A ModifiedPeracid Process f o r Making
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Epoxy Compounds from Unsaturated Fattv Acid Esters J
RALPH J. GALL AND FRANK P. GREENSPAN Buflalo Electro-Chemical Co., Division of Food Machinery & Chemical Corp., Station B, Buflalo 7 , .V. Y.
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patent literature ( 4 ) ; it, employs formic acid and hydrogen peroxide. A successful procedure for the in situ epoxidation of unsaturated fatty acid esters has been developed in these laboratories employing acetic acid and hydrogen peroxide. Hydrogen peroxide is added to an acetic acid solution of the unsat,urated fatty acid ester, in the presence of sulfuric acid, a t 60" to 70" C. Optimum yields of epoxy compound were formed with a molar ratio of 0.5 acetic acid to 1 of ethylenic unsaturation in the presence of an inert solvent--e.g., benzene; 2% sulfuric acid on the weight of acetic acid-hydrogen peroxide mixture was employed as a catalyst. Reaction time varied from 8 to 14 hours. Shorter reaction times ( 5 to 6 hours) were obtained with use of excess hydrogen peroxide. Products with low iodine numbers, of particular importance for many end uses of these products, could readily be obtained. Yields varied from approximately 70 to 85% epoxy ester (Table I). High molar ratios of acetic acid to hydrogen peroxide caused excessive ring opening with resulting low yields of the desired epoxy ester (Table 11). Reaction rates a t low temperatures were slow. Inert solvents, such as benzene, were beneficial in depressing the ring opening of the epoxy compound. Boron trifluoride, nitric acid, p-toluenesulfonic acid, ethanesulfonic acid, and a strong acid cationic exchange resin (sulfonic type) are catalysts for peracid formation (3). The cationic exchange resin and et,hanesulfonic acid gave approximately equivalent results when substitut,ed for sulfuric acid in the in situ cpoxidation reaction. The other cat,alpsts gave low yields of epoxy product.
POXY or oxirane compounds have attracted considerable
interest and assumed commercial importance in recent years. Included among these have been the epoxy fatty acids and their esters. The preparation of epoxy compounds by the h organic peracid was reaction of an unsaturated substance ~ i t an first demonstrated hy Prileschajea ( 5 ) in 1909 utilizing perbenzoic acid. Other peracids that have since been employed inrlude monoperphthalic acid, percamphoric acid, and peracetic acid. Swern and associates ( 1 , 7, 8) studied the reaction of olefins and unsaturated fatty acids and esters with aliphatic peracids. They have described efficient procedures for the preparation of the corresponding glycol and epoxy derivatives, utilizing performic acid and peracetic acid, respectively. Their peracetic acid was an anhydrous product prepared From acetic anhydride and hydrogen peroxide. More recently, peracetic acid solutions ( d ) , based on the reaction of a concentrated hydrogen peroxide and glacial acetic acid in the presence of an acid catalyst, have come into wide we. These solutiolis are equilibrium mixtures of hydrogen peroxide, acetic acid, water, and peracetic acid-Le.,
H+
+ HOAC IT HOOAC + HzO
H~02
They have been applied to the epoxidation of a wide variety of olefinic compounds. Generally, cpoxidation reactions with a peracid are carried out in the absence of strong mineral acids. In using the preformed peracetic acid described, it is tlierefoi e necessary to buffer the solution, prior to use, by addition of sodium acetate or dilute alkali. Under these conditions of use, little further formation of peracetic acid from the hydrogen peroxide occurs during the epoxidation reaction, and essentially only the peracetic acid traction of the equilibrium mixture is constructively consumed. This results in reduced epoxidation reaction efficiencies when calculated on the basis of the total active ovygen content (hldrogen peroxide plus peracetic acid) of the oxidant. By contrast, hydroxylation reactions u i t h a peracid have been conducted utilizing an in situ technique ( 7 ) , whereby hydrogen peroxide is added to an aliphatic acid solution of olefinic material in the presence of a mineral acid vatalyst. (When using formic acid the catalyst may be omitted.) Peracetic acid formation and reaction with the double bond occur simultaneously leading to the eventual consumption of a stoichiometric amount of hydrogen peroxide. Deapite the recognized advantages of an in situ process, comparatively little progress has been made in adapting it to an epoxidation with a peracid. In the main, this stems from the extreme difficulty of setting up reaction conditions favorable to the required peracid formation which, in turn, would not destroy the desired epoxy product. The very same conditions that favor peracid formation-high molar ratio of aliphatic acid to hydrogen peroxide, high temperature, high acidity, and long reaction times-are known to be deleterious to the survival of an epoxy compound. To date, the only published method for an in situ epoxidation of Unsaturated fatty chemicals is described in the
TABLE I. ANALYTICAL DATAFOR EPOXY FATTY ACIDESTERS Yield Oxirane Epoxy Iodine Reacted, Epoxy Ester" Oxygen, 7% Ester, % So. % Methyl epoxy stearate 3.9 72 a 95 Propyl epoxy stearate 3.8 79 7 91 Butyl epoxy stearate 3.7 82 2 97 Butyl epoxy ester of cottonseed f a t t y acids 3.1 77 3 96 Epoxy cottonseed oilb 4.7 82 12 87 Butyl epoxy ester of soybean fatty arids 3.6 72 8 91 Epoxv soybean oilb 6.8 74 9 93 EpoxG soybean oilc 6.0 77 3 98 a Except where noted otherwise 10% excess hydrogen peroxide mas employed for the epoxidation reactioh. b 4% excess hydrogen peroxide used. C 20% excess hydrogen peroxide used.
TABLE 11. EFFECT OF VARIOUS MOLARRATIOSOF ACETICACID TO UNSATURATED ESTERON EPOXY ESTERYIELD (Butyl oleate dissolved in benzene was epoxidized with HzOz and acetic acid, in the presence of a 2% sulfuric acid catalyst, a t 65-65' C.) LIolar Ratio Reaction Acetic Acid-UnTime, Oxirane Yield Epoxy Iodine Reacted, saturated Ester" Hr. Oxygen, 70 Ester, % No. % 15:l 3 0.0 0.0 4 95 1.7:l 8 0.2 4.4 8 89 0.5:l 13 3.6 80.0 5 93 0 Moles of unsaturated ester refer t o moles of ethylenic unsaturation present in the ester.
147
INDUSTRIAL AND ENGINEERING CHEMISTRY
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l ~ ~ i ~ o x t i ) . ~o~~i ~ S' I~oY s B\ YI : Oir.. ' L l i r iti sitri epoxi(hitioi1 or oil iu rc~l".'.'oiit:iti~(~ oi' t l i c ~ ~ ~ o r c ~ c l(iwd i i r c ~for triglycvritlw :
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Two hundred grams ol so)~be:rnoil (Iociiiie S o . I%, eqaiv:tlerit to 1 .06 Inolcs o f ethylenic unsaturntioii), 40.0 grams of I)criwne, 3:j.(i granin of glarial acetic acid (0.,55 mole), and 4.28 grains of 50% sulfuric ticid werc mixed in a thrce-necked flask equippcttl with a reflux condenser, theriiionietrr, and mechanical stirrer; i1.88 grains of 50% hydrog:cin perosidc (1.1 moles) was then slowly : d i e d o v ~ar 2-hour pcriod at,50" C. The reaction mixturc. w a v v,--nriiied to 60" C. and maint~riiiiednt t h a t temperature for 12 to 11 I~OIIYP. The oil layer wits ~ n r h c c l:nid stripped of hciiecwc: :xiid w:itc,r as :ilre:dy outlined.
Oxirarie oxygen, % Tlieoreiiciil AIlalS'sIs
Iodine S o . Hcnze11e
lIcsane s o eolrcllt
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OxirlLno oxyge11, Iodine S o . l.:xw:itniwvrliI. Siieiicw Iiellogg :tiid S o i i ~sii!i!)licd t.iie :tlkali-rt!fitietl superioi,
grade soyhean oil (Iodiiie Xo. 1:35). The cottonwxl oil (Iodine S o . 97) was the Puritttn grttdc of I'i.ortci i t i i d (>:inil)le. 1IcthyI oleitte (Iodine S o . 00) a n d i)roi)yl o l ~ : i rt (Totliiic S o . 80) n.erc obtained from I3nier)- Iiidusrric~x. Butyl oleate (Iodiiic So. i - k j \I it' ~ x c p i i r c dl)y t,lie cstcrific:tt,ioii of but.yl idcoho1 with :t distill(vl ol& acid (1:niery 210) iri t h c s i)resenre of !yc sulfuric acid: \vat er \ v i i h c d , alkali refined, niitl vticuuni distilled. l'lie butyl w t cr or cottonseed fatty arids (Iodiiie S o . 6 7 ) w:ts siiiii':>.rly i ) r r p t r c d froni butyl alcohol and distillrti cottonseed f :xicis from \I7. C. IIr~rtlestyCo. (Iodinc: S o . 00). The but8ylester of soyl)eari fatty acids (Iodine S o . 8 8 ) \vas prepared by t,lie esterificat>ionof soyhean fatty acids (from IT. C. Hardesty Co.) ivitli butJ.1 :~lcoliol. Hoth esters werr distilled. The hydrogen peroxide W R S t,tic, 50% comnirrrial product of the BuKalo 1~:lectro-C~licrriicalCh. Oxirane oxygen was
