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Selective hydrogenation of 1,5,9-cyclo-dodecatriene towards cyclo-dodecene

Gaube, Johann and David, Walter and Sanchayan, Ragunathan and Roy, Sudip and Müller-Plathe, Florian (2008):
Selective hydrogenation of 1,5,9-cyclo-dodecatriene towards cyclo-dodecene.
In: Applied Catalysis A: General, pp. 87-94, 343, (1-2), ISSN 0926860X, [Online-Edition: http://dx.doi.org/10.1016/j.apcata.2008.03.025],
[Article]

Abstract

The liquid phase hydrogenation of 1,5,9-c,t,t-cyclo-dodecatriene (CDT) and of cyclododecadienes (CDD) towards cyclo-dodecene (CDE) using a Pd/Al₂O₃ catalyst of egg-shell type has been studied in discontinuous operation at different hydrogen pressures and for stepwise reduced hydrogen pressure. The yield of CDE is considerably increased if the hydrogen concentration and consequently the rate of hydrogenation are markedly reduced. By this means a CDE yield of 93% at a (CDT + CDD) conversion of 98% could be reached. Because of the low hydrogenation rate the conversion is not influenced by mass transfer effects.

For discussion the partial hydrogenation of CDT is compared with the hydrogenation of cyclo-octadiene for which a cyclo-octene yield of >99% is attainable at a much higher reaction rate. In order to understand the partial hydrogenations of cyclo-octadiene and of CDD ab initio Hartree–Fock calculations have been carried out to study the structure of these molecules. On this basis a hypothesis for the lower selectivity of CDT-hydrogenation towards CDE compared to that of cyclo-octadiene towards cyclo-octene is presented. The increase of CDE selectivity with decreasing hydrogen pressure is traced back to the increased rate of the isomerization of t,t- and c,t-CDDs towards the more strongly adsorbed c,c-CDDs.

The results of the presented study clearly show that the realization of an industrial process of the selective hydrogenation of CDT towards CDE using a simple catalytic reactor is possible. Concepts are proposed for discontinuous and for continuous procedure.

Item Type: Article
Erschienen: 2008
Creators: Gaube, Johann and David, Walter and Sanchayan, Ragunathan and Roy, Sudip and Müller-Plathe, Florian
Title: Selective hydrogenation of 1,5,9-cyclo-dodecatriene towards cyclo-dodecene
Language: English
Abstract:

The liquid phase hydrogenation of 1,5,9-c,t,t-cyclo-dodecatriene (CDT) and of cyclododecadienes (CDD) towards cyclo-dodecene (CDE) using a Pd/Al₂O₃ catalyst of egg-shell type has been studied in discontinuous operation at different hydrogen pressures and for stepwise reduced hydrogen pressure. The yield of CDE is considerably increased if the hydrogen concentration and consequently the rate of hydrogenation are markedly reduced. By this means a CDE yield of 93% at a (CDT + CDD) conversion of 98% could be reached. Because of the low hydrogenation rate the conversion is not influenced by mass transfer effects.

For discussion the partial hydrogenation of CDT is compared with the hydrogenation of cyclo-octadiene for which a cyclo-octene yield of >99% is attainable at a much higher reaction rate. In order to understand the partial hydrogenations of cyclo-octadiene and of CDD ab initio Hartree–Fock calculations have been carried out to study the structure of these molecules. On this basis a hypothesis for the lower selectivity of CDT-hydrogenation towards CDE compared to that of cyclo-octadiene towards cyclo-octene is presented. The increase of CDE selectivity with decreasing hydrogen pressure is traced back to the increased rate of the isomerization of t,t- and c,t-CDDs towards the more strongly adsorbed c,c-CDDs.

The results of the presented study clearly show that the realization of an industrial process of the selective hydrogenation of CDT towards CDE using a simple catalytic reactor is possible. Concepts are proposed for discontinuous and for continuous procedure.

Journal or Publication Title: Applied Catalysis A: General
Volume: 343
Number: 1-2
Divisions: 07 Department of Chemistry > Physical Chemistry
07 Department of Chemistry > Fachgebiet Technische Chemie
07 Department of Chemistry
Date Deposited: 10 Jan 2011 12:39
Official URL: http://dx.doi.org/10.1016/j.apcata.2008.03.025
Identification Number: doi:10.1016/j.apcata.2008.03.025
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