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The separation of the component fatty acids of pilchard oil as a stage in the manufacture of an improved… Hammond, Raymond 1947

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THE SEPARATION OF THE COMPONENT FATTY ACIDS OF PILCHARD OIL AS A STAGE IN THE MANUFACTURE OF AN IMPROVED DRYING OIL  by  Raymond Hammond  A Thesis Submitted i n P a r t i a l F u l f i l l m e n t of  the Requirements f o r  the Degree of  MASTER OF APPLIED SCIENCE  in the Department of Cnemical Engineering  The University of B r i t i s h Columbia May 1947  ACKUOWIEDGEMMT  I wish to acknowledge the many h e l p f u l suggestions and i n v a l u able .criticisms offered by Dr, W. Chalmers of the Western Chemical Industries Limited, under whose d i r e c t i o n t h i s investigation was carried out; also to Miss G. Beresford, also of Western Chemical Industries for her valuable assistance  during the experimental work.  R. Hammond  Ltd.,  THE SEPARATION OF THE COMPONENT FATTY ACIDS OF PILCHARD OIL AS A STAGE IN THE MANUFACTURE OF AN IMPROVED DRYING OIL  TABLE OF CONTENTS  I.  Introduction  Page  II.  Chemistry of Drying O i l s . . . . . . i . . . . . . .  I I I . Composition of Pilchard O i l IV.  V. VI.  •  1 2 4  Methods of Separation (a)  General  7  (b)  Fractional Crystallization  8  (c)  Fractional D i s t i l l a t i o n  9  Methods of Analysis  11  Experimental (a)  Equipment  14  (b)  Procedure  13  (c)  Results  (d)  Discussion  "  20 • 22  VII. A p p l i c a t i o n of Results  26  VIII. Summary  28  EC.  29  Bibliography  THE SEPARATION OF THE COMPONENT FATTY ACIDS OF PILCHARD OIL AS A STAGE IN THE MANUFACTURE OF AN IMPROVED DRYING OIL  Introduction  '  Pilchard o i l i s composed of the glycerides of mixed f a t t y acids.  I t i s desired to e f f e c t a separation of these f a t t y a c i d  groups, into a number of f r a c t i o n s some of which may be r e e s t e r i f i e d with g l y c e r o l to form an o i l with improved drying c h a r a c t e r i s t i c s . This separation i s to be accomplished through the medium of the methyl esters. The value of drying o i l s rests i n t h e i r a b i l i t y to form tough, non-tacky, durable f i l m s over surfaces to which they are applied i n a wet form, and to act as a binder f o r pigments which are used f o r protective and decorative e f f e c t s ( 1 ) . The f i s h o i l s most commonly used as drying o i l s are menhaden, sardine and p i l c h a r d o i l s .  By r e f r i g e r a t i o n and pressing  i t i s possible to remove some of the saturated f a t t y a c i d glycerides from these f i s h o i l s . comparatively  The r e s u l t i n g o i l s s t i l l dry slowly to. a  soft f i l m .  This process of removal i s i n e f f i c i e n t  since only approximately 2 percent of the 23 percent of the saturated f a t t y acids o r i g i n a l l y present i s removed.  2 II.  Chemistry of Drying O i l s Drying o i l s are mixed glycerides of the saturated and unsaturated f a t t y acids, and the properties of the i n d i v i d u a l o i l s depend upon the type and proportion of the constituent acids making up the o i l . The mechanism of oxidation and drying of o i l films i s s t i l l a subject of much controversy although rapid s t r i d e s toward an understanding of the phenomenon have been made i n recent years. I t i s f a i r l y w e l l agreed that both oxidation and some type of polymerizat i o n are involved, as w e l l as the formation of c o l l o i d a l systems which set or g e l as the f i l m d r i e s . Bradley (2) states that drying, i n the chemical sense, i s a mechanism i n which the e s s e n t i a l l y l i n e a r and u s u a l l y l i q u i d  substance  becomes converted into a cross-linked or three-dimensional polymer. In view of t h i s , i n the case o f ' a l l of our natural drying o i l s the primary r e q u i s i t e f o r the drying phenomenon i s the possession of a structure which w i l l permit the formation of a three-dimensional polymer, oxidation being one of these means to an end. The a b i l i t y to dry depends upon the presence of unsaturated double bonds.  The greater the number of unsaturated double bonds  present, the more rapid the drying of the o i l .  C onjugation of the  double bonds has a favourable e f f e c t on the drying and r e s u l t i n g c h a r a c t e r i s t i c s of the resultant f i l m . A comparison of f i s h o i l s with other types of drying o i l s i s given i n the following table ( 3 ) .  3  TABLE I PERCENTAGE COMPOSITION OF DRYING OILS  Fatty Acid Saturated  Formula  Fish  Linseed  - n 2n°2  22.7  8.1  11.5  5.5  5.0  32.0  16.9  48.5  49.3  69.7  34.1  2.2  3.1  c  H  Palmitoleic  C  16 30°2  11.9  Oleic  C  18 34°2  Linoleic  f  C  18 32°2  Linolenic  G  18 30°2  Arachidonic  C  20 32°2  22.9  Clupanodonic  C  22 36°2  . 19.0  H  H  1  H  H  H  E  22.7  \  Soybean  Walnut  AVERAGE CHEMICAL CONSTANTS OF DRYING OILS  Fish  Constants  Linseed  Soybean  Walnut  180  133  150  Iodine number (Wijs)  160-190  S p e c i f i c Gravity 15.5°C  0.9332  0.931  0.923  0.926  Saponification number  193  192  192  192  % Unsaponifiable  0.7  1.0  0.6  0.5  Refractive  index  (  1.4801  1.4800  1.4745  f  1.4751  4 III.  Composition of Pilchard O i l In order to understand  the problem of separating p i l c h a r d  o i l into i t s component f r a c t i o n s , a study of i t s composition i s i n Brocklesby (4) and h i s co-workers state that the  troduced here.  substances present i n most f i s h o i l s include the following: "  TABLE I I  L  COMPOSITION OF FISH OILS  1.  Glycerides  2>  Glycerol 'ethers  ) Saponifiable f r a c t i o n  3. Phospholipides »  Sterols  5.  Vitamins  4  6. Pigments  Y  .,  7. Waxes  Unsaponifiable f r a c t i o n  8. Pigments 9. Hydrocarbons 10.  Fatty alcohols  Although the unsaponifiable f r a c t i o n , c h i e f l y the vitamins, may have high economic value, they wiUUnot be considered f u r t h e r i n t h i s study,  i n pilchard o i l the unsaponifiables account f o r approximately  one percent of the o i l .  '  5 Brocklesby (5) gives the following composition f o r p i l c h a r d o i l , TABLE I I I WEIGHT PERCENTAGE COMPOSITION OF FATTY ACIDS IN PILCHARD OIL  Unsap. Matter Pacific Pilchard B  Saturated — — — — —  *  °14 °16 °18 •  1.0  5.1 14.4 3.2  :  .  °14 ;  Unsaturated  °16 °18  .  °20  °22  °24  Trace 11.7 17.6 17.9 13.8 15.2 (2) (3.3) (4.1) (8.5) (10.9)  l a t h i s table the numbers i n brackets indicate the degree o f unsaturation present i n the unsaturated f a t t y a c i d group.  An unsaturation  of 2H indicates the presence of an average of one unsaturated double bond.  I f the C^g f r a c t i o n were pure o l e i c a c i d , i t would have t h i s  value, but i f i t contained equal quantities of o l e i c and l i n o l e i c acid the value would become 3H. The f a t t y acids are present as mixed glycerides of the following types (6).  Simple T r i g l y c e r i d e s  CHgOCOR!  CH 0C0R  CHOCOR,  CHOCORj,  GHgOGORj  CHgOCORg  CHgOCOR  CHgOCOR-L  CHOCOR,  CHOCOR,  1  Mixed Triglycerides -  I  2  I  2  2  3  CHgOCORg  GHgOCOR,  6  The larger number of glycerides present belong to the mixed triglyceride type. It has been shown by Hilditch (7) that there is a tendency for unlike fatty acid groups to exist side by side in the glyceride molecule. Further discussion on the composition of fish oils is given in the following references (8).  IV.  Methods of Separation (a) General Because of the complex nature of the f i s h - o i l glycerides i t i s obvious that separation of the o i l into large f r a c t i o n s containing i n d i v i d u a l f a t t y acids would be impossible.  The separation of the f a t t y  acid components i s made possible by conversion into the methyl esters, suitable f r a c t i o n s of which can be reconverted to glycerides. The e s t e r i f i c a t i o n i s shown by the general CHgOCOR-L CH0C0R 2  CHgOH 3CH 0H —*-CH^OH •+ CHgOCORi + CHgOCG^ -4- CH 0C0R  2  CH 0C0R  equation:  3  3  3  CHgOH  3  I t i s not expected that the separation of the esters can be accomplished without d i f f i c u l t y ; , I t has been found f o r hydrocarbons, such as straight-chain f a t t y acids, that the b o i l i n g points of i n d i v i d u a l acids of the same chain length are very nearly the same. The presence of unsaturated double bonds has no effect on the b o i l i n g point of the hydrocarbon.  Consequently the separation of s t e a r i c from o l e i c a c i d i n  pilchard o i l , both with the same chain length, would require a very e f f i c i e n t column.  Since the d i s t i l l a t i o n must be carried out a t very  low pressures, about 0.1 mm of Hg, the b o i l i n g points would be even c l o s e r . Some other method of separation of these f a t t y acids of equal chain length must be used i n order to e f f e c t a complete separation since the presence of an unsaturated and a saturated member i n any f r a c t i o n i s undesirable.  8 U n t i l a few years ago the most common means of separating the saturated from unsaturated  acids i n a mixture of both was by the Twitchell  Lead Separation Method (l&). The procedure i s long and only small quantities of- material can be handled conveniently.  The method commonly  used at present i s that of f r a c t i o n a l c r y s t a l l i z a t i o n .  Large quantities  of mixed f a t t y acids or t h e i r methyl esters can be separated  i n a re-  l a t i v e l y short time with a good degree of separation. It would appear possible to separate the esters of the f a t t y acids of p i l c h a r d o i l into a number of f r a c t i o n s by employing a combination of f r a c t i o n c r y s t a l l i z a t i o n and f r a c t i o n a l d i s t i l l a t i o n .  This w i l l  be discussed f u r t h e r .  (b) F r a c t i o n a l C r y s t a l l i z a t i o n This method of separating the saturated components from the unsaturated  components of the mixed f a t t y a c i d esters consists i n cooling  a solution of the mixed ester»in methanol or s i m i l a r type of solvent u n t i l the saturated f r a c t i o n c r y s t a l l i z e s out (9, 10, 11, 12, 13). crystals can be removed by f i l t r a t i o n leaving the unsaturated  fraction  i n the f i l t r a t e .  A f a i r l y complete separation can be obtained by  crystallization.  A  crystallizations.  The  one  more complete separation can be obtained by a d d i t i o n a l C r y s t a l l i z a t i o n temperatures f o r 9 percent solutions  of methyl stearate and methyl oleate are -37°C and -60°C r e s p e c t i v e l y . I t can be seen that the temperatures used are r e l a t i v e l y low.  This i s a  disadvantage since s p e c i a l equipment must be employed f o r the separation of large quantities of material.  9  The solvent selected i n the present work was acetone although methanol would be as s a t i s f a c t o r y . Investigations by J . B. Brown and G.. G. Stoner (14) show that acetone and methanol give granular c r y s t a l s with good f i l t e r i n g c h a r a c t e r i s t i c s whereas petroleum ether and propylene dichloride give plates with poor f i l t r a t i o n properties.  With c e n t r i -  fugation t h i s factor i s not as important but enough so to warrant i t s 4  consideration. A ten percent  solution (approximately) of the ester i n acetone  i s most commonly used f o r t h i s c r y s t a l l i z a t i o n .  With one  crystallization  at -37°C, a good degree of separation (approximately 95 percent) can be obtained.  The time f o r c r y s t a l l i z a t i o n of the esters from solution at  t h i s concentration i s approximately one hour.  For more d i l u t e solutions  of the f a t t y acid esters, the time f o r c r y s t a l l i z a t i o n i n increased. (c) F r a c t i o n a l D i s t i l l a t i o n A table of b o i l i n g points of the methyl esters of some of the common f a t t y acids found i n p i l c h a r d O i l i s given below (15).  TABLE 17 BOILIKG POINTS OF METHYL ESTERS OF FATTY ACIDS AT VARIOUS PRESSURES mm of Hg 2 • i - - 10 . 20 methyl myristate 127°C 162 C 177°C methyl paimitate 148 184 202 methyl< stearate 166 204 a 166.2 methyl oleate 205.3 a 166.5 206 a methyl l i n o l e a t e n  U  a - decomposes  1  .  10  .  iFrom the table i t i s evident that a f r a c t i o n a l d i s t i l l a t i o n at reduced pressures w i l l be required i f high temperatures are to be avoided.  Due to the unstable nature of the unsaturated acids present,  the l a t t e r condition i s desirable. 0.1 mm  H i l d i t c h uses pressures of around  of Hg f o r the analysis of f a t s . The calculations involved i n the designing of a column, f o r  the separation of the esters into fractions containing i n d i v i d u a l f a t t y acids, i s outlined by Badger and McCabe (16), and Walker, Lewis, G u i l l i l a n d and McAdams (17).  Since such an exact separation w i l l not be  these calculations w i l l not be made.  attempted,  The type of column used by most  workers f o r the separation of the f a t t y acids i n f a t s i s an e l e c t r i c a l l y heated and packed column. by H i l d i t c h (18)^  The various types of columns used are outlined  The i d e a l case i n ester f r a c t i o n a t i o n i s to produce  a series of ester f r a c t i o n s , each of which s h a l l contain not more than two saturated esters accompanied by not more than one unsaturated ester, or esters of unsaturated acids with the same number of carbon atoms. If such i s the case, t h e i r composition can be calculated from saponi f i c a t i o n and iodine numbers.  11 Methods of Analysis Although considerable data has been compiled on the physical and chemical properties of the f a t t y acids and f a t t y acid esters there i s much l a c k i n g .  I t i s , therefore, d i f f i c u l t to t r y to obtain any p o s i t i v e  information by comparing t e s t s made on the ester f r a c t i o n s with the existing data.  However, i t i s possible, by means of a number of t e s t s  made on the f r a c t i o n s , to formulate an opinion of the approximate composition of the o r i g i n a l mixed esters. mentioned consist of:  The tests which have been  (a) Iodine Value (b)  Saponification Value  (c)  S p e c i f i c Gravity  (d)  Refractive Index  They w i l l be discussed i n more d e t a i l here. (a)  Iodine Value There are several methods a v a i l a b l e f o r obtaining t h i s value  (21, 22).  The Wijs method was employed here (20).  They are a l l based  on the p r i n c i p l e of quantitative i n t e r a c t i o n with iodine of the double bond i n the unsaturated f a t t y a c i d molecule.  The iodine value i s ex-  pressed as grams of iodine absorbed per 100 grams of o i l .  Since the  iodine value varies d i r e c t l y as the amount of unsaturation i n the molecule, i t s value i n evaluating any p a r t i c u l a r f r a c t i o n i s apparent. To i l l u s t r a t e  t h i s the iodine value f o r S t e a r i c acid i s zero while f o r  Oleic a c i d i t i s 89.9 and f o r L i n o l e i c acid the value i s 181.1.  It is  evident that the iodine number of a f r a c t i o n w i l l be of considerable  12 assistance i n determining the extent of unsaturation  e x i s t i n g i n the f a t t y  acid esters.  (h)  Saponification Value Procedure f o r the determination of t h i s value i s given i n  Elsdon (20) and Lewkowitsch (22).  The saponification value represents  the amount of EOH required to neutralize the free and combined c o n s t i t u ents of a f a t or o i l .  I t can be seen then that as the chain length or  molecular weight of the f a t t y acid increases, the saponification value of the o i l w i l l decrease since i t s value i s based on the amount of acid present (-C00H group) per given weight.  This i s i l l u s t r a t e d i n the  following table (23).  TABLE V SAPONIFICATION VALUES OF SOME PATTY ACIDS Acid  Formula  Saponification Value  Palmitic  C  16 32°2  256.3  Palmi t o l e i c  C  16 30°2  254.2  H  H  c  (c)  Stearic  °18 36°2  284.3  Oleic  C. H 0 18 34 ^  282.2  Arachidic  C H  Gadoleic  G^E^O^  H  0  2 Q  P  0  312.3  3l0.3  S p e c i f i c Gravity The s p e c i f i c gravity can be determined by any of the w e l l -  known methods.  I t was determined i n t h i s investigation^ by means of a  13  Westphal balance.  This i s a rapid and accurate method of determining  specific gravities. temperatures  I f the f a t t y acid to be measured i s s o l i d at room  the s p e c i f i c gravity i s taken at a temperature at which  it is liquid.  This value i s then converted back to the desired reference  temperature by means of the following formula*  S. G. at T  Q  = S p e c i f i c Gravity at t ( l f k ( t - T ) ), where k i s the Q  c o e f f i c i e n t of expansion,  (d)  0  Q  Values f o r k are given i n Brocklesby (25).  Refractive Index This value i s determined at some s p e c i f i e d temperature by the  use of a refractometer*  I t i s possible to convert t h i s value to some  other reference temperature by adding or subtracting 0.0003? f o r each degree too low or too high above the desired temperature.  A  discussion on the use of refractometers f o r determining r e f r a c t i v e indices of o i l s and f a t s i s given by Lewkowitsch and Warburton (22), The v a r i a t i o n of r e f r a c t i v e index with composition i s given by Trim (24). Harrison (25.) found a d e f i n i t e correlation e x i s t i n g between iodine value and r e f r a c t i v e index according to the following equation: Iodine value  =  6,929 X  n  2 5 D  - 10,079.2  Polymerization and oxidation of unsaturated o i l s both increase the r e f r a c t i v e index while conversion of unsaturated to saturated bonds by any means w i l l cause a decrease i n the r e f r a c t i v e index.  VI.  Experimental (a) Equipment (i) Vacuum D i s t i l l a t i o n Equipment i  The apparatus i s shown i n F i g . I and i s described as follows. S t i l l head -  a Corad Multi r a t i o type (29).  Reflux can be controlled  by r o t a t i n g the condenser head or by stop-cock or a combination of both. Water i s circulated through the head f o r cooling.' , Fractionating column - a-60" X 1" vacuum-jacketed glass Vigreaux column wound with 70 turns of No. 20 chromel resistance wire.  A t h i n sheet of  asbestos was used to protect the column from the e f f e c t s of the e l e c t r i c j heating element.  The whole i s jacketed with a l ^  c e l l pipe i n s u l a t i o n .  n  thickness of J.M. A i r -  Voltages i n the column heater are controlled by  a variable resistance box (varitron), voltages.being read" from the enclosed voltmeter.  This instrument i s manufactured by United Trans-  former Co., New York, N. Y. D i s t i l l a t i o n f l a s k and heater - three l i t e r capacity f l a s k with ground glass j o i n t .  Heating i s by means of an e l e c t r i c a l l y heated glass mantle  manufactured by Glass Col Co. ( S c i e n t i f i c Glass Apparatus).  The current  input to the heater i s also regulated by a Varitron type resistance box. Vacuum pump - the type used i s a Welch Duo-seal made by W. M. Welch manufacturing Co. I t has a suction pressure r e a d i l y obtainable of —4.  1 X 10 "mm of Hg. The pump i s protected by a mercury seal glass trap cooled with a dry ice-methanol mixture. S t i r r e r - an external magnetic s t i r r e r i s used to a s s i s t i n obtaining uniform d i s t i l l a t i o n .  15  Pressure indicator - a McLeod gauge with range of 3-X lO** mm 4  of Hg i s  used f o r determining pressures at s t i l l head.  Note - a l l j o i n t s are standard taper ground glass and vacuum s i l i c o n e grease i s used f o r l u b r i c a t i o n , ( i i ) F r a c t i o n a l C r y s t a l l i z a t i o n Equipment The  f r a c t i o n a l c r y s t a l l i z a t i o n equipment i s shown i n F i g I I and  consists of a c r y s t a l l i z e f and of two concentric c y l i n d e r s .  centrifuge.  The  c r y s t a l l i z e r i s made  The inner cylinder has a c o n i c a l shaped  bottom to f a c i l i t a t e the removal of the c r y s t a l s , A stop-cock on the discharge pipe leading from the bottom of t h i s cylinder to the  centrifuge  allows the flow of the l i q u i d - p r e c i p i t a t e mixture to be c o n t r o l l e d . Thermometers inserted i n the cooling and temperature c o n t r o l .  c r y s t a l l i z i n g solutions are f o r  The annular space between the two  f i l l e d with the cooling medium (dry ice-methanol),  cylinders i s  S t i r r i n g of the  cooling and c r y s t a l l i z i n g mediums by means of e l e c t r i c motors i s effected to increase the rate of heat t r a n s f e r . The  centrifuge i s a "Master" Fletcher c e n t r i f u g a l with 12"  monel basket manufactured by Fletcher Works, Pa,  The f i l t r a t e i s r e -  moved by means of a skimmer.  The disadvantage of t h i s type of f i l t r a t e  removal i s the small loss due  to some splashing of the basket caused  by the skimming a c t i o n , ' Since the centrifuging must be done at low temperatures, i t was necessary to design a system f o r cooling the centrifuge to the uired temperatures (-50°C),  req-  This consisted i n removing the rotor of  GftSTALUZEE— CENIHFUGE MOTORS THERMOMETER.  INNER  CYLINDER INNER  CYLINDER  INSULATION, OUTER  CYLINDER  THERMOMETER • LEGS. PCMOVA3LE TOP A  CORK INSULATION  A WOOD SHAVINGS  DRIVING  MOTOR  EXPANSION VALVE  SKIMMER CCNTRlEUGE BASKET AMMONIA KEERIS. SYSTEM  16  the centrifuge and i n s t a l l i n g i t i n an insulated cabinet,  (see F i g II)  The cooling of t h i s cabinet was accomplished by means of cooling c o i l s as a part of an ammonia r e f r i g e r a t i n g system.  The calculations involved  i n t h i s problem are given below.  1.  Heat gain by centrifuge The heat gain i s through the walls and the rotor of the  centrifuge. The rotor can be considered other end uninsulated (1)  q  (2)  M-K  (3)  q  (26).  as a rod heated at one end,  The following equations can then be applied.  -  kAm(M-N)  s  • 9tanh(mL) -  a  kAmStanh(mL)  k q A 9 m L h  = « =  « = = -  Btu/hr/f t/degF heat flow Btu/hr cross-sectional area of rod, temp d i f f deg F hC/kA length of rod f i l m coeff from rod to a i r ; But/hr/ft/degF  Values substituted i n the above equations are: q  =  ?  m  =  L  =  2.1 f t  C  =  2.59  ft  A  =  0.032 sq f t  k  =  27.0  Btu/hr/ft/degF  9  =  40-(-50)  h  =  10 Btu/hr/ft/degF  r  =  90 deg F  hC/kA  =  Substituting i n equation 3: Heat gain through rotor  the  q^,  =  426 Btu/hr  5.48  17 Heat gain through walls;  (4)  %  heat transfer Btu/hr coeff of heat transfer; Btu/hr/degF/sq. f t temp outside centrifuge temp inside centrifuge  UA(t - )  5  G  t i  U  *0 t< Values f o r these variables are: U  =  0.04 Btu/hr/sq ft/degF  A  s 22.5 sq f t  t  Q  =  40 deg F  t  A  -  -50 deg F  Substituting i n equation 4: Heat gain through walls  =  Total heat gain by centrifuge  2,  a  426  f  81  81 Btu/hr  =  507 Btu/hr  Cooling c o i l s required Pipe to be used i s one-half inch standard s t e e l pipe, with an  outside surface area of  4  g  4 ?  sq f t / f t of pipe length.  Applying equation (4) to the heat transfer through the c o i l s :  .  Q,  =  U  =20  507 Btu/hr Btu/hr/sq ft/degF.....(27)  *1"*2  =  A  5.07 sq f t  =  5  d  e  g  F  Length of pipe required  =  22.9 f t  18  (b) Procedure Preparation of the Fatty Acid Esters of Pilchard O i l The pilchard o i l used was single pressed p i l c h a r d o i l with a saturated acid content of approximately 22$ and a free f a t t y acid content of 2.1$.  The l a t t e r was neutralized with KOH and the o i l thoroughly mixed  with Magnesol before f i l t e r i n g .  E s t e r i f i c a t i o n was effected by methods  used by Western Chemical Industries Limited with a conversion to the f a t t y a c i d esters and g l y c e r o l .  A f t e r removal of the excess of methanol,  the esters were subjected to a simple vacuum d i s t i l l a t i o n leaving a residue of approximately 2$.  The d i s t i l l a t e was then subjected to the  following procedures.  (i)  Fractional  Distillation  Fractionation was carried out i n vacuum using a 5* X I " vacuum jacketed Vigreaux column maintaining a pressure of 0.1-0.2 mm of Hg a t the column head.  I t was found necessary to use an external type of  s t i r r e r to maintain a uniform rate of d i s t i l l a t i o n , otherwise bumping occured,  A s i l i c o n e type of l u b r i c a t i o n grease was the only type  t r i e d with which i t was possible to maintain the required vacuum. Temperature control of the column was effected by varying the resistance to the column heater, the voltages being recorded. used f o r b o i l i n g f l a s k temperatures. flask was used to determine b o i l i n g  S i m i l a r control was  However, a thermometer well i n t h i s temperatures.  Temperatures of the ingoining and outgoing condenser water were observed with a constant water flow.  Reflux was controlled by means of a  19  x  stop-cock and variable r e f l u x r a t i o head. determine and control the r e f l u x r a t i o .  A drop count was made to  Head temperatures were taken by  means of a thermometer inserted i n the head.  The d i s t i l l a t e was p e r i o d i -  c a l l y drawn o f f and tested f o r r e f r a c t i v e index.  The r e f r a c t i v e indices  obtained were used to determine the range of the f r a c t i o n s to be taken. The time f o r d i s t i l l a t i o n of each f r a c t i o n was read and recorded. The r e s u l t s were calculated and tabulated as shown i n Table V I .  (ii)  Fractional C r y s t a l l i z a t i o n followed by F r a c t i o n a l D i s t i l l a t i o n  Approximately nine percent solutions of^the mixed f a t t y acid esters were cooled i n the c r y s t a l l i z e r by means of a dry ice-methanol cooling mixture.  I t was found most convenient to handle about 600 ml  of the esters which when d i l u t e d with the acetone would give 6600 mis of solution.  By using these quantities, i t was not necessary to remove  the basket of the centrifuge completed.  to empty i t before the separation was  A g i t a t i o n of the c r y s t a l l i z i n g solution was not too v i o l e n t so  as to avoid breaking up of the c r y s t a l s with the resultant d i f f i c u l t y of -separation.  The c r y s t a l l i z e d solution was l e f t f o r one hour before  centrifugation.  Both the c r y s t a l l i z i n g solution and centrifuge were  'maintained a t «37°C.  The solvent was removed from each of the r e s u l t i n g  fractions by means of d i s t i l l a t i o n under vacuum. ,A f r a c t i o n a l d i s t i l l a t i o n was carried out on the f i l t r a t e (unsaturated f a t t y acid esters) from t h i s f r a c t i o n a l c r y s t a l l i z a t i o n , i n the manner described f o r the previous distillation. A l l r e s u l t s are shown i n Tables VII and VIII.  20  (iii)  Examination of the Fractions  On a l l s t a r t i n g materials and f r a c t i o n s obtained i n procedures I and I I the following tests were conducted:  Saponification value,  Iodine value, S p e c i f i c gravity and Refractive index.  The l a t t e r two  tests were conducted a t 20°C.  (c)  Results Results f o r the f r a c t i o n a l d i s t i l l a t i o n of the mixture of f a t t y  acid esters obtained on the e s t e r i f i c a t i o n of p i l c h a r d o i l are given i n TABLE VI (page 21). The following r e s u l t s were obtained f o r the f r a c t i o n a l c r y s t a l l i z a t i o n of the methyl esters of pilchard o i l . TABLE VII.; FRACTIONAL CRYSTALLIZATION OF METHYL ESTERS OF PILCHARD OIL AT LOW TEMPERATURES  1075 gms of the mixed esters i n 12000 ml of acetone Saponification Value Iodine Value S p e c i f i c Gravity Refractive Index  -  195 170 .8905 1.4642  one c r y s t a l l i z a t i o n a t -37 deg C.  •  <-  Filtrate Unsaturated Methyl Esters 820 gms -• 77.0$ Iodine Value - 213 Sap. Value - 193 Ref. index - 1.4693 Sp ec. Grav. - .8969  I — Crystal P r e c i p i t a t e Saturated Methyl Esters 249 gms - 23,0$ Iodine Value - 26.5 Sap. Value - 181 Ref. Index - 1.4443 Spec.Grav. - .8677  TABLE VI FRACTIONAL DISTILLATION OF METHYL ESTERS OF FATTY ACIDS OF PILCHARD OIL 1337 gms d i s t i l l e d through a 1" X 60" Vigreaux column ( e l e c t r i c a l l y heated) Reflux r a t i o - 6:1  Fract. No. 1 2 3 4 5 6 7 8 9 10 11  Temp, i n ° C. Head Bottom 104-110 110-119 119-127 ' 127-132 132-136 136-137 137-150 150-155 155-166 166-180 Residue Charge  175 177 185 188 194 194 202 210 220 238  Percent Off.  Pressure at column head - .18 mm of Hg  Percent Charge  5.23 5.23 14.28 9.05 34.78 20.50 39.27 ' 4.49 41.55 2.28 54.85 13.30 62.81 7.96 70.03 7.22 81.52 11.49 10.13 91.65 8.35 100.00 100.0  Specific, Gravity  Iodine Value  Sapon. Value  Refractive Index  Mol. ft.  Time i n Minutes  0.8688 0.8726 0.8731 0.8749 0.8782 0.8797 0.8850 0.9067 0.9083 0.9140 0.9639  17.3 60.0 60.5 78.7 100.5 119.5 161.0 280.0 286.0 277.0 243.0  229 214 210 203 200 196 190 186 184 173 170  1.4393 1.4462 1.4470 1.4548 1.4565 1.4615 1.4802 1.4820 1.4870 1.5549  240 257 262 271 275 280 290 296 299 318 324  226 365 700 782 820 1045 1234 1320 1500 1684  0.8910  172.0  195  1.4636  282  1.4510 s  22 A f r a c t i o n d i s t i l l a t i o n carried out on the f r a c t i o n remaining a f t e r separation of saturated components by f r a c t i o n a l c r y s t a l l i z a t i o n at low temperatures yielded the r e s u l t s shown i n TABLE VIII (page 23). (d) Discussion From the data obtained from the ..two . d i s t i l l a t i o n s outlined above, a set of curves can be drawn.  F i g . 3 shows the curves obtained  when r e f r a c t i v e index i s plotted against percentage of o r i g i n a l ester d i s t i l l e d overhead.  In p l o t t i n g the r e s u l t s f o r the d i s t i l l a t i o n of the  mixed unsaturated f r a c t i o n from the f r a c t i o n a l c r y s t a l l i z a t i o n , an amount equal to that removed by the c r y s t a l l i z a t i o n procedure was added to the percentage of charge d i s t i l l e d o f f f o r each f r a c t i o n .  This had the e f f e c t  of bringing the two curves into phase f o r comparison. Examining curves 1 and 2 and r e f e r r i n g to the composition of pilchard o i l , i t w i l l be observed that there are three d i s t i n c t f l a t portions of the curve 1, while curve 2 has two corresponding f l a t portions. To f a c i l i t a t e explanation of the curves they have been l e t t e r e d as shown. Since molecules of equal chain length b o i l at approximately the same temperature we might expect these f l a t portions to consist of molecules of the same chain length.  This w i l l be shown to be true.  I f we p l o t the v a r i a t i o n of the saponification number with percent of esters d i s t i l l e d o f f , the curves 3 and 4 are obtained.  By  means of these curves and molecular weights, the composition of the fractions can be better understood.  The molecular weight referred to  here i s calculated by means of the following r e l a t i o n s h i p :  TABLE VIII FRACTIONAL DISTILLATION OF THE UNSATURATED FRACTION OF THE METHYL ESTERS OF PILCHARD OIL 807 gms d i s t i l l e d through 1" X 60" Vigreaux column ( e l e c t r i c a l l y heated) Reflux ratio: - 6:1  Fract. No. 1 2 3 4 5 6 7 8 9 10  ;  Temp, i n C. Head Flask 108-118 118-123 123-134 134^-139 139-141 141-143 143-157 157-166 166-190 Residue Charge  175 178 187 188 193 197 208 216 277 —  Pressure at column head - .12 mm of Hg  •  Percent Off * 28.26 31.79 41.06 45.52 55.30 58.83 67.07 79.85 92.40 100.00  .  Percent Charge  Specific Gravity  6.83 4.58 12.02 5.78 12.70 4.58 10.70 16.60 16.30 9.91  0.8739 0.8808 0.8819 0.8814 0.8809 0.8817 0.8965 0.9077 0.9142 1.0028  35 113 124 120 130 136 239 295 272 183  217 214 212 198 196 195 188 182 172 162  0.8969  213  193  100.00  i  Iodine Value  Sapon. Value  '  '  Refractive Index 1.4432 1.4518 1.4540 1.4567 1.4575 1.4585 l i 47-18 1.4818 1.4870 1,5158  Mol. Wt.  :  254 257 259 278 281 282 292 302 320 340  Time i n Minutes 90 150 370 470 750 840 975 1115 1320 1320  1.4693  * the amount of saturated f a t t y acid esters, removed by f r a c t i o n a l c r y s t a l l i z a t i o n , i s included here.  OOOQ I  006VI  OOBVI OQl  OOIV'I 06»  OOBVl  00a  OOQVI ©ts  oovvi  02. s  oo<svr  /  24  M. W.  - 56  v  X  ^  n n n  1000; where S.V.  -  saponification value  The molecular weight i s inversely proportional to the saponification value. Examining the curves 1, 2, 3, and 4 i n more d e t a i l ,  consider  now the portion a-b. At the point afl the molecular weight corresponds w  to that of a C^-saturated  fraction.  The low iodine value would indicate  that t h i s f r a c t i o n i s c h i e f l y the methyl ester of myristic acid"(the saturated a c i d ) .  From the point "a" to the point "b? a gradually'  increasing molecular weight and iodine value indicates that there i s an increasing amount of C  1 6  saturated and unsaturated esters being  distilled  off. At "b" we can assume that the d i s t i l l a t e mixture of C-^g-unsaturated and -saturated esters. consider the portion j-d of curve 2.  becomes a constant To confirm this  S ince i n curve 2 the saturated  esters have been removed completely, t h i s portion, due to i t s molecular weight and iodine value, appears to be C^g unsaturated o r p a l m i t o l e i c esters.  I t w i l l also be seen that the curve 3 has a f l a t portion  corresponding to t h i s constant composition of C^g esters. r i s e i n r e f r a c t i v e index from c M  that the C  1 8  M  to d w  w  The sudden „  i s probably due to the f a c t  f r a c t i o n i s s t a r t i n g to d i s t i l o f f .  Considering the portion d-e. that i t i s of constant  composition.  i t i s composed of C esters. 18  The f a c t that i t i s f l a t indicates  The molecular weight suggests that  T he unsaturation  corresponds to one and  a h a l f double bonds so that we can assume that i s i s composed c h i e f l y of unsaturated C  1 8  esters.  The presence of small amounts of  saturated  '  25 i  esters i s shown by the difference between curves 1 and 2 between points "d  w  and " e . w  I t w i l l be noticed that curve 2 has a s l i g h t l y higher r e f -  r a c t i v e index over most of t h i s section.  S ince the saturates have been r  removed i n curve 2 the difference must be due to the s l i g h t l y greater amount, of unsaturation. From e n  n  to " g  n  the curves l i and 2 r i s e r a p i d l y .  From the  iodine values and molecular weight t h i s f r a c t i o n i s a mixture of C^  g  t r i p l e unsaturates and Cg  0  to be a t r a n s i t i o n a l stage.  single and double unsaturates.  This appears  C urves 3 and 4 show no tendency to f l a t t e n  out. From g " to "h" the curves f l a t t e n out but show a tendency to n  gradually r i s e .  I t i s therefore d i f f i c u l t to draw any conclusions.  Since neither the molecular weight nor the iodine value show a tendency toward constancy t h i s f r a c t i o n probably consists of a mixture of Cgg, Cgg, and Cg^ unsaturated esters.  Due to the effects of oxidation and  polymerization the iodine value drops o f f . This may also.be due to the inaccuracy of the Wljs method f o r determining iodine values of such highly unsaturated substances. The above discussion i s summarized i n F i g . 4 which i s s e l f explanatory.  *  1  i  O O O ^ A  »ir  r  i i i i i i i i i i i i i M  OOeVI  r^~i i i ii~ i t T T T T p T i O O l V l  0 0 9 V I  i I i i i~rrrTT~~i 0 0 9 V I  i i rrr ~T ~rri~' i r  O O W l  r  ,  in  OOE-\r I  26 VII.  A p p l i c a t i o n of Results The present commercial methods of processing f i s h o i l s to remove the objectionable saturated f a t t y acids are: 1...Refrigeration - the cooling of o i l and pressing to remove the precipitated saturated glycerides. 2...Solvent  extraction - the use of solvent methods to remove the  saturated glycerides (28). Both of these methods operate on the p r i n c i p l e of separation of the saturated f a t t y a c i d glycerides from a mixture of the glycerides. According to the theory of H i l d i t c h , mentioned previously, the composition of the o r i g i n a l glycerides i s such that separation into saturated and unsaturated  f a t t y acid f r a c t i o n s i s impossible.  Any method employed,  therefore, must include conversion of the mixed glycerides into simple esters. From the r e s u l t s obtained i n t h i s i n v e s t i g a t i o n i t i s impossible to obtain a complete separation of the saturated from unsaturated acid esters by d i s t i l l a t i o n methods.  fatty  I t i s possible by f r a c t i o n a l  c r y s t a l l i z a t i o n to e f f e c t t h i s separation.  However, i n view of the  large i n i t i a l cost of equipment,: i t may not be the best method to use. A f t e r examining the curves f o r f r a c t i o n a l d i s t i l l a t i o n , i t may be possible to remove the majority of the unsaturated by t h i s means.  I f the fraction, from a w  M  to " e  n  f a t t y acids  i s removed, the r e s u l t i n g  f r a c t i o n should have a chain length and iodine value suitable f o r the production of a good grade of drying o i l .  T he y i e l d of drying o i l i s  only 65$ f o r this treatment while f o r c r y s t a l l i z a t i o n procedures the  27 amount -recoverable f o r drying o i l manufacture would be 77$.  This would  have some economic bearing on the choice of methods to be used f o r the separation.  28 VIII.  Summary  (,  '  -  An attempt i s made to separate the component f a t t y acids of Pilchard  o i l a f t e r f i r s t converting them from the glyceride esters to  the methyl esters. and  Two  methods are used, namely; f r a c t i o n a l d i s t i l l a t i o n ,  a combination of f r a c t i o n a l d i s t i l l a t i o n and  tion.  fractional crystalliza-  D i s t i l l a t i o n s are carried out at low pressures and  from acetone, solutions at low  crystallizations  temperatures.  '  A single f r a c t i o n a l c r y s t a l l i z a t i o n on the o r i g i n a l mixed esters removed p r a c t i c a l l y a l l of the saturated f a t t y acid esters.  I t does not  seem possible to completely remove the saturated f r a c t i o n by means of • e f f i c i e n t d i s t i l l a t i o n column. the fractions up to and  The  including  an  separation i s f a i r l y complete i f  the constant b o i l i n g mixture of  Ci6  saturated and unsaturated esters are removed. A larger y i e l d with a more complete separation i s obtained by f r a c t i o n a l c r y s t a l l i z a t i o n than by f r a c t i o n a l d i s t i l l a t i o n methods.  The  larger i n i t i a l cost of the equipment necessary f o r the former operation i s disadvantageous. The  lower i n i t i a l cost, s i m p l i c i t y of design, and  f a i r l y high  y i e l d of a p o t e n t i a l l y good drying o i l indicate a p o s s i b i l i t y f o r f r a c t i o n a l d i s t i l l a t i o n methods.  29 IX.  Bibliography  (1)  Mattiello, J. J . . - Protective and Decorative Coatings, V o l I, 61(1941), John Wiley & Son I n c  (2)  Bradley, T. F. - Ind. Eng. Chem., 29, 440(1937)  (3)  Mattiello, J. J . - Protective and Decorative Coatings, V o l I, 62(1941), John Wiley & Son Inc.  (4)  Brocklesby, H. N. - The Chemistry and Technology of Marine Animal O i l s , F i s h e r i e s Research Board of panada, B u l l . 59, 53(1941)  (5)  Brocklesby, H. N. - Ibid 34  (6)  Brocklesby, H. N. - Ibid 19  (7)  H i l d i t c h , T. P. - The Chemical Constitution of Natural Fats, 14(1940), John Wiley & Son Inc.  (8)  Lewkowitsch, J . , and Warburton, G . H. - Chemical Technology and Analysis of Fats and Waxes, V o l . I, 48(1938), MacMillan & Co., London  (9)  H i l d i t c h , T. P. - The Chemical Constitution of Natural Fats, 413(1940), John Wiley & Son Inc.  (10)  Brown, J . B., and Stoner, G. G. - Studies on the Chemistry of Fatty Acids, J . A. C. S. 59, 3(1937)  (11)  Swern, D., Scanlan, J . T., and Roe, E. T. - O i l and Soap 23, 128(1946)  (12)  De Gray, R. J . , and DeMoise, A. W. - Ind. Eng. Chem., Anal..Ed., 13, 22(1941)  (13)  Philipson, J.'M., Heldman, M. J . , Lynn, R. D., and Void, R. D. - O i l and Soap 21, 315(1944) -  (14)  Brown, J . B., and Stoner, G . G. - J . A. C. S., 59, 3(1937)  30 (15)  Althouse, P. M., and Triebold, H. 0. - Ind. Eng. Chem., Anal. Ed., 16, 605(1944)  (16)  Badger, W. L., and McCabe, V/. L. - P r i n c i p l e s of Chemical Engineering, McGraw H i l l Book Co., London, 1931  (17)  Walker, W. H., Lewis, W. K., G u i l l i l a n d , E. R., and McAdams, W. - Elements of Chemical Engineering, McGraw H i l l Book Co., London  (18)  H i l d i t c h , T. P. • * - The Chemical Constitution of Natural Fats, 367(1940), John Wiley & Son Inc.  (19)  Elsdon, G. D. - Edible O i l s and Fats, . :48 : (1926), Ernest Benn L t d . , London  (20)  Elsdon, G. D. - Ibid 137-43  (21)  Elsdon, G. D. - Ibid 138  (22)  Lewkowitsch, J . , and Warburton, G. E. - Chemical Technology and Analysis of O i l s , Fats and Waxes, Vol. I, 404, MacMillan & Co., Ltd., London  '  H.  "  s  (23)  Brocklesby, H. Ni - The Chemistry and Technology of Marine Animal O i l s , F i s h e r i e s Research Board of Canada, B u l l . 59, 25(1941) .  (24)  Trim - J . S. C. I., 39, 307T(1920)  (25)  Brocklesby, H. N. - The Chemistry and Technology of Marine Animal O i l s , F i s h e r i e s Research Board of Canada, B u l l . 59, 166(1941)  (26)  Jakobs, M., and H awkins, G. 0. - Elements of Heat T ransfer and e a t Insulation, 85(1942), John Wiley and S n Inc. H  0  (27)  Marks, L. S. - Mechanical Engineering Handbook, McGraw H i l l Book Co.  (28)  Solexol Process > - Chemical Industries, 1016(1946)  (29)  Lloyd, L. E., and Hornbacker, H, G. - Ind. Eng. Chem., Anal. Ed., 19, 120(1947)  

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