(143b) Hydroformylation of 1-Dodecene in Microemulsions: Proof of Concept and Long-Term Operability on a Mini-Plant Scale

Within the chemical industry hydroformylation is one of the main reaction steps forming aldehydes. For state of the art industrial processes, it is typically realized as a homogeneously catalyzed process. This offers major advantages regarding product selectivity and mild reaction conditions [1]. Moreover, water soluble, ligand-modified transition metal catalysts offer efficient catalyst recycling by simple means of phase separation. However, with an increasing miscibility gap between reacting olefins and catalyst solution, these processes are limited to short-chained olefins. If long-chained olefins are to be converted, severe conditions regarding pressure (300 bar) and temperature (200 °C) are still necessary for industrial applications [1]. One approach to overcome this issue is the application of microemulsion systems, which is currently being investigated within the Collaborative Research Centre InPROMPT / TRR 63 [2]. Here, microemulsions offer a promising and efficient possibility to enable a homogeneous catalytic reaction at mild conditions as the interfacial area between olefin and catalyst solution is increased. Simultaneously, the thermomorphic behavior of microemulsions with several miscibility gaps and phase separation states can be exploited. Thus, efficient catalyst recycling and product separation becomes feasible [3].

To analyze the applicability of this novel concept, a mini-plant has been built at the Chair of Process Dynamics and Operations of the Technische Universität Berlin [4]. This offers the possibility to verify obtained results from preliminary lab-scale experiments, regarding reaction performance and phase separation behaviour. Also, the identification of effects appearing during long-term continuous operation is possible, which then can be further investigated on lab-scale. Consequently, arising challenges can be tackled at an early stage, reducing the overall time needed for process development.

Therefore, this contribution firstly discusses the installed fully automated mini-plant, which is modularized into a feed, mixer-settler, and recycle section. It can be operated at temperatures of up to 478 K, pressures of up to 100 bar and process streams of a maximum at 1.1 kg/h. Regarding catalyst and reactants cost, the total process volume is kept small at 1.5 l. Given that synthesis gas is a main reactant, the plant and installed equipment are ATEX Zone II-conform and a safety concept, based on a detailed HAZOP analysis has been applied. Using Siemens PCS 7 the plant is fully automated with more than 50 sensors and actuators. Additionally, concentration measurements are carried out with an online micro GC to analyze gas composition, as well as an online Raman spectrometer and an offline GC for liquid composition sampling. The component system consists of 1-dodecene (CAS: 112-41-4) as a model olefin, the non-ionic surfactant Marlipal 24/70 (CAS: 68439-50-9), a rhodium catalyst precursor (CAS: 14874-82-9), and the water soluble ligand SulfoXantPhos (CAS: 161265-03-8). With this set-up, mini-plant operations can be carried out continuously in a three-shift system.

Subsequently, gathered operation data from several long-term mini-plant campaign of around 200 h operation time is presented. Here, two major aspects are discussed. The reaction performance at mild conditions of 95 °C and 15 bar and the phase separation performances with the corresponding catalyst recycling efficiency. Regarding the first, a high reaction yield of 40 % and an overall selectivity of 95 % was achieved. The latter one is highlighted by a total oil phase purity of more than 96 % (total amount of oily components in the oil phase), whereas 99.9 % of the rhodium catalyst was recovered and recycled. Thus, a proof of concept for the hydroformylation of long-chained olefins at mild process conditions is presented for a long-term mini-plant operation. In order to evaluate the reproducibility of the reaction and separation performance in the technical system, these results are then compared to preliminary lab-scale findings.

Additionally, several effects are addressed, which arose from the aforementioned long-term plant operation, such as surfactant loss via the product flow, component fractionation, and accumulation in the settler unit. These effects are not present at the lab-scale, but have a major impact on the operability of the system. Especially an increased byproduct formation of undesired hydrogenates was observed with fractions of up to 30 % of the total conversion. To overcome this obstacle and to enable a successful long-term process operation, several counter measures have been tested and successfully implemented in the mini-plant. Resulting in new mini-plant runs with exceptionally high selectivity and further improved phase separation, as stated above. To outline the applied strategies, the manipulation of recycle streams inside the plant and the variation of residence times in reactor and settler unit are discussed.

Concluding, this contribution constitutes the applicability of microemulsion systems for the hydroformylation of long chained olefins. Based on long-term mini-plant campaigns, a proof of concept for such an application is shown. Here, the benefits of homogenous catalytic systems are exploited at considerably low reaction conditions, whereas also an efficient catalyst recycling was possible. Therefore, opportunities for larger scale processes, but also remaining challenges concerning this novel process concept are pointed out.

Acknowledgements

This work is part of the Collaborative Research Center "Integrated Chemical Processes in Liquid Multiphase Systems" (subproject B4) coordinated by the Technical University of Berlin. Financial support by the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG) is gratefully acknowledged (TRR 63). Furthermore, the authors gratefully acknowledge the support of Umicore N.V. for sponsoring the rhodium catalyst precursor â??Acetylacetonatodicarbonylrhodium(I) (CAS: 14874-82-9)â?, Sasol Ltd. for the surfactant used in the described experiments, the support of SIEMENS AG for sponsoring the entire process control system SIMATIC PCS7 for the automation of the mini-plant, and Rhodius GmbH for sponsoring the knitted fabrics. Finally, the support of the Federal Institute for Materials Research and Testing (BAM) is gratefully acknowledged.

References

[1] R. Franke, D. Selent, A. Börner, Applied Hydroformylation, Chem. Rev, 2012, 112 (11), 5675-5732.

[2] M.-J. Schwuger, K. Stickdorn, R. Schomäcker, Microemulsions in Technical Processes, Chem. Rev , 1995, 95 (4), pp 849â??864.

[3] T. Hamerla, A. Rost, Y. Kasaka, R. Schomäcker, Hydroformylation of 1-Dodecene with Water-Soluble Rhodium Catalysts with Bidentate Ligands in Multiphase Systems, ChemCatChem, 2013, vol. 5 (7), 1854-1862.

[4] M. Müller, Y. Kasaka, D. Müller, R. Schomäcker, G. Wozny, Process Design for the Separation of Three Liquid Phases for a Continuous Hydroformylation Process in a Miniplant Scale. Ind. Eng. Chem. Res., 2013, 52, 7259 â?? 7264.