267351 Development of a Short-Cut Model for Three-Phase Liquid Separation Dynamics for a Hydroformylation Mini-Plant
Development of a Short-Cut Model for Three-phase Liquid Separation Dynamics for a Hydroformylation Mini-Plant
David Müller*, Erik Esche**, Michael Müller***, Günter Wozny****
Chair of Process Dynamics and Operation, Berlin Institute of Technology, Sekr. KWT-9, Str. des 17. Juni 135, D-10623 Berlin, Germany
Corresponding author: *firstname.lastname@example.org,
Within the framework of the Collaborative Research Centre SFB/TR 63 InPROMPT, “Integrated chemical processes in liquid multiphase systems”, a novel process concept for the hydroformylation of long chain alkenes in micro emulsions is investigated and developed at Berlin Institute of Technology (Technische Universität Berlin), Germany. In industry, hydroformylation is an important application in the field of homogenous catalysis and has been established as a standard process for the production of short-chained aldehydes from alkenes. The application for higher alkenes (longer than C12) on the other hand, has not yet been established.
The investigated novel process concept sees opportunities for the continuous hydroformylation of long-chained alkenes in the creation of a micro emulsion system. Through the application of a surfactant this micro emulsion system can be formed and the hydrophilic rhodium-ligand-complex catalyst required for the reaction can be brought into contact with the alkene. The reaction itself is initiated by injecting syngas (H2&CO) into the micro emulsion system formed in a continuously stirred tank reactor. After the reaction, due to the phase separation into an aqueous (catalyst-rich), an emulsion (mixed), and an organic (product-rich) phase, the valuable rhodium catalyst is separated and recycled. To investigate and optimize the described process concept, a mini-plant is built at Berlin Institute of Technology.
Figure 1: Novel process concept for the hydroformylation of long-chained alkdehydes.
The crucial aspects of the concept with regards to technical and economic feasibility are the separation steps to recycle the rare and expensive catalyst. Since there is barely any thermodynamic data on the system available, the temperature and concentration sensitity proves to be a challenging issue. The goal of this contribution is to develop a model of the three-phase liquid separation dynamics for the temperature control of the decanter. Thus, the quality of the phase separation can be adjusted accordingly.
The solution approach is divided into several steps. Firstly, experiments in graduated test tubes for various concentrations and temperatures are performed and the height of each of the phases is measured over time. The idea is that the optimal separation time at a certain temperature indirectly represents the necessary length in a horizontal flow decanter, which can be adjusted by manipulating the superficial velocity of the inlet stream. In the second step, the previously obtained results are used to derive a polynomial function to estimate the heights of each of the three phases hj: hj = f(t, T, ci). These are dependent on time t, the temperature level T, and the concentrations of alkenes, aldehydes, surfactant, and catalyst. Furthermore, the switch from 3-phase to 2-phase systems is included through the intersection of two polynomials describing the phase interfaces. Thirdly, an experimental set-up with a glass replication of the actual decanter in the mini-plant is used to test the validity of the determined results from the test tubes for the decanter.
As a next step, adjustments to the derived equations are made to incorporate the pressure dependency of the system. Afterwards, the results are implemented in the mini-plant allowing for an effective temperature control. Hence, through the determined model the optimal operation conditions can be maintained in the mini-plant and a step towards economic feasibility is taken.
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 German Research Foundation (Deutsche Forschungsgemeinschaft, DFG) is gratefully acknowledged (TRR 63).