The process as described with some probable refinements should be readily adaptable to a commercial operation. Production of dinitriles and diamines from oils other than crambe is already conducted on a plant scale. Other operations in the process are not expected to introduce any serious operating problems.
Acknowledgments The authors acknowledge the technical assistance of J. P. English, S. B. Henry, W. L. Mayfield, A. Hopson, Jr., J. P. Long, W. C. Stoner, Jr., and Robert G. Fecht. K. D. Carlson, W. H. Tallent, and I. A. Wolff contributed to the planning and direction of the work. Most of this work was carried out at the Southern Research Institute, Birmingham, Ala., under Contract 12-14-100-10298(71)with the U.S. Department of Agriculture and authorized by the Research and Marketing Act of 1946. The contract was supervised by the Northern Regional Research Laboratory.
Critchley, S.W., British Patent 896 436 (Geigy Co.. Ltd.). (May 16, 1962). Fallwell, W. F., Chem. Eng. News, 53 (5),8 (1975). Genas, M., French Patent 958 178 (Societe Organico), (Mar 3, 1950). Greene, J. L., Jr., Huffman, E. L., Burks, R. E., Jr., Sheehan, W. C., Wolff, I. A,, J. Polym. Sci., A- 1, 5, 39 1 (1967). Griehl, W., Ruestem. D., Ind. Eng. Chem., 62 (3), 16 (1970). Kohlhase, W. L., Pryde. E. H., Cowan, J. C., J. Am. OiIChem. Soc., 47 (9, 183 (1970). Miller, W. R., Pryde, E. H., Awl, R. A., Kohihase. W. L.. Ind. Eng. Chem., Prod. Res. Dev., 10, 442 (1971). Nieschlag, H. J., Hagemann, J. W., Wolff, I. A,, Palm, W. E., Witnauer. L. P.. lnd. Eng. Chem., Prod. Res. Dev., 3, 146 (1964). Nieschlag. H. J.. Wolff, I. A., #J. Am. OiiChem. SOC., 48 ( I I ) , 723 (1971). Perkins, R. B., Jr., Roden, J. J. IIi, Pryde, E. H.. J. Am. Oil Chem. Soc., 52 (11). 473 (1975). Sittig. M., in "Organic Chemical Process Encyclopedia," pp 47, 302, Noyes Development Corp., Park Ridge, N.J., 1967. Sohns, V. E., J. Am. Oil Chem. Soc., 48 (9), 362A (1971). Sweeny, W., in "Polyamides in Kirk-Othmer Encyclopedia of Chemical Technology," 2nd ed, Vol. 16, p 26. Wiley, New York, N.Y., 1968. Sweeny, W., Zirnmerman. J.. in "Polyamides," N. M. Bikales, Ed., "Encyclopedia of Polymer Science and Technology," Vol. IO, p 576, Wiley-lnterscience, New York, N.Y., 1969.
Received for review October 26,1976 Accepted December 1,1976
Literature Cited Billmeyer, F. W., Jr., in "Textbook of Polymer Science," 2nd ed, p 188, WileyInterscience, New York, N.Y., 1971. Carlson, K. D., Perkins, R. B., Jr., Huffman. E. L.. Sohns, V. E., lnd. Eng. Chem., Prod. Res. Dev., I S , 95 (1977).
T h e mention of firm names or trade products does n o t imply t h a t they are endorsed or recommended by the Department of Agriculture over other f i r m s o r similar products n o t mentioned.
Dehydration of Castor Oil D. N. Bhowmick and S. A. N. Sarma' Depadment of Oil and Paint Technology, Harcourt Butler Technological Institute, Kanpur-208002 (U.P.) lndia
Castor oil is dehydrated using sodium bisulfate to yield high conjugation values. Alcohol extracts of the products are isolated to determine mechanism sequence fission products and cis/trans isomers.
Introduction The dehydration of castor oil has been carried out by many workers (Om Prakash et al., 1953; Sivasamban et al., 1951, 1956) using sodium bisulfate, which is supposed to be one of the best catalysts that could be used for dehydrating castor oil. The possible courses of dehydration are well known and are as follows. 8
9
10
11
13
12
gated and nonconjugated acids balance each other (Von Mikusch, 1955). The catalyst sodium bisulfate ionizes into Na+ and H S 0 4 and forms sulfuric acid and sodium hydroxide along with the liberated water molecule. This causes the lowering of effective concentration of the catalyst, sodium bisulfate.
---*
14
Na+ 9
10
11
12 13 14
Conjugated system
8
9
10
11 12
13
14
Nonconjugated system
It has been found that regardless of the type of catalyst used or procedure adopted, the quantitative formation of conju-
Na+
-
+ OH-
+ NaOH + HzS04
2NaOH 8
-
+ HS042H20 H30+ + OHHS04- + HC3O+ H2S04+ H 2 0 NaHS04
-
NaOH
+ 2H20 NaHS04 + H20 Na2S04
(1)
(2)
However, it is seen that higher conjugation can be obtained by perhaps maintaining a higher hydrogen ion concentration which in turn would maintain the effective concentration of the catalyst throughout the reaction, suppressing the formation of sodium sulfate. Although it could be argued that the differences in H+ ion concentration may not be much lower if dehydration is conducted a t atmospheric pressure instead of a t reduced presInd. Eng. Chem., Prod. Res. Dev., Vol. 16, No. 1, 1977
107
Table 1. Experiment No. 1. Alcohol Fractionation of Dehydrated Castor Oil. (Acetyl values, saponification values and percentage conjugation of various samples of Experiment No. 1. Raw castor oil has saponification value 185: Acetyl value 160)" %
Samples
yield
Saponification value
Acetyl value
%
coniugation ~~
1%
-
lS2
-
lSlM lSlE lSlR 1SyM lSrE lSzR
18.0 20.6 61.4 9.5 12.5 78.0
179.8 163.4 180.2 227.0 160.0 170.5 227.6 151.6
41.3 22.0 110.0 55.2 14.5 112.5 32.5 10.0
~
-
63.6 19.3 23.1 26.7 -
-
" Note: The % conjugations were calculated in solution, taking the specific extinction coefficient E1 cmlu*' as 906 for 9:11 dienoic acid as given by Hilditch et al. (1945). sures, the pH of the solution should essentially be lower in our composition than in other compositions where sodium bisulfate is added alone. Besides, when we examine the mechanism of dehydration, which is to follow this paper, the findings signify a more probable attack of +S03H ion on the oxygen atom of the >CHOH group than of the -0SO3H attack on the "C" atom, which in turn demands the suppression of -OSO:3H ion formation. The use of both HzS04 and NaHS04 meets these requirements by the common ion effect. NaHS04
-
H2S04
-+
+ HS04HO- + S03H+ Na+
-
+ OH- NaOH HS04- + S03H+ + H20 2H2S04 2NaOH + 4H2S04 NaZS04 + 3H2S04 + 2Hz0 NaZS04 + 3H2S04 2NaHS04 + 2HzS04 Na+
-
-
-
Moreover, where sodium bisulfate alone is used, the formation of NaOH and H2S04 would be in equimolar proportions. In addition to this, in the present case the equilibrium shift would be to the right, rather than to the left according to the law of mass action because of efficient wat'er removal. Further, it is quite probable that the 9:12 linoleic acid formation is very much reduced at reduced pressure, perhaps due to the probable higher volume of 9:11 linoleic acid as compared to that of 9:12 linoleic acid. These volume differences are presumed because selectivity in hydrogenation is obtained at low pressure and maximum conjugation preceeds highest selectivity (Allen et al., 1956). This argument can be based on Le Chatelier's principle. The same argument could be extended to the formation of the trans-trans isomer also. Moreover, in atmospheric dehydration, the estolide formation may be exaggerated because of inefficient water removal. This could be due to the greater fat splitting resulting from the presence of water and H30+ ion catalysis increasing the rate of esterification, thereby increasing the side reactions, whereas the fat splitting is minimized at reduced pressure, which in turn minimizes the estolide formation. It is therefore presumed that the low conjugation obtained so far is mainly due to the lowering of effective catalyst concentration. Experiments are planned to conduct dehydration of castor oil in the presence of sodium bisulfate as catalyst and maintaining the acid conditions throughout the reaction. 108
Ind. Eng. Chem., Prod. Res. Dev., Vol. 16, No. 1, 1977
Table 11. Increase in Percent Conjugation during Dehydration" Samples drawn after
Induced conjugation
0 min 20 min 40 min. 60 rnin 80 rnin
0% 13.9%
29.6% 35.3% 51.9%
Note: The % conjugations were calculated in solution, taking as 906 for 9:11 dienoic the specific extinction coefficient E1%l ,c acid as given by Hilditch, et al. (1945). Grummit et al. (1953) obtained 60%conjugated acids, with castor fatty acids,- using activated alumina as a catalyst. However, the vacuum employed was very high, to the order of 1 mm pressure, and besides the acids were recovered by distillation. Further, Schneider et al. (1964) obtained approximately the same value of conjugation by working with ricinelaidic acid, using various catalysts, including sodium bisulfate, although the conjugation obtained with sodium bisulfate is comparatively low. Again, the acids had to be recovered by vacuum distillation. These processes increase the cost abnormally, affecting the economy. This makes the industrial utility of the above processes improbable. Experimental Section Experiment No. 1. Castor oil (500 g) was dehydrated in a Dean and Stark apparatus by using sodium bisulfate as a catalyst with a concentration of 0.16 mol as bisulfateh. of reactants (7.5 g of anhydrous NaHS04 0.1 ml of of BDH Analar grade). The vacuum was maintained around 19 in. Hg. The reaction was carried out a t 200-220 "C. One intermediate sample was drawn after 50 min. The heating was continued for 90 min. The intermediate and final samples were designated as lS1and 1Sz. Both samples were analyzed for acetyl values and saponification values. The sample 1% was also analyzed for ultraviolet spectroscopic measurement at 234 p using cyclohexane as solvent to determine the percentage of diene conjugation. Sample IS1 was first fractionated with methanol and the layers were allowed to separate overnight. The methanol phase was distilled off to get its extract (sample 1SIM). The methanol-insoluble portion was similarly fractionated with ethanol to obtain ethyl alcohol extract (lSIE).The residue was named lSIR. Similarly, lSzM, 1S2E, and lS2R were obtained from sample 1Sz. It was noted that the alcoholic phases were not transparent and had a certain degree of turbidity. The acetyl values and saponification values of different extracts and residues were determined and are given in Table I. Experiment No. 2. In this experiment 500 g of castor oil was dehydrated at 200-220 "C and a vacuum of 25 in. Hg. The
+
0
-
1020304050607080 TIME IN MINUTES
Figure 1. Increase in conjugation during dehydration of castor oil at 25 in. Hg vacuum. Percent conjugation vs. time.
I
I
100-
I
I
I
I
I
I
I
I
I
I
1
l
l
I
I
. d
L-
01 2 000
I
I
I
I
1800
I
I
1600
I
1
lL00
I
1200
I
1000
I
I
I
800
FREQUENCY ( C M " 1
Figure 2. Infrared spectrum of pure castor oil. l o o2000 ,,
, , ,
,
,
1500
,
F R E, Q U E N, C Y iCM?
,
(00~
9q0
so:
0
5
6
7
8
9
10
12
11
71;o
1
I
13
li
1
20-
-
15
0
4
iMlCRINSI
Figure 3. Infrared spectrum of intermediate sample (1S1) drawn after 50 min in experiment 1. FREQUENCY I C f i ' I
1500
2000
looo
700
800
I
100
1 5
I
.
0-
6
7
0
10 I MICRONS)
9
11
12
Figure 5. Infrared spectrum of methyl alcohol extract of 1Sn (ISnM).
13
I1
15
Figure 4. Infrared spectrum of end sample (1s~) drawn after 90 min in experiment 1.
heating was continued for 80 min. The samples were drawn after 0,20,40,60, and 80 min, after the reaction temperature is attained. These samples were analyzed for ultraviolet spectroscopic measurements in order to measure the induced conjugation (Table 11).
Discussion In Table I the acetyl values, saponification values, and % conjugation of some of the samples and fractions are given.
Sample lS1 has a n acetyl value of 41.3 and saponification value of 179.8,while sample 1Sz has an acetyl value of 22 with saponification value 163.4, indicating some high molecular weight products in it. However, both the samples were completely soluble in acetone at room temperature, showing little or no polymerization. Further, the samples 1S1M, lSlE and, lSlR have 110.4, 55.2, and 14.5 acetyl values and 180.2, 227, and 160 saponification values, respectively. It can be seen from this that the methyl alcohol extract (1SIM) contains mostly the undehydrated castor oil, while the ethyl alcohol extract ( l S I E )contains mostly some fission products of low molecular weight along with a little undehydrated castor oil as seen from the higher saponification value. The slightly lower saponification value of the methyl alcohol extract may be due to the slight extraction of estolides present in partially dehydrated castor oil, as the extracts were observed to be turbid even after overnight settling. However, the residue contains mostly the dehydrated castor oil and is rich in estolides, formed during dehydration, as is observed from the low saponification value. It may further indicate, most probably, that the dehydration is more or less selective in the sense that a partially dehydrated glyceride is preferentially dehydrated to the undehydrated glyceride. This probable conclusion is drawn because the methyl alcohol extract of the sample 1S1has an almost equal Ind. Eng. Chem.. Prod. Res. Dev., Vol. 16, No. 1, 1977
109
MICRONS
5
6 I
I
100
7
I
I
I
9
E
I
I
I
10
12
I
I I
I
I
I
I
1L
16
-
I
I
~
1
01 2 000
I
I
1
I
I
I
16 0 0
1800
I
I
1LOO
I
1200
I
I
I
I
800
1000
FREQUENCY ( C M 1 )
Figure 6. Infrared spectrum of ethyl alcohol extract of 1Sp (1SpE).
MICRONS
5 I
100
7
6 I
I
I
I
I
8
I
I
1
9 1
10 I
11 I
12 I
I
1L I
I
16
I
0 2000
1800
1600
1400
1200 TREQUENCY ( C M 1 l
1000
800
Figure 7. Infrared spectrum o residue left after alcohol extractions of sample lS:! (1SZR).
saponification value to that of the original castor oil with a significantly high acetyl value of 110. Further, it has 19.3% conjugation on the basis of the fraction, which implies that the percent conjugation in this fraction on the basis of overall sample IS1 is only around 3.47%. The ethyl alcohol extract (1S1E) having an acetyl value of 55.2 has 23.7% conjugation on the basis of the fraction, which reduces to about 4.9% on the total basis, in spite of its having some low molecular weight, nonconjugated compounds. The residue (1SIR) has a conjugation of only 26.7%, which reduces to around 16.4% on the total basis. It is reasonable to assume that the conjugation in this fraction is much more than that of the value determined from the ultraviolet spectra because of the inverse proportionality of the intensity with the molecular weight. This residue has higher molecular weight compounds such as estolides, as seen from the saponification value. The acetyl 110
Ind. Eng. Chem., Prod. Res. Dev., Vol. 16,No. 1, 1977
value of 14.5 of the residue indicates a theoretical amount of dehydration in it. Similar extracts of sample 1Sz gave acetyl values 112.5,32.5,and 10 for methyl and ethyl alcohol extracts and residue, respectively, while the saponification values of these fractions were 170.5, 227.6, and 151.6, respectively. The methyl alcohol extracts of samples have significantly high acetyl and saponification values very near that of the original castor oil with little conjugation, while the ethyl alcohol extracts of 1S1 and 1Sz have significantly lower acetyl values of 55.2 and 32, respectively. Further, the ethyl alcohol extract has more conjugation than the methyl alcohol extract in spite of the presence of nonconjugated compounds in it. This implies that the conjugation is increasing as we go from methyl alcohol extract to residue indicating significant increases of the concentration of the dehydrated product. In other words, the methyl alcohol extracts contain predomi-
nantly the undehydrated castor glycerides while the concentration of these go down stepwise in the other two fractions. This, along with the large difference in percent conjugation between the alcohol extracts and residue, is perhaps sufficient evidence for the dehydration t o be selective in the sense that the partially dehydrated glycerides would be preferentially dehydrated to the completely undehydrated glycerides. In Table I1 are given the percentages of conjugation of various samples taken during dehydration under similar conditions (except that the vacuum employed was 25 in. of mercury) as in the first experiment. I t is seen from the table that the rate of increase of conjugation falls after 40 min and increases again after 60 min showing a slackening period. This, as well, perhaps substantiates the above mentioned argument for the dehydration to be selective. During the initial stages of dehydration, perhaps those glycerides which are partially dehydrated with the starting of the reaction would predominate for the further dehydration process. After a certain time there may arise a slackening period with the advent of the consumption of most of the partially dehydrated glyceride molecules, after which the other undehydrated or slightly dehydrated glycerides would be dehydrated (see Figure 1).BC is considered to be the slackening period as the rate of dehydration becomes very low. Further, the saponification values of the ethyl alcohol extracts gave evidence to the formation of fission products such as undecylenic acid and heptaldehyde, which might have been converted into heptanoic acid during saponification, while the saponification values of the residues gave evidence to the formation of estolides. The conjugation in the sample 1Sz is found to be around 63.6% as seen from the ultraviolet spectrum, which is unusually high. The film of this sample showed a surface dry period of less than 1h and a tack-free drying time of more than 72 h. Further, the residues were found to be still slower in drying than the overall samples. The slow drying characteristics of these films may also be attributed to the presence of partially undehydrated castor glycerides, which form a part of the monomer present in the gelled films. This monomer may cause a certain amount of incompatibility with the polymer molecules because of its higher polarity due to the presence of hydroxyl groups, as is observed by slight haziness in the films. However, this could not be the sole cause for the slow drying characteristics because the residue which has the insignificant amounts of these partially undehydrated glycerides dry still more slowly. The relatively poor drying characteristics or after-tack in dehydrated castor oil was attributed by Cowan et al. (1949) to the contained trans-trans double bonds. As the trans-trans form is more symmetrical, it is the more stable form and hence it dries more poorly. R1-C-H
H-C-C-H
II
II
R~+-H cis-trans
R,-C-H
II
H-C-C-H
II
H-C-R, trans-trans
The IR spectra of the original castor oil sample as well as of the samples 1S1, 1S2,1S2M, 1S2E, and 1SzR are given in Figures 2,3,4, 5,6, and 7 , respectively. The main features of these spectra are the development of a doublet at the 960975-cm-I region, signifying the presence of cis-trans and trans-trans isomers in Figures 3, 4, 6, and 7 . However, the sample 1S2M (Figure 5) does not show any absorption in this region. Further, the C=O (1735 cm-l) band in Figure 6 showed a split, signifying some other carbonyl groups, other than ester carbonyl, perhaps such as carboxylic carbonyl. Another interesting feature is the absorption at 1010 cm-I in Figure 7 which is the residue of sample IS2after alcohol extractions. This could be attributed to the vinyl group of undecylenic acid which might have combined with the secondary alcohol group of ricinoleic acid to form estolides. Although the characteristic absorptions of vinyl group is given in 995 cm-l, the shift of about 15 cm-' may be due to the solvent effects (Bayliss et al., 1955) of undehydrated ricinoleic acid chain left in this fraction as seen by the OH absorption as well as the acetyl value. I t is, therefore, concluded that the slow-drying characteristics are due to the trans-trans configuration of the dienoic acid. Further, the plasticizing effect of partially undehydrated castor glycerides may also contribute to this. Summary A monomeric dehydrated castor oil is prepared by using sodium bisulfate as catalyst under modified conditions which resulted in an unusually high conjugation in around 90 min. The ultraviolet spectra of the alcohol extracts of the dehydrated castor oil samples indicated a preferential mode of dehydration, in the sense that the dehydration of more dehydrated glycerides precedes that of the less dehydrated glycerides. Infrared spectroscopy gave evidence to the formation of fission products and trans-trans isomers. Acknowledgment The authors thank Dr. S. D. Shukla, Director, H.B.T.I., for providing the facilities and granting a scholarship to D. N.
B. Literature Cited Allen, et al., J. Am. Oil Chem. SOC.,33, 355 (1956). Bayliss. et al.. Aust. J. Chem., 8 , 16 (1955). Cowan, J. C., et al., lnd. Eng. Chem., 41, 294 (1949). Grummit, et al., J. Am. Oil Chem. Soc., 30, 21 (1953). Hilditch, T. P.. Morton, R. A.. Riley, J. P., Analyst(London),70, No. 827. 71 (Feb 1945). Om Prakash, et al., J. lndian Chem. SOC.(Indian and News Ed.), 10, 89 (1947). Schneider, et al., J. Am. Oil Chem. Soc.. 41, 605 (1964). Sivasamban. et al., Proceedings of Symposium of Indian Oils and Fats, National Chemical Laboratory, Poona, India, pp 197-199, 1951. Sivasamban, et al., Indian Patent 55 423, Nov 21 (1956). Von Mikusch, J. D., Paint Manufacture, 386 (1955).
Receiced for reuieu: January 19, 1976 Accepted October 5, 1976
Ind. Eng. Chem., Prod. Res. Dev., Vol. 16, No. 1, 1977
111
