Zusammenfassung
Introduction: Industrial scale hydroformylation of alkenes to aldehydes with syngas is carried out via homogeneous transition metal catalysis [1]. The most important industrial scale process is the Ruhrchemie/Rhône-Poulenc process which is limited to the hydroformylation of short-chain olefins. This drawback is a result of the limited solubility of the organic reactands in the polar phase containing the catalyst [2].
A process for long-chain olefins (C>4), e.g. oleochemicals from renewable sources, on an industrial scale is currently not realized. Against this background it is part of the scope of the German Science Foundation project „SFB/TR-63“ to investigate the kinetics of the hydroformylation of long-chain olefins and oleochemicals including several side reactions.
Experimental: The kinetic experiments were performed with 1-Decene as model substance in a thermomorphic multicomponent solvent system and a Rh-BIPHEPHOS complex as catalyst. The reactions were realized in a 90 ml high pressure multiple batch reactor system under careful consideration of the catalyst pretreatment at 15-18 bar syngas and a molar metal-to-ligand ratio of 1:3 to guarantee reproducible initial conditions and
a defined catalyst state.
The presented detailed catalytic cycle and the reaction network in [4] and [5] give the opportunity to decompose the complex reaction network into 3 subnetworks (isomerization, hydrogenation and hydroformylation) by applying different gas phase conditions. This decomposition allows to „switch off“ several reactions and therefore to simplify the parameter estimation procedure. The estimated parameters from each sub-network can be transported into the next subnetwork without reestimating them.
In order to reduce the experimental effort a design of experiments method based on parameter subset selection was used [4]. This approach gives the opportunity to find a set of experimental conditions by which the number of sensitive kinetic model parameters can be determined and the corresponding confidence intervals can be minimized. The necessary kinetic model in its full and unreduced form was adopted from [4] as well. Model reduction was carried out with the parameter subset selection method and the model was fitted to the experimental data with high accuracy.
Results: In total 20 parameters, including mass transfer, gas solubilitiy and finally kinetic parameters, were estimated. All parameters are within a meaningful order of magnitude and have small confidence intervals (between 1-28%).
Summing up a broad range of experimental conditions (temperature range 95-115C, syngas pressure range 1-20 bar) could be covered and validated by our investigations. A detailed kinetic model for the hydroformylation of 1-Decene including side reactions (isomerization and hydrogenation) could be parameterized successfully and will be presented in this contribution.
Literature:
[1] A. Behr et al., Advances in thermomorphic liquid/liquid recycling of homogeneous transition
metal catalysts, Journal of Molecular Catalysis A, Chemical 285, 20-28, 2008
[2] B. Cornils, and W. A. Herrmann, Concepts in homogeneous catalysis: the industrial view,
Journal of Catalysis, 216, 1-2, 23-31, 2003
[3] A.C.J. Koeken et al., Full kinetic description of 1-octene hydroformylation in a supercritical
medium, Journal of Molecular Catalysis A: Chemical 346, 1-11, 2011
[4] G. Kiedorf et al., Kinetic description of the hydroformylation of 1-dodecene in a
thermomorphic solvent system by using rhodium-biphephos-catalyst, Chemical
Engineering Science, DOI:10.1016/j.ces.2013.06.027, 2013.
[5] J. Markert et al., Analysis of the reaction network for the Rh-catalyzed hydroformylation
of 1-dodecene in a thermomorphic multicomponent solvent system, Applied Catalysis, A:
General 462, 287-295, 2013
