(762e) Development of a Continuous Process for the Rhodium-Catalyzed Hydroformylation of Long Chain Olefins in Aqueous Liquid-Liquid Two-Phase Systems

In this contribution a
novel low pressure process design for the Rhodium-catalyzed hydroformylation of
long chain olefins in an aqueous multiphase system will be presented. The
concept of two-phase catalysis is already a well established process for the
Rhodium-catalyzed hydroformylation of short chain olefins, which allows easy
separation and recycling of the expensive catalyst after the reaction. The
hydrophilic metal-ligand complex is immobilized in
the water phase and is insoluble in the organic phase (olefin and aldehyde). Generally the solubility of long-chain olefins is
too low in the aqueous phase to react with the catalyst. In order to improve
the solubilization, surfactant is added to formulate
a multiphase system. The multiphase system acts as a tunable solvent, through which
the interfacial area is increased during the reaction. The phase separation behaviour can be manipulated through temperature changes,
thus allowing for an easy separation of the metal-ligand
complex from the organic phase after the reaction. Based on that combination of
reaction and phase separation for catalyst recycling a novel process concept
for the hydroformylation of long chain olefins is developed, and the main
challenges for a transfer to a continuous process are shown on the example of a
mini-plant.

The reaction
conditions for the hydroformylation of 1-dodecene (model substrate of a
long-chain olefin) with a Rhodium-ligand-catalyst
system are at temperatures of 80 to 110 °C and at pressures of 20 to 40 bar. The conditions are comparable to the hydroformylation
of propene in the Ruhrchemie-Rhône-Poulence-process, but much lower in comparison to the established
industrial cobalt catalyzed process for the hydroformylation of long chain
olefins. In the hydroformylation reaction the bidentate
ligand SulphoXantPhos is used
to improve the selectivity to linear aldehydes. The
linear aldehyde is the favored product because of its
biodegradability and its further use as plasticizer or for the production of
surfactants. Different aqueous multiphase systems, formulated by ternary
mixtures of 1-dodecene, water and technical grade non-ionic surfactants like nonylphenol ethoxylates or alkyl ethoxylates, are investigated as tunable solvents. Also the
influence of different process parameters such as the type and the amount of
surfactant, metal/ligand ratio, temperature, pressure and water-to-oil ratio is discussed. The partition
coefficients of the different compounds in the single phases of the multiphase
systems are evaluated to describe the system adequately. Also the active
catalyst species was identified. Under optimized reaction conditions turn over
frequencies (TOF) of >300h^-1 and selectivities
of 98:2 to the linear product can be achieved. During the recycling experiments
the loss of rhodium catalyst through the organic phase can be held under
1ppm. 

In order to reduce
development time and to gain experimental data and experience on the
feasibility of the novel continuous process, a fully automated mini-plant, operated
with the process control system Simatic PCS7^© from Siemens, was built at Berlin
Institute of Technology (Technische Universität Berlin) in parallel to the lab scale
experiments. The mini-plant includes a reaction section and a catalyst
separation section, where a separation of both liquid phases takes place in a temperate
decanter. The aqueous phase is recycled to the reaction section to win back the
expensive Rhodium catalyst and therefore to establish a cost efficient process.
Furthermore the mini-plant allows the investigation of the influence of
recycled streams on the performance of the catalyst and on process stability in
general.

This work is
part of the Collaborative Research Centre "Integrated Chemical Processes
in Liquid Multiphase Systems" coordinated by the Technische
Universität Berlin. Financial support by the Deutsche
Forschungsgemeinschaft (DFG) is gratefully
acknowledged (TRR 63).