO conversion and CH4/C1-oxygenate/C2Hn selectivity. In addition to the high-accuracy energetics and rate constants reported for CO dissociation/hydrogenation and the presentation of an updated microkinetic mechanism for Rh catalysts, the applicability of constrained molecular dynamics for reaction barrier calculation is confirmed, and sensitive pathways affecting the selectivity between formaldehyde/methanol over Rh catalysts are highlighted.
KW - ab initio calculations
KW - density functional calculations
KW - microkinetic modeling
KW - molecular dynamics
KW - rhodium
KW - syngas
UR - http://www.scopus.com/inward/record.url?scp=85046083218&partnerID=8YFLogxK
U2 - 10.1002/chem.201705867
DO - 10.1002/chem.201705867
M3 - Article
C2 - 29464790
AN - SCOPUS:85046083218
VL - 24
SP - 7188
EP - 7199
JO - Chemistry - A European Journal
JF - Chemistry - A European Journal
SN - 0947-6539
IS - 28
ER -