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978-3-8439-3599-9, Reihe Verfahrenstechnik
Intensifying the mixing technique – Acceleration of lean aqueous hydroformylation
211 Seiten, Dissertation Technische Universität Dortmund (2018), Softcover, A5
Hydroformylation is an industrially important homogenously catalysed reaction applying rhodium complexes to form aldehydes from syngas and olefins. The high price of rhodium makes an efficient catalyst recycle necessary for industrial scale operation. This is e.g. possible through immobilisation of the rhodium in an immiscible aqueous phase using water soluble sulfonated ligands. The catalyst is separated from the organic products via decantation.
This approach is only possible for short chain olefins due to the decreasing solubility in water with growing carbon chain length. For alkenes larger C4, the reaction rate becomes to slow for industrial purposes. To overcome this limitation chemical additives are used entailing severe drawbacks like increased catalyst leaching or aggravated down-streaming. In the present study a process for the biphasic aqueous hydroformylation of long chain olefins was developed allowing their hydroformylation at industrially interesting rates without additives.
The process is based on intensification of the mixing technique bringing the fluid phases into intense contact. A first investigation showed that fast rates are possible applying only neat substrate as organic phase and sodium triphenylphosphine trisulfonate as ligand. Further rate acceleration was possible intensifying the specific energy input, extending the interfacial area. A kinetic measurement was executed identifying all significant parameters that determine the rate of reaction. The interfacial area was integrated in the rate expression as a procedural factor. A mass transfer analysis was conducted to estimate where the reaction takes place. Because no mass transfer limitation was observable the linear dependence on the interfacial area can only be explained with the surface itself being the place of reaction. Finally this surface reactivity was exploited applying the reaction to a jet loop reactor that creates large interfacial areas. Productivity and catalytic activity was again increased and the reaction operated in long-time experiments proved a high stability of the catalytic system.