Manufacture of soap from fatty acids

Soap manufacture from fatty acids is a well established precess with some advantages over continuous saponification of neutral fats. These include:

1. Ability to use cheaper fats.
2. Easier glycerol recovery.
3. Better control over by-products.
4. Versatility-fatty acids can be used to make other derivatives than soaps.

     

The measurement of the hydrolysis of solutions of sodium salts of fatty acids. I.

1. pH values of recrystallized samples of sodium acetate, NaAc.3H₂O, measured with the Beckman pH meter at 25°C., using the “blue glass” electrode were near pH 8, rather than the calculated and true value for pure sodium acetate of 8.88. Titration curves were made beginning with decinormal solution of the slightly acid salt and adding sodium hydroxide; the pH at the inflection of these curves was near the correct value, 8.8.
2. Sodium hydroxide titration curves in aqueous solution were made at 50°C. for myristic acid and lauric acid, decinormal at the equivalence point. The point of inflection came after the equivalence point, giving the values of hydrolysis alkalinity for these two soaps.
3. Sodium hydroxide titrations in 80% alcohol at room temperature were made in the presence of phenolphthalein for Eastman myristic, Kahlbaum lauric, Lepkovsky myristic and the very pure Francis lauric acid. Concentrations at the equivalence point were about N/60. In every case the equivalence point, the point of inflection, and the color change coincided with the color change occurring near an apparent pH of 10.5 as indicated in alcohol.
4. The solubility of Eastman lauric acid was measured in a number of non-aqueous solvents at temperatures ranging from 23 to 26°C. Solubility was least in a sample of Braun-Knecht-Heimann medicinal mineral oil.

     

The hydrolysis of soap solutions. III. Values of pH and the absence of fatty acid as free liquid or solid

Summary The pH of the laurates, myristates, palmitates, and stearates of sodium and potassium at 25° and 50°C. was determined by use of a glass electrode. pH:concentration curves were constructed, and hydroxyl ion activity was calculated. In general, the concentration of hydroxyl ion ranges from 0.001 to 0.0001 N; for the less dilute solutions of the higher soaps, the upper limit is exceeded by several fold, and in the more dilute solutions the concentration may fall beneath the lower value. Solubilized hexane reduced the pH of potassium and sodium laurate but very slightly. Potassium or sodium chloride reduced the pH of soap solutions over a certain range but caused a slight increase in a narrow intermediate range. Using the pH values obtained, the actual concentration of fatty acid in the soap solutions was calculated, and was found to beless than the saturation concentrations obtained by conductivity measurements through the entire range investigated. Free fatty acid therefore never separates as such from pure soap solutions unless acted upon by excess of acid such as carbon dioxide. Percentage hydrolysis was calculated and curves were constructed. In general, the potassium soaps are hydrolyzed more than the corresponding sodium soaps; the difference is slight for the laurates but is considerably greater for the myristates, palmitates, and stearates in higher concentrations at 25°C. The difference is appreciably smaller at 50° than at 25°. Percentage hydrolysis for the laurates is very much less than for the higher soaps.     

Low temperature solubilities of fatty acids in selected organic solvents

Summary A number of highly purified fatty acids have been prepared and their solubilities determined in six common organic solvents within the temperature range from 10° to −70°. The acids studied were palmitic, stearic, oleic, elaidic, petroselinic, petroselaidic, linoleic, stearolic, arachidic, eicosenoic, behenic, erucic, and brassidic. The solvents used were methanol, ethyl acetate, diethyl ether, acetone, toluene, and n-heptane, representing six different solvent types. A limited study was also made with a series of hydrocarbon solvents in order to note any effects of solvent structure on fatty acid solubility. Data are discussed with respect to their application in separating various fatty acid mixtures by low temperature crystallization. From a dissertation submitted by Doris Kolb to The Ohio State University in partial fulfillment of the requirements for the Ph.D. degree, August, 1953. This work was supported in part from funds granted by the Ohio State University Research Foundation to the university for aid in fundamental research.     

Palm oil fatty acids in soap and detergent formulations

Palm oil fatty acids can be used in increasing quantities in combination with selected minor oils from Indian in making lower cost laundry or toilet soaps and derivatives suitable for use as surface-active compounds in many formulations. Experimental soap formulations using palm oil products and indigenous fats are provided.     

Studies in soap crystallization processes. Part III. Acid soap crystallization in the segregation of tall oil fatty acids

Tall oil fatty acids have been fractionated into 80–90% oleic acid, and 60–80% linoleic acid fractions, by precipitation of the oleic acid as acid soap from polar solvents. Sodium and potassium acid soaps are equally effective, but ammonium acid soaps require lower operating temperatures. The choice of solvent is not critical as regards degree of separation, but technically attractive filtration rates have been obtained only with methanol and acetone. Acidulation gives colorless oleic acid of very low rosin acid and unsaponifiable content, but with 5–10% of conjugated linoleic acid.     

The occurrence of higher fatty acids in corn pollen

Summary The methyl esters of the fatty acids of corn pollen were prepared and fractionated through a Stedman column. Palmitic, stearic, oleic, linoleic, and linolenic acids were identified by the melting points of thep-bromophenacyl esters of the saturated acids and the hydroxy and bromine addition compounds of the unsaturated acids. This investigation was supported by a grant from the National Science Foundation. Journal Article No. 2139 of the Michigan Agricultural Experiment Station.     

Hydrogenation of unsaturated fatty acids to unsaturated fatty alcohols: III. Comparison of different soap catalyst systems

Copper oleate and cadmium oleate catalysts have been replaced by other metal compounds. Silver was the only metal which could be substituted for copper in the ratio range studied. Using nickel oleate, the degree of saturation of the double bond decreased with increasing cadmium oleate concentration. No comparable substitute was found for Cd. The composition of the final components is influenced by the use of a paraffinic solvent, which also has an effect on the saturation of the double bond. An explanation is given for the behavior of the catalyst when the reaction is not selective and is carried out in a paraffinic solvent. The catalytic system Ag/Cd soaps was also studied kinetically and analytically. The results show that the mechanism of the reaction using silver soap is identical with the one using copper soap.     

The acetolysis of glycerides. II. The production of fatty acids and triacetin

Triacetin can be made by the acetolysis of hardened tallow in consistent yields of 70% of theory (18% w/w on fat) accompanied by an 80% yield of good purity saturated fatty acids, and some 10% of a fraction of high diacetoglyceride content. The yields of both triacetin and fatty acids can be materially increased by recycling of the diacetoglycerides and the still bottoms. Tallow gives similar yields of triacetin and fatty acids, but the acetoxystearic acid by-product interferes with the separation of the diacetoglyceride fraction.     

The hydrolysis of soap solutions. IV. The composition of acid potassium laurates and acid sodium oleates as determined by conductivity measurements

The effect of excess lauric and oleic acids on the conductivity and on the pH of 0.2–0.02N potassium laurate and 0.1–0.01N sodium oleate systems was observed. The decrease in the specific conductivity corresponded with the formation of the acid soaps, 2KL·HL, KL·HL, 2NaOl·HOl, NaOl·HOl, and the mixed soaps 2KL·HOl and 2NaOl·HL. The mixed soaps resemble the oleates in appearance. All of these systems, even with 100 or 150 moles per cent excess acid, were slightly alkaline.     

Electrolysis of soap solutions

Summary It is not thought that the electrolytic reactions are simple, nor is it thought that the types of compounds discussed are the only ones in the products of electrolysis. Although the calculated compositions are not precise, they are of the right order of magnitude, and good yields of products consisting mainly of alcohols and olefines are obtained by electrolyzing with graphite anodes a soap solution, preferably containing appreciable amounts of an inorganic salt and a low molecular alcohol.     

The separation of solid fatty acids from liquid fatty acids by the formation of acid soaps. II. Pilot plant studies

On contemplating pilot plant scale-up of the acid soap process for separating fatty acid mixtures into low and high iodine value fractions, improvements were desirable in acidifying agent used, and the method of separating the solid acid soaps. A further objective was to determine the range of applicability of the process. Studies indicated that CO₂ can be replaced by mineral acids, or by the fatty acids themselves. A continuous precoat vacuum filter is suitable for the separation of the solid acid soaps. The process is applicable to refinery foots as well as to distilled and undistilled fatty acids.     

Soap-based detergent formulations: II. Oxyethylated fatty amides as lime soap dispersing agents

Nonionic surface active agents with two oxyalkyl chains were prepared from the triethylamine catalyzed reaction of ethylene oxide with diethanolamides of palmitic, stearic and tallow fatty acids. The addition of 4 moles of ethylene oxide was required to render these diethanolamides water soluble, whereas 9 moles were required to make the corresponding monoethanolamide soluble. Efficiency of lime soap dispersion increased as oxyethyl chain length was increased. Best detergency of soap-nonionic combinations was achieved when the oxyethyl chain length was at the minimum required for water solubility. Theγ-hydroxyethanolamides and -diethanolamides were prepared by the uncatalyzed reaction of the corresponding amines withγ-stearolactone. These compounds became water soluble at lower levels of oxyethylation, but the lime soap dispersing power and detergency were not improved over those of corresponding compounds derived from stearic acid. Presented at the AOCS Meeting, Los Angeles, April 1972. E. Market. Nutr. Res. Div., ARS, USDA.     

Description of the mutual solubilities of fatty acids and water with the CPA EoS

Data for the mutual solubilities of fatty acid + water mixtures are scarce and so measurements for seven fatty acid (C₅‐C₁₀, C₁₂) + water systems were carried out. This new experimental data was successfully modelled with the cubic plus association EoS. Using data from C₆ to C₁₀ and the Elliot's cross‐associating combining rule a correlation for the k_ij binary interaction parameter, as a function of the acid chain length, is proposed. The mutual solubilities of water and fatty acids can be adequately described with average deviations inferior to 6% for the water rich phase and 30% for the acid rich phase. Furthermore, satisfactory predictions of solid‐liquid equilibria of seven fatty acids (C₁₂‐C₁₈) + water systems were achieved based only on the k_ij correlation obtained from liquid–liquid equilibria data. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Lather stability of soap solutions

The stability of soap foams in the presence of calcium ions was studied. Laundry and toilet soap bars available at the local market were used. The soap equivalent/calcium equivalent ratio is pro-posed as an objective quality criterion.     

Foaming properties of soap solutions

Summary This paper reports results, obtained by the “liquid drainage” method and a modified “foam time” method, on the stability of foams from solutions of soaps and detergents. The two methods gave qualitatively equivalent results. Rates of drainage of liquid from soap and detergent foams were not proportional to the volumes of liquid in the foam. The stabilities of foams from 0.1 percent solutions of soaps of most of the natural fats and oils tested were much greater than those of foams from single soaps that were sufficiently soluble to form solutions of this concentration. The foam time of a mixture of equal volumes of two 0.1 percent solutions was not equal to the average of the foam times of the separate solutions. A number of electrolytes, organic liquids, pectic materials, and vegetable gums greatly increased foam stability. Data on 0.03 percent sodium tallow and palm oil soap solutions indicated a maximum foam time at a pH of about 10.6. Increasing the concentrations of ten soaps from 0.05 to 0.1 percent more than doubled the foam time.     

Sodium salts of alkyl esters ofa-sulfo fatty acids. Wetting,lime soap dispersion,and related properties

A series of esters of the general formula RCH(SO₃Na)-CO₂R′ of 14–19 carbon atoms prepared by the α-sulfonation of propionic, butyric, pelargonic, lauric, myristic, palmitie, and stearic acids and esterification with normal primary alcohols were compared for critical micelle concentration, surface and interfacial tension, Ca⁺⁺ stability, wetting properties, foam height, detergency, and lime soap dispersing properties. Comparison of position isomers showed that as the hydrophilic portion moved from the center toward either end, cmc and wetting efficiency decreased, surface and interfacial tension increased, and Ca⁺⁺ stability and lime soap dispersing properties improved. A coconut oil fatty acid forerun sulfonated with SO₃ vapor and esterified with 2-ethylhexanol gave a product with useful wetting properties in soft and hard water. Presented at the fall meeting, American Oil Chemists' Society, Chicago, October 30–November 1, 1961. Eastern Utilization Research and Development Division, Agricultural Research Service, U. S. Department of Agriculture.