Drying column

The ammonolysis of phenol (61—65) is a commercial process in Japan. Aristech Chemical Corporation (formerly USS Chemical Division of USX Corporation) currently operates a plant at Ha verb ill, Ohio to convert phenol to aniline. The plant s design is based on Halcon s process (66). In this process, phenol is vapori2ed, mixed with fresh and recycled ammonia, and fed to a reactor that contains a proprietary Lewis acid catalyst. The gas leaving the reactor is fed to a distillation column to recover ammonia overhead for recycle. Aniline, water, phenol, and a small quantity of by-product dipbenylamines are recovered from the bottom of the column and sent to the drying column, where water is removed. 

LIGHT ENDS COLUMN DRYING COLUMN PRODUCT COLUMN FINISHING COLUMN... 

Figure 8-4. A flow diagram for the hydration of propylene to isopropanol (1) propylene recovery column, (2) reactor, (3) residual gas separation column, (4) aqueous - isopropanol azeotropic distillation column, (5) drying column, (6) isopropyl ether separator, (7) isopropyl ether extraction.

BLEND STATION DRYING COLUMN REACTOR (SEVERAL)... 

Removal of solvent from the extracts leaves a residue that is purified by dry-column chromatography.2 The residue is dissolved in 40 ml. of acetone in a 300-ml., round-bottomed flask, 30 g. of silica gel (Note 8) is added, and the acetone is removed with a rotary evaporator. The resulting solid mixture is placed on top of 360 g. of dry silica gel (Note 8) packed in flexible nylon tubing (Note 9), and the column is developed with 420 ml. of 10 1 (vjv) benzene-acetone. Approximately 150 ml. of solvent drips from the bottom of the column toward the end of development, and this eluent is collected in 25-ml. fractions and checked for product by thin layer chromatography (Note 10). The column itself is then cut into 2-cm. sections, the silica gel in each section is eluted with three 25-ml. portions of ethyl acetate, and the eluent from each section is analyzed by thin-layer chromatography (Note 10). Combination of all the product-containing fractions yields 1.2-1.5g. (40-47%) of the benzylated compound as an oil, n 1.6083 (Notes 11 and 12). 

Silica gel Woelm for dry-column chromatography, activity III/30 mm. [according to Brockmann and Schodder, Ber., 74B, 73 (1941)], was supplied by M. Woelm, Eschwege, Germany. 

The submitters also tried to purify the crude product by distillation (130-145° at 0.005 mm.), but under these conditions decomposition took place. It is possible to substitute thick-layer chromatography for the dry column. Using Merck silica gel F254 precoated plates, layer thickness 2 mm., and developing with 10 1 (vjv) benzene-acetone, the submitters report a 73% yield of pure product. 

Polymerizations were generally carried out as follows Gaseous reagents, i.e.,isobutylene, methyl chloride, were passed through drying columns and condensed in the bath and collected in culture tubes. 

The distillation plant consists of a benzene stripper, benzene drying column, paraffin column and the alkylbenzene column (Fig. 20). In the column BS the excess benzene is distilled and in column BC, together with fresh benzene, it... 

Dry column chromatography 494 Dry packing, columns (LC) 349 Dry test meter 843 Dual oven (GC) 62 Durapak phases (GC) 125 Dwell time, gradient elution, (LC) 489, 563... 

Dry column chromatography [528] provides several improvements over traditional column chromatography, such as better resolution and high speed. Another important characteristic is the near-quantitative applicability of TLC results in dry column analysis. Knowledge of the TLC characteristics of a sample is useful before column chromatography is employed. Careful control of the moisture content of the adsorbent is crucial to the dry column as well as other types of chromatography. 

The crude liquid chlorobenzenes stream leaving the second reactor is washed with water and caustic soda solution to remove all dissolved hydrogen chloride. The product recovery system consists of two distillation columns in series. In the first column (the benzene column ) unreacted benzene is recovered as top product and recycled. In the second column (the chlorobenzene column ) the mono- and dichlorobenzenes are separated. The recovered benzene from the first column is mixed with the raw benzene feed and this combined stream is fed to a distillation column (the drying column ) where water is removed as overhead. The benzene stream from the bottom of the drying column is fed to the reaction system. 

Figure 3. Thermal chamber. 1. Thermal chamber 2. Desorber 3. Silica gel cartridge 4. Flowmeter 5. Thermo relay 6. Fan 7. Contact thermometer 8. Air distributor 9. Drying column 10. Air distributor 11. Water pump.

Figure 7. Flowsheet of the acetic acid process 1) reactor, 2) separator, 3) scrubber, 4) light ends separator, 5) drying column, 6) product recovery, 7) product finishing.

Dry-column chromatography is another approach to the separation of large quantities of a mixture of products. I think it s easier than wet-column chromatography, though more limited. 

The manufacturers of dry-column chromatography adsorbants suggest piercing the bottom of the column with a few pin holes. They would know. 

Once the sample is in the column, there s not much difference between what happens here and what happens in paper, thin-layer, vapor-phase (gas), wet-column, or dry-column chromatography. The components in the mixture will stay on the stationary phase, or move in the mobik phase for different times and end up at different places when you stop the experiment. 

---