INDUSTRIAL AA'D ENGINEERING CHEMISTRY
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Various estimates of this law of attraction between molecules have been made. Sutherland (21) gave reasons for believing that the force of attraction between molecules varies as the inverse fourth power of the distance between them. Chatly (5) suggested for solids an inverse sixthpower law. Kleeman (11) thinks an inverse fifth law the
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exactly fit the data; for the mean distance between the molecules varies inversely as the cube root of the density. Kleeman (12), however, gives evidence to show that such a simple relation is generally not true, but that the surface tension is a function of both the density and the temperature, suggesting that the molecules shrink a t higher temperatures in order to remain stable with their greater rotational energies. Acknowledgment The authors avail themselves of this opportunity to express their thanks to the managements of the Standard Oil Company of New Jersey and the Vacuum Oil Company of New York for furnishing the samples of oils used in these experiments and for supplying the data on their physical characteristics.
E
a" s C
E
d
20
5
Literature Cited I5
200'F 93.C
300'f 149.C
400'F
500'F
600
204'C
260'C
316'C
Temperature Figure 4
F
most probable; and this was also the view which Maxwell ( I S ) reached from viscosity considerations. Kam (IO) favors a n inverse square law. Antonoff (1) from surface tension phenomena and Tomlinson (22) from work on the elasticity of solids suggest an inverse fourth-power law. Edser (6) considers a n inverse eighth law as being the most probable. Finally, Rosenhain (17) gives a n inverse cube law for forces between metallic atoms. I n these experiments both the density and the surface tension varied linearly with the temperature, so that the surface tension plotted against the density would also give B straight-line curve. Xow if the cause of the variation of the surface tension were attributed solely to change in density, it is seen that in this case an inverse cube law would
(1) -4ntonoff. Phil. -'dag,, [6] 36, 377 (1918) (2) Bircumshaw, Ibid., [71 6, 510 (1928). (3) Brown, Ibid., [7] 6, 1044 (1928). (4) Cantor, Wied. Ann., 47, 390 (1892). (5) Chatly, Proc. Phys. SOL.London, 27. ( 6 ) Edser, Brit. Assocn. Advzncemenl Sci. R e m . , 1922. (7) Engineering, 119, 109 (January 23, 1925); 122, 239 (August 20, 1826). (8) Ferguson, Phil. M a g . , [ 6 ] 23, 128 (1914). (9) Harkins and Brown, J . A m . Chem. Soc., 41, 499 (19191. (lo) Kam, Phil. Mag..[ 6 ] 37, 65 (1919). (11) Kleeman, Ibid., [ 6 ] 19, 783 (1910). (12) Kleeman, Ibid., [6] 21, 783 (1910). (13) Maxwell's Collected Papers, Vol. 2, p. 35. (14) Oshorne, Encyclopedia Britannica. 10th ed., Lubricants. (15) Ramsay and Shields, Phil. Trans. Roy. SOC.(London), 184, 647 (1893). (16) Richards and Carver, J . A m . Chem. Soc., 37, 1656 (1915). (17) Rosenhain, Cantor Lectures, 1025. (18) Sauerwald and Drath, Z . anorp. nllgem. Chem., 154, 79 (1926). (19) Selby, Phil. M a g . , [5]31, 430 (1891). (23) Sugden, J . Am. Chem. Soc.. 121, 865 (1922). (21) Sutherland, Phil. Mag., [ 5 ] 24, 113, 168 (1887). (22) Tomlinson, Ibid.,[71 6, 695 (1028). (23) Washburne, Bull. Am. I n s f . Mining En,.., 2368 (1914) (24) Winchester, Phys. Rev., 29, 911 (1927).
Refining of Shale Gasoline I-Relation
of Oxidation t o Colors and Gums Produced in Gasoline from Colorado Oil Shales' Robert A. Baxter 423 S I X T E E X T H
ST.,
I
N VIEW of the present great production of petroleum and comparatively low price of gasoline, it may be well to begin by saying that the purpose of this study is primarily the collection of information which may be useful in the refining of gasoline in general and not the immediate production of motor fuel in commercial quantities from oil shale. It is well known that the oils produced by the thermal decomposition of oil shales are similar to petroleum, but it is not quite so generally realized that those produced from shale oil are generally much more active. For this reason shale gasoline is a very desirable raw material to use in the study of color and gum formation, since it is frequently possible to get as great a change in a crude shale gasoline in a day as is possible in a month with most well gasolines. Several years ago we noticed that when shale gasoline was 1 Presented before t h e Division of Petroleum Chemistry a t t h e American Chemical Society, St. Louis, Mo., April 16 t o 19, 1928. Revised paper received June 6, 1929.
GOLDEX,COLU.
kept in tightly closed bottles away from air it did not change color or form gums to any appreciable extent, but that when the same material was exposed to air it darkened rapidly and soon deposited gums. Like many other discoveries, we soon found that this was well known (6). However, two different explanations had been offered for the gum formation-one group holding that the change was one of oxidation and the other group maintaining that it was one of polymerization. As a contribution to this discussion, there seem to be several additional pieces of information which should be presented, some of which may suggest methods of improving motor fuel quality and simultaneously reducing the cost of refining. The gasolines on which this work was done were derived from the richer beds of western Colorado shales, which were retorted either in the Ginet or Lamb retort or in a laboratory pot retort, and all of the oils were fractionated and treated in the laboratories of the Colorado School of Mines. It
November, 1929
IKD USTRIAL AhTDESGISEERING CHEMIXTR Y
is realized that the information is far from complete, and for this reason analytical work is being done on the original oils and on the color bodies produced and amplification of the work on catalytic agents and on fractional solution is under way and will be reported as rapidly as possible. Effect of Light Waves
As a study of the possible effect of light waves, several filled and partly filled bottles were subjected to x-rays and to ultra-violet light. There was no appreciable effect greater than that of ordinary sunlight; that is, the reaction rate in all three instances was increased, but the nature of the change produced seems to be independent of these light effects. A sample from which air had been carefully excluded did not darken much irrespective of light conditions, but a sample that had been exposed to air or other oxidizing agents did darken and form gums even when kept in a cool, dark place, though not so rapidly as when the .ample was exposed t o light. Study of Oxidizing Agents
A series of experiments with different oxidizing agents was arranged, but the variation in the reactions caused by variations in solubility and by secondary reactions of the materials used was so great as to make the results of little value. Acids and halogens were so active that their reactions were difficult> to control. Most basic materials had very little effect, but silver oxide caused a very rapid darkening of the oil and the silver was deposited as a mirror. Chlorine reacted a t first t o give addition compounds, but soon began to give off hydrogen chloride, indicating the substitution reaction had started. I n one series a 45 per cent volume loss of gasoline was found by chlorination treatment, and even at that stage the product was still unstable. This treatment was stopped and the material discarded because the substitution reactions had become T. ery prominent. Pure oxygen gas was tried, but its reaction rate was not enough greater than that of air t o make it worth while. Ozone was then tried and proved t o be a very satisfactory reagent, not only for producing the oxidation to form the color bodies and gums very rapidly, but as a qualitative test reagent for the detection of hydrocarbons containing multiple linkages. When ozone is passed into shale gasoline, a dense white cloud is evolved and the liquid gets hot. I n an effort t o find the cause of this phenomenon, ozone was passed into several organic compounds. With hexane, cyclohexane, benzene, toluene, xylene, ethyl ether, acetone, paraldehyde>, and with several commercial gasolines produced by straight-run distillation there was no apparent action. With amylene, pinene, cyclohexene, several gasolines prepared in cracking stills, and with allyl alcohol the white fumes were produced and the liquid became hot, as does the shale gasoline. M‘ith oleic acid there was heating but no apparent fumes. This n-ould indicate that ozone is a good qualitative reagent for compounds mith multiple linkages, but that only those of relatively high vapor pressure will give the white fume indication. This test was tried as an indicator in the separation of olefins and aromatics in the method of Egloff and i\lorrell (5’)for the separation of the four main types of hydrocarbons in gasoline and is of considerable value for increasing the certainty of complete elimination of the olefins, a reaction which is sometimes not completed by the 15-minute treatment with 80 per cent sulfuric acid. Many writers have mentioned ozone and its reactions with unsaturated and aromatic hydrocarbons. Brooks (1) states that the products are ozonides and indicates that the
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reactions with olefins and aromatics are the same. We find the reactions different, a t least the phenomenon of the formation of the white fumes, which we do not find with the aromatics but do find with the compounds having multiple linkages. We do find that certain phenols, amines, and mercaptans give the white fumes with ozone, but do not find this action with any of the saturated or aromatic hydrocarbons which we have been able to try. Gurwitsch (4)mentions ozonides prepared from a fraction of Russian oil and states that they are soluble in benzene, chloroform, and ether, but insoluble in petroleum ether. Richter ( 5 ) mentions the reactions of ozone with olefins to give ozonides, with diolefins t o give dioxonides, and with amines to give aldehydes. Brooks ( 2 ) states that the first step in the formation of gums is the formation of peroxides, and he traces the changes produced by air oxidation through to the fully oxidized resins. Our experiments indicate that the reaction products are very similar with air and with ozone, but we have not been able t o prove whether the intermediate products are ozonides or peroxides. We were able to oxidize shale gasoline by the ozone process sufficiently t o remove the gum-forming constituents by converting them to gums, but our losses were always above 30 per cent and the treating costs were high, so that we do not yet suggest such a process for the commercial treatment of the gasolines very rich in unstable compounds such as the shale gasoline. However, we do believe that it might be used on those gasolines in which the amount of gum-forming material is less. Most of the gums formed by the oxidation reaction may be removed by the centrifuge. If necessary, they may be further eliminated by a light acid treatment or by extraction with methanol. The main advantage of the gasoline so treated is that the unsaturates (by the sulfuric acid absorption procedure) are left in the gasoline t o the extent of 30 per cent or more; hence the gasoline should have good anti-detonating characteristics. \$‘e have not yet been able to determine the actual engine characteristics of the motor fuel so prepared. Action of Antioxidants
As soon as the conclusion that the gum-forming reaction was one of oxidation was firmly established, the next logical step was t o try the action of a few antioxidants or negative oxidation catalysts. Of a considerable number of materials tried for this purpose, only phenylhydrazine had any appreciable merit as a material for retarding oxidation. Bottles half filled with gasoline containing a little phenylhydrazine will stand a long time without very much darkening or gum formation, but ozone will produce gums in this mixture in a few minutes in spite of the phenylhydrazine. As we have not finished conclusive tests on the effect of phenylhydrazine on other properties of gasoline, we cannot say that it will be permissible as a stabilizing agent, but do merely state that it does have a material effect in retarding the formation of gums. Solvent for Gums
The gums formed in our shale gasoline nere soluble in ethyl alcohol; hence the deposition of gums may be prevented by the addition of ethyl alcohol to the gasoline. The main difficulty with this procedure is that the gasoline so treated drops the gums when it is vaporized by a n air jet, indicating that the gums will be deposited in the carburetor even though they may not be evident in tanks or lines. I n addition, the alcohol has no retarding effect on the formation of color; hence a dark red color is developed which may be considered objectionable.
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IRDUSTRIAL A N D ENGINEERING CHEMISTRY Conclusions
The conclusions reached from these preliminary investigations on the refining of active gasolines such as those produced from Colorado oil shale are: (1) that the gum formation may be accelerated by o ~ o n eor other oxidizing agents and the gums separated without greatly decreasing the concentration of desirable stable unsaturates in t h e gasoline; (2) that the oxidation reaction may be very greatly retarded by the addition of phenylhydrazine, thereby stabilizing the gasoline without the removal of the active, gum-forming constituents; and (3) that alcohol might in some instances be added to hold the gums in solution after their formation. By-products of the investigation are: (1) that ozone may
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be used as a qualitative reagent for the detection of those compounds which contain multiple linkages; and (2) that the hastening of the formation of colors and gums by the action of ozone suggests that this material may serve as a reagent for indicating the stability of gasoline in a very rapid manner’ and Literature Cited (1) (21 (3) (4)
(5)
(6)
Brooks, “Non-Benzenoid Hydrocarbons,” p. 137. Brooks, IND.END.CHEM.,18, 1198 (1926). Egloff and Morrell. I b i d . . 18, 354 (19261. Gurwitsch and Moore, “Scientific Principles of Petroleum Technology,” p. 55. Richter, “Organic Chemistry,” Spielman’s translation, pp. 84, 90, and 339. Smith and Cooke, U. S. Bur. Mines, Repfs. of I n v e s f i g a t i o m 8944.
Solubilities of Oils and Waxes in Organic Solvents’” John W. Poole FUELAND GAS ENOINEERING, MASSACHUSETTS INSTITUTE OF TECHNOLOQY, CAMBRIDGE, MASS.
Data concerning the relative solubilities of wax and T HAS been recognized Weber and Dunlap (9), in oil in several organic solvents have been secured for for many years that cert h e i r invest,igations of the the purpose of encouraging the commercial use of tain organic solvents possolubility of paraffin wax in extraction processes for the separation of oils and sess the power of selectively n o r m a l p e n t a n e , normal waxes. The work indicates that of the solvents indissolving either the paraffin hexane, normal heptane, norvestigated-acetone, butanol, acetone- butanol mix, waxes from petroleum lubrim a l o c t a n e , and isodecane, ethyl acetate, butyl acetate, chlorobenzene, and q u i t e conclusively substancants or the lubricants from toluene-butanol offers the best possibilities for soltiated the results of Sullivan, the waxes. It has furthervent extraction, when one considers selective solvent McGill, and French. Their more been recognized that power, temperature of use, volatility, and initial cost. w o r k s h o w s a decided desolvent extraction might be Addition of acetone does not appear to improve the crease in solubility with inused to give better separaqualities of butanol. After butanol, ethyl and butyl crease in molecular weight, tions, and consequently imacetates seem to be the most suitable for commerclal indicating more or less that moved moducts, than does applications. ihe usuil procedure of coldequal mok of solvent dissolve equal quantities of wax, and pressing and sweating (7). Probably the greatest factors in preventing the use of suggests the possibility of separdtion using a close-cut kerosene extraction processes have been high prices of organic solvents or heavy naphtha as a selective solvent. In this connection a and lack of reliable data coricerning relative solubilities of patent issued to Greenspar (2) states that “kerosene is added wax and oil. However, within recent years the cost’of many to effect crystallization at 27-32’ F.” The oil is then separated organic solvents has been greatly reduced and methods of from wax crystals and amorphous wax and kerosene is dissolvent recovery have been improved. The Research Divi- tilled off unti! the residue is a high-grade cylinder stock. sion of Fuel and Gas Engineering has therefore started on a Henderson and Ferris (3) found acetone and nitrobenzene program of securing data having as an object the encourage- to have good selective solvent qualities for oil over wax and ment of ccmmercial installations for the separation of oil on this knowledge developcd a method for the determinaand wax, and the first results of this program are given in tion of paraffin wax in crude wax. A modification of this method, considerably simplified in manipulation, the author this paper. has employed satisfactorily on Mexican products. Previous Work I n a summary of investigations using isopropyl and secondSullivan, McGill, and French (6), in investigating the solu- ary butyl alcohols and acetone and thcir mixtures, Smith (5) bility of paraffin wax in midcontinent oils, came to the fol- reported that the constant-boiling mixture of isopropyl lowing important conclusions. alcohol and water has no advantages over acetone but that the alcohol, dehydrated by solid sodium hydroxide and (1) The solubility of wax in oil increases as the melting anhydrous copper sulfate, was an excellent solvent. Eecondpoint of the wax decreases. ary butyl alcohol was claimed to give good results, as also ( 2 ) .The solubility of paraffin wax in oil decreases with increasing viscosity of the solvent. were certain mixes with acetone. However, the article is (3) Difference of solubility due t o difference in melting of limited value since the data are but vaguely quantitative, point of wax decreases with decreasing temperature. and temperatures other than those close to 32” F. (0” C.) 1 Received August 26, 1929. were not investigated. 9 This paper covers experimental work done under the direction of the Finally, there are several patents which have a definite author by R . K . Opper and A. K. Scott and submitted by them in partial bearing on the problem. Wilson (10) separated paraffin wax fulfilment of the requirements for the degree of bnchelor of science from the Massachusetts Institute of Technology. A smill amount of supplementary from mineral oils by treating a thin composition containing work has been done by the author, while a slightly different arrangement such substances with a miscible liquid comprising isopropyl h i s been made of the data together with somewhat different interpretations. alcohol, which precipitates the bulk of the wax. The orixinal data can be found in the thesis, a copy of which is preserved A British patent (1) states that trichloroethylene or other in the Institute Librnry.
