Nov. 12, 1940. K. C. D. H.CKMAN 2,221,691 WACUUM DISTILLATION Filed Sept. 28, 1938

DEGASSED OIL

ENNETH CD, HICEMAN INVENTOR az, 22 /2%

ATTORNEYS Patented Nov. 12, 1940 2,221,691

UNITED STATES PATENT OFFICE 222,891. WACM DST L.A. ON Renneth C. D. Eickman, Rochester, N. Y., as signor to Distillation Products Inc., Rochester, N.Y., a corporation of Delaware Application September 28, 1938, Serial No. 232,157 3 Cairns. (CI 202-52) This invention pertains to a process of vacuum There is a profound difference between colli distillation and particularly to an improved proc Sions of the distilling molecules with themselves eSS of high vacuum distillation wherein vaporiz and collisions with residual gas. Collisions of the ing and condensing surfaces are separated by Sub distilling molecules With residual gas hinder dis stantially unobstructed space. tillation greatly and to an extent depending upon When molecular distillation was first discovered their direction of travel. Collisions of vapor and described, little distinction was made between molecules With one another are Substantially the pressure of the vapor molecules and the pres harnleSS. The residual gas may come from the Sure of the residual non-condensible gas mole distilland by decomposition or liberation from O cules which were both present in the gap between Solution. It may also be present as a result of O the distilling and condensing surfaces. Early in leakage in the apparatus or by reflection or re vestigators considered that it was necessary to entry of gas coming from leakage or decomposi condense the distilling molecules before they had tion. Residual gas derived from the distilland is collided with themselves or molecules of residual proceeding in the same direction as the distilland gas. In other words, for Successful distillation it, Vapor and collisions between the distilland and 5 was thought to be necessary to condense the dis this gas does not seriously hinder the passage of tilling molecules upon a condensing surface locate the vapor to the condensing surface. However, ed at a distance from the vaporizing surface of when these two components arrive at the con less than the mean free path of the distilling va densing Surface, the distilling vapors are con por molecules. It was considered that with dis densed leaving the non-condensible gas free to 20 tances greater than twice the mean free path of Wander backwards. Therefore, residual gas from the distilling molecules, distillation substantially this Source ultimately hinders distillation as ac completely ceased. tively as the gas derived from leakage and other This invention has for its object to provide an SOceS. improved distillation process whereby substances Collisions between the vapor molecules are 25 can be distilled under high vacuum conditions largely unobjectionable because these molecules and the vapors condensed upon a condensing sur have been ejected from the distilland surface in face separated from the vaporizing zone by sub a direction towards the condenser. Collisions be stantially unobstructed space and by a distance Ween one Such molecule and another will retard Substantially greater than that heretofore emi Some and accelerate others, but the average per ployed. Other objects will become apparent from Sistent Velocity of the entire aggregate in the di 30 the following description and claims. rection of the condenser will remain unchanged. In performing distillations under molecular These collisions, therefore, are more in the nature conditions, it was discovered that the distance of of jostlings, much as animals traveling together condensation or, in other words, the gap between in a caravan will jostle one another sideways the vaporizing and condensing surfaces was not a Without impeding the progress of the caravan. 35 critical factor as was originally supposed. It was Such jostlings do not seriously affect the distia found, for instance, that carrying out distillation tion and can, therefore, take place without affect under the same identical conditions, such as pres ing the course of the distillation. Sure, temperature, rate of flow, size of vaporizing The distilland is heated on the vaporizing sur Column, etc., that the rate of distillation was sub face, and preferably in the form of a thin film as 46 stantially the same regardless of whether the it ordinary molecular distillation. This can be vaporizing surface was located at a distance from conveniently accomplished by permitting it to the column of one times the mean free path of flow by gravity doWn the external Wall of a verti the distilling molecules or distances correspond cal heated column. The temperature at which 45 ing to many multiples of the mean free path such the column will be heated will, of course, de as 3 to 20 times the mean free path. These pend upon the particular distilland under con greater distances represented distillation under sideration and will usually vary from about room conditions wherein the distilling molecules co temperature to 325. The temperature of the SO lided with each other numerous times in passing Column should in each case be such as to give a 50 between the two surfaces. Thus it was evident Saturation pressure of distilling vapor of between that it is not essential for low temperature distii about 10 mm. and .001 mm. of mercury as in lation, that the molecules shall suffer few or no Ordinary molecular distillation. Temperatures of collisions as was believed to be the case by earlier between about 90° and 275° and, particularly, 55 investigators. i20-250 will be found to be best for distilling 55 2 - saa1,001 vitamins from fish oils. Pressures of less than in therapeutically active materials. My inven about 1 mm. should be employed. Pressures in tion is of particular advantage for separating the range of about .01 to .0001 will be found to be and purifying honones, vitamins, entynes, and most generally satisfactory. The pressures de the like from materials containing them, such as s fined are measured by a Pirand gauge calibrated fath oils, for instance cod, halbut, tuna, sardine, B against dry air, the gauge tube being situated out bubot pollack, etc. fishols; corn, cottonseed side the still and attached by a pipe not less than wheat Eerm oils; fatty vegetable extract, .5 cm. wide introduced into the distilling gap at a point approximately farthest from the point of A decided advantage of the invention is that 0 exhaustion. much larger condensing surfaces relative to the 10 The mean free path can be determined with vaporixing surface can be used. In all vacuum ample precision by reference to any modern text distillations of this general type it is necessary book on the dynamic theory of gases and to tables that eficient condensation take place when the on physical constants such as 'Physical and distilling vapors arrive at the condensing sur 5 Chemical Constants and Some Mathematical face. With the small separations heretofore con- 15 Functions” by G. W. C. Kaye and T. B. aby, sidered necessary, the area of the condensing published by Longmans Green Co. 1921 pages surfaces was necessarily limited to a size closely 34 and 35. approximating the area of the vaporising sur In the accompanying drawing I have illustrated face. With substantially greater chambers sur 20 apparatus suitable for the carrying out of a dis rounding the vaporizing surface, the condensing 20 tillation process in accordance with my inven surface can be of almost unlimited area resulting tion. Referring to the drawing, numeral 2 desig in greatly increased condensation eficiency. nates a cylindrical casing closed at the top and Thus, a small heated column or sphere situated botton by plates 4 and , respectively. Caskets at the center of a larger hollow sphere many times 2s and serve to make gas-tight connections. its diameter would be entirely suitable for dis- es Numeral 2 designates a conduit connected to an tillation in accordance with my invention. Fur evacuating pump (not shown) for evacuating thermore, it is not necessary that the hot vaporiz this closed system. Nuneral designates a ing surfaces shall be in the center of the cold cylinder of substantially smaller diameter than sphere, nor need their shape be similar. For ex 30 casing 2 which is integral with base plate S and ample, a cylindrical vertical vaporizing surface SO which is located so that it is approximately con could be placed at one end of a horizontal rec centric with casing 2. Cylinder 4 is closed at tangular box serving as a condensing surface. the top by plate to form a small reservoir 8 An added advantage is that with the larger at the lower portion of which is located a plural condensing surfaces, the condensate is spread ity of holes 20. Numeral 22 designates an elec over a much larger area. The condensing sur- is trical heating unit extending throughout the face therefore remains cooler and does not re length of the cylinder 4. Numeral 24 designates quire the application of cooling fluid. Also, if, a conduit which terminates above reservoir during the distillation, solids are deposited on the and is provided with a valve 2 for controlling condenser, the larger container provides useful O the rate of introduction of distand. Numeral storage space so that there is no need to with 2 designates an annular gutter mounted upon draw the solids from the still during a normal the inside wall of casing 2 and at the lower por commercial run. Thus, during the distillation of tion thereof. Numerall, designates a conduit a fish oil in an ordinary molecular still, a layer connecting with gutter 2 and serves to withdraw of cholesterol may become built up on the con 45 liquid dist late from the still. Nuneral 2 desig denses and protrusions may soon meet the dis nates a withdrawal conduit for renoving unds tland and cause intermixture with the distill tilled residue from the still. ... " late. Furthermore, the cholesterol being a poor The distance between the vaporcing and con conductor of heat, the inside layer becomes too densing surfaces 4 and 2, respectively, is geen hot to continue eficient condensation. According so to be unobstructed by any structural elements. to the present invention, the cholesterol is de Also, due to the fact that the condensing sur posited over the much larger area of the distant face or casing 2 is located in front of vaporsing condensing surface. This larger surface pre surface and coextensive therewith, there is no sents greater opportunity for the heat to escape obstruction to the direct And free passage of and the layer of cholesterol is thinner for a given SS vapors from the vaporizing to the condensing weight of material distined, providing greater sis surface. thermal conductivity, so that the advantages are In operating the apparatus illustrated in the twofold drawing the system is evacuated through con Another advantage is that the still can be fitted dult 2 to a low pressure such as, for instance, with mechanical distributors, scraping devices, 60 the .001 Inn. Degassed oil is introduced through etc., which would not be conveniently housed in conduit 24 and electrical unit 22 is put in opera a small shell. Also it may be necessary to with tion. The oil collects in reservoir 8 and flows draw these cumbersonne fittings through the main evenly through holes 2 down the surface of cyl body of the still during the cleaning operation. inder 4 in a thin film. Vapors pass to cool con When the condensing surface closely surrounds 65 densing surface 2, are condensed thereon, and the evaporating surface, disassembly by this is flow by gravity into gutter 28 and removal con means is not possible. duit 8). Undistilled liquid is withdrawn through What I can is: conduit 2. 1. The high vacuun distillation process which The procedure described herein can be en comprises in Conbination, subjecting a distillable 70 ployed to distill difcultly wolatilizable organic Organic substance to distillation by causing it to 70 substances. Examples of materials to which my flow in the form of a thin film Over a heated invention can be applied with particular advan vaporizing surface which is maintained under a tage are hydrocarbons and distates thereof, high vacuum and condensing vaporized mole vegetable and animal oils, fats, waxes, and con cules upon a condensing surface which is located TS centrates thereof, and organic mixtures contain substantially in front of the vaporizing surface S. 2,221,691 3 and coextensive therewith so that there is no pressure of the distilling molecules being main intervening obstruction to the free and direct tained during the distillation at a pressure of passage of vapors from the vaporizing surface to between .001 and 107 mm. the condensing surface, said condensing surface 3. The high vacuum distillation process which being at a distance from the vaporizing surface comprises subjecting an oil which contains a 5 of greater than three times the mean free path vitamin to distillation by causing it to flow in of the distilling molecules and the vapor pres the form of a thin film. Over a vaporizing surface Sure of the distilling molecules being maintained which is maintained under a pressure of less during the distillation at a pressure of between than .01 mm, and which is heated to a tempera O .001 and 10 mm. ture of between approximately 120 and 250° C. O 2. The high Vacuum distillation process which and Condensing distilling vapor molecules upon comprises in combination, subjecting a distillable a condensing Surface which is located substan Organic Substance to distillation by causing it to tially in front of the vaporizing surface and co flow in the form of a thin film over a heated extensive therewith so that there is no inter 5 vaporizing Surface which is maintained at a vening obstruction to the free and direct passage 5 pressure below .1 mm. and condensing vaporized of vapors from the vaporizing surface to the Con molecules upon a condensing surface which is densing Surface, said condensing Surface being located substantially in front of the vaporizing at a distance from the vaporizing surface of Surface and coextensive therewith so that there greater than three times the mean free path of 20 is no intervening obstruction to the free and the distilling molecules and the vapor pressure 20 direct passage of vapors from the vaporizing Sur of the distilling molecules being maintained dur face to the condensing surface, said condensing ing the distillation at a pressure of between .001 surface being at a distance from the vaporizing and iO Inn, Surface of greater than three times the mean free KENNETH. C. D. CKMAN. 26 path of the distilling molecules and the vapor 25