A Compact Integrated Mixer/Separator for Enantioselective Solvent Extraction
Special Symposium - EPIC-1: European Process Intensification Conference - 1
EPIC-1: Multifunctionality (MF-2)
Keywords: chiral liquid-liquid extraction, interfacial area, CINC, process intensification
The demand for enantiopure compounds is growing rapidly. Especially in fragrances, pharmaceutical and food industry there is a clear tendency towards enantiopure compounds as the enantiomers show different bioactivity in the human body. The most commonly applied technique for obtaining enantiopure compounds on commercial scale is classical resolution by crystallization [1]. This technique is however, not always successful and interest for other methods such as chiral synthesis or racemic synthesis followed by enantioseparation by for example chromatography is growing. Recently, the technology of reactive liquid-liquid extraction (RLLE) using a chiral extractant has gained attention as a potential candidate for commercial scale chiral separation [2].
The focus of this study is the use of a compact integrated mixer/separator (CINC) for enantioselective extractions. The CINC is an example of a highly process intensified device, as it combines the unit operations mixing and separation in one compact unit. The CINC consists of a rotating hollow centrifuge in a static house. Both liquids enter the reactor at opposite sides and become intensely mixed in the annular zone in between the rotating centrifuge and the static reactor wall. Subsequently, both well mixed liquids are separated in the hollow centrifuge Although the geometrical volume of the device applied in this study is only 270 mL, it can handle throughputs of up to 2 L per minute. Furthermore, the CINC is not only compact, but also very flexible in use, allowing rapid switching between processes. In addition, the small size minimizes start-up losses. These properties make the CINC ideal for separation of a wide variety of racemates using RLLE with enantioselective extractants.
For optimization and modelling activities, various hydrodynamic parameters need to be known. Examples are the residence times of both phases in the various zone’s of the CINC, the hold-ups of the liquids and the liquid-liquid interfacial area. We here report an experimental study to determine the interfacial area in the CINC as a function of process parameters. For this purpose, a biphasic model reaction (saponification of n-butylformate with NaOH) with known kinetics was applied [Van Woezik and Westerterp] [3]. The organic (transport) phase entering the reactor consisted of pure butyl formate to exclude transport limitations in this phase, whereas the aqueous (reactive) phase feed contained 8 N NaOH in water. By applying the theory of mass transfer with reaction in parallel, the interfacial area was determined as a function of the throughput of the liquid phases and the rotor speed. The interfacial area was found to increase with increasing throughput at constant rate of rotation.Typical interfacial area’s are 5.10-2 - 2 m2. The effect of the rate of rotation on the interfacial area showed a maximum (2 m2 ÷ 1.0.104 m2/m3 reactor volume) at 40 Hz (flowrates of 30 mL/min for both liquid phases). At 30 Hz, the interfacial area dropped to about 0.1 m2 and at 60 Hz the interfacial area dropped to about 0.3 m2.
In conclusion, the interfacial area in the CINC reactor for a typical organic solvent-water combination has been determined as a function of process conditions. This information will be applied for further process optimization and modelling studies.
[1] T. Vries et al; The Family Approach to the Resolution of Racemates, Angewandte Chemie Int. Ed. 1998,37,2349-2354
[2] Steensma, M.; Chiral separation of amino-alcohols and amines by fractional reactive extraction, 2005, Thesis, University of Twente, ISBN 90-901-9313-8
[3] Van Woezik, B.A.A.; Westerterp, K.R.; Measurement of interfacial areas with the chemical method for a system with alternating dispersed phases, Chem. Eng. Proc. 2000, 39, 299-314
Presented Thursday 20, 11:20 to 11:40, in session EPIC-1: Multifunctionality (MF-2).
