RDC

Fig. 15. Mechanically agitated columns (a) Scheibel column (b) rotating-disk contactor (RDC) (c) asymmetric rotating-disk (ARD) contactor (d) Oldshue-Rushton multiple-mixer column (e) Kuhni column and (f) reciprocating-plate column.

The rotating-disk contactor (RDC), developed in the Netherlands (158) in 1951, uses the shearing action of a rapidly rotating disk to interdisperse the phases (Eig. 15b). These contactors have been used widely throughout the world, particularly in the petrochemical industry for furfural [98-01-1] and SO2 extraction, propane deasphalting, sulfolane [126-33-0] extraction for separation of aromatics, and caprolactam (qv) [105-60-2] purification. Columns up to 4.27 m in diameter are in service. An extensive study (159) has provided an excellent theoretical framework for scale-up. A design manual has also been compiled (160). Detailed descriptions and design criteria for the RDC may also be found (161). 

K. Liquid-liquid extraction in Rotating-disc contactor (RDC)... 

Refer to Fig. 15-39. The tower is formed into compartments by horizontal doughnut-shaped or annular baffles, and within each compartment agitation is provided by a rotating, centrally located, horizontal disk. Somewhat similar devices have been known for some time. The features here are that the rotating disk is smooth and flat and of a diameter less than that of the opening in the stationaiy baffles, which facihtates fabrication and apparently improves extraction rates. The typical proportions of the internals of the RDC are as follows ... 

FIG. 15-39 Rotating-disk (RDC) extractor, (Couitesy of Glitsch Frocess Systems Inc.)... 

As stated above, the design of an RDC contactor usually involves the performance of pilot tests due to the large number of factors whicF can influence performance. These pilot plant data must then be scaled-up to Rill commercial size. The following procedure is recommended. 

The Oldshue-Rushton (Mixco) extractor is similar in construction to the RDC in the fact that it is a relativelv open design, consisting of a series of compartments separated by horizontal stator baffles. The major difference from the RDC is that the height/diameter ratio of the compartments is greater, each compartment is fitted with vertical baffles, and the mixing is accomplished by means of a turbine impeller rather than a disc. 

Unhke the RDC and Oldshue-Rusnton columns where the specific throughput of the scaled-up version is the same as the pilot column, it is the characteristic of the Scheibel column that the throughput of the scaled-up column is on the order of 3-5 times greater than that acheived on the pilot column. The reason for this is that the restricted geometry of the 0.075 m diameter column limits throughput these restrictions are removed in the scaled-up columns. 

FIG. 23"37 Equipment for liquid/liquid reactions, a) Batch stirred sulfonator. (h) Raining bucket (RTL S A, London), (c) Spray tower with Loth phases dispersed. (d) Two-section packed tower with light phase dispersed, (e) Sieve tray tower with light phase dispersed, (f ) Rotating disk contactor (RDC) (Escher B V, Holland). (g) Oldshue-Rushton extractor (Mixing Equipment Co. ). 

FIG. 23-38 Efficiency and capacity range of small-diameter extractors, 50 to 150 mm diameter. Acetone extracted from water with toluene as the disperse phase, V /V = 1.5. Code AC = agitated cell PPC = pulsed packed column PST = pulsed sieve tray RDC = rotating disk contactor PC = packed column MS = mixer-settler ST = sieve tray. (Stichlmair, Chem. Ing. Tech. 52(3), 253-255 [1980]). 

Panoxyl (Stiefel) Fatroxid (Fatro) Reloxyl (Rdc) Vanoxide-HC (Dermik)... 

There has been a push for direct data collection (DDC) as an alternative to remote data capture (RDC). In this approach most of the required clinical data are acquired directly from existing patient record systems such as MRI machines, ECG, EEG, TTM, laboratories, and other measurement equipment. This approach eliminates the need for paper transcription and reentry to another system. It promises error-free and resource-efficient data capture, which allows early locking of the database and therefore potentially earlier product launch [30]. 

Instead of measuring only the time-dependent dipolar interaction via NOE, it is also possible to determine dipolar couplings directly if the solute molecule is partially aligned in so-called alignment media. The most important resulting anisotropic parameters are RDCs, but residual quadrupolar couplings (RQCs), residual chemical shift anisotropy (RCSA) and pseudo-contact shifts (PCSs) can also be used for structure determination if applicable. 

Although RDCs were reported as early as 1963 by Englert and Saupe [23], their measurement and applicability for structural investigations has been limited to very small molecules with typically less than 10 protons until a few years ago. RDCs of a solute molecule can only be obtained if it is at least partially aligned with respect to the magnetic field in a so-called alignment medium. For conven-... 

The full potenhal of RDCs, however, can be seen by the incorporation of RDC data in structure calculations. Several programs hke XPLOR-NIH, DISCOVER or GROM ACS allow the incorporation of RDCs as angular or combined angular and distance dependent restraints. Several studies on sugars have been reported (see, e.g. Ref [43] and references therein) and Fig. 9.8 shows the comparison of three structural models for the backbone of the cyclic undecapeptide cyclosporin A, derived from X-ray crystahography, ROE data in CDCI3 as the solvent, and RDCs and ROEs obtained in a PDMS/CDCfi stretched gel [22]. Due to the sensitivity to... 

Fig. 9.7 (A) Structures of the two possible diastereomers of the spiroindene 1. The RDCs determined in a PDMS/CDCf gel are color coded to the structures (red, negative RDCs blue, positive RDCs green, no RDCs or RDCs not used in analysis). The axis systems to the...

B) Correspondence of experimental versus back-calculated RDC values for stmctures la and 1b [44]. 

Fig. 9.8 Comparison of experimentally determined and back-calculated one-bond RDCs for the crystal structure (A), the ROE-derived structure (B) and the (RDC-hROE)-refined structure (C) of cyclosporin A. (D) Evaluation of the resulting models for the...

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