The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
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Preparation and Characterisation of Supported Palladium, Platinum and Ruthenium Catalysts for Cinnamaldehyde Hydrogenation

Mohamed Lashdaf

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Chemical Technology for public examination and debate in Auditorium KE 2 (Komppa Auditorium) at Helsinki University of Technology (Espoo, Finland) on the 15th of October, 2004, at 12 o'clock noon.

Overview in PDF format (ISBN 951-22-7257-1)   [622 KB]
Dissertation is also available in print (ISBN 951-22-7253-9)

Abstract

Hydrocinnamaldehyde and cinnamyl alcohol are produced in cinnamaldehyde hydrogenation. Both are of great practical importance with wide application in the fine chemicals, pharmaceuticals and perfume industries. In addition, cinnamyl alcohol is an important building block in organic synthesis. In view of the importance of these products, work was undertaken to prepare selective hydrogenation catalysts.

Palladium, platinum and ruthenium catalysts supported on alumina and silica were prepared by gas phase deposition in an atomic layer epitaxy (ALE) reactor and by impregnation techniques. For study of the effect of the acidity of the support, Ru/β zeolite and Pt/β zeolite catalysts were prepared solely by impregnation. The materials were characterised by a variety of techniques. The catalytic properties of the catalysts were studied in cinnamaldehyde hydrogenation.

Particle sizes were smaller for the ALE-deposited palladium than the corresponding impregnated samples. For the platinum and ruthenium samples, they were essentially the same for the two methods of preparation. Metal particles were small if a ligand exchange reaction occurred between metal precursor and support. In the ALE deposition, ligand exchange reaction and metal formation occurred for Pd(thd)2 and (CH3)3(CH3C5H4)Pt both on alumina and on silica. Ligand exchange and metal formation also took place for impregnated Pt catalysts with (CH3)3(CH3C5H4)Pt on both supports. In impregnation the interaction of Pd(thd)2 and Ru(thd)3 with the supports was associative adsorption.

Palladium catalysts were more active than ruthenium and platinum catalysts, and the palladium catalysts prepared by ALE showed the highest initial activity in cinnamaldehyde hydrogenation because of the small particle size of metals obtained by ALE. Ruthenium on β zeolites were more active than platinum on β zeolites. The acidity of β zeolites affected the reduction behaviour of ruthenium and the particle size, which subsequently influenced the activity. As acidity increased, particle size decreased and the activity increased.

The adsorption of cinnamaldehyde was preferably via the C=C bond on palladium catalysts, via the C=C and C=O bonds on ruthenium and via the C=O bond on platinum catalysts. Hydrocinnamaldehyde was the main product with all Pd catalysts. Ruthenium catalysts differ in selectivity. Only hydrocinnamaldehyde and 3-phenyl-1-propanol were produced with Ru/SiO2 prepared by ALE. Ruthenium on β zeolites were selective to hydrocinnamaldehyde. The other ruthenium catalysts formed a variety of hydrogenated products.

The best choice of catalysts for cinnamyl alcohol formation is the impregnated 1.2 wt-% Pt/SiO2 catalyst with particle size of 4 nm. With use of this catalyst the selectivity toward cinnamyl alcohol was as much as 90 % at conversion of 15 %. For the formation of hydrocinnamaldehyde, 4.9 wt-% Pd/SiO2 is the best catalyst that was selective only to hydrocinnamaldehyde at conversion below 10 %.

This thesis consists of an overview and of the following 6 publications:

  1. Lashdaf M., Hatanpää T. and Tiitta M., 2001. Volatile β-diketonato complexes of ruthenium, palladium and platinum: preparation and thermal characterization. Journal of Thermal Analysis and Calorimetry 64, number 3, pages 1171-1182.
  2. Lashdaf M., Hatanpää T., Krause A. O. I., Lahtinen J., Lindblad M. and Tiitta M., 2003. Deposition of palladium and ruthenium β-diketonates on alumina and silica supports in gas and liquid phase. Applied Catalysis A: General 241, numbers 1-2, pages 51-63.
  3. Lashdaf M., Krause A. O. I., Lindblad M., Tiitta M. and Venäläinen T., 2003. Behaviour of palladium and ruthenium catalysts on alumina and silica prepared by gas and liquid phase deposition in cinnamaldehyde hydrogenation. Applied Catalysis A: General 241, numbers 1-2, pages 65-75.
  4. Lashdaf M., Tiitta M., Venäläinen T., Österholm H. and Krause A. O. I., 2004. Ruthenium on beta zeolite in cinnamaldehyde hydrogenation. Catalysis Letters 94, numbers 1-2, pages 7-14.
  5. Lashdaf M., Nieminen V., Tiitta M., Venäläinen T., Österholm H. and Krause A. O. I., 2004. Role of acidity in hydrogenation of cinnamaldehyde on platinum beta zeolite. Microporous and Mesoporous Materials, in press.
  6. Lashdaf M., Lahtinen J., Lindblad M., Venäläinen T. and Krause A. O. I., 2004. Platinum catalysts on alumina and silica prepared by gas- and liquid- phase deposition in cinnamaldehyde hydrogenation. Applied Catalysis A: General, in press.

Keywords: cinnamyl alcohol, hydrogenation catalysts, gas phase deposition, impregnation, beta zeolite, ligand exchange

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© 2004 Helsinki University of Technology

Last update 2011-05-26