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.
Aalto

Rhodium and Cobalt Catalysts in the Heterogeneous Hydroformylation of Ethene, Propene and 1-Hexene

Tarja Zeelie (née Kainulainen)

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 KE2 (Komppa Auditorium) at Helsinki University of Technology (Espoo, Finland) on the 16th of November, 2007, at 12 o'clock noon.

Overview in PDF format (ISBN 978-951-22-9025-3)   [777 KB]
Dissertation is also available in print (ISBN 978-951-22-9024-6)

Abstract

Hydroformylation is an important commercial process for the conversion of alkenes, carbon monoxide and hydrogen into aldehydes to be further used in the production of various chemicals. The industrial processes operate in a homogeneous mode. Therefore, the development of a solid catalyst would solve problems related to catalyst separation. The purpose of this work was to study supported cobalt and rhodium catalysts in heterogeneous hydroformylation both in liquid and gas-phase conditions. The effect of different preparation methods, precursors, support modifications and pretreatments on the characteristics of the catalysts was investigated.

Atomic layer deposition (ALD) is a promising technique for the preparation of dispersed Co(A)/SiO2 catalysts using a Co(acac)3 precursor. Higher activity in ethene hydroformylation was obtained with Co(A)/SiO2 catalysts compared to impregnated Co(N)/SiO2 catalyst prepared from nitrate precursor. The dispersion, and consequently the activity and oxo-selectivity of the Co(A)/SiO2 catalyst, was further improved by inert handling of the catalyst. Moreover, by varying the metal content of the Co(A)/SiO2 catalysts, a clear correlation between metal dispersion and oxo-selectivity was found. The basic AlN modification of the silica support did not enhance hydroformylation activity due to low dispersion of the Co(A)/n·AlN/SiO2 catalysts.

For the carbon supported catalysts, the best hydroformylation activity was obtained with coconut-shell based Rh/C(C) catalyst. The presence of dispersed active sites and unreduced rhodium enhanced CO insertion, and also unintentional promotion by potassium was possible. Furthermore, without any pretreatment the catalyst exhibited even better propanal yields than with hydrogen pretreatment, apparently due to the better dispersed active sites. Pretreatment with carbon monoxide partially blocked the catalyst surface with carbonaceous residues, which improved CO insertion selectivity, but suppressed the overall activity.

The fibrous polymer-supported Rh-phosphine catalyst, Fibrecat™, prepared using a Rh(acac)(CO)2 precursor, was the most promising rhodium catalyst in ethene hydroformylation: high propanal selectivity (95%) and high activity were obtained under the mild reaction conditions of 100 °C and 0.5 MPa. The 31P NMR characterisations suggested the formation of both a Rh-monophosphine species, Rh(acac)(CO)(PS-PPh2), and a Rh-bisphosphine species, Rh(CO)2(PS-PPh2)2, on Fibrecat™, which were transformed in contact with CO/H2 to the active Rh-carbonyl hydrides.

In the liquid-phase hydroformylation of 1-hexene, the activity of the Rh/C catalysts appeared to correlate with the support: the larger the pores, the better the mass transfer and the higher the activity. In addition, C21 products were only formed on a support with sufficiently large pores – an indication of the heterogeneous functionality of the catalysts. With the carbonyl based cobalt catalysts, problems were encountered with the catalyst preparation and handling procedure due to the air sensitivity of the carbonyl precursors.

The Co/SiO2 catalysts were stable in gas-phase hydroformylation at 173 °C and 0.5 MPa, whereas Rh/C catalysts lost 10-30% of the metal deposited, mostly due to the formation of volatile carbonyls. However, at a lower temperature, i.e. 100 °C and 0.5 MPa, no volatile carbonyls were formed on Fibrecat™, as confirmed by quantitative 31P NMR characterisations. In liquid-phase conditions, 20-50% of the metal deposited was dissolved from the cobalt and rhodium catalysts. Therefore, the stability of the catalysts in hydroformylation was related to the ability of the catalytic metal to form volatile or soluble carbonyls and thus, to the reaction conditions used.

This thesis consists of an overview and of the following 5 publications:

  1. Kainulainen, T. A., Niemelä, M. K., and Krause, A. O. I., Ethene hydroformylation on Co/SiO2 catalysts, Catalysis Letters 53 (1998) 97-101.
  2. Puurunen, R. L., Zeelie, T. A., and Krause, A. O. I., Cobalt(III) acetylacetonate chemisorbed on aluminum-nitride-modified silica: characteristics and hydroformylation activity, Catalysis Letters 83 (2002) 27-32.
  3. Kainulainen, T. A., Niemelä, M. K., and Krause, A. O. I., Rh/C catalysts in ethene hydroformylation: the effect of different supports and pretreatments, Journal of Molecular Catalysis A: Chemical 140 (1999) 173-184. © 1999 Elsevier Science. By permission.
  4. Zeelie, T. A., Root, A., and Krause, A. O. I., Rh/fibre catalyst for ethene hydroformylation: Catalytic activity and characterisation, Applied Catalysis A: General 285 (2005) 96-109. © 2005 Elsevier Science. By permission.
  5. Kainulainen, T. A., Niemelä, M. K., and Krause, A. O. I., Hydroformylation of 1-hexene on Rh/C and Co/SiO2 catalysts, Journal of Molecular Catalysis A: Chemical 122 (1997) 39-49. © 1997 Elsevier Science. By permission.

Keywords: fibre support, active carbon support, atomic layer deposition, stability of the catalysts

This publication is copyrighted. You may download, display and print it for Your own personal use. Commercial use is prohibited.

© 2007 Helsinki University of Technology

Last update 2011-05-26