SULFONATION OF TALL OIL Separation of Rosin and Fatty Acids
FRANK C. VILBRANDT, PAUL E. CHAPA AN',
Tall oil, a dark odorous material recovered from kraft waste cooking liquor, is a complex mixture of rosin, unsaturated fatty acids, and other organic compounds. Sulfonation, extraction, distillation, and chemical attack have been proposed to separate the rosin and fatty acids from tall oil, but distillation is the commonly used commercial method of both separating and refining in this country. Tall oil is a cheap fatty acid substitute, and is a potential source of various derivatives made from the separated rosin and fatty acids. Extraction with hydrocarbon solvents and purification with concentrated sulfuric acid were investigated a s a means of removing the color and odorous bodies. Extraction removed a small quant i t y of tarry material but did not greatly improve the product. Sulfuric acid treatment produced a clear light-colored oil, and yields of abietic acid crystal of 33.7 and 41.9 per cent were obtained. The best results were obtained at 0' C. where a given quantity of acid is more effective than a t a higher temperature. Selective sulfonation of the fatty acids to the water-soluble sulfuric acid ester was performed a t low temperatures. The effect of acid quantity and of time were studied at -13' C. and the effect of acid concentration a t 0' C. A t -13' C. the fatty acids removed with increasing amounts of 95 per cent acid is accompanied by the simultaneous loss of considerable rosin. The rate of removal of fatty acids with 95 per cent acid is also paralleled by a substantial rosin loss. A t 0' C. acid strengths below 85 per cent sulfuric do not appear to attack either the rosin or fatty acids in tall oil, but when 90 per cent acid is used, the fatty acid content can be reduced without appreciably reducing the rosin content and thus permits separation of these two constituents.
AND JEROME M. CROCICIN Virginia Polytechnic Institute, Blacksburg, Va.
The commercial method of surifving tall oil adoDted n this country appears to be distiilatiin, although prbposals for treatment by extraction and chemical means have been made to overcome such objections to this method as corrosion and losses as pitch incurred a t the relatively high distillation temperatures involved. Abietic acid crystallizes out readily from the fatty acids in tall oil; improved yields and cleaner crystals are obtained if, the tars and other coloring matter are first removed. Aside from uses as a cheap fatty acid substitute, tall oil is a potential source of various derivatives from the separated fatty acids and rosin. Among the former may be listed the chlorinated oils recently introduced for use in transformers, sulfonated fatty acids for detergents, a possible source of drying oils for quick-drying paints, and a possible source of sebacic and adipic acids. Recommended chemical means of separating rosin and fatty acids from tall oil consist of sulfonation, esterification, and the formation of various salts. Noerdlinger (6) used concentrated sulfuric acid to separate resinous substances as a tarry mass and oleaginous fatty acids from a tall oil solution. According to a French patent (6), steam is passed through a mixture of resinous oil and sulfuric acid; the oil is then decanted, dried, and hydrogenated for use in soap manufacture. Geigy (8) treats a mixture of 100 parts of tall oil in 30 parts of phenol with a sulfonating agent to form a resinous watersoluble substance useful in the textile industry. Rosin and fatty acids may be purified by treatment with small quantities of concentrated sulfuric acid, followed by washing out the water-soluble compounds formed. Depending on the time, temperature, acid concentration, and acid quantity, yields of sulfonated, polymerized, or other side-reaction products may be formed. Blengsli ( I ) , sulfonating oleic acid and rosin, states that the former is not attacked below 35" C. or the latter below 40" C. when using 98 per cent sulfuric acid. I n general, acid strengths are above 65 per cent sulfuric and temperatures below 40" C. for both purification and sulfonation, the lower temperatures minimizing side reactions.
VAPORATION of the spent cooking liquor from the kraft pulp process results in the precipitation of soaps of rosin and other higher fatty acids cooked from the wood, plus an occluded portion of unsaponifiable organic material. Separation of this mixture from the liquor and subsequent hydrolysis with an acid medium yields an odorous oily material known as tall oil, from the Swedish tallolja, meaning an oil from the pine. Since the cooking process and the woods used vary from plant to plant, the composition of the spent liquor, and hence of the tall oil, varies considerably. Within limits reported in the literature, tall oil contains: 25-60 per cent fatty acids, mainly of the oleic series; 25-60 per cent rosin acids, which may include 50-90 per cent abietic acid; and 7-20 per cent unsaponifiable material. The latter portion contains 2-3 per cent phytosterol; the remainder is said to be made up of lignin, mercaptans, higher alcohols, etc. 1 Present
Experimental Procedure The removal of undesirable color and odorous bodies, and the separation of fatty acids from the rosin by selective formation of water-soluble sulfuric acid esters of the fatty acids was attempted in this investigation.
REFINING. Toluene, asoline, kerosene, and petroleum ether increase the fluidity of ta% oil and reduce local action with strong sulfuric acid. The last three of these solvents precipitate certain impurities from their tall oil solutions. Data were obtained on impurities removed as follows: (a) by precipitating directly from these solvents, ( b ) by oxidation with air, followed by precipitation in gasoline and (c) by the selective action of sulfuric acid. The solvent redning processes were carried out by dissolving a fixed quantit,y of tall oil invarying quantities of solvent, allowing
address, West Virginia. Pulp and Paper Company, New York,
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
it to settle, and filtering off the precipitated impurities. Purification by oxidation was acconiplished by drawing air through the solution a t 100' C., and then allowing the solution t o cool and settle before filtering. SEPARATION.The same solvent characteristics sought in the refining process are required for the sulfonation procedure. Selective sulfonation of the fatty acids requires establishment of the necessary time-temperature-concentration-quantity relat,ions. This investigation included the effect of time and sulfuric acid weight a t -13' C. and the effect of sulfuric acid concentration at 0" C. I
Vol. 33, No. 2
fatty acid content, color of product, crystal yield (abietic acid). Rosin and fatty acid content of the product was determined bv a modification of methods outlined by the West Virginia Pulp and Paper Company (5),and was based on determination of the rdsin acids number ahd the total acids number. The crystal yield was an approximation made for comparative purposes, and consisted of filtering about 5 grams of the oil on a Gooch filter. The vacuum was maintained for 2-3 hours in order to remove as much oil as possible from the crystals. T o determine the color of the filtered oil, a set of standards was calibrated in a TagRobinson colorimeter. The A. s. T. M. method was ased to determine the color of those oils n-hich fell below the zero reading on the Tag-Robinson scale.
Data on the insoluble material obtained in toluene, petroleum ether, gasoline, and kerosene are given in Table I, and are compared graphically in Figure 1. A characteristic
TABLEI. PERCENTAGE OF TALL OILINSOLUBLES IN VARIOUS SOLVENTS
4 3 6 7 TALL O I L . SOLVENT
I O / /
Toluene Petroleum ether Gasoline Kerosene
Tall Oil-Solvent Ratio
1:l.O 2.21 3.1s 3.36 5.84
1:2.0 1.21 2.49 2.64 3 72
1 : 3 . 5 1:5.0 0.89 2.35 .... 2.22 1.94
.... i:iS 1 SO
1:s.O 1 : 9 , 5 0.36
1 08 R.87
TALL OIL. The oil uwd TVRS a commercial grade of crude material. The analpis as supplied by the inaiiufacturer is as follows: Fatty acids, Yo Kosin acids, % Nonacids, 70 Acid number
Saponification number Kosin acid number X u i s t u r e , 7,
48 8 44 1