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Carbon-carbon double bond versus carbonyl group hydrogenation: controlling the intramolecular selectivity with polyaniline-supported platinum catalysts.

Steffan, Martin and Klasovsky, Florian and Arras, Jürgen and Roth, Christina and Radnik, Jörg and Hofmeister, Herbert and Claus, Peter (2008):
Carbon-carbon double bond versus carbonyl group hydrogenation: controlling the intramolecular selectivity with polyaniline-supported platinum catalysts.
In: Advanced Synthesis & Catalysis, pp. 1337-1348, 350, (9), [Online-Edition: http://dx.doi.org/10.1002/adsc.200800035],
[Article]

Abstract

The use of polyaniline (PANI) as catalyst support for heterogeneous catalysts and their application in chemical catalysis is hitherto rather poorly known. We report the successful synthesis of highly dispersed PANI-supported platinum catalysts (particle sizes between 1.7 and 3.7 nm as revealed by transmission electron microscopy, TEM) choosing two different approaches, namely (i) deposition-precipitation of H₂PtCl₆ onto polyaniline, suspended in basic medium (DP method) and, (ii) immobilization of a preformed nanoscale platinum colloid on polyaniline (sol-method). The PANI-supported platinum catalysts were applied in the selective hydrogenation of the α,β-unsaturated aldehyde citral. In order to benchmark their catalytic performance, citral hydrogenation was also carried out by using platinum supported on the classical support materials silica (SiO₂), alumina (Al₂O₃), active carbon and graphite. The relations of the structural characteristics and surface state of the catalysts with respect to their hydrogenation properties have been probed by EXAFS and XPS. It is found that the DP method yields chemically prepared PtO₂ on polyaniline and, thus, produces a highly dispersed and immobilized Adams catalyst (in the β-PtO₂ form) which is able to efficiently hydrogenate the conjugated C=C bond of citral (selectivity to citronellal=87%), whereas reduction of the C=O group occurs with polyaniline-supported platinum (selectivity to geraniol/nerol=78%) prepared via the sol-method. The complete reversal of the selectivity between the preferred hydrogenation of the conjugated C=C or C=O group is not only particularly useful for the selective hydrogenation of α,β-unsaturated aldehydes but also unveils the great potential of conducting polymer-supported precious metals in the field of hitherto barely investigated chemical catalysis.

Item Type: Article
Erschienen: 2008
Creators: Steffan, Martin and Klasovsky, Florian and Arras, Jürgen and Roth, Christina and Radnik, Jörg and Hofmeister, Herbert and Claus, Peter
Title: Carbon-carbon double bond versus carbonyl group hydrogenation: controlling the intramolecular selectivity with polyaniline-supported platinum catalysts.
Language: English
Abstract:

The use of polyaniline (PANI) as catalyst support for heterogeneous catalysts and their application in chemical catalysis is hitherto rather poorly known. We report the successful synthesis of highly dispersed PANI-supported platinum catalysts (particle sizes between 1.7 and 3.7 nm as revealed by transmission electron microscopy, TEM) choosing two different approaches, namely (i) deposition-precipitation of H₂PtCl₆ onto polyaniline, suspended in basic medium (DP method) and, (ii) immobilization of a preformed nanoscale platinum colloid on polyaniline (sol-method). The PANI-supported platinum catalysts were applied in the selective hydrogenation of the α,β-unsaturated aldehyde citral. In order to benchmark their catalytic performance, citral hydrogenation was also carried out by using platinum supported on the classical support materials silica (SiO₂), alumina (Al₂O₃), active carbon and graphite. The relations of the structural characteristics and surface state of the catalysts with respect to their hydrogenation properties have been probed by EXAFS and XPS. It is found that the DP method yields chemically prepared PtO₂ on polyaniline and, thus, produces a highly dispersed and immobilized Adams catalyst (in the β-PtO₂ form) which is able to efficiently hydrogenate the conjugated C=C bond of citral (selectivity to citronellal=87%), whereas reduction of the C=O group occurs with polyaniline-supported platinum (selectivity to geraniol/nerol=78%) prepared via the sol-method. The complete reversal of the selectivity between the preferred hydrogenation of the conjugated C=C or C=O group is not only particularly useful for the selective hydrogenation of α,β-unsaturated aldehydes but also unveils the great potential of conducting polymer-supported precious metals in the field of hitherto barely investigated chemical catalysis.

Journal or Publication Title: Advanced Synthesis & Catalysis
Volume: 350
Number: 9
Uncontrolled Keywords: Adams catalyst • citral hydrogenation • platinum catalyst • polyaniline
Divisions: 11 Department of Materials and Earth Sciences > Material Science > Erneuerbare Energien
07 Department of Chemistry
07 Department of Chemistry > Fachgebiet Technische Chemie
07 Department of Chemistry > Fachgebiet Technische Chemie > Technische Chemie II
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences
Date Deposited: 20 Mar 2009 08:48
Official URL: http://dx.doi.org/10.1002/adsc.200800035
Additional Information:

Published Online: 9. Mai 2008

Identification Number: doi:10.1002/adsc.200800035
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