March 1949 TABLEVI. Anhydrous Builder Naa0.3.9SiOz Naz0.2.4SiOz Naz0.2.0SiOz NaeSiOa NaOH NazCOa NazBLh NaaPzO7(NaPOsh (adj.) None
INDUSTRIAL AND ENGINEERING CHEMISTRY CONPARISON OF KETTLESOAPCONTENT AT MINIMUM SUDSWITH THATCALCULATED FROM OTHERDATA 0.05 G./100 311. Found, Calod., Diff., g.
g.
8.
0.205 0.152 0.176 0.163 0.139 0.138 0.236 0.159 0.144 0.241
0.201 0.175 0.175 0.166 0.144
-0.004 10.023 -0,001 +0.003 10.005 +0.018 -0.020 +0.008 +0.004
0.166
0.216 0.167 0.148 0.166
-0.055
0.10 G./100 M1. Found, Calcd., Diff., g.
B.
0.166 0.176 0.144 0.149 0.151 0.148 0.153 0.171 0.138 0.130 0.126 0.122 0.235 0.214 0.148 0.151 0.109 0.115 ,
..
,,
.
0.20 G./100 MI. Found, Cttlcd., Diff.
g.
B.
g.
g.
fO.010
0.146 0.134 0.139 0.141 0.136 0.105 0.235 0.129 .0.064
0.160 0,134 0.126 0.147
f0.014
f0.005
-0.003 f0.018
-0.008 -0.004 -0.021 +0.003 f0.006
...
...
0.126
0,112 0.214 0.127 0.053
...
-0:Oi3 10.006 -0,010 +0.007 -0.022 -0.002 -0.011
...
581
Both silicates and phosphates may be employed t o prevent the formation of hard lime-soap curds. The adverse effect of caustic soda and soda ash was not as evident with soaps of lower molecular weight. The dispersion by 2.0and 2.4-silicon dioxide t o sodium oxide weight ratio silicates is notable. The results indicate t h a t a rigorous study of the additive effect of individual constituent soaps on minimum suds formation in hard water should be made. ACKNOWLEDGMENT
about 10% but is the only one showing such a n error in the same direction. The error of nearly 25% when no builder is present is probably caused by the lower fatty acids a t the p H of hydrolysis of the more alkaline soaps. Since the differences are generally less than 10% in spite of the numerous approximations and extrapolations required, there seems good reason to believe t h a t the effect of the individual soaps on the minimum required for formation of a permanent suds is additive under conditions of like pH. The problem deserves a more precise study. CONCLUSIONS
The following conclusions may be drawn from combining the prior work of Bolton (a) with the present work.
All the alkalies except borax decreased the amount of soaps re quired to form permanent suds in hard water when the carbon chain was greater than C = 14. Some silicate8 showed t o peculiar advantage with the high molecular weight soaps, while only the polyphosphates gave any reduction with low molecular weights. The silicates usually increased in value with decreasing silicon dioxide t o sodium oxide ratio. I n some cases the intermediate ratios 2.0 and 2.4 were more effective than 1.6.
Thanks are due to C. L. Baker who directed the project and other colleagues who have contributed from their experience. LITERATURE CITED
Am. Pub. Health Assoc., “Standard Methods of Water Analysis,” 8th ed., p. 61, 1936. Bolton, H. L., IND.ENO.CHEM.,34,737 (1942). Cobbs, W. H., Harris, J. C., and Eck, J. It., Oil & Soap, 17, 4 (1940).
Fuchs, J. N. von, Diliglers Polytech. J . , 17, 465 (1825); 142 305 (1850).
Gilmore, B. H., Oil & Soap, 12, 29-32 (1935). Kuent~el,L. E., Hensley, J. W., and Bacon, L. R., IN^. EKO. CHEM.,35, 1286 (1943). Miles, G. D., and Ross, J., J. Phys. Chem., 48, 280 (1944). Philadelphia Quartz Co., “Beginning Another Century,” 1931. Ruff, E. E.,Oil & Soap, 22, 125 (1945). Vail, J. G.,“Soluble Silicates in Industry,” A.C.S. Monograph 46,p. 12, New York, Reinhold Publishing Corp., 1928. Wegst, W. F., and Wills, J. H., U. 5. Patent 2,179,806(Nov. 14, 1939. RECEIVED April 16, 1946. Presented before the Division of Industrial and Engineering Chemistry a t the 109th Meeting of the AMERICAN CHEMICAL SOCIETY,Atlantic City, N. J.
Composition of Colorado
Shale-Oil Naphtha JOHN S. BALL, G. U. DINNEEN, J..R. SMITH, C. W. BAILEY, AND ROBIN VAN METER United States Bureau of Mines, Laramie, Wyo. Naphthas distilled from crude shale oils produced by several methods of retorting Colorado oil shale were analyzed and found to be remarkably similar. Consequently, only one was selected for a detailed composition study. The results indicate that the approximate composition of raw shale-oil naphtha is: paraffins and naphthenes 30%; olefins 40%; aromatics 20%0; sulfur, nitrogen, and oxygen compounds 10%. Paraffins and aliphatic olefins, which comprise about two thirds of their respective groups, are predominantly straight-chain compounds. The sulfur, nitrogen, and oxygen are present principally in the form of thiophenes, pyridines, and phenols, respectively.
I L shale, as it occurs in nature, consists of solid organic material interspersed in a shale formation. This organic matter can be converted by means of heat to lower molecular weight liquid products. Various retorting processes are used for this conversion of organic material to shale oil. The Bureau
of &fines, as,part of the Synthetic Liquid Fuels Program (6),has established a n Oil-Shale Research and Development Laboratory at Laramie, Wyo., to study retorting and refining processes. One phase of this study is a n investigation of the composition of ahale oil. The present paper reports results on material in the naphtha boiling range. A comparison was made of the composition of naphthas from different shale oils, and a n extensive investigation was made on one of them. This study involved separation of the raw naphtha into neutral naphtha, t a r acids, and t a r bases. A sample of the neutral naphtha was distilled in an efficient fractionating oolumn and a quantitative determination was made of the paraffins, naphthenes, aliphatic olefins, cyclic olefins, aromatics, sulfur compounds, and nitrogen compounds present in each fraction. A similar distillation was performed on a sample of neutral naphtha in which the olefins had been hydrogenated. A sample of the t a r acids was distilled under reduced pressure in a semimicro fractionating column and ultraviolet absorption spectrograms were obtained on the fractions. A sample of the tar bases was
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
582
Vol. 41, No. 3
Pumpherston Crude Shale Oil
naphthenes, olefins, and aromatics, In addition] shale-oil naphDistillation thas contain considerable I amounts of sulfur, nitrogen, and oxygen compounds. DiffiNaphitha Residue culty was experienced in analyzT r e a t i e n t with 20% S a O H ing shale-oil naphthas by usual methods of analysis for hydroRaffinate T a r doids carbon groups, especially those Distillation methods depending on bromine number for the estimation of 29 Fr'aotions TrAatment with 20% H2SO4 Refractive index I olefins. Accordingly, a method Ultraviolet absorption ( 9 ) for hydrocarbon analysis deI I pending on silica gel adsorption Neuiral naphtha Tar bases I was developed. Distillation Naphthas were prepared from 74 F h i o n s Hydrogknation DiAtillation each of the oils listed in Table I ; Refractive index Ultraviolet absorption Silica gel beparation values for the properties determined on them are shown in I I Table 11. Each of the naphthas 106 Fractions Residue Pajkffins & naphthenes Aromatics was light yellow on distillation Boiling point at 760 mni. Silica gel analysis 1 Distillkt ion Refractive index Sulfur content Distillation but within a few days turned Nitrogen content Density a t 20° C. black after successively passSilica gel analysis 124 Fractions 42 Frdotions Boiling point at 760 mm. Boiling point a t 760 mm. Sulfur content ing through amber, purple, and hTitrogen content Refractive indcxes, (nso, Refractive indexes, (nkoO, nz,) brown stages. Sulfur contents Ultraviolet absorption .n2-0 Densitv a t 20' C. "cr' Ultraviolet absorption Density a t 20' C. were determined by the bomb method, and nitrogan by the Figure 1, Schematic Kepresentation of Work Done on Naphtha from Kjeldahl procedure. Tar acids Pumpherston Shale Oil were extracted by 20v0 sodium hvdroxidr solution, and tar bases by 20% sulfuric acid. The neutral naphthas, after removal of treated in the same manner. The composition of the naphtha tar acids and tar bases, mere analyzed for hydrocarbon groups then was deternlined from the various data obtained in these by the silica gel adsorption method. studies. The four naphthas show remarkable similarity in hydrocarbon content. The analyses of the old and new Xevada-Texas-Utah COJIPARISOK O F SHALE-OIL NAPHTHAS naphthas check within experimental error, and the differences from these values shown by the Parry and Pumpherston naphthas Naphthas were obtained from shale oils produced in three are not great. The selection of a naphtha for more extensive types of retorts. During the period 1925-29 the bureau built study therefore was based on other considerations. The Pumand operated retorts of the Pumpherston and Sevada-Texas-Utah pherston naphtha was selected because the volume oi naphtha in (N-T-U) types ( 3 ) . Oils were available from these operations as Pumpherston shale oil is greater than that in any of the other well as from the current production of the Nevada-Texas-Utah three oils, and its boiling range is similar to that of the Xevadaretorts constructed a t Rifle, Colo., under the Synthetic Liquid Texas-Utah naphtha. Also the Pumpherston retort has been Fuels Program, I n addition, oil was available from distillation and is being widely used comrncrcially in foreign countries for of shale in a Parry retort similar t o that described in January retorting shale, while the Parry retort has seen only experimental 1945 ( 7 ) . The properties of these oils are given in Table I. use on oil shale and conditions of operation were not standardized. The nitrogen and sulfur contents are similar, but distillation analyses indicate considerable differences among oils. While the ANALYSIS O F PUMPHEKSTON NAPHTIIA Pumpherston and Parry oils contain similar amounts of naphtha, they differ considerably as regards the residual fraction. The An outline of the work done in analyzing Pumpherston naphtha two Nevada-Texas-Utah oils are similar even though one of them is shown in Figure 1. The naphtha was obtained from the crude has been in storage for approximately 20 years while the other naphtha, shale oil and separated into three fractions-neutral was produced during the past year. tar acids, and tar bases. Naphthas produced by distillation from shale oil resemble cracked gasolines from petroleum in t h a t they contain paraffins,
I
TABLE 11.
COMPARISON O F
TABLE I. COMPARISON OF CRUDESHALE OILS Year produced
A.P.I. gravity
Specific gravity, 60/60° F. Sulfur, weight Yo Xitrogen, weight Yo Distillation volume % N a n h t h a ' i u ~ t o ZOOo C. a t
~-~-.-, 'y distillate (200' to 300' L. a t 40 mm.) Residuum
Pumpherston 1929 25.7 0,900 0.77 1.57
NAPHTHASFROM
Pumpherston 0,805
Parry 1945 20.3 0.932 0.87 1.81
N-T-U 1929 20.3 0.932 0.77 1.98
S-T-l: 1'347 18.6 0.943 0.74 1.78
17.6
14.9
3.6
2.6
29.4
16.6
19.8
15.3
40.0 12.7
27.6 39.9
25.6 49.8
30.9 44.7
,ted
0.84 0.51 27.6 304 348 429 0.8 5.6
Analysis of neutral nauhtha, volume % Paraffins and naphthenes Olefins Aromatics and compounds of sulfur and nitrogcn
Parry 0.705 0.89 0.51 25.5 249 341 437 1.2 4.8
SHALE OILS
N-T-U (Old) 0.816 1.07 0.81 30.0 307 346 412 2.5 6.5
X-T-U (New)
0.833 1.03 0.93 33.0 304 353 421 3.0 7.8
32 43
27 48
33 46
33 48
25
25
21
19
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
March i949
583
PREPARATION OF SAMPLES
Naphtha. A total of 69.3 liters of crude shale oil was distilled batchwise, using a 12-liter flask equipped with a Claissen head and heated by a Glascol heating mantle. The material was distilled under nitrogen at atmospheric pressure (585 mm. mercury) until water ceased to come over. The average final temperature of the vapor was 135" C. Approximately 118 ml. of naphtha and 22 ml. of water were obtained from each 7-liter charge. The distillation then was continued at a n absolute pressure of 8 to 10 mm. of mercury, using a steady, small stream of nitrogen to prevent bumping. An average of 1245 ml. of product was removed from each 7-liter charge during the vacuum distillation. The end temperatures averaged 90" C. The naphtha was separated from the water and stored in brown bottles at 0" C. over anhydrous sodium sulfate under an atmosphere of nitrogen. These precautions were taken to retard the reactions that produce colored and gummy materials. A total of 13.7 liters of dry naphtha was obtained. The properties of this naphtha are given in Table 11. Tar Acids. The naphtha was saturated with nitrogen and was extracted with three successive portions of aqueous 20% sodium hydroxide solution, also saturated with nitrogen. The caustic extract was in turn extracted with ether t o remove occluded oil. The ether was distilled off and the residue returned to the naphtha raffinate. The aqueous caustic extract was acidified by the cautious addition of dilute sulfuric acid. The properties of the 83.4 grams of crude t a r acids obtained are shown in Table 111. Tar Bases. The naphtha raffinate was then extracted with three successive portions of aqueous 20% sulfllric acid saturated with nitrogen. The acid extract was in turn extracted with ether to remove occluded oil. After evaporating off the ether, a
TABLE 111. PROPERTIES OF TARACIDSAND TARBASESFROM PWMPHDRSTON NAPHTHA Density at Z O O C. Refractive index (n'g0) Sulfur weight % Nitrolen. weight % '
Tar Acids 0.9705 1,4887 0.18 0.08
Tar Bases 0,9445 1,5007 0.20 5.06
semisolid sludge remained, so no oil was available from this source for return t o the raffinate. The aqueous acidic extract was made basic with sodium hydroxide. The properties of the 610 grams of the crude tar bases obtained are shown in Table 111. DISTILhATION ANALYSIS OF NEUTRAL NAPHTHA
Four liters of neutral naphtha were charged t o a distilling column having an efficiency of 95 theoretical plates at total reflux. Samples containing 20 m]. each were obtained. The following properties were determined on each of the 105 fractions; boiling point at 760 mm. of mercury pressure; density at 20' C.; refractive indexes for the sodium D and mercury g lines at 20' C.; sulfur content; nitrogen content; silica gel hydrocarbon analysis; and an ultraviolet absorption spectrogram. The residue was analyzed for hydrocarbon content by the silica gel method and for sulfur and nitrogen contents. CALCULATIONS
The silica gel analyses of the 105 fractions and the residue are shown in Figure 2. In this figure the combined value for aro-
VOLUME PERCENT OF NAPHTHA
t q o yoqo '0'
Ib
Ib
qOBpm0 lb lb $5
+ !w
ey3 Ib
3y 145
310 150
165
320
330
160
165
340 170
BOILING POINT
Figure 2. .4mounts of j'arious Classes of Compounds in Each Fraction from the Distillation of Neutral Pumpherston Naphtha
,is RESIDUE FROM DlSTlWTlDN
INDUSTRIAL AND ENGINEERING CHEMISTRY
584
Vol. 41, No. 3
The volume sum (per cent), based on the neutral naphtha, of parafhs thus calculated was plotted against the boiling point (' F.) for each fraction. The volume sum (per cent) of a fraction includes the volume of that fraction and all preceding fractions. A smooth curve was drawn through the points to cnable the determination of the percentage volume of paraffins boiling in any particular degree of the boiling range. This information was utilized in plotting Figure 3. Similar calculations were made with regard to naphthenes and aromatics. The olefins were divided into straight-chain and cyclic olefins in a manner similar to that used to distinguish between paraffins and naphthenes, and the data were used to obtain the volume curveq (per cent per degree) shown in Figure 3.
BO
O ' t
INTERPRETATIONS
;05
=
P
ALlPHeTlC OLEFINS
E goo
UAPHTHENES
I
.
EOlLlNO POINT
** Amounts of Various Classes of Hydrocarbons in Neutral Pumpherston Naphtha !MI
Figure 3.
matic, nitrogen, and sulfur compounds as found by the silica gel method of analysis has been subdivided, From the nitrogen content and an estimated molecular weight based on boiling point, the nitrogen-compound content for each fraction was calculated. The sulfur-compound content was similarly calculated for each fraction. Parafins and naphthenes, which are reported together in the silica gel analysis, also have been divided. To do this, literature values for the refractive indexes of paraffins and naphthenes were plotted against their respective boiling points. An average line was drawn through the paiaffin points and another through the naphthene points, The refractive index of the paraffin-naphthenc plateau may be obtained from the silica gel adsorptogram of any fraction and compared with the average refractive indexes of paraffins and naphthenes having the same boiling point in order to estimate the amounts of paraffins and naphthenes in that particular fraction.
Parafhic and Naphthenic Compounds. Inspection of the curves in Figure 3 reveals definite segregation of certain compounds and groups of compounds. For ready reference, a number of hydrocarbons likely to be in shale oil are shown a t their Loiling points. For example, the large peak extending from 145' to 152" C. is obviously due to n-nonane. From the percentage volume lying under this part of the curve the amount of nnonane present in the naphtha can be estimated. Calculation of the amounts of the various hydrocarbons present in 'the naphtha gives the results shown in Table IF'. Only 30% of thc paraffins in the distillate have branched chains. Although the naphthenes could not be resolved into coinpounds by this method except in a few instances, values have bcen calculated for groups of compounds and are shown in T a b h V. The total amount of naphthenes is considerably less than hall the amount of paraffins. Aromatic Compounds. An ultraviolet absorption spectrogram was obtained for each of the 105 fractions from the distiliation. Using these data qualitatively, the compounds represented by the peaks in Figure 3 \\ere identified. The amounts of compounds or groups of compounds in the naphtha then were calculated, and the results are given in Table VI. The propylbenzenes and the butylbenzenes were not found. Of the xylenes, m-xylene is predominant, as in petroleum. The total aromatic content of 19,4y0 is lower than the value of 25% in Table II, within expcrimental error, by the amount of sulfur and nitrogen conipouiidb present in the naphtha.
TABLE v.
I\TAPHTHENES I?; NEUTRAL PUhfPHERRTON i\r.4PHTH.4 Volume yo 0.03 Ce-Naphthenes 0.03 IvIethylcyolohexane 0.04 Ethylcyrlopentane 1,2,4-Triinethyloyclopentsne 0.1 0.7 Other Ce-naphthenes 2.1 Cp-Nanhthenes 1.6 Cie-Naphthenes 4.2 Residue 8.80
TABLE
VI. AROMATICSI N
NEUTRAL PUMPHERSTON NAPHTIIA
Tolume % Benzene Toluene Ethylbenzene p-Xylene m-Xylene o-Xylene 1-Methyl-3-ethylbenzene l-i\.lethgl-4-ethylbanzene l-~~eth3,!-2-ethylbenl,ene 1,3,5-Trimethylbensene 1,2,4-Trimnthylbeneene 1-Methyl-2-isopropylbenzene 1-Methyl-3-isopropylbenzene l-i\lethyl-4-isopropylben.enea Residue
TABLBIV. PARAFFINS IN XEUTRAL PUMPHERSTON NAPHTHA n-Hexane Methylhexanes %-Heptane Dimethylhexanes Methylheptanes n-Oatme Dimethylheptanes Methyloctanes n-Nonane CLi-Hexanes,heptanes, and octanes Methylnonanes n-Decane
Residue
Volume yo 0.1 0.2 0.2 0.3 0.2
}
1.6 0.6
0.5 3.4 1.7 0.5
4.1
9.3
22.7
0.2 1.1 0.3 0.7 1.6 0.9 0.8 0.4 0.9
1. .5 1.8 9.2 19.4
a
M o s t probable compound based on ultraviolet absorption curves.
March 1949
Oleflnic Compounds. The estimation of the aliphatic olefins was carried out by the same method used for the paraffinic compounds. The results are given in Table VII. The normal compounds predominate over branched-chain compounds even more strongly in the aliphatic olefins than in the paraffins. The straight-chain compounds comprise approximat,ely 80% of the aliphat,ic olefins present in the distillate.
-OD
05
Y
Y
D TABLE VII. COMPARISON OF OLEFINSOBTAINED FROM ORIGINAL DISTILLATION AND CALCULATED FROM HYDROGENATED NAPHTHA Volume of Neutral Naphtha, % From distillation of From distillation of neutral naphtha hydrogenated sample 0.7 0.8 2.6 2.4 1.1 1.0 4.2 3.1
n-Hept,enes n-Octenes Branched nonenes n-Nonenes Branched decenes n-Decenes
585
INDUSTRIAL AND ENGINEERING CHEMISTRY
1 .B
4.3
14 7
13 . O 27.7
Residue
2.2
4.8 14.3 ~- .
IJ
K ID
B
8 4
B
' 00 F I
C BOILING POINT
Figure 4. Amounts of Various Classes of Hydrocarbons in Hydrogenated Pum'pherstonNaphtha
pounds can be estimated in a manner similar to t h a t used on the unhydrogenated naphtha. These amounts include saturated compounds from two sources. The amount of n-nonane, for example, includes that present in the original naphtha and that formed by hydrogenation of n-nonenes. The difference between the amounts of n-nonane before and after hydrogenation represents the amount of n-nonenes in the neutral naphtha. A similar calculation has been made for each group of the aliphatir TABLE VIII. COMPARISON OF CYCLIC O L E F I N S O B T A I N E D FROM olefins; the data are given in Table VII. An excellent check is A N D CALCULATED FROM HYDROGENATEDobtained from the totals of the two calculations of aliphatic O R I G I N A L DISTILLATION NAPHTHA olefins. Some discrepancies are noted in comparing results by Volume of Neutral Naphtha, % the two methods of calculation. These may be caused by overFrom distillation of From distillation of neutral naphtha hydrogenated sample lapping of the boiling ranges of the various groups of olefins. Cyclic olefins 0.1 0.1 Similar calculations concerning the cyclic olefins are much less CS 0.5 0.8 c 7 satisfactory, and the total amount from hydrogenation is some1.4 2.3 CS 3.2 4.8 CO what larger than t h a t from the original naphtha, in part owing t o 2.6 ' 2.9 CIO __ --some hydrogenation of the aromatics in the naphtha, as the 7.8 10.9 8.3 Residue aromatic content was lowered from 19 to 15%. 16.1 Sulfur Compounds. The neutral naphtha was analyzed for sulfur groups by a modification of methods ( I , 5 ) developed by the Bureau of Mines. Thiols from reduction of disulfides were The conversion of the olefins to the corresponding paraffins or determined by difference in sulfur contents before and after naphthenes by hydrogenation offers a possibility of confirming the extraction with alcoholic potassium hydroxide. No determinacharacter of the olefins in the naphtha. Inasmuch as paraffins tion of thiophenic sulfur was made. Results in Table IX. and naphthenes can be identified more readily, information can be obtained regarding the original carbon structure of the molecule if no rearrangements occur during hydrogenation. Mild TABLE IX. GROUPSOF SULFUR CO~VPOUNDS IN NEUTRAL PUMPHERSTON NAPHTHA conditions minimize the possibility of such rearrangements. Weight of Sulfur, % A sample of neutral naphtha was hydrogenated, using Raney Thiol 0.00 nickel as a catalyst, a t a pressure of 500 pounds per square inch Free sulfur 0.00 Disulfide gage and a temperature of 150" C. Seven successive batch opera0.06 Sulfide 0.22 tions were necessary t o hydrogenate the olefins completely. The Residual 0.63 paraffin-naphthene portion of the hydrogenated naphtha was separated from the aromatic portion by means of a silica gel column. %-Pentane was used t o wash the paraffins and naphBecause there is no suitable method for sulfur-group determinations in cracked distillates, the limitations of the method thenes through the column, and the aromatics were desorbed with isopropyl alcohol. The sample of paraffins and naphthenes must be recognized. No adequate method for positive deterwas distilled in a fractionating column having a n efficiency of 95 mination of thiophene in the presence of olefins is available, but the residual sulfur as given by this method of analysis should contheoretical plates at total reflux. Samples containing 10 ml. each (0.5 volume %) were taken, and the following properties tain all of the thiophenic sulfur. Approximately two thirds of determined: boiling point at 760 mm. pressure; refractive indexes the sulfur is in the form of residual sulfur. for the sodium D and mercury g lines at 20" C.; and density at From the d a t a shown in Figure 2, B volume curve (per cent per 20" C. A similar distillation was made on the aromatic portion degree) was drawn for sulfur compounds. This is given in Figure from the silica gel separation of the hydrogenated material, and 5 . Comparison of this curve with boiling points of substituted properties, including ultraviolet absorption data, were obtained thiophenes confirms the belief that the bulk of the sulfur in shale on these fractions. oil is in the form of thiophene homologs. Nitrogen Compounds. The original Pumpherston naphtha Volume data (per cent per degree) were calculated for the paraffins, naphthenes, and aromatics after hydrogenation ( 4 ) . contained 0.51% nitrogen by weight. After treatment with These results are plotted in Figure 4. The amounts of comaqueous 20% sulfuric acid to remove tar bases, the nitrogen con-
Difficulty was encountered in using similar calculations on the cyclic olefins because of the greater number of compounds t o be considered and the lack of data on these compounds. A separation of these compounds into groups according to the number of carbon atoms in the molecule is given in Table VIII.
~
~~
586
INDUSTRIAL AND ENGINEERING CHEMISTRY
..
---vM.--P LEUEND:
0 PYRIDINE
A Ce-PYRID'NES
oC,-PIRIDINE$
0
.'.y
acids, as an ultraviolet spectrogram of the mixture showed no evidence of aromatic compounds. U n s a t u r a t i o'n was indicated by the ultraviolet absorpt,ion dat'a. Owing to the small amount, obtained, no attempt was made to separate and identify individual compounds, A 52.5-gram charge of t,he phenolic compounds released by the carbon dioxide treatment was subjected to fractional d i s t i l l a t i o n i n a s e m i m i c r o column at a pressure of 100 mni. of mercury. Figure 6 shows portions of ultraviolet absorption spectrograms of distillation fractions 1 and 20. The absorption peaks of fraction 1 occur a t the same wave lengths as those of phenol. Solutions of Eract,ion 1 and of phenol having approximately equal concentrations show the same transmittance characteristics. These indicate that fraction 1 contains substantially pure phenol. Fraction 20 shows an absorption peak a t 285.75 m p , as does p-cresol. This absorption peak for p-cresol appears to be unique, so the presence of this compound is indicated in fraction 20. Other cresols are indicated also, but their identities have not been established.
..w.---s
G~-PIRIDINES
NITROGEN COMPOUNDS
OF THIOPHENES
SULFUR
COMPOUNDS
BOILING POINT
Figure 5.
Amounts of Sulfur and Nitrogen Compounds i n Seutral Pumpherston Naphtha
tent of t'he neutral naphtha was 0.18%. M o s t of the material removed was pyridinic, but the extraction of that material may not have been complete. Pyrroles, which are more weakly basic, would tend t o remain in the oil. The volume (per cent per degree) of nitrogen compounds, together with boiling points of typical pyrrolic and pyridinic compounds, is plotted in Figure 5 . The classicol pine-chip test for pyrroles indicated the presence of this class of compounds in the original shale-oil naphtha, in the 'tar bases extracted from it, and in the neutral naphtha. Some pyrrole-type compounds are subject t o polymerization and red discoloration on standing. Gum formation and rapid discoloration were observed in the naphtha from which tar acids and bases had been extracted. A quantity of the neutral naphtha was refluxed over solid pot,assium hydroxide pellets, using a Dean-Stark tube t o collect the water formed by the reaction. After the evolution of water had ceased, the nit,rogen content of t'he naphtha had been reduced to approximately half its former value, and the naphtha was more stable to storage at room temperature. This reaction with potassium hydroxide is characteristic of pyrroles. IDENTIFICATION OF TAR ACIDS
Thp crude tar acids from the isolation procedure were dissolved in aqueous 5% sodium hydroxide solution. Prolonged saturation of the solution with carbon dioxide resulted in the release of phenolic compounds. After their removal by separation and ether extraction, the mother liquo: again was saturated with carbon dioxide, and additional phenolic compounds were released. Several repetitions of the carbon dioxide saturation and subsequent extraction were made, until f i n ~ l l yno additional release of phenolic compounds was effected. The compounds appeared t o be released stepwise in order of increasing acidities. The last fractions produced were found to be largely phenol. The carboxylic acids, being more strongly acidic than carbonic acid, remained in solution in the form of their sodium salts. Acidification of the carbon dioxide-treated mother liquor with dilute sulfuric acid released 1.0 gram of material entirely free from the typical phenolic odor. This miterial was probably carboxylic
0
;2o 8
__
I
Vol. 41, No. 3
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