The Incomplete Hydrogenation of Cottonseed Oil. - Industrial

Hugh K. Moore, G. A. Richter, and W. B. Van. Arsdel. Ind. Eng. Chem. , 1917, 9 (5), pp 451–462. DOI: 10.1021/ie50089a009. Publication Date: May 1917...
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May, 1917

T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C 3 E V I S T R Y

I

451

ORIGINAL PAPERS

THE INCOMPLETE HYDROGENATION OF COTTONSEED OIL B y HUGHK. MOORE.G. A. RICHTER AND W. B. VANARSDEL

cottonseed oil. During t h e experimentation other oils have yielded very similar results although no complete series of results is as yet ready for publication.

Received April 12, 1917

The hardening of liquid oils by means of the addition of hydrogen is a process of vital importance. Hardened fats are employed in t h e manufacture of lard substitutes, artificial waxes, confectionery, butters, lubricants, candle material a n d soap. The present outlook for still wider fields of application lends great significance t o any new d a t a or results achieved b y investigation. The purpose of this article is t o publish certain interesting experimental results obtained during a n investigation on t h e hydrogenation of vegetable oils. This investigation is still under way a t t h e Research Laboratory of t h e Berlin Mills Company a n d more complete a n d detailed results will be presented in book form in the near future. Most of t h e references on catalytic hydrogenation which are obtainable a t present, deal either with t h e purely theoretical phase of t h e reaction or with a rather superficial description of patent literature. Sabatier and his co-workers carried out a splendid research, demonstrating t h e theoretical possibilities in t h e field of hydrogenating organic compounds. Their work, however, was confined primarily t o reactions involving single organic compounds. The modern problem of hardening oils is concerned with materials which consist of a number of unsaturated compounds, each one of which must be considered in the catalysis. The greater t h e number of unsaturated components present, t h e more difficult becomes the problem of studying t h e course of t h e reaction. Previous investigators have avoided this complication by combining t h e unsaturated components as one whole and measuring t h e course of hydrogenation by iodine number determination or hydrogen absorption. Such a method does not give much information regarding the changes actually occurring in t h e oil. Xormann, Ipatiew, Bomer, Fokin’ and others neglect entirely t h e possibility t h a t , depending on t h e conditions of the operation, the glyceride components of a partially hydrogenated oil may differ materially from those of a second partially hydrogenated product which is obtained from t h e same original oil a n d reduced t o t h e same iodine number. Other investigators have likewise measured the hydrogenation by considering t h e unsaturated components as a whole rather t h a n as individual units. The object of our investigation was t o s t u d y the physical a n d chemical changes which take place in an oil during t h e process of hydrogenation and t h e work was limited chiefly t o partially hydrogenated products. The only oil used in obtaining data for this article was 1 Wm. Normann, British Patent KO.1515, 1903, LePrince (%) Sieveke, German Patent h’o. 141,029, 1902; S. Fokin, J . Russ. Phys.-Chem. SOC.. 38 (1906), 419-446; 38 (1916). 855-858; 39 (1907), 607-609; 40 (1908), 304-321; Z . angew. Chem., 2 2 , 1451-9, 1492-1502; Ipatiew, .I. Russ. Phys.Chem. SOC.,40 (1908). 1-60; Bbmer, Z . Nahr. Genussm., 24, 104-113.

SCOPE O F W O R K

Our work has led in several different directions in the general field of oil hydrogenation, so t h a t the results t o be reported may be conveniently grouped in five sections, which may be briefly described as follows: I-Changes in t h e amount and character of t h e various f a t t y glycerides of oils during t h e course of hydrogenation, especially as affected by experimentally variable factors such as temperature, pressure, etc. 11-Changes in t h e chemical characteristics of t h e oil (especially its iodine number) during hydrogenation. 111-Changes in t h e physical characteristics of the oil (e. g., titer and melting point) during hydrogenation. IV-Other changes in properties due t o hydrogenation, such as response t o Halphen test. V-The preparation of catalyzers, and their resistence t o poisons. X E T H O D S OF S T U D Y

The methods of study were in part the analytical procedures in common use for t h e investigation of oils and fats, b u t other useful lines of approach were developed in this laboratory with a special view t o t h e nature of t h e work in hand. Such, for instance, is t h e graphical method of following compositions described in a later paragraph. I-PHYSICAL

CONSTANTS

The physical constants occurring in our work, viz., melting point and titer, were determined by methods in common use. Titer, especially, is a well-defined and standard determination much used in t h e soap, candle and lard-compound industries; briefly, it is the solidification point of the f a t t y acids liberated from a n oil by saponification, or t h e temperature a t which t h e heat of crystallization of these acids balances radiation loss during solidification. The Official Method‘ was followed, using t h e modern glycerol saponification. Melting point, as is well known,2 is a very indefinite “constantJJJwhose value is greatly affected by slight changes in manipulation, and for which there does not exist, as yet, a well-defined, standard method. We have adopted for t h e greater part of our work t h e “open capillary” method mentioned briefly in Lewkowitsch3 and used as a practical test by a large proportion of t h e industries handling solid fats. According t o this method, which must be quite rigidly 1 J . Assoc. Oficial Agr. Chemists, No. 3 , 2 (1916). 304. 2 “Chemical Technology of Oils, Fats and Waxes,” 5th Ed., Lewkowitsch. 1, p. 315. 1 Ibid., 1, p. 318.

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T H E J O G R X A L O F IrVDUSTRIAL A N D E X G I S E E R I - V G C H E M I S T R Y

standardized for results of a n y value,‘ t h e melting point is t h e temperature a t which a column of fat, chilled in a capillary t u b e a n d immersed in water which is slowly heated, softens sufficiently t o be started upward in t h e t u b e due t o t h e hydrostatic pressure of t h e water. 2-CHEMICAL

COKSTANTS

Some of t h e chemical constants are as standard as t h e titer; for instance saponification value a n d acid value2 which indicate t h e amount of alkali which will combine with a f a t or f a t t y acid, a n d hence give indirectly t h e molecular weight of t h e f a t or acid. Others, however, are not so fully standardized-for instance t h e iodine number of t h e fat and of t h e liquid f a t t y acids-so t h a t there is not only some leeway in choice of method, b u t there is even opportunity for improvement through certain modifications. For determining t h e iodine number, which is intended t o represent t h e degree of unsaturation of t h e oil Oi acid as a whole in terms of t h e percentage of iodine which it will absorb under specified conditions, three iodine solutions are in fairly common use, a n d t h e details of manipulation are different for each one; more t h a n t h a t , t h e results are not identical within several per cent. For convenience of manipulation a n d general reliability we have chosen t h e Hanus method3 which we have found t o compare as follows with t h e Hub1 method in t h e case of several different fats and f a t t y acids: HANUS SUBSTANCR IODINBNo. Fat No. 1 . . 65.1 Fat No. 2 . . . . . . . . . . . . . . . . 86.2 Oil No. 3 . . 106.2 Fatty Acid No. 1 . . 102.5 Fatty Acid No. 2 . . 121.6

..............

............... ........ ........

HOBL IODINENo. 67.3 87.8 107.7 104.5 123.6

According t o Meigen a n d Winogradoff t h e iodine number cannot be used for t h e purpose of calculating t h e degree of unsaturation directly because either a n appreciable amount of substitution takes place in t h e saturated part of t h e molecule, or if this is guarded against t h e addition of halogen t o t h e unsaturated p a r t is incomplete; McIlhiney6 proposes t o determine t h e s u m of addition a n d substitution separately, arriving at t h e t r u e addition by difference. Investigation showed t h e addition value so obtained t o be always somewhat higher t h a n t h e result of t h e Hanus method, especially in t h e case of f a t t y acids, but t h e difference was not sufficiently significant to 1 The procedure followed in this laboratory is as follows: thin-walled glass tubes of inside diameter between 0.09 and 0.11 in. are cut to about &in. lengths. With the finger over one end of the tube, the other end is inserted in the melted fat (about 60’ C.) and a plug of the liquid from 1.25 to 1.50 in. long is withdrawn in the tube. A small drop is allowed to collect on the lower end, and the fat is then chilled in the tube in an ice-water bath for thirty minutes. The outside and lower end are then wiped free of excess fat, The melting-point apparatus is a 500 cc. beaker, with a stirring device and separate support for the glass tubes and thermometer. Air-free water (about 400 cc.) is put in the beaker, the tubes are placed vertically in it with the upper surface of the plug of fat just one inch below the water level, and heat is applied to raise the temperature 3 t o 4’ F . per minute. The melting point is taken as that temperature at which the plug of fat just starts to slip up the tube. This procedure gives results which are from 1 to l o o C. lower than those of the “closed capillary” method and 2 to 4O C. lower than those of the Wiley method, both given in J. A . 0. A . C., 2 (1916), No. 3, 301-302. 2 J . A . 0. A . c., a (igi6), NO. 3 , 306. 8 Ibid., 304. 4 Z. angew. Chem., 1914, Aufsatzteil, 241. 6 “Chemical Technology of Oils, Fats and Waxes,” Lewkowitsch. 1, p. 394.

V O ~9. , NO. j

warrant t h e extra labor and complication; for present purposes comparative results, given by t h e simpler methods, are quite as interesting as absolute results. For a more thoroughgoing s t u d y of t h e nature of or changes i n oils, it is necessary t o use other methods t h a n those outlined above; for instance, some of t h e many components may be separated from t h e mixture and then studied separately by t h e known methods. Many such methods of separation have been proposed, b u t t h e only one t h a t has proved t o be of any great value is t h a t known as t h e Gusserow-Varrentrapp leadsalt-ether method, which has been variously modified b y Muter, Lane, Tortelli a n d Ruggieri, and many others, and which is in principle a separation of two groups of lead salts of f a t t y acids based on t h e difference in solubility of t h e two groups in ethyl ether. For convenience t h e acids of t h e soluble group are called liquid f a t t y acids, t h e insoluble ones solid f a t t y acids. The detailed procedure of t h e separation is not b y a n y means agreed upon, five different sets of directions being given by as many different texts on oil analysis; t h e variation arises partly from t h e fact t h a t not all investigators have made this separation with t h e same purpose in view. An a t t e m p t may either be made t o separate t h e groups compIeteIy a n d quantitatively from one another, or else a “sample” of t h e liquid acids may be isolated, in relatively small amount, but quite free of contamination with acids of t h e other group. The latter course, which we have thought preferable, has been fairly well mapped out b y Tortelli a n d Ruggieri’ a n d others. The sample of liquid acids which results from t h e separation is examined by t h e usual methods, iodine number a n d acid value being especially important. The detailed procedure for separating a sample of liquid f a t t y acids is as follows: METHOD-weigh Out 2 0 g. Of the fat into a 300 CC. Erlenmeyer flask. Add 180 cc. of alcoholic potash (40 g. KOH per liter of ethyl alcohol which has been digested with NaOH and redistilled) and boil until completely saponified, then until three-fourths of the alcohol is gone. Add 100 cc. water, and neutralize with glacial acetic acid, using phenolphthalein as an indicator; come back to end-point with N / z NaOH solution. Measure out into a 500 or 600-cc. Erlenmeyer flask I Z O cc. of 20 per cent lead acetate solution and IOO cc. of distilled water, and bring to boiling. If the neutralized soap solution has by this time crystallized out, warm the flask until contents are liquid, then add carefully to the boiling lead acetate solution; after boiling cautiously for about two minutes, remove the flask from source of heat and when cooled to a safe temperature cool in running water. Prepare a 4-in. funnel with 25 cm. paper and pour the liquid contents of the flask into the filter paper; when the liquid has run out of the filter paper, wash the flask twice with 50 cc. each time of distilled water, filtering the washings, then twice with 2 5 cc. each time of 95 per cent alcohol, filtering the washings and taking care to wash the sides of the paper with alcohol. When the alcohol has entirely drained from the funnel, dry the filter paper free from alcohol and return the loosely adhering precipitate to the flask, which has been allowed to drain free from alcohol for I O minutes. Add 2 2 0 cc. of ether (prepared by washing U. S . P. ether five times with I O per cent portions of distilled water, drying with calcium chloride, and distilling). 1

Lewkowitsch, 1, p. 549.

M a y , 1917

T H E JOt‘RNrlL

OF I N D U S T R I A L A.VD E N G I N E E R I N G C I S E M I S T R Y

Boil the ether and lead soaps under a reflux condenser for one hour. After cooling, cork well and allow to stand from 16 to 18 hours a t a temperature of 7 to IO’ C. At the end of this time, filter off the insoluble soaps in a 4-in. water-jacketed funnel kept covered with a watch-glass. Wash the flask and soaps once with 2 5 cc. of cold ether, and add washings to filtrate. Pour this ether solution of soluble soap into 150 cc. of a hydrochloric acid solution (made by adding one part of concentrated hydrochloric acid, sp. gr. 1.2, to 4 parts of water) in a 500-cc. separatory funnel. Cork the separatory funnel and shake until the ether layer becomes practically clear and colorless. If the first treatment does not accomplish this result, repeat the washing with acid. Draw off the acid solution containing the lead chloride, and wash the ether first with 100-cc. portions of sodium chloride solution (125 g. per liter), then with 100-cc. portions of distilled water, until 3 drops of N / z alkali will neutralize the last washing using phenolphthalein. Separate the water layer as completely as possible, and pour the ether solution of liquid fatty acids into a clean flask. Place the flask in a water bath and connect it with a hydrogen generator and a condenser. Pass a gentle stream of dry hydrogen, free from oxygen, below the surface of the solution, and distil off the ether. Finally, boil the water bath until no odor of ether can be detected in the liquid fatty acids. Cool the acids, filter through a j l / z cm. paper in an atmosphere of dry hydrogen, free from oxygen, and dry by exposing the liquid fatty acids in a Petri dish over concentrated sulfuric acid in an atmosphere of hydrogen for 24 hours. Determine the iodine number of the acids with as little delay as possible. REMARKS-Early in our study persistent failure to obtain consistent results on duplicate separations impressed us with the importance of some apparently small details, and as a final conclusion we adopted the following precautions, which are embodied in the above method: ( I ) The alcohol used in saponification should be purified by treatment with caustic alkali and by redistillation. ( 2 ) The washed cake of lead salts should be freed as completely as possible from adhering water or alcohol, so that the purity of the ether used for the separation will not be lowered. (3) Commercial “anesthesia” ether should be purified of all but traces of alcohol and water by washing with water and drying with calcium chloride, since its solvent action is considerably modified by the presence of either impurity. Treatment with metallic sodium is, however, unnecessary. (4) In order to secure uniform treatment of the cake of lead salts, it should be boiled for one hour with the ether, although in many cases it will be completely disintegrated in less time. (5) The lead salt-ether mixture should be held a t a definite temperature for a definite length of time so that crystallization of the solid salts will take place under uniform conditions and to a uniform extent. The temperature should be quite low and the duration fairly long, so that the solids will separate as completely as possible. A tolerance of 3’ C. in temperature (7 to Ioo) and two hours in time (16-18) has been found reasonable. ( 6 ) The contents of the funnel should be kept cool during filtration of the insoluble lead salts from the ether solution, since an appreciable amount of the solids will redissolve if the temperature is allowed t o rise more than a few degrees. (7) The solid salts should not be thoroughly washed with ether, since such washing would increase the relative amount of solids carried into the ether-soluble portion. One small portion of ether is used, however, the object being to displace some of the solution left adherent t o the solid, and thus increase the yield of liquid acids, rather than to wash the solid portion free from liquid salts. As a matter of fact, the acids liberated from the solid portion washed in this manner are found to have an iodine number ranging from 2 0 to 30, instead of zero.

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(8) The operations subsequent to liberation of the acids in ether solution should be carried out in an indifferent atmosphere, preferably hydrogen, since the usual products contain notable quantities of linolic acid, easily oxidized by the air a t room temperature. (9) The isolated liquid acids should be filtered, to separate droplets of water, and then dried in a sulfuric acid desiccator, since small amounts of moisture affect the iodine number determination greatly. ( I O ) The liquid acids should be examined without undue delay, to minimize the effects of oxidation.

T h e liquid f a t t y acid separation has been used with a considerable degree of success a n d certainty; i t is usually possible t o check duplicate determinations within I o r 2 per cent, and different laboratories have agreed almost as closely. The chief limitation is imposed b y t h e decrease in amount of liquid acids present as a n oil approaches saturation ; t h e relative amount of contamination of t h e isolated liquid acids with solid acids becomes finally quite large, so t h a t t h e practical limit t o t h e method is found t o have been reached b y t h e time t h e iodine number has dropped t o jo or 40; its field of greatest usefulness, therefore, is in t h e examination of oils a n d semi-solid fats-the materials with which this paper is especially concerned. If a f a t which is too hard t o be analyzed directly (below iodine number 40-50) is mixed with a n appropriate amount of a n oil whose liquid f a t t y acids have already been examined, t h e mixture may be analyzed a n d from t h e result t h e composition of t h e hard f a t may be calculated. T h e iodine number of liquid f a t t y acids thus calculated is always somewhat higher t h a n t h a t found by direct analysis of t h e fat itself, as would be expected. This procedure we have followed in several cases, with promising results, a n d further work is under way. The chief drawback of t h e method is t h e very considerable loss in accuracy which i t entails. GLYCERIDES O F COTTONSEED O I L

3-THE

Investigation of cottonseed-oil acids has shown in t h e hands of several investigators’ t h a t t h e unsaturated acids present are oleic a n d linolic acids, practically t o t h e exclusion of all others a n d further, t h a t these two are the components of t h e “liquid f a t t y acids.” Our own work, which is not reported in this article, confirms this conclusion. Oleic acid, C17H33COOH, contains one double bond, linolic acid, C17H3,COOH, two double bonds; since each one of these substances has a definite known (calculated, not experimental) iodine number, t h e iodine number of t h e liquid f a t t y acid mixture affords a means of determining t h e percentages of each in t h e mixture, according t o t h e well-known formula : 2 ?O.Oj x 181.42 (100 - X ) = 100 B . . . .(I) where x is t h e percentage oleic acid, B t h e iodine number of t h e mixture, and 90.07 a n d 181.42 t h e iodine number of oleics a n d linolic acids,3 respectively.

+

1

“Chemical Technology of Oils, Fats and Waxes,” Lewkowitsch, I,

pp. 188-190, 197-199; Twitchell, THISJOURNAL, 6 (1914). 564.

I b i d . , 1, p. 563. I b i d . , 1, p. 406. Calculation of these values from the most recent atomic weights give the following values, however: Triolein E 86.03; Oleic acid = 89.89; Trilinolin = 173.26; Linolic acid = 181.09. The percentage difference from the figures given in Lewkowitsch is not significant. 4

3

T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y

454

It has been known for some time t h a t oleic, linolic, palmitic a n d t h e other “fatty” acids do not occur in natural oils a n d f a t s wholly combined in t h e form of simple triglycerides-esters in which all three of t h e glyceryl bonds hold t h e same kind of acid radical, as in tripalmitin, trilinolin, triolein, etc.-but are t o a large extent combined in the “mixed” glycerides, such as palmito-diolein. At present there is no satisfactory method available for t h e study or estimation of t h e mixed glycerides, of which a very large number may exist; valuable information may be obtained, however, if t h e problem is simplified by assuming t h e oil t o be a mixture of simple glycerides. Under t h a t assumption, for instance, three mols of palmitodiolein might be considered a mixture of one mol of tripalmitin with two mols of triolein; or t h e combination of one-third of a glyceryl radical with one acid radical might be taken as a unit, such units being called simply “palmitin,” “olein,” etc. This method of study finds many precedents in other fields of chemistry . Cottonseed oil, then, may be said t o contain “linolin” a n d “olein” as its unsaturated constituents, a n d because of molecular weight relations they are present in t h e same relative proportions (within a few hundredths of I per cent) as are t h e linolic and oleic acids in t h e liquid acids. Linolin and olein have definite iodine numbers-1 73.6, a n d 86.2, respectively’-so t h a t it is possible t o calculate what iodine number t h e “liquid glycerides” of t h e oil would have if they were unmixed with other substances; this iodine number is always higher t h a n the actual iodine number of t h e oil, which is reduced in proportion to the amount of saturated material present, irrespective of t h e molecular weight of t h e latter material. The data are all available, therefore, for calculating t h e actual percentages of olein, linolin, a n d saturated material, given only t h e iodine numbers of the oil a n d of t h e liquid f a t t y acids obtained from it. A simple algebraic process reduces this work t o t h e following three equations :

-

Per cent Saturated Glycerides = 100-104.5 A / B . . . . . . . . . . . . . . Per cent Olein 207.6 A / B 1.144 A , . ..................... Per cent Linolin = 100- (yoSat. Glyc. % ’ Olein).

-

+

...........

necessary condition is t h a t t h e unsaturated glycerides should be olein and linolin. Other unsaturated bodies, if present, would introduce a certain error, since the iodine numbers would differ from those used in the calculation. 4-GRAPHICAL

REPRESENTATION

An oil or f a t of the nature of hydrogenated cottonseed oil may therefore be studied as a three-component system, counting the saturated glycerides together as one component; a n d t h e convenience of graphical methods is available through t h e use of Roozeboom’s triangular diagram. This diagram, well known in work with alloys, slags, ceramics, etc.,’ is so constructed t h a t one, and only one, point on t h e equilateral FIG. I triangle represents any possible mixture of t h e three components. The diagram is drawn as in Fig. I , where P is any point within t h e triangle, A B C , P D is parallel t o A C , PF t o E C BC and P E t o A B . I t follows in a simple manner t h a t BE CF A D = BC, a constant. When each side is divided into IOO parts it is obvious t h a t B E represents the percentage of one component in the mixture represented by P , C F is t h e percentage of a second component, and A D is t h e third, and t h e sum of these three percentages is 100. I t has been our custom t o measure saturated glycerides as B E , linolin as CF and olein as A D , so t h a t point C represents pure saturated glyceride, A pure linolin and B pure

A

+

+

(2) (3)

(4)

in which A is t h e iodine number of t h e f a t and B t h e iodine number of t h e liquid f a t t y acids. I t will be noted in t h e above paragraph t h a t all substances having zero iodine number have been grouped together as “saturated glycerides.” I n t h e case of cottonseed oil this material is nearly all palmitin and in hydrogenated cottonseed oil i t is a mixture of palmitin and stearin (the latter derived from t h e olein a n d linolin by hydrogenation) ; t h e relative proportions are not especially important in t h e present work.2 I n other oils a n d fats different saturated glycerides may be found, but they do not affect t h e calculation; t h e 1

Vol. 9, No. 5

“Chemical Technology of Oils, Fats and Waxes,” Lewkowitsch, 1, P.

406. 2 Dr. W. D. Richardson, of Swift & Co., Chicago, has suggested to us that the proportions of palmitin and stearin in the saturated glycerides may be calculated from the neutralization value of the solid fatty acids liberated from the insoluble lead soaps, making correction for the unsaturated acids remaining in the mixture. By this method he has found a sample of cottonseed oil to contain 2.0 per cent stearin and 22.9 per cent palmitin.

0

shr-r-nd

G1~ur.L-

olein. The following typical examples may be given t o illustrate t h e method, t h e figures being first summarized in t h e table, a n d then plotted on t h e diagram as shown in Fig. 2 . 2 Evidently t h e tendency is for liquid oils t o appear near t h e left-hand side of t h e triangle, solid and semi1 Triangular-ruled paper may be purchased from dealers in draftsmen’s supplies. 2 For obvious reasons we have refrained from including in this l&t any of the trade-marked fats now on the market.

M a y , 1917

T H E JOL7RS.-1L O F I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y

solid fats being shifted toward t h e opposite vertex. Any oil when completely hydrogenated would obviously end u p at t h a t vertex (saturated glycerides)

45s

oil, of iodine number 110.9 and of iodine number of liquid f a t t y acids 149.5 is found graphically t o have t h e same proportion of components as was calculated in Table I. EXPERIMEKTAL PART

t h e experimental work two types of hydrogenation apparatus have been used: ( I ) a simple glass flask heated b y a n oil-bath a n d containing t h e oil-catalyzer mixture, through which hydrogen is bubbled vigorously, a n d ( 2 ) a n iron container, electrically heated, i n which t h e oil-catalyzer mixture is mechanically agitated with hydrogen. T h a t is, all of t h e work herein reported refers particularly t o t h e “batch” processes, in which a given quantity of oil is gradually hardened, b u t we believe our conclusions also apply i n principle t o t h e more complicated continuous processes. I n t h e first apparatus t h e procedure was t o weigh in t h e desired amounts of oil a n d catalyzer, heat t o t h e desired temperature, a n d t h e n s t a r t bubbling t h e hydrogen vigorously. T h e hydrogen was taken from I. 0. C. cylinders a n d was not purified. Its volume was regulated b y means of a small constant-speed blower a n d a gasometer. I n t h e other apparatus t h e oil was brought u p t o temperature in a n atmosphere of hydrogen, t h e catalyzer was added, air again driven out with hydrogen, a n d finally agitation started. I n either case samples were taken at intervals, t h e catalyzer was filtered out, a n d t h e desired tests made. Times were counted beginning a t t h e moment of starting agitation with hydrogen. GENERAL-FOr

b u t as t o t h e compositions it would pass through during t h e progress of saturation, represented graphically by a curve connecting t h e starting-point with t h e righthand vertex, there is no published information; with t h a t problem our experimental work is largely concerned. Certain properties of t h e triangular diagram are of great assistance in connection with t h e problem. I n t h e first place, all possible mixtures of two substances P a n d Q lie on t h e straight line PQ, which is divided in inverse proportion t o t h e amounts of P and Q mixed. I n consequence, all points of equal iodine number lie on a straight line, a n d likewise all points of equal iodine number of liquid f a t t y acids lie on a straight line. Lines of equal iodine number are found t o be parallel, all making a n angle of 90’ 14’ (on t h e lower TABLEI IODINE NUMBER Liquid Calculated Percentages Original Fatty Saturated No. MATERIAL Material Acid Glycerides Olein Linolin 1 Cottonseed oil.. . . . . . . . 110.7 149.5 22.6 26.9 50.5 2 Cottonseed stearine 86.0 149.8 40.0 20.5 39.5 3 Peanut oil 98.0 121.7 15.85 54.9 29.25 4 Corn oil 110.6 133.0 13.0 46.0 41.0 5 O l i v e o i l ............... 8 2 . 0 97.8 12.4 80.1 7.5 63.5 105.3 37.0 52.4 10.6 6 Leaf lard 7 Compound lard . . . . . . . . 97.0 143.3 29.3 29.1 41.6 8 A semi-solid hydrogenated cottonseed o i l . . , 63.0 101.0 34.75 57.2 8.05

..... ............. ............... ..............

side) with t h e right-hand side of t h e triangle; this differs so little from 90’ t h a t it can easily be estimated with t h e aid of a draftsman’s triangle. B y graduating t h e right-hand edge uniformly from zero t o 173.6 t h e line representing a n y given iodine number may be drawn on t h e triangle. Lines of equal iodine number of liquid f a t t y acids all pass through t h e right-hand vertex, hence if t h e opposite side of t h e triangle is graduated uniformly from 90.07 t o 181.4, a n y given iodine number of liquid f a t t y acids (provided t h e liquid acids contain oleic a n d linolic only) may be represented. Then b y drawing these two lines t h e position of a point on t h e triangle may be found graphically, given only t h e iodine number of t h e oil a n d of t h e liquid f a t t y acids, without making a n y numerical calculation. For instance in Fig. 3 cotton-

I-HYDROGENATION

CURVES

For t h e s t u d y of t h e glyceride changes during hydrogenation, t h e tests made on samples included iodine number a n d iodine number of liquid f a t t y acids, calculation giving t h e “component glycerides” (olein, linolin a n d saturated glycerides) of each sample. T h e smooth curves drawn through t h e points plotted on t h e triangular diagram always, in t h e cases studied, h a d t h e same general shape-suggestive of t h e hyperbola, concave toward t h e right-hand side of t h e triangle. T h e linolin is always found t o decrease from t h a t present in t h e original oil and t h e saturated glycerides always increase, while t h e olein rises t o a maximum a n d t h e n falls continuously. These changes are what would be expected, since hydrogenation must cause linolin t o disappear, forming olein, while olein, hydrogenating more slowly, would at first increase a n d t h e n eventually disappear forming stearin, a saturated glyceride. T h e shape of t h e curve depends upon t h e relative velocity of these two actions, a n d i t appears from our work t h a t this relative velocity must be subject t o important variation, according t o t h e experimental conditions. T h e actual experimental graph invariably crosses t h e base-line of t h e triangle before reaching t h e right-hand vertex, owing t o t h e limitations of t h e lead-salt-ether method below iodine number jo or 40; on this account we have not attempted t o secure results in t h e region of very hard fats a n d have made comparisons only in t h e region where t h e method gives trustworthy figures. The conditions which we have varied experimentally are, ( I ) temperature, ( 2 ) pressure, (3) amount of catalyzer,

456

T H E JOERLlrALOF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y

TABLE 11-TESTS FOR HYDROGENATION CCRVES Cottonseed Oil used in all cases with Nickel Catalyzer prepared as described under “Catalyzers,” page 32 Abbreviations: LFA, Liquid F a t t y t2cids; SG, Saturated Glycerides; 01, Olein; Lin, Linolin -EXPERIMENTAL CONDITIONS DURING RUNSAPPAPresCATAOIL SamIODINE No. PERCENTAGES Sam- IODINE No. RATUS RUNTemp. sure LYZER AGITATION USED ple F a t LFA SG 01 Lin ple Fat LFA Glass A 125; Atmos. No. 1 Bubbling . , , , A0 107.8 143.9 21.7 3 2 . 3 46.0 BO 107.8 143.9 B 200 Atmos. 3% X o . 1 Bubbling ,... 1 84.5 1 2 4 . 6 29.0 4 4 . 2 2 6 . 8 1 9 2 . 8 128.2 1 0 . 5 110.2 3 3 . 1 5 2 . 2 14.7 2 8 2 . 3 117.9 2 3 61.9103.4 37.5 5 3 . 1 9.4 3 6 8 . 5 101.1 4 4 5 . 8 87.7 46.9 53.1 . . , . Iron C 155; 201bs. 2% No. 1 135 R. P. M . .,, , CO 107.7 143.9 21.7 3 2 . 3 4 6 . 0 DO 107.7 143.9 D 155 40 lbs. 2% No. 1 135 R. P. M. ... . 1 79.7 108.7 2 3 . 4 6 0 . 7 15.1) 1 70.2 107.6 2 5 9 . 8 92.3 32.4 65.9 1.j 2 52.8 91.0 3 50.3 88.0 41.6 58.4 3 42.2 87.1 Iron E 1.55’ 20 lbs. 4% N-0. 1 135 R. P. M . EO 107.) 143.9 21.7 32.3 4k:O‘ FO 107.7 143.9 F 155’ 201bs. No, 1 2 5 0 R . P . M . ,... 1 77.2 112.0 27.9 5 4 . 4 17.7 1 8 7 . 3 120.4 2 57.6 92.4 34.8 63.3 1.9 2 71.2 108.5 3 42.9 86.4 50.3 49.i . . . . 3 59.’ 97.1 4 52.1 91.3 5 47.1 90.2 No. 2 Bubbling ,... GO 110,9149.1 22.4 27.2 5 0 . 4 HO 110.9 149.1 Glass G 160’ Atmos. H 160’ Atmos. No. 2 Grate doubled ., , . 1 88.4 125.A 26.2 4 5 . 3 28.5 1 74.9 126.9 2 79.6 118.3 29.8 48.2 22.0 2 71.5 124.9 3 75.0 113.3 30.8 51.4 17.8 3 6 6 . 8 119.3 4 71.7108.8 31.0 54.9 14.1 4 6 3 . 5 117.1 5 6 8 . 8 104.7 31.3 57.7 1 1 . 0 5 60.6 114.2 6 57.2 112.6 6 61.6 9 7 . 1 3 3 . 8 60.9 5.3 7 52.2 90.5 39.7 60.0 0.3 I 155O 401bs. 2% KO,1 135 R. P. M. 10 lbs. 10 108.4 142.8 2 0 . 6 33.5 4 5 . 9 JO 108.4 142.8 Iron J 155.. 401bs. 2% No. I, 135 R. P. M. 201bs. 1 97.4 130.6 22.1 4 3 . 4 3 4 . 5 1 77.1 110.5 (Run I in container 25 in. long and 12 in. in diameter) 2 78.9 112.6 2 6 . 8 5 5 . 1 18.1 3 6 6 . 8 101.3 31.2 6 0 . 3 8.5 63.7 ( R u n J i n container 40 in. long and 16 in. in diameter) 4 51.0 91.6 41.8 57.3 0.9 3 42.1 87.5

2%

(4) agitation, a n d ( j ) size of apparatus; these variations are noted in Table 11, along with t h e analytical results, a n d in Figs. 4 t o I O . TEMPERATURE-The ease with which these points, located in Fig. 4, fit smooth curves, such as those drawn, is one indication of t h e trustworthiness of t h e lead salt-ether method when used with care, a n d t h e fact t h a t t h e two curves differ by much more t h a n t h e deviation of a n y of t h e single points from its own curve is assurance t h a t t h e difference is not due t o freaks of analysis-the more so as all of t h e seven samples reported were analyzed a t once, and not in two groups. The result may be interpreted as follows: while both linolin and olein were hydrogenated faster a t t h e high temperature t h a n a t t h e low temperature, relatively linolin was hydrogenated much faster a t t h e high temperature, so t h a t t h e olein h a d a greater tendency t o accumulate under t h e latter conditions. I n other words, both unsaturated radicals are acted upon in both cases, b u t a t t h e higher temperature t h e more highly unsaturated one comes nearer t o being singled out for hydrogenation t h a n a t t h e lower temperaturet h e action is more “selective.” This would be t h e case i f , for instance, t h e temperature coefficient of t h e reaction linolin-olein is greater t h a n t h a t of t h e reaction olein-stearin, b u t in view of t h e complicated nature of t h e glycerides which are actually present t h a t explanation is doubtless too superficial t o be t h e entire truth. PRESSURE-The influence of t h e hydrogen pressure upon t h e course of t h e hydrogenation may be illust r a t e d b y Runs C a n d D (Fig. j ) which were both carried out in t h e apparatus with mechanical agitation. Increasing t h e pressure is here seen t o have t h e opposite effect t o increasing t h e temperature, so t h a t at a high pressure t h e action is less “selective” t h a n at a low pressure. An obvious corollary of this conclusion is t h a t i t would appear t o be possible t o duplicate a t high pressure a n d high temperature a curve obtained at low pressure a n d low temperature, while t h e reaction as a whole might be made t o proceed many times as fast in t h e former experiment as in t h e latter.

1-01. 9, NO.

j

PERCENTAOES SG 01 Lin 21.7 3 2 . 3 4 6 . 0 24.4 43.9 3 1 . 7 27.0 50.8 22.2 29.2 62.2 8.6 21.: 31.i

32.3 55.0

51.0 3 9.4 21.7 24.3 31.1 35.7 40.3 54.6 22.4 38.4 40.1 41.6 43.4 44.6 46.9

5 49.9 0 32.3 50.4 54.9 59.3 59.0 45.3 27.2 36.6 37.0 39.5 39.8

20.6 27.0 33.6 51.1

33.5 56.6 58.9 48.9

46.0 13.3

0.7 46.0 25.3 14.0 5.0 0.7 0.1 50.4 25.0 22.9 18.9 16.8 40.6 14.8 40.0 13.1 t...

45.9 16.4 7.5

....

I n this case again a tentative “mechanism” may be put forward. I t should first be noted t h a t t h e occasional hydrogenation of a linolin chain clear t o stearin instead of only t o olein would have t h e same apparent effect as would a n increase in t h e relative velocity of t h e olein-stearin reaction. Now if a n increase in hydrogen concentration a t t h e catalyzing surface (such as would be produced by increased pressure) caused a n increase in t h e number of linolin chains t o which four atoms of hydrogen were added a t once, t h e observed effect would follow. I N F L U E S C E O F P E R C E N T A G E O F CATALYZER-The influence of percentage of catalyzer was illustrated in Experiments C and E (Fig. 6 ) . In this case t h e observed result, which shows a divergence in t h e same direction for increased percentage of catalyzer as for increased pressure, seems t o be a t variance with what is commonly understood t o be a law of catalytic reactions, namely t h a t if t h e amount (or surface) of t h e catalyzer be increased, all of t h e reactions involved will be speeded up by exactly proportional amounts. I n this case, one reaction (olein-stearin) appears t o be accelerated more t h a n t h e other. The scheme advanced in t h e preceding section may be made t o give a satisfactory explanation; in t h a t section t h e concentration of hydrogen a t t h e catalyzing surface was taken t o be t h e controlling factor. Now increasing t h e percentage of catalyzer must increase this concentration, for t h e average distance between a catalyzer particle and t h e hydrogen bubble-surfaces is made smaller, thereby decreasing t h e lag between t h e “demand” for hydrogen a t t h e catalyzer surface, and t h e “supply,” which must be kept u p b y t h e processes of solution a n d diffusion. Thus a n increase in percentage of catalyzer would cause a n increase in t h e formation of stearin relative t o t h e change in linolin, as in t h e two curves reproduced above. AGITATION-The influence of degree of agitation on t h e p a t h of hydrogenation was determined first by comparing Experiments C a n d F (Fig. 7 ) , in which t h e iron apparatus, mechanical agitator, was used.

May, 1 9 1 7

T H E J O l R . V A L O F IAYDGSTRI.-I L A X D E-VGINEERIiVG C H E M I S T R Y

457

Percent Saturated Glycerides

I

F I G S . 4 TO

,

9-cHAhGES

IN

GLYCERIDES OF COTTONSEED OIL

“Degree of Agitation” is a magnitude which is not easily expressed in quantitative form, b u t the R . P. hl. of a n agitating device may serve as a n index of t h e agitation, as least for moderate speeds. A4notherpair of experiments carried out in t h e glass flask, bubbling hydrogen, conditions were identical in both experiments except t h a t in R u n H, t h e hydrogen was bubbled through t h e flask a t approximately twice t h e rate used in R u n G (Fig. 8). I n both pairs of experiments t h e influence of increased agitation is shown t o be t h e same as t h a t of increased pressure or per cent catalyzer, a n d in t h e case of Runs G and H t h e variation in t h e curves is striking. The effect of doubling t h e volume of gas supplied, when t h e bubbling is already vigorous, may well be t o increase t h e true “agitation” many times. On t h e other hand, doubling t h e R . P. M . of a mechanical agitator possibly does not even double t h e agitation, since a t high speeds there is a strong tendency for t h e whole body of oil t o rotate without much disturbance. I t may readily be seen t h a t t h e “mechanism” suggested in t h e preceding section applies t o t h e present case just as well, since t h e effect of increasing t h e agitation is t o increase t h e number a n d surface of hydrogen bubbles a n d also t o decrease their average distance from catalyzer particles. SIZE O F APPARATUS-The size of t h e apparatus in which t h e hydrogenation is carried out apparently does not affect t h e p a t h of t h e hydrogenation, as appears from t h e d a t a of Runs I and J (Fig. 9 ) . It is,

HYDROGENATION

DURIKG

of course. not certain t h a t 1 3 j R. P. h l . produces t h e same “degree of agitation” in both cases; if t h e agitation is really better a t this speed in t h e large machine, t h e effect of t h e increase in size on t h e p a t h of hydrogenation is in t h e opposite direction t o t h e effect of increased agitation. I S F L U E K C E O F MATERI.4L O F CATALYZER

When some other catalyst t h a n nickel is used, as in Experiment K , in which I per cent palladium (in PdC12, method of Paal patent’) acted as catalyzer (Table 111), t h e hydrogenation curve is found t o have TABLE111-EXPERIMENT Run Samule K 0 ........., , , , . 1

.............. ..............

2 3 ........ , . , , , . 4..............

WITH PALLADIUM A S CATALYZER (FIG. 10) IODINENUMBERPERCENTAGES CALCULATED Liquid Saturated Fat Fattv Acid Glycerides Olein Linolin 45.9 20.6 33.5 142.8 108.4 28.5 25.5 46.0 125.0 89.1 52.8 18.0 113.1 29.2 76.6 30.6 63.8 5.6 64.5 97.1 61.3 0.1 90.3 38.6 53.0

t h e same general characteristics as those described before (Fig. I O ) . Bubbling apparatus was used, a temperature of I j j O C. and atmospheric pressure. No experiment using nickel catalyzer is available t o compare directly with it. S U M U A R Y O F HYDROGEKATION CURVES

T o summarize t h e conclusions from t h e preceding experiments, i t appears t h a t t h e chemical character of a partially hydrogenated oil is determined b y t h e conditions of t h e hydrogenation. Thus t o obtain a product of t h e same iodine number as another, b u t 1 Carl Paal, U. S. Patent No. 1,023,753, April 16, 1912. amount of solid NarCOa is used as a neutralizing agent.

4 n equivalent

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

458

TABLEIV-CHANGES IN CHEMICALCONSTANTS CONDITIONS DURING RUNS-RUN It-. PresCATASam- -RUN IaRUN Temp. sure LYZER AGITATION ple Time I No. Time I N o . IO 155: 20lbs. 2% No. 1 135 R. P. M. 0 0:OO 107.7 0:OO 107.7 Ib 155 40 lbs. 2% No. 1 1 0 : 0 5 79.7 0 : 0 5 70.2 2 0:15 59.8 0:lO 5 2 . 8 3 0:25 50.3 0:15 42.2 4 0 . 3 5 41.4 0:20 34.9 5 0:45 3 7 . 0 ...... -RUN IC-RUN Id- -RUN IA -RUN Time I No. Time I No. Time I No. Time IC 35 Atmos. 5 % No. 1 Bubbling 0:oo 111.0 0 : o o 111.0 0:oo 111.0 0:oo d 87 Atmos. 5 % No. 1 Bubbling 13:40 101.1 2:35 93.2 1:40 9 0 . 3 0 . 1 5 Atmos. 5 % No. 1 Bubbling 125 27:OO 96.7 5 : 5 0 83.0 2 : 5 5 79.5 0:45 Atmos. 5 % No. 1 Bubbling 160‘ 10:30 68.0 4:lO 72.6 1:30 2000 Atmos. 5 7 No. 1 Bubbling h 12:25 62.4 6:lO 5 8 . 9 2:15 240 O Atmos. 5 % No. 1 Bubbling 18:55 53.7 3:15 2 5 : 5 5 40.5 -RUN Ii-RUN I+ Time I No. Time I No. Ii 150-160° Atmos. 5495No.2 Bubbling 0 0:OO 110.9 0:OO 110.0 j 150-16O0 Atmos. 54YONo.2 Rate>doubled 1 1:35 88.4 0 : 2 5 74.9 2 2;22 79.6 0:35 71.5 3 3:lO 75.0 0 : 5 0 66.8 4 3 : 5 8 71.7 1.05 63.5 5 5 : 0 0 68.8 1:20 6 0 . 6 6 6:35 66.5 1:35 6 0 . 6 7 12:OO 61.6 1:50 58.5 8 28:20 5 2 . 2 2 : 2 0 57.2 -RUN Ik-RUN 11-RUN Im--RuN Time I No. Time I No. Time I No. Time 15Jo 20 lbs. 2% No. 1 67 R. P. M. 12 in. diam. I k 0:OO 110.9 0:OO 110.9 0:OO 108.7 0:OO 12 in. diam. I 155O 20 lbs. 2% No. 1 135 R. P. M. 0:45 82.7 0:lO 9 5 . 3 0:04 101.3 0:05 12 in. diam. m 155O 20 lbs. 2% No. 1 270 R. P. M. l:oo 74.4 0 : 2 0 81.5 0:07 9 6 . 8 0:18 18 in. diam. n 155O 20 Ibs. 2% No. 1 270 R. P. M. 1:30 62.9 0:30 70.3 0:12 9 1 . 3 0:33 1:45 5 9 . 8 0:35 64.9 0:27 78.3 0:48 2:15 54.3 0:40 60.5 0:37 73.3 1:lO 0:45 5.46 1:17 56.0 1:35 1:57 50.0 1:55 -RUN Io-RUN I+ Time I No. Time I No. Io 155O 20lbs. 2% No. 1 135 R. P. M. 0 0:OO 107.7 0:OO 107.7 p 155O 20lbs. 4% No. 1 135 R. P. M. 1 0:05 79.7 0:04 77.2 2 0:15 59.8 0:08 57.6 3 0:25 50.3 0:12 42.9 4 0:35 41.4 5 0:45 37.0

Vol. 9, No.

-EXPERIMENTAL APPA-

RATVS

Iron

......

Glass

i

Glass

Iron 24 in. 24 in. 24 in. 40 in.

X X X X

...... .. .. .. .. .. .. ......

.. .. .. .. .. ..

Iron

........

If-

I No. 111.0 103.6 93.1 80.3 67.6 52.1

................

......

-RVN Ig- --RUN IhTime I No. Time I No. 0 : o o 111.0 0:OO 111.9 0:15 96.3 0:15 9 2 . 0 0 : 2 5 88.6 0 : 2 5 83.1 Or36 8 2 . 6 0:36 78.5 0:56 75.3 0:56 72.3 1:26 6 5 . 0 1:26 62.8 1 . 5 6 60.3 1:56 57.9

In-

I No. 108.4 98.0 79.9 64.0 56.4 50.2 44.1 40.0

.. .. .. .. .. ..

relatively higher in saturated glycerides a n d linolin, t h e operating conditions should compare as follows with those in t h e other case: temperature lower, pressure higher, agitation more violent and percentage catalyzer greater. It is interesting t o note t h a t it is possible t o hydrogenate t h e linolin t o olein with only t h e slightest increase in saturated glycerides by operating a t a high

IO

Lo

30

-

FIG IO-HYDROGENATIONCURVE:PALLADIUM CATALYZER

temperature, low pressure and low agitation, and using only a small amount of catalyzer. 11-CHANGES

I N CHEMICAL CONSTAKTS O F OIL DURING HYDROGENATION

Of all t h e “chemical constants” of cottonseed oil, t h e iodine number (with its variations, t h e “hydrogen number,” MaumCn6 number and heat of bromination), is t h e only one which is changed markedly by hydrogenation, Saponification value, acetyl value, Reichert-

Meissl number a n d percentage of free f a t t y acids change either not a t all; or only slightly. It is evident t h a t t h e saponification value could could not be expected t o change greatly, for t h e molecular weight of t h e mixture of stearin a n d palmitin corresponding t o completely hydrogenated cottonseed oil is 873, while t h a t of t h e original oil is about 865, a difference of less t h a n I per cent. It is worth noting here t h a t this I per cent represents all t h e hydrogen t h a t is necessary t o saturate t h e oil completely, a fact which partly accounts for t h e commercial attractiveness of t h e process. T h e drop in iodine number, however, is one of t h e most striking effects of hydrogenation, a n d it has been commonly used in t h e past t o indicate the progress of the reaction.lv2 Fokin concludes, from a study of t h e hydrogen absorption, t h a t “the reduction procedure is included in the category of monomolecular reactions,” but notices t h a t the cur\-es “often show a straightening out toward the abscissa axis.’’ He comes t o the conclusion t h a t the conditions which determine the shape of t h e curve are: ( a ) t h e velocity of diffusion of the gas (presumably through t h e oil); ( b ) the condition of t h e catalyzing surface; and (c) t h e presence of catalyzer poisons. Very similar conclusions were published recently by B ~ e s e k e n ,b~u t most of his work was on organic compounds of lower 1 Paal-Roth, B e y . , 41, pp. 2282-2291; Fokin, Z. angew. Chem.. a% 1451-9, 1492-1502; B6mer. Z. Nahr. Genussnz., 24, 1 0 4 1 13. 2 Paal and his co-workers, and Fokin recorded the volume of hydrogen absorbed a t various stages of the process, thereby determining directly t h e amount of saturation which bad taken place, instead of indirectly by means of the iodine number. a Rcc. fraw. chim., 36 (1916), 260-287.

May, 1917

T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y

o

z

4

Time,

0

4.0 bo 80 100 T i m e , Minutes FIGS. 11

20

I20

0

20

90

Time, TO 1 6 - C H A N G E S

IN I O D I N E

60

80

loo

molecular weight t h a n t h e oils. So far as we know, t h e effect produced in t h e iodine number time curve by varying experimental conditions has not heretofore been investigated. The factors we have considered have been ( I ) pressure; ( 2 ) temperature; (3) agitation, as affected either by changing t h e rate of bubbling hydrogen, changing t h e R. P. M. of a mechanical agitator, or changing t h e size of a machine a t given R . P. M.; a n d (4) amount of catalyzer. The experimental conditions and results appear in Table I V and i n Figs. 11 to 16. PRESSURE-EarlY investigators appreciated t h e fact t h a t the hydrogenation reaction is accelerated by pressure, and so far as is known, all of t h e commercial oilhardening processes are carried out a t gas pressures ranging from 2 0 t o 150 lbs. or even higher. This influence may be illustrated by Experiments I a and b. Samples were withdrawn from time t o time and iodine numbers were determined after filtering out the catalyzer. I n Fig. 11 t h e results are presented, t h e t w o curves of iodine-number us. time being drawn on t h e same cobrdinates. Comparison of the two curves of Fig. 11 shows t h a t the time required t o reduce t h e iodine number of t h e oil t o any specified figure is roughly cut in half by doubling t h e pressure-;. e., in these experiments t h e rate of hydrogenation was approximately proportional t o the hydrogen pressure. TEMPERATURE-It is likewise well known t h a t t h e

6 8 Hours

i o 1 2

IZO

M inutes

NUMBERS O F COTTONSEED

459

Time, Minufes OIL DURING

HYDROGENATION

hydrogenation reactions in oil have a positive temperature coefficient-i. e . , t h e rate is greater t h e higher t h e temperature, although t h e thermal decomposition of the oil sets an upper limit t o t h e available range a t about 250' C. The following Runs IC, d , e, f , g, and h made under conditions identical except as t o temperature (Fig. 1 2 ) . The hydrogenation reactions in oil have a positive temperature coefficient in the range between 35' and somewhat above 200' C.-possibly up t o 240' C., but as may be seen from a study oE t h e curves of Fig. I 2 , this coefficient drops consistently as t h e temperat u r e rises. Thus for the range of temperatures 351 2 5 ' t h e time required t o reach a certain iodine number is on t h e average decreased about 35 per cent for each 10' rise in temperature, while €or t h e range 160-200' this coefficient is less t h a n 2 0 per cent Since the commercial processes nearly all operate a t temperatures of 160-1So0, it is evident t h a t no material gain in time could be made by t h e use of higher temperatures, and t h e point of maximum economy is probably being realized. AGITATION-The increase in velocity of reaction due t o increased agitation of oil and catalyzer with hydrogen may be illustrated for the bubbling apparatus by Runs Ii a n d j , which were made a t 15-160' C. with cotton oil and 54 per cent of its weight of nickel reduced from t h e green oxide, and not on a carrier. I n the second case t h e hydrogen was passed through t h e

460

T H E J O U R N A L OF I N D U S T R I A L A N D ENGIXEERING C H E M I S T R Y

flask a t a little more t h a n twice t h e rate obtaining in t h e first case (Fig. 13). I n this case a n increase of about 100 per cent in t h e volume of hydrogen supplied increased t h e velocity of t h e reaction 800-1000 per cent. I n apparatus of this t y p e handling charges of commercial size i t is not usual t o cause such violent agitation as is easily brought about in a 2-liter flask, a n d i t is doubtful whether doubling t h e hydrogen supply would on a large scale more t h a n double t h e reaction-rate. The :mportance of efficient agitation, or of intimate commixture of t h e oil, catalyzer a n d hydrogen, has apparently been realized by nearly all of t h e workers in this field. as witness t h e patent files, b u t there is no observation recording such a great increase in agitation as t h e above, brought about b y such simple means. For t h e mechanical agitation Runs I k , 2, m and 1% may serve t o show t h e effect of either changing t h e R . P. 51. of t h e agitator (Fig. 14) or of changing t h e size of t h e apparatus without either altering t h e type of agitation or t h e R. P. 14. of t h e agitator (Fig. IS). Increasing t h e R. P. M. of a mechanical agitator is shown in Fig. I4 t o produce a considerable increase in velocity. I n this case t h e speed of rotation is changed from what might be called a crlow” figure, 67, t o a “moderate)) figure, 1 3 5 ; doubling t h e speed again has been found in other experiments t o give only a slight increase in agitation. If t h e machine is increased in size, b u t not in t y p e of agitation, Fig. 1 5 indicates t h a t t h e agitation is more thorough a t t h e same R . P. M. resulting in this case in t h e small machine requiring about jo per cent longer time t o reach a given iodine number, CATALYZER-ASin practically all catalytic reactions, t h e speed of hydrogenation is increased as t h e percentage catalyzer is raised. The quantitative relation will appear from Runs Io a n d fl (Fig. 16). T h e time re.quired t o reach a given iodine number in Curve Ip is seen t o be approximately half of t h a t required in Io, so t h a t t h e reaction velocity is roughly proportional t o t h e percentage of catalyzer. Considerations of outlay required for catalyzer preparation a n d recovery limit t h e amount used in commercial batch processes, however, t o I , or a t most, 2 per cent. When a very good grade of refined oil is used, as little as 0.I per cent nickel is common practice, high pressure a n d agitation being relied upon t o reduce t h e time consumed. SUMMARY OF IODINE KUMBER-TIME CURVES

T o summarize, increasing t h e pressure, temperature, agitation or amount of catalyzer will increase t h e r a t e at which cottonseed oil is hydrogenated. This increase in rate is roughly proportional t o t h e increase in pressure or amount of catalyzer. while raising t h e temperature IO’ in t h e region of common practice, 160 t o 180°, increases t h e rate only about 2 0 per cent. Increase in agitation (difficult t o measure quantitatively) produces a marked increase in t h e reactionrate. It will be noted t h a t all of these curves show a general similarity t o t h e logarithmic curve which represents a monomolecular reaction, as Fokin pointed out.

Vol. 9 , No. 5

As a matter of fact, however, in every case t h e curve flattens out sooner t h a n would be expected, as though t h e catalyzer was losing its activity as t h e experiment progressed. It should be remembered, moreover, t h a t even if all of t h e different reactions involved took place monomolecularly, i t would by no means follow t h a t t h e resultant iodine number-time curve would have t h e same characteristic. T h e relative rates of t h e reactions would determine t h e shape of t h e curve. It should be possible, then, b y studying t h e iodine number time-curves mathematically, t o draw some conclusions as t o t h e relative velocities of t h e reactions involved; this would give indirectly a check on t h e results of t h e component glyceride analysis, as explained under “Hydrogenation Curves.” We hope t o report t h e results of such a study in a future communication. 111-CHAIiGES

I N PHYSICAL CONSTANTS O F OIL DURIKG HYDROGEKATIOX

T h e most striking effect of t h e hydrogenation of a n oil is, of course, t h e gradual increase in solidity, with t h e accompanying change in such physical constants as melting-point a n d titer. We are not aware t h a t a n y quantitative investigation of these physical changes has yet been published. MELTI”G-PoIPiT-The change of melting-point was studied in a n experiment in which t h e oil was hydrogenated with mechanical agitation of 108 R. P. M., temp. 160’ C., pressure 20 lbs., catalyzer 5 per cent. nickel on a carrier. The melting-point a n d iodine number were among t h e constants determined on each sample, a n d these constants compared as follows (Fig. 1 7 ) (the last sample was in reality made in another experiment, b u t t h e product is identically t h e same a s would be made under t h e above conditions) : hlelting point, Iodinenumber

C . ,, . . . . . ..... ... . ...

Ma

MI

Mz

9.0’ 107

39.4 74.3

40.8 66.7

Ma Ma Ms 45.8 48.0 48.9 6 1 . 0 54.5 4 8 . 5

Ma 60.5 0.4

There can be no doubt t h a t while t h e two ends of this curve remain fixed, t h e intermediate points a r e capable of considerable variation from t h e curve, depending on t h e conditions of hydrogenation. We have, for instance, t h e points A a n d B on Fig. 17. Sample A was made b y one of t h e “continuous” processes from t h e same kind of cotton-oil, while Sample B was made a t a very high temperature. TITER-The titer of a n oil or fat, being t h e solidification-point of its f a t t y acids, might be expected t o share t h e characteristic of t h e melting-point of t h e fat, namely, a gradual increase on hydrogenation. It is found, however, t o show t h e peculiarity of first decreasing, passing through a minimum, a n d t h e n increasing steadily, as appears from t h e d a t a from Runs’ Tu t o b. Cotton-oil was hydrogenated in t h e bubbling apparatus with j per cent of nickel, on a carrier, in one case at 1 2 5 ’ C., a n d in t h e other a t 200’ C. Titer a n d iodine number were among t h e determinations made on each sample. Time (from t h e beginning of t h e experiment), iodine number a n d titer are tabulated 1 We have seen the results of experiments made under the direction of Dr. W. D. Richardson which, while conceived and carried out independently of us, confirm our conclusions in every respect.

May, 1917

T H E J O C ' R X A L O F I N D C ' S T R I A L A,VD E.VGIAVEERI.VG C H E M I S T R Y

0

1

2

Time FIGS.17

TO

4

5

6

Hours

CHANGES I N PHYSICAL CONSTA ,NTS OF COTTONSEED OIL D U R I N G HYDROGENATIOX

below; in Fig. 18 titer is plotted against time and in Fig. 19 against iodine number. RUN T u (125' C.) Taa Time.. . . . . . . . . . . . . . . . . Iodine N o . . . . . . . . . . . . . . lO7:i Titer. C . . . . . . . . . . . . . . 3 4 . 2 6 RUN Tb (200° C.) Tba Time. . . . . . . . . . . . . . . . . . Iodine N o . . . . . . . . . . . . . . 107:7 Titer, O C . . . . . . . . . . . . . . 34.26

3

46 1

Tal 1:30 84.4 32.35 Tbi 0:lO 92.4 32.60

Tal

Taa

Tar

3 : O O

3:50 61.8 37.80 Tbs ~. 0:40 68.5 34.35

6:OO 45.7 45.50 Tbr 1:30 34.5 50.7

(0.5 35.50 Tbi 0:20 82.1 32.65

T h e apparently anomalous fact t h a t t h e addition of more saturated, higher melting acids at first lowers, instead of raising t h e solidification point is evidently due t o t h e existence of a eutectic, or low-melting mixture of t h e components. According as t h e p a t h of hydrogenation carries t h e composition close t o or far from this point t h e minimum attained will be lower or higher. From Fig. 19 i t is evident t h a t t h e low-temperature run passed closer t o t h e eutectic point t h a n did t h e high-temperature run. Below iodine number so t h e two runs were practically identical, as would be expected from t h e fact t h a t since linolin has largely disappeared t h e two hydrogenation curves of component glycerides cannot differ very greatly. Variation of other experimental conditions t h a n temperature would probably bring about corresponding variations in t h e iodine number-titer curve. F r o m t h e curves of Fig. 18 i t may be seen t h a t t o reach a given titer at 125' requires about four times as long as a t zooo, a n average coefficient of about 20 per cent for every 10' C.

after I j - m i n . hydrogenation. A similar sample of oil was heated t o I jo-160' for 2 0 minutes in t h e absence of any hydrogen or catalyzer, and was then found t o give t h e same intensity of Halphen test as Sample a. The other samples gave tests as follows: Iodine Sumber . . . . . . . . . . . . . . 104.9 6 . . . . . . . . . . . . . . . . 103.7 d . . . . . . . . . . . . . . . . 102.7 e . , . . . . . . . . . . . . . . 101.3 f... . . . . . . . . . . . . . 9 7 . 6

Sample b.,

RESULT Not noticeably diminished Distinctly weaker test Faint test in 3 minutes Faint test after heating 1 1 1 2 hours Negative even after heating 1 1 / t hours

A drop of four units in iodine number may be said t o have destroyed t h e chromogenetic substance. V-C

A T A L Y Z E RS

Our observations in t h e field of catalyzers are principally of interest as showing t h e effect of various poisons on t h e activity of t h e material. The powerful poisoning effect of certain gases has been known ever since t h e researches of Sabatier and Senderens, b u t t h e influence exerted b y solid a n d liquid impurities does not seem t o have been determined. T h e mode of preparation of t h e catalyzers used in experiments described in this article was as follows: I-Green nickel oxide was ground t o pass a I so-mesh sieve, and was reduced in a current of hydrogen for about 4 hours, temperature 320 t o 340' C.,pressure 30 t o 60 lbs. I t was mixed with a certain amount of cottonseed oil before exposing t o t h e air. 2-Basic nickel carbonate precipitated from t h e IV-RESPOKSE T O HALPHEK TEST sulfate in t h e presence of finely divided infusorial earth Hydrogenated cottonseed oil was first stated by Paal and Rothl t o give n o coloration when subjected t o t h e was calcined t o nickel oxide a n d then reduced in hycharacteristic Halphen test2 a n d t h e same statement drogen at 400 t o j o o o C.,atmospheric pressure, for has been made by later investigators. T h e amount periods ranging from 4 t o 14 hours. This product was of hydrogenation which is required t o render t h e oil also mixed with oil before exposing t o t h e air. The experiments on poisons were carried out in t h e just incapable of responding t o t h e test has not t o our bubbling apparatus, a mixture of oil with I per cent knowledge, been investigated. T o determine t h a t nickel on a carrier being hydrogenated first for one point a quantity of oil was hydrogenated in t h e bubbling apparatus, temperature 1j0-160' C., z per cent hour t o ascertain t h e original activity of t h e catalyzer. nickel on a carrier acting as catalyzer. Samples At t h e end of t h e hour, z per cent of t h e finely powdered were taken ( a ) of t h e original oil, ( b ) of t h e mixed oil solid substance in question was added, and t h e hydroand catalyzer before heating, (c) of t h e mixed oil a n d genation continued. Samples were then taken a t catalyzer when heated t o 150' C., j minutes being intervals t o determine t h e further fall of t h e iodine required t o reach this temperature, ( d ) after 3-min. number, a n d t h e poisoning effect was judged b y t h e hydrogenation, (e) after 9-min. hydrogenation, and (f) shape of t h e iodine number-time curve, compared t o one in which no poison was present. The results may Paal and Roth, Ber., 42 (1909). 1541-1553. * J. A. 0.A . C.. NO. 3, 2 (1916). 313. be summarized as follows:

T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y

462 Swsrmcs

.................................. ............................. .................................. ................................ ................................

Sulfur. NarS.9HzO. NaCl. NarSO4.. NaNOs.. NiClr.6HzO.. Reduced iron

............................ ............................

EFFECT ON ACTIVITY Destroyed immediately Gradually destroyed N o effect No effect No effect No effect N o effect

The three gases HzS, SO2 and Clz were also tried. I n each case t h e activity was destroyed immediately. A small amount of water vapor in t h e hydrogen was found gradually t o destroy the activity of t h e catalyzer. GENERAL SUMMARY

I-The lead-salt-ether method for separating t h e liquid f a t t y acids of oils a n d fats has been studied, a n d certain important precautions are noted. 11-The triangular diagram has been applied t o t h e study of oil hydrogenation. 111-It has been shown t h a t t h e conditions of hydrogenation, namely, pressure, temperature, per cent catalyzer a n d degree of agitation, affect t h e proportions of “saturated glycerides,” “olein,” and “linolin” in partially hydrogenated cottonseed oil. IV-By studying iodine number-time curves the effects within certain limits of pressure, temperature, per cent catalyzer and degree of agitation upon t h e velocity of hydrogenation have been determined. V-The changes undergone by melting-point and titer during hydrogenation are studied by means of curves against iodine number and time as t h e other variables. The titer is shown t o pass through a minimum before beginning its increase. VI-The degree of hydrogenation necessary t o destroy t h e response of cottonseed oil t o the Halphen test has been shown t o be a drop of about four units in iodine number. VII-A number of solid inorganic materials are shown t o have no effect on t h e activity of a catalyzer; sulfur a n d sodium sulfide, o n t h e other hand, are found t o destroy t h e activity. We wish t o acknowledge with thanks t h e many valuable suggestions made by Messrs. R. S. Pease, E . B Sebben and H. C. Fuller of this laboratory, who have in addition carried out most of t h e experimental work described in this article. RESEARCH LABORATORY BERLINMILLSCOMPANY BERLIN,NEW HAMPSHIRE

THE CHEMICAL COMPOSITION OF THE HIGHER FRACTIONS OF MAPLEWOOD CREOSOTE’ By ERNEST J. PIEPER,S. F. ACREEAND C. J. HUMPHREY Received March 7, 1917

Investigatorsz both in Europe and this country have studied t h e constituents of t h e creosote oil obtained from beechwood t a r , and in some cases from oakwood t a r , b u t no one, as far as is known t o t h e writers, has ever before attempted t h e study of maplewood creosote. The fact t h a t different species of hardwoods show a considerable difference in analysis might lead

1

1 The present paper is one of four prepared by the junior author in partial fulfilment of requirements for the degree of Doctor of Philosophy in the University of Wisconsin. ‘Hofmann. B n . , 8, 67; 11, 329; 12, 1371; Liebermann, A n n . . 169, 23; Tiemann and Koppe, Ber., 14, 2005; Behal and Choay, Compf. rend., 116, 197; 119, 166, Kebler, A m . Jour. Pharm., 1889, 409; J . SOC.Chem. 2nd.. 1894, 1087, 1187; 1891, 367. Abstracts.

Vol. 9, No. 5

one t o suppose t h a t there would possibly be a decided difference i n the composition of the wood tars obtained in destructive distillation. A commercial sample of maplewood creosote‘ was obtained by the Forest Products Laboratory. This creosote was heated in a n iron retort, a n d 1 5 liters were distilled in three separate runs, t h e fractions reported in Table I being collected and their volumes and weights determined. TABLE I-FRACTIONS OF MAPLEWOOD CREOSOTE Fraction c.

.... LOSS.. ......

TOTAL..

Volume cc. 7 60 840 815 445 840 590 805 1000 1000 480 740 515 1375 950

Weight Grams 709.46 844.20 811.84 443.22 867.72 605.34 821.50 1,029.60 1,029.50 496.80 771.82 532.51 1,442.38 979.93

-

Per cent by volume of entire distillate 6.23 7.40 7.10 3.89 7.72 5.40 7.20 9.06 9.04 4.36 6.77 4.67 12.66 8.60

__

-

11,155 11,385.62 100.00 95 11,250 cc. = Tot‘ai’ijistillate 75’per cent of Wood Creosote 3,750 cc. = Pitch = 25 per cent of Wood Creosote 15,000 cc. Total Wood Creosote

-

The percentages of total distillate contained in t h e three fractions 93-195’ C., 195-230’ C., a n d 230280’ C. are shown in Table 11. The first fraction consists principally of water and some pyroligneous acid; t h e second principally of the mono- and dihydroxy phenols, especially guaiacol and creosol; and t h e third mainly of t h e tri-hydroxy phenols, especially pyrogallol-dimethyl-ether a n d its homologues. The pitch residue is being thoroughly investigated. TABLE11-FRACTIONS OF MAPLEWOOD CREOSOTE Fraction Volume Per cent of Total Distillate 0 c. cc. 1600 13.63 93-195 3495 31.21 195-230 6060 55.16 230-280

Just as in t h e case of other wood creosotes, t h e relation shown in Table I1 is not absolutely constant, b u t depends upon a number of factors, such as t h e method of distilling t h e raw material, etc. A liter of the crude wood creosote was then distilled from t h e iron retort, and t h e distillate fractionated from a glass vessel connected with a Hempel column. The fraction above 195’ C., which we will term the creosote oil, was a light yellow oil with a specific gravity of 1.04 a t 2 0 ’ C. When well shaken in a separatory funnel with an equal volume of 1 5 per cent NaOH solution t o dissolve and separate t h e acid oil from t h e neutral oil, t h e latter floated t o t h e t o p of t h e mixture and was removed and shaken with more alkali t o dissolve any remaining acid oil. One treatment of t h e refined creosote with a n equal volume of 1 5 per cent NaOH solution is usually sufficient t o dissolve practically all t h e acid oil. The neutral oil obtained was washed with water until free from alkali, and distilled from a glass vessel connected with a Hempel column. The alkali extract was then treated with dilute sulfuric acid until slightly acid. The acid oil which 1 After standing several months the sample showed a gradual and partial change into pitch.