On the key role of hydroxyl groups in platinum-catalysed alcohol oxidation in aqueous medium

Article abstract of DOI:10.1039/c2cy20363d

In the aerobic selective oxidation of alcohols in aqueous medium in a batch reactor, it was observed that the addition of water to dioxane solvent (10-50 vol%) substantially increased the activity of a Pt/C catalyst. Periodic density functional theory (DFT) calculations were carried out to compare the reactivity of alcohols on the bare Pt(111) surface and in the presence of adsorbed water or hydroxyl groups, to explain the effect of water. The calculations indicate that the presence of adsorbed hydroxyl groups promotes the catalytic activity by participating directly in the catalytic pathways and reducing the activation barrier. Good agreement was found between the experiments in aqueous phase and these calculations. Further, decarbonylation of the aldehyde may be involved in the deactivation during oxidation of a primary alcohol. The Royal Society of Chemistry 2013.

Full text of DOI:10.1039/c2cy20363d

Electronic Supplementary Material (ESI) for Catalysis Science & Technology
This journal is © The Royal Society of Chemistry 2012
Supplementary Information
On the key role of hydroxyl groups on platinum-
catalysed alcohol oxidation in aqueous medium.
Siwar Chibania, C. Michela, F. Delbecqa, C. Pinelb, M. Bessonb
a- Université de Lyon, CNRS, École Normale Supérieure de Lyon, 46 allée d’Italie, F-
69364 Lyon Cedex 07 (France),
b- Université de Lyon, CNRS, IRCELYON, 2 avenue A. Einstein, F-69626 Villeurbanne
(France)
TSOH
TSOH-CH
TSCH
TSCH-OH
Figure S1. Transition states structures of the isopropanol oxidation at a bare Pt(111)
TSOH
TSOH-CH
TSCH
TSCH-OH
Figure S2. Transition states structures of the isopropanol oxidation at a H2O@Pt(111)
surface.
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Electronic Supplementary Material (ESI) for Catalysis Science & Technology
This journal is © The Royal Society of Chemistry 2012
Figure S3. Transition state structure of the isopropanol oxidation at a OH@Pt(111)
surface
N
X-H
Pt-X
Pt-H
H...O
1.61
1.76
1.73
E
E‡
OH
Pt(111)
0.72
0.93
0.85
4
4
1.64
1.62
2.07
2.17
1.64
1.64
H2O@Pt(111) 0.59
OH-CH
Pt(111)
-0.64
0.08
0.28
5
5
1.44
1.50
3.02
3.09
1.71
1.68
H2O@Pt(111) -0.46
CH
Pt(111)
0.00
0.81
1.13
3
3
1.98
1.72
3.03
2.60
1.61
1.62
H2O@Pt(111) 0.16
CH-OH
Pt(111)
H2O@Pt(111) -0.08
OH@Pt(111) -0.43
0.47
0.81
0.65
0.27
4
6
5
1.66
1.47
1.49
2.24
3.05
3.08
1.61
1.66
1.68
1.50
1.62
Table S1. Energetics and main geometrical characteristics of the transition state
structures for the isopropanol oxidation at the bare platinum surface (Pt(111)), at the
hydrated platinum surface (H2O@Pt(111)) and at the hydroxylated surface
(OH@Pt(111)). The CH step is the first step of Route C. The CH-OH step is the second
step of route C. The OH step is the first step of route O. The OH-CH is the second step of
route O. The reaction energy E and the activation energy E‡ of each step are provided
in eV. The transition state structures are characterized by the number of involved atoms
(N). The main distances are given in Å: X-H is the breaking bond; Pt-Y corresponds to the
Pt-C (resp. Pt-O) bond for the CH bond scission (resp. OH bond scission). In the case of
reaction at the hydrated and the hydroxylated surfaces, C or O is not adsorbed in the
final product. H...O corresponds to the hydrogen bonds.
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