acidic conditions. the ability to sorb boron as boric acid is decreased to the point where a strong acid can be employed as a regenerant for the boroq-exhausted resin. Columnar studies have demonstrated that the above resin is capable of removing boron as boric acid with little leakage from solutions corresponding to irrigation waters and magnesium chloride brines Since the boron-specific resin can be efficiently regenerated, a material of this structure might be of some utility in removing boron from various waters and from solutions containing objectionable quantities of boron.
literature Cited
(1) Bresler, S. E., Russ. Chem. Rev. 29, No. 8, 469 (1960). (2) Frisch, N., Kunin. R., [nd. En!. Chem. 49, 1365 (1957). (3) Hatcher. J. T.. LVilcoq, I,. V.,Anal. Chem. 22, 567 (1950). (4) Lyman, IV.. Preuss. A,, U. S. Patent 2,813,838(Nov. 19, 1957). (5) McBurney. C. H., [bid., 2,629,710(Feb. 24, 1953). Morris, L. R.?Zbid., 2,840,603 (June 1958\. (6) Mock, R. .4., (7) Skogseid, .4., Ph.D. dissertation. Norges Techniske Hopkole, Trondheim, 1948. RECEIVED for review April 30. 1964 ACCEPTED .\ugust 13. 1964
EPOXIDATION OF ANCHOVY OILS A Study of Variables J A I M E W I S N I A K ,
ALEJANDRO
C A N C I N O , AND JUAN C. VEGA
Department of Chemical Engineering. C'niversidad Cat6lica de Chile. Santiago: Chile
Anchovy oil has been epoxidized in situ to determine the effect of operating variables on the maximum oxirane oxygen attainable. Variables studied included temperature, catalyst nature and concentration, hydrogen peroxide strength and proportion, and acetic acid proportion. An epoxidized oil with 7.8y0 epoxy content and iodine value of 14.1 can b e prepared when operating at 5 3 " to 73' C., using a 33 weight yohydrogen peroxide solution in a proportion of 1.4 moles per mole of ethylenic unsaturation, 1 5y0 concentration of styrene-sulfonic resin as catalyst, and acetic acid in the proportion of 0.5 mole per mole of ethylenic unsaturation.
ELV methods
and materials have been developed for prepar-
N ing epoxy compounds that can be used as plasticizers for
polyvinyl resins. Of the various compounds available, unsaturated fatty esters have proved to be the most suitable, the ester group giving the permanence features and plasticizing qualities required! while providipg an economical means of obtaining the epoxy group. Vegetable oils, and soybean oil in particular, now constitute the most important source of unsaturated glycerides for the commercially available epoxy plasticizers (6-77). T h e main drawback of these materials is their relatively 101s unsaturation that limits the maximum oxirane oxygen percentage attainable to about 77,. I n the past two years. a new product with a relatively high epoxy content (9.5Yc). achieved by epoxidation of an upgraded oil obtained via a Solexol process (3, 3 ) : has come onto the market. T o obtain this level of epoxidation. it is necessary to start kvith an oil of iodine value about 180 tq 200. During investigation of the possibility of obtaining higher oxirane oxygen contents while simultaneously using a simpler process and relatively inexpensive raw materials, it was decided to study the possibility of epoxidizing fish oils under wide experimental conditions. Fish oils seem to be natural raw materials for the process because of their high iodine value (180 to 220). Few references are available in the literature as to the possibility of using this type of oil (6:8: 70). Raw Materials
.A refined and \vinterized anchovy oil was used, which had the characteristics shobvn in Table I. Gas chromatography of the fatty acids indicated the presence of a t least 13 components, 306
I&EC PRODUCT RESEARCH A N D DEVELOPMEN7
with the possibility of identifying only nine of them. Unknowns B. C. and D should have a t least 20 to 22 carbon atoms and six double bonds per chain in order to justify the iodine value of the oil. No attempts were made to identify their nature. T h e catalysts used were styrene-sulfonic resins manufactured by Dow Chemical Co. (Dowex 5OW-X) and Ionac Co. (Ionac '2-244). T h e Dowex resin was used in txvo sieve cuts. 50- to 100- and 20- to 50-mesh. both of loiv porosity and in acid form. T h e Ionac catalyst was a 40- to 80-mesh cut. T h e hydrogen peroxide purchased had a concentration of 27.5 weight %. increased to 45% by vacuum distillation. the p H having previously been adjusted to 4.1 to 4.2 with sodium pyrophosphate. T h e glacial acetic acid used was 99.7% p u r e . . Experimental Procedure
Epoxidation runs were made using the in situ technique ( 7 ) . in a three-necked. 1-liter flask, connected with thermometer, reflux condenser, measuring funnel, and electric heating
Table 1.
Characteristics of Anchovy Oil 0 3 Iodine value. 188 8 Color (Helliae 1.
Acid number. Saponification number.
186
Fatty .hid Composition. $. in Order o j Elution ____
Lauric Myristic Myristoleic Pentadecylic Palmitic Palmitoleic Unknown A
Traces
5 5 Traces
0.5 21.4 11.5 2.1
Stearic Oleic Linoleic Unknown B Unknown C Unknown D
5 4
23.1 4 4
4.2 3.0
19.0
11
mantle. .Agitation was provided w.ith a half-moon-shaped helix powered by a variable-speed motor. Specified quantities of glacial acetic acid. catalyst, and fish oil were introduced in the reactor in the order indicated, then agitation and heating Xvcrc started. .At the desired reaction temperature, addition of hydrogen peroxide was initiated at a constant rate such that it \vas completed in 30 to 50 minutes. Care was exercised during this operation to keep the mixture homogeneous, SO as to avoid zones of high concentration of peroxide that could lead. in principle, to explosive mixtures with the organic materials present. The first sample was taken at the end of the addition of the peroxide and then the temperature was slowly raised 20' C. and kept constant during the time of reaction (6 to 10 hours). Five to six 20-ml. samples were collected a t intervals. Prior to their analysis, the samples were washed a t 60' C . , with a 2% NaCl solution until neutralized, and then de-emulsified by either heating in an air oven a t 60' C. or vacuum filtration. I n some cases. complete de-emulsification was attained only by vacuum distillation of the accompanying water. Analytical Techniques. Oxirane oxygen content was determined using the direct method based on glacial acetic acid solutions of hydrobromic acid, which is faster and more accurate than the ones based on hydrochloric acid dissolved in ether, dioxane, or pyridine (5). A very important advantage of this method is the noninterference of other functional groups such as carboxyl and peroxides. Iodine values were obtained using the LVijs method ( 7 ) . Hydroxyacetate content \vas determined in only a few samples because the available methods are not sufficiently exact (72). Results and Discussion
Thirty-six epoxidation runs were made for the following range of variables: temperatures: 73' to 93" C . ; strength of hydrogen peroxide: 33 to 42% by weight; proportion of hydrogen peroxide (CH~OP):0.8 to 1.7 moles per mole of ethylenic unsaturation ; proportion of acetic acid (C.400H) : 0.35 to 0.75 mole per mole of ethylenic unsaturation; catalyst concentration: Doxvex 5OL\:-X (20- to jo-mesh), 1 to 5%; Dowex 50L\--X (50-to 100-mesh), 2 to 15%; Ionac C-244, 2 to 4 ' 3 . Catalyst concentrations were expressed as percentage of the total Lveight of acetic acid and hydrogen peroxide, on a dry-resin basis The epoxidation reaction was followed in each case by plotting the oxirane oxygen content, iodine value, or hydroxyacetate content w. the time of reaction. T h e plots of oxirane oxygen \\.ere essentially parabolic in nature-that is, they increased to a maximum and then started decreasing. The exothermic nature of the reaction allowed a temperature control to within *2' C . Although this is a small variation? it would have some significance when determining the effect of the t\vo temperature levels used during each run. Agitation of the reaction mixture is necessary to provide adequate contact and mass transfer among the three phases present. .According to the suggested mechanism for the reaction (2) :
+ H20:i % CH3COOOH + H20 ( 1 ) CH3COOOH + -C=C -CH-CH+ CHsCOOH cat.
CH3COOH
+
H
H
1
1
-C--C-
\/ 0
v 0
H
+ CH3COOH
H
I 1
-+
-C-C
'
I
OH 0-C-CH3 II I 0
T h e formation of peracetic acid requires that the solid catalyst be put in intimate contact with the aqueous phase containing acetic acid and hydrogen peroxide. 4 t the same time, the peracetic acid formed will react with the double bonds forming the oxirane ring. Higher 'mixing rates will favor the yield of epoxide, but a t the same time will tend to destroy it through Reaction 3. Thus: the agitation rate is a compromise between the formation of epoxide and hydroxyacetate, Peracetic acid is formed in the active centers of the catalyst and the peracid generated is displaced by more acetic acid and hydrogen peroxide. 'The peracid is extracted into the aqueous phase and then into the organic phase, where the epoxidation reaction takes place. T o continue the cycle, the regenerated acid must diffuse through the organic and aqueous layers, back into the catalyst surface. Proper agitation conditions must be maintained in order to reduce mass transfer resistances. In the experimental work reported herein agitation was maintained at 150 r . p . m . as recommended in the literature for reactors of I-liter capacity (73). De-emulsification of Samples. A common characteristic of all the runs was the emulsification of the mixture as the reaction proceeded. A very stable emulsion was produced, with larger amounts of water being incorporated at the higher temperature levels. S o reference was found in the literature indicating the cause of this phenomenon and the procedure for breaking the emulsion. At the outset; it was thought that the problem was caused by the acidity of the oil, but additional runs with an essentially neutral oil failed to prove this point. Further consultation with manufacturers of the catalysts used indicated that the traces of heavy metals present in fish oils can degrade the resins, thus generating soluble products with emulsifying properties. .4n alternative explanation could be that the glycols formed by hydrolysis of the oxirane ring were responsible, but, contrary to this idea, the emulsification process occurred very early in the reaction, at a time when glycol concentration was very low. Of the several methods explored for breaking the emulsion, the best one was filtration of the product while warm, followed by vacuum distillation. Separation was relatively slow (4 to 6 hours) even under the best operating conditions (60' '2.). Phase separation was attempted after the mixture was rendered acid-free by continuous washing with a 27, solution of sodium chloride followed by washes with dilute sodium carbonate solutions. Effect of T e m p e r a t u r e . Two temperature levels, 'separated by 20 O C., were used in each run. The lowest level was maintained during the addition of the hydrogen peroxide ; immediately thereafter, the temperature was abruptly raised to the second level, and maintained until the end of the reaction. Figure 1 indicates the results obtained for the three pairs of levels: 53 to 73 O, 63 ' to 83 O, and 73 to 93 O C . Increasing temperature has a favorable effect on the formation of peracetic acid, displacing to the right the equilibrium indicated by Equation 1. This results in a more rapid rate of epoxidation, as shown by Figure 1, but also in a higher rate of hydrolysis of the product. I t is also possible that at high temperatures the decomposition of peracetic acid and hydrogen peroxide may become important. Lower reaction temperatures will slow the rate but give a more stable oxirane ring. Maximum conversion to epoxide was obtained in a shorter time by the 53' to 73' C. temperature range. To show the effect of using one single temperature level, a run was made a t 70' C. with results equivalent to those obtained tvhen using two temperature levels (Figure 6 ) . A higher operating temperature will give higher initial rates of VOL.
3
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DECEMBER 1964
307
7
z W
2 X
0 W 2
a
LL
0 53-73
H . 4 : 33
%
'1.
W
C A ~ O H:0.5 "1. cat. :L(Dowex 20-50 mesh)
0
0
2 z
63-83 A 73-93
W 0
a w
n
0
60
120
180
240
TIME
Figure 1 .
0
60
120
180
Figure 2.
240
300
400
540
600
360
420
4 80
540
60 0
(minutes)
Effect of proportion of hydrogen peroxide
reaction, and the maximum oxirane oxygen content will be attained in less time. There is a practical reason, of course, for using a lower temperature during the addition of hydrogen peroxide : the exothermic nature of the reaction may cause an excessive temperature rise in the peroxide-reacting mixture, with potential explosion hazards. Effect of Proportion of Hydrogen Peroxide. As shown in Figure 2. the maximum of the curve of oxirane oxygen us. time increases for proportions of hydrogen peroxide u p to 1.4 moles per mole of ethylenic unsaturation. remaining fairly constant for higher concentrations. T h e maximum is attained in less time for increasing amounts of hydrogen peroxide, a behavior which was observed also a t the other temperature levels. However, under equal temperature conditions the product will 308
420
Effect of temperature
TIME '
300 360 (minutes)
I&EC PRODUCT RESEARCH A N D DEVELOPMENT
degrade more rapidly. I n the experimental range explored in this work, the optimum proportion was 1.4 moles of hydrogen peroxide per mole of ethylenic unsaturation. Effect of Hydrogen Peroxide Strength. Experimental results indicated that a n increase in the concentration of hydrogen peroxide favored the initial rate of the reaction. More dilute solutions tended to produce high oxirane oxygen percentages with longer reaction times. Figure 3 indicates some typical results. Contrary to what could be expected theoretically, a n increase in the concentration of hydrogen peroxide will not favor the maximum epoxide content attainable. I n fact, a lower concentration of peroxide is equivalent to introducing more water in the system and thus apparently favoring hydrolytic conditions. As shown by Figure 3. the net effect
7
z W
2
g W 2
U
E
z5
91.
W
H~O*
(3
U
I-
z
W
V
a W
n.
0
60
120
180
300
240
360
420
480
540
600
480
540
600
T I M E (minutes)
Figure 3.
Effect of hydrogen peroxide strength
7
z
W 0
*
3
5
-
w
$ 4 -
P
2 u
3
-
2
-
1
-
(3
2 z
w V a W
a
0
60
120
180
Figure 4.
240
300 360 T I M E (minutes)
420
Effect of proportion of acetic acid
is only to slow down the initial reaction rate; the presence of more peroxide produces conditions that accelerate the rate of decomposition of the oxirane ring. T h e maximum oxirane content attainable is primarily a function of the relative rates of Reactions 2 and 3. These rates are dependent on the concentrations of peracetic acid and acetic acid, respectively, and both acids are related by Reaction 1. Thus, a hydrogen peroxide of higher strength would tend to increase the concentration of peracetic acid and reduce the concentration of acetic acid. It is possible that under these conditions. the higher concentration of acetic acid retards the rate of formation of peracetic acid, thus offsetting the expected higher rate. In the experimental range studied, a 33% strength hydrogen peroxide produced the maximum epoxide content.
Effect of Proportion of Acetic Acid. Acetic acid participates in the over-all reaction, as a catalyst in the formation of oxirane rings, and as a reactant in their hydrolysis (Reactions 2 and 3). T h e amount of acid cannot be deduced from Equation 1 and an optimum can be expected where both effects are balanced and the maximum oxirane oxygen content is attained. Figure 4 shows the results obtained for the four levels studied-namely, 0.35, 0.50, 0.60: and 0.75 mole of acid per mole of ethylenic unsaturation. The most favorable results appeared to occur for a 0.50 ratio. Effect of Catalyst Nature. T h e maximum percentage of oxirane oxygen obtained with the Dowex 50W-X resin was independent of the catalyst particle size, although shorter reaction times were required for the smallest size (50- to 100mesh). T h e Ionac C-244 resin produced a more stable VOL. 3
NO. 4
DECEMBER 1964
309
7
6
z W
$
5
z
4
5
rr
3 W
3
(3
z
2
w V a
2
W
a 1
0 0
60
120
180
240
Figure 5.
300 360 TIME (minutes)
420
480
TIME
540
600
(minutes)
Effect of catalyst nature
7
z W
2
z
w
2
4
E X
0
A
W (3
3z W
V
a W a
0
60
120
180
300
240
360
420
480
540
600
TIME (minutes) Figure 6.
Effect of catalyst concentration Dowex 20- 50-mesh
epoxide-that is, once the maximum oxirane oxygen content was attained, it decreased very slowly with time. Figure 5 indicates that the catalyst nature did affect the maximum epoxide content; but that shorter reaction times were required when Ionac (2-244 or Dowex 5OW-X of 50- to 100-mesh was used. T h e same figure indicates the low yield obtained when sulfuric acid was used as a catalyst. Effect of Catalyst Concentration. I n general, increasing the catalyst concentration produced an oil with a higher oxirane content in shorter reaction times. Ionac ‘2-244 was evaluated a t the 2! 4, and 5 weight % levels, Dowex ;OW-X (20- to 50-mesh) a t 1, 3, and 5y0, and Dowex 5OW-X (50- to 100mesh) a t 2, 5 , 10, and 15%. Figure 6 indicates results for the latter resin. Optimum conversion was a t the 15y0level. Optimum Operating Conditions. I n the experimental 310
I L E C P R O D U C T RESEARCH A N D DEVELOPMENT
range studied it was possible to prepare a n epoxidized fish oil with a 7.8 oxirane oxygen content, when operating a t 53 O to 73 C., using a 33 weight hydrogen peroxide in a proportion of 1.4 moles of peroxide per mole of ethylenic unsaturation, 15% concentration of the catalyst Dowex ;OW-X (50to 100-mesh, and acetic acid in the proportion of 0.5 mole per mole of ethylenic unsaturation. T h e final product had a n iodine value of 14.1. These results show that it is possible to prepare an epoxidized fish oil with higher oxirane oxygen content than most of the commercially available products, although with a high iodine value. Further experimental work is being done to explore the possibilities of approaching the maximum theoretically possible conteht of epoxide (10.5%) and simultaneously reducing the final iodine value.
(7) Ibid.,47, 147 (1955).
Acknowledgment
L. F. Kaufman of Svift and Co. assisted in the performance of gas-liquid chromatographic analyses. literature Cited
American Oil Chemists’ Society, Chicago, 111.: ”Official and Tentative Methods.” Cd 1-25)revised to April 1956. 12) Chadwick. A. F.. Barlow. D. C.. D’Addieco.’ A. A.. Wallace. .I. G.. J . .4ni,’ Oil Chemists’ $06. 35, 355 (1958). (3) Chm. En?. . V m s 39, 46 (July 24. 1961). (4) Ibid.. 39, 35 (hug. 28. 1961). (5) Durbetaki. A. J.; Anal. Chrm. 28, 2024 (1958). (6) Greenspan. F. P.; Gall. R. J . . Ind. Eng. Chem. 45, 2722 (1953).
(1) \
(8) Greenspan, F. O., Gall, R. J., J . Am. Oil Chemists’ Soc. 33, 391 (1956). (9) Ibid., 34, 161 (1957). (10) Greenspan, F. P., U. S. Patent 2,810,733 (Oct. 22, 1957). (11) Sack, M., Wohlers, H. C., J . Am. Oil Chemists’ SOC.36, 623 (1959). (12) Treadwell, F. P., Hall, W. T., “Analytical Chemistry,” Vol. 11, p. 616, Wiley? New York, 1942. (13) Wohlers, H. C., Sack, M., Le Van, H. P., Ind. Eng. Chem. 50, 1685 (1958).
I
RECEIVED for review June 22, 1964 ACCEPTED September 24. 1964 Work sponsored by Corporation de Foment0 de la Produccion. a Chilean Government Institution.
IDENTIFICATION OF A HEAD-TO-HEAD COUPLING PRODUCT FROM 1-OLEFIN 0 LI GO M ER IZATION D . H . ANTONSEN, R . W . WARREF(, AND
R . H . JOHNSON
Research and Development, Sun Oil Co., Marcus Hook, Pa.
In coordination polymerization of 1 -olefins, a competition between high polymer formation and chain transfer to oligomers depends upon the molecular alignment in the transition states rather than a kinetic process. Thus, the maior portion of the dimer products resulting from the oligomerization of 1 -octene and 1 -decene, using the catalyst system aluminum ethyl sesquichloride-titanium tetrachloride-propylene oxide, has been identified after hydrogenation, as n-hexadecane and n-eicosane. The predominant dimerization product of 1 -olefins occurs therefore as a result of a head-to-head coupling reaction. The coupling product
complex with the catalyst undergoes rapid chain transfer with monomer yielding trans olefins and a new propagation species. Propagation to higher o!igomers probably takes place through head-to-tail reaction and higher oligomers are preferentially chain-transferred with monomer following a head-to-head coupling reaction.
the exception of the dimer, the oligomer properties of 1-octene and 1-decene prepared by a catalyst system Lvhich consists of aluminum erhyl sesquichloride, titanium tetrachloride. and propylene oxide have been reported ( 7 ) . This general process heretofore has been ascribed to a combination of cationic and anionic competing mechanisms to account for the oily products ( 7 , 3 ) . This communication describrs the structure of the major component of the dimer resulting from this reaction and elucidates the mode of its formation and the relationship of the dimer structure to the structure of the other oligomers. .1 programmed high temperature gas chromatogram of the oligomers of 1 -octene is characterized by a single ‘major peak and several smaller peaks in each of the respective molecular Xveight regions. ‘1-he major peak of the 1-octene dimers rrprgsents about 80%; of the dimer fraction. I n follmving oligomers. the intensity of the major peak diminishes with increasing molecular \\-eight to about .joyc in the hexamer fraction. Similar results were obtained with 1-decene oligomers. although it was not possible to obtain data on the individual oligomers higher than the tetramer because of the high boiling poinrs. ITH
T h e major peaks from each of the oligomer fractions when separated by preparative column gas chromatography have been identified by infrared as consisting of trans olefins. T h e components present in lower percentages were identified as a mixture of vinyl and vinylidene olefins. No cis or trisubstituted olefins were found2 although the identification by infrared is not nearly as clear-cut for these two types. Further resolution by gas chromatography of the major peak from the dimers showed the presence of two materials in the ratio of -1 to 3, each of which was identified by infrared analysis as a trans olefin. High temperature gas chromatographic scans of the hydrogenated oligomers were similar to the unhydrogenated ones, with the exception of the dimer. Evaluation of the hydrogenated d i p e r showed a decrease in the amount of material which could be separated by preparative column gas chromatography when compared to the major peak of the unhydrogenated dimer. therefore indicating incomplete resolution of the unhydrogenated products. T h e largest single peak representing 607, of the hydrogenated 1-octene dimer was identified as n-hexadecane and the major peak representing 597, of the hydrogenated 1-decene dimer was identified a t n-eicosane VOL. 3
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311
