(655f) Enabling Hydroformylation in Micro-Emulsion Systems: Long-Term Performance of a Continuously Operated Mini-Plant

In the Collaborative Research Center SFB/TR 63 InPROMPT, novel process concepts for
substitutable base chemicals in multiphase systems are being developed. Hereby,
next generation liquid-liquid processes based on innovative solvent concepts are
currently under research. One of these concepts is concerned with the
hydroformylation of long-chained alkenes in micro emulsions. Hydroformylation has been established as a
standard process for the production of short-chained aldehydes from alkenes.
Its application to higher alkenes (longer than C₁₂) in a biphasic
system with a rhodium catalyst, on the other hand, has not yet been
established. To speed-up and aid in the process development within the collaborative
research center, a mini-plant
has been built at Berlin University
of Technology (Technische Universität
Berlin, TU Berlin).

The investigated process concept aims at reaching two
goals: on the one hand, two normally immiscible liquids are to be mixed, while
on the other hand a near to perfect separation of reactants is to be achieved. A
promising approach lies in the application of a non-ionic surfactant. By
creating a micro-emulsion, the surfactant enables the water soluble
rhodium-ligand-catalyst required for the reaction to be brought into contact
with the alkene [1]. The reaction is started by injecting syngas (H₂&CO)
into the system. After the reaction, the miscibility gap between the hydrophilic
catalyst solution and hydrophobic alkene/aldehyde mixture is exploited in order
to recycle the valuable rhodium catalyst and separate the almost pure organic
product phase. To test the viability of this concept, a long-term test-run in
the mini-plant at TU Berlin has been performed.

Figure 1: Process
concept for the hydroformylation of long-chained aldehydes in micro-emulsions [2].

The mini-plant was operated continuously for 100 hours supported by an
operating team of 14 people in four shifts. The applied substances were
1-dodecene (educt), the non-ionic surfactant Marlipal 24/70 (CAS: 68439-50-9),
a water soluble rhodium-based catalyst (CAS: 14874-82-9), and the water soluble ligand Sulfoxantphos
(sulfonated form of Xantphos, CAS: 161265-03-8). The desired product is n-tridecanal. The crucial aspects of the concept, with
regards to technical and economic feasibility, are the reaction as well as the separation
step. The operating conditions for both steps were determined in previous
analyses [2 - 4].

During mini-plant operation different reactor residence times, such as 45
and 120 minutes, were tested. In both cases the reactor was operated at 40 bar
and 95°C. Batch experiments at similar reaction conditions showed a yield of 2,54%
in 30 minutes and 4% in 60 minutes. These results equal those during the start-up
of the mini-plant. During continuous operation, an average yield of 1-dodecene
to n-tridecanal of about 20% was achieved for a reactor residence time of 45
minutes. In the latter case, where lower feed and recycle streams were applied
to increase the reactor residence time to 120 minutes, a yield of about 31% was
reached.

The second step of the process is the separation of the catalyst from
the product. Here, the phase separation behavior of H₂O-oil-nonionic
surfactant systems is exploited [5, 6]. Due to kinetic reasons, the three phase
state is desired for the continuous process [2, 3]. Here, a separation into a
catalyst-rich, a surfactant rich, and a product rich phase takes place. The
lower two phases, catalyst and surfactant, are recycled. The main challenge
during plant operation is the shift of the feasible operating points over time
due to increasing product concentration inside the system. For the decanter,
this means that the temperature needs to be regulated depending on the
concentration of product inside the system. During plant operation, a
concentration of up to 77 wt.-% of 1-dodecene in the oil and 11 wt.-% in the
water phase could successfully be realized in the correct temperature region. Compared
to test-tube results, where roughly 90 wt.-% of 1-dodecene remains in the oil
phase, this performance is highly satisfactory.

Next to these successful results regarding the reaction and separation
step, the long-term operation revealed noteworthy effects. Among these is fractioning
of the surfactant during the phase separation step. Thus, another undesired
shift of the optimal operating point in the decanter is carried out. As counter
measures, surfactant rectification as well as continuous surfactant feeding
during plant operation are taken into consideration for consecutive plant runs.

In this contribution selected results from the test run are presented,
whereby merits and opportunities for the chemical industry as well as open
challenges regarding the process concept are discussed.

Acknowledgment

This work is part of the Collaborative Research Center "Integrated
Chemical Processes in Liquid Multiphase Systems" coordinated by the
Technische Universität Berlin. Financial support by the German Research
Foundation (Deutsche Forschungsgemeinschaft, DFG) is gratefully acknowledged
(TRR 63). Furthermore, the
authors gratefully acknowledge the support of the company Umicore for
sponsoring the rhodium catalyst ?Acetylacetonatodicarbonylrhodium(I) (CAS:
14874-82-9)? used in the described experiments.

References

[1]           Kupka, J. A.
(2006) Hydroformylierung von 1-Octen in Mikroemulsion. Ph.D. Thesis, Technische Universität
Braunschweig.                

[2]           Müller, D.; Esche, E.; Müller, M.; Wozny, G. (2012) Development of a Short-Cut Model
for Three-phase Liquid Separation Dynamics for a Hydroformylation Mini-Plant,
Presentation at the AIChE 2012, Pittsburgh, USA.

[3]           Müller,
M.; Kasaka, Y.; Müller, D.; Schomäcker, R.; Wozny, G. (2013) Process Design for
the Separa-tion of Three Liquid Phases for a Continuous Hydroformylation
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[4]           Hamerla,
T.; Rost, A.; Kasaka, Y.; Schomäcker, R. (2012) Hydroformylation of 1-dodecene
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[5]           Sottmann,
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Applications, Perspectives; Wiley-Blackwell: Chichester, U.K., DOI: 10.1002/9781444305524.ch1.

[6]           Kahlweit,
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