analysis of several fcrrites I\ (’re precise and compared fal-orably with results reported b\- an independent laborator\-. RESULTS
Typical results for tllc analysis of slathetic inanganese-Inagnesiuin and manganese-magnesium-zinc mixtures are presented in Tables I and 11. The data indicate quantitative recoveries of the mctals, the crror heing generally 0.1 nig. or less. The analyscs may bc performed rapidly. Complete analysis of a svnthetic ternary mixture, including calculations, \vas usually conipletd in less than 40 niiiiuteq.
The fluoride demasking technique can be extended to the determination of other divalent metal ion-magnesium combinations. Also, by utilizing the technique of selectively demasking zinc (\vith formaldehyde) from its cyanide complex, as many as four metal ions can be analyzed by consecutive titration of a single sample solution-e.g., manganese - magnesium - zinc - nickel. Finally, combination of the cupferron extraction method with the fluoride dellinsking procedure makes possible the determination of magnesium in conibination n-ith other metals after reinoval of the interfering species suck a$ titaniuni, zirconium, thorium, bismutli, sild tin, in addition to iron.
LITERATURE CITED
Riedermann, Schwttlzenbach, G,, Chimia 2 , 56 (1948). ( 2 ) Flsschka, H., Abdine, H., ChemzstA n a l y ~ 44, t 8 (1955). ( 3 ) Flaschka, H., Barnard, J., Broad, W.C., Ibad., 46, 106 (1957). (,
(4) Fritz, J. s., M, J , ~ ~ ~ t ~ ~ f .4 s., h A L . CNEM. 29, 577 (1957). ( 5 ) Kinnunen, J., Xferikanto, B., C h e m s f S n n l y s t 4 3 , 9 3 (1954). ( 6 ) Pribil, R., Collectzon Czechoslov Chem.
c
~
,19, 58~ (1954). ~ ~
( 7 ) Zbtd., p. 64. 18) Reillev, C.
~
9
~
~
K,,Schmid, R IT’., -45.4L. ~ Chenb. 154, ~ 122
(1956).
R~~~~~~~ f o r ~ ~ 1 ) .i j 1958, ilccepted September 25, 1958
Se pa ratio n of Pa raf f in- Cyc Io p a raff in Portio n of Naphtha into Normal, Branched, and Cycloparaffins MATTHEW S. NORRIS and JOHN G. O’CONNOR Gulf Research and Development Co., Pittsburgh, Pa.
b Separation of the saturate fraction of
naphthas into straight-chain, branched, and cyclic classes has been investigated using Molecular Sieves and silica gel adsorption with added components. The saturate fraction of a naphtha was chargcd to a column of 5-AMolecular Sieves. The branched and cyclic componsnts were eluted with isopentane, then the straight-chain paraffins were removed with n-pentone. After the pentanes had been distilled off, a sample of n-paraffins and a sample containing both the branched and cyclic classes were obtained. The branched and cyclic material was subjected to a separation using silica gel adsorption with added components. A high pore volume silica gel saturated with diethylene glycol monomethyl ether (methyl Carbitol) was used. The branched and cyclic mixture was then charged to the column and eluted with a perfluorocyclic ether. Examination of the chromatogram of the eluate revealed that the branched material issues from the column first in high purity, followed b y eluent fractions which show a progressive gradation in terms of decreasing branched material content and of increasing naphthenic content. The tail end of the elution yields cyclic materials in high purity.
T
usefulness of liquid adsorption chromatography for the separation of hydrocarbons into aromatic, olefin, HE
and saturated classes has been knon n for some time (7, IO). Additional separation of these classes, especially the saturate fraction, into subclasses becomes more difficult. Mair and others (4) recently separated a CI8to Czsoil fraction of a MidContinent petroleum into an aromatic portion and a paraffin-cycloparaffin portion by adsorption on silica gel. The aromatic portion was further separated into mononuclear, dinuclear, and trinuclear aromatics using alumina gel. The paraffin-cycloparaffin portion was separated with urea into a n-paraffin and a branched plus cycloparaffin portion. The further separation of paraffincycloparaffin hydrocarbons has been described by Sauer and others ( I I ) , who used liquid displacement chromatography with aniline as the stationary phase supported on silica gel. The samples were displaced from the columns with isopropyl alcohol and benzene, making recovery of the fractions relatirely easy. Although separations were not complete, fractions of high purity in paraffins and cycloparaffins were obtained for the separation of binary mixtures of paraffin and cycloparaffins and separation of a naphtha. Mair, Montjar, and Rossini (5) separated branched paraffins from cycloparaffins using either ethylene glycol inonomethyl ether or diethylene glycol monomethyl ether supported on a high pore volume silica gel. They showed that the niethod was good for the sep-
aration of two-component hydrocarbon SJ steins using either heptacosafluorotributylaniine 01’ a perfluorocyclic ether as eluent. The method is hascd on li iuid part it ion ch rotnat og ra ph y . The branched components tend t o concentrate in the inobile fluorochemical phase, d d e the cycloparaffins concentrate in tlie adsorbed phase. Thus, the branc~liedinaterial comes off tlie coliinin first, followed bj- the cycloparaffins. .I nunibcr of methods h a w Iwen used
A L L OlYENSlONS IN CENTIMETERS
A 35/25 SPnERlCAL JOINT B RESERVOIR,IOOOYL. CAPACITY C STAINLESS STEEL BALL B E A R I W S , 3/B* 0 SLASS WOOL PLUG E PRETREATED ADSORBENT F WATER JACKET G 24/40 $ JOINT H FRITTED 6LA¶9 OISK (MI I PRESSURE STOPCOCK, 2 YY BORE J 10136 $ JOINT
Figure
1.
~
Glass adsorption
column
VOL. 31, NO. 2, FEBRUARY 1959
275
~
~
for the separation of normal paraffins from hydrocarbon mixtures. Probably the best known are the crystalline adducts formed with urea and normal paraffins (1, 2, 9). Xelson, Grimes, and Heinrich ( 8 ) have described a method for the determination of normal paraffins and normal olefins in petroleum distillates boiling between 60" and 400' F., based on the selective adsorption of straightchain compounds by a synthetic zeolite, Linde Molecular Sieve, Type 5-A. This method gives reliable data for the normal hydrocarbons, but does not provide a means of recovering the adsorbed and nonadsorbed material. The present investigation was undertaken to determine if the separation reported by Mair (5) was applicable to a more complex system-i.e., an Ordovician naphtha boiling between 109' and 172" C. If the separation produced fractions which were representative of the original material or gave complete separation, it would be an improvement over existing methods. This paper re$' ports on the use of Molecular i~eves and selected eluents for the separation of normal paraffins from a hydrocarbon
mixture. The saturate fraction of an Ordovician naphtha was charged to a column of 5-A Molecular Sieves. The branched and cyclic hydrocarbons were eluted with isopentane, followed by an elution with n-pentane to remove the adsorbed straight-chain paraffins. PROCEDURE
Separation of Normal Paraffins. The straight-chain paraffins were separated from the branched and cyclic material by charging a saturate fraction to a column 1 inch in internal diameter and 3 feet long, packed with 5-A Molecular Sieves. The hydrocarbon charge was moved slowly down the column and eluted with isopentane, which removed the branched and cvclic components. Elution with n-pentane then displaced the adsorbed normal paraffins. The pentanes were removed by distillation, leaving a residue of normal paraffins and a residue of branched plus cyclic hydrocarbons. During this investigation, it became apparent that the total recovery from the sieves varied considerably. The best results were obtained by operating the column near the boiling point of the n-pentane. Perhaps a more quantitative recovery would be possible using a method reported recently by Mair (6), in which steam or hot ethyl alcohol was used to desorb the normal paraffins. Separation of Branched and Cyclic Hydrocarbons. The procedure for separating the branched and cyclic hydrocarbons was the same as t h a t reported by h4air ( 5 ) . The glass adsorption column is shown in Figure 1. Silica gel, grade 70, 60 to 200 mesh (Davison Chemical Corp.) was used as the adsorbent for the stationary liquid, diethylene glycol monomethyl
ether. The perfluorocyclic ether, CsFIBO (Minnesota Mining and hIanufacturing Co. No. 0-75), was used as the eluent. The temperature of the column was adjusted for the particular components in the system. The operating temperature was chosen by making reference to the complete miscibility curves of the various hydrocarbons in the fluorochemical and methyl carbitol (3). The temperature usually chosen was the one nearest the temperature for complete miscibility of the branched hydrocarbon in the fluorochemical. The sample, 6 nil., was charged about 6 inches below the surface of the treated silica gel in a 6-foot column with a 10-ml. capacity hypodermic syringe, fitted with a stainless steel tube 1 mm. in internal diameter X 40 mm. long, thus preventing loss of hydrocarbon due to volatilization. In these experiments the eluent, about 500 ml. of a perfluorocyclic ether, was moved slowly down the column by gravity alone. \\%en the eluent reached the bottom of the column, a pressure of 10 p.s.i.g. inert gas pressure was applied to the top of the column and 5-ml. fractions were collected every 2 to 3 minutes. The refractive index was plotted as a function of volume effiuent off the column, .giving a chromatogram which could be inspected visually for an indication of the degree of separation achieved. The refractive indices were taken with a refractometer on which the prism and scale were adjusted to permit readings below 1.3. These data are not absolute and were reported as A R I , which was the difference between the refractive index of the fluorochemical and of the fluorochemical plus hydrocarbon. The branched and cyclic hydrocarbons were separated from the fluorochemical with absolute ethanol a t -80" C. At this temperature two phases are formed: a phase which is largely fluorochemical and a phase consisting of alcohol and hydrocarbon.
VOLUME EFFLUENT I N M L
Figure 2. Elution of Ordovician naphtha branched and cyclic hydrocarbons from 5-A Molecular Sieves with isopentane
. 0 X
ec. 4
0
VOLUME EFFLUENT IN M L VOLUME E F F L U E N T IN ML
Figure 3. Elution of Ordovician naphtha normal paraffins from 5-A Molecular Sieves with n-pentane
276
ANALYTICAL CHEMISTRY
Figure 4. Separation of an equivolume mixture of a fourcomponent system by adsorption with added components Fractions A and B analyzed b y mass spectrometry
The alcohol-hydrocarbon phase was then washed with water, liberating the pure hydrocarbon. EXPERIMENTAL AND DISCUSSION
Separations with Molecular Sieves.
A 20-ml. synthetic sample, consisting of 25% 2,2,4-trimethylpentanej 25% methylcyclohexane, a n d 50% n-heptane, was charged t o a column containing 110 grams of 5-A powdered Molecular Sieves. The charge was moved slowly doKn the column with 25-ml. increments of isopentane and eluted until the refractive index of the effluent was equivalent to isopentane. The isopentane was removed by distillation, leaving a residue of the branched and cyclic material. The column was then eluted with n-pentane to remove the normal paraffins. The eluent was separated by distillation, leaving a residue of the normal. paraffins. The results of this separation are shown in Table I. These data indicate that the normal paraffin is completely separated from the branched plus cyclic hydrocarbons. An Ordovician naphtha with a boiling range between 109' and 172" C. was separated by regular adsorption on silica gel to yield a saturate fraction. d column containing 134 grams of 5-A Molecular Sieves was charged with 25 nil. of the saturate fraction from the naphtha and it was eluted with isopentane. Figure 2 shows the chromatogram of this separation. The first cuts were rich in branched and cyclic hydrocarbons and all this material was contained in the first 35 ml. of effluent. Figure 3 shows the chromatogram for material eluted n ith n-pentane. The normal paraffins are eluted slowly, about 430 nil. of eluent being required to remo\-e approximately 85% of the paraffins from the sieves. Table I1 shows the composition breakdown of the naphtha saturate fraction as obtained by the hfolecular Sieve separation. The individual straight-chain paraffins were determined by mass spectrometric analysis.
methylcyclohexane was charged t o a column packed with 333 grams of silica gel pretreated with 297 ml. of diethylene glycol monomethyl ether. The column temperature was 55' C. and the eluent was a perfluorocyclic ether. The chromatogram of this separation is shown in Figure 4. The chromatogram shows two &-ell defined peaks, indicating that a separation was obtained. Fractions A and B, representing branched and cyclic hydrocarbons, respectively, were estracted with absolute ethyl alcohol at -80" C. to yield essentially pure hydrocarbon. Mass spectrometric analyses of these blends (Table 111) show that this four-component system can be separated into the branched and cyclic hydrocarbons very well, Table I. Separation of n-Paraffin from Branched and Cyclic Hydrocarbons with 5 - A Molecular Sieves
Charge Recovered, Volume yo From From isopen- n-pentane tane Compound effluent effluent 2,2,4-Trimethylperitane 92 0 Rlethylcyclohesane 96 0 n-Heptane 0 88 Table II. Composition of Ordovician Naphtha Saturate Fraction as Obtained with 5 - A Molecular Sieves
Table 111.
Separation by Adsorption with Added Components. A sample consist-
ing of 6 ml. of a n equal volume misture of 2,4-diniethylpentaneJ 2,2,4trimethylpentane, cyclohexane, and Table IV.
Vol. yo
Class Branched and cyclic hydrocarbons Kormal paraffins n-Heptane n-Octane n-Nonane n-Decane
47 15 20 15 3
Figure 5 shows the separation obtained for an eight-component system consisting of an equivolume mixture of 2,4-dimethylpentanej 2,2,4-trimethylpentane, 2,2,5-trimethylhexaneJ 2,7-dimethyloctane, niethylcyclohesane, ethylcyclohesane, n-propylcyclohexane, and n-butylcyclohexane. The column \\-as packed with 333 grains of silica gel pretreated with 297 ml. of diethylene glycol monomethyl ether and maintained at 45' C. This column temperature appeared to give a better separation than that maintained a t 55' C. The chromatogram reveals two well defined branched and cyclic hydrocarbon peaks, indicating that a good separation was obtained. Mass spectrometric analysis for this separation is shon-n in Table IV. Selected individual cuts were analyzed, where possible, to determine when the various components came off the column. I n some cases the hydrocarbon could not be separated from a single cut; several cuts were combined and then analyzed. These data show that the lower molecular TTeight material tcnds to concentrate in the earlier fractions and the higher molecular n eight material in the later fractions. IndiT idual cuts are not representative of the ;ample, making it necessary to have a complete separation between the two classes of hydrocarbons. Hydrocarbon material could not be recovered from the center portion between the two peaks, but from the appearance of the chromatogram and the data in Table IV, it appears that a good separation has been achieved. Figure 6 shows the separation obtained when 6 ml. of the branched and cyclic material (obtained from the Molecular Sieve separation of the Ordovician naphtha) was charged to 333 grams of silica gel pretreated with
Mass Spectrometric Analysis of a Four-Compound System Separated by Adsorption with Added Components
2,2,4-
Fraction -4 B
Trimethylpentane 52.2 0.0
Volume % 2,4DimethylCyclopentane hexane 47.3 0.5 0.5 42.0
Methylcyclohexane 0.0
57.5
Mass Spectrometric Analysis of an Eight-Compound System Separated by Adsorption with Added Components
Volume yo Isoparaffins 2,42,2,42,2,5Dimethyl- TrimethylTrimethylFraction pentane pentane hexane 74.0 6.2 17.0 64.1 2.6 22.1 C 63.4 2.1 15.1
6
n
E
F
0.0 0.0 0.0
0.0 0.0 0.0
0.0 0.0 0.0
Cycloparaffins 2,7Dimethyloctane 0.0
6.9 17.7 0.0 0.0 0.0
Total 97.2 957 98.3 0.0 0.0 0.0
MethylEthylPropylButylcyclohexane cyclohexane cyclohexane cyclohexane Total 0.5 1.2 0.3 0.8 2 8 0.9 2.5 0.4 0.5 4.3 0.5 1. o 0.1 0.1 1.7 12.6 36.2 34.3 16.9 100.0 5.7 23.0 39.4 31.9 100.0 4.4 13.2 29.7 52.7 100.0
VOL. 31, NO. 2, FEBRUARY 1 9 5 9
277
297 ml. of diethylene glycol nionomethyl ether using a column temperature of 45' C. The chromatogram is not typical of those obtained for the synthetic samples, in that the trTo peaks are not well defined, indicating that only a partial separation has taken place. I n Table V are listed data obtained by mass spectrometric analysis for the carbon number distribution for some selected cuts across the chromatogram. These data do not represent a precise analysis; however, the relative data arr adequate. The carbon number distribution for each class of hydrocarbons is calculated on a 100% basis, allowing direct comparison with the results obtained on the naphtha before the separation was performed. The total percentages listed represent the total concentration of each class. The data indicate that tlw hydrocarbons tend to come off the column according to their solubilities in the solvents as shonn bv Mair (3). T h r data for the individual cuts show that to obtain a representative samplr the entire branched and cyclic material must be separated. The highest purity obtained for the isoparaffins was approximately 94%, while that of the cyclic material was about 91%. The central portions of several separations were blended together and separated again to determine n-hether the lack of complete separation, seen in Figure 6, was an efficiency problem or was due to an overlapping of the solubility characteristics of some of the branched and cyclic components. Figure 7 shows the chromatogram for 6 ml. of branched and cyclic material from the crntral portion of srveral runs. The column conditions n-ere the same as those reported for Figure 6. There appears t o be very little s e p ration, considering that there is just one large peak. Hon-ever, the data in Table VI, as obtained from mass spectrometric analyses, show that some additional separation was obtained. The highest purity obtained for the isoparaffins was about 9370, while the cyclic material was approvimately SS970. The separation s1ion.n in Table VI sug-
Figure 5. Separation of an equivolume mixture of an eight-component system by adsorption with added components Fractions A, B, C, D, E, and F analyzed by mass spectrometry
V'XU'IE
gests that a longer column might give R better separation of the naphtha. d 16-foot column, similar to that shown in Figure 1, n-as constructed from three sections, connected by 21 40 standard-taper glass joints. Six milliliters of branched and cyclic material from the Ordovician naphtha were charged to the column containing 890
EFFLUENT I N ML
40
30
> 2;
C
Sample Ordovician Naphtha
C,
Isoparaffins C, Cs Clo Totala
C
D E
7 . 6 4 7 . 3 3 2 . 8 12.2
37.8
- C,
47.5 3 3 . 9 14.5 4 . 1
62.2
I I
0 0
8.8 10.3 5.9 4.1 4.6
56.3 48.3 42.5 37.9 26.6
34.9 30.6 35.5 37.2 41.0
0 10.8 16.1 20.8 27.8
93.7 84.9 73.6 17.0 9.1
72.4 67.4 43.0 47.6 55.0
23.2 3 . 8 24.0 7 . 2 40.9 12.8 34.8 13.7 37.3 3 . 0
0.6 1.4 3.3 3.9 4.7
6 3 15.1 26.4 83.0 90.9
a Total represents composition of branched and cyclic components; individual cuts for each claw are calculated on a 100% baeis.
278
I
CycloparaffinP Cg CS C,O 'I'o?ala
F inn - r...a.r t~~...
A B
eo -
Carbon Number Distribution for Selected Cuts from Separation of Ordovician Naphtha Branched and Cyclic Hydrocarbons
Table V.
-
ANALYTICAL CHEMISTRY
50
1
I
I
100 150 200 250 VOLUME EFFLUENT IN YL.
0
Figure 7. Separation of unresolved Ordovician naphtha branched and cyclic hydrocarbons by adsorption with added components Fractions A, B, C, and D analyzed b y mass spectrometry
grams of silica gel pretreated 11ltli 790 ml. of diethylene glycol nionomethyl ether. The column mas eluted \\ith a perfluorocyclic ether. The chromatogram obtained is shown in Figure 8. The peaks were separated more than in Figure 6, but complete separation was not obtained. The data for this run are listed in Table VII. The degree of separation 1%as niuch better; some material was 100% cyclic. The hydrocarbons tend to emerge from the column as a function of carbon number. Blend A was devoid of Clo hydrocarbons and had very little C8 and Cg material, whereas the Cla material concentrated in the later fractions.
20
-+A+~----c-D-E---~F--
0 X
t:.
I
0 -
Table VI. CONCLUSIONS
Saturated hydrocarbons n‘ere separated into a riornial paraffin class and a branched plus cy.lic paraffin class with 5-A Molecular Sieves. The separation T, as achieved by displacing the branched and cyclic material from the column of sieves with isopentane. The first fractions issuing from the column were predominantly the branched and cyclic components, n it11 better than 95% hydrocarbon recovered in approuiniately 35 nil. of effluent. It was found that n-pentane displaced the normal paraffins from the Molecular Sieve column. The straight-chain material is desorbed slowly, about 400 nil. of eluent being needed to remove about 85y6 of the n-paraffins. The column temperature for removal of the normal paraffins should be near the boiling point of n-pentane. Isoparaffins may be separated from cycloparaffins in synthetic samples u p to at least an eight-component system. The separation of an Ordovician naphtha into these classes \vas not complete. The individual cuts from the separation, although of high purity as members of a particular class, JTere not representative of tlie total charge to the column. The rnntcrixl in cxch class tends to come off tlic cduiiin as a function of the m o l ( w i l ~ rn t lglit. The UIW e oi complete miscibility (3)shon that the solubility of the highcr nioleculx I\ eight cycloparaffins iq about tlic sani(x as the lon-er molecular iveight b~anclietlhydrocarbons in tlie dietlij lene glycol monomethyl ether; the solubility of tlie Iicavier branched material in the fluoroc.arbon displays about the same ~olitbilityas tlie lighter cyclic hydrocarbons. Therefore, it is believed that the lack of scparation for the Ordovician naphtha was due to some coniponcnts in the two classes displaying a mutual degree of solubility in the dvrmts used. If the lack of separation had just hecm a lack of efficiency for the rystem, the separation of tlie central portions of vi-em1 runs and the sep-
1
10-
Q
,
1
,
,
1
1
I
1
Separation of Central Unresolved Portion of Ordovician Naphtha Using Adsorption with Added Components
Volume 70 Isoparaffins CS CS Cl0
Cycloparaffins Sample CI Totale C, C8 CS CIO Totala Fraction A 4 . 5 46.6 37.2 1 1 . 7 9 2 . 7 74.6 20.7 4 . 3 0 . 4 7.3 B 4 . 0 36.2 40.0 19.8 79.1 6 3 . 9 25.9 8 . 7 1 . 5 20.9 C 5 . 0 25.0 39.8 3 0 . 2 4 1 . 9 3 6 . 7 47.6 1 2 . 9 2 . 8 5 8 . 1 D 6 . 1 2 3 . 1 33.9 3 6 . 9 1 4 . 0 3 6 . 2 46.4 1 3 . 8 3 . 6 86.0 a Total represents composition of branched and cyclic components; individual cuts for each class are calculated on a. 1007Gbasis. Table VII.
Sample Ordovician Naphtha Fraction A B C
n E F
Separation of an Ordovician Naptha Using Adsorption with Added Components on a 16-Foot Column
C7
Volume 70 Isoparaffins Cs C9 Clo TotaP C,
7 6 473 328 122 960 2 8 9 9 671 2 . 4 51.8 2.3 -6.3 0.0 0.0 0.0 0.0
1 3 0 230 0 38.7 7 . 1 4 3 . 4 48.0 2 7 . 0 73.0 0.0 0.0
Cycloparaffins CS CIO Totalo
Cs
378
475 339
808 942 X6.4 38.9 2.5 0.0
275 805 60.3 36.4 58.0 65.5
145 4 1
684 4 1 153 4 2 25.3 4 . 8 50.5 10.6 28.2 1 1 . 3 15.7 1 5 . 3
622
0 0 192 0 0 5 8 0.6 13.6 i . 0 61.1 2 . 5 97.5 3 . 5 100.0
Total represents composition of branched and cyclic components; individual cuts for each class are calculated on a 100% basis.
aration on the 16-foot colunin ~vould have been much better. Perhaps complete separation could be obtained b>separating the paraffin-cycloparaffin portion by distillation into C?, C8, C9, and Clo fractions and then processing each of these fractions separatdy bjadsorption m-ith added component-. ACKNOWLEDGMENT
The authors are grateful to S . D. Coggeshall and R. E. Snvder for many helpful suggestions, to P. C. Talarico for performing some of the separation experiments, and to G. F. Crable and €1. T. Best for interpreting the mass spectrometric data.
(2) Kobe, K. A,, Domask, IV. G., Ibid., 31,106-13 (1952). (3) llair, B. J., A s . 4 ~ . CHEM. 28, 52 119561. 14j W. J.. (4) Rlair. Rlair, B. .J.. J., lfarculaitis. lfarculaitis, W. J.,’ ‘ Rossini, F. D., IIbid., b i d . , 29, 92 (f957). (1957). (5) Ifair, B. J., Montjar, J. J., Rossini, F. D., Zbzd., 28, 56 (1956). (6) lIair, B J., Shainaiengar, lluthii, Zhid., 30, 276 (1958). (7) llair, B. J., Khite, J. D., J . Research S a t l . Bur. Standards 15, 51 (1935). ( 8 ) .Nelson, K. H., Grimes, h f . D., Heinrich, B. J., AXAL.CHERT. 29, 1026 (1957). (9) Iledlich, O., Gable, C. XI., Dunlap, -4.K., Rlillar, R. W.,J -4m. Chem. SOC. 72, 4161 (1950). (10) Ryssini, F. D., LZair, B. J., Streiff, A. J.. Hvdrocarbons from Petroleum.” Reinhold, YeF York, 1953. Kaskall, T. A , , Melpol(11) Sauer, R. W., . 29, 1327 der, F. W.,~ A L CHEiv. (1957).
LITERATURE CITED
( I ) Fetterly, L. C., Petrol. Refine, 34, 12833 (1955).
RECEIVEDfor review M a p 16, 1958. Accepted September 2, 1958. VOL. 31, NO. 2, FEBRUARY 1959
279
