Kinetic Modeling of The Heterogeneously Catalyzed Liquid-Phase
Hydrogenation of Phenylpropanal and Cinnamyl Alcohol over
Ir/Al2O3 Catalysts
Ayman Hammoudeh and Sabri Mahmoud
Chemistry Department, Yarmouk Unversity, P.O.Box 566, Irbid, Jordan
In spite of the elegancy and environmental superiority of cinnamyl alcohol
production through the selective heterogeneously catalyzed hydrogenation of
cinnamaldehyde, the conventional production methods via the Meerwein-PonndorfVerley reduction or by the reduction with alkali borohydrides of cinnamaldehyde
couldn’t be displaced. This is because 100% selectivities toward cinnamyl alcohol
formation couldn’t, for thermodynamic and kinetic obstacles, be achieved. Since both
phenylpropanal (II) and cinnamyl alcohol (III) are intermediates in the above selective
hydrogenation, the kinetic study of their further hydrogenation is, with this respect,
highly appreciated. In this work, a systematic study of the hydrogenation reaction of
phenylpropanol (II) and cinnamyl alcohol (III) under mild conditions over aluminasupported Ir catalysts is presented. The experimental results were analyzed and where
found to conform in both cases with a Langmuir-Hinshelwood surface reaction as the
rate determining step. The kinetic models describe successfully the negative effects of
the initial concentration and temperature in the case of phenylpropanal hydrogenation
and the positive ones in the cinnamyl alcohol hydrogenation. The kinetic models in both
cases indicate a relatively weak interaction of hydrogen with the Ir surface.
k1
Ph-CH=CH-CHO
(I)
k2
Ph-CH2-CH2-CHO
(II)
k3
Ph-CH2CH2CH2OH
(IV)
Ph-CH=CH-CH2OH
(III)
k4
References:
1.
2.
3.
A. Hammoudeh and S. Mahmoud, " A kinetic study of the liquid-phase hydrogenation of
phenylpropanal over alumina-supported Ir catalysts", Reaction Kinetics & Catalysis Letters 91
(2007) 131-139.
A. Hammoudeh and S. Mahmoud, "Kinetic Modeling of the liquid-phase hydrogenation of cinnamyl
alcohol over alumina-supported Ir catalysts", in preparation.
P. Gallezot, D. Richard: Catal. Rev.-Sci. Eng., 40, 81 (1998), and references therein.