V O L U M E 25, N O . 7, J U L Y 1 9 5 3
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ACKNOW LEDGXIEST
This invest,igation was supported by a research grant from the Sationnl Cancer Institute, U. S. Public Health Service. LITERATURE CITED
(1) Cecil, R., Biochem. J . , 47,572 (1950). ( 2 ) Flagg, J. F., “Organic Reagents,” p. 275, Sew York, Interscience
Publishers, 1948. (31 Kolthoff, I. LI,,IXD.EXG.CHEX.,AKAL.ED.,14, 195 (1942). (4) Kolthoff, I. LI., and Barnurn, C..J . A m . Chem. Soc., 62, 306
(1940).
fhid., 63, 520 (1941). Kolthoff, I. 31.,and Stricks, W., . h - . i L . CHEW,23, 763 (1951). Kolthoff, I. X , , and Stricks, R., J . Am. Chein. Soc., 72, 1952 (1950). Lee, T. S., Ph. D. thesis, University of Alinnesota, 1949. Lee, T. S., and Kolthoff, I. JI., Ann. S. 1.. A c n d . S c i . , 53, 1093 (1951). Lingane, J. J., and Kolthoff, I. AI., J . A m . Cheni. Soc., 61, 825 (1939). Schoherl, h.,and Hornung, T., Liebigs Ann., 534, 210 (1934). Stricks. if*., and Kolthoff, I. 31., J . Am. Chem. Soc., 74, 4040 (1952). R E C E I V Efor D review January 26, 1953.
.Xcrei)ted .\larch 27. 19.53
Properties of High Boiling Petroleum Products High Aromatics Characterization by Chromatography L. T. ERY Oil Deuelopnien t Co., Linden,
Esso Laboratories, Standard
.Y.J .
Little information is available on compositions of petroleum products boiling above 600” F. .A rapid method has been developed for characterizing the aromatic and other fractions with the object of predicting carcinogenic potencies. The refractibe index of the aromatic fraction was found useful, even when that of the whole sample was valueless. The aromatic fraction was obtained by a chromatographic separation. The procedure employs an elution method with silica gel adsorbent and three selecti\e sol>ents-n-heptane, benzene, and pyridine. Nonaromatic, aromatic, and o x ) fractions were obtained. Typical results are described for a wide variety of refinery products. Data obtained by this procedure have been found useful in various processing studies involFing high boiling petroleum products.
A
SULIBER of chromatographic procedures have been employed for the analysis of petroleum products (1-21). -4 more satisfactory general procedure for inspection purposes was drsired for high boiling petroleum products, especially those boiling above 600” F. It was required that.the method be as simple and short as possible, b u t that it should provide isolated fractions of the nonaromatic, aromatic. and “oxy” (fraction elut>ed with pyridine) fractions, as \vel1 as quantitatively estimate the amount present. Because of high melting points and high viscosities of the samples and their fractions, displacement techniques were unsatisfactor!.. even with hot columns or with various added solvents. hfter more elaborate procedures involving combinations of elution and displacement techniques had been tried. the folloiving method was developed as most satisfactory for a general procedure. It has been used on a large number of high boiling petrolruni products for purposes of characterization. The fractions f i ~ ~ this m method have been used for spectral investigation as well as for the refractive indices that are presented here. Little emhas heretofore been given to the osy fraction. For the latter, pyridine has been found to be the most, satisfactory eluent twc*auseof its high solvent power, absence of oxygen, and strong odor for detection. This method has been named the “high aromatics characterization.” because it was of interest to characterize the high boiling ni,oniatirs. The information obtained from this method is: 1. The per cent of nonaromatics, which includes paraffin$, olefins, naphthenes, and some polyalkylated aromatics which ran be removed from silica gel with n-heptane. 2.. The per cent of aroniaticp, which includes the compounds that are not removed with n-heptane but nre easily eluted with benzene.
3 . T h per cent of oscy material, which ini*lutlrq all the compounds not eluted with n-heptane or benzene but whirh are removed with pyridine. I n petroleum fractions, these are mainly compounds containing oxygen, as well as some sulfur and nitrogen. 4. The per rent loss. This represents volatility, or lower hydrocarbons, although it may represent nonvolatile material left on the column after washing with pyridine. There is very little organic matter that is not removed by elution with pyridine, but the nonvolatile loss may include insoluble fibers, inorganic material, et?. 5 . The refractive indes a t 50” C. of the nonaromatic fraction. This temperature was cho9en because of the waxy character of many of these fractions a t room temperature. 6. The refractive indes a t 20” C. of the aromatic fraction. This may be taken directly, or in a benzene or toluene solution. -is many of the refractive indices encountered were beyond the range of the instrument, a st’andard procedure was employed for this measurement in a benzene solution. A refractometer designed to use reflected light rather than transmitted light should be employed for correct refractive indices of the highly colored fractions ( 1 7 ) .
.is there is usually a fair-sized fraction after evaporation, it is possitilr to carry out other analyses for special characterization purposes-e.g., the spectral investigations mentioned above. The isolation of any one or two of the fractions may be omitted where only partial information is required. PROCEDURE
Chemicals. n-Heptane, pure grade from Phillips Petroleum co. Benzenr, thiophene-free grade. Pyridine, 2’ grade. Silica gel, 28 to 200-mesh commercial desiccant from Davison Chemical Corp., heated overnight and stored in tightly stoppered, narrow-mouthed bottles. Hyflo, diatomaceous earth filter aid. Adsorption Tube. Four-foot, glass column. 35 nim. in outside
ANALYTICAL CHEMISTRY
1058
Table I.
Dependence of Volatility Loss and Sharpness of Separation on Boiling Range High Aromatics Characterization Xonaroinatics Aromatics oxy, C7c n Lo 70 nZ,O 76
Distillation
' F., a t
Vapor B.P., IBP 5% off
% Off a t
so.
Sample
1
520 435
540 485
551 1000
100
2
DodecylbenaeneQ Heavy aromatic naphtha
3 4 5 6 7 8
Paraffinic white oil Paraffinic white oil Naphthenic white oil Naphthenic white oil Naphthenic white oil Saphthenic white oil0
400 564 573 600
...
500 780 830 >700
100 6 3 0
...
9
.so of dodecylbenzene
597 610 625
...
50% mixture of 1and 8 O
a
= 1 4894.
9570 off
...
... ...
. .
. .
7OOOF.
...
0 0 0.2
...
100 70 50 68 40 40
0.0 97.6 98.4 98.6 96.8 100.0
1.4450 1.4614 1.4620 1.4693 1.4803
0.0 0.4 0 6 0.6 3 0 0.1
...
...
50.0
1.4803
41.6
...
.. =
Distillation Vapor B.P., ' F., a t Initial 5% off 95% off
70 Off a t
114
Virgin residuum (West Texas)
...
878
> 1000
175
Virgin residuum (Tomball)
3 70
574
> 1000
7
704
Heavy virgin gas oil
....
..
16
705
Catalytically cracked 704
....
..
22
...
.
I
.
600' F.
700' 2
546
643
1000
1
56
685
705
1000
0
3
372
456
33
57
1000 ....
15
35
113
T a r from hydroforming
420
436
950
77
92
214
Bunker fuel
469
616
> 1000
4
7
22 1
Bunker fuel
363
529
> 1000
9
23
191
Total heavy catalytic gas oil 685+
245
T a r from suspensoid cracking
109
T a r from steam cracking
550
F. residue, 60% of 191
%
14906 1 6583
0 0 1 2
226 20 2
.... ... ....
....
.... ....
0.0 0.0 0.0 0.0 0.0 0 0
100 0 2.0 1.0 0.8 0.2 0 0
1 4893
0 0
8.4
Repeatability of High Aromatics Characterization Data
so.
344
...
778 78 4
LO*^,
1.4804.
Sample Petroleum product
__
....
100 77
55
nk0 of naphthenic white oil S o . 8
Table 11.
600'F.
diameter, for down flow under 3 pounds per square inch gage pressure of nitrogen. The silica gel adsorbent is packed with vibration over a glass wool plug t o a volume of 600 ml. Five grams of Hyflo is added on top of the adsorbent. This leaves ample space above the adsorbent for later solvent additions. Separation. The adsorbent is prewetted with 50 ml. of nheptane. -45.00-gram sample of high boiling petroleum product
F.
High .Iromatics Characterlzation Sonaromatics Aromatics oxy, Loes, (7 sl, n;D" 70 n%O % 45 0 46 6 52 8 .01 6 64 8 65 0 56 4 55 8 61 6 62 6 61 6 61 2 16 0 16 8 4 6 3 6 33 6
33 0 0 32 30 31 30
2 4 2 0 8 0 8
1 iZL0 1 5212 1 4627 1 4615 1 4608 1 4605 1 4492 1 4494 1 4454 1 4452 1 4472 1 4473 1 4642 1 4540 1 4817 1 4818 1 4606 1 4608
I 4674
1 4692 1 4618 1 4618
43.4 41.2 37.8 38.8 27.6 28.0 41.2 40.6 32.4 30.6 33 8 34.0 62.4
01.6 78 5 7.5 0
47 4 47.8 46.2 to 2 a7.4 56.6 49 8 31.2
1 6045
1 6035
5827 5858 5692 5688 1 6627 1 6655 1 6356 1 6408 1 6509 1 6514 1 6393 1 6334 1 6827 1 6871 1 6077 1 6071 1 6200 1 6259 1 6156 1 6186 1 6129 1 6156 1 1 1 1
3 6 5 5
8 0 2 0
1 6
0 0 0 2
4 8 8 4
1 8
4 0 3 8 4 4 4 8
4.0 4 0 4 0 4 0 0 0 0 4 6 4 6 2 8 6
8 4
3 .8 6 2
4 4 6 6 3 2 3 5
2 6 0 6 4 8 6 0
0 6 1 0 17 2 16 8
12 8 1T 4 I5 0 1.5 0 53 4 59 2 4 2
6 4 9 6 9 6
is vigorously swirled in a 300-1111. Erlenmeyer flask with 200 nil. of n-heptane and 5 grams of Hyflo. This mixture is added to the column. Subsequent additions of solvent are made in 200-ml. portions from the same flask to assure complete addition of the sample even when the latter is not completely soluble in n-heptane. Additions of solvent are made as soon as the last of the previous addition reaches the Hyflo n-ithout letting gas enter the bed of adsorbent. The following solventp are now added in the order: 800 ml. of n-heptane, 800 ml. of benzene, and 800 ml. of pyridine. The nonaromatic effluent is removed immediately after Table 111. Elemental Analyses of Fractions from High Aromatics addition of the first portion of benzene, Characterization The aromatic effluent is removed immediately after addition of the first porSample HAC Determination -4nalyses of Fractions tion of pyridine. The oxy effluent is re(Diff.) KO. Petroleum Rample Fraction R u n Yo. % ' C %H %S %N %0 moved after the last portion of pyridine has gone through the Hyflo. 85.12 14.01 0.13 110 Thermal reformer tar Nonaromatics 51 0.12 0.62 Each effluent is first evaporated under 55 84.80 12.80 0 . 1 4 0.12 2.12a .4romitics 51 90.72 8 . 8 7 0.OOb 0 . 1 4 0.27 a stream of nitrogen to about 100 ml. in 55 90.54 8.63 0.72 0.12 0.00 a steam bath. The concentrate is rinsed 84.26 7 . 4 1 1.12 OXY 51 1.06 6.15 into a 300-mI. Erlenmeyer flask tared to 109 T a r from steam cracking Konaromatics 54 8 6 . 2 0 14.08 0.00 0.00 0.00 f O . O 1 gram. The evaporation is con57 85.64 13.74 0 . 1 1 0.08 0.43 tinued in the same manner until free Aromatics 54 89.22 7.94 0.89 0.16 1.79 from solvent odor. The flask is evac57 90.84 7.39 0.93 0.12 0.72 OXY 57 84.08 7.34 1.14 1.01 6.43 uated to about 175-mm. (mercury) pressure with the flask completely im191 Totalheavycatalyticgasoil Sonaromatics p6 85.85 14.17 0.00 0.00 0.00 mersed in steam for 15 minutes. The Aromatics 56 88.79 8 , 5 4 0.89 0.16 1.62 OXY 56 8 1 . 2 3 7 . 0 7 0.15 1.02 10.53 flask is dried, cooled, and weighed to 1 0 . 0 1 gram. -4 check for constant 114 Virgin residuum (West Texas) Nonaromatics 60 86.02 13.20 0 . 0 0 0.00 0.78 w i g h t after another 15minutes of evacuAromatics 60 84.96 10.06 0 . 7 2 0.09 4.17 at'ion at 100" C. will assure complete a This value of 2.12 is obviously high, owing t o a low hydrogen value. Only oxy fractions were solvent removal. The weights are coranalyzed in duplicate, other analyses are froin single determinations. b Obviously a n error also, as other aromatic fractions contain sulfur as well as repetition on this rected if necessary for a blank detersame tar in run 55. mined by carrying out the above procedure wit'hout the petroleum sample. --
V O L U M E 2 5 , NO. 7, J U L Y 1 9 5 3
1059
The weights of the residues are multiplied by 20 and reported
All data presented in this paper are based on the assumption of unit density of the aromatics.
as: per cent nonaromatics, per rent aromatics, and per cent oxy
material. Refractive Indices of Separated Fractions. The refractive index is measured by reflected light on an Abbe-type refractometer with the back of the upper prism illuminated with a microscope lamp, rather than using transmitted light through the lower prism. The refractive indices of the nonaromatic fractions are taken directly at 50" C. The refractive indices of the aromatic tractions a t 20" C. are taken by assuming unit density of the fraction, adding exactly 5 ml. of benzene (or toluene) to the entire fraction, measuring the refractive index of the solution, and calculating according to the following equation: 70
DISCUSSION
The ratio of silica gel to sample of 120 to 1 was chosen after 910 >goo 950 > 1000
5iooo > 1000 ..
890 910 984 873 96 1 920 904 76 1 693 656 686 717
>loon > 1000 > 1000 > 1000
> 1000 > 1000 > 1000 > 1000 > 1000 > 1000 > 1000 > 1000
> 1000 > 1000
....
< 500
