US2645652A - Fractionation of oleiferous materials - Google Patents

Description

y 4, 1953 E. M. B. PRAMUK ETAL 2,645,652

FRACTIONATION 0F OLEIFEROUS MATERIALS Filed Oct. 15, 1950 5 Sheets-Sheet l HEXANE ACETONE T STORAGE l4 IS IS OLEIFEROUS MATERIAL FlG.l

TH. 64 N f' INVENTORSI EDWARD M.B. PRAMUK EDERICK H. CLAREN B M ATTQRNEYZ July 4, 1953 E. M. B. PRAMUK ETAL FRACTIONATION OF OLEIFEROUS MATERIALS 3 Sheets-Shee't 2 Filed Oct. 15, 1950 x mo .Emommm 8 2. ow on ov on ow u =0 023000 m OMZEPQO ZOFDDEPME lllll IIL 30 .LNlOd QNIL IBW INVENTQRS EDWARD M. B. PRAMUK KjREDERICK ACLAREN BY 41% Ndl ATT RNEY:

July 14, 1953 E. M. B. PRAMUK ETAL ,6

FRACTIONATION 0F OLEIFEROUS MATERIALS Filed 001;. 15, 1950 3 Sheets-Sheeti STEARIC ACID MELTING POINT FRACTIONATION 40 PERCENT STEARIC ACID CHARGE llllllll'lllllllllllllllll'llllll'lllllllllllllllillllllllllillilIIIllllllllllllllllllllllllll EDWARD M. B. PRAMUK DERICK CLAREN BY: M

ATTOR EY FIG. 3

Patented July 14, 1953 FRACTIONATION OF OLEIFEROUS MATERIALS 7 Edward M. B. Pramuk, Whiting, and Frederick H. MacLaren,

Munster,

Ind., assignors to Standard Oil Company, Chicago, 111., a corporation of Indiana Application October-13,1050, Serial No. 190,008

This invention relates to the fractionation of oleiferous materials such as crude hydrocarbon waxes, glyceride fats and fatty oils, fatty acids, etc. and it pertains more particularly to an improved method of separating such materials into individual components of different meltingpoints and hence of different chemical or physical properties.

An object of the invention is to provide a fractionation process which is more precise and re producible than fractionation methods heretofore employed. A further object is toprovide a process which can be performed more quickly and more easily than prior processes and which effects the fractionation without decomposing or altering the composition or structure of any component. As applied to hydrocarbon waxes, an object is to obtain complete deoiling of wax and separation of oil-free wax into components of different melting "points. As applied to fatty materials, an object is to effect complete separation of saturated from unsaturated components as well as to'separate said material into individual components of high purity.

Vacuum distillation isperhaps the most precise method heretofore known for separating waxes and fatty materials into relatively pure individual components but this process-is laborious and time consumingwhen applied to waxes and fatty materials. There is always a tendency toward decomposition or chemical alteration of certain components particularly at high temperatures, and components-which distill at the same temperature may have very different melting points. Extensive work has been done to develop a process for determining petroleum wax melting point distribution from cooling curves but here again results have beenunsatisfactory in that the distributions thus obtained were not of greater precision than can be obtained by any prior methods. Other objects will be apparent 12 Claims. (01. es 419) 2 as the detailed description of the invention proceeds.

Waxes and fatty materials have been fractionated with many different types of solvents of which the most important from a commercial standpoint are ketone-aromatic mixtures and light parafiinic solvents, such as propane. The

ketone-aromatic hydrocarbon mixtures are best solvents likewise present filterability problems at very low temperatures. Neither light hydrocarbons, ketones or ketone-aromatic mixtures have solved the problem of precise fractionation of fatty materials.

In accordance with our invention, an oleiferous material such as a crude hydrocarbon wax, fatty oil or fatty acid is first dissolved in a solvent mixture which will be referred to as a treating agent and which consists essentially of approximately equal parts of a light parafiinic hydrocarbon such [as hexane and a low boiling polar solvent, suchas ketone, preferably acetone. The volumetric proportion of the two components is important and the hexane component should constitute at least 30% but not more than 90% of the total treating agent, best results having been obtained with 50%. The treating agent to charging stock ratio is likewise important and for most purposes should be of the order of 10:1 to 20:1, although with particular charging stocks reasonable success may be obtained with treating agent to charging stock ratios as low as about 5:1. The solution of charging stock in the defined treating agent at the specified treating agent to charge ratio may be chilled in any known manner and even at a rapid rate to a temperature of the order of 50 F. to F. Previously, it has been the belief of those skilled in the art that rapid chilling to such low temperatures would result in the solidification of, solids in unfilterable form covered that even rapid or shock chilling rewould interfere with proper crystallization and/ or separation of other components in later stages of our process.

The solidified material from the lowest temperature filtration is next reslurried and preferably redissolved in an additional amount of the specified treating agent and with the same treating agent-to-charge ratio initially employed and the resulting mixture is then cooled to a f ond filtration step is then repeatedly processed in like manner at higher and higher temperatures until the charging stock has been separated into the desired number of fractions.

When the above procedure was applied to crude hydrocarbon waxes as exemplified'by a 130 F.-132 F. melting point refined wax, it was found that the incremental melting point analysis was repeatable with remarkable accuracy and that the analysis thus obtained in a few hours was closely comparable with and even more accurate than analyses obtained by a tedious vacuum distillation process requiring days to perform. When appliedto fatty acids, it was found that this process effected a remarkably sharp fractionation between different fatty acid components and that it effectively separated saturated from unsaturated components. In all cases; no component of the charging stock was altered, individual components were separated in a state of high purity and the analysis was repeatable with great accuracy. 7

The invention will be more clearly understood from the following detailed description read in conjunction with the accompanying drawings which form a part of this specification'and in which:

Fig. l is a schematic flow sheet diagrammatically illustrating procedural steps.

Fig. 2 is a graph illustrating a representative wax melting point analysis obtained in our process as compared with analyses obtained by vacuum distillation and a, cooling curve method; and

Fig. 3 is a graph illustrating results obtained by fractionating a fatty acid in accordance with our invention.

Since our procedural steps are substantially th same regardless of the particular oleiferous charging stock employed, we will first describe our method of operation as illustrated by Fig. 1. storage tank [0 contains treating agent which inthis case consists of equal volumes of hexane and acetone. Ten volumes of such treating agent is introduced by pump ll and lines l2 and I3 for admixture with one volume of wax or fatty material charging stock which is introduced 4 from source M by pump [5 through line IS. The mixture of the defined treating agent at the defined treating agent-to-charge ratio is heated in heater I! to a temperature sufficient to insure complete solution, i. e. elimination of any previously formed crystal patterns; the particular temperature will depend on the nature of the charging stock and is usually in the range of 60 F. to 160 F; The solution next passes through cooler l8 which may be a conventional scraped surface exchanger or any other cooling means known to those skilled in the art. The

rate of cooling is not of critical importance but it is preferred to cool rapidly, i. e. at the rate of 10 F. to 20 F. per minute; apparently the rapid chilling minimizes occlusion of oil Or lower melting constituents in the material which is solidifying and surprisingly enough the chilled mixture when employing our treating agent and treating agent-to-charge ratio is found to be readily filterable at temperatures as low as 60 F.

After chilling to about 60 F., the slurry is filtered in filter I9, the filtrate passing by line 20 to still 2| from which the treating agent-free oil (or lowest melting component) is withdrawn through line 22 while the treating agent passes I through lines 23 and 24 to condenser 25 and thence back to storage [0.

Filtered crystals withdrawn through line 26 are mixed with an additional 10 to 20 volumes of treating agent from lines l2 and 21 and are preferably heated once more in heater 28 and cooled in chiller 29to a temperature 5 F. higher than the previous filtration temperature. In other words, if the first filtration is at -60 F., the second filtration is preferably at -55 F. for reasonably close fractionation, although it should be understood that a lesser interval may be employed for still closer fractionation while temperature intervals of 10, 20 or 30 F. may be employed where suchyclose fractionation is not required. The filtrate is withdrawn from filter 30 by line 3| and introduced to still 32 wherein the first wax fraction is withdrawn from line 33 and treating agent is returned by lines 34 and 24 to condenser 25 and storage H].

The filtered solids from line 35 are then mixed with an additional 10 to 20 volumes of the defined treating agent from lines I2 and 36, and the mixture is heated to solution in heater 3?, chilled in cooler 38 and filtered in filter 39 at a temperature of 50 F., the filtrate passing by line 40 to still 4! from which the second wax fraction is withdrawn through line 32 and treating agent is returned by line 43 and 24 to condenser 25 and storage l0.

Wax from filter 39 is withdrawn through line 44 and mixed with an additional 10 to 20 volumes of the defined treating agent from lines i2 and 45, the resulting mixture being heated to solution in heater 46, chilled in cooler 47 to a temperature of -45 F. and filtered in filter 48 at said temperature, the filtrate passing by line 49 to still 50 from which the third wax fraction is withdrawn through line 5| and treating agent is returned by lines 52 and 24 to condenser 25 and storage l0.

The stepwise procedure hereinabove described is continued in the same manner until filtration temperatures of +30 to +50 F. or more are reached, i. e. throughout a range of approximately F. Solids from the next-to-the-last filtration step from line 53 are mixed with 10 to 20 volumes of the defined treating agent from lines l2 and 54, the mixture isheated to solution in heater 55, cooled to the final filtration temperature in cooler 56 and filtered in filter 5'1. The final filtrate is introduced by line 58 to still 59 from which the next-to-the-last wax cutis removed through line 60 while the treating agent is returned through lines 6| and 24 to con-denser 25 and storage 19. The final wax cake withdrawn through line 62 is freed from treating agent in still 63 and the final wax fraction withdrawn through line 64, the treating agent being returned by line 24 to condenser 25 and storage Ill.

It is not essential, of course, that separate filters and stills be employed for actual operations since by operating batchwise a single filter and still may be used on all fractions, the fiow sheet hereinabove described representing procedural steps rather than required plant structure. Thus, in laboratory tests, we have added 10 volumes of the defined treating agent to one volume of charging stock in a glass vessel, efiected complete solution by immersing the vessel in a hot water bath, chilled by immersing the vessel in acetone containing a large amount of Dry Ice (solid carbon dioxide) which sublimed in the acetone to obtain the desired low temperature, effected filtration in an ordinary laboratory suction filter, distilled the treating agent from the filtrate and re-employed the treating agent for each succeeding fraction. Such work demonstrated the remarkable filterability of each and every fraction of solidified material, the filter rate being extremely rapid and the resulting'wax cake on the filter being in all cases substantially dry and relatively free from treating agent.

By the above laboratory fractionation technique, we have obtained the melting point distribution or analysis of a large number of refined waxes, some of which contained oil and some of which were substantially free from oil. Such a melting point analysis of a 130-132 F. refined wax substantially free from oil is illustrated by the solid line in Fig. 2, this analysis having been made with the first filtration at 60 F. and with filtration at 5 F. intervals thereafter. The dashed line in Fig. 2 shows the melting point analysis as determined by vacuum distillation; it will be observed that ourprocess showed the existence of low melting fractions which did not show up in vacuum distillation, that our process checks remarkably closely with vacuum distillation, and that from the standpoint of melting point distribution, our process is even more accurate than the laborious vacuum distillation method heretofore employed. Thecooling curve method of obtaining melting point distribution (one of the most recent attempts to solve the problem which confronted the art prior to applicants invention) does not give an accurate picture of the melting point distribution as will be seen from the dotted line on Fig. 2. Our fractionation procedure not only gives an accurate and easily reproducible picture of melting point distribution but it correlates surprisingly well with tests designed to give an indication of other properties of the wax.

When a large part of the charge has the same melting point, fractions of this component may be removed at different filtration temperatures. For most accurate results, it is advisable to repeat the crystallization at the same temperature when removal of treating agent from the filtrate shows that an abnormally large amount of material has been removed in that particular step.

When our procedure was employed for fractionating a sample of stearic acid of purported high purity, we obtained the analytical data graphically shown in Fig. 3. About 1.2% of the so-called stearic acid was removed at 60 F. and this oily fraction had a solidification point of 93.5 F., an iodine number of about 14.8 and a neutralization number of about 185. The next fraction amounted to about .8% of the original charge and was characterized by a solidification point of 116 F., an iodine number of about 5.9 and a neutralization number of about 180. The next fraction amounted to 1.9% of the original charge, had a solidification point of 123 F.,had an iodine number of about 1.6 and a neutralization number of about 198. A plateau was then reached with a solidification point of 126 F. at which a total of about 9.5% of the charge was separated having an iodine number of about .6 and a neutralization number of about 207. The next three fractions combined amounted to about 2% of the total charge, had a solidification point of 131-139 F., an iodine number of about .1 and a neutralization number of about 199. The next four fractions accounted for about 2.4% of the total charge and this material had a solidification point of 143-145 F., an iodine number of about .2 and a neutralization number of about 196. The next plateau constituted 5.7% of the charge and this material had a solidification point of 147 R, an iodine number of about .2 and a neutralization number of about 197. The next fraction amounting to 2.3% of the total charge had a solidification point of 148 R, an iodine number of about .1 and a neutralization number of 198. The next fraction amounting to 7.3% of the charge had a solidification point of'l49 R, an iodine number of approximately .1 and a neutralization number of about 198. The final fraction amounting to 67% of the total charge had a melting point just below 151 F., an iodine number of only about .1 and a neutralization number slightly above 199. Our fractionation method showed that this sample only contained 67 weight per cent of stearic acid while neutralization number of analysis indicated that it contained 86.2% stearic acid. From our analysis we were able to show that the charge contained a large number of acids besides stearic acid; in other words, we were able to obtaina more accurate analysis of the charging stock than was possible by previously known methods.

While our invention has thus been described as a fractionation procedure for the primary purpose of obtaining analytical data, it should be understood that the invention may also be applied to'the fractionating of waxes, fatty materials, etc., for separating components on a commercial scale. Thus, a crude hydrocarbon wax which contains substantial amounts of oil may be almostcompletely deoiled by the first fractionation step at a temperature of the order of to F. and by subsequent recrystallization and filtration at higher temperatures, the wax may be segregated into components of any desired melting point range. When a wax containing 10% of oil was fractionated by the first step of our process at 60 F., the wax was substantially free from oil by the second or third filtration step. If the initial filtration step is at a temperature as high as -40 F., a single filtra tion with our solvent and solvent ratio at said temperature removes all but about .5% of the oil together with about .5 to .9% of the wax. Our process appears to be much more effective than processes employing aromatic-ketone solvents such as benzol'acetone not only because of the avoidance of possible benzene solidification and entrainment in solids but because of better filterability and greater ease in removing solvents from filtrates.

Similarly, fatty oils of. the glyceride type or fatty acids may be separated into more valuable components by our fractionation technique. Here again, where commercial fractionation is desired, it'will, of course, be unnecessary to raise the temperatures at uniform intervals but a first filtration temperature may be suited to remove unsaturated components (as well as components which would interfere with crystallization in subsequent steps) and subsequent fractionations can be made at the particular temperatures required for obtaining relatively pure product fractions.

While the hexane-acetone solvent in substantially equal proportions has been found outstandingly superior in our process, it is contemplated that other light parafilnic hydrocarbons of the C3 to C7 range may be employed instead of hexane and that other polar solvents, particularly low boiling ketones, such as methyl ethyl ketone, methyl butyl ketone, etc. may be employed instead of acetone. Propane may be advantageous as a solvent component particularly in cases where refrigeration is effected by direct vaporization of propane, but propane is not the full equivalentof hexane in our fractionation process nor are other polar solvents the full equivalent of our low boiling ketones, such as acetone.

From the above detailed description, it will be seen that we have accomplished the objects of our invention.

We claim: V

1. The method of fractionating an oleiferous material which comprises dissolving said material in about 10 to volumes of a treatin agent having a freezing point below -60 F.- and consisting essentially of a light paraffinic hydrocarbon and a low boiling ketone with the ratio of parafiinic hydrocarbon to low boiling ketone being in the range of :70 to 90:10, cooling the resulting solution to a temperature of approximately to -60 F. to obtain solids separable by filtration suspended in liquid treating agent containing unsolidified materials in solution, filtering to efiect separation of'the solids from a first filtrate of treating agent containing dissolved material, removing treating agent from said first filtrate to recover a lowest melting fraction, admixing about 10 to 20 volumes of treating agent with separated solids to obtain a second solution, chilling said second solution to a low temperature which is higher than the temperature of the first filtration step, filtering the chilled second solution to obtain a second filtrate, recovering a fraction of the oleiferous material from the second filtrate and recovering at least one other fraction of the oleiferou-s material from the solids separated from the second filtrate.

2. The method of claim 1 wherein the paraffinic hydrocarbon contains at least three, but not more than seven, carbon atoms per molecule.

3. The method of claim 1 wherein the paraffinic hydrocarbon is hexane and the solvent is acetone.

4. The method of claim 1 wherein the oleiferous material consists essentially of a hydrocarbon wax mixture.

5. The method of claim 1 wherein the oleiferous material is a fatty material.

6. The method of claim 5 wherein the fatty material is a fatty acid mixture.

7. The method of claim 5 wherein the fatty material is a crude glyceride fatty oil.

8. The method of fractionating an oleiferous charging stock which comprises dissolving said charging stock in a treating agent having a freezing point below 60 F. and consisting essentially of approximately equal parts of hexane and acetone, employing approximately 10 volumes of treating agent per volume of charging stock, heating the mixture of charging stock and treating agent to a temperature sufficient to efiect complete solution of the charging stock in the treating agent, cooling said solution to a temperature of approximately 50 F. to -60 F. to obtain solids separable by filtration suspended in a solution of unsolidified material in treating agent, filtering to effect separation of the solids from the treating agent solution to obtain a first filtrate, repeating the above procedural steps a plurality of times employing separated solids from previous filtration steps as charging stock and employing higher and higher temperatures in the chilling and filtration steps to obtain a plurality of filtrates and a final separated solid fraction and separating treating agent from each filtrate and from the final separated solids fraction.

9. The method of claim 8 wherein the oleiferous material consists essentially of a hydrocarbon wax mixture.

10. The method of claim 8 wherein the oleiferone. material is a fatty material.

11. The method of claim 8 wherein the fatty material is a fatty acid mixture.

12. The method of claim 8 wherein each chilling step is effected at a rapid rate of the order of 10 F. to 20 F. per minute.

EDWARD M. B. PRAMUK. FREDERICK H. MACLAREN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,113,960 Grote et a1. Apr. 12, 1938 2,340,104 Brown Jan. 25, 1944 2,505,012 Spannuth Apr. 25, 1950 2,510,015 Feldpush May 30, 1950

Claims (1)

1. THE METHOD OF FRACTIONATING AN OLEIFEROUS MATERIAL WHICH COMPRISES DISSOLVING SAID MATERIAL IN ABOUT 10 TO 20 VOLUMES OF A TREATING AGENT HAVING A FREEZING POINT BELOW -60*F. AND CONSISTING ESSENTIALLY OF A LIGHT PARAFFINIC HYDROCARBON AND A LOW BOILING KETONE WITH THE RATIO OF PARAFFINIC HYDROCARBON TO LOW BOILING KETONE BEING IN THE RANGE OF 30:70 TO 90:10, COOLING THE RESULTING SOLUTION TO A TEMPERATURE OF APPROXIMATELY -50* TO -60*F. TO OBTAIN SOLIDS SEPARABLE BY FILTRATION SUSPENDED IN LIQUID TREATING AGENT CONTAINING UNSOLIDIFIED MATERIALS IN SOLUTION, FILTERING TO EFFECT SEPARATION OF THE SOLIDS FROM A

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