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T H E J O C R N A L O F I N D C S T R I A L A N D ENGINEERILVG C H E M I S T R Y SC‘ 31 M A R Y
These experiments have established t h e following facts: I-That a satisfactory naphtha may be obtained b y means of this process wherein t h e oil is cracked in t h e presence of nascent hydrogen. 2-That superheating t h e oil vapors is desirable for “cracking.” 3-That pressure is necessary for “cracking.” 4-That a combination of pressure a n d superheat is essential. 5-That t h e presence of a refractory material in the “cracking chamber” acts as a catalyzer, aids t h e “cracking,” and increases the yield of naphtha obtained. 6-That hydrogen is formed in the manner described, and t h a t i t evidently does unite with a greater portion of t h e unsaturated decomposition products formed, producing saturated compounds. 7-That iron or steel shavings in t h e cracking chamber constitute a satisfactory catalyzer. 8-That t h e catalyzer should be frequently renewed. 9-That t h e yields of naphtha obtained increase as t h e pressure is increased u p t o IOO lbs.; above t h a t pressure we have no data. Io-The best results were obtained when using about I O lbs. of steam per gallon of oil. 11-That the steam should be superheated t o a t least 600’ C. before mixing with t h e oil vapors. 12-That the mixture of superheated steam a n d oil vapors should be heated t o 650’ t o 675Oin t h e “cracking chamber.” 13-That t h e residue, obtained by distilling off t h e naphtha formed, is worth just as much as t h e original “ r a w ” oil. 14-That carbonization takes place in t h e retort a n d more or less gas is formed in t h e process. I 5-0ils having higher boiling points are “cracked” easier t h a n those having lower boiling points, but t h e quantity of gas formed is greater. 16-That t h e cost of naphtha produced by this process may be approximately expressed by t h e equation c = 1.33% 0 . 9 , where C = t h e cost of t h e naphtha in cents per gallon, X = t h e cost of the starting oil in cents per gallon. As t o future work on t h e problem, we have considered the following: I-Nore careful study of t h e temperature t o which t h e steam should be superheated before mixing with t h e oil. This might lead, in t h e construction of a commercial plant, t o placing t h e steam superheater next t o t h e fire and utilizing t h e heat for cracking, after it leaves this superheater. 11--A study of spraying t h e cold oil into the superheated steam in a mixing and l-aporizing chamber, which later might or might not have t o be heated. 111-X more careful study of the construction of t h e cracking- chamber, and t h e method of passing t h e vapors through t h e same, with t h e idea of determining whether it is not better to heat the vapors t o t h e desired temperature as quickly as possible.
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In conclusion, t h e writer desires t o express his thanks t o Mr. W. W. Sanders and t o hlr. L. M . Bourne, under whose supervision these experiments were performed, for their interest and suggestions. CHEMICAL LABORATORY OF THE GOODYEAR TIRESr RUBBERCOXPANY 4KR021, OHIO
REFINING VEGETABLE OILS’ B y CHARLESBASKERVILLE
Crude vegetable and animal oils contain a variety of impurities traceable t o a great variety of causes. The character of the crude oil depends not only upon t h e kind and part of t h e vegetable (wood, n u t , seed, etc.) or animal (fish, whale, etc.) used, but the quality of the raw material a t t h e time of expressage or extraction (rusting, rotting, fermentation, sprouting, heating, etc.), t h e method followed, t h e care exercised in t h e process, and t h e conditions t o which t h e oil is subjected prior t o its refining. I t is not proposed t o discuss these matters in detail, as this communication deals more specifically with certain of t h e vegetable oils. ,4 distinguished oil chemist in a recent interesting summary of t h e “Contributions of t h e Chemist t o the Cottonseed Oil Industry,”* has said, “ t h e chemist * * * found t h a t t h e quality of the oil closely followed t h e free f a t t y acid p r e ~ e n t ” and ~ “The chemist’s greatest service t o t h e industry has been in t h e refining of t h e oil, * * * * and finally bringing into use t h e tintometer for measuring t h e color against standard glasses * * * * .’14 The present customary practice for refining vegetable oils referred to depends upon neutralizing t h e free f a t t y acids in t h e crude oil, usually by agitating t h e oil with a n aqueous solution of a n alkali, t h e strength and t h e amount having been previously determined by laboratory tests, agreed upon as a standard, and then heating t h e mixture during agitation t o a suitable temperature until t h e oil “breaks.” The mass is then allowed t o stand until t h e “foots” settle t o t h e bottom of t h e kettle, when t h e supernatant oil is drawn off by means of a swivel siphon. Invariably some “dreg” floats on top of t h e oil. If this be very great, its settling is sometimes facilitated by throwing salt on top of the oil in t h e kettle. I n any event, t h e oil drawn off is clouded, perhaps on account of t h e presence of some dissolved soap, globulated moisture and suspended matter, doubtless colloidal in nature. This oil is then “brightened” after drawing off, b y throwing in small amounts of fuller’s earth, heating again, and passing through a filter press. The time-factor in settling (6 t o 1 2 hours) of t h e “foots” materially affects the completeness of t h e separation referred t o above, but in any event the “foots” is wet with oil. The “foots” also entrains oil. Consequently, during the rush season, t h e effi1 Read before the h-ew York Section, American Chemical Society, April 9. 1915, and the Inter-State Cottonseed Crushers’ Association, Birmingham, Ala., M a y 18, 1915. Since brought up-to-date, Jan., 1916. 2Wesso11, THISJOURNAL, 7 (1915), 2 7 7 . 3 I have determined t h a t this is true only in a general way, as was no doubt meant by the nriter quoted 4 One familiar with the color changes in glass may question the real accuracy attainable in t h e use of such standards. However, it is the best now available.
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T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
ciency of yield of refined oil must be sacrificed for speed a n d quantity refined; in other words, more speed in refining, more loss of refined oil, whatever t h e analysis upon which purchase and sale are based, may indicate. Cocoanut oil sometimes requires fortyeight hours t o settle. A process which would reduce t h e amount of oil entrained in t h e “foots” t o a minimum, thus increasing t h e yield of a refining,, a n d one which would not be dependent upon t h e slow subsidence of t h e “footsll’
F I G . I-COMPARATIVE
LOSSESI N REFININGC O T T O X S E E D PRACTICE AND NEWPROCESS
OIL
BY
OLD
i. e., admit of rapid separatidn with consequent increase in capacity of a refinery, therefore, seemed not only t o be desirable, but, if secured, would approximate t h e highest efficiency one might hope for in such a n industrial operation. I have succeeded in working out such a process, a n d shall now proceed t o describe the principles involved. The technical laboratory tests with batches of 1 2 t o 2 0 Ibs. have been verified in t h e factory on t h e commercial scale. The aims t o be accomplished are:
119
I-To reduce t h e amount of oil entrained in t h e “foots,” thus increasing t h e yield of “whole oil.” 2-To reduce the time of contact of the excess alkali (necessary for t h e “ b r e a k ” and t o secure t h e best “color”) to t h e minimum. 3-A technological corollary calls for t h e utilization of any by-products. It is assumed t h a t all oils, good, bad and indifferent, are t o be treated. However, this may not be necessary! as in some cases only the good, a n d perhaps the indifferent oils are refined a t some places. I n m y investigations, lasting through several years, I have taken various kinds of crude vegetable oils from various sources with various (extreme) conditions and refined them. I n many cases I have been told t h a t no attempt would ordinarily be made t o refine a particular oil, as it should be sent t o t h e soap kettle, the corresponding price only being expected. Such oils would have presented much better values if they could have been refined by the present practice. These oils have yielded t o my process a n d have been refined. If we can get t h e “foots” into such a condition t h a t it may be filtered and then squeezed, we may reduce t h e amount of whole oil entrained. If we can do this immediately after t h e “ b r e a k ” and while t h e oil is still hot, we shall be able t o reduce t h e time t h e “whole oil” is exposed t o the saponifying action of t h e excess alkali necessary. There are present in oils groups of bodies which in general terms are called colloids. These colloids may or may not be colored; may or may not make t h e oil turbid, for colloids are of such a state of subdivision t h a t they remain suspended in t h e liquid, where they may be, for a long period of time. Some colloids may be and are coagulated b y heat, some by acids, some by alkalies, some by salts, or electrolytes, a n d in time will settle out. For example, linseed oil may be and is refined by adding lime a n d allowing t h e mixture t o stand for several months, during which time the colloids settle out. Colloids t h a t have been coagulated, or lumped, may be filtered out. Some coagulated colloids in their formation absorb coloring matter. Suitably prepared cellulose fiber will absorb some coloring matter. It will bring out a n agglomeration of t h e material precipitated from oils by treating t h e oil with alkalies and heating, and i t will bind the particles together so t h a t they lose their somewhat slimy character and may be filtered away from t h e oil in which they were produced. I have also found shortfibered “linters” is a suitable form of cellulose for some oils. Therefore, I add cellulose suitably prepared along with t h e caustic t o t h e oil t o be refined. The “ b r e a k ” takes place normally on heating as in the ordinary process, but t h e precipitated mass is in such a physical condition t h a t it may be separated from t h e oil immediately by filtration. As mentioned above, some colloids, perhaps colored, are thrown down by salts, so in certain cases some salt ( I per cent of sodium chloride) may be added
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T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
If there be a slight excess of mater present, the sodium chloride serves also t o “salt o u t ” any soap in t h a t water. The addition of salt, however, is not necessary in all cases. I have also discovered t h a t t h e tendency of t h e soaps formed by t h e caustic alkali treatment t o emulsify with the oil, or so t o distribute themselves through t h e oil as t o render their separation difficult, may be overcome by subjecting t h e oil, a t a suitable stage of t h e treatment, t o t h e action of a n anhydrous salt which is capable of taking up water of crystallization, t h e preferred salt being dry sodium carbonate (soda
FIG.11-COIPARATIVELOSSESWITH VARIOUSOILS ash) which, as is well known, is capable of taking up one, seven, or t e n molecules of water of crystallization, according t o temperature conditions. By such treatment, t h e soaps which have already been formed by the treatment with caustic alkali, and which have become so incorporated with t h e oil as t o be incapable of complete separation by ordinary filtration, are hardened, presumably by dehydration, and are so modified t h a t they are readily separated by simple filtration. Sodium sulfate, which acts in t h e same way, may be used instead of t h e soda ash.’ The process is carried out by adding ordinarily z per cent of prepared cellulose (less t h a n I per cent real cellulose), a suitable amount of caustic soda (usually much stronger t h a n commonly used), and a determined amount of soda ash. The whole is thoroughly agitated by mechanical means while it is being heated (45’-65’ C.) t o produce t h e “break,” after 1These ideas are covered b y U.S. Patents Xos. 1,105,744;1,105,743; 1,130.6Y8:1,114,095.
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which it is filtered. At first some soap may pass through t h e filter cloths. I n t h a t event, the first filtered oil may be run directly back into t h e refining kettle, and pumped through the press until the oil is “bright.” This usually occurs within a few minutes. I n fact t h e speed of filtration is directly dependent upon the speed of the pumps. This re-filtration also improves the color. This oil is neutral and can be bleached and deodorized, or both at once, or it may be stored safely. If “linters” is used, to per cent of t h e dry cellulose is added. The danger of making a whole kettle into soapstock through failure of t h e refiner t o be “ o n t h e job” is reduced t o a minimum, as in several thousand trials this has not occurred, the trials having been made by different people with various grades of oils of different character. I n other words, the process is nearly “fool-proof.” Any man of fair intelligence can operate t h e process and the air of mystery surrounding the professional refiner is dissipated. The superintendent has a double check on t h e refinery by weighing the finished oil and cake. The daily reports when summed up should coincide with the annual inventory. I have known of cases where as much as I O O , O O O lbs. of oil have failed to appear in t h e inventory, b u t were reported daily and had t o be charged t o profit and loss when the operation was under t h e usual process. The curves in Fig. I have been made from a series of cottonseed oils very variable in character, to show t h e comparative losses by the normal, present practice and my process. Fig. I1 shows t h e comparative saving with several other oils. I have also been able to secure a farther 1-3 per cent. saving by subjecting t h e “cake” t o hydraulic pressure. This extra saving is not shown in t h e charts. The process is very rapid, t h e controlling factor being filter-press capacity. A study of plate filter-presses has indicated a preference for a center feed press making 11/2- t o 2-in. cakes. The filter press problem in connection with t h e process is not one of filtering area b u t cake capacity. Presses, as the Kelly or Sweetland, which are dumped mechanically, meet t h e conditions better t h a n plate presses. A new Sweetland press recently devised for this process promises t h e best results. I t is provided with bottom exits and t h e under bivalve swings through a n arc of 165‘. Alone1 metal filter cloth makes the machine practically permanent. By a slight increase in filter press capacity the output of a refinery may be doubled or even tripled. UTILIZATSON O F BY-PRODUCT
The cake may be converted directly into soap, the cellulose becoming very finely comminuted. It forms a n unobjectionable filler for some grades of soap, especially soap powders. The cake may he “ c u t ” with acid directly. The cellulose settles quickly in the aqueous layer from t h e black oils, which latter may be drawn off ready for market or use. When t h e cake is t o be converted into black grease, I use anhydrous sodium sulfate “salt cake” in place of soda ash as t h e “agglomerator.” Printed instructions for t h e use of
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
Feb., 1916
the method as a n analytical procedure or working t h e process on a commercial scale may be had on application t o t h e author. COLLEGEOF THE CITY OF NEW YORK
B y J. W. MARDEN Received September 10, 1915 INTRODUCTORY AND HISTORICAL
According to Hehner and Mitchel1,l “the action of bromine upon unsaturated bodies is instantaneous and is attended with a considerable evolution of heat. It is complete a n d quantitative. * * * It is not complicated t o a n y extent by secondary reactions. T h e amount of hydrogen bromide formed measures the substitution, and is very small in most cases.” HehneP found this value, when a number of fats and oils were mixed with bromine, t o be as follows: FATOR OIL
Olive 1.5 t o 2 . 7
Per cent free H B r . .
must be determined, of course, with each individual apparatus, because of its heat capacity. Wileyl has proposed a more convenient method of TABLE 11-RESULTS
THE THERMAL VALUES OF THE FATS AND OILS I-THE HEAT OF BROMINATION
Castor 2.7
Boiled Butter Linseed 0.9 8.8
I21
WILSON (HEHNER-MITCHELL METHOD) IODINE NUMBER DEVIATION Rise in Experi- CacluOIL OR FAT temperature mental lated Absolute Per cent Cocoanut.. 1.4O C. 8.4 8.2 -0.2 -2.4 S. A. Tallow.. 7.3 44.0 43.2 -0.8 -1.8 Olive, pure.. . . . . . . . . . 14.0 82.0 82.5 0.5 0.6 Rape . . . . . . . . . . . . . . . . 1 8 . 0 103.4 104.5 -1.1 -1.06 BY
...........
........
handling t h e oil and bromine which he uses in somewhat t h e same way as Hehner a n d Mitchell. Table I1 gives a few of t h e results obtainedby Wilson,2 using the original Hehner a n d Mitchell method, which show very good agreement between t h e calculated value and t h e iodine number found by analysis. The work of Jenkins3 does not show such good concordance when a n a t t e m p t is made t o obtain t h e iodine number from t h e temperature rise by multiplication with a factor. TABLE111-RESULTS BY JENKINS IODINE NUMBER DEVIATION Exoeri- CalcuOIL mental lated Absolute Per cent ~Blown R a p e . . . . . . . . . . . . . . . . . . 5 5 . 3 54.1 18.8 34.0 Blown Cottonseed . . . . . . . . . . . . 78.1 62.2 15.9 25.6 72.4 71.6 Neat’s F o o t . . . . . . . . . . . . . . . . . . 0.8 1.1 80.1 Olive ........................ 1.4 1.7 81.5 - 0.36 84.1 Castor. ...................... 0.3 83.8 133.4 Japanese W o o d . . . . . . . . . . . . . . . 165.7 -19.5 -32.3 Raw Linseed. . . . . . . . . . . . . . . . . 174.3 - 0.04 - 0.02 173.9 ~
ore recently by McIlhiney’s m e t h ~ d however, ,~ t h a t there are a few fats and oils where t h e substitution is very large. Hehner and Mitchell also showed t h a t each oil, when treated with a n excess of bromine, gave a characteristic temperature rise and t h a t t h e quantitative d a t a obtained by this temperature change, when t h e fats and oils were mixed with bromine in a suitable tube, furnished more reliable d a t a on their purity t h a n t h e Maumen6 sulfuric acid test. They expressed t h e opinion t h a t a method worked out on this basis could well replace t h e longer method for t h e iodine number as a test for t h e purity of a fat or oil. I n their method I gram of oil, dissolved in I O cc. of chloroform, is placed in a Dewar vacuum test t u b e and exactly I cc. of bromine, previously brought to t h e same temperature as t h e oil solution, is added. The rise in temperature is measured by a n accurate thermometer graduated t o one-fifth of one degree. A test tube packed in cotton was first used b u t later replaced by a Dewar tube. As one would expect, t h e test tube packed in cotton gives lower results. The whole operation takes only a few minutes. Table I gives t h e results obtained b y Hehner a n d TABLEI-RESULTS OIL OR FAT Lard
HEHNER AND MITCHELL(a) IODINE NUMBER DEVIATION Rise in Experi- Calcutemperature mental lated Absolute Per ceht 10.6’ C. 57.15 58.3 1.15 2.0 - 2.1 37.07 36.3 --0.77 96.64 96.68 0.04 0.04 80.76 82.50 1.74 2.1 122.0 118.2 3.80 - 3 . 2 107.13 106.7 0.43 - 0 . 4 83.77 82.5 1.27 - 1.5 160.7 167.2 6.5 3.9 8 8 . 3 3 101.2 12.87 12.7 77.2 96.8 19.6 20.0 144.03 140.0 - 4 . 0 3 - 3 . 8 oyiltsch’s “Chemical Technology and es, Vol. I , Macmillan & Co. (1909). BY
.................
Olive. . . . . . . . Maize. ........... Cottonseed. . . . . . .
Cod Liver.
...
-
Mitchell. The rise in temperature due t o t h e bromination of each oil multiplied b y t h e factor 5.5 very nearly gives t h e same value for t h e iodine number as Hehner a n d Mitchell obtained experimentally. The factor 1 2
*
Hehner and Mitchell, Analyst. 1896, p. 148. Hehner, Analyst, 1896, pp. 20, 49. McIlhiney, J. A m . Chcm. Soc., 2 1 (1899). 1084.
-
Since there are many discrepancies between t h e two iodine values, i t is suggested4 t h a t each individual oil be given a constant t o suit t h e apparatus in which t h e work is done. This would, of course, make this method too cumbersome for practical use in replacing the method for t h e determination of the Hub1 iodine number. Gill and Hatch’ have tried the method with about t h e same degree of success. More recently SteipeP has published several contributions on t h e determination of t h e iodine number of t h e fats and oils by means of t h e bromine thermal test. He has repeated practically all of t h e previous work a n d his results agree well with former determinations. He finds t h a t he is unable t o calculate t h e iodine number from t h e bromine thermal value with accuracy but t h a t he must have a constant for each individual oil and each apparatus. An a t t e m p t has been made also t o throw some light on t h e structure of certain unsaturated compounds when they combine with bromine. Louguinene and Koblultoff’ have measured the heat produced when various compounds dissolved in carbon tetrachloride react with bromine, alsodissolved in carbon tetrachloride. They found t h a t t h e heat of solution of most fats and oils in carbon tetrachloride is very small a n d t h a t the heat produced per gram molecule of bromine, when accurately determined, varies considerably with each individual compound. I n spite of these tests, however, there has been no technical attempt t o measure the heat of bromination of t h e fats and oils by a rapid calorimetric method and t o p u t this de1
J A m . Chem. Soc., 18 (1896), 378.
a
Chem. News, 1896, p. 87.
8
J. SOC.Chem. Ind.,
16 (1897), 194.
‘ Archbutt, J. SOC.Chem. Ind., 189’7, p. 310. J . Am. Chem. SOC.,2 1 (1899), 27. OSteipel, Seifenfabrikant, 8 1 (1911), 349, 393, 421, 445, 473, 501, 525. Louguinene and Koblukoff, J . Chem. Phys.. 4 (1906), 209 and 489; 6 (1907), 186; Comfit. rend., 160 (1910). 915. 6
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