June, 1923
IKDUSTRIAL A N D EKGIXEERISG CHEMISTRY
In this paper the principal consideration has been the relative results that may be secured with flames produced from different gases, without consideration of how these data may influence the design of appliances. A number of manufacturers are already making use of this information and are making changes in their burners to secure higher effi-
587
ciency, greater flexibility, and increased safety of operation. G~IENT ACKXOWLED
The author wishes to express his appreciation for the advice and suggestions of Walter AI. Berry, gas engineer of the Bureau of Standards.
T h e Examination of Low -Temperature Coal Tars-I’ By Jerome J. Morgan and Roland P. Soule COLUMBIA UNIVERSITY, N E W
YORK,K. Y.
ISTILLATION a t tion to isolate the phenolic The composition of iars produced in the low-temperature carbonicompounds from the alka500” to BOO” C. of zation of coal presents a problem of analysis with which no standard line solution, but the tar a bituminous coal methods2 are designed to deal, and in this paper and a subsequent one acids recovered by simple containing about 35 per a critical review is made of available methods. neutralization with sulfuric cent volatile matter gives The phenols present a special problem, in view of the presence acid have been found in rise to a tar3 of specific of comparatioely large quantities of higher homologs which must be most cases to consist engravity 1.068 a t 15.5”/15.5” removed before phenol and the cresols may be determined. Methods tirely of phenols. ExtracC. Dry distillation of this based on freezing points and specific gravities of mixtures, together tion by benzene or ether tar yields 68 per cent by with Raschig’s nitration method, are satisfactory for determining of the residual acid liquor weight of pitch melting a t the latter, once they are separated. remaining after the separa53” C. in air. The distilThe hydrocarbons may be separated into two groups, one contion of the bulk of the late contains about 43 per taining parafins and naphthenes, and the other aromatic and unphenols thus liberated, percent phenols, 2 per cent saturated compounds, by the use of 98 per cent sulfuric acid. The mits a more nearly quantinitrogen bases, and 55 per selective solvents, dimethyl sulfate, sulfur dioxide, and selenium tative recovery. Distillacent hydrocarbons, threeoxychloride, as well as oleum and nitrating mixtures, gaoe low results. tion of the combined phequarters of which are cyclic, The specific-graoity and aniline-point modifications of the sulfuric nols and extract then reunsaturated compounds. acid method are inapplicable in the presence of unsaturated hydromoves the solvent together Almost two-thirds of the carbons. Physical methods depending on refractive index and spesaturated hydrocarbons are with any water present. cijic gravity were preferred for determining the relative proportions GENERALEXAMINATIOX naphthenes, while the rest of naphthenes and paraflns to solubility in sulfur dioxide, misci-The composition of the are paraffins. Aromatic bility with aniline, and ultimate analysis. A subsequent publicapurified phenol mixture hydrocarbons are only prestion will discuss the unsaiurated hydrocarbons. ent in traces in most lowt h u s obtained depends temperature tars. principally upon the teniSuccessive extractions with 10 per cent sodium hydroxide perature of carbonization of the coal. Higher temperaand 20 per cent sulfuric acid solutions divide the tar distillate tures result in a decrease in the total quantity of phenols and into three parts: (1) the phenols or “ta.r-acids,” ( 2 ) the in the percentage of higher homologs. Thus, while the tar nitrogen bases, and (3) the neutral compounds, chiefly acids from high-temperature tar consist almost entirely of hydrocarbons. The absence in low-temperature tars of solid phenol and the cresols in the ratio of about 1 to 2 by weight, compounds, such as naphthalene, makes these extractions low-temperature tar acids have been found containing only easier than in the case of ordinary tars. Since the phenols 38 per cent3 phenol and cresols, or in some cases7 even less form compounds4 with the nitrogen bases, however, the large than 2 per cent cresols, with little or no phenol. quantity of phenols present in low-temperature t’arsmakes it Fractional distillation of these mixtures of low-temperature necessary to perform the alkali treatment first, becau,qe ex- phenols gives results capable of only a very general interpretraction of the bases of sulfuric acid is very incomplete in the tation. While binary mixtures of phenol and the cresols presence of an excess of phenols.5 have been showns to possess normal boiling-point curves, the resolution by simple distillation, with a Vigreux or other ANALYSIS OF PHENOLS ordinary column, of this complex mixture of isomers and P u ~ r ~ ~ c a ~ ~ o r v -tar T h eacids are ordinarily purified by closely related homologs into its components is exceedingly steam distillation of the alkaline extract’, or by washing it difficult and unsatisfactory. Fractionation is helpful, however, in obtaining relatively with bcnzene or ether to remove dissolved or entrained hydrocarbons or bases. The presence in some lowtemperature simple mixtures for subsequent examination-i. e., in sepatars6 of carboxylic acids requires a carbon dioxide precipita- rating groups of compounds, such as the cresols, from the xylenols. As far as the determination of the relative quan1 Presented before the Section of Gas and Fuel Chemistry a t the 64th tities of these groups is concerned, two or three distillations Meeting of the American Chemical Society, Pittsburgh, Pa., September 4 to 8, 1922. are nearly as accurate as ten or more, since experiment shows * Weiss, TIZIS JOURNAL, 10 (1918), 732, 817, 911, 1006, for an outline that if the cut is made midway between the boiling points of of standard practice in the examination of high-temperature coal tars. two components, the quantity of the higher-boiling compound a Morgan and Soule, Chem. Met. Elag., 26 (1922), 923, 977, 1025; the primary tar of the “Carbocoal” process, cf. Curtis, I b i d . , 23 (1920), 499; appearing in the lower fraction is very nearly balanced by THISJOURNAL, 13 (1921), 23. the amount of lower-boiling compound in the higher fraction. 4 Bramley, J . Chem. SOC. (London), 109 (19161, 10, 434,469, 496. Quantitative methods of analysis have been developed KHatcher and Skirrow, J. A m . Chem. SOC.,39 (1917), 1939; Skirrow
D
and Binmore, I b i d . , 40 (1918), 1431. 8 Marcusson and Picard, Z.angew. Chem., 34 (1921), 201; cf. Tropsch, Byelanstof Chem., 2 (1921), 251, 312.
7 F i s h e r , Brennstoff Chem., 1 (1920). 31, 47; temperature of carbonization 400’ to 500° C. 8 Fox and Barker, J . SOC.Chem. I n d . , 36 (1917). 842; 37 (1918), 268T.
INDUSTRIAL A N D ENGINEERING CHEMISTRY
588
only for phenol and the three cresols. Certain of the xylenols and higher homologs have been qualitatively identified by methods depending upon the formation of crystalline solids, such as phenoxyacetic acids by treatment with chloracetic acid9 and subsequent fractional crystallization. Naphthol derivatives can be detected3 among the higher homologs by the sharp rise in density of the fractions. Since most methods for the quantitative determination of phenol and the cresols are strictly applicable only when the xylenolS are absent except in traces, the elimination of compounds boiling above 202’ C. is an essential preliminary to the examination of low-temperature phenols. This can be accomplished by an exhaustive fractional distillation. If the entire phenol mixture is distilled, the first cutting temperature must be made high enough (about 240’ C.) to ensure inclusion of all the cresols. By using a 10-in. Vigreux column and carrying each successive distillation as nearly to dryness as the capacity of the column permits, the endtemperature of distillation is lowered gradually toward 207” C., which is the cutting point between the cresol and xylenol fractions. The fifteen distillations required in the case of a commercial low-temperature mixture were found sufficient to eliminate the xylenols and higher homologs, and thus to obtain a mixture comprising essentially phenol and the cresols. ESTIMATION OF PHENOL AND THE CRESOLS-NO reliable method of analysis of all four components in a single quaternary mixture has been developed, although several procedures have been describedl0 for the estimation of phenol alone in the presence of the three cresols. These procedures are designed for mixtures in which phenol is present in considerable quantity, however, and no great accuracy can be obtained in the case of low-temperature tar acids, where the phenol is relatively negligible. It is necessary, therefore, to divide the quaternary mixture into two fractions, one composed of a ternary of the three cresols and the other a binary of phenol and o-cresol, or a quaternary containing an increased percentage of phenol. This division may be accomplished either approximately by fractional neutralization of the alkaline solution of the quaternary or more accurately by fractional distillation. I n the former method1*advantage is taken of the fact that phenol itself is the last compound to be precipitated by acid, and is concentrated in the residual alkaline liquor if insufficient acid is used for complete neutralization. This greater acidity of phenol is the basis of the commercial “interchange” processl2 of isolating it from the cresols of ordinary coal tar. The second method, fractional distillation, is complicated by the fact that phenol (b. p., 182.2’ C.) is separated only with difficulty from m- and p-cresols (b. p,, 202.1” to 202.5” C.), which preponderate in low-temperature tar acids. It has been foundl3 advisable to add to the mixture a known amount of pure o-cresol (b. p., 191.8’ C.) in order to obtain upon distillation a binary of phenol and o-cresol alone. Five or six distillations only are then required to reduce to negligibility the amount of m- and p-cresols distilling below 192” C. Of the many methods14 suggested for the analysis of the binary and ternary mixtures thus obtained, those depending upon the determination of physical constants, in particular the freezing points of the pure mixtures, have been found the Lederer, D. R. P. 79,514 (1894);Gluud and Breuer, Ges. Abhandl. Kennlnis Kohle, 2 (1917),236,257; Fischer and Gluud, Ibid., 3 (19181,75. 10 Weiss and Downs, THIS JOURNAL, 9 (1917), 569; Knight, Lincoln, Formanek, and Follett, Ibid., 10 (1918),9. 11 Fischer and Breuer, Ges. Abhandl. Kennlnis Kohle, 3 (1918), 82; Ibid., 2 (1917),236. 11 Huff, Chem. Met. Eng., 26 (1922), 113. 1s Fox and Barker, J . SOC.Chem. Ind., 36 (1917),842. 14 A thorough bibliography of analytical methods for the phenols published prior to 1918 is given by Fox and Barker, Ibid., 37 (1918), 265T. 9
Vol. 15, No. 6
most reliable. Phenol and the cresols are highly associated liquids, and form substitution compounds15 when mixed. Curves showing the resulting sharp depressions in the freezing points of each component in the various binaries of phenol and the cresols have been accurately determined,lO and are made to serve as the basis of analytical methods17 for the determination of phenol and the three cresols. In the ternary mixture of the three cresols, o-cresol can be estimated by a method depending upon the fact that equal weights of mand p-cresol depress the freezing point of the o-compound to nearly the same extent. Similarly, .p-cresol can be determined by an analogous relationship. I n each of these methods, however, some of the component to be estimated must be added to bring the concentration within the range of the tabulated data. This condition involves not only some loss of sensitiveness, but the necessity of preparing pure oand p-cresols, the latter of which is not readily obtained in a pure state. An alternative procedure is given by Fox and Barker,1’ who state that “the specific gravity of a mixture of the three cresols is additive to the fourth decimal place.” Thus, the determination of the specific gravity of the ternary mixture shows the ratio of o-cresol (density 25’/4O C., 1.0415) to mand p-cresols (density 1.0295). Precision in this calculation, however, requires a knowledge of the densities of the pure components accurate to the fourth decimal place, where even the most careful investigators15 have reported slightly divergent values. By the use of the specific-gravity method alone, the percentage of m-cresol is still unknown, but it may be determined by Raschig’s method,l8 which depends on the fact that strong nitration of a mixture of the three cresols yields only trinitro-m-cresol, while the 0- and p-compounds are decomposed to oxalic acid. The original details of this procedure have been slightly modified by Fox and Barker,17 who state that reliable results can be obtained provided sufficientjpqre m-cresol is always added to ensure the presence of a t least 50 per cent in the mixture. The binary of phenol and o-cresol is also capable of ready analysis, since the compositiorl may be determined from either the freezing point or specific gravity (density phenol 1.0710, 25”/4” C.). If a marked discrepancy is found between the values given by these two determinations, the presence in the mixture of m- and p-cresols is indicated. Recourse may then be taken to methods of estimating phenol in the presence of the three cresols. The Raschig tables19 give the freezing points of varying proportions of phenol in a cresol mixture of the composition “ordinarily found in coal tars (50 per cent o-, 25 per cent m-, and 25 per cent p-cresols).” Curves have been compiled20 to show the variation on the solidification point with specific gravity of mixtures of phenol with various ratios of o-cresols to a 50 per cent mixture of m- and p-cresols. More recently, another graphical solidification-point method21 has been devised to allow for variations in the ratio of m- to p-cresol in the mixture. The “solidification points” of these papers are the temperatures of crystallization obtained in the usual manner with a falling, instead of a rising, temperature, as employed in the case of the freezing points of Dawson and Mountford. It must be emphasized, in reviewing these available means Kendall and Beaver, J . A m , Chem. SOL.,43 (1921),1853. Dawson and Mountford, J . Chem Soc. (London), 113 (1918), 923; cf. Fox and Barker, J . SOC.Chem. I n d ,37(1918),268T. 17 Dawson and Mountford, J . Chem. Sac. (London), 113 (19181, 935; Fox and Baker, J . Sac. Chem. I n d . , 36 (1917),842; 37 (1918), 265T; 39 (1920), 169T; Petrie, Ibid., 38 (1919),132T. 18 Raschig, 2. angezu. Chem., 14 (1900),759. 19 Fischer and GrBppel, Ibid., 30 (1917), 76, Ges. Abhandl. Kenntnis Kohle, 2 (1917),178. 90 Weiss and Downs, THIS JOURNAL, 9 (1917),569. 2 1 Knight, Lincoln, Formanek, and Follett, Ibid , 10 (19181,9. 16 18
June, 1923
INDUSTRIAL AND ENGINEERING CHEMISTRY
of analyzing the phenols of low-temperature tars, that no single method can be recommended as the most comprehensive and accurate under all conditions. Reliable results are to be obtained only by performing duplicate determinations by alternate procedures and checking one analysis against the other.
ANALYSISOF NITROGEN BASES After the sulfuric acid extract is steam-distilled or washed with solvents, the purified bases can be recovered by neutralization with alkali. The relative insignificance in quantity of these bases in either high- or low-temperature tars, the large number of individual compounds present, and the great similarity in their properties, have prevented the development of any thoroughgoing analytical procedure. A salient characteristic of the bases of low-temperature tars is the invariable presence of secondary bases, and in some casesz2of primary bases, such as the toluidines. Hinsberg’s benzene sulfonyl chloride method is applicable here in determining the various classes of amines, and in distinguishing them from the high-temperature bases, which are largely tertiary. The use of physical constants, particularly density and molecular weight, in the establishment of the identity of the bases of low-temperature tars, has been described in a previous paper.3 t!LNALYSIS O F ALCOHOLS AYD SULFUR COMPOUNDS-The neutral compounds consist chiefly of the hydrocarbons with a small amount of sulfur compounds. I n some low-temperature alcohols are present, and may be removed by treatment with metallic sodium. The elimination or analysis of the sulfur compounds is a difficult problem. By analogy with the chemistry of the hydrocarbons and bases, it seems probable that the sulfur in low-temperature tars occurs chiefly in compounds representing hydrogenated derivatives of the thiophene series. There is no concentration of sulfuric acid capable of removing such sulfur compounds without simultaneously attacking the unsaturated hydrocarbons which preponderate in the neutral oil. These unsaturated compounds interfere, moreover, with the usual qualitative thiophene identifications by reacting with the sulfuric acid of the indophene test and the nitric acid of the thalline test23 to give reddish brown shades, which mask the characteristic color reactions, even in the presence of added thiophene. The standard methods r e ~ o m m e n d e dfor ~ ~the quantitative determination of thiophene with mercuric sulfate or acetate are also inapplicable even as qualitative tests, since not only the thiophene, but also the unsaturated compounds form insoluble compounds with these reagents. AKALYSIS OF HYDROCARBONS
589
METHODS DEPENDINGON SELECTIVESoLuTIoN-The dimethyl sulfate method of Valenta,26+27 the liquid sulfur dioxide method of E d e l e a n ~ , ~ *and , ~ 9the selenium oxychloride method of Lenher30 have in common the objection that, while the saturated hydrocarbons may be insoluble in the reagent alone, they are decidedly soluble in the binary formed by the reagent and the unsaturated hydrocarbons. Except for isolated and restricted ranges of composition, satisfactory separations cannot be obtained with these reagents. METHODSBASEDON CHEMICAL AcTIox-The formaldehyde method of NastiukovS1has been to be unreliable. The use of nitration mixtures33 is unsuitable in the present case because of their action on naphthenes and even on paraffins. Oleum34 has no advantage over 98 per cent sulfuric acid. Ninety-eight Per cent Sulfuric Acid-Three volumes of 98 per cent sulfuric acid to one volume of the hydrocarbon have been found34capable of sulfonating completely mixtures containing up to 50 per cent aromatics. The most difficult aromatic hydrocarbon to sulfonate is, of course, benzene, which from its low boiling point can be expected only in small quantities in the hydrocarbon mixtures from low-temperature tars. In the present investigation 98 per cent acid has been tested on synthetic mixtures with perfect success. In the case of the higher-boiling aromatic hydrocarbons, acid of even lower strength proved capable of accomplishing complete sulfonation in a single treatment. Two objections may be raised, however, against this method of separation-first, the possible solubility of saturated hydrocarbons in aryl sulfonic acids; second, the possibility of polymerization and consequent incomplete elimination of the unsaturated hydrocarbons by the sulfuric acid. To remedy the effect of solubility of saturated hydrocarbons in aryl sulfonic acids the specific-gravity and aniline-point modifications have been suggested. Specific-Gravity A!fodificati~n-Thole~~states that “9.5 cc. of aromatic-free spirit shaken with 35.7 cc. of sulfuric acid in which 2.4 cc. of toluene had dissolved, lost 2.2 per cent.” applies a correction of 0.60 per cent for solubility in the case of commercial toluenes containing less than 5 per cent of paraffins. To allow for possible solubility such as this, and to avoid errors due to incomplete separation of layers and drainage of acid from the walls of the measuring vessel, Thole has developed a modified method applicable to the estimation of benzene and toluene in petroleum. In this procedure the specific gravity of the oil under examination is determined before and after sulfonation and, from a knowledge of the specific gravity of the aromatic hydrocarbon present, its percentage is calculated. Correction is Chem.-Ztg., 30 (1906),266; AnaZyst, 31 (1906),202 Harrison and Perkin, AnaZyst, 33 (19081,2; Reve and Lewis, I b i d . , 5 (1913),293; Church and Weiss, I b t d . , 6 (1914), 396; Rittman, Twomey, and Egloff, Met. Chem. Eng., 13 (1915),682. Chem.-Ztg., 38 (1914),391; Engler-Hofer, “Das Erdol,” 4 (1916), 23; Bowrey, J . Inst. Petroleum Tech., 8 (1917), 287; Chem. Trade J., 60 (1917),426; Tauss and Stuber, Z . angew. Chem., 321 (1919),175. 29 Rittmann and Moore, Met. Chem. Eng., 13 (1915), 713; Moore, Morrell, and Egloff, Ibid., 18 (1918),396. 8 0 J . A m . Chem. Soc., 43 (1921),29. J. Rum. Phys.-Chem. SOC.,36 (1904), 881; 42 (1910),1596;Petroleum, 28
27
Listed in the order of their chemical activity, the groups of hydrocarbons which occur in low-temperature tars3 are as follows: (1) unsaturated (olefinic and cyclic), ( 2 ) aromatic (liquid),26(3) naphthene (saturated cyclic), and (4) paraffin (liquid and solid). No method, either physical or chemical, is known for isolating any single class of these hydrocarbons from this mixture. Attempts to remove the unsaturated compounds under conditions which would not affect the aromatics were urtsuccessful, but a relatively sharp separation can be made between the mixed aromatic and unsaturated hydrocarbons from the mixed naphthenes and paraffins. All such procedures, however, are subject to limitations, and required careful consideration before successful modifications could bo devised. 21
28 *4 26
Pictet, Ann.-chim., 10 (1918),249. Kreus, Chem.-Ztg., 26 (1902),523. Spielmann and Schotz, J Soc Chem I n d , 38 (1919),188”. Jones and Wheeler, J Chem Soc. (London), 106 (1914), 140.
4 (1909), 1336, 1397. 8 2 Herr, Chem.-Zlg., 34 (19101,893; Petroleum, 4 (1909),1284, 1339, 1397; Severin, Chem.-Ztg., 34 (1910),840; Petroleum, 6 (1911), 197, 2245; Marcusson, Chem.-Ztg., 35 (19111,729; Engler-Hofer, “Das Erdol,” 4 (1916),22; Lessing, “Allen’s Commercial Organic Analysis,” 9 (1917),235. Lessing, Loc. cat., 9 (1917), 232, 234; some representative nitration methods applied t o petroleum and similar mixtures are due to: Zalozieki and Hausmann, Z. angew. Chem., 20 (1907), 1761; Rittman, Twomey, and Egloff, Met. Chem. E m . , 13 (1915), 682; Florentine and Vanderberge, Bull. SOC. chim., 27 (1920), 204; Engler-Hofer, “Das Erdol,” in 1913, 285, Worstall, A m . Chem. J.. 20 (1898), 202. 3 4 Evans, J . S o c Chem I n d , 88 (1919),402T: Thole, I b i d , , 38 (1919).
39T.
500
b
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 1.5, No. 6
made for the slight expansion which occurs on mixing aro- tions discussed above must be abandoned. Hence, when matic and saturated hydrocarbons. sulfuric acid is used in the separation of the aromatic and It is obvious that this method can be applied to low-tem- unsaturated hydrocarbons from the paraffins and naphthenes, perature tar hydrocarbons only if the specific gravity of the it is necessary to allow ample time for the separation of the mixture of unsaturated and aromatic hydrocarbons in the layers to determine experimentally in advance the extent of sample is known. To determine this value experimentally, the solubility of the saturated hydrocarbons in aryl sulfonic a representative sample of this mixture must be recovered acids, and to correct subsequently for the effect of polymerizafrom the acid layer after sulfonation. The hydrolysis of tion of unsaturated hydrocarbons. the aryl sulfonic acids by steam distillation35 suggested itself Solubility of Saturated Hydrocarbons in Aryl Sulfonic Acidsas a possible means of accomplishing this result, and was A number of experiments demonstrated that the solubility of thoroughly tested on many synthetic mixtures and fractions saturated hydrocarbons in aryl sulfonic acids is negligible. of low-temperature tars. It proved a failure for two reasonsThe aromatic hydrocarbons used were C. P. benzene and tolfirst, the aromatics themselves, even in the absence of un- uene. The benzene was freed from any traces of saturated saturated hydrocarbons, were selectively and incompletely hydrocarbons present by freezing and recrystallizing. The hydrolyzed; and second, on account of polymerization only a toluene was purified by steam distillation of washed crystals small part of the unsaturated compounds could be recovered of toluene sulfonic acid. A sample of saturated hydrocarbons from the acid layer. which boiled between 170' and 220' C. was used, and conAriiline-Point Modification-An alternative method of sisted of a mixture of paraffins and naphthenes. correcting for the possible solubility of saturated hydrocarThe aromatic and saturated hydrocarbons were introduced bons in aryl sulfonic acids has recently been ~uggested.~B successively from a 10-cc. weighing pipet into a ~ ~ O - C C . , This procedure, which does not require in advance a knowl- glass-stoppered separatory funnel containing 75 cc. of 98 edge of the specific aromatics present, depends upon a deter- per cent sulfuric acid. The funnel was shaken mechanimination of the "aniline point" of the sample before and after cally for l/z hr. and the layers allowed a minimum of 15 hrs. treatment with 98 per cent sulfuric acid. The aniline point for complete separation. The bulk of the sulfuric acid, which is the temperature a t which two liquid layers are formed remained water-white, was then separated, and 2 to 3 hrs. upon cooling a solution of equal volumes of the sample and allowed for drainage of oil from the walls of the funnel. It aniline. All ordinary aromatic hydrocarbons lower the ani- was found impossible, however, to transfer the hydrocarbon line point of any saturated hydrocarbon by very nearly the residue from the separatory funnel into a weighing pipet same amount, and hence the percentage of aromatics can be without loss. For this reason the residual oils were washed read directly from the curve showing the relative depressions from the funnel into the buret with more acid, and the of the aniline point. volume WRS read after complete separation of layers had been The difficulty in this connection is the effect of the presence obtained again. From a knowledge of the density of the of unsaturated hydrocarbons, concerning which no informa- oil at the temperature in question, the weight of saturated kion has been advanced by the authors of the method. Ac- hydrocarbons surviving the sulfonation could be readily cordingly, the following brief investigation was made to de- calculated. Trial runs showed that the aniline points of the termine the extent of this effect and the possibilities of cor- saturated and residual oils were the same, indicating complete recting for it. Using toluene and a saturated naphthenic removal of the aromatics in a single treatment. The results fraction of boiling point 160" to 265" C., it was found pos- of these solubility experiments are recorded in Table 11. sible to check very closely the depressions of the aniline point reported by Tizard and RIarshall. The toluene was then TABLE11-SOLUBILITY OF SATURATED HYDROCARBONS I N ARYL SULFONIC ACIDS replaced by various unsaturated hydrocarbons, the effects of Saturated Weight Difference which are shown in Table I. Weight Hydrocarbons Weight Residue %.by TABLE I-DEPRESSIOK O F ANILINE P O I N T
BY
UKSATURATED
HYDROCARBOKS Unsaturated MolecB. p. of DEPRESSIONANHydroular Sample yo in ILINE POINT Ratio O C. Mixture Observed Aromatic % ' carbon Formula Weight 38.0 31.1 36.4 85.4 50 t o 60 70 CjHio Amylene 18.0 24.4 73.8 26.5 1 3 0 t o 170 112 Caprylene C8%5 17.8 33.8 52.6 150 t o 160 3 5 , 7 136 Pinene C10H15 16.2 5.6 34.5 36.3 260 t o 270 224 CinHn Cetene
The samples of unsaturated hydrocarbons available were not pure, as indicated by their boiling-point ranges, but their effect is obvious. Thus, amylene lowered the aniline point 85 per cent and cetene 16 per cent as much as the same percentage of toluene in each case. The depression of the aniline point by unsaturated hydrocarbons, therefore, is a function of the molecular weight of the particular hydrocarbon, and for the same number of double bonds in each case, approximates that of the aromatics, on the one hand, to that of the saturated hydrocarbons, on the other, as the molecular weight increases. It is evident, therefore, that the use of the aniline-point modification in the present case is not practicable. Since the unsaturated hydrocarbons cannot be eliminated from the mixture under examination, both of the modifica85 Armstrong and Miller, J . Chem. Soc. (London), 45 (1884), 148; Kelbe, B e ? , 19 (18S6), 92 88 Tizard and Marshall, J Soc Chem. Znd , 40 (1921), 20T.
AROMATICSample Benzene 18,417 Benzene 16.816 Benzene 17,248 Benzene 18 052 ~. Toluene 14 448 Toluene 9.900 Toluene 16,795 Toluene 18.727 ~~
yo
5.23 46.50 49,02
72.61 5.82 10.18 47.68 68.06
Residue 1.01 7.79 8.41 13,. 07 0.89 1,59 8.05 12.70
%
5.5 46.3 48.8 72.4 6.2 16.1 47.9 67.8
Weight +0.3 -0.2 -0.2 -0.2 +0.4 -0.1 $0.2
+0.3
These results fail to show the functional variation of the weight differences with the percentage of saturated hydrocarbons which would be expected from a solubility relationship. The total of the positive is about the same as that of the negative corrections, indicating that the differences represent chiefly the errors inherent in the method. The consistent correction of 0.60 per cent mentioned by Evans,S4 who used mercury to displace the reaction mixture after sulfonation upwards into a buret, is probably explained by the constant loss of the hydrocarbons which cling persistently to the walls of the reaction vessel. Correction for Eflect of Polymerization of Unsaturated Hydrocarbons-Under the action of sulfuric acidp olymerization of Unsaturated hydrocarbons takes place3' with the formation of a small quantity of high-boiling oils that dissolve in the neutral residue remaining after the treatment. Subsequent distillation cannot remove them completely, but permits of a semi-empiric correction that is fairly accurate. 37
Brooks and Humphrey, J . A m Chem. Soc., 40 (1918),822.
June, '1923
INDUSTRIAL A N D ENGINEERING CHEMISTRY
A distillation curve with temperatures plotted as ordinates is obtained of the neutral oil mixture before sulfonation. The assumption is made that the average boiling point of the saturated hydrocarbons in this mixture is given by the mean ordinate of this curve. A second distillation curve of the residual oils after sulfonation is next obtained; this lies above the first, and its final temperature is considerably higher because of the presence of polymers from the unsaturated hydrocarbons. A point on this curve is then found such that the mean ordinate of the curve up to that point is the same as the average boiling point of the total saturated liydrorarbons determined from the first curve. Finally, the weight of oil distilling before the temperature is reached is taken as the corrected weight of residual paraffins and naphthenes. Thus, the percentage of paraffin plus naphthene hydrocarbons can be determined by treating the total hydrocarbon mixture with three volumes of 98 per cent sulfuric acid, and redistilling the residual saturated hydrocarbons as just described to correct for the presence of dissolved polymers of unsaturated hydrocarbons. Separation of ANALYSISOF SATURATED HYDROCARBONS. Naphthenes from Parafins-No method of accomplishing a quantitative resolution of the saturated hydrocarbons of low-temperature tar has been found. The destruction of the naphthenes with fuming nitric acid38 or with dilute nitric acid in a closed tube39 has been recommended, but general experience points to the conclusions40 that no method based on nitration can completely eliminate naphthenes without attacking paraffins. It has been stated4I recently that mixtures containing less than 25 per cent naphthenes can be separated by extraction with an excess of liquid sulfur dioxide. The experimental work supporting this statement, however, was performed exclusively with naphthenes boiling under 200" C. Experience in the present investigation has demonstrated, on the other hand, i hat this solubility falls off very rapidly as the boiling points of the naphthenes under examination rise above this temperature. A very approximate separation of paraffin hydrocarbons can be obtained by strongly cooling a dilutc acetone solution of the hydrocarbons with liquid air.42 Estimation of Naphthenes i n Presence of Parafins-A convenient method of analyzing the naphthene-paraffin mixtures of gasoline hydrocarbons has recently been announced. 4 3 This procedure depends upon the determination of the critical temperature of solution TCD of the hydrocarbon mixture in aniline. The application of this procedure to oils of high boiling point is incorrect, however, since the TCD relations of low-boiling hydrocarbons no longer hold. A s naphthenes add aliphatic side chains and become more paraffinoid in character, their miscibility with aniline changes accordingly. The TCD's of both groups of hydrocarbons increasc: with gain in molecular weight. Thus, the aniline points (approximations of TCD's) of hydrocarbons which were known from their physical constants to be largely naphthenic were found in the present investigation to be as follows: 170" to 220" C., 73.8; 230" to 270", 83.2; and above 330" (density 2 O o / 4 O C., 0.880), 103.8. Ultimate analysis does not provide a sensitive methqd of establishing the proportions of naphthenes to paraffins in high-boiling hydrocarbons, since the differences a r e not suffiHeusler, Ber , 30 (1898), 2743. Konowaloff, I b z d , 26 (1893), Ref. 878; 28 (1895), 1863. 40 Engler-Hofer, "Das Erdol," 1 (1913), 282. 4 1 LMoore, Morrell, and Egloff, M e t Chem Eng , 13 (1918), 396 4 2 Fischer and Gluud, Ges. Abhandl. K e n n f n i s Kohle, 2 (1917), 295, 58
3 (1918), 39 43
Cbavanne and Simon, Compt. v e n d , 168 (191Y), 1111: 169 (1919),
70 185
591
ciently greater than the possible experimental error to afford a basis for estimating the proportions of the component groups. An examination of certain of the physical constants of the naphthene-paraffin mixture suggests itself as a possible means of determining the approximate ratio of the component classes. The rerationship between boiling points and molecular weights, however, was found to have little value for this purpose. Better success can be obtained with the indices of refraction and specific gravities. The curve of indices of refraction vs. boiling point of the mixed, saturated hydrocarbons lies well above that of the normal paraffins, and thus shows a large percentage of naphthenes in most low-temperature coal tars. Unfortunately, however, the lack in the literature of reliable and concordant data on the indices of refraction of naphthenes boiling above 150' C. prevents any quantitative interpretation of these curves. On the other hand, the graphical relation between the densities and boiling points offers a method of approximating the proportions of paraffins and naphthenes. The naphthene densities may be plotted from those reported4*for hydrocarbons of the formula C,H,, isolated from crude petroleums. The position of the curve for the saturated hydrocarbons of low-temperature tar between the naphthene and paraffin curves can then be used as a basis of estimating the proportion of these groups of hydrocarbons in the various fractions. S o great accuracy can be claimed for such an approximation, for although the densities of the naphthenes are less erratic than their indices of refraction, they vary slightly according to the origin of the hydrocarbon. If representative values are selected, however, it is believed that a fair picture of the composition of the saturated low-temperature hydrocarbons may thus be obtained. 44
Mabery, PYOC. A m . Acad. Arts Sci., 32 (18971, 119, 36 (19011, 258, Engler-Hofer, "Das Erdol," 1
295; 37 (1902), 565, 40 (1904), 323, 334; (1913), 316.
E. P. Hyde Resigns E. P. Hyde, who since 1908 has been continuously in the
employ of the National Lamp Works of t h e General Electric Company, Nela Park, Cleveland, Ohio, has resigned in order t o take a much-needed rest abroad. Dr Hyde joined the staff of the Bureau of Standards shortly after its inception in 1902, and organized the photometric section, which has 4nce become one of the most important sections of t h a t bureau H e has taken a n active interest in the development of illuminating engineering in this country and abroad, and has had much t o do with the successful establishment of the Illuminating Engineerinq Society, of which he was president in 1910 H e organized the very successful course in illuminating engineering at Johns Hopkins University, which did much t o bring about a more definite understanding on t h e part of the commercial as well as the technical and scientific world of the scope and possibilities of this branch of engineering. H e extended his activities along these lines t o foreign fields, when he succeeded in having the old Photometric Commission, which was confined mostly t o gas photometry, reorganized into t h e present International Commission on Illumination, of which he was elected president in 1921. While a t the Bureau of Standards he initiated and carried t o t h e final steps the establishment of the international unit of light, t h e international candle, which eliminated the differences in t h e units used by t h e gas and electrical interests in this country and which is at present the accepted unit of light in the United States, England, and France. I n 1908 he accepted a call t o organize t h e Laboratory of Pure Science for the National Lamp Works of the General Electric Company, at t h a t time the National Electric Lamp Association. This was t h e first laboratory of its kind started by a n industrial concern, and it aroused a great deal of interest in the scientific world. I n 1920, having developed the laboratory t o a point where it had expanded into two departments, one of pure science and one of applied science, Dr. Hyde was made director of research of the National Lamp Works, and it is this position which he has recently resigned. D r Hyde is a member of the Engineering and Foreign Relations Division of the National Research Council, as well as a trustee for the publication of International Critical Tables sponsored by the council.
