Distillation partition column

The partition column has one further advantage over the conventional arrangements in Figure 11.1. In partitioned columns, the material is only reboiled once and its residence time in the high-temperature zones is minimized. This can be important if distilling heat-sensitive materials. 

Standard distillation equipment can be used for the fabrication. Either packing or plates can be used, although packing is more commonly used in practice. Also, the control of partitioned columns is straightforward13 14. 

Kaihel, G., Distillation Columns with Vertical Partitions, Chem. Eng. TechnoL, 10 92, 1987. 

When the mass transfer rates of the two components are equal and opposite the process is said to be one of equimolecular counterdiffusion. Such a process occurs in the case of the box with a movable partition, referred to in Section 10.1. It occurs also in a distillation column when the molar latent heats of the two components are the same. At any point in the column a falling stream of liquid is brought into contact with a rising stream of vapour with which it is not in equilibrium. The less volatile component is transferred from... 

Gel Filtration. The lyophilized protein was redissolved in 50 mM phosphate buffer, pH 7.4 0.15 m NaCl 0.013 % sodium azide and loaded on a Superdex 75HR1030 column equilibrated with the same buffer. Elution was downward flow (0.15 ml/min) and 0.25 ml fi actions were collected. Fractions with pectin lyase activity were combined, dialyzed against distilled water and used in the next step. To estimate the molecular mass of PNL, the column was calibrated with standard proteins (Sigma MW-GF-70 Albumin, 66,000 Da Carbonic Anhidrase, 29,00 Cytochrome, 12,400 and Aprotinin, 6,500). The proteins were eluted in the conditions described above and their volumes (F ) were calculated fi om the peak maximum of the absorbance at 280 nm. The partition coefficient was obtained fi om the relationship where F, represents the bed volmne of column and F the void volume (which was calculated using blue dextran. Sigma). The molecular mass was determined using a standard curve of vs the logarithm of the molecular masses of the standards [28, 29]... 

Propachlor is extracted from plant and animal material with aqueous acetonitrile. After filtration and evaporation of the solvent, the extracted residue is hydrolyzed with base, and the hydrolysis product, NIPA, is steam distilled into dilute acid. The acid distillate is partitioned with dichloromethane. The aqueous layer is adjusted to a basic pH, and NIPA is extracted with isooctane. The extracted residues are cleaned up using a silica SPE column, and NIPA is eluted with isooctane-ethyl acetate (9 1, v/v) solvent mixture. Quantitation is by GC/NPD. 

Kaibel G (1987) Distillation Columns With Vertical Partitions, Chem Eng Technol, 10 92. 

Becker H, Godorr S, Kreis and Vaughan J (2001) Partitioned Distillation Columns - Why, When and How, Chem Eng, Jan 68. 

The ether solution and fractions taken during the subsequent distillation may be assayed by gas-liquid partition chromatography on a 0.8-cm. x 200-cm. column heated at 120° and packed with nonyl phthalate supported on ground firebrick. 

The term plate height comes from distillation theory. Some high-performance distillation columns contain discrete units called plates, in which liquid and vapor equilibrate with each other. As a teenager, A. J. R Martin, coinventor of partition chromatography, built distillation columns in discrete sections from coffee cans. (We don t know what he was distilling ) When he formulated the theory of partition chromatography, he adopted terms from distillation theory. 

The concept of plate theory was originally proposed for the performance of distillation columns (12). However, Martin and Synge (13) first applied the plate theory to partition chromatography. The theory assumes that the column is divided into a number of zones called theoretical plates. One determines the zone thickness or height equivalent to a theoretical plate (HETP) by assuming that there is perfect equilibrium between the gas and liquid phases within each plate. The resulting behavior of the plate column is calculated on the assumption that the distribution coefficient remains unaffected by the presence of other... 

Partitioning is much faster in gas phasq systems than liquid-liquid or liquid-solid systems. This results from the high surface area relative to the liquid volume which provides shorter equilibrations than one could achieve in, say, preparative distillation. Distillations also are limited in terms of high-quality separations of two-component systems and the large sample volume required for efficient columns. 

Kaibel G. Distillation columns with vertical partitions. Chem Eng Technol 1987 10 92. 

Martin and Synge (3) introduced the important concept of theoretical plates into chromatography. Their concept was derived from partition theory and random statistics, and was related to similar ideas developed for extraction and fractional distillation. They supposed that the column could be divided into a number of sections called theoretical plates, and that solutes (dissolved compounds) could be expected to achieve equilibrium between the two phases (mobile and stationary) that exist within each plate. The chromatographic process, like an extraction process, can be visualized to occur when mobile phase (solvent) is transferred to the next plate, where a new equilibrium is established. Theoretical plate numbers of 1000 or more are common for HPLC columns, which means that 1000 separate equilibria must be established to obtain the same degree of separation by solvent... 

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