FURANS IN VEGETABLE 011 REFINING S T E W A R T W. G L O Y E R PITTSBURGH PLATE G L A S S COMPANY. MILWAUKEE, WIS.
4 process has been developed whereby natural glyceride oils may be separated into two or more different fractions. The process is dependeht on the use of selective solvents with which the oils are not completely miscible a t operating temperatures. Thus, when a glyceride oil and a selective solvent are brought together a t a temperature lower than t h a t of complete miscibility, two fractions are obtained. Although many solvents are selective, the most practical and the one used commercially is furfural. Fractionation is accomplished in a packed countercurrent column by passing the solvent downward through a rising column of glyceride oil. In the case of furfural, 6 to 14
parts are employed per part of original feed oil. The process is adapted to the fractionation of many vegetable and animal oils and has been operated commercially on the fractionation of linseed and soya oils. Linseed oil has been fractionated to yield extract resembling Perilla oil; soya oil, to yield an extract essentially equivalent to linseed oil in drying and a raffinate which is an improved food oil. The process, not limited to operations based on degree of unsaturation within a glyceride mixture, may be used to fractionate fatty acids, concentrate valuable minor ingredients of oils, or separate compounds of different molecular w-eight.
iquid fractionation of glyceride oils using furfural as achieved with the use of a hydrocarbon naphtha to keep the the selective solvent is dependent upon the fact that oils system immiscible. are not completely miscible at normal temperatures in furfural. To produce separations of comniercial value, it is necessary t o When a glyceride oil and furfural are contacted a t a temperature apply all the refinements of the selective solvent technique, such beloiv that of complete miscibility, two fractions are obtained, as careful control of solvent ratios, temperature of extraction, a, solvent-predominant fraction and an oil-predominant fraction. height of the extraction column, type of column packing, and It has been found ( S , 4 ) that the more unsaturated glycerides are amount or kind of reflux used. Experience has shown that all preferentially soluble in the furfural-predominant phase, or sothese factors are extremely important for separation and that called extract phase, with the more saturated glycerides remaining control must be precise. in the oil-predominant phase, or so-called raffinate phase. AlIn order t o clarify the operation of solvent fractionation in a though'the degree of separation achieved in a single stage or countercurrent column, a simplified diagram is shown in Figure single batch contacting of furfural with oil is rarely adequate, 1. The column is packed with '/*-inch Raschig rings or '/n-inch remarkable separations of the component glycerides of natural Berl saddles, so that a free space or settling chamber is allowed fats can be achieved by the utilization of continuous counterat both ends of the column. current extraction and reflux. Furfural is introduced near According t o these princithe top, usually in a ratio ples, the PittsburghPlate Glass R A P F I N A T E OIL $OLUTlON of 6 to 14 parts per part Company has operated its mo(RAFFINATE PRODUCT Low I.V.) of feed oil, and travels downlecular selection process comward countercurrent to the mercially with furfural as the rising oil. FURFURAL FEED selective polar solvent. This Oil is introduced a t an process as applied to glyceride intermediate point between the oils utilizes the principles of furfural and reflux feeds and liquid-liquid extraction with at such a position that the selective polar solvents to iodine value of the oil within separate the relatively unsatuthe column is very nearly the rated from the more saturated same as that of the feed glycerides. Fractionation deoil. pends upon the preferential Part of the extract prodsolubility of the more highly uct oil is fed into the bottom unsaturated glycerides in the of the column as reflux. This furfural. is important to obtain a high The furfural extraction prociodine value product and caness is not limited t o sepanot be achieved as efficiently rations based on unsaturation in any other rTay. Naphtha within the glyceride molecule may be used in place of but also operates on differextract product oil as a reences in molecular weight such flux medium; however, less as the carbon chain length of FURFURAL efficient results have been obthe fatty acids within the tained with the use of naphtha glyceride molecule, or on the alone. An efficient reflux differential solubility of the medium is obtained by using various minor ingredients in E X T R A C T OIL SOLUTleN approximately 15% by volthe dil. Separation of free (EXTRACT PRODUCT HIOH LVJ ume of naphtha with extract fatty acids (6, 6) on the basis product oil. of unsaturation may also be Figure 1. Diagram of column operation
1
7-
228
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
February 1948
An inte;face is generally maintained between the oil feed and the solvent feed, with the oil phase predominant in the upper part of the column and the furfural phase predominant in the lower part. The furfural then falls in droplets through the upper, oilpredominant phase, and the oil conversely rises in droplets through the furfural-predominant phase, The interface is controlled by using a n overflow leg on the column or by throttling the flow of extract solution from the column. Figure 2 shows a number of 9-foot-high by 2-inch-diameter laboratory columns, These columns are used to predict the type of separation that might be expected in longer pilot plant columns and are also used t o set the initial conditions of operation for the pilot plants. Figure 3 shows in simplified form the flow sheet of a plant a t present handling a tank car of feed oil a day. It is obvious by comparison with the previous figures that the process mechanically is largely one of solvent recovery. The raffinate or low iodine value (I.V.) fraction flows out of the top of the column to a flash evaporator operating a t 100 mm. mercury vacuum where the greatest amount of solvent is removed. The concentrated oil-furfural solution then passes to t h e top of a bubble-plate stripping column which is operated under 50 mm. mercury vacuum and into which superheated steam is passed at the bottom. I n this unit the solvent is completely removed from the oil. The extract solution passes out of the column at the bottom and likewise is fed to a n evaporator and stripper. Part of the stripped extract oil is returned to the column as reflux, the remainder sen: to extract storage. The furfural from the evaporator condenser is free of water and is sent directly t o solvent storage; however, that from the stripper condenser also contains water from t h e condensed stripping steam, and this mixture is sent to a tlecanter tank where the water and furfural are separated into immiscible layers. Water and furfural form a minimum boiling mixture which makes a convenient system for obtaining anhydrous furfural. The water layer containing approximately 8% furfural is pumped to the top of a bubble-plate still operating at atmospheric pressure, and superheated steam is passed into the bottom. The azeotropic mixture is distilled and caught in the decanter where it again layers out into a water and a furfural. layer. The excess water from the still passes to the sewer. The wet furfural layer from the decanter containing approximately 5% water is sent t o a vacuum dryer operating a t 100 mm. mercury pressure, in which the azeotrope distills, allowing the dry furfural to return to storage. Figure 4 is a picture of the plant handling 8000 gallons of feed oil per day.
229
pilot plant indicated that more efficient fractionations could be obtained by using longer fractionating columns, and by using higher solvent and reflux ratios. In order to test these points, a series of runs was made in a 22-inch-diameter column at 64- and 87-foot heights. I n the first of these runs the same conditions of operation were used, except that of column height. The results obtained in this study are given in Figure 6. The difference in iodine value spread between the extract and raffinate product using the shorter column was 66.2 units as compared to a spread of 73.9 units using the longer column; this shows that the longer fractionating column gave more efficient fractionation. In the second of these runs the 22-inch-diameter by 87-foothigh column was used, but the solvent and reflux ratios were varied. These results are shown in Figure 7. The iodine value spread between extract and raffinate products obtained using the higher solvent ratio was 73.9 units as compared to a spread of 67.5 iodine value units a t the lower solvent and reflux ratio. The results obtained in these two experimental runs (Figures 6 and 7) indicate the value of increased column height and increased solvent and reflux ratios in allowing maximum fractionating efficiency. In another series of studies to determine the effect of column diameter on the efficiency of separation, runs were made in 2-inch, 22-inch, and 66-inch-diameter columns under the same conditions of operation. All columns were operated a t 7.3 to 1 furfural to feed oil ratio, and 0.73 to 1 extract product reflux to feed oil ratio. The results obtained in this series of runs are shown in Table I, which shows that the 2-inch-diameter column is much
LINSEED O I L
During a four-year period more than 6,000,000 gallons of linseed oil were fractionated to yield a high iodine value extract which was similar to Perilla oil in its properties. The linseed oil used for these fractionahons was alkali-refined and bleached. At oil feed rates of 12,000 gallons a day the plant was operated as shown in Figure 5. Studies conducted in the laboratory and
Figure 2.
Laboratory columns 9 feet high and 2 inches i n diameter
230
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 40, No. 2
INDUSTRIAL AND ENGINEERING CHEMISTRY
February 1948
more efficient than the 22- or 66-inch, even though it is shorter. The degree of fractionation obtained in the 22inch and 66-inch columns of relatively similar length is for all practical purposes the same. I n other words, the height per stage of separation is considerably less with a 2-inch-diameter column than with a 22-inch or larger dhmeter, and columns from 22 to 66 inches in diameter have essentially the same height per stage. These results, as well as those shown in Figures 6 and 7, show that it is necessary to have longer columns when the diameter is 22 inches or greater, to obtain the same degree of fractionation as obtained in a 2-inchdiameter column. Although a shortage of equipment has limited commercial extraction of linseed oil thus far t o the use of alkali-refined oil, it has been found that crude oil may be used as a feed if a two-column system is employed and naphtha used in conjunction
'
Figure 4.
TABLE
Diam.
of
Column, In. 2 22 66
1. RELATION Height of Column, Ft. 50 64 b7
231
COLUMN J k A M E T E R TO DEGREE OF FRACTIONATION
OF
Yield of Iodine Value Extract, of Extract % 84.4 196.7 76.5 195.2 76.0 195 8
Iodine Value of Raffinate 115.8 129.0 130.2
Iodine Value of Feed Oil 184.3 179.5 180.1
Plant handling*8000 gallons of feed oil per day
with furfural. When crude oil is used as a feed, a relatively small amount of naphtha is added with either the feed oil or oil reflux in the first column. The extract solution produced in the first column is then fed to the top of a second column, and sufficient naphtha is fed to the bottom of the second column, to remove most of the glyceride oil from the furfural solution; this leaves free fatty acids, traces of break constituents, and unsaponifiable matter in the furfural. The oil removed by the naphtha is break-free and may be employed as a varnish oil. The major portion of the break material is concentrated
RAFF\NATE 2s 7 . 132.2
1.v.
RAFFINATE
RAFFINATL 23.5 Y o \29.01.V.
2 1.5 Y e
FURFURAL --. 6 PARTS
li11.7 I.V.
FURFURAL Z 3 PARTSFURPU R A L
7.3 PARTS LINSEED OIL
-
L I N ~ E EOIL D (\EID.I IYj I PART
(179.5 I.V.) I ?eRT
L ~ N J E E DO I L (179.5 1.U)
EXTRACT PRODUCT REFLUX 0.73 PART EXTRACT PRODUCT REFLUX, 0.6 PARTS
EXTRACT PRODUCT
EXTRACT 7 8.5 Yo
75 7. 196.3
Figure 5.
64FT.
I PART
i95.6 I.V.
1.v.
Refined linseed oil
Figure 6.
REFLUX 0.73 PART
EXTRACT
76.5% 195.2 1.Y.
Results with refined linseed oil showing effect of column height
232
INDUSTRIAL AND ENGINEERING CHEMISTRY
RAFFINATE
RAFFINATE
R AFF INATE
24.57'e
!
21.5 "7121.7 I.v.
FURFURAL
1.v.
128.6
t
i
Vol. 40, No. 2 EXTRACT
7.3 PAnrs
LiNsEED (179.5
OIL
1.v.)
(179.5
I PART
I ! CRUDEL I N ~ E B D
I
87FT.
3 7 FT"
I PART
87FT.
NAPHTHA
0 . 0 6 6 PART
1.v.)
I PART
EXTRACT PRODUCT RrFLur 0.66 PART*
EXTRACT PRon REFLUX 0.73 PARTS
,
REFLUX 0.6 PART6
EXTRACT
EXTRACT
78.5 Y.
75.5 7.
PRoDVCT
195.6
196.1
EXTRACT RAFFINATE.
1.v.
1.v.
Figure 7. Results-with refined linseed oil showing effect of increased solvent and reflux ratios
NAPHTHA 4 PARTS
t
BYPRODUCT
'70
IODINE
% FREE
YIELD
VALUE
FATTYACID 0.5
- 59.6 37.3
141.3
0.6
BY PRODUCT3 . 1
177.0
FCLD
173.5
24.0 2.7
196.5
Figure 8.
RACFINATE 407. 1175 IOOINE VAL* 0.018% FREEFATTYACIDS
COLOR GARDNER 7.5 8.0
BLACK, 9 5
Crude IinseedIoil
R A F F I NATE 42.2 7 ' -
RAFFINATE 37.2%
108.2 I.V.
112.3 I.V.
4
FURFURAL 11.1 PARTS
1
L
:
6 7 FT.
138 IODINE VALUC 0.55% FRCF.FATTY ACID
-5
€%TRACT
i'-
PRODUCT
1.56 PARTS
t
€XTRACT
609'
L FURFURAL 8.3 PARTS
OIL (135.8 I.V.)
SOYA
\
PART
REFLUX 1.1 PARTS
Nonbreak soya oil
in the raffinate phase. This type of fractionation is illustrated in Figure 8. The results shown in the example just cited were obtained in relatively short columns; however, more efficient extractions are expected in longer, well designed towers. The results obtained show that the extract and raffinate are both of better color than is the feed oil, with the coloring components passing into the by-product. Both extract and raffinate are lower in
Figure 10.
4
EXTRACT REFLUX PRODUCT I . \ PARTS
EXTRACT 6 2.8 Y e
151.5 IODINE VALUE 0.85% FRILL FATTYA c i o s Figure 9.
1+
EXTRACT 57.8 Yo
152.1 I.V. 152.8 I.V. Results with nonbreak soya oil showing effect of column height
free fatty acid than the feed oil, and still lower free fatty acid contents are anticipated in longer towers. SOYA ai^
Fractionation of soya oil on a commercial basis has beern accomplished with nonbreak oil as a feed. The conditions of operation and the results being obtained are shown in Figure 9. The raffinate from this plant is low in free fatty acid and has
233
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
February 1948
108.2 I.V.
t
1
RAFFINATE
RATFINA T E 3 0Y o 95.5 I.V.
R AFFIN AT E 37.270
-
25% 105 I.V.
t
FURFURAL 14 PARTJ
87fT.
SOYA
OIL
4 5 F1
(135.8 I.V.) 1 PART
1
/'
-4
REFLUX
EXTRACT PROOUCT REFLUX 1 . 1 PART^ EXTRACT 62.6% 152.1 I.V.
Figure 11.
0 . 8 8 PART
EXTRACT
EXTRACT
EXTRACT 50% 134 I.V.
25%
70 Yo
160 I.V.
i 5 3 . 2 I.V.
Figure 12. Nonbreak soya oil
Results with nonbreak soya oil showing effect of increased solvent and reflux ratios
been processed in tank car quantities directly into food products, such as shortenings and salad oils, without any further refining. The extract fraction is a drying oil which approximates the drying of linseed oil. In making direct replacement of soya extract for linseed, it has been found desirable to adjust drier kind and content. Cobalt driers used along with the usual lead and manganese salts are particularly favorable to soya extract. Experimental results as well as calculations made from equilibrium diagrams have shown that the 67-foot-high by 5.5-footdiameter column is not of optimum length, and therefore fractionations of maximum efficiencycannot be obtained in it. Results obtained in a 2-inch-diameter column 87 feet high show the effect of increased column height and increased solvent and reflux ratio on the degree of fractionation obtained (Figures 10 and 11). The results shown in Figure 10 illustrate the effect of column height on fractionation, all other conditions of operation being the same. An additional 23 feet of column increased the extract yield by 5% and increased the iodine v a h e spread from 40.5 t o 43.9 units. Figure 11 illustrates the effect of increased solvent and reflux ratios on the degree of fractionation obtained with the condition of column height being maintained constant. At the increased solvent and reflux ratio an additional 7.2% of extract was obtained, and the iodine value spread was increased from 43.9 to 57.7 units. These examples illustrate that extra column height can be used t o obtain additional stages of separation and, therefore, greater efficiency of fractionation. It has also been shown that a greater degree of fractionation can be obtained by using increased solvent and reflux ratios in columns 87 feet high. These results indicate that extra column height can be used to compensate for higher solvent ratios to allow t h e most efficient separations. It is then obvious that a n 87-foot column is not of optimum length for the fractionation of soya oil, but that a much longer column is required to obtain efficient fractionation at a relatively low solvent ratio. Soya oil has also been split into three fractions to yield a high iodine value paint fraction, a n intermediate iodine value winter-
t
~NTLRMCDIATL
RMFINATE 39T o 109 I.V. .OS% F ~ c FATTY r ACID
-
FURFURAL 83 PART^
3OYA
OIL
(I35 \.VJ
-
I PART
EXTRACT
60%
152.3 I.V. 0.15 7. FREEFATTY ACID
i -
-
EXTRACTReFLux 1.1 Pm+s NAPHTHA
0.2 PART
BY PR'ODUCT 1.0 7. 139.6
I.V.
1 7 . z r o FREEFATTY ACID 7 . 0 % UN~AP.
Figure 13. Degummed soya oil
ized salad oil fraction, and a low iodine value fraction suitable for hydrogenation. The oil used was also nonbreak soya oil and was fractionated as indicated in Figure 12. I n order to use a less refined grade of oil, it was found that crude soya or degummed soya oil could be fractionated with the use of naphtha in conjunction with furfural. A two-column system is used in this type of fractionation, some naphtha being fed to the
INDUSTRIAL AND ENGINEERING CHEMISTRY
234
first, column with the extract product reflux in order to aid in the separation, and a relatively large $mount of naphtha is fed to the bottom of a second column to remove most of the extract, oil from the furfural solution. Sufficient naphtha is used in this second column to rciiiove most of the glyceride oil from the furfural solution, leaving in the furfural as a by-product a concentration of coloring pigments, free fatty acids, traces of break constituents, and unsaponifiable matter. The naphtha extract is a light-colored oil, break free and relatively lon in free fatty acid. This oil is varnish grade quality and may be used directly without any further refiniig.
RAFFINATE 45 %
Vol. 40, No. 2
SARDINE O I L
Sardine body oil may be fractionated with comparative ease, as is shown in Figure 14. This fractionation was accomplished in a &foot column, and the feed oil vias alkali-refined. DOGFISH LIVER OIL
The molecular selection process using furfural as the solvenu has been applied to the concentration of vitamins from fish liver oil. In this fractionation it has also been found that long fractionating columns are desirable for an efficient concentration of vitamin -4. The vitamin was concentrated under the conditions shob7-n in Figure 15, and the vitamin A potencies n-ere determined using an Evelyn photoelectric colorimeter according to the method of Dann and Evelyn ( 1 ) .
145 I.V.
FURFURAL 6 PARTS
I PART
C X T R A C T PRooucr
R c LUX 0.48 PART
t
EXTRACT 19.1v*
RAFFINAT E
1
I
EXTRACT 5 5 .% 230 I.V. Figure 14. Alkali-refined sardine oil
The raffinate produced in this type of fractionation will have concentrated in it most of the break material present in the original feed oil. For this reason it is more desirable to use a degummed oil and preferably one which is break free. Fractionation of this type of feed oil has yielded raffinates of good color and low free fatty acid content, so that no further refining has been necessary for the preparation of hydrogenated fats. The by-product, a concentration of free fatty acids and unsaponifiable constituents, is a valuable fraction. As such, it is a source of raw material for the preparation of sterols, tocopherols, and free fatty acids. A sample of by-product containing 7.8% unsaponifiable matter analyzed 2,7% tocopherol by a modified Emmerie-Engle method (2, 10, 11) and 2.4y0sterol. The yield of sterol was determined by crystallization of the crude unsaponifiable matter with methyl alcohol. The fatty acids liberated by acidifying saponified by-product which has been extracted for the removal of unsaponifiable matter have varied in iodine value from 155 to 165. These fatty acids show a concentration of drying acids over that of crude soya oil. A fractionation illustrating this type of separation is shown in Figure 13. Although the iodine value of soya extract is considerably less than that of linseed oil, the amount of drying acids in the two oils is virtually the same. This is shon n in Table 11. The thiocyanogen values and final calculations n eir macle according t o the method of Painter and Sesbitt (9).
78.470 J,200U. VIT. A/G
82,000 U.VIT. A/G. 173.8 I.V.
90.2 1.V
4.9 A.V.
.04 A.V
I .I
NAPHTHA SATD, FURFURAL 20 P A R T J
1~000U. VIT.A/G. I O 9 I.V.
3.4 A.V.
EXTRACT REPLUX (0.17 PART)
NAPHTHA REFLUX
t
BY P R O D U C T 2.5 70 6,600 U. Vir. A/c. 161.2 I.V.
99.9 A.V. Figure 15. Dogfish liver oil
In this fractionation an extract containing 82,000 units of vitamin A was obtained in 19.1% yield. The distribution of the original vitamin A present in the dogfish liver oil is shown in Table 111. This example is indicative of the type of concentration that might be effected. If a higher concentration of vitamin A is desired, the operation may be conducted to give a lower yield of extract. Potencies of 150,000 units of vitamin A have been obtained by merely adjusting the yields. TABLE11.
Linseed Soya extract
DRYING!lCIDs LINSEEDOILS
P E R CENT
Iodine S C N Value Value 181.6 118.2 153.4
94.6
IX SOYA EXTR.4CT AND
Glycerides, ?& (Calcd.) SatuLinLinrated Oleic oleic olenic 10.0 24.5 12.3 53.3 10.2 20.5 51.3 18.0
70
Dryink Acids 65.5 69.3
~~
TABLE 111. DOGFISH LIVEROIL Extract Raffinate By-product Vitamin 108s
Yield, $6
yo of Original Vitamin A
19.1
89.5 5.3
78.4
2.8
...
0.9 4.3
INDUSTRIAL A N D ENGINEERING CHEMISTRY
February 1948
235
amount of furfural and naphtha used. The results of these fractionations are shown in Table IV. Although the fractionations obtained with these fatty acids are not so efficient as can be obtained from longer columns, the results show a high concentration of drying acids in the extract fractions (Table V). The thiocyanogen values and calculations were made according to the method of Painter and Nesbitt (9).
RAWI NATE 60% 147 I.V.
f
TALL O I L
(I
Numerous studies have been made on tall oil with the object of separating the fatty acids from the rosin acids. The well known fact that fatty acids may be easily esterified with alcohols, whereas the rosin acids are esterified with great difficulty (8), was coupled with the furfural extraction process to form the basis of an effective separation of the fatty acids from the rosin acids. In this process (7) the fatty acids of crude tall oil are esterified with methyl alcohol by refluxing the foklowing mixture for 2.5 hours: 110 parts by volume crude tall oil, 22 parts by volume methyl alcohol, and 1.9 parts by volume concentrated sulfuric acid. To this esterified mixture were added 30 parts by volume of naphtha, and the mixture was washed with water to remove the excess methyl alcohol and the mineral acid. The washed, partially esterified mixture was diluted with an additional 40 parts by volume of naphtha to give a final mixture containing 35% by weight naphtha and 65% by weight partially esterified tall oil. This naphtha solution was used as a feed to a fractionation column as shown in Figure 17. The furfural used in this fractionation was saturated with naphtha and water at 80' F.
PART)
NAPHTHA (1.5 PARTS)
t EXTRACT 40%
253.5 I.V. Figure 16. Linseed acids
The high potency fraction has ahad removed from it much of the fishy odor and taste that is usually associated with the original oil. Although the iodine value of the concentrate is considerably higher than that of the original oil, there was no destruction of the vitamin on storing this oil over an 8-month period.' The excellent stability of this concentrate may be exp!ained in part a t least by the concentration of tocopherol with the vitamin A. The original.dogfish liver oil was found t o contain 0.08% tocopherol and the concentrate 0.39%, or a fivefold concentration of the tocopherol. LINSEED FATTY ACIDS
Since fatty acids and furfural are completely miscible, naphtha which is immiscible with furfural is employed in order to make the system operable. The results listed were obtained in a 45foot column and are therefore only indicative of the type of fractionation that may be obtained using longer columns. A fractionation of linseed fatty acids is shown in Figure 16. I n this run the furfural used was saturated with water and naphtha at
78"F. Linseed foots acids and soya acids have been fractionated in virtually the same manner with only minor variations in the
TABLEIV. FRACTIONATION OF LINSEED FOOTS ACIDS AND SOYAACIDS
Original Acid Linseed foots Soya
Extract,
% 34 39
I.V. of Extract 236 178
I.V. of
Ra5nate 144 115
I.V. of Orimnal Acid 178.0 137.7
TABLEV. EXTRACT COMPOSITION OF FRACTIONATED FATTY ACIDS SCN Per Cent Found I.V. Value Saturates Oleic Linoleic Linolenic 18.9 80.8 0.8 1.2 Linseedextract 253.5 153.7 11.5 74.9 2.0 11.5 Linseedfootnextract 236.0 147.3 24.0 6.7 14.2 55.3 Soya extract 178.0 116.1
I
4 k % RAFFINATP
H a 0 AND NAPHTnA 4.25 PARTS
2.9% ROUN ACID 82.89. FATTY ACID E 8 r ~ a s
14.3%
UNIAP.
I
NAPHTWA 1.56 PART^
4 1I
1.3% ROSINA L ~ D 6.57. ROSINACID 2 . 9 3 UNIAP. 38.5% UNMP. 95.8% FATTY ACIDESTLR B L ~ c KC O L O R 3 GARDNCRC O L O R
51.5% EXTRACT 84.7% R a s i N A C ~ D COLOR B L A C K
-
Figure 17. Tall oil
The raffinate was produced in 48.5y0 yield of the crude tall oil fed. This raffinate, although it contained only 2.9% rosin acid, had 14.3% unsaponifiable matter in it. I n order t o produce a lighter-colored product and one which is relatively free from unsaponifiable, matter, the raffinate was submitted to vacuum distillation. The methyl esters produced were light-colored and were essentially 96% fatty acid esters. SUMMARY
Furfural has been used commercially for a number of years in the fractionation of the relatively unsaturated from the more saturated glycerides. I n addition, furfural in conjunction with naphtha waa used in the fractionation of free fatty acids to obtain fractions composed of 85 to 98% drying acids from soya and linseed acids. The furfural extraction process has also been employed in the concentration of vitamin A from liver oils. A concentrate in 19% yield containing 82,000 units of vitamin A per gram was obtained from a dogfish liver oil having a potency of 17,500
236
INDUSTRIAL AND ENGINEERING CHEMISTRY
unit's of vitamin -1per gram. Potencies of 150,000 units of vitamin A per gram have been obtained by lowering the yield of extract. These concentrates have also had removed much of the fishy odor and taste associated with the original oil. Tall oil has been fractionated to yield a fraction v,ith only 1.3% rosin acid and 2.9% unsaponifiable matter, the remainder being fatty acid ester. This process involves t,hc preferential esterification of the fatt,y acids folloived by fractionation with a mixture of furfural and naphtha. ACKNOWLEDGMENT
The author gratefully aclrnoivledges the assistance of many eo-workers of the Pittsburgh Plate Glass Company, Paint Division Research Laboratories, and especially W, H. Lycan, S. E. Freeman, E.&I. Christenson, and H. A. Vogel.
Vol. 40, No. 2
LITERATURE CITED
(1) 12) (3)
Dam, \I J., " and . Evelyn, K. A., Biochem. J . , 32,1008 (1938). Emmerie. 8..and Enele. C.. Rcc. trav. chim.. 57. 1351 (1938). Freeman,' S.'E. (to Pittsburgh Plate Glass Co.), U.'S. Patent
2,200,390 (May 14, 1940). (4) I b i d . , 2,200,391 (May 14, 1940). (5) I b i d . , 2,313,636 (March 9, 1943). (6) I b i d . , 2,278,309 (March 31, 1942).
( 7 ) Freeman, S. E., and Gloyer, S. W. (to Pittsbuigh Plate Glass Co.), U. S. Patent 2,423,232 (July 1, 1947). (8) Hiesen, I$., Fette ZL. Seijen, 44, 426 (1937). (9) Painter, E. P., and Nesbitt, L. L., IND. CNG.CHEM.,ANAL. ED., 15, 123-7 (1943). (10) Parker, W. E., and McFarlane, W.D., Can. J . Research, 18, 406 (1940). (11)
Rawlinga, H. W., Oil & S o a p , 21, 257
(1944).
RECEI\EDOctober 9, 1947.
FURAN RES1 A R T H U R J. N O R T O N ,
Z S I ~ F I R S T A V E N U E S O U T H , S E A T T L WASH E.
A review of the advantages of the furans as base chemicals for synthetic resin and high polymer work is given. The five basic reactions now utilized industrially in resin work are reviewed, and the advantages accruing from these are discussed in some detail. Particular emphasis is given to the methods of evaluation of plastic materials by tests on rate of flow. In addition to the utilization of the furans by the standard reactions now used, the possibilities of the newer and less understood reactions are emphasized.
I
N ORDER to qualify for an extensive market in the resin and plastics industry, a chemical or seiie? of chemicals must first of all be potentially available in large quantities and of a consistent quality. Second, for direct participation in the foimation of synthetic resins and polymers, the chemical must have a high degree of reactivity and should preferably be,able to enter into a wide diversity of reactions. Third, a high degree of compatability and good solvent poiveis extend the field of usage in this industry, and fourth, the product should be marketable at a reasonable price. How well the furan chemicals qualify in all these respects is shown by their rapidly increasing rate of usage. In 1947 the amount of furan chemicals used in the resin and plastics field will be about sixteen times that used in 1937. In the same tenyear period phenol usage in the same industry increased only about five times. The development of a complete background of furan chemistry coupled with the ever-increasing understanding of high polymer chemistry has contributed a great deal to the rapidly increasing rate of usage. At the present time there are five basic reactions of the furans that are commonly utilized in the resin and plastics industry: (a) direct aldehyde condensations, such as in phenol-furfural resins; (b) formation of high polymers through ether linkages, as in the reactions of furfuryl alcohol with dimethyl01 urea; (c) methylene bridging, as in the formation of furfuryl alcohol resins; (d) addition polymerization through the conjugated ring structure of the furan molecule, as illustrated by the final stages of the resinification of furfuryl alcohol in the presence of acid; and ( e ) chemical modifications, as in the production of diamines for polyamide resins. This last phase will not be elaborated on here, but is injected as a reminder of the versatility of the furans as a source of chemicals for resin formation as well as by their more direct utilization in condensation and polymerization reactions.
In addition t o the classified reactions there are many special and mixed types of reactions that may become of increasing importance as they become better understood. DIRECT ALDEHYDE CONDENSATIONS
Fuifural reacts in general as do all alpha substituted aldehydes. With phenol it condenses in the presence of either alkali or acid to form synthetic resins in a reaction that is quite analogous t o that of phenol with formaldehyde or acetaldehyde. The reaction is exothermic and requires the usual control methods t o prevent the resinification froin going beyond the workable stage. When one mole of phenol is reacted with less than one mole of furfural in the presence of an acid catalyst, the initial reaction appears to be the formation of dihydroxy diphenyl furan methane by the condensation of one mole of furfural with two moles of phenol. Continued reaction links more phenol groups together to form a Novolak or permanently fusible type of hard brittle resin. This resin is largely zt linear polymer of relatively low molecular weight-perhaps eight to twelve phenol groups per molecule. Since only two of the active positions in the phenol ring have been substituted, this product is capable of further reacting with condensing agents or more furfural to form crosslinked or thermoset resins. It is a typical two-step phenolic resin of commerce. Khen one mole or more of furfural is reacted with one of phenol in the presence of catalytic amounts of alkali, the condensation is more rapid, and, without control of the heat of reaction, it will go to a completely thermoset inert mass. By control it can be stopped a t a point where the condensation product is a hard brittle mass, fusible at about 100" C. and soluble in spirit solvents. With further heating this intermediate resin will condense through the methylol groups to give a cross-linked thermoset product typical of the one-step phenol aldehyde resins. The condensation products of this general type are usually compounded or mixed with modifying ingredients and used for molding compounds, impregnating solutions, bonding agents, coating materials, or adhesives. In all uses, heat or heat and pressure are required to convert the products t o the inert thermoset stage. Consequently, in every use the ratio of the rate of flow of the material under the application of heat or heat and pressure to the time of cure or setting is the governing factor in the usability of the produet. This relation of the physical property of flow t o the time required
