Column for Stripping Solvents from Extracted Oils F. H. SMITH North Carolina Agricultural Experiment Station, Raleigh, N. C.
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LCOTT ( I ) 1i:ts recently pointed out t h a t the removal of
traces of solvent from laboratory-extracted oils is difficult even hen vacuum is employed a t temperatures up t o 50" C. He found t h a t traces of solvent still persisted. KO adequate device t o facilitate the removal of the small amounts of solvent is generally available; hence, the stripping column described belov- meets a definite need. It has been successfully used without causing a n y detectable change in the unsaturated oils given in Table I.
a water-cooled condenser to a receiving vessel. The oil drains past bulb D and forms a thin film on the lower portion of the column. Here any residual traces of solvent are removed by the combined action of heat and the countercurrent of air or nitrogen,
Experimental T h e folloiving d a t a show t h a t the stripping column completely removes the solvent from t h e extracted oil-solvent mixture without a n y detectable influence on the recovered oil. Seventy-five milliliters (69 grams) of refined corn oil (Mazola) were mixed with 400 ml. of petroleum ether, Skellysolve F, boiling range 30" to 60" C. This mixture was passed through the stripping column with a recovery of 68 grams of oil and 340 ml. of solvent. To confirm the completeness of separation of solvent from the stripped corn oil, charges of about 21 grams of the original and of the stripped oil were subjected to drying in a vacuum oven 6 hours at 30" C. a t about 1-mm. pressure, followed by 4 hours' drying a t 50" C. a t 20-mm. pressure. The changes in weight on the charges of each oil mere 0.0115 and 0.0122 gram, respectively. These losses are insignificant and indicate that the solvent had been completely removed by the stripping column. Further, the organoleptic tests of odor and taste for the presence of solvent in the recovered oil were negative, and the values of the fat constants of specific gravity, refractive index, and iodine number of the corn oil both before and after treatment remained the same and showed no change in unsaturation (Table I). k A sample of crude soybean oil, No. 2537, was extracted from Tokyo soybeans with petroleum ether and stripped free of solvent by passing through this apparatus. Sample 2537a was extracted from the same lot of soybeans with ethylene dichloride. The fat constant gave no indication that the unsaturation of these oils had been changed. The odor and taste of the stripped oils gave no detectable evidence of the presence of any remaining solvent.
ABCID-
SEPARATORY FUNNEL TUBE 9 MM. DIAM. STEAM- JACKET 18 MM. DIAM. GLASS BULB 6 MM. DIAM. E- TUBE 12 MM DIAM F - STOPCOCK CONSTRICTION A T - D 5 MM. DIAM.
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TThile efficient solvent recovery in laboratory stripping operations is generally considered unimportant, the amounts of solvent recovered were recorded because the column might be adapted t o industrial usage b y suitable modification. T h e amount of solvent recovery from 5 samples varied from 85 to 93 per cent. A cold t r a p placed in t h e gas exit line below D did not recover a n y more solvent.
TABLE
Sample No.
2707
I.
DATA O S
Oil
EXTRACTED OILS STRIPPED
Solvent rsed
OF
SOLVEXTS
RefracExtract Solvent Specific tive Iodine Mixture Re- G r a v i t y , Inde:, No. Flow Rate covery 2 Z 0 / 2 Z 0 C. n y (Hanus) 92 M1./*Win. , , , 0 9190 1 . 4 7 4 8 1 2 3 . 6 .,.
Refined ,... corn oila Refined, Petroleum 83.0 0 9188 1 . 4 7 4 1 1 2 3 . 3 16 corn oilb ether 2337 C r u d e T o - Petroleum 93.0 0,9203 1 . 4 i 5 l 131.3 1.6 kvo SOYether bean o h 2537a C r u d e T o - Ethylene 88 0 0 9220 1 4753 130 8 0 7 kyo soydichloride bean oil LL hlazola; 21.1804 grams of refined curn oil lost 0.0115 gram when dried i n a Vacuum oven 6 hours at 30° C. a t 1-mm. pressure, followed by 4 hours' f u r t h e r dryin* a t 50' C. a t 20-mm. pressure. b A charee\f 21.2922 grams of stripped corn oil lost 0.0122 gram in weight when-dried-under t h e same conditions.
FIGI-RE1. DIAGRIM OF COLUXS
2707a
The apparatus illustrated in Figure 1 consists of a steamjacketed column made of Pyrex glass. The inner tube is constricted a t D and a small loosely fitting glass bulb a t this point permits the oil to pass through at a slow rate. At the same time the oil forms a seal against the passage of solvent vapors. The section of the inner tube below D is provided n-ith side arms. A current of air is drawn in through the lower arm, or nitrogen under pressure may be admitted, a t the rate of 800 ml. per minute. The stopcock, F, a t the bottom of the column is opened enough to permit the oil as it collects here to drain into a receiving vessel. The filtered extrac,t oil-solvent mixture is fed into the column from the separatory funnel, 9, a t the flow rate of 1.6 to 2 ml. per minute for solvents such as ethyl or petroleum ether, and more slowly for the higher boiling solvents such as ethylene dichloride. As the oil-solvent mixture enters the area surrounded by the stcnm jnckrt. the solvent rolntilizes and pnsses out a t B through
Literature Cited (1) Olcott, H. S.,ISD. EXG.CHEM.,33, 011-15 (1941). PUBLISHED with t h e approval of t h e Director of t h e Korth Carolina Agricultural Evperiment Statlon a s Paper N o . 127 of t h e Journal Series.
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