only partially removed from the surface by 2-propanol, regardless of the concentration. For the same amount of alcohol, the 1y0solution of 2-propanol was more effective than the pure alcohol. The maximum volume of fuel used in the desorption experiments was 2000 ml. At lower concentrations of 2-propanol (0.1 and O.Ol%), the surfactant was removed from the surface a t an impractically slow rate. These results indicate that a purging agent, such as 2-propanol, introduced into a pipeline after the transport of a surfactant-containing fuel should prevent the contamination of following surfactant-free fuels and eliminate the degradation of water reaction properties. In each laboratory experiment, after a purge was completed, jet fuel (JP-4) was passed through the column and its water reaction was tested ( 5 ) . In all cases, with the exception of the lauryl alcohol purge, the water reaction of the effluent, JP-4, was good. Discussion
These experiments are useful in understanding some of the problems associated with adsorption and desorption in a products pipeline. However, the laboratory results can be expected to correlate only qualitatively with pipeline experience. Pipelines are operated under conditions of turbulent flow and with vastly different surface-volume ratios than used in these studies. The surface roughness of a pipeline will vary greatly and depend on the amount of rust present; thus, the surface area is exceedingly difficult to measure. Consequently, accurate predictions of field performance based on laboratory results are not possible a t this time. From these studies, it is expected that the internal wall of a pipeline M ould absorb approximately a monomolecular layer of the additive from a shipment of gasoline containing an aminoamide surfactant. Taking a 100-mile-long smooth 8-inch pipe as an example, it can be calculated from the laboratory data
that 110 grams of the surfactant would be adsorbed on the pipeline wa!ls. A small amount of roughness might easily raise the total available surface tenfold. Then about 2l/2 pounds of the additive could be adsorbed. If a jet fuel, free of surfactant, were passed through this hypothetical line, about 25% of the surfactant would be desorbed into the jet fuel. Depending on surface roughness, this would lead in the considered line to a contamination of about 250 to 2500 barrels of jet fuel with a n average of more than 1 p.p.m. of the surfactant. I n actual product pipeline experience, considerably larger shipments of jet fuel failed the water reaction test. The effective displacement of surfactant from iron filings as observed in the laboratory led us to suggest the purging of pipelines with 2-propanol. \Ve have found by actual field experiments that three barrels of 2-propanol, introduced a t the interface between shipments of a surfactant-containing motor gasoline and jet fuel, are sufficient to purge a 100-mile, 8-inch pipeline and maintain acceptable water reaction properties of aircraft fuels. Literature Cited
(1) Barusch, M. R., Lindstrom, E. G., U. S. Patent 2,839,373
(April 30, 1958).
(2) Bergman, J. I., “Corrosion Inhibitors,” pp. 197-209, Macmillan, New York, 1963. (3) Ettre. L. S., Ciedinski. E. SV.. “Determination of Surface \
I
Areas by Gas Ch;omatographic Methods,” “Ultrafine Particles,’’ Electrochemical Society Symposium, 1963, p. 393. (4) Lindstrom, E. G., Barusch, M. R., U. S. Patent 2,839,372 (June 17, 1958). (5) Military Water Reaction Test, MIL-J-5624E. (6) Sigworth. H. SV., Lindstrom, E. G., Barusch, M. R., U. S. Patent 2,839,371 (June 17, 1958). RECEIVED for review May 6, 1965 A C C E P T E D September 28, 1965 Division of Petroleum Chemistry, 149th Meeting, ACS, Detroit, Mich., April 1965.
ACETYLENIC NONIONIC SURFACTANTS Ethovlation of Aceplenic Alcohols and Glycols, A New Class of Unique Wetting Agents M . W. LEEDS,
R. J . T E D E S C H I , S . J . D U M O V I C H , A N D A.
W . CASEY
Central Research Laboratory, Air Reduction Co., Inc., Murray Hill,N . J .
YDROPHOBIC
moieties containing active hydrogen have
H long been ethoxylated on a large scale to make nonionic
surfactants. Compounds containing hydroxyl groups including phenols and long-chain alcohols and glycols have been one of the major types to be ethoxylated. T h e tertiary acetylenic alcohols and glycols were found in our laboratory to possess novel surfactant properties by virtue of the inclusion of the acetylenic group in the molecules. Compounds such as tetramethyldecynediol, dimethyldecynediol, and hexadecynediol are unique, nonionic, nonfoaming surfaceactive agents which retain their excellent properties even a t relatively low concentrations in aqueous solutions. However, for broader applications higher concentrations were needed and because of the low solubility of the acetylenic diois, performance was poor. For this reason, it was considered desirable to attempt to ethoxylate the acetylenic alcohols and glycols, rendering them more soluble while retaining their surface236
I & E C P R O D U C T RESEARCH A N D DEVELOPMENT
active properties. This work was undertaken with a limited degree of success by earlier investigafors. Nazarov and Romanov (7) described the reaction of vinyl acetylenic alcohols with ethylene and propylene oxide to form a mixture of mono-: di-, and poly- adducts. This method involved reaction of vinylacetylene with ketones in dry ether using K O H . The resulting K O H complex then reacted in situ with ethylene oxide. A large amount (about 5070) of unreacted vinyl acetylenic carbinol was, however, recovered. The resulting products were a mixture of monoand higher adducts. KO reference was made to their surfactant properties. More recently Lagucheva ( 5 )made a large excess of dimethyl (vinyl ethynyl) carbinol (vinylacetylene-acetone carbinol) react with ethylene oxide in the presence of N,,V-dimethylaniline in a n autoclave a t 60’ to 85’ C . for 7 hours. This gave a 69% yield of the desired mono-adduct and 60y0 of the di- adduct
Nonionic, acetylenic surfactants possessing superior wetting powers have been prepared by the ethoxylation of lr4-acetylenic glycols using tertiary amines as catalysts. Trimethylamine in concentrations as low as 0.2 to o.3YOwas a highly effective catalyst promoting ethoxylations at temperatures as low as 45' to 50" C. at moderate pressures and minimizing decomposition reactions catalyzed by strong inorganic bases. The ethoxylated diol, tetramethyldecynedioI, at concentrations of 0.270 and higher shows unique and superior wetting action over conventional nonionics. This action i s characterized by very low fabric absorption, high wetting power after repeated use, superior wet pickup, and low foaming. Potential use in continuous operations i s indicated. Ethylenic and saturated analogs of the acetylenic glycols were also ethoxylated and found to be generally inferior to the corresponding acetylenics as surfactants.
based on recovered starting material. Petrov and Lagucheva (9) extended the S,AV-dimethylanilinesystem to the reaction of methylbutynol (dimethyl ethynyl carbinol) with ethylene oxide and later propylene oxide under pressure a t 145' to 150' C. These workers and others (2, 3, 8, 70, 7 7 ) then extended this technique to dimethylhexynediol (tetramethylbutynediol) to yield mainly the bis-P-hydroxyethyl ether of tetramethyldecynediol together with poly- adducts. T h e molar ratio of glycol to oxide was 1 to 2.4; the desired bis-Phydroxyethyl ethyl could not be isolated in the pure state. I n 1957 a patent (6) was issued for the ethoxylation of 1ethynylcyclohexanol using triethylamine as catalyst a t temperatures varying from 70' to 175' and pressures of 125 to 175 p.s.i. No surfactant applications were noted. T h e literature to 1955 and a recent patent survey ( d ) on ethylene oxide nonionic detergents have revealed no prior art on surfactants derived from primarv. secondar). and tertiary acetylenic carbinols and glycols. Further studies a t this laboratory showed that the tertiary aromatic amine, ,V..V-dimethylaniline, was a relatively inactive catalyst for the ethoxylation of tertiary acetylenic carbinols and glycols, and led to dark by-products and increased cleavage. Triethylamine. in contrast, was a n active catalyst particularly for the ethoxylation of tertiary 1,4-acetylenic diols,
OH
OH
With reactive diols such as dimethylhexynediol, dimethyldecynediol, and tetramethyldecynediol, ethoxylations could be initiated a t temperatures of 70' to 80" C. a t atmospheric pressure. Ethoxylation under such mild conditions is surprising. since even reactive primary alcohols or diols require temperatures of 150" C. and the use of pressure to realize a significant rate of reaction. The secondary or tertiary ethynyl carbinols of C S to C1? chain length were much less reactive than acetylenic diols and temperatures of 100' to 150' C. were generally necessary to activate the reaction. RIRz-C-CECH
OH
Table 1.
Typical Acetylenic Alcohols and Diols Useful as Surfactants
Geneva Kame
3-Methyl-1-nonyn-3-01 4-Ethyl-I -octyn-3-01 4.7-Dimethyl-5-decyne-4,7-diol 2,4,7,9-Tetramethyl-5-decyne-4,7-diol 7,1O-Dimethyl-8-hexadecyne-7,lO-diol 5-Decyne-4-diol
4 fundamental problem associated with reactions of secondary and tertiary acetylenic carbinols and glycols in the presence of either basic or acidic catalysts is their vulnerability to either cleavage (base) or dehydration (acid) a t elevated (>70° C.) temperatures. Acidic catalysts (phosphoric acid, acid-form Dowex resin, boron trifluoride etherate) were inactive catalysts, besides promoting extensive dehydration of the parent acetylenic. Strongly basic catalysts such as sodium and potassium hydroxides used as dry powders were active catalysts above 75" C . Ho\vever, base cleavage to either ethynyl carbinol and ketone or ketone and acetylene was rapid above 100' C.: making these catalysts unsuitable as initiators for ethoxylation. They could, however, be employed as booster catalysts a t higher temperatures (150' to 160' C.) for less reactive starting materials, once an average polyoxyethylene chain length greater than seven units had been attained with a tertiary amine catalyst.
I
I
I
Catalyst Activity
RIR~C-CEC-C-R~RZ
R~R~-C-C~C-C-RIR~ 0H
Surprisingly, two secondary acetylenic glycols were found to be slower reacting than their tertiary counterparts. requiring temperatures of 130' to 150" C . The tertiary 1,4-diol structure apparently has unique structural features which facilitate ethoxylation.
TYP of Hydroxyl 3O 2 O
3" 3" 3" 2"
+
1
RiR2C-C=CH
i
OH
OH
Trimethylamine in later stages of development was found to be a markedly superior catalyst to triethylamine. I t initiated ethoxylations a t temperatures as low as 45" C. a t catalyst concentrations of only 0.376 compared to 27, for triethylamine. Adducts containing eight to ten ethylene oxide units per mole of tetramethyldecynediol could be prepared a t 45' to 75" C. in several hours, while the same reaction for triethylamine required a temperature range of 75' to 130' C . during 4 to 5 hours. Further, base-catalyzed cleavage was negligible a t 45" to 55' C. with trimethylamine and a surfactant of considerably lighter color resulted. T h e low boiling (3' C.) trimethylamine could be conveniently introduced as the anhydrous liquid a t low pressure (50 to 100 p.s.i.g.) through a pressure sight glass gage, to the molten diol or liquid carbinol. Further, most of the amine could be eliminated from the ethoxylated product by vacuum topping a t 100' to 120' C. Triethylamine, while still a n efficient catalyst, had to be water-free ; otherwise increased cleavage (sometimes as high as 1076) resulted. T h e acetylenic starting materials are described in this text without Geneva nomenclature for simplicity. Table I lists the Geneva names of typical types studied. The 2,4,7,9-tetramethyldecynediolis commercially known as Surfynol 104, and its ethylene oxide adducts are referred to as the Surfynol 400 series (Air Reduction Co.). VOL. 4
NO. 4
DECEMBER 1 9 6 5
237
Experimental Details
Reaction System. A 1-gallon stirred autoclave behind a suitable barricade and equipped with a blow-out disk rated a t 1000 p.s.i.g. was the reactor for batch ethoxylations. The important components of the reaction system are: Nitrogen tank with two-stage regulator. Stainless steel high pressure valves, attached to stainless 1/1c-inch-I.D. high pressure tubing. Union Carbide Co. Z type ethylene oxide cylinder equipped with siphon tube and nitrogen blow connection for introducing ethylene oxide into autoclave as a liquid. T\YOconsecutive check valves to stop ethylene oxide flow when autoclave pressure exceeds the nitrogen purge pressure, and located between the autoclave and the ethylene oxide tank. Platform balance accurate to 0.01 pound for weighing ethylene oxide into autoclave, or a high pressure liquid feed buret. Stirred 1-gallon autoclave equipped with heating and cooling jacket, inner coil cooling unit: turbine-type stirrer with hollow shaft which sucks gas under the surface, vent line, and pressure gage. Stainless steel pressure tubing moderately flexible, bent in two to three coils to reduce drag on the balance. Vent valve and vent line. An alternative and convenient method of adding ethylene oxide to the reactor is via a Strahman high pressure glass buret (Type 100 C) rated a t 2000 p.s.i.g. and of 80-cc. capacity. Liquid ethylene oxide under its own vapor pressure is introduced to the buret, which is then pressurized ivith nitrogen to a value 50 to 100 p.s.i.g. higher than the optimum pressure expected during ethoxylation. The liquefied oxide can then be visually added at any prescribed rate. The buret also serves as a convenient method of introducing the low boiling trimethylamine catalyst. In pilot plant operations the oxide has been continuously pumped under the surface of the molten diol with completely satisfactory results. This type of addition is more efficient than addition onto the surface of the charge, but requires a positive pressure at all times, so that no suckback takes place Lvith possible plugging of lines or the check valves. Any suckback of the alkaline reaction mixture past the check valves into the ethylene oxide tank constitutes a grave hazard due to uncontrollable oxide po!ymerization. Recommended Procedure for Tetramethyldecynediol A. Ethylene Oxide Adduct (Molar Ratio 1 to 7.0). METHOD Low PRESSURE METHOD. Into the gallon autoclave is charged 904 grams (4.0 moles) of tetramethyldecynediol as either the solid or molten diol. The glycol is heated a t 55' to 60" C. until molten and with stirring is treated with 20 grams of triethylamine or preferably 2.7 grams of anhydrous trimethylamine. The latter catalyst is added as the liquefied gas either under its own vapor pressure or via the pressure sight glass buret using 50 to 100 p.s.i.g. of nitrogen as a chaser. I t can also be weighed directly into the autoclave. 'The autoclave is sealed and together with all connecting lines purged three times with 25-p.s.i. portions of nitrogen. If trimethylamine is used, the nitrogen purges should be carried out before addition of the amine to avoid its loss. Nitrogen pressure in the autoclave is adjusted to zero gage pressure a t 55' C . and the addition of ethylene oxide liquid on the surface of the charge a t 45' to 60' C. is begun. T o add the ethylene oxide, either the Carbide Z siphon cylinder or the pressure buret is used. I n either case, the oxide is transferred by nitrogen pressure a t least 50 p.s.i.g. above the vapor pressure of the ethylene oxide a t the prevailing temperature in the autoclave room. The exothermic reaction is controlled a t 55' to 90' C. during the addition of the first 8 moles of ethylene oxide. If trimethylamine is used, the exothermic reaction can be readily controlled a t 45' to 55' C. by occasional water cooling during the reaction of the first 4 moles of ethylene oxide to minimize cleavage and color formations. Care must be taken not to overcool the reaction, since a dangerous excess of ethylene oxide will result, which can react uncontrollably a t higher temperatures (100' to 120' C.). 238
l&EC
PRODUCT RESEARCH A N D DEVELOPMENT
After addition of about 75% of the total ethylene oxide a t 55' to 75' C., the absorption rate diminishes somewhat and the pressure begins to rise. T h e reaction temperature is then gradually lowered to 25' to 40" C. to lower the autoclave pressure and allow the remainder of the ethylene oxide to be added a t a pressure of 35 to 50 p s i . When the entire 28.0 moles of ethylene oxide has been added, the ethylene oxide line is blown with nitrogen through the blow line with the ethylene oxide tank closed. The autoclave is then sealed and heated for 1 hour to 125' C. The reaction mixture is heated until the pressure remains constant for 1 hour. The total reaction time is generally 4 to 5 hours. The resulting product is a mobile, light orange-brown oil which can be freed of any unreacted ethylene oxide and amine catalyst by vacuum topping a t 120' to 130' C. a t 25 mm. The color of the product generally lightens to a light amber shade after elimination of amine catalyst. METHODB. ATMOSPHERIC PRESSUREMETHOD.This is essentially the same as Method A, but the rate of reaction is noticeably slower. A large scale pressure run is generally complete in 4 to 5 hours, while the same run a t atmospheric pressure required 12 to 24 hours, depending o n the reaction temperature and agitation. The reaction temperature is initially 55' to 75' C. and after the addition of 2 to 3 moles of ethylene oxide per mole of glycol, the temperature is gradually increased to a maximum of 120' to 125' C. for a seven- to 12-unit chain. Chemistry of Process. The chemical reactions involved in the preparation of a polyoxyethylene adduct of a typical tertiary acetylenic glycol or carbinol are illustrated below:
R?
R2
I1
I
+ + y)CH2CH2
OH-C-CEC-C-OH
(X
I
I
R1
Ri
\ / 0 Ri
Ri
H(OCHZCH~),O-C-C=C-C-O-(CH~CH~-O)~H
I
1
Rz
R?
T h e corresponding adduct from a tertiary acetylenic carbinol has the following structure :
Ri H
I / I 1
H-C=C-C-O-(
CH&HzO),+ yH
Rz H The resulting ethylene oxide adducts are a mixture of different chain lengths of undetermined composition. T h e molar ratio of acetylenic starting material to ethylene oxide reacted serves as a convenient basis for specifying average chain length. The enhanced rate of ethoxylation of tertiary acetylenic diols with triethyl- and particularly trimethylamine over tertiary acetylenic carbinols and secondary acetylenic diols is believed due to the formation of an active tertiary dioltertiary amine complex which via hydrogen bonding weakens the oxyhydrogen bond of the tertiary hydroxy groups so that low temperature (40' to 65' C.) reaction with ethylene oxide is possible. This activation effect would be expected to diminish with increasing average polyoxyethylene chain length, and this is observed experimentally. Temperatures in the range of 100" to 150' C. are needed to obtain ethylene oxide contents up to 85% by weight. Further, tertiary acetylenic diols have been shown (73) to form readily in high conversion stable 1 to 1 potassium hydroxide adducts in which infrared gives no evidence of free hydroxyl. These complexes used in catalytic amount can
Sample NO. A
B C
Tetramethvldecynediol Deriv.
Acetylenic Olefinic Saturated
Mole Ratio 1:6.8 1:6.8 1:6.0
Table II. Comparative Surfactant Properties Surf. Tens. Draves 0.7% 0.5% 0.1%
34 30.3 37.9
27.3 29.3 Insol.
completely repress severe hydrogenolysis (H20 formation) side reactions (72) in the complete hydrogenation of tertiary acetylenic diols. This elimination of by-product water formation is equivalent to stabilizing the tertiary carbon-oxygen bond during hydrogenation. Triethylamine also used in catalytic amount exerted the same effect, presumably through complex formation. While KOH complexes of tertiary acetylenic carbinols and diols rapidly catalyze their cleavage back to ketone, ethynyl carbinol, and acetylene, the same cleavage with tertiary amine complexes is much slower. How ever, no tertiary amine-acetylenic diol complex has been isolated as yet. because of its instability, Base-Catalyzed Cleavage. This is the only significant side reaction associated with the formation of these adducts. This cleavage leads to the decomposition of the starting material into ketone, acetylene, and ethynyl carbinol (in the case of glycols). This side reaction is of importance in the case of strong base catalysts such as K a O H and K O H . but is minor for tertiary amine catalysts of moderate basicity such as trimethyl- and triethylamines when used initially a t 45' to 75' C. Reactivity and Influence of Triple Bond. T h e rapid absorption of bromine. and the decolorization of neutral KMnOd solution, indicate the presence of a reactive triple bond. T h e selective hydrogenation of these acetylenic adducts to form ethylenic polyoxyethylene adducts confirms the presence of the triple bond and together with carbon and hydrogen determination confirms their structure. The triple bond, because of its electrophilic character and ability to form complexes, results in greater reactivity of the
Table 111.
Dimethyldecynediol Tetramethyldecynediol
10 moles E O see-Decvnediol Tetramethyldecenediol
Dimethylhexadecynediol
Grams P, P.S.I.G. (moles) Atm. 198 (1.O) Atm. 199 10.50) 113 (0.50j 35-138 61.8(0.27) Xtm. 50-200 113 (0.50) 40-21 5 904 (4.0) 30-255 104.5 40-68 452 12) 40-70 452 ( z j 45-75 452 (2) 60-75 904 (4) 10-40 700 (3.1) 10-60 1000 90 (0.50) 1 1 0-220 35-226 114 (0.50j 22-309 117 10.50) Atm. 201 (0.7ij 141 5 0-), 26-285 . . 1 0 .\ -
Dimethylhexadecynediol, 7.3 moles E O Diphenylhexynediol Methylnonynol, 3.5 moles EO Ethynylcyclohexanol
0.5%
Inst. Inst. N o wetting
11 .o 9.5 16.8
4.2 4.1 Insol.
tertiary acetylenic glycols toward ethylene oxide than the corresponding olefinic and saturated series. Dimethylhexynediol, dimethyldecynediol, and tetramethyldecynediol react readily with ethylene oxide a t atmospheric pressure and moderate temperatures (50' to 75' C.), to form 1 to 5 adducts. As the carbon chain in the glycol series is increased from 6 to 16 carbon atoms, the reactivity falls off sharply and dimethylhexadecynediol does not react significantly a t atmospheric pressure. Reactivity in the carbinol series falls off sharply a t a nine-carbon chain (methylnonynol). T h e effect of the triple bond upon solubility and detergent properties is discussed below. Chain Growth. Polyoxyethylene chain formation is a nonselective process. Pure mono- and di- adducts of acetylenic carbinols and glycols are isolated only in poor yields. Surfactant Stability. Once the tertiary hydroxy groups of the acetylenic material have reacted with ethylene oxide, the resulting adduct exhibits the marked stability of a n ether. Unlike the starting material, prolonged heating with concentrated alkali a t elevated temperatures has no effect on the polyoxyethylene bond or initial acetylenic molecule. Surfactant Properties and Effect of Triple Bond. Most of the adducts prepared showed surfactant properties to some degree, but the outstanding examples were dimethylhexadecynediol and tetramethyldecynediol. The following comparison of a tetramethyldecynediol adduct with its saturated and olefinic analogs a t essentially the same chain length shows the superior properties of the acetylenic compared to the saturated analog of the same structure. The ability of the
Av. Reaction Time, T , a C. hr. 55-110 31 130-1 50 40 42-151 4 8 65-80 ~. .~ 50-1 20 '!P 55-1 60 5 25-240 2112 3 :5 50-65 45-48 2.5 5 50-64 7i-ii8 5 80-105 6 93-105 4112 100-1 30 6 25-1 53 5 25-152 5 110-150 5 25-156 71/?
30-1 85 25-150 5 30-254 32-141 3 39-1 51 5 58-205 100 25-240 72 (0.55) 25-1 64 i!'l Scl. Soluble in all proportions, cloudy to turbid a S. Soluble in all proportions, clear solution. oxide. 150 133 (0.50)
0.1%
Experimental Conditions and Results
Starting Material Xame
14.5 33 > 300
Int. Fac. Tens. 0.5%
Cat.
NaOH NaOH NaOH TEA NaOH KaOH NaOH TMA TMA TMA TMA TMA TMA TEA TEA TEA TEA TE.4
Grams Cat. 1 .o 0.50 0.55 2.5 1.1 1 .o 0.50 2.7 1.3 5.0 2.0 3.0 20 0.30 5.0 5.0
5 5 .O
CH,ICH?OAdduct Moles EO/mole (25' c.). start mat. SOL. 19.8 S 51.4 S 4.0 Scl. 6.5 Scl. 7.0 Scl. 16 S 30 S 5 Scl. 5.5 Scl. 8 .O S 8.0 S 10 S 30 S 4.4 Scl. 5.3 s1. s 6.0 Insol. 0.6 Insol. 7.3 Scl.
TEA TEA TEA
5 15 S 5 7.0 Scl. 5 .O 10 Scl. NaOH 0.25 4.3 Scl. solution. SI. S. Slightly soluble. E O . Ethylene
VOL. 4
NO. 4
DECEMBER 1 9 6 5
239
Table IV.
7.0 10
25 63
..,
29.3 .
._
,..
33.2
28.0
Insol. 27 . O
Insol.
...
Dimethylhexadecynediol
6.0 7.3
37.9
